Thromboxane biosynthesis and metabolism in relation to cardiovascular risk factors

The role of the PLR-NLR combination in the prediction of the presence of Helicobacter pylori and its associated complications

BACKGROUND/AIM

The aim of this study was to investigate the role of the platelet-to-lymphocyte ratio (PLR)-neutrophil-to-lymphocyte ratio (NLR) combination, in the prediction of the presence of Helicobacter pylori (HP) and its associated complications in the gastrointestinal system.

PATIENTS AND METHODS

In all, 1289 patients who underwent esophagogastroduodenoscopy and biopsy for HP were included in the study.

RESULTS

The ratio of patients with moderate and severe chronic gastritis was higher in HP (+) group than HP (-) group. The ratio of patients with levels 1-3 atrophy and intestinal metaplasia was higher in HP (+) group. Compared with HP (-) group, HP (+) had higher PLR and NLR levels. The ratio of HP (+) patients was higher in high-risk group compared with low- and medium-risk groups. HP invasion stage, the intestinal metaplasia level, and the ratio of patients with atrophy level "3" were higher in high-risk group compared with low- and medium-risk groups. Regression analysis showed that the PLR-NLR combination was an independent risk factor for both HP presence and moderate and severe chronic gastritis.

CONCLUSION

We found the PLR-NLR combination to be a good predictor of HP presence and gastrointestinal complications associated with HP.

Aspirin responsive platelet thrombophilia in essential thrombocythemia and polycythemia vera

Essential thrombocythemia (ET) and polycythemia vera (PV) frequently present with erythromelalgia and acrocyanotic complications, migraine-like microvascular cerebral and ocular transient ischemic attacks (MIAs) and/or acute coronary disease. The spectrum of MIAs in ET range from poorly localized symptoms of transient unsteadiness, dysarthria and scintillating scotoma to focal symptoms of transient monocular blindness, transient mono- or hemiparesis or both. The attacks all have a sudden onset, occur sequentially rather than simultaneously, last for a few seconds to several minutes and are usually associated with a dull, pulsatile or migraine-like headache. Increased hematocrit and blood viscosity in PV patients aggravate the microvascular ischemic syndrome of thrombocythemia to major arterial and venous thrombotic complications. Phlebotomy to correct hematocrit to normal in PV significantly reduces major arterial and venous thrombotic complications, but fails to prevent the platelet-mediated erythromelalgia and MIAs. Complete long-term relief of the erythromelalgic microvascular disturbances, MIAs and major thrombosis in ET and PV patients can be obtained with low dose aspirin and platelet reduction to normal, but not with anticoagulation. Skin punch biopsies from the erythromelalgic area show fibromuscular intimal proliferation of arterioles complicated by occlusive platelet-rich thrombi leading to acrocyanotic ischemia. Symptomatic ET patients with erythromelalgic microvascular disturbances have shortened platelet survival, increased platelet activation markers β-thromboglobulin (β-TG), platelet factor 4 (PF4) and thrombomoduline (TM), increased urinary thromboxane B2 (TXB2) excretion, and no activation of the coagulation markers thrombin fragments F1+2 and fibrin degradation products. Inhibition of platelet cyclooxygenase (COX1) by aspirin is followed by the disappearance and no recurrence of microvascular disturbances, increase in platelet number, correction of the shortened platelet survival times to normal, and reduction of increased plasma levels of β-TG, PF4, TM and urinary TXB2 excretion to normal. These results indicate that platelet-mediated fibromuscular intimal proliferation and platelet-rich thrombi in the peripheral, cerebral and coronary end-arterial microvasculature are responsible for the erythromelalgic ischemic complications, MIAs and splanchnic vein thrombosis. Baseline platelet P-selectin levels and arachidonic acid induced COX1 mediated platelet activation showed a highly significant increase of platelet P-selectin expression (not seen in ADP and collagen stimulated platelets), which was significantly higher in JAK2^V617F mutated compared to JAK2 wild type ET.

Cross-sectional study of biomarkers of exposure and biological effect on monozygotic twins discordant for smoking

BACKGROUND

The aim of this study was to investigate the possible correlation between smoking status and biomarkers of exposure (BoE) and biological effect (BoBE) in monozygotic twins discordant for smoking status (smoker and non-smoker pairs). By eliminating potential genetic variability in this manner, a clearer pattern of the effects of lifestyle and environmental exposures should become apparent.

