Biomedical subjects

M Arock

Publications and source records attributed to M Arock.

At least 19 recordsLinked to original sources

PubMed2006

Dexamethasone and IL-10 stimulate glucocorticoid-induced leucine zipper synthesis by human mast cells.

BACKGROUND: Glucocorticoids (GCs) decrease tissue mast cell (MC) number and prevent their activation via their high-affinity IgE receptor. Glucocorticoid-induced leucine zipper (GILZ) is one of the GC-induced genes, which inhibits the functions of the transcriptional activators AP-1 and NF-kappaB. GILZ appears to be a critical actor in the anti-inflammatory and immunosuppressive effects of GCs in human T lymphocytes, macrophages and dendritic cells. AIMS OF THE STUDY: We investigated whether GILZ was produced by human MCs and whether GILZ synthesis was stimulated by GCs. We also investigated whether GILZ production was modulated by (i) IL-10, because of its common immunosuppressive properties with GCs, (ii) histamine because of its pro-inflammatory properties and (iii) IL-4 and IL-5 because of their ability to favour MC survival and proliferation with SCF. METHODS: The human MC lines HMC-1 5C6 and LAD-2, and cord blood-derived MCs (CB-MCs) were cultured alone or in the presence of GCs, IL-10, histamine, IL-4 or IL-5. The expression of GILZ was evaluated by using RT-PCR, Western blotting or immunocytochemistry. RESULTS: We found that human MC lines and CB-MCs constitutively produce GILZ. We also show that GCs and IL-10 stimulate GILZ production by human MCs. Our present results indicate that histamine, IL-4 and IL-5 alone or in combination with SCF do not downregulate GILZ production by MCs. CONCLUSIONS: These results show that GCs and IL-10 stimulate GILZ production by human MCs. As GILZ mediates anti-inflammatory effects of GCs in immune cells, we speculate that GILZ could account for the deactivation of MCs by GCs and IL-10.

Cell Line↗

PubMed2004

[Mastocytosis: advances in molecular diagnosis and therapeutics].

Systemic mastocytosis is a rare myeloproliferative-like disease, characterized by an abnormal proliferation of mast cells in various organs. Two types of clinical manifestations can be distinguished: those related to release of mast cell mediators release and those related to tumor proliferation involving different organs, these later defining systemic mastocytosis. Until recently, treatment was mainly symptomatic, without anti tumor effect. These last years, advances have been made in the understanding of the disease with the discovery of the presence, in a number of patients, of mutations of the c-kit oncogene, coding for the receptor of the major growth factor for mast cells. These mutations induce autophosphorylation of the c-kit receptor in the absence of its ligand, the Stem Cell Factor. Based on experiences acquired in the treatment of myeloproliferative disorders, evaluation of new therapeutics, such as cladribine or interferon-alpha, is in progress. Finally, it would be possible to design, in the very next future, new tyrosine kinase inhibitors targeting specifically the mutant forms of c-Kit found in patients suffering from systemic mastocytosis.

Humans↗

PubMed2004

On the way to targeted therapy of mast cell neoplasms: identification of molecular targets in neoplastic mast cells and evaluation of arising treatment concepts.

Several emerging treatment concepts for myeloid neoplasms are based on novel drugs targeting cell surface antigens, signalling pathways, or critical effector molecules. Systemic mastocytosis is a haematopoietic neoplasm that behaves as an indolent myeloproliferative disease in most patients, but can also present as aggressive disease or even as an acute leukaemia. In patients with aggressive disease or mast cell leukaemia, the response to conventional therapy is poor in most cases, and the prognosis is grave. Therefore, a number of attempts have been made to define novel treatment strategies for these patients. One promising approach may be to identify novel targets and to develop targeted drug therapies. In this article, we support the notion that neoplastic mast cells indeed express a number of potential molecular targets including immunoreactive CD antigens, the microphthalmia transcription factor (MITF), and members of the Bcl-2 family. In addition, the tyrosine kinase receptor KIT and downstream signalling pathways have been proposed as targets of a specific pharmacological intervention. A particular challenge is the disease-related D816V-mutated variant of KIT, which is resistant against diverse tyrosine kinase inhibitors including STI571, but may be sensitive to more recently developed targeted compounds. The therapeutic potential of target-specific approaches in malignant mast cell disorders should be evaluated in forthcoming clinical trials in the near future.

