Sarcolemmal phospholipid fatty acid composition and permeability

In this study, the mechanism of ischaemia-induced increased sarcolemmal permeability, as manifested by release of intracellular enzymes, was investigated. The role of changes in the sarcolemmal phospholipid bilayer in this process was evaluated by experimental modulation of the phospholipid fatty acid composition. The isolated perfused rat heart subjected to low-flow hypoxia, was used as a model of global ischaemia. Glucose as well as saturated (palmitate) and unsaturated (linoleate) long-chain fatty acids were used as substrates. Hearts perfused with palmitate or linoleate (1.5 mM, fatty acid/albumin ratio, 3.4) showed a significantly higher rate of lactate dehydrogenase release in both control and ischaemic conditions than hearts perfused with glucose (10 mM). Lactate dehydrogenase release in the fatty acid-perfused hearts was associated with a significant increase in the percentage unsaturation of the sarcolemmal phospholipid fatty acids. Glucose-perfused hearts, on the other hand, showed only minor changes in the sarcolemmal phospholipid fatty acid composition. Attempts to correlate enzyme release directly with an increase in the percentage unsaturation of phospholipid fatty acids failed, since enzyme release was also stimulated in control fatty-acid-perfused hearts which (when compared with glucose) contained a higher percentage saturated phospholipid fatty acids. The results suggest that myocardial ischaemia, apart from changes in the sarcolemmal phospholipid fatty acid composition, also induces several other changes in sarcolemmal composition (e.g., cholesterol loss) which may affect is permeability for macromolecules.     

Low-salt diet alters the phospholipid composition of rat colonocytes

The effect of low-salt diet on phospholipid composition and remodeling was examined in rat colon which represents a mineralocorticoid target tissue. To elucidate this question, male Wistar rats were fed a low-salt diet and drank distilled water (LS, low-salt group) or saline instead of water (HS, high-salt group) for 12 days before the phospholipid concentration and fatty acid composition of isolated colonocytes were examined. The dietary regimens significantly influenced the plasma concentration of aldosterone which was high in LS group and almost zero in HS group. Plasma concentration of corticosterone was unchanged. When expressed in terms of cellular protein content, a significantly higher concentration of phospholipids was found in LS group, with the exception of sphingomyelin (SM) and phosphatidylserine (PS). Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) accounted for more than 70% of total phospholipids in both groups. A comparison of phospholipid distribution in LS and HS groups demonstrated a higher percentage of PE and a small, but significant, decrease of PC and SM in LS group. The percentage of phosphatidylinositol (PI), PS and cardiolipin (CL) were not affected by mineralocorticoid treatment. With respect to the major phospholipids (PE, PC), a higher level of n-6 polyunsaturated fatty acids (PUFA) and lower levels of monounsaturated fatty acids were detected in PC of LS group. The increase of PUFA predominantly reflected an increase in arachidonic acid by 53%. In comparison to the HS group, oleic acid content was decreased in PC and PE isolated from colonocytes of the LS group. Our data indicate that alterations in phospholipid concentration and metabolism can be detected in rats with secondary hyperaldosteronism. The changes in phospholipid concentration and their fatty acid composition during fully developed effect of low dietary Na+ intake may reflect a physiologically important phenomenon with long-term consequences for membrane structure and function.     

Age-related changes in mitochondrial membrane composition of rainbow trout (Oncorhynchus mykiss) heart and brain

