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

Objective and Design: We investigated whether estrogen affected COX isoform expressed in human umbilical vein endothelial cells (HUVEC). Materials and Methods: HUVEC were grown to confluence and replaced with fresh medium containing 17 beta-estradiol (0.001, 0.01, 0.1 and 1 nM) or 17 beta-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-PGF(1 alpha) using enzyme immunoassay. To measure COX activity via exogenous substrates, the remaining cells were replaced with fresh medium containing arachidonic acid (10 mu M for 10 min), and then the medium was removed to measure 6-keto-PGF(1 alpha). The COX isoform expressed in cells was detected by immunoblotting using specific antibody. Results: 17 beta-estradiol (0.001 to 1 nM) increased the production of 6-keto-PGF(1 alpha) 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 17 beta-estradiol treated HUVEC and was also inhibited by staurosporine. Conclusion: Our data showed that 17 beta-estradiol increased the release of PGI(2) 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.