Adenylate cyclase/protein kinase A signaling pathway enhances angiogenesisthrough induction of vascular endothelial growth factor in vivo

We previously reported that endogenous prostaglandins (PGs) may increase cA MP facilitated angiogenesis through the induction of vascular endothelial g rowth factor (VEGF) in rat sponge implantation models. In the present exper iment, we tested whether or not adenylate cyclase / protein kinase A (AC/PK A)dependent VEGF induction enhanced angiogenesis in this model. Topical dai ly injections of 8-bromo-cAMP enhanced angiogenesis in a dose-dependent man ner. Forskolin, an activator of AC, also facilitated angiogenesis as did am rinone, an inhibitor of phosphodiesterase. VEGF induction was confirmed by the increased levels in the fluids in the sponge matrix after topical injec tion of 8-bromo-cAMP. Immunohistochemical investigation further revealed th e VEGF-expressed cells in the sponge granulation tissues to be fibroblasts, and the intensity of positive reactions was enhanced by 8-bromo-cAMP, fors kolin and amrinone. Angiogenesis without topical injections of the above co mpounds was suppressed by SQ22,536, an inhibitor for AC, or H-89, an inhibi tor for PKA, with concomitant reductions in VEGF levels. Daily topical inje ctions of neutralizing antibody or anti-sense oligonucleotide against VEGF significantly suppressed angiogenesis. PGE(2)-induced angiogenesis was supp ressed with SQ22,536 or H-89. These results suggested that AC/PKA-dependent induction of VEGF certainly enhanced angiogenesis and that pharmacological tools for controlling this signaling pathway may be able to facilitate the management of conditions involving angiogenesis.