Mast Cell–Mediated Stimulation of Angiogenesis

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Abstract
Adenosine is released during tissue injury, ischemia and tumor growth, and promotes angiogenesis. Because mast cells accumulate in the proximity of new blood vessel development, we examined if they may contribute to adenosine-induced angiogenesis. We found that HMC-1 human mast cells express A 2A , A 2B , and A 3 adenosine receptors. The adenosine agonist NECA (100 μmol/L) increased interleukin-8 (IL-8), vascular endothelial growth factor (VEGF), and angiopoietin-2 mRNA expression. NECA-induced secretion of IL-8 and VEGF was verified by ELISA. A 2B receptors mediate VEGF and IL-8 secretion because neither CGS21680 (selective A 2A agonist) nor IB-MECA (selective A 3 agonist) produced this effect, and it was inhibited by the selective A 2B antagonist IPDX but not by the selective A 2A antagonist SCH58261 or the selective A 3 antagonist MRS1191. In contrast, the selective A 3 agonist IB-MECA (EC 50 1 nmol/L) stimulated angiopoietin-2 expression. Conditioned media from NECA-activated HMC-1 stimulated human umbilical vein endothelial cell proliferation and migration, and induced capillary tube formation. Capillary formation induced by mast cell–conditioned media was maximal if both HMC-1 A 2B and A 3 receptors were activated, whereas activation of A 2B receptor alone was less effective. Thus, adenosine A 2B and A 3 receptors act in a functional cooperative fashion to promote angiogenesis by a paracrine mechanism involving the differential expression and secretion of angiogenic factors from human mast cells.

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