title: Isoflavonoid photoprotection in mouse and human skin is dependent on metallothionein.
abstract: Previous studies report that selected topical isoflavonoids are immunoprotective in both mice and humans, when applied following UV irradiation. Isoflavonoids have documented antioxidant activity, but their mechanism of immunomodulation remains unclear. This study examines whether photoimmunoprotection by the isoflavonoids might result from their interaction with one cutaneous antioxidant known to modulate UV photodamage, metallothionein (MT). In mice bearing a null mutation for MT-I and -II, we found that immunoprotection by the isoflavonoid 4',7-dihydroxyisoflavane (equol) against solar-simulated UV radiation (SSUV) or exogenous cis-urocanic acid was abrogated. Topical equol did not activate MT expression in normal mouse skin, but markedly enhanced the increase in MT expression in murine epidermis following SSUV irradiation. Normal human skin, unlike murine, expressed MT in the basal epidermis. Following SSUV irradiation, topical application of the related synthetic isoflavonoid NV-07alpha to human skin also markedly enhanced epidermal MT expression. The NV-07alpha has been reported previously to protect humans against the UV suppression of Mantoux reactions. Thus, epidermal MT expression appears to protect against photoimmunosuppression in both human and mouse skin. We speculate that equol and its related derivative NV-07alpha may activate the MT gene synergistically with SSUV, to produce the enhanced immunoprotective effect.
authors.affiliation: Faculty of Veterinary Science, University of Sydney, New South Wales, Australia.
authors.forename: Sitarina
authors.initials: S
authors.lastname: Widyarini
authors.forename: Munif
authors.initials: M
authors.lastname: Allanson
authors.forename: Nerida L
authors.initials: NL
authors.lastname: Gallagher
authors.forename: Julie
authors.initials: J
authors.lastname: Pedley
authors.forename: Glen M
authors.initials: GM
authors.lastname: Boyle
authors.forename: Peter G
authors.initials: PG
authors.lastname: Parsons
authors.forename: David C
authors.initials: DC
authors.lastname: Whiteman
authors.forename: Catherine
authors.initials: C
authors.lastname: Walker
authors.forename: Vivienne E
authors.initials: VE
authors.lastname: Reeve
mesh_terms: D000818:Animals; D003877:Dermatitis, Contact / Q000276:immunology* / Q000378:metabolism; D060754:Equol; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects*; D007529:Isoflavones / Q000008:administration & dosage* / Q000494:pharmacology; D008668:Metallothionein / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D012867:Skin / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: C007610:4',7-dihydroxy-3,4-dihydroisoflavone; D007529:Isoflavones; D012333:RNA, Messenger; D060754:Equol; D008668:Metallothionein