Extrahepatic manifestations of cholestatic liver diseases: pathogenesis and therapy

Reduced spontaneous itch in mouse models of cholestasis

Pruritus is one of the most distressing symptoms in cholestatic patients. Plasma autotaxin (ATX) activity correlates with the severity of pruritus in cholestatic patients, but the pathophysiology is unclear. To study pruritus in mice, we measured scratch activity in cholestatic Atp8b1 mutant mice, a model for Progressive Familial Intrahepatic Cholestasis type 1, and wild type mice (WT) with alpha-naphthylisothiocyanate (ANIT)-induced cholestasis. To induce cholestasis, Atp8b1 mutant mice received a diet containing 0.1% cholic acid (CA) and WT mice were treated with ANIT. In these mice ATX was also overexpressed by transduction with AAV-ATX. Scratch activity was measured using an unbiased, electronic assay. Marked cholestasis was accomplished in both Atp8b1 mutant mice on a CA-supplemented diet and in ANIT-treatment in WT mice, but scratch activity was decreased rather than increased while plasma ATX activity was increased. Plasma ATX activity was further increased up to fivefold with AAV-ATX, but this did not induce scratch activity. In contrast to several reports two cholestatic mouse models did not display increased scratch activity as a measure of itch perception. Increasing plasma ATX activity by overexpression also did not lead to increased scratch activity in mice. This questions whether mice are suitable to study cholestatic itch.

Cholestatic pruritus: Emerging mechanisms and therapeutics

Patients suffering from cholestasis often report experiencing a debilitating, unrelenting itch. In contrast to conditions, such as urticaria, in which histamine primarily drives itch (pruritus), cholestatic pruritus is multifactorial and more difficult to treat. Existing therapies are not always effective and have undesirable adverse effect profiles. Here, we conducted a systematic literature review to evaluate conventional treatment strategy, current pathophysiologic understanding, and the role of new therapies in the context of cholestatic pruritus. We discuss novel findings implicating bile acids, lysophosphatidic acid, and bilirubin as potential important mediators of cholestatic itch. New therapies that aim to remove or modulate pruritogens have been supported in observational cohort studies and randomized controlled trials. Although these new therapies show promise, further research is needed to confirm the pathophysiology of cholestatic pruritus so that targeted therapy can be developed.

Low bone mineral density and the severity of cholestasis in biliary atresia

AIM

To investigate the prevalence of osteopenia and osteoporosis in postoperative biliary atresia (BA) children and the association of bone mineral density (BMD) and biochemical parameters in postKasai BA subjects.

METHODS

A total of 70 patients with postKasai BA were enrolled in this prospective study. The patients were classified into two groups according to their jaundice status. BMD of the lumbar spine was analyzed using dual energy X-ray absorptiometry.

RESULTS

The prevalence of low bone mass (osteopenia and osteoporosis) in BA patients were 51.4% (36 out of 70). Ten patients (35.7%) in the jaundice group and 8 patients (19.0%) in the non-jaundice group had osteopenia. Sixteen patients (57.1%) in the jaundice group and 2 patients (4.8%) in the no jaundice group had osteoporosis. In addition, lumbar spine BMD Z-score was substantially lower in the jaundice BA patients compared with non-jaundice patients. BA subjects with persistent jaundice had significantly lower serum 25-hydroxyvitamin D than those without jaundice. Further analysis revealed that lumbar spine BMD was correlated with age (r = 0.774, P < 0.001), serum albumin (r = 0.333, P = 0.005), total bilirubin (r = -0.476, P < 0.001), aspartate aminotransferase (r = -0.583, P < 0.001), alanine aminotransferase (r = -0.428, P < 0.001), and alkaline phosphatase(r = -0.456, P < 0.001).

CONCLUSION

Low BMD was associated with biochemical parameters reflecting the severity of cholestasis in postKasai BA patients.

