1
|
Zhu X, Zuo Q, Xie X, Chen Z, Wang L, Chang L, Liu Y, Luo J, Fang C, Che L, Zhou X, Yao C, Gong C, Hu D, Zhao W, Zhou Y, Zhu S. Rocaglamide regulates iron homeostasis by suppressing hepcidin expression. Free Radic Biol Med 2024; 219:153-162. [PMID: 38657753 DOI: 10.1016/j.freeradbiomed.2024.04.232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 04/18/2024] [Accepted: 04/21/2024] [Indexed: 04/26/2024]
Abstract
The anemia of inflammation (AI) is characterized by the presence of inflammation and abnormal elevation of hepcidin. Accumulating evidence has proved that Rocaglamide (RocA) was involved in inflammation regulation. Nevertheless, the role of RocA in AI, especially in iron metabolism, has not been investigated, and its underlying mechanism remains elusive. Here, we demonstrated that RocA dramatically suppressed the elevation of hepcidin and ferritin in LPS-treated mice cell line RAW264.7 and peritoneal macrophages. In vivo study showed that RocA can restrain the depletion of serum iron (SI) and transferrin (Tf) saturation caused by LPS. Further investigation showed that RocA suppressed the upregulation of hepcidin mRNA and downregulation of Fpn1 protein expression in the spleen and liver of LPS-treated mice. Mechanistically, this effect was attributed to RocA's ability to inhibit the IL-6/STAT3 pathway, resulting in the suppression of hepcidin mRNA and subsequent increase in Fpn1 and TfR1 expression in LPS-treated macrophages. Moreover, RocA inhibited the elevation of the cellular labile iron pool (LIP) and reactive oxygen species (ROS) induced by LPS in RAW264.7 cells. These findings reveal a pivotal mechanism underlying the roles of RocA in modulating iron homeostasis and also provide a candidate natural product on alleviating AI.
Collapse
Affiliation(s)
- Xinyue Zhu
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Quan Zuo
- Natural Product Research Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, PR China; University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, PR China
| | - Xueting Xie
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Zhongxian Chen
- Natural Product Research Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, PR China; University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, PR China
| | - Lixin Wang
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Linyue Chang
- Natural Product Research Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, PR China; University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, PR China
| | - Yangli Liu
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Jiaojiao Luo
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Cheng Fang
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Linlin Che
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Xinyue Zhou
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Chao Yao
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Chenyuan Gong
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Dan Hu
- School of Acupuncture, Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, 1200 CaiLun Rd, Shanghai, 201203, PR China
| | - Weimin Zhao
- Natural Product Research Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, PR China; University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, PR China.
| | - Yufu Zhou
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China.
| | - Shiguo Zhu
- Department of Immunology and Pathogenic Biology, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Center for Traditional Chinese Medicine and Immunology Research, School of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China.
| |
Collapse
|
2
|
Salimi Z, Afsharinasab M, Rostami M, Eshaghi Milasi Y, Mousavi Ezmareh SF, Sakhaei F, Mohammad-Sadeghipour M, Rasooli Manesh SM, Asemi Z. Iron chelators: as therapeutic agents in diseases. Ann Med Surg (Lond) 2024; 86:2759-2776. [PMID: 38694398 PMCID: PMC11060230 DOI: 10.1097/ms9.0000000000001717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 01/03/2024] [Indexed: 05/04/2024] Open
Abstract
The concentration of iron is tightly regulated, making it an essential element. Various cellular processes in the body rely on iron, such as oxygen sensing, oxygen transport, electron transfer, and DNA synthesis. Iron excess can be toxic because it participates in redox reactions that catalyze the production of reactive oxygen species and elevate oxidative stress. Iron chelators are chemically diverse; they can coordinate six ligands in an octagonal sequence. Because of the ability of chelators to trap essential metals, including iron, they may be involved in diseases caused by oxidative stress, such as infectious diseases, cardiovascular diseases, neurodegenerative diseases, and cancer. Iron-chelating agents, by tightly binding to iron, prohibit it from functioning as a catalyst in redox reactions and transfer iron and excrete it from the body. Thus, the use of iron chelators as therapeutic agents has received increasing attention. This review investigates the function of various iron chelators in treating iron overload in different clinical conditions.
Collapse
Affiliation(s)
- Zohreh Salimi
- Department of Clinical Biochemistry, Faculty of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan
| | - Mehdi Afsharinasab
- Department of Clinical Biochemistry, Faculty of Medicine, Tehran University of Medical Sciences, Tehran
| | - Mehdi Rostami
- Department of Clinical Biochemistry, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad
| | - Yaser Eshaghi Milasi
- Department of Clinical Biochemistry, Faculty of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan
| | - Seyedeh Fatemeh Mousavi Ezmareh
- Department of Clinical Biochemistry, Faculty of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan
| | - Fariba Sakhaei
- Department of Clinical Biochemistry, Faculty of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan
| | - Maryam Mohammad-Sadeghipour
- Department of Clinical Biochemistry, Afzalipoor Faculty of Medicine, Kerman University of Medical Sciences, Kerman
| | | | - Zatollah Asemi
- Research Center for Biochemistry and Nutrition in Metabolic Diseases, Institute for Basic Sciences, Kashan University of Medical Sciences, Kashan, Islamic Republic of Iran
| |
Collapse
|
3
|
Seyyar SA, Tokuç EÖ, Soysal GG. Effect of diabetic macular oedema on serum iron status indicators. Clin Exp Optom 2024; 107:313-317. [PMID: 37309021 DOI: 10.1080/08164622.2023.2218997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 05/24/2023] [Indexed: 06/14/2023] Open
Abstract
CLINICAL RELEVANCE The role of subclinical inflammation in the pathophysiology of diabetic macular oedema (DME), which is known to be quite complex, is of much interest. Serum ferritin level, which is an indicator of body iron stores, is both an inflammatory marker for various neurodegenerative diseases and an important indicator in the evaluation of iron-induced oxidative stress. BACKGROUND Iron metabolism indicators play a role in the formation and development of diabetic retinopathy, which is known to be associated with subclinical inflammation, and may also play a role in the pathogenesis of DME. The aim of this study was to investigate the role of serum iron metabolism markers in the pathogenesis of DME. MATERIALS AND METHODS The files of all nonproliferative diabetic retinopathy (NPDR) patients who were scheduled for the first intravitreal injection for DME in the eye clinic between January 2019 and January 2020 were reviewed retrospectively. By examining the files of all diabetes mellitus patients who attended the outpatient eye clinic on the same dates, those without retinopathy and those with NPDR but not DME were recorded. All results, including a comprehensive ophthalmological examination, laboratory data of fasting blood tests, and an internal medicine outpatient examination were collected for analysis. RESULTS Of the 157 participants, 44 were NPDR patients with oedema, 50 were NPDR patients without oedema, and 63 were patients without retinopathy. There was a significant difference between the groups in respect of creatinine, high-density lipoprotein, mean corpuscular volume, serum iron and ferritin, total iron binding capacity and transferrin saturation (p < 0.050). Ferritin values were found to be significantly higher in patients with macular oedema. Other iron status markers were found to be significantly lower (p < 0.050). CONCLUSION Evaluation of serum iron status indicators in the routine follow-up of diabetic patients may be of diagnostic and/or prognostic benefit in terms of DME.
Collapse
Affiliation(s)
- Sevim Ayça Seyyar
- Ophthalmology Department, Gaziantep University Hospital, Gaziantep, Turkey
| | - Ecem Önder Tokuç
- Ophthalmology Department, Kocaeli University Hospital, Kocaeli, Turkey
| | | |
Collapse
|
4
|
Davaanyam D, Lee H, Seol SI, Oh SA, Kim SW, Lee JK. HMGB1 induces hepcidin upregulation in astrocytes and causes an acute iron surge and subsequent ferroptosis in the postischemic brain. Exp Mol Med 2023; 55:2402-2416. [PMID: 37907744 PMCID: PMC10689467 DOI: 10.1038/s12276-023-01111-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 07/25/2023] [Accepted: 07/27/2023] [Indexed: 11/02/2023] Open
Abstract
Dysregulation of brain iron levels causes functional disturbances and damages neurons. Hepcidin (a peptide hormone) plays a principal role in regulating intracellular iron levels by modulating ferroportin (FPN, the only known iron exporter) through triggering its internalization and lysosomal degradation. We observed a significant and rapid iron surge in the cortices of ischemic hemispheres at 3 h after cerebral ischemia (middle cerebral artery occlusion, MCAO) that was maintained until 4 d post-MCAO. We showed upregulation of hepcidin expression in the brain as early as 3 h post-MCAO, mainly in astrocytes, and significant hepcidin accumulation in serum from 6 h post-MCAO, and these inductions were maintained for 1 day and 7 days, respectively. High mobility group box 1 (HMGB1), a prototypic danger-associated molecular pattern, accumulates markedly after transient MCAO and plays critical roles in damage aggravation via its proinflammatory effects. Here, we demonstrated that treatment with recombinant HMGB1 stimulated astrocytes to induce hepcidin expression in a TLR4- and CXCR4-dependent manner. Furthermore, hepcidin-mediated intracellular iron accumulation in neurons was confirmed by an experiment using N-methyl-D-aspartate (NMDA)-conditioned medium-treated primary astrocytes and fresh primary cortical neurons treated with hepcidin-containing astrocyte-conditioned medium. Moreover, HMGB1-mediated local hepcidin upregulation and subsequent local iron surge were found to cause ferroptosis in the postischemic brain, which was suppressed by the functional blocking of HMGB1 using intranasally administered HMGB1 A box or anti-HMGB1 antibody. These findings show that HMGB1 serves as a ferroptosis inducer by upregulating hepcidin in astrocytes and thus aggravates acute damage in the postischemic brain.
Collapse
Affiliation(s)
- Dashdulam Davaanyam
- Department of Anatomy, Inha University School of Medicine, Incheon, 22212, Korea
| | - Hahnbi Lee
- Department of Anatomy, Inha University School of Medicine, Incheon, 22212, Korea
| | - Song-I Seol
- Department of Anatomy, Inha University School of Medicine, Incheon, 22212, Korea
| | - Sang-A Oh
- Department of Anatomy, Inha University School of Medicine, Incheon, 22212, Korea
| | - Seung-Woo Kim
- Department of Biomedical Sciences, Inha University School of Medicine, Inchon, 22212, Korea
| | - Ja-Kyeong Lee
- Department of Anatomy, Inha University School of Medicine, Incheon, 22212, Korea.
| |
Collapse
|
5
|
Longo F, Piga A. Does Hepcidin Tuning Have a Role among Emerging Treatments for Thalassemia? J Clin Med 2022; 11:5119. [PMID: 36079046 PMCID: PMC9457499 DOI: 10.3390/jcm11175119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 08/21/2022] [Accepted: 08/27/2022] [Indexed: 01/19/2023] Open
Abstract
The treatments available for thalassemia are rapidly evolving, with major advances made in gene therapy and the modulation of erythropoiesis. The latter includes the therapeutic potential of hepcidin tuning. In thalassemia, hepcidin is significantly depressed, and any rise in hepcidin function has a positive effect on both iron metabolism and erythropoiesis. Synthetic hepcidin and hepcidin mimetics have been developed to the stage of clinical trials. However, they have failed to produce an acceptable efficacy/safety profile. It seems difficult to avoid iron over-restricted erythropoiesis when directly using hepcidin as a drug. Indirect approaches, each one with their advantages and disadvantages, are many and in full development. The ideal approach is to target erythroferrone, the main inhibitor of hepcidin expression, the plasma concentrations of which are greatly increased in iron-loading anemias. Potential means of improving hepcidin function in thalassemia also include acting on TMPRSS6, TfR1, TfR2 or ferroportin, the target of hepcidin. Only having a better understanding of the crosslinks between iron metabolism and erythropoiesis will elucidate the best single option. In the meantime, many potential combinations are currently being explored in preclinical studies. Any long-term clinical study on this approach should include the wide monitoring of functions, as the effects of hepcidin and its modulators are not limited to iron metabolism and erythropoiesis. It is likely that some of the aspects of hepcidin tuning described briefly in this review will play a role in the future treatment of thalassemia.
Collapse
Affiliation(s)
- Filomena Longo
- Thalassemia Reference Centre, 10043 Orbassano, Italy
- Regional HUB Centre for Thalassaemia and Haemoglobinopathies, Department of Medicine, Azienda Ospedaliero Universitaria S. Anna, 44124 Ferrara, Italy
| | - Antonio Piga
- Thalassemia Reference Centre, 10043 Orbassano, Italy
- University of Torino, 10043 Torino, Italy
| |
Collapse
|
6
|
Qin X, Zou H. The role of lipopolysaccharides in diabetic retinopathy. BMC Ophthalmol 2022; 22:86. [PMID: 35193549 PMCID: PMC8862382 DOI: 10.1186/s12886-022-02296-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 02/03/2022] [Indexed: 11/29/2022] Open
Abstract
Diabetes mellitus (DM) is a complex metabolic syndrome characterized by hyperglycemia. Diabetic retinopathy (DR) is the most common complication of DM and the leading cause of blindness in the working-age population of the Western world. Lipopolysaccharides (LPS) is an essential ingredient of the outer membrane of gram-negative bacteria, which induces systemic inflammatory responses and cellular apoptotic changes in the host. High-level serum LPS has been found in diabetic patients at the advanced stages, which is mainly due to gut leakage and dysbiosis. In this light, increasing evidence points to a strong correlation between systemic LPS challenge and the progression of DR. Although the underlying molecular mechanisms have not been fully elucidated yet, LPS-related pathobiological events in the retina may contribute to the exacerbation of vasculopathy and neurodegeneration in DR. In this review, we focus on the involvement of LPS in the progression of DR, with emphasis on the blood-retina barrier dysfunction and dysregulated glial activation. Eventually, we summarize the recent advances in the therapeutic strategies for antagonising LPS activity, which may be introduced to DR treatment with promising clinical value.
