title: Deletion of TRPC6 Attenuates NMDA Receptor-Mediated Ca2+Entry and Ca2+-Induced Neurotoxicity Following Cerebral Ischemia and Oxygen-Glucose Deprivation.
abstract: Transient receptor potential canonical 6 (TRPC6) channels are permeable to Na+and Ca2+and are widely expressed in the brain. In this study, the role of TRPC6 was investigated following ischemia/reperfusion (I/R) and oxygen-glucose deprivation (OGD). We found that TRPC6 expression was increased in wild-type (WT) mice cortical neurons following I/R and in primary neurons with OGD, and that deletion of TRPC6 reduced the I/R-induced brain infarct in mice and the OGD- /neurotoxin-induced neuronal death. Using live-cell imaging to examine intracellular Ca2+levels ([Ca2+]i), we found that OGD induced a significant higher increase in glutamate-evoked Ca2+influx compared to untreated control and such an increase was reduced by TRPC6 deletion. Enhancement of TRPC6 expression using AdCMV-TRPC6-GFP infection in WT neurons increased [Ca2+]iin response to glutamate application compared to AdCMV-GFP control. Inhibition of N-methyl-d-aspartic acid receptor (NMDAR) with MK801 decreased TRPC6-dependent increase of [Ca2+]iin TRPC6 infected cells, indicating that such a Ca2+influx was NMDAR dependent. Furthermore, TRPC6-dependent Ca2+influx was blunted by blockade of Na+entry in TRPC6 infected cells. Finally, OGD-enhanced Ca2+influx was reduced, but not completely blocked, in the presence of voltage-dependent Na+channel blocker tetrodotoxin (TTX) and dl-α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) blocker CNQX. Altogether, we concluded that I/R-induced brain damage was, in part, due to upregulation of TRPC6 in cortical neurons. We postulate that overexpression of TRPC6 following I/R may induce neuronal death partially through TRPC6-dependent Na+entry which activated NMDAR, thus leading to a damaging Ca2+overload. These findings may provide a potential target for future intervention in stroke-induced brain damage.
authors.affiliation: Division of Neuroscience, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida Orlando, FL, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Chen
authors.affiliation: Division of Neuroscience, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida Orlando, FL, USA.
authors.forename: Zhaozhong
authors.initials: Z
authors.lastname: Li
authors.affiliation: Division of Neuroscience, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida Orlando, FL, USA.
authors.forename: Jeffery T
authors.initials: JT
authors.lastname: Hatcher
authors.affiliation: Department of Kinesiology and Integrative Physiology, Michigan Technological University Houghton, MI, USA.
authors.forename: Qing-Hui
authors.initials: QH
authors.lastname: Chen
authors.affiliation: Department of Clinical Laboratory, The First Central Hospital of Tianjin Tianjin, China.
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Cellular and Molecular Physiology, Stritch School of Medicine, Loyola University Maywood, IL, USA.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Wurster
authors.affiliation: Division of Neuroscience, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida Orlando, FL, USA.
authors.forename: Sic L
authors.initials: SL
authors.lastname: Chan
authors.affiliation: Division of Neuroscience, Burnett School of Biomedical Sciences, College of Medicine, University of Central FloridaOrlando, FL, USA; Division of Metabolic and Cardiovascular Sciences, Burnett School of Biomedical Sciences, College of Medicine, University of Central FloridaOrlando, FL, USA.
authors.forename: Zixi
authors.initials: Z
authors.lastname: Cheng
keywords: Ca2+; NMDA; TRPC6; ischemia; neurotoxicity; oxygen-glucose deprivation (OGD)