The relationship between changes in the cell wall, lipid peroxidation, proliferation, senescence and cell death

Plants and mammals contain polyunsaturated fatty acids (PUFAs) in their membranes. PUFAs belong to the most oxygen sensitive molecules encountered in nature. It would seem that nature has selected this property of PUFAs for signalling purposes: PUFAs are stored in the surface of cells and organelles not in free form but conjugated to phospho‐ and galactolipids. Any change in membrane structure apparently activates membrane‐bound phospholipases, which cleave the conjugates. The obtained free PUFAs are substrates for lipoxygenases (LOX). These transform PUFAs to lipidhydroperoxides (LOOHs). LOOHs are converted to a great variety of secondary products. These lipid‐peroxidation (LPO) products and the resulting generated products thereof represent biological signals, which do not require a preceding activation of genes. They are produced as a non‐specific response to a large variety of external or internal impacts, which therefore do not need interaction with specific receptors. When, due to an external impact, e.g. attack of a microorganism, or to a change in temperature, the amount of liberated free PUFAs exceeds a certain threshold, LOX commit suicide. Thus iron ions, located in the active centre of LOX, are liberated. Iron ions react with LOOHs in the close surroundings by generating alkoxy radicals (LO.). These induce a non‐enzymatic LPO. A fraction of the LO. radicals generated from linoleic acid (LPO products derived from linoleic acid play a dominant role in signalling which was previously overlooked) is converted to 2,4‐dienals which induce the programmed cell death (PCD) and the hypersensitive reaction (HR). While peroxyl radicals (LOO.) generated as intermediates in the course of an enzymatic LPO are transformed within the enzyme complex to corresponding anions (LOO^–), and thus lose their reactivity, peroxyl radicals generated in non‐enzymatic reactions are not deactivated. They not only react by abstraction of hydrogen atoms from activated X‐H bonds of molecules in their close vicinity, but also by epoxidation of double bonds and oxidation of a variety of biological molecules, causing a dramatic change in molecular structure which finally leads to cell death. As long as reducing agents, like glutathione, or compounds with free phenolic groups are available, the amount of LOOHs is kept low. Cell death is induced in a defined way by apoptosis. But when the reducing agents have been consumed, PCD seems to switch to necrotic processes. Thus proliferation is induced by minor changes at the cell membrane, while slow changes at cell membranes are linked with apoptosis (e.g. response to attack of microorganisms or drought) and necrosis (severe wounding), depending only on the amount, but not on the type, of applied stimulus.     

Role of lipid peroxidation in the inhibition of mononuclear cell proliferation by normal lipoproteins

Stimulated peripheral blood mononuclear cells (PBMC) can oxidize normal lipoproteins, and sufficiently oxidized lipoproteins are cytotoxic. However, the role of lipid peroxidation in the inhibition of mitogen-stimulated PBMC proliferation by physiologic concentrations of normal lipoproteins is unclear. In the present investigation, normal low density lipoprotein (LDL) and very low density lipoprotein (VLDL) suppressed [3H]thymidine incorporation and gamma interferon production in concanavalin A-stimulated PBMC without causing cell death. This suppression was accompanied by parallel increases in lipid peroxidation products measured as thiobarbituric acid reactive substances (TBARS). In contrast, high density lipoprotein (HDL) failed to inhibit PBMC and TBARS remains low. Differences between the PBMC suppression from LDL, VLDL, and HDL were best accounted for by normalizing the lipoprotein concentrations by their total lipid content. Moreover, the antioxidants superoxide dismutase and butylated hydroxytoluene each substantially ameliorated the inhibition of PBMC caused by LDL, and reduced the levels of lipid peroxidation products that were generated. Altogether, these results suggest that reactive oxygen species generated by stimulated PMBC may cause oxidative alterations of normal lipoproteins that may, in turn, account for much of the previously reported inhibition of PBMC by normal lipoproteins.     

Retardation of cell aging by lipid peroxidation

Different concentrations of Fe e+/vitamin C mixtures were used as initiators of lipid peroxidation in diploid fibroblasts from cultured human embryonic lung. Malondialdehyde (MDA) formation in the cell cultures was correlated directly with the concentrations of Fe²⁺ and vitamine C. Lipid peroxidation was associated with an increase in life-span, decrease in the population doubling time and increase in cellular DNA synthesis. The effects of lipid peroxidation varied inversely with the MDA level. These data showed that low levels of lipid peroxidation retarded several biological properties of cultured cells that are associated with cell aging.     

