Induction of vascular endothelial growth factor in human astrocytes by lead. Involvement of a protein kinase C/activator protein-1 complex-dependent and hypoxia-inducible factor 1-independent signaling pathway

J Biol Chem. 2000 Sep 8;275(36):27874-82. doi: 10.1074/jbc.M002185200.

Abstract

The mechanism(s) underlying lead neurotoxicity are not fully elucidated. cDNA expression microarray analysis identified lead-sensitive genes in immortalized human fetal astrocytes (SV-FHA). Of the represented genes expressed, vascular endothelial growth factor (VEGF) was one of the most sensitive. Lead induced VEGF mRNA 3-fold and VEGF protein approximately 2-fold with maximum mRNA induction following incubation with 10 micrometer lead acetate for 24 h. Phorbol 12-myristate 13-acetate (PMA), a potent protein kinase C (PKC) activator, increased VEGF mRNA 2-fold and PKC inhibition by GF-109203 completely blocked VEGF induction by lead. Expression of dominant-negative PKC-epsilon, but not PKC-alpha, completely inhibited VEGF mRNA induction by lead. Lead activated the transcription factor AP-1 and increased AP-1-dependent luciferase expression >2-fold. Transfection of cells with a c-jun dominant-negative effectively inhibited both AP-1 activation and VEGF mRNA induction by lead. Hypoxia-inducible factor 1 (HIF-1) activity in SV-FHAs was moderately increased by lead (86%) and PMA (96%). Pretreatment with GF-109203 completely inhibited these effects of lead and PMA. However, lead did not alter HIF-1-dependent luciferase expression and a HIF-1alpha dominant-negative had no effects on the induction of VEGF mRNA by lead. These findings indicate that lead induces VEGF expression in SV-FHAs via a PKC/AP-1-dependent and HIF-1-independent signaling pathway.

Publication types

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

MeSH terms

  • Astrocytes / drug effects
  • Astrocytes / metabolism*
  • Cells, Cultured
  • DNA-Binding Proteins / metabolism*
  • Endothelial Growth Factors / genetics*
  • Fetus
  • Gene Expression Regulation / drug effects*
  • Humans
  • Hypoxia-Inducible Factor 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Lymphokines / genetics*
  • Nuclear Proteins / metabolism*
  • Organometallic Compounds / toxicity*
  • Protein Kinase C / metabolism*
  • RNA, Messenger / genetics
  • Signal Transduction
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transcription Factor AP-1 / metabolism*
  • Transcription Factors / metabolism
  • Transcription, Genetic / drug effects*
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors

Substances

  • DNA-Binding Proteins
  • Endothelial Growth Factors
  • HIF1A protein, human
  • Hypoxia-Inducible Factor 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Lymphokines
  • Nuclear Proteins
  • Organometallic Compounds
  • RNA, Messenger
  • Transcription Factor AP-1
  • Transcription Factors
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate
  • lead acetate