Biomedical subjects

Elena Tremoli

Publications and source records attributed to Elena Tremoli.

53 records · Page 3Linked to original sources

PubMed2003

Reactive oxygen species mediate cyclooxygenase-2 induction during monocyte to macrophage differentiation: critical role of NADPH oxidase.

OBJECTIVE: The objective of this study was to explore the relationship between monocyte differentiation into macrophages and cyclooxygenase-2 (Cox-2) expression, based upon the observation that high amounts of this enzyme, colocalizing mainly with macrophages, have been found in human atherosclerotic lesions. Moreover, the hypothesis that reactive oxygen species (ROS) could be important as mediators of Cox-2 expression during monocyte differentiation was verified. Although ROS are known as modulators of gene expression profile, their involvement in monocyte differentiation has not been explored previously. METHODS: Human adherent monocytes and the promonocytic cell line U937 were differentiated into macrophages by phorbol ester (PMA). Cox-2 was evaluated in terms of protein, mRNA and activity. Intracellular ROS formation was measured by the oxidant sensitive dye 2',7'-dichlorofluorescein diacetate. NADPH oxidase subunit p47(phox) was evaluated by Western blot analysis. RESULTS: Functionally active Cox-2 is expressed during PMA-induced monocyte transition into macrophages and ROS driven by the NADPH oxidase play a critical role in this event. CONCLUSION: Monocyte differentiation into macrophages, possibly triggered by unquenched ROS, may contribute to the increased inflammatory response within atheromata.

Actins↗

PubMed2003

Platelet activation induces cell-surface immunoreactive tissue factor expression, which is modulated differently by antiplatelet drugs.

OBJECTIVE: Tissue factor (TF) is the main activator of the coagulation cascade occurring in physiologic and pathologic conditions. Recent data suggest that human platelets might contain TF that is possibly derived from leukocytes. In this study, we investigated whether intraplatelet TF can be exposed on the membrane by platelet agonists. The modulation of this process by antiplatelet drugs has been evaluated as well. METHODS AND RESULTS: Flow cytometric analysis of unstimulated platelets showed a small amount of membrane-associated immunoreactive TF (irTF) in whole blood, platelet-rich plasma, and washed platelets isolated from healthy subjects. ADP, thrombin receptor-activating peptide, and epinephrine significantly increased functionally active, membrane-associated irTF. ADP induced irTF exposure in a concentration- and time-dependent fashion. Agonist-induced irTF expression was completely inhibited by iloprost but not by aspirin. Interestingly, glycoprotein IIb/IIIa antagonists did not inhibit but rather potentiated the stimulatory effect of ADP on platelet irTF expression. Real-time polymerase chain reaction experiments showed detectable amounts of TF mRNA in unstimulated platelets. CONCLUSIONS: These findings indicate that platelet agonists and antiplatelet drugs might modulate platelet-associated irTF expression. Regulated TF expression establishes the potential for a previously unrecognized role for platelets in sustaining thrombus formation and growth via coagulation-mediated mechanisms.

Antigens, Surface↗

PubMed2003

Endogenous proteolytic activity in a rat model of spontaneous cerebral stroke.

We evaluated the expression of two extra-cellular protease systems in a model of spontaneous cerebrovascular pathology: spontaneously hypertensive stroke-prone rats (SHRSP). The appearance of brain damage in individual animals was imaged and followed by means of magnetic resonance imaging (MRI). In situ zymography of brain slices obtained 3 days after the appearance of brain damage showed an increase in plasminogen activator (PA)/plasmin activity that co-localised with the cerebral damage detected by MRI; there was also concomitant accumulation/activation of inflammatory cells in the damaged area. Proteolytic activity was inhibited by the urokinase-specific inhibitor amiloride but not by an antibody against tissue-type plasminogen activator (t-PA). SDS-PAGE zymography of brain extracts revealed the presence of 58 kDa plasminogen-dependent lysis areas in the ischemic and non-ischemic tissues, and a 33 kDa lysis area in ischemic tissue only. An antibody against t-PA inhibited the former, whereas the latter was inhibited by amiloride. The specific induction of urokinase-type plasminogen activator (u-PA) in the damaged tissue was further confirmed by the fact that both u-PA protein mass and mRNA were markedly increased in the damaged cerebral areas. Concomitant metalloproteinase-2 (MMP-2) activation was only observed in the damaged area. These data suggest that u-PA is expressed and selectively catalyses proteolysis in the injured area of spontaneous brain damage in SHRSP.

