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

Polymyxin B induces pigmentation by upregulating ATG2A-ERK/CREB-MITF-PMEL17 signaling axis

Polymyxin B serves as the last line of defense in treating multidrug-resistant Gram-negative bacterial infections. However, its distinctive side effect of hyperpigmentation significantly impacts patients' psychological well-being and treatment adherence. Currently, the underlying mechanism of polymyxin B-induced pigmentation remains to be incompletely investigated. This study aims to explore the correlation between polymyxin B-induced pigmentation and autophagy in zebrafish and melanoma cells. Comparative analysis between polymyxin B and its analog polymyxin E reveals opposite effects of the two polymyxins on PMEL17 expression and autophagic flux. Polymyxin B increases PMEL17 expression, correlating with elevated LC3B-II/I level and inhibition of autolysosomal degradation activity, while polymyxin E exerts the contrary effects. RNA-seq analysis of autophagy genes identifies a significant upregulation of ATG2A expression induced by polymyxin B. Moreover, polymyxin B, dependent on ATG2A, promotes MITF overexpression through the LC3B-II/pERK/pCREB pathway, subsequently enhancing PMEL17 expression. This study elucidates the mechanism linking polymyxin B-induced pigmentation and autophagy, demonstrating that polymyxin B causes the accumulation of PMEL17 within autophagosomes and inhibits its autophagic degradation, suggesting that autophagosomes may transform into melanosomes. These findings further contribute to the theoretical basis for autophagy regulating melanin synthesis, highlighting the multifaceted functions of autophagic proteins beyond degradation within autolysosomes.

Recombinant human collagen XVII protects skin basement membrane integrity by inhibiting the MAPK and Wnt signaling pathways

Collagen XVII is a key component linking the cytoskeleton to the basement membrane, serving an essential role in maintaining skin integrity. With the advancement of synthetic biology, recombinant human collagen XVII (RHCXVII) has emerged as a promising novel collagen material. The present study aimed to elucidate the efficacy and mechanisms of action of RHCXVII in protecting skin basement membrane integrity. A skin injury model was established using ultraviolet B (UVB) irradiation on human HaCaT keratinocytes treated with RHCXVII. The effects of RHCXVII on cell migration and adhesion were assessed using wound healing assay and hematoxylin and eosin staining, respectively. The expression of key extracellular matrix (ECM) components such as collagen IV, collagen VII, laminin 332 and integrin α6 (ITGA6) were quantified using reverse transcription‑quantitative PCR and western blotting. The mechanism of action of RHCXVII in protecting skin basement membrane integrity was investigated using a phosphorylated‑antibody array and verified by western blotting. RHCXVII significantly increased the migration and adhesion of UVB‑irradiated HaCaT cells (P<0.01). Additionally, RHCXVII significantly upregulated expression levels of collagen type IV α1 chain, collagen type VII α1 chain, laminin subunit β3 and ITGA6 in UVB‑irradiated HaCaT cells (P<0.05). RHCXVII significantly inhibited the phosphorylation of p38 and c‑Jun in the MAPK and Wnt signaling pathways (P<0.01). In conclusion, RHCXVII protected skin basement membrane integrity by enhancing migration and adhesion of keratinocytes, upregulating key ECM components and inhibiting protein phosphorylation in MAPK and Wnt pathways. The present study enhanced the current understanding of RHCXVII as a protector of skin basement membrane integrity. Furthermore, the present study highlighted clinical implications and the broad therapeutic potential of RHCXVII in both medical and cosmetic application.

Youthful Brain-Derived Extracellular Vesicle-Loaded GelMA Hydrogel Promotes Scarless Wound Healing in Aged Skin by Modulating Senescence and Mitochondrial Function

Slow wound healing in the elderly has attracted much attention recently due to the associated infection risks and decreased longevity. The "brain-skin axis" theory suggests that abnormalities in the brain and nervous system can lead to skin degeneration because abnormal mental states, like chronic stress, can have negative physiological and functional effects on the skin through a variety of processes, resulting in delayed wound healing and accelerated skin aging. However, it remains unclear whether maintaining a youthful brain has beneficial effects on aged skin healing. In light of this, we identified youthful brain-derived extracellular vesicles (YBEVs) and created a composite GelMA hydrogel material that encourages scarless wound healing in aged skin. We found that YBEVs reduce the expression of senescence, senescence-associated secretory phenotypes, and inflammation-associated proteins, and even restore dysfunction in senescent cells. Furthermore, by encouraging collagen deposition, angiogenesis, epidermal and dermal regeneration, and folliculogenesis, we demonstrated that YBEV-containing composite hydrogels accelerated scarless wound healing in skin wounds of aged rats. The pro-repairing speed and effect of this composite hydrogel even matched that of young rats. Subsequent proteomic analysis revealed the presence of numerous proteins within YBEVs, some of which may play a role in the regulation of skin energy intake, particularly through oxidative phosphorylation and mitochondrial function. In conclusion, the findings suggest that maintaining a youthful brain could potentially alleviate skin aging, and the proposed YBEVs-GelMA hydrogel emerges as a promising strategy for addressing age-related impairments in skin healing.

Possibility and Potenzial Intervention Targets of Saffron Extract in the Treatment of Atopic Dermatitis: A Review

Atopic dermatitis (AD) is a chronic, recurrent inflammatory skin disorder characterized by dry skin, eczema-like lesions, and severe itching. The multifaceted etiology of AD, which is not yet fully understood, includes genetic predispositions, immune dysfunctions(such as an impaired skin barrier and abnormal immune regulation), imbalances in the skin microbiota, and environmental factors, among others. In the field of AD treatment, the combination of traditional Chinese medicine and modern medicine is becoming an emerging trend. Given the potenzial side effects and reduced efficacy of conventional therapeutic drugs, Chinese herbal medicines offer patients new treatment options because of their unique efficacy and low toxicity. Some saffron extracts derived from saffron and gardenia, such as crocin, crocetin, and safranal, have shown promising potenzial in the treatment of AD. These natural ingredients not only possess anti-inflammatory and immunomodulatory properties similar to those of traditional Chinese medicines but also demonstrate excellent effects in promoting the repair of damaged skin barriers. Therefore, this article reviews the therapeutic potenzial of saffron extract in the treatment of AD, with a special focus on its mechanisms and potenzial interventions, while emphasizing the importance of herbal medicines as alternatives to traditional treatments, providing AD patients with safer and more effective treatment options.

Collagen Hydrolysates from Animal By-Products in Topical Cosmetic Formulations

The circular economy of animal by-products rich in collagen focuses on converting collagen into peptides with a defined molecular weight. Collagen hydrolysates prepared by biotechnological methods from chicken gizzards, deer tendons, and Cyprinus carpio skeletons can be an alternative source of collagen for cosmetic products that traditionally use bovine or porcine collagen hydrolysates. Collagen hydrolysates were characterized by antioxidant activity, surface tension, solution contact angle, and other parameters (dry weight, ash content, and solution clarity). Furthermore, the vibrational characterization of functional groups and their molecular weight was performed using the GPC-RID method. Subsequently, emulsion and gel cosmetic matrices were prepared with 0.5% and 1.5% collagen hydrolysates. Microbiological stability, organoleptic properties, and viscosity were investigated. Verification of the biophysical parameters of the topical formulations was performed in vivo on a group of volunteers by measuring skin hydration and pH and determining trans-epidermal water loss. Fish collagen hydrolysate was the most suitable for cosmetic applications in the parameters investigated. Moreover, it also effectively reduces wrinkles in the periorbital region when used in a gel matrix.

