Dale Viezeliene

Protective effect of selenium on aluminium-induced oxidative stress in mouse liver in vivo.

The aim of the study was to evaluate possible protective effects of selenium (Se) against systemic aluminium (Al) toxicity and the redox status of mouse liver after short-term (16 h) exposure to Al in vivo. BALB/c mice were injected i.p. with AlCl(3) (25mg Al(3+) per kg of body mass) or/and Na(2)SeO(3) (1.25mg Se per kg of body mass). The 4-fold increased activity of ALT in serum showed systemic hepatotoxicity that Se could not prevent by competitive mechanisms. The protective effects of Se could only be observed on intracellular oxidative stress events as determined by glutathione status. Exposure to Al leads to the decrease in the total glutathione (GSH(tot)) and GSH/GSSG redox ratio to about 50% of the control. Upon co-exposure to Se+Al, the concentration of GSH(tot) and the redox ratio was restored to the control values. Our results indicate that Se did not have a protective effect on Al-linked liver toxicity, but did ameliorate intracellular oxidative stress processes mediated by glutathione.

Long-term stability of parameters of antioxidant status in human serum

Abstract The antioxidant status of serum or plasma can be determined using several commercially available assays. Here, four different assays, total antioxidant status (TAS), its second-generation assay (TAS2), biological antioxidant potential (BAP), and enzymatic assay using horseradish peroxidase (EAOC), were applied on human serum samples to test the temperature stability of antioxidants, upon storage of serum for 12 months. The two or three most commonly used temperatures for storage, that is, − 20, − 70 (or − 80), and − 196°C, were selected. The general conclusion is that all assays were stable at the temperatures tested. In addition, there were almost no statistically significant differences between the samples stored at different temperatures. Only the rank order of the EAOC assay was not very good in samples stored at − 20°C. Also three components contributing to the total antioxidant capacity, uric acid, creatinine and bilirubin, showed no statistically significant differences between the temperatures. Therefore, storage at − 20°C is sufficient to maintain a proper assay outcome of most of the total antioxidant assays, although storage at − 70/80°C is to be preferred for longer storage times.

Short-Term Stability of Biomarkers of Oxidative Stress and Antioxidant Status in Human Serum

The oxidation and antioxidant status of serum are often determined in serum samples which have been frozen for some time. The oxidative stress process is prone to fast alterations in the sample because of the possible instability of the reactants. Here one oxidation assay (ROM) and three antioxidant assays (FRAP, TAS, and BAP) have been tested on their performance and stability at short-time storage. The most commonly used temperatures for storage and handling of serum samples (

Long-term stability of cancer biomarkers in human serum: biomarkers of oxidative stress and redox status, homocysteine, CRP and the enzymes ALT and GGT.

AIM Five frequently used biomarkers in cancer research and epidemiological studies were tested for their assay stability upon storage of serum for 12 months at -20 and -70/-80°C. MATERIALS & METHODS The biomarker assays include reactive oxygen metabolites (ROM), the total thiol levels (TTL), homocysteine (HCy), C-reactive protein (HS-CRP) and two liver enzymes, alanine aminotransferase (ALT) and γ-glutamyltransferase (GGT). RESULTS The assays for ROM, HCy, HS-CRP and GGT were stable in human serum samples at the two temperatures tested. The two other assays TTL and ALT, however, showed statistically significant differences in their stability between -20 and -80°C. CONCLUSION Therefore, storage at -80°C is advised to maintain a reliable assay outcome when serum samples have to be stored for longer periods.

Selective induction of IL-6 by aluminum-induced oxidative stress can be prevented by selenium

In this study the acute toxic effects of aluminum (Al) on mice have been investigated, including the interactions of Al and selenium (Se). Focus was put on the systemic effects of (co)exposure to Al and Se as a reflection of the redox status in the liver, kidney and brain. Short-term exposure (16 h) to Al resulted in an increase in the systemic inflammation parameters IL-6 and PAI-1, whereas serum levels of TNF-α remained unaffected. The different response pattern of IL-6 and TNF-α probably indicates an increased intracellular oxidative stress and altered redox status in the liver, because the selective increase in IL-6 serves as a protective intrahepatocellular process driven by oxidative stress. The intracellular glutathione concentration GSHtot decreased significantly upon Al exposure. Both the increase in IL-6 and decrease in glutathione status could be prevented by co-exposure to Se, but not the increase in PAI-1. The redox status of the kidney and brain was not markedly affected. Therefore it was concluded that short-term exposure to Al causes adverse effects on the intracellular oxidative stress processes in the liver, as reflected by the selective increase in the IL-6 concentration. This process can be restored by co-administration of the trace element Se as a part of the glutathione redox system.