Antigens, CD↗

PubMed2003

Immunoglobulin D enhances interleukin-6 release from the KU812 human prebasophil cell line.

Despite the role of secreted immunoglobulin D (IgD) remains still largely unknown, previous studies have suggested that secreted IgD could induce basophils degranulation in some allergic asthma patients. In the present study we have searched direct evidence of the action of IgD on KU812 cells, generally classified as an immature basophilic cell line. We analyzed by flow cytometry the capacity of IgD, purified from IgD myeloma sera, to bind KU812 cells. Biotinylated monomeric IgD (mIgD) and biotinylated oligomeric IgD (oIgD) could bind KU812 cells. Blocking experiments with others immunoglobulin isotypes showed that KU812 cells expressed an unspecific receptor for IgD. However, oIgD but not mIgD enhances the release of interleukin-6 (IL-6) from KU812 cells. On the other hand, mIgD and oIgD failed to induce histamine release from KU812 cells or from cord blood derived basophils. Since IL-6 is known to induce basophil differentiation, we proposed that IgD could be implicated in allergic disorders by stimulating IL-6 release by prebasophil cells, then IL-6 could further induce an autocrine maturation of the cells.

Basophils↗

PubMed2002

Nitric oxide induces the apoptosis of human BCR-ABL-positive myeloid leukemia cells: evidence for the chelation of intracellular iron.

Anti-leukemia activity of human macrophages involves the generation of nitric oxide (NO) derivatives. However, leukemic transformation may involve mechanisms that rescue cells from NO-mediated apoptosis. In the present work, we analyzed the effects of exogenous NO on the proliferation of BCR-ABL(+) chronic myelogenous leukemia (CML) cells. As normal leukocytes, the proliferation of leukemia cells was inhibited by SNAP (S-nitroso-N-acetyl-penicillamine), GEA (Oxatriazolium amino-chloride), and SIN-1 (Morpholino-sydnonimine), whereas SNP (sodium nitroprusside) had no effect on leukemia cell growth. SIN-1 induced higher anti-proliferation activity in BCR-ABL(+) cells, compared to normal hemopoietic cells. Inhibition of leukemia cell proliferation correlated with increased apoptosis and DEVDase activity. The simultaneous addition of exogenous iron reversed NO-mediated inhibition of cell growth, caspase activation and apoptosis in all BCR-ABL(+) cells tested. The quantification of intracellular iron levels in leukemia cells indicated that NO induced an early, dose-dependent decrease in ferric iron levels. Accordingly, elevation of intracellular iron protected leukemia cells from NO-mediated apoptosis. Together, the present work reveals the presence of an iron-dependant mechanism for leukemia cell rescue from NO-induced growth inhibition and apoptosis.

Apoptosis↗

PubMed2001

Kit signaling and negative regulation of daunorubicin-induced apoptosis: role of phospholipase Cgamma.

Previous studies have demonstrated that activation of Kit by stem cell factor (SCF), its natural ligand, or by gain-of-function point mutation in its intracellular domain, confers significant protection against apoptosis induced by growth factor deprivation or radiation. However, the effects of Kit activation on the cellular response to anti-tumor agents have not been so extensively documented. This study shows that daunorubicin-induced apoptosis and cytotoxicity were reduced in the murine Ba/F3 cells transfected with Kit (Ba/F3-Kit) in the presence of SCF and in Ba/F3 cells transfected with a constitutively active Kit variant (Ba/F3-KitDelta27), compared to either parental Ba/F3 (Ba/F3-wt) or unstimulated Ba/F3-Kit cells. In Ba/F3-wt and in Ba/F3-Kit cells, daunorubicin stimulated within 8-15 min neutral sphingomyelinase and ceramide production but not in SCF-stimulated Ba/F3-Kit or in Ba/F3-KitDelta27 whereas all Ba/F3 cells were equally sensitive to exogenous cell-permeant C6-ceramide. In Ba/F3-Kit, SCF-induced Kit activation resulted in a rapid phospholipase Cgamma (PLCgamma) tyrosine phosphorylation followed by diacylglycerol release and protein kinase C (PKC) stimulation. U-73122, a PLCgamma inhibitor, not only blocked diacylglycerol production and PKC stimulation but also restored daunorubicin-induced sphingomyelinase stimulation, ceramide production, and apoptosis. These results suggest that Kit activation results in PLCgamma-mediated PKC-dependent sphingomyelinase inhibition which contributes to drug resistance in Kit-related malignancies.

