Quantitative Detection of Cell Activity by Measuring the Fluctuation of Intracellular Motility

The measurement of cell activity changes during damage is important to understand the process of cell death and evaluate the effect of medicines. To evaluate cell activity generally, we extended the method of intensity fluctuation in which intensity change in the pixel induced by the movement of organelles was calculated. Cancer, endothelial and iPS cells were damaged by reactive oxygen species (ROS) generated by a fluorescent dye (IR700), hydrogen peroxide, and ultraviolet light. The intensity fluctuation in damaged cells gradually decreased independent of the kind of cell, indicating that the decrease in the fluctuation is a general phenomenon in damaged cells. The rupture of vesicles and mitochondria in the cells were observed upon ROS production. The motility of purified kinesin and dynein which transport vesicles and organelles was inhibited by ROS. These suggest that ROS and cytotoxic molecules spreading from ruptured organelles contribute to the reduction in cell activity which brings about the decrease in the motility and intensity fluctuation of organelles driven by kinesin and dynein.