Role of lipids in the formation and maintenance of the cutaneous permeability barrier

Skin barrier: new therapeutic targets for chronic kidney disease-associated pruritus - a narrative review

The current incidence of chronic kidney disease-associated pruritus (CKD-aP) in patients with end-stage renal disease (ESRD) is approximately 70%, especially in those receiving dialysis, which negatively affects their work and private lives. The CKD-aP pathogenesis remains unclear, but uremic toxin accumulation, histamine release, and opioid imbalance have been suggested to lead to CKD-aP. Current therapeutic approaches, such as opioid receptor modulators, antihistamines, and ultraviolet B irradiation, are associated with some limitations and adverse effects. The skin barrier is the first defense in preventing external injury to the body. Patients with chronic kidney disease often experience itch due to the damaged skin barrier and reduced secretion of sweat and secretion from sebaceous glands. Surprisingly, skin barrier-repairing agents repair the skin barrier and inhibit the release of inflammatory cytokines, maintain skin immunity, and ameliorate the micro-inflammatory status of afferent nerve fibers. Here, we summarize the epidemiology, pathogenesis, and treatment status of CKD-aP and explore the possibility of skin barrier repair in CKD-aP treatment.

The Central Roles of Keratinocytes in Coordinating Skin Immunity

The function of keratinocytes (KCs) to form a barrier and produce cytokines is well-known, but recent progress has revealed many different roles for KCs in regulation of skin immunity. In this review, we provide an update on the current understanding of how KCs communicate with microbes, immunocytes, neurons, and other cells to form an effective immune barrier. We catalog the large list of genes and metabolites of KCs that participate in host defense and discuss the mechanisms of immune crosstalk, addressing how KCs simultaneously form a physical barrier, communicate with fibroblasts, and control immune signals. Overall, the signals sent and received by KCs are an exciting group of therapeutic targets to explore in the treatment of dermatologic disorders.

Lipid analysis of human primary dermal fibroblasts and epidermal keratinocytes after near-infrared exposure using mass spectrometry imaging

Photobiomodulation (PBM) therapy is the application of near-infrared (NIR) exposure to injuries or lesions to (among others) improve wound healing, reduce inflammation, and decreases acute and chronic pain. However, the understanding of the molecular mechanism of PBM, more specifically the effects of NIR on skin cells is still lacking behind. Lipids are essential components of cellular membranes that are integral to skin structure and function. This study aims to elucidate the impact of NIR exposure on the skin's lipidome by investigating the molecular effect of NIR exposure on single skin cells. Primary human dermal fibroblasts (NHDFa) and human epidermal keratinocytes (HEKa) were exposed to NIR (850 nm) with a dose of 6.5 J/cm2 for 5 consecutive days between 09.00 and 12.00 am. A workflow utilizing matrix-assisted laser desorption/ionization mass spectrometry imaging combined with liquid chromatography tandem mass spectrometry for lipidomics analysis was performed. This study provides evidence that adequate exposure of NIR influences lipid metabolism in NHDFa, whereas no alterations were found in HEKa. This work lays the groundwork in explaining the beneficial properties on both skin-related effects and systemic health benefits as seen in clinical studies.

Unveiling the Metabolomic Profile of Oily Sensitive Skin: A Non-Invasive Approach

Skin barrier impairment is becoming increasingly common due to changes in lifestyle and modern living environments. Oily sensitive skin (OSS) is a condition that is characterized by an impaired skin barrier. Thus, examining the differences between OSS and healthy skin will enable a more objective evaluation of the characteristics of OSS and facilitate investigations of potential treatments. Initially, a self-assessment questionnaire was used to identify patients with OSS. Biophysical measurements and LAST scores were used to determine whether skin barrier function was impaired. Epidermal biophysical properties, including skin hydration, transepidermal water loss (TEWL), sebum content, erythema index (EI), and a* value, were measured with noninvasive instruments. We subsequently devised a noninvasive D-square sampling technique to identify changes in the skin metabolome in conjunction with an untargeted metabolomics analysis with an Orbitrap Q ExactiveTM series mass spectrometer. In the stratum corneum of 47 subjects, 516 skin metabolites were identified. In subjects with OSS, there was an increase in the abundance of 15 metabolites and a decrease in the abundance of 48 metabolites. The participants with OSS were found to have the greatest disruptions in sphingolipid and amino acid metabolism. The results revealed that an impaired skin barrier is present in patients with OSS and offers a molecular target for screening for skin barrier damage.

Epidermal RORα Maintains Barrier Integrity and Prevents Allergic Inflammation by Regulating Late Differentiation and Lipid Metabolism

The skin epidermis provides a barrier that is imperative for preventing transepidermal water loss (TEWL) and protecting against environmental stimuli. The underlying molecular mechanisms for regulating barrier functions and sustaining its integrity remain unclear. RORα is a nuclear receptor highly expressed in the epidermis of normal skin. Clinical studies showed that the epidermal RORα expression is significantly reduced in the lesions of multiple inflammatory skin diseases. In this study, we investigate the central roles of RORα in stabilizing skin barrier function using mice with an epidermis-specific Rora gene deletion (RoraEKO). While lacking spontaneous skin lesions or dermatitis, RoraEKO mice exhibited an elevated TEWL rate and skin characteristics of barrier dysfunction. Immunostaining and Western blot analysis revealed low levels of cornified envelope proteins in the RoraEKO epidermis, suggesting disturbed late epidermal differentiation. In addition, an RNA-seq analysis showed the altered expression of genes related to "keratinization" and "lipid metabolism" in RORα deficient epidermis. A lipidomic analysis further uncovered an aberrant ceramide composition in the RoraEKO epidermis. Importantly, epidermal Rora ablation greatly exaggerated percutaneous allergic inflammatory responses to oxazolone in an allergic contact dermatitis (ACD) mouse model. Our results substantiate the essence of epidermal RORα in maintaining late keratinocyte differentiation and normal barrier function while suppressing cutaneous inflammation.

Lesional Psoriasis is Associated With Alterations in the Stratum Corneum Ceramide Profile and Concomitant Decreases in Barrier Function

Psoriasis is an inflammatory skin disease associated with an impaired skin barrier. The skin barrier function is dependent on the extracellular lipid matrix which surrounds the corneocytes in the stratum corneum. Ceramides comprise essential components of this matrix. Alterations in the stratum corneum ceramide profile have been directly linked to barrier dysfunction and might be an underlying factor of the barrier impairment in psoriasis. In this study, we investigated the ceramide profile and barrier function in psoriasis. Lesional and non-lesional skin of 26 patients and 10 healthy controls were analysed using in-depth ceramide lipidomics by liquid chromatography-mass spectrometry. Barrier function was assessed by measuring transepidermal water loss. Lesional skin showed a significant decrease in the abundance of total ceramides with significant alterations in the ceramide subclass composition compared to control and non-lesional skin. Additionally, the percentage of monounsaturated ceramides was significantly increased, and the average ceramide chain length significantly decreased in lesional skin. Altogether, this resulted in a markedly different profile compared to controls for lesional skin, but not for non-lesional skin. Importantly, the reduced barrier function in lesional psoriasis correlated to alterations in the ceramide profile, highlighting their interdependence. By assessing the parameters 2 weeks apart, we are able to highlight the reproducibility of these findings, which further affirms this connection. To conclude, we show that changes in the ceramide profile and barrier impairment are observed in, and limited to, lesional psoriatic skin. Their direct correlation provides a further mechanistic basis for the concomitantly observed impairment of barrier dysfunction.

The Caenorhabditis elegans cuticle and precuticle: a model for studying dynamic apical extracellular matrices in vivo

Apical extracellular matrices (aECMs) coat the exposed surfaces of animal bodies to shape tissues, influence social interactions, and protect against pathogens and other environmental challenges. In the nematode Caenorhabditis elegans, collagenous cuticle and zona pellucida protein-rich precuticle aECMs alternately coat external epithelia across the molt cycle and play many important roles in the worm's development, behavior, and physiology. Both these types of aECMs contain many matrix proteins related to those in vertebrates, as well as some that are nematode-specific. Extensive differences observed among tissues and life stages demonstrate that aECMs are a major feature of epithelial cell identity. In addition to forming discrete layers, some cuticle components assemble into complex substructures such as ridges, furrows, and nanoscale pillars. The epidermis and cuticle are mechanically linked, allowing the epidermis to sense cuticle damage and induce protective innate immune and stress responses. The C. elegans model, with its optical transparency, facilitates the study of aECM cell biology and structure/function relationships and all the myriad ways by which aECM can influence an organism.

