Fibrinogen mediated activation of platelet aggregation and thromboxane A2 release: pathological implications in vascular disease

SEMA4D/VEGF surface enhances endothelialization by diminished-glycolysis-mediated M2-like macrophage polarization

Cardiovascular disease remains the leading cause of death and morbidity worldwide. Inflammatory responses after percutaneous coronary intervention led to neoathrosclerosis and in-stent restenosis and thus increase the risk of adverse clinical outcomes. In this work, a metabolism reshaped surface is engineered, which combines the decreased glycolysis promoting, M2-like macrophage polarization, and rapid endothelialization property. Anionic heparin plays as a linker and mediates cationic SEMA4D and VEGF to graft electronically onto PLL surfaces. The system composed by anticoagulant heparin, immunoregulatory SEMA4D and angiogenic VEGF endows the scaffold with significant inhibition of platelets, fibrinogen and anti-thrombogenic properties, also noteworthy immunometabolism reprogram, anti-inflammation M2-like polarization and finally leading to rapid endothelializaiton performances. Our research indicates that the immunometabolism method can accurately reflect the immune state of modified surfaces. It is envisioned immunometabolism study will open an avenue to the surface engineering of vascular implants for better clinical outcomes.

Mass Spectrometric Blood Metabogram: Acquisition, Characterization, and Prospects for Application

In metabolomics, many metabolites are measured simultaneously in a single run. Such analytical performance opens up prospects for clinical laboratory diagnostics. In this work, a mass spectrometric metabogram was developed as a simplified and clinically applicable way of measuring the blood plasma metabolome. To develop the metabogram, blood plasma samples from healthy male volunteers (n = 48) of approximately the same age, direct infusion mass spectrometry (DIMS) of the low molecular fraction of samples, and principal component analysis (PCA) of the mass spectra were used. The seven components of the metabogram defined by PCA, which cover ~70% of blood plasma metabolome variability, were characterized using a metabolite set enrichment analysis (MSEA) and clinical test results of participating volunteers. It has been established that the components of the metabogram are functionally related groups of the blood metabolome associated with regulation, lipid-carbohydrate, and lipid-amine blood components, eicosanoids, lipid intake into the organism, and liver function thereby providing a lot of clinically relevant information. Therefore, metabogram provides the possibility to apply the metabolomics performance in the clinic. The features of the metabogram are also discussed in comparison with the thin-layer chromatography and with the analysis of blood metabolome by liquid chromatography combined with mass spectrometry.

Fibrinolysis Index as a new predictor of deep vein thrombosis after traumatic lower extremity fractures

BACKGROUND

Deep vein thrombosis (DVT) is a common complication in patients with traumatic injury. The purpose of this study was to develop a potential predictor of DVT.

METHODS

This case-control study enrolled adult trauma patients and healthy volunteers. Patients underwent angiography before surgery to diagnose DVT. Patients with or without DVT were matched by gender, age and fracture sites. Laboratory parameters included lysis potential (LP), lysis time (LT), blood cell counts, conventional coagulation tests, tissue plasminogen activator inhibitor complex (tPAIC) and others.

RESULTS

41 of 319 patients with DVT were matched with 41 patients without DVT and 80 healthy volunteers were controls. LP and LT were significantly decreased in patients with DVT than without (P = 0.043 and P = 0.014, respectively). The level of tPAIC in the DVT group was significantly higher than in patients without DVT (P = 0.042). We defined the Fibrinolysis Index as (-10.707) × LP + (-0.607) × LT (min) + 0.012 × fibrinogen (mg/dl) + 0.299 × tPAIC (ng/ml) + 9.917, and found that the area under the receiver operating characteristic curve for the Fibrinolysis Index was 0.802, making it a novel indicator.

CONCLUSION

The Fibrinolysis Index represents a new discriminator for predicting DVT after traumatic lower extremity fractures.

