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Wang X, Wang T, Lam E, Alvarez D, Sun Y. Ocular Vascular Diseases: From Retinal Immune Privilege to Inflammation. Int J Mol Sci 2023; 24:12090. [PMID: 37569464 PMCID: PMC10418793 DOI: 10.3390/ijms241512090] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 07/21/2023] [Accepted: 07/26/2023] [Indexed: 08/13/2023] Open
Abstract
The eye is an immune privileged tissue that insulates the visual system from local and systemic immune provocation to preserve homeostatic functions of highly specialized retinal neural cells. If immune privilege is breached, immune stimuli will invade the eye and subsequently trigger acute inflammatory responses. Local resident microglia become active and release numerous immunological factors to protect the integrity of retinal neural cells. Although acute inflammatory responses are necessary to control and eradicate insults to the eye, chronic inflammation can cause retinal tissue damage and cell dysfunction, leading to ocular disease and vision loss. In this review, we summarized features of immune privilege in the retina and the key inflammatory responses, factors, and intracellular pathways activated when retinal immune privilege fails, as well as a highlight of the recent clinical and research advances in ocular immunity and ocular vascular diseases including retinopathy of prematurity, age-related macular degeneration, and diabetic retinopathy.
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Affiliation(s)
- Xudong Wang
- Department of Ophthalmology, Harvard Medical School, Boston Children’s Hospital, Boston, MA 02115, USA; (X.W.)
| | - Tianxi Wang
- Department of Ophthalmology, Harvard Medical School, Boston Children’s Hospital, Boston, MA 02115, USA; (X.W.)
| | - Enton Lam
- Department of Ophthalmology, Harvard Medical School, Boston Children’s Hospital, Boston, MA 02115, USA; (X.W.)
| | - David Alvarez
- Department of Immunology, Harvard Medical School, Boston, MA 02115, USA
| | - Ye Sun
- Department of Ophthalmology, Harvard Medical School, Boston Children’s Hospital, Boston, MA 02115, USA; (X.W.)
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Solstad AD, Brown JM, Ochrietor JD. The retina-specific basigin isoform does not induce IL-6 expression in mouse monocytes. Mol Vis 2023; 29:13-24. [PMID: 37287642 PMCID: PMC10243675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 04/20/2023] [Indexed: 06/09/2023] Open
Abstract
Purpose Basigin gene products are positioned on adjacent cell types in the neural retina and are thought to compose a lactate metabolon important for photoreceptor cell function. The Ig0 domain of basigin isoform 1 (basigin-1) is highly conserved throughout evolution, which suggests a conserved function. It has been suggested that the Ig0 domain has proinflammatory properties, and it is hypothesized to interact with basigin isoform 2 (basigin-2) for cell adhesion and lactate metabolon formation. Therefore, the purpose of the present study was to determine whether the Ig0 domain of basigin-1 binds to basigin-2 and whether the region of the domain used for binding is also used to stimulate interleukin-6 (IL-6) expression. Methods Binding was assessed using recombinant proteins corresponding to the Ig0 domain of basigin-1 and endogenously expressed basigin-2 from mouse neural retina and brain protein lysates. The proinflammatory properties of the Ig0 domain were analyzed with exposure of the recombinant proteins to the mouse monocyte RAW 264.7 cell line and subsequent measurement of the IL-6 concentration in the culture medium via enzyme-linked immunosorbent assay (ELISA). Results The data indicate that the Ig0 domain interacts with basigin-2 through a region within the amino half of the domain and that the Ig0 domain does not stimulate the expression of IL-6 in mouse cells in vitro. Conclusions The Ig0 domain of basigin-1 binds to basigin-2 in vitro. In addition, contrary to previous reports, there was no evidence that the Ig0 domain potentiates IL-6 expression in a mouse monocyte cell line in vitro. However, it is possible that the Ig0 domain stimulates the expression of proinflammatory cytokines other than IL-6, or that the potential involvement of the Ig0 domain of basigin-1 in the acute inflammatory response is dependent on species.
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Ng TF, Taylor AW. Stimulating the Melanocortin System in Uveitis and Diabetes Preserves the Structure and Anti-Inflammatory Activity of the Retina. Int J Mol Sci 2023; 24:ijms24086928. [PMID: 37108092 PMCID: PMC10138492 DOI: 10.3390/ijms24086928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 04/06/2023] [Accepted: 04/07/2023] [Indexed: 04/29/2023] Open
Abstract
The endogenous neuropeptide α-Melanocyte Stimulating Hormone (α-MSH) is a potent suppressor of inflammation and has an essential role in maintaining the normal anti-inflammatory microenvironment of the retina. While the therapeutic use of α-MSH peptide in uveitis and diabetic retinopathy models has been demonstrated, its short half-life and instability limit its use as a therapeutic drug. A comparable analog, PL-8331, which has a stronger affinity to melanocortin receptors, longer half-life, and, so far, is functionally identical to α-MSH, has the potential to deliver melanocortin-based therapy. We examined the effects of PL-8331 on two mouse models of retinal disease, Experimental Autoimmune Uveoretinitis (EAU) and Diabetic Retinopathy (DR). PL-8331 therapy applied to mice with EAU suppressed EAU and preserved retinal structures. In diabetic mice, PL-8331 enhanced the survival of retinal cells and suppressed VEGF production in the retina. In addition, retinal pigment epithelial cells (RPE) from PL-8331-treated diabetic mice retained normal anti-inflammatory activity. The results demonstrated that the pan-melanocortin receptor agonist PL-8331 is a potent therapeutic drug to suppress inflammation, prevent retinal degeneration, and preserve the normal anti-inflammatory activity of RPE.
