sVCAM-1 levels after segmental antigen challenge correlate with eosinophil influx, IL-4 and IL-5 production, and the late phase response

Identification of a novel splice variant for mouse and human interleukin-5

Expression of interleukins and their receptors is often regulated by alternative splicing. Alternative isoform of IL-5 receptor α-chain is well studied; however, no data on functional alternative splice variants of IL-5 has been reported up today. In the present study, we describe a novel splice variant for the mouse and human IL-5. The new form was found during analysis of PCR-products amplified from different mouse lymphoid tissues with a pair of primers designed to clone full-length mIL-5 ORF. A single short isoform of mIL-5 was detected along with the canonical full-length mRNA in ConA-stimulated lymphoid cells isolated from spleen, thymus, lymph nodes and blood. It was 30-40 nt shorter, and less abundant than classical form. The sequence analysis of an additional form of mIL-5 revealed that it lacks exon-2 (δ2). Using RT-PCR with the splice-specific primers we obtained an additional evidence for δ2 form expression. To verify whether mIL-5δ2 transcript is translated into protein, the coding sequences corresponding to full and δ2 forms of mIL-5 were cloned into an expression plasmid. After transfection into the human 293T cell line, we found that the short form of mIL-5 protein is expressed in cells and secreted into the supernatant, but at the reduced level than that detected for full isoform of mIL-5. Fluorescence microscopy examination revealed a partial translocation of mIL-5δ2 into cytoplasm, whereas mIL-5 resided mostly within endoplasmic reticulum. This can explain why the level of δ2 protein expression was reduced. Using a similar set of experimental approaches, we received the evidence that the human IL-5 mRNA has the δ2 splice form (hIL-5δ2) as well. It can be firmly detected by RT-PCR in PHA-activated mononuclear cells isolated from peripheral blood of healthy persons or patients with asthma. Altogether, our results showed that the human and mouse IL-5 have an alternative mRNA splice isoform, which loses exon-2, but nevertheless is expressed at protein level. However, more comprehensive studies will be required for evaluation of IL-5δ2 expression, regulation, biological function and clinical significance.

Targeting the interleukin-4 and interleukin-13 pathways in severe asthma: current knowledge and future needs

PURPOSE OF REVIEW

Severe asthma is a heterogeneous disease that can be classified into phenotypes and endotypes based upon clinical or biological characteristics. Interleukin (IL)-4 and IL-13 play a key role in type 2 (T2) asthma. This article reviews the signaling pathway of IL-4 and IL-13 and highlights its targeted therapy in severe asthma.

RECENT FINDINGS

Several clinical trials of biologics targeting the IL-4/IL-13 pathway have recently been completed. In patients with severe, uncontrolled asthma, targeting IL-13 alone with biologics including lebrikizumab and tralokinumab has not shown consistent reduction in asthma exacerbations. Simultaneous targeting of both IL-4 and IL-13 by blocking IL-4 receptor α using dupilumab has yielded more consistent results in reducing asthma exacerbations and improving lung function, especially in patients with increased blood eosinophils. Other biomarkers of T2 inflammation such as exhaled nitric oxide and serum periostin may also predict response to biologics targeting the IL-4/IL-13 pathway.

SUMMARY

No biologic targeting the IL-4/IL-13 pathway is currently available for treatment of asthma, but emerging data suggest that biologics targeting IL-4 and IL-13 together may benefit patients with T2 high asthma. Additional data are needed about long-term efficacy and safety prior to incorporating these drugs into routine clinical practice.

Altered levels of blood proteins in Alzheimer's disease longitudinal study: Results from Australian Imaging Biomarkers Lifestyle Study of Ageing cohort

INTRODUCTION

A blood-based biomarker panel to identify individuals with preclinical Alzheimer's disease (AD) would be an inexpensive and accessible first step for routine testing.

METHODS

We analyzed 14 biomarkers that have previously been linked to AD in the Australian Imaging Biomarkers lifestyle longitudinal study of aging cohort.

RESULTS

Levels of apolipoprotein J (apoJ) were higher in AD individuals compared with healthy controls at baseline and 18 months (P = .0003) and chemokine-309 (I-309) were increased in AD patients compared to mild cognitive impaired individuals over 36 months (P = .0008).

DISCUSSION

These data suggest that apoJ may have potential in the context of use (COU) of AD diagnostics, I-309 may be specifically useful in the COU of identifying individuals at greatest risk for progressing toward AD. This work takes an initial step toward identifying blood biomarkers with potential use in the diagnosis and prognosis of AD and should be validated across other prospective cohorts.

Role of Eosinophil Granulocytes in Allergic Airway Inflammation Endotypes

Eosinophil granulocytes are intriguing members of the innate immunity system that have been considered important defenders during parasitic diseases as well as culprits during allergy-associated inflammatory diseases. Novel studies have, however, found new homoeostasis-maintaining roles for the cell. Recent clinical trials blocking different Th2 cytokines have uncovered that asthma is heterogeneous entity and forms different characteristic endotypes. Although eosinophils are present in allergic asthma with early onset, the cells may not be essential for the pathology. The cells are, however, likely disease causing in asthma with a late onset, which is often associated with chronic rhinosinusitis. Assessment of eosinophilia, fraction exhaled nitric oxide (FeNO) and periostin are markers that have emerged useful in assessing and monitoring asthma severity and endotype. Current scientific knowledge suggests that eosinophils are recruited by the inflammatory environment, activated by the innate interleukin (IL)-33 and prevented from apoptosis by both lymphocytes and innate immune cells such as type two innate immune cells. Eosinophils contain four specific granule proteins that exhibit an array of toxic and immune-modulatory activates. The granule proteins can be released by different mechanisms. Additionally, eosinophils contain a number of inflammatory cytokines and lipid mediators as well as radical oxygen species that might contribute to the disease both by the recruitment of other cells and the direct damage to supporting cells, leading to exacerbations and tissue fibrosis. This review aimed to outline current knowledge how eosinophils are recruited, activated and mediate damage to tissues and therapies used to control the cells.

Allergic asthma is distinguished by sensitivity of allergen-specific CD4+ T cells and airway structural cells to type 2 inflammation

Despite systemic sensitization, not all allergic individuals develop asthma symptoms upon airborne allergen exposure. Determination of the factors that lead to the asthma phenotype in allergic individuals could guide treatment and identify novel therapeutic targets. We used segmental allergen challenge of allergic asthmatics (AA) and allergic nonasthmatic controls (AC) to determine whether there are differences in the airway immune response or airway structural cells that could drive the development of asthma. Both groups developed prominent allergic airway inflammation in response to allergen. However, asthmatic subjects had markedly higher levels of innate type 2 receptors on allergen-specific CD4+ T cells recruited into the airway. There were also increased levels of type 2 cytokines, increased total mucin, and increased mucin MUC5AC in response to allergen in the airways of AA subjects. Furthermore, type 2 cytokine levels correlated with the mucin response in AA but not AC subjects, suggesting differences in the airway epithelial response to inflammation. Finally, AA subjects had increased airway smooth muscle mass at baseline measured in vivo using novel orientation-resolved optical coherence tomography. Our data demonstrate that the development of allergic asthma is dependent on the responsiveness of allergen-specific CD4+ T cells to innate type 2 mediators as well as increased sensitivity of airway epithelial cells and smooth muscle to type 2 inflammation.

Strategies targeting the IL-4/IL-13 axes in disease

IL-4 and IL-13 are pleiotropic Th2 cytokines produced by a wide variety of different cell types and responsible for a broad range of biology and functions. Physiologically, Th2 cytokines are known to mediate host defense against parasites but they can also trigger disease if their activities are dysregulated. In this review we discuss the rationale for targeting the IL-4/IL-13 axes in asthma, atopic dermatitis, allergic rhinitis, COPD, cancer, inflammatory bowel disease, autoimmune disease and fibrotic disease as well as evaluating the associated clinical data derived from blocking IL-4, IL-13 or IL-4 and IL-13 together.

