Progressive familial intrahepatic cholestasis. Genetic basis and treatment

Tetrahydroxylated bile acids improve cholestatic liver and bile duct injury in the Mdr2-/- mouse model of sclerosing cholangitis via immunomodulatory effects

Bile salt export pump (Bsep) (Abcb11)-/- mice are protected from acquired cholestatic injury due to metabolic preconditioning with a hydrophilic bile acid (BA) pool with formation of tetrahydroxylated bile acids (THBAs). We aimed to explore whether loss of Bsep and subsequent elevation of THBA levels may have immunomodulatory effects, thus improving liver injury in the multidrug resistance protein 2 (Mdr2) (Abcb4)-/- mouse. Cholestatic liver injury in Mdr2-/- Bsep-/- double knockout (DKO), Mdr2-/- , Bsep-/- , and wild-type mice was studied for comparison. Mdr2-/- mice were treated with a THBA (3α,6α,7α,12α-Tetrahydroxycholanoic acid). RNA/protein expression of inflammatory/fibrotic markers were investigated. Serum BA-profiling was assessed by ultra-performance liquid chromatography tandem mass spectrometry. Hepatic immune cell profile was quantified by flow cytometric analysis (FACS). In vitro, the THBA effect on chenodeoxycholic acid (CDCA)-induced inflammatory signaling in hepatocyte and cholangiocytes as well as lipopolysaccharide (LPS)/interferon-γ (IFN-γ)-induced macrophage activation was analyzed. In contrast to Mdr2-/- , DKO mice showed no features of sclerosing cholangitis. Sixty-seven percent of serum BAs in DKO mice were polyhydroxylated (mostly THBAs), whereas Mdr2-/- mice did not have these BAs. Compared with Mdr2-/- , DKO animals were protected from hepatic inflammation/fibrosis. THBA feeding in Mdr2-/- mice improved liver injury. FACS analysis in DKO and Mdr2-/- THBA-fed mice showed changes of the hepatic immune cell profile towards an anti-inflammatory pattern. Early growth response 1 (EGR1) protein expression was reduced in DKO and in Mdr2-/- THBA-fed mice compared with Mdr2-/- control mice. In vitro, THBA-reduced CDCA induced EGR1 protein and mRNA expression of inflammatory markers in hepatocytes and cholangiocytes. LPS/IFN-γ-induced macrophage activation was ameliorated by THBA. THBAs repress EGR1-related key pro-inflammatory pathways. Conclusion: THBA and their downstream targets may represent a potential treatment strategy for cholestatic liver diseases.

Novel Gene-Correction-Based Therapeutic Modalities for Monogenic Liver Disorders

The majority of monogenic liver diseases are autosomal recessive disorders, with few being sex-related or co-dominant. Although orthotopic liver transplantation (LT) is currently the sole therapeutic option for end-stage patients, such an invasive surgical approach is severely restricted by the lack of donors and post-transplant complications, mainly associated with life-long immunosuppressive regimens. Therefore, the last decade has witnessed efforts for innovative cellular or gene-based therapeutic strategies. Gene therapy is a promising approach for treatment of many hereditary disorders, such as monogenic inborn errors. The liver is an organ characterized by unique features, making it an attractive target for in vivo and ex vivo gene transfer. The current genetic approaches for hereditary liver diseases are mediated by viral or non-viral vectors, with promising results generated by gene-editing tools, such as CRISPR-Cas9 technology. Despite massive progress in experimental gene-correction technologies, limitations in validated approaches for monogenic liver disorders have encouraged researchers to refine promising gene therapy protocols. Herein, we highlighted the most common monogenetic liver disorders, followed by proposed genetic engineering approaches, offered as promising therapeutic modalities.

Long-Term Outcome after Liver Transplantation for Progressive Familial Intrahepatic Cholestasis

Background and Objectives: Progressive familial intrahepatic cholestasis (PFIC) is a rare autosomal recessive inherited disease divided into five types (PFIC 1-5). Characteristic for all types is early disease onset, which may result clinically in portal hypertension, fibrosis, cirrhosis, hepatocellular carcinoma (HCC), and extrahepatic manifestations. Liver transplantation (LT) is the only successful treatment approach. Our aim is to present the good long-term outcomes after liver transplantation for PFIC1, focusing on liver function as well as the occurrence of extrahepatic manifestation after liver transplantation. Materials and Methods: A total of seven pediatric patients with PFIC1 underwent liver transplantation between January 1999 and September 2019 at the Department of Surgery, Charité Campus Virchow Klinikum and Charité Campus Mitte of Charité-Universitätsmedizin Berlin. Long-term follow-up data were collected on all patients, specifically considering liver function and extrahepatic manifestations. Results: Seven (3.2%) recipients were found from a cohort of 219 pediatric patients. Two of the seven patients had multilocular HCC in cirrhosis. Disease recurrence or graft loss did not occur in any patient. Two patients (male, siblings) had persistently elevated liver parameters but showed excellent liver function. Patient and graft survival during long-term follow-up was 100%, and no severe extrahepatic manifestations requiring hospitalization or surgery occurred. We noted a low complication rate during long-term follow-up and excellent patient outcome. Conclusions: PFIC1 long-term follow-up after LT shows promising results for this rare disease. In particular, the clinical relevance of extrahepatic manifestations seems acceptable, and graft function seems to be barely affected. Further multicenter studies are needed to analyze the clinically inhomogeneous presentation and to better understand the courses after LT.

Allogeneic haematopoietic stem cell transplantation eliminates alloreactive inhibitory antibodies after liver transplantation for bile salt export pump deficiency

Progressive familial intrahepatic cholestasis 2 is an autosomal-recessive disorder caused by mutations in the ABCB11 gene, which encodes the bile salt export pump (BSEP). Recurrence of BSEP deficiency after liver transplantation is caused by the development of anti-BSEP antibodies. Antibody-induced BSEP deficiency is typically treated by increasing immunosuppressive therapy. We report, in a child, the first case of allogeneic haematopoietic stem cell transplantation for antibody-induced BSEP deficiency that was refractory to intensive pharmacological immunosuppression and immunoadsorption. After haematopoietic stem cell transplantation, anti-BSEP antibodies were cleared from the patient's serum and later from the canalicular space of the liver graft.

Spectrum of genomic variations in Indian patients with progressive familial intrahepatic cholestasis

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) is caused by variations in ATP8B1, ABCB11 or ABCB4 genes. Data on genetic variations in Indian patients with PFIC are lacking.

METHODS

Coding and splice regions of the three genes were sequenced in unrelated Indian children with PFIC phenotype. The variations identified were looked for in parents, 30 healthy persons and several variation databases, and their effect was assessed in-silico.

