Recombinant stem cell factor-induced mast cell activation and smooth muscle contraction in human bronchi

Tracheal Smooth Muscle Cells Stimulated by Stem Cell Factor-c-Kit Coordinate the Production of Transforming Growth Factor-β1 and Fibroblast Growth Factor-2 Mediated by Chemokine (C-C Motif) Ligand 3

The aim of this study was to evaluate the mechanism involved in the stem cell factor (SCF)-induced production of fibroblast growth factor-2 (FGF-2), transforming growth factor-β1 (TGF-β1), and chemokine (C-C motif) ligand 3 (CCL3) in tracheal smooth muscle cells (tSMCs) and the signaling pathway involved in the process. tSMC primary cultures were stimulated with SCF and evaluated at 24 h. Cells treated with specific antibodies did not show any immunolabeling for cytokeratin or fibroblast activation protein, but were positive for α-smooth muscle actin, indicating the purity of the primary cell line. Western blot analysis showed constitutive phosphorylation of c-Kit, as well as increased total protein and phosphorylated c-Kit levels in tSMCs after SCF stimulation. Flow cytometry analysis also showed an increase in cell-surface c-Kit expression in the presence of SCF. SCF induced TGF-β mRNA expression in tSMCs, as well as the production of TGF-β1, CCL3, and FGF-2. Pretreatment with anti-CCL3 antibody blocked TGF-β1 expression and partially inhibited FGF-2 production. On the other hand, anti-c-Kit antibody blocked TGF-β1 expression and FGF-2 production. Thus, TGF-β1 and FGF-2 production were mediated by CCL3 production through c-Kit. Pretreatment with mitogen-activated protein kinase kinase 1, p38, and Jun N-terminal kinase inhibitors showed that the effects mediated by SCF were involved with the modulation of mitogen-activated protein kinase (MAPK) pathways. Development of inhibitors targeting CCL3 through MAPK activation could thus be an attractive strategy to inhibit tSMC activation during asthma.

Stem Cell Factor and Interleukin-31 Expression: Association with IgE among Egyptian Patients with Atopic and Nonatopic Bronchial Asthma

Bronchial asthma is a chronic inflammatory disorder which remains a significant cause of morbidity. Recently, it has been reported that the stem cell factor (SCF) and interleukin-31 (IL-31) may play a major role in bronchial asthma. The aim of the current study was to study the association of the stem cell factor and interleukin-31 expression with serum immunoglobulin E among Egyptian patients with atopic and nonatopic bronchial asthma. After measuring serum IgE using total enzyme linked immunosorbent assay (ELISA), Ribonucleic acid (RNA) was isolated to determine gene expression of SCF and IL-31 by real-time polymerase chain reaction (PCR). The levels of SCF mRNAs in atopic asthmatic patients' PBMCs were significantly higher than those in controls (p = 0.0001**) and nonatopic asthmatics (p = 0.0001**). There was a high statistical significant difference also with regard to IL-31 between atopic asthmatics and controls (p = 0.0001**) and between them and nonatopic patients (p = 0.014*). There was a strong significant direct correlation between SCF, IL-31 (r = 0.827 and p = 0.0001**) and between both of them and IgE in asthmatics (r = 0.543 and p = 0.0001**) (r = 0.443 and p = 0.0001**), respectively. A direct correlation between SCF, IL-31 and FEV-1/ FVC %, CRP and wheezing existed. These findings suggest that both SCF and IL-31 play an important role in mediating inflammation and enhancing severity of atopic asthma. Augmented inhaled glucocorticoid therapy was associated with significant reductions in SCF and IL-31 mRNA expression as well as improvements in lung function, symptom scores and bronchial hyperresponsiveness to methacholine (PD20) in atopic and nonatopic asthmatics.

