Structure-activity relationship (SAR) models established in vitro with the neutral red cytotoxicity assay

Area of Science:

• Toxicology
• Biochemistry
• Chemical Biology

Background:

• The neutral red (NR) assay is a valuable tool for assessing chemical cytotoxicity.
• Understanding structure-activity relationships (SARs) is crucial for predicting chemical toxicity.
• Lipophilicity and metal properties are key factors influencing chemical toxicity.

Purpose of the Study:

• To apply the NR cytotoxicity assay for determining SARs of various chemical classes.
• To correlate in vitro cytotoxicity with molecular properties like lipophilicity and metal softness.
• To compare in vitro SAR models with existing in vivo data.

Main Methods:

• Utilized the neutral red (NR) cytotoxicity assay to test a series of alcohols, chlorinated phenolics, nitro/methyl-phenolics, and chlorinated toluenes.
• Correlated cytotoxicity with lipophilicity (log P values) and metal softness (sigma(p) parameter).
• Modified the NR assay to incorporate total protein determinations.

Main Results:

• Cytotoxicity of alcohols, phenolics, and toluenes correlated directly with lipophilicity (log P).
• Dinitrotoluenes showed cytotoxicity independent of lipophilicity, acting as outliers.
• Cytotoxicity of divalent metals correlated inversely with their softness parameter (sigma(p)).
• In vitro SAR models were consistent with in vivo findings.

Conclusions:

• The NR assay is effective for establishing in vitro SARs for diverse chemical compounds.
• Lipophilicity and metal softness are significant predictors of cytotoxicity.
• The NR assay provides a reliable in vitro alternative for toxicity assessment, aligning with in vivo outcomes.