The role of lipid peroxidation in aluminium toxicity in soybean cell suspension cultures

The primary reactions leading to Al toxicity in plant cells have not yet been elucidated. We used soybean (Glycine max [L.] Merr.) cell suspension cultures to address the question whether lipid peroxidation plays an important role in Al toxicity. Upon transfer to an Al-containing culture medium with a calculated Al3+ activity of 15 microM soybean cells showed a distinct and longtime increase in lipid peroxidation within 4 h. At the same time a drastic loss of cell viability was observed. Butylated hydroxyanisole (BHA) and N,N'-diphenyl-p-phenylenediamine (DPPD), two lipophilic antioxidants, were able to almost completely suppress lipid peroxidation in Al-treated cells at a concentration of 20 microM. This effect was dose-dependent for DPPD and was observed at minimum concentrations of 1-2 microM. When lipid peroxidation was suppressed by DPPD or BHA cell viability remained high even in the presence of toxic Al concentrations. These results suggest that Al-induced enhancement of lipid peroxidation is a decisive factor for Al toxicity in suspension cultured soybean cells.     

Methemoglobin-induced lipid peroxidation in model membranes]

Lipid peroxidation induced by methemoglobin in liposomes prepared from lecithin, cardiolipin and their mixtures has been investigated. Using absorption spectroscopy technique it was shown that in the bilayers with low initial oxidation methemoglobin caused the formation of diene conjugates. In the bilayers with high degree of oxidation protein activated cleavage of the available fatty acid hydroperoxides. Hydroperoxides were found to induce the reduction of methemoglobin absorption in the Soret band.     

Adaptive response induced by lipid peroxidation products in cell cultures

The adaptive response induced by the lipid peroxidation products, such as phosphatidylcholine hydroperoxide, lysophosphatidylcholine (LysoPC), 15-deoxy-Delta(12,14)-prostaglandin J(2), 4-hydroxynonenal (4-HNE), hydroxyoctadecadienoic acid, 7-hydroxycholesterol, and cholesterol 5beta,6beta-epoxide, was investigated in this study. Although these products have been implicated in oxidative stress-related diseases, pretreatment with such compounds at sublethal concentrations significantly protected PC12 cells against subsequent oxidative stress induced by 6-hydroxydopamine. Moreover, 4-HNE and LysoPC also exhibited adaptive protection in human arterial endothelial cells. These findings suggest a general hormetic effect of such compounds in cell cultures and may lead to a reappraisal of the eventual role of reactive oxygen species and lipid peroxidation in organisms.     

膜脂过氧化产物在光敏诱发细胞突变中的作用

本文选用ＣＨＯ细胞,通过竹红菌甲素（ＨＡ）光敏诱变及ｏｕａ选择性培养液的筛选,证实甲素光敏反应对细胞Ｎａ＾＋／Ｋ＾＋ ＡＴＰ酶基因具有诱变致突作用。对其突变效应与脂质过氧化反应及ＤＮＡ加成物形成关系的分析表明,ＴＢＡ反应产物随着光照时间的增加而增加,同时ＤＮＡ加成物生成迅速增加,突变频率也随之增高。维生素Ｅ可抑制脂质过氧化反应,并减少ＤＮＡ加成物生成,阻止细胞突变率的增加。提示光敏诱发细胞脂质过氧     

Relay model of lipid peroxidation in biological membranes

The present study examines the evidence for the important role of free radicals, localized on carbon atoms of the hydrocarbon chains, in lipid peroxidation. These radicals show a great inter- and intramolecular mobility in membranes by the way of relay-transfer (isomerisation). The sequence of intermediate steps of shift of free radicals in membranes with correction for molecular organization of the hydrocarbon zone of membranes, the intramembrane localization of unsaturated links and the gradient of mobility of the hydrocarbon chains are described. The effect of inhibitors in lipid peroxidation are interpreted in terms of decay of hydrocarbon free radicals as a result of its interaction with the antioxidant molecules. The natural antioxidants having a side chain (such as tocopherols) may be regarded as a some kind of "channel" through which free radicals leave the hydrocarbon moiety of the membrane. The processes of lipid peroxidation in membranes are subjected to a great extent to the requirements of the theory of oxidation of solid polymers and hydrocarbons.     

