Fatty acid ethyl esters, nonoxidative metabolites of ethanol, accelerate the kinetics of activation of the human brain delayed rectifier K+ channel, Kv1.1

FASD: folic acid and formic acid — an unholy alliance in the alcohol abusing mother

Alcohol consumption during pregnancy remains a significant cause of preventable birth defects and developmental disabilities; however, the mechanism of toxicity remains unclear. Methanol is present as a congener in many alcoholic beverages and is formed endogenously. Because ethanol is preferentially metabolized over methanol, it has been found in the sera and cerebro-spinal fluid of alcoholics. Toxicity resulting from methanol has been attributed to formic acid. Formic acid is present in significantly higher quantities in the biofluids of alcoholics. These higher levels can be cytotoxic and cause neuronal cell death. However, the adverse effects can be mitigated by adequate levels of hepatic folic acid, because formic acid elimination depends on folic acid. During pregnancy, folate concentrations are at least 2-fold higher in cord blood then in maternal blood, owing to increased folate requirements. The reverse has been demonstrated in pregnancies with alcohol abuse, suggesting downregulation of folate transporters and low fetal folate levels. Moreover, formic acid can cross the placenta and its adverse effects can be mitigated by folic acid. Thus, the combination of low fetal folate levels and presence of formic acid form a potent cytotoxic combination that may play a significant role in the etiology of fetal alcohol spectrum disorder.

Alkanols inhibit voltage-gated K(+) channels via a distinct gating modifying mechanism that prevents gate opening

Alkanols are small aliphatic compounds that inhibit voltage-gated K⁺ (K_v) channels through a yet unresolved gating mechanism. K_v channels detect changes in the membrane potential with their voltage-sensing domains (VSDs) that reorient and generate a transient gating current. Both 1-Butanol (1-BuOH) and 1-Hexanol (1-HeOH) inhibited the ionic currents of the Shaker K_v channel in a concentration dependent manner with an IC₅₀ value of approximately 50 mM and 3 mM, respectively. Using the non-conducting Shaker-W434F mutant, we found that both alkanols immobilized approximately 10% of the gating charge and accelerated the deactivating gating currents simultaneously with ionic current inhibition. Thus, alkanols prevent the final VSD movement(s) that is associated with channel gate opening. Applying 1-BuOH and 1-HeOH to the Shaker-P475A mutant, in which the final gating transition is isolated from earlier VSD movements, strengthened that neither alkanol affected the early VSD movements. Drug competition experiments showed that alkanols do not share the binding site of 4-aminopyridine, a drug that exerts a similar effect at the gating current level. Thus, alkanols inhibit Shaker-type K_v channels via a unique gating modifying mechanism that stabilizes the channel in its non-conducting activated state.

Fatty acid ethyl esters induce intestinal epithelial barrier dysfunction via a reactive oxygen species-dependent mechanism in a three-dimensional cell culture model

Background & Aims

Evidence is accumulating that ethanol and its oxidative metabolite, acetaldehyde, can disrupt intestinal epithelial integrity, an important factor contributing to ethanol-induced liver injury. However, ethanol can also be metabolized non-oxidatively generating phosphatidylethanol and fatty acid ethyl esters (FAEEs). This study aims to investigate the effects of FAEEs on barrier function, and to explore the role of oxidative stress as possible mechanism.

Methods

Epithelial permeability was assessed by paracellular flux of fluorescein isothiocyanate-conjugated dextran using live cell imaging. Cell integrity was evaluated by lactate dehydrogenase release. Localization and protein levels of ZO-1 and occludin were analyzed by immunofluorescence and cell-based ELISA, respectively. Intracellular oxidative stress and cellular ATP levels were measured by dichlorofluorescein and luciferase driven bioluminescence, respectively.

Results

In vitro, ethyl oleate and ethyl palmitate dose dependently increased permeability associated with disruption and decreased ZO-1 and occludin protein levels, respectively, and increased intracellular oxidative stress without compromising cell viability. These effects could partially be attenuated by pretreatment with the antioxidant, resveratrol, pointing to the role of oxidative stress in the FAEEs-induced intestinal barrier dysfunction.

