Breakdown Of Membrane Phospholipids Research Articles

Chapter 23: Kainic acid-induced excitotoxicity in neurons and glial cells

Publisher Summary Kainic acid (KA) is known to exert a potent neuroexcitatory effect in the brain, causing damage to the neuronal cell body. A number of studies have implicated the involvement of Ca 2+ in this process. Kainic acid is shown to stimulate Ca 2+ influx in cultured neuronal cells, synaptosomes, and perfused hippocampus. The neurotoxicity of KA after peripheral administration is associated with its ability to cause the increase in intraneuronal Ca 2+ level. A number of cellular processes are critically dependent on the level of intracellular Ca2+ in cells. One of these is the activation of phospholipases leading to the breakdown of membrane phospholipids and release of arachidonic acid (AA). Cerebral ischemia as well as other forms of neuronal insults causes the release of AA in the brain. This chapter discusses evidence that AA may be a mediator that inhibits the glutamate uptake, and this phenomenon contributes to the KA-induced excitotoxicity in the brain.

Membrane deterioration during postharvest senescence of broccoli florets: modulation by temperature and controlled atmosphere storage

Abstract When freshly cut heads of broccoli ( Brassica oleracea L.) are stored in air at 23°C or 10°C, the florets rapidly senesce. Chlorophyll levels decline by 80–90% within 4 days at 23°C and within 10 days at 10°C, and under the same storage conditions microsomal phospholipid phosphate and fatty acids in the florets decline by 70–90%. The breakdown of membrane phospholipids is accompanied by a large decrease (… 35%) in bulk lipid fluidity of the membranes. These changes are temperature-dependent inasmuch as they are completely inhibited during storage for comparable periods in air at 5°C. Also, the potential of microsomal membranes isolated from florets to degrade exogenous, radiolabelled phosphatidylcholine increases during storage in air at 23°C or 10°C, but not at 5°C. Storage at 5°C or 10°C in a controlled atmosphere (5% CO 2 , 3% O 2 , 92% N 2 ) at … 80% relative humidity strongly inhibits loss of chlorophyll and the change in microsomal bulk lipid fluidity reflecting phospholipid breakdown. Thus reduced integrity of thylakoids and membrane phospholipid degradation appear to be inherent features of broccoli floret senescence that are sensitive, directly or indirectly, to ambient CO 2 and O 2 concentrations. These observations confirm the potential of using controlled atmospheres to enhance the storability of broccoli and identify physiological and biochemical parameters of floret senescence that can be used to establish optimum controlled atmosphere conditions.

Localized Phosphorus 31 Magnetic Resonance Spectroscopy in Chronic Schizophrenic Patients and Normal Controls

<h3>To the Editor.—</h3> We are most interested in the article by Pettegrew et al¹in this issue of theArchives. The authors report significantly reduced levels of phosphomonoesters (PMEs) and significantly increased levels of phosphodiesters (PDEs) in first-episode, nevertreated schizophrenic patients compared with normal matched control subjects. These findings could indicate decreased synthesis and/or increased breakdown of membrane phospholipids in schizophrenia. We wish to report some preliminary results of localized phosphorus 31 (³¹P) magnetic resonance (MR) spectroscopy in chronic schizophrenic patients and normal control subjects. <h3>Patients and Methods.—</h3> Ten schizophrenic patients (nine men, one woman) between ages 33 and 54 years (mean± SD, 38.7±6.0 years) participated in the study. All were outpatients receiving an average chlorpromazine hydrochloride equivalent dose of 660 ± 436 mg. The diagnosis of schizophrenia was confirmed by a psychiatrist (P.W.) using the Structured Clinical Interview for<i>DSMIII-R</i>.²Length of illness was estimated

