Effect of hypoxia on the melanogenesis of murine B16 melanoma cells

Background: Numerous reports suggest the role of oxygen in melanogenesis. However, little has been repotted on the effect of a hypoxic environment on cellular melanogenesis. Objective: The effect of low oxygen tension on cellular melanogenesis was investigated in B16 murine melanoma cells. Methods: Using cells cultured under an ambient (21% O₂) or hypoxic (5% O ₂) condition, melanin content and tyrosinase activity were measured spectrophotometrically. The expression of tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2 were analyzed by RT-PCR and Western blot. Results: Culture of cells under hypoxic conditions caused significant inhibition of isobutylmethylxanthine (IBMX)-induced increase of melanin content. No cytotoxicity was observed during the hypoxic culture periods. Decreased melanin content occurred through the decrease of tyrosinase protein and activity (p<0.01). The mRNA levels of tyrosinase and TRP-2 were also decreased by hypoxia, while that of TRP-1 was unchanged. Similar inhibitions of melanin content and tyrosinase activity were observed in the cells stimulated with dibutyryl-cAMP. Conclusion: IBMX-induced melanogenesis in B16 cells was significantly inhibited under hypoxic culture conditions, suggesting the important role of oxygen tension in cellular melanogenesis.