Corticosteroids inhibit anti-IgE activities of specialized proresolving mediators on B cells from asthma patients
Nina Kim, Thomas H. Thatcher, Patricia J. Sime, Richard P. Phipps
Nina Kim, Thomas H. Thatcher, Patricia J. Sime, Richard P. Phipps
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Research Article Immunology Inflammation

Corticosteroids inhibit anti-IgE activities of specialized proresolving mediators on B cells from asthma patients

Abstract

Specialized proresolving mediators (SPMs) promote the resolution of inflammation and exert beneficial effects in animal models of chronic inflammatory diseases, including asthma. Previously, we have shown that certain SPMs reduce IgE production in B cells from healthy individuals, which has a critical role in allergic asthma. Here, we investigated the effects of SPMs on B cell IgE production in asthma patients. Peripheral blood mononuclear cells from asthma patients were treated with 17-HDHA or RvD1, and IgE levels were measured. RvD1 and 17-HDHA dampened IgE production in B cells from most asthma patients, whereas B cells from a subset of patients taking oral steroids were refractory to SPM treatment. Molecular mechanisms underlying the interaction between corticosteroids and SPMs were investigated by treating B cells from nonasthmatic donors with corticosteroids in vitro. Corticosteroids blocked the inhibitory effects of 17-HDHA and RvD1 on B cell IgE production by abolishing the suppressive activity of these mediators on IgE class switching. Corticosteroids decreased the expression of transcriptional repressor Bcl-6 as well as its suppressive activity on epsilon germline transcription. We conclude that 17-HDHA and RvD1 can reduce IgE production in asthma patients not taking high doses of steroids but that corticosteroids interfere with the ability of B cells to respond to proresolving mediators.

Authors

Nina Kim, Thomas H. Thatcher, Patricia J. Sime, Richard P. Phipps

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Figure 5

Corticosteroids diminish the ability of 17-HDHA to enhance the binding activity of Bcl-6 on εGLT promoter region (Iε).

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Corticosteroids diminish the ability of 17-HDHA to enhance the binding a...
(A and B) Purified B cells from healthy donors were pretreated with dexamethasone (10 nM) or left untreated for 24 hours. The next day, cells were treated with 17-HDHA or RvD1, followed by stimulation with an IgE-inducing cocktail for 4 hours. Cell lysates were collected, and total Bcl-6 expression levels were measured using Western blot. β-Tubulin was used as a control. (A) Western blot image of Bcl-6 expression in purified human B cells from a representative healthy donor treated with 17-HDHA or RvD1 (Bcl-6 and β-tubulin were probed in a separate membrane for 17-HDHA treatment). (B) Densitometry analysis for 4 different donors treated with 17-HDHA (mean ± SEM). (C and D) PBMCs from healthy donors were treated with 17-HDHA as described for Western blot, and the amount of Bcl-6 bound to Iɛ was measured using ChIP assay. (C) Representative images of PCR products obtained in PBMCs from healthy donors. (D) Quantification of Bcl-6 binding to Iε for 3 different donors (mean ± SEM). Data were analyzed by repeated-measures 2-way ANOVA with Tukey’s post test, *P ≤ 0.05, #P ≤ 0.05, ##P ≤ 0.01 (pound signs compare values with or without dexamethasone, asterisks compare values with or without 17-HDHA). PBMC, peripheral blood mononuclear cell; Iε, ε germline transcript promoter region; Bcl-6, B cell lymphoma-6 protein.