Protection from nonfreezing cold injury by quinacrine, a phospholipase inhibitor

A recent study from our laboratory indicated additional tissue injury during rewarming of a cooled rabbit leg. Oxygen-derived free radicals were believed to play a role in such “rewarming injury.” Since free radicals may attack membrane phospholipids, we analyzed the phospholipid composition in the leg tissue during cooling and rewarming. Our results indicated significant breakdown of membrane phospholipids, particularly phosphatidylcholine and phosphatidylethanolamine, with a corresponding accumulation of lysophosphatidylcholine and nonesterified fatty acids. Quinacrine, a phospholipase inhibitor, was able to preserve membrane phospholipids during rewarming of the cooled leg. Rewarming of cooled tissue was also accompanied by additional tissue injury, as evidenced by the increased release of lactic acid dehydrogenase and creatine kinase, as well as enhanced lipid peroxidation, as evidenced by increased malonaldehyde formation. Quinacrine reduced the release of these intracellular enzymes and decreased lipid peroxidation, suggesting its efficacy as a therapeutic agent against hypothermic injury.

High-performance liquid chromatographic detection of myocardial prostaglandins and thromboxanes

Reperfusion of ischemic myocardium is associated with the breakdown of membrane phospholipids and a corresponding increase in arachidonic acid, ultimately resulting in the production of prostaglandins (PGs) and thromboxanes (TXs). However, quantification of these arachidonic acid metabolites has been limited to radioimmunoassay because of their presence in extremely low amounts. In this report, we describe a method suitable to detect sub-picogram levels of 6-keto-PGF 1α, PGF 1α, PGE 2 and TXB 2 in myocardial perfusates by high-performance liquid chromatography (HPLC) with a high-gain photomultiplier and a xenon—mercury are lamp. Strong Raleigh scatter of the lamp was eliminated by both interference and long-pass cut-off filters. Improved sample clean-up and HPLC separation were achieved by an HPLC system with an Ultrasphere 3-μm C 18 column.

Role of iron on membrane phospholipid breakdown in ischemic-reperfused rat heart

Oxygen-derived free radicals have been implicated in causing degradation of myocardial membrane phospholipids associated with ischemia and reperfusion. Since iron is known to catalyze the hydroxyl radical formation responsible for cellular injury, this study was designed to relate the role of iron with phospholipid breakdown in ischemic-reperfused heart. Isolated rat heart perfused by the Langendorff technique was subjected to 30 min of normothermic ischemia followed by 30 min of reperfusion. The experimental group received 0.6 mM deferoxamine, an iron chelator, before reperfusion of ischemic myocardium. Deacylation and reacylation of membrane phospholipids were monitored by using [14C]arachidonic acid (AA), whereas the de novo phospholipid synthesis was evaluated by using [3H]glycerol in the perfusate. In the deferoxamine group, the loss of [14C]phosphatidylcholine (PC) and the corresponding accumulation of isotopic lysophosphoglycerides as well as AA was significantly lower compared with the control. The incorporation of radioactivity for [14C]AA and [3H]glycerol into phospholipids was significantly increased in the treated group compared with the untreated group. In addition, decreased malonaldehyde formation and lactate dehydrogenase release, a higher recovery of high-energy phosphate compounds, and myocardial contractility were noticed in the deferoxamine-treated hearts. These results indicated that postischemic administration of an iron chelator such as deferoxamine can preserve membrane phospholipids and reduce myocardial dysfunction associated with reperfusion of ischemic heart.

Clinical nuclear magnetic resonance spectroscopy: Insight into metabolism

Nuclear magnetic resonance (NMR) spectroscopy can nondestructively evaluate changes in metabolites with different disease states, as well as with therapeutic interventions. Animal studies have provided the basis for understanding changes in high-energy phosphates with myocardial ischemia. Studies of graded ischemia due to partial coronary stenosis have shown the sensitivity of the ratio of phosphocreatinine to inorganic phosphate to small reductions in myocardial blood flow and its relation to myocardial function. The application of NMR spectroscopy to humans requires precise localization techniques to avoid acquiring contaminating information from structures around the heart, such as the chest wall and diaphragm. With these localization techniques, metabolic evidence of ischemia has been demonstrated in patients with myocardial infarction and patients with known coronary disease, although the sensitivity of this technique for the diagnosis of inducible ischemia is unknown. At rest, patients with dilated and hypertrophic cardiomyopathies often have an elevated phosphodiester resonance, possibly signifying abnormal breakdown of membrane phospholipids. Increasing oxygen demand in these patients does not usually alter high-energy phosphates, suggesting that oxidative energy metabolism is preserved under these conditions. NMR spectroscopy is a powerful tool to increase understanding of metabolic changes in a variety of pathologic conditions.

