title: IFN-γ renders human intestinal epithelial cells responsive to lipopolysaccharide of Vibrio cholerae by down-regulation of DMBT1.
abstract: Although intestinal epithelial cells (IECs) are continuously exposed to high densities of enteric bacteria, they are not highly responsive to microbe-associated molecular patterns (MAMPs). However, inflammatory cytokines such as interferon-γ (IFN-γ) are potentially capable of priming IECs to enhance responsiveness to MAMPs. In this study, we observed that heat-killed Vibrio cholerae (HKVC) and its lipopolysaccharide (LPS) poorly induced IL-8 production in a human IEC line, HT-29. However, both HKVC and the LPS showed a substantial induction of IL-8 production in IFN-γ-primed HT-29 cells. LPS-induced IL-8 production was proportional to the IFN-γ-priming period and LPS could not induce IL-8 production in the presence of polymyxin B. Moreover, LPS-induced IL-8 production in the IFN-γ-primed HT-29 cells was mediated through signaling pathways requiring p38 kinase and ERK, but not the JNK/SAPK pathway. Since deleted in malignant brain tumor 1 (DMBT1) is known to interact with and antagonize the action of LPS, we hypothesized that IFN-γ enhanced the responsiveness to LPS in HT-29 through down-regulation of DMBT1. We found that IFN-γ indeed attenuated DMBT1 expression at both the mRNA and protein levels in HT-29 cells. Conversely, when the cells were transfected with small interfering RNA to specifically silence DMBT1, IL-8 expression was augmented even in the absence of IFN-γ and the augmentation was further enhanced by treatment with V. cholerae LPS. Since IFN-γ is known to increase IFN-β expression in the IECs, we examined if IFN-β functioned similar to IFN-γ. Although IFN-β alone was able to induce IL-8 expression, it failed to render HT-29 cells responsive to V. cholerae LPS. In conclusion, our study suggests that IFN-γ primes IECs to become responsive to V. cholerae and its LPS by suppressing the expression of DMBT1.
authors.affiliation: Department of Oral Microbiology & Immunology, Dental Research Institute, and BK21 Program, School of Dentistry, Seoul National University, Seoul 110-749, Republic of Korea.
authors.forename: Seok-Seong
authors.initials: SS
authors.lastname: Kang
authors.forename: Jun Ho
authors.initials: JH
authors.lastname: Jeon
authors.forename: Sun-Je
authors.initials: SJ
authors.lastname: Woo
authors.forename: Jae Seung
authors.initials: JS
authors.lastname: Yang
authors.forename: Kyoung Whun
authors.initials: KW
authors.lastname: Kim
authors.forename: Cheol-Heui
authors.initials: CH
authors.lastname: Yun
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Han
mesh_terms: D002135:Calcium-Binding Proteins; D004268:DNA-Binding Proteins; D015536:Down-Regulation; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D015870:Gene Expression; D019073:HT29 Cells; D006358:Hot Temperature; D006801:Humans; D016899:Interferon-beta / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology*; D016209:Interleukin-8 / Q000096:biosynthesis / Q000276:immunology; D007422:Intestines / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D011112:Polymyxin B / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors* / Q000235:genetics; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins; D014734:Vibrio cholerae / Q000502:physiology*
chemical_list: D002135:Calcium-Binding Proteins; C108174:DMBT1 protein, human; D004268:DNA-Binding Proteins; D016209:Interleukin-8; D008070:Lipopolysaccharides; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D025521:Tumor Suppressor Proteins; D016899:Interferon-beta; D007371:Interferon-gamma; D011112:Polymyxin B