BBA - Molecular and Cell Biology of Lipids (v.1861, #12PA)
Editorial Board (i).
Stearoyl CoA desaturase-1: New insights into a central regulator of cancer metabolism by R. Ariel Igal (1865-1880).
The processes of cell proliferation, cell death and differentiation involve an intricate array of biochemical and morphological changes that require a finely tuned modulation of metabolic pathways, chiefly among them is fatty acid metabolism. The critical participation of stearoyl CoA desaturase-1 (SCD1), the fatty acyl Δ9-desaturing enzyme that converts saturated fatty acids (SFA) into monounsaturated fatty acids (MUFA), in the mechanisms of replication and survival of mammalian cells, as well as their implication in the biological alterations of cancer have been actively investigated in recent years. This review examines the growing body of evidence that argues for a role of SCD1 as a central regulator of the complex synchronization of metabolic and signaling events that control cellular metabolism, cell cycle progression, survival, differentiation and transformation to cancer.
Keywords: MUFA synthesis; Cancer; Metabolism; Transduction signaling; Tyrosine kinase receptors; Tumor growth;
Calcium-dependent generation of N-acylethanolamines and lysophosphatidic acids by glycerophosphodiesterase GDE7 by Iffat Ara Sonia Rahman; Kazuhito Tsuboi; Zahir Hussain; Ryouhei Yamashita; Yoko Okamoto; Toru Uyama; Naoshi Yamazaki; Tamotsu Tanaka; Akira Tokumura; Natsuo Ueda (1881-1892).
N-Acylethanolamines form a class of lipid mediators and include an endocannabinoid arachidonoylethanolamide (anandamide), analgesic and anti-inflammatory palmitoylethanolamide, and appetite-suppressing oleoylethanolamide. In animal tissues, N-acylethanolamines are synthesized from N-acylated ethanolamine phospholipids directly by N-acylphosphatidylethanolamine-hydrolyzing phospholipase D or through multi-step pathways via N-acylethanolamine lysophospholipids. We previously reported that glycerophosphodiesterase (GDE) 4, a member of the GDE family, has lysophospholipase D (lysoPLD) activity hydrolyzing N-acylethanolamine lysophospholipids to N-acylethanolamines. Recently, GDE7 was shown to have lysoPLD activity toward lysophosphatidylcholine to produce lysophosphatidic acid (LPA). Here, we examined the reactivity of GDE7 with N-acylethanolamine lysophospholipids as well as the requirement of divalent cations for its catalytic activity. When overexpressed in HEK293 cells, recombinant GDE7 proteins of human and mouse showed lysoPLD activity toward N-palmitoyl, N-oleoyl, and N-arachidonoyl-lysophosphatidylethanolamines and N-palmitoyl-lysoplasmenylethanolamine to generate their corresponding N-acylethanolamines and LPAs. However, GDE7 hardly hydrolyzed glycerophospho-N-palmitoylethanolamine. Overexpression of GDE7 in HEK293 cells increased endogenous levels of N-acylethanolamines and LPAs. Interestingly, GDE7 was stimulated by micromolar concentrations of Ca2 + but not by millimolar concentrations of Mg2 +, while GDE4 was stimulated by Mg2 + but was insensitive to Ca2 +. GDE7 was widely distributed in various tissues of humans and mice with the highest levels in their kidney tissues. These results suggested that GDE7 is a novel Ca2 +-dependent lysoPLD, which is involved in the generation of both N-acylethanolamines and LPAs.
Keywords: N-acylethanolamine; Glycerophosphodiesterase; Lysophosphatidic acid; Lysophospholipase D; Phospholipid;
Glucolipotoxicity diminishes cardiomyocyte TFEB and inhibits lysosomal autophagy during obesity and diabetes by Purvi C. Trivedi; Jordan J. Bartlett; Lester J. Perez; Keith R. Brunt; Jean Francois Legare; Ansar Hassan; Petra C. Kienesberger; Thomas Pulinilkunnil (1893-1910).
