Sensing the environment: regulation of local and global homeostasis by the skin's neuroendocrine system

Influence of ultraviolet A1 exposures on mood states: a randomized controlled study

We investigated the effects of daily ultraviolet A1 (UV-A1, 340-400 nm) exposures on mood states (#R19055, approval on 21 October 2020). Based on our earlier findings of the influence of diurnal preference on mood, we investigated further whether diurnal preference plays a role in the influence of UV-A1 on mood states. Forty-one healthy participants aged 19-55 years were randomized to receive either UV-A1 (n = 21) or control (n = 20) exposures (violet light, 390-440 nm). The irradiations were administered on three consecutive mornings on the skin of the buttocks and middle back. Diurnal preference was assessed with the modified 6-item Morningness-Eveningness Questionnaire (mMEQ). Changes in mood were assessed with Total Mood Disturbance (TMD) score of the 40-item Profile of Mood States (POMS) before the first irradiation, immediately after each irradiation and one week after the last irradiation. Mood improved among those subjected to UV-A1 exposures compared with the controls (p = 0.031). Individuals with more pronounced morningness had mood improvement (p = 0.011), whereas those with more pronounced eveningness did not (p = 0.41). At follow-up of one week after the last irradiation the mood improvement had disappeared.

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.

Impact of double-strand breaks induced by uv radiation on neuroinflammation and neurodegenerative disorders

Exposure to UV affects the development and growth of a wide range of organisms. Nowadays, researchers are focusing on the impact of UV radiation and its underlying molecular mechanisms, as well as devising strategies to mitigate its harmful effects. Different forms of UV radiation, their typical exposure effects, the impact of UV on DNA integrity, and the deterioration of genetic material are discussed in this review; furthermore, we also review the effects of UV radiation that affect the biological functions of the organisms. Subsequently, we address the processes that aid organisms in navigating the damage in genetic material, neuroinflammation, and neurodegeneration brought on by UV-mediated double-strand breaks. To emphasize the molecular pathways, we conclude the review by going over the animal model studies that highlight the genes and proteins that are impacted by UV radiation.

Acupuncture in the treatment of cocaine addiction: how does it work?

Cocaine is a frequently abused and highly addictive drug that damages brain health and imposes substantial social and economic costs. Acupuncture has been used in the treatment of cocaine addiction and has been shown to improve abnormal mental and motor states. This article mainly focuses on the neurobiological mechanisms involving the central nervous system (CNS) and peripheral nervous system (PNS) that underlie the effects of acupuncture in the treatment of cocaine addiction. The central dopamine system is a key player in acupuncture treatment of cocaine addiction; the ventral tegmental area (VTA)-nucleus accumbens (NAc) signaling pathway, which has a modulatory influence on behavior and psychology after chronic use of cocaine, is a significant target of acupuncture action. Moreover, acupuncture alleviates cocaine-induced seizures or acute psychomotor responses through the paraventricular thalamus and the lateral habenula (LHb)-rostromedial tegmental (RMTg) nucleus circuits. The data suggest that acupuncture can impact various cocaine-induced issues via stimulation of diverse brain areas; nevertheless, the interconnection of these brain regions and the PNS mechanisms involved remain unknown. In this review, we also discuss the effects of specific acupuncture protocols on cocaine addiction and note that variations in needling modalities, current intensities and traditional acupuncture point locations have led to different experimental results. Therefore, standardized acupuncture protocols (with respect to stimulation methods, point locations and number of sessions) may become particularly important in future studies.

Therapeutic modulation of KIT ligand in melanocytic disorders with implications for mast cell diseases

KIT ligand and its associated receptor KIT serve as a master regulatory system for both melanocytes and mast cells controlling survival, migration, proliferation and activation. Blockade of this pathway results in cell depletion, while overactivation leads to mastocytosis or melanoma. Expression defects are associated with pigmentary and mast cell disorders. KIT ligand regulation is complex but efficient targeting of this system would be of significant benefit to those suffering from melanocytic or mast cell disorders. Herein, we review the known associations of this pathway with cutaneous diseases and the regulators of this system both in skin and in the more well-studied germ cell system. Exogenous agents modulating this pathway will also be presented. Ultimately, we will review potential therapeutic opportunities to help our patients with melanocytic and mast cell disease processes potentially including vitiligo, hair greying, melasma, urticaria, mastocytosis and melanoma.

Cold atmospheric plasma attenuates skin cancer via ROS induced apoptosis

BACKGROUND

Cold atmospheric plasma (CAP) has been widely used in biomedical research, especially in vitro cancer therapy. Cutaneous squamous cell carcinoma (CSCC) is a malignant tumor originating from epidermal keratinocytes. However, the mechanism of CAP therapy on CSCC remains unclear.

METHODS AND RESULTS

The animal models of CSCC induced by 7,12-dimethylbenz(a) anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA) were constructed. For the CAP treatment group, after each TPA application, CAP was administered for 3 min twice weekly after drying. HE staining were used to detect the pathological status of tumor tissue in each group. The levels of PCNA, Bcl-2, Bax, MMP2 and MMP9 were evaluated by western blot and qPCR. TUNEL staining were used to detect apoptosis in tumor tissues. In vivo, serum samples were used for ELISA of total ROS. MTT assay was used to detect the viability of A431 cells. Western blot and qPCR were used to detect the levels of PCNA, Bcl-2, Bax, MMP2 and MMP9 in A431 cells. A431 cell proliferation was examined by colony formation assay. The proportions of apoptosis of A431 cells were detected by flow cytometry. Transwell assessed the ability of A431 cells migration and proliferation. We found that CAP could induce skin cancer cells apoptosis and inhibit the progress of skin cancer. Through experiments in vitro, reactive oxygen species (ROS) generated by N-acetylcysteine (NAC) and CAP inhibited the proliferation and migration of A431 skin cancer cells while promoting apoptosis.

CONCLUSIONS

These evidences suggest the protective effect of CAP in CSCC, and CAP has the potential clinical application of CSCC.

Adjuvant PD-1 Checkpoint Inhibition in Early Cutaneous Melanoma: Immunological Mode of Action and the Role of Ultraviolet Radiation

Melanoma ranks as the fifth most common solid cancer in adults worldwide and is responsible for a significant proportion of skin-tumor-related deaths. The advent of immune checkpoint inhibition with anti-programmed death protein-1 (PD-1) antibodies has revolutionized the adjuvant treatment of high-risk, completely resected stage III/IV melanoma. However, not all patients benefit equally. Current strategies for improving outcomes involve adjuvant treatment in earlier disease stages (IIB/C) as well as perioperative treatment approaches. Interfering with T-cell exhaustion to counteract cancer immune evasion and the immunogenic nature of melanoma is key for anti-PD-1 effectiveness. Yet, the biological rationale for the efficacy of adjuvant treatment in clinically tumor-free patients remains to be fully elucidated. High-dose intermittent sun exposure (sunburn) is a well-known primary risk factor for melanomagenesis. Also, ultraviolet radiation (UVR)-induced immunosuppression may impair anti-cancer immune surveillance. In this review, we summarize the current knowledge about adjuvant anti-PD-1 blockade, including a characterization of the main cell types most likely responsible for its efficacy. In conclusion, we propose that local and systemic immunosuppression, to some extent UVR-mediated, can be restored by adjuvant anti-PD-1 therapy, consequently boosting anti-melanoma immune surveillance and the elimination of residual melanoma cell clones.