Aspirin-sensitive respiratory disease

Aspirin-sensitive respiratory disease (ASRD) is a condition characterized by persistent and often severe inflammation of the upper and lower respiratory tracts. Patients develop chronic eosinophilic rhinosinusitis, nasal polyposis, and asthma. The ingestion of aspirin and other cyclooxygenase-1 (COX-1) inhibitors induces exacerbations of airway disease that may be life-threatening. Thus, aspirin sensitivity is a phenotypic marker for the syndrome, yet nearly all affected individuals can be desensitized by the administration of graded doses of aspirin, leading to long-term clinical benefits. Patients with aspirin sensitivity are often able to tolerate selective COX-2 inhibitors. The pathogenesis of ASRD is underpinned by abnormalities in eicosanoid biosynthesis and eicosanoid receptor expression coupled with intense mast cell and eosinophilic infiltration of the entire respiratory tract. This review focuses on the molecular, cellular, and biochemical abnormalities characterizing ASRD and highlights unanswered questions in the literature and potential future areas of investigation.

Physiological and pathophysiological functions of intestinal mast cells

The normal gastrointestinal (GI) mucosa is equipped with mast cells that account for 2-3% of lamina propria cells under normal conditions. Mast cells are generally associated with allergic disease, and indeed, food allergy that manifests in the GI tract is usually mast cell dependent. On the other hand, mast cells have a number of physiological functions in the GI tract, namely regulatory functions such as control of blood flow and coagulation, smooth muscle contraction and peristalsis, and secretion of acid, electrolytes, and mucus by epithelial cells. One of the most intriguing functions of intestinal mast cells is their role in host defense against microbes like bacteria, viruses, or parasites. Mast cells recognize microbes by antibody-dependent mechanisms and through pattern-recognition receptors. They direct the subsequent immune response by attracting both granulocytes and lymphocytes to the site of challenge via paracrine cytokine release. Moreover, mast cells initiate, by releasing proinflammatory mediators, innate defense mechanisms such as enhanced epithelial secretion, peristalsis, and alarm programs of the enteric nervous This initiation can occur in response to a primary contact to the microbe or other danger signals, but becomes much more effective if the triggering antigen reappears and antibodies of the IgE or IgG type have been generated in the meantime by the specific immune system. Thus, mast cells operate at the interface between innate and adaptive immune responses to enhance the defense against pathogens and, most likely, the commensal flora. In this respect, it is important to note that mast cells are directly involved in controlling the function of the intestinal barrier that turned out to be a crucial site for the development of infectious and immune-mediated diseases. Hence, intestinal mast cells perform regulatory functions to maintain tissue homeostasis, they are involved in host defense mechanisms against pathogens, and they can induce allergy once they are sensitized against foreign antigens. The broad spectrum of functions makes mast cells a fascinating target for future pharmacological or nutritional interventions.

Role of mast cells in allergic and non-allergic immune responses: comparison of human and murine data

The versatile role of mast cells in allergy, in innate immune responses and in the regulation of tissue homeostasis is well recognized. However, it is often not made clear that most mast-cell data derive solely from experiments in mice or rats, species that obviously never suffer from allergic and most other mast-cell-associated human diseases. Data on human mast cells are limited, and the mast-cell source and species from which findings derive are frequently not indicated in the titles and summaries of research publications. This Review summarizes recent data on human mast cells, discusses differences with murine mast cells, and describes new tools to study this increasingly meaningful cell type in humans.

Stem cell factor expression, mast cells and inflammation in asthma

The Kit ligand SCF or stem cell factor (SCF) is a multipotent growth factor, acting as an important growth factor for human mast cells. SCF induces chemotaxis and survival of the mast cell, as well as proliferation and differentiation of immature mast cells from CD34(+) progenitors. Additionally, SCF enhances antigen-induced degranulation of human lung-derived mast cells, and induces a mast cell hyperplasia after subcutaneous administration. SCF expression increases in the airways of asthmatic patients, and this is reversed after treatment with glucocorticoids. A role for SCF may thus be hypothesized in diseases associated with a local increase in the number and/or activation of mast cells, as occurring in the airways in asthma. SCF will be reviewed as a potential therapeutic target in asthma, to control the regulation of mast cell number and activation. We here report the main pathways of SCF synthesis and signalling, and its potential role on airway function and asthma.

