Cytoplasmic fatty acid binding protein: significance for intracellular transport of fatty acids and putative role on signal transduction pathways

Isoforms of rat liver fatty acid binding protein differ in structure and affinity for fatty acids and fatty acyl CoAs

Although native rat liver fatty acid binding protein (L-FABP) is composed of isoforms differing in isoelectric point, their comparative structure and function are unknown. These properties of apo- and holo-L-FABP isoforms were resolved by circular dichroism, time-resolved fluorescence spectroscopy, and binding/displacement of fluorescent ligands. Both apo-isoforms had similar hydrodynamic radii of 18.5 A, but apo-isoform I had a greater alpha-helical content and exhibited a longer Tyr lifetime, indicative of secondary and tertiary structural differences from isoform II. Isoforms I and II both had two fatty acid or fatty acyl CoA binding sites. Ligand binding decreased the isoform hydrodynamic radii by 3-4 A and increased Tyr rotational motions in a more restricted range. Fatty acyl CoAs were more effective than fatty acids in altering the isoform structures. Scatchard analysis showed that both isoforms bound cis- parinaric acid with high affinity (Kd values 41 and 60 nM, respectively) and bound trans-parinaric acid with 2- and 7-fold, respectively, higher affinity than for cis-parinaric acid. In contrast, isoform I had higher affinity for cis- and trans-parinaroyl CoAs (Kd values of 33 and 14 nM) than did isoform II (Kd values of 110 and 97 nM), thereby resulting in biphasic plots of parinaroyl-CoA binding to native L-FABP. Finally, displacement studies indicated that each isoform displayed distinct specificities for fatty acid/fatty acyl CoA chain length and unsaturation. Thus, rat L-FABP isoforms differ markedly in both structure and ligand binding function.

Fatty acid binding proteins reduce 15-lipoxygenase-induced oxygenation of linoleic acid and arachidonic acid

Free fatty acids in plasma and cells are mainly bound to membranes and proteins such as albumin and fatty acid binding proteins (FABP), which can regulate their biological activities and metabolic transformations. We have investigated the effect of FABP and albumin on the peroxidation of linoleic acid (18:2) and arachidonic acid (20:4) by 15-lipoxygenase (15-LO). Rabbit reticulocyte 15-LO produced a rapid conversion of [1-14C]18:2 to 13-hydroxyoctadecadienoic acid (13-HODE) and [3H]20:4 to 15-hydroxyeicosatetraenoic acid (15-HETE). 13-HODE formation was reduced when intestinal FABP (I-FABP). liver FABP (L-FABP) or albumin was added. The relative ability of these proteins to reduce 15-LO induced formation of 13-HODE and 15-HETE was BSA > L-FABP > I-FABP. Smaller reductions in activity were observed with 20:4 as compared to 18:2. The IC50-values of I-FABP and L-FABP, using either 18:2 (3.4 microM) or 20:4 (3.4 microM), were 4.6 +/- 0.6 and 1.9 +/- 0.2 microM, respectively, for reduction of 13-HODE and 6.8 +/- 0.3 and 3.1 +/- 0.2 microM, respectively, for reduction of 15-HETE formation. The smaller 15-HETE reduction correlated with decreased binding of 20:4 to the FABP. Titration calorimetry also showed that the I-FABP IC50 for 18:2, 0.25 microM, was lower then for 20:4, 0.6 microM. Thus the reduction in fatty acid lipid peroxidation relates to the binding capacity of each FABP. We also demonstrated that 18:2 rapidly diffuses (flip-flops) across the phospholipid bilayer of small unilamellar vesicles (SUV) and measured partitioning of 18:2 between proteins and SUV by the pyranin fluorescence method [Kamp, F. and Hamilton, J.A. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 11367-11370]. Addition of proteins to SUV in buffer resulted in a complete desorption of 18:2 from SUV with a relative effect of BSA > L-FABP > I-FABP. This suggests that the relative effects of these proteins on 18:2 peroxidation will not be altered by the presence of membranes. Our results indicate that FAPBs protect intracellular polyunsaturated fatty acids against peroxidation and, through differential binding of 18:2 and 20:4, they may modulate the availability of these polyunsaturated fatty acids to intracellular oxidative pathways.

The sterol carrier protein-2 fatty acid binding site: an NMR, circular dichroic, and fluorescence spectroscopic determination

The interaction and orientation of fatty acids with recombinant human sterol carrier protein-2 (SCP-2) were examined by nuclear magnetic resonance (NMR), circular dichroism (CD), and fluorescence techniques. 13C-NMR spectroscopy of stearic acid and oleic acid as well as fluorescence spectroscopy of cis-parinaric acid demonstrated that SCP-2 bound naturally occurring fatty acids with near 1:1 stoichiometry. Several findings indicated that the fatty acid was oriented in the binding site with its methyl end buried in the protein interior and its carboxylate exposed at the surface: the chemical shift of bound [18-13C]-stearate; dicarboxylic/monocarboxylic acid cis-parinaric acid displacement; complete ionization of the carboxylate group of SCP-2 bound [1-13C]stearate at neutral pH; lack of electrostatic interactions between 13C-fatty acids with SCP-2 cationic residues: pH titratability of the SCP-2 bound [1-13C]stearate carboxylate group. SCP-2 did not undergo global structural changes upon ligand binding or pH decrease as indicated by the absence of significant changes in NMR and only small alterations in time resolved fluorescence parameters. However, SCP-2 did undergo secondary structural changes detected by CD in the pH range 5-6. While these changes in secondary structure did not alter the fatty acid:SCP-2 binding stoichiometry, the affinity for fatty acid was increased severalfold at lower pH. In summary, 13C-NMR, CD, and fluorescence spectroscopy provided a detailed understanding of the interaction of fatty acids with SCP-2 and further showed for the first time the orientation of the fatty acid within the binding site. The pH-induced changes in SCP-2 secondary structure and ligand binding activity may be important to the mechanism whereby this protein interacts with membrane surfaces to enhance lipid binding/transfer.

Changes in gene expression for skin-type fatty acid binding protein in hypoglossal motor neurons following nerve crush

The changeability in the gene expression for five species of fatty acid binding protein (FABP) was investigated in the crushed hypoglossal nucleus by in situ hybridization histochemistry. Increased gene expression for skin-type fatty acid binding protein (S-FABP) was evident in the affected hypoglossal neurons on the 3rd day after nerve crush, and it lasted until the postoperative day 14. On the other hand, no significant gene expression for heart-, liver-, intestinal- or brain-type FABPs was detected in the hypoglossal neurons of normal control or in these neurons for 3 weeks after the nerve crush. These findings suggest that skin-type FABP may selectively contribute to some important roles in morphological and biochemical changes of neuronal cells associated with the nerve regeneration.

Spatio-temporally differential expression of genes for three members of fatty acid binding proteins in developing and mature rat brains

The chronological changes in the gene expression for three species of cytosolic fatty acid-binding proteins (FABPs) in the rat brain were examined by Northern and in situ hybridization analyses. The expression for heart(H)-FABP became evident after birth, with a gradual increase and confined to the gray matter, suggesting that the expression of H-FABP mRNA is neuron-specific in postnatal brain. The expression for brain(B)-FABP was very intense in the ventricular germinal zone, without expression in the cerebellar external granule cell layer, suggesting the dominant expression in the cells of glial lineage. B-FABP mRNA was transiently expressed in perinatal gray as well as white matter and the expression in glial cells persists only in the olfactory nerve fiber layer at the adult stage. On the other hand, the expression for skin type(S)-FABP was evident in the both ventricular germinal zone and cerebellar external granule cell layer, suggesting the expression in cells of neuronal lineage. The expression for S-FABP was evident in the prenatal gray matter and S-FABP mRNA was expressed in glial cells at early postnatal stage, whereafter the expression decreased to, but remained at weak levels in the adult brain. Discrete functions of the three FABPs were suggested in neurons and glia differentially at various developmental stages.

