Targeting Keap1 with Inulae Herba activated the Nrf2 receptor to alleviate LPS-mediated acute lung injury

Inulae Herba (IH) is known as Jinfeicao recorded in Chinese Pharmacopoeia with effects of lowering qi and eliminating phlegm, and used for the treatment of pulmonary diseases. However, its protective mechanism on pulmonary diseases, especially acute lung injury (ALI), is still undefined. This study aimed to explore anti-inflammatory and anti-oxidation effects of IH and its underlying mechanism for treating ALI. We constructed a lipopolysaccharide (LPS)-ALI mouse model to reveal the therapeutical effect of IH. Western blot, real-time quantitative PCR, flow cytometry, small RNA interference, immunohistochemical staining, and the dual-luciferase experiment were performed to study the mechanism of IH for treating ALI. IH attenuated LPS-mediated pathological changes (e.g. pneumonedema and pulmonary congestion) through inactivation of macrophages in an ALI mouse model. The result of flow cytometry demonstrated that IH regulated the homeostasis of M1 (CD80+CD206-) and M2 (CD80+CD206+) phenotype macrophages. Furthermore, IH suppressed mRNA expressions of M1 phenotype markers, such as iNOS and IL-6, whereas promoted mRNA expressions of M2 phenotype markers, such as ARG1 and RETNLA in LPS-mediated mice. Notably, IH targeted Keap1 to activate the Nrf2 receptor, exerting its anti-inflammatory and anti-oxidation effects proved by using immunohistochemical staining, dual-luciferase, and Keap1 knockdown technologies. These findings suggested that targeting Keap1 with IH alleviated LPS-mediated ALI, and it could serve as a herbal agent for developing anti-ALI drugs.