Apoptosis of biliary epithelial cells in primary biliary cirrhosis and primary sclerosing cholangitis

BACKGROUND/AIMS: Primary biliary cirrhosis (PBC) is an autoimmune disease characterized by inflammatory destruction of small bile ducts. Primary sclerosing cholangitis (PSC) is a different, presumed autoimmune cholestatic liver disease where the bile ducts are also destroyed. In this study, apoptosis and portal triad inflammation in liver tissue from patients with PBC is examined and compared to that from patients with PSC and patients with normal liver. METHODS: Explanted liver tissue from patients with PBC and PSC and normal liver from patients with metastases to liver were examined. The liver samples were stained for apoptosis using the terminal deoxynucleotidyl triphosphate (TdT)-mediated deoxyuridine triphosphate nick end labelling (TUNEL) assay. The biliary epithelial cells (BEC) were then scored on the basis of their TUNEL stain and the degree of periductal inflammation. RESULTS: In PBC, apoptosis of BEC, as detected by the TUNEL assay, was significantly increased in the presence of inflammation. Regardless of the presence or absence of inflammation, the small bile ducts in PBC liver tissue exhibited greater evidence of apoptosis than did similar ducts from PSC or control livers. CONCLUSION: These findings suggest that in PBC, unlike PSC, the apoptosis of BEC in PBC is secondary to the invasion of inflammatory cells.     

Lack of Concomitant Expression of ICAM-1 and HLA-DR on Bile Duct Cells from Patients with Primary Sclerosing Cholangitis and Primary Biliary Cirrhosis

In both primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) prominent infiltrates of lymphocytes surround the bile ducts, on which an abberrant expression of major histocompatibility complex class II antigens has been found, suggesting that the immune system is involved in the biliary destruction. Since the lymphocytes presumably must adhere to the bile ducts to initiate a cell-to-cell-mediated destruction, we have studied the expression of the lymphocyte function-associated antigen-1 (LFA-1) together with its ligand, the intercellular adhesion molecule-1 (ICAM-1), and the expression of HLA-DR, using immunoperoxidase staining of cryostat sections from patients with PBC (n = 10), PSC (n = 13), and normal healthy controls (n = 6). Most lymphocytes expressed LFA-1. ICAM-1 expression was found on hepatocytes from 9 of 10 PBC and 10 of 13 PSC patients but was not seen on hepatocytes from the controls. Hepatocytes expressing HLA-DR were only found in one patient with PBC. None of the septal bile ducts expressed ICAM-1, and only one PSC patient and three PBC patients expressed ICAM-1 on their interlobular bile ducts. The bile ducts in 22 of 23 patients, however, expressed HLA-DR. Proliferating bile ductules from two PBC patients and three PSC patients showed a concomitant expression of ICAM-1 and HLA-DR. None of the bile ducts from the controls expressed ICAM-1 or HLA-DR. Thus, since most bile ducts involved in the disease process of both PBC and PSC lack expression of ICAM-1, other adhesion molecules must be involved if a cell-to-cell-mediated destruction accounts for the biliary destruction in these two disease states. Furthermore, the lack of concomitant expression of HLA-DR and ICAM-1 on the bile ducts in PBC and PSC indicates that other regulatory mechanisms exist in the biliary epithelium than in most other epithelial cells.     

Tumor necrosis factor‐α and interferon‐γ directly impair epithelial barrier function in cultured mouse cholangiocytes

