Date Published: April 16, 2019
Publisher: Public Library of Science
Author(s): Jin-Hyun Kim, Byungjun Ahn, Seon-Guk Choi, Sohyun In, A. Reum Goh, Sun-Gyoo Park, Cheon-Koo Lee, Nae-Gyu Kang, Mauro Picardo.
In the stratum corneum, the intercellular junction made up of cadherin proteins provides the structural integrity of the framework. Ca2+ ions are known to play a key role in maintaining this junction. In this study, we hypothesized that Ca2+ chelation in stratum corneum will weaken the bond of the tissue and consequently promote exfoliation. Amino acids, ubiquitously existing as metabolites and building blocks of the body, have the molecular property to chelate Ca2+ ions. In the current study, we verified the Ca2+ chelating property of amino acids and demonstrated that amino acids can interfere with the interaction of cadherins, separate stratum corneum into pieces, and thereby stimulate the exfoliation process of skin. These results validate the importance of Ca2+ ion in the skin exfoliation process. Importantly, our findings indicate that amino acids may be efficiently used for improving skin conditions.
Stratum corneum is the outermost barrier of the skin that maintains the internal physiological environment and prevents damage from the outside. It consists of corneocytes formed by the differentiation of epidermal keratinocyte cells and intercellular lipid matrix filling between the cornified cells. Corneocytes are interconnected by corneodesmosomes, which are adhesive junctions imparting structural integrity to stratum corneum. The intercellular attachments of corneodesmosomes consist of two transmembrane proteins belonging to the cadherin superfamily, mainly desmoglein1 (Dsg1) and desmocollin1 (Dsc1). Classical cadherins have an overall modular structure of four to five extracellular cadherin (EC) domains and are dimerized by swapping N-terminal β-strands in EC1 domains from opposite cells . Dsg1 and Dsc1 have been reported to bind each other through the ‘strand-swap’ mechanism similar to classical cadherins, except that the binding occurs through heterophilic interaction by opposite charge in the binding interface of Dsg1 and Dsc1 . In the exfoliation process, Dsg1 and Dsc1 are detached and corneocytes are shed into the environment .
In this study, we demonstrated that amino acids, such as serine, disrupt Ca2+-dependent adhesion of stratum corneum. Our observations indicate that this function could be attributed to the Ca2+ chelating property of amino acids. Molecules with similar Ca2+ ion chelating abilities are expected to have similar efficacy in stratum corneum. Further studies are necessary to examine the effects of such molecules, including amino acids, on human skin.