• Kathleen M Buchheit, Katherine N Cahill, Howard R Katz, Katherine C Murphy, Chunli Feng, Kathleen Lee-Sarwar, Juying Lai, Neil Bhattacharyya, Elliot Israel, Joshua A Boyce, and Tanya M Laidlaw.
• Department of Medicine, Harvard Medical School, Boston, Mass; Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital, Boston, Mass. Electronic address: kbuchheit@partners.org.
• J. Allergy Clin. Immunol. 2016 May 1; 137 (5): 1566-1576.e5.

BackgroundProstaglandin (PG) D2 is the dominant COX product of mast cells and is an effector of aspirin-induced respiratory reactions in patients with aspirin-exacerbated respiratory disease (AERD).ObjectiveWe evaluated the role of the innate cytokine thymic stromal lymphopoietin (TSLP) acting on mast cells to generate PGD2 and facilitate tissue eosinophilia and nasal polyposis in patients with AERD.MethodsUrinary eicosanoid levels were measured in aspirin-tolerant control subjects and patients with AERD. Nasal polyp specimens from patients with AERD and chronic rhinosinusitis were analyzed by using quantitative PCR, Western blotting, and immunohistochemistry. Human cord blood-and peripheral blood-derived mast cells were stimulated with TSLP in vitro to assess PGD2 generation.ResultsUrinary levels of a stable PGD2 metabolite (uPGD-M) were 2-fold higher in patients with AERD relative to those in control subjects and increased further during aspirin-induced reactions. Peak uPGD-M levels during aspirin reactions correlated with reductions in blood eosinophil counts and lung function and increases in nasal congestion. Mast cells sorted from nasal polyps expressed PGD2 synthase (hematopoietic PGD2 synthase) mRNA at higher levels than did eosinophils from the same tissue. Whole nasal polyp TSLP mRNA expression correlated strongly with mRNA encoding hematopoietic PGD2 synthase (r = .75), the mast cell-specific marker carboxypeptidase A3 (r = .74), and uPGD-M (r = 0.74). Levels of the cleaved active form of TSLP were increased in nasal polyps from patients with AERD relative to those in aspirin-tolerant control subjects. Recombinant TSLP induced PGD2 generation by cultured human mast cells.ConclusionsOur study demonstrates that mast cell-derived PGD2 is a major effector of type 2 immune responses driven by TSLP and suggests that dysregulation of this innate system contributes significantly to the pathophysiology of AERD.Copyright © 2015 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

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