Local administration of antisense phosphorothioate oligonucleotides to the c-kit ligand, stem cell factor, suppresses airway inflammation and IL-4 production in a murine model of asthma

Inhibition of Soluble Stem Cell Factor Promotes Intestinal Mucosal Repair

BACKGROUND

Incidences of inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, are escalating worldwide and can be considered a global public health problem. Given that the gold standard approach to IBD therapeutics focuses on reducing the severity of symptoms, there is an urgent unmet need to develop alternative therapies that halt not only inflammatory processes but also promote mucosal repair. Previous studies have identified increased stem cell factor (SCF) expression in inflamed intestinal mucosal tissues. However, the role that SCF plays in mediating intestinal inflammation and repair has not been explored.

METHODS

Changes in the expression of SCF were evaluated in the colonic tissue of healthy mice and during dextran sodium sulfate (DSS)-induced colitis. Furthermore, mucosal wound healing and colitis severity were analyzed in mice subjected to either mechanical biopsy or DSS treatment, respectively, following intestinal epithelial cell-specific deletion of SCF or anti-SCF antibody administration.

RESULTS

We report robust expression of SCF by intestinal epithelial cells during intestinal homeostasis with a switch to immune cell-produced SCF during colitis. Data from mice with intestinal epithelial cell-specific deletion of SCF highlight the importance of immune cell-produced SCF in driving the pathogenesis of colitis. Importantly, antibody-mediated neutralization of total SCF or the specific SCF248 isoform decreased immune cell infiltration and enhanced mucosal wound repair following biopsy-induced colonic injury or DSS-induced colitis.

CONCLUSIONS

These data demonstrate that SCF functions as a pro-inflammatory mediator in mucosal tissues and that specific neutralization of SCF248 could be a viable therapeutic option to reduce intestinal inflammation and promote mucosal wound repair in individuals with IBD.

A TLR7 antagonist restricts interferon-dependent and -independent immunopathology in a mouse model of severe influenza

Cytokine-mediated immune-cell recruitment and inflammation contribute to protection in respiratory virus infection. However, uncontrolled inflammation and the "cytokine storm" are hallmarks of immunopathology in severe infection. Cytokine storm is a broad term for a phenomenon with diverse characteristics and drivers, depending on host genetics, age, and other factors. Taking advantage of the differential use of virus-sensing systems by different cell types, we test the hypothesis that specifically blocking TLR7-dependent, immune cell-produced cytokines reduces influenza-related immunopathology. In a mouse model of severe influenza characterized by a type I interferon (IFN-I)-driven cytokine storm, TLR7 antagonist treatment leaves epithelial antiviral responses unaltered but acts through pDCs and monocytes to reduce IFN-I and other cytokines in the lung, thus ameliorating inflammation and severity. Moreover, even in the absence of IFN-I signaling, TLR7 antagonism reduces inflammation and mortality driven by monocyte-produced chemoattractants and neutrophil recruitment into the infected lung. Hence, TLR7 antagonism reduces diverse types of cytokine storm in severe influenza.

A Potential circRNA-miRNA-mRNA Regulatory Network in Asthmatic Airway Epithelial Cells Identified by Integrated Analysis of Microarray Datasets

Background: Asthma is one of the most prevalent chronic respiratory diseases worldwide. Bronchial epithelial cells play a critical role in the pathogenesis of asthma. Circular RNAs (circRNAs) act as microRNA (miRNA) sponges to regulate downstream gene expression. However, the role of epithelial circRNAs in asthma remains to be investigated. This study aims to explore the potential circRNA-miRNA-messenger RNA (mRNA) regulatory network in asthma by integrated analysis of publicly available microarray datasets.

Methods: Five mRNA microarray datasets derived from bronchial brushing samples from asthma patients and control subjects were downloaded from the Gene Expression Omnibus (GEO) database. The robust rank aggregation (RRA) method was used to identify robust differentially expressed genes (DEGs) in bronchial epithelial cells between asthma patients and controls. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to annotate the functions of the DEGs. Protein-protein interaction (PPI) analysis was performed to identify hub genes. Three miRNA databases (Targetscan, miRDB, and miRWalk) were used to predict the miRNAs which potentially target the hub genes. A miRNA microarray dataset derived from bronchial brushings was used to validate the miRNA-mRNA relationships. Finally, a circRNA-miRNA-mRNA network was constructed via the ENCORI database.

Results: A total of 127 robust DEGs in bronchial epithelial cells between steroid-naïve asthma patients (n = 272) and healthy controls (n = 165) were identified from five mRNA microarray datasets. Enrichment analyses showed that DEGs were mainly enriched in several biological processes related to asthma, including humoral immune response, salivary secretion, and IL-17 signaling pathway. Nineteen hub genes were identified and were used to construct a potential epithelial circRNA-miRNA-mRNA network. The top 10 competing endogenous RNAs were hsa_circ_0001585, hsa_circ_0078031, hsa_circ_0000552, hsa-miR-30a-3p, hsa-miR-30d-3p, KIT, CD69, ADRA2A, BPIFA1, and GGH.

Conclusion: Our study reveals a potential role for epithelial circRNA-miRNA-mRNA network in the pathogenesis of asthma.

Effect of roflumilast on airway remodelling in a murine model of chronic asthma

BACKGROUND

Airway remodelling is associated with irreversible, or partially reversible, airflow obstruction and ultimately unresponsiveness to asthma therapies such as corticosteroids. Roflumilast is a selective phosphodiesterase-4 inhibitor that has an anti-inflammatory effect in chronic obstructive pulmonary disease (COPD).

OBJECTIVE

The objective of this study was to study the effect of roflumilast on airway inflammation and remodelling in a murine model of chronic asthma.

