A comparative study on lipid peroxidation in cerebral cortex of stroke-prone spontaneously hypertensive and normotensive rats

• 1.1. Lipid peroxidation and membrane-related enzyme changes in the cerebral cortex of stroke-prone rats (SHRSP) and normotensive rats were examined at 5 and 20 weeks of age.
• 2.2. In vivo formation of thiobarbituric acid-reactant substances was higher in SHRSP at 20 weeks of age and in vitro generation of free malondialdehyde was greater in SHRSP brains, both at 5 and 20 weeks of age, as compared with those in WKY.
• 3.3. Membrane-associated enzymes such as Na/K-ATPase and 5'-nucleotidase activities were lower in 20-week-old SHRSP than in age-matched WKY.
• 4.4. These results indicate how very prone the SHRSP brain is toward lipid peroxidation and subsequent membrane-related enzyme changes.

     

Fatty liver induced by free radicals and lipid peroxidation

Abstract

An excessive accumulation of fat in the liver leads to chronic liver injury such as non-alcoholic fatty liver disease (NAFLD), which is an important medical problem affecting many populations worldwide. Oxidative stress has been implicated in the pathogenesis of NAFLD, but the exact nature of active species and the underlying mechanisms have not been elucidated. It was previously found that the administration of free radical-generating azo compound to mice induced accumulation of fat droplet in the liver. The present study was performed aiming at elucidating the changes of lipid classes and fatty acid composition and also measuring the levels of lipid peroxidation products in the liver induced by azo compound administration to mouse. The effects of azo compound on the liver were compared with those induced by high fat diet, a well-established cause of NAFLD. Azo compounds given to mice either by intraperitoneal administration or by dissolving to drinking water induced triacylglycerol (TG) increase and concomitant phospholipid decrease in the liver, whose pattern was quite similar to that induced by high fat diet. Lipid peroxidation products such as hydroxyoctadecadienoic acid and hydroxyeicosatetraenoic acid were increased in the liver in association with the increase in TG. These results show that free radicals as well as high fat diet induce fatty liver by similar mechanisms, in which lipid peroxidation may be involved.     

Fatty liver induced by free radicals and lipid peroxidation

An excessive accumulation of fat in the liver leads to chronic liver injury such as non-alcoholic fatty liver disease (NAFLD), which is an important medical problem affecting many populations worldwide. Oxidative stress has been implicated in the pathogenesis of NAFLD, but the exact nature of active species and the underlying mechanisms have not been elucidated. It was previously found that the administration of free radical-generating azo compound to mice induced accumulation of fat droplet in the liver. The present study was performed aiming at elucidating the changes of lipid classes and fatty acid composition and also measuring the levels of lipid peroxidation products in the liver induced by azo compound administration to mouse. The effects of azo compound on the liver were compared with those induced by high fat diet, a well-established cause of NAFLD. Azo compounds given to mice either by intraperitoneal administration or by dissolving to drinking water induced triacylglycerol (TG) increase and concomitant phospholipid decrease in the liver, whose pattern was quite similar to that induced by high fat diet. Lipid peroxidation products such as hydroxyoctadecadienoic acid and hydroxyeicosatetraenoic acid were increased in the liver in association with the increase in TG. These results show that free radicals as well as high fat diet induce fatty liver by similar mechanisms, in which lipid peroxidation may be involved.     

Relative systolic dysfunction in female spontaneously hypertensive rat myocardium.

Hypertension and exercise independently induce left ventricular (LV) remodeling and alter LV function. The purpose of this study was to determine systolic and diastolic LV pressure-volume relationships (LV-PV) in spontaneously hypertensive rats (SHR) with and without LV hypertrophy, and to determine whether 6 mo of exercise training modified the LV-PV in SHR. Four-month-old female SHR (n = 20), were assigned to a sedentary (SHR-SED) or treadmill-trained (SHR-TRD) group (approximately 60% peak O2 consumption, 5 days/wk, 6 mo), while age-matched female Wistar-Kyoto rats (WKY; n = 13) served as normotensive controls. The LV-PV was determined using a Langendorff isolated heart preparation at 4 (no hypertrophy: WKY, n = 5; SHR, n = 5) and 10 mo of age (hypertrophy: WKY, n = 8; SHR-SED, n = 8; SHR-TRD, n = 7). At 4 mo, the LV-PV in SHR was similar to that observed in WKY controls. However, at 10 mo of age, a rightward shift in the LV-PV occurred in SHR. Exercise training did not alter the extent of the shift in the LV-PV relative to SHR-SED. Relative systolic function, i.e., relative systolic elastance, was approximately 50% lower in SHR than WKY at 10 mo of age (P < 0.05). Doppler-derived LV filling parameters [early wave (E), atrial wave (A), and the E/A ratio] were similar between groups. LV capacitance was increased in SHR at 10 mo (P < 0.05), whereas LV diastolic chamber stiffness was similar between groups at 10 mo. Hypertrophic remodeling at 10 mo of age in female SHR is manifest with relative systolic decompensation and normal LV diastolic function. Exercise training did not alter the LV-PV in SHR.     

