Deficit in autophagy: A possible mechanism involved in melanocyte hyperfunction in melasma

Combining large-spot low-fluence 1064-nm and fractional 1064-nm picosecond lasers for promoting protective melanosome autophagy via the PI3K/Akt/mTOR signalling pathway for the treatment of melasma

Melasma is a common condition of hyperpigmented facial skin. Picosecond lasers are reported to be effective for the treatment of melasma. We aimed to identify the most effective therapeutic mode and elucidate the potential molecular mechanisms of picosecond lasers for the treatment of melasma. Female Kunming mice with melasma-like conditions were treated using four different picosecond laser modes. Concurrently, in vitro experiments were conducted to assess changes in melanin and autophagy in mouse melanoma B16-F10 cells treated with these laser modes. Changes in melanin in mouse skin were detected via Fontana-Masson staining, and melanin particles were evaluated in B16-F10 cells. Real-time polymerase chain reaction and western blotting were used to analyse the expression levels of melanosome and autophagy-related messenger ribonucleic acid (mRNA) and proteins. A combination of large-spot low-fluence 1064-nm and fractional 1064-nm picosecond lasers resulted insignificant decreases in melanin as well as in mRNA and protein expression of melanin-synthesizing enzymes (TYR, TRP-1 and MITF). This combination also led to increased expression of the autophagy-related proteins, Beclin1 and ATG5, with a marked decrease in p62 expression. Intervention with the PI3K activator, 740 Y-P, increased TYR, TRP-1, MITF, p-PI3K, p-AKT, p-mTOR and p62 expression but decreased the expression of LC3, ATG5 and Beclin1. A combination of large-spot low-fluence 1064-nm and fractional 1064-nm picosecond lasers proved more effective and safer. It inhibits melanin production, downregulates the PI3K/AKT/mTOR pathway, enhances melanocyte autophagy and accelerates melanin metabolism, thereby reducing melanin content.

Expression of Endothelin-1, Endothelin Receptor-A, and Endothelin Receptor-B in facial melasma compared to adjacent skin

Background/Objectives

Although melasma is highly prevalent, its pathogenesis is not yet fully understood. In the skin, endothelin-1 (ET-1) is primarily produced by keratinocytes in response to UVB exposure, which is mediated by an increase in IL-1α or reactive oxygen species. ET-1 plays a role in melanogenesis by binding to specific receptor B (ERB) or receptor A (ERA). However, the expression of ET-1, ERA, and ERB in melasma has not been systematically investigated. The objective of this study was to evaluate the expression of ET-1, ERA, and ERB in facial melasma compared to the adjacent unaffected skin.

Methods

Cross-sectional study, with 40 skin samples (20: facial melasma; 20: adjacent unaffected skin) from women with facial melasma without treatment for 30 days except for sunscreen. A triple staining immunofluorescence technique was performed for anti-vimentin, DAPI, plus one of the following antibodies: (a) anti-ET1, (b) anti-ERA; (c) anti-ERB. Interfollicular areas on the slides of each topography (melasma; unaffected skin) were photographed in triplicate under confocal laser microscopy. The mean staining intensities of the image histograms (0-255 pixels intensity) were estimated for different types of cells (suprabasal keratinocytes, basal layer, and upper dermis) and were blindly compared between topographies.

Results

The mean (SD) age of the participants was 44.9 (9.2). The expression of ET-1 was increased in the whole epidermis with melasma when compared to the adjacent skin, being 32.8% (CI95% 14.7%-52.6%) higher in the spinous layer (p=0.013), 30.4% (CI95% 13.7%-47.9%) higher in the basal layer (p=0.014), and 29.7% (CI95% 11.4%-49.7%) higher in the melanocytes (p=0.006). There was no noticeable expression of ET-1 within the cells on the upper dermis. Neither ERA nor ERB resulted in differential epidermal expression between melasma and unaffected skin (p≥0.1).

Conclusion

ET-1 is expressed more intensely on the epidermis from the skin with facial melasma compared to the unaffected adjacent skin.

Adaptability of melanocytes post ultraviolet stimulation in patients with melasma

BACKGROUND

Dynamic in vivo changes in melanin in melasma lesions after exposure to ultraviolet (UV) irradiation have not been described.

OBJECTIVES

To determine whether melasma lesions and nearby perilesions demonstrated different adaptive responses to UV irradiation and whether the tanning responses were different among different locations on face.

METHODS

We collected sequential images from real-time cellular resolution full-field optical coherence tomography (CRFF-OCT) at melasma lesions and perilesions among 20 Asian patients. Quantitative and layer distribution analyses for melanin were performed using a computer-aided detection (CADe) system that utilizes spatial compounding-based denoising convolutional neural networks.

RESULTS

The detected melanin (D) is melanin with a diameter >0.5 µm, among which confetti melanin (C) has a diameter of >3.3 µm and corresponds to a melanosome-rich package. The calculated C/D ratio is proportional to active melanin transportation. Before UV exposure, melasma lesions had more detected melanin (p = 0.0271), confetti melanin (p = 0.0163), and increased C/D ratio (p = 0.0152) in the basal layer compared to those of perilesions. After exposure to UV irradiation, perilesions have both increased confetti melanin (p = 0.0452) and the C/D ratio (p = 0.0369) in basal layer, and this effect was most prominent in right cheek (p = 0.030). There were however no significant differences in the detected, confetti, or granular melanin areas before and after exposure to UV irradiation in melasma lesions in all the skin layers.

CONCLUSIONS

Hyperactive melanocytes with a higher baseline C/D ratio were noted in the melasma lesions. They were "fixed" on the plateau and were not responsive to UV irradiation regardless of the location on face. Perilesions retained adaptability with a dynamic response to UV irradiation, in which more confetti melanin was shed, mainly in the basal layer. Therefore, aggravating effect of UV on melasma was mainly due to UV-responsive perilesions rather than lesions.

Amber photobiomodulation versus tranexamic acid for the treatment of melasma: protocol for a double-blind, randomised controlled trial

INTRODUCTION

Photobiomodulation (PBM) has been suggested as an alternative treatment for melasma. In vitro studies have shown PBM with amber light inhibits the tyrosinase enzyme, induces autophagy and reduces the melanin content, but randomised controlled clinical trials are still needed. This study aims to evaluate the efficacy of amber PBM (590 nm) in the treatment of melasma compared with liposomal tranexamic acid.

METHODS AND ANALYSIS

This study is a controlled, randomised, double-blind, non-inferiority trial. This study will be performed in two centres (Universidade Nove de Julho Facility, Campus Vergueiro, and Galache Odontology Clinic, São Caetano do Sul, both in São Paulo State, Brazil). The sample (54 participants) will be divided into two groups in a 1:1 ratio; one group will receive active PBM and a placebo cosmetic and the other will receive sham PBM and liposomal tranexamic acid. Women presenting facial melasma, aged 35-50 years, with skin phototypes II-IV, will be eligible for inclusion. Women who use oral contraceptives, intrauterine devices, hormone replacement or photosensitive drugs, those with autoimmune disease and those who have undergone facial treatments in the last 3 months will be excluded from the study. The participants will receive PBM weekly for 12 weeks and will use the cosmetic two times per day at home during this period. The severity of melasma will be evaluated through the Melasma Area and Severity Index (MASI) as the primary outcome; pigmentation of the epidermis evaluated by corneomelametry, the photographic records, the global diagnosis of the face and the quality-of-life questionnaire (Brazilian Portuguese version of the Melasma Quality of Life Questionnaire) will assessed as secondary outcomes. All assessments will be made before starting the study (week 0), mid-study at 6 weeks and at the completion of treatment (week 12). MASI will also be evaluated during follow-up (weeks 16 and 20). The data will be analysed based on the intention-to-treat analysis using a generalised mixed model, and α <0.05 will be considered statistically significant.

ETHICS AND DISSEMINATION

The protocol was approved by the Research Ethics Committee of Universidade Nove de Julho (5 332 384). All participants will fill out the patient informed consent form. The results obtained in this trial will be presented at conferences and submitted for publication.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT05326997).

Safety and efficacy of superficial micro-focused ultrasound with visualization for melasma in Asians: An uncontrolled pilot study

BACKGROUND

The pathophysiology of melasma is multifactorial, resulting in treatment resistance and a high recurrence rate. Recent research suggests that focused ultrasound might treat melasma effectively.

OBJECTIVES

To investigate the efficacy and safety of superficial micro-focused ultrasound with visualization (MFU-V) for melasma in Asians.

METHODS

Patients (n = 20) with mixed melasma on both cheeks received 2 MFU-V treatments spaced 1 month apart. At monthly visits over 5 months, treatment efficacy and safety were evaluated. Standardized photographs were clinically assessed using the modified Melasma Area and Severity Index (mMASI), and 6-point grading scales for melasma lightening and area of involvement. Patients provided pain, global aesthetic improvement scale (GAIS), and satisfaction assessments.