RESULTS

Among 25 children (aged 1-144 months), nine (36%) had unique major genomic variations (ATP8B1: 4, ABCB11: 3 and ABCB4: 2). Seven had homozygous variations, which were assessed as 'pathogenic' or 'likely pathogenic'. These included: (i) four amino acid substitutions (ATP8B1: c.1660G > A/p.Asp554Asn and c.2941G > A/p.Glu981Lys; ABCB11: c.548 T > C/p.Met183Thr; ABCB4: c.431G > A/p.Arg144Gln); (ii) one 3-nucleotide deletion causing an amino acid deletion (ATP8B1: c.1587_1589delCTT/p.Phe529del); (iii) one single-nucleotide deletion leading to frame-shift and premature termination (ABCB11: c.1360delG/p.Val454Ter); and (iv) a complex inversion of 4 nucleotides with a single-nucleotide insertion leading to frame-shift and premature termination (ATP8B1: c.[589_592inv;592_593insA]/p.Gly197LeufsTer10). Two variations were found in heterozygous form: (i) a splice-site variation likely to cause abnormal splicing (ABCB11: c.784 + 1G > C), and (ii) a nucleotide substitution that created a premature stop codon (ABCB4: c.475C > T/p.Arg159Ter); these were considered as variations of uncertain significance. Three of the nine variations were novel.

CONCLUSIONS

Nine major genomic variations, including three novel ones, were identified in nearly one-third  of Indian children with PFIC. No variation was identified in nearly two-thirds of patients, who may have been related to variations in promoter or intronic regions of the three PFIC genes, or in other bile-salt transport genes.

Splicing analysis of rare/novel synonymous or intronic variants identified in ABCB11 heterozygotes presenting as progressive intrahepatic cholestasis with low γ-glutamyltransferase

AIM

The aim of this study was to analyze the pathogenicity of rare/novel synonymous or intronic variants identified in ABCB11 heterozygotes presenting as progressive intrahepatic cholestasis with low γ-glutamyltransferase.

METHODS

The enrolled variants were identified in ABCB11 between October 2009 and June 2016. The effects on pre-RNA splicing were analyzed by in silico tools and minigene splicing assay.

RESULTS

There were three intronic (c.908 + 5G > A, c.2815-8A > G, and c.612-15_-6del10bp) and two synonymous (c.1809G > A, p.K603 K and c.2418C > T, p.G806G) variants with unknown significance identified in ABCB11 of five ABCB11 heterozygotes. Parental studies were carried out for four patients, and revealed that the variants with unknown significance were compound heterozygous with other pathogenic variants. The five variants with unknown significance had minor allele frequency <0.1% or were absent from controls, and had positive prediction results by in silico tools. The effects on pre-RNA splicing were further confirmed by minigene splicing assay. c.908 + 5A caused abnormal splicing in at least 78.5 ± 3.8% of products using a cryptic splice site (ss) 22 nucleotides (nt) upstream of the wild-type (WT) 5'ss. Seven nucleotides of intron 22 upstream of the WT 3'ss was retained for all products from c.2815-8G. c.612-15_-6del caused exon 8 skipping in 24.8 ± 7.7% of products, and 55 nt of exon 8 downstream of the WT 3'ss removal in remaining products. c.1809A led to exon 15 skipping. c.2418 T removed exon 20 and 62 nt of exon 21 downstream of the WT 3'ss by using a cryptic ss.

CONCLUSIONS

We successfully identified five pathogenic synonymous or intronic variants with some common features. These features might help to choose the right variant for further functional assay.

Analysis of surgical interruption of the enterohepatic circulation as a treatment for pediatric cholestasis

To evaluate the efficacy of nontransplant surgery for pediatric cholestasis, 58 clinically diagnosed children, including 20 with Alagille syndrome (ALGS), 16 with familial intrahepatic cholestasis-1 (FIC1), 18 with bile salt export pump (BSEP) disease, and 4 others with low γ-glutamyl transpeptidase disease (levels <100 U/L), were identified across 14 Childhood Liver Disease Research Network (ChiLDReN) centers. Data were collected retrospectively from individuals who collectively had 39 partial external biliary diversions (PEBDs), 11 ileal exclusions (IEs), and seven gallbladder-to-colon (GBC) diversions. Serum total bilirubin decreased after PEBD in FIC1 (8.1 ± 4.0 vs. 2.9 ± 4.1 mg/dL, preoperatively vs. 12-24 months postoperatively, respectively; P = 0.02), but not in ALGS or BSEP. Total serum cholesterol decreased after PEBD in ALGS patients (695 ± 465 vs. 457 ± 319 mg/dL, preoperatively vs. 12-24 months postoperatively, respectively; P = 0.0001). Alanine aminotransferase levels increased in ALGS after PEBD (182 ± 70 vs. 260 ± 73 IU/L, preoperatively vs. 24 months; P = 0.03), but not in FIC1 or BSEP. ALGS, FIC1, and BSEP patients experienced less severely scored pruritus after PEBD (ALGS, 100% vs. 9% severe; FIC1, 64% vs. 10%; BSEP, 50% vs. 20%, preoperatively vs. >24 months postoperatively, respectively; P < 0.001). ALGS patients experienced a trend toward greater freedom from xanthomata after PEBD. There was a trend toward decreased pruritus in FIC1 after IE and GBC. Vitamin K supplementation increased in ALGS after PEBD (33% vs. 77%; P = 0.03). Overall, there were 15 major complications after surgery. Twelve patients (3 ALGS, 3 FIC1, and 6 BSEP) subsequently underwent liver transplantation.

CONCLUSION

This was a multicenter analysis of nontransplant surgical approaches to intrahepatic cholestasis. Approaches vary, are well tolerated, and generally, although not uniformly, result in improvement of pruritus and cholestasis. (Hepatology 2017;65:1645-1654).

Intrahepatic cholestasis in two omani siblings associated with a novel homozygous ATP8B1 mutation, c.379C>G (p.L127V)

We report two Omani brothers with intrahepatic cholestasis that resolved with supportive care. In one, cholestasis began in infancy; in the other, only at the age of 18 months. Whole exome sequencing identified a novel homozygous variant, c.379C>G (p.L127V) in ATP8B1. Those attending patients with cholestasis from the Arabian peninsula should be aware of this mutation and of the variation in its phenotypic effects.

MYO5B mutations cause cholestasis with normal serum gamma-glutamyl transferase activity in children without microvillous inclusion disease

Some patients with microvillus inclusion disease due to myosin 5B (MYO5B) mutations may develop cholestasis characterized by a progressive familial intrahepatic cholestasis-like phenotype with normal serum gamma-glutamyl transferase activity. So far MYO5B deficiency has not been reported in patients with such a cholestasis phenotype in the absence of intestinal disease. Using a new-generation sequencing approach, we identified MYO5B mutations in five patients with progressive familial intrahepatic cholestasis-like phenotype with normal serum gamma-glutamyl transferase activity without intestinal disease.

CONCLUSION

These data show that MYO5B deficiency may lead to isolated cholestasis and that MYO5B should be considered as an additional progressive familial intrahepatic cholestasis gene. (Hepatology 2017;65:164-173).

Coupling between ATP hydrolysis and protein conformational change in maltose transporter

As the intracellular part of maltose transporter, MalK dimer utilizes the energy of ATP hydrolysis to drive protein conformational change, which then facilitates substrate transport. Free energy evaluation of the complete conformational change before and after ATP hydrolysis is helpful to elucidate the mechanism of chemical-to-mechanical energy conversion in MalK dimer, but is lacking in previous studies. In this work, we used molecular dynamics simulations to investigate the structural transition of MalK dimer among closed, semi-open and open states. We observed spontaneous structural transition from closed to open state in the ADP-bound system and partial closure of MalK dimer from the semi-open state in the ATP-bound system. Subsequently, we calculated the reaction pathways connecting the closed and open states for the ATP- and ADP-bound systems and evaluated the free energy profiles along the paths. Our results suggested that the closed state is stable in the presence of ATP but is markedly destabilized when ATP is hydrolyzed to ADP, which thus explains the coupling between ATP hydrolysis and protein conformational change of MalK dimer in thermodynamics. Proteins 2017; 85:207-220. © 2016 Wiley Periodicals, Inc.