Abstract: Background/Aims: In primary biliary cirrhosis (PBC), cytokines from CD4 ⁺ T lymphocytes were suggested to contribute to the intralobular bile duct damage together with cellular immunity by CD8 ⁺ T lymphocytes. Recently, we reported that immunolocalization of 7H6 – a tight junction (TJ)‐associated protein – was significantly diminished in cholangiocytes in the PBC liver. In this study, we examined the direct effects of several cytokines – tumor necrosis factor‐α (TNF‐α), interferon‐γ (IFN‐γ), interleukin‐2 and 4 (IL‐2 and 4) – on TJ in immortalized mouse cholangiocytes. Moreover, we examined the inhibitory effect of ursodeoxycholic acid (UDCA) on cytokine‐induced changes in paracellular permeability. Methods: Barrier function of TJ was evaluated by measuring transepithelial electrical resistance (TER) and ³H‐inulin flux. We also performed immunostaining and immunoblotting for TJ‐associated proteins – claudin‐1 and ‐3, occludin, zonula occluden‐1 (ZO‐1) and 7H6. Results: TNF‐α and IFN‐γ, but neither IL‐2 nor IL‐4, significantly decreased TER (P < 0.005). ³H‐inulin flux studies confirmed IFN‐α‐induced increases in paracellular permeability of cholangiocytes (P < 0.001). In immunostaining and immunoblotting studies, TJ‐associated proteins were well preserved in TNF‐α‐ or IFN‐γ‐treated cells. Ursodeoxycholic acidhas been found to have no inhibitory effect on increased paracellular permeability induced by TNF‐α or IFN‐γ. Conclusion: These findings show that TNF‐α and IFN‐γ disrupt barrier function of TJ in cholangiocytes without major structural changes to TJ and suggest that disruption of TJ function and subsequent leakage of the bile constituents may influence the aggravation of cholestasis in PBC.     

In situ nucleic acid hybridization of pyruvate dehydrogenase complex-E2 in primary biliary cirrhosis: Pyruvate dehydrogenase complex-E2 messenger RNA is expressed in hepatocytes but not in biliary epithelium

Pyruvate dehydrogenase-E2, or a cross-reactive molecule, has been shown by a variety of immunohistochemical methods to be present in increased amounts in biliary epithelial cells (BEC) in primary biliary cirrhosis (PBC). In this study, to further understand the nature of the immunoreactive molecule in BEC, we examined the expression of pyruvate dehydrogenase complex-E2 (PDC-E2) messenger RNA (mRNA) and PDC-E2 protein in sections of livers from patients and controls to help identify the molecule found in BEC. We performed in situ hybridization using an antisense probe against the major epitope of PDC-E2. The data were very striking and suggested that there was no increased production of PDC-E2 in BEC. For example, in livers from patients with PBC, PDC-E2 mRNA was found in periportal hepatocytes in 16 of 17 cases (94%). In contrast, interlobular bile ducts and septal bile ducts had detectable levels of PDC-E2 mRNA in only 1 of 17 (6%) and 3 of 8 (38%) cases, respectively. Interestingly, proliferating bile ductules contained detectable levels of mRNA in 12 of 15 cases (80%). In control liver, periportal hepatocytes were positive in 15 of 17 cases (88%). Interlobular bile ducts, septal bile ducts, and proliferating bile ductules expressed mRNA signals in 4 of 17 (24%), 2 of 10 (20%), and 14 of 16 (88%), respectively. When formalin-fixed, paraffin-embedded sections were examined by immunohistochemical staining with anti-PDC-E2 monoclonal antibody (mAb) C355.1, the interlobular bile ducts showed typical aberrant apical staining in all 10 PBC cases, but 0 of 9 liver controls. Periportal hepatocytes, proliferating bile ductules and infiltrating mononuclear cells stained with C355.1 but in a characteristic mitochondrial staining pattern. The presence of a PDC-E2-like molecule recognized by C355.1 is not reflected by the expression levels of PDC-E2 mRNA in the BEC of patients with PBC.(Hepatology 1997 Jan;25(1):27-32)     

Hepatic Met‐enkephalin immunoreactivity is enhanced in primary biliary cirrhosis

Abstract: Background/aims: In contrast to the normal adult liver, the fetal human and rat livers, and the liver of rats with cholestasis secondary to bile duct resection (BDR) express the preproenkephalin (ppENK) mRNA, which codes for the endogenous opioid peptide Met‐enkephalin. In addition, Met‐enkephalin immunoreactivity (MEIR) is detected in hepatocytes and in proliferating bile ductules in the cholestatic rat liver. These data suggest that cholestasis is associated with the resurgence of cells that produce Met‐enkephalin. To explore further the status of opioids in cholestasis, we studied the expression of MEIR in liver tissue. Methods: The MEIR was sought in paraffin‐preserved liver tissues from patients with primary biliary cirrhosis (PBC) (n = 10). Results: The MEIR was detected in all the PBC livers. Its intensity varied from weak to strong on hepatocytes and bile ducts and the strongest expression appeared as coarse granules. The MEIR was either absent or only faintly expressed by some hepatocytes from disease and nondisease control biopsies, but absent from bile ducts. Conclusion: These results suggest that the human liver in cholestasis may be a source of endogenous opioids.     

原发性胆汁性肝硬化免疫分子机制研究进展

原发性胆汁性肝硬化(primary biliary cirrhosis,PBC)是一种免疫介导损伤胆管上皮细胞及肝内小胆管的胆汁淤积性自身免疫性肝病,具有发展为肝硬化的倾向.多种免疫相关基因通过影响疾病易感性、免疫调节等途径,促使PBC的发生、发展.本文就PBC的免疫分子机制研究动态进行综述.     

Peptide antibiotic human beta-defensin-1 and -2 contribute to antimicrobial defense of the intrahepatic biliary tree

Human beta-defensins (hBDs) are important antimicrobial peptides that contribute to innate immunity at mucosal surfaces. This study was undertaken to investigate the expression of hBD-1 and hBD-2 in intrahepatic biliary epithelial cells in specimens of human liver, and 4 cultured cell lines (2 consisting of biliary epithelial cells and 2 cholangiocarcinoma cells). In addition, hBD-1 and hBD-2 were assayed in specimens of bile. hBD-1 was nonspecifically expressed immunohistochemically in intrahepatic biliary epithelium and hepatocytes in all patients studied, but expression of hBD-2 was restricted to large intrahepatic bile ducts in 8 of 10 patients with extrahepatic biliary obstruction (EBO), 7 of 11 with hepatolithiasis, 1 of 6 with primary biliary cirrhosis (PBC), 1 of 5 with primary sclerosing cholangitis (PSC), 0 of 6 with chronic hepatitis C (CH-C), and 0 of 11 with normal hepatic histology. hBD-2 expression was evident in bile ducts exhibiting active inflammation. Serum C reactive protein levels correlated with biliary epithelial expression of hBD-2. Real-time PCR revealed that in all of 28 specimens of fresh liver, including specimens from patients with hepatolithiasis, PBC, PSC, CH-C and normal hepatic histology, hBD-1 messenger RNA was consistently expressed, whereas hBD-2 messenger RNA was selectively expressed in biliary epithelium of patients with hepatolithiasis. Immunobloting analysis revealed hBD-2 protein in bile in 1 of 3 patients with PSC, 1 of 3 with PBC, and each of 6 with hepatolithiasis; in contrast, hBD-1 was detectable in all bile samples examined. Four cultured biliary epithelial cell lines consistently expressed hBD-1; in contrast these cell lines did not express hBD-2 spontaneously but were induced to express hBD-2 by treatment with Eschericia coli, lipopolysaccharide, interleukin-1beta or tumor necrosis factor-alpha. In conclusion, these findings suggest that in the intrahepatic biliary tree, hBD-2 is expressed in response to local infection and/or active inflammation, whereas hBD-1 may constitute a preexisting component of the biliary antimicrobial defense system.     

