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

Low-intensity pulsed ultrasound therapy suppresses coronary adventitial inflammatory changes and hyperconstricting responses after coronary stent implantation in pigs in vivo

Backgrounds

We demonstrated that coronary adventitial inflammation plays important roles in the pathogenesis of drug-eluting stent (DES)-induced coronary hyperconstricting responses in pigs in vivo. However, no therapy is yet available to treat coronary adventitial inflammation. We thus developed the low-intensity pulsed ultrasound (LIPUS) therapy that ameliorates myocardial ischemia by enhancing angiogenesis.

Aims

We aimed to examine whether our LIPUS therapy suppresses DES-induced coronary hyperconstricting responses in pigs in vivo, and if so, what mechanisms are involved.

Methods

Sixteen normal male pigs were randomly assigned to the LIPUS or the sham therapy groups after DES implantation into the left anterior descending (LAD) coronary artery. In the LIPUS group, LIPUS (32 cycles, 193 mW/cm²) was applied to the heart at 3 different levels (segments proximal and distal to the stent edges and middle of the stent) for 20 min at each level for every other day for 2 weeks. The sham therapy group was treated in the same manner but without LIPUS. At 4 weeks after stent implantation, we performed coronary angiography, followed by immunohistological analysis.

Results

Coronary vasoconstricting responses to serotonin in LAD at DES edges were significantly suppressed in the LIPUS group compared with the sham group. Furthermore, lymph transport speed in vivo was significantly faster in the LIPUS group than in the sham group. Histological analysis at DES edges showed that inflammatory changes and Rho-kinase activity were significantly suppressed in the LIPUS group, associated with eNOS up-regulation and enhanced lymph-angiogenesis.

Conclusions

These results suggest that our non-invasive LIPUS therapy is useful to treat coronary functional abnormalities caused by coronary adventitial inflammation, indicating its potential for the novel and safe therapeutic approach of coronary artery disease.

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.

Genetic transfer of fusion proteins effectively inhibits VCAM-1-mediated cell adhesion and transmigration via inhibition of cytoskeletal anchorage

The adhesion of leukocytes to endothelium plays a central role in the development of atherosclerosis and thus represents an attractive therapeutic target for anti-atherosclerotic therapies. Vascular cell adhesion molecule-1 (VCAM-1) mediates both the initial tethering and the firm adhesion of leukocytes to endothelial cells. Our work evaluates the feasibility of using the cytoskeletal anchorage of VCAM-1 as a target for gene therapy. As a proof of concept, integrin α_IIbβ₃-mediated cell adhesion with clearly defined cytoskeletal anchorage was tested. We constructed fusion proteins containing the intracellular domain of β₃ placed at various distances to the cell membrane. Using cell adhesion assays and immunofluorescence, we established fusion constructs with competitive and dominant negative inhibition of cell adhesion. With the goal being the transfer of the dominant negative mechanism towards VCAM-1 inhibition, we constructed a fusion molecule containing the cytoplasmic domain of VCAM-1. Indeed, VCAM-1 mediated leukocyte adhesion can be inhibited via transfection of DNA encoding the designed VCAM-1 fusion protein. This is demonstrated in adhesion assays under static and flow conditions using CHO cells expressing recombinant VCAM-1 as well as activated endothelial cells. Thus, we are able to describe a novel approach for dominant negative inhibition of leukocyte adhesion to endothelial cells. This approach warrants further development as a novel gene therapeutic strategy that aims for a locally restricted effect at atherosclerotic areas of the vasculature.

Inhibition of restenosis formation without compromising reendothelialization as a potential solution to thrombosis following angioplasty?

Stent thrombosis remains an important problem after the implantation of different stent types. A potential solution to this problem may be vasoactive agents with dual effects on different cell types like C-type natriuretic peptide (CNP). Therefore, in vitro and in vivo effects of CNP were investigated in a porcine restenotic model. Gene transfer of CNP in cultures of porcine vascular cells revealed up to 30% reduction of growth of smooth muscle cells (p<.05), but no suppression of endothelial growth using CNP. Applied in vivo, angiography revealed a trend of reduced restenosis formation in balloon-injured porcine arteries treated with CNP gene or beta-galactosidase (beta-Gal) control gene after three months (2.59 +/- 2.04-fold reduction, p = n.s.). Histologically, morphometry revealed significantly reduced neointima formation after treatment with CNP plasmid (7.26 +/- 1.44-fold reduction, p < .05). Evans blue staining demonstrated complete endothelial repair already 3 weeks after intervention using CNP. Transfer of CNP gene resulted in a significant inhibition of neointima formation without compromising endothelial repair. Therefore, use of the CNP gene may offer a solution to suppress restenosis formation while preventing subacute or late thrombosis.

