A critical 'threshold' of beta 2-integrin engagement regulates augmentation of cytokine-mediated superoxide anion release.
1. Neutrophil adhesion regulates a number of processes involved in the pathogenesis of inflammatory diseases including rheumatoid arthritis. Neutrophil destructive potential can be modulated by adhesion, allowing alteration of inflammatory cell behaviour while preserving antimicrobial defences. beta(2)-Integrin-mediated neutrophil adhesion to albumin-coated latex beads (ACLB) allows modulation of integrin clustering and ligation and analysis of the effects of adhesion on neutrophil responses. Tumour necrosis factor-alpha (TNF alpha) enhanced neutrophil binding of different diameter ACLB equally, by almost four-fold, and independently of bead size. Adhesion of neutrophils to ACLB caused a size-dependent generation and release of O(2)(-) and also potentiated TNF alpha-induced O(2)(-) release. 2. Binding of ACLB was not affected by disruption of cytoskeletal integrity with nocodazole or cytochalasin D or following blockade of tyrosine kinase activity. In contrast, tyrosine phosphorylation and an intact cytoskeleton were essential for adhesion- and cytokine-induced O(2)(-) release from neutrophils. Inhibition of adhesion- and cytokine-induced O(2)(-) release by 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazol[3,4-d]pyrimidine (PP2) indicated that a Src-family tyrosine kinase was the principal regulatory pathway mediating this response in neutrophils, a distal role for p38 MAPK was revealed by use of SB203580. 3. Tyrosine phosphorylation of c-Fgr, a Src-family tyrosine kinase, occurred following ACLB adhesion and exposure to TNF alpha, and was susceptible to inhibition by PP2. We suggest that activation of the key regulatory enzyme c-Fgr is achieved following ligation of a critical threshold of integrins following binding of large (>3 microM) ACLB.
Walker
Trevor R
TR
Rayne Laboratory, MRC Centre for Inflammation Research, University of Edinburgh Medical School, Teviot Place, Edinburgh EH8 9AG. Trevor.Walker@ed.ac.uk
Ruchaud-Sparagano
Marie-Helene
MH
McMeekin
Sarah R
SR
Dransfield
Ian
I
D001665:Binding Sites; D018821:CD18 Antigens / Q000502:physiology*; D002448:Cell Adhesion / Q000187:drug effects; D015638:Cytochalasin D / Q000009:adverse effects; D016207:Cytokines / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D003599:Cytoskeleton / Q000502:physiology; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000008:administration & dosage; D039641:Integrin beta Chains / Q000737:chemistry / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D008301:Maleimides / Q000008:administration & dosage; D008863:Microspheres; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D015739:Nocodazole / Q000009:adverse effects; D010316:Particle Size; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D012709:Serum Albumin / Q000737:chemistry / Q000494:pharmacology; D013481:Superoxides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013678:Technology, Pharmaceutical / Q000379:methods; D000267:Tissue Adhesions / Q000517:prevention & control; D014409:Tumor Necrosis Factor-alpha / Q000009:adverse effects / Q000037:antagonists & inhibitors; D019061:src-Family Kinases / Q000378:metabolism
C412373:AG 1879; D018821:CD18 Antigens; D016207:Cytokines; D007093:Imidazoles; D007211:Indoles; D039641:Integrin beta Chains; D008301:Maleimides; D011518:Proto-Oncogene Proteins; D011725:Pyridines; D011743:Pyrimidines; D012709:Serum Albumin; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D015638:Cytochalasin D; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019833:Genistein; D011505:Protein-Tyrosine Kinases; C053102:proto-oncogene proteins c-fgr; D019061:src-Family Kinases; D020928:Mitogen-Activated Protein Kinases; D008274:Magnesium; C070515:bisindolylmaleimide I; C093642:SB 203580; D015739:Nocodazole