Adriane Skaletz-Rorowski

Heparin-Induced Overexpression of Basic Fibroblast Growth Factor, Basic Fibroblast Growth Factor Receptor, and Cell-Associated Proteoheparan Sulfate in Cultured Coronary Smooth Muscle Cells

Basic fibroblast growth factor (bFGF), a potent mitogen for arterial smooth muscle cells (SMCs), plays a pivotal role in the pathogenesis of arteriosclerosis and restenosis. Heparin in nanogram quantities may promote or even be required for binding of bFGF to its cognate receptor. Conversely, heparin in microgram doses is a strong inhibitor of arterial SMC replication in vitro and in vivo. Bovine coronary SMCs (cSMCs) express bFGF, bFGF receptor (FGF-R1), and cell membrane-integrated proteoheparan sulfate (HSPG). These three molecules are known to form a trimolecular complex that promotes signal transduction and mitogenesis. The bFGF synthesized by cSMCs is distributed to an intracellular and a pericellular compartment. Resting cultured cells retain about 80% of their bFGF intracellularly; 20% is found in the pericellular region. During proliferation, 70% to 80% of total bFGF is expressed in the pericellular compartment. Trypsinization generates soluble forms of the complex of bFGF with the ectodomains of the bFGF receptor and cell membrane-integrated HSPG in the pericellular compartment, thus allowing quantification of pericellular bFGF by a highly specific enzyme immunoassay. Standard heparin inhibits the proliferation of cSMCs by up to 80% in a concentration range between 10 and 100 micrograms/mL medium in a dose-dependent manner but increases the protein content of cSMCs compared with proliferating control cells. The heparin-induced increase in cellular protein content includes a 60% to 100% increase in the expression of pericellular bFGF, FGF-R1, and cell membrane-integrated HSPG. Thus, under heparin treatment, the heparan sulfate side chains of cell membrane-integrated HSPG incorporate more [35S]sulfate, and the proportion of [35S]heparan sulfate among total glycosaminoglycans increases from 36% to 52%. Fluorescence-activated cell sorting analysis and [3H]thymidine incorporation experiments provide evidence for multiple effects of heparin, including blocks at early and late checkpoints of the cell cycle in heparin-treated cells. These results indicate that heparin, despite its anti-proliferative potency, stimulates the expression of all components of the bFGF system even in coronary SMCs in which growth is inhibited.

Direct evidence for the importance of p130 in injury response and arterial remodeling following carotid artery ligation

OBJECTIVE Remodeling of arterial morphology in atherosclerosis, hypertension, and restenosis following angioplasty involves controlled alterations in total vascular circumference which critically modulate sequelae of changes in vessel wall mass. Despite the clinical relevance of this process little is known about the pathophysiology, especially the correlation between smooth muscle cell proliferation and remodeling. METHODS Carotid artery ligation was applied to mice with targeted disruption of the p130 gene (p130 -/-). Mice were allowed to recover for 3 weeks after ligation and then perfusion fixed for histologic and morphometric analysis. RESULTS P130 -/- mice were indistinguishable from control littermates concerning size and weight. As for the aorta, carotid arteries and femoral arteries, no significant differences were found between the groups with regard to vessel size and cellular density of the vessel wall of non-instrumented vessels. In contrast, following carotid artery ligation we found p130 -/- mice (n=8) to develop a significant increase in vessel wall area compared to controls (n=9). Mean values ranged from 3.07 x 10(-2)+/-0.20 x 10(-2)-3.56 x 10(-2)+/-0.62 x 10(-2) mm(2) for p130 -/- mice versus 2.26 x 10(-2)+/-0.13 x 10(-2)-2.57 x 10(-2)+/-0.26 x 10(-2) mm(2) for controls (p=0.02) along the lesion studied. This increase in vessel wall area was primarily due to a sevenfold mean increase in neointima in p130 -/- mice yielding mean values of 0.43+/-0.18 - 1.19+/-0.70 x 10(-2) mm(2). Remarkably, despite vessel wall increase, the lumen area was not statistically different for both groups. CONCLUSIONS The data indicate that the loss of the cell cycle inhibitor p130 leads to an enhanced injury response, implicating a central role of p130 in cell cycle control during response to injury in the vessel wall. The enhanced injury response in the context of p130 -/- preserves the ability to perform perfect remodeling, thus the remodeling capacity is preserved even in the context of this injury model.

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.

