Small Lipid Molecules Research Articles

Expression of sphingosine-1-phosphate receptors and lysophosphatidic acid receptors on cultured and xenografted human colon, breast, melanoma, and lung tumor cells

The lysophospholipids sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA) are small lipid molecules with a variety of physiological roles. Additionally, their involvement in the initiation and progression of malignant tumors has been increasingly recognized in recent years. However, the data on the expression of S1P and LPA receptors on different cancer cells are very few. Real-time polymerase chain reaction was used for the analysis of mRNA expression of five S1P((1-5)) and three LPA((1-3)) receptors on a large panel of 13 colon, breast, melanoma, and lung cancer cell lines. Furthermore, the modulation of S1P and LPA receptor mRNA expression was studied upon xenotransplantation of tumor cells into severe combined immunodeficient (SCID) mice. The S1P and LPA receptors were expressed to a variable degree on all tumor cell lines tested (with exception of colon cancer SW480). Most notably, tumor cell lines in vitro expressed S1P(2) mRNA that was down-regulated upon xenotransplantation, whereas LPA(2) receptor mRNA was strongly expressed both in vitro and in vivo (except by breast cancer cells). The latter was especially distinctive for small cell lung tumor cells. The S1P and LPA receptors are differentially expressed on tumor cell lines in vitro. Their expression is modulated upon xenografting into SCID mice in vivo.

Jean‐Marc Reyrat (29/04/1967–28/10/2009)

Jean‐Marc Reyrat (29/04/1967–28/10/2009)

Spatial and temporal alterations of phospholipids determined by mass spectrometry during mouse embryo implantation

Molecular events involved in successful embryo implantation are not well understood. In this study, we used MALDI imaging mass spectrometry (IMS) technologies to characterize the spatial and temporal distribution of phospholipid species associated with mouse embryo implantation. Molecular images showing phospholipid distribution within implantation sites changed markedly between distinct cellular areas during days 4-8 of pregnancy. For example, by day 8, linoleate- and docosahexaenoate-containing phospholipids localized to regions destined to undergo cell death, whereas oleate-containing phospholipids localized to angiogenic regions. Arachidonate-containing phospholipids showed different segregation patterns depending on the lipid class, revealing a strong correlation of phosphatidylethanolamines and phosphatidylinositols with cytosolic phospholipase A(2alpha) and cyclooxygenase-2 during embryo implantation. LC-ESI-MS/MS was used to validate MALDI IMS phospholipid distribution patterns. Overall, molecular images revealed the dynamic complexity of lipid distributions in early pregnancy, signifying the importance of complex interplay of lipid molecules in uterine biology and implantation.

Update on the role of prostaglandins in allergic lung inflammation: Separating friends from foes, harder than you might think

Prostaglandins (PGs), small lipid molecules derived from arachidonic acid by COX enzymes, are critical mediators of allergic inflammation. Our understanding of the role of PGs in allergic lung inflammation has been hampered by the very short biologic half-life of these mediators, which has made mechanistic studies difficult in human subjects. However, advances in molecular biology and pharmacology have given investigators the opportunity to examine the role of specific prostanoids in the development of allergic inflammation in animal models. Studies investigating specific PG receptors are also elucidating the mechanisms by which PGs regulate the pulmonary allergic phenotype. This review summarizes the current literature on the role of PGs and PG receptors in allergic lung inflammation.

Chromatin modification by lipids and lipoprotein components: an initiating event in atherogenesis?

This review examines recent evidence proposing that lipids and lipoproteins can act as nuclear factors regulating chromatin structure. These novel data broaden our understanding of the mechanisms by which lipoproteins can affect basic biological phenomena such as transcription, genome stability, and cell differentiation. Furthermore, they provide novel insights into the mechanisms of diseases associated with abnormal lipid levels, such as atherosclerosis and diabetes. Data consistent with a role for lipids and lipoprotein components as nuclear factors, as well as initiators of cytoplasmic signalling events resulting in chromatin modification, have been published in the past year. In particular, new insights into the mechanisms of interaction between chromatin and small lipid molecules such as short-chain fatty acids and cholesterol, and endogenous lipid peroxidation products have been obtained. Furthermore, it has been shown that hyperlipidaemic lipoprotein profiles are associated with aberrant DNA methylation patterns at early stages of atherosclerosis in mice and in cultured human macrophages, suggesting that a rearrangement of DNA methylation patterns is among early molecular changes associated with atherogenesis. The findings described here are prompting efforts to understand further how lipids and lipoprotein components can affect gene expression in normal and pathological cell behaviour through regulation of the chromatin structure. It is possible that novel candidate therapeutic tools will emerge from these studies.

