Search PubMed⌕ Search

Biomedical subjects

H U Simon

Publications and source records attributed to H U Simon.

At least 37 records · Page 2Linked to original sources
PubMed2001

Critical role for caspases 3 and 8 in neutrophil but not eosinophil apoptosis.

BACKGROUND: Apoptosis is a necessary process to control cell numbers in multicellular organisms. In many chronic inflammatory diseases, reduced cell death of different types of granulocytes is one important mechanism for cell accumulation. Here, we studied the role of caspases in neutrophil and eosinophil apoptosis in the presence or absence of granulocyte-macrophage stimulating factor and anti-CD95 monoclonal antibodies, respectively. METHODS: Granulocytes were isolated from human blood using standard protocols. Immunoblot and functional studies with cell-permeable specific peptide inhibitors were performed to analyze caspase involvement. Fas receptor and Fas ligand expression was analyzed by RT-PCR, flow cytometry, and immunoblotting. Cell death was analyzed by ethidium bromide exclusion test. RESULTS: Caspases 3 and 8 are critically involved in the regulation of neutrophil apoptosis in vitro. In contrast, these two caspases did not appear to play a major role in the regulation of eosinophil apoptosis. However, the broad-range caspase inhibitor VAD prevented eosinophil death, indicating that caspases are also involved within the apoptotic machinery of eosinophils. Functional inhibitor studies suggested that caspase 9 is crucial for both caspase 3 and 8 activation, at least in neutrophils. In contrast, spontaneous apoptosis of neutrophils or eosinophils is unlikely to be the consequence of Fas ligand/Fas receptor molecular interactions. CONCLUSION: The data of this study indicate differences in the usage of caspases between neutrophils and eosinophils.

Antibodies, Monoclonal↗
PubMed2000

Eosinophils maintain their capacity to signal and release eosinophil cationic protein upon repetitive stimulation with the same agonist.

Eosinophils contain in their granules eosinophil cationic protein (ECP) and other basic proteins that have been implicated in immunity to parasites and pathophysiology of chronic allergic responses. In a model of eosinophil degranulation, we show that eosinophils release ECP upon short-term GM-CSF priming and stimulation with either platelet-activating factor (PAF) or the anaphylatoxin C5a, but not eotaxin. Restimulation with the same agonist (PAF or C5a) was unsuccessful as assessed by monitoring intracellular calcium concentration and ECP release. In contrast, upon an intermediate washing step, eosinophils rapidly transduced PAF and C5a signals followed by significant ECP releases. Ligand-binding studies demonstrated that only a proportion of PAF receptors is internalized upon cell stimulation and that washing of the cells removes the agonist from the cell surface. Upon repetitive stimulation, eosinophils with less than 50% of the original ECP content were obtained. Such eosinophils did not increase cellular ECP levels even in the presence of the eosinophil survival factor GM-CSF in overnight cultures. In vivo studies revealed that eosinophils always express detectable amounts of ECP under chronic inflammatory conditions. In conclusion, we have shown that eosinophils maintain their capacity to degranulate upon repetitive stimulation with the same agonist as long as the receptor is not occupied from a previous stimulation. The cellular content of ECP appears to be a no limiting factor in the case of repetitive stimulation, implying that mature eosinophils may not require a significant ECP resynthesis.

Blood Proteins↗
PubMed2000

CD137 activation abrogates granulocyte-macrophage colony-stimulating factor-mediated anti-apoptosis in neutrophils.

CD137 (ILA / 4-1BB) is a member of the TNF / NGF receptor family, and has previously been suggested to be involved in T cell activation and differentiation. Here, we demonstrate that blood neutrophils from control individuals and patients with cystic fibrosis express CD137 mRNA and surface protein. In contrast, lung neutrophils derived from patients with cystic fibrosis did not express detectable CD137 levels. Such CD137-deficient neutrophils could also be generated from normal neutrophils by TNF-alpha stimulation in vitro. TNF-alpha was found to be highly expressed in epithelial cells from cystic fibrosis but not normal lungs, suggesting that TNF-alpha might account for reduced neutrophil CD137 levels under inflammatory conditions in vivo. To investigate whether CD137 is involved in the regulation of apoptosis, neutrophils were activated with functional anti-CD137 antibody in the presence or absence of different neutrophil survival factors in vitro. Activation of CD137 abrogated GM-CSF-mediated anti-apoptosis in normal but not in CD137-deficient neutrophils. Moreover, G-CSF- and IFN-gamma-mediated neutrophil anti-apoptosis was not affected by anti-CD137 antibody treatment. In conclusion, these data suggest that CD137 activation may limit GM-CSF-mediated anti-apoptosis of neutrophils. The absence of this anti-inflammatory mechanism in inflammatory responses might be associated with massive neutrophil accumulation and consequent tissue damage.

