The CMPK2–mtDNA axis mediates doxorubicin cardiotoxicity: mechanistic links to STAT1 transcription and FAD-mediated inhibition

Aims Doxorubicin is a widely used chemotherapeutic agent whose clinical utility is limited by dose-dependent cardiotoxicity. The precise mechanisms bridging mitochondrial dysfunction to cardiac inflammatory responses remain poorly defined. Methods and results We utilized cardiomyocyte-specific CMPK2 knockout and overexpression mouse models, along with AAV9-mediated cardiac gene delivery in vivo and molecular assays in vitro, to define the role of the mitochondrial nucleotide metabolic enzyme CMPK2 in doxorubicin-induced cardiomyopathy. Tumor-bearing mouse models were employed to evaluate the impact on antitumor efficacy. CMPK2 expression was significantly upregulated in doxorubicin-injured hearts. Cardiomyocyte-specific CMPK2 overexpression exacerbated DOX-induced cardiac dysfunction, atrophy, oxidative stress, and fibrosis, whereas CMPK2 knockdown attenuated these pathological alterations. Mechanistically, CMPK2 drove oxidative mitochondrial DNA damage and cytosolic leakage, subsequently triggering NLRP3 inflammasome activation. We further identified STAT1 as a transcriptional activator of CMPK2. Importantly, the natural coenzyme flavin adenine dinucleotide directly bound to CMPK2 and blocked its downstream signaling. Flavin adenine dinucleotide administration mitigated doxorubicin-induced cardiac injury without compromising its antitumor efficacy in mice. Conclusions Our study establishes CMPK2 as a key mediator of doxorubicin cardiotoxicity, integrating STAT1-mediated transcriptional regulation with mtDNA-dependent NLRP3 inflammasome activation into a unified pathological axis. Targeting this axis with flavin adenine dinucleotide represents a promising and selective cardioprotective strategy, addressing a major challenge in cardio-oncology.