title: Involvement of EGF receptor activation in the induction of cyclooxygenase-2 in HaCaT keratinocytes after UVB.
abstract: Because selective inhibition of cyclooxygenase-2 (COX-2) suppressed the induction of skin tumors in mice by UV and as UV has been shown to induce expression of COX-2 in skin and cells, COX-2 may be crucial for photocarcinogenesis of the skin. We studied the mechanism of UVB-induced expression of COX-2 focusing on the signal transduction pathway involved. Hydrogen peroxide (H2O2) treatment of HaCaT cells induced expression of COX-2 and pretreatment with the antioxidant N-acetylcysteine (NAC) partly inhibited the UVB-induced expression of COX-2 protein in HaCaT cells, suggesting that oxidative stress contributes to COX-2 induction. To examine the signaling pathways involved in the UVB-induced expression of COX-2 in HaCaT cells, we analysed the expression of COX-2 protein after treatment with various inhibitors of signaling molecules. Inhibition of EGFR by a specific inhibitor and by a neutralizing antibody suppressed the induction of COX-2 expression by UV. Although a neutralizing antibody to transforming growth factor-alpha (TGF-alpha) suppressed COX-2 expression induced by TGF-alpha, it did not suppress COX-2 expression by UV, indicating that a direct activation of EGFR is involved. Treatment of cells at low temperature (4 degrees C) inhibited UVB-induced JNK activation, but it did not inhibit COX-2 expression by UV. Inhibitors of MEK, p38 MAP kinase and PI3-kinase, suppressed the induction of COX-2 expression by UV. In contrast, an erbB-2 inhibitor augmented the UVB-induced increase of COX-2 protein. These data indicate that oxidative stress in association with activation of EGFR, ERK, p38 MAP kinase, and PI3-kinase plays crucial roles in the UVB induction of expression of COX-2.
authors.affiliation: Division of Dermatology, Clinical Molecular Medicine, Faculty of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ashida
authors.forename: T
authors.initials: T
authors.lastname: Bito
authors.forename: A
authors.initials: A
authors.lastname: Budiyanto
authors.forename: M
authors.initials: M
authors.lastname: Ichihashi
authors.forename: M
authors.initials: M
authors.lastname: Ueda
mesh_terms: D001483:Base Sequence; D002460:Cell Line; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000096:biosynthesis; D004790:Enzyme Induction / Q000528:radiation effects; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics; D015603:Keratinocytes / Q000378:metabolism* / Q000528:radiation effects*; D020935:MAP Kinase Signaling System / Q000528:radiation effects; D008565:Membrane Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000528:radiation effects; D014466:Ultraviolet Rays / Q000009:adverse effects; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D007527:Isoenzymes; D008565:Membrane Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D015232:Dinoprostone