Neurogenic Inflammation in Allergic Contact Dermatitis

Allergic contact dermatitis (ACD) is a skin condition characterized by inflammation resulting from hypersensitivity upon contact with certain allergens. Although ACD is characterized by an immune-mediated pathomechanism, the involvement of the nervous system in this condition has increasingly been considered, particularly in the amplification and persistence of inflammation. This paper aims to present a comprehensive overview of the mechanisms involved in neurogenic inflammation in ACD, focusing on the role of sensory neurons, the release of neuropeptides, their interaction with immune cells, and the potential therapeutic implications related to neurogenic pathways, diversified by age and gender. Innovative therapies for ACD, including topical formulations, may target the mass-bound X2 G-protein-coupled receptor (MRGPRX2) and endocannabinoid systems.

Managing a Burning Face: Clinical Manifestations and Therapeutic Approaches for Neurogenic Rosacea

Rosacea is a common chronic inflammatory condition primarily affecting middle-aged women. It presents with flushing, erythema, telangiectasia, papules, pustules, phymatous changes, and ocular involvement. Although typically grouped into four subtypes-erythematotelangiectatic, papulopustular, ocular, and phymatous-overlapping features often favor a phenotypic diagnostic approach. Neurogenic rosacea (NR) has emerged as a distinct subgroup featuring distinguishing features such as peripheral facial erythema, severe burning and stinging sensations, and resistance to standard rosacea therapies. Recent insights into the pathophysiology of NR propose neural dysregulation as the main driver of the condition. Specifically, the activation of TRP channels at cutaneous sensory nerve endings in the dermis triggers the release of vasoactive peptides, driving neuroinflammation and resulting in burning and stinging. Additionally, there is a marked association with neuropsychiatric comorbidities, which would further mediate the pathogenesis of the condition. In line with this pathophysiological model, NR often fails to respond to conventional rosacea treatments. Instead, patients benefit more from antidepressants and neuroleptic agents that help modulate neuronal activity and alleviate symptoms. This review explores and summarizes the scientific evidence regarding the new insights on disease pathogenesis, clinical manifestations, and proposed treatments for NR.

Melanin and Neurotransmitter Signalling Genes Are Differentially Co-Expressed in Growing Feathers of White and Rufous Barn Owls

Regulation of melanin-based pigmentation is complex, involving multiple genes. Because different genes can contribute to the same pigmentation phenotype, the genes identified in model organisms may not necessarily apply to wild species. In the barn owl (Tyto alba), ventral plumage colour ranges from white to rufous, with genetic variation in the melanocortin 1 receptor gene (MC1R) accounting for at least a third of this variation. In the present study, we used transcriptomic data to compare the gene expression profiles of growing feathers from nestlings with different MC1R genotypes. We identified 21 differentially expressed genes, nine of which are involved in melanogenesis, while seven are related to neurotransmitter function or synaptic activity. With the exception of CALB1, all of the differentially expressed genes were upregulated in rufous owls compared to white barn owls. To the best of our knowledge, this study is the first to link melanin production with neurotransmitter-related genes, and we discuss possible evolutionary explanations for this connection.

Impact of Minimally Manipulated Cell Therapy on Immune Responses in Radiation-Induced Skin Wound Healing

The current treatment of radiation-induced skin wounds utilizes mainly conventional therapies, including topical steroids, creams, ointments, and hydrogel dressings, which do not take into account the immunologic changes that occur in the skin after radiation exposure. Therefore, it is relevant to consider alternative therapies and their impact on changes in the immune landscape of the skin. The aim of this study was to investigate the effect of allogeneic minimally manipulated keratinocytes and fibroblasts on rat skin repair and the development of immune responses. We found that the use of cell therapy compared to treatment with syntazone ointment and no treatment resulted in faster healing and a reduction in the size of radiation-induced skin wounds, area of inflammation, and edema. Additionally, in the group receiving the cell therapy application, there was an observed increase in the number of mast cells (MCs), activation of MC interaction with M2 macrophages, a reduction in the direct contact of MCs with the vascular bed, an increase in the content of collagen fibers due to the intensification of collagen fibrillogenesis, and a restoration of their histotopographic organization. Thus, the positive effect of cell therapy based on allogeneic minimally manipulated keratinocytes and fibroblasts on skin regeneration indicated that it can be used in clinical practice to improve the effectiveness of rehabilitation after radiation therapy.

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.

Antioxidant and membrane-protective effects of the 3-O-ethyl ascorbic acid-cannabigerol system on UVB-irradiated human keratinocytes

The lack of effective protection against UVB radiation, that severely disrupts the metabolism of keratinocytes, underlines the search for bioactive compounds that would provide effective protection without causing side effects. Therefore, the aim of the study has been to assess the effect of two compounds, that are different in terms of structure and properties: 3-O-ethyl ascorbic acid-EAA (a stable derivative of vitamin C) and cannabigerol-CBG, used separately or concurrently, on the metabolism of keratinocytes previously exposed to UVB. The obtained results indicate diverse, yet mutually reinforcing localization of the tested compounds, both within the membrane structures and cytosol. When used concurrently, EAA + CBG effectively prevent modifications of the structure of cell membranes, particularly the increase in their fluidity and permeability caused by UVB. It promotes cell survival and enhances the expression of membrane transporters, especially BCRP. Moreover, the concurrent use of both compounds, by reducing the level of ROS and regulating the expression of both Nrf2 activators (p62, MAPK) and inhibitors (Keap1, Bach1, PAGM5), supports the antioxidant efficiency of cells, visible in the increased activity of antioxidant enzymes (SOD1/2, CAT) and the effectiveness of GSH- and Trx-dependent antioxidant systems. Consequently, oxidative modifications of lipids (assessed as 4-HNE and isoprostanes) and proteins (measured as 4-HNE-protein adducts and carbonyl groups) are reduced. The tested compounds also reveal anti-inflammatory effects by modifying the expression of the activator (p62) and inhibitors (IKKα, IKKβ) of NFκB. The observed EAA + CBG effect in preventing changes in the structure and functionality of keratinocyte membranes, maintaining redox balance, and mitigating inflammatory effects caused by UVB provides the basis for further research.

Nicotinamide: A Multifaceted Molecule in Skin Health and Beyond

Nicotinamide (NAM), the amide form of vitamin B3, is a precursor to essential cofactors nicotinamide adenine dinucleotide (NAD⁺) and NADPH. NAD⁺ is integral to numerous cellular processes, including metabolism regulation, ATP production, mitochondrial respiration, reactive oxygen species (ROS) management, DNA repair, cellular senescence, and aging. NAM supplementation has demonstrated efficacy in restoring cellular energy, repairing DNA damage, and inhibiting inflammation by suppressing pro-inflammatory cytokines release. Due to its natural presence in a variety of foods and its excellent safety profile-even at high doses of up to 3 g/day-NAM is extensively used in the chemoprevention of non-melanoma skin cancers and the treatment of dermatological conditions such as blistering diseases, atopic dermatitis, rosacea, and acne vulgaris. Recently, its anti-aging properties have elevated NAM's prominence in skincare formulations. Beyond DNA repair and energy replenishment, NAM significantly impacts oxidative stress reduction, cell cycle regulation, and apoptosis modulation. Despite these multifaceted benefits, the comprehensive molecular mechanisms underlying NAM's actions remain not fully elucidated. This review consolidates recent research to shed light on these mechanisms, emphasizing the critical role of NAM in cellular health and its therapeutic potential. By enhancing our understanding, this work underscores the importance of continued exploration into NAM's applications, aiming to inform future clinical practices and skincare innovations.

