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BBA - Molecular and Cell Biology of Lipids (v.1811, #3)

Editorial Board (pp. i).

Heterogeneous sphingosine-1-phosphate lyase gene expression and its regulatory mechanism in human lung cancer cell lines by Hiromi Ito; Kayo Yoshida; Masashi Murakami; Kazumi Hagiwara; Noriko Sasaki; Misa Kobayashi; Akira Takagi; Tetsuhito Kojima; Sayaka Sobue; Motoshi Suzuki; Keiko Tamiya-Koizumi; Mitsuhiro Nakamura; Yoshiko Banno; Yoshinori Nozawa; Takashi Murate (pp. 119-128).

The role of sphingolipid metabolic pathway has been recognized in determining cellular fate. Although sphingolipid degradation has been extensively studied, gene expression of human sphingosine 1-phosphate lyase (SPL) catalyzing sphingosine 1-phosphate (S1P) remains to be determined. Among 5 human lung cancer cell lines examined, SPL protein levels paralleled the respective mRNA and enzyme activities. Between H1155 and H1299 cells used for further experiments, higher cellular S1P was observed in H1155 with higher SPL activity compared with H1299 with low SPL activity. GATA-4 has been reported to affect SPL transcription in Dictyostelium discoideum. GATA-4 was observed in H1155 but not in other cell lines. Overexpression of GATA-4 in H1299 increased SPL expression. However, promoter analysis of human SPL revealed that the most important region was located between −136bp and −88bp from the first exon, where 2 Sp1 sites exist but no GATA site. DNA pull-down assay of H1155 showed increased DNA binding of Sp1 and GATA-4 within this promoter region compared with H1299. Electrophoresis mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP) assay, reporter assay using mutated binding motif, and mithramycin A, a specific Sp1 inhibitor, suggest the major role of Sp1 in SPL transcription and no direct binding of GATA-4 with this 5′ promoter region. The collaborative role of GATA-4 was proved by showing coimmunoprecipitation of Sp1 and GATA-4 using GST-Sp1 and overexpressed GATA-4. Thus, high SPL transcription of H1155 cells was regulated by Sp1 and GATA-4/Sp1 complex formation, both of which bind to Sp1 sites of the 5′-SPL promoter.►Sphingosine 1-phosphate lyase expression (SPL) levels vary in lung cancer cell lines. ►SPL and anti-cancer drug sensitivity are correlated in some lung cancer cell lines. ►SPL expression is regulated at the transcription level. ►The 5′-promoter region of SPL important for transcription is determined. ►Sp1 and GATA-4 transcription factors are involved in SPL transcription.

Keywords: Abbreviations; SPL; sphingosine 1-phosphate lyase; DA; daunorubicin; ETP; etoposide; S1P; sphingosine 1-phosphate; Sp1; specificity protein 1; ChIP; chromatin immunoprecipitation; EMSA; electrophoresis mobility shift assaySphingosine 1-phosphate lyase (SPL); Sp1; GATA-4; Promoter analysis; DNA pull-down and EMSA; Chromatin immunoprecipitation assay (ChIP)

Effect of ceramide acyl chain length on skin permeability and thermotropic phase behavior of model stratum corneum lipid membranes by Janůšova Barbora Janůšová; Zbytovska Jarmila Zbytovská; Petr Lorenc; Vavrysova Helena Vavrysová; Palat Karel Palát; Hrabalek Alexandr Hrabálek; Vavrova Kateřina Vávrová (pp. 129-137).

Stratum corneum ceramides play an essential role in the barrier properties of skin. However, their structure–activity relationships are poorly understood. We investigated the effects of acyl chain length in the non-hydroxy acyl sphingosine type (NS) ceramides on the skin permeability and their thermotropic phase behavior. Neither the long- to medium-chain ceramides (8–24C) nor free sphingosine produced any changes of the skin barrier function. In contrast, the short-chain ceramides decreased skin electrical impedance and increased skin permeability for two marker drugs, theophylline and indomethacin, with maxima in the 4–6C acyl ceramides. The thermotropic phase behavior of pure ceramides and model stratum corneum lipid membranes composed of ceramide/lignoceric acid/cholesterol/cholesterol sulfate was studied by differential scanning calorimetry and infrared spectroscopy. Differences in thermotropic phase behavior of these lipids were found: those ceramides that had the greatest impact on the skin barrier properties displayed the lowest phase transitions and formed the least dense model stratum corneum lipid membranes at 32°C. In conclusion, the long hydrophobic chains in the NS-type ceramides are essential for maintaining the skin barrier function. However, this ability is not shared by their short-chain counterparts despite their having the same polar head structure and hydrogen bonding ability.Display Omitted► Short-chain ceramides decrease skin barrier properties. ► Maxima of skin permeability in ceramides with 4–6C acyl. ► Barrier properties of ceramides correlate with their thermotropic behavior.

