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Biomedical subjects

S Bellosta

Publications and source records attributed to S Bellosta.

At least 19 recordsLinked to original sources
PubMed2003

Inhibition of metalloproteinase-9 activity and gene expression by polyphenolic compounds isolated from the bark of Tristaniopsis calobuxus (Myrtaceae).

Excessive breakdown of extracellular matrix by metalloproteinases (MMPs) occurs in many pathological conditions, and thus inhibition of MMP activity might have therapeutic potential. The methanolic extract and the identified compounds from the bark of Tristaniopsis calobuxus Brongniart & Gris (Myrtaceae) were tested on the activity, production, and gene expression of MMP-9. The extract produced a concentration-dependent inhibition (50-95% at 10-50 microg/ml) of MMP-9 activity. The inhibitory activity was retained in the ethyl acetate-soluble fraction (50-95% inhibition at 10-50 microg/ml) which also reduced the release of MMP-9 by mouse peritoneal macrophages up to 80%. In the ethyl acetate-soluble fraction, two active fractions, 5A and 5B were identified. HPLC-MS and NMR analyses of these fractions indicated the presence of gallocatechin, ellagic acid, and its glycoside derivatives. Since the absolute configuration of gallocatechin was not determined, in the next experiments both (+)-gallocatechin (2R,3S) and (-)-gallocatechin (2S,3R) were tested, and (-)-epigallocatechin (2R,3R) was included for comparison. 5A and 5B inhibited MMP-9 secretion, an observation which correlated with the decrease of MMP-9 promoter activity and the downregulation of mRNA levels. All compounds decreased MMP-9 mRNA levels and secretion. Ellagic acid, (+)-gallocatechin and (-)-epigallocatechin, but not (-)gallocatechin inhibited promoter-driven transcription. Thus configuration at C2 (R) of the flavanol seem to be critical for the interaction with the promoter.

Animals↗
PubMed2001

Lacidipine [correction of Lalsoacidipine] modulates the secretion of matrix metalloproteinase-9 by human macrophages.

Activated macrophages within the arterial wall secrete matrix-degrading metalloproteinases (MMPs) that weaken the atherosclerotic plaque and contribute to its fissuration. Preclinical studies have shown that calcium antagonists may reduce atherogenesis in the arterial wall. In the present study we evaluated the effect of lacidipine on 92-kDa gelatinase B (MMP-9) expression in human macrophages in cultures. Cells were treated for 24 h with lacidipine and the conditioned media were analyzed. Lacidipine (1-20 microM) significantly reduced, in a dose-dependent manner, MMP-9 potential gelatinolytic capacity up to 50%. When MMP-9 expression was stimulated by treatment with phorbol esters or tumor necrosis factor-alpha, lacidipine was able to inhibit this enhanced gelatinolytic capacity up to 50 and 60%, respectively. Western blot analysis and enzyme-linked immunosorbent assay showed a reduction of MMP-9 protein actually released by cells. The addition of lacidipine in the incubation media determined no significant variation in Ca(2+) concentration. The drug did not affect MMP-9 mRNA levels, but it effectively reduced the amount of both active and total free MMP-9 secreted by human macrophages. Lacidipine reduced also the secretion of the tissue inhibitor of metalloproteinase-1 (TIMP-1); however we observed an overall reduction of the gelatinolytic activity of the cells. Finally, peritoneal macrophages, obtained from mice treated with lacidipine, showed a reduced secretion of MMP-9. Together, our data indicate that lacidipine may potentially exert an antiatherosclerotic activity by modulating the secretion of MMP-9 by macrophages. This, in addition to the previously demonstrated inhibition of cholesterol esterification, may contribute to increase plaque stability.

Animals↗
PubMed2001

Clinically relevant pleiotropic effects of statins: drug properties or effects of profound cholesterol reduction?

Clinical trials have firmly established that 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) can induce the regression of vascular atherosclerosis and reduce cardiovascular-related morbidity and death in patients with and without coronary artery disease. It is usually assumed that these beneficial effects are due to the ability of statins to reduce cholesterol synthesis. However, because mevalonic acid is not only the precursor of cholesterol but also of many non-steroidal isoprenoid compounds, the inhibition of HMG-CoA reductase may lead to pleiotropic effects. As shown by the data reported in this review, some statins can interfere with major events involved in the formation of atherosclerotic lesions, regardless of their hypolipidemic properties. The relevance of these effects in humans remains to be established (particularly in view of the high statin doses required to produce a direct vascular action), thus their contribution to the reduction in cardiovascular events observed in clinical trials has become one of the major challenges for future studies aimed at clarifying the anti-atherosclerotic benefits of statins.

