作者：Lei; JIAO; Ying; ZHANG; Xue; LIU; Lu; ...
摘要：OBJECTIVE To explore the protection mechanism of metformin and tanshinone IIA on myocardial injury.METHODS The cultured neonatal rat ventricular cells（NRVCs） were exposed to100 μmol·L-1 H2 O2 to simulate the in vitro model of ischemia-reperfusion injury.MTT,TUNEL and Viability/Cytotoxicity Assay were used to evaluate the effect of metformin on the viability of cardiomyocytes after treated with H2 O2.The target of miR-1 was verified by Dual luciferase reporter assay.ChIP analyses was adopted to reveal the relationship between C/EBP β and miR-1.Tanshinone IIA was administrated daily for 7 d before ligation of the left anterior descending artery（LAD） and lasted for 3 months after LAD.Whole-cell patch-clamp techniques were used to measure the inward rectifying K+ current（IK1） in rat isolated ventricular myocytes.GRP94,p-AMPKα,C/EBP β,CHOP,Caspase-3,Kir2.1,p38 MAPK,Cx43,MEF2 and SRF levels were analyzed by Western blot and miR-1 level was quantified by Realtime PCR.RESULTS The expression of miR-1 was significantly increased in NRVCs exposed to H2 O2 in vitro.miR-1 was shown to target the 3′-untranslated region（UTR） of GRP94,which results in the accumulation of un/misfolded proteins,leading to the endoplasmic reticulum（ER） stress.C/EBP β directly induces the upregulation of miR-1 by binding to its promoter.Furthermore,metformin,a direct allosteric AMPK activator,significantly reduces C/EBP β and miR-1 levels comparing with control group.Similarly,tanshinone IIA decreased the incidence of arrhythmias and relieved ischemia-induced injury.Moreover,tanshinone IIA depressed the elevated miR-1 level and inhibited the activation of p38 MAPK and heart special transcription factors SRF and MEF2 in ischemic cardiomyocytes.CONCLUSION Metformin protects cardiomyocytes against H2 O2 damage through AMPK/C/EBPβ/miR-1/GRP94 pathway.Tanshi.none IIA play a role in protection cardiomyocytes from ischemic injury based on inhibiting miR-1 expres.sion through p38 MAPK signal pathway.
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