Role of ceramides in barrier function of healthy and diseased skin

Structure of the yeast ceramide synthase

Ceramides are essential lipids involved in forming complex sphingolipids and acting as signaling molecules. They result from the N-acylation of a sphingoid base and a CoA-activated fatty acid, a reaction catalyzed by the ceramide synthase (CerS) family of enzymes. Yet, the precise structural details and catalytic mechanisms of CerSs have remained elusive. Here we used cryo-electron microscopy single-particle analysis to unravel the structure of the yeast CerS complex in both an active and a fumonisin B1-inhibited state. Our results reveal the complex's architecture as a dimer of Lip1 subunits bound to the catalytic subunits Lag1 and Lac1. Each catalytic subunit forms a hydrophobic crevice connecting the cytosolic site with the intermembrane space. The active site, located centrally in the tunnel, was resolved in a substrate preloaded state, representing one intermediate in ceramide synthesis. Our data provide evidence for competitive binding of fumonisin B1 to the acyl-CoA-binding tunnel.

Lipidomic and Instrumental Evaluation of a Melatonin-Based In & Out Strategy Versus Topical Treatment in Skin Aging: A Randomized Prospective Trial

This study aimed to evaluate the efficacy of a novel "In & Out" strategy, combining topical and oral melatonin supplementation, in managing skin aging compared to topical treatment alone. A randomized, prospective study was conducted on 39 healthy females aged 55-69 years. Participants were divided into two groups: one received both the topical formula and oral melatonin supplementation (Group A), while the other received a topical melatonin-based formula (Group B). Clinical evaluations included lipidomic analysis, skin moisturization, and wrinkle depth analysis at baseline and after 84 days. The addition of oral melatonin supplementation to the topical regimen led to improvements in the skin's lipid profile and moisturization levels. These findings suggest that combining topical and oral melatonin may provide a more comprehensive approach to managing skin aging by addressing both local and systemic factors. Background/Objectives: With age, the endogenous antioxidant capacity of the skin decreases, including melatonin (Mel) synthesis. Skin aging is also associated with alterations in epidermal lipids, particularly a reduction in triglycerides and ceramides, which are essential for maintaining skin structure and hydration. The administration of exogenous melatonin could, therefore, be an effective anti-aging strategy. While some data suggest that melatonin may positively influence the lipid profile, specific data on its effects on skin aging are lacking. This study aimed to evaluate the anti-aging effects of an "In & Out" regimen consisting of a Mel-based cream and dietary supplement in comparison with topical treatment alone, focusing on clinical and lipidomic changes involved in skin homeostasis. Results: A statistically significant variation was observed in both groups compared to baseline (T0) in terms of moisturization (+23.6% in Group A, +18.3% in Group B) and wrinkle depth (-18.5% in Group A, -9.4% in Group B, p < 0.05). Both groups showed improvements in the lipid content of the skin, which typically decreases with age. The "In & Out" strategy resulted in a statistically significant increase in triacylglycerols and ceramides, key lipids that exhibit water-holding properties. Conclusions: The "In & Out" melatonin-based regimen demonstrated greater efficacy in clinical improvement and positive lipid profile modifications compared to topical treatment alone, highlighting its potential as a comprehensive anti-aging strategy.

Penetration of Microplastics and Nanoparticles Through Skin: Effects of Size, Shape, and Surface Chemistry

Skin represents an effective barrier against the penetration of external agents into the human body. Nevertheless, recent research has shown that small particles, especially in the nanosized range, can not only penetrate through the skin but also work as vectors to transport active molecules such as contrast agents or drugs. This knowledge has opened new perspectives on nanomedicine and controlled drug delivery. On the other hand, micro- and nanoplastics represent a form of emerging pollutants, and their concentration in the environment has been reported to drastically increase in the last years. The possible penetration of these particles through the skin has become a major concern for human health. If the actual primary toxicity of these materials is still debated, their possible role in the transport of toxic molecules through the skin, originating as secondary toxicity, is surely alarming. In this review paper, we analyze and critically discuss the most recent scientific publications to underline how these two processes, (i) the controlled delivery of bioactive molecules by micro- and nano-structures and (ii) the unwanted and uncontrolled penetration of toxic species through the skin mediated by micro- and nanoparticles, are deeply related and their efficiency is strongly affected by the nature, size, and shape of the particles.

Ceramide 3 Effect on the Physical Properties of Ambora Extract and Chromabright-Loaded Transethosomes

Spontaneous self-assembly of phospholipids into lipid vesicles in aqueous media is called liposomes, and these structures are widely used as nanocarriers in the cosmeceutical industry. Transethosomes are ethanol and edge activator-containing liposomes that are proven to be very effective in topical applications for penetrating the skin barrier. Many cosmeceutical products contain formulations with ceramides to restore the skin barrier and treat eczema. However, due to the low solubility and penetration ability of the ceramides, the effectiveness of these products is limited. In this study, a transethosome formulation containing ceramide 3 (Cer 3) was achieved by introducing varying concentrations of cholesterol and an edge activator (Tween 80) to improve the effect of the skin products used to treat eczema. The obtained transethosomes were examined in terms of size, homogeneity, zeta potential, morphology, and one-month stability. Loading capability experiments were carried out with lipophilic Chromabright and hydrophilic Ambora extract. The effect of Cer 3 on the loading of the selected payloads was evaluated. Data were analyzed statistically with linear regression analysis and two-way analysis of variance. The results showed that the inclusion of Cer 3 had almost no effect on the physical properties of the loaded or empty transethosomes. Independently of the presence of Cer 3, loading of the lipophilic compound was more efficient than that of the hydrophilic one.

The water extracts from the oil cakes of Prinsepia utilis repair the epidermal barrier via up-regulating Corneocyte Envelope-proteins, lipid synthases, and tight junction proteins

ETHNOPHARMACOLOGICAL RELEVANCE

Prinsepia utilis Royle, native to the Himalayan region, has a long history of use in traditional medicine for its heat-clearing, detoxification, anti-inflammatory, and analgesic properties. Oils extracted from P. utilis seeds are also used in cooking and cosmetics. With the increasing market demand, this extraction process generates substantial industrial biowastes. Recent studies have found many health benefits with using aqueous extracts of these biowastes, which are also rich in polysaccharides. However, there is limited research related to the reparative effects of the water extracts of P. utilis oil cakes (WEPUOC) on disruptions of the skin barrier function.

AIM OF THE STUDY

This study aimed to evaluate the reparative efficacy of WEPUOC in both acute and chronic epidermal permeability barrier disruptions. Furthermore, the study sought to explore the underlying mechanisms involved in repairing the epidermal permeability barrier.

MATERIALS AND METHODS

Mouse models with induced epidermal disruptions, employing tape-stripping (TS) and acetone wiping (AC) methods, were used. The subsequent application of WEPUOC (100 mg/mL) was evaluated through various assessments, with a focus on the upregulation of mRNA and protein expression of Corneocyte Envelope (CE) related proteins, lipid synthase-associated proteins, and tight junction proteins.

RESULTS

The polysaccharide was the major phytochemicals of WEPUOC and its content was determined as 32.2% by the anthranone-sulfuric acid colorimetric method. WEPUOC significantly reduced transepidermal water loss (TEWL) and improved the damaged epidermal barrier in the model group. Mechanistically, these effects were associated with heightened expression levels of key proteins such as FLG (filaggrin), INV (involucrin), LOR (loricrin), SPT, FASN, HMGCR, Claudins-1, Claudins-5, and ZO-1.

