Effect of Angiotensin II on Endothelial Cell Apoptosis and Survival and its Impact on Skeletal Muscle Angiogenesis after Electrical Stimulation

We have previously shown that skeletal muscle angiogenesis induced by electrical stimulation is significantly attenuated when SS‐13BN/Mcwi rats are fed a high salt diet. This effect was associated with a great increase in endothelial cell (EC) apoptosis compared to rats fed low salt. We hypothesized that the low levels of angiotensin II (AII) during high salt diet would increase EC apoptosis and consequently diminish the angiogenic response. To test this hypothesis rats fed a high salt diet (4% NaCl) received continuous infusion of AII (3ng/kg/min) or saline during 7 days of electrical stimulation. The Tibialis anterior (TA) muscles from stimulated and unstimulated hindlimb were removed and the level of EC apoptosis was determined by CD31/TUNEL double staining. In contrast to the saline infusion, AII decreased EC apoptosis and caused a significant increase (40%) in skeletal muscle angiogenesis. The effect of AII on EC apoptosis was confirmed in vitro when EC were incubated with AII under serum free conditions. After 24h of incubation, AII increased EC viability, increased the Bcl‐2/Bax ratio, and decreased EC apoptosis in a dose‐dependent manner. This effect was blocked by an AII type 1 receptor antagonist. Our data suggest that AII increases EC viability and protects EC from apoptosis possibly by inactivation of a mitochondrial apoptotic pathway. The attenuation of AII levels during high salt diet may induce EC apoptosis and consequently block the angiogenic response induced by electrical stimulation. (Support NIH HL29587, N01 HV‐28182)