Objective To investigate the effects of glycyrrhizin on the proliferation, apoptosis and inflammatory response of human embryonic lung fibroblast MRC-5 infected with human cytomegalovirus (HCMV).
Methods MRC-5 cells were cultured in vitro and were divided into control group, virus group, ganciclovir group(50 μg/mL), low dose glycyrrhizin group(0.25 mg/mL), medium dose glycyrrhizin group(0.50 mg/mL) and high dose glycyrrhizin group(1.00 mg/mL). After different periods of virus inoculation, cell proliferation activity was detected by CCK8 assay, cell apoptosis was detected by flow cytometry, cleaved-caspase3 caspase was detected by western blot, and tumor necrosis factor α(TNF-α) and interleukin-6 (IL-6) levels in cell culture supernatant were detected by enzyme-linked immunosorbent assay (ELISA).
Results At 24 and 48 h of HCMV infection, the results of CCK8 experiment showed that the proliferation activity of cells in virus group was significantly reduced compared with the control group, and was higher in the ganciclovir group, medium dose glycyrrhizin group and high dose glycyrrhizin group than that in the virus group(P < 0.05). There were no statistically significant difference in proliferative activity between medium dose glycyrrhizic acid group and high dose glycyrrhizic acid group (P>0.05), so the medium dose glycyrrhizic acid group (0.50 mg/mL) was selected for follow-up experiment and was called glycyrrhizic acid group for short. Flow cytometry showed that after 48 and 72 h of HCMV infection, the apoptosis rate of the virus group was higher than that of the control group, but the apoptosis rates in the ganciclovir group and glycyrrhizic acid group were lower than that of the virus group (P < 0.05). Western blot analysis showed that 48 h after HCMV infection, the relative expression levels of cleaved caspase3, TNF-α, and IL-6 in the virus group were higher than those in the control group, but were lower in the ganciclovir group and glycyrrhizic acid group than those in the virus group (P < 0.05). ELISA results showed that the levels of TNF-α and IL-6 in MRC-5 cells in the virus group were higher than those in the control group at 24, 48 and 72 h after HCMV infection, while those in ganciclovir group and glycyrrhizic acid group were lower than those in the virus group (P < 0.05).
Conclusion Glycyrrhizic acid has anti-HCMV effect in vitro, which could promote the proliferation of infected MRC-5 cells, inhibit cell apoptosis and inflammatory response induced by HCMV infection.
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