An accumulation of glucosylceramide in the stratum corneum due to attenuated activity of beta-glucocerebrosidase is associated with the early phase of UVB-induced alteration in cutaneous barrier function

Horse-Derived Ceramide Accentuates Glucosylceramide Synthase and Ceramide Synthase 3 by Activating PPARβ/δ and/or PPARγ to Stimulate Ceramide Synthesis

Horse-derived ceramide (HC), which contains galactosylceramides as its main component, significantly improves skin symptoms when applied topically to patients with atopic dermatitis. We speculated that efficacy resulted from the amelioration of epidermal ceramide metabolism, and we characterized those effects using reconstructed human epidermal equivalents. Lipid analysis, RT-PCR and Western blotting revealed that HC significantly increased the total ceramide content of the stratum corneum (SC), accompanied by significantly increased gene and/or protein expression levels of ceramide synthase (CERS) 3, fatty acid elongase (ELOVL) 4, glucosylceramide synthase (GCS), β-glucocerebrosidase, sphingomyelin synthase and acid sphingomyelinase. Mechanistic analyses using cultures of primary human keratinocytes revealed the marked stimulatory effects of HC on the mRNA expression levels of CERS3, ELOVL4 and GCS under high calcium-derived differentiation conditions. Signaling analyses demonstrated that an antagonist of PPARβ/δ significantly abrogated the HC-stimulated mRNA expression levels of GCS, CERS3 and ELOVL4. GW9662, an antagonist of PPARγ, significantly abolished the HC-up-regulated mRNA expression levels of GCS and ELOVL4, but not of CERS3. These findings suggest that HC has the distinct potential to accentuate the expression of GCS, CERS3 and ELOVL4 via the activation of PPARβ/δ and/or PPARγ to accelerate ceramide synthesis in the SC.

Roles and therapeutic potential of CD1d-Restricted NKT cells in inflammatory skin diseases

Natural killer T (NKT) cells are innate-like T lymphocytes that recognize glycolipid antigens rather than peptides. Due to their immunoregulatory properties, extensive work has been done to elucidate the immune functions of NKT cells in various immune contexts such as autoimmunity for more than two decades. In addition, as research on barrier immunity such as the mucosa-associated lymphoid tissue has flourished in recent years, the role of NKT cells to immunity in the skin has attracted substantial attention. Here, we review the contributions of NKT cells to regulating skin inflammation and discuss the factors that can modulate the functions of NKT cells in inflammatory skin diseases such as atopic dermatitis. This mini-review article will mainly focus on CD1d-dependent NKT cells and their therapeutic potential in skin-related immune diseases.

Phenotypic and lipidomic characterization of primary human epidermal keratinocytes exposed to simulated solar UV radiation

BACKGROUND

Ultraviolet (UV) radiation is known to be one of the most important environmental hazards acting on the skin. The most part of UV radiation is absorbed in the epidermis, where keratinocytes are the most abundant and exposed cell type. Lipids have an important role in skin biology, not only for their important contribution to the maintenance of the permeability barrier but also for the production and storage of energy, membrane organization and cell signalling functions. However, the effects on the lipid composition of keratinocytes under UV radiation are little explored.

OBJECTIVE

The present work aims to explore the effects on the phenotype and lipid content of primary human keratinocytes exposed to simulated solar UV radiation.

METHODS

Keratinocytes were exposed to a single (acute exposure) and repeated simulated solar UV irradiations for 4 weeks (chronic exposure). Cell viability and morphology were explored, as well as the production of reactive oxygen species. Then, lipid extracts were analysed through liquid chromatography coupled to mass spectrometry (LC-MS) and the data generated was processed using the ROIMCR chemometric methodology together with partial least squares discriminant analysis (PLS-DA), to finally reveal the most relevant lipid changes that occurred in keratinocytes upon UV irradiation. Also, the potential induction of keratinocyte differentiation was explored by measuring the increase of involucrin.

