Taurine protects against low-density lipoprotein-induced endothelial dysfunction by the DDAH/ADMA pathway

Taurine induces hormesis in multiple biological models: May have transformative implications for overall societal health

This paper represents the first integrative assessment and documentation of taurine-induced hormetic effects in the biological and biomedical areas, their dose response features, mechanistic frameworks, and possible public health, therapeutic and commercial applications. Taurine-induced hormetic effects are documented in a wide range of experimental models, cell types and for numerous biological endpoints, with most of these experimental findings being reported within the past five years. It is suggested that the concept of hormesis may have a transformative effect on taurine research and its public health and therapeutic applications.

Altered behavior, brain structure, and neurometabolites in a rat model of autism-specific maternal autoantibody exposure

Maternal immune dysregulation is a prenatal risk factor for autism spectrum disorder (ASD). Importantly, a clinically relevant connection exists between inflammation and metabolic stress that can result in aberrant cytokine signaling and autoimmunity. In this study we examined the potential for maternal autoantibodies (aAbs) to disrupt metabolic signaling and induce neuroanatomical changes in the brains of exposed offspring. To accomplish this, we developed a model of maternal aAb exposure in rats based on the clinical phenomenon of maternal autoantibody-related ASD (MAR-ASD). Following confirmation of aAb production in rat dams and antigen-specific immunoglobulin G (IgG) transfer to offspring, we assessed offspring behavior and brain structure longitudinally. MAR-ASD rat offspring displayed a reduction in pup ultrasonic vocalizations and a pronounced deficit in social play behavior when allowed to freely interact with a novel partner. Additionally, longitudinal in vivo structural magnetic resonance imaging (sMRI) at postnatal day 30 (PND30) and PND70, conducted in a separate cohort of animals, revealed sex-specific differences in total and regional brain volume. Treatment-specific effects by region appeared to converge on midbrain and cerebellar structures in MAR-ASD offspring. Simultaneously, in vivo 1H magnetic resonance spectroscopy (1H-MRS) data were collected to examine brain metabolite levels in the medial prefrontal cortex. Results showed that MAR-ASD offspring displayed decreased levels of choline-containing compounds and glutathione, accompanied by increased taurine compared to control animals. Overall, we found that rats exposed to MAR-ASD aAbs present with alterations in behavior, brain structure, and neurometabolites; reminiscent of findings observed in clinical ASD.

Investigation Covering the Effect of Boron plus Taurine Application on Protein Carbonyl and Advanced Oxidation Protein Products Levels in Experimental Alzheimer Model

Alzheimer's disease (AD) is the most common form of dementia that occurs in the brain. This is a chronic neurodegenerative disease which is valid in 60-70% of all dementia patients. Boron, regarded as a potential antioxidant, has the effect of reducing oxidative stress. Taurine, as one of the thiol-containing amino acids, exists at different concentrations in both the neurons and glial cells of the central nervous system. It plays an important role in the protective and adjuvant therapies as an antioxidant due to its characteristics of maintaining the oxidant-antioxidant balance of the body as well as cell integrity and increasing body resistance. Based on this information, our objective was to reveal the effect of boron alone, taurine alone plus co-administration of taurine and boron application on brain tissue protein carbonyls (PC) and serum advanced oxidation protein products (AOPP) levels in the experimental Alzheimer's model. For this purpose, 5 groups were formed in our study which consisted of 30 Wistar albino male rats. The rats were given a single dose of STZ stereotaxically. At the end of this period, the rats were decapitated, plus their brain tissues and blood were removed. Our findings suggested that taurine alone and co-administration of boron and taurine had a decreasing effect on AOPP and PC levels of the experimental Alzheimer model of the rats.

Sex Differences in X-ray-Induced Endothelial Damage: Effect of Taurine and N-Acetylcysteine

Ionizing radiation (IR) can induce some associated pathological conditions due to numerous cell damages. The influence of sex is scarcely known, and even less known is whether the effect of antioxidants is sex-dependent. Given the increased use of IR, we investigated whether male human umbilical vein endothelial cells (MHUVECs) and female human umbilical vein endothelial cells (FHUVECs) respond differently to IR exposure and whether the antioxidants 10 mM taurine (TAU) and 5 mM N-acetylcysteine (NAC) can prevent IR-induced damage in a sex-dependent way. In untreated cells, sex differences were observed only during autophagy, which was higher in FHUVECs. In non-irradiated cells, preincubation with TAU and NAC did not modify viability, lactate dehydrogenase (LDH) release, migration, or autophagy, whereas only NAC increased malondialdehyde (MDA) levels in FHUVECs. X-ray irradiation increased LDH release and reduced viability and migration in a sex-independent manner. TAU and NAC did not affect viability while reduced LDH release in irradiated cells: they have the same protective effect in FHUVECs, while, TAU was more protective than NAC in male cells.. Moreover, TAU and NAC significantly promoted the closure of wounds in both sexes in irradiated cells, but NAC was more effective at doing this in FHUVECs. In irradiated cells, TAU did not change autophagy, while NAC attenuated the differences between the sexes. Finally, NAC significantly decreased MDA in MHUVECs and increased MDA in FHUVECs. In conclusion, FHUVECs appear to be more susceptible to IR damage, and the effects of the two antioxidants present some sex differences, suggesting the need to study the influence of sex in radiation mitigators.

Research progress in endothelial cell injury and repair

Endothelial cells, which are important metabolic and endocrine cells, play an important role in regulating vascular function. The occurrence and development of various cardiovascular and cerebrovascular diseases are associated with endothelial dysfunction. However, the underlying mechanism of vascular endothelial injury is not fully understood. It has been reported that the mechanism of endothelial injury mainly involves inflammation and oxidative stress. Moreover, endothelial progenitor cells are regarded as important contributors in repairing damaged endothelium. Multiple interventions (including chemical drugs and traditional Chinese medicines) exert endothelial protection by decreasing the release of inducing factors, suppressing inflammation and oxidative stress, and preventing endothelial cell senescence.

Taurine and Its Derivatives: Analysis of the Inhibitory Effect on Platelet Function and Their Antithrombotic Potential

Taurine is a semi-essential, the most abundant free amino acid in the human body, with a six times higher concentration in platelets than any other amino acid. It is highly beneficial for the organism, has many therapeutic actions, and is currently approved for heart failure treatment in Japan. Taurine has been repeatedly reported to elicit an inhibitory action on platelet activation and aggregation, sustained by in vivo, ex vivo, and in vitro animal and human studies. Taurine showed effectiveness in several pathologies involving thrombotic diathesis, such as diabetes, traumatic brain injury, acute ischemic stroke, and others. As human prospective studies on thrombosis outcome are very difficult to carry out, there is an obvious need to validate existing findings, and bring new compelling data about the mechanisms underlying taurine and derivatives antiplatelet action and their antithrombotic potential. Chloramine derivatives of taurine proved a higher stability and pronounced selectivity for platelet receptors, raising the assumption that they could represent future potential antithrombotic agents. Considering that taurine and its analogues display permissible side effects, along with the need of finding new, alternative antithrombotic drugs with minimal side effects and long-term action, the potential clinical relevance of this fascinating nutrient and its derivatives requires further consideration.

