Th1 cytokines synergize to change gene expression and promote corticosteroid insensitivity in pediatric airway smooth muscle

Background: Corticosteroids remain a key therapy for treating children with asthma. Patients with severe asthma are insensitive, resistant, or refractory to corticosteroids and have poorly controlled symptoms that involve airway inflammation, airflow obstruction, and frequent exacerbations. While the pathways that mediate corticosteroid insensitivity in asthma remain poorly defined, recent studies suggest that enhanced Th1 pathways, mediated by TNF alpha and IFN gamma, may play a role. We previously reported that the combined effects ofTNF alpha and IFN gamma promote corticosteroid insensitivity in developing human airway smooth muscle (ASM). Methods: To further understand the effects of TNF alpha and IFN gamma on corticosteroid sensitivity in the context of neonatal and pediatric asthma, we performed RNA sequencing (RNA-seq) on human pediatric ASM treated with fluticasone propionate (FP),TNF alpha, and/or IFN gamma. Results: We found that TNFa had a greater effect on gene expression (similar to 1000 differentially expressed genes) than IFN gamma (similar to 500 differentially expressed genes). Pathway and transcription factor analyses revealed enrichment of several pro-inflammatory responses and signaling pathways. Interestingly, treatment with TNF alpha and IFN gamma augmented gene expression with more than 4000 differentially expressed genes. Effects of TNF alpha and IFN gamma enhanced several pro-inflammatory genes and pathways related to ASM and its contributions to asthma pathogenesis, which persisted in the presence of corticosteroids. Co-expression analysis revealed several gene networks related to TNF alpha- and IFN gamma-mediated signaling, pro-inflammatory mediator production, and smooth muscle contractility. Many of the co-expression network hubs were associated with genes that are insensitive to corticosteroids. Conclusions: Together, these novel studies show the combined effects ofTNF alpha and IFN gamma on pediatric ASM and implicate Th1-associated cytokines in promoting ASM inflammation and hypercontractility in severe asthma.

Automated summary

In this study, the effects of TNF alpha and IFN gamma on corticosteroid sensitivity in pediatric airway smooth muscle tissue were investigated. The results showed that TNF alpha had a greater impact on gene expression compared to IFN gamma, and the combined effects of TNF alpha and IFN gamma enhanced the expression of pro-inflammatory genes and pathways related to asthma pathogenesis. These findings highlight the importance of Th1-associated cytokines in promoting inflammation and hypercontractility in severe asthma.