Endothelial dysfunction in chronic myocardial infarction despite increased vascular endothelial nitric oxide synthase and soluble guanylate cyclase expression: role of enhanced vascular superoxide production

Preserved coronary arteriolar dilatation in patients with type 2 diabetes mellitus: implications for reactive oxygen species

Type 2 diabetes mellitus is associated with clustering of cardiovascular risk factors that may greatly increase individuals' risk of developing coronary artery disease. Type 2 diabetes is believed to impair coronary function. However, its impact on the vasomotor function of coronary resistance vessels in humans is still debated. Reduced, preserved or even augmented dilations of coronary arterioles have been reported in subjects with type 2 diabetes. Interestingly, recent studies have suggested that reactive oxygen species (ROS), particularly hydrogen peroxide, may compensate for the loss of the vasodilatory function of coronary microvessels during disease development. Recent interventional clinical trials have yielded largely negative results, and there has even been some suggestion of harm caused by attempts to reduce ROS. Thus, it is possible that interference with ROS-related signaling might paradoxically temper the function of coronary microvessels, predisposing patients to myocardial ischemia. In this review, we aim to highlight current findings supporting a potential role for ROS in preserving coronary arteriolar dilation in type 2 diabetes mellitus.

The eNOS enhancer AVE 9488: a novel cardioprotectant against ischemia reperfusion injury

Nitric oxide (NO) is an important regulator of vascular and myocardial function. Cardiac ischemia/reperfusion injury is reduced in mice overexpressing endothelial NO synthase (eNOS) suggesting cardioprotection by eNOS. Novel pharmacological substances, so called eNOS enhancers, upregulate eNOS expression and thereby increase NO production. We tested the effects of the eNOS enhancer AVE 9488 on cardiac ischemia/reperfusion injury in vivo in mice. After treatment with the eNOS enhancer AVE 9488 (30 mg/kg/day) or placebo for one week mice underwent 30 min of coronary artery ligation and 24 h of reperfusion in vivo. Ischemia-reperfusion damage was significantly reduced in mice treated with the eNOS enhancer when compared to placebo treated mice (infarct/area at risk 65.4 +/- 4.1 vs. 36.9 +/- 4.0%, placebo vs. eNOS enhancer, P = 0.0002). The protective effect was blunted in eNOS knockout mice treated with the eNOS enhancer (infarct/area at risk 64.1 +/- 6.2%, eNOS knockout + eNOS enhancer vs. WT + eNOS enhancer, P = ns). Reactive oxygen species were significantly reduced in mice treated with the eNOS enhancer as indicated by significantly lower malondialdehyde-thiobarbituric acid levels (placebo vs. eNOS enhancer, 3.2 +/- 0.5 vs. 0.8 +/- 0.07 micromol/l, P = 0.0003). Thus pharmacological interventions addressed to increase eNOS-derived NO production constitute a promising therapeutic approach to prevent myocardial ischemia/reperfusion injury.

Endothelial dysfunction and vascular disease

The endothelium can evoke relaxations (dilatations) of the underlying vascular smooth muscle, by releasing vasodilator substances. The best characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO). The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDHF-mediated responses). Endothelium-dependent relaxations involve both pertussis toxin-sensitive G(i) (e.g. responses to serotonin and thrombin) and pertussis toxin-insensitive G(q) (e.g. adenosine diphosphate and bradykinin) coupling proteins. The release of NO by the endothelial cell can be up-regulated (e.g. by oestrogens, exercise and dietary factors) and down-regulated (e.g. oxidative stress, smoking and oxidized low-density lipoproteins). It is reduced in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively loose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and causing endothelium-dependent hyperpolarizations), endothelial cells also can evoke contraction (constriction) of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factor (EDCF). Most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells. EDCF-mediated responses are exacerbated when the production of NO is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive patients.

Candidate gene microarray analysis in peripheral blood cells for studying hypertension/obesity

AIMS

The gene expression of 182 cardiovascular candidate genes was measured in high quality groups of individuals (n = 20) by microarrays to determine whether a subset of genes would discriminate obese and hypertensive individuals, in spite of the existence of a close link between these two cardiovascular risk factors.

MATERIALS & METHODS

The results were validated on the 20 subjects used for microarray analysis and on 62 additional individuals by real-time PCR.

RESULTS

The first analysis, where patient groups were compared with healthy subjects, revealed 15 out of 182 genes that differed in hypertensive, obese or obesity-related hypertensive individuals. These genes were ALOX5, APOA2, SELL, RGS2, CD14, FPR1, CAMP, DEFA3, DEFA4, CBS, CHRM1, ICAM1, NR1H2, SCNN1B and TGFB1. A second analysis was carried out in which patient groups were compared with each other, demonstrating FPR1 and DEFA3 as being significant genes discriminating patient groups. Furthermore, an analysis stratified by sex revealed that, with the exception of DEFA3, there are no other common genes between men and women.

DISCUSSION

We were able to indentify a number of interesting genes that distinguish patient and healthy subject groups as well as patient groups between them.

CONCLUSION

In addition, it seems that gender plays an important role, at least for some of the genes we tested. These findings may have important implications in the screening and etiology of hypertension or obesity, and could further help to focus on these specific mRNAs as antisense therapy targets.

Mitochondrial oxidative stress and dysfunction in myocardial remodelling

Recent experimental and clinical studies have suggested that oxidative stress is enhanced in myocardial remodelling and failure. The production of oxygen radicals is increased in the failing heart, whereas normal antioxidant enzyme activities are preserved. Mitochondrial electron transport is an enzymatic source of oxygen radical generation and can be a therapeutic target against oxidant-induced damage in the failing myocardium. Chronic increases in oxygen radical production in the mitochondria can lead to a catastrophic cycle of mitochondrial DNA (mtDNA) damage as well as functional decline, further oxygen radical generation, and cellular injury. Reactive oxygen species induce myocyte hypertrophy, apoptosis, and interstitial fibrosis by activating matrix metalloproteinases. These cellular events play an important role in the development and progression of maladaptive myocardial remodelling and failure. Therefore, oxidative stress and mtDNA damage are good therapeutic targets. Overexpression of the genes for peroxiredoxin-3 (Prx-3), a mitochondrial antioxidant, or mitochondrial transcription factor A (TFAM), could ameliorate the decline in mtDNA copy number in failing hearts. Consistent with alterations in mtDNA, the decrease in mitochondrial function was also prevented. Therefore, the activation of Prx-3 or TFAM gene expression could ameliorate the pathophysiological processes seen in mitochondrial dysfunction and myocardial remodelling. Inhibition of oxidative stress and mtDNA damage could be novel and effective treatment strategies for heart failure.

