Efficacy and safety of liposome-encapsulated 4-n-butylresorcinol 0.1% cream for the treatment of melasma: A randomized controlled split-face trial

Melasma: A Step-by-Step Approach Towards a Multimodal Combination Therapy

Melasma is a common challenge in the field of pigmentary skin disorders, exerting a significant emotional and psychosocial burden on patients. The persistent and recurring nature of melasma complicates its management in routine clinical practice. This comprehensive review outlines a stepwise, practical approach encompassing diagnostic, preventive and therapeutic strategies for the management of melasma. A thorough exploration of aggravating and exacerbating factors, including sun exposure, hormonal imbalances, photosensitizing medication and cosmetics, is essential for a holistic assessment of the disease. With an emphasis on consistent and effective photoprotection, initial topical treatment modalities target the melanin production and/or the transfer of melanosomes to keratinocytes. Topical tyrosine inhibitors emerge as the first choice for reducing and preventing hyperpigmentation, with compounds such as thiamidol or tranexamic acid (TXA) being preferred for their safety profile over hydroquinone (HQ), kojic acid and arbutin. Combination with chemical peels can further enhance the therapeutic efficacy, even in cases with resistant melasma. In more severe cases, laser- and light-based interventions may be considered, but with the caveat of the likelihood of recurrence within 3-6 months. Assisted TXA delivery, via either fractional non-ablative laser or microneedling techniques, can further improve clinical outcomes. In conclusion, an optimal melasma management strategy is a multimodal approach, which includes effective photoprotection and a mix of different topical treatments targeting melanin synthesis, the anti-inflammatory environment, senescence and vascularity. Complementary procedures, such as chemical peels, and laser, light-based or microneedling procedures, with or without TXA, can further expedite melanin clearance in more severely affected instances. Individual discussions with patients regarding treatment expectations, recurrence likelihood and potential side effects are paramount to a comprehensive and successful therapeutic journey.

Different therapeutic approaches in melasma: advances and limitations

Melasma is a chronic hyperpigmentation skin disorder that is more common in the female gender. Although melasma is a multifactorial skin disorder, however, sun-exposure and genetic predisposition are considered as the main etiologic factors in melasma occurrence. Although numerous topical and systemic therapeutic agents and also non-pharmacologic procedural treatments have been considered in melasma management, however, the commonly available therapeutic options have several limitations including the lack of sufficient clinical effectiveness, risk of relapse, and high rate of unwanted adverse drug reactions. Recruitment of nanotechnology for topical drug delivery in melasma management can lead to enhanced skin penetration, targeted drug delivery to the site of action, longer deposition at the targeted area, and limit systemic absorption and therefore systemic availability and adverse drug reactions. In the current review, first of all, the etiology, pathophysiology, and severity classification of melasma have been considered. Then, various pharmacologic and procedural therapeutic options in melasma treatment have been discussed. Afterward, the usage of various types of nanoparticles for the purpose of topical drug delivery for melasma management was considered. In the end, numerous clinical studies and controlled clinical trials on the assessment of the effectiveness of these novel topical formulations in melasma management are summarized.

Topical and Systemic Therapies in Melasma: A Systematic Review

Introduction

Melasma is an acquired disorder, which presents with well-demarcated, brown-colored hyperpigmented macules, commonly involving the sun-exposed areas such as the face. It is a chronic and distressing condition, affecting the patients' quality of life, and has been conventionally treated with "first-line" agents including hydroquinone (HQ) alone or as a part of a triple combination cream (TCC), while "second-line" options include chemical peels, and third line options include laser therapy.

Materials and Methods

A systematic search was performed for all topical and systemic treatments for melasma up till May 4, 2021, using the PubMed and EMBASE databases, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. The search terms "melasma" and "treatment" were used to search for the relevant articles on both these databases, and a total of 4020 articles were identified. After removing the duplicate entries and screening the titles, abstracts, and full-text articles, we identified 174 randomized controlled trials (RCTs) or controlled clinical trials.

Results

Based on our review, HQ, TCCs, sunscreens, kojic acid (KA), and azelaic acid receive grade A recommendation. Further large-scale studies are required to clearly establish the efficacy of topical vitamin C, resorcinol, and topical tranexamic acid (TXA). Several newer topical agents may play a role only as an add-on or second-line drugs or as maintenance therapy. Oral TXA has a strong recommendation, provided there are no contraindications. Procyanidins, Polypodium leucotomos (PL), and even synbiotics may be taken as adjuncts.

Discussion

Several newer topical and systemic agents with multimodal mechanisms of action have now become available, and the balance seems to be tipping in favor of these innovative modalities. However, it is worth mentioning that the choice of agent should be individualized and subject to availability in a particular country.

Targeting Tyrosinase in Hyperpigmentation: Current Status, Limitations and Future Promises

Hyperpigmentation is a common and distressing dermatologic condition. Since tyrosinase (TYR) plays an essential role in melanogenesis, its inhibition is considered a logical approach along with other therapeutic methods to prevent the accumulation of melanin in the skin. Thus, TYR inhibitors are a tempting target as the medicinal and cosmetic active agents of hyperpigmentation disorder. Among TYR inhibitors, hydroquinone is a traditional lightening agent that is commonly used in clinical practice. However, despite good efficacy, prolonged use of hydroquinone is associated with side effects. To overcome these shortcomings, new approaches in targeting TYR and treating hyperpigmentation are desperately requiredessentialneeded. In line with this purpose, several non-hydroquinone lightening agents have been developed and suggested as hydroquinone alternatives. In addition to traditional approaches, nanomedicine and nanotheranostic platforms have been recently proposed in the treatment of hyperpigmentation. In this review, we discuss the available strategies for the management of hyperpigmentation with a focus on TYR inhibition. In addition, alternative treatment options to hydroquinone are discussed. Finally, we present nano-based strategies to improve the therapeutic effect of drugs prescribed to patients with skin disorders.

Decrypting the Potential of Nanotechnology-Based Approaches as Cutting-Edge for Management of Hyperpigmentation Disorder

The abundant synthesis and accretion of melanin inside skin can be caused by activation of melanogenic enzymes or increase in number of melanocytes. Melasma is defined as hyperpigmented bright or dark brown spots which are symmetrically distributed and have serrated and irregular borders. The three general categories of pigmentation pattern include centro facial pattern, malar pattern, and mandibular pattern. Exposure to UV rays, heat, use of cosmetics and photosensitizing drugs, female sex hormonal therapies, aberrant production of melanocyte stimulating hormone, and increasing aesthetic demands are factors which cause the development of melasma disease. This review gives a brief overview regarding the Fitzpatrick skin phototype classification system, life cycle of melanin, mechanism of action of anti-hyperpigmenting drugs, and existing pharmacotherapy strategies for the treatment of melasma. The objectives of this review are focused on role of cutting-edge nanotechnology-based strategies, such as lipid-based nanocarriers, i.e., lipid nanoparticles, microemulsions, nanoemulsions, liposomes, ethosomes, niosomes, transfersomes, aspasomes, invasomes penetration-enhancing vesicles; inorganic nanocarriers, i.e., gold nanoparticles and fullerenes; and polymer-based nanocarriers i.e., polymeric nanoparticles, polymerosomes, and polymeric micelles for the management of hyperpigmentation.

In silico modeling and empirical study of 4-n-Butylresorcinol nanoliposome formulation

A study to incorporate in silico modeling with an empirical experiment has been carried out to formulate nanoliposome containing 4-n-butylresorcinol as the active ingredient. The in silico modeling was performed using molecular dynamics simulation followed by radius of gyration observation to provide insight into the mechanisms of 4-n-butylresorcinol stabilization by liposome due to their nano-size. The empirical experiment was conducted by formulating the nanoliposome using soy lecithin phospholipid formula as suggested by the in silico modeling followed by determining its particle size as well as its shape. From their incorporation, it was found that 3200 phospholipid molecules were selected in formulating nanoliposome containing 4-n-butylresorcinol. The results of the nanoliposomes size observation in the modeling of 3200 lipid molecules was 87.01 (± 0.59) nm, whereas the size from the empirical study was 87.57 (± 0.06) nm. Communicated by Ramaswamy H. Sarma.

7-desacetoxy-6,7-dehydrogedunin discovered by high-throughput screening system suppresses melanogenesis through ATP-P2X7 signaling inhibition

BACKGROUND

Hyperpigmented skin disorders such as melasma and lentigo are common photoaging diseases that cause cosmetic problems. The pigmentation is usually exacerbated by ultraviolet (UV) radiation, and various factors and pathways are involved in UV-mediated melanogenesis. Adenosine 5'-triphosphate (ATP), a well-known molecular unit of intracellular energy, is also regarded as a mediator of UV-mediated melanogenesis via the P2X7 purinergic receptor.

OBJECTIVE

To discover natural substances with an anti-melanogenic effect through inhibition of ATP-P2X7 axis by high-throughput screening (HTS).

METHODS

Among natural compounds provided by the Korea Chemical Bank, chemical compounds with a P2X7 inhibiting effect were screened through an HTS system. Then the selected compounds were verified for their anti-melanogenic effect after treating primary human epidermal melanocytes (PHEMs) with and without ATP. The expression of MITF, tyrosinase, and PMEL/gp100 was analyzed by Western blot, and melanin content was measured as 405 nm absorbance.