Animals↗

PubMed2001

Thrombopoietin induces histidine decarboxylase gene expression in c-mpl transfected UT7 cells.

The leukemic cell line UT7 is endowed with both megakaryocyte and basophil differentiation potential, as judged by its capacity to respond to PMA by displaying megakaryocytic and basophilic markers and to produce histamine by neosynthesis. Herein, we addressed the question whether the biological activities characteristic of basophil differentiation were still induced when c-mpl-transfected UT7 cells received a specific megakaryocytic differentiation signal delivered by thrombopoietin (TPO). Surprisingly, we found that histamine synthesis did effectively occur in response to the growth factor. This activity was not associated with megakaryopoiesis since it was not detected in megakaryocytes generated from CD34(+) cells cultured in the presence of TPO. Comparing different c-mpl-transfected cell lines, we found that the amount of histamine generated in response to TPO correlated with their responsiveness to PMA, but not with their level of c-mpl expression, thus revealing an intrinsic basophil differentiation potential. Both PMA- and TPO-induced histamine synthesis was reduced by PKC and MEKs inhibitors, indicating that the induction occurred through a common signalling pathway.

Basophils↗

PubMed2001

Role of iron in tumor cell protection from the pro-apoptotic effect of nitric oxide.

F2The host defense against tumor cells is in part based upon the production of nitric oxide (NO) by activated macrophages. However, carcinogenesis may involve mechanisms that protect tumor cells from NO-mediated apoptosis. In the present study, we have assessed the effects of exogenous NO on the proliferation and survival of human liver (AKN-1), lung (A549), skin (HaCat), and pancreatic (Capan-2) tumor cell lines, compared with normal skin-derived epithelial cell cultures. Except to the HaCat cell line, all of the other human epithelioid cells were sensitive to the antiproliferation effect of S-nitroso-N-acetyl-penicillamine or Deta NONOate, whereas tumor cells had low if any response to sodium nitroprusside. Growth inhibition with exogenous NO correlated with increased apoptosis, but was not mediated by cyclic GMP, peroxynitrite generation, or poly(ADP-ribose) polymerase modulation, all of which involved in NO-mediated growth inhibition of normal skin-derived epithelial cell cultures. The simultaneous addition of iron-containing compounds protected tumor cells from NO-mediated growth inhibition and apoptosis. Intracellular iron quantification indicated that, as deferoxamine, exogenous NO significantly decreased intracellular ferric iron levels in tumor cells. Together, the current study reveals that intracellular iron elevation rescues tumor cells from NO-mediated iron depletion and subsequent growth inhibition and apoptosis.

Apoptosis↗

PubMed2001

Mast cells as a source and target for nitric oxide.

Mast cells (MC), which are tissue-resident cells found widely distributed in the body, are derived from primitive hematopoietic cells. MC produce a variety of biologically active substances such as histamine, proteases, lipid derivatives and numerous cytokines and chemokines in response to immunologic or non-immunologic stimuli. Of interest, it has been reported that rodent MC can also be a source of nitric oxide (NO) derivatives, that they synthesize spontaneously, or only after activation, depending on their subtype. This synthesis appears to be under the control of the expression of the inducible isoform of the nitric oxide synthase (iNOS) and of the constitutive neuronal NOS (nNOS). MC might thus be able to influence the survival and functions of other types of NO-sensitive cells in close vicinity. Apart from being a source of NO, MC can also be the target for NO and its derivatives. Indeed, survival and reactivity of rodent MC is influenced by NO derivatives produced by MC themselves or by other cellular elements in close contact with the MC in tissues. By contrast, the existence of such mechanisms of cross-talk between MC and NO remains poorly documented in humans. If evidence are supplied in favor of such relationship, pharmacological modulation by agents acting at the level of the NO pathway might be of interest in order to regulate the functions of MC in immunologic, neoplastic, inflammatory and other conditions.