METHODS

This was a cross-sectional study on monozygotic healthy twins (44 subjects, 26 males and 18 females) with a mean age 31.5 years. BoE to cigarette smoke and BoBE were measured in body fluids (24 h urine and blood) after medical pre-screening.

RESULTS

All BoE were significantly higher in the smoker twins. Among BoBE, 11-dehydrothromboxane B(2) (11-dehydro TBX), 2,3-dinorthromboxane B(2) (2,3-dinor TBX), 8-epi-prostaglandin F2α (8-epiPGF), hydroxyproline (OH-P), fibrinogen, white blood cell (WBC), neutrophil and lymphocyte counts and heart rate were statistically significantly increased in the smoker compared to the non-smoker twins. Moreover, statistically significant correlations between neutrophil count and 11-dehydro TBX (r=0.32), WBC and 8-epiPGF (r=0.33), OH-P and 8-epiPGF (r=0.49) and heart rate and fibrinogen (r=0.46) were observed.

CONCLUSIONS

The study results confirmed the reliability of the BoE for the evaluation of smoking status. Moreover, a subset of the BoBE, reported as being associated with inflammatory conditions and early stages of vascular disorders, has emerged as showing a consistent relationship with smoking status from the present and the previous studies. By using monozygotic twin pairs, genetic variability has been excluded as a possible source of variability in this study. These results should assist in the interpretation of other population studies using these biomarkers.

Cardiovascular biomarkers in groups of established smokers after a decade of smoking

To investigate tools for evaluation of smoking-associated disease initiation and progression, we examined basic clinical parameters and biomarkers of cardiovascular disease risk, in a group of healthy volunteers with an average 10-year smoking history. A small cross-sectional study of never-smokers, moderate smokers and smokers was performed. Caucasians were recruited to match pre-defined cigarette tar yields and cigarettes smoked per day. For haematological parameters, significant differences between never-smokers and all female smokers combined were seen for haemoglobin concentration, haematocrit, total leucocyte count, neutrophil count and lymphocyte count. For all male smokers combined, only total leucocyte count was statistically different. Analysis of exhaled CO and other smoke exposure biomarker (nicotine and its metabolites) data showed a statistically significant increase in all groups of smokers with a trend related to the number of cigarettes smoked per day. Thromboxane urinary metabolites 11-dehydro-thromboxane B(2) and 2,3-dinor-thromboxane B(2) were statistically significantly elevated in smokers. Significant statistical differences between smokers with approximately 10 years of smoking history and non-smokers in white cells count, hemoglobin and thromboxane turnover were seen, although they did not reach levels associated with overt diseases. These data could provide insight into early biomarkers predictive of risk for coronary and vascular disease.

Determinants of platelet activation in Alzheimer's disease

OBJECTIVES

To investigate the rate of platelet thromboxane (TX) biosynthesis and its determinants in Alzheimer's disease.

METHODS AND RESULTS

A cross-sectional comparison of urinary 11-dehydro-TXB(2) and 8-iso-prostaglandin (PG)F(2alpha) (markers of in vivo platelet activation and lipid peroxidation, respectively), plasma Vitamin E, C-reactive protein (CRP), tumor necrosis factor (TNF)-alpha and interleukin (IL)-6, was carried-out in 44 Alzheimer patients and 44 matched controls. To investigate the cyclooxygenase (COX)-isoform involved in TXA(2) biosynthesis, nine Alzheimer patients were treated with low-dose aspirin (100mg/d) or rofecoxib (25mg/d) for 4 days. Urinary 11-dehydro-TXB(2) and 8-iso-PGF(2alpha) were significantly higher in Alzheimer patients than in controls (Median: 1983.5 versus 517.5pg/mg creatinine and 938.5 versus 304.0pg/mg creatinine, p<0.0001, respectively), with a significant correlation between the two metabolites (rho=0.75, p<0.0001). An inverse correlation was observed between Vitamin E and both urinary metabolites (8-iso-PGF(2alpha): R(s)=-0.51, p=0.0004; 11-dehydro-TXB(2): R(s)=-0.44, p=0.0026) in Alzheimer patients. No difference was found in CRP, TNF-alpha and IL-6 levels between the two groups. Urinary 11-dehydro-TXB(2) was significantly reduced by aspirin, but not by rofecoxib, consistently with a COX-1-mediated TXA(2) biosynthesis. 8-iso-PGF(2alpha) excretion was not modified by either COX-inhibitor, consistently with its oxygen radical-catalyzed formation.

