beta-Sitosterol modulation of monocyte-endothelial cell interaction: a comparison to female hormones

To investigate the effect of beta-sitosterol, 17beta-estradiol and progesterone on oxidized LDL (oxLDL)-stimulated human umbilical venous endothelial cell (HUVEC) expression of intercellular adhesion molecule-1 (ICAM-1), THP-1 monocyte chemotactic activity, migration and adhesion of THP-1 cells co-cultured with HUVECs.

ICAM-1 expression was determined by immunofluorescence in HUVEC monolayers treated with LDL or oxLDL and 17beta-estradiol, progesterone or beta-sitosterol. Monocyte chemotactic activity was performed in Transwell chambers by culturing HUVECs with different stimuli and steroids, THP-1 cells labeled with [(3)H] thymidine were added to the upper chamber and the radioactivity was measured. Migration assays were performed using Transwell chambers but monocytes were labeled with BCECF-AM and THP-1 cells adhered to HUVECs were visualized by fluorescence microscopy. MCP-1 was quantified by ELISA.

ICAM-1 expression was inhibited by beta-sitosterol alone, when combined with 17beta-estradiol or progesterone, or with both hormones. It was shown that 7.5 microM beta-sitosterol decreased migration and adhesion of THP-1 cells to HUVECs cultured in the presence of oxLDL. This effect was also observed in HUVEC cultures in the presence of beta-sitosterol, the 17beta-estradiol and progesterone mixture, and in the presence of the two hormones. It was shown that 7.5 microM beta-sitosterol significantly inhibited chemotaxis of [(3)H] thymidine labeled THP-1 cells in oxLDL-stimulated HUVEC cultures. MCP-1 concentrations in the supernatants of oxLDL-stimulated HUVEC cultures were inhibited by 7.5 microM beta-sitosterol as well as by progesterone and the mixture of the two female hormones.