Skin as the target for allergy prevention and treatment

The fact that genetic and environmental factors could trigger disruption of the epithelial barrier and subsequently initiate a TH2 inflammatory cascade conversely proposes that protecting the same barrier and promoting adequate interactions with other organs, such as the gut, may be crucial for lowering the risk and preventing atopic diseases, particularly, food allergies. In this review, we provide an overview of structural characteristics that support the epithelial barrier hypothesis in patients with atopic dermatitis, including the most relevant filaggrin gene mutations, the recent discovery of the role of the transient receptor potential vanilloid 1, and the role involvement of the microbiome in healthy and damaged skin. We present experimental and human studies that support the mechanisms of allergen penetration, particularly the dual allergen exposure and the outside-in, inside-out, and outside-inside-outside hypotheses. We discuss classic skin-targeted therapies for food allergy prevention, including moisturizers, steroids, and topical calcineurin inhibitors, along with pioneering trials proposed to change their current use (Prevention of Allergy via Cutaneous Intervention and Stopping Eczema and ALlergy). We provide an overview of the novel therapies that enhance the skin barrier, such as probiotics and prebiotics topical application, read-through drugs, direct and indirect FLG replacement, and interleukin and janus kinases inhibitors. Last, we discuss the newer strategies for preventing and treating food allergies in the form of epicutaneous immunotherapy and the experimental use of single-dose of adeno-associated virus vector gene immunotherapy.

Chondroitin/dermatan sulphate proteoglycan, desmosealin, showing affinity to desmosomes

Objective

Desmosomes are the most prominent interkeratinocyte junctions. The correct barrier function of stratified epithelia such as epidermis depends on their expression. During epidermal differentiation, the molecular composition of desmosomes evolves and so do their physical and chemical properties. Desquamation of corneocytes at the surface of the stratum corneum depends on an orderly degradation of desmosomes by endogenous enzymes. This process may be regulated by glycosylated molecules. We focused on the detection and characterization of potentially implicated players bearing ‘sugar’ characteristics.

Methods

Using an original monoclonal antibody and biochemical methods, we partially characterized a proteoglycan of the exclusively chondroitin/dermatan sulphate type, secreted into the interkeratinocyte spaces, that is incorporated into the extracellular parts of desmosomes in quantities proportional to the degree of cell differentiation, as visualized with immuno-electron microscopy.

Results

This antigen, that we named desmosealin, displays biochemical and immunocytochemical characteristics that clearly differentiate it from known desmosomal elements. Unlike so far described epidermal proteoglycans, which belong to the heparan sulphate family, desmosealin displays chondroitin/dermatan sulphate glycosaminoglycan chains. It can be detected within the extracellular ‘cores’ of desmosomes in the upper viable epidermal layers and in corneodesmosomes from the lowermost part of the stratum corneum.

Conclusion

Extensive integration of proteoglycans into the extracellular parts of desmosomes at the late stages of keratinocyte maturation is likely of functional importance. Given its biochemical profile, its pattern of expression in the epidermis and its desmosomal localization, desmosealin may emerge as a key element in the regulation of desmosome processing, epidermal cohesion and formation of a functional epidermal barrier.

Bioactive lipids in the skin barrier mediate its functionality in health and disease

Our skin protects us from external threats including ultraviolet radiation, pathogens and chemicals, and prevents excessive trans-epidermal water loss. These varied activities are reliant on a vast array of lipids, many of which are unique to skin, and that support physical, microbiological and immunological barriers. The cutaneous physical barrier is dependent on a specific lipid matrix that surrounds terminally-differentiated keratinocytes in the stratum corneum. Sebum- and keratinocyte-derived lipids cover the skin's surface and support and regulate the skin microbiota. Meanwhile, lipids signal between resident and infiltrating cutaneous immune cells, driving inflammation and its resolution in response to pathogens and other threats. Lipids of particular importance include ceramides, which are crucial for stratum corneum lipid matrix formation and therefore physical barrier functionality, fatty acids, which contribute to the acidic pH of the skin surface and regulate the microbiota, as well as the stratum corneum lipid matrix, and bioactive metabolites of these fatty acids, involved in cell signalling, inflammation, and numerous other cutaneous processes. These diverse and complex lipids maintain homeostasis in healthy skin, and are implicated in many cutaneous diseases, as well as unrelated systemic conditions with skin manifestations, and processes such as ageing. Lipids also contribute to the gut-skin axis, signalling between the two barrier sites. Therefore, skin lipids provide a valuable resource for exploration of healthy cutaneous processes, local and systemic disease development and progression, and accessible biomarker discovery for systemic disease, as well as an opportunity to fully understand the relationship between the host and the skin microbiota. Investigation of skin lipids could provide diagnostic and prognostic biomarkers, and help identify new targets for interventions. Development and improvement of existing in vitro and in silico approaches to explore the cutaneous lipidome, as well as advances in skin lipidomics technologies, will facilitate ongoing progress in skin lipid research.

Hair follicles modulate skin barrier function

Our skin provides a protective barrier that shields us from our environment. Barrier function is typically associated with the interfollicular epidermis; however, whether hair follicles influence this process remains unclear. Here, we utilize a potent genetic tool to probe barrier function by conditionally ablating a quintessential epidermal barrier gene, Abca12, which is mutated in the most severe skin barrier disease, harlequin ichthyosis. With this tool, we deduced 4 ways by which hair follicles modulate skin barrier function. First, the upper hair follicle (uHF) forms a functioning barrier. Second, barrier disruption in the uHF elicits non-cell-autonomous responses in the epidermis. Third, deleting Abca12 in the uHF impairs desquamation and blocks sebum release. Finally, barrier perturbation causes uHF cells to move into the epidermis. Neutralizing IL-17a, whose expression is enriched in the uHF, partially alleviated some disease phenotypes. Altogether, our findings implicate hair follicles as multi-faceted regulators of skin barrier function.

Efficacy and Safety of Oral Administration of Wine Lees Extract (WLE)-Derived Ceramides and Glucosylceramides in Enhancing Skin Barrier Function: A Randomized, Double-Blind, Placebo-Controlled Study

BACKGROUND

Our search for plant-derived ceramides from sustainable sources led to the discovery of ceramides and glucosylceramides in wine lees.

OBJECTIVE

This study evaluated the efficacy and safety of wine lees extract (WLE)-derived ceramides and glucosylceramides in enhancing skin barrier function.

METHODS

A randomized, double-blind, placebo-controlled study was conducted with 30 healthy Japanese subjects aged 20-64. Subjects were allocated to receive either the WLE-derived ceramides and glucosylceramides (test group) or placebo for 12 weeks. The primary outcome was transepidermal water loss (TEWL), and secondary outcomes included skin hydration, visual analog scale (VAS) of itching sensation, and the Japanese Skindex-29.

RESULTS

One participant withdrew for personal reasons, resulting in 29 subjects for data analysis (placebo n = 15; test n = 14). The test group showed a tendency of lower TEWL compared to the placebo after 8 weeks (p = 0.07). Furthermore, after 12 weeks of administration, the test group had significantly lower TEWL than the placebo (p = 0.04). On the other hand, no significant differences were observed in the secondary outcome parameters. No adverse events related to the supplements were reported.

CONCLUSIONS

Oral supplementation of WLE-derived ceramides and glucosylceramides is a prominent and safe approach to enhancing skin barrier function and health.

TRIAL REGISTRATION

(UMIN000050422).

Changes of Facial Lipidomics by Intense Pulsed Light Treatment Based on LC-MS

BACKGROUND

Intense pulsed light (IPL) has been widely used to improve cutaneous photoaging in recent years. Several studies began to explore the changes of skin barrier function after treatment, but the changes of skin surface lipids (SSL), especially specific lipid content and types are still unclear.

METHODS

A total of 25 female volunteers were included in our study, and each of them received three full-face treatments with one month apart. Before the first treatment and 1 month after the last treatment, we collected clinical photos and skin stratum corneum samples from individuals. A 5-level scale was used to evaluate the efficacy of IPL treatment, liquid chromatography-mass spectrometry (LC-MS), and Orthogonal Partial Least Squares Discrimination Analysis (OPLS-DA) were used to analyze the changes of SSL.

RESULTS

Two patients got no improvement after treatment, 6 patients had poor improvement and mild improvement was achieved in 9 patients, 5 and 3 patients reported moderate and significant improvement. The overall "effective" rate was 68 % and the "significant effective" rate was 32 %. The results showed 18 lipid subclasses and 487 lipid molecules were identified. The change of total lipid volume was not statistically significant (P = 0.088>0.05), but lipid subclass analysis showed the amount of Triglyceride (TG), Phosphatidic Acid (PA), Phosphatidylglycerol (PG) and Lysophosphatidylglycerol (LPG) were significantly increased (P < 0.05). There were 55 kinds of lipid molecules with significant difference after treatment (P < 0.05), and 51 of them belong to TG. The analysis of chain saturation of TG showed that the quantity of TG with 0, 1 and 2 unsaturated bonds increased significantly (P < 0.05).

CONCLUSIONS

IPL treatment does not have a significant effect on the overall amount of lipids while the amount of TG, PA, PG, LPG were significantly increased. These lipid changes may potentially improve the skin barrier function, but more high-quality and comprehensive studies are still needed.

BULLET POINT

Lipidomics analysis based on LC-MS; Changes of skin surface lipid after IPL treatment; the relationships between skin surface lipid and skin barrier functions.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Lipase-mediated detoxification of host-derived antimicrobial fatty acids by Staphylococcus aureus

Long-chain fatty acids with antimicrobial properties are abundant on the skin and mucosal surfaces, where they are essential to restrict the proliferation of opportunistic pathogens such as Staphylococcus aureus. These antimicrobial fatty acids (AFAs) elicit bacterial adaptation strategies, which have yet to be fully elucidated. Characterizing the pervasive mechanisms used by S. aureus to resist AFAs could open new avenues to prevent pathogen colonization. Here, we identify the S. aureus lipase Lip2 as a novel resistance factor against AFAs. Lip2 detoxifies AFAs via esterification with cholesterol. This is reminiscent of the activity of the fatty acid-modifying enzyme (FAME), whose identity has remained elusive for over three decades. In vitro, Lip2-dependent AFA-detoxification was apparent during planktonic growth and biofilm formation. Our genomic analysis revealed that prophage-mediated inactivation of Lip2 was rare in blood, nose, and skin strains, suggesting a particularly important role of Lip2 for host - microbe interactions. In a mouse model of S. aureus skin colonization, bacteria were protected from sapienic acid (a human-specific AFA) in a cholesterol- and lipase-dependent manner. These results suggest Lip2 is the long-sought FAME that exquisitely manipulates environmental lipids to promote bacterial growth in otherwise inhospitable niches.

High-throughput lipidomic profiles sampled with electroporation-based biopsy differentiate healthy skin, cutaneous squamous cell carcinoma, and basal cell carcinoma

BACKGROUND

The incidence rates of cutaneous squamous cell carcinoma (cSCC) and basal cell carcinoma (BCC) skin cancers are rising, while the current diagnostic process is time-consuming. We describe the development of a novel approach to high-throughput sampling of tissue lipids using electroporation-based biopsy, termed e-biopsy. We report on the ability of the e-biopsy technique to harvest large amounts of lipids from human skin samples.

MATERIALS AND METHODS

Here, 168 lipids were reliably identified from 12 patients providing a total of 13 samples. The extracted lipids were profiled with ultra-performance liquid chromatography and tandem mass spectrometry (UPLC-MS-MS) providing cSCC, BCC, and healthy skin lipidomic profiles.

RESULTS

Comparative analysis identified 27 differentially expressed lipids (p < 0.05). The general profile trend is low diglycerides in both cSCC and BCC, high phospholipids in BCC, and high lyso-phospholipids in cSCC compared to healthy skin tissue samples.

CONCLUSION

The results contribute to the growing body of knowledge that can potentially lead to novel insights into these skin cancers and demonstrate the potential of the e-biopsy technique for the analysis of lipidomic profiles of human skin tissues.

Skin Barrier in Atopic Dermatitis

A compromised permeability barrier is a hallmark of atopic dermatitis (AD). Localized to the outermost skin layer, the stratum corneum (SC) is critically dependent on terminal differentiation of epidermal keratinocytes, which transform into protein-rich corneocytes surrounded by extracellular lamellae of unique epidermal lipids, conferring permeability barrier function. These structures are disrupted in AD. A leaky barrier is prone to environmental insult, which in AD elicits type 2-dominant inflammation, in turn resulting in a vicious cycle further impairing the SC structure. Therapies directed at enforcing SC structure and anti-inflammatory strategies administered by topical and systemic route as well as UV therapy have differential effects on the permeability barrier. The expanding armamentarium of therapeutic modalities for AD treatment warrants optimization of their effects on permeability barrier function.

Hair follicles modulate skin barrier function

Our skin provides a protective barrier that shields us from our environment. Barrier function is typically associated with interfollicular epidermis; however, whether hair follicles influence this process remains unclear. Here, we utilize a potent genetic tool to probe barrier function by conditionally ablating a quintessential epidermal barrier gene, Abca12, which is mutated in the most severe skin barrier disease, harlequin ichthyosis. With this tool, we deduced 4 ways by which hair follicles modulate skin barrier function. First, the upper hair follicle (uHF) forms a functioning barrier. Second, barrier disruption in the uHF elicits non-cell autonomous responses in the epidermis. Third, deleting Abca12 in the uHF impairs desquamation and blocks sebum release. Finally, barrier perturbation causes uHF cells to move into the epidermis. Neutralizing Il17a, whose expression is enriched in the uHF, partially alleviated some disease phenotypes. Altogether, our findings implicate hair follicles as multi-faceted regulators of skin barrier function.

Exploring Skin Wound Healing Models and the Impact of Natural Lipids on the Healing Process

Cutaneous wound healing is a complex biological process involving a series of well-coordinated events aimed at restoring skin integrity and function. Various experimental models have been developed to study the mechanisms underlying skin wound repair and to evaluate potential therapeutic interventions. This review explores the diverse array of skin wound healing models utilized in research, ranging from rodent excisional wounds to advanced tissue engineering constructs and microfluidic platforms. More importantly, the influence of lipids on the wound healing process is examined, emphasizing their role in enhancing barrier function restoration, modulating inflammation, promoting cell proliferation, and promoting remodeling. Lipids, such as phospholipids, sphingolipids, and ceramides, play crucial roles in membrane structure, cell signaling, and tissue repair. Understanding the interplay between lipids and the wound microenvironment provides valuable insights into the development of novel therapeutic strategies for promoting efficient wound healing and tissue regeneration. This review highlights the significance of investigating skin wound healing models and elucidating the intricate involvement of lipids in the healing process, offering potential avenues for improving clinical outcomes in wound management.

Facile Fabrication of Sandalwood Oil-Based Nanoemulsion to Intensify the Fatty Acid Composition in Burned and Rough Skin

The restoration process of burned and rough skin takes a long time and remains a critical challenge. It can be repaired through a combination of proper care, hydration, and topical therapies. In this study, a novel nanoemulsion was synthesized through the high-energy ultrasonication method. A total of five nanoemulsions (NE1-5) were prepared with varying concentrations of sandalwood oil, a nonionic surfactant (polysorbate 80), and water. Among them, NE3 had a number of appropriate physicochemical characteristics, such as physiological pH (5.58 ± 0.09), refractive index (∼1.34), electrical conductivity (115 ± 0.23 mS cm-1), and transmittance (∼96.5%), which were suitable for skin care applications. The NE3 had a strong surface potential of -18.5 ± 0.15 mV and a hydrodynamic size of 61.99 ± 0.22 nm with a polydispersity index of 0.204. The structural integrity and a distinct droplet size range between 50 and 100 nm were confirmed by transmission electron microscopic analysis. The skin regeneration and restoration abilities of synthesized nanoemulsions were examined by conducting an in vivo study on Sprague-Dawley rats. Exposure to NE3 significantly increased the healing process in burned skin as compared to untreated control and nonemulsified sandalwood oil. In another set of experiments, the NE3-treated rough skin became softer, smoother, and less scaly than all other treatments. Enhanced fatty acids, i.e., palmitic acid, stearic acid, and cholesterol, were recorded in NE3-supplemented burned and rough skin compared to the untreated control. The NE3 had outstanding compatibility with key components of skincare products without any stability issues. Its biocompatibility with the cellular system was established by the negligible generation of reactive oxygen species (ROS) and a lack of genotoxicity. Considering these results, NE3 can be used in cosmetic products such as creams, lotions, and serums, allowing industries to achieve improved product formulations and provide better healthcare benefits to humanity.

