Corticotropin releasing hormone and proopiomelanocortin involvement in the cutaneous response to stress

Endocrine Controls of Skin Aging

Skin is the largest organ of the human body and undergoes both intrinsic (chronological) and extrinsic aging. While intrinsic skin aging is driven by genetic and epigenetic factors, extrinsic aging is mediated by external threats such as UV irradiation or fine particular matters, the sum of which is referred to as exposome. The clinical manifestations and biochemical changes are different between intrinsic and extrinsic skin aging, albeit overlapping features exist, eg, increased generation of reactive oxygen species, extracellular matrix degradation, telomere shortening, increased lipid peroxidation, or DNA damage. As skin is a prominent target for many hormones, the molecular and biochemical processes underlying intrinsic and extrinsic skin aging are under tight control of classical neuroendocrine axes. However, skin is also an endocrine organ itself, including the hair follicle, a fully functional neuroendocrine "miniorgan." Here we review pivotal hormones controlling human skin aging focusing on IGF-1, a key fibroblast-derived orchestrator of skin aging, of GH, estrogens, retinoids, and melatonin. The emerging roles of additional endocrine players, ie, α-melanocyte-stimulating hormone, a central player of the hypothalamic-pituitary-adrenal axis; members of the hypothalamic-pituitary-thyroid axis; oxytocin, endocannabinoids, and peroxisome proliferator-activated receptor modulators, are also reviewed. Until now, only a limited number of these hormones, mainly topical retinoids and estrogens, have found their way into clinical practice as anti-skin aging compounds. Further research into the biological properties of endocrine players or its derivatives may offer the development of novel senotherapeutics for the treatment and prevention of skin aging.

The IL-6 autocrine loop promoting IFN-γ-induced fibroblast senescence is involved in psychological stress-mediated exacerbation of vitiligo

BACKGROUND

Psychological stress is the most common psychological comorbidity and a significant triggering factor of vitiligo. Moderate to severe psychological stress can markedly affect the efficacy of vitiligo treatment. However, the specific mechanisms underlying its involvement remain insufficiently studied.

METHODS

Chronic unpredictable mild stress (CUMS)-induced major depressive disorder (MDD)-like behavior was modeled in C57BL/6 mice alongside wild-type mice to investigate differences in vitiligo pathogenesis. White spot tissues from mouse tails were subjected to high-throughput transcriptomic sequencing (RNA-seq). In vitro experiments utilized β-galactosidase, P16, and P21 to assess IFN-γ-induced senescence. The effects of exogenous IL-6 on fibroblast senescence were assessed, and the role of blocking the IL-6 autocrine loop with an IL-6R inhibitor in reversing IFN-γ-induced fibroblast senescence was evaluated.

RESULTS

CUMS-induced MDD -like mice exhibited significantly lower body mass index and sugar-water preference index compared to wild-type mice, and their vitiligo severity was markedly increased. Transcriptomic sequencing revealed significant upregulation of cellular senescence and JAK-STAT signaling pathways in white spot tissues of depressive-like vitiligo mice. In vitro findings indicated that IFN-γ induced fibroblast senescence via activation of the JAK2-STAT3 signaling pathway, which subsequently promoted melanocyte apoptosis and increased IL-6 secretion and IL-6R expression. Exogenous IL-6 further activated the JAK2-STAT3 signaling pathway, induced fibroblast senescence, and synergistically intensified IFN-γ-induced fibroblast senescence.

CONCLUSION

Excessive activation of the IL-6 autocrine loop, synergizing with IFN-γ to aggravate fibroblast senescence and promote melanocyte apoptosis. Blocking the IL-6 autocrine loop may serve as an effective approach to mitigate the impact of CUMS on vitiligo pathogenesis and treatment efficacy.

Neuro-immuno-endocrinology of the skin: how environment regulates body homeostasis

The skin, including the hypodermis, is the largest organ of the body. The epidermis, the uppermost layer, is in direct contact with the environment and is exposed to environmental stressors, including solar radiation and biological, chemical and physical factors. These environmental factors trigger local responses within the skin that modulate homeostasis on both the cutaneous and systemic levels. Using mediators in common with brain pathways, immune and neuroendocrine systems within the skin regulate these responses to activate various signal transduction pathways and influence the systemic endocrine and immune systems in a context-dependent manner. This skin neuro-immuno-endocrine system is compartmentalized through the formation of epidermal, dermal, hypodermal and adnexal regulatory units. These units can act separately or in concert to preserve skin integrity, allow for adaptation to a changing environment and prevent the development of pathological processes. Through activation of peripheral nerve endings, the release of neurotransmitters, hormones, neuropeptides, and cytokines and/or chemokines into the circulation, or by priming circulating and resident immune cells, this system affects central coordinating centres and global homeostasis, thus adjusting the body's homeostasis and allostasis to optimally respond to the changing environment.

G Protein-Coupled Receptors in Skin Aging

Skin aging is a complex biological process affected by a plethora of intrinsic and extrinsic factors that alter cutaneous functions through the modulations of signaling pathways and responses. Expressed in various cell types and skin tissue layers, G protein-coupled receptors (GPCRs) play a vital role in regulating skin aging. We have cataloged 156 GPCRs expressed in the skin and reviewed their roles in skin aging, such as pigmentation, loss of elasticity, wrinkles, rough texture, and aging-associated skin disorders. By exploring the GPCRs found in the skin, it may be possible to develop new treatment regimens for aging-associated skin conditions using GPCR ligands.

Implication of Immunobiological Function of Melanocytes in Dermatology

Melanocytes are essential for regulating pigmentation and providing photoprotection in human skin. Originating from neural crest cells, these cells migrate to the basal layer of the epidermis and hair follicles during embryogenesis. Melanosomes, the specialized, membrane-bound organelles are essential for melanin synthesis. Beyond their role in pigmentation, melanocytes exhibit complex immune functions, expressing a variety of immune-related markers and receptors, such as pattern recognition receptors (PRRs), major histocompatibility complex class II (MHC-II) molecules, CD40, intercellular adhesion molecule 1 (ICAM-1), and programmed death-ligand 1 (PD-L1). These receptors allow melanocytes to detect environmental signals and engage in the innate immune response. Furthermore, melanocytes release various immunomodulatory substances, including proinflammatory cytokines, chemokines, and damage-associated molecular patterns (DAMPs), contributing to immune regulation. The immune functions of melanocytes are significantly influenced by external factors such as ultraviolet radiation (UVR), the microbiome, and oxidative stress. In different skin diseases, these immune functions may vary. For example, vitiligo, a common hypopigmentary disorder, is primarily driven by an autoimmune response targeting melanocytes, giving rise to depigmentation and the appearance of white patches. In contrast, melanoma, a form of skin cancer that arises from melanocytes, is closely linked to UV exposure. This review highlights the diverse immunobiological functions of melanocytes and their implications in dermatology.

Effectiveness of Extracellular Vesicle Application in Skin Aging Treatment and Regeneration: Do We Have Enough Evidence from Clinical Trials?

In recent years, there has been a dynamic development in therapies utilizing extracellular vesicles (EVs) including exosomes. Therefore, we have conducted an analysis of the scientific literature to verify the current state of knowledge about these therapies. A total of 12 clinical studies were analyzed, covering the use of EVs in treating skin aging, acne scars, alopecia, and wound healing. The results indicate that EVs and exosomes hold potential in regenerative skin therapies, offering innovative and non-invasive therapeutic approaches. At the same time, significant challenges related to the standardization of their production and the lack of large-scale randomized studies were identified. Thus, we also evaluated the investigated clinical trials in regard to the MISEV (Minimal Information for Studies of Extracellular Vesicles) criteria. This review provides a comprehensive overview of the contemporary applications of EVs in skin therapy and regenerative medicine, highlighting directions for further research.

