Synergistic interaction between vitamin E and the bile pigments bilirubin and biliverdin

The oxidation of soybean phosphatidylcholine (PC) liposomes initiated with a lipid-soluble azo compound within the liposomal membranes has been studied in the absence and presence of membrane-bound vitamin E and water-soluble bile pigments. In the absence of vitamin E, lipid peroxidation proceeded linearly and without delay. Low micromolar amounts of bilirubin ditaurine (BR-DT, a model compound of conjugated bilirubin) or biliverdin (BV) inhibited the oxidation of PC significantly and in a concentration-dependent way. In contrast, neither taurine, ascorbic acid nor reduced glutathione inhibited significantly under these conditions. Both bile pigments were consumed during their protective action. Vitamin E incorporated into the liposomal membranes suppressed the oxidation initially almost completely, thereby producing an induction period. In the combined presence of vitamin E and either of the two bile pigments at 10 microM each, this induction period was increased by at least 200%. In contrast, when 10 microM vitamin E was combined with an equimolar concentration of reduced glutathione, the induction period increased by only about 30%. BR-DT and BV both spared the consumption of vitamin E during the oxidation of PC liposomes. These results demonstrate that conjugated bilirubin and BV located in the aqueous phase can directly scavenge lipid radicals to some extent. Furthermore, both bile pigments can act synergistically with membrane-bound vitamin E to prevent lipid peroxidation initiated in the lipid phase, most likely through regeneration of the vitamin from its chromanoxyl radical.     

Changes in nonpolar aldehydes in bean cotyledons during ageing

Ageing of plant organs is accompanied by an increased production of free radicals what results in membrane lipid peroxidation. Non-polar aldehydes originating from this process interact with the cellular material to form the fluorescent end-products, lipofuscin-like pigments (LFP). Their formation was studied both qualitatively and quantitatively in ageing of bean cotyledons. The concentration of lipofuscin-like pigments increased 9-fold in 14-d-old (senescent) cotyledons in relation to 8-d-old (young) cotyledons. HPLC fractionation patterns indicate changes in their composition during ageing. The LFP increase in old cotyledons was accompanied by elevated levels of non-polar aldehydes that increased during ageing to 167 %. The composition of aldehydes was studied by mass spectrometry. The most abundant fraction in both young and old cotyledon was represented by C12 aldehydes, which comprised both saturated and unsaturated species. We have observed differences in abundances of individual aldehydes between the young and the old cotyledons that might explain the differences in the composition of lipofuscin-like pigments. These results support the involvement of free radicals in plant ageing; however, it is suggested that plant aldehydic products of lipid peroxidation differ from those found in animals.     

Kinetics of lipid peroxidation in isolated surviving rat livers

The kinetics of accumulation of lipid peroxidation products (hydroperoxides as primary products and malonic dialdehyde and "fluorescent pigments" as secondary ones) was investigated in an isolated non-perfused and preliminarily perfused liver during aerobic incubation. In the course of surviving there takes place an intensive accumulation of primary, secondary and final products of lipid peroxidation whose kinetics is of an extreme character. The rate of this process in a non-perfused liver is considerably higher than in a preliminarily perfused liver.     

Effect of melanins on lipid peroxidation

Effects of melanins obtained from cultured Cladosporium cladosporidae fungi and Alpha grape on Fe(2+)-induced, Fe(2+)-ascorbate-induced, and NADPH-induced lipid peroxidation in rat liver, brain, and eye were studied. Melanins were shown to inhibit the accumulation of lipid peroxidation products in vitro. The inhibitory effects of melanins were not due to direct interactions of these pigments with superoxide anion (O2). However, melanins may interact with other free radicals. Melanins were demonstrated to have the ability to oxidize NADPH, which is probably one of the mechanisms of their antioxidant effects.     

Methods for estimating lipid peroxidation: an analysis of merits and demerits

Among the cellular molecules, lipids that contain unsaturated fatty acids with more than one double bond are particularly susceptible to action of free radicals. The resulting reaction, known as lipid peroxidation, disrupts biological membranes and is thereby highly deleterious to their structure and function. Lipid peroxidation is being studied extensively in relation to disease, modulation by antioxidants and other contexts. A large number of by-products are formed during this process. These can be measured by different assays. The most common method used is the estimation of aldehydic products by their ability to react with thiobarbituric acid (TBA) that yield 'thiobarbituric acid reactive substances' (TBARS), which can be easily measured by spectrophotometry. Though this assay is sensitive and widely used, it is not specific and TBA reacts with a number of components present in biological samples. Hence caution should be used while employing this method. Wherever possible this assay should be combined with other assays for lipid peroxidation. Such methods are measurement of conjugated dienes, lipid hydroperoxides, individual aldehydes, exhaled gases like pentane, isoprostanes, etc. The modern methods also involve newer techniques involving HPLC, spectrofluorimetry, mass spectrometry, chemiluminescence etc. These and other modern methods are more specific and can be applied to measure lipid peroxidation. There are certain restraints, in terms of high cost and certain artifacts, and these should be considered while selecting the method for estimation. This review analyses the merits and demerits of various assays to measure lipid peroxidation.     

