title: Release by ultraviolet B (u.v.B) radiation of nitric oxide (NO) from human keratinocytes: a potential role for nitric oxide in erythema production.
abstract: 1. The mechanism of human sunburn is poorly understood but its characteristic features include the development of erythema. In this study we attempted to determine whether human keratinocytes possess a nitric oxide (NO) synthase (NOS), if this enzyme could be activated to release NO following exposure to ultraviolet B (u.v.B) and to define whether this photo-induced response could be involved in the pathogenesis of sunburn erythema. 2. Treatment of human keratinocytes with various doses of u.v.B (290-320 nm) radiation (up to 100 mJ cm-2) resulted in a dose-dependent release of NO and cyclic GMP production that was reduced by NG-monomethyl-L-arginine (L-NMMA). 3. u.v.B irradiation of keratinocyte cytosol at varying doses (up to 50 mJ cm-2), resulted in a gradual rise in NO production, with a concomitant increase in soluble guanylate cyclase activity (sGC). 4. NOS isolated from the keratinocyte cytosol was constitutively expressed and was dependent on NADPH, Ca2+/calmodulin, tetrahydrobiopterin and flavins. 5. In reconstitution experiments, when purified NOS was added to purified sGC, both isolated from keratinocyte cytosol, a four fold increase in cyclic GMP was observed. The GMP was increased by NO synthesized following u.v.B radiation (up to 20 mJ cm-2) of NOS. 6. In in vivo experiments, guinea-pigs were subjected to u.v.B light. A Protection Factor (PF) of 8.71 +/- 2.85 was calculated when an emulsified cream formulation containing L-NMMA (2%) was applied to their skin. 7. The present results indicate that u.v.B radiation acts as a potent stimulator of NOS in keratinocytes. NO is lipophilic and may diffuse out of the keratinocytes, activating sGC in endothelial cells and neighbouring smooth muscle cells. This may be a major part of the integrated response of the skin leading to vasodilatation and erythema.
authors.affiliation: Department of Physiology, University of Athens Medical School, Greece.
authors.forename: G
authors.initials: G
authors.lastname: Deliconstantinos
authors.forename: V
authors.initials: V
authors.lastname: Villiotou
authors.forename: J C
authors.initials: JC
authors.lastname: Stravrides
mesh_terms: D000818:Animals; D002956:Citrulline / Q000096:biosynthesis; D003600:Cytosol / Q000378:metabolism / Q000528:radiation effects; D004890:Erythema / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D006157:Guanosine Monophosphate / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism / Q000528:radiation effects*; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D012867:Skin / Q000098:blood supply; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays
chemical_list: D002956:Citrulline; D009569:Nitric Oxide; D006157:Guanosine Monophosphate