Platelet activation, P-selectin, and eosinophil β1-integrin activation in asthma

RATIONALE

Eosinophil β1-integrin activation correlates inversely with FEV1 and directly with eosinophil-bound P-selectin in subjects with nonsevere allergic asthma.

OBJECTIVES

Determine the relationships between β1-integrin activation and pulmonary function or eosinophil-bound P-selectin in subjects with asthma of varying severity and discern the source of eosinophil-bound P-selectin.

METHODS

Blood was assayed by flow cytometry for P-selectin and activated β1-integrin on eosinophils and platelets. Plasma was analyzed with ELISA for soluble P-selectin, platelet factor 4, and thrombospondin-1.

MEASUREMENTS AND MAIN RESULTS

Activated β1-integrin correlated with eosinophil-bound P-selectin among all subjects with asthma even though activated β1-integrin was higher in subjects with nonsevere asthma than severe asthma. Activated β1-integrin correlated inversely with FEV1 corrected for FVC only in younger subjects with nonsevere asthma. Paradoxically, platelet surface P-selectin, a platelet activation marker, was low in subjects with severe asthma, whereas plasma platelet factor 4, a second platelet activation marker, was high. Correlations indicated that P-selectin-positive platelets complexed to eosinophils are the major source of the eosinophil-bound P-selectin associated with β1-integrin activation. After whole-lung antigen challenge of subjects with nonsevere asthma, a model of asthma exacerbation known to cause platelet activation, circulating eosinophils bearing P-selectin and activated β1-integrin disappeared.

CONCLUSIONS

The relationship between eosinophil β1-integrin activation and pulmonary function was replicated only for younger subjects with nonsevere asthma. However, we infer that platelet activation and binding of activated platelets to eosinophils followed by P-selectin-mediated eosinophil β1-integrin activation occur in both nonsevere and severe asthma with rapid movement of platelet-eosinophil complexes into the lung in more severe disease.

Delayed asthmatic response: a new phenotype of bronchial response to allergen challenge and soluble adhesion molecules in the serum

BACKGROUND

Patients with bronchial asthma develop various types of asthmatic response to bronchial challenge with allergen, such as immediate asthmatic response, late asthmatic response, or delayed asthmatic response (DYAR), due to different immunologic mechanisms.

OBJECTIVES

To investigate the appearance and possible changes in the concentrations of soluble cell adhesion molecules during the DYAR, to explore the involvement of particular cell types in the mechanism(s) leading to DYAR, and to contribute to a fuller understanding of this clinical phenomenon.

METHODS

The DYAR recorded in 28 patients (P < .001), appearing within 26 to 32 hours, reaching maximum within 32 to 48 hours, and resolving within 56 hours after the allergen challenge, was repeated 2 to 6 weeks later. The repeated DYAR (P < .001) was supplemented with blood cell counts and measurement of serum concentrations of soluble adhesion molecules by an enzyme-linked immunoassay.

RESULTS

The prechallenge concentrations of soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cell adhesion molecule 1 (sVCAM-1), soluble platelet endothelial cell adhesion molecule (sPECAM-1), soluble E-selectin, soluble L-selectin, soluble P-selectin, and soluble E-cadherin did not differ significantly from healthy controls. The DYAR was associated with the following changes in the serum: an increase of sICAM-1 at 6 and 12 hours and a decrease at 24 hours; an increase of sVCAM-1 at 24 and 36 hours; an increase of sPECAM-1 at 36 and 48 hours and a decrease at 56 and 72 hours; an increase of soluble E-selectin at 56 hours; an increase of soluble L-selectin at 56 and 72 hours; a decrease of soluble E-cadherin at 48 and 56 hours; and increased counts of blood leukocytes at 36, 48, and 56 hours, neutrophils at 24, 36, 48, and 56 hours, lymphocytes at 24, 36, and 48 hours, and monocytes at 6, 12, and 24 hours. The Th1/Th2 ratio in blood increased at 24, 36, 48, and 56 hours. The intracellular concentration of interferon γ, but not of interleukin 4, increased at 24, 36, 48, and 56 hours.

CONCLUSIONS

These results provide evidence of the involvement of neutrophils, Th1 lymphocytes, monocytes, platelets, and endothelial cells, upon participation of various adhesion molecules, in mechanisms(s) underlying the clinical DYAR.

Soluble vascular cell adhesion molecule-1 induces human eosinophil migration

BACKGROUND

Tissue eosinophilia is one of the hallmarks of allergic diseases and Th2-type immune responses including asthma. Adhesion molecules are known to play an important role in the accumulation of eosinophils in allergic inflammatory foci, and they contribute to eosinophil activation. Elevated levels of the soluble forms of adhesion molecules in the body fluid of asthmatic patients have been observed, although their pathophysiological significance remains to be fully elucidated.

METHODS

Peripheral blood eosinophils were purified, and the effect of soluble vascular cell adhesion molecule-1 (sVCAM-1) on eosinophil migration was investigated using in vitro systems.

RESULTS

We found that sVCAM-1 (1 to 10 mug/ml) induced eosinophil chemotaxis, rather than chemokinesis, in a concentration-dependent fashion. In addition, sVCAM-1 induced cell shape change and actin polymerization, which are necessary for cell movement. Manipulations with very late antigen (VLA)-4-neutralizing antibody and signal inhibitors indicated that the sVCAM-1-induced chemotaxis was mediated through ligand-dependent activation of tyrosine kinase Src, p38 mitogen-activated protein kinase (MAPK), and extracellular signal-regulated kinase (ERK) MAPK. Rapid phosphorylation of these signaling molecules was observed using a bead-based multiplex assay.

CONCLUSION

Our results raise the possibility of sVCAM-1 in the fluid phase as a significant contributor to the heightened eosinophilic inflammatory response.

Up-regulation and activation of eosinophil integrins in blood and airway after segmental lung antigen challenge

We hypothesized that there are clinically relevant differences in eosinophil integrin expression and activation in patients with asthma. To evaluate this, surface densities and activation states of integrins on eosinophils in blood and bronchoalveolar lavage (BAL) of 19 asthmatic subjects were studied before and 48 h after segmental Ag challenge. At 48 h, there was increased expression of alpha(D) and the N29 epitope of activated beta(1) integrins on blood eosinophils and of alpha(M), beta(2), and the mAb24 epitope of activated beta(2) integrins on airway eosinophils. Changes correlated with the late-phase fall in forced expiratory volume in 1 s (FEV(1)) after whole-lung inhalation of the Ag that was subsequently used in segmental challenge and were greater in subjects defined as dual responders. Increased surface densities of alpha(M) and beta(2) and activation of beta(2) on airway eosinophils correlated with the concentration of IL-5 in BAL fluid. Activation of beta(1) and beta(2) on airway eosinophils correlated with eosinophil percentage in BAL. Thus, eosinophils respond to an allergic stimulus by activation of integrins in a sequence that likely promotes eosinophilic inflammation of the airway. Before challenge, beta(1) and beta(2) integrins of circulating eosinophils are in low-activation conformations and alpha(D)beta(2) surface expression is low. After Ag challenge, circulating eosinophils adopt a phenotype with activated beta(1) integrins and up-regulated alpha(D)beta(2), changes that are predicted to facilitate eosinophil arrest on VCAM-1 in bronchial vessels. Finally, eosinophils present in IL-5-rich airway fluid have a hyperadhesive phenotype associated with increased surface expression of alpha(M)beta(2) and activation of beta(2) integrins.

