Smooth muscle cell growth factors

Mean Platelet Volume and Its Association With In-Hospital Outcomes in Patients With Acute ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

Background Mean platelet volume (MPV), reflecting platelet size and activation, has been associated with cardiovascular disease (CVD) risk and mortality. Yet, its prognostic significance in acute coronary syndrome (ACS) patients undergoing primary percutaneous coronary intervention (PCI) remains uncertain. This study investigates whether elevated MPV levels upon admission in ST-segment elevation myocardial infarction (STEMI) patients predict adverse in-hospital outcomes after primary PCI. Objectives The aim of this study was to measure MPV in patients with STEMI who underwent primary PCI and to evaluate its association with in-hospital outcomes such as death, recurrent myocardial infarction, heart failure, and bleeding. Methods We enrolled 400 consecutive patients with STEMI (mean age 56.20 years, 356 males, 44 females) who underwent primary PCI at our center. We obtained MPV values from complete blood count tests performed at admission. We divided the patients into two groups based on the normal MPV range of 7.40 to 12 fL. We compared the baseline characteristics and in-hospital outcomes of the two groups. We used Cox proportional hazards regression analysis to adjust for potential confounders and evaluate the impact of MPV on in-hospital outcomes. Results There was no significant difference in MPV values between the two groups (9.10 ± 1.20 fL vs. 9.00 ± 1.10 fL, p = 0.54). Patients who died exhibited higher age, male predominance, hypertension, diabetes, a lower left ventricular ejection fraction, lower levels of low-density lipoprotein cholesterol, and lower levels of hemoglobin and hematocrit compared to survivors. MPV was not associated with any of the in-hospital outcomes in the unadjusted or adjusted analyses. Conclusion In this cohort of patients with STEMI who underwent primary PCI, admission MPV was not a predictor of in-hospital outcomes. Further studies are needed to clarify the role of MPV in the pathophysiology and prognosis of ACS.

The anatomical sources of neointimal cells in the arteriovenous fistula

Neointimal cells are an elusive population with ambiguous origins, functions, and states of differentiation. Expansion of the venous intima in arteriovenous fistula (AVF) is one of the most prominent remodeling processes in the wall after access creation. However, most of the current knowledge about neointimal cells in AVFs comes from extrapolations from the arterial neointima in non-AVF systems. Understanding the origin of neointimal cells in fistulas may have important implications for the design and effective delivery of therapies aimed to decrease intimal hyperplasia (IH). In addition, a broader knowledge of cellular dynamics during postoperative remodeling of the AVF may help clarify other transformation processes in the wall that combined with IH determine the successful remodeling or failure of the access. In this review, we discuss the possible anatomical sources of neointimal cells in AVFs and their relative contribution to intimal expansion.

Heat shock protein 90 inhibitor AUY922 attenuates platelet-derived growth factor-BB-induced migration and proliferation of vascular smooth muscle cells

Luminespib (AUY922), a heat shock proteins 90 inhibitor, has anti-neoplastic and antitumor effects. However, it is not clear whether AUY922 affects events in vascular diseases. We investigated the effects of AUY922 on the platelet-derived growth factor (PDGF)-BB-stimulated proliferation and migration of vascular smooth muscle cells (VSMC). VSMC viability was detected using the XTT (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) reagent. To detect the attenuating effects of AUY922 on PDGF-BB-induced VSMCs migration in vitro, we performed the Boyden chamber and scratch wound healing assays. To identify AUY922-mediated changes in the signaling pathway, the phosphorylation of protein kinase B (Akt) and extracellular signal-regulated kinase (ERK) 1/2 was analyzed by immunoblotting. The inhibitory effects of AUY922 on migration and proliferation ex vivo were tested using an aortic ring assay. AUY922 was not cytotoxic at concentrations up to 5 nM. PDGF-BB-induced VSMC proliferation, migration, and sprout outgrowth were significantly decreased by AUY922 in a dose-dependent manner. AUY922 significantly reduced the PDGF-BB-stimulated phosphorylation of Akt and ERK1/2. Furthermore, PD98059 (a selective ERK1/2 inhibitor) and LY294002 (a selective Akt inhibitor) decreased VSMC migration and proliferation by inhibiting phosphorylation of Akt and ERK1/2. Greater attenuation of PDGF-BB-induced cell viability and migration was observed upon treatment with PD98059 or LY294002 in combination with AUY922. AUY922 showed anti-proliferation and anti-migration effects towards PDGF-BBinduced VSMCs by regulating the phosphorylation of ERK1/2 and Akt. Thus, AUY922 is a candidate for the treatment of atherosclerosis and restenosis.

Mean platelet volume and clinical outcomes of patients with chest pain discharged from internal medicine wards

BACKGROUND

Currently, there are no clinical scores for risk stratification of low-risk patients with chest pain. We aimed to examine the association between mean platelet volume (MPV) and risk for adverse clinical outcomes in patients with chest pain discharged from internal medicine wards following acute coronary syndrome (ACS) rule-out.

PATIENTS AND METHODS

Included were patients who were admitted to internal medicine wards and were discharged following an ACS-rule-out during 2010-2016. The primary endpoint was the composite of all-cause mortality and hospital admission due to ACS at 30-days following hospital discharge.

RESULTS

Included in the study were12 440 patients who were divided into three groups according to MPV. The composite endpoint of 30-day all-cause mortality and hospital admission for ACS occurred more frequently among patients with high MPV. Each one-point increase in MPV was associated with an 18% increase in the risk for the composite endpoint (P = 0.02). Considering patients with MPV less than 7.8 fl as the reference group yielded adjusted hazard ratios for the composite endpoint that was significantly higher in patients in the high MPV tertile ( > 8.8 fl) (hazard ratio 1.6; 95% confidence interval = 1.1-2.5; P = 0.04). Each one-point increase in MPV was associated with an 11% increase in the risk for 1-year all-cause mortality (P = 0.01) and a 10% increase in the risk for 1-year ACS (P = 0.04).

CONCLUSION

We found an independent association between high MPV and the risk of death and ACS among patients with chest pain who were discharged from internal medicine wards following an ACS-rule-out. MPV may be combined in the risk stratification of patients with chest pain.

Molecular atherectomy for restenosis

Receptors for basic (b) and acidic (a) fibroblast growth factor (FGF) are upregulated in activated smooth muscle cells. These cells, which proliferate in response to bFGF, can thus be killed by a conjugate of bFGF and the ribosome-inactivating enzyme, saporin (which, by itself, does not enter the cells). Quiescent smooth muscle cells and other cells that have few FGF receptors are not killed. In vivo, bFGF-saporin transiently inhibits smooth muscle cell proliferation and neointimal accumulation after balloon injury to the rat carotid artery. Delivery of saporin, diagnostic imaging agents, or antisense oligodeoxynucleotides might be made even more selective by linking these substances to antibodies against the extracellular domains of the putative FGF receptor isoform specific for activated smooth muscle cells.

Mean platelet volume as a predictor of cardiovascular risk: a systematic review and meta-analysis

AIM

To determine whether an association exists between mean platelet volume (MPV) and acute myocardial infarction (AMI) and other cardiovascular events. Platelet activity is a major culprit in atherothrombotic events. MPV, which is widely available in clinical practice, is a potentially useful biomarker of platelet activity in the setting of cardiovascular disease.