RESULTS

In 40 cheeks, the mean mMASI score was significantly reduced from 13.2 at baseline to 2.4 at month 4, and 2.8 at month 5. Twenty-nine cheeks (72.5%) showed lightening of melasma at month 4 that persisted until month 5, with improvements up to 75% compared to baseline. Melasma area decreased overall, with sites containing >30% melasma involvement decreasing from 55% to 20% by month 5, and none with 70%-89% involvement. Melasma lightening and area improved visibly in 40% and 20% of cheeks, respectively, as early as 1 month after index MFU-V treatment. Improvements continued after the second treatment and persisted until study closure, correlating with patient GAIS and satisfaction scores. Procedure was well tolerated with only mild-to-moderate pain reported in 92.5% of treatments.

CONCLUSION

Superficial MFU-V is a safe and effective treatment for melasma.

Shining Light on Autophagy in Skin Pigmentation and Pigmentary Disorders

Autophagy is a vital process for cell survival and it preserves homeostasis by recycling or disassembling unnecessary or dysfunctional cellular constituents. Autophagy ameliorates skin integrity, regulating epidermal differentiation and constitutive pigmentation. It induces melanogenesis and contributes to skin color through melanosome turnover. Autophagy activity is involved in skin phenotypic plasticity and cell function maintenance and, if altered, it concurs to the onset and/or progression of hypopigmentary and hyperpigmentary disorders. Overexpression of autophagy exerts a protective role against the intrinsic metabolic stress occurring in vitiligo skin, while its dysfunction has been linked to the tuberous sclerosis complex hypopigmentation. Again, autophagy impairment reduces melanosome degradation by concurring to pigment accumulation characterizing senile lentigo and melasma. Here we provide an updated review that describes recent findings on the crucial role of autophagy in skin pigmentation, thus revealing the complex interplay among melanocyte biology, skin environment and autophagy. Hence, targeting this process may also represent a promising strategy for treating pigmentary disorders.

Update on Melasma-Part I: Pathogenesis

Melasma is a multifactorial dyschromia that results from exposure to external factors (such as solar radiation) and hormonal factors (such as sex hormones and pregnancy), as well as skin inflammation (such as contact dermatitis and esthetic procedures), in genetically predisposed individuals. Beyond hyperfunctional melanocytes, skin with melasma exhibits a series of structural and functional alterations in the epidermis, basement membrane, and upper dermis that interact to elicit and sustain a focal hypermelanogenic phenotype. Evolution in the knowledge of the genetic basis of melasma and the cutaneous response to solar radiation, as well as the roles of endocrine factors, antioxidant system, endothelium proliferation, fibroblast senescence, mast cell degranulation, autophagy deficits of the melanocyte, and the paracrine regulation of melanogenesis, will lead to the development of new treatments and preventive strategies. This review presents current knowledge on these aspects of the pathogenesis of melasma and discusses the effects of specific treatments and future research on these issues.

Evaluating Whether Radiofrequency Irradiation Attenuated UV-B-Induced Skin Pigmentation by Increasing Melanosomal Autophagy and Decreasing Melanin Synthesis

Autophagy is involved in the degradation of melanosomes and the determination of skin color. TLR4 and tumor necrosis factor (TNF) signaling upregulates NF-kB expression, which is involved in the upregulation of mTOR. The activation of mTOR by UV-B exposure results in decreased autophagy, whereas radiofrequency (RF) irradiation decreases TLR4 and TNF receptor (TNFR) expression. We evaluated whether RF decreased skin pigmentation by restoring autophagy by decreasing the expression of TLR4 or TNFR/NF-κB/mTOR in the UV-B-irradiated animal model. UV-B radiation induced the expressions of TNFR, TLR, and NF-κB in the skin, which were all decreased by RF irradiation. RF irradiation also decreased phosphorylated mTOR expression and upregulated autophagy initiation factors such as FIP200, ULK1, ULK2, ATG13, and ATG101 in the UV-B-irradiated skin. Beclin 1 expression and the expression ratio of LC3-I to LC3-II were increased by UV-B/RF irradiation. Furthermore, melanin-containing autophagosomes increased with RF irradiation. Fontana-Masson staining showed that the amount of melanin deposition in the skin was decreased by RF irradiation. This study showed that RF irradiation decreased skin pigmentation by restoring melanosomal autophagy, and that the possible signal pathways which modulate autophagy could be TLR4, TNFR, NF-κB, and mTOR.