Hyperhomocysteinemia Exaggerates Adventitial Inflammation and Angiotensin II−Induced Abdominal Aortic Aneurysm in Mice

Rationale:A number of epidemiological studies have suggested an association of hyperhomocysteinemia (HHcy) and abdominal aortic aneurysm (AAA), but discrepancies exist. In addition, we lack direct evidence supporting a causal role. Objective:We determined the association and contribution of HHcy to AAA formation. Methods and Results:We first performed a meta-analysis of studies involving 1489 subjects and found a strong association of HHcy and AAA (odds ratio, 7.39). Next, we used angiotensin II–infused male apolipoprotein E–deficient mice and tested whether HHcy contributes to AAA pathogenesis. Homocysteine (Hcy) supplement (1.8 g/L) in drinking water resulted in mild HHcy. Intriguingly, HHcy greatly increased the incidence of angiotensin II–induced AAA and aortic dissection in apolipoprotein E–deficient mice (vehicle versus Hcy: 50% versus 100%; P<0.05). Histology indicated HHcy markedly exaggerated aortic adventitial inflammation. Increased levels of proinflammatory interleukin-6 and monocyte chemoattr...