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Biomedical subjects

F Violi

Publications and source records attributed to F Violi.

At least 55 records · Page 3Linked to original sources
PubMed2000

Fluorescence quenching of dipyridamole associated to peroxyl radical scavenging: a versatile probe to measure the chain breaking antioxidant activity of biomolecules.

Dypiridamole is a highly efficient chain breaking antioxidant (Iuliano et al., Free Radic. Biol. Med. 18 (1995) 239-247) with an aromatic ring system responsible for an intense absorption band in the 400-480-nm region and for an intense fluorescence. Dipyridamole fluorescence is quantitatively quenched upon reaction with peroxyl radicals. In the presence of a flux of peroxyl radicals generated by thermal dissociation of azo-initiators, dipyridamole fluorescence decays linearly, showing a first-order reaction with respect to peroxyl radicals, and zero-order with respect to dipyridamole. The pH optimum for the fluorescence quenching is in the 7-8 range, from pH 7 to 6, the decay of fluorescence rapidly decreases to became negligible below pH 5.5. Dipyridamole consumption is blocked in the presence of an added chain breaking antioxidant for a time that is proportional to the antioxidant concentration. This effect is shown for ascorbic acid, trolox, vitamin E, uric acid, and N, N'-diphenyl-p-phenylenediamine. The slope of the linear correlation relative to trolox allows calculation of the bimolecular rate constant for a given molecule and peroxyl radicals. Comparison of data obtained by the dipyridamole consumption are comparable to values obtained by the oxygen consumption method.

Antioxidants↗
PubMed2000

Radiolabeled native low-density lipoprotein injected into patients with carotid stenosis accumulates in macrophages of atherosclerotic plaque : effect of vitamin E supplementation.

BACKGROUND: Accumulation of LDL within the arterial wall appears to play a crucial role in the initiation and progression of atherosclerotic plaque. The dynamic sequence of this event has not been fully elucidated in humans. METHODS AND RESULTS: In 7 patients with previous transient ischemic attack or stroke and critical (>70%) carotid stenosis, autologous native [(125)I]-labeled LDL or [(125)I]-labeled human serum albumin were injected 24 to 72 hours before endarterectomy. Carotid specimens obtained at endarterectomy were analyzed by autoradiography and immunohistochemistry. Autoradiographic study showed that LDL was localized prevalently in the foam cells of atherosclerotic plaques, whereas the accumulation in the lipid core was negligible. Immunohistochemistry revealed that foam cells that had accumulated radiolabeled LDL were mostly CD68 positive, whereas a small number were alpha-actin positive. No accumulation of the radiotracer was detected in atherosclerotic plaques after injection of radiolabeled human serum albumin. In 3 patients treated for 4 weeks with vitamin E (900 mg/d), an almost complete suppression of radiolabeled LDL uptake by macrophages was observed. CONCLUSIONS: This study shows that circulating LDL rapidly accumulates in human atherosclerotic plaque. The prevalent accumulation of LDL by macrophages provides strong support to the hypothesis that these cells play a crucial role in the pathogenesis of atherosclerosis.

Actins↗
PubMed2000

Inhibition of tissue-factor-mediated thrombin generation by simvastatin.

A previous study has shown that simvastatin reduces in vivo clotting activation and monocyte tissue factor (TF) expression. This effect, however, was only in part attributable to the reduction of serum cholesterol, suggesting that more than one mechanism may be involved. Furthermore, it was not investigated if the inhibition of clotting activation was dependent upon the reduced expression of monocyte TF. In order to assess if simvastatin directly affects clotting activation, we developed an in vitro method in which clotting system is activated by monocytes stimulated with LPS. Monocytes were prepared from blood taken from healthy volunteers or patients with hypercholesterolemia and incubated with heparinized plasma plus either simvastatin (0.01-10 microM) or medium as control. Samples were then stimulated with LPS (4 microg/ml) and after 6 h the rate of thrombin generation, assessed by prothrombin fragment (F) 1+2, was measured. In separate experiments, we measured the expression of TF by monocytes which were incubated with simvastatin and then stimulated with LPS. The study showed that compared to control, LPS-stimulated monocytes induced abundant formation of F1+2, which was inhibited by simvastatin in a dose-dependent manner. Simvastatin also inhibited dose dependently the monocyte expression of TF. This study suggests that simvastatin inhibits the rate of thrombin generation by directly interfering with the monocyte expression of TF.