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Affiliation(s)
- Tat Fong Ng
- Department of Ophthalmology, Boston University Chobanian and Avedisian School of Medicine, Boston, MA 02118, USA
| | - Andrew W Taylor
- Department of Ophthalmology, Boston University Chobanian and Avedisian School of Medicine, Boston, MA 02118, USA
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Du Y, Yan B. Ocular immune privilege and retinal pigment epithelial cells. J Leukoc Biol 2023; 113:288-304. [PMID: 36805720 DOI: 10.1093/jleuko/qiac016] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Indexed: 02/04/2023] Open
Abstract
The ocular tissue microenvironment is immune-privileged and uses multiple immunosuppressive mechanisms to prevent the induction of inflammation. The retinal pigment epithelium plays an essential role in ocular immune privilege. In addition to serving as a blood barrier separating the fenestrated choriocapillaris from the retina, the retinal pigment epithelium is a source of immunosuppressive cytokines and membrane-bound negative regulators that modulate the activity of immune cells within the retina. This article reviews the current understanding of how retinal pigment epithelium cells mediate immune regulation, focusing on the changes under pathologic conditions.
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Affiliation(s)
- Yuxiang Du
- Institute of Precision Medicine, Jining Medical University, No. 133, Hehua Road, Taibaihu New District, Jining, Shandong 272067, People's Republic of China
| | - Bo Yan
- Institute of Precision Medicine, Jining Medical University, No. 133, Hehua Road, Taibaihu New District, Jining, Shandong 272067, People's Republic of China
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Szczepan M, Llorián-Salvador M, Chen M, Xu H. Immune Cells in Subretinal Wound Healing and Fibrosis. Front Cell Neurosci 2022; 16:916719. [PMID: 35755781 PMCID: PMC9226489 DOI: 10.3389/fncel.2022.916719] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Accepted: 05/16/2022] [Indexed: 11/22/2022] Open
Abstract
The subretinal space is devoid of any immune cells under normal conditions and is an immune privileged site. When photoreceptors and/or retinal pigment epithelial cells suffer from an injury, a wound healing process will be initiated. Retinal microglia and the complement system, as the first line of retinal defense, are activated to participate in the wound healing process. If the injury is severe or persists for a prolonged period, they may fail to heal the damage and circulating immune cells will be summoned leading to chronic inflammation and abnormal wound healing, i.e., subretinal or intraretinal fibrosis, a sight-threatening condition frequently observed in rhematogenous retinal detachment, age-related macular degeneration and recurrent uveoretinitis. Here, we discussed the principles of subretinal wound healing with a strong focus on the conditions whereby the damage is beyond the healing capacity of the retinal defense system and highlighted the roles of circulating immune cells in subretinal wound healing and fibrosis.
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Affiliation(s)
- Manon Szczepan
- The Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry & Biomedical Sciences, Queen’s University Belfast, Belfast, United Kingdom
| | - María Llorián-Salvador
- The Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry & Biomedical Sciences, Queen’s University Belfast, Belfast, United Kingdom
| | - Mei Chen
- The Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry & Biomedical Sciences, Queen’s University Belfast, Belfast, United Kingdom
| | - Heping Xu
- The Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry & Biomedical Sciences, Queen’s University Belfast, Belfast, United Kingdom,Aier Institute of Optometry and Vision Science, Changsha, China,*Correspondence: Heping Xu,
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Ng TF, Dawit K, Taylor AW. Melanocortin receptor agonists suppress experimental autoimmune uveitis. Exp Eye Res 2022; 218:108986. [PMID: 35196505 PMCID: PMC9050930 DOI: 10.1016/j.exer.2022.108986] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 02/02/2022] [Accepted: 02/10/2022] [Indexed: 11/18/2022]
Abstract
The melanocortin system plays an essential role in the regulation of immune activity. The anti-inflammatory microenvironment of the eye is dependent on the expression of the melanocortin-neuropeptide alpha-melanocyte stimulating hormone (α-MSH). In addition, the melanocortin system may have a role in retinal development and retinal cell survival under conditions of retinal degeneration. We have found that treating experimental autoimmune uveitis (EAU) with α-MSH suppresses retinal inflammation. Also, this augmentation of the melanocortin system promotes immune tolerance and protection of the retinal structure. The benefit of α-MSH-therapy appears to be dependent on different melanocortin receptors. Therefore, we treated EAU mice with α-MSH-analogs with different melanocortin-receptor targets. This approach demonstrated which melanocortin-receptors suppress inflammation, preserve retinal structure, and induce immune tolerance in uveitis. At the chronic stage of EAU the mice were injected twice 1 day apart with 50 μg of α-MSH or an α-MSH-analog. The α-MSH-analogs were a pan-agonist PL8331, PL8177 (potent MC1r-only agonist), PL5000 (a pan-agonist with no MC5r functional activity), MT-II (same as PL5000) and PG901 (MC5r agonist, but also an antagonist to MC3r, and MC4r). Clinical EAU scores were measured until resolution in the α-MSH-treated mice, when the eyes were collected for histology, and spleen cells collected for retinal-antigen-stimulated cytokine production. Significant suppression of EAU was seen with α-MSH or PL8331 treatment. This was accompanied with significant preservation of retinal structure. A similar effect was seen in EAU-mice that were treated with PL8177, except the suppression of EAU was temporary. In EAU mice treated with PL5000, MTII, or PG901, there was no suppression of EAU with a significant loss in whole retina and outer-nuclear layer thickness. There was significant suppression of IL-17 with induction of IL-10 by retinal-antigen stimulated spleen T cells from EAU mice treated with α-MSH, PL8331, PL8177, or PL5000, but not from EAU mice treated with MT-II, or PG901. Our previous studies show the melanocortin system's importance in maintaining ocular immune privilege and that α-MSH-treatment accelerates recovery and induces retinal-antigen-specific regulatory immunity in EAU. Our current results show that this activity is centered around MC1r and MC5r. In addition, the results suggest that a therapeutic potential to target MC1r and MC5r together to suppress uveitis induces regulatory immunity with potentially maintaining a normal retinal structure.
