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R Paoletti

Publications and source records attributed to R Paoletti.

At least 55 records · Page 3Linked to original sources
PubMed1998

Peripheral markers in testing pathophysiological hypotheses and diagnosing Alzheimer's disease.

Alterations in amyloid precursor protein (APP) metabolism, calcium regulation, oxidative metabolism, and transduction systems have been implicated in Alzheimer's disease (AD). Limitations to the use of postmortem brain for examining molecular mechanisms underscore the need to develop a human tissue model representative of the pathophysiological processes that characterize AD. The use of peripheral tissues, particularly of cultured skin fibroblasts derived from AD patients, could complement studies of autopsy samples and provide a useful tool with which to investigate such dynamic processes as signal transduction systems, ionic homeostasis, oxidative metabolism, and APP processing. Peripheral cells as well as body fluids (i.e., plasma and CSF) could also provide peripheral biological markers for the diagnosis of AD. The criteria required for a definite diagnosis of AD presently include clinical criteria in association with histopathologic evidence obtained from biopsy or autopsy. Thus, the use of peripheral markers as a diagnostic tool, either to predict or at least to confirm a diagnosis, may be of great importance.

Alzheimer Disease↗
PubMed1998

Direct effects of statins on the vascular wall.

The beneficial effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) on coronary events have generally been attributed to their hypocholesterolemic properties. Mevalonate and other intermediates of cholesterol synthesis (isoprenoids) are necessary for cell proliferation and other important cell functions; thus effects other than cholesterol reduction may help to explain the antiatherosclerotic properties of statins. Recently we provided in vitro and in vivo evidence of decreased smooth-muscle cell (SMC) proliferation and migration by fluvastatin and simvastatin, but not by pravastatin, independent of plasma cholesterol reduction. The ability of fluvastatin to interfere with arterial SMC proliferation at therapeutic concentrations (0.1-1 microM) prompted us to investigate the pharmacologic activity of sera from 10 patients treated with fluvastatin, 40 mg once daily, on the proliferation of cultured human arterial myocytes. Pravastatin, 40 mg once daily, displays a lipid-lowering activity similar to that of fluvastatin without affecting SMC proliferation and was investigated as a control for assessing this non-lipid-related effect of fluvastatin. Fluvastatin and pravastatin, given for 6 days to patients with type IIa hypercholesterolemia, resulted in a similar decrease in low-density-lipoprotein (LDL) cholesterol. However, the addition of 15% whole-blood sera from patients treated with fluvastatin to the culture medium resulted in a 43% inhibition of cholesterol synthesis in SMCs (p < 0.01) that mirrored the pharmacokinetic profile of fluvastatin. When SMC proliferation was investigated, a significant inhibition of cell growth (-30%; p < 0.01) was detected with sera obtained 6 h after the last dose. No effect on SMC proliferation or cholesterol biosynthesis was observed when sera from patients treated with pravastatin were evaluated. These results suggest that statins exert a direct antiproliferative effect on the arterial wall, beyond their effects on plasma lipids, which could prevent significant cardiovascular disease.

Adult↗
PubMed1998

HMG-CoA reductase inhibitors reduce MMP-9 secretion by macrophages.

