Sunscreen Practices and Preferences of Skin of Color Patients.

Sunscreen is an essential way to protect against photodamage from ultraviolet (UV) radiation. Despite the recognized benefits of sunscreen in preventing skin damage from UV light, its use varies across different patient groups. This cross-sectional, questionnaire-based study aims to uncover the sunscreen usage patterns, preferences, and barriers among non-Hispanic White (NHW) and skin of color (SOC) individuals. Our findings demonstrate that NHW individuals are more likely to wear sunscreen daily (31% NHW vs 25% SOC) and reapply sunscreen at least once a day (76% NHW vs 45% SOC) compared with SOC individuals. SOC individuals demonstrate a willingness to use sunscreen, but they face barriers such as cost (2% NHW vs 16% SOC), lack of knowledge in finding suitable products (22% NHW vs 41% SOC), and concerns about white cast (7% NHW vs 25% SOC). SOC individuals are less likely to know the difference between mineral and chemical sunscreen (49% NHW vs 29% SOC), less likely to learn about sunscreen from dermatologists (36% NHW vs 22% SOC), and more likely to prefer sunscreen from brands owned by people of color (13% NHW vs 47% SOC).  In addition to analyzing the broader categories of NHW and SOC, subgroup analysis was conducted on specific subgroups, including Black, Asian, and Hispanic groups. Herein, we highlight differences in motivations, sunscreen preferences, sources of information, and knowledge levels about sun protection between NHW and SOC individuals. By uncovering the unique needs and challenges faced by SOC individuals, we aim to improve culturally competent patient education and promote effective sun protection practices across diverse populations. J Drugs Dermatol. 2024;23(6):456-462.     doi:10.36849/JDD.8268.

An Open-label Study to Investigate the Efficacy and Tolerability of Dapsone Gel, 7.5% in the Treatment of Acne Vulgaris in Men and Women With Skin of Color.

INTRODUCTION: Acne vulgaris is a common skin disease prevalent in skin of color patients. Studies have demonstrated that dapsone gel, 7.5% (Aczone) used once daily is effective, safe, and well-tolerated for the treatment of acne in both men and women. However, minimal data are available in skin of color populations. This single-center, open-label clinical study investigated the efficacy and safety of dapsone gel, 7.5% in the treatment of moderate to severe acne vulgaris in patients with Fitzpatrick skin types IV-VI. METHODS: Twenty (20) adult subjects with moderate to severe acne and Fitzpatrick skin types IV-VI were enrolled in this study and treated with dapsone gel, 7.5% once daily for 24 weeks. RESULTS: Dapsone gel, 7.5% applied daily for 24 weeks reduced acne severity, post-inflammatory hyperpigmentation, and decreased new inflammatory and noninflammatory acne lesions in skin of color patients with moderate to severe acne vulgaris. Treatment resulted in improved acne health-related quality of life and patient symptoms related to acne, including patient-reported post-inflammatory hyperpigmentation, especially with a treatment duration of 18 weeks or longer.  Limitations: The sample size was small and underpowered to detect statistically significant changes in some endpoints. CONCLUSION: Dapsone gel 7.5% was safe, well-tolerated, and efficacious in treating acne vulgaris and post-inflammatory hyperpigmentation in skin-of-color patients. Larger studies involving skin-of-color populations with acne vulgaris are warranted. J Drugs Dermatol. 2024;23(6):410-417. doi:10.36849/JDD.7897.

Editor's Highlights - June 2024.

Acne and hidradenitis suppurativa (HS) are chronic inflammatory skin conditions that significantly impact patients' quality of life. In the June issue of the Journal, we highlight the challenges in treating acne in skin of color (SOC) patients. Recent studies focusing on trifarotene, a selective retinoic acid receptor gamma agonist, demonstrated significant improvements in acne severity and postinflammatory hyperpigmentation in SOC patients. We will also delve into the early and aggressive treatment of HS and highlight a link between HS and increased cardiovascular risk. These insights demand a paradigm shift toward a more proactive and holistic management of HS, integrating skin and systemic health considerations to enhance patient outcomes significantly.

Exploring the Influence of Cold Plasma on Epidermal Melanogenesis In Situ and In Vitro.

