Cytokine profiles of BAL T cells and T-cell clones obtained from human asthmatic airways after local allergen challenge

Modulation of calcium signaling by interleukin-13 in human airway smooth muscle: role of CD38/cyclic adenosine diphosphate ribose pathway

CD38/cyclic adenosine diphosphate ribose (cADPR) signaling plays an important role in the regulation of intracellular calcium responses to agonists in a variety of cells, including airway smooth muscle (ASM) cells. The present study was aimed at determining the effect of interleukin (IL)-13, a cytokine implicated in the pathogenesis of asthma, on CD38/cADPR signaling and to ascertain the contribution of CD38/cADPR signaling to IL-13-induced airway hyperresponsiveness. Human ASM cells maintained in culture were exposed to 50 ng/ml IL-13 for 22 h and levels of CD38 expression and intracellular calcium responses to agonists were measured. Treatment of human ASM cells with IL-13 resulted in increased CD38 expression as determined by real-time polymerase chain reaction, Western blot analysis, and indirect immunofluorescence. Increased CD38 expression was reflected as increased ADP-ribosyl cyclase activity in the ASM cell membranes. The net intracellular calcium responses to bradykinin, thrombin, and histamine were significantly (P < or = 0.05) higher in cells treated with IL-13 compared with controls. Furthermore, 8-bromo-cADPR, a cADPR antagonist, attenuated IL-13-induced augmented intracellular calcium responses to agonists in human ASM cells. These findings indicate that the CD38/cADPR-dependent pathway has a major role in IL-13-induced modulation of calcium signaling in human ASM.

Emerging treatments for asthma

Despite the availability of a great number of medications, the asthma epidemic is continuing to increase. It is obvious that a high, unmet medical need remains and innovative therapeutic agents are urgently required. Existing therapies, such as beta-agonists and corticosteroids, provide relief for sufferers of mild-to-moderate asthma, reversing the acute bronchoconstriction and decreasing the inflammation. However, these therapies provide little relief for chronic asthmatics. Asthma is a manifestation of an imbalance in cytokine and signalling pathways that mediate inflammatory and structural changes within the lung. New therapies need to be developed to target these changes. Emerging treatments for asthma include strategies to alter the cytokine/chemokine balance, to skew the cytokine profile away from a T helper (Th)2 response and towards a Th1 response. Strategies designed to do this include therapeutic antibodies or small molecule inhibitors targeted towards IL-13, IL-4 or their receptors, and the Th1 cytokine IL-12. Much interest has focused on the signalling pathways involved in asthma. Among these, the mitogen-activated protein kinase (MAPK) pathway members c-Jun N-terminal kinase (JNK) and p38 have gathered much interest, in addition to the transcription factors nuclear factor kappaB (NF-kappa B), activator protein-1 (AP-1) and signal transducer and activator of transcription (STAT)-6. This review aims to summarise the emerging treatments for chronic asthma, from early discovery, to late clinical stages, and discuss the therapeutic rationale behind these treatments. Much is still to be learned about the mechanisms involved in the development and treatment of chronic asthma; however, much promise lies in the future of these new therapeutics.

Expression of interleukin-5- and granulocyte macrophage-colony-stimulating factor-responsive genes in blood and airway eosinophils

Because interleukin (IL)-5 family cytokines are critical regulators of eosinophil development, recruitment, and activation, this study was initiated to identify proteins induced by these cytokines in eosinophils. Using oligonucleotide microarrays, numerous transcripts were identified as responsive to both IL-5 and granulocyte macrophage-colony-stimulating factor (GM-CSF), but no transcripts were markedly affected by one cytokine and not the other. Expression of several gene products were seen to be increased following in vitro stimulation of human blood eosinophils, including the IL-3 receptor alpha subunit, lymphotoxin beta, Pim-1, and cyclin D3. Given that eosinophils recovered from the bronchoalveolar lavage fluid of allergic patients after antigen challenge are exposed to IL-5 or GM-CSF in the airway prior to isolation, the hypothesis was tested that selected IL-5- and GM-CSF-responsive genes are upregulated in airway eosinophils relative to the expression in blood cells. Airway eosinophils displayed greater cell surface expression of the IL-3 receptor alpha subunit, CD44, CD25, and CD66e, suggesting that these proteins may be markers of eosinophil activation by IL-5 family cytokines in airway eosinophils. Other genes that were induced by both IL-5 and GM-CSF showed protein expression at similar or decreased levels in airway eosinophils relative to their circulating counterparts (i.e., lymphotoxin beta and CD24). These studies have identified several transcriptional targets of IL-5 and GM-CSF in human eosinophils and suggest that a number of protein products are critical to the responsiveness of airway eosinophils.

