Sunscreen Use for Photoprotection in Skin of Color: A Literature Review.

BACKGROUND: To understand the prevalence and types of publications addressing darker skin types within the existing evidence base for sunscreen use.  Evidence Review: PubMed was searched from 1988, the time point at which the first skin of color (SOC) article was identified, through December 2022 using PubMed's Medical Subject Headings terms and keyword searches in title and abstract, with and without terms for SOC and ethnicity. Identified articles were reviewed for relevance, de-duplicated, and categorized; results are summarized. FINDINGS: Of the 5927 articles on sunscreen overall, only 314 (5.3%) articles addressed SOC, with the majority published since 2007 and representing only 4% to 7% of total publications annually except in 2022 when the proportion of SOC articles was 23.5%. Of the articles on SOC, many reported sunscreen knowledge and patient behaviors (29%), but very few reported clinical trials (5%). The 3 conditions most often discussed were melasma, post-inflammatory hyperpigmentation, and dyschromia. South Asian ethnicities (India, Pakistan, Bangladesh) had the highest representation within the literature, followed by Hispanics. CONCLUSIONS AND RELEVANCE: Although it was assumed there would be fewer papers discussing the use of sunscreen in darker skin types, the scale of the disparity revealed by this study is stark. The increase in a number of articles in 2022 suggests an increasing focus on SOC, but further discussion of the issues presented here will help the SOC community address gaps in the evidence base and better inform discussions on sunscreen and photoprotection between clinicians and patients.J Drugs Dermatol. 2024;23(7):575-577.  doi:10.36849/JDD.8250.

Photo Visualization of Skintone Compatibility of an SPF 35 Sunscreen.

BACKGROUND: Visual casts and discoloration are common barriers to sunscreen use in melanin-rich populations. However, photoprotective measures are essential for individuals with all skin types, including darker skin. METHODS: Single-center, 7-day, open-label study of healthy adult females with Fitzpatrick Skin Types (FST) IV to VI and sensitive skin treated with once-daily daily facial moisturizer sun protection factor 35 (DFM SPF35). Subjects completed a cosmetic acceptability questionnaire at days 1 and 7. Photography using VISIA CR was performed at day 7. Adverse events were monitored throughout the study. RESULTS: Thirty-two (32) subjects participated; 31.3% had FST IV, 53.1% V, and 15.6% VI skin. DFM SPF35 was viewed as cosmetically elegant. At day 1, 96.7% of subjects agreed product was easy to apply; 90.0% reported soft skin after product use; 86.7% said it had a lightweight, non-greasy feel and hydrated the skin. At day 7, 93.7% reported no visible white residue on their skin and said the product applied easily/absorbed well. The majority (90.6%) would continue using and would recommend the product; and 87.5% reported the product blended seamlessly into their skin, which agreed with clinical photography. Responses were consistent among subjects with normal, oily, or combination skin. No adverse events were reported. CONCLUSIONS: DFM SPF35 blended well into the skin and was perceived favorably among subjects with SOC after 1 and 7 days of use. Subjects felt it had good cosmetic acceptability without unacceptable white residues or a greasy feeling. Dermatologists need to be versed in products that can be used on a variety of skin types.J Drugs Dermatol. 2024;23(7):515-518.  doi:10.36849/JDD.8223.

Image Analysis of Xerosis and Atopic Dermatitis Following Prebiotic Skincare Regimen in Ethnically Diverse Patients.

Variations in the epidemiology, clinical presentation, and disease course in atopic dermatitis (AD) patients with Skin of Color (SOC) compared with white counterparts have been reported. In this study, we evaluated the capability of a new imaging device (SkinCam) in quantifying skin texture changes in diverse patients, presenting with AD or xerosis, after using a prebiotic skincare routine over 10 weeks.  A total of 39 subjects from diverse racial/ethnic backgrounds, aged 3 to 76 years old, with Fitzpatrick skin phototypes I to VI, presenting with mild AD and moderate to severe xerosis, were enrolled in the study. All subjects used a prebiotic cleanser on its own for 2 weeks, followed by a prebiotic moisturizer in conjunction for an additional 8 weeks. Standardized images of the subjects' legs were taken with SkinCam at several time points (baseline, week 2, and week 10), and analyzed for skin texture parameters. Our results demonstrate that both skin texture irregularity and skin color patterns significantly improve over time with a prebiotic skincare regimen in AD (n=12) and xerosis (n=24) subjects. Interestingly, image analyses showed more improvement over time in xerosis and AD SOC patients (n=18, Fitzpatrick IV-VI). Lastly, skin texture analyses from SkinCam imaging correlated with clinical assessments, showing significant improvement by prebiotic skincare regimen in all subjects by week 10. In summary, our results demonstrate that the SkinCam imaging device has the capability to effectively monitor skin texture parameters over time in both AD and xerosis patients with lightly and darkly pigmented skin. J Drugs Dermatol. 2024;23(7):557-563.  doi:10.36849/JDD.8371.

