1
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Stürmer S, Bolz S, Zrenner E, Ueffing M, Haq W. Sustained Extracellular Electrical Stimulation Modulates the Permeability of Gap Junctions in rd1 Mouse Retina with Photoreceptor Degeneration. Int J Mol Sci 2024; 25:1616. [PMID: 38338908 PMCID: PMC10855676 DOI: 10.3390/ijms25031616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Revised: 01/24/2024] [Accepted: 01/25/2024] [Indexed: 02/12/2024] Open
Abstract
Neurons build vast gap junction-coupled networks (GJ-nets) that are permeable to ions or small molecules, enabling lateral signaling. Herein, we investigate (1) the effect of blinding diseases on GJ-nets in mouse retinas and (2) the impact of electrical stimulation on GJ permeability. GJ permeability was traced in the acute retinal explants of blind retinal degeneration 1 (rd1) mice using the GJ tracer neurobiotin. The tracer was introduced via the edge cut method into the GJ-net, and its spread was visualized in histological preparations (fluorescent tagged) using microscopy. Sustained stimulation was applied to modulate GJ permeability using a single large electrode. Our findings are: (1) The blind rd1 retinas displayed extensive intercellular coupling via open GJs. Three GJ-nets were identified: horizontal, amacrine, and ganglion cell networks. (2) Sustained stimulation significantly diminished the tracer spread through the GJs in all the cell layers, as occurs with pharmaceutical inhibition with carbenoxolone. We concluded that the GJ-nets of rd1 retinas remain coupled and functional after blinding disease and that their permeability is regulatable by sustained stimulation. These findings are essential for understanding molecular signaling in diseases over coupled networks and therapeutic approaches using electrical implants, such as eliciting visual sensations or suppressing cortical seizures.
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Affiliation(s)
| | | | | | | | - Wadood Haq
- Institute for Ophthalmic Research, University of Tuebingen, 72076 Tuebingen, Germany
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2
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Huang F, Deng Z, Zhang Q, Zhang Z, Li X, Zeng W, Wang Y, Hei Z, Yuan D. Dual-regulation by Cx32 in hepatocyte to trigger and worsen liver graft injury. Transl Res 2023; 262:44-59. [PMID: 37507007 DOI: 10.1016/j.trsl.2023.07.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 06/28/2023] [Accepted: 07/23/2023] [Indexed: 07/30/2023]
Abstract
Liver transplantation is the ultimate treatment option for end-stage liver failure. However, liver graft injury remains a challenge. This study aimed to investigate the role of connexin32 (Cx32) in liver graft injury and elucidate its mechanism of action. Through detecting liver graft samples from 6 patients, we observed that changes in the Cx32 level coincided with liver graft injury. Therefore, we established autologous orthotopic liver transplantation (AOLT) models using Cx32-knockout and wild-type mice and hypoxia/reoxygenation (H/R) and lipopolysaccharide (LPS) pretreatment models using alpha mouse liver 12 (AML12) cells, to explore Cx32 mechanisms in liver graft injury. Following in vivo and in vitro Cx32 knockout, oxidative stress and inflammatory response were inhibited through the regulation of PKC-α/NF-κB/NLRP3 and Nrf2/NOX4/ROS signaling pathways, thereby reducing Bak/Bax-related apoptosis and ameliorating liver graft injury. When the Cx32-based gap junction (GJ) was blocked with 2-aminoethoxydiphenyl borate (2-APB), ROS transfer was attenuated between neighboring cells, exacerbated oxidative stress and inflammatory response were prevented, and aggravation of liver graft injury was mitigated. These results highlight the dual regulation mechanism of Cx32 in liver graft injury. Through interaction with PKC-α, Cx32 regulated the NF-κB/NLRP3 and Nrf2/NOX4/ROS signaling pathways, thus directly triggering oxidative stress and inflammatory response. Simultaneously, mass-produced ROS were transferred to neighboring cells through Cx32 channels, for which oxidative stress and the inflammatory response were aggravated indirectly. Finally, Bak/Bax-related apoptosis was activated, thereby worsening liver graft injury. Our findings propose Cx32 as a dual mechanistic factor for oxidative stress and inflammatory signaling pathways in regulating cell apoptosis on liver graft injury, which suggests a promising therapeutic targets for liver graft injury.
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Affiliation(s)
- Fei Huang
- Department of Anesthesiology, Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, P. R. China
| | - Zhizhao Deng
- Department of Anesthesiology, Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, P. R. China
| | - Qian Zhang
- Department of Anesthesiology, Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, P. R. China
| | - Zheng Zhang
- Department of Anesthesiology, Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, P. R. China
| | - Xianlong Li
- Department of Anesthesiology, Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, P. R. China
| | - Weiqi Zeng
- Department of Anesthesiology, Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, P. R. China
| | - Yanling Wang
- Department of Anesthesiology, Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, P. R. China.
| | - Ziqing Hei
- Department of Anesthesiology, Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, P. R. China.
| | - Dongdong Yuan
- Department of Anesthesiology, Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, P. R. China.
