Purpose: Glucocorticoids (GCs) are widely prescribed drugs in a large variety of diseases. Their use are strongly influenced by their associated negative side effects. Bone-related effects are mainly osteoporosis and osteonecrosis (ON). Despite the strong link between GCs and ON, the pathogenic mechanisms by which GCs cause ON are still unclear. Cumulative evidence shows that dysfunction or activation of endothelial cells (ECs) play an important role in ON.

Method: In this study, we investigated the influence of dexamethasone (Dex) on the Tumor Necrosis Factor-alpha [TNF-alpha] or Lipopolysaccharide [LPS] or Thrombin [IIa] -stimulated Human Umbilical Vein Endothelial Cells (HUVEC). We examined the molecular expression of 9 candidate genes (E-selectin [E-Sel], Intracellular adhesion molecule-1 [ICAM-1], Plasminogen activator inhibitor-1 [PAI-1], Tissue Factor [TF], Tissue plasminogen activator [t-PA], Urokinase plasminogen activator [u-PA], Vascular adhesion molecule-1 [VCAM-1], Von Willebrand Factor [vWF] and Thrombomodulin [THBD]) by real-time PCR. Live cell number of HUVEC under exposure to Dex was also assayed by viability test. All experiments were performed in triplicates and Standard error of the mean (SEM) was obtained.

Results: We showed that Dex alone significantly induced the expression of E-Sel, ICAM-1, TF, VCAM-1 and VWF while downregulating THBD and U-PA expression. Our results also showed a significant priming effect of Dex on E-Sel and TF inflammatory-mediated induction by TNF-alpha and LPS respectively. Comparable results were obtained from Northern Blot analysis; results from FACS analysis and Functional assays will be presented at the meeting.

Conclusion: Our observations suggest a procoagulant activity of Dex on HUVEC. We also observed a priming activity of Dex on E-Sel and TF inflammatory-mediated induction. These results suggest a potential endothelial cell activation mechanism and subsequent microvascular thrombosis in glucocorticoid-induced ON.