Melanocyte-stimulating properties of arachidonic acid metabolites: possible role in postinflammatory pigmentation

Treatment of Facial Acne Scarring With Fractional Carbon Dioxide Laser in Asians, a Retrospective Analysis of Efficacy and Complications

BACKGROUND

Fractional carbon dioxide (CO2) laser resurfacing unites the idea of fractional photothermolysis with an ablative 10,600-nm wavelength. This technology permits effective treatment of acne scarring, with shorter recovery and a decreased side effect profile as compared to traditional CO2 laser resurfacing.

OBJECTIVE

The aims of this study were to study the efficacy and safety of fractional CO2 laser for acne scars in Asian patients.

METHODS

This was a retrospective study of all patients treated with the fractional CO2 laser for facial acne scarring between January 2, 2008, and December 31, 2010, at the National Skin Centre, Singapore. Data reviewed included sex, age, and severity of acne, type of scarring, previous treatment history, frequency of treatments, adverse events, and efficacy.

RESULTS

Two hundred and ten fractional CO2 laser treatments for facial acne scars were performed on 107 patients (65 men and 42 women, Fitzpatrick skin Types II to V) during the study period. Sixteen of 107 patients experienced (15.0%) adverse events. The adverse events include hyperpigmentation (6.4%), blistering (4.0%), crusting (2.9%), aggravation of inflammatory acne lesions (1.7%), and scarring (0.6%). There were no reported side effects of hypopigmentation, bacterial or viral infection. Follow-up results after final laser treatment showed that 66.4% of patients reported Grade 1 skin texture improvement, that is, <25% (n = 71); 30.0% had Grade 2 improvement, that is, 25% to 50% improvement (n = 31); 3.7% had Grade 3 improvement, that is, 51% to 75% improvement (n = 4); and 0.9% had Grade 4 improvement, that is, >75% improvement (n = 1).

CONCLUSION

The study demonstrated the efficacy and safety of a fractional CO2 laser in the treatment of acne scars in Asian. Future studies are required to establish optimum treatment parameters and achieve better clinical results.

Ethosomes of Phenylethyl Resorcinol as Vesicular Delivery System for Skin Lightening Applications

Ethosome formulations containing phenylethyl resorcinol (PR) were developed. The formulation was produced from 0.5% w/v PR, 0.5% w/v cholesterol from lanolin, 3% w/v L-α-phosphatidylcholine from soybean, 30% v/v absolute ethanol, and water up to 100% v/v. It was characterized by a vesicular size of 389 nm, low polydispersity index of 0.266, zeta potential of -34.19 ± 0.44 mV, high PR entrapment efficiency of 71%, and good stability on storage at 4 and 30°C at 75% RH for 4 months. In vitro studies using pig skin revealed that permeation coefficient of PR from ethosomes was significantly higher than that from liposomes. In vitro retention profiles showed that PR accumulation in pig skin following application of ethosome formulations was 7.4-, 3.3-, and 1.8-fold higher than that achieved using liposomes, 20% propylene glycol solution, and 30% hydroethanolic solution, respectively. An inhibition value of around 80% was measured for antityrosinase activity of PR in pig skin. Consistently, ethosomes exhibited higher tyrosinase inhibition activity and melanin content reduction when compared to other formulations in B16 melanoma cells. Ethosomes did not cause acute dermal irritation in albino rabbits. These findings demonstrate that ethosomes are capable of delivering PR into the skin efficiently and hold promise for topical application of skin lightening products.

Antioxidant and Anti-tyrosinase Activities of Phenolic Extracts from Rape Bee Pollen and Inhibitory Melanogenesis by cAMP/MITF/TYR Pathway in B16 Mouse Melanoma Cells

Rape bee pollen possesses many nutritional and therapeutic properties because of its abundant nutrimental and bioactive components. In this study, free (FPE) and bound (BPE) phenolic extracts of rape bee pollen were obtained, phenolic and flavonoid contents were determined, and composition of phenolic acids was analyzed. In vitro antioxidant and anti-tyrosinase (TYR) activities of FPE and BPE were compared, and inhibitory melanogenesis of FPE was further evaluated. Results showed FPE and BPE contain total phenolic contents of 11.76 and 0.81 mg gallic acid equivalents/g dry weight (DW) and total flavonoid contents of 19.24 and 3.65 mg rutin equivalents/g DW, respectively. Phenolic profiling showed FPE and BPE fractions contained 12 and 9 phenolic acids, respectively. FPE contained the highest rutin content of 774.87 μg/g. FPE and BPE showed the high antioxidant properties in vitro and high inhibitory activities for mushroom TYR. Higher activities of FPE than those of BPE can be attributed to difference in their phenolic compositions. Inhibitory melanogenesis activities of FPE against B16 were further evaluated. Results showed suppressed intracellular TYR activity, reduced melanin content, and promoted glutathione synthesis (p < 0.05) in FPE-treated cells. FPE reduced mRNA expression of TYR, TYR-related protein (TRP)-1 and TRP-2, and significantly suppressed cyclic adenosine monophosphate (cAMP) levels through down-regulation of melanocortin 1 receptor gene expression (p < 0.05). FPE reduced mRNA expression of microphthalmia-associated transcription factor (MITF), significantly inhibiting intracellular melanin synthesis (p < 0.05). Hence, FPE regulates melanogenesis of B16 cells involved in cAMP/MITF/TYR pathway. These results revealed that FPE can be used as pharmaceutical agents and cosmetics to protect cells from abnormal melanogenesis.

Interferon-γ Attenuates 5-Hydroxytryptamine-Induced Melanogenesis in Primary Melanocyte

Interferon-γ (IFN-γ) is an important cytokine which can be secreted by keratinocytes or macrophages induced by UVB irradiation in skin. Mammalian skin cells have the capability to produce and metabolize 5-hydroxytryptamine (5-HT) whose cutaneous effects are mediated by the interactions with 5-HT receptors. Treatment with 5-HT resulted in a dose-dependent increase of tyrosinase (TYR) activity and melanin contents in normal human foreskin-derived epidermal melanocytes (NHEM), while with IFN-γ a decreased effect resulted. These regulatory results were due to changes of the expression levels of microphthalmia-associated transcription factor (MITF) and its downstream TYR, tyrosinase-related protein 1 (TRP-1) and dopachrome tautomerase (DCT). We proved here that 5-HTR1A/2A participated in the regulation of melanogenesis. IFN-γ could offset the pro-melanogenesis effect of 5-HT in NHEM and the intensity of this neutralization was unanticipated below the baseline level. IFN-γ neutralized the up-regulation effect of 5-HT on MITF and downstream TYR, TRP-1 and DCT. Though functioning as 5-HT1A/2A receptor during the melanogenesis process, IFN-γ played no role in 5-HT1A/2A receptor expressions. Our results also demonstrated that the inhibition of IFN-γ was reversible after its removal. Confusingly, the effect of cross-talk between 5-HT and IFN-γ on NHEM melanogenesis was irreversible. Whether treated with 5-HT for 5 d or 12 d, the pigmentation level neither recovered after displacing the IFN-γ-containing medium. In addition, IFN-γ was able to inhibit the inductive effect of 5-HT on NHEM migration. Taken together, the suppression of IFN-γ on 5-HT-induced melanogenesis further suggests the negative role of IFN-γ in inflammation-associated pigmentary changes.

