Local expression of C-type natriuretic peptide markedly suppresses neointimal formation in rat injured arteries through an autocrine/paracrine loop

N-terminal pro-brain natriuretic peptide and coronary collateral formation in patients undergoing primary percutaneous coronary intervention

There is insufficient information on the relationship between the N-terminal pro-brain natriuretic peptide (NT-proBNP) level and collateral circulation (CC) formation after primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction. We analyzed 857 patients who underwent primary PCI. The serum NT-proBNP levels were measured on the day of admission, and the CC was scored according to Rentrop’s classification. Log-transformed NT-proBNP levels were significantly higher in patients with good CC compared to those with poor CC (6.13 ± 2.01 pg/mL versus 5.48 ± 1.97 pg/mL, p < 0.001). The optimum cutoff value of log NT-proBNP for predicting CC was 6.04 pg/mL. Log NT-proBNP ≥ 6.04 pg/mL (odds ratio 2.23; 95% confidence interval 1.51–3.30; p < 0.001) was an independent predictor of good CC. CC development was higher in patients with a pre-TIMI flow of 0 or 1 than those with a pre-TIMI flow of 2 or 3 (22.6% versus 8.8%, p = 0.001). The incidence of left ventricular (LV) dysfunction (< 50%) was greater in patients with a pre-TIMI flow of 0 or 1 (49.8% versus 35.5%, p < 0.001). The release of NT-proBNP was greater in patients with LV dysfunction (34.3% versus 15.6%, p < 0.001). The incidence of good CC was greater in patients with log NT-proBNP levels ≥ 6.04 pg/ml (16.8% versus 26.2%, p = 0.003). The association between NT-proBNP and collateral formation was not influenced by pre-TIMI flow and LV function. NT-proBNP appears to reflect the degree of collateral formation in the early phase of STEMI and might have a new role as a useful surrogate biomarker for collateral formation in patients undergoing primary PCI.

Endothelial C-Type Natriuretic Peptide Is a Critical Regulator of Angiogenesis and Vascular Remodeling

BACKGROUND

Angiogenesis and vascular remodeling are complementary, innate responses to ischemic cardiovascular events, including peripheral artery disease and myocardial infarction, which restore tissue blood supply and oxygenation; the endothelium plays a critical function in these intrinsic protective processes. C-type natriuretic peptide (CNP) is a fundamental endothelial signaling species that coordinates vascular homeostasis. Herein, we sought to delineate a central role for CNP in angiogenesis and vascular remodeling in response to ischemia.

METHODS

The in vitro angiogenic capacity of CNP was examined in pulmonary microvascular endothelial cells and aortic rings isolated from wild-type, endothelium-specific CNP^-/-, global natriuretic peptide receptor (NPR)-B^-/- and NPR-C^-/- animals, and human umbilical vein endothelial cells. These studies were complemented by in vivo investigation of neovascularization and vascular remodeling after ischemia or vessel injury, and CNP/NPR-C expression and localization in tissue from patients with peripheral artery disease.

RESULTS

Clinical vascular ischemia is associated with reduced levels of CNP and its cognate NPR-C. Moreover, genetic or pharmacological inhibition of CNP and NPR-C, but not NPR-B, reduces the angiogenic potential of pulmonary microvascular endothelial cells, human umbilical vein endothelial cells, and isolated vessels ex vivo. Angiogenesis and remodeling are impaired in vivo in endothelium-specific CNP^-/- and NPR-C^-/-, but not NPR-B^-/-, mice; the detrimental phenotype caused by genetic deletion of endothelial CNP, but not NPR-C, can be rescued by pharmacological administration of CNP. The proangiogenic effect of CNP/NPR-C is dependent on activation of G_i, ERK1/2, and phosphoinositide 3-kinase γ/Akt at a molecular level.

CONCLUSIONS

These data define a central (patho)physiological role for CNP in angiogenesis and vascular remodeling in response to ischemia and provide the rationale for pharmacological activation of NPR-C as an innovative approach to treating peripheral artery disease and ischemic cardiovascular disorders.

Evolving Role of Natriuretic Peptides from Diagnostic Tool to Therapeutic Modality

Natriuretic peptides (NP) are widely recognized as key regulators of blood pressure, water and salt homeostasis. In addition, they play a critical role in physiological cardiac growth and mediate a variety of biological effects including antiproliferative and anti-inflammatory effects in other organs and tissues. The cardiac release of NPs ANP and BNP represents an important compensatory mechanism during acute and chronic cardiac overload and during the pathogenesis of heart failure where their actions counteract the sustained activation of renin-angiotensin-aldosterone and other neurohormonal systems. Elevated circulating plasma NP levels correlate with the severity of heart failure and particularly BNP and the pro-peptide, NT-proBNP have been established as biomarkers for the diagnosis of heart failure as well as prognostic markers for cardiovascular risk. Despite activation of the NP system in heart failure it is inadequate to prevent progressive fluid and sodium retention and cardiac remodeling. Therapeutic approaches included administration of synthetic peptide analogs and the inhibition of NP-degrading enzyme neutral endopeptidase (NEP). Of all strategies only the combined NEP/ARB inhibition with sacubitril/valsartan had shown clinical success in reducing cardiovascular mortality and morbidity in patients with heart failure.

Gene Therapy for the Extension of Vein Graft Patency: A Review

The mainstay of treatment for long-segment small-vessel chronic occlusive disease not amenable to endovascular intervention remains surgical bypass grafting using autologous vein. The procedure is largely successful and the immediate operative results almost always favorable. However, the lifespan of a given vein graft is highly variable, and less than 50% will remain primarily patent after 5 years. The slow process of graft malfunction is a result of the vein's chronic maladaptive response to the systemic arterial environment, its primary component being the uncontrolled proliferation of vascular smooth muscle cells (SMCs). It has recently been suggested that this response might be attenuated through pre-implantation genetic modification of the vein, so-called gene therapy for the extension of vein graft patency. Gene therapy seems particularly well suited for the prevention or postponement of vein graft failure since: (1) the stimulation of SMC proliferation appears to largely be an early and transient process, matching the kinetics of current gene transfer technology; (2) most veins are relatively normal and free of disease at the time of bypass allowing for effective gene transfer using a variety of systems; and (3) the target tissue is directly accessible during operation because manipulation and irrigation of the vein is part of the normal workflow of the surgical procedure. This review briefly summarizes the current knowledge of the incidence and basic mechanisms of vein graft failure, the vector systems and molecular targets that have been proposed as possible pre-treatments, the results of experimental genetic modification of vein grafts, and the few available clinical studies of gene therapy for vascular proliferative disorders.

Arterial Remodeling in B-Type Natriuretic Peptide Knock-Out Females

Sexual dimorphisms are recognized in cardiovascular conditions such as hypertension, stroke, thrombosis and vasculitis. B-type natriuretic peptide (BNP) is a guanylyl cyclase A (GC-A) agonist. The anti-hypertensive, vasodilatory, anti-fibrotic, and anti-hypertrophic properties of BNP are well established in male animal models. Although circulating BNP levels are higher in women, when compared to age-matched men, the cardiovascular protective propensity of BNP in females is poorly understood. We assessed the cardiovascular consequences of BNP deletion in genetically null (Nppb−/−) female rat lines. Throughout the study, blood pressure (BP) remained uninfluenced by genotype, and cardiorenal consequences of BNP knock out remained minor. Unexpectedly, approximately 60% of Nppb−/− females developed mesenteric polyarteritis-nodosa (PAN)-like vasculitis in their life span, some as early as 4 months of age. Mesenteric lesions involved intense arterial remodeling, progressive inflammation, occluded lumens, and less frequently intestinal necrosis and multiple visceral arterial aneurysms. Cumulative pathologies resulted in a significant decline in survival of the Nppb−/− female. This study highlights BNP’s vasoprotective propensity, bringing to light a possible sex specific difference in the cardiovascular protection provided by BNP. Defects in the BNP/GC-A/cGMP pathway may play a role in arteriopathies in women, while GC-A agonists may provide effective therapy for arteritis.