Anti-TNF-α Treatment and Bile Duct Drainage Restore Cellular Immunity and Prevent Tissue Injury in Experimental Obstructive Jaundice

Several experimental studies of obstructive jaundice (OJ) have shown the presence of immunosuppressive state associated with the rise of tumor necrosis factor-α (TNF-α) concentration in plasma. The present study evaluates the impact of anti-TNF-α administration or bile duct drainage on the inflammatory response, liver injury and renal insufficiency in obstructed rats. OJ was induced by the ligation of bile duct in Wistar rats. The parameters were determined at 14 and 21 days after OJ. Two additional groups of animals were treated with anti-TNF-α antibodies or submitted to bile duct drainage at 14 days, and sacrificed 21 days after OJ. Cholestasis decreased glucose, and enhanced urea, Creatinin, bilirubin and transaminases. Cholestasis increased the number of different inflammatory cells (T and B lymphocytes, and monocytes-macrophages) but reduced the expression of the corresponding cellular activation markers. This low responsiveness of the inflammatory cells was related to a decreased free radical production and phagocytic activity of cells. Anti-TNF-α and bile duct drainage reduced tissue injury, and prevented the reduction of the number and activity of T lymphocytes and phagocytic cells observed at the advanced stages of cholestasis. In conclusion, anti-TNF-α and bile duct drainage improved cell immunodeficiency, and reduced liver injury, cholestasis and renal insufficiency in experimental OJ.

Advances in pathogenesis and management of pruritus in cholestasis

Chronic pruritus is a burdensome feature of numerous hepatobiliary disorders such as primary biliary cirrhosis, primary sclerosing cholangitis, cholangiocarcinoma, inherited forms of cholestasis and intrahepatic cholestasis of pregnancy. Bile salts, μ-opioids, serotonin, histamine and steroids have been controversially discussed in the pathogenesis of cholestatic pruritus. However, for these substances neither a correlation with itch severity nor a causative link has ever been established. Recent findings indicate that the potent neuronal activator lysophosphatidic acid and autotaxin, the enzyme forming lysophosphatidic acid, may play a key element in the pathogenesis of cholestatic pruritus. Serum activity of autotaxin correlated with itch intensity and response to antipruritic treatment in patients with cholestatic pruritus, but not other forms of pruritus. Autotaxin activity thereby represents the first biomarker for pruritus and had a positive predictive value of 70% in differentiating cholestatic pruritus from other forms of pruritus. Treatment options for patients with cholestatic pruritus include the anion exchange resin colestyramine, the PXR agonist rifampicin, the μ-opioid antagonist naltrexone, and the serotonin reuptake inhibitor sertraline. These drugs are recommended by evidence-based guidelines as a stepwise therapeutic approach. Patients unresponsive to these drugs should be referred to specialized centers to receive experimental approaches such as UVB phototherapy, albumin dialysis, plasmapheresis or nasobiliary drainage. This review discusses pruritogen candidates in cholestasis, gives novel insights into the neuronal signaling pathway of pruritus and summarizes evidence-based treatment options for patients suffering from pruritus in cholestasis.

Influence of distal ileum exclusion on hepatic and renal functions in presence of extrahepatic cholestasis

OBJECTIVE

To verify whether the ileal exclusion interferes with liver and kidney functional changes secondary to extrahepatic cholestasis.

METHODS

We studied 24 rats, divided into three groups with eight individuals each: Group 1 (control), Group 2 (ligation of the hepatic duct combined with internal biliary drainage), and Group 3 (bile duct ligation combined with internal biliary drainage and exclusion of the terminal ileum). Animals in Group 1 (control) underwent sham laparotomy. The animals of groups 2 and 3 underwent ligation and section of the hepatic duct and were kept in cholestasis for four weeks. Next, they underwent an internal biliary bypass. In Group 3, besides the biliary-enteric bypass, we associated the exclusion of the last ten centimeters of the terminal ileum and carried out an ileocolic anastomosis. After four weeks of monitoring, blood was collected from all animals of the three groups for liver and kidney biochemical evaluation (albumin, ALT, AST, direct and indirect bilirubin, alkaline phosphatase, cGT, creatinine and urea).

RESULTS

there were increased values of ALT, AST, direct bilirubin, cGT, creatinine and urea in rats from Group 3 (p < 0.05).

CONCLUSION

ileal exclusion worsened liver and kidney functions in the murine model of extrahepatic cholestasis, being disadvantageous as therapeutic procedure for cholestatic disorders.

