Modulation of procoagulant and fibrinolytic system components of
mesothelial cells by inflammatory mediators.
Sitter, Thomas, Karin Toet, Harald Fricke, Helmut Schiffl, Eckhard
Held, and Teake Kooistra.
Dept. of Medicine, Klinikum Innenstadt, University of Munich, D
-80336 Munich, Germany, Gaubius Laboratory TNO-PG, 2300 AK Leiden, The
Netherlands
APStracts 3:0157R, 1996.
Human peritoneal mesothelial cells (HMC) play a critical role in
maintaining the intraperitoneal balance between fibrinolysis and
coagulation by expressing the fibrinolytic enzyme, tissue-type
plasminogen activator (t-PA), as well as a specific plasminogen
activator inhibitor, PAI-1, and the pro-coagulant protein, tissue
factor (TF). Of three compounds known to stimulate t-PA synthesis in
cultured human endothelial cells, viz. retinoic acid, the protein
kinase C activator 4[beta]-phorbol 12-myristate 13-acetate (PMA) and
sodium butyrate, only butyrate (1mM) caused about a 3-fold increase
in t-PA synthesis and mRNA expression in HMC after 24 h incubation,
without markedly affecting PAI-1 synthesis. PMA (10nM) induced a 3
-fold increase in urokinase-type plasminogen activator (u-PA) mRNA,
but u-PA antigen levels in the HMC conditioned media remained below
the detection level (0.5 ng/ml), possibly as a result of rapid uptake
and degradation by the u-PA receptor. u-PA receptor mRNA levels were
about 5-fold enhanced above control levels after PMA treatment of the
cells. An increase in intracellular cAMP levels by forskolin
(10[mu]M) diminished both t-PA and PAI-1 levels with 43% and 17%,
respectively. Among the inflammatory mediators tested (tumor necrosis
factor a (TNFa), interleukin-1[alpha], bacterial lipopolysaccharide)
TNF[alpha] (10-1000 U/ml) showed the strongest pro-coagulant effects.
We found that the isoflavone compound genistein (25[mu]g/ml)
prevented the TNFa-induced expression of PAI-1 and TF, while also
slightly counteracting the decrease in t-PA synthesis. The protein
kinase C inhibitor, Ro 31-8220 (3[mu]M), only moderately opposed the
TNF[alpha]-induced changes in t-PA and PAI-1 synthesis, but
completely prevented the induction of TF mRNA. In summary our results
demonstrate that t-PA synthesis in HMC is relatively insensitive to
pharmacological stimulation. To restore the balance between
fibrinolysis and coagulation under inflammatory conditions attempts
to interfere with the TNF[alpha] signaling pathway were more
successful.
Received 7 August 1995; accepted in final form 16 April 1996.
APS Manuscript Number R500-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 May 96