Animals↗

PubMed2003

Treatment with statins after induction of focal ischemia in rats reduces the extent of brain damage.

OBJECTIVE: In the present study, MRI has been used to investigate therapeutic intervention with statins in a model of permanent focal cerebral ischemia in rat. METHODS AND RESULTS: Brain ischemia was induced in rats by the permanent occlusion of middle cerebral artery (MCAO) and the brain infarct size followed up in alive animals 2, 24, and 48 hours after MCAO, using the trace of apparent diffusion coefficient [Tr(D)] maps and T2-weighted images. In vehicle-treated rats, the infarct volumes increased by 38.5% and 89% after 24 and 48 hours, respectively, compared with the damage detected at 2 hours after MCAO. Treatment with simvastatin (20 mg/kg) after MCAO prevented the increase in brain infarct volume occurring at 24 hours and induced a 46.6% reduction after 48 hours. This effect was similar to that observed when simvastatin was administered before the induction of focal ischemia. T2W-MRI images confirmed these findings. The neuroprotective effects of simvastatin were paralleled by an increase in endothelial NO synthase immunoreactivity, detectable in the brain of simvastatin-treated rats. CONCLUSIONS: Statins, in addition to their preventive effect on cerebral ischemia, exert a neuroprotective role in the attenuation of brain damage after acute stroke.

Animals↗

PubMed2003

Off-pump versus on-pump coronary artery bypass: meta-analysis of currently available randomized trials.

BACKGROUND: Off-pump coronary artery bypass (OPCAB) challenges the conventional on-pump coronary artery bypass grafting (CABG) as the standard of surgical therapy for coronary disease. The aim of this study is to assess the differences in clinical outcomes between CABG and OPCAB by meta-analysis of data published in randomized trials. METHODS: A literature search (Medline, Pubmed, Cochrane Controlled Trials Register, and the Cochrane Medical Editors Trial Amnesty of unpublished clinical trials) was done for the period starting from January 1990 until May 2002 and was supplemented with a manual bibliographic review for all peer-reviewed English language publications. A systematic overview (meta-analysis) of the randomized trials was done to define the risk of the composite end point (death, stroke, or myocardial infarction) in CABG versus OPCAB. RESULTS: A literature search yielded nine comparable randomized studies, for a total of 1090 patients, of whom 558 and 532 were randomly assigned to CABG and OPCAB, respectively. Meta-analysis of these studies showed a trend, albeit not statistically significant, toward reduction in the risk of the composite end point for patients who had OPCAB (odds ratio 0.48; 95% confidence interval 0.21 to 1.09; p = 0.08). CONCLUSIONS: Cumulative analysis of the few prospective randomized studies currently available found a potential clinical benefit of OPCAB, indicating that the avoidance of extracorporeal circulation might result in improved clinical outcomes. Further evidence, however, from large randomized trials is needed to assess potential advantages of OPCAB in terms of early outcomes.

Aged↗

PubMed2003

Statins in coronary bypass surgery: rationale and clinical use.

Statin therapy prevents the first occurrence and recurrence of coronary events and reduces cardiovascular and general mortality in patients with coronary artery disease. These compounds modulate a variety of processes involved in the pathophysiology of arteriosclerosis and vascular graft disease by lipid-dependent and lipid-independent (pleiotropic) mechanisms. As a result, statins produce angiographic and clinical benefits in patients undergoing coronary bypass surgery. We review the present knowledge about the effects of statins on this pathologic condition and the evidence supporting an early treatment initiation.

