Simvastatin Restores Superoxide Dismutase Expression And Inhibit Proliferation Of A549 Lung Cancer Cell Though Oxidative Stress

Statins can reduce serum cholesterol levels by competitively inhibiting 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, the rate-limiting enzyme in the synthesis of mevalonate. This effect contributes to their decrease in the incidence of cardiovascular and cerebrovascular disorders and their remarkable prevention of cardiovascular disease. At present, statins, with remarkable cholesterol-lowering effect, less side effect and high security, have been at the top of the list of global best-sale drugs in the therapeutic treatment of hypercholesterolemia. More recently, these agents were shown to have pleiotropic effects including reversal of endothelial dysfunction, inhibition of monocyte recruitment, antioxidant activity,down-regulation of angiotensinⅡreceptors, immunomodulation, reduction in inflammatory response, plaque stabilization, reduction in ventricular arrhythmias, and neuroprotective effects. Indeed, recent studies have also shown that statins have protective effects against cancer, such as anti-proliferation, anti-invasiveness and induction of apoptosis.Although these studies indicate that statins are one of the most promising classes of agents currently available for testing in cancer prevention, the mechanism behind these observations is still not clear.Cell death is associated with oxidative stress and generation of ROS, which cause serious damage to important biological macromolecules such as proteins, lipids and nucleic acids. For decades, reactive oxygen species (ROS) production and metabolic oxidative stress have been associated with cancer. Tumor resistance to oxidative stress prevents the efficacy of cancer therapy based upon a free radical-mediated mechanism. At the same time, an increase in the activity of antioxidative enzymes could be indicative of an increased production of ROS and a build-up of a protection mechanism to reduce oxidative damage triggered by stress experienced. The antioxidative enzymes include superoxide dismutase (SOD), catalase (CAT), GSH-Px and so on. SOD have three isoforms, copper-zinc SOD(SOD1)and manganese SOD(SOD2) are localized within specific cellular compartments, the FeSOD (extracellular SOD or SOD3) is secreted and found primarily bound to heparin sulfate proteoglycan on cell surfaces. Recent research documented that sod2 expresses at a lower level in many types of transformed and neoplastic cells, suggesting that loss of SOD2 activity may be a general characteristic of tumorigenesis.In this article, we evaluated the effects of simvastatin on proliferation,oxidative stress in A549 lung cancer cells and its role in upregulation of tumor suppressor sod2. We analyzed the concentration-dependent and time-dependent cytotoxicity of simvastatin against A549 cells, then chose the concentration of 50μmol/L,60μmol/L to research the effecs of simvastatin on ROS production,lipid peroxidation, SOD activity,SOD2 activity. The cell death of A549 cells incubated with Vc plus simvastatin was partly revered, indicating that oxidative stress is the responsible of the cytotoxic effect of simvastatin. Based on results that simvastain could effectively increase SOD2 activity above that of control, we also analyzed the sod2 mRNA expression after simvastain exposure using semi-quantitative PCR.In this article, we first used MTT reduction assay to evaluate the effects of simvastatin on the cell proliferation and cytotoxicity assay, observing that simvastatin effectively inhibited lung cancer cells'proliferation in vitro. For the lung cancer cell line 549, survival was reduced to nearly 50% at 50μmol/L. Therefore, the subsequent experiments we done used the concentration of 50μmol/L and 60μmol/L. The results reported here also showed that the degree of MDA accumulation, SOD and SOD2 activity were higher in cells exposed to simvastatin than control. The cell death of A549 cells incubated with Vc plus simvastatin was partly revered, indicating that oxidative stress was the responsible of the cytotoxic effect of simvastatin. Manganese superoxide dismutase (SOD2), the form of SOD found in mitochondria, has received considerable attention with regard to cancer. Decreased expression of sod2 gene has been noted in all the tumors examined to date. Overexpression of sod2 in deficient cell lines could reduce the proliferation of cancer cells. Based on results that simvastain could effectively increase SOD2 activity above that of control, we also analyzed the sod2 mRNA expression after simvastain exposure and found that sod2 expression in A549 was 1.13 and 1.28 fold repectively (50μmol/L and 60μmol/L)compared to control.In conclusion, our results suggest that simvastatin can inhibit the proliferation of A549 cells in vitro and induce cell death mediated by oxidative stress. It would be interesting to observe the effect of simvastatin upon the sod2 expression and the underlying mechanism may be our next focus.