Halogenated compounds as inducers of lipid peroxidation in tissue slices

Twenty-seven halogenated compounds were screened as potential inducers of lipid peroxidation in rat liver, kidney, spleen, and testes slices. In addition to the known lipid peroxidation inducers--carbon tetrachloride and bromotrichloromethane--the novel compounds carbon tetrabromide, p-bromobenzyl bromide, and benzyl bromide increased lipid peroxidation in each of the tissues studied. Lipid peroxidation was measured by release of thiobarbituric acid-reactive substances (TBARS) from the tissue slices. The amount of TBARS released from liver slices incubated with bromotrichloromethane, carbon tetrabromide, dichloromethane, bromobenzene, chloroform, bromoform, benzyl chloride, bromochloromethane, and carbon tetrabromide correlated with the lethality of these compounds as evaluated by their oral LD50 in rats. The lethality of a number of the compounds tested did not correlate with their capacity to induce lipid peroxidation.     

The crucial role of hypoxia in halothane-induced lipid peroxidation

Halothane-induced lipid peroxidation in NADPH-reduced liver microsomes from phenobarbital-pretreated male rats was studied under defined steady state oxygen partial pressures (Po2). Under anaerobic conditions, as well as at a Po2 above 10 mm Hg no halothane-induced formation of malondialdehyde was detected. At a Po2 below 10 mm Hg, however, with a maximum near 1 mm Hg oxygen, significant halothane-induced malondialdehyde formation was found. This evidence supports the hypothesis that halothane can induce lipid peroxidation. The Po2 (i) must be low enough to permit the reductive formation of . CF3 CHCl-radicals but (ii), it must be high enough to promote formation of lipid peroxides.     

PEP-1-frataxin significantly increases cell proliferation and neuroblast differentiation by reducing lipid peroxidation in the mouse dentate gyrus

Frataxin plays important roles in the mitochondrial respiratory chain and in the differentiation of neurons during early development. In this study, we observed the effects of frataxin on cell proliferation and neuroblast differentiation in the mouse hippocampal dentate gyrus. For this, we constructed an expression vector, PEP-1, that was fused with frataxin to create a PEP-1-frataxin fusion protein that easily penetrated frataxin into the blood-brain barrier. Three mg/kg PEP-1-frataxin was intraperitoneally administered to mice once a day for 2 weeks. The administration of PEP-1 alone did not result in any significant changes in the number of Ki67-positive cells and doublecortin (DCX)-immunoreactive neuroblasts in the mouse dentate gyrus. However, the administration of PEP-1-frataxin significantly increased the number of Ki67-positive cells and DCX-immunoreactive neuroblasts in the mouse dentate gyrus. In addition, PEP-1-frataxin significantly reduced 4-hydroxynonenal protein levels and malondialdehyde formation, while Cu, Zn-superoxide dismutase protein levels were maintained. These results suggest that frataxin effectively increased cell proliferation and neuroblast differentiation by decreasing lipid peroxidation in the dentate gyrus.     

Mechanisms of enhancing UV lihg-induced lipid peroxidation in isolated erythrocyte membranes by organohalogen compounds

It was found that a number of halogen-containing compounds (chloroform, carbon tetrachloride, difluorodichloromethane, sodium trichloroacetate) enhance the lipid peroxidation induced by UV light (265-300 nm) in isolated erythrocyte membranes. It was shown that the enhancement is realized with participation of excited states of membrane protein tryptophanyls, which may induce the reduction of halogen-containing compounds with formation of radicals having a high oxidative activity. Moreover, halogen-containing compounds decrease the antioxidant protection of membrane lipids owing to an increase in quantum yield of alpha-tocopherol photodestruction.     