Conclusions

These findings show that FAEEs can induce intestinal barrier dysfunction by disrupting the tight junctions, most likely via reactive oxygen species-dependent mechanism.

Polyunsaturated Fatty acids modify the gating of kv channels

Polyunsaturated fatty acids (PUFAs) have been reported to exhibit antiarrhythmic properties, which are attributed to their capability to modulate ion channels. This PUFAs ability has been reported to be due to their effects on the gating properties of ion channels. In the present review, we will focus on the role of PUFAs on the gating of two Kv channels, Kv1.5 and Kv11.1. Kv1.5 channels are blocked by n-3 PUFAs of marine [docosahexaenoic acid (DHA) and eicosapentaenoic acid] and plant origin (alpha-linolenic acid, ALA) at physiological concentrations. The blockade of Kv1.5 channels by PUFAs steeply increased in the range of membrane potentials coinciding with those of Kv1.5 channel activation, suggesting that PUFAs-channel binding may derive a significant fraction of its voltage sensitivity through the coupling to channel gating. A similar shift in the activation voltage was noted for the effects of n-6 arachidonic acid (AA) and DHA on Kv1.1, Kv1.2, and Kv11.1 channels. PUFAs-Kv1.5 channel interaction is time-dependent, producing a fast decay of the current upon depolarization. Thus, Kv1.5 channel opening is a prerequisite for the PUFA-channel interaction. Similar to the Kv1.5 channels, the blockade of Kv11.1 channels by AA and DHA steeply increased in the range of membrane potentials that coincided with the range of Kv11.1 channel activation, suggesting that the PUFAs-Kv channel interactions are also coupled to channel gating. Furthermore, AA regulates the inactivation process in other Kv channels, introducing a fast voltage-dependent inactivation in non-inactivating Kv channels. These results have been explained within the framework that AA closes voltage-dependent potassium channels by inducing conformational changes in the selectivity filter, suggesting that Kv channel gating is lipid dependent.

Facile determination of double bond position in unsaturated fatty acids and esters by low temperature plasma ionization mass spectrometry

Unsaturated fatty acids and esters can be oxidized in situ during ionization using a low temperature plasma (LTP) probe. The discharge generates ozone from air that reacts with and cleaves olefins. The molecular ions of the resulting acid/ester oxidation products are present in the full scan mass spectra and are confirmed by exact mass measurements. The fragmentation information can be used to assign double bond positions. We have successfully applied this strategy to a range of mono-/polyunsaturated fatty acids and fatty acid methyl/ethyl esters to assign their double bond locations. The procedure allows rapid and direct identification of double bond positions in situ at atmospheric pressure without sample preparation prior to mass spectrometric analysis. Microbial fatty acid ethyl ester (FAEE) mixtures from complex bacterial samples were directly analyzed by this method. Structural confirmation of their diagnostic ions by using exact mass measurements and tandem mass spectrometry confirms double bond positions in unsaturated bacterial FAEEs.

Dependence of 6beta-acetoxy-7alpha-hydroxyroyleanone block of Kv1.2 channels on C-type inactivation

Voltage-gated K(+) (Kv) channels exhibit slow or C-type inactivation during continuous depolarization. A selective pharmacological agent targeting C-type inactivation is hitherto lacking. Here, we report that 6beta-acetoxy-7alpha-hydroxyroyleanone (AHR), a diterpenoid compound isolated from Taiwania cryptomerioides, can selectively modify C-type inactivation of Kv1.2 channels. Extracellular, but not intracellular, AHR (50 muM) dramatically accelerated the slow decay of Kv currents and left-shifted the steady-state inactivation curve. AHR blocked Kv currents with an IC(50) of 17.7 muM. AHR did not affect the kinetics and voltage-dependence of Kv1.2 channel activation. Channel block by AHR was independent of intracellular K(+) concentration. In addition, effect of AHR was much attenuated in a Kv1.2 V370G mutant defective in C-type inactivation. Therefore, block of Kv1.2 channels by AHR did not appear to involve direct occlusion of the outer pore but depended on C-type inactivation. AHR could thus be a probe targeting Kv channel C-type inactivation gate.

