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P Marche

Publications and source records attributed to P Marche.

At least 19 recordsLinked to original sources

Novel vascular biology of third-generation L-type calcium channel antagonists: ancillary actions of amlodipine.

Calcium channel blockers (CCBs) were developed as vasodilators, and their use in cardiovascular disease treatment remains largely based on that mechanism of action. More recently, with the evolution of second- and third-generation CCBs, pleiotropic effects have been observed, and at least some of CCBs' benefit is attributable to these mechanisms. Understanding these effects has contributed greatly to elucidating disease mechanisms and the rationale for CCB use. Furthermore, this knowledge might clarify why drugs are useful in some disease states, such as atherosclerosis, but not in others, such as heart failure. Although numerous drugs used in the treatment of vascular disease, including statins and angiotensin-converting-enzyme inhibitors, have well-described pleiotropic effects universally accepted to contribute to their benefit, little attention has been paid to CCBs' potentially similar effects. Accumulating evidence that at least 1 CCB, amlodipine, has pharmacologic actions distinct from L-type calcium channel blockade prompted us to investigate the pleiotropic actions of amlodipine and CCBs in general. There are several areas of research; foci here are (1) the physicochemical properties of amlodipine and its interaction with cholesterol and oxidants; (2) the mechanism by which amlodipine regulates NO production and implications; and (3) amlodipine's role in controlling smooth muscle cell proliferation and matrix formation.

Amlodipine↗

Calcium antagonists and vascular smooth muscle cell reactivity.

OBJECTIVES: To determine the mechanisms whereby calcium channel blockers (CCBs) control the reactivity of vascular smooth muscle cells (VSMCs). BACKGROUND: Although CCBs are known to play an important role in the calcium homeostasis of VSMCs, they are suspected to exert additional effects in this cell type. Thus, the possibility that CCBs could affect VSMC growth/proliferation through a mechanism distinct from the inhibition of calcium channels was investigated. METHODS: VSMCs were isolated from rat aortae and cultured. The influence of nifedipine and amlodipine on basic fibroblast growth factor (bFGF)-stimulated DNA synthesis and proliferation was studied by measuring bFGF-induced BrdU incorporation into VSMCs and cell counts, respectively. The influence of amlodipine (and of isradipine) on the mobilization of intracellular Ca2+ stores was determined by studying the fluorescence of thapsigargin-stimulated VSMCs pre-labeled with the fluoroprobe Fura-2. RESULTS: Both nifedipine and amlodipine inhibited bFGF-induced VSMC growth/proliferation. In the case of nifedipine but not in that of amlodipine, this inhibitory effect could be accounted for by the L-type Ca(2+)-channel antagonist property of the drug. On the other hand, amlodipine but not isradipine, diltiazem, and verapamil, did inhibit thapsigargin-induced Ca2+ mobilization. CONCLUSIONS: These findings suggest that in addition to its L-type Ca(2+)-channel antagonist property, amlodipine also exerts a "thapsigargin-like" activity which, together with its particular antioxidant property, might participate in its antiatherogenic potency.

Amlodipine↗

Amlodipine inhibits thapsigargin-sensitive CA(2+) stores in thrombin-stimulated vascular smooth muscle cells.

Ca(2+) channel blockers, such as amlodipine, inhibit vascular smooth muscle cell (VSMC) growth through interactions with targets other than L-type Ca(2+) channels. The effects of amlodipine on Ca(2+) movements in thrombin- and thapsigargin-stimulated VSMCs were therefore investigated by determining the variations of intracellular free Ca(2+) concentration in fura 2-loaded cultured VSMCs. Results indicated that 10-1,000 nM amlodipine inhibited 1) thrombin-induced Ca(2+) mobilization from a thapsigargin-sensitive pool and 2) thapsigargin-induced Ca(2+) responses, including Ca(2+) mobilization from internal stores and store-operated Ca(2+) entry. These effects of amlodipine do not involve L-type Ca(2+) channels and could not be reproduced with 100 nM isradipine, diltiazem, or verapamil. The inhibition by amlodipine of Ca(2+) mobilization appears therefore to be a specific property of the drug, in addition to its Ca(2+) channel-blocking property. It is suggested that amlodipine acts in this capacity by interacting with Ca(2+)-ATPases of the sarcoplasmic reticulum, thus modulating the enzyme activity. This mechanism might participate in the inhibitory effect of amlodipine on VSMC growth.