Protective Effects of Keratinocyte-Derived GCSF and CCL20 on UVB-Induced Melanocyte Damage

The skin microenvironment created by keratinocytes (KC) influences the stress responses of melanocytes (MC) to UVB insults. This study employed RNA sequencing analysis as well as in vitro and in vivo models to elucidate the underlying mechanisms. Our RNA-Seq analysis revealed a statistically significant upregulation of GCSF and CCL20 genes in UVB-irradiated KC, correlating with the protective effects of KC on MC responses to UVB exposure. Recombinant GCSF and CCL20 exhibited the most pronounced modulation of UVB-induced MC responses. These effects included the attenuation of apoptosis and reduction of ROS formation, along with the upregulation of tyrosinase and tyrosinase-related protein-1, which are involved in the melanogenic pathway. ELISA was also used to confirm that UVB could induce the secretion of GCSF and CCL20 from KC. A similar correlation between GCSF and CCL20 expression in KC and tyrosinase levels in MC was observed in UVB-irradiated mouse skin. Our study provides novel insights into the protective role of GCSF and CCL20 in the paracrine effects of KC on UVB-induced MC damage through the modulation of stress response pathways, the MITF-tyrosinase axis, and the regulation of p53. These findings have implications for the development of pharmacological strategies targeting KC-derived paracrine factors for the prevention of skin photodamage.

Changes in BDNF Concentration in Men after Foam Roller Massage

Massage is one of the oldest forms of therapy practiced since ancient times. Nowadays, it is used in sports practice, recovery from injury, or supportive therapy for various conditions. The practice of massage uses a variety of instruments that facilitate massaging while relieving the stress on the masseur. One of them is a foam roller. Although roller massage is widely used, there are still no scientific studies describing the biological mechanisms of its effects on the body. The purpose of our study was to analyze the effect of roller massage on BDNF levels in men undergoing self-massage 4x/week/7 weeks. The control group consisted of men who did not perform self-massage. Before the test and after the first, third, fifth, and seventh weeks of self-massage, the study participants' blood was drawn, the serum BDNF was determined, and the results were subjected to analysis of variance by ANOVA test. After the first week of self-massage, an increase in BDNF concentration was observed in the self-massage group compared to the control group (p = 0.023). Similarly, changes were observed in week five (p = 0.044) and week seven (p = 0.046). In the massaged group, BDNF concentrations were significantly higher after the first week of self-massage compared to baseline. In the third week of the study, BDNF decreased to a value comparable to the baseline study, then increased significantly in the fifth and seventh weeks compared to the value recorded in the third week (p = 0.049 and p = 0.029). It was significantly higher in week seven compared to week five (p = 0.03). Higher concentrations of BDNF in subjects undergoing roller self-massage may be one of the biological mechanisms justifying the therapeutic effects of massage in both sports and clinical practice. Studies analyzing the stimulation of BDNF synthesis through various massage techniques should be performed on a larger group of healthy individuals, patients after trauma of multiple origins, and sick people with indications for therapeutic massage.

The brain-skin axis in vitiligo

Vitiligo is an acquired autoimmune skin disease characterized by patchy depigmentation of the skin, often accompanied by white hair. The aetiology of vitiligo is complex and difficult to cure, and its disfiguring appearance significantly impacts patients' mental and physical health. Psychological stress is a major factor in inducing and exacerbating vitiligo, as well as affecting its treatment efficacy, though the specific mechanisms remain unclear. Increasing research on the brain-skin axis in skin immunity suggests that psychological stress can influence local skin immunity through this axis, which may play a crucial role in the pathogenesis of vitiligo. This review focuses on the role of brain-skin axis in the pathogenesis of vitiligo, and explores the possible mechanism of brain-skin axis mediating the pathogenesis of vitiligo from the aspects of sympathetic nervous system, hypothalamic-pituitary-adrenal (HPA) axis and hormones and neuropeptides, aiming to provide the necessary theoretical basis for psychological intervention in the prevention and treatment of vitiligo.

Comparison of the Skin Microbiota in the Periocular Region between Patients with Inflammatory Skin Diseases and Healthy Participants: A Preliminary Study

(1) Background: Periocular or periorbital dermatitis is a common term for all inflammatory skin diseases affecting the area of skin around the eyes. The clear etiopathogenesis of periocular dermatitis is still not fully understood. Advances in molecular techniques for studying microorganisms living in and on our bodies have highlighted the microbiome as a possible contributor to disease, as well as a promising diagnostic marker and target for innovative treatments. The aim of this study was to compare the composition and diversity of the skin microbiota in the periocular region between healthy individuals and individuals affected by the specific entity of periocular dermatitis. (2) Methods: A total of 35 patients with periocular dermatitis and 39 healthy controls were enrolled in the study. After a skin swab from the periocular region was taken from all participants, DNA extraction and 16S rRNA gene amplicon sequencing using Illumina NovaSeq technology were performed. (3) Results: Staphylococcus and Corynebacterium were the most abundant bacterial genera in the microbiota of healthy skin. Analysis of alpha diversity revealed a statistically significant change (p < 0.05) in biodiversity based on the Faith's PD index between patients and healthy individuals. We did not observe changes in beta diversity. The linear discriminant analysis effect size (LEfSe) revealed that Rothia, Corynebacterium, Bartonella, and Paracoccus were enriched in patients, and Anaerococcus, Bacteroides, Porphyromonas, and Enhydrobacter were enriched in healthy controls. (4) Conclusions: According to the results obtained, we assume that the observed changes in the bacterial microbiota on the skin, particularly Gram-positive anaerobic cocci and skin commensals of the genus Corynebacterium, could be one of the factors in the pathogenesis of the investigated inflammatory diseases. The identified differences in the microbiota between healthy individuals and patients with periocular dermatitis should be further investigated.

Exploring the interplay between stress mediators and skin microbiota in shaping age-related hallmarks: A review

Psychological stress is a major contributing factor to several health problems (e.g., depression, cardiovascular disease). Around 35 % of the world's population suffers from it, including younger generations. Physiologically, stress manifests through neuroendocrine pathways (Hypothalamic-Pituitary-Adrenal (HPA) axis and Sympathetic-Adrenal-Medullary (SAM) system) which culminate in the production of stress mediators like cortisol, epinephrine and norepinephrine. Stress and its mediators have been associated to body aging, through molecular mechanisms such as telomere attrition, mitochondrial dysfunction, cellular senescence, chronic inflammation, and dysbiosis, among others. Regarding its impact in the skin, stress impacts its structural integrity and physiological function. Despite this review focusing on several hallmarks of aging, emphasis was placed on skin microbiota dysbiosis. In this line, several studies, comprising different age groups, demographic contexts and body sites, have reported skin microbiota alterations associated with aging, and some effects of stress mediators on skin microbiota have also been reviewed in this paper. From a different perspective, since it is not a "traditional" stress mediator, oxytocin, a cortisol antagonist, has been related to glucorticoids inhibition and to display positive effects on cellular aging. This hormone dysregulation has been associated to psychological issues such as depression, whereas its upregulation has been linked to positive social interaction.

Thin Amelanotic and Hypomelanotic Melanoma: Clinicopathological and Dermoscopic Features

Background and Objectives: Amelanotic/hypomelanotic melanomas (AHMs) account for 2-8% of all cutaneous melanomas. Due to their clinical appearance and the lack of specific dermoscopic indicators, AHMs are challenging to diagnose, particularly in thinner cutaneous lesions. The aim of our study was to evaluate the clinicopathological and dermoscopic features of thin AHMs. Identifying the baseline clinical-pathological features and dermoscopic aspects of thin AHMs is crucial to better understand this entity. Materials and Methods: We divided the AHM cohort into two groups based on Breslow thickness: thin (≤1.00 mm) and thick (>1.00 mm). This stratification helped identify any significant clinicopathological differences between the groups. For dermoscopic analysis, we employed the "pattern analysis" approach, which involves a simultaneous and subjective assessment of different criteria. Results: Out of the 2.800 melanomas analyzed for Breslow thickness, 153 were identified as AHMs. Among these, 65 patients presented with thin AHMs and 88 with thick AHMs. Red hair color and phototype II were more prevalent in patients with thin AHMs. The trunk was the most common anatomic site for thin AHMs. Patients with thin AHMs showed a higher number of multiple melanomas. Dermoscopic analysis revealed no significant difference between thin AHMs and thick AHMs, except for a more frequent occurrence of residual reticulum in thin AHMs. Conclusions: Thin AHMs typically affect individuals with lower phototypes and red hair color. These aspects can be related to the higher presence of pheomelanin, which provides limited protection against sun damage. This also correlates with the fact that the trunk, a site commonly exposed to intermittent sun exposure, is the primary anatomical location for thin AHMs. Multiple primary melanomas are more common in patients with thin AHMs, likely due to an intrinsic predisposition as well as greater periodic dermatologic follow-ups in this class of patients. Apart from the presence of residual reticulum, no other significant dermoscopic differences were observed, complicating the differential diagnosis between thin and thick AHMs based on dermoscopy alone.

