correlation between plasma fTFPI and total cholesterol was relatively poor r = 0.31, P B 0.05; Fig. 5A. The
correlation between plasma fTFPI and LDL-cholesterol was also poor r = 0.30, P B 0.05; Fig. 5B. The plasma
level of FVIIc correlated with total cholesterol r = 0.35, P B 0.05; Fig. 6A and triglycerides r = 0.36,
P B 0.05; Fig. 6D, whereas no significant associations were found with LDL-cholesterol r = 0.03; Fig. 6B or
HDL-cholesterol r = 0.23; Fig. 6C. On the other hand, no correlations were found between plasma F1 +
2 and serum lipids data not shown. There were also no significant correlations between Lp a concentra-
tions and any of the hemostatic parameters data not shown.
4. Discussion
The present study demonstrates, as previously re- ported by other authors [14,22], that plasma levels of
tTFPI increase in the patients with type II hyperlipi- demia and that cholesterol-lowering therapy reduces
this increase. However, the results showed that plasma levels of fTFPI also increased and fTFPI levels did not
change after therapy. Furthermore, the plasma F1 + 2 concentrations and FVIIc were higher in hypercholes-
terolemic patients than in normal controls and the plasma levels of F1 + 2 and FVIIc were significantly
decreased after therapy.
4
.
1
. Extrinsic coagulation pathway in hypercholesterolemia
TF is synthesized in perturbed endothelial cells, and can be found in the cores of atherosclerotic plaques
[23]. At sites of vascular injury, exposed subendothe- lium, or plaque rupture, TF comes in contact with
circulating FVII, forming a bimolecular complex and, thus, plays a central role as the initiator of the extrinsic
coagulation pathway [24]. The expression of TF by
Fig. 4. Correlations between total tissue factor pathway inhibitor tTFPI antigen and total cholesterol A, low density lipoprotein LDL-choles- terol B, high density lipoprotein HDL-cholesterol C, and triglyceride D in hypercholesterolemic patients at baseline and after treatment
with simvastatin
and atorvastatin .
Fig. 5. Correlations between free-form tissue factor pathway inhibitor fTFPI antigen and total cholesterol A, low density lipoprotein LDL-cholesterol B, high density lipoprotein HDL-cholesterol C, and triglyceride D in hypercholesterolemic patients at baseline and
after treatment with simvastatin
and atorvastatin .
endothelial cells and macrophages is stimulated by min- imally oxidized LDL and acetyl-modified LDL respec-
tively [25,26]. Transient exposure of TF at the surface of atherosclerotic plaques or pertubated endothelial cells
may cause low-grade triggering of blood coagulation. Actually, the results show elevated plasma levels of
F1 + 2 in the patients with type II hyperlipidemia. Because F1 + 2 is a very sensitive and specific marker of
thrombin generation and activation of the coagulation system [27], the data indicate that there may be an
activation of thrombin generation in hypercholes- terolemic patients. However, plasma concentrations of
TF antigen in the patients with hyperlipidemia were not significantly increased in the present study. Since TF is
cell-associated, plasma TF antigen may not reflect blood circulating levels of TF. So it should be experimentally
demonstrated that topical expression of TF at the surface of macrophages and endothelial cells actually
results in activation of the extrinsic coagulation system.
4
.
2
. Plasma tTFPI antigen and fTFPI antigen in hypercholesterolemic patients
Control of the highly procoagulant activity of the TF-FVIIa complex occurs through feedback inhibition
by TFPI, which is considered to be the principal inhibitor of the complex in vivo [1,2]. It is generally
agreed that TFPI is synthesized primarily in endo- thelial cells [3] and binds with proteoglycans on the cells
[4,5], and that some portion of the endothelial cell-asso- ciated TFPI is constantly released into plasma as the
free form, some of which then binds with lipoprotein particles, becoming lipoprotein-associated TFPI by
some as yet unknown mechanism. Kokawa et al. re- ported that both of fTFPI and endothelial cell-associ-
ated TFPI are in equilibrium in vivo and that the ELISA kit for fTFPI antigen can be used for assessing
changes in the levels of endothelial cell-associated TFPI antigen [9].