RESULTS

Among 962 natural compounds, 58 showed greater than 80% suppression of YO-PRO-1 fluorescence, representing P2X7 activity. Among them, considering cell viability, chemical stability, and availability, 7-desaxacetoxy-6,7-dehydrogedunin (7DG), a limonoid natural compound, was selected. The expression of MITF, tyrosinase, and PMEL/gp100; tyrosinase enzyme activity; and melanin content, which were increased by ATP treatment were abrogated by 7DG. Even when 7DG was treated in PHEMs without addition of ATP, tyrosinase expression and melanin content were significantly decreased. Hypopigmenting effect of 7DG was confirmed in ex vivo culture of human skins.

CONCLUSIONS

7DG has an anti-melanogenic effect through ATP-P2X7 pathway inhibition and could be a potential skin whitening material.

Research-based findings on scope of liposome-based cosmeceuticals: an updated review

Background

Cosmeceuticals are cosmetic products with biologically active components that have drug-like benefits. Cosmeceuticals are currently rapidly growing segments encompassing the personal care industry and numerous topical cosmetics-based therapies for treating different skin conditions. The barrier nature of skin causes limitations to topical treatment. The effectiveness of this cosmeceutical product has been enhanced a few folds by using nanotechnological modifications.

Main body

PubMed electronic searches for the literature were performed using combinations of the following terms: “cosmeceutical,” “liposome-based cosmeceuticals,” “acne and liposome,” “photo-aging and liposome,” “hyperpigmentation and liposome,” “wrinkles and liposome,” “fungal infections and liposome,” and “hair damage and liposome” from the earliest publication date available to January 5, 2022. Among the various nanotechnological approaches, liposomes offer numerous advantages such as topical cosmeceutical products, starting from improved moisturization, biodegradability, biocompatibility, enhanced permeation and retention, improved bioavailability of the active ingredients, increased esthetic appeal of cosmeceutical products, slow and extended dermal release. This review outlines various liposome-based cosmeceutical products that has been investigated to treat skin disorders such as photoaging, wrinkles, hyperpigmentation, hair damage and fungal infections.

Conclusion

Liposome-based cosmeceuticals provide a better opportunity to deliver therapeutic moiety for various skin conditions and offer potential promise for future clinical applications.

Graphical Abstract

Understanding Melasma-How Can Pharmacology and Cosmetology Procedures and Prevention Help to Achieve Optimal Treatment Results? A Narrative Review

Melasma is a chronic skin condition that involves the overproduction of melanin in areas exposed to ultraviolet radiation. Melasma treatment is long-term and complicated with recurrence and resistance to treatment. The pathogenesis of melasma is highly complex with multiple pathologies occurring outside of the skin pigment cells. It includes photoaging, excessive melanogenesis, an increased number of mast cells, increased vascularization, and basement membrane damage. In addition, skin lesions related to melasma and their surrounding skin have nearly 300 genes differentially expressed from healthy skin. Traditionally, melasma was treated with topical agents, including hydroquinone, tretinoin, glucocorticosteroids and various formulations; however, the current approach includes the topical application of a variety of substances, chemical peels, laser and light treatments, mesotherapy, microneedling and/or the use of systemic therapy. The treatment plan for patients with melasma begins with the elimination of risk factors, strict protection against ultraviolet radiation, and the topical use of lightening agents. Hyperpigmentation treatment alone can be ineffective unless combined with regenerative methods and photoprotection. In this review, we show that in-depth knowledge associated with proper communication and the establishment of a relationship with the patient help to achieve good adherence and compliance in this long-term, time-consuming and difficult procedure.

Nanocarriers as Active Ingredients Enhancers in the Cosmetic Industry-The European and North America Regulation Challenges

“Flawless skin is the most universally desired human feature” is an iconic statement by Desmond Morris. Skin indicates one´s health and is so important that it affects a person’s emotional and psychological behavior, these facts having propelled the development of the cosmetics industry. It is estimated that in 2023, this industry will achieve more than 800 billion dollars. This boost is due to the development of new cosmetic formulations based on nanotechnology. Nanocarriers have been able to solve problems related to active ingredients regarding their solubility, poor stability, and release. Even though nanocarriers have evident benefits, they also present some problems related to the high cost, low shelf life, and toxicity. Regulation and legislation are two controversial topics regarding the use of nanotechnology in the field of cosmetics. In this area, the U.S. FDA has taken the lead and recommended several biosafety studies and post-market safety evaluations. The lack of a global definition that identifies nanomaterials as a cosmetic ingredient is a hindrance to the development of global legislation. In the EU, the legislation regarding the biosafety of nanomaterials in cosmetics is stricter. “The cost is not the only important issue, safety and the application of alternative testing methods for toxicity are of crucial importance as well”.

Liposomes: Structure, Biomedical Applications, and Stability Parameters With Emphasis on Cholesterol

Liposomes are essentially a subtype of nanoparticles comprising a hydrophobic tail and a hydrophilic head constituting a phospholipid membrane. The spherical or multilayered spherical structures of liposomes are highly rich in lipid contents with numerous criteria for their classification, including structural features, structural parameters, and size, synthesis methods, preparation, and drug loading. Despite various liposomal applications, such as drug, vaccine/gene delivery, biosensors fabrication, diagnosis, and food products applications, their use encounters many limitations due to physico-chemical instability as their stability is vigorously affected by the constituting ingredients wherein cholesterol performs a vital role in the stability of the liposomal membrane. It has well established that cholesterol exerts its impact by controlling fluidity, permeability, membrane strength, elasticity and stiffness, transition temperature (Tm), drug retention, phospholipid packing, and plasma stability. Although the undetermined optimum amount of cholesterol for preparing a stable and controlled release vehicle has been the downside, but researchers are still focused on cholesterol as a promising material for the stability of liposomes necessitating explanation for the stability promotion of liposomes. Herein, the prior art pertaining to the liposomal appliances, especially for drug delivery in cancer therapy, and their stability emphasizing the roles of cholesterol.

Current Advances of Nanocarrier Technology-Based Active Cosmetic Ingredients for Beauty Applications

Nanocarrier technology has been effectively applied to the development of drug delivery systems to overcome the limitations of traditional preparation. Its application has been extended to various pharmaceutical fields from injection preparation to oral preparation and external preparation, and now it has appeared in the field of cosmetics for beauty applications. The widespread influence of nanocarrier in the cosmetics industry is due to the fact that nanocarrier can effectively promote the percutaneous penetration and significantly increase skin retention of active components in functional cosmetics. Meanwhile, nanocarrier can effectively improve the water dispersion of insoluble active cosmetic ingredients, enhance the stability of efficacy components and achieve the codelivery of diverse cosmetics active ingredients. In this review, we summarized the current progress of nanocarrier technology in the functional cosmetics, including the types and the routes of dermal/transdermal drug delivery nanocarriers used in the functional cosmetics, the mechanism of nanocarriers promoting the percutaneous penetration of active cosmetic ingredients, the application and efficacy evaluation of different active cosmetic ingredients in nanocarriers and discussing the potential risks to human. This will provide a useful reference for the further development of nanocarriers in the field of functional cosmetics.

Liposomal azelaic acid 20% cream vs hydroquinone 4% cream as adjuvant to oral tranexamic acid in melasma: a comparative study

BACKGROUND

Melasma negatively impacts patient's quality of life (QoL). Although hydroquinone 4% is the most prescribed treatment, several side effects had been reported. The traditionally used azelaic acid 20% has poor tolerability and low skin absorption rate.

AIM

To assess the efficacy and tolerability of the liposomal form of azelaic acid 20% as an adjuvant to oral tranexamic acid in the treatment of melasma.

PATIENTS AND METHODS

Fifty females suffering from melasma were divided into two equal groups. The first group used a liposomal form of azelaic acid 20%, and the second group used hydroquinone 4%. Oral tranexamic acid 250 mg was taken by both groups as a single oral daily dose. Melasma severity and the patient's QoL were assessed.

RESULTS

A significant improvement of melasma was detected in females who used the liposomal form of azelaic acid 20% than those who used hydroquinone 4%. This was associated with a significant positive effect on their QoL. Furthermore, the liposomal form of azelaic acid 20% was more significantly tolerable than hydroquinone 4%.

CONCLUSION

The use of the liposomal form of azelaic acid provides an effective and well-tolerated addition to the treatment of melasma.

Advances in the Design of Genuine Human Tyrosinase Inhibitors for Targeting Melanogenesis and Related Pigmentations

Human tyrosinase (hsTYR) is the key enzyme ensuring the conversion of l-tyrosine to dopaquinone, thereby initiating melanin synthesis, i.e., melanogenesis. Although the protein has long been familiar, knowledge about its three-dimensional structure and efficient overexpression protocols emerged only recently. Consequently, for decades medicinal chemistry studies aiming at developing skin depigmenting agents relied almost exclusively on biological assays performed using mushroom tyrosinase (abTYR), producing a plethoric literature, often of little useful purpose. Indeed, several recent reports have pointed out spectacular differences in terms of interaction patterns and inhibition values between hsTYR and abTYR, including for widely used standard tyrosinase inhibitors. In this review, we summarize the last developments regarding the potential role of hsTYR in human pathologies, the advances in recombinant expression systems and structural data retrieving, and the pioneer generation of true hsTYR inhibitors. Finally, we present suggestions for the design of future inhibitors of this highly attractive target in pharmacology and dermocosmetics.

Melasma Treatment: An Evidence-Based Review

BACKGROUND

Melasma is an acquired, chronic pigmentary disorder predominantly affecting women. It may significantly affect quality of life and self-esteem due to its disfiguring appearance. Multiple treatments for melasma are available, with mixed results.

OBJECTIVE

The aim of this article was to conduct an evidence-based review of all available interventions for melasma.

METHODS

A systematic literature search of the PubMed electronic database was performed using the keywords 'melasma' and/or 'chloasma' in the title, through October 2018. The search was then limited to 'randomized controlled trial' and 'controlled clinical trial' in English-language journals. The Cochrane database was also searched for systematic reviews.

RESULTS

The electronic search yielded a total of 212 citations. Overall, 113 studies met the inclusion criteria and were included in this review, with a total of 6897 participants. Interventions included topical agents, chemical peels, laser- and light-based devices, and oral agents. Triple combination cream (hydroquinone, tretinoin, and corticosteroid) remains the most effective treatment for melasma, as well as hydroquinone alone. Chemical peels and laser- and light-based devices have mixed results. Oral tranexamic acid is a promising new treatment for moderate and severe recurrent melasma. Adverse events from all treatments tend to be mild, and mainly consist of skin irritation, dryness, burning, erythema, and post-inflammatory hyperpigmentation.

CONCLUSIONS

Hydroquinone monotherapy and triple combination cream are the most effective and well-studied treatments for melasma, whereas chemical peels and laser- and light-based therapies are equal or inferior to topicals, but offer a higher risk of adverse effects. Oral tranexamic acid may be a safe, systemic adjunctive treatment for melasma, but more studies are needed to determine its long-term safety and efficacy. Limitations of the current evidence are heterogeneity of study design, small sample size, and lack of long-term follow-up, highlighting the need for larger, more rigorous studies in the treatment of this recalcitrant disorder.

4-n-Butylresorcinol-Based Linear and Graft Polymethacrylates for Arbutin and Vitamins Delivery by Micellar Systems

A novel initiator, bromoester modified 4-n-butylresorcinol (4nBREBr₂), was prepared and utilized in controlled atom transfer radical polymerization (ATRP) to obtain three series of amphiphilic copolymers. The V-shaped copolymers of methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), and poly(ethylene glycol) methyl ether methacrylate (MPEGMA), abbreviated to P(HEMA-co-MMA), P(HEMA-co-MPEGMA), and P(MMA-co-MPEGMA), were synthesized. Moreover, P((HEMA-graft-PEG)-co-MMA) graft copolymers were prepared by combining the pre-polymerization modification of HEMA and a "click" reaction using a "grafting onto" approach. All copolymers could form micelles with encapsulated active substances (vitamin C (VitC), vitamin E (VitE), arbutin (ARB)), which are used in cosmetology. In vitro studies carried out in a PBS solution (pH 7.4) demonstrates that in most cases the maximum release of active substance was after 1 h. The polymeric systems presenting satisfactory encapsulation characteristics and release profiles are attractive micellar carriers of cosmetic substances, which show a positive effect on the skin condition.

New oral and topical approaches for the treatment of melasma

Melasma is a common, therapeutically challenging, and universally relapsing disorder of hyperpigmentation that is most often observed in women and individuals with Fitzpatrick Skin Types III through VI. The pathogenesis of melasma is complex and protean. Contributing factors that are often implicated in the etiopathogenesis of this condition include a genetic predisposition, intense ultraviolet radiation exposure, and hormonal influences. Therapeutic interventions for melasma include a multimodality approach incorporating photoprotection agents, topical and oral skin lighteners, and resurfacing procedures. Given our expanding knowledge of the pathogenesis of melasma, new and effective treatments are expanding our therapeutic armamentarium. This article reviews new and emerging oral and topical treatments for melasma.

Melasma: Updates and perspectives

Management of melasma is highly challenging due to inconsistent treatment results and frequent relapses. However, recent studies revealed that melasma may not only be a disease of melanocytes, but also a photoaging skin disorder. Herein, we attempt to validate that melasma is indeed a photoaging disorder by presenting the histopathologic findings of melasma: solar elastosis, altered basement membrane, increased vascularization and increased mast cell count. We also provide some therapeutic implications based on these findings and a discussion on the latest updates and perspectives regarding treatment.

Inhibitors of Melanogenesis: An Updated Review

Melanins are pigment molecules that determine the skin, eye, and hair color of the human subject to its amount, quality, and distribution. Melanocytes synthesize melanin and provide epidermal protection from various stimuli, such as harmful ultraviolet radiation, through the complex process called melanogenesis. However, serious dermatological problems occur when there is excessive production of melanin in different parts of the human body. These include freckles, melasma, senile lentigo, pigmented acne scars, and cancer. Therefore, controlling the production of melanin is an important approach for the treatment of pigmentation related disorderes. In this Perspective, we focus on the inhibitors of melanogenesis that directly/indirectly target a key enzyme tyrosinase as well as its associated signaling pathways.

