Vanderlei Folmer

Oxidative stress in mice is dependent on the free glucose content of the diet

In animals, chronic intake of diets with high proportions of rapidly absorbable glucose promotes the development of insulin resistance. High levels of glucose can produce permanent chemical alterations in proteins and lipid peroxidation. delta-Aminolevulinate dehydratase (delta-ALA-D) is a sulfhydryl-containing enzyme essential for all aerobic organisms and is highly sensitive to the presence of pro-oxidants elements. The heme synthetic pathway is impaired in porphyria and a frequent coexistence of diabetes mellitus and porphyria disease has been reported in humans and experimental animal models, which can be casually linked to the delta-ALA-D inhibition found in diabetics. The present study was designed to evaluate the effect of two different diets, a high glucose (HG) diet and a high starch (HS) diet, on lipid peroxidation levels in different tissues (brain, liver, and kidney) and on delta-ALA-D activity (from liver and kidney) in mice. Plasma glucose and triglyceride levels were significantly higher in mice fed HG than in mice fed HS (P < 0.02 and P < 0.03, respectively). Thiobarbituric acid reactive species (TBA-RS) content was significantly increased in kidney and liver from HG diet-fed mice when compared with animals fed HS diets (P < 0.001). Hepatic delta-ALA-D activity of HG diet-fed animals was significantly lower than that of HS diet-fed animals (P < 0.01). The results of this study support the hypothesis that consumption of a diet with high free glucose can promote the development of oxidative stress that we tentatively attribute to hyperglycemia.

Influence of dietary selenium supplementation and Exercise on thiol-containing enzymes in mice

OBJECTIVE Exercise markedly increases oxygen uptake by active muscles and consequently increases generation of reactive oxygen species. A dietary deficiency in selenium (Se) can increase the sensitivity of the living system to oxidative stress. delta-Aminolevulinate dehydratase (delta-ALA-D), succinate dehydrogenase (SDH), and lactate dehydrogenase (LDH) are sulfhydryl-containing enzymes, and their activities are sensitive to the presence of oxidizing agents. We investigated the effect of Se deficiency and supplementation on delta-ALA-D, SDH, and LDH activities in mice subjected to swim training for 8 wk. METHODS Three-month-old female mice were randomly assigned and fed a basal diet, a basal diet plus 1 ppm of Se, and a basal diet plus 40 ppm of Se. These groups were further divided into sedentary and swim-trained groups. A mass equivalent of 5% of the animals body weight was fixed to the tail. Animals were then exercised for 60 min/d, 4 d/wk. RESULTS Swim-training associated with Se-deficient diet diminished delta-ALA-D activity in the livers and kidneys. SDH activity was diminished in the skeletal and cardiac muscles of this group. CONCLUSIONS These results indicated that exercise associated with dietary Se deficiency can inhibit the production of thiol-containing enzymes, delta-ALA-D and SDH, from different tissues; however, LDH activity was not changed. The decrease in enzyme activities can be tentatively attributed to oxidation of thiol groups by the reactive oxygen species produced by exercise.

Selenoxides inhibit δ-aminolevulinic acid dehydratase

Abstract The effect of two selenides and their selenoxides on δ-aminolevulinic acid dehydratase (δ-ALA-D) from liver of adult rats was investigated. In vivo, selenides can be oxidized to selenoxides by flavin-containing monooxygenases (FMO) and selenoxides can regenerate selenides by thiol oxidation. Phenyl methyl selenide (PhSeCH3) and 1-hexynyl methyl selenide (C4H9CCSeCH3) were converted to selenoxides by reaction with H2O2. PhSeCH3 and C4H9CCSeCH3 had no effect on δ-ALA-D up to 400 μM. Conversely, their selenoxides inhibited δ-ALA-D, and the IC50 for enzyme inhibition was about 100 and 70 μM, respectively. Partially purified δ-ALA-D (P55) from swine liver was also inhibited by these selenoxides. The inhibitory action of selenoxides was antagonized by dithiotreitol (DTT). Moreover, δ-ALA-D from a plant source was inhibited by the selenoxides, suggesting a possible involvement of SH groups in a distinct site of the homologous region implicated in Zn2+ binding in mammalian δ-ALA-D. After exposure to PhSeCH3 (500 μmol/kg/day) for 45 or 30 days, the activity of δ-ALA-D from liver of mice decreased to about 50% of the control group. The in vivo inhibitory action of this compound was not antagonized by DTT. PhSeCH3 and C4H9CCSeCH3 had no effect on the rate of DTT oxidation, but their selenoxides oxidized DTT. The results of the present study suggest that hepatic δ-ALA-D of rodents is a potential molecular target for selenides as a consequence of their metabolism to selenoxides by FMO.

Protective effect of Melissa officinalis aqueous extract against Mn-induced oxidative stress in chronically exposed mice.

