Expression of liver functions following sub-lethal and non-lethal doses of allyl alcohol and acetaminophen in the rat

Hyperammonemia in acetaminophen toxicity

INTRODUCTION

Acetaminophen-induced hepatotoxicity can result in hyperammonemia, but it is not clear if elevated ammonia concentrations predict encephalopathy.

METHODS

We retrospectively studied patients with acetaminophen toxicity at a liver transplant center over 8 years (January 1, 2010-December 31, 2017), who developed hepatotoxicity (AST and/or ALT >1000 IU/L) or hyperammonemia (ammonia > 40 µmol/L). We recorded baseline characteristics, laboratory data, documented grade of encephalopathy, and treatments administered. Sensitivity and specificity values were calculated for varying ammonia concentrations.

RESULTS

A total of 102 patient encounters were included with 75 having ammonia concentrations. On presentation, 40% (30/75) of patients had concentrations greater than 100 µmol/L. However, an [ammonia] > 100 µmol/L was neither sensitive (46 % [95% CI: 26-67%]) nor specific (63% [48 - 76%]) for encephalopathy. Only an increasing ammonia concentration had a significant, but small (1.53 (95% CI: 1.06 - 2.20)) positive likelihood ratio for the development of hepatic encephalopathy.

DISCUSSION

Animal models have suggested that in acetaminophen toxicity, encephalopathy may be secondary to an alternative mechanism other than hyperammonemia which may explain the lack of correlation between initial hyperammonemia and encephalopathy in this cohort. Additionally, a lack of empiric treatment for hyperammonemia did not appear to alter the course of any of the patients. None of these patients developed encephalopathy.

CONCLUSION

In cases of acetaminophen-induced hepatotoxicity, ammonia concentrations do not correlate with encephalopathy and empiric treatment for hyperammonemia does not appear to be beneficial.

Vascular endothelial growth factor receptor-1 signaling promotes liver repair through restoration of liver microvasculature after acetaminophen hepatotoxicity

Vascular endothelial growth factor (VEGF) and its receptors promote liver regeneration. The objective of the present study was to examine the role of VEGF receptor 1 (VEGFR1) signaling in hepatic tissue repair after acetaminophen (N-acetyl-para-aminophenol) (APAP)-induced liver injury. To do this, we treated VEGFR1 tyrosine kinase knockout (VEGFR1 TK(-/-)) and wild-type (WT) mice with APAP (300 mg/kg, ip). In WT mice, serum levels of alanine aminotransferase (ALT) and the necrotic area peaked between 8 and 24 h and then declined. In VEGFR1 TK(-/-) mice, ALT levels remained high at 48 h and extensive hepatic necrosis and hemorrhage were observed, as well as high mortality. Downregulation of hepatic messenger RNA expression of VEGFR1 and VEGFR2 was also noted in VEGFR1 TK(-/-) mice. VEGFR1 TK(-/-) mice displayed lower expression of proliferating cell nuclear antigen and of growth factors including hepatocyte growth factor, CD31, and basic fibroblast growth factor than WT. The hepatic microvasculature in VEGFR1 TK(-/-) was compromised as evidenced by impaired sinusoidal perfusion, suppressed endocytosis in liver sinusoidal endothelial cells (LSECs), and the formation of large gaps in LSECs. In WT mice, immunofluorescence revealed that recruited VEGFR1(+) cells in the necrotic area were positive for CD11b. VEGFR1 TK(-/-) exhibited fewer VEGFR1(+) and VEGFR2(+) cells. These results suggest that VEGFR1 signaling facilitates liver recovery from APAP hepatotoxicity by preventing excessive hemorrhage and reconstituting the sinusoids through recruitment of VEGFR1-expressing macrophages to the injured area and also through affecting expression of genes including hepatotrophic and pro-angiogenic growth factors.

Platelet activating factor (PAF) antagonism with ginkgolide B protects the liver against acute injury. importance of controlling the receptor of PAF

Platelet activating factor (PAF) is an ubiquitous phospholipid that acts as a mediator of numerous pathophysiological conditions, including hepatotoxicity. The present study has been conducted to evaluate the eventual role of the platelet activating factor in post-acetaminophen intoxication of liver, using ginkgolide B, BN52021, a selective PAF receptor antagonist. One group of rats was treated with a toxic dose of acetaminophen (APAP) (3.5 g/kg b.w.) (control group) and a second one with the same dose of APAP followed by a dose of ginkgolide B, BN52021 (10 mg/kg b.w.) (BN52021-treated group). The animals were killed at 8, 16, 24, 32 and 40 h after treatment. APAP was found to cause an acute hepatic injury, evident by alterations of biochemical (serum enzymes: ALT, AST and ALP) and liver histopathological (degree of inflammation and apoptosis) indices, which was followed by liver regeneration evident by three independent indices ([3H] thymidine incorporation into hepatic DNA, liver thymidine kinase activity and hepatocyte mitotic index). Hepatic levels of malondialdehyde and serum cholesterol/HDL cholesterol fraction were also measured as parameters of oxidant-antioxidant balance. The protected effects of ginkgolide B were qualified during post treatment time by: (1) reduction of oxidative stress, (2) high decrease of hepatic injury, and (3) decrease of regenerating activity. These results indicate that PAF may play an important role in APAP-induced liver injury and regeneration, and that the use of ginkgolide B attenuates liver damage providing important means of improving liver function following acetaminophen intoxication.

Platelet-activating factor inactivator (rPAF-AH) enhances liver's recovery after paracetamol intoxication

Platelet-activating factor (PAF) is a potent endogenous phospholipid modulator of diverse biological activities, including inflammation. The aim of this study was to investigate the effects of PAF inactivator, recombinant PAF acetylhydrolase (rPAF-AH) on post-paracetamol treatment functional outcome of the liver in the rat. Fifty male Wistar rats were divided into two groups: the control group received by gastric tube a toxic dose of paracetamol (3.5 g/kg body weight) and the rPAF-AH-treated group received the same dose of paracetamol followed by a dose of rPAF-AH (10 mg/kg body weight) intraperitoneally. The animals were sacrificed at 8, 16, 24, 32, and 40 hr after paracetamol treatment. APAP was found to cause acute hepatic injury, evident by alterations of biochemical (serum enzymes: ALT, AST, and ALP) and liver histopathological (degree of inflammation and apoptosis) indexes, which was followed by liver regeneration evident by three independent indexes ([(3)H]thymidine incorporation into hepatic DNA, liver thymidine kinase activity, and hepatocyte mitotic index). Hepatic levels of malondialdehyde (MDA) and serum cholesterol/HDL cholesterol fraction were also measured as parameters of oxidant-antioxidant balance. The positive effects of rPAF-AH were expressed by (1) a reduction of oxidative stress, (2) a large decrease in hepatic injury, and (3) a reduction of regenerating activity. These results suggest that PAF plays an important role in paracetamol-induced liver injury and regeneration. Furthermore, PAF inactivator enhances liver's recovery and attenuates the severity of experimental liver injury, providing important means of improving liver function following paracetamol intoxication.

VEGF isoforms and receptors expression throughout acute acetaminophen-induced liver injury and regeneration

