Cross-linking of beta2 integrins caused diminished responses of neutrophils to priming agents like lipopolysaccharide or tumor necrosis factor-alpha: possible involvement of tyrosine kinase Syk.
Neutrophils up-regulate beta2 integrins like CD11b/CD18 in response to lipopolysaccharide (LPS). Up-regulation of beta2 integrins causes neutrophils to adhere to surfaces, and to release superoxide anion (O2-). When neutrophils are exposed to LPS plus plasma under conditions not favorable for adherence (absence of Mg2+), the cells do not spontaneously release O2-, but instead they are primed for enhanced release of O2- after subsequent triggering by fMLP. In the presence of Mg2+, neutrophils adhere in response to LPS but fMLP-triggered O2- release by LPS-primed neutrophils is diminished. To understand why adherence interferes with the response of neutrophils to N-formyl-methionyl-leucyl-phenylalanine (fMLP), beta2 integrins were cross-linked by mouse monoclonal antibodies that had been immobilized by surface-bound anti-mouse antibody. When unprimed neutrophils were trapped on the surface by these cross-linked monoclonal antibodies, O2- release was triggered, and priming by LPS for fMLP-triggered O2- release was diminished, indicating that this cross-linking of beta2 integrins mimicked adherence. Alkaline phosphatase is up-regulated by LPS or tumor necrosis factor-alpha, and this response was also diminished by the cross-linking antibodies. The diminished alkaline phosphatase up-regulation was reversed by genistein, a general inhibitor of tyrosine kinases, and by piceatannol, an inhibitor for Syk kinase. Piceatannol also inhibited the phosphorylation of Syk caused by cross-linking of beta2 integrins. These results suggested that adherence-induced triggering and Syk kinase activation might be responsible for the diminished response of LPS-primed neutrophils to fMLP when neutrophils were adherent.
Kusumoto
K
K
Department of Periodontology and Endodontology, Faculty of Dentistry, Kyushu University, Fukuoka, Fukuoka, Japan.
Aida
Y
Y
Maeda
K
K
Pabst
M J
MJ
D000469:Alkaline Phosphatase / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D018821:CD18 Antigens / Q000737:chemistry*; D002448:Cell Adhesion; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000037:antagonists & inhibitors / Q000502:physiology*; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D009240:N-Formylmethionine Leucyl-Phenylalanine; D009504:Neutrophils / Q000187:drug effects* / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D013267:Stilbenes / Q000494:pharmacology; D013481:Superoxides / Q000032:analysis / Q000378:metabolism; D000072377:Syk Kinase; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha
D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D013267:Stilbenes; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D009240:N-Formylmethionine Leucyl-Phenylalanine; C041525:3,3',4,5'-tetrahydroxystilbene; D019833:Genistein; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; D000469:Alkaline Phosphatase