title: Soluble CD40 ligand stimulates CD40-dependent activation of the β2 integrin Mac-1 and protein kinase C zeda (PKCζ) in neutrophils: implications for neutrophil-platelet interactions and neutrophil oxidative burst.
abstract: Recent work has revealed an essential involvement of soluble CD40L (sCD40L) in inflammation and vascular disease. Activated platelets are the major source of sCD40L, which has been implicated in platelet and leukocyte activation, although its exact functional impact on leukocyte-platelet interactions and the underlying mechanisms remain undefined. We aimed to determine the impact and the mechanisms of sCD40L on neutrophils. We studied neutrophil interactions with activated, surface-adherent platelets as a model for leukocyte recruitment to the sites of injury. Our data show that CD40L contributes to neutrophil firm adhesion to and transmigration across activated surface-adherent platelets, possibly through two potential mechanisms. One involves the direct interaction of ligand-receptor (CD40L-CD40), i.e., platelet surface CD40L interaction with neutrophil CD40; another involves an indirect mechanism, i.e. soluble CD40L stimulates activation of the leukocyte-specific β2 integrin Mac-1 in neutrophils and thereby further promotes neutrophil adhesion and migration. Activation of the integrin Mac-1 is known to be critical for mediating neutrophil adhesion and migration. sCD40L activated Mac-1 in neutrophils and enhanced neutrophil-platelet interactions in wild-type neutrophils, but failed to elicit such responses in CD40-deficient neutrophils. Furthermore, our data show that the protein kinase C zeta (PKCζ) is critically required for sCD40L-induced Mac-1 activation and neutrophil adhesive function. sCD40L strongly stimulated the focal clustering of Mac-1 (CD11b) and the colocalization of Mac-1 with PKCζ in wild-type neutrophils, but had minimal effect in CD40-deficient neutrophils. Blocking PKCζ completely inhibited sCD40L-induced neutrophil firm adhesion. Moreover, sCD40L strongly stimulates neutrophil oxidative burst via CD40-dependent activation of PI3K/NF-KB, but independent of Mac-1 and PKCζ. These findings may contribute to a better understanding of the underlying mechanisms by which sCD40L/CD40 pathway contributes to inflammation and vascular diseases.
authors.affiliation: Vascular Biology and Stroke Research Laboratory, Department of Neurosurgery, Louisiana State University Health Science Center in Shreveport, Shreveport, Louisiana, United States of America.
authors.forename: Rong
authors.initials: R
authors.lastname: Jin
authors.forename: Shiyong
authors.initials: S
authors.lastname: Yu
authors.forename: Zifang
authors.initials: Z
authors.lastname: Song
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Zhu
authors.forename: Cuiping
authors.initials: C
authors.lastname: Wang
authors.forename: Jinchuan
authors.initials: J
authors.lastname: Yan
authors.forename: Fusheng
authors.initials: F
authors.lastname: Wu
authors.forename: Anil
authors.initials: A
authors.lastname: Nanda
authors.forename: D Neil
authors.initials: DN
authors.lastname: Granger
authors.forename: Guohong
authors.initials: G
authors.lastname: Li
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D001792:Blood Platelets / Q000502:physiology*; D019013:CD40 Antigens / Q000378:metabolism; D023201:CD40 Ligand / Q000502:physiology*; D002448:Cell Adhesion; D002450:Cell Communication; D002478:Cells, Cultured; D016177:Macrophage-1 Antigen / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D016897:Respiratory Burst; D015398:Signal Transduction; D057688:Transcellular Cell Migration; D051996:Transcription Factor RelA / Q000378:metabolism; D000099221:Protein Kinase C zeta
chemical_list: D019013:CD40 Antigens; D023201:CD40 Ligand; D016177:Macrophage-1 Antigen; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; D051996:Transcription Factor RelA; D000099221:Protein Kinase C zeta; C498144:Rela protein, mouse