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Biomedical subjects

Christoph Walker

Publications and source records attributed to Christoph Walker.

18 recordsLinked to original sources
PubMed2005

The sphingosine 1-phosphate receptor agonist FTY720 differentially affects the sequestration of CD4+/CD25+ T-regulatory cells and enhances their functional activity.

The sphingosine 1-phosphate (S1P) receptor agonist FTY720 is well known for its immunomodulatory activity, sequestering lymphocytes from blood and spleen into secondary lymphoid organs and thereby preventing their migration to sites of inflammation. Because inflammation is critically dependent on a balance between Ag-specific Th/effector cells and T-regulatory cells, we investigated the effect of FTY720 on T-regulatory cell trafficking and functional activity. An increased number of CD4+/CD25+ T cells was found in blood and spleens of FTY720-treated mice, and transfer of these cells resulted in a significantly more pronounced accumulation in spleens but not lymph nodes after treatment, suggesting that this compound differentially affects the homing properties of T-regulatory cells compared with other T cell subsets. Indeed, CD4+/CD25+ T cells express lower levels of S1P1 and S1P4 receptors and demonstrate a reduced chemotactic response to S1P. Moreover, analysis of the functional response of FTY720-treated CD4+/CD25+ T cells revealed an increased suppressive activity in an in vitro Ag-specific proliferation assay. This correlated with enhanced function in vivo, with T-regulatory cells obtained from FTY720-treated mice being able to suppress OVA-induced airway inflammation. Thus, FTY720 differentially affects the sequestration of T-regulatory cells and importantly, increases the functional activity of T-regulatory cells, suggesting that it may have disease-modifying potential in inflammatory disorders.

Animals↗
PubMed2005

Airway inflammation: chemokine-induced neutrophilia and the class I phosphoinositide 3-kinases.

Class I phosphoinositide 3-kinases (PI3K) are known to play a significant role in neutrophil chemotaxis. However, the relative contributions of different PI3K isoforms, and how these impact on lung inflammation, have not been addressed. In vitro studies using wild-type and PI3Kgamma knockout neutrophils demonstrated the major role of the gamma isoform in chemotactic but not chemokinetic events. This was confirmed by a model of direct chemokine instillation into the airways in vivo. Within all studies, a low yet significant degree of neutrophil movement in the absence of PI3Kgamma could be observed. No role for the delta isoform was demonstrated both in vitro and in vivo using PI3Kdelta kinase-dead knock-in mice. Moreover, further studies using the broad-spectrum PI3K inhibitors wortmannin or LY294002 showed no other class I PI3K isoforms to be involved in these chemotactic processes. Here, we identify a contributory PI3K-independent mechanism of neutrophil movement, yet demonstrate PI3Kgamma as the pivotal mediator through which the majority of neutrophils migrate into the lung in response to chemokines. These data resolve the complexities of chemokine-induced neutrophilia and PI3K signaling and define the gamma isoform as a promising target for new therapeutics to treat airway inflammatory diseases.

Animals↗
PubMed2005

CGH2466, a combined adenosine receptor antagonist, p38 mitogen-activated protein kinase and phosphodiesterase type 4 inhibitor with potent in vitro and in vivo anti-inflammatory activities.

Theophylline, a phosphodiesterase inhibitor and adenosine receptor antagonist, is used in asthma and chronic obstructive pulmonary disease (COPD) treatment. However, the relatively low effectiveness of theophylline have recently led to reduced usage. The goal of the present study was to identify a theophylline-like compound with improved effectiveness. We discovered CGH2466, which not only antagonised the adenosine A1, A2b and A3 receptors with IC50 values of 19 +/- 4, 21 +/- 3 and 80 +/- 14 nM, respectively, but also inhibited the p38 mitogen-activated protein (MAP) kinases alpha and beta and the phosphodiesterase 4D (PDE4D) isoenzyme with IC50 values of 187 +/- 18, 400 +/- 38 and 22 +/- 5 nM, respectively. Despite similar potencies on individual targets, CGH2466 inhibited the production of cytokines and oxygen radicals by human peripheral blood leucocytes in vitro, more potently (IC50 values between 30 and 50 nM) than the standard p38 MAP kinase inhibitor SB203580 (30 nM to >1 microM), the PDE4 inhibitor cilomilast (120-400 nM) and the broad spectrum adenosine receptor antagonist CGS15943 (>10 microM). When given either orally or locally into the lungs, CGH2466 (3 to 10 mg kg(-1)) inhibited the ovalbumin- or lipopolysaccharide-induced airway inflammation in mice more potently than the single receptor antagonists or enzyme inhibitors used alone. In conclusion, CGH2466 through its combined activities at multiple targets exerted a powerful anti-inflammatory effect and therefore may have beneficial therapeutic value in diseases such as asthma and COPD.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2004

