Hepatotoxin-induced Liver Injury Research Articles

The role of 2ʹ–5ʹ-oligoadenylate synthase-like protein (OASL1) in biliary and hepatotoxin-induced liver injury in mice

Following an injury, the liver embarks on a process that drives the accumulation and reformation of the extracellular matrix, leading to hepatic fibrosis. Type I interferons (IFNs), including IFN-α and IFN-β, play a crucial role in averting chronic liver injury through the activation of IFN-stimulated genes (ISGs), which are instrumental in sculpting adaptive immunity. The role of 2ʹ–5ʹ-oligoadenylate synthase-like protein 1 (OASL1), an antiviral ISG, in the context of liver fibrosis remains to be elucidated. To elicit liver fibrosis, a diet containing 0.1% diethoxycarbonyl-1,4-dihydrocollidine (DDC) and carbon tetrachloride (CCl4) were employed to induce cholestatic- and hepatotoxin-mediated liver fibrosis, respectively. Histological analyses of both models revealed that OASL1−/− mice exhibited reduced liver damage and, consequently, expressed lower levels of fibrotic mediators, notably α-smooth muscle actin. OASL1−/− mice demonstrated significantly elevated IFN-α and IFN-β mRNA levels, regulated by the IFN regulatory factor 7 (IRF7). Additionally, OASL1−/− ameliorated chronic liver fibrosis through the modulation of nuclear factor-κB (NF-κB) signaling. The effect of OASL1 on type I IFN production in acute liver damage was further explored and OASL1−/− mice consistently showed lower alanine transaminase levels and pro-inflammatory cytokines, but IFN-α and IFN-β mRNA levels were upregulated, leading to amelioration of acute liver injury. Additionally, the study discovered that F4/80-positive cells were observed more frequently in OASL1−/− CCl4 acutely treated mice. This implies that there is a significant synergy in the function of macrophages and OASL1 deficiency. These results demonstrate that in instances of liver injury, OASL1 inhibits the production of type I IFN by modulating the NF-κB signaling pathway, thereby worsening disease.

Non-enzymatic detection of serum glucose using a fluorescent nanopolymer probe.

A fluorescent probe is described for the determination of serum glucose after hepatotoxin-induced liver injury. The probe is based on the use of a water-soluble polymer and has been prepared from a multi-functional azlactone polymer as the linker, amino boronic acid, and Alizarin Red as the signalling moiety. The excitation/emission peaks of the polymeric fluorescent probe are at 468/567nm. Fluorescence is reduced on addition of glucose. Intensity drops linearly in the 0.1mM to 14mM glucose concentration range. The probe was applied to non-enzymatic detection of glucose in rat serum after CCl4-induced liver damage. Graphical abstract A polymer based fluorescent probe has been constructed and applied for non-enzymatic monitoring of serum glucose following hepatotoxin induced liver injury.

Dietary zerumbone, a sesquiterpene, ameliorates hepatotoxin-mediated acute and chronic liver injury in mice.

Acute liver injury (ALI) is a life-threatening clinical syndrome. Long-lasting liver injury can lead to chronic hepatic inflammation and fibrogenic responses. Zerumbone (ZER), the main constituent of rhizomes of Zingiber zerumbet Smith, has a variety of functions including anticancer activity. We investigated the role of ZER on the progression of hepatotoxin-induced liver injury. Single or repeated injection of CCl4 was used to induce acute or chronic liver injury, respectively. Mice were orally administered with ZER (10, 50mg/kg) during the experimental period. Histopathologic analysis and serum biochemical levels revealed that ZER had hepatoprotective activities against ALI. Similar effects of ZER on injured livers were confirmed by analyses of inflammation and apoptosis-related genes. Western blot analysis showed that protein levels of apoptotic molecules were decreased, whereas antiapoptotic protein levels were conversely increased in injured livers treated with ZER. Furthermore, chronic liver injury and its associated fibrogenesis in mice were reduced by ZER treatment. These findings from our in vivo experiments further indicate that ZER could alleviate hepatocellular toxicity and inhibit activation of primary hepatic stellate cells. Our results suggest that ZER might have potential as a safe and prophylactic alternative to prevent acute and chronic liver injury.

Liver Injury Assessment by Vetscan VS2 Analyzer and Most Frequently Used ALT/GTP Reagent.

