Nitroso-redox status and vascular function in marginal and severe ascorbate deficiency

Key circRNAs, lncRNAs, and mRNAs of ShenQi Compound in Protecting Vascular Endothelial Cells From High Glucose Identified by Whole Transcriptome Sequencing

ABSTRACT

Vascular endothelial cells, which make up the inner wall of blood arteries, are susceptible to damage from oxidative stress and apoptosis caused by hyperglycemia. According to certain reports, noncoding RNAs are involved in controlling oxidative stress and apoptosis. ShenQi Compound (SQC), a traditional herbal remedy, has been successfully treating diabetic vascular disease in China for more than 20 years. Although it is well established that SQC protects the vascular endothelium, the molecular mechanism remains unknown. Goto-Kakizaki rats, spontaneous type II diabetes rats, that consistently consume a high-fat diet were chosen as model animals. Six groups (control group, model group, metformin group, and 7.2 g/kg/d SQC group, 14.4 g/kg/d SQC group, and 28.8 g/kg/d SQC group) were included in this work, 15 rats each group. The approach of administration was gavage, and the same volume (5.0 mL/kg/d) was given in each group, once a day, 12 weeks. The thoracic aortas were removed after the rats were sacrificed. Oxidative reduction profile in thoracic aorta, histopathological observation of thoracic aorta, endothelial cell apoptosis in thoracic aorta, whole transcriptome sequencing, bioinformatic analyses, and qRT-PCR were conducted. As a result, SQC prevented the oxidative stress and apoptosis induced by a high glucose concentration. Under hyperglycemia condition, noncoding RNAs, including 1 downregulated novel circRNA (circRNA.3121), 3 downregulated lncRNAs (Skil.cSep08, Shawso.aSep08-unspliced, and MSTRG.164.2), and 1 upregulated mRNA (Pcdh17), were clearly reverse regulated by SQC. SQC plays a role in protecting vascular endothelial cells from high glucose mainly by mediating ncRNA to inhibit cell apoptosis and oxidative stress.

Vitamin C (Ascorbate) and Redox Topics in Cancer

Significance: Vitamin C (ascorbate), in regard to its effectiveness against malignancies, has had a controversial history in cancer treatment. It has been shown that in vitro and in vivo anticancer efficacy of ascorbate relies on its pro-oxidant effect mainly from an increased generation of reactive oxygen species (ROS). A growing understanding of its anticancer activities and pharmacokinetic properties has prompted scientists to re-evaluate the significance of ascorbate in cancer treatment. Recent Advances: A recent resurge in ascorbate research emerged after discovering that, at high doses, ascorbate preferentially kills Kirsten-Ras (K-ras)- and B-raf oncogene (BRAF)-mutant cancer cells. In addition, some of the main hallmarks of cancer cells, such as redox homeostasis and oxygen-sensing regulation (through inhibition of hypoxia-inducible factor-1 alpha [HIF-1α] activity), are affected by vitamin C. Critical Issues: Currently, there is no clear consensus from the literature in regard to the beneficial effects of antioxidants. Results from both human and animal studies provide no clear evidence about the benefit of antioxidant treatment in preventing or suppressing cancer development. Since pro-oxidants may affect both normal and tumor cells, the extremely low toxicity of ascorbate represents a main advantage. This guarantees the safe inclusion of ascorbate in clinical protocols to treat cancer patients. Future Directions: Current research could focus on elucidating the wide array of reactions between ascorbate and reactive species, namely ROS, reactive nitrogen species as well as reactive sulfide species, and their intracellular molecular targets. Unraveling these mechanisms could allow researchers to assess what could be the optimal combination of ascorbate with standard treatments.