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3
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Miller AL, Fuller-Carter PI, Masarini K, Samardzija M, Carter KW, Rashwan R, Lim XR, Brunet AA, Chopra A, Ram R, Grimm C, Ueffing M, Carvalho LS, Trifunović D. Increased H3K27 trimethylation contributes to cone survival in a mouse model of cone dystrophy. Cell Mol Life Sci 2022; 79:409. [PMID: 35810394 PMCID: PMC9271452 DOI: 10.1007/s00018-022-04436-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 06/16/2022] [Accepted: 06/17/2022] [Indexed: 11/30/2022]
Abstract
Inherited retinal diseases (IRDs) are a heterogeneous group of blinding disorders, which result in dysfunction or death of the light-sensing cone and rod photoreceptors. Despite individual IRDs (Inherited retinal disease) being rare, collectively, they affect up to 1:2000 people worldwide, causing a significant socioeconomic burden, especially when cone-mediated central vision is affected. This study uses the Pde6ccpfl1 mouse model of achromatopsia, a cone-specific vision loss IRD (Inherited retinal disease), to investigate the potential gene-independent therapeutic benefits of a histone demethylase inhibitor GSK-J4 on cone cell survival. We investigated the effects of GSK-J4 treatment on cone cell survival in vivo and ex vivo and changes in cone-specific gene expression via single-cell RNA sequencing. A single intravitreal GSK-J4 injection led to transcriptional changes in pathways involved in mitochondrial dysfunction, endoplasmic reticulum stress, among other key epigenetic pathways, highlighting the complex interplay between methylation and acetylation in healthy and diseased cones. Furthermore, continuous administration of GSK-J4 in retinal explants increased cone survival. Our results suggest that IRD (Inherited retinal disease)-affected cones respond positively to epigenetic modulation of histones, indicating the potential of this approach in developing a broad class of novel therapies to slow cone degeneration.
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Affiliation(s)
- Annie L Miller
- Retinal Genomics and Therapy Group, Lions Eye Institute Ltd, 2 Verdun Street, Nedlands, WA, 6009, Australia
- Centre for Ophthalmology and Visual Science, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia
| | - Paula I Fuller-Carter
- Retinal Genomics and Therapy Group, Lions Eye Institute Ltd, 2 Verdun Street, Nedlands, WA, 6009, Australia
| | - Klaudija Masarini
- Institute for Ophthalmic Research, Tübingen University, Elfriede-Aulhorn-Straße 7, 72076, Tübingen, Germany
| | - Marijana Samardzija
- Lab for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zürich, University of Zürich, Zurich, Switzerland
| | - Kim W Carter
- Analytical Computing Solutions, Willetton, WA, 6155, Australia
| | - Rabab Rashwan
- Retinal Genomics and Therapy Group, Lions Eye Institute Ltd, 2 Verdun Street, Nedlands, WA, 6009, Australia
- Department of Microbiology and Immunology, Faculty of Medicine, Minia University, Minia, Egypt
| | - Xin Ru Lim
- Retinal Genomics and Therapy Group, Lions Eye Institute Ltd, 2 Verdun Street, Nedlands, WA, 6009, Australia
- Centre for Ophthalmology and Visual Science, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia
| | - Alicia A Brunet
- Retinal Genomics and Therapy Group, Lions Eye Institute Ltd, 2 Verdun Street, Nedlands, WA, 6009, Australia
- Centre for Ophthalmology and Visual Science, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia
| | - Abha Chopra
- Institute for Immunology and Infectious Diseases, Murdoch University, Murdoch, WA, Australia
- Department of Medicine, Vanderbilt University Medical Centre, Nashville, TN, USA
| | - Ramesh Ram
- Institute for Immunology and Infectious Diseases, Murdoch University, Murdoch, WA, Australia
| | - Christian Grimm
- Lab for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zürich, University of Zürich, Zurich, Switzerland
| | - Marius Ueffing
- Institute for Ophthalmic Research, Tübingen University, Elfriede-Aulhorn-Straße 7, 72076, Tübingen, Germany
| | - Livia S Carvalho
- Retinal Genomics and Therapy Group, Lions Eye Institute Ltd, 2 Verdun Street, Nedlands, WA, 6009, Australia.
- Centre for Ophthalmology and Visual Science, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.
| | - Dragana Trifunović
- Institute for Ophthalmic Research, Tübingen University, Elfriede-Aulhorn-Straße 7, 72076, Tübingen, Germany.
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4
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Visual pigment-deficient cones survive and mediate visual signaling despite the lack of outer segments. Proc Natl Acad Sci U S A 2022; 119:2115138119. [PMID: 35197287 PMCID: PMC8892328 DOI: 10.1073/pnas.2115138119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/30/2021] [Indexed: 11/18/2022] Open
Abstract
Rhodopsin and cone opsins are essential for light detection in vertebrate rods and cones, respectively. It is well established that rhodopsin is required for rod phototransduction, outer segment disk morphogenesis, and rod viability. However, the roles of cone opsins are less well understood. In this study, we adopted a loss-of-function approach to investigate the physiological roles of cone opsins in mice. We showed that cones lacking cone opsins do not form normal outer segments due to the lack of disk morphogenesis. Surprisingly, cone opsin-deficient cones survive for at least 12 mo, which is in stark contrast to the rapid rod degeneration observed in rhodopsin-deficient mice, suggesting that cone opsins are dispensable for cone viability. Although the mutant cones do not respond to light directly, they maintain a normal dark current and continue to mediate visual signaling by relaying the rod signal through rod-cone gap junctions. Our work reveals a striking difference between the role of rhodopsin and cone opsins in photoreceptor viability.
