Balancing mitochondrial dynamics attenuates PM2.5-induced cardiotoxicity via suppression of oxidative stress and NLRP3 inflammasome activation in AC-16 human cardiomyocytes

Background Fine particulate matter (PM2.5) is a major environmental health concern affecting millions worldwide. In addition to lung toxicity, PM2.5 exposure is strongly associated with increased cardiovascular morbidity and mortality. Emerging evidence indicates that PM2.5 induces cardiotoxicity through mitochondrial dynamic disruption (i.e., increased mitochondrial fission and reduced fusion) and excessive oxidative stress, leading to inflammation via activation of NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signalling. However, effective interventions to mitigate PM2.5-induced cardiotoxicity remain limited. Purpose This study aimed to evaluate the therapeutic potential of mitochondrial fission inhibitor Mdivi-1 and fusion promoter M1, and antioxidant treatment in attenuating PM2.5-induced cardiotoxicity in AC-16 human cardiomyocytes. Methods AC16 cells were exposed to increasing concentrations of PM2.5 (0-200 µg/mL) for 24 hours to assess dose-dependent effects on cell viability. Time-dependent intracellular reactive oxygen species (ROS) levels were assessed following exposure to 20 µg/mL of PM2.5 for 3, 6, and 24 hours. For intervention experiments, cells were exposed to PM2.5 (20 µg/mL for 24 h) and co-incubated with Mdivi-1 (2.5 and 5 µM), the M1 (2.5 and 5 µM), or the antioxidant N-acetylcysteine (NAC; 125 and 250 µM). Protective effects were evaluated by assessing cell viability, intracellular ROS levels, and NLRP3 protein expression. Results PM2.5 exposure resulted in a dose-dependent reduction in cell viability and a time-dependent increase in intracellular ROS levels (Fig A-B). Co-incubation with Mdivi-1, M1, or NAC significantly improved cell viability in PM2.5-treated cells (17%, 12%, and 12% increment, respectively), compared with PM2.5 alone (Fig C). Interestingly, Mdivi-1 and M1 markedly reduced ROS levels, while NAC conferred only partial attenuation (50%, 40%, and 32% reduction, respectively) (Fig. D). Furthermore, PM2.5 significantly upregulated NLRP3 expression (Fig E). Treatment with Mdivi-1, M1, or NAC significantly reduced NLRP3 expression compared to PM2.5 alone. Collectively, mitochondrial modulation and antioxidant therapy improved cell survival and reduced oxidative stress and inflammasome activation. Notably, mitochondrial modulation, particularly with Mdivi-1, conferred greater cardioprotective effects than NAC. Conclusion PM2.5 induces cardiotoxicity in human cardiomyocytes through oxidative stress, mitochondrial dynamic imbalance, and NLRP3 inflammasome activation. Pharmacological modulations of mitochondrial dynamics and antioxidant therapy significantly attenuated these pathological responses. Mitochondrial modulation, particularly with Mdivi-1, conferred greater cardioprotective effects than NAC. These findings highlight mitochondria-targeted strategies as potential therapeutic approaches for PM2.5-related cardiovascular injury.PM2.5-Mito Modulator