ER stress activation in the intestinal mucosa but not in mesenteric adipose tissue is associated with inflammation in Crohn's disease patients.

Andressa Coope,Bruno Lima Rodrigues,Rita Barbosa Carvalho,Lício Augusto Velloso,Francesca Aparecida Ramos Da Silva,Maria De Lourdes Setsuko Ayrizono,Lívia Bitencourt Pascoal,José Diego Botezelli,João José Fagundes,Marciane Milanski,Raquel Franco Leal,Arun Rishi

doi:10.1371/journal.pone.0223105

Andressa Coope, Bruno Lima Rodrigues + Show 10 more

Open Access

https://doi.org/10.1371/journal.pone.0223105

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Journal: PloS one	Publication Date: Sep 26, 2019
Citations: 13	License type: CC BY 4.0

Affiliation: Universidade Estadual de Campinas

Abstract

Chronic/abnormal activation of endoplasmic reticulum (ER) stress is linked to the exacerbation of the inflammatory process and has been recently linked to Crohn’s disease (CD) pathophysiology. We investigated the intestinal mucosa and the mesenteric adipose tissue (MAT) collected from CD patients with active disease (CD group) and from non-IBD patients (CTR group) to study ER stress activation and to address tissue-specific modulation in CD. The intestinal mucosa of CD patients showed an upregulation in the expression of ER stress related genes, including ATF3, DNAJC3, STC2, DDIT3, CALR, HSPA5 and HSP90B1. Results showed that EIF2AK3 gene was upregulated, along with increased protein expression of p-eIF2α and p-eIF2α/eIF2α ratio. Additionally, ERN1 gene expression was upregulated, along with an increased spliced/activated form sXBP1 protein. Despite the upregulation of ATF6 gene expression in the intestinal mucosa of CD patients, no differences were found in ATF6 protein expression. Lastly, the analysis of MAT revealed unchanged levels of ER stress markers along with no differences in the activation of UPR. However, chaperone gene expression was modulated in the MAT of CD patients. To conclude, our results address tissue-specific differences in UPR activation in CD and point the ER stress as an important pro-inflammatory mechanism in CD, specifically in the intestinal mucosa.

Highlights

Crohn’s Disease (CD) is a chronic multifactorial inflammatory bowel disease (IBD) characterized by transmural granulomatous inflammation, mucosal immune cell activation, abnormal immune response and cytokine imbalance, due to a complex interaction encompassing genetic predisposition, environmental risk factor, microbiota dysregulation and impaired mucosal immune system [1,2]
Hematoxylin and eosin (H&E) staining in mesenteric adipose tissue (MAT) of Crohn’s disease (CD) patients showed a reduced adipocyte area and perimeter compared to the control group (S2A Fig)
The increased gene expression of ERN1 is in line with the increased protein expression of the active sXBP1 in the intestinal mucosa of CD patients (Fig 1C), which implies the activation of this unfolded-protein response (UPR) branch

Summary

Introduction

Crohn’s Disease (CD) is a chronic multifactorial inflammatory bowel disease (IBD) characterized by transmural granulomatous inflammation, mucosal immune cell activation, abnormal immune response and cytokine imbalance, due to a complex interaction encompassing genetic predisposition, environmental risk factor, microbiota dysregulation and impaired mucosal immune system [1,2]. The MAT of CD patients shows an impaired autophagy and apoptosis regulation [4,5], which display the complex interplay between intestinal mucosa and MAT in the pathogenesis of CD and highlights the importance of dissecting the molecular mechanisms that drive inflammation. Three UPR axis are activated in response to ER stress: IRE1/sXBP1 (inositol requiring enzyme 1/spliced form of X-box binding protein-1), ATF6 (activating transcription factor 6) and PERK/eIF2α (PKR-like eukaryotic initiation factor 2α kinase/ eukaryotic translation initiation factor 2 α). Together, they coordinate a response to the unfolded/misfolded proteins accumulation

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