Fatty Acid Peroxidation Products Research Articles

Lipids and calcium uptake of sperm in relation to cold shock and preservation: a review

When sperm of the ram, bull, boar and stallion are cold-shocked by rapid cooling to near freezing point, motility and metabolic activity are irreversibly depressed and the acrosome and plasma membrane disrupted. Ram sperm become susceptible to cold shock in the proximal corpus region of the epididymis when the cytoplasmic droplet has moved backwards to the distal portion of the sperm midpiece. The membrane constituents phospholipids and cholesterol are important in cold shock which causes loss of lipid from sperm. The susceptibility of sperm to cold shock is linked with a high ratio of unsaturated:saturated fatty acids in the phospholipids and a low cholesterol content. The high unsaturated fatty acid content of sperm also makes them susceptible to damage from peroxidation which adversely affects motility, metabolism, ultrastructure and fertility. Hydroxynonenal, a product of fatty acid peroxidation, depresses the motility and oxygen uptake of ram sperm in vitro and may react with the -SH groups of the axonemal microtubules. High calcium concentrations in the external medium may decrease the motility and metabolism of sperm and 'calcium intoxication' may be a factor in cold shock. Lowering the environmental temperature increases calcium uptake by sperm and the effect is aggravated if the rate of cooling is rapid. Phospholipids, particularly those in egg yolk, protect sperm to some extent from cold shock and also prevent increased calcium flux into the sperm. Suggestions are made for increasing the life span of sperm during preservation and microencapsulation by adding agents that may stabilize membranes, counter peroxidation and decrease calcium uptake.

Recognition of oxidized low density lipoprotein by the scavenger receptor of macrophages results from derivatization of apolipoprotein B by products of fatty acid peroxidation

Uptake of cholesterol-containing lipoproteins by macrophages in the arterial intima is believed to be an important step in the pathogenesis of atherosclerosis. There are a number of possible mechanisms by which macrophages might accumulate cholesterol, and one that has attracted much interest recently involves the uptake of oxidatively modified low density lipoprotein (LDL) via a specific cell surface receptor, termed the scavenger or acetyl-LDL receptor. Previous studies have shown that chemical derivatization of LDL with reagents that result in neutralization of the charge of lysine amino groups also allows recognition by this receptor. As well, it has been shown that oxidation of LDL is accompanied by a decrease in free lysine groups and binding of lipid products to apolipoprotein B. The present studies were done to further characterize the receptor-binding domain on oxidized LDL. It was found that LDL could be modified by incubation with water-soluble products derived from autoxidized unsaturated fatty acids under conditions that inhibited oxidation of the LDL itself. The LDL modified in this way had increased electrophoretic mobility but showed no evidence of the oxidative damage that typifies LDL oxidized by exposure to metal ions. Furthermore, the oxidation product-modified LDL was rapidly degraded by cultured macrophages through the scavenger receptor pathway. Bovine albumin modified by oxidation products also showed greatly accelerated degradation by macrophages. When analyzed by reverse-phase high pressure liquid chromatography, the reactive oxidation products appeared less polar than fatty acids or simple medium-chain aldehydes. When treated with the carbonyl reagent 2,4-dinitrophenylhydrazine, the reactive fractions yielded derivatives, some of which were identified by mass spectrometry as hydrazones of nonenal, heptenal, pentenal, and crotonaldehyde. A series of 2-unsaturated aldehydes (acrolein to 2-nonenal) were all found to modify LDL, but none of these aldehyde-modified LDLs were recognized by the scavenger receptor of macrophages and all were degraded much more slowly by these cells than LDL modified with oxidation products. Furthermore, copper-oxidized LDL had only very slight immunoreactivity toward a panel of antibodies specific for adducts of simple 2-unsaturated aldehydes. Analysis of underivatized autoxidized fatty acids by coupled liquid chromatography/thermospray mass spectrometry revealed compounds with m/z corresponding to M+17, M+31, and 2M+31 in fractions that were capable of modifying LDL. The unoxidized fatty acids showed a dominant peak at M-1. These results indicate that the scavenger receptor of macrophages can recogn

Eicosanoids and myocardial ischaemia.

