Florid duct lesion in primary biliary cirrhosis shows highly proliferative activities

Autoimmune biliary diseases: primary biliary cholangitis and primary sclerosing cholangitis

Autoimmune cholestatic liver diseases are rare hepato-biliary disorders characterized by a progressive, inflammatory destruction of bile ducts. Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are the main autoimmune cholestatic liver diseases. Both may evolve into secondary biliary cirrhosis and its complications. Therapeutic options are limited and liver transplantation remains the only definitive treatment for PBC and PSC.

Most PBC and PSC patients have a typical presentation, which does not require liver biopsy. However, in routine clinical practice, important variants or specific subgroups that benefit from liver biopsy for proper management may be observed. Herein, we provide a general overview of clinical and pathological characteristic of PBC and PSC, highlighting the most important features for routine diagnostic practice.

Novel and emerging therapies for cholestatic liver diseases

While bile acids are important for both digestion and signalling, hydrophobic bile acids can be harmful, especially when in high concentrations. Mechanisms for the protection of cholangiocytes against bile acid cytotoxicity include negative feedback loops via farnesoid X nuclear receptor (FXR) activation, the bicarbonate umbrella, cholehepatic shunting and anti-inflammatory signalling, among others. By altering or overwhelming these defence mechanisms, cholestatic diseases such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) can further progress to biliary cirrhosis, end-stage liver disease and death or liver transplantation. While PBC is currently treated with ursodeoxycholic acid (UDCA) and obeticholic acid (OCA), many fail treatment, and we have yet to find an effective therapy for PSC. Novel therapies under evaluation target nuclear and surface receptors including FXR, transmembrane G-protein-coupled receptor 5 (TGR5), peroxisome proliferator-activated receptor (PPAR) and pregnane X receptor (PXR). Modulation of these receptors leads to altered bile composition, decreased cytotoxicity, decreased inflammation and improved metabolism. This review summarizes our current understanding of the role of bile acids in the pathophysiology of cholestatic liver diseases, presents the rationale for already approved medical therapies and discusses novel pharmacologic therapies under investigation.

Molecular mechanisms of cholangiopathy in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is histologically characterized by chronic nonsuppurative destructive cholangitis (CNSDC) and the progressive loss of intrahepatic small bile ducts. Cellular immune mechanisms involving T-cell reaction are thought to be significantly involved in the formation of CNSDC and bile duct loss. In inflamed portal tracts of PBC, CD4+ T cells of Th1 type expressing IFN-gamma or CXCR3 are aggregated and more commonly detected around injured bile ducts than Th2-type CD4+ T cells expressing IL-4 or CCR4, indicating that Th1-dominant cellular immunity plays a more-prominent role in recruitment of memory T-cell subsets in PBC and may be responsible for the progressive bile duct damage. Biliary epithelial apoptosis is demonstrated to be a major pathogenic process of bile duct loss in PBC. In CNSDC, several biliary apoptotic cells, an aberrant expression of Fas antigen (proapoptotic molecule) and decreased expression of bcl-2 and mcl-1 (antiapoptotic molecules) are found, although interlobular bile ducts express bcl-2 and mcl-2 but lack Fas. In addition, the upregulation of WAF1 and p53 related to biliary apoptosis is found in biliary epithelial cells of PBC, which may be due to cell senescence in response to genotoxic damage such as oxidative stress. Several steps and mechanisms during induction and progression of cholangitis and biliary apoptosis followed by bile duct loss are now being proposed in PBC, but future analysis of an etiopathogenesis to explain the characteristic histopathogenesis of PBC is required.

