IDDF2024-ABS-0338 Mas1 deficiency protects against acute liver failure by suppressing the FXR/S1P/Raf-dependent NETosis in mice

<h3>Background</h3> Mas is a newly discovered G protein-coupled receptor that plays a critical role in inflammatory responses. The gut-liver axis regulates neutrophilic inflammation, which is crucial in acute liver failure (ALF); however, the underlying mechanisms remain poorly understood. The aim of this study is to investigate Mas signaling and neutrophilic inflammation in ALF and to elucidate its underlying mechanisms. <h3>Methods</h3> The 8-10 week-old male <i>Mas1</i>^-/-, <i>Vil1</i>^cre<i>Mas1</i>^f/f, and wild-type control mice were subjected to intraperitoneal challenge with D-galactosamine/lipopolysaccharide(D/L) for<i> in vivo</i> analysis of the gut-liver axis-dependent formation of neutrophil extracellular traps (NET), utilizing pharmacological compounds and genetic tools. Age-matched mice received injections of phosphate-buffered saline as vehicle controls. <h3>Results</h3> The hepatic and ileal expression of Mas was significantly upregulated in ALF patients and mice models (IDDF2024-ABS-0338 Figure 1. The hepatic and ileal expression of Mas1 in D/L-induced ALF mice). The knockout of the <i>Mas1</i> gene in both systemic and intestinal epithelial cells significantly alleviated D/L-induced NETosis and hepatotoxicity in mice (IDDF2024-ABS-0338 Figure 2. The knockout of the Mas1 gene in both systemic and intestinal epithelial cells significantly alleviated D/L-induced ALF in mice). The involvement of gut microbiota in the attenuated hepatotoxicity of <i>Mas1</i>^-/--D/L mice was confirmed through antibiotic experiments. The co-housed experiments between <i>Mas1</i>^-/- and WT mice have demonstrated that <i>Mas1</i>^-/- may confer protection by reducing the intestinal abundance of Eubacterium sp. and inhibiting deoxycholic acid (DCA) production (IDDF2024-ABS-0338 Figure 3. Mas1 may confer protection by reducing the intestinal abundance of Eubacterium sp and inhibiting DCA production). This was accompanied by hepatic activation of farnesoid X receptor (FXR) signaling and suppression of downstream sphingosine-1-phosphate (S1P)-dependent NETosis. As revealed by single-cell transcriptomics, the downregulation of NETosis in <i>Mas1</i>^-/--D/L mice was found to be dependent on the senescence of Cldn1⁺CD177⁺ neutrophils and the activation of Raf signaling (IDDF2024-ABS-0338 Figure 4. The downregulation of NETosis in Mas1Ko-D/L mice was found to be dependent on the senescence of Cldn1+CD177+ neutrophils and the activation of Raf signaling). <h3>Conclusions</h3> <i>Mas1</i>^-/- significantly protects mice from D/L-induced hepatotoxicity by suppressing the FXR/S1P/Raf-dependent NETosis, thereby suggesting Mas as a promising therapeutic target for ALF.