Amlodipine↗

Potential role of macrophage colony-stimulating factor in the proliferation of DEL cells.

The replication and activation of both vascular smooth muscle cells and macrophages, which have previously entered the arterial wall, are key events in the atherosclerotic process. The importance of macrophage colony-stimulating factor (MCSF) in control of the growth/proliferation of both cell types confers to this compound a central role in the development of vascular lesions. In order to gain insight into the mechanisms of macrophage proliferation, we investigated the effect of MCSF upon the proliferation of DEL cells. DEL cells constitute a monocyte/histiocytic cell line that differentiates along a macrophage lineage following exposure to phorbol ester. DEL cells constitutively express MCSF, and its receptor MCSFR is encoded by c-fms. We examined whether MCSF might play a role in the proliferation of cultured DEL cells. [3H]Thymidine or 5-bromo-2-deoxyuridine (BrdU) incorporation was measured following the addition of recombinant MCSF or L929 cell supernatant (as a source of MCSF) to quiescent DEL cells. In DEL cells, serum-free L929 cell supernatant induced DNA synthesis in a dose-dependent manner, and such an effect could be blunted by pretreatment of L929 cell supernatant with anti-mouse MCSF antibody. In these cells, DNA synthesis could also be triggered in a dose-dependent manner by the addition of recombinant human MCSF (rh MCSF) or thrombin. These findings clearly show that MCSF influences DEL cell proliferation and suggest an autocrine loop activation. They indicate that MCSF plays an important role in the development of vascular lesions, which occur during atherosclerotic progression.

Cell Division↗

The inhibitory mechanisms of amlodipine in human vascular smooth muscle cell proliferation.

The abnormal proliferation of vascular smooth muscle cells (VSMCs) is closely related to vascular diseases. There is growing evidence that calcium antagonists inhibit VSMC growth/proliferation, yet their molecular mechanisms remain to be determined. Recent reports suggest that p42/p44 mitogen-activated protein kinases (MAPKs) play an important role in cell growth and proliferation induced by growth factors. This study was designed to determine whether these MAPKs are involved in VSMC proliferation induced by basic fibroblast growth factor (bFGF) and to examine the inhibitory effect of amlodipine. Human VSMCs were obtained from inner mammary artery. p42/p44 MAPKs activity was measured by immunoblotting assay using anti-p42/p44 phospho-MAPK antibody. 1) bFGF (20 ng/ml) significantly activated p42/p44 MAPKs with a peak time of 5-15 min, which was maintained for 3 h. PD98059 (100 nM-10 microM), a specific inhibitor of MAPK kinase, inhibited bFGF-induced p42/p44 MAPKs activation in a dose-dependent manner. 2) Amlodipine (1-100 nM) dose-dependently inhibited p42/p44 MAPKs activation by bFGF. 3) Amlodipine (10 nM) could inhibit both short-term and long-term p42/p44 MAPKs activation by bFGF. Our results indicate that bFGF could activate p42/p44 MAPKs. Amlodipine, which could inhibit bFGF-induced human VSMC proliferation, inhibited both short-term and sustained p42/p44 MAPKs activation by bFGF, suggesting that bFGF-induced VSMC proliferation may be related to p42/p44 MAPKs activation, and that the antiproliferative effect of amlodipine may be related to its inhibition of p42/p44 MAPKs activation.

Amlodipine↗

[Amlodipine and the mechanisms of vascular hypertrophy].

In several cardiovascular diseases, including hypertension, atherosclerosis and restenosis, an uncontrolled proliferation of smooth muscle cells from the arterial wall participates in the vascular hypertrophy that is often observed to be associated with these diseases. In this article, the mechanisms of smooth muscle cell activation and proliferation are briefly reviewed, focusing on the predominant role played by Ca2+ ions and the voltage-dependent Ca2+ channels in cellular Ca2+ homeostasis. In addition, the major alterations in pathways involved in smooth muscle cell activation and proliferation that have been observed in the cardiovascular diseases under discussion are reviewed. The effects of amlodipine on the molecular/cellular pathways discussed above are then presented. Finally, we discuss recent experimental results obtained with amlodipine, which make it an excellent candidate for the treatment of those cardiovascular diseases.

