SIRT3-dependent mitochondrial oxidative stress in sodium fluoride-induced hepatotoxicity and salvage by melatonin

Abstract

Oxidative stress induced by fluoride (F) is associated with fluorosis formation, but the underlying molecular mechanism remains unclear. In this study, Melatonin pretreatment suppressed F-induced hepatocyte injury in HepG2 cells. Melatonin increases the activity of superoxide dismutase (SOD2) by enhancing sirtuin 3 (SIRT3)-mediated deacetylation and promotes SOD2 gene expression via SIRT3-regulated DNA-binding activity of forkhead box O3 (FoxO3a), indicating that melatonin markedly enhanced mROS scavenging in F-exposed HepG2 cells. Notably, melatonin activated the peroxisome proliferator-activated receptor gamma coactivator 1 (PGC-1). PGC-1 interacted with the estrogen-related receptor alpha (ERR) bound to the SIRT3 promoter, where it functions as a transcription factor to regulate SIRT3 expression. Furthermore, daily injection of melatonin for 30 days inhibited F-induced oxidative stress in mice liver, leading to improvement of liver function. Mechanistic study revealed that the protective effects of melatonin were associated with down-regulation of JNK1/2 phosphorylation in vitro and in vivo. Collectively, our data suggest a novel role of melatonin in preventing F-induced oxidative stress through activation of the SIRT3 pathway.