Compound A modulates steroid insensitive chemokines in airway smooth muscle cells via IRF-1 dependent and independent pathways

Abstract

Preclinical models of human conditions including asthma showed the therapeutic potential of the dissociated glucocorticoid(GC) receptor(GR) ligand Compound A(CpdA).Whether CpdA inhibits GC insensitivity, a central feature of severe asthma, has not been addressed.We showed that CpdA suppresses production of GC-resistant chemokines.Our aim was to further investigate the mechanisms underlying CpdA sensitive pathways in airway smooth muscle(ASM) cells. ASM cells were treated with TNFα/IFNγ with or without CpdA to investigate the modulatory effects on chemokine expression (ELISA, qPCR). GRα activation by CpdA was assessed by qPCR, immunostaining and receptor antagonism(RU486). The effect of CpdA on the transcription factor IRF-1 was investigated by immunoblot, immunostaining and siRNA knockdown.CpdA dose-dependently inhibited the production of fluticasone-resistant CCL5, CX3CL1, and CXCL10 induced by TNFα/IFNγ(mRNA, protein).CpdA failed to induce expression of the GRE-inducible gene Glucocorticoid-induced Leucine Zipper, while transiently inducing MAPK phosphatase 1(mRNA,protein).CpdA inhibitory action was not associated with GR nuclear translocation or prevented by RU486 antagonism.Additionally CpdA inhibited cytokine induced IRF-1 activation and nuclear translocation, previously associated with reduced steroid sensitivity in ASM cells. Finally, IRF-1 siRNA knockdown reduced cytokine-induced CCL5 and CX3CL1.In conclusion, CpdA suppresses production of GC-resistant chemokines via IRF-1 dependent and independent mechanisms.Targeting CpdA sensitive pathways in ASM cells represents an alternative therapeutic approach for GC insensitivity treatment in asthma.