アミノ酸誘導体型界面活性剤ラウロイル‐β‐アラニンの皮膚に及ぼす影響

Abstract

Lauroyl beta-alanine (LBA) is a unique amino acid derivative-surfactant which has recently been found to have very low potential of inducing a specific inflammationrelated receptor on epidemal cells, intercellular adhesion molecule-1 (ICAM-1) when incubated with human keratinocytes. This led us to assume that this surfactant possesses very low cutaneous inflammatory properties as opposed to ordinary commercially available anionic surfactants. Thus, we have assessed the biologic effects of LBA on several cellular derangements in the stratum comeum, cytotoxicity against human keratinocytes and an influence on arachidonic metabolism in skin tissue in comparison with those by other ordinary anionic surfactants such as potassium myristate (SOAP), sodium dodecyl sulfate (SDS), sodium cocoyl isethionate (SCI), acylmethyl taurine (AMT) and monoalkyl phosphate (MAP).Permeability experiments using hairless pig skin indicated that LBA is 10 and 3 times as lower permeable as SOAP and MAP, respectively. In in vitro study on human keratinocytes, of all anionic surfactants used, LBA showed the lowest inhibitory effect on cell growth which was accompanied by a lower level of the release of arachidonic metabolite such as prostaglandin E2 (PGE2) from human keratinocytes. This mild cellular effect was also corroborated by the previous observations that LBA elicits on substantial expression of ICAM-1 which has recently been identified on surface of epidermal cells in inflammatory dermatosis typified by T cell infiltration, in contrast to a marked expression by some of other anionic surfactants.In order to clarify in vivo cutaneous effect, cumulative cup shaking test was carried out on the inner surface of human forearm skin by applying surfactant aqueous solutions twice a day for four days. Whereas almost all anionic surfactants induced severe scaling and erythematous reactions during repeated treatments, LBA was the only surfactant which did not elicit any roughness and inflammatory reaction. This non-inflammatory property was also corroborated by an additional study on damaged skin that roughened forearm skin after acetone/ether treatment can be slightly restored even by successive applications of LBA, but not other anionic surfactants used. These findings indicate that LBA has biologically low active properties to both stratum coreum and epidermal cells which may lead to the development of a unique surfactant applicable to damaged skins.