Fast inactivation of Shal (K(v)4) K+ channels is regulated by the novel interactor SKIP3 in Drosophila neurons

Shal K+ (K(v)4) channels across species carry the major A-type K+ current present in neurons. Shal currents are activated by small EPSPs and modulate post-synaptic potentials, backpropagation of action potentials, and induction of LTP. Fast inactivation of Shal channels regulates the impact of this post-synaptic modulation. Here, we introduce SKIP3, as the first protein interactor of Drosophila Shal K+ channels. The SKIP gene encodes three isoforms with multiple protein-protein interaction domains. SKIP3 is nervous system specific and co-localizes with Shal channels in neuronal cell bodies, and in puncta along processes. Using a genetic deficiency of SKIP, we show that the proportion of neurons displaying a very fast inactivation, consistent with Shal channels exclusively in a "fast" gating mode, is increased in the absence of SKIP3. As a scaffold-like protein, SKIP3 is likely to lead to the identification of a novel regulatory complex that modulates Shal channel inactivation.

Rhynchophylline from Uncaria rhynchophylla functionally turns delayed rectifiers into A-Type K+ channels

Rhynchophylline (1), a neuroprotective agent isolated from the traditional Chinese medicinal herb Uncaria rhynchophylla, was shown to affect voltage-gated K(+) (Kv) channel slow inactivation in mouse neuroblastoma N2A cells. Extracellular 1 (30 microM) accelerated the slow decay of Kv currents and shifted the steady-state inactivation curve to the left. Intracellular dialysis of 1 did not accelerate the slow current decay, suggesting that this compound acts extracellularly. In addition, the percent blockage of Kv currents by this substance was independent of the degree of depolarization and the intracellular K(+) concentration. Therefore, 1 did not appear to directly block the outer channel pore, with the results obtained suggesting that it drastically accelerated Kv channel slow inactivation. Interestingly, 1 also shifted the activation curve to the left. This alkaloid also strongly accelerated slow inactivation and caused a left shift of the activation curve of Kv1.2 channels heterologously expressed in HEK293 cells. Thus, this compound functionally turned delayed rectifiers into A-type K(+) channels.

A widespread distinct pattern of cerebral atrophy in patients with alcohol addiction revealed by voxel-based morphometry

BACKGROUND

Patients with alcohol addiction show a number of transient or persistent neurological and psychiatric deficits. The complexity of these brain alterations suggests that several brain areas are involved, although the definition of the brain alteration patterns is not yet accomplished.

AIM

To determine brain atrophy patterns in patients with alcohol dependence.

METHODS

Voxel-based morphometry (VBM) of grey matter (GM) and white matter (WM) was performed in 22 patients with alcohol dependence and in 22 healthy controls matched for age and sex.

RESULTS

In patients with alcohol dependence, VBM of GM revealed a significant decrease in density (p<0.001) in the precentral gyrus, middle frontal gyrus, insular cortex, dorsal hippocampus, anterior thalamus and cerebellum compared with controls. Reduced density of WM was found in the periventricular area, pons and cerebellar pedunculi in patients with alcohol addiction.

CONCLUSIONS

Our findings provide evidence that alcohol addiction is associated with altered density of GM and WM of specific brain regions. This supports the assumption that alcohol dependence is associated with both local GM dysfunction and altered brain connectivity. Also, VBM is an effective tool for in vivo investigation of cerebral atrophy in patients with alcohol addiction.