Liver injury is estimated by serum alanine aminotransferases (ALT) levels in experimental animal models. Laboratories use various techniques to measure ALT levels including assay reagents and chemistry analyzers. VetScan VS2 (VS2) is widely used in veterinary clinics and research laboratories for highly reproducible, convenient and effective testing. Alternatively, ALT liquid reagent is used by laboratories to estimate liver injury in animal studies. The aim of this study was to perform comparative analyses of data obtained from these two assays in two different animal models. In this study, we used two different mouse models and compared the ALT levels measured using VetScan VS2 chemistry analyzer and ALT liquid reagent. Immunohistochemical analysis of hepatic tissue was also performed to document liver pathology. The first model is a high fat diet feeding model that results in a mild hepatic steatosis (fat accumulation in the liver) without elevation of ALT levels. For a severe liver injury model, we employed a hepatotoxin-induced liver injury model (carbon tetrachloride, CCl4), which leads to the development of hepatic fibrosis and very high ALT levels. VetScan VS2 and ALT reagent gave different values of ALT for all animal groups. However, linear regression analysis showed a significantly high association between ALT levels obtained by VS2 and ALT liquid reagent in a high-fat feeding model with no liver injury. For the CCl4 induced liver injury model, serum dilution (5 and 10 times) was performed to obtain accurate results with ALT reagent. ALT levels acquired from both techniques showed a close association. Interestingly, this correlation was closer when serum was diluted 5 fold. This study demonstrates that both methods give similar results when evaluating liver injury in animal studies. However, the serum dilution factor is critical for severe liver injury assessment when using ALT reagent and requires some optimization. In this regard, VetScan VS2 is easier to use and gives comparable results.

Opposing effects of prednisolone treatment on T/NKT cell- and hepatotoxin-mediated hepatitis in mice

Prednisolone is a corticosteroid that has been used to treat inflammatory liver diseases such as autoimmune hepatitis and alcoholic hepatitis. However, the results have been controversial, and how prednisolone affects liver disease progression remains unknown. In the current study we examined the effect of prednisolone treatment on several models of liver injury, including T/NKT cell hepatitis induced by concanavalin A (ConA) and α-galactosylceramide (α-GalCer), and hepatotoxin-mediated hepatitis induced by carbon tetrachloride (CCl4 ) and/or ethanol. Prednisolone administration attenuated ConA- and α-GalCer-induced hepatitis and systemic inflammatory responses. Treating mice with prednisolone also suppressed inflammatory responses in a model of hepatotoxin (CCl4 )-induced hepatitis, but surprisingly exacerbated liver injury and delayed liver repair. In addition, administration of prednisolone also enhanced acetaminophen-, ethanol-, or ethanol plus CCl4 -induced liver injury. Immunohistochemical and flow cytometric analyses demonstrated that prednisolone treatment inhibited hepatic macrophage and neutrophil infiltration in CCl4 -induced hepatitis and suppressed their phagocytic activities in vivo and in vitro. Macrophage and/or neutrophil depletion aggravated CCl4 -induced liver injury and impeded liver regeneration. Finally, conditional disruption of glucocorticoid receptor in macrophages and neutrophils abolished prednisolone-mediated exacerbation of hepatotoxin-induced liver injury. Prednisolone treatment prevents T/NKT cell hepatitis but exacerbates hepatotoxin-induced liver injury by inhibiting macrophage- and neutrophil-mediated phagocytic and hepatic regenerative functions. These findings may not only increase our understanding of the steroid treatment mechanism but also help us to better manage steroid therapy in liver diseases.

Mechanisms of Biliary Damage

Bile duct damage is present in virtually all cholangiopathies, which share the biliary epithelial cells (i.e. cholangiocytes) as a common pathogenic target. Cholangiocyte cell death largely occurs through the process of apoptosis. In this review, we will summarize the mechanisms through which biliary damage occurs in a variety of animal and in vitro models, such as extrahepatic cholestasis induced by bile duct ligation (BDL), cytotoxin- and hepatotoxin-induced liver injury, and biliary atresia. Although we have increased our knowledge of the factors that regulate cholangiocyte cell death mechanisms during cholangiopathies, especially in experimental models, there is still a lack of effective treatment modalities for these biliary disorders. However, future studies will hopefully provide for new therapeutic modalities for the prevention or restoration of biliary mass and function lost during the progression of cholangiopathies.

Silencing of liver-specific microRNA-122 aggravates acute but not chronic hepatotoxin-induced liver injury

Silencing of liver-specific microRNA-122 aggravates acute but not chronic hepatotoxin-induced liver injury

677. Polycationic Liposome-Mediated Extracellular Superoxide Dismutase Gene Delivery Leads to High Levels of the Transgene Expression and Prevents Acute Liver Injury in Mice

