title: The effect of clonidine on VEGF expression in human retinal pigment epithelial cells (ARPE-19).
abstract: BACKGROUND
  The purpose of this study was to investigate the effect of clonidine, an alpha(2)-adrenergic receptor (alpha(2)-ADR) agonist, on vascular endothelial growth factor (VEGF) expression and secretion in the human retinal pigment epithelial cell line (ARPE-19) stimulated with interleukin-1beta (IL-1beta).
  
  
  METHODS
  Alpha(2)-ADRs (alpha(2)A, alpha(2)B, and alpha(2)C) mRNA expression in ARPE-19 cells was examined by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). Clonidine and inhibitors against protein kinases that are involved in the regulation of the intracellular signal transduction were added to serum-free medium before stimulation of IL-1beta. The alpha(2)-ADR antagonist, Yohimbine, was loaded 30 min before the addition of clonidine. The expression of VEGF mRNA and protein was measured by real-time PCR and enzyme-linked immunosorbent assay.
  
  
  RESULTS
  Alpha(2)A-ADR, alpha(2)B-ADR, and alpha(2)C-ADR mRNA was expressed in RPE cells. Clonidine, an inhibitor of p38MAPK and MEK1/2, inhibited the expression of VEGF protein and mRNA in the RPE cells stimulated with IL-1beta. The inhibitory effect of clonidine on the secretion of VEGF protein stimulated with IL-1beta was blocked by alpha(2)-ADR antagonists.
  
  
  CONCLUSIONS
  The effect of clonidine on the expression of VEGF may be via suppression of the p38MAPK and MEK1/2 signal transduction pathways activated with IL-1beta.
authors.affiliation: Department of Ophthalmology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama, 930-0194, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Watanabe
authors.forename: Xue-Yun
authors.initials: XY
authors.lastname: Zhang
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Kitagawa
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yunoki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hayashi
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D002460:Cell Line; D003000:Clonidine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D054755:Imidazoline Receptors / Q000819:agonists / Q000378:metabolism; D053583:Interleukin-1beta / Q000494:pharmacology; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018341:Receptors, Adrenergic, alpha-2 / Q000235:genetics / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics* / Q000378:metabolism; D015016:Yohimbine / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C547768:ADRA2A protein, human; C547771:ADRA2B protein, human; C547774:ADRA2C protein, human; D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D004791:Enzyme Inhibitors; D054755:Imidazoline Receptors; D053583:Interleukin-1beta; D012333:RNA, Messenger; D018341:Receptors, Adrenergic, alpha-2; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C410887:imidazoline I1 receptors; D015016:Yohimbine; C482128:MAP2K2 protein, human; D048051:p38 Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D003000:Clonidine