Gaston, B

Abstract Rationale We hypothesize that corticosteroid resistance causes uncontrolled inflammation and severe asthma. The genetic and molecular mechanisms underlying steroid responsiveness in asthma remain poorly understood (PMID28493293). This study aims to characterize transcriptomic profiles distinguishing steroid responders from steroid resistant asthma. Methods Longitudinal bulk RNA-seq of SARP3 sputum samples was analyzed before and after an “induced phenotype” with 40 mg triamcinolone acetonide (TCA) injection (PMID 27967215). Participants were classified as responders or non-responders based on whether their FEV₁ change after TCA exceeded the median. Paired differential gene expression analyses were performed separately for each group using limma and voom, with participant as a factor and adjustment for sputum cell count differentials. Z-scores were calculated to compare gene expression changes after TCA injection between responders and non-responders, and pathway enrichment was assessed using the fgsea package. Results Baseline demographics and clinical characteristics of 696 SARP3 asthma participants receiving TCA are shown in Table 1. The median [IQR] FEV1 change post-TCA was 1.81% [-2.16, 7.17]. Responders had higher baseline FEV1%, FEV1/FVC ratio, blood eosinophil counts, and sputum eosinophil percentages, but lower serum CRP levels. Steroid responsiveness was associated with asthma severity (Table 1). Among 154 participants with paired sputum RNA-seq data, 70 (45%) exhibited >1.81% improvement in FEV₁ and were classified as responders. Following TCA treatment, non-responders showed no significant changes in gene expression. In responders, 18 genes were upregulated and 203 downregulated. Downregulated genes were associated with Th2 immunity (IL13, IL1RL1, CCL17, SIGLEC8), IgE signaling (FCER1A, FCER2), epithelial barrier function and mucus production (MUC2, MUC7, ALOX15, TFF3), tissue remodeling and fibrosis (MMP10, TIMP3), ciliary function (DNAH5, CFAP43, FOXJ1), and airway hyperreactivity (HRH4, RAMP1). Key genes notably downregulated in responders compared to non-responders included IL13, CCL5, PTGDR2, FCER2, and CLEC10A. Pathway analysis revealed enhanced IL-10-mediated anti-inflammatory signaling, suppression of pro-inflammatory pathways (NF-κB, IL-1, Th1/Th2, asthma, arachidonic acid metabolism, chemokine, NOTCH4), and regulation of mitochondrial oxidative phosphorylation. Conclusions Steroid resistance impairs glucocorticoid-mediated suppression of pro-inflammatory pathways, including NF-κB, IL-1, and Th1/Th2 signaling. This persistent airway inflammation limits improvements in lung function and contributes to worse clinical outcomes, including increased airflow obstruction, and symptom burden. Glucocorticoid resistance in asthma may be driven by receptor dysfunction, airway inflammation, epigenetic changes, and environmental exposures resulting in persistent airway inflammation and remodeling. Elucidating the molecular mechanisms underlying steroid resistance is critical for developing personalized targeted therapies in asthma. This abstract is funded by: NIH-NHLBI - R01 HL161674 (PI: Joe Zein)

Abstract Rationale Primary ciliary dyskinesia (PCD) pathogenic gene variants disrupt motile cilia, leading to both PCD and asthma through epithelial dysfunction. Asthma shows sex differences, and progesterone regulates ciliary beat frequency, indicating that genetic defects in ciliary proteins may exert sex-dependent effects. Therefore, we hypothesize that rare, pathogenic variants in PCD genes contribute to asthma risk in a sex-specific manner. Methods We performed a rare-variant aggregation analysis of the DNAH11 gene using UK Biobank OQFE exome dosages, with sex-stratified analyses. Within each sex, genotype dosages were coded as individual-level minor allele counts (0-2) and filtered to include variants with a minor allele frequency (MAF) ≤1% and a minor allele count (MAC) ≥5 across the cohort. Asthma phenotypes were defined from a curated dataset (N = 452,927), excluding COPD and other lung diseases. For each sex, logistic null models adjusted for age were fitted, and gene-level associations for binary outcomes were tested using SKAT, Burden, and SKAT-O. To assess variant-specific influences, we performed leave-one-out (LOO) analyses, sequentially omitting each variant and recalculating p-values. The effect size across the cohort was calculated by fitting a Firth logistic regression comparing carriers to non-carriers, adjusted for age by sex. Finally, sex modification was tested using a Firth model including carrier-by-sex interaction term. Results After filtering, DNAH11 included two rare variants; 7:21564185-G>T and 7:21591370-G>A in each sex (MAF≈1-2x10-5). Among females (N = 245,718; 28,649 with asthma), 16 carriers were observed (MAC≈16). Gene-based tests showed a significant association with asthma (Burden_p=0.004; SKAT-O_p=0.005; SKAT_p=0.013). Firth carrier model OR was 4.58 (95% CI 1.62-11.98, p = 0.0055) (Figure 1A). LOO analyses (Figure 1B) showed both variants contributed to the signal; removing 7:21591370-G>A increased SKAT-O p to 0.075 (Δ-log10p≈+1.15), while removing 7:21564185-G>T increased p to 0.014 (Δ-log10p≈+0.41, with the association remaining significant after removing the latter. Among males (N = 207,209; 20,777 with asthma), 10 carriers were observed (MAC≈10) with no significant association (Burden_p=0.926; SKAT-O_p=0.797; SKAT_p=0.668; Firth_p=0.781). The carrier-by-sex interaction term in the combined Firth model was not significant (p = 0.190), suggesting the female-specific signal could not be detected in the males due to limited power. Conclusions This analysis provides primary evidence that these rare, pathogenic variants in the DNAH11 PCD gene may contribute to asthma susceptibility in a sex-specific manner, with a significant association observed only in females. The signal was predominantly driven by 7:21591370-G>A. This suggests that genetic disruption of ciliary function may interact with female-specific hormonal factors (i.e., progesterone) to influence asthma risk. This abstract is funded by: NIH