An improved resazurin-based cytotoxicity assay for hepatic cells

Area of Science:

• Biotechnology
• Toxicology
• Cell Biology

Background:

• Cytotoxicity screening is crucial for assessing drug safety and toxicity in liver cells.
• Conventional short-term assays may lack sensitivity and provide limited information.
• Resazurin is a vital dye used to assess cell viability and metabolic activity.

Purpose of the Study:

• To develop and validate a simple, long-term resazurin-based cytotoxicity assay for hepatocytes and liver cell lines.
• To improve the sensitivity and provide dual-endpoint analysis for cytotoxicity screening.
• To investigate the underlying mechanisms of signal generation in the long-term assay.

Main Methods:

• Human hepatoma (HepG2) cells and primary rat hepatocytes were exposed to toxic and control compounds.
• Resazurin (5 micromol/L) was added, and fluorescence was measured at 1 hour and 2-4 days.
• The effect of metabolic inhibitors (dicumarol, disulfiram, SKF525a) on resorufin metabolism was assessed.

Main Results:

• The long-term assay showed increased fluorescence in wells with dead or dying cells due to resazurin conversion to resorufin.
• Viable cells metabolized resorufin to non-fluorescent products, decreasing fluorescence over 2-4 days.
• The assay demonstrated improved signal and allowed for two independent cytotoxicity endpoints.

Conclusions:

• The long-term resazurin assay provides a sensitive and versatile method for screening liver cell cytotoxicity.
• The inversion of the fluorescent signal (high = dead) in the long-term assay offers a distinct advantage.
• This assay enables dual-endpoint determination of cytotoxicity using a single, non-toxic vital dye.