RESULTS

Under acute irradiation, cell viability and morphology were not altered. However, a general increase of phosphatidylcholines (PC) phosphatidylethanolamines (PE) and phosphatidylglycerol (PG) together with a slight sphingomyelin (SM) decrease were found in UV irradiated cells, among other changes. In addition, keratinocyte cultures did not present any differentiation hallmark. Contrary to acute-irradiated cells, in chronic exposures, cell viability was reduced and keratinocytes presented an altered morphology. Also, hallmarks of differentiation, such as the increase of involucrin protein and the autophagy induction were detected. Among the main lipid changes that accompanied this phenotype, the increase of long-chain ceramides, lysoPC and glycerolipid species were found.

CONCLUSION

Important lipid changes were detected under acute and chronic UV irradiation. The lipid profile under chronic exposure may represent a lipid fingerprint of the keratinocyte differentiation phenotype.

Untargeted lipidomic analysis of primary human epidermal melanocytes acutely and chronically exposed to UV radiation

Ultraviolet (UV) radiation present in sunlight has been related to harmful effects on skin such as premature aging and skin cancer.

Permeability Barrier and Microstructure of Skin Lipid Membrane Models of Impaired Glucosylceramide Processing

Ceramide (Cer) release from glucosylceramides (GlcCer) is critical for the formation of the skin permeability barrier. Changes in β-glucocerebrosidase (GlcCer'ase) activity lead to diminished Cer, GlcCer accumulation and structural defects in SC lipid lamellae; however, the molecular basis for this impairment is not clear. We investigated impaired GlcCer-to-Cer processing in human Cer membranes to determine the physicochemical properties responsible for the barrier defects. Minor impairment (5-25%) of the Cer generation from GlcCer decreased the permeability of the model membrane to four markers and altered the membrane microstructure (studied by X-ray powder diffraction and infrared spectroscopy), in agreement with the effects of topical GlcCer in human skin. At these concentrations, the accumulation of GlcCer was a stronger contributor to this disturbance than the lack of human Cer. However, replacement of 50-100% human Cer by GlcCer led to the formation of a new lamellar phase and the maintenance of a rather good barrier to the four studied permeability markers. These findings suggest that the major cause of the impaired water permeability barrier in complete GlcCer'ase deficiency is not the accumulation of free GlcCer but other factors, possibly the retention of GlcCer bound in the corneocyte lipid envelope.

Analytical methods in sphingolipidomics: Quantitative and profiling approaches in food analysis

In recent years, sphingolipidomics has emerged as an interesting omic science that encompasses the study of the full sphingolipidome characterization, content, structure and activity in cells, tissues or organisms. Like other omics, it has the potential to impact biomarker discovery, drug development and systems biology knowledge. Concretely, dietary food sphingolipids have gained considerable importance due to their extensively reported bioactivity. Because of the complexity of this lipid family and their diversity among foods, powerful analytical methodologies are needed for their study. The analytical tools developed in the past have been improved with the enormous advances made in recent years in mass spectrometry (MS) and chromatography, which allow the convenient and sensitive identification and quantitation of sphingolipid classes and form the basis of current sphingolipidomics methodologies. In addition, novel hyphenated nuclear magnetic resonance (NMR) strategies, new ionization strategies, and MS imaging are outlined as promising technologies to shape the future of sphingolipid analyses. This review traces the analytical methods of sphingolipidomics in food analysis concerning sample extraction, chromatographic separation, the identification and quantification of sphingolipids by MS and their structural elucidation by NMR.

Epidermal Hydration Is Improved by Enhanced Ceramide Metabolism in Aged C57BL/6J Mice After Dietary Supplementation of Royal Jelly