The monocyte-derived chemokine is released in the bronchoalveolar lavage fluid of steady-state asthmatics

Infiltration of the airways by T helper type 2 (Th2) lymphocytes is a well-recognized feature of bronchial asthma. Monocyte-derived chemokine (MDC) is a potent attractant which activates Th2 lymphocytes via the chemokine receptor CCR4. We have investigated both leukocyte recruitment and MDC release into the airways of asthmatic patients. Differential cell counts in bronchoalveolar lavage (BAL) fluid showed that numbers of lymphocytes and eosinophils were elevated in asthmatics compared with normal subjects (median, 6.1 vs. 1.0 x 10(3)/ml, P < 0.005 and 1.4 vs. 0.24 x 10(3)/ml, P = 0.001, respectively). By enzyme-linked immunosorbent assay it was demonstrated that MDC concentrations were significantly elevated in BAL fluid from asthmatics compared with normals (medians 282 pg/ml, range 190-780 pg/ml vs. median 29 pg/ml range 17-82 pg/ml, P < 0.001). Interestingly, there was a significant correlation between MDC levels and the bronchoconstrictive response to methacholine [PC20 forced expiratory volume (FEV)1, r = -0.78, P = 0.001], suggesting that MDC may be involved in the severity of the disease. By immunohistochemistry, MDC was localized predominantly to the bronchial epithelium in bronchial biopsies derived from stable asthmatics. Moreover, primary human airway epithelial cells were found to release MDC upon cytokine stimulation. These findings suggest that MDC may play a major role in the pathogenesis of bronchial asthma.

The role of interleukin-4 and interleukin-13 in the non-immunologic aspects of asthma pathogenesis

Bronchial asthma is a complex disease characterized by airway inflammation involving a Th2-cytokine, interleukin (IL)-13. A substantial body of evidence has accumulated pointing to the pivotal role of IL-13 in the pathogenesis of bronchial asthma. The evidence is categorized as (i) analyses of mouse models, (ii) expression of these cytokines in the bronchial lesions, and (iii) genetic association of the signaling molecules of these cytokines. In addition, the molecular mechanism of the signal transduction of IL-13 has also been well characterized. We have applied microarray analyses to human bronchial epithelial cultures to search for genes regulated by IL-13 and have identified a subset of disease-relevant genes by comparison with cDNA libraries derived from normal and asthmatic bronchial biopsies. Expression of squamous cell carcinoma antigen-1 (SCCA1) and SCCA2, the cysteine and serine protease inhibitors, respectively, was the highest in the bronchial epithelial cells stimulated by IL-4 and IL-13 and was augmented in the asthmatic cDNA library. Furthermore, serum levels of SCCA were also elevated in asthmatic patients. Taken together, it was supposed that SCCA may play some role in the pathogenesis of bronchial asthma, and measuring its serum level may be relevant for diagnosing or monitoring the status of bronchial asthma.

Imaging the lungs in asthmatic patients by using hyperpolarized helium-3 magnetic resonance: assessment of response to methacholine and exercise challenge

BACKGROUND

Imaging of gas distribution in the lungs of patients with asthma has been restricted because of the lack of a suitable gaseous contrast agent. Hyperpolarized helium-3 (HHe3) provides a new technique for magnetic resonance imaging of lung diseases.

OBJECTIVE

We sought to investigate the use of HHe3 gas to image the lungs of patients with moderate or severe asthma and to assess changes in gas distribution after methacholine and exercise challenge.

METHODS

Magnetic resonance imaging was performed in asthmatic patients immediately after inhalation of HHe3 gas. In addition, images were obtained before and after methacholine challenge and a standard exercise test.

RESULTS

Areas of the lung with no signal or sharply reduced HHe3 signal (ventilation defects) are common in patients with asthma, and the number of defects was inversely related to the percent predicted FEV(1) (r = 0.71, P <.002). After methacholine challenge (n = 3), the number of defects increased. Similarly, imaging of the lungs after exercise (n = 6) showed increased ventilation defects in parallel with decreases in FEV(1). The increase in defects after challenge in these 9 asthmatic patients was significant both for the number (P <.02) and extent (P <.02) of the defects. The variability and speed of changes in ventilation and the complete lack of signal in many areas is in keeping with a model in which the defects result from airway closure.

