TY - JOUR T1 - Signaling in vascular endothelium by varying degrees of mechanical stretch JF - ERJ Open Research JO - erjor DO - 10.1183/23120541.RFMVC-2020.26 VL - 6 IS - suppl 4 SP - 26 AU - Pratap Karki AU - Chen-Ou Zhao AU - Yunbo Ke AU - Konstantin Birukov AU - Anna Birukova Y1 - 2020/02/13 UR - http://openres.ersjournals.com/content/6/suppl_4/26.abstract N2 - Mechanical ventilation remains an imperative treatment for the patients with ARDS, but can also exacerbate lung injury. We have previously characterized signaling pathways induced in vascular endothelium by high magnitude cyclic stretch (CS) and described a key role of RhoA GTPase in high CS-induced endothelial (EC) barrier dysfunction. This study tested a hypothesis that recovery of vascular EC barrier after pathologic mechanical stress may be accelerated by cell exposure to physiologic CS levels. Using biochemical, molecular, and imaging approaches we found that EC preconditioning at physiologically relevant low magnitude 4% CS promotes resealing of EC tight junctions disrupted by pathologic, high magnitude 18% CS. Moreover, the EC barrier recovery rate was higher in EC exposed to low CS vs. EC culture left at static conditions. Inhibitory analysis showed that low CS-induced tight junction remodeling was dependent on small GTPase Rap1. In a clinically-relevant two-hit model of EC exposed to bacterial particles followed by mechanical stimulation, low magnitude CS was also protective against deleterious effects by high magnitude CS. Using Rap1 knockout mice exposed to mechanical ventilation we found that protective effect of mechanical ventilation at low tidal volume against lung injury caused by i.t. injection of LPS and mechanical ventilation at high tidal volume was suppressed by molecular inhibition of Rap1, whereas administration of Rap1 activator significantly reduced parameters of ALI in the wild type group. Taken together our results demonstrate a prominent role of signaling mechanisms activated by low CS in stimulation of the Rap1-mediated acceleration of lung vascular EC barrier restoration.FootnotesCite this article as: ERJ Open Research 2020; 6: Suppl. 4, 26.This is an ERS Respiratory Failure and Mechanical Ventilation Conference abstract. No full-text version is available. Further material to accompany this abstract may be available at www.ers-education.org (ERS member access only). ER -