Effect of alpha-tocopherol on doxorubicin-induced changes in rat liver and heart microsomes.

Rats were treated with doxorubicin (2.5 mg/kg body wt, iv) once a week for 8 weeks. Alpha-Tocopherol (400 mg/kg body wt/day) was co-administered orally for 2 months. Cytochrome-P450 (Cyt-P450) and Cytochrome-b5 (Cyt-b5) levels decreased significantly in doxorubicin treated rats. Significant decreases were observed in glucose-6-phosphatase, Cyt-P450 and Cyt-b5 reductase activities. In vitro lipid peroxidation study showed that alpha-tocopherol significantly minimises the lipid peroxide formation by doxorubicin. There was a significant change in microsomal cholesterol and phospholipid levels. Alpha-Tocopherol co-administration reduced the alterations in xenobiotic metabolising system and microsomal lipid levels. The results were discussed with reference to drug metabolising enzymes, lipid peroxidation and antioxidant nature of alpha-tocopherol.     

Lipid peroxidation in plasma of rats treated with ferric-nitrilotriacetate, in relation to kidney and liver modifications

Intraperitoneal injection of the iron chelate ferric-nitrilotriacetate (Fe-NTA) induces in rodents renal and hepatic suffering, associated with oxidative damage. We investigated the oxidation pattern in plasma of treated rats in relation to liver and kidney, monitoring the variation of the lipid components more susceptible to oxidation, unsaturated fatty acids (UFA) and alpha-tocopherol, as biomarkers of the oxidative damage. A sublethal dose of Fe-NTA induced a strong and extremely significant decrease of UFA levels at 1 h after injection in the plasma compartment and at 3 h in the kidney, with reductions up to 40-50% of the control values, together with an increase of conjugated dienes fatty acids hydroperoxides and a consumption of alpha-tocopherol. The same modifications were observed in the liver, but to a lesser extent. Histological observation proved that biochemical changes in the lipid fraction were a direct consequence of an ongoing membrane lipid peroxidation process. Our data show that oxidative damage to the lipid fraction is initially evident in the plasma compartment, where Fe-NTA toxicity is assumed to be caused by the elevation of serum free iron concentration, and proceeds with different speed and severity in the kidney and liver.     

Increase in cellular pool of low-molecular-weight iron during ethanol metabolism in rat hepatocyte cultures

Ethanol-induced lipid peroxidation was studied in primary rat hepatocyte cultures supplemented with ethanol at the concentration of 50 mM. Lipid peroxidation was assessed by two indices: (1) conjugated dienes by second-derivative UV spectroscopy in lipid extract of hepatocytes (intracellular content), and (2) free malondialdehyde (MDA) by HPLC-UV detection and quantitation for the incubation medium (extracellular content). In cultures supplemented with ethanol, free MDA increased significantly in culture media, whereas no elevation of conjugated diene level was observed in the corresponding hepatocytes. The cellular pool of low-mol-wt (LMW) iron was also evaluated in the hepatocytes using an electron spin resonance procedure. An early increase of intracellular LMW iron (≤1 hr) was observed in ethanol-supplemented cultures; it was inhibited by 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, whereas α-tocopherol, which prevented lipid peroxidation, did not inhibit the increase of LMW iron. Therefore, the LMW iron elevation was the result of ethanol metabolism and was not secondarily induced by lipid hydroperoxides. Thus, ethanol caused lipid peroxidation in rat hepatocytes as shown by the increase of free MDA, although no conjugated diene elevation was detected. During ethanol metabolism, an increase in cellular LMW iron was observed that could enhance conjugated diene degradation.     

Effect of doxorubicin on the intestinal membranes in rats—Influence of α-tocopherol administration

The effect of α-tocopherol on doxorubicin induced changes in intestinal brush border and basolateral membranes were studied in rats. Rats were treated with doxorubicin (2.5 mg/kg body wt.), intravenously, weekly for 8 weeks. α-Tocopherol (400 mg/kg body wt.) was given orally, daily for 2 months. Intestinal basolateral membrane bound ATPases and brush border membrane bound alkaline phosphatase activities were found to be decreased significantly in doxorubicin treated rats. The lipid peroxide level was found to be elevated with a significant depletion in membrane sulphydryl groups. In α-tocopherol coadministered animals, the enzyme activities were found to be restored with concomitant reduction in lipid peroxide levels and an increase in the membrane sulphydryl groups. The membrane cholesterol and phospholipid levels which were altered in doxorubicin treated animals were found to be maintained significantly. The results are discussed with reference to the effect of α-tocopherol on lipid peroxidation and membrane sulphydryl groups.     

