Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, is emerging as a key contributor for endothelial dysfunction associated with inflammation. Statins can inhibit vascular inflammatory reaction and improve endothelial function. The aim of this study was to investigate in human endothelial cells the signaling pathways of ADMA-induced inflammatory reaction and potential inhibitory effects of simvastatin. Endothelial cells were cultured and used for all of the studies. Tumor necrosis factor-alpha(TNF-alpha) and soluble intercellular adhesion molecule-1 (sICAM-1) were determined by enzyme-linked immunosorbent assay. Nuclear factor-kappaB (NF-kappaB) was assayed by electrophoretic mobility shift assay. The activation of mitogen-activated protein kinases (MAPKs), including p38 MAPK and extracellular signal-related kinase (ERK(1/2)), were characterized by Western blot analysis. Treatment with ADMA (3-30 micromol/L) increased the concentration of sICAM-1 in a dose-dependent manner. ADMA (30 micromol/L) significantly enhanced the concentrations of TNF-alpha and sICAM-1, the activity of NF-kappaB and the phosphorylation of p38 MAPK and ERK(1/2). The increased secretion of TNF-alpha and sICAM-1 and the increased activity of NF-kappaB by ADMA were altered by SB203580 (5 micromol/L) or PD98059 (20 micromol/L), but not by LY294002 (20 micromol/L). Simvastatin (0.1, 0.5, or 2.5 micromol/L) markedly inhibited the elevated concentrations of TNF-alpha and sICAM-1, the activity of NF-kappaB, and the phosphorylation of p38 MAPK and ERK(1/2) induced by ADMA. Simvastatin inhibited ADMA-induced inflammatory reaction by p38 MAPK and ERK(1/2) pathways in cultured endothelial cells.

Previous studies have shown that the phosphatidylinositol 3-kinase / Akt / endothelial nitric oxide synthase / NO (PI3K/Akt/eNOS/NO) pathway is involved in high glucose-induced endothelial cell apoptosis and rosiglitazone has a protective effect on endothelium. In the present study, we investigated the antiapoptotic effect of rosiglitazone on human umbilical vein endothelial cells (HUVECs) exposed to high glucose and explored its possible mechanism. Treatment of high glucose (33 mmol/L) for 48 h significantly induced the apoptosis of HUVECs, concomitantly with increased caspase-3 activity. High glucose treatment also decreased Akt and eNOS phosphorylation levels with subsequent NO production. All these alterations induced by high glucose were attenuated by rosiglitazone (1 micromol/L). Interestingly, the antiapoptotic effect of rosiglitazone was inhibited by PI3K inhibitor (LY294002, wortmannin) or eNOS inhibitor NG-l-nitro-arginine methyl ester (l-NAME). The reverse effects of rosiglitazone on phosphorylation of Akt and eNOS with subsequent NO production were also inhibited by LY294002, wortmannin or l-NAME, respectively. These findings suggest that rosiglitazone inhibits high glucose-induced apoptosis in HUVECs through the PI3K/Akt/eNOS pathway.

Previous studies have indicated that nitric oxide synthase (NOS) inhibitors can induce an increase of blood pressure and exacerbate myocardial injury induced by ischemia and reperfusion, whereas angiotensin II receptor antagonists protect the myocardium against injury induced by ischemia and reperfusion. Isolated hearts from male spontaneously hypertensive rats (SHR) or male Wistar-Kyoto rats (WKY) were subjected to 20 min global ischemia and 30 min reperfusion. Heart rate, coronary flow, left ventricular pressure, and its first derivatives (+/-dP/dt(max)) were recorded, and serum concentrations of asymmetric dimethylarginine (ADMA) and NO and the release of creatine kinase in coronary effluent were measured. The level of ADMA was significantly increased and the concentration of NO was decreased in SHR. Ischemia and reperfusion significantly inhibited the recovery of cardiac function and increased the release of creatine kinase, and ischemia and reperfusion-induced myocardial injury in SHR was aggravated compared with WKY. Vasodilation responses to acetylcholine of aortic rings were decreased in SHR. Treatment with losartan (30 mg/kg) for 14 days significantly lowered blood pressure, elevated the plasma level of NO, and decreased the plasma concentration of ADMA in SHR. Treatment with losartan significantly improved endothelium-dependent relaxation and cardiac function during ischemia and reperfusion in SHR. Exogenous ADMA also aggravated myocardial injury induced by ischemia and reperfusion in isolated perfused heart of WKY, as shown by increasing creatine kinase release and decreasing cardiac function. The present results suggest that the protective effect of losartan on myocardial injury induced by ischemia and reperfusion is related to the reduction of ADMA levels.