Relation Between Globulin, Fibrinogen, and Albumin With the Presence and Severity of Coronary Artery Disease

The albumin to globulin ratio (AGR) is used as a prognostic marker in acute ischemic cardiovascular events. We investigated whether serum AGR, fibrinogen, and fibrinogen to albumin ratio (FAR) are related to the presence and severity of coronary artery disease (CAD). Patients who underwent coronary angiography procedures were analyzed retrospectively. The severity of CAD was assessed by the Gensini score. The study population (3031 patients; 1071 females and 1960 males) was divided into 3 tertiles based on AGR values. Gensini score, lipid levels, diabetes mellitus (DM), hypertension (HT), age, and fibrinogen level were higher in the low AGR group. Pearson correlation analysis showed that AGR (r = -0.068, P < .001) was negatively and fibrinogen (r = 0.187, P < .001) was positively correlated with the Gensini score. Male gender, HT, smoking, DM, age, high triglyceride (TG) level, low-density lipoprotein cholesterol (LDL-C) >160 mg/dL, estimated glomerular filtration rate (eGFR) <60 mL/min, and fibrinogen level >3.5 g/L were independent predictors of CAD. Male gender, age, eGFR, DM, LDL-C, TG, and FAR had an independent positive relation to the Gensini score. In conclusion, similar to traditional risk factors, plasma fibrinogen and albumin levels showed a close relation with the presence and severity of CAD.

Assessment of Coagulation Parameters in Women Affected by Endometriosis: Validation Study and Systematic Review of the Literature

The presence of endometriosis determines an inflammatory response locally. The objective of this validation study and systematic review was to assess systemic levels of coagulation and inflammatory parameters in women with or without the disease. We conducted a retrospective analysis of a database prospectively collected from January 2017 to February 2020 including n = 572 women who underwent laparoscopic surgery for endometriosis (cases, n = 324) or other benign gynecologic diseases (controls, n = 248). Inflammatory markers and coagulation parameters were determined. An advanced systematic search of the literature on the same parameters was conducted up to April 2020. A significantly higher neutrophil count was found in endometriosis patients. Patients with endometriomas and stage III–IV disease had a significantly lower absolute lymphocyte count and shortened activated partial thromboplastin time (aPTT) values. In the final regression model, aPTT retained significant predictive value for stage III–IV endometriosis (odds ratio (OR) = 0.002, 95% confidence interval (CI) = 0.00–0.445; p = 0.024). Results from the n = 14 included studies in the systematic review are characterized by a high variability, but some consistency has been found for alterations in thrombin time, platelet-to-lymphocyte ratio, and neutrophil count associated with endometriosis. Modest systemic changes of some inflammatory and coagulation parameters are associated with endometriosis. Indeed, all the modifications detected are still within the normal reference intervals, explaining the high heterogeneity among studies.

Predictive Value of Fibrinogen-to-Albumin Ratio for Post-Contrast Acute Kidney Injury in Patients Undergoing Elective Percutaneous Coronary Intervention

BACKGROUND Post-contrast acute kidney injury (PC-AKI) is a contributor to adverse outcomes after percutaneous coronary intervention (PCI). This study aimed to investigate whether fibrinogen-to-albumin ratio (FAR), a novel inflammation-based risk index, can predict the occurrence of PC-AKI in patients undergoing elective PCI. MATERIAL AND METHODS We retrospectively enrolled 291 patients who underwent elective PCI from June 2017 to June 2019. PC-AKI was defined as an increase in serum creatinine ≥0.3 mg/dL (≥26.5 μmol/L), or ≥1.5 times baseline within 48 to 72 hours after PCI. The area under the receiver-operating characteristic curve (AUC), continuous net reclassification improvement (NRI), and integrated discrimination improvement (IDI) were calculated to make comparison for PC-AKI prediction. RESULTS PC-AKI occurred in 43 patients (14.8%). FAR showed an AUC of 0.691 (95% confidence interval: 0.64-0.74; P<0.001) in predicting PC-AKI. In stepwise multivariable logistic regression, FAR was independently associated with the occurrence of PC-AKI along with hypertension, diabetes, hemoglobin, estimated glomerular filtration rate, and left ventricular ejection fraction. FAR significantly improved PC-AKI prediction over Mehran risk score in the continuous NRI and IDI, but not AUC. CONCLUSIONS FAR is independently associated with the occurrence of PC-AKI, and can significantly improve PC-AKI prediction over Mehran risk score in patients undergoing elective PCI.

