The inositol-requiring enzyme 1α/X-box protein 1 (IRE1α/XBP1) pathway of the unfolded protein response is impaired in pediatric cholestatic liver disease explants
Background/AimsCholestatic liver diseases (CLD) are the leading indication for pediatric liver transplantation. Increased intrahepatic bile acid concentrations cause endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) is activated to maintain homeostasis. UPR dysregulation, including the inositol-requiring enzyme 1/X-box protein 1 (IRE1/XBP1) pathway, is associated with several adult liver diseases. We evaluated hepatic UPR expression in pediatric patients with end-stage CLD and hypothesize that an inability to appropriately activate the hepatic IRE1/XBP1 pathway is associated with the pathogenesis of CLD. MethodsWe evaluated 34 human liver explants. Cohorts included: pediatric CLD (Alagille, ALGS, and progressive familial intrahepatic cholestasis, PFIC), pediatric non-cholestatic liver disease controls (autoimmune hepatitis, AIH), adult CLD, and normal controls. We performed RNA-seq, quantitative PCR, and western blotting to measure expression differences of the hepatic UPR and other signaling pathways. ResultsMetascape pathway analysis demonstrated that the KEGG protein processing in ER pathway was downregulated in pediatric CLD compared to normal controls. Pediatric CLD had decreased hepatic IRE1/XBP1 pathway gene expression and decreased protein expression of p-IRE1 compared to normal controls. These CLD changes were not disease-specific to ALGS or PFIC. IRE1/XBP1 pathway gene expression was decreased in pediatric CLD compared to AIH disease controls. ConclusionPediatric CLD explants have decreased gene and protein expression of the protective IRE1/XBP1 pathway and down-regulated KEGG protein processing in the ER pathways. IRE1/XBP1 pathway expression differences occur when compared to both normal and non-cholestatic disease controls. Attenuated expression of the IRE1/XBP1 pathway is associated with cholestatic diseases and could be targeted to treat pediatric CLD.