Malignant Melanoma: An Overview, New Perspectives, and Vitamin D Signaling

Melanoma, originating through malignant transformation of melanin-producing melanocytes, is a formidable malignancy, characterized by local invasiveness, recurrence, early metastasis, resistance to therapy, and a high mortality rate. This review discusses etiologic and risk factors for melanoma, diagnostic and prognostic tools, including recent advances in molecular biology, omics, and bioinformatics, and provides an overview of its therapy. Since the incidence of melanoma is rising and mortality remains unacceptably high, we discuss its inherent properties, including melanogenesis, that make this disease resilient to treatment and propose to use AI to solve the above complex and multidimensional problems. We provide an overview on vitamin D and its anticancerogenic properties, and report recent advances in this field that can provide solutions for the prevention and/or therapy of melanoma. Experimental papers and clinicopathological studies on the role of vitamin D status and signaling pathways initiated by its active metabolites in melanoma prognosis and therapy are reviewed. We conclude that vitamin D signaling, defined by specific nuclear receptors and selective activation by specific vitamin D hydroxyderivatives, can provide a benefit for new or existing therapeutic approaches. We propose to target vitamin D signaling with the use of computational biology and AI tools to provide a solution to the melanoma problem.

Spatial Distribution and Functional Impact of Human Scalp Hair Follicle Microbiota

Human hair follicles (HFs) constitute a unique microbiota habitat that differs substantially from the skin surface. Traditional HF sampling methods fail to eliminate skin microbiota contaminants or assess the HF microbiota incompletely, and microbiota functions in human HF physiology remain ill explored. Therefore, we used laser-capture microdissection, metagenomic shotgun sequencing, and FISH to characterize the human scalp HF microbiota in defined anatomical compartments. This revealed significant compartment-, tissue lineage-, and donor age-dependent variations in microbiota composition. Greatest abundance variations between HF compartments were observed for viruses, archaea, Staphylococcus epidermidis, Cutibacterium acnes, and Malassezia restricta, with the latter 2 being the most abundant viable HF colonizers (as tested by propidium monoazide assay) and, surprisingly, most abundant in the HF mesenchyme. Transfection of organ-cultured human scalp HFs with S. epidermidis-specific lytic bacteriophages ex vivo downregulated transcription of genes known to regulate HF growth and development, metabolism, and melanogenesis, suggesting that selected microbial products may modulate HF functions. Indeed, HF treatment with butyrate, a metabolite of S. epidermidis and other HF microbiota, delayed catagen and promoted autophagy, mitochondrial activity, and gp100 and dermcidin expression ex vivo. Thus, human HF microbiota show spatial variations in abundance and modulate the physiology of their host, which invites therapeutic targeting.

Ganoderma lucidum extract attenuates corticotropin-releasing hormone-induced cellular senescence in human hair follicle cells

Corticotropin-releasing hormone (CRH) is a key mediator in stress-induced hair growth inhibition. Here, we investigated the impact of stress-induced senescence and evaluated the potential of Ganoderma lucidum (GL) extract in mitigating CRH-induced senescence in human hair follicle cells (hHFCs). We show that CRH treatment increased the senescence-associated beta-galactosidase (SA-β-GAL) activity and reactive oxygen species (ROS) formation in hHFCs and suppressed alkaline phosphatase (ALP) activity and anagen-inducing genes. However, GL extract restored ALP activity and decreased the expression levels of anagen-related genes in CRH-treated hHFCs. It decreased SA-β-GAL activity, reduced ROS production, and prevented the phosphorylation of MAPK signaling pathways in CRH-related stress response. Moreover, GL reversed the CRH-induced inhibition of two-cell assemblage (TCA) elongation and Ki67 expression. GL extract attenuates stress-induced hair follicular senescence by delaying catagen entry and scavenging ROS. Our findings suggest that GL extract could be used for treating stress-induced hair loss.

Effects on peripheral and central nervous system of key inflammatory intercellular signalling peptides and proteins in psoriasis

Psoriasis is a chronic systemic inflammatory cutaneous disease. Where the immune system plays an important role in its pathogenesis, with key inflammatory intercellular signalling peptides and proteins including IL-17 and IL-23. The psychoneurological system also figures prominently in development of psoriasis. There is a high prevalence of comorbidity between psoriasis and mental health disorders such as depression, anxiety and mania. Patients with psoriasis often suffer from pathological pain in the lesions, and their neurological accidents could improve the lesions in innervated areas. The immune system and the psychoneurological system interact closely in the pathogenesis of psoriasis. Patients with psoriasis exhibit abnormal levels of neuropeptides both in circulating and localized lesion, acting as immunomodulators involved in the inflammatory response. Moreover, receptors for inflammatory factors are expressed in both peripheral and central nervous systems (CNSs), suggesting that nervous system can receive and be influenced by signals from immune system. Key inflammatory intercellular signalling peptides and proteins in psoriasis, such as IL-17 and IL-23, can be involved in sensory signalling and may affect synaptic plasticity and the blood-brain barrier of CNS through the circulation. This review provides an overview of the multiple effects on the peripheral and CNS under conditions of systemic inflammation in psoriasis, providing a framework and inspiration for in-depth studies of neuroimmunomodulation in psoriasis.

Role of neurogenic inflammation in the pathogenesis of alopecia areata

Alopecia areata refers to an autoimmune illness indicated by persistent inflammation. The key requirement for alopecia areata occurrence is the disruption of immune-privileged regions within the hair follicles. Recent research has indicated that neuropeptides play a role in the damage to hair follicles by triggering neurogenic inflammation, stimulating mast cells ambient the follicles, and promoting apoptotic processes in keratinocytes. However, the exact pathogenesis of alopecia areata requires further investigation. Recently, there has been an increasing focus on understanding the mechanisms of immune diseases resulting from the interplay between the nervous and the immune system. Neurogenic inflammation due to neuroimmune disorders of the skin system may disrupt the inflammatory microenvironment of the hair follicle, which plays a crucial part in the progression of alopecia areata.

Photo-neuro-immuno-endocrinology: How the ultraviolet radiation regulates the body, brain, and immune system

Ultraviolet radiation (UVR) is primarily recognized for its detrimental effects such as cancerogenesis, skin aging, eye damage, and autoimmune disorders. With exception of ultraviolet B (UVB) requirement in the production of vitamin D3, the positive role of UVR in modulation of homeostasis is underappreciated. Skin exposure to UVR triggers local responses secondary to the induction of chemical, hormonal, immune, and neural signals that are defined by the chromophores and extent of UVR penetration into skin compartments. These responses are not random and are coordinated by the cutaneous neuro-immuno-endocrine system, which counteracts the action of external stressors and accommodates local homeostasis to the changing environment. The UVR induces electrical, chemical, and biological signals to be sent to the brain, endocrine and immune systems, as well as other central organs, which in concert regulate body homeostasis. To achieve its central homeostatic goal, the UVR-induced signals are precisely computed locally with transmission through nerves or humoral signals release into the circulation to activate and/or modulate coordinating central centers or organs. Such modulatory effects will be dependent on UVA and UVB wavelengths. This leads to immunosuppression, the activation of brain and endocrine coordinating centers, and the modification of different organ functions. Therefore, it is imperative to understand the underlying mechanisms of UVR electromagnetic energy penetration deep into the body, with its impact on the brain and internal organs. Photo-neuro-immuno-endocrinology can offer novel therapeutic approaches in addiction and mood disorders; autoimmune, neurodegenerative, and chronic pain-generating disorders; or pathologies involving endocrine, cardiovascular, gastrointestinal, or reproductive systems.

