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I Dransfield

Publications and source records attributed to I Dransfield.

At least 37 records · Page 2Linked to original sources
PubMed1998

Differential effects of bacterial lipopolysaccharides upon neutrophil function.

Lipopolysaccharide (LPS) is a potent inflammatory agent which augments neutrophil sensitivity to subsequent inflammatory stimuli. In this study, the effects of structurally different LPS types upon neutrophil effector functions were examined. Rough LPS types, which have lost the O-polysaccharide moiety, were found to act more rapidly than smooth LPS types in stimulating neutrophil beta2 integrin activity and fMLP-induced respiratory burst. These findings suggest an involvement of the O-polysaccharide region of LPS in regulating neutrophil responsiveness to different LPS chemotypes with important implications for the mechanisms underlying regulation of the inflammatory response in conditions associated with elevation of LPS in plasma, e.g. septic shock or acute respiratory distress syndrome.

CD18 Antigens↗
PubMed1998

Requirement for in vivo production of IL-4, but not IL-10, in the induction of proliferative suppression by filarial parasites.

Loss of T lymphocyte proliferation and the emergence of a host response that is dominated by a Th2-type profile are well-established features of human filariasis. We have previously reported that adherent peritoneal exudate cells (PEC) from mice transplanted with adult Brugia malayi parasites suppress the proliferation of lymphocytes without blocking Ag-cytokine production in vitro. We now show that infection of mice with the infective larval (L3) stage of B. malayi generates a similar population of PEC. Suppressive cells are generated within 7 days of infection and mediate their effects through a nitric oxide-independent pathway. Both L3 and adult infection elicit high levels of host IL-4 whereas the microfilarial stage of the parasite induces IFN-gamma production and does not generate a similar form of suppression. Production of host IL-4 was necessary to allow the generation of suppressive PEC, given that IL-4-deficient mice implanted with adult parasites failed to induce proliferative block. However, IL-10-deficient mice implanted with adult parasites resulted in T cell suppression, indicating that IL-10 is not essential for the induction of hyporesponsiveness. Neither IL-4 nor IL-10 were directly responsible for ablating cellular proliferation in vitro, as the addition of neutralizing Ab to either cytokine did not reverse the proliferative block. Thus, IL-4 produced in vivo in response to filarial L3 and adult parasites is essential for the induction of proliferative suppression but is not itself the suppressive factor.

Animals↗
PubMed1998

Regulation of macrophage phagocytosis of apoptotic cells by cAMP.

Regulation of macrophage capacity to remove apoptotic cells may control the balance of apoptotic and necrotic leukocytes at inflamed foci and the extent of leukocyte-mediated tissue damage. Although the molecules involved in the phagocytic process are beginning to be defined, little is known about the underlying regulatory and signaling mechanisms controlling this process. In this paper, we have investigated the effects of treatment of human monocyte-derived macrophages with PGs and other agents that elevate intracellular cAMP on phagocytosis. PGE2 and PGD2 specifically reduced the proportion of macrophages that phagocytosed apoptotic cells. Similar results were obtained with the membrane-permeable cAMP analogues dibutyryl-cAMP and 8-bromo-cAMP but not with the cGMP analogue dibutyryl-GMP. Consistent with the observation that phagocytosis was inhibited by cAMP elevation, treatment of monocyte-derived macrophages with PGE2 resulted in rapid, transient increase in levels of intracellular cAMP. These effects were not due to nonspecific inhibition of monocyte-derived macrophage phagocytosis given that ingestion of Ig-opsonized erythrocytes was unaffected. Elevation of cAMP induced morphologic alterations indicative of changes in the adhesive status of the macrophage, including cell rounding and disassembly of structures that represent points of contact with substrate containing actin and talin. These results strongly suggest that rapid activation of cAMP signaling pathways by inflammatory mediators regulates processes that limit tissue injury and that modulation of cAMP levels represents an additional therapeutic target in the control of resolution of inflammation.

