Homocysteine Levels Influence Platelet Reactivity in Coronary Artery Disease Patients Treated With Acetylsalicylic Acid.

BACKGROUND: Suboptimal platelet inhibition with antiplatelet treatments is associated with a severe prognosis in patients with coronary artery disease (CAD), and the identification of its determinants is still challenging. Homocysteine elevation has emerged as a prothrombotic factor, influencing coagulative status and endothelial function and potentially modulating platelet aggregation. We therefore aimed to evaluate the effects of homocysteine (Hcy) levels on platelet reactivity in patients receiving acetylsalicylic acid (ASA) with or without ADP antagonists. METHODS: Patients undergoing coronary angiography and receiving ASA (100-160 mg daily) for >7 days, with or without ADP antagonists, were included. Aggregation tests were performed by multiple electrode aggregometry. Suboptimal platelet inhibition was defined as on-treatment aggregation above the lower limit of normality. RESULTS: Our population is represented by 508 ASA-treated patients, 406 (80.1%) of whom on dual antiplatelet therapy (ASA and ADP antagonists). Hcy levels above the median (15.1 nmol/mL) were associated with male gender (P = 0.04), hypertension (P = 0.004), hypercholesterolemia (P = 0.03), aging, renal failure (P < 0.001, respectively), previous coronary bypass grafting (P = 0.04), therapy with calcium antagonists (P = 0.04) and diuretics (P = 0.001), and multivessel CAD (P = 0.03). Higher Hcy is directly related with serum creatinine and uric acid (P < 0.001). Suboptimal platelet inhibition was found in 16 patients (3.2%) for ASA and for ADP antagonists in 80 patients (19.7%). Hcy levels significantly affected suboptimal response to ASA, but not to ADP-mediated aggregation. In fact, a linear relationship was found between homocysteine and platelet reactivity after stimulation with arachidonic acid (r = 0.14, P = 0.004) and collagen (r = 0.12, P = 0.02), but not with ADP (r = 0.02, P = 0.77). Moreover, after correction for baseline differences, Hcy above the median was confirmed as an independent predictor of impaired ASA response [adjusted odds ratio (95% confidence interval) = 3.7 (1.08-12.4), P = 0.04]. CONCLUSIONS: Among patients with CAD, elevated homocysteine is an independent predictor of suboptimal response to ASA, but not to ADP antagonists.

Platelet-larger cell ratio and the risk of periprocedural myocardial infarction after percutaneous coronary revascularization.

Periprocedural myocardial infarction (PMI) represents a frequent complication in patients undergoing percutaneous coronary revascularization. Despite great attention focused on pharmacological prevention of periprocedural damage, very little is known about using biomarkers to potentially predict the risk of PMI. Larger platelets have been associated with enhanced reactivity, increased cardiovascular risk, and higher rates of complications after coronary stenting. The platelet-larger cell ratio (P-LCR) identifies the largest-sized fraction of platelets, the proportion potentially more closely related to thrombotic events. The present study evaluated the relationship between P-LCR and PMI. We included 1,285 patients undergoing PCI. Myonecrosis biomarkers were dosed at intervals from 6 to 48 h after PCI. Periprocedural myonecrosis was defined as troponin I increase by three times the upper limit of normal (ULN) or by 50 % of an elevated baseline value, whereas PMI was defined as an increase in creatine kinase MB by 3 × ULN or 50 % of baseline. We grouped patients according to tertile values of P-LCR (<27.5; ≥35.1). Higher P-LCR was associated with age (P = 0.01), diabetes (P = 0.001), previous cerebrovascular accidents (P = 0.007), therapy with statins (P < 0.001), angiotensin receptor blockers (P < 0.001), aspirin (P = 0.002), and nitrates (P = 0.01). P-LCR was related to hemoglobin levels (P < 0.001), and inversely related to platelet count (P < 0.001) and glycemia (P = 0.05). Patients with higher P-LCR had a lower presence of coronary thrombus (P = 0.003). Higher P-LCR values did not increase the risk of PMI (P = 0.10; adjusted odds ratio (OR) (95 % confidence interval (CI)) = 0.97 (0.69-1.38)), P = 0.89) or periprocedural myonecrosis (P = 0.96; adjusted OR (95 % CI) = 1.003 (0.76-1.32), P = 0.99). Results were confirmed even in higher-risk subgroups of patients. P-LCR does not increase the risk of periprocedural myocardial infarction and myonecrosis in patients undergoing coronary stenting.

Benefits from new ADP antagonists as compared with clopidogrel in patients with stable angina or acute coronary syndrome undergoing invasive management: a meta-analysis of randomized trials.

AIMS: New P2Y12 receptor inhibitors have provided new and more potent antiplatelet strategies, although raising several concerns on possible increase of bleedings. The aim of current meta-analysis was to evaluate the efficacy and safety of new adenosine diphosphate (ADP) receptor antagonists as compared with clopidogrel in elective or ACS patients managed invasively. METHODS AND RESULTS: Literature archives (Pubmed, EMBASE, Cochrane) and main scientific sessions abstracts were scanned for randomized trials comparing new ADP antagonists with clopidogrel in patients with acute coronary syndromes or stable angina. Primary endpoint was mortality. Secondary endpoints were: (1) nonfatal myocardial infarction (MI), (2) recurrent ischemia symptoms or ischemia-driven revascularization (RI/IDR), (3) stent thrombosis (ST), and (4) safety endpoints, defined as for TIMI major bleeding criteria. A total of 8 randomized clinical trials were finally included, for a total population of 67,851 patients. Mean follow-up was 7.6 months, ranging from 48 hours to 30 months. New ADP antagonists significantly reduced mortality {3.1% vs. 3.6%, odds ratio [OR] [95% confidence interval (CI)], 0.86 [0.79-0.94], P = 0.0008, P(het) = 0.18}, with greater impact of oral drugs. Similar benefits were found for MI [6.1% vs. 7%; OR (95% CI) (random-effect model) = 0.88 (0.79-0.98), P = 0.01, P(het) = 0.02], RI [2.7% vs. 3.1%; OR (95% CI) = 0.85 (0.77-0.93), P = 0.0005, P(het) = 0.09], or ST [1.1% vs. 1.7%; OR (95% CI) = 0.60 (0.51-0.71), P < 0.00001, P(het) = 0.13]. By meta-regression analysis, no relationship was observed between benefits in mortality, new MI, RI, and ST with new ADP antagonists and patients' risk profile [beta (95% CI) = -0.01 [-0.30 to 0.27], P = 0.94; beta (95% CI) = -0.05 [-1.49 to 1.43], P = 0.96); beta (95% CI) = 0.19 (-0.18 to 0.57), P = 0.31, and beta (95% CI) = -0.08 (-0.86 to 0.70), P = 0.84, respectively]. CONCLUSIONS: Present meta-analysis shows that the new ADP antagonists prasugrel, ticagrelor, and cangrelor are associated to significant reduction of mortality, reinfarction, RI, and ST respect to clopidogrel alone, without significant increase in bleeding complications.

Platelet distribution width and the risk of periprocedural myocardial infarction in patients undergoing percutaneous coronary intervention.