METHODS

BALB/c mice sensitized to ovalbumin (OVA) were chronically exposed to intranasal OVA administration twice a week for additional 3 months. Roflumilast was administered orally during the intranasal OVA challenge. A lung fibroblast cell line was used in the proliferation assay.

RESULTS

Compared with control mice, mice chronically exposed to OVA developed eosinophilic airway inflammation, airway hyper-responsiveness (AHR), and exhibited features of airway remodelling. Administration of roflumilast significantly inhibited airway inflammation and AHR. Roflumilast also significantly decreased goblet cell hyperplasia and pulmonary fibrosis, which are parameters of airway remodelling. The levels of interleukin (IL)-4, IL-5, and IL-13 in the bronchoalveolar lavage (BAL) fluids were significantly lower in the roflumilast group. In vitro, roflumilast significantly inhibited stem cell factor (SCF)-induced cell proliferation of fibroblasts. The SCF concentration and mRNA expression in a murine model also significantly decreased with roflumilast treatment.

CONCLUSIONS

These results suggest that the administration of roflumilast regulates airway inflammation, AHR, and airway remodelling in a model of chronic asthma. The beneficial effects from roflumilast may be related to the SCF/c-kit pathway.

Association of stem cell factor gene expression with severity and atopic state in patients with bronchial asthma

Background

Bronchial asthma is a chronic inflammatory and remodeling disorder of the airways, in which many cells, cellular elements, and cytokines play important roles. Stem cell factor (SCF) may contribute to the inflammatory changes occurring in asthma. We aimed to show the expression of SCF gene in patients with asthma as a means of diagnosis and its association with severity and atopic state in these patients.

Methods

This study was carried out on 80 subjects, 50 asthmatic patients and 30 age and gender matched healthy control persons. They were subjected to full history taking, general and local chest examination, spirometric measurements (pre and post broncodilators) using a spirometer, serum IgE, and real time PCR for assessment of SCF mRNA expression.

Results

This study showed significant difference between the studied groups regarding pulmonary function tests (P < 0.001). Asthmatic patients had significant higher SCF expression compared to control (P < 0.001), also atopic patients vs non atopic (P = 0.03) and severe asthmatic patients vs mild ones (P < 0.001). SCF expression at cut off point (0.528) is sufficient to discriminate asthmatic patients from control while at cut off point (1.84) for discrimination of atopic patients from non-atopic patients and at cut off point (1.395) for discrimination of severe asthmatic patients from mild ones. A significant negative correlation between SCF expression and inhaled steroid while significant positive correlation with serum IgE was found.

Conclusion

Measuring SCF mRNA expression can be used as an efficient marker for evaluation of atopy and detection of severity of bronchial 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.

Towards Fluorescence In Vivo Hybridization (FIVH) Detection of H. pylori in Gastric Mucosa Using Advanced LNA Probes

In recent years, there have been several attempts to improve the diagnosis of infection caused by Helicobacter pylori. Fluorescence in situ hybridization (FISH) is a commonly used technique to detect H. pylori infection but it requires biopsies from the stomach. Thus, the development of an in vivo FISH-based method (FIVH) that directly detects and allows the visualization of the bacterium within the human body would significantly reduce the time of analysis, allowing the diagnosis to be performed during endoscopy. In a previous study we designed and synthesized a phosphorothioate locked nucleic acid (LNA)/ 2’ O-methyl RNA (2’OMe) probe using standard phosphoramidite chemistry and FISH hybridization was then successfully performed both on adhered and suspended bacteria at 37°C. In this work we simplified, shortened and adapted FISH to work at gastric pH values, meaning that the hybridization step now takes only 30 minutes and, in addition to the buffer, uses only urea and probe at non-toxic concentrations. Importantly, the sensitivity and specificity of the FISH method was maintained in the range of conditions tested, even at low stringency conditions (e.g., low pH). In conclusion, this methodology is a promising approach that might be used in vivo in the future in combination with a confocal laser endomicroscope for H. pylori visualization.

The activating protein 1 transcription factor basic leucine zipper transcription factor, ATF-like (BATF), regulates lymphocyte- and mast cell-driven immune responses in the setting of allergic asthma

BACKGROUND

Mice without the basic leucine zipper transcription factor, ATF-like (BATF) gene (Batf(-/-)) lack TH17 and follicular helper T cells, which demonstrates that Batf is a transcription factor important for T- and B-cell differentiation.

OBJECTIVE

In this study we examined whether BATF expression would influence allergic asthma.

METHODS

In a cohort of preschool control children and children with asthma, we analyzed BATF mRNA expression using real-time PCR in PBMCs. In a murine model of allergic asthma, we analyzed differences in this allergic disease between wild-type, Batf transgenic, and Batf(-/-) mice.

RESULTS

In the absence of corticosteroid treatment, children with recurrent asthma have a significant increase in BATF mRNA expression in their PBMCs. Batf(-/-) mice display a significant reduction in the pathophysiologic responses seen in asthmatic wild-type littermates. Moreover, we discovered a decrease in IL-3 production and IL-3-dependent mast cell development in Batf(-/-) mice. By contrast, IFN-γ was induced in lung CD4(+) and CD8(+) T cells. Intranasal delivery of anti-IFN-γ antibodies induced airway hyperresponsiveness and inflammation in wild-type but not in Batf(-/-) mice. Transgenic overexpression of Batf under the control of the CD2 promoter/enhancer augmented lung inflammation and IgE levels in the setting of experimental asthma.

CONCLUSION

BATF is increased in non-steroid-treated asthmatic children. Targeting BATF expression resulted in amelioration of the pathophysiologic responses seen in children with allergic asthma, and BATF has emerged as a novel target for antiasthma interventions.

