Protein kinase C inhibitor calphostin C prevents cytokine-induced angiogenesis in the rat.

A rat sponge implant model was used to examine the role of protein kinase C (PKC) in angiogenesis. Neovascular response was determined by measurements of relative sponge blood flow by a 133Xe clearance technique and confirmed histologically. Morphometric analysis was used to quantitate the amount of fibrovascular growth in the sponges. Daily doses of recombinant human basic fibroblast growth factor (bFGF, 100 ng), tumor necrosis factor-alpha (TNF-alpha, 50 ng), or interleukin-1-alpha (IL-1 alpha, 50 ng) caused neovascular responses that were blocked by daily coadministration of the selective PKC inhibitor, calphostin C (4 micrograms). To confirm that calphostin C was able to inhibit PKC in vivo, its effect on the angiogenic response elicited by the PKC activator, phorbol 12-myristate 13-acetate (PMA, 30 micrograms) was examined. The blood flow and morphometric data clearly showed that the intense neovascularization induced by PMA was totally suppressed by coadministration of calphostin C (4 micrograms). Thus, these results suggest that cytokine-induced angiogenesis may be mediated in part through the activation of PKC and that selective inhibition of this enzyme could have therapeutic benefit in angiogenic diseases.