The available data clearly suggest large alterations in myocardial eicosanoid generation during myocardial ischaemia and demonstrate important actions of eicosanoids on myocardial function during ischaemic conditions. These actions include direct effects on the injured myocardium as well as influences on other target cells, such as platelets and leukocytes. Selective modifications of eicosanoid generation, for example by providing exogenous PGI2 or by inhibiting oxygen toxicity are most challenging approaches for the design of new and potentially valuable cardioprotective agents. Antagonism of thromboxane formation and/or action might be of some value in ischaemia but appears to be less important for reperfusion injury. Leukotrienes and other noncyclic fatty acid peroxidation products are another group of potentially deleterious agents and there is a definite need for more selective inhibitors of leukotriene formation and/or action to establish their role in ischaemia.

Rabbit brain lipids during short-term hyperthermia.

Rabbits were subjected to 3 h of hyperthermia at 40 degrees C. The phospholipid content of the brain was unchanged, whereas the free fatty acids increased by about 73% over control levels. Hyperthermia also induced inhibition of fatty acid peroxidation processes. The last products of fatty acid peroxidation, the thiobarbituric acid reactive substances, diminished significantly during hyperthermia, whereas the level of the first intermediate of this pathway, the conjugated double bonds, remained unchanged. Simultaneously, the levels of lipid-soluble antioxidants decreased significantly. The content of free fatty acids, malondialdehyde, and lipid-soluble anti-oxidant returned toward control levels during 3 h of recovery. The content of gangliosides was 10-20% above control values in the groups of animals examined immediately and 3 h after hyperthermia. The ganglioside-specific enzymes, neuraminidase and sialyltransferase, both directed toward endogenous lipid substrates, were activated by hyperthermia, suggesting the stimulation of turnover of the gangliosides during the course of hyperthermia. Lipid alterations resulting from short-term hyperthermia may influence the physicochemical properties of neuronal membranes.

Role of lipid peroxidation in post-traumatic spinal cord degeneration: a review.

A large amount of biochemical, physiological, and pharmacological data has been obtained which supports a mechanistic role of oxygen free radical-induced lipid peroxidation (LP) in post-traumatic spinal cord degeneration. Biochemical evidence of early and progressive lipid peroxidative reactions occurring in the injured spinal cord includes: an increase in polyunsaturated fatty acid peroxidation products (e.g., malonyldialdehyde), a decrease in cholesterol and the appearance of cholesterol oxidation products, an increase in cyclic GMP presumably due to free radical activation of guanylate cyclase, a decrease in tissue anti-oxidant levels (e.g., alpha tocopherol, reduced ascorbate), and inhibition of membrane-bound enzymes such as Na+ + K+-ATPase. In vitro CNS tissue studies have provided support for the possibility that LP may contribute to other early post-traumatic events including intracellular calcium accumulation and arachidonic acid release. Moreover, spinal tissue lactic acidosis, which occurs early after injury, can exacerbate LP reactions. The involvement of LP in the development of progressive post-traumatic spinal white matter ischemia has been strongly inferred from pharmacological studies in cats with known inhibitors of LP. For example, the dose-response curves for the ability of the glucocorticoid methylprednisolone (MP) to inhibit post-traumatic LP and to retard ischemia development are identical. This relationship between LP and post-traumatic ischemia is more directly implied from studies showing that pretreatment of cats with high doses of anti-oxidants (e.g., d-alpha tocopherol plus selenium p.o. or 1-ascorbic acid i.v.) can also significantly antagonize the progressive decrease in spinal cord blood flow that follows severe blunt injury. However, a similar efficacy of certain calcium and prostaglandin antagonists suggests an interrelationship between aberrant calcium fluxes, vasoconstrictor/platelet aggregating prostanoids, and LP in the post-traumatic ischemic phenomenon. In addition to a role of LP in ischemia development, the action of intensive d-alpha tocopherol and selenium pretreatment to retard anterograde cat motor nerve fiber degeneration after nerve section suggests that LP may also be a fundamental mechanism of "Wallerian" axonal degeneration after neural injury. Finally, a critical role of LP in the acute pathophysiology of CNS injury in general has been supported by the finding of an excellent correlation, in terms of efficacy and potency, between the action of glucocorticoid and nonglucocorticoid steroids to inhibit neural tissue LP in vitro and to promote early neurological recovery in severely head-injured mice.