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Affiliation(s)
- Tat Fong Ng
- Department of Ophthalmology, Boston University School of Medicine, 72 East Concord St., Boston, MA, 02118, United States
| | - Kaleb Dawit
- Department of Ophthalmology, Boston University School of Medicine, 72 East Concord St., Boston, MA, 02118, United States
| | - Andrew W Taylor
- Department of Ophthalmology, Boston University School of Medicine, 72 East Concord St., Boston, MA, 02118, United States.
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Taylor AW, Hsu S, Ng TF. The Role of Retinal Pigment Epithelial Cells in Regulation of Macrophages/Microglial Cells in Retinal Immunobiology. Front Immunol 2021; 12:724601. [PMID: 34484232 PMCID: PMC8414138 DOI: 10.3389/fimmu.2021.724601] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Accepted: 07/28/2021] [Indexed: 12/28/2022] Open
Abstract
The ocular tissue microenvironment is immune privileged and uses several mechanisms of immunosuppression to prevent the induction of inflammation. Besides being a blood-barrier and source of photoreceptor nutrients, the retinal pigment epithelial cells (RPE) regulate the activity of immune cells within the retina. These mechanisms involve the expression of immunomodulating molecules that make macrophages and microglial cells suppress inflammation and promote immune tolerance. The RPE have an important role in ocular immune privilege to regulate the behavior of immune cells within the retina. Reviewed is the current understanding of how RPE mediate this regulation and the changes seen under pathological conditions.
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Affiliation(s)
- Andrew W Taylor
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA, United States
| | - Samuel Hsu
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA, United States
| | - Tat Fong Ng
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA, United States
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Extracellular Soluble Membranes from Retinal Pigment Epithelial Cells Mediate Apoptosis in Macrophages. Cells 2021; 10:cells10051193. [PMID: 34068205 PMCID: PMC8153131 DOI: 10.3390/cells10051193] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/10/2021] [Accepted: 05/11/2021] [Indexed: 11/17/2022] Open
Abstract
A central characterization of retinal immunobiology is the prevention of proinflammatory activity by macrophages. The retinal pigment epithelial cells (RPEs) are a major source of soluble anti-inflammatory factors. This includes a soluble factor that induces macrophage apoptosis when the activity of the immunomodulating neuropeptide alpha-melanocyte-stimulating hormone (α-MSH) is neutralized. In this manuscript, isolated extracellular soluble membranes (ESMs) from primary RPE were assayed to see if they could be the soluble mediator of apoptosis. Our results demonstrated that RPE ESMs mediated the induction of macrophage apoptosis that was suppressed by α-MSH. In contrast, the RPE line ARPE-19, cultured under conditions that induce similar anti-inflammatory activity to primary RPEs, did not activate apoptosis in the macrophages. Moreover, only the ESMs from primary RPE cultures, and not those from the ARPE-19 cell cultures, expressed mFasL. The results demonstrate that RPE ESMs are a soluble mediator of apoptosis and that this may be a mechanism by which the RPEs select for the survival of α-MSH-induced suppressor cells.
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Ng TF, Manhapra A, Cluckey D, Choe Y, Vajram S, Taylor AW. Melanocortin 5 Receptor Expression and Recovery of Ocular Immune Privilege after Uveitis. Ocul Immunol Inflamm 2021; 30:876-886. [PMID: 33617397 DOI: 10.1080/09273948.2020.1849735] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Purpose: The therapeutic use of the RPE-neuropeptide α-MSH suppresses experimental autoimmune uveitis (EAU). This suppression is partially through the α-MSH melanocortin 5 receptor (MC5r). Therefore, we examined the possible role of MC5r-expression in the recovery of RPE suppression of phagolysosome-activation in macrophages following α-MSH-treatment of EAUMethods: The conditioned media of cultured in situ RPE-eyecup from α-MSH-treated EAU wild-type and MC5r(-/-) mice were used to treat macrophages to assay for phagolysosome activation.Results: MC5r(-/-) mice treated with α-MSH recovered from EAU, but with greater retinal damage, and the RPE suppressed phagolysosome activation in wild type but not in MC5r(-/-) macrophages. In addition, α-MSH did not suppress phagolysosome activation in MC5r(-/-) macrophages, and resting-MC5r(-/-) macrophages had augmented phagocytic activity.Conclusion: α-MSH treatment of EAU mediates a MC5r-dependent recovery of RPE suppression of phagolysosome activation in macrophages possibly altering antigen processing and presentation. Also, MC5r-expression helps protect the retina from inflammatory damage. In addition, MC5r-expression is important in the homeostatic maintenance of phagosome-maturation within macrophages.