Collapse
Affiliation(s)
- Xinran Qin
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Haidong Zou
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. .,Shanghai Eye Diseases Prevention & Treatment Center, Shanghai Eye Hospital, Shanghai, China. .,Shanghai Engineering Center for Precise Diagnosis and Treatment of Eye Diseases, Shanghai, China. .,National Clinical Research Center for Eye Diseases, Shanghai, China. .,Shanghai Key Laboratory of Fundus Diseases, Shanghai, China.
| |
Collapse
|
7
|
Shahandeh A, Bui BV, Finkelstein DI, Nguyen CTO. Effects of Excess Iron on the Retina: Insights From Clinical Cases and Animal Models of Iron Disorders. Front Neurosci 2022; 15:794809. [PMID: 35185447 PMCID: PMC8851357 DOI: 10.3389/fnins.2021.794809] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 12/17/2021] [Indexed: 01/19/2023] Open
Abstract
Iron plays an important role in a wide range of metabolic pathways that are important for neuronal health. Excessive levels of iron, however, can promote toxicity and cell death. An example of an iron overload disorder is hemochromatosis (HH) which is a genetic disorder of iron metabolism in which the body’s ability to regulate iron absorption is altered, resulting in iron build-up and injury in several organs. The retina was traditionally assumed to be protected from high levels of systemic iron overload by the blood-retina barrier. However, recent data shows that expression of genes that are associated with HH can disrupt retinal iron metabolism. Thus, the effects of iron overload on the retina have become an area of research interest, as excessively high levels of iron are implicated in several retinal disorders, most notably age–related macular degeneration. This review is an effort to highlight risk factors for excessive levels of systemic iron build-up in the retina and its potential impact on the eye health. Information is integrated across clinical and preclinical animal studies to provide insights into the effects of systemic iron loading on the retina.
Collapse
Affiliation(s)
- Ali Shahandeh
- Department of Optometry and Vision Sciences, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, VIC, Australia
| | - Bang V. Bui
- Department of Optometry and Vision Sciences, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, VIC, Australia
| | - David I. Finkelstein
- Florey Department of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
| | - Christine T. O. Nguyen
- Department of Optometry and Vision Sciences, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, VIC, Australia
- *Correspondence: Christine T. O. Nguyen,
| |
Collapse
|
8
|
Canonical Wnt Signaling in the Pathology of Iron Overload-Induced Oxidative Stress and Age-Related Diseases. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2022; 2022:7163326. [PMID: 35116092 PMCID: PMC8807048 DOI: 10.1155/2022/7163326] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 01/04/2022] [Indexed: 12/26/2022]
Abstract
Iron accumulates in the vital organs with aging. This is associated with oxidative stress, inflammation, and mitochondrial dysfunction leading to age-related disorders. Abnormal iron levels are linked to neurodegenerative diseases, liver injury, cancer, and ocular diseases. Canonical Wnt signaling is an evolutionarily conserved signaling pathway that regulates many cellular functions including cell proliferation, apoptosis, cell migration, and stem cell renewal. Recent evidences indicate that iron regulates Wnt signaling, and iron chelators like deferoxamine and deferasirox can inhibit Wnt signaling and cell growth. Canonical Wnt signaling is implicated in the pathogenesis of many diseases, and there are significant efforts ongoing to develop innovative therapies targeting the aberrant Wnt signaling. This review examines how intracellular iron accumulation regulates Wnt signaling in various tissues and their potential contribution in the progression of age-related diseases.
Collapse
|
9
|
Daher R, Ducrot N, Lefebvre T, Zineeddine S, Ausseil J, Puy H, Karim Z. Crosstalk between Acidosis and Iron Metabolism: Data from In Vivo Studies. Metabolites 2022; 12:metabo12020089. [PMID: 35208164 PMCID: PMC8874512 DOI: 10.3390/metabo12020089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 01/05/2022] [Accepted: 01/12/2022] [Indexed: 01/27/2023] Open
Abstract
Iron absorption requires an acidic environment that is generated by the activity of the proton pump gastric H(+)/K(+)ATPase (ATP4), expressed in gastric parietal cells. However, hepcidin, the iron regulatory peptide that inhibits iron absorption, unexpectedly upregulates ATP4 and increases gastric acidity. Thus, a concept of link between acidosis and alterations in iron metabolism, needs to be explored. We investigated this aspect in-vivo using experimental models of NH4Cl-induced acidosis and of an iron-rich diet. Under acidosis, gastric ATP4 was augmented. Serum hepcidin was induced and its mRNA level was increased in the liver but not in the stomach, a tissue where hepcidin is also expressed. mRNA and protein levels of intestinal DMT1(Divalent Metal Transporter 1) and ferroportin were downregulated. Serum iron level and transferrin saturation remained unchanged, but serum ferritin was significantly increased. Under iron-rich diet, the protein expression of ATP4A was increased and serum, hepatic and gastric hepcidin were all induced. Taken together, these results provide evidence of in-vivo relationship between iron metabolism and acidosis. For clinical importance, we speculate that metabolic acidosis may contribute in part to the pathologic elevation of serum hepcidin levels seen in patients with chronic kidney disease. The regulation of ATP4 by iron metabolism may also be of interest for patients with hemochromatosis.
Collapse
Affiliation(s)
- Raêd Daher
- Centre de Recherche sur l’Inflammation (CRI), Université de Paris, INSERM, CNRS, F-75018 Paris, France; (R.D.); (N.D.); (T.L.); (S.Z.); (H.P.)
| | - Nicolas Ducrot
- Centre de Recherche sur l’Inflammation (CRI), Université de Paris, INSERM, CNRS, F-75018 Paris, France; (R.D.); (N.D.); (T.L.); (S.Z.); (H.P.)
| | - Thibaud Lefebvre
- Centre de Recherche sur l’Inflammation (CRI), Université de Paris, INSERM, CNRS, F-75018 Paris, France; (R.D.); (N.D.); (T.L.); (S.Z.); (H.P.)
- Centre Français des Porphyries, Hôpital Louis Mourier, APHP, Nord-Université de Paris, F-75014 Colombes, France
| | - Sofia Zineeddine
- Centre de Recherche sur l’Inflammation (CRI), Université de Paris, INSERM, CNRS, F-75018 Paris, France; (R.D.); (N.D.); (T.L.); (S.Z.); (H.P.)
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), Université de Toulouse, INSERM, CNRS, F-31024 Toulouse, France;
| | - Jérome Ausseil
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), Université de Toulouse, INSERM, CNRS, F-31024 Toulouse, France;
| | - Hervé Puy
- Centre de Recherche sur l’Inflammation (CRI), Université de Paris, INSERM, CNRS, F-75018 Paris, France; (R.D.); (N.D.); (T.L.); (S.Z.); (H.P.)
- Centre Français des Porphyries, Hôpital Louis Mourier, APHP, Nord-Université de Paris, F-75014 Colombes, France
| | - Zoubida Karim
- Centre de Recherche sur l’Inflammation (CRI), Université de Paris, INSERM, CNRS, F-75018 Paris, France; (R.D.); (N.D.); (T.L.); (S.Z.); (H.P.)
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), Université de Toulouse, INSERM, CNRS, F-31024 Toulouse, France;
- Correspondence:
| |
Collapse
|
10
|
Ashok A, Chaudhary S, Wise AS, Rana NA, McDonald D, Kritikos AE, Lindner E, Singh N. Release of Iron-Loaded Ferritin in Sodium Iodate-Induced Model of Age Related Macular Degeneration: An In-Vitro and In-Vivo Study. Antioxidants (Basel) 2021; 10:1253. [PMID: 34439501 PMCID: PMC8389213 DOI: 10.3390/antiox10081253] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 07/20/2021] [Accepted: 07/30/2021] [Indexed: 11/17/2022] Open
Abstract
To evaluate the role of iron in sodium iodate (NaIO3)-induced model of age-related macular degeneration (AMD) in ARPE-19 cells in-vitro and in mouse models in-vivo. ARPE-19 cells, a human retinal pigment epithelial cell line, was exposed to 10 mM NaIO3 for 24 h, and the expression and localization of major iron modulating proteins was evaluated by Western blotting (WB) and immunostaining. Synthesis and maturation of cathepsin-D (cat-D), a lysosomal enzyme, was evaluated by quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR) and WB, respectively. For in-vivo studies, C57BL/6 mice were injected with 40 mg/kg mouse body weight of NaIO3 intraperitoneally, and their retina was evaluated after 3 weeks as above. NaIO3 induced a 10-fold increase in ferritin in ARPE-19 cells, which co-localized with LC3II, an autophagosomal marker, and LAMP-1, a lysosomal marker. A similar increase in ferritin was noted in retinal lysates and retinal sections of NaIO3-injected mice by WB and immunostaining. Impaired synthesis and maturation of cat-D was also noted. Accumulated ferritin was loaded with iron, and released from retinal pigmented epithelial (RPE) cells in Perls' and LAMP-1 positive vesicles. NaIO3 impairs lysosomal degradation of ferritin by decreasing the transcription and maturation of cat-D in RPE cells. Iron-loaded ferritin accumulates in lysosomes and is released in lysosomal membrane-enclosed vesicles to the extracellular milieu. Accumulation of ferritin in RPE cells and fusion of ferritin-containing vesicles with adjacent photoreceptor cells is likely to create an iron overload, compromising their viability. Moreover, reduced activity of cat-D is likely to promote accumulation of other cellular debris in lysosomal vesicles, contributing to AMD-like pathology.
Collapse
Affiliation(s)
- Ajay Ashok
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; (A.A.); (S.C.); (A.S.W.); (N.A.R.); (D.M.); (A.E.K.)
| | - Suman Chaudhary
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; (A.A.); (S.C.); (A.S.W.); (N.A.R.); (D.M.); (A.E.K.)
| | - Aaron S. Wise
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; (A.A.); (S.C.); (A.S.W.); (N.A.R.); (D.M.); (A.E.K.)
| | - Neil A. Rana
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; (A.A.); (S.C.); (A.S.W.); (N.A.R.); (D.M.); (A.E.K.)
| | - Dallas McDonald
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; (A.A.); (S.C.); (A.S.W.); (N.A.R.); (D.M.); (A.E.K.)
| | - Alexander E. Kritikos
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; (A.A.); (S.C.); (A.S.W.); (N.A.R.); (D.M.); (A.E.K.)
| | - Ewald Lindner
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036 Graz, Austria;
| | - Neena Singh
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; (A.A.); (S.C.); (A.S.W.); (N.A.R.); (D.M.); (A.E.K.)
| |
Collapse
|
11
|
Zhao T, Guo X, Sun Y. Iron Accumulation and Lipid Peroxidation in the Aging Retina: Implication of Ferroptosis in Age-Related Macular Degeneration. Aging Dis 2021; 12:529-551. [PMID: 33815881 PMCID: PMC7990372 DOI: 10.14336/ad.2020.0912] [Citation(s) in RCA: 75] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 09/12/2020] [Indexed: 01/19/2023] Open
Abstract
Iron is an essential component in many biological processes in the human body. It is critical for the visual phototransduction cascade in the retina. However, excess iron can be toxic. Iron accumulation and reduced efficiency of intracellular antioxidative defense systems predispose the aging retina to oxidative stress-induced cell death. Age-related macular degeneration (AMD) is characterized by retinal iron accumulation and lipid peroxidation. The mechanisms underlying AMD include oxidative stress-mediated death of retinal pigment epithelium (RPE) cells and subsequent death of retinal photoreceptors. Understanding the mechanism of the disruption of iron and redox homeostasis in the aging retina and AMD is crucial to decipher these mechanisms of cell death and AMD pathogenesis. The mechanisms of retinal cell death in AMD are an area of active investigation; previous studies have proposed several types of cell death as major mechanisms. Ferroptosis, a newly discovered programmed cell death pathway, has been associated with the pathogenesis of several neurodegenerative diseases. Ferroptosis is initiated by lipid peroxidation and is characterized by iron-dependent accumulation. In this review, we provide an overview of the mechanisms of iron accumulation and lipid peroxidation in the aging retina and AMD, with an emphasis on ferroptosis.
Collapse
Affiliation(s)
- Tantai Zhao
- 1Department of Ophthalmology, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,2Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, China
| | - Xiaojian Guo
- 1Department of Ophthalmology, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,2Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, China
| | - Yun Sun
- 1Department of Ophthalmology, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,2Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, China
| |
Collapse
|
12
|
Zhao J, Kim HJ, Ueda K, Zhang K, Montenegro D, Dunaief JL, Sparrow JR. A vicious cycle of bisretinoid formation and oxidation relevant to recessive Stargardt disease. J Biol Chem 2021; 296:100259. [PMID: 33837742 PMCID: PMC7948646 DOI: 10.1016/j.jbc.2021.100259] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 12/09/2020] [Accepted: 01/05/2021] [Indexed: 11/29/2022] Open
Abstract
The ability of iron to transfer electrons enables the contribution of this metal to a variety of cellular activities even as the redox properties of iron are also responsible for the generation of hydroxyl radicals (•OH), the most destructive of the reactive oxygen species. We previously showed that iron can promote the oxidation of bisretinoid by generating highly reactive hydroxyl radical (•OH). Now we report that preservation of iron regulation in the retina is not sufficient to prevent iron-induced bisretinoid oxidative degradation when blood iron levels are elevated in liver-specific hepcidin knockout mice. We obtained evidence for the perpetuation of Fenton reactions in the presence of the bisretinoid A2E and visible light. On the other hand, iron chelation by deferiprone was not associated with changes in postbleaching recovery of 11-cis-retinal or dark-adapted ERG b-wave amplitudes indicating that the activity of Rpe65, a rate-determining visual cycle protein that carries an iron-binding domain, is not affected. Notably, iron levels were elevated in the neural retina and retinal pigment epithelial (RPE) cells of Abca4−/− mice. Consistent with higher iron content, ferritin-L immunostaining was elevated in RPE of a patient diagnosed with ABCA4-associated disease and in RPE and photoreceptor cells of Abca4−/− mice. In neural retina of the mutant mice, reduced Tfrc mRNA was also an indicator of retinal iron overload. Thus iron chelation may defend retina when bisretinoid toxicity is implicated in disease processes.
