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 PLCgamma1.
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 PLCgamma1 was assessed by immunoblots of tyrosine phosphorylation.
Results: Cytotoxicity of H2O2 exposure was concentration-dependent (30% death with 250 microM; 87% with 500 microM at 8 h) and time-dependent (7% at 1 h; 30% at 8 h with 250 microM H2O2. Catalase abolished such relations. H2O2 increased PLCgamma1 expression more than that of PLCdelta1 and almost doubled total PLC enzymatic activity between 2 and 8 h, changes prevented by catalase. The PLC inhibitor U73112 (3 microM) enhanced the cytotoxic concentration and time effects of H2O2. In acute studies, H2O2 rapidly caused tyrosine phosphorylation of PLCgamma1.
Conclusion: H2O2 increased PLCgamma1 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 PLCgamma1 protein level, tyrosine phosphorylation of PLCgamma1 and PLC enzymatic activity to generate IP3.
(c) 2007 S. Karger AG, Basel