Natriuretic Peptides and Cardiometabolic Health

Natriuretic peptides are cardiac-derived hormones with a range of protective functions, including natriuresis, diuresis, vasodilation, lusitropy, lipolysis, weight loss, and improved insulin sensitivity. Their actions are mediated through membrane-bound guanylyl cyclases that lead to production of the intracellular second-messenger cyclic guanosine monophosphate. A growing body of evidence demonstrates that genetic and acquired deficiencies of the natriuretic peptide system can promote hypertension, cardiac hypertrophy, obesity, diabetes mellitus, the metabolic syndrome, and heart failure. Clinically, natriuretic peptides are robust diagnostic and prognostic markers, and augmenting natriuretic peptides is a target for therapeutic strategies in cardiometabolic disease. This review will summarize current understanding and highlight novel aspects of natriuretic peptide biology.

Natriuretic peptides in cardiometabolic regulation and disease

In the 30 years since the identification of the natriuretic peptides, their involvement in regulating fluid and blood pressure has become firmly established. Data indicating a role for these hormones in lifestyle-related metabolic and cardiovascular disorders have also accumulated over the past decade. Dysregulation of the natriuretic peptide system has been associated with obesity, glucose intolerance, type 2 diabetes mellitus, and essential hypertension. Moreover, the natriuretic peptides have been implicated in the protection against atherosclerosis, thrombosis, and myocardial ischaemia. All these conditions can coexist and potentially lead to heart failure, a syndrome associated with a functional natriuretic peptide deficiency despite high circulating concentrations of immunoreactive peptides. Therefore, dysregulation of the natriuretic peptide system, a 'natriuretic handicap', might be an important factor in the initiation and progression of metabolic dysfunction and its accompanying cardiovascular complications. This Review provides a summary of the natriuretic peptide system and its involvement in these cardiometabolic conditions. We propose that these peptides might have an integrating role in lifestyle-related metabolic and cardiovascular disorders.

Natriuretic peptide receptor-3 underpins the disparate regulation of endothelial and vascular smooth muscle cell proliferation by C-type natriuretic peptide

BACKGROUND AND PURPOSE

C-type natriuretic peptide (CNP) is an endothelium-derived vasorelaxant, exerting anti-atherogenic actions in the vasculature and salvaging the myocardium from ischaemic injury. The cytoprotective effects of CNP are mediated in part via the G_i-coupled natriuretic peptide receptor (NPR)3. As GPCRs are well-known to control cell proliferation, we investigated if NPR3 activation underlies effects of CNP on endothelial and vascular smooth muscle cell mitogenesis.

EXPERIMENTAL APPROACH

Proliferation of human umbilical vein endothelial cells (HUVEC), rat aortic smooth muscle cells (RAoSMC) and endothelial and vascular smooth muscle cells from NPR3 knockout (KO) mice was investigated in vitro.

KEY RESULTS

CNP (1 pM–1 µM) facilitated HUVEC proliferation and inhibited RAoSMC growth concentration-dependently. The pro- and anti-mitogenic effects of CNP were blocked by the NPR3 antagonist M372049 (10 µM) and the extracellular signal-regulated kinase (ERK) 1/2 inhibitor PD98059 (30 µM) and were absent in cells from NPR3 KO mice. Activation of ERK 1/2 by CNP was inhibited by Pertussis toxin (100 ng·mL⁻¹) and M372049 (10 µM). In HUVEC, ERK 1/2 activation enhanced expression of the cell cycle promoter, cyclin D1, whereas in RAoSMC, ERK 1/2 activation increased expression of the cell cycle inhibitors p21^waf1/cip1 and p27^kip1.

CONCLUSIONS AND IMPLICATIONS

A facet of the vasoprotective profile of CNP is mediated via NPR3-dependent ERK 1/2 phosphorylation, resulting in augmented endothelial cell proliferation and inhibition of vascular smooth muscle growth. This pathway may offer an innovative approach to reversing the endothelial damage and vascular smooth muscle hyperplasia that characterize many vascular disorders.

Urinary C-type natriuretic peptide excretion: a potential novel biomarker for renal fibrosis during aging

Renal aging is characterized by structural changes in the kidney including fibrosis, which contributes to the increased risk of kidney and cardiac failure in the elderly. Studies involving healthy kidney donors demonstrated subclinical age-related nephropathy on renal biopsy that was not detected by standard diagnostic tests. Thus there is a high-priority need for novel noninvasive biomarkers to detect the presence of preclinical age-associated renal structural and functional changes. C-type natriuretic peptide (CNP) possesses renoprotective properties and is present in the kidney; however, its modulation during aging remains undefined. We assessed circulating and urinary CNP in a Fischer rat model of experimental aging and also determined renal structural and functional adaptations to the aging process. Histological and electron microscopic analysis demonstrated significant renal fibrosis, glomerular basement membrane thickening, and mesangial matrix expansion with aging. While plasma CNP levels progressively declined with aging, urinary CNP excretion increased, along with the ratio of urinary to plasma CNP, which preceded significant elevations in proteinuria and blood pressure. Also, CNP immunoreactivity was increased in the distal and proximal tubules in both the aging rat and aging human kidneys. Our findings provide evidence that urinary CNP and its ratio to plasma CNP may represent a novel biomarker for early age-mediated renal structural alterations, particularly fibrosis. Thus urinary CNP could potentially aid in identifying subjects with preclinical structural changes before the onset of symptoms and disease, allowing for the initiation of strategies designed to prevent the progression of chronic kidney disease particularly in the aging population.

Central role of guanylyl cyclase in natriuretic peptide signaling in hypertension and metabolic syndrome

Studied for nearly 30 years for its ability to control many parameters, such as vascular smooth muscle cell relaxation, heart fibrosis, and kidney function, the natriuretic peptide (NP) system is now considered to be a key element in several other major metabolic pathways. After stimulation by NPs, natriuretic peptide receptors (NPR) convert GTP to the second messenger cGMP. In addition to its vasodilatory effects and natriuretic and diuretic functions, cGMP has been positively associated with fat cell function, apoptosis, and NPR expression/activity modulation. The NP system is also closely linked to metabolic syndrome (MetS) progression and obesity control. A new era is now on its way targeting the NP system to not only treat high blood pressure, but to also assist in the fight against the obesity pandemic. Here, we summarize recent data on the role of NPs in hypertension and MetS.

B-type natriuretic peptide enhances vasculogenesis by promoting number and functional properties of early endothelial progenitor cells

OBJECTIVE

To test the hypothesis that B-type natriuretic peptide (BNP) acts as a potent vasculogenic agent by enhancing the number, proliferation, adhesion, and migration of endothelial progenitor cells (EPCs).

BACKGROUND

BNP is a neurohormonal peptide that predicts outcome and used for treatment in chronic heart failure patients. It has been shown to promote angiogenesis in experimental animals. EPCs have been demonstrated to contribute to postnatal angiogenesis and vasculogenesis.

METHODS

The number of EPC colony forming units (CFU) and levels of N-terminal ProBNP were assayed in patients with severe, yet controlled, New York Heart Association (NYHA) II-IV heart failure. The in vitro effects of BNP on early EPC-CFU numbers, proliferation, migration, adhesive, and vascular tube formation capacities were studied using human and murine systems. The effects of in vivo BNP administration on Sca-1/Flk-1 progenitors and on vasculogenesis in the hindlimb ischemia model were then assayed in wild-type mice.

RESULTS

A significant correlation was found between circulating N-terminal ProBNP levels and EPC-CFU numbers. We observed a dose-dependent effect of BNP on the numbers of CFU and proliferation capacity of human EPCs as well as on their adhesive, migratory, and tube formation properties, in vitro. Systemic BNP administration to mice led to a significant increase in bone marrow Sca-1/Flk-1 EPCs and improvement in blood flow and capillary density in the ischemic limbs of mice.

