Ozone and vitamin E

Lipid hydroperoxides in nutrition, health, and diseases

Research on lipid peroxidation in food degradation, oil and fat nutrition, and age-related diseases has gained significant international attention for the view of improvement of societal health and longevity. In order to promote basic studies on these topics, a chemiluminescence detection-high performance liquid chromatography instrument using a high-sensitivity single photon counter as a detector was developed. This instrument enabled us to selectively detect and quantify lipid hydroperoxides, a primary product of lipid peroxidation reactions, as hydroperoxide groups at the lipid class level. Furthermore, an analytical method using liquid chromatography-tandem mass spectrometry has been established to discriminate the position and stereoisomerization of hydroperoxide groups in lipid hydroperoxides. Using these two methods, the reaction mechanisms of lipid peroxidation in food and in the body have been confirmed.

Ozonation of PC in ethanol: separation and identification of a novel ethoxyhydroperoxide

The product of the ozonolysis of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine in ethanol-containing solvent was analyzed by chemiluminescence detection-HPLC with on-line electrospray MS, and characterized on the basis of NMR spectroscopy and MS in high-resolution fast atom bombardment mode. The reaction yielded a large amount of a novel ethoxyhydroperoxide compound [1-palmitoyl-2-(9-ethoxy-9-hydroperoxynonanoyl)-sn-glycero-3-phosphcholinel. In addition to a structural analysis, we speculate on the reaction pathway and discuss the possibility of ethoxyhydroperoxide as a potentially reactive ozonized lipid in food and biological materials.

Mechanisms of radical formation from reactions of ozone with target molecules in the lung

Ozone is known to cause radicals to be formed in biological systems: for example, it initiates lipid peroxidation and vitamin E protects in vitro model systems, cells, and animals against the effects of ozone. Ozone is not itself a radical, and we have asked: With what molecules does ozone react in the lung and how are radicals produced? Ozone reacts by two quite different mechanisms to produce radicals; one involves an ozone-olefin reaction and the other a reaction with electron donors such as glutathione (GSH). The first mechanism splits an R radical out of an olefin with the structure R-CH = CH2. The R then reacts with dioxygen to become a peroxyl radical (ROO), and both carbon- and oxygen-centered radicals can be detected by the electron spin resonance spin trap method. From the effects of temperature, metal chelators, and water, it is concluded that ozone reacts by the Criegee ozonation pathway to give the classical 1,2,3-trioxolane, which then undergoes O--O bond homolysis to form a diradical. This diradical then either undergoes beta-scission to split out the R radical or forms the more usual carbonyl oxide and a carbonyl compound. (See Figure 3 in the text). The low yield of Criegee ozonide that is generally obtained probably is due in part to the reactions forming radicals from the 1,2,3-trioxolane that compete with production of the Criegee ozonide. The second mechanism for radical production involves the reaction of ozone with electron donors. If the electron donor is, for example, GSH or its ion (GS-), this reaction produces the thiyl radical GS. and 0.3-. The ozone radical anion then reacts with a proton to form the hydroxyl radical and dioxygen: O3.- + H+-->HO. and O2. Using 5,5-dimethyl-1-pyrroline-N-oxide, the spin adduct of the hydroxyl radical is detected. Similar reactions are observed with catechol.

Effective inhibition of hydroxyl radicals by hydroxylated biphenyl compounds

In aqueous media, approximate rate constants for the reactions between hydroxyl radicals (.OH) and biphenyl compounds such as dehydrodieugenol, magnolol, honokiol, dehydrodidihydroeugenol, dehydrodivanillyl alcohol, and dehydrodicreosol were estimated by competition reactions for .OH between these biphenyls and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). By measuring the decrease in the height of the EPR signals of the .OH spin adduct, rate constants in the order of 10(9) to 10(10) M were measured.

Application of the EPR spin-trapping technique to the detection of radicals produced in vivo during inhalation exposure of rats to ozone

Ozone is known to induce lipid peroxidation of lung tissue, although no direct evidence of free radical formation has been reported. We have used the electron paramagnetic resonance (EPR) spin-trapping technique to search for free radicals produced in vivo by ozone exposure. The spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) was administered ip to male Sprague-Dawley rats. The rats were then exposed for 2 hr to either 0, 0.5, 1.0, 1.5, or 2.0 ppm ozone with 8% CO2 to increase their respiratory rate. A six-line 4-POBN/radical spin adduct signal (aN = 15.02 G and a beta H = 3.27 G) was detected by EPR spectroscopy in lipid extracts from lungs of rats treated with 4-POBN and then exposed to ozone. Only a weak signal was observed in the corresponding solution from rats exposed to 0 ppm ozone (air with CO2 only). The concentration of the radical adduct increased as a function of ozone concentration. After administration of 4-POBN, rats were exposed for either 0.5, 1.0, 2.0, or 4.0 hr to either 0 or 2.0 ppm ozone (with CO2). The radical adduct concentration of the ozone-exposed groups at exposure times of 2.0 and 4.0 hr was significantly different from that of the corresponding air control groups. A correlation was observed between the radical adduct concentration and the lung weight/body weight ratio. These results demonstrate that ozone induces the production of free radicals in rat lungs during inhalation exposure and that radical production may be involved in the induction of pulmonary toxicity by ozone. This is the first direct evidence for ozone-induced free radical production in vivo.

