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Lu TH, Su CC, Tang FC, Chen CH, Yen CC, Fang KM, Lee KI, Hung DZ, Chen YW. Chloroacetic acid triggers apoptosis in neuronal cells via a reactive oxygen species-induced endoplasmic reticulum stress signaling pathway. Chem Biol Interact 2014; 225:1-12. [PMID: 25451595 DOI: 10.1016/j.cbi.2014.10.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 10/07/2014] [Accepted: 10/17/2014] [Indexed: 11/18/2022]
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.
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Affiliation(s)
- Tien-Hui Lu
- 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.
| | - Chin-Chuan Su
- Department of Otorhinolaryngology, Head and Neck Surgery, Changhua Christian Hospital, No. 135 Nanxiao St., Changhua City, 500 Changhua County, Taiwan.
| | - Feng-Cheng Tang
- Department of Occupational Medicine, Changhua Christian Hospital, No. 135 Nanxiao St., Changhua City, 500 Changhua County, Taiwan.
| | - Chun-Hung Chen
- Department of Emergency, China Medical University Hospital, No. 2 Yuh-Der Rd., 404 Taichung, Taiwan.
| | - Cheng-Chieh Yen
- 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.
| | - Kai-Min Fang
- 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.
| | - kuan-I Lee
- Department of Emergency, Taichung Tzuchi Hospital, The Buddhist Tzuchi Medical Foundation, No. 66 Section 1, Fongsing Rd., Tanzih Township, Taichung 427, Taiwan.
| | - Dong-Zong Hung
- Division of Toxicology, Trauma & Emergency Center, China Medical University Hospital, No. 2 Yuh-Der Rd., 404 Taichung, Taiwan.
| | - Ya-Wen Chen
- 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.
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Abstract
Dermal absorption of some chemicals and drugs can cause systemic toxicity. We evaluated several case reports from the past decade, which discuss the dermal absorption of a specific chemical and potential local and systemic effects. We focused on herbicide and pesticide exposure along with exposure to cutaneous medication, occupational contact, and cosmeceutical exposure. Although causality cannot be established in most cases, it is critical to be aware of the possible effects of topical absorption that may not be immediately apparent. We recommended further studies on specific chemicals to ascertain causality and determine the highest exposure level with no observed adverse affect level (NOAEL) and the reference dose (RfD). Post-marketing epidemiology data in most geographical areas are markedly limited. A weak link in public health resides in the inadequate reporting and workup of alleged chemically related adverse effects. This arena mandates a re-thinking of how to increase this reporting, and workup, as a backup to our preclinical and clinical studies. Public awareness and funding will be rewarded by increased evidence to backup pre-approval pre-marketing studies.
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