Cytochrome P-450 2C9 signaling does not contribute to age-associated vascular endothelial dysfunction in humans

Oxidative stress impairs endothelium-dependent dilation (EDD) with aging in healthy sedentary adults. Increased cytochrome P-450 2C9 (CYP 2C9) signaling can contribute to oxidative stress-mediated suppression of EDD, but its role in aging is unknown. We hypothesized that inhibition of CYP 2C9 signaling with sulfaphenazole would improve EDD in older, but not young, healthy sedentary adults. At baseline, increases in forearm blood flow (FBF; venous occlusion plethysmography) in response to brachial artery infusions of ACh (1, 2, 4, and 8 microg.100 ml forearm volume(-1).min(-1)), an endothelium-dependent dilator, were smaller in older [n = 14, 63 +/- 1 (SE) yr] than in young (n = 11, 23 +/- 2 yr) adults (P < 0.05), with a reduction in peak FBF of 32% (11.8 +/- 1.7 vs. 17.3 +/- 2.3 ml.100 ml tissue(-1).min(-1)). Infusion of sulfaphenazole at doses that block CYP 2C9 signaling in humans did not affect the FBF responses to ACh in the older (peak FBF = 13.0 +/- 4.3 ml.100 ml tissue(-1).min(-1), P = 0.41) or the young (peak FBF = 17.1 +/- 1.9 ml.100 ml tissue(-1).min(-1), P = 0.55) adults. Coadministration of the nitric oxide inhibitor l-NMMA and sulfaphenazole decreased the FBF response to ACh in young and older subjects (P < 0.05); the effect was smaller in the older subjects, but group differences in EDD remained (P < 0.05). Endothelium-independent dilation assessed with sodium nitroprusside was not different in the young and older subjects. These results provide the first support for the concept that increased CYP 2C9 signaling does not contribute to impairments in EDD with aging in healthy adults.

Endothelial progenitor cells, endothelial dysfunction, inflammation, and oxidative stress in hypertension

With a prevalence in excess of 20%, hypertension is a common finding among Western adult populations. Hypertension is directly implicated in the pathophysiology of various cardiovascular disease states and is a significant contributor to ill health, leading to an excess of both morbidity and mortality. The etiology of hypertension has been explored in depth, but the pathophysiology is multifactorial, complex, and poorly understood. Recent interest has been directed toward investigating the purported role of the endothelium, which acts as an important regulator of vascular homeostasis. Endothelial dysfunction is now recognized to occur in hypertension, regardless of whether the etiology is essential or secondary to endocrine or renal processes. Nitric oxide (NO) is a volatile gas produced by endothelial cells that acts to maintain vascular tone. Reduced bioavailability of NO appears to be the key process through which endothelial dysfunction is manifested in hypertension. The result is of an imbalance of counteracting mechanisms, normally designed to maintain vascular homeostasis, leading to vasoconstriction and impaired vascular function. It has become increasingly apparent that these changes may be effected in response to enhanced oxidative stress, possibly as a result of systemic and localized inflammatory responses. This article provides an overview of endothelial dysfunction in hypertension and focuses on the purported role of oxidative stress and inflammation as the catalysts for this process.

Effects of isoproterenol treatment for 7 days on inflammatory mediators in the rat aorta

The aim of the present study was to evaluate the effect of overstimulation of beta-adrenoceptors on vascular inflammatory mediators. Wistar rats were treated with the beta-adrenoceptor agonist isoproterenol (0.3 mg.kg(-1).day(-1) sc) or vehicle (control) for 7 days. At the end of treatment, the right carotid artery was catheterized for arterial and left ventricular (LV) hemodynamic evaluation. Isoproterenol treatment increased LV weight but did not change hemodynamic parameters. Aortic mRNA and protein expression were quantified by real-time RT-PCR and Western blot analysis, respectively. Isoproterenol enhanced aortic mRNA and protein expression of IL-1beta (124% and 125%) and IL-6 (231% and 40%) compared with controls but did not change TNF-alpha expression. The nuclear-to-cytoplasmatic protein expression ration of the NF-kappaB p65 subunit was increased by isoproterenol treatment (51%); in addition, it reduced the cytoplasmatic expression of IkappaB-alpha (52%) in aortas. An electrophoretic mobility shift assay was performed using the aorta, and increased NF-kappaB DNA binding (31%) was observed in isoproterenol-treated rats compared with controls (P < 0.05). Isoproterenol treatment increased phenylephrine-induced contraction in aortic rigs (P < 0.05), which was significantly reduced by superoxide dismutase (150 U/ml) and sodium salicylate (5 mM). Cotreatment with thalidomide (150 mg.kg(-1).day(-1) for 7 days) also reduced hyperreactivity to phenylephrine induced by isoproterenol. In conclusion, overstimulation of beta-adrenoceptors increased proinflammatory cytokines and upregulated NF-kappaB in the rat aorta. Moreover, local oxidative stress and the proinflammatory state seem to play key roles in the altered vascular reactivity of the rat aorta induced by chronic beta-adrenergic stimulation.

Characterization of the human alpha1 beta1 soluble guanylyl cyclase promoter: key role for NF-kappaB(p50) and CCAAT-binding factors in regulating expression of the nitric oxide receptor

Soluble guanylyl cyclase (sGC) is the principal receptor for NO and plays a ubiquitous role in regulating cellular function. This is exemplified in the cardiovascular system where sGC governs smooth muscle tone and growth, vascular permeability, leukocyte flux, and platelet aggregation. As a consequence, aberrant NO-sGC signaling has been linked to diseases including hypertension, atherosclerosis, and stroke. Despite these key (patho)physiological roles, little is known about the expressional regulation of sGC. To address this deficit, we have characterized the promoter activity of human α₁ and β₁ sGC genes in a cell type relevant to cardiovascular (patho)physiology, primary human aortic smooth muscle cells. Luciferase reporter constructs revealed that the 0.3- and 0.5-kb regions upstream of the transcription start sites were optimal for α₁ and β₁ sGC promoter activity, respectively. Deletion of consensus sites for c-Myb, GAGA, NFAT, NF-κB(p50), and CCAAT-binding factor(s) (CCAAT-BF) revealed that these are the principal transcription factors regulating basal sGC expression. In addition, under pro-inflammatory conditions, the effects of the strongest α₁ and β₁ sGC repressors were enhanced, and enzyme expression and activity were reduced; in particular, NF-κB(p50) is pivotal in regulating enzyme expression under such conditions. NO itself also elicited a cGMP-independent negative feedback effect on sGC promoter activity that is mediated, in part, via CCAAT-BF activity. In sum, these data provide a systematic characterization of the promoter activity of human sGC α₁ and β₁ subunits and identify key transcription factors that govern subunit expression under basal and pro-inflammatory (i.e. atherogenic) conditions and in the presence of ligand NO.

High-fat diet-induced obesity leads to increased NO sensitivity of rat coronary arterioles: role of soluble guanylate cyclase activation

The impact of obesity on nitric oxide (NO)-mediated coronary microvascular responses is poorly understood. Thus NO-mediated vasomotor responses were investigated in pressurized coronary arterioles ( approximately 100 microm) isolated from lean (on normal diet) and obese (fed with 60% of saturated fat) rats. We found that dilations to acetylcholine (ACh) were not significantly different in obese and lean rats (lean, 83 +/- 4%; and obese, 85 +/- 3% at 1 microM), yet the inhibition of NO synthesis with N(omega)-nitro-l-arginine methyl ester reduced ACh-induced dilations only in vessels of lean controls. The presence of the soluble guanylate cyclase (sGC) inhibitor oxadiazolo-quinoxaline (ODQ) elicited a similar reduction in ACh-induced dilations in the two groups of vessels (lean, 60 +/- 11%; and obese, 57 +/- 3%). Dilations to NO donors, sodium nitroprusside (SNP), and diethylenetriamine (DETA)-NONOate were enhanced in coronary arterioles of obese compared with lean control rats (lean, 63 +/- 6% and 51 +/- 5%; and obese, 78 +/- 5% and 70 +/- 5%, respectively, at 1 microM), whereas dilations to 8-bromo-cGMP were not different in the two groups. In the presence of ODQ, both SNP and DETA-NONOate-induced dilations were reduced to a similar level in lean and obese rats. Moreover, SNP-stimulated cGMP immunoreactivity in coronary arterioles and also cGMP levels in carotid arteries were enhanced in obese rats, whereas the protein expression of endothelial NOS and the sGC beta1-subunit were not different in the two groups. Collectively, these findings suggest that in coronary arterioles of obese rats, the increased activity of sGC leads to an enhanced sensitivity to NO, which may contribute to the maintenance of NO-mediated dilations and coronary perfusion in obesity.

