Word count : 3749 Running Title : Activin-A and angiogenesis in asthma Take Home

Introduction: Activin-A is a pleiotropic cytokine that regulates allergic inflammation. Its role in the regulation of angiogenesis, a key feature of airways remodelling in asthma, remains unexplored. Objectives: Investigate the expression of activin-A in asthma and its effects on angiogenesis in vitro. Methods: Expression of soluble/immunoreactive activin-A and its receptors was measured in serum, bronchoalveolar lavage fluid (BALF) and endobronchial biopsies from 16 healthy controls, 19 mild/moderate and 22 severe asthmatics. In vitro activinA effects on baseline and VEGF-induced human endothelial cell angiogenesis, signalling and cytokine release were compared with BALF concentrations of these cytokines in vivo. Measurements and Main Results: Activin-A expression was significantly elevated in serum, BALF and bronchial tissue of the asthmatics, while expression of its protein receptors was reduced. In vitro, activin-A suppressed VEGF-induced endothelial cell proliferation and angiogenesis, inducing autocrine production of anti-angiogenic soluble (s)VEGFR1 and IL-18, while reducing production of pro-angiogenic VEGFR2 and IL-17. In parallel, BALF concentrations of sVEGFR1 and IL-18 were significantly reduced in severe asthmatics in vivo and inversely correlated with angiogenesis. Conclusions: Activin-A is over-expressed and has anti-angiogenic effects in vitro that are not propagated in vivo, where reduced basal expression of its receptors is observed especially in severe asthma.