713-4 Inhibition of Vascular Superoxide Production in Hypercholesterolemic Rabbit Aorta by L-Arginine Contributes to Restored Endothelium-dependent Relaxation

Chronic oral administration of L-arginine (L-ARG) has been shown to enhance endothelial function in cholesterol (CHOL)-fed rabbits and to reduce atherogenesis. We investigated whether modulation of endogenous NO production (as assessed by urinary NO3-excretion) by L-ARG and the inhibitor of NO synthesis, L-NAME, affects vascular superoxide (O2-) production in hypercholesterolemic rabbits. Phorbol-myristate-acetate (PMA)-stimulated O2-production from isolated aortic rings was increased in rabbits given CHOL (+159±28%) or CHOL + L-NAME (+149±37%) as compared to controls (-22±7%), and endothelium-dependent relaxations by acetylcholine were diminished in both groups. In aortic rings from rabbits given CHOL + L-ARG, PMA-induced O2-production was restored to control levels (+14±17%; p<0.05), and endothelium-dependent cholinergic relaxations were also partly restored. Urinary NO3-excretion decreased in all animals fed a CHOL-enriched diet (p<0.01). As NO inactivated by O2-is also oxidized to NO3-, this indicates a decreased endothelial production of NO. NO3-excretion was further decreased by L-NAME (p<0.05 vs. CHOL), and partly restored by L-ARG (p<0.05). We conclude that both a decreased production of NO and an enhanced breakdown of NO by O2-contribute to the diminished biological activity of endothelial NO in hypercholesterolemia. L-ARG restores endothelial function by enhancing NO formation and by protecting NO from early breakdown by O2-

Restoring vascular nitric oxide formation by l-arginine improves the symptoms of intermittent claudication in patients with peripheral arterial occlusive disease

AbstractBackground. Administration of l-arginine improves nitric oxide (NO) formation and endothelium-dependent vasodilation in atherosclerotic patients.Objectives. We investigated in this double-blind, controlled study whether prolonged intermittent infusion therapy with l-arginine improves the clinical symptoms of patients with intermittent claudication, as compared with the endothelium-independent vasodilator prostaglandin E1, and control patients.Methods. Thirty-nine patients with intermittent claudication were randomly assigned to receive 2 × 8 g l-arginine/day, or 2 × 40 μg prostaglandin E1(PGE1)/day or no hemodynamically active treatment, for 3 weeks. The pain-free and absolute walking distances were assessed on a walking treadmill at 3 km/h, 12% slope, and NO-mediated, flow-induced vasodilation of the femoral artery was assessed by ultrasonography at baseline, at 1, 2 and 3 weeks of therapy and 6 weeks after the end of treatment. Urinary nitrate and cyclic guanosine-3′, 5′-monophosphate (GMP) were assessed as indices of endogenous NO production.Results. l-Arginine improved the pain-free walking distance by 230 ± 63% and the absolute walking distance by 155 ± 48% (each p < 0.05). Prostaglandin E1improved both parameters by 209 ± 63% and 144 ± 28%, respectively (each p < 0.05), whereas control patients experienced no significant change. l-Arginine therapy also improved endothelium-dependent vasodilation in the femoral artery, whereas PGE1had no such effect. There was a significant linear correlation between the l-arginine/asymmetric dimethylarginine (ADMA) ratio and the pain-free walking distance at baseline (r = 0.359, p < 0.03). l-Arginine treatment elevated the plasma l-arginine/ADMA ratio and increased urinary nitrate and cyclic GMP excretion rates, indicating normalized endogenous NO formation. Prostaglandin E1therapy had no significant effect on any of these parameters. Symptom scores assessed on a visual analog scale increased from 3.51 ± 0.18 to 8.3 ± 0.4 (l-arginine) and 7.0 ± 0.5 (PGE1; each p < 0.05), but did not significantly change in the control group (4.3 ± 0.4).Conclusions. Restoring NO formation and endothelium-dependent vasodilation by l-arginine improves the clinical symptoms of intermittent claudication in patients with peripheral arterial occlusive disease

An endogenous inhibitor of nitric oxide synthase regulates endothelial adhesiveness for monocytes

