Regulation of the ADMA-DDAH system in endothelial cells: a novel mechanism for the sterol response element binding proteins, SREBP1c and -2

Regulatory effects of resveratrol on nitric oxide signaling in cardiovascular diseases

Cardiovascular illnesses are multifactorial disorders and represent the primary reasons for death worldwide, according to the World Health Organization. As a signaling molecule, nitric oxide (NO) is extremely permeable across cellular membranes owing to its unique molecular features, like its small molecular size, lipophilicity, and free radical properties. Some of the biological effects of NO are vasodilation, inhibition in the growth of vascular smooth muscle cells, and functional regulation of cardiac cells. Several therapeutic approaches have been tested to increase the production of NO or some downstream NO signaling pathways. The health benefits of red wine are typically attributed to the polyphenolic phytoalexin, resveratrol (3,5,4'-trihydroxy-trans-stilbene), which is found in several plant species. Resveratrol has beneficial cardiovascular properties, some of which are mediated through endothelial nitric oxide synthase production (eNOS). Resveratrol promotes NO generation from eNOS through various methods, including upregulation of eNOS expression, activation in the enzymatic activity of eNOS, and reversal of eNOS uncoupling. Additionally, by reducing of oxidative stress, resveratrol inhibits the formation of superoxide and inactivation NO, increasing NO bioavailability. This review discusses the scientific literature on resveratrol's beneficial impact on NO signaling and how this effect improves the function of vascular endothelium.

Regulatory effects of curcumin on nitric oxide signaling in the cardiovascular system

The continuously rising prevalence of cardiovascular disease (CVD) globally substantially impacts the economic growth of developing countries. Indeed, one of the leading causes of death worldwide is unfavorable cardiovascular events. Reduced nitric oxide (NO) generation is the pathogenic foundation of endothelial dysfunction, which is regarded as the first stage in the development of a number of CVDs. Nitric oxide exerts an array of biological effects, including vasodilation, the suppression of vascular smooth muscle cell proliferation and the functional control of cardiac cells. Numerous treatment strategies aim to increase NO synthesis or upregulate downstream NO signaling pathways. The major component of Curcuma longa, curcumin, has long been utilized in traditional medicine to treat various illnesses, especially CVDs. Curcumin improves CV function as well as having important pleiotropic effects, such as anti-inflammatory and antioxidant, through its ability to increase the bioavailability of NO and to positively impact NO-related signaling pathways. In this review, we discuss the scientific literature relating to curcumin's positive effects on NO signaling and vascular endothelial function.

Endothelial dysfunction due to eNOS uncoupling: molecular mechanisms as potential therapeutic targets

Nitric oxide (NO) is one of the most important molecules released by endothelial cells, and its antiatherogenic properties support cardiovascular homeostasis. Diminished NO bioavailability is a common hallmark of endothelial dysfunction underlying the pathogenesis of the cardiovascular disease. Vascular NO is synthesized by endothelial nitric oxide synthase (eNOS) from the substrate L-arginine (L-Arg), with tetrahydrobiopterin (BH₄) as an essential cofactor. Cardiovascular risk factors such as diabetes, dyslipidemia, hypertension, aging, or smoking increase vascular oxidative stress that strongly affects eNOS activity and leads to eNOS uncoupling. Uncoupled eNOS produces superoxide anion (O₂^-) instead of NO, thus becoming a source of harmful free radicals exacerbating the oxidative stress further. eNOS uncoupling is thought to be one of the major underlying causes of endothelial dysfunction observed in the pathogenesis of vascular diseases. Here, we discuss the main mechanisms of eNOS uncoupling, including oxidative depletion of the critical eNOS cofactor BH₄, deficiency of eNOS substrate L-Arg, or accumulation of its analog asymmetrical dimethylarginine (ADMA), and eNOS S-glutathionylation. Moreover, potential therapeutic approaches that prevent eNOS uncoupling by improving cofactor availability, restoration of L-Arg/ADMA ratio, or modulation of eNOS S-glutathionylation are briefly outlined.

Statins reduce vascular inflammation in atherogenesis: A review of underlying molecular mechanisms

Chronic inflammation enhances the detrimental role of dyslipidaemia during atherogenesis. Statins are among the most effective anti-atherosclerotic medications, being able to impact on both cardiovascular morbidity and mortality. Although these molecules have been first described as lipid-lowering medications, several lines of evidence suggest additional benefits through their "pleiotropic" anti-atherosclerotic activities. Specifically, statins can modulate vascular atherosclerotic inflammation by directly improving functions of endothelial cells, vascular smooth muscle cells, platelets, and immune cells. Here, we discuss basic and clinical evidence to provide an update on the molecular mechanisms underlying the protective anti-inflammatory role of statins in atherogenesis.

Inhibition of Dimethylarginine Dimethylaminohydrolase (DDAH) Enzymes as an Emerging Therapeutic Strategy to Target Angiogenesis and Vasculogenic Mimicry in Cancer

The small free radical gas nitric oxide (NO) plays a key role in various physiological and pathological processes through enhancement of endothelial cell survival and proliferation. In particular, NO has emerged as a molecule of interest in carcinogenesis and tumor progression due to its crucial role in various cancer-related events including cell invasion, metastasis, and angiogenesis. The dimethylarginine dimethylaminohydrolase (DDAH) family of enzymes metabolize the endogenous nitric oxide synthase (NOS) inhibitors, asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA), and are thus key for maintaining homeostatic control of NO. Dysregulation of the DDAH/ADMA/NO pathway resulting in increased local NO availability often promotes tumor growth, angiogenesis, and vasculogenic mimicry. Recent literature has demonstrated increased DDAH expression in tumors of different origins and has also suggested a potential ADMA-independent role for DDAH enzymes in addition to their well-studied ADMA-mediated influence on NO. Inhibition of DDAH expression and/or activity in cell culture models and in vivo studies has indicated the potential therapeutic benefit of this pathway through inhibition of both angiogenesis and vasculogenic mimicry, and strategies for manipulating DDAH function in cancer are currently being actively pursued by several research groups. This review will thus provide a timely discussion on the expression, regulation, and function of DDAH enzymes in regard to angiogenesis and vasculogenic mimicry, and will offer insight into the therapeutic potential of DDAH inhibition in cancer based on preclinical studies.

Blond and blood juice supplementation in high fat diet fed mice: effect on antioxidant status and DDAH/ADMA pathway

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease spread throughout the world. The most frequent causes of death in NAFLD patients are due both to liver and cardiovascular damage. Several pathways, including the dimethylarginine dimethylaminohydrolase (DDAH)/asymmetric dimethylarginine (ADMA) pathway, are involved in the pathogenesis of NAFLD. It has been reported that ADMA plasmatic levels are increased in patients with hepatic dysfunction such as NAFLD. Although many studies demonstrated that some foods are effective in the treatment of NAFLD, few studies have evaluated their effects with respect to the prevention of the disease. It has been reported that sweet orange juice (OJ) consumption may be associated with potential health benefits. However, some varieties of sweet orange are more effective than others. The aim of the present paper was to investigate the effect of blond and blood sweet orange juice in prevention of NAFLD by evaluating its ability to improve liver steatosis in mice with diet-induced obesity, reducing oxidative stress and affecting the DDAH/ADMA pathway. Results obtained in our experimental conditions evidenced that blood orange juice rather than blond orange juice was more effective. Blood orange juice or blond orange juice enriched in anthocyanins may represent a promising dietary option for the prevention of fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease spread throughout the world.

Nutritional regulation of renal lipogenic factor expression in mice: comparison to regulation in the liver and skeletal muscle

Regulation of lipogenesis by pathophysiological factors in the liver and skeletal muscle is well understood; however, regulation in the kidney is still unclear. To elucidate nutritional regulation of lipogenic factors in the kidney, we measured the renal expression of lipogenic transcriptional factors and enzymes during fasting and refeeding in chow-fed and high-fat-fed mice. We also examined the regulatory effect of the liver X receptor (LXR) on the expression of lipogenic factors. The renal gene expression of sterol regulatory element-binding protein (SREBP)-1c and fatty acid synthase (FAS) was reduced by fasting for 48 h and restored by refeeding, whereas the mRNA levels of forkhead box O (FOXO)1/3 were increased by fasting and restored by refeeding. Accordingly, protein levels of SREBP-1, FAS, and phosphorylated FOXO1/3 were reduced by fasting and restored by refeeding. The patterns of lipogenic factors expression in the kidney were similar to those in the liver and skeletal muscle. However, this phasic regulation of renal lipogenic gene expression was blunted in diet-induced obese mice. LXR agonist TO901317 increased the lipogenic gene expression and the protein levels of SREBP-1 precursor and FAS but not nuclear SREBP-1. Moreover, increases in insulin-induced gene mRNA and nuclear carbohydrate-responsive element binding protein (ChREBP) levels were observed in the TO901317-treated mice. These results suggest that the kidney shows flexible suppression and restoration of lipogenic factors following fasting and refeeding in lean mice, but this is blunted in obese mice. LXR is involved in the renal expression of lipogenic enzymes, and ChREBP may mediate the response.

