Gut microbiota dysfunction mediates stress-exacerbated aortic dissection via the bacteroides vulgatus-outer membrane...

Aortic dissection (AD) is a lethal condition involving vascular smooth muscle cell (VSMC) transformation and extracellular matrix degradation. While gut microbiota dysbiosis is implicated in cardiovascular diseases, its role in stress-exacerbated AD pathogenesis is unknown. This study investigates the mechanism linking chronic restraint stress (CRS) to AD progression via gut microbiota modulation.

A β-aminopropionitrile (BAPN)-induced AD mouse model combined with CRS was utilized. Aortic dilation, mortality, and VSMC phenotype shift (assessed via α-SMA/SM22α and OPN/MMP2 expression) were evaluated. Gut microbiota composition was analyzed using 16 S rRNA sequencing. Microbiota depletion was achieved via antibiotics, and fecal microbiota transplantation (FMT) from CRS-exposed mice was performed. Serum metabolomics analysis, incorporating liquid chromatography-mass spectrometry (LC-MS), has demonstrated that outer membrane vesicles (OMVs) derived from Bacteroides vulgatus (B. vulgatus) contain high levels of the key metabolite stearic acid (SA). In vitro effects of stearic acid (SA) on AngII-induced JNK phosphorylation in VSMCs were tested, with validation using the JNK agonist anisomycin. Statistical analyses included correlation tests and appropriate comparisons (e.g., t-tests, ANOVA).

CRS significantly accelerated aortic dilation, increased mortality, and promoted a synthetic VSMC phenotype (decreased α-SMA/SM22α, increased OPN/MMP2) in BAPN-treated mice. 16 S sequencing revealed CRS reduced gut microbiota diversity, particularly depleting B. vulgatus, which correlated negatively with AD severity. Antibiotic-mediated microbiota ablation mitigated CRS-aggravated AD, while FMT from CRS mice exacerbated it. Metabolomics identified stearic acid (SA), a metabolite derived from OMVs of B. vulgatus, as negatively correlated with aortic diameter. SA supplementation inhibited VSMC synthetic transformation, reduced AD incidence, and suppressed JNK/MAPK pathway activation in vivo. Mechanistically, SA attenuated AngII-induced JNK phosphorylation in VSMCs in vitro, an effect reversed by the JNK agonist anisomycin.

CRS exacerbates the pathogenesis of AD by disrupting the gut microbiota, particularly by reducing the abundance of B. vulgatus and the levels of SA, which is a metabolite encapsulated in the OMVs of B. vulgatus. This leads to unchecked JNK/MAPK signaling, driving detrimental VSMC transformation. Restoration of SA inhibits this pathway and mitigates AD progression. Targeting the gut microbiota-B. vulgatus-SA axis presents a novel therapeutic strategy for stress-aggravated AD.