T-cell mediated late increase in bronchial tone after allergen provocation in a murine asthma model

Allergen inhalation by sensitized asthmatics induces an IgE and mast cell dependent bronchoconstriction and a Th2-dependent inflammatory airway reaction, mucus hypersecretion and airway hyperreactivity. The link between T cells and bronchoconstriction remains controversial. Here we analyzed allergen-induced changes in airway tone in ovalbumin-sensitized mice with established allergic airway inflammation. Inhalation of nebulized ovalbumin elicited a dose-dependent and allergen-specific increase in airway resistance and bronchial tone with a concomitant increase of lymphocytes and eosinophils in bronchoalveolar lavage fluid. A Th2 pattern of cytokine expression and increased mRNA expression of MCP-1, RANTES and VCAM-1 were demonstrated. Anti-CD4 monoclonal antibody treatment prior to provocation decreased IL-13 and VCAM-1 mRNA expression and abolished the increase in bronchial tone and the inflammatory response. We conclude that allergen inhalation in sensitized mice induces airway narrowing similar to the late asthmatic reactions in humans and that this phenomenon is based on activation of CD4(+) T cells.

Psychological factors in asthma

Asthma has long been considered a condition in which psychological factors have a role. As in many illnesses, psychological variables may affect outcome in asthma via their effects on treatment adherence and symptom reporting. Emerging evidence suggests that the relation between asthma and psychological factors may be more complex than that, however. Central cognitive processes may influence not only the interpretation of asthma symptoms but also the manifestation of measurable changes in immune and physiologic markers of asthma. Furthermore, asthma and major depressive disorder share several risk factors and have similar patterns of dysregulation in key biologic systems, including the neuroendocrine stress response, cytokines, and neuropeptides. Despite the evidence that depression is common in people with asthma and exerts a negative impact on outcome, few treatment studies have examined whether improving symptoms of depression do, in fact, result in better control of asthma symptoms or improved quality of life in patients with asthma.

Lower airways inflammation in allergic rhinitics: a comparison with asthmatics and normal controls

BACKGROUND

Allergic rhinitis (AR) and asthma represent a continuum of atopic disease. AR is believed to pre-dispose an individual to asthma. Compared with asthmatics and normal controls, the inflammatory response in the lower airways of rhinitics is not fully elucidated. To test the hypothesis that the inflammatory response in the airways of subjects with AR is at a level intermediate between that in normal controls and asthmatics, we have characterized bronchial inflammation and cytokine mRNA levels in non-asthmatic allergic rhinitics and compared it with subjects with allergic asthma and with normal controls.

METHODS

Endobronchial mucosal biopsies were obtained at bronchoscopy from 14 allergic rhinitics, 16 asthmatics and 21 normal controls. Biopsies were embedded into glycol methacrylate resin for immunohistochemical analysis of cellular inflammation and snap frozen for semi-quantitative PCR analysis of cytokine mRNA levels.

RESULTS

Airway inflammation in rhinitic subjects was characterized by an increase in submucosal eosinophils, mast cells and the mRNA expression of TNF-alpha, at an intermediate level between healthy and asthmatics. In addition, CD3(+) and CD8(+) lymphocytes in the epithelium, the endothelial expression of vascular adhesion molecule-1 and IL-1 beta mRNA were higher in the allergic rhinitics compared with both normal controls and asthmatics, whereas growth-related oncogene alpha-mRNA was decreased in AR compared with both healthy and asthmatics. Airway inflammation in the asthmatic group was characterized by higher numbers of eosinophils and mast cells, together with an increase in TNF-alpha-mRNA compared with both healthy and rhinitics. IFN-gamma mRNA was the highest in normal controls and lowest in the asthmatics.

CONCLUSIONS

In individuals with AR the present data suggest an intermediate state of airway inflammation between that observed in normal individuals and subjects with clinical asthma. It is also indicated that IFN-gamma production by CD8(+) T lymphocytes could be protective against the development of airway hyperresponsiveness. Further work is needed to evaluate this hypothesis.

2,6-Quinolinyl derivatives as potent VLA-4 antagonists

A new series of 2,6-quinolinyl derivatives was prepared leading to potent low nanomolar VLA-4/VCAM-1 antagonists.

Elevated soluble ADAM8 in bronchoalveolar lavage fluid in patients with eosinophilic pneumonia

BACKGROUND

ADAM (a disintegrin and metalloprotease) family members, characterized by a metalloprotease and a disintegrin domain, are membrane-anchored glycoproteins involved in proteolysis and cell adhesion. ADAM8 might have an important role in allergic inflammation. It can cleave a variety of substrates and is a sheddase for VCAM-1 and CD23, the low-affinity IgE receptors.

METHODS

To evaluate the contribution of ADAM8 to the pathogenesis of eosinophilic pneumonia (EP), we measured the concentrations of soluble ADAM8 (sADAM8) and its substrates, soluble VCAM-1 (sVCAM-1) and soluble CD23 (sCD23), in bronchoalveolar lavage fluid from patients with smoking-induced acute eosinophilic pneumonia (AEP), chronic idiopathic eosinophilic pneumonia (CEP), and drug-induced eosinophilic pneumonia (drug-EP).

RESULTS

The sADAM8 and sVCAM-1 concentrations were increased in AEP and CEP. The sCD23 concentration was elevated in AEP. In AEP, but not CEP, the sADAM8 concentration significantly correlated with those of both sVCAM and sCD23.

CONCLUSION

The pathogenesis of AEP, CEP, and drug-EP was distinct with regard to ADAM8. Our results are the first to associate ADAM8 with eosinophilic responses and lung inflammation in humans.

Cytokines or their antagonists for the treatment of asthma

T helper (Th) type 2 cytokines, particularly interleukin (IL)-4, IL-5, and IL-13, may be important in the development of allergic asthma. Humanized monoclonal antibodies (MoAbs) against IL-5 and a recombinant human soluble IL-4 receptor (sIL-4R) have been developed as possible treatments. These approaches have not yet proven to be successful in patients with persistent asthma. This may suggest that neither IL-4 nor IL-5 is important in asthma pathogenesis. There is, however, insufficient information about the efficacy of sIL-4R and the anti-IL-5 MoAbs in asthma to draw any firm conclusions about the importance of these Th2 cytokines. Also, the administration of the potentially antiinflammatory cytokines IL-12 and interferon-gamma has not shown benefit in asthmatic patients. By contrast, the treatment of severe oral steroid-dependent asthma with soluble tumor necrosis factor-alpha receptor has demonstrated very promising results, suggesting that this cytokine plays an important role in the persistence of severe asthma.

Factors contributing to nasal allergic late phase eosinophilia

OBJECTIVE

This study focused on factors contributing to eosinophilia after intranasal allergen challenge.

METHODS

Nasal secretions of 13 allergic individuals were gained over a period of 8 hours after nasal allergen challenge. Early and late phase reactions were determined by acoustic rhinometry and changes of volume and total protein in nasal secretions. Eosinophilia was demonstrated by nasal eosinophilic cationic protein. Interleukin (IL)-5; the chemokines IL-8, monocyte chemotactic protein (MCP)-1 and MCP-3, and eotaxin; soluble vascular cell adhesion molecule 1 (sVCAM-1); and the leukotriene C4 (LTC4) were analyzed by enzyme-linked immunosorbent assay for their suggested impacts on tissue eosinophilia.

RESULTS

By means of rhinometry, we observed in 69% an alternating type of late phase response, followed by a bilateral (15%) or unilateral (8%) type. A biphasic kinetic could be demonstrated by changes in nasal volume and total protein of nasal secretions, reflecting the early and late phase responses. A typical late phase kinetic was observed for IL-5, MCP-1, eotaxin, sVCAM-1, and LTC4. Interleukin 8 was characteristic for early phase reaction but increased in late phase as well. We could not detect any MCP-3 in our samples.

CONCLUSIONS

Our data point to a relevant role of the T(H)2 cytokine IL-5; of the chemokines IL-8, MCP-1, and eotaxin; of the adhesion molecule sVCAM-1; and of the leukotriene LTC4 for the allergic late phase eosinophilia.

