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Lynch HN, Kozal JS, Vincent MJ, Freid RD, Beckett EM, Brown S, Mathis C, Schoeny RS, Maier A. Systematic review of the human health hazards of propylene dichloride. Regul Toxicol Pharmacol 2023; 144:105468. [PMID: 37562533 DOI: 10.1016/j.yrtph.2023.105468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 06/05/2023] [Accepted: 08/05/2023] [Indexed: 08/12/2023]
Abstract
Propylene dichloride (PDC) is a chlorinated substance used primarily as an intermediate in basic organic chemical manufacturing. The United States Environmental Protection Agency (EPA) is currently evaluating PDC as a high-priority substance under the Toxic Substances Control Act (TSCA). We conducted a systematic review of the non-cancer and cancer hazards of PDC using the EPA TSCA and Integrated Risk Information System (IRIS) frameworks. We identified 12 epidemiological, 16 toxicokinetic, 34 experimental animal, and 49 mechanistic studies. Point-of-contact respiratory effects are the most sensitive non-cancer effects after inhalation exposure, and PDC is neither a reproductive nor a developmental toxicant. PDC is not mutagenic in vivo, and while in vitro evidence is mixed, DNA strand breaks consistently occur. Nasal tumors in rats and lung tumors in mice occurred after lifetime high-level inhalation exposure. Cholangiocarcinoma (CCA) was observed in Japanese print workers exposed to high concentrations of PDC. However, co-exposures, as well as liver parasites, hepatitis, and other risk factors, may also have contributed. The cancer mode of action (MOA) analysis revealed that PDC may act through multiple biological pathways occurring sequentially and/or simultaneously, although chronic tissue damage and inflammation likely dominate. Critically, health benchmarks protective of non-cancer effects are expected to protect against cancer in humans.
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Kozal JS, Lynch HN, Klapacz J, Schoeny RS, Jean PA, Maier A. Mode of action assessment for propylene dichloride as a human carcinogen. Chem Biol Interact 2023; 382:110382. [PMID: 36754223 DOI: 10.1016/j.cbi.2023.110382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 01/16/2023] [Accepted: 02/04/2023] [Indexed: 02/09/2023]
Abstract
As part of a systematic review of the non-cancer and cancer hazards of propylene dichloride (PDC), with a focus on potential carcinogenicity in workers following inhalation exposures, we determined that a mode of action (MOA)-centric framing of cancer effects was warranted. In our MOA analysis, we systematically reviewed the available mechanistic evidence for PDC-induced carcinogenesis, and we mapped biologically plausible MOA pathways and key events (KEs), as guided by the International Programme on Chemical Safety (IPCS)-MOA framework. For the identified pathways and KEs, biological concordance, essentiality of KEs, concordance of empirical observations among KEs, consistency, and analogy were evaluated. The results of this analysis indicate that multiple biologically plausible pathways may contribute to the cancer MOA for PDC, but that the relevant pathways vary by exposure route and level, tissue type, and species; further, more than one pathway may occur concurrently at high exposure levels. While several important data gaps exist, evidence from in vitro mechanistic studies, in vivo experimental animal studies, and ex vivo human tumor tissue analyses indicates that the predominant MOA pathway likely involves saturation of cytochrome p450 2E1 (CYP2E1)-glutathione (GSH) detoxification (molecular initiating event; MIE), accumulation of CYP2E1-oxidative metabolites, cytotoxicity, chronic tissue damage and inflammation, and ultimately tumor formation. Tumors may occur through several subsets of inflammatory KEs, including inflammation-induced aberrant expression of activation-induced cytidine deaminase (AID), which causes DNA strand breaks and mutations and can lead to tumors with a characteristic mutational signature found in occupational cholangiocarcinoma. Dose concordance analysis showed that low-dose mutagenicity (from any pathway) is not a driving MOA, and that prevention of target tissue damage and inflammation (associated with saturation of CYP2E1-GSH detoxification) is expected to also prevent the cascade of processes responsible for tumor formation.
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Affiliation(s)
| | | | - Joanna Klapacz
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, MI, 48674, USA
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Ekuban A, Zong C, Ekuban FA, Kimura Y, Takizawa R, Morikawa K, Kinoshita K, Ichihara S, Ohsako S, Ichihara G. Role of Macrophages in Cytotoxicity, Reactive Oxygen Species Production and DNA Damage in 1,2-Dichloropropane-Exposed Human Cholangiocytes In Vitro. TOXICS 2021; 9:toxics9060128. [PMID: 34205922 PMCID: PMC8228395 DOI: 10.3390/toxics9060128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 05/24/2021] [Accepted: 05/25/2021] [Indexed: 12/13/2022]
Abstract
1,2-Dichloropropane (1,2-DCP), a synthetic chlorinated organic compound, was extensively used in the past in offset color proof-printing. In 2014, the International Agency for Research on Cancer (IARC) reclassified 1,2-DCP from its initial Group 3 to Group 1. Prior to the reclassification, cholangiocarcinoma was diagnosed in a group of workers exposed to 1,2 -DCP in an offset color proof-printing company in Japan. In comparison with other forms of cholangiocarcinoma, 1,2-DCP-induced cholangiocarcinoma was of early onset and accompanied by extensive pre-cancerous lesions in large bile ducts. However, the mechanism of 1,2-DCP-induced cholangiocarcinoma is poorly understood. Inflammatory cell proliferation was observed in various sites of the bile duct in the noncancerous hepatic tissues of the 1,2-DCP-induced cholangiocarcinoma. The aim of this study was to enhance our understanding of the mechanism of 1,2-DCP-related cholangiocarcinogenesis. We applied an in vitro system to investigate the effects of 1,2-DCP, using MMNK-1 cholangiocytes cultured alone or with THP-1 macrophages. The cultured cells were exposed to 1,2-DCP at 0, 0.1, 0.2, 0.4, and 0.8 mM for 24 h, and then assessed for cell proliferation, cell cytotoxicity, DNA damage, and ROS production. Exposure to 1,2-DCP increased proliferation of MMNK-1 cholangiocytes cultured alone, but not those cultured with macrophages. 1,2-DCP also increased LDH cytotoxicity, DNA damage, and ROS production in MMNK-1 cholangiocytes co-cultured with macrophages but not those cultured alone. 1,2-DCP increased TNFα and IL-1β protein expression in macrophages. The results highlight the role of macrophages in enhancing the effects of 1,2-DCP on cytotoxicity, ROS production, and DNA damage in cholangiocytes.
