High-frequency field stimulation of primary neurons enhances ryanodine receptor-mediated Ca2+ release and generates hydrogen peroxide, which jointly stimulate NF-κB activity.

Neuronal electrical activity increases intracellular Ca2+ concentration and generates reactive oxygen species. Here, we show that high frequency field stimulation of primary hippocampal neurons generated Ca2+ signals with an early and a late component, and promoted hydrogen peroxide generation via a neuronal NADPH oxidase. Hydrogen peroxide generation required both Ca2+ entry through N-methyl-D-aspartate receptors and Ca2+ release mediated by ryanodine receptors (RyR). Field stimulation also enhanced nuclear translocation of the NF-kappa B p65 protein and NF-kappa B -dependent transcription, and increased c-fos mRNA and type-2 RyR protein content. Preincubation with inhibitory ryanodine or with the antioxidant N-acetyl L-cysteine abolished the increase in hydrogen peroxide generation and the late Ca2+ signal component induced by electrical stimulation. Primary cortical cells behaved similarly as primary hippocampal cells. Exogenous hydrogen peroxide also activated NF-kappa B-dependent transcription in hippocampal neurons; inhibitory ryanodine prevented this effect. Selective inhibition of the NADPH oxidase or N-acetyl L-cysteine also prevented the enhanced translocation of p65 in hippocampal cells, while N-acetyl L-cysteine abolished the increase in RyR2 protein content induced by high frequency stimulation. In conclusion, the present results show that electrical stimulation induced reciprocal activation of ryanodine receptor-mediated Ca2+ signals and hydrogen peroxide generation, which stimulated jointly NF-kappa B activity. Antioxid. Redox Signal. 14, 1245-1259.