Pharmacology of competitive inhibitors of HMG-CoA reductase.
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Animals↗
Biomedical subjects
A Corsini
Publications and source records attributed to A Corsini.
Severe hypercholesterolaemia: unusual inheritance in an Italian pedigree.
A family presenting several cases of severe primary hypercholesterolaemia and/or premature sudden death was studied. This family is characterized by consanguinity, absence of vertical transmission, bimodal distribution of plasma cholesterol values, and reduction of reproductive fitness in affected individuals. The probands have clinical traits of homozygous familial hypercholesterolaemia, including hypercholesterolaemia, xanthomas and early coronary atherosclerosis, while the parents and grandparents are clinically normal. Eight relatives on the mother's side experienced premature sudden death, and in four cases hypercholesterolaemia was diagnosed. Haplotype segregation analysis of the inheritance of the LDL receptor and apo B genes in the probands' family excluded the involvement of these two genes in the pathogenesis of the disease. LDL receptor activity, as well as the ability of LDL to bind to the LDL receptor, and plasma vegetal sterols were within normal limits both in probands and in their relatives. The study of this pedigree suggests that hypercholesterolaemia is not produced by defects in the LDL receptor or LDL particles, and disease inheritance is consistent with an autosomal recessive trait.
Adult↗
Effects of 26-aminocholesterol, 27-hydroxycholesterol, and 25-hydroxycholesterol on proliferation and cholesterol homeostasis in arterial myocytes.
The major relation existing between cell growth and cholesterol homeostasis prompted us to investigate the effect of 26-aminocholesterol (26-NH2), 27-hydroxycholesterol (27-OH), and 25-hydroxycholesterol (25-OH) on these cellular events. To test this relation, we incubated human and rat arterial myocytes with the sterols for 72 hours. All the tested compounds (0.5 to 7.5 mumol/L) inhibited rat and human myocyte proliferation and cholesterol biosynthesis in a dose-dependent manner. 26-NH2 was more potent than oxysterols in inhibiting human myocyte proliferation but equieffective in rat cells; 27-OH and 25-OH displayed similar activity in both cell lines. Inhibition of nuclear incorporation of thymidine in rat myocytes is consistent with decreased cell count. The antiproliferative effect of the tested sterols was reversible. The high inhibition (80%) of cholesterol biosynthesis necessary to induce a decrease in myocyte proliferation suggests a causal relation between the cholesterol synthetic pathway and these cellular processes. In addition, all the tested sterols were able to inhibit hydroxymethyl glutaryl-coenzyme A reductase activity in intact myocytes but not in cell-free extracts. The finding that 26-NH2 but not 27-OH or 25-OH does not suppress LDL receptor activity in either human or rat myocytes supports the achievement of selectivity over the coordinately regulated LDL receptor gene. The ability of 26-NH2 to interfere with myocyte proliferation and cholesterol synthesis without affecting the LDL receptor pathway confers at least in vitro a pharmacological interest on the compound in the process of atherogenesis.
Animals↗
[The pharmacology of the statins: the evidence of a direct antiatherosclerotic action].
With the increasing knowledge on the pathogenesis of atherosclerosis, it appears that the prevention of cardiovascular disease in the future will involve, besides risk factor correction, direct pharmacological control of processes occurring in the arterial wall. Among them, a pivotal role is played by smooth muscle cell migration and proliferation that, together with lipid deposition, are prominent features of atherogenesis and restenosis after angioplasty. Mevalonate and other intermediates (isoprenoids) of cholesterol synthesis are essential for cell growth, hence drugs affecting this metabolic pathway are potential antiatherosclerotic agents. Recently we provided evidence that fluvastatin, simvastatin, lovastatin, but not pravastatin, dose-dependently decrease smooth muscle cell migration and proliferation, independently of their hypocholesterolemic properties. The in vitro inhibition of cell migration and proliferation induced by simvastatin and fluvastatin (70-90% decrease) was completely prevented by the addition of mevalonate and partially (80%) by farnesol and geranylgeraniol, confirming the specific role of isoprenoid metabolites--probably through prenylated proteins--in regulating these cellular events. The present results provide evidence that HMG-CoA reductase inhibitors interfere directly with processes involved in atherogenesis--beyond their effects on plasma lipids--partially through local inhibition of isoprenoid biosynthesis.