METHODS AND RESULTS

We performed a systematic review and meta-analysis investigating the association between MPV and AMI, all-cause mortality following myocardial infarction, and restenosis following coronary angioplasty. Results were pooled using random-effects modeling. Pooled results from 16 cross-sectional studies involving 2809 patients investigating the association of MPV and AMI indicated that MPV was significantly higher in those with AMI than those without AMI [mean difference 0.92 fL, 95% confidence interval (CI) 0.67-1.16, P < 0.001). In subgroup analyses, significant differences in MPV existed between subjects with AMI, subjects with stable coronary disease (P < 0.001), and stable controls (P < 0.001), but not vs. those with unstable angina (P = 0.24). Pooled results from three cohort studies involving 3184 patients evaluating the risk of death following AMI demonstrated that an elevated MPV increased the odds of death as compared with a normal MPV (11.5% vs. 7.1%, odds ratio 1.65, 95% CI 1.12-2.52, P = 0.012). Pooled results from five cohort studies involving 430 patients who underwent coronary angioplasty revealed that MPV was significantly higher in patients who developed restenosis than in those who did not develop restenosis (mean difference 0.98 fL, 95% CI 0.74-1.21, P < 0.001).

CONCLUSIONS

Elevated MPV is associated with AMI, mortality following myocardial infarction, and restenosis following coronary angioplasty. These data suggest that MPV is a potentially useful prognostic biomarker in patients with cardiovascular disease. Whether the relationship is causal, and whether MPV should influence practice or guide therapy, remains unknown.

Mean platelet volume as a predictor of cardiovascular risk: a systematic review and meta-analysis

AIM

To determine whether an association exists between mean platelet volume (MPV) and acute myocardial infarction (AMI) and other cardiovascular events. Platelet activity is a major culprit in atherothrombotic events. MPV, which is widely available in clinical practice, is a potentially useful biomarker of platelet activity in the setting of cardiovascular disease.

METHODS AND RESULTS

We performed a systematic review and meta-analysis investigating the association between MPV and AMI, all-cause mortality following myocardial infarction, and restenosis following coronary angioplasty. Results were pooled using random-effects modeling. Pooled results from 16 cross-sectional studies involving 2809 patients investigating the association of MPV and AMI indicated that MPV was significantly higher in those with AMI than those without AMI [mean difference 0.92 fL, 95% confidence interval (CI) 0.67-1.16, P < 0.001). In subgroup analyses, significant differences in MPV existed between subjects with AMI, subjects with stable coronary disease (P < 0.001), and stable controls (P < 0.001), but not vs. those with unstable angina (P = 0.24). Pooled results from three cohort studies involving 3184 patients evaluating the risk of death following AMI demonstrated that an elevated MPV increased the odds of death as compared with a normal MPV (11.5% vs. 7.1%, odds ratio 1.65, 95% CI 1.12-2.52, P = 0.012). Pooled results from five cohort studies involving 430 patients who underwent coronary angioplasty revealed that MPV was significantly higher in patients who developed restenosis than in those who did not develop restenosis (mean difference 0.98 fL, 95% CI 0.74-1.21, P < 0.001).

CONCLUSIONS

Elevated MPV is associated with AMI, mortality following myocardial infarction, and restenosis following coronary angioplasty. These data suggest that MPV is a potentially useful prognostic biomarker in patients with cardiovascular disease. Whether the relationship is causal, and whether MPV should influence practice or guide therapy, remains unknown.

Smooth muscle cell signal transduction: implications of vascular biology for vascular surgeons

Vascular smooth muscle cells exhibit varied responses after vessel injury and surgical interventions, including phenotypic switching, migration, proliferation, protein synthesis, and apoptosis. Although the source of the smooth muscle cells that accumulate in the vascular wall is controversial, possibly reflecting migration from the adventitia, from the circulating blood, or in situ differentiation, the intracellular signal transduction pathways that control these processes are being defined. Some of these pathways include the Ras-mitogen-activated protein kinase, phosphatidylinositol 3-kinase-Akt, Rho, death receptor-caspase, and nitric oxide pathways. Signal transduction pathways provide amplification, redundancy, and control points within the cell and culminate in biologic responses. We review some of the signaling pathways activated within smooth muscle cells that contribute to smooth muscle cell heterogeneity and development of pathology such as restenosis and neointimal hyperplasia.

Effects of KTJ740, a Novel Antithrombotic Agent, on Platelet-Derived Growth Factor-Induced Rat Aortic Smooth Muscle Cell Proliferation and Cell Cycle Progression

Hyperproliferation of platelet-derived growth factor (PDGF)-BB-induced vascular smooth muscle cell (VSMC) is a hallmark of atherosclerosis and related vascular disorders. In the previous study, we reported that KTJ740 [2-chloro-3-(4-(ethylcarboxy)-phenyl)-amino-1,4-naphthoquinone], a newly synthesized vitamin K derivative, has potent antithrombotic effects in mice and antiplatelet activity in vitro and ex vivo. In the present study, we have tested that KTJ740 could inhibit PDGF-BB-stimulated VSMC proliferation. We have examined the potential inhibitory effect of this compound on rat aortic smooth muscle cells (RASMCs). Our results show that this compound significantly inhibits PDGF-BB-stimulated RASMC number and DNA synthesis in a concentration-dependent manner. Furthermore, we have examined its effect on cell cycle progression by flow cytometry. KTJ740 treatment resulted in a significant arrest in cell cycle progression of RASMCs induced by PDGF-BB, and this effect was achieved by suppressing activation of PDGF-beta receptor (PDGF-Rbeta) tyrosine kinase pathway. These results suggest that a possibility of KTJ740 can be a potential agent to control vascular disorders and its antiproliferative mechanism may be mediated through PDGF-Rbeta tyrosine kinase-dependent signaling pathway.

Mechanisms of vascular smooth muscle cell migration

Smooth muscle cell migration occurs during vascular development, in response to vascular injury, and during atherogenesis. Many proximal signals and signal transduction pathways activated during migration have been identified, as well as components of the cellular machinery that affect cell movement. In this review, a summary of promigratory and antimigratory molecules belonging to diverse chemical and functional families is presented, along with a summary of key signaling events mediating migration. Extracellular molecules that modulate migration include small biogenic amines, peptide growth factors, cytokines, extracellular matrix components, and drugs used in cardiovascular medicine. Promigratory stimuli activate signal transduction cascades that trigger remodeling of the cytoskeleton, change the adhesiveness of the cell to the matrix, and activate motor proteins. This review focuses on the signaling pathways and effector proteins regulated by promigratory and antimigratory molecules. Prominent pathways include phosphatidylinositol 3-kinases, calcium-dependent protein kinases, Rho-activated protein kinase, p21-activated protein kinases, LIM kinase, and mitogen-activated protein kinases. Important downstream targets include myosin II motors, actin capping and severing proteins, formins, profilin, cofilin, and the actin-related protein-2/3 complex. Actin filament remodeling, focal contact remodeling, and molecular motors are coordinated to cause cells to migrate along gradients of chemical cues, matrix adhesiveness, or matrix stiffness. The result is recruitment of cells to areas where the vessel wall is being remodeled. Vessel wall remodeling can be antagonized by common cardiovascular drugs that act in part by inhibiting vascular smooth muscle cell migration. Several therapeutically important drugs act by inhibiting cell cycle progression, which may reduce the population of migrating cells.

Breast cancer cells secreted platelet-derived growth factor-induced motility of vascular smooth muscle cells is mediated through neuropilin-1

Motility of vascular smooth muscle cells (SMCs) is an essential step for both normal and pathologic angiogenesis. We report here that breast tumor cells, such as MCF-7 and MDA-MB-231, can modulate this SMC migration. We present evidence that the tumor cell-derived platelet-derived growth factor (PDGF) is the key regulator of vascular SMCs motility induced by breast cancer cells. PDGF significantly upregulates neuropilin-1 (NRP-1) mRNA expression and protein production in aortic smooth muscle cells (AOSMCs) and depletion of NRP-1 production by AOSMCs with specific short hairpin RNA (shRNA) prevents the PDGF-dependent migration of vascular SMCs. Moreover, we demonstrate that PDGF physically interacts with NRP-1. We propose that tumor-derived PDGF and NRP-1 of AOSMCs function as a relay system that promotes motility of vascular SMCs.

Hypoxia-inducible factor 1α modulates adhesion, migration, and FAK phosphorylation in vascular smooth muscle cells

Hypoxia promotes angiogenesis by modulating the transcriptional regulator hypoxia-inducible factor 1alpha (HIF-1alpha). HIF-1alpha is a master regulator of the hypoxic response, and its proangiogenic activities include, but are not limited to, regulation of vascular endothelial growth factor (VEGF). The remodeling of the vasculature during angiogenesis requires an initial destabilization step, which facilitates endothelial sprouting, followed by vessel growth, and restabilization through investment of smooth muscle cells. The complex dynamics of hypoxia-induced angiogenesis prompted us to investigate what aspects of this multi-step process are regulated by HIF-1alpha. To do so, we analyzed the molecular properties of aortic and coronary artery smooth muscle cells in response to forced expression of HIF-1alpha, and by treatment with cobalt chloride, which mimics hypoxia. Our results demonstrate that HIF-1alpha causes a marked reduction in the ability of smooth muscle cells to migrate and adhere to extracellular matrices. Analysis of focal adhesion proteins showed no significant difference in expression or localization of vinculin or focal adhesion kinase (FAK). However, investigation of FAK phosphorylation, a critical mediator of adhesion and migration, revealed tyrosine phosphorylation of FAK is diminished in the presence of HIF-1alpha and cobalt chloride. These results indicate that during hypoxia-induced vessel remodeling, HIF-1alpha functions to dampen adhesion and migration of smooth muscle cells by modulating FAK activity. We suggest that HIF-1alpha expression in smooth muscle cells may augment vessel sprouting by loosening smooth muscle cell attachments to the basement membrane and endothelial cells.

TIMP-1 stimulates proliferation of human aortic smooth muscle cells and Ras effector pathways

Tissue inhibitor of metalloproteinases-1 (TIMP-1) is a multifunctional protein, which is found in most tissues and body fluids. Here, we demonstrated that recombinant TIMP-1 but not the synthetic matrix metalloproteinase inhibitor, GM6001, stimulated proliferation of human aortic smooth muscle cells (AoSMC) in a dose-dependent manner. The mitogenic effect was associated with activation of Ras, increased phosphorylation of ERK, and stimulation of cyclin D1 expression. The phosphatidylinositol 3-kinase (PI3K) signaling pathway was also involved since the PI3K inhibitor, LY294002, abolished the TIMP-1-mediated growth stimulation. These data suggest that TIMP-1 activates Ras, which then turns on the ERK and PI3K signaling pathways to promote cell cycle progression of the AoSMC.

The effect of anticoagulation with subcutaneously delivered polyethylene glycol conjugated hirudin and recombinant tissue plasminogen activator on recurrent stenosis in the rabbit double-balloon injury model

Myointimal hyperplasia is the condition usually responsible for recurrent stenosis (restenosis) after endarterectomy, bypass grafting and angioplasty. Its cause is still not known. The present study examined whether inhibition of thrombin by tissue plasminogen activator (r-TPA) or polyethylene glycol recombinant hirudin (PEG-hirudin) could reduce restenosis in an animal model. Restenosis was induced in 20 cholesterol-fed rabbits. The right carotid artery underwent a double-balloon injury while left carotid artery acted as a control. Recombinant tissue plasminogen activator (1 mg kg(-1) s.c.) and PEG-hirudin (0.7 mg kg(-1) s.c.) were given subcutaneously with normal saline acting as a control. Blood levels of PEG-hirudin were measured by both ELISA and an Ecarin (activity) assay. Vessel dimensions were measured in histological sections, obtained from perfusion-fixed tissue, using computerised planimetry. The model reproduced many of the histological changes found in human restenosis, such as intramural thrombus, rupture of the elastic lamina, macrophage infiltration and smooth muscle migration. Reinjury caused an almost three-fold reduction in the area of the lumen (median 0.25 mm(2)) compared with uninjured vessels (median 0.72 mm(2)). The mean plasma levels of PEG-hirudin and r-tPA achieved were 291 ng/ml (S.E.M. 28 ng/ml) and 34 IU/ml (S.E.M. 12 IU/ml), respectively. PEG-hirudin significantly inhibited the effect of balloon injury on luminal area compared with saline-treated controls (0.21 versus 0.44 mm(2), respectively, P<0.05). Recombinant tPA also had a similar inhibitory affect, but this did not reach statistical significance (0.16 versus 0.44 mm(2), respectively, P>0.05). The magnitude of luminal narrowing was significantly reduced by subcutaneous injection of PEG-hirudin. Further studies are required to determine whether this effect can be enhanced by other antithrombins or improved methods of delivery.

Alpha(1)-adrenoceptors (alpha(1)-AR) and vascular smooth muscle cell growth

BACKGROUND

Smooth muscle cells in vascular tissue, like tissue within the urogenital sinus, undergo growth and proliferation.

METHODS

This review attempts to compare and contrast the mechanisms and controlling factors involved in prostatic and vascular tissue. There is a particular focus on the role of catecholamines and alpha-adrenoceptors (alpha-ARs), and on the effects of alpha(1)-AR antagonists (blockers) on cellular dynamics. RESULTS AND CONCLUSIONS The situation in vascular tissue appears analagous to that in prostatic tissue. Certain AR-antagonists, in addition to altering smooth muscle contraction, may have other actions on cellular dynamics.

Inhibitory effect of pentalenolactone on vascular smooth muscle cell proliferation

The effect of pentalenolactone, an inhibitor of glyceraldehyde-3-phosphate dehydrogenase, on rat vascular smooth muscle cell proliferation was studied. Addition of pentalenolactone together with serum to quiescent cells dose-dependently inhibited cell proliferation and DNA synthesis. This inhibition was not associated with cell death. When quiescent cells were stimulated with serum and then treated with pentalenolactone, the inhibitory effect on the DNA synthesis declined gradually. A similar result was obtained when PD 98059 (2'-amino-3'-methoxyflavone), an inhibitor of extracellular signal-regulated kinase1/2 (ERK1/2) kinase (MEK1/2), was added to the cells after serum stimulation. Pentalenolactone inhibited serum or protein kinase C activator (phorbol 12,13-dibutyrate)-induced phosphorylation of ERK1/2 and MEK1/2. In contrast, pentalenolactone had little effect on platelet-derived growth factor receptor autophosphorylation. Taken together, these results indicate that pentalenolactone inhibits vascular smooth muscle cell proliferation, and that this inhibition appears to be mediated by inhibition of the ERK1/2 cascade.

