Activation of redox-sensitive transcription factors like nuclear factor-E2-related factor 2 (Nrf2) can enhance the transcription of cytoprotective genes during oxidative stress. We investigated whether Nrf2 is activated by methamphetamine (METH) thereby altering neurotoxicity in Nrf2 +/+ and -/- adult mouse brain. A single dose of METH can induce the mRNA levels of Nrf2-regulated antioxidant and cytoprotective proteins in mouse brain. Multiple-day dosing with METH enhanced DNA oxidation and decreased tyrosine hydroxylase and dopamine transporter staining in the striatum, indicating dopaminergic nerve terminal toxicity, which was more severe in -/- mice, as were deficits in motor coordination and olfactory discrimination. These Nrf2-dependent effects were independent of changes in METH metabolism or the induction of hyperthermia. Similarly, METH increased striatal glial fibrillary acidic protein, indicating neurotoxicity. METH neurotoxicity was also observed in the glial cells and in the GABAergic system of the olfactory bulbs and was enhanced in -/- mice, whereas dopaminergic parameters were unaffected. With one-day dosing of METH, there were no differences between +/+ and -/- mice in either basal or METH-enhanced DNA oxidation and neurotoxicity markers. Nrf2-mediated pathways accordingly may protect against the neurodegenerative effects and functional deficits initiated by METH and perhaps other reactive oxygen species-enhancing neurotoxicants, when there is time for transcriptional activation and protein induction. In human users of METH, this mechanism may be essential when differences in drug abuse patterns may alter the induction and duration of Nrf2 activation thereby modulating susceptibility to the neurotoxic effects of METH.
Keywords: Behavioral abnormalities; DNA oxidation; Free radicals; Methamphetamine; Neurodegeneration; Nrf2; Reactive oxygen species.
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