Functional Characterization of the Avian Inflammatory Mediators Nod1, MIF and IL-22
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Inflammation can be initiated by an innate immune sensor, followed by activation of a signal mediator, resulting in control of immune response by a signal regulator. Mammalian nucleotide-binding oligomerization domain protein 1 (Nod1) and Nod2 initiate host innate immune response by recognition of specific bacterial molecules, resulting in the production of pro-inflammatory cytokines, chemokines, and anti-microbial peptides. A candidate sequence of chicken Nod1 (ChNod1) was identified with no current evidence of ChNod2. Stimulation of transiently overexpressed ChNod1 and its mutants with mammalian Nod-specific ligands was not conclusive of the function of ChNod1 most likely due to self-activation of ChNod1. In vitro studies showed no significant difference in expression of Nod1, its signaling molecules and pro-inflammatory cytokines in stimulated chicken mononuclear cells with synthetic ligands for mammalian Nod1 or Nod2. A signal mediator, macrophage migration inhibitory factor (MIF) inhibits the random migration of macrophages. Chemotaxis assay using recombinant ChMIF (rChMIF) revealed a substantial decrease in migration of macrophages. qRT-PCR analysis revealed that the presence of rChMIF enhanced levels of IL-1β and iNOS during monocytes stimulation with LPS. Additionally, Con A-stimulated lymphocytes exhibited enhanced IFN-γ and IL-2 transcripts in the presence of rChMIF. IL-22, which may act as a signal regulator, is an important effector of activated Th1 and Th17 as well as natural killer cells during inflammation. Recombinant ChIL-22 alone did not have an impact on chicken embryo kidney epithelial cells (CKECs); however, co-stimulation of CKECs with LPS and rChIL-22 enhanced the production of pro-inflammatory cytokines and anti-microbial peptides. Furthermore, rChIL-22 alone stimulated acute phase reactants in chicken embryo liver cells. These effects of rChIL-22 were abolished by addition of rChIL22 binding protein. Taken together, these results indicate an important role of ChIL-22 on epithelial cells and hepatocytes during inflammation. In this project, we identified and characterized the avian inflammatory mediators ChNod1, ChMIF, and ChIL-22. Studying each of their biological function in avian inflammation, especially under pathogenic challenges in epithelial tissues will provide a foundation for understanding the role of these inflammatory mediators in mucosal immunity.
- Doctoral Dissertations