Apoptosis↗
PubMed1998

Requirement for in vivo production of IL-4, but not IL-10, in the induction of proliferative suppression by filarial parasites.

Loss of T lymphocyte proliferation and the emergence of a host response that is dominated by a Th2-type profile are well-established features of human filariasis. We have previously reported that adherent peritoneal exudate cells (PEC) from mice transplanted with adult Brugia malayi parasites suppress the proliferation of lymphocytes without blocking Ag-cytokine production in vitro. We now show that infection of mice with the infective larval (L3) stage of B. malayi generates a similar population of PEC. Suppressive cells are generated within 7 days of infection and mediate their effects through a nitric oxide-independent pathway. Both L3 and adult infection elicit high levels of host IL-4 whereas the microfilarial stage of the parasite induces IFN-gamma production and does not generate a similar form of suppression. Production of host IL-4 was necessary to allow the generation of suppressive PEC, given that IL-4-deficient mice implanted with adult parasites failed to induce proliferative block. However, IL-10-deficient mice implanted with adult parasites resulted in T cell suppression, indicating that IL-10 is not essential for the induction of hyporesponsiveness. Neither IL-4 nor IL-10 were directly responsible for ablating cellular proliferation in vitro, as the addition of neutralizing Ab to either cytokine did not reverse the proliferative block. Thus, IL-4 produced in vivo in response to filarial L3 and adult parasites is essential for the induction of proliferative suppression but is not itself the suppressive factor.

Animals↗
PubMed1998

Constitutive neutrophil apoptosis in culture is modulated by cell density independently of beta2 integrin-mediated adhesion.

Although inflammatory mediators modulate the rate of constitutive neutrophil apoptosis in vitro the effects of micro-environmental conditions have not been fully investigated. In this study, we demonstrate that the rate of constitutive neutrophil apoptosis is affected by the number of cells per unit surface area, with enhanced survival at high cell density. Furthermore, the presence of protein or serum in the culture medium also enhances neutrophil survival. These effects were independent of beta2 integrin-mediated adhesion and were not influenced by specific adhesion to extracellular matrix components. Thus, the rate of neutrophil apoptosis is fundamentally influenced by microenvironmental conditions and indicates that factors such as cell density and extracellular protein concentration must be considered when investigating mechanisms regulating inflammatory cell apoptosis in vitro.

Animals↗
PubMed1998

Potential pro-inflammatory effects of soluble E-selectin upon neutrophil function.

Appropriate recruitment of neutrophils to sites of infection or tissue injury is a key event in the inflammatory response. A number of studies have shown the critical role of selectins in tethering and rolling of neutrophils on vascular endothelium, as well as a more complex regulatory role, since they have the potential to alter leukocyte recruitment by triggering beta2 integrin-mediated adhesion. In this study, we report that in contrast to patients "at risk" of developing acute respiratory disease syndrome (ARDS), elevated plasma levels of soluble E-selectin are found in patients with established disease. Since neutrophil granulocytes are implicated in ARDS pathogenesis, we have investigated the possibility of a link between elevated soluble plasma E-selectin levels and disease progression by examining the effects of soluble recombinant E-selectin (E-zz) upon neutrophil function. In this paper, we describe the novel finding that exposure of neutrophils to E-zz potentiates a number of neutrophil functions which may act to drive inflammatory processes. Although neutrophil deformability, an important parameter determining retention within the lung microvasculature, was not affected by E-zz, neutrophil polarization was observed. In addition, neutrophil beta2 integrin-mediated adhesion was found to be augmented by E-zz without alteration in levels of surface expression of alphaMbeta2 or the "activation" reporter epitope defined by monoclonal antibody 24. Concomitantly with increased beta2 integrin-mediated adhesion, we observed an inhibition of formyl-Met-Leu-Phe-directed chemotaxis. Together with an augmentation of neutrophil reactive oxidant species production and release of superoxide anions, these data raise the possibility that soluble E-selectin exerts pro-inflammatory effects upon neutrophil function at sites of inflammation, thereby exacerbating disease processes.