CONCLUSION

HHe3 magnetic resonance provides a new technique for imaging the distribution of inhaled air in the lungs. The technique is suitable for following responses to treatment of asthma and changes after methacholine or exercise challenge.

T cell cytokine profiles in childhood asthma

BACKGROUND

An imbalance of T cell subsets in asthma with a predominance of Th2 type cells has been proposed. The aim of this study was simultaneously to detect surface markers and intracellular production of cytokines in T cells from the airways of children with and without asthma.

METHODS

Bronchoalveolar lavage (BAL) fluid was obtained by wedging a suction catheter into the distal airway immediately before elective surgery. Cells were stimulated with phorbol 12-myristrate 13-acetate (PMA) and ionomycin and intracytoplasmic cytokine retention was achieved using monensin. The cells were stained with the relevant antibodies and analysed by flow cytometry.

RESULTS

No statistical difference was observed between children with atopic asthma, atopic non-asthmatic subjects, and normal controls in the percentage of CD3+ cells producing interleukin (IL)-2 or IL-4. Interferon (IFN)gamma+ T cells were, however, present in a much higher percentage than either IL-2 or IL-4 positive cells. The percentage of IFNgamma+ T cells was significantly increased in subjects with atopic asthma (median 71.3%, interquartile range (IQR) 65.1-82.2, n=13) compared with both atopic non-asthmatic subjects (51.9%, IQR 37.2-70.3, n=12), p<0.05 and normal controls (58.1%, IQR 36.1-66.1, n=23), p<0.01.

CONCLUSIONS

These findings indicate that IFNgamma producing T cells are more abundant in the airways of children with atopic asthma than in atopic non-asthmatic subjects and controls. The proinflammatory activities of IFNgamma may play an important role in the pathogenesis of childhood asthma and may suggest that asthma is not simply a Th2 driven response.

IL-13 receptors and signaling pathways: an evolving web

IL-13 is an immunoregulatory cytokine secreted predominantly by activated T(H)2 cells. Over the past several years, it has become evident that IL-13 is a key mediator in the pathogenesis of allergic inflammation. IL-13 shares many functional properties with IL-4, stemming from the fact that they share a common receptor subunit, the alpha subunit of the IL-4 receptor (IL-4Ralpha). Characterization of IL-13-deficient mice, IL-4-deficient mice, and IL-4 receptor alpha-deficient (IL-4Ralpha(-/-)) mice have demonstrated nonredundant roles for IL-13. IL-13 mediates its effects by interacting with a complex receptor system comprised of IL-4Ralpha and two IL-13 binding proteins, IL-13Ralpha1 and IL-13Ralpha2. IL-13 receptors are expressed on human B cells, basophils, eosinophils, mast cells, endothelial cells, fibroblasts, monocytes, macrophages, respiratory epithelial cells, and smooth muscle cells. However, functional IL-13 receptors have not been demonstrated on human or mouse T cells. Thus unlike IL-4, IL-13 does not appear to be important in the initial differentiation of CD4 T cells into T(H)2-type cells but rather appears to be important in the effector phase of allergic inflammation. This is further supported by many in vivo observations, including that administration of IL-13 resulted in allergic inflammation, tissue-specific overexpression of IL-13 in the lungs of transgenic mice resulted in airway inflammation and mucus hypersecretion, IL-13 blockade abolished allergic inflammation independently of IL-4, and IL-13 appears to be more important than IL-4 in mucus hypersecretion. Given the importance of IL-13 as an effector molecule, regulation at the level of its receptors might be an important mechanism of modulating IL-13 responses and thus propagation of the allergic response. Accordingly, IL-13 is an attractive, novel therapeutic target for pharmacologic intervention in allergic disorders. This review will summarize the current understanding of the IL-13 receptors and signaling pathways, emphasizing recent observations.