Potential Antihypertensive Mechanisms of the Egg White-Derived Peptide QIGLF in Spontaneously Hypertensive Rats Revealed Using Untargeted Serum Metabolomics

The angiotensin-converting enzyme (ACE) inhibitory peptide QIGLF derived from egg white was shown to have significant in vivo antihypertensive effects in our previous study, but the intervention mechanisms at the metabolic level are still unclear. The UPLC-QTOF/MS-based untargeted metabolomics approach was used to clarify the potential antihypertensive mechanisms of QIGLF in the serum of spontaneously hypertensive rats (SHRs). Multivariate statistical analysis showed a clear difference in the metabolite profiles between the QIGLF and model groups. The results suggested that eight potential biomarkers were identified, that is, adrenic acid, ursodeoxycholic acid, glycocholic acid, taurocholic acid, tryptophan, acetylindoxyl, tyrosine, and 2-phenylethanol, which were mainly involved in aromatic amino acid biosynthesis and metabolism, biosynthesis of bile acid, and biosynthesis of unsaturated fatty acids. QIGLF might exert antihypertensive effects by improving endothelial dysfunction. This study provides a theoretical basis for future research and application of ACE inhibitory peptides in the prevention and improvement of hypertension.

Alterations to the urinary metabolome following semi-controlled short exposures to ultrafine particles at a major airport

BACKGROUND

Inflammation, oxidative stress and reduced cardiopulmonary function following exposure to ultrafine particles (UFP) from airports has been reported but the biological pathways underlying these toxicological endpoints remain to be explored. Urinary metabolomics offers a robust method by which changes in cellular pathway activity can be characterised following environmental exposures.

OBJECTIVE

We assessed the impact of short-term exposures to UFP from different sources at a major airport on the human urinary metabolome.

METHODS

21 healthy, non-smoking volunteers (aged 19-27 years) were repeatedly (2-5 visits) exposed for 5h to ambient air at Amsterdam Airport Schiphol, while performing intermittent, moderate exercise. Pre- to-post exposure changes in urinary metabolite concentrations were assessed via 1H NMR spectroscopy and related to total and source-specific particle number concentrations (PNC) using linear mixed effects models.

RESULTS

Total PNC at the exposure site was on average, 53,500 particles/cm3 (range 10,500-173,200) and associated with significant reductions in urinary taurine (-0.262 AU, 95% CI: -0.507 to -0.020) and dimethylamine concentrations (-0.021 AU, 95% CI: -0.040 to -0.067). Aviation UFP exposure accounted for these changes, with the reductions in taurine and dimethylamine associating with UFP produced during both aircraft landing and take-off. Significant reductions in pyroglutamate concentration were also associated with aviation UFP specifically, (-0.005 AU, 95% CI: -0.010 - <0.000) again, with contributions from both landing and take-off UFP exposure. While non-aviation UFPs induced small changes to the urinary metabolome, their effects did not significantly impact the overall response to airport UFP exposure.

DISCUSSION

Following short-term exposures at a major airport, aviation-related UFP caused the greatest changes to the urinary metabolome. These were consistent with a heightened antioxidant response and altered nitric oxide synthesis. Although some of these responses could be adaptive, they appeared after short-term exposures in healthy adults. Further study is required to determine whether long-term exposures induce injurious effects.

Protective role of taurine against oxidative stress (Review)

Taurine is a fundamental mediator of homeostasis that exerts multiple roles to confer protection against oxidant stress. The development of hypertension, muscle/neuro‑​associated disorders, hepatic cirrhosis, cardiac dysfunction and ischemia/reperfusion are examples of some injuries that are linked with oxidative stress. The present review gives a comprehensive description of all the underlying mechanisms of taurine, with the aim to explain its anti‑oxidant actions. Taurine is regarded as a cytoprotective molecule due to its ability to sustain normal electron transport chain, maintain glutathione stores, upregulate anti‑oxidant responses, increase membrane stability, eliminate inflammation and prevent calcium accumulation. In parallel, the synergistic effect of taurine with other potential therapeutic modalities in multiple disorders are highlighted. Apart from the results derived from research findings, the current review bridges the gap between bench and bedside, providing mechanistic insights into the biological activity of taurine that supports its potential therapeutic efficacy in clinic. In the future, further clinical studies are required to support the ameliorative effect of taurine against oxidative stress.

Taurine Augments Telomerase Activity and Promotes Chondrogenesis in Dental Pulp Stem Cells

Background: Stem cell therapy has become an advanced and state-of-the-art procedure to regenerate lost tissues of the human body. Cartilage repair is a challenging task in which stem cells find potential application. One of the important biologic modifiers that can cause chondrogenic differentiation of stem cells is taurine. However, taurine has not been investigated for its effects on dental pulp derived stem cell (DPSC) chondrogenic differentiation. Objective: The objective of the study was to investigate if taurine administration to DPSCs heralds chondrogenic differentiation as ascertained by expression of SOX9, COL2A1, ACAN, ELN, and COMP. The study also investigated if the differentiated cells synthesized glycosaminoglycans, a marker of cartilage formation. The study also aimed to assess proliferative activity of the cells after taurine administration by measuring the hTERT gene and protein expression. Materials and methods: DPSCs were obtained from a molecular biology laboratory and characterization of stem cell markers was done by flow cytometry. The cells were subjected to a MTT assay using various concentrations of taurine. Following this, hTERT gene and protein estimation was done in the control, telomerase inhibitor treated DPSC (TI-III), 10 μM taurine treated DPSC, and TI-III + 10 μM taurine treated DPSCs. A polymerase chain reaction was done to assess gene expression of SOX9, COL2A1, ACAN, ELN, and COMP genes and glycosaminoglycans were estimated in control cells, Induced DPSCs, induced and TI-III treated DPSCs, and 10 μM taurine treated DPSCs. Results: DPSCs expressed CD73, CD90, and CD105 and did not express CD34, CD45, and HLA-DR, which demonstrated that they were mesenchymal stem cells. The MTT assay revealed that various concentrations of taurine did not affect the cell viability of DPSCs. A concentration of 10 μM of taurine was used for further assays. With regard to the hTERT gene and protein expression, the taurine treated cells expressed the highest levels that were statistically significant compared to the other groups. Taurine was also found to restore hTERT expression in telomerase inhibitor treated cells. With regard to chondrogenesis related genes, taurine administration significantly increased the expression of SOX9, COL2A1, ACAN, and ELN genes in DPSCs and caused a significant increase in glycosaminoglycan production by the cells. Conclusions: Taurine can be regarded a biologic modifier that can significantly augment chondrogenic differentiation of DPSCs and can find potential applications in regenerative medicine in the area of cartilage regeneration.

