Protective effects of lazaroids against oxygen-free radicals induced lysosomal damage

Lipid peroxidation of membranes by oxygen free radicals has been implicated in various disease states. Different antioxidants and iron chelators have been used to reduce lipid peroxidation. Lazaroids have been used for the acute treatment of central nervous system disorders such as trauma and ischemia wherein lipid peroxidative processes take place.In this study we evaluated the effect of lazaroids (U-785 18F and U-74389F) on the release of acid phosphatase activity and formation of malondialdehyde (MDA) in rat liver lyosomes subjected to exogenously generated oxygen free radicals. There was a significant increase in the acid phosphatase release and MDA formation in the presence of oxygen free radicals. This was prevented by both the lazaroids. In a separate study the effect of lazaroid U-74389F was seen on the zymosan-stimulated polymorphonuclear (PMN) leukocyte-derived chemiluminescence. The PMN leukocyte chemiluminescent activity was attenuated by the lazaroid in a dose-dependent manner. These studies suggest that lazaroids may inhibit lipid peroxidation and stabilize the membrane.     

Action of 6-amino-3-pyridinols as novel antioxidants against free radicals and oxidative stress in solution,plasma, and cultured cells

Free radical-mediated lipid peroxidation has been implicated in the pathogenesis of various diseases. Lipid peroxidation products are cytotoxic and they modify proteins and DNA bases, leading eventually to degenerative disorders. Various synthetic antioxidants have been developed and assessed for their capacity to inhibit lipid peroxidation and oxidative stress induced by free radicals. In this study, the capacity of novel 6-amino-2,4,5-trimethyl-3-pyridinols for scavenging peroxyl radicals, inhibiting plasma lipid peroxidation in vitro, and preventing cytotoxicity induced by glutamate, 6-hydroxydopamine, 1-methyl-4-phenylpyridium (MPP⁺ ), and hydroperoxyoctadecadienoic acid was assessed. It was found that they exerted higher reactivity toward peroxyl radicals and more potent activity for inhibiting the above oxidative stress than α-tocopherol, the most potent natural antioxidant, except against the cytotoxicity induced by MPP⁺. These results suggest that the novel 6-amino-3-pyridinols may be potent antioxidants against oxidative stress.     

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.     

Comparison of iron-catalyzed DNA and lipid oxidation

Lipid and DNA oxidation catalyzed by iron(II) were compared in HEPES and phosphate buffers. Lipid peroxidation was examined in a sensitive liposome system constructed with a fluorescent probe that allowed us to examine the effects of both low and high iron concentrations. With liposomes made from synthetic 1-stearoyl-2-linoleoyl-sn-glycero-3-phosphocholine or from rat liver microsomal lipid, lipid peroxidation increased with iron concentration up to the range of 10--20 microM iron(II), but then rates decreased with further increases in iron concentration. This may be due to the limited amount of lipid peroxides available in liposomes for oxidation of iron(II) to generate equimolar iron(III), which is thought to be important for the initation of lipid peroxidation. Addition of hydrogen peroxide to incubations with 1--10 microM iron(II) decreased rates of lipid peroxidation, whereas addition of hydrogen peroxide to incubations with higher iron concentrations increased rates of lipid peroxidation. Thus, in this liposome system, sufficient peroxide from either within the lipid or from exogenous sources must be present to generate equimolar iron(II) and iron(III). With iron-catalyzed DNA oxidation, hydrogen peroxide always stimulated product formation. Phosphate buffer, which chelates iron but still allows for generation of hydroxyl radicals, inhibited lipid peroxidation but not DNA oxidation. HEPES buffer, which scavenges hydroxyl radicals, inhibited DNA oxidation, whereas lipid peroxidation was unaffected since presumably iron(II) and iron(III) were still available for reaction with liposomes in HEPES buffer.     

Responses of antioxidants and lipid peroxidation in mussels to oxidative damage exposure.