Keywords: Abbreviations; Cer; ceramide/s; Chol; cholesterol; CholS; cholesterol sulfate; DSC; differential scanning calorimetry; FFA; free fatty acid; FT-IR; Fourier transform infrared spectroscopy; IND; indomethacin; NS; non-hydroxyacyl sphingosine; SC; stratum corneum; TH; theophyllineSkin barrier; Stratum corneum; Short-chain ceramides; Structure–activity relationships; Infrared spectroscopy; Differential scanning calorimetry

Manganese lipoxygenase oxidizes bis-allylic hydroperoxides and octadecenoic acids by different mechanisms by Ernst H. Oliw; Jerneren Fredrik Jernerén; Inga Hoffmann; Margareta Sahlin; Ulrike Garscha (pp. 138-147).

Manganese lipoxygenase (MnLOX) oxidizes (11 R)-hydroperoxylinolenic acid (11 R-HpOTrE) to a peroxyl radical. Our aim was to compare the enzymatic oxidation of 11 R-HpOTrE and octadecenoic acids with LOO―H and allylic C―H bond dissociation enthalpies of ~88 and ~87kcal/mol. Mn(III)LOX oxidized (11 Z)- , (12 Z)-, and (13 Z)-18:1 to hydroperoxides with R configuration, but this occurred at insignificant rates (<1%) compared to 11 R-HpOTrE. We next examined whether transitional metals could mimic this oxidation. Ce⁴⁺ and Mn³⁺ transformed 11 R-HpOTrE to hydroperoxides at C-9 and C-13 via oxidation to a peroxyl radical at C-11, whereas Fe³⁺ was a poor catalyst. Our results suggest that MnLOX oxidizes bis-allylic hydroperoxides to peroxyl radicals in analogy with Ce⁴⁺ and Mn³⁺. The enzymatic oxidation likely occurs by proton-coupled electron transfer of the electron from the hydroperoxide anion to Mn(III) and H⁺ to the catalytic base, Mn(III)OH⁻. Hydroperoxides abolish the kinetic lag times of MnLOX and FeLOX by oxidation of their metal centers, but 11 R-HpOTrE was isomerized by MnLOX to (13 R)-hydroperoxy-(9 Z,11 E,15 Z)-octadecatrienoic acid (13 R-HpOTrE) with a kinetic lag time. This lag time could be explained by two competing transformations, dehydration of 11 R-HpOTrE to 11-ketolinolenic acid and oxidation of 11 R-HpOTrE to peroxyl radical; the reaction rate then increases as 13 R-HpOTrE oxidizes MnLOX with subsequent formation of two epoxyalcohols. We conclude that oxidation of octadecenoic acids and bis-allylic hydroperoxides occurs by different mechanisms, which likely reflect the nature of the hydrogen bonds, steric factors, and the redox potential of the Mn(III) center.Display Omitted► Mn-lipoxygenase rapidly oxidizes bis-allylic hydroperoxides (LOOH) to radicals (LOO⋅). ► Monounsaturated fatty acids are oxidized only slowly by Mn-lipoxygenase. ► The dissociation enthalpies of LOO–H and allylic C–H bonds are almost identical. ► Both oxidations occur by proton-coupled electron transfer to the lipoxygenase. ► Proton transfer from LOOH to the catalytic base Mn³⁺OH⁻ is facilitated by dissociation.

