Simvastatin attenuates expression of cytokine-inducible nitric-oxide synthase in embryonic cardiac myoblasts

Cardiac stem cells or myoblasts are vulnerable to inflammatory stimulation in hearts with infarction or ischemic 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 hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase with simvastatin on the expression of inducible nitric-oxide synthase (iNOS) in embryonic cardiac myoblasts stimulated with the proinflammatory cytokines, interleukin-1 or tumor necrosis factor. Treatment with simvastatin significantly reduced the levels of iNOS mRNA and protein in cytokine-treated rat H9c2 cardiac embryonic myoblasts. Addition of the HMG-CoA reductase product, Lmevalonate, and the by-product of cholesterol synthesis, geranylgeranyl pyrophosphate, could reverse the statin inhibitory effect on iNOS expression. Simvastatin treatment 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 IB and reduction of the NF-B nuclear contents in the cytokine-stimulated H9c2 cells. Hence, treatment with simvastatin can attenuate iNOS expression and NO synthesis in cytokine-stimulated embryonic cardiac myoblasts. The statin inhibitory effect may occur through isoprenoid-mediated intracellular signal transduction, which involves several key signal proteins, such as Rho kinase and IB/NF-B. These data suggest that statin therapy may protect the cardiac myocyte progenitors against the cytotoxicity of cytokine-induced high output of NO production in infarcted or ischemic hearts with inflammation.