Enhancement of ethanol-induced lipid peroxidation in rat liver by lowered carbohydrate intake

In order to investigate the effect of carbohydrate intake on ethanol-induced lipid peroxidation and cytotoxicity, rats were maintained on four different test diets, a medium-carbohydrate (carbohydrate intake, 8.4 g/day/rat on average), a low-carbohydrate (carbohydrate intake, 2.8 g/day/rat on average), an ethanol-containing medium-carbohydrate (carbohydrate and an ethanol intake, 8.4 and 2.9 g/day/rat on average, respectively), and an ethanol-containing low-carbohydrate diet (2.8 and 2.9 g/day/rat on average, respectively). Ethanol and the low-carbohydrate diet each increased the liver malondialdehyde content, but the combined effect of both (ethanol-containing low-carbohydrate diet) was much more prominent than either alone. The degree of increase in malondialdehyde content almost paralleled the activity of the microsomal ethanol oxidizing system. Both the low-carbohydrate and the ethanol-containing low-carbohydrate diets decreased the liver glutathione content, but ethanol combined with the medium-carbohydrate diet had no effect on the content. Ethanol treatment increased the liver triglyceride content only when combined with the low-carbohydrate diet. The rate of NADPH-dependent microsomal malondialdehyde formation was much higher in microsomes from rats maintained on the ethanol-containing low-carbohydrate diet than in those from rats on the ethanol-containing medium-carbohydrate diet, indicating that lowered carbohydrate intake augments ethanol-induced malondialdehyde accumulation in the liver by enhancing the rate of lipid peroxidation. In addition, when incubated with red blood cells in the presence of NADPH, microsomes from rats fed the ethanol-containing low-carbohydrate diet caused marked hemolysis, which was prevented by the addition of 5 mM glutathione to the incubation system. Furthermore, addition of 50 mM ethanol to the reaction system greatly accentuated the hemolysis. These results suggest that lowered carbohydrate intake at the time of ethanol consumption potentiates ethanol cytotoxicity by enhancing ethanol-induced lipid peroxidation.

Essential oil phenyl propanoids. Useful as .OH scavengers?

In order to search for radical scavengers which could be used as raw materials for cosmetics, phenyl propanoids (eugenol, isoeugenol, dehydrodieugenol, dehydrodieugenol B and coniferyl aldehyde) were examined for their hydroxyl radical (.OH) scavenging ability. A Fenton system was used to produce .OH. In order to see scavenging by these phenyl propanoids, competition reactions between a spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), and these phenyl propanoids for .OH were studied. The relative yield of the spin adduct of .OH (DMPO-OH) was measured by electron spin resonance spectroscopy. The approximate rate constants of the reactions between these phenyl propanoids and .OH estimated by measuring the reduced height of the ESR signals of DMPO-OH were found to be at least in the order of 10(9) M-1 s-1 (diffusion-controlled). Also, using the TBA tests, the reactions between .OH and several compounds reactive with .OH were investigated in the presence of the phenyl propanoids and it was found that the phenyl propanoids compete with such reactive compounds for .OH. These results indicate that these phenyl propanoids can be used as antioxidants for skin damage perhaps caused by .OH generated by UV-light.

"Activation" of alveolar leukocytes isolated from cats fed taurine-free diets

Taurine is a ubiquitous amino sulfonic acid in mammals, present in high concentrations in tissues, including those exposed to elevated levels of oxidants. Experiments were designed to examine the consequences of taurine deficiency on production of ROI in leukocytes isolated from the lungs and blood of cats fed taurine-deficient diets. Cats were maintained on taurine-free or taurine-supplemented diets for at least 12 months at which time taurine deficiency was evident. To analyze alveolar cells, lungs were lavaged to recover lung macrophages and PMNs. Lung lavage fluid from cats contained macrophages and PMNs, although taurine deficiency was associated with a decrease in the percentage of PMNs in the lungs. This is similar to our findings in blood that taurine deficiency reduced the proportion of PMNs. Taurine measurements revealed 2.1 +/- 1.6 mumol/g wet wt of taurine in the lungs from cats fed a taurine-deficient diet versus 8.3 +/- 2.6 in lungs from cats fed a diet supplemented with taurine (n = 16). The effects of taurine deficiency on the functional activity of lung macrophages and PMNs were analyzed including the production of ROI. Alveolar leukocytes from cats fed taurine-deficient diets produced more superoxide anion in response to phorbol myristate acetate than cats fed taurine supplemented diets. Similar results were obtained using a chemiluminescence assay. Using the highly specific H2O2 indicator dye, dichlorofluorescin, and flow cytometry we found that alveolar leukocytes made more H2O2 than cells from cats fed taurine-supplemented diets. Forty-two percent of the cells from cats fed a taurine-supplemented diet expressed class II antigens. In contrast, 72% of cells from the taurine-deficient cats expressed this antigen. We hypothesize that taurine functions to prevent terminal activation and release of cytotoxic mediators by lung macrophages. Thus, a deficiency of taurine will indeed cause an activation of leukocytes, as evidenced by our data which show an increase in ROI, as well as an increase in class II antigen.

