The Effect Of STVNa On Melanogenesis In Skin

Hyperpigmentation in human skin can cause skin diseases such as freckles,dark spots,sunburn,melasma and age spots.These will affect the individual's external appearance,and in serious cases may also lead to negative emotions and psychological problems,thereby reducing the quality of life.So far,melanin production inhibitors such as corticosteroids,retinoic acid and hydroquinone have been used clinically to improve hyperpigmentation.In view of that remarkable effect of anti-melanogenesis,they have been added into whitening products for a long time in the past.However,people begin to have skin sensitivity,fever,or contact dermatitis after long-term use.Therefore,research and development of safer and more effective melanin production inhibitors has become an urgent need.STVNa is a salt-forming compound derived from Stevia rebaudiana and has antioxidant,anti-inflammatory,myocardial and neuroprotective effects.This study mainly focused on the effect and mechanism of STVNa on melanogenesis.The inhibitory effect of STVNa on melanin production and its mechanism of action were explored,using mouse skin melanoma B16F10 cells,wild-type AB strain zebrafish embryos and mushroom tyrosinase inhibition experiment.To investigate the effects of STVNa on melanin production in vitro,intracellular melanin content was determined and we found that the melanin content was significantly reduced both in or out of B16F10 cells,treated with 100 ?M STVNa for48 hours,when compared to the untreated group.Whereas the tyrosinase activity in the cell was apparently inhibited after the treatment with 200 ?M STVNa.Next,zebrafish embryos at 24 hours post fertilization were used for the following experiment.After treated the embryos with STVNa(25-200 ?M)for 24 hours,the embryos were collected for analysis.The survival rate of zebrafish intact embryos and dechorionic embryos were determined,while we found that the penetration of STVNa in zebrafish embryos was limited by chorionic membrane,and the safe dose range of is 25-100 ?M.The melanin content of embryos was measured by sodium hydroxide lysis method.We demonstrated that there was a significantly inhibited melanin production of dechorionic embryos,when the concentration of STVNa reached 25 ?M,compared with the untreated group.Using Dopa oxidation method,our results revealed that STVNa at 100 ?M can inhibit the tyrosinase activity in vivo.Furthermore,to establish a melanin over-expression in vivo model,Forskolin was used and we successfully increased the melanin content of zebrafish embryos,which increased by 36.7 % compared with the untreated group,by using 1 ?M Forskolin.Our data revealed that administration of 100 ?M STVNa can effectively inhibit embryonic melanin over-expression that the melanin content was reduced to half of the model group.Gene expression levels of embryonic tyrosinase was determined using q RT-PCR and its related proteins were subsequently determined.Our data further suggested that STVNa can down-regulate the m RNA expression levels of melanogenesis-related genes mitfb,tyr,tyrp1 b and trp2,but has no direct effect on tyrosinase activity.In summary,this study demonstrated that STVNa has an inhibitory effect on melanin production by down-regulating gene m RNA expression levels of mitfb,tyr,tyrp1 b and trp2.