Collapse
Affiliation(s)
- Jin Zhao
- Department of Ophthalmology, Columbia University Medical Center, New York, New York, USA
| | - Hye Jin Kim
- Department of Ophthalmology, Columbia University Medical Center, New York, New York, USA
| | - Keiko Ueda
- Department of Ophthalmology, Columbia University Medical Center, New York, New York, USA
| | - Kevin Zhang
- Department of Ophthalmology, University of Pennsylvania, Philadelphia Pennsylvania, USA
| | - Diego Montenegro
- Department of Ophthalmology, Columbia University Medical Center, New York, New York, USA
| | - Joshua L Dunaief
- Department of Ophthalmology, University of Pennsylvania, Philadelphia Pennsylvania, USA
| | - Janet R Sparrow
- Department of Ophthalmology, Columbia University Medical Center, New York, New York, USA; Department of Pathology and Cell Biology, Columbia University Medical Center, New York, New York, USA.
| |
Collapse
|
13
|
Fenofibrate prevents iron induced activation of canonical Wnt/β-catenin and oxidative stress signaling in the retina. NPJ Aging Mech Dis 2020; 6:12. [PMID: 33145027 PMCID: PMC7599211 DOI: 10.1038/s41514-020-00050-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 10/09/2020] [Indexed: 12/20/2022] Open
Abstract
Accumulating evidence strongly implicates iron in the pathogenesis of aging and disease. Iron levels have been found to increase with age in both the human and mouse retinas. We and others have shown that retinal diseases such as age-related macular degeneration and diabetic retinopathy are associated with disrupted iron homeostasis, resulting in retinal iron accumulation. In addition, hereditary disorders due to mutation in one of the iron regulatory genes lead to age dependent retinal iron overload and degeneration. However, our knowledge on whether iron toxicity contributes to the retinopathy is limited. Recently, we reported that iron accumulation is associated with the upregulation of retinal and renal renin-angiotensin system (RAS). Evidences indicate that multiple genes/components of the RAS are targets of Wnt/β-catenin signaling. Interestingly, aberrant activation of Wnt/β-catenin signaling is observed in several degenerative diseases. In the present study, we explored whether iron accumulation regulates canonical Wnt signaling in the retina. We found that in vitro and in vivo iron treatment resulted in the upregulation of Wnt/β-catenin signaling and its downstream target genes including renin-angiotensin system in the retina. We confirmed further that iron activates canonical Wnt signaling in the retina using TOPFlash T-cell factor/lymphoid enhancer factor promoter assay and Axin2-LacZ reporter mouse. The presence of an iron chelator or an antioxidant reversed the iron-mediated upregulation of Wnt/β-catenin signaling in retinal pigment epithelial (RPE) cells. In addition, treatment of RPE cells with peroxisome proliferator-activated receptor (PPAR) α-agonist fenofibrate prevented iron-induced activation of oxidative stress and Wnt/β-catenin signaling by chelating the iron. The role of fenofibrate, an FDA-approved drug for hyperlipidemia, as an iron chelator has potentially significant therapeutic impact on iron associated degenerative diseases.
Collapse
|
14
|
Retinal Degeneration and Alzheimer's Disease: An Evolving Link. Int J Mol Sci 2020; 21:ijms21197290. [PMID: 33023198 PMCID: PMC7582766 DOI: 10.3390/ijms21197290] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 09/15/2020] [Accepted: 09/25/2020] [Indexed: 12/13/2022] Open
Abstract
Age-related macular degeneration (AMD) and glaucoma are degenerative conditions of the retina and a significant cause of irreversible blindness in developed countries. Alzheimer’s disease (AD), the most common dementia of the elderly, is often associated with AMD and glaucoma. The cardinal features of AD include extracellular accumulation of amyloid β (Aβ) and intracellular deposits of hyper-phosphorylated tau (p-tau). Neuroinflammation and brain iron dyshomeostasis accompany Aβ and p-tau deposits and, together, lead to progressive neuronal death and dementia. The accumulation of Aβ and iron in drusen, the hallmark of AMD, and Aβ and p-tau in retinal ganglion cells (RGC), the main retinal cell type implicated in glaucoma, and accompanying inflammation suggest overlapping pathology. Visual abnormalities are prominent in AD and are believed to develop before cognitive decline. Some are caused by degeneration of the visual cortex, while others are due to RGC loss or AMD-associated retinal degeneration. Here, we review recent information on Aβ, p-tau, chronic inflammation, and iron dyshomeostasis as common pathogenic mechanisms linking the three degenerative conditions, and iron chelation as a common therapeutic option for these disorders. Additionally discussed is the role of prion protein, infamous for prion disorders, in Aβ-mediated toxicity and, paradoxically, in neuroprotection.
Collapse
|
15
|
Ashok A, Chaudhary S, Kritikos AE, Kang MH, McDonald D, Rhee DJ, Singh N. TGFβ2-Hepcidin Feed-Forward Loop in the Trabecular Meshwork Implicates Iron in Glaucomatous Pathology. Invest Ophthalmol Vis Sci 2020; 61:24. [PMID: 32182331 PMCID: PMC7401420 DOI: 10.1167/iovs.61.3.24] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Purpose Elevated levels of transforming-growth-factor (TGF)-β2 in the trabecular meshwork (TM) and aqueous humor are associated with primary open-angle glaucoma (POAG). The underlying mechanism includes alteration of extracellular matrix homeostasis through Smad-dependent and independent signaling. Smad4, an essential co-Smad, upregulates hepcidin, the master regulator of iron homeostasis. Here, we explored whether TGF-β2 upregulates hepcidin, implicating iron in the pathogenesis of POAG. Methods Primary human TM cells and human and bovine ex vivo anterior segment organ cultures were exposed to bioactive TGF-β2, hepcidin, heparin (a hepcidin antagonist), or N-acetyl carnosine (an antioxidant), and the change in the expression of hepcidin, ferroportin, ferritin, and TGF-β2 was evaluated by semiquantitative RT-PCR, Western blotting, and immunohistochemistry. Increase in reactive oxygen species (ROS) was quantified with dihydroethidium, an ROS-sensitive dye. Results Primary human TM cells and bovine TM tissue synthesize hepcidin locally, which is upregulated by bioactive TGF-β2. Hepcidin downregulates ferroportin, its downstream target, increasing ferritin and iron-catalyzed ROS. This causes reciprocal upregulation of TGF-β2 at the transcriptional and translational levels. Heparin downregulates hepcidin, and reduces TGF-β2-mediated increase in ferritin and ROS. Notably, both heparin and N-acetyl carnosine reduce TGF-β2-mediated reciprocal upregulation of TGF-β2. Conclusions The above observations suggest that TGF-β2 and hepcidin form a self-sustained feed-forward loop through iron-catalyzed ROS. This loop is partially disrupted by a hepcidin antagonist and an anti-oxidant, implicating iron and ROS in TGF-β2-mediated POAG. We propose that modification of currently available hepcidin antagonists for ocular use may prove beneficial for the therapeutic management of TGF-β2-associated POAG.
Collapse
|
16
|
Picard E, Daruich A, Youale J, Courtois Y, Behar-Cohen F. From Rust to Quantum Biology: The Role of Iron in Retina Physiopathology. Cells 2020; 9:cells9030705. [PMID: 32183063 PMCID: PMC7140613 DOI: 10.3390/cells9030705] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 03/07/2020] [Accepted: 03/09/2020] [Indexed: 12/24/2022] Open
Abstract
Iron is essential for cell survival and function. It is a transition metal, that could change its oxidation state from Fe2+ to Fe3+ involving an electron transfer, the key of vital functions but also organ dysfunctions. The goal of this review is to illustrate the primordial role of iron and local iron homeostasis in retinal physiology and vision, as well as the pathological consequences of iron excess in animal models of retinal degeneration and in human retinal diseases. We summarize evidence of the potential therapeutic effect of iron chelation in retinal diseases and especially the interest of transferrin, a ubiquitous endogenous iron-binding protein, having the ability to treat or delay degenerative retinal diseases.
Collapse
Affiliation(s)
- Emilie Picard
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, USPC, Université Paris Descartes, Team 17, F-75006 Paris, France; (A.D.); (J.Y.); (Y.C.); (F.B.-C.)
- Correspondence: ; Tel.: +331-44-27-81-82
| | - Alejandra Daruich
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, USPC, Université Paris Descartes, Team 17, F-75006 Paris, France; (A.D.); (J.Y.); (Y.C.); (F.B.-C.)
- Ophthalmology Department, Necker-Enfants Malades University Hospital, APHP, 75015 Paris, France
| | - Jenny Youale
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, USPC, Université Paris Descartes, Team 17, F-75006 Paris, France; (A.D.); (J.Y.); (Y.C.); (F.B.-C.)
| | - Yves Courtois
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, USPC, Université Paris Descartes, Team 17, F-75006 Paris, France; (A.D.); (J.Y.); (Y.C.); (F.B.-C.)
| | - Francine Behar-Cohen
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, USPC, Université Paris Descartes, Team 17, F-75006 Paris, France; (A.D.); (J.Y.); (Y.C.); (F.B.-C.)
- Ophtalmopole, Cochin Hospital, AP-HP, Assistance Publique Hôpitaux de Paris, 24 rue du Faubourg Saint-Jacques, 75014 Paris, France
| |
Collapse
|
17
|
Shu W, Baumann BH, Song Y, Liu Y, Wu X, Dunaief JL. Iron Accumulates in Retinal Vascular Endothelial Cells But Has Minimal Retinal Penetration After IP Iron Dextran Injection in Mice. Invest Ophthalmol Vis Sci 2020; 60:4378-4387. [PMID: 31634395 PMCID: PMC6798310 DOI: 10.1167/iovs.19-28250] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Purpose Iron supplementation therapy is used for iron-deficiency anemia but has been associated with macular degeneration in a 43-year-old patient. Iron entry into the neurosensory retina (NSR) can be toxic. It is important to determine conditions under which serum iron might cross the blood retinal barrier (BRB) into the NSR. Herein, an established mouse model of systemic iron overload using high-dose intraperitoneal iron dextran (IP FeDex) was studied. In addition, because the NSR expresses the iron regulatory hormone hepcidin, which could limit iron influx into the NSR, we gave retina-specific hepcidin knockout (RS-HepcKO) mice IP FeDex to test this possibility. Methods Wild-type (WT) and RS-HepcKO mice were given IP FeDex. In vivo retina imaging was performed. Blood and tissues were analyzed for iron levels. Quantitative PCR was used to measure levels of mRNAs encoding iron regulatory and photoreceptor-specific genes. Ferritin and albumin were localized in the retina by immunofluorescence. Results IP FeDex in both WT and RS-HepcKO mice induced high levels of iron in the liver, serum, retinal vascular endothelial cells (rVECs), and RPE, but not the NSR. The BRB remained intact. Retinal degeneration did not occur. Conclusions Following injection of high-dose IP FeDex, iron accumulated in the BRB, but not the NSR. Thus, the BRB can shield the NSR from iron delivered in this manner. This ability is not dependent on NSR hepcidin production.
Collapse
Affiliation(s)
- Wanting Shu
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Ocular Fundus Diseases, Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai, China.,F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Bailey H Baumann
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Ying Song
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Yingrui Liu
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States.,Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, Jilin, China
| | - Xingwei Wu
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Ocular Fundus Diseases, Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai, China
| | - Joshua L Dunaief
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States
| |
Collapse
|
18
|
Ashok A, Chaudhary S, McDonald D, Kritikos A, Bhargava D, Singh N. Local synthesis of hepcidin in the anterior segment of the eye: A novel observation with physiological and pathological implications. Exp Eye Res 2020; 190:107890. [PMID: 31811823 PMCID: PMC6931014 DOI: 10.1016/j.exer.2019.107890] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 10/27/2019] [Accepted: 12/01/2019] [Indexed: 12/22/2022]
Abstract
PURPOSE The avascular cornea, trabecular meshwork (TM), and lens obtain iron, an essential biometal, from the aqueous humor (AH). The mechanism by which this exchange is regulated, however, is unclear. Recently we reported that non-pigmented ciliary epithelial cells express ferroportin (Fpn) (Ashok, 2018b), an iron export protein modulated by hepcidin, the master regulator of iron homeostasis secreted mainly by the liver. Here, we explored whether ciliary epithelial and other cells in the anterior segment synthesize hepcidin, suggesting local regulation of iron exchange at this site. METHODS Human and bovine eyes were dissected to isolate the ciliary body (CB), corneal endothelial (CE), TM, lens epithelial (LE), and outer epithelial cell layer of the iris. Total mRNA and protein lysates were processed to evaluate the synthesis and expression of hepcidin, the iron regulatory peptide hormone, Fpn, the only known iron export protein, ceruloplasmin (Cp), a ferroxidase necessary for iron export, transferrin receptor (TfR), a major iron uptake protein, and ferritin, a major iron storage protein. A combination of techniques including reverse transcription polymerase chain reaction (RT-PCR) of total mRNA, Western blotting of protein lysates, and immunofluorescence of fixed tissue sections were used to accomplish these goals. RESULTS RT-PCR of isolated tissue samples revealed hepcidin-specific mRNA in the CB, TM, CE, and LE of the bovine eye. Western blotting of protein lysates from these tissues showed reactivity for hepcidin, Fpn, ferritin, and TfR. Western blotting and immunohistochemistry of similar tissues isolated from cadaveric human eyes showed expression of hepcidin, Fpn, and Cp in these samples. Notably, Fpn and Cp were expressed on the basolateral membrane of non-pigmented ciliary epithelial cells, facing the AH. CONCLUSIONS Synthesis and expression of hepcidin and Fpn in the ciliary epithelium suggests local regulation of iron transport from choroidal plexus in the ciliary body to the AH across the blood-aqueous barrier. Expression of hepcidin and Fpn in CE, TM, and LE cells indicates additional regulation of iron exchange between the AH and cornea, TM, and lens, suggesting autonomous regulation of iron homeostasis in the anterior segment. Physiological and pathological implications of these observations are discussed.
