Background and aim: TFF1 (pS2) is expressed at a high level in gastric epithelial cells and plays an important role in protecting the gastric mucosa. However, the regulatory mechanisms of TFF1 expression are not fully understood. The aim of this study was to investigate the effect of TNF-alpha, a representative proinflammatory cytokine, on TFF1 expression.
Methods: MKN45 and AGS cells, derived from human gastric carcinoma, were used. Endogenous TFF1 mRNA expression was analyzed by real-time quantitative RT-PCR. The sequences of the human TFF1 promoter were cloned into the pGL3-basic vector and reporter gene assays were performed. Nuclear factor (NF)-kappaB activity was monitored using a reporter vector that contained multiple copies of NF-kappaB responsive element upstream of the luciferase gene. Interaction between NF-kappaB and TFF1 cis-element was examined by electophoretic mobility shift assay (EMSA).
Results: TNF-alpha activated NF-kappaB and up-regulated endogenous TFF1 mRNA expression as well as the transcription of the TFF1 reporter genes in a dose-dependent manner. IL-1beta, another proinflammatory cytokine, also up-regulated TFF1 expression. TNF-alpha responsive element was mapped between -342 and -147 of the human TFF1 promoter and a putative NF-kappaB binding site was identified at -231. When this element was deleted, the reporter genes became almost insensitive to TNF-alpha treatment. EMSA showed binding of NF-kappaB to this element.
Conclusions: Inflammatory stimuli that activate NF-kappaB appear to up-regulate TFF1 expression in gastric epithelial cells. This mechanism may aid in the protection of the gastric mucosa under inflammatory conditions.