Roles of Transcription Factors NMP4 and FOXP3 in Regulating Airway Inflammation

Abstract

Airway inflammation is the most common and important component of respiratory diseases, such as influenza and asthma. Severe influenza A virus infection typically triggers detrimental lung inflammation with massive immune cell infiltration and hyper-production of cytokines and chemokines. We identified a novel function for nuclear matrix protein 4 (NMP4), a zinc-finger-containing transcription factor known for its function in bone formation and spermatogenesis, in regulating antiviral immune responses and immunopathology. Nmp4-deficient mice are protected from influenza induced immunopathology and body weight loss. While having no effects on viral clearance or CD8/CD4 T cell or humoral immune responses, Nmp4 deficiency in either lung structural cells or hematopoietic cells significantly reduces the recruitment of neutrophils and monocytes to the lungs. Furthermore, NMP4 binds to the promoters and/or conserved non-coding sequences of the chemokine genes Ccl2 and Cxcl1 and upregulates their expression in mouse lung epithelial cells and macrophages. These chemokines attract monocytes and neutrophils to the airway, resulting in exaggerated airway inflammation and collateral lung damage. Another transcription factor forkhead box P3 (FOXP3) is critical for the development of regulatory T cells (Tregs) that function to control immune responses. Unlike human FOXP3 gene that encodes two major isoforms, a full length (FOXP3-FL) isoform and a short isoform lacking the exon 2 region (FOXP3-ΔE2), mouse Foxp3 gene only encodes Foxp3-FL isoform. We generate Foxp3-ΔE2 mice to study its function and find that Tregs expressing the Foxp3-ΔE2 isoform have intrinsic defects, thus allowing intensified adaptive immune responses without changes in innate immunity against influenza infection. In a model of chronic asthma, mice expressing only the Foxp3-ΔE2 isoform have significantly increased allergic airway inflammation and elevated production of allergen-specific IgE compared with mice expression the Foxp3-FL isoform. Mechanistically, Tregs expressing the Foxp3-ΔE2 isoform are less stable and prone to trans-differentiation into effector Th9-like cells, which are closely associated with the pathogenesis of asthma. These data suggest that the two Foxp3 isoforms have different functions in regulating airway immune responses. Overall, we have defined the important roles of both transcription factors NMP4 and FOXP3 in regulating airway inflammation.