Arteriosclerosis↗

PubMed2003

Biological effects of off-pump vs. on-pump coronary artery surgery: focus on inflammation, hemostasis and oxidative stress.

Cardiopulmonary bypass (CPB) has been recognized as a cause of complex systemic inflammatory response, which significantly contributes to several adverse postoperative complications. In the last few years, off-pump coronary artery bypass grafting has gained widespread diffusion as an alternative technique to conventional on-pump coronary artery bypass grafting. Surgeons supporting off-pump surgery state that the avoidance of the CPB and myocardial ischemia-reperfusion significantly reduces the postoperative systemic inflammatory response and other biological derangements and, possibly, may improve the clinical outcomes. We review, here, the available evidence concerning possible differences between off-pump and on-pump procedures in terms of inflammation, hemostasis and oxidative stress. Consistent differences in the involvement of these systems are observed, but they are limited to the final steps of the surgical procedures and the early hours after. These findings suggest that the global surgical trauma may be as important, or even more, as the CPB in terms of systemic inflammatory and coagulation-fibrinolytic pathway activation. Further studies are needed in order to confirm this hypothesis.

Biomarkers↗

PubMed2003

Coagulation and fibrinolytic markers in a two-month follow-up of coronary bypass surgery.

OBJECTIVES: The alterations of the coagulation-fibrinolytic profile immediately and up to few days after cardiac surgery have been widely documented. However, less information is available on whether these alterations persist for prolonged periods of time after the operation. In this study we have evaluated the coagulation-fibrinolytic profile of patients who underwent coronary artery surgery with cardiopulmonary bypass during a 2-month follow-up period. METHODS: Twenty-six patients (age range, 50-75 years) were studied. Blood samples were collected before the intervention and at different time points postoperatively up to 2 months after the operation. Measurement of selected coagulation-fibrinolytic variables was carried out in plasma from 16 patients. Evaluation of tissue factor activity determined as procoagulant activity was performed in peripheral blood mononuclear leukocytes obtained from 10 patients. RESULTS: Antigenic levels of clottable fibrinogen, prothrombin fragment F1.2, D-dimer, and thrombin-antithrombin complex were significantly increased during the first week after the intervention compared with preoperative values. Prothrombin fragment F1.2 levels returned to normal within 15 days, fibrinogen levels normalized within 30 days, and thrombin-antithrombin complex levels normalized at 45 days, whereas D-dimer values were still significantly higher 60 days postoperatively respective to baseline values. There was a trend toward an increased procoagulant activity from peripheral blood mononuclear leukocytes 4 days after the operation, whereas no changes of factor VII measured either as antigen or in its coagulant and activated forms were recorded throughout the study. CONCLUSIONS: A marked activation of the coagulation-fibrinolytic system occurs after cardiopulmonary bypass and lasts for at least 2 months thereafter. This finding suggests that these alterations might account for the increased thrombotic risk of these patients during the postoperative period.

Aged↗

PubMed2003

Induction of plasminogen activator inhibitor I by the PPARalpha ligand, Wy-14,643, is dependent on ERK1/2 signaling pathway.