Inhibitors of the Hydrolytic Enzyme Dimethylarginine Dimethylaminohydrolase (DDAH): Discovery, Synthesis and Development

Dimethylarginine dimethylaminohydrolase (DDAH) is a highly conserved hydrolytic enzyme found in numerous species, including bacteria, rodents, and humans. In humans, the DDAH-1 isoform is known to metabolize endogenous asymmetric dimethylarginine (ADMA) and monomethyl arginine (l-NMMA), with ADMA proposed to be a putative marker of cardiovascular disease. Current literature reports identify the DDAH family of enzymes as a potential therapeutic target in the regulation of nitric oxide (NO) production, mediated via its biochemical interaction with the nitric oxide synthase (NOS) family of enzymes. Increased DDAH expression and NO production have been linked to multiple pathological conditions, specifically, cancer, neurodegenerative disorders, and septic shock. As such, the discovery, chemical synthesis, and development of DDAH inhibitors as potential drug candidates represent a growing field of interest. This review article summarizes the current knowledge on DDAH inhibition and the derived pharmacokinetic parameters of the main DDAH inhibitors reported in the literature. Furthermore, current methods of development and chemical synthetic pathways are discussed.

Therapeutic effects of inorganic nitrate and nitrite in cardiovascular and metabolic diseases

Nitric oxide (NO) is generated endogenously by NO synthases to regulate a number of physiological processes including cardiovascular and metabolic functions. A decrease in the production and bioavailability of NO is a hallmark of many major chronic diseases including hypertension, ischaemia-reperfusion injury, atherosclerosis and diabetes. This NO deficiency is mainly caused by dysfunctional NO synthases and increased scavenging of NO by the formation of reactive oxygen species. Inorganic nitrate and nitrite are emerging as substrates for in vivo NO synthase-independent formation of NO bioactivity. These anions are oxidation products of endogenous NO generation and are also present in the diet, with green leafy vegetables having a high nitrate content. The effects of nitrate and nitrite are diverse and include vasodilatation, improved endothelial function, enhanced mitochondrial efficiency and reduced generation of reactive oxygen species. Administration of nitrate or nitrite in animal models of cardiovascular disease shows promising results, and clinical trials are currently ongoing to investigate the therapeutic potential of nitrate and nitrite in hypertension, pulmonary hypertension, peripheral artery disease and myocardial infarction. In addition, the nutritional aspects of the nitrate-nitrite-NO pathway are interesting as diets suggested to protect against cardiovascular disease, such as the Mediterranean diet, are especially high in nitrate. Here, we discuss the potential therapeutic opportunities for nitrate and nitrite in prevention and treatment of cardiovascular and metabolic diseases.

Serum trans fatty acids, asymmetric dimethylarginine and risk of acute myocardial infarction and mortality in patients with suspected coronary heart disease: a prospective cohort study

Background

Trans fatty acids (TFAs) have been found to impair flow mediated vasodilation and nitric oxide (NO) production. We sought to examine if serum TFA levels are associated with plasma levels of the NO inhibitor asymmetric dimethylarginine (ADMA) and if possible relationships between serum TFA and cardiovascular morbidity or mortality are mediated or modified by plasma ADMA levels.

Methods

The cohort included patients who underwent coronary angiography for suspected coronary heart disease in 2000–2001. Serum trans 16:1n7 and trans 18:1 isomers were determined by gas liquid chromatography and the summation of these two TFAs is reported as TFA (percentage by weight (wt%) or concentration). Associations between TFAs and ADMA were estimated by calculating the Spearman’s rank correlation coefficient (ρ), and risk associations with AMI, cardiovascular death and all-cause mortality across quartiles of TFAs (wt% or concentration) were explored by Cox modeling.