Activation of Local 11β-Hydroxysteroid Dehydrogenase Type 1 by Diosmetin Enhances Endogenous Glucocorticoid Levels to Alleviate Skin Inflammation: Insights Into a Novel Therapeutic Strategy for Atopic Dermatitis

Glucocorticoids (GCs) are synthesised de novo by peripheral tissues and the adrenal cortex of the hypothalamic-pituitary-adrenal axis. Skin expresses an enzyme called 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which reduces cortisone to the active hormone cortisol which activates GC receptors. 11β-HSD1 plays a significant role in alleviating atopic inflammation through the elevation of the concentrations of active GC in the skin. This study aimed to investigate the role of diosmetin as an activator of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). In human keratinocytes, diosmetin was found to upregulate 11β-HSD1 protein expression and cortisol levels, as well as the transcriptional expression of 11β-HSD1 mRNA. However, this upregulation of 11β-HSD1 mRNA was abrogated in keratinocytes transfected with 11β-HSD1 small interfering RNA (siRNA). In an atopic dermatitis (AD) murine model, topical administration of diosmetin significantly attenuated basal transepidermal water loss (TEWL) and the Eczema Area and Severity Index (EASI), while enhancing stratum corneum (SC) hydration. Diosmetin also increased corticosterone levels in the SC and upregulated 11β-HSD1 expression in both the serum and epidermis. Furthermore, diosmetin treatment led to a marked reduction in serum immunoglobulin E (IgE) and tumour necrosis factor-α (TNF-α) levels, and suppressed mRNA expression of thymic stromal lymphopoietin (TSLP), interleukin-1β (IL-1β), IL-4, and IL-13 in the epidermis. Collectively, these findings suggest that diosmetin promotes the endogenous activation of glucocorticoids via local 11β-HSD1 activation, underscoring its potential as a novel topical therapeutic agent for the management of inflammatory skin disorders, such as AD.

Steroidogenic acute regulatory protein mediated variations of gender-specific sex neurosteroids in Alzheimer's disease: Relevance to hormonal and neuronal imbalance

The steroidogenic acute regulatory (StAR) protein mediates the rate-liming step in neuro/steroid biosynthesis. Multifaceted and delicate changes during aging, disrupting hormonal and neuronal homeostasis, constitute human senescence, an inevitable phenomenon that attributes to increased morbidity and mortality. Aging, along with progressive decreases in bioactive neurosteroids, is the primary risk factor for Alzheimer's disease (AD), which preferentially impacts two-thirds of women and one-third of men. AD is neuropathologically characterized by the accumulation of extracellular amyloid-β and intracellular phosphorylated Tau containing neurofibrillary tangles, resulting in dementia. Postmortem brains pertaining to gender-specific AD patients exhibit varied suppression of StAR and sex neurosteroid levels compared with age-matched cognitively healthy subjects, in which the attenuation of StAR is inversely correlated with the AD pathological markers. Interestingly, retinoid signaling upregulates StAR-motivated neurosteroid biosynthesis and reinstates various neurodegenerative vulnerabilities that promote AD pathogenesis. This review summarizes current understanding of StAR-driven alterations of sex neurosteroids in gender-specific AD risks and provides biochemical and molecular insights into therapeutic interventions for preventing and/or alleviating dementia for healthy aging.

The Melanocyte and Nerve Fiber Cross-Talk, Facilitated Also by Semaphorin-4A, Enhances UV-B-Induced Melanogenesis

Epidermal melanocytes form synaptic-like contacts with cutaneous nerve fibers, but the functional outcome of these connections remains elusive. In this pilot study we used our fully humanized re-innervated skin organ culture model to investigate melanocyte-nerve fiber interactions in UV-B-induced melanogenesis. UV-B-irradiation significantly enhanced melanin content and tyrosinase activity in re-innervated skin compared to non-innervated controls, indicating that neuronal presence is essential for exacerbating pigmentation upon UV-B irradiation in long-term culture. Comparative transcriptomic analysis between laser-capture-microdissected melanocytes from freshly embedded human skin and published microarray data on in vitro primary melanocytes identified Semaphorin-4A (SEMA4A) as possible mediator of melanocyte-nerve fibers interactions. SEMA4A protein levels in Gp100+-epidermal melanocytes were significantly higher in re-innervated skin, and reduced by UV-B treatment. Analysis of melanocytes in vitro showed reduced SEMA4A protein expression 24 h after UV-B-irradiation while SEMA4A secretion into the medium was increased. Beta-tubulin expression and axon growth in sensory neurons were stimulated by conditioned media (CM) from UV-B irradiated melanocytes. When this neuronal-conditioned medium was transferred to fresh melanocytes, melanin content increased, but only if neurons had been treated with CM from UV-B irradiated melanocytes. These findings highlight the importance of melanocyte-neuron interactions for UV-B-induced melanogenesis and suggest that secreted proteins (e.g., SEMA4A) can function as a novel target to treat hypo- and hyperpigmentation disorders.

Effects of Retinol, Natural Pea Peptide and Antioxidant Blend in a Topical Formulation: In Vitro and Clinical Evidence

INTRODUCTION

Retinol has a long history of treating skin conditions, including photoaging. However, skin irritation with repeated use of retinol is well documented. The present study assessed the effectiveness of a novel topical formulation, referred to as retinol topical formulation (RTF), to improve the quality of skin health. The RTF was composed of a low dose retinol, a synthetic retinoid ester, a pea peptide, and an antioxidant blend.

METHODS

In vitro assessment of RTF on human skin co-cultures (human keratinocytes, melanocytes, and dermal fibroblasts) identified gene expression levels and skin biomarkers after 24 h exposure. An 8-week clinical study was conducted to evaluate once-nightly application of the RTF for short-term and long-term benefits in 30 adult subjects between 35 and 70 years of age (21 female, 9 male). Skin evaluations were conducted via bioinstrumentation (for hydration, transepidermal water loss and elasticity) and at 0, 1-, 2-, 4-, and 8-week self-assessment questionnaires and photo-imaging analysis were performed.

RESULTS

RTF treatment of skin in vitro co-cultures upregulated aquaporin-3, PER1, collagen, and elastin, and downregulated expression of MMP1 and the pigmentation genes TYRP1 and MITF. The clinical assessment significantly improved hydration, transepidermal water loss, and elasticity along with incremental but significant increases in nine skin parameters (hydration, clarity, radiance/glow, smoothness, brightness, texture, appearance of pores, dark spots/hyperpigmentation, and skin tone evenness from baseline) with continuous use over 8 weeks compared to baseline values.

CONCLUSIONS

The RTF in vitro analysis showed significant positive changes for several skin biomarkers, and the clinical assessment showed RTF significantly improved the visible signs of dermal aging, without irritation.