Periprocedural myocardial infarction (PMI) still occurs in a large amount of percutaneous coronary interventions (PCI), mainly due to increased platelet activation. Platelet size has been suggested as an indicator of enhanced reactivity and platelet distribution width (PDW) could reflect morphologic changes in platelets, therefore affecting their function and potentially increasing the risk of complications after coronary stenting. Aim of the present study was to evaluate the relationship between PDW and PMI. We included 1,300 consecutive patients undergoing PCI. Myonecrosis biomarkers were dosed at intervals from 6 to 48 h after PCI. Periprocedural myonecrosis was defined as troponin I increase by three times the ULN or by 50 % of an elevated baseline value, whereas PMI as CKMB increase by three times the ULN or 50 % of baseline. We grouped patients according to tertiles values of PDW (<12.1; ≥13.9). Higher PDW was associated with age (p = 0.03), diabetes (p < 0.001), previous cerebrovascular accidents (p = 0.04), therapy with statins (p = 0.001) and ARBs (p < 0.001), ASA (p = 0.02), nitrates (p = 0.006), calcium antagonists (p = 0.05) and lower pre-procedural clopidogrel bolus (p = 0.005). PDW related with haemoglobin levels (p < 0.001), while inversely to platelet count (p < 0.001) and glycaemia (p = 0.003). Patients with larger PDW had lower presence of coronary thrombus (p < 0.001), higher rate of coronary calcifications (p = 0.02), higher stenting rate (p = 0.03) and lower rate of distal embolization (p = 0.03). Larger PDW did not increase risk of PMI (p = 0.11; adjusted OR [95 % CI] = 0.94 [0.78-1.1], p = 0.55) or periprocedural myonecrosis (p = 0.73; adjusted OR [95 % CI] = 0.95 [0.82-1.1], p = 0.51). Results were confirmed even in higher-risk subgroups of patients. In patients undergoing coronary stenting, PDW does not increase the risk of periprocedural MI and therefore should not be considered a risk factor for thrombotic periprocedural complications after PCI.

Platelet HPA-1 a/HPA-1 b polymorphism and the risk of periprocedural myocardial infarction in patients undergoing elective PCI.

Periprocedural myocardial infarction (PMI) represents a relatively common complication of percutaneous coronary intervention (PCI) and large interests have been focused on platelets in order to prevent such a complication. The single nucleotide polymorphism Leu33Pro of platelet glycoprotein IIIa has been related to an increased platelet reactivity, a lower response to antiplatelet agents and higher risk of stent restenosis. Therefore, aim of our study was to evaluate the impact of this polymorphism on PMI in elective patients undergoing PCI. Our population is represented by 422 consecutive patients with cardiac biomarkers within normality undergoing elective PCI. We measured cardiac biomarkers (CK-MB and Troponin I) at baseline, and 8, 24 and 48 hours after the procedure. For all subjects, we performed genetic analysis to assess the presence of Leu33Pro polymorphism. A total of 136 patients (32.2%) were polymorphic. Those patients were younger (p = 0.03) and more often dislypidemic (p = 0.01). Angiographic features did not differ according to genetic status. Pharmacological treatment pre and during angioplasty was similar. PCI-related complications did not differ according to genotype, with the only exception of higher rate of distal embolization in polymorphic patients. However, Leu33Pro polymorphism was not associated with increased risk of periprocedural myonecrosis and PMI even after correction for baseline differences, (respectively OR = 1.22 [0.81-1.84], p = 0.34 for myonecrosis and OR = 1.66 [0.85-3.23]; p = 0.14 for PMI). At subgroup analysis, the Leu33Pro substitution was associated with higher risk of PMI only among diabetics (adjusted OR = 4.46 [1.12-17.76], p = 0.03). Among patients undergoing elective PCI, the polymorphism Leu33Pro of platelet glycoprotein IIIa is associated with increased risk of PMI only in diabetic patients.

The phytoestrogen 8-prenylnaringenin inhibits agonist-dependent activation of human platelets.

