| Ischemia-reperfusion injury(IRI) refers to tissue or organ that after a period of ischemia, restoring blood flow reperfusion, the metabolism disorders and structural damage of cell function are more exacerbate than ischemic injury. Renal ischemia-reperfusion injury(RI/RI) is a common clinical pathophysiologic phenomenon, it is a complicated pathological process with many factors involved, and it is also one of the main pathogenesis of acute kidney injury. Multi-factorial processes are involved in the development and progression of RIRI with the decrease of ATP, generation of reactive oxygen species,the intracellular calcium overload, increase of inflammatory mediators and adhesion molecules,decrease of nitric oxide and nitric oxide synthase and increase of endothelin(ET), leading to dysfunction, injury, and death of the cells of the kidney.Simvastatin(SIM) belongs to the water-soluble statins, it is a natural compound which turns inactive lactone hydroxylated in the liver into active inhibitor of β-hydroxy acid by pharmacological effects. HMG-Co A cannot be converted into Mevalonate(MVA) by specific inhibition of HMG-Co A, which block the synthesis of cholesterol, and lower blood cholesterol levels. Currently, Statins are widely used in clinical treatment of hyperlipemia. In recent years, studies have found that in addition to its lipid-lowering function, Statins also have strong non-lipid-lowering function. The non-lipid-lowering function which is the pleiotropic effects of Statins, including improving bioavailability of nitric oxide and endothelial function, resisting oxidative stress and inflammation, inhibiting the accumulation of extracellular matrix, reducing the migration and proliferation of vascular smooth muscle cells, and immunoregulation. Studies also found that it has a protective effect on kidney function.Ischemic Postconditioning(IPO) refers to an endogenous protective phenomenon which tissue or organ is implemented short and repeated ischemia reperfusion treatment immediately, and continuous blood flow before reperfusion, but not after ischemia, it can relieve the injury of ischemic-reperfusion. In recent years, domestic and foreign to the liver, brain, heart and limbs IPO conducted a lot of research, various research results showed that IPO has a protective effect on ischemia-reperfusion injury. Kidney is a sensitive to ischemia and hypoxia, they are also susceptible to IRI, there are rare reports on IPO’s protective effects on RIRI currently,and the underlying mechanism for this effect is not fully elucidated. The present study adopts the methods of physiology, biochemistry and immunohistochemical observation the effects of Simvastatin and IPO on RIRI and explored the possible mechanism.Objective: To investigate the effects of SIM and IPO on RIRI in rats and explore its possible mechanism.Methods: The model of RIRI was induced by bilateral clamping the renal artery and vein for 45 minutes followed by reperfusion and observing the effect of SIM and IPO on RIRI in rats. After two days breeding in 18-22 ℃circumstance, forty male Sprague-Dawley rats weighing between 180 to 220 g were divided into five groups randomly(n=8 on each group):(1) sham-operation group(Sham);(2) sham-operation control group(Sham+V);(3) ischemia-reperfusion group(I/R);(4)SIM group(Sim);(5) IPO group(IPO).Sim group were given SIM 20mg/kg once a day for 2 weeks, Sham+V group were given equal volume of saline. Sham group, IPO group and I/R group just fed normally for two weeks.RIRI animal model was made after 2 weeks. The rats must fasting for 12 hours before operation, but they were not limited to drinking water, then fixed on the console after anesthetized with 1% sodium pentobarbital, a ventral midline incision to open the abdominal cavity, free of bilateral renal artery and vein. I/R group and Sim group were used non-invasive arterial clamp close bilateral renal artery and vein for 45 minutes, then removed artery clamps, and observed bilateral renal color changes from dark purple to bright red, which indicate reperfusion was success, suture peritoneum, abdominal muscles and skin layer-by-layer. IPO group were used non-invasive arterial clamp close bilateral renal artery and vein for 45 minutes, then removed artery clamps, clipped after 10 s and reperfusion 10 s for 6 cycles, and then continuous reperfusion. Sham group and Sham+V group were all open the abdominal cavity, but did not occlude renal arteries and veins, the rest operation were same as above. After reperfusion of 24 hours in each group, then took abdominal aortic blood for measeured serum creatinine(Scr), blood urea nitrogen(BUN).After took the blood, quickly removal of the kidneys in rats for determined the contents of renal tissue malondialdehyde(MDA), nitric oxide(NO) and activity of superoxide dismutase(SOD). Detected endothelial nitric oxide synthase in renal tissues(e NOS) content by using Enzyme-linked immunosorbent assay(ELISA). Determined the expression of Bcl-2, Bax and HO-1 protein in renal tissues by using Immunohistochemistry. Observed the degree of kidney damage by Pathomorphological.Results:1 There are no significant anomalies about renal tubules in Sham group and Sham+V Group. There is clearly damage of renal tubules in I/R group, the damage of convoluted tubule is more serious, cloudy swelling of renal tubular epithelial cells, lumen expanded significantly, cast and exfoliated cells can be seen in lumen, widened interstitial edema, inflammatory cell infiltration, the blood vessel clearly expanding and the renal tubular epithelial cell nucleus chromatin margination, cytoplasmic vacuolar degeneration and necrosis. Compared with I/R group, the damage of renal tissue were significantly reduced in Sim and IPO groups. It is showed that the mild edema of renal tubular epithelial cells, vacuolar degeneration, a small amount of tubular interstitial hyperemia and edema reduction, a small amount of inflammatory cell infiltration, slightly bruised in the tube, nuclei were basically normal.2 The renal function was impaired in I/R group, BUN and Scr content were significantly higher than Sham group and Sham+V group(P<0.01). Compared with I/R group, BUN and Scr contents are significantly decreased(P<0.01) in Sim and IPO group.3 After RI/RI, activity of SOD was significantly reduced(P<0.05) in I/R group than in Sham group and Sham+V group. Contents of MDA were significantly increased in I/R group than in Sham group and Sham+V group(P<0.05). Compared with I/R group, SOD activity was significantly increased(P<0.05), and MDA contents were significantly decreased(P<0.05) in Sim and IPO group.4 After RI/RI, the contents of NO were significantly lower in I/R group than in Sham group and Sham+V Group(P<0.05), and contents of e NOS were also significantly reduced.Compared with I/R group, contents of NO and e NOS increased markedly in Sim and IPO group(P<0.05).5 Bcl-2 and Bax protein expression were not obvious in Sham group and Sham+V group. After RI/RI, expression of Bax protein was increased and Bcl-2 protein expression is not obvious in I/R group, compared with I/R group, the expression of Bax protein was reduced but Bcl-2 protein expression was increased in Sim and IPO group.6 Expression of HO-1in renal tubular epithelial cells was not obvious in Sham group and Sham+V group. After RI/RI, the expression of HO-1 in renal tubular epithelial cells were increased in I/R group than in Sham group and Sham+V group, compared with I/R group, the expression of HO-1 in renal tubular epithelial cells were significantly increased in Sim and IPO group.Conclusions:1 Renal ischemic-reperfusion could induce the damage of the renal function and structure in rats, it is showed that contents of Scr and BUN were increased, albuminous swelling and necrosis of renal tubular epithelial cells. Meanwhile the contents of MDA, NO, e NOS and SOD activity were significantly reduced, and expression of Bcl-2 proteins reduced, expression of Bax and HO-1 positive particles significantly increased.2 SIM and IPO, can significantly reduce Scr and BUN level, mitigate damage of renal tissue in rats, improve kidney function, and remarkable decrease the MDA content, improve renal tissue SOD activity, increase the contents of e NOS and NO. It is suggested that Sim and IPO has the protection effects on the RIRI in rats, the mechanisms may be related to oxygen free radical scavenging, inhibition of lipid peroxidation, improving the ability of antioxidation of renal tissue.3 SIM and IPO can reduced the expression of Bax protein but increase the Bcl-2 protein expression. It is suggested that the mechanisms of protection effests of SIM and IPO on the RIRI rats may be associated with upregulation of Bcl-2 expression and down-regulate the Bax expression, inhibiting cell apoptosis in renal tissues.4 SIM and IPO can significantly increased the expression of HO-1 of renal tubular epithelial cells in RIRI rats and mitigated renal ischemia-repufution injury. It is indicated that the protective effects of SIM and IPO to the RI/RI rats may be involved in anti-inflammatory, antioxidant, anti apoptosis pathway. |
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