Clofibric acid or diethylmaleate supplemented diet decrease blood pressure in DOCA-salt treated male Sprague Dawley rats--relation with liver antioxidant status

Cadmium induction of lipid peroxidation and effects on root tip cells and antioxidant enzyme activities in Vicia faba L

The effects of different concentrations (1-50 microM) of Cd on root growth, cell division and nucleoli in root tip cells, protective enzyme activities and lipid peroxidation in Vicia faba were investigated in order to better understand the processes of Cd-induced senescence. The results indicated that lower concentration of Cd (1 microM) had no obviously influence on the root growth during 24-48 h treatment, but higher concentrations (5-50 microM) inhibited significantly after 48 and 72 h. The mitotic index decreased with increasing of Cd concentration and duration of treatment except for the group exposed to 1 microM Cd. Cd induced c-mitosis, chromosome bridges, chromosome stickiness and lagging chromosomes. The rate of aberrant dividing cells increased with prolonging duration of treatment and increasing of Cd concentration. On nucleolus, some particulates containing the argyrophilic proteins were extruded from the nucleus into the cytoplasm in the cells stressed by Cd and some were scattered in the nucleus. After the treatment with Cd (10 microM Cd, 48 h), the nucleolus did not disaggregate normally and still remain its characteristic structure during metaphase and the particles of similar silver-stained materials were localized on chromosomes. In leaves, Catalase (CAT) activity declined but Peroxidase (POD) activity increased with increasing of the duration of treatment. In roots, CAT activity increased with increasing of the duration of treatment, POD activity increased during early days and then declined. Superoxide dismutase (SOD) activity showed an upward trend with increasing of the duration of treatment after 3 and 6 days, then declined both in leaves and roots (9 days). SOD and POD had highest activities at 50 microM Cd in leaves. CAT activity was lowest at 50 microM Cd. Malondialdehyde (MDA) content increased with the increasing of Cd concentrations and duration of treatment in leaves. In roots, MDA content showed an upward trend with increasing of the duration of treatment at early time and then declined.

Effects of subchronic digestive exposure to organic or inorganic cadmium on biomarkers in rat tissues

In an experimental food chain, Wistar rats were fed cadmium (Cd) in an inorganic (CdCl(2)) or organic (mainly associated with metallothionein from Helix aspersa snail viscera) form. After 1 month of exposure to 100 microg inorganic Cd g(-1) in food, an induction of metallothionein was observed in all target tissues. In liver, glutathione peroxidase (GSH-Px) activity decreased and alanine aminotransferase (ALAT) activity increased, suggesting that Cd causes hepatotoxicity. However, lipid peroxidation as well as catalase and caspase 3 (a marker of apoptosis) activities were not modified. At a rather low exposure (2.5 microg Cd g(-1)), metallothionein level in the kidney was found to be the most sensitive biomarker of exposure for both Cd forms. In the small intestine of rats ingesting inorganic Cd, metallothionein expression was significantly higher than that observed for rats fed organic Cd. Present results allowed proposing a simple design to assess the effect of a chemical in a trophic transfer approach.

Effect of salt on isoprostanes in salt-sensitive essential hypertension

The controversy over beneficial versus harmful effects of salt on cardiovascular outcomes may be caused by different effects of salt on intermediate phenotypes of hypertension not characterized in epidemiological studies. Hence, we investigated acute effects of salt on oxidative stress in hypertensive subjects classified as salt sensitive (SS, n=14) or salt resistant (SR, n=13) by an inpatient protocol of salt loading (460 mmol NaCl) and salt depletion (10 mmol NaCl and furosemide). Oxidative stress was assessed by measuring the plasma isoprostane 8-iso-PGF2alpha. SS had lower plasma renin activity, higher aldosterone/renin ratios, and exaggerated endothelin and catecholamine responses to salt depletion compared with SR. Baseline lipid-bound isoprostanes (749+/-70 pmol/L) were 83% of the total and were slightly but not significantly higher in SS than SR. Baseline free isoprostanes did not differ between groups. After salt loading, lipid-bound isoprostanes were higher in SS (945+/-106) than SR (579+/-57; P<0.01). Salt depletion significantly decreased them in SS (-174+/-84) and increased them in SR (+129+/-58), equalizing their levels (771+/-61 versus 708+/-91; P value not significant). Free isoprostanes were decreased by salt depletion only if data in all of the patients were analyzed together. Total isoprostanes followed the pattern of the lipid-bound fraction. Correlations between salt depletion-induced changes in lipid-bound isoprostanes, plasma renin activity (r=0.45; P<0.02), and aldosterone/renin ratios (r=-0.41; P<0.04) suggested that the more SS the patient, the greater the reduction of oxidative stress by salt depletion. Our research is the first to show that salt affects oxidative stress acutely in humans, particularly in SS hypertension, which may explain the controversial results of epidemiological studies on salt and morbidity and may have implications for therapy.

