Phospholipid methylation and biological signal transmission

Neuregulin-1 regulates cell adhesion via an ErbB2/phosphoinositide-3 kinase/Akt-dependent pathway: potential implications for schizophrenia and cancer

Background

Neuregulin-1 (NRG1) is a putative schizophrenia susceptibility gene involved extensively in central nervous system development as well as cancer invasion and metastasis. Using a B lymphoblast cell model, we previously demonstrated impairment in NRG1α-mediated migration in cells derived from patients with schizophrenia as well as effects of risk alleles in NRG1 and catechol-O-methyltransferase (COMT), a second gene implicated both in schizophrenia susceptibility and in cancer.

Methodology/Principal Findings

Here, we examine cell adhesion, an essential component process of cell motility, using an integrin-mediated cell adhesion assay based on an interaction between ICAM-1 and the CD11a/CD18 integrin heterodimer expressed on lymphoblasts. In our assay, NRG1α induces lymphoblasts to assume varying levels of adhesion characterized by time-dependent fluctuations in the firmness of attachment. The maximum range of variation in adhesion over sixty minutes correlates strongly with NRG1α-induced migration (r² = 0.61). NRG1α-induced adhesion variation is blocked by erbB2, PI3K, and Akt inhibitors, but not by PLC, ROCK, MLCK, or MEK inhibitors, implicating the erbB2/PI3K/Akt1 signaling pathway in NRG1-stimulated, integrin-mediated cell adhesion. In cell lines from 20 patients with schizophrenia and 20 normal controls, cells from patients show a significant deficiency in the range of NRG1α-induced adhesion (p = 0.0002). In contrast, the response of patient-derived cells to phorbol myristate acetate is unimpaired. The COMT Val108/158Met genotype demonstrates a strong trend towards predicting the range of the NRG1α-induced adhesion response with risk homozygotes having decreased variation in cell adhesion even in normal subjects (p = 0.063).

Conclusion/Significance

Our findings suggest that a mechanism of the NRG1 genetic association with schizophrenia may involve the molecular biology of cell adhesion.

A model for modulation of neuronal synchronization by D4 dopamine receptor-mediated phospholipid methylation

We describe a new molecular mechanism of dopamine-induced membrane protein modulation that can tune neuronal oscillation frequency to attention-related gamma rhythm. This mechanism is based on the unique ability of D4 dopamine receptors (D4R) to carry out phospholipid methylation (PLM) that may affect the kinetics of ion channels. We show that by deceasing the inertia of the delayed rectifier potassium channel, a transition to 40 Hz oscillations can be achieved. Decreased potassium channel inertia shortens spike duration and decreases the interspike interval via its influence on the calcium-dependent potassium current. This mechanism leads to a transition to attention-related gamma oscillations in a pyramidal cell-interneuron network. The higher frequency and better synchronization is observed with PLM affecting pyramidal neurons only, and recurrent excitation between pyramidal neurons is important for synchronization. Thus dopamine-stimulated methylation of membrane phospholipids may be an important mechanism for modulating firing activity, while impaired methylation can contribute to disorders of attention.

Bridging the gap between protein carboxyl methylation and phospholipid methylation to understand glucose-stimulated insulin secretion from the pancreatic beta cell

Recent findings have implicated post-translational modifications at C-terminal cysteines [e.g., methylation] of specific proteins [e.g., G-proteins] in glucose-stimulated insulin secretion [GSIS]. Furthermore, methylation at the C-terminal leucine of the catalytic subunit of protein phosphatase 2A [PP2Ac] has also been shown to be relevant for GSIS. In addition to these two classes of protein methyl transferases, a novel class of glucose-activated phospholipid methyl transferases have also been identified in the beta cell. These enzymes catalyze three successive methylations of phosphatidylethanolamine to yield phosphatidylcholine. The "newly formed" phosphatidylcholine is felt to induce alterations in the membrane fluidity, which might favor vesicular fusion with the plasma membrane for the exocytosis of insulin. The objectives of this commentary are to: (i) review the existing evidence on the regulation, by glucose and other insulin secretagogues, of post-translational carboxylmethylation [CML] of specific proteins in the beta cell; (ii) discuss the experimental evidence, which implicates regulation, by glucose and other insulin secretagogues, of phosphatidylethanolamine methylation in the islet beta cell; (iii) propose a model for potential cross-talk between the protein and lipid methylation pathways in the regulation of GSIS and (iv) highlight potential avenues for future research, including the development of specific pharmacological inhibitors to further decipher regulatory roles for these methylation reactions in islet beta cell function.

Evaluation of the effect of Neptune Krill Oil on chronic inflammation and arthritic symptoms

OBJECTIVES

a) To evaluate the effect of Neptune Krill Oil (NKO) on C-reactive protein (CRP) on patients with chronic inflammation and b) to evaluate the effectiveness of NKO on arthritic symptoms.

METHODS

Randomized, double blind, placebo controlled study. Ninety patients were recruited with confirmed diagnosis of cardiovascular disease and/or rheumatoid arthritis and/or osteoarthritis and with increased levels of CRP (>1.0 mg/dl) upon three consecutive weekly blood analysis. Group A received NKO (300 mg daily) and Group B received a placebo. CRP and Western Ontario and McMaster Universities (WOMAC) osteoarthritis score were measured at baseline and days 7, 14 and 30.

RESULTS

After 7 days of treatment NKO reduced CRP by 19.3% compared to an increase by 15.7% observed in the placebo group (p = 0.049). After 14 and 30 days of treatment NKO further decreased CRP by 29.7% and 30.9% respectively (p < 0.001). The CRP levels of the placebo group increased to 32.1% after 14 days and then decreased to 25.1% at day 30. The between group difference was statistically significant; p = 0.004 at day 14 and p = 0.008 at day 30. NKO showed a significant reduction in all three WOMAC scores. After 7 days of treatment, NKO reduced pain scores by 28.9% (p = 0.050), reduced stiffness by 20.3% (p = 0.001) and reduced functional impairment by 22.8% (p = 0.008).

CONCLUSION

The results of the present study clearly indicate that NKO at a daily dose of 300 mg significantly inhibits inflammation and reduces arthritic symptoms within a short treatment period of 7 and 14 days.

Effects of chlorpromazine on plasma membrane permeability and fluidity in the rat brain: a dynamic positron autoradiography and fluorescence polarization study

Antipsychotic drugs have been widely used in psychiatry for the treatment of various mental disorders, but the underlying biochemical mechanisms of their actions still remain unclear. Although phenothiazine antipsychotic drugs have been reported to directly interact with the peripheral plasma membrane, it is not known whether these drugs actually affect plasma membrane integrity in the central nervous system. To clarify these issues, we investigated the effect of chlorpromazine (CPZ), a typical phenothiazine antipsychotic drug, on plasma membrane permeability in fresh rat brain slices using a dynamic positron autoradiography technique and [(18)F]2-fluoro-2-deoxy-D-glucose ([(18)F]FDG) as a tracer. Treatment with CPZ (> or =100 microM) resulted in the leakage of [(18)F]FDG-6-phosphate, but not [(18)F]FDG, suggesting that the [(18)F]FDG-6-phosphate efflux was not mediated by glucose transporters, but rather by plasma membrane permeabilization. The leakage of [(18)F]FDG-6-phosphate was followed by slower leakage of cytoplasmic lactate dehydrogenase, suggesting that CPZ could initially induce small membrane holes that enlarged with time. Furthermore, the addition of CPZ (> or =100 microM) caused a decrease in 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy, which implies an increase in membrane fluidity. CPZ loading dose-dependently increased both membrane permeability and membrane fluidity, which suggested the involvement of a perturbation of membrane order in the mechanisms of membrane destabilization induced by antipsychotic drugs.