CD18 Antigens↗
PubMed1998

Regulation of macrophage phagocytosis of apoptotic neutrophils by adhesion to fibronectin.

The potential for leukocyte-mediated host tissue damage during resolution of inflammatory responses is influenced by the rate at which extravasated apoptotic leukocytes are cleared from inflammatory sites. Regulation of macrophage capacity for clearance of apoptotic granulocytes is likely to be an important factor determining whether inflammation ultimately resolves or progresses to a chronic state. In this study we have investigated the molecular basis for rapid augmentation of macrophage phagocytosis of apoptotic neutrophils, which was observed following macrophage adhesion to fibronectin. We used a combination of monoclonal antibodies, blocking peptides, and recombinant fibronectin fragments to investigate the role of beta1 integrins in mediating the fibronectin effects. Blockade of alpha5beta1 or alpha4beta1 alone did not attenuate fibronectin-augmentation of phagocytosis. In addition, adhesion of macrophages to recombinant fibronectins lacking alpha4beta1 recognition motifs failed to promote phagocytosis of apoptotic neutrophils. Our results would be consistent with a model in which multiple fibronectin receptors, including beta1 integrins, act co-operatively to augment macrophage phagocytic responses. Together, these data suggest that the extracellular matrix environment of macrophages may provide regulatory signals that act indirectly to rapidly alter the potential for removal of apoptotic cells and influence the process of resolution of inflammation.

Antibodies, Blocking↗
PubMed1997

Regulation of neutrophil apoptosis by tumor necrosis factor-alpha: requirement for TNFR55 and TNFR75 for induction of apoptosis in vitro.

Granulocyte apoptosis is an important mechanism underlying the removal of redundant neutrophils from an inflammatory focus. The ability of many proinflammatory agents to impede this event suggests that such agents act not only in a priming or secretagogue capacity but also increase neutrophil longevity by delaying apoptosis. We have examined whether this hypothesis holds true for all neutrophil priming agents, in particular tumor necrosis factor-alpha (TNF-alpha), which has been variably reported to either induce, delay, or have no effect on neutrophil apoptosis. After 20 hours coincubation TNF-alpha inhibited neutrophil apoptosis; however, more detailed analysis demonstrated its ability to promote apoptosis in a subpopulation of cells at earlier (2 to 8 hours) times. Formyl-Met-Leu-Phe, platelet-activating factor, inositol hexakisphosphate, lipopolysaccharide, leukotriene B4, and granulocyte-macrophage colony-stimulating factor all inhibited apoptosis at 6 and 20 hours. The early proapoptotic effect of TNF-alpha was concentration-dependent (EC50 2.8 ng/mL), abolished by TNF-alpha neutralizing antibody, and was not associated with any change in cell viability or recovery. Of relevance to the inflamed site, the ability of TNF-alpha to accelerate apoptosis was lost if neutrophils were primed with 1 micromol/L PAF or aged for 6 hours before TNF-alpha addition. The TNFR55-selective TNF-alpha mutants (E146K, R32W-S86T) induced neutrophil apoptosis but with a potency 14-fold lower than wild-type TNF-alpha. Although the TNFR75-selective mutant (D143F) did not induce apoptosis, blocking antibodies to both receptor subtypes abolished TNF-alpha-stimulated apoptosis. Hence, TNF-alpha has the unique ability to induce apoptosis in human neutrophils via a mechanism where TNFR75 facilitates the dominant TNFR55 death effect. This may be an important mechanism controlling neutrophil longevity and clearance in vivo.

Antibodies, Monoclonal↗
PubMed1997

CD44 regulates phagocytosis of apoptotic neutrophil granulocytes, but not apoptotic lymphocytes, by human macrophages.

