COX-2 Regulates the insulin-like growth factor I-induced potentiation of Zn(2+)-toxicity in primary cortical culture.
The pretreatment of cultured cortical neurons with neurotrophic factors markedly potentiates the cytotoxicity induced by low concentrations of Zn(2+) or excitotoxins. In the current study, we investigated the mechanism underlying the insulin-like growth factor-I (IGF-I)-induced Zn(2+) toxicity potentiation. The pretreatment of primary cortical cultures for more than 12 h with 100 ng/ml of IGF-I increased the cytotoxicity induced by 80 microM Zn(2+) by more than 2-fold. The IGF-I-enhanced cell death was blocked by the COX-2-specific inhibitors N-[2-(cyclohexyloxyl)-4-nitrophenyl]-methane sulfonamide (NS-398; 10-100 microM) and 1-[(4-methylsulfonyl)phenyl]-3-trifluoro-methyl-5-[(4-fluoro)phenyl]pyrazole (SC58125; 10 microM) and by the antioxidant trolox (30 microM). In addition, it was observed that COX-2 expression was increased 12 to 24 h after IGF-I treatment. Preincubation of cortical cultures with IGF-I increased arachidonic acid (AA)-induced cytotoxicity, and AA increased Zn(2+) toxicity, which suggested the involvement of COX activity in these cellular responses. Moreover, enhanced COX-2 activity led to a decrease in the cell's reducing power, as indicated by a gradual depletion of intracellular GSH. Cortical neurons pretreated with IGF-I and then Zn(2+) showed consistently enhanced reactive oxygen species production, which was repressed by NS-398 and SC58125. Cortical neurons treated with Zn(2+) and then AA displayed the increased ROS production, which was also suppressed by NS-398 and SC58125. These results suggest that COX-2 is an endogenous factor responsible for the IGF-I-induced potentiation of Zn(2+) toxicity and that enhanced COX-2 activity leads to a decrease in the cell's reducing power and an increase in ROS accumulation in primary cortical cultures.
Im
Joo-Young
JY
Ewha Institute of Neuroscience, Ewha Womans University School of Medicine, 70 Jongno-6-Ga, Jongno-Gu, Seoul, 110-783, Republic of Korea.
Kim
Doyeun
D
Lee
Kang-Woo
KW
Kim
Jung-Bin
JB
Lee
Ja-Kyeong
JK
Kim
Dong Sik
DS
Lee
Young Ik
YI
Ha
Kwon-Soo
KS
Joe
Cheol O
CO
Han
Pyung-Lim
PL
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D016923:Cell Death; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015032:Zinc / Q000633:toxicity*
D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D017382:Reactive Oxygen Species; D016718:Arachidonic Acid; D007334:Insulin-Like Growth Factor I; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D015032:Zinc