Collapse
Affiliation(s)
- Ajay Ashok
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Suman Chaudhary
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Dallas McDonald
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Alexander Kritikos
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Disha Bhargava
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Neena Singh
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA.
| |
Collapse
|
19
|
Loss of NAMPT in aging retinal pigment epithelium reduces NAD + availability and promotes cellular senescence. Aging (Albany NY) 2019; 10:1306-1323. [PMID: 29905535 PMCID: PMC6046249 DOI: 10.18632/aging.101469] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 06/04/2018] [Indexed: 12/21/2022]
Abstract
Retinal pigment epithelium (RPE) performs numerous functions critical to retinal health and visual function. RPE senescence is a hallmark of aging and degenerative retinal disease development. Here, we evaluated the temporal expression of key nicotinamide adenine dinucleotide (NAD+)-biosynthetic genes and associated levels of NAD+, a principal regulator of energy metabolism and cellular fate, in mouse RPE. NAD+ levels declined with age and correlated directly with decreased nicotinamide phosphoribosyltransferase (NAMPT) expression, increased expression of senescence markers (p16INK4a, p21Waf/Cip1, ApoJ, CTGF and β-galactosidase) and significant reductions in SIRT1 expression and activity. We simulated in vitro the age-dependent decline in NAD+ and the related increase in RPE senescence in human (ARPE-19) and mouse primary RPE using the NAMPT inhibitor FK866 and demonstrated the positive impact of NAD+-enhancing therapies on RPE cell viability. This, we confirmed in vivo in the RPE of mice injected sub-retinally with FK866 in the presence or absence of nicotinamide mononucleotide. Our data confirm the importance of NAD+ to RPE cell biology normally and in aging and demonstrate the potential utility of therapies targeting NAMPT and NAD+ biosynthesis to prevent or alleviate consequences of RPE senescence in aging and/or degenerative retinal diseases in which RPE dysfunction is a crucial element.
Collapse
|
20
|
Daher R, Lefebvre T, Puy H, Karim Z. Extrahepatic hepcidin production: The intriguing outcomes of recent years. World J Clin Cases 2019; 7:1926-1936. [PMID: 31423425 PMCID: PMC6695539 DOI: 10.12998/wjcc.v7.i15.1926] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 06/18/2019] [Accepted: 06/27/2019] [Indexed: 02/05/2023] Open
Abstract
Hepcidin is the hyposideremic hormone regulating iron metabolism. It is a defensin-like disulfide-bonded peptide with antimicrobial activity. The main site of hepcidin production is the liver where its synthesis is modulated by iron, inflammation and erythropoietic signaling. However, hepcidin locally produced in several peripheral organs seems to be an important actor for the maintenance of iron homeostasis in these organs. This review highlights the presence of peripheral hepcidin and its potential functions. Understanding the role of extrahepatic hepcidin could be of great physiological and therapeutic importance for several specific pathologies.
Collapse
Affiliation(s)
- Raêd Daher
- Université Paris Diderot, Bichat site, Paris 75018, France
- Inflammation Research Center (CRI), INSERM U1149/ERL CNRS 8252, Paris 75018, France
- Laboratory of Excellence, GR-Ex, Paris 75018, France
| | - Thibaud Lefebvre
- Université Paris Diderot, Bichat site, Paris 75018, France
- Inflammation Research Center (CRI), INSERM U1149/ERL CNRS 8252, Paris 75018, France
- Laboratory of Excellence, GR-Ex, Paris 75018, France
| | - Hervé Puy
- Université Paris Diderot, Bichat site, Paris 75018, France
- Inflammation Research Center (CRI), INSERM U1149/ERL CNRS 8252, Paris 75018, France
- Laboratory of Excellence, GR-Ex, Paris 75018, France
| | - Zoubida Karim
- Université Paris Diderot, Bichat site, Paris 75018, France
- Inflammation Research Center (CRI), INSERM U1149/ERL CNRS 8252, Paris 75018, France
- Laboratory of Excellence, GR-Ex, Paris 75018, France
| |
Collapse
|
21
|
ASSESSMENT OF DRUSEN AND OTHER RETINAL DEGENERATIVE CHANGES IN PATIENTS WITH HEREDITARY HEMOCHROMATOSIS. Retina 2018; 38:594-599. [DOI: 10.1097/iae.0000000000001577] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
22
|
Chaudhary K, Promsote W, Ananth S, Veeranan-Karmegam R, Tawfik A, Arjunan P, Martin P, Smith SB, Thangaraju M, Kisselev O, Ganapathy V, Gnana-Prakasam JP. Iron Overload Accelerates the Progression of Diabetic Retinopathy in Association with Increased Retinal Renin Expression. Sci Rep 2018; 8:3025. [PMID: 29445185 PMCID: PMC5813018 DOI: 10.1038/s41598-018-21276-2] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 01/31/2018] [Indexed: 12/31/2022] Open
Abstract
Diabetic retinopathy (DR) is a leading cause of blindness among working-age adults. Increased iron accumulation is associated with several degenerative diseases. However, there are no reports on the status of retinal iron or its implications in the pathogenesis of DR. In the present study, we found that retinas of type-1 and type-2 mouse models of diabetes have increased iron accumulation compared to non-diabetic retinas. We found similar iron accumulation in postmortem retinal samples from human diabetic patients. Further, we induced diabetes in HFE knockout (KO) mice model of genetic iron overload to understand the role of iron in the pathogenesis of DR. We found increased neuronal cell death, vascular alterations and loss of retinal barrier integrity in diabetic HFE KO mice compared to diabetic wildtype mice. Diabetic HFE KO mouse retinas also exhibited increased expression of inflammation and oxidative stress markers. Severity in the pathogenesis of DR in HFE KO mice was accompanied by increase in retinal renin expression mediated by G-protein-coupled succinate receptor GPR91. In light of previous reports implicating retinal renin-angiotensin system in DR pathogenesis, our results reveal a novel relationship between diabetes, iron and renin-angiotensin system, thereby unraveling new therapeutic targets for the treatment of DR.
Collapse
Affiliation(s)
- Kapil Chaudhary
- Department of Medicine, Washington University, St. Louis, Missouri, USA
| | | | - Sudha Ananth
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Rajalakshmi Veeranan-Karmegam
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Amany Tawfik
- Dental College of Georgia, Augusta University, Augusta, Georgia, USA
| | | | - Pamela Martin
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Sylvia B Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Muthusamy Thangaraju
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Oleg Kisselev
- Department of Ophthalmology and Department of Biochemistry & Molecular Biology, Saint Louis University, St. Louis, Missouri, USA
| | - Vadivel Ganapathy
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, USA
| | - Jaya P Gnana-Prakasam
- Department of Ophthalmology and Department of Biochemistry & Molecular Biology, Saint Louis University, St. Louis, Missouri, USA.
| |
Collapse
|
23
|
Vela D. Hepcidin, an emerging and important player in brain iron homeostasis. J Transl Med 2018; 16:25. [PMID: 29415739 PMCID: PMC5803919 DOI: 10.1186/s12967-018-1399-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 01/31/2018] [Indexed: 02/08/2023] Open
Abstract
Hepcidin is emerging as a new important factor in brain iron homeostasis. Studies suggest that there are two sources of hepcidin in the brain; one is local and the other comes from the circulation. Little is known about the molecular mediators of local hepcidin expression, but inflammation and iron-load have been shown to induce hepcidin expression in the brain. The most important source of hepcidin in the brain are glial cells. Role of hepcidin in brain functions has been observed during neuronal iron-load and brain hemorrhage, where secretion of abundant hepcidin is related with the severity of brain damage. This damage can be reversed by blocking systemic and local hepcidin secretion. Studies have yet to unveil its role in other brain conditions, but the rationale exists, since these conditions are characterized by overexpression of the factors that stimulate brain hepcidin expression, such as inflammation, hypoxia and iron-overload.
Collapse
Affiliation(s)
- Driton Vela
- Department of Physiology, Faculty of Medicine, University of Prishtina, Martyr's Boulevard n.n., 10000, Prishtina, Kosova.
| |
Collapse
|
24
|
Lefebvre T, Reihani N, Daher R, de Villemeur TB, Belmatoug N, Rose C, Colin-Aronovicz Y, Puy H, Le Van Kim C, Franco M, Karim Z. Involvement of hepcidin in iron metabolism dysregulation in Gaucher disease. Haematologica 2018; 103:587-596. [PMID: 29305416 PMCID: PMC5865418 DOI: 10.3324/haematol.2017.177816] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 01/03/2018] [Indexed: 12/21/2022] Open
Abstract
Gaucher disease (GD) is an inherited deficiency of glucocerebrosidase leading to accumulation of glucosylceramide in tissues such as the spleen, liver, and bone marrow. The resulting lipid-laden macrophages lead to the appearance of “Gaucher cells”. Anemia associated with an unexplained hyperferritinemia is a frequent finding in GD, but whether this pathogenesis is related to an iron metabolism disorder has remained unclear. To investigate this issue, we explored the iron status of a large cohort of 90 type I GD patients, including 66 patients treated with enzyme replacement therapy. Ten of the patients treated with enzyme replacement were followed up before and during treatment. Serum levels of hepcidin, the iron regulatory peptide, remained within the physiological range, while the transferrin saturation was slightly decreased in children. Inflammation-independent hyperferritinemia was found in 65% of the patients, and Perl’s staining of the spleen and marrow smear revealed iron accumulation in Gaucher cells. Treated patients exhibited reduced hyperferritinemia, increased transferrin saturation and transiently increased systemic hepcidin. In addition, the hepcidin and ferritin correlation was markedly improved, and, in most patients, the hemoglobin level was normalized. To further explore eventual iron sequestration in macrophages, we produce a Gaucher cells model by treating the J774 macrophage cell line with a glucocerebrosidase inhibitor and showed induced local hepcidin and membrane retrieval of the iron exporter, ferroportin. These data reveal the involvement of Gaucher cells in abnormal iron sequestration, which may explain the mechanism of hyperferritinemia in GD patients. Local hepcidin-ferroportin interaction was involved in this pathogenesis.
Collapse
Affiliation(s)
- Thibaud Lefebvre
- University Sorbonne Paris Cité, Paris Diderot University, Inserm U1149 / ERL 8252, Inflammation Research Center (CRI), Laboratory of Excellence GR-Ex, Paris, France.,AP-HP, Centre Français des Porphyries, Hôpital Louis Mourier, Colombes, France
| | - Niloofar Reihani
- University Sorbonne Paris Cité, Paris Diderot University, Inserm, INTS, "Biologie Intégrée du Globule Rouge" Department, Laboratory of Excellence GR-Ex, Paris, France
| | - Raed Daher
- University Sorbonne Paris Cité, Paris Diderot University, Inserm U1149 / ERL 8252, Inflammation Research Center (CRI), Laboratory of Excellence GR-Ex, Paris, France
| | - Thierry Billette de Villemeur
- Sorbonne Universités, UPMC, GRC ConCer-LD and AP-HP, Hôpital Trousseau, Service de Neuropédiatrie, Centre de Référence des Maladies Lysosomales, Paris, France
| | - Nadia Belmatoug
- Hôpitaux Universitaires Paris Nord Val de Seine, Assistance Publique-Hôpitaux de Paris, Hôpital Beaujon, Service de Médecine Interne, Centre de Référence des Maladies Lysosomales, Clichy, France
| | - Christian Rose
- Université Catholique de Lille, Hôpital Saint Vincent de Paul, Service d'Hématologie, France
| | - Yves Colin-Aronovicz
- University Sorbonne Paris Cité, Paris Diderot University, Inserm, INTS, "Biologie Intégrée du Globule Rouge" Department, Laboratory of Excellence GR-Ex, Paris, France
| | - Hervé Puy
- University Sorbonne Paris Cité, Paris Diderot University, Inserm U1149 / ERL 8252, Inflammation Research Center (CRI), Laboratory of Excellence GR-Ex, Paris, France.,AP-HP, Centre Français des Porphyries, Hôpital Louis Mourier, Colombes, France
| | - Caroline Le Van Kim
- University Sorbonne Paris Cité, Paris Diderot University, Inserm, INTS, "Biologie Intégrée du Globule Rouge" Department, Laboratory of Excellence GR-Ex, Paris, France
| | - Mélanie Franco
- University Sorbonne Paris Cité, Paris Diderot University, Inserm, INTS, "Biologie Intégrée du Globule Rouge" Department, Laboratory of Excellence GR-Ex, Paris, France
| | - Zoubida Karim
- University Sorbonne Paris Cité, Paris Diderot University, Inserm U1149 / ERL 8252, Inflammation Research Center (CRI), Laboratory of Excellence GR-Ex, Paris, France
| |
Collapse
|
25
|
Asthana A, Baksi S, Ashok A, Karmakar S, Mammadova N, Kokemuller R, Greenlee MH, Kong Q, Singh N. Prion protein facilitates retinal iron uptake and is cleaved at the β-site: Implications for retinal iron homeostasis in prion disorders. Sci Rep 2017; 7:9600. [PMID: 28851903 PMCID: PMC5575325 DOI: 10.1038/s41598-017-08821-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 07/17/2017] [Indexed: 12/22/2022] Open
Abstract
Prion disease-associated retinal degeneration is attributed to PrP-scrapie (PrPSc), a misfolded isoform of prion protein (PrPC) that accumulates in the neuroretina. However, a lack of temporal and spatial correlation between PrPSc and cytotoxicity suggests the contribution of host factors. We report retinal iron dyshomeostasis as one such factor. PrPC is expressed on the basolateral membrane of retinal-pigment-epithelial (RPE) cells, where it mediates uptake of iron by the neuroretina. Accordingly, the neuroretina of PrP-knock-out mice is iron-deficient. In RPE19 cells, silencing of PrPC decreases ferritin while over-expression upregulates ferritin and divalent-metal-transporter-1 (DMT-1), indicating PrPC-mediated iron uptake through DMT-1. Polarization of RPE19 cells results in upregulation of ferritin by ~10-fold and β-cleavage of PrPC, the latter likely to block further uptake of iron due to cleavage of the ferrireductase domain. A similar β-cleavage of PrPC is observed in mouse retinal lysates. Scrapie infection causes PrPSc accumulation and microglial activation, and surprisingly, upregulation of transferrin despite increased levels of ferritin. Notably, detergent-insoluble ferritin accumulates in RPE cells and correlates temporally with microglial activation, not PrPSc accumulation, suggesting that impaired uptake of iron by PrPSc combined with inflammation results in retinal iron-dyshomeostasis, a potentially toxic host response contributing to prion disease-associated pathology.
Collapse
Affiliation(s)
- Abhishek Asthana
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Shounak Baksi
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Ajay Ashok
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Shilpita Karmakar
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Najiba Mammadova
- Department of Biomedical Sciences, Iowa State University College of Veterinary Medicine, Ames, Iowa, 50010, USA
| | - Robyn Kokemuller
- Department of Biomedical Sciences, Iowa State University College of Veterinary Medicine, Ames, Iowa, 50010, USA
| | - Mary Heather Greenlee
- Department of Biomedical Sciences, Iowa State University College of Veterinary Medicine, Ames, Iowa, 50010, USA
| | - Qingzhong Kong
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Neena Singh
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, 44106, USA.
| |
Collapse
|
26
|
You LH, Yan CZ, Zheng BJ, Ci YZ, Chang SY, Yu P, Gao GF, Li HY, Dong TY, Chang YZ. Astrocyte hepcidin is a key factor in LPS-induced neuronal apoptosis. Cell Death Dis 2017; 8:e2676. [PMID: 28300826 PMCID: PMC5386583 DOI: 10.1038/cddis.2017.93] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 01/28/2017] [Accepted: 02/10/2017] [Indexed: 12/20/2022]
Abstract
Inflammatory responses involving microglia and astrocytes contribute to the pathogenesis of neurodegenerative diseases (NDs). In addition, inflammation is tightly linked to iron metabolism dysregulation. However, it is not clear whether the brain inflammation-induced iron metabolism dysregulation contributes to the NDs pathogenesis. Herein, we demonstrate that the expression of the systemic iron regulatory hormone, hepcidin, is induced by lipopolysaccharide (LPS) through the IL-6/STAT3 pathway in the cortex and hippocampus. In this paradigm, activated glial cells are the source of IL-6, which was essential in the iron overload-activated apoptosis of neurons. Disrupting astrocyte hepcidin expression prevented the apoptosis of neurons, which were able to maintain levels of FPN1 adequate to avoid iron accumulation. Together, our data are consistent with a model whereby inflammation initiates an intercellular signaling cascade in which activated microglia, through IL-6 signaling, stimulate astrocytes to release hepcidin which, in turn, signals to neurons, via hepcidin, to prevent their iron release. Such a pathway is relevant to NDs in that it links inflammation, microglia and astrocytes to neuronal damage.
Collapse
Affiliation(s)
- Lin-Hao You
- Laboratory of Molecular Iron Metabolism, The Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Cai-Zhen Yan
- Laboratory of Molecular Iron Metabolism, The Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, China.,School of Basic Medical Sciences, Hebei Medical University, Shijiazhuang, China
| | - Bing-Jie Zheng
- Laboratory of Molecular Iron Metabolism, The Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Yun-Zhe Ci
- Laboratory of Molecular Iron Metabolism, The Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Shi-Yang Chang
- Laboratory of Molecular Iron Metabolism, The Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Peng Yu
- Laboratory of Molecular Iron Metabolism, The Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Guo-Fen Gao
- Laboratory of Molecular Iron Metabolism, The Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Hai-Yan Li
- Laboratory of Molecular Iron Metabolism, The Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Tian-Yu Dong
- Laboratory of Molecular Iron Metabolism, The Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Yan-Zhong Chang
- Laboratory of Molecular Iron Metabolism, The Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Science, Hebei Normal University, Shijiazhuang, China
| |
Collapse
|
27
|
Picard E, Le Rouzic Q, Oudar A, Berdugo M, El Sanharawi M, Andrieu-Soler C, Naud MC, Jonet L, Latour C, Klein C, Galiacy S, Malecaze F, Coppin H, Roth MP, Jeanny JC, Courtois Y, Behar-Cohen F. Targeting iron-mediated retinal degeneration by local delivery of transferrin. Free Radic Biol Med 2015; 89:1105-21. [PMID: 26454080 DOI: 10.1016/j.freeradbiomed.2015.08.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2015] [Revised: 08/07/2015] [Accepted: 08/10/2015] [Indexed: 12/11/2022]
Abstract
Iron is essential for retinal function but contributes to oxidative stress-mediated degeneration. Iron retinal homeostasis is highly regulated and transferrin (Tf), a potent iron chelator, is endogenously secreted by retinal cells. In this study, therapeutic potential of a local Tf delivery was evaluated in animal models of retinal degeneration. After intravitreal injection, Tf spread rapidly within the retina and accumulated in photoreceptors and retinal pigment epithelium, before reaching the blood circulation. Tf injected in the vitreous prior and, to a lesser extent, after light-induced retinal degeneration, efficiently protected the retina histology and function. We found an association between Tf treatment and the modulation of iron homeostasis resulting in a decrease of iron content and oxidative stress marker. The immunomodulation function of Tf could be seen through a reduction in macrophage/microglial activation as well as modulated inflammation responses. In a mouse model of hemochromatosis, Tf had the capacity to clear abnormal iron accumulation from retinas. And in the slow P23H rat model of retinal degeneration, a sustained release of Tf in the vitreous via non-viral gene therapy efficently slowed-down the photoreceptors death and preserved their function. These results clearly demonstrate the synergistic neuroprotective roles of Tf against retinal degeneration and allow identify Tf as an innovative and not toxic therapy for retinal diseases associated with oxidative stress.
Collapse
Affiliation(s)
- Emilie Picard
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France.
| | - Quentin Le Rouzic
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France
| | - Antonin Oudar
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France
| | - Marianne Berdugo
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France
| | - Mohamed El Sanharawi
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France
| | - Charlotte Andrieu-Soler
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France
| | - Marie-Christine Naud
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France
| | - Laurent Jonet
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France
| | - Chloé Latour
- INSERM, U1043, Toulouse, France; CNRS, U5282, Toulouse, France; Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France
| | - Christophe Klein
- INSERM, U1138, CICC, Université René Descartes Sorbonne Paris Cité, Université Pierre et Marie Curie Paris, Centre de Recherche des Cordeliers, Paris, France
| | - Stéphane Galiacy
- INSERM U563, Centre de Physiopathologie de Toulouse Purpan, Toulouse, France; Department of Ophthalmology, Purpan Hospital, Toulouse, France
| | - François Malecaze
- INSERM U563, Centre de Physiopathologie de Toulouse Purpan, Toulouse, France; Department of Ophthalmology, Purpan Hospital, Toulouse, France
| | - Hélène Coppin
- INSERM, U1043, Toulouse, France; CNRS, U5282, Toulouse, France; Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France
| | - Marie-Paule Roth
- INSERM, U1043, Toulouse, France; CNRS, U5282, Toulouse, France; Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France
| | - Jean-Claude Jeanny
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France
| | - Yves Courtois
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France
| | - Francine Behar-Cohen
- INSERM, UMRS 1138, team Behar-Cohen, From physiopathology of ocular diseases to clinical development, Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Université René Descartes, Centre de Recherche des Cordeliers UMRS 1138, Paris, France; Jules Gonin Ophthalmic Hospital, Lausanne, Switzerland
| |
Collapse
|
28
|
Theurl M, Song D, Clark E, Sterling J, Grieco S, Altamura S, Galy B, Hentze M, Muckenthaler MU, Dunaief JL. Mice with hepcidin-resistant ferroportin accumulate iron in the retina. FASEB J 2015; 30:813-23. [PMID: 26506980 DOI: 10.1096/fj.15-276758] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 10/13/2015] [Indexed: 12/13/2022]
Abstract
Because ferroportin (Fpn) is the only known mammalian cellular iron exporter, understanding its localization and regulation within the retina would shed light on the direction of retinal iron flux. The hormone hepcidin may regulate retinal Fpn, as it triggers Fpn degradation in the gut. Immunofluorescence was used to label Fpn in retinas of mice with 4 different genotypes (wild type; Fpn C326S, a hepcidin-resistant Fpn; hepcidin knockout; and ceruloplasmin/hephaestin double knockout). No significant difference in Fpn levels was observed in these retinas. Fpn localized to the abluminal side of the outer plexiform vascular endothelial cells, Müller glia cells, and the basolateral side of the retinal pigment epithelium. Adeno-associated virus (AAV)-hepcidin was injected into the eyes of hepcidin knockout mice, while AAV-lacZ was injected into the contralateral eyes as a control. AAV-hepcidin injected eyes had increased ferritin immunolabeling in retinal vascular endothelial cells. Fpn C326S mice had systemic iron overload compared to wild type and had the fastest retinal iron accumulation of any hereditary model studied to date. The results suggest that physiologic hepcidin levels are insufficient to alter Fpn levels within the retinal pigment epithelium and Müller cells, but may limit iron transport into the retina from vascular endothelial cells.
Collapse
Affiliation(s)
- Milan Theurl
- *F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Ophthalmology and Optometry, Innsbruck Medical University, Innsbruck, Austria; Department of Psychiatry and Behavioral Sciences, and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA; Department of Pediatric Hematology, Oncology, and Immunology, University of Heidelberg, Heidelberg, Germany; Molecular Medicine Partnership Unit, Heidelberg, Germany; and European Molecular Biology Laboratory, Heidelberg, Germany
| | - Delu Song
- *F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Ophthalmology and Optometry, Innsbruck Medical University, Innsbruck, Austria; Department of Psychiatry and Behavioral Sciences, and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA; Department of Pediatric Hematology, Oncology, and Immunology, University of Heidelberg, Heidelberg, Germany; Molecular Medicine Partnership Unit, Heidelberg, Germany; and European Molecular Biology Laboratory, Heidelberg, Germany
| | - Esther Clark
- *F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Ophthalmology and Optometry, Innsbruck Medical University, Innsbruck, Austria; Department of Psychiatry and Behavioral Sciences, and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA; Department of Pediatric Hematology, Oncology, and Immunology, University of Heidelberg, Heidelberg, Germany; Molecular Medicine Partnership Unit, Heidelberg, Germany; and European Molecular Biology Laboratory, Heidelberg, Germany
| | - Jacob Sterling
- *F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Ophthalmology and Optometry, Innsbruck Medical University, Innsbruck, Austria; Department of Psychiatry and Behavioral Sciences, and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA; Department of Pediatric Hematology, Oncology, and Immunology, University of Heidelberg, Heidelberg, Germany; Molecular Medicine Partnership Unit, Heidelberg, Germany; and European Molecular Biology Laboratory, Heidelberg, Germany
| | - Steve Grieco
- *F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Ophthalmology and Optometry, Innsbruck Medical University, Innsbruck, Austria; Department of Psychiatry and Behavioral Sciences, and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA; Department of Pediatric Hematology, Oncology, and Immunology, University of Heidelberg, Heidelberg, Germany; Molecular Medicine Partnership Unit, Heidelberg, Germany; and European Molecular Biology Laboratory, Heidelberg, Germany
| | - Sandro Altamura
- *F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Ophthalmology and Optometry, Innsbruck Medical University, Innsbruck, Austria; Department of Psychiatry and Behavioral Sciences, and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA; Department of Pediatric Hematology, Oncology, and Immunology, University of Heidelberg, Heidelberg, Germany; Molecular Medicine Partnership Unit, Heidelberg, Germany; and European Molecular Biology Laboratory, Heidelberg, Germany
| | - Bruno Galy
- *F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Ophthalmology and Optometry, Innsbruck Medical University, Innsbruck, Austria; Department of Psychiatry and Behavioral Sciences, and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA; Department of Pediatric Hematology, Oncology, and Immunology, University of Heidelberg, Heidelberg, Germany; Molecular Medicine Partnership Unit, Heidelberg, Germany; and European Molecular Biology Laboratory, Heidelberg, Germany
| | - Matthias Hentze
- *F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Ophthalmology and Optometry, Innsbruck Medical University, Innsbruck, Austria; Department of Psychiatry and Behavioral Sciences, and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA; Department of Pediatric Hematology, Oncology, and Immunology, University of Heidelberg, Heidelberg, Germany; Molecular Medicine Partnership Unit, Heidelberg, Germany; and European Molecular Biology Laboratory, Heidelberg, Germany
| | - Martina U Muckenthaler
- *F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Ophthalmology and Optometry, Innsbruck Medical University, Innsbruck, Austria; Department of Psychiatry and Behavioral Sciences, and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA; Department of Pediatric Hematology, Oncology, and Immunology, University of Heidelberg, Heidelberg, Germany; Molecular Medicine Partnership Unit, Heidelberg, Germany; and European Molecular Biology Laboratory, Heidelberg, Germany
| | - Joshua L Dunaief
- *F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Ophthalmology and Optometry, Innsbruck Medical University, Innsbruck, Austria; Department of Psychiatry and Behavioral Sciences, and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA; Department of Pediatric Hematology, Oncology, and Immunology, University of Heidelberg, Heidelberg, Germany; Molecular Medicine Partnership Unit, Heidelberg, Germany; and European Molecular Biology Laboratory, Heidelberg, Germany
| |
Collapse
|
29
|
Bhoiwala DL, Song Y, Cwanger A, Clark E, Zhao LL, Wang C, Li Y, Song D, Dunaief JL. CD1 Mouse Retina Is Shielded From Iron Overload Caused by a High Iron Diet. Invest Ophthalmol Vis Sci 2015; 56:5344-52. [PMID: 26275132 DOI: 10.1167/iovs.15-17026] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
PURPOSE High RPE iron levels have been associated with age-related macular degeneration. Mutation of the ferroxidase ceruloplasmin leads to RPE iron accumulation and degeneration in patients with aceruloplasminemia; mice lacking ceruloplasmin and its homolog hephaestin have a similar RPE degeneration. To determine whether a high iron diet (HID) could cause RPE iron accumulation, possibly contributing to RPE oxidative stress in AMD, we tested the effect of dietary iron on mouse RPE iron. METHODS Male CD1 strain mice were fed either a standard iron diet (SID) or the same diet with extra iron added (HID) for either 3 months or 10 months. Mice were analyzed with immunofluorescence and Perls' histochemical iron stain to assess iron levels. Levels of ferritin, transferrin receptor, and oxidative stress gene mRNAs were measured by quantitative PCR (qPCR) in neural retina (NR) and isolated RPE. Morphology was assessed in plastic sections. RESULTS Ferritin immunoreactivity demonstrated a modest increase in the RPE in 10-month HID mice. Analysis by qPCR showed changes in mRNA levels of iron-responsive genes, indicating moderately increased iron in the RPE of 10-month HID mice. However, even by age 18 months, there was no Perls' signal in the retina or RPE and no retinal degeneration. CONCLUSIONS These findings indicate that iron absorbed from the diet can modestly increase the level of iron deposition in the wild-type mouse RPE without causing RPE or retinal degeneration. This suggests regulation of retinal iron uptake at the blood-retinal barriers.
