Lycium barbarum polysaccharide reduces hyperoxic acute lung injury in mice through Nrf2 pathway

The disruption of the balance between antioxidants and oxidants plays a vital role in the pathogenesis of acute lung injury (ALI). Evidence has shown that Lycium barbarum polysaccharide (LBP) has antioxidant feature. We examined the efficacy and mechanisms of LBP on hyperoxia-induced acute lung injury (ALI) in the present study. C57BL/6 wild-type (WT) mice and nuclear factor erythroid 2-related factor 2 (Nrf2)-deficient (Nrf2–/–) mice were used in the present study. LBP was fed by gavages once daily for 1 week. Then, the mice were exposed to hyperoxia or room air for 72 h. Additional dosage of LBP was given per 24 h. Reactive oxygen species production was increased in WT mice exposed to hyperoxia. Inflammatory cytokines including interleukin (IL)-1β as well as IL-6, and inflammatory cells were increased infiltration in the lung after 3 days hyperoxia exposure. Hyperoxia exposure also induced pulmonary edema and histopathological changes. These hyperoxia-induced changes were improved in LBP treated group. Moreover, elevated activities of heme oxygenase-1 and glutathione peroxidase and enhanced activation of Nrf2 were observed in mice treated with LBP. However, the benefit of LBP on hyperoxic ALI was abolished in Nrf2–/– mice. Moreover, our cell study showed that the LBP-induced activation of Nrf2 was dampened in pulmonary microvascular endothelial cells when the AMPK signal was inhibited by siRNA. LBP improves hyperoxic ALI via Nrf2-dependent manner. The LBP-induced activation of Nrf2 is mediated, at least in part, by AMPK pathway.