Glycogen synthase kinase-3β modulation of glucocorticoid responsiveness in COPD

In Chronic Obstructive Pulmonary Disease (COPD), oxidative stress regulates the inflammatory response of bronchial epithelium and monocytes/macrophages through kinase modulation and has been linked to glucocorticoid unresponsiveness. GSK3β inactivation plays a key role in mediating signalling processes upon reactive oxygen species (ROS) exposure. We hypothesized that GSK3β is involved in oxidative stress-induced glucocorticoid insensitivity in COPD. We studied levels of p-GSK3β-ser9, a marker of GSK3β inactivation, in lung sections and cultured monocytes and bronchial epithelial cells of COPD patients, control smokers and non-smokers. We observed increased levels of p-GSK3β-ser9 in monocytes, alveolar macrophages and bronchial epithelial cells from COPD patients and control smokers compared to non-smokers. Pharmacological inactivation of GSK3β did not affect CXCL8 or GM-CSF expression but resulted in glucocorticoid insensitivity in vitro in both inflammatory and structural cells. Further mechanistic studies in monocyte and bronchial epithelial cell lines showed that GSK3β inactivation is a common effector of oxidative stress induced activation of the MEK/ERK-1/2 and PI3K/Akt signalling pathways leading to glucocorticoid unresponsiveness. In primary monocytes, the mechanism involved modulation of histone deacetylase 2 (HDAC2) activity in response to GSK3β inactivation. In conclusion, we demonstrate for the first time that ROS-induced glucocorticoid unresponsiveness in COPD is mediated through GSK3β, acting as a ROS-sensitive hub.