DDAH says NO to ADMA

Crosstalk between autophagy and ferroptosis mediate injury in ischemic stroke by generating reactive oxygen species

Stroke represents a significant threat to global human health, characterized by high rates of morbidity, disability, and mortality. Predominantly, strokes are ischemic in nature. Ischemic stroke (IS) is influenced by various cell death pathways, notably autophagy and ferroptosis. Recent studies have increasingly highlighted the interplay between autophagy and ferroptosis, a process likely driven by the accumulation of reactive oxygen species (ROS). Post-IS, either the inhibition of autophagy or its excessive activation can escalate ROS levels. Concurrently, the interaction between ROS and lipids during ferroptosis further augments ROS accumulation. Elevated ROS levels can provoke endoplasmic reticulum stress-induced autophagy and, in conjunction with free iron (Fe2+), can trigger ferroptosis. Moreover, ROS contribute to protein and lipid oxidation, endothelial dysfunction, and an inflammatory response, all of which mediate secondary brain injury following IS. This review succinctly explores the mechanisms of ROS-mediated crosstalk between autophagy and ferroptosis and the detrimental impact of increased ROS on IS. It also offers novel perspectives for IS treatment strategies.

Proton Pump Inhibitor Use and the Risk of Cardiovascular Complications and Death in Older Adults with Diabetes: A Population-Based Cohort Study

BACKGROUND

The unfavorable effect of proton pump inhibitors (PPIs) on cardiovascular (CV) outcomes and mortality was reported in the general population. We investigated the impact of PPIs on CV outcomes and total mortality in older people with diabetes mellitus (DM) for whom evidence is missing.

METHODS

Using administrative health databases of the Lombardy Region, we analyzed the risk of myocardial infarction (MI), ischemic stroke and total mortality in individuals with DM (≥65 years of age) exposed to PPIs in 2015 and followed up to 2021. The outcomes were analyzed using a multivariable-adjusted Cox proportional hazards model to compute hazard ratios (HRs) with 95% confidence intervals (CIs). HRs between PPI users and non-users were also estimated in selected subgroups. A sensitivity analysis was also performed in a 1:1 propensity score matching population.

RESULTS

A total of 284,068 patients were included in the analysis (49.4% PPI users, 50.6% non-PPI users). A higher prevalence of comorbidities and medications was reported in PPI users as compared with non-users. During a median follow-up of 6.7 years, the use of PPIs was associated with a higher risk for ischemic stroke (HR 1.14, 95% CI 95% 1.08-1.20), MI (HR 1.36, 95% CI 1.31-1.41) and total mortality (HR 1.24, 95% CI 1.22-1.26). These risks were higher in PPI users regardless of the PPI type. Among sexes, previous CV diseases, and insulin subgroups, the use of PPIs was correlated with a statistically significant increased risk of ischemic stroke in men, in individuals without a history of CV disease, and in those who were not treated with insulin. A significantly higher risk of MI was associated with PPIs for all subgroups, as well as for total mortality, with the exception of patients with a previous history of CV diseases. The sensitivity analysis confirmed the results of the unmatched cohort.

CONCLUSIONS

Our findings confirmed an increased risk of CV events and all-cause mortality in a large population of older adults with DM exposed to PPIs. This could have an important impact on public health and costs for National Health Service, therefore a regular assessment of PPI appropriateness is recommended, particularly in this population.

Are Proton Pump Inhibitors Contributing in Emerging New Hypertensive Population?

Balancing the therapeutic advantages of a medicine with its possible risks and side effects is an important part of medical practice and drug regulation. When a drug is designed to treat a particular disease or medical condition ends up causing additional risks or side effects that lead to the development of other serious health problems, it can have detrimental consequences for patients. This article explores the correlation between persistent proton pump inhibitor (PPI) use and hypertension, a common cardiovascular ailment. While PPIs are beneficial in treating various gastrointestinal problems, their availability without a prescription has resulted in self-medication and long-term use without medical monitoring. Recent findings have revealed a link between long-term PPI usage and increased cardiovascular risks, particularly hypertension. This study investigates the intricate mechanisms underlying PPI's effects, focusing on potential pathways contributing to hypertension, such as endothelial dysfunction, disruption of nitric oxide bioavailability, vitamin B deficiency, hypocalcemia, and hypomagnesemia. The discussion explains how long-term PPI use can disrupt normal endothelial function, vascular control, and mineral balance, eventually leading to hypertension. The article emphasizes the significance of using PPIs with caution and ongoing research to better understand the implications of these medications on cardiovascular health.

l-Arginine/nitric oxide pathway and oxidative stress in adults with ADHD: Effects of methylphenidate treatment

INTRODUCTION

Attention deficit hyperactivity disorder (ADHD) is a mental disorder that was once thought to occur only in children. Meanwhile, it is known that adults can also be affected. The first-line drug in children and adults to treat symptoms of inattention, impulsivity, lack of self-regulation, and hyperactivity is methylphenidate (MPH). Known adverse effects of MPH include cardiovascular problems, such as elevated blood pressure and heart rate. Therefore, biomarkers to monitor potential cardiovascular side effects of MPH are needed. The l-Arginine/Nitric oxide (Arg/NO) pathway is involved in noradrenaline and dopamine release as well as in normal cardiovascular functioning and is therefore a prime candidate for the search of biomarkers. The aim of the present study was to investigate the Arg/NO pathway as well as oxidative stress in adult ADHD patients in plasma and urine and the potential influence of MPH medication.

METHODS

In plasma and urine samples of 29 adults with ADHD (39.2 ± 10.9 years) and 32 healthy adults serving as controls (CO) (38.0 ± 11.6 years) the major NO metabolites nitrite and nitrate, Arg, the NO synthesis inhibitor asymmetric dimethylarginine (ADMA) and its major urinary metabolite dimethylamine (DMA) as well as malondialdehyde (MDA) were measured by gas chromatography-mass spectrometry.

RESULTS

Of the 29 patients with ADHD 14 were currently without MPH treatment (-MPH) and 15 were treated with MPH (+MPH). Plasma nitrate concentrations were significantly higher in patients not treated with MPH vs. CO (-MPH 60.3 μM [46.2-76.0] vs. CO 44.4 μM [35.0-52.7]; p = 0.002), while plasma nitrite tended to be higher in -MPH patients (2.77 μM [2.26-3.27]) vs. CO (2.13 μM [1.50-2.93]; p = 0.053). Additionally, plasma creatinine concentrations were significantly different, with -MPH showing significantly higher concentrations than the other two groups (-MPH 141 μM [128-159]; +MPH 96.2 μM [70.2-140]; Co 75.9 μM [62.0-94.7]; p < 0.001). Urinary creatinine excretion tended to be lowest in -MPH group vs. +MPH and CO (-MPH 11.4 ± 8.88 mM; +MPH 20.7 ± 9.82 mM; 16.6 ± 7.82 mM; p = 0.076). None of the other metabolites, including MDA, a marker of oxidative stress, showed a difference between the groups.