Alterations in vasodilator-stimulated phosphoprotein (VASP) phosphorylation: associations with asthmatic phenotype, airway inflammation and beta2-agonist use

BACKGROUND

Vasodilator-stimulated phosphoprotein (VASP) mediates focal adhesion, actin filament binding and polymerization in a variety of cells, thereby inhibiting cell movement. Phosphorylation of VASP via cAMP and cGMP dependent protein kinases releases this "brake" on cell motility. Thus, phosphorylation of VASP may be necessary for epithelial cell repair of damage from allergen-induced inflammation. Two hypotheses were examined: (1) injury from segmental allergen challenge increases VASP phosphorylation in airway epithelium in asthmatic but not nonasthmatic normal subjects, (2) regular in vivo beta2-agonist use increases VASP phosphorylation in asthmatic epithelium, altering cell adhesion.

METHODS

Bronchial epithelium was obtained from asthmatic and non-asthmatic normal subjects before and after segmental allergen challenge, and after regularly inhaled albuterol, in three separate protocols. VASP phosphorylation was examined in Western blots of epithelial samples. DNA was obtained for beta2-adrenergic receptor haplotype determination.

RESULTS

Although VASP phosphorylation increased, it was not significantly greater after allergen challenge in asthmatics or normals. However, VASP phosphorylation in epithelium of nonasthmatic normal subjects was double that observed in asthmatic subjects, both at baseline and after challenge. Regularly inhaled albuterol significantly increased VASP phosphorylation in asthmatic subjects in both unchallenged and antigen challenged lung segment epithelium. There was also a significant increase in epithelial cells in the bronchoalveolar lavage of the unchallenged lung segment after regular inhalation of albuterol but not of placebo. The haplotypes of the beta2-adrenergic receptor did not appear to associate with increased or decreased phosphorylation of VASP.

CONCLUSION

Decreased VASP phosphorylation was observed in epithelial cells of asthmatics compared to nonasthmatic normals, despite response to beta-agonist. The decreased phosphorylation does not appear to be associated with a particular beta2-adrenergic receptor haplotype. The observed decrease in VASP phosphorylation suggests greater inhibition of actin reorganization which is necessary for altering attachment and migration required during epithelial repair.

Human mast cells express multiple EP receptors for prostaglandin E2 that differentially modulate activation responses

Prostaglandin E2 (PGE2) blocks mast-cell (MC)-dependent allergic responses in humans but activates MCs in vitro. We assessed the functions of the EP receptors for PGE2 on cultured human MCs (hMCs). hMCs expressed the EP3, EP2, and EP4 receptors. PGE2 stimulated the accumulation of cyclic adenosine monophosphate (cAMP), and suppressed both Fc epsilonRI-mediated eicosanoid production and tumor necrosis factor-alpha (TNF-alpha) generation. PGE2 also caused phosphorylation of extracellular signal-regulated kinase (ERK), exocytosis, and production of prostaglandin D2 (PGD2), as well as leukotriene C4 (LTC4) when protein kinase A (PKA) was inhibited. An EP3 receptor-selective agonist, AE-248, mimicked PGE2-mediated ERK phosphorylation, exocytosis, and eicosanoid formation. Selective agonists of both EP2 and EP4 receptors (AE1-259-01 and AE-329, respectively) stimulated cAMP accumulation. No selective agonist, alone or in combination, was as effective as PGE2. AE-248, AE1-259-01, and AE-329 all inhibited Fc epsilonRI-mediated TNF-alpha generation, while AE1-259-01 blocked eicosanoid production. PGE2 caused the expression of inducible cAMP early repressor (ICER) by a pathway involving PKA and ERK. Thus, while PGE2 activates MCs through EP3 receptors, it also counteracts Fc epsilonRI-mediated eicosanoid production through EP2 receptors and PKA, and blocks cytokine transcription. These functions explain the potency of PGE2 as a suppressor of early- and late-phase allergic responses.

RU486 blocks the anti-inflammatory effects of exercise in a murine model of allergen-induced pulmonary inflammation

In an ovalbumin (OVA)-driven murine model of allergic pulmonary inflammation, we have shown previously that moderate-intensity aerobic exercise training attenuates inflammatory responses, disease progression, and NF-kappaB activation within the sensitized lung. Glucocorticoids (GCs), potent anti-inflammatory agents, have been shown to alter transcriptional events that are important in asthmatic pathogenesis, such as NF-kappaB activation. Notably, exercise training can alter the production and signaling capacity of endogenous GCs. Because GCs exert their anti-inflammatory effects through binding to intracellular glucocorticoid receptors (GRs), we examined the role of the GR in facilitating the anti-inflammatory effects of exercise. Results show that, in exercised OVA-sensitized mice, treatment with the GR antagonist RU486 blocked the exercise-induced reductions in cellular infiltration of the airways (p < .05), KC and soluble VCAM-1 protein levels in the bronchoalveloar lavage fluid (p < .05), and NF-kappaB translocation and DNA binding within the lung to levels similar to those observed in sedentary OVA-sensitized mice. Importantly, RU486 treatment also blocked exercise-induced increases in GR nuclear translocation to the levels seen in sensitized control mice. Together, these results suggest that GR nuclear translocation and NF-kappaB activation play roles in mediating the anti-inflammatory effects of exercise in allergen-mediated lung pathology.

Adhesion molecules as therapeutic targets

This article focuses on the importance of cell-adhesion molecules in the process of allergic inflammation. After reviewing the contribution of different families of adhesion molecules to the cellular recruitment cascade, phenotypic characteristics of leukocyte subtypes are discussed to illustrate how expression of differing patterns of adhesion molecules and their counterligands within tissues influence the type of inflammatory response that occurs. The involvement of adhesion molecules in allergic inflammation in animal models and human studies is described. Examples of specific adhesion-molecule antagonists are provided, and results of their use in human studies of allergic and other inflammatory conditions are discussed.

TRAIL in the airways

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) is an important immunomodulatory factor that may play a role in the structural changes observed in the asthmatic airways. In vitro as well as in vivo studies have evidenced a dual role for TRAIL: it can either function as a pro- or anti-inflammatory cytokine on inflammatory cells, participating in the initiation and resolution of inflammatory and immune responses. TRAIL is expressed in the airways by inflammatory cells infiltrated in the bronchial mucosa, as well as by structural cells of the airway wall including fibroblasts, epithelial, endothelial, and smooth muscle cells. By releasing TRAIL, these different cell types may then participate in the increased levels of TRAIL observed in bronchoalveolar lavage fluid from asthmatic patients. Taken together, this suggests that TRAIL may play a role in inflammation in asthma. However, concerning its role is dual in the modulation of inflammation, further studies are needed to elucidate the precise role of TRAIL in the airways.

Reassessing the Th2 cytokine basis of asthma

T helper (Th) 2 cytokines, particularly interleukin 4 (IL-4), IL-5 and IL-13, might be important in the development of allergic asthma. Humanized monoclonal antibodies (hMAbs) against IL-5, and a recombinant soluble human IL-4 receptor have been developed as possible treatments for this disorder. However, these approaches have not yet proven to be successful in the treatment of persistent asthma, suggesting that neither IL-4 nor IL-5 is important in asthma pathogenesis. Indeed, there is insufficient information about the efficacy of soluble IL-4 receptor and the anti-IL-5 hMAbs in the treatment of asthma to draw firm conclusions about the importance of these Th2 cytokines. Nevertheless, because IL-4 is required for IgE production and IL-5 is required for eosinophilopoesis, these Th2 cytokines must remain important candidates for a role in the pathogenesis of allergic asthma.

Ligand density modulates eosinophil signaling and migration

Eosinophils are a major component of the inflammatory response in persistent airway inflammation in asthma. The factors that determine the retention of eosinophils in the airway remain poorly understood. Elevated levels of fibronectin have been observed in the airway of patients with asthma, and the levels correlate with eosinophil numbers. To determine if fibronectin density modulates eosinophil function, we investigated the effect of fibronectin and vascular cell adhesion molecule 1 (VCAM-1) density on eosinophil migration and signaling via the p38 and extracellular regulated kinase (ERK)-mitogen-activated protein kinase (MAPK) signaling pathways. There was a dose-dependent inhibition of eosinophil spreading and migration on increasing concentrations of fibronectin but not VCAM-1. In addition, activation of p38 MAPK was inhibited at high fibronectin but not high VCAM-1 concentrations, and ERK activity was slightly reduced at high VCAM-1 and fibronectin concentrations. Together, the results demonstrate that fibronectin but not VCAM-1 inhibits eosinophil migration and signaling.