Alzheimer disease--no target for statin treatment. A mini review

Nosologically, Alzheimer disease (AD) is not a single disorder. A minority of around 400 families worldwide can be grouped as hereditary in origin, whereas the majority of all Alzheimer cases (approx. 25 million worldwide) are sporadic in origin. In the pathophysiology of the latter type, a number of susceptibility genes contribute to the disease among which are allelic abnormalities of the apolipoprotein E4 gene pointing to a link between disturbed cholesterol metabolism and sporadic AD. Cholesterol is a main component of membrane composition enriched in microdomains and is functionally linked to the proteolytic processing of amyloid precursor protein (APP). In sporadic AD, a marked diminution of both membrane phospholipids and cholesterol has been found. Evidence has been provided that high plasma cholesterol may protect from AD. In contrast to these well documented abnormalities observed in AD patients, it was assumed that an elevated cholesterol concentration might favour the generation of beta-amyloid and, thus, AD. However, a series of in vitro-and in vivo-studies did not provide evidence for the assumption that an enhanced cholesterol concentration increased betaA4-production. A harsh reduction of membrane cholesterol only caused a "beneficial" effect of APP metabolism. However, this experimentally induced condition may not be compatible to sporadic AD. The application of statins in sporadic AD did not yield results to assume that this therapeutic strategy may prevent or treat successfully sporadic AD.

Alois Alzheimer revisited: differences in origin of the disease carrying his name

Based on the means of his time, Alois Alzheimer supposed that the disease, later carrying his name, is a disease of older age, and that the pathomorphological structures he described are due to disturbances in brain metabolism. In this contribution, it is discussed which cellular metabolic abnormalities may be representative for age-related sporadic Alzheimer disease (SAD) the predominant form of SAD in contrast to the very rare hereditary early-onset form. In focus are disturbances in glucose/energy metabolism which involve the deficits in acetylcholine, cholesterol and UDP-N-acetylglucosamine beside ATP. Another leading abnormality is the defect in cell membrane composition. The interrelation between abnormal glucose/energy metabolism and membrane defect may be assumed to form the basis for the induction of both the perturbed metabolism of the amyloid precursor protein leading to increased formation of beta-amyloid and hyperphosphorylation of tau-protein destroying cell structures. Alois Alzheimer may have been so prescient to assume most of this 100 years ago.

The relationship between folate and docosahexaenoic acid in men

OBJECTIVE

Docosahexaenoic acid (DHA, 22:6n-3), an essential omega 3 fatty acid, may protect against disorders of emotional regulation as well as cardiovascular disease. Animal studies demonstrate that dietary folate can increase tissue concentrations of DHA, although the literature, to date, includes no human studies examining the possibility that folate status may affect plasma DHA concentrations. The objective of this study is to determine if the blood concentrations of folate and DHA are correlated in humans.

DESIGN

Retrospective study.

SETTING

An American research hospital.

SUBJECTS

A total of 15 normal and 22 hostile and aggressive subjects, with a mean age of 38 years.

METHODS

Concentrations of plasma polyunsaturated essential fatty acids and red blood cell folate (RBC folate) were obtained prior to 1996, before American flour was enriched with folate.

RESULTS

RBC folate was significantly correlated with plasma DHA, r=0.57, P=0.005 in the aggressive group. Age, smoking and alcohol consumption did not alter the results. No other essential fatty acids were significantly associated with RBC folate in either group.

CONCLUSIONS

The positive relationship between plasma DHA and RBC folate concentrations suggests that these two nutrients should be examined together in order to make the most accurate inferences about their relative contributions to disease pathogenesis. Our findings present one explanation why some conditions associated with hostility and low DHA status, such as cardiovascular disease and emotional disorders, are also associated with low folate status.

SPONSORSHIP

National Institutes of Health, National Institute on Alcohol Abuse and Alcoholism.

Phospholipid methylation in skeletal muscle membranes

Phospholipid methylation is thought to modulate such vital cellular processes as calcium transport, receptor function, and membrane microviscosity. As these processes are fundamental to the function of muscle cells and are thought to be altered in disease states, we have characterized several features of phospholipid methylation reactions in skeletal muscle and have defined appropriate assay conditions. In rat leg muscle, methyltransferase activity was assayed radiometrically by measuring the incorporation of methyl groups from S-adenosyl-L-[methyl-3H]methionine into membrane phospholipids, the methylated derivatives of which were separated by thin-layer chromatography. Contrary to previous investigations of whole muscle, phospholipid methyltransferase activity was clearly present in skeletal muscle membranes, being highly localized in sarcoplasmic reticulum and present to a lesser extent in sarcolemma. Both the reaction products and the reaction kinetics were consistent with sequential methylation of phospholipids by two methyltransferase enzymes. S-adenosylhomocysteine and its analogues were potent inhibitors of phospholipid methylation in sarcoplasmic reticulum. The predominant localization of phospholipid methyltransferase activity in sarcoplasmic reticulum suggests that its functional role in skeletal muscle may be in calcium transport.

Double-blind, placebo-controlled pharmacodynamic studies with a nutraceutical and a pharmaceutical dose of ademetionine (SAMe) in elderly subjects, utilizing EEG mapping and psychometry

In a double-blind, placebo-controlled crossover study, the effects of S-adenosyl-l-methionine (SAMe) on brain function measures of 12 normal elderly volunteers (6 m/6 f, aged 57-73 years, mean: 61 years) were investigated by means of EEG mapping and psychometry. In random order, the subjects were orally administered a pharmaceutical dose of 1600 mg SAMe, a nutraceutical dose of 400 mg SAMe and placebo, each over a period of 15 days, with wash-out periods of 2 weeks in between. EEG recordings, psychometric tests and evaluations of tolerability and side effects were carried out 0, 1, 3 and 6 h after drug administration on days 1 and 15. Multivariate analysis based on MANOVA/Hotelling T2 tests of quantitative EEG data demonstrated significant central effects of SAMe as compared with placebo after acute, subacute and superimposed drug administration of both the nutraceutical and the pharmaceutical dose. EEG changes induced by SAMe were characterized by an increase in total power, a decrease in absolute and relative power in the delta/theta and slow alpha frequencies, an increase in absolute and relative power in the alpha-2 and beta frequencies as well as an acceleration of the alpha centroid and the centroid of the total power spectrum. The delta/theta and the beta centroid showed variable changes over time. The dominant alpha frequency was accelerated, the absolute and relative power in the dominant alpha frequency attenuated after SAMe as compared with placebo. These acute and subacute pharmaco-EEG findings in elderly subjects are typical of activating antidepressants. Time-efficacy calculations showed that acute oral administration of SAMe in both the nutraceutical and the pharmaceutical dose induced the pharmacodynamic peak effect in the first hour with a subsequent decline. The 3rd and 6th hours still showed a significant encephalotropic effect after the 1600 mg dose. The maximum EEG effect was noted after 2 weeks of oral administration of both 1600 mg/die and 400 mg/die. The superimposed dose induced significant encephalotropic effects in the 3rd hour after 400 mg and in the 3rd and 6th hours after 1600 mg as compared with pre-treatment. Dose-efficacy calculations showed that the pharmaceutical dose of 1600 mg had a more pronounced effect on the CNS than the nutraceutical dose of 400 mg, with both doses being superior to placebo. Psychometric tests concerning noopsychic and thymopsychic measures as well as critical flicker fusion frequency generally demonstrated a lack of differences between SAMe and placebo, which reflects a good tolerability of the drug in elderly subjects. This was corroborated by the findings on side effects, pulse and blood pressure.

