Biomedical subjects

J Waltenberger

Publications and source records attributed to J Waltenberger.

At least 37 records · Page 2Linked to original sources

PubMed2000

Vascular endothelial growth factor (VEGF)-driven actin-based motility is mediated by VEGFR2 and requires concerted activation of stress-activated protein kinase 2 (SAPK2/p38) and geldanamycin-sensitive phosphorylation of focal adhesion kinase.

In endothelial cells, vascular endothelial growth factor (VEGF) induces an accumulation of stress fibers associated with new actin polymerization and rapid formation of focal adhesions at the ventral surface of the cells. This cytoskeletal reorganization results in an intense motogenic activity. Using porcine endothelial cells expressing one or the other type of the VEGF receptors, VEGFR1 or VEGFR2, or human umbilical vein endothelial cells pretreated with a VEGFR2 neutralizing antibody, we show that VEGFR2 is responsible for VEGF-induced activation of the stress-activated protein kinase-2/p38 (SAPK2/p38), phosphorylation of focal adhesion kinase (FAK), and enhanced migratory activity. Activation of SAPK2/p38 triggered actin polymerization whereas FAK, which was phosphorylated independently of SAPK2/p38, initiated assembly of focal adhesions. Both processes contributed to the formation of stress fibers. Geldanamycin, an inhibitor of HSP90 blocked tyrosine phosphorylation of FAK, assembly of focal adhesions, actin reorganization, and cell migration, all of which were reversed by overexpressing HSP90. We conclude that VEGFR2 mediates the physiological effect of VEGF on cell migration and that two independent pathways downstream of VEGFR2 regulate actin-based motility. One pathway involves SAPK2/p38 and leads to enhanced actin polymerization activity. The other involves HSP90 as a permissive signal transduction factor implicated in FAK phosphorylation and assembly of focal adhesions.

Actins↗

PubMed2000

Elevation of vascular endothelial growth factor-A serum levels following acute myocardial infarction. Evidence for its origin and functional significance.

Following the onset of acute myocardial infarction (AMI), a number of serum parameters show well-defined changes reflecting myocardial injury. During the consecutive repair phase, compensatory processes are initiated including the formation of a collateral circulation on the basis of angiogenesis and arteriogenesis. An important angiogenic factor is vascular endothelial growth factor-A (VEGF-A), shown to be upregulated in the ischemic myocardium. It is unclear, however, whether acute myocardial ischemia leads to a detectable elevation of VEGF-A serum concentrations. With the use of an immunoradiometric assay, we measured the levels of VEGF-A in the serum of patients after AMI at defined time intervals, of patients with unstable angina pectoris (UAP) and of healthy individuals. In addition, in a small group of patients with subacute myocardial infarction VEGF-A concentrations were measured in coronary sinus blood. The data are given as median followed by the 25th and 75th percentiles. In the group with AMI serum VEGF-A measured 105 [78; 176] pg/ml on day 1 and 114 pg/ml [72; 163] pg/ml on day 3 after onset of AMI. Serum levels of VEGF-A significantly increased on day 7 after AMI to 189 [119; 373] pg/ml (P=0.0103) and on day 10 to 255 [162; 371] pg/ml (P=0.0007). The VEGF-A serum level in healthy controls and in patients with UAP measured 98 [75; 137] pg/ml and 116 [57; 140] pg/ml, respectively. Serum at day 10 after AMI contained VEGF-A at a biologically relevant concentration capable of stimulating proliferation of endothelial cells. Surprisingly, VEGF-A serum levels were similar in samples taken from the coronary sinus with 61 [43; 83] pg/ml. Therefore the main source for VEGF-A in the blood stream is not the infarcted myocardium. However, the number of platelets, a rich source of VEGF-A, is significantly increased after myocardial infarction, i.e. 284 [252; 363] x 10(9)/litre v 220 [177; 250] x 10(9)/litre. In conclusion, the time course of VEGF-A elevation following AMI strongly suggests that VEGF-A plays a role as an endogenous activator of coronary collateral formation in the human heart. The most likely source of the elevated VEGF-A are platelets, rather than the infarcted myocardium.

