Effect of dietary fats on hydroperoxide-induced chemiluminescence emission and eicosanoid release in the rat heart

The diverse role of selenium within selenoproteins: a review

Selenium functions within mammalian systems primarily in the form of selenoproteins. Selenoproteins contain selenium as selenocysteine and perform a variety of physiological roles. Eleven selenoproteins have been identified: cellular or classical glutathione peroxidase; plasma (or extracellular) glutathione peroxidase; phospholipid hydroperoxide glutathione peroxidase; gastrointestinal glutathione peroxidase; selenoprotein P; types 1, 2, and 3 iodothyronine deiodinase; selenoprotein W; thioredoxin reductase; and selenophosphate synthetase. Of these, cellular and plasma glutathione peroxidase are the functional parameters used for the assessment of selenium status. Glutathione peroxidases catalyze the reduction of peroxides that can cause cellular damage. Thioredoxin reductase provides reducing power for several biochemical processes and defends against oxidative stress. Selenoprotein P appears to play a role in oxidant defense. Selenoprotein W may play a role in oxidant defense and be involved with muscle metabolism. Thyroid deiodinases function in the formation and regulation of active thyroid hormone. Selenophosphate synthetase is an enzyme required for the incorporation of selenocysteine into selenoproteins. In addition, a protein in the sperm mitochondrial capsule, which is vital to the integrity of sperm flagella, may be a unique selenoprotein. Recommended intakes, food sources, and status assessment of selenium, as well as selenium's role in health and disease processes, are reviewed.

Effects of eicosapentaenoic acid and docosahexaenoic acid diet supplement on tolerance to the cardiotoxicity of epirubicin and to ischaemia reperfusion in the isolated rat heart

We compared the effects of 2 weeks dietary supplement of docosahexaenoic acid, eicosapentaenoic acid or olive oil on myocardial tolerance to the cardiotoxicity of the anthracycline epirubicin and to ischaemia reperfusion. Isolated rat hearts from the dietary groups were perfused at a constant flow rate of 12.5 ml/min. The hearts were subjected to a 20 min. period of epirubicin infusion by a side arm of the perfusion system at a rate of 0.2 mg/min. or a 20 min. period of global ischaemia. After 10 min. of epirubicin infusion a significantly (P < 0.05) higher aortic pressure (an index of coronary resistance during constant flow perfusion) was observed in the olive oil group; 130 +/- 22% (mean +/- S.D.) compared to hearts in the docosahexaenoic acid; 108 +/- 9% (mean +/- S.D.), and eicosapentaenoic acid; 105 +/- 7% (mean +/- S.D.), group. Hearts from docosahexaenoic acid-fed rats showed a significantly increased left ventricular end-diastolic pressure (an index of contracture); of 66 +/- 30 mmHg (mean +/- S.D.) after 15 min. of global ischaemia compared to eicosapetaenoic acid fed rats; 37 +/- 18 mmHg (mean +/- S.D.), and significantly higher release of lactate dehydrogenase during the following 30 min. period of reperfusion compared to olive oil-fed rats. We conclude that eicosapentaenoic acid and docosahexaenoic acid could be useful during epirubicin infusion and that docosahexaenoic acid could be harmful during ischaemia reperfusion.

Peroxides in human leucocytes in acute septic shock: a preliminary study of acute phase changes and mortality

Peroxidation by peripheral blood leucocytes was measured in 15 patients in acute septic shock and 15 uninfected controls, using the probe dichloroflorescein. Mortality in septic subjects was 40%. In 14 of 15 patients from whom serial samples were analysed, periods of increased oxidative activity were detected. Increased peroxidation occurred early in the sequence of clinical changes, at the same time as increases in temperature, blood pressure and C-reactive protein. Peak peroxide production preceded increases in acute phase reactants and changes in leucocyte distribution. Mean peroxide production in leukocytes from patients who died was significantly higher (P < 0.001) than paired controls, and greater (P < 0.05) than peroxide production in patients who survived. The in vitro oxidative response to endotoxin was upregulated in infected patients. This supports the hypothesis that systemic mediators and leucocyte-derived reactive oxygen are involved in the vascular and organ damage associated with fatal septic shock.

