sPLA2GIB Promotes PGD2 and IL-13 Production in Eosinophilic Chronic Rhinosinusitis with Nasal Polyps

Objective: Secreted phospholipase A2 Group IB (sPLA2GIB) regulates the release of arachidonic acid, prostaglandins, and other inflammatory lipid mediators. Although it has been well involved in extensive inflammatory diseases, its specific mechanism in chronic rhinosinusitis with nasal polyps (CRSwNP) remains unclear. In this study, we investigated the role of sPLA2GIB in the pathophysiology of CRSwNP. Methods: Quantitative PCR, immunofluorescence staining, western blotting, and enzyme-linked immunosorbent assay (ELISA) were used to analyze the expression of sPLA2s, phospholipase A2 receptor (PLA2R), and prostaglandin D2 (PGD2) in nasal samples. Human nasal epithelial cells (HNECs) were cultured at an air-liquid interface (ALI) and stimulated with various cytokines. The human mast cell line HMC-1 was stimulated with sPLA2GIB, and the expression of PGD2 and cytokines in the culture supernatant was detected by ELISA. Results: The mRNA and protein levels of sPLA2GIB were significantly higher in eosinophilic CRSwNP than in control tissues. sPLA2GIB was predominantly expressed in the nasal epithelial cells. PLA2R mRNA and protein levels were upregulated in both eosinophilic and non-eosinophilic CRSwNP compared with the control groups. IL-4, IL-13, TNF-a, and IL-1 beta upregulated the expression of sPLA2GIB in ALI-cultured HNECs. sPLA2GIB induced PGD2 and IL-13 production in HMC-1 cells in a hydrolytic activity-independent manner. PGD2 protein expression was elevated in tissue homogenates of eosinophilic CRSwNP, and PGD2 upregulated the expression of IL-13 in HMC-1 cells. Conclusion: Increased secretion of sPLA2GIB by epithelial cells may promote eosinophilic inflammation in CRSwNP by enhancing PGD2 and IL-13 production in mast cells via binding to PLA2R.