CONCLUSIONS

WEPUOC, obtained from the oil cakes of P. utilis, is rich in polysaccharides and exhibits pronounced efficacy in repairing disrupted epidermal barriers through increased expression of critical proteins involved in barrier integrity. Our findings underscore the potential of P. utilis wastes in developing natural cosmetic prototypes for the treatment of diseases characterized by damaged skin barriers, including atopic dermatitis and psoriasis.

Effects of a Protocol Combining a Non-Irritating Shampoo and an Adelmidrol-Based Adsorbent Mousse on Seborrhoea and Other Signs and Symptoms Secondary to Canine Atopic Dermatitis: A Multicenter, Open-Label Uncontrolled Clinical Trial

The present study aimed at evaluating the effect of a gentle shampoo and a mousse containing Adelmidrol, tapioca starch and a non-prescription antimicrobial complex on seborrhoea and other clinical signs secondary to canine atopic dermatitis (cAD). Forty-six dogs with cAD-associated seborrhoea and/or pruritus > 4 cm on the pruritus visual analogue scale (P-VAS) and/or bacterial/Malassezia overgrowth were enrolled. The mousse was applied twice daily, and dogs were evaluated at days (D)0, 7, 14 and optionally 28, by means of a skin seborrheic index (SSI), P-VAS, cAD lesion index (CADLI), and a semiquantitative cytological score. The mean SSI value improved during the first two weeks (4.1 ± 0.37 to 1.9 ± 0.30; p < 0.0001). The mean P-VAS score (cm) decreased from 6.6 ± 0.19 at D0 to 3.8 ± 0.31 at D14 (p < 0.0001). The mean CADLI score dropped from 13.7 ± 1.24 to 8.5 ± 1.14 at D14 (p < 0.001). The cytological score for bacteria and Malassezia decreased from 3.2 ± 0.10 and 3.2 ± 0.11, respectively, to 1.2 ± 0.19 and 1.2 ± 0.24 (p < 0.0001). All the investigated signs further improved at D28. Altogether, these observations suggest that the tested protocol might be useful in managing cAD-associated signs.

Microbiome and lipidomic analysis reveal the interplay between skin bacteria and lipids in a cohort study

Human skin acts as a protective barrier between the body and the external environment. Skin microbiome and intercellular lipids in the stratum corneum (SC) are essential for maintaining skin barrier function. However, the interplay between skin bacteria and the lipids is not fully understood. In this study, we characterized the skin microbiome and SC lipid profiles from the forearm and face in a cohort of 57 healthy participants. 16S rRNA gene sequencing showed the skin microbial composition is significantly different between body locations and genders. Female forearm samples have the highest microbial diversity. The relative abundance of Staphylococcus hominis, Micrococcus luteus, Corynebacterium tuberculostearicum, Finegoldia magna, and Moraxellaceae sp. are significantly higher in the forearm than the face. The predictive functional analysis of 16S rRNA gene sequencing by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2) and ANCOM-BC showed different bacterial metabolic pathway profiles between body locations or genders, and identified 271 differential pathways, including arginine and polyamine biosynthesis, chorismate biosynthesis pathways, which are more abundant in the female forearm, and sulfur oxidation pathway, which is more abundant in the male face. The SC lipid profiles differ between the body locations as well. Total free fatty acids (FFA), cholesterol sulfate and sphingosine are more abundant in the face. Dihydro-/6-hydroxy/phyto-ceramides are more abundant in the forearm. The correlation analysis of 16S rRNA gene sequencing and lipids revealed novel interplay between the bacteria and skin lipids. Shannon entropy and S. hominis negatively correlated with FFA, cholesterol sulfate and sphingosine; while positively correlated with dihydro-/6-hydroxy/phyto-ceramides. The correlation of predictive pathway profiles and lipids identified pathways involved in amino acids metabolism, carbohydrates degradation, aromatic compounds metabolism and fatty acid degradation metabolism are positively correlated with dihydro-/6-hydroxy/phyto-ceramides and negatively correlated with FFA, cholesterol sulfate and sphingosine. This study provides insights on the potential correlation between skin microbiome and lipids.

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.

The Potential of Campanula takesimana Callus Extract to Enhance Skin Barrier Function

Atopic dermatitis (AD) is a prevalent inflammatory skin disease characterized by epidermal barrier dysfunction and Th2-skewed inflammation. Campanula takesimana (C. takesimana), a Korean endemic plant grown on Ulleng Island, has long been associated with a traditional alternative medicine for asthma, tonsillitis, and sore throat. In this study, we reported the effect of C. takesimana callus extract on upregulating epidermal barrier-related proteins dysregulated by Th2 cytokines. C. takesimana callus extract induced the expression of skin barrier proteins, such as filaggrin, claudin-1, and zonula occludens-1, in both human primary keratinocytes and Th2-induced AD-like skin-equivalent models. Additionally, RNA sequencing analysis demonstrated that C. takesimana callus extract partially restored Th2 cytokine-induced dysregulation of the epidermal development and lipid metabolic pathways. Considering the advantages of callus as a sustainable eco-friendly source of bioactive substances, and its effect on skin barrier proteins and lipid metabolic pathways, C. takesimana callus extracts can possibly be utilized to improve the integrity of the skin barrier.

The Design and Optimization of Ceramide NP-Loaded Liposomes to Restore the Skin Barrier

The impairment of skin integrity derived from derangement of the orthorhombic lateral organization is mainly caused by dysregulation of ceramide amounts in the skin barrier. Ceramides, fatty acids, and cholesterol-containing nano-based formulations have been used to impair the skin barrier. However, there is still a challenge to formulate novel formulations consisting of ceramides due to their chemical structure, poor aqueous solubility, and high molecular weight. In this study, the design and optimization of Ceramide 3 (CER-NP)-loaded liposomes are implemented based on response surface methodology (RSM). The optimum CER-NP-loaded liposome was selected based on its particle size (PS) and polydispersity index (PDI). The optimum CER-NP-loaded liposome was imagined by observing the encapsulation by using a confocal laser scanning microscope (CLSM) within fluorescently labeled CER-NP. The characteristic liquid crystalline phase and lipid chain conformation of CER-NP-loaded liposomes were determined using attenuated total reflectance infrared spectroscopy (ATR-IR). The CER-NP-loaded liposomes were imagined using a field emission scanning electron microscope (FE-SEM). Finally, the in vitro release of CER-NP from liposomes was examined using modified Franz Cells. The experimental and predicted results were well correlated. The CLSM images of optimized liposomes were conformable with the other studies, and the encapsulation efficiency of CER-NP was 93.84 ± 0.87%. ATR-IR analysis supported the characteristics of the CER-NP-loaded liposome. In addition, the lipid chain conformation shows similarity with skin barrier lipid organization. The release pattern of CER-NP liposomes was fitted with the Korsmeyer-Peppas model. The cytotoxicity studies carried out on HaCaT keratinocytes supported the idea that the liposomes for topical administration of CER-NP could be considered relatively safe. In conclusion, the optimized CER-NP-loaded liposomes could have the potential to restore the skin barrier function.

Atopic Dermatitis: Molecular Alterations between Lesional and Non-Lesional Skin Determined Noninvasively by In Vivo Confocal Raman Microspectroscopy

Atopic dermatitis (AD)/atopic eczema is a chronic relapsing inflammatory skin disease affecting nearly 14% of the adult population. An important pathogenetic pillar in AD is the disrupted skin barrier function (SBF). The atopic stratum corneum (SC) has been examined using several methods, including Raman microspectroscopy, yet so far, there is no depth-dependent analysis over the entire SC thickness. Therefore, we recruited 21 AD patients (9 female, 12 male) and compared the lesional (LAS) with non-lesional atopic skin (nLAS) in vivo with confocal Raman microspectroscopy. Our results demonstrated decreased total intercellular lipid and carotenoid concentrations, as well as a shift towards decreased orthorhombic lateral lipid organisation in LAS. Further, we observed a lower concentration of natural moisturising factor (NMF) and a trend towards increased strongly bound and decreased weakly bound water in LAS. Finally, LAS showed an altered secondary and tertiary keratin structure, demonstrating a more folded keratin state than nLAS. The obtained results are discussed in comparison with healthy skin and yield detailed insights into the atopic SC structure. LAS clearly shows molecular alterations at certain SC depths compared with nLAS which imply a reduced SBF. A thorough understanding of these alterations provides useful information on the aetiology of AD and for the development/control of targeted topical therapies.

Towards non-invasive monitoring of non-melanoma skin cancer using spatially offset Raman spectroscopy

BCC (basal cell carcinoma) and SCC (squamous cell carcinoma) account for the vast majority of cases of non-melanoma skin cancer (NMSC). The gold standard for the diagnosis remains biopsy, which, however, is an invasive and time-consuming procedure. In this study, we employed spatially offset Raman spectroscopy (SORS), a non-invasive approach, allowing the assessment of deeper skin tissue levels and collection of Raman photons with a bias towards the different layers of epidermis, where the non-melanoma cancers are initially formed and expand. Ex vivo Raman measurements were acquired from 22 skin biopsies using conventional back-scattering and a defocused modality (with and without a spatial offset). The spectral data were assessed against corresponding histopathological data to determine potential prognostic factors for lesion detection. The results revealed a positive correlation of protein and lipid content with the SCC and BCC types, respectively. By further correlating with patient data, multiple factor analysis (MFA) demonstrated a strong clustering of variables based on sex and age in all modalities. Specifically for the defocused modality (zero and 2 mm offset), further clustering occurred based on pathology. This study demonstrates the utility of the SORS technology in NMSC diagnosis prior to histopathological examination on the same tissue.

Osteoporosis and dermatoporosis: a review on the role of vitamin D

Osteoporosis (OP) and Dermatoporosis (DP) are expressions of the aging process at the skin and bone levels, respectively. Both conditions are associated with increased morbidity for elderly people, and this requires necessary interventions. They share many common risk factors; among these, vitamin D (VD) deficiency appears to have a role. VD is involved in either disease with many mechanisms, among which immunomodulation. VD deficiency has been linked to OP because it inhibits the body's capacity to absorb calcium and maintain optimal bone health. Available evidence suggests that proper vitaminosis D also appears to be vital in preventing skin age-related issues. DP is often seen in elderly individuals, particularly those with long-term sun exposure and a history of chronic sun damage. VD deficiency can be linked to DP, since its involvement in collagen production, epidermal barrier function, inflammation regulation, wound healing, and sun protection. Aim of this review is to summarize the most updated existing evidence on the role of VD in the development of fragility syndromes such as DP and OP and the possible benefits of VD supplementation as a simple and harmful weapon against aging.

Detection of Bacterial Neutral Ceramidase in Diabetic Foot Ulcers with an Optimized Substrate and Chemoenzymatic Probes

Ceramidases (CDases) are important in controlling skin barrier integrity by regulating ceramide composition and affording downstream signal molecules. While the functions of epidermal CDases are known, roles of neutral CDases secreted by skin-residing microbes are undefined. Here, we developed a one-step fluorogenic substrate, S-B, for specific detection of bacterial CDase activity and inhibitor screening. We identified a non-hydrolyzable substrate mimic, C6, as the best hit. Based on C6, we designed a photoaffinity probe, JX-1, which efficiently detects bacterial CDases. Using JX-1, we identified endogenous low-abundance PaCDase in a P. aeruginosa monoculture and in a mixed skin bacteria culture. Harnessing both S-B and JX-1, we found that CDase activity positively correlates with the relative abundance of P. aeruginosa and is negatively associated with wound area reduction in clinical diabetic foot ulcer patient samples. Overall, our study demonstrates that bacterial CDases are important regulators of skin ceramides and potentially play a role in wound healing.

Cycloastragenol exerts protective effects against UVB irradiation in human dermal fibroblasts and HaCaT keratinocytes

BACKGROUND

Cycloastragenol (CAG) is a triterpene aglycone of astragaloside IV that possesses various pharmacological actions including improving telomerase activity, inhibiting inflammation and cell proliferation, inducing apoptosis.

OBJECTIVE

CAG has also shown effect to significantly improve the appearance of aging skin but, its molecular mechanism of protective effect against UVB induced-damage have not been elucidated. We investigated the potential effect of CAG on UVB wrinkle promoting activities and skin-moisturizing effects in human dermal fibroblasts (HDF) and HaCaT keratinocytes.

METHODS

After UVB irradiation or H2O2 treatment, the levels of matrix metalloproteinases (MMPs) and ROS generation were measured in CAG-treated HDF cells. In addition, after UVB irradiation, hyaluronic acid and skin hydration factors (filaggrin and SPT) were also analyzed in CAG (0-0.5-1-2 µM)-treated HDF and HaCaT cells.

RESULTS

We found that CAG caused a significant decrease in the levels of UVB-induced MMP-1, MMP-9, MMP-13 and ROS generation, also increased UVB-damaged Collagen Ⅰ. We also noted that CAG increased cell viability and can regulate MMP-1, MMP-9, MMP-13and Collagen Ⅰ in H2O2-damaged HDF cells. Moreover, we noticed that CAG effectively enhanced levels of hyaluronic acid and expression of skin hydration factors (filaggrin and serine palmitoyltransferase (SPT)) in UVB-damaged HDF and HaCaT cells.

CONCLUSION

This is first report indicating that CAG can exhibit protective effect against UVB and H2O2-induced damages and can contribute in maintenance of healthy skin.

Ovol1/2 loss-induced epidermal defects elicit skin immune activation and alter global metabolism

Skin epidermis constitutes the outer permeability barrier that protects the body from dehydration, heat loss, and myriad external assaults. Mechanisms that maintain barrier integrity in constantly challenged adult skin and how epidermal dysregulation shapes the local immune microenvironment and whole-body metabolism remain poorly understood. Here, we demonstrate that inducible and simultaneous ablation of transcription factor-encoding Ovol1 and Ovol2 in adult epidermis results in barrier dysregulation through impacting epithelial-mesenchymal plasticity and inflammatory gene expression. We find that aberrant skin immune activation then ensues, featuring Langerhans cell mobilization and T cell responses, and leading to elevated levels of secreted inflammatory factors in circulation. Finally, we identify failure to gain body weight and accumulate body fat as long-term consequences of epidermal-specific Ovol1/2 loss and show that these global metabolic changes along with the skin barrier/immune defects are partially rescued by immunosuppressant dexamethasone. Collectively, our study reveals key regulators of adult barrier maintenance and suggests a causal connection between epidermal dysregulation and whole-body metabolism that is in part mediated through aberrant immune activation.

Ocular surface sphingolipids associate with the refractory nature of vernal keratoconjunctivitis: newer insights in VKC pathogenesis

BACKGROUND

The etiopathogenesis of vernal keratoconjunctivitis (VKC) is incompletely understood. Bioactive lipids play a key role in allergic disorders. This study focused on the sphingolipid metabolism on the ocular surface of VKC and to explore if it has a contributory role in the refractoriness of the disease.