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5
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Charish J, Shabanzadeh AP, Chen D, Mehlen P, Sethuramanujam S, Harada H, Bonilha VL, Awatramani G, Bremner R, Monnier PP. Neogenin neutralization prevents photoreceptor loss in inherited retinal degeneration. J Clin Invest 2020; 130:2054-2068. [PMID: 32175920 DOI: 10.1172/jci125898] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 01/14/2020] [Indexed: 02/05/2023] Open
Abstract
Inherited retinal degenerations (IRDs) are characterized by the progressive loss of photoreceptors and represent one of the most prevalent causes of blindness among working-age populations. Cyclic nucleotide dysregulation is a common pathological feature linked to numerous forms of IRD, yet the precise mechanisms through which this contributes to photoreceptor death remain elusive. Here we demonstrate that cAMP induced upregulation of the dependence receptor neogenin in the retina. Neogenin levels were also elevated in both human and murine degenerating photoreceptors. We found that overexpressing neogenin in mouse photoreceptors was sufficient to induce cell death, whereas silencing neogenin in degenerating murine photoreceptors promoted survival, thus identifying a pro-death signal in IRDs. A possible treatment strategy is modeled whereby peptide neutralization of neogenin in Rd1, Rd10, and Rho P23H-knockin mice promotes rod and cone survival and rescues visual function as measured by light-evoked retinal ganglion cell recordings, scotopic/photopic electroretinogram recordings, and visual acuity tests. These results expose neogenin as a critical link between cAMP and photoreceptor death, and identify a druggable target for the treatment of retinal degeneration.
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Affiliation(s)
- Jason Charish
- Vision Division, Krembil Research Institute, Toronto, Ontario, Canada.,Department of Physiology and
| | - Alireza P Shabanzadeh
- Vision Division, Krembil Research Institute, Toronto, Ontario, Canada.,Department of Anatomy, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Danian Chen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada.,Research Laboratory of Ophthalmology and Vision Sciences, State Key Laboratory of Biotherapy and.,Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, China
| | - Patrick Mehlen
- Apoptosis, Cancer and Development Laboratory, INSERM U1052, CNRS UMR5286, Université de Lyon, Lyon, France
| | | | - Hidekiyo Harada
- Vision Division, Krembil Research Institute, Toronto, Ontario, Canada
| | - Vera L Bonilha
- Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Gautam Awatramani
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| | - Rod Bremner
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada.,Department of Laboratory Medicine and Pathobiology and.,Department of Ophthalmology and Vision Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Philippe P Monnier
- Vision Division, Krembil Research Institute, Toronto, Ontario, Canada.,Department of Physiology and.,Department of Ophthalmology and Vision Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
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6
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Rod function deficit in retained photoreceptors of patients with class B Rhodopsin mutations. Sci Rep 2020; 10:12552. [PMID: 32724127 PMCID: PMC7387454 DOI: 10.1038/s41598-020-69456-3] [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] [Received: 05/21/2020] [Accepted: 07/09/2020] [Indexed: 12/27/2022] Open
Abstract
A common inherited retinal disease is caused by mutations in RHO expressed in rod photoreceptors that provide vision in dim ambient light. Approximately half of all RHO mutations result in a Class B phenotype where mutant rods are retained in some retinal regions but show severe degeneration in other regions. We determined the natural history of dysfunction and degeneration of retained rods by serially evaluating patients. Even when followed for more than 20 years, rod function and structure at some retinal locations could remain unchanged. Other locations showed loss of both vision and photoreceptors but the rate of rod vision loss was greater than the rate of photoreceptor degeneration. This unexpected divergence in rates with disease progression implied the development of a rod function deficit beyond loss of cells. The divergence of progression rates was also detectable over a short interval of 2 years near the health-disease transition in the superior retina. A model of structure–function relationship supported the existence of a large rod function deficit which was also most prominent near regions of health-disease transition. Our studies support the realistic therapeutic goal of improved night vision for retinal regions specifically preselected for rod function deficit in patients.
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7
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Cx43 Inhibition Attenuates Sepsis-Induced Intestinal Injury via Downregulating ROS Transfer and the Activation of the JNK1/Sirt1/FoxO3a Signaling Pathway. Mediators Inflamm 2019; 2019:7854389. [PMID: 30948926 PMCID: PMC6425293 DOI: 10.1155/2019/7854389] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 12/05/2018] [Indexed: 12/17/2022] Open
Abstract
Intestinal injury has long been considered to play a crucial role in the pathophysiology of sepsis and has even been characterized as the “motor” of it. Thus, we explored the effects of connexin43 (Cx43) on sepsis-induced intestinal injury in order to provide potential therapeutic strategies. Rat cecal ligation and puncture (CLP) models in vivo and cell models (IEC-6 cells) pretreated with LPS in vitro were used in the current study. Firstly, different methods, such as Cx43 inhibitors (18-α-GA and oleamide) or siRNA targeting Cx43 and N-acetyl cysteine (NAC) (a kind of ROS scavenger), were used to observe the effects of Cx43 channels mediating ROS transfer on intestinal injury. Secondly, the influence of ROS content on the activity of the JNK1/Sirt1/FoxO3a signaling pathway was explored through the application of NAC, sp600125 (a JNK1 inhibitor), and nicotinamide (a Sirt1 inhibitor). Finally, luciferase assays and ChIP were used to determine the direct regulation of FoxO3a on proapoptotic proteins, Bim and Puma. The results showed that sepsis-induced intestinal injury presented a dynamic change, coincident with the alternation of Cx43 expression. The inhibition of Cx43 attenuated CLP-induced intestinal injury in vivo and LPS-induced IEC-6 injury in vitro. The changes of Cx43 channel function regulated ROS transfer between the neighboring cells, which mediated the activation of the JNK1/Sirt1/FoxO3a signaling pathway. FoxO3a directly affected its downstream target genes, Bim and Puma, which are responsible for cell or tissue apoptosis. In summary, our results suggest that Cx43 inhibition suppresses ROS transfer and inactivates the JNK1/Sirt1/FoxO3a signaling pathway to protect against sepsis-induced intestinal injury.