CONCLUSION

Adult patients with ADHD, who are not treated with MPH (-MPH), showed varied Arg/NO pathway, but Arg bioavailability seemed to be consistent over the groups. Our findings imply that urinary reabsorption may be increase and/or excretion of nitrite and nitrate may be decreased in ADHD, resulting in an increase in the plasma concentration of nitrite. MPH seems to partially reverse these effects by not yet known mechanisms, and does not affect oxidative stress.

Dissecting VEGF-induced acute versus chronic vascular hyperpermeability: Essential roles of dimethylarginine dimethylaminohydrolase-1

Vascular endothelial cell growth factor (VEGF) is a key regulator of vascular permeability. Herein we aim to understand how acute and chronic exposures of VEGF induce different levels of vascular permeability. We demonstrate that chronic VEGF exposure leads to decreased phosphorylation of VEGFR2 and c-Src as well as steady increases of nitric oxide (NO) as compared to that of acute exposure. Utilizing heat-inducible VEGF transgenic zebrafish (Danio rerio) and establishing an algorithm incorporating segmentation techniques for quantification, we monitored acute and chronic VEGF-induced vascular hyperpermeability in real time. Importantly, dimethylarginine dimethylaminohydrolase-1 (DDAH1), an enzyme essential for NO generation, was shown to play essential roles in both acute and chronic vascular permeability in cultured human cells, zebrafish model, and Miles assay. Taken together, our data reveal acute and chronic VEGF exposures induce divergent signaling pathways and identify DDAH1 as a critical player and potentially a therapeutic target of vascular hyperpermeability-mediated pathogenesis.

Vascular and immunopathological role of Asymmetric Dimethylarginine (ADMA) in Experimental Autoimmune Encephalomyelitis

Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide synthase (NOS) inhibitor/uncoupler inducing vascular pathology. Vascular pathology is an important factor for the development and progression of CNS pathology of MS, yet the role of ADMA in MS remains elusive. Patients with multiple sclerosis (MS) are reported to have elevated blood levels of ADMA, and mice with experimental autoimmune encephalomyelitis (EAE, an animal model of MS) generated by auto-immunization of myelin oligodendrocyte glycoprotein (MOG) and blood-brain barrier (BBB) disruption by pertussis toxin also had increased blood ADMA levels in parallel with induction of clinical disease. To explore the role of ADMA in EAE pathogenesis, EAE mice were treated with a daily dose of ADMA. It is of special interest that ADMA treatment enhanced the BBB disruption in EAE mice and exacerbated the clinical and CNS disease of EAE. ADMA treatment also induced the BBB disruption and EAE disease in MOG-immunized mice even without pertussis toxin treatment, suggesting the role of ADMA in BBB dysfunction in EAE. T-cell polarization studies also documented that ADMA treatment promotes T_H 1- and T_H 17-mediated immune responses but without affecting Treg-mediated immune response in EAE mice as well as in in vitro T-cell culture. Taken together, these data, for the first time, document the vascular and immunopathogenic roles of ADMA in EAE, thus pointing to the potential of ADMA-mediated mechanism as a new target of potential therapy for MS.

PM2.5 induces intestinal damage by affecting gut microbiota and metabolites of rats fed a high-carbohydrate diet

PM_2.5 has a major impact on the gastrointestinal system, but the specific mechanism behind this action is not fully understood. Current studies have focused on the relationship between PM_2.5 and intestinal flora disorder, while ignoring the important influence of diet on gut microbes. In this study, SD rats were fed either a normal, high-fat, or high-carbohydrate diet for two months and exposed to PM_2.5 (7 mg/kg b.w.) by intratracheal instillation. The results showed that the body and kidney weights of the rats in the high-fat diet group were significantly increased relative to those with a normal diet, and changes in the intestinal microbes and metabolites induced by PM_2.5 were observed. Rats in the high-carbohydrate diet group had a significant response, and the diversity and richness indices of the flora were reduced (p < 0.05); additionally, intestinal Biffidobacterium and Lactobacillus were enriched, while many endogenous metabolites were found. Some amino acids derivatives and long-chain fatty acids were increased (p < 0.05). Both diet structure and PM_2.5 exposure can affect the composition of gut microbiota, and intestinal metabolites may be associated with cell membrane damage when a high-carbohydrate diet interacts with PM_2.5. This study considers multiple dietary factors to further supplement the evidence of intestinal damage via PM_2.5.

Human Tissue Kallikrein 1 Is Downregulated in Elderly Human Prostates and Possesses Potential In Vitro Antioxidative and Antifibrotic Effects in Rodent Prostates

Objective

The aim of the present study was to investigate the protective effects and mechanisms of KLK1 on aging-related prostate alterations and search clues about the application of KLK1 to the treatment of human BPH.

Methods

Thirty-six rats including 26 male wild-type SD rats and 10 transgenic rats were fed to 3- or 18-month-old and divided into three groups: young WTR (yWTR) as the control (n = 16), aged WTR (aWTR) (n = 10), and aged TGR (aTGR) (n = 10). The prostates of the three groups of rats (10 rats per group) were harvested to evaluate the levels of KLK1 expression, oxidative stress, fibrosis, and involved signaling pathways, such as NO/cGMP, COX-2/PTGIS/cAMP, and TGF-β1/RhoA/ROCK1, via quantitative PCR, Western blot, histological examinations, and ELISA. Moreover, the remaining 6 yWTRs were sacrificed to obtain primary prostate fibroblast and aortic endothelial cells, and a coculture system was built with the cells for the verification of above signaling pathways in vitro. And the direct effects of bradykinin on prostate cells were detected by MTT experiment. Prostate specimens of 47 patients (age from 48 to 92 years) undergoing BPH surgery were collected after approval. Histological examinations and KLK1 IHC were preformed to analyze the relationship between KLK1 expression and age and prostate fibrosis.

Results

The human KLK1 gene only existed and was expressed in aTGR. The prostate of young rats expressed more KLK1 than the aged and the expression of KLK1 in prostate decreased with age in humans (r = −0.347, P = 0.018). Compared to the aWTR group, the yWTR and aTGR groups showed milder fibrosis, less oxidative stress, upregulated NO/cGMP, and COX-2/PTGIS/cAMP signaling pathways and inhibited TGF-β1/RhoA/ROCK1 signaling pathway. In the coculture system, KLK1 suppressed TGF-β1-mediated fibroblast-to-myofibroblast transdifferentiation via cleaving LMWK to produce the BK which upregulate eNOS expression and NO production in endothelial cells. BK not only slightly stimulated the proliferation ability of prostatic stromal cells but also upregulated iNOS and inhibited TGF-β1 expression in them.

Conclusion

KLK1 protects prostate from oxidative stress and fibrosis via amplified NO/cGMP signal in aged rats. The decrease of KLK1 expression with aging is laying the groundwork for the application of KLK1 to the treatment of human BPH. The current experimental data showed that the side effects of KLK1 on the prostate cell were not obvious.

Treatment of atherosclerosis through transplantation of endothelial progenitor cells overexpressing dimethylarginine dimethylaminohydrolase (DDAH) in rabbits

BACKGROUND

Endothelial dysfunction is a key event in the development of vascular diseases, including atherosclerosis. Endothelial progenitor cells (EPCs) play an important role in vascular repair. Decreased dimethylarginine dimethylaminohydrolase (DDAH) activity is observed in several pathological conditions, and it is associated with an increased risk of vascular disease. We hypothesized that bone marrow-derived EPCs and combination therapy with DDAH2-EPCs could reduce plaque size and ameliorate endothelial dysfunction in an atherosclerosis rabbit model.

METHOD

Four groups of rabbits (n = 8 per group) were subjected to a hyperlipidemic diet for a month. After establishing the atherosclerosis model, rabbits received 4 × 10⁶ EPC, EPCs expressing DDAH2, through femoral vein injection, or saline (the control group with basic food and the untreated group). One month after transplantation, plaque thickness, endothelial function, oxidative stress, and inflammatory mRNAs, DDAH, and eNOS function were assessed.

RESULTS

DDAH2-EPCs transplantation (p < 0.05) and EPCs transplantation (p < 0.05) were both associated with a reduction in plaque size compared to the control saline injection. The antiproliferative and antiatherogenic effects of EPCs were further enhanced by the overexpression of DDAH2 (p < 0.05, DDAH2-EPCs vs. EPCs). Furthermore, DDAH2-EPCs transplantation significantly increased endothelium integrity compared to the EPCs transplantation.

CONCLUSION

Transplantation of EPCs overexpressing DDAH2 may enhance the repair of injured endothelium by reducing inflammation and restoring endothelial function. Therefore, pCMV6-mediated DDAH2 gene-transfected EPCs are a potentially valuable tool for the treatment of atherosclerosis.

Scarred Lung. An Update on Radiation-Induced Pulmonary Fibrosis

Radiation-induced pulmonary fibrosis is a common severe long-time complication of radiation therapy for tumors of the thorax. Current therapeutic options used in the clinic include only supportive managements strategies, such as anti-inflammatory treatment using steroids, their efficacy, however, is far from being satisfactory. Recent studies have demonstrated that the development of lung fibrosis is a dynamic and complex process, involving the release of reactive oxygen species, activation of Toll-like receptors, recruitment of inflammatory cells, excessive production of nitric oxide and production of collagen by activated myofibroblasts. In this review we summarized the current state of knowledge on the pathophysiological processes leading to the development of lung fibrosis and we also discussed the possible treatment options.

The Nitric Oxide System in Peripheral Artery Disease: Connection with Oxidative Stress and Biopterins

Peripheral artery disease (PAD) pathophysiology extends beyond hemodynamics to include other operating mechanisms, including endothelial dysfunction. Oxidative stress may be linked to endothelial dysfunction by reducing nitric oxide (NO) bioavailability. We aimed to investigate whether the NO system and its regulators are altered in the setting of PAD and to assess the relationship between NO bioavailability and oxidative stress. Sera from 35 patients with intermittent claudication (IC), 26 patients with critical limb ischemia (CLI), and 35 non-PAD controls were analyzed to determine levels of tetrahydrobiopterin (BH4), dihydrobiopterin (BH2), nitrate/nitrite (nitric oxides, or NOx), arginine, citrulline, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and the oxidative stress markers 8-Oxo-2′-deoxyguanosine (8-OHdG), 4-hydroxynonenal (4-HNE), advanced glycation end products (AGEs), and protein carbonyls. NOx was significantly lower in IC and CLI patients compared to controls in association with elevated oxidative stress, with the greatest NOx reductions observed in CLI. Compared with controls, IC and CLI patients had reduced BH4, elevated BH2, and a reduced BH4/BH2 ratio. SDMA, the arginine/SDMA ratio, and the arginine/ADMA ratio were significantly higher in CLI patients. The NO system and its regulators are significantly compromised in PAD. This dysregulation appears to be driven by increased oxidative stress and worsens as the disease progresses from claudication to CLI.

Early-Life Stress Induces Depression-Like Behavior and Synaptic-Plasticity Changes in a Maternal Separation Rat Model: Gender Difference and Metabolomics Study

More than 300 million people suffer from depressive disorders globally. People under early-life stress (ELS) are reportedly vulnerable to depression in their adulthood, and synaptic plasticity can be the molecular mechanism underlying such depression. Herein, we simulated ELS by using a maternal separation (MS) model and evaluated the behavior of Sprague-Dawley (SD) rats in adulthood through behavioral examination, including sucrose preference, forced swimming, and open-field tests. The behavior tests showed that SD rats in the MS group were more susceptible to depression- and anxiety-like behaviors than did the non-MS (NMS) group. Nissl staining analysis indicated a significant reduction in the number of neurons at the prefrontal cortex and hippocampus, including the CA1, CA2, CA3, and DG regions of SD rats in the MS group. Immunohistochemistry results showed that the percentages of synaptophysin-positive area in the prefrontal cortex and hippocampus (including the CA1, CA2, CA3, and DG regions) slice of the MS group significantly decreased compared with those of the NMS group. Western blot analysis was used to assess synaptic-plasticity protein markers, including postsynaptic density 95, synaptophysin, and growth-associated binding protein 43 protein expression in the cortex and hippocampus. Results showed that the expression levels of these three proteins in the MS group were significantly lower than those in the NMS group. LC-MS/MS analysis revealed no significant differences in the peak areas of sex hormones and their metabolites, including estradiol, testosterone, androstenedione, estrone, estriol, and 5β-dihydrotestosterone. Through the application of nontargeted metabolomics to the overall analysis of differential metabolites, pathway-enrichment results showed the importance of arginine and proline metabolism; pantothenate and CoA biosyntheses; glutathione metabolism; and the phenylalanine, tyrosine, and tryptophan biosynthesis pathways. In summary, the MS model caused adult SD rats to be susceptible to depression, which may regulate synaptic plasticity through arginine and proline metabolism; pantothenate and CoA biosyntheses; glutathione metabolism; and phenylalanine, tyrosine, and tryptophan biosyntheses.

Enhanced Nitric Oxide (NO) and Decreased ADMA Synthesis in Pediatric ADHD and Selective Potentiation of NO Synthesis by Methylphenidate

Attention deficit hyperactivity disorder (ADHD) is a common pediatric psychiatric disorder, frequently treated with methylphenidate (MPH). Recently, MPH’s cardiovascular safety has been questioned by observational studies describing an increased cardiovascular risk in adults and blood pressure alterations in children. We considered members of the L-arginine (Arg)/nitric oxide (NO) pathway as possible early cardiovascular risk factors in pediatric ADHD children. They include the NO metabolites, nitrite and nitrate, the NO precursor Arg, and asymmetric dimethylarginine (ADMA), an endogenous NO synthase (NOS) inhibitor and a cardiovascular risk factor in adults. We conducted a prospective clinical trial with 42 ADHD children (aged 6–16 years) with (n = 19) and without (n = 23) MPH treatment. Age-matched children without ADHD (n = 43) served as controls. All plasma and urine metabolites were determined by gas chromatography-mass spectrometry. We observed higher plasma nitrite and lower plasma ADMA concentrations in the ADHD children. MPH-treated ADHD children had higher plasma nitrite concentrations than MPH-untreated ADHD children. As NOS activity is basally inhibited by ADMA, MPH treatment seems to have decreased the inhibitory potency of ADMA. Percentiles of systolic blood pressure were higher in MPH-treated ADHD children. The underlying mechanisms and their implications in the MPH therapy of pediatric ADHD with MPH remain to be elucidated in larger cohorts.