Impaired cardiac metabolism in the obese and diabetic heart leads to glucolipotoxicity and ensuing cardiomyopathy. Glucolipotoxicity causes cardiomyocyte injury by increasing energy insufficiency, impairing proteasomal-mediated protein degradation and inducing apoptosis. Proteasome-evading proteins are degraded by autophagy in the lysosome, whose metabolism and function are regulated by master regulator transcription factor EB (TFEB). Limited studies have examined the impact of glucolipotoxicity on intra-lysosomal signaling proteins and their regulators. By utilizing a mouse model of diet-induced obesity, type-1 diabetes (Akita) and ex-vivo model of glucolipotoxicity (H9C2 cells and NRCM, neonatal rat cardiomyocyte), we examined whether glucolipotoxicity negatively targets TFEB and lysosomal proteins to dysregulate autophagy and cause cardiac injury. Despite differential effects of obesity and diabetes on LC3B-II, expression of proteins facilitating autophagosomal clearance such as TFEB, LAMP-2A, Hsc70 and Hsp90 were decreased in the obese and diabetic heart. In-vivo data was recapitulated in H9C2 and NRCM cells, which exhibited impaired autophagic flux and reduced TFEB content when exposed to a glucolipotoxic milieu. Notably, overloading myocytes with a saturated fatty acid (palmitate) but not an unsaturated fatty acid (oleate) depleted cellular TFEB and suppressed autophagy, suggesting a fatty acid specific regulation of TFEB and autophagy in the cardiomyocyte. The effect of glucolipotoxicity to reduce TFEB content was also confirmed in heart tissue from patients with Class-I obesity. Therefore, during glucolipotoxicity, suppression of lysosomal autophagy was associated with reduced lysosomal content, decreased cathepsin-B activity and diminished cellular TFEB content likely rendering myocytes susceptible to cardiac injury.
Keywords: Lysosomal autophagy; Obesity and diabetes; Cardiomyopathy; Glucolipotoxicity; TFEB; LAMP-2A;
Cholesterol 24-hydroxylase: Brain cholesterol metabolism and beyond by Miguel Moutinho; Maria João Nunes; Elsa Rodrigues (1911-1920).
Dysfunctions in brain cholesterol homeostasis have been extensively related to brain disorders. The major elimination pathway of brain cholesterol is its hydroxylation into 24 (S)-hydroxycholesterol by the cholesterol 24-hydroxylase (CYP46A1). Interestingly, there seems to be an association between CYP46A1 and high-order brain functions, in a sense that increased expression of this hydroxylase improves cognition, while a reduction leads to a poor cognitive performance. Moreover, increasing amount of epidemiological, biochemical and molecular evidence, suggests that CYP46A1 has a role in the pathogenesis or progression of neurodegenerative disorders, in which up-regulation of this enzyme is clearly beneficial. However, the mechanisms underlying these effects are poorly understood, which highlights the importance of studies that further explore the role of CYP46A1 in the central nervous system. In this review we summarize the major findings regarding CYP46A1, and highlight the several recently described pathways modulated by this enzyme from a physiological and pathological perspective, which might account for novel therapeutic strategies for neurodegenerative disorders.
Keywords: CYP46A1; Cytochrome P450; Brain cholesterol; Neuronal function; Neurodegeneration; 24 (S)-hydroxycholesterol;
PPARγ regulates exocrine pancreas lipase by Hila Danino; Ronny Peri- Naor; Chen Fogel; Yael Ben-Harosh; Rotem Kadir; Hagit Salem; Ruth Birk (1921-1928).