Acute Disease↗

PubMed2000

[Regulation of the endothelial function and angiogenesis by vascular endothelial growth factor-A (VEGF-A].

VEGF-A (vascular endothelial growth factor-A) is an endothelial-specific growth factor that stimulates endothelial function and angiogenesis. VEGF-A plays an important role during development of the vascular system, wound healing, vascularization of tumors, and for angiogenesis in ischemic tissues including the heart. VEGF-A stimulates many actions of endothelial cells including proliferation, migration, and nitric oxide release via binding to and activation of the two primarily endothelial-specific receptor-tyrosine kinases KDR and Flt-1. KDR and Flt-1 stimulate multiple signal transduction pathways in endothelial cells. This review provides an overview of the role of VEGF-A in the regulation of endothelial function, angiogenesis, and arteriogenesis with regard to activation of signal transduction pathways and their functional consequences in the endothelium. Moreover, this article discusses recent developments exploring the therapeutic potential of VEGF-A for treatment of cardiovascular diseases.

Adult↗

PubMed2000

Local delivery of platelet-derived growth factor receptor-specific tyrphostin inhibits neointimal formation in rats.

Signal transduction through the platelet-derived growth factor (PDGF)/PDGF receptor (PDGFR) system is involved in the process of postangioplasty restenosis. Tyrphostins are low molecular weight inhibitors of protein tyrosine kinases. We assessed the antiproliferative effects of PDGFRbeta-specific tyrphostin AG-1295 in vitro and in vivo. AG-1295 significantly inhibited rat smooth muscle cell growth stimulated by PDGF-BB or FCS. This antiproliferative effect was paralleled by reversible reduction of the total phosphotyrosine level and the degree of PDGFRbeta phosphorylation by the drug in vitro. Local sustained delivery of the drug from perivascularly implanted polymeric matrices resulted in focal AG-1295 levels of 711 and 29.1 ng/mg of dry arterial tissue 1 and 14 days after implantation in rats. AG-1295 delivered from polymeric matrices resulted in a 35% reduction of neointimal formation on day 14 after balloon injury in the rat carotid model. Tyrosine phosphorylation of certain transduction proteins in arterial tissue extracts was significantly upregulated by balloon injury on day 3 but was essentially returned to or below basal levels 14 days after injury. Tyrphostin treatment decreased tyrosine phosphorylation at both time points below the basal levels. Moreover, the enhancement of PDGFRbeta expression 3 and 14 days after arterial injury was strongly inhibited by AG-1295 treatment. It can be concluded that AG-1295 reduces neointimal formation by inhibiting PDGFbeta-triggered tyrosine phosphorylation.

Angioplasty, Balloon↗

PubMed2000

C-reactive protein in the arterial intima: role of C-reactive protein receptor-dependent monocyte recruitment in atherogenesis.

Infiltration of monocytes into the arterial wall is an early cellular event in atherogenesis. Recent evidence shows that C-reactive protein (CRP) is deposited in the arterial intima at sites of atherogenesis. In this study, we demonstrate that CRP deposition precedes the appearance of monocytes in early atherosclerotic lesions. CRP is chemotactic for freshly isolated human blood monocytes. A specific CRP receptor is demonstrated on monocytes in vitro as well as in vivo, and blockage of the receptor by use of a monoclonal anti-receptor antibody completely abolishes CRP-induced chemotaxis. CRP may play a major role in the recruitment of monocytes during atherogenesis.

Antibodies, Monoclonal↗

PubMed2000

Inhibition of VEGF receptors causes lung cell apoptosis and emphysema.

