Platelets have a key role in normal hemostasis and in the pathogenesis of atherothrombotic events, such as acute coronary syndrome. Following plaque rupture, platelets adhere to the subendothelial matrix, become activated and then aggregate to form a prothrombotic surface that promotes clot formation and subsequently vascular occlusion. Multiple pathways are involved in platelet activation, including those activated by adenosine diphosphate (ADP), thromboxane A2, epinephrine, serotonin, collagen, and thrombin. Currently, two groups of inhibitors of platelet activation are approved for clinical use in patients with acute coronary syndromes: cyclooxygenase-1 inhibitors, namely aspirin, and oral ADP receptor antagonists such as clopidogrel. These agents have shown improved short- and long-term clinical outcomes but are associated with increased bleeding risk, and the rates of recurrent ischemic events remain high. These considerations underscore the need for novel antiplatelet agents that can provide greater reduction in recurrent atherothrombotic events without increasing the risk of bleeding. Several novel antiplatelet agents are currently under clinical development, such as more potent ADP receptor antagonists and protease-activated receptor-1 antagonists. This article provides an overview of the basic principles of platelet biology and the current status of knowledge on available oral antiplatelet therapy, as well as those under clinical development.
Risk assessment of cardiovascular diseases (CVD) is shifting from the relative risk to an absolute risk approach. The residual lifetime risk (LTR), which provides an absolute risk assessment, is an epidemiologic measure that expresses the probability of someone of a given age and sex developing a disease condition during their remaining lifespan. The LTR estimation is important because it could be more easily comprehended by clinicians and patients. The LTR for CVD was not estimated for the Japanese population until recently, when the LTR of stroke and acute myocardial infarction (AMI) was reported. The reported LTR of stroke and AMI for middle-aged adults is substantial. The observed probabilities illustrated that approximately 1 in 5 men and women of middle age will suffer from a stroke in their remaining lifetime. On the other hand, approximately 1 in 6 men and 1 in 9 women of middle age will suffer from AMI in their remaining lifetime. Aaginst the backdrop of the aging population and worsening risk factor scenario, these estimates re-emphasize that CVD is a public health burden that requires preventive interventions. These estimates provide a means to communicate the absolute risk of CVD to the lay population, policy makers, as well as health service providers in predicting the disease burden of CVD. This easily comprehended knowledge can be used as an important index to assist in public health education and planning.
Aim: Atrial fibrillation (AF) is characterized by the development of thromboembolic events and is more prevalent among end-stage renal disease patients than in the general population. Vascular access thrombosis (VAT) is a major morbidity in chronic hemodialysis (HD) patients; however, the association between AF and VAT is unknown. Methods: We retrospectively reviewed chronic HD patients with functional vascular access between 1997 and 2006. The association between AF and the development of VAT was analyzed using Kaplan-Meier analysis and multivariate Cox proportional hazards regression. Results: A total of 568 chronic HD patients, including 55 (9.7%) patients with AF, were reviewed and 154 (27.1%) patients developed at least one episode of VAT. Patients with AF had worse VAT-free survival than patients without AF (p< 0.001). In Cox regression, age, type of vascular access, atrial fibrillation, diabetes, hypertension, and C-reactive protein were independently linked to the development of VAT ( p= 0.049, < 0.001, < 0.001, 0.001, 0.028 and 0.045). The hazard ratios were 2.1 (95% CI: 1.00-1.03) for arteriovenous graft, 2.47 (95% CI: 1.66-3.69) for AF, 1.72 (95% CI: 1.25-2.39) for diabetes and 1.09 (95% CI: 1.00-1.18) for serum C-reactive protein (every 1 mg/dL increase), respectively. Conclusion: Atrial fibrillaiton is linked to the development of vascular access thrombosis in chronic hemodialysis patients and is independent of traditional VAT risk factors.