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8
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O'Brien J, Bloomfield SA. Plasticity of Retinal Gap Junctions: Roles in Synaptic Physiology and Disease. Annu Rev Vis Sci 2018; 4:79-100. [DOI: 10.1146/annurev-vision-091517-034133] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Electrical synaptic transmission via gap junctions underlies direct and rapid neuronal communication in the central nervous system. The diversity of functional roles played by electrical synapses is perhaps best exemplified in the vertebrate retina, in which gap junctions are expressed by each of the five major neuronal types. These junctions are highly plastic; they are dynamically regulated by ambient illumination and circadian rhythms acting through light-activated neuromodulators. The networks formed by electrically coupled neurons provide plastic, reconfigurable circuits positioned to play key and diverse roles in the transmission and processing of visual information at every retinal level. Recent work indicates gap junctions also play a role in the progressive cell death and aberrant activity seen in various pathological conditions of the retina. Gap junctions thus form potential targets for novel neuroprotective therapies in the treatment of neurodegenerative retinal diseases such as glaucoma and ischemic retinopathies.
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Affiliation(s)
- John O'Brien
- Department of Ophthalmology and Visual Science, University of Texas Health Science Center, Houston, Texas 77030, USA
| | - Stewart A. Bloomfield
- Department of Biological and Vision Sciences, State University of New York College of Optometry, New York, NY 10036, USA
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9
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Campochiaro PA, Mir TA. The mechanism of cone cell death in Retinitis Pigmentosa. Prog Retin Eye Res 2017; 62:24-37. [PMID: 28962928 DOI: 10.1016/j.preteyeres.2017.08.004] [Citation(s) in RCA: 177] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Revised: 08/31/2017] [Accepted: 08/31/2017] [Indexed: 12/16/2022]
Abstract
Retinitis Pigmentosa (RP) is a group of diseases in which one of a large number of mutations causes death of rod photoreceptors. After rods die, cone photoreceptors slowly degenerate in a characteristic pattern. The mechanism of rod cell death varies depending upon the gene that is mutated and the rate that rods degenerate is an important prognostic feature, because cones do not begin to degenerate until almost all rods have been eliminated. Rod cell death causes night blindness, but visual disability and blindness result from cone degeneration and therefore it is critical to determine the mechanisms by which it occurs. The death of rods reduces oxygen consumption resulting in high tissue levels of oxygen in the outer retina. The excess oxygen stimulates superoxide radical production by mismatches in the electron transport chain in mitochondria and by stimulation of NADPH oxidase activity in cytoplasm. The high levels of superoxide radicals overwhelm the antioxidant defense system and generate more reactive species including peroxynitrite which is extremely damaging and difficult to detoxify. This results in progressive oxidative damage in cones which contributes to cone cell death and loss of function because drugs or gene transfer that reduce oxidative stress promote cone survival and maintenance of function. Compared with aqueous humor samples from control patients, those from patients with RP show significant elevation of carbonyl content on proteins indicating oxidative damage and a reduction in the ratio of reduced to oxidized glutathione indicating depletion of a major component of the antioxidant defense system from ongoing oxidative stress. The first step in clinical trials will be to identify doses of therapeutic agents that reverse these biomarkers of disease to assist in design of much longer trials with functional and anatomic endpoints.
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Affiliation(s)
- Peter A Campochiaro
- Departments of Ophthalmology and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States.
| | - Tahreem A Mir
- Departments of Ophthalmology and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
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10
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Wu W, Fan L, Bao Z, Zhang Y, Peng Y, Shao M, Xiang Y, Zhang X, Wang Q, Tao L. The cytoplasmic translocation of Cx32 mediates cisplatin resistance in ovarian cancer cells. Biochem Biophys Res Commun 2017; 487:292-299. [PMID: 28412364 DOI: 10.1016/j.bbrc.2017.04.053] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 04/11/2017] [Indexed: 01/09/2023]
Abstract
Ovarian cancer is the most lethal gynecologic malignancy, and cisplatin is one of the first-line chemotherapeutic agents. However, acquired cisplatin resistance prevents the successful treatment of patients with ovarian cancer. Gap junction (GJ) and connexin (Cx) are closely related to tumor formation, but the relationship between cisplatin resistance and GJ or Cx are undetermined. In this study, we established the cisplatin-resistant human ovarian cancer cell line A2780-CDDP. Here we showed that cisplatin resistance was correlated to the loss of GJ and the upregulation of Cx32 expression. Enhancing GJ in A2780-CDDP cells could increase the apoptotic response to cisplatin treatment. Furthermore, although Cx32 expression was increased in A2780-CDDP cells, it was more localized to the cytoplasm rather than in the membrane, and knockdown of Cx32 in A2780-CDDP cells sensitized them to cisplatin treatment. In summary, Cx32 is involved in cisplatin resistance, and cytoplasmic Cx32 plays an important role in chemoresistance.
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Affiliation(s)
- Weili Wu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, People's Republic of China
| | - Lixia Fan
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, People's Republic of China
| | - Zeqing Bao
- Zhaoqing Medical College Pharmacology Teaching and Research Section, Zhaoqing 526020, People's Republic of China
| | - Yu Zhang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, People's Republic of China
| | - Yuexia Peng
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, People's Republic of China
| | - Min Shao
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, People's Republic of China
| | - Yuke Xiang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, People's Republic of China
| | - Xiaomin Zhang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, People's Republic of China
| | - Qin Wang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, People's Republic of China
| | - Liang Tao
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, People's Republic of China.
