- Email: [email protected]
Shear stress-dependent platelet function after LDL cholesterol apheresis
Thrombosis Research (2004) 113, 395--398
intl.elsevierhealth.com/journals/thre
Brief Communication
Shear stress-dependent platelet function after LDL cholesterol apheresis Lukas E. Spieker *, Frank Ruschitzka, Juan J. Badimon, Georg Noll, Roberto Corti ¨rich, Switzerland Cardiology, University Hospital, CH-8091 Zu Received 2 February 2004; received in revised form 22 March 2004; accepted 4 April 2004 Available online 14 May 2004
KEYWORDS Cholesterol; Coronary artery disease; Thrombosis; Hemostasis
ABSTRACT Background: Platelets play a crucial role in the pathogenesis of acute coronary syndrome (ACS). Thrombus formation with subsequent arterial occlusion is a major determinant in ACS and stroke. Platelets also essentially contribute to the development and progression of atherosclerotic lesions. The aim of the present study was to investigate the effects lipid lowering by LDL apheresis on platelet function in patients with coronary artery disease. Methods: In six patients with angiographically proven coronary artery disease, venous blood samples were obtained before and after LDL cholesterol apheresis. Citrated whole blood (200 Al) was circulated in polystyrene wells at a shear rate of 1875 s 1 for 2 min with a rotating teflon cone. Shear-stress dependent platelet adhesion was measured before and after apheresis. Results: After apheresis, there were significant reductions in LDL ( 58%) and HDL ( 17%) cholesterol, triglycerides ( 43%), fibrinogen ( 52%), lipoprotein (a) ( 57%) and CRP ( 57%) levels. LDL apheresis significantly reduced shear-stress dependent platelet adhesion. Bolus administration of heparin significantly prolonged activated clotting time, but had no significant effect on platelet adhesion or aggregates. Conclusions: In patients with coronary artery disease, shearstress dependent platelet adhesion is reduced by a single LDL apheresis. In addition to its cholesterol-lowering effect, LDL apheresis reduces circulating levels of fibrinogen and C-reactive protein. A 2004 Elsevier Ltd. All rights reserved.
Platelets play a crucial role in the pathogenesis of acute coronary syndrome. Thrombus formation with subsequent arterial occlusion causes ischemia with its clinical manifestations such as myocardial * Corresponding author. Tel.: +41-1-255-11-11; fax: +41-1255-44-01. E-mail address: [email protected] (L.E. Spieker).
infarction or stroke. However, platelets also essentially contribute to the development and progression of atherosclerotic lesions [1]. The classical triad of blood flow, hemostatic blood factors, and vessel wall damage determines the susceptibility for thrombosis. Vessel wall damage may develop after years of exposure to cardiovascular risk factors. Elevated levels of low-
0049-3848/$ - see front matter A 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.thromres.2004.04.001
396
L.E. Spieker et al. / Thrombosis Research 113 (2004) 395--398
density lipoprotein (LDL) cholesterol are a primary risk factor for the development and progression of atherosclerosis. The use of lipid-lowering drugs thus is a mainstay of anti-atherosclerotic therapy. In patients at high coronary risk, extracorporeal LDL apheresis offers an adjunctive therapy for reducing LDL concentrations in combination with statins. Regular LDL apheresis stabilizes atherosclerotic coronary lesions and even induces regression of plaques in a substantial group of patients [2]. Clinical stabilization is achieved in many patients [3]. Heparin-induced extracorporeal LDL/fibrinogen precipitation (HELP) is based on heparin-induced LDL precipitation at acidic pH. Due to the simultaneous removal of LDL and fibrinogen, regular HELP apheresis can normalize hemorrheologic parameters [4,5]. The aim of the present study was to investigate the effects of HELP apheresis on platelet function in patients with coronary artery disease.
Methods Six patients with familial hypercholesterolemia and angiographically documented coronary artery disease undergoing chronic (bi-weekly) LDL apheresis by HELP, were included in the study after written informed consent. The protocol was approved by the local Institutional Ethical Review Board.
