The induction of tumor necrosis factor-alpha, superoxide anion, myeloperoxidase, and superoxide dismutase in the peritoneal lavage cells of mice after prolonged exposure to dichloroacetate and trichloroacetate

Tumor necrosis factor α upregulates the bile acid efflux transporter OATP3A1 via multiple signaling pathways in cholestasis

Cholestasis is a common condition in which the flow of bile from the liver to the intestines is inhibited. It has been shown that organic anion–transporting polypeptide 3A1 (OATP3A1) is upregulated in cholestasis to promote bile acid efflux transport. We have previously shown that the growth factor fibroblast growth factor 19 and inflammatory mediator tumor necrosis factor α (TNFα) increased OATP3A1 mRNA levels in hepatoma peritoneal lavage cell/PRF/5 cell lines. However, the mechanism underlying TNFα-stimulated OATP3A1 expression in cholestasis is unknown. To address this, we collected plasma samples from control and obstructive cholestasis patients and used ELISA to detect TNFα levels. We found that the TNFα levels of plasma and hepatic mRNA transcripts were significantly increased in obstructive cholestatic patients relative to control patients. A significant positive correlation was also observed between plasma TNFα and liver OATP3A1 mRNA transcripts in patients with obstructive cholestasis. Further mechanism analysis revealed that recombinant TNFα induced OATP3A1 expression and activated NF-κB and extracellular signal–regulated kinase (ERK) signaling pathways as well as expression of related transcription factors p65 and specificity protein 1 (SP1). Dual-luciferase reporter and chromatin immunoprecipitation assays showed that recombinant TNFα upregulated the binding activities of NF-κB p65 and SP1 to the OATP3A1 promoter in peritoneal lavage cell/PRF/5 cells. These effects were diminished following the application of NF-κB and ERK inhibitors BAY11-7082 and PD98059. We conclude that TNFα stimulates hepatic OATP3A1 expression in human obstructive cholestasis by activating NF-κB p65 and ERK–SP1 signaling. These results suggest that TNFα-activated NF-κB p65 and ERK–SP1 signaling may be a potential target to ameliorate cholestasis-associated liver injury.

Comparative toxicity studies on bromochloroacetate, dibromoacetate, and bromodichloroacetate in J774A.1 macrophages: Roles of superoxide anion and protein carbonyl compounds

The brominated and mixed bromo-chloro-haloacetates, such as dibromoacetate (DBA), bromochloroacetate (BCA), and bromodichloroacetate (BDCA), are by-products of water chlorination and are found at lower levels than the fully chlorinated acetates in the drinking water. The toxicities of the compounds were assessed in J774A.1 cells and were found to induce concentration-dependent increases in cell death and superoxide anion and protein carbonyl compounds production. Compared to the previously tested concentrations of dichoroacetate (DCA) and trichloroacetate (TCA) in the same cell line, the tested haloacetates induced similar effects on cellular viability and superoxide anion production but at DBA and BCA concentrations that were approximately 40-160 times lower than those of DCA and TCA, and at BDCA concentrations that were 4-16 times lower than those of DCA and TCA. Also, production of super oxide anion, protein carbonyl compounds, and induction of phagocytic activation are suggested to play a role in their toxicity.

Dichloroacetate Decreases Cell Health and Activates Oxidative Stress Defense Pathways in Rat Alveolar Type II Pneumocytes

Dichloroacetate (DCA) is a water purification byproduct that is known to be hepatotoxic and hepatocarcinogenic and to induce peripheral neuropathy and damage macrophages. This study characterizes the effects of the haloacetate on lung cells by exposing rat alveolar type II (L2) cells to 0–24 mM DCA for 6–24 hours. Increasing DCA concentration and the combination of increasing DCA concentration plus longer exposures decrease measures of cellular health. Length of exposure has no effect on oxidative stress biomarkers, glutathione, SOD, or CAT. Increasing DCA concentration alone does not affect total glutathione or its redox ratio but does increase activity in the SOD/CAT oxidative stress defense pathway. These data suggest that alveolar type II cells rely on SOD and CAT more than glutathione to combat DCA-induced stress.