Effects ofl-arginine andl-NAME on chronic partial bladder outlet obstruction in rabbit

Nitric oxide (NO) is synthesized from l-arginine by nitric oxide synthase (NOS). NOS can be inhibited by NG-nitro-l-arginine methyl ester (l-NAME) and stimulated by supplementing the diet with l-arginine. The aim of this study was to investigate the influence of NOS activity on the response of rabbits to chronic partial bladder outlet obstruction (PBOO). Surgical PBOOs (2 and 8 wk) were performed on male New Zealand White rabbits. Before obstruction, one-third of the animals were premedicated for 7 days with l-NAME and another third with l-arginine. The results are summarized as follows. First, bladder weight after 8-wk PBOO was significantly lower in animals treated with l-arginine compared with both untreated and rabbits treated with l-NAME. Second, contractile function decreased progressively with PBOO duration. However, after 8 wk of PBOO, the l-arginine group had significantly greater contractile function compared with the no-treatment group, and the l-NAME group had significantly lower contractile function compared with the no-treatment group. Third, at 8 wk following PBOO, the level of protein oxidation and nitration was lowest for the l-arginine group and highest in the l-NAME group. These studies clearly demonstrated that increasing blood flow by stimulating NOS significantly protected the bladder from PBOO dysfunctions, whereas inhibiting blood flow by l-NAME enhanced the dysfunctions mediated by PBOO.

Comparative effects of fatty acids on endothelial inflammatory gene expression

BACKGROUND

Endothelial dysfunction may be related to adverse effects of some dietary fatty acids (FAs). Although in vitro studies have failed to show consistent findings, this may reflect the diverse experimental protocols employed and the limited range of FAs and end points studied.

AIMS

To investigate the effect of dietary FA type (saturated, monounsaturated, n-6 and n-3 polyunsaturated fatty acids), concentration, incubation time and cell stimulation state, on a broad spectrum of endothelial inflammatory gene expression.

METHODS

Using human umbilical vein endothelial cells, with and without stimulation (+/-10 ng/ml TNFalpha), the effects of arachidonic (AA), docosahexaenoic (DHA), eicosapentaenoic (EPA), linoleic (LA), oleic (OA) and palmitic acids (PA) (10, 25 and 100 microM), on the expression of genes encoding a number of inflammatory proteins and transcription factors were assessed by quantitative real time RT-PCR.

RESULTS

Individual FAs differentially affect endothelial inflammatory gene expression in a gene-specific manner. EPA, LA and OA significantly up-regulated MCP-1 gene expression compared to AA (p = 0.001, 0.013, 0.008, respectively) and DHA (p < 0.0005, = 0.004, 0.002, respectively). Furthermore, cell stimulation state and FA incubation time significantly influenced reported FA effects on gene expression.

CONCLUSION

The comparative effects of saturated, monounsaturated, n-6 and n-3 polyunsaturated FAs on endothelial gene expression depend on the specific FA investigated, its length of incubation, cell stimulation state and the gene investigated. These findings may explain existing disparity in the literature.

Angiotensin II type 1 receptor blocker attenuates myocardial remodeling and preserves diastolic function in diabetic heart

Blockade of the renin-angiotensin system reduces cardiovascular morbidity and mortality in diabetic patients. Angiotensin II (Ang II) plays an important role in the structural and functional abnormalities of the diabetic heart. We investigated whether or not Ang II type 1 receptor blocker (ARB) could attenuate left ventricular (LV) remodeling in male mice with diabetes mellitus (DM) induced by the injection of streptozotocin (200 mg/kg, i.p.). Diabetic mice were treated with candesartan (1 mg/kg/day; DM+Candesartan, n=7) or vehicle (DM+Vehicle, n=7) for 8 weeks. Heart rate and aortic blood pressure were comparable between the groups. Normal systolic function was preserved in diabetic mice. In contrast, diastolic function was impaired in DM+Vehicle and was improved in DM+Candesartan, as assessed by the deceleration time of the peak velocity of transmitral diastolic flow (40.3+/-0.3 vs. 37.3+/-0.5 ms, p<0.01) and the time needed for relaxation of 50% maximal LV pressure to baseline value (tau; 10.6+/-0.7 vs. 8.7+/-0.6 ms, p<0.05) without significant changes in heart rate and aortic blood pressure. Improvement of LV diastolic function was accompanied by the attenuation of myocyte hypertrophy, interstitial fibrosis and apoptosis in association with the expression of connective tissue growth factor (CTGF) and myocardial oxidative stress. Moreover, candesartan directly inhibited Ang II-mediated induction of CTGF in cultured cardiac fibroblasts. ARB might be beneficial to prevent cardiac abnormalities in DM.

Mechanisms for the role of tetrahydrobiopterin in endothelial function and vascular disease

NO produced by eNOS (endothelial nitric oxide synthase) is a key mediator of vascular homoeostasis. NO bioavailability is reduced early in vascular disease states, such as hypercholesterolaemia, diabetes and hypertension, and throughout the progression of atherosclerosis. This is a result of both reduced NO synthesis and increased NO consumption by reactive oxygen species. eNOS enzymatic activity appears to be determined by the availability of its cofactor BH4 (tetrahydrobiopterin). When BH4 levels are adequate, eNOS produces NO; when BH4 levels are limiting, eNOS becomes enzymatically uncoupled and generates superoxide, contributing to vascular oxidative stress and endothelial dysfunction. BH4 bioavailability is determined by a balance of enzymatic de novo synthesis and recycling, versus oxidative degradation in dysfunctional endothelium. Augmenting vascular BH4 levels by pharmacological supplementation, by enhancing the rate of de novo biosynthesis or by measures to reduce BH4 oxidation have been shown in experimental studies to enhance NO bioavailability. Thus BH4 represents a potential therapeutic target for preserving eNOS function in vascular disease.

