An Investigation into the Effect of the Nitric Oxide Synthase Antagonist L-NAME and Plant Extracts on the Irritability and Barrier Function of the Skin

Background: Nitric oxide (NO) synthesis is upregulated in dermatitis and may be involved in the modulation of keratinocyte proliferation and formation of the cornified envelope. Objective: To examine the possible effects of modulators of NO production on erythema and transepidermal water loss (TEWL) induced by sodium lauryl sulphate (SLS). Methods: Ten volunteers were patch tested with water and SLS 0.2, 0.5 and 1%. The outcomes of TEWL and erythema were assessed at 1, 6, 25 and 49 h. The effects of the NO inhibitors, L-NAME, extracts of Olea europa and Ginkgo biloba (as 1% gel solutions) and of the NO donor, glyceryl trinitrate (as 2% ointment) were evaluated. Results: L-NAME and the plant extracts reduced TEWL. The TEWL induced by 0.5% SLS was significantly diminished by L-NAME at 1 and 6 h and by ginkgo extract at 6 and 49 h. Erythema was too mild for reflectance measurements to show significant inhibition, but erythema scores tended to be lower at 6 h the application of NO inhibitors. Conclusion: NO inhibitors may protect skin barrier function from the adverse effects of chemical irritants.