Inhibition of intestinal bile acid absorption improves cholestatic liver and bile duct injury in a mouse model of sclerosing cholangitis

BACKGROUND AND AIMS

Approximately 95% of bile acids (BAs) excreted into bile are reabsorbed in the gut and circulate back to the liver for further biliary secretion. Therefore, pharmacological inhibition of the ileal apical sodium-dependent BA transporter (ASBT/SLC10A2) may protect against BA-mediated cholestatic liver and bile duct injury.

METHODS

Eight week old Mdr2(-/-) (Abcb4(-/-)) mice (model of cholestatic liver injury and sclerosing cholangitis) received either a diet supplemented with A4250 (0.01% w/w) - a highly potent and selective ASBT inhibitor - or a chow diet. Liver injury was assessed biochemically and histologically after 4weeks of A4250 treatment. Expression profiles of genes involved in BA homeostasis, inflammation and fibrosis were assessed via RT-PCR from liver and ileum homogenates. Intestinal inflammation was assessed by RNA expression profiling and immunohistochemistry. Bile flow and composition, as well as biliary and fecal BA profiles were analyzed after 1week of ASBT inhibitor feeding.

RESULTS

A4250 improved sclerosing cholangitis in Mdr2(-/-) mice and significantly reduced serum alanine aminotransferase, alkaline phosphatase and BAs levels, hepatic expression of pro-inflammatory (Tnf-α, Vcam1, Mcp-1) and pro-fibrogenic (Col1a1, Col1a2) genes and bile duct proliferation (mRNA and immunohistochemistry for cytokeratin 19 (CK19)). Furthermore, A4250 significantly reduced bile flow and biliary BA output, which correlated with reduced Bsep transcription, while Ntcp and Cyp7a1 were induced. Importantly A4250 significantly reduced biliary BA secretion but preserved HCO3(-) and biliary phospholipid secretion resulting in an increased HCO3(-)/BA and PL/BA ratio. In addition, A4250 profoundly increased fecal BA excretion without causing diarrhea and altered BA pool composition, resulting in diminished concentrations of primary BAs tauro-β-muricholic acid and taurocholic acid.

CONCLUSIONS

Pharmacological ASBT inhibition attenuates cholestatic liver and bile duct injury by reducing biliary BA concentrations in mice.

Autoimmune BSEP disease: disease recurrence after liver transplantation for progressive familial intrahepatic cholestasis

Severe cholestasis may result in end-stage liver disease with the need of liver transplantation (LTX). In children, about 10 % of LTX are necessary because of cholestatic liver diseases. Apart from bile duct atresia, three types of progressive familial intrahepatic cholestasis (PFIC) are common causes of severe cholestasis in children. The three subtypes of PFIC are defined by the involved genes: PFIC-1, PFIC-2, and PFIC-3 are due to mutations of P-type ATPase ATP8B1 (familial intrahepatic cholestasis 1, FIC1), the ATP binding cassette transporter ABCB11 (bile salt export pump, BSEP), or ABCB4 (multidrug resistance protein 3, MDR3), respectively. All transporters are localized in the canalicular membrane of hepatocytes and together mediate bile salt and phospholipid transport. In some patients with PFIC-2 disease, recurrence has been observed after LTX, which mimics a PFIC phenotype. It could be shown by several groups that inhibitory anti-BSEP antibodies emerge, which most likely cause disease recurrence. The prevalence of severe BSEP mutations (e.g., splice site and premature stop codon mutations) is very high in this group of patients. These mutations often result in the complete absence of BSEP, which likely accounts for an insufficient auto-tolerance against BSEP. Although many aspects of this "new" disease are not fully elucidated, the possibility of anti-BSEP antibody formation has implications for the pre- and posttransplant management of PFIC-2 patients. This review will summarize the current knowledge including diagnosis, pathomechanisms, and management of "autoimmune BSEP disease."

Presentation of Progressive Familial Intrahepatic Cholestasis Type 3 Mimicking Wilson Disease: Molecular Genetic Diagnosis and Response to Treatment

Progressive familial intrahepatic cholestasis type 3 (PFIC3) is an autosomal recessive disorder of cholestasis of hepatocellular origin, typically seen in infancy or childhood caused by a defect in the ABCB4 located on chromosome 7. Here we report on an older patient, aged 15, who presented with biochemical testing that led to an initial consideration of a diagnosis of Wilson disease (WD) resulting in a delayed diagnosis of PFIC3. Diagnosis of PFIC3 was later confirmed by molecular studies that identified novel mutations in the ABCB4 gene. Cholestasis due to PFIC3 can cause elevated hepatic copper and increased urine copper excretion that overlap with current diagnostic criteria for WD. Molecular diagnostics are very useful for establishing the diagnosis of PFIC3. Ursodeoxycholic acid ameliorates cholestasis in PFIC3, and may help mediate a reduction in hepatic copper content in response to treatment.

Bile acid pool dynamics in progressive familial intrahepatic cholestasis with partial external bile diversion

OBJECTIVES

Partial external bile diversion (PEBD) is an established therapy for low-γ-glutamyl transferase (GGT) progressive familial intrahepatic cholestasis (PFIC). This study sought to determine whether the dynamics of the cholic acid (CA) and chenodeoxycholic acid (CDCA) pools in subjects with low-GGT-PFIC with successful PEBD were equivalent to those achieved with successful liver transplantation (LTX).

METHODS

The kinetics of CA and CDCA metabolism were measured by stable isotope dilution in plasma samples in 5 subjects with PEBD, all with intact canalicular bile salt export pump expression and compared with subjects with low-GGT-PFIC with successful LTX. Stomal loss of bile acids was measured in subjects with PEBD.

RESULTS

The fractional turnover rate for CA in the PEBD group ranged from 0.5 to 4.2/day (LTX group, range 0.2-0.9/day, P = 0.076) and for CDCA from 0.7 to 4.5/day (LTX group 0.3-0.4/day, P = 0.009). The CA and CDCA pool sizes were equivalent between groups; however, pool composition in PEBD was somewhat more hydrophilic. The CA/CDCA ratio in PEBD ranged from 0.9 to 19.5, whereas in LTX it ranged from 0.5 to 2.6. Synthesis rates computed from isotope dilution correlated well with timed output for both CA (r2 = 0.760, P = 0.024) and CDCA (r2 = 0.690, P = 0.021).

CONCLUSIONS

PEBD results in bile acid fractional turnover rates greater than LTX, pool sizes equivalent to LTX, and pool composition that is at least as hydrophilic as produced by LTX.