Animals↗
The antiatherosclerotic effects of calcium antagonists.
It has been known for some time that calcium antagonists demonstrate antiatherosclerotic activity. These agents have been shown to reduce the extension of atherosclerotic lesions in cholesterol-fed rabbits without affecting plasma lipid concentrations or blood pressure, suggesting a direct protective effect on the arterial wall. Lacidipine is a recently developed dihydropyridine calcium antagonist that is extremely lipophilic and has potent and long-lasting antihypertensive properties. Lacidipine directly inhibits the enzyme, acylcoenzyme A-cholesterol acyltransferase, and affects intracellular cholesterol homeostasis by preventing acetyl low-density lipoprotein cholesterol esterification. In vivo studies have shown that lacidipine also reduces the intimal hyperplasia induced by insertion of a plastic collar around one carotid artery in cholesterol-fed rabbits. In animals treated with lacidipine, the rapid proliferation of smooth-muscle cells inside the carotid wall is totally inhibited. Lacidipine, therefore, appears to protect the arterial wall against the development of atherosclerotic lesions in animal or human subjects with severe and multiple risk factors. It seems likely that these effects are achieved by a direct action on the mechanisms involved in atherogenesis.
Animals↗
Direct drug control of the vascular wall.
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Anticholesteremic Agents↗
Experimental and clinical effects of isradipine relevant to atherosclerosis.
A number of studies in experimental animal models have demonstrated the potential direct antiatherosclerotic effects of calcium antagonists. This class of compounds can influence several processes that are involved in the development of atherosclerotic lesions. This action is independent of either blood pressure reduction or hypercholesterolemia. A major problem encountered from the experimental data are the high doses used, which are several times higher than those used in the treatment of humans. One notable exception to this problem is the second-generation calcium antagonist isradipine, which exerts a direct antiatherosclerotic effect in rabbits at doses similar to those used in the clinic. Thus, this review is a summary of the effects and mechanisms of the antiatherosclerotic activity of isradipine.
Animals↗
Efficacy and safety of pidotimod in the treatment of recurrent respiratory infections in children.
The activity of pidotimod ((R)-3-[(S)-(5-oxo-2-pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6) was evaluated in a double-blind, placebo-controlled, randomized, multicentre trial, on 120 pediatric patients affected by recurrent respiratory infections. The clinical course of acute infections was favourable both in placebo and in treatment group, but recovery was quicker with pidotimod than with placebo. Antibiotic therapy and time of hospitalization were shorter in the patients taking pidotimod, and main symptomatic parameters (pharyngalgia, dysphagia, mucous membrane inflammation, adenopathy, anorexia) receded quickly. In patients receiving the drug as well as in placebo group changes in laboratory parameters, indicating recovery from the acute infectious events, were observed. A significant trend to normalization of the immune response, evidenced by chemotaxis and leukocyte phagocytosis index, was found only in patients treated with pidotimod. A significant decrease in the risk of relapses was observed in patients treated with pidotimod (35%), as well as a reduction of hospitalization (86%) and a decreased antibiotic therapy (47%). If a relapse occurred, the response of treated patients was quicker (fever, antibiotic therapy, hospitalization). These findings allow to correlate the individual immune response activation to the resistance to recurrent infections and also to a better response to therapy in case of clinically relevant disease. No side effects were observed. Only in 12 patients (5 pidotimod, 7 placebo) mild reactions were observed, but they were attributed to concomitant antibiotic treatment or other factors. No alterations in main laboratory parameters were seen.(ABSTRACT TRUNCATED AT 250 WORDS)
Adjuvants, Immunologic↗
Pidotimod in the treatment of recurrent respiratory infections in paediatric patients.