Role of undecan-2-one on ethanol-induced apoptosis in HepG2 cells

Based on the reduced expression of ethanol-oxidizing enzymes in human hepatocellular carcinoma (HepG2) cells, we analyzed the role of nonoxidative metabolites in ethanol-induced apoptosis in HepG2 cells. For this purpose, an analysis of volatile metabolites of ethanol using ion-mobility spectrometry and gas chromatography-mass spectrometry was performed. HepG2 cells exposed to 1 mmol/L ethanol exhibited significant synthesis of undecan-2-one compared to untreated cells. Undecan-2-one is a fatty acid ethyl ester metabolite synthesized through a nonoxidative pathway. Undecan-2-one had a dose-dependent cytotoxic effect on HepG2 cells as shown by release of lactate dehydrogenase (LDH). The most notable finding of this study was the potentiation of ethanol-induced apoptosis demonstrated by an increased apoptotic rate induced by undecan-2-one in ethanol-treated HepG2 cells. The data presented in this study contribute to the better understanding of the molecular mechanisms of ethanol exposure at low concentration in HepG2 cells, a human hepatocellular carcinoma-derived cell line.

Modulation of the pancreatic islet beta-cell-delayed rectifier potassium channel Kv2.1 by the polyunsaturated fatty acid arachidonate

Glucose stimulates both insulin secretion and hydrolysis of arachidonic acid (AA) esterified in membrane phospholipids of pancreatic islet beta-cells, and these processes are amplified by muscarinic agonists. Here we demonstrate that nonesterified AA regulates the biophysical activity of the pancreatic islet beta-cell-delayed rectifier channel, Kv2.1. Recordings of Kv2.1 currents from INS-1 insulinoma cells incubated with AA (5 mum) and subjected to graded degrees of depolarization exhibit a significantly shorter time-to-peak current interval than do control cells. AA causes a rapid decay and reduced peak conductance of delayed rectifier currents from INS-1 cells and from primary beta-cells isolated from mouse, rat, and human pancreatic islets. Stimulating mouse islets with AA results in a significant increase in the frequency of glucose-induced [Ca(2+)] oscillations, which is an expected effect of Kv2.1 channel blockade. Stimulation with concentrations of glucose and carbachol that accelerate hydrolysis of endogenous AA from islet phosphoplipids also results in accelerated Kv2.1 inactivation and a shorter time-to-peak current interval. Group VIA phospholipase A(2) (iPLA(2)beta) hydrolyzes beta-cell membrane phospholipids to release nonesterified fatty acids, including AA, and inhibiting iPLA(2)beta prevents the muscarinic agonist-induced accelerated Kv2.1 inactivation. Furthermore, glucose and carbachol do not significantly affect Kv2.1 inactivation in beta-cells from iPLA(2)beta(-/-) mice. Stably transfected INS-1 cells that overexpress iPLA(2)beta hydrolyze phospholipids more rapidly than control INS-1 cells and also exhibit an increase in the inactivation rate of the delayed rectifier currents. These results suggest that Kv2.1 currents could be dynamically modulated in the pancreatic islet beta-cell by phospholipase-catalyzed hydrolysis of membrane phospholipids to yield non-esterified fatty acids, such as AA, that facilitate Ca(2+) entry and insulin secretion.

Activation and impairment of platelet function in vitro by fatty acid ethyl ester, a nonoxidative ethanol metabolite: effect of fatty acid ethyl esters on human platelets

BACKGROUND

The goal of this study was to investigate the effect of fatty acid ethyl esters (FAEE), nonoxidative metabolites of ethanol, on platelet function. We hypothesized that FAEE increase the risk of bleeding by producing an alteration in platelet membrane structure or function.

METHODS

Isolated human platelets incubated with FAEE were prepared and multiple assays for platelet activation were performed; beta-thromboglobulin release from platelet granules, platelet aggregation, arachidonate release from phospholipids, and intracellular cyclic AMP (cAMP) levels. We examined also the combined effect of epinephrine and FAEE on platelet aggregation.

