title: Chloroacetic acid triggers apoptosis in neuronal cells via a reactive oxygen species-induced endoplasmic reticulum stress signaling pathway.
abstract: Chloroacetic acid (CA), a chlorinated analog of acetic acid and an environmental toxin that is more toxic than acetic, dichloroacetic, or trichloroacetic acids, is widely used in chemical industries. Furthermore, CA has been found to be the major disinfection by-products (DBPs) of drinking water. CA has been reported to be highly corrosive and to induce severe tissue injuries (including nervous system) that lead to death in mammals. However, the effects and underlying mechanisms of CA-induced neurotoxicity remain unknown. In the present study, we found that CA (0.5-2.0 mM) significantly increased LDH release, decreased the number of viable cells (cytotoxicity) and induced apoptotic events (including: increases in the numbers of apoptotic cells, the membrane externalization of phosphatidylserine (PS), and caspase-3/-7 activity) in Neuro-2a cells. CA (1.5 mM; the approximate to LD50) also triggered ER stress, which was identified by monitoring several key molecules that are involved in the unfolded protein responses (including the increase in the expressions of p-PERK, p-IRE-1, p-eIF2α, ATF-4, ATF-6, CHOP, XBP-1, GRP 78, GRP 94, and caspase-12) and calpain activity. Transfection of GRP 78- and GRP 94-specific si-RNA effectively abrogated CA-induced cytotoxicity, caspase-3/-7 and caspase-12 activity, and GRP 78 and GRP 94 expression in Neuro-2a cells. Additionally, pretreatment with 2.5 mM N-acetylcysteine (NAC; a glutathione (GSH) precursor) dramatically suppressed the increase in lipid peroxidation, cytotoxicity, apoptotic events, calpain and caspase-12 activity, and ER stress-related molecules in CA-exposed cells. Taken together, these results suggest that the higher concentration of CA exerts its cytotoxic effects in neuronal cells by triggering apoptosis via a ROS-induced ER stress signaling pathway.
authors.affiliation: Department of Physiology and Graduate Institute of Basic Medical Science, School of Medicine, College of Medicine, China Medical University, No. 91 Hsueh-Shih Rd., 404 Taichung, Taiwan. Electronic address: tienylu@gmail.com.
authors.forename: Tien-Hui
authors.initials: TH
authors.lastname: Lu
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, Changhua Christian Hospital, No. 135 Nanxiao St., Changhua City, 500 Changhua County, Taiwan. Electronic address: 91334@cch.org.tw.
authors.forename: Chin-Chuan
authors.initials: CC
authors.lastname: Su
authors.affiliation: Department of Occupational Medicine, Changhua Christian Hospital, No. 135 Nanxiao St., Changhua City, 500 Changhua County, Taiwan. Electronic address: 106159@cch.org.tw.
authors.forename: Feng-Cheng
authors.initials: FC
authors.lastname: Tang
authors.affiliation: Department of Emergency, China Medical University Hospital, No. 2 Yuh-Der Rd., 404 Taichung, Taiwan. Electronic address: drumbeater1978@gmail.com.
authors.forename: Chun-Hung
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Department of Occupational Safety and Health, College of Health Care and Management, Chung Shan Medical University, No. 110 Section 1, Jian-Guo N. Rd., 402 Taichung, Taiwan; Department of Occupational Medicine, Chung Shan Medical University Hospital, No. 110 Section 1, Jian-Guo N. Rd., 402 Taichung, Taiwan. Electronic address: ycj@csmu.edu.tw.
authors.forename: Cheng-Chieh
authors.initials: CC
authors.lastname: Yen
authors.affiliation: Department of Physiology and Graduate Institute of Basic Medical Science, School of Medicine, College of Medicine, China Medical University, No. 91 Hsueh-Shih Rd., 404 Taichung, Taiwan; Department of Otolaryngology, Far Eastern Memorial Hospital, No. 21, Sec. 2, Nanya S. Rd., Banciao Dist., New Taipei City 220, Taiwan. Electronic address: u701048@gmail.com.
authors.forename: Kai-Min
authors.initials: KM
authors.lastname: Fang
authors.affiliation: Department of Emergency, Taichung Tzuchi Hospital, The Buddhist Tzuchi Medical Foundation, No. 66 Section 1, Fongsing Rd., Tanzih Township, Taichung 427, Taiwan. Electronic address: leeguanto2002@yahoo.com.tw.
authors.forename: kuan-I
authors.initials: kI
authors.lastname: Lee
authors.affiliation: Division of Toxicology, Trauma & Emergency Center, China Medical University Hospital, No. 2 Yuh-Der Rd., 404 Taichung, Taiwan. Electronic address: dzhung@mail.cmu.edu.tw.
authors.forename: Dong-Zong
authors.initials: DZ
authors.lastname: Hung
authors.affiliation: Department of Physiology and Graduate Institute of Basic Medical Science, School of Medicine, College of Medicine, China Medical University, No. 91 Hsueh-Shih Rd., 404 Taichung, Taiwan. Electronic address: ywc@mail.cmu.edu.tw.
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Chen
mesh_terms: D000085:Acetates / Q000378:metabolism* / Q000633:toxicity; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002154:Calpain / Q000235:genetics / Q000378:metabolism; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000502:physiology*; D005434:Flow Cytometry; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D012313:RNA / Q000737:chemistry / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism
chemical_list: D000085:Acetates; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; C053387:endoplasmin; D051742:Transcription Factor CHOP; C006972:chloroacetic acid; D012313:RNA; D002154:Calpain; D020169:Caspases; C112682:Capn1 protein, mouse
keywords: Apoptosis; Chloroacetic acid; Endoplasmic reticulum stress; Neurotoxicity; ROS