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.

Quantitative imaging and semiotic phenotyping of mitochondrial network morphology in live human cells

The importance of mitochondria in tissue homeostasis, stress responses and human diseases, combined to their ability to transition between various structural and functional states, makes them excellent organelles for monitoring cell health. There is therefore a need for technologies to accurately analyze and quantify changes in mitochondrial organization in a variety of cells and cellular contexts. Here we present an innovative computerized method that enables accurate, multiscale, fast and cost-effective analysis of mitochondrial shape and network architecture from confocal fluorescence images by providing more than thirty features. In order to facilitate interpretation of the quantitative results, we introduced two innovations: the use of Kiviat-graphs (herein named MitoSpider plots) to present highly multidimensional data and visualization of the various mito-cellular configurations in the form of morphospace diagrams (called MitoSigils). We tested our fully automated image analysis tool on rich datasets gathered from live normal human skin cells cultured under basal conditions or exposed to specific stress including UVB irradiation and pesticide exposure. We demonstrated the ability of our proprietary software (named MitoTouch) to sensitively discriminate between control and stressed dermal fibroblasts, and between normal fibroblasts and other cell types (including cancer tissue-derived fibroblasts and primary keratinocytes), showing that our automated analysis captures subtle differences in morphology. Based on this novel algorithm, we report the identification of a protective natural ingredient that mitigates the deleterious impact of hydrogen peroxide (H2O2) on mitochondrial organization. Hence we conceived a novel wet-plus-dry pipeline combining cell cultures, quantitative imaging and semiotic analysis for exhaustive analysis of mitochondrial morphology in living adherent cells. Our tool has potential for broader applications in other research areas such as cell biology and medicine, high-throughput drug screening as well as predictive and environmental toxicology.

Polyphosphate Nanoparticles: Balancing Energy Requirements in Tissue Regeneration Processes

Nanoparticles of a particular, evolutionarily old inorganic polymer found across the biological kingdoms have attracted increasing interest in recent years not only because of their crucial role in metabolism but also their potential medical applicability: it is inorganic polyphosphate (polyP). This ubiquitous linear polymer is composed of 10-1000 phosphate residues linked by high-energy anhydride bonds. PolyP causes induction of gene activity, provides phosphate for bone mineralization, and serves as an energy supplier through enzymatic cleavage of its acid anhydride bonds and subsequent ATP formation. The biomedical breakthrough of polyP came with the development of a successful fabrication process, in depot form, as Ca- or Mg-polyP nanoparticles, or as the directly effective polymer, as soluble Na-polyP, for regenerative repair and healing processes, especially in tissue areas with insufficient blood supply. Physiologically, the platelets are the main vehicles for polyP nanoparticles in the circulating blood. To be biomedically active, these particles undergo coacervation. This review provides an overview of the properties of polyP and polyP nanoparticles for applications in the regeneration and repair of bone, cartilage, and skin. In addition to studies on animal models, the first successful proof-of-concept studies on humans for the healing of chronic wounds are outlined.

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.

Long Non-Coding RNA Mir17hg Positively Regulates Melanogenesis by Inhibiting TGFβ Receptor 2 under Psychological Stress

Vitiligo is a common skin depigmentation disorder characterized by the patchy loss of skin color. Nowadays, it is recognized as being correlated with multiple genetic factors as well as the psychological conditions of individuals. Long noncoding RNAs have been reported to underlie the pathogenesis of vitiligo; however, the role of long noncoding RNAs in the stress-related depigmentation process remains largely unknown. In this study, the inhibition of melanocyte function was observed in C57BL/6J mice modeled through chronic restraint stress. Furthermore, downregulation of the expression of the long noncoding RNAs Mir17hg was identified using RNA sequencing. The regulatory role of Mir17hg in melanogenesis was also investigated in melanocytes and zebrafish embryos through overexpression or knockdown. Finally, TGFβ receptor 2 was shown to be a downstream target in Mir17hg-mediated melanogenesis regulation, in which the classical TGFβ/SMAD signaling cascade and the PI3K/AKT/mTOR signaling cascade play important roles. In conclusion, our results revealed an important regulatory role of Mir17hg in melanogenesis through inhibition of TGFβR2, which can provide a potential therapeutic target for treating skin depigmentation disorders.

Human skin CD141+ dendritic cells regulate cutaneous immunity via the neuropeptide urocortin 2

Skin immune homeostasis is a multi-faceted process where dermal dendritic cells (DDCs) are key in orchestrating responses to environmental stressors. We have previously identified CD141+CD14+ DDCs as a skin-resident immunoregulatory population that is vitamin-D3 (VitD3) inducible from monocyte-derived DCs (moDCs), termed CD141hi VitD3 moDCs. We demonstrate that CD141+ DDCs and CD141hi VitD3 moDCs share key immunological features including cell surface markers, reduced T cell stimulation, IL-10 production, and a common transcriptomic signature. Bioinformatic analysis identified the neuroactive ligand receptor pathway and the neuropeptide, urocortin 2 (UCN2), as a potential immunoregulatory candidate molecule. Incubation with VitD3 upregulated UCN2 in CD141+ DCs and UVB irradiation induced UCN2 in CD141+ DCs in healthy skin in vivo. Notably, CD141+ DDC generation of suppressive Tregs was dependent upon the UCN2 pathway as in vivo administration of UCN2 reversed skin inflammation in humanized mice. We propose the neuropeptide UCN2 as a novel skin DC-derived immunoregulatory mediator with a potential role in UVB and VitD3-dependent skin immune homeostasis.