Antigens, CD↗
PubMed2000

Induction of the IL-10 gene via the fas receptor in monocytes--an anti-inflammatory mechanism in the absence of apoptosis.

Death receptors play an important role in controlling cell numbers and immune responses. In contrast to TNF receptors, little is known about non-apoptosis functions of the Fas receptor (CD95, APO-1). Here we demonstrate that Fas receptor engagement results in the induction of the IL-10 gene in monocytes, but not in lymphocytes or dendritic cells. In contrast, TNF-alpha stimulated IL-10 production in dendritic cells but not monocytes. Fas receptor-mediated transcriptional activation of the IL-10 gene was followed by the release of large amounts of the cytokine in cell cultures and occurred in the absence of apoptosis induction. Since caspase activation did not occur in monocytes following Fas receptor engagement, it is unlikely that caspases are involved in IL-10 gene activation. Monocyte-derived IL-10 suppressed T cell proliferation induced by anti-CD3 monoclonal antibody without affecting CD3-mediated transmembrane signal transduction. In conclusion, we report about a novel pathway initiated via the Fas receptor leading to transcriptional activation of at least one cytokine gene. Fas ligand-induced IL-10 production in monocytes might represent an important anti-inflammatory mechanism in secondary immune responses.

Apoptosis↗
PubMed2000

[Eosinophilic cellulitis (Wells syndrome)].

Eosinophilic cellulitis (Wells' syndrome) is a rare disorder characterized clinically by recurrent erythematous plaques resembling cellulitis and histologically by a dermal infiltrate of lymphocytes, eosinophils and eosinophil debris between collagen bundles, forming flame figures in typical cases. A 71-year-old woman with Wells' syndrome with blood and bone marrow eosinophilia showed a good response to dapsone. The level of eosinophil cationic protein (ECP) in serum was elevated. Immunophenotyping of peripheral T cells revealed an increased proportion of CD3+CD4+T cells. The patients' cultured peripheral lymphocytes spontaneously released significant amounts of interleukin 5 (IL-5), but not interleukin 4 (IL-4) or interferon gamma (IFN gamma). These findings suggest that activated T cells may be involved in the pathogenesis of blood and tissue eosinophilia in this patient.

Aged↗
PubMed2000

Role of reactive oxygen species (ROS) in apoptosis induction.

Reactive oxygen species (ROS) and mitochondria play an important role in apoptosis induction under both physiologic and pathologic conditions. Interestingly, mitochondria are both source and target of ROS. Cytochrome c release from mitochondria, that triggers caspase activation, appears to be largely mediated by direct or indirect ROS action. On the other hand, ROS have also anti-apoptotic effects. This review focuses on the role of ROS in the regulation of apoptosis, especially in inflammatory cells.

Animals↗
PubMed2000

Effect of 3 weeks' rehabilitation on neutrophil surface antigens and lung function in cystic fibrosis.

Neutrophil leukocytes have been shown to be the predominant cells in inflammatory airway infiltrates of cystic fibrosis (CF) patients. The aim of this study was to investigate the effect of rehabilitation on neutrophil surface antigen expression and lung function in healthy controls and stable CF patients with moderately severe disease. The absolute number of neutrophils and the level of surface marker expression on neutrophils were elevated in 12 CF patients compared with eight healthy controls. The level of neutrophil surface marker expression was similar in bronchoalveolar lavage fluid from CF patients who underwent bronchoscopy for diagnostic or therapeutic reasons. After 3 weeks' rehabilitation, there was a significant reduction in the expression of CD11b (complement receptor type 3), CD13 (aminopeptidase N), CD32 (low-affinity Fc gamma chain receptor II), and CD35 (complement receptor type 1) in only the CF patients. At the same time, lung function improved significantly. The increase in forced vital capacity correlated significantly with the decrease in CD32 level. These results demonstrate that rehabilitation in a specialized clinic can reduce the neutrophil-dominated inflammation and improve the lung function of stable CF patients with moderately severe disease even without changing any medications.

Adult↗
PubMed2000

T cell-mediated Fas-induced keratinocyte apoptosis plays a key pathogenetic role in eczematous dermatitis.

Clinical and histologic similarities between various eczematous disorders point to a common efferent pathway. We demonstrate here that activated T cells infiltrating the skin in atopic dermatitis (AD) and allergic contact dermatitis (ACD) induce keratinocyte (KC) apoptosis. KCs normally express low levels of Fas receptor (FasR) that can be substantially enhanced by the presence of IFN-gamma. KCs are rendered susceptible to apoptosis by IFN-gamma when FasR numbers reach a threshold of approximately 40,000 per KC. Subsequently, KCs undergo apoptosis induced by anti-FasR mAb's, soluble Fas ligand, supernatants from activated T cells, or direct contact between T cells and KCs. Apoptotic KCs show typical DNA fragmentation and membrane phosphatidylserine expression. KC apoptosis was demonstrated in situ in lesional skin affected by AD, ACD, and patch tests. Using numerous cytokines and anti-cytokine neutralizing mAb's, we found no evidence that cytokines other than IFN-gamma participate in this process. In addition, apoptosis-inducing pathways other than FasR triggering were ruled out by blocking T cell-induced KC apoptosis by caspase inhibitors and soluble Fas-Fc protein. Responses of normal human skin and cultured skin equivalents to activated T cells demonstrated that KC apoptosis caused by skin-infiltrating T cells is a key event in the pathogenesis of eczematous dermatitis.

Apoptosis↗
PubMed1999

Cytokine-mediated Bax deficiency and consequent delayed neutrophil apoptosis: a general mechanism to accumulate effector cells in inflammation.

Neutrophils are important effector cells in immunity to microorganisms, particularly bacteria. Here, we show that the process of neutrophil apoptosis is delayed in several inflammatory diseases, suggesting that this phenomenon may represent a general feature contributing to the development of neutrophilia, and, therefore, in many cases to host defense against infection. The delay of neutrophil apoptosis was associated with markedly reduced levels of Bax, a pro-apoptotic member of the Bcl-2 family. Such Bax-deficient cells were also observed upon stimulation of normal neutrophils with cytokines present at sites of neutrophilic inflammation, such as granulocyte and granulocyte-macrophage colony-stimulating factors, in vitro. Moreover, Bax-deficient neutrophils generated by using Bax antisense oligodeoxynucleotides demonstrated delayed apoptosis, providing direct evidence for a role of Bax as a pro-apoptotic molecule in these cells. Interestingly, the Bax gene was reexpressed in Bax-deficient neutrophils under conditions of cytokine withdrawal. Thus, both granulocyte expansion and the resolution of inflammation appear to be regulated by the expression of the Bax gene in neutrophils.

Apoptosis↗
PubMed1999

Abnormal clones of T cells producing interleukin-5 in idiopathic eosinophilia.

BACKGROUND: The cause of persistent eosinophilia and the hypereosinophilic syndrome is unknown. Recent work suggests that in some patients with the hypereosinophilic syndrome, a clone of abnormal T cells produces large amounts of interleukin-5, a cytokine required for the growth and differentiation of eosinophils. We examined T-cell surface markers, rearranged T-cell-receptor genes, and in vitro production of cytokines by T cells from patients with idiopathic eosinophilia. METHODS: The expression of surface molecules on T cells was measured by flow cytometry. Cytokine expression was measured by enzyme-linked immunosorbent assay, flow cytometry, and immunohistochemical analysis. To identify dominant (clonal) rearrangements of the T-cell receptor within the lymphocyte population, Southern blot analysis (beta chain) and the polymerase chain reaction (gamma chain) were performed according to standard protocols. RESULTS: Among 60 patients with idiopathic eosinophilia, 16 had circulating T cells with an aberrant immunophenotype. In each of these patients, the abnormal immunophenotype was unique. Evidence of clonal rearrangements of the T-cell receptor was obtained in 8 of the 16 patients. In most instances, the abnormal T cells expressed large amounts of surface proteins associated with T-cell activation (the alpha chain of the interleukin-2 receptor and the HLA-DR antigen). Moreover, the aberrant T cells produced large amounts of interleukin-5 in vitro. CONCLUSIONS: Clonal populations of abnormal T cells producing interleukin-5 occur in some patients with idiopathic eosinophilia.

Adult↗
PubMed1999

Skin homing (cutaneous lymphocyte-associated antigen-positive) CD8+ T cells respond to superantigen and contribute to eosinophilia and IgE production in atopic dermatitis.

