The Mechanism Of SGK3 Kinase In Promoting Myocardial Cell Proliferation And Alleviating Cardiac Ischemia-reperfusion Injury Through GSK-3β/β-catenin Pathway

Background/Aims:Neonatal heart maintains entire regeneration capacity in a transient regeneration window while loses in adult heart,which involves the expression and activity dysregulation of numerous core hubs.Previously,using quantitative phosphorylation proteomics,we screened a series of kinases with abundant substrates and up-regulated phosphorylation levels after neonatal myocardial infarction(MI).Through further verification,we identified that the expression pattern of serine/ threonine protein kinase 3(SGK3)in mouse heart was consistent with the time window of cardiac regeneration loss,and the expression as well as the activity of SGK3 increased significantly in neonatal heart post MI.This study aimed to explore the effects of SGK3 kinase on cardiomyocyte(CM)proliferation and apoptosis,and the effects of SGK3 kinase on cardiac repair after apical resection(AR)in neonatal mice and ischemia-reperfusion(I/R)in adult hearts,and to further elucidate the molecular mechanism of SGK3’s cardioprotective effect.Methods: We isolated and cultured neonatal mouse primary CMs as an in vitro model to explore the effects of SGK3 on CM proliferation and apoptosis.The effect of SGK3 on CM proliferation was verified by immunofluorescence staining with EDU,Ki67,p H3,Aurora B,and the role of SGK3 on cell cycle of CMs was determined using cell flow cytometry assay.The effect of SGK3 on CM apoptosis in vitro was performed by constructing a model of oxygen glucose deprivation/reoxygenation(OGD/R).In vivo,AR and I/R injury models were established in neonatal mice and adult mice respectively,and the effects of SGK3 on myocardial proliferation and cardiac function repair post cardiac injury were explored by immunofluorescence,echocardiography,Masson and TTC staining.Results: In vitro,overexpression of SGK3 enhanced,while knockdown of SGK3 decreased CM proliferation ratio.SGK3 overexpression significantly increased,while SGK3 inhibition remarkably inhibited the proportion of CMs in DNA synthesis and mitotic state.Moreover,overexpression of SGK3 also significantly improved OGD/R-induced CM apoptosis.In vivo,inhibiting the expression of SGK3 shortened the time window of cardiac regeneration after AR in neonatal mice,and overexpression of SGK3 significantly promoted myocardial repair and cardiac function recovery post I/R injury in adult mice.Mechanistically,SGK3 promoted CM regeneration and myocardial repair post cardiac injury by inhibiting GSK-3β activity and upregulating β-catenin expression.SGK3 also upregulated the expression of cell cycle promoting genes cyclin D1,c-myc and cdc20,but downregulated the expression of cell cycle negative regulators P21 and P27.Conclusion: Our study demonstrates that SGK3 can regulate CM proliferation and improve I/R-induced cardiac injury through GSK-3β/β-catenin pathway,which reveals that SGK3 may become a new target for the treatment of myocardial injury and repair after MI,and re-opens a new way for the treatment of human MI.