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A simple and fast kinetics screening assay for electrophilic dermal sensitizers using nitrobenzenethiol.
Ruwona-TB; Chipinda-I; Ajibola-R; Morakinyo-MK; Simoyi-RH; Siegel-PD
Toxicologist 2010 Mar; 114(1):106
The need for alternatives to animal based skin sensitization testing has spurred research on the use of in-vitro, in silico and in chemico methods. Glutathione and other select peptides have been used to determine the reactivity of electrophilic allergens to nucleophiles but available peptide-based methods are inadequate to accurately measure the rapid kinetics observed with many chemical sensitizers. A kinetic spectrophotometric chemometric assay involving the reactivity of electrophilic sensitizers to nitrobenzenethiol was evaluated. Stopped flow techniques and conventional UV spectrophotometric measurements enabled determination of reaction rate constants ranging from 6 x10-3 M-1s-1 to 2.7 x 104 M-1s-1. Rate constants were measured for 3 extreme, 5 strong, 3 moderate and 2 non-sensitizers. Nine of 13 and 2/13 tested skin sensitizers exhibited pseudo-first order and second order kinetics, respectively. In 2/13 chemicals deviations from first and second order were apparent where the chemicals exhibited complex, likely mixed order kinetics. The reaction rates of the electrophiles correlated positively with their EC3 values within the same mechanistic domain. Detailed specific chemical knowledge of the test chemical is of paramount importance, since false negatives were observed with sensitizers like trimellitic anhydride and oxazolone. Findings from this model show that for the same mechanistic domain, skin sensitization is driven mainly by electrophilic reactivity. This simple and rapid absorbance based method can be incorporated into the battery of alternative non-animal assays for use in skin sensitization prediction.
Allergic-dermatitis; Allergic-reactions; Biological-effects; Cellular-reactions; Chemical-hypersensitivity; Chemical-properties; Chemical-reactions; Exposure-assessment; Exposure-levels; Exposure-methods; Laboratory-animals; Laboratory-testing; Skin; Skin-exposure; Skin-irritants; Skin-sensitivity; Statistical-analysis; Toxic-effects
Issue of Publication
The Toxicologist. Society of Toxicology 49th Annual Meeting and ToxExpo, March 7-11, 2010, Salt Lake City, Utah