EFAVIRENZ INDUCES THE EXPRESSION OF ICAM-1

S Orden1, C de Pablo1, JV Esplugues1, A Alvarez1,2. 1Universidad de Valencia, Facultad de Medicina, Departamento de Farmacología y CIBERehd, Spain, 2Fundación General Universidad de Valencia, FGUV, Spain

Background: Highly active antiretroviral therapy (HAART) has been associated with the development of cardiovascular diseases such as myocardial infarction and atherosclerosis. Efavirenz (EFV) is one of the most widely used antiretroviral agents and may be a causal agent of these side effects. Lopinavir (LPV) is an alternative antiretroviral drug to EFV. We have recently demonstrated in vitro that EFV causes human leukocyte-endothelial cell interactions through activation of the leukocyte integrin Mac-1. The present study was designed to explore further the expression of endothelial adhesion molecules induced by EFV. In addition, we have compared the effects of EFV and LPV on leukocyte-endothelial cell interactions.

Methods: The expression of endothelial adhesion molecules (ICAM-1, VCAM-1 and E-Selectin) in human umbilical vein endothelial cells (HUVEC) treated with EFV (10 - 25 µmol/L) or vehicle (4 or 24 hours) was analysed using inverted fluorescence microscopy. The interaction between human leukocytes –namely, peripheral blood polymorphonuclear (PMN) and mononuclear (PBMC) cells- and HUVEC was determined by means of the parallel plate flow chamber system. HUVEC and leukocytes (PMN or PBMC) were treated independently with EFV (10 - 25 µmol/L), LPV (10 - 25 µmol/L) or vehicle (4 hours). Doses were chosen in order to mimic in cells the plasma levels present in humans. All data were expressed as mean±SEM. A one-way ANOVA was followed by a Newman-Keuls post hoc test analysis, and statistical significance was set at *p<0.05 or **p<0.01 (vs. vehicle). All experiments were performed in groups of n≥4.

Results: Endothelial adhesion molecules were not modified by 4-hour treatment with EFV, but 24-hour treatment induced an increase in ICAM-1 expression (EFV 15 µmol/L: 251.6±54.8%* vs. 100% control). Administration of EFV, but not LPV, produced a significant increase in PMN rolling flux (veh: 57.5±4.8, EFV 15 µmol/L: 129.0±10.3**, LPV 15 µmol/L: 65.8±2.3 cells/min) and adhesion (veh: 10.8±1.4, EFV 15 µmol/L: 25.4±1.6**, LPV 15 µmol/L: 6.5±0.8 cells/mm2), and in PBMC rolling flux (veh: 56.3±5.8, EFV 15 µmol/L: 99.5±4.4**, LPV 15 µmol/L: 64±1.9 cells/min) and adhesion (veh: 10.4±1.8, EFV 15 µmol/L: 24.3±1.8**, LPV 15 µmol/L: 6.2±1.2 cells/mm2).

Conclusions: Acute exposure to EFV induces human leukocyte-endothelial cell interactions at clinically relevant doses in vitro, a process that could be mediated by the ICAM-1 expressed on endothelial cells, which interact with Mac-1 in leukocytes. Our results suggest that EFV, but not LPV, could be involved in the genesis of the cardiovascular diseases observed in HAART-treated patients.