Association of stem cell factor expression in nasal polyp epithelial cells with aspirin sensitivity and asthma

Mast cells constitute a significant proportion of cells infiltrating nasal polyp tissue, and epithelial cells may release stem cell factor (SCF), a cytokine with chemotactic and survival activity for mast cells. We aimed to assess the expression of SCF in human nasal polyp epithelial cells (NPECs) as related to patients' clinical phenotypes. Nasal polyp tissues were obtained from 29 patients [including nine with aspirin (ASA)-hypersensitivity and 12 with bronchial asthma] undergoing polypectomy for nasal obstruction. Epithelial cells were obtained following 6-week culture of nasal polyps explants. The SCF released into the culture supernatant was assessed by enzyme-linked immunosorbent assay (ELISA) and total SCF mRNA in the polyp tissue was determined by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR). For the whole group of patients, the number of polypectomies correlated with expression of SCF mRNA (r = 0.62; P < 0.005), SCF protein in the NPECs supernatants (r = 0.39; P < 0.05) and with density of mast cells in epithelial layer (r = 0.37; P < 0.05) and stromal layer (r = 0.5; P < 0.01) of nasal polyps. The SCF/beta-actin mRNA ratios were significantly higher in ASA-hypersensitive (AH) asthmatics (median 0.97, range: 0.8-1.5) when compared with ASA-tolerant (AT) patients (median 0.5, range: 0.1-0.7; P < 0.001). The SCF protein concentration in NPEC supernatants was also significantly higher in AH asthmatics (median 1.10 pg/microg DNA, range: 0.4-1.9) when compared with AT patients (median 0.1 pg/microg DNA, range: 0.02-1.2; P < 0.001). In the subpopulation of ASA-sensitive asthmatics the number of polypectomies correlated also with the density of mast cells and eosinophils in the polyp tissue.

Treatment of cockroach allergen asthma model with imatinib attenuates airway responses

In the present study it was determined whether a pharmacologic approach to blocking receptor tyrosine kinase-mediated activation during allergic airway responses could be beneficial. To examine these responses, allergic mice were given a single oral dose of imatinib at clinically relevant concentrations, ranging from 0.05 to 50 mg/kg, by oral gavages just before allergen challenge. The reduction in the allergen-induced responses was significant and centered on reducing overall inflammation as well as pulmonary cytokine levels. In particular, the treatment of the mice with imatinib significantly attenuated airway hyperreactivity and peribronchial eosinophil accumulation, and significantly reduced Th2 cytokines, interleukin-4 and interleukin-13. In addition, chemokines previously associated with allergen-induced pulmonary disease, CCL2, CCL5, and CCL6, were significantly reduced in the lungs of the imatinib-treated animals. Together these data demonstrate that the pharmacologic inhibitor imatinib may provide a clinically attractive therapy for allergic, asthmatic responses.

Association of vitamin D receptor gene polymorphisms with childhood and adult asthma

Vitamin D receptor (VDR) polymorphisms have been associated with several immune-related diseases, and VDR and vitamin D itself modulate T cell differentiation. VDR maps to chromosome 12q, near a region commonly linked to asthma. We evaluated VDR as part of a 12q positional candidate survey, and in response to observations of VDR polymorphism associations with asthma and atopy in a founder population of Quebec. Twenty-eight loci in 7 positional candidates (7 in VDR) were genotyped in 582 families. Whereas other candidates demonstrated no association, the VDR ApaI polymorphism demonstrated significant transmission distortion, with undertransmission of the C allele in a ratio of 4:5 (p = 0.01). This association was most prominent in girls, in whom distortion was more marked (p = 0.009). Sex-specific associations between multiple VDR polymorphisms and immunoglobulin E levels were also observed (p = 0.006-0.01). Asthma associations were replicated in a second cohort (517 females with asthma and 519 matched control subjects): 4 of 6 VDR variants demonstrated significant association (p = 0.02-0.04). The direction of association in this second cohort was opposite to the effects seen in the trios, but similar to findings in the Quebec study. These results suggest that VDR influences asthma and allergy susceptibility in a complex manner.

