BM213

Astragaloside IV (AS-IV), derived from Astragalus membranaceus, exhibits significant anti-inflammatory properties in a variety of diseases. However, the specific anti-inflammatory mechanism of AS-IV depends on the different organs and doses. Its protective effect is still unknown in acute lung injury (ALI). This study aims to investigate the potential anti-inflammatory mechanism of AS-IV in ALI. Lipopolysaccharide (LPS) and adenosine triphosphate (ATP) were utilized to form pyroptosis models in MH-S and RAW264.7 cells. Mouse model of ALI was induced by intranasal LPS administration. In addition, the anti-pyroptosis effect of AS-IV was evaluated by using the C5aR1 agonists BM-213, the C5aR1 overexpression plasmids and C5aR1 siRNA. AS-IV significantly reduced pulmonary edema, improved histopathological injury, and decreased inflammatory factors. Meanwhile, AS-IV reduced ROS level and the amount of NLRP3 and GSDMD-N in vitro and in vivo. Inhibiting C5aR1 can effectively and significantly alleviate the pyroptosis of alveolar macrophages. Further studies found that BM-213 and C5aR1 overexpression plasmids partially reversed the anti-pyroptosis effect of AS-IV. The anti-pyroptosis effect of AS-IV was significantly inhibited when C5aR1 was knocked down. Our study demonstrate that AS-IV has anti-inflammatory protective effects on LPS-induced ALI, indicating that AS-IV may be a potential therapeutic agent for the treatment of ALI. This effect may be achieved by reducing the content of C5a, lowering the expression of C5aR1, and inhibiting cell pyroptosis.

The Panton-Valentine leukocidin (PVL) of Staphylococcus aureus is associated with necrotizing infections. After binding to complement 5a receptor (C5aR/CD88) and CD45 it causes cytolysis in polymorphonuclear neutrophils (PMNs) as well as inflammasome activation in monocytes. The objective of this study was to test if (ant)agonists of C5aR and CD45 can attenuate the effect of PVL on PMNs and monocytes. We tested the effect of various concentrations of six C5aR (ant)agonists (avacopan, BM213, DF2593A, JPE-1375, PMX205 and W-54011) and one CD45 antagonist (NQ301) to attenuate the cytotoxic effect of PVL on human PMNs and monocytes in vitro. Shifts in the half-maximal effective concentration (EC50) of PVL to achieve a cytotoxic effect on PMNs and modulation of inflammatory cytokine response from monocytes were determined by flow cytometry and IL-1β detection. Pre-treatment of PMNs with avacopan, PMX205 and W-54,011 resulted in 3.6- to 4.3-fold shifts in the EC50 for PVL and were able to suppress IL-1β secretion by human monocytes in the presence of PVL. BM213, DF2593A and NQ301 were unable to change the susceptibility of PMNs towards PVL or reduce inflammasome activation in monocytes. Avacopan, PMX205 and W-54,011 showed protection against PVL-induced cytotoxicity and suppressed IL-1β secretion by monocytes. Clinical studies are needed to prove whether these substances can be used therapeutically as repurposed drugs.