Age-Related Decline of Neutrophilic Inflammation Is Associated with Better Postoperative Prognosis in Non-eosinophilic Nasal Polyps

BACKGROUND: Innate and adaptive immune responses change with increasing age and affect the course of diseases. Previous study investigated immunologic alteration in Western nasal polyps (NP) which is mostly eosinophilic. However, there are no reports regarding age-related immune changes of non-eosinophilic NP (NE-NP) which is a predominant subtype in Asian population. METHODS: A total of 153 subjects, including 20 with control, 63 with chronic rhinosinusitis (CRS) without NP (CRSsNP), and 70 with CRS with NP were enrolled. Age-related changes in computed tomography (CT), cytokines and clinical information were investigated. Tissue samples were analyzed for protein levels of IL-5, IL-17A, IL-23, interferon (IFN)-γ, CCL-11, and CXCL-8, using Luminex immunoassay and for mRNA expression levels of interleukin (IL)-5, IL-17A, IL-23p19, IFN-γ, CCL-11, CXCL-1, CXCL-2, CXCL-8, and CXCR2 by quantitative RT-PCR. Immunohistochemistry (IHC) was performed for the number of inflammatory cells. RESULTS: We observed that Lund-Mackay CT scores decreased with age in NE-NP. The number of human neutrophil elastase-positive cells and myeloperoxidase gene expression decreased in older patients with NE-NP, but not in control subjects, CRSsNP, and E-NP. Neutrophil-associated cytokines including IL-17A and IL-23, were negatively correlated with age in NE-NP at the protein and mRNA levels. Additionally, the expression of CXCR2, a receptor for CXCL-1 and CXCL-2, was decreased with age in NE-NP. However, there were no age-related changes in blood neutrophil count, and neutrophil-recruiting chemokines such as CXCL-1, CXCL-2, and CXCL-8. Elderly NE-NP patients showed better endoscopic scores at 12 months after surgery compared with the non-elderly. CONCLUSION: Age-related decline in neutrophil inflammation may favorably affect postoperative results in elderly patients with NE-NP.