BACKGROUND: Phytoestrogens are plant-derived polyphenolic compounds that exert beneficial effects on human health, mostly related to their estrogen mimetic activity. In particular a strong correlation between phytoestrogens intake and a lower risk of cardiovascular diseases has been reported. The flavanone 8-prenylnaringenin, extracted from hop flowers, has been identified as a novel phytoestrogen, unique with respect to estrogen receptors specificity and potency. However, to date no investigations on the 8-prenylnaringenin role in modulating platelet function have been undertaken. METHODS: We evaluated the effect of 8-prenylnaringenin on platelet aggregation, intracellular calcium mobilization and protein phosphorylation triggered by thrombin and collagen, and platelet adhesion and dense granule secretion triggered by collagen. RESULTS: 8-Prenylnaringenin inhibited platelet aggregation induced by different agonists and platelet adhesion to collagen matrix. 8-Prenylnaringenin directly increased intracellular cAMP and cGMP levels and thus promoted VASP phosphorylation. However, these molecular events were not responsible for the inhibitory action of 8-prenylnaringenin on platelets. Moreover, 8-prenylnaringenin inhibited the phosphorylation of Pyk2, Akt, and ERK1/2. Finally, 8-prenylnaringenin suppressed the mobilization of calcium and the secretion of dense granules. All these effects were independent of estrogen receptors recruitment. CONCLUSIONS: 8-Prenylnaringenin exerted anti-aggregatory and anti-adhesive effects on human platelets, independently of estrogen receptors, acting as an inhibitor of multiple proteins essential for the morphological and biochemical transformations that occur during platelet activation and aggregation. GENERAL SIGNIFICANCE: 8-Prenylnaringenin may represent a useful tool in the therapy and prevention of vascular diseases associated with platelet aggregation, such as atherosclerosis, myocardial infarction, coronary artery disease, and thrombosis.

Alterations of negative regulators of cytokine signalling in immunodeficiency-related non-Hodgkin lymphoma.

We investigated immunodeficiency-related non-Hodgkin lymphoma for the presence of molecular alterations affecting negative regulators of the Janus family protein tyrosine kinase/signal transducer and activator of transcription pathway. Protein tyrosine phosphatase, non-receptor type 6/Src homology 2-containing tyrosine phosphatase-1 epigenetic silencing was recurrent in primary effusion lymphoma (100%), and diffuse large B-cell lymphoma (63%), with a higher prevalence in the non-germinal centre subtype, and was associated with the activation of the Janus family protein tyrosine kinase/signal transducer and activator of transcription 3 pathway. Suppressor of cytokine signalling (SOCS)1 and SOCS3 epigenetic silencing were occasionally detected, whereas SOCS1 was frequently mutated in diffuse large B-cell lymphoma and polymorphic post-transplant lymphoproliferative disorders, possibly as a cause of aberrant somatic hypermutation. However, the mutation profile of the coding region of the gene was different from that expected from the aberrant somatic hypermutation process, suggesting that, at least in some cases, SOCS1 mutations may have been selected for their functional activity.

SAP-mediated inhibition of diacylglycerol kinase α regulates TCR-induced diacylglycerol signaling.

Diacylglycerol kinases (DGKs) metabolize diacylglycerol to phosphatidic acid. In T lymphocytes, DGKα acts as a negative regulator of TCR signaling by decreasing diacylglycerol levels and inducing anergy. In this study, we show that upon costimulation of the TCR with CD28 or signaling lymphocyte activation molecule (SLAM), DGKα, but not DGKζ, exits from the nucleus and undergoes rapid negative regulation of its enzymatic activity. Inhibition of DGKα is dependent on the expression of SAP, an adaptor protein mutated in X-linked lymphoproliferative disease, which is essential for SLAM-mediated signaling and contributes to TCR/CD28-induced signaling and T cell activation. Accordingly, overexpression of SAP is sufficient to inhibit DGKα, whereas SAP mutants unable to bind either phospho-tyrosine residues or SH3 domain are ineffective. Moreover, phospholipase C activity and calcium, but not Src-family tyrosine kinases, are also required for negative regulation of DGKα. Finally, inhibition of DGKα in SAP-deficient cells partially rescues defective TCR/CD28 signaling, including Ras and ERK1/2 activation, protein kinase C membrane recruitment, induction of NF-AT transcriptional activity, and IL-2 production. Thus SAP-mediated inhibition of DGKα sustains diacylglycerol signaling, thereby regulating T cell activation, and it may represent a novel pharmacological strategy for X-linked lymphoproliferative disease treatment.

