Low concentrations of ethylene bisdithiocarbamate pesticides maneb and mancozeb impair manganese and zinc homeostasis to induce oxidative stress and caspase-dependent apoptosis in human hepatocytes

Kilian Petitjean (1) , Yann Verres (1, 2) , Sébastien Bristeau (3) , Catherine Ribault (1) , Caroline Aninat (1) , Christophe Olivier (4) , Patricia Leroyer (1, 2) , Martine Ropert (1, 2) , Olivier Loréal (1, 2) , Olivier Herault (5, 6) , Laurence Amalric (3) , Nicole Baran (3) , Bernard Fromenty (1) , Anne Corlu (1) , Pascal Loyer (1)

1 NuMeCan - Nutrition, Métabolismes et Cancer
2 Centre Hospitalier Universitaire de Rennes [CHU Rennes] = Rennes University Hospital [Ponchaillou]
3 BRGM - Bureau de Recherches Géologiques et Minières
4 HITH - U1176 Inserm - CHU Bicêtre - Hémostase, Inflammation, Thrombose
5 CHRU Tours - Centre Hospitalier Régional Universitaire de Tours
6 UT - Université de Tours

The worldwide and intensive use of phytosanitary compounds results in environmental and food contamination by chemical residues. Human exposure to multiple pesticide residues is a major health issue. Considering that the liver is not only the main organ for metabolizing pesticides but also a major target of toxicities induced by xenobiotics, we studied the effects of a mixture of 7 pesticides (chlorpyrifos-ethyl, dimethoate, diazinon, iprodione, imazalil, maneb, mancozeb) often detected in food samples. Effects of the mixture was investigated using metabolically competent HepaRG cells and human hepatocytes in primary culture. We report the strong cytotoxicity of the pesticide mixture towards hepatocytes-like HepaRG cells and human hepatocytes upon acute and chronic exposures at low concentrations extrapolated from the Acceptable Daily Intake (ADI) of each compound. Unexpectedly, we demonstrated that the manganese (Mn)-containing dithiocarbamates (DTCs) maneb and mancozeb were solely responsible for the cytotoxicity induced by the mixture. The mechanism of cell death involved the induction of oxidative stress, which led to cell death by intrinsic apoptosis involving caspases 3 and 9. Importantly, this cytotoxic effect was found only in cells metabolizing these pesticides. Herein, we unveil a novel mechanism of toxicity of the Mn-containing DTCs maneb and mancozeb through their metabolization in hepatocytes generating the main metabolite ethylene thiourea (ETU) and the release of Mn leading to intracellular Mn overload and depletion in zinc (Zn). Alteration of the Mn and Zn homeostasis provokes the oxidative stress and the induction of apoptosis, which can be prevented by Zn supplementation. Our data demonstrate the hepatotoxicity of Mn-containing fungicides at very low doses and unveil their adverse effect in disrupting Mn and Zn homeostasis and triggering oxidative stress in human hepatocytes.

Keywords: Hepatocytes; Mancozeb; Maneb; Manganese; Oxidative stress; Zinc

Domains: Earth Sciences

Kilian Petitjean, Yann Verres, Sébastien Bristeau, Catherine Ribault, Caroline Aninat, et al.. Low concentrations of ethylene bisdithiocarbamate pesticides maneb and mancozeb impair manganese and zinc homeostasis to induce oxidative stress and caspase-dependent apoptosis in human hepatocytes. Chemosphere, 2024, 346, pp.140535. ⟨10.1016/j.chemosphere.2023.140535⟩. ⟨hal-04297461⟩