An electron microscopical study on the genesis of lipofuscin, melanin and haemosiderin in the haemopoietic tissues of fish

The mode of origin of the pigments within the macrophages of the haemopoietic tissues of some fish species was studied with the electron microscope. Lipofuscin appears to be derived from damaged cellular components, such as effete mitochondria, through the peroxidation of their unsaturated lipids. Haemosiderin is almost certainly derived from the breakdown of haemoglobin from effete erythrocytes. Melanin appears to be derived from phagocytosis of melanin granules or their precursor organelles from melanin-containing cells. Both lipid peroxidation and haemoglobin breakdown produce free radicals and cations which are potentially toxic. Melanin absorbs free radicals and has strong affinity for cations and it is probable that they are neutralized by the melanin in macrophages. The electron micrographs published here illustrate the association of the lysosomal apparatus with pigment formation in fish melano-macrophages. These findings appear valid for all the species examined and may apply to all fish. It has been suggested that fish melano-macrophage centres represent primitive analogues of the germinal centres of higher animals. This study reveals that melanocyte-like cells outnumber melano-macrophages in the kidney of rainbow trout, Salmo gairdneri. Moreover, like melano-macrophages, these cells increase markedly in number during starvation.     

Physiological and Biochemical Aspects of Halophyte Ecology

Physiological and biochemical features of euhalophytes, сrinohalophytes, and glycohalophytes growing in natural conditions in El’ton Lake area were studied. The water content in tissues, intensity of lipid peroxidation, and membrane permeability were found to determine the differentiation of plants by their salt accumulation strategy. The concentration of pigments and their ratio are related to the mesostructure of leaves and are dependent on the salt accumulation strategy and life form. The membrane complex is connected with the cell structure and photosynthetic apparatus. The specificity of ion transportation depends on the specific features of plants.     

Antioxidant capacity of novel pigments from an Antarctic bacterium

In Antarctica microorganisms are exposed to several conditions that trigger the generation of reactive oxygen species, such as high UV radiation. Under these conditions they must have an important antioxidant defense system in order to prevent oxidative damage. One of these defenses are pigments which are part of the non-enzymatic antioxidant mechanisms. In this work we focused on the antioxidant capacity of pigments from an Antarctic microorganism belonging to Pedobacter genus. This microorganism produces different types of pigments which belong to the carotenoids group. The antioxidant capacity of a mix of pigments was analyzed by three different methods: 1,1-diphenyl-2-picrylhydrazyl, ROS detection and oxygen electrode. The results obtained from these approaches indicate that the mix of pigments has a strong antioxidant capacity. The oxidative damage induced by UVB exposure to liposomes was also analyzed. Intercalated pigments within the liposomes improved its resistance to lipid peroxidation. Based on the analysis carried out along this research we conclude that the antioxidant properties of the mix of pigments protect this bacterium against oxidative damage. These properties make this mix of pigments a powerful antioxidant mixture with potential biotechnological applications.     

Liposomes as membrane model for study of lipid peroxidation

This article describes the properties, production and characterization of liposomes with special reference to their use as membrane model for the study of lipid peroxidation. It presents briefly the methods that can be used for the assay of liposomal lipid peroxidation and brings out the special advantages these liposomes provide in elucidating the mechanism of lipid peroxidation by different physical and chemical agents. Studies involving liposomal lipid peroxidation by different agents and the consequent changes in the structure and function of liposomal membrane have been reviewed briefly.     

Lipid-phenolic radical adducts as a plausible mechanism of "plant ageing" pigment formation

Co-oxidation of chlorogenic acid, caffeic acid, aesculetin and lucigenin with linoleic acid and egg phosphatidyl choline leads to the formation of fluorescent polymer materials. The fluorescent products are more lipophylic, they have lower elution volumes on Sephadex LH-20 column than related phenols and they differ by their fluorescence and chromatographic properties considerably from polymer lipid peroxidation products. From the presence in the excitation fluorescence spectra of a band corresponding to the phenols it was concluded that the fluorophoric groups were similar in both cases. The data are discussed in terms of liquid phase peroxidation and the appearance of the fluorescent species are attributed to the production of molecular adducts as a result of lipid and phenoxyl radical recombination. The characteristics of products obtained are compared with properties of fluorescent "plant ageing" pigments accumulated in aged and damaged plant cells.     