Prognostic Significance of Serum Albumin in Patients With Acute Coronary Syndrome

In patients with unstable angina pectoris (UAP) or non-ST elevation myocardial infarction (NSTEMI), long-term mortality remains high despite improvements in the diagnosis and treatment. In this study, we investigated whether serum albumin level is a useful predictor of long-term mortality in patients with UAP/NSTEMI. Consecutive patients (n = 403) who were hospitalized with a diagnosis of UAP/NSTEMI were included in the study. Patients were divided into 2 groups based on the presence of hypoalbuminemia and the relationship between hypoalbuminemia and mortality was analyzed. Hypoalbuminemia was detected in 34% of the patients. The median follow-up period was 35 months (up to 45 months). Long-term mortality rate was 32% in the hypoalbuminemia group and 8.6% in the group with normal serum albumin levels ( P < .001). On multivariate analysis, hypoalbuminemia, decreased left ventricular ejection fraction, and increased age were found to be independent predictors of mortality ( P < .05). The cutoff value of 3.10 g/dL for serum albumin predicted mortality with a sensitivity of 74% and specificity of 67% (receiver-operating characteristic area under curve: 0.753, 95% CI: 0.685-0.822). All-cause long-term mortality rates were significantly increased in patients with hypoalbuminemia. On-admission albumin level was an independent predictor of mortality in patients with UAP/NSTEMI.

Platelet adhesion on commercially pure titanium plates in vitro I: effects of plasma components and involvement of the von Willebrand factor and fibronectin

Background

Platelet-rich plasma (PRP) is widely used in regenerative dentistry. Furthermore, it is often applied in the pretreatment of titanium implants to improve their surface bioaffinity and initial stability. However, effects of PRP application on implant surface at cellular and molecular levels remain poorly understood. Therefore, we examined platelet adhesion on commercially pure titanium (cp-Ti) plates, with a particular focus on fibrinogen (FGN), von Willebrand factor (vWF), and fibronectin (FN), in the presence or absence of plasma components.

Methods

Citrated blood samples were obtained from six healthy male volunteers, and pure-PRP (P-PRP) and pure platelet suspensions in phosphate-buffered saline (PBS) were prepared. Platelet adhesion on cp-Ti plate surface was evaluated by phalloidin staining and tetrazolium dye assay. Distribution of FGN, vWF, FN, albumin, CD62P, and CD63 was examined by immunocytochemical analysis.

Results

Platelets in PBS suspensions rapidly and time-dependently adhered to cp-Ti plate surface, but this adhesion was substantially disturbed by the presence of plasma components. FGN was most preferably adsorbed regardless of the presence or absence of plasma components, while vWF and FN showed greater accumulation on platelet adhesion area.

Conclusions

Although FGN is rapidly and abundantly adsorbed on cp-Ti plate surface, vWF and FN function as major platelet adhesion molecules in citrated blood samples. After pretreatment with P-PRP, however, platelets adhered to cp-Ti much less efficiently. Therefore, P-PRP pretreatment might not directly contribute to surface functionalization, initial stabilization, and osseointegration of machined or similar types of implants.

Electronic supplementary material

The online version of this article (10.1186/s40729-019-0160-z) contains supplementary material, which is available to authorized users.

Mendelian randomization evaluation of causal effects of fibrinogen on incident coronary heart disease

BACKGROUND

Fibrinogen is an essential hemostatic factor and cardiovascular disease risk factor. Early attempts at evaluating the causal effect of fibrinogen on coronary heart disease (CHD) and myocardial infraction (MI) using Mendelian randomization (MR) used single variant approaches, and did not take advantage of recent genome-wide association studies (GWAS) or multi-variant, pleiotropy robust MR methodologies.

