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.
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.
Hossain
M A
MA
Departments of Neurology, Neuroscience, and Oncology, The Johns Hopkins University School of Medicine and The Kennedy Krieger Research Institute, Baltimore, Maryland 21205, USA. hossain@kennedykrieger.org
Bouton
C M
CM
Pevsner
J
J
Laterra
J
J
D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D016228:Endothelial Growth Factors / Q000235:genetics*; D005333:Fetus; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008222:Lymphokines / Q000235:genetics*; D009687:Nuclear Proteins / Q000378:metabolism*; D009942:Organometallic Compounds / Q000633:toxicity*; D011493:Protein Kinase C / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D004268:DNA-Binding Proteins; D016228:Endothelial Growth Factors; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008222:Lymphokines; D009687:Nuclear Proteins; D009942:Organometallic Compounds; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; C008261:lead acetate