Cells, Cultured↗
PubMed2000

Simvastatin inhibits the monocyte expression of proinflammatory cytokines in patients with hypercholesterolemia.

OBJECTIVE: The purpose of this study was to assess if simvastatin has an anti-inflammatory activity in patients with hypercholesterolemia. BACKGROUND: Simvastatin, an inhibitor of 3-hydroxy-methyl-glutaryl coenzyme A (HMG-CoA) reductase, reduced cardiovascular events in patients with myocardial infarction and hypercholesterolemia. METHODS: Sixteen patients with polygenic hypercholesterolemia were randomly allocated to diet (n = 8) or diet plus 20 mg/day simvastatin (n = 8) for eight weeks. Before and at the end of treatment period, lipid profile and monocyte expression of tumor necrosis factor-alpha (TNF) and interleukin-1beta (IL-1beta) were measured. RESULTS: At baseline no difference in lipid profile and monocyte expression of TNF and IL-1beta were observed between the two groups. In patients allocated to diet alone, no change in lipid profile and monocyte expression of TNF and IL-1beta was seen. In patients with diet plus simvastatin, significant decreases of total cholesterol (-27%, p<0.02), low density lipoprotein-cholesterol (-33%, p<0.02), and monocyte expression of TNF (-49%, p<0.02) and IL-1beta (-35%, p<0.02) were observed. At the end of treatment period, patients treated with simvastatin had lower cholesterol and monocyte TNF and IL-1beta than did patients assigned to diet alone. CONCLUSION: This study suggests that simvastatin possesses anti-inflammatory activity via the inhibition of pro-inflammatory cytokines TNF and IL-1beta expressed by monocytes.

Adult↗
PubMed2000

The flavonoids quercetin and catechin synergistically inhibit platelet function by antagonizing the intracellular production of hydrogen peroxide.

BACKGROUND: Epidemiologic studies have shown an inverse relation between moderate consumption of red wine and cardiovascular disease. Studies have shown that red wine and its component flavonoids inhibit in vivo platelet activation, but the underlying mechanism has not yet been identified. OBJECTIVE: Because we showed previously that collagen-induced platelet aggregation is associated with a burst of hydrogen peroxide, which in turn contributes to stimulating the phospholipase C pathway, the aim of this study was to investigate whether flavonoids synergize in inhibiting platelet function and interfere with platelet function by virtue of their antioxidant effect. DESIGN: We tested the effect of 2 flavonoids, quercetin and catechin, on collagen-induced platelet aggregation and hydrogen peroxide and on platelet adhesion to collagen. RESULTS: Catechin (50-100 micromol/L) and quercetin (10-20 micromol/L) inhibited collagen-induced platelet aggregation and platelet adhesion to collagen. The combination of 25 micromol catechin/L and 5 micromol quercetin/L, neither of which had any effect on platelet function when used alone, significantly inhibited collagen-induced platelet aggregation and platelet adhesion to collagen. Such a combination strongly inhibited collagen-induced hydrogen peroxide production, calcium mobilization, and 1,3,4-inositol triphosphate formation. CONCLUSIONS: These data indicate that flavonoids inhibit platelet function by blunting hydrogen peroxide production and, in turn, phospholipase C activation and suggest that the synergism among flavonoids could contribute to an understanding of the relation between the moderate consumption of red wine and the decreased risk of cardiovascular disease.

Blood Platelets↗
PubMed2000

Superoxide anion and hydroxyl radical release by collagen-induced platelet aggregation--role of arachidonic acid metabolism.

Previous study demonstrated that platelets undergoing anoxia-reoxygenation generate superoxide anion (O2-) and hydroxyl radical (OH ) which in turn contribute to activate arachidonic acid (AA) metabolism. However it has not been clarified if oxygen free radicals (OFRs) are also generated when platelets are aggregated by common agonists. We used two probes, i.e. lucigenin and salicylic acid (SA), to measure platelet release of O2- and OH(0), respectively. Among the agonists used, such as ADP, thrombin and collagen, the release of O2- and OH was observed mainly when platelets were stimulated with collagen. Such release was inhibited in platelets pre-treated by aspirin suggesting that AA metabolism was the main source of O2- and OH(0) formation. To further analyze this relationship, O2- and OH(0) formation was measured during AA-stimulated platelet aggregation (PA); we observed that O2- and OH(0) release were dependent upon AA concentration. Furthermore, we found that the incubation of platelets with AACOCF3, a potent inhibitor of cytosolic phospholipase A2, inhibited collagen-induced platelet O2- and OH(0) release. The incubation of platelets with salicylic acid or ascorbic acid, which blunt OH and O2- respectively, inhibited both collagen-induced platelet aggregation and AA-release. This study demonstrated that collagen-induced platelet aggregation is associated with O2- and OH formation, which is dependent upon AA release and metabolism.