Chronic alpha-adrenergic receptor stimulation modulates the contractile phenotype of cardiac myocytes in vitro

BACKGROUND

Heart failure is characterized by contractile dysfunction of the myocardium and elevated sympathetic activity. We tested the hypothesis that chronic alpha-adrenergic (alpha-ADR) stimulation modifies the molecular and contractile phenotype of cardiac myocytes.

METHODS AND RESULTS

Adult rat ventricular myocytes in culture were exposed to alpha-ADR stimulation (norepinephrine + propranolol) for 48 hours. alpha-ADR stimulation decreased the mRNAs for sarcoplasmic reticulum Ca(2+)-ATPase and Ca(2+) release channel by 56% and 52%, respectively, and increased mRNA and protein for the Na(+)-Ca(2+) exchanger by 70% and 39%, respectively. After washout of the alpha-ADR agonist, simultaneous measurement of [Ca(2+)](i) transients with fura 2 and myocyte shortening by video edge-detection showed that [Ca(2+)](i) amplitude and myocyte shortening were decreased in alpha-ADR-treated myocytes, and the time to peak and time from peak to 80% decline of both [Ca(2+)](i) and myocyte shortening were increased. The concentration-response curve for myocyte shortening by the Na(+) channel activator veratridine was shifted leftward in alpha-ADR-stimulated myocytes (EC(50), 21.6+/-4.6 versus 105.8+/-10.5 nmol/L, P:<0.001).

CONCLUSIONS

Chronic alpha-ADR stimulation of cardiac myocytes causes decreases in the expression of sarcoplasmic reticulum Ca(2+)-ATPase and the Ca(2+) release channel that are associated with decreases in [Ca(2+)](i) and contractility. alpha-ADR stimulation simultaneously increases Na(+)-Ca(2+) exchanger expression, thereby increasing sensitivity to intracellular Na(+).

Platelets and restenosis

Restenosis is currently the major limitation of percutaneous transluminal coronary angioplasty (PTCA). Factors such as elastic recoil, migration of vascular smooth muscle cells from media to intima, neointimal proliferation and vascular remodeling underly the restenotic process. Presently there is no effective therapy available for restenosis. The role of platelets in the development of thrombosis and abrupt closure after PTCA is well recognized. However, the effects of platelets in PTCA extend well beyond the early phase. Although antiplatelet agents such as glycoprotein IIb/IIIa antagonists have been reported to reduce target vessel revascularization, major unresolved controversies still exist. This report reviews the potential role of platelets in restenosis. Various drugs, successfully tested in experimental studies and in a small number of human studies, that inhibit the effect of platelets on the restenotic process are also reviewed.

Overexpression of p21Waf-1 in vascular smooth muscle cells: regulation of proliferation, differentiation, and cell size

Cyclin-dependent kinase inhibitor p21Waf-1 is recognized as a negative regulator of cell cycle progression, and it possibly mediates cell differentiation and apoptosis. To understand the role of p21Waf-1 in phenotypic modulation of vascular smooth muscle cells (SMC), we induced the overexpression of p21Waf-1 in cultured rat SMC. The recombinant adenovirus vector encoding p21Waf-1 (AdvCMVp21) was constructed by homologous recombination and the vector encoding beta-galactosidase (AdvCMVLacZ) was used as an experimental control. Administration of AdvCMVp21 suppressed serum-induced proliferation and cell cycle progression; however, the number of quiescent cells and the population of TUNEL-positive cells were not altered. Overexpression of p21Waf-1 did not affect the expression of contractile proteins and the availability of an endogenous growth factor signal p21Waf-1 may regulate cell cycle progression in SMC without affecting the apoptotic process and cell differentiation. Furthermore, the longitudinal diameter of AdvCMVp21 infected cells was increased compared with that of AdvCMVLacZ infected cells. Total protein content was also increased in AdvCMVp21 infected cells. Responses to the serum stimulation, proliferation and total protein synthesis may be independently regulated. Thus, the suppression of cell cycle progression by p21Waf-1 resulted in cellular hypertrophy of SMC.

Doxazosin inhibits proliferation and migration of human vascular smooth-muscle cells independent of alpha1-adrenergic receptor antagonism

Proliferation and migration of vascular smooth-muscle cells (VSMCs), stimulated by a variety of growth factors, play a critical role in the pathogenesis of vascular diseases. We found unexpectedly that doxazosin, an alpha1-adrenergic-receptor antagonist, inhibits serum-stimulated proliferation of cultured human VSMCs. Subsequent experiments systematically investigated inhibitory effects of doxazosin on mitogenesis stimulated in VSMCs by platelet-derived growth factor (PDGF), epidermal growth factor, and G protein-coupled receptor agonists thrombin and angiotensin II. Doxazosin attenuated the stimulation of DNA synthesis for each of these ligands with median inhibitory concentrations (IC50s) from 0.3 to 1 microM. PDGF-AB (1 nM) increased cell number; doxazosin inhibited this response by 70-80%. Prazosin, a related alpha1-receptor antagonist, had similar but less potent effects on inhibiting mitogenesis in these cells. Doxazosin and prazosin inhibited PDGF-AB-stimulated and insulin-like growth factor (IGF-I)-stimulated migration of VSMCs by approximately 40-50%. These effects of doxazosin were likely unrelated to alpha1-receptor blockade because pretreatment of cells with phenoxybenzamine, an irreversible alpha1 antagonist, did not change the capacity of doxazosin to inhibit of PDGF-stimulated mitogenesis. Also, doxazosin inhibited PDGF-stimulated DNA synthesis in NIH 3T3 cells, which do not express alpha1 receptors. These results suggest that doxazosin is a potent inhibitor of VSMC proliferation and migration through a mechanism unrelated to alpha1-receptor antagonism.

Endothelial activation and cytokine expression in human acute cardiac allograft rejection

By extrapolation from the responses of cultured human umbilical vein endothelial cells (EC) and bovine aortic EC to short-term cytokine stimulation, EC activation is postulated as a likely component of the host response in acute allograft rejection and cardiac transplant-associated accelerated arteriosclerosis. To investigate the extent to which EC activation occurs in vivo in humans and to identify potential targets for therapeutic interventions, we compared the phenotypic characteristics of vascular EC as seen during clinicopathologically significant vs non-significant acute cardiac allograft rejection. We used monoclonal and monospecific polyclonal antibodies to coagulation molecules [tissue factor, thrombomodulin (TM), antithrombin III (AT-III), fibrinogen/fibrin, cross-linked fibrin and von Willebrand factor (vWF)], adhesion molecules (P-selectin, ICAM-1) and major histocompatibility complex (MHC) class I and II molecules. In addition we sought evidence of local cytokine production (IL-1, IL-2R, IL-4, IL-6, IL-7, IL-8, TNF-alpha, PDGF-AA, PDGF-BB), which might mediate alterations in expression of these proteins. We found that in clinically significant grades of cardiac allograft rejection requiring increased immunosuppression, in contrast to lesser grades of rejection not requiring clinical intervention, there was increased microvascular EC activation and differential expression of cytokines. EC changes associated with more extensive cardiac allograft rejection requiring treatment included: (i) disruption of the normal anticoagulant state with downregulation of TM and AT-III, upregulation of tissue factor and vWF expression, and associated extensive fibrin deposition; (ii) upregulation of MHC class I antigens, which are potential targets for host cytotoxic T lymphocytes; (iii) increased expression of the leucocyte adhesion molecules P-selectin and ICAM-1; (iv) expression of the pro-inflammatory cytokines IL-1 beta and TNF-alpha; and (v) increased expression of PDGF-AA and BB, which are known to promote migration and proliferation of intimal cells, and hence may contribute to development of transplant-associated atherosclerosis. Collectively these findings suggest that immune events resulting in EC surface changes and/or production of key cytokines play a role in the pathogenesis of acute transplant rejection and may contribute to the long-term complication of accelerated arteriosclerosis in allograft coronary arteries.

