Effects Of Quercetin On LPS-induced Nitric Oxide Released By Cultured Human Alveolar Epithelial Cells

Objective To investigate the effects of flavanoid quercetin on nitric oxide(NO) release by cultured human alveolar cells(A549) induced by lipopolysaccharide(LPS).Methods Subconflent A549 cells in tissue culure were digested and transfered into twelve- hole plates.when they grew to 80 percentage, cells were treated with various concentrations of LPS and quercetin for 24 hours, then the supernates were collected to froze. Cells were also treated with 10#g/ml of LPS and 15μM of quercetin for 24, 48 and 72 hours, then the supernates were collected. The nitric oxide level in supernates were measured with nitrate reductase assay.Results 1 LPS significantly induced the release of nitric oxide by A549 celle when compared with control cells. The stimulating effect of LPS was dependent on the dose LPS and incubation time(p＜0.05). 2 Quercetin had little effect on basal release of nitric oxide.However,LPS-induced nitric oxide released by A549 cells were significantly reduced with quercetin(p＜0.01).Conclusion Quercetin decreased LPS-induced NO secretions by A549 cells, which suggests that quercetin has anti-inflammatory and anti-oxidant stress properties on A549 cells treated with LPS.