Medical Management of Melasma: A Review with Consensus Recommendations by Indian Pigmentary Expert Group

Melasma is one of the most common hyperpigmentary disorders found mainly in women and dark-skinned patients. Sunlight, hormones, pregnancy, and genetics remain the most implicated in the causation of melasma. Although rather recalcitrant to treatment, topical agents such as hydroquinone, modified Kligman's Regime, azelaic acid, kojic acid, Vitamin C, and arbutin still remain the mainstay of therapy with sun protection being a cornerstone of therapy. There are several new botanical and non botanical agents and upcoming oral therapies for the future. There is a lack of therapeutic guidelines, more so in the Indian setup. The article discusses available evidence and brings forward a suggested treatment algorithm by experts from Pigmentary Disorders Society (PDS) in a collaborative discussion called South Asian Pigmentary Forum (SPF).

Skin whitening agents: medicinal chemistry perspective of tyrosinase inhibitors

Melanogenesis is a process to synthesize melanin, which is a primary responsible for the pigmentation of human skin, eye and hair. Although numerous enzymatic catalyzed and chemical reactions are involved in melanogenesis process, the enzymes such as tyrosinase and tyrosinase-related protein-1 (TRP-1) and TRP-2 played a major role in melanin synthesis. Specifically, tyrosinase is a key enzyme, which catalyzes a rate-limiting step of the melanin synthesis, and the downregulation of tyrosinase is the most prominent approach for the development of melanogenesis inhibitors. Therefore, numerous inhibitors that target tyrosinase have been developed in recent years. The review focuses on the recent discovery of tyrosinase inhibitors that are directly involved in the inhibition of tyrosinase catalytic activity and functionality from all sources, including laboratory synthetic methods, natural products, virtual screening and structure-based molecular docking studies.

Recent development of signaling pathways inhibitors of melanogenesis

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

Calcium triggered self-assembly of alginate-graft-POEGMA via RAFT for the encapsulation of lipophillic actives

Self-assembly of alginate into nanoparticles was realized by grafting hydrophilic brushes via RAFT.

Evidence-based Review, Grade of Recommendation, and Suggested Treatment Recommendations for Melasma

Treatment of melasma is known to be less satisfactory, often incomplete, and relapse is frequent. Although many treatment options are available, they are either known to be unsafe on long-term use or their long-term safety profile is unknown. Patients often use various drugs, even topical steroid-based preparation without any medical supervision for long period of time, making the skin unsuitable for many of the drugs available. Thus, there has been gross disparity among the treating physician about what drugs and what regimen are best suitable for various categories of melasma patients and in different situations. With this background, numerous newer drugs, mostly combinations of some proprietary molecules or even unknown plant extracts, have flooded the market for the management of melasma. Information on efficacy or safety of these products are almost unknown. Studies on Asian people, especially Indian population, are far less commonly available. Therapeutic guideline for use on Indian patients with melasma is almost missing. Extrapolation of data from Caucasian people for use on Asian people may not be scientifically justifiable because Caucasian and Asian people are known to have inherent difference in their response as well as tolerance to the drugs used for melasma. With this background, we have extensively evaluated, following a strict, scientifically designed protocol, all the available studies on melasma management till May 2016 and prepared this document on level of evidence, grade of recommendation and suggested therapeutic guideline for melasma as per the method proposed by Oxford Centre of Evidence-Based Medicine. Various ethical, social, logical, regional, and economic issues in the context of Indian and similar populations were given due importance while preparing the suggested therapeutic recommendation.

4-n-butylresorcinol enhances proteolytic degradation of tyrosinase in B16F10 melanoma cells

OBJECTIVE

4-n-butylresorcinol is a competitive inhibitor of tyrosinase and has been used as an antimelanogenic agent. However, its inhibition mechanism in intact cells is not fully understood. To elucidate the cellular mechanism, we compared in vitro and in vivo inhibitory effects of 4-n-butylresorcinol on tyrosinase activity.

METHODS

B16F10 melanoma cells were cultured in media containing α-MSH in the presence or absence of 4-n-butylresorcinol. Tyrosinase mRNA levels, protein levels and activity in B16F10 cells were compared by real-time PCR, immunostaining combined with western blot and colorimetric analysis, respectively. Melanin concentration was measured by colorimetry both in the cells and in the media. Tyrosinase glycosylation and proteolytic degradation were analysed by immunoblotting after cells were treated with Endo H/PNGase F and E64/proteasome inhibitors, respectively.