Keywords: Abbreviations; BDE; bond dissociation enthalpy; CP; chiral phase; HOME(m; Z; ); hydroxy-(m; Z; )-octadecenoic acid; HOTrE; hydroxyoctadecatrienoic acid; HPLC; high performance liquid chromatography; HpODE; hydroperoxyoctadecadienoic acid; HpOME; hydroperoxyoctadecenoic acid; HpOTrE; hydroperoxyoctadecatrienoic acid; KOME; ketooctadecenoic acid; KOTrE; keto-octadecatrienoic acid; LC; liquid chromatography; LOX; lipoxygenase; MnLOX; manganese lipoxygenase; MS; mass spectrometry; (m; Z; )-18:1; (m; Z; )-octadecenoic acid; 4-NC; 4-nitrocatechol; MS/MS; tandem MS; NL; normalized; NP; normal phase; PCET; proton-coupled electron transfer; PGH; prostaglandin H; RP; reverse phase; sLOX-1; soybean lipoxygenase-1; TIC; total ion currentProton coupled electron transfer; Fatty acid oxidation; PGH synthase; Mass spectrometry; Redox chemistry

Differential substrate specificities of human ABCD1 and ABCD2 in peroxisomal fatty acid β-oxidation by Carlo W.T. van Roermund; Wouter F. Visser; Lodewijk IJlst; Hans R. Waterham; Ronald J.A. Wanders (pp. 148-152).

The gene mutated in X-linked adrenoleukodystrophy (X-ALD) codes for the HsABCD1 protein, also named ALDP, which is a member of the superfamily of ATP-binding cassette (ABC) transporters and required for fatty acid transport across the peroxisomal membrane. Although a defective HsABCD1 results in the accumulation of very long-chain fatty acids in plasma of X-ALD patients, there is still no direct biochemical evidence that HsABCD1 actually transports very long-chain fatty acids. We used the yeast Saccharomyces cerevisiae to study the transport of fatty acids across the peroxisomal membrane. Our earlier work showed that in yeast the uptake of fatty acids into peroxisomes may occur via two routes, either as (1.) free fatty acid or as (2.) acyl-CoA ester. The latter route involves the two peroxisomal half-ABC transporters, Pxa1p and Pxa2p, which form a heterodimeric complex in the peroxisomal membrane. We here report that the phenotype of the pxa1/ pxa2Δ yeast mutant, i.e. impaired growth on oleate containing medium and deficient oxidation of oleic acid, cannot only be partially rescued by human ABCD1, but also by human ABCD2 (ALDRP), which indicates that HsABCD1 and HsABCD2 can both function as homodimers. Fatty acid oxidation studies in the pxa1/ pxa2Δ mutant transformed with either HsABCD1 or HsABCD2 revealed clear differences suggesting that HsABCD1 and HsABCD2 have distinct substrate specificities. Indeed, full rescue of beta-oxidation activity in cells expressing human ABCD2 was observed with C22:0 and different unsaturated very long-chain fatty acids including C24:6 and especially C22:6 whereas in cells expressing HsABCD1 rescue of beta-oxidation activity was best with C24:0 and C26:0 as substrates.Display Omitted► Fatty acid transport across the peroxisomal membrane in S. cerevisiae. ► The phenotype of pxa1/pxa2D cells can be partially rescued by the expression of HsABCD1 and HsABCD2. ► The peroxisomal disorder X-ALD is caused by mutations in the ABCD1 gene. ► The human peroxisomal half-ABC transporter ABCD1 accepts different acyl-CoA esters than ABCD2.

Keywords: Peroxisome; Beta-oxidation; ABC transporter; FA transport; ABCD1; ABCD2

Oxidized LDL and lysophosphatidylcholine stimulate plasminogen activator inhibitor-1 expression through reactive oxygen species generation and ERK1/2 activation in 3T3-L1 adipocytes by Akihiko Kuniyasu; Mariko Tokunaga; Takashi Yamamoto; Shoko Inoue; Keiko Obama; Kohichi Kawahara; Hitoshi Nakayama (pp. 153-162).