Pancreatic lipase (triacylglycerol lipase EC 22.214.171.124) is an essential enzyme in hydrolysis of dietary fat. Dietary fat, especially polyunsaturated fatty acids (PUFA), regulate pancreatic lipase (PNLIP); however, the molecular mechanism underlying this regulation is mostly unknown. As PUFA are known to regulate expression of proliferator-activated receptor gamma (PPARγ), and as we identified in-silico putative PPARγ binding sites within the putative PNLIP promoter sequence, we hypothesized that PUFA regulation of PNLIP might be mediated by PPARγ.We used in silico bioinformatics tools, reporter luciferase assay, PPARγ agonists and antagonists, PPARγ overexpression in exocrine pancreas AR42J and primary cells to study PPARγ regulation of PNLIP.Using in silico bioinformatics tools we mapped PPARγ binding sites (PPRE) to the putative promoter region of PNLIP. Reporter luciferase assay in AR42J rat exocrine pancreas acinar cells transfected with various constructs of the putative PNLIP promoter showed that PNLIP transcription is significantly enhanced by PPARγ dose-dependently, reaching maximal levels with multi PPRE sites. This effect was significantly augmented in the presence of PPARγ agonists and reduced by PPARγ antagonists or mutagenesis abrogating PPRE sites. Over-expression of PPARγ significantly elevated PNLIP transcript and protein levels in AR42J cells and in primary pancreas cells. Moreover, PNLIP expression was up-regulated by PPARγ agonists (pioglitazone and 15dPGJ2) and significantly down-regulated by PPARγ antagonists in non-transfected rat exocrine pancreas AR42J cell line cells.PPARγ transcriptionally regulates PNLIP gene expression. This transcript regulation resolves part of the missing link between dietary PUFA direct regulation of PNLIP.
Keywords: Pancreatic lipase; PPARγ; Polyunsaturated fatty acids; Exocrine pancreas;
Rapamycin negatively impacts insulin signaling, glucose uptake and uncoupling protein-1 in brown adipocytes by Ester García-Casarrubios; Carlos de Moura; Ana I Arroba; Nuria Pescador; María Calderon-Dominguez; Laura Garcia; Laura Herrero; Dolors Serra; Susana Cadenas; Flavio Reis; Eugenia Carvalho; Maria Jesus Obregon; Ángela M Valverde (1929-1941).
New onset diabetes after transplantation (NODAT) is a metabolic disorder that affects 40% of patients on immunosuppressive agent (IA) treatment, such as rapamycin (also known as sirolimus). IAs negatively modulate insulin action in peripheral tissues including skeletal muscle, liver and white fat. However, the effects of IAs on insulin sensitivity and thermogenesis in brown adipose tissue (BAT) have not been investigated. We have analyzed the impact of rapamycin on insulin signaling, thermogenic gene-expression and mitochondrial respiration in BAT. Treatment of brown adipocytes with rapamycin for 16 h significantly decreased insulin receptor substrate 1 (IRS1) protein expression and insulin-mediated protein kinase B (Akt) phosphorylation. Consequently, both insulin-induced glucose transporter 4 (GLUT4) translocation to the plasma membrane and glucose uptake were decreased. Early activation of the N-terminal Janus activated kinase (JNK) was also observed, thereby increasing IRS1 Ser 307 phosphorylation. These effects of rapamycin on insulin signaling in brown adipocytes were partly prevented by a JNK inhibitor. In vivo treatment of rats with rapamycin for three weeks abolished insulin-mediated Akt phosphorylation in BAT. Rapamycin also inhibited norepinephrine (NE)-induced lipolysis, the expression of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and uncoupling protein (UCP)-1 in brown adipocytes. Importantly, basal mitochondrial respiration, proton leak and maximal respiratory capacity were significantly decreased in brown adipocytes treated with rapamycin. In conclusion, we demonstrate, for the first time the important role of brown adipocytes as target cells of rapamycin, suggesting that insulin resistance in BAT might play a major role in NODAT development.
