Gene transfer of endothelial nitric oxide synthase improves nitric oxide-dependent endothelial function in a hypertensive rat model

p53 plays a crucial role in endothelial dysfunction associated with hyperglycemia and ischemia

p53 is a guardian of the genome that protects against carcinogenesis. There is accumulating evidence that p53 is activated with aging. Such activation has been reported to contribute to various age-associated pathologies, but its role in vascular dysfunction is largely unknown. The aim of this study was to investigate whether activation of endothelial p53 has a pathological effect in relation to endothelial function. We established endothelial p53 loss-of-function and gain-of-function models by breeding endothelial-cell specific Cre mice with floxed Trp53 or floxed Mdm2/Mdm4 mice, respectively. Then we induced diabetes by injection of streptozotocin. In the diabetic state, endothelial p53 expression was markedly up-regulated and endothelium-dependent vasodilatation was significantly impaired. Impairment of vasodilatation was significantly ameliorated in endothelial p53 knockout (EC-p53 KO) mice, and deletion of endothelial p53 also significantly enhanced the induction of angiogenesis by ischemia. Conversely, activation of endothelial p53 by deleting Mdm2/Mdm4 reduced both endothelium-dependent vasodilatation and ischemia-induced angiogenesis. Introduction of p53 into human endothelial cells up-regulated the expression of phosphatase and tensin homolog (PTEN), thereby reducing phospho-eNOS levels. Consistent with these results, the beneficial impact of endothelial p53 deletion on endothelial function was attenuated in EC-p53 KO mice with an eNOS-deficient background. These results show that endothelial p53 negatively regulates endothelium-dependent vasodilatation and ischemia-induced angiogenesis, suggesting that inhibition of endothelial p53 could be a novel therapeutic target in patients with metabolic disorders.

Improvement of vascular function by magnetic nanoparticle-assisted circumferential gene transfer into the native endothelium

Gene therapy is a promising approach for chronic disorders that require continuous treatment such as cardiovascular disease. Overexpression of vasoprotective genes has generated encouraging results in animal models, but not in clinical trials. One major problem in humans is the delivery of sufficient amounts of genetic vectors to the endothelium which is impeded by blood flow, whereas prolonged stop-flow conditions impose the risk of ischemia. In the current study we have therefore developed a strategy for the efficient circumferential lentiviral gene transfer in the native endothelium under constant flow conditions. For that purpose we perfused vessels that were exposed to specially designed magnetic fields with complexes of lentivirus and magnetic nanoparticles thereby enabling overexpression of therapeutic genes such as endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF). This treatment enhanced NO and VEGF production in the transduced endothelium and resulted in a reduction of vascular tone and increased angiogenesis. Thus, the combination of MNPs with magnetic fields is an innovative strategy for site-specific and efficient vascular gene therapy.

Mitochondrial Dysfunction Contributes to Hypertensive Target Organ Damage: Lessons from an Animal Model of Human Disease

Mechanisms underlying hypertensive target organ damage (TOD) are not completely understood. The pathophysiological role of mitochondrial oxidative stress, resulting from mitochondrial dysfunction, in development of TOD is unclear. The stroke-prone spontaneously hypertensive rat (SHRSP) is a suitable model of human hypertension and of its vascular consequences. Pathogenesis of TOD in SHRSP is multifactorial, being determined by high blood pressure levels, high salt/low potassium diet, and genetic factors. Accumulating evidence points to a key role of mitochondrial dysfunction in increased susceptibility to TOD development of SHRSP. Mitochondrial abnormalities were described in both heart and brain of SHRSP. Pharmacological compounds able to protect mitochondrial function exerted a significant protective effect on TOD development, independently of blood pressure levels. Through our research efforts, we discovered that two genes encoding mitochondrial proteins, one (Ndufc2) involved in OXPHOS complex I assembly and activity and the second one (UCP2) involved in clearance of mitochondrial ROS, are responsible, when dysregulated, for vascular damage in SHRSP. The suitability of SHRSP as a model of human disease represents a promising background for future translation of the experimental findings to human hypertension. Novel therapeutic strategies toward mitochondrial molecular targets may become a valuable tool for prevention and treatment of TOD in human hypertension.

Origin of the Y chromosome influences intrarenal vascular responsiveness to angiotensin I and angiotensin (1-7) in stroke-prone spontaneously hypertensive rats

The lineage of the Y chromosome accounts for up to 15 to 20 mm Hg in arterial pressure. Genes located on the Y chromosome from the spontaneously hypertensive rat (SHR) are associated with the renin-angiotensin system. Given the important role of the renin-angiotensin system in the renal regulation of fluid homeostasis and arterial pressure, we hypothesized that the origin of the Y chromosome influences arterial pressure via interaction between the intrarenal vasculature and the renin-angiotensin system. Sixteen-week-old normotensive rats (Wistar Kyoto [WKY]), spontaneously hypertensive stroke-prone rat (SHRSP), and 2 reciprocal Y consomic rat strains, 1 comprising the WKY autosomes and X chromosome with the Y chromosome from the hypertensive rat strain (WKY.SPGlaY) and vice versa (SP.WKYGlaY), were examined. SP.WKYGlaY had lower systolic blood pressure than SHRSP (195±5 versus 227±8 mm Hg; P<0.03), whereas WKY.SPGlaY had higher systolic blood pressure compared with WKY (157±3 versus 148±3 mm Hg; P<0.05), measured by radiotelemetry. Compared with WKY rats, SHRSP had higher plasma angiotensin(1-7) (Ang (1-7)):Ang II ratio (WKY: 0.13±0.01 versus SHRSP: 1.33±0.4; P<0.005), greater angiotensin II receptor type 2 and Mas receptor mRNA expression, and a blunted renal constrictor response to intrarenal Ang I and Ang(1-7) infusions. Introgression of the normotensive Y chromosome into the SHRSP background (SP.WKYGlaY) restored responses in the SHRSP to WKY levels, evidenced by a reduction in plasma Ang(1-7):Ang II ratio (SP.WKYGlaY: 0.24±0.02; P<0.01), angiotensin II receptor type 2, and Mas receptor mRNA expression and an increased vasoconstrictor response to intrarenal Ang I and Ang(1-7) infusion. This study demonstrates that the origin of the Y chromosome significantly impacts the renal vascular responsiveness and therefore may influence the long-term renal regulation of blood pressure.