Sulfur-Containing Amino Acids and Lipid Metabolism

The metabolism of methionine and cysteine in the body tissues determines the concentrations of several metabolites with various biologic activities, including homocysteine, hydrogen sulfide (H2S), taurine, and glutathione. Hyperhomocysteinemia, which is correlated with lower HDL cholesterol in blood in volunteers and animal models, has been associated with an increased risk for cardiovascular diseases. In humans, the relation between methionine intake and hyperhomocysteinemia is dependent on vitamin status (vitamins B-6 and B-12 and folic acid) and on the supply of other amino acids. However, lowering homocysteinemia by itself is not sufficient for decreasing the risk of cardiovascular disease progression. Other compounds related to methionine metabolism have recently been identified as being involved in the risk of atherosclerosis and steatohepatitis. Indeed, the metabolism of sulfur amino acids has an impact on phosphatidylcholine (PC) metabolism, and anomalies in PC synthesis due to global hypomethylation have been associated with disturbances of lipid metabolism. In addition, impairment of H2S synthesis from cysteine favors atherosclerosis and steatosis in animal models. The effects of taurine on lipid metabolism appear heterogeneous depending on the populations of volunteers studied. A decrease in the concentration of intracellular glutathione, a tripeptide involved in redox homeostasis, is implicated in the etiology of cardiovascular diseases and steatosis. Last, supplementation with betaine, a compound that allows remethylation of homocysteine to methionine, decreases basal and methionine-stimulated homocysteinemia; however, it adversely increases plasma total and LDL cholesterol. The study of these metabolites may help determine the range of optimal and safe intakes of methionine and cysteine in dietary proteins and supplements. The amino acid requirement for protein synthesis in different situations and for optimal production of intracellular compounds involved in the regulation of lipid metabolism also needs to be considered for dietary attenuation of atherosclerosis and steatosis risk.

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.

Therapeutic role of taurine as antioxidant in reducing hypertension risks in rats

AIM

The current investigation focused on the therapeutic role of the administration of taurine on hypertensive rats to reduce or cure the hazard effects of hypertension problems.

METHODOLOGY

This research included 2 experiments; 1st was done to survey the variations that might occur in blood pressure (BP) of male rats because of the fed 8% NaCl diet for 4 weeks. 2nd experiment, it contains normal control rats', hypertensive rats were served as hypertension recovery group and hypertensive rats were took orally by the help of gastric tube 50 mg taurine/100 g b.wt/day for four weeks and served as taurine group.

RESULTS

1st experimental, clarified a significant elevation in BP, body weight, serum cholesterol, triglycerides, LDL, activities of serum cardiac enzymes, endothelin-1, ADMA, MDA and TNF-α in hypertensive rats' group. On contrary, there is a significant reduction in serum level of TNO and antioxidant enzymes level in relation to the control group. A numerical variation but not statistically significant was happened in HDL in hypertensive rats' group as compared to their matching results in control rats' group. 2nd experimental taurine significantly reduced the BP as compared with hypertensive control. Furthermore, a significant improvement occurred in the mean value of most investigation parameters in hypertensive animal group which treated with taurine.

CONCLUSION

The previous data could be concluded that, there is an obvious amelioration effects of taurine on hypertensive rats by reducing the hazard effects of hypertension problems. The primary mechanisms were discussed according to existing published investigations.

Modulation of endothelium-derived nitric oxide production and activity by taurine and taurine-conjugated bile acids

Taurine is a semiessential amino acid found at high concentrations in mammalian plasma and cells, where it regulates cellular functions such as ion flux, controls cell volume and serves as a substrate for conjugated bile acids (BAs). Exogenous administration of both taurine and taurine-conjugated BAs have also been implicated in the modulation of cardiovascular functions. This brief review summarizes the role of taurine and taurine-conjugated BAs in vascular relaxation through the modulation of endothelium-derived nitric oxide (NO). The effects of taurine on vascular health are controversial. However, in the presence of cardiometabolic risk factors, it has been proposed that taurine can increase vascular NO levels by increasing eNOS expression, eNOS phosphorylation on Ser1177, NO bioavailability, the level of antioxidative defense, and the l-arginine/NOS inhibitor asymmetric dimethylarginine (ADMA) ratio. The taurine-conjugated BA-mediated activation of Farnesoid X receptor (FXR), G protein-coupled BA receptor (TGR5) and/or muscarinic 3 receptor (M3) was also reported to increase vascular NO production. FXR activation increases eNOS expression and may reduce ADMA formation, while TGR5 increases mobilization of Ca²⁺ and phosphorylation of eNOS and Akt in endothelial cells. Furthermore, taurine and taurine-conjugated BAs might regulate NO synthesis and activity by enhancing H₂S generation. Several studies have demonstrated the beneficial effects of both taurine and taurine-conjugated BAs in reversing the endothelial dysfunction associated with diabetes, atherosclerosis, hypertension, obesity, malnutrition, and smoking. In addition, taurine-conjugated BAs have emerged as a potential treatment for portal hypertension. Despite these favorable findings, there is a need to further explore the mechanisms and signaling pathways underlying the endothelial effects of taurine and taurine-conjugated BAs. Here, we summarize the main findings regarding the effects of taurine and taurine-conjugated BAs on the endothelial dysfunction associated with altered NO metabolism in cardiovascular diseases.

Comparison of Mechanisms of Endothelial Cell Protections Between High-Density Lipoprotein and Apolipoprotein A-I Mimetic Peptide

Apolipoprotein A-I (apoA-I) mimetic peptide, D-4F, exhibits anti-atherogenic effects similar to high-density lipoprotein (HDL). However, it remains elusive whether D-4F and HDL share similar molecular mechanisms underlying anti-atherogenic effects and endothelial cell protections. We here compared the metabolic changes in endothelial cells induced by D-4F and HDL against oxidized low-density lipoprotein (ox-LDL), which may be of benefit to understanding the protective mechanisms of HDL and D-4F. Functional assays, including wound healing, transwell migration, and tube formation, were used to evaluate the pro-angiogenic effects of HDL and D-4F. NMR-based metabolomic analysis was employed to explore the protective mechanisms underlying HDL and D-4F. Partial least-squares discriminant analysis (PLS-DA) was performed to assess metabolic profiles, and orthogonal PLS-DA (OPLS-DA) was carried out to identify characteristic metabolites. Moreover, significantly altered metabolic pathways were also analyzed. We found that ox-LDL impaired the migration and tube formation of endothelial cells. Metabolomic analysis showed that ox-LDL triggered oxidative stress, impaired glycolysis, and enhanced glycerophospholipid metabolism. Both HDL and D-4F improved the migration and angiogenesis of endothelial cells, alleviated oxidative stress, and ameliorated disordered glycolysis impaired by ox-LDL. Strikingly, HDL partially attenuated the disturbed glycerophospholipid metabolism, whereas D-4F did not show this effect. In summary, although D-4F shared the similar protective effects with HDL on the migration and angiogenesis of endothelial cells, it could not deduce the molecular mechanisms of HDL completely. Nevertheless, D-4F possesses the potentiality to be exploited as clinically applicable agent for endothelial cell protection and cardiovascular disease treatment.

Dysregulation of Epigenetic Mechanisms of Gene Expression in the Pathologies of Hyperhomocysteinemia

Hyperhomocysteinemia (HHcy) exerts a wide range of biological effects and is associated with a number of diseases, including cardiovascular disease, dementia, neural tube defects, and cancer. Although mechanisms of HHcy toxicity are not fully uncovered, there has been a significant progress in their understanding. The picture emerging from the studies of homocysteine (Hcy) metabolism and pathophysiology is a complex one, as Hcy and its metabolites affect biomolecules and processes in a tissue- and sex-specific manner. Because of their connection to one carbon metabolism and editing mechanisms in protein biosynthesis, Hcy and its metabolites impair epigenetic control of gene expression mediated by DNA methylation, histone modifications, and non-coding RNA, which underlies the pathology of human disease. In this review we summarize the recent evidence showing that epigenetic dysregulation of gene expression, mediated by changes in DNA methylation and histone N-homocysteinylation, is a pathogenic consequence of HHcy in many human diseases. These findings provide new insights into the mechanisms of human disease induced by Hcy and its metabolites, and suggest therapeutic targets for the prevention and/or treatment.

