Inositol-requiring enzyme 1 alpha/X-box protein 1 pathway expression is impaired in pediatric cholestatic liver disease explants

Background Increased intrahepatic bile acids cause endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) is activated to maintain homeostasis. UPR dysregulation, including the inositol-requiring enzyme 1 alpha/X-box protein 1 (IRE1 alpha/XBP1) pathway, is associated with adult liver diseases but has not been characterized in pediatric liver diseases. We evaluated hepatic UPR expression in pediatric cholestatic liver disease (CLD) explants and hypothesize that an inability to appropriately activate the hepatic IRE1 alpha/XBP1 pathway is associated with the pathogenesis of CLD. Methods We evaluated 34 human liver explants, including: 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. Results 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 alpha/XBP1 pathway gene expression and decreased protein expression of phosphorylated IRE1 alpha compared to normal controls. IRE1 alpha/XBP1 pathway gene expression was also decreased in pediatric CLD compared to AIH disease controls. Conclusions Pediatric CLD explants have decreased expression of the protective IRE1 alpha/XBP1 pathway and down-regulated KEGG protein processing in the ER pathways. IRE1 alpha/XBP1 pathway expression differences occur when compared to both normal and non-cholestatic disease controls. Attenuated expression of the IRE1 alpha/XBP1 pathway is associated with cholestatic diseases and may be a target for future therapeutics.