Vascular-targeting antioxidant therapy in a model of hypertension and stroke

Oxidative stress is implicated in the pathogenesis of hypertension and stroke. Superoxide is produced by NAD(P)H oxidase in the vasculature and reduces nitric oxide bioavailability, which leads to increased blood pressure. The objective of this study was to determine whether targeting an antioxidant peptide to the vasculature would increase the antioxidant effect and reduce systolic blood pressure (SBP) in a model of genetic hypertension, the stroke-prone spontaneously hypertensive rat. Vascular-targeting peptides CRPPR and CSGMARTKC were identified by phage display in mice. These peptides retain their selectivity across species and target the aorta (CRPPR) and cardiac vasculature (CSGMARTKC) in the stroke-prone spontaneously hypertensive rat. These vascular-targeting peptides were linked to the antioxidant peptide gp91ds, which selectively inhibits assembly of NAD(P)H oxidase, thereby reducing superoxide production. SBP was determined for 1 week before treatment followed by 3 weeks of study duration before euthanasia. SBP in the control animals increased from 178.1 ± 4.1 mmHg to 201.6 ± 9.0 mmHg. The SBP of the animals treated with gp91ds alone, HIV-tat-gp91ds, and CSGMARTKC-gp91ds increased from 177.8 ± 3.5 mmHg, 179.8 ± 4.7 mmHg, and 177.9 ± 5.2 mmHg, respectively, to 201.6 ± 10.8 mmHg, 200.3 ± 11.7 mmHg and 205.7 ± 10.9 mmHg, respectively. This increase in SBP was significantly attenuated in animals receiving CRPPR-gp91ds (maximum SBP 187.5 mmHg ± 5.2, *P , 0.001 versus other treatment groups and control group). Additionally, animals treated with CRPPR-gp91ds, CSGMARTKC-gp91ds, and gp91ds alone showed significantly improved nitric oxide bioavailability determined by large vessel myography. Therefore, targeting an antioxidant to the aortic vasculature in vivo using peptides can significantly improve nitric oxide bioavailability and attenuate the time-dependent and progressive increase in SBP in the stroke-prone spontaneously hypertensive rat. This study has demonstrated the importance and potential benefit of targeting a biologically active peptide in the context of a preclinical model of endothelial dysfunction and hypertension.

eNOS gene delivery prevents hypertension and reduces renal failure and injury in rats with reduced renal mass

BACKGROUND

Impaired nitric oxide (NO) release in chronic renal failure has been implicated in the pathogenesis of hypertension and the progression of renal insufficiency. We investigated whether gene delivery of the endothelial NO synthase (eNOS) improves NO release and reduces blood pressure and renal failure and injury in rats with reduced renal mass.

METHODS

Renal failure was induced by renal artery branches ligation. Two weeks later, rats with renal failure were divided into three groups and received an intravenous injection of the vehicle or the adenovirus that expresses eNOS or β-galactosidase (β-gal). Systolic blood pressure, renal parameters and histopathology were assessed at Week 4 after gene delivery.

RESULTS

At the end of the study, systolic blood pressures, serum creatinine, proteinuria, urinary endothelin-1 (ET-1) excretion and renal cortex ET-1 levels were increased, whereas plasma and urine NO(2)/NO(3) were reduced in renal failure rats as compared to normal controls. Renal injury comprised blood vessel media hypertrophy, focal and segmental glomerular sclerosis, tubular atrophy and interstitial fibrosis. Gene delivery of eNOS, but not β-gal, prevented an increase in systolic blood pressure and proteinuria, and a reduction in plasma and urine NO(2)/NO(3). eNOS gene delivery also reduced a rise in serum creatinine, urinary ET-1 excretion and renal cortex ET-1 levels, and the renal vascular, glomerular and tubular injury.

CONCLUSION

This study indicates that eNOS gene delivery in rats with renal failure improves NO release, which likely prevents the aggravation of hypertension and slows down the progression of renal failure and injury.

Therapeutic perspectives in hypertension: novel means for renin-angiotensin-aldosterone system modulation and emerging device-based approaches

The conventional antihypertensive therapies including renin–angiotensin–aldosterone system antagonists (converting enzyme inhibitors, receptor blockers, renin inhibitors, and mineralocorticoid receptor blockers), diuretics, β-blockers, and calcium channel blockers are variably successful in achieving the challenging target blood pressure values in hypertensive patients. Difficult to treat hypertension is still a commonly observed problem world-wide. A number of drugs are considered to be used as novel therapies for hypertension. Renalase supplementation, vasopeptidase inhibitors, endothelin antagonists, and especially aldosterone antagonists (aldosterone synthase inhibitors and novel selective mineralocorticoid receptor blockers) are considered an option in resistant hypertension. In addition, the aldosterone antagonists as well as (pro)renin receptor blockers or AT₂ receptor agonists might attenuate end-organ damage. This array of medications has now been complemented by a number of new approaches of non-pharmacological strategies including vaccination, genomic interference, controlled breathing, baroreflex activation, and probably most successfully renal denervation techniques. However, the progress on innovative therapies seems to be slow and the problem of resistant hypertension and proper blood pressure control appears to be still persisting. Therefore the regimens of currently available drugs are being fine-tuned, resulting in the establishment of several novel fixed-dose combinations including triple combinations with the aim to facilitate proper blood pressure control. It remains an exciting question which approach will confer the best blood pressure control and risk reduction in this tricky disease.

Increased CYP2J3 expression reduces insulin resistance in fructose-treated rats and db/db mice

OBJECTIVE

Accumulating evidence suggests that cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid into epoxyeicosatrienoic acids (EETs), which play crucial and diverse roles in cardiovascular homeostasis. The anti-inflammatory, antihypertensive, and pro-proliferative effects of EETs suggest a possible beneficial role for EETs on insulin resistance and diabetes.

RESEARCH DESIGN AND METHODS

This study investigated the effects of CYP2J3 epoxygenase gene therapy on insulin resistance and blood pressure in diabetic db/db mice and in a model of fructose-induced hypertension and insulin resistance in rats.

RESULTS

CYP2J3 gene delivery in vivo increased EET generation, reduced blood pressure, and reversed insulin resistance as determined by plasma glucose levels, homeostasis model assessment insulin resistance index, and glucose tolerance test. Furthermore, CYP2J3 treatment prevented fructose-induced decreases in insulin receptor signaling and phosphorylation of AMP-activated protein kinases (AMPKs) in liver, muscle, heart, kidney, and aorta. Thus, overexpression of CYP2J3 protected against diabetes and insulin resistance in peripheral tissues through activation of insulin receptor and AMPK pathways.

CONCLUSIONS

These results highlight the beneficial roles of the CYP epoxygenase-EET system in diabetes and insulin resistance.

