title: p38 mitogen-activated protein kinase protects human retinal pigment epithelial cells exposed to oxidative stress.
abstract: OBJECTIVE
  To investigate the role of p38 mitogen-activated protein kinase (MAPK) in human retinal pigment epithelial (RPE) cells exposed to acute oxidative stress.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Oxidative stress was induced by the chemical oxidant tert-butyl hydroperoxide (t-BOOH) in the human RPE cell line ARPE-19. Cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The phosphorylation of p38 MAPK was measured by Western blot analysis. Small interfering (si)RNA and plasmid DNA of a constitutive active mutant of a MAPK kinase (MKK6E) were transfected to knock down and activate p38 MAPK in ARPE-19 cells, respectively.
  
  
  RESULTS
  t-BOOH induced ARPE-19 cell death in a time- and dose-dependent manner. t-BOOH increased phosphorylation of p38 MAPK. Both inhibition of p38 MAPK with a selective inhibitor SB203580 and knockdown of p38? MAPK with siRNA enhanced t-BOOH-induced ARPE-19 cell death (by 29% and 20%, respectively). Overexpression of MKK6E, a kinase upstream of p38 MAPK, increased phosphorylation of p38 MAPK and attenuated t-BOOH-induced ARPE-19 cell death by 16%. Preconditioning with a low dose of t-BOOH decreased the ARPE-19 cell death induced by a higher dose of t-BOOH by 13%. This protective effect was absent when ARPE-19 cells were pretreated with SB203580 for 1 hour before preconditioning.
  
  
  CONCLUSIONS
  Under the conditions tested, activation of p38 MAPK protects ARPE-19 cells against oxidant-induced death. Because RPE cells play a key role in retinal homeostasis, this finding may have important implications for retinal disease.
authors.affiliation: Department of Ophthalmology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Cady E
authors.initials: CE
authors.lastname: Pocrnich
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Mary
authors.initials: M
authors.lastname: Feng
authors.forename: Tianqing
authors.initials: T
authors.lastname: Peng
authors.forename: Qingping
authors.initials: Q
authors.lastname: Feng
authors.forename: Cindy M L
authors.initials: CM
authors.lastname: Hutnik
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects; D004247:DNA; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D018384:Oxidative Stress / Q000187:drug effects*; D010766:Phosphorylation; D010957:Plasmids / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000201:enzymology* / Q000473:pathology; D013997:Time Factors; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D020122:tert-Butylhydroperoxide / Q000633:toxicity*
chemical_list: D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D004247:DNA; D020122:tert-Butylhydroperoxide; D048051:p38 Mitogen-Activated Protein Kinases