Acetaminophen (APAP) is a widely-used analgesic and a known hepatotoxic agent. Vascular endothelial growth factor (VEGF) is a growth factor with multiple functional roles. VEGF plays an important role in angiogenesis and hepatic regeneration. The aim of this study was to determine the expression of VEGF isoforms and its receptors throughout liver regeneration after the administration of a toxic dose of APAP in rats. Ten groups of adult male rats received a dose of 3.5 g/kg b.w. of APAP per os. The rats were killed post administration at 0-288 h. Blood and liver tissue were extracted. Determination of serum transaminases and alkaline phosphatase activities was performed. Liver injury and regeneration were assessed with hematoxylin-eosin specimens, morphometric analysis, hepatic thymidine kinase assay and Ki-67 expression. Reverse transcription-polymerase chain reaction and immunohistochemical methods were used for assessment of VEGF isoforms and receptors differential expression. High activities of aspartate aminotransferase were observed at 24 and 36 h with another peak of activity at 192 h post administration. Alanine aminotransferase was highest at 36 h. Alkaline phosphatase was increased post 24 h being higher at 72,192 and 240 h. Centrilobular necrosis was observed at 48-72 h and thorough restoration of the liver microarchitecture was observed at 288 h. Liver regeneration lasted from 24-192 h according to the results from thymidine kinase activity and Ki-67 expression. VEGF and VEGF receptor-2 m-RNA levels presented with a three-peak pattern of expression at 12-24, 72-96 and 192-240 h post administration. Significant difference was noted between periportal and centrilobular immunohistochemical expression. VEGF proves to play a critical role during APAP-induced liver regeneration as it presents with three points of higher expression. The first two time points are associated with the initial inflammatory reaction to the noxious stimulus and the hepatocyte regenerative process where as the third one is indicative of the potential involvement of VEGF in processes of remodeling.

Recombinant platelet-activating factor-acetylhydrolase attenuates paracetamol-induced liver oxidative stress, injury, and regeneration

The aim of this study was to investigate the effects of platelet-activating factor (PAF) inactivator, recombinant PAF-acetylhydrolase (rPAF-AH), on post-paracetamol treatment functional outcome of the liver in the rat. Fifty male Wistar rats were divided into two groups: the control group received a toxic dose of paracetamol (3.5 g/kg body weight [BW]) by gastric tube and the rPAF-AH-treated group received the same dose of paracetamol followed by a dose of rPAF-AH (10 mg/kg BW) intraperitoneally. The animals were sacrificed at time points of 56, 66, 72, 84, and 96 hr after paracetamol treatment. Hepatic injury was evaluated by determination of AST, ALT, and ALP activities and degree of necrosis and apoptosis. Liver regeneration was estimated by [3H]thymidine incorporation into hepatic DNA, liver thymidine kinase activity, and hepatocyte mitotic index. Hepatic levels of malondialdehyde (MDA) and serum cholesterol/high-density lipoprotein cholesterol fraction were also measured as parameters of oxidant-antioxidant balance. The positive effects of rPAF-AH were expressed by (1) reduction of oxidative stress, (2) large decrease in hepatic injury, and (3) diminution of regenerating activity. These results indicate that the use of PAF inactivator enhances the liver's recovery from paracetamol intoxication and attenuates the severity of experimental liver injury, providing important means of improving liver function following paracetamol intoxication.

Effect of platelet-activating factor (PAF) receptor antagonist (BN52021) on acetaminophen-induced acute liver injury and regeneration in rats

BACKGROUND

Platelet-activating factor (PAF) is an endogenous lipid mediator that plays a key role in catalyzing various pro-inflammatory processes associated with acute liver injury. In the present study, the possible influence of PAF-R antagonist (BN52021) on the protection of liver injury after 4-hydroxyacetanilide, N-acetyl-p-aminophenol, paracetamol (APAP) intoxication was investigated.

METHODS

Thereby, one group of rats was treated with a toxic dose of APAP (3.5 g/kg body weight (b.w.). The animals were killed at 56, 66, 72, 84 and 96 h after treatment.

RESULTS

APAP was found to cause an acute hepatic injury, evident by alterations of biochemical (serum enzymes: aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase) and liver histopathological (degree of necrosis and apoptosis) indices, which was followed by liver regeneration, evident by three independent indices ([3H] thymidine incorporation into hepatic DNA, liver thymidine kinase activity and hepatocyte mitotic index). The protective effects of BN52021 were qualified during post-treatment time by: (1) significant reduction of hepatic injury as showed by all biochemical and histological parameters, (2) high decrease of regenerating activity showed by three regenerative markers and (3) remarkable increase of PAF-acetylhydrolase (PAF-AH) activity.

