Induced Liver Injury Model Research Articles

A Discovery of Relevant Hepatoprotective Effects and Underlying Mechanisms of Dietary Clostridium butyricum Against Corticosterone-Induced Liver Injury in Pekin Ducks.

Clostridium butyricum (C. butyricum) can attenuate oxidative stress, inflammation, and hepatic fatty deposition in poultry, however, the underlying mechanisms for this in Pekin ducks remain unclear. This study evaluated these hepatoprotective effects and the underlying mechanisms in a corticosterone (CORT)-induced liver injury model in Pekin ducks fed a C. butyricum intervention diet. A total of 500 Pekin ducks were randomly divided into five groups: one group (CON group) was only provided with a basal diet, three groups were provided a basal diet with 200 mg/kg (LCB group), 400 mg/kg (MCB group), or 600 mg/kg (HCB group) C. butyricum, respectively, and one group was provided a basal diet with 150 mg/kg aureomycin (ANT group) for 42 d. At 37 days-old, all ducks received daily intraperitoneal injections of CORT for five days to establish a liver injury model. C. butyricum intervention alleviated liver injury by decreasing the liver organ indices, hepatic steatosis and hepatocyte necrosis, and improving liver function, antioxidant capacity, and inflammatory factors. Hepatic RNA-seq revealed 365 differentially expressed genes (DEGs) between the MCB and CON groups, with 229 up- and 136 down-regulated DEGs in the MCB group. Between the MCB and ANT groups, 407 DEGs were identified, including 299 up- and 108 down-regulated genes in MCB group. Some DEGs in the MCB group related to oxidative stress and inflammatory responses such as Sod3, Tlr2a/b, and Il10, which were up-regulated, while Apoa1, Cyp7a1, Acsl1/5, Fasn, Ppar-γ, and Scd, which are involved in lipid metabolism, were down-regulated, indicating that these genes were responsive to dietary C. butyricum for the alleviation of corticosterone-induced hepatic injury. Toll-like receptor signaling, PI3K-Akt signaling pathway, cytokine-cytokine receptor interaction, peroxisome proliferator-activated receptor (PPAR) signaling pathway, adipocytokine and glycerophospholipid metabolism signaling pathway were significantly enriched in the MCB group. These findings indicate that C. butyricum intervention can protect Pekin ducks from corticosterone-induced liver injury by the modulation of immunoregulatory- and lipid metabolism-related genes and pathways.

Baicalein Enhances the Oral Bioavailability and Hepatoprotective Effects of Silybin Through the Inhibition of Efflux Transporters BCRP and MRP2.

Although hepatoprotective properties of silybin are well documented, the clinical therapeutic efficacy is limited by its low bioavailability due to absorption rates, extensive phase II metabolism, and biliary excretion. As our previous study indicated that metabolic enzymes may have limited effects on the pharmacokinetic (PK) behavior of silymarin, here, we intended to increase the oral bioavailability and bio-efficacy of silybin through the inhibition of active efflux. In Caco-2 and transfected MDCKII cell models, flavone baicalein significantly inhibited the efflux of silybin as a BCRP and MRP2 inhibitor. In addition, baicalein reduced the biliary excretion index (BEI) and biliary clearance of silybin conjugates in the sandwich-cultured rat hepatocyte (SCH) model, indicating the inhibition of baicalein in biliary excretion of conjugated silybin metabolites. PK study demonstrated that baicalein significantly increased the area under the curve (AUC) and Cmax of silybin and its conjugates, suggesting enhanced absorption in vivo. Moreover, coadministration of silybin with baicalein boosted the liver protective, antioxidant, and anti-inflammatory effects of silybin in the carbon tetrachloride (CCl4)-induced liver injury model in comparison with silybin given alone. In summary, efflux transporters play a critical role in the low bioavailability of silybin, while inhibition of breast cancer resistance protein (BCRP) and multi-drug resistance protein 2 (MRP2) by baicalein can significantly increase the absorption and bio-efficacy of silybin, which provides a new combination therapeutic approach for the treatment of chronic liver diseases.