Molecular and cellular pruritus mechanisms in the host skin

Pruritus, also known as itching, is a complex sensation that involves the activation of specific physiological and cellular receptors. The skin is innervated with sensory nerves as well as some receptors for various sensations, and its immune system has prominent neurological connections. Sensory neurons have a considerable impact on the sensation of itching. However, immune cells also play a role in this process, as they release pruritogens. Disruption of the dermal barrier activates an immune response, initiating a series of chemical, physical, and cellular reactions. These reactions involve various cell types, including keratinocytes, as well as immune cells involved in innate and adaptive immunity. Collective activation of these immune responses confers protection against potential pathogens. Thus, understanding the molecular and cellular mechanisms that contribute to pruritus in host skin is crucial for the advancement of effective treatment approaches. This review provides a comprehensive analysis of the present knowledge concerning the molecular and cellular mechanisms underlying itching signaling in the skin. Additionally, this review explored the integration of these mechanisms with the broader context of itch mediators and the expression of their receptors in the skin.

Molecular Frontiers in Melanoma: Pathogenesis, Diagnosis, and Therapeutic Advances

Melanoma, a highly aggressive skin cancer, is characterized by rapid progression and high mortality. Recent advances in molecular pathogenesis have shed light on genetic and epigenetic changes that drive melanoma development. This review provides an overview of these developments, focusing on molecular mechanisms in melanoma genesis. It highlights how mutations, particularly in the BRAF, NRAS, c-KIT, and GNAQ/GNA11 genes, affect critical signaling pathways. The evolution of diagnostic techniques, such as genomics, transcriptomics, liquid biopsies, and molecular biomarkers for early detection and prognosis, is also discussed. The therapeutic landscape has transformed with targeted therapies and immunotherapies, improving patient outcomes. This paper examines the efficacy, challenges, and prospects of these treatments, including recent clinical trials and emerging strategies. The potential of novel treatment strategies, including neoantigen vaccines, adoptive cell transfer, microbiome interactions, and nanoparticle-based combination therapy, is explored. These advances emphasize the challenges of therapy resistance and the importance of personalized medicine. This review underlines the necessity for evidence-based therapy selection in managing the increasing global incidence of melanoma.

Carotenoids in red fruit (Pandanus conoideus Lam.) have a potential role as an anti‑pigmentation agent (Review)

Melasma is a persistent condition characterized by excessive melanin production in the skin. The management of melasma necessitates a protracted treatment duration, which is associated with diminished levels of patient satisfaction. One effective strategy for mitigating occurrence of melasma is consumption of nutricosmetics with depigmentation properties. The present review aimed to investigate the potential of red fruit as a depigmentation agent. Carotenoids serve a crucial role in human nutrition as a precursor to vitamin A. Carotenoids serve as scavengers of reactive oxygen species generated by ultraviolet radiation. Carotenoids promote skin health. Red fruit, a fruit originating from Papua (Indonesia) has anti-pigmentation properties associated with its ability to block melanogenesis through various protein pathways such as PKA, ERK, and AKT signaling pathways. The consumption of food rich in carotenoids, such as red fruit, has advantageous properties to reduce hyperpigmentation and skin brightening.

Epidermal ET-1 signal induces activation of resting hair follicles by upregulating the PI3K/AKT pathway in the dermis

The prevalence of alopecia has increased recently. Hair loss is often accompanied by the resting phase of hair follicles (HFs). Dermal papilla (DP) plays a crucial role in HF development, growth, and regeneration. Activating DP can revive resting HFs. Augmenting WNT/β-catenin signaling stimulates HF growth. However, the factors responsible for activating resting HFs effectively are unclear. In this study, we investigated epidermal cytokines that can activate resting HFs effectively. We overexpressed β-catenin in both in vivo and in vitro models to observe its effects on resting HFs. Then, we screened potential epidermal cytokines from GEO DATASETs and assessed their functions using mice models and skin-derived precursors (SKPs). Finally, we explored the molecular mechanism underlying the action of the identified cytokine. The results showed that activation of WNT/β-catenin in the epidermis prompted telogen-anagen transition. Keratinocytes infected with Ctnnb1-overexpressing lentivirus enhanced SKP expansion. Subsequently, we identified endothelin 1 (ET-1) expressed higher in hair-growing epidermis and induced the proliferation of DP cells and activates telogen-phase HFs in vivo. Moreover, ET-1 promotes the proliferation and stemness of SKPs. Western blot analysis and in vivo experiments revealed that ET-1 induces the transition from telogen-to-anagen phase by upregulating the PI3K/AKT pathway. These findings highlight the potential of ET-1 as a promising cytokine for HF activation and the treatment of hair loss.

The potential role of ubiquitination and deubiquitination in melanogenesis

Melanogenesis is a critical biochemical process in which melanocytes produce melanin, a crucial element involved in the formation of coat colour in mammals. According to several earlier studies, melanocytes' post-translational modifications of proteins primarily control melanogenesis. Among the many post-translational changes that can affect melanin production, ubiquitination and deubiquitination can keep melanin production going by changing how proteins that are related to melanin are broken down or kept stable. Ubiquitination and deubiquitination maintain ubiquitin homeostasis, which is a highly dynamic process in balance under the action of E3 ubiquitin ligase and deubiquitinating enzymes. However, the regulatory mechanisms underlying ubiquitination and deubiquitination in melanogenesis are yet to be thoroughly investigated. As a result, there has been a growing focus on exploring the potential correlation between melanogenesis, ubiquitination and deubiquitination. This study discusses the mechanisms of ubiquitination and deubiquitination in the context of melanogenesis, a crucial process for enhancing mammalian coat coloration and addressing pigment-related diseases.

Epigenetic regulation of beta-endorphin synthesis in hypothalamic arcuate nucleus neurons modulates neuropathic pain in a rodent pain model

Although beta-endorphinergic neurons in the hypothalamic arcuate nucleus (ARC) synthesize beta-endorphin (β-EP) to alleviate nociceptive behaviors, the underlying regulatory mechanisms remain unknown. Here, we elucidated an epigenetic pathway driven by microRNA regulation of β-EP synthesis in ARC neurons to control neuropathic pain. In pain-injured rats miR-203a-3p was the most highly upregulated miRNA in the ARC. A similar increase was identified in the cerebrospinal fluid of trigeminal neuralgia patients. Mechanistically, we found histone deacetylase 9 was downregulated following nerve injury, which decreased deacetylation of histone H3 lysine-18, facilitating the binding of NR4A2 transcription factor to the miR-203a-3p gene promoter, thereby upregulating miR-203a-3p expression. Further, increased miR-203a-3p was found to maintain neuropathic pain by targeting proprotein convertase 1, an endopeptidase necessary for the cleavage of proopiomelanocortin, the precursor of β-EP. The identified mechanism may provide an avenue for the development of new therapeutic targets for neuropathic pain treatment.

Natural tyrosinase enzyme inhibitors: A path from melanin to melanoma and its reported pharmacological activities

The skin containing melanin pigment acts as a protective barrier and counteracts the UVR and other environmental stressors to maintain or restore disrupted cutaneous homeostasis. The production of melanin pigment is dependent on tyrosine levels. L-tyrosine and L-dihydroxyphenylalanine (L-DOPA) can serve both as a substrates and intermediates of melanin synthetic pathway and as inducers and positive regulators of melanogenesis. The biosynthesis of melanin is stimulated upon exposure to UVR, which can also stimulate local production of hormonal factors, which can stimulate melanoma development by altering the chemical properties of eu- and pheomelanin. The process of melanogenesis can be altered by several pathways. One involves activation of POMC, with the production of POMC peptides including MSH and ACTH, which increase intracellular cAMP levels, which activates the MITF, and helps to stimulate tyrosinase (TYR) expression and activity. Defects in OCA1 to 4 affects melanogenic activity via posttranslational modifications resulting in proteasomal degradation and reducing pigmentation. Further, altering, the MITF factor, helps to regulate the expression of MRGE in melanoma, and helps to increase the TYR glycosylation in ER. CRH stimulates POMC peptides that regulate melanogenesis and also by itself can stimulate melanogenesis. The POMC, P53, ACTH, MSH, MC1R, MITF, and 6-BH4 are found to be important regulators for pigmentation. Melanogenesis can affect melanoma behaviour and inhibit immune responses. Therefore, we reviewed natural products that would alter melanin production. Our special focus was on targeting melanin synthesis and TYR enzyme activity to inhibit melanogenesis as an adjuvant therapy of melanotic melanoma. Furthermore, this review also outlines the current updated pharmacological studies targeting the TYR enzyme from natural sources and its consequential effects on melanin production.

