title: Temporal dependence of cysteine protease activation following excitotoxic hippocampal injury.
abstract: Excitotoxic insults can lead to intracellular signaling cascades that contribute to cell death, in part by activation of proteases, phospholipases, and endonucleases. Cysteine proteases, such as calpains, are calcium (Ca(2+))-activated enzymes which degrade cytoskeletal proteins, including microtubule-associated proteins, tubulin, and spectrin, among others. The current study used the organotypic hippocampal slice culture model to examine whether pharmacologic inhibition of cysteine protease activity inhibits N-methyl-D-aspartate- (NMDA-) induced excitotoxic (20 μM NMDA) cell death and changes in synaptophysin immunoreactivity. Significant NMDA-induced cytotoxicity (as measured by propidium iodide [PI] uptake) was found in the CA1 region of the hippocampus at all timepoints examined (24, 72, 120 h), an effect significantly attenuated by co-exposure to the selective NMDA receptor antagonist DL-2-Amino-5-phosphonopentanoic acid (APV), but not MDL-28170, a potent cysteine protease inhibitor. Results indicated sparing of NMDA-induced loss of the synaptic vesicular protein synaptophysin in all regions of the hippocampus by MDL-28170, though only at early timepoints after injury. These results suggest Ca(2+)-dependent recruitment of cysteine proteases within 24h of excitotoxic insult, but activation of alternative cellular degrading mechanisms after 24h. Further, these data suggest that synaptophysin may be a substrate for calpains and related proteases.
authors: Department of Psychology, Spinal Cord and Brain Injury Research Center, B449 Biomedical and Biological Sciences Research Building, 741 South Limestone Street, Lexington, KY 40536-0509, United States.
authors: J N
authors: JN
authors: Berry
authors: L J
authors: LJ
authors: Sharrett-Field
authors: T R
authors: TR
authors: Butler
authors: M A
authors: MA
authors: Prendergast
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002154:Calpain / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D057056:Cysteine Proteases / Q000378:metabolism*; D004151:Dipeptides / Q000494:pharmacology; D004789:Enzyme Activation / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D007150:Immunohistochemistry; D008297:Male; D016202:N-Methylaspartate / Q000633:toxicity*; D009410:Nerve Degeneration / Q000503:physiopathology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D017470:Receptors, Glutamate / Q000187:drug effects; D016708:Synaptophysin / Q000378:metabolism
chemical_list: D004151:Dipeptides; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; D016708:Synaptophysin; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D057056:Cysteine Proteases; D002154:Calpain; C058076:calpain inhibitor III