A comprehensive time course study of tissue nitric oxide metabolites concentrations after oral nitrite administration

Nitrite and nitrate are considered nitric oxide (NO) storage pools. The assessment of their tissue concentrations may improve our understanding of how they attenuate pathophysiological mechanisms promoting disease. We hypothesized that significant differences exist when the tissue concentrations of nitrite, nitrate, and nitrosylated species (RXNO) are compared among different tissues, particularly when nitrite is administered orally because nitrite generates various NO-related species in the stomach. We studied the different time-dependent changes in plasma and tissue concentrations of nitrite, nitrate, and RXNO after oral nitrite 15 mg/kg was administered rats, which were euthanized 15, 30, 60, 120, 240, 480 or 1440 min after nitrite administration. A control group received water. Arterial blood samples were collected and the rats were perfused with a PBS solution containing NEM/DTPA to prevent the destruction of RXNO. After perfusion, heart, aorta, mesenteric artery, brain, stomach, liver and femoral muscle were harvested and immediately stored at -70°C until analyzed for their nitrite, nitrate and RXNO contents using an ozone-based reductive chemiluminescence assay. While nitrite administration did not increase aortic nitrite or nitrate concentrations for at least 60 min, both aorta and mesenteric vessels stored nitrite from 8 to 24 h after its administration and their tissue concentrations increased from 10 to 40-fold those found in plasma. In contrast, the other studied tissues showed only transient increases in the concentrations of these NO metabolites, including RXNO. The differences among tissues may reflect differences in mechanisms regulating cellular influx of nitrite. These findings have important pharmacological and clinical implications.

Effects of inorganic nitrate and vitamin C co-supplementation on blood pressure and vascular function in younger and older healthy adults: A randomised double-blind crossover trial

BACKGROUND

Vitamin C and inorganic nitrate have been linked to enhanced nitric oxide (NO) production and reduced oxidative stress. Vitamin C may also enhance the conversion of nitrite into NO.

AIMS

We investigated the potential acute effects of vitamin C and inorganic nitrate co-supplementation on blood pressure (BP) and peripheral vascular function. The secondary aim was to investigate whether age modified the effects of vitamin C and inorganic nitrate on these vascular outcomes.

METHODS

Ten younger (age 18-40 y) and ten older (age 55-70 y) healthy participants were enrolled in a randomised double-blind crossover clinical trial. Participants ingested a solution of potassium nitrate (7 mg/kg body weight) and/or vitamin C (20 mg/kg body weight) or their placebos. Acute changes in resting BP and vascular function (post-occlusion reactive hyperemia [PORH], peripheral pulse wave velocity [PWV]) were monitored over a 3-h period.

RESULTS

Vitamin C supplementation reduced PWV significantly (vitamin C: -0.70 ± 0.31 m/s; vitamin C placebo: +0.43 ± 0.30 m/s; P = 0.007). There were significant interactions between age and vitamin C for systolic, diastolic, and mean arterial BP (P = 0.02, P = 0.03, P = 0.02, respectively), with systolic, diastolic and mean BP decreasing in older participants and diastolic BP increasing in younger participants following vitamin C administration. Nitrate supplementation did not influence BP (systolic: P = 0.81; diastolic: P = 0.24; mean BP: P = 0.87) or vascular function (PORH: P = 0.05; PWV: P = 0.44) significantly in both younger and older participants. However, combined supplementation with nitrate and vitamin C reduced mean arterial BP (-2.6 mmHg, P = 0.03) and decreased PWV in older participants (PWV: -2.0 m/s, P = 0.02).

CONCLUSIONS

The co-administration of a single dose of inorganic nitrate and vitamin C lowered diastolic BP and improved PVW in older participants. Vitamin C supplementation improved PWV in both age groups but decreased systolic and mean BP in older participants only.

CLINICAL TRIAL REGISTRATION

Current Controlled Trials (ISRCTN98942199).

Reduced levels of S-nitrosothiols in plasma of patients with systemic sclerosis and Raynaud's phenomenon

Objective

S-Nitrosothiols (RSNOs) are bioactive forms of nitric oxide which are involved in cell signalling and redox regulation of vascular function. Circulating S-nitrosothiols are predominantly in the form of S-nitrosoalbumin. In this study plasma concentrations of S-nitrosothiols were measured in patients with systemic sclerosis (SSc) where NO metabolism is known to be abnormal.

Patients and methods

Venous blood was collected from 16 patients with Raynaud's phenomenon (RP), 45 with systemic sclerosis (SSc) (34 patients had limited SSc (IcSSc) and 11 diffuse cutaneous disease (dcSSc)). Twenty six healthy subjects were used as controls. Plasma S-nitrosothiol concentrations were measured by chemiluminescence. The measurements were related to the extent of biological age, capillary/skin scores and disease duration.

