Monocyte activation, but not granulocyte activation, is inhibited in the presence of developing ovarian follicles

The role of sex steroids on cellular events involved in vascular disease

In this work we checked the hypothesis whether estrone, progesterone, and testosterone are able to modulate the interactions between platelets, monocytes, and endothelial cells either under basal or inflammatory conditions. Using adhesion assays we demonstrated that pretreatment of endothelial cells with estrone, progesterone, or testosterone prevented monocytes and platelets adhesion induced by the proinflammatory agent bacterial lipopolysaccharide. The hormones reduced the expression of mRNA of ICAM-1, VCAM-1, and P-selectin, endothelial surface proteins that mediate monocytes and platelets adhesion respectively. Integrins are the main leukocyte proteins that allow firm adhesion. Using flow cytometry we showed that estrone treatment of monocytes reduced CD11b and CD11c expression, either under basal or injury (lipopolysaccharide) conditions. The three steroids inhibited platelet aggregation in a nitric oxide dependent manner. Platelet function was not affected by the steroid treatment. The molecular mechanisms of action exerted by the steroids included the participation of the intracellular signaling pathways PKC, MAPK, and PI3K, which selectively and differentially mediate the stimulation of nitric oxide release. We evidence that estrone, progesterone, and testosterone modulate monocyte and platelet adhesion to endothelial cells, events that play a major role in the initiation and progression of vascular lesions. The steroid action was evidenced under basal or inflammatory conditions. The mechanisms of action exerted by the steroids included stimulation of nitric oxide production and the participation of PKC, MAPK, and PI3K systems.