CONCLUSIONS

Platelet activation is persistently enhanced in Alzheimer's disease. This is related, at least in part, to increased lipid peroxidation associated with inadequate levels of Vitamin E.

Cigarette smoking is associated with increased circulating proinflammatory and procoagulant markers in patients with chronic coronary artery disease: effects of aspirin treatment

BACKGROUND

Smoking is associated with endothelial dysfunction. Cytokines released by injured endothelium promote vascular interactions with leukocytes and platelets. We investigated whether (a) cigarette smoking is linked to increased cytokine production, which may mediate platelet activation and thrombin generation in chronic coronary artery disease (CAD), and (b) aspirin treatment inhibits smoking-related changes on cytokines, platelets, and thrombin.

METHODS AND RESULTS

Plasma macrophage-colony-stimulating factor (M-CSF) and C-reactive protein (CRP) were measured in 100 patients with chronic CAD, 60 of whom were chronic smokers. Prothrombin fragments 1+2 and urinary 11-dehydro-thromboxane B2 (TXB2) were additionally measured in 60 of 100 patients (30 of whom were smokers) and in 24 healthy controls. Smokers (n = 20) matched for age, myocardial ischemia, and other risk factors with 20 nonsmokers entered a double-blind crossover trial of aspirin (300 mg/d for 3 weeks) versus placebo. Blood and urine measurements were repeated after each treatment. Compared with nonsmokers, smokers had 3-fold median M-CSF (1499 vs 476 pg/mL), 2-fold CRP (1.5 vs 0.8 mg/L), and higher 11-dehydro-TXB 2 (3.6 vs 2.1 ng/mg creatinine, P < .01 for all comparisons). After aspirin treatment, M-CSF, CRP, 11-dehydro-TXB 2 , and prothrombin fragments 1+2 remained higher in smokers compared with nonsmokers despite a significant reduction of these markers by aspirin (P < .05). M-CSF remained related to 11-dehydro-TXB 2 excretion during both treatment phases (P < .01) suggesting that cytokine-mediated thromboxane A 2 production was not altered by aspirin.

CONCLUSIONS

Smoking is associated with increased M-CSF, CRP, and platelet activity. Although aspirin treatment reduces the proinflammatory and procoagulant markers in smokers, it does not abolish the proinflammatory effects of smoking in patients with chronic CAD.

Helicobacter pylori infection causes persistent platelet activation in vivo through enhanced lipid peroxidation

OBJECTIVE

We aimed at investigating the relationship between Helicobacter pylori infection and in vivo lipid peroxidation and platelet activation, as reflected by urinary 8-iso-prostaglandin (PG)F(2alpha) and 11-dehydro-thromboxane (TX)B2, respectively, in otherwise healthy dyspeptic subjects.

METHODS AND RESULTS

We measured urinary 8-iso-PGF2alpha and 11-dehydro-TXB2 excretion in 40 dyspeptic subjects with a positive 13C-urea breath test and 38 dyspeptic individuals with a negative test. Moreover, we investigated the effects of H pylori eradication on prostanoid metabolite excretion in 23 H pylori-positive subjects. We also measured prostanoid metabolite excretion before and after selective cyclooxygenase-2 inhibition with rofecoxib in 4 H pylori-positive subjects. Urinary 8-iso-PGF2alpha and 11-dehydro-TXB2 excretion was significantly higher in the H pylori-positive individuals than in controls. A significant direct correlation was found between the degree of positivity to the 13C-urea breath test and urinary 8-iso-PGF2alpha excretion. The latter was linearly correlated with urinary 11-dehydro-TXB2. Successful eradication of H pylori infection led to a significant reduction in both 8-iso-PGF(2alpha) and 11-dehydro-TXB2. Furthermore, their levels were unaffected after treatment with rofecoxib.

