Endothelin-1 and the Vascular Toxicity of HAART 117 Cardiovascular Toxicology Humana Press Volume 4, 2004 117 *Author to whom all correspondence and reprint requests should be addressed: Tammy R. Dugas, LSU Health Sciences Center, Department of Pharmacology and Therapeutics, 1501 Kings Highway, P.O. Box 33932, Shreveport, LA 71130-3932. E-mail: tdugas@lsuhsc.edu Received: 1/6/2004 Revised: 2/25/2004 Accepted: 2/25/2004 Cardiovascular Toxicology, vol. 4, no. 2, 117–131, 2004 Effects of HIV Drug Combinations on Endothelin-1 and Vascular Cell Proliferation Valeria Y. Hebert, Brian L. Crenshaw, Rachelle L. Romanoff, Viktoriya P. Ekshyyan, and Tammy R. Dugas* Department of Pharmacology and Therapeutics, Louisiana State University Health Sciences Center, Shreveport, LA Cardiovascular Toxicology (2004) 04 117–131 $25.00 (http://www.cardiotox.com) © Copyright 2004 by Humana Press Inc. All rights of any nature whatsoever reserved. 1530-7905/01 Humana Press Abstract Pulmonary arterial hypertension (PAH) is a progressive disease of the pul- monary vasculature involving endothelial and vascular smooth muscle cell (VSMC) proliferation, vasoconstriction, right ventricular hypertrophy, and even- tually, right heart failure and death. PAH occurs 1000-fold more frequently in HIV patients than in the general population. Although conventional HIV ther- apy with nucleoside reverse transcriptase inhibitors (NRTIs) leads to regression of PAH, highly active antiretroviral therapy (HAART; two NRTI plus a protease inhibitor) increases the incidence of HIV-associated PAH as much as twofold. Although there are relatively few models for PAH, previous reports indicate the disease can be initiated by endothelial injury and release of the mitogen endothelin-1 (ET-1). ET-1, in turn, stimulates VSMC proliferation. To deter- mine whether HAART induces endothelial injury and release of cytokines like ET-1, we treated human umbilical vein endothelial cells with micromolar amounts of AZT (3'-azido-3'-deoxythymidine), the protease inhibitor indinavir, or AZT plus indinavir, and measured cell viability, mitochondrial function, and ET-1 release. Both AZT and indinavir induced marked de- creases in cellular oxygen uptake, as well as increases in ET-1 release. Al- though the drugs had no apparent effect on proliferation in VSMCs alone, in cocultures of VSMCs plus endothelial cells, the drugs increased proliferation of both endothelial cells and VSMCs. Finally, when cocultures of endothelial cells and VSMCs were treated with BQ-123 and BQ-788, selective antago- nists for ET A and ET B receptors, respectively, drug-induced proliferation of both VSMCs and endothelial cells was attenuated. These data thus suggest that HIV drug cocktails may exacerbate preexisting HIV-associated PAH by inducing endothelial mitochondrial dysfunction, in turn stimulating the re- lease of ET-1, and ultimately, vascular cell proliferation. Key Words: Vascular smooth muscle cells; endothelial cells; endothelin-1; proliferation; 3'-azido-3'-deoxythymidine; indinavir. Introduction Pulmonary arterial hypertension (PAH) is a vascular disease associated with elevated pulmonary arterial pressure (1) and characterized by vascular smooth mus- cle cell (VSMC) proliferation and intimal thickening, increased pulmonary vascular