Cytometric methods to analyze thermal effects

Publisher Summary An investigation of thermal effects on cells is of critical interest to at least three diverse fields: (1) studies of the regulation of gene expression in the responses of cells to environmental stress; (2) the application of hyperthermia as a single or combined modality in the treatment of cancer; and (3) the identification of thermal artifacts (or effects) in studies of the biological effects of physical agents such as radiofrequency radiation and ultrasound. Hyperthermia in the 41°–45°C range causes a plethora of effects on most cellular organelles and functions. These effects range from the interaction of the plasma membrane with the extracellular matrix to protein aggregation with the nuclear matrix. Functional changes are observed in cytosol and the nucleoplasm. Several cytometric methods are used to assay the effects of hyperthermia on cells. The first assay, the amount of protein that coisolates with nuclei or nuclear matrices, measures a parameter that correlates with numerous heat effects on nuclear function such as inhibition of DNA repair, DNA synthesis, transcription, and processing of hnRNA. This parameter correlates very well with cell death in many cell lines, particularly those that do not die by apoptosis. The next parameter is the expression of heat-shock proteins whose nuclear localization and delocalization correlates with the development of thermotolerance and heat resistance. Another assay measures intracellular prooxidant capacity. One of the effects that can be induced by the exposure of cells to hyperthermia is an imbalance between prooxidant and antioxidant status either by a reduced antioxidant function or an increased prooxidant function, or both.