Effect of the Plant Derivative Compound A on the Production of Corticosteroid-Resistant Chemokines in Airway Smooth Muscle Cells

Abstract

Preclinical models of human conditions including asthma showed the therapeutic potential of Compound A (CpdA), a dissociated glucocorticoid (GC) receptor (GRa) ligand. Whether CpdA inhibits GC resistance, a central feature of severe asthma, has not been addressed. We investigated whether CpdA modulates cytokineinduced GC resistance in human airway smooth muscle (ASM) cells. Healthy and asthmatic ASM cells were treated with TNF-a/IFN-g for 24 hours in the presence or absence of CpdA. ELISA and quantitative PCR assays were used to assess the effect of CpdA on chemokine expression. Activation of GRa by CpdA was assessed by quantitative PCR, immunostaining, and receptor antagonism using RU486. An effect of CpdA on the transcription factor interferon regulatory factor 1 (IRF-1) was investigated using immunoblot, immunostaining, and small interfering RNA (siRNA) knockdown. CpdA inhibited production of fluticasone-resistant chemokines CCL5, CX3CL1, and CXCL10 at protein and mRNA levels in both asthmatic and healthy cells. CpdA failed to induce expression of GC-induced Leucine Zipper while transiently inducing mitogen-activated protein kinase phosphatase 1 (MKP-1) at both mRNA and protein levels. CpdA inhibitory action was not associated with GRa nuclear translocation, nor was it prevented by RU486 antagonism. Activation of IRF-1 by TNF-a/IFN-g was inhibited by CpdA. IRF-1 siRNA knockdown reduced cytokine-induced CCL5 and CX3CL1 production. siRNA MKP-1 prevented the inhibitory effect of CpdA on cytokine-induced CXCL10 production. For the first time, we show that CpdA inhibits the production of GC-resistant chemokines via GRa-independent mechanisms involving the inhibition of IRF-1 and up-regulation of MKP-1. Thus, targeting CpdA-sensitive pathways in ASM cells represents an alternative therapeutic approach to treat GC resistance in asthma.

GR-independent down-modulation on GM-CSF bone marrow-derived dendritic cells by the selective glucocorticoid receptor modulator Compound A

“…Particular GR-independent effects of CpdA have been reported before and are hence not restricted to DC. In a recent report studying airway smooth muscle cells, it was observed that CpdA inhibits the secretion of GC-resistant chemokines in a GR-independent manner59, again emphasizing benefit in absence of GR as a target of CpdA.…”

Compound A influences gene regulation of the Dexamethasone-activated glucocorticoid receptor by alternative cofactor recruitment

“…40 . Recently, another study 31 , using airway smooth muscle cells, reported a CpdA-induced expression of DUSP1, but not GILZ, both at the mRNA and protein level. Similar to our results, this occurred after a short time period, but in a steroid-resistant context, and was found to be GR-independent 31 .…”

“…Recently, another study 31 , using airway smooth muscle cells, reported a CpdA-induced expression of DUSP1, but not GILZ, both at the mRNA and protein level. Similar to our results, this occurred after a short time period, but in a steroid-resistant context, and was found to be GR-independent 31 . As a final explanation, CpdA may degrade more quickly in the cells as compared to the stable steroidal DEX, which is why a consideration of future treatment strategies based on the advantages of a dual GR ligand/modulator combination would definitely require stabler SEGRAM molecules 15 .…”

Protein phosphatase 5 mediates corticosteroid insensitivity in airway smooth muscle in patients with severe asthma

“…In addition, we and others showed the implication of distinct pathways that regulate CXCL10 in ASM cells. Thus, in contrast to CCL5, CCL11 and CX3CL1, the production of CXCL10 in GC resistant conditions was the only chemokine which was (i) not repressed by a combination of fluticasone and KCa3.1 channel blockers , (ii) poorly sensitive to the natural derivative compound A and (iii) not involving IRF‐1‐dependent pathways . This differential action of GCs on CXCL10 expression was also reported in epithelial cells where fluticasone increased cytokine‐induced CXCL10 while inhibiting production of CXCL8 .…”