Decreased C-reactive protein-induced resistin production in human monocytes by simvastatin

Background: Resistin is a novel cysteine-rich protein that plays a role in the development of insulin resistance and atherosclerosis in rodents, while its role in humans is unclear. C-reactive protein (CRP) is an important risk predictor for coronary heart disease, and it can also modify the expression of genes involved in atherogenesis. Statins have been demonstrated to possess lipid lowering effects as well as pleiotropic properties. We hypothesize that CRP may result in overexpression of resistin, and statin may decrease CRP-induced resistin expression in cultured human peripheral blood monocytes (PBMC). Purpose: The aim of the present study, therefore, was to assess the effects of both CRP on resistin expression and simvastatin on CRP-induced of resistin expression in cultured human PBMC. Methods: Human PBMC were isolated from the whole blood of healthy volunteers by density gradient centrifugation. First, cells were incubated with varying concentrations of CRP (0, 5, 10, 25 and 50 μg/ml) for 24 h for assessing the dose-dependent effects on resistin expression. Second, 25 μg/ml of CRP was used to time-dependent evaluation on resistin expression (0, 3, 6, 12 and 24 h). Moreover, cells were pretreated with simvastatin at concentrations from 0.1 to 1 μM for 2 h, and then co-incubated with 25 μg/ml CRP for 24 h for evaluating effect of statin on resistin production subjected to CRP. Finally, in additional experiments, monocytes were incubated with 1 μM simvastatin in the absence or presence of 100 μM mevalonate or 10 μM geranylgeranyl-pyrophosphate (GGPP) or 10 μM farnesylpyrophosphate (FPP) for 2 h, then co-incubated with CRP for 24 h for examining whether effects of statin on CRP-induced resistin expression was independent of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors. Results: The results showed that CRP induced both mRNA expression and protein secretion of resistin in a dose- and time-dependent manner. Co-incubation with simvastatin significantly inhibited CRP-induced up-regulation of mRNA and protein expression of resistin. Treatment with mevalonate, GGPP, but not FPP, reversed the inhibition of resistin expression caused by simvastatin, suggesting that simvastatin regulated resistin expression in culture human PBMC through the mevalonate–GGPP signal pathway. Conclusions: In the present study, the data showed that CRP could significantly increase resistin expression in cultured human PBMC, and this effect was inhibited by simvastatin, suggesting that CRP and resistin might be involved in the pathogenesis of atherosclerosis, and statin therapy might be beneficial for atherosclerotic disease by modifying CRP-induced resistin overexpression in PBMC.