Journal
AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY
Volume 316, Issue 1, Pages L71-L81Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajplung.00547.2017
Keywords
asthma; children; cytokine; steroid resistance
Categories
Funding
- National Heart, Lung, and Blood Institute [R00-HL-131682, R01-HL-056470, R01-HL-138402, R01-HL-109557]
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Corticosteroids (CSs) are commonly used to manage wheezing and asthma in pediatric populations. Although corticosteroids are effective in alleviating airway diseases, some children with more moderate-severe asthma phenotypes show CS resistance and exhibit significant airflow obstruction, persistent inflammation, and more frequent exacerbations. Previous studies have demonstrated that Th1 cytokines, such as TNF-alpha and IFN-gamma, promote CS resistance in adult human airway smooth muscle (ASM). In the present study, using a human fetal ASM cell model, we tested the hypothesis that TNF-alpha /IFN-gamma induces CS resistance. In contrast to TNF-alpha or IFN-gamma alone, the combination of TNF-alpha/IFN-gamma blunted the ability of fluticasone propionate (FP) to reduce expression of the chemokines CCL5 and CXCL10 despite expression of key anti-inflammatory glucocorticoid receptor target genes being largely unaffected by TNF-alpha/IFN-gamma. Expression of the NF-kappa B subunit p65 and phosphorylation of Stat1 were elevated in cells treated with TNF-alpha/IFN-gamma, an effect that remained in the presence of FP. siRNA knockdown studies demonstrated the effects of TNF-alpha/IFN-gamma on increased p65 are mediated by Stat1, a transcription factor activated by IFN-gamma. Expression of TNFAIP3, a negative regulator of NF-kappa B activity, was not altered by TNF-alpha/IFN-gamma. However, the effects of TNF-alpha/IFN-gamma were partially reduced by overexpression of TNFAIP3 but did not influence p65 expression. Together, these data suggest that IFN-gamma augments the effects of TNF-alpha on chemokines by enhancing expression of key inflammatory pathways in the presence of CS. Interactions between TNF-alpha- and IFN-gamma-mediated pathways may promote inflammation in asthmatic children resistant to CSs.
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