Measurement of doxorubicin-induced lipid peroxidation under the conditions that determine cytotoxicity in cultured tumor cells.

We have investigated doxorubicin-induced lipid peroxidation by the measure of malondialdehyde (MDA) formation in rat glioblastoma cells and human breast carcinoma cells in culture. There was a significant production of MDA when the cells were incubated with pharmacologically relevant doxorubicin concentrations, i.e., concentrations that produce a significant cytotoxicity (0.1 micrograms/ml). At equitoxic doses, vincristine provided no lipid peroxidation, indicating that MDA formation is not a consequence of cell death. Doxorubicin-induced lipid peroxidation was maximal 24 h after incubation of the cells with doxorubicin, indicating that a delay was necessary for the free radical-mediated membrane damage induced by doxorubicin. In the presence of alpha-tocopherol in the culture medium, the doxorubicin-induced MDA formation was inhibited. The development of this method will help in defining the role of free radicals and lipid peroxidation in the cytotoxicity of doxorubicin.     

Oxidative stress after moderate to extensive burning in humans

Lipid peroxidation products, lipid antioxidants, and hematologic and blood chemistry changes were evaluated in plasma of patients after acute burning injury involving 10% (n=8), 20% (n=8), and 40% (n=5) of total body surface area (TBSA), 24 h after burning (baseline) up to 30 days after. Markedly increased plasma levels of malondialdehyde (MDA) were observed at baseline in all patients, according to the extent of the injury, then the values declined progressively. However, levels of MDA remained above normal up to 30 days even in less injured patients. On the other hand, the plasma level of conjugated diene lipid hydroperoxides was only slightly higher than control at the baseline, then dropped under the control value in all patients. Cholesterol showed a marked fall at baseline, followed by a rapidly progressive decrease, indicating a massive loss of circulating lipids by the acute thermal injury. Because of such an extensive and rapidly spreading oxidative degradation of lipids, decomposition of conjugated diene hydroperoxides, produced in early stages of the peroxidation process, occurs, so these compounds cannot be a suitable index to value lipid oxidation in burned patients.

Aldehydic products of lipid peroxidation act as endotoxins, causing damage to various tissues and organs. Damage to liver and decrease of erythrocyte survival were assessed by increased plasma levels of asparate and alanine transaminases, within 7-15 days after injury, and by a decreased number of red blood cells, which remained under the normal value at 30 days.

A marked decrease of lipid antioxidants, β-carotene, vitamin A and vitamin E was observed at baseline. The level of β-carotene remained low in all patients at the end of the 30-day observation. A complete recovery of vitamin A did not occur at 30 days post-burn, even in the patients with 10% of burned TBSA. Plasma levels of vitamin E decreased significantly in 1-7 days after burn in all patients, but these levels increased thereafter, with almost total recovery at 30 days.

These data show evidence of a marked, long-lasting oxidant/antioxidant imbalance in burned patients, in accordance with the severity of the injury, which is also reflected as systemic oxidant stress.     

Peroxidation of the dried thin film of lipid by high-energy alpha particles from a cyclotron

High-energy alpha particles produced a dose-dependent linear increase in different lipid peroxidation products (e.g., malondialdehyde (MDA), conjugated dienes, and hydroperoxides) in the dried thin film state. An inverse dose-rate effect was observed when the dose rate was varied by changing either the alpha-particle fluence rate or the alpha-particle energy. The antioxidants alpha-tocopherol and butylated hydroxytoluene (BHT) suppressed the alpha-particle-induced lipid peroxidation in the dried thin film state, and in this respect alpha-tocopherol was found superior to BHT. It was found that alpha-tocopherol was equally efficient in inhibiting lipid peroxidations by alpha particles and ultraviolet light.     

