Fluvastatin increases tyrosinase synthesis induced by α-melanocyte-stimulating hormone in B16F10 melanoma cells

The aim of this study was to evaluate the effect of fluvastatin on the α-melanocyte-stimulating hormone-mediated increase in tyrosinase activity in the melanoma B16F10 cell line and to establish whether Akt and extracellular signal-regulated kinase (Erk) inhibition is involved in tyrosinase synthesis after fluvastatin administration. Fluvastatin modulates α-melanocyte-stimulating hormone induced melanogenesis by increasing tyrosinase mRNA production, as shown by real time PCR, or tyrosinase protein synthesis, as presented by western blot technique. The stimulatory effect of fluvastatin on melanogenesis was, in part, induced by modulation of cell proliferation (decreased melanoma cell proliferation in G2/M phase) and possibly decrease of Akt. These findings indicate that fluvastatin increases tyrosinase synthesis induced by α-melanocyte-stimulating hormone in B16F10 cells and reveal an unknown effect of statin use: their influence on melanin production.     

Quercetin inhibits α-MSH-stimulated melanogenesis in B16F10 melanoma cells

Quercetin is known to inhibit tyrosinase activity and melanin production in melanocytes. However, several reports suggest that quercetin has different and opposite effects on melanogenesis. This study examined the precise effects of quercetin on melanogenesis using cell‐free assay systems and melanocytes. Quercetin inhibited the monophenolase and diphenolase activities of tyrosinase, and melanin synthesis in cell‐free assay systems. Quercetin induced mild stimulation of the tyrosinase activity and dihydroxyphenylalaminechrome tautomerase (TRP‐2) expression but only at low concentrations (<20 μm ) in B16F10 melanoma cells. In contrast, the addition of 50 μm quercetin to the cells led to a significant decrease in the activity and synthesis of tyrosinase, as well as a decrease in the expression of tyrosinase‐related protein‐1 and TRP‐2 proteins, regardless of the presence or absence of α‐melanocyte stimulating hormone (α‐MSH). Quercetin also reduced the intracellular cAMP and the phosphorylated protein kinase A levels in α‐MSH‐stimulated B16F10 cells. Moreover, quercetin (20 μm ) diminished the expression and activity of tyrosinase, and melanin content in cultured normal human epidermal melanocytes. These effects were not related to its cytotoxic action. Although the in vivo effects of quercetin are still unclear, these results suggest that quercetin could play important roles in controlling melanogenesis. Copyright © 2011 John Wiley & Sons, Ltd.     

Inhibitory effects of 5‐chloroacetyl‐2‐piperidino‐1,3‐selenazole,a novel selenium‐containing compound,on skin melanin biosynthesis

Objectives Increased production and accumulation of melanin leads to many hyperpigmentation disorders such as melasma, freckles and geriatric pigment spots. Thus, there is a need for the development of depigmenting agents. Based on our previous reports, selenium derivatives as anti‐melanogenic lead compounds could be very important. The aim of this study was to investigate the depigmenting effect of novel selenium‐containing compounds. Methods The inhibitory effects of 5‐chloroacetyl‐2‐piperidino‐1,3‐selenazole (CS1), a novel selenium‐containing compound, on melanogenesis were investigated in B16F10 melanoma cells and cultured brownish guinea pig skin tissue with α‐melanocyte‐stimulating hormone stimulation. Key findings We found that CS1 inhibited melanin production in B16F10 cells by suppressing tyrosinase activity and its protein expression. In addition, Western blotting analysis revealed that CS1 suppressed the expression of tyrosinase‐related protein (TRP)‐1 and TRP‐2. Therefore, the depigmenting effect of CS1 might have been due to inhibition of tyrosinase activity and expression of melanogenic enzymes. Furthermore, CS1 had inhibitory effects on melanin biosynthesis of primary cultured skin of brownish guinea pig. Conclusions The results suggested that CS1 could be a useful candidate for the treatment of skin hyperpigmentation.     

Melanogenesis inhibitory activities of diarylheptanoids from Alnus hirsuta Turcz in B16 mouse melanoma cell

Four diarylheptanoids, (5R-1,7-bis (3,4-dihydroxyphenyl)-heptane-5-O-beta-D-glucoside (1), (5R) 1,7-bis (3,4-dihydroxyphenyl)-heptane-5-ol (2), oregonin (3), hirsutanonol (4), were isolated from the bark of Alnus hirsuta Turcz and its inhibitory effects on melanogenesis by measuring the melanin level and tyrosinase activity in B16 melanoma cell were examined. Melanin level and tyrosinase activity were reduced to 75 to 85% by addition of diarylheptanoids to incubation medium of the melanoma cell. On the other hand, melanin level and tyrosinase activity were reduced to 13 to 43% by the addition of diarylheptanoids to incubation medium of the melanoma cell treated with melanogenesis stimulator, alpha-MSH and forskolin. These melanogenesis inhibitory effects were significantly different compared with control.     