Localized eosinophil degranulation mediates disease in tropical pulmonary eosinophilia

To explore the mechanisms underlying the eosinophil-mediated inflammation of tropical pulmonary eosinophilia (TPE), bronchoalveolar lavage (BAL) fluid, serum, and supernatants from pulmonary and blood leukocytes (WBC) from patients with acute TPE (n = 6) were compared with those obtained from healthy uninfected individuals (n = 4) and from patients with asthma (n = 4) or elephantiasis (n = 5). Although there were no significant differences in the levels of interleukin-4 (IL-4), IL-5, IL-13, eotaxin, granulocyte-macrophage colony-stimulating factor, RANTES, or eosinophil cationic protein, there was a marked increase in eosinophil-derived neurotoxin (EDN) both systemically and in the lungs of individuals with TPE compared to each of the control groups (P < 0.02). Moreover, there was a compartmentalization of this response, with EDN levels being higher in the BAL fluid than in the serum (P < 0.02). Supernatants from WBC from either whole blood or BAL cells were examined for chemokines, cytokines, eosinophil degranulation products, and arachidonic acid metabolites. Of the many mediators examined-particularly those associated with eosinophil trafficking-only EDN (in BAL fluid and WBC) and MIP-1alpha (in WBC) levels were higher for TPE patients than for the non-TPE control groups (P < 0.02). These data suggest it is the eosinophilic granular protein EDN, an RNase capable of damaging the lung epithelium, that plays the most important role in the pathogenesis of TPE.

Hypersensitivity reactions after respiratory sensitization: effect of intranasal peptides containing T-cell epitopes

BACKGROUND

The intranasal administration of peptides containing T-cell epitopes has been shown to inhibit T-cell and antibody responses of mice injected with allergen, but responses to respiratory sensitization might be regulated differently.

OBJECTIVE

This study was designed to examine the effect of intranasal peptide on antigen-induced lung inflammatory responses and delayed hypersensitivity after sensitization by the respiratory mucosa or without sensitization.

METHODS

Mice were treated with an intranasal tolerizing regimen of a peptide containing the major T-cell epitope of Der p 1. Delayed hypersensitivity and lung inflammation to challenge with Der p 1 was measured either without further treatment or after sensitization induced by means of the intranasal administration of Der p 1 with a mutated enterotoxin adjuvant. Lung inflammatory responses were examined by means of lavage and histologic section, and delayed hypersensitivity responses were measured on the basis of ear swelling.

RESULTS

Delayed hypersensitivity reactions were induced in mice treated with intranasal peptide, and large reactions were found in mice given intranasal peptide and sensitized with intranasal Der p 1 and adjuvant. Mice pretreated with peptide and sensitized with Der p 1 had an increased lymphocytic infiltration after allergen-specific challenge, as measured by means of bronchoalveolar lavage and shown histologically. These hypersensitivity results are in contrast to previous data that show tolerance to injected antigen.

CONCLUSIONS

Although the intranasal administration of a peptide containing a T-cell epitope markedly inhibits responses to sensitization produced by the injection of allergen, the peptide induces immune responses and increases hypersensitivity to respiratory sensitization.

Analysis of novel disease-related genes in bronchial asthma

Bronchial asthma is a complex disease characterized by airway inflammation involving interleukin (IL)-4 and IL-13. We have applied microarray analyses to human bronchial epithelial cultures to probe for genes regulated by these cytokines and have identified a subset of disease-relevant genes by comparison with cDNA libraries derived from normal and asthmatic bronchial biopsies. Squamous cell carcinoma antigen-1 (SCCA1) and SCCA2, the cysteine and serine protease inhibitors, respectively, showed the highest expression by IL-4 and IL-13, and particularly, SCCA1 was significantly increased in the asthmatic cDNA library. STAT6 was shown to be involved in expression of SCCA1 and SCCA2 in vitro. Furthermore, serum levels of SCCA were also elevated in asthmatic patients. Taken together, it was supposed that SCCA may play some role in the pathogenesis of bronchia asthma, and measuring its serum level may be relevant for diagnosing or monitoring the status of bronchial asthma. In a complex disorder such as asthma, this combination of in vitro and in vivo genomic approaches is a powerful discriminatory method enabling identification of novel disease-related genes and their mechanisms of regulation.

On the generation of allergic airway diseases: from GM-CSF to Kyoto

The sharp increase in the prevalence of asthma over the past three decades suggests an important contribution of environmental factors in the generation of this disease, and compels a search for molecular pathways by which such factors could facilitate Th2 immune-inflammatory airway responses; granulocyte-macrophage colony-stimulating factor (GM-CSF) might be one such signal. In this review, we appraise the evidence with respect to the presence of GM-CSF in asthma, the roles played by GM-CSF in these immune responses and environmental triggers that can induce GM-CSF expression. Further, we propose a paradigm that unites these divergent observations, and postulate that GM-CSF produced in response to environmental agents can establish an airway microenvironment that promotes the initiation, influences the evolution and supports the maintenance of an aeroallergen-specific adaptive Th2 immune response.