Adenoviral-mediated overexpression of DDAH improves vascular tone regulation

Dimethylarginine dimethylaminohydrolase (DDAH) degrades asymmetric dimethylarginine (ADMA), an endogenously produced nitric oxide (NO) synthase inhibitor. In mammals, two isoforms of DDAH, DDAH1 and DDAH2, are expressed in the cardiovascular system, suggesting that ADMA concentrations are actively regulated in blood vessels, raising the possibility that cardiovascular metabolism of ADMA constitutes a novel mechanism for the regulation of NO production. The purpose of this study was to determine the role of DDAH-catalyzed asymmetric methylarginine metabolism in the regulation of vascular function. We developed adenoviral vectors for the expression of human DDAH1 and 2. Overexpression of DDAH1 or 2 in human umbilical vein endothelial cells (HUVEC) increases DDAH activity, reduces ADMA concentrations and increases NO production. Similarly, overexpression of DDAH1 or 2 in DDAH1+/ — mice carotid vessels increases NO production and attenuates the response to phenylephrine (PE), enhances acetylcholine (ACh) relaxation and attenuates the effect of exogenously applied ADMA. Finally, overexpression of either DDAH1 or 2 completely reversed the vascular dysfunction seen in DDAH1+/— mice. These data indicate that basal concentrations of ADMA in blood vessels are sufficient to regulate NO production, that increases in the level of either DDAH1 or 2, improves vascular function and that overexpression of either DDAH1 or 2 is sufficient to compensate for life-long exposure to elevated ADMA. Thus, therapeutic manipulation of DDAH expression or activity may represent a novel approach to improve vascular dysfunction in various cardiovascular diseases.

Mitochondria-targeted antioxidant MitoQ10 improves endothelial function and attenuates cardiac hypertrophy

Mitochondria are a major site of reactive oxygen species production, which may contribute to the development of cardiovascular disease. Protecting mitochondria from oxidative damage should be an effective therapeutic strategy; however, conventional antioxidants are ineffective, because they cannot penetrate the mitochondria. This study investigated the role of mitochondrial oxidative stress during development of hypertension in the stroke-prone spontaneously hypertensive rat, using the mitochondria-targeted antioxidant, MitoQ(10). Eight-week-old male stroke-prone spontaneously hypertensive rats were treated with MitoQ(10) (500 mumol/L; n=16), control compound decyltriphenylphosphonium (decylTPP; 500 mumol/L; n=8), or vehicle (n=9) in drinking water for 8 weeks. Systolic blood pressure was significantly reduced by approximately 25 mm Hg over the 8-week MitoQ(10) treatment period compared with decylTPP (F=5.94; P=0.029) or untreated controls (F=65.6; P=0.0001). MitoQ(10) treatment significantly improved thoracic aorta NO bioavailability (1.16+/-0.03 g/g; P=0.002, area under the curve) compared with both untreated controls (0.68+/-0.02 g/g) and decylTPP-treated rats (0.60+/-0.06 g/g). Cardiac hypertrophy was significantly reduced by MitoQ(10) treatment compared with untreated control and decylTPP treatment (MitoQ(10): 4.01+/-0.05 mg/g; control: 4.42+/-0.11 mg/g; and decylTPP: 4.40+/-0.09 mg/g; ANOVA P=0.002). Total MitoQ(10) content was measured in liver, heart, carotid artery, and kidney harvested from MitoQ(10)-treated rats by liquid chromatography-tandem mass spectrometry. All of the organs analyzed demonstrated detectable levels of MitoQ(10), with comparable accumulation in vascular and cardiac tissues. Administration of the mitochondria-targeted antioxidant MitoQ(10) protects against the development of hypertension, improves endothelial function, and reduces cardiac hypertrophy in young stroke-prone spontaneously hypertensive rats. MitoQ(10) provides a novel approach to attenuate mitochondrial-specific oxidative damage with the potential to become a new therapeutic intervention in human cardiovascular disease.

Overexpression of eNOS prevents the development of renovascular hypertension in mice

Gene therapy has become an important tool for understanding several cardiovascular diseases. In the present study we investigated the effects of endothelial nitric oxide synthase (eNOS) overexpression on renovascular hypertension. Experiments were carried out in C57BL/6 mice randomly assigned to either a two-kidney one-clip (2K1C) hypertension group or a sham-operated group. At the same time surgery was carried out, both 2K1C and sham mice received an intravenous injection of recombinant adenovirus expressing the functional gene eNOS or the reporter gene beta-galactosidase (beta-gal). Fourteen days later, arterial pressure, baroreflex sensitivity, and cardiac sympathetic and parasympathetic tone were evaluated in conscious mice. Measurement of mean arterial pressure showed arterial hypertension in 2K1C-betagal mice compared with sham-betagal mice (121 +/- 3 vs. 96 +/- 2 mm Hg, p < 0.01), which was prevented by eNOS overexpression (2K1C-eNOS 100 +/- 4 vs. sham-eNOS 99 +/- 3 mm Hg). Linear regression analysis of the reflex tachycardia response to sodium nitroprusside-induced hypotension showed that baroreflex sensitivity was significantly attenuated in 2K1C-betagal mice (5.8 +/- 0.5 vs. sham-betagal 8.0 +/- 0.8 beats.min-1 x mm Hg-1, p < 0.05), but this decrease was not prevented by eNOS overexpression (2K1C-eNOS 7.2 +/- 0.5 vs. sham-eNOS 8.8 +/- 0.7 beats x min-1 x mm Hg-1, p < 0.05). The cardiac sympathetic tone was augmented and the vagal tone was reduced in 2K1C-betagal (152 +/- 17 and 45 +/- 12 beats.min-1, respectively) compared with sham-betagal mice (112 +/- 6 and 89 +/- 7 beats.min-1, respectively), and similar results were observed in 2K1C-eNOS mice compared with sham-eNOS. The data indicate that eNOS overexpression was able to prevent the development of 2K1C renovascular hypertension in mice, without affecting other characteristic cardiovascular dysfunctions.

Arteriolar genesis and angiogenesis induced by endothelial nitric oxide synthase overexpression results in a mature vasculature

BACKGROUND

Generation of physiologically active vascular beds by delivery of combinations of growth factors offers promise for vascular gene therapy.

METHODS AND RESULTS

In a mesenteric model of physiological angiogenesis, combining endothelial nitric oxide synthase (eNOS) (and hence NO production) with VEGF and angiopoietin-1 overexpression resulted in a more functional vascular phenotype than growth factor administration alone. eNOS gene delivery upregulated eNOS, VEGF, and Ang-1 to similar levels as gene transfer with VEGF or Ang-1. eNOS overexpression resulted in neovascularization to a similar extent as VEGF and Ang-1 combined, but not by sprouting angiogenesis. Whereas combining Ang-1 and VEGF increased both exchange vessels and conduit vessels, neither growth factor nor eNOS alone resulted in vessels with smooth muscle cell (SMC) coverage. In contrast, combining all three generated microvessels with SMCs (arteriolar genesis) and further increased functional vessels. Use of a vasodilator, prazosin, in combination with Ang1 and VEGF, but not alone, also generated SMC-positive vessels.

CONCLUSIONS

Coexpression of eNOS, VEGF, and Ang-1 results in a more mature vascularization of connective tissue, and generates new arterioles as well as new capillaries, and provides a more physiological therapeutic approach than single growth factor administration, by combining hemodynamic forces with growth factors.