Increased expression of the mRNA for brain- and skin-type but not heart-type fatty acid binding proteins following kainic acid systemic administration in the hippocampal glia of adult rats

Increased gene expression for two species of cytosolic fatty acid binding proteins (FABPs) after systemic administration of kainic acid in the rat brain was demonstrated by Northern blotting and in situ hybridization histochemical analyses. The expression of brain (B)- and skin (S)- but not heart (H)-FABP mRNAs were markedly elevated in the hippocampus at 48 h after systemic kainate treatment. The elevated expression patterns of B- and S-FABP mRNAs were quite similar to that for glial fibrillary acidic protein in the normal brain, suggesting strongly that the increased expression for B- and S-FABPs occurs in dedifferentiated and proliferated astrocytes in response to kainic acid-induced seizure.

Smooth muscle fatty acid binding protein: a regulator of smooth muscle contraction?

A fatty acid binding protein has been isolated from chicken gizzard smooth muscle. The partial amino acid sequence (EMBL P80565) of this protein shows high sequence similarities with other members of the fatty acid binding protein family. This is the first fatty acid binding protein isolated from smooth muscle. It may be involved in the regulation of smooth muscle contraction by transporting polyunsaturated fatty acids (e.g. arachidonic acid).

Oleic acid-induced mitogenic signaling in vascular smooth muscle cells. A role for protein kinase C

As an initial step in testing the hypothesis that high oleic acid concentrations contribute to vascular remodeling in obese hypertensive patients by activating protein kinase C (PKC), the effects of oleic acid on primary cultures of rat aortic smooth muscle cells (RASMCs) were studied. Oleic acid, an 18-carbon cis-monounsaturated fatty acid (18:1 [cis]), from 25 to 200 mumol/L significantly increased [3H]thymidine uptake in RASMCs with an EC50 of 41.0 mumol/L and a maximal response of 196 +/- 15% of control (P < .01). Oleic acid from 25 to 200 mumol/L caused a concentration-dependent increase in the number of RASMCs in culture at 6 days, reaching a maximum of 210 +/- 13% of control at 100 mumol/L (P < .001). PKC inhibition with 4 mumol/L bisindolyImaleimide I and PKC depletion (alpha, mu, iota, and zeta) with 24-hour exposure to 200 nmol/L phorbol 12-myristate 13-acetate in RASMCs eliminated the mitogenic effects of oleic acid but did not reduce responses to 10% FBS. Stimulation of intact cells with oleic acid induced a peak increase of cytosolic PKC activity, reaching 328 +/- 8% of control (P < .001), but did not enhance PKC activity in the membrane fraction (105 +/- 4%, P = NS). The oleic acid-induced increase of PKC activity in cell lysates was similar in the presence and absence of Ca2+, phosphatidylserine, and diolein (maximum response, 360 +/- 4% versus 342 +/- 9% of control, P = NS). Unlike phorbol 12-myristate 13-acetate, oleic acid over 24 hours did not downregulate any of the four PKC isoforms detected in RASMCs. Oleic acid treatment activated mitogen-activated protein (MAP) kinase. PKC depletion in RASMCs eliminated the rise in thymidine uptake, activation of PKC, and activation of MAP kinase in response to oleic acid. In contrast to oleic acid, 50 to 200 mumol/L stearic (18:0) and elaidic (18:1 [trans]) acids, which are less effective activators of PKC than oleic acid, did not enhance thymidine uptake. These data suggest that oleic acid induces proliferation of RASMCs by activating PKC, particularly one or more of the Ca(2+)-independent isoforms, and raise the possibility that the higher oleic acid concentrations observed in obese hypertensive patients may contribute to vascular remodeling.

