Expression and Role of BAG-1 in Eosinophilic and Non-eosinophilic Chronic Rhinosinusitis with Nasal Polyps

The pathogenesis of human eosinophilic and non-eosinophilic chronic rhinosinusitis with nasal polyps (ECRSwNP and nECRSwNP) remains undetermined. We aimed to investigate the expression and role of Bcl-2-associated athanogene-1 (BAG-1) and heat shock protein 70 (Hsp70) in ECRSwNP and nECRSwNP. BAG-1 protein expression was investigated by immunohistochemistry and western blotting, and messenger RNA (mRNA) expression of BAG-1 and Hsp70 was assessed by real-time polymerase chain reaction (PCR) in 27 subjects with ECRSwNP, 28 subjects with nECRSwNP, and 23 control subjects. Moreover, the effects of various stimulators with different concentrations and time on BAG-1 were evaluated on a nasal explant culture. Results showed that significant elevations in total visual analog scale (VAS) score, endoscopy score, CT score, and rate of positive skin prick test (SPT) were found in the ECRSwNP group compared with the nECRSwNP group. BAG-1 and Hsp70 were overexpressed in CRSwNP, especially in ECRSwNP, and BAG-1 expression was closely related to Hsp70. BAG-1 mRNA was augmented by IL-4, IL-17A, and IL-1β, but suppressed by IFN-γ, respectively. In conclusion, eosinophils triggered a more severe form of inflammation in CRSwNP compared with non-eosinophilic inflammatory cells. The expressions of BAG-1 and Hsp70 were upregulated in CRSwNP, especially in ECRSwNP. IL-4, IL-17A, and IL-1β may be critical for BAG-1 gene expression.