Amlodipine↗

Superoxide release from interleukin-1B-stimulated human vascular cells: in situ electrochemical measurement.

Release of superoxide anion by cultured vascular cells was investigated with the use of selective microelectrodes. Local concentration of superoxide anion (O2*-) was followed by differential pulse amperometry on a carbon microfiber at 0.1 V/SCE. The oxidation current allows O2*- detection in the 10(-8) M concentration range without interference of the other major oxygen species. Interleukin-1beta-stimulated O2*- release that progressively increased to reach local concentrations at the cell membrane level of 76 +/- 11 nm 40-60 min after stimulation in human cord vein endothelial cells, and 131 +/- 18 nm 1-2 h after stimulation in internal mammary artery smooth muscle cells. In the two types of cells, the O2*- oxidation signal was suppressed in the presence of superoxide dismutase. Spontaneous O2*-release from unstimulated cells was undetectable. These results demonstrate that selective microelectrodes allow direct and real-time monitoring of local O2*- released from vascular endothelial as well as from smooth muscle cells submitted to an inflammatory stimulus.

Cells, Cultured↗

Effects of BAY 10-6734 (Embusartan), a new angiotensin II type I receptor antagonist, on vascular smooth muscle cell growth.

Angiotensin II (AII), an important hypertrophic factor in the cardiovascular system, exerts most of its known effects in vivo through the AII receptor type 1 (AT1) subclass of AII receptors. These receptors are also responsible for the growth-related effects of AII in cultured vascular smooth muscle cells (VSMCs). We presently investigated the effects of BAY 10-6734 (Embusartan), a new orally active AT1 antagonist, on VSMC growth and proliferation of cultured VSMCs isolated from the aortae of Wistar Kyoto rats and spontaneously hypertensive rats. BAY 10-6734 and losartan (considered as AT1 receptor antagonist of reference), as well as their respective active metabolites, were studied for their inhibition of: 1) [125I]AII binding to its receptors, 2) AII-induced DNA and protein synthesis (by measuring the incorporation of 5-bromo-2'-deoxyuridine and [3H]L-leucine, respectively), and 3) AII-induced variations in intracellular Ca2+ concentration, using cells labeled with Fura-2. All of the tested compounds inhibited the aforementioned parameters in a concentration-dependent manner. Half-maximal inhibitory concentration values indicated that BAY 10-6734 was significantly more potent than losartan and that spontaneously hypertensive rat-derived VSMCs were more sensitive than Wistar Kyoto rat-derived ones. Neither BAY 10-6734 nor losartan affected the intracellular Ca2+ concentration of unstimulated VSMCs but both compounds inhibited both AII-induced Ca2+ mobilization from internal stores and Ca2+ influx. Neither compound affected arginine-vasopressin-, basic fibroblast growth factor-, or serum-induced DNA and protein synthesis. BAY 10-6734 appears therefore as a potent and specific new inhibitor of AII-induced growth-related events in VSMCs.

Angiotensin II↗

[Macrophage colony-stimulating factor production and c-fms expression in cultured rat aortic vascular smooth muscle cells].

The resulats of this study are as follows. (1) As measured by a bioassay, a macrophage colony-stimulating activity was detected in the serum-free conditioned medium of rat aortic vascular smooth muscle cells (VSMCs), which could be subdued by the addition of specific anti macrophage colony-stimulating factor (MCSF) antibody. (2) The presence of MCSF receptor was confirmed by immunocytochemistry using a specific anti c-Fms antibody. (3) The presence of mRNAs for MCSF and c-fms (which encoded MCSF receptor) was determined by Northern blot analysis. Their expressions were detectable in quiescent VSMCs and markedly increased after addition of serum. These data demonstrated for the first time the production of MCSF and the presence of MCSF receptor in cultured rat VSMCs. It is suggested that MCSF might modulate VSMCs functions via both autocrine and paracrine mechanisms. Rat VSMCs appear to be a suitable cell model for studying the cell proliferation effect of MCSF.

Animals↗

Automated neural network detection of wavelet preprocessed electrocardiogram late potentials.