Aim: The aim of this study was to identify the threshold level for non-high-density lipoprotein cholesterol (non-HDL-cholesterol) to raise the risk of coronary heart disease (CHD) incidence in a Japanese general population. Methods: A total of 8,132 men and women, aged 40 to 69 years with no history of stroke or CHD, completed the baseline risk factor surveys between 1975 and 1987. Systematic surveillance of cardiovascular disease incidence was performed through 2003 (the median follow-up period was 21.9 years), and 155 incidents of CHD were identified. Results: We found a statistically significant association between non-HDL-cholesterol levels and the risk of CHD with a threshold around 140 mg/dL. After adjustment for potential confounding factors, this association did not change materially. The multivariable hazard ratio of CHD compared with that for levels of < 100 mg/dL was 2.49 (95% confidence interval: 1.35 to 4.61) for 140-159 mg/dL and 3.13 (1.58-6.21) for ≥ 180 mg/dL. Setting the cut-off point at ≥ 140 mg/dL non-HDL-cholesterol resulted in the greatest improvement of integrated discrimination. Conclusions: Higher concentrations of non-HDL-cholesterol are associated with an increased risk of CHD with a threshold around 140 mg/dL, suggesting that the optimal cut-off point for healthy per-sons to prevent increasing the risk of CHD might be around 140 mg/dL non-HDL-cholesterol.
Aim: Mesenchymal stromal cells from human bone marrow (hMSCs) were observed to produce therapeutic benefits in some models for cardiac and vascular injuries but their mode of action was not defined. We tested the effects of hMSCs in models for restricted vascular flow. Methods: We made model for restricted vascular flow produced by permanent ligation of a carotid artery and injected hMSCs to clarify the effects of hMSCs to vascular lesions. Results: Seven, 14, and 28 days after infusion of hMSCs into the cardiac left ventricle of the mice, there was a significant reduction in neointimal hyperplasia (p<0.05). Seven days after administration of the hMSCs, macrophages infiltration into the ligated artery and serum levels of monocyte chemoattractive protein-1 (MCP-1/CCL-2) (p<0.05) were reduced. However, no hMSCs were detected in the lesions by sensitive PCR assays. We then observed that the serum level of MCP-1 was a potential biomarker for the therapeutic effects of hMSCs in a mouse model for high-fat-diet. Conclusions: These results indicated the administration of hMSCs decreased the initial and excess inflammatory responses to carotid artery ligation. The decrease in inflammatory response apparently decreased the subsequent neointimal hyperplasia.
Aims: Metabolic syndrome (MS) represents a cluster of cardiovascular risk factors and an increased risk of cardiovascular events. The carotid intima-media thickness (CIMT) is correlated with coronary and carotid atherosclerosis, and is a significant predictor of cardiovascular events. Tissue factor (TF) is an initiator of the extrinsic coagulation cascade and is expressed on peripheral blood monocytes and macrophages in atherosclerotic plaques. TF plays important roles in both thrombosis and atherosclerosis. No study has investigated the relationship between monocyte TF activity and CIMT in MS patients. Methods: Peripheral blood mononuclear cells (PBMCs) were collected from 39 normal subjects and 110 patients with MS. The procoagulant activity (PCA) in monocytes was measured using a one-stage clotting assay and is expressed as the mean±SD (mU TF/106 PBMCs). Results: The PCA in monocytes in MS patients was significantly higher than in normal subjects (86.2 ±69.5 vs. 52.4±9.9 mU TF/106 PBMCs, p < 0.001). In multivariate analysis, patient age (β coefficient= 0.373, p < 0.001), high-density lipoprotein cholesterol (β coefficient=−0.307, p = 0.001) and PCA (β coefficient= 0.422, p =0.002) were each significantly and independently associated with CIMT. Conclusions: These data indicate that the upregulation of monocyte TF activity is significantly associated with CIMT in MS patients.