Variant forms of cholestatic diseases involving small bile ducts in adults

OBJECTIVE: Cholestasis may result from diverse etiologies. We review chronic cholestatic disorders involving small intrahepatic bile ducts in the adult ambulatory care setting. Specifically, we discuss variant forms of primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) as well as other conditions that may present diagnostic and therapeutic difficulties. METHODS: We conducted a MEDLINE search of the literature (1981-1997) and reviewed the experiences at the Mayo Clinic. All articles were selected that discussed antimitochondrial antibody (AMA)-negative PBC, small-duct PSC (formerly pericholangitis), and idiopathic adulthood ductopenia. RESULTS: The most common chronic cholestatic liver diseases affecting adults are PBC and PSC. Patients without the hallmarks of either syndrome are diagnosed according to their clinical and histological characteristics. Autoimmune cholangitis is diagnosed if clinical and histological features are compatible with PBC but autoantibodies other than AMA are present. Isolated small duct PSC is diagnosed if patients have inflammatory bowel disease, biopsy features compatible with PSC, but a normal cholangiogram. If ductopenia (absence of interlobular bile ducts in small portal tracts) is found histologically in the absence of PSC, inflammatory bowel disease, and other specific cholestatic syndromes such as drug reaction or sarcoidosis, the most likely diagnosis is idiopathic adulthood ductopenia. CONCLUSIONS: Based on these definitions, an algorithm for diagnosis and therapy in patients with laboratory evidence of chronic cholestasis may be constructed, pending results of further investigations into the etiopathogenesis of these syndromes.     

Hepatic Met-enkephalin immunoreactivity is enhanced in primary biliary cirrhosis

BACKGROUND/AIMS: In contrast to the normal adult liver, the fetal human and rat livers, and the liver of rats with cholestasis secondary to bile duct resection (BDR) express the preproenkephalin (ppENK) mRNA, which codes for the endogenous opioid peptide Met-enkephalin. In addition, Met-enkephalin immunoreactivity (MEIR) is detected in hepatocytes and in proliferating bile ductules in the cholestatic rat liver. These data suggest that cholestasis is associated with the resurgence of cells that produce Met-enkephalin. To explore further the status of opioids in cholestasis, we studied the expression of MEIR in liver tissue. METHODS: The MEIR was sought in paraffin-preserved liver tissues from patients with primary biliary cirrhosis (PBC) (n = 10). RESULTS: The MEIR was detected in all the PBC livers. Its intensity varied from weak to strong on hepatocytes and bile ducts and the strongest expression appeared as coarse granules. The MEIR was either absent or only faintly expressed by some hepatocytes from disease and nondisease control biopsies, but absent from bile ducts. CONCLUSION: These results suggest that the human liver in cholestasis may be a source of endogenous opioids.     

Cholestatic liver diseases: slow progress in understanding and treating slowly progressive disorders

BACKGROUND: Cholestatic liver diseases are characterized by failure of normal amounts of physiological bile to reach the gastrointestinal tract. Any interference with normal bile flow from the canalicular membrane of the hepatocyte to the distal common bile duct may result in cholestasis. METHODS: Literature review. RESULTS: In primary biliary cirrhosis (PBC), the small intrahepatic bile ducts are destructed, resulting in obstruction of intrahepatic bile flow, whereas extrahepatic and/or intrahepatic biliary strictures block the passage of bile towards the intestine in primary sclerosing cholangitis (PSC). In contrast, the biliary tree is morphologically unaffected in less common cholestatic liver diseases as benign recurrent intrahepatic cholestasis (BRIC) and progressive familiar intrahepatic cholestasis (PFIC1-4). Genetic defects in hepatic canalicular transport mechanisms and bile salt synthesis deficiencies seem to underlie these types of cholestatic disorders. CONCLUSION: Recent advances in understanding and treatment of cholestatic liver diseases may help in better diagnosing and treating the various conditions characterized by cholestasis.     

Ursodeoxycholic acid treatment of vanishing bile duct syndromes

Vanishing bile duct syndromes (VBDS) are characterized by progressive loss of small intrahepatic ducts caused by a variety of different diseases leading to chronic cholestasis, cirrhosis, and premature death from liver failure. The majority of adult patients with VBDS suffer from primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC). Ursodeoxycholic acid (UDCA), a hydrophilic dihydroxy bile acid, is the only drug currently approved for the treatment of patients with PBC, and anticholestatic effects have been reported for several other cholestatic syndromes. Several potential mechanisms of action of UDCA have been proposed including stimulation of hepatobiliary secretion, inhibition of apoptosis and protection of cholangiocytes against toxic effects of hydrophobic bile acids.     