Membrane composition, particularly of mitochondria, could be a critical factor by determining the propagation of reactions involved in mitochondrial function during periods of high oxidative stress such as rapid growth and aging. Considering that phospholipids not only contribute to the structural and physical properties of biological membranes, but also participate actively in cell signaling and apoptosis, changes affecting either class or fatty acid compositions could affect phospholipid properties and, thus, alter mitochondrial function and cell viability. In the present study, heart and brain mitochondrial membrane phospholipid compositions were analyzed in rainbow trout during the four first years of life, a period characterized by rapid growth and a sustained high metabolic rate. Specifically, farmed fish of three ages (1-, 2- and 4-years) were studied, and phospholipid class compositions of heart and brain mitochondria, and fatty acid compositions of individual phospholipid classes were determined. Rainbow trout heart and brain mitochondria showed different phospholipid compositions (class and fatty acid), likely related to tissue-specific functions. Furthermore, changes in phospholipid class and fatty acid compositions with age were also tissue-dependent. Heart mitochondria had lower proportions of cardiolipin (CL), phosphatidylserine (PS) and phosphatidylinositol, and higher levels of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) with age. Heart mitochondrial membranes became more unsaturated with age, with a significative increase of peroxidation index in CL, PS and sphingomyelin (SM). Therefore, heart mitochondria became more susceptible to oxidative damage with age. In contrast, brain mitochondrial PC and PS content decreased in 4-year-old animals while there was an increase in the proportion of SM. The three main phospholipid classes in brain (PC, PE and PS) showed decreased n-3 polyunsaturated fatty acids, docosahexaenoic acid and peroxidation index, which indicate a different response of brain mitochondrial lipids to rapid growth and maturation.     

Dietary fatty acids modulate liver mitochondrial cardiolipin content and its fatty acid composition in rats with non alcoholic fatty liver disease

No data are reported on changes in mitochondrial membrane phospholipids in non-alcoholic fatty liver disease. We determined the content of mitochondrial membrane phospholipids from rats with non alcoholic liver steatosis, with a particular attention for cardiolipin (CL) content and its fatty acid composition, and their relation with the activity of the mitochondrial respiratory chain complexes. Different dietary fatty acid patterns leading to steatosis were explored. With high-fat diet, moderate macrosteatosis was observed and the liver mitochondrial phospholipid class distribution and CL fatty acids composition were modified. Indeed, both CL content and its C18:2n-6 content were increased with liver steatosis. Moreover, mitochondrial ATP synthase activity was positively correlated to the total CL content in liver phospholipid and to CL C18:2n-6 content while other complexes activity were negatively correlated to total CL content and/or CL C18:2n-6 content of liver mitochondria. The lard-rich diet increased liver CL synthase gene expression while the fish oil-rich diet increased the (n-3) polyunsaturated fatty acids content in CL. Thus, the diet may be a significant determinant of both the phospholipid class content and the fatty acid composition of liver mitochondrial membrane, and the activities of some of the respiratory chain complex enzymes may be influenced by dietary lipid amount in particular via modification of the CL content and fatty acid composition in phospholipid.     

Changes in fatty acid composition of phospholipids and triglycerides of Musca domestica resulting from choline deficiency

The fatty acid composition of the phospholipids and triglycerides extracted from housefly larvae reared on diets containing no added fatty acids but containing differing concentrations of choline has been determined. Reducing the choline content of the diet resulted in a graded reduction of the percentage of phosphatidylcholine present in the phospholipids of the larvae. This was accompanied by changes in the fatty acid composition, choline deficiency causing an increased utilization of 16-C rather than 18-C acids by the phospholipids. Changes in the fatty acid composition of the triglyceride fraction were also observed but these were associated with insects containing very low levels of phosphatidylcholine. Examination of the fatty acids in the different classes of phospholipids showed that the major change resulting from choline deficiency was in the fatty acids of the phosphatidylethanolamine fraction—the phospholipid which increased as the phosphatidylcholine decreased.Although the fatty acid composition of the different classes of phospholipids was not completely fixed, some preferential utilization of certain fatty acids by certain classes was observed, in both larval and adult insects. The fatty acid composition of the phospholipids extracted from larval gut, muscle, fat body, cuticle, trachea, nervous tissue, and haemolymph was determined. Changes resulting from choline deficiency similar to those seen in the whole larva were observed in all tissues except the nervous tissue. The effect of rearing larvae at temperatures between 24 and 35°C resulted in only minor changes in the fatty acid composition of both phospholipid and triglyceride fractions but the difference due to choline deficiency was observed at all temperatures. The possibility that the observed changes in the fatty acids of the phospholipids are compensatory to the changes in the proportion of the choline to the ethanolamine phospholipids is discussed.     