Impaired vascular function in normoglycemic mice prone to autoimmune diabetes: Role of nitric oxide

Type 1 diabetes is an immuno-inflammatory condition which increases the risk of cardiovascular disease, particularly in young adults. This study investigated whether vascular function is altered in mice prone to autoimmune diabetes and whether the nitric oxide (NO)-cyclic GMP axis is involved. Aortic rings suspended in organ chambers and precontracted with phenylephrine were exposed to cumulative concentrations of acetylcholine. To investigate the role of NO, some experiments were performed in the presence of either 1400W (N-(3-aminomethyl)benzyl-acetamidine hydrochloride), a selective inhibitor of the iNOS-isoform, L-NAME (N(G)-nitro-L-arginine methyl ester hydrochloride), an inhibitor of all three NOS-isoforms, or ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one), a selective inhibitor of guanylate cyclase. Moreover, contractility to phenylephrine, big endothelin-1, and endothelin-1 was assessed and histological analysis and iNOS immunohistochemistry were performed. Endothelium-dependent relaxation was reduced in prediabetic NOD mice (78+/-4 vs. 88+/-2%, respectively, P<0.05 vs. control) despite normal plasma glucose levels (n.s. vs. control). Preincubation with 1400W further attenuated responses in prediabetic (P<0.05 vs. untreated) but not in diabetic or in control mice. In contrast, basal NO bioactivity remained unaffected until the onset of diabetes in NOD mice. Contractile responses to big endothelin-1 and endothelin-1 were reduced in prediabetic animals (P<0.05 vs. control), whereas in diabetic mice only responses to big endothelin-1 were decreased (P<0.05 vs. control). These data demonstrate that endothelium-dependent and -independent vascular function in NOD mice is abnormal already in prediabetes in the absence of structural injury. Early proinflammatory activation due to iNOS in diabetes-prone NOD mice appears to be one of the mechanisms contributing to impaired vasoreactivity.

Gene-based therapy for hypertension--do preclinical data suggest a promising future?

Many experimental studies have obtained a prolonged control of blood pressure through gene treatment. This consists in the administration of genes coding for vasodilator proteins (the 'sense' approach), or of nucleotide sequences that are complementary to the mRNA of vasoconstrictor proteins, which are consequently synthesized in smaller amounts (the 'antisense' approach). Examples of the sense approach include the genes encoding endothelial nitric oxide synthase and kallikrein. Examples of the second type of approach are the antisense oligodeoxynucleotides to angiotensin-converting enzyme and endothelin-1. Also, RNA molecules, such as ribozymes and small interfering RNAs, are capable to inhibit RNA function. Whole sense genes are usually administered through viral vectors, while antisense oligonucleotides may be administered with plasmids or liposomes. Both viral and non-viral vectors have advantages and disadvantages. Despite the still persisting limitations, the possibility exists that in the future some forms of genetic treatment will be extended to the clinical setting, allowing a prolonged control of essential hypertension and its end-organ sequelae.

Eplerenone reduces oxidative stress and enhances eNOS in SHR: vascular functional and structural consequences

The aim of the present study was to evaluate the effect of the aldosterone receptor antagonist eplerenone on endothelial function, oxidative stress, and structural alterations present in spontaneously hypertensive rats (SHR). To carry out the study, male SHR (18 weeks old) were treated with two doses of eplerenone (30 and 100 mg/kg/day) for 10 weeks. A group of n = 8 untreated SHR was used as a control-vehicle group, and a group of Wistar Kyoto rats (n = 8) was used as a reference of normotensive conditions. Systolic arterial pressure (SAP) was measured by the tail-cuff method. Endothelium-dependent and -independent relaxations, as well as endothelial nitric oxide synthase (eNOS) and the subunit p22phox of NAD(P)H oxidase mRNA expressions, were studied in aorta from SHR untreated or treated with eplerenone. Media/lumen ratio was also calculated in aortic preparations. In addition, levels of reduced glutathione (GSH), oxidized glutathione (GSSG), and malonyl dialdehyde (MDA) were evaluated in liver homogenates. Treatment with eplerenone reduced (p < 0.05) SAP and normalized aortic media/lumen ratio and acetylcholine relaxations. Both doses of the drug enhanced (p < 0.05) eNOS and reduced p22phox mRNA expressions. Similarly, eplerenone increased (p < 0.05) hepatic GSH/GSSG ratio, and reduced (p < 0.05) hepatic MDA levels in a comparable manner. Consequently, it could be concluded that aldosterone participates in the functional and structural vascular alterations of SHR through the diminution of nitric oxide availability and an enhancement of vascular and systemic oxidative stress.

Targeting endothelial cells with adenovirus expressing nitric oxide synthase prevents elevation of blood pressure in stroke-prone spontaneously hypertensive rats

Local adenoviral (Ad)-mediated gene transfer to the carotid artery of the stroke-prone spontaneously hypertensive rat (SHRSP) is successful in improving endothelial function. Here we explored the potential of systemic delivery of Ad encoding endothelial nitric oxide synthase (AdeNOS) to prevent elevation of blood pressure in the SHRSP using both nontargeted and vector targeting approaches. Systemic administration of nontargeted AdeNOS failed to modify the rise in blood pressure in SHRSP when administered during the 12th week of age (n = 5, P = 0.088, F = 3.0), an effect likely to result from sequestration of Ad by the liver. Rerouting Ad transduction using a bispecific antibody (anti-ACE/anti-Ad capsid, Fab9B9) that blocks Ad binding to the coxsackie and adenovirus receptor and simultaneously retargets AdeNOS to the angiotensin-converting enzyme resulted in efficient eNOS overexpression in the lung vasculature and a sustained hypotensive effect (n = 5, P = 0.007, F = 7.9). This study highlights the importance of vector targeting to achieve therapeutic gain and represents the first such study in cardiovascular gene therapy.

Endothelial cell dysfunction: can't live with it, how to live without it

Endothelial cell dysfunction is emerging as an ultimate culprit for diverse cardiovascular diseases and cardiovascular complications of chronic renal diseases, yet the definition of this new syndrome, its pathophysiology, and therapy remain poorly defined. Here, I summarize some molecular mechanisms leading from hyperhomocystinemia, elevated asymmetric dimethylarginine, and advanced glycolation end product-modified protein level to the proatherogenic, prothrombogenic, and proinflammatory endothelial phenotype and offer a model of endothelial dysfunction based on the interconnectedness of diverse functions. Finally, several therapeutic strategies to prevent and correct endothelial dysfunction are discussed in the light of uncertainty of their action modulated by the endothelial dysfunction per se.