Gender Differences in Post-Operative Human Skin

Although the impact of age, gender, and obesity on the skin wound healing process has been extensively studied, the data related to gender differences in aspects of skin scarring are limited. The present study performed on abdominal human intact and scar skin focused on determining gender differences in extracellular matrix (ECM) composition, dermal white adipose tissue (dWAT) accumulation, and Foxn1 expression as a part of the skin response to injury. Scar skin of men showed highly increased levels of COLLAGEN 1A1, COLLAGEN 6A3, and ELASTIN mRNA expression, the accumulation of thick collagen I-positive fibers, and the accumulation of α-SMA-positive cells in comparison to the scar skin of women. However, post-injured skin of women displayed an increase (in comparison to post-injured men's skin) in collagen III accumulation in the scar area. On the contrary, women's skin samples showed a tendency towards higher levels of adipogenic-related genes (PPARγ, FABP4, LEPTIN) than men, regardless of intact or scar skin. Intact skin of women showed six times higher levels of LEPTIN mRNA expression in comparison to men intact (p < 0.05), men post-injured (p < 0.05), or women post-injured scar (p < 0.05) skin. Higher levels of FOXN1 mRNA and protein were also detected in women than in men's skin. In conclusion, the present data confirm and extend (dWAT layer) the data related to the presence of differences between men and women in the skin, particularly in scar tissues, which may contribute to the more effective and gender-tailored improvement of skin care interventions.

Glucocorticoids are differentially synthesized along the murine and human respiratory tree

BACKGROUND

Synthetic glucocorticoids (GC) are effective in the treatment of inflammatory diseases of the lung. However, long-term use leads to severe side effects. Endogenous GC can be synthesized locally, either de novo from cholesterol in a 11β-hydroxylase (Cyp11b1)-dependent manner, or by reactivation from 11-dehydrocorticosterone/cortisone by 11β-hydroxysteroid dehydrogenase 1 (Hsd11b1). We aimed to define the molecular pathways of endogenous GC synthesis along the respiratory tree to provide a basis for understanding how local GC synthesis contributes to tissue homeostasis.

METHODS

Expression of steroidogenic enzymes in murine lung epithelium was analyzed by macroscopic and laser capture microdissection, followed by RT-qPCR. Flow cytometry analysis was performed to identify the cellular source of steroidogenic enzymes. Additionally, the induction of steroidogenic enzyme expression in the lung was analyzed after lipopolysaccharide (LPS) injection. mRNA and protein expression of steroidogenic enzymes was confirmed in human lung tissue by RT-qPCR and immunohistochemistry. Furthermore, GC synthesis was examined in ex vivo cultures of fresh tissue from mice and human lobectomy patients.

RESULTS

We observed that the murine and human lung tissue differentially expresses synthesis pathway-determining enzymes along the respiratory tree. We detected Hsd11b1 expression in bronchial, alveolar, club and basal epithelial cells, whereas Cyp11b1 expression was detectable only in tracheal epithelial cells of mice. Accordingly, de novo synthesis of bioactive GC occurred in the large conducting airways, whereas reactivation occurred everywhere along the respiratory tree. Strikingly, Cyp11b1 but not Hsd11b1 expression was enhanced in the trachea upon LPS injection in mice.

CONCLUSION

We report here the differential synthesis of bioactive GC along the murine and human respiratory tree. Thus, extra-adrenal de novo GC synthesis and reactivation may differentially contribute to the regulation of immunological and inflammatory processes in the lung.

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.

The Melatonin-Mitochondrial Axis: Engaging the Repercussions of Ultraviolet Radiation Photoaging on the Skin's Circadian Rhythm

Sunlight is a vital element in modulating the central circadian rhythm, such as the regulation of the host's sleep-awake state. Sunlight is also considered to have a significant influence on the circadian rhythm of the skin. Over-exposure or prolonged exposure to sunlight can lead to skin photodamage, including hyperpigmentation, collagen degradation, fibrosis, and even skin cancer. Thus, this review will focus on the adverse effects of sunlight on the skin, not only in terms of photoaging but also its effect on the skin's circadian rhythm. Mitochondrial melatonin, regarded as a beneficial anti-aging substance for the skin, follows a circadian rhythm and exhibits a powerful anti-oxidative capacity, which has been shown to be associated with skin function. Thus, the review will focus on the influence of sunlight on skin status, not only in terms of ultraviolet radiation (UVR)-induced oxidative stress but also its mediation of circadian rhythms regulating skin homeostasis. In addition, this article will address issues regarding how best to unleash the biological potential of melatonin. These findings about the circadian rhythms of the skin have broadened the horizon of a whole new dimension in our comprehension of the molecular mechanisms of the skin and are likely to help pharmaceutical companies to develop more effective products that not only inhibit photoaging but keep valid and relevant throughout the day in future.

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.

Skin drug delivery using lipid vesicles: A starting guideline for their development

Lipid vesicles can provide a cost-effective enhancement of skin drug absorption when vesicle production process is optimised. It is an important challenge to design the ideal vesicle, since their properties and features are related, as changes in one affect the others. Here, we review the main components, preparation and characterization methods commonly used, and the key properties that lead to highly efficient vesicles for transdermal drug delivery purposes. We stand by size, deformability degree and drug loading, as the most important vesicle features that determine the further transdermal drug absorption. The interest in this technology is increasing, as demonstrated by the exponential growth of publications on the topic. Although long-term preservation and scalability issues have limited the commercialization of lipid vesicle products, freeze-drying and modern escalation methods overcome these difficulties, thus predicting a higher use of these technologies in the market and clinical practice.

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.

Characterization of 3D organotypic epithelial tissues reveals tonsil-specific differences in tonic interferon signaling

Three-dimensional (3D) culturing techniques can recapitulate the stratified nature of multicellular epithelial tissues. Organotypic 3D epithelial tissue culture methods have several applications, including the study of tissue development and function, drug discovery and toxicity testing, host-pathogen interactions, and the development of tissue-engineered constructs for use in regenerative medicine. We grew 3D organotypic epithelial tissues from foreskin, cervix, and tonsil-derived primary cells and characterized the transcriptome of these in vitro tissue equivalents. Using the same 3D culturing method, all three tissues yielded stratified squamous epithelium, validated histologically using basal and superficial epithelial cell markers. The goal of this study was to use RNA-seq to compare gene expression patterns in these three types of epithelial tissues to gain a better understanding of the molecular mechanisms underlying their function and identify potential therapeutic targets for various diseases. Functional profiling by over-representation and gene set enrichment analysis revealed tissue-specific differences: i.e. , cutaneous homeostasis and lipid metabolism in foreskin, extracellular matrix remodeling in cervix, and baseline innate immune differences in tonsil. Specifically, tonsillar epithelia may play an active role in shaping the immune microenvironment of the tonsil balancing inflammation and immune responses in the face of constant exposure to microbial insults. Overall, these data serve as a resource, with gene sets made available for the research community to explore, and as a foundation for understanding the epithelial heterogeneity and how it may impact their in vitro use. An online resource is available to investigate these data ( https://viz.datascience.arizona.edu/3DEpiEx/ ).

