Journal Article

1,2-Dichloropropane, but not dichloromethane or trichloropropane, reduces apoptosis of human cholangiocytes co-cultured with macrophages

Ekuban, Abigail, Rahman, Mst Mahfuza, Zong, Cai, Takizawa, Ryoya, Ichihara, Sahoko, Kimura, Yusuke, Ichihara, Gaku, Nagashima, Daichi, Fergany, Alzahraa, Kusagaya, Kyoshiro

2026

Overview

The roles of dichloromethane (DCM) and 1,2,3-trichloropropane (1,2,3-TCP) in occupational cholangiocarcinoma, first reported in 2012, remain elusive. This study aimed to determine the potential of 1,2-dichloropropane (1,2-DCP), DCM, and 1,2,3-TCP to induce DNA damage-a hallmark of carcinogenicity-in human cholangiocytes. Monocultures of human immortalized cholangiocytes (MMNK-1 cholangiocytes) and co-cultures of MMNK-1 cholangiocytes with human THP-1 monocyte-derived macrophages and monocytes were each exposed to 1,2-DCP, DCM or 1,2,3-TCP at 0, 0.1, and 0.4 mM for 24 hours. DNA double-strand break marker γ-H2AX-positive foci and γ-H2AX pan-nuclear staining-which is known to be induced during early or intermediate stages of apoptosis or under replicative stress/checkpoint abrogation in cholangiocytes-were counted in 100 and 200 cholangiocytes, respectively. Apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining. The increase in dense (≥55) γ-H2AX foci induced by all 3 chemical compounds was significantly greater in co-cultures with macrophages, but not with monocytes, than in monocultures. However, only 1,2-DCP decreased the number of γ-H2AX pan-nuclear-positive and TUNEL-positive cholangiocytes in co-cultures with macrophages, but not in monocultured cholangiocytes. Co-treatment with a pan-caspase inhibitor decreased the number of γ-H2AX pan-nuclear-positive cholangiocytes in each group by about 50%, suggesting that apoptotic signaling is involved, at least in part, in the induction of γ-H2AX pan-nuclear-positive cholangiocytes. Our study showed that co-culture with macrophages enhanced DNA double-strand breaks induced by all 3 tested chemical compounds, while only 1,2-DCP exhibited a proliferative effect in monocultures and anti-apoptotic effects in co-cultures with macrophages, which are key characteristics of carcinogens, thus distinguishing 1,2-DCP from DCM and 1,2,3-TCP.

• Publisher: Oxford University Press
• Subject: Apoptosis / Apoptosis - drug effects / Bile Ducts - cytology / Bile Ducts - drug effects / Carcinogenicity / Carcinogens / Caspase / Caspase inhibitors / Chemical compounds / Cholangiocarcinoma / Coculture Techniques / Damage / Deoxyribonucleic acid / Dichloromethane / DNA / DNA damage / DNA Damage - drug effects / DNA nucleotidylexotransferase / Exposure / Foci / Humans / Macrophages / Macrophages - drug effects / Methylene Chloride - pharmacology / Methylene Chloride - toxicity / Monoculture / Monocytes / Original / Propane - analogs & derivatives / Propane - pharmacology / Propane - toxicity / Staining / Trichloropropane