Omega-hydroxyceramides are required for corneocyte lipid envelope (CLE) formation and normal epidermal permeability barrier function

J Invest Dermatol. 2000 Jan;114(1):185-92. doi: 10.1046/j.1523-1747.2000.00846.x.


Omega-hydroxyceramides (omega-OHCer) are the predominant lipid species of the corneocyte lipid envelope in the epidermis. Moreover, their omega-esterified-derivatives (acylCer) are major components of the stratum corneum extracellular lamellae, which regulate cutaneous permeability barrier function. Because epidermal omega-OHCer appear to be generated by a cytochrome P450-dependent process, we determined the effects of a mechanism-based inhibitor of omega-hydroxylation, aminobenzotriazole (ABT), on epidermal omega-OH Cer formation and barrier function. We first ascertained that ABT, but not hydroxybenzotriazole (OHBT), a chemical relative with no P450 inhibitory activity, inhibited the incorporation of [14C]-acetate into the omega-OH-containing Cer species in cultured human keratinocytes (68.1% +/- 6.9% inhibition versus vehicle-treated controls; p < 0.001), without altering the synthesis of other Cer and fatty acid species. In addition, ABT significantly inhibited the omega-hydroxylation of very long-chain fatty acids in cultured human keratinocytes. Topical application of ABT, but not OHBT, when applied to the skin of hairless mice following acute barrier disruption by tape-stripping, resulted in a significant delay in barrier recovery (e.g., 38.3% delay at 6 h versus vehicle-treated animals), assessed as increased transepidermal water loss. The ABT-induced barrier abnormality was associated with: (i) a significant decrease in the quantities of omega-OHCer in both the unbound and the covalently bound Cer pools; (ii) marked alterations of lamellar body structure and contents; and (iii) abnormal stratum corneum extracellular lamellar membrane structures, with no signs of cellular toxicity. Furthermore, pyridine-extraction of ABT- versus vehicle-treated skin, which removes all of the extracellular lamellae, leaving the covalently attached lipids, showed numerous foci with absent corneocyte lipid envelope in ABT- versus vehicle-treated stratum corneum. These results provide the first direct evidence for the importance of omega-OHCer for epidermal permeability function, and suggest further that acylCer and/or corneocyte lipid envelope are required elements in permeability barrier homeostasis.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Administration, Topical
  • Animals
  • Ceramides / antagonists & inhibitors
  • Ceramides / metabolism
  • Ceramides / physiology*
  • Epidermal Cells
  • Epidermis / drug effects
  • Epidermis / metabolism
  • Epidermis / physiology*
  • Homeostasis / drug effects
  • Humans
  • Hydroxylation / drug effects
  • Keratinocytes / metabolism
  • Keratinocytes / physiology*
  • Lipids / physiology*
  • Male
  • Membrane Proteins / physiology*
  • Mice
  • Mice, Hairless
  • Nuclear Envelope / physiology
  • Organelles / drug effects
  • Permeability / drug effects
  • Reference Values
  • Triazoles / pharmacology


  • Ceramides
  • Lipids
  • Membrane Proteins
  • Triazoles
  • 1-aminobenzotriazole