title: Microparticles generated during chronic cerebral ischemia increase the permeability of microvascular endothelial barriers in vitro.
abstract: Numbers of circulating microparticles (MPs) are elevated in a variety of cardiovascular disorders, and recent studies indicate that they are involved in inflammatory intercellular signaling. In the present study the signaling properties of MPs were assessed in an in vitro model of the blood brain barrier. MPs isolated from the plasma of rats exposed to chronic cerebral ischemia caused a significant reduction in the transendothelial electrical resistance (TEER) when applied to in vitro endothelial barriers, while MPs isolated from an equal volume of plasma from unoperated or sham operated rats did not. The reduction in TEER was attenuated by treating endothelial barriers prior to exposure to MPs with the caspase 3 inhibitor AC-DEVD-CHO, the TNF-α inhibitor SPD304, the tumor necrosis factor alpha-converting enzyme (TACE, ADAM 17) inhibitor TAPI-0-1 and the Rho kinase (ROCK) inhibitor Y-27632, and by treating the MPs themselves with these inhibitors prior to applying them to cultured cells. This observation indicates that MPs generated during cerebral ischemia contain pro-TNF-α, active TACE and active ROCK. ROCK and Ras homolog gene family member A (RhoA) were detected in MPs by western blot. The growth factor VEGF stimulated transcellular transport in endothelial barriers while exposure to MPs did not. We conclude that the increase in permeability of artificial barriers induced by MPs is primarily due to enhanced apoptosis induced by activation of the TNF-α pathway and activated caspase 3 and Rho kinases delivered to endothelial cells by MPs.
authors.affiliation: University of Ottawa, Neuroscience Graduate Program, 451 Smyth Road, Ottawa, ON, Canada K1H 8M5.
authors.forename: Hamidreza
authors.initials: H
authors.lastname: Edrissi
authors.affiliation: Ottawa Hospital Research Institute, Neuroscience, 451 Smyth Road, Ottawa, ON, Canada K1H 8M5.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Schock
authors.affiliation: Ottawa Hospital Research Institute, Neuroscience, 451 Smyth Road, Ottawa, ON, Canada K1H 8M5.
authors.forename: Antoine M
authors.initials: AM
authors.lastname: Hakim
authors.affiliation: Ottawa Hospital Research Institute, Neuroscience, 451 Smyth Road, Ottawa, ON, Canada K1H 8M5. Electronic address: charliet@uottawa.ca.
authors.forename: Charlie S
authors.initials: CS
authors.lastname: Thompson
mesh_terms: D000818:Animals; D017209:Apoptosis; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002545:Brain Ischemia / Q000378:metabolism*; D002199:Capillary Permeability; D055252:Cell-Derived Microparticles / Q000378:metabolism*; D002478:Cells, Cultured; D004660:Encephalitis / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D018836:Inflammation Mediators / Q000378:metabolism; D008297:Male; D051381:Rats; D020318:Rats, Long-Evans; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D018836:Inflammation Mediators; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; D054460:rho-Associated Kinases
keywords: Apoptosis; Cerebral ischemia; Endothelial barrier permeability; Microparticles; Rho kinase; TNF-α