Keywords: NODAT; Brown adipocytes; Insulin signaling; Thermogenesis; Bioenergetics;
Lipid fingerprint image accurately conveys human colon cell pathophysiologic state: A solid candidate as biomarker by Joan Bestard-Escalas; Jone Garate; Albert Maimó-Barceló; Roberto Fernández; Daniel Horacio Lopez; Sergio Lage; Rebeca Reigada; Sam Khorrami; Daniel Ginard; José Reyes; Isabel Amengual; José A. Fernández; Gwendolyn Barceló-Coblijn (1942-1950).
Membrane lipids are gaining increasing attention in the clinical biomarker field, as they are associated with different pathologic processes such as cancer or neurodegenerative diseases. Analyzing human colonoscopic sections by matrix assisted laser/desorption ionization (MALDI) mass spectrometry imaging techniques, we identified a defined number of lipid species changing concomitant to the colonocyte differentiation and according to a quite simple mathematical expression. These species felt into two lipid families tightly associated in signaling: phosphatidylinositols and arachidonic acid-containing lipids. On the other hand, an opposed pattern was observed in lamina propria for AA-containing lipids, coinciding with the physiological distribution of the immunological response cells in this tissue. Importantly, the lipid gradient was accompanied by a gradient in expression of enzymes involved in lipid mobilization. Finally, both lipid and protein gradients were lost in adenomatous polyps. The latter allowed us to assess how different a single lipid species is handled in a pathological context depending on the cell type. The strict patterns of distribution in lipid species and lipid enzymes described here unveil the existence of fine regulatory mechanisms orchestrating the lipidome according to the physiological state of the cell. In addition, these results provide solid evidence that the cell lipid fingerprint image can be used to predict precisely the physiological and pathological status of a cell, reinforcing its translational impact in clinical research.Display Omitted
Keywords: Colonocyte differentiation; Lipidomics; MALDI-imaging; Arachidonic acid; Phosphatidylinositol;
A quantitative study on splice variants of N-acylethanolamine acid amidase in human prostate cancer cells and other cells by Yuma Sakura; Kazuhito Tsuboi; Toru Uyama; Xia Zhang; Rikiya Taoka; Mikio Sugimoto; Yoshiyuki Kakehi; Natsuo Ueda (1951-1958).
N-Acylethanolamine acid amidase (NAAA) is a lysosomal enzyme, hydrolyzing various bioactive N-acylethanolamines with a preference for palmitoylethanolamide. Human NAAA mRNA was previously reported to consist of multiple 3′-end splice variants. However, their tissue distributions and roles have not been examined yet. In the present study, we first identified four major splice variants (tentatively referred to as a1, a2, b2, and c2) in a human prostate cancer cell line LNCaP, which were composed of exons 1–11, exons 1–10 and 12, exons 1–9 and 12, and exons 1–8 and 12, respectively. We next developed quantitative polymerase chain reaction methods to individually quantify these NAAA variants as well as collectively measure all the variants. Among various human prostate cancer cells, the total levels of NAAA mRNAs in androgen-sensitive cells like LNCaP were higher than those in androgen-insensitive cells. In all of these prostate cells and other human cells, variants a1 and b2 showed the highest and lowest expression levels, respectively, among the four variants. Interestingly, ratios of the four variants were different by cell type. Variants a1 and a2 encoded the same full-length NAAA protein, which was catalytically active, while b2 and c2 were translated to C-terminally truncated proteins. As expressed in HEK293 cells these truncated forms were detected as catalytically inactive precursor proteins, but not as mature forms. These results revealed wide distribution of multiple variants of NAAA mRNA in various human cells and suggested that the proteins from some variants are catalytically inactive.
Keywords: N-Acylethanolamine acid amidase; Endocannabinoid; Prostate cancer; Quantitative PCR; Splice variant;
Endoplasmic reticulum stress affects the transport of phosphatidylethanolamine from mitochondria to the endoplasmic reticulum in S. cerevisiae by Muthukumar Kannan; Chinnarasu Sivaprakasam; William A. Prinz; Vasanthi Nachiappan (1959-1967).
Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are two of the most abundant phospholipids in cells. Although both lipids can be synthesized in the endoplasmic reticulum (ER), in S. cerevisiae PE can also be produced in mitochondria and endosomes; this PE can be transported back to the ER where it is converted to PC. In this study we found that dithiothreitol (DTT), which induces ER stress, decreases PE export from mitochondria to the ER. This results in decreased levels of total cellular PC and mitochondrial PC. These decreases were not caused by changes in levels of PC synthesizing or degrading enzymes. PE export from mitochondria to the ER during ER stress was further reduced in cells lacking Mdm10p, a component of an ER-mitochondrial tethering complex that may facilitated lipid exchange between these compartments. We also found that reducing mitochondrial PC levels induces mitophagy. In conclusion, we show that ER stress affected PE export from mitochondria to ER and the Mdm10p is important for this process.
Keywords: ER stress; Mitochondria; Phosphatidylcholine; ERMES; Lipid transport;
Cell lipid metabolism modulators 2-bromopalmitate, D609, monensin, U18666A and probucol shift discoidal HDL formation to the smaller-sized particles: implications for the mechanism of HDL assembly by Duyen Quach; Cecilia Vitali; Fiona M. La; Angel X. Xiao; John S. Millar; Chongren Tang; Daniel J. Rader; Michael C. Phillips; Nicholas N. Lyssenko (1968-1979).
ATP-binding cassette transporter A1 (ABCA1) mediates formation of disc-shaped high-density lipoprotein (HDL) from cell lipid and lipid-free apolipoprotein A-I (apo A-I). Discoidal HDL particles are heterogeneous in physicochemical characteristics for reasons that are understood incompletely. Discoidal lipoprotein particles similar in characteristics and heterogeneity to cell-formed discoidal HDL can be reconstituted from purified lipids and apo A-I by cell-free, physicochemical methods. The heterogeneity of reconstituted HDL (rHDL) is sensitive to the lipid composition of the starting lipid/apo A-I mixture. To determine whether the heterogeneity of cell-formed HDL is similarly sensitive to changes in cell lipids, we investigated four compounds that have well-established effects on cell lipid metabolism and ABCA1-mediated cell cholesterol efflux. 2-Bromopalmitate, D609, monensin and U18666A decreased formation of the larger-sized, but dramatically increased formation of the smaller-sized HDL. 2-Bromopalmitate did not appear to affect ABCA1 activity, subcellular localization or oligomerization, but induced dissolution of the cholesterol-phospholipid complexes in the plasma membrane. Arachidonic and linoleic acids shifted HDL formation to the smaller-sized species. Tangier disease mutations and inhibitors of ABCA1 activity wheat germ agglutinin and AG 490 reduced formation of both larger-sized and smaller-sized HDL. The effect of probucol was similar to the effect of 2-bromopalmitate. Taking rHDL formation as a paradigm, we propose that ABCA1 mutations and activity inhibitors reduce the amount of cell lipid available for HDL formation, and the compounds in the 2-bromopalmitate group and the polyunsaturated fatty acids change cell lipid composition from one that favors formation of the larger-sized HDL particles to one that favors formation of the smaller-sized species.
Keywords: HDL heterogeneity; Mechanism of HDL formation; Reconstituted HDL; Inhibitors of ABCA1-mediated cholesterol efflux; Tangier disease mutations;
Lysophosphatidylcholines activate PPARδ and protect human skeletal muscle cells from lipotoxicity by Christian Klingler; Xinjie Zhao; Till Adhikary; Jia Li; Guowang Xu; Hans-Ulrich Häring; Erwin Schleicher; Rainer Lehmann; Cora Weigert (1980-1992).