-Macrophages secrete matrix metalloproteinases (MMPs) that may weaken the fibrous cap of atherosclerotic plaque, predisposing its fissuration. The 92-kDa gelatinase B (MMP-9) has been identified in abdominal aortic aneurysms and in atherosclerotic tissues. Fluvastatin, through the inhibition of the isoprenoid pathway, inhibits major processes of atherogenesis in experimental models (smooth muscle cell migration and proliferation and cholesterol accumulation in macrophages). We studied the effect of fluvastatin on the activity of MMP-9 in mouse and human macrophages in culture. Conditioned media of cells treated for 24 hours with fluvastatin were analyzed by gelatin zymography. In mouse macrophages, fluvastatin (5 to 100 micromol/L) significantly inhibited in a dose-dependent manner MMP-9 activity from 20% to 40% versus control. The drug, at a concentration as low as 5 micromol/L, inhibited MMP-9 activity ( approximately 30%) in human monocyte-derived macrophages as well. Phorbol esters (TPA, 50 ng/mL) stimulated MMP-9 activity by 50%, and fluvastatin inhibited this enhanced activity up to 50% in both mouse and human macrophages. The above results on the secretion of MMP-9 were confirmed by Western blotting and ELISA. The inhibitory effect of fluvastatin was overcome by the simultaneous addition of exogenous mevalonate (100 micromol/L), a precursor of isoprenoids. Fluvastatin's effect was fully reversible, and the drug did not cause any cellular toxicity. The statin did not block directly the in vitro activation of the secreted protease. Similar data were obtained with simvastatin. Altogether, our data indicate an inhibition of MMP-9 secretion by the drug. This effect is mediated by the inhibition of synthesis of mevalonate, a precursor of numerous derivatives essential for several cellular functions.

Animals↗
PubMed1998

Effects of oral and transdermal hormone replacement therapy on lipoprotein(A) and lipids: a randomized controlled trial.

OBJECTIVE: Our purpose was to compare the effect of oral and transdermal hormone replacement therapy on lipoprotein(a) and other plasma lipids in healthy postmenopausal women. DESIGN: A total of 120 postmenopausal women were enrolled in a prospective randomized controlled study, and allocated either to transdermal 17 beta-estradiol (50 micrograms/day) or to oral conjugated estrogen (0.625 mg/day). Forty-one age-matched women were used as the reference group. Plasma lipids and lipoproteins were determined every 3 months and differences were sought by statistical analysis. RESULTS: Plasma lipoprotein(a) dropped after 3 months of treatment either with transdermal estradiol (p < 0.01) or oral estrogen (p < 0.01). Lipoprotein(a) was reduced by 12% and 22%, respectively. No further decreases were seen later on. Plasma total and low-density lipoprotein (LDL) cholesterol concentrations were decreased significantly with both treatments after 3 months of therapy. No difference was seen in the lowering effect on lipoprotein(a), LDL and total cholesterol concentrations between regimens. Plasma high-density lipoprotein (HDL) cholesterol and triglyceride concentrations increased throughout the study only in patients treated with oral estrogen. CONCLUSIONS: These data demonstrate that hormone replacement therapy reduces the concentration of lipoprotein(a) when given both orally and transdermally. The lowering effect is achieved quickly because the maximal effect is observed after 3 months of therapy.

Administration, Cutaneous↗
PubMed1997

Pharmacological control of phagocyte function: inhibition of cholesterol accumulation.

Phagocytes play a major role in several diseases. In particular mononuclear phagocyte-derived foam cells have a prominent role in the development of the atherosclerotic lesions. Macrophages are present in all stages of atherogenesis; they internalize lipoproteins and accumulate cholesterol. Moreover, lipid-filled macrophages, by secreting extracellular matrix-degrading enzymes, may weaken rupture-prone atherosclerotic plaques, thus increasing the probability of precipitating atherosclerotic acute symptoms (i.e., myocardial infarction, angina, etc.). Therefore, control of cellular functions and cholesterol accumulation in macrophages represent pharmacological targets against atherosclerosis. In our laboratory we studied the effect of calcium antagonists on cellular cholesterol esterification in cultured macrophages. We also demonstrated that the HMG-CoA reductase inhibitors (vastatins) fluvastatin and simvastatin prevented cholesterol deposition in cultured human and murine macrophage by inhibiting modified LDL endocytosis. Interestingly, vastatin activity was more pronounced in cholesterol-loaded macrophages (i.e., foam cells) than in normal cells. In conclusion, in vitro pharmacological control of cholesterol accumulation in macrophages may be achieved with some calcium antagonists and vastatins independently of their effects on blood pressure or cholesterolemia.