Plasminogen activator inhibitor-1 (PAI-1) is secreted from adipose tissue and is considered to be a risk factor for both atherosclerosis and insulin resistance. Here we report for the first time that PAI-1 expression is enhanced by oxidized low-density lipoprotein (OxLDL) and its lipid component lysophosphatidylcholine (LPC) in mouse 3T3-L1 adipocytes. In fully differentiated 3T3-L1 cells, OxLDL treatment increased the mRNA expression and protein secretion of PAI-1 in a dose- and time-dependent manner, whereas native LDL had no effect. The addition of an anti-CD36 antibody suppressed OxLDL-stimulated PAI-1 expression by 50%, suggesting that adipose-derived CD36 contributes to roughly half of the PAI-1 expression stimulated by OxLDL. In addition, pharmacological experiments showed that the OxLDL-stimulated enhancement in PAI-1 expression was mediated through the generation of reactive oxygen species (ROS) and phosphorylation of extracellular signal-regulated kinase 1/2. Furthermore, LPC, a major lipid component of OxLDL, was responsible for the enhanced expression of PAI-1 as phospholipase A₂-treated acetyl LDL, which generates LPC, strongly stimulated PAI-1 expression, whereas acetyl LDL itself had no such activity. These data demonstrate that the uptake of OxLDL and, in particular, its lipid component LPC into adipocytes triggers aberrant ROS-mediated PAI-1 expression, which may be involved in the pathogenesis of metabolic syndrome.Display Omitted►OxLDL stimulates PAI-1 expression in adipocytes. ►The up-regulation of PAI-1 is mediated by ROS generation and ERK1/2 activation. ►OxLDL-stimulated PAI-1 expression was mediated by adipose CD36. ►LPC is a lipid component responsible for the enhancement of PAI-1 expression.

Keywords: Abbreviations; LDL; low-density lipoprotein; OxLDL; oxidized LDL; PAI-1; plasminogen activator inhibitor-1; LPC; lysophosphatidylcholine; PLA; ₂; phospholipase A; ₂; MAPK; mitogen-activated protein kinase; ERK1/2; extracellular signal-regulated kinase 1/2Oxidized LDL; Plasminogen activator inhibitor-1; Adipocytes; Lysophosphatidylcholine; Reactive oxygen species; Extracellular signal-regulated kinase

Valproate uncompetitively inhibits arachidonic acid acylation by rat acyl-CoA synthetase 4: Relevance to valproate's efficacy against bipolar disorder by Jakob A. Shimshoni; Mireille Basselin; Lei O. Li; Rosalind A. Coleman; Stanley I. Rapoport; Hiren R. Modi (pp. 163-169).

Background: The ability of chronic valproate (VPA) to reduce arachidonic acid (AA) turnover in brain phospholipids of unanesthetized rats has been ascribed to its inhibition of acyl-CoA synthetase (Acsl)-mediated activation of AA to AA-CoA. Our aim was to identify a rat Acsl isoenzyme that could be inhibited by VPA in vitro. Methods: Rat Acsl3-, Acsl6v1- and Acsl6v2-, and Acsl4-flag proteins were expressed in E. coli, and the ability of VPA to inhibit their activation of long-chain fatty acids to acyl-CoA was estimated using Michaelis–Menten kinetics. Results: VPA uncompetitively inhibited Acsl4-mediated conversion of AA and of docosahexaenoic (DHA) but not of palmitic acid to acyl-CoA, but did not affect AA conversion by Acsl3, Acsl6v1 or Acsl6v2. Acsl4-mediated conversion of AA to AA-CoA showed substrate inhibition and had a 10-times higher catalytic efficiency than did conversion of DHA to DHA-CoA. Butyrate, octanoate, or lithium did not inhibit AA activation by Acsl4. Conclusions: VPA's ability to inhibit Acsl4 activation of AA and of DHA to their respective acyl-CoAs, when related to the higher catalytic efficiency of AA than DHA conversion, may account for VPA's selective reduction of AA turnover in rat brain phospholipids, and contribute to VPA's efficacy against bipolar disorder.► Valproate uncompetitively inhibited activation of recombinant acyl-CoA synthetase 4. ► Inhibition was selective for conversion of arachidonic acid (AA) to its acyl-CoA. ► Acsl4 inhibition may explain valproate’s reduction of AA turnover in rat brain. ► Acsl4 inhibition may account for valproate’s efficacy in bipolar disorder. ► Acsl4 inhibition can help to screen for anti-bipolar drugs less toxic than valproate.

