IRE1α/XBP1 pathway expression is impaired in pediatric cholestatic liver disease explants

Abstract

Background and Aims: Cholestatic liver diseases (CLD) are the leading indication for pediatric liver transplantation. Bile acids are known to trigger endoplasmic reticulum (ER) stress. The unfolded protein response (UPR) is a coordinated response which functions to decrease ER stress and maintain cellular homeostasis. Dysregulation of the UPR, specifically the inositol-requiring enzyme 1α/X-box protein 1 (IRE1α/XBP1) pathway, has been associated with several adult liver diseases. In this study, we sought to evaluate the UPR in pediatric livers with end-stage CLD and hypothesized there would be altered IRE1α/XBP1 pathway activation compared to normal control livers. Methods: We evaluated 34 human liver ex-plants which included pediatric CLD, pediatric normal, pediatric non-cholestatic liver disease (autoimmune hepatitis, AIH), adult CLD and adult normal cohorts. We performed RNA sequencing (RNAseq), qPCR and western blotting to identify significantly different pathway activation and assess for changes within the UPR. Results: Pathway analysis of RNAseq data demonstrated that protein processing in the ER was a significantly differentially expressed pathway in all liver disease cohorts compared to appropriate controls. Pediatric CLD samples had evidence of ongoing ER stress with activation of the PKR-like ER kinase (PERK) pathway but had significantly decreased expression of the IRE1α/XBP1 pathway of the UPR compared to normal controls. Pediatric AIH samples had similar activation of the PERK pathway but notably did not have decreased activation of the IRE1α/XBP1 pathway compared to normal controls.