Regulatory effect of dexamethasone on tracheal calcium processing proteins and mucosal secretion

Dexamethasone inhibits mucin secretion considering the primary option for treating acute asthma exacerbation. However, the mechanism underlying dexamethasone-induced decreased in mucosecretion is unclear. Recent studies have reported that dexamethasone exerts an inhibitory effect on mucosecretion in the lung by modulating the expression of calcium processing genes. However, the expression of the calcium processing genes in the trachea is not examined yet. Thus, the present study is the first to report the localization of calcium processing proteins such as transient receptor potential vanilloid-4 (Trpv4), transient receptor potential vanilloid-6 (Trpv6), calbindin-D_9k (CaBP-9k) and plasma membrane Ca²⁺-ATPase 1 (Pmca1) in the mouse trachea and their glucocorticoid-induced response. In this study, mice were subcutaneously injected with dexamethasone for 5 days, and their tracheal samples were collected by dividing the trachea into the cervical, and thoracic sections based on its anatomical structure. The localization of TRPV4, TRPV6, CaBP-9k, and PMCA1 proteins was detected in the tracheal epithelium, submucosal glands, cartilages and muscles. Dexamethasone treatment downregulated the mRNA expression of the four calcium processing genes and mucin producing genes. The dexamethasone-induced decrease in the secretion of mucosubstances in the trachea was determined by performing Alcian blue-periodic acid-Schiff staining. Thus, the findings of the present study suggest that glucocorticoids simultaneously can regulate the expression of calcium processing genes and tracheal mucosecretion.