Inducible nitric oxide synthase activity does not contribute to the maintenance of peripheral vascular tone in patients with heart failure

Enhanced iNOS (inducible nitric oxide synthase) activity may contribute to vascular dysfunction in patients with heart failure. In the present study, we aimed to determine whether iNOS activity contributes to the maintenance of vascular tone in patients with symptomatic heart failure with the use of the highly selective iNOS inhibitor 1400W {N-[3-(aminomethyl)benzyl] acetamidine}. Bilateral forearm blood flow was measured using venous occlusion plethysmography in 12 patients with New York Heart Association class II-IV heart failure and eight matched healthy control subjects during intra-brachial infusion of 1400W (0.1-1 micromol/min), L-NMMA (N(G)-monomethyl-L-arginine; a non-selective NOS inhibitor; 2-8 micromol/min) and noradrenaline (control vasoconstrictor; 60-480 pmol/min). In both patients and controls, intra-brachial infusion of L-NMMA and noradrenaline caused a dose-dependent reduction in infused forearm blood flow (P<0.05 for both): peak reduction of 32+/-6% and 37+/-4% during L-NMMA and 52+/-6% and 49+/-5% during noradrenaline respectively (P values were not significant when patients were compared with controls). In contrast, 1400W had no effect on blood flow at 1 micromol/min [-3+/-4% in patients (95% confidence intervals, -11 to 5%) and 3+/-8% in controls; P value was not significant]. In conclusion, we have demonstrated that intrabrachial selective iNOS inhibition does not influence forearm blood flow in patients with heart failure. We conclude that iNOS activity does not contribute to peripheral vascular tone in patients with symptomatic heart failure.

Low-dose simvastatin improves survival and ventricular function via eNOS in congestive heart failure

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors increase endothelial nitric oxide synthase (eNOS) activity by multiple mechanisms. We previously reported that genetic overexpression of eNOS improves survival and cardiac function in congestive heart failure (CHF). In the present study, we tested the hypothesis that low-dose treatment with an 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor exerts beneficial effects on survival and/or cardiac function in a murine model of CHF. Mice were subjected to permanent ligation of the left coronary artery and randomized to receive either saline vehicle or simvastatin (0.25 mg/kg) 2 h after myocardial infarction and daily (0.25 mg/kg) for 7 days, followed by 21 days of administration every other day for a total duration of 28 days. Myocardial infarct size was not reduced by simvastatin therapy ( P = not significant between groups). Simvastatin treatment did significantly ( P < 0.05) improve survival (45%) compared with vehicle treatment (25%). In addition, simvastatin treatment significantly improved ( P < 0.01) left ventricular function and significantly ( P < 0.01) abrogated cardiac hypertrophy and pulmonary edema compared with vehicle treatment. The protective effects of simvastatin were abrogated by delayed initiation of treatment or genetic ablation of eNOS. In conclusion, low-dose simvastatin therapy significantly improves survival and cardiac function and reduces both cardiac hypertrophy and pulmonary edema via an eNOS-dependent mechanism in a murine model of CHF.

Functional alterations in NO, PGI2and EDHF pathways in the aortic endothelium after myocardial infarction in rats

BACKGROUND

Previous work on endothelial dysfunction in post-MI heart failure has shown conflicting results.

AIM

To analyze gender related alterations in NO-, PGI(2)- and EDHF-dependent endothelial function in the thoracic aorta 7 and 42 days after myocardial infarction (MI).

METHODS AND RESULTS

MI was induced by coronary artery ligation in female and male Sprague-Dawley rats. There was no gender related difference in infarct-size or in the impairment of fractional shortening of the left ventricle 42 days after coronary ligation. Neither acetylcholine-induced (Ach) vasodilation nor basal PGI(2) production in the aorta was modified by coronary ligation. Interestingly, 7 days after MI, basal NO production was impaired and the EDHF component of Ach-induced vasodilation was up-regulated, in both male and female rats. However, 42 days post-MI, basal NO was only impaired in male rats, while EDHF was only up-regulated in female rats.

CONCLUSION

MI induced impairment of functional activity of basal NO production and adaptive up-regulation of the EDHF component of Ach-induced relaxation. The above alterations in endothelial function in the aorta were gender-specific at 42 days but not 7 days after MI. Some of the previously reported discrepancies in the development of endothelial dysfunction in the post-MI period may be gender related differences.

Muscle microvascular oxygenation in chronic heart failure: role of nitric oxide availability

AIM

To test the hypothesis that diminished vascular nitric oxide availability might explain the inability of individuals with chronic heart failure (CHF) to maintain the microvascular PO(2)'s (PO(2mv) proportional, variant O(2) delivery-to-uptake ratio) seen in healthy animals.

METHODS

We superfused sodium nitroprusside (SNP; 300 microm), Krebs-Henseleit (control, CON) and L-nitro arginine methyl ester (L-NAME; 1.5 mM) onto the spinotrapezius muscle and measured PO(2mv) by phosphorescence quenching in female Sprague-Dawley rats (n = 26) at rest and during twitch contractions (1 Hz). Seven rats served as controls (Sham) while CHF was induced by myocardial infarction. CHF rats were grouped as moderate (MOD; n = 15) and severe CHF (SEV; n = 4) according to morphological data and baseline PO(2mv).

RESULTS

In contrast to Sham and MOD, L-NAME did not affect the PO(2mv) response (dynamics and steady-state) of SEV when compared with CON. SNP restored the PO(2mv) profile of SEV to that seen in Sham animals during CON. Specifically, the effect of L-NAME expressed as Delta(L-NAME - CON) were: Baseline PO(2mv) [in mmHg, DeltaSham = -7.0 +/- 1.6 (P < 0.05); DeltaSEV =-1.2 +/- 2.1], end-contractions PO(2mv) [in mmHg, DeltaSham = -5.0 +/- 1.0 (P < 0.05); DeltaSEV = -2.5 +/- 0.5] and time constant of PO(2mv) decrease [in s, DeltaSham = -6.5 +/- 3.0 (P < 0.05); DeltaSEV = -3.2 +/- 1.8].

CONCLUSION

These data provide the first direct evidence that the pathological profiles of PO(2mv) associated with severe CHF can be explained, in part, by a diminished vascular NO availability.

Mitochondrial oxidative stress, DNA damage, and heart failure

Recent experimental and clinical studies have suggested that oxidative stress is enhanced in heart failure. The production of oxygen radicals is increased in the failing heart, whereas antioxidant enzyme activities are preserved as normal. Mitochondrial electron transport is an enzymatic source of oxygen radical generation and also a target of oxidant-induced damage. Chronic increases in oxygen radical production in the mitochondria can lead to a catastrophic cycle of mitochondrial DNA (mtDNA) damage as well as functional decline, further oxygen radical generation, and cellular injury. Reactive oxygen species induce myocyte hypertrophy, apoptosis, and interstitial fibrosis by activating matrix metalloproteinases. These cellular events play an important role in the development and progression of maladaptive cardiac remodeling and failure. Therefore, mitochondrial oxidative stress and mtDNA damage are good therapeutic targets. Overexpression of mitochondrial transcription factor A (TFAM) could ameliorate the decline in mtDNA copy number and preserve it at a normal level in failing hearts. Consistent with alterations in mtDNA, the decrease in oxidative capacities was also prevented. Therefore, the activation of TFAM expression could ameliorate the pathophysiologic processes seen in myocardial failure. Inhibition of mitochondrial oxidative stress and mtDNA damage could be novel and potentially very effective treatment strategies for heart failure.

