Pattern Recognition Receptors and Cytokine-Mediated Activation of Human Basophils: A Novel Link between Innate Immunity and Allergic Inflammation.

摘要

The incidences of allergic diseases such as allergic asthma and atopic dermatitis (AD) are increasing in Hong Kong and worldwide. Allergic asthma is a chronically relapsing inflammatory pulmonary disease, while AD is a chronic inflammatory skin disorder. Respiratory bacterial and Staphylococcus aureus (S. aureus) infection can provoke allergen sensitization and subsequently amplify and sustain inflammation in allergic asthma and AD, respectively. The innate immune system recognizes bacterial infection through pattern recognition receptors (PRRs), two important PRRs involving in inflammatory and immune responses are nucleotide-binding oligomerization domain-like receptors (NLRs) and Toll-like receptors (TLRs). NOD2 is one member of the NLR family, which senses the conserved structural component muramyl dipeptide (MDP) in almost all bacteria. TLR2 recognizes a wide range of pathogen-associated molecular patterns (PAMPs) including peptidoglycan (PGN) and lipoteichoic acid (LTA) from Gram-positive bacteria and synthetic triacylated lipoprotein N-palmitoyl-S-[2,3-bis (palmitoyloxy)-(2RS)-propyl]-[R]-cysteinyl-[S]-seryl-[S]-lysyl-[S]-lysyl-[S]-lysyl-[S]-lysine (Pam3CSK4).;In the present study, we investigated the effect of NOD2 ligand MDP, asthma-related tumor necrosis factor (TNF) family member LIGHT on human basophils co-cultured with human bronchial epithelial cells and the effect of heat-killed S. aureus, MDP, TLR2 ligands PGN, LTA and Pam3CSK4 on basophils co-cultured with human dermal fibroblasts, and the underlying intracellular mechanisms. The in vivo effect of NOD ligands on ovalbumin (OVA)-sensitized allergic asthmatic mice was also studied.;It was found that MDP could significantly enhance the cell surface expression of adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on basophils and primary human bronchial epithelial cells (HBE) in the co-culture system (all p < 0.05). MDP could further enhance the release of inflammatory cytokine interleukin (IL)-6, chemokine CXCL8, and epithelium derived anti-microbial peptide beta-defensin 2 in the co-culture. HBE cells were the major source while basophils were the minor source to release IL-6, CXCL8 and beta-defensin 2 in the co-culture upon MDP stimulation. The activities of several nuclear transcription factors, including NF-kappaB, were up-regulated in human basophils upon MDP stimulation. The cell surface expression of ICAM-1 and VCAM-1 and the release of IL-6, CXCL8 and beta-defensin 2 were suppressed by the signaling molecule inhibitors, implying that the interaction between basophils and primary human bronchial epithelial cells could be differentially regulated by the NF-kappaB, p38 MAPK and JNK pathways. The animal study showed that iE-DAP and MDP could increase the number of mucin-secreting goblet cells, the thickness and fibrosis of the bronchial subepithelial tissue of airways from the OVA-sensitized mice. The iE-DAP and MDP could further promote the levels of CCL5 and IL-13 (all p < 0.05) in bronchoalveolar lavage fluid (BALF) of allergic asthmatic mice.;It was found that the induction of ICAM-1, IL-6, CXCL8, CCL2 and CCL5 was significantly promoted upon the interaction between human basophils and dermal fibroblasts activated by heat-killed S. aureus, MDP, PGN, LTA or Pam3CSK4. The release of IL-6, CXCL8, CCL2 and CCL5 might depend on the direct interaction of basophils and dermal fibroblasts. The p38 MAPK and NF-kappaB pathways should be involved in the release of the cytokines and chemokines upon the interaction of basophils and human dermal fibroblasts.;LIGHT could significantly promote the cell surface expression of adhesion molecule, the release of IL-6, CXCL8 and MMP-9 from human bronchial epithelial cells upon the interaction with basophils, probably through the receptors HVEM and LTbetaR.;The results suggest that, through the interaction with tissue-resident cells such as bronchial epithelial cells and dermal fibroblasts, basophils may facilitate the activation of tissue-resident cells in response to the PAMPs in allergic inflammation. The results therefore provide a new insight of the crucial link between the bacterial-mediated innate immune response and the exacerbation of allergic inflammation. The above results also enhance our understanding on the immunopathological roles of LIGHT in airway remodeling, and the potential therapeutic target for airway remodeling.