Lipid peroxidation in the aorta of normotensive and spontaneously hypertensive rats with diabetes mellitus]

We have studied the effects of streptozotocin-induced (STI) diabetes on the lipid peroxidation in the aorta from normotensive (NTR) and spontaneously hypertensive (SHR) rats. In the control SHR quantity of malonyldialdehyde (MDA), conjugated dienes (CD) and arterial pressure where higher than in NTR analogous group. It has been shown that Diabetes in NTR results in significantly increased arterial pressure and quantity of MDA and CD. Under certain conditions in SHR arterial pressure and the other factors remain almost unchanged. It is likely that completely different changes in intensity of lipid peroxidation may evidence breaking adaptation mechanism in diabetic SHR.     

Stimulation of microsomal lipid peroxidation by iron and cysteine. Characterization and the role of free radicals.

The stimulation of microsomal lipid peroxidation by FeSO4 and cysteine has been investigated. Although both FeSO4 and cysteine alone promoted an increase in malonaldehyde production, when these agents were added together to microsomes the resultant level of malonaldehyde was greater than the sum of the amounts formed by these pro-oxidants when acting individually. A further indication of an interaction between FeSO4 and cysteine was shown by the inhibitory action of chelating agents. Stimulation of peroxidation was shown to be independent of microsomal protein, including cytochrome P-450. The system has been characterized for the effects of cysteine, Fe2+ and O2 concentrations, pH, temperature and antioxidants. The results indicate that the high level of peroxidation attained with this system, its non-enzymic character and the involvement of hydroxyl radicals make it particularly useful for the investigation of the action of antioxidants. Furthermore it may also be a model of way in which decompartmentalized, delocalized or 'free' iron initiates peroxidation in vivo.     

Age-related changes in antioxidant defence mechanisms and peroxidation in isolated hepatocytes from spontaneously hypertensive and normotensive rats

The effects of age and hypertension on the antioxidant defence systems and the lipid peroxidation in rat isolated hepatocytes were studied. Four different age groups (1,3,6 and 12 months) were considered in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. Age-associated changes were observed on vitamin E status, glutathione (GSH) level, MDA formation and glutathione peroxidase (GSH-Px) activity in both strains. Maximal levels or activities of these parameters were found at 3 and 6 months, except for MDA which was low at 3 months. Then, a fall was observed at 12-month-old compared to 6-month values. In addition, GSH-Px activity was significantly lower in SHR than in WKY rats, except at the age of one month. The decrease of this enzyme activity could induce an increased cellular generation of radical species and lipid peroxidation, which might be link to hypertension.     

The pituitary-adrenal response to ether stress in the spontaneously hypertensive and normotensive rat

The pituitary-adrenal response to ether stress in the spontaneously hypertensive (SHR) and normotensive (WKYN) rat was investigated at three time intervals: 0, 30, and 60 min after exposure to ether vapor. Plasma corticosterone concentrations were significantly higher in the WKYN than SHR rat before stress (0 min), and 30 min after stress. However, 60 min following ether stress the magnitude of increase in plasma and adrenal concentration of corticosterone over basal values was greater in the SHR line than in the WKYN line. The adrenal response to IV administration of 100 μU of ACTH was equivalent in the two lines. The data suggest that the prolonged adrenal response to ether stress in the SHR line is the result of a greater or more prolonged secretion of ACTH in that line than in the WKYN animals.     

Inhibition of rat liver microsomal lipid peroxidation by N-acyldehydroalanines: an in vitro comparative study

Captodative substituted olefins are radical scavengers which react with free radicals to form stabilized radical adducts. One of those compounds, N-(paramethoxyphenylacetyl)dehydroalanine (AD-5), may react and scavenge both superoxide anion (O-2) and alk-oxyl radicals (RO.), and in this way prevent the appearance of their mediated biological effects. Nitrofurantoin and tert-butyl hydroperoxide were used as model compounds to stimulate free radical production and their mediated lipid peroxidation in rat liver microsomes. In addition, lipid peroxidation was also initiated by exposure of rat liver microsomal suspensions to ionizing radiation (gamma rays). The microsomal lipid peroxidation induced by these chemicals and physical agents was inhibited by the addition of AD-5. These effects were dose-dependent in a millimolar range of concentration. In addition, AD-5 has no effect on microsomal electron transport, showing that NADPH-cytochrome P450 reductase activity was not modified. These data, together with the comparisons of the effects of AD-5 and some antioxidant molecules such as superoxide dismutase, uric acid, and mannitol, support the conclusion that inhibition of lipid peroxidation by AD-5 is the result of its free radical scavenger activity. In addition, the inhibitory effect of AD-5 on microsomal lipid peroxidation was dependent of the nature of the free radical species involved in the initiation of the process, suggesting that O-2 is scavenged more efficiently than RO.     

