DNA-dependent protein kinase inhibition blocks asthma in mice and modulates human endothelial and CD4+ T-cell function without causing severe combined immunodeficiency

Background: We reported that DNA-dependent protein kinase (DNA-PK) is critical for the expression of nuclear factor kappa B-dependent genes in TNF-alpha-treated glioblastoma cells, suggesting an involvement in inflammatory diseases. Objective: We sought to investigate the role of DNA-PK in asthma. Methods: Cell culture and ovalbumin (OVA)- or house dust mite-based murine asthma models were used in this study. Results: DNA-PK was essential for monocyte adhesion to TNF-alpha-treated endothelial cells. Administration of the DNA-PK inhibitor NU7441 reduced airway eosinophilia, mucus hypersecretion, airway hyperresponsiveness, and OVA-specific IgE production in mice prechallenged with OVA. Such effects correlated with a marked reduction in lung vascular cell adhesion molecule 1 expression and production of several cytokines, including IL-4, IL-5, IL-13, eotaxin, IL-2, and IL-12 and the chemokines monocyte chemoattractant protein 1 and keratinocyte-derived chemokine, with a negligible effect on IL-10/IFN-gamma production. DNA-PK inhibition by gene heterozygosity of the 450-kDa catalytic subunit of the kinase (DNA-PKcs(+/-)) also prevented manifestation of asthma-like traits. These results were confirmed in a chronic model of asthma by using house dust mite, a human allergen. Remarkably, such protection occurred without causing severe combined immunodeficiency. Adoptive transfer of T(H)2-skewed OT-II wild-type CD4(+) T cells reversed IgE and T(H)2 cytokine production but not airway hyperresponsiveness in OVA-challenged DNA-PKcs(+/-) mice. DNA-PK inhibition reduced IL-4, IL-5, IL-13, eotaxin, IL-8, and monocyte chemoattractant protein 1 production without affecting IL-2, IL-12, IFN-gamma, and interferon-inducible protein 10 production in CD3/CD28-stimulated human CD4(+) T cells, potentially by blocking expression of Gata3. These effects occurred without significant reductions in T-cell proliferation. In mouse CD4(+) T cells in vitro DNA-PK inhibition severely blocked CD3/CD28-induced Gata3 and T-bet expression in CD4(+) T cells and prevented differentiation of T(H)1 and T(H)2 cells under respective T(H)1- and T(H)2-skewing conditions. Conclusion: Our results suggest DNA-PK as a novel determinant of asthma and a potential target for the treatment of the disease.