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Affiliation(s)
- Tat Fong Ng
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Ambika Manhapra
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - David Cluckey
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Yoona Choe
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Srujan Vajram
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Andrew W Taylor
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, USA
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Sun Q, Gong L, Qi R, Qing W, Zou M, Ke Q, Zhang L, Tang X, Nie Q, Yang Y, Hu A, Ding X, Lu L, Liu Y, Li DWC. Oxidative stress-induced KLF4 activates inflammatory response through IL17RA and its downstream targets in retinal pigment epithelial cells. Free Radic Biol Med 2020; 147:271-281. [PMID: 31881336 DOI: 10.1016/j.freeradbiomed.2019.12.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 12/17/2019] [Accepted: 12/21/2019] [Indexed: 11/19/2022]
Abstract
Age-related macular degeneration (AMD) is a leading cause of irreversible blindness worldwide. Oxidative stress (OS), inflammation and genetics are considered the key pathogenic factors contributing to AMD development. Recent evidence shows the pro-inflammatory interleukin 17 (IL17) signaling is activated in AMD patients and promotes disease pathogenesis. However, the interplay between OS and IL17 signaling, and the regulatory mechanism of IL17 pathway are largely unknown. OS-induced retinal pigment epithelial cell (RPE) damage causes both the initial pathogenesis of AMD and secondary degeneration of rods and cones. Healthy RPE is essential for ocular immune privilege, however, damaged RPE cells can activate inflammatory response. In the present study, we identified IL17RA, the principle receptor of IL17 signaling, is one of the most upregulated inflammatory genes in human RPE cells upon OS exposure. The prominent increase of IL17RA was also observed in RPE and retina of an AMD-like mouse model. Knockdown of IL17RA in RPE cells prevented OS-induced RPE cell apoptosis and reduced the inflammatory response in both RPE and macrophages. Furthermore, we found that transcription factor KLF4 directly activates IL17RA expression, therefore, promotes the production of IL1β and IL8 in an IL17RA-dependent manner. In addition, the mRNA level of KLF4 isoform 2 was positively correlated with that of IL17RA in AMD patients. Together, our study demonstrates an unrevealed relationship between IL17RA and OS, and a new regulatory mechanism of IL17RA by KLF4 in RPE cells. These findings suggest that inhibition of IL17RA as a new potential therapeutic target for AMD through RPE protection and inflammatory suppression upon OS exposure.
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Affiliation(s)
- Qian Sun
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Lili Gong
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China.
| | - Ruili Qi
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Wenjie Qing
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Ming Zou
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Qin Ke
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Lan Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Xiangcheng Tang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Qian Nie
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Yuan Yang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Andina Hu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Xiaoyan Ding
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Lin Lu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - Yizhi Liu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China
| | - David Wan-Cheng Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, 510060, China.
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Benque IJ, Xia P, Shannon R, Ng TF, Taylor AW. The Neuropeptides of Ocular Immune Privilege, α-MSH and NPY, Suppress Phagosome Maturation in Macrophages. Immunohorizons 2018; 2:314-323. [PMID: 30613828 PMCID: PMC6319950 DOI: 10.4049/immunohorizons.1800049] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The ocular microenvironment has evolutionarily adapted several mechanisms of immunosuppression to minimize the induction of inflammation. Neuropeptides produced by the retinal pigment epithelial cells regulate macrophage activity. Two neuropeptides, α-melanocyte–stimulating hormone (α -MSH) and neuropeptide Y (NPY), are constitutively expressed by the retinal pigment epithelial cells. Together these two neuropeptides induce anti-inflammatory cytokine production in endotoxin-stimulated macrophages and suppress phagocytosis of unopsonized bioparticles. These neuropeptides do not suppress the phagocytosis of opsonized bioparticles; however, they do suppress phagolysosome activation or formation. In this report, we studied the possibility that α-MSH with NPY suppress phagosome maturation within macrophages using opsonized OVA-coated magnetic beads to isolate and analyze the phagosomes. The magnetic bead–containing intercellular vesicles were isolated and assayed for Rab5, Rab7, LAMP1, Iad, and OVA. The macrophages cotreated with α-MSH and NPY were suppressed in Rab7 recruitment to the phagosome with suppression in LAMP1 expression but not in Iad expression. The results demonstrated that the α-MSH/NPY cotreatment suppressed phagosome maturation. In addition, the a-MSH/NPY–cotreated macrophages were suppressed in their ability to Ag stimulate CD4+ T cell proliferation. These results imply a potential mechanism of ocular immune privilege to divert Ag processing to prevent autoreactive effector T cells from binding their target cognate Ag within the ocular microenvironment.
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Affiliation(s)
- Isaac J Benque
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Pu Xia
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Robert Shannon
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Tat Fong Ng
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Andrew W Taylor
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
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Taylor AW, Ng TF. Negative regulators that mediate ocular immune privilege. J Leukoc Biol 2018; 103:1179-1187. [PMID: 29431864 PMCID: PMC6240388 DOI: 10.1002/jlb.3mir0817-337r] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 12/15/2017] [Accepted: 01/10/2018] [Indexed: 08/13/2023] Open
Abstract
The ocular microenvironment has adapted several negative regulators of inflammation to maintain immune privilege and health of the visual axis. Several constitutively produced negative regulators within the eye TGF-β2, α-melanocyte stimulating hormone (α-MSH), Fas ligand (FasL), and PD-L1 standout because of their capacity to influence multiple pathways of inflammation, and that they are part of promoting immune tolerance. These regulators demonstrate the capacity of immune privilege to prevent the activation of inflammation, and to suppress activation of effector immune cells even under conditions of ocular inflammation induced by endotoxin and autoimmune disease. In addition, these negative regulators promote and expand immune cells that mediate regulatory and tolerogenic immunity. This in turn makes the immune cells themselves negative regulators of inflammation. This provides for a greater understanding of immune privilege in that it includes both molecular and cellular negative regulators of inflammation. This would mean that potentially new approaches to the treatment of autoimmune disease can be developed through the use of molecules and cells as negative regulators of inflammation.