Pulmonary emphysema, a significant global health problem, is characterized by a loss of alveolar structures. Because VEGF is a trophic factor required for the survival of endothelial cells and is abundantly expressed in the lung, we hypothesized that chronic blockade of VEGF receptors could induce alveolar cell apoptosis and emphysema. Chronic treatment of rats with the VEGF receptor blocker SU5416 led to enlargement of the air spaces, indicative of emphysema. The VEGF receptor inhibitor SU5416 induced alveolar septal cell apoptosis but did not inhibit lung cell proliferation. Viewed by angiography, SU5416-treated rat lungs showed a pruning of the pulmonary arterial tree, although we observed no lung infiltration by inflammatory cells or fibrosis. SU5416 treatment led to a decrease in lung expression of VEGF receptor 2 (VEGFR-2), phosphorylated VEGFR-2, and Akt-1 in the complex with VEGFR-2. Treatment with the caspase inhibitor Z-Asp-CH(2)-DCB prevented SU5416-induced septal cell apoptosis and emphysema development. These findings suggest that VEGF receptor signaling is required for maintenance of the alveolar structures and, further, that alveolar septal cell apoptosis contributes to the pathogenesis of emphysema.

Angiography↗

PubMed1999

A novel function of VEGF receptor-2 (KDR): rapid release of nitric oxide in response to VEGF-A stimulation in endothelial cells.

VEGF-A induces angiogenesis and regulates endothelial function via production and release of nitric oxide (NO), which is produced by endothelial nitric oxide synthase (eNOS). While the upregulation of eNOS expression has been shown to be mediated via VEGF receptor KDR, there is controversy about which of the VEGF receptors triggers the release of nitric oxide in endothelial cells. In order to determine the levels of NO produced in response to VEGF-A stimulation in different endothelial cells, a reporter assay measuring the formation of cGMP as the direct product of NO-induced activation of guanylate cyclase was performed. Using two independent experimental strategies, we were able to prove that VEGF receptor KDR, but not VEGF receptor Flt-1, can induce NO release in endothelial cells. First, we made use of porcine aortic endothelial cells (PAE) expressing either KDR or Flt-1. While KDR-expressing PAE/KDR cells responded to VEGF-A stimulation with a significant elevation of intracellular cGMP already after 2 min, Flt-1-expressing PAE/Flt-1 cells did not show any signal in this RIA-based cGMP assay. In a second experimental strategy freshly isolated human umbilical vein endothelial cells (HUVEC) were stimulated either with the KDR-specific ligand VEGF-E or with the Flt-1-specific ligand PIGF-2. VEGF-E induces cGMP elevation in this setting, while PIGF-2 was unable to do so, clearly demonstrating that KDR is responsible for NO release in endothelial cells. In our assays cGMP formation is fully dependent on NO generation since the NOS inhibitor L-NAME can block this VEGF-A-induced action. These data show that the VEGF receptor KDR is responsible for NO release in endothelial cells, highlighting a new function of KDR and further supporting the importance of KDR in the regulation of the vasculature.

Animals↗

PubMed1999

A dual inhibitor of platelet-derived growth factor beta-receptor and Src kinase activity potently interferes with motogenic and mitogenic responses to PDGF in vascular smooth muscle cells. A novel candidate for prevention of vascular remodeling.

PP1 has previously been described as an inhibitor of the Src-family kinases p56(Lck) and FynT. We have therefore decided to use PP1 to determine the functional role of Src in platelet-derived growth factor (PDGF)-induced proliferation and migration of human coronary artery smooth muscle cells (HCASMCs). A synthetic protocol for PP1/AGL1872 has been developed, and the inhibitory activity of PP1/AGL1872 against Src was examined. PP1/AGL1872 potently inhibited recombinant p60(c-src) in vitro and Src-dependent tyrosine phosphorylation in p60(c-srcF572)-transformed NIH3T3 cells. PP1/AGL1872 also potently inhibited PDGF-stimulated migration of HCASMCs, as determined in the modified Boyden chamber, as well as PDGF-stimulated proliferation of HCASMCs. Surprisingly, in addition to inhibition of Src kinase, PP1/AGL1872 was found to inhibit PDGF receptor kinase in cell-free assays and in various types of intact cells, including HCASMCs. PP1/AGL1872 did not inhibit phosphorylation of the vascular endothelial growth factor receptor KDR (VEGF receptor-2; kinase-insert domain containing receptor) in cell-free assays as well as in intact human coronary artery endothelial cells. In line with the insensitivity of KDR, PP1/AGL1872 had only a weak effect on vascular endothelial growth factor-stimulated migration of human coronary artery endothelial cells. On treatment of cells expressing different receptor tyrosine kinases, the activities of the epidermal growth factor receptor, fibroblast growth factor receptor-1, and insulin-like growth factor-1 receptor were resistant to PP1/AGL1872, whereas PDGF alpha-receptor was susceptible, albeit to a lesser extent than PDGF beta-receptor. These data suggest that the previously described tyrosine kinase inhibitor PP1/AGL1872 is not selective for the Src family of tyrosine kinases. It is also a potent inhibitor of the PDGF beta-receptor kinase but is not a ubiquitous tyrosine kinase inhibitor. PP1/AGL1872 inhibits migration and proliferation of HCASMCs probably by interference with 2 distinct tyrosine phosphorylation events, creating a novel and potent inhibitory principle with possible relevance for the treatment of pathological HCASMC activity, such as vascular remodeling and restenosis.