50 young patients suffering from recurrent respiratory infections (RRI) were treated with pidotimod ((R)-3-[(S)-(5-oxo-2- pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6) (one 400 mg ampoule twice a day) or placebo, according to a double-blind experimental design. The treatment period was 20 days and there was then a 60-day follow-up period. Evaluation was both clinical (number and severity of the respiratory infectious episodes) and immunological, investigating the OKT 4 and OKT 8 lymphocyte sub-populations and OKT 4/OKT 8 ratio. The group of children treated with pidotimod showed a decrease in the number of infections. Patients free from RRI episodes, after 20 days of therapy, were 68% of the group treated with pidotimod compared with 8% of the placebo group. In addition, the mean duration of the episodes was lower in treated patients than in patients of the control group. Such differences were statistically significant. It was also observed that administration of the drug potentiated the immune response such that the clinical picture remained improved for a further 60 days after treatment cessation. Furthermore, only in the pidotimod group there were improving changes of OKT 4 and OKT 8 percentages which affected the OKT 4/OKT 8 ratio.
Bronchitis↗
Therapeutic efficacy and safety of pidotimod in the treatment of urinary tract infections in children.
The activity of pidotimod ((R)-3-[(S)-(5-oxo-2-pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6) was studied vs. placebo in a double-blind, randomized, multicentre trial, involving 60 pediatric patients with recurrent urinary tract infections. Recovery from acute events was quicker with pidotimod than with placebo (9.6 vs. 12.3 days). In treated patients antibiotic therapy was shorter (6.9 vs. 8.3 days) and main symptomatic parameters (body temperature, vesical tenesmus, stranguria, pollakiuria, total number of symptoms, total symptomatic intensity, rate of asymptomatic patients, haematuria, leukocyturia, positive urinary culture) receded quickly. In patients receiving the drug as well as in patients treated with placebo changes in laboratory parameters were observed, indicating recovery from the acute infectious disease. A significant trend to normalization of the immune response, expressed by chemotaxis and index of leukocyte phagocytosis, was found only in patients treated with pidotimod. After the acute episode a significant decrease of risk of relapses (69%) was observed in these patients. If a relapse occurs, the response of treated patients is quicker (duration of fever, total time of relapses) than for control patients. These findings allow to correlate the individual immune response activation to the resistance to recurrent infections and also to a better response to therapy if the disease occurs and becomes clinically relevant. No side effects were observed. Mild reactions (4 nausea/vomiting, 1 erythema) occurred only in 5 patients (2 pidotimod, 3 placebo) but were attributed to concomitant antibiotic therapy. No alterations of main laboratory parameters were found. These findings confirm the tolerability of the drug also in long-term treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Anti-Infective Agents, Urinary↗
Pharmacology of lipoprotein receptors.
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Adrenergic beta-Antagonists↗
27-Hydroxycholesterol modulation of low density lipoprotein metabolism in cultured human hepatic and extrahepatic cells.
27-Hydroxycholesterol**, 25-hydroxycholesterol and cholesterol suppressed LDL uptake and degradation in human extrahepatic and hepatic cell lines in a concentration-dependent manner. Cholesterol was the least potent, and the inhibitory effect of oxysterols was more pronounced in skin fibroblasts and in endothelial cell line EAhy 926 than in hepatoma HepG2 cells. Shorter incubations were required for oxysterols to achieve 50% inhibition of LDL uptake and degradation in all cultured cells. The inhibition of LDL catabolism in extrahepatic cells by 27-hydroxycholesterol occurred at concentrations close to those observed in human plasma (0.2-0.6 microM). The results support a possible role of 27-hydroxycholesterol, a physiological oxysterol, in the regulation of cellular cholesterol homeostasis in non-hepatic tissues.