BACKGROUND: We have developed a formulation of polycationic liposomes that has been shown to be non-toxic, highly stable in the bloodsteam, and very effective in liver gene transfer in mice (Gene Therapy 2003; 10:180–187). Extracellular superoxide dismutase (EC-SOD) inhibits the generation of superoxide anions in the interstitial space of tissues, and may play a role in minimizing oxidative stress in liver injury. The aim of the present study is to investigate whether our polycationic liposome-mediated human EC-SOD gene delivery will protect against lipopolysaccharide (LPS)-induced liver toxicity in D-galactosamine (GalN)-sensitized mice. METHODS: Polycationic liposomes were generated from polycationic lipid (PCL) and cholesterol (Chol). Lipoplexes were formed by complexing liposomes with control plasmid (pEGFP-C1) or EC-SOD plasmid (pEGFP-C1-ECSOD) before use. Mice were injected with thyroid hormone (T3, 4 mg/kg, s.c.) two days before lipoplexes were injected via the portal vein. One day following lipoplex injection, mice were treated with GalN (500 mg/kg, i.p.) plus LPS (25 mg/kg, i.p.). Serum alanine aminotransferase (ALT), SOD activity, liver histology, glutathione (GSH) content and lipid peroxidation were evaluated one day after GalN/LPS exposure. Human EC-SOD gene expression in mouse liver tissue was determined by quantitative RT-PCR two days after lipoplex injection. RESULTS: somes and the control lipoplexes were stable in their size for three months at 4°C. Injection of T3, PCL-Chol liposomes or control lipoplexes did not cause a significant change in serum ALT levels. Real time quantitative RT-PCR analysis showed that human EC-SOD mRNA levels in mouse liver tissue in EC-SOD lipoplex-injected group were 55-fold higher than saline, liposome or control lipoplex controls when mouse -actin was employed as a house-keeping control gene. Serum ALT levels in animals receiving portal vein injections of EC-SOD lipoplexes plus GalN/LPS exposure were much lower than in those receiving normal saline, liposomes alone, or control lipoplexes plus GalN/LPS exposure (62583 vs. 150865, 153194, 1880520 units/ml, p<0.01). Liver histology showed much less hepatocyte death in EC-SOD lipoplex-treated group than liposome- or control lipoplex-treated groups. Serum SOD activity in animals receiving injection of EC-SOD lipoplexes were higher than in those treated with liposomes only, or control lipoplexes (28.8 3.3 vs. 15.2 0.9, 17.4 3.4 units/ml, p<0.05). Liver GSH content in animals receiving EC-SOD lipoplex injection was preserved with less lipid peroxidation, as indicated by a lower level of malondialdehyde content. CONCLUSIONS: liposome-mediated EC-SOD gene delivery leads to the marked transgene expression, and attenuates acute liver injury due to reduced oxidative stress in GalN/LPS-exposed mice. To our knowledge, this is a first report which demonstrates that polycationic liposome-mediated EC-SOD gene delivery to the liver represents a potential therapy for hepatotoxin-induced liver injury.

Inhibitory effect of glycyrrhizin on NF-kappaB binding activity in CCl4- plus ethanol-induced liver cirrhosis in rats.

Potenlini is an injectable compound whose active component is glycyrrhizin, which is extracted from licorice. Previous studies showed that it could reduce liver injury, improve alanine aminotransferase (ALT) levels and act as an antifibrotic agent. However, the mechanism of its action remains unclear. The aim of this study was to determine the molecular mechanism of its action by investigating the effects of potenlini on nuclear factor-kappaB (NF-kappaB) binding activity in an animal model of liver cirrhosis. Rats were randomly allocated into a normal control group, a model control group, and a potenlini group. Rats in the latter two groups were treated with CCl4 and ethanol solution in order to induce chronic liver injury. Rats in the potenlini group were given potenlini treatment at the same time. Serum ALT levels were significantly reduced in rats treated with potenlini compared with levels in rats of the model control group, which had dramatically increased ALT levels. Histologically, liver steatosis and fibrosis were severe in the rats of the model group, but were significantly improved in rats of the potenlini group. NF-kappaB binding activity was markedly increased in the liver specimens taken from the rats of the model control group in comparison with the binding of normal livers, but the binding levels were nearly normal in the livers of the potenlini group. The results suggest that potenlini can inhibit the NF-kappaB binding activity in CCl4 and ethanol-induced chronic liver injury, and that effect may be a possible mechanism by which potenlini protects the liver from hepatotoxin-induced liver injury and cirrhosis.

