Suppression of NLRP3 Inflammasome by Erythropoietin via the EPOR/JAK2/STAT3 Pathway Contributes to Attenuation of Acute Lung Injury in Mice.

Fei Cao,Jun Han,Ya Lv,Binyu Ying,Xinyi Tian,Yuqiang Gong,Zhongwang Li,Shengwei Jin,Rong Zhuang,Bihuan Cheng,Ye Gao

doi:10.3389/fphar.2020.00306

Abstract

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common and devastating clinical disorders with high mortality and no specific therapy. An excessive inflammatory response results in the progression of ALI/ARDS, and the NLRP3 inflammasome is a key participant in inflammation. Erythropoietin (EPO), which is clinically used for anemia, reportedly exerts pleiotropic effects in ALI. However, whether EPO could protect against lipopolysaccharide (LPS)-induced ALI by regulating the NLRP3 inflammasome and its underlying mechanisms remain poorly elucidated. This study aimed to explore whether the therapeutic effects of EPO rely on the suppression of the NLRP3 inflammasome and the specific mechanisms in an LPS-induced ALI mouse model. ALI was induced in C57BL/6 mice by intraperitoneal (i.p.) injection of LPS (15 mg/kg). EPO was administered intraperitoneally at 5 U/g after LPS challenge. The mice were sacrificed 8 h later. Our findings indicated that application of EPO markedly diminished LPS-induced lung injury by restoring histopathological changes, lessened lung wet/dry (W/D) ratio, protein concentrations in bronchoalveolar lavage fluid (BALF) and myeloperoxidase (MPO) levels. Meanwhile, EPO evidently decreased interleukin-1β (IL-1β) and interleukin-18 (IL-18) secretion, the expression of NLRP3 inflammasome components including pro-IL-1β, NLRP3, and cleaved caspase-1 as well as phosphorylation of nuclear factor-κB (NF-κB) p65, which may be associated with activation of EPO receptor (EPOR), phosphorylation of Janus-tyrosine kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3). However, all the beneficial effects of EPO on ALI and modulation NLRP3 inflammasome were remarkably abrogated by the inhibition of EPOR/JAK2/STAT3 pathway and knockout (KO) of NLRP3 gene. Taken together, this study indicates that EPO can effectively attenuate LPS-induced lung injury in mice by suppressing the NLRP3 inflammasome, which is dependent upon activation of EPOR/JAK2/STAT3 signaling and inhibition of the NF-κB pathway.

Highlights

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common life-threatening critical illnesses with substantial morbidity and mortality (ARDS Definition Task Force et al, 2012; Rezoagli et al, 2017)
The results revealed that the EPO receptor (EPOR) antagonist (EMP9), Janus-tyrosine kinase 2 (JAK2) inhibitor (Fedratinib), and signal transducer and activator of transcription 3 (STAT3) inhibitor (NSC 74859) abolished EPO-mediated alleviation of lung injury with higher IL-1β and IL-18 concentrations, W/D ratio, bronchoalveolar lavage fluid (BALF) protein levels, and MPO production (Figures 7A–G)
The inhibition of EPOR, JAK2, and STAT3 and deletion of NLR family pyrin domain containing 3 (NLRP3) abolished suppression of the NLRP3 inflammasome and diminished the beneficial effects of EPO on ALI. These results suggest that EPO can attenuate lung inflammation of LPS-induced ALI by suppressing the NLRP3 inflammasome in a process that depends on the EPOR/JAK2/STAT3/nuclear factor-κB (NFκB) signaling axis

Summary

Introduction

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common life-threatening critical illnesses with substantial morbidity and mortality (ARDS Definition Task Force et al, 2012; Rezoagli et al, 2017). ALI/ARDS is characterized by exaggerated lung parenchyma inflammation, which leads to massive infiltration of activated neutrophils, progressive alveolar filling, and intractable hypoxemia (Giacomo Bellani et al, 2016). Recent studies have suggested that the NLRP3 inflammasome plays a pivotal role in the progression of ALI/ARDS caused by various pathogenic microorganisms, such as influenza A virus (Allen et al, 2009), Pseudomonas aeruginosa (Cohen and Prince, 2013), and Staphylococcus aureus (Miller et al, 2007)

Objectives

Methods

Results

Discussion

Conclusion