Arteriosclerosis↗
PubMed2000

Lipophilic calcium antagonists in antiatherosclerotic therapy.

Two key events in atherosclerotic plaque formation are the deposition of lipids in cells of the vascular wall, and migration and proliferation of arterial smooth muscle cells from the tunica intima toward the media. It has been shown that various calcium-channel antagonists may delay plaque formation in animal models. Among these, the new and highly lipophilic calcium antagonists, such as lacidipine and lercanidipine, display the most promising antiatherosclerotic activities. This paper will review and discuss these beneficial effects.

Arteriosclerosis↗
PubMed2000

Non-lipid-related effects of statins.

The beneficial effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) on coronary events have generally been attributed to their hypocholesterolaemic properties. However, as mevalonate and other intermediates of cholesterol synthesis (isoprenoids) are necessary for cell proliferation and other important cell functions, effects other than cholesterol reduction may explain the pharmacological properties of statins. In the present review, we discuss the current knowledge on the nonlipid-related effects of statins, with a special emphasis on their potential benefits in different diseases, such as atherosclerosis and cancer. The mechanism(s) responsible for their favourable properties are also reviewed.

Animals↗
PubMed2000

Pleiotropic effects of statins in atherosclerosis and diabetes.

OBJECTIVE: To investigate the direct anti-atherosclerotic properties of statins. RESEARCH DESIGN AND METHODS: Using in vitro and ex vivo models, the effect of different statins on key events involved in atherogenesis has been investigated. We studied the ability of statins to modulate modified LDL-induced cholesterol esterification, metalloproteinase secretion by macrophages, and arterial myocyte migration and proliferation. The mechanisms underlying the inhibitory effect of statins have also been explored. Finally, the antiproliferative effect of sera from statin-treated patients has been confirmed in a cell culture system. RESULTS: Fluvastatin, simvastatin, lovastatin, atorvastatin, and cerivastatin, but not pravastatin, dose-dependently decrease smooth muscle cell (SMC) migration and proliferation. Moreover, statins are able to reduce cholesterol accumulation in macrophages in vitro by blocking cholesterol esterification and endocytosis of modified lipoproteins and matrix-degrading enzyme secretion. This in vitro inhibition was completely prevented by mevalonate and partially by all-trans farnesol and all-trans geranylgeraniol, confirming the specific role of isoprenoid metabolites (probably through prenylated protein[s]) in regulating these cellular events. The inhibitory effect of statins on SMC proliferation has been shown in different models of proliferating cells, such as cultured arterial myocytes and rapidly proliferating carotid and femoral intimal lesions in rabbits, independently of their ability to reduce plasma cholesterol. Finally, ex vivo studies showed that sera from fluvastatin-treated patients interfere with SMC proliferation. CONCLUSIONS: These results suggest that 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors exert a direct anti-atherosclerotic effect in the arterial wall, beyond their effects on plasma lipids that could translate into a more significant prevention of cardiovascular disease. These findings provide a basis for the beneficial effect of statins in clinical trials also involving diabetic patients--a population with a higher absolute risk of recurrent cardiovascular events.

Animals↗
PubMed1999

Expression of human apolipoprotein E3 or E4 in the brains of Apoe-/- mice: isoform-specific effects on neurodegeneration.

Apolipoprotein (apo) E isoforms are key determinants of susceptibility to Alzheimer's disease. The apoE4 isoform is the major known genetic risk factor for this disease and is also associated with poor outcome after acute head trauma or stroke. To test the hypothesis that apoE3, but not apoE4, protects against age-related and excitotoxin-induced neurodegeneration, we analyzed apoE knockout (Apoe-/-) mice expressing similar levels of human apoE3 or apoE4 in the brain under control of the neuron-specific enolase promoter. Neuronal apoE expression was widespread in the brains of these mice. Kainic acid-challenged wild-type or Apoe-/- mice had a significant loss of synaptophysin-positive presynaptic terminals and microtubule-associated protein 2-positive neuronal dendrites in the neocortex and hippocampus, and a disruption of neurofilament-positive axons in the hippocampus. Expression of apoE3, but not of apoE4, protected against this excitotoxin-induced neuronal damage. ApoE3, but not apoE4, also protected against the age-dependent neurodegeneration seen in Apoe-/- mice. These differences in the effects of apoE isoforms on neuronal integrity may relate to the increased risk of Alzheimer's disease and to the poor outcome after head trauma and stroke associated with apoE4 in humans.

