title: NMDA-evoked excitotoxicity increases tissue transglutaminase in cerebellar granule cells.
abstract: In neuronal cells, excessive activation of glutamate receptors causes excitotoxic damage culminating in apoptotic and necrotic cell death. The molecular mechanism of excitotoxicity has been associated with excessive Ca(2+) influx and overload, triggering biochemical events that lead to cell death and tissue degeneration. Following mild insults via NMDA-receptor activation, central neurons undergo several biochemical modifications recognizable as early events in apoptotic machinery.Tissue transglutaminase, the most ubiquitous among cell transglutaminases, catalyzes the Ca(2+)-dependent protein cross-linking probably associated with morphological changes in several neurodegenerative disorders. The possible involvement of this enzyme in excitotoxicity-mediated events was investigated in primary cultures of cerebellar granule cells exposed for 30 min to NMDA (100 microM) in Locke's buffer. Under these conditions time-dependent increases in transglutaminase activity were observed. Tissue transglutaminase expression reached the highest levels within 3-4 h of NMDA exposure. Similarly, high levels of incorporation of fluorescent substrates were observed in living cells. Confocal laser microscopy analysis showed that fluorescein-labelled structures were distributed within the cytoplasm and close to the membranes of NMDA-exposed cells. These effects were dependent on the Ca(2+) influx triggered by the excitotoxic stimulus. Morphological changes in NMDA-treated cells gave evidence of significant cell damage which appeared within 5-6 h of NMDA exposure. These results suggest that increases in tissue transglutaminase may be associated to the effects of NMDA-induced excitotoxicity. Therefore, it is reasonable to hypothesize that if tissue transglutaminase levels and activity are up-regulated under such conditions, the protein cross-linking could be likely involved in excitotoxic response.
authors.affiliation: Department of Biochemical, Physiological and Nutritional Sciences, Faculty of Medicine, University of Messina, Via Consolare Valeria, 98125, Messina, Italy. ientile@unime.it
authors.forename: R
authors.initials: R
authors.lastname: Ientile
authors.forename: D
authors.initials: D
authors.lastname: Caccamo
authors.forename: V
authors.initials: V
authors.lastname: Macaione
authors.forename: V
authors.initials: V
authors.lastname: Torre
authors.forename: S
authors.initials: S
authors.lastname: Macaione
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002525:Cerebellar Cortex / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D016202:N-Methylaspartate / Q000494:pharmacology; D019636:Neurodegenerative Diseases / Q000201:enzymology* / Q000503:physiopathology; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D009498:Neurotoxins / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D011503:Transglutaminases / Q000187:drug effects / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D009498:Neurotoxins; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D016202:N-Methylaspartate; D011503:Transglutaminases