Postinflammatory hyperpigmentation associated with treatment of solar lentigines using a Q-Switched 532-nm Nd: YAG laser: a multicenter survey

PURPOSE

To characterize the risk factors of Korean patients for postinflammatory hyperpigmentation (PIH) during treatment of solar lentigines using a Q-switched 532-nm Nd: YAG (QS 532 NY) laser.

MATERIALS AND METHODS

The present retrospective multicenter study was conducted at the dermatology clinics of five tertiary hospitals in Korea. Between October 2007 and January 2013, 516 patients were enrolled and reviewed for clinical features and factors associated with PIH.

RESULTS

The overall incidence of PIH was 20.3%. We demonstrated that patients with erythematous lentigines presented with PIH more frequently compared with those without erythematous lentigines. Among several coexisting conditions, facial diffuse dyschromia was significantly associated with PIH. Furthermore, PIH occurred more frequently in patients with invisible pores and velvety skin. However, age, sex, Fitzpatrick skin's phototype and season of treatment showed little association with PIH.

CONCLUSIONS

When a QS 532 NY laser is used to treat individuals with erythematous lentigines, invisible pores and velvety skin, and facial diffuse dyschromia, clinicians should be cautious and consider preventive measures.

Cross-talk between interferon-gamma and interleukin-18 in melanogenesis

Skin is the largest organ in our body and strategically placed to provide a metabolically active biological barrier against a range of noxious stressors. A lot of inflammatory cytokines, which are increased after ultraviolet (UV) irradiation produced by keratinocytes or other immunocytes, are closely related to pigmentary changes, including interleukin-18 (IL-18) and interferon-γ (IFN-γ). In this study, the effect of cross-talk between IL-18 and IFN-γ on melanogenesis was investigated. Treatment with IL-18 resulted in a dose-dependent increase of melanogenesis, while IFN-γ made an opposite effect. This influence of IL-18 and IFN-γ was mediated by regulations of microphthalmia-associated transcription factor (MITF) and its downstream enzymatic cascade expressions. Furthermore, IFN-γ inhibited basal and IL-18-induced melanogenesis. IFN-γ increased signal transducer and activator of transcription-1 (STAT-1) phosphorylation to play its position in regulating melanin pigmentation, and its inhibitory effect could be prevented by Janus Kinase 1 (JAK 1) inhibitor. IFN-γ could inhibit melanogenesis by decreasing melanocyte dendrite formation. In addition, IFN-γ inhibited the expressions of Rab Pases to suppress the mature and transport of melanosomes. IL-18 could rapidly induce Akt and PTEN phosphorylation and p65 expression in B16F10 cells. When treatment with IL-18 and IFN-γ together, the phosphorylation level of Protein Kinase B (Akt) and phosphatase and tensin homolog deleted on chromosome ten (PTEN) and expression of p65 NF-κB were inhibited, compared with treated with IL-18 only. Our studies indicated that IFN-γ could directly induce B16F10 cells apoptosis in vitro. Furthermore, we demonstrated that IFN-γ markedly up-regulated IL-18 binding protein (BP) production in normal human foreskin-derived epidermal keratinocytes in dose-dependent manner. UVB irradiation induced protease-activated receptor-2 (PAR-2) expression in NHEK, IFN-γ could inhibit this enhancement in a dose-dependent manner. These data suggest that IFN-γ plays a role in regulating inflammation- or UV-induced pigmentary changes, in direct/indirect manner.

CD4, IL-17, and COX-2 Are Associated With Subclinical Inflammation in Malar Melasma

The pathogenesis of melasma, a common, photo-induced hyperpigmentary disorder, is not clearly understood. Significant factors linked to melasma are ultraviolet radiation exposure and genetic predisposition. Histological analysis has demonstrated that melasma is caused by a network of cellular interactions among melanocytes, keratinocytes, mast cells, fibroblasts, and dermal vasculature exhibits, features similar to chronic sun damage. Dermal inflammation caused by ultraviolet radiation might play an important role in the hyperpigmentation and reactivation of melasma lesions through the production of melanogenic cytokines and growth factors. Because the role of inflammation in this disorder is unknown, we used histochemistry, immunohistochemistry, and quantitative real-time polymerase chain reaction to evaluate melasma lesions from healthy female patients (n = 20) with malar melasma. Lesional skin without specific solar exposure or photoprotection measures within the previous 4 weeks was compared with nonlesional skin. The increased lymphocytic infiltrate in lesional skin was mainly composed of CD4 T cells, mast cells, and macrophages. Levels of the cytokine interleukin (IL)-17 and the proinflammatory mediator cyclooxygenase (COX)-2 were significantly elevated in affected skin compared with healthy skin. In addition, the Melasma Activity and Severity Index score, fraction of solar elastosis, and epidermal melanin were positively associated with COX-2 expression. There was no statistically significant difference in IL-1α, IL-1β, R-IL1, IL-6, IL-8, vascular endothelial growth factor, and tumor necrosis factor alpha expression levels. Together, these data indicated that melasma under unchallenged conditions is characterized by chronic inflammatory cells and mediators, which may explain its recurrent nature.

Alternol inhibits the proliferation and induces the differentiation of the mouse melanoma B16F0 cell line

High malignant potential and low susceptibility to treatment are characteristics of malignant melanoma. Alternol, a novel compound purified from microbial fermentation products obtained from the bark of the yew tree, exhibits a variety of antitumor activities. Based on these findings, the aim of the present study was to extend the knowledge on the antineoplastic effect of alternol in the mouse melanoma B16F0 cell line. Alternol significantly inhibited the proliferation and colony formation of B16F0 cells in a dose-dependent manner as detected by MTT and soft agar colony formation assays. NaOH alkaline lysis and oxidation of Dopa indicated that alternol enhanced the melanin content and tyrosinase activity of the B16F0 cells and results also showed a dose‑response relationship. Morphologic changes accompanied by extended dendrites were discovered in the B16F0 cells after treatment with alternol. Furthermore, the mRNA levels of tyrosinase, Trp1 and Trp2 were increased by alternol. Our results confirmed that alternol possesses marked antineoplastic properties against melanoma cells, indicating that this microbial fermentation product is a promising agent for the differentiation therapy of cancer. The inhibition of cell proliferation and colony formation by alternol was associated with both cytotoxicity and induction of differentiation.