Modeling hepatic osteodystrophy in Abcb4 deficient mice

Hepatic osteodystrophy (HOD) denotes the alterations in bone morphology and metabolism frequently observed in patients with chronic liver diseases, in particular in case of cholestatic conditions. The molecular mechanisms underlying HOD are only partially understood. In the present study, we characterized the bone phenotypes of the ATP-binding cassette transporter B4 knockout mouse (Abcb4(-/-)), a well-established mouse model of chronic cholestatic liver disease, with the aim of identifying and characterizing a mouse model for HOD. Furthermore, we investigated the influence of vitamin D on bone quality in this model. The bone morphology analyses revealed reduced bone mineral contents as well as changes in trabecular bone architecture and decreased cortical bone densities in Abcb4(-/-) mice with severe liver fibrosis. We observed dysregulation of genes involved in bone remodeling (osteoprotegerin, osteocalcin, osteopontin) and vitamin D metabolism (7-dehydrocholesterol reductase, Gc-globulin, Cyp2r1, Cyp27a1) as well as alterations in calcium and vitamin D homeostasis. In addition, serum RANKL and TGF-β levels were increased in Abcb4(-/-) mice. Vitamin D dietary intervention did not restore the bone phenotypes of Abcb4(-/-) animals. We conclude that the Abcb4(-/-) mouse provides an experimental framework and a preclinical model to gain further insights into the molecular pathobiology of HOD and to study the systemic effects of therapeutic interventions.

Use and indications of cholestyramine and bile acid sequestrants

Cholestyramine is a bile acid sequestrant, like colestipol and colesevelam. These molecules are positively charged non-digestible resins that bind to bile acids in the intestine to form an insoluble complex, which is excreted in the feces. They are used mainly for the treatment of primary hypercholesterolemia and hypercholesterolemia associated with mild hypertriglyceridemia, in patients not responding to dietary treatment as well as a second line-treatment for pruritus associated with cholestatic disease, in patients with incomplete biliary obstruction. Several data indicate that modulation of bile acid homeostasis has a good clinical effect in managing diabetes mellitus and the diarrhea from bile acid malabsorption. In this review, we present the "in label" use and indication for these compounds, revisiting the other clinical applications that may benefit from the use of bile acid sequestrants in the near future.

Regulatory T cells suppress sickness behaviour development without altering liver injury in cholestatic mice

BACKGROUND & AIMS

Cholestatic liver diseases are commonly accompanied by debilitating symptoms, collectively termed sickness behaviours. Regulatory T cells (T(regs)) can suppress inflammation; however, a role for T(regs) in modulating sickness behaviours has not been evaluated.

METHODS

A mouse model of cholestatic liver injury due to bile duct ligation (BDL) was used to study the role of T(regs) in sickness behaviour development.

RESULTS

BDL mice developed reproducible sickness behaviours, as assessed in a social investigation paradigm, characterized by decreased social investigative behaviour and increased immobility. Depletion of peripheral T(regs) in BDL mice worsened BDL-associated sickness behaviours, whereas infusion of T(regs) improved these behaviours; however, liver injury severity was not altered by T(reg) manipulation. Hepatic IL-6 mRNA and circulating IL-6 levels were elevated in BDL vs. control mice, and were elevated further in T(reg)-depleted BDL mice, but were decreased after infusion of T(regs) in BDL mice. IL-6 knock out (KO) BDL mice exhibited a marked reduction in sickness behaviours, compared to wildtype BDL mice. Furthermore, IL-6 KO BDL mice injected with rmIL-6 displayed sickness behaviours similar to wildtype BDL mice, whereas saline injection did not alter behaviour in IL-6 KO BDL mice. BDL was associated with increased hippocampal cerebral endothelial cell p-STAT3 expression, which was significantly reduced in IL-6 KO BDL mice.

CONCLUSIONS

T(regs) modulate sickness behaviour development in the setting of cholestatic liver injury, driven mainly through T(reg) inhibition of circulating monocyte and hepatic IL-6 production, and subsequent signalling via circulating IL-6 acting at the level of the cerebral endothelium.

Hepatic osteodystrophy: An important matter for consideration in chronic liver disease

Hepatic osteodystrophy (HO) is the generic term defining the group of alterations in bone mineral metabolism found in patients with chronic liver disease. This paper is a global review of HO and its main pathophysiological, epidemiological and therapeutic aspects. Studies examining the most relevant information concerning the prevalence, etiological factors, diagnostic and therapeutic aspects involved in HO were identified by a systematic literature search of the PubMed database. HO generically defines overall alterations in bone mineral density (BMD) (osteoporosis or osteopenia) which appear as a possible complication of chronic liver disease. The origin of HO is multifactorial and its etiology and severity vary in accordance with the underlying liver disease. Its exact prevalence is unknown, but different studies estimate that it could affect from 20% to 50% of patients. The reported mean prevalence of osteoporosis ranges from 13%-60% in chronic cholestasis to 20% in chronic viral hepatitis and 55% in viral cirrhosis. Alcoholic liver disease is not always related to osteopenia. HO has been commonly studied in chronic cholestatic disease (primary biliary cirrhosis and primary sclerosing cholangitis). Several risk factors and pathogenic mechanisms have been associated with the loss of BMD in patients with chronic liver disease. However, little information has been discovered in relationship to most of these mechanisms. Screening for osteopenia and osteoporosis is recommended in advanced chronic liver disease. There is a lack of randomized studies assessing specific management for HO.

