title: Short-term depletion of catalase suppresses cadmium-elicited c-Jun N-terminal kinase activation and apoptosis: role of protein phosphatases.
abstract: The c-Jun N-terminal kinase (JNK) is a vital stress-activated signal that can be regulated differentially under oxidant or antioxidant conditions. Recently, we have reported that activation of JNK by cadmium chloride (Cd) contributes to apoptosis in CL3 human lung adenocarcinoma cells. Although oxidative stress has been implicated in numerous biochemical effects altered by Cd, its role in Cd-elicited JNK activation has not been established. Here we report that catalase is crucial for the activation of JNK by Cd. Short-term treatment of 3-amino-1,2,4-triazole (3AT), a specific catalase inhibitor, completely suppressed the Cd-elicited JNK activation, conversely, exogenous addition of catalase increased the intensity and duration of JNK activation in Cd-treated CL3 cells. Co-administering high doses of H(2)O(2) (500-1000 micro M) with Cd also markedly decreased JNK activity, although at doses <200 micro M H(2)O(2) enhanced the Cd-elicited JNK activation in CL3 cells. 3AT also blocked JNK activation in Cd-treated normal human fibroblasts and Chinese hamster ovary cells, and in UV-irradiated CL3 cells. However, mannitol, a hydroxyl radical scavenger, did not alter the JNK activity in Cd-treated human and rodent cells. Intriguingly, sodium fluoride or okadaic acid, inhibitors for serine/threonine protein phosphatases (PP), recovered the JNK activity in CL3 cells exposed to Cd plus 3AT; however, the protein tyrosine phosphatases inhibitor sodium orthovanadate did not. Furthermore, 3AT decreased but catalase increased the Cd-induced cytotoxicity, apoptosis and procaspase-3 degradation in CL3 cells. Together, these results indicate that persistent activation of apoptotic JNK signal by Cd requires functional catalase and that short-term depletion of catalase activity may facilitate okadaic acid-sensitive PP to down-regulate the JNK activation and may predispose these cells to carcinogenic transformation upon Cd exposure.
authors.affiliation: Molecular Carcinogenesis Laboratory, Department of Life Sciences, National Tsing Hua University, Hsinchu 300, Taiwan, Republic of China.
authors.forename: Show-Mei
authors.initials: SM
authors.lastname: Chuang
authors.forename: I-Ching
authors.initials: IC
authors.lastname: Wang
authors.forename: Yi-Shi
authors.initials: YS
authors.lastname: Hwua
authors.forename: Jia-Ling
authors.initials: JL
authors.lastname: Yang
mesh_terms: D000640:Amitrole / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D016466:CHO Cells; D002104:Cadmium / Q000494:pharmacology*; D002374:Catalase / Q000378:metabolism*; D006224:Cricetinae; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007231:Infant, Newborn; D048031:JNK Mitogen-Activated Protein Kinases; D008297:Male; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D010545:Peroxides / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D004791:Enzyme Inhibitors; D010545:Peroxides; D002104:Cadmium; D019319:Okadaic Acid; D006861:Hydrogen Peroxide; D002374:Catalase; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D000640:Amitrole