Upregulation of thrombomodulin on human cultured umbilical vein endothelial cells by cAMP

268

ABSTRACTS;

THROMBIN-INDUCED VASCULAR ENDOTHELIUM . , F. wta. N. SW

w**I

,

CHINESE-JAPANESE RESPONSES

SYMP. 1990

Vol. 63, No. 2

IN RABBIT AORTA-MODULATION

I. Wakwh

i* .

K. Hatake **

and

OF s c

Second Department of Internal Medicine, Departments of Hygiene* and Legal Med.**, Hyogo College of Medicine, Hyogo, Japan It is generally known that thrombin has vascular action in addition to the catalytic effect on the conversion of fibrinogen to fibrin. We investigated the effect of endothelium on thrombininduced contractile response in rabbit aorta. Helical strips of thoracic aortas from New Zealand White Rabbits were prepared. Their tension development was isometrically measured. Thrombin caused concentration-dependent contractions in both intact and denuded strips. This contraction was markedly enhanced by removal of the endothelium, but this enhancement was inhibited by a phospholipase A2 inhibitor, and a guanylate cyclase inhibitor, but not by a lipoxygenase inhibitor, or a cyclooxygenase inhibitor. Increment of tissue c-GMP level by stimulation of thrombin was significantly less than that by stimulation of acetylcholine. Production of 6-Keto PGFla(PGI2) by stimulation of thrombin was also less than that by stimulation of acetylcholine. These results suggested that thrombin-induced contraction of rabbit and this of the endothelium aorta is enhanced by removal derived enhancement may be due to reduction of "endothelium relaxing factor (EDRF) ", which may be spontaneously released from to the change of vascular tonus endothelium in association thrombin-induced contraction.

UPREGULATION OF THROMBOMODULIN ON HUMAN CULTURED UMBILICAL VEIN ENDOTHELIAL CELLS BY CAMP *I S. Yamamoto* .and M OSI.-&la Y. Soew. K. 0 qawa*. Third Dept. Int. Med., Kagoshima Univ. of Med., Kagoshima, and Life Sci. Res. Lab., Asahi Med. Ind. Fuji*, Japan Thrombomodulin (TM) is an endothelial cell associated glycoprotein that convert thrombin from a procoagulant protease to Some agents such as IL-l, TNF and endotoxin an anticoagulant. We examined downregulate the expression of the cell surface TM. effects of the agents that increase in intracellular CAMP on the expression of TM on the cultured human umbilical vein endothelial TM was measured by functional assay (protein C cells (HUVEC). activating cofactor activity) and radio-labeled anti-TM monoclonal Incubation of the HUVEC monolayers with 3mM IgG binding assay. dbcAMP increased the cell-surface TM by about 2-fold after 2 hours Northern blotting of of incubation and continued up to 24 hours. mRNA of TM also demonstrated an Treatment of HUVEC with 20 PM of

increase

in

the

time

course.

forskolin or 100 PM IBMX also increased in the cell-surface TM. These agents prevented the IL-1 These data suggest that or TNF induced decrease in TM on HUVEC. expression of TM on HUVEC may be regulated by intracellular CAMP. CAMP mediates the hormonal induction of numerous eukaryotic genes However, the through a conserved CAMP responsive element (CRE). mechanism of enhancement of TM expression by CAMP remains to be elucidated at present.