Modulatory influence of dietary resveratrol during different phases of 1,2-dimethylhydrazine induced mucosal lipid-peroxidation, antioxidant status and aberrant crypt foci development in rat colon carcinogenesis

To shed light on the association of lipid peroxidation and antioxidant status with the development of aberrant crypt foci (ACF), we studied the modulatory influence of resveratrol, supplemented in three dietary regimens (initiation, post-initiation and entire period) on 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis. Rats were administered DMH (20 mg/kg body weight, s.c.) for 15 weeks and were supplemented with resveratrol (8 mg/kg body weight, p.o. everyday) in three dietary regimens. Intestines and colons were analyzed for the levels of diene conjugates (DC), lipid hydroperoxides (LOOHs) and thiobarbituric acid reactive substances (TBARS). Enzymic antioxidants (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX; glutathione S-transferase, GST; and glutathione reductase, GR) and non-enzymic reserve (reduced glutathione, GSH; ascorbate; and alpha-tocopherol) were also assessed in the intestine and colon. Unsupplemented DMH exposed rats showed significantly decreased levels/activities of tissue DC, LOOHs, TBARS, SOD, CAT, GSH, GR and significantly elevated (P<0.05) GPX, GST, alpha-tocopherol and ascorbate as compared to control rats. Resveratrol supplementation during the entire period of the study resulted in significant (P<0.01) modulation of lipid peroxidation markers and antioxidants status, which were paralleled with ACF suppression, as compared to DMH-alone treated rats. These results indicate that resveratrol effectively inhibits DMH-induced ACF and colonic tumor development.     

Fluorescence imaging of lipid peroxidation in isolated rat lungs during nonhypoxic lung ischemia

We have shown previously that ischemia results in reactive oxygen species production by lung endothelium that occurs within 3-5 s after flow cessation and is followed by lipid peroxidation at 15-30 min as determined by assay of thiobarbituric acid-reactive substances, conjugated dienes, and protein carbonyls in lung homogenate. The present study evaluated membrane lipid peroxidation in isolated, ventilated rat lungs using a fluorescence imaging method that permits continuous observation of pulmonary subpleural microvascular endothelial cells in situ. Diphenyl-1-pyrenylphosphine (DPPP), a fluorescent probe which localizes in the plasma membrane and shows increased fluorescence emission after its oxidation by lipid hydroperoxides, was used for detection of membrane lipid peroxidation. Compared to continuously perfused control lungs, endothelial cell DPPP fluorescence increased significantly within 1 min of ischemia (i.e., flow cessation); these changes were prevented by pretreatment with 0.5 mM alpha-tocopherol succinate (vitamin E) added to the perfusate. Increased DPPP fluorescence was confirmed by spectrofluorometry of lipid extracts of lung homogenates. These data indicate that DPPP can be used for the real-time detection of lipid peroxidation in an intact organ. Ischemia results in peroxidation of the pulmonary microvascular endothelial cell membrane and this insult can be detected as early as 1 min after the onset of ischemia compatible with a radical-mediated process.     

Green tea protection of hypoxia/reoxygenation injury in cultured cardiac cells

Antioxidant-rich diets exert a protective effect in diseases involving oxidative damage. Among dietary components, green tea is an excellent source of antioxidants. In this study, cultured neonatal rat cardiomyocytes were used to clarify the protective effect of a green tea extract on cell damage and lipid peroxidation induced by different periods of hypoxia followed by reoxigenation. Cultures of neonatal rat cardiomyocytes were exposed to 2--8 hr hypoxia, eventually followed by reoxygenation, in the absence or presence of alpha-tocopherol or green tea. LDH release and the production of conjugated diene lipids were measured, and appeared linearly related to the duration of hypoxia. During hypoxia, both LDH release and conjugated diene production were reduced by alpha-tocopherol and, in a dose dependent manner, by green tea, the 50 &mgr;g/ml being the most effective dose. Reoxygenation caused no further increase in LDH leakage, while it caused a significant increase in conjugate dienes, which absolute value was lower in antioxidant supplemented cells. Anyway, the ratio between conjugated diene production after hypoxia and after reoxygenation was similar in all groups, indicating that the severity of free radical-induced reoxygenation injury is proportional to the severity of previous hypoxic injury. Since hypoxic damage is reduced by alpha-tocopherol and green tea, our data suggest that any nutritional intervention to attenuate reoxygenation injury must be directed toward the attenuation of the hypoxic injury. Therefore, recommendations about a high dietary intake of antioxidants may be useful not only in the prevention, but also in the reduction of cardiac injury following ischemia.     