Manganese (Mn) is an essential element for biological systems; however occupational exposure to high levels of this metal may lead to neurodegenerative disorders, resembling Parkinsons disease (PD). While its mechanisms of neurotoxicity have yet to be fully understood, oxidative stress plays a critical role. Thus, the main goal of this study was to investigate the efficacy of aqueous extract of Melissa officinalis in attenuating Mn-induced brain oxidative stress in mice. Sixteen male mice were randomly divided into two groups and treated for 3 months: the first group consumed tap water (control group) and the second group was treated with Mn (50 mg/kg/day for habituation during the first 15 days followed by 100 mg/kg/day for additional 75 days) in the drinking water. After 3 months both groups were sub divided (n=4 per group) and treated for additional 3 months with Mn and/or M. officinalis in the drinking water. The first group (control) was treated with water and served as control; the second group (M. officinalis) was treated with M. officinalis (100 mg/kg/day); the third group was treated with Mn (100 mg/kg/day); the fourth group (Mn+M. officinalis) was treated with both Mn and M. officinalis (100 mg/kg/day each). Mn-treated mice showed a significant increase in thiobarbituric acid reactive species (TBARS) levels (a marker of oxidative stress) in both the hippocampus and striatum. These changes were accompanied by a decrease in total thiol content in the hippocampus and a significant increase in antioxidant enzyme activity (superoxide dismutase and catalase) in the hippocampus, striatum, cortex and cerebellum. Co-treatment with M. officinalis aqueous extract in Mn-treated mice significantly inhibited the antioxidant enzyme activities and attenuated the oxidative damage (TBARS and decreased total thiol levels). These results establish that M. officinalis aqueous extract possesses potent antioxidative properties, validating its efficacy in attenuating Mn-induced oxidative stress in the mouse brain.

Diphenyl diselenide and 2,3-dimercaptopropanol increase the PTZ-induced chemical seizure and mortality in mice

The aim of the present study was to evaluate the interaction between a classic GABAergic antagonist -- pentylenetetrazol (PTZ) with an organoselenium compound -- diphenyl diselenide (PhSe)(2) and with the metal chelating agent -- 2,3 dimercaptopropanol (BAL). Mice were pre-treated with 150 micromol/kg (PhSe)(2) or BAL (250, 500 or 1000 micromol/kg) before treatment with PTZ. Pre-treatment with (PhSe)(2) reduced the latency for PTZ-induced seizure at doses of 40 and 60 mg/kg and cause a decrease in the latency for PTZ-induced death at the dose of 60 mg/kg. However, treatment with PTZ at dose of 80 mg/kg was not affected by (PhSe)(2) pre-treatment. Pre-treatment with BAL reduced the latency for PTZ-induced seizure at doses of 40 and 50 mg/kg. In addition, the latency for PTZ-induced death at the dose of 40 mg/kg was decreased significantly by pre-treatment with all doses of BAL. At the dose of 50mg/kg, a significant decrease in the latency for death occurred only in mice pre-treated with 500 and 1000 micromol/kg of BAL. Our results indicate that the PTZ-induced chemical seizures and mortality was enhanced by (PhSe)(2) and BAL. These results indicated that (PhSe)(2) and BAL interact with PTZ possibly by modulating the GABAergic system.

Ebselen and diphenyl diselenide do not change the inhibitory effect of lead acetate on delta-aminolevulinate dehidratase

It is known that lead is toxic to several species of animals, and growing data support the participation of oxidative in lead toxicity. Selenium compounds, like diphenyl diselenide and Ebselen have a thiol-peroxidase like and other antioxidant properties. In this work, we determine whether these non-thiol-containing compounds with antioxidant properties could reverse the toxicity produced by Pb(2+). Lead acetate injection followed by injection with Ebselen or diphenyl diselenide did not change the levels of non-protein thiol groups (NPSH), whereas simultaneous treatment with lead plus Ebselen reduced NPSH levels in liver. Lead and Ebselen caused a marked reduction in TBARS level in kidney, whereas lead or selenium compounds did not change TBARS levels in brain or liver. Lead acetate inhibited, δ-aminolevulinate dehydratase (ALA-D) activity in blood, liver, kidney and brain. Selenium compounds did not change enzyme activity nor the inhibitory effect of lead acetate in kidney and liver. Ebselen reversed brain ALA-D inhibition caused by Pb(2+). Reactivation index for ALA-D by DTT was higher in lead-treated groups than control groups in all tissues. Lead acetate or selenium compounds did not demonstrate alteration on [(3)H]-glutamate uptake by synaptosomes, whereas lead acetate plus Ebselen showed an increase on [(3)H]-glutamate uptake. The results of the present study indicate that ALA-D inhibition antecedes the overproduction of reactive oxygen species, which is becoming well documented in the literature.