CONCLUSIONS

BNP promotes vessel growth by increasing the number of endothelial progenitors and enhancing their functional properties. These provasculogenic properties of BNP could account for some of its beneficial effects in chronic heart failure patients and may be harnessed for the purpose of improving collateral formation in ischemic subjects.

C-type natriuretic peptide in prostate cancer

C-type natriuretic peptide (CNP) is expressed in the male reproductive organs in pigs. To examine whether the human prostate also expresses the CNP gene, we measured CNP and N-terminal proCNP in prostate cancer tissue extracts and performed immunohistochemical biopsy staining. Additionally, proCNP-derived peptides were quantitated in plasma from patients with prostate cancer. Blood was collected from healthy controls and patients before surgery for localized prostate cancer. Tissue extracts were prepared from tissue biopsies obtained from radical prostatectomy surgery. N-terminal proCNP, proCNP (1-50) and CNP were measured in plasma and tissue extracts. Biopsies were stained for CNP-22 and N-terminal proCNP. Tissue extracts from human prostate cancer contained mostly N-terminal proCNP [median 5.3 pmol/g tissue (range 1.0-12.9)] and less CNP [0.14 pmol/g tissue (0.01-1.34)]. Immunohistochemistry demonstrated the presence of the peptides in prostatic epithelial cells. The N-terminal proCNP concentrations in plasma were marginally lower in patients with localized prostate cancer compared with control subjects [13.8 pmol/l (11.0-17.2) vs. 15.1 pmol/l (10.4-23.2), p=0.002] but not enough to justify the use of N-terminal proCNP as a cancer marker. Further research is needed to establish whether measurement of proCNP-derived peptides may offer clinical information.

C-type natriuretic peptide for reduction of restenosis: gene transfer is superior over single peptide administration

BACKGROUND

Restenosis is still a significant clinical problem limiting the long-term therapeutic success following balloon dilation or stent implantation. New approaches are necessary inhibiting neointima formation and simultaneously promoting re-endothelialization. Therefore, long-term therapeutic effects of adventitial liposome-mediated C-type natriuretic protein (CNP) gene and CNP peptide applications in a porcine model for restenosis post-angioplasty were investigated.

METHODS

For in vitro applications, primary cultures of porcine vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) were used. Gene transfer was performed with cationic lipid DOCSPER [1,3-dioleoyloxy-2-(N5-carbamoylspermine)propane]. In vivo treatment of pig femoral arteries was adventitial using a needle injection catheter following balloon angioplasty. Arteries were investigated by angiography, Evan's blue staining, histomorphometry, immunohistochemistry, PCR and RT-PCR.

RESULTS

Using CNP gene transfer in vitro, 29.4+/-7.2% reduction of cell proliferation in VSMCs was observed. In ECs, the CNP gene did not compromise cellular growth. For the CNP peptide the optimal concentration was 1 mM with 50.7+/-11.3% reduction of VSMC proliferation and 12.1+/-5.3% enhancement of growth of ECs. Three weeks following application in vivo complete re-endothelialization was observed in all treated groups. At 3 months significant reduction of neointima formation was observed using CNP gene vs. CNP peptide (85.9+/-7.8% vs. 63.3+/-27.6% reduction, P<0.05) compared to control treatment.

CONCLUSION

Periadventitial liposome-mediated CNP gene transfer in vivo resulted in a significant long-term reduction of neointima formation without compromising endothelial repair and was superior over single CNP peptide administration. Advantages of CNP are its physiological origin and simultaneous inhibition of VSMC proliferation and promotion of EC growth.

Membrane guanylyl cyclase receptors: an update

Recent studies have demonstrated key roles for several membrane guanylyl cyclase receptors in the regulation of cell hyperplasia, hypertrophy, migration and extracellular matrix production, all of which having an impact on clinically relevant diseases, including tissue remodeling after injury. Additionally, cell differentiation, and even tumor progression, can be profoundly influenced by one or more of these receptors. Some of these receptors also mediate important communication between the heart and intestine, and the kidney to regulate blood volume and Na+ balance.

Heart specific up-regulation of genes for B-type and C-type natriuretic peptide receptors in diabetic mice

BACKGROUND

Diabetes may cause cardiomyopathy characterized by cardiac fibrosis. Recent studies of genetically modified mice have elucidated a role of the natriuretic peptides (NP), type-A and type-B (ANP and BNP), and their common receptor [natriuretic peptide receptor (NPR), type-A] in development of cardiac fibrosis. The role of NP type-C (CNP) and NPR type-B (NPR-B) in the heart is less well established. In this study we examined if diabetes alters heart expression of the genes encoding the NP and its receptors.

MATERIALS AND METHODS

Cardiac mRNA was quantified by real-time PCR in diabetic streptozotocin (STZ)-treated and ob/ob-mice and nondiabetic control mice.

RESULTS

The ob/ob-mice with type-II diabetes displayed highly significant increases of the cardiac mRNA expression of NPR-B and NPR-C while the expression levels of NPR-A, ANP, BNP, and CNP mRNA were similar in ob/ob-mice and controls. Mice with STZ-induced type-I diabetes also showed an increase of heart NPR-B mRNA expression at 12 weeks, but not at 3, 6 or 9 weeks after STZ-treatment. The ANP and NPR-C mRNA expressions were only altered after 3 weeks, whereas BNP, CNP and NPR-A mRNA expressions were not altered in STZ-treated-mouse hearts at any of the time points.

CONCLUSIONS

The results show that diabetes in mice confers increased NPR-B gene expression in the heart, suggesting that increased NPR-B signalling may affect development of diabetic cardiomyopathy.

C-type natriuretic Peptide down-regulates expression of its cognate receptor in rat aortic smooth muscle cells

The C-type natriuretic (CNP) peptide signals through the type B natriuretic peptide receptor (NPR-B) in vascular smooth muscle cells to activate the particulate guanylyl cyclase activity intrinsic to that receptor and raise cellular cyclic GMP levels. In the present study, we demonstrate that CNP down-regulates the expression of this receptor leading to a reduction in NPR-B activity. Pretreatment of rat aortic smooth muscle cells with CNP reduces NPR-B activity, NPR-B protein levels, NPR2 (NPR-B gene) mRNA levels, and NPR2 promoter activity. The decrease in NPR2 promoter activity is dependent on DNA sequence present between -441 and -134 relative to the transcription start site. The reduction in NPR2 gene expression appears to operate through generation of cyclic GMP. 8-Bromo cyclic GMP, a membrane-permeable cyclic GMP analog, reduced NPR2 mRNA levels and NPR2 promoter activity. Atrial natriuretic peptide, which signals through the type A natriuretic peptide receptor (NPR-A) to increase cyclic GMP levels in these cells, also reduced NPR-B mRNA levels and inhibited NPR-B promoter activity; however, this inhibition was not additive with that produced by CNP, implying that the two ligands traffic over a common signal transduction pathway. This report provides the first documentation that CNP is capable of autoregulating the expression of its cognate receptor.

C-Type Natriuretic Peptide Relaxes Human Coronary Artery Bypass Grafts Preconstricted by Endothelin-1

BACKGROUND

Endothelin is implicated in graft spasm after coronary artery bypass grafting. We assessed reversal by the endothelium-derived vasodilator C-type natriuretic peptide of prior contraction of radial artery and other vessels commonly used for coronary artery bypass surgery.

METHODS

Segments of human radial artery, saphenous vein, and internal mammary artery were mounted in organ baths after removal from patients undergoing cardiac surgery (n = 34; 64 +/- 2 years). Effects of increasing concentrations of C-type natriuretic peptide (with or without aprotinin, 1,000 U/mL) on endothelin-induced contraction were compared with acetylcholine, sodium nitroprusside, and papaverine.

