Chlorpyrifos induces delayed cytotoxicity after withdrawal in primary hippocampal neurons through extracellular signal-regulated kinase inhibition.
In this study, the delayed effect and related mechanism after chlorpyrifos (CPF) withdrawal was studied in primary rat hippocampal neurons. The results showed that 10 muM CPF induced no detectable cytotoxicity during 96 h continuous exposure while its withdrawal after 48 h exposure induced evident cytotoxicity, as indexed by decreased methyl thiazolyl tetrazolium (MTT) metabolism, increased loss of neurons immunostained by neuron-specific enolase (NSE) antibody, and the increased terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) positive cell rate in the following 24 h and 48 h incubation in the absence of CPF. Extracellular signal-related kinase (ERK)1/2 activation by phosphorylation was observed and persisted during CPF exposure. However, CPF withdrawal after 48 h exposure led to inhibition of ERK1/2 phosphorylation. Carbacol and nerve growth factor (NGF), which are ERK1/2 activators, protected the neurons after CPF withdrawal, while atropine and PD98059, which are ERK1/2 inhibitors, exacerbated the cytotoxicity, indicating the involvement of inhibition of ERK1/2 phosphorylation in CPF-induced delayed cytotoxicity. In conclusion, CPF withdrawal after exposure induced delayed cytotoxicity in cultured neurons. Inhibition of ERK1/2 phosphorylation was found to be related to the delayed cytotoxicity. This finding may provide a new insight into the toxicological mechanism of organophosphorus pesticides, especially chronic organophosphate-induced neuropsychiatric disorder characterized by delayed occurrence.
Evaluation and Research Center for Toxicology, Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Fengtai District, Beijing 100071, PR. China.
De-Hong
DH
Tan
Shuang-Qing
SQ
Peng
Ying-Liang
YL
Wu
Yi-Mei
YM
Wang
Chun-Feng
CF
Lu
Wei
W
Ding
Qiao-Xu
QX
Wang
Chang-Hui
CH
Yan
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D004390:Chlorpyrifos / Q000633:toxicity*; D018679:Cholinergic Agonists / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors*; D005419:Flavonoids / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects*; D020287:In Situ Nick-End Labeling; D007306:Insecticides / Q000633:toxicity*; D020932:Nerve Growth Factor / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects*; D010751:Phosphopyruvate Hydratase / Q000276:immunology; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley
D018679:Cholinergic Agonists; D005419:Flavonoids; D007306:Insecticides; D001285:Atropine; D002217:Carbachol; D020932:Nerve Growth Factor; D048049:Extracellular Signal-Regulated MAP Kinases; D010751:Phosphopyruvate Hydratase; D004390:Chlorpyrifos; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one