Results

Plasma RSNO levels in patients with Raynaud's phenomenon (RP) and in those with SSc was significantly lower compared to the concentrations in control subjects. In SSc, plasma S-nitrosothiols were often below the level of detection (1nM).

Conclusions

Low S-nitrosothiol concentrations were observed in the blood of patients with SSc and patients with RP indicating a profound disturbance of nitric oxide metabolism.

Does vitamin C deficiency increase lifestyle-associated vascular disease progression? Evidence based on experimental and clinical studies

SIGNIFICANCE

Despite continuous advances in the prevention of cardiovascular disease (CVD), critical issues associated with an unhealthy lifestyle remain an increasing cause of morbidity and mortality in industrialized countries.

RECENT ADVANCES

A growing body of literature supports a specific role for vitamin C in a number of reactions that are associated with vascular function and control including, for example, nitric oxide bioavailability, lipid metabolism, and vascular integrity.

CRITICAL ISSUES

A large body of epidemiological evidence supports a relationship between poor vitamin C status and increased risk of developing CVD, and the prevalence of deficiency continues to be around 10%-20% of the general Western population although this problem could easily and cheaply be solved by supplementation. However, large intervention studies using vitamin C have not found a beneficial effect of supplementation. This review outlines the proposed mechanism by which vitamin C deficiency worsens CVD progression. In addition, it discusses problems with the currently available literature, including the discrepancies between the large intervention studies and the experimental and epidemiological literature.

FUTURE DIRECTIONS

Increased insights into vitamin C deficiency-mediated CVD progression will enable the design of future randomized controlled trials that are better suited to test the efficacy of vitamin C in disease prevention as well as the identification of high-risk individuals which could possibly benefit from supplementation.

Analysis of GSH and GSSG after derivatization with N-ethylmaleimide

This protocol describes a procedure for determining glutathione (GSH) and glutathione disulfide (GSSG) concentrations in blood and other tissues. Artifactual oxidation to GSSG of 5-15% of the GSH found in a sample can occur during deproteination of biological samples with any of the commonly used acids, with consequent marked overestimation of GSSG. This can be prevented by derivatizing GSH with the alkylating agent N-ethylmaleimide (NEM) to form GS-NEM before acid deproteination, followed by back-extraction of excess NEM from the deproteinized samples with dichloromethane. GSSG concentration is then measured by spectrophotometry with the GSH recycling method, on the basis of conversion of GSSG to GSH by glutathione reductase and NADPH and reaction with 5,5'-dithiobis-(2-nitrobenzoic acid). GSH concentration is instead measured by either of two methods: by analysis of GS-NEM conjugates by HPLC in the same sample that is used to measure GSSG or, alternatively, by analysis of GSH by spectrophotometry (GSH recycling method) on one additional sample aliquot that has not been derivatized with NEM. The procedure can assay GSH and GSSG in blood and other tissues in 30 min or less.

1H and 13C NMR analysis of 2-acetamido-3-mercapto-3-methyl-N-aryl-butanamides and 2-acetamido-3-methyl-3-nitrososulfanyl-N-aryl-butanamide derivatives

The complete assignment of the (1)H and (13)C NMR spectra of various 2-acetamido-3-mercapto-3-methyl-N-aryl-butanamides and 2-acetamide-3-methyl-3-nitrososulfanyl-N-aryl-butanamides with p-methoxy, o-chloro and m-chloro substituents is reported.

S-nitrosation: current concepts and new developments

The S-nitrosation (also referred to as S-nitrosylation) of cysteine residues is an important post-translational protein modification that regulates protein function and cell signaling. The original research articles and reviews in this Forum cover important concepts in protein S-nitrosation and identify key developments and opportunities for progress in this area. Defining the mechanisms by which S-nitrosothiols (RSNOs) may be formed and decomposed in cells and tissues, the integration of the biological chemistry associated with nitric oxide (NO) and other derivatives such as nitrite, and the development of new methodologies merging proteomics and direct quantitation are all key issues that we believe would require detailed attention.