Previously, Huangqi decoction (HQD) has been found to have a potential therapeutic effect on DMN-induced liver cirrhosis. Here, the mechanisms of HQD action against liver fibrosis were investigated in relation to hepatocyte apoptosis and hepatic inflammation regulation.
Liver fibrosis was induced by DMN administration for 2 or 4 weeks. Hepatocyte apoptosis and of Kupffer cells (KC) and hepatic stellate cells (HSC) interaction were investigated using confocal microscopy. The principle cytokines, fibrogenic proteins and apoptotic factors were investigated using western blot analysis.
Compared with the DMN-water group, HQD showed decreased hepatocyte apoptosis and reduced expression of apoptotic effectors, cleaved-caspase-3, and fibrotic factors, such as smooth muscle α-actin (α-SMA), transforming growth factor beta-1 (TGF-β1). However, the KC marker CD68 increased significantly in DMN-HQD liver. Confocal microscopy demonstrated widespread adhesion of KCs to HSCs in DMN-water and DMN-HQD rats liver.
HQD exhibited positive protective effects against liver fibrosis; its mechanism of action was associated with protection from hepatocyte apoptosis and the promotion of CD68 expression in the devolopment of liver fibrosis to cirrhosis development.
Background and aims
Integrin αvβ6 is highly expressed on certain activated epithelia, where it mediates attachment to fibronectin and serves as coreceptor for the activation of latent TGFβ1. Since its role in liver fibrosis is unknown, we studied αvβ6 function in vitro and explored the antifibrotic potential of the specific αvβ6 antagonist EMD527040.
Experimental liver fibrosis was studied in rats after bile duct ligation (BDL) and in MDR2(abcb4)-/- mice. Different doses of EMD527040 were given to rats from week 2 to 6 after BDL and to Mdr2-/- mice from week 4 to 8. Liver collagen was quantified and expression of αvβ6 and fibrosis related transcripts were determined by quantitative RT-PCR. αvβ6 expressing cells, bile duct proliferation and apoptosis were assessed histologically. The effect of EMD527040 on cholangiocyte adhesion, proliferation, apoptosis and TGFβ1 activation was studied in vitro.
αvβ6 was highly expressed on proliferating bile duct epithelia in fibrosis, with 100-fold increased transcript levels in advanced fibrosis. EMD527040 attenuated bile ductular proliferation and peribiliary collagen deposition by 40-50%, induced downregulation of fibrogenic and upregulation of fibrolytic genes, and improved liver architecture and function. In vitro αvβ6 inhibition reduced activated cholangiocyte proliferation, their adhesion to fibronectin and endogenous activation of TGFβ1 by 50% but did not affect bile duct apoptosis.
Integrin αvβ6 is strongly upregulated in proliferating bile duct epithelia and drives fibrogenesis via adhesion to fibronectin and auto/paracrine TGFβ1 activation. Pharmacological inhibition of αvβ6 potently inhibits the progression of primary and secondary biliary fibrosis.
Abcb4; animal model; antagonist; bile duct; antifibrotic therapy; bile duct ligation; biliary epithelial cell; cell adhesion; cirrhosis; CTGF; fibrogenesis; fibrolysis; fibronectin; fibrosis; gene deletion; gene expression; inhibitor; integrin; liver; MDR2; MMP; nonpeptide; procollagen; proliferation; smooth muscle actin; TGFbeta; TIMP-1
The vitronectin receptor integrin alpha v beta 3 (αvβ3) promotes angiogenesis by mediating migration and proliferation of endothelial cells, but also drives fibrogenic activation of hepatic stellate cells (HSC) in vitro. Expecting antifibrotic synergism, we studied the effect of αvβ3 inhibition in two in vivo models of liver fibrogenesis. Liver fibrosis was induced in rats by bile duct ligation (BDL) for 6 weeks or by thioacetamide (TAA) injections for 12 weeks. A specific αvβ3 (αvβ5) inhibitor (Cilengitide) was given i.p. twice daily at 15 mg/kg during BDL or after TAA-administration. Liver collagen was determined as hydroxyproline and gene expression was quantified by quantitative PCR. Liver angiogenesis, macrophage infiltration and hypoxia were assessed by CD31, CD68 and HIF-1α immunostaining.
Cilengitide decreased overall vessel formation. This was significant in portal areas of BDL and septal areas of TAA fibrotic rats, and was associated with a significant increase of liver collagen by 31% (BDL) and 27% (TAA), and upregulation of profibrogenic genes and matrix metalloproteinase-13. Treatment increased GGT in both models, while other serum markers remained unchanged. αvβ3 inhibition resulted in mild liver hypoxia, as evidenced by upregulation of hypoxia inducible genes. Liver infiltration by macrophages/Kupffer cells was not affected, although increases in TNF-α, IL-18 and COX-2 mRNA indicated modest macrophage activation.