Inhibition of stem cell factor reduces pulmonary cytokine levels during allergic airway responses

Stem cell factor (SCF) has a significant role in the inflammation and activation of allergic airway responses. When monoclonal anti-SCF was administered intratracheally during allergen challenge there was a significant alteration of eosinophil accumulation and airway hyperreactivity (AHR). Anti-SCF treatment also attenuated pulmonary cytokine and chemokine levels. In particular, there was an antibody dose-dependent decrease in interleukin (IL)-5 and tumour necrosis factor (TNF)-alpha. There was also a significant reduction of CCL2 and CCL5, which correlated with the reduction in AHR. Mice treated with anti-SCF demonstrated a significant decrease in pulmonary gob-5 gene expression, which has been shown to correlate to goblet cell hyperplasia/metaplasia relating to airway mucus production. Blocking SCF-mediated activation within the airway using a monoclonal antibody indicates that this cytokine may represent a viable target for therapeutic intervention that could affect multiple aspects of allergen-induced immunopathology.

Stem cell factor induces eosinophil activation and degranulation: mediator release and gene array analysis

Eosinophils are effector cells that play an important role in the damage induced by the allergic process by releasing inflammatory mediators and proteolytic factors after activation. Stem cell factor (SCF) is a primary cytokine involved in hematopoiesis and mast cell differentiation, proliferation, and activation. Studies have also indicated that SCF is directly involved in pathogenesis of allergic airway inflammation. In the present study, we examined the ability of SCF to activate murine eosinophils for increased mediator release and up-regulation of chemokines. Initial data demonstrated that eosinophils have significant levels of surface c-kit protein, SCF receptor. SCF-activated eosinophils degranulate and release eosinophil peroxidase and leukotriene C(4) in a dose-dependent manner. In addition, SCF was further shown to induce the release of CC chemokines, RANTES, macrophage-derived chemokine (MDC), macrophage inflammatory protein-1beta (MIP-1beta), and C10 from eosinophils. To identify the extent of SCF-induced activation of eosinophils, we also performed gene array analysis using an array containing 1153 genes related to inflammation, including cytokines and their receptors, growth factors, structural and cytoskeletal genes, signal transduction genes as well as several other classes related to immune/inflammatory responses. The gene analysis indicated that more than 150 genes were significantly up-regulated in eosinophils after SCF stimulation. The gene array results were verified using a quantitative real-time polymerase chain reaction analysis to identify the expression of several chemokine and chemokine receptor genes. Altogether, these studies indicate that SCF is a potent eosinophil degranulator and activator that may play a number of roles during an inflammatory/immune response.

Human mast cell and airway smooth muscle cell interactions: implications for asthma

Asthma is characterized by inflammation, hyperresponsiveness, and remodeling of the airway. Human mast cells (HMCs) play a central role in all of these changes by releasing mediators that cause exaggerated bronchoconstriction, induce human airway smooth muscle (HASM) cell proliferation, and recruit and activate inflammatory cells. Moreover, the number of HMCs present on asthmatic HASM is increased compared with that on nonasthmatic HASM. HASM cells also have the potential to actively participate in the inflammatory process by synthesizing cytokines and chemokines and expressing surface molecules, which have the capacity to perpetuate the inflammatory mechanisms present in asthma. This review specifically examines how the mediators of HMCs have the capacity to modulate many functions of HASM; how the synthetic function of HASM, particularly through the release and expression of stem cell factor, has the potential to influence HMC number and activation in an extraordinarily potent and proinflammatory manner; and how these interactions between HMCs and HASM have potential consequences for airway structure and inflammation relevant to the disease process of asthma.

