Effects of glucocorticoids on cytokine stimulated CCR4 promoter activity

Abstract

C-C motif chemokine receptor 4 (CCR4) is a G-protein coupled receptor (GPCR) which is highly expressed in Th2 cells and is believed to have a prominent role in mediating the asthmatic response. There are two distinct promoter regions upstream of the CCR4 gene named promoter A and promoter B. Previous experiments have shown upregulation of CCR4 promoter activity through cytokines which were elevated in asthmatic individuals. Glucocorticoids are commonly used in treating asthma and may do so partly by affecting CCR4 promoter activity. The effect of dexamethasone (a glucocorticoid) on cytokine stimulated CCR4 promoter activity has been investigated in the H460 cell line using magnetofected dual luciferase reporter constructs containing upstream CCR4 promoter fragments. Dexamethasone was found to have a dose dependent effect on promoter activity that varied with the promoter fragments and cytokines used. The most common response to dexamethasone treatment was a reduction in cytokine stimulated promoter activity at low dexamethasone concentrations (0.05 and 0.1µM) which rebound at higher dexamethasone concentrations (1 and 10µM). The most significant results were for fragments of CCR4 promoter A stimulated with IL-9, which observed a 35-59% reduction in promoter activity at 0.10µM dexamethasone. Results for fragments of promoter A were more consistent and more effected than those of promoter B which had different trends. Previously developed CCR4 antagonists weren’t successful on their own in clinical testing for asthma treatment, but findings in this dissertation indicate that combinatorial treatments of glucocorticoids and CCR4 antagonists could prove more fruitful.