Specific inhibition of integrin αvβ3 (αvβ5) in vivo decreased angiogenesis but worsened biliary (BDL) and septal (TAA) fibrosis, despite its antifibrogenic effect on HSC in vitro. Angiogenesis inhibitors should be used with caution in patients with hepatic fibrosis. (248 words).
Angiogenesis; collagen; liver fibrosis; rat model; vitronectin receptor
Peroxisome proliferator activated receptor γ (PPARγ) agonists have been shown to prevent hepatic fibrosis in rodents. We evaluated the therapeutic antifibrotic potential of the PPARγ agonist pioglitazone on established hepatic fibrosis.
Repeated injections of carbon tetrachloride (CCl4), a choline deficient diet, or bile duct ligation (BDL) were used to induce hepatic fibrosis in rats. Pioglitazone treatment was introduced at various time points. Therapeutic efficacy was assessed by comparison of the severity of hepatic fibrosis in pioglitazone treated versus untreated fibrotic controls.
When introduced after two weeks of CCl4, pioglitazone reduced hepatic fibrosis, OH proline content, hepatic mRNA expression of collagen type I, and profibrotic genes, as well as the number of activated α smooth muscle actin positive hepatic stellate cells, compared with rats receiving CCl4 only, with no significant change in necroinflammation. When pioglitazone treatment was initiated after five weeks of CCl4, no antifibrotic effect was observed. Similarly, pioglitazone was associated with a reduced severity of fibrosis induced by a choline deficient diet when introduced early, while delayed treatment with pioglitazone remained ineffective. In contrast, pioglitazone failed to interrupt progression of fibrosis due to BDL, irrespective of the timing of its administration.
In rats, the therapeutic antifibrotic efficacy of pioglitazone is limited and dependent on the type of injury, duration of disease, and/or the severity of fibrosis at the time of initiation of treatment.
peroxisome proliferator activated receptor gamma; hepatic fibrosis; hepatic stellate cells; pioglitazone
Epithelial-mesenchymal transitions (EMTs) play an important role in tissue construction during embryogenesis, and evidence suggests that this process may also help to remodel some adult tissues after injury. Activation of the hedgehog (Hh) signaling pathway regulates EMT during development. This pathway is also induced by chronic biliary injury, a condition in which EMT has been suggested to have a role. We evaluated the hypothesis that Hh signaling promotes EMT in adult bile ductular cells (cholangiocytes). In liver sections from patients with chronic biliary injury and in primary cholangiocytes isolated from rats that had undergone bile duct ligation (BDL), an experimental model of biliary fibrosis, EMT was localized to cholangiocytes with Hh pathway activity. Relief of ductal obstruction in BDL rats reduced Hh pathway activity, EMT, and biliary fibrosis. In mouse cholangiocytes, coculture with myofibroblastic hepatic stellate cells, a source of soluble Hh ligands, promoted EMT and cell migration. Addition of Hh-neutralizing antibodies to cocultures blocked these effects. Finally, we found that EMT responses to BDL were enhanced in patched-deficient mice, which display excessive activation of the Hh pathway. Together, these data suggest that activation of Hh signaling promotes EMT and contributes to the evolution of biliary fibrosis during chronic cholestasis.
Over-activation of TGFβ signaling pathway and uncontrolled cell proliferation of hepatic stellate cells (HSCs) play pivotal roles in liver fibrogenesis, while the protein serine/threonine phosphatase PP2Cα was reported to negatively regulate TGFβ signaling pathway and cell cycle. Our study aimed to investigate the role of PP2Cα in liver fibrogenesis.
The effects of PP2Cα activation on liver fibrosis were investigated in human HSCs and primary rat HSCs in vitro using western blotting, real-time PCR, nuclear translocation, cell viability and cell cycle analyses. The antifibrogenic effects in carbon tetrachloride (CCl4)- and bile duct ligation (BDL)-induced mice in vivo were assessed using biochemical, histological and immunohistochemical analyses. The results demonstrated that activation of PP2Cα by overexpression or the new discovered small molecular activator NPLC0393 terminated TGFβ-Smad3 and TGFβ-p38 signaling pathways, induced cell cycle arrest in HSCs and decreased α-smooth muscle actin (α-SMA) expression, collagen deposition and hepatic hydroxyproline (HYP) level in CCl4- and BDL-induced mice.
Our findings suggested that PP2Cα activation might be an attractive new strategy for treating liver fibrosis while the small molecular activator NPLC0393 might represent a lead compound for antifibrogenic drug development. Moreover, our study might provide the first evidence for the role of PP2C family members in the fibrotic disease.
Fibrosis can be described as the excess deposition of extracellular matrix (ECM) components, such as collagens and proteoglycans. Fibrosis of the liver, which eventually leads to cirrhosis, is a major global health problem. Being able to measure fibrosis progression may enable timely preventative intervention. The aim of the current study was to investigate the utility of serum procollagen type I N-terminal propeptide (PINP) as a marker of hepatic fibrosis, as distinct from bone formation, during three different periods of fibrosis development following hepatic injury induced by bile duct ligation (BDL) in rats.
