Glycyrrhizic Acid Alleviates Atherosclerosis in ApoE−/− Mice via Microbial Indole-3-Lactic Acid-Mediated AhR-p65 Interaction in the Endothelium

Glycyrrhizic acid (GL), a natural triterpenoid glycoside extracted from the “medicine food homology” herb Glycyrrhiza glabra L., exhibits potent anti-atherosclerotic effects; yet its underlying mechanisms remain unclear due to its poor oral bioavailability. The gut microbiota plays a pivotal role in the development of atherosclerosis (AS). In this study, the microbiota-dependent anti-AS effects of GL were evaluated in high-fat diet (HFD)-fed ApoE−/− mice using antibiotic depletion and fecal microbiota transplantation (FMT). Integrated metagenomic and metabolomic analyses were performed to identify the key bioactive microbial metabolite. Further in vivo and in vitro experiments, including co-immunoprecipitation and dual-luciferase reporter assays, were utilized to elucidate the underlying molecular mechanisms. It was demonstrated that oral administration of GL alleviated AS in a microbiota-dependent manner by reversing gut dysbiosis, improving intestinal barrier function, and reducing pro-inflammatory lipopolysaccharide (LPS) levels. GL shifted intestinal tryptophan metabolism toward bacterial-derived indole-3-lactic acid (ILA) production, suppressing LPS-induced vascular endothelial adhesion dysfunction by activating the aryl hydrocarbon receptor (AhR). Mechanistically, ILA-activated AhR interacted with the NF-κB subunit p65 in the cytoplasm, effectively preventing the nuclear translocation of p65 and suppressing the promoter activities of adhesion molecules (VCAM1 and ICAM1), resulting in the amelioration of HFD-induced AS. These findings elucidate the microbiota-dependent mechanism of orally administered GL against AS, and highlight the therapeutic potential of targeting the ILA-AhR-p65 axis in the vascular endothelium as a strategy for AS.