In allergic inflammations of the skin, activation of CD4+ T cells was demonstrated to play an important role; however, a minor role for CD8+ T cells is implied. In the present study, we compared cutaneous lymphocyte-associated Ag (CLA)-expressing CD4+ and CD8+ subsets, which were isolated from peripheral blood and lesional skin biopsies in atopic dermatitis (AD) patients. We demonstrated that CD8+CLA+ T cells proliferate in response to superantigen and are as potent as CD4+CLA+ T cells in IgE induction and support of eosinophil survival. In atopic skin inflammation, the existence of high numbers of CD4+ and CD8+ T cells was demonstrated by immunohistochemistry and by culturing T cells from skin biopsies. In peripheral blood, both CD4+ and CD8+ subsets of CLA+CD45RO+ T cells were in an activated state in AD. The in vivo-activated CLA+ T cells of both subsets spontaneously released an IL-5- and IL-13-dominated Th2 type cytokine pattern. This was confirmed by intracytoplasmic cytokine staining immediately after isolation of the cells from peripheral blood. In consequence, both CD4+ and CD8+, CLA+ memory/effector T cells induced IgE production by B cells mainly by IL-13, and enhanced eosinophil survival in vitro by delaying eosinophil apoptosis, mainly by IL-5. These results indicate that in addition to the CD4+ subset, the CD8+CLA+ memory/effector T cells are capable of responding to superantigenic stimulation and play an important role in the pathogenesis of AD.

Adult↗
PubMed1999

[Cytokine-producing lymphoma T cells in the skin and peripheral blood associated with atopy and hypereosinophilia].

A 47 year old female with a history of hay fever and a family history of atopic eczema developed localized pruritic eczematous lesions over a three year period. The lesions became generalized within just three months. Episodes of recurrent erythroderma followed and became resistant towards any therapy. Many immediate and some delayed hypersensitivity reactions were diagnosed. In the peripheral blood, leukocytosis and hypereosinophilia were observed. In addition, levels of total IgE were highly increased in serum. Immunophenotyping of the peripheral blood T cells revealed evidence for a clonal expansion of highly activated CD4(+) T cells with reduced CD2 and CD5 surface expression. After a three-year course of severe disease, the diagnosis of a pleomorphic T cell lymphoma of the small-cell variant was established by histological examination and a polymerase-chain reaction technique to determine the rearrangements of the gamma chain of the T cell receptor. Moreover, analysis of cytokine gene expression suggested that the high IgE concentrations and eosinophil numbers observed in this patient were likely due to an increased IL-5 and IL-13 production by lymphoma T cells.

CD4-Positive T-Lymphocytes↗
PubMed1999

T cells and T cell-derived cytokines as pathogenic factors in the nonallergic form of atopic dermatitis.

A subgroup of patients with atopic dermatitis are known to have normal serum total immunoglobulin E levels, undetectable specific immunoglobulin E, and negative skin prick tests towards allergens. This form of the disease has been termed nonallergic atopic dermatitis. In this study, we found that, among 1151 chronic atopic dermatitis patients, about 10% had normal serum immunoglobulin E levels with no evidence for immunoglobulin E sensitization. We investigated immunologic mechanisms of patients with "allergic" and "nonallergic" atopic dermatitis using peripheral blood and skin biopsy samples. Our data suggest that T cells are likely involved in the pathogenesis of both forms of atopic dermatitis. Skin T cells equally responded to superantigen, staphylococcal enterotoxin B, and produced interleukin-2, interleukin-5, interleukin-13, and interferon-gamma in both forms of the disease. Interleukin-4, however, was not detectable in the skin biopsies of both atopic dermatitis types and was secreted in very low amounts by T cells cultured from the skin biopsies. Moreover, skin T cells from nonallergic atopic dermatitis patients expressed lower interleukin-5 and interleukin-13 levels compared with allergic atopic dermatitis patients. Accordingly, T cells isolated from skin biopsies of atopic dermatitis, but not from the nonallergic atopic dermatitis, induced high immunoglobulin E production in cocultures with normal B cells that was mediated by interleukin-13. In addition, B cell activation with high CD23 expression was observed in the peripheral blood of atopic dermatitis, but not nonallergic atopic dermatitis patients. These data suggest, although high numbers of T cells are present in lesional skin of both types, a lack of interleukin-13-induced B cell activation and consequent immunoglobulin E production in nonallergic atopic dermatitis.

Adult↗