Epidermal melanin synthesis determines an individual's skin color. In humans, melanin is formed by melanocytes within the epidermis. The process of melanin synthesis strongly depends on a range of cellular factors, including the fine-tuned interplay with reactive oxygen species (ROS). In this context, a role of cold atmospheric plasma (CAP) on melanin synthesis was proposed due to its tunable ROS generation. Herein, the argon-driven plasma jet kINPen® MED was employed, and its impact on melanin synthesis was evaluated by comparison with known stimulants such as the phosphodiesterase inhibitor IBMX and UV radiation. Different available model systems were employed, and the melanin content of both cultured human melanocytes (in vitro) and full-thickness human skin biopsies (in situ) were analyzed. A histochemical method detected melanin in skin tissue. Cellular melanin was measured by NIR autofluorescence using flow cytometry, and a highly sensitive HPLC-MS method was applied, which enabled the differentiation of eu- and pheomelanin by their degradation products. The melanin content in full-thickness human skin biopsies increased after repeated CAP exposure, while there were only minor effects in cultured melanocytes compared to UV radiation and IBMX treatment. Based on these findings, CAP does not appear to be a useful option for treating skin pigmentation disorders. On the other hand, the risk of hyperpigmentation as an adverse effect of CAP application for wound healing or other dermatological diseases seems to be neglectable.

Serpentine supravenous hyperpigmentation induced by chemotherapy: a systematic review.

Serpentine supravenous hyperpigmentation (SSH) describes increased skin pigmentation that develops in the area immediately overlying the vessels through which chemotherapeutic drugs are administered. While SSH can be cosmetically distressing and there are no definitive management options, the literature is severely limited and the variations in clinical presentation, risk factors, and histopathology of SSH across patients are not well understood. We aimed to systematically summarize characteristics from current available data, and thus improve SSH awareness and management. A literature search was conducted in PubMed using specific eligibility criteria through the end of December 2022. Included articles focused on patients who experienced SSH after chemotherapy infusion. Study quality was assessed using a modified Oxford Centre for Evidence-Based Medicine quality rating scheme. Of the 41 articles identified by literature search, 24 met eligibility criteria. Two additional articles were identified through the reference sections of retrieved articles, for 26 articles total. All articles were case reports, representing 28 patients total. Locations of SSH were mostly in the forearm near the site of injection (85%), and the most common associated symptom was erythema. Histopathologic analysis was available for half of cases, the majority of which were inflammatory in nature. The most common inflammatory pattern observed was a vacuolar/lichenoid interface dermatitis. Duration of SSH ranged from days to > 1 year after the chemotherapy was stopped. Six (21%) patients were managed with topical steroids and oral vasodilators, six (21%) patients switched to central venous infusion rather than peripheral infusion, five (18%) patients received only supportive care, three (11%) patients received venous washing with chemotherapy, three (11%) patients stopped chemotherapy, and one (4%) patient reduced the chemotherapy dosage. Ten (36%) patients attained complete resolution, seven (25%) had SSH that was near resolution/fading, and three (11%) had persistent hyperpigmentation. Although SSH often spontaneously resolves once the chemotherapeutic agent is stopped, it can persist in some patients and cause significant distress. As the literature is severely limited and there are no definitive treatments, additional research using more standardized definitions and methods of assessments is necessary to improve characterization of SSH and evaluate potential interventions.

Understanding the perception of sunscreen utility in African Americans.

Dyschromia is a top diagnosis among African Americans (AA). Sunscreen is an essential part of its management, but AA have low sunscreen use. We sought to examine the perception of sunscreen utility in dyschromia and photoaging among patients who identify as AA or Black. This cross-sectional study recruited participants from the Case Western Reserve University Academic Dental Clinic. Participants completed an electronic survey that contained questions related to sunscreen use, knowledge of the sun's role in hyperpigmentation and photoaging, and whether sunscreen could be used for hyperpigmentation and photoaging. Of the 151 participants recruited, 63.6% (n = 96) were women and 36.4% (n = 57) were men. Consistent with previous reports, participants had lower sunscreen use (20.5%) than whites (43.5%). The majority of participants (80.1% and 58.3%, respectively) didn't attribute the sun to hyperpigmentation or photoaging. Participants with dark/brown spots were significantly more likely to not attribute the sun to hyperpigmentation than those without spots. (p = 0.003) Limitations for this study include its small sample size, recall and reporter bias, question misinterpretation, and lack of question neutrality. This study highlights the knowledge gap of a major contributing factor to dyschromia which in turn could be leading to their view of the decreased utility of sunscreen.