Keywords: Abbreviations; VPA; valproate; AA; arachidonic acid; DHA; docosahexaenoic acid; Acsl; acyl-CoA synthetase; COX; cyclooxygenase; cPLA; ₂; cytosolic phospholipase A; ₂; BD; bipolar disorderBipolar disorder; Valproate; Arachidonic acid; Acyl-CoA synthetase; Mood stabilizer; Acsl4; Brain; Rat

Fenofibrate, a peroxisome proliferator-activated receptor α agonist, alters triglyceride metabolism in enterocytes of mice by Aki Uchida; Mikhail N. Slipchenko; Ji-Xin Cheng; Kimberly K. Buhman (pp. 170-176).

Fenofibrate, a drug in the fibrate class of amphiphathic carboxylic acids, has multiple blood lipid modifying actions, which are beneficial to the prevention of atherosclerosis. One of its benefits is in lowering fasting and postprandial blood triglyceride (TG) concentrations. The goal of this study was to determine whether the hypotriglyceridemic actions of fenofibrate in the postprandial state include alterations in TG and fatty acid metabolism in the small intestine. We found that the hypotriglyceridemic actions of fenofibrate in the postprandial state of high-fat (HF) fed mice include a decrease in supply of TG for secretion by the small intestine. A decreased supply of TG for secretion was due in part to the decreased dietary fat absorption and increased intestinal fatty acid oxidation in fenofibrate compared to vehicle treated HF fed mice. These results suggest that the effects of fenofibrate on the small intestine play a critical role in the hypotriglyceridemic effects of fenofibrate.► Fenofibrate decreases postprandial triglyceride secretion from enterocytes. ► Fenofibrate increases fatty acid oxidation in enterocytes. ► Fenofibrate decreases quantitative dietary fat absorption.

Keywords: Abbreviations; CM; chylomicrons; CARS; coherent anti-Stokes Raman scattering; CLD; cytoplasmic lipid droplets; FEN; fenofibrate; HF; high-fat; LPL; lipoprotein lipase; PPARα; peroxisome proliferator-activated receptor-α; TG; triglyceride; VEH; vehicleChylomicron; Cytoplasmic lipid droplet; Dietary fat absorption; Fatty acid oxidation; Fenofibrate; Triglyceride

Identification and the developmental formation of carotenoid pigments in the yellow/orange Bacillus spore-formers by Laura Perez-Fons; Sabine Steiger; Reena Khaneja; Peter M. Bramley; Simon M. Cutting; Gerhard Sandmann; Paul D. Fraser (pp. 177-185).

Spore-forming Bacillus species capable of synthesising carotenoid pigments have recently been isolated. To date the detailed characterisation of these carotenoids and their formation has not been described. In the present article biochemical analysis on the carotenoids responsible for the yellow/orange pigmentation present in Bacilli has been carried out and the identity of the carotenoids present was elucidated. Chromatographic, UV/Vis and Mass Spectral (MS) data have revealed the exclusive presence of a C₃₀ carotenoid biosynthetic pathway in Bacillus species. Apophytoene was detected representing the first genuine carotenoid formed by this pathway. Cultivation in the presence of diphenylamine (DPA), a known inhibitor of pathway desaturation resulted in the accumulation of apophytoene along with other intermediates of desaturation (e.g. apophytofluene and apo-ζ-carotene). The most abundant carotenoids present in the Bacillus species were oxygenated derivatives of apolycopene, which have either undergone glycosylation and/or esterification. The presence of fatty acid moieties (C₉ to C₁₅) attached to the sugar residue via an ester linkage was revealed by saponification and MS/MS analysis. In source fragmentation showed the presence of a hexose sugar associated with apolycopene derivatives. The most abundant apocarotenoids determined were glycosyl-apolycopene and glycosyl-4′-methyl-apolycopenoate esters. Analysis of these carotenoids over the developmental formation of spores revealed that 5-glycosyl-4′-methyl-apolycopenoate was related to sporulation. Potential biosynthetic pathways for the formation of these apocarotenoids in vegetative cells and spores have been reconstructed from intermediates and end-products were elucidated.Identification and the developmental formation of carotenoid pigments in the yellow/orange Bacillus spore-formers. Laura Perez-Fons, Sabine Steiger, Reena Khaneja, Simon M. Cutting, Gerhard Sandmann and Paul D. Fraser.Display Omitted►Pigmented Bacillus species are capable of forming apocarotenoids ►The apocarotenoids formed in Bacillus are complex undergoing derivatisation with sugar and fatty acid groups. ►The apocarotenoid pathway in the Bacillus species is inhibited by the presence of diphenylamine (DPA). ►The predominant apocarotenoids in these Bacillus species are glycosyl-apolycopene and glycosyl-4′-methyl-apolycopenoate. ►Developmental analysis revealed that 5-glycosyl-4′-methyl-apolycopenoate was related to sporulation.

Keywords: Apocarotenoids; Bacillus; Diphenylamine (DPA); Sporulation; Mass spectrometry

Structural characterization of the polar lipids of Clostridium novyi NT. Further evidence for a novel anaerobic biosynthetic pathway to plasmalogens by Ziqiang Guan; Norah C. Johnston; Semra Aygun-Sunar; Fevzi Daldal; Christian R.H. Raetz; Howard Goldfine (pp. 186-193).

A study of the polar lipids of Clostridium novyi NT has revealed the presence of phosphatidylethanolamine (PE) and cardiolipin as major phospholipids with smaller amounts of phosphatidylglycerol (PG), lysyl-PG and alanyl-PG. Other minor phospholipids included phosphatidic acid, CDP-diacylglycerol, phosphatidylserine (PS) and phosphatidylthreonine (PT). PE, PG and amino acyl PG were present in both the diacyl and alk-1′-enyl acyl (plasmalogen) forms and cardiolipin plasmalogens were found to contain one or two alk-1′-enyl chains. In contrast, the precursor lipids phosphatidic acid, CDP-diacylglycerol and PS were present almost exclusively as diacyl phospholipids. These findings are consistent with the hypothesis that plasmalogens are formed from diacylated phospholipids at a late stage of phospholipid formation in Clostridium species. This novel pathway contrasts with the route in animals in which a saturated ether bond is formed at an early stage of plasmalogen biosynthesis and the alk-1-enyl bond is formed by an aerobic mechanism.► The lipidome of Clostridium novyi is presented for the first time. ► The end-products of lipid biosynthesis are found in all acyl or plasmalogen species. ► The intermediates of phospholipid biosynthesis contain very little plasmalogen form. ► Plasmalogens in clostridia are formed from the corresponding all acyl lipids.

Keywords: Abbreviations; LC; liquid chromatography; MS; mass spectrometry; PA; phosphatidic acid; PE; phosphatidylethanolamine; PG; phosphatidylglycerol; PS; phosphatidylserine; PT; phosphatidylthreonine; TLC; thin layer chromatographyMass spectrometry; Plasmalogen; Phospholipid; Aminoacyl–phosphatidylglycerol

Transcriptional control mechanisms of genes of lipid and fatty acid metabolism in the Atlantic salmon ( Salmo salar L.) established cell line, SHK-1 by Matteo Minghetti; Michael J. Leaver; Douglas R. Tocher (pp. 194-202).

The regulatory control mechanisms of lipid and fatty acid metabolism were investigated in Atlantic salmon. We identified sterol regulatory element binding protein (SREBP) genes in salmon and characterised their response, and the response of potential target and other regulatory genes including liver X receptor (LXR), to cholesterol and long-chain polyunsaturated fatty acids (LC-PUFA) in the salmon established cell line, SHK-1. Two cDNAs for SREBPs homologous to mammalian SREBP-1 and SREBP-2 were characterised. We identified three groups of genes whose expression responded differently to the treatments. One group of genes, including cholesterol biosynthetic genes, showed increased expression in response to lipid depletion but supplementary cholesterol or LC-PUFA had no further effect. The expression of a second group of genes belonging to fatty acid biosynthetic pathways, included fatty acid synthase, Δ6 and Δ5 fatty acyl desaturases, also increased after lipid depletion but this was negated by cholesterol or by LC-PUFA supplementation. The expression of a third group of genes including acyl-CoA oxidase, HMG-CoA reductase and Elovl5 elongase was increased by cholesterol treatment but was not affected by lipid depletion or by LC-PUFA. This same pattern of expression was also shown by liver X receptor (LXR), indicating that acyl-CoA oxidase, HMG-CoA reductase and Elovl5 are possible direct targets of LXR. This suggests that salmon Elovl5 may be regulated differently from mammalian Elovl5, which is an indirect target of LXR, responding to LXR-dependent increases in SREBP-1.► cDNAs for SREBP-1 and SREBP-2 were characterised in Atlantic salmon. ► Response of SREBP and target genes to lipids investigated in cell culture. ► Three groups of genes were identified whose expression responded differently. ► Interaction of SREBP with LXR in regulation of lipid genes in salmon. ► Salmon Elovl5 elongase may be regulated differently from mammalian Elovl5.