Diacylglycerol kinase alpha mediates HGF-induced Rac activation and membrane ruffling by regulating atypical PKC and RhoGDI.

Diacylglycerol kinases (DGKs) convert diacylglycerol (DAG) into phosphatidic acid (PA), acting as molecular switches between DAG- and PA-mediated signaling. We previously showed that Src-dependent activation and plasma membrane recruitment of DGKalpha are required for growth-factor-induced cell migration and ruffling, through the control of Rac small-GTPase activation and plasma membrane localization. Herein we unveil a signaling pathway through which DGKalpha coordinates the localization of Rac. We show that upon hepatocyte growth-factor stimulation, DGKalpha, by producing PA, provides a key signal to recruit atypical PKCzeta/iota (aPKCzeta/iota) in complex with RhoGDI and Rac at ruffling sites of colony-growing epithelial cells. Then, DGKalpha-dependent activation of aPKCzeta/iota mediates the release of Rac from the inhibitory complex with RhoGDI, allowing its activation and leading to formation of membrane ruffles, which constitute essential requirements for cell migration. These findings highlight DGKalpha as the central element of a lipid signaling pathway linking tyrosine kinase growth-factor receptors to regulation of aPKCs and RhoGDI, and providing a positional signal regulating Rac association to the plasma membrane.

Expression of the endocannabinoid system in the bi-potential HEL cell line: commitment to the megakaryoblastic lineage by 2-arachidonoylglycerol.

The role of the endocannabinoid system in haematopoietic cells is not completely understood. We investigated whether human erythroleukemia (HEL) cells were able to bind, metabolise and transport the main endocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol (2-AG). We also investigated whether AEA or 2-AG could modulate HEL differentiation. Although able to internalise both endocannabinoids, HEL cells had the machinery to metabolise 2-AG only, since they were devoid of the enzymes needed to synthesise and degrade AEA. Nonetheless, the intracellular transport of exogenous AEA might be required to activate the vanilloid receptors, with yet unknown implications for vascular biology. On the contrary, 2-AG appeared to play a role in lineage determination. Indeed, 2-AG itself drove HEL cells towards megakaryocytic differentiation, as it enhanced expression of beta3 integrin subunit, a megakaryocyte/platelet surface antigen, and glycoprotein VI, a late marker of megakaryocytes; in parallel, it reduced the amount of messenger RNA encoding for glycophorin A, a marker of erythroid phenotype. All these effects were mediated by activation of CB(2) cannabinoid receptors that triggered an extracellular signal-regulated kinase-dependent signalling cascade. In addition, classical inducers of megakaryocyte differentiation reduced 2-AG synthesis (although they did not affect the binding efficiency of CB(2) receptors), suggesting that levels of this endocannabinoid may be critical for committing HEL cells towards the megakaryocytic lineage.

Diacylglycerol kinase-alpha mediates hepatocyte growth factor-induced epithelial cell scatter by regulating Rac activation and membrane ruffling.

Diacylglycerol kinases (Dgk) phosphorylate diacylglycerol (DG) to phosphatidic acid (PA), thus turning off and on, respectively, DG-mediated and PA-mediated signaling pathways. We previously showed that hepatocyte growth factor (HGF), vascular endothelial growth factor, and anaplastic lymphoma kinase activate Dgkalpha in endothelial and leukemia cells through a Src-mediated mechanism and that activation of Dgkalpha is required for chemotactic, proliferative, and angiogenic signaling in vitro. Here, we investigate the downstream events and signaling pathways regulated by Dgkalpha, leading to cell scatter and migration upon HGF treatment and v-Src expression in epithelial cells. We report that specific inhibition of Dgkalpha, obtained either pharmacologically by R59949 treatment, or by expression of Dgkalpha dominant-negative mutant, or by small interfering RNA-mediated down-regulation of endogenous Dgkalpha, impairs 1) HGF- and v-Src-induced cell scatter and migration, without affecting the loss of intercellular adhesions; 2) HGF-induced cell spreading, lamellipodia formation, membrane ruffling, and focal adhesions remodeling; and 3) HGF-induced Rac activation and membrane targeting. In summary, we provide evidence that Dgkalpha, activated downstream of tyrosine kinase receptors and Src, regulates crucial steps directing Rac activation and Rac-dependent remodeling of actin cytoskeleton and focal contacts in migrating epithelial cells.