Effects and Mechanisms of Taurine as a Therapeutic Agent

Taurine is an abundant, β-amino acid with diverse cytoprotective activity. In some species, taurine is an essential nutrient but in man it is considered a semi-essential nutrient, although cells lacking taurine show major pathology. These findings have spurred interest in the potential use of taurine as a therapeutic agent. The discovery that taurine is an effective therapy against congestive heart failure led to the study of taurine as a therapeutic agent against other disease conditions. Today, taurine has been approved for the treatment of congestive heart failure in Japan and shows promise in the treatment of several other diseases. The present review summarizes studies supporting a role of taurine in the treatment of diseases of muscle, the central nervous system, and the cardiovascular system. In addition, taurine is extremely effective in the treatment of the mitochondrial disease, mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), and offers a new approach for the treatment of metabolic diseases, such as diabetes, and inflammatory diseases, such as arthritis. The review also addresses the functions of taurine (regulation of antioxidation, energy metabolism, gene expression, ER stress, neuromodulation, quality control and calcium homeostasis) underlying these therapeutic actions.

Piper sarmentosum attenuates TNF-α-induced VCAM-1 and ICAM-1 expression in human umbilical vein endothelial cells

Objectives

Inflammation plays a key role in the pathogenesis of atherosclerosis. Piper sarmentosum is an herb with antioxidant and anti-atherosclerotic activities. The aim of this study was to evaluate the anti-inflammatory properties of an aqueous extract of P. sarmentosum (AEPS) in human umbilical vein endothelial cells (HUVECs).

Methods

HUVECs were divided into six groups: control, treatment with 10 ng/ml TNF-α, and co-treatment of 10 ng/ml TNF-α with four different concentrations of AEPS (100, 150, 250, and 300 μg/ml) for 24 h. Subsequently, vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) protein expression, U937 monocyte cells adhesion, and nuclear factor-kappaB (NF-κB) p65 expression in HUVECs were measured.

Results

Treatment of TNF-α-stimulated HUVECs with AEPS at different concentrations resulted in decreased VCAM-1 and ICAM-1 protein expression in a dose-dependent manner. Furthermore, AEPS also inhibited TNF-α-stimulated U937 monocyte cells adhesion to HUVECs. In addition, AEPS reduced TNF-α-induced NF-κB p65 expression in a dose-dependent manner.

Conclusions

The results indicated that AEPS suppressed TNF-α-induced VCAM-1 and ICAM-1 expression NF-κB signaling.

•

Piper sarmentosum attenuates VCAM-1 and ICAM-1 expression in TNF-α-induced HUVEC.

•

P. sarmentosum inhibits TNF-α-stimulated monocytes adhesion to HUVEC.

•

P. sarmentosum reduces TNF-α-induced NF-κB p65 expression in HUVEC.

Toxic Dimethylarginines: Asymmetric Dimethylarginine (ADMA) and Symmetric Dimethylarginine (SDMA)

Asymmetric and symmetric dimethylarginine (ADMA and SDMA, respectively) are toxic, non-proteinogenic amino acids formed by post-translational modification and are uremic toxins that inhibit nitric oxide (NO) production and play multifunctional roles in many human diseases. Both ADMA and SDMA have emerged as strong predictors of cardiovascular events and death in a range of illnesses. Major progress has been made in research on ADMA-lowering therapies in animal studies; however, further studies are required to fill the translational gap between animal models and clinical trials in order to treat human diseases related to elevated ADMA/SDMA levels. Here, we review the reported impacts of ADMA and SDMA on human health and disease, focusing on the synthesis and metabolism of ADMA and SDMA; the pathophysiological roles of these dimethylarginines; clinical conditions and animal models associated with elevated ADMA and SDMA levels; and potential therapies against ADMA and SDMA. There is currently no specific pharmacological therapy for lowering the levels and counteracting the deleterious effects of ADMA and SDMA. A better understanding of the mechanisms underlying the impact of ADMA and SDMA on a wide range of human diseases is essential to the development of specific therapies against diseases related to ADMA and SDMA.

Taurine Supplementation Lowers Blood Pressure and Improves Vascular Function in Prehypertension: Randomized, Double-Blind, Placebo-Controlled Study

Taurine, the most abundant, semiessential, sulfur-containing amino acid, is well known to lower blood pressure (BP) in hypertensive animal models. However, no rigorous clinical trial has validated whether this beneficial effect of taurine occurs in human hypertension or prehypertension, a key stage in the development of hypertension. In this randomized, double-blind, placebo-controlled study, we assessed the effects of taurine intervention on BP and vascular function in prehypertension. We randomly assigned 120 eligible prehypertensive individuals to receive either taurine supplementation (1.6 g per day) or a placebo for 12 weeks. Taurine supplementation significantly decreased the clinic and 24-hour ambulatory BPs, especially in those with high-normal BP. Mean clinic systolic BP reduction for taurine/placebo was 7.2/2.6 mm Hg, and diastolic BP was 4.7/1.3 mm Hg. Mean ambulatory systolic BP reduction for taurine/placebo was 3.8/0.3 mm Hg, and diastolic BP was 3.5/0.6 mm Hg. In addition, taurine supplementation significantly improved endothelium-dependent and endothelium-independent vasodilation and increased plasma H2S and taurine concentrations. Furthermore, changes in BP were negatively correlated with both the plasma H2S and taurine levels in taurine-treated prehypertensive individuals. To further elucidate the hypotensive mechanism, experimental studies were performed both in vivo and in vitro. The results showed that taurine treatment upregulated the expression of hydrogen sulfide-synthesizing enzymes and reduced agonist-induced vascular reactivity through the inhibition of transient receptor potential channel subtype 3-mediated calcium influx in human and mouse mesenteric arteries. In conclusion, the antihypertensive effect of chronic taurine supplementation shows promise in the treatment of prehypertension through improvement of vascular function.

Synthesis of Stilbene Derivatives: A Comparative Study of their Antioxidant Activities

A series of structurally simple compounds belonging to thestilbene family were synthesized by means of a Ti(III)-mediated methodology that allows access, in an efficient manner, to derivatives of dihydrostilbene, E-stilbene, and stilbene oxide, with high yields. The antioxidant activity of these compounds has been evaluated by means of two electrochemical assays, which provide complementary information, showing that the majority of these stilbene analogs exhibit significant antioxidant activity dependent on the electronic structure and functionalization of the molecule in each case.

Aerobic exercise training decreases plasma asymmetric dimethylarginine concentrations with increase in arterial compliance in postmenopausal women

BACKGROUND

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, increase with advancing age and menopausal status. ADMA plays a role in endothelial dysfunction and increasing arterial stiffness. Regular aerobic exercise has a positive effect on arterial function (i.e., arterial compliance). This study investigated the effects of aerobic exercise training on plasma ADMA concentrations and arterial compliance in postmenopausal women.

