Neutrophil Mac-1 Expression Research Articles

DioxolaneA3-phosphatidylethanolamines are generated by human platelets and stimulate neutrophil integrin expression

Activated platelets generate an eicosanoid proposed to be 8-hydroxy-9,10-dioxolane A3 (DXA3). Herein, we demonstrate that significant amounts of DXA3 are rapidly attached to phosphatidylethanolamine (PE) forming four esterified eicosanoids, 16:0p, 18:0p, 18:1p and 18:0a/DXA3-PEs that can activate neutrophil integrin expression. These lipids comprise the majority of DXA3 generated by platelets, are formed in ng amounts (24.3±6.1ng/2×108) and remain membrane bound. Pharmacological studies revealed DXA3-PE formation involves cyclooxygenase-1 (COX), protease-activated receptors (PAR) 1 and 4, cytosolic phospholipase A2 (cPLA2), phospholipase C and intracellular calcium. They are generated primarily via esterification of newly formed DXA3, but can also be formed in vitro via co-oxidation of PE during COX-1 co-oxidation of arachidonate. All four DXA3-PEs were detected in human clots. Purified platelet DXA3-PE activated neutrophil Mac-1 expression, independently of its hydrolysis to the free eicosanoid. This study demonstrates the structures and cellular synthetic pathway for a family of leukocyte-activating platelet phospholipids generated on acute activation, adding to the growing evidence that enzymatic PE oxidation is a physiological event in innate immune cells.

Staphylococcal enterotoxin A regulates bone marrow granulocyte trafficking during pulmonary inflammatory disease in mice

Pulmonary neutrophil infiltration produced by Staphylococcal enterotoxin A (SEA) airway exposure is accompanied by marked granulocyte accumulation in bone marrow (BM). Therefore, the aim of this study was to investigate the mechanisms of BM cell accumulation, and trafficking to circulating blood and lung tissue after SEA airway exposure. Male BALB/C mice were intranasally exposed to SEA (1μg), and at 4, 12 and 24h thereafter, BM, circulating blood, bronchoalveolar lavage (BAL) fluid and lung tissue were collected. Adhesion of BM granulocytes and flow cytometry for MAC-1, LFA1-α and VLA-4 and cytokine and/or chemokine levels were assayed after SEA-airway exposure. Prior exposure to SEA promoted a marked PMN influx to BAL and lung tissue, which was accompanied by increased counts of immature and/or mature neutrophils and eosinophils in BM, along with blood neutrophilia. Airway exposure to SEA enhanced BM neutrophil MAC-1 expression, and adhesion to VCAM-1 and/or ICAM-1-coated plates. Elevated levels of GM-CSF, G-CSF, INF-γ, TNF-α, KC/CXCL-1 and SDF-1α were detected in BM after SEA exposure. SEA exposure increased production of eosinopoietic cytokines (eotaxin and IL-5) and BM eosinophil VLA-4 expression, but it failed to affect eosinophil adhesion to VCAM-1 and ICAM-1. In conclusion, BM neutrophil accumulation after SEA exposure takes place by integrated action of cytokines and/or chemokines, enhancing the adhesive responses of BM neutrophils and its trafficking to lung tissues, leading to acute lung injury. BM eosinophil accumulation in SEA-induced acute lung injury may occur via increased eosinopoietic cytokines and VLA-4 expression.

Pharmacological inhibition of p38 mitogen‐activated protein kinases affects KC/CXCL1‐induced intraluminal crawling, transendothelial migration, and chemotaxis of neutrophils in vivo

Leukocyte recruitment to the inflammation site is a multi‐step process governed by specific signalling cascades. After adhesion in the lumen, leukocytes crawl to optimal sites at endothelial junctions and transmigrate to extravascular tissue in a Mac‐1‐dependent manner. The signalling mechanisms that regulate post‐adhesion steps of intraluminal crawling, transmigration and chemotaxis in tissue remain incompletely understood. The present study explored the effect of p38 MAPK inhibitor SB203580 on various steps of neutrophil recruitment triggered by chemokine KC (CXCL1) gradient in microvasculature of murine cremaster muscle using intravital microscopy and time‐lapsed video analysis. SB203580 (100 nM) did not change leukocyte rolling but significantly attenuated neutrophil adhesion, emigration, transmigration time and detachment time, and impaired the initiation of crawling and transmigration. In response to KC chemotactic gradient, SB203580 significantly reduced the velocity of migration and chemotaxis index of neutrophils in tissue. The upregulation of Mac‐1 expression in neutrophils stimulated by KC was significantly blunted by SB203580 in vitro. Collectively, our findings demonstrate that pharmacological suppression of p38 MAPK significantly impairs multiple steps of neutrophil recruitment in vivo.

