Epidemiological studies suggest that Mediterranean diets rich in resveratrol are associated with reduced risk of coronary artery disease. Resveratrol was also shown to confer vasoprotection in animal models of type 2 diabetes and aging. However, the mechanisms by which resveratrol exerts its antioxidative vasculoprotective effects are not completely understood. Using a nuclear factor-E(2)-related factor-2 (Nrf2)/antioxidant response element-driven luciferase reporter gene assay, we found that in cultured coronary arterial endothelial cells, resveratrol, in a dose-dependent manner, significantly increases transcriptional activity of Nrf2. Accordingly, resveratrol significantly upregulates the expression of the Nrf2 target genes NAD(P)H:quinone oxidoreductase 1, gamma-glutamylcysteine synthetase, and heme oxygenase-1. Resveratrol treatment also significantly attenuated high glucose (30 mM)-induced mitochondrial and cellular oxidative stress (assessed by flow cytometry using MitoSox and dihydroethidine staining). The aforementioned effects of resveratrol were significantly attenuated by the small interfering RNA downregulation of Nrf2 or the overexpression of Kelch-like erythroid cell-derived protein 1, which inactivates Nrf2. To test the effects of resveratrol in vivo, we used mice fed a high-fat diet (HFD), which exhibit increased vascular oxidative stress associated with an impaired endothelial function. In HFD-fed Nrf2(+/+) mice, resveratrol treatment attenuates oxidative stress (assessed by the Amplex red assay), improves acetylcholine-induced vasodilation, and inhibits apoptosis (assessed by measuring caspase-3 activity and DNA fragmentation) in branches of the femoral artery. In contrast, the aforementioned endothelial protective effects of resveratrol were diminished in HFD-fed Nrf2(-/-) mice. Taken together, our results indicate that resveratrol both in vitro and in vivo confers endothelial protective effects which are mediated by the activation of Nrf2.

Peroxynitrite (ONOO−) contributes to coronary microvascular dysfunction in diabetes mellitus (DM). We hypothesized that in DM, ONOO− interferes with the function of coronary endothelial caveolae, which plays an important role in nitric oxide (NO)-dependent vasomotor regulation. Flow-mediated dilation (FMD) of coronary arterioles was investigated in DM (n = 41) and non-DM (n = 37) patients undergoing heart surgery. NO-mediated coronary FMD was significantly reduced in DM patients, which was restored by ONOO− scavenger, iron-(III)-tetrakis(N-methyl-4'pyridyl)porphyrin-pentachloride, or uric acid, whereas exogenous ONOO− reduced FMD in non-DM subjects. Immunoelectron microscopy demonstrated an increased 3-nitrotyrosine formation (ONOO−-specific protein nitration) in endothelial plasma membrane in DM, which colocalized with caveolin-1 (Cav-1), the key structural protein of caveolae. The membrane-localized Cav-1 was significantly reduced in DM and also in high glucose–exposed coronary endothelial cells. We also found that DM patients exhibited a decreased number of endothelial caveolae, whereas exogenous ONOO− reduced caveolae number. Correspondingly, pharmacological (methyl-β-cyclodextrin) or genetic disruption of caveolae (Cav-1 knockout mice) abolished coronary FMD, which was rescued by sepiapterin, the stable precursor of NO synthase (NOS) cofactor, tetrahydrobiopterin. Sepiapterin also restored coronary FMD in DM patients. Thus, we propose that ONOO− selectively targets and disrupts endothelial caveolae, which contributes to NOS uncoupling, and, hence, reduced NO-mediated coronary vasodilation in DM patients.

, via competing with nitric oxide (NO) synthase for the substrate L-arginine, may interfere with NO-mediated vascular responses. We tested the hypothesis that arginase 1 contributes to coronary vasomotor dysfunction in patients with diabetes mellitus (DM). Coronary arterioles were dissected from the right atrial appendages of 41 consecutive patients with or without DM (the 2 groups suffered from similar comorbidities), and agonist-induced changes in diameter were measured with videomicroscopy. We found that the endothelium-dependent agonist ACh elicited a diminished vasodilation and caused constriction to the highest ACh concentration (0.1 M) with a similar magnitude in patients with (18 Ϯ 8%) and without (17 Ϯ 9%) DM. Responses to ACh were not significantly affected by the inhibition of NO synthesis with N G -nitro-L-arginine methyl ester in either group. The NO donor sodium nitroprusside-dependent dilations were not different in patients with or without DM. Interestingly, we found that the presence of N G -hydroxy-L-arginine (10 M), a selective inhibitor of arginase or application of L-arginine (3 mM), restored ACh-induced coronary dilations only in patients with DM (to 47 Ϯ 6% and to 40 Ϯ 19%, respectively) but not in subjects without DM. Correspondingly, the protein expression of arginase 1 was increased in coronary arterioles of patients with DM compared with subjects without diabetes. Moreover, using immunocytochemistry, we detected an abundant immunostaining of arginase 1 in coronary endothelial cells of patients with DM, which was colocalized with NO synthase. Collectively, we provided evidence for a distinct upregulation of arginase 1 in coronary arterioles of patients with DM, which contributes to a reduced NO production and consequently diminished vasodilation. coronary microvessel; endothelium; endothelial nitric oxide synthase PATIENTS WITH DIABETES exhibit endothelial dysfunction, which is characterized by an impaired flow-and acetylcholine (ACh)-induced, endothelium-dependent relaxation of brachial artery (8) and forearm resistance vessels (36). Kaneda et al. (17) performed a study in which 165 patients underwent intracoronary injection of ACh and found that diabetes was the strongest predictor for ACh-induced vasospasm, a response that indicates coronary endothelial dysfunction. This and other studies indicated that diabetes is also associated with an impaired dilator function of coronary arteries, and this is manifested and measured as a reduced vasodilator or even vasoconstrictor response to ACh (5, 23). Our previous studies have demonstrated that coronary arterioles isolated from animals with experimental diabetes also exhibit impaired ACh-induced dilation, which is primarily due to the reduced synthesis and/or availability of nitric oxide (NO) (1, 2, 9, 16). The exact mechanism(s) responsible for the diminished NO production in human diabetes is still incompletely understood.L-Arginine, the substrate for NO synthase, is the precursor for NO synthesis in the vascular endothelium. Experimenta...