Gene therapy for restenosis: biological solution to a biological problem

Coronary artery disease remains a significant health threat afflicting millions of individuals worldwide. Despite the development of a variety of technologies and catheter based interventions, post-procedure restenosis is still a significant concern. Gene therapy has emerged as a promising approach aimed at modification of cellular processes that give rise to restenosis. When juxtaposed alongside the failure of traditional pharmacotherapeutics to eliminate restenosis, gene therapy has engendered great expectations for cubing coronary restenosis. In this review we have discussed an overview of gene therapy approaches that hve been utilized to reduce restenosis in preclinical and clinical studies, current status of anti-restenosis gene therapy and perspectives on its future application. For brevity, we have limited our discussion on anti-restenosis gene therapy to the introduction of a nucleic acid to the cell, tissue, organ or organism in order to give rise to the expression of a protein, the function of which will confer therapeutic effect. For the purpose of this review, we have focused ou discussion on two relevant anti-restenosis strategies, anti-proliferative and pro-endothelialization.

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.

Cardiac endocrine function is an essential component of the homeostatic regulation network: physiological and clinical implications

The discovery of cardiac natriuretic hormones required a profound revision of the concept of heart function. The heart should no longer be considered only as a pump but rather as a multifunctional and interactive organ that is part of a complex network and active component of the integrated systems of the body. In this review, we first consider the cross-talk between endocrine and contractile function of the heart. Then, based on the existing literature, we propose the hypothesis that cardiac endocrine function is an essential component of the integrated systems of the body and thus plays a pivotal role in fluid, electrolyte, and hemodynamic homeostasis. We highlight those studies indicating how alterations in cardiac endocrine function can better explain the pathophysiology of cardiovascular diseases and, in particular of heart failure, in which several target organs develop a resistance to the biological action of cardiac natriuretic peptides. Finally, we emphasize the concept that a complete knowledge of the cardiac endocrine function and of its relation with other neurohormonal regulatory systems of the body is crucial to correctly interpret changes in circulating natriuretic hormones, especially the brain natriuretic peptide.

NEP inhibitors enhance C-type natriuretic peptide-induced relaxation in porcine isolated coronary artery

C-type natriuretic peptide (CNP), a local regulator of vascular tone and cell proliferation, is eliminated from the circulation via NPR-C receptors and neutral endopeptidase enzyme (NEP, EC. 3.4.24.11). The increased contractility of coronary arteries in different cardiovascular diseases made us study the possible enhancement of vasodilator capacity of exogenously added CNP with concomitant NEP inhibition on porcine coronary arteries in vitro. CNP (0.006-1.4 microM) concentration dependently relaxed the U46619 (0.07-0.4 microM) precontracted preparations in an almost equally effective manner in the presence and absence of functional endothelium with maximum effects of about 40%. The combined NEP/endothelin-converting enzyme inhibitor (NEP/ECE inhibitor), phosphoramidon (10 microM) or the specific inhibitor of the NEP, thiorphan (10 microM) resulted in an enhanced magnitude of CNP-induced relaxation without significant change in the EC50 both on endothelium intact and endothelium deprived preparations. The inhibition of endothelin receptors by PD 142893 (10 microM) enhanced the relaxing effect of CNP in the presence but not in the absence of functional endothelium indicating a functional antagonism between CNP and endothelin. Our results suggest that inhibition of CNP degradation may endue this endogenous peptide with therapeutic potency in cardiovascular diseases.

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.

C-type natriuretic peptide inhibits constrictive remodeling without compromising re-endothelialization in balloon-dilated renal arteries

PURPOSE

To investigate the long-term effect of local, liposome-mediated gene transfer of C-type natriuretic peptide (CNP) plasmid versus CNP protein on restenosis in porcine renal arteries following balloon angioplasty.

