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1.
J Innate Immun ; 6(4): 553-60, 2014.
Article in English | MEDLINE | ID: mdl-24516072

ABSTRACT

Signal regulatory protein alpha (SIRPα) is a cell surface glycoprotein with inhibitory functions, which may regulate neutrophil transmigration. SIRPα is mobilized to the neutrophil surface from specific granules, gelatinase granules, and secretory vesicles following inflammatory activation in vitro and in vivo. The lack of SIRPα signaling and the ability to upregulate SIRPα to the cell surface promote neutrophil accumulation during inflammation in vivo.


Subject(s)
Cell Membrane/metabolism , Neutrophils/immunology , Secretory Vesicles/metabolism , Adult , Antigens, Differentiation/genetics , Antigens, Differentiation/immunology , Antigens, Differentiation/metabolism , Cell Degranulation/genetics , Cells, Cultured , Feedback, Physiological , Gene Expression Regulation/immunology , Humans , Inflammation/genetics , Protein Transport , Receptors, Immunologic/genetics , Receptors, Immunologic/immunology , Receptors, Immunologic/metabolism
2.
J Leukoc Biol ; 93(3): 403-12, 2013 Mar.
Article in English | MEDLINE | ID: mdl-23271705

ABSTRACT

Cells of the innate immune system, including monocytes, macrophages, and neutrophils, play a major role in the development of inflammatory diseases. During inflammation, large numbers of neutrophils are recruited from the blood and subsequently undergo apoptosis, which involves changes in the cell surface expression of a number of receptors. Neutrophils express the Ig superfamily member, SIRPα, which is a receptor involved in regulating cell adhesion and migration. As apoptotic neutrophils down-regulate their capacity for adhesion and migration, we here investigated whether neutrophil expression of SIRPα was affected during apoptosis. We found that apoptotic neutrophils lost SIRPα from their cell surface with kinetics similar to the loss of CD16. The majority of neutrophils with reduced SIRPα also expressed PS on their surface, and the loss of the receptor was reduced proportional to the reduction of apoptosis by caspase inhibitors during Fas-induced apoptosis but less so during spontaneous apoptosis. Neutrophil loss of SIRPα or CD16 was inhibited by the protease inhibitor TAPI-2, as well as specific inhibitors of MMP3 or -8, suggesting that proteolytic mechanisms were involved. Finally, SIRPα was also found on smaller membrane vesicles released from the cells during apoptosis. Our data suggest that neutrophils reduce their SIRPα expression during apoptosis, which may be part of the functional down-regulation seen in apoptotic neutrophils.


Subject(s)
Antigens, Differentiation/immunology , Apoptosis/immunology , Cell Membrane/immunology , Down-Regulation/immunology , Neutrophils/immunology , Receptors, Immunologic/immunology , Antigens, Differentiation/biosynthesis , Cell Membrane/metabolism , Female , GPI-Linked Proteins/immunology , GPI-Linked Proteins/metabolism , Humans , Hydroxamic Acids/immunology , Hydroxamic Acids/metabolism , Male , Matrix Metalloproteinase 3/immunology , Matrix Metalloproteinase 3/metabolism , Matrix Metalloproteinase 8/immunology , Matrix Metalloproteinase 8/metabolism , Neutrophils/metabolism , Receptors, IgG/immunology , Receptors, IgG/metabolism , Receptors, Immunologic/biosynthesis , fas Receptor/immunology , fas Receptor/metabolism
3.
Exp Diabesity Res ; 4(2): 125-32, 2003.
Article in English | MEDLINE | ID: mdl-14630574

ABSTRACT

The aim of this study was to investigate the effects of elevated glucose concentrations on complement receptor- and Fcgamma receptor-mediated phagocytosis in normal human neutrophils. D-Glucose at 15 or 25 mM dose-dependently inhibited both complement receptor- and Fcgamma receptor-mediated phagocytosis, as compared to that at a normal physiological glucose concentration. The protein kinase C (PKC) inhibitors GF109203X and Go6976 both dose-dependently and completely reversed the inhibitory effect of 25 mM D-glucose on phagocytosis. Complement receptor-mediated phagocytosis was dose-dependently inhibited by the cell permeable diacylglycerol analogue 1,2-dioctanoyl-sn-glycerol (DAG), an effect that was abolished by PKC inhibitors. Furthermore, suboptimal inhibitory concentrations of DAG and glucose showed an additive inhibitory effect on complement receptor-mediated phagocytosis. The authors conclude that elevated glucose concentrations can inhibit complement receptor and Fcgamma receptor-mediated phagocytosis in normal human neutrophils by activating PKCalpha and/or PKCbeta, an effect possibly mediated by DAG.


Subject(s)
Complement C3b/physiology , Immunoglobulin G/blood , Neutrophils/metabolism , Phagocytosis/physiology , Protein Kinase C/blood , Carbazoles/pharmacology , Enzyme Activation , Enzyme Inhibitors/pharmacology , Humans , Indoles/pharmacology , Maleimides/pharmacology , Neutrophils/drug effects , Neutrophils/enzymology , Neutrophils/microbiology , Phagocytosis/drug effects , Protein Kinase C/antagonists & inhibitors , Saccharomyces cerevisiae
4.
Am J Physiol Cell Physiol ; 282(6): C1199-204, 2002 Jun.
Article in English | MEDLINE | ID: mdl-11997233

ABSTRACT

The length of the silent lag time before elevation of the cytosolic free Ca2+ concentration ([Ca2+]i) differs between individual pancreatic beta-cells. One important question is whether these differences reflect a random phenomenon or whether the length of lag time is inherent in the individual beta-cell. We compared the lag times, initial dips, and initial peak heights for [Ca2+]i from two consecutive glucose stimulations (with either 10 or 20 mM glucose) in individual ob/ob mouse beta-cells with the fura 2 technique in a microfluorimetric system. There was a strong correlation between the lengths of the lag times in each beta-cell (10 mM glucose: r = 0.94, P < 0.001; 20 mM glucose: r = 0.96, P < 0.001) as well as between the initial dips in [Ca2+]i (10 mM glucose: r = 0.93, P < 0.001; 20 mM glucose: r = 0.79, P < 0.001) and between the initial peak heights (10 mM glucose: r = 0.51, P < 0.01; 20 mM glucose: r = 0.77, P < 0.001). These data provide evidence that the response pattern, including both the length of the lag time and the dynamics of the subsequent [Ca2+]i, is specific for the individual beta-cell.


Subject(s)
Calcium/metabolism , Islets of Langerhans/metabolism , Animals , Cell Separation , Cells, Cultured , Cytosol/metabolism , Fluorescent Dyes , Fura-2 , Glucose/pharmacology , Intracellular Fluid/metabolism , Islets of Langerhans/cytology , Islets of Langerhans/drug effects , Mice , Mice, Obese , Reaction Time/physiology , Stimulation, Chemical
5.
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