Polymorphisms in corticotrophin-releasing hormone-proopiomalanocortin (CRH-POMC) system genes: Neuroimmune contributions to psoriasis disease

BACKGROUND

Skin is a target organ and source of the corticotropin-releasing hormone-proopiomelanocortin (CRH-POMC) system, operating as a coordinator and executor of responses to stress. Environmental stress exacerbates and triggers inflammatory skin diseases through modifying the cellular components of the immune system supporting the importance of CRH-POMC system in the pathogenesis of psoriasis. The aim of this study was to analyse the association of CRH-POMC polymorphisms with psoriasis and evaluate transcript expression of lesional psoriatic and normal skin in RNA-seq data.

METHODS

Samples of 104 patients with psoriasis and 174 healthy controls were genotyped for 42 single nucleotide polymorphisms (SNPs) of CRH-POMC using Applied Biosystems SNPlex™ method. The transcript quantification was performed using Salmon software v1.3.0.

RESULTS

This study demonstrated the associations between melanocortin 1 receptor (MC1R) polymorphisms rs2228479, rs3212369, dopachrome tautomerase (DCT) polymorphisms rs7987802, rs2031526, rs9524501 and psoriasis in the Tatar population. Very strong association was evident for the SNP rs7987802 in the DCT gene (pc  = 5.95е-006) in psoriasis patients. Additionally, the haplotype analysis provided AT DCT (rs7992630 and rs7987802) and AGA MC1R (rs3212358, 2228479 and 885479) haplotypes significantly associated (pc  ˂ 0.05) with psoriasis in the Tatar population, supporting the involvement of DCT and MC1R to the psoriasis susceptibility. Moreover, MC1R-203 and DCT-201 expression levels were decreased in psoriasis lesional skin compared with healthy control skin.

CONCLUSIONS

This study is the first to identify genetic variants of the MC1R and DCT genes significantly associated with psoriasis in Tatar population. Our results support potential roles of CRH-POMC system genes and DCT in the pathogenesis of psoriasis.

Anti-Melanogenic and Antioxidant Activity of Bifidobacterium longum Strain ZJ1 Extracts, Isolated from a Chinese Centenarian

Melanin produced by melanocytes protects our skin against ultraviolet (UV) radiation-induced cell damage and oxidative stress. Melanin overproduction by hyperactivated melanocytes is the direct cause of skin hyperpigmentary disorders, such as freckles and melasma. Exploring natural whitening agents without the concern of toxicity has been highly desired. In this study, we focused on a Bifidobacterium longum strain, ZJ1, isolated from a Chinese centenarian, and we evaluated the anti-melanogenic activity of the distinctive extracts of ZJ1. Our results demonstrated that whole lysate (WL) and bacterial lysate (BL) of ZJ1 ferments efficiently reduce α-melanocyte-stimulating hormone (α-MSH)-induced melanin production in B16-F10 cells as well as the melanin content in zebrafish embryos. BL and WL downregulate melanogenesis-related gene expression and indirectly inhibit intracellular tyrosinase activity. Furthermore, they both showed antioxidant activity in a menadione-induced zebrafish embryo model. Our results suggest that ZJ1 fermentation lysates have application potential as therapeutic reagents for hyperpigmentary disorders and whitening agents for cosmetics.

Environmental Air Pollutants Affecting Skin Functions with Systemic Implications

The increase in air pollution worldwide represents an environmental risk factor that has global implications for the health of humans worldwide. The skin of billions of people is exposed to a mixture of harmful air pollutants, which can affect its physiology and are responsible for cutaneous damage. Some polycyclic aromatic hydrocarbons are photoreactive and could be activated by ultraviolet radiation (UVR). Therefore, such UVR exposure would enhance their deleterious effects on the skin. Air pollution also affects vitamin D synthesis by reducing UVB radiation, which is essential for the production of vitamin D3, tachysterol, and lumisterol derivatives. Ambient air pollutants, photopollution, blue-light pollution, and cigarette smoke compromise cutaneous structural integrity, can interact with human skin microbiota, and trigger or exacerbate a range of skin diseases through various mechanisms. Generally, air pollution elicits an oxidative stress response on the skin that can activate the inflammatory responses. The aryl hydrocarbon receptor (AhR) can act as a sensor for small molecules such as air pollutants and plays a crucial role in responses to (photo)pollution. On the other hand, targeting AhR/Nrf2 is emerging as a novel treatment option for air pollutants that induce or exacerbate inflammatory skin diseases. Therefore, AhR with downstream regulatory pathways would represent a crucial signaling system regulating the skin phenotype in a Yin and Yang fashion defined by the chemical nature of the activating factor and the cellular and tissue context.

Dark pigmentation and related low FMOD expression increase IL-3 and facilitate plasmacytoid dendritic cell maturation

According to epidemiological research, skin autoimmune diseases are more prevalent among black Americans. We postulated that pigment-producing melanocytes may contribute to local immune regulation in the microenvironment. We examined murine epidermal melanocytes in vitro to determine the role of pigment production in immune responses mediated by dendritic cell (DC) activation. Our study revealed that darkly pigmented melanocytes produce more IL-3 and the pro-inflammatory cytokines, IL-6 and TNF-α, and consequently induce plasmacytoid DC (pDC) maturation. Additionally, we demonstrate that low pigment-associated fibromodulin (FMOD) interferes with cytokine secretion and subsequent pDC maturation.

Hydrolyzed Conchiolin Protein (HCP) Extracted from Pearls Antagonizes both ET-1 and α-MSH for Skin Whitening

Pearl powder is a famous traditional Chinese medicine that has a long history in treating palpitations, insomnia, convulsions, epilepsy, ulcers, and skin lightining. Recently, several studies have demonstrated the effects of pearl extracts on protection of ultraviolet A (UVA) induced irritation on human skin fibroblasts and inhibition of melanin genesis on B16F10 mouse melanoma cells. To further explore the effect we focused on the whitening efficacy of pearl hydrolyzed conchiolin protein (HCP) on human melanoma MNT-1 cells under the irritation of alpha-melanocyte-stimulating hormone (α-MSH) or endothelin 1 (ET-1) to evaluate the intracellular tyrosinase and melanin contents, as well as the expression levels of tyrosinase (TYR), tyrosinase related protein 1 (TRP-1), and dopachrome tautomerase (DCT) genes and related proteins. We found that HCP could decrease the intracellular melanin content by reducing the activity of intracellular tyrosinase and inhibiting the expression of TYR, TRP-1, DCT genes and proteins. At the same time, the effect of HCP on melanosome transfer effect was also investigated in the co-culture system of immortalized human keratinocyte HaCaT cells with MNT-1. The result indicated that HCP could promote the transfer of melanosomes in MNT-1 melanocytes to HaCaT cells, which might accelerate the skin whitening process by quickly transferring and metabolizing melanosomes during keratinocyte differentiation. Further study is needed to explore the mechanism of melanosome transfer with depigmentation.

How cancer hijacks the body's homeostasis through the neuroendocrine system

During oncogenesis, cancer not only escapes the body's regulatory mechanisms, but also gains the ability to affect local and systemic homeostasis. Specifically, tumors produce cytokines, immune mediators, classical neurotransmitters, hypothalamic and pituitary hormones, biogenic amines, melatonin, and glucocorticoids, as demonstrated in human and animal models of cancer. The tumor, through the release of these neurohormonal and immune mediators, can control the main neuroendocrine centers such as the hypothalamus, pituitary, adrenals, and thyroid to modulate body homeostasis through central regulatory axes. We hypothesize that the tumor-derived catecholamines, serotonin, melatonin, neuropeptides, and other neurotransmitters can affect body and brain functions. Bidirectional communication between local autonomic and sensory nerves and the tumor, with putative effects on the brain, is also envisioned. Overall, we propose that cancers can take control of the central neuroendocrine and immune systems to reset the body homeostasis in a mode favoring its expansion at the expense of the host.

