Related Experiment Videos
Antioxidant compounds interfere with the 3
M Natarajan1, S Mohan, B R Martinez
1Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 78229-3900, USA.
Abstract:
Antioxidants are often added to culture media as cytoprotective agents. We examined the effects of antioxidants on the results and interpretation of the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay for cell viability. Without cells, the thiol-containing antioxidant compounds beta-mercaptoethanol, dithiothreitol, pyrrolidine-dithiocarbamate, and N-acetyl-L-cysteine (acetylcysteine) reduced MTT tetrazolium salts to a blue formazan product in a dose-dependent manner. Addition of the compounds L-ascorbic acid and (+)-alpha-tocopherol acid succinate had different effects. In contrast, addition of the antioxidants N-acetyl-5-methoxytryptamine and (-)-2-oxo-4-thiazolidine carboxylic acid, which do not contain reactive thiol groups, did not result in the development of blue formazan product. These results showed that antioxidants, and potentially other chemotherapeutic compounds that contain free thiol groups or other reducing equivalents, readily reduce MTT to produce the blue formazan, irrespective of the viability of the cells present. This undescribed reaction can, therefore, significantly influence the results and interpretation of cell-viability experiments.
Insights
Antioxidants with thiol groups can interfere with cell viability assays. These compounds reduce MTT tetrazolium to formazan, affecting results even without cells, impacting experimental interpretation.
Area of Science:
- Cell Biology
- Biochemistry
- Pharmacology
Background:
- Antioxidants are commonly used as cytoprotective agents in cell culture media.
- The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay is a standard method for assessing cell viability.
- Potential interference in MTT assays can compromise the accuracy of cell viability studies.
Purpose of the Study:
- To investigate the impact of various antioxidants on the MTT assay.
- To determine if antioxidants can directly reduce MTT tetrazolium salts independently of cellular activity.
- To assess the implications of this interaction for interpreting cell viability data.
Main Methods:
- Culturing cells and performing MTT assays in the presence of different antioxidants.
- Testing the direct reduction of MTT tetrazolium salts by antioxidants in acellular conditions.
- Quantifying formazan production spectrophotometrically.
Main Results:
- Thiol-containing antioxidants (e.g., beta-mercaptoethanol, N-acetyl-L-cysteine) significantly reduced MTT tetrazolium to formazan in a dose-dependent manner without cells.
- Antioxidants lacking reactive thiol groups did not produce formazan.
- The reduction of MTT by antioxidants occurred independently of cell viability.
Conclusions:
- Certain antioxidants, particularly those with thiol groups, can directly interfere with the MTT assay by reducing tetrazolium salts.
- This direct chemical reduction can lead to inaccurate interpretations of cell viability.
- Researchers should consider the potential for antioxidant interference when designing and analyzing MTT-based cell viability experiments.