RESULTS

C-type natriuretic peptide relaxed endothelin precontraction in all vessels (F = 17.8, 36.3, and 48.4, respectively; p < 0.001), with maximum relaxations of 44%, 54%, and 66% in saphenous vein, internal mammary artery, and radial artery, respectively. Aprotinin did not affect relaxation to C-type natriuretic peptide. Acetylcholine relaxed the saphenous vein weakly, with maximal relaxation of 9% at 10(-6) M. However, the radial artery and internal mammary artery relaxed strongly to acetylcholine. The highest concentration of papaverine completely relaxed all vessels, but responses were less sensitive than to sodium nitroprusside or acetylcholine.

CONCLUSIONS

C-type natriuretic peptide reverses endothelin-induced constriction in arterial and venous conduits used for coronary artery bypass, particularly the radial artery. Proteolytic breakdown of C-type natriuretic peptide by local vascular enzymes appears of little importance in vitro. This signals the therapeutic potential of using C-type natriuretic peptide as an antagonist of graft vasospasm after coronary artery bypass surgery.

Serine proteases and cardiac function

The serine proteases of the trypsin superfamily are versatile enzymes involved in a variety of biological processes. In the cardiovascular system, the importance of these enzymes in blood coagulation, platelet activation, fibrinolysis, and thrombosis has been well established. Recent studies have shown that trypin-like serine proteases are also important in maintaining cardiac function and contribute to heart-related disease processes. In this review, we describe the biological function of corin, tissue kallikrein, chymase and urokinase and discuss their roles in cardiovascular diseases such as hypertension, cardiac hypertrophy, heart failure, and aneurysm.

C-type natriuretic peptide and guanylyl cyclase B receptor

Guanylyl cyclases (GC) are widely distributed enzymes that signal via the production of the second messenger cGMP. The particulate guanylyl cyclases share a similar topology: an extracellular ligand binding domain and intracellular regulatory kinase-homology and cyclase catalytic domains. The natriuretic peptide receptors GC-A and -B mediate the effects of a family of peptides, atrial, B- and C-type natriuretic peptide (ANP, BNP and CNP, respectively), with natriuretic, diuretic and vasorelaxant properties. ANP and BNP, through the activation of GC-A, act as endocrine hormones to regulate blood pressure and volume, and inhibit cardiac hypertrophy. CNP, on the other hand, acts in an autocrine/paracrine fashion to induce vasorelaxation and vascular remodeling, and to regulate bone growth through its cognate receptor GC-B. GC-B, like GC-A, is phosphorylated in the basal state, and undergoes both homologous and heterologous desensitization, reflected by dephosphorylation of specific sites in the kinase-homology domain. This review will examine the structure and function of GC-B, and summarize the physiological processes in which this receptor is thought to participate.

Atrial Natriuretic Peptide Preserves Endothelial Function during Intimal Hyperplasia

BACKGROUND

Atrial and C-type natriuretic peptides (ANP and CNP), acting through different receptors, have antiproliferative effects in vitro. Beneficial effects of CNP in vivo on early atherosclerosis have been described, but it is not known if ANP is antiproliferative in vivo. In the present study, the effects of chronic in vivo ANP were tested and compared with CNP on endothelial dysfunction and intimal thickening caused by peri-arterial collars.

METHODS

Non-occlusive collars were placed bilaterally around the common carotid arteries of rabbits. One collar was filled with saline vehicle. The contralateral collar was filled with ANP or CNP (1 or 10 microM, n = 5-7) with slow replacement of peptide via mini-pump (1 or 10 fmol/h).

RESULTS

After 7 days, endothelium-dependent vasorelaxation in saline-collared arteries was 33 +/- 3% of maximum [averaged over 0.03-1 muM acetylcholine (ACh)] compared to 64 +/- 2% in normal (uncollared) arteries (p < 0.05, n = 23). In vivo ANP restored the ACh relaxation to normal (e.g., 57 +/- 6%, 1 microM ANP), similar to effects seen with CNP in vivo. Endothelium-independent vasorelaxation of collared-vessels was not altered by either peptide. Intimal hyperplasia induced by the collars was not prevented by peri-arterial natriuretic peptides. In additional rabbits (n = 6), CNP (100 pmol/h) given directly into the lumen of collared carotid arteries for 7 days reduced neointima formation by 16 +/- 5% (p < 0.05), whereas ANP given intraluminally (100 pmol/h; n = 6) did not.

CONCLUSIONS

The more potent actions of CNP on vascular smooth muscle cell migration and proliferation (established in vitro) may explain differences between the peptides on intimal hyperplasia in vivo. The major hallmark of atherosclerosis and restenosis, endothelial dysfunction, was prevented by chronic, peri-arterial administration of ANP or CNP.

Alteration in the IL-2 signal peptide affects secretion of proteinsin vitro andin vivo

BACKGROUND

Although hundreds of different signal peptides have now been identified, few studies have examined the factors enabling signal peptides to augment secretion of mature proteins. Signal peptides, located at the N-terminus of nascent secreted proteins, characteristically have three domains: (1) a basic domain at the N-terminus, (2) a central hydrophobic core, and (3) a carboxy-terminal cleavage region. In this study, we investigated whether alterations in the basic and/or the hydrophobic domains of a commonly used signal peptide from interleukin-2 (IL-2) affected secretion of two proteins: placental alkaline phosphatase (AP) and endostatin.

METHODS

A series of modifications in the basic and/or hydrophobic domains of the IL-2 signal peptide were made by polymerase chain reaction with endostatin or AP plasmids as templates. Transfection of wild-type or modified IL-2 signal peptides fused in-frame with endostatin or AP were done with Superfect in vitro or by the hydrodynamic method in vivo.

RESULTS

Increasing both the basicity and hydrophobicity of the signal peptide augmented the secretion of AP and endostatin by approximately 2.5- and 3.5-fold, respectively, from MDA-MB-435 cells in vitro. Over a range of DNA concentrations and times, the most effective IL-2 signal peptide increased AP levels in the medium compared to the wild-type IL-2 signal peptide. Comparable results from these modified IL-2 signal peptides were found to increase AP levels in the medium from bovine aortic endothelial cells. Moreover, the combined changes in basic and hydrophobic domains of the IL-2 signal peptide augmented serum levels of endostatin and placental AP by 3-fold when the optimal plasmid constructs were injected in vivo.

CONCLUSIONS

Modification of the IL-2 signal peptide augments protein secretion both in vitro and in vivo. As a result, optimizing the signal peptide should be considered for increasing the therapeutic levels of secreted proteins.

Matrilysin (MMP-7) expression in renal tubular damage: association with Wnt4

BACKGROUND

Matrilysin, a secreted matrix metalloproteinase and target gene of Wnt signaling, functions in epithelial repair and host defense, but no role in renal injury has been described.

METHODS

Matrilysin expression was assessed in human kidney specimens by immunohistochemistry, and in experimental renal injury in mice by immunohistochemistry, Northern blotting, and RNase protection assays (RPA). A relationship to Wnt4, which is also induced in renal injury, was determined by RPA and in situ hybridization.

RESULTS

Matrilysin was not detected in the normal human renal tubular epithelium by immunohistochemistry. However, prominent staining was detected in sections from autosomal-dominant polycystic kidney disease in the cyst lining epithelium, atrophic tubules, and cyst micropolyps, and from hydronephrosis in dilated and atrophic tubules. Matrilysin expression was also induced by acute folic acid nephropathy and unilateral ureteral obstruction (UUO) in the mouse, and expression increased as acute injury progressed to tubulointerstitial fibrosis. Matrilysin staining was primarily localized to epithelium of distal tubule/collecting duct origin in both human and murine renal disease. Wnt signaling can induce matrilysin expression, and we found that the pattern of matrilysin expression during progression of renal fibrosis in the mouse after UUO or folic acid nephropathy, and in the jck model of murine polycystic kidney disease, closely paralleled that of Wnt4.

CONCLUSION

These observations suggest that matrilysin may have a role in renal tubular injury and progression of tubulointerstitial fibrosis, and that Wnt4 may regulate matrilysin expression in the kidney.