3T3 Cells↗

PubMed1999

Molecular mediators of tumor angiogenesis: enhanced expression and activation of vascular endothelial growth factor receptor KDR in primary breast cancer.

The progression of breast cancer growth and its ability to metastasize are associated with the process of angiogenesis. In this study, we examined the protein expression of vascular endothelial growth factor (VEGF) and its specific and functional receptor KDR in human breast tissue. We investigated a total of 13 mammary carcinomas, 3 fibroadenomas, 5 specimens with fibrocystic breast disease as well as normal (adjacent to malignant) breast tissue using immunohistochemistry and Western blot analysis. In all carcinomas examined, functional KDR protein was present independent of tumor type, tumor stage and histological grade as demonstrated by tyrosine phosphorylation analysis of KDR. When malignant tissues were compared with their neighboring non-neoplastic regions, activated KDR was found to be expressed to a much higher extent within the malignant tissue samples. In fibroadenomas, KDR was barely detectable, whereas in fibrocystic breast disease KDR expression was variable. Immunostaining of KDR was localized to endothelium and epithelium of mammary ducts in malignant and benign breast tissue, while VEGF immunoreactivity was primarily found in the endothelium and also in tumor cells and macrophages. Our data demonstrate that KDR activation is enhanced in breast cancer in vivo and emphasize the functional role of VEGF and KDR in the development of malignant breast disease.

Breast Neoplasms↗

PubMed1999

A novel vascular endothelial growth factor encoded by Orf virus, VEGF-E, mediates angiogenesis via signalling through VEGFR-2 (KDR) but not VEGFR-1 (Flt-1) receptor tyrosine kinases.

The different members of the vascular endothelial growth factor (VEGF) family act as key regulators of endothelial cell function controlling vasculogenesis, angiogenesis, vascular permeability and endothelial cell survival. In this study, we have functionally characterized a novel member of the VEGF family, designated VEGF-E. VEGF-E sequences are encoded by the parapoxvirus Orf virus (OV). They carry the characteristic cysteine knot motif present in all mammalian VEGFs, while forming a microheterogenic group distinct from previously described members of this family. VEGF-E was expressed as the native protein in mammalian cells or as a recombinant protein in Escherichia coli and was shown to act as a heat-stable, secreted dimer. VEGF-E and VEGF-A were found to possess similar bioactivities, i.e. both factors stimulate the release of tissue factor (TF), the proliferation, chemotaxis and sprouting of cultured vascular endothelial cells in vitro and angiogenesis in vivo. Like VEGF-A, VEGF-E was found to bind with high affinity to VEGF receptor-2 (KDR) resulting in receptor autophosphorylation and a biphasic rise in free intracellular Ca2+ concentration, whilst in contrast to VEGF-A, VEGF-E did not bind to VEGF receptor-1 (Flt-1). VEGF-E is thus a potent angiogenic factor selectively binding to VEGF receptor-2. These data strongly indicate that activation of VEGF receptor-2 alone can efficiently stimulate angiogenesis.

Amino Acid Sequence↗

PubMed1999

Neovascularization in the human heart is associated with expression of VEGF-A and its receptors Flt-1 (VEGFR-1) and KDR (VEGFR-2). Results from cardiomyopexy in ischemic cardiomyopathy.

