The induction of cyclooxygenase-2 by 17beta-estradiol in endothelial cells is mediated through protein kinase C

We investigated whether estrogen affected COX isoform expressed in human umbilical vein endothelial cells (HUVEC). HUVEC were grown to confluence and replaced with fresh medium containing 17beta-estradiol (0.001, 0.01, 0.1 and 1 nM) or 17beta-estradiol (1 nM) plus staurosporine (0.1, 1 and 10 ng/ml) for 24 h, after which the supernatant medium was collected to measure 6-keto-PGF1alpha using enzyme immunoassay. To measure COX activity via exogenous substrates, the remaining cells were replaced with fresh medium containing arachidonic acid (10 microM for 10 min), and then the medium was removed to measure 6-keto-PGF1alpha. The COX isoform expressed in cells was detected by immunoblotting using specific antibody. 17beta-estradiol (0.001 to 1 nM) increased the production of 6-keto-PGF1alpha via either endogenous or exogenous substrate in a dose dependent manner. These increases were significantly inhibited when cells were coincubated with staurosporine. Interestingly, only COX-2 protein, but not COX-1 protein, was induced in 17beta-estradiol treated HUVEC and was also inhibited by staurosporine. Our data showed that 17beta-estradiol increased the release of PGI2 from HUVEC via the induction of COX-2 which was mediated through protein kinase C. The results suggested that COX-2 might have a role in the cardiovascular protective effect of estrogen.