Essential role for the p110delta phosphoinositide 3-kinase in the allergic response.

Inflammatory substances released by mast cells induce and maintain the allergic response. Mast cell differentiation and activation are regulated, respectively, by stem cell factor (SCF; also known as Kit ligand) and by allergen in complex with allergen-specific immunoglobulin E (IgE). Activated SCF receptors and high-affinity receptors for IgE (FcvarepsilonRI) engage phosphoinositide 3-kinases (PI(3)Ks) to generate intracellular lipid second messenger signals. Here, we report that genetic or pharmacological inactivation of the p110delta isoform of PI(3)K in mast cells leads to defective SCF-mediated in vitro proliferation, adhesion and migration, and to impaired allergen-IgE-induced degranulation and cytokine release. Inactivation of p110delta protects mice against anaphylactic allergic responses. These results identify p110delta as a new target for therapeutic intervention in allergy and mast-cell-related pathologies.

Anaphylaxis↗
PubMed2004

A locally active antiinflammatory macrolide (MLD987) for inhalation therapy of asthma.

One of the characteristic features of asthma is a persistent pulmonary inflammation, with increased numbers of eosinophils and activated T-lymphocytes in the airways. T-helper cells of the Th2 phenotype play a pivotal role in the pathogenesis of asthma, and they are believed to orchestrate the asthmatic response by releasing a wide repertoire of cytokines. Herein, we describe the design, synthesis, and evaluation in models of allergic asthma of a locally active T-cell modulator, MLD987 (1). Compound 1 is a potent immunosuppressant that inhibits the activation, proliferation, and release of cytokines from T-cells with IC(50) values in the low nanomolar range. In a Brown-Norway rat model of allergic asthma, 1, when given into the airways by intratracheal administration (ED(50) = 1 mg/kg) or by inhalation (ED(50) = 0.4 mg/kg), potently reduced the influx of leukocytes into bronchoalveolar lavage fluid samples obtained from antigen-challenged animals. In contrast, 1 had an appreciably weaker activity in this model when given orally or intravenously. Pharmacokinetic evaluation in rat and rhesus monkey showed that 1 had both a low oral (2-4%) and a low pulmonary (7%, monkey) bioavailability. These findings are consistent with a local site of action of the compound and rule out that its antiinflammatory activity in the lung was caused by systemically absorbed material, which had been swallowed during inhalation or which had entered the circulation via the airways. Local administration and the metabolically soft structure of 1, which favors rapid systemic metabolism to less immunosuppressive metabolite 2, are the main reasons for the low exposure and weak systemic activity of the compound. Administration of a locally active compound such as 1, by inhalation, should reduce systemic side effects. Our results indicate that 1 has the potential to serve as an alternative to inhaled glucocorticosteroids for the long-term therapy of asthma of all grades of severity.

Administration, Inhalation↗
PubMed2004

Inhibition of interleukin-1beta reduces mouse lung inflammation induced by exposure to cigarette smoke.

