Inhibition of human neutrophil beta2-integrin-dependent adherence by hyperbaric O2

1997 ◽  
Vol 272 (3) ◽  
pp. C770-C777 ◽  
Author(s):  
S. R. Thom ◽  
I. Mendiguren ◽  
K. Hardy ◽  
T. Bolotin ◽  
D. Fisher ◽  
...  
Keyword(s):  
Guanylate Cyclase ◽  
Human Neutrophil ◽  
Animal Studies ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Human Neutrophils ◽  
Membrane Guanylate Cyclase ◽  
Binding Studies ◽  
Beta2 Integrins ◽  
Cell Fractions

Animal and clinical investigations have reported that exposure to hyperbaric O(2) improved the outcome of some reperfusion injuries. Animal studies have suggested that this may be due to an inhibition of leukocyte adherence to injured endothelium. This investigation tested the hypothesis that exposure to hyperbaric O(2) would inhibit beta2-integrin-dependent adherence of human neutrophils. Subjects were exposed to O(2) at partial pressures of up to 3 atmospheres absolute (ATA; 1 ATA = 0.1 MPa) for 45 min, and neutrophil binding to nylon columns and to fibrinogen-coated surfaces was measured. Exposure to O(2) at 2.8 or 3.0 ATA inhibited beta2-integrin-dependent neutrophil adherence but had no effect on the cell-surface expression of beta2-integrins, respiratory burst in response to phorbol ester, or non-beta2-integrin-dependent adherence to plastic plates coated with a fibronectin-like protein. beta2-Integrin adherence was restored by incubating blood with 8-bromoguanosine 3',5'-cyclic monophosphate (cGMP) and hyperbaric O(2) inhibited synthesis of cGMP by neutrophils stimulated with N-formyl-Met-Leu-Phe (FMLP). In studies of cell fractions, the activity of membrane guanylate cyclase was found to be increased by incubation with FMLP as well as by atrial natriuretic peptide (ANP) plus ATP. Hyperbaric O(2) had no effect on the basal activity of soluble or membrane-bound guanylate cyclase. However, hyperbaric O(2) inhibited the function of both the extracellular binding domain of membrane guanylate cyclase as well as intracellular catalytic activity. There are approximately 7,300 membrane guanylate cyclase molecules per cell, based on binding studies with ANP, with a dissociation constant of approximately 450 pM. Hyperbaric O(2) inhibits the function of human neutrophil beta2-integrins by a process linked to impaired synthesis of cGMP. a

scholarly journals Na+/H+ exchange activity during phagocytosis in human neutrophils: role of Fcgamma receptors and tyrosine kinases.

1996 ◽  
Vol 132 (6) ◽  
pp. 1037-1052 ◽  
Author(s):  
T Fukushima ◽  
T K Waddell ◽  
S Grinstein ◽  
G G Goss ◽  
J Orlowski ◽  
...  
Keyword(s):  
Tyrosine Phosphorylation ◽  
Tyrosine Kinases ◽  
Plasma Membranes ◽  
Kinase Inhibitors ◽  
Human Neutrophils ◽  
Cross Linking ◽  
Fcgamma Receptors ◽  
Beta2 Integrins ◽  
Cytosolic Acidification

In neutrophils, binding and phagocytosis facilitate subsequent intracellular killing of microorganisms. Activity of Na+/H+ exchangers (NHEs) participates in these events, especially in regulation of intracellular pH (pHi) by compensating for the H+ load generated by the respiratory burst. Despite the importance of these functions, comparatively little is known regarding the nature and regulation of NHE(s) in neutrophils. The purpose of this study was to identify which NHE(s) are expressed in neutrophils and to elucidate the mechanisms regulating their activity during phagocytosis. Exposure of cells to the phagocytic stimulus opsonized zymosan (OpZ) induced a transient cytosolic acidification followed by a prolonged alkalinization. The latter was inhibited in Na+-free medium and by amiloride analogues and therefore was due to activation of Na+/H+ exchange. Reverse transcriptase PCR and cDNA sequencing demonstrated that mRNA for the NHE-1 but not for NHE-2, 3, or 4 isoforms of the exchanger was expressed. Immunoblotting of purified plasma membranes with isoform-specific antibodies confirmed the presence of NHE-1 protein in neutrophils. Since phagocytosis involves Fcgamma (FcgammaR) and complement receptors such as CR3 (a beta2 integrin) which are linked to pathways involving alterations in intracellular [Ca2+]i and tyrosine phosphorylation, we studied these pathways in relation to activation of NHE-1. Cross-linking of surface bound antibodies (mAb) directed against FcgammaRs (FcgammaRII > FcgammaRIII) but not beta2 integrins induced an amiloride-sensitive cytosolic alkalinization. However, anti-beta2 integrin mAb diminished OpZ-induced alkalinization suggesting that NHE-1 activation involved cooperation between integrins and FcgammaRs. The tyrosine kinase inhibitors genistein and herbimycin blocked cytosolic alkalinization after OpZ or FcgammaR cross-linking suggesting that tyrosine phosphorylation was involved in NHE-I activation. An increase in [Ca2+]i was not required for NHE-1 activation because neither removal of extracellular Ca2+ nor buffering of changes in [Ca2+]i inhibited alkalinization after OpZ or Fc-gammaR cross-linking. In summary, Fc-gammaRs and beta2 integrins cooperate in activation of NHE-1 in neutrophils during phagocytosis by a signaling pathway involving tyrosine phosphorylation.

