Peroxisome proliferator-activated receptor γ (PPARγ) regulates trefoil factor family 2 (TFF2) expression in gastric epithelial cells

Abstract

Although trefoil factor family 2 (TFF2) plays a critical role in the defense and repair of gastric mucosa, the regulatory mechanism of TFF2 expression is not fully understood. In this study, we investigated the regulation of TFF2 expression by peroxisome proliferator-activated receptor γ (PPARγ) in gastric epithelial cells. MKN45 gastric cells were used. TFF2 mRNA expression was analyzed by real-time quantitative RT-PCR. The promoter sequence of the human TFF2 gene was cloned into pGL3-basic vector for reporter gene assays. Ciglitazone was mainly used as a specific PPARγ ligand. MKN45 cells expressed functional PPARγ proteins. Endogenous TFF2 mRNA expression and TFF2 reporter gene transcription was significantly up-regulated by ciglitazone in a dose-dependent manner. Reporter gene assays showed that two distinct cis-elements are involved in the response to PAPRγ activation. Within one of these element (nucleotides −558 to −507), we identified a functional peroxisome proliferator responsive element (PPRE) at −522 (5′-GGGACAAAGGGCA-3′). Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay confirmed the binding of PPARγ to this sequence. Another element (nucleotides −407 to −358) appeared to be a composite enhancer element indirectly regulated by PPARγ and a combination of these two cis-elements was required for the full response of the human TFF2 gene expression to PPARγ. These data demonstrate that human TFF2 gene is a direct target of PPARγ in gastric epithelial cells. Since TFF2 is a critical gastroprotective agent, PPARγ may be involved in the gastric mucosal defense through regulating TFF2 expression in humans.