Despite recent identification of eicosanoid mediators that resolve inflammation, the regulation of these factors during infection is not well understood. Asthma exacerbations are commonly triggered by infection with human rhinoviruses, but the lack of time-sensitive, patient-centered tools to study these events hinders development of acute asthma therapies. Our long-range goal is to more completely understand the resolution of asthma exacerbations, in order to hasten recovery. We have shown that the nucleotide receptor P2X7 regulates expression of cox-2 and PGE2 production (the latter of which induces pro-resolution lipids such as lipoxins). As such, the overall objective of the present proposal is o define the mechanisms regulating the expression and function of eicosanoid-metabolizing enzymes during infection by HRV in vitro and in vivo. As part of this broader objective, the central hypothesis is that transcellular generation of PGE2 and lipoxins is regulated by P2X7-induced cox-2 expression in alveolar macrophages, and that this process facilitates resolution of an HRV-triggered exacerbation. We propose the following Specific Aims. SA1) Determine the mechanisms of transcellular lipoxin generation during HRV infection. Our working hypothesis is that priming by HRV-infected epithelial cells enhances P2X7 induced cox-2 expression and PGE2 generation by alveolar macrophages, and that generation of lipoxins under these conditions requires airway epithelial 15-LO activity. The primary approach for this aim is to utilize primary cultures of airway cells from patients with mild asthma to study the P2X7-depndent mechanisms governing the expression and activity of cox-2 and 15-LO during infection with HRV. SA2) Identify the patient characteristics and airway sample eicosanoid factors during HRV- induced exacerbations that are associated with rapid resolution of asthma symptoms. The working hypothesis is that relative to those with attenuated pore function, asthma patients with normal P2X7 activity will have a greater proportion of subjects with a resolving Asthma Index within 7 days of starting a prednisone burst for an HRV-triggered exacerbation and have higher levels of PGE2 in acute airway samples. In this case, the primary approach is to study exacerbations with a newly developed time-sensitive tool, the Asthma Index, in the context of a Longitudinal and Exacerbation Protocols within the Severe Asthma Research Program-3. The functional capacity of P2X7, the presence or absence of HRV in nasal secretions during the exacerbation period and the levels of PGE2 and LXA4 levels in acute airway samples will be assessed to establish their roles as biomarkers in the time to resolving the exacerbation. This contribution is significant because it is the first step in a continuum of research that is expected to lead to development of pharmacologic strategies that will allow for a patient-individualized management strategy to more quickly restore asthma control and represents a new and substantive departure from the status quo by using a transcellular model to identify in vitro mechanisms, coupled with the infrastructure of the Severe Asthma Research Program and the time-sensitive Asthma Index.
The proposed work on the resolution of inflammation after airway infection with rhinoviruses will have a positive impact on the ability to more clearly defin clinical asthma exacerbation phenotypes relevant to the NIH Mission, while also providing foundation for the development of novel therapeutics. In addition to benefiting treatment decisions in asthma, the biomarkers studied herein may be relevant to other lung, infectious and inflammatory disorders. These finding may be broadly applicable to human health.
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