Lipid peroxidation and haemoglobin degradation in red blood cells exposed to t-butyl hydroperoxide. The relative roles of haem- and glutathione-dependent decomposition of t-butyl hydroperoxide and membrane lipid hydroperoxides in lipid peroxidation and haemolysis

Red cells exposed to t-butyl hydroperoxide undergo lipid peroxidation, haemoglobin degradation and hexose monophosphate-shunt stimulation. By using the lipid-soluble antioxidant 2,6-di-t-butyl-p-cresol, the relative contributions of t-butyl hydroperoxide and membrane lipid hydroperoxides to oxidative haemoglobin changes and hexose monophosphate-shunt stimulation were determined. About 90% of the haemoglobin changes and all of the hexose monophosphate-shunt stimulation were caused by t-butyl hydroperoxide. The remainder of the haemoglobin changes appeared to be due to reactions between haemoglobin and lipid hydroperoxides generated during membrane peroxidation. After exposure of red cells to t-butyl hydroperoxide, no lipid hydroperoxides were detected iodimetrically, whether or not glucose was present in the incubation. Concentrations of 2,6-di-t-butyl-p-cresol, which almost totally suppressed lipid peroxidation, significantly inhibited haemoglobin binding to the membrane but had no significant effect on hexose monophosphate shunt stimulation, suggesting that lipid hydroperoxides had been decomposed by a reaction with haem or haem-protein and not enzymically via glutathione peroxidase. The mechanisms of lipid peroxidation and haemoglobin oxidation and the protective role of glucose were also investigated. In time-course studies of red cells containing oxyhaemoglobin, methaemoglobin or carbonmono-oxyhaemoglobin incubated without glucose and exposed to t-butyl hydroperoxide, haemoglobin oxidation paralleled both lipid peroxidation and t-butyl hydroperoxide consumption. Lipid peroxidation ceased when all t-butyl hydroperoxide was consumed, indicating that it was not autocatalytic and was driven by initiation events followed by rapid propagation and termination of chain reactions and rapid non-enzymic decomposition of lipid hydroperoxides. Carbonmono-oxyhaemoglobin and oxyhaemoglobin were good promoters of peroxidation, whereas methaemoglobin relatively spared the membrane from peroxidation. The protective influence of glucose metabolism on the time course of t-butyl hydroperoxide-induced changes was greatest in carbonmono-oxyhaemoglobin-containing red cells followed in order by oxyhaemoglobin- and methaemoglobin-containing red cells. This is the reverse order of the reactivity of the hydroperoxide with haemoglobin, which is greatest with methaemoglobin. In studies exposing red cells to a wide range of t-butyl hydroperoxide concentrations, haemoglobin oxidation and lipid peroxidation did not occur until the cellular glutathione had been oxidized. The amount of lipid peroxidation per increment in added t-butyl hydroperoxide was greatest in red cells containing carbonmono-oxyhaemoglobin, followed in order by oxyhaemoglobin and methaemoglobin. Red cells containing oxyhaemoglobin and carbonmono-oxyhaemoglobin and exposed to increasing concentrations of t-butyl hydroperoxide became increasingly resistant to lipid peroxidation as methaemoglobin accumulated, supporting a relatively protective role for methaemoglobin. In the presence of glucose, higher levels of t-butyl hydroperoxide were required to induce lipid peroxidation and haemoglobin oxidation compared with incubations without glucose. Carbonmono-oxyhaemoglobin-containing red cells exposed to the highest levels of t-butyl hydroperoxide underwent haemolysis after a critical level of lipid peroxidation was reached. Inhibition of lipid peroxidation by 2,6-di-t-butyl-p-cresol below this critical level prevented haemolysis. Oxidative membrane damage appeared to be a more important determinant of haemolysis in vitro than haemoglobin degradation. The effects of various antioxidants and free-radical scavengers on lipid peroxidation in red cells or in ghosts plus methaemoglobin exposed to t-butyl hydroperoxide suggested that red-cell haemoglobin decomposed the hydroperoxide by a homolytic scission mechanism to t-butoxyl radicals.     