1. The aim of this work was to evaluate the relationships between free radical scavengers and lipid peroxidation in the common mussel Mytilus edulis. 2. Mussels were exposed to compounds known for their ability to produce free radicals (carbon tetrachloride, CCl4) and reactive oxygen species via redox cycling (menadione) and the effects on digestive gland, gills and remaining tissues were studied. 3. Lipid peroxidation parameters and the status of free radical scavengers (glutathione, vitamins A, E and C) were affected more by exposure to menadione than to CCl4. 4. The observed changes in the free radical scavengers content are indicative of a role in detoxication of damaging reactive species.     

Mechanisms of Hemolysis Induced by Copper

An excess of copper is the cause of hemolysis in a number of clinical conditions. Incubation of human erythrocyte (RBC) suspensions with copper (II) causes the formation of methemoglobin, lipid peroxidation and hemolysis.

A new variant of the thiobarbituric acid (TBA) method, which minimizes the formation of interfering chromophores, was used to detect lipid peroxidation. Lipid peroxidation precedes hemolysis and the antioxidant vitamins C and E, which inhibit lipid peroxidation, also inhibit hemolysis. Consequently lipid peroxidation appears to be the cause of RBC destruction. Lipid peroxidation arises mostly from the oxidation of oxyhemoglobin by copper as it is inhibited in RBCs with carbon monoxyhemoglobin or methemoglobin. A direct interaction of copper with the red cell membrane seems to play only a minor role. Copper effects depend on the presence of free SH groups. Lipid peroxidation is probably initiated by activated forms of oxygen as it is increased by an inhibitor of catalase and reduced by hydroxyl radical scavengers. With higher copper concentrations hemolysis is greater: its mechanism appears different as lipid peroxidation is smaller but hemoglobin alterations, namely precipitation, are more pronounced.     

Mechanisms of Hemolysis Induced by Copper

An excess of copper is the cause of hemolysis in a number of clinical conditions. Incubation of human erythrocyte (RBC) suspensions with copper (II) causes the formation of methemoglobin, lipid peroxidation and hemolysis.

A new variant of the thiobarbituric acid (TBA) method, which minimizes the formation of interfering chromophores, was used to detect lipid peroxidation. Lipid peroxidation precedes hemolysis and the antioxidant vitamins C and E, which inhibit lipid peroxidation, also inhibit hemolysis. Consequently lipid peroxidation appears to be the cause of RBC destruction. Lipid peroxidation arises mostly from the oxidation of oxyhemoglobin by copper as it is inhibited in RBCs with carbon monoxyhemoglobin or methemoglobin. A direct interaction of copper with the red cell membrane seems to play only a minor role. Copper effects depend on the presence of free SH groups. Lipid peroxidation is probably initiated by activated forms of oxygen as it is increased by an inhibitor of catalase and reduced by hydroxyl radical scavengers. With higher copper concentrations hemolysis is greater: its mechanism appears different as lipid peroxidation is smaller but hemoglobin alterations, namely precipitation, are more pronounced.     

Lipid peroxidation by gamma-radiation in Salmonella typhi membranes: the effect of ascorbic acid

Lipid peroxidation in isolated membranes of Salmonella typhi occurred following gamma irradiation. The presence of the sensitizer, ascorbic acid, during irradiation resulted in a stimulation in the level of peroxidation. This enhancement of lipid damage could be prevented by the addition of the free radical scavenger sodium formate. Catalase and superoxide dismutase appeared less effective in this respect. Peroxidation in an unsaturated fatty acid and a phospholipid was also affected by gamma radiation and ascorbic acid in a manner similar to that observed in the cell membranes. The results suggest that hydroxyl radicals may be the major species responsible for the increased peroxidation effected by the sensitizer.     