METHODS

The renal arteries of 15 pigs were dilated and the adventitia at the site of balloon injury injected with CNP protein, pCR3.1 plasmid encoding CNP, or the beta-galactosidase gene (control) via a needle injection catheter. Five animals receiving the CNP and control genes in dilated arteries were sacrificed after 3 weeks to analyze re-endothelialization, proliferation, and early CNP expression. Ten animals designated for the long-term experiments (3 months) were treated with the CNP gene versus CNP protein (n=3), the CNP gene versus the control gene (n=3), and the CNP protein versus the control gene (n=3). One animal served as a dilated non-treated control. Transfection and expression of CNP and beta-galactosidase were measured by polymerase chain reaction (PCR) and reverse transcription PCR. Renal arterial lumen narrowing was measured with angiography and histology. Endothelialization was assessed using Evans blue stain; vWF, CD31, factor VIII, and Ki67 were markers for immunohistochemical analysis.

RESULTS

An intact endothelial layer was seen at 3 weeks following angioplasty in all transfected arteries. Three months following treatment, computer-assisted morphometric analysis revealed significant enlargement of the arterial cross-sectional areas in CNP plasmid- treated vessels compared to dilated but untreated arteries (CNP plasmid +34.8%+/-13.9% versus CNP protein -1.75%+/-19.9% versus beta-galactosidase -47.0%+/-13.9%, p<0.01). Angiographic analysis showed significant enlargement of the arterial diameter compared to dilated, untreated arteries (CNP plasmid +20.8%+/-6.8% versus CNP protein +5.7%+/-6.0% versus beta-galactosidase -24.5%+/-10.2%, p<0.01).

CONCLUSIONS

Local application of CNP plasmid proved superior to CNP protein in producing rapid re-endothelialization and significantly enlarging the renal arterial lumen following dilation.

C-Type natriuretic peptide and natriuretic peptide receptors are expressed by smooth muscle cells in the neointima after percutaneous coronary intervention

Understanding restenosis after percutaneous coronary intervention (PCI) remains a challenge. Neointimal proliferation is the main cause of restenosis. C-Type natriuretic peptide (CNP) plays a role in relaxation and growth inhibition of vascular smooth muscle cells (SMCs); the effects depend on the presence of specific natriuretic peptide receptors (NPRs) consisting of NPR-A, NPR-B, and NPR-C. To test the hypothesis that CNP and NPRs may be involved in restenosis, we immunohistochemically studied the expression of CNP and NPRs during the post-PCI healing process; 10 sites after PCI obtained at autopsy and 14 atherectomy specimens obtained from restenotic sites were investigated. Frozen sections were stained with antibodies against CNP, NPRs, SMCs, macrophages, and endothelial cells. Within 2 months after PCI, most neointimal SMCs expressed CNP and NPR-A. The expression of CNP and NPR-A in these neointimal SMCs decreased from 6 months onward. In contrast, NPR-C was strongly expressed in neointimal SMCs from 1 to 9 months after PCI. In atherectomy specimens, most neointimal SMCs showed weak positivity for CNP and NPR-A, but NPR-C was strongly expressed in the neointimal SMCs. These findings strongly suggest that a paracrine and autocrine system of CNP and NPRs may be important in controlling neointimal growth after PCI in humans.

Functional Analysis of Genomic DNA, cDNA, and Nucleotide Sequence of the Mature C-Type Natriuretic Peptide Gene in Vascular Cells

OBJECTIVE

The aim of this study was to investigate the effect of various C-type natriuretic peptide (CNP) sequences (genomic DNA [CNPDNA], cDNA derived from mRNA [CNPcDNA], and sequence coding for 22 amino acids of the mature CNP [CNP22aa]) on the growth of primary porcine vascular cells.

METHODS AND RESULTS

Gene transfer was performed with cationic lipid DOCSPER or linear polyethylenimine. All 3 CNP sequences led to significant inhibition of smooth muscle cell (SMC) proliferation. In contrast, significant stimulation of cell growth was observed in endothelial cells (ECs) using CNPDNA or CNPcDNA but not CNP22aa. In a porcine restenosis model, a significant reduction in neointima hyperplasia was found 3 months after application of the CNPcDNA vector compared with the control transfection.

CONCLUSIONS

The results demonstrate that the first intron in the CNP sequence does not contain any additional enhancer-binding sites. However, the signal sequence is indispensable for secretion of CNP and its appropriate physiological function. Furthermore, the results show for the first time the therapeutic effect of CNP using liposome-mediated gene transfer and local adventitial delivery. Advantages of the CNP gene are its dual effects with inhibition of SMC proliferation and simultaneous promotion of EC growth. Functional analysis of various C-type natriuretic peptide (CNP) sequences on growth of vascular cells. For the first time, dual therapeutic effects of CNP with inhibition of smooth muscle cell proliferation and stimulation of re-endothelialization were demonstrated in a pig restenosis model using liposome-mediated gene transfer and local adventitial delivery.

