A Pharmacodynamics Analysis of Glucocorticoid Receptor-Mediated Gene Expression in BEAS-2B Human Airway Epithelial Cells
Creators: name: Joshi, Taruna
Publisher: name: Graduate Studies
Year: 2016
Subjects: subject: Biology--Molecular
subject: Pharmacology
subject: Glucocorticoid
subject: Glucocorticoid Receptor
subject: Pharmacodynamics
subject: Long acting beta adrenergic agonist
subject: antagonist
subject: partial agonist
subject: Potency
subject: Affinity
subject: Efficacy
subject: Concentration-response curves
subject: Glucocorticoid response element

description: International treatment guidelines recommend that inhaled glucocorticoids be used as a monotherapy to control mild-to-moderate asthma. However, a combination of an inhaled glucocorticoid with a long-acting β2-adrenoceptor agonist is recommended for managing moderate-to-severe asthma, which cannot be controlled by glucocorticoids alone. Increasing evidence supports the idea that glucocorticoids acting through the glucocorticoid receptor (GR) can attenuate inflammatory responses either by inducing anti-inflammatory genes (a process called transactivation) or by suppressing pro-inflammatory genes (a process called transrepression). Gene transactivation by glucocorticoids was initially thought to be responsible for causing the metabolic side-effects and, hence, is relatively understudied when compared to transrepression. However, it has become increasingly clear that transactivation plays an important role in the anti-inflammatory actions of glucocorticoids. Moreover, the extent to which clinically-relevant glucocorticoids are equivalent in their ability to promote gene expression is unclear. This thesis describes the first pharmacodynamic approach to evaluate the transactivation potential of a panel of glucocorticoids alone and in combination with indacaterol (Ind), a long-acting β2-adrenoceptor agonist. Pharmacodynamic analyses showed that magnitude of luciferase gene induction was agonist dependent (i.e. seven different glucocorticoids tested displayed varying degrees of agonism). In addition, there were significant differences in agonist potency and, more importantly, the relationship between GR occupancy and response. To complement the reporter studies, similar analyses were performed on four glucocorticoid-inducible candidate genes. Three of these (GILZ, p57kip2 and CRISPLD2) are genes with potential anti-inflammatory activity and a fourth gene, PDK4 is predicted to promote metabolic side-effects. Similar to the luciferase reporter system, the expression of these genes was agonist-dependent and displayed markedly different GR occupancy-response relationships. Furthermore, Ind, when combined with the seven GR agonists tested, synergistically enhanced transactivation, the magnitude of which was agonist and gene dependent. These studies demonstrate that when gene transactivation is used as a functional output, glucocorticoids used to treat asthma are not biologically-equivalent. It is proposed that these differences may be exploited to therapeutic advantage. Thus, the generation of gene expression ‘fingerprints’ in target and off-target human tissues may allow new GR agonists to be rationally designed for asthma with an improved therapeutic index.