AbstractOBJECTIVESWe sought to determine whether asymmetric dimethylarginine (ADMA) inhibits nitric oxide (NO) elaboration in cultured human endothelial cells and whether this is associated with the activation of oxidant-sensitive signaling mediating endothelial adhesiveness for monocytes.BACKGROUNDEndothelial NO elaboration is impaired in hypercholesterolemia and atherosclerosis, which may be due to elevated concentrations of ADMA, an endogenous inhibitor of NO synthase.METHODSHuman umbilical vein endothelial cells (ECV 304) and human monocytoid cells (THP-1) were studied in a functional binding assay. Nitric oxide and superoxide anion (O2−) were measured by chemiluminescence; ADMA by high pressure liquid chromatography; monocyte chemotactic protein-1 (MCP-1) by ELISA and NF-κB by electromobility gel shift assay.RESULTSIncubation of endothelial cells with ADMA (0.1 μM to 100 μM) inhibited NO formation, which was reversed by coincubation with L-arginine (1 mM). The biologically inactive stereoisomer symmetric dimethylarginine did not inhibit NO release. Asymmetric dimethylarginine (10 μM) or native low-density lipoprotein cholesterol (100 mg/dL) increased endothelial O2− to the same degree. Asymmetric dimethylarginine also stimulated MCP-1 formation by endothelial cells. This effect was paralleled by activation of the redox-sensitive transcription factor NF-κB. Preincubation of endothelial cells with ADMA increased the adhesiveness of endothelial cells for THP-1 cells in a concentration-dependent manner. Asymmetric dimethylarginine-induced monocyte binding was diminished by L-arginine or by a neutralizing anti-MCP-1 antibody.CONCLUSIONSWe concluded that the endogenous NO synthase inhibitor ADMA is synthesized in human endothelial cells. Asymmetric dimethylarginine increases endothelial oxidative stress and potentiates monocyte binding. Asymmetric dimethylarginine may be an endogenous proatherogenic molecule

Asymmetric Dimethylarginine Determines the Improvement of Endothelium-Dependent Vasodilation by Simvastatin Effect of Combination With Oral L-Arginine

ObjectivesWe hypothesized that the level of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of endothelial nitric oxide (NO) synthase (eNOS), might determine the endothelial effects of statins.BackgroundEndothelial NO synthase is up-regulated by statins. However, statins failed to improve endothelial function in some studies. Asymmetric dimethylarginine inhibits eNOS by a mechanism that is reversible by L-arginine.MethodsNinety-eight clinically asymptomatic elderly subjects had their plasma ADMA levels screened. Those in the highest (high ADMA, n = 15) and lowest quartiles of the ADMA distribution (low ADMA, n = 13) were eligible to receive, in a randomized order, simvastatin (40 mg/day), L-arginine (3 g/day), or a combination of both, each for 3 weeks. Endothelium-dependent vasodilation (EDD) was assessed by brachial artery ultrasound.ResultsSimvastatin had no effect on EDD in subjects with high ADMA (6.2 ± 1.2% vs. 6.1 ± 0.9%), whereas simvastatin plus L-arginine significantly improved EDD (9.8 ± 1.5% vs. 5.3 ± 0.8%; p < 0.01). In subjects with low ADMA, simvastatin improved endothelial function when given alone (9.5 ± 3.2% vs. 6.1 ± 3.8%; p < 0.001) or in combination with L-arginine (9.0 ± 3.1% vs. 6.3 ± 3.3%; p = 0.001). L-arginine alone improved endothelial function in both groups. Endothelium-independent vasodilation was not affected.ConclusionsSimvastatin does not enhance endothelial function in subjects with elevated ADMA, whereas it does so in patients with low ADMA. Combination of simvastatin with oral L-arginine improves endothelial function in subjects with high ADMA, but has no additional effect in subjects with low ADMA. As NO-mediated effects may play a major role in the therapeutic effects of statins, ADMA concentration is an important factor that influences the “pleiotropic” effects of simvastatin

Dimethylarginine Dimethylaminohydrolase-1 Transgenic Mice Are Not Protected from Ischemic Stroke

Methylated arginines are endogenous analogues of L-arginine, the substrate for nitric oxide (NO) synthase. Asymmetric dimethylarginine (ADMA) interferes with NO formation, causing endothelial dysfunction. ADMA is a predictor of cardiovascular events and mortality in humans. It is eliminated primarily by enzymatic activity of dimethylarginine dimethylaminohydrolase (DDAH).We investigated whether human DDAH-1 (hDDAH-1) transgenicity protects from ischemic tissue damage in temporary middle cerebral artery occlusion (tMCAO) in mice. Infarct sizes did not significantly differ between hDDAH-1 transgenic (TG) mice and wild-type littermates (WT). As expected, ADMA plasma concentrations were significantly decreased, cerebral hDDAH expression and protein significantly increased in transgenic animals. Interestingly, neither brain tissue DDAH activity nor ADMA concentrations were different between TG and WT mice. In contrast, muscular DDAH activity was generally lower than in brain but significantly increased in TG mice.Our study demonstrates that hDDAH-1 transgenic mice are not protected from ischemic cerebral tissue damage in tMCAO. This lack of protection is due to high basal cerebral DDAH activity, which is not further increasable by transgenic overexpression of DDAH

A study of endothelial function and circulating asymmetric dimethylarginine levels in people with Type 1 diabetes without macrovascular disease or microalbuminuria