Impairment of the fibrinolytic system, mostly due to elevated plasma levels of plasminogen activator inhibitor 1 (PAI-1), is often associated with metabolic disorders such as diabetes mellitus and insulin-resistance syndrome. Moreover, insulin, as we have previously shown, directly stimulates PAI-1 production with a mechanism underlying a complex signaling network which ultimately leads to ERK activation. In this study we have analyzed the effects of agonists of the peroxisome proliferator-activated receptor (PPAR) alpha and gamma on PAI-1 biosynthesis in HepG2 cells in the presence or absence of insulin. The high affinity PPARalpha agonist, Wy-14,643, increased basal and insulin-stimulated PAI-1 antigen release with a mechanism involving gene transcription. We then investigated whether the MAP kinase pathway also plays a role in the stimulatory properties of Wy-L4,643. Wy-L4,643 increases phosphorylation of ERK and p38 in a time-dependent manner without affecting that of SAPK/JNK or ERK5. Moreover, the MEK (ERK kinase) inhibitors, PD98059 and UO126, completely prevented PAI-1 induction by Wy-14,643 without inhibiting the activation of a reporter gene carrying the PPRE element. Interestingly, the addition of p38 inhibitor followed by insulin and Wy-14,643 resulted in a greater than additive stimulation of PAI-1 secretion acting through ERK1/2 phosphorylation. In contrast, the synthetic PPARgamma agonist, rosiglitazone, did not change PAI-1 level, although this compound induced transcription from the PPRE-driven luciferase reporter construct. In conclusion, Wy-14,643 induces PAI-1 gene expression, in the presence or absence of insulin, with a mechanism which is independent on PPARalpha activation and requires signaling through the ERK1/2 signaling pathway.

Cell Line, Tumor↗

PubMed2003

Vascular thrombogenicity induced by progressive LDL oxidation: protection by antioxidants.

Oxidative modification of LDL, which dysregulates the homeostasis between blood and vascular cells, and alterations of endothelial function are considered among the early events in the pathogenesis of atherosclerosis. This study was designed to evaluate the impact of progressive LDL oxidation on the thrombotic response both in vitro and in vivo, and to address the potential effect of antioxidants. Tissue factor was induced by progressive LDL oxidation in HUVEC, and this event was in parallel to the appearance of the apoptotic phenotype. Both these phenomena were mediated by ERK1/2 activation and were prevented by LDL pre-enrichment with antioxidants. In contrast, antioxidants failed to affect tPA and PAI-1 secretion, which was increased by LDL, either native or oxidized. Tissue factor-pathway inhibitor was also increased upon HUVEC exposure to progressively oxidized LDL. LDL, in the presence of an oxidative agent, trigger a thrombogenic response in vivo, mostly TF-dependent, in an in situ model of platelet deposition. This effect was markedly attenuated when LDL were enriched with antioxidants. It can be concluded that vascular thrombogenicity is induced by progressive LDL oxidation and that alterations of the antioxidant/oxidant balance of the LDL particle in favor of the antioxidant tone are protective against the thrombotic response triggered by oxidative stress. The extrapolation of these data in a clinical setting, even if not easy, offers potential insights for the use of antioxidants in the prevention of thrombotic complications associated with atherothrombosis.

Antioxidants↗

PubMed2002

Lack of association between serum immunoreactivity and Chlamydia pneumoniae detection in the human aortic wall.

BACKGROUND: Only a few studies have focused the attention on the relation between elevated anti-Chlamydia pneumoniae (CP) antibodies and the detection of CP in the arterial wall. The aim of our study is thus to investigate the relationship between immune response to CP and detection of CP in the aortic walls of patients with abdominal aortic aneurysm. METHODS AND RESULTS: A specimen of aortic wall was obtained from 102 consecutive patients who underwent abdominal aneurysm repair. The possible presence of CP was studied by polymerase chain reaction and confirmed by nonradioactive DNA hybridization. Antibody response to CP was studied (IgG, IgA titers). We found 33 patients (32.4%) with CP DNA+. No correlation between CP DNA detection and antibody titers was found (IgG P=0.52, IgA P=0.66). High correlation between IgG and IgA titer was observed (P<0.01). Endovascular presence of CP and antibody titers was not related to the age of the patient. CONCLUSIONS: CP antibody titers are not associated with the presence of CP in the aortic wall of patients with abdominal aortic aneurysm.

Antibodies, Bacterial↗

PubMed2002

Oxidized phospholipids inhibit cyclooxygenase-2 in human macrophages via nuclear factor-kappaB/IkappaB- and ERK2-dependent mechanisms.