We examined nuclear factor kappaB activation, release of inflammatory mediators and cellular infiltration in acute cigarette smoke inflammation models. One hour after exposure to one puff of cigarette smoke, alveolar macrophages from bronchoalveolar lavage (BAL) fluid of C57BL/6J mice showed an increased activity of nuclear factor kappaB-DNA binding but similar numbers as compared to that of BAL fluid from mice exposed to ambient air. Exposure to 1 cigarette/day for 1, 4 or 7 days led to an increase in interleukin-1beta and monocyte chemoattractant protein-1 levels and to a progressive influx of nuclear factor kappaB-activated alveolar macrophages into the BAL fluid and lung tissue. Exposure to 2 cigarettes/day for 7 days led to a significant increase in interleukin-1beta levels accompanied by a massive alveolar macrophage influx into the BAL fluid. Tumor necrosis factor-alpha levels and subsequent neutrophil influx were only detected after exposure to 4 or 8 cigarettes/day for 7 days. Treatment of mice with an antibody anti-interleukin-1beta during cigarette smoke exposure for 7 days significantly reduced both interleukin-1beta levels and alveolar macrophage influx. These data show that a single exposure to cigarette smoke rapidly activates alveolar macrophages, inducing the production of interleukin-1beta, which may play an important role in triggering chronic cigarette smoke-mediated lung inflammation.

Analysis of Variance↗
PubMed2004

Induction of TNF-alpha autoantibody production by AutoVac TNF106: a novel therapeutic approach for the treatment of allergic diseases.

BACKGROUND: Cytokines play an integral role in the coordination and persistence of allergic inflammatory processes and therefore represent prime targets for novel therapies in diseases such as asthma. Multiple attempts to generate low-molecular-weight cytokine inhibitors have failed, and the main attention has focused on the development of biological agents such as neutralizing antibodies. The present work describes a simple and effective method to induce the production of therapeutic anti-cytokine autoantibodies by active immunization against a modified endogenous cytokine. METHODS: Balb/c mice were subcutaneously injected with AutoVac TNF106, a recombinant murine TNF-alpha molecule containing a foreign immunogenic T helper epitope, and the induction of neutralizing anti-TNF-alpha autoantibodies was analysed. These mice were then sensitized with ovalbumin (OVA), and the effect of neutralizing anti-TNF-alpha autoantibodies on the allergen-induced airway inflammation was analysed. RESULTS: AutoVac TNF106-immunized mice developed high titres of neutralizing anti-TNF-alpha autoantibodies, which were maintained for at least 4 weeks after the last booster injection. Mice vaccinated with AutoVac TNF106 and further immunized against OVA showed diminished TNF-alpha levels in the bronchoalveolar lavage (BAL) fluid after OVA challenge. Moreover, pretreatment with AutoVac TNF106 resulted in significantly reduced numbers of eosinophils and neutrophils in BAL fluid in response to single or multiple allergen exposure. CONCLUSION: The induction of anti-TNF-alpha autoantibody production by the AutoVac TNF106 technology not only confirmed the role of TNF-alpha in the induction of allergic inflammation but also offers a novel approach to block the activity of cytokines in order to treat allergic inflammatory conditions.

Animals↗
PubMed2004

Tc2 cells respond to soluble antigen in the respiratory tract and induce lung eosinophilia and bronchial hyperresponsiveness.

The key role of T helper 2 (Th2) cells in asthma is well established. In contrast, the function of CD8+ T cells producing a distinct cytokine profile similar to Th2 cells is largely unknown. To analyze a potential role of CD8+ T cell subsets, allergen-specific, in vitro-differentiated T cytotoxic (Tc1 or Tc2) cells from T cell receptor transgenic OT-I mice were adoptively transferred into naive C57BL/6 mice. Subsequent allergen challenge of mice injected with Tc1 cells (producing IFN-gamma but no IL-4) resulted in a neutrophilic airway inflammation without induction of bronchial hyperresponsiveness (BHR). In contrast, the inflammatory response of recipients of adoptively transferred Tc2 cells (producing high levels of IL-4 but little IFN-gamma) was characterized by significantly increased numbers of eosinophils and induction of BHR to methacholine. The response of antigen-specific CD8+ T cells to soluble antigen was also observed in an in vitro system. A low concentration of antigen was shown to favor the generation of Tc2 cells, whereas high antigen load resulted in the differentiation of Tc1 cells. Thus, allergen-specific Tc2 cells respond to inhaled soluble antigen, produce an inflammatory response qualitatively similar to Th2 cells and therefore may exacerbate the Th2-driven airway inflammation in asthma.