Serotonin-mediated responses in autism

372 young adult controls (27 -+ 2 years). The following metabolic alterations were observed in the dorsal prefrontal cortex of the autistic patients. (1) Decreased levels of phosphomonoesters (p = .Ol), (2) increased levels of phosphodiesters (p = .004), and (3) decreased levels of UDP-sugars (p = .004). The PCr levels were non-significantly decreased (p = .08) and the levels of ATP and intracellular pH were normal. These findings suggest (1) decreased synthesis and increased breakdown of membrane phospholipids, (2) decreased glycosylation of membrane gangliosides, and (3) normal or slightly increase utilization of PCr. The membrane phospholipid alterations are similar to those demonstrated in never-medicated first episode schizophrenics, but the PCr changes are in the opposite direction from those demonstrated in schizophrenics.

An investigation on lipoperoxidation mechanisms in boar spermatozoa

Aerobic incubation of washed boar spermatozoa in a heavy metal free medium at 37°C results in a peroxidative breakdown of membrane phospholipids as revealed by malondialdehyde production. In the presence of iron ions, alone and with ascorbate, the amount of malondialdehyde produced increases noticeably. Alkoxy and lipoperoxy radicals are likely involved in these peroxidative processes, while OH • radical does not seem to be essential in the pathway of malondialdehyde formation.

Effect of Oxygen-Derived Free Radicals and Oxidants on the Degradationin vitroof Membrane Phospholipids

The abilities of chemically generated hydroxyl radical (OH.), superoxide anion (O.-) and hydrogen peroxide (H2O2) to degrade rat myocardial membrane phospholipids previously labeled with [1-14C]arachidonic acid were studied. HO. and H2O2, but not O2.-, caused the degradation of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (PI). With OH. and H2O2, the loss of radiolabel in PC was accompanied by an increase in the radiolabel of lysophosphatidylcholine (LPC), but not in that of free fatty acid (FFA). These results suggest the hydrolysis of 1-oxygen ester bond of PC by HO. and that H2O2 and that HO. and H2O2, but not O.-, are detrimental to the structure and function of membrane phospholipids. However, since microM amounts of HO. and mM amounts of H2O2 were necessary to affect the membrane phospholipids, it is likely that in the reperfused myocardium only HO., but not H2O2, may directly cause the breakdown of membrane phospholipids.

Deferoxamine reduces neutrophil-mediated free radical production during cardiopulmonary bypass in man

We assessed the effects of the iron chelator deferoxamine in 24 adult patients (12 controls, 12 treated) undergoing cardiopulmonary bypass for various cardiac operations. Deferoxamine was given both intravenously (30 mg/kg of body weight, starting 30 minutes before and ending 30 minutes after bypass) and as an additive to the cardioplegic solution (250 mg/L). Right atrial blood samples were taken before, during, and after bypass, and isolated polymorphonuclear neutrophils were evaluated for their capacity to generate superoxide radicals after stimulation with N-formyl-methionyl-leucyl-phenylalanine (FLMP, 10(-7) mol) and phorbol myristate acetate (100 ng/ml). At the same sampling times, measurement of the plasma levels of 6-keto-prostaglandin F1 alpha, the stable derivative of prostacyclin, was used as an index of membrane phospholipid breakdown. The two groups were not significantly different with regard to age, duration of bypass, and quantitative changes in polymorphonuclear neutrophil counts during the operation. Before bypass, the superoxide production of FMLP-stimulated polymorphonuclear neutrophils was comparable in the two groups. Conversely, after bypass, polymorphonuclear neutrophils harvested from deferoxamine-treated patients produced significantly fewer superoxide radicals than those of control patients (1.9 +/- 0.3 versus 3.7 +/- 0.2 nmol/10(6) polymorphonuclear neutrophils per minute, p less than 0.05). Stimulation of polymorphonuclear neutrophils by phorbol myristate acetate yielded similar changes, as the postbypass superoxide production was 12.6 +/- 2.5 nmol/10(6)/min in control patients and 7.1 +/- 0.9 nmol/10(6)/min in those receiving deferoxamine (p less than 0.05). In contrast, plasma levels of 6-keto-prostaglandin F1 alpha were not significantly different between the two groups. We conclude that deferoxamine-exposed polymorphonuclear neutrophils have a decreased oxidative responsiveness, compatible with the fact that they may have been less "primed" by secretagogues released during bypass, as compared with cells of untreated patients. Our results are consistent with the hypothesis that deferoxamine, by inhibiting iron-catalyzed free radical production, may limit the free radical-mediated amplification of the inflammatory response to bypass and as such could be effective in reducing the harmful effects of extracorporeal circulation.

