Th1 Inflammatory Cytokines Induce Corticosteroid Resistance in Pediatric Airway Smooth Muscle Cells

Abstract

IntroductionSteroid‐based therapies are anti‐inflammatory and commonly used to manage asthmatic symptoms in pediatric patients. Although manageable for most children, some patients with moderate‐severe asthma require administrations of high doses of steroids, which is relatively ineffective in limiting asthmatic symptoms. Airway smooth muscle (ASM) plays a central role by contributing to airway inflammation, remodeling, and hyperreactivity in asthma. ASM contributes to airway inflammation during responses to allergen exposures (Th2 inflammation) and infection (Th1 inflammation). Previous studies have suggested that adult ASM exposed to Th1 cytokines, TNFα and IFNγ, reduce steroid sensitivity and efficacy. In the present study, we examined the effects of TNFα and IFNγ on steroid sensitivity in pediatric ASM.Methods and ResultsHuman ASM was isolated from trachea of patients (1–10 years old) undergoing tracheal reconstruction surgery (approved by NCH IRB). Cultured ASM were treated with vehicle (0.01% DMSO), 10 nM fluticasone propionate (FP), 10 ng/mL TNFα, and/or 25 ng/mL IFNγ for 24 h. Cells were harvested to measure mRNA levels of pro‐inflammatory genes (CCL5, CXCL10, p65) and glucocorticoid receptor target genes (FKBP5, GILZ) by qRT‐PCR. Media was collected to measure CCL5 levels by ELISA. Effects of TNFα or IFNγ alone on CCL5 and CXCL10 mRNA levels were inhibited by FP, however CCL5 and CXCL10 mRNA levels remained increased in cells treated with TNFα/IFNγ and FP. Similarly, TNFα‐induced CCL5 secretion was reduced by FP, but this anti‐inflammatory effect was absent in cells treated with TNFα/IFNγ. Transcription of glucocorticoid receptor target genes, FKBP5 and GILZ, were increased by FP, evidence of glucocorticoid receptor activity. In contrast to FKBP5, GILZ mRNA levels were attenuated by TNFα and IFNγ treatment, and blunted by TNFα/IFNγ. Treatment with TNFα/IFNγ substantially increased mRNA expression of the NFκB subunit, p65, an effect that remained in the presence of FP.ConclusionsTogether these findings suggest that TNFα/IFNγ induce steroid resistance in pediatric ASM. Although there is evidence of glucocorticoid receptor activity, we speculate that interactions between TNFα‐ and IFNγ‐mediated pathways promotes inflammation in the presence of steroids. Th1‐mediated inflammation may contribute to development of steroid resistance in children with severe asthma.Support or Funding InformationThis study is funded by National Institutes of Health R00 HL131682 (RDB).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.