Asthmatic bronchial smooth muscle migration towards rhinovirus-infected epithelium through a CXCR3 isoform-dependant pathway

Abstract

Asthma is the most common chronic respiratory disease. In severe patients, one of the main feature of the physiopathology is the increased bronchial smooth muscle (BSM) mass, which is related to frequency and severity of asthma exacerbations. Exacerbations are mainly triggered by rhinovirus infection of the epithelium. In addition, histology analysis has shown that distance between BSM cells and epithelium decrease proportionally to the severity of the disease. We thus hypothesis that rhinovirus infection of the epithelium increase the migration of asthmatic BSM cells. Primary BSM cells from control and asthmatic patients were obtained from bronchial biopsies. Epithelial cells were cultivated in an air-liquid Interface. After complete differentiation, epithelium were exposed to RVA-16 (MOI 0,1) and epithelium supernatant were collected 24 h post infection. BSM migration was assessed in response to epithelium supernatant in a chemotaxis assay for 24 h using live microscopy. Transcriptomics and ELISA were used to analysed chemokine content within the epithelial supernatant. Immunohistochemistry and flow cytometry were used to quantify CXCR3 isoforms distribution ( i.e CXCR3 A and B). Finally, western blot, cAMP assay and Ca2+ fluorometric probes were used to assess CXCR3 activation pathway. BSM cells from asthmatics migrates towards RV-infected epithelium whereas such a chemotactic effect was not observed in control BSM cells. Analysis of epithelium supernatant show that CXCL9 and CXCL10 were both induced by RVA-16. Interestingly, blocking of CXCR3 receptor, which is activated, by both CXCL9 and 10 abolished asthmatic BSM migration. They are two main isoforms of CXCR3 (A and B) which are described as activator and inhibitor of cell migration reciprocally. Interestingly, CXCR3-B expression and activation pathway through PKC and cAMP are increased in control BSM cells whereas CXCR3-A signalling pathway through calcium and Raf-1 activation are increase in asthmatic BSM cells. Asthmatic BSM cells specifically migrate toward RV-infected epithelium through the activation of CXCR3-A. This new mechanism could be a new therapeutic target against BSM remodelling in asthma.