Naringin suppressed airway inflammation and ameliorated pulmonary endothelial hyperpermeability by upregulating Aquaporin1 in lipopolysaccharide/cigarette smoke-induced mice

Naringin is one of the natural flavonoids extracted from many Chinese medicines. It ameliorates endothelial dysfunctions in atherosclerosis, diabetes, and cardiovascular diseases through free radical scavenging and antioxidant activities. The aim of the present study was to investigate the protective effects of naringin against pulmonary endothelial permeability in addition to airway inflammation in lipopolysaccharide/cigarette smoke (LPS/CS)-induced chronic obstructive pulmonary disease (COPD) mice.The COPD mice were exposed to LPS twice through intranasal inhalation and then to cigarette smoke daily for 6 weeks. The mice were orally administrated with naringin at doses of 40 or 80 mg/kg one hour before cigarette smoke exposure since the first day of the experiment. Naringin significantly alleviated pulmonary histopathological injury, and suppressed inflammatory cell infiltration and cytokine release in bronchoalveolar lavage fluid. Naringin decreased fluorescence intensity of Evans Blue in the lung tissues, and elevated the expression levels of tight junctional proteins. Meanwhile, naringin decreased neutrophil/lymphocyte/platelet counts and MDA content in blood, and upregulated Aquaporin1 (AQP1) in the lung tissues. However, the effect of naringin on airway inflammation and pulmonary endothelial permeability was inhibited in LPS/CS-treatment AQP1 deficiency mice. These results indicated that naringin attenuated LPS/CS-induced airway inflammatory and pulmonary hyperpermeability via upregulating AQP1 expression.