Mechanisms underlying the inhibitory effect of glycyrrhetinic acid on epidermal growth factor-induced proliferation of HaCaT cells

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Objective To estimate the effect of glycyrrhetinic acid on epidermal growth factor (EGF)-induced proliferation of HaCaT cells,and to investigate its possible mechanism.Methods Methyl thiazolyl tetrazolium (MTT) assay was used to evaluate the proliferation of HaCaT cells treated with different concentrations of EGF (0,1,5,10,25,50,100 μg/L) and glycyrrhetinic acid (0,0.1,1.0,10,25,50,100μmol/L) alone,or the combination of 25 μg/L EGF with 25 μ mol/L glycyrrhetinic acid or 10 μ mol/L U0126 (an inhibitor of MEK1/2).Western blot was carried out to measure the protein expression of proliferating cell nuclear antigen (PCNA),Notch-1,ERK 1/2 and phosphorylated ERK 1/2 in HaCaT cells treated with 25 μg/L EGF,10 μmol/L U0126,25μmol/L glycyrrhetinic acid alone or in combination.Data were statistically analyzed by using t test,analysis of variance and correlation analysis with SPSS 17.0 software.Results EGF of 0-100 μg/L promoted the proliferation of HaCaT cells in a dose-dependent manner (r =0.798,P ＜ 0.05),and there was a linear correlation between the effect and concentration within the concentration range 0-50 μg/L (r =0.859,P ＜ 0.05).However,glycyrrhetinic acid of 10-100 μmol/L inhibited the proliferation of HaCaT cells in a dose-dependent manner (r =-0.945,P ＜0.01),and 10 μmol/L glycyrrhetinic acid could suppress the EGF (25 μg/L)-induced proliferation and phosphorylation of ERK1/2 in HaCaT cells.Also,both 25 μmol/L glycyrrhetinic acid and 10 μmol/L U0126 could attenuate the increase in PCNA and Notch-1 expression in HaCaT cells induced by 25 μg/L EGF.Conclusion Glycyrrhetinic acid can inhibit the EGF-induced proliferation of HaCaT cells,likely by suppressing the activation of ERK1/2 signaling pathway.