RESULTS

FAEE induced platelet shape change, release of alpha granules and release of arachidonate from phospholipids without an increase in eicosanoid production and decreased cAMP levels. The platelets did not aggregate in response to FAEE alone, but did shorten the time to maximum aggregation with epinephrine.

CONCLUSION

These studies show that FAEE potentiate platelet activation but do not induce aggregation, presumably because they do not stimulate thromboxane A(2) production.

Functional lipidomics: the roles of specialized lipids and lipid–protein interactions in modulating neuronal function

Lipids fulfill multiple specialized roles in neuronal function. In brain, the conduction of electrical impulses, synaptic function, and complex signaling pathways depend on the temporally and spatially coordinated interactions of specialized lipids (e.g., arachidonic acid and plasmalogens), proteins (e.g., ion channels, phospholipases and cyclooxygenases) and integrative lipid-protein interactions. Recent technical advances in mass spectrometry have allowed unparalled insight into the roles of lipids in neuronal function. Through shotgun lipidomics and multidimensional mass spectrometry, in conjunction with the identification of new classes of phospholipases (e.g., calcium dependent and calcium independent intracellular phospholipases), new roles for lipids in cerebral function have been accrued. This review summarizes the advances in our understanding of the types of lipids and phospholipases in the brain and the role of functional lipidomics in increasing our chemical understanding of complex neuronal processes.

Different pharmacological profile of two closely related endocannabinoid ester analogs

The pharmacological and neuroprotective properties of two ester analogs of the endocannabinoids, arachidonoylethyleneglycol (AA-EG) and alpha,alpha,-dimethyl arachidonoylethyleneglycol (DMA-EG), were investigated. We examined the interaction of both compounds with cannabinoid receptors (CB1 and CB2) and their efficacy in functional assays. In competition binding assays, AA-EG and DMA-EG had low potency to displace the CB1/CB2 agonist [3H]CP-55,940 in membrane preparations expressing rodent or human receptors. Binding data correlate with low efficacy of both compounds as regards to inhibition of adenylyl cyclase activity. It was also shown that DMA-EG resists hydrolysis by rat brain membranes while AA-EG undergo complete splitting under these conditions. In the cannabinoid tetrad, AA-EG induced hypomotility, analgesia, catalepsy and decreased rectal temperature indicating cannabimimetic activity. By contrast, DMA-EG was completely inactive in the same models. DMA-EG and AA-EG potently protected rat cortical neurons in culture against oxygen deprivation at nanomolar concentrations. In glutamate-induced damage, the compounds were less active protecting neurons at micromolar concentrations. The data obtained indicate that the ester endocannabinoid template can be used for the development of new compounds with potent biological activity lacking some of the undesirable behavioral side effects.

Complex transcriptional and translational regulation of iPLAgamma resulting in multiple gene products containing dual competing sites for mitochondrial or peroxisomal localization

Membrane-associated calcium-independent phospholipase A2gamma (iPLA2gamma) contains four potential in-frame methionine start sites (Mancuso, D.J. Jenkins, C.M. & Gross, R.W. (2000) J. Biol. Chem.275, 9937-9945), but the mechanisms regulating the types, amount and subcellular localization of iPLA2gamma in cells are incompletely understood. We now: (a) demonstrate the dramatic transcriptional repression of mRNA synthesis encoding iPLA2gamma by a nucleotide sequence nested in the coding sequence itself; (b) localize the site of transcriptional repression to the most 5' sequence encoding the iPLA2gamma holoprotein; (c) identify the presence of nuclear protein constituents which bind to the repressor region by gel shift analysis; (d) demonstrate the translational regulation of distinct iPLA2gamma isoforms; (e) identify multiple novel exons, promoters, and alternative splice variants of human iPLA2gamma; (f) document the presence of dual-competing subcellular localization signals in discrete isoforms of iPLA2gamma; and (g) demonstrate the functional integrity of an N-terminal mitochondrial localization signal by fluorescence imaging and the presence of iPLA2gamma in the mitochondrial compartment of rat myocardium. The intricacy of the regulatory mechanisms of iPLA2gamma biosynthesis in rat myocardium is underscored by the identification of seven distinct protein products that utilize multiple mechanisms (transcription, translation and proteolysis) to produce discrete iPLA2gamma polypeptides containing either single or dual subcellular localization signals. This unanticipated complex interplay between peroxisomes and mitochondria mediated by competition for uptake of the nascent iPLA2gamma polypeptide identifies a new level of phospholipase-mediated metabolic regulation. Because uncoupling protein function is regulated by free fatty acids in mitochondria, these results suggest that iPLA2gamma processing contributes to integrating respiration and thermogenesis in mitochondria.

