Endoplasmic reticulum stress is upregulated in inflammatory bowel disease and contributed TLR2 pathway-mediated inflammatory response

Abstract

Objective

Endoplasmic reticulum stress (ERS) and Toll-like receptor 2 (TLR2) signaling play an important role in inflammatory bowel disease (IBD); however, the link between TLR2 and ERS in IBD is unclear. This study investigated whether Thapsigargin (TG) -induced ER protein expression levels contributed to TLR2-mediated inflammatory response.

Methods

The THP-1 cells were treated with TLR2 agonist (Pam3CSK4), ERS inducer Thapsigargin (TG) or inhibitor (TUDCA). The mRNA expressions of TLR1-TLR10 were detected by qPCR. The production and secretion of inflammatory factors were detected by PCR and ELISA. Immunohistochemistry was used to detect the expressions of GRP78 and TLR2 in the intestinal mucosa of patients with Crohn’s disease (CD). The IBD mouse model was established by TNBS in the modeling group. ERS inhibitor (TUDCA) was used in the treatment group.

Results

The expression of TLRs was detected via polymerase chain reaction (PCR) in THP-1 cells treated by ERS agonist Thapsigargin (TG). According to the findings, TG could promote TLR2 and TLR5 expression. Subsequently, in TLR2 agonist Pam3CSK4 induced THP-1 cells, TG could lead to increased expression of the inflammatory factors such as TNF-α, IL-1β and IL-8, and ERS inhibitor (TUDCA) could block this effect. However, Pam3CSK4 did not significantly impact the GRP78 and CHOP expression. Based upon the immunohistochemical results, TLR2 and GRP78 expression were significantly increased in the intestinal mucosa of patients with Crohn’s disease (CD). For in vivo experiments, TUDCA displayed the ability to inhibit intestinal mucosal inflammation and reduce GRP78 and TLR2 proteins.

Conclusions

ERS and TLR2 is upregulated in inflammatory bowel disease, ERS may promote TLR2 pathway-mediated inflammatory response. Moreover, ERS and TLR2 signaling could be novel therapeutic targets for IBD.

Keywords:

• inflammatory bowel disease
• endoplasmic reticulum stress
• TLR2
• GRP78
• TNF-a

Ethics approval

The experimental protocol was approved by the ethics committee of Changsha Central Hospital (Approval No. 20200512). All animals were maintained and experimented in compliance with the international declaration as well as the regulations of animal care and use policy of Changsha Central Hospital. Research involving human subjects or human tissues must comply with The Code of Ethics of the World Medical Association (Declaration of Helsinki).

Contributions

WW, YZ, TH, YL, YZ, ML, SP, and JH performed experiments; YS conceived the study. All the authors have read and approved the final version of the manuscript and agreed to be accountable for all aspects of the work.

Disclosure statement

The authors declare that they have no competing interests, and all authors confirm accuracy.

Additional information

Funding

This study was supported by grants from Hunan Science and Technology Innovation Plan Project (No. 2020SK53306) and Natural Science Foundation of Hunan Province (No. 2023JJ30067). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.