CONCLUSION

These results suggest that PAF may play an important role in APAP-induced liver injury and regeneration, and PAF-R antagonist (BN52021) attenuates liver damage.

Allyl alcohol and garlic (Allium sativum) extract produce oxidative stress in Candida albicans

Both the growth and respiration of Candida albicans are sensitive to extracts of Allium sativum and investigations into the anticandidal activities are now focussing on the purified constituents to determine the targets of inhibition. Of particular interest is allyl alcohol (AA), a metabolic product that accumulates after trituration of garlic cloves. Putative targets for AA were investigated by monitoring changes in intracellular responses after exposure of C. albicans cells to AA or a commercially available garlic extract. Two-photon laser scanning microscopy and other techniques were used. Changes typical of oxidative stress--NADH oxidation and glutathione depletion, and increased reactive oxygen species--were observed microscopically and by flow cytometry. Known targets for AA are alcohol dehydrogenases Adh1 and 2 (in the cytosol) and Adh3 (mitochondrial), although the significant decrease in NAD(P)H after addition of AA is indicative of another mechanism of action.

A toxicologist's guide to biomarkers of hepatic response

Biological markers (biomarkers) are used to recognize, characterize and monitor treatment-related responses following exposure to xenobiotics. Biomarkers serve three primary applications in toxicology: 1) to confirm exposure to a deleterious agent, 2) to provide a system for monitoring individual susceptibility to a toxicant, and 3) to quantitatively assess deleterious effects of a toxicant to an organism or individual. Because the liver is a general target for adverse effects of drugs and other chemicals, biomarkers of untoward hepatic response to xenobiotics are of particular interest to the pharmaceutical toxicologist. General requirements for the latter category of biomarkers are sample availability, target organ specificity, sensitivity for the toxicity of interest, accessibility, a relatively short half-life, and available detection systems. Biomarkers that can be assayed in biological fluids from both human and animal subjects are particularly desirable. Histologically, acute and subacute hepatic toxicity commonly involves necrosis, steatosis, cholestasis, vascular disorders, or multiple lesions. The purpose of this review is to summarize reported applications using clinical analytes and biochemical indicators of hepatic dysfunction with emphasis on those that show promise of supplementing or improving upon standard laboratory procedures. Liver function markers refer to peripheral indicators of hepatic synthetic and secretory activities, enterohepatic function, or perturbations of the hepatic uptake and clearance of circulating biomolecules. Liver injury biomarkers include various peripheral proteins released in response to a cellular damage or locally, proteins that are significantly altered within the liver. These include both circulating cytosolic, mitochondrial, or canalicular membrane markers, and the up-regulation or depletion of radical scavengers, modulators, and stabilizers of intracellular damage. Subsequent recovery from a toxic insult involves repair, regenerative, and proliferative responses that constitute the third class of biomarkers. Of these, protein markers found either in sera, plasma, or urine either during or just prior to the early manifestation of histological hepatic lesions are of greatest interest. Examples of a number of these markers, their documented applications in humans or animals, and potential advantages as well as limitations are presented.

Messenger RNA profiles in liver injury and stress: a comparison of lethal and nonlethal rat models

Liver damage activates processes aimed at repairing damage; simultaneously, liver functions required for survival must be maintained. The expression of genes responsible for both in rat models of lethal (lipopolysaccharide, 90% hepatectomy, and d-galactosamine) and nonlethal (turpentine, 70% hepatectomy, and acetaminophen) liver damage and stress was measured at 3, 6, 12, and 24 h after the intervention and quantitated as the area between the control curves and the test curves (AUC). The expression of genes for cell division and remodeling was upregulated most in the lethal models. The expression of most liver-specific function genes was reduced. Positive AUC was found for ARG, ASL, CPT1, Mdr1b, Mdr2, and PEPCK. It is concluded that a high expression of genes for repair of liver damage is associated with reduced expression of genes for several liver-specific functions, possibly reflecting a limited capacity for transcriptional activity. Maintained or increased expression of selected function genes indicates that the corresponding functions have high priority. The liver sustains metabolic homeostasis ensuring that other organs in the body function normally. Simultaneously, the processes required for the integrity of its own structure and function are maintained as a result of regulated expression of the genes that produce the proteins needed to perform both set of functions.