Metabolomics studies of human plasma demonstrate a correlation of lower plasma lysophosphatidylcholines (LPC) concentrations with insulin resistance, obesity, and inflammation. This relationship is not unraveled on a molecular level. Here we investigated the effects of the abundant LPC(16:0) and LPC(18:1) on human skeletal muscle cells differentiated to myotubes. Transcriptome analysis of human myotubes treated with 10 μM LPC for 24 h revealed enrichment of up-regulated peroxisome proliferator-activated receptor (PPAR) target transcripts, including ANGPTL4, PDK4, PLIN2, and CPT1A. The increase in both PDK4 and ANGPTL4 RNA expression was abolished in the presence of either PPARδ antagonist GSK0660 or GSK3787. The induction of PDK4 by LPCs was blocked with siRNA against PPARD. The activation of PPARδ transcriptional activity by LPC was shown as PPARδ-dependent luciferase reporter gene expression and enhanced DNA binding of the PPARδ/RXR dimer. On a functional level, further results show that the LPC-mediated activation of PPARδ can reduce fatty acid-induced inflammation and ER stress in human skeletal muscle cells. The protective effect of LPC was prevented in the presence of the PPARδ antagonist GSK0660. Taking together, LPCs can activate PPARδ, which is consistent with the association of high plasma LPC levels and PPARδ-dependent anti-diabetic and anti-inflammatory effects.
Keywords: Lysophospholipids; Nuclear receptors/lipid ligands; Transcription; Skeletal muscle; Diabetes; Human myotubes; AMPK;
Diacylglycerol kinase epsilon suppresses expression of p53 and glycerol kinase in mouse embryo fibroblasts by Vincent So; Divyanshi Jalan; Mathieu Lemaire; Matthew K. Topham; Grant M. Hatch; Richard M. Epand (1993-1999).
The incorporation of glycerol into lipid was measured using SV40 transformed mouse embryo fibroblasts (MEFs) from either wild-type (WT) mice or from mice in which the epsilon isoform of diacylglycerol kinase (DGKε) was knocked out (DGKε−/−). We present an explanation for our finding that DGKε−/− MEFs exhibited greater uptake of 3H-glycerol into the cell and a greater incorporation into lipids compared with their WT counterparts, with no change in the relative amounts of various lipids between the DGKε−/− and WT MEFs. Glycerol kinase is more highly expressed in the DGKε−/− cells than in their WT counterparts. In addition, the activity of glycerol kinase is greater in the DGKε−/− cells than in their WT counterparts. Other substrates that enter the cell independent of glycerol kinase, such as pyruvate or acetate, are incorporated into lipid to the same extent between DGKε−/− and WT cell lines. We also show that expression of p53, a transcription factor that increases the synthesis of glycerol kinase, is increased in DGKε−/− MEFs in comparison to WT cells. We conclude that the increased incorporation of glycerol into lipids in DGKε−/− cells is a consequence of up-regulation of glycerol kinase and not a result of an increase in the rate of lipid synthesis. Furthermore, increased expression of the pro-survival gene, p53, in cells knocked out for DGKε suggests that cells over-expressing DGKε would have a greater propensity to become tumorigenic.Display Omitted
Keywords: Diacylglycerol kinase; p53; Lipid synthesis; Signal transduction;
Oleate dose-dependently regulates palmitate metabolism and insulin signaling in C2C12 myotubes by Frédéric Capel; Naoufel Cheraiti; Cécile Acquaviva; Carole Hénique; Justine Bertrand-Michel; Christine Vianey-Saban; Carina Prip-Buus; Béatrice Morio (2000-2010).