Mammary derived growth inhibitor is not a distinct protein but a mix of heart-type and adipocyte-type fatty acid-binding protein

The amino acid sequence of the mammary derived growth inhibitor (MDGI) from bovine mammary gland (Böhmer, F.-D., Kraft, R., Otto, A. , Wernstedt, C., Hellman, U., Kurtz, A., Müller, T., Rohde, K., Etzold, G., Lehmann, W., Langen, P., Heldin, C.-H., and Grosse, R. (1987) J. Biol. Chem. 262, 15137-15143) revealed 95% identity to bovine heart fatty acid-binding protein (H-FABP), explaining the observed immunocross-reactivity. However, a cDNA encoding MDGI has not been found to date. Artificial MDGI cDNA was expressed in an in vitro transcription/translation assay. Analysis by isoelectric focusing of the immunoprecipitated in vitro translation products of lactating bovine mammary gland mRNA did not indicate a protein corresponding to the in vitro translation product of artificial MDGI mRNA. Moreover, two-dimensional electrophoresis of bovine mammary gland proteins confirmed the absence of a protein with the pI of the in vitro translated artificial MDGI mRNA in bovine mammary gland and instead revealed, apart from H-FABP, an unknown protein that was recognized by anti-H-FABP antibodies. From lactating bovine mammary gland the cDNA for adipocyte fatty acid-binding protein (A-FABP) was cloned. The in vitro translation of recombinant mRNA derived from this cDNA yielded a polypeptide that behaved like the unknown immunoreactive protein. Western blotting and immunofluorescence using monospecific antibodies demonstrated the coexistence of H-FABP and A-FABP in the lactating mammary gland. Taking into account that deviations of the MDGI sequence from the bovine H-FABP sequence correspond with A-FABP we attribute the structure originally reported as MDGI to a mix of these proteins.

Expression of cutaneous fatty acid-binding protein and its mRNA in rat skin

Cutaneous fatty acid-binding protein (C-FABP) has been purified from rat skin. Since there was little information about the role of C-FABP in the skin, we investigated the expression of C-FABP and its mRNA in normal rat skin using an immunohistochemical technique and in situ hybridization. In the epidermis, C-FABP mRNA was found to be expressed in basal cells and highly in prickle cells, while C-FABP itself was strongly expressed in the upper prickle and the granular cell layers. In sebaceous glands, both C-FABP and its mRNA were expressed in both peripheral and differentiating cells, although the expression of C-FABP mRNA gradually reduced during differentiation of sebocytes. Since epidermis and sebaceous glands are active sites of fatty acid synthesis, these results suggest that C-FABP may have important roles in the transport and synthesis of fatty acids.

Purification and structural characterization of a fatty acid-binding protein from the liver of the catfish Rhamdia sapo

We report here the isolation of a fatty acid-binding protein (FABP) from the liver of the catfish Rhamdia sapo. The purification procedure involves gel filtration, anion-exchange chromatography and reverse-phase high-performance liquid chromatography. The purified protein is basic (pI > 8.7) and migrates on sodium dodecyl sulfate-gel electrophoresis as a single entity of about 15 kDa. Its amino acid composition resembles those of FABPs isolated from other animals. Unlike mammalian liver FABPs, catfish liver FABP contains at least one tryptophan residue per molecule. No significant cross-reactivity was observed between the purified protein and polyclonal antibodies against either rat liver FABP or rat heart FABP. Amino acid sequencing of peptides obtained by digestion with Lys-C revealed that the catfish protein is structurally more similar to chicken liver FABP (69% identity in a 67-residue overlap) than to human liver FABPs (36%), nurse shark (Ginglymostoma cirratum) liver FABP (30%) and human heart FABP (31%). Taken together, these results suggest that catfish liver FABP is far more closely related to chicken liver FABP than to the FABPs isolated from the liver of mammals or elasmobranchs.

Membrane-associated and cytoplasmic fatty acid-binding proteins

A number of cellular fatty acid-binding proteins are being implicated in the uptake and intracellular transport of long-chain fatty acids by parenchymal cells. Having been a topic of research for more than 20 years, cytoplasmic fatty acid-binding proteins now are assigned various pivotal functions in intracellular fatty acid transport and metabolism. More recently several membrane-associated fatty acid-binding proteins have been identified and these proteins are thought to function in the transmembrane transport of fatty acids. In this review, a short summary is provided of the latest developments in this research area.