Exercise,free radicals,and lipid peroxidation in type 1 diabetes mellitus

Indirect biochemical techniques have solely been used to ascertain whether type 1 diabetes mellitus patients are more susceptible to resting and exercise-induced oxidative stress. To date there is no direct evidence to support the contention that type 1 diabetic patients have increased levels of free radical species. Thus, the aim of this study was to use electron spin resonance (ESR) spectroscopy in conjunction with alpha-phenyl-tert-butylnitrone (PBN) spin trapping to measure pre- and postexercise free radical concentration in the venous blood of young male patients with type 1 diabetes mellitus (HbA(1c) = 8.2 +/- 1%, n = 12) and healthy matched controls (HbA(1c) = 5.5 +/- 0.2%, n = 13). Supporting measures of lipid peroxidation (malondialdehyde and lipid hydroperoxides), ambient blood glucose and selected antioxidants were also measured. The diabetic patients presented with a comparatively greater concentration of free radicals as measured by ESR and lipid hydroperoxides (LH) compared to the healthy group (p <.05, pooled rest and exercise data), although there was no difference in malondialdehyde (MDA) concentration. alpha-Tocopherol was comparatively lower in the healthy group (p <.05, pooled rest and exercise data vs. diabetic group) due to a selective decrease during physical exercise (p <.05 vs. rest). The hyperfine coupling constants recorded from the ESR spectra (a(Nitrogen) = 1.37 mT and abeta(Hydrogen) = 0.17 mT) are suggestive of either oxygen or carbon-centered species and are consistent with literature values. We suggest that the greater concentration of oxidants seen in the diabetic group may be due to increased glucose autoxidation as a function of this pathology and/or a lower exercise-induced oxidation rate of the major lipid soluble antioxidant alpha-tocopherol. We suggest that the ESR-detected radicals are secondary species derived from decomposition of LH because these are the major initial reaction products of free radical attack on cell membranes.     

A comparative study of the effects of laser and LED radiation on lipid peroxidation in rat wound fluid

The effect of laser (632 nm) and LED (630 nm) on lipid peroxidation in rat wound fluid (exudate) was studied with the aim of comparing the efficiency of coherent and incoherent light on the processes that take place during wound healing. The study was performed using the model of cut aseptic wounds proposed by L.I. Slutskii. It was shown that irradiation of wounds with light of both laser and LED caused a decrease in the concentration of lipid peroxidation products in wound fluid as compared with the control group. An increase in the antioxidative activity of wound fluid was observed. It was concluded that irradiation with light of both laser and LED decreases the level of oxidative stress in wound fluid and that radiation coherence does not play a significant role.     

Norepinephrine concentration in kidneys of normotensive Wistar-Kyoto and spontaneously hypertensive rats.

Renal norepinephrine (NE) concentration was measured in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) at 7, 9, 11, and 13 weeks of age. Although the weight of kidneys was similar in the two strains of rats, renal NE concentration was significantly lower in SHR at all ages (147 +/- 9 to 175 +/- 13 ng/g for SHR, and 216 +/- 8 to 262 +/- 17 ng/g for WKY rats). The difference in renal NE concentration during this time of rapidly increasing arterial pressure in the SHR suggests that renal NE may in some way be related to the development of hypertension.     

Effects of temperature on oxidative stress defense systems, lipid peroxidation and lipoxygenase activity in Phalaenopsis.