The assessment of the phototoxic potential of drugs forming complexes with melanin - Screening in vitro studies using normal skin cells with varying pigmentation irradiated by a sunlight simulator

Phototoxic reactions are among the most common skin-related adverse effects induced by drugs. It is believed that the binding of chemicals to melanin biopolymers is a significant factor influencing skin toxicity. The formation of drug-melanin complexes can lead to the accumulation of drugs or their photodegradation products in pigmented cells, potentially affecting phototoxic reactions. Current procedures for assessing the phototoxic potential of drugs are based on tests using immortalized mouse fibroblasts. This study aimed to assess the phototoxic potential of selected drugs that form complexes with melanin (chloroquine, chlorpromazine, doxycycline) using human melanocytes with varying degrees of pigmentation. Parallel research was conducted on human dermal fibroblasts. To induce phototoxicity, cell cultures were irradiated using a sunlight simulator (5 J/cm2 for UVA spectrum). To account for the process of drug accumulation, two experimental models with different incubation times of cells with drugs before irradiation were used. The photo-irritation factor (PIF) was calculated based on NRU and WST-1 screening tests. Additionally, cell viability was examined cytometrically, and analyses of the cell cycle and reduced glutathione levels were conducted. The results indicated that drugs binding with melanin exhibited different levels of cytotoxicity and phototoxicity towards fibroblasts and melanocytes. These observed differences impact the values of PIF, potentially complicating the interpretation of the studies. Additional analyses, such as examining cell subpopulations in the sub-G1 phase and determining the level of reduced glutathione, can enhance the assessment of the phototoxicity of drugs on pigmented cells.

Biotics as novel therapeutics in targeting signs of skin ageing via the gut-skin axis

Skin ageing is a phenomenon resulting from the aggregative changes to skin structure and function and is clinically manifested by physical features such as wrinkles, hyperpigmentation, elastosis, telangiectasia, and deterioration of skin barrier integrity. One of the main drivers of skin ageing, UV radiation, negatively influences the homeostasis of cells and tissues comprising the skin by triggering production of immune-mediated reactive oxygen species (ROS) and pro-inflammatory cytokines, as well as a various hormones and neuropeptides. Interestingly, an established link between the gut and the skin coined the 'gut-skin axis' has been demonstrated, with dysbiosis and gut barrier dysfunction frequently observed in certain inflammatory skin conditions and more recently, implicated in skin ageing. Therapeutic use of 'biotics' including prebiotics, probiotics, postbiotics, and synbiotics, which modulate the gut microbiota and production of microbially associated metabolites, influence the activity of the gut mucosal and immune systems and are showing promise as key candidates in addressing signs of skin ageing. In this review we aim to focus on the structure and function of the gut-skin axis and showcase the recent in-vitro and clinical evidence demonstrating the beneficial effects of select biotics in targeting signs of skin ageing and discuss the proposed mechanisms mediated via the gut-skin axis underpinning these effects.

Systematic establishment of the relationship between skin absorption and toxicity of furanoids via in silico, in vitro, and in vivo assessments

Furanoids are a class of contaminants prevalent in both airborne and occupational environments, with potential health implications through inhalation, oral ingestion, and skin penetration. Given their diminutive molecular size, there is a presumption that furanoids can readily permeate the skin. To systematically explore this presumption, we investigated the skin absorption and toxicity of a series of furans (furfuryl alcohol, furfuryl acetate, furfural, methyl 2-furoate, and 5-methylfurfural) using in silico, in vitro, and in vivo models. The in vitro permeation test (IVPT) from neat and aqueous suspension (5 mM) of furans demonstrated a facile absorption through pig and nude mouse skins. The lipophilicity of furans significantly influenced skin deposition, with higher lipophilicity displaying greater deposition. However, an opposing trend emerged in the receptor compartment accumulation. In barrier-defective skin simulating atopic dermatitis (AD) and psoriasis, enhanced deposition occurred with more hydrophilic furans but not with the more lipophilic ones. In the cell-based study, furanoids induced the proliferation of keratinocytes and skin fibroblasts except for the compounds with the aldehyde group (furfural and 5-methylfurfural). Both furfuryl acetate and 5-methylfurfural activated keratinocytes via the overexpression of COX-2 and PGE2 by 1.5‒2-fold. This stimulation involved the mitogen-activated protein kinase (MAPK) signaling pathway. For the in vivo mouse skin treatment, we selected furfuryl acetate (hydrophilic) and 5-methylfurfural (lipophilic). Both furans showed different patterns of skin lesions, where repeated application of furfuryl acetate caused epidermal hyperplasia and scaling, while 5-methylfurfural predominantly evoked skin inflammation and barrier disintegration. Toxicokinetics analysis revealed a higher plasma concentration of topically applied furfuryl acetate than that of the 5-methylfurfural (5.04 versus 2.34 nmol/ml), resulting in the mild injury of furfuryl acetate-treated peripheral organs. Conversely, no notable adverse effects on organs were observed for the 5-methylfurfural. This study established the relationship between cutaneous absorption and the toxicity of furans following skin exposure.

Insight into adenosine pathway in psoriasis: Elucidating its role and the potential therapeutical applications

Psoriasis is an inflammatory skin disease, that can manifest as different phenotypes, however its most common form is psoriasis vulgaris (plaque psoriasis), characterized by abnormal keratinocyte proliferation, leading to characteristic histopathological signs of acanthosis, hyperkeratosis and parakeratosis. For many years, there has been a debate regarding whether keratinocyte dysfunction leads to immune system dysregulation in psoriasis or vice versa. It is now understood that epidermal hyperplasia results from immune system activation. Besides epidermal hyperplasia, psoriatic skin shows leukocyte infiltration, evident angiogenesis in the papillary dermis, characterized by tortuous, dilated capillaries, as well as oedema. There is substantial early evidence that adenosine is a key mediator of the immune response; it derives from ATP hydrolysis and accumulates into tissue in response to systemic and local stress conditions, hypoxia, metabolic stress, inflammation. Adenosine controls several cell functions by signalling through its 4 receptor subtypes, A1, A2A, A2B and A3. Evidence suggests that adenosine may play a role in psoriasis pathogenesis by controlling several immune cell functions, keratinocyte proliferation, neo-angiogenesis. Expression of adenosine receptor varies in psoriatic skin, and this can significantly impact on tissue homeostasis. Indeed, an altered adenosine receptor profile may contribute to the dysregulation observed in psoriasis, affecting immune responses and inflammatory pathways. Here, we discuss the role of adenosine in regulating the functions of the main cell populations implied in the pathogenesis of psoriasis. Furthermore, we give evidence for adenosine signalling pathway as target for therapeutic intervention in psoriasis.

Targeting Periplakin of Novel Benzenesulfonamides as Highly Selective Agonists for the Treatment of Vitiligo

Vitiligo is the most common cause of depigmentation worldwide, with immunosuppressive treatments often being inefficient and prone to recurrence, making it essential to identify new therapeutic targets. Periplakin (PPL) has been identified and confirmed as a key factor in vitiligo-related depigmentation. Based on this, a series of selective PPL agonists, specifically benzenesulfonamides, have been developed. Among these, compound I-3 exhibits superior efficacy compared to ruxolitinib, the only FDA-approved treatment for vitiligo. I-3 has been shown to increase cAMP levels by regulating PPL, which enhances MITF expression, a key transcription factor in melanin biosynthesis. Additionally, I-3 promotes melanin production by regulating tryptophan metabolism. In summary, PPL is a promising drug target, and I-3 has strong potential for future treatment of vitiligo due to its high selectivity and favorable druggability.

