title: Calcium/calmodulin-dependent protein kinase II (CaMKII) inhibition induces neurotoxicity via dysregulation of glutamate/calcium signaling and hyperexcitability.
abstract: Aberrant glutamate and calcium signalings are neurotoxic to specific neuronal populations. Calcium/calmodulin-dependent kinase II (CaMKII), a multifunctional serine/threonine protein kinase in neurons, is believed to regulate neurotransmission and synaptic plasticity in response to calcium signaling produced by neuronal activity. Importantly, several CaMKII substrates control neuronal structure, excitability, and plasticity. Here, we demonstrate that CaMKII inhibition for >4 h using small molecule and peptide inhibitors induces apoptosis in cultured cortical neurons. The neuronal death produced by prolonged CaMKII inhibition is associated with an increase in TUNEL staining and caspase-3 cleavage and is blocked with the translation inhibitor cycloheximide. Thus, this neurotoxicity is consistent with apoptotic mechanisms, a conclusion that is further supported by dysregulated calcium signaling with CaMKII inhibition. CaMKII inhibitory peptides also enhance the number of action potentials generated by a ramp depolarization, suggesting increased neuronal excitability with a loss of CaMKII activity. Extracellular glutamate concentrations are augmented with prolonged inhibition of CaMKII. Enzymatic buffering of extracellular glutamate and antagonism of the NMDA subtype of glutamate receptors prevent the calcium dysregulation and neurotoxicity associated with prolonged CaMKII inhibition. However, in the absence of CaMKII inhibition, elevated glutamate levels do not induce neurotoxicity, suggesting that a combination of CaMKII inhibition and elevated extracellular glutamate levels results in neuronal death. In sum, the loss of CaMKII observed with multiple pathological states in the central nervous system, including epilepsy, brain trauma, and ischemia, likely exacerbates programmed cell death by sensitizing vulnerable neuronal populations to excitotoxic glutamate signaling and inducing an excitotoxic insult itself.
authors.affiliation: Stark Neuroscience Research Institute, Indiana University of School of Medicine, Indianapolis, Indiana 46202, USA.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Ashpole
authors.forename: Weihua
authors.initials: W
authors.lastname: Song
authors.forename: Tatiana
authors.initials: T
authors.lastname: Brustovetsky
authors.forename: Eric A
authors.initials: EA
authors.lastname: Engleman
authors.forename: Nickolay
authors.initials: N
authors.lastname: Brustovetsky
authors.forename: Theodore R
authors.initials: TR
authors.lastname: Cummins
authors.forename: Andy
authors.initials: A
authors.lastname: Hudmon
mesh_terms: D000200:Action Potentials; D000818:Animals; D001930:Brain Injuries / Q000378:metabolism / Q000473:pathology; D002545:Brain Ischemia / Q000378:metabolism / Q000473:pathology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004827:Epilepsy / Q000378:metabolism / Q000473:pathology; D018698:Glutamic Acid / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism
chemical_list: D009419:Nerve Tissue Proteins; D011500:Protein Synthesis Inhibitors; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D003513:Cycloheximide; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; C505410:Casp3 protein, rat; D053148:Caspase 3; D002118:Calcium