Interleukin-4 and interleukin-4 soluble receptor alpha levels in bronchoalveolar lavage from children with asthma

BACKGROUND

In asthma there is increased expression of the Th2-type cytokine interleukin-4 (IL-4). IL-4 is important in immunoglobulin isotype switching to immunoglobulin E and adhesion of eosinophils to endothelium.

OBJECTIVE

We hypothesized that levels of IL-4 in bronchoalveolar lavage (BAL) fluid would be increased in stable, atopic asthmatic children compared with controls and that levels of its physiologic inhibitor IL-4 soluble receptor alpha (IL-4sR alpha) would be correspondingly decreased.

METHODS

One hundred sixteen children attending a children's hospital for elective surgery were recruited. A nonbronchoscopic BAL was performed, and IL-4 and IL-4sR alpha were measured in the BAL supernatants.

RESULTS

There was no significant difference in IL-4 concentrations between atopic asthmatic children, atopic normal controls, and nonatopic normal controls [0.13 pg/mL (0.13 to 0.87) vs 0.13 pg/mL (0.13 to 0.41) vs 0.13 pg/mL (0.13 to 0.5), P = 0.65]. IL-4sR alpha levels were significantly increased in asthmatic patients compared with atopic controls [6.4 pg/mL (5.0 to 25.5) vs 5.0 pg/mL (5.0 to 9.9), P = 0.018], but not when compared with the nonatopic controls [5.2 pg/mL (5.0 to 10.6), P = 0.19].

CONCLUSIONS

Contrary to expectation, IL-4sR alpha levels are increased in BAL from stable asthmatic children compared with nonatopic controls, and we speculate that IL-4sR alpha is released by inflammatory cells in the airways to limit the proinflammatory effects of IL-4.

A comparison of the airway response to segmental antigen bronchoprovocation in atopic asthma and allergic rhinitis

BACKGROUND

Patients with allergic asthma and those with allergic rhinitis (without asthma) share many immunopathologic features but differ in the presence of lower airway symptoms in response to antigen.

OBJECTIVES

We sought to compare the airway inflammatory response to antigen in patients with atopic asthma and allergic rhinitis.

METHODS

Segmental bronchoprovocation with saline or ragweed antigen was performed in 9 patients with atopic asthma and 9 patients with allergic rhinitis without asthma. The antigen dose used in segmental bronchoprovocation was 10% of the dose that caused a 20% decrease in FEV1 in response to inhalation challenge. Bronchoalveolar lavage (BAL) was performed from the saline- and antigen-challenged segments at 5 minutes and 48 hours after challenge. BAL fluid was analyzed for cell count and differential, distribution of lymphocytes, and concentration of soluble factors (histamine, IL-5, matrix metalloproteinase 9, tissue inhibitor of metalloproteinase 1, and fibronectin). In addition, BAL cells were cultured ex vivo, and IL-5, IFN-gamma, and IL-10 generation was measured.

RESULTS

Antigen challenge led to similar patterns of cellular recruitment, mediator levels, and BAL cell cytokine generation in both groups; however, the dose of antigen required to promote comparable responses in the airway was significantly less in patients with asthma.

CONCLUSION

These data suggest that the pattern of acute airway inflammation in response to allergen does not by itself explain antigen-induced lower airway obstruction and asthma symptoms. We speculate that other factors, such as increased airway sensitivity to allergen or preexisting airway injury and remodeling, might explain why patients with asthma and rhinitis differ in their clinical and physiologic response to antigen exposure.

T lymphocyte-mediated changes in airway smooth muscle responsiveness are attributed to induced autocrine release and actions of IL-5 and IL-1beta

BACKGROUND

Bidirectional stimulatory cross-talk was recently found to exist between activated T cells and airway smooth muscle (ASM) cells, a process that involves coligation of specific cellular adhesion-costimulatory molecules that results in the induction of proasthmatic-like changes in ASM responsiveness.

OBJECTIVE

The present study examined whether the cooperative intercellular signaling between activated T cells and ASM cells is coupled to the induced expression and actions of IL-5 and IL-1beta.

METHODS

Agonist-induced constrictor and relaxant responses were examined in rabbit ASM segments exposed to resting and anti-CD3-activated T cells in the absence and presence of either an anti-IL-5 receptor mAb or the recombinant human IL-1 receptor antagonist. In addition, mRNA and protein expression of IL-5 and IL-1beta were assayed under control and anti-CD3-stimulated conditions.

RESULTS

Relative to inactive T cells, incubation of ASM tissues with anti-CD3-activated T cells induced proasthmatic-like changes in agonist-mediated ASM responsiveness. This T cell-induced perturbation in ASM responsiveness was ablated by pretreating the tissues with either an anti-IL-5 receptor mAb or IL-1 receptor antagonist. Moreover, exposure of ASM cells to anti-CD3-activated T cells elicited an initial increased mRNA expression and release of IL-5, followed by an enhanced expression and release of IL-1beta, and the induced release of these cytokines was prevented in ASM cells that were pretreated with an anti-IL-5 receptor mAb.

CONCLUSION

Collectively, these observations provide new evidence demonstrating that exposure of naive ASM cells to activated T cells induces the sequential release of IL-5 and IL-1beta from the ASM cells and that the latter cytokines act in an autocrine manner to elicit the proasthmatic phenotype of altered ASM responsiveness.

The role of transcription factors in allergic inflammation

The induction of allergic inflammation and the expression of allergic disorders are dependent on the coordinated regulation of numerous genes. The products of these genes determine lymphocyte phenotype, immunologic responsiveness, eosinophil and mast cell development, activation, migration and life span, adhesion molecule expression, cytokine synthesis, cell-surface receptor display, and processes governing fibrosis and tissue repair. Although the expression of gene products involved in these processes is regulated at multiple levels (eg, transcription, mRNA processing, translation, phosphorylation, and degradation), transcription represents an essential and often the most important determinant of their contribution to cellular function. Signal-dependent and cell type-specific regulation of gene expression is generally achieved by means of combinatorial interactions between sequence-specific transcription factors that recruit chromatin remodeling machinery and general transcription factors to promoter and enhancer regions of RNA polymerase II-dependent genes. As targets of signal-transduction pathways, transcription factors integrate the response of the cell to the myriad of inputs it receives. This integration can be accomplished by the effect of signaling cascades on the activation status or subcellular locus of transcription factors or by transcription factor dimerization induced by means of ligand binding. This review will identify the major families of transcription factors important in allergic mechanisms and discuss their interactions, their mechanisms of action, and their interrelated and competitive actions, as well as implications for therapy of allergic disorders.

IL-4 induces IL-6 and signs of allergic-type inflammation in the nasal airways of nonallergic individuals

In addition to its more widely recognized role in promoting IgE synthesis, we speculate that interleukin-4 (IL-4) may modulate both allergic- and nonallergic-type inflammatory processes in the airway mucosa. We examined in vivo the effect of IL-4 on granulocyte and cytokine homeostasis in the nasal airways of nonallergic volunteers. Ten (N = 10) healthy subjects received nasal IL-4 (10 microg) or saline (0.9%) challenges on separate occasions. Nasal lavage was obtained before and 24 h after nasal challenges. We report that IL-4 induced a significant increase in IL-6 and produced elevated levels of eosinophils and neutrophils compared to saline. These data demonstrate that IL-4 can modulate both allergic- and nonallergic-type inflammatory responses in the nasal airways of nonallergic individuals.