Vascular effects of a common gene variant of extracellular superoxide dismutase in heart failure

A common gene variant of human extracellular superoxide dismutase (ecSOD), in ∼5% of humans, is associated with increased risk of ischemic heart disease. The purpose of this study was to examine vascular effects of ecSOD with effects of the ecSOD variant (ecSODR213G) in rats with heart failure. Seven weeks after coronary artery ligation, we studied rats with heart failure and sham-operated rats. Adenoviral vectors expressing human ecSOD, ecSODR213G, or a control virus were injected intravenously. In the aorta from rats with heart failure, responses to acetylcholine (69 ± 4% relaxation, means ± SE) and basal levels of nitric oxide (NO) (vasoconstrictor responses to a NO synthase inhibitor) were greatly impaired, and levels of superoxide and peroxynitrite were increased. Gene transfer of ecSOD restored responses to acetylcholine (92 ± 2% relaxation) and basal levels of NO to normal and reduced levels of superoxide [from 2.3 ± 0.2 to 0.9 ± 0.2 relative light units per second per millimeter squared (RLU·s−1·mm−2)] and peroxynitrite (from 2.4 ± 0.2 to 0.9 ± 0.1 RLU·s−1·mm−2) in the aorta from rats with heart failure. Gene transfer of ecSODR213G produced little or no improvement. Responses to nitroprusside were not different among the groups. Expression of endogenous mRNA for SODs (CuZnSOD, MnSOD, and ecSOD) and endothelial NOS in the aorta was not different among the groups. In contrast to ecSOD, gene transfer of ecSODR213G in rats with heart failure has minimal beneficial effect on oxidative stress, endothelial function, or basal bioavailability of NO. We speculate that greatly diminished efficacy of ecSODR213G in protection against oxidative stress and endothelial dysfunction may contribute to increased risk of cardiovascular disease in humans with ecSODR213G.

Isosorbide dinitrate and hydralazine hydrochloride: a review of efficacy and safety

In the USA alone, there are over 5,000,000 people diagnosed with heart failure. A disproportionate number of African-Americans are affected by this disease, with increased morbidity and mortality, yet they are tremendously under-represented in clinical trials. Several drugs have been approved for use in heart failure based on clinical trials, with percentages of African-American subjects as low as 1%. In the African-American Heart Failure Trial the use of BiDil, a drug combining isosorbide dinitrate and hydralazine hydrochloride, demonstrated a 43% decrease in overall mortality and a 39% decrease in first hospitalization. The combination consists of 20 mg of isosorbide and 37.5 mg hydralazine hydrochloride in a fixed dose that functions as a nitric oxide enhancer and an antioxidant, and helps to prevent tolerance to the prolonged use of nitrate. The hemodynamic effects of the combination drug in heart failure includes increased cardiac output. The US Food and Drug Administration approved the combination of isosorbide dinitrate based on the African-American Heart Failure Trial. Further clinical trials utilizing isosorbide dinitrate will hopefully determine the benefit of this combination in a larger population, including caucasians and other racial/ethnic groups.

Acetylcholine stimulated dilatation and stretch induced myogenic constriction in mesenteric artery of rats with chronic heart failure

Rats with chronic heart failure (CHF) develop increased myogenic constriction in mesenteric resistance arteries. Here we investigated increased myogenic constriction in relation to alterations in EDHF- and NO-mediated dilatation in CHF-rats. Male Spraque-Dawley rats were subjected to myocardial-infarction or sham-surgery. At 9-10 weeks after surgery, isolated mesenteric artery ring preparations were studied in a wire-myograph. Stretch-induced myogenic constriction was obtained by stepwise increase of the internal circumference diameter (0.5-1.2 L100). Cyclooxygenase- and eNOS-inhibitors were employed to study NO- and EDHF-mediated dilatation in response to acetylcholine. Rats with CHF (n=8), but not sham-rats (n=6), developed significant myogenic constriction. In addition, the contribution of endothelial dilator mediators was significantly altered in CHF-rats, with increased dependency on NO and decreased EDHF-mediated dilatation. Moreover, EDHF-mediated dilatation was inversely correlated with myogenic constriction in individual CHF-rats (r=-0.74, p=0.04). These data demonstrate increased myogenic constriction in mesenteric arteries of rats with CHF post-MI to be correlated to decreased EDHF-mediated dilatation. These findings extend the previous observation that myogenic constriction antagonizes EDHF-mediated dilatation in rat coronary artery under normal conditions, and suggests this relationship also to become functional in mesenteric arteries under pathophysiological conditions of CHF.

Dietary antioxidants in preventing atherogenesis

Several naturally occurring constituents have received considerable attention because of their potential antioxidant activity. Consuming a diet rich in natural antioxidants has been associated with prevention from and/or treatment of atherosclerosis. Bioactive components of food, which are of special interest, include the Vitamins E and C, polyphenols, carotenoids-mainly lycopene and beta-carotene, and coenzyme Q10, featured by antioxidant properties. Antioxidant therapy is supposed to be effective in the early stages of atherosclerosis by preventing LDL oxidation and the oxidative lesion of endothelium. This review focuses on the effect of dietary antioxidants pertained to LDL oxidation and to the vascular endothelial dysfunction. Now that the human genome has been completely sequenced, genetic factors involved in oxidation may open new horizons to identify persons at risk for cardiovascular disease, allowing effective dietary intervention strategies to recover normal homeostasis and to prevent diet-related implications. On this basis, current studies on the action of selected antioxidant nutraceuticals on the activity of transcription factors, such as final targets in the signal transduction cascade and gene regulation, may emerge into new treatment concepts.

Transcriptional and posttranscriptional regulation of endothelial nitric oxide synthase expression

The ability of the endothelium to produce nitric oxide is essential to maintenance of vascular homeostasis; disturbance of this ability is a major contributor to the pathogenesis of vascular disease. In vivo studies have demonstrated that expression of endothelial nitric oxide synthase (eNOS) is vital to endothelial function and have led to the understanding that eNOS expression is subject to modest but significant degrees of regulation. Subsequently, numerous physiological and pathophysiological stimuli have been identified that modulate eNOS expression via mechanisms that alter steady-state eNOS mRNA levels. These mechanisms involve changes in the rate of eNOS gene transcription (transcriptional regulation) and alteration of eNOS mRNA processing and stability (posttranscriptional regulation). In cultured endothelial cells, shear stress, transforming growth factor-beta1, lysophosphatidylcholine, cell growth, oxidized linoleic acid, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, and hydrogen peroxide have been shown to increase eNOS expression. In contrast, tumor necrosis factor-alpha, hypoxia, lipopolysaccaride, thrombin, and oxidized LDL can decrease eNOS mRNA levels. For many of these stimuli, both transcriptional and posttranscriptional mechanisms contribute to regulation of eNOS expression. Recent studies have begun to further define signaling pathways responsible for changes in eNOS expression and have characterized cis- and trans-acting regulatory elements. In addition, a role has been identified for epigenetic control of eNOS mRNA levels. This review will discuss transcriptional and posttranscriptional regulation of eNOS with emphasis on the molecular mechanisms that have been identified for these processes.

