Regulation by prostaglandin E2 and histamine of angiogenesis in inflammatory granulation tissue

In an air pouch-type carrageenin-induced inflammation model in rats, the selective cyclooxygenase (COX)-2 inhibitor NS-398 dose dependently inhibited the granulation tissue formation, angiogenesis and the level of vascular endothelial growth factor (VEGF) in the granulation tissue. In culture of the minced granulation tissue, PGE2 induced VEGF production in a concentration-dependent manner. Histamine also induced VEGF production in the granulation tissue in vitro. The H2 receptor antagonist cimetidine, the cAMP antagonist Rp-cAMP and the protein kinase A inhibitor H-89 suppressed the histamine-induced VEGF production in the granulation tissue. However, the H1 receptor antagonist pyrilamine maleate, the H3 receptor antagonist thioperamide, the protein kinase C inhibitors Ro 31-8425 and calphostin C or the tyrosine kinase inhibitor genistein showed no effect. Subcutaneous implantation of a cotton thread in the dorsum of histidine decarboxylase-deficient (HDC-/-) mice, but not in mast cell-deficient (WBB6F1-W/Wv) mice, induced less angiogenesis with lower levels of VEGF in the granulation tissue than in their corresponding wild-type (HDC+/+ and WBB6F1(-)+/+) mice. In HDC-/- mice, the topical injection of histamine or the H2 receptor agonist dimaprit rescued the defective angiogenesis and granulation tissue formation. In addition, cimetidine but not pyrilamine maleate and thioperamide inhibited the histamine-induced angiogenesis in the granulation tissue in HDC-/- mice. These findings suggest that PGE2 and histamine augment angiogenesis in the inflammatory granulation tissue by inducing VEGF production, and histamine induces VEGF production possibly through the H2 receptor--cAMP--protein kinase A pathway.