Vitamin E protects proteins against free radical damage in lipid environments

The fragmentation of the membrane protein monoamine oxidase in submitochondrial particles was induced by defined free radicals during radiolysis and by a system dependent on hydrogen peroxide and a transition metal. By injection of alpha-tocopherol in vivo, the levels of this physiological antioxidant in the mitochondrial preparations could be elevated more than ten-fold. In both radical-generating systems the presence of high levels of alpha-tocopherol in the membrane substantially retarded the protein fragmentation, in parallel with lipid peroxidation. It is suggested that membrane-bound proteins are damaged during lipid peroxidation and that alpha-tocopherol protects cells against both types of damage.     

Green tea extracts can counteract the modification of fatty acid composition induced by doxorubicin in cultured cardiomyocytes

Doxorubicin cardiotoxicity is associated with the generation of free radicals, and involves not only lipid peroxidation but also a decreased biosynthesis of highly unsaturated fatty acids, leading to significant modification in cardiomyocyte fatty acid composition. We have evaluated whether naturally occurring antioxidants could counteract this side-effect. Green tea is an excellent source of catechins; we supplemented cultured rat cardiomyocytes with different green tea extracts to relate their catechin content and composition to their ability in protecting cells against doxorubicin-induced damage. The determination of total lipid fatty acid composition, of conjugated diene production (indicator of lipid peroxidation), and of lactate dehydrogenase release revealed that supplementation with tea extracts could counteract significant modifications in the fatty acyl pattern due to doxorubicin exposure, although to different extents. These differences could be ascribed to the different total catechin content and to qualitative differences among the tea extracts, determined by HPLC analysis.     

Shigella dysenteriae type 1 toxin induced lipid peroxidation in enterocytes isolated from rabbit ileum

To evaluate the role of reactive oxygen species (ROS) in Shigella dysenteriae 1 toxin (STx) mediated intestinal infection, the ligated rabbit small intestinal loops were injected with STx. The enterocytes isolated from STx treated rabbit ileal loops had a significantly higher level of lipid peroxidation as compared to enterocytes isolated from control rabbit ileum. To study the role of second messengers in STx mediated intestinal damage, the in vivo and in vitro effects of modulators of lipid peroxidation of enterocytes were used. The presence of Ca²⁺-ionophore A23187 enhanced the extent of lipid peroxidation in enterocytes isolated from the control and STx treated rabbit ileum. However, l-verapamil only marginally decreased the lipid peroxidation level of enterocytes isolated from STx treated rabbit ileum. The in vitro effect of modulators was in agreement with in vivo studies. Dantrolene significantly decreased the extent of lipid peroxidation of enterocytes isolated from STx treated rabbit ileum. PMA significantly increased the lipid peroxidation level of enterocytes isolated from control ileum. However, PMA could not further enhance the lipid peroxidation level of enterocytes isolated from STx treated rabbit ileum. The presence of H-7 significantly decreased the extent of lipid peroxidation of enterocytes isolated from STx treated rabbit ileum. In vitro effect of PMA and H-7 was in agreement with that of in vivo findings. The role of arachidonic acid metabolites, prostaglandins (PGs), in mediating STx induced lipid peroxidation was also studied. The presence of indomethacin (a PG synthesis inhibitor) significantly decreased the lipid peroxidation induced by STx. These findings suggest that lipid peroxidation induced by STx is mediated through cytosolic calcium. The increase in (Ca²⁺)_i leads to activation of PKC.A significant decrease in the enterocyte levels of antioxidant enzymes superoxide dismutase, catalase and reduced glutathione in STx treated rabbit ileum as compared to control was seen. A significant decrease in vitamin E levels was also observed. This suggests that there is decreased endogenous intestinal protection against ROS in STx mediated intestinal infection which could contribute to enterocyte membrane damage that ultimately leads to changes in membrane permeability and thus to fluid secretion.     