Protein Arginine Methyltransferases in Cardiovascular and Neuronal Function

The methylation of arginine residues by protein arginine methyltransferases (PRMTs) is a type of post-translational modification which is important for numerous cellular processes, including mRNA splicing, DNA repair, signal transduction, protein interaction, and transport. PRMTs have been extensively associated with various pathologies, including cancer, inflammation, and immunity response. However, the role of PRMTs has not been well described in vascular and neurological function. Aberrant expression of PRMTs can alter its metabolic products, asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA). Increased ADMA levels are recognized as an independent risk factor for cardiovascular disease and mortality. Recent studies have provided considerable advances in the development of small-molecule inhibitors of PRMTs to study their function under normal and pathological states. In this review, we aim to elucidate the particular roles of PRMTs in vascular and neuronal function as a potential target for cardiovascular and neurological diseases.

Metabolites downstream of predicted loss-of-function variants inform relationship to disease

A small minority (< 3%) of protein-coding genetic variants are predicted to lead to loss of protein function. However, these predicted loss-of-function (pLOF) variants can provide insight into mode of transcriptional effect. To examine how these changes are propagated to phenotype, we determined associations with downstream metabolites. We performed association analyses of 37 pLOF variants - previously reported to be significantly associated with disease in >400,000 subjects in UK Biobank - with metabolites. We conducted these analyses in three community-based cohorts: the Framingham Heart Study (FHS) Offspring Cohort, FHS Generation 3, and the KORA F4 cohort. We identified 19 new low-frequency or rare (minor allele frequency (MAF) <5%) pLOF variant-metabolite associations, and 12 new common (MAF > 5%) pLOF variant-metabolite associations. Rare pLOF variants in the genes BTN3A2, ENPEP, and GEM that have been associated with blood pressure in UK Biobank, were associated with vasoactive metabolites indoxyl sulfate, asymmetric dimethylarginine (ADMA), and with niacinamide, respectively. A common pLOF variant in gene CCHCR1, associated with asthma in UK Biobank, was associated with histamine and niacinamide in FHS Generation 3, both reported to play a role in this disease. Common variants in olfactory receptor gene OX4C11 that associated with blood pressure in UK Biobank were associated with the nicotine metabolite cotinine, suggesting an interaction between altered olfaction, smoking behaviour, and blood pressure. These findings provide biological validity for pLOF variant-disease associations, and point to the effector roles of common metabolites. Such an approach may provide novel disease markers and therapeutic targets.

Possible Effects of Proton Pump Inhibitors on Hearing Loss Development

Considered safe and often available as over-the-counter (OTC) drugs, proton pump inhibitors (PPI) are one of the most frequently used medicines. Over recent years much research analyzing PPI has been conducted and these studies shed light on PPI side effects and the mechanisms of these processes. In this study we summarize the findings of these studies and through deduction present some hypotheses on the impact of PPI on health. Of particular interest is the impact of PPI on hearing loss development. However, despite this side effect being localized, its mechanisms are complex, systemic and involve changes in whole body. This paper summarizes how through, inter alia, alterations in the circulatory system, respiratory system, central nervous system and metabolism PPI can cause hearing impairment, which can occur in every age group and is connected with long-term use of this group of drugs. This article also discusses the role PPI plays in the acceleration of presbycusis development, in relation to the fact that older people are the group who most frequently use PPI in long term. Hearing loss negatively impacts affects quality of life, especially among older patients who are also the most afflicted group; administration of PPI should therefore be considered carefully, taking into consideration all potential benefits and side effects.

Asymmetric dimethylarginine predicts impaired epicardial coronary vasomotion in patients with angina in the absence of obstructive coronary artery disease

BACKGROUND

Impaired epicardial coronary vasomotion is a potential mechanism of angina and a predictor of adverse cardiovascular outcomes in patients without angiographic evidence of obstructive coronary artery disease (CAD). We sought to evaluate the association of asymmetric dimethylarginine (ADMA)-a marker of nitric oxide-mediated vascular dysfunction-with epicardial coronary vasomotor dysfunction in this select population.

METHODS

Invasive testing for epicardial vasomotor dysfunction was performed using intracoronary acetylcholine in the left anterior descending coronary artery. Impaired vasomotor response was defined as a luminal constriction of >20% on quantitative coronary angiography. Plasma ADMA levels were measured using high performance liquid chromatography. A robust multivariate linear mixed-effect model approach and Akaike information criterion were used to determine predictors of vasomotor dysfunction.

RESULTS

In 191 patients with angina in the absence of obstructive CAD, abnormal epicardial vasomotion was observed in 137 (71.7%) patients. Median ADMA rose as the extent of impairment progressed: none (0.48 [0.44-0.59] μM), any (0.51 [0.46-0.60] μM, p = 0.12), focal (0.54 [0.49,0.61] μM, p = 0.17), and diffuse (0.55 [0.49,0.63] μM, p = 0.02). In unadjusted analysis, ADMA was highly predictive of vasomotor dysfunction (χ²=15.1, p = 0.002). Notably, ADMA remained a significant predictor even after adjusting for other factors in the best fit model (χ²=10.0, p = 0.02).

CONCLUSIONS

ADMA is an independent predictor of epicardial coronary vasomotor dysfunction in patients with angina in the absence of obstructive CAD. These data support a very early mechanistic role of ADMA in the continuum of atherosclerotic heart disease.

Class I histone deacetylase inhibitor MS-275 attenuates vasoconstriction and inflammation in angiotensin II-induced hypertension

Objective

Non-selective histone deacetylase (HDAC) inhibitors are known to improve hypertension. Here, we investigated the therapeutic effect and regulatory mechanism of the class I HDAC selective inhibitors, MS-275 and RGFP966, in angiotensin (Ang) II-induced hypertensive mice.

Methods and results

MS-275 inhibited the activity of HDAC1, HDAC2, and HDAC3, while RGFP966 weakly inhibited that of HDAC3 in a cell-free system. MS-275 and RGFP966 treatment reduced systolic blood pressure and thickness of the aorta wall in Ang II-induced hypertensive mice. MS-275 treatment reduced aorta collagen deposition, as determined by Masson’s trichrome staining. MS-275 decreased the components of the renin angiotensin system and increased vascular relaxation of rat aortic rings via the nitric oxide (NO) pathway. NO levels reduced by Ang II were restored by MS-275 treatment in vascular smooth muscle cells (VSMCs). However, MS-275 dose (3 mg·kg^-1·day^-1) was not enough to induce NO production in vivo. In addition, MS-275 did not prevent endothelial nitric oxide synthase (eNOS) uncoupling in the aorta of Ang II-induced mice. Treatment with MS-275 failed to inhibit Ang II-induced expression of NADPH oxidase (Nox)1, Nox2, and p47phox. MS-275 treatment reduced proinflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and monocyte chemoattractant protein (MCP)-1, as well as adhesion molecules. Histological analysis showed that Ang II-induced macrophage infiltration was reduced by MS-275 and RGFP966 administration.

