Interferon-? Induced Relatively Insufficient Autophagy Leads To P62-dependent Apoptosis Of Epithelial Cells In Chronic Rhinosinusitis With Nasal Polyps

Background:Autophagy is a lysosomal degradation pathway that is essential for survival, differentiation, development, and homeostasis. Its role in chronic rhinosinusitis with nasal polyps (CRSwNP) remains poorly studied.Objective:To investigate the involvement of autophagy in CRSwNP, particularly in the apoptosis of nasal epithelial cells (NECs) in CRSwNP.Methods:The expression of autophagic proteins [microtubule-associated protein 1 light chain 3B (LC3B)-?, autophagy-related protein (Atg)3,5 and 7, and Beclin 1], lysosome marker (lysosomal-associated membrane protein 1), substrate proteins (p62 and ubiquitinated protein), and apoptotic markers [cysteine-aspartic protease (casapase)-3 and 8, and poly-ADP-ribose polymerase] in the sinonasal mucosa and epithelial cells were detected by immunohistochemistry and western blotting. Polyp derived NECs were treated with rapamycin or bafilomycin Al to study the autophagic flux. Normal NECs were stimulated with interferon (IFN)-? and/or transfected with small interfering RNA targeting p62 (sip62) or Atg5 to observe the changes of autophagy and apoptosis. The treated NECs were analyzed by western blotting and flow cytometry.Results:The protein levels of autophagic proteins, lysosome marker, p62, ubiquitinated proteins, and apoptotic markers were increased in both eosinophilic and non-eosinophilic polyps, particularly in epithelial cells, in comparison with normal nasal mucosa. Bafilomycin Al up-regulated the levels of LC3B-? and p62 in polyp derived NECs simultaneously, whereas rapamycin had no significant effect. Sip62 transfection suppressed caspase-8 activation and cell apoptosis in polyp derived NECs. IFN-? up-regulated expression of LC3B-? and p62 in normal NECs and induced cell apoptosis depending on autophagy and p62. IFN-? protein level was increased in both eosinophilic and non-eosinophilic CRSwNP compared with normal tissues.Conclusion:IFN-? can induce relatively insufficient autophagy and thus lead to p62-dependent apoptosis of NECs in CRSwNP.Clinical implication:Effective strategies can be designed to target IFN-y and p62 to control relatively insufficient autophagy and nasal epithelial cell death, and subsequently alleviate mucosal barrier defect in both eosinophilic and non-eosinophilic CRSwNP.Capsule summary:There is a relatively insufficient autophagy in both eosinophilic and non-eosinophilic polyps, particularly in epithelial cells. This relatively insufficient autophagy may be induced by IFN-y and lead to p62-dependent apoptosis of nasal epithelial cells.