Usnic acid ameliorates bleomycin-induced pulmonary fibrosis in mice via inhibition of inflammatory responses and oxidative stress

Purpose: To Investigate the effect of usnic acid (UA) on bleomycin (BLM)-induced pulmonary fibrosis in mice, and the underlying mechanism. Methods: Male Kunming mice with bleomycin-induced pulmonary fibrosis (PF) were exposed to different concentrations of usnic acid. Lung coefficient and histopathological changes were determined, while MDA, superoxide dismutase (SOD) activity, and expression levels of hydroxyproline, tumor necrosis factor-alpha, interleukins-1 beta & 6, and transforming growth factor-beta 1 were assayed in lung homogenates. Results: UA significantly mitigated lung coefficient and histopathological changes in mice. Compared to the bleomycin group, MDA level was significantly reduced while the content of SOD markedly increased after UA pretreatment (p < 0.05). Moreover, UA significantly reduced the expression levels of all the parameters, relative to bleomycin group (p < 0.05). Conclusion: These results indicate that UA protects mice against bleomycin-induced PF via a mechanism associated with attenuation of pro-oxidant stress and inflammation. Therefore, UA has therapeutic potential for the management of pulmonary fibrosis.