Effects of a Sheer 100% Mineral Sunscreen Moisturizer on Facial Photodamage Across Fitzpatrick Skin Types.

BACKGROUND: All skin tones need to be protected from the damaging effects of solar radiation. Although mineral sunscreens offer protection, they can have a thick, greasy feel and leave a white cast, particularly on darker skin tones. Tints offset white cast and provide visible light protection; however, patients may prefer a sheer option. Therefore, a multifunctional, sheer, 100% mineral sunscreen moisturizer (MSM) with broad-spectrum SPF 50 was developed to have positive aesthetics and deliver anti-aging and skin health benefits to all skin tones.  Methods: An IRB-approved, 12-week, open-label clinical study was conducted to investigate the efficacy and tolerability of the MSM. Thirty-nine (39) females aged 35 to 60 years with moderate-severe overall facial photodamage and representing all Fitzpatrick skin types (FST) were recruited. Participants applied the MSM to the face and neck in the morning and reapplied per US Food and Drug Administration requirements. Efficacy and tolerability grading, photography, ultrasound imaging, corneometer measurements, and questionnaires were completed at baseline and weeks 4, 8, and 12.  Results: Statistically significant progressive improvements were demonstrated from baseline to week 12. At week 12, 23.4% and 26.5% mean improvements in overall photodamage were seen for FST I-III and FST IV-VI, respectively. Favorable tolerability was shown for both the face and neck. Photography corroborated clinical grading, and ultrasound imaging indicated a trend in skin density improvement. The MSM was well-perceived.  Conclusion: The MSM is an efficacious and well-tolerated product for patients of all skin tones who desire a sheer, 100% mineral sunscreen moisturizer with anti-aging and skin health benefits. J Drugs Dermatol. 2024;23(7):538-544.  doi:10.36849/JDD.8082.

Evaluation of ruxolitinib cream 1.5% as an at-home therapy for repigmentation in non-segmental vitiligo.

INTRODUCTION: Vitiligo is a chronic, autoimmune condition characterized by skin depigmentation caused by inflammatory-mediated melanocyte degradation. Treatment of vitiligo is challenging due to the chronic nature of the condition. Ruxolitinib cream 1.5% was recently approved by the Food and Drug Administration (FDA) as a Janus kinase 1 and 2 inhibitor for use in nonsegmental vitiligo for those 12 years and older. AREAS COVERED: The purpose of this review is to describe the role of ruxolitinib in treating nonsegmental vitiligo.We searched PubMed using search terms nonsegmental vitiligo, jak inhibitor, and ruxolitinib. Clinicaltrials.gov was used to identify clinical trial data including efficacy, pharmacodynamics, pharmacokinetics, safety, and tolerability. EXPERT OPINION: In both phase II and phase III (TRuE-V1 and TRuE-V2) trials, ruxolitinib cream 1.5% improved repigmentation with minimal adverse effects. Topical ruxolitinib is a much needed new vitiligo treatment option.  Real life efficacy may not match that seen in clinical trials if the hurdle of poor adherence to topical treatment is not surmounted.

Combination of total glucosides of paeony, narrow-band ultraviolet B, and oral corticosteroid mini-pulse therapy for nonsegmental vitiligo: A retrospective study.

BACKGROUND: The total glucoside of paeony (TGP) is recognized for its immunomodulatory properties and anti-inflammatory effects. This study evaluates the efficacy of TGP combined with oral mini-pulse therapy (OMP) and narrow-band ultraviolet B (NB-UVB) in treating active nonsegmental vitiligo (NSV). MATERIALS AND METHODS: The combination therapy was contrasted against those from a group treated solely with OMP and NB-UVB. Data from 62 patients undergoing TGP combination treatment and 55 without were analyzed over a 3-month period. After 6 months, the differences in recurrence rate were investigated by follow-up. RESULTS: The findings indicate that integrating TGP may yield superior outcomes compared to OMP + NB-UVB alone. Moreover, the patient's oxidative stress makers were significantly reduced after the treatment. The majority of patients in the TGP cohort exhibited enhanced skin pigmentation over the duration. Notably, no increase in side effects or recurrence was observed in this group. Especially, patients with vitiligo on their head and neck experienced pronounced improvements. CONCLUSION: The efficacy of the combination treatment group was better than that of the control group at 2 and 3 months, and there was no difference in recurrence rate and side effects, suggesting that TGP may continue to show efficacy in NSV for a longer period of time by reducing the level of oxidative stress, and is especially suitable for patients with head and neck lesions.

Identification of Yellow Advanced Glycation End Products in Human Skin.

