Shenmai Injection Attenuates Myocardial Ischemia/Reperfusion Injury by Targeting Nrf2/GPX4 Signalling-Mediated Ferroptosis

Objective:To examine the effect of Shenmai Injection(SMJ)on ferroptosis during myocardial ischemia reperfusion(I/R)injury in rats and the underlying mechanism.Methods:A total of 120SPF-grade adult male SD rats,weighing 220–250 g were randomly divided into different groups according to a random number table.Myocardial I/R model was established by occluding the left anterior descending artery for 30 min followed by 120 min of reperfusion.SMJ was injected intraperitoneally at the onset of 120 min of reperfusion,and erastin(an agonist of ferroptosis),ferrostatin-1(Fer-1,an inhibitor of ferroptosis)and ML385(an inhibitor of nuclear factor erythroid-2 related factor 2(Nrf2))were administered intraperitoneally separately 30 min before myocardial ischemia as different pretreatments.Cardiac function before ischemia,after ischemia and after reperfusion was analysed.Pathological changes in the myocardium and the ultrastructure of cardiomyocytes were observed,and the myocardial infarction area was measured.Additionally,the concentration of Fein heart tissues and the levels of creatine kinase-MB(CK-MB),troponin I(cTnI),malondialdehyde(MDA)and superoxide dismutase(SOD)in serum were measured using assay kits,and the expressions of Nrf2,glutathione peroxidase 4(GPX4)and acyl-CoA synthetase long-chain family member 4(ACSL4)were examined by Western blot.Results:Compared with the sham group,I/R significantly injured heart tissues,as evidenced by the disordered,ruptured and oedematous myocardial fibres;the increases in infarct size,serum CK-MB,cTnI and MDA levels,and myocardial Feconcentrations;and the decreases in SOD activity(P<0.05).These results were accompanied by ultrastructural alterations to the mitochondria,increased expression of ACSL4 and inhibited the activation of Nrf2/GPX4 signalling(P<0.05).Compared with the I/R group,pretreatment with 9 mL/kg SMJ and 2 mg/kg Fer-1 significantly reduced myocardial I/R injury,Feconcentrations and ACSL4 expression and attenuated mitochondrial impairment,while 14 mg/kg erastin exacerbated myocardial I/R injury(P<0.05).In addition,cardioprotection provided by 9 mL/kg SMJ was completely reversed by ML385,as evidenced by the increased myocardial infarct size,CK-MB,cTnI,MDA and Feconcentrations,and the decreased SOD activity(P<0.05).Conclusions:Ferroptosis is involved in myocardial I/R injury.Pretreatment with SMJ alleviated myocardial I/R injury by activating Nrf2/GPX4 signalling-mediated ferroptosis,thereby providing a strategy for the prevention and treatment of ischemic heart diseases.