The Safety and Efficacy of 1-Monoeicosapentaenoin Isolated from the Trebouxiophyceae Micractinium on Anti-Wrinkle: A Split-Face Randomized, Double-Blind Placebo-Controlled Clinical Study

The skin aging process is governed by intrinsic and extrinsic factors causing skin wrinkles, sagging, and loosening. The 1-monoeicosapentaenoin (1-MEST) is a component isolated from Micractinium, a genus of microalgae (Chlorophyta, Trebouxiophyceae). However, the anti-wrinkle effects of 1-MEST are not yet known. This study aimed to evaluate the anti-wrinkle effects of 1-MEST in vitro and in clinical trials. The cytotoxicity of 1-MEST was investigated in vitro using the MTS assay in human epidermal keratinocytes (HEKs). Expression of matrix metalloproteinase (MMP)-1 and MMP-9 was determined by ELISA in HEKs irradiated with UVB after treatment with 1-MEST. A split-face randomized, double-blind, placebo-controlled study was conducted to evaluate the safety and efficacy of 1-MEST. The study evaluated wrinkle parameters and visual assessment, self-efficacy and usability questionnaires, and adverse events. The study showed that the 1-MEST was not cytotoxic in HEKs, suppressed MMP-1 secretion and MMP-9 protein expression in HEKs irradiated with UVB. The wrinkle parameters and mean visual assessment score were significantly decreased in the test group after 12 weeks and differed from the control group. There were no significant differences in efficacy and usability. Adverse effects were also not observed. The 1-MEST showed anti-wrinkle properties to slow down or prevent skin aging.

Disease-Gene Networks of Skin Pigmentation Disorders and Reconstruction of Protein-Protein Interaction Networks

Melanin, a light and free radical absorbing pigment, is produced in melanocyte cells that are found in skin, but also in hair follicles, eyes, the inner ear, heart, brain and other organs. Melanin synthesis is the result of a complex network of signaling and metabolic reactions. It therefore comes as no surprise that mutations in many of the genes involved are associated with various types of pigmentation diseases and phenotypes ('pigmentation genes'). Here, we used bioinformatics tools to first reconstruct gene-disease/phenotype associations for all pigmentation genes. Next, we reconstructed protein-protein interaction (PPI) networks centered around pigmentation gene products ('pigmentation proteins') and supplemented the PPI networks with protein expression information obtained by mass spectrometry in a panel of melanoma cell lines (both pigment producing and non-pigment producing cells). The analysis provides a systems network representation of all genes/ proteins centered around pigmentation and melanin biosynthesis pathways ('pigmentation network map'). Our work will enable the pigmentation research community to experimentally test new hypothesis arising from the pigmentation network map and to identify new targets for drug discovery.

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.

The Hypothalamic-Pituitary-Thyroid Axis Equivalent in Normal and Cancerous Oral Tissues: A Scoping Review

The hypothalamic-pituitary-thyroid (HPT) axis is crucial in regulating thyroid hormone levels that contribute to the development and homeostasis of the human body. Current literature supports the presence of a local HPT axis equivalent within keratinocytes of the skin, with thyroid hormones playing a potential role in cancer progression. However, this remains to be seen within oral tissue cells. An electronic search of Scopus and PubMed/Medline databases was conducted to identify all original publications that reported data on the production or effects of HPT axis components in normal or malignant cells of the oral cavity. The search identified 221 studies, of which 14 were eligible. Eight studies were retrospective analyses of clinical samples, one study involved both in vivo and in vitro experiments, and the remaining five studies were conducted in vitro using cell lines. The search identified evidence of effects of HPT components on oral cancer cells. However, there were limited data for the production of HPT axis components by oral tissues. We conclude that a possible role of the local HPT axis equivalent in the oral mucosa may not be established at present. The gaps in knowledge identified in this scoping review, particularly regarding the production of HPT components by oral tissues, warrant further investigation.

Skin Aging in Long-Lived Naked Mole-Rats Is Accompanied by Increased Expression of Longevity-Associated and Tumor Suppressor Genes

Naked mole-rats (NMRs) (Heterocephalus glaber) are long-lived mammals that possess a natural resistance to cancer and other age-related pathologies, maintaining a healthy life span >30 years. In this study, using immunohistochemical and RNA-sequencing analyses, we compare skin morphology, cellular composition, and global transcriptome signatures between young and aged (aged 3‒4 vs. 19‒23 years, respectively) NMRs. We show that similar to aging in human skin, aging in NMRs is accompanied by a decrease in epidermal thickness; keratinocyte proliferation; and a decline in the number of Merkel cells, T cells, antigen-presenting cells, and melanocytes. Similar to that in human skin aging, expression levels of dermal collagens are decreased, whereas matrix metalloproteinase 9 and matrix metalloproteinase 11 levels increased in aged versus in young NMR skin. RNA-sequencing analyses reveal that in contrast to human or mouse skin aging, the transcript levels of several longevity-associated (Igfbp3, Igf2bp3, Ing2) and tumor-suppressor (Btg2, Cdkn1a, Cdkn2c, Dnmt3a, Hic1, Socs3, Sfrp1, Sfrp5, Thbs1, Tsc1, Zfp36) genes are increased in aged NMR skin. Overall, these data suggest that specific features in the NMR skin aging transcriptome might contribute to the resistance of NMRs to spontaneous skin carcinogenesis and provide a platform for further investigations of NMRs as a model organism for studying the biology and disease resistance of human skin.

Human milk oligosaccharide 2'-fucosyllactose promotes melanin degradation via the autophagic AMPK-ULK1 signaling axis

There is still an unmet need for development of safer antimelanogenic or melanin-degrading agents for skin hyperpigmentation, induced by intrinsic or extrinsic factors including aging or ultraviolet irradiation. Owing to the relatively low cytotoxicity compared with other chemical materials, several studies have explored the role of 2'-fucosyllactose (2'-FL), the most dominant component of human milk oligosaccharides. Here, we showed that 2'-FL reduced melanin levels in both melanocytic cells and a human skin equivalent three-dimensional in vitro model. Regarding the cellular and molecular mechanism, 2'-FL induced LC3I conversion into LC3II, an autophagy activation marker, followed by the formation of LC3II⁺/PMEL⁺ autophagosomes. Comparative transcriptome analysis provided a comprehensive understanding for the up- and downstream cellular processes and signaling pathways of the AMPK–ULK1 signaling axis triggered by 2'-FL treatment. Moreover, 2'-FL activated the phosphorylation of AMPK at Thr172 and of ULK1 at Ser555, which were readily reversed in the presence of dorsomorphin, a specific AMPK inhibitor, with consequent reduction of the 2'-FL-mediated hypopigmentation. Taken together, these findings demonstrate that 2'-FL promotes melanin degradation by inducing autophagy through the AMPK–ULK1 axis. Hence, 2'-FL may represent a new natural melanin-degrading agent for hyperpigmentation.

