Co-Expression and Localization of Angiotensin-Converting Enzyme-2 (ACE2) and the Transmembrane Serine Protease 2 (TMPRSS2) in Paranasal Ciliated Epithelium of Patients with Chronic Rhinosinusitis.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uses angiotensin-converting enzyme-2 (ACE2) and the transmembrane serine protease 2 (TMPRSS2) as a primary receptor for invasion. Cell entry by the virus requires the co-expression of these molecules in the host cells. OBJECTIVE: We investigated ACE2 and TMPRSS2 expression and localization in paranasal epithelium of eosinophilic chronic rhinosinusitis (ECRS) patients (n = 38), non-ECRS (n = 31), and healthy controls (n = 25). CRS inflammatory patterns are characterized by the type of cytokines; we investigated whether inflammatory endotypes are associated with cell-entry molecules, as this could be linked to susceptibility to SARS-CoV-2 infection. METHODS: The ACE2, TMPRSS2, and other inflammatory cytokine mRNA levels were assessed by quantitative RT-PCR. The localizations of ACE2- and TMPRSS2-positive cells were examined with immunofluorescent double-staining using laser scanning confocal microscopy (LSCM). RESULTS: The non-ECRS patients showed significantly increased ACE2 and TMPRSS2 mRNA expressions compared to the ECRS patients. The CRS patients' ACE2 and TMPRSS2 mRNA levels were positively correlated with IFN-γ (r = 0.3227 and r = 0.3264, respectively) and TNF-α (r = 0.4008, r = 0.3962, respectively). ACE2 and TMPRSS2 were negatively correlated with tissue eosinophils (r = -0.3308, r = -0.3112, respectively), but not with IL-13. ACE2 mRNA levels were positively correlated with TMPRSS2 (r = 0.7478). ACE2 and TMPRSS2 immunoreactivities were localized mainly in the epithelial ciliated cells, as confirmed by co-staining with TMPRSS2 and acetylated α-tubulin, a cilia organelle marker. Using LSCM imaging, we observed higher expressions of these molecules in the non-ECRS patients versus the ECRS patients. CONCLUSION: ECRS patients with type 2 inflammation showed decreased ACE2 and TMPRSS2 expressions in their sinus mucosa. ACE2 and TMPRSS2 regulation seems to be positively related to IFN-γ and TNF-α production in CRS patients; ACE2 and TMPRSS2 were co-expressed in the ciliated epithelium of their paranasal mucosa, implicating the paranasal epithelium as a portal for initial infection and transmission.

The Functional Diversity of Nitric Oxide Synthase Isoforms in Human Nose and Paranasal Sinuses: Contrasting Pathophysiological Aspects in Nasal Allergy and Chronic Rhinosinusitis.

The human paranasal sinuses are the major source of intrinsic nitric oxide (NO) production in the human airway. NO plays several roles in the maintenance of physiological homeostasis and the regulation of airway inflammation through the expression of three NO synthase (NOS) isoforms. Measuring NO levels can contribute to the diagnosis and assessment of allergic rhinitis (AR) and chronic rhinosinusitis (CRS). In symptomatic AR patients, pro-inflammatory cytokines upregulate the expression of inducible NOS (iNOS) in the inferior turbinate. Excessive amounts of NO cause oxidative damage to cellular components, leading to the deposition of cytotoxic substances. CRS phenotype and endotype classifications have provided insights into modern treatment strategies. Analyses of the production of sinus NO and its metabolites revealed pathobiological diversity that can be exploited for useful biomarkers. Measuring nasal NO based on different NOS activities is a potent tool for specific interventions targeting molecular pathways underlying CRS endotype-specific inflammation. We provide a comprehensive review of the functional diversity of NOS isoforms in the human sinonasal system in relation to these two major nasal disorders' pathologies. The regulatory mechanisms of NOS expression associated with the substrate bioavailability indicate the involvement of both type 1 and type 2 immune responses.