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Antimicrobial Agents and Chemotherapy Apr 1997The antifungal effects of amphotericin B are believed to be due to two possibly interrelated mechanisms: an increase in permeation by binding to sterols in cellular...
The antifungal effects of amphotericin B are believed to be due to two possibly interrelated mechanisms: an increase in permeation by binding to sterols in cellular membranes and a prooxidant effect causing oxidative damage in target cells. However, the seven conjugated double bonds in amphotericin B raise the possibility that it could be highly susceptible to autoxidation, causing an antioxidant effect. In the present study, we investigated the prooxidant and antioxidant properties of amphotericin B in a model system in which oxidation of a reporter molecule, cis-parinaric acid, was induced by azo initiators of peroxyl radicals. Since interactions of amphotericin B with sterols are essential for its pharmacological and toxic actions, we also studied the effects of cholesterol on the prooxidant and antioxidant properties of amphotericin B. Amphotericin B caused a noncollisional quenching of a characteristic fluorescence of cholesteryl cis-parinarate integrated in liposomes, suggesting the formation of amphotericin B-cholesteryl cis-parinarate complex. This effect of amphotericin B was ablated by increasing concentrations of cholesterol. We found that amphotericin B inhibited oxidation of cis-parinaric acid complexed with human serum albumin [using a water-soluble azo initiator, 2,2'-azobis(2aminopropane)dihydrochloride] and in liposomes [using a lipid-soluble azo initiator, 2,2'-azobis(2,4-dimethylvaleronitrile)]. The inhibitory effect of amphotericin B on 2,2'-azobis(2,4-dimethylvaleronitrile)-induced peroxidation of cis-parinaric acid in liposomes was also diminished by cholesterol. The antioxidant effect of amphotericin B in this model system suggests that amphotericin B does not exert its pharmacological and toxicological responses through a prooxidant effect to cause damage in target cells.
Topics: Amphotericin B; Anti-Bacterial Agents; Antioxidants; Cholesterol; Chromatography, High Pressure Liquid; Fatty Acids, Unsaturated; Free Radicals; Liposomes; Oxidation-Reduction; Peroxides; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet
PubMed: 9087481
DOI: 10.1128/AAC.41.4.743 -
European Journal of Biochemistry Jan 1999Up until now, the primary structure of fatty-acid-binding proteins (FABPs) from the livers of four mammalian (rat, human, cow and pig) and three nonmammalian (chicken,... (Comparative Study)
Comparative Study
Isolation, amino acid sequence determination and binding properties of two fatty-acid-binding proteins from axolotl (Ambistoma mexicanum) liver. Evolutionary relationship.
Up until now, the primary structure of fatty-acid-binding proteins (FABPs) from the livers of four mammalian (rat, human, cow and pig) and three nonmammalian (chicken, catfish and iguana) species has been determined. Based on amino acid sequence comparisons, it has been suggested that mammalian and nonmammalian liver FABPs may be paralogous proteins that originated by gene duplication, rather than as a consequence of mutations of the same gene. In this paper we report the isolation and amino acid sequence determination of two FABPs from axolotl (Ambistoma mexicanum) liver. One of them is similar to mammalian liver FABPs (L-FABPs) and the other to chicken, catfish and iguana liver FABPs (Lb-FABPs). The finding of both L-FABP and Lb-FABP in a single species, as reported here, indicates that they are paralogous proteins. The time of divergence of these two liver FABP types is estimated to be of approximately 694 million years ago. The ligand-binding properties of axolotl liver FABPs were studied by means of parinaric-acid-binding and parinaric-acid-displacement assays. L-FABP binds two fatty acids per molecule but Lb-FABP displays a fatty-acid-conformation-dependent binding stoichiometry; L-FABP shows a higher affinity for fatty acids, especially oleic acid, while Lb-FABP has a higher affinity for other hydrophobic ligands, especially retinoic acid. In addition, the tissue-expression pattern is different, L-FABP is present in liver and intestinal mucosa while the expression of Lb-FABP is restricted to liver. Data indicate distinct functional properties of both liver FABP types.