Adenosine Diphosphate↗
PubMed2000

Improvement of walking distance by defibrotide in patients with intermittent claudication--results of a randomized, placebo-controlled study (the DICLIS study). Defibrotide Intermittent CLaudication Italian Study.

Defibrotide is an antithrombotic drug which enhances prostacyclin production and activates fibrinolytic system. The aim of this study was to investigate the improvement of walking distance in patients with intermittent claudication treated with defibrotide. DICLIS was a double blind, placebo-controlled study which included patients with walking distance autonomy at a standardized treadmill test < or =350 > or =100 meters. A total of 310 patients were randomly allocated to placebo (n = 101), defibrotide 800 mg/day (n = 104) or defibrotide 1200 mg/day (n = 105). During a one year follow-up, the Absolute Walking Distance (AWD) was measured six times (0, 30, 60, 90, 180, 360 days). Similar improvement in walking distance was found in the three groups until the 90th day; thereafter placebo group showed no further increase, while AWD continued to increase in the defibrotide groups. Between the 180th and 360th day visits, AWD was significantly higher (P <0.01) in patients given defibrotide than in patients given placebo. No difference in efficacy was observed between the two dosages of defibrotide. No differences in side effects were observed among the three groups. The results of the present trial suggest that long-term administration of defibrotide improves walking distance in patients with intermittent claudication.

Adult↗
PubMed2000

Down's syndrome is associated with increased 8,12-iso-iPF2alpha-VI levels: evidence for enhanced lipid peroxidation in vivo.

Postmortem and in vitro studies have shown that oxidative stress plays a role in the pathogenesis of many of the clinical features of Down's syndrome. The isoprostane 8,12-iso-iPF2alpha-VI is a specific marker of lipid peroxidation. We found elevated levels of this isoprostane in urine samples of subjects with Down's syndrome compared with those of matched controls, which correlated with the duration of the disease. These results suggest that increased in vivo lipid peroxidation is a prominent component early in the course of Down's syndrome.

Adolescent↗
PubMed1999

Iron-dependent human platelet activation and hydroxyl radical formation: involvement of protein kinase C.

BACKGROUND: Iron is an important modulator of lipid peroxidation, and its levels have been associated with the progression of atherosclerosis. Little is known about the possibility that this metal, when released from tissue stores, may modulate the reactivity of blood cell components, in particular platelets. Therefore, we investigated a possible link between iron, oxygen free radical formation, and platelet function. METHODS AND RESULTS: Human whole blood was stimulated with collagen 2 micrograms/mL, and an irreversible aggregation with thromboxane (Tx)B2 formation was observed (15+/-4 versus 130+/-10 ng/mL). Deferoxamine (DSF), a specific iron chelator, and catalase, an H2O2 scavenger, inhibited collagen-induced whole-blood aggregation. The aggregation was accompanied by an increase in hydroxyl radical (OH.) levels (30+/-8 versus 205+/-20 nmol/L dihydroxybenzoates), which were reduced by DSF and by 2 specific OH. scavengers, mannitol and deoxyribose. Iron (Fe2+) dose-dependently induced platelet aggregation, TxB2 formation (6+/-2 versus 135+/-8 ng/mL), and protein kinase C (PKC) translocation from the cytosol to the cell membrane when added to platelets that have been primed with a low concentration of collagen (0.2 micrograms/mL). In the same system, an increase in OH. levels was observed (37+/-12 versus 230+/-20 nmol/L dihydroxybenzoates). Mannitol and deoxyribose, but not urea, were able to reduce OH. formation, PKC activation, and platelet aggregation. Selective inhibition of PKC activity by GF 109203X prevented iron-dependent platelet aggregation without influencing OH. production. CONCLUSIONS: The present study shows that iron can directly interact with human platelets, resulting in their activation. Its action is mediated by OH. formation and involves PKC activity. Our findings provide an additional contribution to the understanding of the mechanism(s) by which iron overload might promote atherosclerosis and coronary artery disease.

Adult↗
PubMed1999

Ongoing prothrombotic state in patients with antiphospholipid antibodies: a role for increased lipid peroxidation.