Local overexpression of C-type natriuretic peptide ameliorates vascular adaptation of porcine hemodialysis grafts

BACKGROUND

Outflow obstruction at the outflow tract of arteriovenous grafts contributes significantly to the poor patency rates of dialysis grafts in vivo. We addressed the potential of local periadventitial gene therapy at the outflow tract for improving access patency in a validated porcine model of arteriovenous grafts using an adenoviral vector encoding murine C-type natriuretic peptide (Ad.CNP).

METHODS

Gene transfer efficiency and optimal virus concentration were determined using Ad.LacZ on porcine jugular veins in vivo (N= 2). Next, in 14 pigs, arteriovenous grafts were implanted bilaterally between the carotid artery and the jugular vein, followed local venous transduction with Ad.CNP (right) and Ad.mock (left). Transduction efficiency of Ad.CNP was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and cyclic guanosine monophosphate (cGMP) measurements (N= 2). Fourteen days after gene transfer, arteriovenous grafts were excised for histologic analysis (N= 12).

RESULTS

Ad.LacZ transduction (1 x 10E10 IU) of porcine veins resulted in evident expression of beta-galactosidase, mainly in the adventitia. At termination, intima/media ratio was decreased by 37% in CNP-treated veins, predominantly due to medial thickening (Ad.CNP 3.1 +/- 0.6 mm(2) vs. Ad.mock 1.70 +/- 0.3 mm(2); P < 0.01) rather than decreased intimal hyperplasia (NS). Adventitial delivery of CNP resulted in increased external elastic lamina (EEL) (Ad.CNP 11.8 +/- 1.4 mm vs. Ad.mock 9.4 +/- 1.0 mm; P= 0.04) and luminal area (Ad.CNP 10.7 +/- 1.4 mm(2) vs. Ad.mock 8.8 +/- 1.7 mm(2); P= 0.05) at the venous anastomosis.

CONCLUSION

Overexpression of CNP enhances venous medial thickening and increases outward remodeling in the outflow tract of porcine arteriovenous grafts. These findings underscore the potential of local gene-therapeutic interventions in preventing luminal narrowing at the outflow tract of hemodialysis grafts.

Vitamin E improves fibrinolytic activity in patients with coronary spastic angina

INTRODUCTION

The fibrinolytic system has a major role as a defense mechanism against thrombus formation. Net fibrinolytic activity in plasma reflects the balance between tissue-type plasminogen activator and plasminogen activator inhibitor (PAI). PAI is the main factor determining overall fibrinolytic activity.

MATERIALS AND METHODS

We examined the effects of oral administration of vitamin E, an antioxidant, on fibrinolytic activity and oxidative stress in patients with coronary spastic angina. Forty patients with coronary spastic angina were randomly assigned into two treatment groups, either vitamin E group (alpha-tocopherol acetate, 400 mg/day) or placebo group by means of computerized system. PAI activity and thioredoxin, a marker of oxidative stress, levels were measured before and at the end of 1 month treatment.

RESULTS

Before treatment, the levels of PAI activity and thioredoxin were increased in patients with coronary spastic angina as compared with control subjects (n=17) (PAI activity levels: 13.6+/-1.4 vs. 7.6+/-2.2 IU/ml, p<0.05, thioredoxin levels: 22.8+/-1.7 vs. 16.0+/-1.4 ng/ml, p<0.05). In patients with coronary spastic angina, administration of vitamin E decreased both PAI activity and thioredoxin levels (PAI activity levels: 14.7+/-1.7 to 7.5+/-1.6 IU/ml, p<0.01, thioredoxin levels: 23.3+/-2.4 to 15.1+/-2.5 ng/ml, p<0.01), whereas placebo had no effect on these variables.

CONCLUSIONS

Oral administration of vitamin E improved fibrinolytic activity and the improvement was associated with a decrease in oxidative stress. Administration of vitamin E is possible to be an effective adjunct therapy of coronary spasm in the absence of coronary atherosclerosis.

Effect of plasminogen activator inhibitor-1 in diabetes mellitus and cardiovascular disease

Concentrations of plasminogen activator inhibitor-1 (PAI-1) are elevated beginning at the stage of impaired glucose tolerance and continuing through the development of diabetes mellitus and the metabolic syndrome. Evolving evidence of the central role of PAI-1 in mediating fibrosis and thrombosis increasingly supports the theory that it is a significant risk factor for macrovascular complications and cardiovascular disease, particularly in patients with diabetes. Several clinical studies have demonstrated a strong correlation between circulating PAI-1 levels and cardiovascular events and mortality. With the potentially severe effects of elevated PAI-1 levels becoming evident, there is increased interest in developing therapies targeted at reducing PAI-1 expression or circulating concentrations. Thus far, weight loss, inhibitors of the renin-angiotensin system, and insulin sensitization through use of thiazolidinediones (TZDs) appear to be the most promising strategies for managing elevated PAI-1 levels. Of these, TZD therapy is the only one that provides the benefits of both long-term glycemic control and improved cardiovascular risk profile. This article reviews the regulation of PAI-1, its activity in various disease states, and available treatment options.

Identification of a potent serum factor that causes desensitization of the receptor for C-Type natriuretic peptide

Background

Guanylyl cyclase-B (GC-B; NPR-B), the receptor for C-type natriuretic peptide (CNP) is rapidly and effectively desensitized by a factor(s) in serum. Given the potential importance of this receptor in remodeling after tissue injury, identification of the serum factor(s) is of significant medical importance.

Results

Partial purification of desensitization activity in serum by DEAE-Sepharose and reverse phase C18 chromatography, followed by mass spectroscopy, identified peptide sequences identical to those of apolipoprotein A2 (Apo A2), a known component of high density lipoprotein (HDL). Apo A2, however, could be eliminated as the active desensitization factor. Never the less, substantial desensitization activity was associated with purified preparations of bovine or human HDL. Since HDL is a well-known transporter of various lipids and phospholipids, we extracted either HDL or partially purified serum preparations with butanol and all activity extracted into the solvent. Of various lipophilic signaling molecules known to be associated with HDL, a prominent component is sphingosine-1-phosphate (S1P). We therefore tested authentic S1P as well as other known components of HDL (sphingosylphosphorylcholine; platelet activating factor) for activity; only S1P caused desensitization of GC-B. S1P was relatively potent, causing one-half maximal desensitization of GC-B at concentrations of 5–10 nM. These effects were seen within a few minutes after addition. Lysophosphatidic acid, another component of serum capable of desensitizing GC-B, was only effective at Micromolar concentrations. The pathway by which serum or S1P desensitizes GC-B seems unique in that pertussis toxin failed to inhibit GC-B desensitization, and yet blocked serum or S1P activation of extracellular signal-regulated kinase (ERK) or Akt/protein kinase B (Akt/PKB).

Conclusion

Since the concentrations of S1P that desensitize GC-B are well within serum physiological ranges, this mitogenic signaling molecule likely functions as a strong adversary of the CNP/GC-B signaling pathway in the regulation of cell proliferation and other growth factor-induced phenotypes. The mechanism by which S1P desensitizes GC-B appears different than the known S1P signaling pathways.

Furin-mediated processing of Pro-C-type natriuretic peptide

C-type natriuretic peptide (CNP) is a member of the natriuretic peptide family that is involved in a variety of homeostatic processes. Here we characterize the processing essential for the conversion of the precursor, human pro-CNP, to the biologically active hormone. In human embryonic kidney 293 and chondrosarcoma SW 1353 cells, recombinant pro-CNP was converted into a mature peptide intracellularly as detected by Western analysis. Expression of recombinant human corin, a proatrial natriuretic peptide convertase, did not enhance the processing of pro-CNP in these cells. The processing of pro-CNP was inhibited in the presence of an inhibitor of the endoprotease furin but was not affected by inhibitors of matrix metalloproteinases and tumor necrosis factor-alpha convertase. In furin-deficient human colon adenocarcinoma LoVo cells, no conversion of recombinant pro-CNP to CNP was detected. Expression of recombinant human furin in LoVo cells restored the ability of these cells to process pro-CNP. Furthermore, incubation of purified recombinant human furin with LoVo cell lysate containing pro-CNP led to the conversion of the precursor to a mature peptide. The furin-processed CNP was shown to be biologically active in a cell-based cGMP assay. These results demonstrate that furin is a critical enzyme for the processing of human pro-CNP.

