Angiotensin II Plays as a Survival Factor in the Retinal Endotherial Cells Through Type 1 Receptor and PI 3-kinase-akt Pathway

Abstract

Abstract: : Purpose: Angiotensin II (Ang II) plays essential roles in the maintenance of vascular homeostasis. Recent experiments have shown that Ang II has specific effects on cell growth and apoptosis. The goal of this study was to investigate the effects of Ang II on retinal vascular endothelial cell survival. Methods: To quantitate the anti-apoptotic effects of Ang II, TUNEL assay and Caspase-3 activity of porcine retinal endothelial cells (PRECs) incubated with serum-free medium for 24 hrs. Western blot analysis for detection of the effects of Ang II on Akt and ERK1/2 phosphorylation and survivin expression was performed. The retinal vascular area of wild type and Ang II Type 1a receptor knock out (AT1a KO) mice exposed to 75% O2 from postnatal day 7 (P7) to P12 was evaluated. Results: Ang II dose-dependently inhibited apoptosis and Caspase-3 activation of PRECs under a serum-deprived state. 100nM of Ang II significantly inhibited the apoptotic cell rates (50%, p<0.0001) and Caspase-3 activity (40%, p<0.05) for 24 hrs. AT1 antagonist and LY294002, PI 3-kinase inhibitor, reversed the Ang II-induced anti-apoptotic effect, Akt and ERK1/2 phosphorylation and Caspase-3 inactivation. Ang II induced a significant increase of survivin expression in a time- and dose-dependent manner, with a maximal 7 folds increase after 24-hour stimulation (p<0.01). Expression of a dominant-negative form of Akt blocked the Ang II-induced survivin expression, anti-apoptotic effect and caspase-3 inactivity. AT1a KO mice showed 50.5% avascular area whereas wild type mice 38.6% (p<0.0001). Conclusions: The results indicates that Ang II can be a survival factor for retinal endothelial cells through AT1 activation and PI 3-kinase-Akt pathway.

Keywords: molecular biology • apoptosis/cell death • retina