| Renal ischemia-reperfusion injury (RI/RI) is acommon pathophysiologic phenomenon,and it is a complex and important patho- process with many factors in acute renal ischemia injury. The main damage factors are free radical damage, leukocyte-endothelial cell interaction, intracellular calcium overload, NO and other vasodilator substances decrease, Endothelin and other vasoconstrictor substances increase.Statins, a group of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, are widely used in clinical practice for theI/R efficacy in producing significant reductions in plasma cholesterol and LDL cholesterol via inhibited mevalonic acid (MVA) pathway of cholesterol synthesis. A number of recent reports have shown that statins may also have important kidney protection effects, in addition to theI/R lipid-lowering effects on plasma lipids. Simvastatin and lovastatin could induce eNOS gene transcription in the cultured human endothelial cells, promote NO synthesis. NO can dilate efferent and afferent glomerular arterioles, lower renal vascular resistance while increase renal plasma flow and glomerular filtration rate. The molecular basis of the observed effects of statins may relate to theI/R ability block the production and/or activity of ROS. The inhibition of ROS generation by statins, through interference with NAD(P)H oxidase expression and activity, and the actions of statins that serve to blunt the damaging effects of these radicals, including effects on antioxidant enzymes, lipid peroxidation and nitric oxide synthase. These antioxidant effects of statins likely contribute to theI/R clinical efficacy in treating cardiovascular disease as well as other chronic conditions associated with increased oxidative stress in humans.However, whether statins has a protective effect on renal ischemia-reperfusion injury is still unknown. The present study observed the protective effects and explored mechanisms of Simvastatin on renal ischemia-reperfusion injury through use of physiological, biochemical, molecular biological and immunohistological methods.Objective: This study aimed to investigate the role of simvastatin on RI/RI and to explore its possible mechanism.Method: The model of RI/RI was induced by bilateral clamping the renal artery and vein for 45 minutes followed by reperfusion and observing the effect of simvastatin on RI/RI in rats. After two days breeding in 18-22℃cI/Rcumstance, Sixty male Sprague-Dawley rats weighing between 150g to 180g were divided into five groups randomly (n=12 on each group): (1) sham-operation group (Sham); (2) ischemia-reperfusion group (I/R); (3) low-dose Simvastatin group (Sim-L, 5mg/kg/d); (4) middle-dose Simvastatin (Sim-M, 20mg/kg/d); (5) high-dose simvastatin group (Sim-H , 40mg/kg/d).Sim-L, M and H group rats were started on oral Simvastatin 50, 20 and 40 mg/kg/d treatment respectively for 2 weeks. Sham and I/R group rats were given the same doses solution in the same way. The model of RI/RI was made after two weeks later.The animals were anesthetized with 1% pentobarbital sodium,the bilateral renal artery and vein were clamped for 45 minutes followed by reflow in I/R, Sim-L, M and H group rats. After reperfusion, each layer opened was closed with suture, including the peritoneum, abdominal wall muscle and skin. The rats in the sham group were treated identically except for the clamping. After 6 and 24 hours of reperfusion, the blood samples were taken for detecting contents of serum creatinine (Scr), serum urea nitrogen (BUN). After blood was taken, both side of kidney were excised for observing renal histological examination, content of Nitric Oxide (NO), activity of superoxide dismutase (SOD), the content of malondialdehyde (MDA), inducible nitric oxide synthase (iNOS), the expression of endothelial nitric oxide synthase (eNOS) and P47phox.Results:1. After RI/RI, the renal tubule epithelial cells showed signs of damage in I/R group rats, especially proximal convoluted tubule in I/R group rats, in which the lumen of tubule was enlarged; also there were some cast in many of the renal tubules. Chromatin was localized in the cell nucleus periphery. The degree of renal tissue injury significantly mitigate in Sim-M and Sim-H group rats compared with I/R group rats at different time point, but no any improvement of renal tissue injury in Sim-L group rats compared with I/R group rats.2. After RI/RI, the contents of Scr and BUN were significantly increased in I/R group rats than that of sham group rats at different time point (P﹤0.01); Compared with the I/R group rats, contents of Scr and BUN were significantly lower in Sim-L , Sim-M and Sim-H group rats at different time point (P﹤0.05～0.01).3. After RI/RI, activities of SOD were significantly decreased (P﹤0.01) and the contents of MDA were significantly increased (P﹤0.01) in I/R group rats at different time point; Compared with I/R group rats, the activities of SOD were significantly increased (P﹤0.01) and the contents of MDA were significantly decreased (P﹤0.01) in Sim-L and Sim-H group rats, but not in Sim-L group rats.4. After RI/RI, NO and iNOS were significantly increased in I/R group rats at different time point (P <0.01); compared with the I/R group rats, NO contents were significantly increased (P <0.01) and iNOS were decreased (P <0.01) in Sim-M and Sim-H group rats; there were no significant eNOS expression of renal cortex in Sham group rats, Positive immunoreactive particles of eNOS in renal proximal convoluted tubular epithelial cells were significantly increased in I/R group rats. Compared with I/R group rats, Sim-M and Sim-H group rats were showed more positive immunoreactive particles expression; eNOS protein expression were up-regulated in I/R group rats than that of Sham group rats, Compared with the I/R group, eNOS protein expression were significantly increased in Sim-M and Sim-H group rats, but not in Sim-L group rats.5. The expression of positive immunoreactive particles and protein of P47 phox were increased in I/R group rats than that of in Sham group rats. Compared with I/R group rats, both of positive immunoreactive particles and protein expression of P47phox were decreased in Sim-M and Sim-H group rats, but not in Sim-L group rats.Conclusions:1. After RI/RI, the renal function was markedly impaI/Red and renal tubule epithelial cells showed signs of damage. It was found that Scr,MDA and iNOS were increased, the activity of SOD and expression of eNOS were decreased in RI/RI rats. The positive immunoreactive particles and protein of P47phox in renal proximal convoluted tubular epithelial cells were markedly increased in RI/RI rats. These results indicated that P47phox is involved in the pathogenesis of RI/RI in rats.2. Simvastatin could decreased the Scr, BUN, MDA and iNOS, increased the activity of SOD and content of NO, upregulated the expression of eNOS in the renal tissue. It is indicated that Simvastatin could reduced renal tissue injury and improved renal function in RI/RI rats.3. Simvastatin could down-regulated the expression of P47phox of renal tissue in RI/RI rats and mitigated renal ischemia-repufution injury. It is indicated that the protective effects of Simvastatin to the RI/RI may be related to block the NAD (P) H oxidate pathway and anti-free radical damage. |
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