GM-CSF expression by human lung microvascular endothelial cells: in vitro and in vivo findings

Recently, many findings indicate that granulocyte-macrophage colony-stimulating factor (GM-CSF) plays an important role in the pathogenesis of acute and chronic lung diseases. In the present paper, the production of this cytokine in human pulmonary microvascular endothelial cells (HPMEC) is investigated. In an in vitro study, quiescent HPMEC did not express GM-CSF, either at the transcriptional or at the protein level. After activation for 4 h with tumor necrosis factor (TNF)-alpha (30/300 U/ml), lipopolysaccharide (LPS; 0.1/1 microg/ml), or interleukin (IL)-1 beta (100 U/ml), a significant release of GM-CSF was measured by enzyme-linked immunosorbent assay, with a time-dependent increase over 72 h. IL-8 (4, 16, or 64 ng/ml) or IL-1 beta at a concentration of 10 U/ml did not induce the release of GM-CSF. Human umbilical vein endothelial cells (HUVEC) and the angiosarcoma cell line HAEND served as reference cell lines. GM-CSF release in HPMEC was significantly (P < 0.025-0.05) less inducible by IL-1 beta than in HUVEC. A constitutive expression of GM-CSF by HAEND was observed. Additionally, GM-CSF expression in vivo by the lung microvasculature was confirmed by immunohistochemistry in lung tissue. To our knowledge, this is the first report of the ability of human pulmonary endothelial cells to synthesize and release GM-CSF. These results support the hypothesis that the lung microvasculature via the production of GM-CSF is a potential contributor to the cytokine network in lung diseases. This could be of particular importance in the pathogenesis of the acute respiratory distress syndrome in which endothelial dysfunction plays a central pathogenetic role.

Role of cytokines and chemokines in bronchial hyperresponsiveness and airway inflammation

Over the last decade there has been an intense interest in the potential role of cytokines and chemokines as important mediators in various atopic diseases, including asthma and the mechanisms by which these mediators regulate airway inflammation and bronchial hyperresponsiveness. This research effort has recently culminated in the publication of clinical studies that have assessed the role of interleukin (IL)-4 [Borish et al., Am J Respir Crit Care Med 160, 1816-1823 (1999)], IL-5 [Leckie et al., Lancet 356, 2144-2148 (2000)], and IL-12 [Bryan et al., Lancet 356, 2149-2153 (2000)] in allergic asthma, and the results have been disappointing. This is not surprising given the pleiotropic role cytokines play in the allergic response confirmed by numerous animal studies providing evidence of functional redundancy. The alternative view is that our current concepts in asthma pathogenesis need significant revision. This review will summarise the evidence for the role of cytokines and chemokines in various aspects of asthma pathophysiology; namely, bronchial hyperresponsiveness, eosinophil recruitment to the airways, mucus secretion, and airway remodelling.

Upregulation of IL-13 concentration in vivo by the IL13 variant associated with bronchial asthma

BACKGROUND

A substantial body of evidence exists to support the pivotal role of IL-13 in the pathogenesis of bronchial asthma. We recently found that a variant of the IL13 gene (Arg110Gln) is genetically associated with bronchial asthma, which is concordant with animal experiments using IL-13 in the development of asthma.

OBJECTIVE

To address whether the Gln110 variant of IL13 influences IL-13 function, contributing to the pathogenesis of bronchial asthma, we studied the functional properties of the variant.

METHODS

We generated 2 types of recombinant IL-13 proteins, the amino acids of which at 110 were arginine or glutamine, and analyzed the binding affinities with the IL-13 receptors, as well as the stability of the proteins. We further compared the relationship between the genotype and serum levels of IL-13.

RESULTS

The variant showed a lower affinity with the IL-13 receptor alpha2 chain, a decoy receptor, causing less clearance. The variant also demonstrated an enhanced stability in both human and mouse plasma. We further identified that asthmatic patients homozygous for the Gln110 variant have higher serum levels of IL-13 than those without the variant.

CONCLUSION

These results suggested that the variant might act as a functional genetic factor of bronchial asthma with a unique mechanism to upregulate local and systemic IL-13 concentration in vivo.