Tissue-Specific Effects of Vitamin E Supplementation

A multivitamin and mineral supplementation study of 6 weeks was conducted with male and female mice. The control group received a standard dose of vitamins and minerals of 1× the Recommended Daily Intake (RDI), whereas a second group received 3× RDI. A third group received a high dose of vitamin E (25× RDI), close to the upper limit of toxicity (UL), but still recommended and considered to be harmless and beneficial. The high dose of vitamin E caused a number of beneficial, but also adverse effects. Different biomarkers of tissue toxicity, oxidative stress related processes and inflammation were determined. These biomarkers did not change in plasma and erythrocytes to a large extent. In the liver of male mice, some beneficial effects were observed by a lower concentration of several biomarkers of inflammation. However, in the kidney of male mice, a number of biomarkers increased substantially with the higher dose of vitamin E, indicating tissue toxicity and an increased level of inflammation. Since this dose of vitamin E, which is lower than the UL, cause some adverse effects, even after a short exposure period, further studies are required to reconsider the UL for vitamin E.

Mice liver protein synthesis in vivo and in vitro after cadmium chloride administration

Objective: To evaluate effects of cadmium ions on the protein synthesis in mice liver in vivo and in vitro. Methods: Experiments were done on white laboratory mice using i.p. injections of appropriate amounts of cadmium chloride solution. Protein synthesis or tRNA acceptor activity was evaluated by the incorporation of [ 14 C]-leucine into newly synthesized peptides and proteins or formation of aminoacyl-tRNA. Liver cell-free translation system was made on the basis of post-mitochondrial supernatant. Results: Single doses of Cd 2+ at the amounts equal to 0.025 LD 50 and 0.05 LD 50 (0.08 mg/kg and 0.16 mg/kg) do not have very significant impact on the protein synthesis in liver 24 h after the heavy metal administration. Only 0.5 LD 50 Cd 2+ (1.6 mg/kg) reduces protein synthesis by approximately one third. However, within 24 h after the intoxication with 0.5 LD 50 , cadmium revealed initial inhibition of translation within the first 2 - 4 h, which progressed into stimulation, reaching its maximum at the 8th h and subsequent decrease. In vitro cadmium at lower concentration (40 μM) demonstrated stimulatory effect on both measured parameters of translation -the rate and level, while sharp inhibition of protein synthesis began only at relatively high concentration of this heavy metal (above 60 pM). When treated in vivo, 0.5 LD 50 cadmium 2 h after injection reduced the acceptor activity of tRNA almost by 50%, but already 8 h after the injection acceptor activity of tRNA was back at the level of control. Cadmium chloride when added directly to the liver extracts of control animals displayed very strong inhibitory effect on the tRNA acceptor activity, which had linear dependence on the cadmium concentration. Conclusions: Cadmium induces significant fluctuations of liver protein synthesis at the early stages of intoxication in vivo, which includes both inhibition and stimulation. Cadmium significantly reduces the acceptor activity of liver tRNA both in vivo and in vitro.

Biomarkers of Selenium Toxicity after Sub-Acute Exposure in Mice

Selenium (Se) is a trace element, essential for human health but it can be toxic at moderately higher intake levels. In this study biomarkers of Se toxicity after sub-acute intra-peritoneal exposure to Se (62.5 µg Se/kg bw/ day; 14 days) were investigated in mice. Such exposure corresponds to high human Se-intake levels. Focus was put on the biomarkers of systemic effects and on the toxicity in liver, kidney and brain. The sub-acute exposure to Se resulted in an increase in the concentrations of systemic inflammation biomarkers IL-6 (p=0.025) and resistin (p=0.049) and in a decrease of TNF-α (p=0.008). No effect on concentrations of MCP-1, tPAI-1, leptin and insulin was observed in serum. Also biomarkers of oxidative stress, anti-oxidant parameters and enzymes ALT and AST were not affected. In the tissue homogenates of liver, kidney and brain changes were observed in the activities of enzymes LDH (p=0.013), ALP (p=0.0009) and GGT (p=0.0047). In the brain homogenate an influx of TG (p=0.0044) and a decrease in the total GSH concentration (p=0.008) was observed. It was concluded that although the sub-acute exposure to a relatively high concentration of Se causes an increase in concentration of some biomarkers of intracellular processes, especially in the brain, the effect of Se can be considered as low toxicity.

Long-term stability of oxidative stress biomarkers in human serum.

Abstract The storage time and storage temperature might affect stability of oxidative stress biomarkers, therefore, they have to be analyzed after long-term storage of serum samples. The stability of three biomarkers reflecting oxidative stress: reactive oxygen metabolites (ROM) for hydroperoxides, total thiol levels (TTL) for the redox status and biological antioxidant potency (BAP) for the antioxidant status, was investigated at several time points during 60 months of storage at −20 and −80 °C. Biomarkers ROM and BAP showed a very good stability during storage for 60 months at both temperatures. In addition, the correlation of the data after 60 months of storage compared with the starting data was very good with correlation coefficients >0.9. The TTL assay showed good results in serum samples stored at −80 °C, but not in samples stored at −20 °C. Serum samples for analysis of the set of oxidative stress biomarkers ROM, BAP and TTL can be stored up to 60 months at −80 °C. ROM and BAP can also be stored at −20 °C during this period. The present results are very important for the biomarker-related epidemiological studies that make use of biobanks with samples stored for many years and for new project planning, including sample storage conditions.