Aldehydes, hydrogen peroxide, and organic radicals as mediators of ozone toxicity

It is generally agreed that unsaturated fatty acids (UFA) are an important class of target molecule for reaction with ozone when polluted air is inhaled. Most discussions have implicated the UFA in cell membranes, but lung lining fluids also contain fatty acids that are from 20 to 40% unsaturated. Since UFA in lung lining fluids exist in a highly aquated environment, ozonation would be expected to produce aldehydes and hydrogen peroxide, rather than the Criegee ozonide. In agreement with this expectation, we find that ozonations of emulsions of fatty acids containing from one to four double bonds give one mole of H2O2 for each mole of ozone reacted. Ozonation of oleic acid emulsions and dioleoyl phosphatidyl choline gives similar results. with two moles of aldehydes and one mole of H2O2 formed per mole of ozone reacted. The net reaction that occurs when ozone reacts with pulmonary lipids is suggested to be given by equation 1. [formula: see text]. From 5 to 10% yields of Criegee ozonides also appear to be formed. In addition, a direct reaction of unknown mechanism occurs between ozone and UFA in homogeneous organic solution, in homogeneous solutions in water, in aqueous emulsions, and in lipid bilayers to give organic radicals that can be spin trapped. These radicals are suggested to be responsible for initiating lipid peroxidation of polyunsaturated fatty acids. Thus, aldehydes, hydrogen peroxide, and directly produced organic radicals are suggested to be mediators of ozone-induced pathology.

Effects of in vitro ozone exposure on peroxidative damage, membrane leakage, and taurine content of rat alveolar macrophages

Rat alveolar macrophages (AM) were isolated by pulmonary lavage, allowed to adhere to a tissue culture flask, and then exposed to 0.45 +/- 0.05 ppm ozone. After exposures ranging from 0 to 60 min, the medium was decanted and cells were harvested. Cells were assayed for oxidant damage and media analyzed for leakage of intracellular components. Increasing length of exposure to ozone resulted in a decreased number of adherent AM and decreased cell viability. Resting and zymosan-stimulated chemiluminescence increased immediately after ozone exposure and reached a maximum at 15-30 min, then declined to initial levels after 60 min of ozone exposure. Lipid peroxidation and leakage of protein and K+ ions increased with increasing length of exposure to ozone, while leakage of reduced and oxidized glutathione increased through 30 min, then declined (reduced) or leveled off (oxidized). Activity of the Na+/K+ ATPase decreased with time while intracellular taurine concentration exhibited an initial rise, peaked at 30 min, and then returned to the untreated level. Leakage of taurine into the medium increased with time of exposure, suggesting that exposure of AM to ozone results in a shift from bound to free intracellular taurine. These data indicate that in vitro exposure of AM to ozone results in a time-dependent alteration of cell function, membrane integrity, and viability.

Biochemical basis of ozone toxicity

Ozone (O3) is the major oxidant of photochemical smog. Its biological effect is attributed to its ability to cause oxidation or peroxidation of biomolecules directly and/or via free radical reactions. A sequence of events may include lipid peroxidation and loss of functional groups of enzymes, alteration of membrane permeability, and cell injury or death. An acute exposure to O3 causes lung injury involving the ciliated cell in the airways and the type 1 epithelial cell in the alveolar region. The effects are particularly localized at the junction of terminal bronchioles and alveolar ducts, as evident from a loss of cells and accumulation of inflammatory cells. In a typical short-term exposure the lung tissue response is biphasic: an initial injury-phase characterized by cell damage and loss of enzyme activities, followed by a repair-phase associated with increased metabolic activities, which coincide with a proliferation of metabolically active cells, for example, the alveolar type 2 cells and the bronchiolar Clara cells. A chronic exposure to O3 can cause or exacerbate lung diseases, including perhaps an increased lung tumor incidence in susceptible animal models. Ozone exposure also causes extrapulmonary effects involving the blood, spleen, central nervous system, and other organs. A combination of O3 and NO2, both of which occur in photochemical smog, can produce effects which may be additive or synergistic. A synergistic lung injury occurs possibly due to a formation of more powerful radicals and chemical intermediates. Dietary antioxidants, for example, vitamin E, vitamin C, and selenium, can offer a protection against O3 effects.

Perturbations in cerebral oxygen radical formation and membrane order following vitamin E deficiency

The effects of dietary vitamin E deficiency on mouse cerebral membrane order and oxygen reactive species were studied. Quantitation of vitamin E levels in several brain regions showed greatest deficiencies in striatum and cerebellum, followed by substantia nigra, and cortex. Vitamin E deficiency increased central-core membrane order in cerebral P2 fraction, but was without effect in the superficial hydrophilic membrane domain. Oxygen radical formation was studied using the probe 2',7'-dichlorofluorescein diacetate. Basal generation rates of oxygen reactive species were 2.5-fold higher when compared to control animals. While hepatic levels of vitamin E are much more reduced than brain levels, in deficient mice, the rate of oxygen radical formation in the liver was unaltered. This implies an special susceptibility of the brain to deficiency of this lipophilic antioxidant vitamin. Data demonstrate that endogenous levels of free radical scavengers, such as vitamin E, may play an important role in maintaining basal oxygen radical levels and membrane integrity. The dietary vitamin E depletion paradigm suggests that a relation exists between elevated levels of oxygen radicals and more rigid hydrophobic central-cores in cerebral membranes, effects that may play a role in mechanisms underlying the neuropathologic lesions observed following vitamin E deficiency.

