Dexamethasone inhibits epidermal growth factor-stimulated gastric epithelial cell proliferation.
Epidermal growth factor (EGF) is essential to heal gastric ulcers, whereas glucocorticoid delays rat gastric ulcer healing. We found that dexamethasone inhibited EGF-stimulated rat gastric epithelial cell (RGM-1) proliferation by cell count and DNA synthesis analysis of flow cytometry and attempted to elucidate the possible mechanistic pathway via Western blot analysis. EGF (10 ng/ml) treatment for 24 h significantly increased RGM-1 cell proliferation, and dexamethasone (10(-8) and 10(-6) M) markedly suppressed EGF-stimulated cell proliferation. Western blotting results demonstrated that the phosphorylated extracellular signal-regulated kinase (pERK) (pERK1/pERK2) significantly increased at 10 min after EGF treatment. This was followed by increase of cyclooxygenase (COX)-2 expression at 3 h after EGF treatment. The continued increase of COX-2 (up to 18 h) resulted in increased intracellular prostaglandin E(2) and cyclin D1 expression significantly after 8 and 12 h of EGF treatment. Dexamethasone substantially reduced EGF-stimulated COX-2 expression at 3 and 6 h and cyclin D1 expression at 8 and 12 h. Pretreatment of RGM-1 cells with dexamethasone or 2'-amino-3'-methoxyflavone (PD98059)-mitogen-activated protein kinase kinase inhibitor (5 x 10(-5) M) significantly reduced EGF-stimulated pERK1/pERK2 expression. Simultaneous treatment of RGM-1 cells with PD98059 and EGF also markedly decreased EGF-stimulated COX-2 expression at 6 h. These findings indicate that dexamethasone significantly suppresses EGF-stimulated gastric epithelial cell proliferation, and one of the pathways involved is via inhibiting activation of ERK1/ERK2, followed by inhibition of COX-2, cyclin D1 expression, and finally DNA synthesis.
Luo
Jiing-Chyuan
JC
Division of Gastroenterology, Department of Medicine, Taipei Veterans General Hospital, National Yang-Ming University, Taipei, Taiwan 11217.
Chi
Chin-Wen
CW
Lin
Hsiao-Yi
HY
Chang
Full-Young
FY
Lu
Ching-Liang
CL
Chen
Chih-Yen
CY
Lee
Shou-Dong
SD
D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004815:Epidermal Growth Factor / Q000037:antagonists & inhibitors*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D005753:Gastric Mucosa / Q000166:cytology / Q000187:drug effects*; D009578:Nitrobenzenes / Q000494:pharmacology; D010766:Phosphorylation; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D005419:Flavonoids; D009578:Nitrobenzenes; D013449:Sulfonamides; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D004815:Epidermal Growth Factor; D003907:Dexamethasone; D051546:Cyclooxygenase 2; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one