Glucosamine attenuates cigarette smoke-induced lung inflammation by inhibiting ROS-sensitive inflammatory signaling
Free Radical Biology and Medicine Available online 28 January 2014 Yuh-Lin Wua
Highlights
• Cigarette smoke induces oxidative stress, AMPK activation, and lung inflammation in mice.
• Cigarette smoke extract (CSE) activates NADPH oxidase and increases ROS in HBECs.
• CSE induces IL-8 expression via ROS-sensitive AMPK/MAPK/NF-κB/STAT3 signaling.
• All cigarette smoke effects on the mouse lung or HBECs are suppressed by glucosamine.
• Glucosamine may be a potential therapy to treat lung inflammation among smokers.
Cigarette smoking causes persistent lung inflammation that is mainly regulated by redox-sensitive pathways.
We have reported that cigarette smoke (CS) activates a NADPH oxidase-dependent reactive oxygen species (ROS)-sensitive AMP-activated protein kinase (AMPK) signaling pathway leading to induction of lung inflammation.
Glucosamine, a dietary supplement used to treat osteoarthritis, has antioxidant and anti-inflammatory properties. However, whether glucosamine has similar beneficial effects against CS-induced lung inflammation remains unclear. Using a murine model we show that chronic CS exposure for 4 weeks increased lung levels of 4-hydroxynonenal (an oxidative stress biomarker), phospho-AMPK, and macrophage inflammatory protein 2, and induced lung inflammation; all of these CS-induced events were suppressed by chronic treatment with glucosamine. Using human bronchial epithelial cells (HBECs), we demonstrate that cigarette smoke extract (CSE) sequentially activated NADPH oxidase; increased intracellular levels of ROS; activated AMPK, mitogen-activated protein kinases (MAPKs), nuclear factor-κB (NF-κB), and signal transducer and activator of transcription proteins 3 (STAT3); and induced interleukin-8 (IL-8). Additionally, using a ROS scavenger, a siRNA that targets AMPK, and various pharmacological inhibitors, we identified the signaling cascade that leads to induction of IL-8 by CSE. All these CSE-induced events were inhibited by glucosamine pretreatment.
Our findings suggest a novel role for glucosamine in alleviating the oxidative stress and lung inflammation induced by chronic CS exposure in vivo and in suppressing the CSE-induced IL-8 in vitro by inhibiting both ROS-sensitive NADPH oxidase/AMPK/MAPK signaling pathway and the downstream transcriptional factors NF-κB and STAT3.