We measured the urinary excretion of Isoprostane F2alpha-III and Isoprostane-F2alpha-VI, two markers of in vivo lipid peroxidation, and the circulating levels of the prothrombin fragment F1+2, a marker of thrombin generation, in 18 antiphospholipid antibodies-positive patients, in 18 antiphospholipid antibodies-negative patients with systemic lupus erythematosus, and in 20 healthy subjects. Furthermore, 12 patients positive for antiphospholipid antibodies were treated with (n = 7) or without (n = 5) antioxidant vitamins (vitamin E at 900 IU/d and vitamin C at 2, 000 mg/d) for 4 weeks. Compared with antiphospholipid antibodies-negative patients, antiphospholipid antibodies-positive patients had higher urinary values of Isoprostane-F2alpha-III (P =. 0001), Isoprostane-F2alpha-VI (P =.006), and plasma levels of the prothrombin fragment F1+2 (P =.0001). In antiphospholipid-positive patients, F1+2 significantly correlated with Isoprostane-F2alpha-III (Rho =.56, P =.017) and Isoprostane-F2alpha-VI (Rho =.61, P =.008). After 4 weeks of supplementation with antioxidant vitamins, we found a significant decrease in F1+2 levels (P <.005) concomitantly with a significant reduction of both Isoprostane-F2alpha-III (P =.007) and Isoprostane-F2alpha-VI (P <.005). No change of these variables was observed in patients not receiving antioxidant treatment. This study suggests that lipid peroxidation might contribute to the activation of clotting system in patients positive for antiphospholipid antibodies.

Adolescent↗
PubMed1999

Vitamin E reduces monocyte tissue factor expression in cirrhotic patients.

Clotting activation may occur in liver cirrhosis, but the pathophysiological mechanism has not been fully elucidated. Because a previous study demonstrated that lipid peroxidation is increased in cirrhosis, we analyzed whether there is a relationship between lipid peroxidation and clotting activation. Thirty cirrhotic patients (19 men and 11 women; age, 34 to 79 years) and 30 controls matched for sex and age were investigated. In all subjects, monocyte expression of tissue factor (TF) antigen and activity; plasma levels of prothrombin fragment 1+2 (F1+2), a marker of thrombin generation; and urinary excretion of Isoprostane-F2alpha-III, a marker of lipid peroxidation, were measured. Furthermore, the above-reported variables were re-evaluated after 30 days of treatment with standard therapy (n = 5) or standard therapy plus 300 mg vitamin E twice daily (n = 9). In addition, we analyzed in vitro if vitamin E (50 micromol/L) influenced monocyte TF expression and F1+2 generation. Cirrhotic patients had higher values of Isoprostane-F2alpha-III (P <. 0001), F1+2 (P <.0001), and monocyte TF antigen (P <.0001) and activity (P <.03) than controls. Isoprostane-F2alpha-III was significantly correlated with F1+2 (Rho = 0.85; P <.0001) and TF antigen (Rho = 0.95; P <.0001) and activity (Rho = 0.94; P <.0001). After vitamin E treatment, Isoprostane-F2alpha-III (P =.008), F1+2 (P <.008), and monocyte TF antigen (P =.012) and activity (P =.008) significantly decreased; no changes of these variables were detected in patients not receiving vitamin E. In vitro, vitamin E significantly reduced the expression of monocyte TF antigen (-52%; P =.001) and activity (-55%; P =.003), as well as F1+2 generation (-51%; P =.025). This study shows that vitamin E reduces both lipid peroxidation and clotting activation and suggests that lipid peroxidation may be an important mediator of clotting activation in liver cirrhosis.

Adult↗
PubMed1999

Protection of low density lipoprotein oxidation by the antioxidant agent IRFI005, a new synthetic hydrophilic vitamin E analogue.

