Inhibition of platelet activation using vitamins

Improving the Stability, Water Solubility, and Antioxidant Activity of α-Tocopherol by Encapsulating It into Niosomes Modified with Cationic Carbamate-Containing Surfactants

The low solubility of α-tocopherol in water and its susceptibility to photodegradation make it difficult for biological systems to absorb this natural antioxidant. To overcome these limitations, α-tocopherol was encapsulated in low-toxicity nanocontainers, namely, niosomes based on Tween 80 and cholesterol. The niosomes were modified with cationic surfactants containing a carbamate fragment. The size and charge of the particles were determined and their stability was assessed using dynamic and electrophoretic light scattering methods. It was found that the introduction of cationic surfactants to niosome formulations significantly improved their physicochemical properties and increased stability due to a positive charge of up to +40 mV being generated. Modified niosomes loaded with α-tocopherol were characterized by a hydrodynamic diameter of 100-120 nm, a narrow particle size distribution, and a high encapsulation efficiency of more than 90%. Testing the photochemical stability of α-tocopherol using a spectrophotometric method demonstrated that niosomes were able to protect this substance from UV irradiation. Luminescence analysis showed that the inclusion of α-tocopherol in niosomes increased their antioxidant activity by 30%. An acute toxicity study has demonstrated the safety of the systems. The LD50 value for niosomes modified with carbamate-containing surfactants and loaded with α-tocopherol exceeded 10,000 mg·kg-1 (mice, intraperitoneal and oral administration).

Metabolism of FAD, FMN and riboflavin (vitamin B2) in the human parasitic blood fluke Schistosoma mansoni

BACKGROUND

Schistosomiasis is a parasitic disease caused by trematodes of the genus Schistosoma. The intravascular worms acquire the nutrients necessary for their survival from host blood. Since all animals are auxotrophic for riboflavin (vitamin B2), schistosomes too must import it to survive. Riboflavin is an essential component of the coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD); these support key functions of dozens of flavoenzymes.

METHODS

Here, using a combination of metabolomics, enzyme kinetics and in silico molecular analysis, we focus on the biochemistry of riboflavin and its metabolites in Schistosoma mansoni (Sm).

RESULTS

We show that when schistosomes are incubated in murine plasma, levels of FAD decrease over time while levels of FMN increase. We show that live schistosomes cleave exogenous FAD to generate FMN and this ability is significantly blocked when expression of the surface nucleotide pyrophosphatase/phosphodiesterase ectoenzyme SmNPP5 is suppressed using RNAi. Recombinant SmNPP5 cleaves FAD with a Km of 178 ± 5.9 µM and Kcat/Km of 324,734 ± 36,347 M- 1.S- 1. The FAD-dependent enzyme IL-4I1 drives the oxidative deamination of phenylalanine to produce phenylpyruvate and H2O2. Since schistosomes are damaged by H2O2, we determined if SmNPP5 could impede H2O2 production by blocking IL-4I1 action in vitro. We found that this was not the case; covalently bound FAD on IL-4I1 appears inaccessible to SmNPP5. We also report that live schistosomes can cleave exogenous FMN to generate riboflavin and this ability is significantly impeded when expression of a second surface ectoenzyme (alkaline phosphatase, SmAP) is suppressed. Recombinant SmAP cleaves FMN with a Km of 3.82 ± 0.58 mM and Kcat/Km of 1393 ± 347 M- 1.S- 1.

CONCLUSIONS

The sequential hydrolysis of FAD by tegumental ecto-enzymes SmNPP5 and SmAP can generate free vitamin B2 around the worms from where it can be conveniently imported by the recently described schistosome riboflavin transporter SmaRT. Finally, we identified in silico schistosome homologs of enzymes that are involved in intracellular vitamin B2 metabolism. These are riboflavin kinase (SmRFK) as well as FAD synthase (SmFADS); cDNAs encoding these two enzymes were cloned and sequenced. SmRFK is predicted to convert riboflavin to FMN while SmFADS could further act on FMN to regenerate FAD in order to facilitate robust vitamin B2-dependent metabolism in schistosomes.

Ferroptosis: a potential therapeutic target for stroke

Ferroptosis is a form of regulated cell death characterized by massive iron accumulation and iron-dependent lipid peroxidation, differing from apoptosis, necroptosis, and autophagy in several aspects. Ferroptosis is regarded as a critical mechanism of a series of pathophysiological reactions after stroke because of iron overload caused by hemoglobin degradation and iron metabolism imbalance. In this review, we discuss ferroptosis-related metabolisms, important molecules directly or indirectly targeting iron metabolism and lipid peroxidation, and transcriptional regulation of ferroptosis, revealing the role of ferroptosis in the progression of stroke. We present updated progress in the intervention of ferroptosis as therapeutic strategies for stroke in vivo and in vitro and summarize the effects of ferroptosis inhibitors on stroke. Our review facilitates further understanding of ferroptosis pathogenesis in stroke, proposes new targets for the treatment of stroke, and suggests that more efforts should be made to investigate the mechanism of ferroptosis in stroke.

