피부장벽과 항균작용 = Skin barrier and antimicrobial activity

다국어 초록 (Multilingual Abstract)

The human skin is constantly exposed to microbial pathogens but infections only rarely occur. The stratum corneum (SC) (i.e., the outermost layer of human skin) composed of corneocytes and a matrix of intercellular lipids playing an essential role as the skin`s protective barrier. In order to protect the epidermis and to maintain its integrity, the SC uses various strategies, including enzymatic reactions, colonization by bacterial flora, immune signaling, antimicrobial lipids and peptides, low pH, antioxidants, and natural moisturizing factor(s). Innate cutaneous immunity is a primary system for protection against infection, and antimicrobial peptides (AMPs) expressed in skin are essential defense molecules. Cutaneous AMPs are multifunctional molecules, killing the microbes or inhibit their growth with a broad-spectrum of antimicrobial activity. Their amino acid composition, amphipathicity, cationic charge and small size allow them to attach to and insert into microbial membrane bilayers to form pores. Also, they are playing a role as signaling molecules, which could mediate host inflammation. Several skin diseases such as atopic dermatitis, psoriasis, and rosacea are associated with AMP dysfunction. In atopic eczema, for example, cathelicidin expression is suppressed, whereas in rosacea cathelicidin peptides are abnormally processed to forms that induce cutaneous inflammation and a vascular response. In psoriasis cathelicidin peptide converts self-DNA to a potent stimulus in an autoinflammatory cascade. Cutaneous vitamin D3 system and pro-inflammatory cytokines (IL-1, TNF-α, and IFN-γ) are known as a major factor involved in the regulation of antimicrobial barrier as well as permeability barrier. The strategies for control or application of AMPs might provide new approaches in both medicine and related industry. This minireview reports on current understanding of the antimicrobial barrier function of the skin.