Intracellular balance of oxidative stress and cytoprotective molecules in damaged interlobular bile ducts in autoimmune hepatitis and primary biliary cirrhosis: In situ detection of 8-hydroxydeoxyguanosine and glutathione-S-transferase-pi

Aim: Bile duct injury has been thought to be absent in autoimmune hepatitis (AIH), but recent studies have indicated that AIH patients do have bile duct injury. In this study, the intracellular balance of oxidative stress and cytoprotection in biliary epithelial cells was investigated to clarify the pathogenesis of bile duct injury in AIH. Methods: The intracellular status of oxidative DNA damage caused by oxidative stress and glutathione, an endogenous cytoprotective molecule, were examined in patients with AIH, primary biliary cirrhosis (PBC), and normal controls by immunostaining of 8-hydroxydeoxyguanosine (8-OHdG) and glutathione-S-transferase-pi. Results: Immunohistochemically, 8-OHdG expression was detected as abundantly in the damaged bile ducts of AIH patients as in PBC patients. Moreover, in AIH, 8-OHdG expression was detected in damaged bile ducts more than in undamaged bile ducts. Glutathione-S-transferase-pi expression was relatively preserved in the damaged bile ducts of AIH patients compared to PBC patients, reflecting preservation of intracellular glutathione. Conclusions: In AIH, oxidative stress and DNA damage may be involved in the pathogenesis of bile duct injury in a manner similar to that found in PBC. However, relatively preserved intracellular glutathione may play a key role in preventing progressive bile duct loss following bile duct injury in AIH.     

Medical treatment of primary sclerosing cholangitis

Until 1970, primary sclerosing cholangitis (PSC) was considered to be a medical curiosity. With the development of endoscopic cholangiography, PSC is now recognized more frequently and is a common indication for liver transplantation. PSC is usually progressive, leading to cirrhosis, portal hypertension, and liver failure. The manifestations of disease may be clinically similar to those of other causes of bile duct obstruction and must be distinguished from gallstone disease, bile duct carcinoma, primary biliary cirrhosis, and secondary biliary cirrhosis due to bile duct stricture. Medical management of PSC must take into account the likelihood that destroyed bile ducts do not regenerate as hepatocytes do. Hence, PSC should be treated early in its course. The goal of therapy is to prevent further damage and destruction of bile ducts. In this article, we will present relevant data concerning the medical management of primary sclerosing cholangitis.     

原发性胆汁性肝硬化的发病机制及影响预后的危险因素研究进展

原发性胆汁性肝硬化(PBC)是一种原因不明的,自身免疫介导的,以肝内中、小胆管胆汁淤积为特征的肝病。本文就目前国内外已报道的PBC的发病机制及影响其预后的相关危险因素进行综述。     

Decreased anion exchanger 2 immunoreactivity in the liver of patients with primary biliary cirrhosis

Chloride-bicarbonate anion exchanger 2 (AE2) is expressed in a variety of tissues, including the liver and salivary glands, where it may participate in the generation of hydroionic fluxes into secretions. We have previously reported decreased hepatic levels of AE2 messenger RNA in patients with primary biliary cirrhosis (PBC), a cholestatic condition frequently associated with pluriglandular exocrine failure. Here we investigated the expression of AE2 protein in the liver of PBC patients. Using a monoclonal antibody against an AE2 peptide, immunohistochemistry was performed on liver biopsy specimens from subjects with normal liver (n = 7), patients with PBC (n = 13), and patients with cirrhosis or cholestasis other than PBC (n = 17 and 11, respectively). Immunostaining was graded from 0 to 7, according to its intensity and distribution. AE2 immunoreactivity was observed in normal livers, as previously reported, and in many pathological liver biopsy specimens, being mainly restricted to canaliculi and the luminal membrane of terminal and interlobular bile ducts. Canalicular and ductular scores were significantly reduced in the PBC group compared with each control group (normal liver and cirrhosis or cholestasis other than PBC), whereas no differences in immunoreactivity scores were observed among control groups. When four patients with primary sclerosing cholangitis (PSC) were analyzed, they also differed from those with PBC. These results suggest that PBC is characterized by diminished expression of AE2 in the liver. Reduced levels of this transporter protein might be involved in the pathogenesis of cholestasis in PBC.(Hepatology 1997 Jan;25(1):12-7)     

