Biological properties of vitamin B12.

Vitamin B12, cobalamin, is indispensable for humans owing to its participation in two biochemical reactions: the conversion of l-methylmalonyl coenzyme A to succinyl coenzyme A, and the formation of methionine by methylation of homocysteine. Eukaryotes, encompassing plants, fungi, animals and humans, do not synthesise vitamin B12, in contrast to prokaryotes. Humans must consume it in their diet. The most important sources include meat, milk and dairy products, fish, shellfish and eggs. Due to this, vegetarians are at risk to develop a vitamin B12 deficiency and it is recommended that they consume fortified food. Vitamin B12 behaves differently to most vitamins of the B complex in several aspects, e.g. it is more stable, has a very specific mechanism of absorption and is stored in large amounts in the organism. This review summarises all its biological aspects (including its structure and natural sources as well as its stability in food, pharmacokinetics and physiological function) as well as causes, symptoms, diagnosis (with a summary of analytical methods for its measurement), prevention and treatment of its deficiency, and its pharmacological use and potential toxicity.

3-methoxycatechol causes vasodilation likely via KV channels: ex vivo, in silico docking and in vivo study.

Substituted catechols include both natural and synthetic compounds found in the environment and foods. Some of them are flavonoid metabolites formed by the gut microbiota which are absorbed afterwards. Our previous findings showed that one of these metabolites, 4-methylcatechol, exerts potent vasorelaxant effects in rats. In the current study, we aimed at testing of its 22 structural congeners in order to find the most potent structure and to investigate the mechanism of action. 3-methoxycatechol (3-MOC), 4-ethylcatechol, 3,5-dichlorocatechol, 4-tert-butylcatechol, 4,5-dichlorocatechol, 3-fluorocatechol, 3-isopropylcatechol, 3-methylcatechol and the parent 4-methylcatechol exhibited high vasodilatory activities on isolated rat aortic rings with EC50s ranging from ∼10 to 24 µM. Some significant sex-differences were found. The most potent compound, 3-MOC, relaxed also resistant mesenteric artery but not porcine coronary artery, and decreased arterial blood pressure in both male and female spontaneously hypertensive rats in vivo without affecting heart rate. It potentiated the vasodilation mediated by cAMP and cGMP, but did not impact L-type Ca2+-channels. By using two inhibitors, activation of voltage-gated potassium channels (KV) was found to be involved in the mechanism of action. This was corroborated by docking analysis of 3-MOC with the KV7.4 channel. None of the most active catechols decreased the viability of the A-10 rat embryonic thoracic aorta smooth muscle cell line. Our findings showed that various catechols can relax vascular smooth muscles and hence could provide templates for developing new antihypertensive vasodilator agents without affecting coronary circulation.

When time does not heal all wounds: three decades' experience of immigrants living in Sweden.

Aim: To investigate how immigrants from the Balkan region experienced their current life situation after living in Sweden for 30 years or more. Materials: The study was designed as a qualitative study using data from interviews with informants from five Balkan countries. The inclusion criteria were informants who were immigrants to Sweden and had lived in Sweden for more than 30 years. Five groups comprising sixteen informants were invited to participate in the study, and they all agreed. Results: The analysis of the interviews resulted in three main categories: "from someone to no one", "labour market", and "discrimination". All the informants reported that having an education and life experience was worth-less, having a life but having to start over, re-educating, applying for many jobs but often not being answered, and finally getting a job for which every in-formant was educated but being humiliated every day and treated separately as well as being discriminated against. Conclusion: Coming to Sweden with all their problems, having an education and work experience that was equal to zero in Sweden, studying Swedish and re-reading/repeating all their education, looking for a job and not receiving answers to applications, and finally getting a job but being treated differently and discriminated against on a daily basis was experienced by all the in-formants as terrible. Even though there are enough similar studies in Sweden, it is always good to write more to help prospective immigrants and prospective employers in Sweden.

3-Hydroxyflavone is a mildly active and safe cobalt chelator while cobalt markedly enhances baicalein toxicity toward erythrocytes.

Cobalt intoxication can occur after its release from metal-based prostheses, which is generally clinically severe. Therefore, there is a need for the development of a cobalt chelator since there are currently no approved drugs for cobalt intoxication. As flavonoids are known for their metal chelating properties and safety, the screening of cobalt chelating properties was performed in a total of 23 flavonoids by our recently developed new spectrophotometric assay. Further assessment of positive or negative consequences of cobalt chelation was performed both in vitro and ex vivo. Six and thirteen flavonoids significantly chelated cobalt ions at pH 7.5 and 6.8, respectively. Baicalein demonstrated a significant activity even at pH 5.5; however, none of the flavonoids showed chelation at pH 4.5. In general, baicalein and 3-hydroxyflavone were the most active. They also mildly decreased the cobalt-triggered Fenton reaction, but baicalein toxicity toward red blood cells was strongly increased by the addition of cobalt. Quercetin, tested as an example of flavonoid unable to chelate cobalt ions significantly, stimulated both the cobalt-based Fenton reaction and the lysis of erythrocytes in the presence of cobalt. Therefore, 3-hydroxyflavone can serve as a potential template for the development of novel cobalt chelators.

The effects of bisphenols on the cardiovascular system ex vivo and in vivo.