Relationships between lipid peroxidation and anoxia tolerance in a range of species during post-anoxic reaeration

Peroxidation was studied in anoxically treated plant tissues and quantified as conjugated dienes/trienes in the total lipid fraction and as the production of thiobarbituric acid reactive substances (TBARS). Oxidative stress caused by re-exposure of plants to oxygen led to an increase of conjugated diene/triene formation in rhizomes of Iris germanica and roots of wheat ( Triticum aestivum L.) and oats ( Avena sativa L.), and after a long anoxic exposure (45 days) in the rhizomes of the very anoxia tolerant Iris pseudacorus . Second derivative (SD) spectrophotometry of the UV spectrum of lipid extracts confirmed the formation of dienes. However, determination of TBARS in Iris spp. showed no lipid peroxidation in the anoxia tolerant I. pseudacorus . In the rhizomes of the anoxia intolerant I. germanica , elevated levels of TBARS correlated positively with conjugated diene/triene formation. The results suggest that anoxic stress may induce qualitative changes in membrane lipids, as indicated by lipid peroxidation after restoration of aerobic conditions. The rate of lipid peroxidation correlated negatively with anoxic stress tolerance.     

Vanadium and lipid peroxidation: evidence for involvement of vanadyl and hydroxyl radical

The present study was designed to determine which form of vanadium is involved in initiating conjugated diene formation in both purified and partially peroxidized fatty acids, and to determine if active oxygen radicals are involved in this process. We report that vanadyl is the active form of vanadium in initiating conjugated diene formation in micelles prepared from purified fatty acids or partially peroxidized fatty acids. Vanadate did not initiate conjugated diene formation in either case. Hydroxyl radicals were shown to be involved in the initiation of diene conjugation when vanadyl and hydrogen peroxide were added together in a reaction mixture. In this case, there was a rapid burst of conjugated diene formation which quickly leveled off. Using spin trapping techniques, hydroxyl radicals were shown to be generated in the vanadyl-catalyzed break-down of fatty acid hydroperoxides. A comparison was made between the ability of vanadyl or vanadyl chelates to decompose hydrogen peroxide and catalyze the decomposition of fatty acid hydroperoxides. It was found that strongly chelated vanadyl (vanadyl/EDTA) was much less effective in decomposing both hydrogen peroxide and fatty acid hydroperoxides than the weak vanadyl chelates (e.g., vanadyl/ADP). This study suggests a mechanism to explain the effects of vanadium on lipid peroxidation.     

Citronellol disrupts membrane integrity by inducing free radical generation

Citronellol, an oxygenated monoterpene, is found naturally in the essential oils of several aromatic plants and has been reported to exhibit growth inhibitory and pesticidal activities. However, its mechanism of action is largely unexplored. We investigated the effect of citronellol, which is lipophilic in nature on membrane integrity in terms of lipid peroxidation, conjugated dienes content, membrane permeability, cell death, and activity of the enzyme lipoxygenase in roots of hydroponically grown wheat. Citronellol (50-250 microM) caused a significant inhibition of root and shoot growth. Furthermore, exposure to citronellol enhanced the solute leakage, increased the malondialdehyde content and lipoxygenase activity, and decreased the conjugated diene content. This indicates that citronellol induces generation of reactive oxygen species (ROS) resulting in lipid peroxidation and membrane damage. This was confirmed by in situ histochemical studies indicating cell death and disruption of membrane integrity. We conclude from this study that citronellol inhibits the root growth by ROS-mediated membrane disruption.     

