Distinct glucocorticoid sensitivity of Th17 cytokines in murine T hybridomas and primary cells (IRC11P.428)

Cytokine suppression contributes to the anti-inflammatory actions of glucocorticoids (GCs). However, IL-17 has been reported to be resistant to GC regulation in asthma, nasal polyps, and Crohn’s disease. In contrast, a negative GC-response element has been identified in the promoter region of the IL-17 gene and IL-17 was sensitive to GC suppression in a murine asthma model. To clarify whether IL-17 and other Th17 cytokines are sensitive to GC regulation, we generated Th17 hybridoma cells by fusing in vitro differentiated murine (bl/6) Th17 cells with BW5147 thymoma. Two clones selectively expressing IL-17A, IL-17F, IL-22 and GM-CSF were stable for over 30 generations. Additional clones selectively expressing IFN-γ or IL-4, but not Th17 cytokines and BW5147 cells that produce little or no cytokines were used as controls. Dexamethasone, a potent GC, significantly inhibited anti-CD3 and anti-CD28-stimulated IFN-γ, IL-4, as well as IL-17A, IL-17F, and IL-22 in various clones. Interestingly, IL-17A and IL-17F, but not IL-22, were resistant to GC suppression in in vitro differentiated Th17 cells. Furthermore, hybridomas, but not in vitro differentiated Th17 cells underwent GC-induced apoptosis. IL-6 partially rescues hybridomas from GC-induced apoptosis, however it did not modulate IL-17 suppression by GCs. Our findings support that IL-17A and IL-17F are capable of being downregulated by GCs and Th17 cell microenvironment and cellular milleu engender GC resistance.