Hepatic injury induced by thioacetamide causes aortic endothelial dysfunction by a cyclooxygenase-dependent mechanism

Liver cirrhosis is associated with a wide range of cardiovascular abnormalities including hyperdynamic circulation and cirrhotic cardiomyopathy. The pathogenic mechanisms of these cardiovascular changes are multifactorial and include vascular dysregulations. AimThe present study tested the hypothesis that the systemic vascular hyporesponsiveness in thioacetamide (TAA)-induced liver injury model is dependent on nitric oxide (NO) and cyclooxygenase (COX) derivatives. Main methodsWistar rats were treated with TAA for eight weeks to induce liver injury. Key findingsThe maximal contractile response in concentration-effect curves to phenylephrine was decreased in aorta from TAA-treated rats, but no differences were found in aorta without endothelium, suggesting an endothelium-dependent mechanism in decreased contractile response. There was no difference in the contractile response with and without L-NAME (N(ω)-nitro-l-arginine methyl ester) in rats with liver injury, showing that the TAA treatment impairs NO synthesis. Pre-incubation of the aorta with indomethacin, a COX-inhibitor, normalized the reduced contractile response to phenylephrine in arteries from TAA group. Also, COX-2 and iNOS (inducible nitric oxide syntase) protein expression was increased in aorta from TAA group compared to control group. Animals submitted to TAA treatment had a reduction in systolic blood pressure. Our findings demonstrated that liver injury induced by TAA caused a decrease in aortic contractile response by a COX-dependent mechanism but not by NO release. Also, it was demonstrated an inflammatory process in the aorta of TAA-treated rats by increased expression of COX-2 and iNOS. SignificanceTherefore, there is an essential contribution of COX-2 activation in extra-hepatic vascular dysfunction and inflammation present in cirrhosis induced by TAA.

Oxidative stress and inflammatory responses in the liver of swamp eel (Monopterus albus) exposed to carbon tetrachloride

“Liver and gall syndrome” disease often caused dramatic economic losses in swamp eel (Monopterus albus) which is one of the most economically important freshwater aquaculture fish in China. Carbon tetrachloride (CCl4)-induced liver injury model has been evidenced as a useful method to screen the hepatoprotective agents to study and prevent this disease in fish. Therefore, in order to provide a better research platform for prevention and treatment liver diseases in swamp eel, we evaluated the hepatotoxicity effects of CCl4 on swamp eel based on the acute toxicity and biochemical responses of glutamate pyruvate transaminase (GPT), glutamate oxalate transaminase (GOT), lactate dehydrogenase (LDH), catalase (CAT), superoxide dismutase (SOD) and malondialdehyde (MDA), as well as mRNA expression levels of cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LO). The 96 h LD50 value of CCl4 in swamp eel was 2.54 g/kg. Sublethal levels of CCl4 induced time-depended liver injury in swamp eel, evidenced by the significant increases of serum GPT, GOT and LDH levels at the first 48 h injection, but restoration after 96 h injection. CCl4 led to oxidative stress, supported by the enhanced of MDA contents, and decreased of SOD and CAT activities. Moreover, CCl4 caused hepatic inflammatory reaction, evidenced by the significant changes of the transcription of COX and 5-LO genes in liver tissues. Overall, our results suggested that lipid peroxidation, antioxidant enzymes and COX and 5-LO pathways are important mechanisms involved in CCl4-induced liver injury, and could be used as the effective biomarkers of CCl4-induced liver injury model to screen the hepatoprotective agents in swamp eel.

Proliferating EpCAM-Positive Ductal Cells in the Inflamed Liver Give Rise to Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) originates from regenerating liver cells with genetic alterations in chronically inflamed liver. Ductal cells and hepatocytes proliferate for liver regeneration, and proliferating ductal cells (PDC) derived from bile ductules have long been considered putative liver stem/progenitor cells and candidate cellular origins of HCC. The potential of PDC as tumor-originating cells, however, remains controversial in contrast to accumulating evidence that HCC originates from hepatocytes. Here, we demonstrate that PDCs expressing the established surface and cancer stem cell marker EpCAM give rise to HCC in inflamed liver. EpCAM-expressing PDCs were specifically labeled in newly developed EpcamCreERT2 mice and traced in a chemically induced liver injury model. Stepwise accumulation of genetic alterations in EpCAM-positive cells was induced by the mutagenesis activity of activation-induced cytidine deaminase using conditional transgenic mice. Lineage-tracing experiments revealed that labeled PDC differentiated into cholangiocytes, but not into hepatocytes, in the chemically damaged liver. Nevertheless, EpCAM-positive PDC with genetic alterations gave rise to HCC after 8 months of chemical administration. PDC-derived HCC showed histologic characteristics of concomitant ductule-like structures resembling human cholangiolocellular carcinoma (CLC) and exhibited serial transitions from PDC-like CLC cells to hepatocyte-like HCC cells. The Wnt signaling pathway was specifically upregulated in the CLC components of PDC-derived HCC. Our findings provide direct experimental evidence that EpCAM-expressing PDC could be a cellular origin of HCC, suggesting the existence of stem/progenitor-derived hepatocarcinogenesis. Cancer Res; 77(22); 6131-43. ©2017 AACR.

