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Background We reported that DNA-PK is critical for the expression of NF-κB-dependent genes in TNF-α-treated glioblastoma cells, suggesting an involvement in inflammatory diseases. Objective To investigate the role of DNA-PK in asthma. Methods Cell culture and ovalbumin or house dust mite (HDM)-based murine asthma models were used in this study. Results DNA-PK was essential for monocyte adhesion to TNF-α–treated-endothelial cells. Administration of the DNA-PK inhibitor, NU7441, reduced airway eosinophilia, mucus hypersecretion, airway hyperresponsiveness (AHR), and OVA-specific IgE production in mice that were pre-challenged with ovalbumin. Such effects correlated with a marked reduction in lung VCAM-1 expression and production of several cytokines, including IL-4/IL-5/IL-13/eotaxin/IL-2/IL-12 and the chemokines MCP-1/KC with negligible effect on IL-10/IFN-γ production. DNA-PK inhibition, by gene heterozygosity, also prevented manifestation of asthma-like traits. These results were confirmed in a chronic model of asthma using HDM, a human allergen. Remarkably, such protection occurred without causing SCID. Adoptive transfer of Th2-skewed OT-II-WT CD4+ T cells reversed IgE and Th2 cytokine production but not AHR in ovalbumin-challenged DNA-PKcs+/− mice. DNA-PK inhibition reduced IL-4/IL-5/IL-13/eotaxin/IL-8/MCP-1 production without affecting IL-2/IL-12/IFN-γ/IP-10 production in CD3/CD28-stimulated human CD4+T cells potentially by blocking expression of gata-3. These effects occurred without significant reductions in T-cell proliferation. In mouse CD4+T cells, DNA-PK inhibition, in vitro, severely blocked C3/CD28-induced gata-3 and t-bet expression in CD4+T cells and prevented differentiation of Th1 and Th2 cells under respective Th1- and Th2-skewing conditions. Conclusion Our results suggest DNA-PK as a novel determinant of asthma and a potential target for the treatment of the disease.

BackgroundAn important portion of asthmatics do not respond to current therapies. Thus, the need for new therapeutic drugs is urgent. We have demonstrated a critical role for PARP in experimental asthma. Olaparib, a PARP inhibitor, was recently introduced in clinical trials against cancer. The objective of the present study was to examine the efficacy of olaparib in blocking established allergic airway inflammation and hyperresponsiveness similar to those observed in human asthma in animal models of the disease.MethodsWe used ovalbumin (OVA)-based mouse models of asthma and primary CD4+ T cells. C57BL/6J WT or PARP-1−/− mice were subjected to OVA sensitization followed by a single or multiple challenges to aerosolized OVA or left unchallenged. WT mice were administered, i.p., 1 mg/kg, 5 or 10 mg/kg of olaparib or saline 30 min after each OVA challenge.ResultsAdministration of olaparib in mice 30 min post-challenge promoted a robust reduction in airway eosinophilia, mucus production and hyperresponsiveness even after repeated challenges with ovalbumin. The protective effects of olaparib were linked to a suppression of Th2 cytokines eotaxin, IL-4, IL-5, IL-6, IL-13, and M-CSF, and ovalbumin-specific IgE with an increase in the Th1 cytokine IFN-γ. These traits were associated with a decrease in splenic CD4+ T cells and concomitant increase in T-regulatory cells. The aforementioned traits conferred by olaparib administration were consistent with those observed in OVA-challenged PARP-1−/− mice. Adoptive transfer of Th2-skewed OT-II-WT CD4+ T cells reversed the Th2 cytokines IL-4, IL-5, and IL-10, the chemokine GM-CSF, the Th1 cytokines IL-2 and IFN-γ, and ovalbumin-specific IgE production in ovalbumin-challenged PARP-1−/−mice suggesting a role for PARP-1 in CD4+ T but not B cells. In ex vivo studies, PARP inhibition by olaparib or PARP-1 gene knockout markedly reduced CD3/CD28-stimulated gata-3 and il4 expression in Th2-skewed CD4+ T cells while causing a moderate elevation in t-bet and ifn-γ expression in Th1-skewed CD4+ T cells.ConclusionsOur findings show the potential of PARP inhibition as a viable therapeutic strategy and olaparib as a likely candidate to be tested in human asthma clinical trials.

The present study establishes poly(ADP-ribose)polymerase's (PARP's) role in chronic asthma, demonstrates that it is activated in human asthma, increases the clinical relevance of targeting PARP for blocking or preventing chronic asthma in humans and presents olaparib as a likely candidate drug.