Th1 cytokine-induced downregulation of PPARgamma in human biliary cells relates to cholangitis in primary biliary cirrhosis

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is known to inhibit the production of proinflammatory cytokines. In Th1-predominant diseases, PPARgamma ligands can ameliorate clinical severity by downregulating the expression of proinflammatory cytokines. Primary biliary cirrhosis (PBC) is characterized by chronic destructive cholangitis with a Th1-predominant cytokine milieu. Unusual immune responses to infectious agents are suspected to underlie its etiopathogenesis. We examined the significance of PPARgamma in biliary inflammation in connection to PBC. To this end, we performed immunohistochemistry, quantitative polymerase chain reaction, and nuclear factor-kappaB (NF-kappaB) DNA-binding assays to clarify the intrahepatic distribution of PPARgamma and the regulation of PPARgamma by inflammatory cytokines and PPARgamma ligand in five cultured biliary cell lines including one derived from PBC liver. In liver specimens from patients with PBC, PPARgamma protein was ubiquitously expressed in intrahepatic biliary epithelium, whereas the expression of PPARgamma protein and mRNA was reduced in damaged bile ducts. PPARgamma expression in cultured cells was upregulated by interleukin-4 (IL-4; Th2-type), but downregulated by IFN-gamma (Th1-type). PPARgamma ligand negatively modulated lipopolysaccharide-induced NF-kappaB activation. Moreover, this inhibitory effect of PPARgamma ligand was attenuated by pretreatment with IFN-gamma. In conclusion, PPARgamma may be important to maintain homeostasis in the intrahepatic biliary epithelium, and its reduction in the bile ducts of PBC liver may be associated with the Th1-predominant milieu and with the development of chronic cholangitis in PBC. Immunosuppression using PPARgamma ligands may be of therapeutic benefit to attenuate biliary inflammation in PBC.

Similarity between hepatic graft-versus-host disease and primary biliary cirrhosis

Similarities between hepatic graft-versus-host disease (GVHD) and primary biliary cirrhosis (PBC) have been reported recently. To examine this association, we studied 60 patients who underwent allogeneic bone marrow transplantation (BMT) consecutively at a single medical institution.Among the 60 patients, 12 developed hepatic GVHD after BMT and 48 did not. These two groups were compared with respect to various characteristics seen in PBC, such as autoantibodies, human leukocyte antigen (HLA) status, infection and inflammatory cytokines. The two groups showed a significant difference in HLA DR status. There was also a significant difference in the febrile period and in cytokine levels between the patients with hepatic GVHD and 12 other patients who had no complications after transplantation. These findings suggest that hepatic GVHD resembles PBC and that HLA DR features of PBC may also be risk factors for the onset of hepatic GVHD.

Increased expression of WAF1 in intrahepatic bile ducts in primary biliary cirrhosis relates to apoptosis

BACKGROUND/AIMS

In primary biliary cirrhosis (PBC), the intrahepatic small bile ducts are selectively damaged by immune attacks, followed by progressive loss mainly due to apoptosis. Compared to the intercellular signaling such as the CD95/CD95 ligand interaction, little is known about alterations in intracellular cell cycle regulatory proteins and genotoxic damage in this apoptotic process. WAF1 is a potent and reversible inhibitor of cell cycle progression at both the G1 and G2 checkpoint and upregulated WAF1 induces irreversible G1 arrest and apoptosis. Transcriptional activation of the WAF1 gene is induced by the upregulated p53 in response to DNA damage. In this study, the cell cycle regulatory process of apoptosis in PBC was examined with respect to expression of WAF1.

METHODS

Immunostaining for WAF1 and p53 was performed using 11 liver sections of PBC and 26 control livers. In addition, Ki67, apoptosis (TUNEL-positive), and human telomerase RNA (hTR) were also detected.

RESULTS

WAF1 was expressed in the nuclei of several epithelial cells in most damaged bile ducts in PBC but infrequently or rarely in controls. Some of these cells were also positive for p53, while the remainder were not. Ki67 immunostaining and TUNEL disclosed that the bile ducts in PBC showed increased cell division as well as enhanced apoptosis. Immunostaining of Ki67 and TUNEL staining showed that WAF1-positive cells were not proliferating, while some WAF1-positive cells were undergoing apoptosis. Moreover, the bile ducts lacked hTR expression, implying progressive shortening of telomeres during increased cell divisions.

