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Pyridoxylamine reactivity kinetics as an amine-based probe for screening electrophilic contact allergens.
Chipinda-I; Mbiya-W; Simoyi-RH; Siegel-PD
Toxicologist 2012 Mar; 126(Suppl 1):565-566
Covalent protein binding is an initial step in dermal contact sensitization. We previously reported the utility of a nitrobenzenethiol (NBT) binding assay for screening thiol reactive haptens (Chipinda et al Chem. Res. Tox. 2010). The present study describes an amine (pyridoxylamine (PDA)) absorbance and fluorescence-based reactivity kinetic probe to complement the NBT assay for identification of amine-selective haptens. Rate constants for 32 chemicals including 5 anhydrides, 6 aldehydes, 2 quinones, among other classes, were determined where reaction times to completion ranged from 20 s to > 2 h. Preliminary assessment suggests labile reactive intermediates are formed during PDA reaction to quinones and benzyl bromide. No reactivity was observed with some thiol-selective sensitizers such as propiolactone or nonsensitizers such as sulfanilamide and benzocaine. Strong correlation (R2 = 0.81) was obtained between PDA reactivity constant (pseudo-first order; k) and the local lymph node assay threshold (EC3) values. Reaction completion time of the sensitizers also correlated strongly (R2 = 0.74) with EC3 values suggesting utility of transforming this chemical reactivity method into a simple, inexpensive end-point assay. The results from the PDA method also highlight the utility of combining this amine based method with the previous NBT based model to be able to identify thiol selective, amine selective and non-selective electrophilic contact allergens.
Dermatology; Sensitization; Allergens; Proteins; Amines; Kinetics; Skin-absorption; Skin-exposure; Skin-sensitivity; Antigens; Bioassays; Binding-energy; Anhydrides; Aldehydes; Quinones; Thiols; Lymph-nodes; Reaction-rates; Chemical-kinetics
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Healthcare and Social Assistance; Services
The Toxicologist. Society of Toxicology 51st Annual Meeting and ToxExpo, March 11-15, 2012, San Francisco, California
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