Enhancing Skin Wound Healing in Diabetic Mice Using SIKVAV-Modified Chitosan Hydrogels

Diabetic foot ulcers (DFUs), a prevalent chronic disease caused by various factors, significantly impact patients' quality of life due to prolonged healing times and increased infection risks. Current treatment modalities, including pharmacological, physical, and surgical interventions, often yield limited efficacy and adverse effects, highlighting the urgent need for novel therapeutic strategies. The objective of this research is to create SIKVAV-modified chitosan hydrogels with the intention of improving the process of skin wound healing in diabetic mice. We synthesized the hydrogels and established a diabetic mice model with skin wounding to evaluate its healing effects and underlying mechanisms. The results of our study indicate that the SIKVAV-modified chitosan hydrogels markedly enhance the wound healing process in diabetic mice. This effect may be attributed to several mechanisms, including differentiation of fibroblasts, proliferation of keratinocytes, the promotion of angiogenesis, stimulation of collagen synthesis, upregulation of growth factor expression, and possible involvement of the TGF-β1/Smad3 signaling pathway. This research not only provides a new biomaterial for the treatment of diabetic wounds but also elucidates the related molecular mechanisms involved in wound healing of DFUs, offering valuable insights for future clinical applications.

Controlled therapeutic cholesterol delivery to cells for the proliferation and differentiation of keratinocytes

The challenge of enhancing wound healing and skin regeneration, particularly in conditions like burns and diabetic wounds, necessitates innovative solutions. Cholesterol, often associated with cardiovascular diseases, plays vital roles in cellular functions, maintaining skin integrity and preserving the skin barrier. Here, we explore cholesterol's significance, its influence on keratinocytes, and its potential application in skin regeneration. The study utilizes electrospun polyimide (PI) fibers as a cholesterol carrier model and investigates its impact on HaCaT keratinocytes, marking the first time tracked cholesterol delivery from the scaffold into cells. We demonstrate that an optimal concentration of 0.7 mM cholesterol in the medium enhances cell proliferation, while higher concentrations have negative effects. Cholesterol-enriched scaffolds significantly increase cell proliferation and replicative activity, especially in a 3D culture environment. Moreover, cholesterol influences keratinocyte differentiation, promoting early differentiation while inhibiting late differentiation. These findings suggest that cholesterol-loaded scaffolds can have applications in wound healing by promoting cell growth, regulating differentiation, and potentially accelerating wound closure. Further research in this area will lead to innovative wound management and tissue regeneration strategies.

Beneficial Effects of Epigallocatechin Gallate in Preventing Skin Photoaging: A Review

Skin photoaging, primarily caused by ultraviolet (UV) radiation, leads to skin metabolic disorders, which have adverse psychological and physiological effects on individuals. However, traditional medications for repairing skin photoaging cause side effects. Natural bioactive compounds have been shown to prevent and treat skin photoaging with fewer side effects. Epigallocatechin gallate (EGCG), the main substance in tea polyphenols, is a natural bioactive compound with a range of properties. This review summarizes the beneficial effects and mechanisms of EGCG, as well as the application forms of EGCG in repairing photoaged skin. Results indicated that EGCG has repair effects, including improving elasticity, enhancing moisturization, inhibiting damage, and reducing pigmentation of photoaged skin. It has also been demonstrated that EGCG delivery systems, modified EGCG, and combinations with other bioactive substances could be used for repairing photoaged skin due to its poor stability and low bioavailability. EGCG effectively repairs various types of skin damage caused by UV radiation while maintaining normal skin structure and function. It is, therefore, an effective candidate for repairing photoaged skin. These results could provide references for the development and application of EGCG products for the treatment of photoaged skin.

Current Insights into the Role of UV Radiation-Induced Oxidative Stress in Melanoma Pathogenesis

Cutaneous melanoma accounts for the majority of skin cancer-related deaths, and its incidence increases each year. The growing number of melanoma cases, especially in advanced stages, poses a significant socio-medical challenge throughout the world. Extensive research on melanoma pathogenesis identifies UV radiation as the most important factor in melanocytic transformation. Oxidative effects of UV irradiation exert their influence on melanoma pathogenesis primarily through modification of nucleic acids, proteins, and lipids, further disrupting cellular signaling and cell cycle regulation. Its effects extend beyond melanocytes, leading to immunosuppression in the exposed skin tissue, which consequently creates conditions for immune surveillance evasion and further progression. In this review, we focus on the specific molecular changes observed in the UV-dependent oxidative stress environment and their biological consequences in the course of the disease, which have not been considered in previous reviews on melanoma. Nonetheless, data show that the exact role of oxidative stress in melanoma initiation and progression remains unclear, as it affects cancerous cells differently depending on the specific context. A better understanding of the pathophysiological basis of melanoma development holds promise for identifying potential targets, which could lead to effective melanoma prevention strategies.

Biological Effects of CYP11A1-Derived Vitamin D and Lumisterol Metabolites in the Skin

Novel pathways of vitamin D3, lumisterol 3 (L3), and tachysterol 3 (T3) activation have been discovered, initiated by CYP11A1 and/or CYP27A1 in the case of L3 and T3. The resulting hydroxymetabolites enhance protection of skin against DNA damage and oxidative stress; stimulate keratinocyte differentiation; exert anti-inflammatory, antifibrogenic, and anticancer activities; and inhibit cell proliferation in a structure-dependent manner. They act on nuclear receptors, including vitamin D receptor, aryl hydrocarbon receptor, LXRα/β, RAR-related orphan receptor α/γ, and peroxisome proliferator-activated receptor-γ, with selectivity defined by their core structure and distribution of hydroxyl groups. They can activate NRF2 and p53 and inhibit NF-κB, IL-17, Shh, and Wnt/β-catenin signaling. Thus, they protect skin integrity and physiology.

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.

Signaling pathways and targeted therapy for rosacea

Rosacea is a chronic skin inflammatory disease with a global prevalence ranging from 1% to 20%. It is characterized by facial erythema, telangiectasia, papules, pustules, and ocular manifestations. Its pathogenesis involves a complex interplay of genetic, environmental, immune, microbial, and neurovascular factors. Recent studies have advanced our understanding of its molecular basis, focusing on toll-like receptor (TLR) 2 pathways, LL37 expression, mammalian target of rapamycin (mTOR) activation, interleukin (IL)-17 signaling, transient receptor potential vanilloid (TRPV) functions, and the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathways. LL37-associated signaling pathways, particularly involving TLR2 and mTORC1, are critical in the pathogenesis of rosacea. LL37 interacts with signaling molecules such as extracellular signal-regulated kinases 1 and 2 (ERK1/2), nuclear factor kappa B (NF-κB), inflammasomes, C-X-C motif chemokine ligand 8 (CXCL8), mas-related G-protein-coupled receptor X2 (MRGPRX2)-TRPV4, and vascular endothelial growth factor (VEGF). This interaction activates macrophages, neutrophils, mast cells, and vascular endothelial cells, leading to cytokine release including tumor necrosis factor-alpha (TNF-α), IL-6, IL-1β, C motif chemokine ligand (CCL) 5, CXCL9, and CXCL10. These processes contribute to immune response modulation, inflammation, and angiogenesis in rosacea pathophysiology. The IL-17 signaling pathway also plays a crucial role in rosacea, affecting angiogenesis and the production of inflammatory cytokines. In addition, recent insights into the JAK/STAT pathways have revealed their integral role in inflammatory and angiogenic mechanisms associated with rosacea. Rosacea treatment currently focuses on symptom management, with emerging insights into these molecular pathways providing more targeted and effective therapies. Biological agents targeting specific cytokines, IL-17 inhibitors, JAK inhibitors, and VEGF antagonists are promising for future rosacea therapy, aiming for enhanced efficacy and fewer side effects. This review provides a comprehensive overview of the current knowledge regarding signaling pathways in rosacea and potential targeted therapeutic strategies.