Conclusions

Our results indicate that class I HDAC selective inhibitors may be good therapeutic agents for the treatment of hypertension through the regulation of vascular remodeling and vasoconstriction, as well as inflammation.

Usefulness of Asymmetric Dimethylarginine to Predict Outcomes After Heart Transplantation

Asymmetric dimethylarginine (ADMA) is a key mediator of vascular homeostasis and an independent predictor of the development of accelerated cardiac allograft vasculopathy after heart transplantation. However, its association with clinical outcomes in heart transplant recipients has not been described. Plasma levels of ADMA were assayed within 8 weeks following transplantation (baseline) using a competitive enzyme-linked immunosorbent assay. The primary end point was the composite of nonfatal myocardial infarction, percutaneous coronary intervention, retransplantation, or death at 5-year follow-up. Kaplan-Meier curves were generated to assess the association between baseline ADMA levels (stratified at 0.70 µM, a previously established cutoff) and cumulative event-free survival. Multivariate Cox regression was performed to adjust for other candidate predictors. In 69 heart transplant recipients at Stanford, the primary end point occurred in 11 patients (16%)-4 percutaneous coronary intervention, 1 retransplant, and 6 deaths-during 5-years follow-up. Patients with baseline ADMA ≥0.70 µM had lower cumulative 5-year event-free survival (77% vs 93%, p = 0.059). In multivariate Cox analysis, baseline ADMA was the only significant predictor of the primary end point (hazard ratio 1.33, 95% confidence interval 1.03 to 1.72 per 0.1 µM; p = 0.031). This association remained significant even after restricting the end point to death or retransplantation (hazard ratio 1.48, 95% confidence interval 1.12 to 1.97 per 0.1 µM; p = 0.006). In conclusion, elevated baseline plasma levels of ADMA independently predicted 5-year clinical outcomes after heart transplantation, suggesting that ADMA has potential prognostic value in the heart transplant arena.

ADMA, homocysteine and redox status improvement affected by 7-nitroindazole in spontaneously hypertensive rats

Inhibition of nitric oxide (NO) production can influence blood pressure regulation and increase hypertension. Asymmetric dimethylarginine, ADMA, an analogue of L-arginine, can inhibit NO synthesis, impair endothelial function, and is a risk marker of cardiovascular diseases. Homocysteine (Hcy) level affects oxidative stress production of reactive oxygen species (ROS) in hypertension and also influences changes in signaling and cell damage. The present study was focused on experimental effects of exogenous NOS inhibitors and their effect on ADMA, an endogenous NOS inhibitor, homocysteine and ROS production measured as reactive oxidative metabolites (ROM). We compared effects of the two potential exogenous NO-inhibitors: N^G-nitro L-arginine methyl ester (L-NAME) and 7-nitroindazole (7-NI). Levels of ADMA, Hcy, ROM and total thiols (TTL) were not changed in the L-NAME group. With 7-NI administration, we observed unchanged NOS activity in the left ventricle and a pronounced decrease of ADMA and Hcy levels, accompanied by ROM over-production in plasma. TTL/ROM ratio was more favorable than in the L-NAME group. We observed that 7-NI, an exogenous NOinhibitor, can decrease and improve the levels of ADMA, Hcy, and ROM, and increase TTL/ROM ratio in the plasma of spontaneously hypertensive rats.

Post-Transcriptional Regulation of Hepatic DDAH1 with TNF Blockade Leads to Improved eNOS Function and Reduced Portal Pressure In Cirrhotic Rats

Portal hypertension (PH) is a major cause of morbidity and mortality in chronic liver disease. Infection and inflammation play a role in potentiating PH and pro-inflammatory cytokines, including TNF, are associated with severity of PH. In this study, cirrhotic bile duct ligated (BDL) rats with PH were treated with Infliximab (IFX, a monoclonal antibody against TNF) and its impact on modulation of vascular tone was assessed. BDL rats had increased TNF and NFkB compared to sham operated rats, and their reduction by IFX was associated with a reduction in portal pressure. IFX treatment also reduced hepatic oxidative stress, and biochemical markers of hepatic inflammation and injury. IFX treatment was associated with an improvement in eNOS activity and increased l-arginine/ADMA ratio and DDAH1 expression. In vitro analysis of HepG2 hepatocytes showed that DDAH1 protein expression is reduced by oxidative stress, and this is in part mediated by post-transcriptional regulation by the 3′UTR. This study supports a role for the DDAH1/ADMA axis on the effect of inflammation and oxidative stress in PH and provides insight for new therapies.

Oxidative Stress and Cardiovascular Aging: Interaction Between NRF-2 and ADMA

Background:

The concept of antioxidant therapies assumes high importance as oxidative stress is associated with cardiovascular aging via endothelial dysfunction. This review focuses on exploring the interaction between nrf-2 and ADMA in influencing the nitric oxide pathway and cardiovascular function.

Objective:

A systematic review of literature from 1990 to 2016 was conducted using Pubmed and Google Scholar. The literature suggests a strong influence of nrf-2 activation on up regulation of DDAH I which degrades ADMA, the endogenous inhibitor of nitric oxide synthase. The resulting decrease of ADMA would in turn enhance nitric oxide (NO) production. This would support endothelial function by adequate NO production and homeostasis of endothelial function.

Conclusion:

As NO production has many positive pleiotropic effects in the cardiovascular system, such an interaction could be utilized for designing molecular therapeutics. The targets for therapy need not be limited to activation of nrf-2. Modulation of molecules downstream such as DDAH I can be used to regulate ADMA levels. Most current literature is supported by animal studies. The concept of antioxidant therapies needs to be tested in well-defined randomized control trials. The biochemical basis of nrf-2 activation needs to be substantiated in human studies.

Decreased serum L-arginine and L-citrulline levels in major depression

RATIONALE

It has been suggested that endothelial dysfunction caused by a decreased endothelial production of nitric oxide (NO) may contribute to the consistently observed increased risk of developing cardiovascular disease (CVD) in physically healthy patients suffering from major depression (MD). NO is a gas synthesized from Larginine (a conditionally essential amino acid) and oxygen by endothelial nitric oxide synthase (eNOS). The end products of NO production include both NO and L-citrulline. NO is rapidly reduced to the anions nitrite and nitrate, classically referred to as NO metabolites. Their measurement has been used as a surrogate measurement for endothelial NO production. We and others have shown decreased levels of NO metabolites in the serum of MD patients. The mechanism of this decreased production of NO by the endothelium has not yet been elucidated.

OBJECTIVES

The purpose of this study is to assess serum levels of L-arginine and L-citrulline in patients with MD.

METHODS

Levels of L-arginine and L-citrulline were measured in 35 unmedicated physically healthy MD patients and 36 healthy controls (HCs).