Epidermal hydration is maintained by the epidermal lipid barrier, of which ceramide (Cer) is the major constituent. We examined the dietary effect of royal jelly (RJ) on epidermal hydration in aged mice. Altered Cer metabolism was further determined by measuring epidermal levels of individual Cer, glucosylceramide (GC), and sphingomyelin (SM) species, and of Cer-metabolizing enzymes. Aged C57BL/6J mice were fed a control diet (group AGED) or diets with 1% RJ harvested from two different areas (groups AGED+RJ1:AGED + RJ2) for 16 weeks. Aged C57BL/6J mice with no dietary intervention (the control group: group C) represented the onset of aging. In group AGED, epidermal levels of hydration, Cer1/2/5/6/7, GC-A/B/C/D, SM1/2/3, and β-glucocerebrosidase (GCase) protein, an enzyme of GC hydrolysis for Cer generation, were lower than in group C; these levels, as well as those of Cer3/4 and acidic sphingomyelinase (aSMase) protein, an enzyme of SM hydrolysis for Cer generation, were higher in group AGED + RJ1 than in group AGED. Despite increases in GC-B, SM1/2/3, and serine palmitoyltransferase2 protein, an enzyme of de novo Cer synthesis, in group AGED + RJ2 to levels higher than in group AGED, epidermal levels of hydration, Cer1-7, GC-A/C/D, GCase, and aSMase proteins were similar in these two groups. Expression of GCase and aSMase mRNAs, and of Cer synthase3 and ceramidase proteins, enzymes of de novo Cer synthesis and degradation, did not differ among groups. Dietary RJ1 improved epidermal hydration by enhancing Cer metabolism with increased levels of all Cer, GC, and SM species, and of GCase and aSMase proteins.

Effects of sphingomyelin/ceramide ratio on the permeability and microstructure of model stratum corneum lipid membranes

The conversion of sphingomyelin (SM) to a ceramide (Cer) by acid sphingomyelinase (aSMase) is an important event in skin barrier development. A deficiency in aSMase in diseases such as Niemann-Pick disease and atopic dermatitis coincides with impaired skin barrier recovery after disruption. We studied how an increased SM/Cer ratio influences the barrier function and microstructure of model stratum corneum (SC) lipid membranes. In the membranes composed of isolated human SC Cer (hCer)/cholesterol/free fatty acids/cholesteryl sulfate, partial or full replacement of hCer by SM increased water loss. Partial replacement of 25% and 50% of hCer by SM also increased the membrane permeability to theophylline and alternating electric current, while a higher SM content either did not alter or even decreased the membrane permeability. In contrast, in a simple membrane model with only one type of Cer (nonhydroxyacyl sphingosine, CerNS), an increased SM/Cer ratio provided a similar or better barrier against the permeation of various markers. X-ray powder diffraction revealed that the replacement of hCer by SM interferes with the formation of the long periodicity lamellar phase with a repeat distance of d=12.7nm. Our results suggest that SM-to-Cer processing in the human epidermis is essential for preventing excessive water loss, while the permeability barrier to exogenous compounds is less sensitive to the presence of sphingomyelin.

Collagen hydrolysate intake improves the loss of epidermal barrier function and skin elasticity induced by UVB irradiation in hairless mice

BACKGROUND

Ultraviolet B (UVB) irradiation induces serious damage to the skin. Collagen hydrolysate and collagen-derived peptides have effects on skin function in vivo and in vitro. However, few studies have investigated changes in the epidermal barrier or dermal elasticity caused by UVB. Here, we investigated the loss of epidermal barrier function and skin elasticity induced by UVB irradiation in hairless mice fed collagen hydrolysate.

METHODS

Mice were orally administered collagen hydrolysate, in a single dose (20 mJ/cm(2) ) or repeated doses (10-30 mJ/cm(2) , 3 times/week for 6 weeks), and the dorsal skin was exposed to UVB. Skin measurements and histological and analytical studies were performed.

RESULTS

In control mice, a single UVB irradiation induced epidermal barrier dysfunction including an increase in transepidermal water loss (TEWL), epidermal hyperplasia, and a decrease in stratum corneum water content. Administration of collagen hydrolysate significantly decreased TEWL and epidermal thickness and increased stratum corneum water content. Repeated UVB irradiation decreased skin elasticity and dermal hyaluronic acid (HA) content in control mice, whereas collagen hydrolysate significantly suppressed both the increase in TEWL and the decrease in stratum corneum water content and improved skin elasticity and dermal HA content.

CONCLUSIONS

Collagen hydrolysate administration affects epidermal barrier function and dermal skin elasticity.