Relationships between intracellular vitamin E, lipid peroxidation, and chemical toxicity in hepatocytes

The cellular content of vitamin E was measured in isolated rat hepatocytes exposed to various types of chemical injury. Vitamin E was determined as alpha-tocopherol by HPLC with in-line uv and electrochemical detection. The cytotoxicity of diquat, a redox cycling compound, was accompanied by a decrease in cellular alpha-tocopherol and a stimulation of lipid peroxidation. Both the loss of alpha-tocopherol and the accumulation of lipid peroxidation products could be prevented by addition of either the antioxidant N,N'-diphenyl-p-phenylenediamine (DPPD) or the reducing agent dithiothreitol (DTT). DTT also prevented the oxidation of soluble and protein thiols and completely protected against cytotoxicity, while DPPD addition only delayed the onset of hepatocyte death. Cytotoxic doses of the naphthoquinone, menadione, and the pyridine compounds 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and 1-methyl-4-phenyl-pyridinium ion did not deplete alpha-tocopherol levels, nor did they result in significant lipid peroxidation. On the other hand, a peroxidizing, but noncytotoxic dose of ADP-Fe3+ rapidly decreased cellular alpha-tocopherol levels. These data demonstrate that cellular alpha-tocopherol loss is neither a prerequisite for, nor a necessary consequence of toxicity. Moreover, a substantial depletion (ca. 50%) of alpha-tocopherol does not necessarily result in cell death. Although alpha-tocopherol protects against the oxidation of cellular lipids, the maintenance of hepatocyte alpha-tocopherol content does not prevent the oxidation of soluble and protein thiols. These other targets of oxidative damage seem to play a more critical role in hepatocyte toxicity.

Lipid peroxidation and mechanisms of toxicity

Aerobic organisms by definition require oxygen, and the importance of iron in aerobic respiration has long been recognized, but despite their beneficial roles, these elements can pose a real threat to the organism. During oxygen reduction, reactive species such as O2-. and H2O2 are formed readily. Iron can combine with these species, or with molecular oxygen itself, to generate free radicals which will attack the polyunsaturated fatty acids of membrane lipids. This oxidative deterioration of membrane lipids is known as lipid peroxidation. To protect itself against this form of attack, the organism possesses several types of defense mechanisms. Under normal conditions, these defenses appear to offer adequate protection for cell membranes, but the possibility exists that certain foreign compounds may interfere with or even overwhelm these defenses, and herein could lie a general mechanism of toxicity. This possible cause of toxicity is discussed in relation to other suggested causes.

Initiation of lipid peroxidation in biological systems

The direct oxidation of PUFA by triplet oxygen is spin forbidden. The data reviewed indicate that lipid peroxidation is initiated by nonenzymatic and enzymatic reactions. One of the first steps in the initiation of lipid peroxidation in animal tissues is by the generation of a superoxide radical (see Figure 16), or its protonated molecule, the perhydroxyl radical. The latter could directly initiate PUFA peroxidation. Hydrogen peroxide which is produced by superoxide dismutation or by direct enzymatic production (amine oxidase, glucose oxidase, etc.) has a very crucial role in the initiation of lipid peroxidation. Hydrogen peroxide reduction by reduced transition metal generates hydroxyl radicals which oxidize every biological molecule. Hydrogen peroxide also activates myoglobin, hemoglobin, and other heme proteins to a compound containing iron at a higher oxidation state, Fe(IV) or Fe(V), which initiates lipid peroxidation even on membranes. Complexed iron could also be activated by O2- or by H2O2 to ferryl iron compound, which is supposed to initiate PUFA peroxidation. The presence of hydrogen peroxide, especially hydroperoxides, activates enzymes such as cyclooxygenase and lipoxygenase. These enzymes produce hydroperoxides and other physiological active compounds known as eicosanoids. Lipid peroxidation could also be initiated by other free radicals. The control of superoxide and perhydroxyl radical is done by SOD (a) (see Figure 16). Hydrogen peroxide is controlled in tissues by glutathione-peroxidase, which also affects the level of hydroperoxides (b). Hydrogen peroxide is decomposed also by catalase (b). Caeruloplasmin in extracellular fluids prevents the formation of free reduced iron ions which could decompose hydrogen peroxide to hydroxyl radical (c). Hydroxyl radical attacks on target lipid molecules could be prevented by hydroxyl radical scavengers, such as mannitol, glucose, and formate (d). Reduced compounds and antioxidants (ascorbic acid, alpha-tocopherol, polyphenols, etc.) (e) prevent initiation of lipid peroxidation by activated heme proteins, ferryl ion, and cyclo- and lipoxygenase. In addition, cyclooxygenase is inhibited by aspirin and nonsteroid drugs, such as indomethacin (f). The classical soybean lipoxygenase inhibitors are antioxidants, such as nordihydroguaiaretic acid (NDGA) and others, and the substrate analog 5,8,11,14 eicosatetraynoic acid (ETYA), which also inhibit cyclooxygenase (g). In food, lipoxygenase is inhibited by blanching. Initiation of lipid peroxidation was derived also by free radicals, such as NO2. or CCl3OO. This process could be controlled by antioxidants (e).(ABSTRACT TRUNCATED AT 400 WORDS)

