title: L-type calcium channels reduce ROS generation in cerebellar granule cells following kainate exposure.
abstract: Cerebellar granule cells (CGC) deprived of serum or trophic factors develop sensitivity to kainate neurotoxicity that is mediated by the alpha-amino-3-hydroxy-5-methyl-isoxazole proprionic acid (AMPA) subtypes of glutamate receptors (GluR). The L-type voltage-gated calcium channel (L-type VGCC) blocker nifedipine increases the potency of kainate 50-fold. Thus, one goal of this laboratory is to determine the underlying protective mechanism triggered by calcium influx through this channel. The cell-permeable heavy metal chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine effected complete protection against kainate treatment in the presence of nifedipine, as did the iron chelator deferoxamine. The chelatable heavy metal pool decreased approximately 70% immediately following treatment with kainate, but did not change following kainate/nifedipine treatment. Tetramethylrhhodamine ethyl ester (TMRE) fluorescence, an indicator of mitochondrial membrane potential, decreased approximately 70% following kainate treatment but displayed a more modest decrease ( approximately 15%) when CGC were treated with kainate/nifedipine. Reactive oxygen species (ROS) formation decreased in CGC immediately following kainate treatment but was slightly elevated following kainate/nifedipine treatment. Electron microscopic examinations of the CGC indicated severe swelling and distortion of mitochondria immediately following kainate/nifedipine treatment and the appearance of mitochondrial herniations, whorls, and bridges 2 h later, features that were rarely observed following kainate treatment. These results support the hypothesis that calcium entry through L-type VGCCs protects CGC during kainate treatment by lowering the chelatable heavy metal pool and the mitochondrial membrane potential, thereby mitigating the formation of ROS.
authors.affiliation: Laboratory of Molecular Neuroscience, McLean Hospital, Belmont, Massachusetts 02178, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Leski
authors.forename: Linda C
authors.initials: LC
authors.lastname: Hassinger
authors.forename: Stacey L
authors.initials: SL
authors.lastname: Valentine
authors.forename: Jesse D
authors.initials: JD
authors.lastname: Baer
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Coyle
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002490:Central Nervous System / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002493:Central Nervous System Diseases / Q000378:metabolism* / Q000503:physiopathology; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002614:Chelating Agents / Q000494:pharmacology; D004579:Electron Transport / Q000187:drug effects / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000494:pharmacology; D007501:Iron / Q000378:metabolism; D007608:Kainic Acid / Q000494:pharmacology; D008854:Microscopy, Electron; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D009498:Neurotoxins / Q000494:pharmacology*; D009543:Nifedipine / Q000494:pharmacology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D017470:Receptors, Glutamate / Q000187:drug effects / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002614:Chelating Agents; D018691:Excitatory Amino Acid Antagonists; D005456:Fluorescent Dyes; D009498:Neurotoxins; D017382:Reactive Oxygen Species; D017470:Receptors, Glutamate; D007501:Iron; D009543:Nifedipine; D007608:Kainic Acid