Effect of pyrroloquinoline quinone (PQQ) on melanogenic protein expression in murine B16 melanoma

Background: Increased production and accumulation of melanin leads to various hyperpigmentation disorders. Melanin synthesis is regulated by melanogenic proteins such as tyrosinase, tyrosinase-related protein (TRP)-1 and -2, and their transcription factors. Objective: In this study, we assessed the effects of PQQ on melanogenic protein expression of murine B16 melanoma cells. Methods: We assessed melanin production of PQQ-treated B16 melanoma cells. Furthermore, we investigated the effect of PQQ on the activity of melanogenic enzymes and their expression using Western blot and semi-quantitative RT-PCR analyses. Results: In the present study, PQQ inhibited melanin synthesis in cultured melanoma cells stimulated by either alpha-melanocyte stimulating hormone (alpha-MSH) or 3-isobutyl-1-methylxanthine (IBMX). To elucidate the mechanism of the effect of PQQ on melanogenesis, we performed Western blotting for melanogenic proteins, such as tyrosinase, TRP-1, and TRP-2. PQQ inhibited tyrosinase expression, however, it did not inhibit TRP-2 expression. Used as the stimulant for melanogenesis, both alpha-MSH and IBMX gave the same results for melanogenic protein expression. Semi-quantitative RT-PCR analysis showed that the depigmentation effect of PQQ might be due to the inhibition of tyrosinase gene transcription but not the inhibition of microphthalmia-associated transcription factor (Mitf). Conclusion: This report indicates that PQQ is a possible anti-melanogenic agent and might be effective against hyperpigmentation disorders. (C) 2008 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.