BDL was performed on 30 female Sprague-Dawley rats aged 6 months, and sham operations on 30 controls. Animals were killed after 14, 28, or 35 days. The extent of liver fibrosis was evaluated by quantitative histology after Sirus Red staining. Levels of serum PINP and osteocalcin (a marker solely for osteoblastic bone formation) were determined using ELISA at baseline and post termination.
Collagen formation increased by 30% compared to 3% in sham-operated animals (P < 0.0001). PINP levels increased significantly in all BDL groups compared with baseline (14 days: baseline 13.9 ng/ml, termination 17.7 ng/ml, P = 0.047; 28 days: baseline 17.9 ng/ml, termination 26.2 ng/ml, P = 0.005; 35 days: baseline 18.0 ng/ml, termination 27.4 ng/ml P = 0.015, an increase of 52%). PINP levels did not change from baseline in the sham-operated rats, indicating that the increased PINP levels were due to hepatic injury. The bone-specific marker, osteocalcin, did not increase in either BDL or sham-operated rats. PINP measured in serum correlated to the extent of liver fibrosis as evaluated by quantitative histology (R2 = 0.42, P < 0.001).
PINP was associated with the development of liver fibrosis, but not bone formation, in mature rats subjected to BDL. Thus, PINP may be useful in studying the pathogenesis of liver fibrosis. However, caution should be applied when interpreting PINP levels in other disease states.
AIM: To investigate the anti-hepatofibrotic effects of Gardenia jasminoides in liver fibrosis.
METHODS: Male Sprague-Dawley rats underwent common bile duct ligation (BDL) for 14 d and were treated with Gardenia jasminoides by gavage. The effects of Gardenia jasminoides on liver fibrosis and the detailed molecular mechanisms were also assessed in human hepatic stellate cells (LX-2) in vitro.
RESULTS: Treatment with Gardenia jasminoides decreased serum alanine aminotransferase (BDL vs BDL + 100 mg/kg Gardenia jasminoides, 146.6 ± 15 U/L vs 77 ± 6.5 U/L, P = 0.0007) and aspartate aminotransferase (BDL vs BDL + 100 mg/kg Gardenia jasminoides, 188 ± 35.2 U/L vs 128 ± 19 U/L, P = 0.005) as well as hydroxyproline (BDL vs BDL + 100 mg/kg Gardenia jasminoides, 438 ± 40.2 μg/g vs 228 ± 10.3 μg/g liver tissue, P = 0.004) after BDL. Furthermore, Gardenia jasminoides significantly reduced liver mRNA and/or protein expression of transforming growth factor β1 (TGF-β1), collagen type I (Col I) and α-smooth muscle actin (α-SMA). Gardenia jasminoides significantly suppressed the upregulation of TGF-β1, Col I and α-SMA in LX-2 exposed to recombinant TGF-β1. Moreover, Gardenia jasminoides inhibited TGF-β1-induced Smad2 phosphorylation in LX-2 cells.
CONCLUSION: Gardenia jasminoides exerts antifibrotic effects in the liver fibrosis and may represent a novel antifibrotic agent.
Gardenia jasminoides; Liver fibrosis; Collagen type I; Transforming growth factor-β1/Smad2 pathway; α-smooth muscle actin
Hepatic stellate cells, the main mediators in the pathogenesis of fibrosis, are triggered by free radicals and produce collagen. Melatonin is a powerful physiologic scavenger of hydroxyl radicals. It is also involved in the inhibitory regulation of the collagen content in tissue. There is no effective treatment available for liver fibrosis. Our objective was to evaluate the effects of melatonin on liver fibrosis induced by bile-duct ligation (BDL) in rats.
We divided male Wistar rats (n = 32) into 4 groups. Two groups received BDL and 2 groups received sham operations. One of the BDL groups and one of the sham groups were administered melatonin (100 mg/kg/day via intraperitoneal injection), and the controls were given vehicle only. After 1 month, we biochemically evaluated the changes in hepatic fibrosis by measuring tissue collagen levels and histopathologic examination. We evaluated the levels of malondialdehyde (MDA), glutathione (GSH), luminal and lucigenin in tissue homogenates, and we studied proinflammatory cytokines in serum using commercially available kits.
Bile-duct ligation caused hepatic fibrotic changes, whereas melatonin suppressed these changes in 5 of 8 rats (p < 0.001). Bile-duct ligation resulted in increased collagen, MDA, luminal and lucigenin levels and decreased GSH levels, whereas melatonin reversed these effects.
We found that melatonin functions as an effective fibrosuppressant and antioxidant, and the results suggest that it can be used as a therapeutic option.
