title: Pyridoxylamine reactivity kinetics as an amine based nucleophile for screening electrophilic dermal sensitizers.
abstract: Chemical allergens bind directly, or after metabolic or abiotic activation, to endogenous proteins to become allergenic. Assessment of this initial binding has been suggested as a target for development of assays to screen chemicals for their allergenic potential. Recently we reported a nitrobenzenethiol (NBT) based method for screening thiol reactive skin sensitizers, however, amine selective sensitizers are not detected by this assay. In the present study we describe an amine (pyridoxylamine (PDA)) based kinetic assay to complement the NBT assay for identification of amine-selective and non-selective skin sensitizers. UV-Vis spectrophotometry and fluorescence were used to measure PDA reactivity for 57 chemicals including anhydrides, aldehydes, and quinones where reaction rates ranged from 116 to 6.2 × 10(-6) M(-1) s(-1) for extreme to weak sensitizers, respectively. No reactivity towards PDA was observed with the thiol-selective sensitizers, non-sensitizers and prohaptens. The PDA rate constants correlated significantly with their respective murine local lymph node assay (LLNA) threshold EC3 values (R(2) = 0.76). The use of PDA serves as a simple, inexpensive amine based method that shows promise as a preliminary screening tool for electrophilic, amine-selective skin sensitizers.
authors: Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505-2888, United States.
authors: Itai
authors: I
authors: Chipinda
authors: Department of Chemistry, Portland State University, Portland, OR 97207-0751, United States.
authors: Wilbes
authors: W
authors: Mbiya
authors: Department of Chemistry, Portland State University, Portland, OR 97207-0751, United States.
authors: Risikat Ajibola
authors: RA
authors: Adigun
authors: Department of Chemistry, Portland State University, Portland, OR 97207-0751, United States.
authors: Moshood K
authors: MK
authors: Morakinyo
authors: Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505-2888, United States.
authors: Brandon F
authors: BF
authors: Law
authors: Department of Chemistry, Portland State University, Portland, OR 97207-0751, United States.
authors: Reuben H
authors: RH
authors: Simoyi
authors: Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505-2888, United States. Electronic address: pds3@cdc.gov.
authors: Paul D
authors: PD
authors: Siegel
mesh_terms: D000447:Aldehydes / Q000378:metabolism / Q000633:toxicity*; D000485:Allergens / Q000378:metabolism / Q000633:toxicity*; D000812:Anhydrides / Q000378:metabolism / Q000633:toxicity*; D017449:Dermatitis, Allergic Contact / Q000209:etiology / Q000276:immunology; D023441:Local Lymph Node Assay; D011733:Pyridoxamine / Q000737:chemistry*; D011809:Quinones / Q000378:metabolism / Q000633:toxicity*; D012867:Skin / Q000276:immunology / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000447:Aldehydes; D000485:Allergens; D000812:Anhydrides; D011809:Quinones; D011733:Pyridoxamine
keywords: AA; ACD; LLNA; Local lymph node assay; MA; Michael acceptor; NBT; Nucleophilic Substitution (1 or 2); Nucleophilic Substitution (aromatic); PDA; Pyridoxylamine; Reactivity assay; S(N)1/S(N)2; S(N)Ar; SBF; Schiff Base Formers; Skin sensitization; acylating agents; allergic contact dermatitis; local lymph node assay; nitrobenzenethiol; pyridoxylamine