Neutrophil extracellular traps impair intestinal barrier functions in sepsis by regulating TLR9-mediated endoplasmic reticulum stress pathway

Shilong Sun,Xinyu Wang,Zehua Duan,Qiurong Li,Weiwei Ding,Chengnan Chu,Fang Chen,Chao Yang,Chenyang Wang,Daojuan Wang

doi:10.1038/s41419-021-03896-1

Abstract

Increased neutrophil extracellular traps (NETs) formation has been found to be associated with intestinal inflammation, and it has been reported that NETs may drive the progression of gut dysregulation in sepsis. However, the biological function and regulation of NETs in sepsis-induced intestinal barrier dysfunction are not yet fully understood. First, we found that both circulating biomarkers of NETs and local NETs infiltration in the intestine were significantly increased and had positive correlations with markers of enterocyte injury in abdominal sepsis patients. Moreover, the levels of local citrullinated histone 3 (Cit H3) expression were associated with the levels of BIP expression. To further confirm the role of NETs in sepsis-induced intestinal injury, we compared peptidylarginine deiminase 4 (PAD4)-deficient mice and wild-type (WT) mice in a lethal septic shock model. In WT mice, the Cit H3-DNA complex was markedly increased, and elevated intestinal inflammation and endoplasmic reticulum (ER) stress activation were also found. Furthermore, PAD4 deficiency alleviated intestinal barrier disruption and decreased ER stress activation. Notably, NETs treatment induced intestinal epithelial monolayer barrier disruption and ER stress activation in a dose-dependent manner in vitro, and ER stress inhibition markedly attenuated intestinal apoptosis and tight junction injury. Finally, TLR9 antagonist administration significantly abrogated NETs-induced intestinal epithelial cell death through ER stress inhibition. Our results indicated that NETs could contribute to sepsis-induced intestinal barrier dysfunction by promoting inflammation and apoptosis. Suppression of the TLR9–ER stress signaling pathway can ameliorate NETs-induced intestinal epithelial cell death.

Highlights

Sepsis is defined as life-threatening organ dysfunction caused by the dysregulation of the host response secondary to infection, which remains a leading cause of high mortality in the intensive care unit [1, 2]
Increased intestinal neutrophil extracellular traps (NETs) infiltration and endoplasmic reticulum (ER) stress activation in human abdominal sepsis To determine NETs performance and ER stress levels in sepsis and their possible pathological impact on intestinal barrier dysfunction, we compared the relative expression in serum and relative protein levels in intestinal samples of healthy and abdominal sepsis patients
We firstly investigated whether the expression of NETs is altered in the peripheral system of these patients

Summary

Introduction

Sepsis is defined as life-threatening organ dysfunction caused by the dysregulation of the host response secondary to infection, which remains a leading cause of high mortality in the intensive care unit [1, 2]. The breakdown of the gut barrier can result in many bacteria and toxins entering the internal environment, driving lethal sepsis and even multiple organ dysfunction syndrome (MODS) [5]. A more thorough understanding of the inflammatory mechanism involved in intestinal barrier dysfunction is pivotal for developing more efficient treatments against sepsis and MODS. Since neutrophil extracellular traps (NETs) were firstly described by Brinkman in 2004, excessive NETs formation has been shown to be involved in the pathophysiology of sepsis [6, 7]. Excessive NETs formation has been indicated to have a role in both infectious and noninfectious diseases, including but not limited to thrombosis, diabetes, vasculitis, and cancer [11, 12]. The biological function and downstream signaling pathway of NETs in sepsisinduced intestinal barrier dysfunction are not yet fully understood

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