Cardiomyopexy is a novel means of revascularization in end-stage ischemic heart disease leading to neovascularization and increased perfusion of the damaged heart. So far, the mediators of this process have not yet been identified. However, among others, vascular endothelial growth factor-A (VEGF-A) is a strong candidate for inducing this process. We have performed cardiomyopexy in humans by transplanting a flap of the musculus latissimus dorsi onto the epicardium. One of the patients died 7 weeks after cardiomyopexy due to a septic process unrelated to the underlying cardiac disease. Tissue specimen from the transplanted muscle flap, from the myocardium and from the native musculus latissimus dorsi were analysed by histological and immunohistochemical methods. The transplanted muscle appeared severely degenerated and showed no immunoreactivity for von Willebrandt factor (vWF) and for VEGF-A nor for its receptors KDR and Flt-1. However, a granulation zone had developed next to the transplanted muscle enriched with monocytes and macrophages which is characterized by a network of capillaries reaching into the ischemic myocardium and providing evidence for strong induction of angiogenesis. This process is accompanied by the abundance of VEGF-A expression in the endothelial layer of vessels. In parallel, VEGF-receptor KDR is present in capillaries passing into the subepicardial region supporting the idea of VEGF-A-induced angiogenesis. The spatial expression pattern of VEGF-A and KDR suggests VEGF-A to be a promotor of angiogenesis leading to indirect myocardial revascularization.

Journal Article↗

PubMed1999

Protein kinase C mediates basic fibroblast growth factor-induced proliferation through mitogen-activated protein kinase in coronary smooth muscle cells.

Proliferation of coronary smooth muscle cells (cSMCs) contributes to the pathogenesis of arteriosclerosis and restenosis after angioplasty, and basic fibroblast growth factor (bFGF) is a powerful mitogen for cSMCs. In this study, we investigated the involvement of mitogen-activated protein kinase (MAPK), protein kinase C (PKC), and the transcription factor c-myc in bFGF-stimulated mitogenesis, as well as the functional relationship between these factors. cSMC stimulation with bFGF resulted in phosphorylation of p42 MAPK, as well as the phosphorylation and increased expression of c-myc. The MAPK kinase (MEK) inhibitor PD98059 blocked bFGF-stimulated MAPK phosphorylation and resulted in both a decrease of c-myc expression and inhibition of bFGF-stimulated DNA synthesis in cSMCs. bFGF also increased PKC activity in cSMCs in a time-dependent manner. The inhibition of PKC by chelerythrine or its downregulation by phorbol 12-myristate 13-acetate (PMA) inhibited bFGF-induced DNA synthesis and blocked the phosphorylation of MAPK and c-myc expression in response to bFGF. This indicates an involvement of phorbol ester-sensitive PKC isoforms in MAPK activation and mitogenic signaling by bFGF. Western blot analysis revealed the presence of the phorbol ester-sensitive isoforms PKC alpha, epsilon, and gamma as well as the PKC isoforms iota, lambda, micro, and zeta in cSMCs. In this study, we show that the MAPK cascade is required for bFGF-induced proliferation and that phorbol ester-sensitive PKC isoforms contribute to the bFGF-induced cSMC mitogenesis in cSMCs.

Animals↗

PubMed1999

The coronary endothelium: a target for vascular endothelial growth factor. Human coronary artery endothelial cells express functional receptors for vascular endothelial growth factor in vitro and in vivo.

Vascular endothelial growth factor (VEGF) is an angiogenic peptide that can stimulate endothelial cell proliferation and migration in vitro and collateral development in ischemic organs in vivo. Although postulated, the expression of functional VEGF receptors in the heart has not been demonstrated yet. To prove this hypothesis and to extend the molecular basis of myocardial angiogenesis, we have characterized the expression and function of VEGF receptors in human coronary artery endothelial cells (HCAEC) and in human heart tissue. VEGF strongly induces proliferation and migration of HCAEC. These cells express transcripts of the two VEGF receptors KDR and Flt-1. Their expression levels are higher in HCAEC as compared with human umbilical vein endothelial cells. In HCAEC, VEGF stimulates phosphorylation of KDR in a concentration-dependent manner proving that KDDR is a functional receptor tyrosine kinase. Scatchard analysis demonstrated the presence of the high affinity receptor Flt-1 in HCAEC with a kd of 8 pM. Flt-1 protein could be visualized as a single band corresponding to a size of 210 kd. In addition mature KDR protein could be detected in adult human heart. Taken together, HCAEC and human heart tissue express high levels of functional VEGF receptors. These results broaden the molecular basis for understanding and manipulating VEGF-induced endothelial function and angiogenesis in the coronary circulation.