S-adenosyl-methionine in depression: a comprehensive review of the literature

As many as 29% to 46% of patients with major depressive disorder (MDD) show only partial or no response to an adequate course of an antidepressant. The current practice is to increase the dose, switch to another antidepressant, or to combine the initial antidepressant with an antidepressant of a different class or a non-antidepressant agent. A growing number of studies have also been directed toward exploring the potential use of augmenting traditional antidepressants with nonpharmaceutic supplements, or even using such supplements as monotherapy for depression. S-adenosyl-methionine (SAMe) is one such compound. Compared with many other nonpharmaceutic supplements, SAMe has been extensively studied, and impressive literature extending back three decades suggests the antidepressant efficacy of SAMe. In the present work, the authors summarize the literature, focusing on the potential role of SAMe and its precursors in the pathophysiology of MDD, followed by a review of studies examining the use of SAMe for the treatment of MDD. Finally, the authors propose a model that would explain the actions of SAMe in the central nervous system.

Pulmonary inflammation and edema induced by phospholipase A2: global gene analysis and effects on aquaporins and Na+/K+-ATPase

Victims of snakebite quickly succumb to severe respiratory failure, which can be fatal if left untreated. One of the most toxic components of snake venom is phospholipase A2 (PLA2; EC 3.1.1.4). PLA2 isolated from the elapid, Naja sputatrix, induced pulmonary inflammation and edema when administered intravenously and intratracheally to rats. Analysis of pulmonary gene expression profiles using oligonucleotide microarrays revealed 60 genes whose expression was altered by at least 3-fold in response to intratracheal instillation of PLA2 for 3 h as compared with controls. In addition to genes encoding cytokines and chemokines responsible for inflammatory processes, the Na+/K+-ATPase gene has been found to be involved in edema formation. Real-time PCR, Western blot, and immunohistochemical analyses confirmed that the expression of AQP1 and AQP5 mRNAs and proteins was decreased. Besides providing an experimental model for studies on the pathophysiology of the lung, this investigation yields a clue to the mechanisms by which endogenous PLA2s could mediate inflammation in conditions such as allergy and rheumatoid arthritis.

Annexin I is an endogenous ligand that mediates apoptotic cell engulfment

Engulfment of apoptotic cells requires presentation of new cell surface ligands by the dying cells. Using a differential proteomics technology, we identify that annexin I is a caspase-dependent engulfment ligand; it is recruited from the cytosol and exported to the outer plasma membrane leaflet, colocalizes with phosphatidylserine, and is required for efficient clearance of apoptotic cells. Furthermore, phosphatidylserine receptor (PSR) clustering around apoptotic cells indicates a requirement for annexin I. In the nematode Caenorhabditis elegans, downregulation of the annexin homolog prevents efficient engulfment of pharyngeal cell corpses. These results provide novel mechanistic insights into how apoptotic cells are removed and may explain a pathogenic mechanism of chronic inflammatory diseases where annexin I autoantibodies have been described.

Investigation of antioxidant enzymes in children with autistic disorder

Impaired antioxidant mechanisms are unable to inactivate free radicals that may induce a number of pathophysiological processes and result in cell injury. Thus, any abnormality in antioxidant defence systems could affect neurodevelopmental processes and could have an important role in the etiology of autistic disorder. The plasma levels of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), and erythrocyte levels of GSH-Px were investigated in 45 autistic children and compared with 41 normal controls. Levels of erythrocyte SOD, erythrocyte and plasma GSH-Px were assayed spectrophotometrically. Activities of erythrocyte SOD, erythrocyte and plasma GSH-Px in autistic children were significantly lower than normals. These results indicate that autistic children have low levels of activity of blood antioxidant enzyme systems; if similar abnormalities are present in brain, free radical accumulation could damage brain tissue.

Biochemical markers related to Alzheimer's dementia in serum and cerebrospinal fluid

The diagnosis of Alzheimer's disease (AD) is currently based on clinical and neuropsychological examination. To date there is no blood test available that can discriminate dementia patients from healthy individuals. In the present paper, an overview of the current state of knowledge on biologic markers in serum (plasma) and CSF is presented. The combination of characteristic plaque markers tau and amyloid bèta may constitute a specific and sensitive CSF marker for AD. Glial fibrillary acidic protein and antibodies in CSF may be a marker for severe neurodegeneration. CSF concentrations of the oxidative stress markers 3-nitrotyrosine, 8-hydroxy-2'-deoxyguanosine and isoprostanes are increased in AD patients. Serum 24S-OH-cholesterol may be an early whereas glial fibrillary acidic protein autoantibody level may be a late marker for neurodegeneration. To date, serum alpha(1)-Antichymotripsin concentration is the most convincing marker for CNS inflammation. Increased serum homocysteine concentrations have also been consistently reported in AD. In summary, a large overlap in mean concentrations has been observed in studies comparing AD patients with healthy controls for single markers. These studies together support the theory of testing several serum markers in combination for the diagnosis of AD.

Nerve growth factor activates mast cells through the collaborative interaction with lysophosphatidylserine expressed on the membrane surface of activated platelets

Effect of nerve growth factor (NGF) on platelet-associated mast cell activation was investigated. Although neither NGF alone nor platelets alone induced significant 5-hydroxytriptamine (5-HT) release from rat peritoneal mast cells, marked 5-HT release was detected when costimulated with NGF and calcium ionophore-activated platelets. This response reached maximal levels as early as 5 min after the initiation of the coincubation and was completely blocked by anti-NGF Ab or by an inhibitor for a tyrosine kinase of the trkA NGF receptor. Paraformaldehyde-fixed platelets activated with either calcium ionophore or thrombin exhibited the collaborative ability, suggesting the possible involvement of some membrane molecules expressed on activated platelets in mast cell activation. Because activation of platelets induced expression of phosphatidylserine (PS) and/or lysoPS on membrane surface, and since lysoPS, unlike PS, initiated the NGF-induced 5-HT release, lysoPS expressed on activated platelets may be involved in the mast cell activation. Moreover, intradermal injection of NGF and activated platelets into the rat skin increased local vascular permeability. These findings suggested that NGF collaboratively worked with membrane lysoPS of activated platelets to induce mast cell activation. Thus, NGF released in response to inflammatory stimuli may contribute to mast cell activation in collaboration with locally activated platelets in the process of inflammations and tissue repair.

Methionine synthase. a possible prime site of the ethanolic lesion in liver

Among the most important pathways for liver integrity in the body are the two that synthesize methionine and S-adenosylmethionine (SAM) through methylation of homocysteine. Results of studies in this laboratory have demonstrated ethanolic inhibition of one of these pathways catalyzed by methionine synthetase. It has been shown elsewhere that alcohol per se does not inhibit the enzyme, but that the metabolite of ethanol, acetaldehyde, is responsible through the formation of an inhibiting covalent adduct. Because hepatic SAM has been shown to be essential in the transport of fat from the liver, avoiding steatosis and further liver damage, it is entirely feasible that this repression of methionine synthase is an important site of the injurious action of alcohol metabolism in the liver. This loss of activity is particularly important in human beings who cannot produce methionine and SAM by means of the alternate pathway mediated by betaine:homocysteine:transmethylase, because of the lack of production of the betaine substrate for this enzyme.