Comprehensive Analysis of Crucial m6A-Related Differentially Expressed Genes in Psoriasis

BACKGROUND

Psoriasis is a common, chronic, and multifactorial inflammatory cutaneous disorder that involves genetic and epigenetic factors. N6-methyladenosine methylation (m6A) is the most prevalent RNA modification implicated in various diseases; however, its role in psoriasis still needs to be further explored. We aimed to explore the mechanisms underlying the effects of m6A in psoriasis pathogenesis, prompting new therapeutic targets.

METHODS

Three psoriasis-related datasets, including GSE155702, GSE109248, and GSE142582, were collected. Differentially m6A methylated genes (DMGs) between psoriasis lesions of psoriasis patients and healthy skin controls were identified from the GSE155702 dataset, and corresponding Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed. Differentially expressed genes (DEGs) and the common DEGs between the two groups were screened from the GSE109248 and GSE142582 datasets; the expression and interactions of the m6A regulators were analyzed. The m6A levels of total RNAs and the protein expression levels of METTL3, WTAP, ALKBH5, FTO, and METTL14 in imiquimod (IMQ)-induced psoriasiform lesions were evaluated.

RESULTS

66 significantly upregulated and 381 significantly downregulated m6A peaks were identified, corresponding to 414 genes which were particularly associated with cell and tissue development processes and cell cycle related items. 271 common DEGs were identified, associating with keratinocyte differentiation, epidermis development, cytokine-cytokine receptor interaction, and fatty acid metabolic processes. 15 crucial m6A related differentially expressed genes were obtained after the intersection of the DMGs and common DEGs, including NEU2, GALNT6, MTCL1, DOC2B, CAMK2N1, SNTB1, RNF150, CGNL1, CCDC102A, MEOX2, EEF2K, OBSCN, SLC46A2, CCDC85A, and DACH1. In addition, we found that m6A methylation and these five m6A regulators were both upregulated in psoriatic lesions.

CONCLUSIONS

It revealed that psoriasis pathophysiological processes encompass m6A epigenetic alterations, and that m6A alterations may specifically influence cell proliferation and neural regulation, and closely associated with osteoarticular involvement and metabolic syndrome in psoriasis.

Psoriatic skin transcript phenotype: androgen/estrogen and cortisone/cortisol imbalance with increasing DNA damage response

BACKGROUND

Patients prone to psoriasis suffer after a breakdown of the epidermal barrier and develop poorly healing lesions with abnormal proliferation of keratinocytes. Strong inflammatory reactions with genotoxicity (short telomeres) suggest impaired immune defenses with DNA damage repair response (DDR) in patients with psoriasis. Recent evidence indicates the existence of crosstalk mechanisms linking the DDR machinery and hormonal signaling pathways that cooperate to influence both progressions of many diseases and responses to treatment. The aim of this study was to clarify whether steroid biosynthesis and genomic stability markers are altered in parallel during the formation of psoriatic skin. Understanding the interaction of the steroid pathway and DNA damage response is crucial to addressing underlying fundamental issues and managing resulting epidermal barrier disruption in psoriasis.

METHODS

Skin (Lesional, non-lesional) and blood samples from twenty psoriasis patients and fifteen healthy volunteers were collected. Real-Time-PCR study was performed to assess levels of known transcripts such as: estrogen (ESR1, ESR2), androgen (AR), glucocorticoid/mineralocorticoid receptors (NR3C1, NR3C2), HSD11B1/HSD11B2, and DNA damage sensors (SMC1A, TREX1, TREX2, SSBP3, RAD1, RAD18, EXO1, POLH, HUS1).

RESULTS

We found that ESR1, ESR2, HSD11B1, NR3C1, NR3C2, POLH, and SMC1A transcripts were significantly decreased and AR, TREX1, RAD1, and SSBP3 transcripts were increased dramatically in the lesional skin compared to skin samples of controls.

CONCLUSION

We found that the regulation of the steroidogenic pathway was disrupted in the lesional tissue of psoriasis patients and that a sufficient glucocorticoid and mineralocorticoid response did not form and the estrogen/androgen balance was altered in favour of androgens. We suggest that an increased androgen response in the presence of DDR increases the risk of developing psoriasis. Although this situation may be the cause or the consequence of a disruption of the epidermal barrier, our data suggest developing new therapeutic strategies.

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.

Polynucleotides in Aesthetic Medicine: A Review of Current Practices and Perceived Effectiveness

Polynucleotides, complex molecules composed of nucleotides, have gained attention in aesthetic medicine for their potential to regulate gene expression and promote tissue regeneration. This review aims to provide an overview of the current practices and perceived effectiveness of polynucleotides in aesthetic medicine. A comprehensive search of the literature was conducted using keywords related to polynucleotides, cosmetic application, and aesthetic application. Studies were selected based on their relevance to aesthetic medicine and the inclusion of human subjects. The review found that polynucleotides have been used to improve skin texture, reduce wrinkle depth, and enhance facial appearance. The studies reported varying degrees of efficacy and safety, with some studies demonstrating significant improvements in skin elasticity and hydration. However, others reported limited or no benefits. The review also highlighted the need for further research to establish the optimal use and efficacy of polynucleotides in aesthetic medicine. While the existing literature suggests that polynucleotides may have potential benefits in aesthetic medicine, more research is needed to fully understand their mechanisms of action and optimal use. Clinicians should be aware of the current limitations and potential risks associated with the use of polynucleotides in aesthetic medicine.

Tumor Necrosis Factor-Alpha: Ally and Enemy in Protean Cutaneous Sceneries

Skin is the forestage for a series of many-sided functions of tumor necrosis factor-alpha (TNF-α), a proinflammatory cytokine with staggering versatility and sizable implications for tissue homeostasis, immune responses, angiogenesis, apoptosis, local and systemic inflammation. An aberrant TNF-α-mediated crosstalk has been linked to the pathogenesis of acute and chronic skin inflammatory diseases, and indeed, TNF-α dysregulation can contribute to the development and progression of psoriasis, vitiligo, local damage following exposition to ultraviolet light radiations, cutaneous lupus erythematosus, and acne vulgaris. Therapies that target TNF-α are conspicuously used in the treatment of different skin disorders, aiming to modulate the in vivo immune functions triggered by many cutaneous cells, including keratinocytes, mast cells, or Langerhans cells, and reduce inflammation taking place within the skin. Herein, we focus on the key relationships between TNF-α and distinct skin non-neoplastic inflammatory or physiologic conditions, showing that a natural induction of TNF-α may have a protective significance but that TNF-α overproduction may be harmful or even lethal. Many questions remain unraveled in the therapeutic practice, and caution should be exercised due to eventual backlashes exerted by TNF-α in maintaining skin health or in provoking skin disease.