RESULTS

L-arginine and L-citrulline concentrations were significantly lower in MD patients than in healthy controls (L-arginine, 73.54 + 21.53 μmol/L and 84.89 + 25.16, p = 0.04 μmol/L and L-citrulline 31.58 + 6.05 μmol/L and 35.19 + 6.85 μmol/L, p = 0.03, respectively).

CONCLUSIONS

The decrease in L-arginine levels in MD patients is a possible explanation for the decrease in NO metabolites in MD patients and therefore may contribute, through endothelial dysfunction, to the increased CV risk associated with MD.

Impact of Asymmetric Dimethylarginine on Coronary Physiology Early After Heart Transplantation

Cardiac allograft vasculopathy is a major cause of long-term graft failure following heart transplantation. Asymmetric dimethylarginine (ADMA), a marker of endothelial dysfunction, has been mechanistically implicated in the development of cardiac allograft vasculopathy, but its impact on coronary physiology early after transplantation is unknown. Invasive indices of coronary physiology, namely, fractional flow reserve (FFR), the index of microcirculatory resistance, and coronary flow reserve, were measured with a coronary pressure wire in the left anterior descending artery within 8 weeks (baseline) and 1 year after transplant. Plasma levels of ADMA were concurrently assayed using high-performance liquid chromatography. In 46 heart transplant recipients, there was a statistically significant correlation between elevated ADMA levels and lower FFR values at baseline (r = -0.33; p = 0.024); this modest association persisted 1 year after transplant (r = -0.39; p = 0.0085). Patients with a baseline FFR <0.90 (a prognostically validated cutoff) had significantly higher baseline ADMA levels (0.63 ± 0.16 vs 0.54 ± 0.12 µM; p = 0.034). Baseline ADMA (odds ratio 1.80 per 0.1 µM; 95% confidence interval 1.07 to 3.03; p = 0.027) independently predicted a baseline FFR <0.90 after multivariable adjustment. Even after dichotomizing ADMA (≥0.60 µM, provides greatest diagnostic accuracy by receiver operating characteristic curve), this association remained significant (odds ratio 7.52, 95% confidence interval 1.74 to 32.49; p = 0.006). No significant relationship between ADMA and index of microcirculatory resistance or coronary flow reserve was detected. In conclusion, baseline ADMA was a strong independent predictor of FFR <0.90, suggesting that elevated ADMA levels are associated with abnormal epicardial function soon after heart transplantation.

HIV-infected persons with type 2 diabetes show evidence of endothelial dysfunction and increased inflammation

Background

Increased incidence of cardiovascular diseases (CVD) in both HIV infection and type 2 diabetes (T2D) compared to the general population has been described. Little is known about the combined effect of HIV infection and T2D on inflammation and endothelial function, both of which may contribute to elevated risk of CVD.

Methods

Cross-sectional study including 50 HIV-infected persons on combination anti-retroviral therapy (cART), with HIV RNA <200 copies/mL (n = 25 with T2D (HIV + T2D+), n = 25 without T2D (HIV + T2D-)) and 50 uninfected persons (n = 22 with T2D (HIV-T2D+) and n = 28 without T2D (HIV-T2D-)). Groups were matched on age and sex.

High sensitive C-reactive protein (hsCRP) was used to determine inflammation (cut-off 3 mg/L). The marker of endothelial dysfunction asymmetric dimethylarginine (ADMA) was measured using high performance liquid chromatography. Trimethylamine-N-oxide (TMAO), a microbiota-dependent, pro-atherogenic marker was measured using stable isotope dilution LC/MS/MS.

Results

The percentage of HIV + T2D+, HIV + T2D-, HIV-T2D+, and HIV-T2D- with hsCRP above cut-off was 50%, 19%, 47%, and 11%, respectively. HIV + T2D+ had elevated ADMA (0.67 μM (0.63-0.72) compared to HIV + T2D- (0.60 μM (0.57-0.64) p = 0.017), HIV-T2D+ (0.57 μM (0.51-63) p = 0.008), and HIV-T2D- (0.55 μM (0.52-0.58) p < 0.001). No differences in TMAO between groups were found. However, a positive correlation between ADMA and TMAO was found in the total population (r_s = 0.32, p = 0.001), which was mainly driven by a close correlation in HIV + T2D+ (r_s = 0.63, p = 0.001).

Conclusion

Elevated inflammation and evidence of endothelial dysfunction was found in HIV-infected persons with T2D. The effect on inflammation was mainly driven by T2D, while both HIV infection and T2D may contribute to endothelial dysfunction. Whether gut microbiota is a contributing factor to this remains to be determined.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2334-8) contains supplementary material, which is available to authorized users.

The Unknown Association of PPIs With Chest Pain in Patients With Known, Treated Coronary Artery Disease-A Diagnostic Dilemma

Patients with coronary artery disease (CAD) are destined to lifelong antiplatelet therapy in form of aspirin (acetylsalicylic acid) alone, or in combination with other P2Y2 inhibitors. Proton pump inhibitors (PPIs) are the preferred agents for the treatment and prophylaxis of gastrointestinal injury associated with nonsteroidal anti-inflammatory drug or acetylsalicylic acid or both,¹ but recent data has raised questions about their association with negative cardiovascular events. We report 2 cases of patients with known CAD presented with chest pain mimicking angina pectoris that successfully resolved on discontinuation of the PPIs. One male and one female patient with known history of CAD receiving PPIs were referred to us with symptoms of refractory angina that was unresponsive to conventional optimized medical therapy. The angina was reported to be related to exertion in both the patients. Neither patient had a diagnosis of Prinzmetal angina or peptic ulcer disease; however, both patients reported a history of gastroesophageal reflux disease. Both patients were on dual antiplatelet therapy. No ischemic changes on the electrocardiogram were noted for either patient. Patient 1 had an exercise stress test that was negative for any inducible ischemia whereas patient 2 had no obstructive lesion seen on coronary angiography. Both patients reported to be symptom free after discontinuation of PPIs at 8 months of follow-up. It is our opinion that a relationship between PPIs and angina-like chest pain is plausible, as these 2 cases demonstrate the causative role of PPIs in precipitation of their symptoms. We postulate that this association should be considered in differential diagnosis of chest pain. In light of above findings we suggest that this is hypothesis generating and we are exploring the role of PPIs in patients with history of CAD and refractory angina-like symptoms despite complete revascularization.

l-citrulline prevents asymmetric dimethylarginine-mediated reductions in nitric oxide and nitrosative stress in primary human airway epithelial cells

BACKGROUND

Asthma is associated with reduced systemic levels of l-arginine and increased asymmetric dimethylarginine (ADMA). This imbalance leads to nitric oxide synthase (NOS) uncoupling with reduced nitric oxide (NO) formation and greater oxidative and nitrosative stress. Whether this imbalance also occurs in bronchial epitheliumof asthmatics is unknown.

OBJECTIVES

We used primary human bronchial epithelial cells (HBECs) from asthmatics and healthy controls to evaluate: (i) ADMA-mediated NOS uncoupling reduces epithelial production of NO and increases oxygen and nitrogen reactive species, and (ii) l-citrulline can reverse this mechanism by recoupling NOS, restoring NO production and reducing oxidative and nitrosative stress.