Adoptive Transfer↗
PubMed2003

Inhibition of Th1- and Th2-mediated airway inflammation by the sphingosine 1-phosphate receptor agonist FTY720.

The sphingosine 1-phosphate receptor agonist FTY720 is a novel immunomodulator that sequesters lymphocytes in secondary lymphoid organs and thereby prevents their migration to sites of inflammation. However, there is currently no information available on whether this drug affects Th1 or Th2 cell-mediated lung-inflammatory responses. The effect of FTY720 was therefore investigated in a murine airway inflammation model using OVA-specific, in vitro differentiated, and adoptively transferred Th1 and Th2 cells. Both Th1 and Th2 cells express a similar pattern of FTY720-targeted sphingosine 1-phosphate receptors. The OVA-induced Th1-mediated airway inflammation characterized by increased numbers of lymphocytes and neutrophils in bronchoalveolar lavage fluid was significantly inhibited by oral FTY720 treatment. Similarly, FTY720 suppressed the Th2 cell-induced bronchoalveolar lavage fluid eosinophilia and the infiltration of T lymphocytes and eosinophils into the bronchial tissue. Moreover, the Ag-induced bronchial hyperresponsiveness to inhaled metacholine was almost completely blocked. The inhibitory effect of FTY720 on airway inflammation, induction of bronchial hyperresponsiveness, and goblet cell hyperplasia could be confirmed in an actively Ag-sensitized murine asthma model, clearly indicating that Th2 cell-driven allergic diseases such as asthma could benefit from such treatment.

Animals↗
PubMed2003

Differential regulation of aminopeptidase N (CD13) by transendothelial migration and cytokines on human eosinophils.

Aminopeptidase N (CD13) is a cell surface metalloprotease involved in growth regulation, tumor invasion, and down-regulation of regulatory peptides. CD13 expression on eosinophils in bronchoalveolar lavage (BAL) of asthmatics 10 minutes and 18 hours after segmental allergen provocation was significantly increased (+225% to +294%) compared to blood eosinophils. In vitro CD13 expression could be induced on blood eosinophils by transendothelial migration of the cells across interlenkin (IL) 1beta-activated human umbilical cord vein endothelial cells (HUVECs) as well as by the exposure to the cytokines IL-3, IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF). The cytokines GM-CSF and IL-5 were significantly less effective in inducing CD13 compared to IL-3. The IL-3-induced expression of CD13 was decreased in the presence of the protein-synthesis inhibitor cycloheximide (-8.8%). Moreover, blocking of CD13 by the protease inhibitors actinonin and bestatin significantly enhanced migration (+40.0% to +80.0%) of eosinophils across HUVEC monolayers. In summary, the data suggest that CD13 is regulated both by the process of transmigration and by the cytokine IL-3. Further, CD13 itself seems to be involved in the process of eosinophil transmigration. aminopeptidase Nendothelial cellseosinophilsinterleukin-3interleukin-5transendothelial migration

Adult↗
PubMed2003

Immunotherapy with mycobacteria.

PURPOSE OF REVIEW: To summarize and evaluate critically recent progress with mycobacteria as a potential novel disease modifying treatment strategy in asthma. RECENT FINDINGS: The link between exposure to pathogenic or saprophytic mycobacteria and protection from allergic diseases is still controversial, and recent epidemiological studies, which addressed only exposure to Mycobacterium tuberculosis or bacillus Calmette-Guérin, did not help to clarify this issue. Moreover, the clear efficacy of mycobacterial treatment seen in animal models has not been reproduced in human asthma, and a recent small study testing the hypothesis that heat-killed Mycobacterium vaccae attenuates asthmatic reactions after allergen challenge did not provide convincing results. However, it has been shown that treatment of mice with M. vaccae induces the generation of allergen-specific T regulatory cells capable of suppressing allergen-mediated eosinophilic lung inflammation, suggesting that a general deficiency of T regulatory cell activity might be responsible for the increased prevalence of asthma. This hypothesis is supported by findings that a lack of T regulatory cells, as found in genetic disorders of man and mouse attributable to a mutation of Foxp3, a transcription factor specifically expressed by T regulatory cells, is associated with manifestations of severe atopy and autoimmunity, precisely the spectrum of diseases linked to the hygiene hypothesis. SUMMARY: Further studies on the relationship between mycobacteria and atopic disorders are needed, but there is reason to believe that the novel findings and molecular mechanisms associated with mycobacterial infections will further strengthen the currently unproved therapeutic value of immunotherapy with mycobacteria.