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11
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Asteriti S, Gargini C, Cangiano L. Connexin 36 expression is required for electrical coupling between mouse rods and cones. Vis Neurosci 2017; 34:E006. [PMID: 28965521 DOI: 10.1017/s0952523817000037] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Rod-cone gap junctions mediate the so-called "secondary rod pathway", one of three routes that convey rod photoreceptor signals across the retina. Connexin 36 (Cx36) is expressed at these gap junctions, but an unidentified connexin protein also seems to be expressed. Cx36 knockout mice have been used extensively in the quest to dissect the roles in vision of all three pathways, with the assumption, never directly tested, that rod-cone electrical coupling is abolished by deletion of this connexin isoform. We previously showed that when wild type mouse cones couple to rods, their apparent dynamic range is extended toward lower light intensities, with the appearance of large responses to dim flashes (up to several mV) originating in rods. Here we recorded from the cones of Cx36del[LacZ]/del[LacZ] mice and found that dim flashes of the same intensity evoked at most small sub-millivolt responses. Moreover, these residual responses originated in the cones themselves, since: (i) their spectral preference matched that of the recorded cone and not of rods, (ii) their time-to-peak was shorter than in coupled wild type cones, (iii) a pharmacological block of gap junctions did not reduce their amplitude. Taken together, our data show that rod signals are indeed absent in the cones of Cx36 knockout mice. This study is the first direct demonstration that Cx36 is crucial for the assembly of functional rod-cone gap junctional channels, implying that its genetic deletion is a reliable experimental approach to eliminate rod-cone coupling.
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Affiliation(s)
- Sabrina Asteriti
- Department of Translational Research,University of Pisa,Pisa,Italy
| | | | - Lorenzo Cangiano
- Department of Translational Research,University of Pisa,Pisa,Italy
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12
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Brüggen B, Kremser C, Bickert A, Ebel P, Vom Dorp K, Schultz K, Dörmann P, Willecke K, Dedek K. Defective ceramide synthases in mice cause reduced amplitudes in electroretinograms and altered sphingolipid composition in retina and cornea. Eur J Neurosci 2016; 44:1700-13. [PMID: 27086873 DOI: 10.1111/ejn.13260] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 04/08/2016] [Indexed: 01/24/2023]
Abstract
Complex sphingolipids are strongly expressed in neuronal tissue and contain ceramides in their backbone. Ceramides are synthesized by six ceramide synthases (CerS1-6). Although it is known that each tissue has a unique profile of ceramide synthase expression and ceramide synthases are implicated in several neurodegenerative disorders, the expression of ceramide synthase isoforms has not been investigated in the retina. Here we demonstrate CerS1, CerS2 and CerS4 expression in mouse retina and cornea, with CerS4 ubiquitously expressed in all retinal neurons and Müller cells. To test whether ceramide synthase deficiency affects retinal function, we compared electroretinograms and retina morphology between wild-type and CerS1-, CerS2- and CerS4-deficient mice. Electroretinograms were strongly reduced in amplitude in ceramide synthase-deficient mice, suggesting that signalling in the outer retina is affected. However, the number of photoreceptors and cone outer segment length were unaltered and no changes in retinal layer thickness or synaptic structures were found. Mass spectrometric analyses of ceramides, hexosyl-ceramides and sphingomyelins showed that C20 to C24 acyl-containing species were decreased whereas C16-containing species were increased in the retina of ceramide synthase-deficient mice. Similar but smaller changes were also found in the cornea. Thus, we hypothesize that the replacement of very long-chain fatty acyl residues by shorter C16 residues may affect the electrical properties of retina and cornea, and alter receptor-mediated signal transduction, vesicle-mediated synaptic transmission or corneal light transmission. Future studies need to identify the molecular targets of ceramides or derived sphingolipids in light signal transduction and transmission in the eye.
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Affiliation(s)
- Bianca Brüggen
- Neurobiology, University of Oldenburg, 26111, Oldenburg, Germany
| | | | - Andreas Bickert
- Life and Medical Sciences Institute, University of Bonn, Bonn, Germany
| | - Philipp Ebel
- Life and Medical Sciences Institute, University of Bonn, Bonn, Germany
| | - Katharina Vom Dorp
- Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, Bonn, Germany
| | - Konrad Schultz
- Neurobiology, University of Oldenburg, 26111, Oldenburg, Germany
| | - Peter Dörmann
- Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, Bonn, Germany
| | - Klaus Willecke
- Life and Medical Sciences Institute, University of Bonn, Bonn, Germany
| | - Karin Dedek
- Neurobiology, University of Oldenburg, 26111, Oldenburg, Germany.,Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
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13
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Mathematical and computational models of the retina in health, development and disease. Prog Retin Eye Res 2016; 53:48-69. [PMID: 27063291 DOI: 10.1016/j.preteyeres.2016.04.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Revised: 04/05/2016] [Accepted: 04/05/2016] [Indexed: 12/12/2022]
Abstract
The retina confers upon us the gift of vision, enabling us to perceive the world in a manner unparalleled by any other tissue. Experimental and clinical studies have provided great insight into the physiology and biochemistry of the retina; however, there are questions which cannot be answered using these methods alone. Mathematical and computational techniques can provide complementary insight into this inherently complex and nonlinear system. They allow us to characterise and predict the behaviour of the retina, as well as to test hypotheses which are experimentally intractable. In this review, we survey some of the key theoretical models of the retina in the healthy, developmental and diseased states. The main insights derived from each of these modelling studies are highlighted, as are model predictions which have yet to be tested, and data which need to be gathered to inform future modelling work. Possible directions for future research are also discussed. Whilst the present modelling studies have achieved great success in unravelling the workings of the retina, they have yet to achieve their full potential. For this to happen, greater involvement with the modelling community is required, and stronger collaborations forged between experimentalists, clinicians and theoreticians. It is hoped that, in addition to bringing the fruits of current modelling studies to the attention of the ophthalmological community, this review will encourage many such future collaborations.