A new category of psychotropic drugs: neuroactive lipids as exemplified by ethyl eicosapentaenoate (E-E)

New treatments for psychiatric disorders are urgently required. Recent reviews show that there have been no improvements in efficacy of drugs for either affective disorders or schizophrenia since the first compounds were introduced over 40 years ago. Neuroactive lipids represent an entirely novel class of psychotropic compounds. Ethyl eicosapentaenoate is the first example of this group. Placebo-controlled studies have found it to be effective in depression, in treatment-unresponsive schizophrenia and in tardive dyskinesia. It is extremely well tolerated with none of the usual side-effects of either antidepressants or neuroleptics. It probably works by modulating postreceptor signal transduction processes.

Neuropathological features of mitochondrial disorders

Genetic defects affecting the mitochondrial respiratory chain comprise an important cause of encephalomyopathies. Considering the structural complexity of the respiratory chain, its dual genetic control, and the numerous nuclear genes required for proper assembly of the enzyme complexes, the phenotypic heterogeneity is not surprising. From a neuropathological view point, application of in situ hybridization and immunohistochemistry to study the choroid plexus and brain-blood barrier in "prototypes" of mitochondrial encephalopathies have revealed alterations that we think are important in the pathogenesis of central nervous system dysfunction in these disorders. As the role of the blood-cerebrospinal fluid (CSF) and brain-blood barriers in mitochondrial encephalopathies is better understood, manipulation of their functions offers promises for therapeutic interventions.

The first product of phospholipid N-methylation, phosphatidylmonomethylethanolamine, is a lipid mediator for progesterone action at the amphibian oocyte plasma membrane

Progesterone has been shown to act at plasma membrane receptors on the amphibian oocyte to trigger a cascade of changes in membrane phospholipids and to initiate the G(2)/M transition of the first meiotic division. The earliest event (0-1 min) is the transient N-methylation of phosphatidylethanolamine (PE) to form phosphatidylmonomethylethanolamine (PME), demonstrated using [(3)H]glycerol to prelabel oocyte plasma membrane PE. [(3)H]Glycerol-labeled PME rises 10-fold within the 1-2 min after exposure to progesterone and accounts for conversion of about 50% of the [3H]Glycerol-labeled PE. [(3)H]PME levels slowly decline over the following 10-30 min. [(3)H] or [(14)C] labeled fatty acid experiments showed that newly formed PME is enriched in linoleic or palmitic, but not in arachidonic acid, indicating that specific PE pools undergo progesterone-induced N-methylation. Two plasma membrane changes: activation of serine protease, and Ca(2+) release from the oocyte surface coincide with PME formation; both are prevented by pretreatment of oocytes with the N-methylation inhibitor, 2-methylaminoethane. Media containing PME micelles release both protease and Ca(2+) from intact oocytes within the first 1-2 min. The immediate downstream metabolites of PME, PDE and PC, do not induce serine protease activity or Ca(2+) release. We conclude that progesterone initially activates N-methyltransferase in the oocyte plasma membrane, and that the first product, PME, is responsible for activation of serine protease in the plasma membrane and the release of Ca(2+) from the oocyte surface.

Protein kinase C regulates dopamine D4 receptor-mediated phospholipid methylation

Dopamine D4 receptors (D4 receptors) mediate dopamine-stimulated, folate-dependent phospholipid methylation. To investigate possible regulation of this multi-step D4 receptor-mediated phospholipid methylation cycle by protein kinases, specific kinase activators and inhibitors were studied in SK-N-MC human neuroblastoma cells, using [14C] formate to label folate-derived single-carbon groups. Phorbol dibutyrate (PDB), an activator of protein kinase C, stimulated basal phospholipid methylation and also shifted the dose-response curve for dopamine-stimulated phospholipid methylation to the right by more than an order of magnitude. Calphostin C, an inhibitor of protein kinase C, had little effect on basal phospholipid methylation but significantly inhibited dopamine-stimulated phospholipid methylation and also blocked the stimulatory response to PDB. Chelerythrine, which inhibits protein kinase C and other kinases, strongly inhibited both basal and dopamine-stimulated phospholipid methylation. Forskolin, an activator of protein kinase A, inhibited basal and dopamine-stimulated phospholipid methylation, but only at high concentrations while Rp-cAMP, an inhibitor of protein kinase A, did not block this effect. Inhibition of protein kinase G produced a modest decrease in dopamine-stimulated phospholipid methylation, but neither sodium nitroprusside, which increases nitric oxide (NO) production and activates protein kinase G, nor the NO synthase inhibitor N-nitro-L-arginine had any effect on basal or dopamine-stimulated phospholipid methylation. These observations indicate that protein kinase C is an important regulator of basal and D4 receptor-mediated folate-dependent phospholipid methylation, whereas protein kinase A and protein kinase G have a lesser or minimal role.

1-Methyl-4-phenyl-pyridinium increases S-adenosyl-L-methionine dependent phospholipid methylation

1-Methyl-4-phenyl-pyridinium (MPP(+)) and S-adenosyl-L-methionine (SAM) cause Parkinson's disease (PD)-like changes. SAM and MPP(+) require their charged S-methyl and N-methyl groups, so the PD-like symptoms may be related to their ability to modulate the methylation process. The SAM-dependent methylation of phosphatidylethanolamine (PTE) to produce phosphatidylcholine (PTC), via phosphatidylethanolamine-N-methyltransferase (PEMT), and the hydrolysis of PTC to form lyso-PTC, a cytotoxic agent, are potential loci for the action of MPP(+). In this study, the effects of MPP(+) on the methylation of PTE to PTC and the production of lyso-PTC were determined. The results showed that SAM increased PTC and lyso-PTC. The rat striatum showed the highest PEMT activity and lyso-PTC formation, which substantiate with the fact that the striatum is the major structure that is affected in PD. MPP(+) significantly enhanced PEMT activity and the formation of lyso-PTC in the rat liver and brain. MPP(+) increased the affinity and the V(max) of PEMT for SAM. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) effect was lesser and inhibited by deprenyl (MAO-B inhibitor). The nor-methyl analogs of MPP(+) were inactive, but some of the charged analogs of MPP(+) showed comparable effects to those of MPP(+). Lyso-PTC that can be increased by SAM and MPP(+) caused severe impairments of locomotor activities in rats. These results indicate that SAM and MPP(+) have complementary effects on phospholipid methylation. Thus, SAM-induced hypermethylation could be involved in the etiology of PD and an increase of phospholipid methylation could be one of the mechanisms by which MPP(+) causes parkinsonism.

Betaine, a promising new agent for patients with nonalcoholic steatohepatitis: results of a pilot study

OBJECTIVES

No effective therapy currently exists for patients with nonalcoholic steatohepatitis (NASH). Betaine, a naturally occurring metabolite of choline, has been shown to raise S-adenosylmethionine (SAM) levels that may in turn play a role in decreasing hepatic steatosis. Our aim was to determine the safety and effects of betaine on liver biochemistries and histological markers of disease activity in patients with NASH.