RESULTS

In HBECsIL-13 and INFγ stimulated NOS2 and increased NOx levels. The addition of ADMA reduced NOx and increased H₂ O₂ levels (p<0.001). Treatment with l-citrulline (800, 1600 μm) rescued NOx when the l-arginine media concentration was 25 μm but failed to do so with higher concentrations (100 μm). Under reduced l-arginine media conditions, HBECs treated with l-citrulline increased the levels of argininosuccinate, an enzyme that metabolizes l-citrulline to l-arginine. l-citrulline prevented the ADMA-mediated increase in nitrotyrosine in HBECs in cells from asthmatics and controls.

CONCLUSIONS AND CLINICAL RELEVANCE

Increasing ADMA reduces NO formation and increases oxidative and nitrosative stress in airway epithelial cells. l-citrulline supplementation restores NO formation, while preventing nitrosative stress. These results, suggest that l-citrulline supplementation may indeed be a powerful approach to restore airway NO production and may have a therapeutic potential in diseases in which there is a defective production of NO.

How May Proton Pump Inhibitors Impair Cardiovascular Health?

Proton pump inhibitors (PPIs) are among the most widely used drugs worldwide. They are used to treat a number of gastroesophageal disorders and are usually prescribed as a long-term medication or even taken without a prescription. There are a number of clinical studies that associate PPI use with an increased cardiovascular risk. In this article, we review the clinical evidence for adverse cardiovascular effects of PPIs, and we discuss possible biological mechanisms by which PPIs can impair cardiovascular health.

New Insights Into Tobacco-Induced Vascular Disease: Clinical Ramifications

Tobacco smoke contains more than 4,000 compounds. These include phenols, carbonyls, and nitrosamines that may be irritants and carcinogens; particulate matter such as tars; volatiles and gases such as carbon monoxide; and nicotine. Many of these compounds may contribute to the adverse health effects of tobacco. For example, recent findings have shown that the angiogenic and proliferative effects of nicotine are mediated by activation of nicotinic receptors on the vascular cells. Nicotine-induced activation of vascular cells may contribute to pathological neovascularization in cancer, age-related macular degeneration, and atherosclerosis. This review focuses on how nicotine adversely affects cardiovascular health and highlights intriguing new data about nicotine's potent angiogenic and proliferative properties.

Placental NRP1 and VEGF expression in pre-eclamptic women and in a homocysteine-treated mouse model of pre-eclampsia

OBJECTIVES

To investigate the expression levels of neuropilin 1 (NRP1) and vascular endothelial growth factor (VEGF) in the placentas of women with pre-eclampsia (PE), determine whether homocysteine (Hcy) contributes to the development of PE in mice, and detect alterations in placental NRP1 and VEGF in Hcy-treated mice.

STUDY DESIGN

Placental tissue samples were obtained from 16 patients with and without PE. Using reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis, the expression levels of NRP1 and VEGF in PE and control placental tissues were examined. Immunohistochemical (IHC) assay was used to detect the localization of NRP1 and VEGF proteins. Pregnant mice were treated with DL-Hcy on embryonic day 7.5. The symptoms of the treated mice were examined. The expression levels of Ddah1, Ddah2, eNos, Cbs and Cse were determined by quantitative RT-PCR to study the possible mechanism of hyperhomocysteinemia (HHcy). Nrp1 and Vegf expression levels in the placentas of treated mice were measured by quantitative RT-PCR, western blot analysis and IHC.

RESULTS

NRP1 and VEGF were expressed at lower levels in women with PE compared with control women. The immunoreactivity of NRP1 was detected in villous trophoblast cells and villous capillary endothelial cells (ECs). Immunoreactive VEGF was observed mainly in vascular ECs within the villi. The pregnant mice treated with DL-Hcy showed PE-like symptoms such as higher systolic blood pressure and proteinuria in late pregnancy. Compared with the control mice, Ddah1, Ddah2 and eNos mRNA were expressed at lower levels, and Cbs and Cse mRNA were expressed at significantly higher levels in the placentas of the Hcy-treated group. Expression levels of Nrp1 and Vegf in mice placentas were decreased in the Hcy-treated group.

CONCLUSIONS

DL-Hcy can induce PE-like symptoms in mice. Both placental NRP1 and VEGF were expressed at lower levels in women with PE and Hcy-treated mice, which may contribute to endothelial damage.

Inhibition of DDAH1, but not DDAH2, results in apoptosis of a human trophoblast cell line in response to TRAIL

STUDY QUESTION

Does inhibition of dimethylarginine dimethylaminohydrolase (DDAH) increase the sensitivity of trophoblasts to TRAIL-induced apoptosis?

SUMMARY ANSWER

Inhibition of DDAH1, but not DDAH2, increases the sensitivity of trophoblasts to TRAIL-induced apoptosis.

WHAT IS KNOWN ALREADY

Successful human pregnancy is dependent on adequate trophoblast invasion and remodelling of the maternal spiral arteries. Increased trophoblast apoptosis is seen in pregnancies complicated by pre-eclampsia. The mechanism underlying this increase is unknown. We have previously shown that nitric oxide (NO) is involved in regulating trophoblast motility and invasion, and have also demonstrated an important role for NO in regulating trophoblast sensitivity to apoptotic stimuli. DDAH is an enzyme that metabolizes asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO synthesis, previously shown to be elevated in the plasma of pre-eclamptic mothers.

STUDY DESIGN, SIZE, DURATION

This study used the human extravillous trophoblast-derived cell line SGHPL-4 cells. All experiments were performed at least three times.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The effect of DDAH on trophoblast apoptosis was examined using siRNA and time-lapse microscopy. Changes in the expression of DDAH were followed by PCR and western blot analysis. Receptor expression was followed by flow cytometry.

MAIN RESULTS AND THE ROLE OF CHANCE

Inhibiting the expression of DDAH1, but not DDAH2, resulted in a significant increase in the sensitivity of the EVT cell line SGHPL-4 to tumour necrosis factor related apoptosis inducing ligand (TRAIL) induced apoptosis (P < 0.01). This response could be mimicked by the addition of Asymmetric Dimethylarginine (ADMA), an endogenous inhibitor of NO synthesis and the substrate for both isoforms of DDAH. We further showed that this increased sensitivity to apoptosis is accompanied by a significant increase in the expression of TRAIL receptor 2 (TR2; P < 0.05) but not TRAIL receptor 1 (TR1).

LIMITATIONS, REASONS FOR CAUTION

This study was performed only in vitro using a well characterized trophoblast cell line, SGHPL-4, derived from first trimester extravillous trophoblasts.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides new insight into the role of the DDAH/ADMA pathway in the regulation of trophoblast function. Both dysregulation of DDAH and the accumulation of ADMA have been associated with the development of pre-eclampsia. This is the first study to implicate the DDAH/ADMA pathway as a mechanism that might underlie the poor trophoblast invasion seen in this common pregnancy disorder.