Increased expression of membrane-type matrix metalloproteinase and preferential localization of matrix metalloproteinase-2 to the neointima of balloon-injured rat carotid arteries

BACKGROUND

Remodeling of the injured vascular wall is dependent on the action of several extracellular proteases. Previous studies have shown that expression of matrix metalloproteinases (MMP-2 and MMP-9) is upregulated after vascular injury and that MMP-2 is required for the migration of cultured vascular smooth muscle cells across complex extracellular matrix barriers. The present study examined changes in the expression of membrane-type metalloproteinase (MT-MMP-1), a putative regulator of MMP-2, in the tissue localization of MMP-2, and in the expression of activated and latent forms of MMP-2 and the tissue inhibitor of metalloproteinases, TIMP-2, in rat carotid arteries subjected to balloon catheter injury.

METHODS AND RESULTS

MT-MMP-1 mRNA levels increased sixfold after 3 days of injury, coinciding with an increase in MMP-2 activation assessed by gelatin zymography. Western blotting and gelatin zymography showed an increase in MMP-2 protein levels beginning 5 to 7 days after injury; immunocytochemistry and Western blotting showed that the increase occurred preferentially in the developing neointima.

CONCLUSIONS

These results show that increased expression of MT-MMP-1 and activation of MMP-2 occurs early after injury to the rat carotid artery and that at later times MMP-2 is preferentially localized to the developing neointima.

High and constant plasma levels of tissue plasminogen activator and PEG-hirudin can be achieved by subcutaneous delivery

Intramural thrombosis is a consistent finding in the arteries of patients who die following coronary angioplasty. This thrombosis is thought to have a role in restenosis, which is a common complication of coronary angioplasty. It has been hypothesised that antithrombotics such as hirudin or tissue-type plasminogen activator (tPA), may be therapeutically useful following angioplasty. This report describes the bioavailability of both agents following subcutaneous (sc) injection in cholesterol-fed rabbits. Intravenously delivered tPA has a half-life of 3-5 minutes. The half-life of intravenously administered hirudin is less than one hour in many species. In order to prolong the duration of action recombinant hirudin was conjugated to polyethylene glycol (PEG). Polyethylene glycol conjugated recombinant hirudin (PEG-rH) (0.7 mg/kg) antigen and activity were measurable after just 1 hr, reaching a maximum (663 and 884 ng/ml respectively) at 12 hours. Significant levels were present in rabbit plasma 24 hours after injection. Subcutaneously delivered recombinant (r-tPA) (1 mg/kg) was present in significant amounts 1 hr after injection, reaching a maximum (92 IU/ml) at 2 hours. Levels of tPA at 9 hours were approximately 80x normal circulating levels. High and constant levels of functional activity of both PEG-rH and r-tPA in rabbit plasma are achieved by subcutaneous delivery.

Antifibrinolytic properties of the vascular wall. Dependence on the history of smooth muscle cell doublings in vitro and in vivo

Increased expression of plasminogen activator inhibitor-1 (PAI-1) mRNA in atherosclerotic human arteries suggests a linkage between PAI-1 gene expression and cellular proliferation, the fundamental feature of atherosclerosis. To investigate whether smooth muscle cell (SMC) proliferation influences overall fibrinolytic properties of the vascular wall, we examined the effect of serial in vitro passaging of human SMCs on tissue plasminogen activator (TPA) and PAI-1 synthesis levels as well as the ability to modulate TPA and PAI-1 synthesis of human umbilical vein endothelial cells (HUVECs). As in vivo correlates for such late-passage cells in culture, SMCs derived from human atherosclerotic plaques were used, because they are thought to have already undergone numerous cell doublings. We observed an increase of PAI-1 secretion (from 591 +/- 106 to 2952 +/- 290 ng PAI-1.10(5) cells-1.24 h-1) with a concomitant fourfold to fivefold increase of PAI-1 mRNA levels, as well as a decrease of TPA secretion (from 118 +/- 34 to 8 +/- 1.3 ng TPA.10(5) cells-1.24 h-1) and a twofold to threefold decrease of TPA mRNA levels with increasing in vitro passage number (from passage 3 to 11) of normal pulmonary artery smooth muscle cells (PASMCs) (P < .05). SMCs derived from atherosclerotic plaques of coronary arteries (CASMCs) displayed higher levels of PAI-1 antigen synthesis (3093 +/- 507 ng PAI-1.10(5) cells-1.24 h-1) with an approximately twofold increase of PAI-1 mRNA levels, as well as decreased levels of TPA antigen synthesis (10 +/- 1.6 ng TPA.10(5) cells-1.24 h-1) with an approximately 1.5- to 2-fold decrease of TPA mRNA levels in passage 1, compared with their counterparts derived from normal-appearing arterial tissue of the same vessel (1794 +/- 525 ng PAI-1.10(5) cells-1.24 h-1; 17 +/- 5 ng TPA.10(5) cells-1.24 h-1) (P < .001; P < .01). Incubation of HUVEC cultures with the 24-hour conditioned media (CM) of early-passage PASMCs decreased endothelial PAI-1 antigen synthesis by approximately 42% (P < .001) and endothelial PAI-1 mRNA levels about twofold to threefold (P < .001), whereas by incubation with the 24-hour CM of late-passage PASMCs, endothelial PAI-1 antigen synthesis was upregulated by 68% (P = .001), with a concomitant twofold increase of endothelial PAI-1 mRNA levels (P < .001). The apparent MW of this heat- and acid-stable PAI-1 upregulating factor appears to be between 50 and 100 kD, as judged by ultrafiltration. Incubation of HUVEC cultures with the 24-hour CM of early-passage CASMCs derived from normal-appearing arterial tissue showed no significant influence on endothelial PAI-1 synthesis, whereas incubation with late-passage normal CASMCs, as well as early-passage atherosclerotic CASMCs from the same vessel, increased endothelial PAI-1 antigen secretion by 45% and 48% (P < .001), with a concomitant 1.5 fold to 2-fold increase of endothelial PAI-1 mRNA levels (P < .05). No significant change in endothelial TPA synthesis was observed by incubation with CM of either PASMCs (early or late passage) or CASMCs (atherosclerotic or normal). These data suggest that SMC proliferation is associated with (1) increased SMC PAI-1 synthesis as well as decreased TPA synthesis and (2) upregulation of endothelial PAI-1 synthesis by SMC CM. This phenomenon is observed with either late passages of normal PASMCs and CASMCs or early passages of atherosclerotic plaque CASMCs. This suggests that proliferating SMCs are a major regulator of the fibrinolytic potential within the vessel wall, thereby contributing to the thrombotic risk associated with the development of atherosclerosis.

