Insulin and TGFbeta-2 Potentiate VEGF Secretion from ARPE-19 Cells

Abstract

Abstract: : Purpose: Previous studies have demonstrated that insulin increases vascular endothelial growth factor (VEGF) mRNA and secreted protein levels in RPE cells through enhanced transcription of the VEGF gene. In the present study, we examined the effects of insulin on transforming growth factor beta two (TGFß2) secretion and the effects of insulin and exogenous TGFß2 on VEGF secretion. Methods: Human retinal pigment epithelial cells (ARPE-19) were exposed to 100 nM insulin for 24 hours. TGFß2 levels were measured at 6-hour time-points by an enzyme linked immunosorbant assay (ELISA). In a subsequent experiment, 2 ng/ml of exogenous TGFß2 with and without 100 nM insulin was added to the culture medium for 24 hours. Results: Secreted TGFß2 levels were increased at all time points with the 18 and 24-hour points displaying an accumulation of TGFß2 at 109% and 91.1% above control values. Insulin alone resulted in an increase of VEGF levels by 61.6% while TGFß2 alone resulted in an increase of VEGF by 141% over control values. The combination of TGFß2 and insulin for 24 hours resulted in a potentiated increase of secreted VEGF levels by 263%. Conclusion: These findings suggest that insulin and TGFß2 interact to promote VEGF secretion from ARPE-19 cells.

Keywords: 567 retinal pigment epithelium • 423 growth factors/growth factor receptors • 388 diabetic retinopathy