Changes in vascular reactivity following administration of isoproterenol for 1 week: a role for endothelial modulation

1. The aim of this study was to assess the effects of treatment with isoproterenol (ISO, 0.3 mg kg-1 day-1, s.c.) for 7 days on the vascular reactivity of rat-isolated aortic rings. Additionally, potential mechanisms underlying the changes that involved the endothelial modulation of contractility were investigated. 2. Treatment with ISO induced cardiac hypertrophy without changes in haemodynamic parameters. Aortic rings from ISO-treated rats showed an increase in the contraction response to phenylephrine (PHE) and serotonin, but did not change relaxations produced by acetylcholine or isoproterenol. Removal of the endothelium increased the responses to PHE in both groups. However, this procedure was less effective in ISO-treated as compared with control rats. Endothelial cell removal abolished the increase in the response to PHE in ISO-treated rats. The presence of Nomega-nitro-L-arginine methyl ester shifted the concentration-response curve to PHE to the left in both groups of rats. However, this effect was more pronounced in the ISO group. In addition, aminoguanidine (50 microM) potentiated the actions of PHE only in the ISO group. ISO treatment increased nitric oxide synthase (NOS) activity and neuronal NOS and endothelial NOS protein expression in the aorta. 3. Neither losartan (10 microM) nor indomethacin (10 microM) abolished the effects of ISO on the actions of PHE. Superoxide dismutase (SOD, 150 U ml-1) and L-arginine (5 mM), but neither catalase (300 U ml-1) nor apocynin (100 microM), blocked the effect of ISO treatment. In addition, we observed an increase in superoxide anion levels as measured by ethidium bromide fluorescence and of copper and zinc superoxide dismutase protein expression in ISO-treated rats. 4. In conclusion, our data suggest that ISO treatment alters the endothelial cell-mediated modulation of the contraction to PHE in rat aorta. The increased maximal response of PHE seems to be due to an increase in superoxide anion generation, which inactivates some of the basal NO produced and counteracts NO-mediated negative modulation even in the presence of high NO production and antioxidant defence.

Oxidative stress at the vascular wall. Mechanistic and pharmacological aspects

During the process of energy production in aerobic respiration, vascular cells produce reactive oxygen species (ROS). A growing body of evidence indicates that oxidative stress refers to a condition in which cells are subjected to excessive levels of ROS. Overall vascular function is dependent upon a fine balance of oxidant and antioxidant mechanisms, which determine endothelial functions. Considerable experimental and clinical data indicate that intracellular oxidant milieu is also involved in several redox-sensitive cellular signaling pathways such as ion transport systems, protein phosphorylation, and gene expression and thus also plays important roles as modulator of vascular cell functions such as cell growth, apoptosis, migration, angiogenesis and cell adhesion. Overproduction of ROS under pathophysiologic conditions is integral in the development of cardiovascular diseases. This fact has raised an intensive search of new pharmacological approaches to improve vascular hemostasis and particularly those intended to decrease oxidative stress or augment the antioxidant defense mechanisms.

NADPH oxidases in cardiovascular health and disease

Increased oxidative stress plays an important role in the pathophysiology of cardiovascular diseases such as hypertension, atherosclerosis, diabetes, cardiac hypertrophy, heart failure, and ischemia-reperfusion. Although several sources of reactive oxygen species (ROS) may be involved, a family of NADPH oxidases appears to be especially important for redox signaling and may be amenable to specific therapeutic targeting. These include the prototypic Nox2 isoform-based NADPH oxidase, which was first characterized in neutrophils, as well as other NADPH oxidases such as Nox1 and Nox4. These Nox isoforms are expressed in a cell- and tissue-specific fashion, are subject to independent activation and regulation, and may subserve distinct functions. This article reviews the potential roles of NADPH oxidases in both cardiovascular physiological processes (such as the regulation of vascular tone and oxygen sensing) and pathophysiological processes such as endothelial dysfunction, inflammation, hypertrophy, apoptosis, migration, angiogenesis, and vascular and cardiac remodeling. The complexity of regulation of NADPH oxidases in these conditions may provide the possibility of targeted therapeutic manipulation in a cell-, tissue- and/or pathway-specific manner at appropriate points in the disease process.

Impact of endothelial dysfunction on left ventricular remodeling after successful primary coronary angioplasty for acute myocardial infarction--analysis by quantitative ECG-gated SPECT--

BACKGROUND

We hypothesized that endothelial cell integrity in the risk area would influence left ventricular remodeling after acute myocardial infarction.

PATIENTS AND METHODS

Twenty patients (61 +/- 8 y.o.) with acute myocardial infarction underwent 99mTc-tetrofosmin imaging in the subacute phase and three months after successful primary angioplasty due to myocardial infarction. All patients were administered angiotensin-converting enzyme inhibitor after revascularization. Cardiac scintigraphies with quantitative gated SPECT were performed at the sub-acute stage and again 3 months after revascularization to evaluate left ventricular (LV) remodeling. The left ventricular ejection fraction (EF) and end-systolic and end-diastolic volume (ESV, EDV) were determined using a quantitative gated SPECT (QGS) program. Three months after myocardial infarction, all patients underwent cardiac catheterization examination with coronary endothelial function testing. Bradykinin (BK) (0.2, 0.6, 2.0 microg/min) was administered via the left coronary artery in a stepwise manner. Coronary blood flow was evaluated by Doppler flow velocity measurement. Patients were divided into two groups by BK-response: a preserved endothelial function group (n = 10) and endothelial dysfunction group (n = 10).

RESULTS

At baseline, both global function and LV systolic and diastolic volumes were similar in both groups. However, LV ejection fraction was significantly improved in the preserved-endothelial function group, compared with that in the endothelial dysfunction group (42 +/- 10% to 48 +/- 9%, versus 41 +/- 4% to 42 +/- 13%, p < 0.05). LV volumes progressively increased in the endothelial dysfunction group compared to the preserved-endothelial, function group (123 +/- 45 ml to 128 +/- 43 ml, versus 111 +/- 47 ml to 109 +/- 49 ml, p < 0.05).

CONCLUSION

In re-perfused acute myocardial infarction, endothelial function within the risk area plays an important role with left ventricular remodeling after myocardial infarction.

Progressive left ventricular hypertrophy after withdrawal of long-term ACE inhibition following experimental myocardial infarction

BACKGROUND

Although discontinuation of chronic ACE inhibitor (ACEi) therapy after myocardial infarction (MI) is common in clinical practice, some clinical studies reported an increased incidence of ischemia-related events after withdrawal. To further address this issue, we assessed hemodynamic, neurohormonal and vascular consequences of withdrawing long-term ACEi treatment after experimental MI.

METHODS

Rats were subjected to coronary ligation to induce MI, and received quinapril (15 mg/kg/day) from 2 weeks to 14 months post-MI. Subsequently, surviving rats were randomized to sacrifice at 0, 4, and 6 weeks after ACEi withdrawal. Rats were studied for signs of heart failure, hemodynamics and cardiac function, neurohormones, and vascular edothelial function.

RESULTS

After discontinuation of ACEi treatment, plasma aldosterone levels increased between 0-4 weeks without further increment thereafter, suggesting persistent RAAS activation. Acetylcholine-induced aortic relaxation was impaired at 4 and 6 weeks, indicating rapid and sustained development of endothelial vasodilator dysfunction after withdrawal. Moreover, 24% of the rats developed heart failure signs (edema, dyspnea), and 3 rats died, all within 4 weeks after withdrawal. Significantly increased N-ANP levels and lung weights at 4, but not at 6 weeks suggest a transient volume overload. Finally, LV/body weight ratios significantly increased between 0-4 as well as 4-6 weeks, indicating progressive LV hypertrophy.

