Submitted to: Keystone Symposia
Publication Type: Abstract Only
Publication Acceptance Date: 10/17/2005
Publication Date: 2/10/2006
Citation: He, H., Genovese, K.J., Kogut, M.H. 2006. Phosphatidylinositol-phospholipase C modulates TLR4-mediated immune responses to Salmonella lipopolysaccharide in chicken macrophage cells (HD11) [abstract]. Innate Immunity Keystone Symposia. p. 65.
Technical Abstract: The activation of phospholipases is one of the earliest key events in receptor-mediated cellular responses to a number of extracellular signaling molecules. Lipopolysaccharide (LPS) is a principle component of the outer membrane of Gram-negative bacteria and a prime target for recognition by the innate immune system. Recognition of LPS by immune cells is mediated by Toll-like receptor 4 (TLR4) and its signaling pathway that leads to the activation of nuclear factor NF-'B and subsequent expression of genes that regulate functions in the innate and adaptive immune responses to gram-negative bacterial infection. It is not clear whether phospholipase activities are involved in TLR4-mediated LPS signaling in chicken macrophage. In the present study, we evaluated the role of specific phospholipase in the activation of chicken macrophage cell line HD-11 by LPS. Activation of HD-11 cells by LPS results in induction of nitric oxide (NO). Using selective inhibitors, we have identified that phosphatidylinositol (PI)-phospholipase C (PI-PLC), but not phosphatidylcholine (PC)-phospholipase C (PC-PLC) nor PC-phospholipase D (PC-PLD), was required for LPS-induced NO production. Preincubation with PI-PLC selective inhibitors (U-73122 and ET-18-OCH3) abrogated LPS-induced NO production in HD-11 cells, whereas PC-PLC inhibitor (D609), PAP inhibitor (propranolol), and PC-PLD inhibitor (n-butanol) had no inhibitory effects. We also showed that inhibition of protein kinase C (PKC) by selective inhibitors Ro 31-8220 and calphostin C and chelating intracellular Ca**2+ by BAPTA-AM significantly reduced NO production in LPS-stimulated HD-11 cells. Our results demonstrate that PI-PLC plays a critical role, most likely through activation of PKC pathway, in TLR4 mediated immune responses of avian macrophage cells to LPS.