Oxidized low-density lipoprotein impairs the anti-coagulant function of tissue-factor-pathway inhibitor through oxidative modification by its high association and accelerated degradation in cultured human endothelial cells
S. Horie et al., Oxidized low-density lipoprotein impairs the anti-coagulant function of tissue-factor-pathway inhibitor through oxidative modification by its high association and accelerated degradation in cultured human endothelial cells, BIOCHEM J, 352, 2000, pp. 277-285
We have examined whether oxidized low-density lipoprotein (ox-LDL) affects
the function of tissue-factor-pathway inhibitor (TFPI), an anti-coagulant r
egulator in the extrinsic pathway of coagulation, in cultured human umbilic
al vein endothelial cells (HUVEC). Treatment of culture medium of HUVEC wit
h ox-LDL, but not with native or acetylated LDLs, drastically decreased the
reactivity of TFPI to its antibody specific for Kunitz domain 1 or one spe
cific for the conformation between Kunitz 1 and 2 of TFPI, and caused a rap
id, concentration-dependent decrease in the functional activity of TFPI to
inhibit Factor X activation. When 5 ng of recombinant TFPI (rTFPI) was mixe
d with 10 mug of ox-LDL for 30 min, almost all of the rTFPI was detected in
the ox-LDL fraction and no free rTFPI was observed on non-denaturing PAGE,
in contrast with the virtual absence of rTFPI in the native LDL fraction.
Ox-LDL decreased the antigen level of TFPI in the lysate of HUVEC in a time
-dependent manner. It did not affect the mRNA level, but ox-LDL-dependent r
eduction of the TFPI antigen level in HUVEC was reversed by the simultaneou
s treatment of ox-LDL with bafilomycin A1, an inhibitor of the lysosomal pr
oton pump. These results indicate that ox-LDL lessens the anti-coagulant fu
nction of TFPI through both oxidative modification and accelerated degradat
ion of the molecule outside and inside HUVEC respectively.