The purpose of the proposal is to understand the role of ET and its receptors in modulating retinal hemodynamics in the normal and diabetic state in vivo and in cultured retinal vascular cells. Since the first report showing the existence of ETA receptors in the retinal pericytes and the regulation of ET-1 expression by insulin, ET-1 and ET-3 have been shown to have many actions in retinal vascular cells. The investigator's results have established the fact that ET-1 via ETA receptor is a major regulator of vascular tone in the retina during normal homeostasis and hyperoxia and in the early stages of diabetic retinopathy. The increased vasoconstriction observed in these states are due to either overexpression of ET-1 or increase in its processing by endothelin converting enzyme (ECE) in the retina. Recently, the applicant has shown that insulin can decrease ET-1 gene expression in pericytes and smooth muscle cells which could partially explain the in vivo vasodilatory effect of insulin. At the signal transduction level, ET-1 and angiotensin can affect phospholipase C (PLC)-protein kinase C (PKC) activation and the tyrosine kinase cascade involving MAP kinase in pericytes and smooth muscle cells. The investigator has recently found that angiotensin and ET-1 can also activate a G-protein associated phosphatidylinositol 3-kinase (PI 3-kinase), thereby identifying a whole new signal transduction pathway for ET-1. Lastly, the finding that hyperglycemia can blunt ET-1's effect on PLC activation has been confirmed by smooth muscle cells and mesangial cells as well. The investigator proposes: (1) to characterize the expression and processing of ET-1 in retinal vascular cells as regulated by insulin, oxygen tension, angiotensin and hyperglycemia; (2) to identify the various signal transduction pathways used by ET-1 in retinal pericytes and in smooth muscle cells specifically on the activation of G-protein-associated PI 3-kinase and the association of these pathways to biological actions such as calcium flux, NO production and DNA synthesis; and (3) to determine the expression and the effect of ET-1 and ET-3 and their receptors in vivo on normal retinal hemodynamics and in diabetes.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY009178-08
Application #
2856909
Study Section
Visual Sciences C Study Section (VISC)
Project Start
1992-01-01
Project End
2001-12-31
Budget Start
1999-01-01
Budget End
1999-12-31
Support Year
8
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Joslin Diabetes Center
Department
Type
DUNS #
071723084
City
Boston
State
MA
Country
United States
Zip Code
02215
Kuroki, Tatsuya; Isshiki, Keiji; King, George L (2003) Oxidative stress: the lead or supporting actor in the pathogenesis of diabetic complications. J Am Soc Nephrol 14:S216-20
Yokota, Tamotsu; Ma, Ronald C; Park, Joong-Yeol et al. (2003) Role of protein kinase C on the expression of platelet-derived growth factor and endothelin-1 in the retina of diabetic rats and cultured retinal capillary pericytes. Diabetes 52:838-45
Veves, A; King, G L (2001) Can VEGF reverse diabetic neuropathy in human subjects? J Clin Invest 107:1215-8
Way, K J; Katai, N; King, G L (2001) Protein kinase C and the development of diabetic vascular complications. Diabet Med 18:945-59
Meier, M; King, G L (2000) Protein kinase C activation and its pharmacological inhibition in vascular disease. Vasc Med 5:173-85
Park, J Y; Takahara, N; Gabriele, A et al. (2000) Induction of endothelin-1 expression by glucose: an effect of protein kinase C activation. Diabetes 49:1239-48
Mori, F; King, G L; Clermont, A C et al. (2000) Endothelin-3 regulation of retinal hemodynamics in nondiabetic and diabetic rats. Invest Ophthalmol Vis Sci 41:3955-62
King, G L; Wakasaki, H (1999) Theoretical mechanisms by which hyperglycemia and insulin resistance could cause cardiovascular diseases in diabetes. Diabetes Care 22 Suppl 3:C31-7
Ishii, H; Koya, D; King, G L (1998) Protein kinase C activation and its role in the development of vascular complications in diabetes mellitus. J Mol Med 76:21-31
Takagi, H; King, G L; Aiello, L P (1998) Hypoxia upregulates glucose transport activity through an adenosine-mediated increase of GLUT1 expression in retinal capillary endothelial cells. Diabetes 47:1480-8

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