[Vitamin E, antioxidants and atherosclerosis]

Atherosclerosis is a process in which lipid and factors are mixed. When LDL are oxydized, they are catabolized by the macrophage's pathway, leading to foam cells which constitute the fatty streak, the earliest lesion in atherogenesis, and they have cytotoxic, chemotactic effects. Many protective devices against free radicals and oxydation mechanisms exist, particularly antioxydant vitamins and other natural dietary antioxydants. After a brief recall of their mechanisms, epidemiological, experimental and clinical data are reviewed. To day it seems necessary to take into consideration these factors in prevention and therapeutic of atherosclerosis and dylipidaemia. Many inquiries keep going, particularly about susceptible of LDL to oxydation. One is waiting for intervention surveys in order to conclude about nutritional and medical treatments.

Myocardial vitamin E is consumed during cardiopulmonary bypass: indirect evidence of free radical generation in human ischemic heart

Although a role for free radicals in myocardial damage during cardiopulmonary bypass for open heart surgery has been postulated, direct evidence of free radical production as well as consumption of tissue antioxidants such as vitamin E is still lacking. Twenty patients (age 26-66 yr, mean 48) undergoing elective open heart surgery with moderate hypothermia, and cold crystalloid cardioplegia, were studied. Cardiopulmonary bypass time was 61.4 +/- 31.2 min. The specimens of atrial tissue collection before and after cardiopulmonary bypass, were immediately frozen in liquid nitrogen. Mean vitamin E atrial content, measured by reverse phase HPLC, was 355 +/- 249 pmol/mg of dry weight basally, 135 +/- 85 pmol/mg (p < 0.05) at the end of the ischemic period and 405 +/- 288 pmol/mg after the reperfusion period (p < 0.01). Microscopic examination of right atrial biopsies ruled out differences in fibrosis or cellular damage as the cause of vitamin E changes. Although a great basal variability in atrial vitamin E content was observed, which was independent of age, sex and clinical status, a reproducible and substantial decrease in atrial vitamin E content after cardiopulmonary bypass occurred (mean reduction 45 +/- 17% and 55 +/- 22%, respectively, after ischemia and after reperfusion). This was directly related to the aorta cross-clamping duration and partially to the minimum temperature achieved. In conclusion, apart from the great variability observed in basal vitamin E tissue content, vitamin E was always reduced during cardiopulmonary bypass, suggesting an oxidative stress on the myocardium during open heart surgery.

Effects of high fat-, cholesterol-enriched diet on the antioxidant defence mechanisms in the rabbit heart

In 7 rabbits fed on hyperlipidic diet (0.5% cholesterol, 5% peanut oil and 5% lard) for 4 weeks, the ventricular myocardium was tested for antioxidant defences and thiobarbituric acid reactive substances. Seven age-matched rabbits served as controls. The hearts were previously subjected to 45 min Langendorff perfusion to study coronary flow, developed tension and resting tension; coronary effluent values of CPK activity, pH and UV absorbance at 250 nm (i.e., low molecular weight ATP catabolites) were also investigated. After 4 weeks of diet, a significant rise of plasma cholesterol (P < 0.0001) and triglycerides (P < 0.0001) was observed. Total superoxide dismutase, catalase and glutathione transferase activities underwent a significant increase (P < 0.05) in the hyperlipidemic animals. On the contrary, a depression of glutathione reductase (P < 0.01) and selenium-dependent glutathione peroxidase (P < 0.01) activities, associated with decreased levels of non proteic thiol compounds (P < 0.01), was assessed. The selenium-independent glutathione peroxidase activity was not detectable in both groups. Thiobarbituric acid reactive substances levels were significantly increased in the hyperlipidemic rabbit myocardium (P < 0.01). Even though heart hemodynamics, CPK release and perfusate pH did not differ in control and experimental animals, higher 250 nm absorbance values (P < 0.05) were detected in the myocardial effluent of hyperlipidemic rabbits. In conclusion, high fat-, cholesterol-enriched diet induces an imbalance in the rabbit heart antioxidant defences, some of which are increased, whereas others are depressed, eventually resulting in enhanced myocardial lipid peroxidation. These biochemical changes are associated with higher perfusate values of UV absorbance at 250 nm, but not with significant CPK leakage or myocardial hemodynamics derangement.

