title: Chronic oxidative stress modulates TRPC3 and TRPM2 channel expression and function in rat primary cortical neurons: relevance to the pathophysiology of bipolar disorder.
abstract: Recent findings implicate the calcium-permeable transient receptor potential (TRP) melastatin subtype 2 (TRPM2) and canonical subtype 3 (TRPC3) channels in the pathogenesis of bipolar disorder (BD). As both channels are involved in calcium and oxidative stress signaling, thought to be disrupted in BD, we sought to determine the effects of elevated oxidative stress on their expression and function. Primary rat cortical neurons and astrocytes were treated with oxidative stressors for 1 (acute) and 4 days (chronic). Expression of TRPC3 and TRPM2 were determined by immunoblotting and real-time PCR. Channel functionality was assessed using a TRPC3 activator, 1-oleoyl-2-acetyl-sn-glycerol (OAG), and live cell, ratiometric fluorometry with the calcium sensitive dye, Fura-2. Neurons treated with rotenone (15-30nM) for 4 days but not 24h showed significant dose-dependent decreases in TRPC3 mRNA (31%, p<0.001) and protein levels (60%, p<0.001). Similar dose-dependent attenuation of TRPC3-mediated calcium fluxes was demonstrated upon chronic rotenone exposure relative to vehicle controls. In contrast, TRPM2 mRNA but not protein levels increased (47%, p=0.017) after acute and chronic rotenone treatment. Chronic exposure of neurons to paraquat (1-2µM), an alternate oxidative stressor, similarly decreased TRPC3 expression (mRNA: 41%; protein: 61%). Unlike neurons, rotenone treatment incurred no changes in astrocyte TRPC3 levels. These findings demonstrate that TRPC3 and TRPM2 channel expression and/or function is sensitive to the redox status of rat primary neurons and that these changes are time dependent. This provides a critical mechanistic link between altered oxidative stress markers, dysfunction of these TRP channels and calcium dyshomeostasis in BD.
authors.affiliation: Department of Pharmacology and Toxicology, University of Toronto, 1 King's College Circle, Toronto, ON, Canada M5S 1A8.
authors.forename: A S
authors.initials: AS
authors.lastname: Roedding
authors.forename: S Y
authors.initials: SY
authors.lastname: Tong
authors.forename: W
authors.initials: W
authors.lastname: Au-Yeung
authors.forename: P P
authors.initials: PP
authors.lastname: Li
authors.forename: J J
authors.initials: JJ
authors.lastname: Warsh
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D004075:Diglycerides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006540:Herbicides / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D010269:Paraquat / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D012402:Rotenone / Q000494:pharmacology; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*; D050053:TRPM Cation Channels / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
chemical_list: D004075:Diglycerides; D006540:Herbicides; D017382:Reactive Oxygen Species; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; D050053:TRPM Cation Channels; C557080:Trpm2 protein, rat; D012402:Rotenone; C038237:1-oleoyl-2-acetylglycerol; D010269:Paraquat; D002118:Calcium