title: Homocysteine and cytosolic GSH depletion induce apoptosis and oxidative toxicity through cytosolic calcium overload in the hippocampus of aged mice: involvement of TRPM2 and TRPV1 channels.
abstract: Oxidative stress and apoptosis were induced in neuronal cultures by inhibition of glutathione (GSH) biosynthesis with d,l-buthionine-S,R-sulfoximine (BSO). Transient receptor potential melastatin 2 (TRPM2) and transient receptor potential vanilloid 1 (TRPV1) cation channels are gated by oxidative stress. The oxidant effects of homocysteine (Hcy) may induce activation of TRPV1 and TRPM2 channels in aged mice as a model of Alzheimer's disease (AD). We tested the effects of Hcy, BSO and GSH on oxidative stress, apoptosis and Ca2+ and influx via TRPM2 and TRPV1 channels in the hippocampus of mice. Native mice hippocampal neurons were divided into five groups as follows; control, Hcy, BSO, Hcy+BSO and Hcy+BSO+GSH groups. The neurons in TRPM2 and TRPV1 experiments were stimulated by hydrogen peroxide and capsaicin, respectively. BSO and Hcy incubations increased intracellular free Ca2+ concentrations, reactive oxygen species, apoptosis, mitochondrial depolarization, and levels of caspase 3 and 9. All of these increases were reduced by GSH treatments. Treatment with 2-aminoethoxydiphenyl borate (2-APB) and N-(p-amylcinnamoyl)anthranilic acid (ACA) as potent inhibitors of TRPM2, capsazepine as a potent inhibitor of TRPV1, verapamil+diltiazem (V+D) as inhibitors of the voltage-gated Ca2+ channels (VGCC) and MK-801 as a N-methyl-d-aspartate (NMDA) channel antagonist indicated that GSH depletion and Hcy elevation activated Ca2+ entry into the neurons through TRPM2, TRPV1, VGCC and NMDA channels. Inhibitor roles of 2-APB and capsazepine on the Ca2+ entry higher than in V+D and MK-801 antagonists. In conclusion, these findings support the idea that GSH depletion and Hcy elevation can have damaging effects on hippocampal neurons by perturbing calcium homeostasis, mainly through TRPM2 and TRPV1 channels. GSH treatment can partially reverse these effects.
authors.affiliation: Department of Biophysics, Faculty of Medicine, University of Suleyman Demirel, Isparta, Turkey.
authors.forename: İ S
authors.initials: İS
authors.lastname: Övey
authors.affiliation: Department of Biophysics, Faculty of Medicine, University of Suleyman Demirel, Isparta, Turkey; Neuroscience Research Center, University of Suleyman Demirel, Isparta, Turkey. Electronic address: mustafanaziroglu@sdu.edu.tr.
authors.forename: M
authors.initials: M
authors.lastname: Naziroğlu
mesh_terms: D000375:Aging; D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002211:Capsaicin / Q000633:toxicity; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D006710:Homocysteine / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000633:toxicity; D008297:Male; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D050053:TRPM Cation Channels / Q000378:metabolism; D050916:TRPV Cation Channels / Q000378:metabolism
chemical_list: D000963:Antimetabolites; D050053:TRPM Cation Channels; C544443:TRPM2 protein, mouse; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; D006710:Homocysteine; D019328:Buthionine Sulfoximine; D006861:Hydrogen Peroxide; D005978:Glutathione; D002211:Capsaicin; D002118:Calcium
keywords: TRPM2 and TRPV1 channels; apoptosis; hippocampus; homocysteine; oxidative stress