Topics: Ambystoma; Amino Acid Sequence; Animals; Binding, Competitive; Carrier Proteins; Evolution, Molecular; Fatty Acid-Binding Protein 7; Fatty Acid-Binding Proteins; Fatty Acids; Fatty Acids, Unsaturated; Gene Expression; Ligands; Liver; Molecular Sequence Data; Myelin P2 Protein; Neoplasm Proteins; Nerve Tissue Proteins; Sequence Analysis; Sequence Homology, Amino Acid; Species Specificity; Tissue Distribution
PubMed: 9914484
DOI: 10.1046/j.1432-1327.1999.00015.x -
Biophysical Journal Nov 2015Polyunsaturated phospholipids are common in biological membranes and affect the lateral structure of bilayers. We have examined how saturated sphingomyelin (SM;...
Polyunsaturated phospholipids are common in biological membranes and affect the lateral structure of bilayers. We have examined how saturated sphingomyelin (SM; palmitoyl and stearoyl SM (PSM and SSM, respectively)) and phosphatidylcholine (PC; dipalmitoyl PC and 1-palmitoyl-2-stearoyl PC (DPPC and PSPC, respectively)) segregate laterally to form ordered gel phases in increasingly unsaturated PC bilayers (sn-1: 16:0 and sn-2: 18:1...22:6; or sn-1 and sn-2: 18:1...22:6). The formation of gel phases was determined from the lifetime analysis of trans-parinaric acid. Using calorimetry, we also determined gel phase formation by PSM and DPPC in unsaturated PC mixed bilayers. Comparing PSM with DPPC, we observed that PSM formed a gel phase with less order than DPPC at comparable bilayer concentrations. The same was true when SSM was compared with PSPC. Furthermore, we observed that at equal saturated phospholipid concentration, the gel phases formed were less ordered in unsaturated PCs having 16:0 in sn-1, as compared to PCs having unsaturated acyl chains in both sn-1 and sn-2. The gel phases formed by the saturated phospholipids in unsaturated PC bilayers did not appear to achieve properties similar to pure saturated phospholipid bilayers, suggesting that complete lateral phase separation did not occur. Based on scanning calorimetry analysis, the melting of the gel phases formed by PSM and DPPC in unsaturated PC mixed bilayers (at 45 mol % saturated phospholipid) had low cooperativity and hence most likely were of mixed composition, in good agreement with trans-parinaric acid lifetime data. We conclude that both interfacial properties of the saturated phospholipids and their chain length, as well as the presence of 16:0 in sn-1 of the unsaturated PCs and the total number of cis unsaturations and acyl chain length (18 to 22) of the unsaturated PCs, all affected the formation of gel phases enriched in saturated phospholipids, under the conditions used.
Topics: Calorimetry, Differential Scanning; Fatty Acids, Unsaturated; Fluorescence; Freezing; Gels; Lipid Bilayers; Phosphatidylcholines; Sphingomyelins
PubMed: 26536267
DOI: 10.1016/j.bpj.2015.09.009 -
Fundamental and Applied Toxicology :... Dec 1997This symposium focused on the research which documents benefit and toxicity in beta-carotene supplementation. Reflecting on past and current studies, the panel of... (Review)
Review
This symposium focused on the research which documents benefit and toxicity in beta-carotene supplementation. Reflecting on past and current studies, the panel of experts discussed: (1) the potential harm of a high intake of beta-carotene on selected populations, (2) biochemical antioxidant/prooxidant mechanisms of beta-carotene at the cellular level, (3) potential benefits of other carotenoids and antioxidants, and (4) future directions for research in beta-carotene and other antioxidants.
Topics: Animals; Antioxidants; Carotenoids; Cell Line; Contraindications; Dietary Supplements; Epidemiologic Methods; Fatty Acids, Unsaturated; Fluorescent Dyes; Forecasting; Free Radicals; Humans; Lipid Peroxidation; Neoplasms; Oxidative Stress; Randomized Controlled Trials as Topic; Smoking; Structure-Activity Relationship; beta Carotene
PubMed: 9441712
DOI: 10.1006/faat.1997.2387 -
American Journal of Physiology.... Mar 2006The mechanism(s) of fatty acid uptake by liver cells is not fully understood. We applied new approaches to address long-standing controversies of fatty acid uptake and...