CONCLUSIONS

It seems possible that in PBC, expression of WAF1 on biliary epithelial cells relates to the apoptosis. p53 may be involved in this upregulation. This may be due to physiological upregulation of WAF1 and p53 in response to genotoxic damage such as oxidative stress associated with cholangitis, suggesting other processes than CD95/CD95 ligand interaction in biliary epithelial apoptosis in PBC.

Intrahepatic cholangitis and arteritis after transcatheter arterial embolization in a patient with tumor-like lesion-associated autoimmune hepatitis

Autoimmune hepatitis is a chronic liver disease characterized by immune-mediated, progressive hepatocellular damage, although the target autoantigen remains speculative. Intrahepatic biliary lesions are not a feature of this disease. We describe herein a female patient, 57 years, with autoimmune hepatitis who developed hepatic regenerative mass after acute exacerbation of hepatitis. This hepatic regenerative mass was clinically diagnosed as hepatocellular carcinoma and was surgically resected after transcatheter arterial embolization therapy. Widespread nonsuppurative destructive granulomatous cholangitis as well as necrotizing, granulomatous arteritis of the intrahepatic small arteries were found in the surgically resected hepatic regenerative mass. The bile duct lesions were histologically and immunohistochemically very similar to the granulomatous cholangitis of primary biliary cirrhosis. We would like to propose that these unusual lesions in the intrahepatic bile ducts and intrahepatic arteries represent a reaction of this patient to an anti-cancer drug included in chemoembolization. No such cases have been reported so far.

Distribution of apoptotic cells and expression of apoptosis-related proteins along the intrahepatic biliary tree in normal and non-biliary diseased liver

AIMS

The cell kinetics and homeostasis of biliary epithelial cells may be maintained differently along the biliary tree. In this study, the role of apoptosis in the maintenance and homeostasis of the intrahepatic biliary tree was evaluated.

METHODS AND RESULTS

By counting apoptotic biliary cells and by immunostaining apoptosis-related proteins in normal liver, fatty liver, and those with acute viral hepatitis, chronic viral hepatitis, and hepatitis virus-related cirrhosis, it was found that the larger the intrahepatic bile ducts became, the more biliary epithelial cells underwent apoptosis. bcl-2, an inhibitor of apoptosis, was diffusely expressed in the interlobular bile ducts, but rarely detectable in the large and septal bile ducts. bcl-XL and mcl-1, inhibitors of apoptosis, and bax, a promoter of apoptosis, were diffusely expressed along the intrahepatic biliary tree. CD95, a direct inducer of apoptosis, was present in the large and septal bile ducts, but rarely in the interlobular bile ducts.

CONCLUSION

The ratio of bax to bcl-2, as well as the expression of CD95 which differed at the interlobular versus large and septal bile ducts, may be responsible for the unique distribution of apoptotic biliary cells and involved in the homeostasis of the intrahepatic biliary tree.

The effect of interleukin-6 (IL-6)/gp130 signalling on biliary epithelial cell growth, in vitro

The effect of IL-6 on the growth of mouse biliary epithelial cells (BEC), in vitro, was tested by comparing BEC obtained IL-6-deficient mice (IL-6(-/-)) to wild-type littermate controls (IL-6(+/+)), in two different media: simple serum-free media (S-SFM), and complete serum-free media (C-SFM) containing forskolin, which stimulates BEC IL-6 production. In S-SFM, neither IL-6(+/+)nor IL-6(-/-)BEC constitutively produced IL-6 mRNA or protein, and there was no difference between IL-6(+/+)and IL-6(-/-)BEC growth. In contrast, when the BEC were maintained in C-SFM, over 48 h, the growth of IL-6(+/+)BEC was 40% greater than IL-6(-/-)BEC (P<0.006). Enhanced IL-6(+/+)BEC growth in C-SFM was associated with induced expression of IL-6 mRNA and IL-6 protein secretion into the medium, upregulation of the IL-6Ralpha (gp80) and phosphorylation of the signal transducing molecule gp130. In C-SFM, anti-IL-6 neutralizing antibodies blocked enhanced IL-6(+/+)BEC growth, whereas exogenous rhIL-6 stimulated retarded growth of IL-6(-/-)BEC. Thus, under conditions that mimic an inflammatory or stressful microenvironment in vivo, BEC produce, secrete and respond to IL-6, via upregulation and activation of the IL-6Ralpha (gp80)/gp130 signaling system in an autocrine/paracrine manner.

