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Journal of Lipids 2018The primary purpose of the epidermis of terrestrial vertebrates is to produce the stratum corneum, which serves as the interface between the organism and the... (Review)
Review
The primary purpose of the epidermis of terrestrial vertebrates is to produce the stratum corneum, which serves as the interface between the organism and the environment. As such, the stratum corneum provides a permeability barrier which both limits water loss through the skin and provides a relatively tough permeability barrier. This provides for a degree of resistance to mechanical trauma and prevents or limits penetration of potentially harmful substances from the environment. The stratum corneum consists of an array of keratinized cells embedded in a lipid matrix. It is this intercellular lipid that determines the permeability of the stratum corneum. The main lipids here are ceramides, cholesterol, and fatty acids. In addition, the skin surface of mammals, including humans, is coated by a lipid film produced by sebaceous glands in the dermis and secreted through the follicles. Human sebum consists mainly of squalene, wax monoesters, and triglycerides with small proportions of cholesterol and cholesterol esters. As sebum passes through the follicles, some of the triglycerides are hydrolyzed by bacteria to liberate free fatty acids. Likewise, near the skin surface, where water becomes available, some of the ceramides are acted upon by an epithelial ceramidase to liberate sphingosine, dihydrosphingosine, and 6-hydroxysphingosine. Some of the free fatty acids, specifically lauric acid and sapienic acid, have been shown to have antibacterial, antifungal, and antiviral activity. Also, the long-chain bases have broad spectrum antibacterial activity.
PubMed: 30245886
DOI: 10.1155/2018/5954034 -
The Journal of Investigative Dermatology Dec 2022Atopic dermatitis (AD) is a chronic inflammatory skin disease. Prevention of exacerbation of AD is a crucial issue for all physicians. However, exacerbation of AD often...
Atopic dermatitis (AD) is a chronic inflammatory skin disease. Prevention of exacerbation of AD is a crucial issue for all physicians. However, exacerbation of AD often is seen during reduction of AD treatment, even with appropriate follow-up by tapered topical corticosteroids and daily topical moisturizers, indicating the need for good indicators of AD remission. We hypothesized that the presence of mutations in FLG or the stratum corneum ceramide profile on AD remission phase may predict the ease of AD exacerbation. This study examined the differences in the frequency of FLG mutations or stratum corneum ceramide profiles (stratum corneum levels and carbon chain length for 11 ceramide classes [ceramides containing nonhydroxy fatty acids and dihydrosphingosines; nonhydroxy fatty acids and sphingosines; nonhydroxy fatty acids and 6-hydroxysphingosines; nonhydroxy fatty acids and phytosphingosines; a-hydroxy fatty acids and dihydrosphingosines; a-hydroxy fatty acids and sphingosines; a-hydroxy fatty acids and 6-hydroxysphingosines; a-hydroxy fatty acids and phytosphingosines; ester-linked fatty acids, o-hydroxy fatty acids, and sphingosines; ester-linked fatty acids, o-hydroxy fatty acids, and 6-hydroxysphingosines; and ester-linked fatty acids, o-hydroxy fatty acids, and phytosphingosines]) at AD remission phase between the two AD study groups: subsequent exacerbation (‒) and (+) of AD. The frequency of FLG mutations did not differ between the study groups. On the other hand, the carbon chain lengths of ceramides containing nonhydroxy fatty acids and dihydrosphingosines, nonhydroxy fatty acids and sphingosines, and nonhydroxy fatty acids and 6-hydroxysphingosines were shorter in the exacerbated AD group than in the maintained-AD group. Thus, the stratum corneum ceramide profile at the remission phase of AD is a potential biomarker, predicting the likelihood of substantial AD remission or subsequent AD exacerbation.
Topics: Humans; Ceramides; Dermatitis, Atopic; Fatty Acids; Esters; Carbon
PubMed: 35870561
DOI: 10.1016/j.jid.2022.06.012 -
Cureus Aug 2022Thismanuscript focuses on the physiological, environmental, nutritional, circadian, and aging factors affecting skin tissue water and hydration parameters. The... (Review)
Review
Thismanuscript focuses on the physiological, environmental, nutritional, circadian, and aging factors affecting skin tissue water and hydration parameters. The literature findings indicate a multiplicity of interacting processes among these parameters, ultimately impacting skin hydration in normal skin and playing a role in conditions such as atopic dermatitis and psoriasis. The maintenance of adequate skin hydration, aided by the proper functioning of the skin's protective barrier, is facilitated by stratum corneum integrity with the presence of tight junctions and lipids such as ceramides, each of which is impacted by changes in most of the evaluated parameters. Abnormalities in aquaporin 3 (AQP3) expression and associated deficits in skin hydration appear to have a role in atopic dermatitis and psoriasis. AQP3 hydration-related aspects are influenced by circadian rhythms via modulations associated with CLOCK genes that alter AQP3 protein expression. Ultraviolet exposure, aging, and low temperatures are among those factors that affect skin ceramide composition, potentially leading to increased transepidermal water loss and negatively impacting skin hydration. Vitamin C, collagen, and probiotics may increase ceramide production and improve skin hydration. The extent to which each of the different evaluated factors affects skin hydration varies but is usually large enough to consider their potential effects when investigating skin in research and clinical settings.