The human population is regularly exposed to bisphenols. The first compound of this class, bisphenol A, is burdened by numerous reports of its potential toxicity and has been hence replaced by its analogues, so-called next generation bisphenols. Their widespread use has made them pervasive throughout the environment. These endocrine disrupting chemicals can affect the cardiovascular system, and hence the aim of this study was to test 14 bisphenols (A, AF, AP, B, BP, C, E, F, G, M, P, PH, S and Z), and compare their effects in vitro (human and rat cell lines), ex vivo (isolated rat aorta) and in vivo (Wistar Han rats, acutely or chronically exposed to low environmental and high toxic doses). The majority of the tested bisphenols relaxed rat aorta, but their potency varied markedly. The most potent compound, bisphenol AF, had an EC50 of 57 µM. The mechanism of action was likely based on the inhibition of calcium influx via L-type calcium channels. The cytotoxicity of bisphenols towards 4 human and rat cell lines (H9c2, A-10, MCF7/S0.5 and MCF7/182R-6) showed variable potencies ranging from units of micromolar to millimolar concentrations. Based on these data, an effect on arterial blood pressure and possible cardiotoxicity was expected. Contrarily, the in vivo acute effects of three doses (0.005, 0.05 and 2.5 mg/kg) of bisphenol AF and 3 other analogues (A, S and F) on the cardiovascular system were rather biologically negligible. The most potent bisphenol, AF, was also administered chronically at a dose of 2.5 mg/kg for 4 weeks to rats, but had no impact on arterial blood pressure. Our results showed that bisphenols can relax vascular smooth muscles, but the effective concentrations are too high to produce clear cardiovascular effects in relation to common biological exposure as was confirmed with the most potent bisphenol AF.

A Complex Methodological Approach for the Screening of Efficient and Safe Cobalt Chelators.

BACKGROUND: Cobalt is an essential trace element, but it can also rarely cause cobalt toxicity due to its release from cobalt-containing medical devices. Currently, there are no approved selective cobalt chelators, which would represent an optimal treatment modality. OBJECTIVE: This study aimed to develop a simple and complex methodological approach for screening potential cobalt chelators and evaluating their potential toxicity. METHODS: Firstly, a simple spectrophotometric assay employing 1-nitroso-2-naphthol-3,6- disulfonic acid disodium salt (NNDSA) for screening cobalt chelation was standardized at a pathophysiologically relevant range of pH 4.5-7.5. Then, the suitability of the method was verified using four known metal chelators (EDTA, 8-hydroxyquinoline, chloroxine and nitroxoline). As cobalt can catalyse the Fenton reaction, the potential toxicity of cobalt-chelator complexes was also determined by employing a novel HPLC method with coulometric detection. The effect on erythrocyte haemolysis was tested as well. RESULTS: The NNDSA method had high sensitivity enabling the detection of 25-200 nM of cobalt ions depending on pH conditions. Measurements could be carried out in a wide range of wavelengths from 470 to 540 nm. All tested complexes of the selected chelators decreased the rate of the Fenton reaction. Interestingly, chloroxine mixed with cobalt ions caused marked lysis of erythrocytes in contrast to the other compounds. CONCLUSION: The described complex methodological approach could serve as a simple yet precise tool for evaluating novel, effective and safe cobalt chelators.

The effect of flavonoids on the reduction of cupric ions, the copper-driven Fenton reaction and copper-triggered haemolysis.

Flavonoids are considered beneficial, but they may exhibit pro-oxidative effects likely due to metal reducing properties. For the first time, 24 structurally related flavonoids were compared for copper reduction, and modulation of the copper-triggered Fenton reaction and lysis of erythrocytes. The vast majority of flavonoids reduced cupric ions; their behaviour ranged from progressive gradual reduction through bell-shaped, neutral, to a blockade of spontaneous reduction. Similarly, different behaviours were observed with the Fenton reaction. Flavone was the only flavonoid that potentiated copper-triggered haemolysis (155 ± 81 % at twice the amount of Cu2+), while 18 flavonoids were at least partly protective in some concentrations. Only 5-hydroxyflavone did not reduce Cu2+ and behaved as an antioxidant in both assays (reduction of 60 ± 10 % and 88 ± 1%, respectively, at an equimolar ratio with Cu2+). In conclusion, relatively subtle structural differences resulted in very different anti/prooxidant behaviour depending on the model.

Comparison of Antiplatelet Effects of Phenol Derivatives in Humans.

Flavonoids are associated with positive cardiovascular effects. However, due to their low bioavailability, metabolites are likely responsible for these properties. Recently, one of these metabolites, 4-methylcatechol, was described to be a very potent antiplatelet compound. This study aimed to compare its activity with its 22 close derivatives both of natural or synthetic origin in order to elucidate a potential structure-antiplatelet activity relationship. Blood from human volunteers was induced to aggregate by arachidonic acid (AA), collagen or thrombin, and plasma coagulation was also studied. Potential toxicity was tested on human erythrocytes as well as on a cancer cell line. Our results indicated that 17 out of the 22 compounds were very active at a concentration of 40 µM and, importantly, seven of them had an IC50 on AA-triggered aggregation below 3 µM. The effects of the most active compounds were confirmed on collagen-triggered aggregation too. None of the tested compounds was toxic toward erythrocytes at 50 µM and four compounds partly inhibited proliferation of breast cancer cell line at 100 µM but not at 10 µM. Additionally, none of the compounds had a significant effect on blood coagulation or thrombin-triggered aggregation. This study hence reports four phenol derivatives (4-ethylcatechol, 4-fluorocatechol, 2-methoxy-4-ethylphenol and 3-methylcatechol) suitable for future in vivo testing.