Assessment of ATP8B1 Deficiency in Pediatric Patients With Cholestasis Using Peripheral Blood Monocyte-Derived
Hisamitsu Hayashi1, Sotaro Naoi1, Takao Togawa2
1Laboratory of Molecular Pharmacokinetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan.
Insights
Diagnosing Progressive Familial Intrahepatic Cholestasis type 1 (PFIC1) is challenging. Analyzing macrophages reveals ATP8B1 deficiency impairs M2c polarization, offering a new diagnostic method for PFIC1.
Area of Science:
- Genetics
- Immunology
- Hepatology
Background:
- Progressive Familial Intrahepatic Cholestasis type 1 (PFIC1) is a rare inherited liver disease caused by ATP8B1 gene mutations.
- Current diagnostic methods for PFIC1, including clinical, histological, and genomic analyses, face limitations in differentiating it from other PFIC subtypes.
- A novel diagnostic approach is needed to accurately identify PFIC1 patients.
Purpose of the Study:
- To investigate the role of ATP8B1 in macrophage polarization.
- To explore the potential of using human peripheral blood monocyte-derived macrophages (HMDM) as a diagnostic marker for PFIC1.
- To establish an alternative method for diagnosing PFIC1, particularly in cases with ambiguous genetic findings.
Main Methods:
- Analysis of ATP8B1 expression in interleukin-10 (IL-10)-induced M2c macrophages.
- SiRNA-mediated depletion of ATP8B1 in IL-10-treated HMDM to assess its impact on M2c phenotype and the IL-10/STAT3 pathway.
- Phenotypic analysis of M2c macrophages from PFIC1 patients and patients with other PFIC subtypes.
Main Results:
- ATP8B1 is predominantly expressed in IL-10-induced M2c macrophages.
- ATP8B1 depletion in HMDM suppressed M2c surface markers and increased side scatter (SSC), indicating impaired M2c polarization via the IL-10/STAT3 pathway.
- These phenotypic changes were observed in HMDM from PFIC1 patients but not from patients with other PFIC subtypes, enabling the identification of previously undiagnosed PFIC1 cases.
Conclusions:
- ATP8B1 deficiency leads to incomplete polarization of HMDM into M2c macrophages.
- Phenotypic analysis of M2c macrophages serves as a valuable diagnostic tool for identifying PFIC1 patients, including those without apparent ATP8B1 mutations.
- This macrophage-based approach offers a promising alternative for PFIC1 diagnosis.
Abstract:
Progressive familial intrahepatic cholestasis type 1 (PFIC1), a rare inherited recessive disease resulting from a genetic deficiency in ATP8B1, progresses to liver failure. Because of the difficulty of discriminating PFIC1 from other subtypes of PFIC based on its clinical and histological features and genome sequencing, an alternative method for diagnosing PFIC1 is desirable. Herein, we analyzed human peripheral blood monocyte-derived macrophages (HMDM) and found predominant expression of ATP8B1 in interleukin-10 (IL-10)-induced M2c, a subset of alternatively activated macrophages. SiRNA-mediated depletion of ATP8B1 in IL-10-treated HMDM markedly suppressed the expression of M2c-related surface markers and increased the side scatter (SSC) of M2c, likely via impairment of the IL-10/STAT3 signal transduction pathway. These phenotypic features were confirmed in IL-10-treated HMDM from four PFIC1 patients with disease-causing mutations in both alleles, but not in those from four patients with other subtypes of PFIC. This method identified three PFIC1 patients in a group of PFIC patients undiagnosed by genome sequencing, an identical diagnostic outcome to that achieved by analysis of liver specimens and in vitro mutagenesis studies. In conclusion, ATP8B1 deficiency caused incomplete polarization of HMDM into M2c. Phenotypic analysis of M2c helps to identify PFIC1 patients with no apparent disease-causing mutations in ATP8B1.