Aging↗
PubMed1999

Best practice--ongoing polemics.

Current treatment strategies and disease management programs for hyperlipidemia employ a range of lipid-lowering drugs. Results from early lipid-lowering trials using diet, fibrates, niacin and other classes of drug showed that lowering plasma cholesterol can significantly reduce the risk of developing ischemic cardiovascular events. The landmark statin trials have clearly demonstrated the benefits of lipid-lowering therapy in coronary heart disease (CHD) prevention and unlike early lipid-lowering studies, a reduction in mortality may become evident with statin therapy during the first year of treatment. The number of successful lipid-intervention trials continues to increase and evidence is accumulating that lipid modification can also reduce the risk of cardiovascular events among individuals with only modest degrees of blood-lipid abnormalities. With increasingly powerful drugs to modify blood lipids, the potential levels at which to initiate treatment and the appropriate target levels are rapidly changing and debate surrounds the question of where the line to initiate treatment should be drawn. The relative lack of major adverse events with statin therapy means that the level of CHD risk at which clinical benefit occurs cannot be determined by the degree of risk at which benefit exceeds adverse events. Therefore, patients with only moderately raised cholesterol levels can be treated because statin treatment is well tolerated. One of the most important aspects of the statin trials is the finding that clinical events, such as death and disability due to coronary artery disease, may be preventable or limited in a significant number of patients if they receive aggressive therapy. Current goals for cholesterol levels in patients with established CHD are rarely achieved with non-aggressive treatment; however, with aggressive lipid lowering statins can achieve these goals in a safe and effective manner.

Cardiovascular Diseases↗
PubMed1999

New insights into the pharmacodynamic and pharmacokinetic properties of statins.

The beneficial effects of statins are assumed to result from their ability to reduce cholesterol biosynthesis. However, because mevalonic acid is the precursor not only of cholesterol, but also of many nonsteroidal isoprenoid compounds, inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase may result in pleiotropic effects. It has been shown that several statins decrease smooth muscle cell migration and proliferation and that sera from fluvastatin-treated patients interfere with its proliferation. Cholesterol accumulation in macrophages can be inhibited by different statins, while both fluvastatin and simvastatin inhibit secretion of metalloproteinases by human monocyte-derived macrophages. The antiatherosclerotic effects of statins may be achieved by modifying hypercholesterolemia and the arterial wall environment as well. Although statins rarely have severe adverse effects, interactions with other drugs deserve attention. Simvastatin, lovastatin, cerivastatin, and atorvastatin are biotransformed in the liver primarily by cytochrome P450-3A4, and are susceptible to drug interactions when co-administered with potential inhibitors of this enzyme. Indeed, pharmacokinetic interactions (e.g., increased bioavailability), myositis, and rhabdomyolysis have been reported following concurrent use of simvastatin or lovastatin and cyclosporine A, mibefradil, or nefazodone. In contrast, fluvastatin (mainly metabolized by cytochrome P450-2C9) and pravastatin (eliminated by other metabolic routes) are less subject to this interaction. Nevertheless, a 5- to 23-fold increase in pravastatin bioavailability has been reported in the presence of cyclosporine A. In summary, statins may have direct effects on the arterial wall, which may contribute to their antiatherosclerotic actions. Furthermore, some statins may have lower adverse drug interaction potential than others, which is an important determinant of safety during long-term therapy.

Animals↗
PubMed1999

Natural anti-endothelial cell antibodies (AECA).

Natural AECA constitute a pool of autoantibodies circulating in healthy subjects, which react with a restricted and conserved set of endothelial antigens and establish idiotypic interactions within the immunoglobulin networks. Normal IgG interacts with living endothelial cells and is internalized with a mechanism involving microtubules and resembling that of ligand-receptor internalization. IgG-endothelial cell interaction appears to be dependent on the variable region of antibodies and is followed by modifications of endothelial cell function. Natural AECA increase anti-inflammatory properties of endothelial cells through the selective inhibition of thromboxane A2, endothelin and metalloproteinase-9 secretion, and also through the inhibition of endothelial cell proinflammatory response to TNF-alpha. We have gathered evidence demonstrating that natural AECA constitute a strictly controlled autoantibody pool, interact with living endothelial cells and take part in the regulation of endothelial function, through direct anti-inflammatory effects.

