Human immunodeficiency virus type 1 (HIV-1) tat induces nitric-oxide synthase in human astroglia

J Biol Chem. 2002 Oct 18;277(42):39312-9. doi: 10.1074/jbc.M205107200. Epub 2002 Aug 7.


Human immunodeficiency virus type 1 (HIV-1) infection is known to cause neuronal injury and dementia in a significant proportion of patients. However, the mechanism by which HIV-1 mediates its deleterious effects in the brain is poorly defined. The present study was undertaken to investigate the effect of the HIV-1 tat gene on the expression of inducible nitric-oxide synthase (iNOS) in human U373MG astroglial cells and primary astroglia. Expression of the tat gene as RSV-tat but not that of the CAT gene as RSV-CAT in U373MG astroglial cells led to the induction of NO production and the expression of iNOS protein and mRNA. Induction of NO production by recombinant HIV-1 Tat protein and inhibition of RSV-tat-induced NO production by anti-Tat antibodies suggest that RSV-tat-induced production of NO is dependent on Tat and that Tat is secreted from RSV-tat-transfected astroglia. Similar to U373MG astroglial cells, RSV-tat also induced the production of NO in human primary astroglia. The induction of human iNOS promoter-derived luciferase activity by the expression of RSV-tat suggests that RSV-tat induces the transcription of iNOS. To understand the mechanism of induction of iNOS, we investigated the role of NF-kappaB and C/EBPbeta, transcription factors responsible for the induction of iNOS. Activation of NF-kappaB as well as C/EBPbeta by RSV-tat, stimulation of RSV-tat-induced production of NO by the wild type of p65 and C/EBPbeta, and inhibition of RSV-tat-induced production of NO by deltap65, a dominant-negative mutant of p65, and deltaC/EBPbeta, a dominant-negative mutant of C/EBPbeta, suggest that RSV-tat induces iNOS through the activation of NF-kappaB and C/EBPbeta. In addition, we show that extracellular signal-regulated kinase (ERK) but not that p38 mitogen-activated protein kinase (MAPK) is involved in RSV-tat induced production of NO. Interestingly, PD98059, an inhibitor of the ERK pathway, and deltaERK2, a dominant-negative mutant of ERK2, inhibited RSV-tat-induced production of NO through the inhibition of C/EBPbeta but not that of NF-kappaB. This study illustrates a novel role for HIV-1 tat in inducing the expression of iNOS in human astrocytes that may participate in the pathogenesis of HIV-associated dementia.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Astrocytes / enzymology*
  • CCAAT-Enhancer-Binding Protein-beta / metabolism
  • Cells, Cultured
  • Dose-Response Relationship, Drug
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Flavonoids / pharmacology
  • Gene Products, tat / metabolism*
  • Genes, Dominant
  • Humans
  • Immunoblotting
  • Luciferases / metabolism
  • Mitogen-Activated Protein Kinases / metabolism
  • NF-kappa B / physiology
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase / metabolism*
  • Nitric Oxide Synthase Type II
  • Promoter Regions, Genetic
  • Time Factors
  • Transcriptional Activation
  • Transfection
  • eIF-2 Kinase / metabolism
  • p38 Mitogen-Activated Protein Kinases


  • CCAAT-Enhancer-Binding Protein-beta
  • Enzyme Inhibitors
  • Flavonoids
  • Gene Products, tat
  • NF-kappa B
  • Nitric Oxide
  • Luciferases
  • NOS2 protein, human
  • Nitric Oxide Synthase
  • Nitric Oxide Synthase Type II
  • eIF-2 Kinase
  • Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one