Quercetin protects against lipopolysaccharide-induced acute lung injury in rats through suppression of inflammation and oxidative stress

Introduction: Acute lung injury (ALI) is an acute inflammatory disease characterized by excess production of inflammatory factors in lung tissue. Quercetin, a herbal flavonoid, exhibits anti-inflammatory and anti-oxidative properties. This study was performed to assess the effects of quercetin on lipopolysaccharide (LPS)-induced ALI. Material and methods: Sprague-Dawley rats were randomly divided into 3 groups: the control group (saline alone), the LPS group challenged with LPS (Escherichia coli 026:B6; 100 mu g/kg), and the quercetin group pretreated with quercetin (50 mg/kg, by gavage) 1 h before LPS challenge. Bronchoalveolar lavage fluid (BALF) samples and lung tissues were collected 6 h after LPS administration. Histopathological and biochemical parameters were measured. Results: The LPS treatment led to increased alveolar wall thickening and cellular infiltration in the lung, which was markedly prevented by quercetin pretreatment. Moreover, quercetin significantly (p < 0.05) attenuated the increase in the BALF protein level and neutrophil count and lung wet/dry weight ratio and myeloperoxidase activity in LPS-challenged rats. The LPS exposure evoked a 4- to 5-fold rise in BALE levels of tumor necrosis factor-a and interleukin-6, which was significantly (p < 0.05) counteracted by quercetin pretreatment. Additionally, quercetin significantly (p < 0.05) suppressed the malondialdehyde level and increased the activities of superoxide dismutase, catalase, and glutathione peroxidase in the lung of LPS-treated rats. Conclusions: Quercetin pretreatment effectively ameliorates LPS-induced ALI, largely through suppression of inflammation and oxidative stress, and may thus have therapeutic potential in the prevention of this disease.