Mechanisms of inhibition of IgE synthesis by nedocromil sodium: nedocromil sodium inhibits deletional switch recombination in human B cells

Andolast acts at different cellular levels to inhibit immunoglobulin E synthesis

The anti-asthmatic agent andolast is thought to inhibit the release of allergic mediators, but its mechanism of action is not fully understood. We investigated whether the compound inhibits immunoglobulin E (IgE) synthesis and tested the hypothesis that andolast affects immunoglobulin class switching. Interleukin (IL)-4 and the interaction of CD40 expressed on B cells with its ligand on T cells are necessary for IgE synthesis. Thus, peripheral blood mononuclear cells (PBMCs) from 40 asthmatic, 16 non-asthmatic allergic, and 9 normal donors were stimulated with IL-4 and/or anti-CD40 antibody. T cells from 9 additional allergic donors were activated with anti-CD3/CD28 antibodies to express IL-4 mRNA. After incubation in the absence or presence of test compounds, immunoglobulin concentrations were measured by enzyme immunoassay, and mRNA levels were analyzed by RT-PCR. Andolast significantly inhibited IgE synthesis by stimulated PBMCs from both asthma patients and combined allergic/normal donors. In mechanistic studies, andolast was found to act at different cellular levels. Firstly, it reduced by about 45 percent (p<0.05) the levels of IL-4 mRNA in T cells stimulated with anti-CD3/CD28. Secondly, andolast reduced by about 36 percent (p<0.05) the expression of epsilon germline transcripts in PBMCs stimulated with IL-4/anti-CD40. Thirdly, the effect of andolast on immunoglobulin synthesis was selective in that the production of IgG4 antibodies was not significantly inhibited. Our findings, while supporting the evidence that andolast is effective for the treatment of asthma, provide new insights into its mechanism of action.

Topical immunopharmacology of ocular allergies

PURPOSE OF REVIEW

To review the histamine-1 receptor antagonists, mast cell blockers and natural agents with such actions that can be used for the topical treatment of ocular allergies.

RECENT FINDINGS

Increasing evidence indicates that some histamine-1 receptor antagonists have additional actions to inhibit secretion of inflammatory mediators, especially cytokines, from ocular mast cells and other cell types. Emerging information suggests that such actions may be through regulation of intracellular calcium ion levels of NF-kappaB activation.

SUMMARY

A number of available drugs and natural non-prescription agents may have anti-histaminic and anti-inflammatory actions.

Double-blind, randomized, placebo-controlled trial of effect of nedocromil sodium on clinical and inflammatory parameters of asthma in children allergic to dust mite

BACKGROUND

The purpose of this study was to determine the clinical effect of nedocromil sodium and its relationship with serum levels of inflammatory mediators by monitoring lung function and noninvasive markers of airway inflammation, such as eosinophil blood counts; serum ECP, sIL-2R, IL-4 and sICAM; and total IgE. Anti-inflammatory medications cause a reduction in the markers of airway inflammation, decrease the intensity of airway hyperresponsiveness, and improve clinical symptoms of asthma. Among the available choices is nedocromil sodium, which is favored in the treatment of asthmatic children due to its very mild side-effects. It has been previously shown to improve the clinical parameters of asthma, but there are limited data on its effect on inflammatory mediators in the serum of asthmatic children.

METHODS

In this double-blind, randomized, placebo-controlled 8-week trial, 39 children, aged 9-16 years, with moderate atopic asthma were randomly allocated to receive either nedocromil sodium, two puffs twice daily, 0.002 g/puff, or placebo, two puffs twice daily. The primary end points were the clinical parameters of asthma measured by asthma symptom score, FEV1, and PC20H. Other end points included the serum levels of various inflammatory markers - ECP, sIL-2R, IL-4, sICAM, and IgE.

RESULTS

Clinical and inflammatory parameters improved with the use of nedocromil sodium, compared with placebo. Nedocromil significantly decreased serum levels of inflammatory markers, as shown in the following table. No correlation was found between any of the measured parameters.

CONCLUSION

Nedocromil sodium provided effective anti-inflammatory treatment for children with moderate atopic asthma.

The effects of cromolyn sodium and nedocromil sodium in early asthma prevention

The possibility of irreversible obstruction and therefore the need for early intervention is being much debated. Some investigators suggested that delay in starting inhaled corticosteroids will result in irreversible obstruction. Our own long-term study, specifically designed to detect irreversible obstruction showed that a step-wise approach (starting with cromolyn sodium and switching to inhaled corticosteroids if clinical control and pulmonary function tests are not satisfactorily controlled) resulted in an increase in pulmonary function and not a deterioration. There was no evidence that a delay in starting inhaled corticosteroids will result in irreversible obstruction or clinical worsening. However, delay in starting cromolyn sodium in patients treated with bronchodilators alone did result in worsening pulmonary function tests and worse clinical outcomes. One study from Finland and another study from Australia came to the same conclusion. Even though some studies with cromolyn sodium did not show benefit in the first year of life, other studies did show a good response. The choice between nonsteroidal drugs, such as cromolyn sodium and inhaled corticosteroids as first-line drugs, has to be made on the risk/benefit ratio of these drugs. Although in severe asthma inhaled corticosteroids have greater efficacy, in mild-to-moderate asthma there is comparable efficacy, and the nonsteroidal drugs have better safety. A step-wise approach is still a logical approach

Molecular mechanisms of IgE regulation

IgE antibody plays an important role in allergic diseases. IgE synthesis by B cells requires two signals. The first signal is delivered by the cytokines IL-4 or IL-13, which target the Cepsilon gene for switch recombination. The second signal is delivered by interaction of the B cell surface antigen CD40 with its ligand (CD40L) expressed on activated T cells. This activates deletional switch recombination. We review the molecular mechanisms of IL-4 and CD40 signaling that lead to IgE isotype switching and discuss the implications for intervening to abort or suppress the IgE antibody response.

Regular albuterol or nedocromil sodium--effects on airway subepithelial tenascin in asthma

Both albuterol and nedocromil sodium have been recognized to possess certain anti-inflammatory properties. However, there are no data on the impact of these drugs on the pathophysiology of the bronchial extracellular matrix in asthma characterized by enhanced tenascin (Tn) expression, known to occur proportional to the severity of asthma. This paper reports data from a morphometric study on the effects of regular treatment with inhaled albuterol or nedocromil sodium on the extent of bronchial subepithelial deposition of Tn, collagen types III, IV, and VII and mucosal infiltration with macrophages. Thirty-two patients (14 women) with chronic asthma, aged 38.7 years (median) with a median forced expiratory volume in 1 sec (FEV1) of 74.4% predicted, were selected to undergo fibre-optic bronchoscopy with bronchial biopsies before and after 12 weeks of treatment with either inhaled albuterol 0.2 mg or nedocromil sodium 4 mg four times daily according to a double-blind protocol. Cryostat sections of the biopsy specimens were studied by indirect immunostaining techniques using monoclonal antibodies and computer-assisted quantitative image analysis. Albuterol treatment significantly reduced the median thickness of subepithelial Tn expression from 9.7 to 6.3 microns (P = 0.023) and macrophage numbers in the epithelium (P = 0.034), lamina propria (P = 0.039) and entire mucosa (P = 0.033), whereas nedocromil sodium had no effect. Expression of the collagen types was not affected by either treatment. There was no identifiable statistical difference between the two treatments for any of the outcome variables measured. Nevertheless, the results demonstrate that even a short-acting beta 2-agonist may exert anti-inflammatory potential sufficient to interfere with the basic mechanisms of asthma as shown by reduction of subepithelial Tn content and mucosal macrophage count.

T lymphocyte activation in myasthenic thymoma

The functional and phenotypic characteristics of lymphocytes separated from myasthenic thymoma (Th-L) were compared with those of lymphocytes separated from non-thymomatous thymus associated with thymoma (NTh-L) of the same patients and NTh-L of myasthenia gravis (MG) patients without thymoma. We examined whether Th-L and NTh-L of MG patients reacted to interleukin-2 (IL-2) to develop lymphokine-activated killer (LAK) activity and/or cytolytic activity against K562 (natural killer (NK) activity), and the phenotypic changes in such cells during incubation. Ten MG patients with thymoma and six MG patients without thymoma, and four non-MG thymoma patients were included in this study. Th-L and NTh-L of MG patients reacted with IL-2 to develop LAK and NK activities. The LAK activity developed from Th-L was significantly higher than that from NTh-L, and the LAK activity developed from Th-L was as high as that from peripheral blood lymphocytes (PBL) in MG patients without thymoma. The proportions of CD3+ cells, CD4+/CD8- cells, and CD4-/CD8+ cells in Th-L of MG patients increased significantly during incubation. On the other hand, the proportion of CD4+/CD8+ cells in Th-L of MG patients decreased significantly. The proportions of CD4+/CD8- cells, CD4-/CD8+ cells, and CD4+/CD8+ cells in NTh-L of MG patients with and without thymoma exhibited no change during incubation. These findings suggest that CD4+/CD8+ Th-L of MG patients may have a higher potential to react to IL-2 than NTh-L, and that the former cells might develop LAK activity like that of PBL on maturation to CD4+/CD8- cells and CD4-/CD8+ cells. Our findings also suggested that Th-L might play an important role in the pathogenesis of MG with thymoma.

Oral food challenge increases in vitro IL-4 production by peripheral blood mononuclear cells in allergic patients

The aim of this study was to investigate interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) production by peripheral blood mononuclear cells (PBMC) in response to oral challenge in patients with food allergy. Thirty-one patients were compared with 10 healthy subjects. Cell cultures were prepared before and 150 min after single-blind, placebo-controlled, oral food challenge. In vitro production of cytokines was observed after stimulation with phytohemagglutinin (PHA) plus phorbol myristate acetate (PMA). Patients were characterized according to their reactions. In vitro IL-4 production was significantly greater in patients with food sensitization than in controls. The 18 patients with positive food challenge presented significantly greater IL-4 production after food challenge than before. IFN-gamma production was not modified. In the 10 control subjects and in 13 patients with negative food challenge, IL-4 and IFN-gamma production was comparable before and after food challenge. The increased IL-4 production in patients with positive oral food challenge could account for the development of polysensitization. This situation might be relevant to other allergic diseases and to treatments.