CNP gene expression is activated by Wnt signaling and correlates with Wnt4 expression during renal injury

C-type natriuretic peptide (CNP) regulates salt excretion, vascular tone, and fibroblast proliferation and activation. CNP inhibits fibroblast activation in vitro and fibrosis in vivo, but endogenous CNP gene (Nppc) expression during tissue fibrosis has not been reported. We determined that Nppc is induced in renal tubular epithelia and then in interstitial myofibroblasts after unilateral ureteral obstruction (UUO). Induction of Nppc occurred in identical cell populations to those in which Wnt4 is induced after renal injury. In addition, Nppc was activated in Wnt4-expressing cells during nephrogenesis. Wnt signaling components beta-catenin and T cell factor/lymphoid enhancer binding factor (TCF/LEF) specifically bound to cognate elements in the Nppc proximal promoter. Wnt-4, beta-catenin, and LEF-1 activated an Nppc transgene in cultured cells, and transgene activation by Wnt-4 and LEF-1 was dependent on the presence of intact cognate elements. These findings suggest that Wnt-4 stimulates Nppc in a TCF/LEF-dependent manner after renal injury and thus may contribute to limiting renal fibrosis.

Molecular biology and gene transfer in atherosclerosis in the stenting era

Atherosclerosis is the major cause of death in the developed world. Understanding the pathogenesis of atherosclerosis has been a major challenge to cardiovascular research over the past several decades. During this period a number of advances in various scientific disciplines has increased our understanding of this disease. These include improved understanding of the structural and functional components of normal vessel wall and more recently the use of cell biology and molecular biology techniques to elucidate the pathogenesis of atherosclerosis. None of these advances has been more dramatic nor has potentially more far reaching consequences as the application of molecular biology and gene technology to the practice of cardiovascular medicine. These developments have already opened new and exciting areas of vascular research and may in the future provide for earlier identification of genetic predisposition to atherosclerosis, strategic planning of preventive therapy and more tailored pharmacologic approaches for established disease.

Vasopressin-dependent inhibition of the C-type natriuretic peptide receptor, NPR-B/GC-B, requires elevated intracellular calcium concentrations

Natriuretic peptides bind their cognate cell surface guanylyl cyclase receptors and elevate intracellular cGMP concentrations. In vascular smooth muscle cells, this results in the activation of the type I cGMP-dependent protein kinase and vasorelaxation. In contrast, pressor hormones like arginine-vasopressin, angiotensin II, and endothelin bind serpentine receptors that interact with G(q) and activate phospholipase Cbeta. The products of this enzyme, diacylglycerol and inositol trisphosphate, activate the conventional and novel forms of protein kinase C (PKC) and elevate intracellular calcium concentrations, respectively. The latter response results in vasoconstriction, which opposes the actions of natriuretic peptides. Previous reports have shown that pressor hormones inhibit natriuretic peptide receptors NPR-A or NPR-B in a variety of different cell types. Although the mechanism for this inhibition remains unknown, it has been universally accepted that PKC is an obligatory component of this pathway primarily because pharmacologic activators of PKC mimic the inhibitory effects of these hormones. Here, we show that in A10 vascular smooth muscle cells, neither chronic PKC down-regulation nor specific PKC inhibitors block the AVP-dependent desensitization of NPR-B even though both processes block PKC-dependent desensitization. In contrast, the cell-permeable calcium chelator, BAPTA-AM (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, tetraacetoxymethyl ester), abrogates the AVP-dependent desensitization of NPR-B, and ionomycin, a calcium ionophore, mimics the AVP effect. These data show that the inositol trisphosphate/calcium arm of the phospholipase C pathway mediates the desensitization of a natriuretic peptide receptor in A10 cells. In addition, we report that CNP attenuates AVP-dependent elevations in intracellular calcium concentrations. Together, these data reveal a dominant role for intracellular calcium in the reciprocal regulation of these two important vasoactive signaling systems.

Intraluminal gene transfer of endothelial cell-nitric oxide synthase suppresses intimal hyperplasia of vein grafts in cholesterol-fed rabbit: a limited biological effect as a result of the loss of medial smooth muscle cells

BACKGROUND

The intimal hyperplasia of vein grafts is a major cause of late graft failure and is more pronounced under hyperlipidemia. We previously reported that endothelial cell (ec)-type nitric oxide synthase (NOS) gene transfer inhibited graft intimal hyperplasia under poor runoff conditions. However, little information is available on either ecNOS gene transfer or intimal thickening under hypercholesterolemia.

METHODS

Using the hemagglutinating virus of Japan liposomes, bovine ecNOS complentary DNA (5000 hemagglutinating activity units/mL) was transfected intraluminally to the right jugular vein, and these veins were then implanted as reversed vein grafts in an end-to-side fashion to the ipsilateral carotid artery.

RESULTS

The cyclic guanosine 3',5'-monophosphate content of the ecNOS vein significantly increased in the grafts at 4 days after gene transfer, but the levels were only 25% greater than those found in the untreated veins. An immunohistochemical analysis at the same time suggested a large loss of medial smooth muscle cells that might have led to a reduction in the exogenous gene expression. The neointima of the ecNOS grafts was significantly reduced 4 weeks after implantation (P <.05), but the effect of ecNOS was limited to about a 30% inhibition. This reduction was associated with a reduced population of proliferating cells and decreased macrophage accumulation in the graft wall.

CONCLUSIONS

These results demonstrated that the ecNOS gene transfer suppressed intimal hyperplasia of the vein grafts under hyperlipidemic conditions. However, this effect may be limited because of the smooth muscle cell loss related to the use of an intraluminal delivery methods. These data lead to speculation that the outcome of ecNOS gene transfer could be improved using different methods of gene delivery.

Local delivery of single low-dose of C-type natriuretic peptide, an endogenous vascular modulator, inhibits neointimal hyperplasia in a balloon-injured rabbit iliac artery model

C-type natriuretic peptide (CNP) is an endogenous vascular modulator. In addition to vasodilation, CNP exerts multifunctions including anti-thrombus and anti-proliferation actions against vascular smooth muscle cells and myofibroblasts. Therefore, CNP is a potential therapeutic agent for the prevention of restenosis following angioplasty. The current study investigated whether local delivery of CNP, even at microgram levels about three orders of magnitude lower than doses (high milligram levels) used for systemic administration in the previous study, attenuates neointimal hyperplasia. The rabbit iliac artery was denuded, and then CNP (100 microg, n = 5) or control vehicle (n = 5) was administered locally over 20 min, via a local drug delivery catheter. During drug delivery, blood pressure was monitored with a high-fidelity micromanometer catheter. There was no significant decrease in arterial pressure immediately after the CNP administration. Four weeks after the treatment, computer-assisted morphometric analysis revealed significant reduction in the intimal area (CNP 0.44 +/- 0.27 versus control 0.96 +/- 0.20 mm2, p < 0.01), but no changes in the medial area (CNP 0.93 +/- 0.23 versus control 0.79 +/- 0.29 mm2, p = NS). This resulted in a significant decrease in the ratio of the intimal area to the medial area in CNP-treated vessels compared with control vessels (CNP 0.45 +/- 0.26 versus control 1.40 +/- 0.66, p < 0.05). Local delivery of a single low dose of CNP effectively inhibits neointimal hyperplasia with a minimal likelihood of compromising hemodynamics. Considering its multipotent actions and its role as an important regulator of the vascular system, this treatment may have a therapeutic advantage for clinical use.