Gromwell (Lithospermum erythrorhizon) supplementation enhances epidermal levels of ceramides, glucosylceramides, β-glucocerebrosidase, and acidic sphingomyelinase in NC/Nga mice

We have previously reported that dietary gromwell (Lithospermum erythrorhizon; LE) prevents the development of atopic dermatitis (AD) with increased epidermal levels of total ceramide (Cer), the major lipid maintaining epidermal barrier. In this study, we investigated whether the increased level of total Cer induced by dietary LE would be related to the altered metabolism of glucosylceramide (GlcCer) and sphingomyelin (SM), two major precursor lipids in Cer generation. NC/Nga mice, an animal model of AD, were fed a control diet (group CA: atopic control) or a diet with 70% ethanol LE extracts (1% in diet; group LE) for 10 weeks. Individual species of Cer, GlcCer, and SM were analyzed by high-performance thin layer chromatography. In the epidermis of group CA, total Cer (including Cer2 and Cer5-7) and total GlcCer (including GlcCer-B/C/D) were significantly reduced; these levels in group LE were increased to levels similar to the normal control group of BALB/c mice (group C). In addition, protein expressions and activities of β-glucocerebrosidase (β-GlcCer'ase) and acidic sphingomyelinase (aSMase), enzymes for GlcCer or SM hydrolysis, respectively, were increased in group LE. However, alterations of Cer1, Cer3/4, GlcCer-A, and all SM species (including SM1-3) were not significant among groups C, CA, and LE. Dietary gromwell increases GlcCer-B/C/D, and further enhances the generation of Cer2 and Cer5-7 with high protein expressions and activities of β-GlcCer'ase and aSMase.

Epidermal barrier: Adverse and beneficial changes induced by ultraviolet B irradiation depending on the exposure dose and time (Review)

Exposure of the skin to ultraviolet (UV) radiation induces various harmful effects in the tissues, particularly disruption of the epidermal barrier. However, ultraviolet B (UVB) irradiation has been applied in the treatment of atopic dermatitis, a skin disease in which the epidermal barrier is defective. We reviewed the homeostasis of the epidermal barrier and several studies investigating the adverse and beneficial effects caused by different doses of UVB irradiation in the epidermal barrier. It may be concluded that, despite the harmful effects of UVB irradiation on the skin, UVB irradiation is able to exert beneficial effects in the epidermal barrier when administered in suberythemal doses and over a relatively short period of time, with no clinically evident inflammation or barrier disruption. This may be a useful therapeutic strategy for the use of UVB irradiation in the treatment of skin diseases with a disrupted epidermal barrier, such as atopic dermatitis, while reducing or avoiding the side-effects.

Langerhans cells serve as immunoregulatory cells by activating NKT cells

Ultraviolet exposure alters the morphology and function of epidermal Langerhans cells (LCs), which play a role in UV-induced immune suppression. It is generally believed that UV exposure triggers the migration of immature LCs from the skin to the draining lymph nodes (LNs), where they induce tolerance. However, because most of the previous studies employed in vitro UV-irradiated LCs, the data generated may not adequately reflect what is happening in vivo. In this study, we isolated migrating LCs from the LNs of UV-irradiated mice and studied their function. We found prolonged LC survival in the LNs of UV-irradiated mice. LCs were necessary for UV-induced immune suppression because no immune suppression was observed in LC-deficient mice. Transferring LCs from UV-irradiated mice into normal recipient animals transferred immune suppression and induced tolerance. We found that LCs colocalized with LN NKT cells. No immune suppression was observed when LCs were transferred from UV-irradiated mice into NKT cell-deficient mice. NKT cells isolated from the LNs of UV-irradiated mice secreted significantly more IL-4 than NKT cells isolated from nonirradiated controls. Injecting the wild-type mice with anti-IL-4 blocked the induction of immune suppression. Our findings indicate that UV exposure activates the migration of mature LC to the skin draining LNs, where they induce immune regulation in vivo by activating NKT cells.

