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Title: Inhibition of N-methyl-D-aspartate receptors increases paraoxon-induced apoptosis in cultured neurons

Organophosphorus (OP) compounds, used as insecticides and chemical warfare agents, are potent neurotoxins. We examined the neurotoxic effect of paraoxon (O,O-diethyl O-p-nitrophenyl phosphate), an organophosphate compound, and the role of NMDA receptors as a mechanism of action in cultured cerebellar granule cells. Paraoxon is neurotoxic to cultured rat cerebellar granule cells in a time- and concentration-dependent manner. Cerebellar granule cells are less sensitive to the neurotoxic effects of paraoxon on day in vitro (DIV) 4 than neurons treated on DIV 8. Surprisingly, the N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801, enhances paraoxon-mediated neurotoxicity suggesting that NMDA receptors may play a protective role. Pretreatment with a subtoxic concentration of N-methyl-D-aspartate (NMDA) [100 {mu}M] protects about 40% of the vulnerable neurons that would otherwise die from paraoxon-induced neurotoxicity. Moreover, addition of a neuroprotective concentration of NMDA 3 h after treatment with paraoxon provides the same level of protection. Because paraoxon-mediated neuronal cell death is time-dependent, we hypothesized that apoptosis may be involved. Paraoxon increases apoptosis about 10-fold compared to basal levels. The broad-spectrum caspase inhibitor (Boc-D-FMK) and the caspase-9-specific inhibitor (Z-LEHD-FMK) protect against paraoxon-mediated apoptosis, paraoxon-stimulated caspase-3 activity and neuronal cell death. MK-801 increases, whereas NMDA blocks paraoxon-induced apoptosis and paraoxon-stimulated caspase-3 activity. Thesemore » results suggest that activation of NMDA receptors protect neurons against paraoxon-induced neurotoxicity by blocking apoptosis initiated by paraoxon.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2]
  1. Department of Neurology, Uniformed Services University of the Health Sciences, Building A, Room 1036, 4301 Jones Bridge Road, Bethesda, MD 20814 (United States)
  2. Department of Neurology, Uniformed Services University of the Health Sciences, Building A, Room 1036, 4301 Jones Bridge Road, Bethesda, MD 20814 (United States). E-mail: amarini@usuhs.mil
Publication Date:
OSTI Identifier:
20722006
Resource Type:
Journal Article
Resource Relation:
Journal Name: Toxicology and Applied Pharmacology; Journal Volume: 208; Journal Issue: 1; Other Information: DOI: 10.1016/j.taap.2005.01.018; PII: S0041-008X(05)00038-4; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ACETYLCHOLINE; APOPTOSIS; IN VITRO; INHIBITION; INSECTICIDES; NERVE CELLS; PHOSPHATES; RATS; RECEPTORS; SAFETY; TIME DEPENDENCE