METHODS

Thirty postmenopausal women were divided into 2 groups: an exercise group (n = 20) and a control group (n = 10). Subjects in the exercise group completed 12 weeks of aerobic exercise training (65%-80% of maximal heart rate, 40-60 min/day, 3-6 days/week). Before and after each intervention, plasma ADMA concentrations and carotid arterial compliance were measured in all participants.

RESULTS

The baseline plasma ADMA concentrations, carotid arterial compliance, and most other key dependent variables did not differ between the 2 groups. In the exercise group, carotid arterial compliance significantly increased after exercise intervention (P < 0.01), and plasma ADMA concentrations significantly decreased (P < 0.05). In addition, changes in carotid arterial compliance after the exercise intervention were inversely correlated with changes in plasma ADMA concentrations (r = -0.367; P < 0.05).

CONCLUSIONS

We demonstrated that aerobic exercise training significantly decreased plasma ADMA concentrations with increase in carotid arterial compliance in postmenopausal women. These results suggest that reduction in ADMA may play an important role in the aerobic exercise training-induced increase in arterial compliance.

Nutraceutical strategies for ameliorating the toxic effects of alcohol

Rodent studies reveal that oxidative stress, much of it generated via induction/activation of NADPH oxidase, is a key mediator of a number of the pathogenic effects of chronic ethanol overconsumption. The highly reactive ethanol metabolite acetaldehyde is a key driver of this oxidative stress, and doubtless works in other ways to promote alcohol-induced pathology. Effective antioxidant measure may therefore be useful for mitigating the adverse health consequences of alcohol consumption; spirulina may have particular utility in this regard, as its chief phycochemical phycocyanobilin has recently been shown to function as an inhibitor of certain NADPH oxidase complexes, mimicking the physiological role of its chemical relatives biliverdin/bilirubin in this respect. Moreover, certain nutraceuticals, including taurine, pantethine, and lipoic acid, may have the potential to boost the activity of the mitochondrial isoform of aldehyde dehydrogenase, ALDH-2, accelerating conversion of acetaldehyde to acetate (which arguably has protective health effects). Little noticed clinical studies conducted nearly three decades ago reported that pre-ingestion of either taurine or pantethine could blunt the rise in blood acetaldehyde following ethanol consumption. Other evidence suggests that lipoic acid may function within mitochondria to maintain aldehyde dehydrogenase in a reduced active conformation; the impact of this agent on ethanol metabolism has however received little or no study. Studies evaluating the impact of nutracetical strategies on prevention of hangovers - which likely are mediated by acetaldehyde - may represent a quick, low-cost way to identify nutraceutical regimens that merit further attention for their potential impact on alcohol-induced pathology. Measures which boost or preserve ALDH-2 activity may also have important antioxidant potential, as this enzyme functions physiologically to protect cells from toxic aldehydes generated by oxidant stress.

Transsulfuration pathway thiols and methylated arginines: the Hunter Community Study

Background

Serum homocysteine, when studied singly, has been reported to be positively associated both with the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine [ADMA, via inhibition of dimethylarginine dimethylaminohydrolase (DDAH) activity] and with symmetric dimethylarginine (SDMA). We investigated combined associations between transsulfuration pathway thiols, including homocysteine, and serum ADMA and SDMA concentrations at population level.

Methods

Data on clinical and demographic characteristics, medication exposure, C-reactive protein, serum ADMA and SDMA (LC-MS/MS), and thiols (homocysteine, cysteine, taurine, glutamylcysteine, total glutathione, and cysteinylglycine; capillary electrophoresis) were collected from a sample of the Hunter Community Study on human ageing [n = 498, median age (IQR) = 64 (60–70) years].

Results

Regression analysis showed that: a) age (P = 0.001), gender (P = 0.03), lower estimated glomerular filtration rate (eGFR, P = 0.08), body mass index (P = 0.008), treatment with beta-blockers (P = 0.03), homocysteine (P = 0.02), and glutamylcysteine (P = 0.003) were independently associated with higher ADMA concentrations; and b) age (P = 0.001), absence of diabetes (P = 0.001), lower body mass index (P = 0.01), lower eGFR (P<0.001), cysteine (P = 0.007), and glutamylcysteine (P<0.001) were independently associated with higher SDMA concentrations. No significant associations were observed between methylated arginines and either glutathione or taurine concentrations.

Conclusions

After adjusting for clinical, demographic, biochemical, and pharmacological confounders the combined assessment of transsulfuration pathway thiols shows that glutamylcysteine has the strongest and positive independent associations with ADMA and SDMA. Whether this reflects a direct effect of glutamylcysteine on DDAH activity (for ADMA) and/or cationic amino acid transport requires further investigations.

Vaspin increases nitric oxide bioavailability through the reduction of asymmetric dimethylarginine in vascular endothelial cells

Vaspin is an adipocytokine recently identified in the visceral adipose tissue of diabetic rats and having anti-diabetic effects. We have recently shown that vaspin has anti-atherogenic effect through Akt-mediated inhibition of endothelial cell apoptosis. Decreased activity of endothelial nitric oxide synthase (eNOS) plays an important role in the pathogenesis of atherosclerosis. Asymmetric dimethylarginine (ADMA) is a well-known endogenous competitive inhibitor of eNOS and risk factor of cardiovascular diseases. The aim of this study was to examine whether vaspin might protect against atherosclerosis through its beneficial effects on the ADMA-eNOS system. Treatment of vaspin significantly increased NO secretion from endothelial cells and isolated aorta from Sprague-Dawley (SD) rats. Furthermore, treatment of vaspin prevented fatty acid-induced decrease in endothelium-dependent vasorelaxation in isolated aorta of SD rat. For the mechanism of vaspin-induced NO biosynthesis, vaspin activated the STAT3 signaling pathway and stimulated eNOS phosphorylation (Ser 1177), a marker of eNOS activation, through STAT3-dependent mechanism. Furthermore, vaspin treatment increased the expression of dimethylarginine dimethylaminohydrolase (DDAH) II, the responsible enzyme for the degradation of ADMA, leading to a reduction in ADMA levels. Vaspin-induced increase in DDAH II gene expression was through STAT3-mediated stimulation of DDAH II promoter activity. These results suggest that vaspin increases eNOS activity by reducing ADMA level through STAT3-mediated regulation of DDAH II expression. Our findings provide a novel molecular mechanism of antiatherogenic actions of vaspin.

Taurine and atherosclerosis

Taurine is abundantly present in most mammalian tissues and plays a role in many important physiological functions. Atherosclerosis is the underlying mechanism of cardiovascular disease including myocardial infarctions, strokes and peripheral artery disease and remains a major cause of morbidity and mortality worldwide. Studies conducted in laboratory animal models using both genetic and dietary models of hyperlipidemia have demonstrated that taurine supplementation retards the initiation and progression of atherosclerosis. Epidemiological studies have also suggested that taurine exerts preventive effects on cardiovascular diseases. The present review focuses on the effects of taurine on the pathogenesis of atherosclerosis. In addition, the potential mechanisms by which taurine suppress the development of atherosclerosis will be discussed.