Skin Pigmentation and Pigmentary Disorders: Focus on Epidermal/Dermal Cross-Talk

Variation in human skin and hair color is the most notable aspect of human variability and several studies in evolution, genetics and developmental biology contributed to explain the mechanisms underlying human skin pigmentation, which is responsible for differences in skin color across the world's populations. Despite skin pigmentation is primarily related to melanocytes functionality, the surrounding keratinocytes and extracellular matrix proteins and fibroblasts in the underlying dermal compartment actively contribute to cutaneous homeostasis. Many autocrine/paracrine secreted factors and cell adhesion mechanisms involving both epidermal and dermal constituents determine constitutive skin pigmentation and, whenever deregulated, the occurrence of pigmentary disorders. In particular, an increased expression of such mediators and their specific receptors frequently lead to hyperpigmentary conditions, such as in melasma and in solar lentigo, whereas a defect in their expression/release is related to hypopigmented disorders, as seen in vitiligo. All these interactions underline the relevant role of pigmentation on human evolution and biology.

Interleukin 10 protects primary melanocyte by activation of Stat-3 and PI3K/Akt/NF-κB signaling pathways

Vitiligo is a common melanocytopenic disorder of the skin, with acquired focal depigmentation. Normal human skin relies on melanocytes to provide photoprotection and thermoregulation by producing melanin. Interleukin 10 (IL-10) is a pleiotropic immunoregulatory cytokine drawing more and more researchers' attention. The present study was conducted to investigate the effects of IL-10 on melanocytes and elucidate the underlying mechanisms. We proved that IL-10 play no role in regulating melanogenesis of normal human foreskin-derived epidermal melanocytes (NHEM). IL-10 stimulation activated the JAK/Stat-3 and PI3K/Akt signaling pathways. Moreover, IL-10 treatment increased translocation of p65 NF-κB into the nuclear compartment, and up-regulated expression of the pro-survival proteins Bcl-2 and Bcl-xL. IL-10 restored anti-apoptotic proteins expression and suppressed cytochrome c release in H2O2-induced apoptosis. In conclusion, IL-10 may provide pro-survival cues to melanocytes and be applied in the treatment of vitiligo and other depigmenting disorders.

Q-Switched 660-nm Versus 532-nm Nd: YAG Laser for the Treatment for Facial Lentigines in Asian Patients: A Prospective, Randomized, Double-Blinded, Split-Face Comparison Pilot Study

BACKGROUND

Q-switched (QS) 532-nm lasers are widely used to treat solar lentigines.

OBJECTIVE

To compare the efficacy and safety of 660-nm and 532-nm QS neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers in the treatment for lentigines in Asians.

MATERIALS AND METHODS

The halves of each face (randomly chosen) of 8 Korean Fitzpatrick Skin Type III-IV women with facial solar lentigines were treated with either 660-nm or 532-nm lasers. Pigmentation was measured objectively using a profilometric skin analysis tool and subjectively using the pigmentation area and severity index (PSI) score, global assessment of the aesthetic improvement scale (GAIS), and a patient satisfaction score at Weeks 4 and 8.

RESULTS

Seven patients completed the study. No significant differences were found in the PSI, GAIS, patient satisfaction score, and melanin average score between the lasers. The melanin average level was significantly reduced by the 660-nm laser but not the 532-nm laser at Week 8 compared with the baseline.

CONCLUSION

Both 660-nm and 532-nm QS Nd:YAG lasers effectively reduce pigmentation for up to 8 weeks with high patient satisfaction. The new 660-nm laser therefore increases the treatment options for lentigines in Asian skin.

Oxidative stress-induced overexpression of miR-25: the mechanism underlying the degeneration of melanocytes in vitiligo

Oxidative stress has a critical role in the pathogenesis of vitiligo. However, the specific molecular mechanism involved in oxidative stress-induced melanocyte death is not well characterized. Given the powerful role of microRNAs (miRNAs) in the regulation of cell survival as well as the fact that the generation of miRNAs can be affected by oxidative stress, we hypothesized that miRNAs may participate in vitiligo pathogenesis by modulating the expression of vital genes in melanocytes. In the present study, we initially found that miR-25 was increased in both serum and lesion samples from vitiligo patients, and its serum level was correlated with the activity of vitiligo. Moreover, restoration of miR-25 promoted the H2O2-induced melanocyte destruction and led to the dysfunction of melanocytes. Further experiments proved that MITF, a master regulator in melanocyte survival and function, accounted for the miR-25-caused damaging impact on melanocytes. Notably, other than the direct role on melanocytes, we observed that miR-25 inhibited the production and secretion of SCF and bFGF from keratinocytes, thus impairing their paracrine protective effect on the survival of melanocytes under oxidative stress. At last, we verified that oxidative stress could induce the overexpression of miR-25 in both melanocytes and keratinocytes possibly by demethylating the promoter region of miR-25. Taken together, our study demonstrates that oxidative stress-induced overexpression of miR-25 in vitiligo has a crucial role in promoting the degeneration of melanocytes by not only suppressing MITF in melanocytes but also impairing the paracrine protective effect of keratinocytes. Therefore, it is worthy to investigate the possibility of miR-25 as a potential drug target for anti-oxidative therapy in vitiligo.

Laser Resurfacing for Latin Skins: The Experience with 665 Cases

BACKGROUND

CO2 resurfacing and CO2 microfractionated laser systems are reliable tools to improve different facial pathologic skin conditions but are associated with a high rate of complications specially in Fitzpatrick III, IV, and V skin phototypes, predominant in the Latin population, which has pushed many surgeons to change technologies and abandon its use.

OBJECTIVE

To compare patient results with the CO2 resurfacing laser and microfractionated CO2 laser resurfacing in all skin types and show similar results to those obtained worldwide in patients with phototypes III, IV, and V.

METHODS

Standardized review of medical records from a database of private practice patients treated since January 1998 to July 2012 with SlimE30 MiXto SX(®) CO2 laser. Evaluation of outcomes, complications, and satisfaction of three different modalities of treatment (CO2 ablative laser, CO2 microfractionated and a combination of both) was made.

RESULTS

A total of 665 treated patients were included. Ablative CO2 was applied to 80.3 %, CO2 microfractionated to 15.1 %, and mixed treatment to 4.5 % of cases. Globally, hyperpigmentation rates were 30.4 % in the CO2 resurfacing group, 16.3 % when a combination of modalities was applied and 11 % in microfractionated CO2 cases. A steady increase of these rates is shown as the phototype becomes higher. Satisfaction rates were high for all groups: 86.7 % in the mixed group, 82.2 % in the microfractionated CO2, and 79.6 % in the CO2 ablative.