Lipids of dystrophic and normal mouse muscle: whole tissue and particulate fractions

Myofibrillar, mitochondrial, and microsomal fractions were prepared from normal and dystrophic mouse limb muscle by differential centrifugation and analyzed for phospholipids and cholesterol. Fatty acids and aldehydes of neutral lipids and of phospholipids from whole muscle and particulate fractions were also determined. Normal microsomes contained more lecithin and less total ethanolamine phospholipids and cardiolipin than mitochondria. The myofibrils had an intermediate phospholipid composition, but their cholesterol-phospholipid ratio was smaller than that of the other two fractions. Except for an increased percentage of phosphatidalethanolamine in the dystrophic mitochondria, only the composition of the dystrophic microsomes differed from normal by containing less lecithin but more total ethanolamine phospholipid, phosphatidalethanolamine, sphingomyelin, and cholesterol. No significant differences were found in the fatty acid composition of neutral lipid extracts from normal and dystrophic preparations, but there was a significant decrease in the percentage of 22:6 in phospholipids from both dystrophic whole muscle and microsomes (-25% and -37%, respectively), whereas the 20:4 content was unaltered. By contrast, the percentages of 18:0 and total fatty aldehyde increased significantly. Phospholipid extracts from all dystrophic samples showed a significant decrease in 16:0 and an increase in 18:1 as compared with the normal.     

Aldosterone alters the phospholipid composition of rat colonocytes

Previous studies have shown that aldosterone treatment of amphibian epithelial cells results not only in stimulation of Na(+) absorption but also in changes in phospholipid composition which are necessary for the mineralocorticoid action of aldosterone. The present study was designed to investigate the effect of aldosterone on phospholipids of mammalian epithelia. Phospholipid and fatty acid composition was examined in colonic epithelium (mineralocorticoid target tissue) and thymus (non-mineralocorticoid but glucocorticoid target tissue) of rats which had received aldosterone or vehicle by a miniosmotic pump for 7 days. Aldosterone increased the mass of colonic phospholipids relative to cellular proteins with concomitant changes in the percentage distribution of fatty acids, whereas the relative distribution of membrane phospholipds was not changed. Phosphatidylcholine increased the content of polyunsaturated and decreased that of monounsaturated fatty acids, which predominantly reflected the accretion of arachidonic and a decrease in oleic and palmitoleic acids. Within the phosphatidylethanolamine subclass, pretreatment of rats with aldosterone decreased the content of monounsaturated fatty acids (predominantly oleic and palmitoleic acid) and of n-3 fatty acids, and increased the content of saturated fatty acids (palmitic acid). The saturated-to-nonsaturated fatty acid ratio also significantly increased after aldosterone treatment. No changes in thymic phospholipids were seen. The results are consistent with the contention that aldosterone specifically modulates phospholipid concentration and metabolism in mineralocorticoid target tissue. The changes in phospholipid content and its fatty acid composition during the fully developed effect of aldosterone may reflect a physiologically important phenomenon with long-term consequences for membrane structure and function.     

Effect of Osmotic Stress on Ion Transport Processes and Phospholipid Composition of Wheat (Triticum aestivum L.) Mitochondria

The effect of osmotic stress on wheat (Triticum aestivum L.) mitochondrial activity and phospholipid composition was investigated. Preliminary growth measurements showed that osmotic stress (−0.25 or −0.5 megapascal external water potential) inhibited the rate of shoot dry matter accumulation while root dry matter accumulation was less sensitive. We have determined that differences in sensitivity to osmotic stress existed between tissues at the mitochondrial level. Mitochondria isolated from roots or shoots of stressed seedlings showed respiratory control and ADP/O ratios similar to control seedlings which indicates that stressed mitochondria were well coupled. However, under passive swelling conditions in a KCl reaction mixture, the rate and extent of valinomycin-induced swelling of shoot mitochondria were increased by osmotic stress while root mitochondria were largely unaffected. Active ion transport studies showed efflux transport by stressed-shoot mitochondria to be partially inhibited since mitochondrial contraction required the addition of N-ethylmaleimide or nigericin. Efflux ion transport by root mitochondria was not inhibited by osmotic stress which indicates that stress-induced changes in ion transport were largely limited to shoot mitochondria. Characterization of mitochondrial fatty acid and phospholipid composition showed an increase in the percentage of phosphatidylcholine in stressed shoot mitochondria compared to the control. Mitochondrial fatty acid composition was not markedly altered by stress. No significant changes in either the phospholipid or fatty acid composition of stressed root mitochondria were observed. Hence, these results suggest that a tissue-specific response to osmotic stress exists at the mitochondrial level.     