Protocol After resting supine for at least 10 min, venous blood was sampled with citrat-containing vacutainers from an indwelling apheresis catheter lying in an antecubital vein. Five minutes after intravenous bolus administration of heparin (individual dosage, 3000--5000 IE), another blood sample was taken for the measurement of activated clotting time (ACT) and platelet function. Then, LDL apheresis was started and after finalization of apheresis, blood sampling was repeated. Heparin was continually infused (4000 IE/h iv) until 20 min before the end of the apheresis.
Measurement of shear-dependent platelet function Citrated whole blood (200 Al) was circulated in polystyrene wells at a shear rate of 1875 s 1 for 2 min with a rotating teflon cone, as described previously [6--8]. Physiologic wall shear rate is below 100 s 1 in large veins, averages 100--1000
s 1 in large to medium-sized arteries, and about 1500 s 1 in arterioles [9]. Wells were washed, stained with May-Gru ¨nwald, and analyzed with a microscope connected to an image analysis system. Results are expressed as the percentage surface covered by platelets as well as the size of the platelet aggregates (NIH Image 1.63).
Statistical analysis Group comparisons were performed using paired ttest for parametric continuous data, and Wilcoxon’s signed rank test for nonparametric data. All probability values are two-tailed, and a P < 0.05 was considered statistically significant (SPSS 11).
Results The clinical characteristics of the patients are shown in Table 1. All patients had known stable coronary artery disease and were treated with LDL apheresis on top of aspirin (or clopidogrel) and a statin. Biochemic parameters before and after LDL apheresis are shown in Table 2. Baseline LDL cholesterol before apheresis was already relatively low as a result of aggressive chronic LDL apheresis on top of lipid-lowering statin therapy. After apheresis, there were significant reductions in LDL ( 58%) and HDL ( 17%) cholesterol, triglycerides ( 43%), fibrinogen ( 52%), lipoprotein-a ( 57%) and CRP ( 57%) levels. Activated clotting time and prothrombin time (3.5 fold) both remained prolonged at the end of the apheresis procedure, i.e. 20 min after stopping heparin infusion. The changes in platelet function after apheresis are shown in Fig. 1. LDL apheresis significantly reduced shear-stress dependent platelet adhesion on high shear rate conditions (Fig. 1A). In contrast,
Table 1 Clinical characteristics and concomitant medication of the study patients Female/male Age (years) Blood pressure (mm Hg) Heart rate (min 1) Diabetes mellitus Smokers Coronary artery disease Aspirin Clopidogrel Coumarine Statin
1/5 50 F 9 125 F 9/77 F 8 72 F 13 0% 0% 100% 83% 17% 33% 100%
Values represent mean F standard deviation.
L.E. Spieker et al. / Thrombosis Research 113 (2004) 395--398
Table 2 Biochemical parameters before and after LDL apheresis Before
After
P
LDL apheresis HDL cholesterol (mmol/l) LDL cholesterol (mmol/l) Triglycerides (mmol/l) Lipoprotein a (mg/l) Fibrinogen (g/l) C-reactive protein (mg/dl) PTT (s) ACT (s)
1.2 F 0.1 3.6 F 0.7 3.0 F 0.6 425 F 200 2.7 F 0.3 2.8 F 1.9
1.0 F 0.1 1.5 F 0.2 1.7 F 0.4 181 F 98 1.3 F 0.6 1.2 F 0.7
0.011 0.016 0.004 0.043 0.003 0.027
29 F 1 111 F 4
100 F 16 0.013 147 F 7 0.010
397
the GpIIb/IIIa pathways, as well as the presence of fibrinogen [7,8]. Fibrinogen is effectively removed by HELP apheresis, as is von Willebrand factor [14,15]. These changes may thus contribute to the observed antithrombotic effect of HELP apheresis. The effects of heparin on platelet adhesion have been separately assessed in the present study. As platelet adhesion was not significantly affected by heparin, a confounding role of heparin on the observed effect of HELP apheresis on platelet function is excluded.