Ghrelin and des-acyl ghrelin promote differentiation and fusion of C2C12 skeletal muscle cells.

Ghrelin is an acylated peptidyl gastric hormone acting on the pituitary and hypothalamus to stimulate appetite, adiposity, and growth hormone release, through activation of growth hormone secretagogue receptor (GHSR)-1a receptor. Moreover, ghrelin features several activities such as inhibition of apoptosis, regulation of differentiation, and stimulation or inhibition of proliferation of several cell types. Ghrelin acylation is absolutely required for both GHSR-1a binding and its central endocrine activities. However, the unacylated ghrelin form, des-acyl ghrelin, which does not bind GHSR-1a and is devoid of any endocrine activity, is far more abundant than ghrelin in plasma, and it shares with ghrelin some of its cellular activities. In here we show that both ghrelin and des-acyl ghrelin stimulate proliferating C2C12 skeletal myoblasts to differentiate and to fuse into multinucleated myotubes in vitro through activation of p38. Consistently, both ghrelin and des-acyl ghrelin inhibit C2C12 proliferation in growth medium. Moreover, the ectopic expression of ghrelin in C2C12 enhances differentiation and fusion of these myoblasts in differentiation medium. Finally, we show that C2C12 cells do not express GHSR-1a, but they do contain a common high-affinity binding site recognized by both acylated and des-acylated ghrelin, suggesting that the described activities on C2C12 are likely mediated by this novel, yet unidentified receptor for both ghrelin forms.

Ghrelin and des-acyl ghrelin inhibit cell death in cardiomyocytes and endothelial cells through ERK1/2 and PI 3-kinase/AKT.

Ghrelin is an acyl-peptide gastric hormone acting on the pituitary and hypothalamus to stimulate growth hormone (GH) release, adiposity, and appetite. Ghrelin endocrine activities are entirely dependent on its acylation and are mediated by GH secretagogue (GHS) receptor (GHSR)-1a, a G protein-coupled receptor mostly expressed in the pituitary and hypothalamus, previously identified as the receptor for a group of synthetic molecules featuring GH secretagogue (GHS) activity. Des-acyl ghrelin, which is far more abundant than ghrelin, does not bind GHSR-1a, is devoid of any endocrine activity, and its function is currently unknown. Ghrelin, which is expressed in heart, albeit at a much lower level than in the stomach, also exerts a cardio protective effect through an unknown mechanism, independent of GH release. Here we show that both ghrelin and des-acyl ghrelin inhibit apoptosis of primary adult and H9c2 cardiomyocytes and endothelial cells in vitro through activation of extracellular signal-regulated kinase-1/2 and Akt serine kinases. In addition, ghrelin and des-acyl ghrelin recognize common high affinity binding sites on H9c2 cardiomyocytes, which do not express GHSR-1a. Finally, both MK-0677 and hexarelin, a nonpeptidyl and a peptidyl synthetic GHS, respectively, recognize the common ghrelin and des-acyl ghrelin binding sites, inhibit cell death, and activate MAPK and Akt.These findings provide the first evidence that, independent of its acylation, ghrelin gene product may act as a survival factor directly on the cardiovascular system through binding to a novel, yet to be identified receptor, which is distinct from GHSR-1a.

Membrane lipid rafts coordinate estrogen-dependent signaling in human platelets.