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14
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Tse DY, Lotfi P, Simons DL, Sardiello M, Wu SM. Electrophysiological and Histological Characterization of Rod-Cone Retinal Degeneration and Microglia Activation in a Mouse Model of Mucopolysaccharidosis Type IIIB. Sci Rep 2015; 5:17143. [PMID: 26607664 PMCID: PMC4660851 DOI: 10.1038/srep17143] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 10/26/2015] [Indexed: 02/07/2023] Open
Abstract
Sanfilippo syndrome Type B or Mucopolysaccharidosis IIIB (MPS IIIB) is a neurodegenerative autosomal recessive lysosomal storage disorder in which patients suffer severe vision loss from associated retinopathy. Here we sought to study the underlying retinal functional and morphological changes associated with MPS IIIB disease progression using the established model of MPS IIIB, the B6.129S6-Naglu(tm1Efn)/J mouse line. Electroretinogram (ERG) was recorded from MPS IIIB and wild-type (WT) mice at the age of 28 and 46 weeks, and retinal tissues were subsequently collected for immunohistochemistry analysis. At the 28th week, rod a- and b-wave amplitudes were significantly diminished in MPS IIIB compared to WT mice. The cone a- and b-waves of MPS IIIB mice were not significantly different from those of the control at the 28th week but were significantly diminished at the 46 th week, when MPS IIIB mice showed a major loss of rods and rod bipolar cells in both central and peripheral regions and a minor loss of cones in the periphery. Activation of microglia and neovascularization were also detected in the MPS IIIB retina. The new findings that cones and rod bipolar cells also undergo degeneration, and that retinal microglia are activated, will inform future development of therapeutic strategies.
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Affiliation(s)
- Dennis Y Tse
- Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston TX, USA.,School of Optometry, The Hong Kong Polytechnic University, Hong Kong
| | - Parisa Lotfi
- Department of Human and Molecular Genetics, Baylor College of Medicine, Jan and Dun Duncan Neurological Research Institute, Texas Children's Hospital, Houston TX, USA
| | - David L Simons
- Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston TX, USA
| | - Marco Sardiello
- Department of Human and Molecular Genetics, Baylor College of Medicine, Jan and Dun Duncan Neurological Research Institute, Texas Children's Hospital, Houston TX, USA
| | - Samuel M Wu
- Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston TX, USA
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15
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Sothilingam V, Garcia Garrido M, Jiao K, Buena-Atienza E, Sahaboglu A, Trifunović D, Balendran S, Koepfli T, Mühlfriedel R, Schön C, Biel M, Heckmann A, Beck SC, Michalakis S, Wissinger B, Seeliger MW, Paquet-Durand F. Retinitis pigmentosa: impact of different Pde6a point mutations on the disease phenotype. Hum Mol Genet 2015; 24:5486-99. [PMID: 26188004 DOI: 10.1093/hmg/ddv275] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 07/09/2015] [Indexed: 11/13/2022] Open
Abstract
Mutations in the PDE6A gene can cause rod photoreceptors degeneration and the blinding disease retinitis pigmentosa (RP). While a number of pathogenic PDE6A mutations have been described, little is known about their impact on compound heterozygous situations and potential interactions of different disease-causing alleles. Here, we used a novel mouse model for the Pde6a R562W mutation in combination with an existing line carrying the V685M mutation to generate compound heterozygous Pde6a V685M/R562W animals, exactly homologous to a case of human RP. We compared the progression of photoreceptor degeneration in these compound heterozygous mice with the homozygous V685M and R562W mutants, and additionally with the D670G line that is known for a relatively mild phenotype. We investigated PDE6A expression, cyclic guanosine mono-phosphate accumulation, calpain and caspase activity, in vivo retinal function and morphology, as well as photoreceptor cell death and survival. This analysis confirms the severity of different Pde6a mutations and indicates that compound heterozygous mutants behave like intermediates of the respective homozygous situations. Specifically, the severity of the four different Pde6a situations may be categorized by the pace of photoreceptor degeneration: V685M (fastest) > V685M/R562W > R562W > D670G (slowest). While calpain activity was strongly increased in all four mutants, caspase activity was not. This points to the execution of non-apoptotic cell death and may lead to the identification of new targets for therapeutic interventions. For individual RP patients, our study may help to predict time-courses for Pde6a-related retinal degeneration and thereby facilitate the definition of a window-of-opportunity for clinical interventions.