Values represent mean F standard error. PTT denotes partial thromboplastin time, and ACT, activated clotting time.
there was an increased size of adhering platelet aggregates after apheresis (Fig. 1B) possibly reflecting platelet activation (cross-linking) during extracorporeal blood circulation due to prolonged contact with artificial surfaces of the HELP-system. Bolus administration of heparin before apheresis significantly prolonged activated clotting time, but had no significant effect on platelet adhesion (Fig. 1C).
Discussion This study shows that a single LDL apheresis reduces shear-stress dependent platelet adhesion in patients with coronary artery disease. LDL apheresis reduced circulating levels of LDL cholesterol, triglycerides, fibrinogen, and C-reactive protein. We tested platelet adhesion in high shear rate conditions and therefore mimicking the clinical presentation of high-degree coronary stenosis. Platelets play a crucial role in the pathogenesis of acute coronary syndrome. Moreover, the crosstalk between platelets, the endothelium, and inflammatory blood cells determines the development and progression of atherosclerosis [10]. The present results demonstrate reduced shearstress induced platelet adhesion after LDL apheresis. Cholesterol-lowering with statins reduces platelet reactivity [11--13]. The hypolipidemic effect of statins is an important mechanism of the antithrombotic effect. However, other effects may contribute to the beneficial effects of statins. Likewise, HELP apheresis exerts pleiotropic actions in addition to cholesterol removal, as other prothrombotic factors are affected. Platelet adhesion to a polystyrene surface depends on the von Willebrand Factor-GpIb and
Fig. 1 (A) Shear-stress dependent platelet adhesion and size of adhering platelet aggregates at baseline, after bolus administration of heparin, and after heparininduced extracorporal low-density lipoprotein (HELP) apheresis. There is a significant decrease in shear-stress dependent platelet adhesion after HELP apheresis. (B) In contrast, there is an increased size of adhering platelet aggregates after HELP apheresis. AU denotes arbitrary units, i.e. square pixels. (C) Activated clotting time (ACT) before, after bolus administration of intravenous heparin, and at the end of HELP apheresis (i.e. 20 min after stopping heparin infusion). *P < 0.05, yP V 0.01.
398
L.E. Spieker et al. / Thrombosis Research 113 (2004) 395--398
Of particular interest is the lowering of CRP levels by HELP apheresis [16]. CRP is an inflammatory marker with prognostic significance both in an asymptomatic population, as well as in patients with acute or chronic coronary artery disease [17,18]. CRP increases the expression of tissue factor in monocytes and thus activates the clotting system. In a transgenic mouse model overexpressing human CRP, an exuberant thrombotic response to arterial injury was recently observed [19]. CRP may thus indeed play a prothrombotic role, as suggested by the results of the present study. The surface coverage of platelets is mainly determined by the GpIb interaction with vWF, and the size of the platelet aggregates depends on the GpIIb/IIIa activity [20]. The efficacy of GpIIb/IIIa receptor antagonists can thus be reliably monitored [6]. The size of platelet aggregates was increased after LDL apheresis. Possibly, these changes reflect influences of the apheresis system on platelets. As HELP apheresis depends on extracorporeal precipitation of LDL cholesterol, artificial surfaces such as the used tubing system may have led to enhanced cross-linking of platelets via GpIIb/IIIa. In conclusion, in patients with coronary artery disease shear-stress dependent platelet adhesion is reduced by a single LDL cholesterol apheresis. The effects of LDL apheresis on platelet function were observed in patients with coronary artery disease receiving intensive medical treatment consisting of platelet inhibition with aspirin or clopidogrel, and cholesterol lowering with a statin. HELP apheresis could have a potential beneficial effect not only for reducing plasma lipid levels of hyperlipidemic patients but also via reduced platelet reactivity as a consequence of the intervention. Acknowledgements The authors thank Elvira Dietl for expert technical assistance.