Skin yellowness is a hallmark of dull or unhealthy skin, particularly among Asians. Previous research has indicated a link between skin glycation and skin yellowness. However, the specific glycated chemicals contributing to yellowish skin appearance have not been identified yet. Using HPLC-PDA-HRMS coupled with native and artificially glycated human epidermal explant skin, we identified intensely yellow colored glycated chromophores "(1R, 8aR) and (1S, 8aR)-4-(2-furyl)-7-[(2-furyl)-methylidene]-2-hydroxy-2H,7H,8AH-pyrano-[2,3-B]-pyran-3-one" (abbreviated as AGEY) from human skin samples for the first time. The abundance of AGEY was strongly correlated with skin yellowness in the multiple skin explant tissues. We further confirmed the presence of AGEY in cultured human keratinocytes and 3D reconstructed human epidermal (RHE) models. Additionally, we demonstrated that a combination of four cosmetic compounds with anti-glycation properties can inhibit the formation of AGEY and reduce yellowness in the RHE models. In conclusion, we have identified specific advanced glycation end products with an intense yellow color, namely AGEY, in human skin tissues for the first time. The series of study results highlighted the significant contribution of AGEY to the yellow appearance of the skin. Furthermore, we have identified a potential cosmetic solution to mitigate AGEY formation, leading to a reduction in yellowness in the in vitro RHE models.

Comparative study between efficacy of Excimer light with topical Tacrolimus 0.1% versus excimer light with topical Bimatoprost 0.01% in treatment of facial Vitiligo.

Loss and absence of melanocytes due to a number of factors is responsible for vitiligo; known to be the commonest disorder of pigmentation. The aim of the current work was to compare the efficacy and safety of excimer light with topical tacrolimus ointment 0.1% versus excimer light with topical bimatoprost gel 0.01% in treatment of facial vitiligo. The study was carried out on 48 patients presented with facial vitiligo. The patients were divided randomly using sealed envelope method into two groups (24 patients each). Group 1 were treated with excimer light plus topical tacrolimus ointment 0.1% and group 2 treated with excimer light plus topical bimatoprost gel 0.01%. Clinical improvement based on the quartile grading scale at the end of treatment did not show any statistically significant difference between groups. The majority of subjects in both groups experienced good to excellent improvement. Only 20.9% of patients in group 1 and 33.3% of subjects in group 2 achieved less than 50% repigmentation (p = 0.889). Our study demonstrated that 0.01% topical bimatoprost gel in combination with excimer light is considered safe and effective as treatment of nonsegmental facial vitiligo with comparable results to 0.1% tacrolimus.

Melanin for Photoprotection and Hair Coloration in the Emerging Era of Nanocosmetics.

Nanotechnology is revolutionizing fields of high social and economic impact. such as human health preservation, energy conversion and storage, environmental decontamination, and art restoration. However, the possible global-scale application of nanomaterials is raising increasing concerns, mostly related to the possible toxicity of materials at the nanoscale. The possibility of using nanomaterials in cosmetics, and hence in products aimed to be applied directly to the human body, even just externally, is strongly debated. Preoccupation arises especially from the consideration that nanomaterials are mostly of synthetic origin, and hence are often seen as "artificial" and their effects as unpredictable. Melanin, in this framework, is a unique material since in nature it plays important roles that specific cosmetics are aimed to cover, such as photoprotection and hair and skin coloration. Moreover, melanin is mostly present in nature in the form of nanoparticles, as is clearly observable in the ink of some animals, like cuttlefish. Moreover, artificial melanin nanoparticles share the same high biocompatibility of the natural ones and the same unique chemical and photochemical properties. Melanin is hence a natural nanocosmetic agent, but its actual application in cosmetics is still under development, also because of regulatory issues. Here, we critically discuss the most recent examples of the application of natural and biomimetic melanin to cosmetics and highlight the requirements and future steps that would improve melanin-based cosmetics in the view of future applications in the everyday market.

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.

Tokishakuyakusan alleviates ultraviolet-induced skin pigmentation by decreasing the expression of melanogenesis-related enzymes.