Membrane Deterioration in Senescing Carnation Flowers

The lipid fluidity of microsomal membranes from the petals of cut carnation flowers decreases as the flowers senesce. A comparable change in fluidity was induced by in vitro aging of microsomal membranes from young flowers under conditions in which membranous lipoxygenase-like activity was active. There was no change in fluidity when the membranes were aged in the presence of inhibitors of lipoxygenase or were heat-denatured prior to aging. Membranes from naturally senesced flowers and membranes that had been aged in vitro both sustained an increase in saturated:unsaturated fatty acid ratio that accounted for the decrease in lipid fluidity, and in both instances there was evidence for depletion of the unsaturated fatty acids, linoleic acid, and linolenic acid, which are substrates for lipoxygenase. Loss of lipid phosphate reflecting breakdown of membrane phospholipids preceded the depletion of unsaturated fatty acids attributable to the lipoxygenase-like activity. The data have been interpreted as indicating that fatty acid substrates for membrane-associated lipoxygenase-like activity are made available by the initiation of phospholipid degradation, and that the utilization of these substrates results in a selective depletion of unsaturated fatty acids from the membrane and an ensuing decrease in bulk lipid fluidity.

Calcium entry blockers protect brain energy metabolism against ischemic damage.

Under physiological conditions the intracellular calcium ion activity is regulated at a level several orders of magnitude lower than that of the extracellular space. However, under the conditions of energy failure the cytosolic Ca2+ concentration increases markedly. The reasons for this are the opening of the voltage-dependent calcium channels within the plasma membrane, the release of Ca2+ from the ATP-dependent sites of sequestration in the endoplasmatic reticulum and the impaired ability of mitochondria to accumulate calcium. The resulting increase in free cytosolic calcium activity disrupts a variety of cellular functions and, in particular, may be responsible in part for the breakdown of membrane phospholipids.

Cyclic nucleotides in stroke and related cerebrovascular disorders

Evidence has steadily accumulated to indicate that the rapid fluctuations in cyclic nucleotides during primary and secondary stroke are more than epiphenomena of the disease. During acute phases of ischemia, anoxia or hypoxia cyclic AMP rapidly accumulates in cerebral tissue, cerebrospinal fluid (CSF) and venous plasma, while cyclic GMP either remains unchanged or declines. The massive release of transmitters (catecholamines and adenosine) or ionic fluxes (Na+ and K+) may account for these observations. If reflow is established through a previously occluded vessel cyclic AMP content rises even higher in conjunction with a sharp rise in cyclic GMP. It is during this reflow period subsequent to longer term stroke (30–60 min) that the synaptic membrane enzyme, adenylate cyclase, is especially vulnerable. Presumably the cause of injury to cell membrane systems results from excess lactic acid accumulation and/or Ca++ entry through the damaged blood-brain barrier. The latter initiates breakdown of membrane phospholipids with resultant synthesis of vasoactive prostaglandins and formation of free radicals causing further insult to membrane phospholipids. Thus drugs acting to inhibit formation of prostaglandins, scavenge free radicals, reduce lactate formation, inhibit Ca++ entry or stabilize cell membranes have been shown to possess varying degrees of protective action toward adenylate cyclase. Moreover, cyclic AMP has been found to reverse stroke-induced vasospasm in central vessels. Reduced cyclic AMP content in CSF has been used to monitor the severity of coma, whereas clinical improvement was associated with predictable increases in the cyclic nucleotide. Therefore, cyclic nucleotides and related membrane enzyme systems might be used as target molecules in which to develop future therapeutic strategies for prevention or treatment of stroke.

