School of Medicine and Health Sciences Poster Presentations

Mechanisms Involved in the Antioxidant Properties of Azithromycin in Lung Epithelial Cells

Poster Number

121

Document Type

Poster

Publication Date

3-2016

Abstract

Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality world-wide. Macrolide antibiotics, e.g., azithromycin, have antioxidant and anti-inflammatory properties and decrease the frequency of acute exacerbations of COPD. The aim of this study was to identify the molecular mechanisms whereby azithromycin decreases oxidative stress and inflammation. We have reported that azithromycin decreased intracellular Nrf2 protein (-55±6%) and its target gene, downstream phase II detoxifying enzyme NQO1 (-45±4%), suggesting that Nrf2 activity is also decreased; reactive oxygen species (ROS) production (-1.6-fold), pro-inflammatory cytokine interleukin 8 (IL-8) secretion (-2.1-fold), and histone deacetylase 2 (HDAC2) expression are also decreased (-41±4%) in A549 cells (human airway epithelial cells) exposed to cigarette smoke extract (CSE) (200 mg/ml, 24 h). Pretreatment of A549 cells with azithromycin (0.5µg/ml) decreased ROS (-29±4%) and IL-8 (-45±6%) and G protein-coupled receptor kinase 4 (GRK4) expression (-33%). Furthermore, azithromycin promoted Nrf2 nuclear translocation (270±24%), catalyzing the reduction of hyper-oxidized peroxiredoxins (Prx) (-70±3%), leading to the reduction of oxidative stress. H2O2 (200 mM/24 h) increased GRK4 (191±4%) and decreased HDAC2 (-29±4%) expressions, suggesting that oxidative stress can regulate these proteins. GRK4 co-localize with surfactant protein-A (marker for alveolar epithelium type II) in human lung tissue and GRK4 and HDAC2 colocalize in human bronchus. Sestrin2, an antioxidant enzyme, was increased after treatment with azithromycin in a time- and concentration-dependent manner. Silencing Nrf2 resulted in suppression of azithromycin-induced sestrin2 expression (-35±3%). Silencing sestrin2 abolished the azithromycin-induced decrease in peroxiredoxin hyper-oxidation and partially attenuated the inhibitory effect of azithromycin on ROS production and IL-8 expression (by 26% and 41%, respectively). Our results suggest that the antioxidant and anti-inflammatory effects of azithromycin in COPD may be, in part, mediated by induction of sestrin2, via Nrf2, involving the GRK4 and HDAC2 pathways.

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Presented at: GW Research Days 2016

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Mechanisms Involved in the Antioxidant Properties of Azithromycin in Lung Epithelial Cells

Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality world-wide. Macrolide antibiotics, e.g., azithromycin, have antioxidant and anti-inflammatory properties and decrease the frequency of acute exacerbations of COPD. The aim of this study was to identify the molecular mechanisms whereby azithromycin decreases oxidative stress and inflammation. We have reported that azithromycin decreased intracellular Nrf2 protein (-55±6%) and its target gene, downstream phase II detoxifying enzyme NQO1 (-45±4%), suggesting that Nrf2 activity is also decreased; reactive oxygen species (ROS) production (-1.6-fold), pro-inflammatory cytokine interleukin 8 (IL-8) secretion (-2.1-fold), and histone deacetylase 2 (HDAC2) expression are also decreased (-41±4%) in A549 cells (human airway epithelial cells) exposed to cigarette smoke extract (CSE) (200 mg/ml, 24 h). Pretreatment of A549 cells with azithromycin (0.5µg/ml) decreased ROS (-29±4%) and IL-8 (-45±6%) and G protein-coupled receptor kinase 4 (GRK4) expression (-33%). Furthermore, azithromycin promoted Nrf2 nuclear translocation (270±24%), catalyzing the reduction of hyper-oxidized peroxiredoxins (Prx) (-70±3%), leading to the reduction of oxidative stress. H2O2 (200 mM/24 h) increased GRK4 (191±4%) and decreased HDAC2 (-29±4%) expressions, suggesting that oxidative stress can regulate these proteins. GRK4 co-localize with surfactant protein-A (marker for alveolar epithelium type II) in human lung tissue and GRK4 and HDAC2 colocalize in human bronchus. Sestrin2, an antioxidant enzyme, was increased after treatment with azithromycin in a time- and concentration-dependent manner. Silencing Nrf2 resulted in suppression of azithromycin-induced sestrin2 expression (-35±3%). Silencing sestrin2 abolished the azithromycin-induced decrease in peroxiredoxin hyper-oxidation and partially attenuated the inhibitory effect of azithromycin on ROS production and IL-8 expression (by 26% and 41%, respectively). Our results suggest that the antioxidant and anti-inflammatory effects of azithromycin in COPD may be, in part, mediated by induction of sestrin2, via Nrf2, involving the GRK4 and HDAC2 pathways.