CONCLUSIONS

Our study provides evidence of enhanced in vivo lipid peroxidation and platelet activation in association with H pylori infection and suggests a novel mechanism by which an infectious agent could contribute to atherothrombosis.

Reduction of daily life ischaemia by aspirin in patients with angina: underlying link between thromboxane A2 and macrophage colony stimulating factor

OBJECTIVES

To evaluate whether aspirin reduces the incidence and frequency of daily life myocardial ischaemia in a cohort of patients with chronic stable coronary artery disease.

SETTING

Tertiary referral centre.

METHODS

60 patients with chronic stable coronary artery disease underwent 48 hour Holter monitoring to assess the incidence and frequency of daily life myocardial ischaemia. Those with myocardial ischaemia (40/60) entered a double blind, crossover trial of aspirin (300 mg/day for three weeks) versus placebo. After each treatment arm, 48 hour Holter monitoring was repeated and urinary thromboxane (Tx) B2, 11-dehydro-TxB2, plasma prothrombin fragment F1+2, macrophage colony stimulating factor (MCSF), and interleukin (IL)-6 were measured.

RESULTS

Aspirin reduced the total number and duration of ischaemic episodes from 339 to 251 and from 1765 to 1365 minutes, respectively (p < 0.01 for both). TxB2 was also reduced from 0.2 to 0.1 ng/mg creatinine, 11-dehydro-TxB2 from 3.3 to 1.3 ng/mg creatinine, F1+2 from 1.5 to 1.2 nmol/l, MCSF from 991 to 843 pg/ml, and IL-6 from 3.5 to 2.9 pg/ml (p < 0.05 for all). 11-dehydro-TxB2 excretion with and without aspirin was related to MCSF concentrations (p < 0.01), and the percentage reduction of MCSF by aspirin was related to the reduction of 11-dehydro-TxB2 (p < 0.05) and the reduction of the ischaemic burden compared with placebo (p < 0.05).

CONCLUSIONS

In patients with daily life ischaemia, aspirin reduces the incidence and frequency of ischaemic episodes as well as the systemic concentrations of haemostatic/inflammatory markers. Aspirin may prevent transient coronary flow reductions through platelet, thrombin, and cytokine inhibition.

Determinants of enhanced thromboxane biosynthesis in renal transplantation

BACKGROUND

Despite great improvement in patient and graft survival, the long-term morbidity and mortality in renal transplant recipients (RTRs) are still significant, with a high incidence of cardiovascular disease-related deaths.

METHODS

We investigated thromboxane (TXA2) biosynthesis and endothelial and coagulative activation in 65 patients who received a renal transplant.

RESULTS

The rate of TXA2 biosynthesis (urinary 11-dehydro-TXB2 excretion largely reflects platelet TXA2 production in vivo) was significantly (P < 0.0001) higher in RTRs than in healthy subjects. Plasma von Willebrand factor (vWF) and thrombin-antithrombin (TAT) complexes were significantly higher (P < 0.001) in RTRs compared with controls. Urinary 11-dehydro-TXB2 directly correlated with plasma vWF and cholesterol. We next examined the relative influence of cyclosporine A (CsA) on TXA2 biosynthesis and endothelial activation, comparing a group of RTRs not receiving CsA with an age- and sex-matched group of patients treated with CsA. Urinary excretion of 11-dehydro-TXB2 and plasma levels of vWF were significantly increased in RTRs who received CsA compared with those who did not. After an overall follow-up of 120 months, RTRs who experienced cardiovascular events had a higher frequency of abnormal plasma levels of vWF than patients who remained event free.

CONCLUSION

Renal transplantation is associated with in vivo platelet activation highly related to endothelial activation. This is particularly evident in CsA-treated patients. Administration of drugs that are able to reduce or eliminate thromboxane-dependent platelet activation in vivo may be beneficial to reduce the risk of cardiovascular events in RTRs.

