ABCB4/MDR3 in health and disease – at the crossroads of biochemistry and medicine

Abstract Several ABC transporters of the human liver are responsible for the secretion of bile salts, lipids and cholesterol. Their interplay protects the biliary tree from the harsh detergent activity of bile salts. Among these transporters, ABCB4 is essential for the translocation of phosphatidylcholine (PC) lipids from the inner to the outer leaflet of the canalicular membrane of hepatocytes. ABCB4 deficiency can result in altered PC to bile salt ratios, which led to intrahepatic cholestasis of pregnancy, low phospholipid associated cholelithiasis, drug induced liver injury or even progressive familial intrahepatic cholestasis type 3. Although PC lipids only account for 30–40% of the lipids in the canalicular membrane, 95% of all phospholipids in bile are PC lipids. We discuss this discrepancy in the light of PC synthesis and bile salts favoring certain lipids. Nevertheless, the in vivo extraction of PC lipids from the outer leaflet of the canalicular membrane by bile salts should be considered as a separate step in bile formation. Therefore, methods to characterize disease causing ABCB4 mutations should be considered carefully, but such an analysis represents a crucial point in understanding the currently unknown transport mechanism of this ABC transporter.

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Molecular Mechanisms for Biliary Phospholipid and Drug Efflux Mediated by ABCB4 and Bile Salts

BioMed Research International ◽

10.1155/2014/954781 ◽

2014 ◽

Vol 2014 ◽

pp. 1-11 ◽

Cited By ~ 31

Author(s):

Shin-ya Morita ◽

Tomohiro Terada

Keyword(s):

Intrahepatic Cholestasis ◽

Bile Salts ◽

Molecular Mechanisms ◽

Mixed Micelles ◽

Biliary Cirrhosis ◽

Culture Studies ◽

Physiological Relevance ◽

Type 3 ◽

Cholestasis Of Pregnancy

On the canalicular membranes of hepatocytes, several ABC transporters are responsible for the secretion of bile lipids. Among them, ABCB4, also called MDR3, is essential for the secretion of phospholipids from hepatocytes into bile. The biliary phospholipids are associated with bile salts and cholesterol in mixed micelles, thereby reducing the detergent activity and cytotoxicity of bile salts and preventing cholesterol crystallization. Mutations in theABCB4gene result in progressive familial intrahepatic cholestasis type 3, intrahepatic cholestasis of pregnancy, low-phospholipid-associated cholelithiasis, primary biliary cirrhosis, and cholangiocarcinoma.In vivoand cell culture studies have demonstrated that the secretion of biliary phospholipids depends on both ABCB4 expression and bile salts. In the presence of bile salts, ABCB4 located in nonraft membranes mediates the efflux of phospholipids, preferentially phosphatidylcholine. Despite high homology with ABCB1, ABCB4 expression cannot confer multidrug resistance. This review summarizes our current understanding of ABCB4 functions and physiological relevance, and discusses the molecular mechanism for the ABCB4-mediated efflux of phospholipids.

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O136 A NOVEL, HYBRID RECOMBINANT AAV-piggyBac TRANSPOSON VECTOR PERMITS ROBUST LONG-TERM PHENOTYPE CORRECTION OF THE PROGRESSIVE FAMILIAL INTRAHEPATIC CHOLESTASIS TYPE 3 MOUSE MODEL IN VIVO

Journal of Hepatology ◽

10.1016/s0168-8278(14)60138-0 ◽

2014 ◽

Vol 60 (1) ◽

pp. S57-S58

Author(s):

S.M. Siew ◽

S.C. Cunningham ◽

I.E. Alexander

Keyword(s):

Mouse Model ◽

Intrahepatic Cholestasis ◽

Piggybac Transposon ◽

Progressive Familial Intrahepatic Cholestasis ◽

Type 3

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ABCB4 Gene Aberrations in Human Liver Disease: An Evolving Spectrum

