A SYSTEMS BIOLOGY APPROACH TO UNDERSTANDING THE SALMONELLA-HOST INTERACTOME IN POULTRY AND SWINE
Location: Food and Feed Safety Research
Title: Bacterial toll-like receptor agonists induce sequential NF-kB-mediated leukotriene B4 and prostaglandin E2 production in chicken heterophils
Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 3, 2011
Publication Date: November 11, 2011
Citation: Kogut, M.H., He, L.H., Genovese, K.J. 2011. Bacterial toll-like receptor agonists induce sequential NF-kB-mediated leukotriene B4 and prostaglandin E2 production in chicken heterophils. Veterinary Immunology and Immunopathology. 145:159-170.
Interpretive Summary: During the first week of life after hatching, the baby chick must fight off bacterial infections such as Salmonella. We have shown that the baby chicks "see" the bacteria by using structures on their immune cells. The purpose of these experiments was to see what kind of chemicals are produced by the immune cells when they see bacteria. We found that the immune cells produce two different chemicals that control a host response and kill the bacteria before they can hurt the chick. The results of this study are important to the pharmaceutical industry in the United States because we now know which chemicals are produced (or not) by the baby chick’s cells of the immune system when they see Salmonella. Thus, we can now determine if there are ways for us to get the baby chick to make these chemicals which will help the chick fight Salmonella infections.
Studies of the response of the primary avian polymorphonuclear leukocyte, the heterophil, to microbe-associated molecular patterns (MAMPs) through toll-like receptors (TLR) have concentrated on the activation of the respiratory burst, release of intracellular granules, and the induction of cytokine and chemokine expression. Virtually no studies have been described on the role of the lipid mediators leukotrienes and prostaglandins as effectors of the avian inflammatory response. We have previously shown that flagellin (FLG), the bacterial lipoprotein mimic palmitoly-3-cysteine-serine-lysine-4 (PAM), and unmethylated CpG motifs of bacteria DNA (CpG) are all potent activators of the avian innate immune system. In the present studies, we hypothesized that FLG, PAM, and CpG are also capable of eliciting the production of these lipid mediators of inflammation by avian heterophils. Compared to non-stimulated control heterophils, all three TLR agonists were potent inducers (3-5 fold increase) of a rapid production (30 min) of leukotriene B4 (LTB4) followed by a later release (60-120 min) of prostaglandin (PGE2) by the heterophils. LTB4 and PGE2 production were derived from lipoxygenase-5 (5-LO) and cyclooxygenase-2 (COX-2) enzymatic activities, respectively, as the selective 5-LO (caffeic acid) and COX-2 (NS-398) inhibitors eliminated LTB4 and PGE2 production from the MAMP-stimulated heterophils. These results demonstrate that both the lipoxygenase and cycloxygenase pathways are operational in avian heterophils in response to bacterial MAMPs. Treatment of heterophils with either FLG, PAM, or CpG also induced a significant increase in DNA binding by NF-'B family members’ p50, c-Rel, and RelB. Additionally, the production of LTB4 and PGE2 were inhibited following treatment of heterophils with the specific pharmacologic inhibitor of NF-'B (Bay 11-7086), thus suggesting that TLR pathway activation of NF-'B controls LTB4 and PGE2 production. This is the first report of the production of lipid mediators of inflammation by avian heterophils in response to PAMPs. Since FLG, lipoproteins, and bacterial CpG DNA are abundant during bacterial infections, these data support their role in the inflammatory response mediated by avian heterophils.