Background: Zinc oxide nanoparticles (ZnO NPs) are one of the most widely used nanomaterials in a variety of fields such as industrial, pharmaceutical, and household applications. Increasing evidence suggests that ZnO NPs could elicit unignorable harmful effect to the cardiovascular system, but the potential deleterious effects to human cardiomyocytes remain to be elucidated. Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have been increasingly used as a promising in vitro model of cardiomyocyte in various fields such as drug cardiac safety evaluation. Herein, the present study was designed to elucidate the cardiac adverse effects of ZnO NPs and explore the possible underlying mechanism using hiPSC-CMs.
Methods: ZnO NPs were characterized by transmission electron microscopy and dynamic light scattering. The cytotoxicity induced by ZnO NPs in hiPSC-CMs was evaluated by determination of cell viability and lactate dehydrogenase release. Cellular reactive oxygen species (ROS) and mitochondrial membrane potential were measured by high-content analysis (HCA). Mitochondrial biogenesis was assayed by detection of mtDNA copy number and PGC-1α pathway. Moreover, microelectrode array techniques were used to investigate cardiac electrophysiological alterations.
Results: We demonstrated that ZnO NPs concentration- and time-dependently elicited cytotoxicity in hiPSC-CMs. The results from HCA revealed that ZnO NPs exposure at low-cytotoxic concentrations significantly promoted ROS generation and induced mitochondrial dysfunction. We further demonstrated that ZnO NPs could impair mitochondrial biogenesis and inhibit PGC-1α pathway. In addition, ZnO NPs at insignificantly cytotoxic concentrations were found to trigger cardiac electrophysiological alterations as evidenced by decreases of beat rate and spike amplitude.
Conclusion: Our findings unveiled the potential harmful effects of ZnO NPs to human cardiomyocytes that involve mitochondrial biogenesis and the PGC-1α pathway that could affect cardiac electrophysiological function.
Keywords: Zinc oxide nanoparticles, ZnO NPs, human induced pluripotent stem cells-derived cardiomyocytes, hiPSC-CMs, cardiac dysfunction, mitochondrial biogenesis, PGC-1α