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Published on: May 2, 2018
Toll-like receptor 4 damages the intestinal epithelial cells by activating endoplasmic reticulum stress in septic
Xue Wu1, Jilin Yang1, Xin Bao2
1Department of Critical Care Medicine, First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, China.
Background:
The severity of acute gastrointestinal injury (AGI) is a critical determinant of survival in sepsis. However, there is no specifically interventional management for gastrointestinal dysfunction. Toll-like Receptor 4 (TLR4) is an important contributor to sepsis-induced multiple organ dysfunction syndrome. So, we investigated the effect of TLR4 on leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5) + cells and goblet cells and its potential mechanism.
Methods:
A cecal ligation and puncture (CLP) model reflecting the development of clinical sepsis was developed. Tak-242, a TLR4 inhibitor, was administered to septic rats at a dose of 3 mg/kg via intraperitoneal injection. Immunohistochemistry was performed to detect TLR4 and Lgr5+ cells. AB-PAS staining was performed to detect goblet cells. MUC1 and MUC2 secreted by goblet cells, biomarkers of endoplasmic reticulum (ER) stress and inflammatory cytokines in the intestine were detected by western blotting and real-time PCR.
Results:
We found that the upregulation of the TLR4/NF-κB signaling pathway activated intestinal inflammatory response in sepsis. Meanwhile, the structure of intestinal mucosa was destroyed, Lgr5+ cells and goblet cells count were significantly reduced, and the secretory function of goblet cells also decreased. Further studies have found that TLR4 increased the levels of activating transcription factor-6 (ATF6), XBP1, ER chaperone (Bip) and CHOP, but did not activate the protein kinase RNA (PKR)-like ER kinase (P-PERK).
Conclusion:
We concluded that the inhibition of TLR4/NF-κB signaling pathway can reduce intestinal inflammatory response, protect intestinal mucosa, protect Lgr5+ cells, goblet cells and relieve ER stress. Our findings suggest that Tak-242 protects Lgr5+ cells and goblet cells after sepsis, partly may be through the suppression of ER stress. Thus, inhibition of TLR4-mediated ER stress may be a promising therapy of septic AGI.
Insights
Inhibition of Toll-like Receptor 4 (TLR4) mitigates sepsis-induced gastrointestinal injury by protecting Lgr5+ and goblet cells and reducing endoplasmic reticulum stress. This suggests TLR4 inhibition as a potential therapy for septic acute gastrointestinal injury.
Area of Science:
- Gastroenterology
- Immunology
- Cell Biology
Background:
- Sepsis-induced acute gastrointestinal injury (AGI) significantly impacts patient survival.
- Current management lacks specific interventions for gastrointestinal dysfunction.
- Toll-like Receptor 4 (TLR4) plays a key role in sepsis-related multiple organ dysfunction.
Purpose of the Study:
- To investigate the impact of TLR4 on leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5)+ cells and goblet cells in sepsis.
- To elucidate the underlying mechanisms of TLR4's effect on intestinal cells during sepsis.
- To evaluate the therapeutic potential of TLR4 inhibition in septic AGI.
Main Methods:
- A cecal ligation and puncture (CLP) rat model was used to simulate clinical sepsis.
- The TLR4 inhibitor Tak-242 was administered intraperitoneally.
- Immunohistochemistry, AB-PAS staining, western blotting, and real-time PCR were employed to assess cellular changes, protein expression, and inflammatory markers.
Main Results:
- Sepsis upregulated the TLR4/NF-κB pathway, increasing intestinal inflammation and damaging mucosal structure.
- Lgr5+ cells and goblet cells were significantly reduced in number and function.
- TLR4 activation led to endoplasmic reticulum (ER) stress markers (ATF6, XBP1, Bip, CHOP) without activating P-PERK.
Conclusions:
- Inhibiting the TLR4/NF-κB pathway ameliorates intestinal inflammation and protects intestinal mucosa, Lgr5+ cells, and goblet cells.
- Tak-242 protects intestinal cells post-sepsis, potentially by suppressing ER stress.
- Targeting TLR4-mediated ER stress offers a promising therapeutic strategy for septic AGI.
