Journal of Clinical and Aesthetic Dermatology

Epidermal Barrier Supplement 2016

An evidence-based, peer-reviewed journal for practicing clinicians in the field of dermatology

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U nderstanding the Epidermal Barrier in Healthy and Compromised Skin: Clinically Relevant Information for the Dermatology Practitioner [APRIL 2016 • VOLUME 9 • NUMBER 4 • SUPPLEMENT 1] SUPPLEMENT TO THE JOURNAL OF CLINICAL AND AESTHETIC DERMATOLOGY S3 TABLE 1. The stratum corneum and simultaneous multitasking: Individual epidermal barrier functions BARRIER FUNCTION MAJOR COMPONENTS PERMEABILITY BARRIER Formation of stratum corneum lipids in specific ratio from precursor lipids Production of lamellar bodies packaging precursor lipids and some antimicrobial peptides Formation of natural moisturizing factor from filaggrin (converted from profillagrin) Formation of cornified envelope and the corneocyte-lipid envelope Maintenance of water gradient, calcium gradient, acid mantle (acidic pH) Response of primary proinflammatory cytokines to impairment of permeability barrier ANTIMICROBIAL BARRIER Maintenance of an acidic skin pH decreases skin colonization by pathogenic bacteria and yeasts Antibacterial activity of stratum corneum lipids (e.g., free fatty acids, sphingosine, others) Genetically encoded primary antimicrobial peptides (defensins, cathelicidins, dermcidins) synthesized in SC, present in sebum and in sweat (dermicidin-derived) Multiple agents with antimicrobial activity as alternative function (some chemokines, some neuropeptides, others) ANTIOXIDANT BARRIER Network of enzymatic and nonenzymatic antioxidant systems to counter oxidative stress Antioxidants present in epidermis (stratum corneum, skin surface lipids) and dermis Hydrophilic nonenzymatic antioxidants include ascorbic acid (vitamin C) and uric acid Major lipid-soluble nonenzymatic antioxidant is alpha-tocopherol (vitamin E) Co-antioxidants (ascorbic acid, ubiquinol [coenzyme Q10]) allow tocopherol regeneration Gradients in stratum corneum for ascorbic acid and tocopherol (lowest near surface) Interceptive antioxidant enzymes (catalase, superoxide dismutases, glutathione peroxidases) Antioxidant repair enzymes (e.g., methionine sulfoxide reductase) High concentration of alpha-tocopherol in sebum accounts for high levels in facial sebaceous gland stratum corneum (sebum serves as a physiological delivery pathway) IMMUNE RESPONSE BARRIER Dendritic cells involved in immune surveillance and antigen recognition (e.g., plasmacytoid dendritic cells, myeloid dendritic cells, Langerhans cells) Toll-like receptors involved in recognition of microbial pathogens and other agonists Antimicrobial peptides and some of their enzymatic conversion products (e.g., LL-37) Innate and acquired immune response pathways and balance with T regulatory cell system PHOTOPROTECTION BARRIER Epidermal melanin barrier (degree of protection related to Fitzpatrick skin ttype) Stratum corneum protein barrier Antioxidants within stratum corneum (protection against photo-oxidative stress) Optical reflective properties of the stratum corneum (stratum corneum thickness more important than epidermal thickness for ptrotection against ultraviolet/solar radiation) Reprinted with permission from: Del Rosso JQ, Levin J. The clinical relevance of maintaining the functional integrity of the stratum corneum in both healthy and disease-affected skin. J Clin Aesthet Dermatol. 2011;4(9): 22–42. © 2011 Matrix Medical Communications

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