CONCLUSIONS

The observed alterations after withdrawing long-term post-MI quinapril treatment in the present study may account for an increased risk for ischemic events. Thus, our findings highlight the potentially harmful effects associated with abrupt discontinuation of long-term post-MI ACE inhibition, and imply careful clinical consideration in this matter.

Involvement of endothelium and endothelin-1 in lead-induced smooth muscle cell dysfunction in rats

Lead exposure induces dysfunction of the cyclic guanosine monophosphate-dependent vasodilator system through downregulation of soluble guanylate cyclase (sGC) expression. The endothelium not only releases vasodilators but also vasoconstrictors such as endothelin-1 (ET-1). Our aim was to explore the role of the vascular endothelium and ET-1 as possible mediators of lead-induced downregulation of sGC. Isolated aortic segments from Wistar Kyoto rats were incubated in the presence or absence of lead (1 parts per million) for 24 h. Endothelium was mechanically removed in some of the aorta segments. As reported previously, lead exposure induced downregulation of sGC protein expression in the intact aortic segments. However, lead exposure failed to significantly modify sGC-beta1 subunit expression in the endothelium-denuded aortic segments. Incubation with a selective ETA-type receptor inhibitor, BQ-123 (10(-6) mol/l), restored sGC protein expression in lead-exposed intact aortic segments. As it has also been previously observed, incubation in lead-containing medium resulted in the upregulation of cyclooxygenase-2 (COX-2) in the intact aortic segments. Denudation of endothelium partially abrogated this effect of lead. Incubation with BQ-123 prevented the lead-induced upregulation COX-2 in the intact aortic segments. However, neither ET-1 content nor ETA-type receptor expression were modified by lead exposure of the aortic segments. As conclusion, the endothelium through the activation of ETA-type receptors mediates the downregulation of sGC expression by lead in the vascular wall.

Role of oxidative stress in cardiac remodelling after myocardial infarction

Recovery from myocardial infarction is associated with a series of alterations in heart structure and function, collectively known as cardiac remodelling, which play a major role in the subsequent development of heart failure. Early remodelling involves infarct scar formation in the ischaemic zone whereas subsequent ventricular remodelling affects mainly the viable non-infarcted myocardium with especially profound alterations in the extracellular matrix. There is growing evidence for a role of oxidative stress and redox signalling in the processes underlying cardiac remodelling. Reactive oxygen species are a group of highly reactive molecules which have the potential to modulate several biological processes as well as cause tissue damage and dysfunction. Their effects can be beneficial or deleterious, depending on the concentrations produced, the site of production, and the overall redox status of the cell. Reactive oxygen species can be generated by all cardiovascular cell types. Under pathophysiological conditions, major enzymatic sources appear to be mitochondria, xanthine oxidase and the non-phagocytic NADPH oxidases. In this review, we outline the mechanisms underlying the progression of early and late cardiac remodelling with particular focus on the role of oxidative stress and the potential sources of reactive oxygen species which may be involved.

Exercise training in normobaric hypoxia in endurance runners. II. Improvement of mitochondrial properties in skeletal muscle

This study investigates whether adaptations of mitochondrial function accompany the improvement of endurance performance capacity observed in well-trained athletes after an intermittent hypoxic training program. Fifteen endurance-trained athletes performed two weekly training sessions on treadmill at the velocity associated with the second ventilatory threshold (VT2) with inspired O2 fraction = 14.5% [hypoxic group (Hyp), n = 8] or with inspired O2 fraction = 21% [normoxic group (Nor), n = 7], integrated into their usual training, for 6 wk. Before and after training, oxygen uptake (VO2) and speed at VT2, maximal VO2 (VO2 max), and time to exhaustion at velocity of VO2 max (minimal speed associated with VO2 max) were measured, and muscle biopsies of vastus lateralis were harvested. Muscle oxidative capacities and sensitivity of mitochondrial respiration to ADP (Km) were evaluated on permeabilized muscle fibers. Time to exhaustion, VO2 at VT2, and VO2 max were significantly improved in Hyp (+42, +8, and +5%, respectively) but not in Nor. No increase in muscle oxidative capacity was obtained with either training protocol. However, mitochondrial regulation shifted to a more oxidative profile in Hyp only as shown by the increased Km for ADP (Nor: before 476 +/- 63, after 524 +/- 62 microM, not significant; Hyp: before 441 +/- 59, after 694 +/- 51 microM, P < 0.05). Thus including hypoxia sessions into the usual training of athletes qualitatively ameliorates mitochondrial function by increasing the respiratory control by creatine, providing a tighter integration between ATP demand and supply.

Recent advances in the understanding of the role of nitric oxide in cardiovascular homeostasis

Nitric oxide synthases (NOS) are the enzymes responsible for nitric oxide (NO) generation. To date, 3 distinct NOS isoforms have been identified: neuronal NOS (NOS1), inducible NOS (NOS2), and endothelial NOS (NOS3). Biochemically, NOS consists of a flavin-containing reductase domain, a heme-containing oxygenase domain, and regulatory sites. NOS catalyse an overall 5-electron oxidation of one Nomega-atom of the guanidino group of L-arginine to form NO and L-citrulline. NO exerts a plethora of biological effects in the cardiovascular system. The basal formation of NO in mitochondria by a mitochondrial NOS seems to be one of the main regulators of cellular respiration, mitochondrial transmembrane potential, and transmembrane proton gradient. This review focuses on recent advances in the understanding of the role of enzyme and enzyme-independent NO formation, regulation of NO bioactivity, new aspects of NO on cardiac function and morphology, and the clinical impact and perspectives of these recent advances in our knowledge on NO-related pathways.

Dimethylarginine dimethylaminohydrolase and endothelial dysfunction in failing hearts

Congestive heart failure (CHF) is associated with impaired endothelium-dependent nitric oxide (NO)-mediated vasodilation (endothelial dysfunction). We hypothesized that coronary endothelial dysfunction in CHF may be due in part to decreased dimethylarginine dimethylaminohydrolase (DDAH), the enzyme that degrades endogenous inhibitors of NO synthase (NOS), including asymmetric dimethylarginine. Coronary blood flow and the endothelium-dependent vasodilator response to acetylcholine were studied in dogs in which CHF was produced by rapid ventricular pacing for 4 wk. Coronary flow and myocardial O2consumption at rest and during treadmill exercise were decreased after development of CHF, and the vasodilator response to intracoronary acetylcholine (75 μg/min) was decreased by 39 ± 5%. DDAH activity and DDAH isoform 2 (DDAH-2) protein content were decreased by 53 ± 13% and 58 ± 14%, respectively, in hearts with CHF, whereas endothelial NOS and DDAH isoform 1 (DDAH-1) were increased. Caveolin-1 and protein arginine N-methyltransferase 1, the enzyme that produces asymmetric dimethylarginine, were unchanged. Immunohistochemical staining showed DDAH-1 strongly expressed in coronary endothelium and smooth muscle and in the sarcolemma of cardiac myocytes. In cultured human endothelial cells, DDAH-1 was uniformly distributed in the cytosol and nucleus, whereas DDAH-2 was found only in the cytosol. Decreased DDAH activity and DDAH-2 protein expression may cause accumulation of endogenous inhibitors of endothelial NOS, thereby contributing to endothelial dysfunction in the failing heart.

