Background TH 17 cells are proposed to play a role in the pathology of asthma, including steroid-resistant (SR) disease. We previously identified a steroid-enhancing function of vitamin D in patients ...with SR asthma in restoring the impaired response to steroids for production of the anti-inflammatory cytokine IL-10. Objective We sought to investigate the production of the TH 17-associated cytokines IL-17A and IL-22 in culture in patients with moderate-to-severe asthma defined on the basis of their clinical response to steroids and the susceptibility of this response to inhibition by steroids and the active form of vitamin D, 1α,25-dihydroxyvitamin D3 (1,25OH2 D3). Methods PBMCs were stimulated in culture with or without dexamethasone and 1,25(OH)2 D3. A cytometric bead array, ELISA, and intracellular cytokine staining were used to assess cytokine production. The role of CD39 in inhibition of the TH 17 response was studied by using quantitative real-time PCR, flow cytometry, and addition of the antagonist POM-1 to culture. Results Asthmatic patients synthesized much higher levels of IL-17A and IL-22 than nonasthmatic control subjects, with patients with SR asthma expressing the highest levels of IL-17A. Glucocorticoids did not inhibit IL-17A cytokine expression in patients and enhanced production in cultures from control subjects. Treatment with 1,25(OH)2 D3 with or without dexamethasone significantly reduced both IL-17A and IL-22 levels. An antagonist of the ectonucleotidase CD39 reversed 1,25(OH)2 D3-mediated inhibition of the IL-17A response. Conclusion Patients with severe asthma exhibit increased levels of TH 17 cytokines, which are not inhibited by steroids. 1,25(OH)2 D3 inhibits TH 17 cytokine production in all patients studied, irrespective of their clinical responsiveness to steroids, identifying novel steroid-enhancing properties of vitamin D in asthmatic patients.
A number of mechanisms have been proposed to contribute to glucocorticoid-resistant asthma, including increased expression of nuclear factor kappa B and activating protein 1 (AP-1), increased ...expression of histone deacetylase, polymorphisms in IL-10, increased expression of the dominant negative isoform of the glucocorticoid receptor beta (GRβ), and vitamin D insufficiency.2-4 Our earlier data showed that peripheral blood CD4+ T cells from glucocorticoid-resistant as compared with glucocorticoid-sensitive asthmatic patients failed to synthesize the anti-inflammatory cytokine IL-10 in response to glucocorticoid in vitro.5 The active form of vitamin D (calcitriol; 1,25-dihydroxyvitamin D3 1,25(OH)2D3) when used in combination with glucocorticoid restored this IL-10 response both in vitro and ex vivo following patient ingestion of calcitriol.6 These data, together with epidemiologic evidence linking vitamin D insufficiency/deficiency with a poor clinical response to treatment in asthma,3,4 provided the rationale for this proof-of-concept clinical trial. On the one hand, the decision to study a well-characterized cohort of glucocorticoid-resistant asthmatic patients produced significant challenges with recruitment and retention, but on the other hand may have facilitated our ability to observe a clinical effect that may be manifest most clearly in this small but important subset of patients.\n Study subjects were asked to report any adverse events from the day of commencement of the first course of oral prednisolone until 4 weeks after the second course by telephone or e-mail or at study visits.
Corticosteroids enhance the production of the antiinflammatory cytokine IL-10 by T cells in vitro, but notably this response is impaired in cultures from SR asthmatic patients, implying an ...association between impaired IL-10 response and poor asthma control.2 This defect in steroid-induced IL-10 can be restored by the addition of the active form of vitamin D3 (1,25-hydroxyvitamin D3) into the culture, thus suggesting that vitamin D may play a role in controlling steroid responsiveness.3 These data are complemented by a number of independent clinical studies that highlight a high prevalence of vitamin D deficiency and insufficiency worldwide and its association with an increased incidence, severity, and poor control of asthma.4,5 The importance and status of a well-defined subset of Treg cells, as defined by the expression of the transcription factor forkhead box P3 (Foxp3), in SS and SR asthma are less well understood.1,6 Although 1,25-hydroxyvitamin D3 has been shown to enhance the frequency of human Foxp3+ Treg cells in vitro, no in vivo correlates of these data exist.7 The aim of the present study was therefore to investigate whether differences exist in the frequency of Foxp3+ Treg cells in the peripheral blood of SS and SR adult asthma patients, and the relationship between vitamin D status and the Foxp3+ Treg-cell compartment.
Background A small population of patients with severe asthma does not respond to glucocorticoids (steroid resistant SR). They have high morbidity, highlighting an urgent need for strategies to ...enhance glucocorticoid responsiveness. Objective We investigated the immunologic differences between steroid-sensitive (SS) and SR asthmatic patients and the effect on immunophenotype of oral calcitriol treatment because it has been previously shown to beneficially modulate the clinical response to glucocorticoids in patients with SR asthma. Methods CD8-depleted PBMCs were isolated from 12 patients with SS and 23 patients with SR asthma and cultured for 7 days with anti-CD3 and IL-2 with or without dexamethasone. Cytokine production was assessed in supernatants by using the Cytometric Bead Array. Patients with SR asthma were subsequently randomized to oral calcitriol or placebo therapy, and identical studies were repeated. Results Patients with SR asthma produced significantly increased IL-17A and IFN-γ levels compared with those in patients with SS asthma, although it was evident that cells from individual patients might overproduce one or the other of these cytokines. Production of IL-17A was inversely and production of IL-13 was positively associated with the clinical response to prednisolone. Oral calcitriol, compared with placebo, therapy of the patients with SR asthma significantly improved dexamethasone-induced IL-10 production in vitro while suppressing dexamethasone-induced IL-17A production. This effect mirrored the previously demonstrated improvement in clinical response to oral glucocorticoids in calcitriol-treated patients with SR asthma. Conclusions IL-17Ahigh and IFN-γhigh immunophenotypes exist in patients with SR asthma. These data identify immunologic pathways that likely underpin the beneficial clinical effects of calcitriol in patients with SR asthma by directing the SR cytokine profile toward a more SS immune phenotype, suggesting strategies for identifying vitamin D responder immunophenotypes.
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