Transforming growth factor-beta: vasculogenesis, angiogenesis, and vessel wall integrity

Genetic studies have recently revealed a role for transforming growth factor-beta-1 (TGF-beta 1) and its receptors (TGF-beta Rs I and II as well as endoglin) in embryonic vascular assembly and in the establishment and maintenance of vessel wall integrity. The purpose of this review is threefold: first, to reassess previous studies on TGF-beta and endothelium in the light of these recent findings; second, to describe some of the well-established as well as controversial issues concerning TGF-beta and its regulatory role in angiogenesis; and third, to explore the notion of "context' with respect to TGF-beta and endothelial cell function. Although the focus of this review will be on the endothelium, other vascular wall cells are also likely to be important in the pathogenesis of the vascular lesions revealed by genetic studies.

Wall remodeling during luminal expansion of mesenteric arterial collaterals in the rat

Wall remodeling associated with rapid luminal enlargement of collateral mesenteric arteries in rats was investigated 1 and 4 weeks after creation of a collateral pathway by ligating three to four sequential arteries. Paired observations were made of inner diameters of collateral and normal arteries in the same animals. Arterial blood flow was measured at the final observation. Sections of arteries were processed for morphological measurements. After 4 weeks, inner arterial diameter was increased more at the beginning (63 +/- 6%) than the end (25 +/- 9%) of the collateral pathway. At 1 and 4 weeks, respectively, cross-sectional areas of collateral relative to normal arteries were increased by 46 +/- 5% and 59 +/- 13% (lumen), 55 +/- 8% and 65 +/- 14% (media), and 89 +/- 18% and 60 +/- 31% (intima). The wall expansion during luminal enlargement resulted in a normal medial thickness:luminal radius relationship. At 1 week postligation, wall shear rate remained elevated and endothelial but not smooth muscle hyperplasia had occurred (intimal nuclei: 40 +/- 1.7 collateral versus 24 +/- 3.0 normal; medial nuclei: 42 +/- 6.8 collateral versus 37 +/- 2.1 normal). At 4 weeks, wall shear rate in collaterals was similar to normal arteries, and smooth muscle hyperplasia had taken place (medial nuclei: 84 +/- 9.4 collateral versus 44 +/- 4.7 normal). The data demonstrate that wall expansion associated with rapid luminal enlargement of these collaterals involves hyperplasia of both endothelial and smooth muscle cells; however, smooth muscle proliferation does not occur until after wall shear rate is reduced. The specific cellular adaptations that occur during collateral development may depend on the level of wall shear and shear-dependent modulation of endothelial growth factors.

Controlled delivery of a tyrphostin inhibits intimal hyperplasia in a rat carotid artery injury model

We examined the inhibitory effect of AG-17, a potent inhibitor of protein tyrosine kinase activity on injury-induced vascular SMC proliferation by polymeric-based, periadventitial controlled release implant in the balloon catheter carotid injury model in rats. The AG-17 delivery system was formulated from ethylenevinyl acetate copolymer and the release kinetics as well as drug stability were determined. Polymeric matrices containing 2 or 10% AG-17 were implanted perivascularly in rats following balloon catheter injury. Western blot analysis of explanted arterial segments revealed enhanced tyrosine phosphorylation in injured arteries that was essentially reduced to normal levels in treated arteries. The mean neointima to media ratios were significantly reduced in both 2% (0.79 +/- 0.17, n = 9, P < 0.02) and 10% AG-17 (0.59 +/- 0.09, n = 12, P < 0.001) groups in comparison to the control group (1.38 +/- 0.18, n = 16). The mean areas of the media in the control and the 2% AG-17 group did not differ significantly but a significant reduction of the mean area of the media was observed in 10% AG-17 group. Embedding of the unstable tyrphostin compound, AG-17, in a hydrophobic matrix stabilizes the drug both in vitro and in vivo, and allows delivery-rate modulation as well as protracted site-specific therapy. Perivascular controlled release delivery of the tyrphostin AG-17 inhibits neointimal formation in the rat carotid injury model.

Lack of effect of recombinant human superoxide dismutase on cold ischemia-induced arteriosclerosis in syngeneic rat aortic transplants

Prolonged cold ischemia time and the generation of free oxygen radicals during reperfusion are risk factors for allograft arteriosclerosis. Growth factors are the main pro-proliferative mediators of smooth muscle cells in classical and in allograft arteriosclerosis. Superoxide dismutase is an enzyme that catalyzes the dismutation of superoxide anions into hydrogen peroxide. This study was designed to investigate which smooth muscle cell growth factor contribute to the formation of arteriosclerosis in syngenic vascular grafts with prolonged ischemia time, and whether perioperative intravenous administration of recombinant human superoxide dismutase (rh-SOD) prevents arteriosclerosis in these grafts. DA aortas were transplanted into DA recipients. One group of transplants was made with a short ex vivo ischemia time (15 min), while the other group transplant grafts was stored for 24 hr in cold saline. In addition to morphometric quantitation of the histological alterations, RNA isolated from grafts with short cold ischemia time in a semiquantitative polymerase chain reaction specific for various known smooth muscle cell growth factors. Syngeneic grafts with prolonged cold ischemia time showed severe intimal thickening and prominent medical necrosis, which were not seen in control groups. Approximately 3-fold levels of insulin-like growth factor-1 were found in ischemic syngeneic grafts compared with non-ischemic syngenic grafts, whereas epidermal growth factor levels were slightly lower. No changes in other growth factor mRNAs were found. Perioperative treatment with rh-SOD did not have significant effect on the extent of intimal thickening nor on the intensity of medial necrosis in grafts with prolonged ischemia time, and administration of rh-SOD did not change the expression level of insulin-like growth factor-1 in the grafts, either.

Distribution of hyaluronan during extracellular matrix remodeling in human restenotic arteries and balloon-injured rat carotid arteries

BACKGROUND

The glycosaminoglycan hyaluronan (HA) is present in developing tissues and healing wounds and forms a loose, hydrated extracellular matrix (ECM) that promotes processes such as cell migration. To investigate the potential contribution of HA to the pathogenesis of restenosis, we studied (1) human lesions obtained by directional atherectomy and (2) experimentally induced neointima formation in balloon-injured rat carotid arteries.

METHODS AND RESULTS

A biotinylated proteoglycan fragment that binds specifically to HA was used to stain atherectomy specimens from 29 human restenotic lesions (mean restenosis interval, 6.0+/-4.4 months) and 8 human primary lesions. The loose myxoid ECM typical of human restenotic arteries demonstrated intense, diffuse staining for HA. The intensity was inversely related to the density of immunostaining for collagen types I and III and was lowest in hypocellular primary atherosclerotic plaque. Among 24 rat carotid arteries retrieved 3, 7, 14, 28, 42, or 56 days after balloon injury and immunostained as well for proliferating cell nuclear antigen, staining for HA in the neointima reached a maximum 7 days after balloon injury and was associated with the presence of proliferating, PCNA-positive smooth muscle cells.

CONCLUSIONS

Hyaluronan is a characteristic constituent of the loose myxoid ECM in human restenotic arteries and of the neointima in experimentally injured arteries. The presence of hyaluronan may be a marker for an initial phase of the extracellular matrix remodeling that occurs during the development of a fibroproliferative lesion and could facilitate biological processes such as cell migration.

