Abstract:Objective: To explore the effect of glycyrrhizic acid on the apoptosis of bronchial epithelial cells infected with respiratory syncytial virus (RSV) and to analyze whether the mechanism is related to the endogenous Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway.Methods: Human bronchial epithelial (HBE) cells were divided into seven groups: control group, infection group (RSV group), low-dose glycyrrhizic acid group (RSV+L-glycyrrhizic acid group), medium-dose glycyrrhizic acid group (RSV+M-glycyrrhizic acid group), high-dose glycyrrhizic acid group (RSV+H-glycyrrhizic acid group), RSV+Colivelin group, and RSV+H-glycyrrhizic acid+SD-1029 group. The control group cells were untreated. The RSV group cells were cultured with RSV virus solution at 0.0001 PFU/mL for 2 hours and then switched to normal culture medium for 24 hours. The RSV+L-glycyrrhizic acid group, RSV+M-glycyrrhizic acid group, and RSV+H-glycyrrhizic acid group were cultured with media containing glycyrrhizic acid at concentrations of 30, 60, and 120μg/mL respectively after RSV infection. The RSV+Colivelin group cells were cultured with media containing 0.5μmoL/L of JAK2/STAT3 signaling pathway activator Colivelin after RSV infection. The RSV+H-glycyrrhizic acid+SD-1029 group cells were cultured with media containing 120μg/mL glycyrrhizic acid and 10μmoL/L JAK2/STAT3 signaling pathway inhibitor SD-1029 after RSV infection. After 24 hours, cells were collected. Cell viability was detected using the CCK-8 kit. Apoptosis was detected by flow cytometry. Levels of IL-6 and TNF-α in cell supernatants were measured by ELISA. Protein expression of Bax, cleaved-Caspase-3, Bcl-2, p-JAK2, JAK2, p-STAT3, and STAT3 was analyzed by western blot.Results: Compared to the control group, the RSV group showed significantly lower OD value, Bcl-2, cleaved-Caspase-3, p-JAK2/JAK2, and p-STAT3/STAT3 protein expression (P<0.05), and significantly higher cell apoptosis rate, IL-6, TNF-α levels, and Bax protein expression (P<0.05). Compared to the RSV group, the RSV+L-glycyrrhizic acid group, RSV+M-glycyrrhizic acid group, RSV+H-glycyrrhizic acid group, and RSV+Colivelin group showed significantly higher OD value, Bcl-2, cleaved-Caspase-3, p-JAK2/JAK2, and p-STAT3/STAT3 protein expression (P<0.05), and significantly lower cell apoptosis rate, IL-6, TNF-α levels, and Bax protein expression (P<0.05). Compared to the RSV+H-glycyrrhizic acid group, the RSV+H-glycyrrhizic acid+SD-1029 group showed significantly lower OD value, Bcl-2, cleaved-Caspase-3, p-JAK2/JAK2, and p-STAT3/STAT3 protein expression (P<0.05), and significantly higher cell apoptosis rate, IL-6, TNF-α levels, and Bax protein expression (P<0.05).Conclusion: Glycyrrhizic acid may promote the proliferation of bronchial epithelial cells infected with RSV and inhibit their apoptosis by activating the JAK2/STAT3 signaling pathway.
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