The impact of estrogens on the viability of cardiovascular system and their ability to regulate platelet function is still an open and debated question. We have previously shown that estrogen is able to significantly potentiate the aggregation induced by low doses of thrombin and to initiate a rapid and reversible signaling pathway mediated by ERbeta-directed activation of the tyrosine kinases Src and Pyk2 at the level of the plasma membrane. Lipid rafts are critical, cholesterol-enriched membrane domains, which play a major role in blood platelet activation processes. In this work, we investigated the role of lipid rafts in 17beta-estradiol signaling in human platelets. We observed that membrane rafts were essential for both 17beta-estradiol-dependent potentiation of platelet aggregation induced by subthreshold concentrations of thrombin and 17beta-estradiol-induced phosphorylation of Src. 17beta-estradiol caused the reversible translocation of ERbeta to the raft fractions and promoted the rapid and transient recruitment to, and activation within the membrane raft domains of the tyrosine kinases Src and Pyk2. The raft integrity was essential with this respect, as these effects of 17beta-estradiol were completely inhibited by cholesterol depletion. This paper provides evidence for the first time that membrane lipid rafts coordinate estrogen signaling in human platelets.

Activation of diacylglycerol kinase alpha is required for VEGF-induced angiogenic signaling in vitro.

Vascular endothelial growth factor-A (VEGF-A) promotes angiogenesis by stimulating migration, proliferation and organization of endothelium, through the activation of signaling pathways involving Src tyrosine kinase. As we had previously shown that Src-mediated activation of diacylglycerol kinase-alpha (Dgk-alpha) is required for hepatocytes growth factor-stimulated cell migration, we asked whether Dgk-alpha is involved in the transduction of angiogenic signaling. In PAE-KDR cells, an endothelial-derived cell line expressing VEGFR-2, VEGF-A165, stimulates the enzymatic activity of Dgk-alpha: activation is inhibited by R59949, an isoform-specific Dgk inhibitor, and is dependent on Src tyrosine kinase, with which Dgk-alpha forms a complex. Conversely in HUVEC, VEGF-A165-induced activation of Dgk is only partially sensitive to R59949, suggesting that also other isoforms may be activated, albeit still dependent on Src tyrosine kinase. Specific inhibition of Dgk-alpha, obtained in both cells by R59949 and in PAE-KDR by expression of Dgk-alpha dominant-negative mutant, impairs VEGF-A165-dependent chemotaxis, proliferation and in vitro angiogenesis. In addition, in HUVEC, specific downregulation of Dgk-alpha by siRNA impairs in vitro angiogenesis on matrigel, further suggesting the requirement for Dgk-alpha in angiogenic signaling in HUVEC. Thus, we propose that activation of Dgk-alpha generates a signal essential for both proliferative and migratory response to VEGF-A165, suggesting that it may constitute a novel pharmacological target for angiogenesis control.

Met identification on human platelets: role of hepatocyte growth factor in the modulation of platelet activation.

Circulating HGF is significantly increased in a number of thrombus-associated disorders. Since platelets play a pivotal role in thrombogenesis, the ability of HGF to interact with human platelets was investigated. This paper shows for the first time that human platelets express HGF receptor, the tyrosine kinase encoded by c-MET gene. At physiological concentrations HGF was found to inhibit both glycoprotein (alpha)IIb(beta)3 activation and thrombin-dependent platelet aggregation in a dose- and time-dependent manner. These results suggest that circulating HGF may counteract thrombogenesis by negatively modulating platelet functions.

Impact of age on mean platelet volume and its relationship with coronary artery disease: a single-centre cohort study.

