Platycodin D protects against cigarette smoke-induced lung inflammation in mice
Cigarette smoke is the one of the major factors that leads to chronic obstructive pulmonary disease (COPD). Inflammation and oxidant stress have been known to play critical roles in the development of COPD. Platycodin D (PLD) has been reported to have anti-inflammatory and anti-oxidant effects. In this study, we aimed to investigate the protective effects of PLD on cigarette smoke (CS)-induced lung inflammation in mice. PLD was adminstrated i.p. to mice 2 h before CS exposure daily for five consecutive days. The production of inflammatory cytokines TNF-α and IL-1β were measured by ELISA. The levels of malonaldehyde (MDA) and nitric oxide (NO) were also detected in this study. The expression of nuclear factor-erythroid 2–related factor 2 (Nrf2), heme oxygenase-1 (HO-1), NF-κB, and IκBα were detected by western blot analysis. The results showed that PLD significantly attenuated CS-induced lung pathological changes, inflammatory cells infiltration, as well as TNF-α and IL-1β production. CS-induced MDA and NO production were also inhibited by treatment of PLD. Western blot analysis showed that PLD significantly suppressed CS-induced NF-κB activation. In addition, PLD was found to increase the expression of Nrf2 and HO-1. Taken together, these results indicated that PLD protected against CS-induced lung inflammation by inhibiting inflammatory and oxidative response through activating Nrf2 signaling pathway. PLD might be an effective treatment for CS-induced lung inflammation.