Porphyromonas gingivalis GroEL Accelerates Abdominal Aortic Aneurysm Formation by Induction of M1 Polarization in Macrophages

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease characterized by chronic inflammation, extracellular matrix degradation, and smooth muscle cell apoptosis. <i>Porphyromonas gingivalis</i> (<i>P. gingivalis</i>), a key periodontal pathogen, has been implicated in the progression of cardiovascular diseases, including AAA, but the underlying mechanisms remain unclear. In this study, we investigated the role of GroEL, a bacterial heat shock protein 60 homolog derived from <i>P. gingivalis</i>, in AAA development. We employed a CaCl₂-induced AAA mouse model to evaluate the in vivo effects of GroEL. Mice received periaortic CaCl₂ application followed by intravenous injections of recombinant GroEL. Histological analyses were performed to assess aneurysmal dilation, elastin degradation, and inflammatory cell infiltration. Flow cytometry and immunohistochemistry were used to determine macrophage phenotypes, while cytokine profiles were quantified via ELISA. In vitro, THP-1 monocytes were treated with GroEL to evaluate its impact on macrophage polarization and cytokine expression. Our results showed that GroEL administration significantly enhanced aortic diameter expansion and elastin breakdown, accompanied by increased infiltration of M1-like macrophages and elevated levels of pro-inflammatory cytokines such as TNF-α and IL-6. In vitro findings confirmed that GroEL promotes M1 polarization and inhibits M2 marker expression in THP-1-derived macrophages. These findings suggest that <i>P. gingivalis</i>-derived GroEL plays a pathogenic role in AAA by modulating macrophage polarization toward a pro-inflammatory phenotype. Targeting microbial components such as GroEL may offer new therapeutic strategies for AAA management.