Anti-melanogenic Activity of Calocedrus formosana Wood Essential Oil and Its Chemical Composition Analysis

Calocedrus formosana (Cupressaceae) is one of the five precious woods of Taiwan. In this study, we investigated the anti-melanogenic activity of C. formosana wood essential oil (CFEO) and its bioactive components in vitro. Initially, CFEO exhibited strong mushroom tyrosinase activity in the cell-free mushroom tyrosinase assay system with an IC50 value of 2.72 µg/mL. Next, treatment with CFEO significantly as well as dose-dependently reduced a combination of a-melanocyte-stimulating hormone and forskolin (a-MSH-FSK)-induced melanin synthesis in B16-F10 cells. Indeed, 80 mg/mL CFEO completely inhibited melanin production, which is similar to that of control cells. Further studies revealed that treatment with CFEO significantly inhibited melanogenesis regulatory proteins, including TRP-1, TRP-2, and MITF, whereas tyrosinase was unaffected by either a-MSH-FSK or CFEO. In addition, the composition of the CFEO was characterized. The major components of CFEO were α-terpineol (23.47%), shonanic acid (10.45%), terpinen-4-ol (12.23%), thymol (5.3%), piperitone (3.44%), berbenone (2.81%), thujic acid (1.65%), and chaminic acid (0.13%). Among them, shonanic acid (1), thujic acid (2), and chaminic acid (3) were uncommon constitutes in essential oils, which could be the index compounds of CFEO, and the structure of these compounds were confirmed by spectral analysis. Furthermore, we found that thymol is an active ingredient responsible for CFEO’s anti-melanogenic activity. Based on these results, we suggest that CFEO or thymol could be a potential candidate for the development of skin whitening products for cosmetic purposes.

Various Plants and Bioactive Constituents for Pigmentation Control: A Review

Hyperpigmentation disorders caused by excessive melanin synthesis may significantly affect the psychosocial aspect of an individual. Being the current gold standard used for the treatment of hyperpigmentation disorders, hydroquinone is associated with several adverse effects including skin irritation, contact dermatitis, mutagenic to mammalian cells, cytotoxic to melanocytes as well as exogenous ochronosis in darker-complexioned individuals. Botanically derived agents have received increased attention in treating hyperpigmentation as they are perceived to be milder, safer, healthier and more cost-effective. Several herbs, plant extracts and phytochemicals with multitude mechanisms of action have been reported to be effective depigmenting agents with milder side effects. Some of the agents were studied in combination and their hypopigmentation effects may be resulting from synergistic effects of the various components. Mechanisms involved in depigmentation include tyrosinase inhibition, inhibition of α-melanocyte-stimulating hormone-induced melanogenesis and antioxidant properties. Use of plant-derived agents for the treatment of hyperpigmentation disorders is promising with the need for more rigorous clinical studies to support the use of these agents. This review summarizes the use of various plants and bioactive constituents and their effectiveness in the control of pigmentation.

Interferon-gamma Induces Melanogenesis Via Post-Translational Modification of Tyrosinase

Melanogenesis (melanin pigment production) in melanocytes is canonically stimulated by the alpha-melanocyte stimulating hormone (αMSH), which activates the cyclic-AMP-mediated expression of the melanocyte inducing transcription factor (MITF) and its downstream melanogenic genes, including the principal rate-limiting melanogenic enzyme tyrosinase (Tyr). Here we report that interferon-gamma (IFNG; type II interferon), but not IFN-alpha (a type I interferon), induces a noncanonical melanogenic pathway. Inhibition of IFNG pathway by the JAK inhibitor ruxolitinib or knocking out Stat1 abrogated the IFNG-induced melanogenesis. Interestingly, IFNG-induced melanogenesis was independent of MITF. IFNG markedly increased the Tyr protein expression but did not affect the mRNA expression, suggesting a post-translational regulatory mechanism. In contrast, IFNG had no effect on the expression of other melanogenesis-related proteins, e.g. tyrosinase-related protein 1 (Tyrp1) and dopachrome tautomerase (Dct). Glycosidase digestion assays revealed that IFNG treatment increased the mature glycosylated form of Tyr, but not its de novo synthesis. Moreover, cycloheximide chase assay showed that degradation of Tyr was decreased in IFNG-treated cells. These results suggest that the IFNG-STAT1 pathway regulates melanogenesis via modulation of the post-translational processing and protein stability of Tyr.