Microprecision delivery of oligonucleotides in a 3D tissue model and its characterization using optical imaging

Despite significant potential of oligonucleotides (ONs) for therapeutic and diagnostic applications, rapid and widespread intracellular delivery of ONs in cells situated in tissues such as skin, head and neck cavity, and eye has not been achieved. This study was aimed at evaluating the synergistic combination of microneedle (MN) arrays and biochemical approaches for localized intratissue delivery of oligonucleotides in living cells in 3D tissue models. This synergistic combination was based on the ability of MNs to precisely deliver ONs into tissues to achieve widespread distribution, and the ability of biochemical agents (streptolysin O (SLO) and cholesterol conjugation to ONs) to enhance intracellular ON delivery. The results of this study demonstrate that ON probes were uniformly coated on microneedle arrays and were efficiently released from the microneedle surface upon insertion in tissue phantoms. Co-insertion of microneedles coated with ONs and SLO into 3D tissue models resulted in delivery of ONs into both the cytoplasm and nucleus of cells. Within a short incubation time (35 min), ONs were observed both laterally and along the depth of a 3D tissue up to a distance of 500 μm from the microneedle insertion point. Similar widespread intratissue distribution of ONs was achieved upon delivery of ON-cholesterol conjugates. Uniformity of ON delivery in tissues improved with longer incubation times (24 h) postinsertion. Using cholesterol-conjugated ONs, delivery of ON probes was limited to the cytoplasm of cells within a tissue. Finally, delivery of cholesterol-conjugated anti-GFP ON resulted in reduction of GFP expression in HeLa cells. In summary, the results of this study provide a novel approach for efficient intracellular delivery of ONs in tissues.

Stem Cell Factor Receptor/c-Kit: From Basic Science to Clinical Implications

Stem cell factor (SCF) is a dimeric molecule that exerts its biological functions by binding to and activating the receptor tyrosine kinase c-Kit. Activation of c-Kit leads to its autophosphorylation and initiation of signal transduction. Signaling proteins are recruited to activated c-Kit by certain interaction domains (e.g., SH2 and PTB) that specifically bind to phosphorylated tyrosine residues in the intracellular region of c-Kit. Activation of c-Kit signaling has been found to mediate cell survival, migration, and proliferation depending on the cell type. Signaling from c-Kit is crucial for normal hematopoiesis, pigmentation, fertility, gut movement, and some aspects of the nervous system. Deregulated c-Kit kinase activity has been found in a number of pathological conditions, including cancer and allergy. The observation that gain-of-function mutations in c-Kit can promote tumor formation and progression has stimulated the development of therapeutics agents targeting this receptor, e.g., the clinically used inhibitor imatinib mesylate. Also other clinically used multiselective kinase inhibitors, for instance, sorafenib and sunitinib, have c-Kit included in their range of targets. Furthermore, loss-of-function mutations in c-Kit have been observed and shown to give rise to a condition called piebaldism. This review provides a summary of our current knowledge regarding structural and functional aspects of c-Kit signaling both under normal and pathological conditions, as well as advances in the development of low-molecular-weight molecules inhibiting c-Kit function.

Defective eosinophil hematopoiesis ex vivo in inbred Rocky Mountain White (IRW) mice

We examine the proliferation and differentiation of bone marrow (BM) progenitors from inbred Rocky Mountain White (IRW) mice, a strain used primarily for retrovirus infection studies. In contrast to findings with BALB/c and C57BL/6 strains, IRW BM cells cannot proliferate or generate pure eosinophil cultures ex vivo in response to a defined cytokine regimen. Analysis of IRW BM at baseline was unremarkable, including 0.08 ± 0.03% Lin(-)Sca-1(+)c-kit(+) (LSK) hematopoietic stem cells and 5.2 ± 0.3% eosinophils; the percentage of eosinophil progenitors (EoPs; Lin(-)Sca-1(-)c-kit(+)CD34(+)IL-5Rα(+)) was similar in all three mouse strains. Transcripts encoding GM-CSFRα and the IL-3/IL-5/GM-CSF common β chain were detected at equivalent levels in IRW and BALB/c BM, whereas expression of transcripts encoding IL-5Rα, IL-3Rα, and GATA-2 was diminished in IRW BM compared with BALB/c. Expression of membrane-bound IL-5Rα and intracellular STAT5 proteins was also diminished in IRW BM cells. Diminished expression of transcripts encoding IL-5Rα and GATA-2 and immunoreactive STAT5 in IRW BM persisted after 4 days in culture, along with diminished expression of GATA-1. Western blot revealed that cells from IRW BM overexpress nonsignaling soluble IL-5Rα protein. Interestingly, OVA sensitization and challenge resulted in BM and airway eosinophilia in IRW mice; however, the responses were significantly blunted. These results suggest that IRW mice have diminished capacity to generate eosinophils in culture and in vivo, likely as a result of diminished signaling via IL-5Rα.

Mast cell: insight into remodeling a tumor microenvironment

Mast cells are of paramount importance to allergies, pathogen immune responses during infections, and angiogenesis, as well as innate and adaptive immune regulations. Beyond all these roles, mast cells are now more and more being recognized as modulators of tumor microenvironment. Notwithstanding mounting evidences of mast cell accumulation in tumors, their exact role in tumor microenvironment is still incompletely understood. In this review, we discuss the significant role of mast cells in the remodeling of tumor microenvironment by either releasing various factors after activation or interacting with other cells within tumor and, as a result, the possible role of mast cell in cancer invasion and metastasis. We also discuss recent findings that mast cells actively release microparticles, which account for the transfer of membrane-type receptor signal and regulatory molecules such as microRNAs to tumor cells and immune cells. These findings on mast cells provide further insights into the complexity of tumor microenvironment remodeling.