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.

A healthy, functional microcirculation in combination with non-obstructed epicardial coronary arteries is the prerequisite of normal myocardial perfusion. Quantitative assessment in myocardial perfusion and determination of absolute myocardial blood flow (MBF) can be achieved noninvasively using dynamic imaging with multiple imaging modalities. Extensive evidence supports the clinical value of noninvasively assessing indices of coronary flow for diagnosing coronary microvascular dysfunction (CMVD); in certain diseases the degree of coronary microvascular impairment carries important prognostic relevance. Although, currently positron emission tomography (PET) is the most commonly used tool for the quantification of MBF, other modalities including single-photon emission computed tomography (SPECT), computed tomography (CT), magnetic resonance imaging (MRI) and myocardial contrast echocardiography (MCE) have emerged as techniques with great promise for determination of CMVD. The following review will describe basic concepts of coronary and microvascular physiology, review available modalities for dynamic imaging for quantitative assessment of coronary perfusion and MBF, and discuss their application in distinct forms of CMVD.

It is believed that obesity has detrimental effects on the coronary circulation. These include immediate changes in coronary arterial vasomotor responsiveness and the development of occlusive large coronary artery disease. Despite its critical role in regulating myocardial perfusion, the altered behavior of coronary resistance arteries, which gives rise to coronary microvascular disease (CMD) is poorly understood in obesity. A chronic, low-grade vascular inflammation has been long considered as one of the main underlying pathology behind CMD. The expanded adipose tissue and the infiltrating macrophages are the major sources of pro-inflammatory mediators that have been implicated in causing inadequate myocardial perfusion and, in a long term, development of heart failure in obese patients. Much less is known the mechanisms regulating the release of these cytokines into the circulation that enable them to exert their remote effects in the coronary microcirculation. This mini review aims to examine recent studies describing alterations in the vasomotor function of coronary resistance arteries and the role of adipose tissue-derived pro-inflammatory cytokines and adipokines in contributing to CMD in obesity. We provide examples of regulatory mechanisms by which adipokines are released from adipose tissue to exert their remote inflammatory effects on coronary microvessels. We identify some of the important challenges and opportunities going forward.

Background Echo-derived linear dimensions offer straightforward indices of right ventricular (RV) structure but have not been systematically compared to RV volumes on cardiac magnetic resonance (CMR). Methods Echo and CMR were interpreted among CAD patients imaged via prospective (90%) or retrospective (10%) registries. For echo, American Society of Echocardiography (ASE) recommended RV dimensions were measured in apical 4-chamber (basal RV width, mid RV width, RV length), parasternal long (proximal RV outflow tract [pRVOT]) and short axis (distal RVOT) views. For CMR, RV end-diastolic (RV-EDV) and end-systolic (RV-ESV) volumes were quantified via border planimetry. Results 272 patients underwent echo and CMR within a narrow interval (0.4±1.0 days); complete acquisition of all ASE dimensions was feasible in 98%. All echo dimensions differed between patients with and without RV dilation on CMR (p<0.05). Basal RV width (r=0.70), pRVOT width (r=0.68), and RV length (r=0.61) yielded highest correlations with RV-EDV on CMR; end-systolic dimensions yielded similar correlations (r=0.68, 0.66, 0.65 respectively). In multivariable regression, basal RV width (regression coefficient 1.96 per mm [CI 1.22–2.70], p<0.001), RV length (0.97[0.56–1.37], p<0.001) and pRVOT width (2.62 [1.79–3.44], p<0.001) were independently associated with CMR RV-EDV[r= 0.80]. RV-ESV was similarly associated with echo dimensions (basal RV width; 1.59 per mm [CI 1.06–2.13], p<0.001) | RV length; 1.00 [0.66–1.34], p<0.001) | pRVOT width; 1.80 [1.22–2.39], p<0.001) [r= 0.79]. Conclusions RV linear dimensions provide readily obtainable markers of RV chamber size. Proximal RVOT and basal width are independently associated with CMR volumes, supporting use of multiple linear dimensions when assessing RV size on echo.

Thus, under normal conditions, Cav-1 limits the contribution of the BK(Ca) channel to EDHF-mediated arteriolar dilation. In obesity, a reduced expression of Cav-1 leads to greater contribution of the BK(Ca) channel to EDHF-mediated response, which seems essential for maintained coronary dilation.