Organic solute transporter alpha-beta (Ostα-Ostβ) is a heteromeric bile acid and sterol transporter that facilitates the entero- and renal-hepatic circulation of bile acids. Hepatic expression of this basolateral membrane protein is increased in cholestasis, presumably to facilitate removal of toxic bile acids from the liver. In this study we show that the cholestatic phenotype induced by common bile duct ligation (BDL) is reduced in mice genetically deficient in Ostα. Although Ostα−/− mice have a smaller bile acid pool size which could explain lower serum and hepatic levels of bile acids after BDL, gallbladder bilirubin and urinary bile acid concentrations were significantly greater in Ostα−/− BDL mice, suggesting additional alternative adaptive responses. Livers of Ostα−/− mice had higher mRNA levels of constitutive androstane receptor (Car) than wild-type BDL mice and increased expression of Phase I enzymes (Cyp7a1, Cyp2b10, Cyp3a11), Phase II enzymes (Sult2a1, Ugt1a1) and Phase III transporters (Mrp2, Mrp3). Following BDL, the bile acid pool size increased in Ostα−/− mice and protein levels for the hepatic basolateral membrane export transporters, Mrp3 and Mrp4, and for the apical bilirubin transporter, Mrp2, were all increased. In the kidney of Ostα−/− mice after BDL the apical bile acid uptake transporter, Asbt, is further reduced, while apical export transporters, Mrp2 and Mrp4, are increased, resulting in a significant increase in urinary bile acid excretion. Conclusions: These findings indicate that loss of Ostα provides protection from liver injury in obstructive cholestasis through adaptive responses in both the kidney and liver that enhance clearance of bile acids into urine and through detoxification pathways most likely mediated by the nuclear receptor, Car.
adaptive regulation; urinary bile acids; nuclear receptor; kidney, bile acid homeostasis
Adeno-associated virus (AAV) vectors can achieve long-term gene expression and are now feasible for use in human gene therapy. We constructed hepatocyte growth factor (HGF) expressing AAV (AAV5-HGF) and examined its effect in two mouse hepatic fibrosis models.
A model of hepatic fibrosis was established by carbon tetrachloride (CCl4) administration in Balb/c mice. After the establishment of liver fibrosis, AAV5-HGF was injected once into the portal vein. Mice were killed 3, 6, 9, and 12 weeks after injection. Another model was established by bile duct ligation (BDL). Seven weeks after AAV5-HGF injection, mice underwent BDL, and were then killed 2 weeks after BDL.
Mice that received AAV5-HGF achieved stable HGF expression both in the serum and liver for at least 12 weeks. In both models, significant improvement of the liver fibrosis was found in all mice receiving AAV5-HGF based on Azan-Mallory staining. Suppression of hepatic stellate cells (HSC) was confirmed by immunohistochemistry. Fibrogenic markers were significantly suppressed and collagenase activity increased in the livers of mice receiving AAV5-HGF.
A single injection of AAV vector containing HGF gene achieved long-term expression of HGF and resulted in resolution of mouse liver fibrosis. HGF gene therapy mediated by AAV is feasible for the treatment of liver fibrosis.
HGF; Liver fibrosis; AAV; CCl4; BDL
AIM: To investigate the preventive effect of N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) on bile duct ligation (BDL)-induced liver fibrosis in rats.
METHODS: Liver fibrosis in rats was induced by BDL and AcSDKP was infused subcutaneously for 2 wk via a osmotic minipump (Alzet 2ML4) immediately after BDL operation. After scarifying, serum and liver specimens were collected. Hematoxylin and eosin staining, Sirius red staining, enzyme linked immunosorbent assay, Western blot or real-time polymerase chain reaction were used to determinate liver functions, histological alterations, collagen deposition, mRNA expression of markers for fibroblasts, transforming growth factor-β1 (TGF-β1) and bone morphogenetic protein-7 (BMP-7).
RESULTS: When compared to model rats, chronic exogenous AcSDKP infusion suppressed profibrogenic TGF-β1 signaling, α-smooth muscle actin positivity (α-SMA), fibroblast specific protein-1 (FSP-1) staining and collagen gene expression. Col I, Col III, matrix metalloproteinase-2, tissue inhibitors of metalloproteinase-1 and tissue inhibitors of metalloproteinase-2 mRNA expressions were all significantly downregulated by AcSDKP infusion (2.02 ± 1.10 vs 14.16 ± 6.50, 2.02 ± 0.45 vs 10.00 ± 3.35, 2.91 ± 0.30 vs 7.83 ± 1.10, 4.64 ± 1.25 vs 18.52 ± 7.61, 0.46 ± 0.16 vs 0.34 ± 0.12, respectively, P < 0.05). Chronic exogenous AcSDKP infusion attenuated BDL-induced liver injury, inflammation and fibrosis. BDL caused a remarkable increase in alanine transaminase, aspartate transaminase, total bilirubin, and prothrombin time, all of which were reduced by AcSDKP infusion. Mast cells, collagen accumulation, α-SMA, TGF-β1, FSP-1 and BMP-7 increased. The histological appearance of liver specimens was also improved.
CONCLUSION: Infusion of exogenous AcSDKP attenuated BDL-induced fibrosis in the rat liver. Preservation of AcSDKP may be a useful therapeutic approach in the management of liver fibrosis.
