[Effects of glycyrrhizin on airway mucus hypersecretion induced by interleukin-13 in rats].

Objective: To explore the effects of glycyrrhizin on airway mucus hypersecretion induced by interleukin-13 (IL-13) in rats.

Methods: A total of 50 SD rats were divided randomly into 5 groups with a random digit table: control group, IL-13 group, and different dosage (25, 50, 75 mg/kg) glycyrrhizin groups. The integral of expression intensity in positive cells of airway epithelium under mucus histochemical stain was calculated with modality-quantitative method. HBE-16 cells were divided into 6 groups: negative control (physiological saline), IL-13 control (10 µg/L IL-13+physiological saline), different concentration glycyrrhizin interference (10 µg/L IL-13+25, 50 and 75 µmol/L glycyrrhizin, respectively) and positive control (10 µg/L IL-13+25 µmol/L zopolrestat). The expression of mucin (MUC) 5AC mRNA, MUC5AC protein, aldose reductase (AR) activity and reactive oxygen species (ROS) content were detected by reverse transcription-polymerase chain reaction (RT-PCR), Western blot, fluorometric method and fluorescence intensity with General Oxidative Stress Indicator (CM-H2DFDA) catheter respectively.

Results: In vivo, the integral of expression intensity in positive stain cells of airway epithelium were 0.12 ± 0.03, 0.87 ± 0.13, 0.56 ± 0.08, 0.46 ± 0.06 and 0.35 ± 0.04 respectively while the integral of different dosage glycyrrhizin groups was significantly lower than that of IL-13 group (all P < 0.05) with dose depentency and the IL-13 group was stronger than control group (P < 0.05). In vitro, the index of AR activity and ROS at 48 h of HBE16 cells in every group were 0.156 ± 0.021, 0.692 ± 0.039, 0.436 ± 0.019, 0.323 ± 0.042 and 0.290 ± 0.027; 5.127 ± 0.033, 24.257 ± 3.263, 11.966 ± 0.283, 8.892 ± 0.521 and 6.426 ± 0.173 respectively. The indices of IL-13 control group were higher than those of negative control group (P < 0.05) while those of different concentration glycyrrhizin interference groups were lower than those of IL-13 control group (all P < 0.05). The expressions of MUC5AC mRNA and protein of HBE16 cells in every group were 0.82 ± 0.05, 3.22 ± 0.12, 2.57 ± 0.34, 2.09 ± 0.54 and 1.58 ± 0.22; 0.18 ± 0.04, 0.65 ± 0.15, 0.48 ± 0.11, 0.33 ± 0.19 and 0.26 ± 0.06 respectively. The indices of IL-13 control group were higher than those of negative control group (P < 0.05) and those of different concentration glycyrrhizin interference groups were lower than those of IL-13 control group (P < 0.05).

Conclusion: Glycyrrhizin may inhibit the expression of MUC5AC mRNA and MUC5AC protein induced by IL-13 and control the hypersecretion of airway mucus.