The mechanism(s) of fatty acid uptake by liver cells is not fully understood. We applied new approaches to address long-standing controversies of fatty acid uptake and to distinguish diffusion and protein-based mechanisms. Using HepG2 cells containing an entrapped pH-sensing fluorescence dye, we showed that the addition of oleate (unbound or bound to cyclodextrin) to the external buffer caused a rapid (seconds) and dose-dependent decrease in intracellular pH (pH(in)), indicating diffusion of fatty acids across the plasma membrane. pH(in) returned to its initial value with a time course (in min) that paralleled the metabolism of radiolabeled oleate. Preincubation of cells with the inhibitors phloretin or triacsin C had no effect on the rapid pH(in) drop after the addition of oleate but greatly suppressed pH(in) recovery. Using radiolabeled oleate, we showed that its esterification was almost completely inhibited by phloretin or triacsin C, supporting the correlation between pH(in) recovery and metabolism. We then used a dual-fluorescence assay to study the interaction between HepG2 cells and cis-parinaric acid (PA), a naturally fluorescent but slowly metabolized fatty acid. The fluorescence of PA increased rapidly upon its addition to cells, indicating rapid binding to the plasma membrane; pH(in) decreased rapidly and simultaneously but did not recover within 5 min. Phloretin had no effect on the PA-mediated pH(in) drop or its slow recovery but decreased the absolute fluorescence of membrane-bound PA. Our results show that natural fatty acids rapidly bind to, and diffuse through, the plasma membrane without hindrance by metabolic inhibitors or by an inhibitor of putative membrane-bound fatty acid transporters.
Topics: Biological Transport, Active; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Membrane; Coenzyme A Ligases; Diffusion; Fatty Acids, Unsaturated; Fluoresceins; Fluorescent Dyes; Humans; Hydrogen-Ion Concentration; Oleic Acid; Phloretin; Triazenes; beta-Cyclodextrins
PubMed: 16254047
DOI: 10.1152/ajpgi.00386.2005 -
Biophysical Journal Apr 2019Ceramide is an important intermediate in sphingolipid homeostasis. We examined how colipids, with negative intrinsic curvature and which may induce curvature stress in...
Ceramide is an important intermediate in sphingolipid homeostasis. We examined how colipids, with negative intrinsic curvature and which may induce curvature stress in the bilayers, affected the segregation of palmitoyl ceramide (PCer). Such colipids include 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and tetra-linoleoyl cardiolipin (CL). In 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers, PCer formed ordered, gel-like domains at concentrations above 10 mol% at 23°C, as evidenced by the change in the average lifetime of the trans-parinaric acid emission. When POPE or DOPE were included in the DOPC bilayer (at 20:80 or 40:60 POPE or DOPE to DOPC, by mol), the lateral segregation of PCer was facilitated in a concentration-dependent manner, and less PCer was required for the formation of the ordered ceramide-rich domains. Inclusion of CL in the DOPE bilayer (at 10:90 or 20:80 CL to PC, by mol) also caused a similar facilitation of the lateral segregation of PCer. The PCer-rich domains formed in the presence of POPE, DOPE, or CL in DOPC bilayers were slightly more thermostable (by 2-10°C) when compared to PCer-rich domains in DOPC-only bilayers. Nonlamellar phases were not present in bilayers in which the effects of POPE or DOPE on PCer segregation were the largest, as verified by P NMR. When palmitoyl sphingomyelin was added to the different bilayer compositions at 5 mol%, relative to the phospholipids, PCer segregated into gel domains at lower concentrations (2-3 mol% PCer), and the effect of POPE on PCer segregation was eliminated. We suggest that the effects of POPE, DOPE, and CL on PCer segregation was in part influenced by their effects on membrane curvature stress and in part because of unfavorable interactions with PCer due to their unsaturated acyl chains. These lipids are abundant in mitochondrial membranes and are likely to affect functional properties of saturated ceramides in them.
Topics: Ceramides; Lipid Bilayers; Phospholipids
PubMed: 30940348
DOI: 10.1016/j.bpj.2019.03.004 -
PLoS Neglected Tropical Diseases 2012Fatty acid (FA) binding proteins (FABPs) of helminths are implicated in acquisition and utilization of host-derived hydrophobic substances, as well as in signaling and...
BACKGROUND
Fatty acid (FA) binding proteins (FABPs) of helminths are implicated in acquisition and utilization of host-derived hydrophobic substances, as well as in signaling and cellular interactions. We previously demonstrated that secretory hydrophobic ligand binding proteins (HLBPs) of Taenia solium metacestode (TsM), a causative agent of neurocysticercosis (NC), shuttle FAs in the surrounding host tissues and inwardly transport the FAs across the parasite syncytial membrane. However, the protein molecules responsible for the intracellular trafficking and assimilation of FAs have remained elusive.