METHODS

Active VKC cases, (n=87) (classified as mild/moderate and severe/very severe based on the disease symptoms) and age-matched healthy controls (n=60) were recruited as part of a 2-year prospective study at a tertiary eye care centre in South India. Conjunctival imprint cytology was used to assess gene expression of enzymes of sphingolipids metabolism. Sphingolipids were estimated in the tears by LC-MS/MS analysis. In vitro study was done to assess IgE-induced alterations in sphingosine-1-phosphate (S1P) receptor expression and histone modification in cultured mast cells.

RESULTS

Significantly altered gene expression of the sphingolipids enzymes and S1P receptor (SIP3R) were observed in conjunctival imprint cells of VKC cases. Pooled tears analysis revealed significantly lowered levels of S1P(d17:0), S1P(d20:1) (p<0.001) and S1P(d17:1) (p<0.01) specifically in severe/very severe VKC compared with both mild/moderate VKC and control. Cer(d18:/17:0) (p<0.001), ceramide-1-phosphate (C1P)(d18:1/8:0) (p<0.01) and C1P(d18:1/2.0 (p<0.05) were lowered in severe/very severe VKC compared with mild/moderate VKC. Cultured mast cells treated with IgE revealed significantly increased gene expression of S1P1 and 3 receptors and the protein expression of histone deacetylases (1, 6).

CONCLUSION

Altered sphingolipid metabolism in the ocular surface results in low tear ceramide and sphingosine levels in severe/very severe VKC compared with the mild/moderate cases. The novel finding opens up fresh targets for intervention in these refractory cases.

Cera-Glow, ferment lysates of Lacticaseibacillus rhamnosus IDCC 3201, improves skin barrier function in clinical study

BACKGROUND

Ceramides are essential lipids in stratum corneum for skin permeability barrier function in that they retain the skin moisture and protect from the invasion of foreign pathogens. Previously, we demonstrated that ferment lysates of Lacticaseibacillus rhamnosus IDCC 3201 enhanced ceramide production in human epidermal keratinocytes. Furthermore, for comprehensive knowledge of this effect, in vitro experiments and multi-omics analysis were conducted to explore the underlying mechanisms.

AIMS

This study was designed to identify whether a cosmetic sample (i.e., Cera-Glow) containing the lysates improves the skin barrier function in clinical trials.

PATIENTS/METHODS

Twenty-four female participants (45.46 ± 9.78 years) had been enrolled in the transepidermal water loss (TEWL) measurement for 5 days and 21 female participants (50.33 ± 5.74 years) had undergone a skin hydration evaluation for 4 weeks. TEWL and skin hydration were evaluated using a Tewameter and the Epsilon Permittivity Imaging System, respectively. After applying the Cera-Glow sample, all participants recorded a satisfaction survey questionnaire (e.g., satisfaction, efficacy, and adverse reactions).

RESULTS

Application of Cera-Glow significantly improved transepidermal water loss induced by 1% (w/v) sodium lauryl sulfate (p < 0.05-0.01) and increased skin hydration (p < 0.01). Metabolic analysis suggested that Cera-Glow should contain beneficial gradients for skin barrier function. According to the questionnaire, most of participants were satisfied with the skin hydration improvement and efficacy of Cera-Glow.

CONCLUSIONS

Cera-Glow, ferment lysates of Lacticaseibacillus rhamnosus IDCC 3201, can significantly improve skin barrier function.

Hyaluronic Acid Nanoparticles as a Topical Agent for Treating Psoriasis

Although conventional topical approaches for treating psoriasis have been offered as an alternative, there are still unmet medical needs such as low skin-penetrating efficacy and off-target adverse effects. A hyaluronic acid nanoparticle (HA-NP) formed by self-assembly of HA-hydrophobic moiety conjugates has been broadly studied as a nanocarrier for long-term and target-specific delivery of drugs, owing to their excellent physicochemical and biological characteristics. Here, we identify HA-NPs as topical therapeutics for treating psoriasis using in vivo skin penetration studies and psoriasis animal models. Transcutaneously administered HA-NPs were found to be accumulated and associated with pro-inflammatory macrophages in the inflamed dermis of a psoriasis mouse model. Importantly, HA-NP exerted potent therapeutic efficacy against psoriasis-like skin dermatitis in a size-dependent manner by suppressing innate immune responses and restoring skin barrier function without overt toxicity signs. The therapeutic efficacy of HA-NPs on psoriasis-like skin dermatitis was due to the outermost hydrophilic HA shell layer of HA-NPs, independent of the molecular weight of HA and hydrophobic moiety, and comparable with that of other conventional psoriasis therapeutics widely used in the clinical settings. Overall, HA-NPs have the potential as a topical nanomedicine for treating psoriasis effectively and safely.

The Role of Sphingolipids in the Pathogenesis of Psoriasis

Psoriasis is a complex, chronic, immunologically mediated disease which involves skin and joints. Psoriasis is commonly connected with numerous other diseases such as liver diseases, metabolic syndrome, impaired glucose tolerance, diabetes mellitus, atherosclerosis, hypertension, and ischemic heart disease. Interestingly, comorbidities of psoriasis are an attention-grabbing issue. Additionally, it can cause impairment of quality of life and may be associated with depressive disorders. Altered levels of ceramides in psoriatic skin may lead to anti-apoptotic and pro-proliferative states, consequently leading to an over-proliferation of keratinocytes and the development of skin lesions. The pathophysiology of psoriasis and its comorbidities is not fully understood yet. Sphingolipids (including ceramides) and their disturbed metabolism may be the link between psoriasis and its comorbidities. Overall, the goal of this review was to discuss the role of sphingolipid disturbances in psoriasis and its comorbidities. We searched the PubMed database for relevant articles published before the beginning of May 2022. The systematic review included 65 eligible original articles.

Metabolomic Differences between the Skin and Blood Sera of Atopic Dermatitis and Psoriasis

Atopic dermatitis (AD) and psoriasis (PS) are common chronic inflammatory dermatoses. Although the differences at the intercellular and intracellular signaling level between AD and PS are well described, the resulting differences at the metabolism level have not yet been systematically analyzed. We compared the metabolomic profiles of the lesional skin, non-lesional skin and blood sera of AD and PS. Skin biopsies from 15 patients with AD, 20 patients with PS and 17 controls were collected, and 25 patients with AD, 55 patients with PS and 63 controls were recruited for the blood serum analysis. Serum and skin samples were analyzed using a targeted approach to find the concentrations of 188 metabolites and their ratios. A total of 19 metabolites differed in the comparison of lesional skins, one metabolite in non-lesional skins and 5 metabolites in blood sera. Although we found several metabolomic similarities between PS and AD, clear differences were outlined. Sphingomyelins were elevated in lesional skin of AD, implying a deficient barrier function. Increased levels of phosphatidylcholines, carnitines and asymmetric dimethylarginine in PS lesional skin and carnitines amino acids in the PS serum pointed to elevated cell proliferation. The comparison of the metabolomic profiles of AD and PS skin and sera outlined distinct patterns that were well correlated with the differences in the pathogenetic mechanisms of these two chronic inflammatory dermatoses.

Low-flux electron diffraction study on body site dependence of stratum corneum structures in human skin

For analysis of the structure of human skin stratum corneum (SC), we introduced low-flux electron diffraction (ED) and developed a new statistical analysis method for obtained ED intensity profiles. By use of this method we compared the differences in the intercellular lipid organization on the SC corneocytes collected at human forehead, cheek, and forearm by the grid-stripping method. As a result, we found a significant regional difference in the distribution of lipid hydrocarbon chain packing domains in the SC; the ring-type ED pattern with orthorhombic symmetry was more often observed in the forearm SC than in the forehead and cheek SCs. We also found that the dependence of the background electron diffraction intensity on the modulus of the scattering vector differed significantly among them. The present method for the analysis of a large number of ED patterns of noninvasively obtained SC samples could be a powerful tool to scrutinize the structural difference between the SCs under various experimental conditions.