Animals↗
PubMed1997

Secretory processing of amyloid precursor protein is inhibited by increase in cellular cholesterol content.

Plasma-membrane composition plays a crucial role in most of the cellular functions that depend on membrane processes. In virtually all cell types the proteolytic processing of Alzheimer amyloid precursor protein (APP) to generate soluble APP (sAPP) is believed to occur at the plasma membrane or in its immediate proximity. Alteration of this metabolic pathway has been linked to the pathogenesis of Alzheimer's disease. We analysed the effect of membrane cholesterol enrichment on APP metabolism. Incubation of COS cells with increasing concentrations of non-esterified cholesterol carried by rabbit beta-very low-density lipoprotein caused a dose-dependent inhibition of sAPP release: 70% inhibition with 10 microg/ml non-esterified cholesterol. A less pronounced inhibitory effect was observed on treatment with human low-density lipoprotein. Inhibition of sAPP release was independent of receptor-mediated lipoprotein metabolism since simultaneous treatment with chloroquine did not modify the effect of lipoprotein treatment. In addition, treatment with cholesterol dissolved in either ethanol or methyl-beta-cyclodextrin elicited the same effect. Excess non-esterified cholesterol did not cause cell toxicity. Cell cholesterol mass inversely correlated with sAPP release. Progesterone, which inhibits shuttling of non-esterified cholesterol between the plasma membrane and intracellular pools, had no effect on the inhibition of sAPP release from cholesterol-loaded cells, providing indirect evidence that cholesterol may act at the plasma membrane.

Amyloid beta-Protein Precursor↗
PubMed1997

Direct antiatherogenic activity of isradipine and lacidipine on neointimal lesions induced by perivascular manipulation in rabbits.

The in vivo antiatherogenic activity of two calcium antagonists of the dihydropyridine class (isradipine and lacidipine) was investigated in a new experimental model. The proliferative lesion induced in the rabbit carotid artery was obtained by positioning a hollow silastic collar around the vessel. The neointimal formation was determined by measuring cross sectional thickness of intimal (I) and medial (M) tissue of fixed arteries obtained 14 days after collar placement. The effectiveness in inhibiting neointimal formation was assessed for isradipine (0.5, 1 and 4 mg kg-1 day-1) in normocholesterolemic (NC) animals and for lacidipine (1, 3, and 10 mg kg-1 day-1) in hypercholesterolemic (HC) rabbits. In NC control animals a neointimal formation was clearly detectable (I/M 0.53 +/- 0.18, n = 5). In isradipine-treated groups I/M ratios were significantly decreased (0.15 +/- 0.03, 0.12 +/- 0.02, 0.1 +/- 0.02 for the 0.5, 1 and 4 mg kg-1 day-1 doses respectively). In HC rabbits the administration of cholesterol 1% mixed with food and drug treatment started either 60 days before collar insertion (pretreated group, HC60) or on the same day (non pretreated group, HC15) of the collar placement. Only the pharmacological pretreatment was effective in reducing neointimal formation (0.47 +/- 0.02, 0.4 +/- 0.09, and 0.32 +/- 0.02 for dose 1, 3 and 10 mg kg-1 day-1 vs 1.1 +/- 0.14 in control animals). The inhibition of neointimal hyperplasia was much less evident in nonpretreated animals (0.7 +/- 0.15, 0.6 +/- 0.18 and 0.43 +/- 0.08 for dose 1, 3, and 10 mg kg-1 day-1 vs 0.72 +/- 0.2 in control animals). These results suggest a direct antiatherosclerotic effect of isradipine and lacidipine on neointimal hyperplasia induced in NC and HC pretreated rabbits independently of modulation of risk factors such as hypercholesterolemia and/or hypertension.

Animals↗
PubMed1997

Proapoptotic effect of atorvastatin on stimulated rabbit smooth muscle cells.