Seminars in Liver Disease ◽

10.1055/s-0038-1667299 ◽

2018 ◽

Vol 38 (04) ◽

pp. 299-307 ◽

Cited By ~ 21

Author(s):

Matthias Reichert ◽

Frank Lammert

Keyword(s):

Intrahepatic Cholestasis ◽

Association Studies ◽

Compound Heterozygous ◽

Genome Wide Association Studies ◽

Therapeutic Approaches ◽

Drug Induced ◽

Drug Induced Liver Injury ◽

Genome Wide ◽

Abcb4 Gene ◽

Type 3

AbstractATP-binding cassette subfamily B member 4 (ABCB4) is a phospholipid translocator at the canalicular membrane of the hepatocyte, which “flops” phosphatidylcholine into bile. Dysfunction of this transporter due to ABCB4 gene variants can cause liver diseases and has been called ABCB4 deficiency. Several diseases including progressive familial intrahepatic cholestasis type 3 (PFIC3), low phospholipid-associated cholelithiasis (LPAC), a subgroup of patients developing intrahepatic cholestasis of pregnancy (ICP), drug-induced liver injury and chronic cholangiopathy with biliary fibrosis and cirrhosis were attributed to ABCB4 deficiency and characterized in the past decade. LPAC and ICP are usually caused by monoallelic variants, whereas patients affected by PFIC3 are homozygous or compound heterozygous carriers of ABCB4 variants. Treatment with ursodeoxycholic acid is often effective, but as the more severe forms of ABCB4 deficiency progress, nevertheless, new diagnostic and therapeutic approaches are warranted. Current functional classifications for ABCB4 deficiency–associated mutations can guide the development of novel genotype–based targeted pharmacotherapies for these conditions. Recently, increasing evidence from genome-wide association studies is emerging on associations of ABCB4 variants with hepatobiliary malignancies.

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Defective hepatocyte aquaporin-8 expression and reduced canalicular membrane water permeability in estrogen-induced cholestasis

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00386.2006 ◽

2007 ◽

Vol 292 (3) ◽

pp. G905-G912 ◽

Cited By ~ 31

Author(s):

Flavia I. Carreras ◽

Guillermo L. Lehmann ◽

Domenico Ferri ◽

Mariana F. Tioni ◽

Giuseppe Calamita ◽

...

Keyword(s):

Water Permeability ◽

Protein Level ◽

Intrahepatic Cholestasis ◽

Rat Hepatocytes ◽

Functional Expression ◽

Bile Secretion ◽

Northern Blotting ◽

Bile Formation ◽

Canalicular Membrane ◽

Lysosomal Protease

Our previous work supports a role for aquaporin-8 (AQP8) water channels in rat hepatocyte bile formation mainly by facilitating the osmotically driven canalicular secretion of water. In this study, we tested whether a condition with compromised canalicular bile secretion, i.e., the estrogen-induced intrahepatic cholestasis, displays defective hepatocyte AQP8 functional expression. After 17α-ethinylestradiol administration (5 mg·kg body wt−1·day−1 for 5 days) to rats, the bile flow was reduced by 58% ( P < 0.05). By subcellular fractionation and immunoblotting analysis, we found that 34 kDa AQP8 was significantly decreased by ∼70% in plasma (canalicular) and intracellular (vesicular) liver membranes. However, 17α-ethinylestradiol-induced cholestasis did not significantly affect the protein level or the subcellular localization of sinusoidal AQP9. Immunohistochemistry for liver AQPs confirmed these observations. Osmotic water permeability ( Pf) of canalicular membranes, measured by stopped-flow spectrophotometry, was significantly reduced (73 ± 1 vs. 57 ± 2 μm/s) in cholestasis, consistent with defective canalicular AQP8 functional expression. By Northern blotting, we found that AQP8 mRNA expression was increased by 115% in cholestasis, suggesting a posttranscriptional mechanism of protein level reduction. Accordingly, studies in primary cultured rat hepatocytes indicated that the lysosomal protease inhibitor leupeptin prevented the estrogen-induced AQP8 downregulation. In conclusion, hepatocyte AQP8 protein expression is downregulated in estrogen-induced intrahepatic cholestasis, presumably by lysosomal-mediated degradation. Reduced canalicular membrane AQP8 expression is associated with impaired osmotic membrane water permeability. Our data support the novel notion that a defective expression of canalicular AQP8 contributes as a mechanism for bile secretory dysfunction of cholestatic hepatocytes.