SCF-induced airway hyperreactivity is dependent on leukotriene production

Stem cell factor (SCF) is directly involved in the induction of airway hyperreactivity during allergen-induced pulmonary responses in mouse models. In these studies, we examined the specific mediators and mechanisms by which SCF can directly induce airway hyperreactivity via mast cell activation. Initial in vitro studies with bone marrow-derived mast cells indicated that SCF was able to induce the production of bronchospastic leukotrienes, LTC4and LTE4. Subsequently, when SCF was instilled in the airways of naive mice, we were able to observe a similar induction of LTC4and LTE4in the bronchoalveolar lavage (BAL) fluid and lungs of treated mice. These in vivo studies clearly suggested that the previously observed SCF-induced airway hyperreactivity may be related to the leukotriene production after SCF stimulation. To further investigate whether the released leukotrienes were the mediators of the SCF-induced airway hyperreactivity, an inhibitor of 5-lipoxygenase (5-LO) binding to the 5-LO activating protein (FLAP) was utilized. The FLAP inhibitor MK-886, given to the animals before intratracheal SCF administration, significantly inhibited the release of LTC4and LTE4into the BAL fluid. More importantly, use of the FLAP inhibitor nearly abrogated the SCF-induced airway hyperreactivity. In addition, blocking the LTD4/E4, but not LTB4, receptor attenuated the SCF-induced airway hyperreactivity. In addition, the FLAP inhibitor reduced other mast-derived mediators, including histamine and tumor necrosis factor. Altogether, these studies indicate that SCF-induced airway hyperreactivity is dependent upon leukotriene-mediated pathways.

Human skin-derived mast cells can proliferate while retaining their characteristic functional and protease phenotypes

Human mast cells in adult tissues have been thought to have limited, if any, proliferative potential. The current study examined mast cells obtained from adult skin and cultured in serum-free medium with recombinant human stem cell factor. During the first 4 weeks of culture, the percentages of mast cells increased from 10 to almost 100. After 8 weeks, a 150-fold increase in the number of mast cells was observed. When freshly dispersed mast cells were individually sorted onto human fibroblast monolayers and cultured for 3 weeks, one or more mast cells were detected in about two thirds of the wells, and in about two thirds of these wells the surviving mast cells showed evidence of proliferation, indicating most mast cells in skin can proliferate. Such mast cells all expressed high surface levels of Kit and Fc epsilon RI, each of which were functional, indicating IgE was not required for Fc epsilon RI expression on mast cells. Such mast cells also retained the MC(TC) protease phenotype of mast cells that normally reside in the dermis. After 4 to 8 weeks of culture these mast cells degranulated in response to substance P and compound 48/80, characteristics of skin-derived mast cells that persist outside of the cutaneous microenvironment. (Blood. 2001;97:2045-2052)

Mast cell tryptase as a mediator of hyperresponsiveness in human isolated bronchi

BACKGROUND

Although the role of mediators and cytokines produced by mast cells is well established in asthmatic bronchial inflammation, the contribution of mast cell-derived proteases to the development of hyperresponsiveness remains unclear. There have been reports indicating that tryptase alters the mechanical activity of animal airway smooth muscle or spontaneously sensitized human isolated airways.

OBJECTIVE

The aim of this study was to analyse the effect of purified mast cell tryptase on non-sensitized human isolated bronchi.

METHODS

Both central and peripheral bronchi, dissected from lung specimens obtained at thoracotomy, were studied in terms of both mechanical activity i.e. isometric contraction in response to a variety of agonists and distribution of inflammatory cells i.e. immunohistochemistry.

RESULTS

In both proximal and distal bronchi, the reactivity to histamine was significantly increased by a previous incubation in the presence of 1 microg/mL of tryptase (increase in maximal force, DeltaFmax was 12.1 +/- 3.8%, and 8.8 +/- 3.1%, respectively). This effect of tryptase on histamine-induced contraction was completely abrogated in the presence of the protease inhibitor benzamidine (100 micromol/L). Histological examination of specimens exposed to tryptase demonstrated an increase in mast cell number within the subepithelial tissue whereas mast cell numbers in the epithelial layer concomittently decreased.