Results

A total of 1364 patients (75 % men) with median (25^th,75^th percentile) age 61 (54, 69) years, serum TFA 0.46 (0.36, 0.56) wt% and plasma ADMA 0.59 (0.50, 0.70) μmol/L were studied. Serum TFA levels (ρ = 0.21, p < 0.001), trans 16:1n7 (ρ = 0.22, p < 0.001) and trans 18:1 (ρ = 0.20, p < 0.001) levels were significantly correlated with plasma ADMA levels. During the median (25^th,75^th percentile) follow-up time of 5.8 (4.5, 6.4) years, 129 (9.5 %) patients experienced an AMI, 124 (9.1 %) died, whereof 66 (53 %) due to cardiovascular causes. After multivariate adjustments no significant associations between serum TFA levels (wt% or concentration) and incident AMI, CV death and all-cause mortality were observed. Similar results were obtained when repeating the analyses with trans 16:1n7 and trans 18:1 individually. Plasma ADMA levels did not significantly modify the associations between TFA levels and outcomes.

Conclusions

Serum TFA levels were positively correlated with plasma ADMA levels. After multivariate adjustments, TFAs were not associated with incident AMI or mortality, and associations were not influenced by ADMA.

Trial registration

Clinicaltrials.gov Identifier: NCT00354081

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-016-0204-9) contains supplementary material, which is available to authorized users.

Statins in Asthma: Potential Beneficial Effects and Limitations

Asthma's sustenance as a global pandemic, across centuries, can be attributed to the lack of an understanding of its workings and the inability of the existing treatment modalities to provide a long lasting cure without major adverse effects. The discovery of statins boosted by a better comprehension of the pathophysiology of asthma in the past few decades has opened up a potentially alternative line of treatment that promises to be a big boon for the asthmatics globally. However, the initial excellent results from the preclinical and animal studies have not borne the results in clinical trials that the scientific world was hoping for. In light of this, this review analyzes the ways by which statins could benefit in asthma via their pleiotropic anti-inflammatory properties and explain some of the queries raised in the previous studies and provide recommendations for future studies in this field.

Integrative Mouse and Human Studies Implicate ANGPT1 and ZBTB7C as Susceptibility Genes to Ischemic Injury

BACKGROUND AND PURPOSE

The extent of ischemic injury in response to cerebral ischemia is known to be affected by native vasculature. However, the nonvascular and dynamic vascular responses and their genetic basis are not well understood.

METHODS

We performed a genome-wide association study in 235 mice from 33 inbred strains using the middle cerebral artery occlusion model. Population structure and genetic relatedness were accounted for using the efficient mixed-model association method. Human orthologs to the genes associated with the significant and suggestive single-nucleotide polymorphisms from the mouse strain survey were examined in patients with M1 occlusions admitted with signs and symptoms of acute ischemic stroke.

RESULTS

We identified 4 genome-wide significant and suggestive single-nucleotide polymorphisms to be associated with infarct volume in mice (rs3694965, P=2.17×10(-7); rs31924033, P=5.61×10(-6); rs32249495, P=2.08×10(-7); and rs3677406, P=9.56×10(-6)). rs32249495, which corresponds to angiopoietin-1 (ANGPT1), was also significant in the recessive model in humans, whereas rs1944577, which corresponds to ZBTB7C, was nominally significant in both the additive and dominant genetic models in humans. ZBTB7C was shown to be upregulated in endothelial cells using both in vitro and in vivo models of ischemia.

CONCLUSIONS

Genetic variations of ANGPT1 and ZBTB7C are associated with increased infarct size in both mice and humans. ZBTB7C may modulate the ischemic response via neuronal apoptosis and dynamic collateralization and, in addition to ANGPT1, may serve as potential novel targets for treatments of cerebral ischemia.

Strategies to increase nitric oxide signalling in cardiovascular disease

Nitric oxide (NO) is a key signalling molecule in the cardiovascular, immune and central nervous systems, and crucial steps in the regulation of NO bioavailability in health and disease are well characterized. Although early approaches to therapeutically modulate NO bioavailability failed in clinical trials, an enhanced understanding of fundamental subcellular signalling has enabled a range of novel therapeutic approaches to be identified. These include the identification of: new pathways for enhancing NO synthase activity; ways to amplify the nitrate-nitrite-NO pathway; novel classes of NO-donating drugs; drugs that limit NO metabolism through effects on reactive oxygen species; and ways to modulate downstream phosphodiesterases and soluble guanylyl cyclases. In this Review, we discuss these latest developments, with a focus on cardiovascular disease.