Bacterial Skin and Soft Tissue Infections in Older Adults

This article focuses on bacterial infections that commonly affect geriatric patients. The elderly population is at a higher risk of contracting bacterial infections due to weakened immune systems and comorbidities. The article explores the cause, pathogenesis, clinical manifestations, and treatment options of these infections. Additionally, antibiotic resistance is a growing concern in the treatment of bacterial infections. The article highlights the importance of preventing these infections through proper hygiene and wound care. This article aims to provide an understanding of bacterial infections in geriatric patients and inform health-care providers on the most effective ways to manage and prevent these infections.

Combining protection with skin health: In vivo studies of an innovative gelatin/tannic acid-based hydrogel patch to prevent PPE-related skin lesions

The prolonged use of Personal Protective Equipment (PPE) can lead to skin problems due to persistent pressure, friction, and tension. This issue has prompted the exploration of solutions to protect the skin while maintaining the effectiveness of the PPE. This study aimed to evaluate the in vivo effectiveness of a gelatin/tannic acid-based hydrogel patch positioned beneath a mask to alleviate skin damage resulting from mask-wearing. To understand the pressure exerted by PPE, in vitro tests were conducted to measure the tensile strength of three types of facial masks. The FFP2 masks exhibited the highest tensile strength and were selected for subsequent in vivo biometric investigations. Biometric parameters were evaluated using the Flir E50bx® thermographic camera, Corneometer®, MoistureMap®, Sebumeter®, Tewameter®, and VISIA® systems. The results showed that when the hydrogel patch was used under the mask, there were no significant differences in facial skin temperature, sebum levels, or TEWL values (p > 0.05). However, a statistically significant increase in skin hydration and a decrease in frontal redness (p < 0.05) were observed. Consumer acceptance was assessed through sensory analysis questionnaires. In summary, the observed attenuation of physiological changes in the facial area and the positive consumer feedback suggest that this polymeric film-forming system is a simple yet effective solution to prevent PPE use-related skin issues.

Benefits of topical natural ingredients in epidermal permeability barrier

Because of the crucial role of epidermal permeability barrier in regulation of cutaneous and extracutaneous functions, great efforts have been made to identify and develop the regimens that can improve epidermal permeability barrier function. Studies have demonstrated that oral administration of natural ingredients can improve epidermal permeability barrier in various skin conditions, including inflammatory dermatoses and UV-irradiation. Moreover, topical applications of some natural ingredients can also accelerate the repair of epidermal permeability barrier after acute barrier disruption and lower transepidermal water loss in the intact skin. Natural ingredient-induced improvements in epidermal permeability barrier function can be attributable to upregulation of keratinocyte differentiation, lipid production, antioxidant, hyaluronic acid production, expression of aquaporin 3 and sodium-hydrogen exchanger 1. In this review, we summarize the benefits of topical natural ingredients in epidermal permeability barrier in normal skin with or without acute barrier disruption and the underlying mechanisms.

Comparison of skin barrier abnormalities and epidermal ceramide profiles among three ω-O-acylceramide synthesis-deficient mouse strains

BACKGROUND

The epidermis contains many structurally diverse ceramides, which form the skin permeability barrier (skin barrier). Mutations in genes involved in the synthesis of ω-O-acylceramides (acylceramides) and protein-bound ceramides cause ichthyosis.

OBJECTIVE

We aimed to elucidate the relationship between the degree of skin barrier impairment and changes in epidermal ceramide profiles caused by mutations in acylceramide synthesis genes.

METHODS

Knockout (KO) mice of three genes-fatty acid (FA) ω-hydroxylase Cyp4f39 (human CYP4F22 ortholog), FA elongase Elovl1, and acyl-CoA synthetase Fatp4-were subjected to transepidermal water loss measurement, toluidine blue staining, and epidermal ceramide profiling via liquid chromatography coupled with tandem mass spectrometry.

RESULTS

Transepidermal water loss was highest in Cyp4f39 KO mice, followed by Elovl1 KO and Fatp4 KO mice, and Cyp4f39 KO mice also showed the strongest degree of toluidine blue staining. In Cyp4f39 KO, Elovl1 KO, and Fatp4 KO mice, acylceramide levels were 0.6%, 1.6%, and 12%, respectively, of those in wild-type mice. Protein-bound ceramide levels were 0.2%, 30%, and 33%, respectively, of those in wild-type mice. We also observed a near-complete absence of ω-hydroxy ceramides in Cyp4f39 KO mice, reduced total ceramide levels and shortened FA moieties in Elovl1 KO mice, and increased hydroxylated ceramide levels and slightly shortened FA moieties in Fatp4 KO mice.

CONCLUSIONS

The degree of reduction in protein-bound ceramide levels is probably related to the severity of skin barrier defects in these three strains. However, reduced acylceramide levels and other changes in ceramide composition unique to each KO strain are also involved.

Cytokines and Epidermal Lipid Abnormalities in Atopic Dermatitis: A Systematic Review

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease and presents a major public health problem worldwide. It is characterized by a recurrent and/or chronic course of inflammatory skin lesions with intense pruritus. Its pathophysiologic features include barrier dysfunction, aberrant immune cell infiltration, and alterations in the microbiome that are associated with genetic and environmental factors. There is a complex crosstalk between these components, which is primarily mediated by cytokines. Epidermal barrier dysfunction is the hallmark of AD and is caused by the disruption of proteins and lipids responsible for establishing the skin barrier. To better define the role of cytokines in stratum corneum lipid abnormalities related to AD, we conducted a systematic review of biomedical literature in PubMed from its inception to 5 September 2023. Consistent with the dominant TH2 skewness seen in AD, type 2 cytokines were featured prominently as possessing a central role in epidermal lipid alterations in AD skin. The cytokines associated with TH1 and TH17 were also identified to affect barrier lipids. Considering the broad cytokine dysregulation observed in AD pathophysiology, understanding the role of each of these in lipid abnormalities and barrier dysfunction will help in developing therapeutics to best achieve barrier homeostasis in AD patients.

Molecular Organization of the Skin Barrier

Cryo-electron microscopy of vitreous sections allows for investigation directly in situ of the molecular architecture of skin. Recently, this technique has contributed to the elucidation of the molecular organization of the skin's permeability barrier and its stepwise formation process. The aim of this review is to provide an overview of the procedure for cryo-electron microscopy of vitreous sections, its analysis using atomic detail molecular dynamics modelling and electron microscopy simulation, and its application in the investigation of the barrier structure and formation process of the skin.

Characterization of Epidermal Function in Individuals with Primary Cutaneous Amyloidosis

Purpose

To compare epidermal biophysical properties, indicators of epidermal function, in individuals with and without primary cutaneous amyloidosis (PCA).

Patients and Methods

This study incorporated 189 patients with PCA and 166 healthy individuals. The GPSkin Barrier was employed to measure transepidermal water loss (TEWL) rates and hydration levels of the stratum corneum. The Sebumeter and the Skin pH Meter were utilized to determine the skin surface's sebum content and pH, respectively. The severity of pruritus in participants was evaluated using the visual analog scale (VAS).

