title: Hyperthermia-induced upregulation of vascular endothelial growth factor in retinal pigment epithelial cells is regulated by mitogen-activated protein kinases.
abstract: OBJECTIVE
  Localized application of hyperthermia is a potential treatment for retinal diseases. Vascular endothelial growth factor (VEGF) derived from the retinal pigment epithelium (RPE) is implicated in a variety of retinal pathologies. As it has been recently shown that hyperthermia may induce VEGF in the RPE, the aim of this study was to investigate hyperthermia-induced VEGF secretion and the pathways of hyperthermal VEGF upregulation in the RPE.
  
  
  METHODS
  The human RPE cell line (Arpe-19) was exposed to 40°, 42°, 45° and 50 °C for one, five and 15 min. Cell viability was evaluated using a trypan blue exclusion assay, VEGF secretion was evaluated by an enzyme-linked immunosorbent assay ELISA) and VEGF expression was investigated using a Western blot. Involvement of mitogen-activated protein kinase (MAPK) pathways (ERK1/2, JNK, p38) and transient receptor potential vanilloid (TRPV) channels on VEGF induction was investigated using commercially available inhibitors (U0126, SB203580, SP600125, ruthenium red). Expression and phosphorylation of MAPKs was investigated using a Western blot.
  
  
  RESULTS
  Hyperthermia induces time- and temperature-dependent cell death in human RPE cells. VEGF expression and secretion is induced by hyperthermia in a time- and temperature-dependent manner mediated by p38 and to a lesser degree by JNK. TRPV channels seem to play a minor role in regulation of hyperthermia-induced VEGF secretion.
  
  
  CONCLUSIONS
  Hyperthermia induces temperature-dependent secretion of VEGF in the RPE, which is mediated by p38 and, to a lesser extent, JNK. This may lead to undesired effects from hyperthermal treatment of retinal diseases.
authors.affiliation: Department of Ophthalmology, University Medical Center, University of Kiel, Arnold-Heller-Str. 3, 24105, Kiel, Germany.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Faby
authors.forename: Jost
authors.initials: J
authors.lastname: Hillenkamp
authors.forename: Johann
authors.initials: J
authors.lastname: Roider
authors.forename: Alexa
authors.initials: A
authors.lastname: Klettner
mesh_terms: D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D006979:Hyperthermia, Induced; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D055213:Retinal Pigment Epithelium / Q000378:metabolism*; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4