METHODS

Ten adult patients with NASH were enrolled. Patients received betaine anhydrous for oral solution (Cystadane) in two divided doses daily for 12 months. Seven out of 10 patients completed 1 yr of treatment with betaine.

RESULTS

A significant improvement in serum levels of aspartate aminotransferase (p = 0.02) and ALAT (p = 0.007) occurred during treatment. Aminotransferases normalized in three of seven patients, decreased by >50% in three of seven patients, and remained unchanged in one patient when compared to baseline values. A marked improvement in serum levels of aminotransferases (ALT -39%; AST -38%) also occurred during treatment in those patients who did not complete 1 yr of treatment. Similarly, a marked improvement in the degree of steatosis, necroinflammatory grade, and stage of fibrosis was noted at 1 yr of treatment with betaine. Transitory GI adverse events that did not require any dose reduction or discontinuation of betaine occurred in four patients.

CONCLUSIONS

Betaine is a safe and well tolerated drug that leads to a significant biochemical and histological improvement in patients with NASH. This novel agent deserves further evaluation in a randomized, placebo-controlled trial.

1H- and (31)P-MR spectroscopy of primary and recurrent human brain tumors in vitro: malignancy-characteristic profiles of water soluble and lipophilic spectral components

In vitro NMR spectroscopy was performed on specimen of human brain tumors. From all patients, tissue samples of primary tumors and their first recurrences were examined. (31)P- and (1)H-spectra were recorded from samples of meningioma, astrocytoma and glioblastoma. A double extraction procedure of the tissue samples permitted acquisition of information from the membrane fraction and from the cytosolic fraction. (31)P-spectra were used to analyze the lipophilic fraction (phospholipids of the membrane) of the tissue extracts, while the (1)H-spectra reflected information on the metabolic alterations of the hydrophilic, cytosolic fraction of the tissue. The tumor types showed distinctive spectral patterns in both the (31)P- and the (1)H-spectra. Based on the total detectable (31)P signal, the level of phosphatidylcholine was about 34% lower in primary astrocytomas than in primary glioblastomas (p = 0.0003), whereas the level of sphingomyelin was about 45% lower in primary glioblastomas than in primary astrocytomas (p = 0.0061). A similar tendency of these phospholipids was observed when comparing primary and recurrent astrocytoma samples from the same individuals [+15% (p = 0.0103) and -23% (p = 0.0314) change, respectively]. (1)H-spectra of gliomas were characterized by an increase of the ratios of alanine, glycine and choline over creatine as a function of the degree of malignancy. In agreement with findings in the (31)P-spectra, the (1)H-spectra of recurrent astrocytomas showed metabolic profiles of increased malignancy in comparison to their primary occurrence. Since gliomas tend to increase in malignancy upon recurrence, this may reflect evolving tumor metabolism. (1)H-spectra of meningiomas showed the highest ratio of alanine over creatine accompanied by a near absence of myo-inositol. Phospholipid profiles of meningiomas showed higher fractional contents of phosphatidylcholine along with lower phosphatidylserine compared to astrocytomas, while higher phosphatidylethanolamine and sphingomyelin fractional contents distinguished meningiomas from glioblastomas. The extraction method being used in this study combined with high-resolution (1)H- and (31)P-MRS provides a wide range of biochemical information, which enables differentiation not only between tumor types but also between primary and recurrent gliomas, reflecting an evolving tumor metabolism.

Relationship between dopamine-stimulated phospholipid methylation and the single-carbon folate pathway

In a previous study we demonstrated the ability of dopamine (DA) to stimulate phospholipid methylation (PLM) via a novel mechanism involving the D4 dopamine receptor (D4R) in which single-carbon folates appeared to be the primary source of methyl groups. To further understand the relationship between D4R-mediated PLM and folate metabolism, we examined the effect of several folate pathway interventions on the level of basal and DA-stimulated incorporation of [14C]-labeled formate into phospholipids in cultured SH-SY5Y neuroblastoma cells. These interventions included: (i) Overexpression of methenyltetrahydrofolate synthetase (MTHFS). (ii) Treatment with 5-formylTHF. (iii) Treatment with the MTHFS inhibitor 5-formyltetrahydrohomofolic acid (5-formylTHHF). (iv) Growth in nucleoside-free media. 31P-NMR was also used to follow DA-induced changes in cell phospholipid composition. MTHFS overexpression and 5-formylTHHF treatment, both of which lower 5-methylTHF levels, each reduced basal PLM and its stimulation by DA. In contrast, 5-formylTHF, which increases 5-methylTHF, caused a dose-dependent increase in both basal and DA-stimulated PLM. Growth in nucleoside-free media caused time-dependent changes in PLM, which were due to the absence of purine nucleosides. While basal PLM was maintained at a reduced level, DA-stimulated PLM was initially increased followed by a later decrease. Together, these findings indicate a close functional relationship between single-carbon folate metabolism and DA-stimulated PLM, consistent with a role for 5-methylTHF as the methyl donor for the D4R-mediated process.

E1 mice epilepsy shows genetic polymorphism for S-Adenosyl-L-homocysteine hydrolase

E1 mice are an animal model of human epilepsy (idiopathic complex partial seizures). We have previously demonstrated abrupt poly(A)(+) RNA expression in liver from 1-day-old E1 mouse [Mita et al., 1991. Devl. Brain Res. 64, 27-35]. In the present study, we constructed a cDNA library of the poly(A)(+) RNA. By analyzing cDNA clones and nucleotide sequences, we found a clone that was homologous to a rat gene of S-adenosyl-L-homocysteine hydrolase (EC 3.3.1.1.) (SAHH) (a key enzyme in the active methyl transfer pathway) and showed the gene polymorphism/RFLP(PstI) between the epileptic strain, E1, and the non-epileptic mother strain, ddY, as indicated in a gel electrophoresis by cleaving 2.6 kb with PstI into 1.9 kb and 0.7 kb fragment bands. F1(E1xddY) showed the heterozygosity. An attempt to determine the mutation on the genomic SAHH gene in the E1 disclosed a single nucleotide polymorphism indicated by a C-->T transition in the 8th intron, by which the PstI site was created. SAHH enzymatic activity in the liver in 1-day-old E1 mice was slight (approximately 10%), and in fact was significantly lower than that of the control ddY. Results suggested that the abrupt primary mRNA transcribed on the SAHH gene in the liver of 1-day-old E1 mice was processed partially or incompletely because of the presence of the point mutation in the intron. Accordingly, poor energy supply by the insufficient SAHH enzymatic activity in the brain postnatally may be responsible for epileptogenesis in this animal model. It is concluded that a single nucleotide SAHH gene polymorphism may be associated with epilepsy in E1 mice.

Electrospray ionization mass spectrometry analysis of lysophospholipids in human ascitic fluids: comparison of the lysophospholipid contents in malignant vs nonmalignant ascitic fluids

Lysophospholipids (lyso-PLs), including various glycerol-based and sphingosine-based lysophospholipids, play important roles in many biochemical, physiological, and pathological processes. The classical methods to analyze these lipids involve gas chromatography and/or high-performance liquid chromatography, which are time-consuming, cumbersome, and sometimes inaccurate due to the incomplete separation of closely related lipid species. We now describe the quantitative analysis of lyso-PLs in ascites samples from patients with ovarian cancer using electrospray ionization spectrometry. Three new classes of lyso-PL molecules are detected: alkyl-LPA, alkenyl-LPA, and methylated lysophosphatidylethanolamine. Importantly, the following lysophospholipid species are significantly increased in ascites from patients with ovarian cancer, compared to patients with nonmalignant diseases (e.g., liver failure): LPA (including acyl-, alkyl-, and alkenyl-LPA species), lysophosphatidylinositol, and sphingosylphosphorylcholine. Lysophosphorylcholine contents are also significantly different among ascitic fluids from the two groups of patients. However, the total phosphate content in ascites samples from patients with ovarian cancer is not significantly different compared to that from patients with nonmalignant disease.