Animals↗

PubMed2001

Inhibition of IgE-induced activation of human mast cells by IL-10.

BACKGROUND: IL-10 exhibits anti-inflammatory effects on activated rodent mast cells (MC) in vitro and inhibits allergen-induced airway inflammation in vivo in murine models. The effects of IL-10 on the allergic activation of human MC are presently unknown. OBJECTIVE: In light of the well-known heterogeneity of mast cell reactivity between animal species, one cannot readily predict the response of human MC to IL-10. Moreover, the impact of IL-10 on MC-derived proinflammatory mediators is still unknown. Thus, the objective of this study was to investigate the effects of IL-10 on the release of inflammatory mediators by IgE/anti-IgE-challenged human cord blood-derived mast cells (CBMC), used as an in vitro model of MC phenotypically similar to human lung MC. MATERIALS AND METHODS: Highly purified human MC were obtained by a first step of long-term culture of cord blood mononuclear cells in the presence of human recombinant stem cell factor (rhSCF) and of human recombinant IL-6 (rhIL-6), followed by a second step of purification by depletion of contaminating cells with an immunomagnetic METHOD: The cells were treated with human IgE, then challenged with anti-human IgE, in the presence or the absence of recombinant rhIL-10 used at various concentrations. Histamine, tumour necrosis factor-alpha (TNF-alpha), IL-5 and IL-8 were measured in the various supernatants collected at different times after the beginning of the challenge. RESULTS: IL-10 inhibited the release of TNF-alpha and of IL-8, but not of IL-5, by activated CBMC. Interestingly, IL-10 also inhibited the release of histamine by activated CBMC, contrasting with data reported for rodent MC. CONCLUSIONS: These findings suggest that IL-10 might have anti-inflammatory effects on IgE/anti-IgE-challenged human MC by inhibiting their release of TNF-alpha, IL-8 and histamine. These data provide new insights into the control of human mast cell activation and might lead to a better knowledge of the cellular mechanisms controlling allergic reactions.

Cell Culture Techniques↗

PubMed2001

Autocrine regulation of cord blood-derived human mast cell activation by IL-10.

BACKGROUND: Ligation of the high-affinity receptor for IgE on human mast cells (MCs) induces the release of proinflammatory mediators, including vasoactive amines and cytokines (TNF-alpha, IL-5, and IL-8). Moreover, we have recently shown that IL-10 inhibits the release of proinflammatory mediators by activated MCs. OBJECTIVE: We investigated whether human cord blood-derived MCs (CBMCs) could produce IL-10 and whether this production could inhibit their activation in an autocrine fashion. METHODS: IL-10 synthesis by resting or activated human MCs derived from cord blood progenitors was investigated in cell supernatants or by using immunostaining and RT-PCR methods. In addition, the effect of IL-4 on such synthesis was also studied. Anti-IL-10-neutralizing antibodies were used to investigate the validity of the hypothesis of an autocrine regulation of MCs by IL-10. Finally, the presence of specific receptors for IL-10 was searched on human CBMCs by using flow cytometric analysis. RESULTS: Human CBMCs spontaneously synthesize and release IL-10, and this synthesis is increased after IgE/anti-IgE stimulation. In addition, the presence of IL-10 in resting or in activated MCs was proved by immunostaining. Interestingly, the release of IL-10 was also increased after incubation of the cells with IL-4. Besides, the use of neutralizing antibodies against IL-10 confirmed that IL-10 released inhibited MC activation in an autocrine fashion. Finally, the presence of specific receptors for this cytokine was observed on the membranes of our population of human CBMCs. CONCLUSION: Taken together, our data are in favor of an autocrine regulation pathway through synthesis and release of IL-10 by human MCs. Such an autoregulatory mechanism is, to our knowledge, the first described for these elements.