Activity of the enzymes of the antioxidative system in cadmium-treated Oxya chinensis (Orthoptera Acridoidae)

One purpose in this research was to determine the toxic effects of Cd on antioxidant enzymes of Oxya chinensis (Orthoptera: Acridoidae). Changes in the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and guaiacol peroxidase (GPx) were measured in O. chinensis insects injected with Cd(2+). Fifth-nymphs of O. chinensis insects were injected with Cd(2+) at different concentrations (0, 0.55×10(-4), 1.10×10(-4), 1.65×10(-4), 2.20×10(-4), and 2.75×10(-4)gg(-1)). An increase in SOD activity in O. chinensis was observed at 1.10×10(-4) to 2.75×10(-4)gg(-1) Cd(2+). The SOD activity was lower at 2.20×10(-4)and 2.75×10(-4)gg(-1) than that at 1.10×10(-4) and 1.65×10(-4)gg(-1). It appears that SOD had a positive protective effect at low Cd(2+) concentrations, and that this effect disappeared at high Cd(2+) concentrations. CAT activity was accelerated to varying degrees at 1.10×10(-4) to 2.75×10(-4)gg(-1) for males and at 1.10×10(-4), 2.20×10(-4), and 2.75×10(-4)gg(-1) for females. CAT showed a strong detoxification effect with all treatments. GPx activity decreased with increasing Cd(2+) concentration with all treatments for males and at 2.20×10(-4) and 2.65×10(-4)gg(-1) for females. We showed that GPx activity had a weak detoxification function with all treatments for males and at high Cd(2+) for females. Thus, CAT had a strong detoxification effect, whereas SOD had a medium and GPx had a weak detoxification effect. Among the three enzymes, CAT played an important role in the damaging mechanisms of reactive oxygen species in O. chinensis insects. Alterations of the antioxidant enzyme level under environmental stresses are suggested as indicators of biotic and abiotic stress.

How Could Aortic Arginase Activity Enhancement Be Involved in DOCA‐Salt Hypertension?

This study was to examine whether the increase in aortic arginase activity observed in DOCA-salt hypertensive rats is involved in the mechanism of physiological hypertension by participating to vessel hypertrophy and/or to the impairment of endothelium-dependent relaxation to acethylcholine. We measured polyamine content and relaxation-response to acethylcholine in aortic rings isolated from control and DOCA-salt treated Sprague-Dawley rats after in vitro modification of arginase activity. Polyamine content was significantly increased in aorta from DOCA-salt hypertensive rats compared with controls. In the normotensive rats, the addition of L-valine (an inhibitor of arginase) decreased the relaxation response to acethylcholine whereas the addition of arginase increased the relaxation dependent response. On the contrary, in DOCA-salt hypertensive rats, the addition of L-valine or of arginase did not change the endothelium dependent relaxation. The results obtained suggest that the increase in aortic arginase activity in DOCA-salt hypertension could contribute to vascular hypertrophy but not to the impairment of endothelium-dependent relaxation.

Antioxidant status in the liver of hypertensive and metallothionein-deficient mice

