Intracellular regulatory mechanisms of the activation of human eosinophils by TSLP, IL-27 and ligands of NOD-like receptors in allergic inflammation.
Accumulating evidence has indicated that microbial infection could intensify allergic responses. Previous findings demonstrated that eosinophil activation could be elicited by bacterial and viral conserved molecular pattern through TLR. Recently, two cytoplasmic pattern recognition receptors, NLR pr...
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| Format: | Others |
| Language: | English Chinese |
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2010
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| Online Access: | http://library.cuhk.edu.hk/record=b6074862 http://repository.lib.cuhk.edu.hk/en/item/cuhk-344495 |
| Summary: | Accumulating evidence has indicated that microbial infection could intensify allergic responses. Previous findings demonstrated that eosinophil activation could be elicited by bacterial and viral conserved molecular pattern through TLR. Recently, two cytoplasmic pattern recognition receptors, NLR protein NOD1 and NOD2, have been discovered and the important roles in innate immunity have been elucidated. Eosinophils alone have little responses upon the stimulation with ligands of NOD1 and NOD2. Since airway eosinophils increase in more numbers of asthmatic patients compared to control subjects, we investigated the co-culture system of eosinophils and human bronchial epithelial cells to illustrate the potential immunopathological roles of NOD1 and NOD2 in asthma processes. In the co-culture system, NOD1 ligand gamma-D-Glu-mDAP (iE-DAP) and NOD2 ligand muramyl dipeptide (MDP) could upregulate cell surface expression of CD1 8 and ICAM-1 on eosinophils and ICAM-1 and vascular cell adhesion molecule-1 (VCAM-1) on bronchial epithelial cells, as well as induce chemokines CCL2 and CXCL8 release. These findings therefore imply the direct interaction and activation between the two cells upon NOD1 and NOD2 ligand stimulation. === Allergic diseases are prevalent and their incidences have been increasing worldwide. Eosinophils are the principal effector cells for the late phase response in allergic inflammation. The infiltration of eosinophils together with other inflammatory cells at the local inflammatory sites is the major characteristic in allergic inflammation. However, the detailed innnunopathological responses and mechanisms of the activation of eosinophils in allergic inflammation are not well defined. In the present study, we investigated and attempted to elucidate the mechanisms of eosinophil activation induced by various stimuli, including thymic stromal lymphopoietin (TSLP), the novel interleukin (IL)-12 family cytokine IL-27, and ligands of nucleotide-binding oligomerization domain (NOD) like receptor (NLR) protein NOD1 and NOD2 upon interaction with bronchial epithelial cells. === In conclusion, the above findings demonstrated that eosinophils could be potently activated by diverse stimuli and regulated by multiple intracellular regulatory mechanisms. The elucidation of eosinophil activation may offer new therapeutic stategies and clues for the treatment of allergic diseases. === Recently, the novel IL-12 family member IL-27 was found to regulate immune responses, exerting either stimulation or suppression effects. We found that eosinophils constitutively expressed IL-27 receptor heterodimer, gp130 and WSX-1. IL-27 could prolong eosinophil survival by reducing apoptosis, modulate the expression of adhesion molecules to facilitate eosinophil adhesion and accumulation, and induce the release of proinflammatory cytokines IL-6, tumor necrosis factor (TNF)-aalpha IL-1beta and chemokines CCL2, CXCL8 and CXCL1. The stimulatory effects of IL-27 on eosinophils could not be abrogated by IL-25, hematopoietic cytokine granulocyte-macrophage colony stimulating factor (GM-CSF) and toll-like receptor (TLR) 4 ligand lipopolysaccharide (LPS). These findings were different from the effects of IL-27 and LPS on monocytes. Intracellular signaling mechanistic studies showed that IL-27-mediated eosinophil activation was differentially regulated by MAPKs and NF-kappaB. Based on the above results, IL-27 could play crucial roles in allergic diseases by the activation of eosinophils via differential intracellular signaling cascades. However, IL-27 has been shown to suppress allergic diseases in mouse models. According to our findings of its activating effects on human eosinophils, IL-27 may play pleiotropic roles in human allergic responses. === TSLP is a novel IL-7-like cytokine highly expressed by bronchial epithelial cells and skin keratinocytes in allergic diseases. TSLP acts as a master switch for allergic inflammation through the activation of dendritic cells and mast cells for initiating inflammatory Th2 responses. To elucidate the immunological cascades of epithelium/keatinocyte-eosinophil mediated allergic inflammation, we examined the modulating effects of TSLP on human eosinophils. We observed that human eosinophils constitutively expressed TSLP receptor complex comprising TSLP-binding chain TSLPR and IL-7Ralpha chain. TSLP could significantly delay eosinophil apoptosis, up-regulate the cell surface expression of adhesion molecule CD18 and intercellular adhesion molecule-1 (ICAM-1) but down-regulate L-selectin, enhance eosinophil adhesion to fibronectin, and induce the release of inflammatory cytokine 1L-6 and chemokines CXCL8, CXCL1 and CCL2. All these effects were concentration-dependent and TSLP-specific. TSLP regulated the above effects through the activation of extracellular signal-regulated protein kinase (ERK), p38 mitogen activated protein kinase (MAPK) and nuclear factor (NF)-kappaB signaling pathway, but not signal transducer and activator of transcription (STAT)-5 and STAT-3 which were usually activated in other effector cells upon TSLP stimulation. Collectively, the above findings elucidated the pro-allergic mechanisms of TSLP via the activation of distinct intracellular signaling pathways in eosinophils. === Hu, Shuiqing. === Adviser: Wong Chin Kwok. === Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . === Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. === Includes bibliographical references (leaves 176-216). === Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. === Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. === Abstract also in Chinese. |
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