Pulmonary IL-17E (IL-25) production and IL-17RB+ myeloid cell-derived Th2 cytokine production are dependent upon stem cell factor-induced responses during chronic allergic pulmonary disease

In the present studies local neutralization of allergen-induced stem cell factor (SCF) leads to decreased production of Th2 cytokines, a reduction in inflammation, allergen-specific serum IgE/IgG1, and attenuation of severe asthma-like responses. The local blockade of pulmonary SCF also resulted in a significant reduction of IL-17E (IL-25). Sorted cell populations from the lung indicated that IL-25 was produced from c-kit(+) cells, whereas Th2 cytokine production was primarily from c-kit(-) cell populations. SCF stimulated c-kit(+) eosinophils produced IL-25, whereas bone marrow-derived mast cells did not. Using 4get mice that contain a IL-4-IRES-eGFP that when transcribed coexpress GFP and IL-4, our studies identified cells that comprised a CD11b(+), GR1(+), Ly6C(+/-), c-kit(-), CD4(-), CD11c(-), MHC class II(low) cell population as a source of IL-4 in the lung after chronic allergen challenge. In the bone marrow a similar cell was identified with approximately a third of the IL-4(+) cells also expressing c-kit(+). The pulmonary and bone marrow IL-4(+) cell populations were significantly reduced upon local pulmonary anti-SCF treatment. Subsequently, when IL-25R was examined during the chronic allergen responses the expression was found on the IL-4(+) myeloid cell population that expressed CD11b(+)GR1(+). Interestingly, the IL-25R(+) cells in the bone marrow were also all CD11b(+)GR1(+), similar to the lung cells, but they were also all c-kit(+), potentially suggesting a maturation of the bone marrow cell once it enters the lung and/or is stimulated by SCF. Overall, these studies suggest a complex relationship between SCF, bone marrow-derived IL-25-responsive myeloid cells, Th2 cytokines, and chronic allergic disease.

Role of stem cell factor and bone marrow-derived fibroblasts in airway remodeling

Recent evidence suggests that bone marrow-derived fibroblasts are involved in airway remodeling in asthma, but the role and mechanism of recruitment of these fibroblasts remains unclear. Stem cell factor (SCF), a key factor in the propagation of hematopoietic stem cells, is important in the process of airway remodeling as well. To test the hypothesis that SCF is involved in the recruitment and differentiation of bone marrow-derived progenitor cells, GFP-bone marrow chimeric mice were created. These mice were then sensitized and chronically challenged with cockroach antigen to induce chronic airway disease. Fluorescence microscopy revealed an influx of significant numbers of GFP-expressing fibroblasts in the airways of these mice, which was confirmed by flow cytometric analysis of cells co-expressing both GFP and collagen I. These cells preferentially expressed c-kit, interleukin-31 receptor, and telomerase reverse transcriptase when compared with control lung-derived fibroblasts. Interestingly, SCF stimulated interleukin-31 receptor expression in bone marrow cells, whereas interleukin-31 strongly induced telomerase reverse transcriptase expression in fibroblasts. Treatment with neutralizing antibodies to SCF significantly reduced airway remodeling and suppressed the recruitment of these bone marrow-derived cells to the lung. Thus SCF in conjunction with interleukin-31 may play a significant role in airway remodeling by promoting the recruitment of bone marrow-derived fibroblast precursors into the lung with the capacity to promote lung myofibroblast differentiation.

Eosinophil activation of fibroblasts from chronic allergen-induced disease utilizes stem cell factor for phenotypic changes

In the present studies the role of stem cell factor (SCF) in mediating eosinophil and fibroblast activation during their interaction was investigated. SCF was significantly higher in fibroblasts grown from lungs of chronic allergen-challenged mice compared to fibroblasts grown from normal mice. When eosinophils were layered onto fibroblasts from allergic mice, a significant increase in SCF was detected compared to fibroblasts from nonallergic mice. The interaction of fibroblasts with eosinophils also increased the production of asthma-associated chemokines, CCL5 and CCL6, was dependent on cell-to-cell interaction, and was observed only with fibroblasts derived from lungs of chronic allergen-challenged mice and not from those derived from unchallenged normal mice. Chemokine production was significantly decreased when anti-SCF antibodies were added during eosinophil-fibroblast interaction. The interaction of fibroblasts from chronic allergen-challenged mice with eosinophils also increased alpha-smooth muscle cell actin and procollagen I expression as well as induced transforming growth factor-beta. The changes in myofibroblast activation were dependent on SCF-mediated pathways because anti-SCF antibody treatment reduced the expression of all three of these latter fibrosis-associated markers. Thus, our data suggest that SCF mediates an important activation pathway for fibroblasts during chronic allergic responses on interaction with recruited eosinophils and suggest a potential mechanism of airway remodeling during chronic disease.

Kit ligand 2 promotes murine oocyte growth in vitro

Oocyte-granulosa cell communication, mediated by paracrine factors, is essential for oocyte development. Kit ligand (KITL) is expressed in granulosa cells as soluble (KITL1) or membrane-associated (KITL2) proteins. However, the relative biopotency of each isoform during oocyte development is unknown. Our initial results showed that Kitl2 was down-regulated in cultured granulosa cells. To determine the effect of the two isoforms of KITL on oocyte growth, Kitl-deficient fibroblasts were transfected with constructs expressing either KITL1 or KITL2, and growing oocytes were isolated from 12-day-old mice and cultured on the transfected fibroblasts for 2 days. At the end of culture, oocyte diameters were measured, the incidence of spontaneous germinal vesicle breakdown (GVBD) was noted, and oocytes were analyzed for KIT receptor expression. Oocyte growth occurred only in the presence of the KITL2-producing fibroblasts, and suppression of KITL2 expression impaired oocyte growth. Up-regulation of KIT expression occurred in the presence of KITL2 but not KITL1. The presence of KITL2 inhibited spontaneous GVBD. Meiosis inhibitors did not attenuate the GVBD that occurred in the absence of KITL2, suggesting that this process reflects oocyte degeneration rather than meiotic progression. These results indicate that KITL2 is the principal KITL isoform required for oocyte growth and survival in vitro.