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.

CYP11A1‑derived vitamin D hydroxyderivatives as candidates for therapy of basal and squamous cell carcinomas

Hydroxyderivatives of vitamin D3, including classical 1,25(OH)2D3 and novel CYP11A1‑derived hydroxyderivatives, exert their biological activity by acting as agonists on the vitamin D receptor (VDR) and inverse agonists on retinoid‑related orphan receptors (ROR)α and γ. The anticancer activities of CYP11A1‑derived hydroxyderivatives were tested using cell biology, tumor biology and molecular biology methods in human A431 and SCC13 squamous (SCC)‑ and murine ASZ001 basal (BCC)‑cell carcinomas, in comparison with classical 1,25(OH)2D3. Vitamin D3‑hydroxyderivatives with or without a C1α(OH) inhibited cell proliferation in a dose‑dependent manner. While all the compounds tested had similar effects on spheroid formation by A431 and SCC13 cells, those with a C1α(OH) group were more potent in inhibiting colony and spheroid formation in the BCC line. Potent anti‑tumorigenic activity against the BCC line was exerted by 1,25(OH)2D3, 1,20(OH)2D3, 1,20,23(OH)3D3, 1,20,24(OH)3D3, 1,20,25(OH)3D3 and 1,20,26(OH)3D3, with smaller effects seen for 25(OH)D3, 20(OH)D3 and 20,23(OH)2D3. 1,25(OH)2D3, 1,20(OH)2D3 and 20(OH)D3 inhibited the expression of GLI1 and β‑catenin in ASZ001 cells. In A431 cells, these compounds also decreased the expression of GLI1 and stimulated involucrin expression. VDR, RORγ, RORα and CYP27B1 were detected in A431, SCC13 and ASZ001 lines, however, with different expression patterns. Immunohistochemistry performed on human skin with SCC and BCC showed nuclear expression of all three of these receptors, as well as megalin (transmembrane receptor for vitamin D‑binding protein), the level of which was dependent on the type of cancer and antigen tested in comparison with normal epidermis. Classical and CYP11A1‑derived vitamin D3‑derivatives exhibited anticancer‑activities on skin cancer cell lines and inhibited GLI1 and β‑catenin signaling in a manner that was dependent on the position of hydroxyl groups. The observed expression of VDR, RORγ, RORα and megalin in human SCC and BCC suggested that they might provide targets for endogenously produced or exogenously applied vitamin D hydroxyderivatives and provide excellent candidates for anti‑cancer therapy.

Distribution of Cannabinoid Receptors in Keratinocytes of Healthy Dogs and Dogs With Atopic Dermatitis

It is commonly accepted that some form of skin barrier dysfunction is present in canine atopic dermatitis (AD), one of the most common cutaneous pruritic inflammatory diseases of dogs. The impaired skin barrier function facilitates the penetration of allergens and subsequently stronger sensitization responses. The role of the endocannabinoid system (ECS) in the physiology and pathology of the skin is becoming increasingly established. It has been demonstrated that cannabinoid receptors are expressed in healthy and diseased skin and, based on current knowledge, it could be stated that cannabinoids are important mediators in the skin. The present study has been designed to immunohistochemically investigate the expression of the cannabinoid receptors type 1 (CB1R) and 2 (CB2R) and the cannabinoid-related receptors G protein-coupled receptor 55 (GPR55), transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1), peroxisome proliferator-activated receptors alpha (PPARα), and serotoninergic receptor 1a (5-HT1aR) in keratinocytes of healthy dogs and of dogs with AD. Samples of skin tissues were collected from 7 healthy controls (CTRL-dogs) and from 8 dogs with AD (AD-dogs). The tissue samples were processed using an immunofluorescence assay with commercially available antibodies, and the immunolabelling of the receptors studied was quantitatively evaluated. The keratinocytes of the CTRL- and the AD-dogs showed immunoreactivity for all the receptors investigated with a significant upregulation of CB2R, TRPA1, and 5-HT1aR in the epidermis of the AD-dogs. The presence of cannabinoid and cannabinoid-related receptors in healthy keratinocytes suggested the possible role of the ECS in canine epidermal homeostasis while their overexpression in the inflamed tissues of the AD-dogs suggested the involvement of the ECS in the pathogenesis of this disease, having a possible role in the related skin inflammation and itching. Based on the present findings, the ECS could be considered a potential therapeutic target for dogs with AD.

Human placental extract activates a wide array of gene expressions related to skin functions

As skin aging is one of the most common dermatological concerns in recent years, scientific research has promoted treatment strategies aimed at preventing or reversing skin aging. Breakdown of the extracellular matrix (ECM), such as collagen and elastin fibers, in the skin results in decreased skin elasticity and tension. Cutaneous cells, especially fibroblasts in the dermis layer of the skin, mainly produce ECM proteins. Although clinical studies have demonstrated that placental extract (PE) has positive effects on skin health, the molecular mechanisms by which PE acts against skin aging are still largely unknown. In this study, we performed RNA-sequence analysis to investigate whether human PE (HPE) alters ECM-related gene expression in normal human dermal fibroblast (NHDF) cells. Gene ontology analysis showed that genes related to extracellular matrix/structure organization, such as COL1A1, COL5A3, ELN, and HAS2 were highly enriched, and most of these genes were upregulated. We further confirmed that the HPE increased the type I collagen, proteoglycan versican, elastin, and hyaluronan levels in NHDF cells. Our results demonstrate that HPE activates global ECM-related gene expression in NHDF cells, which accounts for the clinical evidence that the HPE affects skin aging.

Exosomes Derived From Umbilical Cord Mesenchymal Stem Cells Treat Cutaneous Nerve Damage and Promote Wound Healing

Wound repair is a key step in the treatment of skin injury caused by burn, surgery, and trauma. Various stem cells have been proven to promote wound healing and skin regeneration as candidate seed cells. Therefore, exosomes derived from stem cells are emerging as a promising method for wound repair. However, the mechanism by which exosomes promote wound repair is still unclear. In this study, we reported that exosomes derived from umbilical cord mesenchymal stem cells (UC-MSCs) promote wound healing and skin regeneration by treating cutaneous nerve damage. The results revealed that UC-MSCs exosomes (UC-MSC-Exo) promote the growth and migration of dermal fibroblast cells. In in vitro culture, dermal fibroblasts could promote to nerve cells and secrete nerve growth factors when stimulated by exosomes. During the repair process UC-MSC-Exo accelerated the recruitment of fibroblasts at the site of trauma and significantly enhanced cutaneous nerve regeneration in vivo. Interestingly, it was found that UC-MSC-Exo could promote wound healing and skin regeneration by recruiting fibroblasts, stimulating them to secrete nerve growth factors (NGFs) and promoting skin nerve regeneration. Therefore, we concluded that UC-MSC-Exo promote cutaneous nerve repair, which may play an important role in wound repair and skin regeneration.

