CoCl2 induces apoptosis via a ROS-dependent pathway and Drp1-mediated mitochondria fission in periodontal ligament stem cells

Oxygen deficiency is associated with various oral diseases, including chronic periodontitis, age-related alveolar bone loss, and mechanical stress-linked cell injury from orthodontic appliances. Nevertheless, our understanding of the impact of hypoxia on periodontal tissues and its biochemical mechanism is still rudimentary. The purpose of this research was to elucidate the effects of hypoxia on the apoptosis of human periodontal ligament stem cells (PDLSCs) in vitro and the underlying mechanism. Herein, we showed that cobalt chloride (CoCl2) triggered cell dysfunction in human PDLSCs in a concentration- dependent manner and resulted in cell apoptosis and oxidative stress overproduction and accumulation in PDLSCs. In addition, CoCl2 promoted mitochondrial fission in PDLSCs. Importantly, CoCl2 increased the expression of dynamin-related protein 1 (Drp1), the major regulator in mitochondrial fission, in PDLSCs. Mitochondrial division inhibitor-1, pharmacological inhibition of Drp1, not only inhibited mitochondrial fission but also protected against CoCl2-induced PDLSC dysfunction, as shown by increased mitochondrial membrane potential, increased ATP level, reduced reactive oxygen species (ROS) level, and decreased apoptosis. Furthermore, N-acetyL- cysteine, a pharmacological inhibitor of ROS, also abolished CoCl2-induced expression of Drp1 and protected against CoCl2-induced PDLSC dysfunction, as shown by restored mitochondrial membrane potential, ATP level, inhibited mitochondrial fission, and decreased apoptosis. Collectively, our data provide new insights into the role of the ROS-Drp1-dependent mitochondrial pathway in CoCl2-induced apoptosis in PDLSCs, indicating that ROS and Drp1 are promising therapeutic targets for the treatment of CoCl2-induced PDLSC dysfunction.