In vivo and in vitro effects of simvastatin on inflammatory markers in pre-dialysis patients

Background. The beneficial effects of statins in reducing cardiovascular events have been attributed predominantly to their lipid-lowering effects, recent studies suggest that these effects might be due to their anti-inflammatory properties. We here investigate the in vivo and in vitro effects of simvastatin on cytokine production in pre-dialysis chronic renal failure patients. Methods. Our clinical study has been designed as a randomized double-blind placebo controlled study. A total of 55 chronic kidney disease (CKD) patients at stages 3 and 4 (mean creatinine clearance 45 ml/min, range 15-60) were randomly assigned to receive simvastatin 40 mg/day or placebo, added to their ongoing treatment, for 6 months. Blood samples were obtained at baseline, and after 3 and 6 months of observation for the determination of lipids, inflammatory markers and renal function. For the in vitro studies, the effect of increasing doses of simvastatin on cytokine production [namely interleukin (IL)-6 and IL-8] in human cultured monocytes from 10 healthy subjects (HS) and 15 CKD patients stimulated by lipopolysaccharide (LPS) was investigated. Results. A significant reduction in total cholesterol from 221 +/- 44 mg/dl to 184 +/- 41 mg/dl (3 months) and to 186 +/- 39 mg/dl (6 months) (P < 0.02) and low-density lipoprotein cholesterol from 139 +/- 40 mg/dl to 104 +/- 29 mg/dl (3 months) and to 100 +/- 31 mg/dl (6 months) (P < 0.001) was observed in the 28 patients treated with simvastatin. In this group, C-reactive protein (CRP) levels significantly decreased from 2.6 mg/l [interquartile range (IQR 4.9)] to 2.0 mg/l (IQR 1.9) (P = 0.03) at 6 months (P < 0.05). A parallel reduction of IL-6 levels from 5.1 pg/ml (IQR 3.8) to 3.5 pg/ml (IQR 3.1) (P = 0.001) at 6 months was also observed. No significant reduction in inflammatory markers [CRP from 5.1 mg/l (IQR 1.9) to 5.4 mg/l (IQR 1.3) (P = NS) at 6 months] or plasma lipids [LDL-cholesterol from 127 +/- 32 mg/dl to 131 +/- 21 mg/dl (6 months)] was observed in the 27 patients of the placebo group. In the in vitro studies, the average value for cell-associated IL-6 and IL-8 was higher in CKD (155 +/- 95 pg/ml monocytes for IL-6 and 722 +/- 921 pg/ml monocytes for IL-8) vs HS (137 +/- 87 pg/ml monocytes and 186 +/- 125 pg/ml monocytes) (P < 0.01) and was not affected by simvastatin alone. LPS resulted in a significant increase in cytokine production (IL-6: 1954 +/- 321 pg/ml monocytes for CKD and 1451 +/- 237 pg/ml monocytes for HS; P < 0.001); the simultaneous addition of increasing doses of simvastatin to these cultures induced a dose-dependent inhibition of IL-6 and IL-8 production in stimulated peripheral blood mononuclear cells in all groups. Conclusions. These results indicate that simvastatin in commonly used doses has an in vitro and in vivo anti-inflammatory effect in CKD patients, and may play an important role in counteracting the mechanisms involved on the pathogenesis of cardiovascular disease.