The Arginine/ADMA Ratio Is Related to the Prevention of Atherosclerotic Plaques in Hypercholesterolemic Rabbits When Giving a Combined Therapy with Atorvastatine and Arginine

Supplementation with arginine in combination with atorvastatin is more efficient in reducing the size of an atherosclerotic plaque than treatment with a statin or arginine alone in homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits. We evaluated the mechanism behind this feature by exploring the role of the arginine/asymmetric dimethylarginine (ADMA) ratio, which is the substrate and inhibitor of nitric oxide synthase (NOS) and thereby nitric oxide (NO), respectively. Methods: Rabbits were fed either an arginine diet (group A, n = 9), standard rabbit chow plus atorvastatin (group S, n = 8), standard rabbit chow plus an arginine diet with atorvastatin (group SA, n = 8) or standard rabbit chow (group C, n = 9) as control. Blood was sampled and the aorta was harvested for topographic and histological analysis. Plasma levels of arginine, ADMA, cholesterol and nitric oxide were determined and the arginine/ADMA ratio was calculated. Results: The decrease in ADMA levels over time was significantly correlated to fewer aortic lesions in the distal aorta and total aorta. The arginine/ADMA ratio was correlated to cholesterol levels and decrease in cholesterol levels over time in the SA group. A lower arginine/ADMA ratio was significantly correlated to lower NO levels in the S and C group. Discussion: A balance between arginine and ADMA is an important indicator in the prevention of the development of atherosclerotic plaques.

Principles of targeting endothelial cell metabolism to treat angiogenesis and endothelial cell dysfunction in disease

The endothelium is the orchestral conductor of blood vessel function. Pathological blood vessel formation (a process termed pathological angiogenesis) or the inability of endothelial cells (ECs) to perform their physiological function (a condition known as EC dysfunction) are defining features of various diseases. Therapeutic intervention to inhibit aberrant angiogenesis or ameliorate EC dysfunction could be beneficial in diseases such as cancer and cardiovascular disease, respectively, but current strategies have limited efficacy. Based on recent findings that pathological angiogenesis and EC dysfunction are accompanied by EC-specific metabolic alterations, targeting EC metabolism is emerging as a novel therapeutic strategy. Here, we review recent progress in our understanding of how EC metabolism is altered in disease and discuss potential metabolic targets and strategies to reverse EC dysfunction and inhibit pathological angiogenesis.

A systematic review and meta-analysis of the effect of statins on plasma asymmetric dimethylarginine concentrations

The impact of statin therapy on plasma asymmetric dimethylarginine (ADMA) levels has not been conclusively studied. Therefore the aim of the meta-analysis was to assess the effect of statins on circulating ADMA levels. We searched selected databases (up to August 2014) to identify randomized controlled trials (RCTs) that investigate the effect of statins on plasma ADMA concentrations. A weighted meta-regression (WMD) using unrestricted maximum likelihood model was performed to assess the impact of statin dose, duration of statin therapy and baseline ADMA concentrations as potential variables on the WMD between statin and placebo group. In total, 1134 participants in 9 selected RCTs were randomized; 568 were allocated to statin treatment and 566 were controls. There was a significant reduction in plasma ADMA concentrations following statin therapy compared with placebo (WMD: − 0.104 μM, 95% confidence interval: − 0.131 to − 0.077, Z = − 7.577, p < 0.0001). Subgroups analysis has shown a significant impact of hydrophilic statins (WMD: − 0.207 μM, 95%CI: − 0.427 to + 0.013, Z = − 7.250, p < .0001) and a non-significant effect of hydrophobic statins (WMD: − 0.101 μM, 95%CI: − 0.128 to − 0.074, Z = − 1.845, p = 0.065). In conclusion, this meta-analysis of available RCTs showed a significant reduction in plasma ADMA concentrations following therapy with hydrophilic statins.

MiR-132 inhibits expression of SIRT1 and induces pro-inflammatory processes of vascular endothelial inflammation through blockade of the SREBP-1c metabolic pathway

PURPOSE

Inflammation participates centrally in all stages of atherosclerosis (AS), which begins with pro-inflammatory processes and inflammatory changes in the endothelium, related to lipid metabolism. MicroRNA (miRNA) inhibition of inflammation related to SIRT1 has been shown to be a promising therapeutic approach for AS. However, the mechanism of action is unknown.

METHODS

We investigated whether miRNAs regulate the SIRT1 and its downstream SREBP-lipogenesis-cholesterogenesis metabolic pathway in human umbilical vein endothelial cells (HUVECs). HUVECs were transfected with miR-132 mimics and inhibitors, and then treated with or without tumor necrosis factor α (TNFα). The effects of miR-132 on pro-inflammatory processes, proliferation and apoptosis were assessed.