ALCOHOL: its metabolism and interaction with nutrients

In the past, alcoholic liver disease was attributed exclusively to dietary deficiencies, but experimental and judicious clinical studies have now established alcohol's hepatotoxicity. Despite an adequate diet, it can contribute to the entire spectrum of liver diseases, mainly by generating oxidative stress through its microsomal metabolism via cytochrome P4502E1 (CYP2E1). It also interferes with nutrient activation, resulting in changes in nutritional requirements. This is exemplified by methionine, one of the essential amino acids for humans, which needs to be activated to S-adenosylmethionine (SAMe), a process impaired by liver disease. Thus, SAMe rather than methionine is the compound that must be supplemented in the presence of significant liver disease. In baboons, SAMe attenuated mitochondrial lesions and replenished glutathione; it also significantly reduced mortality in patients with Child A or B cirrhosis. Similarly, decreased phosphatidylethanolamine methyltransferase activity is associated with alcoholic liver disease, resulting in phosphatidylcholine depletion and serious consequences for the integrity of membranes. This can be offset by polyenylphosphatidylcholine (PPC), a mixture of polyunsaturated phosphatidylcholines comprising dilinoleoylphosphatidylcholine (DLPC), which has high bioavailability. PPC (and DLPC) opposes major toxic effects of alcohol, with down-regulation of CYP2E1 and reduction of oxidative stress, deactivation of hepatic stellate cells, and increased collagenase activity, which in baboons, results in prevention of ethanol-induced septal fibrosis and cirrhosis. Corresponding clinical trials are ongoing.

The mechanism for lindane-induced inhibition of steroidogenesis in cultured rat Leydig cells

The in vitro effect of the gamma-isomer of hexachlorocyclohexane, lindane, on rat Leydig cell steroidogenesis was studied. Leydig cells from mature male rats were incubated with human chorionic gonadotropin (hCG, 1 IU) for 3 h at 34 degrees C in the presence of different doses of lindane (2-200 microg/ml; 2-200 ppm). Results demonstrate that lindane produces a dose-dependent inhibition of testosterone production in hCG-stimulated Leydig cells. The decreased testosterone synthesis was accompanied with a half-reduced LH/hCG receptor number without any modification in the K(d) value. In addition, lindane also decreased cAMP production. These effects were not due to a detrimental action of lindane on cell viability. Results of this study demonstrate a direct inhibitory action of lindane on testicular steroidogenesis, at least in part, through a reduction in the classical second messenger production involved in this pathway.

Hepatic, metabolic, and nutritional disorders of alcoholism: from pathogenesis to therapy

Much progress has been made in the understanding of the pathogenesis of alcoholic liver disease, resulting in an improvement in treatment. Nutritional deficiencies should be corrected when present but, because of the alcohol-induced disease process, some of the nutritional requirements change. For instance, methionine, one of the essential amino acids for humans, must be activated to S-adenosylmethionine (SAMe), but, in severe liver disease, the activity of the corresponding enzyme is depressed. Therefore, the resulting deficiencies and associated pathology can be attenuated by the administration of SAMe, but not by methionine. Similarly, phosphatidylethanolamine methyltransferase (PEMT) activity, which is important for hepatic phosphatidylcholine (PC) synthesis, is also depressed in alcoholic liver disease, therefore calling for the administration of the products of the reaction. Inasmuch as free radical generation by the ethanol-induced CYP2E1 plays a key role in the oxidative stress, inhibitors of this enzyme have great promise and PPC, which is presently being evaluated clinically, is particularly interesting because of its innocuity. In view of the striking negative interaction between alcoholic liver injury and hepatitis C, an antiviral agent is eagerly awaited that, unlike Interferon, is not contraindicated in the alcoholic. Antiinflamatory agents may also be useful. In addition to steroids, down-regulators of cytokines and endotoxin are being considered. Finally, anticraving agents such as naltrexone or acamprosate should be incorporated into any contemplated therapeutic cocktail.

Prebiotic methylation and the evolution of methyl transfer reactions in living cells

An hypothesis is presented for the prebiotic origin of methyl groups and the evolution of methyl transfer reactions in living cells. This hypothesis, described in terms of prebiotic and early biotic chemical evolution, is based on experimental observations in our lab and in those of others, and on the mechanisms of enzymatic methyl transfer reactions that occur in living cells. Of particular interest is our demonstration of the reductive methylation of ethanolamine and glycine in aqueous solution by excess formaldehyde. These reactions, involving prebiotic compounds and conditions, are mechanistically analogous to the de novo origin of methyl groups in modern cells by reduction of methylene tetrahydrofolate. Furthermore, modern cellular methyl transfers from S-adenosylmethionine to amine nitrogen may involve formaldehyde as an intermediate and subsequent reductive methylation, analogous to the prebiotic chemistry observed herein.

NMR structure of antibiotics plipastatins A and B from Bacillus subtilis inhibitors of phospholipase A(2)

Plipastatins A and B are antifungal antibiotics belonging to a family of lipopeptides capable of inhibiting phospholipase A(2) (PLA(2)) and are biosynthesised under certain circumstances by Bacillus subtilis. U-(15)N plipastatins A and B were obtained from cultures of the strain NCIB 8872 on a Landy medium modified for stable-isotope labelling by the substitution of the L-glutamic acid used as the sole nitrogen source, by (15)NH(4)Cl. These two lipo-decapeptides, lactonised by esterification of the Ile10 C-terminus with the phenolic hydroxyl of Tyr3, differ only by a D-Ala (plipastatin A)/D-Val (plipastatin B) substitution at the position 6. The (1)H- and (15)N-nuclear magnetic resonance (NMR) signals of a 4:6 mixture of plipastatins A and B were unambiguously assigned and their structures in dimethylsulfoxide solution were calculated on the basis of a set of NMR-derived restraints. Plipastatins A and B are well-defined structures in solution stabilised by a type 1 beta-turn comprising residues 6-9 and several other specific hydrogen bonds. The structures afford a first molecular basis for the future studies of their biological activities both in lipidic layers or on PLA(2).

S-Adenosyl-Methionine improves depression in patients with Parkinson's disease in an open-label clinical trial

We report a pilot study of S-adenosyl-methionine (SAM) in 13 depressed patients with Parkinson's disease. All patients had been previously treated with other antidepressant agents and had no significant benefit or had intolerable side effects. SAM was administered in doses of 800 to 3600 mg per day for a period of 10 weeks. Eleven patients completed the study, and 10 had at least a 50% improvement on the 17-point Hamilton Depression Scale (HDS). One patient did not improve. Two patients prematurely terminated participation in the study because of increased anxiety. One patient experienced mild nausea, and another two patients developed mild diarrhea, which resolved spontaneously. The mean HDS score before treatment was 27.09 +/- 6.04 (mean +/- standard deviation) and was 9.55 +/- 7.29 after SAM treatment (p < 0.0001). Although uncontrolled and preliminary, this study suggests that SAM is well tolerated and may be a safe and effective alternative to the antidepressant agents currently used in patients with Parkinson's disease.