Role of kinin receptors in skin pigmentation.

Previous studies have shown that all kinin system is constitutively expressed in the normal and inflamed skin, with a potential role in both physiological and pathological processes. However, the understanding regarding the involvement of the kinin system in skin pigmentation and pigmentation disorders remains incomplete. In this context, the present study was designed to determine the role of kinins in the Monobenzone (MBZ)-induced vitiligo-like model. Our findings showed that MBZ induces higher local skin depigmentation in kinin receptors knockout mice (KOB1R, KOB2R and KOB1B2R) than in wild type (WT). Remarkably, lower levels of melanin content and reduced ROS generation were detected in KOB1R and KOB2R mice treated with MBZ. In addition, both KOB1R and KOB2R show increased dermal cell infiltrate in vitiligo-like skin, when compared to WT-MBZ. Additionally, lack of B1R was associated with greater skin accumulation of IL-4, IL-6, and IL-17 by MBZ, while KOB1B2R presented lower levels of TNF and IL-1. Of note, the absence of both kinin B1 and B2 receptors demonstrates a protective effect by preventing the increase in polymorphonuclear and mononuclear cell infiltrations, as well as inflammatory cytokine levels induced by MBZ. In addition, in vitro assays confirm that B1R and B2R agonists increase intracellular melanin synthesis, while bradykinin significantly enhanced extracellular melanin levels and proliferation of B16F10 cells. Our findings highlight that the lack of kinin receptors caused more severe depigmentation in the skin, as well as genetic deletion of both B1/B2 receptors seems to be linked with changes in levels of constitutive melanin levels, suggesting the involvement of kinin system in crucial skin pigmentation pathways.

Importance of treating acne sequelae in skin of color: 6-month phase IV study of trifarotene with an appropriate skincare routine including UV protection in acne-induced post-inflammatory hyperpigmentation.

BACKGROUND: Acne-induced hyperpigmentation (AIH) may accompany acne vulgaris (AV) inflammation in all skin phototypes. Trifarotene has shown depigmenting properties in vivo. This study evaluated trifarotene plus skincare because it is increasingly recognized that holistic AV management should include skincare and treatments. METHODS: This is a phase IV double-blind, parallel-group study of patients (13-35 years) with moderate AV and AIH treated with trifarotene (N = 60) or vehicle (N = 63) plus skincare regimen (moisturizer, cleanser, and sunscreen) for 24 weeks. Assessments included the AIH overall disease severity (ODS) score, post-AV hyperpigmentation index (PAHPI), exit interviews, photography, and acne assessments. Standard safety assessments were included. RESULTS: Trifarotene 50 µg/g cream improved significantly from baseline in ODS score versus vehicle (-1.6 vs. -1.1, P = 0.03) at Week 12, but scores were comparable between groups at Week 24 (primary endpoint). Trifarotene had a better reduction in PAHPI score at Week 24 (-18.9% vs. -11.3% vehicle, P < 0.01). Lesion count reductions were higher with trifarotene at Week 12 versus vehicle (P < 0.001) and at Week 24 (P < 0.05), as were IGA success rates versus vehicle at Weeks 12 (P < 0.05) and 24 (P < 0.05). Patients agreed that the skincare regimen contributed to less irritation, making treatment adherence easier. Photography showed improvements in pigmentation and erythema across all skin types. AEs were more common in the vehicle group versus trifarotene (30.2 vs. 16.7%, respectively). CONCLUSIONS: In all skin phototypes, there was more rapid improvement in the ODS and PAHPI scores with trifarotene by Weeks 12 and 24, respectively. The combination of trifarotene and skincare correlated with high patient satisfaction and adherence to the treatment protocol.

