Aspects of cellular damage induced by physical and chemical (mitochondriotropic) agents
Various agents such as heat, ultrasound, rhodamine derivatives and carbonylcyanide m-chlorophenylhydrazone are used to induce cellular damage so as to understand certain events leading to cell death using a mammalian cell culture system - HeLa S3 cells. Clonogenic assay is insensitive as it is an end-point technique for determining the effectiveness of cell-killing. A combined approach using protein synthesis, oxygen consumption, time-sequenced morphological study, flow cytometric analysis and others is used instead. Ultrasound is used also because it can produce heat especially when focussing beams are employed. However, with the present experimental set-up system, it is the formation of microbubbles (cavitations) together with microstreaming in a fluid medium and not heat, that produce the 'shattering' damage to the HeLa S3 cells in suspensions. Heating e.g. at 42oC for a brief period can produce 'thermoprotection' to other stimuli, in this case ultrasound. Mitochondria are found to be highly sensitive to heat especially at 45oC and the compounds used in this study. Multivesicular and myelinoid-multivesicular bodies are related to mitochondria. Lysosomes do not appear to play a critical role in the early events leading to cell death. It is suggested that by damaging mitochondria leading to an irreversible state of cellular 'energy crisis' could be the earliest event in cell death.