CONCLUSIONS

Good results and an acceptable rate of complications in latin skins are obtainable after treating patients with CO2 ablative and microfractionated CO2 systems alone or in combination. Staged treatments and adequate post-procedure care reduce these complications.

Dermatopathology effects of simulated solar particle event radiation exposure in the porcine model

The space environment exposes astronauts to risks of acute and chronic exposure to ionizing radiation. Of particular concern is possible exposure to ionizing radiation from a solar particle event (SPE). During an SPE, magnetic disturbances in specific regions of the Sun result in the release of intense bursts of ionizing radiation, primarily consisting of protons that have a highly variable energy spectrum. Thus, SPE events can lead to significant total body radiation exposures to astronauts in space vehicles and especially while performing extravehicular activities. Simulated energy profiles suggest that SPE radiation exposures are likely to be highest in the skin. In the current report, we have used our established miniature pig model system to evaluate the skin toxicity of simulated SPE radiation exposures that closely resemble the energy and fluence profile of the September, 1989 SPE using either conventional radiation (electrons) or proton simulated SPE radiation. Exposure of animals to electron or proton radiation led to dose-dependent increases in epidermal pigmentation, the presence of necrotic keratinocytes at the dermal-epidermal boundary and pigment incontinence, manifested by the presence of melanophages in the derm is upon histological examination. We also observed epidermal hyperplasia and a reduction in vascular density at 30 days following exposure to electron or proton simulated SPE radiation. These results suggest that the doses of electron or proton simulated SPE radiation results in significant skin toxicity that is quantitatively and qualitatively similar. Radiation-induced skin damage is often one of the first clinical signs of both acute and non-acute radiation injury where infection may occur, if not treated. In this report, histopathology analyses of acute radiation-induced skin injury are discussed.

Visible Light Induces Melanogenesis in Human Skin through a Photoadaptive Response

Visible light (400–700 nm) lies outside of the spectral range of what photobiologists define as deleterious radiation and as a result few studies have studied the effects of visible light range of wavelengths on skin. This oversight is important considering that during outdoors activities skin is exposed to the full solar spectrum, including visible light, and to multiple exposures at different times and doses. Although the contribution of the UV component of sunlight to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology in terms of inflammation, and limited information is available regarding the role of visible light on pigmentation. The purpose of this study was to determine the effect of visible light on the pro-pigmentation pathways and melanin formation in skin. Exposure to visible light in ex-vivo and clinical studies demonstrated an induction of pigmentation in skin by visible light. Results showed that a single exposure to visible light induced very little pigmentation whereas multiple exposures with visible light resulted in darker and sustained pigmentation. These findings have potential implications on the management of photo-aggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions.

Orange peel extract, containing high levels of polymethoxyflavonoid, suppressed UVB-induced COX-2 expression and PGE2 production in HaCaT cells through PPAR-γ activation

Ultraviolet light (UV) induces an inflammatory response in the skin by cyclooxygenase (COX)-2 expression and prostaglandin (PG) E2 production. Citrus peel has been used as a natural medicine. It contains polymethoxyflavonoids (PMFs) as a major ingredient, which have anti-inflammatory activity. We obtained orange peel extract containing high levels of PMFs. The extract suppressed UVB-induced COX-2 expression and PGE2 production in HaCaT cells. Furthermore, it was found that this extract acted as a peroxisome proliferator-activated receptor (PPAR)-γ agonist. The suppression of UVB-induced COX-2 expression by this extract was inhibited by GW 9662 and T0070907, which are both PPAR-γ antagonists. It is therefore suggested that orange peel extract, containing high levels of PMFs, suppresses UVB-induced COX-2 expression and PGE2 production through PPAR-γ. Hence, these extracts could provide useful protection against or alleviation of UV damage.

Calcitonin gene-related peptide cooperates with substance P to inhibit melanogenesis and induces apoptosis of B16F10 cells

Skin is the largest organ in human body and works as biologically active barrier to provide critical preservation of body homeostasis. The skin is highly innervated by a plenitude of nerve fiber subpopulations, each carrying one or more neuronal mediators. Melanocyte itself also intimately contact with nerve fibers to form 'synaptic-like structure' and its functions may be directly regulated by the mediators contained in terminals of intra-epidermal nerve fibers. Clinical and biochemical studies have suggested that calcitonin gene-related peptide (CGRP) is involved in vitiligo skin. The present study was designed to investigate the effect of CGRP on epidermal melanocytes. After treatment with CGRP ranging from 0 to 500 ng/mL for 48 h, tyrosinase activity and melanogenesis were with little changes compared to treatment with medium only in B16F10 cells. Treatment with 500 ng/mL of CGRP cooperates with substance P (SP) (0.1-10 nM) to decrease tyrosinase activity and decrease melanin biosynthesis in B16F10 cells in a concentration-dependent manner. Furthermore, CGRP (8-37) antagonizes the synergistic effect of CGRP. The effect of CGRP on the cell apoptosis was examined. Treatments with 0-500 ng/mL of CGRP for 24 h, the expression levels of cleaved caspase-3, total caspase-3, cleaved caspase-9 and total caspase-9 were increased in a concentration-dependent manner. And 500 ng/mL of CGRP induced B16F10 cell apoptosis showed by TUNEL assay. In addition, Bax expression was up-regulated and Bcl-2 down-regulated in response to CGRP treatment. Hence, the Bax/Bcl-2 ratio was significantly increased. These in vitro observations indicate the pro-apoptotic impact of CGRP on B16F10 cell.

Melasma: a clinical and epidemiological review

Melasma is a chronic acquired hypermelanosis of the skin, characterized by irregular brown macules symmetrically distributed on sun-exposed areas of the body, particularly on the face. It is a common cause of demand for dermatological care that affects mainly women (especially during the menacme), and more pigmented phenotypes (Fitzpatrick skin types III-V). Due to its frequent facial involvement, the disease has an impact on the quality of life of patients. Its pathogeny is not yet completely understood, although there are some known triggering factors such as sun exposure, pregnancy, sexual hormones, inflammatory processes of the skin, use of cosmetics, steroids, and photosensitizing drugs. There is also a clear genetic predisposition, since over 40% of patients reported having relatives affected with the disease. In this manuscript, the authors discuss the main clinical and epidemiological aspects of melasma.

