Regulation of intracellular Ca2+by reactive oxygen species in osteoblasts treated with antimycin A

This study evaluated the effects of antimycin A (AMA), an inhibitor of electron transport in mitochondria, on the release of intracellular calcium ion ([Ca2+]i), ROS and bone resorbing factors in osteoblastic MC3T3-E1 cells. Pretreatment of osteoblasts with trolox, a ROS scavenger, and cyclosporin A, a potent inhibitor of calcium release from mitochondria, prevented the AMA-induced increases in [Ca2+]i. However, [Ca2+]i increase by AMA was unaffected by dantrolene, which blocks the ryanodine receptor channel of the endoplasmic reticulum. BAPTA/AM (an intracellular Ca2+ chelator), dantrolene and cyclosporine A did not reverse the effect of AMA on ROS release. We also investigated whether intracellular calcium release inhibitor and antioxidant protect against AMA-induced bone resorbing cytokine release. Trolox prevented the release of receptor activator of nuclear factor-?B ligand (RANKL), IL-6, and TNF-a induced by AMA. Moreover, the increased IL-6 and TNF-a release by AMA was markedly reduced by BAPTA/AM and cyclosporin A. However, BAPTA/AM did not reverse the effect of AMA on osteoprotegerin and RANKL. Taken together, these results demonstrate that mitochondrial ROS generation and Ca2+ influx by AMA is required for osteoblast death and bone resorbing cytokine release. Copyright (C) 2011 John Wiley & Sons, Ltd.