A method to enable the investigation of murine bronchial immune cells, their cytokines and mediators

Innovative therapies for severe lung diseases (such as allergic and chronic asthma, chronic obstructive pulmonary disease or any type of lung cancer) require a detailed understanding of the cellular and immune processes in the lung. This protocol details a method to obtain the immune cells of the bronchi as well as the cytokines and mediators produced by these cells for further investigation. The broncho-alveolar lavage fluid (BALF) is taken by injecting physiological solution through the tracheal tube into the murine airways and carefully regained by winding up the connected syringe. After centrifugation, the resulting BALF supernatant can be stored for detection of cytokines or other mediators by enzyme-linked immunosorbent assay or other methods; the resuspended cell pellet can also be used for flow cytometric analyses, to check cell viability and the level of apoptosis, as well as other applications. In addition, CD4+ T cells isolated from wild-type and genetically modified mice alone or along with other immunologically important cells such as T regulatory cells, which can be used to reconstitute immunodeficient mice, may be retrieved from the airways with this method. This protocol can be completed within 35 min.

Mast cell, a promising therapeutic target in tubulointerstitial fibrosis

Tubulointerstitial fibrosis is a final common pathway to the eventual structural desolation of kidneys. However, the mechanism involved in this phenomenon is still poorly understood, and current therapies are ineffective or only marginally effective. Mast cell has a variety of physiological and pathological functions through the production of heparin, histamine, neutrophil chemoattractants, immunoregulatory cytokines, and mast cell-specific serine proteases tryptase and chymase. The survival and proliferation of mast cell are dependent upon stem cell factor. Presently, mast cells are known to participate in the pathogenesis of tubulointerstitial fibrosis in many kidney diseases. Several therapeutic approaches to inhibit mast cell activation have already demonstrated some clinical utility in tissue fibrosis or inflammatory diseases such as the use of mast cell stabilizers, inhibitors of tryptase or chymase, blockade of stem cell factor and anti-IgE therapy. We hypothesize that mast cell has a significant role in the progression of tubulointerstitial fibrosis, thus the treatment strategies based on mast cell appear to be promising in these conditions. Development of these novel therapeutic approaches will enable us to target any types of renal disease.

The future of antisense oligonucleotides in the treatment of respiratory diseases

Antisense oligonucleotides (ASO) are short synthetic DNA molecules designed to inhibit translation of a targeted gene to protein via interaction with messenger RNA. More recently, small interfering (si)RNA have been developed as potent tools to specifically inhibit gene expression. ASO directed against signaling molecules, cytokine receptors, and transcription factors involved in allergic immune and inflammatory responses, have been applied in experimental models of asthma and demonstrate potential as therapeutics. Several ASO-based drugs directed against oncogenes have been developed for therapy of lung cancer, and some have recently reached clinical trials. ASO and siRNA to respiratory syncytial virus infection have demonstrated good potential to treat this condition, particularly in combination with an antiviral drug. Although ASO-based therapeutics are promising for lung diseases, issues of specificity, identification of correct molecular targets, delivery and carrier systems, as well as potential adverse effects must be carefully evaluated before clinical application.

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.

Inhibition of SCF attenuates peribronchial remodeling in chronic cockroach allergen-induced asthma

The progression and severity of chronic asthma likely depends upon the intensity of the damage and remodeling of the tissue. We have developed a chronic model of allergic asthma using multiple cockroach allergen challenges. Using this clinically relevant allergen we have established significant peribronchial fibrosis and mucus overproduction. These remodeling events are accompanied by intense peribronchial inflammation, including lymphocytes and eosinophils. A cytokine that has been identified as having a prominent role in short-term allergic events, stem cell factor (SCF), appears to have a significant role in this late-stage process. Using our polyclonal antibody specific for SCF administered into the airways of mice during the final allergen challenges, we find a significant effect on the chronic peribronchial allergen-induced fibrotic remodeling. This was characterized by reduced inflammation, especially eosinophils, as well as reduced hydroxyproline levels in anti-SCF compared to control antibody-treated animals. In addition, when we examined chemokines associated with the chronic disease and neutralized SCF in vivo we observed a corresponding decrease in CCL6 and CCL17. Using an inhibitor, imatinib mesylate, that blocks SCF/c-kit-associated RTK, we find similar results as with anti-SCF for attenuating AHR and fibrotic changes, suggesting that a potential clinical treatment for chronic asthma already exists related to this pathway. These results further support the potential use of SCF/c-kit inhibition for targeting chronic severe asthmatic responses.

Polyethylenimine-based antisense oligodeoxynucleotides of IL-4 suppress the production of IL-4 in a murine model of airway inflammation

BACKGROUND

Interleukin-4 (IL-4) plays a crucial role as an inflammatory mediator in allergic asthma via inducing Th2 inflammation and IgE synthesis. To develop an effective therapeutic agent which specifically inhibits production of IL-4, antisense oligodeoxynucleotides (AS-ODNs) against murine IL-4 mRNA were generated and complexed with polyethylenimine (PEI) to improve intracellular delivery.

METHODS

AS-ODNs were generated against the translation initiation region of murine IL-4 mRNA, and complexed with linear PEI. In vitro efficacy of AS-ODNs/PEI complexes was tested by measuring IL-4 production in the D10.G4.1 cell line, and cytotoxicity was tested by XTT assay. Physicochemical properties of polyplexes were examined using atomic force microscopy (AFM) and DNase I protection assay. In vivo effects of IL-4 AS-ODNs/PEI complexes were tested in a murine model of airway inflammation. IL-4 concentrations in the bronchoalveolar lavage (BAL) fluid and circulating IgE levels were measured by ELISA, and histological analysis of lung tissues was performed.