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Gene therapy for progressive familial intrahepatic cholestasis type 3 in a clinically relevant mouse model

Nature Communications ◽

10.1038/s41467-019-13614-3 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 4

Author(s):

Nicholas D. Weber ◽

Leticia Odriozola ◽

Javier Martínez-García ◽

Veronica Ferrer ◽

Anne Douar ◽

...

Keyword(s):

Gene Therapy ◽

Mouse Model ◽

Therapeutic Effect ◽

Intrahepatic Cholestasis ◽

Bile Salts ◽

Monogenic Disease ◽

Progressive Familial Intrahepatic Cholestasis ◽

Disease Biomarkers ◽

Type 3 ◽

Old Females

AbstractProgressive familial intrahepatic cholestasis type 3 (PFIC3) is a rare monogenic disease caused by mutations in the ABCB4 gene, resulting in a reduction in biliary phosphatidylcholine. Reduced biliary phosphatidylcholine cannot counteract the detergent effects of bile salts, leading to cholestasis, cholangitis, cirrhosis and ultimately liver failure. Here, we report results from treating two- or five-week-old Abcb4−/− mice with an AAV vector expressing human ABCB4, resulting in significant decreases of PFIC3 disease biomarkers. All male mice achieved a sustained therapeutic effect up through 12 weeks, but the effect was achieved in only 50% of females. However, two-week-old females receiving a second inoculation three weeks later maintained the therapeutic effect. Upon sacrifice, markers of PFIC3 disease such as, hepatosplenomegaly, biliary phosphatidylcholine and liver histology were significantly improved. Thus, AAV-mediated gene therapy successfully prevented PFIC3 symptoms in a clinically relevant mouse model, representing a step forward in improving potential therapy options for PFIC3 patients.

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ATP8B1 and ATP11C: Two Lipid Flippases Important for Hepatocyte Function

Digestive Diseases ◽

10.1159/000371665 ◽

2015 ◽

Vol 33 (3) ◽

pp. 314-318 ◽

Cited By ~ 6

Author(s):

Jyoti Naik ◽

Dirk R. de Waart ◽

Karina Utsunomiya ◽

Suzanne Duijst ◽

Kam Ho Mok ◽

...

Keyword(s):

Intrahepatic Cholestasis ◽

Bile Salts ◽

Membrane Transporters ◽

Cholestatic Liver Disease ◽

Canalicular Membrane ◽

Transport Vesicles ◽

Benign Recurrent Intrahepatic Cholestasis ◽

Conjugated Hyperbilirubinemia ◽

Deficient Mice

P4 ATPases are lipid flippases and transport phospholipids from the exoplasmic to the cytosolic leaflet of biological membranes. Lipid flipping is important for the biogenesis of transport vesicles. Recently it was shown that loss of the P4 ATPases ATP8B1 and ATP11C are associated with severe Cholestatic liver disease. Mutation of ATP8B1 cause progressive familial Intrahepatic Cholestasis type 1 (PFIC1)and benign recurrent intrahepatic cholestasis type 1 (BRIC 1). From our observations we hypothesized that ATP8B1 deficiency causes a phospholipids randomization at the canalicular membrane, which results in extraction of cholesterol due to increase sensitivity of the canalicular membrane. Deficiency of ATP11C causes conjugated hyperbilirubinemia. In our preliminary result we observed accumulation of unconjugated bile salts in Atp11c deficient mice probably because of regulation in the expression or function of OATP1B2. Similar to ATP8B1, ATP11C have regulation on membrane transporters.