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Affiliation(s)
- Andrew W Taylor
- Boston University School of Medicine, Boston, Massachusetts, USA
| | - Tat Fong Ng
- Boston University School of Medicine, Boston, Massachusetts, USA
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13
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Wang E, Choe Y, Ng TF, Taylor AW. Retinal Pigment Epithelial Cells Suppress Phagolysosome Activation in Macrophages. Invest Ophthalmol Vis Sci 2017; 58:1266-1273. [PMID: 28241314 PMCID: PMC5341620 DOI: 10.1167/iovs.16-21082] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Purpose The eye is an immune-privileged microenvironment that has adapted several mechanisms of immune regulation to prevent inflammation. One of these potential mechanisms is retinal pigment epithelial cells (RPE) altering phagocytosis in macrophages. Methods The conditioned media of RPE eyecups from eyes of healthy mice and mice with experimental autoimmune uveitis (EAU) were used to treat primary macrophage phagocytizing pHrodo bacterial bioparticles. In addition, the neuropeptides were depleted from the conditioned media of healthy RPE eyecups and used to treat phagocytizing macrophages. The conditioned media from healthy and EAU RPE eyecups were assayed for IL-6, and IL-6 was added to the healthy conditioned media, and neutralized in the EAU conditioned media. The macrophages were treated with the conditioned media and assayed for fluorescence. The macrophages were imaged, and the fluorescence intensity, relative to active phagolysosomes, was measured. Also, the macrophages were assayed using fluorescent viability dye staining. Results The conditioned media from healthy, but not from EAU RPE eyecups suppressed phagolysosome activation. Depletion of the neuropeptides alpha-melanocyte–stimulating hormone and neuropeptide Y from the healthy RPE eyecup conditioned media resulted in macrophage death. In the EAU RPE eyecup conditioned media was 0.96 ± 0.18 ng/mL of IL-6, and when neutralized the conditioned media suppressed phagolysosome activation. Conclusions The healthy RPE through soluble molecules, including alpha-melanocyte–stimulating hormone and neuropeptide Y, suppresses the activation of the phagolysosome in macrophages. In EAU, the IL-6 produced by the RPE promotes the activation of phagolysosomes in macrophages. These results demonstrate that under healthy conditions, RPE promotes an altered pathway of phagocytized material in macrophages with implications on antigen processing and clearance.
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Affiliation(s)
- Eric Wang
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
| | - Yoona Choe
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
| | - Tat Fong Ng
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
| | - Andrew W Taylor
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
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Knickelbein JE, Liu B, Arakelyan A, Zicari S, Hannes S, Chen P, Li Z, Grivel JC, Chaigne-Delalande B, Sen HN, Margolis L, Nussenblatt RB. Modulation of Immune Responses by Extracellular Vesicles From Retinal Pigment Epithelium. Invest Ophthalmol Vis Sci 2017; 57:4101-7. [PMID: 27537259 PMCID: PMC4991022 DOI: 10.1167/iovs.15-18353] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Purpose Extracellular vesicles (EV), such as exosomes, are important mediators of intercellular communication and have been implicated in modulation of the immune system. We investigated if EV released from retinal pigment epithelium (RPE) modulate immune responses in vitro. Methods Extracellular vesicles were isolated from ARPE-19 cultures stimulated or not with the inflammatory cytokines IL-1β, IFN-γ, and TNF-α. Isolated EV were characterized by nanoparticle flow and Western blot analyses. Retinal pigment epithelium–derived EV were cultured with human peripheral blood mononuclear cells, which were assayed for T-cell proliferation by 3H-thymidine incorporation. Retinal pigment epithelium–derived EV were also independently cultured with enriched lymphocytes or monocytes. Cell phenotype and cell death were evaluated by flow cytometric analysis. Cytokine levels were assayed in culture supernatants by multiplex bead analysis. Results The concentration of ARPE-derived EV from cytokine-stimulated cultures was slightly higher than from nonstimulated cultures. The size of EV was approximately 100 nm in both groups. Extracellular vesicles from both nonstimulated and cytokine-stimulated ARPE-19 significantly inhibited T-cell proliferation without affecting T-cell viability. Culture of EV from nonstimulated ARPE-19 with undifferentiated human monocytes induced an immunoregulatory phenotype with a significantly higher percentage of CD14++CD16+ monocytes and upregulation of TGF-β1. Culture of EV from cytokine-stimulated ARPE-19 cells with human monocytes induced upregulation of several proinflammatory cytokines and monocyte death. Conclusions Retinal pigment epithelium cells constitutively secrete EV in the size range of exosomes, with increased release from RPE cells stimulated with inflammatory cytokines. Extracellular vesicles from both nonstimulated and cytokine-stimulated RPE inhibited T-cell stimulation. Extracellular vesicles from nonstimulated ARPE-19 cells promoted an immunoregulatory CD14++CD16+ phenotype in human monocytes, while EV from cytokine-stimulated ARPE-19 cells caused human monocyte death. These findings suggest that RPE cells use EV to induce a downregulatory immune environment under homeostatic conditions. In an inflammatory milieu, RPE-derived EV may mitigate a potentially harmful inflammatory response through killing of monocytes.
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Affiliation(s)
- Jared E Knickelbein
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Baoying Liu
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Anush Arakelyan
- Section of Intercellular Interactions, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, United States
| | - Sonia Zicari
- Section of Intercellular Interactions, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, United States
| | - Susan Hannes
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Ping Chen
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Zhiyu Li
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Jean-Charles Grivel
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States 2Section of Intercellular Interactions, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, Bethesda, Maryland
| | - Benjamin Chaigne-Delalande
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - H Nida Sen
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Leonid Margolis
- Section of Intercellular Interactions, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, United States
| | - Robert B Nussenblatt
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
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Manthey AL, Chiu K, So KF. Effects of Lycium barbarum on the Visual System. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2017; 135:1-27. [PMID: 28807155 DOI: 10.1016/bs.irn.2017.02.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Lycium barbarum (wolfberry, gogi berry, gouqizi, ) is one of the most widely used Chinese herbal medicines (CHMs) and is also one of the most scientifically studied. Indeed, the polysaccharide component of this berry (LBP) has been shown to have antioxidant, antiinflammatory, antiexcitotoxic, and antiapoptotic properties. These properties make it a particularly useful treatment option for the ocular environment. Although there are a handful of studies investigating the use of LBP to treat diseases affecting the lens, the vast majority of the published literature investigating LBP in the visual system focus on the retina. In this chapter, we have described what is currently understood concerning the effects of LBP treatment on various retinal diseases, including glaucoma, ischemia/reperfusion, age-related macular degeneration, retinitis pigmentosa, and diabetic retinopathy. We then describe the functions attributed to LBP using other cellular contexts to elucidate the full mechanisms this CHM utilizes in the retina. By making connections between what is known about the function of LBP in a variety of tissues and its function as a therapy for retinal degenerative diseases, we hope to further emphasize the continued use of this CHM in clinical medicine in addition to providing a platform for additional study.