References [1] Ruggeri ZM. Platelets in atherothrombosis. Nat Med 2002; 8:1227--34. [2] Schuff-Werner P, Gohlke H, Bartmann U, et al. The HELPLDL-apheresis multicentre study, an angiographically assessed trial on the role of LDL-apheresis in the secondary prevention of coronary heart disease: II. Final evaluation of the effect of regular treatment on LDL-cholesterol plasma concentrations and the course of coronary heart disease. The HELP-Study Group. Heparin-induced extra-corporeal LDL-precipitation. Eur J Clin Investig 1994;24:724--32.
[3] Park JW, Merz M, Braun P. Effect of HELP-LDL-apheresis on outcomes in patients with advanced coronary atherosclerosis and severe hypercholesterolemia. Atherosclerosis 1998;139:401--9. [4] Walzl M, Lechner H, Walzl B, Schied G. Improved neurological recovery of cerebral infarctions after plasmapheretic reduction of lipids and fibrinogen. Stroke 1993;24:1447--51. [5] Fadul JE, Linde T, Sandhagen B, Wikstrom B, Danielson BG. Effects of extracorporeal hemapheresis therapy on blood rheology. J Clin Apher 1997;12:183--6. [6] Osende JI, Fuster V, Lev EI, et al. Testing platelet activation with a shear-dependent platelet function test versus aggregation-based tests relevance for monitoring long-term glycoprotein IIb/IIIa inhibition. Circulation 2001; 103:1488--91. [7] Varon D, Dardik R, Shenkman B, et al. A new method for quantitative analysis of whole blood platelet interaction with extracellular matrix under flow conditions. Thromb Res 1997;85:283--94. [8] Shenkman B, Savion N, Dardik R, Tamarin I, Varon D. Testing of platelet deposition on polystyrene surface under flow conditions by the cone and plate(let) analyzer: role of platelet activation, fibrinogen and von Willebrand factor. Thromb Res 2000;99:353--61. [9] Strony J, Beaudin A, Brands D, Adelman B. Analysis of shear stress and hemodynamic factors in a model of artery stenosis and thrombosis. Am J Physiol 1993;265:H1787--96. [10] Henn V, Slupsky JR, Grafe M, et al. CD40 ligand on activated platelets triggers an inflammatory reaction of endothelial cells. Nature 1998;391:591--4. [11] Rauch U, Osende JI, Chesebro JH, et al. Statins and cardiovascular diseases: the multiple effects of lipid-lowering therapy by statins. Atherosclerosis 2000;153:181--9. [12] Dangas G, Badimon JJ, Smith DA, et al. Pravastatin therapy in hyperlipidemia: effects on thrombus formation and the systemic hemostatic profile. J Am Coll Cardiol 1999;33: 1294--304. [13] Dangas G, Smith DA, Unger AH, et al. Pravastatin: an antithrombotic effect independent of the cholesterollowering effect. Thromb Haemost 2000;83:688--92. [14] Julius U, Siegert G, Gromeier S. Intraindividual comparison of the impact of two selective apheresis methods (DALI and HELP) on the coagulation system. Int J Artif Organs 2000; 23:199--206. [15] Kojima S. Low-density lipoprotein apheresis and changes in plasma components. Therap Apher 2001;5:232--8. [16] Moriarty PM, Gibson CA, Shih J, Matias MS. C-reactive protein and other markers of inflammation among patients undergoing HELP LDL apheresis. Atherosclerosis 2001; 158:495--8. [17] Ridker PM, Rifai N, Pfeffer MA, et al. Inflammation, pravastatin, and the risk of coronary events after myocardial infarction in patients with average cholesterol levels. Cholesterol and Recurrent Events (CARE) Investigators. Circulation 1998;98:839--44. [18] Liuzzo G, Biasucci LM, Gallimore JR, et al. The prognostic value of C-reactive protein and serum amyloid a protein in severe unstable angina. N Engl J Med 1994;331:417--24. [19] Danenberg HD, Szalai AJ, Swaminathan RV, et al. Increased thrombosis after arterial injury in human C-reactive protein-transgenic mice. Circulation 2003;108:512--5. [20] Varon D, Lashevski I, Brenner B, et al. Cone and plate(let) analyzer: monitoring glycoprotein IIb/IIIa antagonists and von Willebrand disease replacement therapy by testing platelet deposition under flow conditions. Am Heart J 1998;135:S187--93.