Sws2 Gene Positively Regulates Melanin Production in Plectropomus leopardus Skin via Direct Regulation of the Synthesis of Retinoic Acid

Opsins are a class of transmembrane proteins encoded by opsin genes, and they play a variety of functional roles. Short wavelength-sensitive opsin 2 (sws2), one of the five classes of visual opsin genes, mainly senses blue light. Previous research has indicated that sws2 is essential for melanocyte formation in fish; however, its specific role in skin color differentiation remains to be elucidated. Here, we identified the sws2 gene in a prized reef-dwelling fish, Plectropomus leopardus. The full-length P. leopardus sws2 gene encodes a protein consisting of 351 amino acids, and exhibits substantial homology with other fish species. The expression of the sws2 gene was widespread across P. leopardus tissues, with high expression in eye and skin tissues. Through immunohistochemistry and in situ hybridization analyses, we discovered that the sws2 gene was primarily localized in the rod and cone cells of the retina, and epidermal cells of the skin. Furthermore, dsRNA interference was used for sws2 gene knockdown in living P. leopardus to elucidate its function in skin color differentiation. Black-color-related genes, melanin contents, and tyrosinase activity in the skin significantly decreased after sws2 knockdown (p < 0.05), but red-color-related genes and carotenoid and lutein contents significantly increased (p < 0.05). Retinoic acid injection produced the opposite results. Our results suggested that the sws2 gene influences P. leopardus skin color regulation by affecting vitamin synthesis and melanin-related gene expression levels. This study establishes a foundation for elucidating the molecular mechanisms by which sws2 regulates melanocyte formation in fish skin.

The involvement of keratinocytes in pruritus of chronic inflammatory dermatosis

Frequent itching and incessant scratching are commonly observed in various chronic inflammatory skin conditions, including atopic dermatitis and psoriasis. The persistent and prolonged nature of pruritus can worsen one's quality of life. Keratinocytes (KCs), the predominant cells of the epidermis, have been confirmed to interact with sensory neurons and immune cells and be involved in chronic skin inflammatory diseases associated with pruritus. Initially, KCs and sensory neurons form a unique synapse-like connection within the epidermis, serving as the structural foundation for their interaction. Additionally, several receptors, including toll-like receptors and protease-activated receptor 2, expressed on KCs, become activated in an inflammatory milieu. On the one hand, activated KCs are sources of pro-inflammatory cytokines and neurotrophic factors, such as adenosine triphosphate, thymic stromal lymphopoietin, and nerve growth factor, which directly or indirectly participate in stimulating sensory neurons, thereby contributing to the itch sensations. On the other hand, KCs also function as primary transducers alongside intraepidermal nerve endings, directly initiating pruritic responses. This review summarizes the current literature and highlights the critical role of KCs in the development and persistence of chronic itch in inflammatory skin disorders.

Exosomes Derived from Hypertrophic Scar Fibroblasts Suppress Melanogenesis in Normal Human Epidermal Melanocytes

Post-burn hypertrophic scars often exhibit abnormal pigmentation. Exosomes play important roles in maintaining normal physiological homeostasis and in the pathological development of diseases. This study investigated the effects of the exosomes derived from hypertrophic scar fibroblasts (HTSFs) on melanocytes, which are pigment-producing cells. Normal fibroblasts (NFs) and HTSFs were isolated and cultured from normal skin and hypertrophic scar (HTS) tissue. Both the NF- and HTSF-exosomes were isolated from a cell culture medium and purified using a column-based technique. The normal human epidermal melanocytes were treated with both exosomes at a concentration of 100 μg/mL at different times. The cell proliferation, melanin content in the medium, apoptotic factors, transcription factors, melanin synthesis enzymes, signaling, signal transduction pathways, and activators of transcription factors (STAT) 1, 3, 5, and 6 were investigated. Compared with the Dulbecco's phosphate-buffered saline (DPBS)-treated controls and NF-exosomes, the HTSF-exosomes decreased the melanocyte proliferation and melanin secretion. The molecular patterns of apoptosis, proliferation, melanin synthesis, Smad and non-Smad signaling, and STATs were altered by the treatment with the HTSF-exosomes. No significant differences were observed between the DPBS-treated control and NF-exosome-treated cells. HTSF-derived exosomes may play a role in the pathological epidermal hypopigmentation observed in patients with HTS.

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.

Air pollution and skin diseases: A comprehensive evaluation of the associated mechanism

Air pollutants deteriorate the survival environment and endanger human health around the world. A large number of studies have confirmed that air pollution jeopardizes multiple organs, such as the cardiovascular, respiratory, and central nervous systems. Skin is the largest organ and the first barrier that protects us from the outside world. Air pollutants such as particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs) will affect the structure and function of the skin and bring about the development of inflammatory skin diseases (atopic dermatitis (AD), psoriasis), skin accessory diseases (acne, alopecia), auto-immune skin diseases (cutaneous lupus erythematosus(CLE) scleroderma), and even skin tumors (melanoma, basal cell carcinoma (BCC), squamous-cell carcinoma (SCC)). Oxidative stress, skin barrier damage, microbiome dysbiosis, and skin inflammation are the pathogenesis of air pollution stimulation. In this review, we summarize the current evidence on the effects of air pollution on skin diseases and possible mechanisms to provide strategies for future research.

Mapping and annotating genomic loci to prioritize genes and implicate distinct polygenic adaptations for skin color

Evidence for adaptation of human skin color to regional ultraviolet radiation suggests shared and distinct genetic variants across populations. However, skin color evolution and genetics in East Asians are understudied. We quantified skin color in 48,433 East Asians using image analysis and identified associated genetic variants and potential causal genes for skin color as well as their polygenic interplay with sun exposure. This genome-wide association study (GWAS) identified 12 known and 11 previously unreported loci and SNP-based heritability was 23-24%. Potential causal genes were determined through the identification of nonsynonymous variants, colocalization with gene expression in skin tissues, and expression levels in melanocytes. Genomic loci associated with pigmentation in East Asians substantially diverged from European populations, and we detected signatures of polygenic adaptation. This large GWAS for objectively quantified skin color in an East Asian population improves understanding of the genetic architecture and polygenic adaptation of skin color and prioritizes potential causal genes.

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.

Investigating Distinct Skin Microbial Communities and Skin Metabolome Profiles in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder influenced by genetic predisposition, environmental factors, immune dysregulation, and skin barrier dysfunction. The skin microbiome and metabolome play crucial roles in modulating the skin's immune environment and integrity. However, their specific contributions to AD remain unclear. We aimed to investigate the distinct skin microbial communities and skin metabolic compounds in AD patients compared to healthy controls (HCs). Seven patients with AD patients and seven HCs were enrolled, from whom skin samples were obtained for examination. The study involved 16S rRNA metagenomic sequencing and bioinformatics analysis as well as the use of gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) to detect metabolites associated with AD in the skin. We observed significant differences in microbial diversity between lesional and non-lesional skin of AD patients and HCs. Staphylococcus overgrowth was prominent in AD lesions, while Cutibacterium levels were decreased. Metabolomic analysis revealed elevated levels of several metabolites, including hypoxanthine and glycerol-3-phosphate in AD lesions, indicating perturbations in purine metabolism and energy production pathways. Moreover, we found a positive correlation between hypoxanthine and glycerol-3-phosphate and clinical severity of AD and Staphylococcus overgrowth. These findings suggest potential biomarkers for monitoring AD severity. Further research is needed to elucidate the causal relationships between microbial dysbiosis, metabolic alterations, and AD progression, paving the way for targeted therapeutic interventions.