Quercetin-3-O-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranoside suppresses melanin synthesis by augmenting p38 MAPK and CREB signaling pathways and subsequent cAMP down-regulation in murine melanoma cells

In this study, the effect of purified quercetin-3-O-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosid (QCGG) on melanogenesis was investigated. QCGG was isolated from the calyx of a traditional Korean medicinal herb, Persimmon (Diospyros kaki). The hypopigmentation effects of QCGG were determined by examination of cellular melanin contents, tyrosinase activity assay, cAMP assay, and Western blotting of α-MSH-stimulated B16F10 mouse melanoma cells. Our results showed that QCGG inhibited both melanin synthesis and tyrosinase activity in a concentration-dependent manner as well as significantly reduced the expression of melanogenic proteins such as microphthalmia-associated transcription factor (MITF), tyrosinase-related protein-1, tyrosinase-related protein-2, and tyrosinase. Moreover, QCGG inhibited intracellular cAMP levels, cAMP response element-binding protein (CREB), and p38 MAPK expression in α-MSH-stimulated B16F10 cells. Taken together, the suppressive effects of QCGG on melanogenesis may involve down-regulation of MITF and its downstream signaling pathway via phosphorylation of p38 MAPK and CREB along with reduced cAMP levels. These results indicate that QCGG reduced melanin synthesis by reducing expression of tyrosine and tyrosine-related proteins via extracellular signal-related protein kinase (ERK) activation, followed by down-regulation of CREB, p38, and MITF.

ADAM protease inhibitors reduce melanogenesis by regulating PMEL17 processing in human melanocytes

BACKGROUND

ADAMs (a disintegrin and metalloprotease) are a family of proteases involved in ectodomain shedding that play a role in various biological processes such as cell adhesion and migration. ADAM10 and ADAM17 are suggested to be involved in pigmentary disorders.

OBJECTIVE

We examined the effect of ADAM protease inhibitors on the modulation of melanogenesis in normal human epidermal melanocytes (NHEM).

METHODS

NHEMs and B16F10 treated with ADAM protease inhibitors were analyzed. AlamarBlue cell proliferation assay, melanin content assay, tyrosinase activity assay, Western blotting analysis, electron microscopic analysis, and RNA interference were employed.

RESULTS

In NHEMs, melanin content was reduced by treatment with ADAM protease inhibitors. The inhibitors did not change the protein expression of tyrosinase, TRP-1, and MITF. In B16F10 cells, treatment of the cells with ADAM protease inhibitor diminished the α-MSH-induced increase in melanin content. Electron microscopy showed that the number of fibrillar and mature melanosomes was significantly reduced and that the vacuolar compartments were filled with dense unstructured aggregates after treatment with ADAM protease inhibitors. We therefore focused on the processing of PMEL17, a melanosomal glycoprotein that forms a fibrillar matrix on which melanin gets deposited. Proteolytic processing of PMEL17 is required to form functional fibrils during melanogenesis. Recently, γ-secretase and β-site amyloid precursor protein-cleaving enzyme 2 (BACE2) were found to cleave PMEL17. We found that ADAM protease inhibitors exerted effects on the processing of C-terminal and N-terminal fragments of PMEL17. Using BACE2 siRNA and γ-secretase inhibitor, we showed that ADAM protease inhibitor affected PMEL17 processing in a γ-secretase and BACE2-independent mechanism.

CONCLUSION

Several proteases, including ADAM proteases, can contribute to the formation of fibrils and their assembly into sheets in melanosomes.

A potential anti-inflammation activity and depigmentation effect of Lespedeza bicolor extract and its fractions

Postinflammatory hyperpigmentation (PIH) is an acquire hypermelanosis after cutaneous inflammation and injury. The aim of the present study was to investigate a natural ingredient with the anti-inflammatory and depigmentation activities into possible applications of postinflammatory hyperpigmentation. Methanol extracts of Lespedeza bicolor and its various fractions inhibited LPS-induced NO production in RAW 264.7 macrophages in a concentration-dependent manner. In particular, the ethyl acetate fraction was shown to be inhibition of NO production (89%) and down-regulation of iNOS mRNA without causing cytotoxicity. In addition, ethyl acetate fraction significantly attenuated LPS-induced NF-κB activation (P < 0.05), indicating the anti-inflammatory activity due to NF-κB inhibition. Moreover, extracts, mainly ethyl acetate fraction, exhibited not only DPPH free radical scavenging activity (IC₅₀, 112.45 μg/mL) with 4 times lower activity than ascorbic acid, but also anti-tyrosinase activity (IC₅₀, 1 μg/mL) with a similar activity to arbutin showing a competitive inhibitor. Furthermore, vitexin and haginins A, B and C were identified through LC–MS analysis as potential compounds responsible for these effects. These results suggest that L. bicolor extract have anti-inflammatory, antioxidant activities and tyrosinase inhibitory effect and it might be used in the management of postinflammatory pigmentation through inhibition of pathogenic process involved in hyperpigmentation.

Kaliziri extract upregulates tyrosinase, TRP-1, TRP-2 and MITF expression in murine B16 melanoma cells

Background

Kaliziri extract (KZE) is a traditional Uyghur medicine (TUM), used by traditional hospitals in China as an injection for treatment of vitiligo for more than 30 years. Clinical application has shown that this medicine has obvious therapeutic effects. However, its phytochemical analysis and mechanism have not been examined.

Methods

KZE was extracted from seeds of Kaliziri [Vernonia anthelmintica (L.) Willd.] in ethanol-water (80:20, v/v), its components were identified by LC-MS/MS, and the signaling pathway of melanin synthesis in KZE treated murine B16 melanoma cells was examined by western blotting.

Results

Liquid chromatography-mass spectrometry analysis confirmed that the main components of KZE are flavonoids. KZE increased the tyrosinase activity and melanin content in a dose-dependent manner at concentrations of 5-40 μg/ml, and treatment with 20 μg/ml of KZE enhanced the expression of tyrosinase in B16 cells in a time-dependent manner.

Conclusions

KZE induced melanogenesis by increasing the expression of TYR, TRP-1, TRP-2 and MITF in B16 cells.