Human eNOS gene delivery attenuates cold-induced elevation of blood pressure in rats

We previously showed that chronic cold exposure inhibits endothelial nitric oxide synthase (eNOS) expression and decreases nitric oxide (NO) production. The aim of the present study was to evaluate the possible role of the NO system in the development of cold-induced hypertension (CIH) by testing the hypothesis that adenoviral delivery of human eNOS gene increases NO production and attenuates CIH in rats. The effect of in vivo delivery of adenovirus carrying human eNOS full-length cDNA (rAdv.heNOS) on CIH was tested using four groups of Sprague-Dawley rats (6 rats/group). Blood pressure (BP) did not differ among the four groups during the control period at room temperature (24 degrees C). Two groups of rats received intravenous injection of rAdv.heNOS (1 x 10(9) plaque-forming units/rat), and the other two groups received the same dose of rAdv.LacZ to serve as controls. After gene delivery, one rAdv.heNOS-treated group and one rAdv.LacZ-treated group were exposed to cold (6 degrees C) while the remaining groups were kept at 24 degrees C. We found that the BP of the rAdv.LacZ group increased significantly within 1 wk of exposure to cold and reached a peak level at week 5 (152.2 +/- 6.4 mmHg). In contrast, BP (118.7 +/- 8.4 mmHg) of the cold-exposed rAdv.heNOS group did not increase until 5 wk after exposure to cold. The rAdv.heNOS increased plasma and urine levels of NO significantly in cold-exposed rats, which indicates that eNOS gene transfer increased NO production. Notably, rAdv.heNOS decreased plasma levels of norepinephrine and plasma renin activity in cold-exposed rats, which suggests that eNOS gene transfer may decrease the activities of the sympathetic nervous system and the renin-angiotensin system. Immunohistochemical analysis showed that the transferred human eNOS was expressed in both endothelium and adventitia of mesenteric arteries. We conclude that 1) eNOS gene transfer attenuates CIH by increasing NO production and inhibiting the sympathetic nervous system and the renin-angiotensin system; and 2) the NO system appears to mediate this nongenetic, nonpharmacological, nonsurgical model of hypertension.

Expression of human eNOS in cardiac and endothelial cells

In this chapter we provide a detailed technique-focused protocol for expression of human endothelial nitric oxide synthase (eNOS) gene delivered by replication-deficient adenovirus. It includes construction of recombinant plasmid with human eNOS gene full-length cDNA (heNOS), packaging of adenovirus with heNOS (Adv-heNOS) in 293 cells, confirmation of Adv-heNOS, amplification of high-titer stockAdv-heNOS, determination of the Adv-heNOS titer, expression of Adv-heNOS in the human abdominal aorta endothelial (HAAE1) cell line and rat heart myoblast cell line (H9C2), and measurement of human eNOS activity and NO production.

Comparison of the effects of omapatrilat and irbesartan/hydrochlorothiazide on endothelial function and cardiac hypertrophy in the stroke-prone spontaneously hypertensive rat

OBJECTIVE

The novel antihypertensive agent, omapatrilat, is both an inhibitor of neutral endopeptidase and angiotensin-converting enzyme. This study investigated the effects of omapatrilat in comparison with an angiotensin I-receptor antagonist/diuretic combination on blood pressure, endothelial function and cardiac hypertrophy in stroke-prone spontaneously hypertensive rats (SHRSP).

METHODS

Male and female SHRSP were treated orally with omapatrilat or irbesartan plus hydrochlorothiazide (I + H) or vehicle for 8 weeks. Systolic blood pressure was measured weekly by tail-cuff. Cardiac hypertrophy was monitored by echocardiography at 8, 12 and 16 weeks of age. Endothelial function [basal nitric oxide (NO) bioavailability and stimulated NO release] was examined in carotid arteries using organ bath pharmacology and in mesenteric resistance arteries using wire myography.

RESULTS

Compared with untreated controls, omapatrilat and I + H significantly attenuated hypertension [male control, 198.3 +/- 6.9 mmHg versus omapatrilat, 149.6 +/- 3.8 mmHg (F = 8.63 P < 0.0001), versus I + H, 145.6 +/- 5.1 mmHg (F = 7.38 P < 0.0001); female control, 170.3 +/-8.3 mmHg versus omapatrilat, 120.0 +/- 4.6 mmHg (F = 8.36, P < 0.0001), versus I + H, 112.2 +/- 2.9 mmHg (F = 9.08, P < 0.0001)] and left ventricular hypertrophy [male + female controls, 3.02 +/- 0.38 mg/g versus omapatrilat, 2.47 +/- 0.26 mg/g (P < 0.0001; 95% confidence interval, 0.27, 0.83), versus I + H, 2.49 +/- 0.21 mg/g (P < 0.0001; 95% confidence interval, 0.25, 0.83)]. Both treatments also significantly increased male carotid artery basal NO bioavailability relative to control [control, 0.62 +/- 0.17 g/g versus omapatrilat, 1.95 +/- 0.17 g/g (P < 0.0001; 95% confidence interval, -1.83, -0.36), versus I + H, 1.57 +/- 0.21 g/g (P < 0.026; 95% confidence interval, -1.31, -0.12)]. However, stimulated NO (EC50) was only improved in omapatrilat-treated males [controls, 0.19 +/- 0.06 micromol/l versus omapatrilat, 0.05 +/- 0.01 micromol/l (P = 0.05; 95% confidence interval, -1.16, -0.03)].

CONCLUSIONS

Omapatrilat treatment significantly reduced left ventricular hypertrophy and improved endothelial function in carotid arteries from male SHRSP by NO-dependent mechanisms. Despite equivalent antihypertensive and antihypertrophic actions, a similar improvement in endothelial function, specifically stimulated NO release, was not observed after treatment with I + H.

Polyethylene Glycol Additives Reduce Hemolysis in Red Blood Cell Suspensions Exposed to Mechanical Stress

Mechanical damage to blood cells is of considerable concern in the development and use of circulatory assist devices and other blood contacting systems. Furthermore, hemodilution with saline, dextran, and other plasma expanders applied during extracorporeal circulation and dialysis increases red blood cell (RBC) susceptibility to the high shear stresses associated with these procedures. In this paper, we present polyethylene glycol (PEG) as a potential erythrocyte protective agent against mechanically induced cellular trauma. Bovine RBCs were subjected to mechanical stress induced by rolling stainless steel shots through RBC suspensions for a constant exposure time. The suspensions were prepared at a hematocrit of 30% in various media: PEG (20,000 molecular weight), autologous bovine plasma, Dextran 40 solution, and phosphate buffered saline (PBS). RBC suspensions in Dextran 40 were prepared at a viscosity similar to the PEG suspensions. We found the hemolysis level of RBCs suspended in plasma and in PEG solutions to be several times lower (p < 0.001) than in the Dextran and PBS solutions. No statistically significant difference was found between the hemolysis that occurred in suspensions of RBCs in autologous plasma and in 2.0% PEG solutions. Even PEG concentration as low as 0.1% reduced hemolysis by more than 40% compared with PBS or the same concentration of Dextran in suspension medium. Our data demonstrate the efficacy of PEG molecules in reducing mechanical trauma to erythrocytes and suggest the potential for using PEG in assisted circulation, dialysis, and other procedures where RBCs are subjected to extensive mechanical stress.