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Affiliation(s)
| | - Kin Chiu
- The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong, SAR, China.
| | - Kwok-Fai So
- The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong, SAR, China; Guangdong-Hong Kong-Macau Institute of CNS Regeneration and Guangdong Key Laboratory of Brain Function and Diseases, Jinan University, Guangzhou, China; Ministry of Education Joint International Research Laboratory of CNS Regeneration, Jinan University, Guangzhou, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China.
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Taylor AW. Ocular Immune Privilege and Transplantation. Front Immunol 2016; 7:37. [PMID: 26904026 PMCID: PMC4744940 DOI: 10.3389/fimmu.2016.00037] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 01/25/2016] [Indexed: 11/30/2022] Open
Abstract
Allografts are afforded a level of protection from rejection within immune-privileged tissues. Immune-privileged tissues involve mechanisms that suppress inflammation and promote immune tolerance. There are anatomical features, soluble factors, membrane-associated proteins, and alternative antigen-presenting cells (APC) that contribute to allograft survival in the immune-privileged tissue. This review presents the current understanding of how the mechanism of ocular immune privilege promotes tolerogenic activity by APC, and T cells in response to the placement of foreign antigen within the ocular microenvironment. Discussed will be the unique anatomical, cellular, and molecular mechanisms that lessen the chance for graft destroying immune responses within the eye. As more is understood about the molecular mechanisms of ocular immune privilege greater is the potential for using these molecular mechanisms in therapies to prevent allograft rejection.
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Affiliation(s)
- Andrew W Taylor
- Department of Ophthalmology, Boston University School of Medicine , Boston, MA , USA
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Taylor AW, Dixit S, Yu J. Retinal Pigment Epithelial Cell Line Suppression of Phagolysosome Activation. INTERNATIONAL JOURNAL OF OPHTHALMOLOGY & EYE SCIENCE 2015; Suppl 2:1-6. [PMID: 25905107 PMCID: PMC4403791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
The eye is an immune privileged tissue with multiple mechanisms of immunosuppression to protect the light gathering tissues from the damage of inflammation. One of theses mechanisms involves retinal pigment epithelial cell suppression of phagosome activation in macrophages. The objective of this work is to determine if the human RPE cell line ARPE-19 is capable of suppressing the activation of the phagolysosome in macrophages in a manner similar to primary RPE. The conditioned media of RPE eyecups, sub-confluent, just confluent cultures, or established confluent cultures of human ARPE-19 cells were generated. These condition media were used to treat macrophages phagocytizing pHrodo bioparticles. After 24 hours incubation the macrophages were imaged by fluorescent microscopy, and fluorescence was measured. The fluorescent intensity is proportional to the amount of bioparticles phagocytized and are in an activated phagolysosome. The conditioned media of in situ mouse RPE eyecups significantly suppressed the activation of phagolysosome. The conditioned media from cultures of human ARPE-19 cells, grown to sub-confluence (50%) or grown to confluence had no effect on phagolysosome activation. In contrast, the conditioned media from established confluent cultures significantly suppressed phagolysosome activation. The neuropeptides alpha-MSH and NPY were depleted from the conditioned media of established confluent ARPE-19 cell cultures. This depleted conditioned media had diminished suppression of phagolysosome activation while promoting macrophage cell death. In addition, the condition media from cultures of ARPE-19 monolayers wounded with a bisecting scrape was diminished in suppressing phagolysosome activation. This technical report suggests that like primary RPE monolayers, established confluent cultures of ARPE-19 cells produce soluble factors that suppress the activation of macrophages, and can be used to study the molecular mechanisms of retinal immunobiology. In addition, the results further demonstrate the importance of an intact monolayer of RPE cells to modulate immune cell activity within the eye.
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Affiliation(s)
- AW Taylor
- Corresponding Author: Andrew W. Taylor, PhD, Department of Ophthalmology, Boston University School of Medicine, 72 East Concord Street, Room L915, Boston, MA 02118, USA., Tel: 617-912-7452,
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The retinal pigment epithelium (RPE) induces FasL and reduces iNOS and Cox2 in primary monocytes. Graefes Arch Clin Exp Ophthalmol 2014; 252:1747-54. [PMID: 25059476 DOI: 10.1007/s00417-014-2742-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 06/30/2014] [Accepted: 07/08/2014] [Indexed: 12/24/2022] Open
Abstract
PURPOSE Retinal pigment epithelium (RPE) cells may alter the phenotype of monocytes by soluble factors that may be influenced by stimulation of the RPE. Since RPE cells carry the toll-like receptor-3 (TLR3) that detects and reacts to viral infection through binding of dsRNA we investigated the effects of RPE cells with or without TLR3 stimulation on blood-derived monocytes with respect to regulation of pro-/anti-inflammatory cytokines, anti-angiogenic factors and migratory properties. METHODS Primary RPE cells were prepared from porcine eyes; monocytes were prepared from porcine blood. TLR3 activation was induced by polyinosinic:polycytidylic acid (Poly I:C). RPE cells were stimulated with Poly I:C in different concentrations for 24 hours and a cell culture supernatant was applied to the monocytes. Expression of CD14 and Fas ligand (FasL) was determined via flow cytometry. The expression of IL-6, IL-1ß, TNFα, Cox2, iNOS and IL-10 was determined via quantitative RT-PCR. Migration was determined using Boyden chamber experiments. RESULTS The supernatant of RPE cells, irrespective of TLR3 activation, induced FasL expression in the monocytes. Expression of iNOS and Cox2 was reduced by RPE cells and the reduction of Cox2 but not if iNOS was lost under TLR3 activation. No induction of IL-6, IL-1ß, IL-10 or TNFα by the RPE was seen. TLR3-activated RPE cells induced monocyte migration. CONCLUSION RPE cells induce an upregulation of FasL and a downregulation of iNOS and Cox2 without upregulating inflammatory cytokines, possibly inducing an anti-angiogenic phenotype in the monocytes. This phenotype is still upheld after challenging RPE cells with dsRNA, mimicking a viral infection.
