The skin of the ear and the back are frequently selected sites in skin research using mouse models. However, distinct responses to treatment have been described between these two sites in several... Show moreThe skin of the ear and the back are frequently selected sites in skin research using mouse models. However, distinct responses to treatment have been described between these two sites in several studies. Despite the crucial role of the stratum corneum (SC) in the skin barrier function of both dorsal back and ear skin, it remains unclear whether differences in lipid composition might underlie altered responses. Here, we compared the skin morphology and the barrier lipid composition of the ear with the back skin of wild-type mice. The ear contained more corneocyte layers in the SC and its barrier lipid composition was enriched with sphingosine ceramide subclasses, especially the short ones with a total chain length of 33-34 carbons. The free fatty acid (FFA) profile in the ear skin shifted towards shorter chains, significantly reducing the mean chain length to 23.3 vs 24.7 carbons in the back skin. In line, FFA species in the ear displayed a twofold increase in unsaturation index (P < .001). Gene expression in the ear skin revealed low expression of genes involved in lipid synthesis and uptake, indicating a reduced metabolic activity. Finally, the effects of hypercholesterolaemia on SC FFA composition was compared in ear and back skin of apolipoprotein E knockout (APOE(-/-)) mice. Interestingly, the FFA profile in APOE(-/-) ear skin was minimally affected, while the FFA composition in the back skin was markedly changed in response to hypercholesterolaemia. In conclusion, ear and back skin have distinct barrier lipids and respond differently to elevated plasma cholesterol. Show less
Smeden, J. van; Al-Khakany, H.; Wang, Y.; Visscher, D.; Stephens, N.; Absalah, S.; ... ; Bouwstra, J.A. 2020
Individuals with Netherton syndrome (NTS) have increased serine protease activity, which strongly impacts the barrier function of the skin epidermis and leads to skin inflammation. Here, we... Show moreIndividuals with Netherton syndrome (NTS) have increased serine protease activity, which strongly impacts the barrier function of the skin epidermis and leads to skin inflammation. Here, we investigated how serine protease activity in NTS correlates with changes in the stratum corneum ceramides, which are crucial components of the skin barrier. We examined two key enzymes involved in epidermal ceramide biosynthesis, glucocerebrosidase (GBA) and acid-sphingomyelinase (ASM). We compared in situ expression levels and activities of GBA and ASM between NTS patients and controls and correlated the expression and activities with i) stratum corneum ceramide profiles, ii) in situ serine protease activity, and iii) clinical presentation of patients. Using activity-based probe labeling, we visualized and localized active, epidermal GBA, and a newly developed in situ zymography method enabled us to visualize and localize active ASM. Reduction in active GBA in NTS patients coincided with increased ASM activity, particularly in areas with increased serine protease activity. NTS patients with scaly erythroderma exhibited more pronounced anomalies in GBA and ASM activities than patients with ichthyosis linearis circumflexa. They also displayed a stronger increase in stratum corneum ceramides processed via ASM. We conclude that changes in the localization of active GBA and ASM correlate with i) altered stratum corneum ceramide composition in NTS patients, ii) local serine protease activity, and iii) the clinical manifestation of NTS. Show less
Boer, D.E.C.; Smeden, J. van; Al-Khakany, H.; Melnik, E.; Dijk, R. van; Absalah, S.; ... ; Bouwstra, J.A. 2020
Patients with Atopic Dermatitis (AD) suffer from inflamed skin and skin barrier defects. Proper formation of the outermost part of the skin, the stratum corneum (SC), is crucial for the skin... Show morePatients with Atopic Dermatitis (AD) suffer from inflamed skin and skin barrier defects. Proper formation of the outermost part of the skin, the stratum corneum (SC), is crucial for the skin barrier function. In this study we analyzed the localization and activity of lipid enzymes β-glucocerebrosidase (GBA) and acid sphingomyelinase (ASM) in the skin of AD patients and controls. Localization of both the expression and activity of GBA and ASM in the epidermis of AD patients was altered, particularly at lesional skin sites. These changes aligned with the altered SC lipid composition. More specifically, abnormal localization of GBA and ASM related to an increase in specific ceramide subclasses [AS] and [NS]. Moreover we related the localization of the enzymes to the amounts of SC ceramide subclasses and free fatty acids (FFAs). We report a correlation between altered localization of active GBA and ASM and a disturbed SC lipid composition. Localization of antimicrobial peptide beta-defensin-3 (HBD-3) and AD biomarker Thymus and Activation Regulated Chemokine (TARC) also appeared to be diverging in AD skin compared to control. This research highlights the relation between correct localization of expressed and active lipid enzymes and a normal SC lipid composition for a proper skin barrier. Show less
Martins Cardoso, R.; Creemers, E.; Absalah, S.; Hoekstra, M.; Gooris, G.S.; Bouwstra, J.A.; Eck, M. van 2019