<p>Abstract</p> <p>Background</p> <p>Asymmetric dimethylarginine (ADMA) is a competitive inhibitor of endothelial nitric oxide synthase (eNOS) that is associated with endothelial dysfunction, and is a risk marker for cardiovascular disease, a significant problem in Type 1 diabetes. The aim of the present study was to measure circulating ADMA, and define its association with endothelial dysfunction and endothelial markers in people with Type 1 diabetes with low likelihood of macrovascular disease.</p> <p>Methods</p> <p>Sixty-one young people with Type 1 diabetes without macrovascular disease or nephropathy and 62 healthy volunteers underwent brachial artery flow-mediated dilatation (FMD) and assay of plasma ADMA and adhesion molecules.</p> <p>Results</p> <p>Age, gender, BMI, lipid profile and renal function were similar in the two groups. People with Type 1 diabetes had impaired FMD compared to healthy controls (5.0 ± 0.4 vs 8.9 ± 0.4%; p < 0.001). Plasma ADMA levels were significantly lower in the people with diabetes compared to healthy controls (0.52 ± 0.12 vs 0.66 ± 0.20 μmol/l, p < 0.001). Plasma ICAM-1, E-selectin and PAI-1 levels were significantly higher in people with diabetes compared to healthy controls (median 201 (IQR 172–226) vs 180 (156–216) μg/l, p = 0.027; 44.2 (32.6–60.9) vs. 33.1 (22.4–51.0) μg/l; p = 0.003 and 70.8 (33.3–85.5) vs 46.3 (23.9–76.8) μg/l, p = 0.035). Plasma ADMA and VCAM-1 levels were positively correlated (r = 0.37, p = 0.003) in people with diabetes. There was no correlation between the plasma ADMA and FMD.</p> <p>Conclusion</p> <p>ADMA levels are not associated with endothelial dysfunction in young adults with Type 1 diabetes without microalbuminuria or known macrovascular disease. This suggests that the impaired endothelial function in these individuals is not a result of eNOS inhibition by ADMA.</p

Reduction of fossil fuel use and adoption of alternative energy sources

Reduction of carbon dioxide emissions means a much more radical change in the energy supply structure than any possibly successful strategy to replace scarce petroleum could ever be. Moreover, the vulnerability of oil supplies leads to problem solutions, which even aggravate the carbon dioxide problem. Therefore, any improvements must heavily rely on forced energy saving and enhanced use of renewable and nuclear energy. Although the theoretical potential to substitute carbon - and hydrocarbon - fuels has the rather high value of about 2/3 of final energy demand, the technical and economical feasibility of alternative fuels must be judged much more pessimistically. Some recent results of an analysis sponsored by the lEA show, that nuclear and renewable energy supplies may only be able to sustain about 50% of the growth or primary energy demand of the lEA-countries. Thus, if we want to be sure of having enough energy to sustain our lifestyle, we must not expect reductions of carbon dioxide emissions. This can only be achieved by huge efforts in energy saving, connected with a full utilization of the nuclear and renewable resources

Biomarkers of the L-arginine / dimethylarginine / nitric oxide pathway in people with chronic airflow obstruction and obstructive sleep apnoea

Background: Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnoea (OSA) are common chronic diseases that are associated with chronic and intermittent hypoxemia, respectively. Patients affected by the overlap of COPD and OSA have a particularly unfavourable prognosis. The L-arginine/nitric oxide (NO) pathway plays an important role in regulating pulmonary vascular function. Asymmetric (ADMA) and symmetric dimethylarginine (SDMA) interfere with NO production. Methods: We analysed the serum concentrations of ADMA, SDMA, L-arginine, L-citrulline, and L-ornithine in a large sample of the Icelandic general population together with chronic airflow obstruction (CAO), a key physiological marker of COPD that was assessed by post-bronchodilator spirometry (FEV1/FVC 0.5. SDMA was significantly higher in individuals with CAO (0.518 [0.461–0.616] vs. 0.494 [0.441–0.565] µmol/L; p = 0.005), but ADMA was not. However, ADMA was significantly associated with decreasing FEV1 percent predicted among those with CAO (p = 0.002). ADMA was 0.50 (0.44–0.56) µmol/L in MAP ≤ 0.5 versus 0.52 (0.46–0.58) µmol/L in MAP > 0.5 (p = 0.008). SDMA was 0.49 (0.44–0.56) µmol/L versus 0.51 (0.46–0.60) µmol/L, respectively (p = 0.004). The highest values for ADMA and SDMA were observed in individuals with overlap of CAO and MAP > 0.5, which was accompanied by lower L-citrulline levels. Conclusions: The plasma concentrations of ADMA and SDMA are elevated in COPD patients with concomitant intermittent hypoxaemia. This may account for impaired pulmonary NO production, enhanced pulmonary vasoconstriction, and disease progression