Liver gene regulation in rats following both 70 or 90% hepatectomy and endotoxin treatment

BACKGROUND

The metabolic state effect of liver failure on liver gene regulation was evaluated in a rat model.

METHODS

Following 70 or 90% hepatectomy and lipopolysaccharide or vehicle treatment at intervals up to 24 h, the liver remnants were analyzed for mRNA levels for acute-phase, liver-specific and growth-related proteins.

RESULTS

After 70% hepatectomy mRNA for alpha 1-acid glycoprotein, alpha 2-macroglobulin, thiostatin and fibrinogen, haptoglobin increased three- to sevenfold (P < 0.05), and mRNA for cyclin D and histone 3 increased seven- and 15-fold (P < 0.05), respectively. After lipopolysaccharide injection and 70% hepatectomy were done, mRNA for acute-phase proteins raised significantly (P < 0.05), more to five to 20-fold, while mRNA for growth-related proteins raised significantly (P < 0.05) less to three- to fourfold. After 90% hepatectomy, acute-phase protein mRNA increased five- to ninefold (P < 0.05) more than after 70% hepatectomy, while mRNA for histone 3 and cyclin D did not increase within 24 h, which indicates a delayed growth after 90% hepatectomy. In 90% of hepatectomized rats treated with lipopolysaccharide, acute-phase protein mRNA raised three- to sixfold (P < 0.05) less than after vehicle treatment.

CONCLUSION

In endotoxemia from liver failure, the synthesis of acute-phase proteins is upregulated by gene regulation at the expense of that for regeneration, which may be an appropriate response for immediate survival. In severe liver failure, endotoxin may interfere with the appropriate gene regulation.

The microaerophilic flagellate Giardia intestinalis: Allium sativum (garlic) is an effective antigiardial

Whole garlic (Allium sativum L.) extract and some of its components were assayed for antigiardial activity. Whole garlic extract gave an IC(50) at 24 h of 0.3 mg ml(-1). Most of the components assayed were inhibitory to the organism, especially allyl alcohol and allyl mercaptan, with IC(50) values of 7 microg ml(-1) and 37 microg ml(-1) respectively. Studies with calcofluor white indicated that whole garlic and allyl alcohol collapse the transmembrane electrochemical membrane potential (Deltapsi) of the organism, as indicated by uptake of the fluorochrome. Electron microscopy allowed the morphological changes that occur with garlic inhibition to be recorded. Both the surface topography and internal architecture of the organism changed during incubation with the biocides. Both whole garlic and allyl alcohol resulted in fragmentation of the disc and an overexpression of disc microribbons, internalization of flagella, vacuole formation and an increase in distended vesicles. Allyl mercaptan, however, only gave an increase in distended vesicles, suggesting that this biocide has a different mode of action.

GH decreases hepatic amino acid degradation after small bowel resection in rats without enhancing bowel adaptation

Growth hormone (GH) treatment in short bowel syndrome is controversial, and the mechanisms of a possible positive effect remain to be elucidated. Rats were randomly subjected to either an 80% jejunoileal resection or sham operation and were given either placebo (NaCl) or biosynthetic rat GH (brGH). The in vivo capacity of urea nitrogen synthesis (CUNS) and the expression of urea cycle enzymes were measured and related to changes in body weight and adaptive growth in ileal segments on days 7 and 14. Ileal segments were examined by unbiased stereological techniques. brGH treatment decreased CUNS among the resected rats by 19% (P<0.05) and 36% (P<0.05) on days 7 and 14, respectively. The mRNA levels of urea cycle enzyme genes were not influenced by brGH treatment. brGH treatment did not increase the adaptive growth in the ileal segments. In conclusion, we found that GH treatment decreased the accelerated postoperative hepatic amino acid degradation in experimental short bowel syndrome without enhancing the morphological intestinal adaptation.