Assessment of Adenosine Triphosphatase Phospholipid Transporting 8B1 (ATP8B1) Function in Patients With Cholestasis With ATP8B1 Deficiency by Using Peripheral Blood Monocyte-Derived Macrophages

Abstract

Adenosine triphosphatase phospholipid transporting 8B1 (ATP8B1) deficiency, an ultrarare autosomal recessive liver disease, includes severe and mild clinical forms, referred to as progressive familial intrahepatic cholestasis type 1 (PFIC1) and benign recurrent intrahepatic cholestasis type 1 (BRIC1), respectively. There is currently no practical method for determining PFIC1 or BRIC1 at an early disease course phase. Herein, we assessed the feasibility of developing a diagnostic method for PFIC1 and BRIC1. A nationwide Japanese survey conducted since 2015 identified 25 patients with cholestasis with ATP8B1 mutations, 15 of whom agreed to participate in the study. Patients were divided for analysis into PFIC1 (n = 10) or BRIC1 (n = 5) based on their disease course. An in vitro mutagenesis assay to evaluate pathogenicity of ATP8B1 mutations suggested that residual ATP8B1 function in the patients could be used to identify clinical course. To assess their ATP8B1 function more simply, human peripheral blood monocytederived macrophages (HMDMs) were prepared from each patient and elicited into a subset of alternatively activated macrophages (M2c) by interleukin-10 (IL-10). This was based on our previous finding that ATP8B1 contributes to polarization of HMDMs into M2c. Flow cytometric analysis showed that expression of M2c-related surface markers cluster of differentiation (CD)14 and CD163 were 2.3-fold and 2.1-fold lower (95% confidence interval, 2.0-2.5 for CD14 and 1.7-2.4 for CD163), respectively, in patients with IL-10-treated HMDMs from PFIC1 compared with BRIC1. Conclusion: CD14 and CD163 expression levels in IL-10-treated HMDMs may facilitate diagnosis of PFIC1 or BRIC1 in patients with ATP8B1 deficiency. (Hepatology Communications 2020;0:1-11). F amilial cholestatic liver disease comprises a variety of clinically and genetically heterogeneous disorders. Mutations in adenosine triphosphatase phospholipid transporting 8B1 (ATP8B1), adenosine triphosphate binding cassette subfamily B member 11 (ABCB11), tight junction Abbreviations: ATP8B1, adenosine triphosphatase phospholipid transporting 8B1; BRIC, benign recurrent intrahepatic cholestasis; CD, cluster of differentiation; CDC50A, heterodimer complex with transmembrane protein 30A; GGT, gamma-glutamyltransferase; HA, hemagglutinin antigen; HMDM, human peripheral blood monocyte-derived macrophage; HPBMo, human peripheral blood monocytes; IL-10, interleukin-10; M2c, subset of alternatively activated macrophages; MFI, mean fluorescence intensity; NBD-PC, nitrobenzoxadiazole-labeled phosphatidylcholine; PFIC, progressive familial intrahepatic cholestasis; WT, wild type.

Clinical phenotype of adult‐onset liver disease in patients with variants in ABCB4 , ABCB11 , and ATP8B1

“…Functional work suggests that residual FIC1 function determines the clinical phenotype of patients with biallelic variants in ATP8B1 , with most patients with early‐onset FIC1 deficiency predicted to have a complete loss of function, and those with benign recurrent intrahepatic cholestasis 5%–20% function of a healthy subject. [ 21 ] The correlation with higher levels of functional FIC1 and phenotype has not been explored, and most patients from our cohort are heterozygotes and therefore have much higher levels of FIC1, at least 50% of healthy subjects. The exact pathogenesis of FIC1 deficiency is not clear [ 22 ] ; however, it appears integral in the role of other proteins, including BSEP, farnesoid X receptor, and cystic fibrosis transmembrane conductance regulator.…”

Case Report: A Rare Case of Benign Recurrent Intrahepatic Cholestasis-Type 1 With a Novel Heterozygous Pathogenic Variant of ATP8B1

“…In addition, this difference may also be due to the rare genetic variant of ATP8B1. In a recent Japanese nationwide survey, it was shown that there are no critical methods to distinguish between PFIC1 and BRIC1 at the early phase of the disease (13). Therefore, further accumulation and evaluation of BRIC1 cases are desirable for more appropriate follow-up of these patients.…”

Case Report: A Rare Heterozygous ATP8B1 Mutation in a BRIC1 Patient: Haploinsufficiency?

“…ATP8B1 mutations reduced BSEP activity and impaired bile excretion by affecting PS turnover ( 13 ). In ATP8B1 deficient patients, the nuclear translocation of the Farnesoid X receptor (FXR), a transcription factor that controls bile acid homeostasis, is disrupted, and BSEP expression on the hepatic duct membrane is reduced due to its transcriptional inhibition ( 14 , 15 ) ( Figure 3 ).…”

“…In the future, a reliable ATP8B1 protein function detection method is needed to evaluate the severity and prognosis of disease. Research has found that human peripheral blood monocyte-derived macrophages (HMDMs) can be used evaluate ATP8B1 function ( 15 , 26 ).…”