Involvement of reactive oxygen species-mediated NF-kappa B activation in TNF-alpha-induced cardiomyocyte hypertrophy

We examined the intracellular signaling mechanism for tumor necrosis factor-alpha (TNF-alpha)-induced cardiac hypertrophy in isolated rat neonatal cardiomyocytes. TNF-alpha enhanced the expression of a kappa B-dependent reporter gene construct in a dose-dependent manner, which was transiently transfected in cardiomyocytes. Electrophoretic mobility shift assay demonstrated that TNF-alpha induced nuclear factor- kappa B (NF-kappa B)-specific DNA binding. Cultured cardiomyocytes were infected with a recombinant adenoviral vector expressing a degradation-resistant mutant of I kappa B alpha (AdI kappa B alpha 32/36A). The I kappa B alpha mutant suppressed NF-kappa B activation induced by TNF- alpha. In cardiomyocytes infected with AdI kappa B alpha 32/36A, TNF-alpha-induced hypertrophic responses, including increases in cell size, protein synthesis and atrial natriuretic factor production and enhancement of sarcomeric organization, were remarkably attenuated compared to the cells infected with an adenovirus expressing bacterial beta-galactosidase. Using a reactive oxygen species (ROS)-sensitive fluorescent dye, 2', 7'-dichlorofluorescin, we observed an increase in fluorescent signal in cardiomyocytes over time, upon addition of TNF-alpha. Preincubation of n-acetyl cysteine (NAC), an antioxidant, prior to TNF-alpha treatment, abolished TNF-alpha -induced ROS generation. NAC abolished TNF-alpha-induced NF-kappa B activation and hypertrophic responses. These findings indicated that TNF-alpha-induced cardiomyocyte hypertrophy is mediated through NF-kappa B activation via the generation of ROS.

Gene therapy in vascular surgery comes of age

In the last decade, gene therapy for cardiovascular diseases has been becoming a reality. However, although numerous successful experimental studies have suggested possible strategies of gene therapy for cardiovascular disorders, the clinical outcome remains limited. Because cardiovascular diseases are the result of complex causes, there is no exact answer to the following question: Which is the best gene to treat vascular diseases? In addition, current limitations include less clinically relevant vectors regarding both gene-transfer efficiency and safety, and at present, most efforts are focused on identifying more effective therapeutic genes, as well as developing more effective vectors. Furthermore, greater pathophysiologic understanding of these diseases, including vein-graft remodeling and ischemic limbs, is required. Regarding the relevant vector, we recently developed a novel mononegavirus-based gene-transfer vector, namely recombinant Sendai virus, which has shown dramatically superior gene-transfer efficiency to other vectors, including adenovirus, in several organs (eg, the vessel wall and skeletal muscles). These efforts now offer new possibilities to get more fruits in the field of gene therapy for vascular surgery.

Prevention of restenosis by a herpes simplex virus mutant capable of controlled long-term expression in vascular tissue in vivo

Neointimal hyperplasia resulting from vascular smooth muscle cell (SMC) proliferation and luminal migration is the major cause of autologous vein graft failure following vascular coronary or peripheral bypass surgery. Strategies to attenuate SMC proliferation by the delivery of oligonucleotides or genes controlling cell division rely on the use of high concentrations of vectors, and require pre-emptive disruption of the endothelial cell layer. We report a genetically engineered herpes simplex virus (HSV-1) mutant that, in an in vivo rabbit model system, infects all vascular layers without prior injury to the endothelium; expresses a reporter gene driven by a viral promoter with high efficiency for at least 4 weeks; exhibits no systemic toxicity; can be eliminated at will by administration of the antiviral drug acyclovir; and significantly reduces SMC proliferation and restenosis in vein grafts in immunocompetent hosts.

Local gene delivery to the vessel wall

This review will provide an overview of delivery strategies that are being evaluated for vascular gene therapy. We will limit our discussion to those studies that have been demonstrated, utilizing in vivo model systems, to limit post-interventional restenosis. We also discuss the efficacy of the vectors and methods currently being used to transfer genetic material to the vessel wall. The efficiency of these techniques is a critical issue for the successful application of gene therapy.

Gene therapy in heart disease

Application of gene therapy to the field of cardiovascular disorders has been the subject of intensive work over the recent period. Gene therapy for cardiovascular disorders is now fast developing with most therapies being devoted to the consequences (ischemia) rather than the causes of atherosclerotic diseases. Recent human clinical trials have shown that injection of naked DNA encoding vascular endothelial growth factor promotes collateral vessel development in patients with critical limb ischemia or chronic myocardial ischemia. Promising studies in animals have also fueled enthusiasm for treatment of human restenosis by gene therapy, but clinical applications are warranted. Application of gene transfer to other cardiovascular diseases will require the coordinated development of a variety of new technologies, as well as a better definition of cellular and gene targets.

Adenovirus-mediated transfer of the atrial natriuretic peptide gene in rat pulmonary vascular smooth muscle cells leads to apoptosis

Atrial natriuretic peptide (ANP) exhibits relaxant and growth-inhibiting effects on vascular smooth muscle cells (VSMCs). To obtain ANP gene expression in VSMCs, we built a recombinant adenovirus containing the ANP cDNA controlled by the adenovirus major late promotor (AdMLP-ANP). After pulmonary VSMC treatment with AdMLP-ANP at a multiplicity of infection ranging from 5 to 100 TCID(50)/cell, immunoreactive ANP was detectable in the cell culture medium at a level that reached 101 +/- 27 pmol/well after 2 days. The newly expressed ANP was biologically active, as evidenced by its ability to induce cyclic guanosine monophosphate accumulation in target cells and to mimic the effect of exogenous ANP (10(-8) to 10(-7) mol/L). Cell growth and survival of AdMLP-ANP-infected cells were decreased and were associated with the promotion of VSMC apoptosis. These effects, which occurred at a multiplicity of infection of 10 to 100 TCID(50)/cell, were observed neither in cells infected with the control adenoviral constructs (AdMLP-betaGAL and AdMLP-gD) nor in cells treated with exogenous ANP (10(-7) to 10(-6) mol/L). These results showing VSMC apoptosis in response to ANP gene expression may have important implications for the prevention of vascular remodeling by gene therapy.

Molecular pathways of cyclic nucleotide-induced inhibition of arterial smooth muscle cell proliferation

Cyclic adenosine 3',5'-monophosphate (cAMP) and cyclic guanosine 3',5'-monophosphate (cGMP) are second messengers involved in the intracellular signal transduction of a wide variety of extracellular stimuli. These signals regulate many biological processes including cell proliferation, differentiation, migration, and apoptosis. Recently, significant progress has been achieved in the molecular basis underlying cyclic nucleotide regulation of cell proliferation. This review summarizes our knowledge of the signaling pathways regulated by cyclic nucleotides in arterial smooth muscle cells.

Gene Therapy for Cardiovascular Disease

During the past decade, gene therapy for the treatment of many inherited and acquired medical problems has become the subject of increasing focus in both the scientific litera ture and the lay press. This review examines the history and current status of gene therapy for advanced chronic periph eral and myocardial ischemia.