The effect of chronic alcohol feeding on lipid peroxidation in microsomes: lack of relationship to hydroxyl radical generation

Chronic alcohol feeding causes microsomal induction including increased generation of hydroxyl radicals. Ethanol induced liver injury may be mediated by lipid peroxidation for which hydroxyl radicals have been proposed as major mediators. Ethanol promotes lipid peroxidation when given acutely but also may serve as a hydroxyl radical scavenger. Therefore, we studied the acute and chronic effects of alcohol on microsomal lipid peroxidation and hydroxyl radical generation. Chronic alcohol feeding in rats increased microsomal generation of hydroxyl radicals but lipid peroxidation of endogenous lipid was inversely related to hydroxyl radical generation. Ethanol (50mM) had a slight inhibitory effect on hydroxyl radical production in peroxidizing microsomes, no effect on endogenous lipid peroxidation and enhanced the lysis of RBCs added as targets of peroxidation. Enhanced microsomal generation of hydroxyl radicals following chronic alcohol feeding is not an important mediator of lipid peroxidation.     

脂质过氧化引起的DNA损伤研究进展

脂质过氧化可以引起各种碱基损伤、DNA链断裂和各种荧光产物生成,并对DNA分子鸟嘌呤碱基具有选择性损伤.过渡金属离子可以明显加深脂质过氧化对DNA的损伤程度.多种抗氧化剂、活性氧自由基清除剂对脂质过氧化引起的DNA损伤有一定程度的保护作用.具有致突、致癌作用的8－羟基鸟嘌呤已经观察到．脂质过氧化的致突变、致癌变作用机制引起了人们的极大兴趣．     

Lipid peroxidation and neurodegenerative disease

Lipid peroxidation is a complex process involving the interaction of oxygen-derived free radicals with polyunsaturated fatty acids, resulting in a variety of highly reactive electrophilic aldehydes. Since 1975, lipid peroxidation has been extensively studied in a variety of organisms. As neurodegenerative diseases became better understood, research establishing a link between this form of oxidative damage, neurodegeneration, and disease has provided a wealth of knowledge to the scientific community. With the advent of proteomics in 1995, the identification of biomarkers for neurodegenerative disorders became of paramount importance to better understand disease pathogenesis and develop potential therapeutic strategies. This review focuses on the relationship between lipid peroxidation and neurodegenerative diseases. It also demonstrates how findings in current research support the common themes of altered energy metabolism and mitochondrial dysfunction in neurodegenerative disorders.     

Free radicals, lipid peroxidation and muscular ischemia]

The role of oxygen free radicals in ischemia and reperfusion injury of skeletal muscle has not been well defined, partly because of the relative resistance of this tissue to normothermic ischemia. Under normal conditions small quantities of oxygen free radicals are produced but they are quenched by intracellular free radical scavenging enzymes (superoxide dismutase, catalase and glutathione peroxidase) or alpha-tocopherol. The increase in malondialdehyde suggests increased lipid peroxidation initiated by free radical reactions. Lipid peroxidation is potentially a very damaging process to the organized structure and function of membranes. The results of recent studies indicate that: a) oxygen free-radicals mediates, at least in part, the increased microvascular permeability produced by reoxygenation, b) free radical scavengers can reduce skeletal muscle necrosis occurring after prolonged ischemia. Additional evidence support the hypothesis of the interrelationship between ischemic tissue and inflammatory cells. So capillary plugging by granulocytes and oxygen free radical formation may contribute to the ischemic injury.     

Central nervous system trauma and stroke. I. Biochemical considerations for oxygen radical formation and lipid peroxidation

The generation of oxygen radicals and the process of lipid peroxidation have become a focus of attention for investigators in the fields of central nervous system (CNS) trauma and stroke (e.g., ischemia). Considering our level of understanding of free radical and lipid peroxidation chemistry, absolute proof for their involvement in the pathophysiology of traumatic and ischemic damage to the CNS has been meager. While direct, unequivocal evidence for the participation of free radicals and lipid peroxidation as primary contributors to the death of neuronal tissue waits to be established, numerous recent studies have provided considerable support for the occurrence of free radical and lipid peroxidation reactions in the injured or ischemic CNS. In addition, the pharmacological use of antioxidants and free radical scavengers in the treatment of experimental CNS trauma and ischemia has provided convincing, although indirect evidence, for the involvement of oxygen radicals and lipid peroxidation in these conditions. The intent of this and its companion paper is to review: 1) the biochemical processes which may give rise to free radical reactions in the CNS, 2) the environment of the ischemic cell as it may affect the generation of oxygen radicals and the catalysis of lipid peroxidation reactions, 3) the evidence for the involvement of free radical mechanisms in CNS trauma and ischemia, and 4) the pathophysiological consequences of these phenomena.     