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Ma J, Mehta M, Lam G, Cyr D, Ng TF, Hirose T, Tawansy KA, Taylor AW, Lashkari K. Influence of subretinal fluid in advanced stage retinopathy of prematurity on proangiogenic response and cell proliferation. Mol Vis 2014; 20:881-93. [PMID: 24966660 PMCID: PMC4067231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 06/19/2014] [Indexed: 11/03/2022] Open
Abstract
PURPOSE The clinical phenotype of advanced stage retinopathy of prematurity (ROP, stages 4 and 5) cannot be replicated in an animal model. To dissect the molecular events that can lead up to advanced ROP, we examined subretinal fluid (SRF) and surgically dissected retrolental membranes from patients with advanced ROP to evaluate its influences on cell proliferation, angiogenic properties, and macrophage polarity. METHODS We compared our findings to SRF collected from patients with uncomplicated rhegmatogenous retinal detachment (RD) without proliferative vitreoretinopathy and surgically dissected epiretinal membrane from eyes with macular pucker. All subretinal fluid samples were equalized for protein. The angiogenic potential of SRF from ROP eyes was measured using a combination of capillary cord formation in a fibrin clot assay, and its proliferative effect was tested with a DNA synthesis of human retinal microvascular endothelial cells. Findings were compared with SRF collected from participants with uncomplicated rhegmatogenous RD without proliferative vitreoretinopathy. The ability of SRF to induce nitric oxide production was measured in vitro using murine J774A.1 macrophages. Cytokine profiles of SRF from ROP and RD eyes were measured using a multienzyme-linked immunosorbent assay (ELISA). Fluorescent immunohistochemistry of retrolental membranes from ROP was performed to detect the presence of leukocytes and the composition of tissue macrophages using markers for M1 and M2 differentiation. RESULTS The cytokine composition in SRF revealed that in ROP, not only were several proangiogenic factors were preferentially elevated but also the profile of proinflammatory factors was also increased compared to the RD eyes. SRF from ROP eyes supported cell proliferation and endothelial cord formation while SRF from RD eyes had inhibitory effects. SRF from eyes with ROP but not RD robustly induced nitric oxide production in macrophages. Furthermore, fluorescent immunostaining revealed a preponderance of M1 over M2 macrophages in retrolental fibrous membranes from ROP eyes. The cytokine profile and biologic properties of SRF in ROP promote a proangiogenic environment, which supports the maintenance and proliferation of fibrous membranes associated with advanced stages of ROP. In contrast, SRF from RD eyes exhibits a suppressive environment for endothelial cell proliferation and angiogenesis. CONCLUSIONS Our investigation demonstrates that the microenvironment in advanced ROP eyes is proangiogenic and proinflammatory. These findings suggest that management of advanced ROP should not be limited to the surgical removal of the fibrovascular membranes and antiangiogenic therapy but also directed to anti-inflammatory therapy and to promote M2 activation over M1 activity.
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Affiliation(s)
- Jie Ma
- Schepens Eye Research Institute, Mass. Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA
| | - Manisha Mehta
- Department of Pathology, Boston University School of Medicine, Boston, MA
| | - Godfrey Lam
- Schepens Eye Research Institute, Mass. Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA
| | - Desireé Cyr
- Schepens Eye Research Institute, Mass. Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA
| | - Tat Fong Ng
- Schepens Eye Research Institute, Mass. Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA
| | - Tatsuo Hirose
- Schepens Eye Research Institute, Mass. Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA
| | | | - Andrew W. Taylor
- Department of Ophthalmology, Boston University School of Medicine, Boston MA
| | - Kameran Lashkari
- Schepens Eye Research Institute, Mass. Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA
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Lee DJ, Taylor AW. Both MC5r and A2Ar are required for protective regulatory immunity in the spleen of post-experimental autoimmune uveitis in mice. THE JOURNAL OF IMMUNOLOGY 2013; 191:4103-11. [PMID: 24043903 DOI: 10.4049/jimmunol.1300182] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The ocular microenvironment uses a poorly defined mela5 receptor (MC5r)-dependent pathway to recover immune tolerance following intraocular inflammation. This dependency is seen in experimental autoimmune uveoretinitis (EAU), a mouse model of endogenous human autoimmune uveitis, with the emergence of autoantigen-specific regulatory immunity in the spleen that protects the mice from recurrence of EAU. In this study, we found that the MC5r-dependent regulatory immunity increased CD11b(+)F4/80(+)Ly-6C(low)Ly-6G(+)CD39(+)CD73(+) APCs in the spleen of post-EAU mice. These MC5r-dependent APCs require adenosine 2A receptor expression on T cells to activate EAU-suppressing CD25(+)CD4(+)Foxp3(+) regulatory T cells. Therefore, in the recovery from autoimmune disease, the ocular microenvironment induces tolerance through a melanocortin-mediated expansion of Ly-6G(+) regulatory APCs in the spleen that use the adenosinergic pathway to promote activation of autoantigen-specific regulatory T cells.
