Exosomes mediate interepithelial transfer of functional P‐glycoprotein in chronic rhinosinusitis with nasal polyps

Objective P‐glycoprotein (P‐gp) drives type‐2 helper T‐cell inflammation in chronic rhinosinusitis with nasal polyps (CRSwNP) through unknown posttranslational mechanisms of overexpression. A recent randomized clinical trial demonstrated that inhibition of P‐gp was as effective as oral steroids and biologics in treating CRSwNP. Exosomes are 30‐ to 150‐nm vesicles capable of intercellular membrane protein transfer. The aims of this study were 1) to determine whether CRSwNP mucus exosomes are enriched with P‐gp, and 2) whether exosomal P‐gp can be functionally transferred to autologous epithelial cells as a putative mechanism for the proinflammatory overexpression of P‐gp in CRSwNP. Study Design Institutional review board‐approved study in CRSwNP and control patients (n = 10 per group). Methods P‐gp content of purified mucus exosomes was characterized by transmission electron microscopy and enzyme‐linked immunosorbent assay. Epithelial transfer of exosomal P‐gp was determined by time‐lapse fluorescent microscopy and calcein acetoxymethylester functional P‐gp assay. Results CD63+/P‐gp+ exosomes were detected in both groups. P‐gp was significantly enriched in CRSwNP exosomes relative to control (median 198.5; interquartile range 123.6–270.5 vs. 74.4; 41.3–95.0 pcg P‐gp/10 9 exosomes, P = 0.002). Exosomes were absorbed by epithelial cells within 10 minutes, resulting in a significant increase in P‐gp activity in CRSwNP patients relative to control ( P = 0.006). Conclusion Here we demonstrate the presence and P‐gp enrichment of mucus‐derived exosomes, or rhinosomes , in CRSwNP. These rhinosomes are capable of rapid intercellular transfer of P‐gp, leading to increased P‐gp function within recipient cells. This represents a novel mechanism for maintaining P‐gp overexpression in CRSwNP, and more generally for interepithelial transfer of other proteins between mucosal epithelial cells. Level of Evidence NA. Laryngoscope , 127:E295–E300, 2017