Amelioration of ionizing radiation induced lipid peroxidation in mouse liver by Moringa oleifera Lam. leaf extract

Protective effect of Moringa oleifera leaf extract (MoLE) against radiation-induced lipid peroxidation has been investigated. Swiss albino mice, selected from an inbred colony, were administered with MoLE (300 mg/kg body wt) for 15 days before exposing to a single dose of 5 Gy 60Co-gamma radiation. After treatments, animals were necropsied at different post irradiation intervals (days 1, 7 and 15) and hepatic lipid peroxidation and reduced glutathione (GSH) contents were estimated to observe the relative changes due to irradiation and its possible amelioration by MoLE. It was observed that, MoLE treatment restored GSH in liver and prevented radiation induced augmentation in hepatic lipid peroxidation. Phytochemical analysis showed that MoLE possess various phytochemicals such as ascorbic acid, phenolics (catechin, epicatechin, ferulic acid, ellagic acid, myricetin) etc., which may play the key role in prevention of hepatic lipid peroxidation by scavenging radiation induced free radicals.     

Neutrality of amiodarone on the initiation and propagation of membrane lipid peroxidation.

Amiodarone is an iodinated benzofuran derivative largely used as an antiarrhythmic. Owing to the sensitivity of heart tissue to radicals, amiodarone was assayed for putative effects on lipid peroxidation studied in liposomes of soybean phosphatidylcholine and of bovine heart mitochondrial lipids used as model systems. Lipid peroxidations were initiated with Fe2+/ascorbic acid, and with peroxyl radicals generated from the azocompounds, AAPH and AMVN. These assays were carried out by following the quenching of the fluorescent probe cis-parinaric acid and by monitoring oxygen consumption. It has been ascertained that amiodarone does not protect or potentiate significantly the lipid peroxidation both lipidic systems. To fully ascertain the neutral behaviour of amiodarone in the lipid peroxidation process, the degradation of phospholipid acyl chains has been checked by GLC. These data confirm that amiodarone does not protect or potentiate lipid peroxidation to a significant extent. It is concluded that the limited effects of amiodarone might be related only indirectly with the lipid peroxidation. It is possible that the drug causes limited conformational and biophysical alterations in membrane phospholipid bilayers that can affect the process of peroxidation. Therefore, it is concluded that the therapeutic effects and benefits as a heart antiarrhythmic agent are independent of lipid peroxidation processes. Furthermore, the interaction of the drug with lipid bilayers does not induce significant conformational perturbations that could significantly favour or depress the peroxidation process.     

Antioxidant activity of extract from Polygonum cuspidatum

Numerous diseases are induced by free radicals via lipid peroxidation, protein peroxidation and DNA damage. It has been known that a variety of plant extracts have antioxidant activities to scavenge free radicals. Whether Polygonum cuspidatum Sieb. et Zuce has antioxidant activity is unknown. In this study, dried roots of Polygonum cuspidatum were extracted by ethanol and the extract was lyophilized. Free radical scavenging assays, superoxide radical scavenging assays, lipid peroxidation assays and hydroxyl radical-induced DNA strand scission assays were employed to study antioxidant activities. The results indicate that the IC50 value oí Polygonum cuspidatum extract is 110 microg/ml in free radical scavenging assays, 3.2 microg/ml in superoxide radical scavenging assays, and 8 microg/ml in lipid peroxidation assays, respectively. Furthermore, Polygonum cuspidatum extract has DNA protective effect in hydroxyl radical-induced DNA strand scission assays. The total phenolics and flavonoid content of extract is 641.1 +/- 42.6 mg/g and 62.3 +/- 6.0 mg/g. The results indicate that Polygonum cuspidatum extract clearly has antioxidant effects.     