Laparoscopic cholecystocolostomy: a novel surgical approach for the treatment of progressive familial intrahepatic cholestasis

OBJECTIVE

Conventionally, liver transplantation, ileoileal bypass, and partial external or internal biliary diversion are used in the treatment of progressive familial intrahepatic cholestasis (PFIC). However, postoperative recurrence, chronic diarrhea, and permanent stoma are the major concerns. We present a novel approach of laparoscopic cholecystocolostomy with antireflux Y-loop for the management of children with PFIC.

METHODS

Between August 2003 and April 2011, 20 children with PFIC (median age: 1.47 years; range: 10.8 months to 5.11 years) successfully underwent laparoscopic cholecystocolostomies for bile diversions. Gallbladder was incised longitudinally for cholecystocolostomy. Transverse colon was divided proximal to splenic flexure. End-to-side anastomosis was established between distal transverse colon and mid-descending colon. The mobilized splenic flexure and proximal descending colon, that is, the stem of the Y-loop, was anastomosed to the gallbladder.

RESULTS

The mean operative time was 2.02 ± 0.18 hours (range: 2-2.5 hours). The mean postoperative hospital stay was 8 days (range: 5-10 days). Average time for full resumption of diet was 3 days (range: 2-4 days). Average Y-loop length was 17.65 cm (range: 15-20 cm). The median follow-up period was 54 months (range: 12-104 months). All patients were jaundice free after 7 to 20 days and pruritus subsided in 3 to 14 days. Liver function parameters significantly improved postoperatively. Success rate (normalization of serum bile acids at postoperative 12 months) was 85%. No mortality or morbidities associated with diarrhea, cholangitis, or intrahepatic reflux were observed.

CONCLUSIONS

The novel approach of laparoscopic cholecystocolostomy offers a safe and effective treatment option for PFIC in children with good success rates and minimal morbidity.

Multidrug resistance and cancer stem cells in neuroblastoma and hepatoblastoma

Chemotherapy is one of the major modalities in treating cancers. However, its effectiveness is limited by the acquisition of multidrug resistance (MDR). Several mechanisms could explain the up-regulation of MDR genes/proteins in cancer after chemotherapy. It is known that cancer stem cells (CSCs) play a role as master regulators. Therefore, understanding the mechanisms that regulate some traits of CSCs may help design efficient strategies to overcome chemoresistance. Different CSC phenotypes have been identified, including those found in some pediatric malignancies. As solid tumors in children significantly differ from those observed in adults, this review aims at providing an overview of the mechanistic relationship between MDR and CSCs in common solid tumors, and, in particular, focuses on clinical as well as experimental evidence of the relations between CSCs and MDR in neuroblastoma and hepatoblastoma. Finally, some novel approaches, such as concomitant targeting of multiple key transcription factors governing the stemness of CSCs, as well as nanoparticle-based approaches will also be briefly addressed.

FXR and PXR: potential therapeutic targets in cholestasis

Cholestatic liver disorders encompass hepatobiliary diseases of diverse etiologies characterized by the accumulation of bile acids, bilirubin and cholesterol as the result of impaired secretion of bile. Members of the nuclear receptor (NR) family of ligand-modulated transcription factors are implicated in the adaptive response to cholestasis. NRs coordinately regulate bile acid and phospholipid transporter genes required for hepatobiliary transport, as well as the phases I and II metabolizing enzymes involved in processing of their substrates. In this review we will focus on FXR and PXR, two members of the NR family whose activities are regulated by bile acids. In addition, we also discuss the potential of pharmacological modulators of these receptors as novel therapies for cholestatic disorders.

Inter-domain communication mechanisms in an ABC importer: a molecular dynamics study of the MalFGK2E complex

ATP-Binding Cassette transporters are ubiquitous membrane proteins that convert the energy from ATP-binding and hydrolysis into conformational changes of the transmembrane region to allow the translocation of substrates against their concentration gradient. Despite the large amount of structural and biochemical data available for this family, it is still not clear how the energy obtained from ATP hydrolysis in the ATPase domains is “transmitted” to the transmembrane domains. In this work, we focus our attention on the consequences of hydrolysis and inorganic phosphate exit in the maltose uptake system (MalFGK₂E) from Escherichia coli. The prime goal is to identify and map the structural changes occurring during an ATP-hydrolytic cycle. For that, we use extensive molecular dynamics simulations to study three potential intermediate states (with 10 replicates each): an ATP-bound, an ADP plus inorganic phosphate-bound and an ADP-bound state. Our results show that the residues presenting major rearrangements are located in the A-loop, in the helical sub-domain, and in the “EAA motif” (especially in the “coupling helices” region). Additionally, in one of the simulations with ADP we were able to observe the opening of the NBD dimer accompanied by the dissociation of ADP from the ABC signature motif, but not from its corresponding P-loop motif. This work, together with several other MD studies, suggests a common communication mechanism both for importers and exporters, in which ATP-hydrolysis induces conformational changes in the helical sub-domain region, in turn transferred to the transmembrane domains via the “coupling helices”.

ABC transporters are membrane proteins that couple ATP binding and hydrolysis with the active transport of substrates across membranes. These transporters form one of the largest families of membrane proteins and they can be found in all phyla of life. Moreover, some members of this family are involved in several genetic diseases (such as cystic fibrosis) and in multidrug resistance in bacteria, fungi and mammals. In this work, we use molecular dynamics simulations to study conformational changes due to ATP hydrolysis in an ABC transporter responsible for maltose uptake in E. coli. These conformational changes arising from one side of the protein (NBDs – Nucleotide Binding domains) where ATP binds, are propagated across the protein to more distant regions. Additionally, we can observe an NBD dimer interface dissociation event upon inorganic phosphate exit. These simulations together with other theoretical studies suggest that there is a general inter-domain communication mechanism common to importers and exporters.

The Multiple Facets of ABCB4 (MDR3) Deficiency

ABCB4 (MDR3), a lipid translocator, moves phosphatidylcholine from the inner to the outer leaflet of the canalicular membrane. Genetic mutations of ABCB4 lead to three distinct but related hepatobiliary diseases. Progressive familial intrahepatic cholestasis (PFIC) type 3 is a chronic cholestatic syndrome characterized by a markedly elevated gamma-glutamyltranspeptidase. Patients present with jaundice, pruritus, and hepatosplenomegaly. Periportal inflammation progresses to biliary cirrhosis and causes portal hypertension. Ursodeoxycholic acid (UDCA) normalizes liver function tests in approximately one half of treated PFIC type 3 patients. Partial responders or nonresponders eventually will require liver transplantation. Gallstone patients with ABCB4 mutations may have low phospholipid-associated cholelithiasis syndrome, characterized by cholesterol gallstones and intrahepatic microlithiasis, along with recurrent biliary symptoms, despite cholecystectomy. Patients with ABCB4 mutations also may develop intrahepatic brown pigment stones. UDCA may improve biliary symptoms even before the dissolution of stones occurs. Additional therapies such as farnesoid X receptor ligands/agonists and benzfibrates show future therapeutic promise. Intrahepatic cholestasis of pregnancy affects pregnant women with abnormal ABCB4. These women suffer from disabling pruritus and also may experience steatorrhea. Fetuses are at high risk for prematurity and stillbirths. The definitive treatment is delivery of the baby. In the interim, limited fat intake, fat-soluble vitamin supplementation, and UDCA with or without S-adenosylmethionine can provide symptomatic relief. Additional hepatobiliary diseases related to ABCB4 mutations are likely to be identified. This may result in the discovery of additional therapies for PFIC type 3, gallstones, and intrahepatic cholestasis of pregnancy.