Antibodies↗

PubMed2000

c-Kit and c-kit mutations in mastocytosis and other hematological diseases.

Mast cells (MC) are tissue elements derived from hematopoietic stem cells. Their differentiation and proliferation processes are under the influence of cytokines, including one of utmost importance known as stem cell factor (SCF). SCF receptor is encoded by the protooncogene c-kit, belongs to the type III receptor tyrosine kinase subfamily, and is also expressed on other hematopoietic or non-hematopoietic cells. Ligation of c-kit receptor by SCF induces its dimerization, followed by induction of multiple intracellular signaling pathways leading to cell proliferation and activation. Mastocytosis, a relatively rare group of diseases characterized by accumulation of MC in various tissues, are found isolated or sometimes associated with other hematological malignancies in humans. Although the initial events leading to mastocytosis are not yet unraveled, alterations of the c-kit gene have been described. Particularly interesting are acquired mutations resulting in a constitutively activated receptor, possibly involved in the increased numbers of MC in tissues. For this reason, future strategies might be envisaged to target specifically the mutated c-kit and/or its intracellular signaling.

Amino Acid Substitution↗

PubMed2000

Immunologic stimulation of mast cells leads to the reversible exposure of phosphatidylserine in the absence of apoptosis.

BACKGROUND: Loss of phospholipid asymmetry represents one of the hallmarks of apoptosis and results in the surface exposure of phosphatidylserine (PS) which can be indirectly monitored by the calcium-dependent binding of annexin V. METHODS AND RESULTS: Here, we provide evidence that the IgE-dependent stimulation of a rat mast cell line, as well as murine and human nontransformed mast cells, leads to the exposure of PS at the plasma membrane. The appearance of PS was quantitatively related to allergic mediator release. Pharmacological agents that prevent stimulus-secretion coupling blocked PS cell surface exposure and calcium ionophore-induced PS appearance, suggesting that it is a direct consequence of exocytosis rather than early signaling events initiated by the aggregation of the high-affinity IgE receptor (FcepsilonRI). The surface exposure of PS in mast cells was reversible even in the continuous presence of stimulus and was not associated with the appearance of apoptotic nuclei, demonstrating that it was independent of physiological cell death. CONCLUSIONS: In addition to providing a means of monitoring exocytosis at the single cell level, our results indicate that PS externalization in mast cells is not necessarily related to apoptosis but could be an important feature of the degranulation process.

Animals↗

PubMed1999

MHC class II-dependent activation of CD4+ T cell hybridomas by human mast cells through superantigen presentation.

Human mast cells (MC) were examined for expression of MHC class II antigens and for their ability to activate CD4+ T cell hybridomas through presentation of superantigen (SAg). HMC-1, a leukemic immature MC line expressing class II Ags, was shown to efficiently present the staphylococcal enterotoxin B (SEB) SAg to responding T cell hybridoma on treatment with interferon-gamma (IFN-gamma), which up-regulated class II molecules. The study was then extended to human normal MC. Almost pure (>99%) cord blood-derived MC (CBMC) were shown to express class II Ags (HLA-DR and HLA-DQ) and CD80, which were up-regulated by IFN-gamma treatment and, to a lesser extent, by interleukin-4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GM-CSF). CBMC directly activated CD4+ T cell hybridomas through presentation of SEB and TSST1 SAgs. The production of IL-2 required a cell-to-cell contact between T cells and CBMC and it was inhibited by anti-class II antibodies. Furthermore, an additional pretreatment of CBMC by IFN-gamma or GM-CSF or IL-4 had no effect on their presenting efficiency. This previously unknown function of human MC, i.e., MHC class II-dependent activation of CD4+ T cells, may be critical in subsequent cellular activation events because colocalization of mast and T cells is frequently observed at sites of antigen entry.

Animals↗

PubMed1999

Internalization of FimH+ Escherichia coli by the human mast cell line (HMC-1 5C6) involves protein kinase C.

