Transforming growth factor-beta1 as a regulator of the serpins/t-PA axis in cerebral ischemia.
The tissue type plasminogen activator (t-PA) is a serine protease that is involved in neuronal plasticity and cell death induced by excitotoxins and ischemia in the brain. t-PA activity in the central nervous system is regulated through the activation of serine protease inhibitors (serpins) such as the plasminogen activator inhibitor (PAI-1), the protease nexin-1 (PN-1), and neuroserpin (NSP). Recently we demonstrated in vitro that PAI-1 produced by astrocytes mediates the neuroprotective effect of the transforming growth factor-beta1 (TGF-beta1) in NMDA-induced neuronal cell death. To investigate whether serpins may be involved in neuronal cell death after cerebral ischemia, we determined, by using semiquantitative RT-PCR and in situ hybridization, that focal cerebral ischemia in mice induced a dramatic overexpression of PAI-1 without any effect on PN-1, NSP, or t-PA. Then we showed that although the expression of PAI-1 is restricted to astrocytes, PN-1, NSP, and t-PA are expressed in both neurons and astrocytes. Moreover, by using semiquantitative RT-PCR and Western blotting, we observed that only the expression of PAI-1 was modulated by TGF-beta1 treatment via a TGF-beta-inducible element contained in the PAI-1 promoter (CAGA box). Finally, we compared the specificity of TGF-beta1 action with other members of the TGF-beta family by using luciferase reporter genes. These data show that TGF-beta and activin were able to induce the overexpression of PAI-1 in astrocytes, but that bone morphogenetic proteins, glial cell line-derived neutrophic factor, and neurturin did not. These results provide new insights into the regulation of the serpins/t-PA axis and the mechanism by which TGF-beta may be neuroprotective.
Docagne
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Université de Caen, CNRS UMR 6551, IFR 47, bd H. Becquerel, BP 5229, 14074 Caen Cedex, France Max-Planck-Institut, für physiologische und klinische Forschung, D-61231 Bad-Nauheim, Germany.
Nicole
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Marti
H H
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MacKenzie
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Buisson
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Vivien
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D016564:Amyloid beta-Protein Precursor; D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology; D002545:Brain Ischemia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death / Q000235:genetics; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D051379:Mice; D009474:Neurons / Q000473:pathology; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism*; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism*; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D015843:Serpins / Q000235:genetics / Q000378:metabolism*; D010959:Tissue Plasminogen Activator / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D000097522:Neuroserpin
D016564:Amyloid beta-Protein Precursor; D002352:Carrier Proteins; D009479:Neuropeptides; D017395:Plasminogen Activator Inhibitor 1; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D015843:Serpins; D010959:Tissue Plasminogen Activator; D016212:Transforming Growth Factor beta; D000097522:Neuroserpin