Omalizumab as a treatment option for antihistamine-refractory aquagenic urticaria

A teenage girl presented with symptoms of itching and hives on contact with water for 3 years. On specific provocative testing and ruling out underlying systemic conditions, she was diagnosed with aquagenic urticaria. Following failed attempts to control her symptoms with second-generation antihistamines, she was started on monthly subcutaneous injections of the monoclonal antibody, omalizumab. The patient demonstrated significant improvement, with symptoms being well-controlled for 2 years now. She enjoys a good quality of life and can take a shower without developing itching or hives.

Atopic Dermatitis: The Fate of the Fat

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease in which dry and itchy skin may develop into skin lesions. AD has a strong genetic component, as children from parents with AD have a two-fold increased chance of developing the disease. Genetic risk loci and epigenetic modifications reported in AD mainly locate to genes involved in the immune response and epidermal barrier function. However, AD pathogenesis cannot be fully explained by (epi)genetic factors since environmental triggers such as stress, pollution, microbiota, climate, and allergens also play a crucial role. Alterations of the epidermal barrier in AD, observed at all stages of the disease and which precede the development of overt skin inflammation, manifest as: dry skin; epidermal ultrastructural abnormalities, notably anomalies of the lamellar body cargo system; and abnormal epidermal lipid composition, including shorter fatty acid moieties in several lipid classes, such as ceramides and free fatty acids. Thus, a compelling question is whether AD is primarily a lipid disorder evolving into a chronic inflammatory disease due to genetic susceptibility loci in immunogenic genes. In this review, we focus on lipid abnormalities observed in the epidermis and blood of AD patients and evaluate their primary role in eliciting an inflammatory response.

The impact of external factors on psoriasis

Psoriasis is one of the most common chronic inflammatory skin diseases, constituting a significant health and socioeconomic problem. Despite numerous therapeutic options, the results of treatment very often remain insufficient. It is extremely important to remember that many external factors impact the effectiveness of therapy. This article discusses the importance of emollients in therapy and the influence of infectious agents and injuries on the course of psoriasis. Understanding the above-mentioned factors in the treatment of psoriasis is critical to achieve satisfactory therapeutic effects.

Transcriptional Differences in Lipid-Metabolizing Enzymes in Murine Sebocytes Derived from Sebaceous Glands of the Skin and Preputial Glands

Sebaceous glands are adnexal structures, which critically contribute to skin homeostasis and the establishment of a functional epidermal barrier. Sebocytes, the main cell population found within the sebaceous glands, are highly specialized lipid-producing cells. Sebaceous gland-resembling tissue structures are also found in male rodents in the form of preputial glands. Similar to sebaceous glands, they are composed of lipid-specialized sebocytes. Due to a lack of adequate organ culture models for skin sebaceous glands and the fact that preputial glands are much larger and easier to handle, previous studies used preputial glands as a model for skin sebaceous glands. Here, we compared both types of sebocytes, using a single-cell RNA sequencing approach, to unravel potential similarities and differences between the two sebocyte populations. In spite of common gene expression patterns due to general lipid-producing properties, we found significant differences in the expression levels of genes encoding enzymes involved in the biogenesis of specialized lipid classes. Specifically, genes critically involved in the mevalonate pathway, including squalene synthase, as well as the sphingolipid salvage pathway, such as ceramide synthase, (acid) sphingomyelinase or acid and alkaline ceramidases, were significantly less expressed by preputial gland sebocytes. Together, our data revealed tissue-specific sebocyte populations, indicating major developmental, functional as well as biosynthetic differences between both glands. The use of preputial glands as a surrogate model to study skin sebaceous glands is therefore limited, and major differences between both glands need to be carefully considered before planning an experiment.

The Epidemiology and Global Burden of Atopic Dermatitis: A Narrative Review

The global epidemiology of atopic dermatitis (AD) in the current decade (2009-2019) has not been extensively reported. Epidemiological studies play an important role in presenting the risk factors of AD, as detailed prevalence and incidence data could demonstrate the burden of disease in the population of adults, adolescents, and children in different geographical regions. Thus, the primary objective of this review was to assess and summarize the epidemiological studies of the prevalence and incidence of AD in different age groups, focusing on data from studies published for 2009 to 2019. After a thorough literature search, six countries were identified from African, Asian, and European regions respectively, who published studies on AD. In contrast, only two studies were identified from Australia and New Zealand, three countries from North America and two from South America published AD studies, respectively. The highest prevalence of AD from included studies was noted among Swedish children with 34%, while the lowest prevalence was in Tunisian children with 0.65%; studies reporting incidence data were far less numerous. A common trend in the prevalence of AD was that children would have a higher prevalence as compared to adolescents and adults. The severity and morbidity of the disease showed variance with age, sex, socioeconomic characteristics, geographical location, and ethnicity. Environmental factors played an important role as causative agents in AD. The risk factors that were proven to cause and induce AD were skin barrier impairments due to FLG mutation, changes in the environment, and diet. FLG mutation may impair the skin barrier function by disruption of pH and hydration maintenance of the skin. Lastly, there were only a few studies on the incidence of AD in the 21st century. Therefore, epidemiological studies on childhood and adulthood AD in different continents are still needed, especially on the incidence of AD during adulthood.

Characterization of Ex Vivo Nonmelanoma Skin Tissue Using Raman Spectroscopy

Raman spectroscopy has shown great potential in detecting nonmelanoma skin cancer accurately and quickly; however, little direct evidence exists on the sensitivity of measurements to the underlying anatomy. Here, we aimed to correlate Raman measurements directly to the underlying tissue anatomy. We acquired Raman spectra of ex vivo skin tissue from 25 patients undergoing Mohs surgery with a fiber probe. We utilized a previously developed biophysical model to extract key biomarkers in the skin from the Raman spectra. We then examined the correlations between the biomarkers and the major skin structures (including the dermis, sebaceous glands, hair follicles, fat, and two types of nonmelanoma skin cancer—basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)). SCC had a significantly different concentration of keratin, collagen, and nucleic acid than normal structures, while ceramide differentiated BCC from normal structures. Our findings identified the key proteins, lipids, and nucleic acids that discriminate nonmelanoma tumors and healthy skin using Raman spectroscopy. These markers may be promising surgical guidance tools for detecting tumors in resection margins.

Peristomal Skin Health: A WOCN Society Consensus Conference

The Wound, Ostomy, and Continence Nurses (WOCN) Society identified the need to define and promote peristomal skin health. A task force was appointed to complete a scoping literature review, to develop evidence-based statements to guide peristomal skin health best practices. Based on the findings of the scoping review, the Society convened a panel of experts to develop evidence- and consensus-based statements to guide care in promoting peristomal skin health. These consensus statements also underwent content validation using a different panel of clinicians having expertise in peristomal skin health. This article reports on the scoping review and subsequent 6 evidenced-based statements, along with the generation and validation of 19 consensus-based statements, to assist clinical decision-making related to promoting peristomal skin health in adults.