Mechanisms of ozone toxicity in cultured cells. I. Reduced clonogenic ability of polyunsaturated fatty acid-supplemented fibroblasts. Effect of vitamin E

The direct action of ozone on viability and survival of normal and modified mouse lung fibroblasts has been studied. By cell manipulation of fibroblasts in culture, the content of polyunsaturated fatty acids (PUFA) in the phospholipids was increased from about 6% to about 40%. The cellular content of alpha-tocopherol (alpha-T) (vitamin E) could be drastically enhanced. Vitamin E supplementation to the cell did not influence the PUFA manipulation. Normal, PUFA, and PUFA(alpha-T) fibroblasts were exposed to ozone by bubbling 10 ppm through the cell suspensions for different periods of time (0-6 h). No significant effects of the ozone exposure could be established when normal fibroblasts were used. The PUFA fibroblasts, however, were very vulnerable to ozone toxicity, both in terms of dye uptake (Trypan blue) and cell death (clonogenic ability). When alpha-tocopherol was present in the cell (200 ng/10(6) cells), a clear protection against ozone toxicity was found. It is concluded that ozone toxicity might be higher under conditions of a relative high amount of polyunsaturated fatty acids in the membrane phospholipids of the cell and a low cellular antioxidant capacity. Cellular membranes are probably an important target for ozone-induced cell death.

Changes in lipids of lung lavage in monkeys after chronic exposure to ambient levels of ozone

A group of 8 sub-adult bonnet monkeys (Macaca radiata) was exposed to 0.3 ppm ozone (O3) and another group of 7 monkeys to 0.15 ppm O3 for 8 h/day for 90 days. A third group of 4 monkeys was exposed to 0.15 ppm O3 for 8 h/day for 21 days. The control group consisted of 7 monkeys which breathed filtered air for 90 days. Levels of linoleic and arachidonic acids in the total lipids from lung lavage increased about 2-fold in those exposed to O3 as compared to the levels in the controls. Furthermore, the relative level of cholesterol ester (CE) decreased and phosphatidylcholine (PC) increased markedly with chronic exposure of animals to O3. Enhanced polyunsaturated fatty acid (PUFA) composition in lung lavage and changes in the levels of CE and PC may be related to animals' adaptation to O3-exposure.

Influence of age on the biochemical response of rat lung to ozone exposure

We have previously examined the influence of animal age on the pulmonary response to ozone (O3) in rats between 7 and 90 days of age (Elsayed et al., 1982a). In the present study, we expanded the age groups of rats, and examined in greater detail the relationship between animal age and pulmonary response to inhaled O3. We exposed 7 groups of specific pathogen free, male Sprague-Dawley rats, aged 24, 30, 45, 60, 90, 180, and 365 days, to 0.8 ppm (1568 micrograms/m3) O3 continuously for 3 days. After O3 exposure, we sacrificed the exposed rats and a matched number of controls from each age group, and analyzed their lungs for a series of physical and biochemical parameters, including glutathione metabolizing and NADPH producing enzyme activities. We observed that in control rats all the parameters increased as a function of age. However, the rate of increase was generally slower after age 60 days. After O3 exposure there was an increase in all the parameters for all age groups relative to their corresponding controls, but the extent of increase was significantly larger in rats 60 days and older than in younger rats. A regression of the difference in mean values between control and exposed animals for each parameter against age showed a linear correlation, indicating that the response was age-dependent. Since the magnitude of such increases is thought to reflect the degree of lung injury, the results suggest that O3 exposure causes greater lung injury in older rats than in younger rats. We tested this assumption by exposing rats from four different age groups (24, 45, 60 and 90 days) to a lethal dose of O3 (4 ppm or 7840 micrograms/m3 for 8 hours). The mortality rates were 50% and 83% for 24 and 45 day old rats, respectively, and 100% for 60 and 90 day old rats. The results of these studies further demonstrate that older rats are more susceptible to lung injury from O3 than younger rats.

Pulmonary antioxidant defense mechanisms

Intrinsic enzymatic and non-enzymatic pulmonary antioxidant defense mechanisms undoubtedly protect the lung against oxidant-mediated environmental stresses and diseases. In addition, new ways of augmenting pulmonary antioxidant defenses are being developed which can be used to bolster disease-overwhelmed intrinsic lung defense mechanisms. Improved understanding of antioxidant defense mechanisms will increase our knowledge of the causes and suggest rational approaches for treating oxidant-induced lung injury.

Skin-tumour promoting activity of methyl ethyl ketone peroxide—a potent lipid-peroxidizing agent

The tumour-promoting activity of methyl ethyl ketone peroxide (MEKP) was tested on the skin of hairless mice using a two-stage initiation-promotion protocol. When ultraviolet radiation in the UVB region (280-320 nm) was used as tumour initiator, MEKP showed weak promoting activity. The promotional activity of MEKP was potentiated by diethyl maleate, which is known to deplete intracellular glutathione, suggesting that lipid peroxidation may be important in the tumour promotion.

