Lipid metabolism in liver injury caused by carbon tetrachloride in the rat

Integrating Publicly Available Data to Generate Computationally Predicted Adverse Outcome Pathways for Fatty Liver

Newin vitrotesting strategies make it possible to design testing batteries for large numbers of environmental chemicals. Full utilization of the results requires knowledge of the underlying biological networks and the adverse outcome pathways (AOPs) that describe the route from early molecular perturbations to an adverse outcome. Curation of a formal AOP is a time-intensive process and a rate-limiting step to designing these test batteries. Here, we describe a method for integrating publicly available data in order to generate computationally predicted AOP (cpAOP) scaffolds, which can be leveraged by domain experts to shorten the time for formal AOP development. A network-based workflow was used to facilitate the integration of multiple data types to generate cpAOPs. Edges between graph entities were identified through direct experimental or literature information, or computationally inferred using frequent itemset mining. Data from the TG-GATEs and ToxCast programs were used to channel large-scale toxicogenomics information into a cpAOP network (cpAOPnet) of over 20 000 relationships describing connections between chemical treatments, phenotypes, and perturbed pathways as measured by differential gene expression and high-throughput screening targets. The resulting fatty liver cpAOPnet is available as a resource to the community. Subnetworks of cpAOPs for a reference chemical (carbon tetrachloride, CCl4) and outcome (fatty liver) were compared with published mechanistic descriptions. In both cases, the computational approaches approximated the manually curated AOPs. The cpAOPnet can be used for accelerating expert-curated AOP development and to identify pathway targets that lack genomic markers or high-throughput screening tests. It can also facilitate identification of key events for designing test batteries and for classification and grouping of chemicals for follow up testing.

In vivo (1)H-MRS hepatic lipid profiling in nonalcoholic fatty liver disease: an animal study at 9.4 T

The applicability of the in vivo proton magnetic resonance spectroscopy hepatic lipid profiling (MR-HLP) technique in nonalcoholic fatty liver disease was investigated. Using magnetic resonance spectroscopy, the relative fractions of diunsaturated (fdi), monounsaturated (fmono), and saturated (fsat) fatty acids as well as total hepatic lipid content were estimated in the livers of 8 control and 23 CCl4-treated rats at 9.4 T. The mean steatosis, necrosis, inflammation, and fibrosis scores of the treated group were all significantly higher than those of the control group (P < 0.01). There was a strong correlation between the histopathologic parameters and the MR-HLP parameters (r = 0.775, P < 0.01) where both steatosis and fibrosis are positively correlated with fmono and negatively correlated with fdi. Both necrosis and inflammation, however, were not correlated with any of the MR-HLP parameters. Hepatic lipid composition appears to be changed in association with the severity of steatosis and fibrosis in nonalcoholic fatty liver disease, and these changes can be depicted in vivo by using the MR-HLP method at 9.4 T. Thus, while it may not likely be that MR-HLP helps differentiate between steatohepatitis in its early stages and simple steatosis, these findings altogether are in support of potential applicability of in vivo MR-HLP at high field in nonalcoholic fatty liver disease.

Celecoxib, a selective cyclooxygenase-2 inhibitor, lowers plasma cholesterol and attenuates hepatic lipid peroxidation during carbon-tetrachloride-associated hepatotoxicity in rats

Cyclooxygenase-2 (COX-2) expression and prostaglandin production are suggested to play important, complex roles in the pathogenesis of various liver diseases. Studies on the effects of COX-2 inhibitors on the progression of liver fibrosis present controversial results, and the proposed therapeutic potential of these agents in chronic liver disease is predicated largely on their effectiveness in modulating hepatic stellate cell activation in vitro. This study investigated the modulatory effect of celecoxib, a selective COX-2 inhibitor, in CCl(4)-mediated hepatotoxicity in rats. Thirty Wistar albino rats, weighing 120-180 g, were assigned into five groups of 6 rats/group. Groups 1 and 2 received saline (10 mL/kg) and CCl(4) (80 mg/kg), respectively. Group 3 was given celecoxib (5.7 mg/kg), whereas groups 4 and 5 were pretreated with 2.9 and 5.7 mg/kg/day of celecoxib, respectively, 1 hour before CCl(4) treatment. Plasma aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase activities increased significantly by 118.5, 150.0, and 51.3%, respectively, with an accompanying decrease (P < 0.05) in total protein and albumin after CCl(4) treatment. Hepatotoxicity was associated with a significant increase in plasma cholesterol, hepatic lipid peroxidation (LPO), and severe hepatic necrosis with marked fatty and cellular (i.e., mononuclear cells) infiltration. Although celecoxib neither reduced CCl(4)-induced increases in marker enzymes of hepatotoxicity nor significantly attenuated hepatic necrosis, it, however, was effective in reducing elevated cholesterol by 16.5 and 20.8% and LPO by 12.9 and 35.5% at 2.9 and 5.7 mg/kg, respectively. Data suggest that COX-2 inhibitors may be effective in controlling hypercholesterolemia and peroxidative changes associated with liver injury.