Recognition of Melanocytes in Immuno-Neuroendocrinology and Circadian Rhythms: Beyond the Conventional Melanin Synthesis

Melanocytes produce melanin to protect the skin from UV-B radiation. Notwithstanding, the spectrum of their functions extends far beyond their well-known role as melanin production factories. Melanocytes have been considered as sensory and computational cells. The neurotransmitters, neuropeptides, and other hormones produced by melanocytes make them part of the skin’s well-orchestrated and complex neuroendocrine network, counteracting environmental stressors. Melanocytes can also actively mediate the epidermal immune response. Melanocytes are equipped with ectopic sensory systems similar to the eye and nose and can sense light and odor. The ubiquitous inner circadian rhythm controls the body’s basic physiological processes. Light not only affects skin photoaging, but also regulates inner circadian rhythms and communicates with the local neuroendocrine system. Do melanocytes “see” light and play a unique role in photoentrainment of the local circadian clock system? Why, then, are melanocytes responsible for so many mysterious functions? Do these complex functional devices work to maintain homeostasis locally and throughout the body? In addition, melanocytes have also been shown to be localized in internal sites such as the inner ear, brain, and heart, locations not stimulated by sunlight. Thus, what can the observation of extracutaneous melanocytes tell us about the “secret identity” of melanocytes? While the answers to some of these intriguing questions remain to be discovered, here we summarize and weave a thread around available data to explore the established and potential roles of melanocytes in the biological communication of skin and systemic homeostasis, and elaborate on important open issues and propose ways forward.

The assessment of the protective impact of spidroin extract against UV-A radiation damage by using earthworms (Aporrectodea caliginosa) as a robust human skin model via macroscopic and histological observations

Numerous studies have confirmed the damage caused by excessive exposure to ultraviolet-A rays. Malignant melanoma and skin cancer are two of the most serious health consequences. Thus, the UV-A protectant is intended to protect the skin, especially the two primary layers of skin (epidermis that represents the interface between the body and its surroundings and dermis). Spider silk is the most powerful natural fibre due to its regeneration, biocompatibility, antimicrobial, wound healing, antiseptic, and blood clotting properties. This work targeted to determine the protective effect of spidroin extract against UV-A radiation damage. Earthworms Aporrectodea caliginosa were collected from Assiut University's farm. Each set of ten earthworms was separated into six groups and placed in a plastic container. Webs of spiders collected from trees and old houses. Spidroin was extracted and utilised in this work to determine the potential effects of topical application on UV-A protection. The experiment is divided into two sections: (1) UV-A exposure and (2) the use of spidroin extract to protect the earthworms from ultraviolet radiation. Two control groups (1،2) of worms were not received UV-A exposure, and four groups (3,4,5,6) were exposed to UVR-A. In contrast, groups (5,6) were received spidroin extract before exposure to UV-A. Each group from the groups (3,4,5,6) was exposed for three consecutive days (¼ hour/day, ½ hour/day, and 1 h/day), using a UV-Lamp with a wavelength of 366 nm. The histopathological changes revealed that after 1⁄4 h of UV exposure, the cuticle was swollen with a slightly detached epithelium. The cuticle was down after 1⁄2 h of exposure, and the epidermis was totally damaged and necrosed. After 1 h, the exposure showed destruction of the epidermis in the circular muscle with a loss of muscle filament integrity, varying size, and altered nucleus form, along with mild disintegration of longitudinal muscle. Spidroin extract is critical for earthworm protection against UV-A radiation damage and able to regeneration. For the first time, morphological and histological analysis was established to detect the Spidroin extract evaluated for topical application on earthworms. Earthworms can be considered as a robust human skin model prior to UV-A exposure. It induces a complete protective effect against UV-A radiation damage in earthworms.

Photoprotective and Antiaging Effects of a Standardized Red Orange (Citrus sinensis (L.) Osbeck) Extract in Asian and Caucasian Subjects: A Randomized, Double-Blind, Controlled Study

The increase in solar ultraviolet radiation (UVR) that reaches the Earth’s surface should make us reflect on the need to develop new approaches in protecting the skin from UVR exposure. The present study aims to evaluate the photoprotective and antiaging efficacy of a red orange extract (100 mg/day) in both Asian and Caucasian subjects. A randomized, double-blind, controlled study was carried out in 110 Asian and Caucasian subjects. Product efficacy was measured as follows: (1) the photoprotective effect was measured by the minimal erythema dose (MED) assessment; (2) the efficacy in decreasing the UVA+B-induced skin redness was measured by colorimetry; (3) the antioxidant efficacy was measured by the ferric-reducing antioxidant power (FRAP) and the malondialdehyde (MDA) assay; and (4) skin moisturization, skin elasticity, skin radiance, the intensity of melanin staining, transepidermal water loss (TEWL), and wrinkles were measured to assess the antiaging efficacy. The intake of the product for 56 days was effective in improving the skin reaction to UV exposure; in increasing the skin antioxidant capacity as well as in decreasing UVA-induced lipid peroxidation; in increasing the skin moisturization, skin elasticity, and skin radiance; and in decreasing TEWL, the intensity of melanin staining inside dark spots, and wrinkle depth. Our results suggest that the test product is effective in counteracting both the harmful effects of UVR exposure and aging signs.

UVB-Induced Microvesicle Particle Release and Its Effects on the Cutaneous Microenvironment

Ultraviolet B radiation (UVB) has profound effects on human skin that results in a broad spectrum of immunological local and systemic responses and is the major cause of skin carcinogenesis. One important area of study in photobiology is how UVB is translated into effector signals. As the skin is exposed to UVB light, subcellular microvesicle particles (MVP), a subtype of bioactive extracellular vesicles, are released causing a variety of local and systemic immunological effects. In this review, we highlight keratinocyte MVP release in keratinocytes in response to UVB. Specifically, Platelet-activating factor receptor agonists generated by UVB result in MVP released from keratinocytes. The downstream effects of MVP release include the ability of these subcellular particles to transport agents including the glycerophosphocholine-derived lipid mediator Platelet-activating factor (PAF). Moreover, even though UVB is only absorbed in the epidermis, it appears that PAF release from MVPs also mediates systemic immunosuppression and enhances tumor growth and metastasis. Tumor cells expressing PAF receptors can use this mechanism to evade chemotherapy responses, leading to treatment resistance for advanced cancers such as melanoma. Furthermore, novel pharmacological agents provide greater insight into the UVB-induced immune response pathway and a potential target for pharmacological intervention. This review outlines the need to more clearly elucidate the mechanism linking UVB-irradiation with the cutaneous immune response and its pathological manifestations. An improved understanding of this process can result in new insights and treatment strategies for UVB-related disorders from carcinogenesis to photosensitivity.

