Effects Of Retinoic Acid On B16 Murine Melanoma Cells And Normal Human Melanocyte

The melanocyte is the pigment-producing dendritic cell of the epidermis. Melanocytes reside in the basal layer in normal adult epidermis. One melanocyte is therefore in contact with about 36 keratinocytes; together they form the so-called epidermal melanin unit. Melanocytes are most commonly in epidermis and follicle. Melanin involves eumelanin and pheomelanin, if s synthesized through a series of stages in which the enzyme tyrosinase acts on melanin precursors to produce the densely pigmented granules. Tyrosinase is the key enzyme of melanogenesis and determine the synthesis and quantity of melanin. Because melanin is the main pigment that determines the skin color, some researchers pay much attention to the modulation of melanocytes and melagenesis. The relationship between melanocytes and other cells, the contact between melanocytes and endocrine system or immune system, the effect of cytokine and the gene family of tyronase were investigated based on the culture of melanocytes in vitro. The most practical study is to find some drugs which are safe and effective to regulate the melanocytes and melagenesis. Retinoids are used abroad now and with much pharmacological activity. The effect of it on skin color is found in clinic.We investigated the effects of retinoic acid and other drugs on B16 murine melanoma cells and normal human melanocytes in vitro, in search of the most effective concentration and get insight on the mechanisms involved. B16 murine melanoma cells and normal human melanocytes were cultured in vitro. The cells from the same original bottle were transplanted to the 96 well cell culture cluster. The cell concentration were about 5*105/ml. B16 murine melanoma cells were incubated for 24 hours, while the normal human melanocytes were incubated for 48 hours. Then the culture medium was replaced and retinoic acid or other drugswere added to it. After treating for 72 hours, tyrosinase activity, melanin content and cell proliferation rate were detected.The results showed that retinoic acid exhibited an inhibitory effect on tyrosinase activity and melanin production at high concentration (>500 μmol/L), and could promote the cell proliferation. Retinoic acid and hydroquinone could be cooperative at high concentration(>500μmol/L), enhanced the down regulation of tyrosinase activity and melanin content. Retinoic acid could also mitigate the inhibitory effect of hydroquinone on cell proliferation, so as to protect the cells from injure. Retinoic acid showed slight inhibitory effect on the up regulation of tyrosinase activity and melanin content which were induced by TPA,IBMX and CT,it could promote the cell proliferation with IBMX and CT over 1000 μ mol/L.