Collapse
Affiliation(s)
- Devang L Bhoiwala
- F. M. Kirby Center for Molecular Ophthalmology Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States 2Albany Medical College, Albany, New York, United States
| | - Ying Song
- F. M. Kirby Center for Molecular Ophthalmology Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Alyssa Cwanger
- F. M. Kirby Center for Molecular Ophthalmology Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Esther Clark
- F. M. Kirby Center for Molecular Ophthalmology Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Liang-liang Zhao
- F. M. Kirby Center for Molecular Ophthalmology Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States 3Department of Ophthalmology, The Second Hospital of Jilin University, Jilin, China
| | - Chenguang Wang
- F. M. Kirby Center for Molecular Ophthalmology Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States 3Department of Ophthalmology, The Second Hospital of Jilin University, Jilin, China
| | - Yafeng Li
- F. M. Kirby Center for Molecular Ophthalmology Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Delu Song
- F. M. Kirby Center for Molecular Ophthalmology Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Joshua L Dunaief
- F. M. Kirby Center for Molecular Ophthalmology Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| |
Collapse
|
30
|
Houamel D, Ducrot N, Lefebvre T, Daher R, Moulouel B, Sari MA, Letteron P, Lyoumi S, Millot S, Tourret J, Bouvet O, Vaulont S, Vandewalle A, Denamur E, Puy H, Beaumont C, Gouya L, Karim Z. Hepcidin as a Major Component of Renal Antibacterial Defenses against Uropathogenic Escherichia coli. J Am Soc Nephrol 2015; 27:835-46. [PMID: 26293821 DOI: 10.1681/asn.2014101035] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 06/11/2015] [Indexed: 12/20/2022] Open
Abstract
The iron-regulatory peptide hepcidin exhibits antimicrobial activity. Having previously shown hepcidin expression in the kidney, we addressed its role in urinary tract infection (UTI), which remains largely unknown. Experimental UTI was induced in wild-type (WT) and hepcidin-knockout (Hepc-/-) mice using the uropathogenic Escherichia coli CFT073 strain. Compared with infected WT mice, infected Hepc-/- mice showed a dramatic increase in renal bacterial load. Moreover, bacterial invasion was significantly dampened by the pretreatment of WT mice with hepcidin. Infected Hepc-/- mice exhibited decreased iron accumulation in the renal medulla and significant attenuation of the renal inflammatory response. Notably, we demonstrated in vitro bacteriostatic activity of hepcidin against CFT073. Furthermore, CFT073 repressed renal hepcidin, both in vivo and in cultured renal cells, and reduced phosphorylation of SMAD kinase in vivo, suggesting a bacterial strategy to escape the antimicrobial activities of hepcidin. In conclusion, we provide new mechanisms by which hepcidin contributes to renal host defense and suggest that targeting hepcidin offers a strategy to prevent bacterial invasion.
Collapse
Affiliation(s)
- Dounia Houamel
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Nicolas Ducrot
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Thibaud Lefebvre
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France; AP-HP, French Center for Porphyrias, Louis Mourier Hospital, Colombes, France
| | - Raed Daher
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Boualem Moulouel
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Marie-Agnes Sari
- The National Centre for Scientific Research (CNRS), UMR 8601, Descartes University, Paris, France
| | - Philippe Letteron
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France
| | - Said Lyoumi
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Sarah Millot
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Jerome Tourret
- Paris Diderot University, Sorbonne Paris Cité, Paris, France; INSERM U1137, Infection Antimicrobials Modelling Evolution (IAME) Laboratory, Paris, France; and
| | - Odile Bouvet
- Paris Diderot University, Sorbonne Paris Cité, Paris, France; INSERM U1137, Infection Antimicrobials Modelling Evolution (IAME) Laboratory, Paris, France; and
| | - Sophie Vaulont
- Laboratory of Excellence, GR-Ex, Paris, France; INSERM U1016, Cochin Institute, Descartes University, Paris, France
| | - Alain Vandewalle
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France
| | - Erick Denamur
- Paris Diderot University, Sorbonne Paris Cité, Paris, France; INSERM U1137, Infection Antimicrobials Modelling Evolution (IAME) Laboratory, Paris, France; and
| | - Hervé Puy
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France; AP-HP, French Center for Porphyrias, Louis Mourier Hospital, Colombes, France
| | - Carole Beaumont
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Laurent Gouya
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France; AP-HP, French Center for Porphyrias, Louis Mourier Hospital, Colombes, France
| | - Zoubida Karim
- National Institute of Health and Medical Research (INSERM) U1149, Research Centre on inflammation, Paris, France; Paris Diderot University, Sorbonne Paris Cité, Paris, France; Laboratory of Excellence, GR-Ex, Paris, France;
| |
Collapse
|
31
|
Anaemia, iron deficiency and susceptibility to infections. J Infect 2014; 69 Suppl 1:S23-7. [DOI: 10.1016/j.jinf.2014.08.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/20/2014] [Indexed: 12/11/2022]
|
32
|
Association of the TLR4 signaling pathway in the retina of streptozotocin-induced diabetic rats. Graefes Arch Clin Exp Ophthalmol 2014; 253:389-98. [PMID: 25359392 DOI: 10.1007/s00417-014-2832-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 08/21/2014] [Accepted: 10/06/2014] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Diabetic retinopathy is severe damage to the retina caused by complications of diabetes, and is the prevailing cause of blindness. Accumulating evidence from both animal models and humans suggests that the inflammatory process plays a key role in the development of diabetic retinopathy and is facilitated by innate immune response. The aim of this study was to examine whether the TLR4 signaling pathway was involved in the streptozotocin-induced diabetic rat retina. METHODS Diabetes was induced by a single intraperitoneal injection of streptozotocin, and rat diabetic retinopathy was examined at 4 weeks of diabetes duration. Then the accumulated leukocytes were counted in vivo by acridine orange leukocyte fluorography, and the retinal vascular permeability was measured by the Evans blue assay. The expressions of TLR4 and its downstream signaling molecules were measured by RT-PCR or Western blot respectively. To evaluate the effect of blocking TLR4 on diabetic retinopathy, TAK-242, a selective TLR4 antagonist, was administered by intraperitoneal injection. RESULTS Our results showed that the retina of diabetic rats demonstrated accumulated leukocytes and retinal vascular permeability. The mRNA and protein expressions of TLR4 were upregulated in streptozotocin-treated diabetic rat retina. Furthermore, the protein levels of TLR4 downstream signaling molecules were significantly increased in streptozotocin-treated animals. In addition, the protein levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and interferon (IFN)-β, three downstream proinflammatory cytokines of TLR4 signal transduction pathway, were also markedly increased in diabetic rats. Administration of TAK-242 attenuated leukocytes accumulated and retinal vascular permeability, and decreased TLR4 downstream signaling molecules and proinflammatory cytokines in streptozotocin-induced animals. CONCLUSIONS Together, these data have demonstrated that TLR4 has a critical role in streptozotocin-induced diabetic retinopathy at the level of inflammatory cytokine induction, in both the MyD88-dependent and MyD88-independent pathways. TLR4 may become a new potential pharmacological target for treating diabetic retinopathy.
Collapse
|
33
|
Zhao L, Li Y, Song D, Song Y, Theurl M, Wang C, Cwanger A, Su G, Dunaief JL. A high serum iron level causes mouse retinal iron accumulation despite an intact blood-retinal barrier. THE AMERICAN JOURNAL OF PATHOLOGY 2014; 184:2862-7. [PMID: 25174877 DOI: 10.1016/j.ajpath.2014.07.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 06/23/2014] [Accepted: 07/17/2014] [Indexed: 12/31/2022]
Abstract
The retina can be shielded by the blood-retinal barrier. Because photoreceptors are damaged by excess iron, it is important to understand whether the blood-retinal barrier protects against high serum iron levels. Bone morphogenic protein 6 (Bmp6) knockout mice have serum iron overload. Herein, we tested whether the previously documented retinal iron accumulation in Bmp6 knockout mice might result from the high serum iron levels or, alternatively, low levels of retinal hepcidin, an iron regulatory hormone whose transcription can be up-regulated by Bmp6. Furthermore, to determine whether increases in serum iron can elevate retinal iron levels, we i.v. injected iron into wild-type mice. Retinas were analyzed by real-time quantitative PCR and immunofluorescence to assess the levels of iron-regulated genes/proteins and oxidative stress. Retinal hepcidin mRNA levels in Bmp6 knockout retinas were the same as, or greater than, those in age-matched wild-type retinas, indicating that Bmp6 knockout does not cause retinal hepcidin deficiency. Changes in mRNA levels of L ferritin and transferrin receptor indicated increased retinal iron levels in i.v. iron-injected wild-type mice. Oxidative stress markers were elevated in photoreceptors of mice receiving i.v. iron. These findings suggest that elevated serum iron levels can overwhelm local retinal iron regulatory mechanisms.
Collapse
Affiliation(s)
- Liangliang Zhao
- Department of Ophthalmology, The Second Hospital of Jilin University, Jilin, China; F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Yafeng Li
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Delu Song
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Ying Song
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Milan Theurl
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Chenguang Wang
- Department of Ophthalmology, The Second Hospital of Jilin University, Jilin, China; F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Alyssa Cwanger
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Guanfang Su
- Department of Ophthalmology, The Second Hospital of Jilin University, Jilin, China
| | - Joshua L Dunaief
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania.
| |
Collapse
|
34
|
Song D, Zhao L, Li Y, Hadziahmetovic M, Song Y, Connelly J, Spino M, Dunaief JL. The oral iron chelator deferiprone protects against systemic iron overload-induced retinal degeneration in hepcidin knockout mice. Invest Ophthalmol Vis Sci 2014; 55:4525-32. [PMID: 24970260 DOI: 10.1167/iovs.14-14568] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
PURPOSE To investigate the retinal-protective effects of the oral iron chelator deferiprone (DFP) in mice lacking the iron regulatory hormone hepcidin (Hepc). These Hepc knockout (KO) mice have age-dependent systemic and retinal iron accumulation leading to retinal degeneration. METHODS Hepc KO mice were given DFP in drinking water from age 6 to 18 months. They were then compared to Hepc KO mice not receiving DFP by fundus imaging, electroretinography (ERG), histology, immunofluorescence, and quantitative PCR to investigate the protective effect of DFP against retinal and retinal pigment epithelial (RPE) degeneration. RESULTS In Hepc KO mice, DFP diminished RPE depigmentation and autofluorescence on fundus imaging. Autofluorescence in the RPE layer in cryosections was significantly diminished by DFP, consistent with the fundus images. Immunolabeling with L-ferritin and transferrin receptor antibodies showed a decreased signal for L-ferritin in the inner retina and RPE cells and an increased signal for transferrin receptor in the inner retina, indicating diminished retinal iron levels with DFP treatment. Plastic sections showed that photoreceptor and RPE cells were well preserved in Hepc KO mice treated with DFP. Consistent with photoreceptor protection, the mRNA level of rhodopsin was significantly higher in retinas treated with DFP. The mRNA levels of oxidative stress-related genes heme oxygenase-1 and catalase were significantly lower in DFP-treated Hepc KO retinas. Finally, ERG rod a- and b- and cone b-wave amplitudes were significantly higher in DFP-treated mice. CONCLUSIONS Long-term treatment with the oral iron chelator DFP diminished retinal and RPE iron levels and oxidative stress, providing significant protection against retinal degeneration caused by chronic systemic iron overload in Hepc KO mice. This indicates that iron chelation could be a long-term preventive treatment for retinal disease involving iron overload and oxidative stress.
Collapse
Affiliation(s)
- Delu Song
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Liangliang Zhao
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania Department of Ophthalmology, Second Hospital of Jilin University, Changchun, China
| | - Yafeng Li
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Majda Hadziahmetovic
- Department of Ophthalmology, Drexel University School of Medicine, Philadelphia, Pennsylvania
| | - Ying Song
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | | | - Michael Spino
- ApoPharma, Inc., Toronto, Canada Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada
| | - Joshua L Dunaief
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| |
Collapse
|
35
|
Chen S, Zhou S, Zang K, Kong F, Liang D, Yan H. CD73 expression in RPE cells is associated with the suppression of conventional CD4 cell proliferation. Exp Eye Res 2014; 127:26-36. [PMID: 24880143 DOI: 10.1016/j.exer.2014.05.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 05/04/2014] [Accepted: 05/07/2014] [Indexed: 01/01/2023]
Abstract
CD73 is intensively involved in the regulation of immune responses through the conversion of pro-inflammatory ATP to immunosuppressive adenosine. Herein, we clarified whether cells in the retina express CD73 and participate in the regulation of inflammatory eye diseases such as experimental autoimmune uveitis (EAU). First, immunofluorescence staining was performed to compare the distribution of CD73(+) cells in the retinas of EAU-induced and normal B10RIII mice. The results revealed that a layer of cells in the normal retina that was consistent with the location of retinal pigment epithelial (RPE) cells strongly expressing CD73, and the expression was markedly reduced in the presence of EAU. Thereafter, EAU was also induced in C57BL/6 mice by active immunization or adoptive transfer. CD73 expression in isolated RPE cells was assessed by real-time RT-PCR and western blotting, and the catalytic abilities of the cells to convert AMP to adenosine were determined using HPLC analyses. Compared to the normal control, significantly decreased CD73 expression and AMP catalytic ability were found in the RPE cells isolated from inflamed eyes. CD73 expression and activity were also studied in cultured RPE cells treated with different stimuli, such as Toll-like receptor ligands and cytokines. Highly varied functional CD73 expression was observed in RPE cells through cytokines or Toll-like receptor agonist treatments. Finally, whether RPE cells could regulate the immune response, particularly the proliferation of CD4 cells, through surface-expressed CD73 was determined using a two-chamber assay. The robust inhibition of conventional T-cell proliferation was uniquely observed when CD73(+) RPE cells in the upper chamber were in the presence of AMP. To further confirm the function of CD73 in RPE cells, Cd73(-/-) RPE cells were isolated, and CD73-rescued control cells were constructed. CD73(+)Cd73(-/-) RPE, not Cd73(-/-) RPE, significantly suppressed interacted CD4 cells proliferation and cytokine production. Taken together, these data suggest that naive RPE cells suppressed the immune response through their high expression of CD73. The expression of CD73 in RPE cells could be regulated through many factors, and down-regulated CD73 expression attenuated the suppressive effect of RPE on the proliferation of conventional CD4 cells.