Pharmacological Inhibition of p38 Mitogen-Activated Protein Kinases Affects KC/CXCL1-Induced Intraluminal Crawling, Transendothelial Migration, and Chemotaxis of NeutrophilsIn Vivo

p38 mitogen-activated protein kinase (MAPK) signalling is critical in the pathophysiology of a variety of inflammatory processes. Leukocyte recruitment to the site of inflammation is a multistep process governed by specific signalling cascades. After adhesion in the lumen, many leukocytes crawl to optimal sites at endothelial junctions and transmigrate to extravascular tissue in a Mac-1-dependent manner. The signalling mechanisms that regulate postadhesion steps of intraluminal crawling, transmigration, and chemotaxis in tissue remain incompletely understood. The present study explored the effect of p38 MAPK inhibitor SB203580 on various parameters of neutrophil recruitment triggered by chemokine KC (CXCL1) gradient. Neutrophil-endothelial interactions in microvasculature of murine cremaster muscle were determined using intravital microscopy and time-lapsed video analysis. SB203580 (100 nM) did not change leukocyte rolling but significantly attenuated neutrophil adhesion, emigration, and transmigration and impaired the initiation of neutrophil crawling and transmigration. In response to KC chemotactic gradient, SB203580 significantly reduced the velocity of migration and chemotaxis index of neutrophils in tissue. The upregulation of Mac-1 expression in neutrophils stimulated by KC was significantly blunted by SB203580 in vitro. Collectively, our findings demonstrate that pharmacological suppression of p38 MAPK significantly impairs multiple steps of neutrophil recruitment in vivo.

Abacavir and didanosine induce the interaction between human leukocytes and endothelial cells through Mac-1 upregulation

Abacavir and didanosine are nucleoside reverse transcriptase inhibitors (NRTI) widely used in therapy for HIV-infection but which have been linked to cardiovascular complications. The objective of this study was to analyze the effects of clinically relevant doses of abacavir and didanosine on human leukocyte-endothelium interactions and to compare them with those of other NRTIs. The interactions between human leukocytes - specifically peripheral blood polymorphonuclear (PMN) or mononuclear (PBMC) cells - and human umbilical vein endothelial cells were evaluated in a flow chamber system that reproduces conditions in vivo. The expression of adhesion molecules was analyzed by flow cytometry. Abacavir induced a dose-dependent increase in PMN and PBMC rolling and adhesion. This was reproduced by didanosine but not by lamivudine or zidovudine. Both abacavir and didanosine increased Mac-1 expression in neutrophils and monocytes, but produced no effects on either lymphocytes or the expression of endothelial adhesion molecules. The PMN/PBMC rolling and adhesion induced by abacavir or didanosine did not occur when antibodies against Mac-1 or its ligand ICAM-1 were blocked. Abacavir induces significant human leukocyte accumulation through the activation of Mac-1, which in turn interacts with its endothelial ligand ICAM-1. The fact that didanosine exhibits similar effects and that lamivudine and zidovudine do not points to a relationship between the chemical structure of NRTIs and the induction of leukocyte/endothelial cell interactions. This mechanism may be especially relevant to the progression of the vascular damage associated with atherosclerosis and myocardial infarction in abacavir and didanosine-treated patients.

Sulfatides are associated with neointimal thickening after vascular injury

BackgroundSulfatides are known to be a native ligand of P-selectin. Platelet-leukocyte interaction via the cross-talk between P-selectin and Mac-1 (CD11b/CD18) plays an important role in the mechanism of neointimal thickening after vascular injury such as that seen in post-stent restenosis. However, the roles of sulfatides on restenosis have not been elucidated. MethodsSerum sulfatide levels, P-selectin expression on the surface of platelets, and activated Mac-1 on the surface of neutrophils were serially measured using both coronary sinus and peripheral blood samples in 21 patients who underwent coronary stent implantation. ResultsThe trans-cardiac gradient (coronary sinus minus peripheral blood) of the sulfatide levels significantly increased at 15min (−1.47±2.87 to 0.59±1.44nmol/ml, p<0.001), compared to baseline levels. The maximum response of the trans-cardiac gradient of P-selectin expression on the surface of platelets at 15min after stent implantation (R=0.55, p<0.01), and that of activated Mac-1 on the surface of neutrophils at 48h (R=0.59, p<0.01), were both positively correlated with that of serum sulfatide levels at 15min. The angiographic late lumen loss was correlated with the trans-cardiac gradient of sulfatide levels at 15min (R=0.48, p<0.05), platelet P-selectin expression at 15min (R=0.42, p<0.05) and activated neutrophil Mac-1 expression at 48h (R=0.46, p<0.05), but not with values at other sampling points. ConclusionsSulfatides may play a physiological role on inflammation in vascular injury and the development of neointimal thickening.