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.

Melatonin/Sericin Wound Healing Patches: Implications for Melanoma Therapy

Melatonin and sericin exhibit antioxidant properties and may be useful in topical wound healing patches by maintaining redox balance, cell integrity, and regulating the inflammatory response. In human skin, melatonin suppresses damage caused by ultraviolet radiation (UVR) which involves numerous mechanisms associated with reactive oxygen species/reactive nitrogen species (ROS/RNS) generation and enhancing apoptosis. Sericin is a protein mainly composed of glycine, serine, aspartic acid, and threonine amino acids removed from the silkworm cocoon (particularly Bombyx mori and other species). It is of interest because of its biodegradability, anti-oxidative, and anti-bacterial properties. Sericin inhibits tyrosinase activity and promotes cell proliferation that can be supportive and useful in melanoma treatment. In recent years, wound healing patches containing sericin and melatonin individually have attracted significant attention by the scientific community. In this review, we summarize the state of innovation of such patches during 2021-2023. To date, melatonin/sericin-polymer patches for application in post-operational wound healing treatment has been only sparingly investigated and it is an imperative to consider these materials as a promising approach targeting for skin tissue engineering or regenerative dermatology.

Research Progress in Skin Aging and Immunity

Skin aging is a complex process involving structural and functional changes and is characterized by a decrease in collagen content, reduced skin thickness, dryness, and the formation of wrinkles. This process is underpinned by multiple mechanisms including the free radical theory, inflammation theory, photoaging theory, and metabolic theory. The skin immune system, an indispensable part of the body's defense mechanism, comprises macrophages, lymphocytes, dendritic cells, and mast cells. These cells play a pivotal role in maintaining skin homeostasis and responding to injury or infection. As age advances, along with various internal and external environmental stimuli, skin immune cells may undergo senescence or accelerated aging, characterized by reduced cell division capability, increased mortality, changes in gene expression patterns and signaling pathways, and altered immune cell functions. These changes collectively impact the overall function of the immune system. This review summarizes the relationship between skin aging and immunity and explores the characteristics of skin aging, the composition and function of the skin immune system, the aging of immune cells, and the effects of these cells on immune function and skin aging. Immune dysfunction plays a significant role in skin aging, suggesting that immunoregulation may become one of the important strategies for the prevention and treatment of skin aging.

Multi-System-Level Analysis Reveals Differential Expression of Stress Response-Associated Genes in Inflammatory Solar Lentigo

Although the pathogenesis of solar lentigo (SL) involves chronic ultraviolet (UV) exposure, cellular senescence, and upregulated melanogenesis, underlying molecular-level mechanisms associated with SL remain unclear. The aim of this study was to investigate the gene regulatory mechanisms intimately linked to inflammation in SL. Skin samples from patients with SL with or without histological inflammatory features were obtained. RNA-seq data from the samples were analyzed via multiple analysis approaches, including exploration of core inflammatory gene alterations, identifying functional pathways at both transcription and protein levels, comparison of inflammatory module (gene clusters) activation levels, and analyzing correlations between modules. These analyses disclosed specific core genes implicated in oxidative stress, especially the upregulation of nuclear factor kappa B in the inflammatory SLs, while genes associated with protective mechanisms, such as SLC6A9, were highly expressed in the non-inflammatory SLs. For inflammatory modules, Extracellular Immunity and Mitochondrial Innate Immunity were exclusively upregulated in the inflammatory SL. Analysis of protein-protein interactions revealed the significance of CXCR3 upregulation in the pathogenesis of inflammatory SL. In conclusion, the upregulation of stress response-associated genes and inflammatory pathways in response to UV-induced oxidative stress implies their involvement in the pathogenesis of inflammatory SL.

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.

Transforming growth factor-β1 and soluble co-inhibitory immune checkpoints as putative drivers of immune suppression in patients with basal cell carcinoma

The current study compared the levels and possible associations between systemic soluble immune checkpoints (sICPs, n = 17) and a group of humoral modulators of immune suppressor cells (n = 7) in a cohort of patients with basal cell carcinoma (BCC, n = 40) and a group of healthy control subjects (n = 20). The seven humoral modulators of immunosuppressor cells were represented by the enzymes, arginase 1 and fibroblast activation protein (FAP), the chemokine, RANTES (CCL5) and the cytokines, interleukin-10 and transforming growth factor-β1 (TGF-β1), as well as the M2-type macrophage markers, soluble CD163 (sCD163) and sCD206. The plasma levels of six co-inhibitory sICPs, sCTLA-4, sLAG-3, sPD-1, sPD-L1, sTIM-3 and sPD-L2 were significantly elevated in the cohort of BCC patients (p<0.001-p<0.00001), while that of sBTLA was significantly decreased (p<0.006). Of the co-stimulatory sICPs, sCD27 and sGITR were significantly increased (p<0.0002 and p<0.0538) in the cohort of BCC patients, while the others were essentially comparable with those of the control participants; of the dual active sICPs, sHVEM was significantly elevated (p<0.00001) and TLR2 comparable with the control group. A correlation heat map revealed selective, strong associations of TGF-β1 with seven co-stimulatory (z = 0.618468-0.768131) and four co-inhibitory (z = 0.674040-0.808365) sICPs, as well as with sTLR2 (z = 0.696431). Notwithstanding the association of BCC with selective elevations in the levels of a large group of co-inhibitory sICPs, our novel findings also imply the probable involvement of TGF-β1 in driving immunosuppression in this malignancy, possibly via activation of regulatory T cells. Notably, these abnormalities were present in patients with either newly diagnosed or recurrent disease.

Unmet Needs in Psychodermatology: A Narrative Review

Psychodermatology, the multidisciplinary field that explores the intricate interplay between the mind and the skin, has gained increasing recognition over the past decade. However, several knowledge gaps and unmet needs persist in the field. The objective of this narrative review was to investigate the unmet needs in the field of psychodermatology as they pertain to medical training, treatment, research, and care access. PubMed was searched from inception through December 2023 to identify articles related to psychodermatology. Findings revealed several unmet needs within the field of psychodermatology. First, there is a need for further investigation into the pathophysiology that links psychological stress to cutaneous disease including the development of novel therapies targeting key neuropeptides. Second, the existing literature focuses primarily on the pharmacologic treatment of body dysmorphic disorder and body-focused repetitive behaviors, as well as delusional parasitosis, for which the first-line agents are selective serotonin reuptake inhibitors and atypical antipsychotics, respectively. However, additional research into the efficacy and safety of the remaining psychotropic medications and the treatment of other common psychocutaneous diseases is required. Finally, there exists a significant gap in knowledge amongst clinicians tasked with treating psychocutaneous diseases. Dermatologists report low rates of training in psychodermatology and discomfort with prescribing psychotropic medications. In conclusion, increasing resources for dermatologist education on psychotropic agent use, development of new drugs targeting stress-induced skin conditions, and research on the psychocutaneous applications of current medications may greatly improve the quality and access of psychodermatology care.