The ADMA/DDAH/NO pathway in human vein endothelial cells exposed to arsenite

Arsenic Exposure-Related Hypertension in Bangladesh and Reduced Circulating Nitric Oxide Bioavailability

BACKGROUND

Hypertension is a major cause of death worldwide. Although arsenic exposure has been associated with the risk of hypertension, this association appears nonuniform due to inconsistent results from studies conducted in different populations. Moreover, hypertension is a complex condition with multiple underlying mechanisms and factors. One factor is impaired production and bioavailability of vascular nitric oxide (NO). However, the implications of the effects of arsenic exposure on circulating NO and its association with hypertension in humans are largely unknown.

OBJECTIVE

We investigated the dose-response relationship between arsenic exposure and hypertension with vascular NO levels as a potential mediator of arsenic-related hypertension in individuals exposed to a broad range of arsenic.

METHODS

A total of 828 participants were recruited from low- and high-arsenic exposure areas in Bangladesh. Participants' drinking water, hair, and nail arsenic concentrations were measured by inductively coupled plasma mass spectroscopy. Hypertension was defined as a systolic blood pressure (SBP) value of ≥ 140 and a diastolic (DBP) value of ≥ 90  mmHg . Serum NO levels reflected by total serum nitrite concentrations were measured by immunoassay. A formal causal mediation analysis was used to assess NO as a mediator of the association between arsenic level and hypertension.

RESULTS

Increasing concentrations of arsenic measured in drinking water, hair, and nails were associated with the increasing levels of SBP and DBP. The odds of hypertension were dose-dependently increased by arsenic even in participants exposed to relatively low to moderate levels (10 - 50 μ g / L ) of water arsenic [odds ratios (ORs) and 95% confidence intervals (CIs): 2.87 (95% CI: 1.28, 6.44), 2.67 (95% CI: 1.27, 5.60), and 5.04 (95% CI: 2.71, 9.35) for the 10 - 50 μ g / L , 50.01 - 150 μ g / L , and > 150 μ g / L groups, respectively]. Causal mediation analysis showed a significant mediating effect of NO on arsenic-related SBP, DBP, and hypertension.

CONCLUSION

Increasing exposure to arsenic was associated with increasing odds of hypertension. The association was mediated through the reduction of vascular NO bioavailability, suggesting that impaired NO bioavailability was a plausible underlying mechanism of arsenic-induced hypertension in this Bangladeshi population. https://doi.org/10.1289/EHP13018.

Analysis of Relationships between Metabolic Changes and Selected Nutrient Intake in Women Environmentally Exposed to Arsenic

Nutrients involved in the metabolism of inorganic arsenic (iAs) may play a crucial role in mitigating the adverse health effects associated with such exposure. Consequently, the objective of this study was to analyze the association between the intake levels of nutrients involved in iAs metabolism and alterations in the metabolic profile during arsenic exposure. The study cohort comprised environmentally exposed women: WL (lower total urinary arsenic (As), n = 73) and WH (higher As, n = 73). The analysis included urinary untargeted metabolomics (conducted via liquid chromatography-mass spectrometry) and the assessment of nutrient intake involved in iAs metabolism, specifically methionine, vitamins B2, B6, and B12, folate, and zinc (based on 3-day dietary records of food and beverages). In the WL group, the intake of all analyzed nutrients exhibited a negative correlation with 5 metabolites (argininosuccinic acid, 5-hydroxy-L-tryptophan, 11-trans-LTE4, mevalonic acid, aminoadipic acid), while in the WH group, it correlated with 10 metabolites (5-hydroxy-L-tryptophan, dihyroxy-1H-indole glucuronide I, 11-trans-LTE4, isovalerylglucuronide, 18-oxocortisol, 3-hydroxydecanedioic acid, S-3-oxodecanoyl cysteamine, L-arginine, p-cresol glucuronide, thromboxane B2). Furthermore, nutrient intake demonstrated a positive association with 3 metabolites in the WL group (inosine, deoxyuridine, glutamine) and the WH group (inosine, N-acetyl-L-aspartic acid, tetrahydrodeoxycorticosterone). Altering the intake of nutrients involved in iAs metabolism could be a pivotal factor in reducing the negative impact of arsenic exposure on the human body. This study underscores the significance of maintaining adequate nutrient intake, particularly in populations exposed to arsenic.

Association between Heavy Metals, Metalloids and Metabolic Syndrome: New Insights and Approaches

Metabolic syndrome (MetS) is an important public health issue that affects millions of people around the world and is growing to pandemic-like proportions. This syndrome is defined by the World Health Organization (WHO) as a pathologic condition characterized by abdominal obesity, insulin resistance, hypertension, and hyperlipidemia. Moreover, the etiology of MetS is multifactorial, involving many environmental factors, including toxicant exposures. Several studies have associated MetS with heavy metals exposure, which is the focus of this review. Environmental and/or occupational exposure to heavy metals are a major risk, contributing to the development of chronic diseases. Of particular note, toxic metals such as mercury, lead, and cadmium may contribute to the development of MetS by altering oxidative stress, IL-6 signaling, apoptosis, altered lipoprotein metabolism, fluid shear stress and atherosclerosis, and other mechanisms. In this review, we discuss the known and potential roles of heavy metals in MetS etiology as well as potential targeted pathways that are associated with MetS. Furthermore, we describe how new approaches involving proteomic and transcriptome analysis, as well as bioinformatic tools, may help bring about an understanding of the involvement of heavy metals and metalloids in MetS.