Saturable binding sites for the coenzyme A ester of nafenopin, a peroxisome proliferator, in rat liver cytosol

1. At least three different molecular weight binding sites exist in rat liver cytosol for nafenopin-CoA, the coenzyme A ester and metabolic product of the carcinogenic peroxisome proliferator nafenopin. No binding sites for the free drug were observed. 2. Polypeptides of 35-40 kDa molecular weight range where no acyl-CoA binding proteins have been previously described bind the highest proportion of nafenopin-CoA (60-70%). Binding is displaceable by the CoA esters of other peroxisome proliferators (ciprofibrate and tibric acid) and also by oleoyl-CoA but by palmitoyl-CoA. Direct binding studies show that 35-40-kDa polypeptides bind oleoyl-CoA but not oleic or palmitic acid, or palmitoyl-CoA. 3. Polypeptides of 10-14 and 65-70 kDa also bind nafenopin-CoA. However, in contrast with 35-40-kDa polypeptides they also bind oleic and palmitic acid as well as their correspondent acyl-CoA thioesters.

Developmental role of fatty acid-binding proteins in mouse brain

While the functions of the cytoplasmic fatty acid-binding proteins (FABPs) are not well defined, one possibility in neural tissue is in establishing and maintaining the high levels of polyunsaturated fatty acids in membrane lipids characteristic of this tissue and thought essential for normal function. We investigated the reactivity of a protein in developing mouse brain to antiserum prepared against rat heart (H)-FABP. By immunoblot analysis, levels of H-FABP in brain were nearly undetectable until fetal day 17-19, after which levels increased until at least postnatal day 14. Levels of H-FABP were lower in the adult mouse brain, suggesting a function for the protein during differentiation of neural tissue. In immunohistochemical studies with postnatal day 14 mouse brain, the most intensely stained area was the choroid plexus. H-FABP also localized to regions of the somatosensory cortex and to the spinal trigeminal nucleus. In addition, H-FABP was present in the thalamus, entorhinal and piriform cortex, and throughout the pontine and medullary nuclei. Tracts related to the auditory system, including ventral cochlear nucleus and lateral lemniscus, also were H-FABP-positive. In cerebellum, the molecular layer was heavily labeled in cells and processes; in the granule cell layer, there was punctate staining suggestive of mossy fiber terminals. Small cells adjacent to Purkinje cells were intensely stained, while the Purkinje cells were negative. We conclude that H-FABP in brain participates in neurite formation and synapse maturation, and may be related to the similar pattern of expression of GABA related markers.

Purification and characterization of fatty acid-binding protein from aerobic muscle of the Antarctic icefish Chaenocephalus aceratus

Intracellular fatty acid-binding protein is purified and characterized from aerobic skeletal muscle of the Antarctic icefish Chaenocephalus aceratus. Molecular mass of C. aceratus FABP (CA-FABP) is 14,936 Da as estimated by electrospray mass spectrometry. CA-FABP is expressed at an intracellular concentration of 0.984 +/- 0.115 mg CA-FABP g-1 wet weight aerobic muscle and binds 0.859 +/- 0.013 moles oleic acid per mole of protein at a physiological temperature of 0 degrees C. Dissociation constants (KdS for various fatty acid ligands range from 1.38 to 2.71 microM; KdS are not significantly different among palmitic acid (16:0), palmitoleic acid (16:1), and oleic acid (18:1). Competition assays reveal that CA-FABP does not have preferential affinity for the very-long-chain, polyunsaturated fatty acids that are common in Antarctic fish (e.g., docosahexaenoic acid; 22:6). Partial amino acid sequence from CA-FABP aligns with mammalian heart-type FABPs with as high as 74% identity. These data are strikingly similar to mammalian values, yet they are derived from an organism that is distant from mammals in terms of phylogeny, body temperature, and physiology. This suggests that the FABP family is conserved not only in primary sequence, but also in its physiological properties.