Membrane lipid profile alterations are associated with the metabolic adaptation of the Caco-2 cells to aglycemic nutritional condition

Cancer cells can adapt their metabolic activity under nutritional hostile conditions in order to ensure both bioenergetics and biosynthetic requirements to survive. In this study, the effect of glucose deprivation on Caco-2 cells bioenergetics activity and putative relationship with membrane lipid changes were investigated. Glucose deprivation induces a metabolic remodeling characterized at mitochondrial level by an increase of oxygen consumption, arising from an improvement of complex II and complex IV activities and an inhibition of complex I activity. This effect is accompanied by changes in cellular membrane phospholipid profile. Caco-2 cells grown under glucose deprivation show higher phosphatidylethanolamine content and decreased phosphatidic acid content. Considering fatty acid profile of all cell phospholipids, glucose deprivation induces a decrease of monounsaturated fatty acid (MUFA) and n-3 polyunsaturated fatty acids (PUFA) simultaneously with an increase of n-6 PUFA, with consequent drop of n-3/n-6 ratio. Additionally, glucose deprivation affects significantly the fatty acid profile of all individual phospholipid classes, reflected by an increase of peroxidability index in zwitterionic phospholipids and a decrease in all anionic phospholipids, including mitochondrial cardiolipin. These data indicate that Caco-2 cells metabolic remodeling induced by glucose deprivation actively involves membrane lipid changes associated with a specific bioenergetics profile which ensure cell survival.     

Effect of hyper- and hypothyroidism on phospholipid fatty acid composition and phospholipases activity in sarcolemma of rabbit cardiac muscle.

Lipid content and composition of fatty acids esterified to phospholipids of cardiac sarcolemma isolated from hyperthyroid, hypothyroid and control rabbits were analysed. Hyperthyroidism resulted in a significant reduction of the cholesterol to phospholipid molar ratio as compared to control animals, while hypothyroidism exerted the opposite effect. Complex changes in composition of phospholipid fatty acids observed in hyperthyroid state led to an elevation of the fatty acid unsaturation index over the control value. The unsaturation index value was, however, not affected in the hypothyroid state. Thyroxine hormone administration increased phospholipase A1 and decreased phospholipase A2 activity. The opposite effect was observed in thyreodectomized animals. The effect of changes in sarcolemmal bulk phospholipids upon thyroxine administration or deficiency on regulation of activity of membrane-bound enzymes is discussed.     

Cyclic changes in phospholipid content and composition in human endometrium during the menstrual cycle

A significant increase in total phospholipid content of the endometrium took place during the secretory phase of the human menstrual cycle (26% increase from mid-proliferative to premenstrual stage). The major phospholipid, phosphatidylcholine, was increased by 30%, whereas phosphatidylethanolamine was unchanged. Phosphatidyl-serine and -inositol underwent the largest percentage increases (40%). Phosphatidic acid levels were the only ones to decrease (-52%), a finding consistent with the role of this lipid as precursor of the increased phospholipids. The changes did not markedly affect phospholipid composition, except for a significant decrease in the proportions of phosphatidate and phosphatidylethanolamine. Arachidonate and eicosatrienoate (n-6) were the major polyunsaturated fatty acids. C22 tetra-, penta- and hexa-enoic fatty acids of the n-3 and n-4 families were also present in all major endometrial glycerophospholipids throughout the cycle. The mass changes in phospholipids during the cycle occurred without alteration of their fatty acid composition.     

Effects of cold adaptation and re-adaptation upon the mitochondrial phospholipids of brown adipose tissue.