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.

Gene transfer of a novel vasoactive natriuretic peptide stimulates cGMP and lowers blood pressure in mice

Dendroaspis natriuretic peptide (DNP) is a recently described peptide produced by Dendroaspis angusticeps with structural and functional similarities to mammalian natriuretic peptides. These similarities suggest a potential role for DNP in cardiovascular therapeutics. To determine the physiological effects of chronic delivery of DNP, a gene transfer approach using first generation adenoviral vectors was utilized. Although the gene for DNP has not been cloned in any species, the peptide sequence in the snake is known. Preferred mammalian codons for snake DNP were cloned downstream of either the leader sequence (referred to as pBDNP-1) or prepropeptide sequence of human brain natriuretic peptide (BNP) cDNA (referred to as pBDNP-2). Transfections with pBDNP-1 or pBDNP-2 resulted in expected forms of chimeric DNP (cDNP) in cell lysates and conditioned media. Functional studies demonstrated the ability of both forms of cDNP within conditioned media to stimulate cGMP production in human vascular smooth muscle cells (hVSMC). Expressed cDNP inhibited hVSMC proliferation and stimulated vasorelaxation in a similar fashion. To investigate the chronic physiological effects of administration of cDNP, an adenoviral vector expressing cDNP (Ad-BDNP) was generated. Intravenous delivery of Ad-BDNP in mice resulted in dose-dependent systemic expression of cDNP. The highest level of expression was associated with consistent elevation of its presumed second messenger (cGMP) for 21 days but with transient lowering of systolic blood pressure in normotensive mice. This study demonstrates the biological features of the expression of the xenogenic peptide DNP.

Applied gene therapy in preclinical models of vascular injury

Atherosclerosis remains the major cause of morbidity and mortality in Western countries. Atherothrombotic complications, including vascular occlusions and severe narrowing of nutrient blood vessels in the cerebral, coronary, or peripheral circulation, usually require invasive revascularization strategies. As molecular mediators contributing to these complications are being identified in more representative experimental injury models, and as gene transfer platforms and vectors acquire improved safety and efficacy profiles, there is ground for cautious optimism that gene-based interventions will likely reduce the clinical burden of these diseases. Increased generation of reactive oxygen species in diseased atherosclerotic vessels has been implicated in vasospasm, exaggerated neointima formation, and enhanced thrombosis. Ex vivo pressurized vascular gene transfer in venous bypass grafts using antisense oligonucleotides directed against cell-cycle control genes can modify the venous graft's phenotype and confer clinical benefit with improved long-term graft survival. Alternatively, percutaneous intra-arterial gene transfer is feasible, but at relatively low transgene expression levels. Although this may suffice in the case of secreted gene products with marked paracrine or bystander effects, including nitric oxide synthase and heme oxygenase-1, drug- and gene-eluting stents may provide the preferred future vehicle for well-controlled, quantifiable, and safe vascular gene transfer. Continued efforts to improve gene transfer technology in diseased human vessels and to increase our understanding of molecular targets are required before the full therapeutic potential of vascular gene therapy can be realized.

Pathophysiological and clinical relevance of circulating levels of cardiac natriuretic hormones: are they merely markers of cardiac disease?

Several specific and sensitive markers for myocardial injury as well as diagnostic tests for the assessment and stratification of cardiovascular risk have been recently introduced in clinical laboratories. However, until a few years ago, there were no laboratory tests for diagnosis, stratification and follow-up of patients with heart failure. The assay for cardiac natriuretic hormones (CNH) fills this gap. Heart failure is not only the most frequent "final common pathway" in cardiovascular disease, but is also the most common primary hospital discharge diagnosis, as well as the most common cause of death in patients over 50 years of age in Western countries; therefore, CNH assay may be destined to assume a growing relevance in clinical cardiology. However, to consider CNH assay only as a general and functional indicator of cardiac structural disease, without recalling that atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are powerful hormones, may lead to underestimation of the physiological role they play in healthy subjects as well as in patients with heart failure. Indeed, the circulating levels of CNH should be always interpreted taking into account not only hemodynamic factors and myocardial performance, but also their relationship with the counter-regulatory neuroendocrine system (including renin-angiotensin-aldosterone system, sympathetic system, endothelins, cytokines and vasopressin), as well as other hormones (such as sex steroid hormones, thyroid hormones and glucocorticoids).