Arachidonic acid and free fatty acids as second messengers and the role of protein kinase C

In addition to serving as the precursor to a plethora of eicosanoids and other bioactive molecules, arachidonate may function as a bona fide second messenger. A number of studies have documented the ability of arachidonate to regulate the function of multiple targets in vitro systems. This has been particularly well established and studied with the activation of protein kinase C by arachidonate in a mechanism distinct from activation by diacylglycerol. In cells, arachidonate induces a number of activities, many of which may be independent of further metabolism to eicosanoids; suggesting possible direct action of arachidonate. This review summarizes the current state of knowledge on the possible second messenger function of arachidonate with specific emphasis on the regulation of protein kinase C.

Histochemical localization of heart-type fatty-acid binding protein in human and murine tissues

Cellular fatty acid-binding proteins (FABP) are a highly conserved family of proteins consisting of several subtypes, among them the mammary-derived growth inhibitor (MDGI) which is quite homologous to or even identical with the heart-type FABP (H-FABP). The FABPs and MDGI have been suggested to be involved in intracellular fatty acid metabolism and trafficking. Recently, evidence for growth and differentiation regulating properties of MDGI and H-FABP was provided. Using four affinity-purified polyclonal antibodies against bovine and human antigen preparations, the cellular localization of MDGI/H-FABP in human and mouse tissues and organs was studied. The antibodies were weakly cross-reactive with adipose tissue extracts known to lack H-FABP, but failed to react by Western blot analysis with liver-type FABP (L-FABP) and intestinal-type FABP (I-FABP). MDGI/H-FABP protein was mainly detected in myocardium, skeletal and smooth muscle fibres, lipid and/or steroid synthesising cells (adrenals, Leydig cells, sebaceous glands, lactating mammary gland) and terminally differentiated epithelia of the respiratory, intestinal and urogenital tracts. The results provide evidence that expression of H-FABP is associated with an irreversibly postmitotic and terminally differentiated status of cells. Since all the antisera employed showed spatially identical and qualitatively equal immunostaining, it is suggested that human, bovine and mouse MDGI/H-FABP proteins share highly homologous epitopes.

Fatty acids in cell signalling: modulation by lipid binding proteins

Long-chain fatty acids and several of their metabolites have now been shown to be involved as primary or secondary messengers in specific cell signalling pathways. In view of their extremely low aqueous solubility, the extracellular as well as intracellular transport of these compounds is assumed to be facilitated by specific lipid binding proteins, such as cytoplasmic fatty acid-binding protein (FABP). In this paper a survey is given on the biological significance and possible modulatory action of intracellular lipid binding proteins for fatty acid-mediated signal transduction pathways.

Members of the fatty acid binding protein family are differentiation factors for the mammary gland

Mammary gland development is controlled by systemic hormones and by growth factors that might complement or mediate hormonal action. Peptides that locally signal growth cessation and stimulate differentiation of the developing epithelium have not been described. Here, we report that recombinant and wild-type forms of mammary-derived growth inhibitor (MDGI) and heart-fatty acid binding protein (FABP), which belong to the FABP family, specifically inhibit growth of normal mouse mammary epithelial cells (MEC), while growth of stromal cells is not suppressed. In mammary gland organ culture, inhibition of ductal growth is associated with the appearance of bulbous alveolar end buds and formation of fully developed lobuloalveolar structures. In parallel, MDGI stimulates its own expression and promotes milk protein synthesis. Selective inhibition of endogenous MDGI expression in MEC by antisense phosphorothioate oligonucleotides suppresses appearance of alveolar end buds and lowers the beta-casein level in organ cultures. Furthermore, MDGI suppresses the mitogenic effects of epidermal growth factor, and epidermal growth factor antagonizes the activities of MDGI. Finally, the regulatory properties of MDGI can be fully mimicked by an 11-amino acid sequence, represented in the COOH terminus of MDGI and a subfamily of structurally related FABPs. This peptide does not bind fatty acids. To our knowledge, this is the first report about a growth inhibitor promoting mammary gland differentiation.

