Animal Model Of Liver Failure Research Articles

Effect of Resveratrol on Thioacetamide-induced Liver Damage in Rat Models

Background: The current treatments of liver diseases are not sufficiently effective, and there has been no therapy that can successfully prevent liver failure and its complications. Previous studies have suggested that resveratrol could inhibit the progression of hepatic diseases based on its antioxidative and anti-inflammatory potentials. Objectives: The present study evaluated the hepato-protective effects of resveratrol in thioacetamide (TAA)-induced acute liver damage in rats using neurobehavioral and biochemical parameters. Methods: Forty-eight healthy adult Wistar rats were divided into four groups: C1: healthy control group, C2: non-treated liver failure, E1: liver failure treated with resveratrol 5 mg/kg/day, and E2: liver failure treated with resveratrol 10 mg/kg/day. Aspartate aminotransferase/alanine aminotransferase (AST/ALT), alkaline phosphatase (Alk), total bilirubin (TB), and plasma-ammonia (NH4) were analyzed, and histopathological evaluations of the specimens were carried out after sacrificing the models. Hepatic encephalopathy (HE) grading, open-field, elevated plus arms, and forced-swimming tests were performed in the study. Results: The resveratrol-treated groups had lower serum concentrations of NH4, ALT, and AST than the C2 group (P < 0.05). The pathological evaluations demonstrated that resveratrol-treated groups had better outcomes in inflammatory cell infiltration, apoptosis, vacuolization, liver tissue necrosis, and liver damage stage than the C2 group (P < 0.05). They also showed lower grades of HE, higher locomotor activity (open-field test), and diminished levels of depression (forced-swimming) when compared to the C2 group (P < 0.05). Conclusions: Resveratrol supplementation can improve liver damage as AST, ALT, NH4, and tissue damages were decreased after administering the agent in TAA-induced liver damage. Resveratrol can also improve the neurobehavioral manifestations in animal models of liver failure.

Sex Difference and Hormones in the Regulation of Vasopressin Secretion during Dilutional Hyponatremia

Dilutional hyponatremia due to elevated arginine vasopressin (AVP) secretion increases mortality in patients with liver failure. No previous studies have addressed sex difference in dilutional hyponatremia in animal models of liver failure. The aim of this study is to investigate sex difference in dilutional hyponatremia and the effect of ovarian hormones in AVP secretion. We have used chronic bile duct ligated (BDL) rats, a model of dilutional hyponatremia associated with liver failure.Adult male Sprague Dawley rats, female Sprague Dawley rats and ovariectomized (OVX) female rats were used. After two weeks, the rats had BDL or sham ligation surgery. Four weeks later, the brains were processed for immunohistochemistry analysis of FosB and AVP expression. Blood samples were collected to measure plasma osmolality, hematocrit, circulating estradiol and copeptin concentration. Copeptin was used as biomarker for plasma AVP. Liver weight, body weight, and fluid accumulation were recorded to verify if the rats developed liver failure and ascites. Data were analyzed by one ANOVA with Bonferroni post hoc comparisons.All the BDL rats had significant increase in liver to body weight ratio compared to sham rats indicating liver failure and ascites with bile duct ligation. Male BDL rats had hyponatremia along with significant increases in plasma copeptin and FosB expression in Supraoptic AVP neurons compared to male shams (all p<0.05; 5–7). Unlike male BDL rats, the female BDL rats did not become hyponatremia and did not had increases Supraoptic AVP neuron activation and copeptin secretion compared to female sham.Ovariectomy significantly decreased plasma estradiol concentration in sham rats compared to intact female sham (p< 0.05; 6–10). However, circulating estradiol concentration was significantly elevated in ovariectomized BDL (OVX BDL) rats compared to the ovariectomized sham (OVX sham) and female sham rats (p<0.05; 6–10). To identify the source of estradiol contributing to the observed increase in OVX BDL rats, adrenal glands were collected at the end of protocol. Adrenal gland steroids were extracted to measure estradiol and its precursors, testosterone and DHEA concentration.The OVX BDL rats had significantly increased adrenal estradiol along with significant decrease in adrenal testosterone and DHEA compared to OVX sham rats (all p< 0.05; 6–7). Plasma osmolality, hematocrit and copeptin concentration were not different between OVX BDL and OVX sham rats. Our results show that unlike male BDL rats, female BDL rats did not develop hyponatremia, supraoptic AVP neuron activation, or increased copeptin secretion compared to sham ligated females. Female OVX BDL rats did not become hyponatremia or increased copeptin secretion compared to female OVX sham rats. It is possible that the increase in adrenal estradiol compensated for the lack of ovarian estrogens in OVX BDL rats. Additional experiments will be required to determine the effects of estrogen in this model.Support or Funding InformationSupported by R01 HL119458 and 18PRE34060035This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Kynurenic Acid Protects against Thioacetamide-Induced Liver Injury in Rats.