Phagocytosis of apoptotic neutrophil granulocytes by macrophages at inflammatory sites is an important determinant of the process by which inflammation resolves. We demonstrate that phagocytosis of apoptotic neutrophils, but not apoptotic lymphocytes, by human monocyte-derived macrophages is augmented rapidly following ligation of CD44 by bivalent Abs in vitro. Previously defined inhibitors of apoptotic cell recognition did not affect CD44-augmented phagocytosis of apoptotic neutrophils, suggesting that unique molecular recognition pathways are involved. These observations, together with the lack of effect of CD44 Abs upon macrophage phagocytosis of zymosan or Ig-opsonized erythrocytes, imply that CD44 may regulate the differential clearance of apoptotic leukocytes during evolution of inflammatory responses. This represents a novel role for CD44 in inflammation and tissue repair.

Apoptosis↗
PubMed1997

Activation of neutrophil function via CD66: differential effects upon beta 2 integrin mediated adhesion.

To further define the role of CD66 glycoproteins in the regulation of neutrophil function, we analysed the effects of a CD66 monoclonal antibody, Kat4c, which recognizes an epitope present on AB domains of CD66a, CD66b and CD66c. Intact Kat4c and F(ab')2 fragments were found to augment fMLP-induced oxidation of 1,2,3-dihydrorhodamine (oxidant species production) and beta 2 integrin-mediated adhesion to fibrinogen but did not promote beta 2 integrin-mediated binding of albumin coated latex beads. Since the latter assay is a sensitive indicator of neutrophil CD11b/CD18 functional activation, these results imply CD66 may exert differential effects upon beta 2 integrin activity. Neutrophil oxidant species production and spreading on fibrinogen substrates were further potentiated by cross-linking of Kat4c F(ab')2, in keeping with the suggestion that ligation of CD66 regulates neutrophil function. However, although intact Kat4c promoted beta 2 integrin-dependent homotypic neutrophil adhesion, F(ab')2 fragments were without effect, implying a role for Fc receptors in this effect which has previously been attributed to CD66. Together these data define more clearly the role of CD66 in regulation of neutrophil function and further suggest that augmented beta 2 integrin-mediated adhesion following CD66 ligation occurs independently of affinity regulation.

Antibodies, Monoclonal↗
PubMed1996

Recognition of apoptotic cells by phagocytes.

Effective removal of dying cells is crucial to a variety of processes in health and disease. Cells undergoing apoptosis are recognized and ingested intact by phagocytes, which are not stimulated to release inflammatory mediators. The alternative uncontrolled form of cell death, necrosis, is associated with release of cell contents with the potential to cause tissue damage and inflammation. Four distinct molecular mechanisms have been identified to date which mediate recognition by phagocytes of mammalian cells undergoing apoptosis, but further mechanisms remain to be discovered. The capacity for phagocyte removal of cells undergoing apoptosis may be closely regulated, for example by local cytokines.

Animals↗
PubMed1996

Inhibition of neuropeptide-stimulated tyrosine phosphorylation and tyrosine kinase activity stimulates apoptosis in small cell lung cancer cells.

Small cell lung cancer (SCLC) cell growth is sustained by multiple autocrine and paracrine growth loops involving neuropeptides. The bombesin family of peptides are autocrine growth factors in H345 SCLC cells and provide a paradigm for the study of growth factors and mitogenic signaling in SCLC cells. We show that bombesin (and other neuropeptides) stimulates protein tyrosine phosphorylation (particularly focal adhesion kinase) and protein tyrosine kinase (PTK) activity in intact SCLC cells. Furthermore, the broad spectrum neuropeptide receptor antagonist [D-Arg, D = Phe, D-Trp, Leu11]substance P inhibits all neuropeptide-mediated signals (including PTK activation), SCLC cell growth in vivo and in vitro, and also increases the natural rate of apoptosis seen in growing SCLC cell lines. Hence the effect of selective PTK inhibition on SCLC cell growth and apoptosis was examined. We show that selective inhibition of PTK activity, with genistein and (3,4,5-tri-hydroxyphenyl)-methylene(-propanedinitrile) tyrphostin-25 inhibits basal and neuropeptide-stimulated SCLC cell growth. Genistein and tyrphostin-25 also stimulate apoptosis in SCLC cells. Inhibition of proliferation in these cells is intimately linke to apoptosis, because these changes occurred without any effect on SCLC cell cycle kinetics, suggesting that apoptosis occurs independently of the cell cycle and that failure to progress through the cell cycle results in apoptosis. Because tyrphostin-25 fails to influence p53 or Bcl-2 expression in these cells, this mode of programmed cell death appears to be via a p53- and Bcl-2-independent mechanism. These results provide evidence that tyrosine phosphorylation is a mitogenic signal in SCLC cells and suggest that regulation of the level of protein tyrosine phosphorylation represents a critical determinant of whether SCLC cells survive and proliferate or die by apoptosis. Thus PTK inhibition may provide a novel therapeutic option in SCLC that has become resistant to conventional chemotherapeutic agents.