Aim: Numerous studies have shown an increase in NT-pro BNP, troponin I and D-dimer levels with right ventricular dysfunction on echocardiography in patients with acute pulmonary thromboembolism (PTE). We found no data about the relation between tenascin-C and acute PTE in the litera-ture. The aim of this study was to evaluate tenascin-C levels in acute PTE and correlate them with NT-pro BNP, troponin I and D-dimer. Method: Thirty-four patients who have massive or submassive PTE on spiral thorax CT (PTE group) and twenty healthy volunteers (non-PTE group) were evaluated. In all patients, right ventricular functions were obtained on transthoracic echocardiography and plasma tenascin-C, NT-pro BNP, troponin I, and D-dimer levels were measured. Results: The left ventricular systolic diameter, left ventricular diastolic diameter and left ventricular ejection fraction were similar in the two groups. The right heart chamber sizes and main pulmonary artery diameter were significantly larger in the PTE group and systolic pulmonary artery pressures were also significantly higher in this group. Tenascin-C, NT-pro BNP, and D-dimer levels were also significantly higher in the PTE group than in the non-PTE group (p< 0.001). The troponin I levels did not differ between the two groups (p=0.4). Tenascin-C was found to be highly correlated with sPAP and NT-pro BNP and correlated with D-dimer; however, troponin I was not correlated with tenascin-C. Conclusion: This study demonstrates that tenascin-C may be an indicator of acute PTE.
Aim: Dietary supplements in polyunsaturated fatty acids (PUFA), particularly omega-3, are well known for their beneficial effects in preventing cardiovascular diseases (CVD). The aim of this study was to determine the role of PUFA on the modulation of apoptosis induced by hypochlorous acidoxidized LDL (HOCl-oxLDL) in U937 cells. Methods: We tested the effect of monocyte cell line U937 supplementation with eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), arachidonic acid (ARA) or oleic acid (OA) on the modulation of HOCl-oxLDL-induced apoptosis. Results: First, we showed the incorporation of fatty acids in the cellular membrane in U937 cells. Then, we showed that both EPA and ARA exerted a pro-apoptotic effect through the intrinsic mitochondrial apoptotic pathway including the dissipation of mitochondrial membrane potential followed by cardiolipin depletion, the downstream activation of caspase-3 and the increase in DNA fragmentation. The pro-apoptotic effect of EPA or ARA was completely blocked in U937/Bcl-2 cells. Conclusions: A new mechanism of dietary supplements in PUFA with likely consequences in apoptosis could be suggested through the mitochondrial pathway in monocytes.
Aim: We aimed to develop a new approach to risk stratification using metabolic syndrome as well as traditional non-metabolic risk factors, and to examine its validity in carotid atherosclerosis. Methods: A total of 1,189 men and women aged 21-93 years old were stratified according to the absence or presence of metabolic syndrome defined by Japanese criteria, non-metabolic risk factors, and a past history of coronary heart disease. The risk stratification was as follows: (S-1) persons without a past history, non-metabolic risk factors and metabolic syndrome, (S-2a) those with metabolic syndrome only, (S-2b) those with non-metabolic risk factors only, (S-3) those with non-metabolic risk factors and metabolic syndrome but no past history, and (S-4) those with a past history. Carotid atherosclerosis was defined as maximum intima-media thickness ≥1.1 mm of the far wall of the common carotid artery. Results: Compared with individuals without these three risk components (S-1), the odds ratio was 7.2 (2.8-18.6) for a past history (S-4), 4.3 (1.7-10.9) for non-metabolic risk factors plus metabolic syndrome but no past history (S-3), 2.6 (1.1-6.4) for non-metabolic risk factors only (S-2b) and 0.5 (0.0-5.7) for metabolic syndrome only (S-2a). Net reclassification improvement from metabolic syndrome only (presence versus absence) to our risk stratification (≥S-3 versus < S-3) was 16.4% (p< 0.0001), suggesting that our risk stratification improved the classification of atherosclerosis in comparison to metabolic syndrome only. Conclusion: Risk stratification based on traditional non-metabolic risk factors plus metabolic syndrome rather than metabolic syndrome only appears to be more useful for the clinical assessment of atherosclerosis, and probably in the prevention and control of atherosclerotic disease.
