Etoposide (ETO) is an anticancer drug that inhibits topoisomerase II but also causes cellular senescence. 7,8-Dihydroxyflavone (7,8-DHF), a small-molecule tropomyosin receptor kinase B agonist, has demonstrated cardioprotective effects in multiple injury models; however, its ability to prevent DNA damage in cardiomyocytes remains unclear. We therefore examined whether 7,8-DHF protects H9c2 cardiomyocytes from ETO-induced genotoxicity and investigated the underlying mechanisms. Short-term (2 h) ETO exposure induced a concentration-dependent increase in the DNA damage marker γ-H2AX without immediate cytotoxicity. 7,8-DHF pretreatment significantly attenuated this early DNA damage and blunted acute p53 upregulation. Nutlin-3a, a p53 agonist, abolished the protective effect of 7,8-DHF against early DNA damage. In contrast, prolonged (24 h) ETO exposure induced marked cytotoxicity, as evidenced by increased apoptosis, elevated lactate dehydrogenase (LDH) release, and sustained γ-H2AX elevation. 7,8-DHF significantly preserved cell morphology, reduced LDH release, and decreased apoptosis. Mechanistically, while ETO alone upregulated p53, co-treatment with 7,8-DHF further enhanced p53 expression after prolonged exposure, and p53 knockdown reversed the cardioprotective effect of 7,8-DHF, indicating a p53-dependent mechanism under chronic insult. In summary, 7,8-DHF mitigates ETO-induced DNA damage and cytotoxicity in cardiomyocytes through time-dependent, biphasic modulation of the p53 pathway, highlighting its potential as an adjuvant cardioprotective strategy during genotoxic chemotherapy.