Protective effects of hepatocyte-specific glycyrrhetic derivatives against carbon tetrachloride-induced liver damage in mice

Glycyrrhetic acid (GA), the main hydrolysate of glycyrrhizic acid extracted from the roots of the Chinese herb Glycyrrhiza glabra, was reported to be accumulated in hepatocytes due to the extensive distribution of GA receptors in liver. A series of hepatocyte-specific derivatives on the basis of anetholtrithione and glycyrrhizic were designed and synthesized. The potential beneficial effect was evaluated in carbon tetrachloride (CCl4)-induced liver injury model. In addition, the hepatoprotective activity of these derivatives was assessed by measuring levels of serum marker enzymes, including serum glutamate oxaloacetate transaminase (GOT), serum glutamate pyruvate transaminase (GPT), alkaline phosphatase (AKP), lactate dehydrogenase (LDH) and the ratio of GSH to GSSG. Gratifyingly, compounds 5a–c (100mg/kg, p.o.) markedly prevented CCl4-induced elevation of levels of serum GPT, GOT. A comparative histopathological study of liver exhibited almost a normal liver lobular architecture and cell structure of the livers, as compared to CCl4-treated group. These findings were confirmed with the histopathological observations, where hepatocyte-specific glycyrrhetic acid derivatives 5a–c were capable of reversing the toxic effects of CCl4 on hepatocytes.

Polydatin alleviates alcohol-induced acute liver injury in mice: Relevance of matrix metalloproteinases (MMPs) and hepatic antioxidants

BackgroundAlcohol, a most commonly consumed beverage, is the foremost cause of liver injury throughout the world. Polydatin, a stilbenoid glucoside, was known to possess antioxidant and anti-inflammatory properties and is being investigated for use in various disorders. PurposeThe present study was intended at investigating the hepatoprotective efficacy of polydatin against acute-alcohol induced liver injury model in mice. Study designC57BL/6 mice were fed with five doses of 50% ethyl alcohol (10ml/kg body weight) to induce acute liver injury. Effect of polydatin against alcohol induced hepatic injury was investigated by giving 50 or 100mg/kg polydatin, orally, for 8 days. MethodsSerum markers of liver injury, morphology, histology and fibrosis of liver tissue, levels of enzymatic and non-enzymatic antioxidants and the mitochondrial respiratory enzyme activities in liver tissue were investigated. The activities and the protein expression of matrix metalloproteinases (MMP-2 and -9), the expression of NF-κB in the liver tissue were also studied. ResultsPolydatin pre-treatment significantly alleviated the alcohol induced hepatic injury by reducing the serum liver injury markers, alanine aminotransferase (ALT) and aspartate aminotransferase (AST), attenuating oxidative stress and restoring antioxidant balance in the hepatic tissue. Simultaneously, polydatin pre-treatment also prevented alcohol induced mitochondrial damage and refurbished the matrix metalloproteinases levels of the hepatic tissue. ConclusionThe findings of the present study suggest that polydatin may have a potential benefit in preventing alcohol-induced acute hepatic 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.