METHODOLOGY/PRINCIPAL FINDINGS
We isolated two novel TsMFABP genes (TsMFABP1 and TsMFABP2), which encoded 133- and 136-amino acid polypeptides with predicted molecular masses of 14.3 and 14.8 kDa, respectively. They shared 45% sequence identity with each other and 15-95% with other related-members. Homology modeling demonstrated a characteristic β-barrel composed of 10 anti-parallel β-strands and two α-helices. TsMFABP2 harbored two additional loops between β-strands two and three, and β-strands six and seven, respectively. TsMFABP1 was secreted into cyst fluid and surrounding environments, whereas TsMFABP2 was intracellularly confined. Partially purified native proteins migrated to 15 kDa with different isoelectric points of 9.2 (TsMFABP1) and 8.4 (TsMFABP2). Both native and recombinant proteins bound to 11-([5-dimethylaminonaphthalene-1-sulfonyl]amino)undecannoic acid, dansyl-DL-α-amino-caprylic acid, cis-parinaric acid and retinol, which were competitively inhibited by oleic acid. TsMFABP1 exhibited high affinity toward FA analogs. TsMFABPs showed weak binding activity to retinol, but TsMFABP2 showed relatively high affinity. Isolation of two distinct genes from an individual genome strongly suggested their paralogous nature. Abundant expression of TsMFABP1 and TsMFABP2 in the canal region of worm matched well with the histological distributions of lipids and retinol.
CONCLUSIONS/SIGNIFICANCE
The divergent biochemical properties, physiological roles and cellular distributions of the TsMFABPs might be one of the critical mechanisms compensating for inadequate de novo FA synthesis. These proteins might exert harmonized or independent roles on lipid assimilation and intracellular signaling. The specialized distribution of retinol in the canal region further implies that cells in this region might differentiate into diverse cell types during metamorphosis into an adult worm. Identification of bioactive systems pertinent to parasitic homeostasis may provide a valuable target for function-related drug design.
Topics: Amino Acid Sequence; Animals; DNA, Helminth; Fatty Acid-Binding Proteins; Fatty Acids; Molecular Sequence Data; Molecular Weight; Phylogeny; Protein Binding; Protein Conformation; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Taenia solium
PubMed: 23150743
DOI: 10.1371/journal.pntd.0001868 -
The Journal of Biological Chemistry Nov 1976A naturally occurring fluorescent compound, beta-parinaric acid, was employed as a probe to measure the effects of temperature changes on plasma membrenes, microsomes,...
A naturally occurring fluorescent compound, beta-parinaric acid, was employed as a probe to measure the effects of temperature changes on plasma membrenes, microsomes, and mitochondria and on their respective lipids after isolation form LM cells grown in suspension culture. A computer-centered spectrofluorimenter simultaneously measured the absorbance, absorbance-corrected fluorescence, and relative fluorescence efficiency of beta-parinaric acid incorporated into the membranes or isolated membrane lipids. These parameters were measured as a function of temperature. The probe revealed five characteristic breaks or changes in slope with both the plasma membranes as well as their extracted lipids. These discontinuities occurred at approximately 18, 23, 31, 38, and 43 degrees. The other isolated subcellular organelles, microsomes, and mitochondria, as well as their respective isolated lipids, exhibited approximately the same characteristic temperatures (+/- 1 degree) as plasma membranes. Thus, these data negate one criterion of the theory that an asymmetric distribution of characteristic temperatures exist across the membranes of LM cells.
Topics: Cell Line; Cell Membrane; Electric Conductivity; Fatty Acids, Unsaturated; Fluorescent Dyes; Membrane Lipids; Spectrometry, Fluorescence; Temperature
PubMed: 977594
DOI: No ID Found -
The Journal of Biological Chemistry Jun 2003Although liver fatty acid-binding protein (L-FABP) is an important binding site for various hydrophobic ligands in hepatocytes, its in vivo significance is not...
