Promotion of SIRT1 protein degradation and lower SIRT1 gene expression via reactive oxygen species is involved in Sb-induced apoptosis in BEAS-2b cells

Abstract

Antimony (Sb) has been reported to lead to pulmonary damage, but the underlying mechanism remains unclear. Accumulating evidence indicates that silent mating type information regulation 2 homolog 1 (SIRT1), an NAD⁺-dependent deacetylase, mediates stimuli-induced cellular apoptosis. Here, we investigated whether SIRT1 plays a role in Sb-triggered apoptosis in human bronchial epithelial cells (BEAS-2b). First, we showed that Sb initiated apoptosis. Furthermore, the expression of SIRT1 was markedly downregulated by Sb treatment, while overexpression of SIRT1 through resveratrol treatment or transfection with SIRT1-Flag plasmid attenuated the Sb-induced apoptosis. Accelerated degradation of SIRT1 protein and lower SIRT1 gene expression contributed to low expression of SIRT1. In addition, Sb activated the ERK and JNK pathways; however, inhibition of ERK rather than JNK rescued SIRT1 suppression. Subsequent analyses demonstrated that antioxidant N-acetylcysteine (NAC) attenuated SIRT1 repression, increased SIRT1 mRNA levels and decreased SIRT1 protein degradation in Sb-treated cells. In addition, NAC also inhibited JNK and ERK activation by Sb exposure. These data suggest that reactive oxygen species-dependent SIRT1 suppression mediates Sb-stimulated cell apoptosis in BEAS-2b cells via lower SIRT1 gene expression and protein stability.

Keywords: Antimony; Apoptosis; Pulmonary toxicity; ROS; SIRT1.