The overall goal of this research is to establish whether maintenance of connexin 43 (Cx43)-mediated gap junction intercellular communication (GJIC) and Cx43 hemichannel (HC) activity in the retinal capillaries of diabetic patients plays a protective role against the development of retinal vascular cell loss and vascular permeability associated with diabetic retinopathy (DR). Substantial evidence suggests that reduced GJIC activity in retinal vascular cells may contribute to the breakdown of homeostatic balance in DR (1-4). We have shown that the expression of Cx43, the principal gap junction protein, is downregulated in retinal vascular cells in high glucose (HG) condition with concomitant reduction in GJIC activity (3, 4) that contributes to loss of retinal vascular cells and capillary leakage. Preliminary data indicate HG reduces Cx43 HC activity and trigger apoptotic cell death (5). Recently, we observed that maintenance of cell-cell coupling inhibits HG-induced apoptosis and excess cell monolayer permeability in vitro (6). Based on these findings, we hypothesize that preventing hyperglycemia-induced Cx43 downregulation and GJIC activity would promote vascular homeostasis, restore Cx43 HC activity and Cx43 phosphorylation, ultimately preventing loss of retinal vascular cells and capillary leakage in DR. The hypothesis is supported by findings from previous funding period that showed (i) HG-induced downregulation of Cx43 expression contributes to the breakdown of endothelial barrier tight junctions by reducing ZO-1 and occludin expression (7, 8) and that restoration of Cx43 expression (7) and gap junction coupling prevents HG-induced apoptosis and cell monolayer permeability in retinal endothelial cells (6); (ii) Cx43 expression is downregulated in human retinas, and that the severity of retinal vascular cell loss is linked to the extent to which Cx43 downregulation develops (9). The hypothesis is also supported by key preliminary data that Cx43 phosphorylation is altered at s368 and s373 negatively impacting Cx43 functionality in GJIC and HC activity. Additionally, reports indicate that ZO-1, a component of the tight junction, interacts directly with Cx43 (10), and regulates Cx43-mediated GJIC activity (11, 12). Having observed ZO-1 to be reduced in retinal vascular cells by HG/diabetes (13), we propose to examine whether Cx43 downregulation, compromised GJIC, altered HC activity, and altered Cx43 phosphorylation promotes retinal vascular cell loss and tight junction dysfunction in vascular permeability. Findings are expected to provide valuable insight into a novel mechanism underlying retinal vascular cell loss and capillary leakage, and a potential strategy to prevent retinal vascular lesions in DR.

Public Health Relevance

Diabetic retinopathy is characterized by retinal vascular lesions that ultimately lead to vision loss and blindness. Currently, there is no cure for diabetic retinopathy, the leading cause of blindness in the working age Americans. It is expected that findings from this project would provide valuable insight towards testing a novel mechanism underlying retinal vascular cell loss and capillary leakage, the two prominent retinal vascular lesions associated with the pathogenesis of diabetic retinopathy.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY018218-06
Application #
9981197
Study Section
Diseases and Pathophysiology of the Visual System Study Section (DPVS)
Program Officer
Shen, Grace L
Project Start
2009-01-01
Project End
2023-08-31
Budget Start
2020-09-01
Budget End
2021-08-31
Support Year
6
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Boston Medical Center
Department
Type
DUNS #
005492160
City
Boston
State
MA
Country
United States
Zip Code
02118
Roy, Sayon; Kim, Dongjoon; Lim, Remington (2017) Cell-cell communication in diabetic retinopathy. Vision Res 139:115-122
Roy, Sayon; Kern, Timothy S; Song, Brian et al. (2017) Mechanistic Insights into Pathological Changes in the Diabetic Retina: Implications for Targeting Diabetic Retinopathy. Am J Pathol 187:9-19
Roy, Sayon; Jiang, Jean X; Li, An-Fei et al. (2017) Connexin channel and its role in diabetic retinopathy. Prog Retin Eye Res 61:35-59
Tien, Thomas; Muto, Tetsuya; Zhang, Joyce et al. (2016) Association of reduced Connexin 43 expression with retinal vascular lesions in human diabetic retinopathy. Exp Eye Res 146:103-6
Roy, Sayon; Amin, Shruti; Roy, Sumon (2016) Retinal fibrosis in diabetic retinopathy. Exp Eye Res 142:71-5
Roy, Sumon; Kim, Dongjoon; Hernández, Cristina et al. (2015) Beneficial effects of fenofibric acid on overexpression of extracellular matrix components, COX-2, and impairment of endothelial permeability associated with diabetic retinopathy. Exp Eye Res 140:124-129
Muto, Tetsuya; Tien, Thomas; Kim, Dongjoon et al. (2014) High glucose alters Cx43 expression and gap junction intercellular communication in retinal Müller cells: promotes Müller cell and pericyte apoptosis. Invest Ophthalmol Vis Sci 55:4327-37
Tien, Thomas; Muto, Tetsuya; Barrette, Kevin et al. (2014) Downregulation of Connexin 43 promotes vascular cell loss and excess permeability associated with the development of vascular lesions in the diabetic retina. Mol Vis 20:732-41
Oshitari, Toshiyuki; Yamamoto, Shuichi; Roy, Sayon (2014) Increased expression of c-Fos, c-Jun and c-Jun N-terminal kinase associated with neuronal cell death in retinas of diabetic patients. Curr Eye Res 39:527-31
Roy, Sayon; Trudeau, Kyle; Roy, Sumon et al. (2013) Mitochondrial dysfunction and endoplasmic reticulum stress in diabetic retinopathy: mechanistic insights into high glucose-induced retinal cell death. Curr Clin Pharmacol 8:278-84

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