http://www.mdpi.com/journal/ijms/special_issues/melanogenesis_related_processes/ Dear Colleagues, Melanogenesis occurs ubiquitously in microorganism, plants and all animals. The enzyme tyrosinase also known as phenoloxidase initiates this process by hydroxylating monphenols to o-diphenols and further oxidizing o-diphenols to o-quinones. O-Quinones being unstable, undergo rapid nonenzymatic as well as enzyme catalyzed transformations to eventually produce different kinds of polymeric products. Quinones in general are very reactive and tend to deplete cellular antioxidant pools as well as cause deleterious effects on cellular macromolecules. In plants, such oxidative browning reactions reduce the nutritive values thereby helping the plant to cope up with infections and invasions. Oxidative browning certainly reduces the consume ability and hence their market value. The melanosis observed in crustaceans similarly reduces the market value of sea food drastically. In arthropods and especially insects, melanogenesis is used for wound healing and defense reactions. Mammals use melanin mostly as skin, coat and eye pigments. Therefore, prevention of oxidative browning of plant products as well as sea food, alteration of skin color, and prevention and/or reduction of melanogenesis in animals has great commercial potentials. This special edition will cover a broad range of phenoloxidase/tyrosinase chemistry, biochemistry of inhibitor and ways to develop new and novel natural and synthetic bioactive compounds against melanogenesis and related process. Manickam Sugumaran Guest Editor Submission All manuscripts should be submitted to ijms@mdpi.com with a copy to the Guest Editor. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website. Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. The International Journal of Molecular Sciences is an international peer-reviewed Open Access monthly journal published by MDPI. Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this Open Access journal is 1000 CHF per accepted paper. http://www.mdpi.com/1422-0067/11/7/2699/ One additional skin lightening or whitening quasi-drug (QD) has been developed and officially approved by the Ministry of Health, Labor and Welfare of Japan. http://www.mdpi.com/1422-0067/11/7/2699/ Mon, 12 Jul 2010 00:00:00 CEST International Journal of Molecular Sciences 2010-07-12 11 7 Addendum 2699 2700 1422-0067 Quasi-Drugs Developed in Japan for the Prevention or Treatment of Hyperpigmentary Disorders. Int. J. Mol. Sci. 2010, 11, 2566–2575 2010-07-12 doi: 10.3390/ijms11072699 Ando Matsui Ichihashi http://www.mdpi.com/1422-0067/11/6/2566/ Excess production of melanin or its abnormal distribution, or both, can cause irregular hyperpigmentation of the skin, leading to melasma and age spots. To date, various quasi-drugs that prevent or improve hyperpigmentary disorders have been developed and officially approved by the Ministry of Health, Labor and Welfare of Japan. Many of these inhibit the activity of tyrosinase, an enzyme required for melanin synthesis, for example, by competitive or non-competitive inhibition of its catalytic activity, by inhibiting its maturation, or by accelerating its degradation. In this review, we categorize the quasi-drugs developed in Japan to prevent or treat hyperpigmentary disorders, or both, and discuss perspectives for future development. http://www.mdpi.com/1422-0067/11/6/2566/ Fri, 18 Jun 2010 00:00:00 CEST International Journal of Molecular Sciences 2010-06-18 11 6 Review 2566 2575 1422-0067 Quasi-Drugs Developed in Japan for the Prevention or Treatment of Hyperpigmentary Disorders 2010-06-18 doi: 10.3390/ijms11062566 Ando Matsui Ichihashi http://www.mdpi.com/1422-0067/11/3/1082/ Oxidized metabolites of dopamine known as dopamine quinone derivatives are thought to play a pivotal role in the degeneration of nigrostriatal dopaminergic neurons in Parkinson’s disease. Although such quinone derivatives are usually produced via the autoxidation of catecholamines, tyrosinase, which is a key enzyme in melanin biosynthesis via the production of DOPA and subsequent molecules, can potentially accelerate the induction of catecholamine quinone derivatives by its oxidase activity. We have developed neuronal cell lines in which the expression