Pharmacologic Response of a Controlled-Release PLGA Formulation for the Alpha-Melanocyte Stimulating Hormone Analog,Melanotan-I

Purpose. The objective of this study was to evaluate in vitro and invivo the melanogenic activity of one-month duration Melanotan-I(MT-I) implants prepared using poly (D,L lactide-co-glycolide) polymer. Methods. The biological activity of the samples of MT-I released invitro from the non-irradiated or gamma irradiated implants wasmeasured using a frog skin bioassay. The effect of MT-I on skinpigmentation was measured using a Chroma meter (reflectometer) aftersubcutaneous administration of implants containing 4 mg MT-I toguinea pigs. Eumelanin, the black/brown melanin pigment, wasquantified in skin biopsies as pyrrole-2, 3, 5-tricarboxylic acid using HPLC. Results. The MT-I released in vitro from implants after 24 hoursexhibited 100% melanotropic activity in frog skins compared to an identicalconcentration of a freshly prepared MT-I standard. The reflectancereadings demonstrated a prolonged skin darkening for up to threemonths as evidenced by the decrease in the luminance values from 0to –4.82. A 2.5-fold increase in eumelanin levels was observed afterone month and the increased pigmentation lasted for 3 months. Conclusions. The melanogenic response to MT-I implants persisted forthree months and the increase in pigmentation, especially the increasedeumelanin levels, could provide protection from ultraviolet radiation.     

Artepillin C and Other Herbal PAK1‐blockers: Effects on Hair Cell Proliferation and Related PAK1‐dependent Biological Function in Cell Culture

PAK1 (RAC/CDC42‐activated kinase 1) is the major oncogenic kinase, and a number of herbal PAK1‐blockers such as propolis and curcumin have been shown to be anti‐oncogenic and anti‐melanogenic as well as anti‐alopecia (promoting hair growth). Previously, we found several distinct PAK1‐inhibitors in Okinawa plants including Alpinia zerumbet (alpinia). Thus, here, we tested the effects of these herbal compounds and their derivatives on the growth of cancer or normal hair cells, and melanogenesis in cell culture of A549 lung cancer, hair follicle dermal papilla cell, and B16F10 melanoma. Among these herbal PAK1‐inhibitors, cucurbitacin I from bitter melon (Goya) turned out to be the most potent to inhibit the growth of human lung cancer cells with the IC₅₀ around 140 nM and to promote the growth of hair cells with the effective dose around 10 nM. Hispidin, a metabolite of 5,6‐dehydrokawain from alpinia, inhibited the growth of cancer cells with the IC₅₀ of 25 μM as does artepillin C, the major anti‐cancer ingredient in Brazilian green propolis. Mimosine tetrapeptides (MFWY, MFYY, and MFFY) and hispidin derivatives (H1–3) also exhibited a strong anti‐cancer activity with the IC₅₀ ranging from 16 to 30 μM. Mimosine tetrapeptides and hispidin derivatives strongly suppressed the melanogenesis in melanoma cells. Copyright © 2015 John Wiley & Sons, Ltd.     

Differential expression of nitric oxide synthases in human scalp epidermal and hair follicle pigmentary units: implications for regulation of melanogenesis

BACKGROUND: Nitric oxide (NO) is a ubiquitous gaseous lipophilic molecule generated from the conversion of L-arginine to L-citrulline by the NO synthases (NOSs). Ultraviolet radiation (UVR)-induced NO production appears to stimulate epidermal melanogenesis. However, given their relative protection from UVR, it is unclear whether NO plays a similar role in hair bulb melanocytes. OBJECTIVES: We aimed to identify the expression profiles of the NOS isoforms endothelial NOS (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS) and of phosphorylated eNOS and nitrotyrosine within the epidermal and follicular melanin units of normal human haired scalp during the hair growth cycle. METHODS: This study employed single and double immunohistochemical and immunofluorescence staining techniques using haired scalp from 10 healthy individuals (six women and four men). RESULTS: Melanocytes in the basal layer of the epidermis expressed eNOS, nNOS and nitrotyrosine. By contrast, melanogenically active melanocytes of the anagen hair bulb were wholly negative for these markers. However, other follicular melanocytes not actively involved in pigment production, including undifferentiated melanocytes located in the outer root sheath and melanocytes surviving the apoptosis-driven hair follicle (HF) regression during catagen/telogen, expressed eNOS, nNOS and nitrotyrosine. While iNOS was only weakly expressed in the basal layer of the human epidermis, it was highly expressed in keratinocytes of the inner root sheath (IRS), where it colocalized with trichohyalin, a differentiation-associated protein of the IRS that requires enzyme-catalysed conversion of arginine to citrulline. CONCLUSIONS: The NOS isoforms and nitrotyrosine are differentially expressed in different cutaneous melanocyte subpopulations. Results of this study suggest a possible role for eNOS, nNOS, iNOS and nitrotyrosine in melanocyte biology, particularly with respect to melanogenesis and melanocyte survival during HF regression. Another example of possible NO involvement in HF biology is the postsynthetic modification of trichohyalin in differentiating keratinocytes of the IRS. These results suggest that NO may influence several aspects of HF biology.