1. A study of the mitochondrial phospholipids, phospholipid fatty acid patterns and enzyme activities was investigated in brown tissue (B.A.T.) from rats chronically exposed to cold and/or treated with thyroxine. 2. The total activities of the oxidative enzymes were increased after cold exposure, but not after thyroxine treatment. 3. Cold exposure increased the amount of phosphatidylethanolamine, phosphatidylcholine, cardiolipin and lysophospholipids, the effect being greatest for phosphatidylethanolamine. At the same time, there were marked alterations in the fatty acid composition of the mitochondrial phospholipids (decrease of palmitic, palmitoleic and oleic acids ; increase of stearic, linoleic and arachidonic acids). 4. All these cold-induced alterations were reversed by re-adaptation of the animal to a normal temperature range. 5. The alterations of the fatty acid composition of phospholipids could be explained by changes in the rate of individual fatty acid biosynthesis.     

Rotational relaxation times of 1,6-diphenyl-1,3,5-hexatriene in phospholipids isolated from LM cell membranes. Effects of phospholipid polar head-group and fatty acid composition.

Phospholipids were isolated from mitochondrial, microsomal, and plasma membranes of LM cells and fractionated into individual phospholipid classes on silicic acid columns. The fatty acid composition and the rotational relaxation time of 1,6-diphenyl-1,3,5-hexatriene (DPH) were determined for each phospholipid class. Sphingomyelin was the only phospholipid isolated from LM cell membranes that showed a phase transition within the temperature range investigated, 5-40 degrees C. The rotational relaxation times for DPH were lowest in phosphatidylcholine in all the membrane fractions. Phosphatidylcholine isolated from the three membrane fractions of choline-supplemented cells had similar rotational relaxation times and phosphatidylcholine isolated from microsomal membranes of linoleate-supplemented cells had lower rotational relaxation times. The results indicate that the differences in the rotational relaxation times of DPH between mitochondrial, microsomal, and plasma membrane phospholipids could be explained primarily by differences in the polar head-group composition, while differences in the fatty acid composition had only a minor effect. This provides a basis for understanding how the different lipid components in these cells contribute to membrane fluidity.     

Effect of ionizing radiation on the functional state of snail neurons. Phospholipid composition and levels of free fatty acids

A study was made of the effect of ionizing radiation on the phospholipid composition and the level of free fatty acids in nervous ganglia of edible snails (Helix pomatia). Ionizing radiation was shown to decrease the total content of phospholipids and to change certain fractions and accumulation of lysoforms. The increase in the free fatty acid content indicated an activation of endogenous phospholipase hydrolysis. Model experiments on treatment of nervous ganglia with phospholipase A2 demonstrated a similarity of radiation-induced changes in the phospholipid content.     

Altered lipid composition of adipose tissue in human muscular dystrophy

Lipids of subcutaneous adipose tissue from normal and dystrophic human samples were investigated with particular reference to the fatty acid composition of neutral lipids and phospholipids. The free fatty acid pattern did not show much change. Triglyceride, which together with cholesterol composed most of the neutral lipid fraction, showed significant changes in fatty acid composition by gas-liquid chromatography (GLC). There was a decrease in the total phospholipids. Analysis of the levels of individual phospholipids, however, showed an increase in sphingomyelin and ethanolamine phosphoglyceride contents. Fatty acid composition of the different phospholipid classes analyzed by GLC showed significant changes.     

Changes of fatty acid composition of phospholipids and lipid structural order in rat liver mitochondrial membrane subsequent to galactosamine intoxication. Effect of clofibrate

Since it has been earlier reported that D-galactosamine induces an inhibition of palmitoylcarnitine transferase I and a depletion of mitochondrial phospholipids which were both prevented by clofibrate, an evaluation of the effects of these drugs on mitochondrial fatty acid composition was made. Galactosamine does not alter the fatty acid pattern of these fatty acids whereas clofibrate induces a 2-fold increase in monounsaturated/saturated fatty acids ratio and a 10-fold decrease of the 20:4 (n - 6)/20:3 (n - 6) ratio in phosphatidylcholine. These alterations suggest an increase of delta 9-desaturation and a decrease of delta 5-desaturation. To determine whether the drug-induced changes in mitochondrial phospholipids has an effect on the physical properties of the membrane, the lipid structural order of mitochondrial preparations was studied using the lipophilic probes DPH and TMA-DPH. Mitochondrial isolated either from galactosamine- or clofibrate-treated rats showed a decrease in fluorescence polarization, indicating an overall decrease in lipid structural order. This alteration is more drastic when both drugs are administered. This phenomenon suggests drastic changes in the bulk phase of inner mitochondrial membrane lipids after treatments and could explain the altered kinetic properties of palmitoylcarnitine transferase I.     