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.

Adenovirus-mediated transfer of dominant-negative rho-kinase induces a regression of coronary arteriosclerosis in pigs in vivo

Small GTPase Rho and its target Rho-kinase/ROK/ROCK play an important role in various cellular functions, including smooth muscle contraction, actin cytoskeleton organization, and cell adhesion and migration, all of which may be involved in the pathogenesis of arteriosclerosis. Here, we show that adenovirus-mediated transfer of dominant-negative Rho-kinase (DNRhoK) induces a marked regression of coronary constrictive remodeling and abolishes coronary vasospastic activity in vivo. Porcine coronary segments were chronically treated with interleukin-1beta, which resulted in the development of constrictive remodeling and vasospastic responses to serotonin, as previously reported. Adenovirus-mediated transfer of DNRhoK, but not that of beta-galactosidase, into the interleukin-1beta-treated coronary segment caused a marked regression of the constrictive remodeling and abolished the vasospastic activity in 3 weeks. Western blot analysis showed that the phosphorylation of adducin and the ezrin/radixin/moesin family, the target proteins of Rho-kinase, were upregulated at the coronary lesions and were significantly suppressed by the transfer of DNRHOK: These results indicate that Rho-kinase is substantially involved in coronary constrictive remodeling and vasospastic responses, both of which can be reversed by the selective inhibition of the molecule in our porcine model in vivo.

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.

Gene transfer of dominant negative Rho kinase suppresses neointimal formation after balloon injury in pigs

Restenosis after angioplasty still remains a major problem for which neointimal formation appears to play an important role. Recent studies in vitro suggested that Rho kinase, a target protein of Rho, is important in various cellular functions. We thus examined whether Rho kinase is involved in the restenotic changes after balloon injury. In vivo gene transfer was performed immediately after balloon injury in both sides of the porcine femoral arteries with adenoviral vector encoding either a dominant negative form of Rho kinase (AdDNRhoK) or beta-galactosidase (AdLacZ) as a control. One week after the transfer, immunohistochemistry confirmed the successful gene expression in the vessel wall, whereas 2 wk after the transfer, Western blotting showed the functional upregulation of Rho kinase at the AdLacZ site and its suppression at the AdDNRhoK site. Angiography showed the development of a stenotic lesion at the AdLacZ site where histological neointimal formation was noted, whereas those changes were significantly suppressed at the AdDNRhoK site. These results indicate that Rho kinase is involved in the pathogenesis of neointimal formation after balloon injury in vivo.

Cellular and molecular mechanisms of coronary artery spasm: lessons from animal models

Coronary artery spasm plays an important role in the pathogenesis of a wide variety of ischemic heart diseases, especially in the Japanese population. Because coronary artery spasm can be induced by a variety of stimuli with different mechanisms of action, the occurrence of the spasm appears to be due to the local hyperreactivity of the coronary artery rather than to an enhanced stimulation with a single mechanism of action. Several lines of evidence indicate that coronary artery spasm is caused primarily by smooth muscle hypercontraction whereas the contribution of endothelial dysfunction may be minimal. In order to elucidate the cellular and molecular mechanisms of the spasm, porcine models of the spasm were developed. In the first model with balloon injury and high-cholesterol feeding, a close topological correlation between the early atherosclerotic lesions and the spastic sites was noted, whereas in the second model with an inflammatory cytokine the potential importance of coronary inflammatory changes, especially at the adventitia, was noted. Subsequent studies in vivo and in vitro demonstrated that protein kinase C (PKC) and Rho-kinase are substantially involved in the intracellular mechanism of the spasm, resulting in increases in the mono- and diphosphorylations of myosin light chain (MLC). Furthermore, molecular biological analyses demonstrated that Rho-kinase is upregulated at the spastic site (at all levels, including mRNA, protein, and activity), resulting in the inhibition of MLC phosphatase through the phosphorylation of its myosin binding subunit and thereby causing the increase in MLC phosphorylations. Preliminary results also suggest that the long-term inhibition of Rho-kinase is effective in inhibiting the development of arteriosclerotic vascular lesions in several porcine models. Thus, Rho-kinase could be regarded as a novel therapeutic target for coronary arteriosclerosis in general and coronary artery spasm in particular.