Axin acts as a negative regulator in Wnt signaling through interaction with various molecules involved in this pathway, including beta-catenin, adenomatous polyposis coli, and glycogen synthase kinase 3beta. We show here that Axin also regulates the effects of Smad3 on the transforming growth factor beta (TGF-beta) signaling pathway. In the absence of activated TGF-beta receptors. Axin physically interacted with Smad3 through its C-terminal region located between the beta-catenin binding site and Dishevelled-homologous domain. An Axin homologue, Axil (also called conductin), also interacted with Smad3. In the absence of ligand stimulation, Axin was colocalized with Smad3 in the cytoplasm in vivo. Upon receptor activation, Smad3 was strongly phosphorylated by TGF-beta type I receptor (TbetaR-I) in the presence of Axin, and dissociated from TbetaR-I and Axin. Moreover, the transcriptional activity of TGF-beta was enhanced by Axin and repressed by an Axin mutant which is able to bind to Smad3. Axin may thus function as an adapter of Smad3, facilitating its activation by TGF-beta receptors for efficient TGF-beta signaling.

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. 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). 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. DPP4 may be involved in the pathologic features of asthmatic airway inflammation and cell proliferation and FN production.

Intelectin-1 (ITLN-1) is secreted by intestinal goblet cells and detectable in blood. Its expression is increased in IL-13-overexpressing mouse airways. However, its expression and function in human airways is poorly understood. Distal and proximal bronchial epithelial cells (BECs) were isolated from bronchoscopic brushings of disease control (D-CON), COPD, inhaled corticosteroid-treated asthma (ST-Asthma) and inhaled corticosteroid-naïve asthma (SN-Asthma) patients. ITLN-1 mRNA expression in freshly isolated BECs, primary cultured BECs with or without IL-13 and inhibition effects of mometasone furoate (MF) were investigated by quantitative real-time PCR (qPCR). Correlations between ITLN-1 mRNA and Type-2 related parameters (e.g. FeNO, IgE, iNOS, CCL26, periostin and DPP4 mRNA) were analyzed. ITLN-1 protein distribution in asthmatic airway tissue was assessed by immunohistochemistry. Bronchial alveolar lavage (BAL) and serum ITLN-1 protein were measured by ELISA. The effect of recombinant human (rh) ITLN-1 on stimulated production of CXCL10 and phospho(p)-STAT1 expression examined in lung fibroblasts. ITLN-1 mRNA was expressed in freshly isolated BECs and was correlated with Type-2 related parameters. ITLN-1 protein was increased in goblet cells in SN-Asthmatics and increased in SN-Asthmatic BAL fluid. There were no any differences in serum ITLN-1 concentration between ST and SN-Asthma. IL-13 enhanced ITLN-1 expression and inhibited by MF from BECs in vitro, while rhITLN-1 inhibited CXCL10 production and p-STAT1 expression in HFL-1 cells. ITLN-1 is induced by IL-13 and expressed mainly in goblet cells in untreated asthma where its levels correlate with known Type-2 related parameters. Further, ITLN-1 inhibits Type-1 chemokine expression.

Receptor-interacting protein (RIP)-2 is a serine/threonine kinase containing a caspase recruitment domain (CARD) that is involved in the Toll-like receptor-signaling pathway. Although associations between endotoxin exposure or respiratory infection and asthma have been recognized, the genetic influences in these conditions are unclear. The aim of our study was to examine whether polymorphisms or haplotypes in RIP2 were associated with childhood atopic asthma in a Japanese population. We screened the RIP2 gene for polymorphisms by direct sequencing and characterized the linkage disequilibrium (LD) mapping of the gene. Seven variants were genotyped in childhood atopic asthma (n = 300) and normal controls (n = 637) . We conducted case-control and case-only association studies between the variants and asthma-related phenotypes. Haplotype association analyses were also performed. A total of 31 variants were identified and none of the alleles or haplotypes of RIP2 were associated with asthma susceptibility. In the case-only study, an association between an RIP2 promoter polymorphism and childhood severe asthma (P=0.0032; odds ratio (OR) 3.37, 95% confidence interval (CI) 1.45-7.87) was observed. Although polymorphisms in RIP2 are not likely to be associated with the development of asthma, the genetic variants might contribute to asthma severity in the Japanese population.

Background: The purpose of this study is to clarify the changes in peripheral blood eosinophil (PBE) counts and eosinophilic granulomatosis with polyangiitis (EGPA) onset in patients with asthma who were treated with dupilumab in clinical practice. Methods: The primary outcome of this study is to determine the onset of EGPA in patients whose PBE counts continued to rise within 6 months of dupilumab initiation (rising group) and in patients whose PBE counts peaked and subsequently declined within 6 months (peaked and declined group). As a secondary outcome, the incidence of developing EGPA in patients with PBE counts greater than 1500 cells/μL at 3 or 6 months after dupilumab administration is investigated. Results: A total of 37 individual were enrolled (male/female = 14/23, median age = 57.0 years old). The development of EGPA was significantly more frequent in the rising group compared with the peaked and declined group (p = 0.042, effect size = 0.455, moderate association). Patients with PBE counts greater than 1500 cells/μL showed a significantly higher risk of developing EGPA (p = 0.017, effect size = 0.678, strong association). Conclusions: Physicians should check for the onset of EGPA by monitoring the elevation of eosinophils within 6 months after dupilumab administration, especially in patients with PBE counts greater than 1500 cells/μL at 3 months.

Idiopathic pulmonary fibrosis (IPF) is a representative disease that causes fibrosis of the lungs. Its pathogenesis is thought to be characterized by sustained injury to alveolar epithelial cells and the resultant abnormal tissue repair, but it has not been fully elucidated. IPF is currently difficult to cure and is known to follow a chronic progressive course, with the patient’s survival period estimated at about three years. The disease occasionally exacerbates acutely, leading to a fatal outcome. In recent years, it has become evident that lipid metabolism is involved in the fibrosis of lungs, and various reports have been made at the cellular level as well as at the organic level. The balance among eicosanoids, sphingolipids, and lipid composition has been reported to be involved in fibrosis, with particularly close attention being paid to a bioactive lipid “lysophosphatidic acid (LPA)” and its pathway. LPA signals are found in a wide variety of cells, including alveolar epithelial cells, vascular endothelial cells, and fibroblasts, and have been reported to intensify pulmonary fibrosis via LPA receptors. For instance, in alveolar epithelial cells, LPA signals reportedly induce mitochondrial dysfunction, leading to epithelial damage, or induce the transcription of profibrotic cytokines. Based on these mechanisms, LPA receptor inhibitors and the metabolic enzymes involved in LPA formation are now considered targets for developing novel means of IPF treatment. Advances in basic research on the relationships between fibrosis and lipid metabolism are opening the path to new therapies targeting lipid metabolism in the treatment of IPF.