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Affiliation(s)
- Darren J Lee
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
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Taylor AW. Alpha-melanocyte stimulating hormone (α-MSH) is a post-caspase suppressor of apoptosis in RAW 264.7 macrophages. PLoS One 2013; 8:e74488. [PMID: 24009773 PMCID: PMC3757010 DOI: 10.1371/journal.pone.0074488] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 08/01/2013] [Indexed: 01/04/2023] Open
Abstract
The neuropeptide alpha-melanocyte stimulating hormone (α-MSH) is an important regulator of immune cell activity within the immunosuppressive ocular microenvironment. Its constitutive presence not only suppresses macrophage inflammatory activity, it also participates in retinal pigment epithelial cell (RPE) mediated activation of macrophages to function similar to myeloid suppressor cells. In addition, α-MSH promotes survival of the alternatively activated macrophages where without α-MSH RPE induce apoptosis in the macrophages, which is seen as increased TUNEL stained cells. Since there is little know about α-MSH as an anti-apoptotic factor, the effects of α-MSH on caspase activity, mitochondrial membrane potential, Bcl2 to BAX expression, along with TUNEL staining, and Annexin V binding were examined in RAW 264.7 macrophages under serum-starved conditions that trigger apoptosis. There was no effect of α-MSH on activated Caspase 9 and Caspase 3 while there was suppression of Caspase 8 activity. In addition, α-MSH did not improve mitochondrial membrane potential, change the ratio between Bcl-2 and BAX, nor reduce Annexin V binding. These results demonstrate that the diminution in TUNEL staining by α-MSH is through α-MSH mediating suppression of the apoptotic pathway that is post-Caspase 3, but before DNA fragmentation. Therefore, as α-MSH promotes the alternative activation of macrophages it also provides a survival signal, and the potential for the caspases to participate in non-apoptotic activities that can contribute to an immunosuppressive microenvironment.
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Affiliation(s)
- Andrew W Taylor
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, USA.
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The neuropeptides α-MSH and NPY modulate phagocytosis and phagolysosome activation in RAW 264.7 cells. J Neuroimmunol 2013; 260:9-16. [PMID: 23689030 DOI: 10.1016/j.jneuroim.2013.04.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 04/17/2013] [Accepted: 04/22/2013] [Indexed: 11/20/2022]
Abstract
Within the immunosuppressive ocular microenvironment, there are constitutively present the immunomodulating neuropeptides alpha-melanocyte stimulating hormone (α-MSH) and neuropeptide Y (NPY) that promote suppressor functionality in macrophages. In this study, we examined the possibility that α-MSH and NPY modulate phagocytic activity in macrophages. The macrophages treated with α-MSH and NPY were significantly suppressed in their capacity to phagocytize unopsonized Escherichia coli and Staphylococcus aureus bioparticles, but not antibody-opsonized bioparticles. The neuropeptides significantly suppressed phagolysosome activation, and the FcR-associated generation of reactive oxidative species as well. This suppression corresponds to neuropeptide modulation of macrophage functionality within the ocular microenvironment to suppress the activation of immunogenic inflammation.
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Diffuse Ventricular Fibrosis in Atrial Fibrillation. J Am Coll Cardiol 2012; 60:2402-8. [DOI: 10.1016/j.jacc.2012.07.065] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 07/22/2012] [Accepted: 07/24/2012] [Indexed: 11/24/2022]
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The alpha-melanocyte stimulating hormone induces conversion of effector T cells into treg cells. J Transplant 2011; 2011:246856. [PMID: 21941624 PMCID: PMC3175390 DOI: 10.1155/2011/246856] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 06/20/2011] [Accepted: 07/04/2011] [Indexed: 11/17/2022] Open
Abstract
The neuropeptide alpha-melanocyte stimulating hormone (α-MSH) has an important role in modulating immunity and homeostasis. The production of IFN-γ by effector T cells is suppressed by α-MSH, while TGF-β production is promoted in the same cells. Such α-MSH-treated T cells have immune regulatory activity and suppress hypersensitivity, autoimmune diseases, and graft rejection. Previous characterizations of the α-MSH-induced Treg cells showed that the cells are CD4(+) T cells expressing the same levels of CD25 as effector T cells. Therefore, we further analyzed the α-MSH-induced Treg cells for expression of effector and regulatory T-cell markers. Also, we examined the potential for α-MSH-induced Treg cells to be from the effector T-cell population. We found that the α-MSH-induced Treg cells are CD25(+) CD4(+) T cells that share similar surface markers as effector T cells, except that they express on their surface LAP. Also, the α-MSH treatment augments FoxP3 message in the effector T cells, and α-MSH induction of regulatory activity was limited to the effector CD25(+) T-cell population. Therefore, α-MSH converts effector T cells into Treg cells, which suppress immunity targeting specific antigens and tissues.
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Localized retinal neuropeptide regulation of macrophage and microglial cell functionality. J Neuroimmunol 2010; 232:17-25. [PMID: 20965575 DOI: 10.1016/j.jneuroim.2010.09.025] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2010] [Revised: 09/21/2010] [Accepted: 09/23/2010] [Indexed: 11/20/2022]
Abstract
The functionality of immune cells is manipulated within the ocular microenvironment to protect the sensitive and non-regenerating light-gathering tissue from the collateral damage of inflammation. This is mediated partly by the constitutive presence of immunomodulating neuropeptides. Treating primary resting macrophages with soluble factors produced by the posterior eye induced co-expression of Arginase1 and NOS2. The neuropeptides alpha-melanocyte stimulating hormone and Neuropeptide Y alternatively activated the macrophages to co-express Arginase1 and NOS2 like myeloid suppressor cells. Similar co-expressing cells were found within healthy, but not in wounded retinas. Therefore, the healthy retina regulates macrophage functionality to the benefit of ocular immune privilege.
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