Effect of AT1 receptor blockade on hepatic redox status in SHR: possible relevance for endothelial function?

The study investigated whether the amelioration of endothelial dysfunction by candesartan (2 mg.kg-1.day-1; 10 wk) in spontaneously hypertensive rats (SHR) was associated with modification of hepatic redox system. Systolic arterial pressure (SAP) was higher (P < 0.05) in SHR than in Wistar-Kyoto rats (WKY) and was reduced (P < 0.05) by candesartan in both strains. Acetylcholine (ACh) relaxations were smaller (P < 0.05) and contractions induced by ACh + NG-nitro-l-arginine methyl ester (l-NAME) were greater (P < 0.05) in SHR than in WKY. Treatment with candesartan enhanced (P < 0.05) ACh relaxations in SHR and reduced (P < 0.05) ACh + l-NAME contractions in both strains. Expression of aortic endothelial nitric oxide synthase (eNOS) mRNA was similar in WKY and SHR, and candesartan increased (P < 0.05) it in both strains. Aortic mRNA expression of the subunit p22phox of NAD(P)H oxidase was higher (P < 0.05) in SHR than in WKY. Treatment with candesartan reduced (P < 0.05) p22phox expression only in SHR. Malonyl dialdehyde (MDA) levels were higher (P < 0.05), and the ratio reduced/oxidized glutathione (GSH/GSSG) as well as glutathione peroxidase activity (GPx) were lower (P < 0.05) in liver homogenates from SHR than from WKY. Candesartan reduced (P < 0.05) MDA and increased (P < 0.05) GSH/GSSG ratio without affecting GPx. Vessel, lumen, and media areas were bigger (P < 0.05) in SHR than in WKY. Candesartan treatment reduced (P < 0.05) media area in SHR without affecting vessel or lumen area. The results suggest that hypertension is not only associated with elevation of vascular superoxide anions but with alterations of the hepatic redox system, where ANG II is clearly involved. The results further support the key role of ANG II via AT1 receptors for the functional and structural vascular alterations produced by hypertension.

[Endothelium-derived factors in hypertensive blood vessels, especially nitric oxide and hypertension]

Endothelium-dependent relaxation (EDR) in the blood vessels of spontaneously hypertensive rats (SHR) and the role of nitric oxide (NO) in the initiation of hypertension are reviewed. EDR was impaired in blood vessels of SHR depending on age and degree of hypertension when compared with those of normotensive rats. The cause of the impairment varied among the type of blood vessels: a decrease in the production of NO and endothelium-derived relaxing factor (EDRF) and an increase in the production of endothelium-derived contracting factor (EDCF) are the main causes of the impairment in large arteries, while a decrease in endothelium-dependent hyperpolarization and increased release of EDCF are the main causes of the impairment in small arteries. Interactions among these endothelium-derived factors and changes in the interactions are also causes of impairment. Superoxide may be involved in the impairment of EDR by destroying NO. The endothelium depresses smooth muscle contraction, including spontaneous tone developed in vascular smooth muscle, and the depressing effect of the endothelium is impaired in the preparations from SHR. The endothelium of blood vessels of SHR are structurally injured as demonstrated by scanning electron microscopy. Antihypertensive treatment prevented these functional and structural changes. Chronic treatment with inhibitors of NO production in normotensive rats impaired EDR and elevated blood pressure. The impairment of EDR is a secondary change due to continued hypertension, and early initiation of antihypertensive therapy is recommended.

Gene therapy for cerebral vascular disease: update 2003

Gene therapy is a promising strategy for cerebrovascular diseases. Several genes that encode vasoactive products have been transferred via cerebrospinal fluid for the prevention of vasospasm after subarachnoid hemorrhage. Transfer of neuroprotective genes, including targeting of proinflammatory mediators, is a current strategy of gene therapy for ischemic stroke. Stimulation of growth of collateral vessels, stabilization of atherosclerotic plaques, inhibition of thrombosis, and prevention of restenosis are important objectives of gene therapy for coronary and limb arteries, but application of these approaches to carotid and intracranial arteries has received little attention. Several fundamental advances, including development of safer vectors, are needed before gene therapy achieves an important role in the treatment of cerebrovascular disease and stroke.

In vivo gene transfer of inducible nitric oxide synthase to carotid arteries from hypercholesterolemic rabbits

BACKGROUND AND PURPOSE

Hypercholesterolemia is associated with endothelial dysfunction. Inducible nitric oxide synthase (iNOS) is upregulated in atherosclerotic vessels. However, its role in the regulation of vascular function is not completely understood. We examined the effect of adenovirus-mediated gene transfer of iNOS to the hypercholesterolemic rabbit carotid artery in vivo.

METHODS

Rabbits were fed a high-cholesterol or chow diet for 10 weeks. Two doses (1x10(8) and 1x10(9) plaque-forming units [pfu]/mL) of adenoviral vectors encoding iNOS (AdiNOS) or beta-galactosidase (Ad(beta)gal) were luminally delivered to the carotid arteries from chow- and cholesterol-fed animals. Vascular reactivity and superoxide levels were assessed in Ad(beta)gal- and AdiNOS-transduced vessels from chow- and cholesterol-fed animals after 3 days.

RESULTS

Endothelium-dependent vasorelaxation was impaired in the carotid artery from cholesterol-fed animals. In AdiNOS-transduced arteries, transgene expression was demonstrated by positive immunostaining in the endothelium. Transduction with low-dose (1x10(8) pfu/mL) AdiNOS did not affect vascular reactivity in arteries from chow- and cholesterol-fed animals. In contrast, high-dose (1x10(9) pfu/mL) AdiNOS significantly reduced endothelium-dependent relaxation in vessels from cholesterol- but not chow-fed rabbits. After both low- and high-dose iNOS gene transfer, levels of O2*(-) were significantly (P<0.05) elevated in carotid arteries from cholesterol-fed animals. Incubation with an O2*(-) scavenger did not reverse vascular dysfunction in these arteries.

CONCLUSIONS

Adenoviral-mediated overexpression of iNOS results in increased production of O2*(-) in carotid arteries from cholesterol- but not chow-fed animals. High-dose AdiNOS gene transfer is associated with reduced endothelium-dependent and -independent relaxation in vessels from cholesterol-fed animals.

