title: Hypochlorous acid induces apoptosis of cultured cortical neurons through activation of calpains and rupture of lysosomes.
abstract: 3-Chlorotyrosine, a bio-marker of hypochlorous acid (HOCl) in vivo, was reported to be substantially elevated in the Alzheimer's disease (AD) brains. Thus, HOCl might be implicated in the development of AD. However, its effect and mechanism on neuronal cell death have not been investigated. Here, we report for the first time that HOCl treatment induces an apoptotic-necrotic continuum of concentration-dependent cell death in cultured cortical neurons. Neurotoxicity caused by an intermediate concentration of HOCl (250 microm) exhibited several biochemical markers of apoptosis in the absence of caspase activation. However, the involvement of calpains was demonstrated by data showing that calpain inhibitors protect cortical neurons from apoptosis and the formation of 145/150 kDa alpha-fodrin fragments. Moreover, an increase in cytosolic Ca2+ concentration was associated with HOCl neurotoxicity and Ca2+ channel antagonists, and Ca2+ chelators prevented cleavage of alpha-fodrin and the induction of apoptosis. Finally, we found that calpain activation ruptured lysosomes. Stabilization of lysosomes by calpain inhibitors or imidazoline drugs, as well as inhibition of cathepsin protease activities, rescued cells from HOCl-induced neurotoxicity. Our results showed for the first time that HOCl induces apoptosis in cortical neurons, and that the cell death process involves calpain activation and rupture of lysosomes.
authors.affiliation: Department of Biochemistry, National University of Singapore, Singapore.
authors.forename: Yann Wan
authors.initials: YW
authors.lastname: Yap
authors.forename: Matthew
authors.initials: M
authors.lastname: Whiteman
authors.forename: Boon Huat
authors.initials: BH
authors.lastname: Bay
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Li
authors.forename: Fwu-Shan
authors.initials: FS
authors.lastname: Sheu
authors.forename: Robert Z
authors.initials: RZ
authors.lastname: Qi
authors.forename: Chee Hong
authors.initials: CH
authors.lastname: Tan
authors.forename: Nam Sang
authors.initials: NS
authors.lastname: Cheung
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000494:pharmacology; D002154:Calpain / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006997:Hypochlorous Acid / Q000494:pharmacology*; D008247:Lysosomes / Q000187:drug effects* / Q000473:pathology / Q000648:ultrastructure; D051379:Mice; D046529:Microscopy, Electron, Transmission / Q000379:methods; D019579:Neocortex / Q000166:cytology*; D009474:Neurons / Q000187:drug effects* / Q000473:pathology / Q000648:ultrastructure; D009543:Nifedipine / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology*; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors
chemical_list: D015220:Calcium Channels; D004151:Dipeptides; D004791:Enzyme Inhibitors; C109145:N-(4-fluorophenylsulfonyl)-L-valyl-L-leucinal; D016877:Oxidants; D013778:Tetrazolium Salts; D013844:Thiazoles; C071482:calpeptin; D006997:Hypochlorous Acid; D000255:Adenosine Triphosphate; D002154:Calpain; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; C022616:thiazolyl blue; D009543:Nifedipine; D002118:Calcium