Collapse
Affiliation(s)
- Song Chen
- General Hospital of Tianjin Medical University, Department of Ophthalmology, Tianjin 300052, China
| | - Shumin Zhou
- The 2nd Hospital of Tianjin Medical University, Clinical Laboratory, Tianjin 300211, China
| | - Kai Zang
- The Wilmer Eye Institute at Johns Hopkins, Baltimore, MD 21287, USA
| | - Fanqiang Kong
- General Hospital of Tianjin Medical University, Department of Ophthalmology, Tianjin 300052, China
| | - Dongchun Liang
- Doheny Eye Institute, University of Southern California, CA 90032, USA
| | - Hua Yan
- General Hospital of Tianjin Medical University, Department of Ophthalmology, Tianjin 300052, China.
| |
Collapse
|
36
|
Tawfik A, Gnana-Prakasam JP, Smith SB, Ganapathy V. Deletion of hemojuvelin, an iron-regulatory protein, in mice results in abnormal angiogenesis and vasculogenesis in retina along with reactive gliosis. Invest Ophthalmol Vis Sci 2014; 55:3616-25. [PMID: 24812553 DOI: 10.1167/iovs.13-13677] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
PURPOSE Loss-of-function mutations in hemojuvelin (HJV) cause juvenile hemochromatosis, an iron-overload disease. Deletion of Hjv in mice results in excessive iron accumulation and morphologic changes in the retina. Here, we studied the retinal vasculature in Hjv(-/-) mice. METHODS Age-matched wild-type and Hjv(-/-) mice were used for fluorescein angiography and preparation of retinal cryosections, flat-mounts, and trypsin-digested blood vessels. Retinal angiogenesis was monitored by immunofluorescent detection of isolectin-B4, endoglin, and VEGF. Retinal vasculogenesis was monitored by immunofluorescent detection of collagen IV. Reactive gliosis was assessed based on the expression of glial fibrillary acidic protein and vimentin and CD11b/c as markers for Müller cells and microglia. RESULTS Between 18 and 24 months of age, retinas of Hjv(-/-) mice displayed marked disruptions in angiogenesis and vasculogenesis. Blood vessels in Hjv(-/-) mice were tortuous and dilated, with a decrease in the tight-junction protein occludin. There was also evidence of neovascularization in Hjv(-/-) mice with blood vessels appearing in the vitreous, which were leaky. There was reactive gliosis in these mice involving both Müller cells and microglia. Such changes were not detected at 2 weeks of age. Even at the age of 4 months, retinas of Hjv(-/-) mice were almost normal with changes just beginning to appear. Thus, the vascular changes in Hjv(-/-) mouse retinas represent an age-dependent phenomenon. CONCLUSIONS Deletion of Hjv in mice leads to abnormal retinal angiogenesis/vasculogenesis, with proliferation of new, leaky blood vessels in the vitreous. These changes are accompanied with reactive gliosis involving Müller cells and microglia.
Collapse
Affiliation(s)
- Amany Tawfik
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States James & Jean Culver Vision Discovery Institute, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States
| | - Jaya P Gnana-Prakasam
- James & Jean Culver Vision Discovery Institute, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States
| | - Sylvia B Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States James & Jean Culver Vision Discovery Institute, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States
| | - Vadivel Ganapathy
- James & Jean Culver Vision Discovery Institute, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States
| |
Collapse
|
37
|
Gnana-Prakasam JP, Baldowski RB, Ananth S, Martin PM, Smith SB, Ganapathy V. Retinal expression of the serine protease matriptase-2 (Tmprss6) and its role in retinal iron homeostasis. Mol Vis 2014; 20:561-74. [PMID: 24791141 PMCID: PMC4000719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 04/24/2014] [Indexed: 11/01/2022] Open
Abstract
PURPOSE Matriptase-2 (also known as TMPRSS6) is a critical regulator of the iron-regulatory hormone hepcidin in the liver; matriptase-2 cleaves membrane-bound hemojuvelin and consequently alters bone morphogenetic protein (BMP) signaling. Hemojuvelin and hepcidin are expressed in the retina and play a critical role in retinal iron homeostasis. However, no information on the expression and function of matriptase-2 in the retina is available. The purpose of the present study was to examine the retinal expression of matriptase-2 and its role in retinal iron homeostasis. METHODS RT-PCR, quantitative PCR (qPCR), and immunofluorescence were used to analyze the expression of matriptase-2 and other iron-regulatory proteins in the mouse retina. Polarized localization of matriptase-2 in the RPE was evaluated using markers for the apical and basolateral membranes. Morphometric analysis of retinas from wild-type and matriptase-2 knockout (Tmprss6(msk/msk) ) mice was also performed. Retinal iron status in Tmprss6(msk/msk) mice was evaluated by comparing the expression levels of ferritin and transferrin receptor 1 between wild-type and knockout mice. BMP signaling was monitored by the phosphorylation status of Smads1/5/8 and expression levels of Id1 while interleukin-6 signaling was monitored by the phosphorylation status of STAT3. RESULTS Matriptase-2 is expressed in the mouse retina with expression detectable in all retinal cell types. Expression of matriptase-2 is restricted to the apical membrane in the RPE where hemojuvelin, the substrate for matriptase-2, is also present. There is no marked difference in retinal morphology between wild-type mice and Tmprss6(msk/msk) mice, except minor differences in specific retinal layers. The knockout mouse retina is iron-deficient, demonstrable by downregulation of the iron-storage protein ferritin and upregulation of transferrin receptor 1 involved in iron uptake. Hepcidin is upregulated in Tmprss6(msk/msk) mouse retinas, particularly in the neural retina. BMP signaling is downregulated while interleukin-6 signaling is upregulated in Tmprss6(msk/msk) mouse retinas, suggesting that the upregulaton of hepcidin in knockout mouse retinas occurs through interleukin-6 signaling and not through BMP signaling. CONCLUSIONS The iron-regulatory serine protease matriptase-2 is expressed in the retina, and absence of this enzyme leads to iron deficiency and increased expression of hemojuvelin and hepcidin in the retina. The upregulation of hepcidin expression in Tmprss6(msk/msk) mouse retinas does not occur via BMP signaling but likely via the proinflammatory cytokine interleukin-6. We conclude that matriptase-2 is a critical participant in retinal iron homeostasis.
Collapse
Affiliation(s)
- Jaya P. Gnana-Prakasam
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Regents University, Augusta, GA
| | - Renee B. Baldowski
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Regents University, Augusta, GA
| | - Sudha Ananth
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Regents University, Augusta, GA
| | - Pamela M. Martin
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Regents University, Augusta, GA
| | - Sylvia B. Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, GA
| | - Vadivel Ganapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Regents University, Augusta, GA
| |
Collapse
|
38
|
Abstract
Hepcidin is a 25-amino-acid peptide demonstrated to be the iron regulatory hormone capable of blocking iron absorption from the duodenum and iron release from macrophages. Mutations affecting hepcidin regulators or the hepcidin gene itself cause hemochromatosis, a common genetic disorder. Hepcidin is produced mainly by the liver, but many cells and tissues express low levels of the hormone. To determine the contribution of these hepcidin-producing tissues in body iron homeostasis, we have developed a new mouse model in which the hepcidin gene can be conditionally inactivated. Here we compare a liver-specific knockout (KO) mouse model with total KO mice. We show that the liver-specific KO mice fully recapitulate the severe iron overload phenotype observed in the total KO mice, with increased plasma iron and massive parenchymal iron accumulation. This result demonstrates that the hepatocyte constitutes the predominant reservoir for systemic hepcidin and that the other tissues are unable to compensate.
Collapse
|
39
|
Singh PK, Shiha MJ, Kumar A. Antibacterial responses of retinal Müller glia: production of antimicrobial peptides, oxidative burst and phagocytosis. J Neuroinflammation 2014; 11:33. [PMID: 24548736 PMCID: PMC3937076 DOI: 10.1186/1742-2094-11-33] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 02/06/2014] [Indexed: 01/31/2023] Open
Abstract
Background We have previously shown that, in response to microbial infection, activated Müller glia secrete inflammatory cytokines/chemokines and exhibit antimicrobial properties. The aim of this study is to understand the mechanisms and the key components involved in this response. Methods Immortalized human retinal Müller glia (MIO-M1 cells) were challenged with Staphylococcus (S) aureus, the leading cause of severe intraocular infection followed by RT2 profile PCR array analysis. The expression of human β-defensin 1 (HBD1), 2 (HBD2), 3 (HBD3), hepcidine and cathelicidin LL37 was checked by RT-PCR and quantified by Taqman® qPCR. The expression of AMPs was confirmed at protein level by dot-blot analysis. The production of ROS was measured by dicholoro-dihydro-fluorescein diacetate (DCFH-DA) staining by flow cytometry as well as fluorescence microscopy. The level of nitric oxide (NO) was measured by measuring a stable metabolite, nitrite using the Griess reagent. In vitro killing assay was performed by Live/Dead® BacLight™ staining as well as by dilution plating in suspension and adherent conditions following S. aureus infection. Phagocytosis was measured by CFU enumeration following infection. Results PCR array data showed that, in comparison to uninfected control cells, bacterial challenge significantly (> two-fold) induced the expression of 26 genes involved in cytokine/chemokine, antimicrobials, Toll-like receptor, apoptotic, and NF-κB signaling. RT-PCR analysis showed time-dependent increased expression of HBD1, HBD2, HBD3, LL-37, and hepcidin mRNA in bacteria-challenged Müller glia. The expression of these antimicrobial molecules was also increased at the protein level in the culture supernatant, as detected by dot-blot analysis. Additionally, the bacteria-stimulated Müller glia were found to produce reactive oxygen (ROS) and reactive nitrogen (RNS) species. In vitro, killing assays revealed that Müller glia exhibited bactericidal activity against S. aureus in both adherent and suspension cultures. Furthermore, our data demonstrated that Müller glia can phagocytize and kill the bacteria in a time-dependent manner. Conclusions These data suggest that retinal Müller glia behave like classical innate immune cells by producing a variety of antimicrobial molecules in response to bacterial challenge, suggesting their pivotal role in retinal innate defense.
Collapse
Affiliation(s)
| | | | - Ashok Kumar
- Department of Ophthalmology/Kresge Eye Institute, Wayne State University School of Medicine, 4717 St, Antoine, Detroit, MI 48201, USA.
| |
Collapse
|
40
|
Cau M, Melis MA, Congiu R, Galanello R. Iron-deficiency anemia secondary to mutations in genes controlling hepcidin. Expert Rev Hematol 2014; 3:205-16. [DOI: 10.1586/ehm.10.2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
41
|
Ugarte M, Osborne NN, Brown LA, Bishop PN. Iron, zinc, and copper in retinal physiology and disease. Surv Ophthalmol 2013; 58:585-609. [DOI: 10.1016/j.survophthal.2012.12.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 12/09/2012] [Accepted: 12/11/2012] [Indexed: 12/26/2022]
|
42
|
Kokotas H, Kroupis C, Chiras D, Grigoriadou M, Lamnissou K, Petersen MB, Kitsos G. Biomarkers in primary open angle glaucoma. Clin Chem Lab Med 2013; 50:2107-19. [PMID: 22745021 DOI: 10.1515/cclm-2012-0048] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 05/20/2012] [Indexed: 11/15/2022]
Abstract
Glaucoma, a leading cause of blindness worldwide, is currently defined as a disturbance of the structural or functional integrity of the optic nerve that causes characteristic atrophic changes in the optic nerve, which may lead to specific visual field defects over time. This disturbance usually can be arrested or diminished by adequate lowering of intraocular pressure (IOP). Glaucoma can be divided roughly into two main categories, ‘ open angle ’ and ‘ closed angle ’ glaucoma.Open angle, chronic glaucoma tends to progress at a slower rate and patients may not notice loss of vision until the disease has progressed significantly. Primary open angle glaucoma(POAG) is described distinctly as a multifactorial optic neuropathy that is chronic and progressive with a characteristic acquired loss of optic nerve fibers. Such loss develops in the presence of open anterior chamber angles, characteristic visual field abnormalities, and IOP that is too high for the healthy eye. It manifests by cupping and atrophy of the optic disc, in the absence of other known causes of glaucomatous disease. Several biological markers have been implicated with the disease. The purpose of this study was to summarize the current knowledge regarding the non-genetic molecular markers which have been predicted to have an association with POAG but have not yet been validated.
Collapse
Affiliation(s)
- Haris Kokotas
- Department of Genetics, Institute of Child Health , Aghia Sophia Children's Hospital, Athens, Greece.
| | | | | | | | | | | | | |
Collapse
|
43
|
Song D, Dunaief JL. Retinal iron homeostasis in health and disease. Front Aging Neurosci 2013; 5:24. [PMID: 23825457 PMCID: PMC3695389 DOI: 10.3389/fnagi.2013.00024] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 06/11/2013] [Indexed: 12/21/2022] Open
Abstract
Iron is essential for life, but excess iron can be toxic. As a potent free radical creator, iron generates hydroxyl radicals leading to significant oxidative stress. Since iron is not excreted from the body, it accumulates with age in tissues, including the retina, predisposing to age-related oxidative insult. Both hereditary and acquired retinal diseases are associated with increased iron levels. For example, retinal degenerations have been found in hereditary iron overload disorders, like aceruloplasminemia, Friedreich's ataxia, and pantothenate kinase-associated neurodegeneration. Similarly, mice with targeted mutation of the iron exporter ceruloplasmin and its homolog hephaestin showed age-related retinal iron accumulation and retinal degeneration with features resembling human age-related macular degeneration (AMD). Post mortem AMD eyes have increased levels of iron in retina compared to age-matched healthy donors. Iron accumulation in AMD is likely to result, in part, from inflammation, hypoxia, and oxidative stress, all of which can cause iron dysregulation. Fortunately, it has been demonstrated by in vitro and in vivo studies that iron in the retinal pigment epithelium (RPE) and retina is chelatable. Iron chelation protects photoreceptors and retinal pigment epithelial cells (RPE) in a variety of mouse models. This has therapeutic potential for diminishing iron-induced oxidative damage to prevent or treat AMD.
