Aim To study the effects of baicalein （BC）, a phenolic flavonoid extracted mainly from Scutellaria ba- icalensis Georgi, on lipopolysaccharide （LPS）-induced acute lung injury （ALI） in mice and the molecular mecha- nisms underlying. Methods Mice were administrated intranasally with LPS （20 mg · kg^-1/body weight） to estab- lish the ALI model. Then the mice were treated twice with BC （50,100 and 200 mg · kg^-1, p. o. ） 0. 5 hour and 12 hours after LPS stimulation, following another 12 hours, the lungs were collected for histological study. Results LPS caused marked inflammatory cell infiltration and myeloperoxidase activation in lungs, accompanied by significantly in- creased lung W/D ratio, from 7.97±0. 60 in normal group to 12. 49 ± 1.49 in the model. 77.88% reduction in the lung W/D ratio was observed in 200 mg· kg^-1 dose of baicalein. The myeloperoxidase activity was reduced to 40. 14% in mice treated with 200 mg · kg^-1. The number of total cells, neutrophils, and macrophages in BALF de- creased with increasing concentration of baicalein. Inflammatory cytokines level in serum declined significantly while insignificant changes of the same in BALF was observed in mice treated with 50,100 and 200 mg · kg^-1 doses of ba- icalein. Furthermore, LPS induced markedly the expression of inflammasomes and other inflammation-related genes in lung tissue. Treatment of LPS-exposed mice with BC significantly reduced the expression levels of these genes and al- leviated the pathological changes in lungs. Moreover, 1 μmol · L^-1 and 10 μmol · L^-1 BC inhibited remarkably the nuclear translocation of NF-kappaB p65 in Raw264.7 cells. Conclusion Baicalein alleviates LPS-induced acute lung injury in mice by suppressing NF-KB-mediated inflammatory responses and downregulation of inflammasomes.
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