Disease-specific autoantibodies in primary biliary cirrhosis

Anti-mitochondrial autoantibodies (AMA) are specific markers of primary biliary liver cirrhosis (PBC), a cholestatic autoimmune disease which is characterised by a progressive destruction of the biliary epithelial cells followed by fibrosis, cirrhosis and liver failure. The prevalence of AMA in PBC is more than 90% and they can precede long before the clinical symptoms. AMA are conventionally detected by indirect immunofluorescence (IIF) using rodent liver, kidney, and stomach sections as substrates. Additionally, different PBC-specific anti-nuclear autoantibodies (ANA) can be observed in 30% of patients presenting with multiple nuclear dot or nuclear membrane staining patterns, which preferentially are identified using HEp-2 cells as substrate. The identification of the major PBC-specific mitochondrial and nuclear targets has allowed the generation of monospecific antigenic targets which are increasingly used in solid-phase assays for routine detection of AMA and ANA in mono- or multiparametric screen test systems. In the present paper, we give an overview of the diagnostic significance of autoantibodies in PBC, discuss the competencies of different techniques used for their determination and propose an effective diagnostic strategy.

Pathophysiology and current management of pruritus in liver disease

Pruritus is frequently reported by patients with cholestatic hepatobiliary diseases such as primary biliary cirrhosis, primary sclerosing cholangitis, intrahepatic cholestasis of pregnancy and hereditary cholestatic syndromes, but may accompany almost any other liver disease. Increased concentrations of bile salts, histamine, progesterone metabolites or endogenous opioids have been controversially discussed as potential pruritogens in cholestasis in the past. Most recently, novel insights unravelled lysophosphatidic acid (LPA), a potent neuronal activator, as a potential pruritogen in pruritus of cholestasis. Nevertheless, the pathogenesis of pruritus in cholestasis is still not clearly defined and current antipruritic treatment strategies provide relief only in a part of the affected patients. Based on recent experimental and clinical findings, this review outlines the actual insight in pathogenesis of pruritus in cholestasis and summarizes evidence-based and experimental therapeutic interventions for cholestatic patients suffering from itch.

Cholestasis and metabolic bone disease - a clinical review

Metabolic bone disease, mainly osteopenia/osteoporosis and occasionally osteomalacia, is a major extrahepatic manifestation of chronic cholestatic liver disease (synonym: hepatic osteodystrophy). Reduced bone mineral density is found in up to 60% and atraumatic fractures in about 20% of patients with chronic liver disease. Hepatic osteodystrophy is characterized by reduced formation and increased resorption of bone; major risk factors are chronic cholestasis and advanced cirrhosis. Pathogenetic mechanisms include genetic factors, abnormalities of calcium, vitamin D, vitamin K and bilirubin metabolism, IGF-1 deficiency, the RANKL/OPG-system, hypogonadism, drugs harmful to bone, lifestyle factors (smoking, alcoholism, immobility), malnutrition and low body mass index. Screening for osteopenia should be performed and reversible risk factors must be corrected. At present, bisphosphonates are the predominantly used specific drugs for the treatment of osteoporosis in chronic liver disease. After orthotopic liver transplantation bone mineral density improves in long-term follow-up. Studies are needed for fracture prevention in chronic liver disease.

Pathogenesis and treatment of pruritus in cholestasis

Pruritus is an enigmatic, seriously disabling symptom accompanying cholestatic liver diseases and a broad range of other disorders. Most recently, novel itch-specific neuronal pathways, itch mediators and their relevant receptors have been identified. In addition, new antipruritic therapeutic strategies have been developed and/or are under evaluation. This review highlights recent experimental and clinical findings focusing on the pathogenesis and actual treatment of pruritus in cholestatic liver disease. Evidence-based therapeutic recommendations, including the use of anion exchange resins cholestyramine, colestipol and colesevelam, the microsomal enzyme inducer rifampicin, the opioid receptor antagonists naltrexone and naloxone, and the serotonin reuptake inhibitor sertraline, are provided.