Keywords: Transcription factor; Nuclear receptor; Gene expression; Lipid; Fatty acid; Cell culture

H₂O₂ disposal in cardiolipin-enriched brain mitochondria is due to increased cytochrome c peroxidase activity by Lara Macchioni; Magdalena Davidescu; Roberta Mannucci; Ermelinda Francescangeli; Ildo Nicoletti; Rita Roberti; Lanfranco Corazzi (pp. 203-208).

The mitochondrial electron transport chain is a source of oxygen superoxide anion (O₂^-) that is dismutated to H₂O₂. Although low levels of ROS are physiologically synthesized during respiration, their increase contributes to cell injury. Therefore, an efficient machinery for H₂O₂ disposal is essential in mitochondria. In this study, the ability of brain mitochondria to acquire cardiolipin (CL), phosphatidylglycerol (PG), and phosphatidylserine (PS) in vitro through a fusion process was exploited to investigate lipid effects on ROS. MTT assay, oxygen consumption, and respiratory ratio indicated that the acquired phospholipids did not alter mitochondrial respiration and O₂⁻ production from succinate. However, in CL-enriched mitochondria, H₂O₂ levels where 27% and 47% of control in the absence and in the presence of antimycin A, respectively, suggesting an increase in H₂O₂ elimination. Concomitantly, cytochrome c (cyt c) was released outside mitochondria. Since free oxidized cyt c acquired peroxidase activity towards H₂O₂ upon interaction with CL in vitro, a contribution of cyt c to H₂O₂ disposal in mitochondria through CL conferred peroxidase activity is plausible. In this model, the accompanying CL peroxidation should weaken cyt c-CL interactions, favouring the detachment and release of the protein. Neither cyt c peroxidase activity was elicited by PS in vitro, nor cyt c release was observed in PS-enriched mitochondria, although H₂O₂ levels were significantly decreased, suggesting a cyt c-independent role of PS in ROS metabolism in mitochondria.►Phospholipids fused to brain mitochondria do not alter respiration. ►Fused cardiolipin favours H₂O₂ elimination through cyt c peroxidase activity. ►Cyt c-dependent cardiolipin peroxidation favours cyt c release. ►Phosphatidylserine decreases H₂O₂ independently of cyt c.

Keywords: Abbreviations; HEPES; 4-(2-hydroxyethyl)-1-piperazineethansulfonic acid; Thesit; dodecylpoly (ethylenglycolether)9; cyt c; cytochrome c; CL; cardiolipin; TOCL; tetraoleylcardiolipin; PC; phosphatidylcholine; PS; phosphatidylserine; PG; phosphatidylglycerolCytochrome c; Cytochrome c peroxidase activity; Brain mitochondria; Cardiolipin; Reactive Oxygen Species

Inhibition of macrophage inflammatory cytokine secretion by chylomicron remnants is dependent on their uptake by the low density lipoprotein receptor by Valerie S. Graham; Paola Di Maggio; Sandra Armengol; Charlotte Lawson; Caroline P.D. Wheeler-Jones; Kathleen M. Botham (pp. 209-220).