METHODS AND FINDINGS

We evaluated evidence for a causal effect of fibrinogen on both CHD and MI using MR. We used both an allele score approach and pleiotropy robust MR models. The allele score was composed of 38 fibrinogen-associated variants from recent GWAS. Initial analyses using the allele score used a meta-analysis of 11 European-ancestry prospective cohorts, free of CHD and MI at baseline, to examine incidence CHD and MI. We also applied 2 sample MR methods with data from a prevalent CHD and MI GWAS. Results are given in terms of the hazard ratio (HR) or odds ratio (OR), depending on the study design, and associated 95% confidence interval (CI). In single variant analyses no causal effect of fibrinogen on CHD or MI was observed. In multi-variant analyses using incidence CHD cases and the allele score approach, the estimated causal effect (HR) of a 1 g/L higher fibrinogen concentration was 1.62 (CI = 1.12, 2.36) when using incident cases and the allele score approach. In 2 sample MR analyses that accounted for pleiotropy, the causal estimate (OR) was reduced to 1.18 (CI = 0.98, 1.42) and 1.09 (CI = 0.89, 1.33) in the 2 most precise (smallest CI) models, out of 4 models evaluated. In the 2 sample MR analyses for MI, there was only very weak evidence of a causal effect in only 1 out of 4 models.

CONCLUSIONS

A small causal effect of fibrinogen on CHD is observed using multi-variant MR approaches which account for pleiotropy, but not single variant MR approaches. Taken together, results indicate that even with large sample sizes and multi-variant approaches MR analyses still cannot exclude the null when estimating the causal effect of fibrinogen on CHD, but that any potential causal effect is likely to be much smaller than observed in epidemiological studies.

Exposure to hypoglycemia and risk of stroke

In the treatment of both type 1 and type 2 diabetes mellitus, maintaining a euglycemic state represents one of the key challenges. Improper dosing and administration of glucose-lowering drugs is associated with an increased risk of recurrent hypoglycemia episodes. In addition, the risk of adverse cardiovascular events in diabetic patients, particularly myocardial infarctions and strokes, is well established. Current research indicates a potential link between the baseline risk of cardio/cerebrovascular events in diabetic patients and exposure to hypoglycemia. In this review of the literature, we aim to determine if a relationship exists between recurrent hypoglycemia and adverse neurovascular events.

Platelets as Predictors of Vascular Risk: Is There a Practical Index of Platelet Activity?

Activated platelets play a role in the pathogenesis of coronary heart disease (CHD). Following activation, platelets change shape, aggregate, and release several bioactive substances. The aim of this review is to identify if there is a simple and cost-effective method that indicates platelet activation and predicts the risk of CHD and vascular events. The rationale for identifying high-risk patients is to reduce their risk of vascular events by administering appropriate and effective antiplatelet treatment, like aspirin, clopidogrel, or combination regimens. Many laboratory tests estimating platelet activity have been described. Some are relatively simple, such as spontaneous or agonist-induced platelet aggregation. Other tests include measuring the mean platelet volume (MPV) or plasma soluble P-selectin levels. Some more complex tests include flow cytometry to determine platelet GP Ilb/Illa receptors, platelet surface P-selectin, plateletmonocyte aggregates, and microparticles. Only few prospective studies assessed the predictive value of platelet activation in healthy individuals. Although the MPV seems an 'easy method, there are insufficient data supporting its ability to predict the risk of a vascular event in healthy adults. Platelet aggregation, in whole blood or in platelet-rich plasma was not consistently predictive of vascular risk. Soluble P-selectin measurement is a promising method but it needs further evaluation. Flow cytometry methods are costly, time-consuming, and need specialized equipment. Thus, they are unlikely to be useful in estimating the risk in large numbers of patients. There is as yet no ideal test for the detection of platelet activation. Each currently available test has merits and disadvantages. Simple methods such as the MPV and the determination of platelet release products need further evaluation.

The Relationship Between Circulating Fibrinogen and Lipoprotein (a) Levels in Patients With Primary Dyslipidemia

The correlation between 2 predictors of vascular events, plasma fibrinogen and serum lipoprotein (a), was evaluated in patients referred to a specialist clinic because of primary hyperlipidemia. A significant correlation existed between fibrinogen and lipoprotein (a) in nonsmokers but not in smokers. Plasma fibrinogen concentration correlated positively and significantly with serum lipoprotein (a) levels in men nonsmokers without cardiovascular disease and in women nonsmokers with cardiovascular disease. Nonsmoker women without cardiovascular disease had significantly higher plasma fibrinogen (3.63 g/L versus 3.07 g/L, P < .0001) than the corresponding men. Nonsmoker women with and without cardiovascular disease had significantly higher lipoprotein (a) levels than the corresponding groups of men (0.36 versus 0.18 g/L; P = .0015 and 0.40 versus 0.26 g/L; P = .008), respectively. The relationship between fibrinogen and lipoprotein (a) levels alters markedly depending on the population selected. This relationship is influenced by gender, the presence of cardiovascular disease and smoking status.