Stimulation of endothelial cells by doses of basic FGF-saporin that are lethal to smooth muscle cells

Basic fibroblast growth factor (FGF) receptors are up-regulated in proliferating (vs. quiescent) aortic smooth muscle cells, according to the results of recent studies. This up-regulation allows the ribosome inactivator saporin (if linked to basic FGF) to enter and kill proliferating, but not quiescent smooth muscle cells in vitro and in vivo. The authors now report that endothelial cells exhibit a different response. In 10% serum, FGF-SAP (0.1-1 nM) stimulates protein synthesis and cell division in subconfluent endothelial cells, but inhibits protein synthesis and cell division in subconfluent smooth muscle cells. Endothelial cells were inhibited at 10 nM FGF-SAP. A stimulatory response was seen in smooth muscle cells only at 0.1 nM FGF-SAP, and only after serum deprivation. Both cell types were resistant to FGF-SAP at high cell density. These responses correlated with FGF receptor density, which was sixfold higher in smooth muscle than endothelial cells and twice as high in serum-free smooth muscle cells as in serum-deprived smooth muscle cells. Moreover, a dose of FGFSAP that inhibited neointimal smooth muscle accumulation after balloon injury did not inhibit reendothelialization. Thus, there is a dose range at which FGF-SAP has unique properties that may make it useful in the treatment of vascular injury.

Rapamycin selectively inhibits angiotensin II-induced increase in protein synthesis in cardiac myocytes in vitro. Potential role of 70-kD S6 kinase in angiotensin II-induced cardiac hypertrophy

It has been suggested that phosphorylation of a 40S ribosomal protein, S6, regulates protein synthesis. Two distinct families of S6 kinase have been identified, the rsk-encoded 85- to 92-kD S6 kinase (RSK) and the 70- or 85-kD S6 kinase (p70S6K). We have previously shown that hypertrophic stimuli, such as angiotensin II (Ang II), rapidly activate RSK in cardiac myocytes. However, RSK and p70S6K are regulated by distinct mechanisms, and p70S6K, but not RSK, is the physiological S6 kinase in vivo in other cell types. Using cultured neonatal rat ventricular myocytes, we examined whether Ang II activates p70S6K and investigated the effect of rapamycin, a potent yet indirect inhibitor of p70S6K, on the Ang II-induced hypertrophic response. Immunoblot analyses indicate that cardiac myocytes express the 70- and 85-kD forms of p70s6K. Ang II caused a rapid and sustained activation of p70S6K through the type I Ang II receptor. Rapamycin inhibited Ang II-induced activation of p70S6K in a dose-dependent manner, with an IC50 of 0.14 ng/mL (0.15 nmol/L). Rapamycin did not inhibit Ang II-induced activation of tyrosine kinase, mitogen-activated protein kinase, RSK, and protein kinase C. The effect of rapamycin is unlikely to be mediated by its effect on p34cdc2 and p33cdk2 because Ang II did not activate these cell cycle-dependent kinases in cardiac myocytes. In contrast, a dose-dependent inhibition of p70S6K by rapamycin is very closely correlated with its inhibition of the Ang II-induced increase in protein synthesis. Interestingly, rapamycin did not affect the Ang II-induced activation of specific gene expression, including the immediate-early gene c-fos and fetal type genes, such as atrial natriuretic factor and skeletal alpha-actin. Moreover, rapamycin did not suppress Ang II-induced phenotypic changes at the protein level, such as increased atrial natriuretic factor secretion, expression of beta-myosin heavy chain, and organization of actin into sarcomeric units. These results indicate that p70S6K is activated by Ang II and that a rapamycin-sensitive signaling mechanism, most likely p70S6K, plays an essential role in the Ang II-induced increase in overall protein synthesis but not in Ang II-induced specific phenotypic changes in cardiac myocytes.

Quantification of myotrophin from spontaneously hypertensive and normal rat hearts

A novel peptide, myotrophin, has been isolated, purified, cloned, and sequenced from the hearts of spontaneously hypertensive rats (SHR) and from dilated cardiomyopathic human heart tissue. Myotrophin accelerates myocyte growth by stimulating protein synthesis (not by altering myocardial cell division). Our successive studies were conducted to evaluate the pathophysiological significance of myotrophin; a solid-phase radioimmunoassay technique was developed for quantifying the protein in hypertrophied and normal hearts. Specific antipeptide antibody was raised in rabbits against a peptide that represents a selected amino acid sequence of a 17-amino acid myotrophin segment by using the multiple antigenic peptide technique. The specificity of the antibody was evaluated by determining the affinity constant after constructing the Scatchard plot obtained from the ratio of bound to free myotrophin against bound myotrophin. The value obtained was 2.61 x 10(7) L/mol. The specificity was further demonstrated by Western blot analysis, in which a single protein band was obtained in the region of 12 kD. Pretreatment of the antibody with myotrophin completely blocked the binding sites, because no protein band was detected on the immunoblot. The antibody prevented the myocardial protein synthesis induced by myotrophin as revealed by the blockage of the stimulation of [3H]leucine incorporation into myocyte protein. Quantification of myotrophin from different heart tissues was achieved by Western blot and dot blot analyses. Amounts of myotrophin present in different dots were determined by using a video image analyzer. The level of myotrophin in the embryonic tissue was found to be similar in male normal and SHR hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of growth factors in vascular cell development and differentiation

The control of vascular growth and differentiation is a complex system of activity and interaction between positive and negative modulators of these processes. A number of important stimulators and inhibitors of both smooth muscle cells and endothelial cells have now been purified and biochemically characterized. Imbalances in the activity of these factors can result in serious pathologies. In this chapter, we briefly discuss the biology of blood vessel development and growth, review the current literature which describes these stimulators and inhibitors, and discuss current therapeutic strategies designed around these growth modulators.

Stimulation of PAI-1 expression in endothelial cells by cultured vascular smooth muscle cells

Regulation of endothelial cell (EC) plasminogen activator inhibitor type-1 (PAI-1), the primary physiological inhibitor of tissue-type plasminogen activator (TPA) and urokinase-type plasminogen activator (UPA), by various stimuli has been well characterized. We report the upregulation of secreted and intracellular PAI-1 in human umbilical ECs when cocultured with human smooth muscle cells (SMCs) on amniotic membranes or incubated with SMC conditioned medium (CM) under serum-free conditions as determined by enzyme-linked immunosorbent assay. Cocultured human umbilical vein ECs and SMCs, or human umbilical artery ECs and SMCs, displayed a 73% and 68% increase, respectively, in released PAI-1. SMC-derived stimulatory factor release showed tissue specificity, since only human aortic, umbilical vein, and umbilical artery SMCs upregulated PAI-1 synthesis, whereas SMCs from human mammary artery, pulmonary artery, and saphenous vein did not. Stimulation of EC PAI-1 by SMC CM was both time and concentration dependent, with as much as five- and fourfold increases in supernatants and lysates, respectively. PAI-1 synthesis and activity in ECs from other vascular beds were also upregulated by SMC CM. Northern blot analysis paralleled the protein results, showing as much as a 2.7-fold increase in specific EC PAI-1 mRNA expression after incubation with SMC CM for 8 hours. PAI-1 stimulatory activity in SMC CM was completely abolished by boiling or incubation with protamine sulfate and was reduced by transient acidification or heparin-Sepharose pretreatment by 33% or 48%, respectively. The stimulatory factor(s) appeared to have a molecular mass of 23 kD as determined by gel filtration.(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of 5-HT2 receptors in chronic endothelial dysfunction after balloon injury of porcine coronary arteries

BACKGROUND

Endothelium-dependent, pertussis toxin-sensitive relaxation to 5-hydroxytryptamine (5-HT) is impaired selectively after balloon injury of porcine coronary artery, followed by regeneration of the endothelial cells. The present study was designed to test the hypothesis that 5-HT, released from aggregating platelets, affects the progression of the endothelial dysfunction.