PubMed: 36072192
DOI: 10.7759/cureus.27666 -
Dermatology Online Journal Mar 2018Circumscribed palmar hypokeratosis (CPH) is a benign dermatologic condition characterized by local thinning of the stratum corneum. Herein, we present a 52-year-old...
Circumscribed palmar hypokeratosis (CPH) is a benign dermatologic condition characterized by local thinning of the stratum corneum. Herein, we present a 52-year-old woman who presented with an asymptomatic pink depressed papule on the right palm. This was treated with clobetasol 0.05% topically twice a day with no improvement.
Topics: Biopsy; Epidermis; Female; Hand; Hand Dermatoses; Humans; Keratosis; Middle Aged
PubMed: 29634888
DOI: No ID Found -
Frontiers in Immunology 2023The skin functions as a physical barrier and represents the first line of the innate immune system. There is increasing evidence that toll-like receptors (TLRs) are... (Review)
Review
The skin functions as a physical barrier and represents the first line of the innate immune system. There is increasing evidence that toll-like receptors (TLRs) are involved in the pathomechanisms of not only infectious diseases, but also non-infectious inflammatory diseases. Interestingly, it has been demonstrated that TLRs recognize both exogenous threats, e.g. bacteria and viruses, and endogenous danger signals related to inflammation, cell necrosis, or tissue damage. Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease, which is associated with impaired skin barrier function, increased skin irritability to non-specific stimuli, and percutaneous sensitization. The impairment of skin barrier function in AD allows various stimuli, such as potential allergens and pathogens, to penetrate the skin and activate the innate immune system, including TLR signaling, which can lead to the development of adaptive immune reactions. In this review, I summarize the current understanding of the roles of TLR signaling in the pathogenesis of AD, with special emphasis on skin barrier function and inflammation.
Topics: Humans; Dermatitis, Atopic; Toll-Like Receptors; Skin; Inflammation; Necrosis; Noncommunicable Diseases
PubMed: 37731494
DOI: 10.3389/fimmu.2023.1239244 -
Progress in Lipid Research Nov 2023The barrier function of the skin is primarily located in the stratum corneum (SC), the outermost layer of the skin. The SC is composed of dead cells with highly... (Review)
Review
The barrier function of the skin is primarily located in the stratum corneum (SC), the outermost layer of the skin. The SC is composed of dead cells with highly organized lipid lamellae in the intercellular space. As the lipid matrix forms the only continuous pathway, the lipids play an important role in the permeation of compounds through the SC. The main lipid classes are ceramides (CERs), cholesterol (CHOL) and free fatty acids (FFAs). Analysis of the SC lipid matrix is of crucial importance in understanding the skin barrier function, not only in healthy skin, but also in inflammatory skin diseases with an impaired skin barrier. In this review we provide i) a historical overview of the steps undertaken to obtain information on the lipid composition and organization in SC of healthy skin and inflammatory skin diseases, ii) information on the role CERs, CHOL and FFAs play in the lipid phase behavior of very complex lipid model systems and how this knowledge can be used to understand the deviation in lipid phase behavior in inflammatory skin diseases, iii) knowledge on the role of both, CER subclasses and chain length distribution, on lipid organization and lipid membrane permeability in complex and simple model systems with synthetic CERs, CHOL and FFAs, iv) similarity in lipid phase behavior in SC of different species and complex model systems, and vi) future directions in modulating lipid composition that is expected to improve the skin barrier in inflammatory skin diseases.
Topics: Humans; Skin; Fatty Acids, Nonesterified; Epidermis; Skin Diseases; Ceramides
PubMed: 37666282
DOI: 10.1016/j.plipres.2023.101252 -
Membranes Jan 2023The stratum corneum (SC), the outer layer of the skin, plays a crucial role as a barrier protecting the underlying cells from external stress. The SC comprises three key...