Effect of fish oil and coconut oil on antioxidant defence system and lipid peroxidation in rat liver

Diets high in fish oil containing polyunsaturated fatty acids of the n-3 family, have been suggested to decrease the risk of cardiovascular disease. However these lipids are highly susceptible to oxidative deterioration. In order to investigate the influence of n-3 fatty acids on oxidative status, the effect of feeding rats with fish oil or coconut oil diets was studied by measuring different parameters related to an oxidative free radical challenge. Synthetic diets containing 15% (w/v) fish oil or coconut oil were used to feed growing rats for 4 weeks. As compared to control diet, the fish oil containing diet produced a significant decrease of cholesterol and triglyceride concentration in serum, however there was a significant increase in lipid peroxidation products. In addition, in fish oil fed animals, there was also a decrease in vitamin E and A concentration. Furthermore, the rate of lipid peroxidation in isolated microsomes was three fold higher in rats fed fish oil as compared to rats with coconut oil diet. No significant differences between the two experimental groups were observed in superoxide dismutase (SOD) and phospholipid hydroperoxide glutathione peroxidase (PHGPX) activities. However, there was a decrease in glutathione peroxidase (GPX) activity. These results suggest that fish oil feeding at an amount compatible with human diet, although decreasing plasma lipids, actually challenge the antioxidant defence system, thus increasing the susceptibility of tissues to free radical oxidative damage.

Oxidative stress in the rat heart, studies on low-level chemiluminescence

Detection of ultraweak chemiluminescence (CL) emission from the surface of the organ is a sensitive and non-disruptive tool to evaluate the oxidative stress in rat heart. Indeed, an increased photon emission rate can be observed when cellular antioxidants such as glutathione or vitamin E are depleted, or when organic hydroperoxides are infused. We used CL recording to demonstrate in rat heart that: (i) different diets may lead to different heart sensitivity to an oxidative stress; and (ii) post-ischaemic reoxygenation induces an oxidative stress. CL emission induced by an oxidative stress is accompanied by an increased release of eicosanoids. However, while non-steroid anti-inflammatory drugs (aspirin, indomethacin and ibuprofen) prevented eicosanoid release, these compounds dramatically enhanced hydroperoxide-dependent CL. The nature of this phenomenon is still obscure, but the increase of steady-state concentration of excited species caused by anti-inflammatory drugs seems to be pathophysiologically relevant, since in all our experimental conditions tissue damage was proportional to CL emission rate.

Increased ultra weak chemiluminescence emission from rat heart at postischemic reoxygenation: protective role of vitamin E

Aim of this study was to confirm an increased free radical generation rate during ischemia-reoxygenation, by ultra-weak chemiluminescence detection at the surface of perfused rat heart. We observed that reoxygenation following 30 min global ischemia, induces an increase of ultraweak chemiluminescence emission in isolated perfused heart only if partial depletion of vitamin E is induced by dietary manipulation. Moreover, in normal diet fed rats, vitamin E is partially consumed during global ischemia, but not during reoxygenation. Since chemiluminescence increases during post-ischemic reperfusion, when vitamin E myocardial content is lowered, the most probable free radicals involved are the hydroperoxyl radical derivatives of lipids. These radicals, indeed, are known both to produce photoemission by disproportion and to react with vitamin E. On the other hand, the nature of the reaction that consumes vitamin E during ischemia is still obscure. Accordingly, the basal level of vitamin E myocardial content seems to be a key factor for protecting the heart against reoxygenation injury and its consumption during ischemia could be a determinant of myocardial sensitivity to oxidative stress during reperfusion.