The in vitro and in vivo activity of atorvastatin and other 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase inhibitors (fluvastatin, pravastatin and simvastatin) has been investigated. Atorvastatin, fluvastatin, pravastatin and simvastatin caused a significant and dose-dependent (0.1-50 microM) reduction in cell multiplication of vascular smooth muscle cells (SMC) in cultures associated with the retardation of cycling cells in the G1 and G2/M compartments at 24 h, a phenomenon leading to apoptosis (programmed cell death) in several experimental in vitro models. The effects on the cell cycle resulted in a strong inhibition of cell proliferation at 48 h, followed by apoptosis when incubation was prolonged to 72 h as assessed by nuclei morphology and cytofluorimetric analysis of DNA. The apoptotic effect observed for the statins is completely prevented by the addition of exogenous mevalonate at a 100 microm concentration. in vivo SMC proliferation was stimulated by applying a silastic collar to the outside surface of carotid arteries in normocholesterolemic rabbits in the presence of an anatomically intact endothelium. The positioning of the collar promoted apoptosis in control vessels as assessed by Terminal Deoxynucleotidyl Transferase-dUTP-Biotin Nick-End Labeling (TUNEL) assay. The pre-treatment with 5 mg kg-1 per day of atorvastatin before collar insertion strongly increased the number of TUNEL-positive cells, suggesting a pro-apoptotic effect of HMGCoA reductase inhibitors also in vivo, even though cell DNA rearrangement still needs to be excluded. No apoptotic signal was detectable in sham operated arteries with no collar in either control or atorvastatin-treated rabbits. These data indicate that HMGCoA reductase inhibitors effect on the arterial wall may involve the modulation of both cell proliferation and programmed cell deaths supporting a possible role of statins in the prevention of early lesion and restenosis.

Animals↗
PubMed1997

The role of anchoring protein RACK1 in PKC activation in the ageing rat brain.

High levels of expression of Ca2+/phospholipid-dependent protein kinase C (PKC) occur in neuronal tissues and play a strategic role in the modulation of short- and long-term functions (ion channels, receptor desensitization, neurotransmitter release and synaptic efficiency) that become modified during the brain ageing process. Recent studies have clarified the key role played by the anchoring proteins in mediating subcellular PKC location, that is, in driving the enzyme to specific sites of action. The protein, receptor for activated C-kinase 1 (RACK1) is involved in PKC-mediated signal transduction. A postnatal developmental increase in RACK1 levels indicates their significance in the outgrowth of neuronal processes. In a physiological model of impairment in PKC translocation-the aged rat brain cortex-RACK1 levels are reduced and the PKC isoenzymes known to interact with it do not translocate to membrane compartments upon stimulation. Anchoring proteins might represent new targets for compounds that modulate PKC signal transduction processes.

Aging↗
PubMed1997

N-3 fatty acids do not lead to an increased diabetic risk in patients with hyperlipidemia and abnormal glucose tolerance. Italian Fish Oil Multicenter Study.

A multicenter, randomized, double-blind, place-bo-controlled study evaluated the possible worsening of glycemic control after a moderate daily intake of n-3 fatty acid ethyl esters in patients with hypertriglyceridemia with and without glucose intolerance or diabetes. A total of 935 patients of both sexes in 63 Italian clinical centers were selected; 55% had either impaired glucose tolerance or non-insulin-dependent diabetes mellitus (NIDDM). They received for 2 mo either 1 g n-3 ethyl esters three times a day or a corresponding placebo, followed by 4 mo of either 1 g n-3 ethyl esters twice a day or placebo. In addition to the complete lipid and lipoprotein evaluation, patients with impaired glucose tolerance also underwent an oral-glucose-tolerance test; in patients with NIDDM, serum insulin and glycated hemoglobin (Hb A1c) concentrations were determined. Plasma triacylglycerol concentrations decreased significantly, up to 21.53% at 6 mo compared with baseline (decreased 15% compared with placebo), with a tendency toward a progressive reduction with time. There was no evidence for a different response in patients with either NIDDM or impaired glucose tolerance. Among NIDDM patients, the triacylglycerol reduction was greater in those with high-density-lipoprotein cholesterol < or = 0.91 mmol/L. There was no alteration in the major glycemic indexes: fasting glucose, Hb A1c, insulinemia, and oral glucose tolerance in patients with impaired glucose tolerance or NIDDM after treatment with n-3 ethyl esters. Treatment with a moderate daily dose of n-3 ethyl esters over a prolonged period of time significantly reduced triacylglycerol concentrations without any worsening of glucose tolerance in patients with hypertriglyceridemia with and without impaired glycemic regulation.