Ebselen and diphenyl diselenide change biochemical hepatic responses to overdosage with paracetamol

The toxicity of paracetamol is largely related to its conversion to the reactive intermediate alkylating metabolite N-acetyl-para-benzo-quinoneimine (NAPQI). δ-Aminolevulinate dehydratase (δ-ALA-D) is a sulfhydril containing enzyme which is extremely sensitive to oxidizing and alkylating agents. In the present study, we examined whether acute treatment with paracetamol changes δ-ALA-D activity. The influence of two organochalcogenides with glutathione peroxidase-like activity, diphenyl diselenide [(PhSe)(2)] and ebselen was also assessed as potential protecting agents against paracetamol toxicity. Paracetamol (1200mg/kg for three days 4h after the injection of DMSO, diphenyl diselenide (100μmol/kg) or ebselen (100μmol/kg) caused an inhibition of about 40% (P < 0.01) in hepatic δ-ALA-D. Ebselen restored enzyme activity to control values. Non-protein-SH and ascorbic acid were diminished to 50% of control value by paracetamol, independent of chalcogenides treatment (all P values <0.05). In view of the fact that paracetamol caused a massive reduction in non-protein-SH and ascorbic acid, we realize that the protective effect of ebselen on δ-ALA-D activity is mediated by its thiol peroxidase-like activity or by a direct interaction with NAPQI and other reactive species formed during paracetamol metabolism.

The influence of Bauhinia forficata Link subsp. pruinosa tea on lipid peroxidation and non-protein SH groups in human erythrocytes exposed to high glucose concentrations

ETHNOPHARMACOLOGICAL RELEVANCE Bauhinia forficata (BF) has been traditionally used as tea in folk medicine of Brazil for treatment of Diabetes mellitus (DM). AIM OF THE STUDY To evaluate the effects of BF leaf tea on markers of oxidative damage and antioxidant levels in an experimental model of hyperglycemia in human erythrocytes in vitro. MATERIALS AND METHODS Human erythrocytes were incubated with high glucose concentrations or glucose and BF tea for 24h and 48h. After incubation lipid peroxidation and non-protein SH levels were analyzed. Moreover, quantification of polyphenols and flavonoids, iron chelating property, scavenging of DPPH, and prevention of lipid peroxidation in isolated lipids were also assessed. RESULTS A significant amount of polyphenols and flavonoids was observed. The main components found by LC-MS analysis were quercetin-3-O-(2-rhamnosyl) rutinoside, kaempferol-3-O-(2-rhamnosyl) rutinoside, quercetin-3-O-rutinoside and kaempferol-3-O-rutinoside. BF tea presents important antioxidant and chelating properties. Moreover, BF tea was effective to increase non-protein SH levels and reduce lipid peroxidation induced by high glucose concentrations in human erythrocytes. CONCLUSION The antioxidant effects of BF tea could be related to the presence of different phenolic and flavonoids components. We believe that these components can be responsible to protect human erythrocytes exposed to high glucose concentrations against oxidative damage.

Human erythrocyte δ-aminolevulinate dehydratase inhibition by monosaccharides is not mediated by oxidation of enzyme sulfhydryl groups

The heme pathway enzyme δ‐aminolevulinate dehydratase is a good marker for oxidative stress and metal intoxication. This sulfhydryl enzyme is inhibited in such oxidative pathologies as lead, mercury and aluminum intoxication, exposure to selenium organic species and diabetes. Oxidative stress is a complicating factor in diabetes, inducing non‐enzymatic glucose‐mediated reactions that change protein structures and impair enzyme functions. We have studied the effects of high glucose, fructose and ribose concentrations on δ‐ALA‐D activity in vitro. These reducing sugars inhibited δ‐ALA‐D with efficacies in the order fructose = ribose > glucose. The possible mechanism of glucose inhibition was investigated using lysine, DTT, and t‐butylamine. Oxidation of the enzymes critical sulfhydryl groups was not involved because DTT had no effect. We concluded that high concentrations of reducing sugars or their autoxidation products inhibit δ‐ALA‐D by a mechanism not related to thiol oxidation. Also, we are not able to demonstrate that the formation of a Schiff base with the critical lysine residue of the enzyme is involved in the inhibition of δ‐ALA‐D by hexoses.

Yerba mate (Ilex paraguariensis St. Hill.)-based beverages: How successive extraction influences the extract composition and its capacity to chelate iron and scavenge free radicals

Chimarrão or mate is a popular beverage from South America that is drank with successive infusions. Although yerba mate extracts have been widely studied, few studies have described the extract contents in beverages. Using yerba mate samples from Brazil, Argentina, and Uruguay, we examined the extract chromatographic profiles, total polyphenol content and their capacities to chelate iron. In addition, we analyzed antioxidant activity by examining the ability of the extracts to scavenge DPPH and NO. Our results showed that the amount of extracted compound was highest in yerba mate extract from Uruguay, followed by Argentina, then Brazil. Herbs from all three areas had a significant capacity to inhibit DPPH and NO free radicals. The Brazilian and Uruguayan herbs had an 80% iron chelation capacity (p<0.001), while the iron chelation capacity of the Argentinean herb was lower but still significant (p⩽0.05). We conclude that the compound concentration decreases with successive extractions, while the antioxidant capacity is maintained at significant levels.