As in other recent studies [13,14], the findings show that plasma levels of tTFPI antigen increase in hyperc-
holesterolemic patients and that tTFPI antigen in plasma is positively correlated with serum total choles-
terol and LDL-cholesterol. However, the findings show that plasma levels of fTFPI antigen were also signifi-
cantly higher in those patients than in normal subjects. This result of this study is contrary to those of
Kokawa’s [9], although Kokawa et al. and plasma levels of fTFPI antigen were measured using the same
ELISA kit. In their study, hyperlipidemic patients were found to have higher plasma levels of lipoprotein-
bound TFPI and lower levels of fTFPI, in comparison to control subjects. These opposite results observed
between two studies may be likely to be due to differ- ences in patient groups, baseline levels of cholesterol, or
the extent of atherosclerosis and the endothelial injury. The patients in their study contained some FH and had
higher levels of total cholesterol than those in this study. Therefore their patients would promote athero-
genesis and have severe endothelial injury, so that the endothelial cell-associated TFPI might decrease.
On the other hand, the mechanism of increase in the plasma fTFPI in the patients with hypercholesterolemia
remains unknown. It was speculated that at least the endothelial cell-associated TFPI would not decrease in
the hyperlipidemic patients, as the patients would have mild endothelial injury, and that the increase in fTFPI
in plasma of the patients may have been caused by the following: 1 reflection to increased endothelial cell-as-
sociated TFPI hypercoagulability activates the produc- tion of TFPI in endothelial cells and bind to surface of
them; or 2 release from the endothelial cells by thrombin stimulation. Clinical studies have demon-
strated that the inhibition of the coagulation system by the administration of recombinant TFPI prevents reoc-
clusion [28]. Moreover, Lindahl et al. suggest that the anticoagulant potential of plasma TFPI is restricted to
Fig. 6. Correlations between factor VIIc FVIIc and total cholesterol A, low density lipoprotein LDL-cholesterol B, high density lipoprotein HDL-cholesterol C, and triglyceride D in hypercholesterolemic patients at baseline and after treatment with simvastatin
and
atorvastatin .
carrier-free TFPI [15]. If this assumption is correct, the increased fTFPI levels may inhibit the blood coagula-
tion in the hyperlipidemic patients. It may be hypothe- sized that the elevated plasma fTFPI concentrations
andor lipoprotein-associated TFPI concentrations seen in hypercholesterolemia represent a compensatory
mechanism to prevent activation of the blood coagula- tion system by TF and FVII.
4
.
3
. Effect of HMG-CoA reductase inhibitor on plasma hemostatic parameters
As expected, total cholesterol was reduced in the 25 patients receiving HMG CoA-reductase inhibitors in
the present study. Interestingly, recent clinical trials have documented that intensive lipid lowering therapy,
especially employing HMG-CoA reductase inhibitors, significantly reduces ischemia-related clinical cardiac
events despite only minimal regression of coronary artery stenosis, as measured angiographically [29,30].
Plaque stabilization due to decreased lipid content of lesions [31], improved endothelial function [32,33] and
decreased tendency to form platelet thrombi [34] are three direct mechanisms that may account for the re-
duction in coronary events associated with this lower- ing of cholesterol.
Lipids and lipoproteins modulate hemostasis by al- tering the expression and function of thrombotic and
fibrinolytic factors. Consequently additional beneficial effects of HMG-CoA reductase inhibitors on coronary
events may involve secondary mechanisms that modify thrombus formation. This study shows that cholesterol-
lowering treatment induces a significant reduction in plasma levels of F1 + 2 and FVIIc. These changes
suggest that there may be an improvement in the hypercoagulable state with reduction of serum choles-
terol levels. Although the reduction in these parameters of hypercoagulation did not correlate with reduction in
serum cholesterol concentrations and may have resulted in part from the lowered fat intake or a non specific
effect of the drug, the reduction in F1 + 2 and FVIIc during lipid-lowering treatment may, in part, be respon-
sible for a decreased risk of thrombosis.
4
.
4
. Effect of HMG-CoA reductase inhibitor on plasma tTFPI and fTFPI le6els
The present study also demonstrated that therapeutic lowering of total cholesterol in patients with type II
hyperlipoproteinemia was paralleled by a decrease in plasma concentrations of tTFPI but did not effect the
plasma concentrations of fTFPI. The fall in tTFPI is believed to be due mainly to a lowering of the amount
of circulating LDL – TFPI complexes [16]. If the as- sumption that the anticoagulant activity of fTFPI is
markedly higher than that of lipoprotein-associated TFPI [15] is correct, HMG-CoA reductase inhibitor
treatment, which caused a specific drop in LDL – TFPI complexes and maintained fTFPI levels, would not
affect the anticoagulant potency of TFPI in plasma. Recently, Hansen et al. have also demonstrated that a
specific and prominent decrease in the amount of LDL – TFPI complexes by the HMG-CoA reductase
inhibitor, lovastatin, did not affect the anticoagulant potency of TFPI either in human plasma or in the
vascular endothelium [22].
5. Conclusions
