The Effects of Naringin on Cigarette Smoke-Induced Dynamic Changes in Oxidation/Antioxidant System in Lung of Mice

Naringin possesses strong antioxidative activity and can protect against some respiratory diseases. Oxidative stress is thought to be a major factor in the development of many tobacco-caused diseases. The nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway plays a critical role in the regulation of oxidative stress. The dynamic changes in the antioxidant system in the lung that are induced by cigarette smoke (CS) are not well investigated, and how naringin affects these changes remains unknown. This study aimed to investigate the dynamic changes between the oxidation and antioxidant systems resulting from CS exposure and the effects of naringin on these changes in mice. Mice were chronically exposed to CS for 30 days. The levels of malondialdehyde (MDA), glutathione (GSH), interleukin (IL)-6, and tumor necrosis factor-alpha (TNE-alpha); the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px); and the expressions of Nrf2, heme oxygenase-1 (HO-1), and nicotinamide adenine dinucleotide phosphate quinone dehydrogenase 1 (NQO1) in lung tissue were measured on days 2, 7, and 30. The levels of MDA, GSH, IL-6, and TNF-alpha in the lung were found to increase throughout the exposure. SOD and GSH-Px activities showed an increase on day 2 and a decrease on days 7 and 30. The messenger ribonucleic acid expressions of Nrf2,1-10-1, and NQ01 were elevated on day 2 and decreased on day 7; Nrf2 and HO-1 expressions were continually decreased, but NQO1 expression was increased again, on day 30. Naringin restored the levels of these biochemical indices to normal throughout the experiment, suggesting that naringin protected against the CS-induced oxidative damage by suppressing the increase of antioxidants resulting from the early stage of CS exposure, as well as inhibiting the depletion of antioxidants due to long-term oxidative stress. Naringin also suppressed lung inflammation by inhibiting IL-6 and TNF-alpha. These results indicate that naringin possesses a powerful ability to maintain the balance of the oxidation/antioxidant system in the lung when subjected to CS exposure, probably by regulating the Nrf2 signaling pathway.