On the in vitro vasoactivity of bile acids

We compared the vasorelaxant action of nine different bile acids and correlated their vasorelaxant activity with their individual indices for hydrophobicity or lipophilicity. Vasorelaxant activity correlated with the relative lipid solubility of bile acids with lipophilic bile acids exhibiting the greatest vasorelaxant activity with modest to no vasorelaxant activity exhibited by hydrophilic bile acids. We also investigated whether bile acid-induced vasorelaxation is mediated by antagonism of a prototypal contractile receptor, the alpha(1)-adrenoceptor, by stimulation of a bile acid surface membrane receptor, by the release of endothelium-derived relaxant factors, by promoting the generation of reactive oxygen species and increasing the extent of lipid peroxidation, or by modifying membrane fluidity. Lipophilic bile acids induce vasorelaxation possibly by antagonizing alpha(1)-adrenoceptors, a phenomenon that manifests itself as a lowering of the affinity of vascular alpha(1)-adrenoceptors. Bile acid-induced vasorelaxation was not dependent upon stimulation of a bile acid surface membrane receptor or the release of endothelium-derived relaxant factors. Lipophilic bile acids can also increase the extent of lipid peroxidation with a subtle reduction in the fluidity of rat vascular smooth muscle membranes not associated with loss of membrane cholesterol or phospholipid. We have concluded that lipophilic bile acids are non-selective vasorelaxants whose mechanism of action is a multifaceted process involving antagonism of contractile surface membrane receptors possibly effected by an increased extent of lipid peroxidation and/or membrane fluidity but occurs independent of the release of endothelial-derived relaxant factors or stimulation of a surface membrane bile acid binding site.

Kearns-sayre syndrome: oncocytic transformation of choroid plexus epithelium

Kearns-Sayre syndrome (KSS) is a sporadic multisystem disorder due to a defect of oxidative phosphorylation and associated with clonally-expanded rearrangements of mitochondrial DNA (mtDNA) deletions (Delta-mtDNAs) and/or duplications (dup-mtDNAs). To gain further insight into the pathogenesis of CNS dysfunction in KSS, we studied the choroid plexus from two autoptic cases using in situ hybridization (ISH) of mtDNA, and immunohistochemistry to detect mtDNA and nuclear DNA-encoded subunits of the respiratory chain. Neuropathological examination of both cases showed oncocytic transformation of choroid plexus epithelial cells. In the same cells, ISH demonstrated that the predominant species of mtDNA were Delta-mtDNAs, and immunohistochemistry showed a decreased expression of mtDNA-encoded proteins. We suggest that mitochondrial abnormalities due to the presence of abundant Delta-mtDNAs in the choroid plexus play an important role in causing the increased cerebrospinal fluid (CSF) protein and reduced folic-acid levels that are characteristic of KSS.

Nitric oxide and peroxynitrite anion modulate liver plasma membrane fluidity and Na(+)/K(+)-ATPase activity

Free radicals attack membranes and frequently alter their fluidity and function. The aim of the present work was to study the effect of nitric oxide (NO) radical and peroxynitrite anion on basolateral liver plasma membrane fluidity and on the activity of Na(+)/K(+)-ATPase. Basolateral membranes (BM) were isolated by ultracentrifugation in sucrose gradients and characterized enzymatically. BM were incubated with SNAP (a NO donor) or SIN-1 (a peroxynitrite donor). The release of NO or peroxynitrite was monitored by measuring NO(-)(2) + NO(-)(3). Relative fluidity was measured by polarization of fluorescence. NO increased membrane fluidity while peroxynitrite decreased it in a concentration-dependent manner. Na(+)/K(+)-ATPase activity was reduced by NO or peroxynitrite. Peroxynitrite anion inhibits ATPase activity in part by decreasing fluidity. However, it is very likely that both compounds inhibit ATPase activity by oxidation of the thiol groups of the enzyme. Our results suggest that NO may exert part of its biological effects by modulating membrane fluidity and function.

The effects of bile acids on beta-adrenoceptors, fluidity, and the extent of lipid peroxidation in rat cardiac membranes

Bile acids have been proposed as a causative factor for the cardiomyopathy of cholestatic liver disease, since they cause negative inotropism and chronotropism and attenuate cardiac responsiveness to sympathetic stimulation. Bile acids can also modify membrane fluidity and generate reactive oxygen species (ROS). The effects of 10(-6)-10(-3) M deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA) and their taurine conjugates, TDCA and TCDCA, on (1) the binding characteristics of beta-adrenoceptors, (2) membrane fluidity, and (3) the extent of lipid peroxidation in rat cardiac membranes were assessed. The results were compared to the effects of the oxidant, 10(-4)-10(-3) M hydrogen peroxide (H(2)O(2)), and the membrane-fluidizing compound, 5 x 10(-5) M 2-(2-methoxyethoxy)ethyl 8-(cis-2-n-octylcyclopropyl)octanoate (A(2)C). Cardiac beta-adrenoceptor density alone was reduced at 10(-4) M bile acid concentration while, at 10(-3) M bile acids, reductions in both receptor density and affinity were seen. At 10(-4) M H(2)O(2), receptor number and affinity were reduced, whereas A(2)C increased receptor affinity without affecting receptor density. Bile acids (10(-3) M) and 10(-4) M H(2)O(2) reduced membrane fluidity. H(2)O(2) caused a concentration-dependent increase in the extent of lipid peroxidation, whereas the bile acids and A(2)C had no effect. Bile acids (10(-4) M) reduced beta-adrenoceptor density in the absence of variations in membrane fluidity and in the extent of membrane lipid peroxidation. This result suggests that bile acids, at concentrations equivalent to the plasma/serum total or estimated free bile acid concentration, may have a possible role in the etiology of cardiomyopathy of cholestatic liver disease. At 10(-3) M bile acid concentration, beta-adrenoceptor number and affinity were adversely affected, accompanied by a decrease in membrane fluidity but without any significant increase in the extent of membrane lipid peroxidation. Although cardiac beta-adrenoceptor density and affinity and membrane fluidity were adversely affected by bile acids, the relevance of these findings to our understanding of the etiological basis of hepatic cardiomyopathy is questionable, since such concentrations exceeded the highest concentrations seen in the plasma and/or tissues of patients with cholestatic liver disease.

Can nutrient supplements modify brain function?

Over the past 40 y, several lines of investigation have shown that the chemistry and function of both the developing and the mature brain are influenced by diet. Examples are the effect of folate deficiency on neural tube development during early gestation, the influence of essential fatty acid deficiency during gestation and postnatal life on the development of visual function in infants, and the effects of tryptophan or tyrosine intake (alone or as a constituent of dietary protein) on the production of the brain neurotransmitters derived from them (serotonin and the catecholamines, respectively). Sometimes the functional effects are clear and the underlying biochemical mechanisms are not (as with folate and essential fatty acids); in other cases (such as the amino acids tyrosine and tryptophan), the biochemical effects are well understood, whereas the effect on brain function is not. Despite the incomplete knowledge base on the effects of such nutrients, investigators, physicians, and regulatory bodies have promoted the use of these nutrients in the treatment of disease. Typically, these nutrients have been given in doses above those believed to be required for normal health; after they have been given in pure form, unanticipated adverse effects have occasionally occurred. If this pharmacologic practice is to continue, it is important from a public safety standpoint that each nutrient be examined for potential toxicities so that appropriate purity standards can be developed and the risks weighed against the benefits when considering their use.