TCR usage and cytokine expression in peripheral blood and BAL T cells

T cells are thought to play an important regulatory role in atopic asthma. We hypothesized that human blood and BAL T cell subsets bearing various TCR-Vbeta genes might show selective differences in their cytokine profile. Peripheral blood (PB) and bronchoalveolar lavage (BAL) T cells from seven atopic asthmatic and six non-atopic non-asthmatic subjects were stimulated with PMA and ionomycin in the presence of monensin and analysed for TCR-Vbeta expression and production of cytokines at the single cell level. The percentage of IFN-gamma- and IL-2-producing BAL T cells was elevated compared with PB T cells from both the asthmatic subjects and the non-atopic, non-asthmatic controls. A small percentage of PB and BAL T cells produced IL-4 and IL-5, in asthmatic and normal subjects. In peripheral blood, the percentage of T cells expressing each cytokine was similar in the various TCR-Vbeta subsets and in total CD3+ T cells in all normal and six of seven asthmatic subjects. However, there was a substantial degree of heterogeneity in the cytokine profile of BAL TCR-Vbeta subsets compared with the total CD3+ T cells. This was more obvious in the asthmatic subjects with a reduction in the percentage of IFN-gamma- and IL-2-expressing T cells (five of seven asthmatic subjects) and an increase in the percentage of IL-4- and IL-5-expressing T cells (two of seven asthmatic subjects). These data confirm previous findings of an elevated proportion of IFN-gamma- and IL-2-producing BAL T cells while only a small proportion of PB and BAL T cells produce IL-4 and IL-5. Moreover, subsets of BAL T cells, defined by their TCR-Vbeta usage, may differ in their cytokine profile compared with the total CD3+ T cells, implying that T cells expressing different Vbeta elements may play different roles in regulating the airway inflammation in asthma.

Acquired immune responses to Plasmodium falciparum merozoite surface protein-1 in the human fetus

Infants born in areas of stable malaria transmission are relatively protected against severe morbidity and high density Plasmodium falciparum blood-stage infection. This protection may involve prenatal sensitization and immunologic reactivity to malaria surface ligands that participate in invasion of red cells. We examined cord blood T and B cell immunity to P. falciparum merozoite surface protein-1 (MSP-1) in infants born in an area of stable malaria transmission in Kenya. T cell cytokine responses to the C-terminal 19-kDa fragment of MSP-1 (MSP-1(19)) were detected in 24 of 92 (26%) newborns (4-192 IFN-gamma and 3-88 IL-4-secreting cells per 10(6)/cord blood lymphocytes). Peptide epitopes in the N-terminal block 3 region of MSP-1 also drove IFN-gamma and/or IL-13 production. There was no evidence of prenatal T cell sensitization to liver-stage Ag-1. A total of 5 of 86 (6%) newborns had cord blood anti-MSP-1(19) IgM Abs, an Ig isotype that does not cross the placenta and is therefore of fetal origin. The frequency of neonatal B cell sensitization was higher than that indicated by serology alone, as 5 of 27 (18%) cord blood samples contained B cells that produced IgG when stimulated with MSP-1(19) in vitro. Neonatal B cell IgG responses were restricted to the Q-KNG allele of MSP-1(19), the major variant in this endemic area, whereas T cells responded to all four MSP-1(19) alleles evaluated. In utero sensitization to MSP-1 correlated with the presence of malaria parasites in cord blood (chi(2) = 20, p < 0.0001). These data indicate that prenatal sensitization to blood-stage Ags occurs in infants born in malaria endemic areas.

Administration of pentoxifylline during allergen sensitization dissociates pulmonary allergic inflammation from airway hyperresponsiveness

Asthma, a chronic inflammatory disease characterized by intermittent, reversible airflow obstruction and airway hyperresponsiveness (AHR), is classically characterized by an excess of Th2 cytokines (IL-13, IL-4) and depletion of Th1 cytokines (IFN-gamma, IL-12). Recent studies indicating an important role for Th1 immunity in the development of AHR with allergic inflammation suggest that Th1/Th2 balance may be important in determining the association of AHR with allergic inflammation. We hypothesized that administration of pentoxifylline (PTX), a phosphodiesterase inhibitor known to inhibit Th1 cytokine production, during allergen (OVA) sensitization and challenge would lead to attenuation of AHR in a murine model of allergic pulmonary inflammation. We found that PTX treatment led to attenuation of AHR when administered at the time of allergen sensitization without affecting other hallmarks of pulmonary allergic inflammation. Attenuation of AHR with PTX treatment was found in the presence of elevated bronchoalveolar lavage fluid levels of the Th2 cytokine IL-13 and decreased levels of the Th1 cytokine IFN-gamma. PTX treatment during allergen sensitization leads to a divergence of AHR and pulmonary inflammation following allergen challenge.