Cells, Cultured↗
Relationship between mevalonate pathway and arterial myocyte proliferation: in vitro studies with inhibitors of HMG-CoA reductase.
The role of mevalonate and its products (isoprenoids) in the control of cellular proliferation was examined by investigating the effect of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (vastatins) on growth and on cholesterol biosynthesis of cultured arterial myocytes (SMC). Simvastatin (S) and fluvastatin (F), but not pravastatin (P), decreased the rate of growth of rat vascular SMC. The inhibition, evaluated as cell number, was dose-dependent with IC50 values of 2.8 and 2.2 microM for S and F, respectively; P (1-500 microM) was inactive. The inhibition of cell growth induced by 3.5 microM S (70% decrease) was prevented completely by the addition of 100 microM mevalonate, partially (70-85%) by the addition of 10 microM geraniol, 10 microM farnesol and 5 microM geranylgeraniol, but not by the addition of squalene, confirming the specific role of isoprenoid metabolites in regulating cell proliferation. All the tested vastatins inhibited the incorporation of [14C]acetate into cholesterol but P had 800 times lower potency than S and F. Similar results were obtained in SMC from human femoral artery. At least 80% inhibition of cholesterol synthesis was necessary to induce a decrease in SMC proliferation. To further investigate the relationship between cholesterol synthesis and cell growth, two enantiomers of F were investigated. The enantiomer more active on HMG-CoA reductase was 70- and 1.6-fold more potent on arterial myocyte proliferation than its antipode and the racemic mixture, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Acyclic Monoterpenes↗
Effects of lacidipine on experimental models of atherosclerosis.
AIM: To evaluate the effect of lacidipine on the major processes of atherogenesis. METHODS: Cell-culture methods were used to study the effect of lacidipine. Low-density lipoprotein (LDL) receptor expression and cholesterol esterification were evaluated in human skin fibroblasts and in mouse peritoneal macrophages, respectively. The effect of lacidipine on cellular proliferation was tested on aortic myocytes cultured from rat aorta. RESULTS: Lacidipine did not affect LDL receptor expression, but it inhibited the ability of acetyl LDL to stimulate cholesterol esterification in macrophages by more than 95%. The drug inhibited cellular proliferation in a dose-dependent manner. This antiproliferative effect was confirmed in human femoral artery myocytes. In accord with the inhibitory effect on cellular growth, preliminary in vivo studies suggest that lacidipine may reduce neointimal formation induced by perivascular manipulation of the carotid artery in hypercholesterolemic rabbit. CONCLUSIONS: Our results indicate that lacidipine may be antiatherosclerotic through an effect on the major processes involved in atheroma formation.
Animals↗
Increased synthesis of plasminogen activator inhibitor-1 by cultured human endothelial cells exposed to native and modified LDLs. An LDL receptor-independent phenomenon.
The effects of native and acetylated low density lipoproteins (LDLs and acetyl-LDLs, respectively) on the release of plasminogen activator inhibitor type 1 (PAI-1) by cultured human umbilical vein endothelial cells (ECs) were evaluated. LDL and acetyl-LDL incubated with ECs for 16-18 hours increased the PAI-1 antigen levels in conditioned medium. At a concentration of 100 micrograms/mL, LDL and acetyl-LDL increased PAI-1 by 10.8 and 12.0 ng/mL, respectively (p < 0.05 and p < 0.01 versus control). The increases in PAI-1 antigen levels exerted by the lipoproteins paralleled the changes in PAI-1 activity. The effect of LDL and acetyl-LDL was concentration dependent and specific for PAI-1 because tissue-type plasminogen activator and expression of procoagulant activity were not affected by either lipoprotein. In addition, total protein synthesis evaluated in [35S] methionine-labeled ECs was not affected, and studies with cycloheximide showed that the effect of LDL and acetyl-LDL on PAI-1 release was due to de novo protein synthesis. Experiments using the C7 monoclonal antibody against the LDL receptor and binding-defective LDL indicated that the effect of LDL on the synthesis of PAI-1 was not dependent on the interaction of the LDLs with their specific receptors. Finally, extensive oxidation of LDL prevented and even reversed the effect of LDL on PAI-1 release by ECs. It is concluded that LDL specifically increases the synthesis of PAI-1 by ECs with mechanisms that are not receptor mediated.
Cells, Cultured↗
Effect of atherogenic lipoproteins on PAI-1 synthesis by endothelial cells.
Cultured human umbilical vein endothelial cells (EC) exposed to native and acetylated low density lipoproteins (LDL and acetyl-LDL) show an increased synthesis of PAI-1. Confluent EC monolayers were incubated for 16-18 hours in medium 199 with or without different concentrations of LDL and acetyl-LDL and PAI-1 antigen levels were measured in conditioned medium. LDL and acetyl-LDL increased the release of PAI-1 by EC in a concentration-dependent manner. The effect was specific for PAI-1 because tissue type plasminogen activator (t-PA) and expression of procoagulant activity were not affected by either lipoprotein. The observation that native and acetyl-LDL, which are known to interact with different receptors on EC, exert the same stimulatory effect on PAI-1 release rules out the possibility of an involvement of the LDL receptor in mediating this effect. Experiments carried out incubating native LDL in the presence of a monoclonal antibody against LDL receptor and using binding-defective LDL with a reduced affinity for the LDL receptor (approximately 50% with respect to normal LDL) further excluded an involvement of the classical LDL receptor in mediating the effect of the lipoproteins on PAI-1 synthesis by EC.
Arteriosclerosis↗
Effect of trapidil derivative AR 12456 on intracellular cholesterol homeostasis in human hepatoma cell line Hep G2.
The effect of trapidil derivative AR12456 on intracellular cholesterol metabolism was investigated in human hepatoma cell line HepG2. AR12456 enhanced the uptake and degradation of 125I-LDL in a dose-dependent manner. The drug inhibited cholesterol synthesis and esterification without affecting cellular cholesterol content and bile acid synthesis; cholesterol efflux was slightly increased. These results show that the inhibition of cholesterol synthesis together with the enhanced expression of LDL receptors may partially explain the hypocholesterolemic activity of compound AR12456.
Anticholesteremic Agents↗
Alternative splicing of mutant LDL-receptor mRNA in an Italian patient with familial hypercholesterolemia due to a partial deletion of LDL-receptor gene (FHPotenza).
An analysis of LDL-receptor gene was performed on an Italian patient with heterozygous familial hypercholesterolemia. Restriction enzyme analysis showed that the proband was heterozygous for a deletion of 4.5 kb spanning the 5' end of exon 13 (45 nucleotide residues) to intron 15. Amplification of genomic DNA, using polymerase chain reaction (PCR), followed by direct sequencing, showed that this deletion was identical to the one reported by Lehrman et al. (1986. Proc. Natl. Acad. Sci. 83: 3679-3683). As only the normal LDL-receptor mRNA was detectable in proband fibroblasts by Northern blot, we used reverse transcription-PCR to amplify the mutant mRNA using primers complementary to exon 6 (sense) and exon 18 (antisense). The amplification of control cDNA resulted in a single fragment of 1725 nucleotides containing the normal sequence. The amplification of cDNA from the proband produced the 1725-nucleotide fragment (as in the control) and three additional fragments (F1, F2, and F3) of smaller size. The direct sequence showed that in the F1 fragment exon 12 was joined to exon 16; in the F2 fragment exon 12 was joined to exon 17; and in the F3 fragment exon 11 was joined to exon 16. Thus, the deletion-bearing allele generated three mRNAs, two of which resulted from alternative splicings leading to the skipping of exons 16 and 12, respectively. It is expected that the translation of these mutant mRNAs will generate three aberrant proteins, the synthesis of which should be negligible in view of the very low content of the corresponding mRNAs.
Alternative Splicing↗