Animals↗

PubMed1998

VEGF-A induces expression of eNOS and iNOS in endothelial cells via VEGF receptor-2 (KDR).

Vascular Endothelial Growth Factor-A (VEGF-A) is an endothelial-specific growth factor that induces angiogenesis, i.e., sprouting of capillaries from preexisting vessels in vivo. Endothelial nitric oxide synthase (eNOS) is an essential molecule in mediating VEGF-A-induced angiogenesis and endothelial function via production of nitric oxide (NO). Moreover, the protein level of eNOS is upregulated in response to VEGF-A. While VEGF-A-induced NO release in human trophoblast cells appears to be initiated via VEGF receptor-1, it is not clear which of the VEGF-receptors is mediating the signal for induction of eNOS protein expression. In addition, it is unclear whether other NOS isoforms are upregulated in response to VEGF-A stimulation. To address these questions, we stimulated human umbilical vein endothelial cells (HUVEC) with VEGF-A for 24 hours and evaluated expression of eNOS and iNOS protein. VEGF-A induces expression of both members of the NOS family. Using porcine aortic endothelial cells overexpressing either VEGF receptor-2 (PAE/KDR cells) or VEGF receptor-1 (PAE/Flt-1 cells), we have studied the regulation of iNOS and eNOS expression in response to VEGF-A stimulation. The activation of VEGF receptor-2 leads to an upregulation of both eNOS and iNOS protein, while stimulation of VEGF receptor-1 did not generate such a signal. Therefore, only VEGF receptor-2 mediates stimulation of eNOS and iNOS expression. We conclude that the two VEGF receptors have different and distinct functions regarding NO formation and NO release during VEGF-A-induced angiogenesis.

Animals↗

PubMed1998

Differential binding characteristics and cellular inhibition by soluble VEGF receptors 1 and 2.

The FLT-1 and KDR genes encode transmembrane tyrosine kinases which function as high-affinity receptors for vascular endothelial growth factor (VEGF). We have used the baculovirus system to express the extracellular parts of the FLT-1 receptor and KDR receptor in soluble form (sFLT-1 and sKDR), for in vitro binding and competition assays. Here, we show that the binding of VEGF165 to sKDR but not sFLT-1 is dependent on heparin, regardless of whether VEGF165 or sKDR is immobilized. Further, only sFLT-1 acts as a receptor antagonist in solution and sKDR can neither compete with the binding of VEGF165 to human endothelial cells carrying both receptors nor block VEGF165 induced mitogenicity. Soluble KDR only partially inhibits cell migration even at high concentrations, in contrast to sFLT which can almost completely block (82%) VEGF-induced cell proliferation and migration. Taken together these results show that the two soluble VEGF receptor proteins, sFLT-1 and sKDR, despite binding the same ligand, behave very differently when immobilized with regard to their dependence on heparin for VEGF binding. In solution their respective ability to function as receptor antagonists is also strikingly different, possibly a reflection of their different dependency on heparin.

Animals↗

PubMed1998

PDGF-receptor tyrosine kinase blocker AG1295 selectively attenuates smooth muscle cell growth in vitro and reduces neointimal formation after balloon angioplasty in swine.

