Allergic sensitization enhances anion current responsiveness of murine trachea to PAR-2 activation
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Protease-activated receptor 2 (PAR-2) is a G protein-coupled receptor possibly involved in the pathogenesis of asthma. PAR-2 also modulates ion transport in cultured epithelial cells, but these effects in native airways are controversial. The influence of allergic inflammation on PAR-2-induced changes in ion transport has received little attention. Here, we studied immediate changes in transepithelial short circuit current (I sc) induced by PAR-2 activation in the tracheas of naive and allergic mice. Activation of PAR-2 with an apically added activation peptide (AP) induced a small increase in I sc, while a much larger increase was observed following basolateral AP addition. In ovalbumin-sensitized and -challenged animals used as a model of allergic airway inflammation, the effect of basolateral AP addition was enhanced. Responses to basolateral AP in both naive and allergic mice were not decreased by blocking sodium absorption with amiloride or CFTR function with CFTRinh172 but were reduced by the cyclooxygenase inhibitor indomethacin and largely blocked (>80%) by niflumic acid, a calcium-activated chloride channels’ (CaCC) blocker. Allergic mice also showed an enhanced response to ATP and thapsigargin. There was no change in mRNA expression of Par-2 or of the chloride channels Ano1 (Tmem16a) and Bestrophin 2 in tracheas from allergic mice, while mRNA levels of Bestrophin 1 were increased. In conclusion, basolateral PAR-2 activation in the mouse airways led to increased anion secretion through apical CaCC, which was more pronounced in allergic animals. This could be a protective mechanism aimed at clearing allergens and defending against mucus plugging.
KeywordsPAR-2 Asthma Bestrophin Airway surface liquid Calcium-activated chloride channels
We thank Dr. Dean Befus for critically reviewing the manuscript, Dr. Criss Hartzell for providing Best1 plasmid, Drew Nahirney and Dr. Valentine Duta for their help with the design and construction of the Ussing chamber used in this study, and Dr. Muhammad Asaduzzaman and Dr. Narcy Arizmendi for their help with the immunization of animals. This work was supported by the Canadian Cystic Fibrosis Foundation, the Canadian Institutes of Health Research and the Alberta Heritage Foundation for Medical Research.
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