TY - JOUR
T1 - Role of astrocyte-derived tissue-type plasminogen activator in the regulation of endotoxin-stimulated nitric oxide production by microglial cells
AU - Vincent, Valérie A.M.
AU - Löwik, Clemens W.G.M.
AU - Verheijen, Jan H.
AU - De Bart, Anton C.W.
AU - Tilders, Fred J.H.
AU - Van Dam, Anne Marie
PY - 1998/2
Y1 - 1998/2
N2 - In mixed glial cell cultures from cerebral cortices of newborn rats, endotoxin induces nitric oxide (NO) production in microglial cells. Earlier we demonstrated that endotoxin induced NO production by microglial cells is inhibited in the presence of astroglial cells by transforming growth factor β (TGFβ). Both microglial and astroglial cells produce TGFβ in a biologically inactive form, which can be activated by plasmin generated by plasminogen activators (PA). In the present paper we describe studies on the mechanism by which glial cells may activate inactive TGFβ and its potential inhibitory effect on NO production by microglial cells. Inhibition of plasmin increased NO production in endotoxin-treated mixed glial cell cultures. Subsequently, antibodies against tissue-type plasminogen activator (tPA) increased NO production in endotoxin-treated mixed glial cell cultures while amiloride, an inhibitor for urokinase (uPA), had no effect. We hereby concluded that tPA is the crucial PA involved in plasmin production resulting in inhibition of NO production in mixed glial cell cultures. Zymography and Northern blot analysis of purified astroglial, microglial, and mixed glial cell cultures demonstrated that astroglial cells produce tPA and a plasminogen activator inhibitor (PAI-1) and are thereby responsible for the production of plasmin which may activate the inactive TGFβ in these cultures. In conclusion, astroglial-derived tPA plays a major role in the inhibition of NO production by endotoxin-treated microglial cells through enhanced plasmin production and possible subsequent TGFβ activation.
AB - In mixed glial cell cultures from cerebral cortices of newborn rats, endotoxin induces nitric oxide (NO) production in microglial cells. Earlier we demonstrated that endotoxin induced NO production by microglial cells is inhibited in the presence of astroglial cells by transforming growth factor β (TGFβ). Both microglial and astroglial cells produce TGFβ in a biologically inactive form, which can be activated by plasmin generated by plasminogen activators (PA). In the present paper we describe studies on the mechanism by which glial cells may activate inactive TGFβ and its potential inhibitory effect on NO production by microglial cells. Inhibition of plasmin increased NO production in endotoxin-treated mixed glial cell cultures. Subsequently, antibodies against tissue-type plasminogen activator (tPA) increased NO production in endotoxin-treated mixed glial cell cultures while amiloride, an inhibitor for urokinase (uPA), had no effect. We hereby concluded that tPA is the crucial PA involved in plasmin production resulting in inhibition of NO production in mixed glial cell cultures. Zymography and Northern blot analysis of purified astroglial, microglial, and mixed glial cell cultures demonstrated that astroglial cells produce tPA and a plasminogen activator inhibitor (PAI-1) and are thereby responsible for the production of plasmin which may activate the inactive TGFβ in these cultures. In conclusion, astroglial-derived tPA plays a major role in the inhibition of NO production by endotoxin-treated microglial cells through enhanced plasmin production and possible subsequent TGFβ activation.
KW - Astroglia
KW - Microglia
KW - Rat
KW - Transforming growth factor β
UR - http://www.scopus.com/inward/record.url?scp=0032006604&partnerID=8YFLogxK
U2 - https://doi.org/10.1002/(SICI)1098-1136(199802)22:2<130::AID-GLIA4>3.0.CO;2-B
DO - https://doi.org/10.1002/(SICI)1098-1136(199802)22:2<130::AID-GLIA4>3.0.CO;2-B
M3 - Article
C2 - 9537833
SN - 0894-1491
VL - 22
SP - 130
EP - 137
JO - GLIA
JF - GLIA
IS - 2
ER -