IL‐2 modulates Th2 cell responses to glucocorticosteroid: A cause of persistent type 2 inflammation?

Abstract

Background Glucocorticosteroids (GCs) are the main treatment for asthma as they reduce type 2 cytokine expression and induce apoptosis. Asthma severity is associated with type 2 inflammation, circulating Th2 cells and higher GC requirements. Objective The aim of this study was to assess whether ex vivo production of interleukin 2 (IL‐2), a T‐cell survival factor, associated with clinical features of asthma severity, the proportion of blood Th2 cells and Th2 cell responses to GC. Methods Peripheral blood from asthma patients (n = 18) was obtained and the proportion of Th2 cells determined by flow cytometry. Peripheral blood cells were activated with mitogen (24 hours) and supernatant levels of IL‐2 and IL‐13 measured by enzyme‐linked immunosorbent assay. In vitro differentiated Th2 cells were treated with dexamethasone (DEX) and IL‐2 and assessed for apoptosis by flow cytometry (annexin V). Level of messenger RNA (mRNA) for antiapoptotic (BCL‐2) and proapoptotic (BIM) genes, IL‐13, GC receptor (GR) and FKBP5 were determined by quantitative real‐time polymerase chain reaction. GR binding was assessed by chromatin immunoprecipitation. Results IL‐2 produced by activated peripheral blood cells correlated negatively with lung function and positively with a daily dose of inhaled GC. When patients were stratified based on IL‐2 level, high IL‐2 producers made more IL‐13 and had a higher proportion of circulating Th2 cells. In vitro, increasing the level of IL‐2 in the culture media was associated with resistance to DEX‐induced apoptosis, with more BCL‐2/less BIM mRNA. Th2 cells cultured in high IL‐2 had more IL‐13, less GR mRNA, showed reduced binding of the GR to FKBP5, a known GC‐induced gene, and required higher concentrations of DEX for cytokine suppression. Conclusions and Clinical Relevance IL‐2 downregulates Th2 cell responses to GC, supporting both their survival and pro‐inflammatory capacity. These results suggest that a patient's potential to produce IL‐2 may be a determinant in asthma severity.

Comparative Efficacy of Glucocorticoid Receptor Agonists on Th2 Cell Function and Attenuation by Progesterone

“…This result indicates that in vivo type 2 cytokines are likely su ciently controlled with an optimal dose of either prednisolone or dexamethasone and, in line with other reports, are anticipated to reduce the proportion of CD4 + T cells expressing IL-4 and IL-5 [50]. However, we recently showed that the suppressive effect of dexamethasone on IL-13 was reversed after activation unless cells were continuously exposed to dexamethasone [45], suggesting the effect could be temporary. The lack of increase in IL-10 or IL-17 following dexamethasone treatment [45], coupled with our new data showing that dexamethasone reduced IFNg mRNA levels (Table 1), indicates active suppression of type 2 cytokine transcription, rather than shifting Th2 cells toward a Th1, Th17 or T regulatory cell phenotype.…”

“…Early apoptotic cells were identi ed as those staining for Annexin V only, but not 7-AAD, and cells positive for 7-AAD alone were considered necrotic ( Figure S3). We recently reported similar responses to dexamethasone-induced apoptosis when comparing the CCRF-CEM cell line to primary Th2 cells [45]. When we examined the response to prednisolone and dexamethasone we found that both CSs induce necrosis of CCRF-CEM cells in a dose dependent manner (Figure 2A).…”

“…However, we recently showed that the suppressive effect of dexamethasone on IL-13 was reversed after activation unless cells were continuously exposed to dexamethasone [45], suggesting the effect could be temporary. The lack of increase in IL-10 or IL-17 following dexamethasone treatment [45], coupled with our new data showing that dexamethasone reduced IFNg mRNA levels (Table 1), indicates active suppression of type 2 cytokine transcription, rather than shifting Th2 cells toward a Th1, Th17 or T regulatory cell phenotype. Type 2 cytokines mediate many features of asthma and therapies blocking their action are effective and are now recommended as frontline controllers in severe asthma [24].…”

“…Since corticosteroid withdrawal studies have shown that suppression of type 2 in ammation requires continuous exposure to steroid [45,57,58], therapeutic approaches aimed at eliminating Th2 cells may provide more sustained repression of allergic responses. Th2 cells are highly differentiated with a strong ability to survive, mediated through expression of the anti-apoptotic factor BCL-2 [59,60].…”

“…These results suggest that the progesterone effect on CS-induced apoptosis was not through progesterone receptor signaling. Since progesterone has also been shown to have a nity for the GR [41], we next assessed whether it could in uence the dexamethasone mediated induction of FKBP5 mRNA, a gene highly induced by CS [45,48,49]. Indeed, the level of FKBP5 mRNA following exposure to dexamethasone was signi cantly blunted when progesterone was added to the culture ( Figure 4C), indicating this sex hormone interferes with GC:GR signaling.…”