Results

Compared to the control group without PCA, individuals with PCA displayed a notable increase in skin surface pH and TEWL and a decrease in the hydration levels of the stratum corneum (p<0.0001 for all parameters). Additionally, the sebum content was markedly lower in those with PCA than in the controls (p<0.0001). Of particular note, both TEWL and skin surface pH at the lesion sites on the back and the shin were more elevated in lichenoid amyloidosis (LA) and in macular amyloidosis (MA), whereas hydration levels of the stratum corneum and sebum levels were diminished in LA compared to MA (p<0.05). In conclusion, both hydration levels of the stratum corneum and sebum content exhibited an inverse relationship with pruritus severity, whereas TEWL and skin surface pH demonstrated a positive correlation with pruritus intensity.

Conclusion

The function of the epidermis is compromised in individuals diagnosed with PCA. However, the mechanisms underlying these changes await further investigation.

Plant Extracts as Skin Care and Therapeutic Agents

Natural ingredients have been used for centuries for skin treatment and care. Interest in the health effects of plants has recently increased due to their safety and applicability in the formulation of pharmaceuticals and cosmetics. Long-known plant materials as well as newly discovered ones are increasingly being used in natural products of plant origin. This review highlights the beneficial effects of plants and plant constituents on the skin, including moisturizing (e.g., Cannabis sativa, Hydrangea serrata, Pradosia mutisii and Carthamus tinctorius), anti-aging (e.g., Aegopodium podagraria, Euphorbia characias, Premna odorata and Warburgia salutaris), antimicrobial (e.g., Betula pendula and Epilobium angustifolium), antioxidant (e.g., Kadsura coccinea, Rosmarinus officinalis, Rubus idaeus and Spatholobus suberectus), anti-inflammatory (e.g., Antidesma thwaitesianum, Helianthus annuus, Oenanthe javanica, Penthorum chinense, Ranunculus bulumei and Zanthoxylum bungeanum), regenerative (e.g., Aloe vera, Angelica polymorpha, Digitaria ciliaris, Glycyrrihza glabra and Marantodes pumilum), wound healing (e.g., Agrimonia eupatoria, Astragalus floccosus, Bursera morelensis, Jatropha neopauciflora and Sapindus mukorossi), photoprotective (e.g., Astragalus gombiformis, Calea fruticose, Euphorbia characias and Posoqueria latifolia) and anti-tyrosinase activity (e.g., Aerva lanata, Bruguiera gymnorhiza, Dodonaea viscosa, Lonicera japonica and Schisandra chinensis), as well as their role as excipients in cosmetics (coloring (e.g., Beta vulgaris, Centaurea cyanus, Hibiscus sabdariffa and Rubia tinctiorum), protective and aromatic agents (e.g., Hyssopus officinalis, Melaleuca alternifolia, Pelargonium graveolens and Verbena officinalis)).

The in vitro effects of black soldier fly larvae (Hermitia illucens) oil as a high-functional active ingredient for inhibiting hyaluronidase, anti-oxidation benefits, whitening, and UVB protection

Objective: Larvae of Hermitia illucens, or black soldier fly larvae (BSFL), have been recognized for their high lipid yield with a remarkable fatty acid profile. BSFL oil (SFO) offers the added value of a low environmental footprint and a sustainable product. In this study, the characteristics and cosmetic-related activities of SFO were investigated and compared with rice bran oil, olive oil and krill oil which are commonly used in cosmetics and supplements. Methods: The physicochemical characteristics were determined including acid value, saponification value, unsaponifiable matter and water content of SFO. The fatty acid composition was determined using GC-MS equipped with TR-FAME. The in vitro antioxidant properties were determined using DPPH, FRAP and lipid peroxidation inhibition assays. Antihyaluronidase (anti-HAase) activity was measured by detecting enzyme activity and molecular docking of candidate compounds toward the HAase enzyme. The safety assessment towards normal human cells was determined using the MTT assay and the UVB protection upon UVB-irradiated fibroblasts was determined using the DCF-DA assay. The whitening effect of SFO was determined using melanin content inhibition. Results: SFO contains more than 60% polyunsaturated fatty acids followed by saturated fatty acids (up to 37%). The most abundant component found in SFO was linoleic acid (C18:2 n-6 cis). Multiple anti-oxidant mechanisms of SFO were discovered. In addition, SFO and krill oil prevented hyaluronic acid (HA) degradation via strong HAase inhibition comparable with the positive control, oleanolic acid. The molecular docking confirmed the binding interactions and molecular recognition of major free fatty acids toward HAase. Furthermore, SFO exhibited no cytotoxicity on primary human skin fibroblasts, HaCaT keratinocytes and PBMCs (IC50 values > 200 μg/mL). SFO possessed significant in-situ anti-oxidant activity in UVB-irradiated fibroblasts and the melanin inhibition activity as effective as well-known anti-pigmenting compounds (kojic acid and arbutin, p < 0.05). Conclusion: This study provides scientific support for various aspects of SFO. SFO can be considered an alternative oil ingredient in cosmetic products with potential implications for anti-skin aging, whitening and UVB protection properties, making it a potential candidate oil in the cosmetic industry.

Association of Epidermal Biophysical Properties with Obesity and Its Implications

BACKGROUND

Obesity is a condition defined by an excess amount of body fat, with body mass index (BMI) of 30 and higher. It is associated with a number of other medical conditions, including insulin resistance, diabetes mellitus, and cardiovascular diseases, as well as dyslipidemia, and it is also associated with several cutaneous disorders such as atopic dermatitis, psoriasis, intertriginous dermatitis, acanthosis nigricans and skin infections.

SUMMARY

Evidence suggests a link between obesity and epidermal dysfunction. Generally, individuals with obesity display higher transepidermal water loss rate and lower stratum corneum hydration levels, although no association of obesity with epidermal dysfunction has been documented. Results of skin surface pH are controversial. But study demonstrated a positive correlation of BMI with skin surface pH on both the forearm and the shin in males, suggesting that the changes in epidermal function vary with gender in individuals with obesity.

KEY MESSAGES

This review summarizes the association between obesity and epidermal function, and discusses possible underlying mechanisms. Individuals with obesity exhibit poor epidermal permeability barrier and lower stratum corneum hydration levels. Because of the pathogenic role of compromised epidermal function in inflammation, which is also linked to obesity, improvement in epidermal function could benefit individuals with obesity, particularly those with abnormalities in epidermal function.

A systematic review of natural products for skin applications: Targeting inflammation, wound healing, and photo-aging

BACKGROUND

Every day the skin is constantly exposed to several harmful factors that induce oxidative stress. When the cells are incapable to maintain the balance between antioxidant defenses and reactive oxygen species, the skin no longer can keep its integrity and homeostasis. Chronic inflammation, premature skin aging, tissue damage, and immunosuppression are possible consequences induced by sustained exposure to environmental and endogenous reactive oxygen species. Skin immune and non-immune cells together with the microbiome are essential to efficiently trigger skin immune responses to stress. For this reason, an ever-increasing demand for novel molecules capable of modulating immune functions in the skin has risen the level of their development, particularly in the field of natural product-derived molecules.

PURPOSE

In this review, we explore different classes of molecules that showed evidence in modulate skin immune responses, as well as their target receptors and signaling pathways. Moreover, we describe the role of polyphenols, polysaccharides, fatty acids, peptides, and probiotics as possible treatments for skin conditions, including wound healing, infection, inflammation, allergies, and premature skin aging.

METHODS

Literature was searched, analyzed, and collected using databases, including PubMed, Science Direct, and Google Scholar. The search terms used included "Skin", "wound healing", "natural products", "skin microbiome", "immunomodulation", "anti-inflammatory", "antioxidant", "infection", "UV radiation", "polyphenols", "polysaccharides", "fatty acids", "plant oils", "peptides", "antimicrobial peptides", "probiotics", "atopic dermatitis", "psoriasis", "auto-immunity", "dry skin", "aging", etc., and several combinations of these keywords.

RESULTS

Natural products offer different solutions as possible treatments for several skin conditions. Significant antioxidant and anti-inflammatory activities were reported, followed by the ability to modulate immune functions in the skin. Several membrane-bound immune receptors in the skin recognize diverse types of natural-derived molecules, promoting different immune responses that can improve skin conditions.

CONCLUSION

Despite the increasing progress in drug discovery, several limiting factors need future clarification. Understanding the safety, biological activities, and precise mechanisms of action is a priority as well as the characterization of the active compounds responsible for that. This review provides directions for future studies in the development of new molecules with important pharmaceutical and cosmeceutical value.