The microbiota regulates susceptibility to Fas-mediated acute hepatic injury

Whereas a significant role for intestinal microbiota in affecting the pathogenesis and progression of chronic hepatic diseases is well documented, the contribution of the intestinal flora to acute liver injury has not been extensively addressed. Elucidating the influence of the intestinal microbiota on acute liver inflammation would be important for better understanding the transition from acute injury to chronic liver disease. Using the Concanavalin A (ConA)-induced liver injury model in laboratory mice, we show that the severity of acute hepatic damage varies greatly among genetically identical mice raised in different environments and harboring distinct microbiota. Through reconstitution of germ-free (GF) mice, and the co-housing of conventional mice, we provide direct evidence that manipulation of the intestinal flora alters susceptibility to ConA-induced liver injury. Through deep sequencing of the fecal microbiome, we observe that the relative abundance of Ruminococcaceae, a Gram(+) family within the class Clostridia, but distinct from segmented filamentous bacteria, is positively associated with the degree of liver damage. Searching for the underlying mechanism(s) that regulate susceptibility to ConA, we provide evidence that the extent of liver injury following triggering of the death receptor Fas varies greatly as a function of the microbiota. We demonstrate that the extent of Fas-induced liver injury increases in GF mice after microbiota reconstitution, and decreases in conventionally raised mice following reduction in intestinal bacterial load, by antibiotic treatment. We also show that the regulation of sensitivity to Fas-induced liver injury is dependent upon the toll-like receptor signaling molecule MyD88. In conclusion, the status and composition of the intestinal microbiota determine the susceptibility to ConA-induced acute liver injury. The microbiota acts as a rheostat, actively modulating the extent of liver damage in response to Fas triggering.

Hepatoprotective role of green tea extract in acetaminophen induced liver injury in mice

the world. Overdose of APAP is linked to many cases of hepatic failure and death in many countries. APAP is also used as a model toxin to understand the hepatoprotective activities of many pharmacological compounds. In the present study, the protective efficacy of green tea extracts (GTE) in APAP induced liver injury has been evaluated in mice. Mice were treated with 400 mgkg‐1 body weight of APAP alone or with GTE (50 & 100 mgkg‐1). Serum Alanine aminotransferase (ALT), Aspartate aminotransferase (AST), Glutathione reduced (GSH), Lipid peroxidation (LPO) and nitrite level in liver tissues were estimated 6 hrs after APAP and GTE treatment. GTE was shown to be efficient in reducing ALT and AST released from liver hepatocytes up to 50 % when compared to APAP alone treated group. GTE also inhibited production of nitrite and LPO, whereas supplementation with GTE maintained near normal GSH level in liver of APAP treated mice. Histopathological examination of liver samples revealed reduced necrotic areas (47%) in GTE treated APAP group compared to APAP alone treated group. GTE treatment also prevents hepatocytes DNA fragmentation compared to APAP treated group. The survival test conducted confirmed that mice receiving APAP + GTE are more resistant to the deleterious effect of APAP overdose than APAP alone. Together, this study confirmed the hepatoprotective activities of GTE in APAP induced liver injury model in mice and thus illustrated the benefit of continuous consumption of green tea.

Hepatoprotective activity of ethanolic extract of Acanthopanax koreanum Nakai in induced liver injury model in Wistar rats

This study was performed to examine the effect of ethanolic extract of Acanthopanax koreanum Nakai (AE) and Acanthoic acid (AA) in D‐galactosamine/lipopolysaccharide (D‐GalN/LPS) liver injury model in 6 week‐old Wistar rat. Rats were randomly divided into 5 groups (Normal control, AE0%, AE1%, AE3%, AA) based on body weight. After the experimental diets were fed for 15 days, the experimental groups were injected D‐GalN (250mg/kg b.w)/LPS (10ug/kg b.w). Liver injury was assessed by plasma glutamic oxaloacetic transminase (GOT) and glutamic‐pyruvic transaminase (GPT) activities. We evaluated the inflammation indicators, such as TNF‐alpha, IL‐6, and NO. In the AE and AA treat groups, GPT, TNF‐alpha, IL‐6 in plasma significantly reduced as well as NO in the liver. Results of this study revealed that ethanolic extract of Acanthopanax koreanum Nakai could afford a significant protection against liver injury. This experiment suggests that ethanolic extract of Acanthopanax koreanum Nakai can be available for enhancing liver condition as a functional food. *This study was supported by JEJU TECHNOPARK (Project No.2011‐0655‐1)

Hepatitis B Virus X (HBx) Induces Tumorigenicity of Hepatic Progenitor Cells in 3,5–Diethoxycarbonyl–1,4–Dihydrocollidine–Treated HBx Transgenic Mice