Because the protective effect of oleate against palmitate-induced insulin resistance may be lessened in skeletal muscle once cell metabolism is overloaded by fatty acids (FAs), we examined the impact of varying amounts of oleate on palmitate metabolic channeling and insulin signaling in C2C12 myotubes. Cells were exposed to 0.5 mM of palmitate and to increasing doses of oleate (0.05, 0.25 and 0.5 mM). Impacts of FA treatments on radio-labelled FA fluxes, on cellular content in diacylglycerols (DAG), triacylglycerols (TAG), ceramides, acylcarnitines, on PKCθ, MAPKs (ERK1/2, p38) and NF-ΚB activation, and on insulin-dependent Akt phosphorylation were examined.Low dose of oleate (0.05 mM) was sufficient to improve palmitate complete oxidation to CO2 (+ 29%, P < 0.05) and to alter the cellular acylcarnitine profile. Insulin-induced Akt phosphorylation was 48% higher in that condition vs. palmitate alone (p < 0.01). Although DAG and ceramide contents were significantly decreased with 0.05 mM of oleate vs. palmitate alone (− 47 and − 28%, respectively, p < 0.01), 0.25 mM of oleate was required to decrease p38 MAPK and PKCθ phosphorylation, thus further improving the insulin signaling (+ 32%, p < 0.05). By contrast, increasing oleate concentration from 0.25 to 0.5 mM, thus increasing total amount of FA from 0.75 to 1 mM, deteriorated the insulin signaling pathway (− 30%, p < 0.01). This was observed despite low contents in DAG and ceramides, and enhanced palmitate incorporation into TAG (+ 27%, p < 0.05). This was associated with increased incomplete FA β-oxidation and impairment of acylcarnitine profile. In conclusion, these combined data place mitochondrial β-oxidation at the center of the regulation of muscle insulin sensitivity, besides p38 MAPK and PKCθ.
Keywords: Skeletal muscle; Lipid metabolism; Substrate partitioning; Lipotoxicity; Insulin signaling;
Retinoylation (covalent modification by retinoic acid) of Rho-GDIβ in the human myeloid leukemia cell line HL60 and its functional significance by Noriko Takahashi; Toshihiro Ohba; Masahiko Imai; Shinya Hasegawa; Katsuhiko Takahashi; Masahiro Yamasaki; Yuri Kameoka (2011-2019).
Retinoic acid (RA) has a variety of biological effects in mammalian cells and tissues. It is well known that RA induces differentiation of human acute promyelocytic leukemia (APL) HL60 cells, fresh human APL cells, and clinical remission in patients with APL. Retinoylation (acylation of proteins by RA) is a possible pathway for RA action. However, an understanding of the role that retinoylation plays in the actions of RA is lacking. In the current study, several retinoylated proteins were detected in RA-treated HL60 fractions following Mono Q anion exchange chromatography and analysis using two-dimensional polyacrylamide gel electrophoresis. One of the retinoylated proteins was identified as Rho-GDIβ (28 kDa) by TOF-MS and co-migration with Rho-GDIβ (28 kDa). Truncated Rho-GDIβ (23 kDa, N ∆ 19), a product of cleavage by caspase-3, was not retinoylated. RA covalently bound to the Thr2 residue in Rho-GDIβ (5 kDa), which is the second product resulting from the cleavage of Rho-GDIβ (28 kDa) by caspase-3. RA treatment increased the level of Rho-GDIβ (28 kDa) and decreased the level of Rho-GDIβ (23 kDa). RA did not induce caspase-3 activity or Rho-GDIβ mRNA expression. It is likely that retinoylation of Rho-GDIβ increases its metabolic stability.
Keywords: Retinoylated proteins; Rho-GDIβ; Retinoic acid; HL60; Post-translational modification of proteins;
Docosahexaenoyl serotonin, an endogenously formed n-3 fatty acid-serotonin conjugate has anti-inflammatory properties by attenuating IL-23–IL-17 signaling in macrophages by Mieke Poland; Jean Paul ten Klooster; Zheng Wang; Raymond Pieters; Mark Boekschoten; Renger Witkamp; Jocelijn Meijerink (2020-2028).