Effect of prenatal and perinatal acrylamide on the biochemical and morphological changes in liver of developing albino rat

Acrylamide has been employed as an experimental probe to investigate biochemical and morphological changes in developing rat liver following toxin administration in pregnant rats. Non-anesthetized pregnant rats were given acrylamide by gastric intubation at a dose of 10 mg/kg/day. The pups were divided into three groups: Group A, mothers were treated with saline (control group); Group B, mothers were treated with acrylamide from day D7 of gestation till birth (prenatal intoxication); Group C, mothers were treated with acrylamide from D7 of gestation to D28 after birth (perinatal intoxication). Acrylamide-induced biochemical changes (in liver and serum) and morphological changes (in liver) were studied in control and acrylamide-treated developing pups. Prenatally and perinatally administered acrylamide significantly increased lipid peroxidation and reduced glutathione and total thiol levels in liver. Significant inhibition of peroxidase and superoxide dismutase activities was observed in liver tissue. Total lipids including cholesterol and triglycerides were significantly increased in the serum. Acrylamide treatment increased serum alanine aminotransferase and aspartate aminotransferase activities and inhibited alkaline phosphatase activity. Sodium and potassium concentrations were increased, but calcium, phosphorus and iron levels were significantly reduced in the serum. Acrylamide produced significant electrophoretic changes in serum proteins. The most noticeable change was splitting of beta-globulin into beta1- and beta2-globulins. Light microscopy showed acrylamide-induced fatty deposits, congested central vein, vacuolization and chromatolysis in hepatocytes. Ultrastructural studies revealed vacuolated cytoplasm, lipid droplets of variable size and mitochondria with damaged cristae and vacuolization. The nuclei in acrylamide-treated groups showed marked decrease in the staining of nuclear DNA.

[11C]choline uptake in regenerating liver after partial hepatectomy or CCl4-administration

To characterize [methyl-(11)C]choline ([(11)C]choline) as an oncologic PET radiopharmaceutical, [(11)C]choline uptake in regenerating livers after partial hepatectomy as a model of typical proliferating tissue and after CCl(4) insult as that of proliferating tissue with inflammation, was studied in rats. [(11)C]Choline, [(18)F]2-fluoro-2-deoxy-D-glucose ([(18)F]FDG) and [2-(14)C]thymidine ([(14)C]TdR) uptake was studied in regenerating rat liver after 70% partial hepatectomy or CCl(4)-administration. [(11)C]Choline uptake in regenerating liver after partial hepatectomy was significantly increased with [(14)C]TdR uptake as a marker of DNA synthesis at 18 hours after surgery. On the other hand, the uptake was not accelerated by CCl(4)-administration, though it significantly increased [(14)C]TdR uptake. There were no differences of [(11)C]choline uptake acceleration following partial hepatectomy among the three parts of the regenerating liver. [(18)F]FDG uptake was accelerated in the regenerating liver on either partial hepatectomy or CCl(4)-administration. The magnitude of the increase in [(18)F]FDG uptake in the regenerating liver induced by partial hepatectomy was greater than that for [(11)C]choline. [(11)C]Choline uptake in the liver was accelerated by partial hepatectomy, but not by CCl(4)-administration. This might be expected given that the differentiation between proliferating tissues such as tumor and inflammatory tissue was possible by [(11)C]choline-PET.

Actinomycin D-induced enhancement of ubiquinone biosynthesis in rat

Administration of actinomycin D to fasted rats induces an enhancement of the labeling of hepatic ubiquinone by [2-14C] acetate both in vivo and in vitro. The incorporation of [2-14C] mevalonate into ubiquinone is also increased, although to a significantly lesser extent; this, however, presumably results from greater uptake of the labeled precursor by liver of drug-treated rats. The drug-administered animals show increased activity of liver microsomal mevalonate: NADP oxidoreductase, the rate-limiting enzyme in isoprenoid biogenesis. The incorporation of [u-14C] benzoic acid and CH3-[14C] methionine into ubiquinone in liver slices, however, reveals a decrease in actinomycin D administered rats. This appears to be due to a specific inhibition of the pathway leading to the benzoquinone moiety of ubiquinone and not to an increase in the pool-size of the precursors. The stimulatory effect of the drug on ubiquinone biosynthesis is also observable in cholesterol-fed rats. The actinomycin D-induced increase in ubiquinone biosynthesis is dependent on new protein synthesis since the effect is abolished by treating the animals with either cycloheximide or puromycin.

The effect of carbon tetrachloride on the lipoproteins of rat-liver cell sap and serum

1. The lipoproteins of the liver cell sap can be resolved by paper electrophoresis into five components. Almost two-thirds of the total lipid, cholesterol and phospholipid are present in the slowest- and the fastest-moving components. 2. There is a two- to three-fold increase in the lipid content of the liver cell sap after the administration of carbon tetrachloride. 3. The cholesterol and phospholipid contents of the serum alpha- and beta-lipoproteins separated by paper electrophoresis fall after treatment with carbon tetrachloride, whereas the total lipid content of that fraction that remains at the origin rises.