Chronic obstructive pulmonary disease (
COPD), which comprises
emphysema and
chronic bronchitis resulting from prolonged exposure to cigarette
smoke (CS), is a major public health burden with no effective treatment.
Emphysema is also associated with
pulmonary hypertension, which can progress to right ventricular failure, an important cause of morbidity and mortality among patients with
COPD. Nuclear erythroid 2 p45 related factor-2 (Nrf2) is a redox-sensitive
transcription factor that up-regulates a battery of antioxidative genes and cytoprotective
enzymes that constitute the defense against oxidative stress. Recently, it has been shown that patients with advanced
COPD have a decline in expression of the Nrf2 pathway in lungs, suggesting that loss of this antioxidative protective response is a key factor in the pathophysiological progression of
emphysema. Furthermore, genetic disruption of Nrf2 in mice causes early-onset and severe
emphysema. The present study evaluated whether the strategy of activation of Nrf2 and its downstream network of cytoprotective genes with a small molecule would attenuate CS-induced oxidative stress and
emphysema. Nrf2(+/+) and Nrf2(-/-) mice were fed a diet containing the potent Nrf2 activator, 1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl]
imidazole (
CDDO-Im), while being exposed to CS for 6 months.
CDDO-Im significantly reduced lung oxidative stress, alveolar cell apoptosis, alveolar destruction, and
pulmonary hypertension in Nrf2(+/+) mice caused by chronic exposure to CS. This protection from CS-induced
emphysema depended on Nrf2, as Nrf2(-/-) mice failed to show significant reduction in alveolar cell apoptosis and alveolar destruction
after treatment with
CDDO-Im. These results suggest that targeting the Nrf2 pathway during the etiopathogenesis of
emphysema may represent an important approach for prophylaxis against
COPD.