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This Article Full Text Full Text (PDF) All Versions of this Article: 297/6/G1172    most recent ajpgi.00065.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Lim, D. M. Articles by Wang, M.-L. PubMed PubMed Citation Articles by Lim, D. M. Articles by Wang, M.-L.

Mucosal Biology

TLR3-mediated NF-B signaling in human esophageal epithelial cells

¹Division of Gastroenterology and Nutrition, Children's Hospital of Philadelphia, Philadelphia; ²Gastroenterology Division, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania

Submitted February 23, 2009 ; accepted in final form September 21, 2009

Despite its position at the front line against ingested pathogens, very little is presently known about the role of the esophageal epithelium in host innate immune defense. As a key player in the innate immune response, Toll-like receptor (TLR) signaling has not been well characterized in human esophageal epithelial cells. In the present study, we investigated the inflammatory response and signaling pathways activated by TLR stimulation of human esophageal cells in vitro. Using quantitative RT-PCR, we profiled the expression pattern of human TLRs 1–10 in primary esophageal keratinocytes (EPC2), immortalized nontransformed esophageal keratinocytes (EPC2-hTERT), and normal human esophageal mucosal biopsies and found that TLRs 1, 2, 3, and 5 were expressed both in vivo and in vitro. Using the cytokine IL-8 as a physiological read out of the inflammatory response, we found that TLR3 is the most functional of the expressed TLRs in both primary and immortalized esophageal epithelial cell lines in response to its synthetic ligand polyinosinic polycytidylic acid [poly(I:C)]. Through reporter gene studies, we show that poly(I:C)-induced NF-B activation is critical for the transactivation of the IL-8 promoter in vitro and that nuclear translocation of NF-B occurs at an early time point following poly(I:C) stimulation of esophageal epithelial cells. Importantly, we also show that poly(I:C) stimulation induces the NF-B-dependent esophageal epithelial expression of TLR2, leading to enhanced epithelial responsiveness of EPC2-hTERT cells to TLR2 ligand stimulation, suggesting an important regulatory role for TLR3-mediated NF-B signaling in the innate immune response of esophageal epithelial cells. Our findings demonstrate for the first time that TLR3 is highly functional in the human esophageal epithelium and that TLR3-mediated NF-B signaling may play an important regulatory role in esophageal epithelial homeostasis.

esophagus; Toll-like receptor 3