Aim: Reverse cholesterol transport (RCT) is a critical mechanism for the anti-atherogenic property of HDL. The inhibitory effect of the sulfonylurea agent (SUA) glibenclamide on ATP binding-cassette transporter (ABC) A1 may decrease HDL function but it remains unclear whether it attenuates RCT in vivo. We therefore investigated how the SUAs glibenclamide and glimepiride affected the functionality of ABCA1/ABCG1 and scavenger receptor class B type I (SR-BI) expression in macrophages in vitro and overall RCT in vivo. Methods: RAW264.7, HEK293 and BHK-21 cells were used for in vitro studies. To investigate RCT in vivo, 3H-cholesterol-labeled and acetyl LDL-loaded RAW264.7 cells were injected into mice. Results: High dose (500µM) of glibenclamide inhibited ABCA1 function and apolipoprotein A-I (apoA-I)-mediated cholesterol efflux, and attenuated ABCA1 expression. Although glimepiride maintained apoA-I-mediated cholesterol efflux from RAW264.7 cells, like glibenclamide, it inhibited ABCA1-mediated cholesterol efflux from transfected HEK293 cells. Similarly, the SUAs inhibited SR-BI-mediated cholesterol efflux from transfected BHK-21 cells. High doses of SUAs increased ABCG1 expression in RAW264.7 cells, promoting HDL-mediated cholesterol efflux in an ABCG1-independent manner. Low doses (0.1-100 µM) of SUAs did not affect cholesterol efflux from macrophages despite dose-dependent increases in ABCA1/G1 expression. Furthermore, they did not change RCT or plasma lipid levels in mice. Conclusion: High doses of SUAs inhibited the functionality of ABCA1/SR-BI, but not ABCG1. At lower doses, they had no unfavorable effects on cholesterol efflux or overall RCT in vivo. These results indicate that SUAs do not have adverse effects on atherosclerosis contrary to previous findings for glibenclamide.
Lipoprotein glomerulopathy (LPG) is a rare disease characterized by the presence of thrombuslike deposition in markedly dilated glomerular capillaries and is often accompanied by an increased serum apolipoprotein E (apoE) level. Several gene mutations of apoE have been reported to be associated with LPG. In the current study, we report an LPG patient with a novel apoE mutation, apoE Osaka. The patient was a 45-year-old man who was hospitalized due to nephrotic syndrome. Light and electron microscopic observations of renal biopsy clearly showed characteristic findings of LPG, including lamellate thrombi in the lumen of dilated glomerular capillaries. His apoE phenotype was apoE3/2 and he had mild dyslipidemia with a mid-band on polyacrylamide gel electrophoresis. It is intriguing that the serum apoE level was within normal limits. We determined the sequence of the apoE gene using direct sequencing of the polymerase chain reaction (PCR) products. ApoE gene analysis showed a nucleotide substitution of G to C at codon 158 of exon 4. This mutation denoted an amino acid substitution of arginine residue for the proline residue at position 158 of apoE. The result of PCR associated with restriction fragment length polymorphism analysis also suggested that this mutation is heterozygous. It is possible that apoE Osaka mutation causes a conformational change of apoE protein and affects the interaction between abnormal apoE-containing lipoproteins and the endothelial cells of glomerular capillaries. The precise mechanism of LPG related with apoE Osaka, however, remains to be elucidated.
Lipoprotein glomerulopathy (LPG) is a rare glomerulopathy caused by lipoprotein thrombi. In almost all cases of LPG, several apolipoprotein (apo) E mutations were reported. Here, we present a case of LPG caused by a novel mutation that we named ApoE2 Kurashiki, which substitutes arginine with proline at apoE codon 158. ApoE2 polymorphism is well known for its relationship to type III hyperlipoproteinemia, and the common apoE2 isoform is encoded by the R158C allele. ApoE2 Kurashiki substitutes at the same codon and cannot be distinguished from common apoE2 by stan-dard apoE genotyping or phenotyping.