Prophylactic efficacy of Quercetin in ameliorating the hypoxia induced vascular leakage in lungs of rats

The objective of the study was to find out the prophylactic efficacy of Quercetin in ameliorating the hypoxia induced vascular leakage in lungs of rats. Male SD rats received different doses of quercetin@ 25mg, 50mg, 100mg and 200mg/Kg BW, 1h prior to hypobaric hypoxia exposure (7,620m, for 6h). Quercetin 50 mg/kg BW supplemented orally 1h prior to hypoxia exposure was considered to be the optimum dose, due to significant reduction (p< 0.001) in lung water content and lung transvascular leakage compared to control (hypoxia, 6h). Further, biochemical analysis (ROS, MDA, GSH, GPx, LDH, and albumin) and differential expressions of proteins (IKK-alpha/beta, NFB, Nrf-2, TNF-alpha, ICAM-1, VCAM, P-selectin, Hif-1 alpha, VEGF, TNF-alpha, TGF-beta, INF-gamma and IL-4) were determined by western blotting and ELISA. Changes in lung parenchyma were assessed by histopathology. Quercetin (50 mg/kg BW) prophylaxis under hypoxia showed significant reduction in oxidative stress (ROS and MDA), concomitant increase in antioxidants (GSH, GPx and SOD) followed by decreased LDH and albumin extravasation in BAL fluid over hypoxia. Quercetin prophylaxis significantly down regulated hypoxia induced increase in IKK alpha/beta and NFB expressions leading to reduction in the levels of pro-inflammatory cytokines (TNF-alpha and INF-gamma) followed by up regulation of anti-inflammatory cytokines (IL-4 and INF-gamma) in lungs. Further, hypoxia mediated increase in HIF-1 alpha was stabilized and VEGF levels in lungs were significantly down regulated by quercetin supplementation, leading to reduction in vascular leakage in lungs of rats under hypoxia. However, Quercetin has also enacted as Nrf-2 activator which significantly boosted up the synthesis of GSH under hypoxic condition compared to hypoxia. Histopathological observations further confirmed that quercetin preconditioning has an inhibitory effect on progression of oxidative stress and inflammation via attenuation of NF kappa B and stabilization HIF-1 alpha in lungs of rats under hypoxia. These studies indicated that quercetin prophylaxis abrogates the possibility of hypobaric hypoxia induced pulmonary edema in rats.