Acute liver failure (ALF) is a life-threatening disorder of liver function. Kynurenic acid (KYNA), a tryptophan metabolite formed along the kynurenine metabolic pathway, possesses anti-inflammatory and antioxidant properties. Its presence in food and its potential role in the digestive system was recently reported. The aim of this study was to define the effect of KYNA on liver failure. The Wistar rat model of thioacetamide-induced liver injury was used. Morphological and biochemical analyses as well as the measurement of KYNA content in liver and hepatoprotective herbal remedies were conducted. The significant attenuation of morphological disturbances and aspartate and alanine transaminase activities, decrease of myeloperoxidase and tumor necrosis factor-α, and elevation of interleukin-10 levels indicating the protective effect of KYNA in thioacetamide (TAA) - induced liver injury were discovered. In conclusion, the hepatoprotective role of KYNA in an animal model of liver failure was documented and the use of KYNA in the treatment of ALF was suggested.

Mild Hypothermia Attenuates Liver Injury and Improves Survival in Mice With Acetaminophen Toxicity

Body temperature may critically affect mechanisms of liver injury in acetaminophen (APAP) hepatotoxicity. In addition, mild hypothermia is used to treat intracranial hypertension in human liver failure without detailed information on its effects on the injured liver itself. Therefore, we investigated the effects of body temperature on the progression of APAP-induced liver injury in mice. Male C57BL6 mice treated with saline or APAP (300 mg/kg intraperitoneally) were maintained at normothermia (35.5-37.5 degrees C) by external warming or were allowed to develop mild hypothermia (32.0-35.0 degrees C) after 2 hours from APAP administration. Mild hypothermia resulted in improved survival after APAP intoxication. Liver damage was reduced, as assessed histologically and by plasma alanine aminotransferase levels. Early effects of hypothermia included a reduction of hepatic congestion and improved recovery of glycogen stores. At later time points (8-12 hours), APAP-treated mice that were maintained at normothermia manifested increased hepatocyte apoptosis, as assessed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining and cleavage of poly(adenosine diphosphate-ribose) polymerase. Mild hypothermia did not affect the formation of APAP-protein adducts or the depletion of glutathione, nor did it abrogate hepatocyte DNA synthesis. Mild hypothermia improved survival and attenuated liver injury and apoptosis in APAP-treated mice by reducing hepatic congestion and improving glycogen recovery without affecting hepatic regeneration. Results of the study underscore the need for a strict control of body temperature in animal models of liver failure and suggest that the benefits of mild hypothermia in liver failure may extend beyond those related to reduced cerebral complications.

Brain edema and intracranial hypertension in fulminant hepatic failure: Pathophysiology and management

Intracranial hypertension is a major cause of morbidity and mortality of patients suffering from fulminant hepatic failure. The etiology of this intracranial hypertension is not fully determined, and is probably multifactorial, combining a cytotoxic brain edema due to the astrocytic accumulation of glutamine, and an increase in cerebral blood volume and cerebral blood flow, in part due to inflammation, to glutamine and to toxic products of the diseased liver. Validated methods to control intracranial hypertension in fulminant hepatic failure patients mainly include mannitol, hypertonic saline, indomethacin, thiopental, and hyperventilation. However all these measures are often not sufficient in absence of liver transplantation, the only curative treatment of intracranial hypertension in fulminant hepatic failure to date. Induced moderate hypothermia seems very promising in this setting, but has to be validated by a controlled, randomized study. Artificial liver support systems have been under investigation for many decades. The bioartificial liver, based on both detoxification and swine liver cells, has shown some efficacy on reduction of intracranial pressure but did not show survival benefit in a controlled, randomized study. The Molecular Adsorbents Recirculating System has shown some efficacy in decreasing intracranial pressure in an animal model of liver failure, but has still to be evaluated in a phase III trial.

