Necrostatin-1 Ameliorates Neutrophilic Inflammation in Asthma by Suppressing MLKL Phosphorylation to Inhibiting NETs Release.

X A Han,E W Sun,C X Yu,J Q Chen,J H Wang,X M Zhang,H Y Jie,J L Zhang,K F Lai,J He,Jun Wang

doi:10.3389/fimmu.2020.00666

Abstract

Neutrophilic inflammation occurs during asthma exacerbation, and especially, in patients with steroid-refractory asthma, but the underlying mechanisms are poorly understood. Recently, a significant accumulation of neutrophil extracellular traps (NETs) in the airways of neutrophilic asthma has been documented, suggesting that NETs may play an important role in the pathogenesis. In this study, we firstly demonstrated that NETs could induce human airway epithelial cell damage in vitro. In a mouse asthmatic model of neutrophil-dominated airway inflammation, we found that NETs were markedly increased in bronchoalveolar lavage (BAL), and the formation of NETs exacerbated the airway inflammation. Additionally, a small-molecule drug necrostatin-1 (Nec-1) shown to inhibit NETs formation was found to alleviate the neutrophil-dominated airway inflammation. Nec-1 reduced total protein concentration, myeloperoxidase activity, and the levels of inflammatory cytokines in BAL. Finally, further experiments proved that the inhibition of Nec-1 on NETs formation might be related to its ability to inhibiting mixed lineage kinase domain-like (MLKL) phosphorylation and perforation. Together, these results document that NETs are closely associated with the pathogenesis of neutrophilic asthma and inhibition of the formation of NETs by Nec-1 may be a new therapeutic strategy to ameliorate neutrophil-dominated airway inflammation.

Highlights

Asthmatic inflammation is dominated by the accumulation of eosinophils, neutrophils, or both, in the airways
It has been reported that sputum extracellular DNA in asthma is associated with airway neutrophilic inflammation, and increases in soluble neutrophil extracellular traps (NETs) components
We found that sputum extracellular DNA (eDNA) levels were significantly correlated with sputum neutrophil percentage in asthmatics and chronic cough patients (Figures 1A,B), but not significantly correlated with sputum eosinophil percentage in asthmatics and chronic cough patients (Figures 1C,D)

Summary

Introduction

Asthmatic inflammation is dominated by the accumulation of eosinophils, neutrophils, or both, in the airways. Half of the patients with asthma have eosinophilic inflammation, while the rest are characterized by increased number of neutrophils in sputum [1]. In patients with acute or persistent asthma, the number of neutrophils is increased and correlates with a poor response to inhaled corticosteroids [3, 4]. Airway neutrophil counts are associated with the severity of the disease [5, 6]. Neutrophils have been demonstrated to play a critical role in airway inflammation in patients with acute and severe asthma [5, 7, 8]. Neutrophil-predominant inflammation frequently occurs during asthma exacerbation, or in steroid-refractory patients, while the molecular mechanisms has not been determined

Methods

Results

Conclusion