Molecular Mechanisms of Neurogenic Inflammation of the Skin

The skin, including the hypodermis, is the largest body organ and is in constant contact with the environment. Neurogenic inflammation is the result of the activity of nerve endings and mediators (neuropeptides secreted by nerve endings in the development of the inflammatory reaction in the skin), as well as interactions with other cells such as keratinocytes, Langerhans cells, endothelial cells and mast cells. The activation of TRPV-ion channels results in an increase in calcitonin gene-related peptide (CGRP) and substance P, induces the release of other pro-inflammatory mediators and contributes to the maintenance of cutaneous neurogenic inflammation (CNI) in diseases such as psoriasis, atopic dermatitis, prurigo and rosacea. Immune cells present in the skin (mononuclear cells, dendritic cells and mast cells) also express TRPV1, and their activation directly affects their function. The activation of TRPV1 channels mediates communication between sensory nerve endings and skin immune cells, increasing the release of inflammatory mediators (cytokines and neuropeptides). Understanding the molecular mechanisms underlying the generation, activation and modulation of neuropeptide and neurotransmitter receptors in cutaneous cells can aid in the development of effective treatments for inflammatory skin disorders.

The role of cytokines/chemokines in an aging skin immune microenvironment

Reversing or slowing down the skin aging process is one of the most intriguing areas of focus across the social and scientific communities around the world. While aging is considered a universal and inevitable natural process of physiological decline, the aging of the skin is the most apparent visual representation of an individual's health. Aging skin may be objectively defined by epidermal thinning; increased transepidermal water loss; decreased cutaneous barrier function; loss of elasticity, laxity, and textured appearance; and gradual deterioration of the epidermal immune environment. As the largest structure of the immune system and of the body as a whole, the skin is the most vulnerable barrier of defense against the environment. The skin reflects an individual's exposures, lifestyle habits, and overall health. From an immunological perspective, cytokines and chemokines act as a central character in the communicating of the immunity in skin aging. These cell signaling proteins serve as the intercellular communication link. This review aims to elucidate how cell-cell crosstalk through cytokines and chemokines, and the interplay between host cells, infiltrating immune cells, and exogenous factors contribute to the overall aging skin.

Melanopsin (OPN4) is a novel player in skin homeostasis and attenuates UVA-induced effects

The presence of melanopsin (OPN4) has been shown in cultured murine melanocytes and was associated with ultraviolet A radiation (UVA) reception. Here we demonstrated the protective role of OPN4 in skin physiology and the increased UVA-induced damage in its absence. Histological analysis showed a thicker dermis and thinner hypodermal white adipose tissue layer in Opn4^-/- (KO) mice than in wild-type (WT) animals. Proteomics analyses revealed molecular signatures associated with proteolysis, remodeling chromatin, DNA damage response (DDR), immune response, and oxidative stress coupled with antioxidant responses in the skin of Opn4 KO mice compared to WT. Skin protein variants were found in Opn4 KO mice and Opn2, Opn3, and Opn5 gene expressions were increased in the genotype. We investigated each genotype response to UVA stimulus (100 kJ/m²). We found an increase of Opn4 gene expression following stimulus on the skin of WT mice suggesting melanopsin as a UVA sensor. Proteomics findings suggest that UVA decreases DDR pathways associated with ROS accumulation and lipid peroxidation in the skin of Opn4 KO mice. Relative changes in methylation (H3-K79) and acetylation sites of histone between genotypes and differentially modulated by UVA stimulus were also observed. We also identified alterations of molecular traits of the central hypothalamus-pituitary- adrenal (HPA) and the skin HPA-like axes in the absence of OPN4. Higher skin corticosterone levels were detected in UVA-stimulated Opn4 KO compared to irradiated WT mice. Taken altogether, functional proteomics associated with gene expression experiments allowed a high-throughput evaluation that suggests an important protective role of OPN4 in regulating skin physiology in the presence and absence of UVA radiation.

Recent Advances and Progress on Melanin: From Source to Application

Melanin is a biological pigment formed by indoles and phenolic compounds. It is widely found in living organisms and has a variety of unique properties. Due to its diverse characteristics and good biocompatibility, melanin has become the focus in the fields of biomedicine, agriculture, the food industry, etc. However, due to the wide range of melanin sources, complex polymerization properties, and low solubility of specific solvents, the specific macromolecular structure and polymerization mechanism of melanin remain unclear, which significantly limits the further study and application of melanin. Its synthesis and degradation pathways are also controversial. In addition, new properties and applications of melanin are constantly being discovered. In this review, we focus on the recent advances in the research of melanin in all aspects. Firstly, the classification, source, and degradation of melanin are summarized. Secondly, a detailed description of the structure, characterization, and properties of melanin is followed. The novel biological activity of melanin and its application is described at the end.

Melanocortin therapies to resolve fibroblast-mediated diseases

Stromal cells have emerged as central drivers in multiple and diverse diseases, and consequently, as potential new cellular targets for the development of novel therapeutic strategies. In this review we revise the main roles of fibroblasts, not only as structural cells but also as players and regulators of immune responses. Important aspects like fibroblast heterogeneity, functional specialization and cellular plasticity are also discussed as well as the implications that these aspects may have in disease and in the design of novel therapeutics. An extensive revision of the actions of fibroblasts on different conditions uncovers the existence of numerous diseases in which this cell type plays a pathogenic role, either due to an exacerbation of their 'structural' side, or a dysregulation of their 'immune side'. In both cases, opportunities for the development of innovative therapeutic approaches exist. In this regard, here we revise the existing evidence pointing at the melanocortin pathway as a potential new strategy for the treatment and management of diseases mediated by aberrantly activated fibroblasts, including scleroderma or rheumatoid arthritis. This evidence derives from studies involving models of in vitro primary fibroblasts, in vivo models of disease as well as ongoing human clinical trials. Melanocortin drugs, which are pro-resolving mediators, have shown ability to reduce collagen deposition, activation of myofibroblasts, reduction of pro-inflammatory mediators and reduced scar formation. Here we also discuss existing challenges, both in approaching fibroblasts as therapeutic targets, and in the development of novel melanocortin drug candidates, that may help advance the field and deliver new medicines for the management of diseases with high medical needs.

New Butyroside D from Argan Press Cake Possess Anti-Melanogenesis Effect via MITF Downregulation in B16F10 and HEM Cells

Hyperpigmentation is a skin condition where patches of skin become darker in color due to excess melanin production upon UV exposure leading to melasma, which are lentigines or post inflammatory hyperpigmentation that psychologically affecting a great number of people. The present study investigates the anti-melanogenic effect of Butyroside D and the underling mechanism. After the confirmation of the non-cytotoxic effect of Butyroside D on B16F10 cells, we proceeded with analyzing the impact of the treatment at low and high concentration (i.e., 0.2 μM and 2 μM) using gene profiling analysis and examined the differentiation in gene expression. Our results identify cyclic adenosine monophosphate (cAMP), Wnt/β-catenin and Mitogen-Activated Protein Kinase (MAPK) signaling pathways to be downregulated upon treatment with Butyroside D. These pathways were targeted to further validate the effect of Butyroside D on membrane receptors melanocortin 1 receptor (MC1R) and receptor tyrosine kinase (c-Kit), related microphthalmia-associated transcription factor (MITF) and consequently tyrosinase (TYR), and tyrosine-related protein-1 (TYRP-1) that were all shown to be downregulated and, therefore, leading to the repression of melanin biosynthesis. Finally, the anti-melanogenic effect of Butyroside D was confirmed on human epidermal melanocytes (HEM) cells by inhibiting the activation of cAMP pathway generally mediated through α-melanocyte-stimulating hormone (α-MSH) and MC1R. Overall, this study suggests the potential applicability of this purified compound for the prevention of hyperpigmentation conditions.

Alopecia Areata: Case report and review of pathophysiology and treatment with Jak inhibitors

Alopecia Areata (AA) is a T-cell mediated autoimmune attack on hair follicles resulting in rapidly developing areas of hair loss involving the scalp and beard that can progress to total scalp hair loss (alopecia totalis) and loss of eyebrows, eyelashes, and total body hair (alopecia universalis). Affected patients have high rates of psychological disorders and decreased quality of life. There are no FDA approved treatments, and the available treatments have a high failure rate. JAK inhibitors are remarkably effective in many autoimmune diseases including Alopecia Areata. Presented is a case report of successful treatment with tofacitinib, and a literature review of the pathophysiology of alopecia areata, the mechanism of action of JAK inhibitors, and the JAK inhibitors in phase 2 and 3 trials.