Copper deficiency-induced changes in the fatty acid composition of mitochondrial and microsomal membranes of rat liver

The effects of copper deficiency on the fatty acid composition of mitochondrial and microsomal phospholipids in rat liver were studied. Copper deficiency was induced by a milk powder diet. To evaluate the effect of the milk diet on the fatty acid pattern of mitochondrial and microsomal phospholipids, one group of rats was fed Cusupplemented powdered milk. A decrease in the relative proportion of linoleic acid and an increase in the level of oleic and docosahexaenoic acids in membrane phospholipids were found in this group. However, no changes in the fatty acid pattern characteristic of essential fatty acid deficiency were observed. Dietary copper deficiency produced a significant decrease in the relative amounts of linoleic and arachidonic acids, as well as an increase in the docosahexaenoic acid content in both mitochondrial and microsomal membranes compared to the nondeficient controls. The disproportionate quantities of polyunsaturated fatty acids are discussed with a view to the disturbances of membrane function in copper deficiency.     

Effects of ethanol on the lipid composition of bovine vascular smooth muscle cells in culture

Ethanol (50 mM) had no effect on the growth rate or viability of arterial smooth muscle cells over 3.5 days. The cholesterol:phospholipid ratio of the cells was unchanged after 7 days exposure. The major phospholipid components phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol were unchanged by ethanol exposure. Sphingomyelin content fell significantly within 12 hr. There were major changes in the fatty acid composition of the phospholipids with a reduction in saturated fatty acids and an increase in unsaturated fatty acids.     

Fatty acid composition of phospholipids in mitochondria and microsomes during diethylnitrosamine carcinogenesis in rat liver

Changes in lipid composition and function of subcellular organelles have been described in transplanted and primary tumours. We examine here the fatty acid composition of individual phospholipids (PL) in hyperplastic nodules and primary hepatoma induced by diethylnitrosamine (DEN), compared to that of normal liver and of transplantable Yoshida AH-130 hepatoma. Phosphatidylcholine and phosphatidylethanolamine fatty acid composition in mitochondria and microsomes from primary hepatoma were markedly different from normal liver; C18:0/C18:1 ratio was lower and the ratio between monosaturated and polyunsaturated fatty acids was higher. Linoleic acid content of mitochondrial cardiolipin, usually very high in normal rat liver, was notably lower in primary hepatoma. Cholesterol/phospholipid ratio in both microsomes and mitochondria from DEN-induced hepatoma was higher than in normal liver. Hyperplastic nodules showed no changes in cholesterol content whereas modifications in fatty acid composition were already observable. These modifications of membrane structure may be related to the functional changes found in nodular cells. Changes in fatty acid composition of membrane phospholipids, occurring in both primary hepatoma and preneoplastic nodules, might be one of the causes for decreased rate of lipid peroxidation peculiar to these tissues.     

Lipid composition of brown adipose tissue mitochondria and microsomes in hyperthyroid rats

1. The effects of triiodothyronine on the lipid composition of rat brown adipose tissue (BAT) mitochondria and microsomes was investigated by high performance liquid chromatography (HPLC). 2. An increase of about 20% was noted in mitochondrial cholesterol and phospholipids, while a decrease of about 20% for both total cholesterol and phospholipids was observed in microsomes from hyperthyroid rats. 3. The BAT phospholipid composition was altered significantly in mitochondria from T3-treated rats with an increase (41%) of cardiolipin and a decrease (18%) in phosphatidylcholine. 4. In microsomes, a decrease by 25% in phosphatidylinositol was accompanied by a similar additional percentage increase in phosphatidylethanolamine. 5. Important alterations in the fatty acid pattern were found in mitochondrial neutral lipids.