Effect of magnesium and calcium ions on photoinduced lipid peroxidation and thylakoid breakdown of cell-free chloroplasts

Aging of cell-free chloroplasts at pH 7.0 and 9.0 causes a decline in the level of photosynthetic pigments, quenching of chlorophyll a fluorescence and enhancement in fluorescence polarization. These changes are correlated with photoinduced enhancement of thylakoid lipid peroxidation. The alkaline earth metal cations, namely magnesium and calcium, show opposite actions on lipid peroxidation and modulate thylakoid disorganisation differently. Magnesium ion may stabilise thylakoid membrane by retarding lipid peroxidation. It lowers aging-induced quenching of fluorescence intensity and enhancement of fluorescence polarization. Calcium ion, on the other hand, stimulates disorganisation of thylakoid membranes. It enhances membrane lipid peroxidation, quenching of chlorophyll a fluorescence intensity and fluorescence polarization.     

Oxidative Stress in Relation to Lipid Peroxidation, Sclerotial Development and Melanin Production by Sclerotium rolfsii

Melanin pigments constituted 13.9% of the chemical composition of the sclerotial walls of Sclerotium rolfsii and was associated with proteins, reducing sugars and amino acids. The lipid and ash contents in the sclerotial walls were double those in the hyphal walls of the fungus. Increasing age of the culture and maturation of the sclerotia were always accompanied by elevation of lipid peroxides and melanin pigments. Such behaviour may indicate that lipid peroxidation and melanin formation are operating in parallel during sclerotial biogenesis and maturation. These two processes depend on the theory of oxidative stress, as affected by growth conditions. Both processes could be stopped or sharply retarded when subjected to some antioxidant growth factors such as vitamins (ascorbic acid), micro-elements (selenium) and sulfhydryl compounds (glutathione). A clear relation between oxidative stress, myceliogenic germination and lytic activity via melanin production was observed. This finding appears promising in applying a new control measure against diseases caused by sclerotia-producing fungi without using traditional toxic fungicides.     

Studies on lipid peroxidation in rat liver nuclei and isolated nuclear membranes

Non-enzymatic and enzymatically-driven lipid peroxidation processes were studied in rat liver nuclei and isolated nuclear membranes, by evaluating the formation of thiobarbituric acid-chromophore, free malondialdehyde, lipofuscin-like pigments, and the degradation of polyunsaturated fatty acids of the nuclear membrane lipids. The results obtained show that: (1) both non-enzymatic and enzymatically driven lipid peroxidation processes are operative in cell nuclei and isolated nuclear membranes; (2) only for isolated nuclear membranes, a good qualitative and up to a great extent quantitative correlation between malondialdehyde and lipofuscin-like pigment formation was obtained; (3) there is a qualitative but not quantitative correlation between malondialdehyde formation and polyunsaturated fatty acid degradation; (4) lipid peroxidation processes in isolated nuclear membranes and intact nuclei have an essentially identical kinetic behaviour. No statistical differences in the relative increases in the concentrations of malondialdehyde and lipofuscin-like pigments or in the degradation of polyunsaturated fatty acids were obtained, when the two systems were compared, except in the presence of NADPH-ADP-Fe3+, which induced a significantly larger degradation of polyunsaturated fatty acids in isolated nuclear membranes than in intact nuclei, and (5) no malondialdehyde-DNA fluorescent adduct formation was observed in any of the experimental groups studied, as inferred from the characteristics of the fluorescent spectra of lipofuscin-like pigments extracted from incubated nuclear preparations.     

End products of lipid peroxidation in erythrocyte membranes in Alzheimer's disease

Alzheimer's disease (AD) is accompanied by oxidative stress in the brain. Because the brain tissue is rich in polyunsaturated fatty acids, it is prone to the free radical attack resulting in lipid peroxidation. Intermediates of lipid peroxidation may diffuse from the primary site, cross the blood-brain barrier and modify erythrocyte membranes in the bloodstream. We exposed isolated erythrocyte membranes from patients with AD and the control group to in vitro free radical damage and monitored the accumulation of the end products of lipid peroxidation, lipofuscin-like pigments (LFPs), by fluorescence spectroscopy. LFPs were analyzed by means of tridimensional and synchronous fluorescence spectroscopy. The levels of LFP formed during in vitro peroxidation were significantly higher in erythrocyte membranes from patients with AD compared with the control group. Furthermore, the chemical composition of LFP in AD was different from the control group. The analysis of the specific modifications of erythrocyte membranes in AD is of great medical importance regarding the need of a diagnostic blood biomarker.     