Differential effects of ammonia on the benzodiazepine modulatory site on the GABA-A receptor complex of human brain

Ammonia is a key factor in the pathogenesis of encephalopathies associated with liver failure. A direct effect of ammonia on GABAergic neurotransmission was proposed as a mechanism that may explain its neurotoxic effect on the basis of electrophysiological and biochemical studies performed in animal models of liver failure. In the present study, we investigated using a radiometric assay the effect of ammonia on the binding of GABA-A receptor ligands to membranes from normal human brains. Ammonium tartrate significantly decreased the maximal binding of [ 3H]flunitrazepam to well-washed frontal cortical membranes (366 ± 63 fmol/mg protein in absence of ammonia versus 294.1 ± 51 fmol/mg protein in presence of 2 mM ammonia; p < 0.05). The efficacy of the effects of ammonia was within the millimolar range (IC 50 = 4.8 mM). This effect was not seen in cerebellum or hippocampus. Ammonia exposure decreased the maximal binding of [ 3H]flumazenil (284.9 ± 24.2 fmol/mg protein in absence of ammonia versus 146.4 ± 15.6 fmol/mg protein in presence of 2 mM ammonia; p < 0.01). This effect was seen with a greater potency ( I max = 32.4%) and a lower IC 50 (0.1 mM). Inhibition of [ 3H]flumazenil binding was significant in all brain regions. The apparent ammonia-induced decrease of [ 3H]flunitrazepam and [ 3H]flumazenil binding was due to a decrease in the binding affinities of these ligands for the benzodiazepine site. In contrast, ammonium tartrate exposure did not cause significant changes to the binding of [ 3H]muscimol in any brain region. These findings demonstrate that ammonia interacts negatively with components of the benzodiazepine-associated site at the GABA-A receptor complex in human brain in contrast to previous reports in the rat, and thus, does not support the notion that ammonia directly activates the GABA-A receptor complex resulting in increased GABAergic neurotransmission in human hepatic encephalopathy. These findings also suggest that positron emission tomography studies in cirrhotic patients using [ 11C]flumazenil may be underestimating GABA-A receptor sites depending upon the degree of hyperammonemia of the patient.

Alterations in soluble guanylate cyclase content and modulation by nitric oxide in liver disease

Hyperammonemia is the main responsible for the neurological alterations in hepatic encephalopathy in patients with liver failure. We studied the function of the glutamate–nitric oxide (NO)–cGMP pathway in brain in animal models of hyperammonemia and liver failure and in patients died with liver cirrhosis. Activation of glutamate receptors increases intracellular calcium that binds to calmodulin and activates neuronal nitric oxide synthase, increasing nitric oxide, which activates soluble guanylate cyclase (sGC), increasing cGMP. This glutamate–NO–cGMP pathway modulates cerebral processes such as circadian rhythms, the sleep-waking cycle, and some forms of learning and memory. These processes are impaired in patients with hepatic encephalopathy. Activation of sGC by NO is significantly increased in cerebral cortex and significantly reduced in cerebellum from cirrhotic patients died in hepatic coma. Portacaval anastomosis in rats, an animal model of liver failure, reproduces the effects of liver failure on modulation of sGC by NO both in cerebral cortex and cerebellum. In vivo brain microdialisis studies showed that sGC activation by NO is also reduced in vivo in cerebellum in hyperammonemic rats with or without liver failure. The content of α but not β subunits of sGC are increased both in frontal cortex and cerebellum from patients died due to liver disease and from rats with portacaval anastomosis. We assessed whether determination of activation of sGC by NO-generating agent SNAP in lymphocytes could serve as a peripheral marker for the impairment of sGC activation by NO in brain. Chronic hyperammonemia and liver failure also alter sGC activation by NO in lymphocytes from rats or patients. These findings show that the content and modulation by NO of sGC are strongly altered in brain of patients with liver disease. These alterations could be responsible for some of the neurological alterations in hepatic encephalopathy such as sleep disturbances and cognitive impairment.

