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

Secondary glaucoma: Toward interventions based on molecular underpinnings

Glaucoma is a heterogeneous group of progressive diseases that leads to irreversible blindness. Secondary glaucoma refers to glaucoma caused by a known underlying condition. Pseudoexfoliation and pigment dispersion syndromes are common causes of secondary glaucoma. Their respective deposits may obstruct the trabecular meshwork, leading to aqueous humor outflow resistance, ocular hypertension, and optic neuropathy. There are no disease-specific interventions available for either. Pseudoexfoliation syndrome is characterized by fibrillar deposits (pseudoexfoliative material) on anterior segment structures. Over a decade of multiomics analyses taken together with the current knowledge on pseudoexfoliative glaucoma warrant a re-think of mechanistic possibilities. We propose that the presence of nucleation centers (e.g., vitamin D binding protein), crosslinking enzymes (e.g., transglutaminase 2), aberrant extracellular matrix, flawed endocytosis, and abnormal aqueous-blood barrier contribute to the formation of proteolytically resistant pseudoexfoliative material. Pigment dispersion syndrome is characterized by abnormal iridolenticular contact that disrupts iris pigment epithelium and liberates melanin granules. Iris melanogenesis is aberrant in this condition. Cytotoxic melanogenesis intermediates leak out of melanosomes and cause iris melanocyte and pigment epithelium cell death. Targeting melanogenesis can likely decrease the risk of pigmentary glaucoma. Skin and melanoma research provides insights into potential therapeutics. We propose that specific prostanoid agonists and fenofibrates may reduce melanogenesis by inhibiting cholesterol internalization and de novo synthesis. Additionally, melatonin is a potent melanogenesis suppressor, antioxidant, and hypotensive agent, rendering it a valuable agent for pigmentary glaucoma. In pseudoexfoliative glaucoma, where environmental insults drive pseudoexfoliative material formation, melatonin's antioxidant and hypotensive properties may offer adjunct therapeutic benefits. This article is categorized under: Neurological Diseases > Molecular and Cellular Physiology.

Research Progress of Small Molecules as Anti-vitiligo Agents

Vitiligo is a disease characterized by skin discoloration, and no safe and effective drugs have been developed until now. New drug research and development are imminent. This article reviews the research on small-molecule drugs for vitiligo from 1990 to 2021 at home and abroad. They are classified according to their structures and mechanisms of action, including natural products and derivatives, anti-oxidative stress drugs, immunosuppressants, prostaglandins, etc. The research on their anti-vitiligo activity, structural modification, new dosage forms, clinical trials, and the development trend in new anti-vitiligo drugs are reviewed, which provides important references for the development of new drugs.

Simvastatin in vitiligo: an update with recent review of the literature

Patients with vitiligo often seek medical attention, as it diminishes their quality of life resulting in significant morbidity. Several topical and systemic therapies are in vogue targeting the immunological aspect of this disease, but results are often unsatisfactory, and complete cure remains elusive. Recently, simvastatin, a 3-hydroxy-3-methylyglutaryl-coenzyme A (HMG-CoA) reductase inhibitor, is being evaluated for vitiligo management because of its multimodal action, easy availability, and low cost. The proposed multimodal actions range from anti-inflammatory, antioxidant, to immunomodulatory properties which may be of therapeutic benefit in vitiligo patients. The authors intend to evaluate the role of simvastatin as a novel therapeutic agent for vitiligo along with relevant review of literature.

The Surprising Effect of Phenformin on Cutaneous Darkening and Characterization of Its Underlying Mechanism by a Forward Chemical Genetics Approach

Melanin in the epidermis is known to ultimately regulate human skin pigmentation. Recently, we exploited a phenotypic-based screening system composed of ex vivo human skin cultures to search for effective materials to regulate skin pigmentation. Since a previous study reported the potent inhibitory effect of metformin on melanogenesis, we evaluated several biguanide compounds. The unexpected effect of phenformin, once used as an oral anti-diabetic drug, on cutaneous darkening motivated us to investigate its underlying mechanism utilizing a chemical genetics approach, and especially to identify alternatives to phenformin because of its risk of severe lactic acidosis. Chemical pull-down assays with phenformin-immobilized beads were performed on lysates of human epidermal keratinocytes, and subsequent mass spectrometry identified 7-dehydrocholesterol reductase (DHCR7). Consistent with this, AY9944, an inhibitor of DHCR7, was found to decrease autophagic melanosome degradation in keratinocytes and to intensely darken skin in ex vivo cultures, suggesting the involvement of cholesterol biosynthesis in the metabolism of melanosomes. Thus, our results validated the combined utilization of the phenotypic screening system and chemical genetics as a new approach to develop promising materials for brightening/lightening and/or tanning technologies.

