Clinical and genetic study of ABCB4 gene-related cholestatic liver disease in China: children and adults.

BACKGROUND: ABCB4 gene-related cholestatic liver diseases have a wide spectrum of clinical and genetic variations. The correlation between genotype and clinical phenotype still unclear. This study retrospectively analyzed the clinical and pathological characteristics of 23 patients with ABCB4 gene-related cholestatic liver diseases. Next-generation sequencing was used to identify the genetic causes. RESULTS: The 23 included patients (15 children and 8 adults) were diagnosed as progressive familial intrahepatic cholestasis type 3 (PFIC3), drug-induced liver injury (DILI), cirrhosis cholestasis, cirrhosis, and mild liver fibrosis. Nineteen patients underwent liver pathological examination of the liver, exhibiting fibrosis, small bile duct hyperplasia, CK7(+), Cu(+), bile duct deletion, and cirrhosis. Thirty ABCB4 variants were identified, including 18 novel variants. CONCLUSION: ABCB4 gene-related cholestatic liver diseases have a wide spectrum of clinical and genetic variations. Biallelic ABCB4 mutation carriers tended to severe PFIC3, which mostly occurs in children; while ABCB4 non-biallelic variants can lead to milder ICP, LACP, DILI or overlapping, mostly in adults. Thus, the ABCB4 genotype has a specific correlation with the phenotype, but there are exceptions. Non-biallelic null mutations can cause severe diseases. The mechanisms underlying this genetic phenotype require further investigation.

Comprehensive Bile Acid Profiling of ABCB4-mutated Patients and the Prognostic Role of Taurine-conjugated 3α,6α,7α,12α-Tetrahydroxylated Bile Acid in Cholestasis.

Background and Aims: We asked if comprehensive bile acid profiling could provide insights into the physiopathology of ABCB4-mutated patients and evaluated the prognostic value of taurine-conjugated tetrahydroxylated bile acid (tauro-THBA) in cholestasis. Methods: Serum bile acid profiles were evaluated in 13 ABCB4-mutated patients with 65 healthy controls by ultra-high-performance liquid chromatography/multiple-reaction monitoring-mass spectrometry (UPLC/MRM-MS). The concentration of tauro-THBA was compared between ABCB4-mutated patients with different prognoses. The areas under the curve (AUCs) of tauro-THBA were compared between ABCB11-mutated patients with native liver survival and those who died or underwent liver transplantation before 3 years of age by receiver operating characteristic curve (ROC), with another patient cohort for further verification. Results: The overall hydrophobicity indices of bile acids in ABCB4-mutated patients (12.99±3.25 m) were significantly lower than those of healthy controls (14.02±1.74 m, p<0.000). That was due to markedly increased bile acid modifications including conjugation, sulfation, and ketonization. Differences in the tauro-THBA concentration in ABCB4-mutated patients with different prognoses were not significant. ROC analysis indicated that levels of tauro-THBA of <60 nM yielded an AUC of 0.900 with a sensitivity of 80% and specificity of 87.5% for ABCB11-mutated patients with different prognoses (p=0.0192). Of the 15 patients with good prognosis, 14 were classified correctly and four of the five patients with a poor prognosis were classified correctly (14:15 vs. 1:5, p=0.005) with tauro-THBA as a classifier. Conclusions: Tauro-THBA concentration may be a biomarker for predicting the clinical outcome in low gamma-glutamyl transferase intrahepatic cholestasis patients.

Evaluation of ABT-751, a novel anti-mitotic agent able to overcome multi-drug resistance, in melanoma cells.

