The effect of ethchlorvynol on cultured endothelial cells. A model for the study of the mechanism of increased vascular permeability.

Ethchlorvynol (ECV), an agent which produces reversible pulmonary edema, was studied for its effects on cultured bovine pulmonary artery endothelial cell (BPAE) and human umbilical vein endothelial cell (HUVE) monolayers. Endothelial cell monolayers 6 days post-confluent were treated with 1 mg/ml ECV for time intervals of from 5 minutes to 15 hours. ECV treatment caused a mild endothelial cell retraction evident at 10 minutes which increased in severity with increasing duration of exposure to ECV. Retraction of endothelial cells resulted in the formation of irregularly delineated gaps between cells, which remained attached to one another by slender filamentous processes. Despite the severity of the endothelial cell lesion, no cell lysis or cell detachment from the substratum occurred. Furthermore, removal of ECV from cell cultures resulted in the reversal of the endothelial cell lesion. Cytochemical distribution of actin microfilaments in control monolayers localized to a dense peripheral band of actin filaments and to a set of interconnected central microfilaments oriented in general parallel to the long axis of the cell. Endothelial cells treated with ECV for as little as 10 minutes showed a loss of F-actin from the dense peripheral band of microfilaments progressing until the dense peripheral band was entirely lost after 4 hours' exposure to ECV. By 4 hours central microfilaments had reorganized into a prominent series of microfilament bundles aligned parallel to each other and to the long axis of the cell. For investigation of a possible loss of attachment sites of actin filaments as the basis for the lesion, the localization of vinculin was examined in control and ECV-treated BPAE monolayers. After 2 hours' exposure to ECV, vinculin localization within monolayers was affected little, if at all. No effects of ECV on intermediate filaments were observed either. It is proposed that the dense peripheral band of actin bundles is important in maintaining well-spread endothelial cells in monolayers and that ECV acts to destroy the integrity of this structure. It is further proposed that a reaction of endothelial cells to ECV in vivo analogous to that seen in tissue culture accounts for the production of pulmonary edema by creating gaps between cells.