Inhibition of monoamine oxidase-B by selegiline reduces cigarette smoke-induced oxidative stress and inflammation in airway epithelial cells

Chronic obstructive pulmonary disease (COPD) is caused by the build-up of oxidative stress-induced damages due to cigarette smoking, but how monoamine oxidase (MAO)-B signaling is involved remains unclear. This study aims to establish the involvement of MAO-B signaling pathways in cigarette smoke medium (CSM)-induced oxidative stress and inflammation in human airway epithelial cells (AECs). CSM treatment increased MAO-B activity, ROS levels and IL-8 release in AECs. Pretreatment with MAO-B selective inhibitor selegiline reversed the CSM-induced changes in MAO-B activity, ROS levels and IL-8 release in a dose-dependent manner. Selegiline also reversed CSM-induced changes of anti-oxidant enzymes superoxide dismutase (SOD) and catalase (CAT) activities, GSH/GSSG ratio, as well expression of heme oxygenase-1 (HO-1) and NAD(P)H quinone dehydrogenase 1 (NQO1). The effects of selegiline are partially driven through the nuclear factor erythroid 2 related factor 2 (Nrf2) and cytosol translocation of its negative regulator, BTB and CNC homolog 1 (Bach1). Nevertheless, selegiline fully reversed the CSM-induced effects on IKK, cytoplasmic IκB expression, and nuclear translocation of nuclear factor-κB (NF-κB) p65 subunit. Our study demonstrated that in AECs, inhibition of MAO-B using selegiline reversed the CSM-induced oxidative stress and inflammation. These data may provide a novel strategy for therapy in COPD.