RESULTS

4-n-butylresorcinol inhibited tyrosinase activity and melanin synthesis more effectively in intact cells than in cell lysates. Western blotting and real-time RT-PCR showed that 4-n-butylresorcinol reduced protein levels, but not mRNA levels, of tyrosinase in B16F10 cells. 4-n-butylresorcinol showed no effect on the processing of tyrosinase glycosylation or on trafficking to melanosomes. However, treatment of B16F10 cells with E64 or proteasome inhibitor abrogated the 4-n-butylresorcinol-induced decrease of tyrosinase. Moreover, 4-n-butylresorcinol activated p38 MAPK, resulting in increased ubiquitination of tyrosinase.

CONCLUSION

4-n-butylresorcinol inhibits melanogenesis by enhancing proteolytic degradation of tyrosinase as well as competitive binding to tyrosinase. These findings will help to develop new, effective and safe chemicals for the treatment of hyperpigmentation disorders.

Characterization of the action of tyrosinase on resorcinols

The action of tyrosinase on resorcinol and some derivatives (4-ethylresorcinol, 2-methylresorcinol and 4-methylresorcinol) was investigated. If the catalytic cycle is completed with a reductant such as ascorbic acid or an o-diphenol such as 4-tert-butylcatechol, these compounds act as substrates of tyrosinase in all cases. The reaction can also be carried out, adding hydrogen peroxide to the medium. All the above compounds were characterized as substrates of the enzyme and their kinetic constants, KM (Michaelis constant) and kcat (catalytic constant) were determined. Measurement of the activity of the enzyme after pre-incubation with resorcinol, 4-ethylresorcinol or 4-methylresorcinol points to an apparent loss of activity at short times, which could correspond to an enzymatic inactivation process. However, if the measurements are extended over longer times, a burst is observed and the enzymatic activity is recovered, demonstrating that these compounds are not suicide substrates of the enzyme. These effects are not observed with 2-methylresorcinol. The docking results indicate that the binding of met-tyrosinase with these resorcinols occurs in the same way, but not with 2-methylresorcinol, due to steric hindrance.

Melasma update

Melasma is an acquired pigmentary disorder characterized by symmetrical hyperpigmented macules on the face. Its pathogenesis is complex and involves the interplay of various factors such as genetic predisposition, ultraviolet radiation, hormonal factors, and drugs. An insight into the pathogenesis is important to devise treatment modalities that accurately target the disease process and prevent relapses. Hydroquinone remains the gold standard of treatment though many newer drugs, especially plant extracts, have been developed in the last few years. In this article, we review the pathogenetic factors involved in melasma. We also describe the newer treatment options available and their efficacy. We carried out a PubMed search using the following terms “melasma, pathogenesis, etiology, diagnosis, treatment” and have included data of the last few years.

Treatment of melasma with topical agents, peels and lasers: an evidence-based review

BACKGROUND

Melasma is an acquired disorder of hyperpigmentation occurring on the face and predominantly affecting women of childbearing age. It is a chronic, often relapsing condition with a negative impact on quality of life. Current treatments for melasma are unsatisfactory.

OBJECTIVE

The aim of this article was to conduct an evidence-based review of interventions available for the treatment of melasma.

METHODS

A systematic literature search was performed using PubMed and the keywords 'melasma' or 'chloasma' in the title. The search was further refined by using a filter for 'controlled clinical trials' and 'randomized controlled trial'. The included studies were used to develop recommendations for treatment.

RESULTS

The electronic search yielded a total of 80 citations. Forty studies were included in this review, which had a total of 2,912 participants. Three different therapeutic modalities were investigated-topical agents, chemical peels, and laser and light therapies. Topical depigmenting agents were found to be the most effective in treating moderate-to-severe melasma, with combination therapies, such as triple-combination therapy (hydroquinone, tretinoin, and fluocinolone acetonide), yielding the best results. Chemical peels as well as laser and light therapies were found to have moderate benefit but more studies are needed to determine their efficacy and long-term safety. Adverse events associated with treatment were mild and short-lasting and included skin irritation, dryness, burning, and erythema. The data could not be statistically pooled because of the heterogeneity of treatments and lack of consistency across study designs.

CONCLUSIONS

Topical combination therapies were found to be more effective than monotherapy. Triple combination therapy was found to be the most effective, but approximately 40 % of patients develop erythema and peeling. Chemical peels and laser and light therapies produced mixed results, with increased risk of irritation and subsequent hyperpigmentation, particularly in darker-skinned individuals. Hence, current treatments available for melasma remain unsatisfactory. Many of the studies lacked long-term follow-up. Limitations of current literature include the heterogeneity of study designs, small sample sizes, and poor follow-up rates. Additional evidence for the effects and role of sunscreens is needed. Categorization or stratification of demographic data should also be included in future studies, such as age, melasma type, and duration of melasma prior to initiation of treatment. Patient's perception of improvement versus investigator's assessment of improvement should also be included in future studies and standardized methods of study design and assessment of outcomes are needed to form definitive conclusions on the efficacy of different treatment modalities.