PURPOSE: Drug efflux transporter associated multi-drug resistance (MDR) is a potential limitation in the use of taxane chemotherapies for the treatment of metastatic melanoma. ABT-751 is an orally bioavailable microtubule-binding agent capable of overcoming MDR and proposed as an alternative to taxane-based therapies. METHODS: This study compares ABT-751 to taxanes in vitro, utilizing seven melanoma cell line models, publicly available gene expression and drug sensitivity databases, a lung cancer cell line model of MDR drug efflux transporter overexpression (DLKP-A), and drug efflux transporter ATPase assays. RESULTS: Melanoma cell lines exhibit a low but variable protein and RNA expression of drug efflux transporters P-gp, BCRP, and MDR3. Expression of P-gp and MDR3 correlates with sensitivity to taxanes, but not to ABT-751. The anti-proliferative IC50 profile of ABT-751 was higher than the taxanes docetaxel and paclitaxel in the melanoma cell line panel, but fell within clinically achievable parameters. ABT-751 IC50 was not impacted by P-gp-overexpression in DKLP-A cells, which display strong resistance to the P-gp substrate taxanes compared to DLKP parental controls. The addition of ABT-751 to paclitaxel treatment significantly decreased cell proliferation, suggesting some reversal of MDR. ATPase activity assays suggest that ABT-751 is a potential BCRP substrate, with the ability to inhibit P-gp ATPase activity. CONCLUSION: Our study confirms that ABT-751 is active against melanoma cell lines and models of MDR at physiologically relevant concentrations, it inhibits P-gp ATPase activity, and it may be a BCRP and/or MDR3 substrate. ABT-751 warrants further investigation alone or in tandem with other drug efflux transporter inhibitors for hard-to-treat MDR melanoma.

Clinical, histopathological, and immunohistochemical spectrum of hepatolithiasis: a tertiary care center-based study from north India.

Hepatolithiasis (HL), an uncommon disease among Indians, occurs due to a complex interplay of various structural and functional factors. We retrospectively evaluated the clinical and histopathological spectrum of HL (N = 19) with immunohistochemical evaluation for biliary apomucins and canalicular transporter proteins, both crucial for lithogenesis. Nineteen surgically resected cases were included. Histopathology was systematically evaluated. Immunohistochemistry for apomucins (MUC1, MUC2, MUC4, MUC5AC, and MUC6) and canalicular transporter proteins (BSEP and MDR3) was applied to all cases. The median age was 51 years with female preponderance (F:M = 1.4:1). The stone was cholesterol-rich in 71.4% and pigmented in 28.6% (n = 14). Histopathology showed variable large bile-duct thickening due to fibrosis and inflammation with peribiliary gland hyperplasia. Structural causes (Caroli disease, choledochal cyst, and post-surgical complication) were noted in 15.8% of cases (secondary HL). Expression of gel-forming apomucin MUC1, MUC2, and MUC5AC was seen in either bile duct epithelia or peribiliary glands in 84.2%, 10.5%, and 84.2% cases respectively. Loss of canalicular expression of MDR3 was noted in 42.1% of cases while BSEP was retained in all. Primary HL in the north Indian population can be associated with the loss of MDR3 expression (with retained BSEP) and/ or a shift in the phenotype of biliary apomucins to gel-forming apomucins. The former factor alters the bile acid/ phospholipid ratio while the latter parameter promulgates crystallization. In conjunction, these factors are responsible for the dominantly cholesterol-rich stones in the index population.

Recurrent early-onset severe obstetric cholestasis in a patient with two variants in the ABCB4 gene.

A 36-year-old patient presented with severe early-onset obstetric cholestasis on a background of having pre-term induction of labor at 33 weeks during her only previous pregnancy. The patient had significantly abnormal liver biochemistry with a bilirubin of 78 µmol/L, ALP of 318 u/L, ALT of 280 µmol/L, and bile acid levels of 420 µmol/L. The patient received ursodeoxycholic acid 750 mg 3 times a day, rifampicin 500 mg twice a day, aspirin 150 mg once a day, and metformin 500 mg 3 times a day. However, despite this, the patient still suffered from intractable pruritus and her bile acid level was still above the 100 µmol/L target that the obstetrics team was aiming for to avoid early delivery at 32 weeks. Due to the nature and severity of her cholestasis, the patient had a number of investigations done postnatally including genetic analysis, which confirmed that the patient was heterozygous for a pathogenic variant of the ATP-binding cassette subfamily B member 4 gene (c.959C>T [p.Ser320Phe]) and also a variant of unknown significance (c.1679C>T [p.Thr560Met]).

Outcomes of 38 patients with PFIC3: Impact of genotype and of response to ursodeoxycholic acid therapy.

Background & Aims: Progressive familial intrahepatic cholestasis type 3 (PFIC3) is a rare liver disease caused by biallelic variations in ABCB4. Data reporting on the impact of genotype and of response to ursodeoxycholic acid (UDCA) therapy on long-term outcomes are scarce. Methods: We retrospectively describe a cohort of 38 patients with PFIC3 with a median age at last follow-up of 19.5 years (range 3.8-53.8). Results: Twenty patients presented with symptoms before 1 year of age. Thirty-one patients received ursodeoxycholic acid (UDCA) therapy resulting in serum liver test improvement in 20. Twenty-seven patients had cirrhosis at a median age of 8.1 years of whom 18 received a liver transplant at a median age of 8.5 years. Patients carrying at least one missense variation were more likely to present with positive (normal or decreased) canalicular MDR3 expression in the native liver and had prolonged native liver survival (NLS; median 12.4 years [range 3.8-53.8]). In contrast, in patients with severe genotypes (no missense variation), there was no detectable canalicular MDR3 expression, symptom onset and cirrhosis occurred earlier, and all underwent liver transplantation (at a median age of 6.7 years [range 2.3-10.3]). The latter group was refractory to UDCA treatment, whereas 87% of patients with at least one missense variation displayed an improvement in liver biochemistry in response to UDCA. Biliary phospholipid levels over 6.9% of total biliary lipid levels predicted response to UDCA. Response to UDCA predicted NLS. Conclusions: Patients carrying at least one missense variation, with positive canalicular expression of MDR3 and a biliary phospholipid level over 6.9% of total biliary lipid levels were more likely to respond to UDCA and to exhibit prolonged NLS. Impact and implications: In this study, data show that genotype and response to ursodeoxycholic acid therapy predicted native liver survival in patients with PFIC3 (progressive familial intrahepatic cholestasis type 3). Patients carrying at least one missense variation, with positive (decreased or normal) immuno-staining for canalicular MDR3, and a biliary phospholipid level over 6.9% of total biliary lipids were more likely to respond to ursodeoxycholic acid therapy and to exhibit prolonged native liver survival.

A female of progressive familial intrahepatic cholestasis type 3 caused by heterozygous mutations of ABCB4 gene and her cirrhosis improved after treatment of ursodeoxycholic acid: a case report.

BACKGROUND: Progressive familial intrahepatic cholestasis (PFIC) is a group of rapidly progressive autosomal recessive disorders characterized by intrahepatic cholestasis. PFIC-3 is caused by mutations in the ATP-binding cassette subfamily B member 4 gene (ABCB4), which encodes multidrug resistance protein 3 (MDR3/ABCB4). Patients are usually in infancy or childhood, but cirrhosis and portal hypertension may be the first manifestation in older children or young adults. CASE PRESENTATION: A 25-year-old young woman with recurrent abnormal hepatic function was mainly characterized by increased gamma glutamyl transpeptidase (GGT) and bile acid with cryptogenic cirrhosis. After 7 months of treatment with ursodeoxycholic acid (UDCA), her hepatic pathology suggested there were also obvious widening and venous fibrosis around the portal vein, and slight bile duct hyperplasia at the edge of the portal area. Infiltration of inflammatory cells around the portal vein and hepatocyte ABCB4/MDR3 protein was basically normal. Sequencing indicated the patient had heterozygous mutations in the ABCB4 gene: c.2696C > G and wes [hg19]7q21.12(87032513-87033422) × 1. Through SWISS-MODEL Predict for protein structures, the missense mutation results in protein side chain missing a methyl group (-CH3), and the deletion mutation results in the serious damage to the structure of MDR3 protein which lead to phosphatidylcholine deficiency of bile in the capillary bile ducts. The toxic effect of bile salts then damages the bile ducts, causing cholestasis and cholangitis, which can then develop into biliary cirrhosis. Through the analysis of pathogenicity prediction software, the mutations led to PFIC3. After treatment of UDCA for 29 months, her cirrhosis was improved, hepatic function was close to normal. CONCLUSION: Novel heterozygous mutations are the molecular pathological cause of PFIC3 in this patient. All young adult patients with occult cirrhosis should be tested for ABCB4. Early diagnosis of PFIC3 and continued treatment with UDCA are key to improving prognosis and delaying the onset of end-stage liver disease.

MDR3 rs2109505 and rs1202283 polymorphisms are associated with susceptibility to intrahepatic cholestasis of pregnancy: A meta-analysis.

BACKGROUND: Many studies have assessed the relationship between gene polymorphisms in multidrug resistance protein 3 (MDR3) and the risk of intrahepatic cholestasis of pregnancy (ICP); however, there are many conflicting narratives. OBJECTIVES: This meta-analysis was conducted to assess the association between MDR3 gene polymorphisms and ICP. MATERIAL AND METHODS: A multi-database search was conducted using Web of Science, Embase, PubMed, and Chinese Biomedical Literature (CBM) databases. Eleven eligible studies focusing on 4 single nucleotide polymorphisms (SNPs) in the MDR3 gene were selected for analysis. A fixedor random-effects model was utilized for allelic, dominant, recessive, and superdominant genes. RESULTS: The pooled results indicated a statistically significant association between MDR3 polymorphism rs2109505 and an increased risk of ICP in both the general population and the Caucasian population. No statistically significant associations were found between MDR3 polymorphism rs2109505 and ICP in Italian or Asian populations for the 4 genetic models. The MDR3 polymorphism rs1202283 was associated with susceptibility to ICP in both the general and Italian populations. CONCLUSION: The MDR3 rs2109505 and rs1202283 polymorphisms are associated with ICP susceptibility: however, they displayed no correlation with an increased risk of ICP.

Molecular and Clinical Links between Drug-Induced Cholestasis and Familial Intrahepatic Cholestasis.

Idiosyncratic Drug-Induced Liver Injury (iDILI) represents an actual health challenge, accounting for more than 40% of hepatitis cases in adults over 50 years and more than 50% of acute fulminant hepatic failure cases. In addition, approximately 30% of iDILI are cholestatic (drug-induced cholestasis (DIC)). The liver's metabolism and clearance of lipophilic drugs depend on their emission into the bile. Therefore, many medications cause cholestasis through their interaction with hepatic transporters. The main canalicular efflux transport proteins include: 1. the bile salt export pump (BSEP) protein (ABCB11); 2. the multidrug resistance protein-2 (MRP2, ABCC2) regulating the bile salts' independent flow by excretion of glutathione; 3. the multidrug resistance-1 protein (MDR1, ABCB1) that transports organic cations; 4. the multidrug resistance-3 protein (MDR3, ABCB4). Two of the most known proteins involved in bile acids' (BAs) metabolism and transport are BSEP and MDR3. BSEP inhibition by drugs leads to reduced BAs' secretion and their retention within hepatocytes, exiting in cholestasis, while mutations in the ABCB4 gene expose the biliary epithelium to the injurious detergent actions of BAs, thus increasing susceptibility to DIC. Herein, we review the leading molecular pathways behind the DIC, the links with the other clinical forms of familial intrahepatic cholestasis, and, finally, the main cholestasis-inducing drugs.

A Unique In Vitro Assay to Investigate ABCB4 Transport Function.

ABCB4 is almost exclusively expressed in the liver, where it plays an essential role in bile formation by transporting phospholipids into the bile. ABCB4 polymorphisms and deficiencies in humans are associated with a wide spectrum of hepatobiliary disorders, attesting to its crucial physiological function. Inhibition of ABCB4 by drugs may lead to cholestasis and drug-induced liver injury (DILI), although compared with other drug transporters, there are only a few identified substrates and inhibitors of ABCB4. Since ABCB4 shares up to 76% identity and 86% similarity in the amino acid sequence with ABCB1, also known to have common drug substrates and inhibitors, we aimed to develop an ABCB4 expressing Abcb1-knockout MDCKII cell line for transcellular transport assays. This in vitro system allows the screening of ABCB4-specific drug substrates and inhibitors independently of ABCB1 activity. Abcb1KO-MDCKII-ABCB4 cells constitute a reproducible, conclusive, and easy to use assay to study drug interactions with digoxin as a substrate. Screening a set of drugs with different DILI outcomes proved that this assay is applicable to test ABCB4 inhibitory potency. Our results are consistent with prior findings concerning hepatotoxicity causality and provide new insights for identifying drugs as potential ABCB4 inhibitors and substrates.

PPAR agonists for the treatment of primary biliary cholangitis: Old and new tales.

Introduction: Primary biliary cholangitis (PBC) is an autoimmune liver disease involving the small intrahepatic bile ducts; when untreated or undertreated, it may evolve to liver fibrosis and cirrhosis. Ursodeoxycholic Acid (UDCA) is the standard of care treatment, Obeticholic Acid (OCA) has been approved as second-line therapy for those non responder or intolerant to UDCA. However, due to moderate rate of UDCA-non responders and to warnings recently issued against OCA use in patients with cirrhosis, further therapies are needed.Areas covered. Deep investigations into the pathogenesis of PBC is leading to proposal of new therapeutic agents, among which peroxisome proliferator-activated receptor (PPAR) ligands seem to be highly promising given the preliminary, positive results in Phase 2 and 3 trials. Bezafibrate, the most evaluated, is currently used in clinical practice in combination with UDCA in referral centers. We herein describe completed and ongoing trials involving PPAR agonists use in PBC, analyzing pits and falls. Expert opinion: Testing new therapeutic opportunities in PBC is challenging due to its low prevalence and slow progression. However, new drugs including PPAR agonists, are currently under investigation and should be considered for at-risk PBC patients.

Case series of progressive familial intrahepatic cholestasis type 3: Characterization of variants in ABCB4 in China.

Objective: To improve the accuracy of the diagnosis of familial progressive intrahepatic cholestasis type 3 (PFIC3, https://www.omim.org/entry/602347). Materials and methods: Between September 2019 and March 2021, we recruited four patients with PFIC3 from two liver centers in East China. Molecular genetic findings of ATP-binding cassette subfamily B member 4 [ATP binding cassette transporter A4 (ABCB4), https://www.omim.org/entry/171060] were prospectively examined, and clinical records, laboratory readouts, and macroscopic and microscopic appearances of the liver were analyzed. Results: Four patients experienced cholestasis, mild jaundice, and elevated levels of serum direct bilirubin, γ-glutamyltransferase, or total bile acids. All patients had moderate-to-severe liver fibrosis or biliary cirrhosis, and their liver biopsy specimens stained positive with rhodamine. Molecular immunohistochemistry revealed reduced or absent MDR3 expression in all liver specimens. A novel mutation of ABCB4 (c.1560 + 2T > A) was identified in patients with PFIC3, which is of high clinical significance and may help understand mutant ABCB4 pathogenesis. Conclusion: MDR3 immunohistochemistry and molecular genetic analyses of ABCB4 are essential for the accurate diagnosis of PFIC3.

Heterozygous mutations of ATP8B1, ABCB11 and ABCB4 cause mild forms of Progressive Familial Intrahepatic Cholestasis in a pediatric cohort / Mutaciones en heterocigosis en ATP8B1, ACB11 y ABCB4 como causa de formas leves de Colestasis Intrahepática Progresiva Familiar en una cohorte pediátrica

Introduction: Heterozygous defects in genes implicated in Progressive Familial Intrahepatic Cholestasis have been described in milder forms of cholestatic diseases. Our aim is to describe clinical, laboratory and imaging characteristics as well as treatment and outcome of a cohort of pediatric patients with heterozygous mutations in ATP8B1, ABCB11 or ABCB4. Patients and methods: We present a retrospective descriptive study including pediatric patients with at least one heterozygosis defect in ATP8B1, ABCB11 or ABCB4 diagnosed after a cholestatic episode. Clinical, diagnostic and outcome data were collected including gene analysis (panel of PFIC NextGeneDx®). Results: 7 patients showed a heterozygous mutation: 3 patients in ABCB4, 1 in ABCB11, 2 in ABCB4 and ABCB11 and 1 in ATP8B1. The median onset age was 5.5 years with a median time of follow-up of 6 years. The initial presentation was pruritus followed by asymptomatic hypertransaminasemia and persistent cholestasis. Two patients had family history of gallbladder stones and mild hepatitis. All showed elevated transaminases and bile acids, high gamma glutamyl-transferase (GGT) in 3 and conjugated bilirubin in 2 patients. Liver biopsy showed inflammatory infiltrate or mild fibrosis with normal immunohistochemistry. All patients were treated with ursodeoxycholic acid, two patients requiring the addition of resincholestyramine. During follow-up, 3 patients suffered limited relapses of pruritus. No disease progression was observed. Conclusion: Heterozygous mutations in genes coding proteins of the hepatocellular transport system can cause cholestatic diseases with great phenotypic variability. The presence of repeated episodes of hypertransaminasemia or cholestasis after a trigger should force us to rule out the presence of these heterozygous mutations in genes involved in CIFP.(AU)

Introducción: Se han descrito defectos en los genes implicados en las colestasis intrahepáticas familiares progresivas (CIFP) causantes de colestasis más leves. El objetivo es estudiar las manifestaciones clínicas, analíticas y de imagen así como la evolución y respuesta al tratamiento de los portadores en heterocigosis de mutaciones en ATP8B1, ABCB11 y ABCB4. Pacientes y métodos: Estudio descriptivo retrospectivo de pacientes con al menos una mutación en heterocigosis en los genes ATP8B1, ABCB11 o ABCB4 diagnosticados tras un episodio de colestasis. Se recogieron variables demográficas y datos clínicos, diagnósticos, incluyendo estudio genético (panel de CIFP NextGeneDx®), tratamiento y evolución. Resultados: 7 pacientes presentaron al menos una mutación en heterocigosis: 3 en ABCB4, 1 en ABCB11, 2 en ABCB4 y ABCB11 y 1 en ATP8B1. La edad media de inicio fue de 5.5 años con un tiempo medio de evolución de 6 años. La clínica inicial fue prurito seguida de hipertransaminasemia asintomática y colestasis persistente. Dos pacientes tenían antecedentes familiares de litiasis biliar y hepatitis leve. Todos mostraron transaminasas y ácidos biliares elevados, 3 gamma-glutamiltransferasa (GGT) y 2 bilirrubina directa. La biopsia hepática mostró infiltrado inflamatorio o fibrosis leve, inmunohistoquímica normal. Fueron tratados con ácido ursodeoxicólico añadiéndose colestiramina en 2. Durante el seguimiento 3 presentaron episodios autolimitados de prurito. No se observó progresión de la enfermedad. Conclusiones: Mutaciones en heterocigosis en los genes implicados en el sistema de transporte hepatocelular pueden ocasionar cuadros de colestasis con gran variabilidad fenotípica. Episodios repetidos de hipertransaminasemia o colestasis tras un desencadenante deben hacernos sospechar mutaciones en los genes implicados en las CIFP.(AU)

A BCB4 variant is associated with hepatobiliary MR abnormalities in people with low-phospholipid-associated cholelithiasis syndrome.

Background & Aims: The low-phospholipid-associated cholelithiasis (LPAC) syndrome is a recently described peculiar form of cholelithiasis associated with the ATP-binding-cassette subfamily B, member 4 (ABCB4) gene deficiency. The purpose of our study was to analyse the relationship between magnetic resonance (MR) features and the genetic status of ABCB4 in people with LPAC syndrome. Methods: A total of 233 individuals with proven LPAC syndrome were enrolled between January 2003 and June 2018 in a retrospective single-centre study. Inclusion criteria included availability of clinical files, MR images, and genetic data. MR images were analysed by consensus among 3 senior radiologists blinded to the status of ABCB4 gene mutation. Results: A total of 125 individuals (mean age at first MR imaging 40.8 years; 66% females; 48% ABCB4 variant) were included. MR abnormalities were found in 61 (49%) of the 125 individuals. Forty (67%) of the 60 individuals with an ABCB4 gene variant had MR abnormalities as compared with 21 (33%) of the 65 individuals without an ABCB4 gene variant (odds ratio [OR] 4.1, 95% CI 1.9-9.5, p = 0.0001). Compared to individuals with no variant, individuals with an ABCB4 variant were more likely to show intrahepatic macrolithiasis (56 vs. 17%; OR 6.3, 95% CI 2.6-16.2, p <0.0001), bile duct dilatation (60 vs. 18%; OR 6.5, 95% CI 2.7-16.3, p <0.0001), and at least 1 MR feature of complication (35 vs. 15%; OR 2.9, 95% CI 1.1-7.8, p <0.05). Conclusions: ABCB4-related LPAC syndrome is associated with more frequent and severe hepatobiliary MR abnormalities. This finding strongly supports the major role of the ABCB4 gene in the pathogenesis of LPAC syndrome and highlights a genotype-phenotype association in this inherited disease with genetic heterogeneity. Lay summary: ABCB4-related LPAC syndrome associated with an ABCB4 gene variant demonstrates more frequent and severe hepatobiliary MR abnormalities. This finding supports the major role of the ABCB4 gene in the pathogenesis of LPAC syndrome.

Overview of Progressive Familial Intrahepatic Cholestasis.

Bile acid transport is a complex physiologic process, of which disruption at any step can lead to progressive intrahepatic cholestasis (PFIC). The first described PFIC disorders were originally named as such before identification of a genetic cause. However, advances in clinical molecular genetics have led to the identification of additional disorders that can cause these monogenic inherited cholestasis syndromes, and they are now increasingly referred to by the affected protein causing disease. The list of PFIC disorders is expected to grow as more causative genes are discovered. Here forth, we present a comprehensive overview of known PFIC disorders.

A New Variant of an Old Itch: Novel Missense Variant in ABCB4 Presenting with Intractable Pruritus.

We report a novel homozygous missense variant in ABCB4 gene in a Yemeni child born to consanguineous parents, with a significant family history of liver disease-related deaths, resulting in a progressive familial intrahepatic cholestasis (PFIC) type 3 phenotype requiring liver transplantation for intractable pruritus.

Progressive Familial Intrahepatic Cholestasis: A Study in Children From a Liver Transplant Center in India.

Background/Aims: This study aimed to delineate the clinical profile of children diagnosed with progressive familial intrahepatic cholestasis (PFIC). Methods: This study was a retrospective analysis of case records of children in the tertiary care hospital, with the diagnosis of PFIC from January 2017 to January 2020. The diagnosis was made using clinical and laboratory parameters and with genetic testing when available. Medical and surgical management was according to the departmental protocol. Liver transplant was offered to children with end-stage liver disease, intractable pruritus, or severe growth failure. Result: There were 13 identified PFIC cases (familial intrahepatic cholestasis 1 [FIC1] deficiency-4, bile salt export pump (BSEP) deficiency-3, tight junction protein [TJP2] deficiency 3, multidrug-resistant protein 3 [MDR3] deficiency 2 and farnesoid X receptor deficiency-1). PFIC subtypes 1, 2, and 5 presented in infancy, whereas MDR3 presented in childhood. TJP2 deficiency had varied age of presentation from infancy to adolescence. Jaundice with or without pruritus was present in most cases. Genetic testing was carried out in 10 children, of which five had a homozygous mutation, three had a compound heterozygous mutation, and two had a heterozygous mutation. Three children (FIC1-2 and TJP2-1) underwent biliary diversion, of which clinical improvement was seen in two. Six children underwent liver transplantation, which was successful in four. Conclusion: Byler's disease was the most common subtype. A clinicopathologic correlation with molecular diagnosis leads to early diagnosis and management. Liver transplantation provides good outcomes in children with end-stage liver disease.

Gestational Age Variation in Human Placental Drug Transporters.

Patient and providers' fear of fetal exposure to medications may lead to discontinuation of treatment, disease relapse, and maternal morbidity. Placental drug transporters play a critical role in fetal exposure through active transport but the majority of data are limited to the 3rd trimester, when the majority of organogenesis has already occurred. Our objective was to define gestational age (GA) dependent changes in protein activity, expression and modifications of five major placental drug transporters: SERT, P-gp, NET, BCRP and MRP3. Apical brush border membrane fractions were prepared from fresh 1st, 2nd and 3rd trimester human placentas collected following elective pregnancy termination or planned cesarean delivery. A structured maternal questionnaire was used to identify maternal drug use and exclude exposed subjects. Changes in placental transporter activity and expression relative to housekeeping proteins were quantified. There was evidence for strong developmental regulation of SERT, NET, P-gp, BCRP and MRP3. P-gp and BCRP decreased with gestation (r = -0.72, p < 0.001 and r = -0.77, p < 0.001, respectively). Total SERT increased with gestation but this increase was due to a decrease in SERT cleavage products across trimesters. Uncleaved SERT increased with GA (r = 0.89, p < 0.001) while cleaved SERT decreased with GA (r = -0.94, p < 0.001). Apical membrane NET overall did not appear to be developmentally regulated (r = -0.08, p = 0.53). Two forms of MRP3 were identified; the 50 kD form did not change across GA; the 160 kD form was steady in the 1st and 2nd trimester and increased in the 3rd trimester (r = 0.24, p = 0.02). The 50 kD form was expressed at higher levels. The observed patterns of SERT, NET P-gp, BCRP and MRP3 expression and activity may be associated with transporter activity or decreased placental permeability in the 1st trimester to transporter specific substrates including commonly used psychoactive medications such as anti-depressants, anti-psychotics, and amphetamines, while transport of nutrients and serotonin is important in the 1st trimester. Overall these observations are consistent with a strong protective effect during organogenesis. 3rd trimester estimates of fetal exposure obtained from cord blood likely significantly overestimate early fetal exposure to these medications at any fixed maternal dose.

Mdr3 gene mutation in preterm infants with parenteral nutrition-associated cholestasis.

To investigate the relationship of multidrug resistance 3 (Mdr3) gene mutation and parenteral nutrition-associated cholestasis (PNAC) in preterm infants. Preterm infants who had received total parenteral nutrition for at least 14 days were enrolled: 76 preterm infants in the PNAC group and 80 preterm infants in the non-PNAC group. Genomic DNA was extracted from white blood cells. Twenty-eight exons of the Mdr3 gene were amplified by polymerase chain reaction. PNAC infants of 1 month corrected age with the Mdr3 gene mutation and abnormal liver biochemistry were selected for the experimental liver biopsy group. Five normal adult living liver transplantation donors were enrolled in a normal donor group. The Mdr3 missense mutations c.1031G>A, c.3347G>A, and c.485T>A, and the Mdr3 frameshift mutation c.2793_2794insA were found in the PNAC group. The allele frequency and genotype frequency of c.1031G>A, c.3347G>A, and c.485T>A in the Mdr3 gene in the PNAC group were significantly higher than those in non-PNAC group (p < 0.05). The rate of Mdr3 gene mutations c.1031G>A, c.485T>A, c.3347G>A, and c.2793_2794insA in the PNAC group was higher than in the non-PNAC group (21.05% vs. 1.25%, respectively, χ2  = 15.747, p < 0.05). Mdr3 gene mutations c.2793_2794insA, c.1031G>A, c.3347G>A, and c.485T>A may be the genetic cause of PNAC.