Scavenger receptor class B type I (SR-BI) mediates the selective uptake of cholesteryl esters (CE) from high-density lipoproteins (HDL). An impaired SR-BI function leads to... Show moreScavenger receptor class B type I (SR-BI) mediates the selective uptake of cholesteryl esters (CE) from high-density lipoproteins (HDL). An impaired SR-BI function leads to hyperalphalipoproteinemia with elevated levels of cholesterol transported in the HDL fraction. Accumulation of cholesterol in apolipoprotein B (apoB)-containing lipoproteins has been shown to alter skin lipid composition and barrier function in mice. To investigate whether these hypercholesterolemic effects on the skin also occur in hyperalphalipoproteinemia, we compared skins of wild-type and SR-BI knockout (SR-BI−/−) mice. SR-BI deficiency did not affect the epidermal cholesterol content and induced only minor changes in the ceramide subclasses. The epidermal free fatty acid (FFA) pool was, however, enriched in short and unsaturated chains. Plasma CE levels strongly correlated with epidermal FFA C18:1 content. The increase in epidermal FFA coincided with downregulation of cholesterol and FFA synthesis genes, suggesting a compensatory response to increased flux of plasma cholesterol and FFAs into the skin. Importantly, the SR-BI−/− epidermal lipid barrier showed increased permeability to ethyl-paraminobenzoic acid, indicating an impairment of the barrier function. In conclusion, increased HDL-cholesterol levels in SR-BI−/− mice can alter the epidermal lipid composition and lipid barrier function similarly as observed in hypercholesterolemia due to elevated levels of apoB-containing lipoproteins. Show less
Berkers, M.A.J.; Boiten, W.A.; Absalah, S.; Smeden, J. van; Lavrijsen, A.P.M.; Bouwstra, J.A. 2019
Ex vivo regenerated stratum corneum (SC) after tape-stripping can be used as a model to study the barrier function of compromised skin. Yet, details about how close the regenerated SC model mimics... Show moreEx vivo regenerated stratum corneum (SC) after tape-stripping can be used as a model to study the barrier function of compromised skin. Yet, details about how close the regenerated SC model mimics the lipid properties (e.g. lipid composition and lipid ordering) of the in vivo situation are not known. Here, we examined using a comprehensive ceramide analysis whether human ex vivo regenerated SC showed similar lipid properties as human in vivo regenerated SC. Both in vivo and ex vivo regenerated SC had an altered ceramide subclass composition, with increased percentages of sphingosine-based subclass and decreased percentages of phytosphingosine-based subclass ceramides, a reduced mean ceramide chain length, and a higher percentage of unsaturated ceramides. Overall, regenerated SC ex vivo showed more pronounced but similar changes compared to the in vivo response. One of the purposes of these models is to use them to mimic compromised skin of inflammatory skin diseases. The altered lipid properties in regenerated SC were comparable to those observed in several inflammatory skin diseases, which makes them a valuable model for the barrier properties in inflammatory skin diseases. Show less
Cardoso, R.M.; Creemers, E.; Absalah, S.; Gooris, G.S.; Hoekstra, M.; Eck, M. van; Bouwstra, J.A. 2019
Long-term exposure to hypercholesterolemia induces the development of skin xanthoma's characterized by the accumulation of lipid-laden foam cells in humans and in mice. Early skin changes in... Show moreLong-term exposure to hypercholesterolemia induces the development of skin xanthoma's characterized by the accumulation of lipid-laden foam cells in humans and in mice. Early skin changes in response to hypercholesterolemia are however unknown. In this study, we investigated the skin lipid composition and associated barrier function in young adult low-density lipoprotein receptor knockout (LDLR−/−) and apolipoprotein E knockout (APOE−/−) mice, two commonly used hypercholesterolemic mouse models characterized by the accumulation of apolipoprotein B containing lipoproteins. No effects were observed on cholesterol content in the epidermis in LDLR−/− mice nor in the more extremely hypercholesterolemic APOE−/− mice. Interestingly, the free fatty acids in the APOE−/− epidermis shifted towards shorter and unsaturated chains. Genes involved in the synthesis of cholesterol and fatty acids were downregulated in APOE−/− skin suggesting a compensation for the higher influx of plasma lipids, most probably as cholesteryl esters. Importantly, in vivo transepidermal water loss and permeability studies with murine lipid model membranes revealed that the lipid composition of the APOE−/− skin resulted in a reduced skin barrier function. In conclusion, severe hypercholesterolemia associated with increased apolipoprotein B containing lipoproteins affects the epidermal lipid composition and its protective barrier. Show less
Boiten, W.A.; Berkers, M.A.J.; Absalah, S.; Smeden, J. van; Lavrijsen, A.P.M.; Bouwstra, J.A. 2018
In several skin diseases both the lipid composition and organization in the stratum corneum (SC) are altered which contributes to the impaired skin barrier function in patients. One of the... Show moreIn several skin diseases both the lipid composition and organization in the stratum corneum (SC) are altered which contributes to the impaired skin barrier function in patients. One of the approaches for skin barrier repair is treatment with topical formulations to normalize SC lipid composition and organization. Vernix caseosa, a white cheesy cream on the skin during gestational delivery, has shown to enhance skin barrier repair. In the present study, we examined how a fatty acid containing formulation mimicking the lipid composition of vernix caseosa interacts with the lipid matrix in the SC. The formulation was applied on ex vivo human skin after SC removal. Subsequently, the ex vivo human skin generated SC during culture. The effect of fatty acid (FA) containing formulations on the lipid organization and composition in the regenerated SC was analyzed by Fourier transformed infrared (FTIR) spectroscopy and liquid chromatography mass spectroscopy (LC/MS), respectively. FTIR results demonstrate that the FAs are intercalated in the lipid matrix of the regenerated SC and partition in the same lattice with the endogenous SC lipids, thereby enhancing the fraction of lipids forming an orthorhombic (very dense) packing in the SC. LC/MS data show that the topically applied FAs are elongated before intercalation in the lipid matrix and are thus involved in the lipid biosynthesis in the skin. This article is protected by copyright. All rights reserved. Show less