Alterations of Autophagy Modify Lipids in Epidermal Keratinocytes

Background

The skin barrier is the first line of defense of the body, while skin lipids play an important role in the skin permeability barrier. Lamellar bodies are also involved in maintaining the stability of the skin permeability barrier. However, the exact origin of lamellar bodies remains unclear. Recent studies have suggested that autophagy may participate in the formation of lamellar bodies.

Aim

This study aimed to investigate the role of autophagy in the formation of lamellar bodies in keratinocytes and the regulation of keratinocyte lipids.

Methods

Keratinocytes were incubated with autophagy inducer Rapamycin and autophagy inhibitor Bafilomycin A1. The changes in autophagy flux were detected by Western blot, and the formation of lamellar bodies was observed by transmission electron microscopy. Furthermore, the changes in keratinocytes lipidomics were detected by liquid chromatography-mass spectrometry.

Results

Our research showed that the autophagy inducer promoted autophagy activation and formation of lamellar bodies in keratinocytes, while the inhibitor inhibited autophagy signals and the formation of lamellar bodies in keratinocytes. In addition, the lipidomics results revealed a significant change in glycerophospholipids after autophagy induction and autophagy inhibition.

Conclusion

These results demonstrate that autophagy may play an essential role in skin lipids via glycerophospholipids pathway.

Deletion of NRF2 disturbs composition, morphology, and differentiation of the murine tail epidermis in chronological aging

NRF2 is a master regulator of the cellular protection against oxidative damage in mammals and of multiple pathways relevant in the mammalian aging process. In the epidermis of the skin NRF2 contributes additionally to the formation of an antioxidant barrier to protect from environmental insults and is involved in the differentiation process of keratinocytes. In chronological aging of skin, the capacity for antioxidant responses and the ability to restore homeostasis after damage are impaired. Surprisingly, in absence of extrinsic stressors, NRF2 deficient mice do not show any obvious skin phenotype, not even at old age. We investigated the differences in chronological epidermal aging of wild type and NRF2-deficient mice to identify the changes in aged epidermis that may compensate for absence of this important transcriptional regulator. While both genotypes showed elevated epidermal senescence markers (increased Lysophospholipids, decreased LaminB1 expression), the aged NRF2 deficient mice displayed disturbed epidermal differentiation manifested in irregular keratin 10 and loricrin expression. The tail skin displayed less age-related epidermal thinning and a less pronounced decline in proliferating basal epidermal cells compared to the wildtype controls. The stratum corneum lipid composition also differed, as we observed elevated production of barrier protective linoleic acid (C18:2) and reduced abundance of longer chain saturated lignoceric acid (C24:0) among the stratum corneum fatty acids in the aged NRF2-deficient mice. Thus, despite epidermal differentiation being disturbed in aged NRF2-deficient animals in homeostasis, adaptations in keratinocyte proliferation and barrier lipid synthesis could explain the lack of a more severe phenotype.

ZFP750 affects the cutaneous barrier through regulating lipid metabolism

An essential function of the epidermis is to provide a physical barrier that prevents the loss of water. Essential mediators of this barrier function include ceramides, cholesterol, and very long chain fatty acids, and their alteration causes human pathologies, including psoriasis and atopic dermatitis. A frameshift mutation in the human ZNF750 gene, which encodes a zinc finger transcription factor, has been shown to cause a seborrhea-like dermatitis. Here, we show that genetic deletion of the mouse homolog ZFP750 results in loss of epidermal barrier function, which is associated with a substantial reduction of ceramides, nonpolar lipids. The alteration of epidermal lipid homeostasis is directly linked to the transcriptional activity of ZFP750. ZFP750 directly and/or indirectly regulates the expression of crucial enzymes primarily involved in the biosynthesis of ceramides. Overall, our study identifies the transcription factor ZFP750 as a master regulator epidermal homeostasis through lipid biosynthesis and thus contributing to our understanding of the pathogenesis of several human skin diseases.

Investigation of β-caryophyllene as terpene penetration enhancer: Role of stratum corneum retention

Terpenes are usually used as penetration enhancers (PE) for transdermal drug delivery (TDD) of various molecules. However, TDD of hydrophilic macromolecules is becoming an urgent challenge due to their potent activities. The aim of this study was to investigate the potential application of β-caryophyllene (β-CP), a sequiterpene, as PE for TDD of hydrophilic macromolecules for the first time. Commonly used PEs, namely azone and 1,8-cineole (1,8-CN), were applied as controls. Transepidermal water loss (TEWL) analysis revealed that the reduction of skin barrier function caused by β-CP was reversible. Transdermal experiments showed that when skin was treated with β-CP or azone, there was a significant permeation-enhancing effect on fluorescein isothiocyanate (FITC) and FITC-dextran with different molecular weight (MW) of 4k or 10k. CLSM analysis confirmed that β-CP and azone can facilitate the penetration of FD-4k through epidermis and dermis. However, the cytotoxicity of azone against epidermal keratinocytes was significantly higher than β-CP and 1,8-CN. Additionally, application of β-CP and 1,8-CN didn't increase erythema index (EI) but the EI values of azone group increased significantly and irreversibly, indicating the high biocompatibility of the natural terpenes. β-CP had better permeation-enhancing effect and higher stratum corneum (SC) retention than 1,8-CN due to its increased carbon chain length and lipophilicity, as further demonstrated by molecular dynamics (MD) simulation studies. Skin electrical resistance (SER) and attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR) studies revealed a significant interfering effect of β-CP on SC lipids. Taken together, β-CP exhibited significant penetration enhancement of hydrophilic macromolecules due to its SC retention and SC lipid fluidization ability.

Quantification methods comparing in vitro and in vivo percutaneous permeation by microneedles and passive diffusion

Microneedles (MNs) are needles with a tip diameter ranging from 10 to 100 um and a length ranging up to 1 mm. The first patent for drug delivery device for percutaneous administration filed by Alza corporation dates back to 1976 (Gerstel and Place, 1976), and in between 1989 and 2021 the filed patents for MNs are more than 4500 (Banks et al., 2010). These devices can potential overcome some drawbacks of traditional needles, such as the pain generated during insertion, requirement for trained personnel to manipulate syringes, and difficulty of performing injections in elderly and obese patients. MNs and MNs arrays are emerging as a convenient method to deliver compounds and extract blood without causing any pain. A promising application is the use of MNs as alternative solution to topical creams (TC) and transdermal patches (TP) for transdermal drug delivery. The external layer of human skin, the epidermis, offers a major barrier to transdermal drug delivery, thanks to the stratum corneum (SC). Exposed to the external environment, SC ultimately protects the human body from UV light radiation, heat, water loss, bacteria, fungi and viruses, and it is the barrier that controls diffusion rate for almost all compounds. TC and TP applications are limited by the skin permeability to lipophilic compounds and small molecules, and by the slow delivery rate of some compounds. MNs have been around for more than 35 year now, and it is a general opinion that MN increase delivery compared to passive diffusion, thanks to the feature of penetrating the SC and reaching the dermis. This review recollects the existing studies that compare MNs delivery of drugs with passive diffusion of the same drugs in alive organisms, giving an overview of what are the type of MNs, the chemical delivered and the methods employed to quantify drug delivery into skin and/or in the bloodstream. The final aim is to quantify the enhancement factor of MNs with respect to passive diffusion, and establish a possible standard on how tests can be performed in order to compare different data.

