Activation of Phospholipase C[gamma]1 Protects Renal Arteriolar VSMCs from H2O2-Induced Cell Death

Background: We evaluated the effect of hydrogen peroxide (H2O2) on viability of vascular smooth muscle cells (VSMCs) of renal resistance arterioles and determined whether responses are modulated by activation of PLC[gamma]1. Methods: Phospholipase C (PLC)-isozyme protein levels and activity were measured using Western blot analysis and enzymatic production of phosphoinositol 1,4,5-trisphosphate (IP3), respectively. Stimulation of PLC[gamma]1 was assessed by immunoblots of tyrosine phosphorylation. Results: Cytotoxicity of H2O2 exposure was concentration-dependent (30% death with 250 μM; 87% with 500 μM at 8 h) and time-dependent (7% at 1 h; 30% at 8 h with 250 μM H2O2). Catalase abolished such relations. H2O2 increased PLC[gamma]1 expression more than that of PLCδ1 and almost doubled total PLC enzymatic activity between 2 and 8 h, changes prevented by catalase. The PLC inhibitor U73112 (3 μM) enhanced the cytotoxic concentration and time effects of H2O2. In acute studies, H2O2 rapidly caused tyrosine phosphorylation of PLC[gamma]1. Conclusion: H2O2 increased PLC[gamma]1 expression and almost doubled total PLC activity, changes abolished by catalase. We conclude that H2O2 is cytotoxic to cultured VSMCs of renal preglomerular arterioles, a process that is attenuated by compensatory increases in PLC[gamma]1 protein level, tyrosine phosphorylation of PLC[gamma]1 and PLC enzymatic activity to generate IP3. Copyright © 2007 S. Karger AG, Basel [PUBLICATION ABSTRACT]