METHODS AND RESULTS

Yorkshire pigs were assigned randomly to three groups: control group (standard diet), denudation group (high-cholesterol diet plus balloon denudation of the endothelium of coronary artery under fluoroscopy), and DV-7028-treated group (denudation group plus chronic treatment with the selective 5-HT2 receptor antagonist DV-7028, given from the first day on after balloon denudation). Four weeks after the denudation, quantitative angiography revealed that 5-HT injected into the coronary artery decreased the luminal diameter of the left anterior descending coronary artery at the denuded site in the denudation group but not in the control or the DV-7028-treated group. Then, animals were killed so we could study the endothelium-dependent responses of their coronary arteries in conventional organ chambers. The arteries from the denudation group exhibited less relaxation to 5-HT and sodium fluoride (a stimulant of G proteins) than those of the control group. Relaxations to 5-HT and sodium fluoride were greater in arteries from the DV-7028-treated group than in those from the denudation group. In contrast, the endothelium-dependent, pertussis toxin-insensitive relaxations to bradykinin and thrombin and the endothelium-independent relaxations to sodium nitroprusside and isoproterenol were not affected significantly by chronic treatment with DV-7028.

CONCLUSIONS

These results suggest that 5-HT2 receptors are involved in the chronic progression of endothelial dysfunction after balloon denudation in the porcine coronary artery.

Triggers, acute risk factors and vulnerable plaques: the lexicon of a new frontier

A neglected area of cardiovascular research--study of the mechanisms of acute disease onset-is receiving increased attention. The new interest is based on the undisputed findings that onset of myocardial infarction and sudden cardiac death are more likely soon after awakening, indicating that activities of the patient frequently trigger the diseases. Triggering may occur when stressors produce hemodynamic, vasoconstrictive and prothrombotic forces--acute risk factors--that, in the presence of a vulnerable atherosclerotic plaque, cause plaque disruption and thrombosis. Triggering research may clarify mechanisms and suggest measures to sever the linkage between a potential trigger and its pathologic consequence.

Regulation of cell proliferation and growth by angiotensin II

The peptide hormone angiotensin II (AngII) has clearly defined physiologic roles as a regulator of vasomotor tone and fluid homeostasis. In addition AngII has trophic or mitogenic effects on a variety of target tissues, including vascular smooth muscle and adrenal cells. More recent data indicate that AngII exhibits many characteristics of the 'classical' peptide growth factors such as EGF/TGF alpha, PDGF and IGF-1. These include the capacity for local generation ('autocrine or paracrine' action) and the ability to stimulate tyrosine phosphorylation, to activate MAP kinases and to increase expression of nuclear proto-oncogenes. The type 1 AngII receptor, which is responsible for all known physiologic actions of AngII, has been cloned. Activation of this receptor leads to elevated phosphoinositide hydrolysis, mobilization of intracellular Ca2+ and diacylglycerol, and activation of Ca2+/calmodulin and Ca2+/phospholipid-dependent Ser/Thr kinases, as well as Ca2+ regulated tyrosine kinases. The existence of other AngII receptor subtypes has been postulated, but the function(s) of these sites remains unclear. In vascular smooth muscle, AngII can promote cellular hypertrophy and/or hyperplasia, depending in part on the patterns of induction of secondary factors that are known to stimulate (PDGF, IGF-1, basic FGF) or inhibit (TGF-beta) mitosis. Together, these findings have suggested that AngII plays important roles in both the normal development and pathophysiology of vascular, cardiac, renal and central nervous system tissues.

Restenosis after coronary angioplasty

Coronary angioplasty is used to treat coronary disease in many patients. Indications for angioplasty have expanded since it was first performed, mainly as a result of improvement in equipment and techniques. One problem with coronary angioplasty is the phenomenon of renarrowing of the treated coronary lesion, a process called restenosis. The events that constitute restenosis appear to be a universal response to the arterial wall injury of angioplasty. They are currently characterized as follows: platelet adhesion and aggregation on the damaged endothelium and within deep splits into the tunica media; release of platelet-derived growth factors; inflammation of the mechanically injured medial zone; transformation of smooth muscle cells of the tunica media after their activation by several of the growth-promoting substances; migration and proliferation of transformed smooth muscle cells, with secretion of copious amounts of extracellular matrix material; and, finally, termination of the growth process with regrowth of endothelium over the injured area. A decade of research work has helped identify clinical correlates of restenosis after coronary angioplasty procedures. This work is hindered by lack of a uniform angiographic definition of restenosis. In addition, much of the information has come from small studies, with incomplete follow-up and retrospective orientation. Nevertheless, some data are available. Patient-related correlates include male gender, unstable angina, diabetes, and continued smoking after angioplasty. Lesion-related correlates include multilesional and multivessel procedures, higher postangioplasty residual stenosis, proximal vessel location, location in the left anterior descending artery, location in a vein graft, long lesions, and total occlusions. The only consistent procedure-related correlate has been incorrect sizing of the angioplasty balloon to the treated artery. For the purposes of individual patient care, clinical correlates are not helpful. No group of variables has been found to be associated with complete freedom from restenosis, and no group is completely predictive of restenosis. All patients undergoing angioplasty procedures require some follow-up through subsequent months and years. Symptom status and the results of noninvasive studies have been investigated for purposes of follow-up. Symptoms are virtually useless by themselves for predicting restenosis or its absence. When symptom status is combined with exercise thallium 201 scintigraphy performed 4 to 6 months after an angioplasty procedure, the two factors are less than ideal but have a negative predictive value of more than 90%. This means that more than 90% of patients who have neither symptoms nor evidence of ischemia by thallium 201 scintigraphy will not have angiographic restenosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Suppression of neointimal thickening and smooth muscle cell proliferation after arterial injury in the rat by inhibitors of Na(+)-H+ exchange

Replication of vascular smooth muscle cells is a key event in the pathogenesis of restenosis following angioplasty. Little is known about early biochemical events involved in the proliferation of smooth muscle cells following arterial injury. In the present study, the effect of Na(+)-H+ exchange inhibitors on neointima formation after balloon injury of the rat carotid artery was investigated. Neointima formation was quantified 14 days after injury by morphometric measurement of cross-sectional neointimal area and by fluorometric determination of DNA content. The specific Na(+)-H+ exchange inhibitor 3-methylsulfonyl-4-piperidino-benzoyl guanidine mesylate (Hoe 694) dose-dependently reduced neointimal area and DNA content, the latter finding indicating a true antiproliferative effect. The structurally different Na(+)-H+ exchange blocker 5-(N-ethyl-N-isopropyl)amiloride hydrochloride had comparable inhibitory effects on neointimal area and DNA content, whereas 5-methylsulfonyl-2-piperidino-benzoyl guanidine hydrochloride, a position isomer of Hoe 694 lacking Na(+)-H+ exchange blocking properties, did not suppress neointima formation. The effect of Na(+)-H+ exchange blockers on neointima formation depended on the duration of drug application. Maximal suppression was achieved only when Hoe 694 was applied throughout the entire experiment for 14 days. This inhibitory effect of Na(+)-H+ exchange blocker application for the first 2 weeks following injury lasted for 2 months. In conclusion, the results of the present study reveal a potential role of Na(+)-H+ exchange for smooth muscle cell proliferation in vascular disease.