title: Specific adducts formed through a radical reaction between peptides and contact allergenic hydroperoxides.
abstract: The first step in the development of contact allergy (allergic contact dermatitis) includes the penetration of an allergy-causing chemical (hapten) into the skin, where it binds to macromolecules such as proteins. The protein-hapten adduct is then recognized by the immune system as foreign to the body. For hydroperoxides, no relevant hapten target proteins or protein-hapten adducts have so far been identified. In this work, bovine insulin and human angiotensin I were used as model peptides to investigate the haptenation mechanism of three hydroperoxide haptens: (5R)-5-isopropenyl-2-methyl-2-cyclohexene-1-hydroperoxide (Lim-2-OOH), cumene hydroperoxide (CumOOH), and 1-(1-hydroperoxy-1-methylethyl) cyclohexene (CycHexOOH). These hydroperoxides are expected to react via a radical mechanism, for which 5,10,15,20-tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)TPPCl) was used as a radical initiator. The reactions were carried out in 1:1 ethanol/10 mM ammonium acetate buffer pH 7.4, for 3 h at 37 degrees C, and the reaction products were either enzymatically digested or analyzed directly by MALDI/TOF-MS, HPLC/MS/MS, and 2D gel electrophoresis. Both hydroperoxide-specific and unspecific reaction products were detected, but only in the presence of the iron catalyst. In the absence of catalyst, the hydroperoxides remained unreacted. This suggests that the hydroperoxides can enter into the skin and remain inert until activated. Through the detection of a Lim-2-OOH adduct bound at the first histidine (of two) of angiotensin I, it was confirmed that hydroperoxides have the potential to form specific antigens in contact allergy.
authors.affiliation: Department of Chemistry, Dermatochemistry and Skin Allergy, Medicinal Chemistry, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Theres
authors.initials: T
authors.lastname: Redeby
authors.forename: Ulrika
authors.initials: U
authors.lastname: Nilsson
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Altamore
authors.forename: Leopold
authors.initials: L
authors.lastname: Ilag
authors.forename: Annalisa
authors.initials: A
authors.lastname: Ambrosi
authors.forename: Kerstin
authors.initials: K
authors.lastname: Broo
authors.forename: Anna
authors.initials: A
authors.lastname: Börje
authors.forename: Ann-Therese
authors.initials: AT
authors.lastname: Karlberg
mesh_terms: D000803:Angiotensin I / Q000737:chemistry*; D000818:Animals; D001555:Benzene Derivatives / Q000737:chemistry*; D002417:Cattle; D002712:Chlorides; D002851:Chromatography, High Pressure Liquid; D053138:Cyclohexenes / Q000737:chemistry*; D017449:Dermatitis, Allergic Contact / Q000276:immunology; D005290:Ferric Compounds / Q000737:chemistry; D006241:Haptens / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry; D011407:Propane / Q000031:analogs & derivatives* / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry
chemical_list: C547966:(5R)-5-isopropenyl-2-methyl-2-cyclohexene-1-hydroperoxide; C547967:1-(1-hydroperoxy-1-methylethyl) cyclohexene; C509964:5,10,15,20-tetraphenylporphyrin; D001555:Benzene Derivatives; D002712:Chlorides; D053138:Cyclohexenes; D005290:Ferric Compounds; D006241:Haptens; D007328:Insulin; D011166:Porphyrins; D000803:Angiotensin I; C007164:cumene hydroperoxide; D011407:Propane; C024555:ferric chloride