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Affiliation(s)
- Abigail Ekuban
- Department of Occupational and Environmental Health, Tokyo University of Science, Noda 278-8510, Japan; (A.E.); (C.Z.); (F.A.E.); (Y.K.); (R.T.); (K.M.)
| | - Cai Zong
- Department of Occupational and Environmental Health, Tokyo University of Science, Noda 278-8510, Japan; (A.E.); (C.Z.); (F.A.E.); (Y.K.); (R.T.); (K.M.)
| | - Frederick Adams Ekuban
- Department of Occupational and Environmental Health, Tokyo University of Science, Noda 278-8510, Japan; (A.E.); (C.Z.); (F.A.E.); (Y.K.); (R.T.); (K.M.)
| | - Yusuke Kimura
- Department of Occupational and Environmental Health, Tokyo University of Science, Noda 278-8510, Japan; (A.E.); (C.Z.); (F.A.E.); (Y.K.); (R.T.); (K.M.)
| | - Ryoya Takizawa
- Department of Occupational and Environmental Health, Tokyo University of Science, Noda 278-8510, Japan; (A.E.); (C.Z.); (F.A.E.); (Y.K.); (R.T.); (K.M.)
- Department of Environmental and Preventive Medicine, Jichi Medical University School of Medicine, Shimotsuke 329-0498, Japan;
| | - Kota Morikawa
- Department of Occupational and Environmental Health, Tokyo University of Science, Noda 278-8510, Japan; (A.E.); (C.Z.); (F.A.E.); (Y.K.); (R.T.); (K.M.)
| | - Kazuo Kinoshita
- Evolutionary Medicine, Shizuoka Graduate University of Public Health, Shizuoka 420-0881, Japan;
| | - Sahoko Ichihara
- Department of Environmental and Preventive Medicine, Jichi Medical University School of Medicine, Shimotsuke 329-0498, Japan;
| | - Seiichiroh Ohsako
- Laboratory of Environmental Health Sciences, Faculty of Medicine, University of Tokyo, Tokyo 113-8655, Japan;
| | - Gaku Ichihara
- Department of Occupational and Environmental Health, Tokyo University of Science, Noda 278-8510, Japan; (A.E.); (C.Z.); (F.A.E.); (Y.K.); (R.T.); (K.M.)
- Correspondence:
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Wang H, Chen J, Suda M, Yanagiba Y, Weng Z, Wang RS. Acute inhalation co-exposure to 1,2-dichloropropane and dichloromethane cause liver damage by inhibiting mitochondrial respiration and defense ability in mice. J Appl Toxicol 2018; 39:260-270. [PMID: 30240022 DOI: 10.1002/jat.3715] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/19/2018] [Accepted: 07/24/2018] [Indexed: 11/07/2022]
Abstract
1,2-Dichloropropane (1,2-DCP) is used as an industrial solvent, insecticide fumigant and household dry cleaning product. Carcinogenicity caused by long-term exposure to 1,2-DCP is well established. However, the possible liver damage and related toxic mechanisms associated with acute inhalation exposure to 1,2-DCP are rarely reported. In this study, we investigated the effects of individual and combined exposure to 1,2-DCP and dichloromethane (DCM) on mice liver. The results showed that 1,2-DCP significantly caused liver necrosis, possibly due to 1,2-DCP-induced inhibition of the mitochondrial respiratory chain complex I-IV activities, resulting in mitochondrial dysfunction and extreme ATP consumption. Moreover, 1,2-DCP also decreased mitochondrial defense ability by inhibiting the mitochondrial glutathione S-transferase 1 (MGST1) activity, further aggravating liver damage. Additionally, we found that DCM co-exposure potentially enhanced 1,2-DCP toxicity. Our findings suggest that inhibition of mitochondrial function and MGST1 activity play critical roles in modulating 1,2-DCP-induced liver damage. Furthermore, our results contribute to study the new mechanism of mitochondria-dominated signaling pathways underlying liver injury induced by 1,2-DCP and DCM.
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Affiliation(s)
- Hufei Wang
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, China
| | - Jiamin Chen
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, China
| | - Megumi Suda
- Japan National Institute of Occupational Safety and Health, Kawasaki, Japan
| | - Yukie Yanagiba
- Japan National Institute of Occupational Safety and Health, Kawasaki, Japan
| | - Zuquan Weng
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, China
| | - Rui-Sheng Wang
- Japan National Institute of Occupational Safety and Health, Kawasaki, Japan
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