N-acetyl-seryl-aspartyl-lysyl-proline; Liver fibrosis; Transformating growth factor-β1; α-smooth mucle actin; Bone morphological protein-7; Fibroblast specific protein-1; Epithelial-mesenchymal transition
BACKGROUND & AIMS
Hepatocyte apoptosis and activation of hepatic stellate cells (HSC) are critical events in fibrogenesis. We previously demonstrated that phagocytosis of apoptotic hepatocytes by HSC is profibrogenic. Based on this, as well as the observation that NADPH oxidase induction is central to fibrogenesis, our aim was to study the phagocytic NADPH oxidase, NOX2.
An in vivo phagocytosis model was developed by injecting wild type (wt) or NOX2-/- mice with lentiviral-GFP containing a hepatocyte-specific promoter, and ad-TRAIL. Fibrosis was evaluated in bile duct ligated (BDL) wt and NOX2-/- mice with or without gadolinium treatment. NOX2 expression was studied in human liver samples and in HSC isolated from fibrotic livers. The fibrogenic activity of NOX2 was assessed by collagen reporter assays.
In the phagocytosis model engulfment of GFP-labeled apoptotic bodies was seen, and the expression of α-SMA and collagen I increased significantly in the wt, but not in the NOX2-/- mice. Inhibiting apoptosis decreased the profibrogenic response. NOX2-/- animals exhibited significantly less fibrosis following BDL. Inactivating macrophages in wt BDL mice did not lower collagen production to the level observed in NOX2-/- mice suggesting that NOX2-expressing HSC are important in fibrogenesis. NOX2 was upregulated in HSC from fibrotic livers, and phagocytosis-induced NOX2 expression and activity were demonstrated. Based on reporter assays, NOX2-mediated ROS directly induced collagen promoter activity in HSC.
Apoptosis and phagocytosis of hepatocytes directly induce HSC activation and initiation of fibrosis. NOX2, the phagocytic NADPH oxidase plays a key role in this process and in liver fibrogenesis in vivo.
liver fibrosis; apoptosis; NADPH oxidase
The contribution of tumor necrosis factor–related apoptosis-inducing ligand (TRAIL), a death ligand expressed by cells of the innate immune system, to cholestatic liver injury has not been explored. Our aim was to ascertain if TRAIL contributes to liver injury in the bile duct–ligated (BDL) mouse. C57/BL6 wild-type (wt), TRAIL heterozygote (TRAIL+/−), and TRAIL knockout (TRAIL−/−) mice were used for these studies. Liver injury and fibrosis were examined 7 and 14 days after BDL, respectively. Hepatic TRAIL messenger RNA(mRNA) was 6-fold greater in BDL animals versus sham-operated wt animals (P < 0.01). The increased hepatic TRAIL expression was accompanied by an increase in liver accumulation of natural killer 1.1 (NK 1.1)–positive NK and natural killer T (NKT) cells, the predominant cell types expressing TRAIL. Depletion of NK 1.1–positive cells reduced hepatic TRAIL mRNA expression and serum alanine aminotransferase (ALT) values. Consistent with a role for NK/NKT cells in this model of liver injury, stress ligands necessary for their recognition of target cells were also up-regulated in hepatocytes following BDL. Compared to sham-operated wt mice, BDL mice displayed a 13-fold increase in terminal deoxynucleotidyl transferase–mediated dUTP nick-end labeling (TUNEL) and an 11-fold increase in caspase 3/7–positive hepatocytes (P < 0.01). The number of TUNEL and caspase 3/7–positive cells was reduced by >80% in BDL TRAIL knockout animals (P < 0.05). Likewise, liver histology, number of bile infarcts, serum ALT values, hepatic fibrosis, and animal survival were also improved in BDL TRAIL−/− animals as compared to wt animals.
These observations support a pivotal role for TRAIL in cholestatic liver injury mediated by NK 1.1–positive NK/NKT cells.