Hepatitis B virus X (HBx) protein is implicated in hepatitis B virus (HBV)-associated liver carcinogenesis. However, it remains unclear whether HBx-expressing hepatic progenitor cells (HPCs) are attributed to liver tumor formation. In this study, by using HBx transgenic mice and a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced liver injury model, the relationship between HBx expression and tumorigenicity of HPCs was analyzed. Compared with control mice, an elevated number of EpCAM(+) cells with characteristics of HPCs was observed in HBx mice after 1 month and 4 months of DDC diet feeding. All HBx transgenic mice developed liver tumors characterized by histological features of both hepatocellular carcinoma (HCC) and cholangiocarcinoma after 7 months of DDC feeding. Notably, EpCAM(+) HPCs isolated from premalignant HBx mice exposed to a DDC diet for 4 months formed subcutaneous mixed-lineage tumors (four out of six) in nonobese diabetic/severe-combined immunodeficient (NOD/SCID) mice, and none of the cells from wildtype (WT) induced tumor, indicating that HBx may induce malignant transformation of HPCs that contributes to tumorigenesis. We also found higher titers of circulating interleukin (IL)-6, activities of IL-6/STAT3, and Wnt/β-catenin signaling pathways in HBx transgenic mice, suggesting HBx may induce intrinsic changes in HPCs by way of the above signaling that enables HPCs with tumorigenicity potential. Finally, clinical evidence showed that high HBx expression in human HBV-related HCC was statistically associated with expansion of EpCAM(+) or OV6(+) tumor cells and aggressive clinicopathologic features. HBx induces intrinsic cellular transformation promoting the expansion and tumorigenicity of HPCs in DDC-treated mice, which may be a possible origin for liver cancer induced by chronic hepatitis infection.

Hepatoprotective Effect of Caffeic Acid Phenethyl Ester (CAPE) on Carbon Tetrachloride (CCI4) Induced Acute Hepatotoxicity in Rats

In this study, hepatoprotective activity of CAPE, which has antiinflammatory, anticancer, antiviral, and immunomodulatory effects, was investigated in the CCI4 induced liver injury model in rats. Twenty-one Sprague Dawley rats were divided into the three groups: Control (n=7), CCI4 (n=7), CCI4 + CAPE (n=7). The serum levels of AST, ALT, LDH, and bilirubin were measured on the first and last day (10 th day) in all experimental animals. Histopathological examinations were carried out in the rats sacrificed on the tenth day. For histopathological evaluation, livers of all rats were removed and processed for light microscopy. The levels of unconjugated bilirubin, AST, ALT, ALP in CCI4 group were markedly higher than those in the control group (p<0.01, p<0.01, p<0.001 and p<0.05 respectively). The values of these parameters in CAPE+CCI4 group were lower than those in CCI4 (p<0.01, p<0.05, p<0.05, p<0.001 respectively). Histopathological findings also corfirmed that CCI4 induced hepadic damage and support the wiev that CAPE has a hepatoprotective activity. The results of this study indicate that CAPE has a hepatoprotective action in acute liver injury.

Oxidative stress-associated rise of hepatic protein glycation increases inflammatory liver injury in uncoupling protein-2 deficient mice

Mitochondrial dysfunction seems to be intrinsically involved in the pathogenesis of multiple organ failure because of enhanced production of reactive oxygen species and induction of oxidative damage. Chronic oxidative stress in turn causes an accumulation of advanced glycation end products (AGEs). To investigate whether mitochondrial dysfunction-associated oxidative stress leads to increased formation and accumulation of AGE, we studied hepatic glycation in uncoupling protein-2 (UCP2−/−) knockout mice. Using the galactosamine/lipopolysaccharide (G/L)-induced liver injury model, we further tested the hypothesis that a mitochondrial dysfunction-associated increase of hepatic glycation is causative for increased liver injury. Under baseline conditions, UCP2−/− mice showed higher malondialdehyde levels and reduced glutathione/glutathione disulfide ratios as well as significantly higher hepatic levels of AGE and hepatic expression of receptor for AGE (RAGE) when compared with UCP2+/+ mice, indicative for increased oxidative stress and hepatic glycation. Further, livers of G/L-challenged UCP2−/− mice revealed significantly more pronounced tissue injury and were found to express higher levels of AGE and RAGE compared with wild-type mice. Functional blockade of RAGE by application of recombinant RAGE significantly diminished liver damage particularly in UCP2−/− mice. This in turn increased survival from 30% in UCP2+/+ mice to 50% in UCP2−/− mice. In summary, we show for the first time that mitochondrial dysfunction-associated oxidative stress enhances hepatic protein glycation, which aggravates inflammation-induced liver injury. Targeting the AGE/RAGE interaction by the blockade of RAGE might be of therapeutic value for the oxidative stress-exposed liver.

