Progesterone, but not medroxyprogesterone, inhibits vascular cell adhesion molecule-1 expression in human vascular endothelial cells.

-It has been shown that ovarian steroid hormones can reduce the incidence of cardiovascular disease in postmenopausal women. As hormone replacement therapy for postmenopausal women, progestins are added to estrogens to eliminate the increased risk of endometrial cancer. However, the effects of progestins on the atherogenic process have not been well understood. In the present study, we examined the effects of progestins on the expression of vascular cell adhesion molecule-1 (VCAM-1) in human umbilical vein endothelial cells (HUVECs). Immunocytochemical analysis revealed the presence of progesterone receptors in HUVECs. Progesterone clearly inhibited tumor necrosis factor-alpha-activated expression of VCAM-1 protein and its mRNA in HUVECs. Synthetic progesterone receptor agonist R5020 also inhibited the tumor necrosis factor-alpha-activated VCAM-1 expression, whereas medroxyprogesterone acetate (MPA) failed to do so. Electrophoretic mobility shift assays demonstrated that progesterone, but not MPA, inhibited DNA binding of the transcription nuclear factor-kappaB, which is critical for the inducible expression of VCAM-1. Because the expression of VCAM-1 is one of the earliest events that occurs in the atherogenic process, this adhesion molecule might be a target molecule for progesterone on vascular walls. The contrasting effects of progesterone and MPA seem clinically important, inasmuch as MPA is a widely used progestin in the regimen of hormone replacement therapy.