UNLABELLED: Elderly patients represent a high risk category among subjects with atherosclerosis, due to the presence of comorbidities and suboptimal response to antiplatelet drugs. Mean platelet volume (MPV) has been indicated as a marker of platelet reactivity, with contrasting data on its role on coronary artery disease. Aim of the present study was to evaluate the impact of age on the MPV and its role on the extent of coronary artery disease (CAD). METHODS: Our population is represented by a cohort of 3750 patients undergoing coronary angiography. Elderly were defined according to age ≥ 75 years. MPV was measured at admission. Significant coronary artery disease was defined as a stenosis >50% in at least 1 coronary vessel, while severe CAD was defined as left main and/or three-vessel disease. RESULTS: A total of 1170 out of 3750 (31.2%) patients were ≥ 75 years old. Advanced age was associated with female gender (p<0.001), hypertension (p<0.001), renal failure (p<0.001), previous myocardial infarction (p=0.03) coronary artery bypass grafting (p<0.001) indication to angiography (p<0.001), therapy with angiotension-receptor blockers, (p=0.003), nitrates, diuretics and calcium-antagonists (p<0.001), serum creatinine (p<0.001), fibrinogen (p<0.001) and C reactive protein (p=0.02), but inversely to percutaneous coronary interventions (p=0.02), dyslipidemia, family history of CAD and smoking (p<0.001, respectively), use of statins (p=0.02) and beta blockers (p=0.003), haemoglobin, total cholesterol and triglycerides (p<0.001, respectively), white blood cells (p=0.009) and platelet count (p=0.006). Elderly patients displayed a significantly larger platelet volume (p<0.001), with a direct linear relationship between age and the MPV (r=0.08, p<0.001), with age being confirmed as an independent predictor of larger MPV (≥10.85fl) at multivariate analysis (adjusted OR [95% CI]=1.18 [1.01-1.40], p=0.04). Among the elderly, MPV value above the median (≥10.85fl) was not associated with a higher prevalence of coronary artery disease (77.3 vs. 79.4%, p=0.39, adjusted OR [95% CI]=0.94 [0.66-1.33], p=0.71), or higher prevalence of severe CAD (35.2 vs. 32.4%, p=0.28, adjusted OR [95% CI]=1.34 [0.99-1.82], p=0.06). CONCLUSION: Advanced age was directly associated with larger mean platelet volume that, however, did not contribute to explain the higher prevalence and extent of coronary artery disease observed in elderly patients.

Impact of diabetes on fibrinogen levels and its relationship with platelet reactivity and coronary artery disease: A single-centre study.

BACKGROUND: Previous reports have suggested an association between elevated fibrinogen and CAD. Few studies have so far investigated the impact of diabetes on fibrinogen levels and its association with coronary artery disease (CAD) and platelet reactivity in diabetic patients that are therefore the aims of the current study. METHODS: We measured fibrinogen in 3280 consecutive patients undergoing coronary angiography. Samples were collected at admission for fibrinogen levels assessment. Coronary disease was defined for at least 1 vessel stenosis >50% as evaluated by QCA. RESULTS: Diabetes was observed in 1201 out of 3280 patients. Diabetic patients were older with more hypercholesterolemia, hypertension, higher BMI, more renal failure, previous MI or coronary revascularization (p<0.001, respectively) and smoking (p=0.001). Diabetic patients were more often on ACE-inhibitors, ARBs, b-blockers, calcium-antagonists, diuretics, statins (p<0.001, respectively), and ASA (p=0.004). Diabetic patients displayed higher glycaemia and HbA1c (p<0.001), higher creatinine and triglycerides (p<0.001) but lower total and HDL cholesterol (p<0.001) and haemoglobin (p<0.001). Diabetic patients had higher fibrinogen levels (p=0.003), however neither diabetes nor glucose homeostasis parameters resulted as independent predictors of hyperfibrinogenemia. Furthermore, among diabetic patients, higher fibrinogen levels did not affect platelet reactivity and were not associated with the prevalence of CAD (adjusted OR[95%CI]=0.99 [0.82-1.19], p=0.9). Similar results were found for severe CAD (adjusted OR[95%CI]=0.94 [0.82-1.08], p=0.40). CONCLUSIONS: Our study showed that diabetes and glycaemic control are not independent predictors of hyperfibrinogenemia. Among diabetic patients, elevated fibrinogen is not associated with platelet reactivity and the prevalence and extent of CAD.