Dietary vitamin E and pulmonary biochemical responses of rats to cigarette smoking

The effect of dietary vitamin E on cellular susceptibility to cigarette smoking was studied in rats. Young male rats maintained on a basal vitamin E-deficient diet with or without 100 ppm vitamin E supplementation for 4 or 5 weeks were exposed to either sham or cigarette smoke for up to 7 days. Higher animal mortality rate was observed in the animals fed the vitamin E-deficient diet than in the supplemented group when they were subjected to acute levels of cigarette smoking. Relative to the respective sham groups, a greater alteration of biochemical parameters, such as reduced glutathione (GSH) and related enzymes, was found in the lungs of smoked rats fed the deficient diet than in the supplemented group. Animal lungs exhibited a greater biochemical response to whole smoke than the gaseous phase of smoke. The results suggest that the nutritional status of vitamin E may influence the cellular susceptibility of rats to cigarette smoking.

Toxicity of activated oxygen: lack of dependence on membrane unsaturated fatty acid composition

Membrane unsaturated fatty acid oxidation has been suggested as a mechanism of toxicity for a variety of activated oxygen species. We have tested this hypothesis by manipulating the fatty acid composition of an Escherichia coli mutant that is unable to synthesize unsaturated fatty acids. To provide a wide range of susceptibility to membrane oxidation we have replaced the naturally occurring monoenoic acyl chains with cyclopropanes to greatly reduce the unsaturation level and with linoleate to increase the membrane unsaturation. These cultures were treated with ozone, hydrogen peroxide, singlet oxygen and paraquat. In no case was there substantial protection from toxicity afforded by cyclopropanes nor was there enhancement of toxicity to cells with the polyunsaturated membranes. We suggest, therefore, that oxidation of membrane unsaturated fatty acids is not an essential component of the toxicity to E. coli of active oxygen species.

Lipid peroxidation: a possible mechanism of cephaloridine-induced nephrotoxicity

Cephaloridine produces renal cortical injury, but the precise mechanism responsible for this nephrotoxicity remains unclear. Recently cephaloridine has been shown to deplete reduced glutathione (GSH) concentration selectively in renal cortex. Cephaloridine nephrotoxicity can be potentiated by diethyl maleate (a GSH depletor), but no glutathione conjugate can be detected. Thus, it was of interest to investigate further the mechanism of depletion of renal cortical GSH by cephaloridine. In the present study, cephaloridine markedly decreased GSH in rat and rabbit renal cortex while concomitantly increasing oxidized glutathione (GSSG). Furthermore, cephaloridine increased lipid peroxidation specifically in renal cortical cells. Conjugated diene formation (an index of lipid peroxidation) was increased in renal cortex but not in the liver shortly following administration of cephaloridine. Removal of selenium and/or vitamin E from the diet, which should enhance lipid peroxidation, potentiated cephaloridine nephrotoxicity and enhanced cephaloridine-induced morphological damage in the kidney. These findings are consistent with a major role of lipid peroxidation in the etiology of cephaloridine nephrotoxicity.

Phospholipids of the lung in normal, toxic, and diseased states

The highly pulmonary concentration of 1,2-dipalmitoyl-sn-glycerol-3-phosphorylcholine (dipalmitoyllecithin) and its implication as an important component of lung surfactant have promoted investigation of phospholipid metabolism in the lung. This review will set the contents including recent informations for better understanding of phospholipid metabolism of the lung in normal state (physiological significances of lung phospholipids, characteristics of phospholipids in lung tissue and alveolar washing, biosynthetic pathways of dipalmitoyllecithin, etc.) as well as in toxic states (pulmonary oxygen toxicity, etc.) and in diseased states (idiopathic respiratory distress syndrome, pulmonary alveolar proteinosis, etc.) Since our main concern has been to clarify the most important route for supplying dipalmitoyllecithin, this review will be focused upon the various biosynthetic pathways leading to the formation of different molecular species of lecithin and their potential significance in the normal, toxic, and diseased lungs.

Free radical initiation in proteins and amino acids by ionizing and ultraviolet radiations and lipid oxidation--part III: free radical transfer from oxidizing lipids

Parallels and similarities in chemical and functional damage to proteins by ionizing and uv radiations and oxidizing lipids have been recognized for some time. However, only recently have oxidizing lipids been shown directly by electron spin resonance to be radiomimetic also in their capacity for protein free radical production. Free radicals play a key role in the transformation of energy to molecular and cellular damage. It is thus of critical importance to elucidate the general mechanisms of free radical formation and reactions in proteins in order to understand protein involvement in various pathological conditions and in food deterioration. Accordingly, this review is a detailed comparison of gamma-radiation, UV radiation, and lipid oxidation for what is presently known concerning (1) the specific modes of energy deposition and free radical formation, (2) the free radicals formed in proteins and amino acids, and (3) the typical damage correlating with these radicals.

Liver lipids in Letterer-Siwe disease

A case of Letterer-Siwe disease in a thirteen-month-old girl with markedly swollen gums, an enlarged liver, and seborrhoic skin eruptions is reported. She died from pyopneumothorax in spite of treatment with prednisolone and vinblastine. Analysis of hepatic lipids showed that there was remarkable increase in free fatty acid, which is not seen in normal human liver. Cholesterol ester was also accumulated in the liver tissue. However, the concentrations of phospholipids and glycerides were low and lysophospholipid was found. It is assumed that there was increased intracellular lipolysis in the proliferating reticuloendothelial cells.