In vivo externalization of phosphatidylserine and phosphatidylethanolamine in the membrane bilayer and hypercoagulability by the lipid peroxidation of erythrocytes in rats.

Phospholipid distribution across erythrocyte membrane bilayer is asymmetrical. In normal erythrocytes, entire phosphatidylserine (PS) and most of the phosphatidylethanolamine (PE) is present on the cytoplasmic side of membrane bilayer, whereas phosphatidylcholine (PC) and sphingomyelin (SM) are predominantly present at the outer side of membrane bilayer. The present study was undertaken to determine whether membrane lipid peroxidation has any effect on the distribution of PS, PE, and PC across erythrocyte membrane bilayer in vivo in an animal model. Erythrocyte membrane lipid peroxidation was induced in rats by administering phenylhydrazine, an oxidant drug. Membrane phospholipid organization was determined by using bee venom phospholipase-A2 and indirectly by measuring clotting time on recalcification of normal human platelet-poor plasma in the presence of Russell's viper venom. Phenylhydrazine administration to rats caused significant membrane lipid peroxidation as measured by the accumulation of malonyldialdehyde (MDA), an end product of fatty acid peroxidation, as well as externalization of a significant portion of PS and PE from the inner to the outer side of membrane bilayer in erythrocytes. There was a significant positive correlation (r) between the amount of MDA accumulated in the erythrocytes and the movement of PS (r = 0.92) and PE (r = 0.96) from inner to the outer membrane bilayer and PC (r = 0.81) from outer to the inner membrane bilayer. Erythrocytes of phenylhydrazine-treated rats also showed significantly reduced clotting time. This reduction in clotting time had a significant positive correlation with MDA accumulation (r = 0.92) and PS externalization (r = 0.90). Both the effect of phenylhydrazine on erythrocyte membrane lipid peroxidation and alterations in phospholipid organization and coagulability were blocked when rats were simultaneously administered with vitamin E or C antioxidants.

The accumulation of malonyldialdehyde, a product of fatty acid peroxidation, can disturb aminophospholipid organization in the membrane bilayer of human erythrocytes.

The distribution of phospholipids across erythrocyte membrane bilayer is asymmetrical. The present study reports the effect of malonyldialdehyde (MDA), a product of fatty acid peroxidation, on the organization of phosphatidylserine (PS) and phosphatidylethanolamine (PE) in human erythrocytes using a nonpermeable bee venom phospholipase A2 and trinitrobenzene-sulfonilic acid. MDA accumulation in the erythrocytes was accomplished both by its increased endogenous generation after exposure of cells to H2O2, as well as by the treatment of erythrocytes with exogenous authentic MDA. The above treatments resulted in a significantly increased movement of PS and PE from inner bilayer to outer bilayer, which had a highly positive correlation with the concentration of MDA in the erythrocyte membranes. Antioxidants vitamin E, butylated hydroxytoluene, and butylated hydroxyanisole inhibited the effect of H2O2 treatment on erythrocyte membrane lipid organization by scavenging fatty acid peroxidation and formation of MDA. Thus, lipid peroxidation and MDA accumulation can disturb organization of PS and PE in the human erythrocyte membrane bilayer.

The effect of malonyldialdehyde, a product of lipid peroxidation, on the deformability, dehydration and 51Cr-survival of erythrocytes.

Erythrocyte membrane lipid peroxidation has been reported to occur in various haemolytic anaemias. In the present study, treatment of human erythrocytes with malonyldialdehyde (MDA), a product of fatty acid peroxidation, induced membrane rigidity, cellular dehydration and reduced whole cell deformability. These effects of MDA were blocked by histamine and fluorescamine, which can act as alternate substrates for MDA. Additionally, reduced deformability of MDA-treated rabbit cells was associated with shortened 51Cr survival in vivo. These findings suggest a biochemical basis for decreased survival of erythrocytes undergoing peroxidative damage of the membrane.