The Tie-2 agonist PMC-403 inhibits endothelial damage induced by e-cigarette vapor or LPS

The use of e-cigarettes is currently increasing despite potential harmful effects of e-cigarettes. Acute e-cigarette exposure may cause endothelial damage thereby contributing to acute lung injury or vascular dysfunction after chronic use. These effects may be enhanced by concomitant inflammatory stimuli. We investigated the acute effect of e-cigarette vapor (ECV) with or without concomitant lipopolysaccharide (LPS) stimulation on endothelial cell function in vitro and on vascular permeability in isolated lungs. Further potentially protective effects of the Tie2 agonist PMC-403 were studied.

Human umbilical cord endothelial cells (HUVECs) were cultured with different types of ECV extracts (ECVE) and/or LPS, and endothelial activation was determined in vitro by measuring secreted protein and mRNA levels of angiopoietin-2 (Angpt-2) and soluble Tie2 (sTie2). Barrier dysfunction was analyzed by continuous transendothelial electrical resistance (TER) measurements using electric cell-substrate impendence sensing (ECIS). An ex vivo isolated mouse lung model was used to analyze endothelial permeability and edema formation upon intratracheal ECV exposure. The Tie2 agonist PMC-403 was applied in vitro and ex vivo and its effect on endothelial permeability was determined.

Angpt-2 secretion and transcription were significantly increased in HUVECs after 24h stimulation with nicotine-containing ECVE (ECVE_nic), but not nicotine-free ECVE. Preincubation with ECVE_nic significantly enhanced the LPS-induced increase of Angpt-2 secretion. On a functional level, ECVE_nic exposure resulted in greater susceptibility to an LPS-induced increase in endothelial barrier permeability. In isolated, ventilated and perfused mouse lungs intratracheal nicotine-containing ECV application (ECV_nic) or LPS application via the perfusate increased endothelial permeability and lung edema, however, combination of ECV_nic and LPS did not have additive effects. A novel synthetic Tie2 agonist PMC-403 decreased both the LPS-induced loss of endothelial barrier function in vitro and the ECV_nic- or LPS-induced endothelial barrier dysfunction ex vivo.

ECV_nic exposure increased endothelial permeability and lung edema formation in an angiopoietin/Tie2 dependent manner ex vivo, and susceptibility to LPS stimulation in vitro. We identified the Tie2 activating anti-permeability agent PMC-403 as a potential therapeutic agent of acute lung injury in this context.