The aim of the study is to investigate the potential of a feedforward neural network for detecting wavelet preprocessed late potentials. The terminal parts of a simulated QRS complex are processed with a continuous wavelet transform, which leads to a time-frequency representation of the QRS complex. Then, diagnostic feature vectors are obtained by subdividing the representations into several regions and by processing the sum of the decomposition coefficients belonging to each region. The neural network is trained with these feature vectors. Simulated ECGs with varying signal-to-noise ratios are used to train and test the classifier. Results show that correct classification ranges from 79% (high-level noise) to 99% (no noise). The study shows the potential of neural networks for the classification of late potentials that have been preprocessed by a wavelet transform. However, clinical use of this method still requires further investigation.

Arrhythmias, Cardiac↗

Amlodipine inhibition of serum-, thrombin-, or fibroblast growth factor-induced vascular smooth-muscle cell proliferation.

Atherosclerosis, like several other vascular diseases, exhibits structural and functional abnormalities resulting partially from an exaggerated proliferation of vascular smooth-muscle cells (VSMCs). Ca2+ channel blockers, such as amlodipine, have been suggested to retard or even prevent the progression of atherosclerosis. To determine the mechanisms involved in these effects, we investigated the influence of amlodipine on VSMC proliferation by using rat aortic VSMCs in culture. Amlodipine (0.1-10 microM) inhibited serum-, basic fibroblast growth factor (bFGF)-, and thrombin-induced VSMC proliferation and DNA synthesis in a concentration-dependent manner, as demonstrated by cell count and bromodeoxyuridine (BrdU)-incorporation measurements, respectively. Delayed addition of amlodipine after VSMC stimulation showed that the drug exerted its effect early in G1 phase of the cell cycle. This observation was confirmed by the finding that amlodipine did not influence DNA synthesis in VSMCs arrested to the G1/S boundary by hydroxyurea treatment. Consistent with its effects on VSMC growth/proliferation, amlodipine also decreased c-myc, c-fos, and c-jun protooncogene expression induced by serum, thrombin, or bFGF within 1 h after cell activation, as assessed by semiquantitative reverse transcriptase (RT)-polymerase chain reaction (PCR) analysis. The calcium channel agonist Bay K 8644, which counteracted the inhibition by nifedipine of bFGF-, thrombin- or serum-induced DNA synthesis, was ineffective to antagonize the inhibitory effect of amlodipine. The aforementioned effects of amlodipine were of similar amplitude, irrespective of the growth-enhancing agent used. This strongly indicates that amlodipine acts downstream of receptor activation to exert its antiproliferative action, probably early in the G1 phase of the cell cycle. Moreover, the lack of antagonistic effect between amlodipine and Bay K 8644 suggests that, in addition to its L-type Ca2+ channel inhibitory effect, amlodipine inhibits other intracellular signaling pathways. Such an interference of amlodipine with mitogenic signaling pathways might contribute to confer a blood vessel-protecting potential on amlodipine.

Amlodipine↗

L-phenylalanine and smooth muscle cell proliferation from SHR and WKY rats.

Cell growth and proliferation were evaluated in cultured vascular smooth muscle cells (VSMCs) isolated from spontaneously hypertensive rat (SHR) and normotensive Wistar-Kyoto (WKY) rat aortae by measuring [3H]-thymidine incorporation into newly synthesized DNA and by determining cell number, respectively. The results showed that in cultures from both rat strains (1) serum-, basic fibroblast growth factor (bFGF)- and thrombin-induced DNA synthesis were inhibited by L-phenylalanine dose-dependently; (2) L-phenylalanine inhibited cell proliferation in response to serum in a concentration-dependent manner; (3) L-phenylalanine inhibited serum-induced proto-oncogene c-fos and c-myc expression; (4) L-tyrosine, L-histidine and D-phenylalanine failed to mimic the inhibitory effect of L-phenylalanine. All these data demonstrate that L-phenylalanine could exert a direct and specific antiproliferative effect on VSMCs suggesting that such effect can account for the antihypertensive action of this amino acid observed in SHR.

Animals↗

Pharmacologic treatment of atherosclerosis: beyond lipid-lowering therapy.

