Discriminative cytotoxicity assessment based on various cellular damages

There are several assays currently available for the assessment of cell cytotoxicity, including trypan blue exclusion, lactate dehydrogenase (LDH) release, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assays. Trypan blue exclusion and LDH release assays are appropriate for evaluating cell membrane damage and a colorimetric MTT assay is available for measuring mitochondrial-related reduction capacity. As these assays were randomly utilized to assess the extent of cell damage, we suggest herein that the assay should be selected in accordance with the prevailing cellular situation. This can be determined by using a variety of cell types with differing reduction status, exogenous and endogenous oxidative stressors, and several different oxidized/reduced molecules. Although the trypan blue exclusion and released LDH assay have proven useful for assessments of necrotic and apoptotic cell death with membrane damage, the LDH assay is not appropriate for the measurement of the number of varied cells without membrane damage. In addition, when the cells were treated with exogenous and endogenous oxidative stressors, MTT reduction was shown to be sensitive to a shift to a more oxidizing cellular environment within a narrow range without loss of membrane integrity, and this effect increased in a linear fashion, dependent on the dosage of cytosolic extracts containing various physiological reductants, small reductive molecules (NADPH and GSH), and artificial DTT reducing agent. Finally, we noted that the MTT assay is available for the determination of small-scale oscillations in cellular reduction status and changes in mitochondrial functional activity, but not for evaluating the cytotoxicity of cells with a higher cellular reduction capacity. Altogether, the findings of this study indicate that tools for the testing of cytotoxicity should be selected differently by considering the correlation between the cellular conditions for various stimuli and the principle underlying the assay system.