ETHNOPHARMACOLOGICAL RELEVANCE: Tokishakuyakusan (TSS), a traditional Kampo medicine, can effectively alleviate symptoms unique to women, such as menstrual pain and menopausal symptoms, and this effect is believed to be related to its ability to increase the secretion of female hormones. TSS is also believed to be effective against skin pigmentation. However, no studies have examined the effect of TSS on pigmentation. AIM OF THE STUDY: In this study, we conducted basic research to determine the effects of TSS on pigmentation. MATERIALS AND METHODS: Female HRM-2 mice were given free access to a normal diet or a TSS-containing diet for 7 weeks. For 3 weeks starting from the 4th week of treatment, the back of the skin was irradiated with ultraviolet (UV) light, and the melanin level was measured. The expression levels of melanogenesis-related genes and inflammatory markers in the skin were analyzed. RESULTS: The melanin level in the skin of the mice exposed to UV radiation was approximately three times greater than that in the skin of the mice in the non-UV-irradiated group, confirming pigmentation due to UV irradiation. The protein expression levels of tyrosinase (Tyr), tyrosinase-related protein-1 (Tyrp1), and dopachrome tautomerase (Dct), which are important for melanin production, were significantly greater in the UV irradiation group than in the non-UV irradiation group. In contrast, the amount of skin melanin in the mice treated with TSS was significantly lower than that in the UV-irradiated group, and the expression levels of melanogenesis-related enzymes were also lower. Furthermore, TSS significantly decreased the expression of microphthalmia transcription factor (Mitf), a transcription factor for melanogenesis-related enzymes, and the inflammatory cytokines interleukin-1ß and interleukin-6. CONCLUSIONS: TSS inhibits melanin production in melanocytes by suppressing the increase in the expression of melanogenesis-related enzymes caused by UV irradiation. These findings suggested that this effect of TSS is exerted through the combined regulation of MITF expression and anti-inflammatory responses.

Effects of EGFR-TKI on epidermal melanin unit integrity: Therapeutic implications for hypopigmented skin disorders.

Epidermal melanin unit integrity is crucial for skin homeostasis and pigmentation. Epidermal growth factor (EGF) receptor (EGFR) is a pivotal player in cell growth, wound healing, and maintaining skin homeostasis. However, its influence on skin pigmentation is relatively unexplored. This study investigates the impact and underlying mechanisms of EGFR inhibitors on skin pigmentation. We evaluated EGF and EGFR expression in various skin cells using quantitative real-time PCR, Western blot, and immunofluorescence. EGF and EGFR were predominantly expressed in epidermal keratinocytes, and treatment with the EGFR tyrosine kinase inhibitors (EGFR-TKIs) gefitinib and PD153035 significantly increased stem cell factor (SCF) and endothelin-1 (ET-1) expression in cultured keratinocytes. Enhanced melanocyte migration and proliferation were observed in co-culture, as evidenced by time-lapse live imaging and single-cell tracking assays. Furthermore, topical application of gefitinib to guinea pig dorsal skin induced increased pigmentation and demonstrated efficacy in mitigating rhododendrol-induced leukoderma. Suppression of EGF signaling indirectly enhanced skin pigmentation by upregulating SCF and ET-1 in epidermal keratinocytes. This novel mechanism highlights the pivotal role of EGF signaling in regulating skin pigmentation, and topical EGFR-TKI therapy at an appropriate dose may be a promising approach for depigmentation disorder management.

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.

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.

A randomised investigation of film-forming silicone gel in superficial partial thickness face and neck burn patients: Indication of improved early scar pigmentation outcomes.

INTRODUCTION: Burns to the face and neck are a source of considerable distress and a challenge to manage with dressings. Further, these often superficial injuries pose a risk of scarring and altered pigmentation. Silicone gels have emerged as a potential solution to the challenges of conservative management for face and neck burn injuries. The aims of this study were to explore the effect of topical silicone compared to routine treatment of conservatively managed burns to the face and neck. METHODS: This single-blind, randomised, controlled trial compared topical silicone film-forming dressing to standard of care for superficial partial thickness burns to the face and neck. Time to healing was the primary outcome and secondary outcomes included: 1) scar assessments (modified Vancouver Scar Scale, Dermalab Combo and Patient and Observer Scar Assessment Scale) at six weeks and three months; and 2) pain intensity scale at wound review appointments. RESULTS: Of the 55 participants in the face/neck study, 34 were male and 21 were female. Median age was 36 years (range from 25 to 47 years). The median time to healing for the silicone group was 9 days (CI 7.6 -10.4) and the control group was 7 days (CI 5.3- 8.7), p = 0.056. Analysis demonstrated significantly reduced pigmentation at six weeks in mVSS scores for the silicone group (Md = 0, IQR = 0) compared to the control group (Md = 0, IQR = 0 - 3), p = 0.043. We found no evidence of differences in reported pain between the groups (Silicone - Md = 1.15, IQR 0.3 - 4.5 vs control group - Md = 1.5, IQR 0.6 - 3.8, z = -0.63, p = 0.53). No other differences were observed, and no adverse events were associated with the topical silicone in the study whereas an infection and a reaction were experienced in the control group. CONCLUSION: Film-forming silicone gel had comparable effects to standard of care emollient on wound healing of superficial partial thickness burns of the face and neck. Silicone treated wounds were associated with a significant improvement in scar pigmentation outcome at six weeks post-burn.

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.

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.