title: Regulation of vascular endothelial growth factor expression by insulin-like growth factor-II in human keratinocytes, differential involvement of mitogen-activated protein kinases and feedback inhibition of protein kinase C.
abstract: BACKGROUND
  Vascular endothelial growth factor (VEGF) is overexpressed in hyperproliferative diseases such as psoriasis and cancer, which are characterized by an increased angiogenesis. It was reported that insulin-like growth factor (IGF)-II is highly expressed during hepatocarcinogenesis and is increased in psoriatic lesions. The increase in IGF-II is believed to be associated with the pathogenesis of these diseases by increasing angiogenesis.
  
  
  OBJECTIVE
  In order to investigate the relationship between IGF-II and angiogenesis-related VEGF, VEGF expression in the IGF-II-treated human keratinocytes was monitored and the IGF-II signalling pathways were examined with respect to VEGF expression.
  
  
  METHODS
  Northern blot analysis for the VEGF mRNA levels and an enzyme-linked immunosorbent assay for the VEGF protein were performed to determine if IGF-II (100 ng mL(-1)) can increase the VEGF expression levels with or without a pretreatment with protein inhibitors in primary normal human keratinocytes and HaCaT cells.
  
  
  RESULTS
  The mRNA and protein levels of VEGF by IGF-II were increased in a time-dependent manner and reached the maximum level 2 h and 8 h after the IGF-II treatment, respectively. However, this increase was abrogated by pretreatment with an extracellular signal-regulated kinase (ERK) inhibitor but not by a p38 inhibitor. The IGF-II-mediated VEGF induction was also effectively inhibited by a pretreatment with the tyrosine kinase inhibitor and Src inhibitor. The PI3-kinase inhibitor also inhibited the expression of VEGF by IGF-II. However, the phospholipase C (PLC) and protein kinase C (PKC) inhibitors did not block the increases of VEGF mRNA level and its protein level by IGF-II, and the PKC inhibitor instead increased VEGF expression by IGF-II.
  
  
  CONCLUSIONS
  These results suggest that the tyrosine kinase-Src-ERK1/2 pathway and the PI3-kinase pathway are involved in IGF-II-mediated VEGF expression, but PKC is negatively associated in the IGF-II-mediated VEGF expression.
authors.affiliation: Department of Pharmacology, College of Medicine, Gyeongsang National University, 92 Chilan-dong, Jinju, South Korea.
authors.forename: H J
authors.initials: HJ
authors.lastname: Kim
authors.forename: T-Y
authors.initials: TY
authors.lastname: Kim
mesh_terms: D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology* / Q000502:physiology; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D042461:Vascular Endothelial Growth Factor A; D007335:Insulin-Like Growth Factor II; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases