Pharmacological Postconditioning With Tanshinone ⅡA Attenuate Myocardial Ischemia-reperfusion Injury Through PI3K/AKt Pathway In Rats

Objective Tanshinone IIA, one of the active ingredients in danshen, whichderived from the dried root or rhizome of Salviae miltiorrhizae BGE, iscardioprotective when applied before myocardial sustained ischemia. This study is toinvestigate the effect of pharmacological postconditioning with tanshinone IIA onattenuating myocardial ischemia-reperfusion injury when applied after myocardialsustained ischemia, and the potential mechanism involved in it.Methods Eighty Sprague-Dawley rats, receiving30min ischemia and5min or120min reperfusion, were randomly divided into6groups: the sham group withoutischemia (Sham)(n=8); the control group without other intervention (Control)(n=16);the ischemic postconditioning group (Post)(n=16), given3cycles of10s reperfusionand10s ischemia before120min reperfusion; the low-dose and high-dose tanshinoneIIA treatment group (Tan-L, n=16, and Tan-H, n=8, respectively), given an injectionof10mg/Kg or20mg/Kg tanshinone during25-30min ischemia; the low-dosetanshinone IIA plus a specific inhibitor of phosphatidylinositol3-kinase (PI3K/Akt),LY294002group (Tan+LY)(n=16), with an additional injection of PI3Kinhibitor(LY294002)0.3mg/kg in external jugular vein slowly15min beforereperfusion. Serum CK-MB、LDH level before ischemia and at the end of120minreperfusion were detected by automatic biochemistry analyzer, myocardial infarct sizeby triphenyltetrazolium chloride and Evan’s blue, mitochondrial permeabilitytransition (MPT) by spectrophotometry, and the contents of p-Akt and p-eNOS inmyocardium by Western blot.Results1. The sham group had lower serum CK-MB, LDH level than othergroups, and there was no ischaemic or necrotic area.2. Compared with the Control group, the Post, Tan-L and Tan-H groups had lower serum CK-MB, LDH level(CK-MB：3356±360U/L vs.2139±272U/L,2279±246U/L,2214±220U/L,P<0.01; LDH:2549±273U/L vs.1734±234U/L,1764±189U/L,1752±195U/L,P<0.01. respectively), smaller infarct size (46.9%±3.6%vs.25.3%±4.3%,29.2%±4.5%,28.5±3.0%, P<0.01), without difference among Post, Tan-L and Tan-H groups(P>0.05).3. The Post and Tan-L groups had less reduction in optical density at540nm (OD540) for MPT (13.2%±2.2%,13.7%±2.2%vs.20.5%±2.7%, P<0.01),greater p-Akt and p-eNOS protein expression than the Control group (p-Akt/t-Akt:2.3±0.3,2.2±0.3vs.1.0±0.0, P<0.01; p-eNOS/t-eNOS:2.1±0.2,1.8±0.2, vs.1.0±0.0, P<0.01, respectively).4. The Tan-L-induced cardioprotection and the inhibitionof MPT were abrogated completely by LY294002(P<0.01).Conclusion Pharmacological postconditioning with tanshinone IIA mayprotect myocardium from ischemia-reperfusion injury through PI3K-Akt-eNOSpathway, and MPT may be involved in this protection effect.