Chemical properties of epidermal lipids, especially sphingolipids, of the Antarctic minke whale

It is well known that sphingolipids specifically exist in the terrestrial mammal epidermis and correlate with skin barrier functions. However, the lipid properties of the marine mammal epidermis have not been examined in detail. We thus investigated the chemical composition of lipid components, especially sphingolipids, in the black epidermis (outer skin) of Antarctic minke whales (six mature and six immature specimens). Complex lipid fractions mainly contained cerebroside (CE), cholesteryl sulfate and sphingomyelin (SM), as well as two glycerophospholipids. Moreover, in the superficial layer of the black epidermis, CE was richly abundant but phospholipids were scarce. As component fatty acids, the non-hydroxy monounsaturated very long chain fatty acids (VLFA) within 34 carbons were generally present in CE and SM in the black epidermis. CE also consisted of alpha-hydroxy fatty acids with monounsaturation within C34 (17%) and a slight proportion of omega-hydroxy ones (32:1 and 34:1), the latter being probably derived from acyl-CE. Component sphingoid bases of both sphingolipids were predominantly 4-sphingenine (64%), followed by a C16 analogue (21%). When comparing these by different maturities, mature whales showed sphingolipid profiles with higher levels of unsaturated fatty acids and with shorter sphingoid base chains than those of immature ones. Component analysis revealed that CE sugars were 67% glucose and 33% galactose, and alpha-hydroxy fatty acids only bound to galactose.

Analysis of sphingolipid classes and their contents in meals

Sphingolipids have attracted attention as physiologically functional lipids. We determined their class and content in Japanese meals that had been prepared by a nutritionist, mainly by using HPLC-ELSD. In all 12 meals tested, cerebroside and/or sphingomyelin were generally detected as the major sphingolipids. The total amounts of sphingolipids in typical high- and low-calorie meal samples over 2 days were 292 and 128 mg/day, and 81 and 45 mg/day, respectively.

Accumulation of topical naproxen by cultured oral epithelium

Topically administered non-steroidal anti-inflammatory drugs (NSAIDs) inhibit periodontal bone loss, but little is known about the mechanism by which they penetrate oral epithelium. Active transporters could potentially play a role in this process. In this study, we used a cell line derived from oral epithelium to investigate a role for transporters and to characterize conditions that enhance epithelial penetration. Using fluorescence to monitor uptake, we demonstrated that SCC-25 cell monolayers transport naproxen with a Michaelis constant (K(m)) and maximum velocity (V(max)) of 164 microg/mL and 0.94 ng/min/microg protein, respectively. At steady state, the intra-cellular/extracellular concentration ratio was 3.4. Naproxen accumulation was more efficient at acidic pH than under neutral or alkaline conditions. Small proportions of glycerol, Pluronic F-127, and glucosylceramide enhanced naproxen entry. The individual and combined effects of glycerol and Pluronic F-127 were of lesser magnitude than those obtained with glucosylceramide or at pH 6.3. Thus, SCC-25 cells possess transporters for naproxen.

Dietary glucosylceramide improves skin barrier function in hairless mice

BACKGROUND

Sphingolipids are known to play an important role in both water retention and epidermal permeability barrier function in mammalian stratum corneum. However, little is known about the effects on epidermal function of orally administered sphingolipids.

OBJECTIVE

We examined the effect of dietary glucosylceramide (GluCer) on the maintenance and recovery of epidermal barrier function.

METHODS

Hairless mice were fed a particular diet (HR-AD) for 4 weeks to induce chronic skin perturbation. Subsequently, a normal diet supplemented with GluCer (from rice bran and germ) was provided for the next 4 weeks. Transepidermal water loss (TEWL) and stratum corneum flexibility were measured throughout this recovery phase. Additional hairless mice were fed a diet with or without a maize-extracted GluCer supplement for 5 weeks, then their skin was acutely perturbed with repeated tape-stripping, and the TEWL was measured.

RESULTS

Although skin functions were generally lower following chronic perturbation, in GluCer-fed mice the TEWL was significantly reduced at 2 weeks and the stratum corneum flexibility was increased at 3 weeks compared to controls. Following acute barrier perturbation by tape-stripping, mice an HR-AD fed a GluCer diet exhibited enhanced recovery compared with the control diet group.

CONCLUSION

These results demonstrate that in hairless mice skin barrier functions impaired by chronic or acute perturbations were improved by dietary GluCer. The oral administration of GluCer may be useful for the preservation and recovery of epidermal barrier functions an HR-AD.