Lipid oxidation: biologic effects and antioxidants--a review

The detection and measurement of lipid oxidation in biological systems and some biologic effects of this oxidation are reviewed. The role of lipid oxidation in the process of photocarcinogenesis and the protective effect of antioxidants against this process also are discussed. The mechanism of such protection is unknown and studies directed at elucidating the mechanism of antioxidant effect in photocarcinogenesis and in some other pathological conditons believed to involve lipid oxidation are needed. In addition to this, epoxidation of lipids observed in monolayer studies requires further investigation, particularly in the presence of some other unsaturated molecules. The possible significance of such a study--particularly in the presence of polycyclic aromatic hydrocarbon carcinogens, where formation of epoxides is generally accepted as active intermediates--is also discussed. In addition, present knowledge on the role of lipid peroxides in the destruction of proteins and biomembranes, in chemically induced toxicity and in generation of singlet oxygen is presented.

Ozone sensitivity in aging WI-38 cells based on acid phosphatase content

Young [16-19 population doubling level (PDL)] and senescing (50-53 PDL) WI-38 cell populations were exposed to 1 ppm ozone for 2 hr and the resultant extracellular and intracellular acid phosphatase concentration was measured. Dose-response curves were also determined for surviving populations of young and old cells after a 1 hr ozone exposure ranging in concentration from 0 to 1.00 ppm. Senescing cells released 8 times more acid phosphatase per million cells than the young cells. Both old and young cells showed a clear dose-response to the 1 hr ozone gradient exposure. However, the older cells demonstrated a consistent 17% average lower survival rate than the young cells. The higher acid hydrolase level in older WI-38 cells is probably related to the lower survival rate observed in the older cells in vitro.

Human biochemical response to ozone and vitamin E

To determine whether vitamin E (dl-alpha-tocopherol) supplementation of the diet provides protection from inhaled oxidants such as ozone (O3) in community air pollution, its effects were studied in healthy adult volunteers, Experimental groups received 800 or 1600 IU of vitamin E for 9 wk or more; control groups received placebos. Double-blind conditions were maintained throughout the study. Biochemical parameters studied included red blood cell fragility; hematocrit and hemoglobin values; red cell glutathione concentration; and the enzymes acetylcholinesterase, glucose-6-phosphate dehydrogenase, and lactic acid dehydrogenase. No significant differences between the responses of the supplemented and placebo groups to a controlled O3 exposure (0.5 ppm for 2 h) were found for any of these parameters. The results indicate that vitamin E supplementation in humans, at the levels employed in this experiment, gives no added protection against blood biochemical effects of O3 in intermittently exercising subjects under exposure conditoins simulating summer ambient air pollution episodes.

Reactions of ozone with fatty acid monolayers: a model system for disruption of lipid molecular assemblies by ozone

Ozone concentrations of 0.03 ppm are shown to initiate physical disruption of both oleic and linoleic acid spread monolayers in a few seconds. Approximately equal yields of water soluble products in nitrogen- and oxygen-containing environments as well as in the two acid systems suggest that the dominant reaction pathway involves direct attack on fatty acid double bonds and not oxidative chain reactions. A possible explanation for the observed loss of monolayer material is provided by the Criegee mechanism for ozonide rearrangement following ozone attachment to double bonds. In this scheme polar intermediates are generated which could pass into the aqueous subphase before recombination can occur. alpha-Tocopherol exhibits a protective effect only when present at a high fraction in the fatty acid monolayer (6 mole%). These systems provide an efficient elementary model for studying the physical effects of ozone on lipid membrane structure.

The antioxidant vitamins

This article is an attempt to study the metabolic functions of vitamin C and E together. Such a study must necessarily be imcomplete owing to the extreme richness of the literature. The increasing importance of the work on free radical reactions, their toxicity and carcinogenic action, and also their relation to the metabolism of metals, particularly iron, copper, selenium, and zinc, shows a number of metabolic pathways with which both vitamins interact. It is hoped that this article will indicate future research possibilities.

Long-term NO2 exposure of mice in the presence and absence of vitamin E. I. Effect on body weights and lipofuscin pigments

Mice on diets deficient in vitamin E, normal diets, diets with high supplements of vitamin E, and diets supplemented with N, N'-diphenyl-p-phenylenediamine (DPPD) were continuously exposed to 0.5 ppm or to 1.0 ppm nitrogen dioxide (NO2) or to filtered room air from weaning to 18 months of age. The effects of NO2 exposure on body weights, tissue weights, survival rates, and tissue organic solvent soluble lipofuscin (age) pigment concentrations were examined. Vitamin E deficiency resulted in lower body weights by 18 months of age; exposure to NO2 further increased this weight loss. With the exception of the kidney, tissue weights were not affected by NO2 exposure. Mice exposed to NO2 had lower survival rates than unexposed control animals. Tissue organic solvent soluble lipofuscin pigment (LFP) concentrations in the uterus, lung, spleen, kidney, liver, brain, and heart were not afffected by NO2 exposure. Only in the liver did vitamin E deficiency lead to an increase in LFP concentration; it did not occur in any of the other tissues examined.