Newly identified peptide Nigrocin-OA27 inhibits UVB induced melanin production via the MITF/TYR pathway.

Melasma is a common skin disease induced by an increase in the content of melanin in the skin, which also causes serious physical and mental harm to patients. In this research, a novel peptide (Nigrocin-OA27) from Odorrana andersonii is shown to exert a whitening effect on C57 mice pigmentation model. The peptide also demonstrated non-toxic and antioxidant capacity, and can significantly reduce melanin content in B16 cells. Topical application effectively delivered Nigrocin-OA27 to skin's epidermal and dermal layers and exhibited significant preventive and whitening effects on the UVB-induced ear pigmentation model in C57 mice. The whitening mechanism of Nigrocin-OA27 may be related to reduced levels of the microphthalmia-associated transcription factor and the key enzyme for melanogenesis-tyrosinase (TYR). Nigrocin-OA27 also inhibited the catalytic activity by adhering to the active core of TYR, thereby reducing melanin formation and deposition. In conclusion, Nigrocin-OA27 may be a potentially effective external agent to treat melasma by inhibiting aberrant skin melanin synthesis.

Evaluation of efficacy and safety of vitiligo treatment with micro-needling combined with N-Acetylcysteine and micro-needling alone: A double-blinded randomized controlled clinical trial.

INTRODUCTION: Vitiligo is a skin pigmentation disorder caused by the selective degradation of melanocytes. This study investigates the therapeutic effects of microneedling with and without N-acetylcysteine (NAC) in patients with persistent and limited vitiligo. METHOD: This research employed a clinical trial design with double-blind randomization. Individuals affected by vitiligo and seeking treatment at Rasool Akram Medical Complex were divided into two separate treatment groups. In the intervention group, 24 affected areas underwent meso-microneedling using 5% NAC ampoules over six sessions, in addition to the application of 4.7% NAC cream once daily on the specified area. Conversely, the control group, consisting of 22 lesions, underwent microneedling using distilled water during six sessions. The severity of lesions and the extent of repigmentation were gauged using the Modified VETI Score. Assessment of treatment efficacy was determined through both physician evaluations and patient feedback. RESULTS: Twenty patients with a mean age of 36.4 years were recruited. The mean percentage of lesions and their intensity were significantly improved 2 weeks after the third session and 1 month after the end of the treatment (p < 0.01). There was no statistically significant difference between the intervention and control groups. Gender, age, family history, duration of disease, duration of disease stability, and history of hypothyroidism had no statistically significant relationship with patients' treatment outcomes (p > 0.05). CONCLUSION: Microneedling with or without the application of NAC appears to be an effective treatment option for persistent vitiligo lesions. However, despite the higher improvement rate with the application of NAC, the difference was not significant.

Efficacy and tolerability of a depigmenting gel serum comprising tranexamic acid, niacinamide, 4-butylresorcinol, phytic acid, and a mixture of hydroxy acids that targets the biological processes regulating skin melanogenesis.

BACKGROUND: The diverse causes of hyperpigmentation and complex nature of melanogenesis make it a challenge to manage. Current approaches either fail to deliver effective pigmentation control or have undesirable safety profiles that preclude their long-term use. AIMS: To evaluate the capacity of a cosmetic gel serum comprising tranexamic acid, niacinamide, 4-butylresorcinol, phytic acid, and a mixture of hydroxy acids that was designed to target the biological processes regulating skin melanogenesis to attenuate melanin production in vitro and reduce hyperpigmentation clinically. METHODS: Capacity to reduce melanin production in vitro was determined in melanocyte-containing reconstructed human epidermis (RHEm). Clinical efficacy and skin tolerability following twice daily application were assessed in 35 subjects with slight to moderate facial hyperpigmentation by instrumental (VISIA®-CR, Mexameter®) and clinical (mMASI, clinical score, IGA for hyperpigmentation) evaluation on D14, D28, D56, and D84. Maintenance of pigmentation control was followed up 1 month after cessation of treatment on D112. RESULTS: In RHEm in vitro, melanin production was reduced by 50.0% from baseline (D0) on D14 (p < 0.001) and by 67.0% on D21 (p < 0.001). Clinical reductions from baseline in brown spots count (-9.0%; p < 0.05), brown spots area (-16.7%; p < 0.001), and the melanin index (-11.4%; p < 0.001) were observed within 14 days of use. Statistically significant improvements in all clinical parameters were achieved by D28. By the end of treatment on D84, the number and surface area of brown spots were reduced by 28.4% and 40.3% compared to D0, respectively (p < 0.001, both), the melanin index was reduced by 31.1% (p < 0.001), mMASI was reduced by 63.0% (p < 0.001), and skin luminosity was increased by 79.0% (p < 0.001). IGA was reduced from 2.3 on D0 to 1.3 on D84 (p < 0.001). Improvements to all these parameters were maintained until D112, 1 month after termination of treatment. The product also demonstrated very good skin tolerability. CONCLUSION: A gel serum comprising tranexamic acid, niacinamide, 4-butylresorcinol, and hydroxy acids, designed to target the biological processes regulating skin melanogenesis, demonstrates rapid, robust, and sustained pigmentation control in this cohort.