Secretion of pro-inflammatory chemokines and cytokines by macrophages is a contributory factor in the pathogenesis of atherosclerosis. In this study, the effects of chylomicron remnants (CMR), the lipoproteins which transport dietary fat in the blood, on the production of pro-inflammatory chemokine and cytokine secretion by macrophages was investigated using CMR-like particles (CRLPs) together with THP-1 macrophages or primary human macrophages (HMDM). Incubation of CRLPs or oxidized CRLPs (oxCRLPs) with HMDM or THP-1 macrophages for up to 24h led to a marked decrease in the secretion of the pro-inflammatory chemokine monocyte chemoattractant protein-1 (MCP-1) and the pro-inflammatory cytokines tumour necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β (−50–90%), but these effects were reduced or abolished when CRLPs protected from oxidation by incorporation of the antioxidant drug, probucol, (pCRLPs) were used. In macrophages transfected with siRNA targeted to the low density lipoprotein receptor (LDLr), neither CRLPs nor pCRLPs had any significant effect on chemokine/cytokine secretion, but in cells transfected with siRNA targeted to the LDLr-related protein 1 (LRP1) both types of particles inhibited secretion to a similar extent to that observed with CRLPs in mock transfected cells. These findings demonstrate that macrophage pro-inflammatory chemokine/cytokine secretion is down-regulated by CMR, and that these effects are positively related to the lipoprotein oxidative state. Furthermore, uptake via the LDLr is required for the down-regulation, while uptake via LRP1 does not bring about this effect. Thus, the receptor-mediated route of uptake of CMR plays a crucial role in modulating their effects on inflammatory processes in macrophages.► Chylomicron remnants (CMR) induce foam cell formation in human macrophages. ► CMR-like particles (CRLP) reduce macrophage cytokine secretion. ► This effect was reversed when CRLPs contain the anti-oxidant drug probucol. ► LDL receptor depletion (siRNA) prevented CRLP’s suppression of cytokine release. ► Anti-inflammatory actions of CMR in macrophages require their uptake via the LDLr.

Keywords: Abbreviations; Apo; apolipoprotein; CMR; chylomicron remnants; CRLPs; chylomicron remnant-like particles; DiI; 1′1′-dioctadecyl-3,3-3′,3′-tetramethylindo-carbocyanide perchlorate; IL; interleukin; LDL; low density lipoprotein; LDLr; low density lipoprotein receptor; LRP1; low density receptor-related protein 1; MCP-1; monocyte chemoattractant protein-1; oxCRLPs; oxidized chylomicron remnant-like particles; pCRLPs; chylomicron remnant-like particles containing probucol; TBARS; thiobarbituric acid reacting substances; TG; triacylglycerol; TGF-β; transforming growth factor-β; TNF-α; tumour necrosis factor-α; TRL; triglyceride-rich lipoprotein; siRNA; small interfering RNAChylomicron remnant; Pro-inflammatory cytokine; Lipoprotein oxidation; Low density lipoprotein receptor; Low density lipoprotein receptor-related protein; Macrophage

Interactions of phosphorus-containing dendrimers with liposomes by Dominika Wrobel; Maksim Ionov; Konstantinos Gardikis; Costas Demetzos; Jean-Pierre Majoral; Bartlomiej Palecz; Barbara Klajnert; Maria Bryszewska (pp. 221-226).

The influence of cationic phosphorus-containing dendrimers generation 3 and 4 on model DMPC or DPPC lipid membranes was studied. Measurements of fluorescence anisotropy and differential scanning calorimetry (DSC) were applied to assess changes in lipid bilayer parameters, including fluidity, anisotropy, and phase-transition temperature. Interaction with both hydrophobic and hydrophilic regions of the bilayer was followed by these methods. Dendrimers of both generations influence lipid bilayers by decreasing membrane fluidity. The results suggest that dendrimers can interact both with the hydrophobic part and the polar head-group region of the phospholipid bilayer. Higher generation dendrimers interact more strongly with model membranes, and the concentration, as well as the generation, is of similar importance.► Dendrimers of both generations influence lipid bilayers by decreasing membrane fluidity. ► Dendrimers can interact both with the hydrophobic part and the polar head-group region of the phospholipid bilayer. ► Higher generation dendrimers interact more strongly with model membranes, and the concentration, as well as the generation, is of similar importance.

Keywords: Cationic phosphorus-containing dendrimers; Liposomes; DSC; Anisotropy; Membrane fluidity

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BBA - Molecular and Cell Biology of Lipids (v.1811, #3)