Apoptosis↗
PubMed1996

In vivo fate of the inflammatory macrophage during the resolution of inflammation: inflammatory macrophages do not die locally, but emigrate to the draining lymph nodes.

The resolution of acute inflammation requires bulk clearance of extravasated inflammatory cells in an ordered manner. Neutrophils undergo apoptosis and are ingested by macrophages (M psi) via a novel recognition mechanism that fails to provoke proinflammatory responses. Thereafter, the fate of inflammatory M psi themselves remains unclear. We investigated this in vivo, developing a semiallogeneic adoptive transfer system to track the fate of inflammatory M psi in a murine model of resolving peritonitis. Fluorescently labeled M psi from H-2k/d mice were transferred into the peritoneal cavity of H-2k mice at the same stage of resolving inflammation as the donor mice. Dual color flow cytometry permitted discrimination among donor cells, recipient cells, and donor cells that had been phagocytosed by recipient M psi. Despite the absence of significant local phagocytosis, the number of transferred M psi free in the peritoneum of recipient mice declined rapidly, being undetectable by 96 h. These data suggest that inflammatory M psi normally emigrate rapidly from the peritoneal cavity during the resolution of inflammation, contrasting with resident M psi, which persist in the noninflamed peritoneum for weeks. Accordingly, labeled nonphagocytosed cells were detected in the draining lymph nodes, but not in a variety of other tissues. Thus, unlike the polymorphonuclear leukocyte, which dies by apoptosis and is ingested by M psi, the inflammatory M psi itself does not die locally. Having performed its acute inflammatory and scavenging roles, it emigrates in a nonrandom fashion to the draining lymph node, where it may play an important part in the presentation of Ags from the inflamed site.

Adoptive Transfer↗
PubMed1996

CD66: role in the regulation of neutrophil effector function.

Neutrophils express several heavily glycosylated carcinoembryonic antigen (CEA)-related glycoproteins (CD66 antigens) which have been implicated in adhesion to E-selectin and as receptors for the lectins galectin 3 and bacterial type-1 fimbriae. The role of the CD66 antigens in neutrophil effector function was examined using non-cross-reacting and cross-reacting domain-mapped CD66 monoclonal antibody (mAb), which recognize epitopes on biliary glycoprotein (BGP; CD66a), CEA gene family member 6 (CGM6; CD66b), nonspecific cross-reacting antigen 90 (NCA90; CD66c) or CGM1 (CD66d). We show that BGP-specific mAb which recognize an AB-domain epitope strongly augment adhesion to fibrinogen by an Fc receptor- and beta2 integrin-dependent mechanism. Co-ligation of BGP with the glycophosphatidylinositol (GPI)-anchored CGM6 and NCA90 also caused increased beta2 integrin-mediated adhesion, receptor clustering and priming of formyl-Met-Leu-Phe (fMLP)-induced oxidant production by neutrophils, but only a small change in expression of L-selectin and CR3 compared to the chemotactic peptide fMLP. Ligation of CGM6 or NCA90 alone did not cause activation of the neutrophil in any of the assays used and did not cause priming of fMLP-induced oxidant production even when a secondary cross-linking reagent was used. We propose that specific cross-linking of neutrophil BGP with CGM6 and NCA90 contributes significantly to the regulation of neutrophil function during neutrophil recruitment.