Protective action of fenugreek (Trigonella foenum graecum) seed polyphenols against alcohol-induced protein and lipid damage in rat liver

The study investigates the effect of fenugreek seed polyphenol extract (FPEt) on ethanol-induced damage in rat liver. Chronic ethanol administration (6 g kg(-1) day(-1) x 60 days) caused liver damage that was manifested by excessive formation of thiobarbituric-acid-reactive substances, lipid hydroperoxides, and conjugated dienes, the end products of lipid peroxidation, and significant elevation of protein carbonyl groups and diminution of sulfhydryl groups, a marker of protein oxidation. Decreased activities of enzymic and non-enzymic antioxidant levels and decreased levels of thiol groups (both non-protein and protein) were observed in ethanol-treated rats. Further, ethanol significantly increased the accumulation of 4-hydroxynonenal protein adducts, nitrated and oxidized proteins in liver which was evidenced by immunohistochemistry. Administration of FPEt to ethanol-fed rats (200 mg kg(-1) day(-1)) significantly reduced the levels of lipid peroxidation products and protein carbonyl content, increased the activities of antioxidant enzymes, and restored the levels of thiol groups. The effects of FPEt were comparable with those of a positive control, silymarin. These findings show that FPEt ameliorates the pathological liver changes induced by chronic ethanol feeding.     

Influence of 6-week exercise training on erythrocyte and liver antioxidant defense in hyperinsulinemic rats

High dosage of fructose in rats causes insulin resistance and hyperinsulinemia. This study investigates the effect of physical exercise on oxidant-antioxidant balance in rats fed a high fructose diet, which show characteristic features of insulin resistance. Products of lipid peroxidation and the activity of enzymic antioxidants namely superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase and glutathione reductase, in red blood cells (RBCs) and liver were assayed. Levels of non-enzymic antioxidants alpha-tocopherol and ascorbic acid and of protein and non-protein thiols were also determined. The levels of lipid peroxides, diene conjugates, lipofuscin and hydroperoxides were significantly higher in the liver of fructose-fed rats. The RBCs showed significantly higher susceptibility to H(2)O(2)-induced stress compared to control rats. Inadequate antioxidant system was noted in high fructose-fed rats. Physical training to these rats reversed the adverse effects, which could be important in alleviating the pathological consequences of insulin resistance.     

Aging alters the functional expression of enzymatic and non-enzymatic anti-oxidant defense systems in testicular rat Leydig cells

In aged rats, trophic hormone-stimulated testosterone secretion by isolated Leydig cells is greatly reduced. The current studies were initiated to establish a functional link between excess oxidative stress and the age-related decline in steroidogenesis. Highly purified Leydig cell preparations obtained from 5-month (young mature) and 24-month (old) Sprague-Dawley rats were employed to measure and compare levels of lipid peroxidation, non-enzymatic (alpha-tocopherol, ascorbic acid, and reduced/oxidized glutathione) and enzymatic (Cu, Zn-superoxide dismutase, Cu, Zn-SOD; Mn-superoxide dismutase, Mn-SOD; glutathione peroxidase-1, GPX-1, and catalase, CAT) anti-oxidants. The extent of lipid peroxidation (oxidative damage) in isolated membrane fractions was quantified by measuring the content of thiobarbituric acid-reactive substances (TBARS) under basal conditions, or in the presence of non-enzymatic or enzymatic pro-oxidants. Membrane preparations isolated from Leydig cells from old rats exhibited two- to three-fold enhancement of basal TBARS formation. However, aging had no significant effect on TBARS formation in response to either non-enzymatic or enzymatic pro-oxidants. Among the non-enzymatic anti-oxidants, the levels of reduced glutathione were drastically reduced during aging, while levels of alpha-tocopherol and ascorbic acid remained unchanged. Both steady-state mRNA levels and catalytic activities of Cu, Zn-SOD, Mn-SOD, and GPX-1 were also significantly lower in Leydig cells from 24-month-old rats as compared with 5-month-old control rats. In contrast, neither mRNA levels nor enzyme activity of catalase was sensitive to aging. From these data we conclude that aging is accompanied by reduced expression of key enzymatic and non-enzymatic anti-oxidants in Leydig cells leading to excessive oxidative stress and enhanced oxidative damage (lipid peroxidation). It is postulated that such excessive oxidative insult may contribute to the observed age-related decline in testosterone secretion by testicular Leydig cells.