Inositol-Requiring Kinase 1 Regulates Apoptosis via Inducing Endoplasmic Reticulum Stress in Colitis Epithelial Cells

Background Endoplasmic reticulum stress (ERS) has been studied as critical factor during occurrence and development of ulcerative colitis (UC). However, the role of ERS in inflamed UC remains unclear. Aims The purpose of this study was to analyze the role of inositol-requiring kinase 1 (IRE-1), a major regulator of ER, in regulating ERS and cell viability. Methods In UC mucosa tissue,IRE-1,BiP,XBP-1s,CHOP caspase-12andGADD34mRNA were assayed by qRT-PCR. Then, human normal colon epithelial cell line (NCM-460) and colon fibroblast cell line (CCD-33Co) were cultured, and downregulated or upregulated IRE-1 expression. ERS was induced with 100 ng/mL of Interleukin 6 (IL-6). CCK8 assay was performed to analyze cell proliferation. Flow cytometry analysis was conducted to detect the apoptosis. Western blot assay was used to examine ERS markers. Results IRE-1,BiP,XBP-1s,caspase-12andCHOPmRNA were highly expressed in UC mucosa tissue, and the expression ofGADD34mRNA significantly decreased. These results show that ERS-induced unfolded protein response was enhanced in UC mucosa tissue. In cells, silencing the expression of IRE-1 could suppress cell proliferation and promote apoptosis through activating unfolded protein response, while the over-expression of IRE-1 had the opposite effect. IL-6 could induce ERS and cells apoptosis. Furthermore, we demonstrated that shRNA IRE-1 could enhance the inhibition of IL-6 on cells viability. Conclusions Inhibition of IRE-1 enhanced unfolded protein response and cells apoptosis and IL-6-induced ERS and suggested that IRE-1 might be a potential target of UC.

Automated summary

ERS, particularly the role of IRE-1, was analyzed in UC mucosa tissue and cell lines, revealing its involvement in regulating cell proliferation, apoptosis, and response to IL-6-induced ERS. Targeting IRE-1 could enhance unfolded protein response and apoptosis in UC, suggesting its potential as a therapeutic target.