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Affiliation(s)
- Vithiyanjali Sothilingam
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Schleichstr.4/3, Tuebingen 72076, Germany
| | - Marina Garcia Garrido
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Schleichstr.4/3, Tuebingen 72076, Germany
| | - Kangwei Jiao
- Cell Death Mechanisms Group, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany, Second People's Hospital of Yunnan Province and Fourth Affiliated Hospital of Kunming Medical University, 176 Qingnian Road, Wuhua, Kunming, Yunnan 650021, China
| | - Elena Buena-Atienza
- Molecular Genetics Laboratory, Centre for Ophthalmology, University Clinics Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Ayse Sahaboglu
- Cell Death Mechanisms Group, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Dragana Trifunović
- Cell Death Mechanisms Group, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Sukirthini Balendran
- Molecular Genetics Laboratory, Centre for Ophthalmology, University Clinics Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Tanja Koepfli
- Molecular Genetics Laboratory, Centre for Ophthalmology, University Clinics Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Regine Mühlfriedel
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Schleichstr.4/3, Tuebingen 72076, Germany
| | - Christian Schön
- Center for Integrated Protein Science Munich (CIPSM) at the Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich 81377, Germany and
| | - Martin Biel
- Center for Integrated Protein Science Munich (CIPSM) at the Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich 81377, Germany and
| | | | - Susanne C Beck
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Schleichstr.4/3, Tuebingen 72076, Germany
| | - Stylianos Michalakis
- Center for Integrated Protein Science Munich (CIPSM) at the Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich 81377, Germany and
| | - Bernd Wissinger
- Molecular Genetics Laboratory, Centre for Ophthalmology, University Clinics Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Mathias W Seeliger
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Schleichstr.4/3, Tuebingen 72076, Germany
| | - François Paquet-Durand
- Cell Death Mechanisms Group, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany,
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16
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Gene therapy restores vision in rd1 mice after removal of a confounding mutation in Gpr179. Nat Commun 2015; 6:6006. [PMID: 25613321 PMCID: PMC4354202 DOI: 10.1038/ncomms7006] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 12/01/2014] [Indexed: 12/21/2022] Open
Abstract
The rd1 mouse with a mutation in the Pde6b gene was the first strain of mice identified with a retinal degeneration. However, AAV-mediated gene supplementation of rd1 mice only results in structural preservation of photoreceptors, and restoration of the photoreceptor-mediated a-wave, but not in restoration of the bipolar cell-mediated b-wave. Here we show that a mutation in Gpr179 prevents the full restoration of vision in rd1 mice. Backcrossing rd1 with C57BL6 mice reveals the complete lack of b-wave in a subset of mice, consistent with an autosomal recessive Mendelian inheritance pattern. We identify a mutation in the Gpr179 gene, which encodes for a G-protein coupled receptor localized to the dendrites of ON-bipolar cells. Gene replacement in rd1 mice that are devoid of the mutation in Gpr179 successfully restores the function of both photoreceptors and bipolar cells, which is maintained for up to 13 months. Our discovery may explain the failure of previous gene therapy attempts in rd1 mice, and we propose that Grp179 mutation status should be taken into account in future studies involving rd1 mice.
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17
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Gap junction-mediated death of retinal neurons is connexin and insult specific: a potential target for neuroprotection. J Neurosci 2014; 34:10582-91. [PMID: 25100592 DOI: 10.1523/jneurosci.1912-14.2014] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Secondary cell death via gap junctions (GJs) plays a role in the propagation of neuronal loss under a number of degenerative disorders. Here, we examined the role of GJs in neuronal death in the retina, which has arguably the most diverse expression of GJs in the CNS. Initially, we induced apoptotic death by injecting single retinal ganglion cells and glia with cytochrome C and found that this resulted in the loss of neighboring cells to which they were coupled via GJs. We next found that pharmacological blockade of GJs eradicated nearly all amacrine cell loss and reduced retinal ganglion cell loss by ∼70% after induction of either excitotoxic or ischemic insult conditions. These data indicate that the GJ-mediated secondary cell death was responsible for the death of most cells. Whereas genetic deletion of the GJ subunit Cx36 increased cell survivability by ∼50% under excitotoxic condition, cell loss in Cx45 knock-out mouse retinas was similar to that seen in wild-type mice. In contrast, ablation of Cx45 reduced neuronal loss by ∼50% under ischemic insult, but ablation of Cx36 offered no protection. Immunolabeling of the connexins showed differential changes in protein expression consistent with their differing roles in propagating death signals under the two insults. These data indicate that secondary cell death is mediated by different cohorts of GJs dependent on the connexins they express and the type of initial insult. Our results suggest that targeting specific connexins offers a novel therapeutic strategy to reduce progressive cell loss under different neurodegenerative conditions.
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18
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Hoon M, Okawa H, Della Santina L, Wong ROL. Functional architecture of the retina: development and disease. Prog Retin Eye Res 2014; 42:44-84. [PMID: 24984227 DOI: 10.1016/j.preteyeres.2014.06.003] [Citation(s) in RCA: 348] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 06/08/2014] [Accepted: 06/22/2014] [Indexed: 12/22/2022]
Abstract
Structure and function are highly correlated in the vertebrate retina, a sensory tissue that is organized into cell layers with microcircuits working in parallel and together to encode visual information. All vertebrate retinas share a fundamental plan, comprising five major neuronal cell classes with cell body distributions and connectivity arranged in stereotypic patterns. Conserved features in retinal design have enabled detailed analysis and comparisons of structure, connectivity and function across species. Each species, however, can adopt structural and/or functional retinal specializations, implementing variations to the basic design in order to satisfy unique requirements in visual function. Recent advances in molecular tools, imaging and electrophysiological approaches have greatly facilitated identification of the cellular and molecular mechanisms that establish the fundamental organization of the retina and the specializations of its microcircuits during development. Here, we review advances in our understanding of how these mechanisms act to shape structure and function at the single cell level, to coordinate the assembly of cell populations, and to define their specific circuitry. We also highlight how structure is rearranged and function is disrupted in disease, and discuss current approaches to re-establish the intricate functional architecture of the retina.
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Affiliation(s)
- Mrinalini Hoon
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Haruhisa Okawa
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Luca Della Santina
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Rachel O L Wong
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA.