BACKGROUND: Signaling through protein tyrosine kinases (PTKs) is a major contributor to the transmission of mitogenic stimuli to the interior of the cell and nucleus. The present study was designed to determine the effect of the tyrphostin AG1295, a selective blocker of PDGF-receptor PTK, on the growth of porcine and human smooth muscle cells (SMCs) in culture, on the outgrowth kinetics of SMCs from porcine and human arterial explants, and on neointimal formation after balloon injury in pigs. METHODS AND RESULTS: SMCs for culture were obtained from porcine abdominal aortas, human internal mammary arteries, and endarterectomy tissue from a single human carotid artery. Addition of AG1295 to SMCs before PDGF stimulation completely inhibited PDGF-beta-receptor tyrosine phosphorylation without affecting the level of PDGF-beta-receptor. AG1295 resulted in a selective, reversible inhibition of SMC proliferation in culture (76%) with only mild (13.5%) inhibition of endothelial cell proliferation. The number of SMCs accumulating around explants of porcine carotid arteries and human endarterectomy specimens 12, 15, 19, 22, and 24 days after plating was reduced by 82% to 92% in AG1295-treated compared with nontreated specimens, and initiation of SMC outgrowth was markedly delayed. The numbers of cells accumulated 10 days after initiation of outgrowth were significantly lower in treated versus control explants. Local intravascular delivery of AG1295-impregnated polylactic acid-based nanoparticles (130+/-25 nm) to the site of balloon injury to porcine femoral arteries resulted in significant reductions in intima/media area ratio and luminal cross-sectional area narrowing by neointima compared with contralateral control arteries to which empty nanoparticles were applied (0.15+/-0.07 versus 0.09+/-0.03, P=.046 and 20+/-4% versus 10+/-4%, P=.0009, n=6 for both). CONCLUSIONS: The tyrphostin AG1295, a selective blocker of PDGF-receptor kinase, exerts a marked inhibitory effect on the activation, migration, and proliferation of porcine and human SMCs in vitro and an approximately 50% inhibitory effect on neointimal formation after balloon injury in porcine femoral arteries when delivered via biodegradable nanoparticles. Further studies appear to be warranted to evaluate the applicability of this novel approach to the interventional setting.

Angioplasty, Balloon↗

PubMed1998

[Prospects of gene therapy in treatment of coronary heart disease].

Gene therapy describes the transfer of genetic material into a cell for therapeutic purposes. This opens new therapeutic perspectives for cardiovascular medicine. It includes the inhibition of restenosis following angioplasty, e.g., by transfer of suicide genes such as CMV-thymidine kinase or by inhibition of the cell cycle of cells within the vessel wall. On the other hand, there is promising data concerning the induction of therapeutic angiogenesis using the transfer of angiogenic genes such as the one for vascular endothelial growth factor VEGF. During the past three years significant progress was made by a number of preclinical studies. On the other hand, the therapeutic success of gene therapy in humans is still missing, and this is true for all different strategies tested so far. Important and basic issues of gene transfer and the resulting cellular response need to be solved before a therapeutic use might become a routine procedure. In the meanwhile, an important focus of the experimental work lies in the identification and characterization of molecular targets for therapeutic interventions, another in the improvement of gene transfer systems. Such work will provide new information about the biology of cellular and viral structures including their functional interrelation; in addition a better insight into the pathogenesis of the various disease processes should be obtained.

Animals↗

PubMed1998

Modulation of Ca2+-activated K+ channels in human vascular cells by insulin and basic fibroblast growth factor.

Insulin and basic fibroblast growth factor (bFGF) play an important role in the pathogenesis of atherosclerosis and have been shown to have vasodilatory effects. Since modulation of vascular ion channels determines membrane potential and thereby influences essential Ca2+-dependent intracellular pathways, we have investigated the effect of insulin and bFGF on Ca2+-activated K+ channels (BKCa) in human umbilical vein endothelial cells (HUVEC) and smooth muscle cells. The latter were obtained from either atherosclerotic plaques (SMCP) or from media segments (SMCM) of human coronary arteries. Using the patch-clamp technique, insulin (100 microU/ml) caused a significant increase in BKCa open-state probability in SMCP and HUVEC, whereas no significant changes were observed in SMCM. Basic FGF (30 ng/ml) revealed a significant increase in BKCa activity in HUVEC and a significant decrease in the BKCa open-state probability in SMCP, but caused no changes in SMCM. Thus, growth factors modulate vascular BKCa in a cell-type specific manner, which may be of importance concerning vasoactive and atherogenic effects of growth factors.

Arteriosclerosis↗