Androgen exposure increases human monocyte adhesion to vascular endothelium and endothelial cell expression of vascular cell adhesion molecule-1

Abstract

Background - Male sex is an independent risk factor for coronary artery disease. Owing to the importance of monocyte adhesion to endothelial cells in the development of atherosclerosis. We hypothesized that androgens might promote this process. We therefore studied the effects of the nonaromatizable androgen dihydrotestosterone (DHT) on human monocyte adhesion to human endothelial cells and on endothelial cell-surface expression of adhesion molecules. Methods and Results - Human umbilical vein endothelial cells (HUVECs) were grown to confluence in media supplemented with postmenopausal female serum, then exposed for 48 hours to either DHT (40 and 400 nmol/L), with or without the androgen receptor blocker hydroxyflutamide (HF) (4 μmol/L); HF alone; or vehicle control (ethanol 0.1%). Human monocytes obtained by elutriation were incubated for 1 hour with the HUVECs at 37°C, and adhesion was measured by light microscopy. Compared with vehicle control, monocyte adhesion was increased in the androgen-treated HUVECs in a dose- dependent manner (116±6% and 128±3% for DHT 40 and 400 nmol/L respectively; P<0.001). HF blocked this increase (P≥0.3 compared with control). Surface expression of endothelial cell adhesion molecules was measured by ELISA and revealed an increased expression of vascular cell adhesion molecule-1 (VCAM- 1) in the DHT-treated HUVECs (125±5% versus 100±4% in controls; P=0.002), an effect also antagonized by HF (P≥0.3 compared with controls). Furthermore, the DHT-related increase in adhesion was completely blocked by coincubation with anti-VCAM-1 antibody. Comparable results were obtained in arterial endothelial cells and in endothelium stimulated with the cytokine tumor necrosis factor-α. Conclusions - Androgen exposure is associated with increased human monocyte adhesion to endothelial cells, a proatherogenic effect mediated at least in part by an increased endothelial cell-surface expression of VCAM-1.