Modulation of oxidative stress and Ca(2+) mobilization through TRPM2 channels in rat dorsal root ganglion neuron by Hypericum perforatum.

A main component of St. John's Wort (Hypericum perforatum, HP) is hyperforin which has antioxidant properties in dorsal root ganglion (DRG) neurons, due to its ability to modulate NADPH oxidase and protein kinase C. Recent reports indicate that oxidative stress through NADPH oxidase activates TRPM2 channels. HP may be a useful treatment for Ca(2+) entry and oxidative stress through modulation of TRPM2 channels in the DRG. We aimed to investigate the protective role of HP on Ca(2+) entry and oxidative stress through TRPM2 channels in DRG neurons of rats. The native rat DRG neurons were used in whole-cell patch-clamp, Fura-2 and antioxidant experiments. Appropriate, nontoxic concentrations and incubation times for HP were determined in the DRG neurons by assessing cell viability. The H2O2-induced TRPM2 currents were inhibited by 2-aminoethyl diphenylborinate (2-APB) and N-(p-amylcinnamoyl)anthranilic acid (ACA). TRPM2 current densities and cytosolic free Ca(2+) concentration in the neurons were also reduced by HP (2 and 24h). In Fura-2 experiments, cytosolic Ca(2+) mobilization was reduced by voltage-gated calcium channel blockers (verapamil+diltiazem, V+D) and HP. Glutathione peroxidase activity and GSH values in the DRG were high in HP, 2-APB and V+D groups although lipid peroxidation level was low in the groups. In conclusion, we observed a protective role for HP on Ca(2+) entry through a TRPM2 channel in the DRG neurons. Since over-production of oxidative stress and Ca(2+) entry are implicated in the pathophysiology of neuropathic pain and neuronal inflammation, our findings may be relevant to the etiology and treatment of neuropathology in DRG neurons.

Melatonin modulates wireless (2.45 GHz)-induced oxidative injury through TRPM2 and voltage gated Ca(2+) channels in brain and dorsal root ganglion in rat.

We aimed to investigate the protective effects of melatonin and 2.45 GHz electromagnetic radiation (EMR) on brain and dorsal root ganglion (DRG) neuron antioxidant redox system, Ca(2+) influx, cell viability and electroencephalography (EEG) records in the rat. Thirty two rats were equally divided into four different groups namely group A1: Cage control, group A2: Sham control, group B: 2.45 GHz EMR, group C: 2.45 GHz EMR+melatonin. Groups B and C were exposed to 2.45 GHz EMR during 60 min/day for 30 days. End of the experiments, EEG records and the brain cortex and DRG samples were taken. Lipid peroxidation (LP), cell viability and cytosolic Ca(2+) values in DRG neurons were higher in group B than in groups A1 and A2 although their concentrations were increased by melatonin, 2-aminoethyldiphenyl borinate (2-APB), diltiazem and verapamil supplementation. Spike numbers of EEG records in group C were lower than in group B. Brain cortex vitamin E concentration was higher in group C than in group B. In conclusion, Melatonin supplementation in DRG neurons and brain seems to have protective effects on the 2.45 GHz-induced increase Ca(2+) influx, EEG records and cell viability of the hormone through TRPM2 and voltage gated Ca(2+) channels.