2-Mercaptonicotinoyl glycine prevents UV-induced skin darkening and delayed tanning in healthy subjects: A randomized controlled clinical study.

BACKGROUND: Chronic nonextreme sun exposure induces two mechanisms of skin pigmentation, causing immediate darkening and delayed tanning. A new molecule, 2-mercaptonicotinoyl glycine (2-MNG), has been shown in vitro to inhibit both immediate darkening and new melanin synthesis via covalent conjugation of the thiol group of 2-MNG to melanin precursors. OBJECTIVE: To evaluate 2-MNG in preventing both mechanisms in vivo. METHODS: In a randomized, intra-individual and controlled study, 33 subjects with melanin-rich skin were exposed to UV daylight on designated areas on the back and treated with a cosmetic formula containing 0.5% or 1% 2-MNG alone or 0.5% 2-MNG in association with lipohydroxy acid (LHA, 0.3%) plus Mexoryl-SX (MSX, 1.5%). The respective vehicles were used as controls and 4-n-butyl-resorcinol (4-n-BR, 2.5%) as a positive reference. RESULTS: 2-MNG alone significantly reduced immediate darkening and inhibited new melanin production when compared with vehicle, with higher performance at 1% than at 0.5%. 2-MNG at 0.5% in association with LHA and MSX showed significantly higher performance than 2-MNG 0.5% alone. 2-MNG at 0.5% and 1% showed significantly better performance than 4-n-BR. CONCLUSIONS: 2-MNG inhibited both UV-induced skin pigmentation mechanisms in vivo. The association of 2-MNG with LHA plus MSX showed the highest efficacy on melanin-rich skin with pigmentation induced by UV exposure.

Skin lightening properties of zerumbone cream: A placebo-controlled study.

OBJECTIVE: Despite the demonstrated anti-melanogenic and UV protective effects of Zerumbone (ZER) in vitro, there is a lack of clinical trials that have been done to assess these properties. The primary objective of this study was to assess the effectiveness of ZER in lightening the skin tone of human participants with a single-blind approach. METHODS: Twenty-six participants were randomly assigned to two groups to investigate the application location (left or right volar forearm) for the placebo and ZER creams. Both creams were topically administered to the volar forearms twice daily over a duration of 4 weeks. Initial skin irritation was assessed before and 30 min after applying creams. The melanin and erythema levels were quantified with Mexameter MX 18. RESULTS: Twenty participants were included in the analysis. The cream formulation had excellent physical properties and was well-received by the participants. The initial skin irritation study results indicated that neither of the creams elicited an allergic reaction. The administration of ZER cream resulted in a statistically significant reduction in melanin levels (p < 0.05) after 1 week compared to the initial baseline. Furthermore, after 2 weeks of application, ZER cream demonstrated significant differences in melanin levels compared to placebo (p < 0.05). No adverse effects were observed in the group using ZER cream. CONCLUSION: ZER demonstrated significant potential as a skin-lightening agent.

Neurog1-Derived Peptides RMNE1 and DualPep-Shine Penetrate the Skin and Inhibit Melanin Synthesis by Regulating MITF Transcription.