The potential of nitric oxide therapeutics in stroke

The therapeutic modulation of the nitric oxide (NO) system has generated considerable interest as a new way for managing many disease processes. In stroke, a useful strategy is to increase NO availability and thereby exploit its beneficial antiplatelet, antiatherosclerotic, haemodynamic and neuroprotective properties. Pharmacologically, this can be achieved by providing NO substrate, using NO donors or by upregulating nitric oxide synthase. Alternatively, one can reduce NO availability by inhibiting NO synthase and thereby limiting its pro-inflammatory and neurotoxic properties. This article reviews developments in NO-related therapeutics for treatment of stroke, with a particular emphasis on compounds that are in the clinical research and development pipeline. Although the routine use of NO therapeutics for the prevention or treatment of stroke cannot currently be recommended, we are evidently at an exciting stage in their pharmacological development. Definitive randomised controlled trials in stroke patients are required as a matter of urgency.

Protective role of endothelial nitric oxide synthase

Nitric oxide is a versatile molecule, with its actions ranging from haemodynamic regulation to anti-proliferative effects on vascular smooth muscle cells. Nitric oxide is produced by the nitric oxide synthases, endothelial NOS (eNOS), neural NOS (nNOS), and inducible NOS (iNOS). Constitutively expressed eNOS produces low concentrations of NO, which is necessary for a good endothelial function and integrity. Endothelial derived NO is often seen as a protective agent in a variety of diseases. This review will focus on the potential protective role of eNOS. We will discuss recent data derived from studies in eNOS knockout mice and other experimental models. Furthermore, the role of eNOS in human diseases is described and possible therapeutic intervention strategies will be discussed.

NAD(P)H oxidase inhibition improves endothelial function in rat and human blood vessels

The NO/superoxide (O2-) balance is a key regulator of endothelial function. O2- levels are elevated in many forms of cardiovascular disease; therefore, decreasing O2- should improve endothelial function. To explore this hypothesis, internal mammary arteries and saphenous veins, obtained from patients undergoing coronary artery revascularization, and aortic and carotid arteries from Wistar-Kyoto and spontaneously hypertensive stroke-prone rats were incubated with O2- dismutase or NAD(P)H oxidase inhibitors. O2- levels were measured using lucigenin chemiluminescence; NO bioavailability was assessed in organ chambers; and mRNA expression of NAD(P)H oxidase components was quantified by use of a Light Cycler. In rat arteries, phenylarsine oxide, 4-(2-aminoethyl)-benzenesulfanyl fluoride, and apocynin all decreased NADH-stimulated O2- production, but only apocynin increased NO bioavailability. In human internal mammary arteries and saphenous veins, apocynin decreased NAD(P)H-stimulated O2- generation and caused vasorelaxation that was endothelium dependent and reversed on addition of the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester. In addition, it increased NO production from cultured human endothelial saphenous vein cells. Polyethylene-glycolated O2- dismutase also increased NO bioavailability in rat carotid arteries and human blood vessels, but the effects were smaller than those observed with apocynin. NADH-generated O2- and mRNA expression of p22(phox), gp91(phox), and nox-1 were comparable between the 2 strains of rat. This is the first study to demonstrate pharmacological effects of apocynin in human blood vessels. The increases in NO bioavailability shown here suggest that the NAD(P)H oxidase pathway may be a novel target for drug intervention in cardiovascular disease.

Development and use of gene transfer for treatment of cardiovascular disease

Gene therapy holds promise for the treatment of cardiovascular diseases for which effective pharmacological therapies are insufficient or unavailable. Recent studies have suggested that modification of current gene delivery systems combined with the use of efficacious therapeutic genes may ultimately be successful for clinical vascular gene therapy. Although certain applications such as vein-graft failure may be best suited for short-term transient overexpression of therapeutic genes, other disorders including human essential hypertension and atherosclerosis require sustained overexpression of genes. Hence, design and use of vector systems for delivery of genes to the required site in vivo requires careful consideration. Both viral and nonviral gene therapy vectors show low efficiency for gene transfer into vascular cells and demonstrate a lack of selectivity, as vectors have natural tropism for other cells and tissues. Recent work has focused on the design, development, and utility of vascular cell-selective gene therapy vectors for use in distinct and diverse vascular gene therapy scenarios. Using phage display technology we have isolated small peptide ligands that mediate selective binding to either vascular endothelial cells or vascular smooth muscle cells. When engineered into either adenoviral (Ad) or adeno-associated viral (AAV) vectors, candidate peptides enabled the virus to selectively bind to the desired cell type thus generating novel vascular cell-selective gene transfer. As preclinical studies have highlighted both the potential for vascular gene therapy as well as defining the potential pitfalls, the development of disease-selective gene therapeutics will increase safety and efficiency of gene therapy for future clinical use.

Nitric oxide synthase gene therapy for cardiovascular disease

Gene therapy refers to the transfer of specific genes to the host tissue to intervene in a disease process, with resultant alleviation of the symptoms of a particular disease. Cardiovascular gene transfer is not only a powerful technique for studying the function of specific genes in cardiovascular biology and pathobiology, but also a novel and promising strategy for treating cardiovascular diseases. Since the mid-1990s, nitric oxide synthase (NOS), the enzyme that catalyzes the formation of nitric oxide (NO) from L-arginine, has received considerable attention as a potential candidate for cardiovascular gene therapy, because NO exerts critical and diverse functions in the cardiovascular system, and abnormalities in NO biology are apparent in a number of cardiovascular disease processes including cerebral vasospasm, atherosclerosis, postangioplasty restenosis, transplant vasculopathy, hypertension, diabetes mellitus, impotence and delayed wound healing. There are three NOS isoforms, i.e., endothelial (eNOS), neuronal (nNOS) and inducible (iNOS). All three NOS isoforms have been used in cardiovascular gene transfer studies with encouraging results. This review will discuss the rationale of NOS gene therapy in different cardiovascular disease settings and summarize the results of experimental NOS gene therapy from various animal models of cardiovascular disease to date.

Genetic targeting of the renin-angiotensin system for long-term control of hypertension

Although traditional approaches are effective for the treatment and control of hypertension, they have not succeeded in curing the disease, and have therefore reached a plateau. As a result of the completion of the Human Genome Project and the continuous advancement in gene delivery systems, it is now possible to investigate genetic means for the treatment and possible cure for hypertension. In this review we discuss the potential of genetic targeting of the renin-angiotensin system for the treatment of hypertension. We provide examples of various approaches that have used antisense technology with a high degree of success. We focus on our own research, which targets the use of antisense of the angiotensin type I receptor in various models of hypertension. Finally, we discuss the future of antisense technology in the treatment of human hypertension.

Irbesartan lowers superoxide levels and increases nitric oxide bioavailability in blood vessels from spontaneously hypertensive stroke-prone rats

OBJECTIVE

To determine the effects of the angiotensin II receptor antagonist irbesartan, the calcium-channel blocker amlodipine, and hydrochlorothiazide/hydralazine on superoxide, NAD(P)H oxidase and nitric oxide bioavailability in spontaneously hypertensive stroke-prone rats (SHRSP).