Assessment of cell damage caused by spontaneous lipid peroxidation in rabbit spermatozoa

Damage to the plasma membrane of rabbit epididymal spermatozoa during spontaneous lipid peroxidation was examined by means of trypan blue uptake and expression of activity of the intracellular enzymes, lactate dehydrogenase and pyruvate kinase. Both the dye uptake and the expression of enzyme activity probe cell damage from lipid peroxidation as loss of integrity of the plasma membrane. A linear correlation was obtained between trypan blue staining of the cells and malondialdehyde production, a quantifiable measure of the extent of lipid peroxidation. At the point of trypan blue staining of all cells, 0.5 nmol malondialdehyde/10(8) cells was produced. This is the same amount produced at the point of complete loss of motility and superoxide dismutase activity. We have defined this as the "lipoperoxidative lethal end point." Expression of lactate dehydrogenase and pyruvate kinase activities increased with time of aerobic incubation. In the high Na+ medium, NTP, in which lipid peroxidation is slow, there is a linear correlation between increase in expressed enzyme activities and malondialdehyde production. But in the high K+ medium, KTP, in which lipid peroxidation is rapid, there is an initial rapid rise in expressed enzyme activity over 3 h, followed by a slower increase. Activities of rabbit sperm lactate dehydrogenase, pyruvate kinase, and flagellar ATPase were unaffected by aerobic incubations for up to 48 h, double the incubation period used for the assay of enzymatic activities for the first two. The activity of glyceraldehyde-3-phosphate dehydrogenase decreased during aerobic incubation, the time course matching the loss of motility. The subcellular distribution of lactate dehydrogenase in rabbit spermatozoa was determined: 4% in the mitochondrial matrix, 10% in the plasma membrane and 85% in the cytosolic compartment.     

Stemodin-derived analogues with lipid peroxidation, cyclooxygenase enzymes and human tumour cell proliferation inhibitory activities

A series of analogues, derived from the antiviral and cytotoxic diterpene stemodin, were prepared and evaluated for their lipid peroxidation (LPO), cyclooxygenase enzyme-1 (COX-1) and -2 (COX-2), and tumour cell proliferation inhibitory activities. Oxidation of stemodin produced stemodinone, which was then converted to stemod-12-en-2-one. Reaction of the latter under Petrow conditions (bromine; silver acetate/pyridine) yielded mainly dibrominated abeo-stachanes. Solvolysis of the dibromo compounds gave products of hydrolysis, some with rearranged skeleta. In the lipid peroxidation inhibitory assay three of the compounds exhibited prominent activity. Interestingly, all the analogues showed higher COX-1 enzyme inhibition than COX-2. Although a few of the diterpenes limited the growth of some human tumour cell lines, most compounds induced proliferation of such cells.     

Fe2+-supported in vivo lipid peroxidation induced by compounds undergoing redox cycling

Treatment of male mice with the redox cycling compounds nitrofurantoin, paraquat, diquat or menadione failed to elicit in vivo lipid peroxidation as evidenced by ethane exhalation. The first three led to an enhanced ethane production, however, when the animals were pretreated with a low dose of Fe2+. While GSH-depletion by phorone pretreatment alone had no influence on the in vivo lipid peroxidation as evidenced by ethane expiration in the presence of either compound, the combined treatment with phorone, Fe2+ and nitrofurantoin, paraquat or diquat led to a further enhancement of ethane exhalation. These results indicate that redox cycling compounds do not initiate lipid peroxidation by themselves, but are well capable of stimulating the iron-induced LPO.     

The role of iron in the initiation of lipid peroxidation

Iron is required for the initiation of lipid peroxidation. Evidence is presented that lipid peroxidation requires both Fe3+ and Fe2+, perhaps with oxygen to form a Fe3+-dioxygen-Fe2+ complex. Other mechanisms of initiation, mostly involving the iron-catalyzed formation of hydroxyl radical, are described and discussed from both theoretical and experimental view points.     

The role of lipid peroxidation in the mechanism of stress

A concept on the mechanism of stress response is substantiated proceeding from the data available in literature and obtained from the author's research made on the radiation stress model. The conception envisages that products of lipid peroxidation (LPO) appear as primary (under direct effect of a stress factor on tissues) and secondary (as a consequence of high- and long-term catecholamine++) mediators. Mobilization of stress-realizing systems in that process is regarded as an adequate response of the auto-oxidative++ system to the primary activation of LPO. Transformation of catecholamines into the factor of LPO stimulation (secondary) is a result of an increase in the relative role of the quinoid way to transform catecholamines in the case of their high concentration. Radical intermediates of the quinoid metabolism appear as LPO initiators. An important pathogenetic role of LPO activation in the stress mechanism substantiates expedience to use antioxidants as agents for prophylaxis and early treatment of stress-factor injuries.     