RESULTS

We identified that the relative 3' UTR luciferase activities of SIRT1 were significantly decreased in miR-132 transfected HUVECs (0.338 ± 0.036) compared to control (P = 0.000). miR-132 inhibited SIRT1 expression of mRNA level in HUVECs (0.53 ± 0.06) (P < 0.01) as well as proteins of SIRT1. mRNA expression and protein levels of SREBP (0.45 ± 0.07), fatty acid synthase (FASN) (0.55 ± 0.09) and 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR) (0.62 ± 0.08) (P < 0.01), which are downstream regulated genes, were reduced in HUVECs by miR-132. MiR-132 promoted pro-inflammatory processes and apoptosis of HUVECs induced by TNF-α, and inhibited its proliferation, viability and migration.

CONCLUSIONS

SIRT1 mRNAs are direct targets of miR-132. miR-132 controls lipogenesis and cholesterogenesis in HUVECs by inhibiting SIRT1 and SREBP-1c expression and their downstream regulated genes, including FASN and HMGCR. Inhibition of SIRT1 by miR-132 was associated with lipid metabolism-dependent pro-inflammatory processes in HUVECs. The newly identified miRNA, miR-132 represents a novel targeting mechanism for AS therapy.

Association of the AGXT2 V140I polymorphism with risk for coronary heart disease in a Chinese population

AIM

Asymmetric dimethylarginine (ADMA) is a nitric oxide synthase (NOS) inhibitor that decreases NO production and promotes the development of cardiovascular diseases. Alanine-glyoxylate aminotransferase 2 (AGXT2) plays an important role in ADMA metabolism. This study was designed to explore the association of the AGXT2 V140I (rs37369 G＞A) polymorphism with risk for coronary heart disease (CHD) in a Chinese population.

METHODS

A case-control study including 1103 controls and 942 CHD patients was performed. The patients were genotyped for rs37369 using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Plasma ADMA concentration in healthy controls was measured by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The rs37369 GG genotype was significantly overrepresented in CHD patients compared to the controls (18.5% versus 14.8%, p=0.025), and it was significantly associated with increased risk for CHD in smokers (OR=2.21, 95% CI: 1.24-3.92, p=0.007) and marginally increased CHD risk for individuals with diabetes mellitus (OR=1.92; 95% CI: 0.94-3.91, p=0.074). The association between rs37369 and CHD risk was further increased in smokers with diabetes mellitus (OR=3.32, 95% CI:1.14-9.67, p=0.028). Patients who smoked and were rs37369 GG homozygous showed significantly higher plasma ADMA levels than carriers of the rs37369 A allele (p=0.004). However, in non-smokers, patients homozygous for rs37369 GG showed significantly lower plasma ADMA concentrations than carriers of the rs37369 A allele (p=0.003). Furthermore, smokers homozygous for rs37369 GG showed significantly higher plasma ADMA concentrations than non-smokers with the same genotype (p=0.012).

CONCLUSION

The AGXT2 rs37369 polymorphism is associated with increased risk for CHD in smokers and in diabetes mellitus patients. This increased risk may be due to increased plasma ADMA levels.

The endothelial ADMA/NO pathway in hypoxia-related chronic respiratory diseases

Since its discovery, many adhere to the view that asymmetric dimethylarginine (ADMA), as an inhibitor of the synthesis of nitric oxide (NO), contributes to the pathogenesis of various diseases. Particularly, this is evident in disease of the cardiovascular system, in which endothelial dysfunction results in an imbalance between vasoconstriction and vasodilatation. Even if increased ADMA concentrations are closely related to an endothelial dysfunction, several studies pointed to a potential beneficial effect of ADMA, mainly in the context of angioproliferative disease such as cancer and fibrosis. Antiproliferative properties of ADMA independent of NO have been identified in this context. In particular, the regulation of ADMA by its degrading enzyme dimethylarginine dimethylaminohydrolase (DDAH) is the object of many studies. DDAH is discussed as a promising therapeutic target for the indirect regulation of NO. In hypoxia-related chronic respiratory diseases, this controversy discussion of ADMA and DDAH is particularly evident and is therefore subject of this review.

Correlations of DDAH1 transcript variants with human endothelial asymmetric dimethylarginine metabolizing activity

BACKGROUND

Dimethylarginine dimethylaminohydrolases 1 (DDAH1) is the major enzyme responsible for inactivation of asymmetric dimethylarginine (ADMA). This study seeks to clarify the correlations between mRNA expression levels of DDAH1 transcript variants and the relationship with ADMA metabolizing activity in human.

