Pb2+-induced toxicity is associated with p53-independent apoptosis and enhanced by glutamate in GT1-7 neurons.
Recent studies indicate that the glutamatergic neurotransmitter system is involved in neurotoxicity caused by inorganic lead (Pb2+). We studied the role of apoptosis in the effects induced by Pb2+ (0.01-100 microM) and glutamate (0.1 and 1 mM) in mouse hypothalamic GT1-7 neurons. Although glutamate alone had no effect on cell viability, it enhanced neuronal cell death induced by Pb2+ (1-100 microM) within 72 h. Glutamate alone neither induced caspase-3-like protease activity nor promoted internucleosomal DNA fragmentation, both biochemical hallmarks of apoptosis. However, concurrent exposure to Pb2+ (10 or 100 microM) and glutamate (1 mM) resulted in more prominent cleavage of the fluorogenic caspase-3 substrate (Ac-DEVD-AMC) than caused by the same Pb2+ concentrations alone at 24-72 h. The highest caspase-3-like protease activities were measured at 48 h. Internucleosomal DNA fragmentation caused by Pb2+ (10 or 100 microM) alone or together with glutamate (1 mM) was evident at 96 h, less clear at 72 h and absent at 48 h. Immunoblotting did not reveal any changes in p53 protein levels in cells exposed to Pb2+, glutamate or their combination at any studied time point (3-72 h). Our results suggest that Pb2+-induced neurotoxicity may partially be mediated through p53-independent apoptosis and enhanced by glutamate.
Loikkanen
Jarkko
J
Department of Pharmacology and Toxicology, University of Kuopio, P.O.Box 1627, FIN-70211 Kuopio, Finland. jarkko.loikkanen@uku.fi
Chvalova
Katerina
K
Naarala
Jonne
J
Vähäkangas
Kirsi H
KH
Savolainen
Kai M
KM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D053938:DNA Fragmentation; D016158:Genes, p53 / Q000235:genetics*; D018698:Glutamic Acid / Q000633:toxicity*; D007031:Hypothalamus / Q000166:cytology* / Q000187:drug effects; D015151:Immunoblotting; D007854:Lead / Q000633:toxicity*; D051379:Mice; D009474:Neurons / Q000187:drug effects*; D009707:Nucleosomes / Q000187:drug effects / Q000648:ultrastructure
D009707:Nucleosomes; D007854:Lead; D018698:Glutamic Acid; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases