Cholestasis is characterized by hepatic accumulation of bile acids. Clinical manifestation of cholestasis only occurs in a small proportion of exposed individuals. The present study aims to develop a new approach methodology (NAM) to predict drug-induced cholestasis as a result of drug-induced hepatic bile acid efflux inhibition and the resulting bile acid accumulation. To this end, hepatic concentrations of a panel of drugs were predicted by a generic physiologically based kinetic (PBK) drug model. Their effects on hepatic bile acid efflux were incorporated in a PBK model for bile acids. The predicted bile acid accumulation was used as a measure for a drug\'s cholestatic potency. The selected drugs were known to inhibit hepatic bile acid efflux in an assay with primary suspension-cultured hepatocytes and classified as common, rare, or no for cholestasis incidence. Common cholestasis drugs included were atorvastatin, chlorpromazine, cyclosporine, glimepiride, ketoconazole, and ritonavir. The cholestasis incidence of the drugs appeared not to be adequately predicted by their Ki for inhibition of hepatic bile acid efflux, but rather by the AUC of the PBK model predicted internal hepatic drug concentration at therapeutic dose level above this Ki. People with slower drug clearance, a larger bile acid pool, reduced bile salt export pump (BSEP) abundance, or given higher than therapeutic dose levels were predicted to be at higher risk to develop drug-induced cholestasis. The results provide a proof-of-principle of using a PBK-based NAM for cholestasis risk prioritization as a result of transporter inhibition and identification of individual risk factors.

Triazole fungicides such as propiconazole (Pi) or tebuconazole (Te) show hepatotoxicity in vivo, e.g., hypertrophy and vacuolization of liver cells following interaction with nuclear receptors such as PXR (pregnane-X-receptor) and CAR (constitutive androstane receptor). Accordingly, azoles affect gene expression associated with these adverse outcomes in vivo but also in human liver cells in vitro. Additionally, genes indicative of liver cholestasis are affected in vivo and in vitro. We therefore analyzed the capability of Pi and Te to cause cholestasis in an adverse outcome pathway (AOP)-driven approach in hepatic cells of human origin in vitro, considering also previous in vivo studies. Bile salt export pump (BSEP) activity assays confirmed that both azoles are weak inhibitors of BSEP. They alternate the expression of various cholestasis-associated target genes and proteins as well as the mitochondrial membrane function. Published in vivo data, however, demonstrate that neither Pi nor Te cause cholestasis in rodent bioassays. This discrepancy can be explained by the in vivo concentrations of both azoles being well below their EC50 for BSEP inhibition. From a regulatory perspective, this illustrates that toxicogenomics and human in vitro models are valuable tools to detect the potential of a substance to cause a specific type of toxicity. To come to a sound regulatory conclusion on the in vivo relevance of such a finding, results will have to be considered in a broader context also including toxicokinetics in a weight-of-evidence approach.

Progressive familial intrahepatic cholestasis type 2 (PFIC2) is a rare autosomal recessive disorder caused by mutations in the ABCB11 gene. Clinical manifestations include cholestasis with low γ-glutamyltransferase (GGT), hepatosplenomegaly, and severe pruritus. Liver transplantation is required for individuals with progressive liver disease or failure of the bypass procedure and has been considered curative. However, in the case of PFIC2, although bile salt excretory pump (BSEP) deficiency is a liver-specific condition rather than a systemic disease, evidence of recurrent BSEP disease has been shown in a small proportion of allografts. We describe an unusual case of a 21-year-old individual with PFIC2 and evidence of recurrent BSEP disease after liver transplantation, with clinical and laboratory improvement after pulse therapy with methylprednisolone for 3 days and adjustment of oral immunosuppression. This case report highlights the recurrence of PFIC2 in patients post liver transplant. It also emphasizes the importance of clinical suspicion, which should be considered in cases of posttransplant cholestasis in PFIC2 patients, especially those with low γ-glutamyltransferase (GGT) and without signs of acute graft rejection. Having knowledge of the condition favors a targeted diagnostic approach and contributes to early therapeutic management and a higher success rate.

Idiopathic or transient neonatal cholestasis (TNC) represents a group of cholestatic disorders with unidentified origin and remains a diagnosis of exclusion. Dysfunction of hepatobiliary transporters mediating excretion of biliary constituents from hepatocytes may play a central role in the pathogenesis of cholestasis. Despite variants of bile salt (BS) export pump (BSEP/ABCB11) have already been described in TNC, the pathogenic role of BSEP dysfunction in TNC remained so far elusive.
We report on a newly-identified heterozygous ABCB11 missense variant (c.1345G > A, p.Glu449Lys) which was associated with prolonged cholestasis in a term infant after a complicated neonatal period. Moreover, we show for the first time almost completely abolished BSEP expression on the hepatocellular membrane in TNC.
This report demonstrates for the first time a close association between the prolonged cholestasis in infancy and impaired BSEP expression on the hepatocyte canalicular membrane in a heterozygous carrier of newly-identified ABCB11 variant.

The purpose of this meta-analysis was to investigate the relationship between bile salt export pump (BSEP) polymorphisms and intrahepatic cholestasis of pregnancy (ICP) susceptibility. Retrieved studies from Pubmed, EMBASE, Web of Science, Cochrane Library and CBM databases about BSEP polymorphisms and ICP susceptibility were included. Odds ratio (OR) and 95% confidence interval (CI) and publication bias were calculated. Ten related case-control studies on BSEP polymorphisms and ICP susceptibility were included. The pooled results showed a significant association between BSEP rs2287622 polymorphism and ICP risk in Asian population (OR >1, p < .01 for A vs. a and AA vs. Aa/aa) and general population (OR >1, p < .05 for A vs. a, Aa vs. aa, AA/Aa vs. aa), and a borderline statistical significance was found between BSEP rs473351 polymorphism and ICP susceptibility (OR = 1.66, p < .05), and no statistical significance was found in D482G or rs853782 polymorphisms and ICP risk (all p > .05). Additionally, no publication bias was found in these studies (all p > .05). Our current meta-analysis indicated that BSEP rs2287622 polymorphism could increase the susceptibility of ICP in Asians and in general populations, while rs473351, D482G, and rs853782 polymorphisms were not obviously associated with ICP risk, but it needs further larger study with ethnicity and various etiologies.

BACKGROUND: Nonobstructive cholestasis after pediatric liver transplantation is a common diagnostic and therapeutic dilemma. We describe a girl with neonatal cholestasis because of progressive familial intrahepatic cholestasis 2 (PFIC-2) and presence of a homozygous splice site mutation in the ABCB11 gene. Liver transplantation was performed because of end-stage liver disease at the age of 6. Cholestasis with normal gamma-glutamyl transferase (GGT) developed 8 years after liver transplantation. A liver biopsy showed canalicular cholestasis and giant cell hepatitis without evidence of rejection, mimicking PFIC-2. Immunofluorescence staining of normal human liver sections with patient\'s serum revealed reactivity toward a canalicular epitope, which could be identified as bile salt export pump (BSEP) using BSEP-yellow fluorescent protein (YFP) transfected cells. Our patient developed a recurrence of a PFIC-2 phenotype due to production of antibodies against BSEP (alloimmune BSEP disease [AIBD]). Intensification of immunosuppressive therapy as well as antibody treatment with plasmapheresis and Rituximab were initiated, leading to stabilization of the clinical condition and depletion of anti-BSEP antibodies in serum. However, after 1 year liver transplantation was necessary again because of end-stage liver insufficiency. Afterward, immunomodulatory treatment consisted of tacrolimus, mycophenolate mofetil, prednisone, immunoadsorption, and high-dose immunoglobulin therapy (1 g/kg/d).
CONCLUSIONS: Cholestasis after liver transplantation may indicate an AIBD with a PFIC-2 phenotype. Besides enhancement of immunosuppressive therapy, an antibody depletion with plasmapheresis, immunoadsorption, immunoglobulins, and B-cell depletion represents a therapeutic option.

Intrahepatic cholestasis of pregnancy (ICP) represents the most common pregnancy-related liver disease in women. Women frequently present in the third trimester with pruritus and elevated serum bile acid and/or alanine transaminase levels. Clinical symptoms quickly resolve after delivery; however, recurrence in subsequent pregnancies has to be expected. Intrahepatic cholestasis of pregnancy is associated with increased perinatal complications, such as premature delivery, meconium staining of the amniotic fluid, respiratory distress, low Apgar scores, and even stillbirth. The risk for the fetus is significantly increased with maternal serum bile acid levels above 40 µmol/L, which characterize severe ICP. An important factor for ICP development is a rise of gestational hormones leading to cholestasis in genetically predisposed women. Variants in the bile salt export pump (BSEP) and the multidrug resistance protein 3 (MDR3) are most often identified in ICP. Here, we give an overview of the current literature on ICP and present the case of a woman with recurrent severe ICP. A common BSEP polymorphism as well as a rare MDR3 mutation may underlie the development of ICP in our patient. She had a premature delivery with meconium staining of the amniotic fluid. The neonate showed signs of respiratory distress with a low Apgar score. This case emphasizes that women with severe ICP have an increased risk for perinatal complications. Furthermore, severe ICP was associated with a MDR3 mutation, which has already been described in adult patients with liver cirrhosis. Thus, ICP may unmask an underlying MDR3 defect, which may predispose to development of hepatobiliary diseases such as gallstone disease, liver fibrosis/cirrhosis, as well as hepatobiliary malignancies. Therefore, genetic testing should be considered in women with severe as well as early onset ICP. Furthermore, regular follow-up should be discussed for women with genetic variants.

BACKGROUND: Progressive familial intrahepatic cholestasis 2 (PFIC2) is the result of mutations in the ABCB11, which encodes for bile salt export pump (BSEP). An absence of BSEP in the canalicular membrane causes cholestasis and leads to the development of end-stage liver disease in the first decade of life. Liver transplantation (LT) has been considered curative for BSEP disease. However, patients with PFIC2 having undergone LT have recently been reported to develop recurrence of cholestasis together with the clinical and histological features of primary BSEP disease.
METHODS: We herein present a rare case of a patient with PFIC2 who developed post-transplantation recurrence of progressive intrahepatic cholestasis due to antibodies against BSEP after living-donor LT, which mimicked primary BSEP disease. The patient had mutations in the ABCB11 gene, resulting in the complete absence of BSEP in the native liver, explaining the lack of tolerance. Immunofluorescence staining of normal human liver sections with the patient\'s serum and using an anti-human immunoglobulin G antibody to detect serum antibodies showed reactivity to the BSEP epitope in the canalicular membrane. We suggest that the patients having undergone LT had been associated with a risk of autoantibody formation against the BSEP protein. The absence of primary tolerance for the BSEP epitopes may explain the formation of the anti-BSEP antibodies after LDLT.

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