RESULTS

IL-4 AS-ODNs/PEI complexes were spheres with an average diameter of 98 nm and resistant to DNase I-mediated degradation. IL-4 AS-ODNs/PEI complexes showed up to 35% inhibition of IL-4 production in D10.G4.1 cells without causing any toxicity, while naked ODNs gave less than 1% reduction. Furthermore, IL-4 AS-ODNs/PEI complexes were effective in suppressing secretion of IL-4 (up to 30% reduction) in the BAL fluid in an ovalbumin-sensitized murine model of airway inflammation. Circulating IgE levels were decreased, and airway inflammation was alleviated by treatment with IL-4 AS-ODNs polyplexes.

CONCLUSIONS

These data demonstrate that complexation of IL-4 AS-ODNs with PEI provides a potential therapeutic tool in controlling inflammation associated with allergic asthma, and further presents an opportunity to the development of clinical therapy based on combination of multiple AS-ODNs of cytokines and/or signaling effectors involved in Th2 inflammation and eosinophilia.

Antisense- and RNA interference-based therapeutic strategies in allergy

Modern therapeutic methods for manipulation of gene expression in allergic diseases have been receiving increased attention in the emerging era of functional genomics. With the growing application of gene silencing technologies, pharmacological modulation of translation represents a great advance in molecular therapy for allergy. Several strategies for sequence-specific post-transcriptional inhibition of gene expression can be distinguished: antisense oligonucleotides (AS-ONs), ribozymes (RZs), DNA enzymes (DNAzymes), and RNA interference (RNAi) triggered by small interfering RNAs (siRNAs). Potential anti-mRNA drugs in asthma and other allergic disorders may be targeted to cell surface receptors (adenosine A1 receptor, high-affinity receptor Fc-epsilon RI-alpha, cytokine receptors), adhesion molecules and ligands (ICAM-1, VLA-4), ion channels (calcium-dependent chloride channel-1), cytokines and related factors (IL-4, IL-5, IL-13, SCF, TNF-alpha, TGF-beta1), intracellular signal transduction molecules, such as tyrosine-protein kinases (Syk, Lyn, Btk), serine/ threonine-protein kinases (p38 alpha MAPkinase, Raf-1), non-kinase signaling proteins (RasGRP4), and transcription factors involved in Th2 differentiation and allergic inflammation (STAT-6, GATA-3, NF-kappaB). The challenge to scientists is to determine which of the candidate targets warrants investment of time and resources. New-generation respirable AS-ONs, external guide sequence ribozymes, and RNA interference-based therapies have the potential to satisfy unmet needs in allergy treatment, acting at a more proximal level to a key etiopathogenetic molecular process, represented by abnormal expression of genes. Moreover, antisense and siRNA technologies imply a more rational design of new drugs for allergy.

Stem cell factor and its receptor c-Kit as targets for inflammatory diseases

Stem cell factor (SCF), the ligand of the c-Kit receptor, is expressed by various structural and inflammatory cells in the airways. Binding of SCF to c-Kit leads to activation of multiple pathways, including phosphatidyl-inositol-3 (PI3)-kinase, phospholipase C (PLC)-gamma, Src kinase, Janus kinase (JAK)/Signal Transducers and Activators of Transcription (STAT) and mitogen activated protein (MAP) kinase pathways. SCF is an important growth factor for mast cells, promoting their generation from CD34+ progenitor cells. In vitro, SCF induces mast cells survival, adhesion to extracellular matrix and degranulation, leading to expression and release of histamine, pro-inflammatory cytokines and chemokines. SCF also induces eosinophil adhesion and activation. SCF is upregulated in inflammatory conditions both in vitro and in vivo, in human and mice. Inhibition of the SCF/c-Kit pathway leads to significant decrease of histamine levels, mast cells and eosinophil infiltration, interleukin (IL)-4 production and airway hyperresponsiveness in vivo. Taken together, these data suggest that SCF/c-Kit may be a potential therapeutic target for the control of mast cell and eosinophil number and activation in inflammatory diseases.

Stem cell factor stimulates the chemotaxis, integrin upregulation, and survival of human basophils

BACKGROUND

Little is known about the mechanisms that regulate the selective recruitment of basophils to sites of allergic inflammation.

OBJECTIVE

Here we examine the role of stem cell factor (SCF) in the regulation of basophil function.

METHODS

Human basophils were isolated from peripheral blood, and their migration was investigated in chemotaxis assays. Apoptosis was detected by means of annexin V and propidium iodide staining. The expression of cell-surface molecules was measured by means of flow cytometry.

RESULTS

SCF amplified the chemotactic responsiveness of human peripheral blood basophils to the chemoattractants eotaxin, monocyte chemotactic protein 2 and macrophage inflammatory protein 1alpha, and C5a, without being chemotactic or chemokinetic by itself. SCF synergized with chemoattractants in causing basophil upregulation of the integrin CD11b, and this effect was inhibited by a c-kit antibody, the tyrosine kinase inhibitor imatinib mesylate (STI-571), and a phosphatidylinositol 3 kinase inhibitor but not by inhibitors of p38 mitogen-activated protein kinase or mitogen-activated protein kinase/extracellular signal-regulated kinase kinase. Basophils bound fluorescence-labeled SCF and expressed its receptor, c-kit, which was markedly upregulated in culture for 24 to 48 hours in the presence of IL-3. Moreover, SCF prolonged basophil survival in concert with IL-3 by delaying apoptosis. These effects of SCF were selective for basophils because chemotaxis and CD11b upregulation of eosinophils or neutrophils were unchanged.

CONCLUSION

SCF might be an important selective modulator of basophil function through a phosphatidylinositol 3 kinase-dependent pathway.

