The Enterococcus-putrescine-hadh axis drives mitochondrial redox imbalance and endothelial barrier breakdown in aortic dissection.

Growing evidence indicates that gut microbiota-derived metabolites contribute to aortic dissection (AD), yet the molecular mechanisms linking microbial metabolism to endothelial barrier failure remain unclear. Untargeted metabolomics identified putrescine as a markedly elevated circulating metabolite in AD patients, and higher putrescine levels were associated with disease severity and adverse clinical characteristics. Targeted polyamine metabolomics further confirmed putrescine as the most prominently altered metabolite among the measured polyamine-related metabolites. Integrated microbiome-metabolome analysis suggested that Enterococcus may represent an important contributor to elevated putrescine levels through AguA-associated metabolism. In vivo administration and fecal microbiota transplantation showed that increased putrescine was associated with impaired endothelial barrier integrity, aggravated mitochondrial injury, enhanced vascular leakage, and accelerated AD progression. Mechanistically, CHX chase, surface plasmon resonance, molecular docking, and pull-down assays supported a direct interaction between putrescine and the mitochondrial fatty acid β-oxidation enzyme 3-hydroxyacyl-CoA dehydrogenase (HADH), involving Ala107 and Ser137, and showed that putrescine was associated with reduced HADH stability. In endothelial cells, putrescine impaired fatty acid oxidation, mitochondrial ultrastructure, and oxidative phosphorylation, promoted cytoskeletal remodeling and biomechanical dysfunction, and compromised barrier homeostasis. In human aortic endothelial cells, NMN and Mito-TEMPO partially rescued mitochondrial dysfunction and the loss of barrier-associated proteins, indicating that mitochondrial redox imbalance, particularly mtROS accumulation, serves as a downstream amplifier of putrescine-HADH-associated endothelial injury. Collectively, these findings support the existence of a functional Enterococcus-associated putrescine-HADH pathway linking microbial metabolism to mitochondrial dysfunction, redox imbalance, and endothelial barrier disruption in AD, and nominate putrescine as a potential metabolic biomarker and therapeutic target.