OBJECTIVETo study the effect of progesterone on interleukin-6 (IL-6) release from human umbilic vein endothelial cells (HUVECs) induced by high mobility group box-1 protein (HMGB1).

METHODThe recombinant expression plasmid pET14b-HMGB1 was constructed and transformed into competent E.coli BL21 cells to obtain HMGB1 protein, which was purified with chromatography on Ni-NTA Sepharose column. Cultured HUVECs were treated with purified HMGB1 protein alone at the concentrations 0, 10, 100, 500, and 1000 ng/ml, progesterone alone at the concentrations of 0, 0.1, 1, 10, 100 mmol/L, or with both HMGB1 protein (500 ng/ml) and progesterone at the terminal concentrations of 0, 0.1, 1, 10, and 100 mmol/L. Twenty-four hours later, the supernatant of the cell culture medium was collected to detect the levels of IL-6 using enzyme-linked immunosorbent assay (ELISA).

RESULTSThe IL-6 levels in HUVEC culture medium was slightly decreased after treatment with low-concentration HMGB1 but increased obviously following treatment with high-concentration HMGB1, and these effects could be dose-dependently inhibited by progesterone. Progesterone alone did not result in any noticeable changes of IL-6 levels in the cell culture medium.

CONCLUSIONSProgesterone can dose-dependently inhibit HMGB1-induced IL-6 release from HUVECs, suggesting the protective role of progesterone in endotoxemia.