CONCLUSION

These results indicate that human mast cell tryptase alters the contractile response of non-sensitized human isolated bronchi and that this alteration is accompanied by a change in the mast cell distribution within the airway wall.

Stem cell factor-induced airway hyperreactivity in allergic and normal mice

The induction of airway hyperreactivity during allergic responses involves multiple ill-defined mechanisms. Recently a role for stem cell factor (SCF) in the development of allergic eosinophilic airway inflammation has been identified. In the present study we demonstrate that SCF has a role in both the inflammatory response and airway hyperreactivity. Neutralization of SCF or examination of SCF-mutant mice, which were deficient in SCF and pulmonary mast cells, demonstrated significant alterations in the allergen-induced airway hyperreactive responses. The reduced hyperreactivity response was accompanied by a significant reduction in eosinophil accumulation. To examine the direct role of SCF on airway hyperreactivity, we administered SCF into the airways of normal mice via intratracheal injections and demonstrated a dose dependent increase in airway hyperreactivity at 4 hours that was maintained at 24 hours after administration. Instillation of SCF into SCF-deficient (mast cell deficient) mice demonstrated significantly lower increases in airway hyperreactivity compared with the littermate controls with normal mast cell numbers. These studies demonstrate that locally expressed SCF can induce changes in airway physiology via mast cell activation, verifying the role of SCF in allergic airway inflammation and hyperreactivity.

Novel Role of Transmembrane SCF for Mast Cell Activation and Eotaxin Production in Mast Cell-Fibroblast Interactions

Mast cell activation can be induced by multiple mechanisms, including IgE-, complement-, and stem cell factor (SCF)-mediated pathways. In addition, the interaction of mast cells with particular cell populations, such as fibroblasts, have also demonstrated increased mast cell reactivity. In these studies, we have investigated the role of fibroblast-mast cell interaction for induction of histamine release and chemokine production and the specific role of SCF during this interaction. Primary pulmonary fibroblast cell lines were grown in culture and used throughout these studies. Mast cells were grown in parallel with fibroblasts by incubation of bone marrow cells with SCF and IL-3. During mast cell-fibroblast coculture, increased histamine release could be attenuated either by separation of the cell populations using a Trans-Well setup, which did not allow cellular contact, or by specific anti-SCF Ab. In addition, a significant increase in eotaxin, a potent eosinophil-specific C-C chemokine, was also observed during fibroblast-mast cell interaction. The production of eotaxin was cell contact dependent and could be inhibited using an anti-SCF Ab or specific antisense therapy. SCF was constitutively produced from fibroblasts in its transmembrane form and could be induced by TNF. SCF-coated plates induced significant mast cell-derived eotaxin production, whereas soluble SCF induced little or no eotaxin, suggesting a necessity for receptor cross-linking for activation. These studies indicate that fibroblast-mast cell contact plays a role in exacerbation of histamine release and eotaxin production.

Selective potentiation of IGE-dependent histamine release from rat peritoneal mast cells by stem cell factor

Effect of stem cell factor on histamine release from rat peritoneal mast cells was studied. Although stem cell factor did not evoke histamine release by itself, it clearly potentiated histamine release from sensitized mast cells caused by antigen, anti-IgE and concanavalin A. However, stem cell factor did not affect histamine release caused by compound 48/80, calcium ionophore A23187 and substance P. Although maximum potentiation of antigen-induced histamine release by stem cell factor was accomplished after 1-10 minute-preincubation, potentiation was decline after a longer incubation period. Potentiation of histamine release by phosphatidylserine and non-mast cells in the rat peritoneal cavity was incubation time-dependent. Potentiation by stem cell factor was additive to that by phosphatidylserine or non-mast cells. These results indicate that stem cell factor selectively potentiates IgE-dependent histamine release from rat peritoneal mast cells, and suggest that the mechanism involved is distinct from that of phosphatidylserine or non-mast cells in the rat peritoneal cavity.