Diabetes enhances oxidative stress-induced TRPM2 channel activity and its control by N-acetylcysteine in rat dorsal root ganglion and brain.

N-acetylcysteine (NAC) is a sulfhydryl donor antioxidant that contributes to the regeneration of glutathione (GSH) and also scavengers via a direct reaction with free oxygen radicals. Recently, we observed a modulatory role of NAC on GSH-depleted dorsal root ganglion (DRG) cells in rats. NAC may have a protective role on oxidative stress and calcium influx through regulation of the TRPM2 channel in diabetic neurons. Therefore, we investigated the effects of NAC on DRG TRPM2 channel currents and brain oxidative stress in streptozotocin (STZ)-induced diabetic rats. Thirty-six rats divided into four groups: control, STZ, NAC and STZ + NAC. Diabetes was induced in the STZ and STZ + NAC groups by intraperitoneal STZ (65 mg/kg) administration. After the induction of diabetes, rats in the NAC and STZ + NAC groups received NAC (150 mg/kg) via gastric gavage. After 2 weeks, DRG neurons and the brain cortex were freshly isolated from rats. In whole-cell patch clamp experiments, TRPM2 currents in the DRG following diabetes induction with STZ were gated by H2O2. TRPM2 channel current densities in the DRG and lipid peroxidation levels in the DRG and brain were higher in the STZ groups than in controls; however, brain GSH, GSH peroxidase (GSH-Px), vitamin C and vitamin E concentrations and DRG GSH-Px activity were decreased by diabetes. STZ + H2O2-induced TRPM2 gating was totally inhibited by NAC and partially inhibited by N-(p-amylcinnamoyl) anthranilic acid (ACA) and 2-aminoethyl diphenylborinate (2-APB). GSH-Px activity and lipid peroxidation levels were also attenuated by NAC treatment. In conclusion, we observed a modulatory role of NAC on oxidative stress and Ca(2+) entry through the TRPM2 channel in the diabetic DRG and brain. Since excessive oxidative stress and overload Ca(2+) entry are common features of neuropathic pain, our findings are relevant to the etiology and treatment of pain neuropathology in DRG neurons.

Apple cider vinegar modulates serum lipid profile, erythrocyte, kidney, and liver membrane oxidative stress in ovariectomized mice fed high cholesterol.

The purpose of this study was to investigate the potentially beneficial effects of apple cider vinegar (ACV) supplementation on serum triglycerides, total cholesterol, liver and kidney membrane lipid peroxidation, and antioxidant levels in ovariectomized (OVX) mice fed high cholesterol. Four groups of ten female mice were treated as follows: Group I received no treatment and was used as control. Group II was OVX mice. Group III received ACV intragastrically (0.6% of feed), and group IV was OVX and was treated with ACV as described for group III. The treatment was continued for 28 days, during which the mice were fed a high-cholesterol diet. The lipid peroxidation levels in erythrocyte, liver and kidney, triglycerides, total, and VLDL cholesterol levels in serum were higher in the OVX group than in groups III and IV. The levels of vitamin E in liver, the kidney and erythrocyte glutathione peroxidase (GSH-Px), and erythrocyte-reduced glutathione (GSH) were decreased in group II. The GSH-Px, vitamin C, E, and ß-carotene, and the erythrocyte GSH and GSH-Px values were higher in kidney of groups III and IV, but in liver the vitamin E and ß-carotene concentrations were decreased. In conclusion, ACV induced a protective effect against erythrocyte, kidney, and liver oxidative injury, and lowered the serum lipid levels in mice fed high cholesterol, suggesting that it possesses oxidative stress scavenging effects, inhibits lipid peroxidation, and increases the levels of antioxidant enzymes and vitamin.

Aminoethoxydiphenyl borate and flufenamic acid inhibit Ca2+ influx through TRPM2 channels in rat dorsal root ganglion neurons activated by ADP-ribose and rotenone.

Exposure to oxidative stress causes health problems, including sensory neuron neuropathy and pain. Rotenone is a toxin used to generate intracellular oxidative stress in neurons. However, the mechanism of toxicity in dorsal root ganglion (DRG) neurons has not been characterized. Melastatin-like transient receptor potential 2 (TRPM2) channel activation and inhibition in response to oxidative stress, ADP-ribose (ADPR), flufenamic acid (FFA) and 2-aminoethoxydiphenyl borate (2-APB) in DRG neurons are also not clear. We tested the effects of FFA and 2-APB on ADPR and rotenone-induced TRPM2 cation channel activation in DRG neurons of rats. DRG neurons were freshly isolated from rats and studied with the conventional whole-cell patch-clamp technique. Rotenone, FFA and 2-APB were extracellularly added through the patch chamber, and ADPR was applied intracellularly through the patch pipette. TRPM2 cation currents were consistently induced by ADPR and rotenone. Current densities of the neurons were higher in the ADPR and rotenone groups than in control. The time courses (gating times) in the neurons were longer in the rotenone than in the ADPR group. ADPR and rotenone-induced TRPM2 currents were totally blocked by 2-APB and partially blocked by FFA. In conclusion, TRPM2 channels were constitutively activated by ADPR and rotenone, and 2-APB and FFA induced an inhibitory effect on TRPM2 cation channel currents in rat DRG neurons. Since oxidative stress is a common feature of neuropathic pain and diseases of sensory neurons, the present findings have broad application to the etiology of neuropathic pain and diseases of DRG neurons.