Moderate zinc deficiency influences arterial blood pressure and vascular nitric oxide pathway in growing rats

There is an increasing interest in the involvement of trace elements such as zinc in the pathogenesis of cardiovascular diseases. This study was designed to examine whether moderate zinc deficiency during growth influences blood pressure (BP) and vascular nitric oxide (NO) pathway. Three-week-old weaned male Wistar rats were randomly divided into two dietary groups and fed either a moderately zinc-deficient diet (zinc content 9 mg/kg; n = 12) or a control diet (zinc content 30 mg/kg; n = 12) for 60 d. The following were measured: systolic BP, nitrates and nitrites urinary excretion, urinary chemiluminescence intensity, NADPH-diaphorase activity in the thoracic aorta and intestinal arterioles, and NO synthase (NOS) catalytic activity using L-[U14C]-arginine as substrate in the thoracic aorta. Zinc deficiency during growth induced an increase in BP from day 30 of the experimental period, leading to hypertension on day 60. Animals that were fed the zinc-deficient diet had lower urinary excretion levels of nitrates and nitrites and higher intensity of spontaneous luminescence on day 60. At the end of the experiment, zinc-deficient rats showed decreased NADPH diaphorase activity in endothelium and smooth muscle of the thoracic aorta and intestinal arterioles and decreased activity of NOS in thoracic aortic tissue. An imbalance in zinc bioavailability during postnatal and growing periods may be may be a risk factor in development of cardiovascular alterations in adult life. The mechanisms involved may include an impaired vascular NO system as a result of decreased NOS activity and higher systemic oxidative stress.

Stimulation of soluble guanylate cyclase slows progression in anti-thy1-induced chronic glomerulosclerosis

BACKGROUND

A critical role of soluble guanylate cyclase and nitric oxide-dependent cyclic 3',5'-guanosine monophosphate (cGMP) production for glomerular matrix expansion has recently been documented in a rat model of acute anti-thy1 glomerulonephritis. The present study analyzes the renal activity of the nitric oxide-cGMP signaling cascade in and the effect of the specific soluble guanylate cyclase stimulator Bay 41-2272 on a progressive model of anti-thy1-induced chronic glomerulosclerosis.

METHODS

Anti-thy1 glomerulosclerosis was induced by injection of anti-thy1 antibody into uninephrectomized rats. One week after disease induction, animals were randomly assigned to chronic glomerulosclerosis, chronic glomerulosclerosis plus Bay 41-2272 (10 mg/kg body weight/day) or chronic glomerulosclerosis plus hydralazine (15 mg/kg body weight/day). In week 16, analysis included effects on systolic blood pressure, proteinuria, kidney function, glomerular and tubulointerstitial matrix protein accumulation, expression of transforming growth factor-beta1 (TGF-beta1), fibronectin and plasminogen activator inhibitor type 1 (PAI-1), macrophage infiltration, cell proliferation, basal and nitric oxide-stimulated cGMP production as well as tubulointerstitial mRNA expression of alpha 1 and beta 1 soluble guanylate cyclase.

RESULTS

The moderately elevated systolic blood pressure seen in the chronic glomerulosclerosis group was comparably decreased by both treatments. Compared to normal controls, soluble guanylate cyclase mRNA expression and nitric oxide-stimulated cGMP production were up-regulated in the tubulointerstitium of the untreated chronic glomerulosclerosis animals, while its activity was decreased in glomeruli. Bay 41-2272 treatment enhanced glomerular and tubulointerstitial nitric oxide-cGMP signaling significantly. This went along with markedly reduced glomerular and tubulointerstitial macrophage infiltration, number of proliferating cells, matrix expression and accumulation, as well as improved kidney function. In contrast, hydralazine therapy did not significantly affect renal nitric oxide-cGMP signaling, macrophage number, cell proliferation, matrix protein expression and accumulation.

CONCLUSION

Glomerular and tubulointerstitial soluble guanylate cyclase activity are discordantly altered in anti-thy1-induced chronic glomerulosclerosis. Stimulation of soluble guanylate cyclase signaling by Bay 41-2272 limits the progressive course of this model toward tubulointerstitial fibrosis and impaired renal function at least in part in a blood pressure-independent manner. The results suggest that soluble guanylate cyclase activation counteracts fibrosis and progression in chronic renal disease.

Myocardial infarction increases reactivity to phenylephrine in isolated aortic rings of ovariectomized rats

Clinical studies demonstrated that the incidence of cardiovascular disease is low in premenopausal women, rises in postmenopausal women, and is reduced to premenopausal levels in postmenopausal women who receive estrogen therapy. The interaction between gender and myocardial infarction indicates that the survival advantage of women is modified by the occurrence of myocardial infarction. Therefore, the effect of myocardial infarction on mortality is greater in women than men. The aim of our study was to investigate the influence of the ovariectomy on the reactivity to phenylephrine in aortic rings of female rats post-myocardial infarction. Animals were divided in four groups: Control (Cont), Ovariectomized (Ovx), Infarcted (Inf) and Ovariectomized and Infarcted (Ovx-Inf). Aortic rings were studied 60 days after ovariectomy and infarction surgery. The infarct area was similar among groups. The maximal response to phenylephrine was increased in the Ovx-Inf group compared to all the other groups (Cont = 2.411+/-0.131 (N = 11); Ovx = 2.863+/-0.121(N = 15); Inf = 2.794+/-0.102 (N = 13); Ovx-Inf = 3.40+/-0.201* (N = 12) g; *P < 0.05). In the absence of endothelium and L-NAME perfusion, the maximal response to phenylephrine was similarly increased in all groups. Relaxation to acetylcholine was also similar. The indirect evaluation of NO bioavailability analyzed by the area under the curve demonstrated a reduction on NO on the Ovx-Inf group that could contributes to increased response to phenylephrine. In conclusion our results showed that ovariectomy associated to a myocardial infarction leads to an increment of aorta reactivity to phenylephrine associated to a reduction of basal NO bioavailability in spite of a normal endothelium-dependent relaxation induced by acetylcholine.

NADPH oxidase and endothelial cell function

Intracellular ROS (reactive oxygen species) such as superoxide and H2O2 have been increasingly appreciated to have a role in endothelial pathophysiology. Of the several sources within the vasculature, a family of multi-subunit NADPH oxidases appears to be a predominant contributor of endothelial superoxide. More importantly, this enzyme system is activated by numerous stimuli and is involved in triggering diverse intracellular signalling pathways (‘redox-sensitive’ signalling pathways) that have a central role in conditions such as endothelial activation and inflammation, cell growth, apoptosis and hypertrophy. Furthermore, NADPH oxidase-derived superoxide contributes to the impairment of endothelium-dependent vasodilatation by inactivating nitric oxide; the resultant endothelial dysfunction is implicated in the pathophysiology of diseases such as atherosclerosis, hypertension, diabetic vasculopathy and heart failure. A detailed understanding of the regulation of NADPH oxidases and their modulation and downstream effects may define novel therapeutic targets for cardiovascular disease prevention and treatment in the clinical setting, in contrast with global antioxidant therapy which has to date been disappointing.