Hydrogen peroxide is a normal by-product of cellular metabolism that in higher concentrations can cause oxidative stress. Cultured cerebellar granule neurons efficiently disposed of micromolar concentrations of hydrogen peroxide with half-times in the minute range in a process that predominately involved catalase. Application of up to 100 µM hydrogen peroxide did not affect the cell viability for up to 4h, but caused a time- and concentration-dependent increase in the extracellular glutathione (GSH) content that was accompanied by a matching decrease in the cellular GSH content. Hydrogen peroxide at 100 µM stimulated maximally the GSH export from viable neurons, but did not affect GSH export from cultured astrocytes. The peroxide-induced extracellular GSH accumulation from neurons was lowered by 70% in the presence of MK571, an inhibitor of multidrug resistance protein (Mrp) 1. The extracellular GSH content determined after 4h of incubation was already significantly increased after a 5-min exposure of neurons to hydrogen peroxide and became maximal after 15 min of peroxide application. These data demonstrate that just a short exposure of viable cerebellar granule neurons to micromolar concentrations of hydrogen peroxide stimulates a prolonged Mrp1-mediated export of cellular GSH. This process may compromise the antioxidative potential of neurons and increase their sensitivity toward drugs and toxins.
Keywords: Cerebellar granule neurons; Free radicals; GSH; GSSG; Mrp1; Oxidative stress.
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