Antibody Specificity↗
PubMed1999

Characterization of a new form of inherited hypercholesterolemia: familial recessive hypercholesterolemia.

We previously described a Sardinian family in which the probands had a severe form of hypercholesterolemia, suggestive of familial hypercholesterolemia (FH). However, low density lipoprotein (LDL) receptor activity in fibroblasts from these subjects and LDL binding ability were normal. The characteristics of the pedigree were consistent with an autosomal recessive trait. Sitosterolemia and pseudohomozygous hyperlipidemia were ruled out. A second Sardinian kindred with similar characteristics was identified. Probands showed severe hypercholesterolemia, whereas their parents and grandparents were normolipidemic. FH, familial defective apoprotein (apo) B, sitosterolemia, and cholesteryl ester storage disease were excluded by in vitro studies. We addressed the metabolic basis of this inherited disorder by studying the in vivo metabolism of LDL in 3 probands from these 2 families. 125I-LDL turnover studies disclosed a marked reduction in the fractional catabolic rate (0.19+/-0.01 versus 0.36+/-0.03 pools per day, respectively; P<0.001) and a significant increase in the production rate [20.7+/-4.4 versus 14. 0+/-2.4 mg. kg-1. d-1, respectively; P<0.01] of LDL apoB in the probands compared with normolipidemic controls. We then studied the in vivo biodistribution and tissue uptake of 99mtechnetium-labeled LDL in the probands and compared them with those in normal controls and 1 FH homozygote. The probands showed a significant reduction in hepatic LDL uptake, similar to that observed in the FH homozygote. A reduced uptake of LDL by the kidney and spleen was also observed in all patients. Our findings suggest that this recessive form of hypercholesterolemia is due to a marked reduction of in vivo LDL catabolism. This appears to be caused by a selective reduction in hepatic LDL uptake. We propose that in this new lipid disorder, a recessive defect causes a selective impairment of LDL receptor function in the liver.

Adult↗
PubMed1998

Isoform-specific effects of human apolipoprotein E on brain function revealed in ApoE knockout mice: increased susceptibility of females.

Apolipoprotein E (apoE) mediates the redistribution of lipids among cells and is expressed at highest levels in brain and liver. Human apoE exists in three major isoforms encoded by distinct alleles (epsilon2, epsilon3, and epsilon4). Compared with APOE epsilon2 and epsilon3, APOE epsilon4 increases the risk of cognitive impairments, lowers the age of onset of Alzheimer's disease (AD), and decreases the response to AD treatments. Besides age, inheritance of the APOE epsilon4 allele is the most important known risk factor for the development of sporadic AD, the most common form of this illness. Although numerous hypotheses have been advanced, it remains unclear how APOE epsilon4 might affect cognition and increase AD risk. To assess the effects of distinct human apoE isoforms on the brain, we have used the neuron-specific enolase (NSE) promoter to express human apoE3 or apoE4 at similar levels in neurons of transgenic mice lacking endogenous mouse apoE. Compared with NSE-apoE3 mice and wild-type controls, NSE-apoE4 mice showed impairments in learning a water maze task and in vertical exploratory behavior that increased with age and were seen primarily in females. These findings demonstrate that human apoE isoforms have differential effects on brain function in vivo and that the susceptibility to apoE4-induced deficits is critically influenced by age and gender. These results could be pertinent to cognitive impairments observed in human APOE epsilon4 carriers. NSE-apoE mice and similar models may facilitate the preclinical assessment of treatments for apoE-related cognitive deficits.

Age Factors↗
PubMed1998

Low-dose expression of a human apolipoprotein E transgene in macrophages restores cholesterol efflux capacity of apolipoprotein E-deficient mouse plasma.