Keratinocytes take part in the regulation of substance P in melanogenesis through the HPA axis

BACKGROUND

Clinical findings have shown that skin depigmentation disorder such as vitiligo may be closely associated with the release of central and peripheral substance P (SP) resulted from chronic psychological stress or sudden mental blow. But the regulatory role of SP and its receptor, tachykinin receptor in the pathogenesis of vitiligo is unclear.

OBJECTIVES

To investigate the function and mechanism of SP in melanogenesis.

METHODS

The chronic mental stress was used to explore the intrinsic association between psychological factors, SP and melanogenesis disorder. The effect of SP on melanogenesis through hypothalamic pituitary adrenocortical (HPA) axis was studied by skin culture in vitro. The conditioned medium experiment demonstrated the indirect effect of SP on melanogenesis of B16F10 cells through HaCaT cells. The ability to produce melanin was evaluated by detecting melanin and tyrosinase activity. qRT-PCR, western blotting and immunohistochemistry were used to detect the expression of related genes and proteins in melanogenesis and HPA axis.

RESULTS

Increased SP expression and reduction of melanogenesis in the skin of mice were observed under mental stress. Melanogenesis was suppressed in the cultured human skin treated with SP due to the down-regulation of melanin-related proteins and HPA axis genes. The melanogenesis of B16F10 cells was inhibited by the conditioned medium of HaCaT cells treated with SP.

CONCLUSIONS

Overall, these results indicate that excess SP originated from mental stress interferes with melanogenesis through keratinocytes in the skin. The HPA axis is the key downstream to perceive the SP signaling and furtherly regulate the melanogenesis.

Epigenetic Mechanisms of Epidermal Differentiation

Keratinocyte differentiation is an essential process for epidermal stratification and stratum corneum formation. Keratinocytes proliferate in the basal layer of the epidermis and start their differentiation by changing their functional or phenotypical type; this process is regulated via induction or repression of epidermal differentiation complex (EDC) genes that play a pivotal role in epidermal development. Epidermal development and the keratinocyte differentiation program are orchestrated by several transcription factors, signaling pathways, and epigenetic regulators. The latter exhibits both activating and repressive effects on chromatin in keratinocytes via the ATP-dependent chromatin remodelers, histone demethylases, and genome organizers that promote terminal keratinocyte differentiation, and the DNA methyltransferases, histone deacetylases, and Polycomb components that stimulate proliferation of progenitor cells and inhibit premature activation of terminal differentiation-associated genes. In addition, microRNAs are involved in different processes between proliferation and differentiation during the program of epidermal development. Here, we bring together current knowledge of the mechanisms controlling gene expression during keratinocyte differentiation. An awareness of epigenetic mechanisms and their alterations in health and disease will help to bridge the gap between our current knowledge and potential applications for epigenetic regulators in clinical practice to pave the way for promising target therapies.

Ectopic odorant receptors responding to flavor compounds in skin health and disease: Current insights and future perspectives

Skin, the largest organ of human body, acts as a barrier to protect body from the external environment and is exposed to a myriad of flavor compounds, especially food- and plant essential oil-derived odorant compounds. Skin cells are known to express various chemosensory receptors, such as transient potential receptors, adenosine triphosphate receptors, taste receptors, and odorant receptors (ORs). We aim to provide a review of this rapidly developing field and discuss latest discoveries related to the skin ORs activated by flavor compounds, their impacts on skin health and disease, odorant ligands interacting with ORs exerting specific biological effects, and the mechanisms involved. ORs are recently found to be expressed in skin tissue and cells, such as keratinocytes, melanocytes, and fibroblasts. To date, several ectopic skin ORs responding to flavor compounds, are involved in different skin biological processes, such as wound healing, hair growth, melanin regulation, pressure stress, skin barrier function, atopic dermatitis, and psoriasis. The recognition of physiological role of skin ORs, combined with the fact that ORs belong to a highly druggable protein family (G protein-coupled receptors), underscores the potential of skin ORs responding to flavor compounds as a novel regulating strategy for skin health and disease.

Coriander (Coriandrum sativum L.) essential oil and oil-loaded nano-formulations as an anti-aging potentiality via TGFβ/SMAD pathway

Aging has become a concern for many people, especially women. Given that high-quality anti-aging products are of high cost; it has imperative to search for other economical sources. Essential oils are frequently used in cosmetics products due to a wide range of biological activities as well as their pleasant odor. The current study aimed to investigate the biochemical effect of the cosmetic potential of selected Apiaceous essential oils, traditionally used for skincare, by evaluating their anti-wrinkle activity. It is worth noting that, coriander essential oil showed the highest collagenase, elastase, tyrosinase, and hyaluronidase inhibitory activities compared to other Apiaceous oils (fennel, anise, and cumin). GC–MS proved that coriander essential oil showed a very high level of oxygenated monoterpenes, with linalool (81.29%) as the most abundant constituent. Intriguingly, coriander oil cream and Coriander Essential Oil-loaded Lipid Nanoparticles (CEOLNs) formulations attenuated in vivo UV-induced skin photoaging that was manifested by significantly decreased MDA, COX-2, PGE-2, MMP-1, JNK, and AP-1 levels. Moreover, these pharmaceutical dosage forms significantly increased skin collagen content compared to UV-injured group. Also, coriander essential oil significantly increased TGFβ, TGFβII, and SMAD3 protein expression levels compared to UV-injured group. In conclusion, the pharmaceutical dosage forms of coriander oil possess anti-wrinkle activities that could have an auspicious role in amending extrinsic aging.

Integrated bioinformatic analysis of gene expression profiling data to identify combinatorial biomarkers in inflammatory skin disease

Selection of appropriate biomarker to identify inflammatory skin diseases is complicated by the involvement of thousands of differentially expressed genes (DEGs) across multiple cell types and organs. This study aimed to identify combinatorial biomarkers in inflammatory skin diseases. From one gene expression microarray profiling dataset, we performed bioinformatic analyses on dataset from lesional skin biopsies of patients with inflammatory skin diseases (atopic dermatitis [AD], contact eczema [KE], lichen planus [Li], psoriasis vulgaris [Pso]) and healthy controls to identify the involved pathways, predict upstream regulators, and potential measurable extracellular biomarkers. Overall, 434, 629, 581, and 738 DEGs were mapped in AD, KE, Li, and Pso, respectively; 238 identified DEGs were shared among four different inflammatory skin diseases. Bioinformatic analysis on four inflammatory skin diseases showed significant activation of pathways with known pathogenic relevance. Common upstream regulators, with upregulated predicted activity, identified were CNR1 and BMP4. We found the following common serum biomarkers: ACR, APOE, ASIP, CRISP1, DKK1, IL12B, IL9, MANF, MDK, NRTN, PCSK5, and VEGFC. Considerable differences of gene expression changes, involved pathways, upstream regulators, and biomarkers were found in different inflammatory skin diseases. Integrated bioinformatic analysis identified 12 potential common biomarkers of inflammatory skin diseases requiring further evaluation.

