title: Nelfinavir suppresses insulin signaling and nitric oxide production by human aortic endothelial cells: protective effects of thiazolidinediones.
abstract: BACKGROUND
  In human immunodeficiency virus 1 (HIV-1)-infected individuals, exposure to a protease inhibitor (PI)-based highly active antiretroviral therapy (HAART) regimen increases cardiovascular disease and endothelial dysfunction. However, the mechanisms of PI-induced effects on endothelial cells (ECs) are not known. Furthermore, strategies to suppress these deleterious outcomes of PIs need to be developed. Insulin-induced PI3K/Akt signaling and endothelial nitric oxide (NO)-synthase (eNOS) phosphorylation regulates NO production by ECs that maintain vascular homeostasis. We evaluated whether nelfinavir (NEL), a potent HIV-1 PI that suppresses Akt phosphorylation, can alter insulin-induced NO production in human aortic endothelial cells (HAECs) and whether insulin sensitization of HAECs via the peroxisome proliferator-activated receptor-gamma agonists, thiazolidinediones, can ameliorate these side effects.
  
  
  METHODS
  Real-time NO production in HAECs was monitored by fluorimetric dyes DAF-FM DA and DAF-2 DA. Immunodetection studies were used to determine the phosphorylation of Akt, eNOS, insulin receptor-β (IR-β), insulin receptor substrate-1 (IRS-1), and PI3K/p85α. Expression of eNOS messenger RNA was measured by reverse transcription polymerase chain reaction.
  
  
  RESULTS
  In vitro exposure (72 hours) of HAECs to NEL (0.25-2 μg/mL) decreased both basal (2.5-fold) and insulin-induced NO production (4- to 5-fold). NEL suppressed insulin-induced phosphorylation of both Akt and eNOS at serine residues 473 and 1177, respectively. NEL decreased tyrosine phosphorylation of IR-β, IRS-1, and PI3K. Coexposure to troglitazone (TRO; 250 nM) ameliorated the suppressive effects of NEL on insulin signaling and NO production. Coexposure to TRO also increased eNOS expression in NEL-treated HAECs.
  
  
  CONCLUSIONS
  Our findings indicate that treatment with potent insulin sensitizers may protect against PI-mediated endothelial dysfunction during long-term HAART.
authors.affiliation: Department of Pharmacology and.
authors.forename: Debasis
authors.initials: D
authors.lastname: Mondal
authors.forename: Kai
authors.initials: K
authors.lastname: Liu
authors.forename: Milton
authors.initials: M
authors.lastname: Hamblin
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Lasky
authors.forename: Krishna C
authors.initials: KC
authors.lastname: Agrawal
keywords: Endothelial cells; HIV-1; nelfinavir; nitric oxide; thiazolidinediones