Because oxidative stress is involved in arterial hypertension, impairment of hepatic antioxidant defences could develop in the course of this disease. Metallothionein (MT), an antioxidant protein, is present in high rates in the liver. The aim of this study was to investigate the effect of a mineralocorticoid-salt treatment on blood pressure, hepatic antioxidant enzyme activities, and cardiac MT levels in transgenic MT null mice compared with control mice to further clarify the role of MT during the experimental development of arterial hypertension. Control and transgenic MT –/– mice were submitted to an 8-week mineralocorticoid-salt treatment. Hepatic glutathione peroxidase, glutathione reductase, superoxide dismutase, and catalase activities and cardiac MT and mineral levels were measured. Mineralocorticoid-salt treatment induced an increase in blood pressure in both transgenic MT –/– and control mice that was associated with an impairment of liver antioxidant status. MT deficiency was associated with modifications of hepatic antioxidant enzyme activities and with a decrease in cardiac iron levels. Adaptive processes of antioxidant systems may explain the absence of an effect of metallothionein deficiency on the development of mineralocorticoid-salt hypertension. The interactions that occur between the in vivo antioxidant systems probably produce a complex regulation of the oxidative balance and consequently prevent antioxidant deficiency.Key words: hepatic antioxidant enzymes, metallothionein, transgenic mice, DOCA-salt hypertension.

Dietary vitamin C supplementation decreases blood pressure in DOCA-salt hypertensive male Sprague-Dawley rats and this is associated with increased liver oxidative stress

The effects of a vitamin C supplemented diet on blood pressure, body and liver weights, liver antioxidant status, iron and copper levels were investigated in DOCA-salt treated and untreated Sprague-Dawley (SD) male rats after 8 weeks of treatment. Vitamin C supplementation had no effect on blood pressure in SD rats but induced a significant decrease in blood pressure in DOCA-salt treated rats, the decrease being more efficient at 50 mg/kg of vitamin C than at 500 mg/kg. Hepatic lipid peroxidation and iron levels were significantly increased in DOCA-salt hypertensive rats whereas total hepatic antioxidant capacity (HAC), glutathione peroxidase (GSH-Px) and catalase (CAT) activities were decreased. Vitamin C supplementation did not affect the overall antioxidant defences of control SD rat livers. In contrast, vitamin C supplementation accentuated the DOCA-salt induced accumulation of liver iron and lipid peroxidation. This occurred without any notable aggravation in the antioxidant deficiency of vitamin C supplemented DOCA-salt treated rat livers. Our data suggest that DOCA-salt treatment induces an accumulation of iron in rat livers which is responsible for the prooxidant effect of vitamin C. The normalization of blood pressure in DOCA-salt treated rats by vitamin C supplementation appears thus independent from liver antioxidant status.

Strain difference (WKY, SPRD) in the hepatic antioxidant status in rat and effect of hypertension (SHR, DOCA). Ex vivo and in vitro data

We assessed the hepatic antioxidant status of spontaneously (SHR) and desoxicorticosterone acetate (DOCA)-induced hypertensive rats and that of respective normotensive Wistar Kyoto (WKY) and Sprague-Dawley (SPRD) rats. For this we evaluated, ex vivo in liver cytosols, reduced glutathione (GSH) content, glutathione-related enzyme (peroxidase, reductase and transferase) activities as well as the rate of lipid peroxidation in 9-11 week-old rats. The antioxidant status and the cytotoxicity of acetaminophen, a radical- and hydrogen peroxide-mediated hepatotoxic compound, were also assessed in vitro in cultured hepatocytes isolated from hypertensive (SHR, DOCA) and normotensive control (WKY, SPRD) rats. Our results suggest that a difference exists in the hepatic antioxidant status between rat strains, with GSH levels being lower (-15%) and lipid peroxidation rate higher (+30%) in WKY compared to SPRD rats. In hepatocyte cultures from WKY rats, both GSH content and catalase activity were lower (-30 and -70% respectively) compared to hepatocyte cultures from SPRD rats. This was associated with a 35% higher cytotoxicity of acetaminophen in cultured hepatocytes from WKY rats compared to that in hepatocytes from SPRD rats. Hypertension in DOCA rats (mmHg: 221+/-9 vs. 138+/-5 in control SPRD rats) was associated with decreases (about 30%) in both glutathione peroxidase (GSH-Px) and catalase activities, ex vivo in livers and in vitro in hepatocyte cultures. Hypertension in SHR (mmHg: 189+/-7 vs. 130+/-5 in control WKY rats) was also associated with decreases (about 50%) in GSH-Px activity, ex vivo in livers and in vitro in hepatocyte cultures but catalase activity was not modified. The IC50 of acetaminophen was also lower in hepatocytes from hypertensive rats compared to respective controls, which could be related to the weakened antioxidant status in hepatocytes from hypertensive rats. Our data thus suggest that hepatocyte cultures are appropriated tools in which to assess hepatotoxicity and hepatoprotection in hypertension.