Summary
Thrombin induces Ca2+ transients and subsequent nitric oxide (NO) production in vascular endothelial cells.
Thrombin cleaves protease-activated receptors, resulting in activation of intracellular
signals, but it is not clarified how the extracellular thrombin stays around the cells
to exert its enzyme activities. This study aimed to investigate the possible involvement
of heparin sulfate proteoglycan (HSPG) in the effects of thrombin on vascular endothelium.
Heparinase III completely removed the polysaccharide chain of HSPG in bovine aortic
endothelial cells (BAECs).Thrombin induced Ca2+ transients in control BAECs, but not in heparinase III-treated BAECs. In contrast,
ATP induced Ca2+ transients both in control and heparinase III-treated BAECs. Thrombin that was pre-incubated
with heparin also failed to induced Ca2+ transients in BAECs. Furthermore, thrombin-induced NO production, as assessed with
DAF-2 flu-orescence, was suppressed in heparinase III-treated BAECs and by the pre-incubation
of thrombin with heparin. ATP-induced NO production was, however, not affected in
heparinase III-treated BAECs. These results indicate that it is essential for thrombin
to bind to the polysaccharide chain of HSPG for inducing Ca2+ transients and NO production in BAECs.
Keywords
Calcium - endothelial cells - heparan sulfate proteoglycan - nitric oxide - thrombin