NOX2-derived hydrogen peroxide impedes the AMPK/Akt-mTOR signaling pathway contributing to cell death in neuronal cells.

Oxidative stress is closely related to the pathogenesis of Parkinson's disease (PD), a typical neurodegenerative disease. NADPH oxidase 2 (NOX2) is involved in hydrogen peroxide (HO) generation. Recently, we have reported that treatment with HO and PD toxins, including 6-hydroxydopamine (6-OHDA), 1-Methyl-4-phenylpyridin-1-ium (MPP) and rotenone, induces neuronal apoptosis by inhibiting the mTOR pathway. Here, we show that treatment with 6-OHDA, MPP or rotenone induced HO generation by upregulating the levels of NOX2 and its regulatory proteins (p22, p40, p47, p67, and Rac1), leading to apoptotic cell death in PC12 cells and primary neurons. Inhibition of NOX2 with apocynin or diphenyleneiodonium, or knockdown of NOX2 powerfully attenuated PD toxins-evoked NOX2 and HO, thereby hindering activation of AMPK, inhibition of Akt/mTOR, and induction of apoptosis in neuronal cells. Pretreatment with catalase, a HO-scavenging enzyme, blocked the effects of PD toxins on NOX2-dependent HO production, AMPK/Akt/mTOR signaling and apoptosis in the cells. Similar effects were also seen in the cells pretreated with Mito-TEMPO, a mitochondria-selective superoxide scavenger, implying a mitochondrial HO-dependent mechanism involved. Further research revealed that ectopic expression of constitutively active Akt or dominant negative AMPKα, or inhibition of AMPK with compound C suppressed PD toxins-induced expression of NOX2 and its regulatory proteins, as well as consequential HO production and apoptosis in the cells. Taken together, these results indicate that certain PD toxins can impede the AMPK/Akt-mTOR signaling pathway leading to neuronal apoptosis by eliciting NOX2-derived HO production. Our findings suggest that neuronal loss in PD may be prevented by regulating the NOX2, AMPK/Akt-mTOR signaling and/or applying antioxidants to ameliorate oxidative stress.