Human chronic cholestatic liver diseases are characterized by cholangiocyte proliferation, hepatocyte injury, and fibrosis. Yes-associated protein (YAP), the effector of the Hippo tumor-suppressor pathway, has been shown to play a critical role in promoting cholangiocyte and hepatocyte proliferation and survival during embryonic liver development and hepatocellular carcinogenesis. Therefore, the aim of this study was to examine whether YAP participates in the regenerative response after cholestatic injury. First, we examined human liver tissue from patients with chronic cholestasis. We found more-active nuclear YAP in the bile ductular reactions of primary sclerosing cholangitis and primary biliary cirrhosis patient liver samples. Next, we used the murine bile duct ligation (BDL) model to induce cholestatic liver injury. We found significant changes in YAP activity after BDL in wild-type mice. The function of YAP in the hepatic response after BDL was further evaluated with liver-specific Yap conditional deletion in mice. Ablating Yap in the mouse liver not only compromised bile duct proliferation, but also enhanced hepatocyte necrosis and suppressed hepatocyte proliferation after BDL. Furthermore, primary hepatocytes and cholangiocytes isolated from Yap-deficient livers showed reduced proliferation in response to epidermal growth factor in vitro. Finally, we demonstrated that YAP likely mediates its biological effects through the modulation of Survivin expression. Conclusion: Our data suggest that YAP promotes cholangiocyte and hepatocyte proliferation and prevents parenchymal damage after cholestatic injury in mice and thus may mediate the response to cholestasis-induced human liver disease. (Hepatology 2012;56:1097–1107)
Activation of hepatic stellate cells (HSCs) plays a crucial role in liver fibrogenesis. armepavine (Arm, C19H23O3N), an active compound from Nelumbo nucifera, has been shown to exert immunosuppressive effects on T lymphocytes and on lupus nephritic mice. The aim of this study was to investigate whether Arm could exert anti-hepatic fibrogenic effects in vitro and in vivo. A cell line of rat HSCs (HSC-T6) was stimulated with tumor necrosis factor-α (TNF-α) or lipopolysaccharide (LPS) to evaluate the inhibitory effects of Arm. An in vivo therapeutic study was conducted in bile duct-ligated (BDL) rats. BDL rats were given Arm (3 or 10 mg/kg) by gavage twice daily for 3 weeks starting from the onset of BDL. Liver sections were taken for fibrosis scoring, immuno-fluorescence staining and quantitative real-time mRNA measurements. In vitro, Arm (1-10 μM) concentration-dependently attenuated TNF-α- and LPS-stimulated α-SMA protein expression and AP-1 activation by HSC-T6 cells without adverse cytotoxicity. Arm also suppressed TNF-α-induced collagen collagen deposition, NFκB activation and MAPK (p38, ERK1/2, and JNK) phosphorylations. In vivo, Arm treatment significantly reduced plasma AST and ALT levels, hepatic α-SMA expression and collagen contents, and fibrosis scores of BDL rats as compared with vehicle treatment. Moreover, Arm attenuated the mRNA expression levels of col 1α2, TGF-β1, TIMP-1, ICAM-1, iNOS, and IL-6 genes, but up-regulated metallothionein genes. Our study results showed that Arm exerted both in vitro and in vivo antifibrotic effects in rats, possibly through anti-NF-κB activation pathways.
Hepatic encephalopathy (HE) arises from acute or chronic liver diseases and leads to several problems, including motor impairment. Animal models of chronic liver disease have extensively investigated the mechanisms of this disease. Impairment of locomotor activity has been described in different rat models. However, these studies are controversial and the majority has primarily analyzed activity parameters. Therefore, the aim of the present study was to evaluate locomotor and exploratory behavior in bile duct-ligated (BDL) rats to explore the spatial and temporal structure of behavior. Adult female Wistar rats underwent common bile duct ligation (BDL rats) or the manipulation of common bile duct without ligation (control rats). Six weeks after surgery, control and BDL rats underwent open-field, plus-maze and foot-fault behavioral tasks. The BDL rats developed chronic liver failure and exhibited a decrease in total distance traveled, increased total immobility time, smaller number of rearings, longer periods in the home base area and decreased percentage of time in the center zone of the arena, when compared to the control rats. Moreover, the performance of the BDL rats was not different from the control rats for the elevated plus-maze and foot-fault tasks. Therefore, the BDL rats demonstrated disturbed spontaneous locomotor and exploratory activities as a consequence of altered spatio-temporal organization of behavior.
Background & Aims
c-Jun N-terminal kinase (JNK) is activated by multiple profibrogenic mediators; JNK activation occurs during toxic, metabolic, and autoimmune liver injury. However, its role in hepatic fibrogenesis is unknown.
JNK phosphorylation was detected by immunoblot analysis and confocal immunofluorescent microscopy in fibrotic livers from mice after bile duct ligation (BDL) or CCl4 administration and in liver samples from patients with chronic hepatitis C and non-alcoholic steatohepatitis. Fibrogenesis was investigated in mice given the JNK inhibitor SP600125 and in JNK1- and JNK2-deficient mice following BDL or CCl4 administration. Hepatic stellate cell (HSC) activation was determined in primary mouse HSCs incubated with pan-JNK inhibitors SP600125 and VIII.
JNK phosphorylation was strongly increased in livers of mice following BDL or CCl4 administration as well as in human fibrotic livers, occurring predominantly in myofibroblasts. In vitro, pan-JNK inhibitors prevented transforming growth factor (TGF)β-, platelet-derived growth factor (PDGF)-, and angiotensin II-induced murine HSC activation and decreased PDGF and TGFβ signaling in human HSCs. In vivo, pan-JNK inhibition did not affect liver injury but significantly reduced fibrosis after BDL or CCl4. JNK1-deficient mice had decreased fibrosis after BDL or CCl4 whereas JNK2-deficient mice displayed increased fibrosis after BDL but fibrosis was not changed after CCl4. Moreover, patients with chronic hepatitis C who displayed decreased fibrosis in response to the angiotensin receptor type 1 blocker losartan showed decreased JNK phosphorylation.