Inhibition of transforming growth factor beta prevents progression of liver fibrosis and enhances hepatocyte regeneration in dimethylnitrosamine-treated rats

We investigated whether anti-transforming growth factor beta (TGF-beta) molecular intervention can halt the progression of liver fibrosis in rats. To block TGF-beta action in a specific manner, we prepared an adenovirus expressing a truncated type II TGF-beta receptor (AdTbeta-TR), which specifically inhibits TGF-beta signaling as a dominant-negative receptor. We also used an adenovirus expressing bacterial beta-galactosidase (AdLacZ) as a control adenovirus. Rats were treated with dimethylnitrosamine (DMN) for 3 weeks; then, AdTbeta-TR, AdLacZ, or saline was intravenously applied once, followed by an additional 3-week DMN treatment. The ratio between the truncated receptor and the wild-type receptor at the mRNA level was 15 at 1 week and 10 at 3 weeks after gene transfer. Immunohistostaining analysis showed that the truncated receptor was expressed mainly in septal cells including hepatic stellate cells. Liver fibrosis, as assessed by histology, hydroxyproline content, and the serum level of hyaluronic acid, progressed during the additional 3-week DMN treatment. However, in rats infected with AdTbeta-TR, the fibrosis remained at the level seen in rats given DMN for only 3 weeks. All AdTbeta-TR-treated rats remained alive, whereas DMN-treated rats infused with either AdLacZ or saline died of liver dysfunction. In the livers of AdTbeta-TR-treated rats, electron microscopy showed: 1) less accumulation of extracellular matrix proteins in the Disse's spaces; 2) regenerated hepatocytes; and 3) fat droplet-rich "quiescent" hepatic stellate cells. Our results demonstrate that TGF-beta plays a critical role in the progression of liver fibrosis, and suggest that anti-TGF-beta intervention should be therapeutic in already-established fibrotic livers, not only by suppressing fibrosis, but by facilitating hepatocyte regeneration.

Type-C natriuretic peptide prevents development of experimental atherosclerosis in rabbits

1. We investigated the effect of local administration of type-C natriuretic peptide (CNP) on the endothelial dysfunction and development of an atheroma-like neointima induced by a peri-arterial collar in rabbits. 2. Peri-arterial collars were placed on both common carotid arteries allowing local treatment of the collared region with either CNP (10 micromol/L) or saline. After 7 days, uncollared (control) and collared sections were taken from both arteries for pharmacological and morphological analysis. 3. Application of the collar markedly attenuated (P < 0.05) endothelium-dependent vasorelaxation induced by acetylcholine (ACh); inhibition of 5-hydroxytryptamine contraction was 80+/-5% in control sections compared with 44+/-4% in collared sections from the same arteries. Local infusion of CNP (10 micromol/L) into the collar restored ACh-induced vasorelaxation (74+/-3% from collared arteries + CNP vs 77+/-2% from control sections from the same arteries). 4. Type-C natriuretic peptide treatment also reduced (P < 0.05) intimal thickening compared with contralateral collared arteries (intima/media ratio 0.06+/-0.01 vs 0.16+/-0.01). 5. These results provide evidence that locally administered CNP is effective in preventing the endothelial dysfunction and development of a neointima in this model.

Restenosis: a challenge for pharmacology

The quest for an anti-restenotic drug continues to be a major challenge in the field of cardiovascular pharmacology because most therapies with proven efficacy in experimental neointima models have failed to limit restenosis. Some drug classes, including glycoprotein IIb/IIIa antagonists, nitric oxide donors and the antioxidant probucol, have recently demonstrated potential benefits in clinical trials. Progress in the development of local delivery systems for administration of drugs, antisense oligonucleotides or genes, in combination with an improved understanding of the pathogenesis of restenosis holds promise for ultimate pharmacotherapy of this condition.

The regulatory expression of procollagen COOH-terminal proteinase enhancer in the proliferation of vascular smooth muscle cells

Intimal hyperplasia following arterial endothelial denudation results in large part from the proliferation of vascular smooth muscle cells (SMCs) and matrix accumulation. Procollagen COOH-terminal proteinase enhancer (PCPE) binds procollagen COOH-propeptides and potentiates procollagen COOH-proteinase activity to cleave COOH-propeptides of procollagens I-III. Here we report the enhanced expression of PCPE in cultured SMCs and in intimal thickening induced by arterial injury. The levels of PCPE mRNA in parallel with the level of p21(Cip1) mRNA, as a negative regulator of cellular proliferation, increased under serum deprivation or reduced cellular proliferation in cultured SMCs. In contrast, rapidly proliferating cells show the decreased levels of PCPE mRNA. In vivo, the marked induction of PCPE in injured rat arteries occurred at 14 days after endothelial denudation. The induced expression levels of PCPE as well as p21(Cip1) were maintained until 42 days, although cyclin E expression declined. Furthermore, transforming growth factor beta1 (TGF-beta1), an important regulator of cellular proliferation in atheroma, increased the levels of the PCPE mRNA in cultured SMCs. Thus, the regulatory expression of PCPE dependent on cellular proliferation, and particularly contact inhibition, may play a key role in the proliferation of SMCs and matrix production during the process of atheroma formation.

Local adenovirus-mediated transfer of C-type natriuretic peptide suppresses vascular remodeling in porcine coronary arteries in vivo

OBJECTIVE

This study was designed to examine whether or not adenovirus-mediated gene transfer of C-type natriuretic peptide (CNP) can prevent coronary restenotic changes after balloon injury in pigs in vivo.

BACKGROUND

Gene therapy to prevent restenosis after percutaneous transluminal coronary angioplasty (PTCA) might be useful but requires a method applicable for in vivo gene delivery into the coronary artery as well as the efficient vector encoding a potent antiproliferative substance. We tested whether the adenovirus-mediated gene transfer of CNP by use of an infiltrator angioplasty balloon catheter (IABC) might prevent the coronary restenotic changes after balloon injury.

METHODS

Balloon angioplasty was performed in the left anterior descending and the left circumflex coronary artery in pigs. Immediately after the balloon injury, adenovirus solution encoding either CNP (AdCACNP) or beta-galactosidase (AdCALacZ) gene was injected with IABC into the balloon-injured coronary segments. Expression of CNP was assessed by immunohistochemical staining and cyclic guanosine 3',5'-monophosphate (cGMP) measurement. Coronary restenotic changes were evaluated by both angiographic and histological examinations.

RESULTS

CNP was highly expressed in the media and the adventitia of the coronary artery at the AdCACNP-transfected but not at the AdCALacZ-transfected segment. In the AdCALacZ-transfected segment, vascular cGMP levels tended to be reduced as compared with the untreated segment, whereas in the AdCACNP-transfected segment, vascular cGMP levels were restored. Angiographic coronary stenosis was significantly less at the AdCACNP-transfected than at the AdCALacZ-transfected segment. Histological examination revealed that this was achieved primarily by the marked inhibition of the geometric remodeling of the coronary artery by the CNP gene transfer.

CONCLUSIONS

Adenovirus-mediated CNP gene transfer with the IABC system may be a useful gene therapy to prevent restenosis after PTCA in vivo.

Dual regulatory effects of nitric oxide on plasminogen activator inhibitor type 1 expression in endothelial cells

In this report we compared the mechanism by which nitric oxide (NO), generated exogenously and endogenously, affects the plasminogen activator inhibitor type 1 (PAI-1) expression in endothelial cells. For this purpose, we stimulated the endothelial cell line EA.hy 926 with tumour necrosis factor alpha (TNFalpha) in the presence of the exogenously NO-releasing donors, sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine, or regulators of nitric oxide synthase (NOS) inhibitor N-nitro-L-arginine-methyl ester hydrochloride and substrate L-Arg. Expression of PAI-1 in EA.hy 926 cells was determined by measuring the level of mRNA, using relative quantitative reverse transcriptase PCR, and protein, using ELISA. In addition, we estimated the level of activation of two mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase (ERK1/2) and c-Jun N-terminal kinase (JNK1/2), in the cells before and after treatment with TNFalpha, in the presence or absence of NO donors and inhibitors. In contrast to exogenously released NO that significantly reduced mostly basal PAI-1 expression, endogenously generated NO by NOS potentiated TNFalpha-induced upregulation of PAI-1 expression. Exogenously and endogenously generated NO causes different effects on activation of the MAPKs ERK1/2 and JNK1/2. Specifically, the SNP-released NO activates only ERK1/2, while endogenously generated NO in a pathway induced by TNFalpha activates both MAPKs. Thus our data indicate that due to different cellular locations and mechanisms of generation, NO may participate in various signalling pathways leading to opposite effects on PAI-1 expression in endothelial cells.