Rodent mast cells (MC) play critical roles in host defense against bacterial infection. However, bacteria-mediated signaling mechanisms in MC have not been studied. In addition, the response of human MC to bacteria is not fully investigated. This study examined the interaction between human MC and type 1 fimbriated Escherichia coli and the mechanisms involved using the human MC line HMC-1 5C6 and human cord blood-derived MC. These MC internalized significant numbers of FimH+ E. coli, but not its isogenic FimH- mutant. In HMC-1 cells, bacterial internalization was stimulated by protein kinase C (PKC) activation [short-term phorbol myristate acetate (PMA) treatment] and dramatically decreased by PKC inhibitors or PKC depletion (long-term PMA treatment). Moreover, bacterial internalization was accompanied by significant expression of PKCbeta1 and delta. Fluorescence microscopy demonstrated accumulation of PKCbeta1 on internalized bacteria. These data indicate that human MC has the capacity to internalize bacteria and PKC may be a critical intracellular mediator of this function.

Adhesins, Bacterial↗

PubMed1999

Inhibition of mouse mast cell proliferation and proinflammatory mediator release by benzodiazepines.

Mast cell (MC) activation may occur in vitro and in vivo following stimulation with various immunologic or nonimmunologic agents. Such activation leads to the release of several biological mediators, including vasoactive amines, nitric oxide and cytokines, which account for the adverse effects observed during allergic reactions. While high affinity binding sites for benzodiazepines (BZDs) have been reported on MC, the effects of the ligation of these receptors on the proliferation of, and the mediator release from, these cells are poorly documented. In the present work, we have examined the effects of midazolam and of diazepam on the proliferation of mucosal (MMC)-like and of serosal (CTMC)-like mouse MC. In addition, we have studied the effects of these BZDs on beta-hexosaminidase, TNF-alpha and nitrite release induced from mouse mast cells through IgE receptor activation. We demonstrated that each of the two BZDs studied inhibited the proliferation of MMC- and CTMC-like elements in a dose-dependent fashion (10 to 100 microM). Furthermore, the BZDs inhibited the IgE-mediated release of beta-hexosaminidase, TNF-alpha and nitrites from MMC- or CTMC-like cells. Altogether, these data provide new insights into the pharmacological regulation of MC activation and may lead to the discovery of new and potent antiallergic compounds.

Animals↗

PubMed1999

The human immune response during cutaneous leishmaniasis: NO problem.

During some helminth infections, increased expression of the low-affinity receptor for IgE (CD23/FcepsilonRII) by macrophages and/or increased levels of plasma IgE have been seen, but their role in host protection or disease progression remains unclear. Recently, crosslinking of CD23 was shown to promote intracellular killing of Leishmania parasites in human macrophages, a phenomenon involving the production of tumor necrosis factor alpha and nitric oxide (NO). Based upon various in vitro and in vivo studies of human cutaneous leishmaniasis, Djavad Mossalayi, Michel Arock, Dominique Mazier, Philipe Vincendeau and Ioannis Vouldoukis here propose a model for an immune response that involves CD23-IgE-mediated NO release during protection, as well as during active cutaneous leishmaniasis.

Humans↗

PubMed1998

Mast cells and basophils in innate immunity.

Mast cells and basophils are primarily associated with the pathophysiology of allergic diseases. Considering that these cells have been preserved through evolution they must serve a valuable function. Intrinsically, mast cells are ideally placed and well endowed with inflammatory mediators to play a critical role in immune surveillance. Recent studies have shown that mast cells and basophils can bind various bacteria even in the absence of opsonizing antibodies. The resulting interaction caused release of a variety of inflammatory mediators and, in the case of mast cells, also uptake of bacteria. Among the mediators released by these inflammatory cells, TNF-alpha appears critical as it potentiates the early neutrophil responses to bacteria. Observations in mutant mice that are deficient in mast cells has provided further evidence for the specific role of mast cells in host defense against bacteria. We believe that there is now sufficient evidence (at least for mast cells) to propose a multi-faceted and significant role for these cells in the host's innate immune response to infectious agents.

Animals↗