Conjugates of fatty acids and amines, including endocannabinoids, are known to play important roles as endogenous signaling molecules. Among these, the ethanolamine conjugate of the n-3 poly unsaturated long chain fatty acid (PUFA) docosahexaenoic acid (22:6n-3) (DHA) was shown to possess strong anti-inflammatory properties.Previously, we identified the serotonin conjugate of DHA, docosahexaenoyl serotonin (DHA-5-HT), in intestinal tissues and showed that its levels are markedly influenced by intake of n-3 PUFAs. However, its biological roles remain to be elucidated. Here, we show that DHA-5-HT possesses potent anti-inflammatory properties by attenuating the IL-23-IL-17 signaling cascade in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Transcriptome analysis revealed that DHA-5-HT down-regulates LPS-induced genes, particularly those involved in generating a CD4+ Th17 response. Hence, levels of PGE2, IL-6, IL-1β, and IL-23, all pivotal macrophage-produced mediators driving the activation of pathogenic Th17 cells in a concerted way, were found to be significantly suppressed by concentrations as low as 100–500 nM DHA-5-HT. Furthermore, DHA-5-HT inhibited the ability of RAW264.7 cells to migrate and downregulated chemokines like MCP-1, CCL-20, and gene-expression of CCL-22 and of several metalloproteinases. Gene set enrichment analysis (GSEA) suggested negative overlap with gene sets linked to inflammatory bowel disease (IBD) and positive overlap with gene sets related to the Nrf2 pathway. The specific formation of DHA-5-HT in the gut, combined with increasing data underlining the importance of the IL-23-IL-17 signaling pathway in the etiology of many chronic inflammatory diseases merits further investigation into its potential as therapeutic compound in e.g. IBD or intestinal tumorigenesis.
Keywords: Acyl serotonines; DHA; DHA-5-HT; Nrf2; Intestine; Endocannabinoids;
Stearoyl-CoA desaturase 1 deficiency reduces lipid accumulation in the heart by activating lipolysis independently of peroxisome proliferator-activated receptor α by Tomasz Bednarski; Adam Olichwier; Agnieszka Opasinska; Aleksandra Pyrkowska; Ana-Maria Gan; James M. Ntambi; Pawel Dobrzyn (2029-2037).
Stearoyl-CoA desaturase 1 (SCD1) has recently been shown to be a critical control point in the regulation of cardiac metabolism and function. Peroxisome proliferator-activated receptor α (PPARα) is an important regulator of myocardial fatty acid uptake and utilization. The present study used SCD1 and PPARα double knockout (SCD1−/−/PPARα−/−) mice to test the hypothesis that PPARα is involved in metabolic changes in the heart that are caused by SCD1 downregulation/inhibition. SCD1 deficiency decreased the intracellular content of free fatty acids, triglycerides, and ceramide in the heart of SCD1−/− and SCD1−/−/PPARα−/− mice. SCD1 ablation in PPARα−/− mice decreased diacylglycerol content in cardiomyocytes. These results indicate that the reduction of fat accumulation in the heart associated with SCD1 deficiency occurs independently of the PPARα pathway. To elucidate the mechanism of the observed changes, we treated HL-1 cardiomyocytes with the SCD1 inhibitor A939572 and/or PPARα inhibitor GW6471. SCD1 inhibition decreased the level of lipogenic proteins and increased lipolysis, reflected by a decrease in the content of adipose triglyceride lipase inhibitor G0S2 and a decrease in the ratio of phosphorylated hormone-sensitive lipase (HSL) at Ser565 to HSL (pHSL[Ser565]/HSL). PPARα inhibition alone did not affect the aforementioned protein levels. Finally, PPARα inhibition decreased the phosphorylation level of 5′-adenosine monophosphate-activated protein kinase, indicating lower mitochondrial fatty acid oxidation. In summary, SCD1 ablation/inhibition decreased cardiac lipid content independently of the action of PPARα by reducing lipogenesis and activating lipolysis. The present data suggest that SCD1 is an important component in maintaining proper cardiac lipid metabolism.
Keywords: Triglyceride; Lipolysis; Lipogenesis; PPARα; ATGL; Cardiomyocytes;