Hepatoprotective potential of Decalepis hamiltonii (Wight and Arn) against carbon tetrachloride-induced hepatic damage in rats

Hepatoprotective activity of the roots of Decalepis hamiltonii (Wight and Arn) was studied using carbon tetrachloride (CCl4) induced liver injury model in albino rats. The hepatotoxicity produced by acute CCl4 administration was found to be inhibited by pretreating the rats with crude methanolic extract of the roots of D. hamiltonii (Dh) prior to CCl4 induction. Hepatotoxic inhibition was measured with the decreased levels of hepatic serum marker enzymes (glutamate-pyruvate transaminase (GPT), glutamate oxaloacetate transaminase (GOT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) and lipid peroxide formation. Imbalance level of glutathione (GSH) and antioxidant enzymes such as catalase, glutathione peroxidase, and glutathione reductase were normalized in rats pretreated with Dh extract followed by CCl4 administration. Pathological changes of hepatic lesions caused by CCl4 were also improved by pretreatment with the Dh root extract. The results of this study indicate that roots of D. hamiltonii could afford a significant protective action in the alleviation of CCl4-induced hepatic damage in rats.

Hepatoprotective effect of Foeniculum vulgare essential oil

Hepatoprotective activity of Foeniculum vulgare (fennel) essential oil (FEO) was studied using carbon tetrachloride (CCl 4) induced liver injury model in rats. The hepatotoxicity produced by acute CCl 4 administration was found to be inhibited by FEO with evidence of decreased levels of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and bilirubin. The results of this study indicate that FEO has a potent hepatoprotective action against CCl 4-induced hepatic damage in rats.

The sympathetic nervous system promotes carbon tetrachloride-induced liver cirrhosis in rats by suppressing apoptosis and enhancing the growth kinetics of regenerating hepatocytes

Norepinephrine is considered to possess potent anti-apoptotic action in regenerating hepatocytes. To clarify the role of the sympathetic nervous system in apoptosis that occurs in chronic liver damage and following the promotion of liver cirrhosis, we studied a carbon tetrachloride (CCl4)-induced liver injury model, using spontaneously hypertensive rats (SHR), Wistar-Kyoto rats (WKY), and chemically sympathectomized WKY. At 24 h after CCl4 administration. acute damage, characterized by vacuolated hepatocytes in the centrilobular zone, was greater in SHR than in WKY. This vacuolated change in WKY hepatocytes was significantly reduced by chemical sympathectomy with 6-hydroxydopamine (6-OHDA). After 48 h, the acute damage was dramatically improved in each animal, without significant differences between the three groups. In chronic damage after weekly repetition of CCl4 treatment for 4 weeks, fibrosis was evident in SHR, while in the other groups there was only scant fibrosis in the centrilobular zone. After 8 weeks' repetition of CCl4, liver cirrhosis was seen only in SHR. The incidence of apoptotic cells in areas of both acute and chronic damage in WKY, detected by terminal deoxynucleotidyl transferase-dUTP nick end labeling, was significantly increased in comparison with that in SHR, and was further increased by 6-OHDA pretreatment. In contrast, there was significantly greater enhancement of the growth of hepatocytes in SHR than in WKY in both acute and chronic damage. Moreover. hepatocyte growth kinetics in WKY was significantly inhibited after sympathectomy in acute injury, as evidenced by immunohistochemistry for proliferating cell nuclear antigen (PCNA). In vitro, the amount of hepatocellular apoptosis induced by transforming growth factor-beta1 was significantly decreased by incubation with norepinephrine. These findings suggest that the anti-apoptotic effect of the sympathetic nervous system increases cell growth kinetics and promotes liver cirrhosis in this animal model.