Calcitriol/vitamin D receptor system alleviates PM2.5-induced human bronchial epithelial damage through upregulating mitochondrial bioenergetics in association with regulation of HIF-1α/PGC-1α signaling

PM2.5 exposure causes lung injury by triggering oxidative stress, mitochondrial dysfunction, and modulating HIF-1α signaling. Calcitriol activates VDR, which regulates cellular homeostasis. This study evaluated the protective role of the calcitriol/VDR system in PM2.5-induced damage to BEAS-2B bronchial epithelial cells by reducing oxidative stress, upregulating mitochondrial bioenergetics, and downregulating HIF-1α. We found that the calcitriol/VDR system decreased ROS formation and restored mitochondrial bioenergetics in PM2.5-treated cells. This improvement correlated with reduced HIF-1α nuclear translocation and increased PGC-1α protein and mitochondrial gene expressions. This study is the first to suggest that targeting the calcitriol/VDR system could be a promising pharmacological strategy for mitigating PM2.5-induced lung epithelial damage by promoting mitochondrial bioenergetics and regulating PGC-1α and HIF-1α signaling.