The relationship between fibrinogen to albumin ratio and severity of coronary artery disease in patients with STEMI

OBJECTIVE

Previous studies show that serum fibrinogen levels are established risk factors for coronary artery disease (CAD) and that serum albumin levels are of a higher specificity and sensitivity in ST-elevation myocardial infarction (STEMI). In this study, we sought to evaluate the association between fibrinogen to albumin ratio (FAR) and the extent and severity of CAD evaluated by TAXUS Drug-Eluting Stent Versus Coronary Artery Bypass Surgery for the Treatment of Narrowed Arteries (SYNTAX) Score (SS) in patients with STEMI.

METHODS

A total of 278 patients with STEMI were included in the study. FAR was calculated using specified variables. The extent and severity of CAD were evaluated using the SS. The patients were divided into low- (SS <22) and high- (SS ≥22) risk groups. A Spearman rank correlation coefficient analysis was used for the relationship between FAR and SS. The cutoff points for sensitivity and specificity of FAR in predicting SS were estimated by performing a receiver operator characteristic curve analysis.

RESULTS

There were significant differences in the mean age (P=.016), admission serum albumin (P=.041), serum fibrinogen (P<.001), FAR (P<.001), and SS risk groups. Positive correlation was detected between FAR and SS (r=0.458, P<.001). A cutoff level of >87 FAR predicted SS (sensitivity, 70%; specificity, 70%), and an area under the curve of 0.758 serum fibrinogen and albumin level was an independent predictor for SS in patients with STEMI (b=0.039; 95% confidence interval, 0.016-0.062; P=.001 and b=-6.906; 95% confidence interval, -12.284 to -1.527; P=.013, respectively).

CONCLUSION

In the present study, we showed that FAR is significantly related to SS in predicting the severity of CAD in patients with STEMI.

Effects of oral hypoglycemic agents on platelet function

Platelet dysfunction plays a role in diabetic macrovascular complications. Several studies have assessed the effect of oral hypoglycemic agents (OHAs) on platelet function. Data from both in vivo and in vitro studies show a favorable effect for most of the traditional glucose-lowering therapies, while evidence is limited for the newer ones. Metformin, sulfonylureas, glitazones and acarbose exert a favorable effect on platelet function. Among incretin therapies, only sitagliptin has so far been demonstrated to have a beneficial effect on platelet aggregation. More in vivo and in vitro evidence is required to increase our knowledge on any potential beneficial effects of OHAs on platelet function. Any such effect may have implications for the reduction of cardiovascular risk in type 2 diabetes mellitus.

Testing Clinical Scores to Diagnose Incident Deep Vein Thrombosis in Patients Hospitalized in a Department of Medicine: Can Biomarkers Improve Accuracy?

Shifting the context from the emergency department to the department of medicine, we compared different scores to diagnose deep vein thrombosis (DVT) in patients with several comorbidities, hospitalized in a department of internal medicine. We prospectively recruited 178 consecutive hospitalized patients in whom clinical suspicion of DVT was assessed by Wells modified score for DVT, Hamilton, Kahn, and St Andrè Hospital scores. Deep vein thrombosis was confirmed in 85 (48%) patients by both echocolor Doppler and angiocomputed tomography scan. The use of risk scores based on symptoms and clinical signs was weakly useful (area under the curve [AUC]: 0.69, positive predictive value: 59%, and negative predictive value: 74%). Patients with DVT had significantly (P < .0001) lower serum albumin and protein S levels compared to those without DVT. Moreover, serum protein S (AUC: 0.82) and albumin in percentage (AUC: 0.80) showed a better accuracy than clinical scores (P < .001) in assessing the diagnosis of DVT. Therefore, serum albumin and protein S improved the accuracy of clinical scores for the diagnosis of incident DVT in patients hospitalized in a department of medicine.

Serum albumin levels on admission are associated with angiographic no-reflow after primary percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction

Low serum albumin (SA) levels are associated with increased cardiovascular mortality. We investigated whether baseline SA levels are associated with no-reflow following primary percutaneous coronary intervention (pPCI). A total of 536 patients (aged 60 ± 13 years; 74% men) who underwent pPCI were enrolled. The patients were divided into 2 groups: no-reflow and normal-reflow. No-reflow was defined as thrombolysis in myocardial infarction ≤2 flow. Admission SA levels were significantly lower in the no-reflow group than in the normal-reflow group (3.55 ± 0.44 vs 4.01 ± 0.32 mg/dL, P < .001). Also, high-sensitivity C-reactive protein (hsCRP), creatinine, creatine kinase myocardial band isoenzyme, and troponin T were significantly higher while hemoglobin and left ventricular ejection fraction (LVEF) were significantly lower in the no-reflow group. In multivariate analysis, SA level remained an independent predictor of angiographic no-reflow (odds ratio 0.114, 95% confidence interval 0.032-0.405, P = .001) together with LVEF, hsCRP, and baseline culprit artery patency. Admission SA level was an independent predictor of no-reflow after pPCI.

Plasma albumin and platelet function: relevance to atherogenesis and thrombosis

Two papers published in this journal(1,2) during the past year remind us that plasma albumin concentrations can influence platelet function. These publications, together with epidemiological evidence showing that low plasma concentrations of albumin predict mortality from cardiovascular disease(3,4) have prompted this review.

Thrombocytopenia in Patients With Chronic Hepatitis C: A Possible Role of HCV on Platelet Progenitor Cell Maturation

A total of 30 patients with chronic hepatitis C (HCV) thrombocytopenia (TP) and 20 healthy controls were studied. Both groups were subjected to complete medical history, clinical examination in addition to assessment of hepatitis markers: level of thrombopoietin (Tpo), Geimsa-stained bone marrow smears, and in vitro short-term megakaryocytic progenitors culture (CFU-MK). Serum Tpo level was significantly elevated in patients with TP HCV. Short-term CFU-MK showed an evident depression in the colony-forming unit—megakaryocyte (CFU-meg). There is a positive correlation between the number of CFU-meg and the platelet count and between serum Tpo level and prothrombin time, transaminase, albumin, and the Child Pugh score of liver disease; a negative correlation between serum Tpo level and the number of CFU-meg and between serum Tpo level and the platelet count. Thus, the level of Tpo could be an indicator of intact functional response of the hepatocytes.

The effect of tirofiban on fibrinogen/agonist-induced platelet shape change and aggregation

There is evidence linking raised plasma fibrinogen (fib) and platelet hyperactivity with vascular events. One way to inhibit platelets is to block the platelet membrane glycoprotein (GP) IIb/IIIa receptor, which binds circulating fib or von Willebrand factor and cross-links platelets at the final common pathway to platelet aggregation. Tirofiban is a potent and specific fib receptor antagonist, used in the treatment of unstable angina. The authors assessed the effect of tirofiban on spontaneous platelet aggregation (SPA), fib-induced, serotonin (5HT)-induced, and adenosine diphosphate (ADP)-induced aggregation in whole blood by calculating the percentage free platelet count. These various agonists were used alone and in combination. The authors also measured the effect of tirofiban on agonists-induced (ADP, 5HT) platelet shape change (PSC). The effect of fib on PSC was also evaluated in platelet-rich plasma using a high-resolution (0.07 fL) channelyzer. Tirofiban significantly inhibited SPA, fib (2, 4, 8 g/L), ADP, ADP + fib combination, and 5HT-induced aggregation. Tirofiban had no effect on agonist-induced PSC. There was no apparent change in platelet volume with fib. In conclusion, tirofiban does not appear to have an effect on PSC, an early phase of platelet activation. Tirofiban seems to be a nonspecific and an effective inhibitor of platelet aggregation (a later phase of platelet activation) in whole blood. The clinical significance of these findings remains to be established.