intl.elsevierhealth.com/journals/thre
Brief Communication
Shear stress-dependent platelet function after LDL cholesterol apheresis Lukas E. Spieker *, Frank Ruschitzka, Juan J. Badimon, Georg Noll, Roberto Corti ¨rich, Switzerland Cardiology, University Hospital, CH-8091 Zu Received 2 February 2004; received in revised form 22 March 2004; accepted 4 April 2004 Available online 14 May 2004
KEYWORDS Cholesterol; Coronary artery disease; Thrombosis; Hemostasis
ABSTRACT Background: Platelets play a crucial role in the pathogenesis of acute coronary syndrome (ACS). Thrombus formation with subsequent arterial occlusion is a major determinant in ACS and stroke. Platelets also essentially contribute to the development and progression of atherosclerotic lesions. The aim of the present study was to investigate the effects lipid lowering by LDL apheresis on platelet function in patients with coronary artery disease. Methods: In six patients with angiographically proven coronary artery disease, venous blood samples were obtained before and after LDL cholesterol apheresis. Citrated whole blood (200 Al) was circulated in polystyrene wells at a shear rate of 1875 s 1 for 2 min with a rotating teflon cone. Shear-stress dependent platelet adhesion was measured before and after apheresis. Results: After apheresis, there were significant reductions in LDL ( 58%) and HDL ( 17%) cholesterol, triglycerides ( 43%), fibrinogen ( 52%), lipoprotein (a) ( 57%) and CRP ( 57%) levels. LDL apheresis significantly reduced shear-stress dependent platelet adhesion. Bolus administration of heparin significantly prolonged activated clotting time, but had no significant effect on platelet adhesion or aggregates. Conclusions: In patients with coronary artery disease, shearstress dependent platelet adhesion is reduced by a single LDL apheresis. In addition to its cholesterol-lowering effect, LDL apheresis reduces circulating levels of fibrinogen and C-reactive protein. A 2004 Elsevier Ltd. All rights reserved.
Platelets play a crucial role in the pathogenesis of acute coronary syndrome. Thrombus formation with subsequent arterial occlusion causes ischemia with its clinical manifestations such as myocardial * Corresponding author. Tel.: +41-1-255-11-11; fax: +41-1255-44-01. E-mail address: [email protected] (L.E. Spieker).
infarction or stroke. However, platelets also essentially contribute to the development and progression of atherosclerotic lesions [1]. The classical triad of blood flow, hemostatic blood factors, and vessel wall damage determines the susceptibility for thrombosis. Vessel wall damage may develop after years of exposure to cardiovascular risk factors. Elevated levels of low-
0049-3848/$ - see front matter A 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.thromres.2004.04.001
396
L.E. Spieker et al. / Thrombosis Research 113 (2004) 395--398
density lipoprotein (LDL) cholesterol are a primary risk factor for the development and progression of atherosclerosis. The use of lipid-lowering drugs thus is a mainstay of anti-atherosclerotic therapy. In patients at high coronary risk, extracorporeal LDL apheresis offers an adjunctive therapy for reducing LDL concentrations in combination with statins. Regular LDL apheresis stabilizes atherosclerotic coronary lesions and even induces regression of plaques in a substantial group of patients [2]. Clinical stabilization is achieved in many patients [3]. Heparin-induced extracorporeal LDL/fibrinogen precipitation (HELP) is based on heparin-induced LDL precipitation at acidic pH. Due to the simultaneous removal of LDL and fibrinogen, regular HELP apheresis can normalize hemorrheologic parameters [4,5]. The aim of the present study was to investigate the effects of HELP apheresis on platelet function in patients with coronary artery disease.
Methods Six patients with familial hypercholesterolemia and angiographically documented coronary artery disease undergoing chronic (bi-weekly) LDL apheresis by HELP, were included in the study after written informed consent. The protocol was approved by the local Institutional Ethical Review Board.