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Genetic Cholestasis: Lessons from the Molecular Physiology of Bile Formation

Canadian Journal of Gastroenterology ◽

10.1155/2000/514172 ◽

2000 ◽

Vol 14 (3) ◽

pp. 233-238 ◽

Cited By ~ 13

Author(s):

Peter LM Jansen ◽

Michael Müller

Keyword(s):

Intrahepatic Cholestasis ◽

Acid Synthesis ◽

Bile Acid Synthesis ◽

Normal Serum ◽

Chromosome 2 ◽

Chromosome 18 ◽

Molecular Physiology ◽

Bile Formation ◽

Mild Disease ◽

Type 3

Progressive familial intrahepatic cholestasis (PFIC) is a group of severe genetic cholestatic liver diseases of early life. PFIC types 1 and 2 are characterized by cholestasis and a low to normal serum gamma-glutamyltransferase (GGT) activity, whereas in PFIC type 3, the serum GGT activity is elevated. PFIC types 1 and 2 occur due to mutations in loci at chromosome 18 and chromosome 2, respectively. The pathophysiology of PFIC type 1 is not well understood. PFIC types 2 and 3 are caused by transport defects in the liver affecting the hepatobiliary secretion of bile acids and phospholipids, respectively. Benign recurrent intrahepatic cholestasis (BRIC) is linked to a mutation in the same familial intrahepatic cholestasis 1 locus at chromosome 18. Defects of bile acid synthesis may be difficult to differentiate from these transport defects.Intrahepatic cholestasis of pregnancy (ICP) appears to be related to these cholestatic diseases. For example, heterozygosity in families with PFIC type 3 is associated with ICP, but ICP has also been reported in families with BRIC.In Dubin-Johnson syndrome there is no cholestasis; only the hepatobiliary transport of conjugated bilirubin is affected. This, therefore, is a mild disease, and patients have a normal lifespan.

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New Insights in Genetic Cholestasis: From Molecular Mechanisms to Clinical Implications

Canadian Journal of Gastroenterology and Hepatology ◽

10.1155/2018/2313675 ◽

2018 ◽

Vol 2018 ◽

pp. 1-12 ◽

Cited By ~ 18

Author(s):

Eva Sticova ◽

Milan Jirsa ◽

Joanna Pawłowska

Keyword(s):

Intrahepatic Cholestasis ◽

Bile Salts ◽

Autosomal Recessive ◽

Molecular Mechanisms ◽

Current Knowledge ◽

Clinical Manifestations ◽

Bile Secretion ◽

Drug Induced ◽

Benign Recurrent Intrahepatic Cholestasis ◽

End Stage

Cholestasis is characterised by impaired bile secretion and accumulation of bile salts in the organism. Hereditary cholestasis is a heterogeneous group of rare autosomal recessive liver disorders, which are characterised by intrahepatic cholestasis, pruritus, and jaundice and caused by defects in genes related to the secretion and transport of bile salts and lipids. Phenotypic manifestation is highly variable, ranging from progressive familial intrahepatic cholestasis (PFIC)—with onset in early infancy and progression to end-stage liver disease—to a milder intermittent mostly nonprogressive form known as benign recurrent intrahepatic cholestasis (BRIC). Cases have been reported of initially benign episodic cholestasis that subsequently transitions to a persistent progressive form of the disease. Therefore, BRIC and PFIC seem to represent two extremes of a continuous spectrum of phenotypes that comprise one disease. Thus far, five representatives of PFIC (named PFIC1-5) caused by pathogenic mutations present in both alleles ofATP8B1,ABCB11,ABCB4,TJP2,andNR1H4have been described. In addition to familial intrahepatic cholestasis, partial defects inATP8B1,ABCB11,andABCB4predispose patients to drug-induced cholestasis and intrahepatic cholestasis in pregnancy. This review summarises the current knowledge of the clinical manifestations, genetics, and molecular mechanisms of these diseases and briefly outlines the therapeutic options, both conservative and invasive, with an outlook for future personalised therapeutic strategies.

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