The human Kv1.1 channel is palmitoylated, modulating voltage sensing: Identification of a palmitoylation consensus sequence

Voltage-dependent K(+) channels rely on precise dynamic protein interactions with surrounding plasma membrane lipids to facilitate complex processes such as voltage sensing and channel gating. Many transmembrane-spanning proteins use palmitoylation to facilitate dynamic membrane interactions. Herein, we demonstrate that the human Kv1.1 ion channel is palmitoylated in the cytosolic portion of the S(2)-S(3) linker domain at residue C243. Through heterologous expression of the human Kv1.1 protein in Sf9 cells, covalent radiolabeling with [(3)H]palmitate, chemical stability studies of the [(3)H]-palmitoylated protein, and site-directed mutagenesis, C243 was identified as the predominant site of palmitoylation. The functional sequelae of palmitoylation were examined by analysis of whole cell currents from WT and mutant channels, which identified a 20-mV leftward shift in the current-voltage relationship when palmitoylation at C243 (but not with other cysteine deletions) is prevented by site-directed mutagenesis, implicating a role for palmitoylated C243 in modulating voltage sensing through protein-membrane interactions. Database searches identified an amino acid palmitoylation consensus motif (ACP/RSKT) that is present in multiple other members of the Shaker subfamily of K(+) channels and in several other unrelated regulatory proteins (e.g., CD36, nitric oxide synthase type 2, and the mannose-6 phosphate receptor) that are known to be palmitoylated by thioester linkages at the predicted consensus site cysteine residue. Collectively, these results (i) identify palmitoylation as a mechanism for K(+) channel interactions with plasma membrane lipids contributing to electric field-induced conformational alterations, and ii) define an amino acid consensus sequence for protein palmitoylation.

Additive effects of endogenous cannabinoid anandamide and ethanol on alpha7-nicotinic acetylcholine receptor-mediated responses in Xenopus Oocytes

The interaction between the effects of the endogenous cannabinoid receptor agonist anandamide and ethanol on the function of homomeric alpha(7)-nicotinic acetylcholine (nACh) receptors expressed in Xenopus oocytes were investigated using the two-electrode voltage-clamp technique. Anandamide and ethanol reversibly inhibited currents evoked with 100 microM acetylcholine in a concentration-dependent manner. Coapplication of anandamide and ethanol caused a significantly greater inhibition of alpha(7)-nACh receptor function than anandamide or ethanol alone. The IC(50) value of 238 +/- 34 nM for anandamide inhibition decreased significantly to 104 +/- 23 nM in the presence of 30 mM ethanol. The inhibition of alpha(7)-mediated currents by coapplication of anandamide and ethanol was not altered by phenylmethylsulfonyl fluoride, an inhibitor of anandamide hydrolyzing enzyme, or N-(4-hydroxyphenyl)-arachidonylamide, an anandamide transport inhibitor. Analysis of oocytes by matrix-assisted laser desorption/ionization technique indicated that ethanol treatment did not alter the lipid profile of oocytes, and there is negligible, if any, anandamide present in these cells. Results of studies with chimeric alpha(7)-nACh-5-HT(3) receptors comprised of the amino-terminal domain of the alpha(7)-nACh receptor and the transmembrane and carboxyl-terminal domains of 5-HT(3) receptors suggest that although ethanol inhibition of the alpha(7)-nACh receptor is likely to involve the N-terminal region of the receptor, the site of action for anandamide is located in the transmembrane and carboxyl-terminal domains of the receptors. These data indicate that endocannabinoids and ethanol potentiate each other's inhibitory effects on alpha(7)-nACh receptor function through distinct regions of the receptor.