OBJECTIVE: Oxidized low-density lipoproteins (ox-LDL) or their components suppress macrophage inflammatory response by down-regulating cytokine synthesis, nitric oxide synthase and inducible cyclooxygenase (Cox-2). This event is crucial for the pathophysiological process leading to the formation of atherosclerotic plaque. Our present study focused on the mechanisms through which oxidized phospholipids inhibit LPS-induced Cox-2 expression in human macrophages. METHODS: Macrophages were incubated with a mixture of oxidized fragmented phospholipids (ox-PAPC), present in modified LDL, and then exposed to LPS. Cox-2 was evaluated in terms of protein levels, mRNA and activity. RESULTS: Ox-PAPC dose-dependently inhibited Cox-2 protein, mRNA and activity by preventing NF-kappaB binding to DNA. This effect was consequent to alterations of the degradation pattern of IkappaBalpha. Moreover, ox-PAPC markedly prevented extracellular signal-regulated kinase (ERK2) activation, leading to Cox-2 expression, whereas activation of the transcription factor peroxisome proliferator-activated receptors (PPARs) was not influenced. CONCLUSION: ox-PAPC down-regulates LPS-induced Cox-2 expression in human macrophages by targeting both NF-kappaB/IkappaB and ERK2 pathways. An altered inflammatory response by macrophages within atheromata may contribute to the progression of atherosclerosis.

Cell Culture Techniques↗

PubMed2002

Fluvastatin reduces tissue factor expression and macrophage accumulation in carotid lesions of cholesterol-fed rabbits in the absence of lipid lowering.

The expression of tissue factor (TF), mainly by infiltrated inflammatory cells, has been shown to be responsible for the thrombogenicity associated with atheroma. The contribution of the nonlipid-related effects of statins to the clinical benefits of statin therapy is currently under intense investigation. In this study, we evaluated the ability of fluvastatin to modulate TF expression and macrophage accumulation in rabbit carotid intimal lesions independently of cholesterol lowering. Male rabbits were fed for 30 days a 1% cholesterol-rich diet with or without fluvastatin at 5 mg/kg per day. Two weeks from the start of treatment, a silastic collar was placed around the carotid artery. Fifteen days later, the animals were killed, and carotid segments were excised and processed. The atherogenic diet caused a consistent increase in plasma cholesterol levels (610+/-231 mg/dL versus 50+/-9 mg/dL at baseline), which were not affected by fluvastatin (603+/-248 mg/dL). In the rabbits fed a high cholesterol diet without fluvastatin, an intimal lesion with macrophage accumulation and TF expression was detected. Fluvastatin significantly reduced TF and macrophage content of the lesion (-50% for both). Results indicate that fluvastatin may attenuate the inflammatory and thrombogenic potential of atherosclerotic lesions through a mechanism(s) other than cholesterol reduction, providing new insight regarding the complex mode of action of statins.

Animals↗

PubMed2002

Increased carotid artery intima-media thickness in subjects with primary hypoalphalipoproteinemia.

The plasma concentration of high-density lipoprotein cholesterol (HDL-C) is inversely correlated with the incidence of atherosclerotic vascular events. In the present study, we evaluated pre-intrusive atherosclerosis in subjects with plasma HDL-C at the extremities of normal distribution. Fifty-five subjects with primary hypoalphalipoproteinemia (HypoALP) or hyperalphalipoproteinemia (HyperALP) were compared with fifty-five control subjects with average HDL-C levels, matched for sex, age, and plasma cholesterol. The average and maximal intima-media thicknesses (Avg-IMT and Max-IMT) of 48 carotid segments for each subject were approximately 40% greater in HypoALP than in control subjects (0.94 +/- 0.06 versus 0.69 +/- 0.04 mm, P=0.004, and 1.86 +/- 0.16 versus 1.35 +/- 0.10 mm, P=0.025, respectively). The IMT values in HyperALP subjects (Avg-IMT, 0.71 +/- 0.04 and Max-IMT, 1.38 +/- 0.14 mm) were the same as in controls. In a large cohort of hyperlipidemic subjects (n=559), significantly greater Avg-IMT and Max-IMT were found in subjects belonging to the first HDL-C quintile (<42 mg/dL) than in all the others. The measurement of carotid IMT in cases with HypoALP and HyperALP, and in a large series of hyperlipidemic patients, thus indicates that a low HDL-C is associated with significant pre-intrusive atherosclerosis, whereas a HDL-C level above average values does not lead to a further reduction of arterial wall thickening.