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.     

Lipid peroxidation induced by phenylbutazone radicals

Lipid peroxidation was investigated to evaluate the deleterious effect on tissues by phenylbutazone (PB). PB induced lipid peroxidation of microsomes in the presence of horseradish peroxidase and hydrogen peroxide (HRP-H2O2). The lipid peroxidation was completely inhibited by catalase but not by superoxide dismutase. Mannitol and dimethylsulfoxide had no effect. These results indicated no paticipation of superoxide and hydroxyl radical in the lipid peroxidation. Reduced glutathione (GSH) efficiently inhibited the lipid peroxidation. PB radicals emitted electron spin resonance (ESR) signals during the reaction of PB with HRP-H2O2. Microsomes and arachidonic acid strongly diminished the ESR signals, indicating that PB radicals directly react with unsaturated lipids of microsomes to cause thiobarbituric acid reactive substances. GSH sharply diminished the ESR signals of PB radicals, suggesting that GSH scavenges PB radicals to inhibit lipid peroxidation. Also, 2-methyl-2-nitrosopropan strongly inhibited lipid peroxidation. R-Phycoerythrin, a peroxyl radical detector substance, was decomposed by PB with HRP-H2O2. These results suggest that lipid peroxidation of microsomes is induced by PB radicals or peroxyl radicals, or both.     

Lipid peroxidation in membranes and low-density lipoproteins: similarities and differences

Lipid peroxidation has been a central aspect of studies of the nature of free radical species and their origin in biological systems. Moreover, there has been a growing interest in lipid peroxidation based on evidence that biologically active products are formed that influence cell function and the course of major human diseases. A review of the work in this area is contributed by Lars Ernster is presented with an emphasis on the mechanisms by which lipid peroxidation is initiated in biological lipid systems. Based on what was described for metal catalyzed oxidation of cell membranes, and the seminal studies on cytochrome P-450-mediated lipid peroxidation, several parallel and distinct aspects of lipid peroxidation are described. A key distinction between lipid peroxidation in cell membranes and lipoproteins reveals aspects of free radical initiated reactions involving proteins and lipids that determine pro- vs. anti-oxidant outcomes, and the role of lipid structure and order in delineating the progress of oxidation.     

Cooperation of antioxidants in protection against photosensitized oxidation

The aim of this study was to determine whether alpha-tocopherol and zeaxanthin offer synergistic protection against photosensitized lipid peroxidation mediated by singlet oxygen and free radicals. The antioxidant action of zeaxanthin and alpha-tocopherol was studied in liposomes made of phosphatidylcholine and cholesterol. Progress of lipid peroxidation, induced by aerobic photoexcitation of rose bengal, was monitored by the detection of lipid hydroperoxides and by electron spin resonance oximetry. In addition, cholesterol was employed as a mechanistic reporter molecule, which forms characteristic products of the interaction with singlet oxygen or free radicals. Cholesterol hydroperoxides were quantitatively determined by HPLC/electrochemical detection. HPLC/ultraviolet-visible (UV-VIS) absorption detection was used to measure concentrations of zeaxanthin and alpha-tocopherol. Zeaxanthin, even at concentrations of 2.5 microM, effectively protected against singlet oxygen-mediated lipid peroxidation but was rapidly consumed due to interaction with free radicals. alpha-Tocopherol alone was not effective in protecting against lipid peroxidation, even at concentration of 0.1 mM. Combinations of zeaxanthin and alpha-tocopherol exerted a synergistic protection against lipid peroxidation. The synergistic effect may be explained in terms of prevention of carotenoid consumption by effective scavenging of free radicals by alpha-tocopherol therefore allowing zeaxanthing to quench the primary oxidant-singlet oxygen effectively.