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Application of the Hard and Soft, Acids and Bases (HSAB) Theory as a Method to Predict Cumulative Neurotoxicity
Citation:
Melnikov, F., B. Geohagen, T. Gavin, R. LoPachin, P. Anastas, P. Coish, AND D. Herr. Application of the Hard and Soft, Acids and Bases (HSAB) Theory as a Method to Predict Cumulative Neurotoxicity. NEUROTOXICOLOGY. Elsevier B.V., Amsterdam, Netherlands, 79:95-103, (2020). https://doi.org/10.1016/j.neuro.2020.04.009
Impact/Purpose:
In silico modeling using the Hard and Soft Acid and Bases (HSAB) theory has shown to be able to predict neurotoxic chemicals fin the class of Type 2 alkenes. This paper extends the use of in silico HSAB models for neurotoxicity to a wider range of chemicals, and also analyses the results with respect to known positive and negative controls substances. These in silico predictions resulted in prioritization of chemicals for follow up testing using in vitro and in vivo methods.
Description:
Xenobiotic electrophiles can form covalent adducts that impair protein function, damage DNA, and may lead a range of adverse effects. Cumulative neurotoxicity is one adverse effect that has been linked to covalent protein binding as a Molecular Initiating Event (MIE). This paper describes mechanistic in silico chemical screening approach for cumulative neurotoxicity based on hard-soft acid-base (HSAB) theory. We evaluated the applicability of HSAB-based electrophilicity screening protocol for cumulative neurotoxicity on 39 positive and negative reference chemicals. Reference chemicals were identified from the literature and mechanisms of cumulative neurotoxicity was considered whenever possible. In silico screening was based on structural alerts for protein binding motifs and electrophilicity index in the range of known neurotoxicants. The approach demonstrated high positive prediction rate (82-90%) and specificity (90%). The overall sensitivity was lower (47%). However, when predicting the toxicity of chemicals known or suspected of acting via non-specific adduct formation mechanism, the HSAB approach identified 7/8 (sensitivity 88%) of positive control chemicals correctly. Consequently, the HSAB-based screening is a promising approach of identifying possible cumulative neurotoxins with adduct formation molecular initiating events. While the approach must be expanded over time to capture a wider range of MIEs involved in cumulative neurotoxicity, the mechanistic nature of the screen allows users to flag chemicals for possible adduct formation MIEs. Thus, the HSAB based toxicity screening is a promising strategy for toxicity assessment and chemical triage in neurotoxicology and other health endpoints that involve adduct formation.
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DOI: Application of the Hard and Soft, Acids and Bases (HSAB) Theory as a Method to Predict Cumulative Neurotoxicity