Anti-melanogenesis effect from Wampee fruit pectin via α-MSH/TRY pathway in A375 cells

Background

Polysaccharides from wampee have been reported to process various biological activities, while the relationship between structure and bioactivities has been barely addressed. Pectin, an abundant water-soluble polysaccharide in wampee, showed significant antioxidant activity, which was associated with the anti-melanogenic activity. Therefore, this study investigated the physicochemical characteristics and the anti-melanogenesis effect of pectin extracted from wampee fruit in A375 cells.

Methods

The physicochemical characterization of pectin from wampee fruit was investigated by gel chromatography (GCP), FT-IR spectroscopy, and NMR spectroscopy methods. The anti-melanogenesis effects and mechanism were evaluated by mushroom tyrosine enzyme and human melanin cell model in vitro.

Results

The results showed that a molecular weight of 5.271 × 10⁵ Da wampee fruit pectin (WFP) were mainly composed of mannose (Man), ribose (Rib), rhamnose (Rha), glucuronic acid (Glc A), glucose (Glc), galacturonic acid (Gal A), galactose (Gal), and arabinose (Ara), which linked with →4)-β-D-Galp-(1 → units. The current study revealed that WFP could significantly suppress mushroom TRY activity in vitro. Furtherly, WFP significantly reduced intracellular and extracellular melanin formation in A375 melanoma cells depending on the presence of alpha-melanocyte stimulating hormone (α-MSH). TRY activity was only inhibited in α-MSH treated A375 cells. Western blot analysis demonstrated that WFP reverse α-MSH induced melanogenesis in A375 melanoma cells, including in down-regulated TRY, TYRP-1, TYRP-2, MITF and CREB expressions.

Conclusion

These results indicated that WFP could inhibit α-MSH induced melanogenesis in A375 melanoma cells via α-MSH/TRY pathway. In conclusion, these data provided a new perspective to annotate WFP anti-melanogenesis activity mechanism.

Neuroendocrine signaling in the skin with a special focus on the epidermal neuropeptides

The skin, which is comprised of the epidermis, dermis, and subcutaneous tissue, is the largest organ in the human body and it plays a crucial role in the regulation of the body's homeostasis. These functions are regulated by local neuroendocrine and immune systems with a plethora of signaling molecules produced by resident and immune cells. In addition, neurotransmitters, endocrine factors, neuropeptides, and cytokines released from nerve endings play a central role in the skin's responses to stress. These molecules act on the corresponding receptors in an intra-, juxta-, para-, or autocrine fashion. The epidermis as the outer most component of skin forms a barrier directly protecting against environmental stressors. This protection is assured by an intrinsic keratinocyte differentiation program, pigmentary system, and local nervous, immune, endocrine, and microbiome elements. These constituents communicate cross-functionally among themselves and with corresponding systems in the dermis and hypodermis to secure the basic epidermal functions to maintain local (skin) and global (systemic) homeostasis. The neurohormonal mediators and cytokines used in these communications regulate physiological skin functions separately or in concert. Disturbances in the functions in these systems lead to cutaneous pathology that includes inflammatory (i.e., psoriasis, allergic, or atopic dermatitis, etc.) and keratinocytic hyperproliferative disorders (i.e., seborrheic and solar keratoses), dysfunction of adnexal structure (i.e., hair follicles, eccrine, and sebaceous glands), hypersensitivity reactions, pigmentary disorders (vitiligo, melasma, and hypo- or hyperpigmentary responses), premature aging, and malignancies (melanoma and nonmelanoma skin cancers). These cellular, molecular, and neural components preserve skin integrity and protect against skin pathologies and can act as "messengers of the skin" to the central organs, all to preserve organismal survival.

Genetic adaptation of skin pigmentation in highland Tibetans

Strong ultraviolet (UV) radiation at high altitude imposes a serious selective pressure, which may induce skin pigmentation adaptation of indigenous populations. We conducted skin pigmentation phenotyping and genome-wide analysis of Tibetans in order to understand the underlying mechanism of adaptation to UV radiation. We observe that Tibetans have darker baseline skin color compared with lowland Han Chinese, as well as an improved tanning ability, suggesting a two-level adaptation to boost their melanin production. A genome-wide search for the responsible genes identifies GNPAT showing strong signals of positive selection in Tibetans. An enhancer mutation (rs75356281) located in GNPAT intron 2 is enriched in Tibetans (58%) but rare in other world populations (0 to 18%). The adaptive allele of rs75356281 is associated with darker skin in Tibetans and, under UVB treatment, it displays higher enhancer activities compared with the wild-type allele in in vitro luciferase assays. Transcriptome analyses of gene-edited cells clearly show that with UVB treatment, the adaptive variant of GNPAT promotes melanin synthesis, likely through the interactions of CAT and ACAA1 in peroxisomes with other pigmentation genes, and they act synergistically, leading to an improved tanning ability in Tibetans for UV protection.

Immunomodulatory Role of Neuropeptides in the Cornea

The transparency of the cornea along with its dense sensory innervation and resident leukocyte populations make it an ideal tissue to study interactions between the nervous and immune systems. The cornea is the most densely innervated tissue of the body and possesses both immune and vascular privilege, in part due to its unique repertoire of resident immune cells. Corneal nerves produce various neuropeptides that have a wide range of functions on immune cells. As research in this area expands, further insights are made into the role of neuropeptides and their immunomodulatory functions in the healthy and diseased cornea. Much remains to be known regarding the details of neuropeptide signaling and how it contributes to pathophysiology, which is likely due to complex interactions among neuropeptides, receptor isoform-specific signaling events, and the inflammatory microenvironment in disease. However, progress in this area has led to an increase in studies that have begun modulating neuropeptide activity for the treatment of corneal diseases with promising results, necessitating the need for a comprehensive review of the literature. This review focuses on the role of neuropeptides in maintaining the homeostasis of the ocular surface, alterations in disease settings, and the possible therapeutic potential of targeting these systems.

Tenets in Microbial Endocrinology: A New Vista in Teleost Reproduction

Climate vulnerability and induced changes in physico-chemical properties of aquatic environment can bring impairment in metabolism, physiology and reproduction in teleost. Variation in environmental stimuli mainly acts on reproduction by interfering with steroidogenesis, gametogenesis and embryogenesis. The control on reproductive function in captivity is essential for the sustainability of aquaculture production. There are more than 3,000 teleost species across the globe having commercial importance; however, adequate quality and quantity of seed production have been the biggest bottleneck. Probiotics are widely used in aquaculture as a growth promoter, stress tolerance, pathogen inhibition, nutrient digestibility and metabolism, reproductive performance and gamete quality. As the gut microbiota exerts various effects on the intestinal milieu which influences distant organs and pathways, therefore it is considered to be a full-fledged endocrine organ. Researches on Gut-Brain-Gonad axis (GBG axis) and its importance on physiology and reproduction have already been highlighted for higher mammals; however, the study on fish physiology and reproduction is limited. While looking into the paucity of information, we have attempted to review the present status of microbiome and its interaction between the brain and gut. This review will address a process of the microbiome physiological mechanism involved in fish reproduction. The gut microbiota influences the BPG axis through a wide variety of compounds, including neuropeptides, neurotransmitter homologs and transmitters. Currently, research is being conducted to determine the precise process by which gut microbial composition influences brain function in fish. The gut-brain bidirectional interaction can influence brain biochemistry such as GABA, serotonin and tryptophan metabolites which play significant roles in CNS regulation. This review summarizes the fact, how microbes from gut, skin and other parts of the body influence fish reproduction through the Gut-Brain-Gonad axis.