JNK is involved in HSC activation and fibrogenesis and represents a potential target for antifibrotic treatment approaches.
Chinese medicine decoctions such as Yinchenhao Tang (YCHT), Xiayuxue Tang (XYXT), Huangqi Tang (HQT), Yiguan Jian (YGJ) and Xiaochaihu Tang (XCHT)) were used to treat liver cirrhosis. The present study evaluates the effects of these decoctions on fibrosis in rats induced by dimethylnitrosamine (DMN).
DMN solution (0.5%) was injected to rats for three consecutive days per week for four weeks. At the beginning of week 3, rats were randomly divided into 4-week DMN control group, YCHT, XYXT, HQT, YGJ, XCHT and vehicle groups. Each group was orally administered with specific decoctions daily for two weeks. Rats in the vehicle group were orally administered with only water.
Liver fibrosis and cirrhosis were observed in weeks 2 and 4 in DMN-intoxicated rats. Compared with normal rats, alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) activities and level of total bilirubin acid (TBA) in serum and content of Hydroxyproline (Hyp) in liver tissue of model group rats rose significantly. However, the albumin (Alb) level in serum decreased significantly. Compared with the 4-week DMN group, the pathological conditions and functions of the liver in the YCHT group improved significantly, and the content of Hyp decreased remarkably: only one rat in this group developed liver cirrhosis and the ratio of cirrhosis was only 8.3%. On the other hand, the other decoctions did not show remarkable effects. YCHT inhibited α-SMA activation, including its gene expression into mRNA and protein.
Among the five Chinese medicine decoctions, YCHT exerted the most significant therapeutic effects on DMN-induced cirrhosis/fibrosis in rats.
Reactive oxygen species (ROS) generated by Nicotinamide adenine dinucleotide phosphate oxidase (NOX) is required for liver fibrosis. This study investigates role of NOX in ROS production and the differential contribution of NOX from bone marrow (BM) derived and non-BM derived liver cells. Hepatic fibrosis was induced by bile duct ligation (BDL) for 21 days or by methionine-choline deficient (MCD) diet for 10 weeks in wild-type (WT) mice and mice deficient in p47phox (p47phox KO), a component of NOX. p47phox KO chimeric mice were generated by the combination of liposomal clodronate injection, irradiation and BM transplantation of p47phox KO BM into WT recipients and vice versa. Upon BDL, chimeric mice with p47phox KO BM-derived cells, including Kupffer cells (KC), and WT endogenous liver cells showed a ~25% reduction of fibrosis, while chimeric mice with WT BM-derived cells and p47phox KO endogenous liver cells, including hepatic stellate cells (HSC), showed a ~60% reduction of fibrosis. In addition, p47phox KO compared to WT mice treated with an MCD-diet showed no significant changes in steatosis and hepatocellular injury, but a ~50% reduction in fibrosis. Cultured WT and p47phox KO HEP treated with free fatty acids (FFA) had a similar increase in lipid accumulation. FFA promoted a 1.5 fold increase in ROS production both in p47phox KO and in WT hepatocytes (HEP).
NOX in both BM derived and non-BM derived cells contributes to liver fibrosis. NOX does not play a role in experimental steatosis and the generation of ROS in HEP, but exerts a key role in fibrosis.
hepatic stellate cells; reactive oxygen species; fibrogenesis; bone marrow transplantation; methionine and choline deficient diet
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.
cholangiocyte; cholangiocarcinoma; apoptosis; cholestatic liver diseases
Ischemic injury by hepatic artery ligation (HAL) during obstructive cholestasis induced by bile duct ligation (BDL) results in bile duct damage, which can be prevented by administration of VEGF-A. The potential regulation of VEGF and VEGF receptor expression and secretion by bile acids in BDL with HAL is unknown.
We evaluated whether taurocholic acid (TC) can prevent HAL-induced cholangiocyte damage via the alteration of VEGFR-2 and/or VEGF-A expression.
Utilizing BDL, BDL+TC, BDL+HAL, BDL+HAL+TC, and BDL+HAL+wortmannin+TC treated rats, we evaluated cholangiocyte apoptosis, proliferation, and secretion as well VEGF-A and VEGFR-2 expression by immunohistochemistry. In vitro, we evaluated the effects of TC on cholangiocyte secretion of VEGF-A and the dependence of TC-induced proliferation on the activity of VEGFR-2.
In BDL rats with HAL, chronic feeding of TC prevented HAL-induced loss of bile ducts and HAL-induced decreased cholangiocyte secretion. TC also prevented HAL-inhibited VEGF-A and VEGFR-2 expression in liver sections and HAL-induced circulating VEGF-A levels, which were blocked by wortmannin administration. In vitro, TC stimulated increased VEGF-A secretion by cholangiocytes, which was blocked by wortmannin and stimulated cholangiocyte proliferation that was blocked by VEGFR-2 kinase inhibitor.
TC prevented HAL-induced biliary damage by upregulation of VEGF-A expression.
