Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 10, 2002
Publication Date: N/A
Technical Abstract: Toll-like receptors (TLRs) have been previously shown to mediate oxidative burst in chicken heterophils. This study was conducted to determine which molecular pathways are involved in 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°C. The cells were then stimulated for 30 min at 39°C with either Salmonella enteritidis lipopolysaccharide (LPS) or Staphylococcus aureus lipoteichoic acid (LTA). 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 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 LTA, a gram-positive TLR agonist, demonstrated a different signal transduction pathway than that of LPS stimulated cells, as chelerythrine was the only inhibitor that significantly reduced (72%) LTA stimulated oxidative burst. 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 agonists. A protein kinase C dependent signal transduction pathway plays a major role in 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.