title: t-PA-specific modulation of a human blood-brain barrier model involves plasmin-mediated activation of the Rho kinase pathway in astrocytes.
abstract: Tissue-type plasminogen activator (t-PA) can modulate permeability of the neurovascular unit and exacerbate injury in ischemic stroke. We examined the effects of t-PA using in vitro models of the blood-brain barrier. t-PA caused a concentration-dependent increase in permeability. This effect was dependent on plasmin formation and potentiated in the presence of plasminogen. An inactive t-PA variant inhibited the t-PA-mediated increase in permeability, whereas blockade of low-density lipoprotein receptors or exposed lysine residues resulted in similar inhibition, implying a role for both a t-PA receptor, most likely a low-density lipoprotein receptor, and a plasminogen receptor. This effect was selective to t-PA and its close derivative tenecteplase. The truncated t-PA variant reteplase had a minor effect on permeability, whereas urokinase and desmoteplase were ineffective. t-PA also induced marked shape changes in both brain endothelial cells and astrocytes. Changes in astrocyte morphology coincided with increased F-actin staining intensity, larger focal adhesion size, and elevated levels of phosphorylated myosin. Inhibition of Rho kinase blocked these changes and reduced t-PA/plasminogen-mediated increase in permeability. Hence plasmin, generated on the cell surface selectively by t-PA, modulates the astrocytic cytoskeleton, leading to an increase in blood-brain barrier permeability. Blockade of the Rho/Rho kinase pathway may have beneficial consequences during thrombolytic therapy.
authors.affiliation: Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct, 89 Commercial Road, Melbourne, VIC 3004, Australia.
authors.forename: Be'eri
authors.initials: B
authors.lastname: Niego
authors.forename: Roxann
authors.initials: R
authors.lastname: Freeman
authors.forename: Till B
authors.initials: TB
authors.lastname: Puschmann
authors.forename: Ann M
authors.initials: AM
authors.lastname: Turnley
authors.forename: Robert L
authors.initials: RL
authors.lastname: Medcalf
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D001812:Blood-Brain Barrier / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology / Q000502:physiology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D004789:Enzyme Activation / Q000187:drug effects; D005341:Fibrinolysin / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008962:Models, Theoretical; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D010959:Tissue Plasminogen Activator / Q000494:pharmacology*; D054460:rho-Associated Kinases / Q000378:metabolism*
chemical_list: D054460:rho-Associated Kinases; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin