Intracellular Ca²⁺ Responses in Cultured Endothelial Cells to Mechanical Stimulation by Laser Tweezers

抄録

It is well known that endothelial cells (ECs) respond to the fluid imposed shear stress and change their shapes and functions. We have focused on the importance of cytoplasmic micro-mechanical strain in mechano-sensing mechanism of ECs. To this end, the cytosolic Ca²⁺ responses of ECs to the mechanical stimulus by laser tweezers that can apply the micro-mechanical force to nano/micro-organisms without any physical contact, were investigated. When the laser spot focused on the nucleus of EC was slightly moved, the cytosolic Ca²⁺ increased immediately in the same EC, whereas there was no Ca²⁺ increase without laser spot movement. In the absence of extracellular Ca²⁺ in the medium or the blockade of stretch activated ion channels, there was also an increase of Ca²⁺ in stimulated ECs. Therefore, the increased Ca²⁺ in stimulated ECs is considered to be derived from intracellular Ca²⁺ store. The heterogeneous Ca²⁺ propagation from the stimulated EC to surrounding ECs was also observed. Two types of Ca²⁺ wave propagation were observed, the fast one that the velocity was more than 20 μm/sec, and the slow one that the velocity was less than 1 μm/sec. The micro-stress induced by the micro-movement of the nucleus can be a trigger of the cytosolic Ca²⁺ increase and the cytoplasmic micro-mechanical strain may play an important role in mechano-sensing mechanism of ECs.