Il-13 and IFN-gamma: interactions in lung inflammation

Chronic inflammatory diseases of the lungs, such as asthma, are frequently associated with mixed (Th2 and Th1) T cell responses. We examined the impact of critical Th1 and Th2 cytokines, IFN-gamma and IL-13, on the responses in the lungs. In a mouse model of airway inflammation induced by mixed T cell responses, the number of Th1 (IFN-gamma-positive) cells was found to be negatively correlated with airway hyperreactivity. In these mice, blockade of IL-13 partially inhibited airway hyperreactivity and goblet cell hyperplasia but not inflammation. In contrast, in mice that responded with a polarized Th2 response to the same Ag, blockade of IL-13 inhibited airway hyperreactivity, goblet cell hyperplasia, and airway inflammation. These results indicated that the presence of IFN-gamma would modulate the effects of IL-13 in the lungs. To test this hypothesis, wild-type mice were given recombinant cytokines intranasally. IFN-gamma inhibited IL-13-induced goblet cell hyperplasia and airway eosinophilia. At the same time, IFN-gamma and IL-13 potentiated each other's effects. In the airways of mice given IL-13 and IFN-gamma, levels of IL-6 were increased as well as numbers of NK cells and of CD11c-positive cells expressing MHC class II and high levels of CD86. In conclusion, IFN-gamma has double-sided effects (inhibiting some, potentiating others) on IL-13-induced changes in the lungs. This may be the reason for the ambiguous role of Th1 responses on Th2 response-induced lung injury.

Direct effects of interleukin-13 on signaling pathways for physiological responses in cultured human airway smooth muscle cells

Numerous studies have suggested an important role for the Th2 cytokines interleukin (IL)-13 and IL-4 in the development of allergic asthma. We tested the hypothesis that IL-13 and IL-4 have direct effects on cultured airway smooth muscle cells (HASM). Using RT-PCR, we showed that HASM cells express transcripts for IL-4alpha, IL-13RalphaI, and IL-13RalphaII, but not for the common IL-2Rgamma chain. We then analyzed the capacity of the two cytokines to activate signaling pathways in HASM cells. Both IL-13 and IL-4 caused STAT-6 phosphorylation, but the time course was different between the two cytokines, with peak effects occurring 15 min after addition of IL-4 and 1 h after addition of IL-13. Effects on signaling were observed at cytokine concentrations as low as 0.3 ng/ml. IL-4 and IL-13 also caused phosphorylation of ERK MAP kinase. As suggested by the signaling studies, the biological responses of the two cytokines were also different. We used magnetic twisting cytometry to measure cell stiffness of HASM cells and tested the capacity of IL-4 and IL-13 to interfere with the reductions in cell stiffness induced by the beta-agonist isoproterenol (ISO). IL-13 (50 ng/ml for 24 h), but not IL-4, significantly reduced beta-adrenergic responsiveness of HASM cells, and the MEK inhibitor U0126 significantly reduced the effects of IL-13 on ISO-induced changes in cell stiffness. We propose that these direct effect of IL-13 on HASM cells may contribute at least in part to the airway narrowing observed in patients with asthma.

Persistent wheezing in very young children is associated with lower respiratory inflammation

Despite advances in understanding the pathophysiology of asthma, morbidity and mortality in pediatrics continue to rise. Little is known about the initiation and chronicity of inflammation resulting in asthma in this young population. We evaluated 20 "wheezing" children (WC) (median age 14.9 mo) with a minimum of two episodes of wheezing or prolonged wheezing > or = 2 mo in a 6-mo period with bronchoscopy and bronchoalveolar lavage (BAL). Comparisons were made with six normal controls (NC) (median age 23.3 mo) undergoing general anesthesia for elective surgery. BAL fluid cell counts and differentials were determined. The eicosanoids, leukotriene (LT) B(4), LTE(4), prostaglandin (PG)E(2), and 15-hydroxyeicosatetraenoic acid (HETE) and the mast cell mediators, beta-tryptase and PGD(2), were evaluated by enzyme immunoassay (EIA). WC had significant elevations in total BAL cells/ml (p = 0.01), as well as, lymphocytes (LYMPH, p = 0.007), macrophages/monocytes (M&M, p = 0.02), polymorphonuclear cells (PMN, p = 0.02), epithelial cells (EPI, p = 0.03), and eosinophils (EOS, p = 0.04) compared with NC. Levels of PGE(2) (p = 0.0005), 15-HETE (p = 0.002), LTE(4) (p = 0.04), and LTB(4) (p = 0.05) were also increased in WC compared with NC, whereas PGD(2) and beta-tryptase were not. This study confirms that inflammation is present in the airways of very young WC and may differ from patterns seen in adults with asthma.