Apoptosis; cAMP; intrahepatic biliary epithelium; mitosis; VEGF
The concept of endotoxin-mediated rather than direct liver injury in biliary obsruction was
investigated using the experimental rat model of bile duct ligation (BDL) and small bowel
bacterial overgrowth (SBBO). Small identical doses of intravenous endotoxin (bacterial LPS)
caused a significantly more severe liver injury in rats with BDL, compared with sham-operated
rats, suggesting the possible contribution of LPS in this type of liver damage. BDL was then
combined with surgically created jejunal self-filling blind loops, which resulted in SBBO. Plasma
LPS level increased significantly, and once again a more severe liver injury, determined by liver
histology and serum gamma-glutamyl transpeptidase levels, was observed compared with the
control group of rats with BDL+self-emptying blind loops. The data presented suggest that
small amounts of exogenous LPS and/or the ordinarily innocous amounts of LPS constantly
absorbed from the intestinal tract may be critical in the hepatic damage caused by obstruction
of the biliary tract.
Rat and human biliary epithelium is morphologically and functionally heterogeneous. Since no information exists on the heterogeneity of the murine intrahepatic biliary epithelium, and with increased usage of transgenic mouse models to study liver disease pathogenesis, we sought to evaluate the morphological, secretory and proliferative phenotypes of small and large bile ducts and purified cholangiocytes in normal and cholestatic mouse models.
For morphometry, normal and BDL mouse livers (C57/BL6) were dissected into blocks of 2-4 μm2, embedded in paraffin, sectioned, and stained with H&E. Sizes of bile ducts and cholangiocytes were evaluated by using SigmaScan to measure the diameters of bile ducts and cholangiocytes. In small and large normal and BDL cholangiocytes, we evaluated the expression of cholangiocyte specific markers, keratin-19 (KRT19), secretin receptor (SR), cystic fibrosis transmembrane conductance regulator (CFTR), and chloride bicarbonate anion exchanger 2 (Cl-/HCO-3 AE2) by immunofluorescence and western blot; and intracellular cAMP levels and chloride efflux in response to secretin (100 nM). To evaluate cholangiocyte proliferative responses after bile duct ligation (BDL), small and large cholangiocytes were isolated from BDL mice. The proliferation status was determined by analysis of the cell cycle by FACS and bile duct mass was determined by the number of KRT19-positive bile ducts in liver sections.
In situ morphometry established that the biliary epithelium of mice is morphologically heterogeneous, which smaller cholangiocyte lining smaller bile ducts and larger cholangiocytes lining larger ducts. Both small and large cholangiocytes express KRT19 and only large cholangiocytes from normal and BDL mice express SR, CFTR, and Cl-/HCO-3 exchanger and respond to secretin with increased cAMP levels and chloride efflux. Following BDL, only large mouse cholangiocytes proliferate.
Similar to rats, mouse intrahepatic biliary epithelium is morphologically, and functionally heterogeneous. The mouse is a suitable model for defining the heterogeneity of the biliary tree.
Bicarbonate secretion; bile ducts; cAMP; cholangiocytes; mitosis; secretin; secretin receptor
During the neonatal and infancy periods, some chronic liver diseases may lead to progressive hepatic fibrosis, which is a condition that can ultimately result in the loss of organ function and severe portal hypertension necessitating hepatic transplantation. In a previous report, pharmacological interventions were demonstrated to modulate hepatic fibrosis induced by bile duct ligation in young rats. The administration of pentoxifylline or prednisolone, or the combination of both, resulted in reduced fibrogenesis in portal spaces. The objectives of the present study were to evaluate the expression of transforming growth factor β and vascular endothelial growth factor after bile duct ligation in young rats and to assess the effect of those same drugs on cytokine expression.
In this experimental study, 80 young rats (21 or 22 days old) were submitted either to laparotomy and common bile duct ligation or to sham surgery. The animals were allocated into four groups according to surgical procedure, and the following treatments were administered: (1) common bile duct ligation + distilled water, (2) sham surgery + distilled water, (3) common bile duct ligation + pentoxifylline, or (4) common bile duct ligation + prednisolone. After 30 days, a hepatic fragment was collected from each animal for immunohistochemical analysis using monoclonal antibodies against transforming growth factor β and vascular endothelial growth factor. Digital morphometric and statistical analyses were performed.
The administration of pentoxifylline reduced the transforming growth factor β-marked area and the amount of transforming growth factor β expressed in liver tissue. This effect was not observed after the administration of prednisolone. There was a significant reduction in vascular endothelial growth factor expression after the administration of either drug compared with the non-treatment group.
The administration of pentoxifylline to cholestatic young rats resulted in the diminished expression of transforming growth factor β and vascular endothelial growth factor in liver tissue. The administration of steroids resulted in the diminished expression of vascular endothelial growth factor only. These pathways may be involved in hepatic fibrogenesis in young rats submitted to bile duct ligation and exposed to pentoxifylline or prednisolone.
Liver Fibrogenesis; Experimental Cholestasis; Steroids; Pentoxifylline; TGFβ; VEGF