Retinoic acid induces expression of PA-FABP (psoriasis-associated fatty acid-binding protein) gene in human skin in vivo but not in cultured skin cells

PA-FABP (psoriasis-associated fatty acid-binding protein) is a new member of a group of low-molecular-weight proteins that are highly up-regulated in psoriatic skin and that share similarity to fatty acid-binding proteins. In this study we demonstrate that PA-FABP transcripts are expressed in human skin in vivo and that topical application of 0.05% retinoic acid (RA) cream results in a rapid induction of PA-FABP transcripts following treatment for 16 hours and persists at increasing levels after 48 and 96 h of RA treatment. The PA-FABP mRNA response to RA was reduced by approximately 50% when patients concurrently were treated with RA and 0.025% clobetasol propionate (CLO) for 48 and 96 h, whereas treatment with CLO alone resulted in PA-FABP transcript levels not significantly different from vehicle-treated skin. When comparing the effects of a well-known irritant, sodium lauryl sulfate (SLS), to those of RA and its vehicle, 0.05% RA cream but not 2% SLS in RA vehicle caused PA-FABP mRNA induction after 16 h. SLS treatment of human skin for 96 h caused a slight increase in PA-FABP transcripts, but markedly less than that observed in response to RA treatment. Incubation of cultured human keratinocytes or skin fibroblasts with RA for up to 48 h did not significantly induce PA-FABP transcripts. Expression of PA-FABP message in keratinocytes was observed to be induced by calcium and fetal calf serum (FCS), while tetra-decanoyl phorbol acetate (TPA) caused little or no induction.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential cytotoxic effects of gamma-linolenic acid on MG-63 and HeLa cells

Gamma-linolenic acid (GLA) inhibited cell proliferation in MG-63 and HeLa cells. Different morphological lesions were present in dividing cells; abnormal spindle formation in MG-63 cells and chromosome hypercondensation in HeLa cells. Different types of cell death were also present in interphase cells, no apoptosis but only 6% pycnosis in MG-63 cells and 90% apoptosis in HeLa cells. In MG-63 cells immunofluorescence showed segregation of nucleoli components, abnormal spindle formation and decreased labelling of microtubuli during interphase. In HeLa interphase cells prominently labelled abnormally arranged microtubuli were observed. The effects of GLA on protein synthesis in synchronized cells were determined with [35S]-methionine incorporation and SDS-PAGE. Decreased protein synthesis in both G1- and S-phase MG-63 cells was present. In S-phase HeLa cells, proteins of approximately 40, 92 and 150 kD were markedly expressed. Signalling mechanisms involved in cell proliferation and cell death may be differently affected in MG-63 and HeLa cells.

Developmental regulation of fatty acid binding protein in neural tissue

Fatty acid binding proteins (FABP) constitute a family of small, cytosolic carriers of hydrophobic ligands. These proteins are thought to be important for lipid trafficking toward specific metabolic pathways, and are potentially important for the establishment of characteristic lipid compositions of neural tissue. In the embryonic chick retina and brain, FABP resembles the heart subtype, as determined by protein characterization and immunoblot studies. In this paper, the developmental expression and cellular localization of chick retinal FABP were examined. Results of immunoblot analysis suggest that FABP is maximally expressed around embryonic day 9 (E9) and declines thereafter. In adult retinas, FABP is barely detectable on a Western blot. Immunohistochemical staining of the retina shows light labeling on day E6 and a more intense staining throughout the retina on day E9. As the retina differentiates, labeling becomes increasingly localized. By day E18 subpopulations of ganglion cells and photoreceptor inner segments are stained, as are all photoreceptor cell bodies, most of the inner nuclear layer, and the nerve fiber layer. Staining is decreased in older retinas such that in adult animals, only light staining of the photoreceptor cell bodies is visible. The decrease in relative amount of FABP in the retina after day E9 suggests a role for FABP in the early stages of retinal differentiation. Localization in the retina is consistent with this hypothesis, as label becomes more restricted to those cells undergoing maturation at a particular developmental age. Thus, in young embryos (E6-E9), FABP immunolabeling is apparent throughout the retina, and transiently localizes at different ages (E12-E15) to plexiform and nuclear layers.(ABSTRACT TRUNCATED AT 250 WORDS)