Increased proliferation of intimal smooth muscle cells (SMCs), resulting in myointimal hyperplasia and luminal narrowing, is a characteristic of the early phase of atherogenesis. Since agents that reduce this process could potentially be considered as alternatives to lipid-lowering therapy in the prevention/treatment of atherosclerosis, it is of interest to elucidate the mechanisms involved in myointimal proliferation. This review focuses on the main mechanisms that control vascular SMC reactivity/proliferation with particular reference to spontaneously hypertensive rat-derived arterial cells, which exhibit exaggerated growth and hyperresponsiveness to stimuli compared with cells from normotensive Wistar-Kyoto rats. In view of the fact that overall cell reactivity is under the control of free Ca2+ ions, the beneficial effects of calcium antagonists on the prevention/treatment of atherosclerosis are discussed. In particular, the mechanisms whereby amlodipine--a vascular selective inhibitor of inward Ca2+ current carried by the L-type Ca2+ channels--can affect cell growth and exhibit antiatherogenic properties are reviewed.

Animals↗

Amlodipine and vascular hypertrophy.

In both atherosclerosis and arterial hypertension, structural and functional abnormalities result in vascular hypertrophy that is associated with an increased ratio of vascular media thickness to lumen diameter and hyperreactivity of vascular smooth muscle cells (VSMCs), resulting in uncontrolled cell migration and growth in vivo. In culture, VSMCs isolated from the spontaneously hypertensive rat (SHR) also display exaggerated growth and/or proliferation compared to VSMCs isolated from normotensive control Wistar Kyoto (WKY) rats. In vitro studies of cultured VSMCs can therefore be used as a model to investigate the mechanisms whereby a drug such as amlodipine can exert its antihypertensive and antiatherogenic effects. The present in vitro investigations examine the mechanisms whereby amlodipine reduces VSMC growth/proliferation promoted by basic fibroblast growth factor (bFGF), a peptide growth factor likely to participate in the vascular smooth muscle hypertrophy of the SHR. VSMCs from SHR and/or WKY rat aortae were isolated, passaged, and cultured. The influence of amlodipine on VSMC growth/proliferation was studied by measuring DNA synthesis and cell number under experimental conditions, which allowed us to determine the cell cycle phase in which amlodipine exerts its effects. Amlodipine was found to inhibit growth and bFGF-induced DNA synthesis in a concentration-dependent manner. Delayed addition of amlodipine showed that the drug exerts its effect early in the G1 phase, a result that was confirmed by the finding that amlodipine could not inhibit bFGF-induced DNA synthesis in VSMCs arrested at the G1/S boundary. In comparative experiments, the inhibitory effect of amlodipine on both cell growth and DNA synthesis was found to be of similar magnitude in SHR- and WKY-derived VSMCs. It is therefore likely that by modulating cell growth/proliferation induced by bFGF, amlodipine may reduce the vascular hypertrophy of the SHR. Since amlodipine also has been found to inhibit VSMC migration, one may reasonably envisage that these characteristics are important components of the antiatherogenic properties of the drug.

Amlodipine↗

Control of vascular smooth-muscle cell growth by macrophage-colony-stimulating factor.

Since in several vascular diseases abnormal vascular smooth-muscle cell (VSMC) proliferation is often associated with the presence of macrophages, we examined whether macrophage-colony-stimulating factor (M-CSF) might play a role in the control of VSMC growth. VSMCs were isolated from rat aorta and maintained in culture. Using a bioassay, a macrophage-colony-stimulating activity was detected in the serum-free supernatant of VSMCs, which could be inhibited by the addition of specific anti-M-CSF antibodies. The presence of M-CSF receptor protein and of M-CSF and M-CSF receptor gene transcripts was demonstrated by immunocytochemistry, using a specific anti-c-Fms antibody and Northern blot analysis respectively. [3H]Thymidine incorporation was measured following the addition to quiescent VSMCs of various dilutions of L929 cell supernatant (as a source of M-CSF) or of recombinant M-CSF. Both exogenous M-CSF and serum-free VSMC conditioned medium promoted DNA synthesis in a concentration-dependent manner, and this effect could be abrogated by the presence of a specific anti-M-CSF antibody. Under similar experimental conditions, L929 cell supernatant modulated proto-oncogene expression, as assessed by Northern blot analysis of c-fos, c-myc, egr-1 and junB. It was further demonstrated that M-CSF could act in synergy with thrombin, platelet-derived growth factor or basic fibroblast growth factor in promoting VSMC DNA synthesis. These results support the hypothesis that M-CSF affects the growth of cultured rat VSMCs through paracrine/autocrine mechanisms. Its effects at both the macrophage and the VSMC level confer to M-CSF a central role in the development of vascular lesions that occurs during atherosclerotic progression.