Diet and haemostatic processes

Diet plays an important role in the primary and secondary prevention of cardiovascular disease. The growing perception that abnormal haemostatic processes of coagulation, platelet aggregation and fibrinolysis contribute to cardiovascular disease aetiology motivated this review on the relationships of diet, specific foods and nutrients with haemostatic function. Functional endpoints that reflect the function and status of some of these processes and which can be measured in dietary trials are identified. The effects of energy intake and expenditure, alcohol, total fat and specific fatty acids, non-starch polysaccharides (dietary fibre), antioxidant nutrients and some foods on a variety of haemostatic markers are reviewed. The results indicate that the prudent low-fat, high-fibre diet and maintenance of ideal body weight recommended to protect against and treat hyperlipidaemia and coronary heart disease will also benefit haemostatic profiles. It is concluded that more research on specific effects is needed for improved recommendations on a population level for prevention of cardiovascular disease.

The role of fibrinogen and fibrinolysis in peripheral arterial disease

Peripheral arterial disease (PAD) is associated with high rates of cerebrovascular and cardiovascular events; PAD is a marker of systemic atherosclerosis. As a result, standard therapy for all PAD patients should be directed at both peripheral and systemic atherosclerosis. Modification of established risk factors in the form of smoking cessation, correcting hypertension, optimizing diabetic control and normalizing lipids is essential. Furthermore, novel risk factors have emerged including fibrinogen and other hemostatic factors. Fibrinogen is a coagulation factor and a marker of the acute phase response (inflammation), a platelet activator, a major determinant of plasma viscosity and a component of the atherosclerotic plaque. Fibrinogen appears not only to predict the severity of PAD, but also serves as a marker for future development of PAD. Whether reducing the levels of fibrinogen and other coagulation factors will decrease the incidence and progression of PAD remains to be resolved. This review summarizes the role of fibrinogen in the pathogenesis of PAD and its association with other hemostatic factors. The role of fibrinolysis in patients with PAD is also considered.

Favourable modulation of the inflammatory changes in hypercholesterolemic atherogenesis by a low-molecular-weight heparin derivative

BACKGROUND

In the hypercholesterolemic state, the net result of combined oxidative and nitrosative stress is a pro-inflammatory phenotype that is manifested as increased adhesion molecule expression, enhanced leucocyte trafficking, and increased vascular permeability. The present work explores the inflammatory aspects of hypercholesterolemic atherogenesis, and also evaluates the role of a low-molecular-weight heparin derivative (LMWH), Certoparin, on a biochemical basis.

METHODS AND RESULTS

Two groups of male Wistar rats were fed an atherogenic diet (normal rat chow plus 4% cholesterol, 1% cholic acid and 0.5% thiouracil-CCT diet) for 2 weeks. While one was left untreated, the other was administered LMWH (300 microg/day/rat commencing on day 8 and continued for a week). Increased concentrations of plasma C-reactive protein and fibrinogen and cardiac TNF-alpha indicated severe inflammation in the atherogenic diet fed rats. In comparison, these biochemical indices of inflammation diminished significantly in the LMWH treated group (p < 0.001). Significant depletion of thiols, along with accentuated activities of the glutathione metabolising was observed in the cardiac and hepatic tissues of the untreated atherogenic rats, indicating heightened oxidative response. Tissue damage was marked by elevated levels of plasma and tissue hexose, hexosamine, hexuronic acid and sialic acid, which were reversed towards normalcy on LMWH administration. The activities of lysosomal enzymes (N-acetyl glucosaminidase, beta-glucuronidase, beta-galactosaminidase and cathepsin-D) showed a marked increase in the CCT-diet fed rats, while LMWH treated rats showed normal activities (p < 0.001). The osmotic fragility test revealed that the untreated hyperlipidemic rat erythrocytes were significantly fragile at high salt concentrations, while the response was normalized in the LMWH treated group (p < 0.05). Further, hypercholesterolemia induced downregulation of physiological nitric oxide levels was corrected upon treatment with heparin-derivative.

CONCLUSION

The results of this work highlight the inflammatory changes in atherogenic conditions and that the low-molecular-weight heparin derivative affords substantial protection.