Higher plants growing in natural environments experience various abiotic stresses. The aim of this study was to determine whether exposure to temperature-stress would lead to oxidative stress and whether this effect varied with different exposure periods. The thermal dependencies of the activities of protective enzymes, photosynthetic efficiency (Fv/Fm), protein, non-protein thiol (NP-SH), cysteine content, lipoxygenase (LOX) activity (EC 1.13.11.12) and malondialdehyde (MDA) content at 25-40 degrees C were determined for 4, 24 and 48 h in leaf and root segments of Phalaenopsis. The increase in MDA level and LOX activity may be due to temperature-associated oxidative damage to leaf and root segments. Temperature-stress induced not only activities of active oxygen species (AOS) scavenging enzymes but also protein, NP-SH and cysteine content in both leaf and root segments at 30 degrees C for 4 and 24 h (except for 48 h in some cases) compared to 25 degrees C-and greenhouse-grown leaf and root segments indicating that antioxidants enzymes played an important role in protecting plant from temperature-stress. However, activities of dehydroascorbate reductase (DHAR, EC 1.8.5.1), glutathione peroxidase (GPX, EC 1.11.1.9) and glutathione-S-transferase (GST, EC 2.5.1.18) in leaf and root, glutathione reductase (GR, EC 1.6.4.2) in leaf and guaiacol peroxidase (G-POD, 1.11.1.7) in root segments were induced significantly at 40 degrees C compared to 25 degrees C and greenhouse-grown plants suggesting that these enzymes play protective roles at high temperature. In contrast, activities of superoxide dismutase (SOD, EC 1.15.1.1) and monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) in leaf and root, catalase (CAT, EC 1.11.1.6) in root, GR in root, and protein, cysteine, NP-SH content in both root and leaf and Fv/Fm ratio were diminished significantly at 40 degrees C compared to 25 degrees C-and greenhouse-grown plants. These indicate that these enzymes were apparently not involved in detoxification process and sensitive at higher temperature. Also, the close relation between activities of enzymes with their metabolites at 30 degrees C than 40 degrees C indicated that the antioxidants enzymes and metabolites both may play an important role in protecting cells against the temperature-stress.     

Capacity of fucoxanthin for scavenging peroxyl radicals and inhibition of lipid peroxidation in model systems

Abstract

Carotenoids act as physiological antioxidant by scavenging reactive-free radicals as well as quenching singlet oxygen. Fucoxanthin is one of the abundant carotenoids found in edible brown seaweeds. The assessment of radical scavenging capacity of carotenoids has been the subject of extensive studies, which, however, gave inconsistent results. In the present study, the capacity of fucoxanthin for scavenging peroxyl radicals, chain carrying species of lipid peroxidation, was assessed quantitatively by measuring the effect of α-tocopherol on the decay of fucoxanthin induced by peroxyl radicals. It was found that α-tocopherol was 7.1 times more reactive than fucoxanthin in heptane solution, but interestingly fucoxanthin exerted 1.6 times higher reactivity than α-tocopherol in methanol solution. In SDS micelles, the relative reactivity of fucoxanthin and α-tocopherol depended on the site of peroxyl radical formation. The efficacy of lipid peroxidation inhibition by fucoxanthin was much less than that of α-tocopherol.     

Alpha-lactorphin lowers blood pressure measured by radiotelemetry in normotensive and spontaneously hypertensive rats

Cardiovascular effects of subcutaneous administration of synthetic alpha-lactorphin, a tetrapeptide (Tyr-Gly-Leu-Phe) originally derived from milk alpha-lactalbumin, were studied in conscious spontaneously hypertensive rats (SHR) and in normotensive Wistar Kyoto rats (WKY) with continuous radiotelemetric monitoring. Alpha-lactorphin dose-dependently lowered blood pressure (BP) without affecting heart rate in SHR and WKY. The lowest dose which reduced BP was 10 microg/kg, and the maximal reductions in systolic and diastolic BP (by 23+/-4 and 17+/-4 mm Hg, respectively) were observed at 100 microg/kg dose in SHR. No further reductions were obtained at a higher dose of 1 mg/kg. There were no significant differences in the BP responses to alpha-lactorphin between SHR and WKY. Naloxone (1 and 3 mg/kg s.c.), a specific opioid receptor antagonist, abolished the alpha-lactorphin-induced reduction in BP and reversed it into a pressor response, which provides evidence for an involvement of opioid receptors in the depressor action of the tetrapeptide.     

The effect of concentration on the antioxidant effectiveness of alpha-tocopherol in lipid peroxidation induced by superoxide free radicals

Egg yolk phosphatidylcholine liposomes were rapidly oxidized in the presence of chelated iron and a superoxide-generating system. alpha-Tocopherol incorporated in the bilayer was oxidized at the same time. No lipid or alpha-tocopherol oxidation occurred in liposomes composed of dimyristoyl phosphatidylcholine. The antioxidant did not inhibit lipid peroxidation until its concentration reached a critical level, which depended on the effectiveness of the oxidative stress. Beyond this level, peroxidation was inhibited completely and, simultaneously, the rate of oxidation of tocopherol was lowered. The results suggest that the antioxidant efficiency of alpha-tocopherol depends on its ability to react mainly with the chain-initiating or chain-propagating lipid radicals. This, in turn, is closely tied to the tocopherol content of the membrane. Ascorbate inhibited the consumption of alpha-tocopherol, possibly by regenerating its reduced form.     