Animals↗
PubMed2002

Long-term protective and antigen-specific effect of heat-killed Mycobacterium vaccae in a murine model of allergic pulmonary inflammation.

This report examines the effect of heat-killed Mycobacterium vaccae in a mouse model of allergic pulmonary inflammation. The s.c. administration of M. vaccae 3 wk before the immunization significantly reduced Ag-induced airway hyperreactivity and the increase in the numbers of eosinophils observed in the bronchoalveolar lavage fluid, blood, and bone marrow, even though no detectable changes in either cytokine (IL-4, IL-13, IL-5, and IFN-gamma) or total IgE levels were observed. Furthermore, transfer of splenocytes from OVA-immunized and M. vaccae-treated mice into recipient, OVA-immunized mice significantly reduced the allergen-induced eosinophilia by an IFN-gamma-independent mechanism, clearly indicating that the mechanism by which M. vaccae induces its inhibitory effect is not due to a redirection from a predominantly Th2 to a Th1-dominated immune response. The protective effect of M. vaccae on the allergen-induced eosinophilia lasted for at least 12 wk after its administration, and the treatment was also effective in presensitized mice. Moreover, the allergen specificity of the inhibitory effect could be demonstrated using a double-immunization protocol, where M. vaccae treatment before OVA immunization had no effect on the eosinophilic inflammation induced by later immunization and challenge with cockroach extract Ag. Taken together, these results clearly demonstrate that M. vaccae is effective in blocking allergic inflammation by a mechanism independent of IFN-gamma, induces long term and Ag-specific protection, and therefore has both prophylactic and therapeutic potential for the treatment of allergic diseases.

Adoptive Transfer↗
PubMed2002

Suppression of airway eosinophilia by killed Mycobacterium vaccae-induced allergen-specific regulatory T-cells.

Allergic asthma is a chronic inflammatory disease and despite the introduction of potent and effective drugs, the prevalence has increased substantially over the past few decades. The explanation that has attracted the most attention is the 'hygiene hypothesis', which suggests that the increase in allergic diseases is caused by a cleaner environment and fewer childhood infections. Indeed, certain mycobacterial strains can cause a shift from T-helper cell 2 (Th2) to Th1 immune responses, which may subsequently prevent the development of allergy in mice. Although the reconstitution of the balance between Th1 and Th2 is an attractive theory, it is unlikely to explain the whole story, as autoimmune diseases characterized by Th1 responses can also benefit from treatment with mycobacteria and their prevalence has also increased in parallel to allergies. Here we show that treatment of mice with SRP299, a killed Mycobacterium vaccae-suspension, gives rise to allergen-specific CD4+CD45RB(Lo) regulatory T cells, which confer protection against airway inflammation. This specific inhibition was mediated through interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta), as antibodies against IL-10 and TGF-beta completely reversed the inhibitory effect of CD4+CD45RB(Lo) T cells. Thus, regulatory T cells generated by mycobacteria treatment may have an essential role in restoring the balance of the immune system to prevent and treat allergic diseases.

Adoptive Transfer↗
PubMed2002

Toll-like receptors as potential therapeutic targets for multiple diseases.

The family of Toll-like receptors (TLRs) is receiving considerable attention as potential regulators and controllers of the immune response through their ability to recognize pathogen-associated molecular patterns. The discovery that endogenous ligands, as well as microbial components, are recognized by TLRs, and that small-molecular-mass synthetic compounds activate TLRs, raised interest in these receptors as potential targets for the development of new therapies for multiple diseases. In this review, we discuss the current and future use of TLR agonists or antagonists in chronic inflammatory diseases and highlight potential problems that are associated with such approaches.