Construction of a Tandem Repeat Peptide Sequence with Pepsin Cutting Sites to Produce Recombinant α-Melanocyte-Stimulating Hormone

The production of α-melanocyte-stimulating hormone (α-MSH), a peptide hormone composed of 13 amino acids, is attempted by recombinant expression using E. coli as the host. To achieve this aim, a synthetic gene containing eight tandem repeats of msh gene (8msh) was designed for ribosomal synthesis of 8 α-MSH. The merit of the strategy is to diminish the peptide toxicity against the host cell and to achieve a higher production yield. Pepsin cleavage sites are introduced between the peptides for enzymatic proteolysis to obtain the monomeric peptide of α-MSH. The constructed plasmid was transformed into different strains of E. coli hosts, and E. coli XL1-Blue with gene 8msh revealed the highest yield of 8 α-MSH. Although 8 α-MSH was fractionalized in the insoluble pellets after cell lysis, pepsin cleavage was able to produce soluble α-MSH peptide, as analyzed and confirmed by mass spectrometry and peptide activity assays. The production of α-MSH was quantified using HPLC with a yield of 42.9 mg/L of LB culture. This study demonstrates the feasibility of producing α-MSH using recombinant expression of tandem repeat gene. The production procedure involves minimal post-treatment and processing and can be scaled up for industrial application.

Melanotan II User Experience: A Qualitative Study of Online Discussion Forums

<b><i>Background:</i></b> Melanotan II (MT II) is a synthetic analogue of α-melanocyte-stimulating hormone that, via interaction with the melanocortin 1 receptor, induces skin hyperpigmentation. The unregulated acquisition of MT II injections via the internet and other outlets has become popular over the last decades in order to exploit its properties for use as a tanning agent. Due to the covert nature of MT II use, it is difficult to assess the extent of its use among the general population and to characterise any associated side effects. <b><i>Objectives:</i></b> The aim of this study was to qualitatively examine MT II use, as portrayed on online forums, and to explore the motivations for its use and side effect profile. <b><i>Methods:</i></b> Data were extracted retrospectively from UK and Ireland online chatrooms and forums from January 2016 to October 2017. Inclusion criteria were active MT II chatrooms and forums considered to be within the public domain. An inductive thematic analysis identified themes within discussion threads. <b><i>Results:</i></b> A total of 623 discussion entries were extracted; 205 participants contributed to these entries. Emergent themes included motivation for MT II use, misinformation in the context of using an unregulated product, product preparation and administration, dosing regimens, sunbed use, side effects and concerning practices associated with MT II use. <b><i>Conclusion:</i></b> Motivations for MT II use included the pursuit of a tanned appearance, often in anticipation of sun holidays and fitness/body building competitions. Clinicians should be aware not only of the potential risks in relation to pigmented skin lesions, but also remain cognisant of the other medical hazards associated with the use of this substance, namely transmission of infectious diseases, use of potentially contaminated products, polypharmacy, and sunbed exposure.

Zebrafish Bioassay for Screening Therapeutic Candidates Based on Melanotrophic Activity

In this study, we used the zebrafish animal model to establish a bioassay by which physiological efficacy differential of alpha-melanocyte-stimulating hormone (α-MSH) analogues could be measured by melanosome dispersion in zebrafish larvae. Brain-skin connection research has purported the interconnectedness between the nervous system and skin physiology. Accordingly, the neuropeptide α-MSH is a key regulator in several physiological processes, such as skin pigmentation in fish. In mammals, α-MSH has been found to regulate motivated behavior, appetite, and emotion, including stimulation of satiety and anxiety. Several clinical and animal model studies of autism spectrum disorder (ASD) have already demonstrated the effectiveness of α-MSH in restoring the social deficits of autism. Therefore, we sought to analyze the effect of synthetic and naturally-occurring α-MSH variants amongst different species. Our results showed that unique α-MSH derivatives from several fish species produced differential effects on the degree of melanophore dispersion. Using α-MSH human form as a standard, we could identify derivatives that induced greater physiological effects; particularly, the synthetic analogue melanotan-II (MT-II) exhibited a higher capacity for melanophore dispersion than human α-MSH. This was consistent with previous findings in an ASD mouse model demonstrating the effectiveness of MT-II in improving ASD behavioral symptoms. Thus, the melanophore assay may serve as a useful screening tool for therapeutic candidates for novel drug discovery.