Although liver fatty acid-binding protein (L-FABP) is an important binding site for various hydrophobic ligands in hepatocytes, its in vivo significance is not understood. We have therefore created L-FABP null mice and report here their initial analysis, focusing on the impact of this mutation on hepatic fatty acid binding capacity, lipid composition, and expression of other lipid-binding proteins. Gel-filtered cytosol from L-FABP null liver lacked the main fatty acid binding peak in the fraction that normally comprises both L-FABP and sterol carrier protein-2 (SCP-2). The binding capacity for cis-parinaric acid was decreased >80% in this region. Molar ratios of cholesterol/cholesterol ester, cholesteryl ester/triglyceride, and cholesterol/phospholipid were 2- to 3-fold greater, reflecting up to 3-fold absolute increases in specific lipid classes in the order cholesterol > cholesterol esters > phospholipids. In contrast, the liver pool sizes of nonesterified fatty acids and triglycerides were not altered. However, hepatic deposition of a bolus of intravenously injected [14C]oleate was markedly reduced, showing altered lipid pool turnover. An increase of approximately 75% of soluble SCP-2 but little or no change of other soluble (glutathione S-transferase, albumin) and membrane (fatty acid transport protein, CD36, aspartate aminotransferase, caveolin) fatty acid transporters was measured. These results (i) provide for the first time a quantitative assessment of the contribution of L-FABP to cytosolic fatty acid binding capacity, (ii) establish L-FABP as an important determinant of hepatic lipid composition and turnover, and (iii) suggest that SCP-2 contributes to the accumulation of cholesterol in L-FABP null liver.
Topics: Acetyl-CoA C-Acetyltransferase; Animals; Blotting, Western; Carrier Proteins; Cell Membrane; Cholesterol; Cholesterol Esters; Chromatography, Gel; Cytosol; DNA, Complementary; Dose-Response Relationship, Drug; Electrophoresis, Polyacrylamide Gel; Fatty Acid-Binding Protein 7; Fatty Acid-Binding Proteins; Fatty Acids; Fatty Acids, Unsaturated; Glutathione Transferase; Kinetics; Ligands; Lipid Metabolism; Liver; Mice; Mice, Transgenic; Models, Genetic; Mutation; Neoplasm Proteins; Nerve Tissue Proteins; Phospholipids; Protein Binding; Rats; Recombinant Proteins; Reverse Transcriptase Polymerase Chain Reaction; Subcellular Fractions; Triglycerides
PubMed: 12670956
DOI: 10.1074/jbc.M300287200 -
Cytometry 1992A method for measuring lipid peroxidation using time resolved flow cytometry is described. Because of its chemical nature, the naturally fluorescent fatty acid... (Comparative Study)
Comparative Study
A method for measuring lipid peroxidation using time resolved flow cytometry is described. Because of its chemical nature, the naturally fluorescent fatty acid cis-parinaric acid is readily consumed in lipid peroxidation reactions. It could be loaded into Chinese hamster ovary cells in a time and concentration dependent manner at 37 degrees C, with 5 microM for 60' giving consistent, bright fluorescence without evidence of cytotoxicity. Examination of cells by fluorescence microscopy showed diffuse staining of surface and internal membranes. Cells were maintained at 37 degrees C while being examined in an Epics Elite flow cytometer equipped with a 325 nm HeCd laser, and parinaric acid fluorescence at 405 nm was measured over time. Addition of the oxidant tert-butyl hydroperoxide resulted in a burst of intracellular oxidation, shown by simultaneously loading the cells with dichlorofluorescein, and loss of parinaric fluorescence over time. This was followed by cell death, indicated by loss of forward light scatter and uptake of propidium iodide. Pretreatment of the cells with the antioxidant alpha-tocopherol, 200 microM, reduced the rate of loss of parinaric acid fluorescence and delayed the onset of cell death. Simultaneous biochemical determination of the lipid peroxidation breakdown product malondialdehyde confirmed a close temporal relationship with loss of parinaric acid fluorescence, both with and without alpha-tocopherol pretreatment and suggested that the flow cytometric assay for lipid peroxidation is of comparable sensitivity. The mitochondrial stain dodecyl acridine orange and the cyanine dye DiOC(6)3 were combined with cis-parinaric acid staining and could be excited by the latter using resonance energy transfer.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Animals; CHO Cells; Cell Survival; Cricetinae; Energy Transfer; Fatty Acids, Unsaturated; Flow Cytometry; Lipid Peroxidation; Oxidation-Reduction; Peroxides; Vitamin E; tert-Butylhydroperoxide
PubMed: 1451599
DOI: 10.1002/cyto.990130704