Living-donor liver transplantation for progressive familial intrahepatic cholestasis

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) results in liver cirrhosis during the disease course, although the etiology includes unknown mechanisms. Some PFIC patients require liver transplantation (LT).

METHODS

In this study, 11 patients with PFIC type 1 (PFIC1) and 3 patients with PFIC type 2 (PFIC2) who underwent living-donor LT (LDLT) were evaluated.

RESULTS

Digestive symptoms after LDLT were confirmed in 10 PFIC1 recipients (90.9%); 8 PFIC1 recipients showed steatosis after LDLT (72.7%), which began during the early postoperative period (71.5±55.1 days). Seven of the eight steatosis-positive PFIC1 recipients (87.5%) showed a steatosis degree of ≥80%, which was complicated with steatohepatitis and resulted in fibrosis. Cirrhotic findings persisted in six PFIC1 recipients even after LDLT (54.5%), and three PFIC1 recipients finally died. The survival rates of the PFIC1 recipients at 5, 10, and 15 years were 90.9%, 72.7%, and 54.5%, respectively. In contrast, the PFIC2 recipients showed good courses and outcomes without any steatosis after LDLT.

CONCLUSIONS

The clinical courses and outcomes after LDLT are still not sufficient in PFIC1 recipients owing to steatosis/steatohepatitis and subsequent fibrosis, in contrast to PFIC2 recipients. PFIC2 is good indication for LDLT. PFIC1 patients require LT during the disease course; therefore, we suggest that the therapeutic strategies for PFIC1 patients, including the timing of LDLT, under the donor limitation should be reconsidered. The establishment of more advanced treatments for PFIC1 patients is required to improve the long-term prognosis of these patients.

Progressive familial intrahepatic cholestasis: a single-center experience of living-donor liver transplantation during two decades in Japan

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) results in liver cirrhosis. Therefore, some PFIC patients require liver transplantation (LT). Although three types of PFIC have been identified, their etiologies include unknown mechanisms.

PATIENTS

A total of 717 recipients who underwent living-donor LT (LDLT) at <20 yr old were enrolled in this study. Among these recipients, 14 PFIC recipients comprising 11 PFIC type 1 (PFIC1) and three PFIC type 2 (PFIC2) were evaluated.

RESULTS

Three of 11 PFIC1 recipients died, while all three PFIC2 recipients survived. Eight of 11 PFIC1 recipients showed steatosis after LDLT. Among the eight steatosis-positive PFIC1 recipients, seven showed severe steatosis and seven were complicated with steatohepatitis. Nine of 11 PFIC1 recipients showed fibrosis after LDLT, and eight of the nine fibrosis-positive PFIC1 recipients showed severe fibrosis. In contrast to the PFIC1 recipients, the PFIC2 recipients did not show any steatosis or fibrosis after LDLT.

CONCLUSIONS

The clinical courses and outcomes of PFIC1 recipients after LDLT are still not sufficient owing to steatosis/fibrosis, unlike the case for PFIC2 recipients. As PFIC1 patients will require LT during the long-term progression of the disease, further strategy improvements are required for PFIC1 patients.

Biopsy Diagnosis of Inherited Liver Disease

Hepatic dysfunction during childhood can be due to acquired or inherited etiologies or a combination. The distinction can be difficult to make on liver biopsy, because the inherited disorders are rare and often lack pathognomonic light microscopic features. Recent progress in understanding the pathogenesis of these disorders has led to advances in molecular genetic screening and confirmatory tests. For a majority of these disorders, the liver biopsy continues to play a crucial role in primary diagnosis or confirmation. This article discusses algorithms that may aid pathologists in differential diagnosis of common inherited disorders of the liver, with emphasis on ancillary diagnostic tools and reference assays that are critical in establishing the diagnosis.

New molecular insights into the mechanisms of cholestasis

Recent progress in basic research has enhanced our understanding of the molecular mechanisms of normal bile secretion and their alterations in cholestasis. Genetic transporter variants contribute to an entire spectrum of cholestatic liver diseases and can cause hereditary cholestatic syndromes or determine susceptibility and disease progression in acquired cholestatic disorders. Cholestasis is associated with complex transcriptional and post-transcriptional alterations of hepatobiliary transporters and enzymes participating in bile formation. Ligand-activated nuclear receptors for bile acids and other biliary compounds play a key role in the regulation of genes required for bile formation. Pharmacological interventions in cholestasis may aim at modulating such novel regulatory pathways. This review will summarize the principles of molecular alterations in cholestasis and will give an overview of potential clinical implications.

Compensatory role of P-glycoproteins in knockout mice lacking the bile salt export pump

Bile salt export pump (BSEP; ATP-binding cassette, subfamily B, member 11) mutations in humans result in progressive familial intrahepatic cholestasis type 2, a fatal liver disease with greatly reduced bile flow. However in mice, Bsep knockout leads only to mild cholestasis with substantial bile flow and up-regulated P-glycoprotein genes (multidrug resistance protein 1a [Mdr1a] and Mdr1b). To determine whether P-glycoprotein is responsible for the relatively mild phenotype observed in Bsep knockout mice, we have crossed mouse strains knocked out for Bsep and the two P-glycoprotein genes and generated a triple knockout mouse. We found that a knockout of the three genes leads to a significantly more severe phenotype with impaired bile formation, jaundice, flaccid gallbladder, and increased mortality. The triple knockout mouse is the most severe genetic model of intrahepatic cholestasis yet developed.

CONCLUSION

P-glycoprotein functions as a critical compensatory mechanism, which reduces the severity of cholestasis in Bsep knockout mice.

Nontransplant surgical interventions in progressive familial intrahepatic cholestasis

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) is a family of rare childhood diseases that was universally fatal until the development of liver transplant. In the last 20 years, the use of nontransplant surgery to treat PFIC has become the standard of care. There are various surgical techniques that have been performed. There are no reviews evaluating the outcome of these operations.

METHODS

A systematic search of the literature for articles evaluating the outcome of nontransplant surgical interventions in PFIC patients was performed. Data from these studies was abstracted and summarized.

RESULTS

No trials have been performed addressing nontransplant surgical interventions in PFIC patients. We analyzed 11 case series and case reports. Generally, patients had successful outcomes (81%) with cessation of progression of disease and resolution of symptoms. Treatment failures were often associated with more advanced disease.

DISCUSSION

There is no evidence to demonstrate a superiority of one type of nontransplant surgical intervention in PFIC patients. We propose the development of a registry and standardization of outcomes measurements to allow improved comparison of results.

