Our long-term objective is to establish the role of poly(ADP-ribose) polymerase-1 (PARP-1) in the pathogenesis of allergen-induced respiratory diseases such as asthma and to develop a treatment strategy based on the inhibition of this enzyme for asthma. Airway inflammation is a central feature of the pathogenesis of asthma. Reactive oxygen (ROS) and nitrogen (RNS) species contribute to inflammation by damaging DNA, which, in turn, results in the activation of PARP-1. The depletion both of the substrate of this enzyme (NAD) and of the NAD precursor ATP as a result of persistent activation of PARP-1 leads to a cellular energy crisis and, eventually, to cell death. We propose to test the hypothesis that ROS and RNS generated during allergen exposure induce DNA damage and persistent activation of PARP-1 in airway epithelial cells, resulting in the depletion of cellular energy reserves and airway inflammation. For the proposed studies, we intend to use the well-established mouse model of allergen (ovalbumin)-triggered lung inflammation. Our preliminary data show that PARP-1 is activated in lungs of ovalbumin-challenged mice may exacerbate the inflammatory response by promoting the expression of the inducible nitric oxide synthase (iNOS), in part, through its promotion of the activation of the pro-inflammatory transcription factor, NF-kappaB. Inhibition of PARP-1, either pharmacologically or by gene knockout, results in a marked decrease in the extent of inflammation in the lungs of ovalbumin-challenged mice and almost a complete inhibition of iNOS expression. We therefore plan (1) to demonstrate further and to characterize the role of PARP-1-mediated depletion of NAD and ATP in the pathogenesis of allergen-induced lung inflammation. (2) We will investigate the mechanism by which PARP-1 is activated in lungs of ovalbumin-exposed mice and establish the relation between iNOS expression, RNS generation, and PARP-1 activation in allergen-induced lung inflammation. (3) Finally, with the use of the animal model and primary lung epithelial cells, we will examine the mechanism by which PARP-1 promotes the activation of NF-?B during allergen-induced lung inflammation. We will establish the connection between PARP-1 activation, ROS/RNS generation, and NF-kappaB activation. The results of the proposed study should provide insight into the suitability of PARP-1 as a novel target for the treatment of allergen-induced respiratory diseases such as asthma.
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