"Golf ball liver": agent orange hepatitis

Exposure to 2,4-dichlorophenoxyacetic acid induced PPARβ-dependent disruption of glucose metabolism in HepG2 cells

2,4-Dichlorophenoxyacetic acid is one of the most widely used herbicides. Its impact on health is increasingly attracting great attentions. This study aimed to investigate the effect of 2,4-dichlorophenoxyacetic acid on glucose metabolism in HepG2 cells and the underlying mechanism. After 24 h exposure to 2,4-dichlorophenoxyacetic acid, glycogen was measured by PAS staining and glucose by ELISA in HepG2 cells. The expression of genes involved in glucose metabolism was measured by real-time PCR, Western blotting, and immunofluorescence. HepG2 cells presented more extracellular glucose consumption and glycogen content after exposed to 2,4-dichlorophenoxyacetic acid. Expression of gluconeogenesis-related genes, FoxO1, and CREB is significantly elevated. Moreover, PPARβ was up-regulated dose-dependently. SiRNA knockdown of PPARβ completely rescued the increase of glycogen accumulation and glucose uptake, and the up-regulation of FOXO1 and CREB expression. Our findings propose novel mechanisms that 2,4-dichlorophenoxyacetic acid causes glucose metabolism dysfunction through PPARβ in HepG2 cells.

Metabolism of xenobiotic carboxylic acids: focus on coenzyme A conjugation, reactivity, and interference with lipid metabolism

While xenobiotic carboxylic acids (XCAs) have been studied extensively with respect to their enzymatic conversion to potentially reactive acyl glucuronides with implications to drug induced hepatotoxicity, the formation of xenobiotic-S-acyl-CoA thioesters (xenobiotic-CoAs) have been much less studied in spite of data indicating that such conjugates may be equally or more reactive than the corresponding acyl glucuronides. This review addresses enzymes and cell organelles involved in the formation of xenobiotic-CoAs, the reactivity of such conjugates toward biological macromolecules, and in vitro and in vivo methodology to assess consequences of such reactivity. Further, the propensity of xenobiotic-CoAs to interfere with endogenous lipid metabolism, e.g., inhibition of β-oxidation or depletion of the CoA or carnitine pools, adds to the complexity of the potential contribution of XCAs to hepatotoxicity by a number of mechanisms in addition to those in common with the corresponding acyl glucuronides. On the basis of our review of the literature on xenobiotic-CoA conjugates, there appear to be a number of gaps in our understanding of the bioactivation of XCA both with respect to the mechanisms involved and the experimental approaches to distinguish between the role of acyl glucuronides and xenobiotic-CoA conjugates. These aspects are focused upon and described in detail in this review.

Alteration of lipid status and lipid metabolism, induction of oxidative stress and lipid peroxidation by 2,4-dichlorophenoxyacetic herbicide in rat liver

This study aims to investigate the effects of the 2,4-dichlorophenoxyacetic herbicide (2,4-D) on plasma lipids, lipoproteins concentrations, hepatic lipid peroxidation, fatty acid composition and antioxidant enzyme activities in rats. Animals were randomly divided into four groups of 10 each: control group and three 2,4-D-treated groups G1, G2 and G3 were administered 15, 75 and 150 mg/kg/BW/d 2,4-D by gavage for 28 d, respectively. Results showed that 2,4-D caused significant negative changes in the biochemical parameters investigated. The malondialdehyde level was significantly increased in 2,4-D-treated groups. Fatty acid composition of the liver was also significantly changed with 2,4-D exposure. Furthermore, the hepatic antioxidant enzyme activities were significantly affected. Finally, 2,4-D at the studied doses modifies lipidic status, disrupt lipid metabolism and induce hepatic oxidative stress. In conclusion, at higher doses, 2,4-D may play an important role in the development of vascular disease via metabolic disorder of lipoproteins, lipid peroxidation and oxidative stress.

[Liver and sport]

The liver is a vital organ and plays a central role in energy exchange, protein synthesis as well as the elimination of waste products from the body. Acute and chronic injury may disturb a variety of liver functions to different degrees. Over the last three decades, the effects of physical activity and competitive sport on the liver have been described by various investigators. These include viral hepatitis and drug-induced liver disorders. Herein, we review acute and chronic liver diseases potentially caused by sport. Team physicians, trainers and others, responsible for the health of athletes, should be familiar with the risk factors, clinical features, and consequences of liver diseases that occur in sports.

Investigating the in vitro metabolism of fipexide: characterization of reactive metabolites using liquid chromatography/mass spectrometry