5-HT1A/1B receptors as targets for optimizing pigmentary responses in C57BL/6 mouse skin to stress

Stress has been reported to induce alterations of skin pigmentary response. Acute stress is associated with increased turnover of serotonin (5-hydroxytryptamine; 5-HT) whereas chronic stress causes a decrease. 5-HT receptors have been detected in pigment cells, indicating their role in skin pigmentation. To ascertain the precise role of 5-HT in stress-induced pigmentary responses, C57BL/6 mice were subjected to chronic restraint stress and chronic unpredictable mild stress (CRS and CUMS, two models of chronic stress) for 21 days, finally resulting in abnormal pigmentary responses. Subsequently, stressed mice were characterized by the absence of a black pigment in dorsal coat. The down-regulation of tyrosinase (TYR) and tyrosinase-related proteins (TRP1 and TRP2) expression in stressed skin was accompanied by reduced levels of 5-HT and decreased expression of 5-HT receptor (5-HTR) system. In both murine B16F10 melanoma cells and normal human melanocytes (NHMCs), 5-HT had a stimulatory effect on melanin production, dendricity and migration. When treated with 5-HT in cultured hair follicles (HFs), the increased expression of melanogenesis-related genes and the activation of 5-HT1A, 1B and 7 receptors also occurred. The serum obtained from stressed mice showed significantly decreased tyrosinase activity in NHMCs compared to that from nonstressed mice. The decrease in tyrosinase activity was further augmented in the presence of 5-HTR1A, 1B and 7 antagonists, WAY100635, SB216641 and SB269970. In vivo, stressed mice received 5-HT precursor 5-hydroxy-l-tryptophan (5-HTP), a member of the class of selective serotonin reuptake inhibitors (fluoxetine; FX) and 5-HTR1A/1B agonists (8-OH-DPAT/CP94253), finally contributing to the normalization of pigmentary responses. Taken together, these data strongly suggest that the serotoninergic system plays an important role in the regulation of stress-induced depigmentation, which can be mediated by 5-HT1A/1B receptors. 5-HT and 5-HTR1A/1B may constitute novel targets for therapy of skin hypopigmentation disorders, especially those worsened with stress.

The use of sunscreen starting on the first day after ablative fractional skin resurfacing

BACKGROUND

The most common side-effect of ablative fractional skin resurfacing in Asians is post inflammatory hyperpigmentation (PIH). Various attempts have been made to reduce the occurrence of PIH after laser treatment including sun avoidance, the use of preoperative and postoperative treatment regimens, and treatment using conservative energy settings and epidermal protection.

OBJECTIVES

To determine whether the use of broad-spectrum sunscreen with anti-inflammatory agents starting on the first day after fractional CO2 laser skin resurfacing reduces the incidence of post laser PIH.

MATERIALS AND METHODS

Thirty patients were treated with ablative fractional CO2 resurfacing on both sides of their faces at 10 mJ and 10% density. Each subject was randomly treated on one side of the face with petrolatum ointment four times a day for the first week after laser treatment and on the other side of the face with petrolatum ointment four times a day plus broad-spectrum sunscreen with anti-inflammatory agents in the morning starting on the first day after laser treatment. Transepidermal water loss was recorded at baseline and every day for 1 week. Melanin and erythema indexes were measured at baseline, 1-, 2-week, 1-, 2- and at 3-month post treatment.

RESULTS

Of the 30 patients involved in the study, 26 received the treatment and attended 1-, 2-week, 1-, 2- and 3-month post-treatment visits. Four patients were withdrawn from the study because they could not attend every follow-up visit. There was no statistically significant difference in transepidermal water loss at baseline, immediately after laser treatment, or at the D1 to D7 follow-up visits. Erythema index had no significantly statistical difference at baseline, 1-, 2- and at 3-month after laser treatment. Furthermore, there was a statistically significant difference in melanin index at 1-week post laser treatment between both sides (P = 0.001). Melanin index at the 1-week follow-up visit on the side treated with broad-spectrum sunscreen with anti-inflammatory agents starting on the first day after laser treatment was significantly less than the control side.

CONCLUSION

The use of broad-spectrum sunscreen with anti-inflammatory agents starting on the first day after ablative fractional skin resurfacing can decrease the incidence of PIH after laser treatment at 1-week postoperatively.

The use of botanically derived agents for hyperpigmentation: a systematic review

BACKGROUND

Hyperpigmentation disorders are common among those seeking care from dermatologists and primary care physicians. The cosmeceutical and natural product industries are rapidly growing and many botanical agents are purported to improve hyperpigmentation disorders.

OBJECTIVE

We sought to review clinical evidence for the use of botanical agents in the treatment of hyperpigmentation.

METHODS

We searched MEDLINE and Embase databases and a total of 26 articles met inclusion criteria. Study methodology was analyzed and the reproducibility of the studies was graded.

RESULTS

Several botanical agents appear promising as treatment options but few studies were methodologically rigorous. Several plant extract and phytochemicals effectively lighten signs of epidermal melasma and hyperpigmentation induced by ultraviolet radiation exposure. Results were mixed for treatment of solar lentigines or dermal hyperpigmentation.

LIMITATIONS

There were few rigorously designed studies; future research will be critical to further ascertain the discussed results.

CONCLUSIONS

The subtype of hyperpigmentation is important for treatment prognosis, with dermal hyperpigmentation less responsive to treatment. Botanical extracts may play an integrative role in the treatment of hyperpigmentation and further studies that integrate them with standard therapies are needed. Side effects, including worsened hyperpigmentation, need to be discussed when considering these therapies.

Inhibition of melanogenesis by gallic acid: possible involvement of the PI3K/Akt, MEK/ERK and Wnt/β-catenin signaling pathways in B16F10 cells

Gallic acid is one of the major flavonoids found in plants. It acts as an antioxidant, and seems to have anti-inflammatory, anti-viral, and anti-cancer properties. In this study, we investigated the effects of gallic acid on melanogenesis, including the activation of melanogenesis signaling pathways. Gallic acid significantly inhibited both melanin synthesis and tyrosinase activity in a dose- and time-dependent manner, and decreased the expression of melanogenesis-related proteins, such as microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein-1 (TRP1), and dopachrome tautomerase (Dct). In addition, gallic acid also acts by phosphorylating and activating melanogenesis inhibitory proteins such as Akt and mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK). Using inhibitors against PI3K/Akt (LY294002) or MEK/ERK-specific (PD98059), the hypopigmentation effect was suppressed, and the gallic acid-initiated activation of MEK/ERK and PI3K/Akt was also revoked. Gallic acid also increased GSK3β and p-β-catenin expression but down-regulated p-GSK3β. Moreover, GSK3β-specific inhibitor (SB216763) restored gallic acid-induced melanin reduction. These results suggest that activation of the MEK/ERK, PI3K/Akt, and inhibition of Wnt/β-catenin signaling pathways is involved in the melanogenesis signaling cascade, and that activation by gallic acid reduces melanin synthesis via down-regulation of MITF and its downstream signaling pathway. In conclusion, gallic acid may be a potentially agent for the treatment of certain skin conditions.

Enhancement of the p38 MAPK and PKA signaling pathways is associated with the pro-melanogenic activity of Interleukin 33 in primary melanocytes

BACKGROUND

Interleukin-33 (IL-33) was recently recognized as a member of the IL-1 cytokine family. The triggers no matter environmental or endogenous that provoke IL-33 cellular release may be associated with inflammation, infection or tissue damage. However, to date, the regulatory role of IL-33 in the control of melanogenesis has not been elucidated.

OBJECTIVE

The present study was designed to investigate the effect of IL-33 on melanogenesis and to explore its underlying mechanisms.

