Probucol via inhibition of NHE1 attenuates LPS-accelerated atherosclerosis and promotes plaque stability in vivo.

Activation of Na(+)/H(+) exchanger 1 (NHE1) by lipopolysaccharide (LPS) via Ca(2+)/calpain is responsible in vascular smooth muscle cell (VSMC) apoptosis and to the process of atherosclerosis. Probucol is a lipid-lowering drug which has an anti-atherosclerosis effect. The mechanism remains poorly understood. Here we hypothesized that probucol via inhibition of NHE1 in VSMCs attenuates LPS-accelerated atherosclerosis and promotes plaque stability. Our results revealed that treatment of VSMCs with LPS increased the NHE1 activity in a time-dependent manner, associated with the increased Ca(2+)i. Probucol inhibited the LPS-induced increase of NHE1 activity in a dose-dependent manner in VSMCs for 24-hour co-incubation, as well as the change of Ca(2+)i. In addition, LPS enhanced the calpain activity. Both probucol and calcium chelation of Ca(2+) abolished the LPS-induced increase of calpain activity. Treatment of VSMCs with LPS reduced the expression of Bcl-2 without altering the mRNA level. Probucol inhibited the LPS-reduced expression of Bcl-2 protein in VSMCs. Animal studies indicated administration of probucol suppressed LPS-accelerated apoptosis, atherosclerosis and plaque instability in Apoe(-/-) mice. In conclusion, probucol via inhibition of NHE1 attenuates atherosclerosis lesion growth and promotes plaque stability.