Chronic inflammation, hypertrophy and squamous metaplasia of the normal, pseudostratified columnar epithelium within the sinuses is a consistent feature of chronic sinusitis, and it is the central premise of this program application that alterations in epithelial cell function may contribute to the pathophysiology of this disease. This project will examine the hypothesis that viral infection of the epithelium plays an important role in the development or exacerbation of chronic sinusitis by triggering alterations in epithelial cell function, particularly increased production of proinflammatory cytokines. To examine the link between viral infection and sinusitis, we will prospectively monitor subjects who have undergone sinus surgery. We will collect nasal and sinus lavages from subjects during periods when their disease is quiescent and as soon as possible after they report exacerbations of their sinusitis. We will use both PCR and standard culture methods for a range of common respiratory viruses to determine the incidence of viral infection in these samples and to correlate the presence of infections with disease exacerbations and with alterations in nasal potential difference (Project 3). Our preliminary data clearly show that rhinovirus infection of epithelial cells in vitro leads to increased release of cytokines. Treatment of cells with glucocorticoids can inhibit virally-induced cytokine production. We will use cultured cells to determine the molecular mechanisms by which viral infection and glucocorticoids regulate epithelial cell cytokine production. We will use Northern blot analysis, nuclear run-on experiments, and cells transfected with promoter constructs to determine if cytokine production is regulated at the transcriptional or posttranscriptional level. The role of NF-kappaB and AP-1 transcriptional regulation sites in the control of epithelial cytokine production by viruses and glucocorticoids will also be examined. To determine if these changes in epithelial cell cytokine production may occur, and play a role in exacerbations of sinusitis, in vivo, we will monitor levels of the epithelial cytokines, IL-8, IL-6 and GM-CSF, in nasal and sinus lavages obtained from our patient populations during periods when their disease is quiescent and during exacerbations. In addition, we will use immunocytochemistry and in situ hybridization to examine sinus biopsies from a subpopulation of subjects to confirm the cellular origin of these cytokines. We will also determine if patients receiving glucocortocoids show a lower incidence of disease exacerbations during viral infections, and will relate any such differences to epithelial cytokine production in vivo and to predisposing factors in our population, such as atopic status, immune competence, or asthmatic status. These studies should provide important insights into the pathogenesis of sinusitis and may lead to the development of improved therapies for the treatment of this major health problem. Our studies on viral alterations of epithelial cell function may also have broader implications of relevance to the pathogenesis of asthma and the common cold.
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