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GATA4 REGULATES THE INFLAMMATORY RESPONSE IN INTESTINAL EPITHELIAL CELLS
C Asselin, A Rémillard, C Deschênes
Département d'anatomie et biologie cellulaire, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Quebec
Aims: The GATA4 transcription factor controls intestinal epithelial cell differentiation. We previously showed that GATA4 regulates C/EBP-dependent expression of IL-1beta-mediated induction of acute phase protein genes. We hypothesize that GATA4 modulates the intestinal inflammatory response mediated by lipopolysaccharides (LPS) and flagellin, two bacterial products which bind to respectively toll-like receptor-4 and -5 (TLR-4, TLR-5).
Methods: We established IEC-6 crypt-derived rat intestinal epithelial cells expressing GATA4 by retroviral infection. Cells were treated with IL-1beta, LPS or flagellin. We performed Western blots to study MAP kinase and Akt activation, electrophoretic mobility shift and supershift assays to determine C/EBP, AP-1 and NF-kappaB DNA-binding capacity, and semi-quantitative RT-PCR to assess inflammatory gene expression.
Results: 1) In contrast to LPS and flagellin, IL-1beta-dependent p38 activation is decreased in GATA4-expressing cells. 2) Akt phosphorylation is decreased in GATA4-expressing cells treated with bacterial products. 3) GATA4 decreases both basal and induced C/EBP DNA-binding. 4) NF-kappaB DNA-binding is not significantly altered. 5) TLR-4 mRNA expression is induced in GATA-4 expressing cells, independently of the inflammatory response. 6) GATA4 overexpression leads to a decrease of iNOS induction in response to bacterial products or IL-1beta, in contrast to CXCL10 or CXCL2.
Conclusions: GATA4 may affect the intestinal inflammatory response by modulating various transcriptional and cell signaling pathways.
Supported by CCFC.