The Experimental Studies On The Hepatoprotective Effects Of Icaritin Against Ischemia Reperfusion

【Background and Objective】It is widely accepted that liver blood is supplied by portal vein and hepatic artery.In both of them,the former has 70-80 percent of total hepatic blood inflow,and the latter is 20%-30%of that.In modern hepatic surgery, clamping of liver hilum(Pringle's maneuver),has been utilized in order to reduce blood loss before hepatectomy.However,hepatic pedicle clamping would cause severe liver ischemia reperfusion injury(IRI),which has been one of the vital causes of hepatic failure after hepatectomy and hepatic primary nonfunction after transplantation.Therefore,how to attenuate liver IRI during the process of preventing blood loss has been a problem urgently needing solution.Icaritin,molecular weight:368,is a compound extracted from natural Epimedium herb.Ranging from inducing cellular proliferation and differentiation,cardiovascular relaxing,anti-tumor,estrogenic activities, promoting erectile function to preventing osteoporosis,icaritin possesses many kinds of biological functions.Based on the relative studies of other Epimedium compounds and the molecular structure analysis of icaritin,we supposed that icaritin has the hepatoprotective effects against organ IRI by means of clearing the oxygen free raical(OFR),reducing lipidperoxidation, inducing expression of endothelial nitric oxide synthase(eNOS) and elevating the NO content.This study was undertaken to prove our hypothesis in the rats suffered from hepatic IRI and explain the precise pharmacological mechanism.We hope it would be of benefit to improvement of therapeutic efficacy after liver operations.【Methods】1.Preparation of Icaritin-liposomes;Icaritin powder is made into liposomes through the method of film dispersion. 2.Animal Protocol:male SD rats were randomly divided into 4 groups: icaritin-liposomes group(A),vechicle liposomes group(B),ischemia reperfusion group(I/R)(C),and sham group(D).Except for sham-operated group,all rats were subjected to 70%liver(left and medium lobes)ischemia for 60 min.Blood and liver samples were obtained in all animals after 2h and 6h of reperfusion to assess the following determinations:(1) serumALT, AST;(2) liver NO and malondialdehyde(MDA) content;(3) superoxide dismutase(SOD),nitric oxide synthase(NOS),inducible nitric oxide synthase(iNOS),endogenous nitric oxide synthase(eNOS) and myeloperoxidase (MPO) activity in the liver;(4) hepatocyte apoptosis index(AI); (5) observation of hepatic histologic changes.【Results】1.we have made the icaritin-liposomes successfully,which meet the demands of intravenous injection for animals in Part 2.Judging from the concerning index,the content and envelopment ratio of icaritin-liposomes we invented is at the high level.2.Reperfusion of 2 h:compared with group B and C,serum ALT,liver tissue MDA,MPO and AI decreased significantly in group A;Reperfusion of 6 h:compared with group B and C,serum ALT,AST,liver tissue MDA, MPO and AI in group A were reduced promptly,moreover a higher increase of NO content,SOD activities and NOS,eNOS expression.The degrees of liver injury by histologic observation consisted with the content of serum ALT in all groups.【Conclusions】The hypothesis on the pharmacological function of icaritin we preferred before the experiment was confirmed in vivo.We concluded that icaritin pretreatment could reduce liver I/R injury and the protective mechanism related to scavenging OFR,enforcing the activity of SOD and reducing hepatocytes apoptosis by enhancing the expression of eNOS.