Reduction of carbon tetrachloride-induced hepatotoxic effects by oral administration of betaine in male Han-Wistar rats: a morphometric histological study

Eighty-five male Han-Wistar rats were arranged into three groups: CCl4-exposed rats, CCl4 + betaine-exposed rats, and control rats. To see the effect of betaine alone, five rats of the control and of the CCl4 + betaine groups were sacrificed after 7 days, before exposure to CCl4. After that, two of the groups (the CCl4 and CCl4 + betaine groups) were exposed to CCl4 (1 ml/kg per day subcutaneously [SC] for 4 consecutive days), and one of the groups (control group) was given olive oil (1 ml/kg per day SC for 4 consecutive days). At the start of the study (day 0), day 1, day 2, day 3, day 4, and 3 days after the last CCl4 and olive oil injections (day 7), samples of five rats per group were sacrificed, and the livers were taken for chemical analyses and histological examination. Oral betaine, after the acclimation period of a week, increased the number of mitochondria but not mitochondria size (day 0), compared with the case in control rats. Exposure to CCl4 resulted in centrilobular hepatic steatosis, and the administration of betaine significantly reduced this. Morphometric analyses also revealed that the addition of betaine increased the volume density of rough endoplasmic reticulum (RER) in the perinuclear areas of liver cell cytoplasm (day 7). Additionally, the administration of betaine prevented the reduction of Golgi complexes and mitochondrial figures in the cytoplasm observed after the exposures to CCl4. Also, the volume density of mitochondria was smallest in the CCl4-group, but the difference was not statistically significant. The results indicate that oral betaine either improves recovery or reduces the toxic effects of CCl4 on cell organelles in liver cells of male Han-Wistar rats.

Alcoholic liver disease: new insights in pathogenesis lead to new treatments

Much progress has been made in the understanding of the pathogenesis of alcoholic liver disease, resulting in improvement of prevention and therapy, with promising prospects for even more effective treatments. The most successful approaches that one can expect to evolve are those that deal with the fundamental cellular disturbances resulting from excessive alcohol consumption. Two pathologic concepts are emerging as particularly useful therapeutically. Whereas it continues to be important to replenish nutritional deficiencies, when present, it is crucial to recognize that because of the alcohol-induced disease process, some of the nutritional requirements change. This is exemplified by methionine, which normally is one of the essential amino acids for humans, but needs to be activated to S-adenosylmethionine (SAMe), a process impaired by the disease. Thus, SAMe rather than methionine is the compound that must be supplemented in the presence of significant liver disease. Indeed, SAMe was found to attenuate mitochondrial lesions in baboons, replenish glutathione, and significantly reduce mortality in patients with Child A or B cirrhosis. Similarly, polyenylphosphatidylcholine (PPC) corrects the ethanol-induced hepatic phospholipid depletion as well as the decreased phosphatidylethanolamine methyltransferase activity and opposes oxidative stress. It also deactivates hepatic stellate cells, whereas its dilinoleoyl species (DLPC) increases collagenase activity, resulting in prevention of ethanol-induced septal fibrosis and cirrhosis in the baboon. Clinical trials with PPC are ongoing in patients with alcoholic liver disease. Furthermore, enzymes useful for detoxification, such as CYP2E1, when excessively induced, become harmful and should be downregulated. PPC is one of the substances with anti-CYP2E1 properties that is now emerging. Another important aspect is the association of alcoholic liver disease with hepatitis C: a quarter of all patients with alcoholic liver disease also have markers of HCV infection, with an even higher incidence in some urban areas but, at present, no specific therapy is available since interferon is contraindicated in that population. However, in addition to antiviral medications, agents that oppose oxidative stress and fibrosis should also be tested for hepatitis C treatment since these two processes contribute much to the pathology and mortality associated with the virus. In addition to antioxidants (such as PPC, silymarin, alpha-tocopherol and selenium), anti-inflammatory medications (corticosteroids, colchicine, anticytokines) are also being tested as antifibrotics. Transplantation is now accepted treatment in alcoholics who have brought their alcoholism under control and who benefit from adequate social support but organ availability is still the major limiting factor and should be expanded more aggressively. Finally, abstinence from excessive drinking is always indicated; it is difficult to achieve but agents that oppose alcohol craving are becoming available and they should be used more extensively.

Localization of S-adenosylhomocysteine hydrolase in the rat kidney

S-adenosylhomocysteine (SAH) hydrolase is a cytosolic enzyme present in the kidney. Enzyme activities of SAH hydrolase were measured in the kidney in isolated glomeruli and tubules. SAH hydrolase activity was 0.62 +/- 0.02 mU/mg in the kidney, 0.32 +/- 0.03 mU/mg in the glomeruli, and 0.50 +/- 0.02 mU/mg in isolated tubules. Using immunohistochemical methods, we describe the localization of the enzyme SAH hydrolase in rat kidney with a highly specific antibody raised in rabbits against purified SAH hydrolase from bovine kidney. This antibody crossreacts to almost the same extent with the SAH hydrolase from different species such as rat, pig, and human. Using light microscopy, SAH hydrolase was visualized by the biotin-streptavidin-alkaline phosphatase immunohistochemical procedure. SAH hydrolase immunostaining was observed in glomeruli and in the epithelium of the proximal and distal tubules. The collecting ducts of the cortex and medulla were homogeneously stained. By using double immunofluorescence staining and two-channel immunofluorescence confocal laser scanning microscopy, we differentiated the glomerular cells (endothelium, mesangium, podocytes) and found intensive staining of podocytes. Our results show that the enzyme SAH hydrolase is found ubiquitously in the rat kidney. The prominent staining of SAH hydrolase in the podocytes may reflect high rates of transmethylation. (J Histochem Cytochem 48:211-218, 2000)

Tumour phospholipid metabolism

Following the impetus of early clinical and experimental investigations, in vivo and in vitro MRS studies of tumours pointed in the eighties to the possible significance of signals arising from phospholipid (PL) precursors and catabolites as novel biochemical indicators of in vivo tumour progression and response to therapy. In the present decade, MRS analyses of individual components contributing to the 31P PME (phosphomonoester) and PDE (phosphodiester) resonances, as well as to the 1H 'choline peak', have reinforced some of these expectations. Moreover, the absolute quantification of these signals provided the basis for addressing more specific (although still open) questions on the biochemical mechanisms responsible for the formation of intracellular pools of PL derivatives in tumours, under different conditions of cell proliferative status and/or malignancy level. This article is aimed at providing an overview on: (a) quantitative MRS measurements on the contents of phosphocholine (PCho), phosphoethanolamine (PEtn) and their glycerol derivatives ģlycerol 3-phosphocholine (GPC) and glycerol 3-phosphoethanolamine (GPE)[ in human tumours and cells (with particular attention to breast and brain cancer and lymphomas), as well as in normal mammalian tissues (including developing organs and rapidly proliferating tissues); (b) possible correlations of MRS parameters like PEtn/PCho and PCho/GPC ratios with in vitro cell growth status and/or cell tumorigenicity; and (c) current and new hypotheses on the role and interplay of biosynthetic and catabolic pathways of the choline and ethanolamine cycles in modulating the intracellular sizes of PCho and PEtn pools, either in response to mitogenic stimuli or in relation to malignant transformation.