Induction of apoptosis by fatty acid ethyl esters in HepG2 cells

Fatty acid ethyl esters (FAEEs) are esterification products of ethanol and fatty acids which have been found particularly in the organ damaged by ethanol abuse. To evaluate any effect of FAEEs on HepG2 cells, we added FAEEs to cell culture medium. Electrophoresis of DNA from HepG2 cells exposed to 18.5 microM ethyl palmitate (EP) and 10.6 microM ethyl stearate (ES) for 24 h revealed a smear which is typical of non-specific degradation by DNA ladder assay. Apoptosis was characterized by electron microscopy, flow cytometry revealed that the cell cycle of HepG2 cells was perturbed by exposure to FAEEs. In the present study we demonstrate that treatment of HepG2 cells with EP and ES induces apoptosis, as well as perturbing the cell cycle as the number of cells in the G(2)/M and S phases decreased.

Fatty acid ethyl esters: markers of alcohol abuse and alcoholism

Chronic alcoholism, which is associated with hepatic, pancreatic, and myocardial diseases, is one of the major health problems in the United States with high morbidity and mortality. Many individuals who abuse alcohol chronically die even before reaching the clinical stage of the disease. Reliable biomarkers of the diseases induced by chronic alcohol abuse, as well as for alcoholism, currently are not available. In the current study, we measured plasma concentrations of fatty acid ethyl esters [(FAEEs), nonoxidative metabolites of ethanol] in 39 patients with a detectable concentration of alcohol in their blood samples. In turn, we determined the relation of FAEE concentrations with blood alcohol concentration (BAC). Of 39 patients in whom we evaluated this relation, only five had a history of chronic alcohol abuse, and six had a history of acute alcohol abuse. Patients' age ranged from 25 to 71 years. Within this age range, greater concentrations of FAEEs were found in the plasma samples obtained from patients in the 41- to 50-year age group. There were no sex-related differences in BAC, nor in FAEE concentrations. Thirteen patients had a BAC greater than 300 mg%. For 11 patients, the BAC ranged between 200 and 299 mg%, and, for 12 patients, the BAC ranged between 100 and 199 mg%. In comparison with findings for patients with a BAC that ranged between 100 and 299 mg%, the FAEE concentrations were approximately twofold higher in patients with a BAC greater than 300 mg%. Ethyl palmitate and ethyl oleate were the main FAEEs detected in most patients. In general, FAEE concentrations increased with increasing BAC. However, in comparison with patients with a history of acute alcohol abuse, a greater increase in total FAEE concentrations was observed in patients with a history of chronic alcohol abuse (4,250 ng/ml and 15,086 ng/ml, respectively). Fatty acid ethyl esters were either detected in trace amounts or not detectable in the plasma of control subjects with no known alcohol ingestion. These results support our hypothesis that nonoxidative metabolism of ethanol to FAEEs is an important pathway of ethanol disposition during chronic alcohol abuse, and that FAEE concentrations can be a more reliable biomarker of chronic alcohol abuse than a history of acute alcohol abuse.

Nonoxidative ethanol metabolites alter extracellular matrix protein content in rat pancreas

BACKGROUND & AIMS

The mechanisms involved in ethanol-induced pancreas fibrosis are poorly understood. Here we show that fatty acid ethyl esters (FAEEs), nonoxidative ethanol metabolites, increase extracellular matrix (ECM) protein levels in pancreas.