Aged↗
PubMed1997

Vastatins inhibit tissue factor in cultured human macrophages. A novel mechanism of protection against atherothrombosis.

We examined the effect of fluvastatin, the first entirely synthetic 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor that is structurally different from other vastatins, on tissue factor (TF) expression in human macrophages spontaneously differentiated in culture from blood monocytes. Fluvastatin decreased TF activity in a dose-dependent manner (1 to 5 mumol/L) in both unstimulated and lipopolysaccharide-stimulated macrophages, and this reduction paralleled the decrease in immunologically recognized TF protein. The same results were obtained with another lipophilic vastatin, simvastatin, but not with hydrophilic pravastatin. The reduction in TF expression was also observed in macrophages enriched in cholesterol after exposure to 50 micrograms/mL acetylated low density lipoprotein. The inhibitory effect of fluvastatin on TF activity and antigen was fully reversible by coincubation with 100 mumol/L mevalonate or 10 mumol/L all-trans-geranylgeraniol but not with dolichol, farnesol, or geraniol. Suppression of TF antigen and activity was accompanied by a diminution in TF mRNA levels, which was completely prevented by mevalonate. Furthermore, fluvastatin impaired bacterial lipopolysaccharide-induced binding of c-Rel/p65 heterodimers to a kappa B site in the TF promoter, indicating that this drug influences induction of the TF gene. We conclude that lipophilic vastatins inhibit TF expression in macrophages, and because this effect is prevented by mevalonate and geranylgeraniol, a geranylgeranylated protein plays a crucial role in the regulation of TF biosynthesis. The suppression of TF in macrophages by vastatins indicates a potential mechanism by which these drugs interfere with the formation and progression of atherosclerotic plaque as well as thrombotic events in hyperlipidemic patients.

Arteriosclerosis↗
PubMed1997

Pharmacological control of the mevalonate pathway: effect on arterial smooth muscle cell proliferation.

The mevalonate (MVA) pathway is involved in cell proliferation. We investigated drugs acting at different enzymatic steps on rat aorta smooth muscle cell (SMC) proliferation. Competitive inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (0.1-10 microM) dose-dependently decreased (up to 90%) SMC proliferation. This effect was prevented by 100 microM MVA, 10 microM all-trans farnesol (F-OH) and 5 microM all-trans geranylgeraniol (GG-OH), precursors of protein prenyl groups, but not by 2-cis GG-OH, precursor of dolichols, squalene and ubiquinone. The same inhibitory effect was obtained with 6-fluoromevalonate (1-50 microM), an inhibitor of MVA-pyrophosphate decarboxylase. Partial recovery of cell proliferation was possible by all-trans F-OH and all-trans GG-OH, but not MVA. Squalestatin 1 (1-25 microM), a potent squalene synthase inhibitor, blocked cholesterol synthesis and slightly inhibited (21% decrease) SMC proliferation only at the highest tested concentration. NB-598 (1-10 microM), a potent squalene epoxidase inhibitor, blocked cholesterol synthesis without affecting SMC proliferation. Finally, the benzodiazepine peptidomimetic BZA-5B (10-100 microM), a specific inhibitor of protein farnesyltransferase, time- and dose-dependently decreased SMC proliferation (up to 62%) after 9 days. This effect of BZA-5B was prevented by MVA and all-trans GG-OH, but not by all-trans F-OH. SMC proliferation was not affected by the closely related compound BZA-7B, which does not inhibit protein farnesyltransferase. Altogether, these findings focus the role of the MVA pathway in cell proliferation and call attention to the involvement of specific isoprenoid metabolites, probably through farnesylated and geranylgeranylated proteins, in the control of this cellular event.