Modification of reperfusion-induced ionic imbalance by free radical scavengers in spontaneously hypertensive rat retina

We studied the effects of free radical scavengers, superoxide dismutase (SOD), vitamin E, and EGB 761, on ion shifts (Na⁺, K⁺, and Ca²⁺) induced by ischemia reperfusion in rat retina obtained from spontaneously hypertensive rats. Eyes were subjected to 90 min of retinal ischemia followed by 24 h of reperfusion. Two basic protocols were used: (1) chronic application, in which rats received SOD (7500, 15,000, and 30,000 U/kg, i.v.), vitamin E (50, 100, and 200 mg/kg, i.v.), and EGB 671 (50, 100, and 200 mg/kg, orally) for 10 d, respectively; and (2) acute administration, in which 7500, 15,000, and 30,000 U/kg of SOD, 50, 100, and 200 mg/kg of vitamin E, and 50, 100, and 200 mg/kg of EGB 761 were administered after an ischemic episode, at the onset of reperfusion, respectively. In the drug-free control group, 90 min ischemia followed by 24 h of reperfusion resulted in an accumulation of retinal sodium and calcium from their nonischemic control values of 76 ± 4 and 3.2 ± 0.1 μmol/g dry weight to 112 ± 6 (p < .001) and 6.2 (p < .001) μmol/g dry weight, respectively. Tissue potassium loss was also observed in this model of retinal ischemia reperfusion, and after 90 min ischemia followed by 24 h of reperfusion potassium content was significantly reduced from its nonischemic control value of 266 ± 5 to 207 ± 6 (p < .001) μmol/g dry weight. The chronic administration of SOD, vitamin E, and EGB 761 dose dependently reduced the reperfusion-induced ionic imbalance and improved the recovery of retinal ion contents. When these drugs were administered at the onset of reperfusion (acute administration), SOD and EGB 761 still significantly improved the recovery of retinal ion contents, but vitamin E failed to protect the ischemic reperfused retina. Our results indicate that the elimination of oxygen free radicals by free radicals scavengers may reduce the reperfusion-induced ionic imbalance and improve the ionic homeostasis in the injured retinal cells obtained from spontaneously hypertensive rats.     

Effect of ethanol and the catalase inhibitor aminotriazole on lipid peroxidation in the rat myocardium

The influence of chronic alcohol consumption and catalase inhibitor aminotriazole administration on the level of nonenzymatic lipid peroxidation has been studied in the rat myocardium. It was demonstrated that combined as well as separate treatment with ethanol or aminotriazole elevated the levels of chemiluminescence and enhanced the rate of accumulation of thiobarbituric acid-reactive products in the nuclei-free and total particulate fraction of the rat heart homogenate. The most pronounced effect was noted during combined application of ethanol and aminotriazole. The induction of chemiluminescence by ethanol was prevented by addition of natural (vitamin E, reduced glutathione) or artificial (dibunol) antioxidants into the incubation media. A putative role of the myocardial catalase-containing micro-peroxisomes in stimulation of the intracellular lipid peroxidation is discussed.     

Kinetics of lipid peroxidation in compartmentalized systems initiated by a water-soluble free radical source

Kinetic rate laws arising from theoretical expectations for the oxidation of lipids initiated by water-soluble free radicals in compartmentalized systems under different experimental conditions are deduced. In particular, the predictions for the kinetic reaction orders in: (a) intra-particle oxidizable compound concentration (at fixed number of particles and particle size), alpha; (b) number of particles or analytical lipid concentration (at fixed intra-particle concentration and particle size), beta and (c) initiator, gamma, are obtained. The reaction orders beta and gamma are determined by the fraction of initiator derived radicals captured by the particles (f) and the mean number of chain carrying radicals per particle () when the system reaches the steady state condition. Predicted orders in initiator range from 0 ( = 0.5) to 0.5 (f-->1; > > 1), while the order in number of particles ranges between 0.5 (f-->1; > > 1) and 1. These predictions are tested by measuring the kinetic law for the oxidation of SUV's egg yolk phosphatidylcholine vesicles initiated by the thermal decomposition of ABAP. The results indicate that, under the conditions employed, beta = 0.68 +/- 0.05 and gamma = 0.46 +/- 0.04. These values are close to those expected for a system in which > > 1 and the efficiency of capture is relatively high. This last condition is confirmed by estimating the efficiency of capture from a comparison of induction times elicited by similar concentrations of Trolox and alpha-tocopherol.