METHODS

Melanocytes were exposed to IL-33. Then cell viabilities were measured by MTT assay. The improving activities of IL-33 were examined by melanin synthesis, tyrosinase (TYR) activity assay. The expressions of relative proteins were assessed by Western blotting.

RESULTS

IL-33 increased the TYR activity and melanin content in a dosage-dependent manner at concentrations of 1-10ng/ml. Treatment with 10ng/ml of IL-33 enhanced the expression of microphthalmia-associated transcription factor (MITF), TYR, tyrosinase-related protein 1 (TRP-1) and dopachrome tautomerase (DCT) in normal human foreskin-derived epidermal melanocytes (NHEM). Furthermore, IL-33 could remarkably promote the phosphorylation levels of p38 mitogen-activated protein kinases (MAPKs) and cyclic AMP-responsive element-binding protein (CREB). This pro-melanogenic effect could be partially reversed by the pre-treatment with the special p38 MAPK inhibitor, SB203580, and protein kinase A (PKA) inhibitor, H89.

CONCLUSIONS

Our results collectively indicated that IL-33 improved melanin biosynthesis in NHEM. This function might be attributed to the fact that IL-33 stimulates the phosphorylation of p38 MAPK and CREB, increases the TYR, TRP-1 and DCT expression through MITF, finally resulting in the augment of melanogenesis.

Tranexamic acid: an important adjuvant in the treatment of melasma

This article reviews an old drug tranexamic acid to its new use in the treatment of melasma. Its mechanism of preventing the activation of melanocyte from UV light, hormone and injured kerationcyte through the inhibition of the plasminogen activator system will be explored. The detail usage for such indication and its safety profile will also be thoroughly evaluated.

Octaphlorethol A isolated from Ishige foliacea inhibits α-MSH-stimulated induced melanogenesis via ERK pathway in B16F10 melanoma cells

In this study, the potent skin-whitening effects of Octaphlorethol A (OPA) isolated from Ishige foliacea was investigated through inhibitory effect of melanin synthesis and tyrosinase activity in alpha-melanocyte stimulating hormone (α-MSH) induced B16F10 melanoma cells. OPA markedly inhibited melanin synthesis and tyrosinase activity in a concentration-dependent manner. We also found that OPA decreased microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein-1 and -2 (TRP-1 and TRP-2) protein expressions. Moreover, OPA reduces p38 MAPK protein levels and activates extracellular signal-regulated kinase (ERK) and c-jun N-terminal kinases (JNKs) protein expressions in B16F10 cells. A specific ERK inhibitor PD98059 significantly blocks OPA-inhibited melanin synthesis and tyrosinase activity, whereas a p38MAP and JNK inhibitor had no effect. These findings provide evidence demonstrating that the anti-melanogenic effect of OPA is mediated through the activation of ERK signal pathway in B16F10 cells. These results indicate that OPA has the potential to be used as a melanogenesis inhibitor in the food and cosmetics industry.

Topical niacinamide 4% and desonide 0.05% for treatment of axillary hyperpigmentation: a randomized, double-blind, placebo-controlled study

Background

Axillary hyperpigmentation is a frequent cause of cosmetic consultations in dark-skinned women from tropical areas, including Latin America. Currently, there is no widely accepted treatment for the disorder, but it is usually treated with bleaching agents because it is considered a variant of inflammatory hyperpigmentation. The purpose of this study was to assess the efficacy of niacinamide 4% and desonide 0.05% emulsions compared with placebo in the treatment of axillary hyperpigmentation.

Methods

Twenty-four women aged 19–27 years with hyperpigmented axillae (phototype III–V) were randomly assigned to receive the study treatments in the axillary region. Improvement was assessed at baseline, then clinically and by colorimetry 9 weeks later. Quantitative evaluation including melanin, inflammatory infiltrates, NKI/Beteb, CD1a, CD68, and collagen type IV content was performed by histochemistry and immunohistochemistry, assisted by computerized morphometric analysis.

Results

Both niacinamide and desonide induced significant colorimetric improvement compared with placebo; however, desonide showed a better depigmenting effect than niacinamide. A good to excellent response was achieved in 24% of cases for niacinamide, 30% for desonide, and 6% for placebo. We observed a marked disruption of the basal membrane in axillary hyperpigmentation and an inflammatory infiltrate that improved after treatment. Decreased pigmentation in the desonide-treated axillae was associated with recovery of disruption at the basal membrane.

Conclusion

Niacinamide and desonide showed depigmenting properties in women with axillary hyperpigmentation. These findings may be explained by their antimelanogenic and anti-inflammatory properties, respectively.

Interleukin-18 augments growth ability of primary human melanocytes by PTEN inactivation through the AKT/NF-κB pathway

Normal human skin relies on melanocytes to provide photoprotection and thermoregulation by producing melanin. The growth and behavior of melanocytes are controlled by many factors. Interleukin-18 (IL-18) is expressed in both immune and non-immune cells and participates in the adjustment of multitude cellular functions. Nonetheless, the regulative roles of IL-18 in melanogenesis and growth of melanocytes have not been explored. The present study was conducted to investigate the effects of IL-18 on melanocytes and elucidate the underlying mechanisms. We proved that IL-18 increased the tyrosinase activity and melanin content in normal human foreskin-derived epidermal melanocytes (NHEM). Treatment with IL-18 (20 ng/ml) enhanced the expression of c-Kit, microphtalmia-associated transcription factor (MITF) and its downstream tyrosinase-related protein 1 (TRP-1), and TRP-2. In addition, IL-18 induced NHEM migration at concentration of 20 ng/ml. These results indicated a promotive action of IL-18 on melanogenesis in NHEM. Our data revealed that IL-18 stimulated ERK1/2 and NF-κB activation, improved p-Akt, p70 S6K and anti-apoptotic Bcl-2 levels, and deactivated phosphatase and tensin homolog deleted on chromosome 10 (PTEN) in NHEM. Besides, IL-18 increased level of PTEN phosphorylation to protect NHEM from damage induced by H(2)O(2). These results in vitro showed the accommodation of IL-18 in melanocytes growth. Therefore, we suggested an important regulating action of IL-18 to melanogenesis and cell growth ability of skin melanocytes.

Alcohol extract from Vernonia anthelmintica (L.) willd seed enhances melanin synthesis through activation of the p38 MAPK signaling pathway in B16F10 cells and primary melanocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Vernonia anthelmintica (L.) willd has been used in folk medicine to treat leukoderma in China for centuries. The promoting activities of its extract (AVE) in melanogenesis and possible signaling pathways were investigated in this article.

MATERIALS AND METHODS

The improving activities of AVE were examined by melanin synthesis, tyrosinase activity assay and Western blot in B16F10 mouse melanoma cells and normal human primary melanocytes (NHMC).

