Usnic acid is a
dibenzofuran derivative found in several lichen species, which has been shown to possess several activities, including
antiviral,
antibiotic, antitumoral,
antipyretic,
analgesic, antioxidative and anti-inflammatory activities. However, there were few reports on the effects of
usnic acid on LPS-induced
acute lung injury (ALI). The aim of our study was to explore the effect and possible mechanism of
usnic acid on LPS-induced
lung injury. In the present study, we found that pretreatment with
usnic acid significantly improved survival rate,
pulmonary edema. In the meantime,
protein content and the number of inflammatory cells in bronchoalveolar lavage fluid (BALF) significantly decreased, and the levels of MPO, MDA, and H2O2 in lung tissue were markedly suppressed
after treatment with
usnic acid. Meanwhile, the activities of SOD and GSH in lung tissue significantly increased
after treatment with
usnic acid. Additionally, to evaluate the anti-inflammatory activity of
usnic acid, the expression of pro-inflammatory
cytokines including
tumor necrosis factor alpha (TNF-α),
interleukin-6 (IL-6) and anti-inflammatory
cytokine IL-10, and
chemokines interleukin-8 (IL-8) and macrophage inflammatory protein-2 (MIP-2) in BALF were studied. The results in the present study indicated that
usnic acid attenuated the expression of TNF-α,
IL-6,
IL-8 and MIP-2. Meanwhile, the improved level of
IL-10 in BALF was observed. In conclusion, these data showed that the protective effect of
usnic acid on LPS-induced ALI in mice might relate to the suppression of excessive inflammatory responses and oxidative stress in lung tissue. Thus, it was suggested that
usnic acid might be a potential therapeutic agent for ALI.