The effect of prostanoids on hepatic bile flow in dogs with normal liver and bile duct cell hyperplasia

Bile flow rates and composition are subject to a wide variety of neural, endocrine and paracrine influences. The effects of these multiple factors may be different in the diseased liver compared to the response produced in the normal liver. As prostanoids may have a therapeutic role in liver disease it was intended to evaluate the effects of two principal therapeutic prostanoids, prostaglandin E 2 and prostacyclin, on bile flow in dogs with a normal liver and in dogs with hepatotoxin-induced liver injury. Initially, in awake animals with chronic biliary and gastric fistulas the bile flow response to prostaglandin E 2 and prostacyclin was evaluated and compared to the response produced by bile salt infusion alone and to that produced by the standard choleretic hormones, secretin and glucagon. The animals were then fed α-naphthylisothiocyanate (ANIT) and the studies repeated. ANIT is a hepatotoxin that produces bile duct cell hyperplasia which was confirmed in dogs by demonstrating that ANIT increased [ 3H]thymidine incorporation by isolated canine bile duct cells. In normal dogs, the prostanoids, secretin, and glucagon increased hepatic bile flow. 10 days of ANIT feeding produced a hypercholeresis. While secretin was able to stimulate the hyperplastic biliary epithelium and increase bile flow over values produced by the hyperplastic biliary epithelium alone, neither prostaglandin E 2, prostacyclin, or glucagon appeared to stimulate the hyperplastic biliary epithelium. As ANIT produced evidence of cholestasis and hepatocellular damage, only secretin would seem to have a potential therapeutic role in increasing bile flow in cholestatic liver disorders associated with bile duct cell hyperplasia.

Plasma alpha 1-acid glycoprotein concentration in rats with chemical liver injury.

The influence of liver injury on the plasma concentrations of alpha 1-acid glycoprotein (AGP) and albumin was examined in several different models of chemically-induced liver injury. The plasma AGP concentration in carbon tetrachloride (CCl4), allyl alcohol, bromobenzene, acetaminophen or N-nitrosodimethylamine-induced liver injury was increased to 2-3.5 times the normal level at 24 h after the intoxication. The plasma AGP concentration was unchanged in ethionine-induced liver injury and was markedly decreased in galactosamine-induced injury. The plasma albumin concentration was significantly decreased by the damage due to galactosamine, allyl alcohol or N-nitrosodimethylamine-induced liver injury, while no influence was observed by other hepatotoxin-induced liver injury. The plasma protein binding of propranolol was also determined in relation to the plasma concentrations of AGP and albumin in all the experimental models. Propranolol binding, expressed as bound to free ratio, showed a good correlation with the AGP concentration (r = 0.940; p < 0.001), but not with the albumin concentration.

Therapeutic effect of taurine administration on carbon tetrachloride-induced hepatic injury.

To determine the therapeutic efficacy of taurine administration on liver injury, the effect of taurine on hepatic lipid peroxide level following carbon tetrachloride (CCl4) administration was investigated. To CCl4 intoxicated rats (CCl4, 2 ml/kg, i.p.), 3 ml of a 10% aqueous solution of taurine was administered after CCl4 administration (at 12, 16, and 20 hr after), and rats were sacrificed at 24 hr after CCl4 administration in order to estimate the level of lipid peroxides in the liver. The decrease of hepatic lipid peroxidation induced by CCl4 was noticed in the taurine-treated rats. Taurine had no effect on mixed function oxidase activity in hepatic microsomes as well as no effect on hepatic antioxidant content in the CCl4-intoxicated rats. Hepatic taurine content decreased significantly 12 and 24 hr after CCl4 administration, whereas oral administration of taurine to CCl4-intoxicated rats was able to protect these rats from hepatic taurine depletion. These results suggest that hepatic taurine may play a critical role on the protection of hepatocytes against hepatotoxins such as CCl4 and the administration of taurine may be useful in the treatment of hepatotoxin-induced liver injury.

THERAPEUTIC EFFECT OF TAURINE ADMINISTRATION ON CARBON TETRACHLOR1DE-INDUCED HEPATIC INJURY

AbstractTo determine the therapeutic efficacy of taurine administration on liver injury, the effect of taurine on hepatic lipid peroxide level following carbon tetrachloride (CCl4) administration was investigated. To CCl4 intoxicated rats (CCl4, 2 ml/kg, i.p.), 3 ml of a 10% aqueous solution of taurine was administered after CCl4 administration (at 12, 16.. and 20 hr after), and rats were sacrificed at 24 hr after CCl4 administration in order to estimate the level of lipid peroxides in the liver. The decrease of hepatic lipid peroxidation induced by CCl4 was noticed in the taurine-treated rats. Taurine had no effect on mixed function oxidase activity in hepatic microsomes as well as no effect on hepatic antioxidant content in the CCl4-intoxicated rats. Hepatic taurine content decreased significantly 12 and 24 hr after CCl4 administration, whereas oral administration of taurine to CCl4-intoxicated rats was able to protect these rats from hepatic taurine depletion. These results suggest that hepatic taurine may play a critical role on the protection of hepatocytes against hepatotoxins such as CCl4 and the administration of taurine may be useful in the treatment of hepatotoxin-induced liver injury.