|Lowry, Virginia - TX A&M UNIVERSITY|
|Farnell, Morgan - TX A&M UNIVERSITY|
Submitted to: Immunopharmacology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 18, 2003
Publication Date: June 20, 2003
Citation: KOGUT, M.H., LOWRY, V.K., FARNELL, M. THE USE OF SELECTIVE PHARMACOLOGICAL INHIBITORS TO DELINEATE SIGNAL TRANSDUCTION PATHWAYS ACTIVATED DURING COMPLEMENT RECEPTOR-MEDIATED DEGRANULATION IN CHICKEN HETEROPHILS. IMMUNOPHARMACOLOGY. 2003. v. 3 p. 693-706. Interpretive Summary: During the first week of life after hatching, the immune system of the baby chick is not very good at fighting bacterial infections such as Salmonella, and we do not know why. The objective of this experiment was to look at a specific white blood cell of the chicken--called the heterophil--and determine whether the cells' internal machinery are controlled by the same chemical reactions. We found that various parts of the cells' machinery are controlled by totally different chemical processes that are independent of each other. Therefore, the cell can control different parts of its internal machinery at different times without using other parts of the machinery. The results of this experiment are important to the pharmaceutical industry in the United States because it shows that we can stimulate different parts of the baby chick's immune system cells, without affecting other parts. Thus, it is possible to help the immune response without causing damage to the chick.
Technical Abstract: Complement receptors (CR), along with Fc receptors, play a primary role in the removal of bacterial pathogens in poultry. The binding of serum-opsonized bacteria to CR results in the secretion of both toxic oxygen metabolites and anti-bacterial granules. We have previously shown that the stimulation of chicken heterophils with serum-opsonized Salmonella enteritidis induced tyrosine kinase-dependent phosphorylation regulated degranulation. In the present studies, we used selective pharmacological inhibitors to investigate the roles of protein tyrosine kinses, phopholipases C and D (PLC and PLD), phosphatidylinositol 3'-kinase (PI3-K), and the super family of mitogen activated protein kinases (MAPK) on CR-mediated heterophil degranulation. Inhibitors of receptor-linked tyrosine kinases (the tryphostins AG1478 and AG1296) had no attenuating effects on CR-mediated degranulation. However, PP2, a selective inhibitor of the src family of protein tyrosine kinases, and piceatannol, an inhibitor of Syk tyrosine kinases, both significantly attenuated the CR-mediated degranulation. Additionally, the specific inhibitors of PLC, U73122, and PI-3K, LY294002, significantly decreased CR-mediated heterophil degranulation. Since PLD has also been linked to mammalian neutrophil activation, two inhibitors of PLD-mediated signaling, 2,3-diphosphoglycerate and 1-butanol, hindered degranulation. Addition of purified PLD restored control levels of degranulation in heterophils in which PLD was inhibited. Lastly, SP600125, a selective inhibitor of c-Jun N-terminal kinase (JNK), inhibited degranulation; whereas, neither PD98059, the inhibitor of p38 MAPK, nor SB203580, the inhibitor of extracellular signal-regulated kinase, had any effect on CR-mediated heterophil degranulation. These studies demonstrate that CR on chicken heterophils lack intrinsic tyrosine kinase activity, but that binding of serum-opsonized bacteria activates both proximal tyrosine kinases (src and Syk kinases), but differentially activates downstream tyrosine kinases (JNK, but not p38 nor ERK). Activation of src and Syk kinases play a significant role in signal transduction of heterophil degranulation probably by stimulating downstream phosphorylation of PLC, PLD, and PI-3K. PI3-K has also been recently shown to be an upstream mediator of JNK activation suggesting that this enzyme can induce signaling as both a lipid kinase and protein kinase.