Animals↗
PubMed2002

Pharmacological profile of PKF242-484 and PKF241-466, novel dual inhibitors of TNF-alpha converting enzyme and matrix metalloproteinases, in models of airway inflammation.

1. TNF-alpha converting enzyme (TACE) and matrix metalloproteinases (MMPs) are believed to play a role in various airway inflammatory disorders. Therefore we have tested the effect of two new inhibitors of TACE/MMPs (PKF242-484, PKF241-466) in models of airway inflammation. 2. PKF242-484 and PKF241-466 inhibited purified MMP-1, -2, -3, -9, -13 and rat collagenase at low nanomolar range. Both compounds inhibited the TNF-alpha release from activated human peripheral blood mononuclear cells with IC(50) values of 56+/-28 and 141+/-100 nM, respectively and had no significant effect on the activation of other human leukocytes, as neither neutrophils and eosinophils oxidative burst nor proliferation or cytokines production by T cells were inhibited in vitro. 3. PKF242-484 and PKF241-466 had beneficial effects in two different murine models of acute lung inflammation in vivo. The influx of neutrophils and lymphocytes into the airways was reduced 3 and 24 h after intranasal LPS challenge. This was accompanied by reduced levels of myeloperoxidase and elastase activities in the bronchoalveolar lavage. Furthermore, a complete inhibition of TNF-alpha release into the airways was observed. In addition, PKF242-484 effectively reduced the influx of neutrophils, eosinophils and lymphocytes in a model of acute allergic lung inflammation. 4. PKF242-484 and PKF241-466 are two novel and potent dual inhibitors of TACE and MMPs, which show activity in in vivo models of lung inflammation. Such compounds could have beneficial effects in airway inflammatory conditions such as asthma and chronic obstructive pulmonary disease.

ADAM Proteins↗
PubMed2002

Pharmacological profile of a novel phosphodiesterase 4 inhibitor, 4-(8-benzo[1,2,5]oxadiazol-5-yl-[1,7]naphthyridin-6-yl)-benzoic acid (NVP-ABE171), a 1,7-naphthyridine derivative, with anti-inflammatory activities.

We investigated the pharmacology of a new class of phosphodiesterase 4 (PDE4) inhibitor, 6,8-disubstituted 1,7-naphthyridines, by using 4-(8-benzo[1,2,5]oxadiazol-5-yl-[1,7]naphthyridin-6-yl)-benzoic acid (NVP-ABE171) as a representative compound and compared its potency with the most advanced PDE4 inhibitor, undergoing clinical trials, Ariflo [cis-4-cyano-4-(3-cyclopentyloxy-4-methoxyphenyl-r-1-cyclohexanecarboxylic acid)]. NVP-ABE171 inhibited the activity of phosphodiesterase 4A, 4B, 4C, and 4D with respective IC(50) values of 602, 34, 1230, and 1.5 nM. Ariflo was about 40 times less potent. In human cells, NVP-ABE171 inhibited the eosinophil and neutrophil oxidative burst, the release of cytokines by T cells, and the tumor necrosis factor-alpha release from monocytes, in the nanomolar range. Ariflo presented a similar inhibition profile but was 7 to 50 times less potent. In BALB/c mice challenged with lipopolysaccharide, NVP-ABE171 inhibited the airway neutrophil influx and activation with an ED(50) in the range of 3 mg/kg. Ariflo was inactive up to a dose of 10 mg/kg. In ovalbumin sensitized Brown Norway rats, NVP-ABE171 inhibited the lipopolysaccharide-induced airway neutrophil influx and activation (ED(50) of 0.2 mg/kg) and the ovalbumin-induced airway eosinophil influx and activation (ED(50) of 0.1 mg/kg). Ariflo was about 100 times less potent in both models. In the ovalbumin model, NVP-ABE171 had a duration of action of more than 24 h. NVP-ABE171 is a novel PDE4 inhibitor that shows activity both in vitro on human inflammatory cells and in vivo in animal models of lung inflammation. This compound class may have potential for the treatment of airway inflammatory conditions such as asthma and chronic obstructive pulmonary diseases.

3',5'-Cyclic-AMP Phosphodiesterases↗