Asthmatic changes in mice lacking T-bet are mediated by IL-13

Mice with a targeted deletion of the T-bet gene exhibit spontaneous airway hyperresponsiveness (AHR), airway inflammation, enhanced recovery of T(h)2 cytokines from bronchoalveolar lavage fluid, sub-epithelial collagen deposition and myofibroblast transformation. Here we analyze the mechanisms responsible for the chronic airway remodeling observed in these mice. CD4+ T cells isolated from the lung of T-bet-deficient mice were spontaneously activated CD44(high)CD69(high) memory T cells, with a typical T(h)2 cytokine profile. Neutralization of IL-13 but not IL-4 resulted in amelioration of AHR in airways of mice lacking T-bet. IL-13 blockade also led to reduced eosinophilia and decreased vimentin, transforming growth factor beta (TGF-beta) and alpha smooth muscle actin (alphaSMA) levels. T-bet(-/-) lung fibroblasts proliferated very rapidly and released increased amounts of TGF-beta. Interestingly, neutralization of TGF-beta ameliorated aspects of the chronic airway remodeling phenotype but did not reduce AHR. These data highlight a T-bet-directed function for IL-13 in controlling lung remodeling that is both dependent on and independent of its interaction with TGF-beta in the asthmatic airway.

Sense and antisense: therapeutic potential of oligonucleotides and interference RNA in asthma and allergic disorders

Advances in our understanding of asthma pathogenesis and delineation of the human genome project are yielding novel candidate targets for therapeutic intervention. In parallel with target identification, the past decade has produced novel approaches to normalizing expression genes that are upregulated in disease processes. Single-stranded antisense oligonucleotides and double-stranded short-interfering RNA molecules, which specifically mark target transcripts for degradation, are being investigated for their ability to modulate disease processes. In both cases, the targets are RNA transcripts, and not protein; therefore, all types of molecular gene products can be inhibited, including historically undrugable species such as transcription factors and phosphatases. Various RNA interference strategies have been successfully tested in vitro and in animal models of disease, and data is beginning to accumulate from human clinical trials.EPI-2010, a 21-mer phosphorothioate against the adenosine A1 receptor promoter region,has completed preclinical pharmacology testing and its initial clinical trials. The rationale for EPI-2010 is that overactivity of the adenosine signaling pathway in asthmatic lungs contributes to airway inflammation and hyperresponsiveness. Phase I/IIa clinical trials have shown EPI-2010 to be safe and well-tolerated, with modest indications of efficacy in patients with mild asthma.

The expression of stem cell factor and c-kit receptor in human asthmatic airways

BACKGROUND

Asthmatic airways are characterized by infiltration with a variety of inflammatory cells such as mast cells and eosinophils. Stem cell factor (SCF) is an important activating and chemotactic factor for both mast cells and eosinophils. In addition, it is a critical growth and differentiation factor for mast cells.

OBJECTIVES

To investigate the contribution of SCF to the pathogenesis of asthma, we examined the expression of SCF and its receptor c-kit in bronchial biopsies and bronchoalveolar lavage (BAL) specimens obtained from asthmatic subjects (n=13) and non-asthmatic control subjects (n=10).

METHODS

SCF and c-kit were detected by in situ hybridization (ISH) and immunocytochemistry (ICC). In order to phenotype the cells expressing SCF and c-kit in asthmatic tissue and BAL cells, combined ISH and ICC were also performed.

RESULTS

There was a significant difference (P<0.001) in the SCF mRNA expression in asthmatic airway epithelium (70.38+/-12.33% positive cells) compared with controls (12.7+/-17.21% positive cells). There was also a significant difference in subepithelial SCF-mRNA expression, being higher in asthmatics (P<0.001). A significant difference was also found in c-kit receptor mRNA expression in asthmatic biopsies both in epithelium (P<0.001) and subepithelium (P<0.05) compared with controls. ICC results were consistent with the ISH for both SCF and c-kit receptor from asthmatics and controls. The SCF and c-kit receptor mRNA and immunoreactivity in cells recovered from bronchial washing were also significantly higher in asthmatics compared with controls (P<0.05). While SCF expression was localized predominantly in the epithelial layer in bronchial biopsy tissues, alveolar macrophages were found to be the major source of SCF in bronchial washing from asthmatic subjects.

CONCLUSION

The results of this study demonstrate the increased expression of SCF and its receptor, c-kit within human asthmatic airways, which suggests an important role of this cytokine in the pathophysiology of asthma.

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.

Respirable antisense oligonucleotides: a new, third drug class targeting respiratory disease

PURPOSE OF REVIEW

To describe the potential of a new class of respiratory drugs, respirable antisense oligonucleotides.

RECENT FINDINGS

The first respirable antisense oligonucleotide, EPI-2010, has now reached clinical trials. It has shown intriguing initial indications of efficacy and the potential to be the first once-per-week asthma preventative. Respirable antisense oligonucleotides are capable of addressing targets that have proven to be intractable to traditional 'small molecule' approaches, and against which newer monoclonal antibody strategies may also not be optimal. Respirable antisense oligonucleotides functionally, but not genetically, ablate gene expression by blocking the template function of target respiratory messenger RNAs by as yet incompletely defined mechanisms. They do so with an avidity and specificity which can be several orders of magnitude greater than those shown by small molecule antagonists for their protein targets. The target properties of respiratory messenger RNAs are strikingly different from those of respiratory proteins, enabling respirable antisense oligonucleotides to offer the potential of longer duration of effect, increased specificity of effect, and lack of systemic side effects compared with either traditional small molecule protein antagonists or monoclonal antibodies.

SUMMARY

Respirable antisense oligonucleotides represent a new, third class of respiratory drugs with the potential to extend the range of therapeutic responses to otherwise intractable respiratory targets, and to address precedented targets with the possibility of improving on such features as safety and durability of response.

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.

