Peroxisome Proliferator-Activated Receptor-γ Is Expressed in Eosinophils in Nasal Polyps

Abstract

Background: Peroxisome proliferator-activated receptor-γ (PPARγ) is a member of the nuclear receptors, which regulate fatty acid metabolites. One of the natural ligands for PPARγ is 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂), a major metabolite of prostaglandin D₂ (PGD₂). Recently, PPARγ has been shown to play an important role in anti-inflammatory reactions, including within-airway allergic diseases, in a mouse model. Our aim was to clarify the expression and localization of PPARγ and PGD₂ synthase, which produces ligands of PPARγ, in nasal polyps by immunohistochemical analysis. Methods: Nasal polyps of chronic rhinosinusitis patients (6 asthmatic patients and 6 nonasthmatic patients) were obtained during surgery. May-Grünwald-Giemsa staining was performed to evaluate the eosinophil infiltration of the polyps. To identify the cells expressing PPARγ protein and PGD₂ synthase, double immunostaining was performed using anti-PPARγ antibody, monoclonal antileukocyte antibodies, and PGD₂ synthase antibody. Results: The number of eosinophils and the number of PPARγ-positive cells in the nasal polyps of the asthmatic patients were significantly higher than those in the nonasthmatic patients. PPARγ was expressed on eosinophils and T cells of the infiltrating cells in the nasal polyps. PGD₂ synthase was also expressed on PPARγ-positive cells. Conclusion: PPARγ is involved in nasal polyposis pathogenesis, acting on eosinophils and T cells.