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

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 (H₂O₂) generation. Recently, we have reported that treatment with H₂O₂ 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 H₂O₂ generation by upregulating the levels of NOX2 and its regulatory proteins (p22^phox, p40^phox, p47^phox, p67^phox, 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 H₂O₂, thereby hindering activation of AMPK, inhibition of Akt/mTOR, and induction of apoptosis in neuronal cells. Pretreatment with catalase, a H₂O₂-scavenging enzyme, blocked the effects of PD toxins on NOX2-dependent H₂O₂ 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 H₂O₂-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 H₂O₂ 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 H₂O₂ 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.