METHODS

Rat pancreatic acini were incubated for 1-4 hours with FAEEs or acetaldehyde. In another set of experiments, rats received an intravenous infusion of FAEEs for 6 hours. Collagens were assessed by a hydroxyproline assay. Laminin and fibronectin were analyzed by Western blotting. Gene expression of ECM proteins was measured by conventional and real-time reverse-transcription polymerase chain reaction (RT-PCR). Matrix metalloproteinase (MMP), plasmin, and urokinase-type plasminogen activator (uPA) activities were determined by zymography and fluorogenic assays.

RESULTS

FAEEs increased collagen, laminin, and fibronectin levels in pancreatic acini without affecting messenger RNA (mRNA) expression for these proteins. Actinomycin D, a transcriptional inhibitor, did not block the increase in ECM proteins induced by FAEEs. FAEEs reduced the activity of the serine protease, plasmin, and that of the uPA. Consistent with these results, the serine protease inhibitor aprotinin reproduced the effects of FAEEs and prevented the further increase in ECM proteins induced by FAEEs. In vivo administration of FAEEs reduced plasmin and uPA activities and increased ECM protein levels in pancreas. Acetaldehyde had minor effects on ECM protein levels and did not affect plasmin activity.

CONCLUSIONS

FAEEs increase ECM protein levels in pancreas. The results suggest that this effect is caused primarily by an inhibition in ECM degradation via serine proteases including the plasminogen system.

Linoleic acid both enhances activation and blocks Kv1.5 and Kv2.1 channels by two separate mechanisms

Linoleic acid (LA) had two effects on human Kv1.5 and Kv2.1 channels expressed in Chinese hamster ovary cells: an increase in the speed of current activation process (EC(50) = 2.4 and 2.7 microM for Kv1.5 and Kv2.1, respectively) and current inhibition (IC(50) = 6.6 and 7.4 for Kv1.5 and Kv2.1, respectively). LA affected the activation kinetics via two processes: a leftward shift in the instantaneous activation curves and an increase in the rate of current rise. Current inhibition by LA was time dependent but voltage independent. Hill slopes for plots of current inhibition (3.5 and 3.9 for Kv1.5 and Kv2.1, respectively) vs. dose of LA suggested that cooperativity was involved in the mechanism of current inhibition. A similar analysis of the effects of LA on current activation did not reveal cooperative interactions. The effects of LA were mediated from the external side of the channels, since addition of 10 microM LA to the patch pipette solution was without effect. Additionally, the methyl ester of LA was effective at enhancing peak current and promoting channel activation for Kv1.5 and Kv2.1 without inducing significant current inhibition.

Functional expression of TrpC1: a human homologue of the Drosophila Trp channel

TrpC1 appears to be a store-operated channel (SOC) when expressed in mammalian cells. In the present study, TrpC1 was expressed in Sf9 insect cells using the baculovirus expression system. Expression of TrpC1 caused an increase in basal cytosolic free Ca2+ concentration ([Ca2+]i) as a function of post-infection time. Basal Ba2+ influx, an index of plasmalemmal Ca2+ permeability, was also increased and was blocked by La3+. Although the thapsigargin-induced change in [Ca2+]i was greater in TrpC1-expressing cells than controls, Ba2+ influx was unaffected by thapsigargin. Whole-cell membrane currents recorded in TrpC1-expressing cells increased as a function of post-infection time and were (1) inwardly rectifying in symmetrical sodium gluconate solutions, (2) non-selective with respect to Na+, Ca2+ and Ba2+, and (3) blocked by La3+. Furthermore TrpC1 currents were unaffected by (1) thapsigargin, (2) dialysis of the cell with Ins(1,4,5)P3 or (3) dialysis of the cell with solutions containing high concentrations of the Ca2+ chelator, EGTA. These results suggest that TrpC1 forms non-selective cation channels that are constitutively active when expressed in Sf9 cells, but insensitive to depletion of the internal Ca2+ stores. Thus TrpC1 may be a subunit of a SOC which alone can form functional channels in Sf9 cells, but which requires additional subunits or cytoplasmic factors present in mammalian cells for expression of SOC activity.