Partial preservation of motor function by inhibition of arachidonate metabolism in rats with phospholipase A 2-induced caudate lesions

Dexamethasone pretreatment prevents motor impairment manifested by ipsilateral rotation and phospholipid alterations resulting from phospholipase A 2-induced caudate nucleus lesions in rats. If motor function preservation is attributed solely to the antiprostaglandin activity of dexamethasone, then indomethacin (an inhibitor of cyclooxygenase) and phenidone (an inhibitor of both lipoxygenase and cyclooxygenase) should also diminish rotation. Phenidone offered dose-related, partial protection whereas indomethacin did not. Histologic sections of rat brain indicated that a positive correlation existed between the size of the caudate lesion and number of rotations for the various treatments. Because dexamethasone produced essentially complete protection, it is hypothesized that dexamethasone protects caudate motor function by interfering with breakdown of membrane phospholipids, as well as by preventing formation of arachidonate and its products.

Choline production from choline-containing phospholipids: A hypothetical role in Alzheimer's disease and aging

1. Deficits in certain long-axon cholinergic brain neurons have been demonstrated both in senile dementia of the Alzheimer type (SDAT) and, to a lesser degree, in association with the cognitive and memory impairments sometimes seen with normal aging. Our studies support a hypothesis concerning the selective vulnerability of these neurons. 2. In our superfused brain slice system, acetylcholine (ACh) release was dependent on the concentration of exogenous choline, at rest and during electrical stimulation. 3. Decreases in intracellular levels of ACh and choline accounted for only a small fraction of the quantities of these compounds released into the superfusates, suggesting that some tissue pool of bound choline, such as the phospholipids (PL), might have liberated choline. 4. In choline-free medium, the release and tissue content of ACh were sustained: thus, choline released from the putative endogenous pool can be utilized for ACh synthesis. 5. We hypothesize that the use, by cholinergic neurons, of choline originating from the breakdown of membrane PL, may result in an impoverishment in certain PL. Since only cholinergic neurons use their membrane PL as a reservoir for their neurotransmitter's precursor, this relationship might explain the major deficits in long-axon cholinergic nerve terminals seen in SDAT and other age-related memory disorders.

The membrane attack complex of complement and its precursor proteins lack phospholipase activity

The membrane attack complex of human complement and its highly purified precursor proteins have been analyzed for phospholipase activity. Using three different sensitive assays, phospholipase a 1, A 2, C or D activity could not be detected. Based on the sensitivity of the assays employed, these results indicate the complement-mediated membrane damage is not enhanced by covalent breakdown of membrane phospholipids, but is entirely caused by physical action of the membrane attack complex. The results also imply that the putative serine esterase sites of C6 and C7 are not acting on phospholipids.

Incorporation of phosphatide precursors from serum into erythrocytes

Although mercury (Hg) is an important environmental and occupational pollutant, its toxicological effects, especially in serum and red blood cells (RBCs), have been scarcely studied. A toxicometabolomics workflow based on high resolution mass spectrometry approaches has been applied to investigate the toxicological effects of Hg in Mus musculus mice after subcutaneous injection for 10 days, which produced inflammation and vacuolization, steatosis and karyolysis in the hepatic tissue. To this end, direct infusion mass spectrometry (DIMS) of polar and lipophilic extracts from serum and RBCs, using positive and negative mode of acquisition (ESI+/ESI−), and gas chromatography–mass spectrometry were used. A quantitative analysis of reversible oxidized thiols in serum proteins demonstrated a strong oxidative stress induction in the liver of Hg-exposed mice. Endogenous metabolites alterations were identified by partial least squares-discriminant analysis (PLS-DA). Mercury-exposed mice show perturbations in energy metabolism, amino acid metabolism, membrane phospholipid breakdown and oxidative stress-related metabolites in serum along the exposure. This work reports for the first time the effects of Hg-exposure on RBCs metabolic pathways, and reveals disturbances in glycolysis, membrane turnover, glutathione and ascorbate metabolisms.