Effects Of Glycyrrhizin On Melanogenesis And Apoptosis Of Normal Human Melanocyte

Backgrounds and objectives: Vitiligo is a depigmenting disorder characterized by the loss of melanocytes from the epidermis. The exact aetiology of vitiligo has not yet been established. There are several hypothesizes, including theory of neurochemistry factors, theory of autoimmunity, theory of melanocyte self destroying, theory of heredity and so on. Local and general depigmenting patches are the clinical manif- estation. The pathologic findings of the skin lesion show that melanocytes and melanin are decreased. The agents promoting melanogenesis may have therapeutic effect on vitiligo.Glycyrrhizin is composed of one molecule of glycyrrhetinic acid and two molecules of glucuronate, which is decomposed by p-glucuronate enzyme in the body. In the recent years, glycyrrhizin has been used widely in clinical treatment. It's reported that glycyrrhizin was used to treat vitiligo and could increase the melanin content of cultured B16 cells. Chu et al. reported that catecholamine and its metabolites including dopamine were increased in urine and skin lesion of the patients with vitiligo, and that dopamine could induce apoptosis of melanocytes. To study the effect and action mechanism of glycyrrhizin on melanogenesis in melanocytes, we established the primary culture of melanocytes and observed the effect of glycyrrhizin on melanogenesis and apoptosis induced by dopamine.Methods: Melanocytes were derived from the prepuce of 6-10 years old boys after operation, and were identified by L-Dopa staining and immunocytochemistry method. The cell proliferation, tyrosinase and melanogenesis of cultured melanocytes affected by glycyrrhizin were measured by MTT,oxidation DOPA in vitro and NaOH fragmentation methods respectively. Cell proliferation of melanocytes affected by dopamine was measured by MTT method. Cell apoptosis was measured by transmission electron microscope and flow cytometry. The effect of glycyrrhizin on the apoptosis of melanocytes induced by dopamine was measured by MTT method and flow cytometry.Results: The results of MTT indicated that glycyrrhizin at different concentrations had no effect on proliferation of melanocytes (P>0.05). The results of oxidation DOPA in vitro and NaOH fragmentation method indicated that 0.2mM,0.5mM,1.0mM and 1.5mM glycyrrhizin could promote tyrosinase activity and melanogenesis of melanocytes(P<0.05). The results of MTT indicated that dopamine at 500μM significantly inhibited the cell proliferation by 44.60%. Apoptotic bodies were seen by electron microscope. Flow cytometry showed that the ratio of early stage melanocyte apoptosis was 45.48%, induced by dopamine at 500μM. The results of MTT and flow cytometry showed that glycyrrhizin at different concentrations had no effect on inhibition of melanocytes apoptosis induced by dopamine (P>0.05).Conclusions:(1)Glycyrrhizin has no obvious effect on proliferation of melanocytes.(2)Glycyrrhizin can promote tyrosinase activity and melano- genesis of melanocytes.(3)Glycyrrhizin has no effect on inhibition of melanocyte apoptosis induced by dopamine.(4)Glycyrrhizin may have certain therapeutic effect on hypopigmentation diseases such as vitiligo, because of the effect on promoting melanogenesis.