Prior work from our group has shown that the permeability and antimicrobial barriers in normal skin share many common features, and are co-regulated, such that perturbations in one function inevitably impact the other. We also showed that a variety of conditions that compromise the permeability barrier, including neonatal and aging skin, are also accompanied by a reduction in the production of the cathelicidin antimicrobial peptide, LL-37, a key defender against S. Aureus and Streptococcal infections.
In this study, we asked whether strategies that improve permeability barrier function also enhance production of LL-37. We first assessed the effects of a variety of ingredients, commonly included in cosmetic and prescription devices, such as urea, petrolatum, and activators of a family of lipid-sensing receptors in the same family as retinoids and vitamin D, that we had previously shown enhance skin barrier funciton. We also tested a triple-lipid prescription device (EpiCeram® emulsion). Previously, we had demonstrated that only EpiCeram® among a large cohort of OTC and prescription ‘barrier-repair’ formulations, accelerated barrier repair both in normal and atopic dermatitis skin. In all cases, agents that improved permeability barrier function stimulated the production of LL-37 in parallel, and the EpiCeram formulation also stimulated the secretion of LL-37.
Bottom Line: These results show that a variety of approaches that enhance permeability barrier function also likely improve the skin’s defense against invading pathogenic microorganisms.