Apolipoprotein E- (apoE) deficient (E-/-) mice develop severe hyperlipidemia and diffuse atherosclerosis. Low-dose expression of a human apoE3 transgene in macrophages of apoE-deficient mice (E-/-hTgE+/0), which results in about 5% of wild-type apoE plasma levels, did not correct hyperlipidemia but significantly reduced the extent of atherosclerotic lesions. To investigate the contribution of apoE to reverse cholesterol transport, we compared plasmas of wild-type (E+/+), E-/-, and E-/-hTgE+/0 mice for the appearance of apoE-containing lipoproteins by electrophoresis and their capacity to take up and esterify 3H-labeled cholesterol from radiolabeled fibroblasts or J774 macrophages. Wild-type plasma displayed lipoproteins containing apoE that were the size of high density lipoprotein and that had either electrophoretic alpha or gamma mobilities. Similar particles were also present in E-/-hTgE+/0 plasma. Depending on incubation time, E-/- plasma released 48-74% less 3H-labeled cholesterol from fibroblasts than E+/+ plasma, whereas cholesterol efflux into E-/-hTgE+/0 plasma was only 11-25% lower than into E+/+ plasma. E-/-hTgE+/0 plasma also released 10% more 3H-labeled cholesterol from radiolabeled J774 macrophages than E-/- plasma. E+/+ and E-/-hTgE+/0 plasma each esterified significantly more cell-derived 3H-labeled cholesterol than E-/- plasma. Moreover, E-/- plasma accumulated much smaller proportions of fibroblast-derived 3H-labeled cholesterol in fractions with electrophoretic gamma and alpha mobility than E+/+ and E-/-hTgE+/0 plasma. Thus, low-dose expression of apoE in macrophages nearly restored the cholesterol efflux capacity of apoE-deficient plasma through the formation of apoE-containing particles, which efficiently take up cell-derived cholesterol, and through the increase of cholesterol esterification activity. Thus, macrophage-derived apoE may protect against atherosclerosis by increasing cholesterol efflux from arterial wall cells.

Animals↗
PubMed1998

Direct vascular effects of HMG-CoA reductase inhibitors.

Several studies have demonstrated that any beneficial effect of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) on coronary events are linked to their hypocholesterolemic properties. However, since mevalonic acid (MVA), the product of the enzyme reaction, is the precursor of numerous metabolites, inhibition of HMG-CoA reductase has the potential to result in pleiotropic effects. MVA and other intermediates of cholesterol synthesis (isoprenoids) are necessary for cell proliferation and other important cell functions, hence effects other than cholesterol reduction may help to explain the antiatherosclerotic properties of statins. Recently, we provided in vitro evidence that fluvastatin, simvastatin, lovastatin, cerivastatin, but not pravastatin, dose-dependently decrease smooth muscle cells (SMC) migration and proliferation, independently of their ability to reduce plasma cholesterol. Moreover, statins are able to reduce the in vitro cholesterol accumulation in macrophages, by blocking cholesterol esterification and endocytosis of modified lipoproteins. This in vitro inhibition was completely prevented by the addition of mevalonate and partially by all-trans farnesol and all-trans geranylgeraniol, confirming the specific role of isoprenoid metabolites--probably through a prenylated protein(s)--in regulating these cellular events. The inhibitory effect of lipophilic statins on SMC proliferation has been recently shown in different models of proliferating cells such as cultured arterial myocytes and rapidly proliferating carotid and femoral intimal lesions in rabbits. Finally, ex vivo studies recently showed that sera from fluvastatin-treated patients interfere with smooth muscle cell proliferation. These results suggest that HMG-CoA reductase inhibitors exert a direct antiatherosclerotic effect in the arterial wall, beyond their effects on plasma lipids, that could translate into a more significant prevention of cardiovascular disease.

Animals↗
PubMed1998

Oleuropein, the bitter principle of olives, enhances nitric oxide production by mouse macrophages.

The Mediterranean diet, rich in fresh fruits and vegetables, has been associated with a lower incidence of cardiovascular disease and cancer, partly because of its high proportion of bioactive compounds such as vitamins, flavonoids and polyphenols. The major lipid component of such diet is the drupe-derived olive oil, that can be distinguished from other seed oils for the peculiar composition of its non-triglyceride fraction. In fact, several minor components, including polyphenols, grant the oil its particular taste and aroma. Oleuropein, the most abundant among these components, has been shown to be a potent antioxidant endowed with antiinflammatory properties. We investigated the effects of oleuropein on NO release in cell culture and its activity toward nitric oxide synthase (iNOS) expression. The results show that oleuropein dose-dependently enhance nitrite production in LPS-challenged mouse macrophages. This effect was blocked by the iNOS inhibitor L-NAME, indicating increased iNOS activity. Also, Western blot analysis of cell homogenates show that oleuropein increases iNOS expression in such cells. Taken together, our data suggest that, during endotoxin challenge, oleuropein potentiates the macrophage-mediated response, resulting in higher NO production, currently believed to be beneficial for cellular and organismal protection.

Animals↗
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↗