Transforming growth factor-beta mediates astrocyte-specific regulation of brain endothelial anticoagulant factors.
OBJECTIVE
Astrocytes are potent regulators of brain capillary endothelial cell function. Recently, astrocytes were shown to regulate brain capillary endothelial expression of the fibrinolytic enzyme tissue plasminogen activator (tPA) and the anticoagulant thrombomodulin (TM). To study the mechanism of this process, we examined the hypothesis that astrocyte regulation of endothelial tPA and TM is mediated by transforming growth factor-beta (TGF-beta).


METHODS
Brain capillary endothelial cells were grown in blood-brain barrier models. We examined astrocyte-endothelial cocultures, endothelial monocultures, and astrocyte-conditioned media (ACM) for the expression of TGF-beta. We also incubated endothelial cells with ACM to determine the role of TGF-beta. Following 24 hours of incubation, we assayed for tPA and TM mRNA, as well as tPA and TM activity.


RESULTS
Astrocyte-endothelial cocultures and ACM exhibited significantly higher levels of active TGF-beta than brain endothelial monocultures and endothelial cells grown in nonconditioned media, respectively. Brain endothelial cells incubated with ACM exhibited reduced tPA and TM mRNA and activity. Treatment with exogenous TGF-beta produced dose-dependent reductions in tPA and TM. The effects of ACM on both tPA and TM were blocked by TGF-beta neutralizing antibody.


CONCLUSIONS
These data indicate that TGF-beta mediates astrocyte regulation of brain capillary endothelial expression of tPA and TM.
Tran
N D
ND
Department of Neurology, University of Southern California School of Medicine, Los Angeles, USA.
Correale
J
J
Schreiber
S S
SS
Fisher
M
M
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000098:blood supply*; D002417:Cattle; D002452:Cell Count; D002478:Cells, Cultured; D002536:Cerebral Arteries / Q000166:cytology / Q000378:metabolism; D017077:Culture Media, Conditioned; D017931:DNA Primers / Q000737:chemistry; D015536:Down-Regulation / Q000187:drug effects; D004730:Endothelium, Vascular / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D051379:Mice; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics; D011994:Recombinant Proteins; D018180:Thrombomodulin / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D010959:Tissue Plasminogen Activator / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D017077:Culture Media, Conditioned; D017931:DNA Primers; D012333:RNA, Messenger; D011994:Recombinant Proteins; D018180:Thrombomodulin; D016212:Transforming Growth Factor beta; D010959:Tissue Plasminogen Activator