A missense mutation in ABCB4 gene involved in progressive familial intrahepatic cholestasis type 3 leads to a folding defect that can be rescued by low temperature

Progressive familial intrahepatic cholestasis type 3 (PFIC3) is a rare liver disease characterized by early onset of cholestasis that leads to cirrhosis and liver failure before adulthood. PFIC3 may be improved by chronic administration of ursodeoxycholic acid, although in many cases liver transplantation is the only therapy. The disease is caused by mutations of the adenosine triphosphate (ATP)-binding cassette, sub-family B, member 4 (ABCB4) [multidrug resistance 3 (MDR3)] gene encoding a specific hepatocellular canalicular transporter involved in biliary phosphatidylcholine secretion. Several mutations have been reported; however, the effect of individual mutations has not been investigated. ABCB4 is highly homologous to ATP-binding cassette, sub-family B, member 1 (ABCB1) (MDR1), the multidrug transporter responsible for drug resistance of cancer cells. We have studied the effect of mutation I541F localized to the first nucleotide-binding domain, which is highly conserved between ABCB4 and ABCB1. Plasmids encoding the wild-type human ABCB4 or rat ABCB1-green fluorescing protein (GFP) construct, and corresponding I541F-mutants, were expressed in hepatocellular carcinoma, human (HepG2) and Madin-Darby canine kidney (MDCK) cells. Expression studies showed that ABCB4 was localized at the bile canalicular membrane in HepG2 cells and at the apical surface in MDCK cells, whereas the I541F mutant was intracellular. In MDCK cells, ABCB1-I541F also accumulated intracellularly in compartments, which were identified as the endoplasmic reticulum and cis-Golgi, and remained partially endoH-sensitive. After shifting cells to 27 degrees C, ABCB1-I541F was expressed at the apical cell surface in a mature and active form. Similarly, ABCB4 was significantly trafficked to the membrane of bile canaliculi in HepG2 cells.

CONCLUSION

Mutation I541F causes mislocalization of both ABCB4 and ABCB1. Intracellular retention of ABCB4-I541F can explain the disease in PFIC3 patients bearing this mutation. The observation that plasma membrane expression and activity can be rescued by low temperature opens perspectives to develop novel therapies for the treatment of PFIC3.

Progressive familial intrahepatic cholestasis

Progressive familial intrahepatic cholestasis (PFIC) refers to heterogeneous group of autosomal recessive disorders of childhood that disrupt bile formation and present with cholestasis of hepatocellular origin. The exact prevalence remains unknown, but the estimated incidence varies between 1/50,000 and 1/100,000 births.

Three types of PFIC have been identified and related to mutations in hepatocellular transport system genes involved in bile formation. PFIC1 and PFIC2 usually appear in the first months of life, whereas onset of PFIC3 may also occur later in infancy, in childhood or even during young adulthood. Main clinical manifestations include cholestasis, pruritus and jaundice. PFIC patients usually develop fibrosis and end-stage liver disease before adulthood. Serum gamma-glutamyltransferase (GGT) activity is normal in PFIC1 and PFIC2 patients, but is elevated in PFIC3 patients. Both PFIC1 and PFIC2 are caused by impaired bile salt secretion due respectively to defects in ATP8B1 encoding the FIC1 protein, and in ABCB11 encoding the bile salt export pump protein (BSEP). Defects in ABCB4, encoding the multi-drug resistant 3 protein (MDR3), impair biliary phospholipid secretion resulting in PFIC3.

Diagnosis is based on clinical manifestations, liver ultrasonography, cholangiography and liver histology, as well as on specific tests for excluding other causes of childhood cholestasis. MDR3 and BSEP liver immunostaining, and analysis of biliary lipid composition should help to select PFIC candidates in whom genotyping could be proposed to confirm the diagnosis. Antenatal diagnosis can be proposed for affected families in which a mutation has been identified. Ursodeoxycholic acid (UDCA) therapy should be initiated in all patients to prevent liver damage. In some PFIC1 or PFIC2 patients, biliary diversion can also relieve pruritus and slow disease progression. However, most PFIC patients are ultimately candidates for liver transplantation. Monitoring of hepatocellular carcinoma, especially in PFIC2 patients, should be offered from the first year of life. Hepatocyte transplantation, gene therapy or specific targeted pharmacotherapy may represent alternative treatments in the future.

Partial external biliary diversion for the treatment of intractable pruritus in children with progressive familial intrahepatic cholestasis: report of two cases

Progressive familial intrahepatic cholestasis (PFIC) is a cholestatic liver disease of childhood. Pruritus secondary to increased bile salts in the serum may not respond to medical treatment. Partial external biliary diversion (PEBD), which reduces the serum bile salt level in the enterohepatic cycle, is used in the treatment of this symptom. In this study, our experience in performing this technique and the early promising results of PEBD in two children with PFIC are reported along with a review of the current literature. Partial external biliary diversion was performed by interposing a 15-cm jejunum between the gallbladder and abdominal wall. Biliary drainage through a stoma began in the fi rst postoperative day and reached 120-200 ml/day. Pruritus improved and then stopped on the 15th postoperative day, while the serum bile acid concentration also decreased. Partial external biliary diversion by jejunal interposition provides an excellent control of pruritus in children with PFIC with no adverse effects. A cholecystectomy should therefore be avoided in patients with PFIC.

Update on the treatment of the pruritus of cholestasis

The pruritus of cholestasis is a difficult clinical problem to manage. It can be severe and interfere with sleep. Clinical behavioral studies have confirmed that the pruritus is mediated at least in part by endogenous opioids. Other neurotransmitter systems may be involved in the mediation of pruritus. Work continues to identify the mechanisms that mediate the pruritus and to develop specific drugs to treat this often maddening symptom.

[Cholestasis-associated hepatopathies in neonates and infants]

Cholestasis in neonates and infants frequently confronts pediatricians and pathologists with diagnostic problems. A specific feature of the liver in neonates is the ability to react to different causative factors with a non-specific hepatitis-like picture, the so-called neonatal hepatitis. A diagnostic discrimination of the various diseases is histologically only possible with close attention to typical morphologic features. Thus, extrahepatic biliary obstructions, such as atresia or stenosis of the hepatic duct or choledochal cysts present with portal bile duct proliferation and signs of bile retention in the neoducts. In Alagille syndrome (arteriohepatic dysplasia), however, paucity of intrahepatic bile ducts is an important diagnostic feature. Metabolic disorders, such as fructosemia and galactosemia are additionally associated with steatosis. Knowledge of the clinical course and laboratory and imaging data are necessary to make the definitive diagnosis in synopsis with the morphologic findings and requires a close co-operation between the pediatrician and the pathologist.

Liver transplantation in children with progressive familial intrahepatic cholestasis

Progressive familial intrahepatic cholestasis (PFIC) is caused by mutations of the bile salt export pump or the multidrug resistance P-glycoprotein, resulting in chronic hepatic failure. Partial external diversion of bile or ileal bypass is effective in some cases and, in others, liver transplantation (OLT) is necessary. Forty-two children were included in this study. Twenty-six children suffered from PFIC type 2 and 16 from PFIC type 3. Symptoms included pruritus, cholestasis, liver cirrhosis, and growth retardation. Seventeen patients received external biliary diversion. Ten had to undergo OLT in the following course. As of this report, three of the remaining patients were on the wait list for OLT. Twenty-three children received a liver graft primarily with excellent outcome. Our data show that OLT is the option of choice in symptomatic PFIC and whenever liver cirrhosis is present. We suggest a very restrictive recommendation of external biliary diversion. However, gene therapy may be a future option for children with PFIC.

Partial internal biliary diversion through a cholecystojejunocolonic anastomosis--a novel surgical approach for patients with progressive familial intrahepatic cholestasis: a preliminary report

BACKGROUND/PURPOSE

The purpose of the study was to describe the initial experience with a novel approach to the surgical treatment of progressive familial intrahepatic cholestasis (PFIC), avoiding the creation of a permanent stoma.

METHODS

Two teenaged patients, aged 15 and 17 years, underwent partial internal biliary diversion to treat uncontrollable pruritus associated with PFIC. The surgical technique involved the creation of an isolated jejunal conduit, anastomosed proximally in a terminolateral fashion to the gallbladder and distally to the ascending colon. This operation combines the advantages of partially diverting the biliary flow from the enterohepatic cycle, avoiding an external biliary fistula. In one of the patients, this technique was used as a primary procedure, whereas in the other, a previous partial external diversion was converted to an internal diversion.

RESULTS

Both patients had complete resolution of their pruritus and normalization of hepatic laboratory tests. One of the patients developed a mild choleretic diarrhea that can be controlled with eventual use of cholestyramine. No complications were observed related to this operation.

CONCLUSIONS

Biliary diversion appears to be a very attractive surgical option for the treatment of PFIC in children with a normal gallbladder. Long-term follow-up is necessary to evaluate late results and eventual complications of this approach.

Structure and function of ABC transporters

ATP binding cassette transporters are ubiquitous integral membrane proteins that actively transport ligands across biological membranes, a process critical for most aspects of cell physiology. These proteins are important clinically and economically. Their dysfunction underlies a number of human genetic diseases, and the ability of some to pump cytotoxic molecules from cells confers resistance to antibiotics, herbicides, and chemotherapeutic drugs. Recent structure analyses interpreted in light of a large body of biochemistry has resulted in the ATP-switch model for function in which the paired nucleotide binding domains switch between an ATP-dependent closed conformation and a nucleotide-free, open conformation to drive the translocation of ligand.

[Treatment of cholestatic hepatic diseases: more than the substitution of fat soluble vitamins?]

The clinical-biochemical syndrome of cholestasis is characterized by an alteration in bile constituents. As a consequence, the concentrations of bilirubin, bile acids, phospholipids and cholesterol are elevated. The main clinical symptoms of cholestasis are icterus and pruritus, and in severe cases xanthelasma and xanthoma. Primary intrahepatic cholestasis, caused by impaired bile secretion in the liver, should be separated from the extrahepatic secondary cholestasis which is a consequence of a biliary obstruction. This paper evaluates the therapy of liver diseases which developed as consequence of a primary disturbance in bile secretion.

Genetics of familial intrahepatic cholestasis syndromes

Bile acids and bile salts have essential functions in the liver and in the small intestine. Their synthesis in the liver provides a metabolic pathway for the catabolism of cholesterol and their detergent properties promote the solubilisation of essential nutrients and vitamins in the small intestine. Inherited conditions that prevent the synthesis of bile acids or their excretion cause cholestasis, or impaired bile flow. These disorders generally lead to severe human liver disease, underscoring the essential role of bile acids in metabolism. Recent advances in the elucidation of gene defects underlying familial cholestasis syndromes has greatly increased knowledge about the process of bile flow. The expression of key proteins involved in bile flow is tightly regulated by transcription factors of the nuclear hormone receptor family, which function as sensors of bile acids and cholesterol. Here we review the genetics of familial cholestasis disorders, the functions of the affected genes in bile flow, and their regulation by bile acids and cholesterol.

Altered hepatobiliary gene expressions in PFIC1: ATP8B1 gene defect is associated with CFTR downregulation

Recent reports in patients with PFIC1 have indicated that a gene defect in ATP8B1 could cause deregulations in bile salt transporters through decreased expression and/or activity of FXR. This study aimed to: (1) define ATP8B1 expression in human hepatobiliary cell types, and (2) determine whether ATP8B1 defect affects gene expressions related to bile secretion in these cells. ATP8B1 expression was detected by RT-PCR in hepatocytes and cholangiocytes isolated from normal human liver and gallbladder. ATP8B1 mRNA levels were 20- and 200-fold higher in bile duct and gallbladder epithelial cells, respectively, than in hepatocytes. RT-PCR analyses of the liver from two patients with PFIC1, one with PFIC2, one with biliary atresia, showed that, compared to normal liver, hepatic expressions of FXR, SHP, CYP7A1, ASBT were decreased at least by 90% in all cholestatic disorders. In contrast, NTCP transcripts were less decreased (by < or = 30% vs. 97%) in PFIC1 as compared with other cholestatic disorders, while BSEP transcripts, in agreement with BSEP immunohistochemical signals, were normal or less decreased (by 50% vs. 97%). CFTR hepatic expression was decreased (by 80%), exclusively in PFIC1, while bile duct mass was not reduced, as ascertained by cytokeratin-19 immunolabeling. In Mz-ChA-2 human biliary epithelial cells, a significant decrease in CFTR expression was associated with ATP8B1 invalidation by siRNA. In conclusion, cholangiocytes are a major site ofATP8B1 hepatobiliary expression. A defect of ATP8B1 along with CFTR downregulation can impair the contribution of these cells to bile secretion, and potentially explain the extrahepatic cystic fibrosis-like manifestations that occur in PFIC1.

24-norUrsodeoxycholic acid is superior to ursodeoxycholic acid in the treatment of sclerosing cholangitis in Mdr2 (Abcb4) knockout mice

BACKGROUND & AIMS

Current therapy for primary sclerosing cholangitis is of limited efficacy. Multidrug resistance gene 2 knockout mice (Mdr2(-/-)) represent a well-characterized model for sclerosing cholangitis. Experiments were performed to test in such mice the therapeutic effects of 24-norUrsodeoxycholic acid, a C(23) homologue of ursodeoxycholic acid with 1 fewer methylene group in its side chain.

METHODS

Mdr2(-/-) mice were fed a diet containing 24-norUrsodeoxycholic acid (0.5% wt/wt) or ursodeoxycholic acid (0.5% wt/wt) as a clinical comparator for 4 weeks; controls received standard chow. Effects on serum liver tests, liver histology, markers of inflammation and fibrosis, and bile acid transport and metabolism were compared. 24-norUrsodeoxycholic acid metabolism was studied in serum, liver, bile, and urine.

RESULTS

24-norUrsodeoxycholic acid markedly improved liver tests and liver histology and significantly reduced hydroxyproline content and the number of infiltrating neutrophils and proliferating hepatocytes and cholangiocytes. 24-norUrsodeoxycholic acid underwent extensive phase I/II metabolism (hydroxylation, sulfation, and glucuronidation), thereby increasing the hydrophilicity of biliary bile acid secretion. There was a coordinated induction of bile acid detoxifying enzymes (Cyp2b10, Cyp3a11, and Sult2a1) and efflux pumps (Mrp3 and Mrp4). Ursodeoxycholic acid, in contrast, increased alanine transaminase and alkaline phosphatase levels, had no significant effects on hydroxyproline content, and induced biliary transporters and detoxification enzymes to a much smaller extent than 24-norUrsodeoxycholic acid.

CONCLUSIONS

24-norUrsodeoxycholic acid ameliorates sclerosing cholangitis in Mdr2(-/-) mice. Its therapeutic mechanisms involve (1) increasing the hydrophilicity of biliary bile acids, (2) stimulating bile flow with flushing of injured bile ducts, and (3) inducing detoxification and elimination routes for bile acids.