Pathogenesis of asthma

There is now strong evidence that airway inflammation is a predominant underlying problem in patients with asthma, and it has been suggested that ongoing inflammation may lead to airway injury and remodeling. There is also recent evidence that longstanding asthma could be associated with loss of elastic recoil, which can enhance airway obstruction and worsen asthma control [82,83]. Therefore, the use of anti-inflammatory therapy has been advocated in all guidelines, including the National Asthma Education and Prevention Program (NAEPP) Expert Panel Report [84] and its recent update [85] that recommended inhaled steroids as a first mode of therapy for patients with mild, moderate, or severe, persistent asthma. There is preliminary evidence that early institution of anti-inflammatory therapy might lead to disease modification and limit the progression of subepithelial fibrosis and airway remodeling. The pathogenesis of asthma clearly involves many cells and mediators, although the contribution of each individual factor is probably different from patient to patient depending on the setting and stimulus. Although currently available therapies are highly effective in controlling asthma symptoms and limiting exacerbations in the majority of patients, there is still a subset of patients that proceed to develop severe asthma with decreased lung function, lack of responsiveness to therapy, or frequent exacerbations. It is hoped that rapid progress in the area of asthma genetics and pharmacogenetics will yield a more precise and patient-specific understanding of asthma pathogenesis and allow practitioners to prescribe therapies that are designed for a particular patient or exacerbation. That will undoubtedly help to improve the care of asthma, limit its morbidity, and reduce the side effect of medications.

Pulmonary function changes and immunomodulation of Th 2 cytokine expression induced by aminophylline after sensitization and allergen challenge in brown Norway rats

BACKGROUND AND OBJECTIVE

Evidence has shown that aminophylline has bronchoprotective, anti-inflammatory, and immunomodulatory effects. Our purpose was to evaluate the effect of different doses of aminophylline on the late-phase reaction, bronchial hyperresponsiveness (BHR) and T cell-related cytokine mRNA expression in brown Norway rats induced by ovalbumin (OA) sensitization.

METHODS

Forty rats were equally divided into four groups. Groups I, II, and III animals were sensitized and subsequently provoked with OA. Aminophylline 25 mg/kg was given intraperitoneally to the group I animals and 5 mg/kg to group II animals. Group III animals received intraperitoneal normal saline. Group IV breathed aerosolized saline as a control. After OA provocation, the animals were anesthetized. Pulmonary function tests were performed at baseline and after varying doses of acetylcholine. Thereafter, bronchoalveolar lavage was performed and the lungs were examined histologically. Total RNA was extracted from lung tissue and reverse transcriptase-polymerase chain reaction was performed using primers for interleukin (IL)-2, IL-4, IL-5, IL-6, IL-10, interferon-gamma, inducible nitric oxide synthase, and beta-actin.

RESULTS

Group III had worse pulmonary function tests, more severe BHR, and more severe lung inflammation, higher IL-4 and IL-10 cytokine levels in bronchoalveolar lavage fluid, and higher IL-4, IL-5, IL-6, IL-10, tumor necrosis factor-alpha and inducible nitric oxide synthase mRNA expression than the other three groups. Expression of IL-2 and interferon-gamma was significantly reduced in group III.

CONCLUSIONS

Both low and high dose aminophylline are effective in preventing late-phase bronchoconstriction, BHR, and an inflammatory response. Aminopylline decreases T helper cell 2-related cytokine mRNA expression but increases T helper cell 1-related cytokines mRNA expression.

Serum levels of interleukins (IL)-4, IL-5, IL-13, and interferon-gamma in acute asthma

T-cell activation and alteration of cytokine levels are involved in the pathogenesis of bronchial asthma. However, the profile of circulating T-lymphocyte subsets and related cytokines during acute asthmatic attacks is still unclear. We hypothesized that serum levels of interleukin (IL)-4, IL-5, and IL-13 would be increased, whereas IFN-y would be decreased in acute asthma. The subjects enrolled in this study included 58 acute asthmatics, 22 asymptomatic asthmatics, and 10 healthy controls. Serum levels of IL-4, IL-5, IL-13, and IFN-gamma were measured using a sandwich enzyme-linked immunosorbent assay. We correlated serum levels of IL-4, IL-5, IL-13, and IFN-gamma with initial forced expiratory volume in 1 sec (FEV1). Compared with control subjects, acute asthmatics had significantly increased levels of circulating IL-4 (p < 0.001), IL-5 (p < 0.001), and IL-13 (p < 0.001), although the differences were of borderline significance in serum IFN-gamma (p = 0.069). There were also significant differences in the circulating levels of IL-4, IL-5, and IL-13 between acute asthmatics and asymptomatic asthmatics. There was no significant association between initial FEV1 and serum levels of IL-4 or IL-13, however, among acute asthmatics, a lower initial FEV1 was associated with higher IL-5 and/or lower IFN-gamma levels. Our results suggest that serum levels of IL-4, IL-5, and IL-13 may be elevated in acute asthma, and that higher levels of IL-5 and/or lower levels of IFN-gamma are associated with severe airway obstruction.

Th2 cytokines and asthma. The role of interleukin-5 in allergic eosinophilic disease

Interleukin-5 is produced by a number of cell types, and is responsible for the maturation and release of eosinophils in the bone marrow. In humans, interleukin-5 is a very selective cytokine as a result of the restricted expression of the interleukin-5 receptor on eosinophils and basophils. Eosinophils are a prominent feature in the pulmonary inflammation that is associated with allergic airway diseases, suggesting that inhibition of interleukin-5 is a viable treatment. The present review addresses the data that relate interleukin-5 to pulmonary inflammation and function in animal models, and the use of neutralizing anti-interleukin-5 monoclonal antibodies for the treatment of asthma in humans.

Antisense inhibition of membrane-bound human interleukin-5 receptor-alpha chain does not affect soluble receptor expression and induces apoptosis in TF-1 cells

Binding of human interleukin-5 (HuIL-5) to its membrane-anchored receptor (IL-5R) triggers multiple signaling pathways, cellular proliferation, and maturational responses, as well as protection from apoptosis. In contrast, soluble forms of the HuIL-5R have been shown to inhibit IL-5 signaling and, therefore, may represent naturally occurring negative regulators of IL-5 function. Because of the central role of IL-5 in promoting eosinophilia and airway hyperresponsiveness in animal models of asthma, antisense oligonucleotides specific either for the membrane form alone or for sequences shared between both the membrane and soluble forms of the HuIL-5Ralpha ligand binding chain were designed. The activities of these oligonucleotides were characterized in IL-5R-expressing erythroleukemic TF-1 cells. Herein we report that an antisense oligonucleotide targeted to a sequence unique to the alternatively spliced membrane-bound form of the HuIL-5Ralpha chain has been developed that selectively inhibits membrane, but not soluble, mRNA isoform expression. Both this membrane-specific oligonucleotide and an antisense oligonucleotide targeted to sequence common to both membrane and soluble isoforms were found to potently suppress cell surface IL-5Ralpha levels and IL-5-mediated cell survival by inducing apoptosis similar to IL-5 withdrawal. Thus, these oligonucleotides represent unique genetic agents with therapeutic potential for diseases with an eosinophilic component.

Relationship between infiltrating cells and adhesion molecules in the nasal mucosa of patients with allergic rhinitis

Antigen-induced changes of cell adhesion molecules and their relationships to infiltrating cells were investigated immunohistochemically in nasal mucosa of perennial allergic rhinitis patients. An increased expression of E-selectin and VCAM-1 was noted on the vascular endothelium of the nasal mucosa 15-25 h after the topical antigen challenge. Although there was no increased expression of ICAM-1, we noted a positive correlation between the expression of E-selectin and ICAM-1. The expression of E-selectin and VCAM-1 as well as ICAM-1 was revealed to be correlated with the number of EG2-positive cells and CD4-positive cells, but not with elastase-positive cells. These findings suggest that all these adhesion molecules play a role in the topical influxes of eosinophils and CD4-positive cells in allergic nasal mucosa.