RESULTS

AVE increased the tyrosinase activity and melanin content in a dosage-dependent manner at concentrations of 1-40 μg/ml and treatment with 20 μg/ml AVE enhanced the expression of tyrosinase time-dependently in both B16F10 cells and NHMC. Whether AVE affects the expression of microphthalmia-associated transcription factor (MITF), which is required for tyrosinase expression, was investigated. Our results showed that AVE induced MITF protein expression up-regulation. Besides, Western blot analysis revealed that AVE promoted the level of phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) markedly at 0-6 h, while the level of phosphorylation of CREB at 0-2 h. The special p38 MAPK inhibitor, SB203580, and protein kinase A (PKA) inhibitor, H89, both attenuated the AVE-induced up-regulation of MITF and tyrosinase expression in B16F10 cells and NHMC. However, SB203580 could significantly decrease the melanin biosynthesis induced by AVE, but not H89.

CONCLUSION

AVE exerts its improving effect on melanogenesis mainly by p38 MAPK activation and MITF induction of tyrosinase.

β-Gal gene expression MRI reporter in melanoma tumor cells. Design, synthesis, and in vitro and in vivo testing of a Gd(III) containing probe forming a high relaxivity, melanin-like structure upon β-Gal enzymatic activation

The aim of this work is to design and test an MRI probe (Gd-DOTAtyr-gal) able to report on the gene expression of β-galactosidase (β-Gal) in melanoma cells. The probe consists of a Gd-DOTA reporter bearing on its surface a tyrosine-galactose-pyranose functionality that, upon the release of the sugar moiety, readily transforms, in the presence of tyrosinase, into melanin oligomeric/polymeric mixture. The formation of Gd-DOTA-containing melanin oligomers and polymers is accompanied by a marked increase of the water proton relaxation rate. The steps involving the release of the galactose-pyranose group and the formation of the melanin-like structure have been carefully investigated in vitro by relaxometric and UV-vis measurements. Cellular uptake studies of Gd-DOTAtyr-gal by melanoma cells have shown that the probe enters the cells, and it appears not to be confined in endosomal vesicles. Using B16-F10LacZ transfected cells, the fast formation of paramagnetic melanin-Gd(III)-containing species has been assessed by the measurement of increased longitudinal relaxation rates of the cellular pellets suspensions. The in vitro results have been confirmed in in vivo MRI investigations on murine melanoma tumor bearing mice. Upon direct injection of Gd-DOTAtyr-gal, a good contrast is observed after 5 h post injection in B16-F10LacZ tumors, but not in B16-F10 tumors lacking the β-Gal enzyme. Gd-DOTAtyr-gal in combination with tyrosinase introduces a novel approach for the detection of β-Gal expression by MRI in vivo.

Melanin and melanogenesis in adipose tissue: possible mechanisms for abating oxidative stress and inflammation?

Obesity has become a worldwide epidemic and can lead to multiple chronic diseases. Adipose tissue is increasingly thought to play an active role in obesity-related pathologies such as insulin resistance and non-alcoholic fatty liver disease. Obesity has been strongly associated with systemic inflammation and, to a lesser degree, with oxidative stress, although the causal relationships among these factors are unclear. A recent study demonstrating an expression of the components of the melanogenic pathway and the presence of melanin in visceral adipose has raised questions regarding the possible role of melanogenesis in adipose tissue. As this study also found larger amounts of melanin in the adipose tissue of obese patients relative to lean ones, we hypothesize that melanin, a pigment known for its antioxidant and anti-inflammatory properties, may scavenge reactive oxygen species and abate oxidative stress and inflammation in adipose tissue. This review considers the evidence to support such a hypothesis, and speculates on the role of melanin within adipocytes. Furthermore, we consider whether the α-melanocyte-stimulating hormone or its synthetic analogues could be used to stimulate melanin production in adipocytes, should the hypothesis be supported in future experiments.

Postinflammatory hyperpigmentation: etiologic and therapeutic considerations

Postinflammatory hyperpigmentation (PIH) is a reactive hypermelanosis and sequela of a variety of inflammatory skin conditions. PIH can have a negative impact on a patient's quality of life, particularly for darker-skinned patients. Studies show that dyschromias, including PIH, are one of the most common presenting complaints of darker-skinned racial ethnic groups when visiting a dermatologist. This is likely due to an increased production or deposition of melanin into the epidermis or dermis by labile melanocytes. A variety of endogenous or exogenous inflammatory conditions can culminate in PIH and typically most epidermal lesions will appear tan, brown, or dark brown while dermal hypermelanosis has a blue-gray discoloration. Depigmenting agents target different steps in the production of melanin, most commonly inhibiting tyrosinase. These agents include hydroquinone, azelaic acid, kojic acid, arbutin, and certain licorice (glycyrrhiza) extracts. Other agents include retinoids, mequinol, ascorbic acid (vitamin C), niacinamide, N-acetyl glucosamine, and soy, and these products depigment by different mechanisms. Certain procedures can also be effective in the treatment of PIH including chemical peeling and laser therapy. It is important to note that these same therapeutic modalities may also play a role in causing PIH. Lastly, those lesions that are not amenable to medical or surgical therapy may experience some improvement with cosmetic camouflage.

Inhibitory effects of 1-O-methyl-fructofuranose from Schisandra chinensis fruit on melanogenesis in B16F0 melanoma cells

AIM OF THE STUDY

1-O-methyl-fructofuranose (1-O-MFF) from the fruit of Schisandra chinensis is a traditional Korean medicinal herb that has a variety of beneficial properties. The effect of purified 1-O-MFF on melanogenesis including the activation of related signaling pathways was investigated.

MATERIALS AND METHODS

The inhibitory activities of 1-O-MFF were examined by melanin synthesis, tyrosinase activity assay, Western blot and flow cytometric analyses in B16F0 mouse melanoma cells.

RESULTS

1-O-MFF significantly inhibited both melanin synthesis and tyrosinase activity in a concentration-dependent manner, and reduced the expression of melanogenic proteins including microphthalmia-associated transcription factor (MITF), tyrosinase and tyrosinase-related protein-1. 1-O-MFF phosphorylated and activated melanogenesis inhibitory proteins such as mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) and Akt. Flow cytometry confirmed that 1-O-MFF phosphorylated ERK and Akt proteins and recovered partially phosphorylated forms in cells treated with the MEK/ERK inhibitor compound PD98059 and the phosphatidylinositol 3-kinase (PI3K)/Akt inhibitor compound LY294002.

CONCLUSIONS

The suppressive effects of 1-O-MFF on melanogenesis may involve down-regulation of MITF and its downstream signal pathway via the activation of MEK/ERK or PI3K/Akt.