Triclosan-induced glycolysis drives inflammatory activation in microglia via the Akt/mTOR/HIF 1α signaling pathway

Abstract

Exposure to triclosan (TCS) has been implicated in neurotoxicity including autism spectrum disorders in vivo and oxidative stress and cell apoptosis in vitro. Thus, the molecular mechanisms underlying TCS-induced neurotoxicity warrants further research. In this study, we try to address the mode of action that TCS induced the expression of inflammatory cytokines by shifting metabolism to glycolysis. BV-2 cells were treated with 20 μM TCS for 24 h, and the conditional medium from TCS-induced activated microglia reduced the viability of the murine hippocampal neurons cell line HT22. Protein expression levels in the nuclear factor kappa B (NF-κB) signaling pathway were measured through Western blotting, and the expression levels of inflammatory cytokine were measured using quantitative real-time PCR. The results showed that exposure to TCS enhanced NF-κB activation, increased inflammatory cytokine expression including interleukin (IL) 1β, IL-6, and tumor necrosis factor (TNF) α in the BV-2 cells. The glucose consumption and lactate production in BV2 cell increased sharply after exposure to TCS for 24 h. Based on our qPCR and Western blotting results, the expression of the key glycolysis enzymes—namely hexokinase 1, pyruvate kinase M2, and lactate dehydrogenase A—increased after treatment with 20 μM TCS. Furthermore, inhibiting glycolysis by 2-deoxy-D-glucose reduced the activation of NF-κB and the mRNA expression of the inflammatory cytokines in the TCS-activated BV-2 microglia. The expression of the proteins of the Akt/mTOR/HIF1α pathway examined through Western blotting, which regulates glycolysis, also increased in the BV2 cells exposed to TCS. Moreover, Akt and mTOR inhibition by using LY294002 and rapamycin, respectively, blocked inflammatory cytokine overexpression induced by TCS. In conclusion, TCS can induce glycolysis and directly drive inflammatory activation in microglia; with the mediation of the Akt/mTOR/HIF1α pathway.