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Triptolide (TP), a major active component of Tripterygium wilfordii Hook f., is widely used in the treatment of inflammation and autoimmune disorders. Its clinical application is limited by severe adverse effects, especially cardiotoxicity. Accumulative evidences indicate that TP induces DNA damage by inhibiting RNA polymerase. Considering the relationship among DNA damage, p53, and the role of p53 in mitochondria-dependent apoptosis, we speculate that TP-induced cardiotoxicity results from p53 activation. In this study, the role of p53 in TP-induced cardiotoxicity was investigated in H9c2 cells, primary cardiomyocytes, and C57BL/6 genetic background p53−/− mice. p53 protein level was elevated by TP in vitro and in acute heart injury models. With TP administration (1.2mg/kg), p53 deficiency prevented heart histology injury and decreased serum cardiac troponin I (cTn-I) and apoptotic proteins. Mechanistically, immunoblotting and immunofluorescence staining identified that TP-induced toxicity is dependent on p53 nuclear translocation and transactivation of Bcl2 family genes, leading to mitochondrial outer membrane permeabilization (MOMP) and mitochondria dysfunction. Consistently, p53 antagonist PFTα counteracted TP-induced p53 overexpression and regulation of Bcl2 family transcription, which improved mitochondrial membrane integrity and prevented apoptosis. Moreover, Bax antagonist Bax inhibitor peptide (BIP) V5 ameliorated TP-induced apoptosis through suppressing membrane depolarization and ROS accumulation. These results suggest that TP-induced cardiotoxicity is p53-dependent by promoting Bax-induced mitochondria-mediated apoptosis.p53 activation contributes to TP-induced cardiotoxicity in vitro and in vivo.TP-induced p53 accumulation and translocation affect Bcl2 family expression.p53 regulates MOMP and apoptosis in H9c2 cells by Bax and Bak overexpression.p53 deficiency or Bax inhibition reduces TP-induced cardiotoxicity.