Collapse
Affiliation(s)
- Delu Song
- The F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at University of Pennsylvania Philadelphia, PA, USA
| | | |
Collapse
|
44
|
Urrutia P, Aguirre P, Esparza A, Tapia V, Mena NP, Arredondo M, González-Billault C, Núñez MT. Inflammation alters the expression of DMT1, FPN1 and hepcidin, and it causes iron accumulation in central nervous system cells. J Neurochem 2013; 126:541-9. [PMID: 23506423 DOI: 10.1111/jnc.12244] [Citation(s) in RCA: 265] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 02/27/2013] [Accepted: 03/01/2013] [Indexed: 12/23/2022]
Abstract
Inflammation and iron accumulation are present in a variety of neurodegenerative diseases that include Alzheimer's disease and Parkinson's disease. The study of the putative association between inflammation and iron accumulation in central nervous system cells is relevant to understand the contribution of these processes to the progression of neuronal death. In this study, we analyzed the effects of the inflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) and of lipopolysaccharide on total cell iron content and on the expression and abundance of the iron transporters divalent metal transporter 1 (DMT1) and Ferroportin 1 (FPN1) in neurons, astrocytes and microglia obtained from rat brain. Considering previous reports indicating that inflammatory stimuli induce the systemic synthesis of the master iron regulator hepcidin, we identified brain cells that produce hepcidin in response to inflammatory stimuli, as well as hepcidin-target cells. We found that inflammatory stimuli increased the expression of DMT1 in neurons, astrocytes, and microglia. Inflammatory stimuli also induced the expression of hepcidin in astrocytes and microglia, but not in neurons. Incubation with hepcidin decreased the expression of FPN1 in the three cell types. The net result of these changes was increased iron accumulation in neurons and microglia but not in astrocytes. The data presented here establish for the first time a causal association between inflammation and iron accumulation in brain cells, probably promoted by changes in DMT1 and FPN1 expression and mediated in part by hepcidin. This connection may potentially contribute to the progression of neurodegenerative diseases by enhancing iron-induced oxidative damage.
Collapse
Affiliation(s)
- Pamela Urrutia
- Department of Biology, Faculty of Sciences, Universidad de Chile and Research Ring on Oxidative Stress in the Nervous System, Santiago, Chile
| | | | | | | | | | | | | | | |
Collapse
|
45
|
Gnana-Prakasam JP, Veeranan-Karmegam R, Coothankandaswamy V, Reddy SK, Martin PM, Thangaraju M, Smith SB, Ganapathy V. Loss of Hfe leads to progression of tumor phenotype in primary retinal pigment epithelial cells. Invest Ophthalmol Vis Sci 2013; 54:63-71. [PMID: 23169885 DOI: 10.1167/iovs.12-10312] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
PURPOSE Hemochromatosis is a disorder of iron overload arising mostly from mutations in HFE. HFE is expressed in retinal pigment epithelium (RPE), and Hfe(-/-) mice develop age-related iron accumulation and retinal degeneration associated with RPE hyperproliferation. Here, the mechanism underlying the hyperproliferative phenotype in RPE was investigated. METHODS Cellular senescence was monitored by β-galactosidase activity. Gene expression was monitored by real-time PCR. Survivin was analyzed by Western blot and immunofluorescence. Migration and invasion were monitored using appropriate kits. Glucose transporters (GLUTs) were monitored by 3-O-methyl-D-glucose uptake. Histone deacetylases (HDACs) were studied by monitoring catalytic activity and acetylation status of histones H3/H4. RESULTS Hfe(-/-) RPE cells exhibited slower senescence rate and higher survivin expression than wild type cells. Hfe(-/-) cells migrated faster and showed greater glucose uptake and increased expression of GLUTs. The expression of HDACs and DNA methyltransferase (DNMTs) also was increased. Similarly, RPE cells from hemojuvelin (Hjv)-knockout mice, another model of hemochromatosis, also had increased expression of GLUTs, HDACs, and DNMTs. The expression of Slc5a8 was decreased in Hfe(-/-) RPE cells, but treatment with a DNA methylation inhibitor restored the transporter expression, indicating involvement of DNA methylation in the silencing of Slc5a8 in Hfe(-/-) cells. CONCLUSIONS RPE cells from iron-overloaded mice exhibit several features of tumor cells: decreased senescence, enhanced migration, increased glucose uptake, and elevated levels of HDACs and DNMTs. These features are seen in Hfe(-/-) RPE cells as well as in Hjv(-/-) RPE cells, providing a molecular basis for the hyperproliferative phenotype of Hfe(-/-) and Hjv(-/-) RPE cells.
Collapse
Affiliation(s)
- Jaya P Gnana-Prakasam
- Department of Biochemistry and Molecular Biology, Georgia Health Sciences University, Augusta, Georgia 30912, USA.
| | | | | | | | | | | | | | | |
Collapse
|
46
|
Tseng WA, Thein T, Kinnunen K, Lashkari K, Gregory MS, D'Amore PA, Ksander BR. NLRP3 inflammasome activation in retinal pigment epithelial cells by lysosomal destabilization: implications for age-related macular degeneration. Invest Ophthalmol Vis Sci 2013; 54:110-20. [PMID: 23221073 DOI: 10.1167/iovs.12-10655] [Citation(s) in RCA: 223] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
PURPOSE To evaluate the effect of lysosomal destabilization on NLRP3 inflammasome activation in RPE cells and to investigate the mechanisms by which inflammasome activation may contribute to the pathogenesis of age-related macular degeneration (AMD). METHODS Human ocular tissue sections from patients with geographic atrophy or neovascular AMD were stained for NLRP3 and compared to tissues from age-matched controls. Expression of the IL-1β precursor, pro-IL-1β, was induced in ARPE-19 cells by IL-1α treatment. Immunoblotting was performed to assess expression of NLRP3 inflammasome components (NLRP3, ASC, and procaspase-1) and pro-IL-1β in ARPE-19 cells. Lysosomes were destabilized using the lysosomotropic agent L-leucyl-L-leucine methyl ester (Leu-Leu-OMe). Active caspase-1 was detected using FAM-YVAD-FMK, a fluorescent-labeled inhibitor of caspases (FLICA) specific for caspase-1. IL-1β was detected by immunoblotting and ELISA, and cytotoxicity was evaluated by LDH quantification. RESULTS RPE of eyes affected by geographic atrophy or neovascular AMD exhibited NLRP3 staining at lesion sites. ARPE-19 cells were found to express NLRP3, ASC, and procaspase-1. IL-1α dose-dependently induced pro-IL-1β expression in ARPE-19 cells. Lysosomal destabilization induced by Leu-Leu-OMe triggered caspase-1 activation, IL-1β secretion, and ARPE-19 cell death. Blocking Leu-Leu-OMe-induced lysosomal disruption with the compound Gly-Phe-CHN(2) or inhibiting caspase-1 with Z-YVAD-FMK abrogated IL-1β release and ARPE-19 cytotoxicity. CONCLUSIONS NLRP3 upregulation occurs in the RPE during the pathogenesis of advanced AMD, in both geographic atrophy and neovascular AMD. Destabilization of RPE lysosomes induces NLRP3 inflammasome activation, which may contribute to AMD pathology through the release of the proinflammatory cytokine IL-1β and through caspase-1-mediated cell death, known as "pyroptosis."
Collapse
Affiliation(s)
- Wen Allen Tseng
- Schepens Eye Research Institute/Massachusetts Eye and Ear, Boston, Massachusetts, USA
| | | | | | | | | | | | | |
Collapse
|
47
|
Sun C, Song N, Xie A, Xie J, Jiang H. High hepcidin level accounts for the nigral iron accumulation in acute peripheral iron intoxication rats. Toxicol Lett 2012; 212:276-81. [PMID: 22659129 DOI: 10.1016/j.toxlet.2012.05.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 05/11/2012] [Accepted: 05/11/2012] [Indexed: 12/12/2022]
Abstract
Hepcidin is considered to be a circulatory hormone and a major mechanism regulating iron homeostasis. Our previous publication revealed that acute iron intoxication induced iron deposit and dopaminergic neuron degeneration in the substantia nigra (SN) of a rat model. However, whether and how hepcidin functions in this nigral iron accumulation has not been elucidated. In the present study, we observed a decreased of FPN1 protein level in the SN triggered by peripheral iron overload within 4 h, which correlated with a high hepcidin level. To further investigate the role of intracellular hepcidin under iron overload circumstances, we assessed the expression of hepcidin mRNA and FPN1 protein in vitro. We observed that hepcidin mRNA level was up-regulated and FPN1 protein level was down-regulated in MES23.5 dopaminergic cells in a period of 4h incubation with iron. Both in pCMV-XL4-hepcidin transfected and hepcidin-treated cells, decreased FPN1 protein levels were observed. Our data provide direct evidence that the role for intracellular hepcidin generated in the SN is particularly relevant to restrict iron release by down-regulation FPN1 expression in this region, thus an important contributor to the abnormal iron deposit occurred at an early stage in conditions of peripheral iron intoxication.
Collapse
Affiliation(s)
- Chao Sun
- Department of Neurology, The Affiliated Hospital of Medial College, Qingdao University, Qingdao 266003, China
| | | | | | | | | |
Collapse
|
48
|
Hunter A, Spechler PA, Cwanger A, Song Y, Zhang Z, Ying GS, Hunter AK, Dezoeten E, Dunaief JL. DNA methylation is associated with altered gene expression in AMD. Invest Ophthalmol Vis Sci 2012; 53:2089-105. [PMID: 22410570 DOI: 10.1167/iovs.11-8449] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
PURPOSE Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. Evidence suggests oxidative stress plays a role in the disease. To assess the potential contribution of epigenetic regulation of antioxidant genes relevant to AMD pathogenesis, we evaluated DNA methylation, a tissue-specific genetic modulation that affects gene expression. METHODS Using the Infinium HumanMethylation27 Illumina platform, we performed DNA bisulfite sequencing to compare the methylation status in postmortem retina pigment epithelium (RPE)/choroid between patients with AMD and age-matched controls. Gene expression was assessed with the Affymetrix Exon Array. TaqMan gene expression assays were used for relative quantification (RT-PCR) confirmation of the expression array results: Glutathione S-transferase isoform mu1 (GSTM1) and mu5 (GSTM5) promoter methylation was confirmed by CpG island bisulfite pyrosequencing. To assess protein levels and localization, we used Western analysis, immunohistochemistry, and immunofluorescence with murine and human samples. RESULTS The mRNA levels of GSTM1 and GSTM5 were significantly reduced in AMD versus age-matched controls in RPE/choroid and neurosensory retina (NSR), which corresponded to hypermethylation of the GSTM1 promoter. mRNA and protein levels were decreased (RPE to a greater extent than NSR) in AMD postmortem samples, irrespective of age. Immunohistochemistry and immunofluorescence confirm the presence of the enzymes in the NSR and RPE. CONCLUSIONS Comparison of DNA methylation, together with mRNA levels, revealed significant differences between AMD versus normal retinas. The evidence presented suggests that GSTM1 and GSTM5 undergo epigenetic repression in AMD RPE/choroid, which may increase susceptibility to oxidative stress in AMD retinas.
Collapse
Affiliation(s)
- Allan Hunter
- FM Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Wolkow N, Song D, Song Y, Chu S, Hadziahmetovic M, Lee JC, Iacovelli J, Grieco S, Dunaief JL. Ferroxidase hephaestin's cell-autonomous role in the retinal pigment epithelium. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 180:1614-24. [PMID: 22342521 DOI: 10.1016/j.ajpath.2011.12.041] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 12/11/2011] [Accepted: 12/20/2011] [Indexed: 01/04/2023]
Abstract
Hephaestin (Heph) is a ferroxidase protein that converts ferrous to ferric iron to facilitate cellular iron export by ferroportin. Many tissues express either Heph or its homologue, ceruloplasmin (Cp), but the retina expresses both. In mice, a combined systemic mutation of Heph and systemic knockout of Cp (Cp(-/-), Heph(sla/sla)) causes retinal iron accumulation and retinal degeneration, with features of human age-related macular degeneration; however, the role of Heph and Cp in the individual retinal cells is unclear. Herein, we used conditional knockout mice to study Heph's role in retinal pigment epithelial (RPE) and photoreceptor cells. Loss of both Heph and Cp from RPE cells alone results in RPE cell iron accumulation and degeneration. We found, however, that RPE iron accumulation in these conditional knockout mice is not as great as in systemic knockout mice. Photoreceptor-specific Heph knockout indicates that the additional iron in the RPE cells does not result from loss of ferroxidases in the photoreceptors, and Cp and Heph play minor roles in photoreceptors. Instead, loss of ferroxidases in other retinal cells causes retinal iron accumulation and transfer of iron to the RPE cells. Cp and Heph are necessary for iron export from the retina but are not essential for iron import into the retina. Thus, our studies, revise how we think about iron import and export from the retina.
Collapse
Affiliation(s)
- Natalie Wolkow
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
50
|
Abstract
Haemochromatosis is a genetic disorder of iron overload resulting from loss-of-function mutations in genes coding for the iron-regulatory proteins HFE (human leucocyte antigen-like protein involved in iron homoeostasis), transferrin receptor 2, ferroportin, hepcidin and HJV (haemojuvelin). Recent studies have established the expression of all of the five genes in the retina, indicating their importance in retinal iron homoeostasis. Previously, we demonstrated that HJV is expressed in RPE (retinal pigment epithelium), the outer and inner nuclear layers and the ganglion cell layer. In the present paper, we report on the consequences of Hjv deletion on the retina in mice. Hjv-/- mice at ≥18 months of age had increased iron accumulation in the retina with marked morphological damage compared with age-matched controls; these changes were not found in younger mice. The retinal phenotype in Hjv-/- mice included hyperplasia of RPE. We isolated RPE cells from wild-type and Hjv-/- mice and examined their growth patterns. Hjv-/- RPE cells were less senescent and exhibited a hyperproliferative phenotype. Hjv-/- RPE cells also showed up-regulation of Slc7a11 (solute carrier family 7 member 11 gene), which encodes the 'transporter proper' subunit xCT in the heterodimeric amino acid transporter xCT/4F2hc (cystine/glutamate exchanger). BMP6 (bone morphogenetic protein 6) could not induce hepcidin expression in Hjv-/- RPE cells, confirming that retinal cells require HJV for induction of hepcidin via BMP6 signalling. HJV is a glycosylphosphatidylinositol-anchored protein, and the membrane-associated HJV is necessary for BMP6-mediated activation of hepcidin promoter in RPE cells. Taken together, these results confirm the biological importance of HJV in the regulation of iron homoeostasis in the retina and in RPE.
Collapse
|