CD40 Ligand Promotes Mac-1 Expression, Leukocyte Recruitment, and Neointima Formation after Vascular Injury

High levels of circulating soluble CD40 ligand (sCD40L) are frequently found in patients with hypercholesterolemia, diabetes, ischemic stroke, or acute coronary syndromes, predicting an increased rate of atherosclerotic plaque rupture and restenosis after coronary/carotid interventions. Clinical restenosis is characterized in part by exaggerated neointima formation, but the underlying mechanism remains incompletely understood. This study investigated the role of elevated sCD40L in neointima formation in response to vascular injury in an atherogenic animal model and explored the molecular mechanisms involved. apoE(-/-) mice fed a Western diet developed severe hypercholesterolemia, significant hyperglycemia, and high levels of plasma sCD40L. Neointima formation after carotid denudation injury was exaggerated in the apoE(-/-) mice. In vivo, blocking CD40L with anti-CD40L monoclonal antibody attenuated the early accumulation of Ly-6G(+) neutrophils and Gr-1(+) monocytes (at 3 days) and the late accumulation of Mac-2(+) macrophages (at 28 days) in the denudated arteries; it also reduced the exaggerated neointima formation at 28 days. In vitro, recombinant CD40L stimulated platelet P-selectin and neutrophil Mac-1 expression and platelet-neutrophil co-aggregation and adhesive interaction. These effects were abrogated by anti-CD40L or anti-Mac-1 monoclonal antibody. Moreover, recombinant CD40L stimulated neutrophil oxidative burst and release of matrix metalloproteinase-9 in vitro. We conclude that elevated sCD40L promotes platelet-leukocyte activation and recruitment and neointima formation after arterial injury, potentially through enhancement of platelet P-selectin and leukocyte Mac-1 expression and oxidative activity.

Systemic neutrophil activation in acute preschool viral wheeze

Background: In preschool children, attacks of wheeze are usually triggered by viral colds. The inflammatory substrate in preschool viral wheeze (PVW) is unclear, but epidemiological data suggest that most PVW...

Selective Regulation of Expression of Surface Adhesion Molecules Mac-1, L-selectin, and VLA-4 on Human Eosinophils and Neutrophils

We studied the differential expression of cellular adhesion molecules on the surface of purified human eosinophils and neutrophils caused by ex vivo activation with platelet-activating factor (PAF), formylmethionylleucylphenylalanine (FMLP), or recombinant human interleukin-5 (IL-5). PAF (10(-7) M) caused a 42.8 +/- 5.7% (mean +/- SEM) increase in Mac-1 expression in eosinophils (P < 0.01) and a 34.6 +/- 9.2% increase in Mac-1 expression in neutrophils (P < 0.05). PAF also caused a decrease in L-selectin expression in eosinophils (-37.0 +/- 8.1%, P < 0.001) and neutrophils (-14.1 +/- 3.2%, P < 0.05). FMLP (10(-6) M) caused a similar increase in Mac-1 expression in both eosinophils (P < 0.001 versus controls) and neutrophils (P < 0.01) and a comparable decrease in L-selectin expression in both eosinophils and neutrophils (P < 0.01). In contrast to the effects of PAF and FMLP, IL-5 affected selectively the surface expression of adhesion molecules in eosinophils but not neutrophils. Expression of Mac-1 increased by 44.3 +/- 7.5% in eosinophils (P < 0.001 versus controls) and by 0.7 +/- 1.2% in neutrophils (P = NS versus controls) after exposure to 10(-9) M IL-5. IL-5 also caused a 49.5 +/- 4.2% decrease in eosinophil L-selectin expression (P < 0.001) but had no effect on L-selectin expression in neutrophils. Eosinophil VLA-4 expression was not altered by any stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

The anti mac-1 monoclonal antibody inhibits neutrophil sequestration in lung and liver in a septic murine model

We investigated the mechanism by which leukocytes adhere to the pulmonary and liver microvascular endothelium in a septic murine model. After C57BL/6 mice were intraperitoneally (ip) injected with lipopolysaccharide (LPS), a striking peripheral leukocytopenia occurred as neutrophils accumulated rapidly in the lung and liver. When the anti-Mac-1 monoclonal antibody (mAb) was administered intravenously (iv) 2 hr before the ip administrated LPS, leukocytopenia and neutrophil accumulation in the lung and liver were inhibited significantly at 3 hr after the LPS injection. An immunofluorescence study revealed that Mac-1 expression on leukocytes from LPS-injected mice were greatly increased when compared to that of controls. Additionally, an in vitro assay demonstrated that LPS-activated serum increased neutrophil Mac-1 expression and neutrophil adhesion to the endothelial monolayer and that these phenomena are inhibited by pretreatment of neutrophils with anti-Mac-1 mAb. These results indicate that a marked increase in Mac-1 antigen expression by leukocytes plays a crucial role in striking neutrophil attachment to the vascular endothelium and is likely to be the cause of neutrophil accumulation in the lung and liver during endotoxemia.