The natural antioxidants, pomegranate extract and soy isoflavones, favourably modulate canine endothelial cell function

Cardiovascular disease, preceded by vascular endothelial dysfunction, is a prominent cause of death in dogs. L-carnitine and taurine, well known for their antioxidative capacity, beneficially affect cardiovascular disease as well as certain dog cardiomyopathies. It is well established that vascular endothelial dysfunction precedes cardiovascular disease and that “vasoprotective factors” (NO and antioxidants) prevent apoptosis, whereas “risk factors” such as oxidized LDL, hyperglycemia, and free fatty acids trigger it in cultured human vascular endothelial cells. Whereas human vascular cell in vitro models are widely established and used for the characterisation of potential vasoprotective substances, such models are not available for canine endothelial cells. In the present study we therefore developed an in vitro model, which allows the testing of the effects of different substances on proliferation and apoptosis in canine aortic endothelial cells. This model was used to test L-carnitine, taurine, pomegranate extract, and Soy Isoflavones in comparison to reference substances (glutathione and pioglitazone) previously shown to modulate human endothelial cell function. L-carnitine and taurine neither exhibited antiproliferative nor antiapoptotic activities in the context of this study. However extracts from pomegranate and soy isoflavones dramatically reduced proliferation and apoptosis in a dose dependent fashion, being in line with a vasoprotective activity in dogs.

Serum taurine and risk of coronary heart disease: a prospective, nested case-control study

PURPOSE

Taurine (2-aminoethanesulfonic acid), a molecule obtained from diet, is involved in bile acid conjugation, blood pressure regulation, anti-oxidation and anti-inflammation. We performed the first prospective study of taurine and CHD risk.

METHODS

We conducted a case-control study nested in the New York University Women's Health Study to evaluate the association between circulating taurine levels and risk of coronary heart disease (CHD). Taurine was measured in two yearly pre-diagnostic serum samples of 223 CHD cases and 223 matched controls and averaged for a more reliable measurement of long-term taurine levels.

RESULTS

Mean serum taurine was positively related to age and dietary intake of poultry, niacin, vitamin B1, fiber and iron, and negatively related to dietary intake of saturated fat (all p values ≤ 0.05). There was no statistically significant association between serum taurine levels and the risk of CHD in the overall study population. The adjusted ORs for CHD in increasing taurine tertiles were 1.0 (reference), 0.85 (95% CI, 0.51-1.40) and 0.66 (0.39-1.13; p for trend = 0.14). There was a significant inverse association between serum taurine and CHD risk among women with high total serum cholesterol (>250 mg/dL) (adjusted OR = 0.39 (0.19-0.83) for the third versus first tertile; p for trend = 0.02) but not among those with low total serum cholesterol (p for interaction = 0.01). The data suggest a possible inverse association of serum taurine with diabetes and hypertension risk.

CONCLUSIONS

The findings suggest that high levels of taurine may be protective against CHD among individuals with high serum cholesterol levels.

Increased asymmetric dimethylarginine (ADMA) dimethylaminohydrolase (DDAH) activity in childhood hypercholesterolemia type II

Asymmetric dimethylarginine (ADMA) systemic concentrations are elevated in hypercholesterolemic adults and contribute to nitric oxide (NO) dependent endothelial dysfunction. Decreased activity of the key ADMA-hydrolyzing enzyme dimethylarginine dimethylaminohydrolase (DDAH) may be involved. Yet, the ADMA/DDAH/NO pathway has not been investigated in childhood hypercholesterolemia. We studied 64 children with hypercholesterolemia type II (HCh-II) and 54 normocholesterolemic (NCh) children (mean ± SD; age, years: 11.1 ± 3.5 vs. 11.9 ± 4.6). Plasma and urine ADMA was measured by GC-MS/MS. Dimethylamine (DMA), the ADMA metabolite, creatinine, nitrite and nitrate in urine were measured by GC-MS. The DMA/ADMA molar ratio in urine was calculated to estimate whole body DDAH activity. ADMA plasma concentration (mean ± SD; nM: 571 ± 85 vs. 542 ± 110, P = 0.17) and ADMA urinary excretion rate (mean ± SD: 7.1 ± 2 versus 7.2 ± 3 μmol/mmol creatinine, P = 0.6) were similar in HCh-II and NCh children. Both DMA excretion rate [median (25th-75th percentile): 56.3 (46.4-109.1) vs. 45.2 (22.2-65.5) μmol/mmol creatinine, P = 0.0004] and DMA/ADMA molar ratio [median (25th-75th percentile): 9.2 (6.0-16.3) vs. 5.4 (3.8-9.4), P = 0.0004] were slightly but statistically significantly increased in HCh-II children compared to NCh children. Plasma and urinary nitrite and nitrate were similar in both groups. In HCh-II whole body DDAH activity is elevated as compared to NCh. HCh-II children treated with drugs for hypercholesterolemia had lower plasma ADMA levels than untreated HCh-II or NCh children, presumably via increased DDAH activity. Differences between treated and untreated HCh-II children were not due to differences in age. In conclusion, HCh-II children do not have elevated ADMA plasma levels, largely due to an apparent increase in DDAH activity. While this would tend to limit development of endothelial dysfunction, it is not clear whether this might be medication-induced or represent a primary change in HCh-II children.

Protective effect of neferine on endothelial cell nitric oxide production induced by lysophosphatidylcholine: the role of the DDAH–ADMA pathway

Neferine, extracted from the seed embryo of Nelumbo nucifera Gaertn., has multiple cardiovascular pharmacological effects. The dimethylarginine dimethylaminohydrolase (DDAH) – asymmetric dimethylarginine (ADMA) system is a novel pathway for modulating nitric oxide (NO) production. The aim of this study was to investigate whether the protective effect of neferine on endothelial NO production was related to the DDAH–ADMA pathway. Human umbilical vein endothelial cells (HUVECs) were first exposed to neferine (0.1, 1.0, or 10.0 μmol/L) for 1 h, and then incubated with lysophosphatidylcholine (LPC; 10 μg/mL) in the presence of neferine for 24 h. The medium was collected for measuring the levels of NO, maleic dialdehyde (MDA), as well as ADMA. The endothelial cells were collected for measuring DDAH activity and the level of reactive oxygen species (ROS). LPC significantly decreased NO concentration and DDAH activity and increased the levels of ADMA, ROS, and MDA. Neferine could partially counteract the changes induced by LPC. These findings suggested that neferine could modulate the DDAH–ADMA pathway via its antioxidant properties, which was involved in its beneficial effect on endothelial NO production.

Alpha-lipoic acid activates dimethylarginine dimethylaminohydrolase in cultured endothelial cells

Asymmetric dimethylarginine (ADMA) is a risk factor of cardiovascular diseases. alpha-Lipoic acid (ALA) was shown to improve vascular dysfunction, and to decrease plasma ADMA level. In this study, we investigated whether ALA activates dimethylarginine dimethylaminohydrolase (DDAH), the metabolizing enzyme of ADMA, in cultured endothelial cells. ALA significantly decreased ADMA level in culture media of endothelial cells. ALA increased the gene expression and activity of DDAH, and signal transducer and activator of transcription (STAT)3 phosphorylation. Transfection of STAT3 increased DDAH II promoter activity, and ALA amplified it. ALA-induced increase in DDAH II promoter activity was attenuated in the promoter that had mutation in putative STAT3-binding site. These results suggest that ALA reduces ADMA level by enhancing DDAH activity and DDAH II gene expression, thus providing a novel mechanism by which ALA regulates endothelial function.