Cutting Edge of the Pathogenesis of Atopic Dermatitis: Sphingomyelin Deacylase, the Enzyme Involved in Its Ceramide Deficiency, Plays a Pivotal Role

Atopic dermatitis (AD) is characterized clinically by severe dry skin and functionally by both a cutaneous barrier disruption and an impaired water-holding capacity in the stratum corneum (SC) even in the nonlesional skin. The combination of the disrupted barrier and water-holding functions in nonlesional skin is closely linked to the disease severity of AD, which suggests that the barrier abnormality as well as the water deficiency are elicited as a result of the induced dermatitis and subsequently trigger the recurrence of dermatitis. These functional abnormalities of the SC are mainly attributable to significantly decreased levels of total ceramides and the altered ceramide profile in the SC. Clinical studies using a synthetic pseudo-ceramide (pCer) that can function as a natural ceramide have indicated the superior clinical efficacy of pCer and, more importantly, have shown that the ceramide deficiency rather than changes in the ceramide profile in the SC of AD patients plays a central role in the pathogenesis of AD. Clinical studies of infants with AD have shown that the barrier disruption due to the ceramide deficiency is not inherent and is essentially dependent on postinflammatory events in those infants. Consistently, the recovery of trans-epidermal water loss after tape-stripping occurs at a significantly slower rate only at 1 day post-tape-stripping in AD skin compared with healthy control (HC) skin. This resembles the recovery pattern observed in Niemann-Pick disease, which is caused by an acid sphingomyelinase (aSMase) deficiency. Further, comparison of ceramide levels in the SC between before and after tape-stripping revealed that whereas ceramide levels in HC skin are significantly upregulated at 4 days post-tape-stripping, their ceramide levels remain substantially unchanged at 4 days post-tape-stripping. Taken together, the sum of these findings strongly suggests that an impaired homeostasis of a ceramide-generating process may be associated with these abnormalities. We have discovered a novel enzyme, sphingomyelin (SM) deacylase, which cleaves the N-acyl linkage of SM and glucosylceramide (GCer). The activity of SM deacylase is significantly increased in AD lesional epidermis as well as in the involved and uninvolved SC of AD skin, but not in the skin of patients with contact dermatitis or chronic eczema, compared with HC skin. SM deacylase competes with aSMase and β-glucocerebrosidase (BGCase) to hydrolyze their common substrates, SM and GCer, to yield their lysoforms sphingosylphosphorylcholine (SPC) and glucosylsphingosine (GSP), respectively, instead of ceramide. Consistently, those reaction products (SPC and GSP) accumulate to a greater extent in the involved and uninvolved SC of AD skin compared with chronic eczema or contact dermatitis skin as well as HC skin. Successive chromatographies were used to purify SM deacylase to homogeneity with a single band of ≈43 kDa and with an enrichment of >14,000-fold. Analysis of a protein spot with SM deacylase activity separated by 2D-SDS-PAGE using MALDI-TOF MS/MS allowed its amino acid sequence to be determined and to identify it as the β-subunit of acid ceramidase (aCDase), an enzyme consisting of α- and β-subunits linked by amino-bonds and a single S-S bond. Western blotting of samples treated with 2-mercaptoethanol revealed that whereas recombinant human aCDase was recognized by antibodies to the α-subunit at ≈56 and ≈13 kDa and the β-subunit at ≈43 kDa, the purified SM deacylase was detectable only by the antibody to the β-subunit at ≈43 kDa. Breaking the S-S bond of recombinant human aCDase with dithiothreitol elicited the activity of SM deacylase with an apparent size of ≈40 kDa upon gel chromatography in contrast to aCDase activity with an apparent size of ≈50 kDa in untreated recombinant human aCDase. These results provide new insights into the essential role of SM deacylase as the β-subunit aCDase that causes the ceramide deficiency in AD skin.

The emerging potential of cold atmospheric plasma in skin biology

The maintenance of skin integrity is crucial to ensure the physiological barrier against exogenous compounds, microorganisms and dehydration but also to fulfill social and aesthetic purposes. Besides the development of new actives intended to enter a formulation, innovative technologies based on physical principles have been proposed in the last years. Among them, Cold Atmospheric Plasma (CAP) technology, which already showed interesting results in dermatology, is currently being studied for its potential in skin treatments and cares. CAP bio-medical studies gather several different expertise ranging from physics to biology through chemistry and biochemistry, making this topic hard to pin. In this review we provide a broad survey of the interactions between CAP and skin. In the first section, we tried to give some fundamentals on skin structure and physiology, related to its essential functions, together with the main bases on cold plasma and its physicochemical properties. In the following parts we dissected and analyzed each CAP parameter to highlight the already known and the possible effects they can play on skin. This overview aims to get an idea of the potential of cold atmospheric plasma technology in skin biology for the future developments of dermo-cosmetic treatments, for example in aging prevention.

Microbial Biosurfactants in Cosmetic and Personal Skincare Pharmaceutical Formulations

Cosmetic and personal care products are globally used and often applied directly on the human skin. According to a recent survey in Europe, the market value of cosmetic and personal care products in Western Europe reached about 84 billion euros in 2018 and are predicted to increase by approximately 6% by the end of 2020. With these significant sums of money spent annually on cosmetic and personal care products, along with chemical surfactants being the main ingredient in a number of their formulations, of which many have been reported to have the potential to cause detrimental effects such as allergic reactions and skin irritations to the human skin; hence, the need for the replacement of chemical surfactants with other compounds that would have less or no negative effects on skin health. Biosurfactants (surfactants of biological origin) have exhibited great potential such as lower toxicity, skin compatibility, protection and surface moisturizing effects which are key components for an effective skincare routine. This review discusses the antimicrobial, skin surface moisturizing and low toxicity properties of glycolipid and lipopeptide biosurfactants which could make them suitable substitutes for chemical surfactants in current cosmetic and personal skincare pharmaceutical formulations. Finally, we discuss some challenges and possible solutions for biosurfactant applications.

Aquagenic urticaria: Water, friend, or foe?

There are <100 reported cases of aquagenic urticaria. Although most are sporadic, several diseases have been associated. Diagnosis is based on provocation tests. Second-generation antihistamines are the first-line treatment.

The effects of obesity on the human body, part I: Skin and musculoskeletal

Obesity is a worldwide issue that many global health authorities consider a growing epidemic. Having a positive correlation between increases in the industrialization of processed foods and sedentary occupations as well as a lack of access to healthcare in poorer socioeconomic areas, obesity is a multifactorial disease affecting several organ systems. The tendency for obesity to cause detrimental changes to the human body is a focal point for healthcare providers to establish more effective clinical treatment and management plans. Implementing comprehensive global educational programs to decrease the prevalence of this unforgiving disease is imperative for a healthier future. Herein, we have provided a comprehensive review of the health effects of obesity upon the human body for the interest of many practicing clinicians managing this health crisis.

The adaptation of lipid profile of human fibroblasts to alginate 2D films and 3D printed scaffolds

BACKGROUND

The investigation of the interactions between cells and active materials is pivotal in the emerging 3D printing-biomaterial application fields. Here, lipidomics has been used to explore the early impact of alginate (ALG) hydrogel architecture (2D films or 3D printed scaffolds) and the type of gelling agent (CaCl₂ or FeCl₃) on the lipid profile of human fibroblasts.

METHODS

2D and 3D ALG scaffolds were prepared and characterized in terms of water content, swelling, mechanical resistance and morphology before human fibroblast seeding (8 days). Using a liquid chromatography-triple quadrupole-tandem mass spectrometry approach, selected ceramides (CER), lysophosphatidylcholines (LPC), lysophosphatidic acids (LPA) and free fatty acids (FFA) were analyzed.