Vitamin D Signaling in Psoriasis: Pathogenesis and Therapy

Psoriasis is a systemic, chronic, immune-mediated disease that affects approximately 2-3% of the world's population. The etiology and pathophysiology of psoriasis are still unknown, but the activation of the adaptive immune system with the main role of T-cells is key in psoriasis pathogenesis. The modulation of the local neuroendocrine system with the downregulation of pro-inflammatory and the upregulation of anti-inflammatory messengers represent a promising adjuvant treatment in psoriasis therapies. Vitamin D receptors and vitamin D-mediated signaling pathways function in the skin and are essential in maintaining the skin homeostasis. The active forms of vitamin D act as powerful immunomodulators of clinical response in psoriatic patients and represent the effective and safe adjuvant treatments for psoriasis, even when high doses of vitamin D are administered. The phototherapy of psoriasis, especially UVB-based, changes the serum level of 25(OH)D, but the correlation of 25(OH)D changes and psoriasis improvement need more clinical trials, since contradictory data have been published. Vitamin D derivatives can improve the efficacy of psoriasis phototherapy without inducing adverse side effects. The anti-psoriatic treatment could include non-calcemic CYP11A1-derived vitamin D hydroxyderivatives that would act on the VDR or as inverse agonists on RORs or activate alternative nuclear receptors including AhR and LXRs. In conclusion, vitamin D signaling can play an important role in the natural history of psoriasis. Selective targeting of proper nuclear receptors could represent potential treatment options in psoriasis.

Enhanced Anti-Melanogenic Effect of Adlay Bran Fermented with Lactobacillus brevis MJM60390

Fermentation is a traditional technique used to increase nutrients, flavonoids, vitamins, minerals, and the flavor of raw materials. In this study, adlay bran was fermented by Lactobacillus brevis MJM60390 (FAB), and the anti-melanogenic effect was investigated. The results demonstrated that FAB significantly suppressed melanin accumulation in mouse melanogenic B16F10 cells, and the activity was higher than non-fermented adlay bran (NFAB). The molecular mechanism study showed that FAB inhibited melanin synthesis by suppressing the gene expression of melanocortin 1 receptor (Mc1r), melanocyte-inducing transcription factor (Mitf), tyrosinase (Tyr), tyrosinase-related protein-1 (Trp-1), and tyrosinase-related protein-2 (Trp-2) genes. Western blotting analysis showed that FAB strongly decreased the expression of Tyr, Trp-1, and Trp-2 compared to NFAB. Furthermore, phenolic compounds such as gallic acid, p-coumaric acid, ferulic acid, and sinapic acid, which are known for their anti-melanogenic effects, were significantly increased in FAB compared with NFAB. These findings suggest that FAB holds great potential as an anti-melanogenic agent and can be used for the development of whitening cosmetics.

Melanocortin-1 receptor mutations and pigmentation: Insights from large animals

The melanocortin-1 receptor (MC1R) is a G protein-coupled receptor expressed in cutaneous and hair follicle melanocytes, and plays a central role in coat color determination in vertebrates. Numerous MC1R variants have been identified in diverse species. Some of these variants have been associated with specific hair and skin color phenotypes in humans as well as coat color in animals. Gain-of-function mutations of the MC1R gene cause dominant or partially dominant black/dark coat color, and loss-of-function mutations of the MC1R gene cause recessive or partially recessive red/yellow/pale coat color phenotypes. These have been well documented in a large number of mammals, including human, dog, cattle, horse, sheep, pig, and fox. Higher similarities between large mammals and humans makes them better models to understand pathogenesis of human diseases caused by MC1R mutations. High identities in MC1Rs and similar variants identified in both humans and large mammals also provide an opportunity for receptor structure and function study. In this review, we aim to summarize the naturally occurring mutations of MC1R in humans and large animals.

The Trinity of Skin: Skin Homeostasis as a Neuro-Endocrine-Immune Organ

For a long time, skin was thought to be no more than the barrier of our body. However, in the last few decades, studies into the idea of skin as an independent functional organ have gradually deepened our understanding of skin and its functions. In this review, we gathered evidence that presented skin as a "trinity" of neuro-endocrine-immune function. From a neuro perspective, skin communicates through nerves and receptors, releasing neurotrophins and neuropeptides; from an endocrine perspective, skin is able to receive and secrete most hormones and has the cutaneous equivalent of the hypothalamic-pituitary-adrenal (HPA) axis; from an immune perspective, skin is protected not only by its physical barrier, but also immune cells and molecules, which can also cause inflammation. Together as an organ, skin works bidirectionally by operating peripheral neuro-endocrine-immune function and being regulated by the central nervous system, endocrine system and immune system at the same time, maintaining homeostasis. Additionally, to further explain the "trinity" of cutaneous neuro-endocrine-immune function and how it works in disease pathophysiology, a disease model of rosacea is presented.

Role of Phytochemicals in Skin Photoprotection via Regulation of Nrf2

Ethnopharmacological studies have become increasingly valuable in the development of botanical products and their bioactive phytochemicals as novel and effective preventive and therapeutic strategies for various diseases including skin photoaging and photodamage-related skin problems including abnormal pigmentation and inflammation. Exploring the roles of phytochemicals in mitigating ultraviolet radiation (UVR)-induced skin damage is thus of importance to offer insights into medicinal and ethnopharmacological potential for development of novel and effective photoprotective agents. UVR plays a role in the skin premature aging (or photoaging) or impaired skin integrity and function through triggering various biological responses of skin cells including apoptosis, oxidative stress, DNA damage and inflammation. In addition, melanin produced by epidermal melanocytes play a protective role against UVR-induced skin damage and therefore hyperpigmentation mediated by UV irradiation could reflect a sign of defensive response of the skin to stress. However, alteration in melanin synthesis may be implicated in skin damage, particularly in individuals with fair skin. Oxidative stress induced by UVR contributes to the process of skin aging and inflammation through the activation of related signaling pathways such as the mitogen-activated protein kinase (MAPK)/activator protein-1 (AP-1), the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt), the nuclear factor kappa B (NF-κB) and the signal transducer and activator of transcription (STAT) in epidermal keratinocytes and dermal fibroblasts. ROS formation induced by UVR also plays a role in regulation of melanogenesis in melanocytes via modulating MAPK, PI3K/Akt and the melanocortin 1 receptor (MC1R)-microphthalmia-associated transcription factor (MITF) signaling cascades. Additionally, nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated antioxidant defenses can affect the major signaling pathways involved in regulation of photoaging, inflammation associated with skin barrier dysfunction and melanogenesis. This review thus highlights the roles of phytochemicals potentially acting as Nrf2 inducers in improving photoaging, inflammation and hyperpigmentation via regulation of cellular homeostasis involved in skin integrity and function. Taken together, understanding the role of phytochemicals targeting Nrf2 in photoprotection could provide an insight into potential development of natural products as a promising strategy to delay skin photoaging and improve skin conditions.

The Dark Side of Melanin Secretion in Cutaneous Melanoma Aggressiveness

Skin cancers are among the most common cancers worldwide and are increasingly prevalent. Cutaneous melanoma (CM) is characterized by the malignant transformation of melanocytes in the epidermis. Although CM shows lower incidence than other skin cancers, it is the most aggressive and responsible for the vast majority of skin cancer-related deaths. Indeed, 75% of patients present with invasive or metastatic tumors, even after surgical excision. In CM, the photoprotective pigment melanin, which is produced by melanocytes, plays a central role in the pathology of the disease. Melanin absorbs ultraviolet radiation and scavenges reactive oxygen/nitrogen species (ROS/RNS) resulting from the radiation exposure. However, the scavenged ROS/RNS modify melanin and lead to the induction of signature DNA damage in CM cells, namely cyclobutane pyrimidine dimers, which are known to promote CM immortalization and carcinogenesis. Despite triggering the malignant transformation of melanocytes and promoting initial tumor growth, the presence of melanin inside CM cells is described to negatively regulate their invasiveness by increasing cell stiffness and reducing elasticity. Emerging evidence also indicates that melanin secreted from CM cells is required for the immunomodulation of tumor microenvironment. Indeed, melanin transforms dermal fibroblasts in cancer-associated fibroblasts, suppresses the immune system and promotes tumor angiogenesis, thus sustaining CM progression and metastasis. Here, we review the current knowledge on the role of melanin secretion in CM aggressiveness and the molecular machinery involved, as well as the impact in tumor microenvironment and immune responses. A better understanding of this role and the molecular players involved could enable the modulation of melanin secretion to become a therapeutic strategy to impair CM invasion and metastasis and, hence, reduce the burden of CM-associated deaths.