Loss of ability to self-heal malaria upon taurine transporter deletion

Deletion of the taurine transporter gene (taut) results in lowered levels of taurine, the most abundant amino acid in mammals. Here, we show that taut-/- mice have lost their ability to self-heal blood-stage infections with Plasmodium chabaudi malaria. All taut-/- mice succumb to infections during crisis, while about 90% of the control taut(+/+) mice survive. The latter retain unchanged taurine levels even at peak parasitemia. Deletion of taut, however, results in the lowering of circulating taurine levels from 540 to 264 micromol/liter, and infections cause additional lowering to 192 micromol/liter. Peak parasitemia levels in taut-/- mice are approximately 60% higher than those in taut(+/+) mice, an elevation that is associated with increased systemic tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) levels, as well as with liver injuries. The latter manifest as increased systemic ammonia levels, a perturbed capacity to entrap injected particles, and increased expression of genes encoding TNF-alpha, IL-1beta, IL-6, inducible nitric oxide synthase (iNOS), NF-kappaB, and vitamin D receptor (VDR). Autopsy reveals multiorgan failure as the cause of death for malaria-infected taut-/- mice. Our data indicate that taut-controlled taurine homeostasis is essential for resistance to P. chabaudi malaria. Taurine deficiency due to taut deletion, however, impairs the eryptosis of P. chabaudi-parasitized erythrocytes and expedites increases in systemic TNF-alpha, IL-1beta, and ammonia levels, presumably contributing to multiorgan failure in P. chabaudi-infected taut-/- mice.

Asymmetric dimethylarginine association with antioxidants intake in healthy young adults: a role as an indicator of metabolic syndrome features

The purpose of this study was to evaluate the potential associations between serum asymmetric dimethylarginine (ADMA) and several anthropometric, biochemical, and lifestyle features in healthy young adults, emphasizing on the putative effects of the antioxidant intake on ADMA concentrations. Anthropometric and blood pressure measurements as well as lifestyle features and antioxidant intake were analyzed in 93 healthy young adults aged 18 to 34 years. Fasting blood samples were collected for the measurement of glucose, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triacylglycerols, and ADMA concentrations, as well as erythrocyte glutathione peroxidase activity. Nail samples were collected for the analysis of selenium and zinc concentrations. Values of body mass index (P = .004), waist circumference (P = .008), waist-to-height ratio (P = .046), systolic blood pressure (P < .001), serum glucose (P < .001), and nail selenium (P = .004) and zinc (P = .018) were significantly different between subjects with serum ADMA higher and lower than the median (cutoff, 458 nmol/L). Furthermore, ADMA showed a positive association with several adiposity markers such as body weight (P < .001), body mass index (P < .001), waist circumference (P = .006), waist-to-height ratio (P = .020), body fat mass (P = .001), systolic blood pressure (P = .001), and serum glucose (P < .001), whereas erythrocyte glutathione peroxidase activity (P = .021) and nail selenium (P = .040) and zinc values (P = .013) were statistically significant negative predictors of ADMA concentrations. In conclusion, ADMA seems to be related with selenium and zinc status and several anthropometric and biochemical measurements linked to metabolic syndrome in apparently healthy young adults. These findings support a role for antioxidant/trace element intake in the modulation of ADMA, whose assessment may be a marker of metabolic syndrome manifestations.

Dimethylarginine dimethylaminohydrolase regulation: a novel therapeutic target in cardiovascular disease

Asymmetric dimethylarginine (ADMA), an endogenous methylated form of the amino acid L-arginine, inhibits the activity of the enzyme endothelial nitric oxide synthase, with consequent reduced synthesis of nitric oxide. ADMA is metabolised to L-citrulline and dimethylamine by the enzyme dimethylarginine dimethylaminohydrolase (DDAH). The modulation of DDAH activity and expression plays a pivotal role in regulating intracellular ADMA concentrations, with important effects on vascular homeostasis. For example, impairment in DDAH activity, resulting in elevated ADMA concentrations and reduced nitric oxide synthesis, can promote the onset and progression of atherosclerosis in experimental models. This review discusses the current role of ADMA and DDAH in vascular health and disease, the techniques used to assess DDAH activity and expression, and the results of recent studies on pharmacological and biological agents modulating DDAH activity and expression. Suggestions for future basic and clinical research directions are also discussed.

High dietary taurine reduces apoptosis and atherosclerosis in the left main coronary artery: association with reduced CCAAT/enhancer binding protein homologous protein and total plasma homocysteine but not lipidemia

We sought to determine whether taurine could specifically protect against coronary artery disease during an atherogenic diet and whether taurine affects the lipid profile, metabolites of methionine, and endothelial atherogenic systems. Rabbits were fed one of the following diets for 4 weeks: (1) control diet; (2) 0.5% cholesterol+1.0% methionine; or (3) 0.5% cholesterol+1.0% methionine+2.5% taurine. Endothelial function was examined, and the left main coronary artery atherosclerosis was quantified by stereology and semiquantitative immunohistochemistry to determine the endothelial expression of proteins related to the NO, renin-angiotensin, endoplasmic reticulum, and oxidative stress systems, as well as apoptosis. Taurine normalized hyperhomocysteinemia (P<0.05) and significantly reduced hypermethioninemia (P<0.05) but not lipidemia. The intima:media ratio was reduced by 28% (P=0.034), and atherosclerosis was reduced by 64% (P=0.012) and endothelial cell apoptosis by 30% (P<0.01). Endothelial cell CCAAT/enhancer binding protein homologous protein was normalized (P<0.05). Taurine failed to improve hyperlipidemia, endothelial function, or endothelial proteins related to the NO, renin-angiotensin, and oxidative stress systems. Taurine reduces left main coronary artery wall pathology associated with decreased plasma total homocysteine, methionine, apoptosis, and normalization of CCAAT/enhancer binding protein homologous protein. These results elucidate the antiapoptotic and antiatherogenic properties of taurine, possibly via normalization of endoplasmic reticulum stress.

The aggravatory effect of nicotine on Helicobacter pylori-induced gastric mucosa injury: role of asymmetric dimethylarginine

BACKGROUND AND GOAL

Nitric oxide (NO) is a well-known gastric mucosa protection factor. Recently, it has been reported that methylated arginine compound such as asymmetric dimethylarginine (ADMA), which inhibits nitric oxide synthesis, may be related to the development of gastric mucosa injury in patients with Helicobacter pylori infection. In the present study, we tested the relationship between endogenous ADMA and gastric mucosa injury in H. pylor- infected patients and cultured gastric epithelial cells.

METHODS

One hundred and fifty subjects with gastric diseases were entered in this study. The levels of ADMA in gastric juice and plasma were measured in both H. pylori+ and H. pylori- patients. We analyzed independent risk factors that contribute to ADMA levels by multiple linear regression analyses. Mucosal epithelium cells were treated with nicotine (10 microM) for 24 hours in the presence or absence of H. pylori. The concentrations of ADMA in the culture medium and the rate of cell apoptosis were determined.

RESULTS

The ADMA level in gastric juice was significantly increased in H. pylori+ patients (P<0.05), whereas there were no differences in the content of ADMA in the plasma between H. pylori+ patients and H. pylori- patients. Smoking and H. pylori infection were 2 independent risk factors contributing to ADMA levels, and in the population of H. pylori+ patients, the level of ADMA in smokers was higher compared with nonsmokers. Incubation of nicotine (10 microM) with epithelial cells for 24 hours further increased the elevated level of ADMA and the rate of cell apoptosis owing to H. pylori infection.

