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Background: Fractional exhaled nitric oxide concentration (FeNO) is widely used to support diagnosis and monitoring of bronchial asthma (BA). Tsoukias and George proposed a two-compartment model (2CM) for assessing the alveolar concentration of NO, referred to as CANO(2CM), while Condorelli et al proposed a model based on the trumpet shape of the airway tree and axial diffusion (TMAD), referred to as CANO(TMAD). In addition, Högman et al proposed non-linear model, referred to as CANO(non-linear)., Objective: We examined associations between the expression of inducible nitric oxide synthase (iNOS) mRNA in airway cells (ACs) by bronchoscopy and NO-parameters calculated by the three methods and identified which of them accurately reflected expression of iNOS mRNA from different airway portions., Methods: We retrospectively analysed data of 18 patients with stable, mild-moderate asthma, including 10 steroid-naïve BA (snBA) patients. Samples were obtained from airway brushings and bronchoalveolar lavage (BAL). Expressions of iNOS protein in tissue samples were evaluated by immunostaining. The iNOS mRNA in ACs was measured by qPCR. NO-parameters calculated by the three methods above and evaluated whether they were associated with iNOS mRNA in ACs derived from proximal (2nd carina), distal (10-15th) airways and alveolar regions., Results: Immunostaining revealed expression of iNOS proteins mainly in epithelial cells in the airways, while it was mainly expressed in macrophages in the alveolar region in the snBA group. The iNOS mRNA expression was increased in both proximal and distal ACs in the snBA group compared with steroid-treated BA group (stBA). CANO(2CM) negatively associated with FEV 1 (%predicted) and also associated with iNOS mRNA in distal ACs significantly. However, CANO(TMAD) and CANO(non-linear) showed no correlation with lung function nor iNOS mRNA expression in any portions of ACs., Conclusions: These results suggested that CANO(2CM) reflected distal airway inflammation in steroid-naïve asthma., (© 2019 The Authors. Clinical & Experimental Allergy Published by John Wiley & Sons Ltd.)

Background: Type 2 helper T-cell cytokines including IL-13 play a central role in the pathogenesis of bronchial asthma (BA). During the course of our research, our attention was drawn to dipeptidyl peptidase-4 (DPP4) as one of the molecules that were induced from bronchial epithelial cells (BECs) by IL-13 stimulation. DPP4 could become a new biomarker or therapeutic target. The aim of this study was to investigate the expression of DPP4 in the asthmatic airway, and its role in the pathophysiology of asthma., Methods: BECs were isolated from patients with inhaled corticosteroid-treated asthma (stBA) and inhaled corticosteroid-naïve asthma (snBA) using bronchoscopy. DPP4 mRNA expression in freshly isolated BECs and primary cultured BECs with or without IL-13 stimulation was investigated by microarray analysis and quantitative real-time PCR (qPCR). The distribution of DPP4 protein was determined by immunostaining of transbronchial lung biopsy specimens from asthma patients. The effect of recombinant human (rh) DPP4 on the proliferation of lung fibroblasts (HFL-1) and bronchial smooth muscle cells (BSMCs) was examined, as well as its effect on the production of fibronectin (FN)., Results: DPP4 mRNA was strongly expressed in freshly isolated BECs in snBA, and its expression was significantly enhanced by IL-13 stimulation. DPP4 mRNA expression in BECs of snBA significantly correlated with exhaled nitric oxide. Biopsied tissues of the asthmatic airway revealed strong expression of DPP4 protein in BECs from snBA subjects. rhDPP4 stimulated the proliferation of HFL-1 and BSMCs, and it also enhanced production of FN from these airway cells., Conclusion: DPP4 may be involved in the pathologic features of asthmatic airway inflammation and cell proliferation and FN production.