Protocol After resting supine for at least 10 min, venous blood was sampled with citrat-containing vacutainers from an indwelling apheresis catheter lying in an antecubital vein. Five minutes after intravenous bolus administration of heparin (individual dosage, 3000--5000 IE), another blood sample was taken for the measurement of activated clotting time (ACT) and platelet function. Then, LDL apheresis was started and after finalization of apheresis, blood sampling was repeated. Heparin was continually infused (4000 IE/h iv) until 20 min before the end of the apheresis.
Measurement of shear-dependent platelet function Citrated whole blood (200 Al) was circulated in polystyrene wells at a shear rate of 1875 s 1 for 2 min with a rotating teflon cone, as described previously [6--8]. Physiologic wall shear rate is below 100 s 1 in large veins, averages 100--1000
s 1 in large to medium-sized arteries, and about 1500 s 1 in arterioles [9]. Wells were washed, stained with May-Gru ¨nwald, and analyzed with a microscope connected to an image analysis system. Results are expressed as the percentage surface covered by platelets as well as the size of the platelet aggregates (NIH Image 1.63).
Statistical analysis Group comparisons were performed using paired ttest for parametric continuous data, and Wilcoxon’s signed rank test for nonparametric data. All probability values are two-tailed, and a P < 0.05 was considered statistically significant (SPSS 11).
Results The clinical characteristics of the patients are shown in Table 1. All patients had known stable coronary artery disease and were treated with LDL apheresis on top of aspirin (or clopidogrel) and a statin. Biochemic parameters before and after LDL apheresis are shown in Table 2. Baseline LDL cholesterol before apheresis was already relatively low as a result of aggressive chronic LDL apheresis on top of lipid-lowering statin therapy. After apheresis, there were significant reductions in LDL ( 58%) and HDL ( 17%) cholesterol, triglycerides ( 43%), fibrinogen ( 52%), lipoprotein-a ( 57%) and CRP ( 57%) levels. Activated clotting time and prothrombin time (3.5 fold) both remained prolonged at the end of the apheresis procedure, i.e. 20 min after stopping heparin infusion. The changes in platelet function after apheresis are shown in Fig. 1. LDL apheresis significantly reduced shear-stress dependent platelet adhesion on high shear rate conditions (Fig. 1A). In contrast,
Table 1 Clinical characteristics and concomitant medication of the study patients Female/male Age (years) Blood pressure (mm Hg) Heart rate (min 1) Diabetes mellitus Smokers Coronary artery disease Aspirin Clopidogrel Coumarine Statin
1/5 50 F 9 125 F 9/77 F 8 72 F 13 0% 0% 100% 83% 17% 33% 100%
Values represent mean F standard deviation.
L.E. Spieker et al. / Thrombosis Research 113 (2004) 395--398
Table 2 Biochemical parameters before and after LDL apheresis Before
After
P
LDL apheresis HDL cholesterol (mmol/l) LDL cholesterol (mmol/l) Triglycerides (mmol/l) Lipoprotein a (mg/l) Fibrinogen (g/l) C-reactive protein (mg/dl) PTT (s) ACT (s)
1.2 F 0.1 3.6 F 0.7 3.0 F 0.6 425 F 200 2.7 F 0.3 2.8 F 1.9
1.0 F 0.1 1.5 F 0.2 1.7 F 0.4 181 F 98 1.3 F 0.6 1.2 F 0.7
0.011 0.016 0.004 0.043 0.003 0.027
29 F 1 111 F 4
100 F 16 0.013 147 F 7 0.010
397
the GpIIb/IIIa pathways, as well as the presence of fibrinogen [7,8]. Fibrinogen is effectively removed by HELP apheresis, as is von Willebrand factor [14,15]. These changes may thus contribute to the observed antithrombotic effect of HELP apheresis. The effects of heparin on platelet adhesion have been separately assessed in the present study. As platelet adhesion was not significantly affected by heparin, a confounding role of heparin on the observed effect of HELP apheresis on platelet function is excluded.