Paclitaxel and cyclosporine A show supra-additive antiproliferative effects on smooth muscle cells by activation of protein kinase C

Abstract We intended to establish a pharmacologic concept of synergistic antiproliferative effects on smooth muscle cells (SMC) by using paclitaxel and cyclosporine A at clinically applicable doses. Coronary SMC were incubated with paclitaxel and cyclosporine A at concentrations of 10 – 20 nmol/L and 83 – 415 nmol/L, respectively. Antiproliferative effects were assessed by cell counts, [3H]thymidine incorporation and cell cycle analysis. In addition, apoptosis was studied by cytoplasmic histone-associated DNA fragments and in vitro protein kinase C activity (PKC) was determined by immunoassay. We found paclitaxel and cyclosporine A to exert a highly supra-additive antiproliferative effect on SMC with significant reductions of cell counts (p < 0.01) and [3H]thymidine incorporation (p < 0.05). SMC were found to be arrested at the G2/M transition. This antiproliferative effect was observed in the absence of DNA fragmentation above values obtained for single compound treatment, which had virtually no impact on cell proliferation. DNA fragmentation started to increase at a drug combination comprising paclitaxel at the higher dose of 20 nmol/L. Under the treatment with both paclitaxel and cyclosporine A, PKC activity showed a 1.8-fold increase (p < 0.05) compared with untreated controls. In conclusion, PKC mediates supra-additive antiproliferative effects of paclitaxel and cyclosporine A on SMC. The data demonstrate a highly efficient pharmacologic concept for the inhibition of SMC proliferation. Further studies are needed to test this concept under in vivo conditions for the prevention of restenosis or transplant vasculopathy by systemic application of cyclosporine A – when already applied for immunosuppressive purposes – and local delivery of paclitaxel.

Lovastatin blocks basic fibroblast growth factor-induced mitogen-activated protein kinase signaling in coronary smooth muscle cells via phosphatase inhibition

We have recently reported that the activation of mitogen-activated protein kinase (MAPK) through specific protein kinase C (PKC) isoforms is required for basic fibroblast growth factor (bFGF)-induced proliferation of coronary smooth muscle cells (cSMC). In this study, we investigated the effects of the 3hydroxy-3-methyl glutaryl coenzyme A (HMG CoA) reductase inhibitor lovastatin on bFGF-induced signal transduction in cSMC. The present study shows that lovastatin inhibits bFGF-stimulated DNA synthesis in cSMC, and that this inhibition is reversed by mevalonate (50 micromol/l) and by geranylgeranyl-pyrophosphate (1-5 micromol/l). Although lovastatin prevented Ras farnesylation the amount of bFGF-stimulated MAPK phosphorylation decreased only partially after lovastatin treatment. In addition, lovastatin pretreatment resulted in a sustained phosphorylation of MAPK. We observed a dose-dependent lovastatin-dependent increase in PKC activity, which could be prevented by mevalonate. This increase was comparable to the one induced by calyculin A (2 nmol/l), an inhibitor of protein phosphatase PP-1 and PP-2A. Lovastatin inhibited the expression of the PP-1 protein, which is involved in bFGF-induced DNA synthesis in cSMC. Thus, our data suggest that, lovastatin possibly affects the dephosphorylation processes of PKC and MAPK by inhibition of PP-1/PP-2A protein phosphatases which are involved in the bFGF-induced mitogenesis in cSMC.

Angiotensin AT1 receptor upregulates expression of basic fibroblast growth factor, basic fibroblast growth factor receptor and coreceptor in human coronary smooth muscle cells

Abstract.Autocrine stimulation and paracrine interaction between coronary smooth muscle cells (cSMC) and endothelial cells (EC) act as regulators of the vascular angiogenesis. Basic fibroblast growth factor (bFGF), its receptor FGF-R1, and coreceptor heparansulfate proteoglycan (HSPG) are important components involved in this angiogenic process. We investigated the influence of angiotensin (Ang) II on this trimolecular bFGF complex, the underlying signaling and the proliferative process in human cSMC. Ang II induces an AT1 receptor-dependent expression of bFGF and also upregulates the FGF-R1 and HSPG expression which is suppressed by losartan, the AT1 receptor blocker. AT1 receptor signaling which is characterized by phosphorylation of p42-mitogen-activated protein kinase (MAPK) is involved in Ang II-induced bFGF, FGF-R1 and HSPG upregulation and DNA synthesis in human cSMC. In contrast, inhibition of the AT2 receptor by PD123,319 has no influence on these Ang II-stimulated and via the MAPK cascade-mediated proangiogenic effects. Finally, our data show that the Ang II-induced DNA synthesis in cSMC is mediated via the bFGF expression. In conclusion, our results suggest that the Ang II-induced angiogenic effects in the vessel wall are supported by the AT1 receptor-stimulated and MAPK pathway-mediated upregulation of the autocrine/paracrine trimolecular bFGF complex in cSMC.

Molecular effects of HMG-CoA reductase inhibitors on smooth muscle cell proliferation

We read with great interest the report by Indolfi et al. [(1)][1]. The data reported are very interesting because, to the best of our knowledge, this is the first report demonstrating simultaneously that: 1) a hydroxymethylglutaryl Coenzyme A (HMG-CoA) reductase inhibitor blocks smooth muscle cell (