Influence of smoking on predictors of vascular disease

Beyond the already well-established strong causative relationship with cancer, smoking increases the risk for vascular disease. Smoking may act directly or adversely influence risk factors contributing to the development of vascular disease. Smoking causes endothelial dysfunction, dyslipidemia (decreased high-density lipoprotein cholesterol levels, hypertriglyceridemia and increased oxidation of low-density lipoprotein cholesterol) and platelet activation leading to a prothrombotic state. Smoking increases emerging risk factors (eg, fibrinogen, homocysteine, and high-sensitivity C-reactive protein) and increases insulin resistance and the risk of developing type 2 diabetes mellitus. The beneficial effects of statins and antioxidants (eg, vitamins C and E, beta-carotene) are counteracted by smoking. Smoking-induced alterations in growth factors, adhesion molecules, and even in genes can accelerate the progression of atherosclerosis. The aim of this review is to consider the adverse consequences of smoking on the factors predisposing to vascular disease and to emphasize the beneficial effects of smoking cessation.

The role of platelets in peripheral arterial disease: therapeutic implications

Peripheral arterial disease (PAD) is associated with platelet hyperaggregability as well as an increase in morbidity and mortality from myocardial infarction and stroke. Enhanced platelet activation in PAD may substantially contribute to these adverse outcomes. A relative resistance to aspirin therapy has been reported in patients with PAD. Therefore, clopidogrel may be superior to aspirin in treatment of PAD. Furthermore, the aspirin + clopidogrel combination could be more effective than monotherapy but its risk-benefit ratio has yet to be evaluated. Clopidogrel is preferable to ticlopidine because of its safer profile and the convenience of once-daily administration. The glycoprotein (Gp) IIb/IIIa inhibitors may also find a place as short-term therapy after peripheral angioplasty. There is a need to consider the use of clopidogrel in patients who cannot tolerate aspirin. Patients who have an event while taking aspirin also present a problem. One possibility here is to substitute aspirin with clopidogrel or to add clopidogrel to the aspirin. Although these options are currently not evidence based in patients with PAD, there is emerging evidence showing that they are realistic choices.

Lipoprotein (a) and stroke

Strokes are one of the most common causes of mortality and long term severe disability. There is evidence that lipoprotein (a) (Lp(a)) is a predictor of many forms of vascular disease, including premature coronary artery disease. Several studies have also evaluated the association between Lp(a) and ischaemic (thrombotic) stroke. Several cross sectional (and a few prospective) studies provide contradictory findings regarding Lp(a) as a predictor of ischaemic stroke. Several factors might contribute to the existing confusion--for example, small sample sizes, different ethnic groups, the influence of oestrogens in women participating in the studies, plasma storage before Lp(a) determination, statistical errors, and selection bias. This review focuses on the Lp(a) related mechanisms that might contribute to the pathogenesis of ischaemic stroke. The association between Lp(a) and other cardiovascular risk factors is discussed. Therapeutic interventions that can lower the circulating concentrations of Lp(a) and thus possibly reduce the risk of stroke are also considered.

The effect of ethanol on platelet function and vascular prostanoids

The present review will discuss the effects of ethanol on platelet function and vascular prostanoids. Whenever possible we have considered human studies because there are marked species differences in platelet function and vascular prostanoid release even in the absence of ethanol. Because of the specialised nature of some parts of the text, we have included brief introductions to help readers who are not familiar with this field.

An investigation into the effects of bacterial lipopolysaccharide on human platelets

The addition of lipopolysaccharide (LPS) from Gram-negative bacteria to whole blood induced a consistent enhancement of platelet impedance aggregation (WB-PIA) and an increase in median platelet volume (MPV). In contrast, the addition of LPS to platelet rich plasma (PRP) resulted in inconsistent changes in turbidometric platelet aggregation (TPA) and no significant change in MPV. The LPS-induced increase of MPV in whole blood was inhibited by verapamil, a calcium channel blocker. We conclude that: (a) LPS consistently activates platelets in whole blood but not in PRP; (b) LPS-induced activation of platelets is probably mediated by products released by leucocytes and/or erythrocytes; (c) the increase in MPV induced by LPS is probably dependent upon calcium influx; and (4) an increase in MPV may be a useful and sensitive model for the study of platelet activation by LPS, in vitro and in vivo.