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19
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Ferrer-Martín RM, Martín-Oliva D, Sierra A, Carrasco MC, Martín-Estebané M, Calvente R, Marín-Teva JL, Navascués J, Cuadros MA. Microglial cells in organotypic cultures of developing and adult mouse retina and their relationship with cell death. Exp Eye Res 2014; 121:42-57. [PMID: 24582572 DOI: 10.1016/j.exer.2014.02.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Revised: 01/14/2014] [Accepted: 02/13/2014] [Indexed: 12/31/2022]
Abstract
Organotypic cultures of retinal explants allow the detailed analysis of microglial cells in a cellular microenvironment similar to that in the in situ retina, with the advantage of easy experimental manipulation. However, the in vitro culture causes changes in the retinal cytoarchitecture and induces a microglial response that may influence the results of these manipulations. The purpose of this study was to analyze the influence of the retinal age on changes in retinal cytoarchitecture, cell viability and death, and microglial phenotype and distribution throughout the in vitro culture of developing and adult retina explants. Explants from developing (3 and 10 postnatal days, P3 and P10) and adult (P60) mouse retinas were cultured for up to 10 days in vitro (div). Dead or dying cells were recognized by TUNEL staining, cell viability was determined by flow cytometry, and the numbers and distribution patterns of microglial cells were studied by flow cytometry and immunocytochemistry, respectively. The retinal cytoarchitecture was better preserved at prolonged culture times (10 div) in P10 retina explants than in P3 or adult explants. Particular patterns of cell viability and death were observed at each age: in general, explants from developing retinas showed higher cell viability and lower density of TUNEL-positive profiles versus adult retinas. The proportion of microglial cells relative to the whole population of retinal cells was higher in explants fixed immediately after their dissection (i.e., non-cultured) from adult retinas than in those from developing retinas. This proportion was always higher in non-cultured explants than in explants at 10 div, suggesting the death of some microglial cells during the culture. Activation of microglial cells, as revealed by their phenotypical appearance, was observed in both developing and adult retina explants from the beginning of the culture. Immunofluorescence with the anti-CD68 antibody showed that some activated microglial cells were CD68-positive but others were CD68-negative. Flow cytometry using CD68-labeling revealed that the percentage of CD68-positive microglial cells was much higher in developing than in adult retina explants, despite the activation of microglia in both types of explants, indicating that CD68-labeling was more closely related to the maturity degree of microglia than to their activation. Some swollen activated microglial cells entered the outer nuclear layer in developing and adult cultured retinal explants, whereas this layer was devoid of microglia in non-cultured explants. There was no apparent correlation between the distribution of microglia and that of TUNEL-labeled profiles. However, some swollen activated microglial cells in the outer and inner nuclear layers engulfed clusters of cell nuclei that were negative or weakly positive for TUNEL. This engulfment activity of microglia mimicked that observed in degenerative pathologies of the retina. We conclude that organotypic cultures from developing retinas show a higher rate of cell viability and better preservation of the normal cytoarchitecture in comparison to those obtained from adult retinas. In addition, the features of microglial response in cultured retinal explants show them to be a useful model for studying interactions between microglial cells and degenerating neurons in retinal diseases.
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Affiliation(s)
- Rosa M Ferrer-Martín
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain
| | - David Martín-Oliva
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain
| | - Ana Sierra
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain
| | - Maria-Carmen Carrasco
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain
| | - María Martín-Estebané
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain
| | - Ruth Calvente
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain
| | - José L Marín-Teva
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain
| | - Julio Navascués
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain
| | - Miguel A Cuadros
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain.
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20
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Abstract
Rod and cone photoreceptors are coupled by gap junctions (GJs), relatively large channels able to mediate both electrical and molecular communication. Despite their critical location in our visual system and evidence that they are dynamically gated for dark/light adaptation, the full impact that rod–cone GJs can have on cone function is not known. We recorded the photovoltage of mouse cones and found that the initial level of rod input increased spontaneously after obtaining intracellular access. This process allowed us to explore the underlying coupling capacity to rods, revealing that fully coupled cones acquire a striking rod-like phenotype. Calcium, a candidate mediator of the coupling process, does not appear to be involved on the cone side of the junctional channels. Our findings show that the anatomical substrate is adequate for rod–cone coupling to play an important role in vision and, possibly, in biochemical signaling among photoreceptors. DOI:http://dx.doi.org/10.7554/eLife.01386.001 People can see in a range of light levels—from dim moonlight to bright midday sun—because our eyes contain two types of light-sensitive cells: rods and cones. Rods are more plentiful than cones, and while they are sensitive at low light levels, rods can only provide grey-scale vision. Further, bright light can rapidly ‘dazzle’ the ability of rods to see in near-darkness, and they are slow to recover when this happens. In contrast, cones need bright light to function, but allow us to see in colour. The signals received by rods and cones are sent through the optic nerve to the brain, where they are interpreted as vision. However, ‘gap junctions’ that connect the rods and cones allow for electrical and chemical ‘crosstalk’ between these cells, before the signals then travel along the optic nerve. Furthermore, even though it is thought that the connections between rods and cones are regulated in response to light, the body’s daily rhythms and other biochemical signals, their importance for vision is not known. Now, Asteriti et al. have taken tissue slices from the retinas at the back of mice eyes, and measured the electrical signals generated when cones are exposed to light. This revealed that the rod-cone coupling is strong enough to make the cones responsive to dim light, just like rods. Moreover, the cones also recovered slowly after being exposed to flashes of bright light. When chemical inhibitors were used to block the gap junctions, the cones stopped behaving like rods and became less sensitive to dim light. The findings of Asteriti et al. show that rod-cone coupling is sufficient to play an important role in vision. The next challenge is to find out what this role is, and how it might be affected by different physiological conditions, including stress and injury. DOI:http://dx.doi.org/10.7554/eLife.01386.002
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Affiliation(s)
- Sabrina Asteriti
- Department of Translational Research, University of Pisa, Pisa, Italy
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