Diabetic retinopathy remains a leading cause of blindness in the United States. Recent clinical trials have demonstrated that targeting vascular endothelial growth factor (VEGF) can effectively prevent progression of vision loss and for some patients restore visual acuity. These studies demonstrate that medical therapy for the retina can effectively treat diabetic retinopathy. However, not all patients respond to anti-VEGF therapies, which require repeat intra-ocular injections with the risk of endophthalmitis. In addition to VEGF, a number of inflammatory factors are elevated in patients with diabetic retinopathy that are believed to contribute to disease pathology including tumor necrosis factor, the chemokine (C-C motif) ligand 2 (CCL2), interleukin 6 and 8. Therefore, understanding the mechanisms by which growth factors and inflammatory cytokines alter the retinal vascular endothelium leading to vascular permeability and angiogenesis remains of high significance. Research from the previous funding period has identified two important signaling pathways that control permeability in response to VEGF. The first pathway involves conventional protein kinase C (PKC) activation and phosphorylation of the tight junction protein occludin and is required for VEGF induced vascular permeability. Published and preliminary data also reveal that occludin phosphorylation contributes to growth control and angiogenesis. Thus, occludin phosphorylation downstream of VEGF activation contributes to both vascular permeability and angiogenesis suggesting an important role in growth and blood-retinal barrier differentiation. Further, research over the previous funding period has identified a second signaling pathway involving atypical PKC activation as required for permeability response to both VEGF and inflammatory cytokines such as TNF and CCL2. Utilizing mass spectrometry phosphoproteomic analysis we have identified downstream targets linking this pathway to small G-protein regulation and control of permeability. Here we propose to define the role of occludin phosphorylation in permeability and angiogenesis in vivo while also elucidating the aPKC activation pathway to the control of vascular permeability. Collectively, these studies will provide novel insight into the mechanisms of VEGF induced permeability and angiogenesis specifically through the control of the tight junctions' complex and small G-protein regulation of the cytoskeleton. This research is expected to provide new insight into the nature of blood vessel growth and maturation and identify new targets for therapeutic intervention that are effective against both growth factors and inflammatory cytokines.

Public Health Relevance

This proposal provides innovative research to determine the mechanisms by which endothelial cells proliferate and mature contributing to the blood-retinal barrier and how diabetes alters these vessels leading to macular edema and pathologic angiogenesis. Importantly, this research explores required pathways that regulate vascular permeability and may lead to new therapies for macular edema.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY012021-21
Application #
9608739
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Shen, Grace L
Project Start
1998-09-01
Project End
2019-12-31
Budget Start
2019-01-01
Budget End
2019-12-31
Support Year
21
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
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Dreffs, Alyssa; Henderson, Desmond; Dmitriev, Andrey V et al. (2018) Retinal pH and Acid Regulation During Metabolic Acidosis. Curr Eye Res 43:902-912
Lin, Cheng-Mao; Titchenell, Paul M; Keil, Jason M et al. (2018) Inhibition of Atypical Protein Kinase C Reduces Inflammation-Induced Retinal Vascular Permeability. Am J Pathol 188:2392-2405
Kady, Nermin M; Liu, Xuwen; Lydic, Todd A et al. (2018) ELOVL4-Mediated Production of Very Long-Chain Ceramides Stabilizes Tight Junctions and Prevents Diabetes-Induced Retinal Vascular Permeability. Diabetes 67:769-781
Ramos, Carla J; Lin, Chengmao; Liu, Xuwen et al. (2018) The EPAC-Rap1 pathway prevents and reverses cytokine-induced retinal vascular permeability. J Biol Chem 293:717-730
Díaz-Coránguez, Mónica; Ramos, Carla; Antonetti, David A (2017) The inner blood-retinal barrier: Cellular basis and development. Vision Res 139:123-137
Ramos, Carla J; Antonetti, David A (2017) The role of small GTPases and EPAC-Rap signaling in the regulation of the blood-brain and blood-retinal barriers. Tissue Barriers 5:e1339768
Díaz-Coránguez, Mónica; Chao, Daniel L; Salero, Enrique L et al. (2017) Cell autonomous sonic hedgehog signaling contributes to maintenance of retinal endothelial tight junctions. Exp Eye Res 164:82-89
Liu, Xuwen; Dreffs, Alyssa; Díaz-Coránguez, Monica et al. (2016) Occludin S490 Phosphorylation Regulates Vascular Endothelial Growth Factor-Induced Retinal Neovascularization. Am J Pathol 186:2486-99
Gonçalves, Andreia; Lin, Cheng-Mao; Muthusamy, Arivalagan et al. (2016) Protective Effect of a GLP-1 Analog on Ischemia-Reperfusion Induced Blood-Retinal Barrier Breakdown and Inflammation. Invest Ophthalmol Vis Sci 57:2584-92

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