Temporal transcript profiling identifies a role for unfolded protein stress in human gut ischemia-reperfusion injury.

Abstract Background & Aim Intestinal ischemia-reperfusion injury is a serious and life-threatening condition. A better understanding of molecular mechanisms related to intestinal ischemia-reperfusion injury in man is imperative in order to find therapeutic targets and improve patient outcome. Methods First, the in vivo dynamic modulation of mucosal gene expression of the ischemia-reperfusion injured human small intestine was studied. Based on functional analysis of the changing transcriptome, one of the predominantly regulated pathways was selected for further investigation in an in vitro human intestinal organoid model. Results Ischemia-reperfusion massively changed the transcriptional landscape of the human small intestine. Functional analysis based on gene ontology and pathways pointed to the response to unfolded protein as a predominantly regulated process. In addition, regulatory network analysis identified hypoxia-inducing factor 1A (HIF1A) as one of the key mediators of ischemia-reperfusion induced changes, including the unfolded protein response (UPR). Differential expression of genes involved in the UPR was confirmed using quantitative PCR analysis. Electron microscopy showed signs of endoplasmic reticulum stress. Collectively, these findings point to a critical role for unfolded protein stress in intestinal ischemia-reperfusion injury in man. In a human intestinal organoid model exposed to hypoxia-reoxygenation, attenuation of UPR activation with integrated stress response inhibitor ISRIB strongly reduced pro-apoptotic ATF4-CHOP signaling. Conclusions Transcriptome analysis revealed a crucial role for unfolded protein stress in the response to ischemia-reperfusion in human small intestine. UPR inhibition during hypoxia-reoxygenation in an intestinal organoid model, suggests that downstream PERK signaling may be a promising target to reduce intestinal ischemia-reperfusion injury.