Recent development of signaling pathways inhibitors of melanogenesis

Human skin, eye and hair color rely on the production of melanin, depending on its quantity, quality, and distribution, Melanin plays a monumental role in protecting the skin against the harmful effect of ultraviolet radiation and oxidative stress from various environmental pollutants. However, an excessive production of melanin causes serious dermatological problems such as freckles, solar lentigo (age spots), melasma, as well as cancer. Hence, the regulation of melanin production is important for controlling the hyper-pigmentation. Melanogenesis, a biosynthetic pathway to produce melanin pigment in melanocyte, involves a series of intricate enzymatic and chemical catalyzed reactions. Several extrinsic factors include ultraviolet radiation and chemical drugs, and intrinsic factors include molecules secreted by surrounding keratinocytes or melanocytes, and fibroblasts, all of which regulate melanogenesis. This article reviews recent advances in the development of melanogenesis inhibitors that directly/indirectly target melanogenesis-related signaling pathways. Efforts have been made to provide a description of the mechanism of action of inhibitors on various melanogenesis signaling pathways.

Ardisia crenata extract stimulates melanogenesis in B16F10 melanoma cells through inhibiting ERK1/2 and Akt activation

Melanin protects the skin against ultraviolet radiation by scattering incoming light and absorbing diverse free radicals. Agents that increase melanin synthesis in melanocytes may reduce the risk of photodamage and skin cancer. The present study investigated the effect of a methanol extract of Ardisia crenata (AC) on melanogenesis in B16F10 cells. Treatment of cultured B16F10 cells with AC extract (10, 20 and 40 µg/ml) stimulated an increase in melanin levels in a concentration-dependent manner, without cytotoxicity. Tyrosinase is key in the regulation of melanin production, thus the effect of AC extract on tyrosinase activity and protein expression was analyzed. AC extract was observed to significantly increase tyrosinase activity and protein expression in B16F10 cells. Furthermore, AC extract was found to markedly increase the protein expression of microphthalmia-associated transcription factor, which is an important transcription factor involved in tyrosinase gene expression. In addition, AC extract (40 µg/ml) was observed to suppress the activation of extracellular signal-regulated kinase (ERK) and Akt, which negatively regulate melanin synthesis in B16F10 cells. In conclusion, to the best of our knowledge, the present study is the first to show that a methanol extract of AC stimulates melanogenesis by increasing tyrosinase expression via the inhibition of ERK and Akt. Thus, methanol extract of AC may be a potential treatment for hypopigmentation diseases and may be a candidate for skin-tanning cosmetic products.

Fluvastatin influences hair color in C57BL/6 mice

Our recent in vitro experiments suggest that fluvastatin may influence tyrosinase (key enzyme of melanogenesis) synthesis. The aim of the present study was to verify those findings in experiments, in vitro, in melanoma cell line, and in vivo, in mice. The expression of tyrosinase in B16F10 melanoma cell line, after induction of melanogenesis by UVB irradiation, was examined by Western blot analysis. Afterwards, the effect of fluvastatin on melanin synthesis in hair follicles of C57Bl/6 mice was investigated. The expression of tyrosinase was reduced in the presence of fluvastatin. In mice after anagen induction over the dorsal skin, gel containing fluvastatin in various concentrations was injected subcutaneously, while in part of control groups of mice, gel with placebo was injected. In addition, gel with fluvastatin was injected to four week-old mice (mice in first postnatal anagen) without anagen induction. In extension, injections of gel with fluvastatin or placebo were performed in mice without anagen induction (but after first postnatal anagen). In part of study group of mice (mice after anagen induction and injection of fluvastatin) regrowth of depigmented hair was observed, while in all control groups (mice after injection of placebo), such hair depigmentation over the skin area was not found. In conclusion, this study, for the first time, shows that fluvastatin might affect melanin synthesis in vivo.

Melanogenesis effect of Cordyceps militaris culture broth on the melanin formation of B16F0 melanoma cells

The effect of Cordyceps militaris culture broth (CMB) on melanogenesis in B16F0 melanoma cells was evaluated by measurement of the melanin concentration after 3 days of incubation. The B16F0 melanoma cells were treated with various concentrations of CMB 10-100 μg/mL and arbutin of 200 μM. Phenolic content and antioxidant activity of CMB were also measured. Phenolic content of CMB was 3.28 mg/g. The DPPH radical scavenging and ferric ion donating activities were 79.64% and 0.16, respectively. The melanin concentration and cell viability of melanoma cells by arbutin treatment decreased to 43% and 91% of the control, respectively. The CMB treatment showed a significant inhibitory effect of melanin production by 29%, 50%, and 56% at 50, 80, and 100 μg/mL concentration treatment, respectively, while over 90% of cells were viable. The CMB treatment at 50, 80, and 100 μg/mL concentrations in cultivation decreased extracellular melanin release induced by 3-isobutyl-1-methylxanthine (IBMX) treatment by 19%, 38%, and 48%, respectively. The CMB showed inhibitory activity against intracellular tyrosinase extracted from melanoma cells, while it had no inhibition on the activity of mushroom tyrosinase. The cellular glutathione contents were enhanced by CMB treatment in a concentration-dependent manner. These results suggested that CMB suppressed cellular tyrosinase activity and total melanin content in cultured B16F0 melanoma cells without any significant effects on cell proliferation and it might be candidate anti-melanogenic agent.