Live Imaging of Nitric Oxide Dynamics Reveals Cell Type-Specific NO Signaling in Air-Liquid Interface Cultures of...

Background/Objectives: Chronic rhinosinusitis with nasal polyps (CRSwNP) is associated with epithelial remodeling, impaired mucociliary clearance, and altered nitric oxide (NO) metabolism. However, cell type-specific mechanisms underlying epithelial NO signaling remain poorly understood. This study investigated NO-related signaling in differentiated human sinonasal epithelial cells. Methods: Human sinonasal tissues were obtained from patients with CRSwNP (n = 20) and control subjects (n = 20). Air-liquid interface (ALI) cultures were established from donor-derived epithelial cells. Ciliated and non-ciliated cells were identified by immunostaining for acetylated α-tubulin and BCAM. Expression of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) was analyzed by quantitative RT-PCR. Intracellular NO-related fluorescence signals were evaluated using DAF-FM fluorescence imaging. Results: CRSwNP tissues exhibited significantly increased iNOS expression and elevated iNOS/eNOS ratios, whereas eNOS expression did not differ significantly from that in controls. ALI cultures reproduced differentiated sinonasal epithelium containing both ciliated and non-ciliated cell populations. DAF-FM fluorescence signals were significantly higher in ciliated cells than in non-ciliated cells (80.3 ± 25.3 vs. 49.3 ± 21.1). Non-selective NOS inhibition markedly reduced fluorescence signals in both cell types, whereas selective iNOS inhibition reduced but did not abolish signals in ciliated cells. Conclusions: NO-related signaling appears to differ among epithelial cell subtypes. Persistence of fluorescence signals after selective iNOS inhibition suggests a contribution of constitutive NOS activity in ciliated cells, whereas non-ciliated cells appear to rely more heavily on iNOS-dependent pathways. These findings support the hypothesis that altered epithelial NO signaling contributes to epithelial dysfunction and impaired mucociliary homeostasis in CRSwNP.