RESULTS

The results showed a clear alteration in the CER expression profile depending of both the geometry and the gelling agent used to prepare the hydrogels. As for LPCs, the main parameter affecting their distribution is the scaffold architecture with a significant decrease in the relative expression levels of the species with higher chain length (C20 to C22) for 3D scaffolds compared to 2D films. In the case of FFAs and LPAs only slight differences were observed as a function of scaffold geometry or gelling agent.

CONCLUSIONS

Variations in the cell membrane lipid profile were observed for 3D cell cultures compared to 2D and these data are consistent with activation processes occurring through the mutual interactions between fibroblasts and ALG support. These unknown physiologically relevant changes add insights into the discussion about the relationship between biomaterial and the variations of cell biological functions.

Sphingolipids in food and their critical roles in human health

Sphingolipids (SLs) are ubiquitous structural components of cell membranes and are essential for cell functions under physiological conditions or during disease progression. Abundant evidence supports that SLs and their metabolites, including ceramide (Cer), ceramide-1-phosphate (C1P), sphingosine (So), sphingosine-1-phosphate (S1P), are signaling molecules that regulate a diverse range of cellular processes and human health. However, there are limited reviews on the emerging roles of exogenous dietary SLs in human health. In this review, we discuss the ubiquitous presence of dietary SLs, highlighting their structures and contents in foodstuffs, particularly in sea foods. The digestion and metabolism of dietary SLs is also discussed. Focus is given to the roles of SLs in both the etiology and prevention of diseases, including bacterial infection, cancers, neurogenesis and neurodegenerative diseases, skin integrity, and metabolic syndrome (MetS). We propose that dietary SLs represent a "functional" constituent as emerging strategies for improving human health. Gaps in research that could be of future interest are also discussed.

Treatment with Synthetic Pseudoceramide Improves Atopic Skin, Switching the Ceramide Profile to a Healthy Skin Phenotype

Little is known about the pathophysiological linkages between altered ceramide profiles in the stratum corneum (SC) of patients with atopic dermatitis and their impaired skin barrier and water-holding functions. We studied those characteristics following topical treatment with a designed synthetic pseudoceramide (pCer) and analyzed that pathophysiological linkage by microanalyzing ceramides using normal phase liquid chromatography-electrospray ionization mass spectrometry. Four weeks of treatment with pCer significantly reduced skin symptoms, accompanied by significant decreases in transepidermal water loss and increases in water content. In the SC ceramide profiles, ceramides containing nonhydroxy fatty acids and 6-hydroxysphingosines (Cer[NH]) and ceramides containing nonhydroxy fatty acids and phytosphingosines (Cer[NP]) increased, whereas ceramides containing nonhydroxy fatty acids and sphingosines (Cer[NS]) and ceramides containing a-hydroxy fatty acids and sphingosines (Cer[AS]) decreased, with larger alkyl chain lengths in Cer[NS], distinctly representing a switch from an atopic dermatitis to a healthy skin phenotype. The level of pCer that penetrated into the SC was significantly correlated with the SC water content but not with transepidermal water loss. The level and the average carbon chain length of Cer[NS] were closely correlated with the pCer level in the SC. These findings indicate that the penetrated pCer contributes to shift the ceramide profile from an atopic dermatitis to a healthy skin phenotype. Taken together, the observed clinical efficacy of treatment with pCer provides a deep insight into the pathogenesis of atopic dermatitis as a ceramide-deficient disease.

Rab25 Deficiency Perturbs Epidermal Differentiation and Skin Barrier Function in Mice

Rab25, a member of the Rab11 small GTPase family, is central to achieving cellular polarity in epithelial tissues. Rab25 is highly expressed in epithelial cells of various tissues including breast, vagina, cervix, the gastrointestinal tract, and skin. Rab25 plays key roles in tumorigenesis, mainly by regulating epithelial differentiation and proliferation. However, its role in skin physiology is relatively unknown. In this study, we demonstrated that Rab25 knock-out (KO) mice show a skin barrier dysfunction with high trans-epidermal water loss and low cutaneous hydration. To examine this observation, we investigated the histology and epidermal differentiation markers of the skin in Rab25 KO mice. Rab25 KO increased cell proliferation at the basal layer of epidermis, whereas the supra-basal layer remained unaffected. Ceramide, which is a critical lipid component for skin barrier function, was not altered by Rab25 KO in its distribution or amount, as determined by immunohistochemistry. Notably, levels of epidermal differentiation markers, including loricrin, involucrin, and keratins (5, 14, 1, and 10) increased prominently in Rab25 KO mice. In line with this, depletion of Rab25 with single hairpin RNA increased the expression of differentiation markers in a human keratinocyte cell line, HaCaT. Transcriptomic analysis of the skin revealed increased expression of genes associated with skin development, epidermal development, and keratinocyte differentiation in Rab25 KO mice. Collectively, these results suggested that Rab25 is involved in the regulation of epidermal differentiation and proliferation.

Recent Advances on Topical Application of Ceramides to Restore Barrier Function of Skin

Human skin is the largest organ of the body and is an effective physical barrier keeping it from environmental conditions. This barrier function of the skin is based on stratum corneum, located in the uppermost skin. Stratum corneum has corneocytes surrounded by multilamellar lipid membranes which are composed of cholesterol, free fatty acids and ceramides (CERs). Alterations in ceramide content of the stratum corneum are associated with numerous skin disorders. In recent years, CERs have been incorporated into conventional and novel carrier systems with the purpose of exogenously applying CERs to help the barrier function of the skin. This review provides an overview of the structure, function and importance of CERs to restore the barrier function of the skin following their topical application.

Breaking the Itch-Scratch Cycle: Topical Options for the Management of Chronic Cutaneous Itch in Atopic Dermatitis

Chronic itch is an unpleasant sensation that triggers a desire to scratch that lasts for six weeks or more. It is a major diagnostic symptom of myriad diseases, including atopic dermatitis for which it is the most prominent feature. Chronic itch can be hugely debilitating for the sufferer, damaging in terms of both the monetary cost of treatment and its socioeconomic effects, and few treatment options exist that can adequately control it. Corticosteroids remain the first line treatment strategy for atopic dermatitis, but due to the risks associated with long-term use of corticosteroids, and the drawbacks of other topical options such as topical calcineurin inhibitors and capsaicin, topical options for itch management that are efficacious and can be used indefinitely are needed. In this review, we detail the pathophysiology of chronic pruritus, its key features, and the disease most commonly associated with it. We also assess the role of the skin and its components in maintaining a healthy barrier function, thus reducing dryness and the itch sensation. Lastly, we briefly detail examples of topical options for the management of chronic pruritus that can be used indefinitely, overcoming the risk associated with long-term use of corticosteroids.

Unravelling effects of relative humidity on lipid barrier formation in human skin equivalents

Relative humidity (RH) levels vary continuously in vivo, although during in vitro generation of three-dimensional human skin equivalents (HSEs) these remain high (90-95%) to prevent evaporation of the cell-culture medium. However, skin functionality is directly influenced by environmental RH. As the barrier formation in HSEs is different, there is a need to better understand the role of cell-culture conditions during the generation of HSEs. In this study, we aim to investigate the effects of RH on epidermal morphogenesis and lipid barrier formation in HSEs. Therefore, two types of HSEs were developed at 90% or at 60% RH. Assessments were performed to determine epidermal morphogenesis by immunohistochemical analyses, ceramide composition by lipidomic analysis, and lipid organization by Fourier transform infrared spectroscopy and small-angle X-ray diffraction. We show that reduction of RH mainly affected the uppermost viable epidermal layers in the HSEs, including an enlargement of the granular cells and induction of epidermal cell activation. Neither the composition nor the organization of the lipids in the intercorneocyte space were substantially altered at reduced RH. In addition, lipid processing from glucosylceramides to ceramides was not affected by reduced RH in HSEs as shown by enzyme expression, enzyme activity, and substrate-to-product ratio. Our results demonstrate that RH directly influences epidermal morphogenesis, albeit the in vitro lipid barrier formation is comparable at 90% and 60% RH.

Korean red ginseng water extract alleviates atopic dermatitis-like inflammatory responses by negative regulation of mitogen-activated protein kinase signaling pathway in vivo

Atopic dermatitis (AD) is a chronic inflammatory skin disease. Korean red ginseng is a Korean traditional medicine. In this study, we estimated the effects of Korean red ginseng water extract (RGE) in the 1-chloro-2,4-dinitrobenzene (DNCB)-induced BALB/c mouse model which develops AD-like lesions. After RGE administration (100, 200, and 400 mg/kg) to DNCB-induced mice there were improvements in the dermatitis score and skin pH, a decrease in trans-epidermal water loss, and improved skin hydration. RGE also significantly inhibited eosinophil infiltration, increased filaggrin protein levels, and decreased serum IgE levels, epidermal thickness, mast cell infiltration, and ceramidase release. Compared with that in DNCB-induced mice, RGE effectively decreased the mRNA expression levels of interleukin-6 (IL-6), thymic stromal lymphopoietin (TSLP), and tumor necrosis factor-α (TNF-α), as well as the protein level of thymus and activation-regulated chemokine (TARC). These inhibitory RGE effects are mediated by inhibiting the phosphorylation of mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK. Furthermore, we confirmed that RGE suppresses interferon-γ (IFN-γ) and TNF-α-induced expression of macrophage-derived chemokine (MDC) and TARC genes in human keratinocyte (HaCaT) cells. Taken together, these results demonstrate that RGE may exert anti-atopic related to responses by suppression the expression of inflammatory mediators, cytokines, and chemokines via downregulation of MAPK signaling pathways, suggesting that RGE may be an effective therapeutic approach for prevention of AD-like disease.

A human skin high-throughput formulation screening method using a model hydrophilic drug

Franz cell (FC) experiments in topical and transdermal drug development represent the gold standard in vitro method but require a relatively high quantity of human skin, are low-throughput, and are time-consuming to perform. To address these issues, we studied a micro-well plate-based screening method for permeability and retention that could enable the direct screening of large numbers of formulations simultaneously across human skin. Using freshly excised dermatomed human skin modified to reflect poor barrier function and a model hydrophilic compound, Sulforhodamine B (SRB), FC permeation and retention quantification was compared to the 96-well high-throughput system (HTS). The skin was analyzed using 2-photon microscopy to determine the drug distribution within the skin. A screen of 15 different formulations in triplicate in a single piece of human skin, using full factorial design was then conducted. Permeability of SRB across the skin as well as the drug distribution profile of SRB retained in the skin were similar for the FC and HTS system. The influence of different excipients on drug retention was observed in the full factorial formulation screen. The HTS method is promising for the investigation of large numbers of formulations and the influence of formulations changes in skin retention of drug.

PEBBLES study protocol: a randomised controlled trial to prevent atopic dermatitis, food allergy and sensitisation in infants with a family history of allergic disease using a skin barrier improvement strategy

INTRODUCTION

The skin is an important barrier against environmental allergens, but infants have relatively impaired skin barrier function. There is evidence that impaired skin barrier function increases the risk of allergic sensitisation, atopic dermatitis (AD) and food allergy. We hypothesise that regular prophylactic use of emollients, particularly those that are designed to improve skin barrier structure and function, will help prevent these conditions. With the aim of determining if application of a ceramide-dominant emollient two times per day reduces the risk of AD and food allergy, we have commenced a multicentre phase III, outcome assessor blinded, randomised controlled trial of this emollient applied from birth to 6 months.

METHODS AND ANALYSIS

Infants (n=760) with a family history of allergic disease will be recruited from maternity hospitals in Melbourne. The primary outcomes are as follows: the presence of AD, assessed using the UK Working Party criteria, and food allergy using food challenge, in the first 12 months of life as assessed by a blinded study outcome assessor. Secondary outcomes are as follows: food sensitisation (skin prick test), skin barrier function, AD severity, the presence of new onset AD after treatment cessation (between 6 and 12 months) and the presence of parent reported AD/eczema. Recruitment commenced in March 2018.

ETHICS AND DISSEMINATION

The PEBBLES Study is approved by the Human Research Ethics Committees of the Royal Children's Hospital (RCH) (#37090A) and the Mercy Hospital for Women (2018-008). Parents or guardians will provide written informed consent. Outcomes will be disseminated through peer-reviewed publications and presented at scientific conferences.

TRIAL REGISTRATION NUMBERS

ACTRN12617001380381 and NCT03667651.

Development of a Label-Free LC-MS/MS-Based Glucosylceramide Synthase Assay and Its Application to Inhibitors Screening for Ceramide-Related Diseases

Ceramide metabolism is known to be an essential etiology for various diseases, such as atopic dermatitis and Gaucher disease. Glucosylceramide synthase (GCS) is a key enzyme for the synthesis of glucosylceramide (GlcCer), which is a main ceramide metabolism pathway in mammalian cells. In this article, we developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine GCS activity using synthetic non-natural sphingolipid C8-ceramide as a substrate. The reaction products, C8-GlcCer for GCS, could be separated on a C18 column by reverse-phase high-performance liquid chromatography (HPLC). Quantification was conducted using the multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m/z 588.6 → 264.4 for C8-GlcCer at positive ionization mode. The calibration curve was established over the range of 0.625–160 ng/mL, and the correlation coefficient was larger than 0.999. This method was successfully applied to detect GCS in the human hepatocellular carcinoma cell line (HepG2 cells) and mouse peripheral blood mononuclear cells. We also evaluated the inhibition degree of a known GCS inhibitor 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) on GCS enzymatic activity and proved that this method could be successfully applied to GCS inhibitor screening of preventive and therapeutic drugs for ceramide metabolism diseases, such as atopic dermatitis and Gaucher disease.

The skin as a target for prevention of the atopic march

OBJECTIVE

Allergic diseases have increased dramatically in the developed world during the past few decades, yet the understanding of risk factors and effective prevention approaches remain limited. In this review, we summarize the evidence supporting the hypothesis that skin-barrier impairment and early-life atopic dermatitis (AD) could play a causal role in the development of sensitization and subsequent food allergies and allergic airways disease (allergic asthma and rhinitis). We further discuss the potential to target the skin barrier as a means to lower the incidence of allergic disease.

DATA SOURCES

Review of published literature.

STUDY SELECTIONS

Narrative.

RESULTS

There is a strong link between AD and sensitization, food allergy, asthma, and allergic rhinitis, particularly AD that is severe and commences in the first 6 months of life. There also is emerging evidence that regular use of prophylactic emollients can significantly decrease the expression of AD, at least while treatment continues. Studies are exploring whether decreased AD expression might modulate the allergic response at a more fundamental level and potentially alter the association between early-life AD and subsequent development of food allergy and allergic airways disease.

CONCLUSION

Although at this point there is only indirect evidence that early-life emollient use might prevent AD and food allergy, early studies are encouraging. The results of high-quality prevention trials that are in progress are eagerly anticipated. If found to be effective, then neonatal emollient use could be a simple public health measure to lower the incidence of AD, food allergies, and allergic airways disease in future generations.