QSOX1 exerts anti-inflammatory effects in sepsis-induced acute lung injury: Regulation involving EGFR phosphorylation mediated M1 polarization of macrophages

Sepsis is a systemic inflammatory response caused by an infection, which can easily lead to acute lung injury. Quiescin Q6 sulfhydryl oxidase 1 (QSOX1) is a sulfhydryl oxidase involved in oxidative stress and the inflammatory response. However, there are few reports on the role of QSOX1 in sepsis-induced acute lung injury (SALI). In this study, mice model of SALI was constructed by intraperitoneal injection with lipopolysaccharide (LPS). The increased inflammatory response and lactate dehydrogenase activity in bronchoalveolar lavage fluid (BALF) indicated successful modeling. Increased QSOX1 expression was both observed in lung tissues and lung macrophages of sepsis mice accompanied by increased polarization of M1-type macrophages. To explore the role of QSOX1 in the SALI, lentivirus containing QSOX1-specific overexpression or knockdown vectors were used to change QSOX1 expression in LPS-treated RAW264.7 cells. QSOX1 suppressed LPS-induced M1 polarization and further inhibited inflammatory response in RAW264.7 cells. Interestingly, the phosphorylation of epidermal growth factor receptor (EGFR), the promoter of M1 polarization in macrophages, was found to be downregulated upon QSOX1 overexpression in RAW264.7 cells. Mechanically, the binding of QSOX1 to EGFR protein promoted EGFR ubiquitination and degradation, thereby down-regulating EGFR phosphorylation. Moreover, inhibiting EGFR expression or its phosphorylation restored the impact of QSOX1 silencing on M1 polarization and inflammation in the LPS-treated RAW264.7 cells. In summary, QSOX1 may exert anti-inflammatory effects in SALI by inhibiting EGFR phosphorylation-mediated M1 macrophage polarization. This presented a potential target for the treatment and prevention of SALI.