METHODS

The mRNA expression levels of DDAH1 transcript variants in primarily cultured human umbilical vein endothelial cells (HUVECs) and peripheral blood mononuclear cells (PBMCs) from healthy control subjects and patients suffering from both acute ischemic stroke (AIS) and acute myocardial infarction (AMI) were determined by real-time polymerase chain reaction. ADMA metabolizing activity of the cell lysates from HUVECs was determined by enzyme-linked immunosorbent assay.

RESULTS

A novel DDAH1 transcript variant DDAH1-V3 was identified. DDAH1-V3 mRNA expression correlated significantly with that of both -V2 (R = 0.811; P = 0.000008) and -V1 (R = 0.454; P = 0.04) in HUVECs. In PBMCs from healthy subjects, significant correlation was observed only between DDAH1-V2 and -V3 (R = 0.571; P = 0.001; n = 36). Delta threshold cycle (DCT) values for both DDAH1-V2 and -V3 transcripts were increased significantly in PBMCs from AIS patients (P < 0.05, respectively). In PBMCs from patients suffering from both AIS and AMI, positive pairwise correlations between mRNA levels of DDAH1 transcripts were also observed as analyzed by partial correlation analysis (P < 0.05, respectively). However, only mRNA expression level of the DDAH1-V1 transcript correlated significantly with intracellular ADMA metabolizing activity in HUVECs (R = 0.805; P=0.002).

CONCLUSIONS

This study demonstrated that although there are positive correlations between mRNA expression levels of DDAH1 transcript variants, only the DDAH1-V1 transcript is responsible for ADMA metabolism, and transcript specific primers are recommended to determine DDAH1 mRNA expression.

Omega-3 Status and the Relationship between Plasma Asymmetric Dimethylarginine and Risk of Myocardial Infarction in Patients with Suspected Coronary Artery Disease

Background. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase. A previous rat study revealed an ADMA lowering effect following treatment with omega-3 polyunsaturated fatty acids (n-3 PUFAs). We sought to examine if an association between plasma ADMA and risk of acute myocardial infarction (AMI) was modified by serum n-3 PUFA status. Methods. The cohort included 1364 patients who underwent coronary angiography for suspected coronary artery disease in 2000-2001. Fatal and nonfatal AMI events were registered until December 31, 2006. Risk associations with AMI were estimated across ADMA quartiles (linear trend) and the upper decile. Results. No association between concentration of any n-3 PUFA and ADMA was observed. Only ADMA levels in upper decile were significantly associated with AMI with a multivariate adjusted hazard ratio (HR) (95% confidence interval) versus the rest of the population of 2.11 (1.34, 3.32). The association was strengthened among patients with below median levels of α-linolenic acid (ALA) (HR 3.12 (1.64, 5.93)), but was only influenced by longer chain n-3 PUFA after additional adjustments for HbA1c, estimated glomerular filtration rate, and hypercholesterolemia. Conclusions. The association of ADMA with risk of AMI is influenced by serum n-3 PUFA and particularly ALA.

Atorvastatin modulates the DDAH1/ADMA system in high-fat diet-induced insulin-resistant rats with endothelial dysfunction

Dimethylarginine dimethyl-aminohydrolase 1 (DDAH1) is a metabolic enzyme for asymmetric dimethylarginine (ADMA), both of which are closely related to endothelial function. Endothelial dysfunction, a main risk factor of cardiovascular diseases, can be attributed to insulin resistance. We aimed to determine the effects of atorvastatin, an endothelium-protective drug, on DDAH1/ADMA in insulin-resistant rats. Insulin resistance in male Sprague-Dawley rats was induced with a high-fat diet for 8 weeks. Some rats received atorvastatin (30 mg/kg/day) for an additional 8 weeks. Insulin-resistant rats exhibited not only decreases in the DDAH activity and aortic expression of DDAH1 and sterol regulatory element-binding protein 1 (SREBP1) but also increases in plasma ADMA levels, all of which were inhibited by atorvastatin. Insulin sensitivity and DDAH activity showed a significant positive correlation. In conclusion, our results suggest that atorvastatin may modulate DDAH1/ADMA to improve endothelial function in insulin-resistant rats; SREBP1 may also play a role in this.

