Endoplasmic Reticulum Stress in Colonic Mucosa of Ulcerative Colitis Patients Is Mediated by PERK and IRE1 Pathway Activation.

Bruno Lima Rodrigues,Joseane Morari,Raquel Franco Leal,Maria De Lourdes Setsuko Ayrizono,Azucena Salas,Andressa Coope,Lívia Bitencourt Pascoal,Isabella Dotti,Miriam Esteller,Eduardo Dalmarco

doi:10.1155/2022/6049500

Abstract

Ulcerative colitis (UC) is characterized by a chronic overproduction of proinflammatory cytokines. During an acute phase, the endoplasmic reticulum (ER) is overloaded and the protein folding process is impaired, a condition named ER stress. This state induces a response (unfolded protein response (UPR)), initiated by the activation of IRE1/Xbp-1, PERK/eIF2α, and ATF6 pathways, which has previously been linked to intestinal inflammation in experimental models. ER stress and UPR activation trigger the activation of proinflammatory, autophagy, and apoptosis genes, in addition to promoting protein degradation. Therefore, the goal of this study was to evaluate the activation of ER stress and UPR in colonic mucosa of UC patients. Patient and Methods. Transcriptional analysis of ER stress- and UPR-related genes was performed by qPCR from intestinal mucosa of patients with UC. We also performed in situ hybridization (ISH) and immunohistochemistry (IHQ) of PERK/eIF2α and IRE1/Xbp-1 pathways and UPR-related chaperones. Results. We first evaluated inflammatory genes via qPCR, and we observed that all analyzed proinflammatory transcripts were upregulated in UC patients. ISH and IHQ images showed that ER stress is activated via PERK/eIF2α and IRE1/Xbp-1 pathways not only in intestinal epithelial cells but also in cells of the lamina propria of UC colonic mucosa. Transcriptional analysis confirmed that EIF2AK3 was upregulated in UC patients. UPR-related genes, such as ATF3, STC2, and DDIT3, along with the chaperones and cochaperones DNAJC3, CALR, HSP90B1, and HSPA5, were also upregulated in UC patients. In addition, we observed that proapoptotic and autophagy genes (Bax and ATG6L1, respectively) were also upregulated. Conclusion. Our results suggest that ER stress and UPR are indeed activated in UC patients and this may contribute to the chronic inflammatory process seen in UC. The increased apoptosis and autophagy markers further support the activation of these findings once they are activated to counterbalance tissue damage. These findings provide new insights into the molecular mechanisms that maintain UC activity and open new possibilities to attenuate intestinal inflammation.

Highlights

Ulcerative colitis (UC) refers to a chronic inflammatory bowel disease (IBD) with a relapsing and remitting course that affects the rectum and extends to proximal segments of the colon
To confirm the proinflammatory signalling in the UC colonic mucosa, we evaluated the expression of cytokines often modulated in IBD
As apoptosis may occur as a result of inflammation and/or endoplasmic reticulum (ER) stress activation, we evaluated the transcriptional levels of pro- and antiapoptotic genes

Summary

Introduction

Ulcerative colitis (UC) refers to a chronic inflammatory bowel disease (IBD) with a relapsing and remitting course that affects the rectum and extends to proximal segments of the colon. It is characterized by abdominal pain, faecal urgency, and diarrhea [1]. The increase in the production of proinflammatory cytokines is one of the many reasons that overloads the endoplasmic reticulum (ER), impairing the folding of proteins and their final conformation. The accumulation of unfolded proteins in the ER lumen leads to a condition named endoplasmic reticulum stress (ER stress) [4]

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