Development and Application of Activity-based Fluorescent Probes for High-Throughput Screening

High-throughput screening facilitates the rapid identification of novel hit compounds; however, it remains challenging to design effective high-throughput assays, partially due to the difficulty of achieving sensitivity in the assay techniques. Among the various analytical methods that are used, fluorescence-based assays dominate owing to their high sensitivity and ease of operation. Recent advances in activity-based sensing/imaging have further expanded the availability of fluorescent probes as monitors for high-throughput screening of result outputs. In this study, we have reviewed various activity-based fluorescent probes used in high-throughput screening assays, emphasizing their structure-related working mechanisms. Moreover, we have explored the possibility of the development of additional and better probes to boost hit identification and drug development against various targets.

Cadmium-induced endothelial dysfunction mediated by asymmetric dimethylarginine

Cadmium (Cd) is a naturally occurring toxic heavy metal with no known essential biological functions. Exposure to Cd increases the risk of cardiovascular disease by disrupting vascular homeostasis at the endothelium. The aim of the study was to evaluate the effect of chronic low-dose Cd on vascular structure and function. Fifty adult male Sprague Dawley rats were grouped and assigned to one of two treatments for 14 weeks. The control group received normal water for 14 weeks while the Cd-treated group received 15 mg Cd/kg B.W. as CdCl₂ in water for 10 weeks. A subset of the Cd-treated group received 15 mg Cd/kg B.W. as CdCl₂ in water for 10 weeks followed by 4 weeks of normal water. Results show an overall decline in vascular function and structure. Withdrawal of Cd treatment showed a considerable restoration of vascular structure and vasorelaxation function. Additionally, asymmetric dimethylarginine (ADMA) bioavailability was found to be lowered over time. Interestingly, the expression of eNOS in the Cd-treated group was found to be significantly elevated during the exposure by more than 3-fold in comparison with that in the control group. This protein expression was similar to the control group after the withdrawal of Cd treatment. Taken together, the results suggest that ADMA, an eNOS inhibitor, may play a role in altering endothelial function in the presence of cadmium. In conclusion, the findings indicate that even at low doses, Cd leads to endothelial dysfunction mediated by ADMA.

Quercetin protects the vascular endothelium against iron overload damages via ROS/ADMA/DDAHⅡ/eNOS/NO pathway

The aberrant accumulation of iron causes vascular endothelium damage, which is thought to be associated with excess reactive oxygen species (ROS) generation. Quercetin (Que), as a flavonoid, has a certain ability to scavenge free radicals. Therefore, we aimed to explore the protective mechanism of Que on iron overload induced HUVECs injury focused on ROS/ADMA/DDAHⅡ/eNOS/NO pathway. In this study, HUVECs was treated with 50 μM iron dextran and 20 μM Que for 48 h. We found that Que attenuated the damages induced by iron, as evidenced by decreased ROS generation, increased DDAHⅡexpression and activity, reduced ADMA level, increased NO content and p-eNOS/eNOS ratio, and eventually caused a decrease in apoptosis. After addition of pAD/DDAHⅡ-shRNA, the effects of Que mentioned above were reversed. Meanwhile, iron overload induced mitochondrial oxidative stress, reduced mitochondrial membrane potential and increased mitochondrial permeability transition pores (mPTP) opening, which were also partially alleviated by Que. In addition, L-arginine (L-Arg), a ADMA competition substrate, ciclosporin A (CsA), a mPTP blocking agent, and edaravone (Eda), a free radical scavenger, were used as positive control reagents. The effects of Que were similar to that of L-Arg, CsA and Eda treatment. These results illustrated that Que could attenuate iron overload induced HUVECs mitochondrial dysfunction via ROS/ADMA/DDAHⅡ/eNOS/NO pathway.

Asymmetric dimethylarginine targets MAPK pathway to regulate insulin resistance in liver by activating inflammation factors

Insulin resistance is associated with impaired glucose uptake and altered protein kinase B (Akt) signaling. Previous studies have suggested asymmetric dimethylarginine (ADMA) and inflammation are two distinguish factors that correlate with insulin resistance (IR). How ADMA and inflammation factors interact and synchronize in the regulation of IR in liver remain to be elucidated. In this study, we systematically investigated whether ADMA is involved in IR using primary hepatocytes, if yes, by via which molecular mechanism. Our results demonstrated that ADMA inhibits insulin sensitivity in a concentration-dependent manner by activating inflammation factors tumor necrosis factor (TNF)-α, interleukin (IL)-1, and IL-6 in primary hepatocytes. Further analysis revealed that mitogen-activated protein kinase (MAPK) signaling pathway act downstream of ADMA and inflammation factors, and inhibition of MAPK pathway rescued the IR. Furthermore, metformin effects has been found which could reverse ADMA-induced IR by suppressing MAPK signaling pathway. To our knowledge, we, for the first time, unveiled the complicated regulatory network and interactions among ADMA, inflammation, and MAPK signaling pathway, which advanced current research on the development and regulation of IR in liver. This study also certainly provided novel insights on comprehensive diagonistics roles of ADMA as a potential biomarker.