Biliary tract inflammatory disorders: Primary sclerosing cholangitis and primary biliary cirrhosis

Primary sclerosing cholangitis (PSC) and primary biliary cirrhosis (PBC) are chronic progressive cholestatic diseases that frequently lead to biliary cirrhosis. The exact pathogenesis of these diseases remains elusive but is likely immunologically based. Complications range from fatigue and pruritus to end-stage liver disease. The risk of developing hepatocellular carcinoma is low for patients with PBC, whereas cholangiocarcinoma is common in PSC and carries an ominous prognosis. Although ursodeoxycholic acid is effective in slowing the progression of PBC, no effective medical therapy exists for PSC. Liver transplantation is the only option for patients with endstage liver disease and yields excellent long-term survival in both groups.     

Biliary tract inflammatory disorders: Primary sclerosing cholangitis and primary biliary cirrhosis

Primary sclerosing cholangitis (PSC) and primary biliary cirrhosis (PBC) are chronic progressive cholestatic diseases that frequently lead to biliary cirrhosis. The exact pathogenesis of these diseases remains elusive but is likely immunologically based. Complications range from fatigue and pruritus to end-stage liver disease. The risk of developing hepatocellular carcinoma is low for patients with PBC, whereas cholangiocarcinoma is common in PSC and carries an ominous prognosis. Although ursodeoxycholic acid is effective in slowing the progression of PBC, no effective medical therapy exists for PSC. Liver transplantation is the only option for patients with end-stage liver disease and yields excellent long-term survival in both groups.     

High-dose ursodeoxycholic acid for the treatment of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a cholestatic liver disease that results in progressive fibrosis of intrahepatic and extrahepatic bile ducts. No effective therapy currently exists for this disease. Ursodeoxycholic acid (UDCA), a hydrophilic bile acid, is the most promising treatment option because of its benign side effect profile and documented benefit in the treatment of other cholestatic liver diseases, including primary biliary cirrhosis. Multiple studies using standard-dosage (8–15 mg/kg/d) and high-dosage (20–30 mg/kg/d) UDCA generally show improvement in liver chemistries in PSC patients, and several show improvement in liver histology. However, the majority of trials using UDCA in PSC are underpowered and fail to show improvements in clinically relevant endpoints, such as delayed progression to cirrhosis, portal hypertension, liver transplantation, development of cholangiocarcinoma, or death.     

Medical treatment of primary biliary cirrhosis and primary sclerosing cholangitis.

Treatment of primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) with ursodeoxycholic acid (UDCA) has been in common use since 1985. In PBC, treatment with UDCA improves laboratory data, liver histology, enables a longer transplantation-free interval and prolongs disease survival. Because UDCA is unable to cure the disease newer drugs or combination therapies are still needed. Studies with UDCA and immunosuppressants such as prednisone, budesonide and azathioprine have shown that in selected patients combination therapy may be superior to UDCA monotherapy. PSC is treated successfully with UDCA and endoscopic dilatation of the bile duct strictures. Treatment of extrahepatic manifestations of cholestatic liver disease such as pruritus, fatigue, osteoporosis and steatorrhea can be problematic and time-consuming.     

Autoimmune hepatitis and overlap syndromes

Autoimmune hepatitis (AIH) is an immune-mediated, autodestructive liver disease with hepatocytes as target cells, mostly affecting young women. Primary biliary cirrhosis (PBC) is also regarded as an autoimmune liver disease with bile duct epithelia as the target cells, resulting in a continuous loss of bile ducts. Both diseases may occur simultaneously in their full manifestations in about 10% to 20% of cases, thus constituting an overlap syndrome with PBC directing the course of the disease. AIH may also occur simultaneously with primary sclerosing cholangitis (PSC), with a frequency of between 2% and 8% of patients with PSC. In most cases, AIH precedes manifestation of PSC. In children, the overlap syndrome of AIH and PSC seems to make up an entity of its own: autoimmune sclerosing cholangitis.