YKT6 suppression contributes to 6PPD-induced cardiotoxicity by impairing autophagosome-lysosome fusion in zebrafish

6PPD, a widely used antioxidant in tires, has emerged as an environmental contaminant linked to cardiotoxicity in aquatic organisms, yet the molecular mechanism underlying 6PPD-induced cardiac injury remains unclear. Here, the mechanisms of 6PPD induced cardiotoxicity were investigated utilizing a combination of in vivo zebrafish and in vitro cardiomyocyte models. We found that 6PPD exposure caused cardiac dysfunction, myocardial injury, and pathological remodeling, accompanied by impaired autophagic flux, mitochondrial damage, and cardiomyocyte apoptosis. Mechanistically, 6PPD markedly downregulated YKT6, a SNARE protein essential for autophagosome-lysosome fusion, in both heart of zebrafish and H9C2 cells. Molecular dynamics simulations predicted a potential xenobiotic-protein interaction between 6PPD and YKT6 that restricted its conformational flexibility. Moreover, loss of YKT6 disrupted autophagosome maturation and promoted P62 accumulation, whereas YKT6 overexpression restored autophagosome-lysosome fusion, alleviated mitochondrial injury, and rescued 6PPD-induced cardiomyocyte dysfunction. Consistently, overexpressing YKT6 in adult zebrafish hearts through pericardial injection can also reduce the accumulation of P62 and heart damage. Overall, our findings suggest that 6PPD-induced cardiotoxicity involves YKT6 suppression, which is associated with impaired autophagosome-lysosome fusion and mitochondrial dysfunction, contributing to cardiomyocyte apoptosis in zebrafish. Thus, it was possible that restoring YKT6 emerged as a promising strategy to mitigate 6PPD-associated cardiac injury.