Analysis of alpha‐1‐antitrypsin (AAT)‐regulated, glucocorticoid receptor‐dependent genes in macrophages reveals a novel host defense function of AAT

Abstract Alpha‐1‐antitrypsin (AAT) plays a homeostatic role in attenuating excessive inflammation and augmenting host defense against microbes. We demonstrated previously that AAT binds to the glucocorticoid receptor (GR) resulting in significant anti‐inflammatory and antimycobacterial consequences in macrophages. Our current investigation aims to uncover AAT‐regulated genes that rely on GR in macrophages. We incubated control THP‐1 cells (THP‐1 control ) and THP‐1 cells knocked down for GR (THP‐1 GR‐KD ) with AAT, performed bulk RNA sequencing, and analyzed the findings. In THP‐1 control cells, AAT significantly upregulated 408 genes and downregulated 376 genes. Comparing THP‐1 control and THP‐1 GR‐KD cells, 125 (30.6%) of the AAT‐upregulated genes and 154 (41.0%) of the AAT‐downregulated genes were significantly dependent on GR. Among the AAT‐upregulated, GR‐dependent genes, CSF‐2 that encodes for granulocyte‐monocyte colony‐stimulating factor (GM‐CSF), known to be host‐protective against nontuberculous mycobacteria, was strongly upregulated by AAT and dependent on GR. We further quantified the mRNA and protein of several AAT‐upregulated, GR‐dependent genes in macrophages and the mRNA of several AAT‐downregulated, GR‐dependent genes. We also discussed the function(s) of selected AAT‐regulated, GR‐dependent gene products largely in the context of mycobacterial infections. In conclusion, AAT regulated several genes that are dependent on GR and play roles in host immunity against mycobacteria.