Metformin Alleviates Epirubicin-induced Vascular Endothelial Cell Injury By Regulating The Expression And Release Of Mitochondrial Transcription Factor A

The irreversible cardiotoxicity induced by anthracyclines significantly reduces the prognosis and the quality of life in cancer survivors.Previous studies have focused on myocardial toxicity induced by anthracyclines;The pathogenic effect of vascular endothelial cell injury was ignored.Therefore,there are very few studies on anthracycline-induced vascular endothelial cell injury and its prevention and treatment strategies.Metformin,a traditional first-line hypoglycemic drug,has been shown to ameliorate cardiomyocyte damage induced by anthracyclines through antiinflammatory and antioxidant effects.However,whether metformin can improve epirubicin-induced vascular endothelial cells injury and its mechanism remain unclear.Then we investigated the underlying mechanisms by which epirubicin impaired endothelial cells,and investigated whether metformin could alleviate epirubicininduced endothelial impairment by restoring mitochondrial homeostasis,promoting intracellular TFAM expression or decreasing extracellular TFAM release.The main results were as follows:(1)Metformin alleviated epirubicin-induced vascular endothelial cells injury by promoting intracellular TFAM expression.Metformin pretreatment could decrease epirubicin-induced DNA damage,excessive ROS production,and excessive Angiotensin Ⅱ(Ang Ⅱ)secretion,and improve DNA repair ability in vascular endothelial cells.Then,by si-RNA to inhibit TFAM expression,it was found that metformin played a protective role in vascular endothelium by promoting intracellular TFAM expression.Finally,by si-RNA and CsA,it was found that metformin could promote intracellular TFAM expression by Calcineurin/TFEB/pathway.(2)Metformin could inhibite excessive mitochondrial fission to promote intracellular TFAM expression and extert an endothelial protective role.Metformin could restore mitochondrial dynamin by adjusting the expression of mitochondrial dynamin-related protein(DRP1,MFF,OPA1,MFN1)and the phosphorylation of DRP1 protein.Finally,it was found that metformin could adjust DRP1 expression through Calcineurin/TFEB pathway,and promote intracellular TFAM expression by Calcineurin/TFEB/DRP1 pathway.(3)Metformin could reduce extracellular TFAM release to alleviated epirubicininduced vascular endothelial cells injury.Epirubicin could increase the acetylation of TFAM by increasing PCAF expression and reducing SIRT3 expression to promote TFAM release to supernatant.In addition,3-TYP,a SIRT3 inhibitor,could also promote extracellular TFAM release.Moreover,inhibition of PCAF expression by siRNA could reduce epirubicin-induced TFAM release.TFAM neutralizing antibody could alleviate epirubicin-induced DNA damage and excessive apoptosis,suggesting that extracellular TFAM has a harmful effect to vascular endothelial cells.By reducing PCAF expression and increasing SIRT3 expression,metformin pretreatment could reduce TFAM acetylation.In conclusion,metformin could exert an endothelial protection by reducing extracellular TFAM release.In brief,metformin could alleviate epirubicin-induced vascular endothelial cells injury by promoting intracellular TFAM expression,reducing extracellular TFAM release,and maintaining mitochondrial homeostasis.Inhibition of extracellular TFAM release could become a new therapeutic target.