Actins↗

Molecular mechanisms of vascular hypertrophy in the spontaneously hypertensive rat.

1. In primary hypertension, an abnormally high vascular resistance can be explained in terms of alterations in vessel wall structure. Arterial cell hypertrophy and/or hyperplasia have been implicated as playing a central role in the vascular abnormalities noted in spontaneously hypertensive rats (SHR). Cultured arterial cells appear therefore as attractive models for studying in vitro the mechanisms whereby cells originating from hypertensives exhibit hyperproliferation and/or hyperresponsiveness. 2. This review summarized our present knowledge on growth and related biochemical events of cultured SHR-derived vascular smooth muscle cells or aortic adventitial fibroblasts, in response to various polypeptide growth factors and vasoactive agents. 3. Exaggerated growth response to various mitogens in cultured SHR-derived vascular cells has been well documented. However, the molecular mechanisms of abnormal growth in SHR remain unknown. This abnormality seems not to be a consequence of the alterations at the levels of receptors or of some key mitogenic events of early signalling pathways such as phospholipase C, protein kinase C and G-proteins. Further studies should therefore focus on the more distal events related to cell growth.

Animals↗

Mechanism of action of the inhibitory effect of nifedipine on the growth of cultured aortic cells from spontaneously hypertensive and normotensive rats.

1. To gain insight into the parameters which control vascular structure, we investigated the mechanisms whereby nifedipine, and other dihydropyridines, inhibit the growth of cultured fibroblasts isolated from the adventitia of the aorta of spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats. 2. The effects of nifedipine on cell proliferation and on serum-induced DNA synthesis were determined by measuring the cell number and the incorporation of [3H]-thymidine, respectively. The mechanism of action of nifedipine was studied by adding the drug either to randomly growing cells or to quiescent, G0/G1 arrested and synchronized cells. The effects of varying the duration of drug treatment were also examined. 3. In randomly growing cultures nifedipine, like other dihydropyridines concentration-dependently inhibited cell proliferation; the rank order of effect (measured at a concentration of 10 microM) was nifedipine > nisoldipine > nitrendipine approximately nimodipine. 4. In G0/G1 arrested cell cultures, nifedipine concentration-dependently inhibited serum-induced [3H]-thymidine incorporation. In this respect it had similar effects in cell cultures from WKY and SHR. In both SHR and WKY cultures, nifedipine delayed the transition from G0/G1 to S phase, and inhibited serum-induced DNA synthesis possibly by acting on the early G1 phase. 5. In cell cultures from both SHR and WKY, serum-induced DNA synthesis was similarly (approximately 40%) inhibited after a 1 day treatment with 10 microM nifedipine. In contrast, after 5 days treatment with the drug, the inhibition of DNA synthesis was approximately 65% and approximately 10% in SHR and WKY cultures, respectively. The inhibitory effects of nifedipine against proliferation of fibroblasts were 25% and 60%, respectively,after 1 and 5 days of treatment, and were similar in cells derived from SHR and WKY. This indicates that 5 days treatment with nifedipine inhibited the proliferation of SHR and WKY fibro blasts by acting mostly on the early G1 phase and the M phase, respectively.6. Irrespective of the duration of treatment (1 or 5 days) with 10 microM nifedipine, the inhibition of DNA synthesis could be abolished and partially reduced by Bay K 8644 (1 microM) in WKY and SHR fibroblasts,respectively. In cell cultures from both SHR and WKY the inhibitory effects of a short term and of along term treatment with nifedipine against cell proliferation were reduced and unaffected, respectively by Bay K 8644.7. These results indicate that nifedipine inhibited cell proliferation and serum-induced DNA synthesis by altering the cell cycle through different mechanisms in SHR and WKY fibroblasts. They also suggest the existence in aortic fibroblasts of interactions between calcium channel blockers of the dihydropyridine series and the mitogenic signalling pathways of growth factors contained in serum.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