title: Altered calcium/calmodulin kinase II activity changes calcium homeostasis that underlies epileptiform activity in hippocampal neurons in culture.
abstract: Epilepsy is characterized by the occurrence of spontaneous recurrent epileptiform discharges (SREDs) in neurons. A decrease in calcium/calmodulin-dependent protein kinase II (CaMK-II) activity has been shown to occur with the development of SREDs in a hippocampal neuronal culture model of acquired epilepsy, and altered calcium (Ca(2+)) homeostasis has been implicated in the development of SREDs. Using antisense oligonucleotides, this study was conducted to determine whether selective suppression of CaMK-II activity, with subsequent induction of SREDs, was associated with altered Ca(2+) homeostasis in hippocampal neurons in culture. Antisense knockdown resulted in the development of SREDs and a decrease in both immunocytochemical staining and enzyme activity of CaMK-II. Evaluation of [Ca(2+)](i) using Fura indicators revealed that antisense-treated neurons manifested increased basal [Ca(2+)](i), whereas missense-treated neurons showed no change in basal [Ca(2+)](i). Antisense suppression of CaMK-II was also associated with an inability of neurons to restore a Ca(2+) load. Upon removal of oligonucleotide treatment, CaMK-II suppression and Ca(2+) homeostasis recovered to control levels and SREDs were abolished. To our knowledge, the results demonstrate the first evidence that selective suppression of CaMK-II activity results in alterations in Ca(2+) homeostasis and the development of SREDs in hippocampal neurons and suggest that CaMK-II suppression may be causing epileptogenesis by altering Ca(2+) homeostatic mechanisms.
authors.affiliation: Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, P.O. Box 980599, Richmond, VA 23298, USA.
authors.forename: Dawn S
authors.initials: DS
authors.lastname: Carter
authors.forename: S Naqeeb
authors.initials: SN
authors.lastname: Haider
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blair
authors.forename: Laxmikant S
authors.initials: LS
authors.lastname: Deshpande
authors.forename: Sompong
authors.initials: S
authors.lastname: Sombati
authors.forename: Robert J
authors.initials: RJ
authors.lastname: DeLorenzo
mesh_terms: D000465:Algorithms; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003627:Data Interpretation, Statistical; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004827:Epilepsy / Q000503:physiopathology*; D005456:Fluorescent Dyes; D018698:Glutamic Acid / Q000633:toxicity; D006624:Hippocampus / Q000166:cytology / Q000503:physiopathology*; D006706:Homeostasis / Q000502:physiology*; D007150:Immunohistochemistry; D008274:Magnesium / Q000502:physiology; D020125:Mutation, Missense / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D016376:Oligonucleotides, Antisense; D018698:Glutamic Acid; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D008274:Magnesium; D002118:Calcium