Antibodies, Monoclonal↗
PubMed1996

Priming differentially regulates neutrophil adhesion molecule expression/function.

Lung injury in a variety of disease states is critically dependent on neutrophil-mediated inflammatory responses. Neutrophil recruitment to sites of infection or tissue damage requires co-ordinated regulation of neutrophil adhesion and activation status. We have examined the effects of treatment of human peripheral blood neutrophils with priming agents [lipopolysaccharide (LPS). tumor necrosis factor-alpha (TNF-alpha) and platelet-activating factor (PAF)] upon expression of CD11a. CD11b. CD11c. CD35 and CD62-1 and CD11b function to assess whether subtle regulation of neutrophil adhesion potential accompanies augmented formyl-methionyl-leucyl-phenylalanine-stimulated superoxide production. We have found that there are differential effects of priming concentrations of these agents. For LPS. CD62L loss occurs in the absence of changes in CD11b, whereas for PAF. CD11b up-regulation occurs in the absence of detectable loss of CD62-L. However, for TNF-2, decreased expression of CD62-L occurs concomitantly with increased expression of CD11b. In addition, we have shown that priming agents augment CD11b functional activity in a manner that parallels the priming of the respiratory burst. Thus, priming agents may differentially regulate neutrophil adhesive capacity and data presented in this manuscript suggest that the increased effector cell function observed in primed cells may be associated with a distinct repertoire of potential adhesive interactions.

Antigens, CD↗
PubMed1995

Agents that elevate cAMP inhibit human neutrophil apoptosis.

Neutrophil apoptosis, determined after 20 h in culture using standard criteria and shedding of cell surface CD16 (Fc gamma RIII), is dramatically inhibited, in a concentration-dependent manner, by the cAMP analogs, dibutyryl-cAMP and 8-Br-cAMP, and the adenylyl cyclase activator, forskolin. Furthermore, the stable receptor-directed PGD2 mimetic, ZK 118.182, and the PGE2 mimetic, 11-deoxy PGE1, similarly inhibited apoptosis. The DP-receptor antagonist BW A868C blocked the effect of ZK 118.182 and the protein kinase A inhibitor H-89 reversed the inhibition of apoptosis induced by dibutyryl-cAMP. These results clearly show that neutrophil apoptosis is markedly attenuated by cAMP elevating agents. This nucleotide second messenger may play a fundamental role in controlling neutrophil longevity and pharmacological regulation of cAMP levels or actions may influence neutrophil apoptosis in vivo.

Alprostadil↗
PubMed1995

Regulation of cell adhesion molecule expression and function associated with neutrophil apoptosis.

We have investigated the adhesive capacity of neutrophils after spontaneous apoptosis, which occurs during in vitro culture. Apoptotic neutrophils show reduced adhesion to E selectin and the CD18 integrin ligand fibrinogen. Neutrophil apoptosis is associated with changes in the levels of surface expression of key receptors that mediate neutrophil adhesion events. Notably, apoptotic neutrophils show reduced expression of L-selectin/selectin ligand. In contrast, CD11b/CD18 and CD11c/CD18 integrins are expressed at increased levels. The reduced capacity for adhesion of apoptotic neutrophils may be achieved by very different mechanisms. Regulation of the levels of surface expression of receptors/ligand may control selectin-mediated adhesion, possibly as a result of protease/sialidase activity. In contrast, modulation of integrin-mediated adhesion may involve functional uncoupling of receptors present on the surface of the apoptotic cell without alteration in levels of surface expression. The altered adhesive potential of the apoptotic neutrophil may serve to limit release of its histotoxic contents and reduce inappropriate tissue injury.

Antigens, CD↗