Metabolism of FAD, FMN and riboflavin (vitamin B2) in the human parasitic blood fluke Schistosoma mansoni

Schistosomiasis is a parasitic disease caused by trematode worms of the genus Schistosoma. The intravascular worms acquire the nutrients necessary for their survival from host blood. Since all animals are auxotrophic for riboflavin (vitamin B2), schistosomes too must import it to survive. Riboflavin is an essential component of the coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD); these support key functions of dozens of flavoenzymes. In this work we focus on the biochemistry of riboflavin and its metabolites in Schistosoma mansoni. We show that when schistosomes are incubated in murine plasma, levels of FAD decrease over time while the levels of FMN increase. We show that live schistosomes can cleave exogenous FAD to generate FMN and this ability is significantly blocked when expression of the surface ectoenzyme SmNPP5 is suppressed using RNAi. Recombinant SmNPP5 cleaves FAD with a Km of 178 ± 5.9 µM. The FAD-dependent enzyme IL-4I1 drives the oxidative deamination of phenylalanine to produce phenylpyruvate and H2O2 in the extracellular environment. Since schistosomes can be damaged by H2O2, we determined if SmNPP5 could impede H2O2 production by blocking IL-4I1 action in vitro. We found that this was not the case, suggesting that covalently bound FAD on IL-4I1 is inaccessible to SmNPP5. We also report here that live schistosomes can cleave exogenous FMN to generate riboflavin and this ability is significantly impeded when expression of a second surface ectoenzyme (alkaline phosphatase, SmAP) is suppressed. Recombinant SmAP cleaves FMN with a Km of 3.82 ± 0.58 mM. Thus, the sequential hydrolysis of FAD by tegumental ecto-enzymes SmNPP5 and SmAP can generate free vitamin B2 around the worms from where it can be conveniently imported by, we hypothesize, the recently described schistosome riboflavin transporter SmaRT. In this work we also identified in silico schistosome homologs of enzymes that are involved in intracellular vitamin B2 metabolism. These are riboflavin kinase (SmRFK) as well as FAD synthase (SmFADS); cDNAs encoding these two enzymes were cloned and sequenced. SmRFK is predicted to convert riboflavin to FMN while SmFADS could further act on FMN to regenerate FAD in order to facilitate robust vitamin B2-dependent metabolism in schistosomes.

Insulin Resistance and Vitamin D Deficiency: A Link Beyond the Appearances

Vitamin D is a steroid hormone that plays a key role in the regulation of body homeostasis, including cardiovascular function. Although the chronic deficiency of vitamin D is associated with cardiovascular risk factors, as well as with an adverse prognosis, randomized controlled trials have failed in demonstrating that dietary vitamin D supplementation could ameliorate the prognosis of patients with cardiovascular diseases, and suggested that vitamin D deficiency is the expression of the effects of other determinants of cardiovascular risk. Thus, the supplementation of vitamin D is not sufficient to improve the cardiovascular risk profile and prognosis. Insulin resistance is a complex phenomenon that plays a key role in the pathogenesis of conventional cardiovascular risk factors. Interestingly, defects of vitamin D and insulin resistance have a superimposable epidemiological distribution. According to the common view, Insulin resistance is considered the direct or indirect consequence of vitamin D deficiency. However, it is also reasonable to speculate that the deficit or the impaired action of vitamin D, in some circumstances, could be the result of the same pathogenic mechanisms responsible of insulin resistance development. In this case, vitamin D deficiency could be considered an epiphenomenon of insulin resistance. Insulin resistance is a reversible condition, being possibly ameliorated by physical activity and hypocaloric diets. Notably, both physical exercise and energy-restricted dietary regimens are associated with an increase of vitamin D levels. These findings indicate that improving insulin resistance condition is a necessary step to ameliorate vitamin D supplementation-based strategies in cardiovascular prevention.

Effects of Nutrients on Platelet Function: A Modifiable Link between Metabolic Syndrome and Neurodegeneration?

Metabolic syndrome increases the risk of vascular dementia and other neurodegenerative disorders. Recent studies underline that platelets play an important role in linking peripheral with central metabolic and inflammatory mechanisms. In this narrative review, we address the activation of platelets in metabolic syndrome, their effects on neuronal processes and the role of the mediators (e.g., serotonin, platelet-derived growth factor). Emerging evidence shows that nutritional compounds and their metabolites modulate these interactions-specifically, long chain fatty acids, endocannabinoids and phenolic compounds. We reviewed the role of activated platelets in neurovascular processes and nutritional compounds in platelet activation.

The impact of plasma vitamin C levels on the risk of cardiovascular diseases and Alzheimer's disease: A Mendelian randomization study

BACKGROUND & AIMS

Previous observational studies have reported associations between plasma vitamin C levels, and cardiovascular diseases (CVDs) and Alzheimer's disease (AD); however, no conclusive results have been obtained. We conducted a Mendelian randomization (MR) study to investigate the causality of vitamin C on the risk of nine CVDs [including coronary artery disease (CAD), myocardial infarction (MI), atrial fibrillation (AF), heart failure (HF), stroke, ischemic stroke (IS), and IS subtypes] and Alzheimer's disease.

METHODS

Eleven single-nucleotide polymorphisms (SNPs) identified in a recent genome-wide meta-analysis (N = 52,018) were used as the instrumental variables for plasma vitamin C levels. The summary-level data for CVDs and AD were extracted from consortia and genome-wide association studies (GWAS). We performed MR analyses using the fixed-effects inverse-variance-weighted (IVW) method, weighted median, and MR-Egger approaches.

RESULTS

This MR study found suggestive evidence that genetic liability to higher vitamin C levels was associated with a lower risk of cardioembolic stroke [odds ratio (OR, presented per 1 standard deviation increase in plasma vitamin C levels) = 0.773; 95% confidence interval (CI), 0.623-0.959; P = 0.020] and AD (OR = 0.968; 95% CI, 0.946-0.991; P = 0.007) using the fixed-effects IVW method. Sensitivity analysis yielded directionally similar results. A null-association was observed between vitamin C and the other CVDs.

CONCLUSION

Our MR study provided suggestive evidence that higher vitamin C levels were casually associated with a decreased risk of cardioembolic stroke and AD. No evidence was observed to suggest that vitamin C affected the risk of CAD, MI, AF, HF, stroke, IS, large artery stroke, or small vessel stroke. However, well-designed studies are warranted to confirm these results and determine the underlying mechanisms of the causal links.