Animals↗
PubMed1997

[Pharmacological control of biosynthesis pathway of mevalonate: effect on the proliferation of arterial smooth muscle cells].

The role of mevalonic acid (MVA) and its products (isoprenoids) in cell proliferation prompted us to investigate the effect of drugs affecting diverse enzymatic steps of the MVA pathway on rat aorta smooth muscle cell (SMC) proliferation. Competitive inhibitors of HMG-CoA reductase (statins) decreased SMC proliferation in a dose-dependent manner. The inhibitory effect induced by simvastatin 3.5 microM (70% +/- 3.8 decrease) was prevented by addition of 100 microM MVA, (100% +/- 2.3), 10 microM farnesol (F-OH) (85% +/- 1.2) and 5 microM of all-trans geranylgeraniol (GG-OH) (precursor of prenylated proteins) (81% +/- 1.1), but not by 2-cis GG-OH (precursor of dolichols), squalene and ubiquinone. The same inhibitory effect was obtained with 6-fluoromevalonate (1-50 microM), an inhibitor of MVA-PP decarboxylase. Squalestatin 1 (1-25 microM) and NB-598 (1-10 microM), potent squalene synthase and epoxidase inhibitors, respectively, caused a complete inhibition of cholesterol synthesis without affecting SMC proliferation. Finally, BZA-5B (10-50 microM) a specific inhibitor of protein farnesyl tranferase (PFTase), inhibited SMC proliferation in a dose- (10-50 microM) and time-dependent manner, reaching 52% +/- 6.3 inhibition after 9 days, in the presence of 50 microM BZA-5B, without affecting cholesterol synthesis. This effect was partially prevented by mevalonate (76% +/- 3.2) and GG-OH (87% +/- 7.3) but not by F-OH. On the other hand, SMC proliferation was not affected by the closely related compound BZA-7B (93% +/- 4), which does not inhibit PFTase. Taken together, these findings support the involvement of specific isoprenoid metabolites, probably through farnesylated and geranylgeranylated proteins in cell proliferation.

Animals↗
PubMed1996

Effect of the new HMG-CoA reductase inhibitor cerivastatin (BAY W 6228)on migration, proliferation and cholesterol synthesis in arterial myocytes.

The major relation existing between cell growth, migration and cholesterol homeostasis prompted us to investigate the effect of the new 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor cerivastatin (BAY W 6228) on these cellular events. The molecule inhibited in a dose-dependent manner the migration and the replication (evaluated as cell number and nuclear incorporation of 3H-thymidine) of rat arterial SMC with IC50 values of 2.7 microM and 0.5 microM, respectively. Among the tested statins BAY W 6228 resulted to be the most potent inhibitor of cholesterol synthesis and cell proliferation. Conditions producing 80-90% inhibition of cholesterol synthesis correlate with approximately 50% inhibition of cell growth. Similar results were obtained in SMC from human femoral artery. The in vitro inhibition of cell migration and proliferation induced by BAY W 6228 (80% decrease) was completely prevented by the addition of mevalonate and partially prevented (60-80%) by farnesol and geranylgeraniol, confirming the specific role of isoprenoid metabolites-probably through a prenylated protein(s)-in regulating these cellular events. The present results provide evidence that BAY W 6228 interferes, at least in vivo, with smooth muscle cells migration and proliferation, major processes involved in atherogenesis.

Animals↗