In Silico Prediction of Stratum Corneum Partition Coefficients via COSMOmic and Molecular Dynamics Simulations

Stratum corneum (SC) is the main barrier of human skin where the inter-corneocytes lipids provide the main pathway for transdermal permeation of functional actives of skin care and health. Molecular dynamics (MD) has been increasingly used to simulate the SC lipid bilayer structure so that the barrier property and its affecting factors can be elucidated. Among reported MD simulation studies, solute partition in the SC lipids, an important parameter affecting SC permeability, has received limited attention. In this work, we combine MD simulation with COSMOmic to predict the partition coefficients of dermatologically relevant solutes in SC lipid bilayer. Firstly, we run MD simulations to obtain equilibrated SC lipid bilayers with different lipid types, compositions, and structures. Then, the simulated SC lipid bilayer structures are fed to COSMOmic to calculate the partition coefficients of the solutes. The results show that lipid types and bilayer geometries play a minor role in the predicted partition coefficients. For the more lipophilic solutes, the predicted results of solute partition in SC lipid bilayers agree well with reported experimental values of solute partition in extracted SC lipids. For the more hydrophilic molecules, there is a systematical underprediction. Nevertheless, the MD/COSMOmic approach correctly reproduces the phenomenological correlation between the SC lipid/water partition coefficients and the octanol/water partition coefficients. Overall, the results show that the MD/COSMOmic approach is a fast and valid method for predicting solute partitioning into SC lipids and hence supporting the assessment of percutaneous absorption of skin care ingredients, dermatological drugs as well as environmental pollutants.

Role of Omega-Hydroxy Ceramides in Epidermis: Biosynthesis, Barrier Integrity and Analyzing Method

Attached to the outer surface of the corneocyte lipid envelope (CLE), omega-hydroxy ceramides (ω-OH-Cer) link to involucrin and function as lipid components of the stratum corneum (SC). The integrity of the skin barrier is highly dependent on the lipid components of SC, especially on ω-OH-Cer. Synthetic ω-OH-Cer supplementation has been utilized in clinical practice for epidermal barrier injury and related surgeries. However, the mechanism discussion and analyzing methods are not keeping pace with its clinical application. Though mass spectrometry (MS) is the primary choice for biomolecular analysis, method modifications for ω-OH-Cer identification are lacking in progress. Therefore, finding conclusions on ω-OH-Cer biological function, as well as on its identification, means it is vital to remind further researchers of how the following work should be done. This review summarizes the important role of ω-OH-Cer in epidermal barrier functions and the forming mechanism of ω-OH-Cer. Recent identification methods for ω-OH-Cer are also discussed, which could provide new inspirations for study on both ω-OH-Cer and skin care development.

Pseudomonas Aeruginosa Theft Biofilm Require Host Lipids of Cutaneous Wound

OBJECTIVE

This work addressing complexities in wound infection, seeks to test the reliance of bacterial pathogen Pseudomonas aeruginosa (PA) on host skin lipids to form biofilm with pathological consequences.

BACKGROUND

PA biofilm causes wound chronicity. Both CDC as well as NIH recognizes biofilm infection as a threat leading to wound chronicity. Chronic wounds on lower extremities often lead to surgical limb amputation.

METHODS

An established preclinical porcine chronic wound biofilm model, infected with PA or Pseudomonas aeruginosa ceramidase mutant (PA ∆Cer ), was used.

RESULTS

We observed that bacteria drew resource from host lipids to induce PA ceramidase expression by three orders of magnitude. PA utilized product of host ceramide catabolism to augment transcription of PA ceramidase. Biofilm formation was more robust in PA compared to PA ∆Cer . Downstream products of such metabolism such as sphingosine and sphingosine-1-phosphate were both directly implicated in the induction of ceramidase and inhibition of peroxisome proliferator-activated receptor (PPAR)δ, respectively. PA biofilm, in a ceram-idastin-sensitive manner, also silenced PPARδ via induction of miR-106b. Low PPARδ limited ABCA12 expression resulting in disruption of skin lipid homeostasis. Barrier function of the wound-site was thus compromised.

CONCLUSIONS

This work demonstrates that microbial pathogens must co-opt host skin lipids to unleash biofilm pathogenicity. Anti-biofilm strategies must not necessarily always target the microbe and targeting host lipids at risk of infection could be productive. This work may be viewed as a first step, laying fundamental mechanistic groundwork, toward a paradigm change in biofilm management.

The epidermal lipid barrier in microbiome-skin interaction

The corneocyte layers forming the upper surface of mammalian skin are embedded in a lamellar-membrane matrix which repels harmful molecules while retaining solutes from subcutaneous tissues. Only certain bacterial and fungal taxa colonize skin surfaces. They have ways to use epidermal lipids as nutrients while resisting antimicrobial fatty acids. Skin microorganisms release lipophilic microbe-associated molecular pattern (MAMP) molecules which are largely retained by the epidermal lipid barrier. Skin barrier defects, as in atopic dermatitis, impair lamellar-membrane integrity, resulting in altered skin microbiomes, which then include the pathogen Staphylococcus aureus. The resulting increased penetration of MAMPs and toxins promotes skin inflammation. Elucidating how microorganisms manipulate the epidermal lipid barrier will be key for better ways of preventing inflammatory skin disorders.

Protective effect of Saussurea involucrata polysaccharide against skin dryness induced by ultraviolet radiation

Background: Exposure to ultraviolet B (UVB) radiation can damage the epidermis barrier function and eventually result in skin dryness. At present, little work is being devoted to skin dryness. Searching for active ingredients that can protect the skin against UVB-induced dryness will have scientific significance. Methods: Saussurea involucrata polysaccharide (SIP) has been shown to have significant antioxidant and anti-photodamage effects on the skin following UVB irradiation. To evaluate the effect of SIP on UVB-induced skin dryness ex vivo, SIP-containing hydrogel was applied in a mouse model following exposure to UVB and the levels of histopathological changes, DNA damage, inflammation, keratinocyte differentiation, lipid content were then evaluated. The underlying mechanisms of SIP to protect the cells against UVB induced-dryness were determined in HaCaT cells. Results: SIP was found to lower UVB-induced oxidative stress and DNA damage while increasing keratinocyte differentiation and lipid production. Western blot analysis of UVB-irradiated skin tissue revealed a significant increase in peroxisome proliferator-activated receptor-α (PPAR-α) levels, indicating that the underlying mechanism may be related to PPAR-α signaling pathway activation. Conclusions: By activating the PPAR-α pathway, SIP could alleviate UVB-induced oxidative stress and inhibit the inflammatory response, regulate proliferation and differentiation of keratinocytes, and mitigate lipid synthesis disorder. These findings could provide candidate active ingredients with relatively clear mechanistic actions for the development of skin sunscreen moisturizers.

Skin Ageing: A Progressive, Multi-Factorial Condition Demanding an Integrated, Multilayer-Targeted Remedy

Of the human organs, skin is the most visible one that displays the manifestations of ageing. It has a very intricate microanatomical structure and performs several key physiological functions. The pathophysiology of cutaneous ageing is characterized by deterioration of structural stability and functional integrity, implying a continuous reduction in maximal function and reserve capacity, as a result of the accumulating damage due to both intrinsic and extrinsic factors. Elimination of unfavorable expressions associated with facial and cutaneous ageing is the key patient demand in aesthetic dermatology. Even though the progress has been made in nonsurgical therapies like fillers and lasers, non-invasive interventions by using skin care products designed for rejuvenation at an early stage are the most popular and accessible solution among people. In this review, we have scrutinized the ageing-associated cutaneous changes at molecular, cellular and tissue levels. To optimize the ageing process towards a healthy skin, we propose an integrated, multilayer-targeted intervention, which involves both topical application of anti-ageing formulations from outside and oral supplementation from inside. Additionally, several promising naturally derived ingredients are reviewed from an anti-aging perspective. Most of them possess various bioactivities and may contribute to the development of the mentioned anti-ageing remedy.

Improved Topical Drug Delivery: Role of Permeation Enhancers and Advanced Approaches

The delivery of drugs via transdermal routes is an attractive approach due to ease of administration, bypassing of the first-pass metabolism, and the large skin surface area. However, a major drawback is an inability to surmount the skin's stratum corneum (SC) layer. Therefore, techniques reversibly modifying the stratum corneum have been a classical approach. Surmounting the significant barrier properties of the skin in a well-organised, momentary, and harmless approach is still challenging. Chemical permeation enhancers (CPEs) with higher activity are associated with certain side effects restricting their advancement in transdermal drug delivery. Furthermore, complexity in the interaction of CPEs with the skin has led to difficulty in elucidating the mechanism of action. Nevertheless, CPEs-aided transdermal drug delivery will accomplish its full potential due to advancements in analytical techniques, synthetic chemistry, and combinatorial studies. This review focused on techniques such as drug-vehicle interaction, vesicles and their analogues, and novel CPEs such as lipid synthesis inhibitors (LSIs), cell-penetrating peptides (CPPs), and ionic liquids (ILs). In addition, different types of microneedles, including 3D-printed microneedles, have been focused on in this review.

