ASTRAGALOSIDE â £ MODULATES GUT MACROPHAGES M1/M2 POLARIZATION BY RESHAPING GUT MICROBIOTA AND SHORT CHAIN FATTY ACIDS IN SEPSIS.

ABSTRACT: M1 macrophage-mediated inflammation is critical in sepsis. We previously found the protective role of astragaloside intravenous (AS-IV) in sepsis-associated gut impairment, whose specific mechanism remains unknown. Gut microbiota modulates gut homeostatic balance to avoid excessive inflammation. Here, we aimed to investigate effects of AS-IV on gut macrophages polarization and potential roles of gut microbiota and short chain fatty acids (SCFAs) in septic gut damage. Mice were pretreated by AS-IV gavage for 7 days before cecal ligation and puncture. M1 polarization of gut lamina propria macrophages (LpMs) was promoted by cecal ligation and puncture, accompanied by abnormal cytokines release and intestinal barrier dysfunction. NLRP3 inflammasome was activated in M1 LpMs. 16S rRNA sequencing demonstrated gut microbiota imbalance. The levels of acetate, propionate, and butyrate in fecal samples decreased. Notably, AS-IV reversed LpMs M1/M2 polarization, lightened gut inflammation and barrier injury, reduced NLRP3 inflammasome expression in LpMs, restored the diversity of gut microbiome, and increased butyrate levels. Similarly, these benefits were mimicked by fecal microbiota transplantation or exogenous butyrate supplementation. In Caco-2 and THP-1 cocultured model, LPS and interferon γ caused THP-1 M1 polarization, Caco-2 barrier impairment, abnormal cytokines release, and high NLRP3 inflammasome expression in THP-1 cells, all of which were mitigated by butyrate administration. However, these protective effects of butyrate were abrogated by NLRP3 gene overexpression in THP-1. In conclusion, AS-IV can ameliorate sepsis-induced gut inflammation and barrier dysfunction by modulating M1/M2 polarization of gut macrophages, whose underlying mechanism may be restoring gut microbiome and SCFA to restrain NLRP3 inflammasome activation.

Astragaloside IV attenuates sepsis-induced intestinal barrier dysfunction via suppressing RhoA/NLRP3 inflammasome signaling.

Intestinal barrier dysfunction is a trigger for sepsis progression. NLRP3 inflammasome and RhoA contribute to sepsis and intestinal inflammation. The current study aimed to explore the effects of Astragaloside IV (AS-IV), a bioactive compound from Astragalus membranaceus, on sepsis-caused intestinal barrier dysfunction and whether NLRP3 inflammasome and RhoA are involved. Septic mice modeled by cecal ligation and puncture (CLP) operation were administered with 3 mg/kg AS-IV intravenously. AS-IV decreased mortality, cytokines release, I-FABP secretion, intestinal histological score and barrier permeability, and increased tight junction (TJ) expression in intestine in CLP model. Also, in Caco-2 cells subjected to lipopolysaccharide (LPS), 200 µg/mL AS-IV co-incubation reduced cytokines levels and enhanced in vitro gut barrier function without cytotoxicity. Subsequently, NLRP3 inflammasome and RhoA were highly activated both in intestinal tissue in vivo and in Caco-2 cells in vitro, both of which were significantly suppressed by AS-IV treatment. In addition, the benefits of AS-IV on Caco-2 monolayer barrier were largely counteracted by RhoA agonist CN03 and NLRP3 gene overexpression, respectively. Furthermore, LPS-induced NLRP3 inflammasome activation was abrogated by RhoA inhibitor C3 exoenzyme. However, NLRP3 knockdown by siRNA hardly affected RhoA activation in Caco-2 cells. These data suggest that AS-IV protects intestinal epithelium from sepsis-induced barrier dysfunction via inhibiting RhoA/NLRP3 inflammasome signal pathway.