Abstract 3915: Del-1, A New β2-Integrin Ligand, Which Inhibits Adhesion and Homing of Progenitor Cells

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Emmanouil Chavakis ◽  
Andreas Hain ◽  
Alessia Orlandi ◽  
Guillaume Carmona ◽  
Thomas Quertermous ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Hind Limb ◽  
Limb Ischemia ◽  
Inflammatory Cells ◽  
Inhibitory Effect ◽  
Hind Limb Ischemia ◽  
Beta2 Integrins ◽  
Integrin Ligand

Progenitor cells (PC) are recruited to ischemic tissues and improve neovascularization. Beta2-integrins are essential for adhesion, transmigration and homing of PC to ischemic tissues. Developmental Endothelial Locus-1 (Del-1) is an extracellular matrix protein, that binds alphaVbeta3- and alphaVbeta5-integrins and is up-regulated during ischemia. Therefore, we investigated the role of endogenous Del-1 for angiogenesis and homing functions of PC. The Del-1-deficient mice (Del-1 −/− ) displayed a significantly increased angiogenic response in ischemic muscles in comparison to the wild type (WT) mice in the model of hind limb ischemia. However, when we assessed the role of Del-1 in HUVEC in vitro , silencing of Del-1 by siRNA did not affect angiogenic sprouting. Moreover, the ischemic muscles of Del-1 −/− mice displayed a higher infiltration with CD45 + hematopoietic cells than WT mice, suggesting that Del-1 may have an inhibitory effect on homing of PC and inflammatory cells to ischemic tissues. Interestingly, in adhesion assays human endothelial progenitor cells (EPC) and murine Lin − progenitor cells bound to Del-1 via beta2-integrins, but not via the alphaVbeta3- and alphaVbeta5- integrins. Furthermore, soluble Del-1 significantly inhibited the adhesion of EPC to HUVEC monolayers and to the major beta2-integrin-ligand, ICAM-1, raising the possibility that Del-1 is a beta2-integrin-inhibitor. Indeed, WT murine bone marrow mononuclear cells displayed higher adhesion rates on Del-1-deficient murine lung endothelial cells (LEC) than on WT LEC. In order to investigate the role of Del-1 for in vivo homing of PC, we intravenously injected murine fluorescence-labeled WT Lin − bone marrow PC in WT and Del-1 −/− mice 2 days after the induction of hind limb ischemia. Interestingly, the homing of injected Lin − cells to ischemic muscles was significantly increased in Del-1 −/− in comparison to WT mice (200± 30 % increase). Taken together, endogenous Del-1 is a new beta2-integrin ligand, which blocks beta2-integrin-dependent adhesion and homing of PC to ischemic tissues. It is conceivable, that endogenous Del-1 may reduce ischemia-induced neovascularization through an inhibitory effect on the beta2-integrins of progenitor and inflammatory cells.

ALPHA M AND ALPHA X BETA2 INTEGRINS CO-OPERATE TO MEDIATE MONOCYTE ADHESION TO PLATELETS UNDER FLOW

2004 ◽  
Vol 13 (3) ◽  
pp. 7-8
Author(s):  
Varuni Kanagasundaram ◽  
Thanae Georgakopoulos ◽  
Suhasini Kulkarni ◽  
Warwick Nesbitt ◽  
Hatem H Salem ◽  
...  
Keyword(s):  
Monocyte Adhesion ◽  
Beta2 Integrins

Beta2 integrins are required for follicular helper T cell differentiation in humans

2017 ◽  
Vol 180 ◽  
pp. 60-62 ◽  
Author(s):  
Jolanda Gerosa ◽  
Vassilios Lougaris ◽  
Manuela Baronio ◽  
Alessandro Plebani ◽  
Maria Pia Cicalese ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
T Cell ◽  
T Cell Differentiation ◽  
Helper T Cell ◽  
Beta2 Integrins ◽  
Follicular Helper ◽  
Follicular Helper T Cell
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