Values represent mean F standard error. PTT denotes partial thromboplastin time, and ACT, activated clotting time.
there was an increased size of adhering platelet aggregates after apheresis (Fig. 1B) possibly reflecting platelet activation (cross-linking) during extracorporeal blood circulation due to prolonged contact with artificial surfaces of the HELP-system. Bolus administration of heparin before apheresis significantly prolonged activated clotting time, but had no significant effect on platelet adhesion (Fig. 1C).
Discussion This study shows that a single LDL apheresis reduces shear-stress dependent platelet adhesion in patients with coronary artery disease. LDL apheresis reduced circulating levels of LDL cholesterol, triglycerides, fibrinogen, and C-reactive protein. We tested platelet adhesion in high shear rate conditions and therefore mimicking the clinical presentation of high-degree coronary stenosis. Platelets play a crucial role in the pathogenesis of acute coronary syndrome. Moreover, the crosstalk between platelets, the endothelium, and inflammatory blood cells determines the development and progression of atherosclerosis [10]. The present results demonstrate reduced shearstress induced platelet adhesion after LDL apheresis. Cholesterol-lowering with statins reduces platelet reactivity [11--13]. The hypolipidemic effect of statins is an important mechanism of the antithrombotic effect. However, other effects may contribute to the beneficial effects of statins. Likewise, HELP apheresis exerts pleiotropic actions in addition to cholesterol removal, as other prothrombotic factors are affected. Platelet adhesion to a polystyrene surface depends on the von Willebrand Factor-GpIb and
Fig. 1 (A) Shear-stress dependent platelet adhesion and size of adhering platelet aggregates at baseline, after bolus administration of heparin, and after heparininduced extracorporal low-density lipoprotein (HELP) apheresis. There is a significant decrease in shear-stress dependent platelet adhesion after HELP apheresis. (B) In contrast, there is an increased size of adhering platelet aggregates after HELP apheresis. AU denotes arbitrary units, i.e. square pixels. (C) Activated clotting time (ACT) before, after bolus administration of intravenous heparin, and at the end of HELP apheresis (i.e. 20 min after stopping heparin infusion). *P < 0.05, yP V 0.01.
398
L.E. Spieker et al. / Thrombosis Research 113 (2004) 395--398
Of particular interest is the lowering of CRP levels by HELP apheresis [16]. CRP is an inflammatory marker with prognostic significance both in an asymptomatic population, as well as in patients with acute or chronic coronary artery disease [17,18]. CRP increases the expression of tissue factor in monocytes and thus activates the clotting system. In a transgenic mouse model overexpressing human CRP, an exuberant thrombotic response to arterial injury was recently observed [19]. CRP may thus indeed play a prothrombotic role, as suggested by the results of the present study. The surface coverage of platelets is mainly determined by the GpIb interaction with vWF, and the size of the platelet aggregates depends on the GpIIb/IIIa activity [20]. The efficacy of GpIIb/IIIa receptor antagonists can thus be reliably monitored [6]. The size of platelet aggregates was increased after LDL apheresis. Possibly, these changes reflect influences of the apheresis system on platelets. As HELP apheresis depends on extracorporeal precipitation of LDL cholesterol, artificial surfaces such as the used tubing system may have led to enhanced cross-linking of platelets via GpIIb/IIIa. In conclusion, in patients with coronary artery disease shear-stress dependent platelet adhesion is reduced by a single LDL cholesterol apheresis. The effects of LDL apheresis on platelet function were observed in patients with coronary artery disease receiving intensive medical treatment consisting of platelet inhibition with aspirin or clopidogrel, and cholesterol lowering with a statin. HELP apheresis could have a potential beneficial effect not only for reducing plasma lipid levels of hyperlipidemic patients but also via reduced platelet reactivity as a consequence of the intervention. Acknowledgements The authors thank Elvira Dietl for expert technical assistance.
References [1] Ruggeri ZM. Platelets in atherothrombosis. Nat Med 2002; 8:1227--34. [2] Schuff-Werner P, Gohlke H, Bartmann U, et al. The HELPLDL-apheresis multicentre study, an angiographically assessed trial on the role of LDL-apheresis in the secondary prevention of coronary heart disease: II. Final evaluation of the effect of regular treatment on LDL-cholesterol plasma concentrations and the course of coronary heart disease. The HELP-Study Group. Heparin-induced extra-corporeal LDL-precipitation. Eur J Clin Investig 1994;24:724--32.
