Effects of Glycyrrhizin on chronic histologic changes of lung in BALB/c mice in which murine model of asthma was established

Objective: Glycyrrhizin is a triterpene glycoside, a major active constituent of licorice (Glycyrrhiza glabra) root. It has numerous pharmacological effects like anti-inflammatory, anti-viral, anti-tumor and hepatoprotective activities. Licorice has been used as an asthma-relieving medicinal herb from ancient times. However, effects of this herb on chronic structural changes of lung are not fully known. In this study, we aimed to determine the effects of oral administration of glycyrrhizin, an active constituent of licorice root, on lung histology in BALB/c mice in which the model of chronic asthma was established.Material and methods: Twenty-eight BALB/c mice were divided into four groups; Group I, II, III and IV. All mice except controls (Group I) were sensitized and challenged with ovalbumin. Mice in Group II (placebo) received saline, Group III dexamethasone 1mg/kg and Group IV glycyrrhizin 10 mg/kg via orogastric gavage for seven consecutive days. Lung histology was evaluated by using light and electron microscopy in all groups.Results: Evaluation of lung histology demonstrated that thicknesses of basement membrane (p: 0.000), subepithelial smooth muscle (p: 0.001), epithelium (p: 0.000), and the number of mast (p: 0.018) and goblet cells (p: 0.000), were significantly decreased in glycyrrhizin group (Group IV) when compared with the placebo group (Group II). When glycyrrhizin (Group IV) and dexamethasone groups (Group III) were compared each other, there was no statistically significant difference between the two groups in histological parameters including thicknesses of basement membrane (p: 0.514), subepithelial smooth muscle (p: 0.054), epithelium (p: 1.0) and the number of mast (p: 0.075) and goblet cells (p: 0.988).Conclusion: Glycyrrhizin reversed all the established chronic histological changes of lung in the mouse model of asthma in this study. Also, no statistically significant difference was found between dexamethasone and glycyrrhizin groups in terms of evaluated histological changes. The results of this study pointed to the ameliorating effect of glycyrrhizin on chronic structural changes in the asthmatic airways, but further studies which evaluate the effects of glycyrrhizin on lung inflammation and remodeling are needed.