The Journal of Neuroscience, April 1, 2000, 20(7):2543-2550
Thrombomodulin as a New Marker of Lesion-Induced Astrogliosis:
Involvement of Thrombin through the G-Protein-Coupled
Protease-Activated Receptor-1
Armelle
Pindon1,
Martin
Berry2, and
Daniel
Hantaï1
1 Institut National de la Santé et de la
Recherche Médicale Unité 523 (formerly 153), Institut de
Myologie, Hôpital de la Salpêtrière, F-75013 Paris,
France, and 2 Guy's, King's, and St. Thomas' School of
Biomedical Sciences, Centre of Neuroscience, Unit of Brain Damage and
Repair, Guy's Campus, London SE1 1UL, United Kingdom
Because injury of the CNS causes an astrogliosis, characterized by
cell swelling and proliferation, similar to the effects of the serine
protease thrombin on astrocytes, we hypothesized that a high level of
thrombin at the site of injury might initially induce an astrocyte
reaction and later increase the expression of its specific inhibitor,
thrombomodulin. Thrombomodulin could then stabilize the astroglial scar
through its adhesive properties.
Here, we studied the in vivo injury response of
astrocytes in the anterior medullary velum of adult rat by
immunostaining and in situ hybridization of
thrombomodulin. Thrombomodulin was poorly expressed on astrocytes in
normal tissue, increased up to 2 d after injury, and was still
highly expressed at 6 d.
To check that thrombin had a direct effect on thrombomodulin expression
by astrocytes, we used brain cortical astrocyte primary cultures
treated with either thrombin or the agonist peptide thrombin receptor-activating peptide-6, known to activate directly the thrombin G-protein-coupled receptor (GPCR) protease-activated receptor-1 (PAR-1). Modification of thrombomodulin expression was
studied by Western blotting and quantitative reverse transcription-PCR. There was a dose-dependent increase in thrombomodulin after 48 hr of
treatment, with gene expression peaking at 24 hr but falling to control
levels by 48 hr.
Together, these results show the following: (1) injury increases
astrocyte thrombomodulin expression; (2) thrombin might mediate thrombomodulin expression via the specific receptor PAR-1; and (3)
serine proteases, their inhibitors, and the new family of GPCR, PARs,
are active on astrogliosis.
Key words:
astrocyte; glial scar; rat; serine protease; lesion; thrombomodulin
Copyright © 2000 Society for Neuroscience 0270-6474/00/2072543-08$05.00/0