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P.C. Kothary, S. Yu, S.S. Shah, R. Gupta, M.A. Del Monte; Insulin Stimulated Proliferation of Human Retinal Pigment Epithelial Cells Is Mediated by Stat5 Synthesis . Invest. Ophthalmol. Vis. Sci. 2005;46(13):440.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Several years after the onset of diabetes, diabetic retinopathy can occur in patients (DR) with diabetes mellitus (DM). Since insulin is the most common therapy in advance DM and its effect on signaling molecule like signal transducer and activator of transcription5 (STAT5) in hRPE cell is unknown, we investigated the effect of insulin on STAT5 synthesis in hRPE cells. Methods: Primary hRPE cell cultures were established from human eyes. Cells were treated with insulin and tyrphostin AG490 (AG490), an inhibitor of STAT signaling pathway. Cell proliferation was monitored by 3H–thymidine (3H–thy) incorporation and trypan blue exclusion methods. 14C–methionine labeled intracellular STAT5 (14C–STAT5) synthesis was determined by immunoprecipitating using STAT5 specific antibody. STAT5 specific antibody was also used for immunohistochemistry. Data were analyzed by Student 't' test. Results: Insulin increased hRPE cell proliferation in a dose dependent manner. Addition of AG490 inhibited insulin stimulated hRPE cell proliferation as monitored by 3H–thy incorporation (3521.0±224.4 vs. 1433.5±112.4, p<=0.05, mean±SEM, n=4). Insulin also increased 14C–STAT5 synthesis in a dose dependent manner. Addition of AG490 to insulin inhibited corresponding 14C–STAT5 synthesis (1858.46±285.3 vs.877.62±400.53, p<=0.05, mean±SEM, n=4). Immunohistochemical studies showed increased positive immunoreactivity of STAT5 in hRPE cells exposed to insulin. Addition of AG490 to individual insulin inhibited corresponding STAT5 protein immunoreactivity. Conclusions: Insulin is a mitogen for hRPE cells and it stimulates STAT5 synthesis. AG490 inhibits insulin stimulated STAT5 synthesis as well as hRPE cell proliferation. The data suggest that STAT5 produced locally in hRPE cells may be involved in the pathogenesis of diabetic retinopathy.
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