The H3K27me3-NR1D1-IFN-γ axis in trained macrophages induced by early respiratory virus infection drives non-T2 asthma in children.

Unlike that of T2 asthma, the pathophysiology of non-T2 asthma remains largely unexplored. However, increasing evidence supports a role for trained macrophages in asthma. In this study, we utilized a non-T2 asthma mouse model associated with early respiratory viral infection to identify the H3K27me3-NR1D1-IFN-γ axis in lung-trained macrophages, which drives non-T2 asthma by promoting Th1 differentiation. Early infection combined with allergen sensitization induced the formation of trained macrophages, which displayed hyperactive methionine cycling and elevated levels of S-adenosylmethionine (SAM). As a substrate for methyltransferase, SAM enhanced the trimethylation of H3K27, subsequently suppressing the expression of the nuclear receptor subfamily 1 group D member 1 (NR1D1) gene through enrichment at its promoter. Interestingly, NR1D1 interacted with the Ifng gene and negatively regulated its expression. High levels of IFN-γ from trained macrophages were observed because NR1D1 was inhibited by elevated H3K27me3 levels. Following allergen challenge, the increased expression of IFN-γ, MHC-II, and CD80/CD86 in trained macrophages positively regulated the activation and differentiation of Th1 cells, which subsequently produced more IFN-γ, thereby promoting non-T2 asthma. Consistently, in patients with asthma, peripheral blood mononuclear cells (PBMCs) and monocytes downregulated NR1D1 expression, resulting in elevated IFN-γ levels. Conversely, treatment of patient monocytes with an NR1D1 agonist led to a marked decrease in IFN-γ production. In mice, non-T2 asthma was significantly inhibited by either the inhibition of H3K27me3, the activation of NR1D1, or the neutralization of IFN-γ. Our results demonstrate that the H3K27me3-NR1D1-IFN-γ axis in lung-trained macrophages, which is associated with early infection, drives non-T2 asthma during childhood in mice. Consequently, SAM, NR1D1, and IFN-γ may serve as potential drug targets for the treatment of non-T2 asthma.