A Molecular Basis Approach of Eczema and Its Link to Depression and Related Neuropsychiatric Outcomes: A Review

"What about my eczema do I love the most? The hurt? A scratch? The humiliation of the public? Oh, there are so many options available!" Studies have shown an association between atopic eczema (AE), a common inflammatory skin condition, and an increased risk of mental health problems. Despite this, experts are still examining the causes of the links between common mental diseases (such as depression and anxiety) and skin conditions. We collected studies that were published in the past 10 years. We searched the following databases: PubMed, PubMed Central, Science Direct, and Google Scholar. Further relevant research was assessed by examining the bibliographies of eligible studies and related ones. Two reviewers looked at the titles and abstracts of the studies to see if they were eligible, and then they read the full texts. We went through eczema and depression relationships, their etiopathogenesis, molecular basis, immune response, the role of genetic factors, and possible interactions between neurons and the immune system. Another possible contributing factor could be a change in cutaneous microbiota in eczema patients. Part of the initial connection could be explained by psychological stress, which further leads to depression in eczema patients. Healthcare professionals treating eczema patients must be aware of the comorbidity of mental problems and the potential that people with poor mental health may need social or emotional support. Patients with eczema, especially youngsters, can benefit from routine health checks since they can help identify neuropsychiatric issues like depression early and lessen the burden of both physical sickness and poor mental health. Given that AE is a condition that appears to be related to depression and anxiety, more research with larger samples is needed to determine a potential role for targeted mental health screening in people with AE, as well as the possibility of mental health modification through improved AE control (e.g., using new biologic agents).

3D Molecular Imaging of Stratum Corneum by Mass Spectrometry Suggests Distinct Distribution of Cholesteryl Esters Compared to Other Skin Lipids

The crucial barrier properties of the stratum corneum (SC) depend critically on the design and integrity of its layered molecular structure. However, analysis methods capable of spatially resolved molecular characterization of the SC are scarce and fraught with severe limitations, e.g., regarding molecular specificity or spatial resolution. Here, we used 3D time-of-flight secondary ion mass spectrometry to characterize the spatial distribution of skin lipids in corneocyte multilayer squams obtained by tape stripping. Depth profiles of specific skin lipids display an oscillatory behavior that is consistent with successive monitoring of individual lipid and corneocyte layers of the SC structure. Whereas the most common skin lipids, i.e., ceramides, C24:0 and C26:0 fatty acids and cholesteryl sulfate, are similarly organized, a distinct 3D distribution was observed for cholesteryl oleate, suggesting a different localization of cholesteryl esters compared to the lipid matrix separating the corneocyte layers. The possibility to monitor the composition and spatial distribution of endogenous lipids as well as active drug and cosmetic substances in individual lipid and corneocyte layers has the potential to provide important contributions to the basic understanding of barrier function and penetration in the SC.

Bioelectric Signaling: Role of Bioelectricity in Directional Cell Migration in Wound Healing

In wound healing, individual cells' behaviors coordinate movement toward the wound center to restore small or large barrier defects. The migration of epithelial cells as a continuous sheet structure is one of the most important processes by which the skin barrier is restored. How such multicellular and tissue level movement is initiated upon injury, coordinated during healing, and stopped when wounds healed has been a research focus for decades. When skin is wounded, the compromised epithelial barrier generates endogenous electric fields (EFs), produced by ion channels and maintained by cell junctions. These EFs are present across wounds, with the cathodal pole at the wound center. Epithelial cells detect minute EFs and migrate directionally in response to electrical signals. It has long been postulated that the naturally occurring EFs facilitate wound healing by guiding cell migration. It is not until recently that experimental evidence has shown that large epithelial sheets of keratinocytes or corneal epithelial cells respond to applied EFs by collective directional migration. Although some of the mechanisms of the collective cell migration are similar to those used by isolated cells, there are unique mechanisms that govern the coordinated movement of the cohesive sheet. We will review the understanding of wound EFs and how epithelial cells and other cells important to wound healing respond to the electric signals individually as well as collectively. Mounting evidence suggests that wound bioelectrical signaling is an important mechanism in healing. Critical understanding and proper exploitation of this mechanism will be important for better wound healing and regeneration.

Application of mevalonolactone prevents deterioration of epidermal barrier function by accelerating the lamellar granule lipid transport system

BACKGROUND

Fatty acids increase ATP-binding cassette ABC transporter A12 (ABCA12) levels via an increase in peroxisome proliferator-activated receptor β/δ (PPAR β/δ). Promoting lipid transport to lamellar granules has been suggested to improve epidermal barrier function in patients with dry skin.

OBJECTIVE

We investigated whether mevalonolactone (MVL) produced by Saccharomycopsis fibuligera improves dry skin by promoting ABCA12 expression and the amount of free fatty acids in epidermal keratinocytes.

METHODS

We examined whether MVL increases ABCA12 mRNA and protein levels and the amount of Nile red-positive lipids in cultured epidermal keratinocytes and in a three-dimensional epidermal model by cell staining. Promotion of fatty acid production by MVL was analyzed by liquid chromatography-mass spectrometry. We also evaluated whether MVL addition increases PPAR β/δ mRNA expression in cultured keratinocytes. Based on the results, a randomized controlled trial was conducted in which milky lotions containing MVL and placebo were applied to dry facial skin of healthy female volunteers in winter.

RESULTS

MVL increased ABCA12 mRNA and protein levels and lamellar granule number and size. Fatty acid analysis revealed that MVL elevated myristic acid, palmitic acid, and palmitoleic acid levels as well as PPAR β/δ mRNA expression. In human tests, milky lotions containing MVL were shown to significantly improve transepidermal water loss (TEWL) in the stratum corneum compared to placebo.

CONCLUSION

The results suggest that MVL increases fatty acid uptake and ABCA12, promotes fatty acid transport to lamellar granules, and improves epidermal barrier function in dry skin through increased expression of PPAR β/δ.

Alterations in epidermal function in type 2 diabetes: Implications for the management of this disease

Epidermal function is regulated by numerous exogenous and endogenous factors, including age, psychological stress, certain skin disorders, ultraviolet irradiation and pollution, and epidermal function itself can regulate cutaneous and extracutaneous functions. The biophysical properties of the stratum corneum reflect the status of both epidermal function and systemic conditions. Type 2 diabetes in both murine models and humans displays alterations in epidermal functions, including reduced levels of stratum corneum hydration and increased epidermal permeability as well as delayed permeability barrier recovery, which can all provoke and exacerbate cutaneous inflammation. Because inflammation plays a pathogenic role in type 2 diabetes, a therapy that improves epidermal functions could be an alternative approach to mitigating type 2 diabetes and its associated cutaneous disorders.

Current knowledge of the implication of lipid mediators in psoriasis

The skin is an organ involved in several biological processes essential to the proper functioning of the organism. One of these essential biological functions of the skin is its barrier function, mediated notably by the lipids of the stratum corneum, and which prevents both penetration from external aggression, and transepidermal water loss. Bioactive lipid mediators derived from polyunsaturated fatty acids (PUFAs) constitute a complex bioactive lipid network greatly involved in skin homeostasis. Bioactive lipid mediators derived from n-3 and n-6 PUFAs have well-documented anti- and pro-inflammatory properties and are recognized as playing numerous and complex roles in the behavior of diverse skin diseases, including psoriasis. Psoriasis is an inflammatory autoimmune disease with many comorbidities and is associated with enhanced levels of pro-inflammatory lipid mediators. Studies have shown that a high intake of n-3 PUFAs can influence the development and progression of psoriasis, mainly by reducing the severity and frequency of psoriatic plaques. Herein, we provide an overview of the differential effects of n-3 and n-6 PUFA lipid mediators, including prostanoids, hydroxy-fatty acids, leukotrienes, specialized pro-resolving mediators, N-acylethanolamines, monoacylglycerols and endocannabinoids. This review summarizes current findings on lipid mediators playing a role in the skin and their potential as therapeutic targets for psoriatic patients.