[3] Park JW, Merz M, Braun P. Effect of HELP-LDL-apheresis on outcomes in patients with advanced coronary atherosclerosis and severe hypercholesterolemia. Atherosclerosis 1998;139:401--9. [4] Walzl M, Lechner H, Walzl B, Schied G. Improved neurological recovery of cerebral infarctions after plasmapheretic reduction of lipids and fibrinogen. Stroke 1993;24:1447--51. [5] Fadul JE, Linde T, Sandhagen B, Wikstrom B, Danielson BG. Effects of extracorporeal hemapheresis therapy on blood rheology. J Clin Apher 1997;12:183--6. [6] Osende JI, Fuster V, Lev EI, et al. Testing platelet activation with a shear-dependent platelet function test versus aggregation-based tests relevance for monitoring long-term glycoprotein IIb/IIIa inhibition. Circulation 2001; 103:1488--91. [7] Varon D, Dardik R, Shenkman B, et al. A new method for quantitative analysis of whole blood platelet interaction with extracellular matrix under flow conditions. Thromb Res 1997;85:283--94. [8] Shenkman B, Savion N, Dardik R, Tamarin I, Varon D. Testing of platelet deposition on polystyrene surface under flow conditions by the cone and plate(let) analyzer: role of platelet activation, fibrinogen and von Willebrand factor. Thromb Res 2000;99:353--61. [9] Strony J, Beaudin A, Brands D, Adelman B. Analysis of shear stress and hemodynamic factors in a model of artery stenosis and thrombosis. Am J Physiol 1993;265:H1787--96. [10] Henn V, Slupsky JR, Grafe M, et al. CD40 ligand on activated platelets triggers an inflammatory reaction of endothelial cells. Nature 1998;391:591--4. [11] Rauch U, Osende JI, Chesebro JH, et al. Statins and cardiovascular diseases: the multiple effects of lipid-lowering therapy by statins. Atherosclerosis 2000;153:181--9. [12] Dangas G, Badimon JJ, Smith DA, et al. Pravastatin therapy in hyperlipidemia: effects on thrombus formation and the systemic hemostatic profile. J Am Coll Cardiol 1999;33: 1294--304. [13] Dangas G, Smith DA, Unger AH, et al. Pravastatin: an antithrombotic effect independent of the cholesterollowering effect. Thromb Haemost 2000;83:688--92. [14] Julius U, Siegert G, Gromeier S. Intraindividual comparison of the impact of two selective apheresis methods (DALI and HELP) on the coagulation system. Int J Artif Organs 2000; 23:199--206. [15] Kojima S. Low-density lipoprotein apheresis and changes in plasma components. Therap Apher 2001;5:232--8. [16] Moriarty PM, Gibson CA, Shih J, Matias MS. C-reactive protein and other markers of inflammation among patients undergoing HELP LDL apheresis. Atherosclerosis 2001; 158:495--8. [17] Ridker PM, Rifai N, Pfeffer MA, et al. Inflammation, pravastatin, and the risk of coronary events after myocardial infarction in patients with average cholesterol levels. Cholesterol and Recurrent Events (CARE) Investigators. Circulation 1998;98:839--44. [18] Liuzzo G, Biasucci LM, Gallimore JR, et al. The prognostic value of C-reactive protein and serum amyloid a protein in severe unstable angina. N Engl J Med 1994;331:417--24. [19] Danenberg HD, Szalai AJ, Swaminathan RV, et al. Increased thrombosis after arterial injury in human C-reactive protein-transgenic mice. Circulation 2003;108:512--5. [20] Varon D, Lashevski I, Brenner B, et al. Cone and plate(let) analyzer: monitoring glycoprotein IIb/IIIa antagonists and von Willebrand disease replacement therapy by testing platelet deposition under flow conditions. Am Heart J 1998;135:S187--93.