Urocortin 2 is associated with abdominal aortic aneurysm and mediates anti-proliferative effects on vascular smooth muscle cells via corticotrophin releasing factor receptor 2.

Theophilus I. Emeto, Joseph V. Moxon, Erik Biros, Catherine M. Rush, Paula Clancy, Lynn Woodward, Corey S. Moran, Roby J. Jose, Tam Nguyen, Philip J. Walker, Jonathan Golledge

AAA (abdominal aortic aneurysm) is an important cause of sudden death in older adults, but there is no current effective drug therapy for this disease. The UCNs (urocortins1-3) and their receptors: CRFR (corticotrophin-releasing factor receptor)-1 and -2 have been implicated in various CVDs (cardiovascular diseases). We assessed the relative expression of UCN1-3 in AAA by qRT-PCR (quantitative reverse transcription-PCR) and ELISA, and examined in vitro how UCN2 affects human aortic VSMC (vascular smooth muscle cell) Akt phosphorylation, pro-inflammatory cytokine IL (interleukin)-6 secretion, proliferation, cell cycle and apoptosis. UCN2 and CRFR2 expression were significantly up-regulated in biopsies from the AAA body. AAA body biopsies released high amounts of UCN2 in vitro. Median plasma UCN2 concentrations were 2.20 ng/ml (interquartile range 1.14-4.55 ng/ml, n=67) in AAA patients and 1.11 ng/ml (interquartile range 0.76-2.55 ng/ml, n=67) in patients with non-aneurysmal PAD (peripheral artery disease) (P=0.001). Patients with UCN2 in the highest quartile had a 4.12-fold (95% confidence interval, 1.37-12.40) greater prevalence of AAA independent of other risk factors, P=0.012. In vitro, UCN2 significantly inhibited VSMC Akt phosphorylation and proliferation in a dose-dependent manner. UCN2 induced VSMC G1 cell-cycle arrest and increased IL-6 secretion over 24 h. The CRFR2 antagonist astressin-2B significantly abrogated the effects of UCN2 on VSMCs. In conclusion, UCN2 is significantly associated with AAA and inhibits VSMC proliferation by inducing a G1 cell cycle arrest suggesting a plausible regulatory role in AAA pathogenesis.