β-Sitosterol modulation of monocyte–endothelial cell interaction: A comparison to female hormones

ObjectiveTo investigate the effect of β-sitosterol, 17β-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.MethodsICAM-1 expression was determined by immunofluorescence in HUVEC monolayers treated with LDL or oxLDL and 17β-estradiol, progesterone or β-sitosterol. Monocyte chemotactic activity was performed in Transwell chambers by culturing HUVECs with different stimuli and steroids, THP-1 cells labeled with [3H] 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.ResultsICAM-1 expression was inhibited by β-sitosterol alone, when combined with 17β-estradiol or progesterone, or with both hormones. It was shown that 7.5 μM β-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 β-sitosterol, the 17β-estradiol and progesterone mixture, and in the presence of the two hormones. It was shown that 7.5 μM β-sitosterol significantly inhibited chemotaxis of [3H] 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 μM β-sitosterol as well as by progesterone and the mixture of the two female hormones.