New asthma drugs acting on gene expression

New asthma drugs acting on transcription are transcription factor agonists (dissociated steroids, peroxisome proliferator-activated receptor gamma agonists), transcription factor inhibitors (NF-kappaB / AP-1 inhibitors, STAT6 inhibitors), inhibitors of protein kinases acting on transcription factors (p38 MAP kinase inhibitors), and chromatin modifying agents. Pharmacological approach of translation in asthma includes therapeutic ribozymes and antisense oligonucleotides targeting receptors (adenosine A1 receptor, alpha chain of IL-5 receptor, common beta chain of IL-3/IL-5/GM-CSF receptor), cytokines (IL-4, IL-5, SCF), signal transduction molecules (Syk, Lyn), transcription factors (STAT-6, GATA-3). Some of these drugs acting on gene expression have the potential to improve therapeutic benefits compared with traditional drugs.

Functional expression of neurokinin 1 receptors on mast cells induced by IL-4 and stem cell factor

It is widely accepted that neurokinin 1 (NK(1)) receptors are not generally expressed on mast cells but little is known about their expression in inflammation. The present study shows expression of NK(1) receptors on bone marrow-derived mast cells (BMMC) under the influence of IL-4 or stem cell factor (SCF). Highest expression was found when both cytokines are present. Six days of coculture with the cytokines IL-4 and SCF showed significant expression of NK(1) receptors (NK(1) receptor(+)/c-kit(+) BMMC; control: 7%, IL-4/SCF: 16%), while 12 days of cytokine coculture increased this expression to 37% positive cells. A longer coculture with IL-4 and SCF did not give an additional effect. Increased expression in IL-4/SCF-treated BMMC was further confirmed using Western blot analysis. Next, we demonstrated the functional relevance of NK(1) receptor expression for mast cell activation, resulting in an enhanced degranulation upon stimulation by substance P. BMMC activation was significantly diminished by the NK(1) receptor antagonist RP67580 (10 micro M) when stimulated with low concentrations of substance P. The inactive enantiomer RP65681 had no effect. In addition, BMMC cultured from bone marrow of NK(1) receptor knockout mice showed significantly decreased exocytosis to low concentrations of substance P. The present study clearly shows that NK(1) receptor-induced activation contributes significantly at low physiological substance P concentrations (<100 micro M). In conclusion, BMMC were shown to express NK(1) receptors upon IL-4/SCF coculture. This expression of NK(1) receptors has been demonstrated to be of functional relevance and leads to an increase in the sensitivity of BMMC to substance P.

The role of Kit-ligand in melanocyte development and epidermal homeostasis

Kit-ligand (Kitl) also known as steel factor, stem cell factor and mast cell growth factor plays a crucial role in the development and maintenance of the melanocyte lineage in adult skin. Kitl exerts permanent survival, proliferation and migration functions in Kit receptor-expressing melanocytes. A comprehensive overview over the differential roles of Kitl in melanocyte development and homeostasis is provided. I discuss species-specific differences of the Kitl/Kit signalling system, regulation at the transcriptional level and also covering the regulation of cell surface Kitl presentation by cytoplasmic targeting sequences. In addition, recent studies evoked the importance of Kitl misexpression in some hyperpigmented lesions that may open the avenue for Kitl-dependent treatment of pathological skin conditions.

Asthma: future directions

Asthma continues to be a significant health care problem, as reflected by the increasing rise in disease morbidity and mortality. Because steroids are relatively safe, clinically effective, and easy to administer, they remain the gold standard of treatment. After many decades of use, however, it is apparent that inhaled corticosteroids have failed to halt the progression of the asthma epidemic. Newer, more effective drugs are being developed to combat this disease, and the interest in developing new medications to treat allergic disease and asthma has increased exponentially. The financial burden of asthma has also been a significant motivating factor in the development of new medications. It is estimated that in 1998 the total cost of asthma on society was $11 billion [175]. This consideration has further intensified the quest to develop more effective asthma medications. Table 1 reviews the wide array of drugs currently being investigated. With the development and approval of novel asthma treatments, millions of asthma sufferers will undoubtedly have increased therapeutic options for control of their disease in the near future.

Discovery and development of respirable antisense therapeutics for asthma

Respirable antisense oligonucleotides (RASONs) represent a novel class of respiratory therapeutic molecules with the potential to specifically address the challenges posed by the successes of the Human Genome Program, namely, the need to rapidly identify the critical pulmonary disease-relevant drugable targets from the vast pool of 30,000-40,000 human genes and to discover and develop drugs that specifically attack these targets. We have shown that EPI-2010, a RASON targeting the adenosine A1 receptor, a G-protein coupled receptor that has been implicated in the regulation of three major determinants of asthma, can be delivered directly to the target disease tissue as an aerosol formulation. In vivo efficacy, absorption, distribution, metabolism, and excretion (ADME), and safety studies of inhaled EPI-2010 employing animal models of human asthma suggest that the RASON approach enables the specific delivery of efficacious, safe, and long-acting doses of phosphorothioate oligonucleotides to the respiratory tract. Moreover, these data indicate that RASONs truly have the potential to address the respiratory drug discovery bottleneck of the postgenomic era, that is, the ability to rapidly validate disease targets and develop pulmonary disease therapeutics for these validated targets.

DNA therapy for asthma

Asthma therapy, like other therapies, has been moving towards a molecular basis for several years. This year, there have been several preclinical studies published which utilize attributes or facets of DNA to address asthma therapeutics. These include antisense oligonucleotides (against the nuclear transcription factor GATA-3 and the mast cell chemotactic agent, stem cell factor), gene transfer (of interleukin-18, both by plasmid and viral vectors), and CpG oligodeoxynucleotides (which suppress Th2 and stimulate Th1 responses). No clinical experience has yet been reported for any of these areas of research in asthma, but clinical trials are ongoing utilizing CpG oligonucleotides.