Skin, hair and beyond: the impact of menopause

The skin is an endocrine organ and a major target of hormones such as estrogens, androgens and cortisol. Besides vasomotor symptoms (VMS), skin and hair symptoms often receive less attention than other menopausal symptoms despite having a significant negative effect on quality of life. Skin and mucosal menopausal symptoms include dryness and pruritus, thinning and atrophy, wrinkles and sagging, poor wound healing and reduced vascularity, whereas skin premalignant and malignant lesions and skin aging signs are almost exclusively caused by environmental factors, especially solar radiation. Hair menopausal symptoms include reduced hair growth and density on the scalp (diffuse effluvium due to follicular rarefication and/or androgenetic alopecia of female pattern), altered hair quality and structure, and increased unwanted hair growth on facial areas. Hormone replacement therapy (HRT) is not indicated for skin and hair symptoms alone due to the risk-benefit balance, but wider potential benefits of HRT (beyond estrogen's effect on VMS, bone, breast, heart and blood vessels) to include skin, hair and mucosal benefits should be discussed with women so that they will be able to make the best possible informed decisions on how to prevent or manage their menopausal symptoms.

Assessment of Melatonin-Cultured Collagen/Chitosan Scaffolds Cross-Linked by a Glyoxal Solution as Biomaterials for Wound Healing

Chitosan (CTS) and collagen (Coll) are natural biomaterials that have been extensively used in tissue engineering or wound healing applications, either separately or as composite materials. Most methods to fabricate CTS/Coll matrices employ chemical crosslinking to obtain solid and stable scaffolds with the necessary porosity and mechanical properties to facilitate regeneration. In this study, we comparatively assessed the physicochemical properties of 3D scaffolds loaded with a cross-linker, glyoxal. Using a scanning electron microscope, we evaluated the microstructure of resultant matrices and their mechanistic testing by the determination of the compressive modulus (E_mod), the maximum force (F_max), thermogravimetric analysis (TG), Fourier Transform Infrared Spectroscopy–Attenuated Total Reflectance (FTIR-ATR), and proliferation rate in vitro using human epidermal keratinocytes and dermal fibroblasts cultured in presence of melatonin solution (10⁻⁵ M). We observed that enhanced content of collagen (50CTS/50Coll or 20CTS/80Coll compared to 80CTS/20Coll) significantly elevated the physicochemical capacities of resultant materials. Besides, presence of 5% glyoxal increased porosity, E_mod and F_max, compared to scaffolds without glyoxal. Finally, keratinocytes and dermal fibroblasts cultured on subjected matrices in presence of melatonin revealed a prominently enhanced growth rate. This indicates that the combination of glyoxal and melatonin make it imperative to consider these materials as a promising approach for targeting skin tissue engineering or regenerative dermatology.

CB2R Deficiency Exacerbates Imiquimod-Induced Psoriasiform Dermatitis and Itch Through the Neuro-Immune Pathway

Background: Cannabinoid receptor 2 (CB2R) is a potential target for anti-inflammatory and pain therapeutics given its significant immunomodulatory and analgesic effects. However, the role of CB2R in imiquimod (IMQ)-induced psoriasiform dermatitis (PsD) and itch is poorly understood.

Objective: To investigate the function and mechanism of CB2R in PsD and itch in mice.

Methods: Following daily treatment with topical IMQ cream for 5-7 consecutive days in C56BL/6 wild-type (WT) and CB2R gene knockout (KO) mice, we assessed the Psoriasis Area and Severity Index (PASI) scores and the scratch bouts every day, and hematoxylin and eosin (H&E) staining, toluidine blue staining were used to observe the histological changes. mRNA levels were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Protein levels were detected by western blotting (WB), immunohistochemistry (IHC), immunofluorescence (IF) and cytometric bead array (CBA). Flow cytometry (FCM) was used to examine the proportion of Th17/Treg cells.

Results: We found that CB2R expression levels were increased in mice with psoriasis. Compared with WT mice, CB2R deficiency exacerbated IMQ-induced PsD and scratching bouts and upregulated the expression of proinflammatory cytokines by increasing the infiltration of CD4⁺ T cells and the Th17/Treg ratio. Obvious proliferation and prolongation of nerve fibers and high expression of nerve growth factor (NGF) were observed in PsD and CB2R KO mice. Pretreatment with the CB2R agonist, JWH-133 significantly reversed inflammation and scratching bouts. CB2R didn't participate in the induction of itch in psoriasis by regulating the expression of IL-31, thymic stromal lymphopoietin (TSLP) and mast cells in mouse skins.

Conclusion: Our results demonstrate that CB2R plays a pivotal role in the pathophysiology of psoriasis, providing a new potential target for anti-inflammatory and antipruritic drugs.

Evolutionary context of psoriatic immune skin response

The skin is vital for protecting the body and perceiving external stimuli in the environment. Ability to adapt between environments is in part based on skin phenotypic plasticity, indicating evolved homeostasis between skin and environment. This homeostasis reflects the greater relationship between the body and the environment, and disruptions in this balance may lead to accumulation of susceptibility factors for autoimmune conditions like psoriasis. In this study, we examined the relationship between rapid, lineage-specific evolution of human skin and formation of psoriatic skin responses at the transcriptome level. We collected skin tissue biopsies from individuals with psoriasis and compared gene expression in psoriatic plaques to non-plaque psoriatic skin. We then compared these data with non-psoriatic skin transcriptome data from multiple primate species. We found 67 genes showing human-specific skin expression that are also differentially regulated in psoriatic skin; these genes are significantly enriched for skin barrier function, immunity and neuronal development. We identified six gene clusters with differential expression in the context of human evolution and psoriasis, suggesting underlying regulatory mechanisms in these loci. Human and psoriasis-specific enrichment of neuroimmune genes shows the importance of the ongoing evolved homeostatic relationship between skin and external environment. These results have implications for both evolutionary medicine and public health, using transcriptomic data to acknowledge the importance of an individual’s surroundings on their overall health.

The skin is important for protecting the body from the environment and perceiving external stimuli, creating an evolved balance between skin and the environment. We compare skin gene expression in humans with psoriasis to humans and non-human primates without psoriasis to better understand human-specific evolutionary changes in the skin. Our results suggest important evolutionary links between skin perception, human-specific skin development and immune response.