Fatty acid binding of myoglobin depends on its oxygenation

In the present work we show with different binding assays chicken gizzard myoglobin is able to bind fatty acids and bromosulphophthalein (BSP) in vitro. The fatty acid binding depends on the oxygenation of the myoglobin. Freshly prepared chicken gizzard, chicken or bovine heart myoglobin have a high fatty acid binding capability. However, when oxy-myoglobin in converted to met-myoglobin by dialysis against acidic buffer at high ionic strength (or when commercially available myoglobins are used) a 60-70% lower fatty acid binding capacity is found. Like bovine serum albumin (BSA), gizzard myoglobin has the highest affinity for unsaturated fatty acids and a lower affinity for saturated fatty acids or dyes. Chicken gizzard smooth muscle myoglobin may function as an additional fatty acid binding protein in vivo.

Fatty acid-binding proteinuria diagnoses myocardial infarction in the rat

Cytoplasmic heart-type fatty acid-binding protein (H-FABPc) is a low molecular weight protein with abundant presence in the myocardium. Upon ischemia it is released from the heart and can subsequently be detected in plasma and urine. In this study, the value of measurement of H-FABPc excreted into urine for the diagnosis of myocardial infarction (MI) is investigated in the rat. To this end, firstly the kinetic behaviour of H-FABPc in plasma was examined and its release into urine quantified. After injection of purified H-FABPc in normal animals, a net recovery in urine of 14-29% was found. The kinetic behaviour of H-FABPc in plasma was characterized by a total clearance of 0.33 ml/min and a half-life value of total elimination of about 270 min. Knowing these plasma characteristics of H-FABPc, a comparison was made between the cumulative amounts of H-FABPc released in the 24-hour urine of MI rats and of sham-operated animals. In MI rats, with a mean morphometric MI size of 43%, the mean total amount of H-FABPc excreted into urine was 79 micrograms, while in sham-operated rats this was 23 micrograms. This difference between both groups is significant (p < 0.001). It is concluded that urinary H-FABPc can be used as a noninvasive marker for MI in the rat.

Significance of cytoplasmic fatty acid-binding protein for the ischemic heart

Ischemia of the heart is accompanied by the tissue accumulation of long-chain fatty acids and their metabolic derivatives such as beta-hydroxy fatty acids and fatty acyl-CoA and acyl-L-carnitine esters. These substances might be detrimental for proper myocardial function. Previously, it has been suggested that intracellular lipid binding proteins like cytoplasmic fatty acid-binding protein (FABP) and acyl-CoA binding protein (ACBP) may bind these accumulating fatty acyl moieties to prevent their elevated levels from potentially harmful actions. In addition, the suggestion has been made that the abundantly present FABP may scavenge free radicals which are generated during reperfusion of the ischemic heart. However, these protective actions are challenged by the continuous physico-chemical partition of fatty acyl moieties between FABP and membrane structures and by the rapid release of FABP from ischemic and reperfused cardiac muscle. Careful evaluation of the available literature data reveals that at present no definite conclusion can be drawn about the potential protective effect of FABP on the ischemic and reperfused heart.

The effects of gamma-linolenic acid on breast pain and diabetic neuropathy: possible non-eicosanoid mechanisms

Gamma-linolenic acid (GLA) has recently been found to be beneficial in the management of breast pain and of diabetic neuropathy. GLA is a precursor of unsaturated fatty acids which are important in membrane structures, as second messengers in their own right and as precursors of eicosanoids. While the mechanisms of GLA action are likely to be complex, non-eicosanoid effects are probably of substantial importance. These effects include modification of membrane fluidity and of the functions of lipid-associated receptors and changes in the inositol cycle.