Simvastatin Attenuates Expression of Cytokine-inducible Nitric-oxide Synthase in Embryonic Cardiac Myoblasts

Cardiac stem cells or myoblasts are vulnerable to in- flammatory stimulation in hearts with infarction or ische- mic injury. Widely used for the prevention and treatment of atherosclerotic heart disease, the cholesterol-lowering drugs statins may exert anti-inflammatory effects. In this study, we examined the impact of inhibition of hydroxy- methylglutaryl coenzyme A (HMG-CoA) reductase with simvastatin on the expression of inducible nitric-oxide synthase (iNOS) in embryonic cardiac myoblasts stimu- lated with the proinflammatory cytokines, interleukin-1 or tumor necrosis factor. Treatment with simvastatin sig- nificantly reduced the levels of iNOS mRNA and protein in cytokine-treated rat H9c2 cardiac embryonic myo- blasts. Addition of the HMG-CoA reductase product, L - mevalonate, and the by-product of cholesterol synthesis, geranylgeranyl pyrophosphate, could reverse the statin inhibitory effect on iNOS expression. Simvastatin treat- ment lowered the Rho GTPase activities, whereas the Rho-associated kinase inhibitor Y27632 partially blocked the statin inhibitory effect on nitrite production in the cytokine-treated H9c2 cells. Treatment with simvastatin led to inactivation of NF- B by elevation of the NF- B inhibitor I B and reduction of the NF- B nuclear con- tents in the cytokine-stimulated H9c2 cells. Hence, treat- ment with simvastatin can attenuate iNOS expression and NO synthesis in cytokine-stimulated embryonic car- diac myoblasts. The statin inhibitory effect may occur through isoprenoid-mediated intracellular signal trans- duction, which involves several key signal proteins, such as Rho kinase and I B/NF- B. These data suggest that statin therapy may protect the cardiac myocyte progeni- tors against the cytotoxicity of cytokine-induced high out- put of NO production in infarcted or ischemic hearts with inflammation.