title: The effect of bilayer and hexagonal H(II) phase lipid films on transepidermal water loss.
abstract: The common membrane phospholipids tend to adopt either the familiar bilayer phase or the less familiar hexagonal H(II) phase when isolated and hydrated in excess water. The objective of this study was to compare the effects of these very different macroscopic lipid structures on transepidermal water loss (TEWL) when they are applied to the surface of pig skin mounted in Franz diffusion cells. First, a novel in vitro method for monitoring TEWL was developed and characterized in which the flux of water from the subphase through skin was measured through the absorption of (3H)-water by lyophilized polyethylene glycol (PEG) mounted above the skin surface. TEWL was varied by disrupting the skin barrier to different degrees by tape stripping or solvent extraction. Bilayer-forming egg phosphatidylcholine (EPC) or hexagonal H(II)-forming dioleoyl phosphatidylethanolamine (DOPE) were applied topically as solutions in ethanol and subsequently dried to films. The molecular configuration adopted by each lipid at the skin surface was confirmed by phosphorus NMR. TEWL for normal skin was approximately 2 g H2O/h/m2, increasing to a maximum of 80 g H2O/h/m2 after the stratum corneum was completely removed by tape stripping. On tape-stripped skin, films of lipid doses as low as 10 mg/cm2 significantly reduced TEWL, and DOPE (hexagonal H(II)) was approximately twofold more effective than EPC (bilayer). Furthermore, the effects of EPC and Vaseline on reducing TEWL from damaged skin were readily reversed by a simple aqueous wash, whereas the DOPE effect was unaltered even by vigorous washing. Similar results were obtained with lipid films applied to solvent-extracted skin. The data are consistent with the formation of extensive hydrophobic interactions between the skin and the outwardly facing acyl chains of the inverted, hexagonal H(II) phase adopted by DOPE. This results in the formation of a durable surface barrier capable of significantly reducing TEWL from damaged skin.
authors.affiliation: University of British Columbia, Vancouver, BC, Canada.
authors.forename: Sameersingh G
authors.initials: SG
authors.lastname: Raney
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hope
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D002725:Chloroform / Q000494:pharmacology; D004643:Emollients / Q000737:chemistry / Q000494:pharmacology; D004817:Epidermis / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D005260:Female; D008051:Lipid Bilayers / Q000737:chemistry / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy; D000432:Methanol / Q000494:pharmacology; D010577:Petrolatum / Q000494:pharmacology; D010713:Phosphatidylcholines / Q000737:chemistry / Q000494:pharmacology; D010714:Phosphatidylethanolamines / Q000737:chemistry / Q000494:pharmacology; D010743:Phospholipids / Q000737:chemistry / Q000494:pharmacology*; D011092:Polyethylene Glycols / Q000737:chemistry; D012867:Skin / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D013552:Swine; D014867:Water / Q000737:chemistry / Q000378:metabolism*
chemical_list: C410262:1,2-dioleoyl-glycero-3-phosphatidyl ethanolamine; D004643:Emollients; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010743:Phospholipids; D014867:Water; D011092:Polyethylene Glycols; D002725:Chloroform; D010577:Petrolatum; D000432:Methanol