Effects of anti-VLA-4 monoclonal antibody treatment in murine model of allergic rhinitis

In order to study the role of VLA-4 in allergic rhinitis, the effects of anti-mouse VLA-4 monoclonal antibody (mAb) were evaluated in a murine model. BALB/c mice were sensitized first by i.p. injections (general sensitization) and then by daily nasal dripping of antigen (local sensitization) before performing a nasal antigen challenge. The mAb was applied either before the antigen challenge (BC group), before the local sensitization (BL group) or before the general sensitization (BS group). The effects were evaluated in terms of antigen-induced early-phase nasal symptoms (sneezing), late-phase nasal eosinophilia and the serum level of antigen-specific IgE. Antigen-induced nasal eosinophilia was significantly (p = 0.009) reduced in the BL group but not in the BC group (number of eosinophils = 114 +/- 15.1, 244 +/- 52.8 and 347 +/- 50.5 in the BL, BC and control groups, respectively). The serum level of the specific IgE was also significantly (p = 0.038) reduced in the BL group but not in the BC group (optical density = 1.18 +/- 0.07, 1.28 +/- 0.13 and 1.58 +/- 0.14 in the BL, BC and control groups, respectively). The suppressive effect on sneezing was not significant in either the BL or BC groups. In the BS group, suppressive effects on antigen-induced nasal responses and the specific IgE level were not statistically significant. These findings suggest that VLA-4 plays an important role in the topical booster or priming effects during repeated nasal antigen exposures in pre-sensitized animals.

New induction of leukotriene A4 hydrolase by interleukin-4 and interleukin-13 in human polymorphonuclear leukocytes

Interleukin (IL)-4, IL-10, and IL-13, Th2 cell–derived cytokines, play major roles in the pathophysiology of allergic diseases. These cytokines up-regulate or down-regulate the production of arachidonic acid metabolites. In this study, we have investigated the effect of IL-4, IL-10, IL-13, and other cytokines on A23187-stimulated synthesis of leukotriene (LT) B4 in human polymorphonuclear leukocytes (PMNs). Production of LTB4 was measured by specific radioimmunoassay and high performance liquid chromatography. Messenger RNA (mRNA) expression of cytosolic phospholipase A2 (cPLA2), 5-lipoxygenase (5-LO), and LTA4 hydrolase, which were involved in the synthesis of LTB4, was determined by reverse transcription–polymerase chain reaction and Northern blot analysis. Protein synthesis of their enzymes was determined by Western blot analysis. IL-4 and IL-13 enhanced A23187-stimulated LTB4 synthesis and increased mRNA expression and protein synthesis of LTA4hydrolase, but not those of cPLA2 or 5-LO. These results indicate that IL-4 and IL-13 transcriptionally or post-transcriptionally up-regulate the synthesis of LTB4, a potent chemotactic factor to PMNs, at the enzyme level of LTA4 hydrolase, and this up-regulation mechanism may participate in the development of allergic inflammation.

New induction of leukotriene A4 hydrolase by interleukin-4 and interleukin-13 in human polymorphonuclear leukocytes

Interleukin (IL)-4, IL-10, and IL-13, Th2 cell–derived cytokines, play major roles in the pathophysiology of allergic diseases. These cytokines up-regulate or down-regulate the production of arachidonic acid metabolites. In this study, we have investigated the effect of IL-4, IL-10, IL-13, and other cytokines on A23187-stimulated synthesis of leukotriene (LT) B4 in human polymorphonuclear leukocytes (PMNs). Production of LTB4 was measured by specific radioimmunoassay and high performance liquid chromatography. Messenger RNA (mRNA) expression of cytosolic phospholipase A2 (cPLA2), 5-lipoxygenase (5-LO), and LTA4 hydrolase, which were involved in the synthesis of LTB4, was determined by reverse transcription–polymerase chain reaction and Northern blot analysis. Protein synthesis of their enzymes was determined by Western blot analysis. IL-4 and IL-13 enhanced A23187-stimulated LTB4 synthesis and increased mRNA expression and protein synthesis of LTA4hydrolase, but not those of cPLA2 or 5-LO. These results indicate that IL-4 and IL-13 transcriptionally or post-transcriptionally up-regulate the synthesis of LTB4, a potent chemotactic factor to PMNs, at the enzyme level of LTA4 hydrolase, and this up-regulation mechanism may participate in the development of allergic inflammation.

NOVEL THERAPEUTIC APPROACHES FOR ALLERGIC RHINITIS

The last 2 decades have witnessed enormous changes in our understanding of allergic rhinitis. As we have begun to unravel the complex underlying immunologic and inflammatory pathophysiology of the disease, new therapeutic strategies as well as specific molecular and cellular constituents have emerged as potential targets for clinical intervention. These efforts also have shed light on the mechanisms by which current antiallergy medications act—or sometimes fail to be effective.7, 31, 51, 89 The similar pathophysiologic basis for allergic rhinitis and the often comorbid condition, asthma, was underscored in the recently published American Thoracic Society Workshop Summary on the Immunobiology of Asthma and Rhinitis: Pathogenic Factors and Therapeutic Options.¹⁸ In his conclusion, workshop chair, Thomas Casale,¹⁸ counsels readers to consider that “…allergic asthma and rhinitis represent a systemic disease affecting two organs, the lung and the nose. Asthma and allergic rhinitis share many of the same pathogenic factors, but they operate in different parts of the airway. Inflammatory cells and mediators are often the same, and there may be common alterations that occur in the immune system.” Thus, therapeutic strategies and potential therapeutic agents found to be beneficial in the treatment of one airway target may show similar effects in the other. For this reason, and because many of the therapies now being developed are at early stages in their evolution, physicians interested in rhinitis therapy also must examine what is known about these agents in asthma.

One avenue of active research has been the role of leukotrienes and other mediators in the pathophysiology of asthma and rhinitis. Three leukotriene modifiers now have been approved for the treatment of asthma in the United States; their potential use in the treatment of rhinitis has been a focus of considerable speculation and investigation. An early “day in the park” study showed that with antileukotriene therapy, patients with rhinitis had demonstrable improvements in their rhinitic symptoms.²⁹ Roquet et al⁸³ reported that in the treatment of asthma, there was a synergistic effect when an antileukotriene agent and an antihistamine were used, compared with either drug alone. A product combining an antileukotriene with an antihistamine is currently under development.

The most exciting developments, however, may be in the immunology arena. As described by Baraniuk elsewhere in this issue, the pathophysiology of allergic rhinitis is highly complex. Multiple interacting, interdependent, and redundant pathways and molecular and cellular constituents are involved in the pathogenesis of allergic rhinitis.

Briefly, exposure of the nasal mucosa to allergen in a sensitized individual leads to the release and further production of inflammatory mediators and the release of cytokines.⁵ These released cytokines activate endothelial cells, thereby inducing expression of adhesion receptors on the cell surface and initiating a cascade of events that facilitates transendothelial migration of inflammatory cells. T lymphocytes also are activated by these cytokines. Within a given tissue, specific patterns of cytokines are released, dependent on the dominant subset of local T lymphocytes. These, in turn, lead to the preferential activation and recruitment of specific inflammatory cells and the characteristic cellular inflammation observed in allergic rhinitis.

The increased number of very late activation antigen-4-positive cells correlates with eosinophils and severity of disease in the induced sputum of asthmatic patients

BACKGROUND

Lymphocyte function associate-1 (LFA-1), macrophage antigen-1 (Mac-1), and very late activation antigen-4 (VLA-4) are involved in the infiltration of leukocytes into the tissues. Experimental models of allergic inflammation suggest that VLA-4 could determine the selective recruitment of eosinophils into the inflamed airways.

OBJECTIVE

Our purpose was to evaluate the involvement of integrins in eosinophil recruitment in asthma.

