POLYMORPHONUCLEAR LEUKOCYTES ENHANCE RELEASE OF GROWTH-FACTORS BY CULTURED ENDOTHELIAL-CELLS

Porcine aortic endothelial cells (PAECs) in culture constitutively sec rete polypeptide (endothelium-derived) growth factors (EDGFs) into the surrounding medium. Incubation of PAECs with human peripheral blood p olymorphonuclear leukocytes (PMNs) caused a significant increase in ED GF release as assessed by [H-3]thymidine incorporation into BALB/c 3T3 mouse fibroblasts and cell proliferation assay. The effect was time d ependent and correlated with the number of PMNs, reaching a maximum wi th a 1:1 PAEC to PMN ratio. Generation of mitogenic activity was preve nted by cycloheximide, indicating a requirement for de novo protein sy nthesis. Antibody-mediated inhibition assays suggested that mitogenic activity was due to platelet-derived growth factor and basic fibroblas t growth factor. When supernatant from N-formyl-methionyl-leucyl-pheny lalanine-stimulated PMNs was substituted for PMNs during incubation wi th PAECs, powerful mitogenic activity was generated, indicating the in volvement of soluble mediators. A role for free oxygen radicals was ru led out by experiments in which superoxide dismutase and catalase did not prevent the increase in mitogenic activity. By contrast, serine pr otease inhibitors such as soybean trypsin inhibitor, alpha(1),-antitry psin, and eglin C reduced the PMN-stimulating activity by 70%, 80%, an d 100%, respectively. The possible involvement of cathepsin G and elas tase was investigated. Cathepsin C and elastase, when substituted for PMNs, increased the release of EDGFs in a dose-dependent fashion, mimi cking the effect of PMNs. These findings suggest a new role for leukoc yte-vessel wall interactions in the proliferative feature of atheroscl erosis.