New horizons in treating disorders of hyperpigmentation in skin of color

Pigmentary abnormalities are among the most common reasons why patients with skin of color visit a dermatologist. Hydroquinone has been a cornerstone for the treatment of hyperpigmentation; however, concerns regarding adverse effects have prompted a search for alternative agents. Some promising topical treatments include soy, licorice, rucinol, mulberry, niacinamide, ellagic acid, resveratrol, and dioic acid. Oral agents, primarily used for the prevention of postprocedural hyperpigmentation, include procyanidins, tranexamic acid, and Polypodium leucotomos. Advances in Q-switched lasers, intense pulse light, fractional photothermolysis, and the advent of tretinoin peeling add to the clinician's armamentarium for treating hyperpigmentation.

Topical hypopigmenting agents for pigmentary disorders and their mechanisms of action

Melanin is produced in melanocytes and stored in melanosomes. In spite of its beneficial sun-protective effect, abnormal accumulation of melanin results in esthetic problems. Hydroquinone, competing with tyrosine, is a major ingredient in topical pharmacological agents. However, frequent adverse reactions are amongst its major limitation. To solve this problem, several alternatives such as arbutin, kojic acid, aloesin, and 4-n-butyl resorcinol have been developed. Herein, we classify hypopigmenting agents according to their mechanism of action; a) regulation of enzyme, which is subdivided into three categories, i) regulation of transcription and maturation of tyrosinase, ii) inhibition of tyrosinase activity, and iii) post-transcriptional control of tyrosinase; b) inhibition of melanosome transfer, and c) additional mechanisms such as regulation of the melanocyte environment and antioxidant agents.

Interventions for melasma

BACKGROUND

Melasma is an acquired symmetrical pigmentary disorder where confluent grey-brown patches typically appear on the face. Available treatments for melasma are unsatisfactory.

OBJECTIVES

To assess interventions used in the management of all types of melasma: epidermal, dermal, and mixed.

SEARCH STRATEGY

In May 2010 we searched the Cochrane Skin Group Specialised Register, the Cochrane Central Register of Controlled Trials (Clinical Trials) in The Cochrane Library, MEDLINE, EMBASE, PsycINFO, and LILACS. Reference lists of articles and ongoing trials registries were also searched.

SELECTION CRITERIA

Randomised controlled trials that evaluated topical and systemic interventions for melasma.

DATA COLLECTION AND ANALYSIS

Study selection, assessment of methodological quality, data extraction, and analysis was carried out by two authors independently.

MAIN RESULTS

We included 20 studies with a total of 2125 participants covering 23 different treatments. Statistical pooling of the data was not possible due to the heterogeneity of treatments. Each study involved a different set of interventions. They can be grouped into those including a bleaching agent such as hydroquinone, triple-combination creams (hydroquinone, tretinoin, and fluocinolone acetonide), and combination therapies (hydroquinone cream and glycolic acid peels), as well as less conventional therapies including rucinol, vitamin C iontophoresis, and skin-lightening complexes like Thiospot and Gigawhite.Triple-combination cream was significantly more effective at lightening melasma than hydroquinone alone (RR 1.58, 95% CI 1.26 to 1.97) or when compared to the dual combinations of tretinoin and hydroquinone (RR 2.75, 95% CI 1.59 to 4.74), tretinoin and fluocinolone acetonide (RR 14.00, 95% CI 4.43 to 44.25), or hydroquinone and fluocinolone acetonide (RR 10.50, 95% CI 3.85 to 28.60).Azelaic acid (20%) was significantly more effective than 2% hydroquinone (RR 1.25, 95% CI 1.06 to 1.48) at lightening melasma but not when compared to 4% hydroquinone (RR 1.11, 95% CI 0.94 to 1.32).In two studies where tretinoin was compared to placebo, participants rated their melasma as significantly improved in one (RR 13, 95% CI 1.88 to 89.74) but not the other. In both studies by other objective measures tretinoin treatment significantly reduced the severity of melasma.Thiospot was more effective than placebo (SMD -2.61, 95% CI -3.76 to -1.47).The adverse events most commonly reported were mild and transient such as skin irritation, itching, burning, and stinging.

AUTHORS' CONCLUSIONS

The quality of studies evaluating melasma treatments was generally poor and available treatments inadequate. High-quality randomised controlled trials on well-defined participants with long-term outcomes to determine the duration of response are needed.