METHODS

Drugs or vehicle were administered for 8 weeks to SHRSP and blood pressure was measured weekly by tail-cuff plethysmography. After 8 weeks, superoxide levels in carotid arteries and aortas were measured by lucigenin chemiluminescence and p22phox expression quantified by immunohistochemistry. In vitro the effects of exposure to drugs and vehicle for 30 min and 4 h on superoxide levels and nitric oxide bioavailability were examined. The latter was expressed as the increase in contractile responses of carotid arteries to phenylephrine in the presence of the nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester(l-NAME).

RESULTS

In vivo irbesartan, amlodipine and hydrochlorothiazide/hydralazine produced similar falls in blood pressure, from 162 +/- 4 to 125 +/- 5, 132 +/- 4 and 131 +/- 6 mmHg, respectively, but irbesartan caused a greater reduction in superoxide and p22phox; superoxide levels in carotid arteries being 3.1 +/- 0.3, 1.1 +/- 0.2, 1.9 +/- 0.3 and 2.0 +/- 0.3 nmoles/mg per min, respectively. In vitro 4 h exposure to irbesartan decreased superoxide levels in the aorta from 2.08 +/- 0.68 to 1.48 +/- 0.62 nmoles/mg per min and increased nitric oxide bioavailability in carotid arteries. Neither 30 min incubation with irbesartan nor 4 h with amlodipine or hydrochlorothiazide/hydralazine altered superoxide levels.

CONCLUSIONS

These studies support the hypothesis that AT1 receptor blockade has beneficial effects on superoxide production and nitric oxide bioavailability above that of other classes of antihypertensive agents. Reduced expression of components of the NAD(P)H oxidase may contribute to these effects.

Adenovirus-mediated overexpression of extracellular superoxide dismutase improves endothelial dysfunction in a rat model of hypertension

Gene transfer may be appropriate for therapeutic protocols targeted at the vascular endothelium. Endothelial dysfunction is the principal phenotype associated with atherosclerosis and hypertension. Oxidative stress has been implicated in the development of endothelial dysfunction. We have explored the ability of overexpressing anti-oxidant genes (superoxide dismutases; SODs) in vitro and in vivo to assess their potential for reversing endothelial dysfunction in a rat model, the stroke-prone spontaneously hypertensive rat (SHRSP). Western blotting and immunofluorescence assays in vitro showed efficient overexpression of MnSOD and ECSOD with respect to localisation to the mitochondria and extracellular surface, respectively. Transgene functional activity was quantified with SOD activity assays. MnSOD and ECSOD overexpression in intact SHRSP vessels in vivo led to endothelial and adventitial overexpression. Pharmacological assessment of transduced vessels following in vivo delivery by basal NO availability quantification demonstrated that the "null" adenovirus and MnSOD adenovirus did not significantly increase NO availability. However, AdECSOD-treated carotid arteries showed a significant increase in NO availability (1.91 +/- 0.04 versus 0.75 +/- 0.08 g/g, n = 6, P = 0.029). In summary, efficient overexpression of ECSOD, but not MnSOD in vivo, results in improved endothelial function in a rat model of hypertension and has important implications for the development of endothelial-based vascular gene therapy.

Recent developments in gene therapy for cardiac disease

Cardiovascular[TRACE;del] disease is the leading cause of death in the US and world-wide. Advances in molecular biology and the human genome project have revealed opportunities for novel strategies for cardiac gene therapy. This review discusses general and specific aspects of gene transfer strategies in cardiac tissues. These include 1) the selection and/or optimization of the vector for gene transfer; 2) the identification of the target gene(s); 3) the use of cardiac-specific promoters; and 4) the use of an appropriate delivery system for administration. Currently, several vectors (e.g., viral and nonviral vectors) have been developed and many target genes have been identified (e.g., VEGF, FGF, beta-AR, etc.). Many investigations have provided experimental models for gene delivery systems but the most efficient cardiac gene transfer was obtained from intramyocardial injection or perfusion of explanted myocardium. The data available thus far have suggested favorable immediate effects following gene transfer, but long-term value of cardiac gene therapy has not been proven. Further refinements in appropriate vectors that provide cell or tissue selectivity and long-lasting effects are necessary as well as the development of minimally invasive procedures for gene transfer.

Nitric oxide synthase in atherosclerosis and vascular injury: insights from experimental gene therapy

Gene therapy aims to intervene in a disease process by transfer and expression of specific genes in a target tissue or organ. Cardiovascular gene therapy in humans remains in its infancy, but in the last decade, experimental gene transfer has emerged as a powerful biological tool to investigate the function of specific genes in vascular disease pathobiology. Nitric oxide synthases, the enzymes that produce nitric oxide, have received considerable attention as potential candidates for vascular gene therapy because nitric oxide has pleiotropic antiatherogenic actions in the vessel wall, and abnormalities in nitric oxide biology are apparent very early in the atherogenic process. In this article, we review the use of nitric oxide synthases in experimental vascular gene therapy and assess the utility of these approaches for investigating the role of nitric oxide in atherosclerosis and their potential for human gene therapy.

Genes and hypertension: from gene mapping in experimental models to vascular gene transfer strategies

Human essential hypertension is a complex, multifactorial, quantitative trait under a polygenic control. Several strategies have been developed over the last decade to dissect genetic determinants of hypertension. Of these, the most successful have been studies that identified rare mendelian syndromes in which a single gene mutation causes high blood pressure. The attempts to identify multiple genes, each with a small contribution to the common polygenic form of hypertension, have been less successful. Several laboratories focused their attention on rat models of genetic hypertension, which can be considered as a reductionist paradigm for human disease. Using numerous crosses between hypertensive and normotensive strains, investigators identified several quantitative trait loci (QTL) for blood pressure subphenotypes and for cardiovascular complications such as left ventricular hypertrophy, kidney failure, stroke, and insulin resistance. Furthermore, congenic strains have been produced to confirm the existence of some of these QTL and to narrow down the chromosomal regions of interest. A number of interesting strategies have been developed, including a "speed" congenic strategy perfected by our group in Glasgow. However, the limit of congenic strategy is estimated at 1 cM, which corresponds to 2x10(6) base pairs of DNA and approximately 50 candidate genes. It is envisaged that gene expression profiling with cDNA microarrays might allow a quick progression toward the gene identification within cardiovascular QTL. In parallel experimental effort, several laboratories have been developing gene transfer/therapy strategies with adenoviral or adeno-associated viral vectors used, for example, to overexpress protective vascular genes such as vascular endothelial growth factor or endothelial nitric oxide synthase. It is anticipated that further developments in positional cloning of susceptibility and severity genes in hypertension and its complications will lead to a direct transfer of these discoveries to essential hypertension in humans and will ultimately produce novel targets for local and systemic gene therapy in cardiovascular disease.