Biochemical response of squirrel monkeys to ozone

Biochemical studies were performed on blood and lung tissue of squirrel monkeys (Saimiri sciureus) following acute exposure to 0.75 ppm ozone (O3) for 4 h/d for 4 consecutive days. One group of animals was sacrificed at the end of the last exposure day and another group was sacrificed 4 d later after the last exposure. Evidence was sought for oxidation-induced changes known to occur in rodents when high levels of O3 are inhaled. A significant increase in red blood cell membrane fragility was observed, as well as significant decreases in red blood cell glutathione and erythrocyte acetylcholinesterase; however, the red blood cell enzymes, lactic acid dehydrogenase (LDH), and glucose-6-phosphate dehydrogenase (G6PDH) were not changed significantly. Lung tissue analysis showed that lipid peroxidation was markedly increased and tissue vitamin E levels were significantly decreased. The tissue enzymes G6PDH, glutathione reductase, and LDH significantly increased in activity. No significant changes were seen in either superoxide dismutase or malic acid dehydrogenase. The results of this experiment indicate that O3, or reaction products resulting from O3-tissue interaction in the lung, pass the air-blood barrier and are capable of producing biochemical changes in blood as well as in lung tissue.

The pulmonary and extrapulmonary effects of ozone

The toxicity of ozone is solely due to its action as an oxidant. It is an extremely reactive gas which rapidly forms intermediate oxidizing derivatives after inhalation. High concentrations cause death from pulmonary oedema. Both pulmonary and extrapulmonary toxicity have been observed at lower concentrations of ozone, including those currently present in urban air. Pulmonary cellular and subcellular membranes appear to be particularly susceptible. A primary mechanism of this effect is the oxidative decomposition of polyunsaturated fatty acids, which has been demonstrated in rodent lungs after inhalation of ozone. Supporting evidence includes the potentiation of ozone toxicity by vitamin E deficiency and an increased use of this antioxidant vitamin during repetitive exposure to ozone. Other membrane effects include oxidation of thiol groups and, perhaps, of tryptophan. Microsomal alterations include a loss of lung cytochrome P450 which may also be related to lipid peroxidation. Extrapulmonary toxicity is not directly due to ozone but may represent in effect due to lipid peroxide decomposition products, particularly malonaldehyde. This three-carbon dialdehyde has been shown to alter cell membrane fluidity and to have mutagenic properties; the latter perhaps due to cross-linkage of DNA to histone.

Determination of lipid conjugated dienes with tetracyanoethylene-14C: significance for study of the pathology of lipid peroxidation

A method for quantitative analysis of conjugated diene unsaturation has been developed utilizing tetracyanoethylene-14C (TCNE-14C) in a Diels-Alder condensation. The amount of C14 found in the Diels-Alder adduct has been shown to be a measure of conjugated diene content. The method has proven successful in analysis of a variety of triglycerides, phospholipids, and peroxidized tissue lipids. In the course of this work, a method for removing the fatty acid substituents from phospholipids using lithium aluminum hydride was developed. TCNE-14C analysis for conjugated dienes in rat liver microsomal lipids after dosing with CCl4 or BrCCl3 has provided conclusive evidence that the increase in ultraviolet absorption at 233 nm of these lipids is due to conjugated dienes.

Prelytic damage of red cells in filtrates from peroxidizing microsomes

When liver microsomes are incubated in the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH), their constituent lipids undergo peroxidative degeneration. If erythrocytes are present in such a peroxidizing system, they hemolyze. Filtrates obtained by ultrafiltration of peroxidizing microsomal systems were found to have the capacity to produce prelytic damage in red cells. Filtrates obtained from microsomes that had not undergone peroxidative lipid decomposition were inert. The toxic activity in the active filtrates was not due to continuing oxidation of NADPH nor to continuing liver microsomal lipid peroxidation. Neither the chemical identity of the toxic product or products in active filtrates nor the mechanisms involved in the erythrocyte damage are known at this time.

Autoxidation of polyunsaturated fatty acids. Part I. Effect of ozone on the autoxidation of neat methyl linoleate and methyl linolenate

Neat samples of polyunsaturated fatty acids were exposed to ozone in air in a flow system, and the formation of peroxides, conjugated dienes and thiobarbituric acid (TBA)-reactive material was followed as a function of time. The effect of ozone is to shorten the induction period normally observed in autoxidation studies, but the ozone, at the concentrations used here (0-1.5 ppm), appears to have no effect on the rates of product formation after the induction period. During the induction period, increasing ozone concentrations give rise to substantially increased rates of peroxide (or materials which titrate like peroxide) formation, a slightly increased rate of conjugated diene formation, and no significant increase in the rate of production of TBA-reactive material. Vitamin E lengthens the induction period but appears to have no other effect. Some of these data are in conflict with earlier reports of Menzel et al.

Heinz bodies formed in erythrocytes by fatty acid ozonides and ozone

Ozonides of the methyl esters of oleic, linoleic, linolenic and arachidonic acids were found to produce Heinz body inclusions in human and mouse erythrocytes. No simple relationships between structure and activity were noted. Concomitant with Heinz body formation, methemoglobin and loss of cellular thiols were observed. Methyl ozonides readily oxidized glutathione and 1 mole of oxidized glutathione was formed per mole of methyl oleate ozonide. Methyl ozonides catalyzed the formation of disulfide-linked interchain polymers between hemoglobin and ovalbumin. Heinz bodies were not produced with ozone in the absence of unsaturated lipids. Heinz bodies were observed in the blood of mice exposed to ozone (0.85 ppm) for 48 hours. These observations suggest that fatty acid ozonides could serve as a toxic chemical species formed on ozone inhalation and could explain the divergent protective effects of lipid antioxidants and thiol generating systems in vivo.