The oxidative modification of low density lipoprotein (LDL) is thought to be an important factor in the initiation and development of atherosclerosis. Antioxidants have been shown to protect LDL from oxidation and to inhibit atherosclerosis development in animals. Potent synthetic antioxidants are currently being tested, but they are not necessarily safe for human use. We here characterize the antioxidant activity of IRFI005, the active metabolite of Raxofelast (IRFI0016) that is a novel synthetic analog of vitamin E under clinical development, and demonstrate that it prevents oxidative modification of LDL. IFI005 inhibited the oxidative modification of LDL, measured through the generation of MDA, electrophoretic mobility and apo B100 fluorescence. During the oxidation process IRF1005 was consumed with the formation of the benzoquinone oxidation product. The powerful antioxidant activity of IRFI005 is at least in part mediated by a chain breaking mechanism as it is an efficient peroxyl radical scavenger with a rate constant k(IRFI005 + LOO(o)) of 1.8 X 10(6) M(-1)s(-1). 4. IRFI005 substantially preserved LDL-associated antioxidants, alpha-tocopherol and carotenoids, and when co-incubated with physiologic levels of ascorbate provoked a synergistic inhibition of LDL oxidation. Also the co-incubation of IRFI005 with Trolox caused a synergistic effect, and a lag phase in the formation of the trolox-benzoquinone oxidation product. A synergistic inhibition of lipid peroxidation was also demonstrated by co-incubating IRFI005 and alpha-tocopherol incorporated in linoleic acid micelles. These data strongly suggest that IRFI005 can operate by a recycling mechanism similar to the vitamin E/ascorbate sysem.

Adult↗
PubMed1999

Vitamin E inhibits collagen-induced platelet activation by blunting hydrogen peroxide.

In this study, we investigated whether vitamin E at concentrations achievable in blood after supplementation inhibits platelet function in humans. Gel-filtered platelets were incubated 30 minutes with scalar concentrations (50 to 250 mmol/L) of vitamin E and then stimulated with collagen. Compared with controls, vitamin E inhibited collagen-induced platelet aggregation and thromboxane A2 formation in a dose-dependent manner. Furthermore, vitamin E inhibited, in a dose-dependent manner, Ca(2+) mobilization and formation of inositol 1,4,5-triphosphate. Because it was previously shown that hydrogen peroxide formation mediates arachidonic acid metabolism and phospholipase C activation in collagen-induced platelet activation, we investigated whether vitamin E was able to blunt hydrogen peroxide. In experiments performed in unstimulated platelets supplemented with hydrogen peroxide and in collagen-stimulated platelets, vitamin E was able to blunt hydrogen peroxide. In 6 healthy subjects given vitamin E for 2 weeks (600 mg/d), we found a significant decrease of collagen-induced H(2)O(2) formation, platelet aggregation, and calcium mobilization. This study demonstrated in vitro and ex vivo that vitamin E inhibits collagen-induced platelet activation by blunting hydrogen peroxide formation.

Adult↗
PubMed1999

[Oxidative stress and hypercholesterolemia: increase of radical hydroxyl in patients with hypercholesterolemia].

A close relationship exists between high blood cholesterol levels and atherosclerosis. This relationship, which represents an important risk factor for cardiovascular diseases, may be dependent on enhanced oxidative stress. To investigate this hypothesis, we studied 20 patients (12 females and 8 males, aged between 40 and 65 years) with high blood cholesterol levels (240-450 mg/dl) but without other risk factors for atherosclerosis and 20 healthy individuals matched for sex and age, with blood cholesterol levels < 240 mg/dl. We elaborated a laboratory technique that identifies two metabolites of the hydroxyl radical, the 2,3 and the 2,5 dihydroxybenzoic acid (DHBA), in basal conditions and after stimulation by 0.5-1 microM formyl-methionine-leucyl-phenylalanine, which is a specific activator of leukocytes. Results show that patients with hypercholesterolemia have a significant increase of 2,3 e 2,5 DHBA both in basal conditions and after stimulation (p = 0.03). A significant correlation (rho = 0.474; p = 0.004) was found between 2,3-2,5 DHBA and serum cholesterol. This study shows that patients with hypercholesterolemia have enhanced leukocyte oxidative stress and suggests that cholesterol could play a pivotal role.

Adult↗
PubMed1999

Clotting activation after transjugular intrahepatic portosystemic stent shunt.

BACKGROUND AND AIM: Aim of the study was to investigate the behaviour of clotting system in peripheral circulation of cirrhotic patients undergoing transjugular intrahepatic portosystemic stent shunt (TIPS). METHODS: Clotting variables and endotoxemia were measured 48 h and 30 days after TIPS in patients randomised to receive heparin or not. RESULTS: Forty-eight hours after TIPS, a significant increase of prothrombin fragment F1+2 was observed; such increase was less evident in patients given heparin. Similar findings were observed for endotoxemia, which, however, was not affected by heparin treatment. Thirty days after TIPS procedure prothrombin fragment F1+2 and endotoxemia returned to baseline values independently of the treatment given. CONCLUSION: This study shows that TIPS is associated with an increase of clotting activation which might contribute to acute thrombosis observed after this procedure.

Adult↗