Anti-pigmentation peptides have been developed as alternative skin-lightening agents to replace conventional chemicals that have adverse effects on the skin. However, the maximum size of these peptides is often limited by their low skin and cell penetration. To address this issue, we used our intra-dermal delivery technology (IDDT) platform to identify peptides with hypo-pigmenting and high cell-penetrating activity. Using our cell-penetrating peptides (CPPs) from the IDDT platform, we identified RMNE1 and its derivative RMNE3, "DualPep-Shine", which showed levels of α-Melanocyte stimulating hormone (α-MSH)-induced melanin inhibition comparable to the conventional tyrosinase inhibitor, Kojic acid. In addition, DualPep-Shine was delivered into the nucleus and regulated the gene expression levels of melanogenic enzymes by inhibiting the promoter activity of microphthalmia-associated transcription factor-M (MITF-M). Using a 3D human skin model, we found that DualPep-Shine penetrated the lower region of the epidermis and reduced the melanin content in a dose-dependent manner. Furthermore, DualPep-Shine showed high safety with little immunogenicity, indicating its potential as a novel cosmeceutical ingredient and anti-pigmentation therapeutic agent.

In vivo melanin 3D quantification and z-epidermal distribution by multiphoton FLIM, phasor and Pseudo-FLIM analyses.

Characterizing melanins in situ and determining their 3D z-epidermal distribution is paramount for understanding physiological/pathological processes of melanin neosynthesis, transfer, degradation or modulation with external UV exposure or cosmetic/pharmaceutical products. Multiphoton fluorescence intensity- and lifetime-based approaches have been shown to afford melanin detection, but how can one quantify melanin in vivo in 3D from multiphoton fluorescence lifetime (FLIM) data, especially since FLIM imaging requires long image acquisition times not compatible with 3D imaging in a clinical setup? We propose an approach combining (i) multiphoton FLIM, (ii) fast image acquisition times, and (iii) a melanin detection method called Pseudo-FLIM, based on slope analysis of autofluorescence intensity decays from temporally binned data. We compare Pseudo-FLIM to FLIM bi-exponential and phasor analyses of synthetic melanin, melanocytes/keratinocytes coculture and in vivo human skin. Using parameters of global 3D epidermal melanin density and z-epidermal distribution profile, we provide first insights into the in vivo knowledge of 3D melanin modulations with constitutive pigmentation versus ethnicity, with seasonality over 1 year and with topical application of retinoic acid or retinol on human skin. Applications of Pseudo-FLIM based melanin detection encompass physiological, pathological, or environmental factors-induced pigmentation modulations up to whitening, anti-photoaging, or photoprotection products evaluation.

A Mixture of Topical Forms of Polydeoxyribonucleotide, Vitamin C, and Niacinamide Attenuated Skin Pigmentation and Increased Skin Elasticity by Modulating Nuclear Factor Erythroid 2-like 2.

It is well-known that increased oxidative stress caused by ultraviolet B (UV-B) radiation induces melanogenesis and activates metalloproteinases (MMPs), which degrade collagen and elastin fibers, leading to decreased skin elasticity. Various antioxidant agents, such as vitamin C and niacinamide, have been evaluated for use as treatments for photoaging or skin pigmentation. In this study, we evaluated the ability of a topical liquid formula of polydeoxyribonucleotide (PDRN), vitamin C, and niacinamide (PVN) delivered via a microneedling therapy system (MTS) to attenuate photoaging and pigmentation by increasing nuclear factor erythroid 2-like 2 (NRF2)/heme oxygenase-1 (HO-1) and decreasing MMP expression in a UV-B-radiated animal model. The effects of the PVN were compared with those of individual PDRN and hydroquinone (HQ) compounds. The expression of NRF2/HO-1 significantly increased in response to HQ, PDRN, and PVN in UV-B-radiated animal skin. The activity of nicotinamide adenine dinucleotide phosphate hydrogen oxidase decreased in response to HQ, PDRN, and PVN, and the superoxide dismutase activity increased. The expression of tumor protein p53 and microphthalmia-associated transcription factor and tyrosinase activity decreased in response to HQ, PDRN, and PVN, and this decrease was accompanied by decreased melanin content in the skin. The expression of nuclear factor kappa-light-chain enhancer of activated B cells and MMP2/3/9 decreased in response to HQ, PDRN, and PVN in UV-B-radiated skin. However, the expression of collagen type I α1 chain and the amount of collagen fibers that were evaluated by Masson's trichrome staining increased in response to HQ, PDRN, and PVN. The contents of elastin fibers, fibrillin 1/2 and fibulin 5 increased in response to HQ, PDRN, and PVN. In conclusion, PVN delivered via MTS led to decreased melanogenesis and destruction of collagen and elastin fibers by MMPs, and, thus, PVN decreased skin pigmentation and increased skin elasticity.