Tannic acid inhibits cholangiocyte proliferation after bile duct ligation via a cyclic adenosine 5',3'-monophosphate-dependent pathway

Chronic cholestatic diseases are characterized by morphological changes involving cholangiocyte proliferation and functional alterations of secretory capacity. The plant polyphenol tannic acid inhibits the growth of malignant human cholangiocytes. However, the mechanisms by which tannic acid limits excessive cholangiocyte proliferation are unknown. In this study we assessed the effect of tannic acid on cholangiocyte proliferation after bile duct ligation in rats. Tannic acid feeding decreased cholangiocyte proliferation and ductal mass in vivo after bile duct ligation. These changes were associated with functional changes in bile secretion and with decreases of intracellular cyclic adenosine 5',3'-monophosphate. The anti-proliferative effect of tannic acid was associated with a reduction of ERK1,2 phosphorylation. Additionally, tannic acid feeding decreased protein kinase A phosphorylation and activity. Similar changes were observed in isolated cholangiocytes during in vitro incubation with tannic acid. Furthermore, forskolin abolished the anti-proliferative effect of tannic acid on cholangiocyte proliferation after bile duct ligation. In conclusion, the anti-proliferative effects of tannic acid in cholangiocytes involve modulation of ERK1,2 by a cyclic adenosine 5',3'-monophosphate-protein kinase A-dependent pathway. These data suggest that tannic acid may be useful in limiting excessive cholangiocyte proliferation and modulating secretion during cholestasis.

Benign recurrent intrahepatic cholestasis

Benign recurrent intrahepatic cholestasis is a rare autosomal recessive disorder characterized by repeated episodes of intense pruritus, profound elevations in serum alkaline phosphatase and bilirubin, with normal or nearly normal values for serum gamma-glutamyl transferase. Attack lasts from several weeks to months and resolve spontaneously. Between attacks patients remain asymptomatic for months to years. The disorder does not lead to progressive liver injury and is not fatal. Genetic studies have demonstrated that the disorder is the result of a mutation in ATP8BI, a gene that codes for the FIC1 (familial intrahepatic cholestasis) protein, which is also affected in other forms of familial intrahepatic cholestasis. It is believed this protein plays a role in bile acid secretion, in aminophospholid transport, and in maintaining fluidity of the cell membrane. Therapy is supportive and aimed at relieving pruritus and other complications of severe cholestasis until the episode resolves spontaneously.

Biliary diversion for progressive familial intrahepatic cholestasis: improved liver morphology and bile acid profile

BACKGROUND AND AIMS

Progressive familial intrahepatic cholestasis (PFIC) is characterized by pruritus, intrahepatic cholestasis, low serum gamma-glutamyltransferase levels, and characteristic "Byler bile" on electron microscopy. Many patients require liver transplantation, but partial external biliary diversion (PEBD) has shown therapeutic promise. However, the effect of PEBD on liver morphology and bile composition has not been evaluated.

METHODS

We reviewed liver biopsy specimens from 3 children with low gamma-glutamyltransferase PFIC before and after PEBD. Follow-up liver biopsies were performed 9-60 months after PEBD. Light and electron microscopic features were scored blindly. Biliary bile acid composition was analyzed by gas chromatography-mass spectrometry before and after PEBD in 1 patient and after PEBD in 2 patients.

RESULTS

Following PEBD, all patients improved clinically. Preoperative biopsy specimens showed characteristic features of PFIC, including portal fibrosis, chronic inflammation, cholestasis, giant cell transformation, and central venous mural sclerosis. Ultrastructural findings included coarse, granular canalicular Byler bile, effaced canalicular microvilli, and proliferative pericanalicular microfilaments. Following diversion, histology showed almost complete resolution of cholestasis, portal fibrosis, and inflammation with resolution of ultrastructural abnormalities. Biliary bile acids before PEBD consisted predominantly of cholic acid. After PEBD, the proportion of chenodeoxycholic acid increased significantly in 1 patient and was above the PFIC range in a second patient.

CONCLUSIONS

The resolution of hepatic morphologic abnormalities following PEBD supports PEBD as an effective therapy for PFIC. The improved biliary bile acid composition suggests enhanced bile acid secretion after PEBD, perhaps by induction of alternative canalicular transport proteins.

Progressive familial intrahepatic cholestasis type 1 and extrahepatic features: no catch-up of stature growth, exacerbation of diarrhea, and appearance of liver steatosis after liver transplantation

BACKGROUND/AIMS

Progressive familial intrahepatic cholestasis characterized by normal serum gamma-glutamyltransferase activity can be due to mutations in familial intrahepatic cholestasis type 1 (FIC1) (ATP8B1), a gene expressed in several organs. In some cases, it is associated with extrahepatic features. We searched for FIC1 mutations and analyzed the outcome of extrahepatic features after liver transplantation in two children with this form of progressive familial intrahepatic cholestasis associated with chronic unexplained diarrhea and short stature.

METHODS

FIC1 sequence was determined after polymerase chain reaction (PCR) of genomic lymphocyte DNA and/or reverse transcription-PCR of liver or lymphocyte RNA.

RESULTS

A homozygous amino acid change deletion was found in one child. The second child harboured compound heterozygous missense and nonsense mutations. In both children, despite successful liver transplantation, evolution (follow-up: 9.5-11 years) was characterized by exacerbation of diarrhea and no catch-up of stature growth, and appearance of liver steatosis.

CONCLUSIONS

Progressive familial intrahepatic cholestasis characterized by normal serum gamma-glutamyltransferase activity and extrahepatic features corresponds to progressive familial intrahepatic cholestasis type 1. Extrahepatic symptomatology is not corrected or may be aggravated by liver transplantation, impairing life quality.

Molecular genetics of 3beta-hydroxy-Delta5-C27-steroid oxidoreductase deficiency in 16 patients with loss of bile acid synthesis and liver disease

The 3beta-hydroxy-Delta(5)-C(27)-steroid oxidoreductase (C(27) 3beta-HSD) is a membrane-bound enzyme of the endoplasmic reticulum that catalyzes an early step in the synthesis of bile acids from cholesterol. Subjects with autosomal recessive mutations in the encoding gene, HSD3B7, on chromosome 16p11.2-12 fail to synthesize bile acids and develop a form of progressive liver disease characterized by cholestatic jaundice and malabsorption of lipids and lipid-soluble vitamins from the gastrointestinal tract. The gene encoding the human C(27) 3beta-HSD enzyme was isolated previously, and a 2-bp deletion in exon 6 of HSD3B7 was identified in a well characterized subject with this disorder. Here, we report a molecular analysis of 15 additional patients from 13 kindreds with C(27) 3beta-HSD deficiency. Twelve different mutations were identified in the HSD3B7 gene on chromosome 16p11.2-12. Ten mutations were studied in detail and shown to cause complete loss of enzyme activity and, in two cases, alterations in the size or amount of the transcribed mRNA. Mutations were inherited in homozygous form in 13 subjects from 10 families and compound heterozygous form in four subjects from three families. We conclude that a diverse spectrum of mutations in the HSD3B7 gene underlies this rare form of neonatal cholestasis.