The ethylene bisdithiocarbamate fungicides mancozeb and nabam alter essential metal levels in liver and kidney and glutathione enzyme activity in liver of Sprague-Dawley rats

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

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.

Low Level Mancozeb Exposure Causes Copper Bioaccumulation in the Renal Cortex of Rats Leading to Tubular Injury

Mancozeb is a widely-used, broad-spectrum contact dithiocarbamate fungicide. Dithiocarbamates are known to trans-chelate metals. This study was designed to evaluate the potential of Mancozeb to mobilize and bioaccumulate essential trace metals in various tissues. Long-Evans rats were orally gavaged with 0, 50, or 100mg/kg/day of Mancozeb for 28 days. Mancozeb caused a significant increase in copper and manganese in the hippocampus and manganese in the liver. Exceedingly higher level of copper was detected in the renal cortex using ICP-OES in both dose groups. This was confirmed histologically in the tubular epithelial cells. In addition, copper-associated protein levels were also increased. Copper bioaccumulation in the renal cortex was accompanied by oxidative damage and tubular insult indicated by increased 4-HNE, KIM-1, and NGAL immunoreactivity. These findings demonstrate that low-dose Mancozeb exposure is a potential risk for kidney injury due to copper overload and warrants further in vivo and human population-based investigations.

Exposure to dithiocarbamate fungicide Ziram results in hepatic and renal toxicity in Long Evan rats

Ziram is a dimethyldithiocarbamate fungicide that is complexed to the metal zinc. The focus of this study is to examine the effects of dimethyldithiocarbamate exposure on metal homeostasis, glutathione levels, and the physiological parameters of the kidney and liver in Long-Evan rats. Our results indicate significant accumulation of copper or zinc, and changes in total GSH or GSH/GSSG ratio in the liver and kidneys of animals treated with Ziram only. Histopathological examination of liver and kidney sections indicate the presence of infiltrates in the liver of animals treated with Ziram only, whereas protein aggregates, sloughing of cells and increased KIM-1 positive cells, an indicator of tubule deterioration, are seen in the kidneys of animals treated with Ziram and sodium-dimethyldithiocarbamate, the salt form of the dimethyldithiocarbmate backbone. These findings suggest that the overall toxicological effect of Ziram is mediated by an intrinsic property rather than to dimethyldithiocarbamate backbone or metal moiety.

Histopathological, immunohistochemical and biochemical alterations in liver tissue after fungicide-mancozeb exposures in Wistar albino rats

PURPOSE

To evaluate the histopathological, immunohistochemical, and biochemical effects of liver changes after mancozeb administration.

METHODS

Rats were divided into groups-the control group (n=7) and the mancozeb group (n=7)-, given 500 mg/kg mancozeb dissolved in corn oil daily for four weeks by an orogastric tube. Caspase-3 and tumor necrosis factor-alpha (TNF-α) primary antibodies were used for immunohistochemical analysis.

RESULTS

Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) values of the mancozeb group increased significantly than ones of the control group. Venous dilatation, inflammation, hepatocyte degeneration, TNF-α, and caspase-3 expression scores increased significantly in the mancozeb group. In the mancozeb group, intensive caspase-3 expression was observed in hepatocyte cells around the central vein in the center of the liver lobule, and there was an increase in TNF-α expression in the inflammatory cells around the enlarged central vein and Kupffer cells and apoptotic hepatocyte cells.

CONCLUSIONS

Subacute mancozeb exposure in rats leads to elevated toxicity with impaired liver function, increased inflammation in tissue and increased apoptosis due to cellular damage in the liver, and decreased liver regeneration ability due to congestion and degeneration of blood vessels.