Carotid Arteries↗

PubMed2002

Endothelial damage during myocardial preservation and storage.

Preservation and storage techniques represent two major issues in routine cardiac surgery and heart transplantation. Historically, these methods were conceived to prevent ischemic injury to myocardium after cardiac arrest during heart operations. Evidence shows that endothelium plays a critical role in the maintenance of normal heart function after cardiac operation, mainly by controlling the coronary circulation. Methods for preservation and storage, developed initially to protect cardiomyocyte function, may be deleterious for vascular endothelium and compromise myocardial protection. In this review article the present knowledge about endothelial injury secondary to preservation and storage techniques is discussed.

Cardioplegic Solutions↗

PubMed2002

New insights into brain damage in stroke-prone rats: a nuclear magnetic imaging study.

BACKGROUND AND PURPOSE: The spontaneously hypertensive stroke-prone rat (SHRSP) is an animal model for a complex form of cerebrovascular pathology. MRI provides an efficient and noninvasive tool for studying the time course of brain damage. The aim of this study was to gain new insights into the pathological phenomena responsible for the occurrence of brain injury in SHRSP with the use of the apparent diffusion coefficient of water (ADC), one of the most efficient MRI parameters for detecting brain abnormalities. To this end, the pattern of ADC variation observed in SHRSP was compared with that of focal ischemia induced in both SHRSP and Sprague-Dawley rats. METHODS: Four groups of animals were studied: SHRSP developing spontaneous brain lesions fed with a salt-loaded (n=15, group 1) or standard diet (n=3, group 2) and Sprague-Dawley rats (n=8, group 3) and SHRSP (n=8, group 4) with permanent middle cerebral artery occlusion. ADC maps and T2-weighted images of brains were performed by MRI. After the rats were killed, the brains were removed and histologically processed. RESULTS: There was no decrease in ADC during spontaneous stroke in the SHRSP fed with a normal or salt-enriched diet, while both the SHRSP and Sprague-Dawley rats with middle cerebral artery occlusion showed a marked decrease that lasted for 24 to 48 hours. CONCLUSIONS: Cerebral ischemia cannot be considered a major factor in the onset of spontaneous brain lesions in SHRSP, which show only vasogenic edema after the beginning of the damage with no evidence of metabolic impairment.

Animals↗

PubMed2002

Cholesterol-induced thrombogenicity of the vessel wall: inhibitory effect of fluvastatin.

High cholesterol levels are a known risk factor for coronary events. The molecular links between high serum cholesterol and the increased thrombogenicity of the arterial wall are still matter of investigation. In the present study we investigate the relationship between plasma cholesterol, thrombus formation and TF expression in a atherosclerotic rabbit model. Hypercholesterolemic rabbits showed a pronounced TF staining as well as NF-kappaB activation in the aortic arch. A consistent vessel wall platelet deposition was also observed. Treatment with fluvastatin reduced lipid accumulation, TF overexpression (-60%), NF-kappaB activation, and platelet deposition (-56%). In vitro studies showed that the drug upregulated IkappaB alpha in unstimulated as well as in TNFalpha-stimulated cells and also impaired the TNFalpha-induced Cdc42 prenylation, indicating that fluvastatin interferes with the transcriptional activation of TF gene. These results indicate that the prothrombotic phenotype of arterial wall, associated with elevated serum cholesterol levels, is mediated by TF overexpression. Fluvastatin treatment reduces the prothrombotic tendency by inhibiting TF synthesis.

Animals↗