STUDY FUNDING/COMPETING INTEREST(S)

B.A.L. was supported by a grant from Action Medical Research UK (SP4577). A.E.W. was supported by a grant from the Wellcome Trust (091550). There are no competing interests and the authors have no conflict interest to declare.

Proton Pump Inhibitor Usage and the Risk of Myocardial Infarction in the General Population

Background and Aims

Proton pump inhibitors (PPIs) have been associated with adverse clinical outcomes amongst clopidogrel users after an acute coronary syndrome. Recent pre-clinical results suggest that this risk might extend to subjects without any prior history of cardiovascular disease. We explore this potential risk in the general population via data-mining approaches.

Methods

Using a novel approach for mining clinical data for pharmacovigilance, we queried over 16 million clinical documents on 2.9 million individuals to examine whether PPI usage was associated with cardiovascular risk in the general population.

Results

In multiple data sources, we found gastroesophageal reflux disease (GERD) patients exposed to PPIs to have a 1.16 fold increased association (95% CI 1.09–1.24) with myocardial infarction (MI). Survival analysis in a prospective cohort found a two-fold (HR = 2.00; 95% CI 1.07–3.78; P = 0.031) increase in association with cardiovascular mortality. We found that this association exists regardless of clopidogrel use. We also found that H₂ blockers, an alternate treatment for GERD, were not associated with increased cardiovascular risk; had they been in place, such pharmacovigilance algorithms could have flagged this risk as early as the year 2000.

Conclusions

Consistent with our pre-clinical findings that PPIs may adversely impact vascular function, our data-mining study supports the association of PPI exposure with risk for MI in the general population. These data provide an example of how a combination of experimental studies and data-mining approaches can be applied to prioritize drug safety signals for further investigation.

Relationship between dimethylarginine dimethylaminohydrolase gene variants and asymmetric dimethylarginine in patients with rheumatoid arthritis

OBJECTIVE

The aim of our study was to determine whether Dimethylarginine Dimethylaminohydrolase (DDAH) 1 and 2 gene polymorphisms - the main enzyme involved in ADMA degradation - are associated with high Asymmetric Dimethylarginine (ADMA) levels in Rheumatoid Arthritis (RA).

METHODS

Serum ADMA levels were measured in 201 individuals with RA [155 females median age 67 (59-73)]. Four tag SNPs in DDAH1 gene and 2 in the DDAH2 gene were genotyped by using the LightCycler™ System. ADMA was initially compared across the genetic variables using one-way ANOVA and then multivariate analysis examined each of the genes after adjustment for parameters of systemic inflammation and insulin resistance, namely erythrocyte sedimentation rate (ESR) and homeostatic model assessment (HOMA), which we have previously shown affect ADMA levels in RA.

RESULTS

No significant relationship between DDAH genetic variables and ADMA levels was established in ANOVA analysis. Multivariate model adjusted for age, HOMA and ESR did not demonstrate any significant association between DDAH variants and ADMA.

CONCLUSION

The results of our study give no evidence to suggest that increased ADMA levels in RA relate to DDAH genetic polymorphisms. Better understanding of disease-related factors and their interactions with traditional CV risk factors may represent mechanisms responsible for ADMA accumulation in this population.

Increased levels of asymmetric dimethylarginine are associated with pulmonary arterial hypertension in HIV infection

OBJECTIVE

To examine the relationship between asymmetric dimethylarginine (ADMA) and HIV-associated pulmonary arterial hypertension (PAH).

DESIGN

HIV infection is an independent risk factor for PAH, but the underlying pathogenesis remains unclear. Chronic inflammation resulting in nitric oxide-mediated endothelial dysfunction is a key mechanism underlying other types of PAH. ADMA is an endogenous inhibitor of endothelial nitric oxide synthase. Among uninfected individuals, ADMA is associated with PAH and predicts disease-related mortality.

METHODS

We measured ADMA, high sensitivity C-reactive protein, interleukin-6 (IL-6), D-dimer, and pulmonary artery systolic pressure (PASP) using echocardiography in HIV-infected individuals. Right heart catheterization (RHC) was performed in individuals with a PASP at least 30  mmHg. We performed multivariable analysis to identify factors associated with high PASP by echocardiogram and PAH by RHC.

RESULTS

Among 214 HIV-infected individuals, the median age was 50 years, 82% were men, 71% were on antiretroviral therapy, and 4.2% carried a prior diagnosis of PAH. ADMA and IL-6 were associated with increased values of PASP following multivariable adjustment (7.2% per 0.1 μmol/l, P = 0.0049 and 3.9% per doubling, P = 0.027, respectively). In adjusted analysis among the 85 participants who underwent RHC, ADMA and IL-6 were associated with higher values of mean PAP (14.2% per 0.1 μmol/l, P = 0.0014 and 5.8% per doubling, P = 0.038, respectively). However, only ADMA was associated with PAH (prevalence ratio = 1.74, P = 0.029).

CONCLUSION

Elevated levels of ADMA are independently associated with PAH among HIV-infected individuals. Our findings suggest that chronic HIV-associated inflammation leading to an accumulation of ADMA and subsequent nitric oxide-mediated endothelial dysfunction may represent a novel mechanism for HIV-associated PAH.

Elevated levels of asymmetric dimethylarginine are associated with lower CD4+ count and higher viral load in HIV-infected individuals

OBJECTIVES

To compare asymmetric dimethylarginine (ADMA) among HIV-infected and uninfected individuals and to evaluate predictors of ADMA in HIV infection.

BACKGROUND

HIV-infected individuals have high rates of atherosclerosis. Endothelial dysfunction is central to atherogenesis and is one possible mechanism underlying this increased cardiovascular risk. ADMA is an endogenous inhibitor of endothelial nitric oxide synthase. Among uninfected individuals, higher ADMA levels predict cardiovascular events and mortality. The association between HIV infection, HIV-related factors, and ADMA has not been well described.

METHODS

We compared ADMA in 248 HIV-infected individuals and 50 uninfected controls. We performed multivariable analysis using traditional cardiovascular and HIV-specific factors as covariates to identify factors associated with ADMA.

RESULTS

HIV-infected men were older, less often Caucasian, more hypertensive, and had lower HDL than uninfected men. The median duration of HIV infection was 13 years, median CD4+ count was 592 cells/μL, 76% had an undetectable viral load, and 76% were on antiretroviral therapy. ADMA levels were modestly higher in HIV-infected individuals than controls [median (IQR): 0.46 μM (0.41-0.52) vs. 0.44 μM (0.38-0.46), p = 0.019], but the association lost statistical significance after controlling for cardiovascular risk factors (+0.028 μM, p = 0.054). Lower CD4+ count and both detectable and higher viral load were independently associated with increased ADMA.

CONCLUSIONS

ADMA levels were modestly elevated in the setting of HIV infection. Notably, a greater HIV-associated inflammatory burden, as evidenced by lower CD4+ counts and higher viral loads, was associated with increased ADMA levels. Our findings suggest that HIV infection impairs endothelial function and predisposes to atherosclerosis through chronic inflammation and subsequent accumulation of ADMA.