The C-C chemokine receptors CCR4 and CCR8 identify airway T cells of allergen-challenged atopic asthmatics

In vitro polarized human Th2 cells preferentially express the chemokine receptors CCR3, CCR4, and CCR8 and migrate to their ligands: eotaxin, monocyte-derived chemokine (MDC), thymus- and activation-regulated chemokine (TARC), and I-309. We have studied the expression of chemokines and chemokine receptors in the airway mucosa of atopic asthmatics. Immunofluorescent analysis of endobronchial biopsies from six asthmatics, taken 24 hours after allergen challenge, demonstrates that virtually all T cells express IL-4 and CCR4. CCR8 is coexpressed with CCR4 on 28% of the T cells, while CCR3 is expressed on eosinophils but not on T cells. Expression of the CCR4-specific ligands MDC and TARC is strongly upregulated on airway epithelial cells upon allergen challenge, suggesting an involvement of this receptor/ligand axis in the regulation of lymphocyte recruitment into the asthmatic bronchi. In contrast to asthma, T cells infiltrating the airways of patients with chronic obstructive pulmonary disease and pulmonary sarcoidosis produce IFN-gamma and express high levels of CXCR3, while lacking CCR4 and CCR8 expression. These data support the role of CCR4, of its ligands MDC and TARC, and of CCR8 in the pathogenesis of allergen-induced late asthmatic responses and suggest that these molecules could be considered as targets for therapeutic intervention.

Tumour necrosis factor-alpha: the role of this multifunctional cytokine in asthma

Tumour necrosis factor-alpha (TNF-alpha) is recognized as an important mediator in many cytokine- dependent inflammatory events. It is known that TNF-alpha is released in allergic responses from both mast cells and macrophages via IgE-dependent mechanisms, and elevated levels have been demonstrated in the bronchoalveolar fluid (BALF) of asthmatic subjects undergoing allergen challenge. Inhaled TNF-alpha increases airway responsiveness to methacholine in normal and asthmatic subjects associated with a sputum neutrophilia. Additional data indicate that TNF-alpha can upregulate adhesion molecules, facilitate the immigration of inflammatory cells into the airway wall and activate pro-fibrotic mechanisms in the subepithelium. These data suggest that TNF-alpha plays a role in the initiation of allergic asthmatic airway inflammation and the generation of airway hyper-reactivity. In addition, polymorphisms of the TNF-alpha gene 5' untranslated region, particularly at -308 bp, have been described as being associated with asthma. This polymorphism is associated with increased levels of TNF-alpha, but as yet, no asthma studies have demonstrated a phenotypic difference between those individuals with the polymorphism and those with the wild type gene. The TNF receptors (TNF-R p55 and p75), also known as CD120a and b, have also been shown to be present in the lung, but their functional importance is only just emerging. In asthma, TNF may function as a pro-inflammatory cytokine that causes the recruitment of neutrophils and eosinophils. Treatment directed specifically at a reduction in TNF-alpha activity may conceivably be useful as a glucocorticosteroid-sparing asthma therapy.

Localization of human interleukin 13 receptor in non-haematopoietic cells

Although the functional roles of interleukin (IL-)13 in haematopoietic cells are well investigated, those in non-haematopoietic cells remain to be addressed. IL-13 exerts its actions by binding to the IL-13 receptor (IL-13R) on target cells, which is composed of IL-13Ralpha1 and the IL-4 receptor alpha chain (IL-4Ralpha). However, there has been no study of localization of IL-13R in each tissue. To address this question, we generated monoclonal anti-IL-13Ralpha1 antibody, and performed immunohistochemistry using this antibody and anti-IL-4Ralpha antibody. Distribution of these two components was the same in all examined tissues. Staining was positive in keratinocytes, hair follicles, and sebaceous and sweat glands in skin; in ciliated respiratory epithelial cells in nasal tissue; in heart muscle cells; in foveola cells, gastric glands, and the smooth muscle layer in stomach; and in hepatocytes in liver. However, staining was undetectable in brain and bone marrow. Fibroblasts and endothelial cells were stained in some tissues. These results provide clues to elucidate the known pathological roles of IL-13 in atopic dermatitis and allergic rhinitis, as well as its unknown physiological roles.