The antimicrobial protein short palate, lung, and nasal epithelium clone 1 (SPLUNC1) is differentially modulated in eosinophilic and noneosinophilic chronic rhinosinusitis with nasal polyps

Background: Chronic rhinosinusitis with nasal polyps (CRSwNP) is a highly heterogeneous disease with aberrant host defense responses. However, whether innate immunity is similarly impaired in patients with eosinophilic and those with noneosinophilic CRSwNP remains unclear. Objectives: We sought to evaluate the expression and possible modulation of short palate, lung, and nasal epithelium clone 1 (SPLUNC1), an innate immune molecule, in the 2 CRSwNP subsets. Methods: Polyp tissue and uncinate processes were collected from 40 patients with CRSwNP, 27 patients with chronic rhinosinusitis without nasal polyps (CRSsNP), and 22 control subjects. Expression of SPLUNC1; Toll-like receptor (TLR) 2, TLR3, and TLR4; and the proinflammatory cytokines IL-1 alpha, IL-4, IL-13, IL-17A, and IFN-gamma was examined in nasal tissues. Additionally, SPLUNC1 expression in response to specific inflammatory stimulation was measured in cultured polyp epithelial cells and A549 cells. Results: Polyp tissues exhibited significantly decreased expression of SPLUNC1 and other innate immune molecules compared with uncinate process tissues from patients with CRSwNP (P<.05), patients with CRSsNP, and healthy control subjects. Moreover, the eosinophilic CRSwNP subset exhibited significantly decreased SPLUNC1 expression and numbers of submucosal glands, as well as significantly increased IL-4 and IL-13 mRNA levels, compared with the noneosinophilic subset (P<.05). Accordingly, SPLUNC1 expression in polyp epithelial cells was significantly inhibited by IL-4 and IL-13 stimulation in vitro but was significantly upregulated after stimulation with TLR agonists and glucocorticoids (P<.05). Conclusion: Differential SPLUNC1 suppression between the eosinophilic and noneosinophilic CRSwNP subsets suggests that they possess distinct pathogenic mechanisms. This finding might benefit the design of appropriate therapeutic interventions targeted to each subset.