Enhanced thromboxane biosynthesis in patients with chronic obstructive pulmonary disease. The Chronic Obstructive Bronchitis and Haemostasis Study Group

Thrombotic complications of pulmonary circulation occur in patients with chronic obstructive pulmonary disease (COPD). In the present study, we sought to evaluate in vivo platelet activation through the measurement of 11/dehydro-thromboxane (Tx) B2 TxA2 major metabolite in the urine, in 29 patients with COPD, compared with 29 sex- and age-matched healthy subjects. The urinary excretion of 11-dehydro-TxB2 was significantly higher in patients with COPD than in control subjects: median (range), 753 (277-4,409) and 275 (129-612) pg/mg creatinine, respectively; p < 0.0001). Moreover, 11-dehydro-TxB2 excretion was inversely related with arterial oxygen tension (rho = -0.46; p = 0.0145). In five of the 29 patients a short-term therapeutic course with oxygen supplementation induced a significant decrease of urinary 11-dehydro-TxB2 excretion: median range, 941 (452-2,640) to 445 (166-1,560) pg/mg creatinine. Moreover, selective inhibition of platelet cyclooxygenase activity by low-dose aspirin was associated with more than 90% inhibition of thromboxane metabolite excretion, demonstrating its being of platelet origin. Plasma levels of prothrombin fragment F1 + 2 were higher in patients than in control subjects (2.6 +/- 1.5 versus 0.9 +/- 0.4 nM, p = 0.0001). No relation between 11-dehydro-TxB2 excretion and plasma F1 + 2 levels was found. We conclude that platelet TxA2 biosynthesis is enhanced in patients with COPD and may be influenced by arterial oxygen tension changes.

Isoprostanes: potential markers of oxidant stress in atherothrombotic disease

Isoprostanes are emerging as a new class of biologically active products of arachidonic acid metabolism of potential relevance to human vascular disease. Their formation in vivo seems to reflect primarily, if not exclusively, a nonenzymatic process of lipid peroxidation. Enhanced urinary excretion of 8-iso-PGF2 alpha has been described in association with cardiac reperfusion injury and with cardiovascular risk factors, including cigarette smoking, diabetes mellitus, and hypercholesterolemia. Besides providing a likely noninvasive index of lipid peroxidation in these settings, measurements of specific F2 isoprostanes in urine may provide a sensitive biochemical end point for dose-finding studies of natural and synthetic inhibitors of lipid peroxidation. Although the biological effects of 8-iso-PGF2 alpha in vitro suggest that it and other isoeicosanoids may modulate the functional consequences of lipid peroxidation, evidence that this is likely in vivo remains inadequate at this time.

Diabetes mellitus, hypercholesterolemia, and hypertension but not vascular disease per se are associated with persistent platelet activation in vivo. Evidence derived from the study of peripheral arterial disease

BACKGROUND

Previous studies relating increased thromboxane (TX) biosynthesis to cardiovascular risk factors do not answer the question whether platelet activation is merely a consequence of more prevalent atherosclerotic lesions or reflects the influence of metabolic and hemodynamic disturbances on platelet biochemistry and function.

METHODS AND RESULTS

We examined 64 patients with large-vessel peripheral arterial disease and 64 age- and sex-matched control subjects. TXA2 biosynthesis was investigated in relation to cardiovascular risk factors by repeated measurements of the urinary excretion of its major enzymatic metabolite, 11-dehydro-TXB2, by radioimmunoassay. Urinary 11-dehydro-TXB2 was significantly (P = .0001) higher in patients with peripheral arterial disease (57 +/- 26 ng/h) than in control subjects (26 +/- 7 ng/h). Seventy percent of patients had metabolite excretion > 2 SD above the normal mean. However, 11-dehydro-TXB2 excretion was enhanced only in association with cardiovascular risk factors. Multivariate analysis showed that diabetes, hypercholesterolemia, and hypertension were independently related to 11-dehydro-TXB2 excretion. During a median follow-up of 48 months, 8 patients experienced major vascular events. These patients had significantly (P = .001) higher 11-dehydro-TXB2 excretion at baseline than patients who remained event free.