Rhamnazin suppresses melanosome transport by promoting the ubiquitin-mediated proteasomal degradation of melanophilin.

BACKGROUND: Melanosomes are intracellularly transported from the perinuclear region to the cell periphery and then to neighboring keratinocytes. We recently reported that the flavonoid rhamnazin suppresses melanosomal transport within pigment cells, yet the action mechanism remained unclear. OBJECTIVE: Our aim was to elucidate how rhamnazin influences the intracellular transport of melanosomes. METHODS: A melanosome distribution assay and immunostaining were performed using B16F10 mouse melanoma cells and normal human epidermal melanocytes, respectively. Expression levels of melanosome transport-related proteins, including melanophilin (MLPH), RAB27A, and myosin VA (MYO5A), were analyzed by immunoblotting. Ubiquitinated MLPH was detected using a commercial ubiquitin detection kit. To investigate the interaction between rhamnazin and MLPH, we prepared rhamnazin conjugated with magnetic FG beads. RESULTS: Immunoblotting analysis revealed that rhamnazin specifically reduces the expression of MLPH but not RAB27A or MYO5A proteins. The ubiquitin detection assay, which made use of a proteasome inhibitor, showed that MLPH accumulated as a polyubiquitinated protein after treatment with rhamnazin. We speculated that the affinity of rhamnazin for the components of the melanosome transport-related tripartite complex may alter the stability of the formation of the tripartite assembly. By using affinity-based techniques with B16F10 whole cell lysates or recombinant MLPH and RAB27A proteins, we revealed the interaction of rhamnazin with the components of the tripartite complex. CONCLUSION: We found that rhamnazin inhibits intracellular transport of melanosomes through proteasomal degradation of MLPH. Our results suggest that topical application of rhamnazin may provide a new approach for treating skin pigmentation disorders.

The effects of the oral supplementation of L-Cystine associated with reduced L-Glutathione-GSH on human skin pigmentation: a randomized, double-blinded, benchmark- and placebo-controlled clinical trial.

BACKGROUND: Glutathione has become a potential skin-lightening ingredient after the discovery of its anti-melanogenic properties. Various mechanisms of action have been considered to explain this property, one of them being the skewing of the melanin synthesis pathway toward the production of lighter pheomelanin instead of darker eumelanin, consequently producing a lightening effect. AIMS: To evaluate the skin lightening and anti-dark spot effects of oral supplementation with L-Cystine associated with L-Glutathione as compared to placebo and benchmark. METHODS: Effects of this L-Cystine-L-Glutathione oral combination were investigated in a 12-week randomized, double-blind, parallel-group, benchmark- and placebo-controlled trial involving 124 Asian female subjects. Women were randomly allocated into 4 equal groups (500 mg L-Cystine and 250 mg L-Glutathione, 250 mg reduced L-Glutathione, 500 mg L-Cystine, or a placebo, daily). Skin color was measured at baseline, after 6 and 12 weeks by spectrophotometry. Size and color of facial dark spots were determined from digital photographs. RESULTS: A significant skin lightening was observed after 12 weeks of oral supplementation with L-Cystine associated with L-Glutathione. This combination also induced a significant reduction in the size of facial dark spots after 6 and 12 weeks. It is noteworthy that the observed effects were not only significantly better than those obtained with placebo, but also with L-Cystine alone or L-Glutathione alone. CONCLUSION: The daily oral administration of 500 mg L-Cystine and 250 mg L-Glutathione during 12 weeks was a safe treatment to effectively lighten the skin and reduce the size of facial dark spots of Asian women.