CONCLUSIONS

H. pylori infection caused an increase of ADMA levels in gastric juice, which was aggravated by smoking. Endogenous ADMA may be an important factor contributing to gastric mucosa injury.

The prominent role of the liver in the elimination of asymmetric dimethylarginine (ADMA) and the consequences of impaired hepatic function

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS), the enzyme which converts the amino acid arginine into nitric oxide (NO). ADMA has been identified as an important risk factor for cardiovascular diseases. Besides the role of ADMA in cardiovascular diseases, it also seems to be an important determinant in the development of critical illness, (multiple) organ failure, and the hepatorenal syndrome. ADMA is eliminated from the body by urinary excretion, but it is mainly metabolized by the dimethylarginine dimethylaminohydrolase (DDAH) enzymes that convert ADMA into citrulline and dimethylamine. DDAH is highly expressed in the liver, which makes the liver a key organ in the regulation of the plasma ADMA concentration. The prominent role of the liver in the elimination of ADMA and the consequences of impaired hepatic function on ADMA levels will be discussed in this article.

Asymmetric dimethylarginine induces TNF-alpha production via ROS/NF-kappaB dependent pathway in human monocytic cells and the inhibitory effect of reinioside C

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor, has been implicated in vascular inflammation through induction of reactive oxygen species (ROS) and proinflammatory genes in endothelial cells. However, relatively few attentions have been paid to the effect of ADMA on monocytes, one of the important cells throughout all stages of atherosclerosis. In the present study, we found that reinioside C, the main component extracted from Polygala fallax Hemsl., dose-dependently inhibited tumor necrosis factor-alpha (TNF-alpha) production induced by ADMA in monocytes, Furthermore, reinioside C attenuated ADMA-induced generation of reactive oxygen species and activation of nuclear factor-kappaB (NF-kappaB) activity in monocytes in a dose-dependent manner, this effect was inhibited by l-arginine (NOS substrate) and PDTC (inhibitor of NF-kappaB). These data suggest that reinioside C could attenuate the increase of TNF-alpha induced by exogenous ADMA through inhibition ROS/NF-kappaB pathway in monocytes.

Down-regulation of endogenous nitric oxide synthase inhibitors on endothelial SK3 expression

OBJECTIVES

To investigate role of endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) in down-regulation of the expression of endothelial SK3 in atherosclerosis.

METHODS

Apolipoprotein E deficient (apo E(-/-)) mice aged 11 approximately 12 weeks were treated with ADMA (5 mg/kg per day, subcutaneous injection) for 4 weeks. Cultured human umbilical venous endothelial cells (HUVECs) were treated with different concentrations of lysophosphatidylcholine (LPC) or ADMA for 48 h. Plasma levels of ADMA were determined by high performance liquid chromatogram (HPLC); protein and mRNA levels of SK3 in the aortas of mice and cultured cells were detected by immunofluorescence, western blot and RT-PCR, respectively.

RESULTS

Concomitantly with the elevated plasma levels of ADMA, the expressions of both SK3 protein and mRNA in aortas of apo E(-/-) mice were significantly reduced in comparison to those of the wild-type mice. Moreover, 4-week treatment of ADMA made levels of SK3 expression even lower. In cultured HUVECs, either LPC or ADMA notably decreased the expressions of both SK3 protein and mRNA in a concentration dependent manner.

CONCLUSIONS

Endogenous ADMA may be an important factor for down-regulation of the expression of endothelial SK3 in atherosclerotic animals.

Protective effects of taurine on endothelial cells impaired by high glucose and oxidized low density lipoproteins

BACKGROUND

Endothelial dysfunction, common to diabetes and cardiovascular diseases, is an early step in the development of atherosclerosis and diabetic angiopathies. Deficiencies of taurine have been related to diabetes and cardiovascular diseases.

AIMS OF THE STUDY

We investigated whether taurine provides protective action against endothelial dysfunction induced by hyperglycemia and/or oxidized low density lipoproteins (oxLDL).

METHODS

Quiescent human umbilical cord venous endothelial cells were exposed for 20 h to high glucose (35 mM) and/or oxLDL (60 microg/ml) alone and in presence of taurine (0.5-2.5 mg/ml). Apoptosis, caspase-3 activity, soluble(s) and cell surface expressions of vascular cellular (VCAM-1) and intercellular (ICAM-1) adhesion molecules were determined. Results are given as a percentage of the low glucose medium control. Apoptosis, VCAM-1 and ICAM-1 expressions were related to cell number.

RESULTS

Hyperglycemia increased apoptosis to 162.5 +/- 19.2%, caspase-3 activity to 153.2 +/- 10.3%, cell-surface expression of VCAM-1 to 125.1 +/- 5.8%, the expression of ICAM-1 to 123.7 +/- 2.8% and sICAM-1 to 146.5 +/- 7.9%. Taurine (0.5-2.5 mg/ml) restored apoptosis, caspase-3 activity and expressions of VCAM-1 and ICAM-1. OxLDL (60 microg/ml) increased apoptosis to 114.8 +/- 3.1%; taurine (2.5 mg/ml) reduced this apoptosis to 40.5 +/- 4.1%. The combination of hyperglycemia and oxLDL increased apoptosis to 211.7 +/- 11.6%. This increase was normalized by taurine (2.5 mg/ml) to 97.9 +/- 12.8%.

CONCLUSION

Taurine protects HUVECs from endothelial dysfunction induced by hyperglycemia through down-regulation of apoptosis and adhesion molecules. Counteracting the combination of oxLDL and hyperglycemia requires pharmacological concentrations of taurine.

Dimethylarginine dimethylaminohydrolase (DDAH): expression, regulation, and function in the cardiovascular and renal systems

Asymmetric (N(G),N(G))-dimethylarginine (ADMA) inhibits nitric oxide (NO) synthases (NOS). ADMA is a risk factor for endothelial dysfunction, cardiovascular mortality, and progression of chronic kidney disease. Two isoforms of dimethylarginine dimethylaminohydrolase (DDAH) metabolize ADMA. DDAH-1 is the predominant isoform in the proximal tubules of the kidney and in the liver. These organs extract ADMA from the circulation. DDAH-2 is the predominant isoform in the vasculature, where it is found in endothelial cells adjacent to the cell membrane and in intracellular vesicles and in vascular smooth muscle cells among the myofibrils and the nuclear envelope. In vivo gene silencing of DDAH-1 in the rat and DDAH +/- mice both have increased circulating ADMA, whereas gene silencing of DDAH-2 reduces vascular NO generation and endothelium-derived relaxation factor responses. DDAH-2 also is expressed in the kidney in the macula densa and distal nephron. Angiotensin type 1 receptor activation in kidneys reduces the expression of DDAH-1 but increases the expression of DDAH-2. This rapidly evolving evidence of isoform-specific distribution and regulation of DDAH expression in the kidney and blood vessels provides potential mechanisms for nephron site-specific regulation of NO production. In this review, the recent advances in the regulation and function of DDAH enzymes, their roles in the regulation of NO generation, and their possible contribution to endothelial dysfunction in patients with cardiovascular and kidney diseases are discussed.