Chloroplast pigments,proteins, lipid peroxidation and activities of antioxidative enzymes during maturation and senescence of leaves and reproductive organs of Cajanus cajan L.

A comparative investigation was undertaken with pigeon pea leaves and attached flower buds/flowers/pods during their developmental stages including senescence in a natural system in experimental plots. Alterations in chloroplast pigments, total soluble proteins, lipid peroxidation, malondialdehyde (MDA) content and activities of guaiacol peroxidase (POD, EC 1.11.1.7) and superoxide dismutase (SOD, EC 1.15.1.1) were studied at 5-day interval from initial to 40-day stage. Chloroplast pigments and proteins of leaves increased upto 15 and 20-day stages respectively followed by a steady decline. Reproductive parts, however, exhibited rise in chloroplast pigments upto 25-day and protein till last stage as developing pods gain the amount from the senescing leaves which are nearest to them. Senescing leaves show very high POD activity than the developing and senescing pods and POD appears to be associated with chlorophyll degradation. Considerably higher activity and amount of LOX and MDA respectively have been noticed in senescing leaves than in flowers and pods. Increase in SOD activity during early stage of leaf growth and maturation indicates protective role that declined at senescent stages. Pods are unique in having very high SOD activity, only last stage of senescence does show a decline.     

Sclerotial development, melanin production and lipid peroxidation bySclerotium rolfsii

Melanin pigments constituted 13.9% (W/W) of sclerotial walls ofSclerotium rolfsii. The lipid and ash contents in sclerotial walls were twice those in hyphal walls of the fungus. Progress in culture age and maturation of sclerotia were always accompanied by increased levels of lipid peroxidation products and melanin. Lipid peroxidation and melanin formation may thus proceed in parallel during sclerotial biogenesis and maturation. Both these processes are strongly affected by Fe²⁺ and by antioxidant vitamins (ascorbic acid), microelements (selenium) and mercapto compounds (glutathione). Myceliogenic germination and lytic activityvia melanin production can thus be affected by (anti)oxidants that could potentially be used for controlling sclerotia-producing fungi without using traditional toxic fungicides.     

Early postnatal development of rat brain is accompanied by generation of lipofuscin-like pigments

The increased generation of free radicals results in the formation of fluorescent end-products of lipid peroxidation, lipofuscin-like pigments (LFPs). The authors observed that LFPs are generated in rat brain after a normal birth during 5 postnatal days. The experimental design of the study comprised 10 groups of animals. The authors measured prenatal values 1 day and 7 days before birth, and then the animals were sampled on postnatal day 1, 2, 5, 10, 15, 25, 35, and 90. Maximum LFP concentration is achieved on the postnatal day 2. Starting from postnatal day 10, LFP concentration returns to prenatal values. A new rise in LFP concentration is observed at 3 months of age. This is associated with the beginning of the aging process. LFPs were characterized by fluorescence spectroscopy using tridimensional excitation spectra, synchronous spectra and their derivatives, and HPLC with fluorescence detection. It was possible to discern several tens of fluorescent compounds of unknown structure that are generated and metabolized during early development. The authors suggest that LFPs are formed after respiratory burst of microglia phagocytosing apoptotic cells.     

Antioxidant action of acteoside and its analogs on lipid peroxidation

Summary

We have investigated antioxidant actions of acteoside (ACT) and another natural phenylpropanoid glycoside, cistanoside F (CIS-F) on lipid peroxidation in rat liver mitochondria (RLM) and rat liver mitochondrial lipid (RLML) liposomes induced by Fe²⁺/ADP. A synthetic ACT analogue, TX-1847, was also examined. Oxygen consumption, the formation of thiobarbituric acid reactive substances (TBARs) and glutathione concentration were determined simultaneously during lipid peroxidation. The radical scavenging activity of the compounds was evaluated by using 1,1-diphenyl-2-picrylhydrazyl. ACT and its analogs produced dose-dependent inhibitions of mitochondrial and liposomal lipid peroxidation (ACT ≈ CIS-F > TX-1847). Their radical scavenging activities were ranked as follows: TX-1847 > ACT > CIS-F. ACT, CIS-F, and TX-1847 spared reduced glutathione (GSH) during mitochondrial lipid peroxidation. The radical scavenging activities of the compounds did not parallel their anti-peroxidative activities. The data are consistent with the idea that the inhibitory activities of phenylpropanoids were primarily due to a radical chain-breaking mechanism. The sugar moieties in ACT and CIS-F, and/or the conformational structure of the compounds, also seem to play an important role in their inhibitory effects on lipid peroxidation.     

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.