Tumor necrosis factor-α stimulates gastric epithelial cell proliferation

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Abstract
TNF-α is a cytokine produced during gastric mucosal injury. We examined whether TNF-α could promote mucosal repair by stimulation of epithelial cell proliferation and explored further the underlying mechanisms in a rat gastric mucosal epithelial cell line (RGM-1). TNF-α treatment (1–10 ng/ml) for 12 or 24 h significantly increased cell proliferation but did not induce apoptosis in RGM-1 cells. TNF-α treatment significantly increased cytosolic phospholipase A2 and cyclooxygenase-2 (COX-2) protein expression and PGE2 level but did not affect the protein levels of EGF, basic fibroblast growth factor, and COX-1 in RGM-1 cells. The mRNA of TNF receptor (TNF-R) 2 but not of TNF-R1 was also increased. Dexamethasone dose dependently inhibited the stimulatory effect of TNF-α on cell proliferation, which was associated with a significant decrease in cellular COX-2 expression and PGE2 level. A selective COX-2 inhibitor 3-(3-fluorophenyl)-4-[4-(methylsulfonyl)phenyl]-5,5-dimethyl-5H-furan-2-one (DFU) by itself had no effect on basal cell proliferation but significantly reduced the stimulatory effect of TNF-α on RMG-1 cells. Combination of dexamethasone and DFU did not produce an additive effect. PGE2 significantly reversed the depressive action of dexamethasone on cell proliferation. These results suggest that TNF-α plays a regulatory role in epithelial cell repair in the gastric mucosa via the TNF-α receptor and activation of the arachidonic acid/PG pathway.