The stratum corneum (SC), the outer layer of the skin, plays a crucial role as a barrier protecting the underlying cells from external stress. The SC comprises three key components: ceramide (CER), free fatty acid (FFA), and cholesterol, along with small fractions of cholesterol sulfate and cholesterol ester. In order to gain a deeper understanding about the interdependence of the two major components, CER and FFA, on the organizational, structural, and functional properties of the SC layer, a library of SC lipid liposome (SCLL) models was developed by mixing CER (phytosphingosine or sphingosine), FFA (oleic acid, palmitic acid, or stearic acid), cholesterol, and cholesterol sulfate. Self-assembly of the SC lipids into lamellar phases was first confirmed by small-angle X-ray scattering. Short periodicity and long periodicity phases were identified for SCLLs containing phytosphingosines and sphingosine CERs, respectively. Furthermore, unsaturation in the CER acyl and FFA chains reduced the lipid conformational ordering and packing density of the liposomal bilayer, which were measured by differential scanning calorimetry and Fourier transform infrared spectroscopy. The introduction of unsaturation in the CER and/or FFA chains also impacted the lamellar integrity and permeability. This extensive library of SCLL models exhibiting physiologically relevant lamellar phases with defined structural and functional properties may potentially be used as a model system for screening pharmaceuticals or cosmetic agents.
PubMed: 36837639
DOI: 10.3390/membranes13020135 -
Progress in Lipid Research Nov 2022Skin's effectiveness as a barrier to permeation of water and other chemicals rests almost entirely in the outermost layer of the epidermis, the stratum corneum (SC),... (Review)
Review
Skin's effectiveness as a barrier to permeation of water and other chemicals rests almost entirely in the outermost layer of the epidermis, the stratum corneum (SC), which consists of layers of corneocytes surrounded by highly organized lipid lamellae. As the only continuous path through the SC, transdermal permeation necessarily involves diffusion through these lipid layers. The role of the SC as a protective barrier is supported by its exceptional lipid composition consisting of ceramides (CERs), cholesterol (CHOL), and free fatty acids (FFAs) and the complete absence of phospholipids, which are present in most biological membranes. Molecular simulation, which provides molecular level detail of lipid configurations that can be connected with barrier function, has become a popular tool for studying SC lipid systems. We review this ever-increasing body of literature with the goals of (1) enabling the experimental skin community to understand, interpret and use the information generated from the simulations, (2) providing simulation experts with a solid background in the chemistry of SC lipids including the composition, structure and organization, and barrier function, and (3) presenting a state of the art picture of the field of SC lipid simulations, highlighting the difficulties and best practices for studying these systems, to encourage the generation of robust reproducible studies in the future. This review describes molecular simulation methodology and then critically examines results derived from simulations using atomistic and then coarse-grained models.
Topics: Ceramides; Epidermis; Skin; Fatty Acids, Nonesterified; Cholesterol
PubMed: 35988796
DOI: 10.1016/j.plipres.2022.101184 -
Dermatology Online Journal Feb 2017Tinea versicolor (TV) is typically an asymptomatic fungal infection of the stratum corneum owing to Malassezia overgrowth. It presents as hypo or hyperpigmented macules...
Tinea versicolor (TV) is typically an asymptomatic fungal infection of the stratum corneum owing to Malassezia overgrowth. It presents as hypo or hyperpigmented macules with fine scale that coalesce into patches on the trunk, neck, and/or arms. Presented in this report is a 34-year-old man with an interesting case of folliculocentric tinea versicolor manifesting as perifollicular hypopigmented macules on the lower back.
Topics: Adult; Hair Follicle; Humans; Hypopigmentation; Male; Tinea Versicolor
PubMed: 28329492
DOI: No ID Found -
Skin Research and Technology : Official... Jan 2023Physiological skin properties of neonates and infants change drastically after birth and are implicated in the onset of atopic dermatitis and other diseases. Studies...
BACKGROUND
Physiological skin properties of neonates and infants change drastically after birth and are implicated in the onset of atopic dermatitis and other diseases. Studies have measured physiological skin properties in infants; however, how these properties change over time remains unclear. No reports have measured ceramide in the stratum corneum of infants using confocal Raman spectroscopy; hence, we used it to measure the physiological properties of the skin, including ceramide, in infants.
MATERIALS AND METHODS
The water content and other factors in the skin of infants aged 0, 1, and 6 months were measured. All measurements were performed five times indoors at 22 ± 2°C and 50% ± 10% relative humidity in the middle of the calf at 4-µm distances, and their mean was calculated.
RESULTS
The water content of the area between the skin surface and superficial layers was the lowest in newborns as compared with other ages, and the deeper the skin layer, the higher the water content. The stratum corneum, evaluated using confocal Raman spectroscopy, was the thickest in newborns and gradually thinned with age. Its water content was the lowest in newborns. The levels of natural moisturizing factor, ceramide, and cholesterol were higher in newborns and tended to decrease with age.
CONCLUSION
This report is the first to evaluate ceramide in the stratum corneum of infants using confocal Raman spectroscopy and could help in conducting subsequent longitudinal measurements of physiological skin properties in neonates and infants.
Topics: Humans; Infant; Infant, Newborn; Pilot Projects; Spectrum Analysis, Raman; East Asian People; Epidermis; Skin; Water; Ceramides
PubMed: 36704885
DOI: 10.1111/srt.13276