Endothelin is an important determinant of renal function in a rat model of acute liver and renal failure.

Renal failure occurs in approximately 55% of patients with acute liver failure. We have previously shown that plasma endothelin 1 concentrations are elevated in patients with acute liver failure and the hepatorenal syndrome. There are few reported satisfactory animal models of liver failure together with functional renal failure. In this study, a rat model of acute liver failure induced by galactosamine that also develops renal failure was first characterised. This model was used to investigate the hypothesis that endothelin 1 is an important mediator involved in the pathogenesis of renal impairment that occurs in acute liver failure. Acute liver failure was induced in male Sprague-Dawley rats by intraperitoneal injection of galactosamine together with treatment with the endothelin receptor antagonist Bosentan. Twenty four hour urine collections were made using a metabolic cage. Renal blood flow was measured in anaesthetised animals. This model developed renal failure and liver failure in the absence of any significant renal pathology, and with an accompanying fall in renal blood flow. Plasma concentrations of endothelin 1 were increased twofold following the onset of liver and renal failure (p<0.05), and there was significant upregulation of the endothelin receptor A (ET(A)) in the renal cortex (p<0.05). Administration of Bosentan prevented the development of renal failure when given before or 24 hours after the onset of liver injury (p<0.05) but had no effect on liver injury itself, or on renal blood flow. This study demonstrates that this animal model has many of the features needed to be regarded as a model of renal failure that occurs in acute liver failure. The observation that plasma levels of endothelin 1 and ET(A) receptors are increased and upregulated, and that renal failure is prevented by an endothelin antagonist supports the hypothesis originally put forward that ET(A) is important in the pathogenesis of renal failure that occurs in patients with acute liver failure.

Advances in bioartificial liver assist devices.

Rapid advances in development of bioartificial liver assist devices (BLADs) are exciting clinical interest in the application of BLAD technology for support of patients with acute liver failure. Four devices (Circe Biomedical HepatAssist, Vitagen ELAD, Gerlach BELS, and Excorp Medical BLSS) that rely on hepatocytes cultured in hollow-fiber membrane technology are currently in various stages of clinical evaluation. Several alternative approaches for culture and perfusion of hepatocytes have been evaluated in preclinical, large animal models of liver failure, or at a laboratory scale. Engineering design issues with respect to xenotransplantation, BLAD perfusion, hepatocyte functionality and culture maintenance, and ultimate distribution of a BLAD to a clinical site are delineated.

Perioperative Anti-endotoxin Strategies

Lipopolysaccharides from the outer membrane of Gram-negative bacteria are potent stimuli for the production of numerous cytokines by the immune cells. The systemic inflammatory response to these gut-derived endotoxins is therefore dependent on the responsiveness of the immune system. This paper presents results on anti-endotoxin strategies and the responsiveness to endotoxin in animal models of liver failure. Following partial hepatectomy in the normal rat, anti-endotoxin treatment using the enteral endotoxin binder cholestyramine and the bactericidal permeability-increasing protein showed beneficial effects in terms of reducing the exaggerated metabolic and inflammatory responses. Similar beneficial effects of gut endotoxin restriction were found in bile duct ligated rats subjected to a laparotomy. The beneficial effects of anti-endotoxin strategies in these models were explained by completely different mechanisms. In partial hepatectomized rats the effects were explained by the direct inhibition of the stimulatory action of endotoxin on immune cells preventing an exaggerated inflammatory response. In contrast, in postoperative BDL rats the effects of anti-endotoxin therapy were explained by the restoration of endotoxin sensitivity of the immune cells resulting in an inflammatory response necessary for an adequate reaction to surgery. These different mechanism will be discussed in the light of the phenomenon of endotoxin tolerance.