ИСТИНА

Disturbance of the endothelial barrier is characterized by dramatic cytoskeleton reorganization, activation of actomyosin contraction and, finally, leads to intercellular gap formation. Here we demonstrate that the edemagenic agent, thrombin, causes a rapid increase in the endothelial cell (EC) barrier permeability accompanied by fast decreasing in the peripheral microtubules quantity and reorganization of the microtubule system in the internal cytoplasm of the EC within 5 min of the treatment. The actin stress-fibers formation occurs gradually and the maximal effect is observed relatively later, 30 min of the thrombin treatment. Thus, microtubules reaction develops faster than the reorganization of the actin filaments system responsible for the subsequent changes of the cell shape during barrier dysfunction development. Direct microtubules depolymerization by nocodazole induces an increase in the EC monolayer permeability and starts the cascade of barrier dysfunction reactions. Nocodazole-induced barrier disruption is connected directly with the degree of peripheral microtubules depolymerization. Short-term loss of endothelial barrier function occurs at the minimal destruction of peripheral microtubules, when actin filament system is still intact. Under these conditions, microtubule plus ends growth rate significantly decreased near the cell periphery. Our data demonstrate the leading role of microtubules in the development of endothelial barrier loss. The microtubules, apparently, are the first target in the circuit of reactions leading to the pulmonary EC barrier compromise. Our results show that dynamic microtubules play an essential role in the barrier function in vitro; peripheral microtubules depolymerization is necessary and sufficient condition of endothelial barrier dysfunction. Supported by RFBR (12-04-00488) and NIH (HL067307, HL080675).