DL-3-n-butylphthalide attenuates lipopolysaccharide-induced acute lung injury via SIRT1-dependent and -independent regulation of Nrf2.

The acute respiratory distress syndrome (ARDS), a devastating clinical syndrome, is one of the most severe complications of acute lung injury (ALI). Despite of decades of clinical trials and supportive ventilation strategies, the incidence and mortality of ALI/ARDS remain high. DL-3-n-butylphthalide (NBP) is a synthesized raceme of L-3-n-butylphthalide which has been approved to possess various activities. In the current study, we aimed to investigate the effect of NBP on ALI in lipopolysaccharide (LPS)-treated mice. We found that 10 mg/kg and 50 mg/kg NBP significantly prevented LPS-induced increase of W/D ratio of lung, histological injury of lung, infiltration of inflammatory cells, release of pro-inflammatory cytokines and chemokines, and oxidative damage. Sirtuin 1 (SIRT1) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression was increased by NBP in lung of LPS-treated mice. Knockout of SIRT1 significantly aggravated LPS-induced ALI. Moreover, the absence of SIRT1 notably inhibited NBP-induced protective effects against LPS-induced increase of W/D ratio of lung, histological injury of lung, infiltration of inflammatory cells, release of pro-inflammatory cytokines and chemokines, and oxidative damage. However, knockout of SIRT1 did not completely inhibit NBP-induced upregulation of Nrf2 and attenuation of ALI. The results demonstrated that NBP could activate Nrf2 antioxidant signaling in a SIRT1-dependent and SIRT1-independent manner, resulting in the amelioration of oxidative stress, inflammation and pulmonary edema. The data highlights the importance of SIRT1/Nrf2 signaling in the protective effects of NBP.