The effects of mixtures of dichloroacetate and trichloroacetate on induction of oxidative stress in livers of mice after subchronic exposure

Dichloroacetate (DCA) and trichloroacetate (TCA) are drinking-water chlorination by-products previously found to induce oxidative stress (OS) in hepatic tissues of B6C3F1 male mice. To assess the effects of mixtures of the compounds on OS, groups of male B6C3F1 mice were treated daily by gavage with DCA at doses of 7.5, 15, or 30 mg/kg/d, TCA at doses of 12.5, 25, or 50 mg/kg/d, and 3 mixtures of DCA and TCA (Mix I, Mix II, and Mix III), for 13 wk. The concentrations of the compounds in Mix I, Mix II, and Mix III corresponded to those producing approximately 15, 25, and 35%, respectively, of maximal induction of OS by individual compounds. Livers were assayed for production of superoxide anion (SA), lipid peroxidation (LP), and DNA single-strand breaks (SSB). DCA, TCA, and the mixtures produced dose-dependent increases in the three tested biomarkers. Mix I and II effects on the three biomarkers, and Mix III effect on SA production were found to be additive, while Mix III effects on LP and DNA-SSB were shown to be greater than additive. Induction of OS in livers of B6C3F1 mice after subchronic exposure to DCA and TCA was previously suggested as an important mechanism in chronic hepatotoxicity/hepatocarcinogenicity induced by these compounds. Hence, there may be rise in exposure risk to these compounds as these agents coexist in drinking water.

The induction of phagocytic activation by mixtures of the water chlorination by-products, dichloroacetate- and trichloroacetate, in mice after subchronic exposure

In this study, groups of B6C3F1 male mice were treated with dichloroacetate (DCA), trichloroacetate (TCA), and mixtures of the compounds (Mix I, II, and III) daily by gavage, for 13 weeks. The tested doses were 7.5, 15, and 30 mg DCA/kg/day and 12.5, 25, and 50 mg TCA/kg/day. The DCA: TCA ratios in Mix I, II, and III were 7.5:12.5, 15:25, and 30:50 mg/kg/day, respectively. Peritoneal lavage cells were collected at the end of the treatment period and assayed for the biomarkers of phagocytic activation, including superoxide anion and tumor necrosis factor-alpha production, and myeloperoxidase activity. The mixtures produced nonlinear effects on the biomarkers of phagocytic activation, with Mix I and II effects were found to be additive, but Mix III effects were found to be less than additive.

Vitamin E restriction in the diet enhances phagocytic activation by dichloroacetate and trichloroacetate in mice

The effects of a vitamin E-restricted diet on the induction of phagocytic activation by dichloroacetate (DCA) and trichloroacetate (TCA) was investigated. Groups of B6C3F1 male mice were either kept on standard diet (Std diet group) or diet that had the vitamin provided only by its natural ingredients (Low-E diet group). The animals in each diet group were administered 77 mg of DCA or TCA/ kg/day, or 5 ml/kg water (controls), by gavage, for 13 weeks. Thereafter, peritoneal lavage cells (PLC) were assayed for superoxide anion (SA), tumor necrosis factor (TNF)-α, and myeloperoxidase (MPO), as well as for the activities of the anti-oxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). SA and TNFα production, as well as MPO, SOD, CAT and GSH-Px activities were significantly increased in the cells from the Low-E diet group treated with the compounds as compared with cells from hosts in the Std-diet group that received the corresponding treatments. The results indicate that consumption of a Vitamin E-restricted diet enhances the induction of phagocytic activation by DCA and TCA, a mechanism that was previously suggested to be an initial adaptive/protective response against the compounds long-term effects.