The in vitro metabolism of the nootropic drug fipexide was studied using different liquid chromatography/mass spectrometry (LC/MS) techniques. This drug has been withdrawn from the market due to toxic effects. No previous reports have investigated the possible involvement of reactive metabolites in the toxicity of fipexide. The hydrolysis of this drug leads to the formation of two potentially toxic species, 3,4-methylenedioxybenzylpiperazine (MDBP) and 4-chlorophenoxyacetic acid (4-CPA). Here, we investigate the in vitro metabolism of fipexide in human, rat, mouse and dog, as well as of MDBP and 4-CPA in human and rat, while focusing on the formation of reactive metabolites. A combination of LC/MS analyses on a hybrid quadrupole-linear ion trap instrument and accurate mass data from QqTOF measurements was employed for the characterization of these metabolites. Microsomal metabolites of fipexide were MDBP, 4-CPA, fipexide N-oxide or hydroxyl, demethylenated fipexide and other minor ones, all of which were investigated by tandem mass spectrometry. Reactive metabolites were detected using several trapping procedures with small molecules such as glutathione, its ethyl ester derivative and N-acetylcysteine. The demethylenated metabolite, a catechol, formed its corresponding ortho-quinone, which readily reacts with these nucleophiles. MDBP was studied in a similar manner, due to its ability to form an analogous catechol. Because of its acidic nature, 4-CPA was assessed for possible acylglucuronide and acyl-CoA thioester metabolites, which could also be involved in bioactivation pathways. Several important metabolites were identified as potential mediators of toxicity via protein binding.

Altered gene expression in human hepatoma HepG2 cells exposed to low-level 2,4-dichlorophenoxyacetic acid and potassium nitrate

2,4-dichlorophenoxyacetic acid (2,4-D) and nitrate are agricultural contaminants found in rural ground water. It is not known whether levels found in groundwater pose a human or environmental health risk, nor is the mechanism of toxicity at the molecular/cellular level understood. This study focused on determining whether 2,4-D or nitrate at environmentally realistic levels elicit gene expression changes in exposed cells. cDNA microarray technology was used to determine the impact of 2,4-D and nitrate in an in vitro model of exposure. Human hepatoma HepG2 cells were incubated with 2,4-D or nitrate alone for 24 h. Cell viability (neutral red assay) and proliferation (BrdU incorporation) were assessed following exposure. Total RNA from treated and control cells were isolated, reverse transcribed and reciprocal labelled with Cy3 or Cy5 dyes, and hybridized to a human cDNA microarray. The hybridized microarray chips were scanned, quantified and analyzed to identify genes affected by 2,4-D or nitrate exposure based on a two-fold increase or decrease in gene expression and reproducibility (affected in three or more treatments). Following filtering, normalization and hierarchical clustering initial data indicate that numerous genes were found to be commonly expressed in at least three or more treatments of 2,4-D or nitrate tested. The affected genes indicate that HepG2 cells respond to environmental, low-level exposure and produce a cellular response that is associated with alterations in the expression of many genes. The affected genes were characterized as stress response, cell cycle control, immunological and DNA repair genes. These findings serve to highlight new pathway(s) in which to further probe the effects of environmental levels of 2,4-D and nitrate.

[Liver and sports]

Physical exercise does not have harmful effects on liver, yet it can be an occasional cause of heat stroke in long-distance runners if they do not drink enough. Practicing sports does not have harmful liver effects as long as some risk behaviors are avoided such as consumption of anabolizers, sharing syringes or traveling to hepatitis endemic countries without being vaccinated. In patients with acute or chronic liver diseases, physical activity or practicing sports can be allowed as long as these do not lead to an excessive fatigue.

Fulminant liver disease

Fulminant liver disease, acute liver failure (ALF), is one of the most intriguing and challenging conditions in the entire field of internal medicine. ALF is defined as the onset of hepatic encephalopathy and coagulopathy in patients with no known underlying liver disease within 8 to 26 weeks of onset of illness. Many cases develop within a few days, dramatically transforming an otherwise healthy individual to a patient with a high risk for developing multi-organ failure and death.

In vitro studies on the chemical reactivity of 2,4-dichlorophenoxyacetyl-S-acyl-CoA thioester

2,4-Dichlorophenoxyacetic acid (2,4-D) is a widely used broadleaf herbicide that has been associated with acute liver toxicity in exposed humans or animals. Chemically reactive metabolites of 2,4-D are proposed as mediators of 2,4-D-induced hepatotoxicity. The aim of the present study was to investigate a novel reactive metabolite of 2,4-D, namely 2,4-dichlorophenoxyacetyl-S-acyl-CoA (2,4-D-CoA), and to determine its involvement in 2,4-D covalent adduct formation. Thus, incubations of synthetic 2,4-D-CoA (106 microM) with GSH (1 mM) in phosphate buffer (pH 7.4) showed 2,4-D-CoA to be able to transacylate the cysteine sulfhydryl of GSH, resulting in the formation of 2,4-D-S-acyl-glutathione (2,4-D-SG) thioester and reaching a concentration of 65 microM after 1 h of incubation. Under similar conditions, 2,4-D-CoA was shown to covalently bind to nucleophilic groups on human serum albumin (HSA, 30 mg/ml), resulting in time-dependent 2,4-D-HSA covalent adduct formation that reached a maximum of 440 pmol/mg HSA after 1 h of incubation. In addition to these studies, incubations of [1-(14)C]2,4-D (1 mM) with rat hepatocytes showed a time-dependent covalent binding of 2,4-D to hepatocyte protein. Inhibition of acyl-CoA formation by trimethylacetic acid (2 mM) decreased the amount of covalent binding to protein in rat hepatocytes by 50%. These results indicate that 2,4-D-CoA thioester is a reactive metabolite of 2,4-D that may contribute to 2,4-D-protein adduct formation in vivo and therefore the associated hepatotoxicity.