CONCLUSIONS

The occurrence of large-vessel peripheral arterial disease per se is not a trigger of platelet activation in vivo. Rather, the rate of TXA2 biosynthesis appears to reflect the influence of coexisting disorders such as diabetes mellitus, hypercholesterolemia, and hypertension on platelet biochemistry and function. Enhanced TXA2 biosynthesis may represent a common link between such diverse risk factors and the thrombotic complications of peripheral arterial disease.

Hemostatic variables and ischemic cardiovascular disease: do we need a concerted effort for more profitable future clinical investigations?

Abnormally high levels of some hemostatic variables are often associated with the occurrence of the major ischemic complications of atherosclerosis, myocardial infarction, and stroke. Intervention studies have shown that prolonged treatment with antiplatelet drugs significantly reduces the recurrence of coronary and cerebral ischemic episodes. The association of the ischemic event with the hemostatic abnormality has often been just descriptive. Although suggestive, the link between the abnormality and the development and progression of atherosclerosis is only circumstantial. Finally, no information is available on the presence of one or more abnormal variables in subjects who did or did not experience a recurrence of thrombosis with treatment. To strengthen the clinical relevance of these hemostatic variables and to maximize the effectiveness of antithrombotic strategies, these indices should be taken into account in studies evaluating nonpharmacological and pharmacological interventions against arterial thrombosis. We believe that a task force on this subject would serve a useful purpose. The task force should develop and publicize within the cardiological community guidelines for (a) defining the size of the problem, (b) identifying the variables to measure, (c) standardizing detection and monitoring techniques, and (d) suggesting appropriate strategies of prevention and treatment.

Effect of diets containing different amounts of precursor and derivative fatty acids on serum TXB2

Dietary precursor and derivative polyunsaturated fatty acids influence metabolic parameters, such as eicosanoid synthesis. We have studied the effect of dietary intakes of lipids containing different amounts of precursor and derivative fatty acids (olive oil, olive-blackcurrant-fish oil mixture, blackcurrant-fish oil mixture, MCT (medium chain triglycerides)-soyabean oil mixture) on serum thromboxane B2 (TXB2) in four groups of rats. Plasma fatty acid composition showed differences related to dietary intakes. TXB2 levels were similar in all conditions except in the group receiving the mixture of olive-blackcurrant-fish oils which showed lower values.

Aspirin in ischemic cerebrovascular disease. How strong is the case for a different dosing regimen?

BACKGROUND

A vast consensus exists in defining a narrow range of recommended daily doses of aspirin, ie, 75 to 160 mg, for the prevention of myocardial infarction, stroke, and vascular death in patients with different manifestations of coronary hearth disease. In contrast, for patients with cerebrovascular disease, a much larger degree of uncertainty still exists, with recommendations ranging from 30 to 1300 mg daily.

SUMMARY OF COMMENT

The contention that higher doses of aspirin (650 to 1300 mg) are more effective than lower doses in stroke prevention is based on indirect and selective comparisons of different trial data, mini-meta-analyses, or subgroup analyses of individual trials. In the absence of definitive evidence from direct randomized comparisons of low-dose versus high-dose aspirin in trials of adequate size to detect a moderate difference between the two, the biological hypotheses that underpin the suggestion of greater efficacy of higher aspirin doses in cerebrovascular disease patients are reviewed and disputed. Practical implications of the use of higher doses of aspirin are also assessed on the basis of theoretical calculations of absolute benefits and risks.

CONCLUSIONS

Until additional information from ongoing trials is available, good clinical practice should dictate the use of the lowest dose of aspirin shown effective in the prevention of stroke and death in patients with ischemic cerebrovascular disease, ie, 75 mg daily.