of human tyrosinase was inducible. Overexpression of tyrosinase resulted in increased intracellular dopamine content in association with the formation of melanin pigments in neuronal somata, which eventually causes apoptotic cell death. This cellular model will provide a useful tool for detailed analyses of the neurotoxicity of oxidized catechol metabolites. http://www.mdpi.com/1422-0067/11/3/1082/ Fri, 12 Mar 2010 00:00:00 CET International Journal of Molecular Sciences 2010-03-12 11 3 Review 1082 1089 1422-0067 Tyrosinase-Expressing Neuronal Cell Line as in Vitro Model of Parkinson’s Disease 2010-03-12 doi: 10.3390/ijms11031082 Hasegawa http://www.mdpi.com/1422-0067/10/12/5326/ Skin whitening products are commercially available for cosmetic purposes in order to obtain a lighter skin appearance. They are also utilized for clinical treatment of pigmentary disorders such as melasma or postinflammatory hyperpigmentation. Whitening agents act at various levels of melanin production in the skin. Many of them are known as competitive inhibitors of tyrosinase, the key enzyme in melanogenesis. Others inhibit the maturation of this enzyme or the transport of pigment granules (melanosomes) from melanocytes to surrounding keratinocytes. In this review we present an overview of (natural) whitening products that may decrease skin pigmentation by their interference with the pigmentary processes. http://www.mdpi.com/1422-0067/10/12/5326/ Thu, 10 Dec 2009 00:00:00 CET International Journal of Molecular Sciences 2009-12-10 10 12 Review 5326 5349 1422-0067 The Hunt for Natural Skin Whitening Agents 2009-12-10 doi: 10.3390/ijms10125326 Nico Smit Jana Vicanova Stan Pavel http://www.mdpi.com/1422-0067/10/10/4428/ Pigmentation of the skin, hair and eyes is regulated by tyrosinase, the critical rate-limiting enzyme in melanin synthesis by melanocytes. Tyrosinase is degraded endogenously, at least in part, by the ubiquitin proteasome system (UPS). Several types of inherited hypopigmentary diseases, such as oculocutaneous albinism and Hermansky-Pudlak syndrome, involve the aberrant processing and/or trafficking of tyrosinase and its subsequent degradation which can occur due to the quality-control machinery. Studies on carbohydrate modifications have revealed that tyrosinase in the endoplasmic reticulum (ER) is proteolyzed via ER-associated protein degradation and that tyrosinase degradation can also occur following its complete maturation in the Golgi. Among intrinsic factors that regulate the UPS, fatty acids have been shown to modulate tyrosinase degradation in contrasting manners through increased or decreased amounts of ubiquitinated tyrosinase that leads to its accelerated or decelerated degradation by proteasomes. http://www.mdpi.com/1422-0067/10/10/4428/ Thu, 15 Oct 2009 00:00:00 CEST International Journal of Molecular Sciences 2009-10-15 10 10 Review 4428 4434 1422-0067 Role of the Ubiquitin Proteasome System in Regulating Skin Pigmentation 2009-10-15 doi: 10.3390/ijms10104428 Hideya Ando Masamitsu Ichihashi Vincent J. Hearing http://www.mdpi.com/1422-0067/10/10/4257/ In our previous study, 8-hydroxydaidzein (8-OHDe) was demonstrated to be a potent and unique suicide substrate of mushroom tyrosinase. In this study, the compound was evaluated for in vitro cellular tyrosinase and melanogenesis inhibitory activities in mouse B16 melanoma cells and for in vivo skin-whitening activity in human volunteers. Tyrosinase activity and melanogenesis in the cell culture incubated with 10 µM of 8-OHDe were decreased to 20.1% and 51.8% of control, respectively, while no obvious cytotoxicity was observed in this concentration. In contrast, a standard tyrosinase inhibitor, kojic acid, showed 69.9% and 71.3% of control in cellular tyrosinase and melanogenesis activity, respectively, at a concentration as high as 100 µM. Hence, 8-OHDe exhibited more than an inhibitory effects on melanin production in B16 cells 10-fold stronger than kojic acid. In addition, when a cream containing 4% 8-OHDe was applied to human skin in an in vivo study, significant increases in the dL*-values were observed after three weeks. Moreover, the increase in the dL*-values after 8-week treatment with 4% 8-OHDe (from -0.57 to 1.94) is stronger than those of 2% 8-OHDe treatment (from 0.26 to 0.94) and 2% ascorbic acid-2-glucoside treatment (from 0.07 to 1.54). From the results of the study, it was concluded that 8-OHDe, the potent suicide substrate of mushroom tyrosinase, has depigmenting activities in both mouse melanoma cells and in human volunteers. Thus, the compound has significant potential for use in cosmetics as a skin-whitening ingredient. http://www.mdpi.com/1422-0067/10/10/4257/ Tue, 29 Sep 2009 00:00:00 CEST International Journal of Molecular Sciences 2009-09-29 10 10 Article 4257 4266 1422-0067 Evaluation of Depigmenting Activity by 8-Hydroxydaidzein in Mouse B16 Melanoma Cells and Human Volunteers 2009-09-29 doi: 10.3390/ijms10104257 Sorgan Shou-Ku Tai Ching-Gong Lin Mon-Han Wu Te-Sheng Chang http://www.mdpi.com/1422-0067/10/9/4066/ Skin pigmentary abnormalities are seen as aesthetically unfavorable and have led to the development of cosmetic and therapeutic treatment modalities of varying efficacy. Hence, several putative depigmenting agents aimed at modulating skin pigmentation are currently being researched or sold in commercially available products. In this review we will discuss the regulation of processes that control skin complexion coloration. This includes direct inhibition of tyrosinase and related melanogenic enzymes, regulation of melanocyte homeostasis, alteration of constitutive and facultative pigmentation and down-regulation of melanosome transfer to the keratinocytes. These various processes, in the complex mechanism of skin pigmentation, can be regulated individually or concomitantly to alter complexion coloration and thus ameliorate skin complexion diseases. http://www.mdpi.com/1422-0067/10/9/4066/ Tue, 15 Sep 2009 00:00:00 CEST International Journal of Molecular Sciences 2009-09-15 10 9 Review 4066 4087 1422-0067 Mechanisms Regulating Skin Pigmentation: The Rise and Fall of Complexion Coloration 2009-09-15 doi: 10.3390/ijms10094066 Jody P. Ebanks R. Randall Wickett Raymond E. Boissy http://www.mdpi.com/1422-0067/10/9/3811/ The effects of various inhibitors on crude, commercial and partially purified commercial mushroom tyrosinase were examined by comparing IC50 values. Kojic acid, salicylhydroxamic acid, tropolone, methimazole, and ammonium tetrathiomolybdate had relatively similar IC50 values for the crude, commercial and partially purified enzyme. 4-Hexylresorcinol seemed to have a somewhat higher IC50 value using crude extracts, compared to commercial or purified tyrosinase. Some inhibitors (NaCl, esculetin, biphenol, phloridzin) showed variations in IC50 values between the enzyme samples. In contrast, hydroquinone, lysozyme, Zn2+, and anisaldehyde showed little or no inhibition in concentration ranges reported to be effective inhibitors. Organic solvents (DMSO and ethanol) had IC50 values that were similar for some of the tyrosinase samples. Depending of the source of tyrosinase and choice of inhibitor, variations in IC50 values were observed. http://www.mdpi.com/1422-0067/10/9/3811/ Wed, 02 Sep 2009 00:00:00 CEST International Journal of Molecular Sciences 2009-09-02 10 9 Article 3811 3823 1422-0067 Variations in IC50 Values with Purity of Mushroom Tyrosinase 2009-09-02 doi: 10.3390/ijms10093811 Elizabeth Neeley George Fritch Autumn Fuller Jordan Wolfe Jessica Wright William Flurkey http://www.mdpi.com/1422-0067/10/6/2440/ Tyrosinase is a multifunctional, glycosylated, and copper-containing oxidase, which catalyzes the first two steps in mammalian melanogenesis and is responsible for enzymatic browning reactions in damaged fruits during post-harvest handling and processing. Neither hyperpigmentation in human skin nor enzymatic browning in fruits are desirable. These phenomena have encouraged researchers to seek new potent tyrosinase inhibitors for use in foods and cosmetics. This article surveys tyrosinase inhibitors newly discovered from natural and synthetic sources. The inhibitory strength is compared with that of a standard inhibitor, kojic acid, and their inhibitory mechanisms are discussed. http://www.mdpi.com/1422-0067/10/6/2440/ Tue, 26 May 2009 00:00:00 CEST International Journal of Molecular Sciences 2009-05-26 10 6 Review 2440 2475 1422-0067 An Updated Review of Tyrosinase Inhibitors 2009-05-26 doi: 10.3390/ijms10062440 Te-Sheng Chang