Expression of Bcl-2 familial proteins is reduced in small bile duct lesions of primary biliary cirrhosis

In primary biliary cirrhosis, biliary epithelial cell death by apoptosis results in progressive bile duct loss. We examined immunohistochemically 4 apoptosis-regulating bcl-2 familial proteins (bcl-2, mcl-1, bcl-X, and bax) in the biliary epithelium in 19 cases of primary biliary cirrhosis. Ten cases of chronic hepatitis C, 9 cases of extrahepatic biliary obstruction, and 10 cases of normal liver were used as a control. Bcl-2 and mcl-1 are inhibitors of apoptosis, bcl-X, probably bcl-XL in biliary epithelial cells, an inhibitor, and bax, a promoter of apoptosis. First, we clarified the distribution of bcl-2 familial proteins on the intrahepatic biliary tree in normal livers. Bcl-2 was detected in the interlobular bile ducts and bile ductules, but not in the large and septal bile ducts in all cases examined. Mcl-1, bcl-X, and bax were diffusely detectable at the any level of the intrahepatic biliary tree, with a staining pattern that was diffuse and cytoplasmic. This distribution pattern was preserved in extrahepatic biliary obstruction. Bcl-2 expression was lost or markedly reduced in the damaged interlobular bile ducts in primary biliary cirrhosis, whereas the reduction was only focal or mild in the bile ducts with hepatitis-associated damage in chronic hepatitis C. Expression levels of mcl-1, bcl-X, and bax were similarly reduced to that of bcl-2 in these 2 diseases. These findings suggest that bax is not important as a proapoptotic factor in the damaged bile ducts and that downregulation of bcl-2 and mcl-1, and probably that of bcl-XL, leads to a decrease in the threshold of apoptosis and increase in the vulnerability to apoptotic stimuli in these bile ducts, followed by the progressive apoptotic loss of interlobular bile ducts, in primary biliary cirrhosis.

Pathogenesis of primary biliary cirrhosis, primary sclerosing cholangitis, and autoimmune cholangiopathy

Autoimmune liver diseases have much in common with each other, and there are clear associations with genetic haplotypes. Elegant studies have shown autoimmune liver disease induced by viruses and drugs. Although there is evidence for nonimmunological events precipitating immune disease, especially in primary sclerosing cholangitis, the precise pathways, what is bystander and what is essential, have not been determined. This article reviews some of the mechanisms involved in pathogenesis.

Detection of transforming growth factor-alpha protein and messenger RNA in hepatobiliary diseases by immunohistochemical and in situ hybridization techniques

Transforming growth factor-alpha (TGF-alpha) is a cytokines related to cell proliferation and transformation. Immunoreactive TGF-alpha protein is expressed in regenerating hepatocytes and interlobular bile ducts as well as in hepatocellular carcinoma. Although TGF-alpha is thought to play an important role in the intrahepatic biliary tree, its role in cellular physiology is poorly understood. This study investigates the expression of TGF-alpha and its messenger RNA (mRNA) in various hepatobiliary diseases. The authors showed by immunohistochemistry that TGF-alpha and its receptor, epidermal growth factor receptor (EGFR), were expressed in interlobular bile ducts, proliferating bile ductules, and most hepatocytes in various hepatobiliary liver tissues. They also showed by Western blot analysis that TGF-alpha protein was present in hepatic bile samples obtained from patients with obstructive jaundice. In situ hybridization showed that TGF-alpha mRNA was localized in hepatocytes of some pathological liver tissues, but it was absent in biliary epithelial cells of the same tissues. These findings suggest that TGF-alpha protein is produced by hepatocytes, and hepatocyte stimulation occurred as autocrine growth regulation. The release of TGF-alpha into hepatic bile caused biliary proliferation and transformation through EGFR, present on the existing cell surface membrane of biliary epithelial cells.