Protective role of arzanol against lipid peroxidation in biological systems

This study examines the protective effect of arzanol, a pyrone–phloroglucinol etherodimer from Helichrysum italicum subsp. microphyllum, against the oxidative modification of lipid components induced by Cu²⁺ ions in human low density lipoprotein (LDL) and by tert-butyl hydroperoxide (TBH) in cell membranes. LDL pre-treatment with arzanol significantly preserved lipoproteins from oxidative damage at 2 h of oxidation, and showed a remarkable protective effect on the reduction of polyunsaturated fatty acids and cholesterol levels, inhibiting the increase of oxidative products (conjugated dienes fatty acids hydroperoxides, 7β-hydroxycholesterol, and 7-ketocholesterol). Arzanol, at non-cytotoxic concentrations, exerted a noteworthy protection on TBH-induced oxidative damage in a line of fibroblasts derived from monkey kidney (Vero cells) and in human intestinal epithelial cells (Caco-2), decreasing, in both cell lines, the formation of oxidative products (hydroperoxides and 7-ketocholesterol) from the degradation of unsaturated fatty acids and cholesterol. The cellular uptake and transepithelial transport of the compound were also investigated in Caco-2 cell monolayers. Arzanol appeared to accumulate in Caco-2 epithelial cells. This phenol was able to pass through the intestinal Caco-2 monolayers, the apparent permeability coefficients (P_app) in the apical-to-basolateral and basolateral-to-apical direction at 2 h were 1.93 ± 0.36 × 10⁻⁵ and 2.20 ± 0.004 × 10⁻⁵ cm/s, respectively, suggesting a passive diffusion pathway. The results of the work qualify arzanol as a potent natural antioxidant with a protective effect against lipid oxidation in biological systems.     

Species differences in adrenal lipid peroxidation: role of alpha-tocopherol

Previous reports have noted high levels of lipid peroxidation (LP) in vitro in a variety of adrenocortical preparations. However, we have observed that susceptibility to adrenal LP seems to vary considerably from species to species. The current study was done to confirm these apparent species differences in adrenal LP in vitro and to determine if they were attributable to differences in alpha-tocopherol content. Incubation of mitochondrial or microsomal preparations from guinea pig or rabbit adrenal glands with ferrous ion (Fe2+) caused a time-dependent increase in the formation of thiobarbituric acid reactive substances (TBARS) accompanied by depletion of alpha-tocopherol. By contrast, incubation of adrenal mitochondria or microsomes from rats or monkeys with Fe2+ had little or no detectable effect on TBARS and basal adrenal alpha-tocopherol levels were five to ten-fold greater than those in guinea pigs or rabbits. In addition, there was little change in alpha-tocopherol concentrations during incubation of rat or monkey adrenal tissue. Dietary alpha-tocopherol deficiency in rats reduced adrenal alpha-tocopherol to concentrations approximating those in guinea pigs. Incubation with Fe2+ induced high levels of TBARS in adrenal mitochondria and microsomes from the alpha-tocopherol deficient rats. Conversely, dietary alpha-tocopherol supplementation in rabbits increased adrenal alpha-tocopherol levels and prevented Fe2+ induced TBARS formation in mitochondria and microsomes. The results indicate that there are large species differences in adrenal susceptibility to LP in vitro and that these differences are at least partly attributable to species differences in adrenal alpha-tocopherol concentrations.     

The possible role of lipid peroxidation in breast cancer risk

Breast cancer remains the commonest cause of death from cancer in women in most of the Western world. There is considerable evidence that breast cancer risk is influenced by environmental factors and can therefore potentially be modified. In this paper we describe evidence suggesting a relationship of lipid peroxidation to breast cancer risk, and propose that the method used to generate this information might usefully be applied to other disease states, and make some suggestions for further work. We have compared the urinary excretion of the mutagen malonaldehyde (MDA) in premenopausal women at different risks for breast cancer as determined by the appearance of the breast parenchyma on mammography. MDA was measured in 24-h urine samples from both groups and excretion in 30 women with mammographic dysplasia (high risk) was found to be approximately double that of 16 women without these radiological changes (p less than 0.02). These results suggest that mammographic dysplasia may be associated with lipid peroxidation. Further study of environmental factors associated with states that precede the development of breast and other cancers may lead to the identification of factors that can be modified and that may prevent the development of malignant disease.