Submitted to: Journal of Inflammation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 18, 2003
Publication Date: August 20, 2003
Citation: FARNELL, M.B., HE, H., KOGUT, M.H. DIFFERENTIAL ACTIVATION OF SIGNAL TRANSDUCTION PATHWAYS MEDIATING OXIDATIVE BURST BY CHICKEN HETEROPHILS IN RESPONSE TO STIMULATION WITH LIPOPOLYSACCHARIDE AND LIPOTEICHOIC ACID. INFLAMMATION. 2003. V. 27. P. 225-231. Interpretive Summary: Baby chicks are very vulnerable to bacterial infections during the first two weeks of life. Chickens have cells that fight these infections. One group of these cells, called heterophils, is especially good at killing bacteria in baby chicks. Chicken heterophils have been previously shown to recognize bacteria by a group of receptors called Toll-like receptors. These Toll-like receptors tell the heterophil what to do by initiating a cascade of chemical interactions within the cell. The objective of this study was to identify some of these chemical interactions in chicken heterophils. We found that different chemical patterns are seen in heterophils when they are stimulated with different bacteria thru Toll-like receptors. These studies are important to the pharmaceutical industry because if these chemical patterns can be manipulated they may be able to protect baby chicks from infection.
Technical Abstract: Toll-like receptors (TLRs) have been previously shown to mediate oxidative burst in chicken heterophils. This study was conducted to begin to map the molecular pathways that regulate TLR-mediated oxidative burst. Peripheral blood heterophils from neonatal chicks were isolated and exposed to known inhibitors of signal transduction pathways for either 20 min (genistein, verapamil, or chelerythrine) or 120 min (pertussis toxin) at 39 deg C. The cells were then stimulated for 30 min at 39 deg C with Salmonella enteritidis lipopolysaccharide (LPS) or Staphylococcus aureus lipoteichoic acid (LTA). The heterophil oxidative burst was then quantitated by luminol-dependent-chemiluminescence (LDCL). Genistein (a tyrosine kinase inhibitor), verapamil (a calcium channel blocker), chelerythrine (a protein kinase C inhibitor) and pertussis toxin (a G-protein inhibitor) significantly reduced LPS-stimulated oxidative burst in chicken heterophils when compared to a LPS stimulated control by 34, 50, 63, and 51%, respectively. Although genistein had a statistically significant effect on reducing LPS-stimulated LDCL biologically it seems to play only a minor role within the oxidative burst pathway. Heterophils stimulated with the gram-positive TLR agonist, LTA, activated a different signal transduction pathway since chelerythrine was the only inhibitor that significantly reduced (72%) LTA-stimulated oxidative burst when compared to a LTA stimulated control. These findings demonstrate that distinct signal transduction pathways differentially regulate the stimulation of oxidative burst in avian heterophils. Pertussis toxin-sensitive, protein kinase C-dependent, Ca*++-dependent G proteins appear to regulate oxidative burst of avian heterophils stimulated with gram-negative agonist LPS; whereas, a protein kinase C-dependent signal transduction pathway plays the major role activating the oxidative burst of avian heterophils stimulated with gram-positive agonists. The distinct differences in the response of heterophils to these two agonists illustrate the specificity of TLRs to pathogen-associated molecular patterns (PAMP) s.