Cytosolic phospholipase A2

To summarize the regulation of cPLA2, we have proposed a model for the activation of cPLA2 based both on our previous studies (Clark et al., 1991; Lin et al., 1993) and the work of many others (Fig. 5). In this model, cPLA2 is tightly regulated by multiple pathways, including those that control Ca2+ concentration, phosphorylation states and cPLA2 protein levels, to exert both rapid and prolonged effects on cellular processes, such as inflammation. cPLA2 is rapidly activated by increased intracellular Ca2+ concentration and phosphorylation by MAP kinase. When cells are stimulated with a ligand for a receptor, such as ATP or PDGF, PLC is activated via either a G protein-dependent or -independent process, leading to the production of diacylglycerol (DAG) and inositol triphosphate (IP3). The rise in these intracellular messengers cause the activation of PKC and mobilization of intracellular Ca2+. Alternatively, the increase in intracellular Ca2+ can result from a Ca2+ influx. Increased Ca2+ acts through the CaLB domain to cause translocation of cPLA2 from the cytosol to the membrane where its substrate, phospholipid, is localized. This step is essential for the activation of cPLA2 and may account for the partial activation of cPLA2 in the absence of phosphorylation. MAP kinase activation can occur through both PKC-dependent and -independent mechanisms (Cobb et al., 1991; Posada and Cooper, 1992; Qiu and Leslie, 1994). In many cases, this pathway is also G protein-dependent. Activated MAP kinase phosphorylates cPLA2 at Ser-505, causing increased enzymatic activity of cPLA2, which is realized only upon translocation of cPLA2 to the membrane. Therefore, full activation of cPLA2 requires both increased cytosolic Ca2+ and cPLA2 phosphorylation at Ser-505. In a more delayed response, cPLA2 activity in the cells can be controlled by changes in its expression levels, such as in response to inflammatory cytokines and certain growth factors. Thus the expression level of cPLA2 is regulated by both transcriptional and post-transcriptional mechanisms.

Effects of picotamide, an antithromboxane agent, on carotid atherosclerotic evolution. A two-year, double-blind, placebo-controlled study in diabetic patients

BACKGROUND AND PURPOSE

We assessed the effects of long-term treatment with picotamide, an antiplatelet agent with dual antithromboxane activity, on the evolution of early asymptomatic carotid atherosclerotic lesions in diabetic patients.

METHODS

In a double-blind, placebo-controlled, 2-year study, 50 type II normotensive diabetic patients (35 men; mean age, 66 +/- 5 years) with asymptomatic mild or moderate nonstenotic (< 50%) carotid atherosclerotic lesions and negative history of cerebrovascular ischemic events were enrolled and randomly given picotamide (300 mg TID) or the corresponding placebo. A high-resolution, real-time B-scan echographic assessment of carotid arteries was performed at baseline and after 1, 3, 6, 12, 18, and 24 months of double-blind treatment. Prevalence and evolutionary trends of carotid atherosclerotic lesions (number per patient and mean stenosis expressed as percent) were considered as efficacy primary end points.

RESULTS

At baseline, mean +/- SD numbers of carotid atherosclerotic lesions per patient were 2.7 +/- 1.8 and 2.2 +/- 1.2 in the picotamide and placebo groups, respectively. Mean +/- SD percent stenosis was 25.3 +/- 7% in the picotamide group and 27.3 +/- 6% in the placebo group. Forty-nine patients completed the study. At month 24, the placebo group (n = 24) showed a significant progression in number of carotid atherosclerotic lesions (3.04 +/- 1.8; P < .02 versus baseline) and in mean percent stenosis (35 +/- 17%; 95% confidence interval, 33% to 37%; P < .01 versus baseline). In the picotamide group (n = 25), mean number of carotid atherosclerotic lesions (2.7 +/- 1.6) and percent stenosis (26 +/- 9%; 95% confidence interval, 24.8% to 27.2%) remained unchanged. At month 24, compared with randomized placebo, lesion numbers (P < .03) and percent stenosis (P < .01) in the picotamide group were significantly lower. During the study, 12 patients experienced major or minor ischemic vascular events (9 in the placebo group and 3 in the picotamide group; P = .07).

CONCLUSIONS

In diabetic patients compared with patients receiving placebo, long-term treatment with picotamide can slow the evolution of early carotid atherosclerotic lesions, inhibiting progression of plaque number and growth.