METHODS

We evaluated by immunocytochemistry the expression of VLA-4, LFA-1, and Mac-1 and their relationship with inflammatory cells and severity of disease in the induced sputum of 20 mild to moderate atopic asthmatic subjects and in 8 healthy subjects.

RESULTS

The number of VLA-4+ cells is increased in asthmatic patients and VLA-4 is mainly localized on eosinophils. Furthermore, VLA-4+ cells are significantly related to eosinophils. In contrast, LFA-1 and Mac-1 cellular expressions do not differ between asthmatic and control subjects and are not related to any specific cell type. Eosinophils and VLA-4+ cells are significantly higher in moderately compared with mildly asthmatic patients (P <.01, P <.05) and with healthy control subjects (P <.0005, P <.001). Eosinophils and VLA-4+ cells are also higher in mildly asthmatic patients compared with control subjects (P <.001, P <.005).

CONCLUSION

This is the first report demonstrating, by a noninvasive method in humans, that VLA-4+ cells are increased and correlate with the eosinophils in the induced sputum of atopic patients with mild to moderate asthma and that VLA-4 expression is related to the severity of disease.

Molecular pathology of allergic disease: I: lower airway disease

Asthma is a complex disorder associated with eosinophil infiltration and the activation of T lymphocytes within the airways. Recent advances in the pathophysiologic mechanisms of asthma point to the importance of eosinophil-basophil progenitor cells and a family of transcription factors that underlie the development of T(H)2-type responses. Further research is needed to address the development of chronic inflammatory changes, the role of profibrotic cytokines, and especially their reliance on eosinophils in the lungs.

Inflammation markers in the serum of salt miners

The inflammation markers alpha-1-antitrypsin (AAT), Clara cell protein (CC-16), soluble interleukin-2-receptor (IL-R) and the soluble adhesion molecule E-selectin, the intercellular adhesion molecule (ICAM-1) and the vascular adhesion molecule (VCAM-1) were determined in the serum of 195 salt-exposed miners to analyse dose-response relationships between markers and potash dust. Alpha-1-antitrypsin, Clara-cell protein, IL2-R, E-selectin and VCAM-1 were not changed by salt exposure, however the ICAM-1 level in the serum fell slightly as the salt exposure increased. This effect was strongest in the group of smokers, still visible in the group of ex-smokers, no effect was seen in non-smokers. Markers, with the exception of VCAM-1, were influenced by tobacco exposure. Since markers were not elevated in relation to salt dust exposure, the results do not support an inflammatory effect of potash dust on the respiratory system.

Engagement of α4β7 Integrins by Monoclonal Antibodies or Ligands Enhances Survival of Human Eosinophils In Vitro

Asthma is characterized by an airway inflammatory infiltrate that is rich in eosinophilic leukocytes. Cellular fibronectin and VCAM-1, ligands for α4 integrins, are enriched in the fluid of airways of allergic patients subjected to Ag challenge. We therefore hypothesized that ligands of α4 integrins can promote eosinophil survival independent of cell adhesion. Cellular fibronectin and VCAM-1 increased viability of human peripheral blood eosinophil in a dose- and time-dependant manner whether the ligand was coated on the culture well or added to the medium at the beginning of the assay. Eosinophils cultured with cellular fibronectin were not adherent to the bottom of culture wells after 3 days. Treatment with mAb Fib 30 to β7, but not mAb P4C10 or TS2/16 to β1, increased eosinophil survival. The increased survival of eosinophils incubated with Fib 30 was blocked by Fab fragments of another anti-β7 mAb, Fib 504. Eosinophils incubated with soluble cellular fibronectin or mAb Fib 30 for 6 h demonstrated a higher level of GM-CSF mRNA than eosinophils incubated with medium alone. Addition of neutralizing mAb to GM-CSF during incubation, but not mAbs to IL-3 or IL-5, reduced the enhancement of eosinophil survival by soluble cellular fibronectin or mAb Fib 30 to control levels. Thus, viability of eosinophils incubated with cellular fibronectin or VCAM-1 is due to engagement, probably followed by cross-linking, of α4β7 by soluble ligand (or mAb) that stimulates autocrine production of GM-CSF and promotes eosinophil survival.

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

BACKGROUND

This study assessed the heterogeneity of cytokine expression in asthma before and after local allergen challenge.

METHODS

BAL T cells were obtained 10 min or 24 h after local endobronchial allergen challenge in atopic asthmatic subjects. T cells were cloned by direct limiting dilution. mRNA expression was assessed by RT-PCR, and cytokine protein production by ELISA.

RESULTS

Unstimulated baseline BAL T cells expressed mRNA for IFN-gamma, IL-13, and TNF-alpha. A minority of samples expressed IL-4 and IL-5, but no IL-3 mRNA was detected. PHA stimulation increased expression of IL-3, IL-4, and IL-5 mRNA in 4/6 samples. IL-13 and GM-CSF mRNA were found in BAL cells after allergen challenge, but expression of IFN-gamma was reduced. Both IL-4 and IL-3 were strongly upregulated after PHA stimulation, while the expression of TNF-alpha and IFN-gamma was reduced, compared to equivalent baseline samples. Seventeen panels of BAL T-cell clones were derived (average cloning efficiency 1/40 T cells). Seven panels survived to 8 weeks for analysis. Clones derived 4 h after saline challenge showed strong mRNA signals for IL-13, IL-4, and IFN-gamma, whereas clones derived 24 h after allergen challenge expressed IL-13, GM-CSF, IL-3, IL-4, and often IL-5 (i.e., closer to the Th2 profile). There was considerable heterogeneity in the patterns of cytokine mRNA and protein production by different clones.

CONCLUSIONS

T cells from asthmatic airways produce IL-13, IFN-gamma, and TNF-alpha, but after allergen challenge, type 2 cytokines are upregulated. mRNA and protein analysis provide complementary information on airways T-cell cytokine profiles.

Autocrine interaction between IL-5 and IL-1beta mediates altered responsiveness of atopic asthmatic sensitized airway smooth muscle

T-helper type 2 (Th2) cytokines have been implicated in the pathogenesis of the pulmonary inflammatory response and altered bronchial responsiveness in allergic asthma. To elucidate the mechanism of Th2-dependent mediation of altered airway responsiveness in the atopic asthmatic state, the expression and actions of specific cytokines were examined in isolated rabbit and human airway smooth muscle (ASM) tissues and cultured cells passively sensitized with sera from atopic asthmatic patients or nonatopic/nonasthmatic (control) subjects. Relative to control tissues, the atopic asthmatic sensitized ASM exhibited significantly enhanced maximal isometric contractility to acetylcholine and attenuated relaxation responses to isoproterenol. These proasthmatic changes in agonist responsiveness were ablated by pretreating the atopic sensitized tissues with either an IL-5 receptor blocking antibody (IL-5ra) or the human recombinant IL-1 receptor antagonist (IL-1ra), whereas an IL-4 neutralizing antibody had no effect. Moreover, relative to controls, atopic asthmatic sensitized ASM cells demonstrated an initial, early (after 3 hours of incubation) increased mRNA expression and protein release of IL-5. This was followed (after 6 hours of incubation) by an enhanced mRNA expression and release of IL-1beta protein, an effect that was inhibited in sensitized cells pretreated with IL-5ra. Extended studies demonstrated that naive ASM exposed to exogenously administered IL-5 exhibited an induced upregulated mRNA expression and protein release of IL-1beta associated with proasthmatic-like changes in ASM constrictor and relaxant responsiveness, and that these effects were ablated in tissues pretreated with IL-1ra. Taken together, these observations provide new evidence that (a) the Th2 cytokine IL-5 and the pleiotropic proinflammatory cytokine IL-1beta are endogenously released by atopic asthmatic sensitized ASM and mechanistically interact to mediate the proasthmatic perturbations in ASM responsiveness; and (b) the nature of this interaction is given by an initial endogenous release of IL-5, which then acts to induce the autologous release of IL-1beta by the sensitized ASM itself, resulting in its autocrine manifestation of the proasthmatic phenotype.