Human fibroblast cells produce a factor that stimulates prostacyclin synthesis by vascular endothelial cells

The prostacyclin (PGI2) produced by vascular endothelium plays a key role in maintaining vascular homeostasis. The present study demonstrated that the conditioned medium (CM) of human diploid fibroblast cells contained PGI2-stimulatory activity (PSA) for bovine aortic endothelial cells (BAEC) and human umbilical vein endothelial cells (HUVEC). CM significantly stimulated the production of 6-keto-PGF1 alpha, a stable PGI2 metabolite, by both cultured BAEC and HUVEC in a concentration-dependent manner. Since the factor responsible for the PSA seemed to be negatively charged, PSA was partially purified using a DEAE-5PW high performance liquid chromatography column. The partially purified PSA was completely inhibited by preincubation with 15 microM indomethacin, a cyclooxygenase inhibitor. However, partially purified PSA was partially inhibited by preincubation with 50 microM mepacrine, a phospholipase A2 inhibitor. These findings suggest that PSA stimulates preferentially cyclooxygenase relative to phospholipase A2 in vascular endothelial cells. The partially purified PSA showed no effect on thromboxane A2 production by human washed platelets, and had no growth-promoting activity on BAEC. We conclude that cultured human fibroblast cells produce factor that stimulate the synthesis of prostaglandin by vascular endothelial cells but not by platelets.