Gemfibrozil enhances platelet activity in patients with combined hyperlipoproteinemia

A placebo-controlled crossover study was conducted to evaluate whether lipid-lowering with gemfibrozil (10 to 12 weeks) affects platelet function in vivo at rest and during mental stress in 21 men with combined hyperlipoproteinemia. Gemfibrozil lowered plasma triglycerides and total and VLDL cholesterol (P < .001 for all), whereas HDL cholesterol increased (P < .001). Gemfibrozil increased platelet counts by 18% (P < .001) and, according to filtragometry measurements, enhanced overall (means of rest and stress values) platelet aggregability in vivo (P = .014); this effect was more evident during mental stress (P = .027) than at rest (P = .18). Moreover, the urinary excretion of 11-dehydro-thromboxane-B2 was 54% higher during treatment with gemfibrozil (P < .001), whereas the excretion of beta-thromboglobulin in urine was unaltered. Plasma beta-thromboglobulin tended to be slightly elevated during active treatment (P = .15). Mental stress increased heart rate and catecholamine levels and elevated all cholesterol fractions (P < .01) and plasma beta-thromboglobulin (during placebo, P = .02), but platelet aggregability did not increase significantly. A positive correlation was found between 11-dehydrothromboxane-B2 excretion and LDL cholesterol levels during placebo (r = .62, P = .0057). In conclusion, gemfibrozil has beneficial effects on plasma lipoprotein levels but enhances several aspects of platelet activity in vivo and increases platelet counts. These changes might be prothrombotic and thus adverse for the hyperlipidemic patient. Primary preventive effects of gemfibrozil might be enhanced if a platelet inhibitor such as aspirin is administered with gemfibrozil.

Atherosclerosis and thrombosis. Old and new drugs

Thanks to the increasing knowledge of the pathogenesis of atherosclerosis, much effort has been made in the last years to develop new drugs aimed at controlling risk factors correlated with the disease as well as to investigate more deeply their mechanism of action. In particular, this brief review will describe some new aspects of the mechanism of action of drugs widely used in the control of risk factors like hyperlipemia, hypertension and blood viscosity. Among drugs active on plasma lipid profile, HMG-CoA reductase inhibitor are, at present, under study for their promising activity in the modulation of the interaction between the cells of the arterial wall and circulating blood elements. Indeed, these compounds have been found to control the proliferation of smooth muscle cells and other events related to the formation of atheroma. As far as antithrombotic drugs are concerned, the efficacy of low doses of aspirin has emerged by recent clinical trials. The successful use of low doses of aspirin has been possible following the comprehension of the mechanism by which this compound inhibits TXA-dependent platelet function, thus allowing a dose-dependent dissociation of the antithrombotic activity from other undesirable effects. Also for calcium antagonist an antiatherogenic effect which deserves further investigations has been recently clarified. Indeed it has been demonstrated that calcium antagonists have a protective effect against vascular lesions because they inhibit smooth muscle cell proliferation, lipid uptake by macrophages and the production of collagen and elastin. Another class of drugs which represents a new approach in the control of some risk factors is represented by n-3 fatty acids. Besides their activity on triglycerides, these compounds exert a positive effect on hemostatic and thromboembolic event, by reducing platelet aggregation and blood viscosity. Also for those molecules which appear to exert promising antiatherosclerotic and antithrombotic action, further studies will define their exact mechanism of action.

High plasma concentrations of cortisol and thromboxane B2 in patients with depression

Modulation of the hypothalamic-pituitary-adrenal axis in major depression is thought to depend on the hypothalamus and other areas of the central nervous system, or both. Hypothalamic over-activity may be responsible for the hypercortisolism observed in 50% of depressed subjects. To investigate the relation between psychosocial factors and cardiovascular disease, morning (8 AM) plasma concentrations of cortisol and thromboxane B2 (the stable metabolite of thromboxane A2, an eicosanoid closely linked to thrombotic disorders) were measured by radioimmunoassay in 32 patients with major depression (DSM III) triggered by psychosocial events and in 9 nondepressed volunteers. The depressed patients were studied in two groups, 16 with cortisol levels under 90 ng/mL and 16 with levels over 90 ng/mL. All the healthy non-depressed subjects had cortisol values over 100 ng/mL. The depressed patients with high cortisol had significantly higher plasma TxB2 concentrations than the other two groups. In addition, plasma cortisol and TxB2 concentrations correlated significantly over the whole group of depressed patients and in the high cortisol sub-group but not in the low-cortisol sub-group or in the nondepressed subjects. These findings appear to support the recently proposed role of the hypothalamic dysfunction associated with affective disorders in the pathogenesis of cardiovascular disease.