Glucocorticoid receptor-beta up-regulation and steroid resistance induction by IL-17 and IL-23 cytokine stimulation in peripheral mononuclear cells.

PURPOSE

Most asthmatic patients have well controlled symptoms with regular treatment, but some require much higher doses of inhaled and oral corticosteroids, or in rare cases fail to respond; these patients may present Th-17 cell infiltration and associated cytokines (IL-17A and -F) in the airways, sputum and peripheral blood. Because glucocorticoid receptor-beta (GR-beta) is associated with corticosteroid resistance, we investigated whether Th-17 associated cytokines induce steroid insensitivity in PBMCs via GR-beta up-regulation.

METHODS

GR-alpha, GR-beta, GILZ and IL-6 expression were analyzed in PBMCs stimulated with IL-2/IL-4, IL-17A/IL-17F and IL-23 cytokines by quantitative RT-PCR. Dexamethasone-inhibition of PHA-induced proliferation and Dexamethasone-induced apoptosis were determined by either (3)H-thymidine or CFSE-labelled cells and by Annexin-V staining and flow cytometry.

RESULTS

IL-17 and IL-23 cytokines significantly increased GR-beta expression. IL-2/IL-4 significantly decreased GR-alpha expression without affecting GR-beta. IL17, IL-23 and IL2 + 4 stimulations significantly hampered Dexamethasone-inhibition of proliferation (Dex EC(50) for: IL-17A + F = 251 nM; IL-23 = 435 nM; IL2 + 4 = 950 nM; Medium = 90 nM). IL2 + 4 and IL17A + F but not IL-23, significantly hampered Dexamethasone-induced apoptosis (1400 and 320 nM Dex, respectively). Dexamethasone's trans-activation of GILZ and trans-repression of NF-kB-driven IL-6 expression were both inhibited by IL2 + 4; IL17 + IL23 antagonized Dex trans-repression in PBMC from asthmatics.

CONCLUSIONS

GR-beta up-regulation by IL-17/IL-23 cytokines is associated with induced steroid insensitivity in PBMCs, observed as diminished Dexamethasone's effects on cell proliferation, apoptosis and gene regulation. Steroid resistance induced by IL-2/IL-4 was associated with decreased GR-alpha expression. This study supports the possibility that Th-17 lymphocytes and associated cytokines play a role in the mechanism of steroid hypo-responsiveness in severe asthmatics.