Statins as anti-inflammatory agents in atherogenesis: molecular mechanisms and lessons from the recent clinical trials

Ample evidence exists in support of the potent anti-inflammatory properties of statins. In cell studies and animal models statins exert beneficial cardiovascular effects. By inhibiting intracellular isoprenoids formation, statins suppress vascular and myocardial inflammation, favorably modulate vascular and myocardial redox state and improve nitric oxide bioavailability. Randomized clinical trials have demonstrated that further to their lipid lowering effects, statins are useful in the primary and secondary prevention of coronary heart disease (CHD) due to their anti-inflammatory potential. The landmark JUPITER trial suggested that in subjects without CHD, suppression of low-grade inflammation by statins improves clinical outcome. However, recent trials have failed to document any clinical benefit with statins in high risk groups, such in heart failure or chronic kidney disease patients. In this review, we aim to summarize the existing evidence on statins as an anti-inflammatory agent in atherogenesis. We describe the molecular mechanisms responsible for the anti-inflammatory effects of statins, as well as clinical data on the non lipid-lowering, anti-inflammatory effects of statins on cardiovascular outcomes. Lastly, the controversy of the recent large randomized clinical trials and the issue of statin withdrawal are also discussed.

Effects of rosuvastatin on serum asymmetric dimethylarginine levels and atrial structural remodeling in atrial fibrillation dogs

BACKGROUND

Circulating asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, is increased in atrial fibrillation (AF). The purpose of this study was to investigate the effects of rosuvastatin on serum ADMA levels and atrial structural remodeling in AF dogs induced by chronic rapid atrial pacing.

METHODS

Twenty dogs were randomly divided into the sham-operated (n=6), control (n=7), or rosuvastatin (n=7) groups. Sustained AF was induced by rapid pacing of the right atrium at 400 beats per minute for 6 weeks. Rosuvastatin was administered orally (1 mg/kg d) for 3 days before rapid pacing and was continued for 6 weeks. Transthoracic and transesophageal echocardiography were performed to detect left atrial structure and function. Serum levels of nitric oxide and ADMA were measured. Interstitial fibrosis and cardiomyocyte apoptosis in the atria were also identified.

RESULTS

After 6 weeks, compared with the control group, dramatic smaller left atrium and left atrial appendage volumes and higher atrial contractile function were observed in the rosuvastatin group. Serum nitric oxide concentration was increased, whereas ADMA was decreased in the rosuvastatin group compared with the control group. The percentages of interstitial fibrosis and atrial apoptosis in the control group were significantly higher than those in the sham-operated group, and rosuvastatin attenuated these changes induced by atrial rapid pacing.

CONCLUSION

A short course of rosuvastatin treatment decreased apoptosis and prevented atrial structural remodeling in association with a decrease in ADMA levels in AF dogs.

Simvastatin inhibits goblet cell hyperplasia and lung arginase in a mouse model of allergic asthma: a novel treatment for airway remodeling?

Airway remodeling in asthma contributes to airway hyperreactivity, loss of lung function, and persistent symptoms. Current therapies do not adequately treat the structural airway changes associated with asthma. The statins are cholesterol-lowering drugs that inhibit the enzyme 3-hydroxy-3-methyl-glutaryl-CoA reductase, which is the rate-limiting step of cholesterol biosynthesis in the mevalonate (MA) pathway. These drugs have been associated with improved respiratory health, and ongoing clinical trials are testing their therapeutic potential in asthma. We hypothesized that simvastatin treatment of ovalbumin (OVA)-exposed mice would attenuate early features of airway remodeling by a mevalonate-dependent mechanism. BALB/c mice initially were sensitized to OVA and then exposed to 1% OVA aerosol for 2 weeks after sensitization for 6 exposures. Simvastatin (40 mg/kg) or simvastatin plus MA (20 mg/kg) were injected intraperitoneally before each OVA exposure. Treatment with simvastatin attenuated goblet cell hyperplasia, arginase-1 protein expression, and total arginase enzyme activity, but it did not alter airway hydroxyproline content or transforming growth factor-β1. Inhibition of goblet cell hyperplasia by simvastatin was mevalonate-dependent. No appreciable changes to airway smooth muscle cells were observed in any control or treatment groups. In conclusion, in an acute mouse model of allergic asthma, simvastatin inhibited early hallmarks of airway remodeling, which are indicators that can lead to airway thickening and fibrosis. Statins are potentially novel treatments for airway remodeling in asthma. Additional studies using subchronic or chronic allergen exposure models are needed to extend these initial findings.