The Impact of Bronchial Allergen Challenge on Eosinophil Subtype-Specific miRNA and Their Target Gene Expression in Allergic Asthma

<bold>Introduction:</bold> In allergic asthma (AA), eosinophils and their miRNAs play crucial roles, yet their specific functions during exacerbations, which could unveil eosinophil subtype distinctions and pathophysiological roles, remain unclear <bold>Aim:</bold> To assess the effects of bronchial allergen challenge (BAC) on the expression of miR-146b-5p, miR-185-5p, and miR-21-5p target genes (PRG2,CYSLTR1,RANTES,IL-1β) in lung-resident-like (rEOS-like) and inflammatory-like eosinophils (iEOS-like) in AA patients <bold>Methods:</bold> We studied 12 AA patients before and 24 h after BAC with <italic>D. Pteronyssinus</italic> and 16 healthy subjects (HS). Total blood eosinophils were isolated by high-density centrifugation and magnetic separation, phenotyped using CD62L-conjugated magnetic beads. miRNA and their target gene expressions in eosinophils were quantified by RT-qPCR <bold>Results:</bold> In AA's rEOS-like and iEOS-like cells, miR-185-5p expression was elevated and remained post-BAC. Its target genes,CYSLTR1 and PRG2,showed reduced expression in both subtypes;notably,PRG2 reduction in iEOS-like cells observed only after BAC,compared to HS,p<0.05.miR-146b-5p expression in iEOS-like cells decreased post-BAC,aligning with HS,whereas in rEOS-like cells remained elevated. The miR-146b-5p target RANTES showed no change after BAC,maintaining reduced expression in both subtypes compared to HS,p<0.05. After BAC,miR-21-5p expression in the AA group continued to be lower in iEOS-like cells than in AA rEOS-like cells and HS,p<0.05. Furthermore, while miR-21-5p target gene FOXO3 expression remained downregulated in both eosinophil subtypes after BAC,IL-1β expression was specifically reduced in iEOS-like cells compared to HS,p<0.05 <bold>Findings:</bold> BAC specifically reduces PRG2,IL-1β,and miR-146b-5p expression in iEOS-like cells, underlining their unique allergen sensitivity in AA