The molecular perspective: protein farnesyltransferase.

The Oncologist 2003;8:597-598 www.TheOncologist.com In cell signaling, a lot of the action occurs at the cell membrane. Messages arrive at the cell surface and are picked up by receptors. Then, they are processed by a collection of proteins on the inner surface of the membrane and, finally, they are dispatched to their different recipients in the cytoplasm or nucleus. Most of these proteins need ways of staying close to the membrane, where the action is, and not wandering off to other areas. Receptors are often built with large segments that cross the membrane, anchoring them permanently in place. The various signal-processing proteins on the inner surface, however, take a leaner approach. Proteins like Ras and the trimeric G proteins use small lipid molecules to anchor themselves to the inner surface of the cell membrane. These lipids are attached directly to the protein chain. Some are snaky saturated lipids, like 14-carbon myristoyl chains or 16-carbon palmitoyl chains, and some are rigidified unsaturated lipids built from isoprene units, such as 15-carbon farnesyl groups and 20-carbon geranylgeranyl groups. All of them strongly prefer the lipid environment of the membrane rather than the watery environment of the cytoplasm, so they insert into the membrane, tethering the protein in place. The enzyme protein farnesyltransferase attaches farnesyl groups to cysteine amino acids at the ends of certain protein chains, such as that of the Ras protein (Fig. 1). The enzyme Fundamentals of Cancer Medicine The Oncologist

Lipids and retroviruses.

The role that lipids may play in enveloped viruses is reviewed. Small lipid molecules can influence retrovirus binding to cell receptors, plasma membrane fusion, and transcription. Palmitoylation following myristoylation of viral glycoproteins is required at the transmembrane level for signal transduction as well as for virion budding and maturation. Cholesterol, ether lipids, phospholipids, platelet-activating factor, phosphatidic acids, diacylglycerols, and several analogs and derivatives influence human immunodeficiency virus (HIV) activity; when conjugated with inhibitors of the viral reverse transcriptase (RT) or aspartyl protease these compounds increase drug effectiveness. On the other hand, L-carnitine, in association with the mitochondrial cardiolipins, inhibits myopathy due to continued prescription of drugs [AZT (zidovudine), ddl (didanoside), or ddC (zalcitabine)], and the redox couple of alpha-lipoic-dihydrolipoic acid prevents production of the reactive oxygen species that trigger apoptosis of infected cells, with sphingomyelin breakdown to ceramides. Retroviral infection induces a shift from phospholipid to neutral fat synthesis in host cells, and a long antiviral, i.e., antiprotease, treatment may lead to lipodystrophy. Multitherapy involving lipids and their analogs in association with anti-RT and antiproteases might enhance the inhibition of growth and proliferation of retroviruses.

Prostaglandin E2 as a modulator of lymphocyte mediated inflammatory and humoral responses.

Prostaglandins are a family of structurally related small lipid molecules that can regulate cellular growth, differentiation, and homeostasis. Prostaglandins are primarily derived from arachidonic acid, which is released from the membrane by phospholipases in response to a variety of extrinsic stimuli. Constitutive and inducible forms of cyclooxygenase in conceit with isomerses convert arachidonic acid into different prostaglandins including prostaglandin E2 (PGE2). PGE2 was previously known as an immunosuppressive prostaglandin as it inhibits T cell production of IL-2 and B lymphocyte production of IgM. Recently a new concept emerged that PGE2 is a critical modulator of B and T cell function and is not necessarily immunosuppressive. The focus of this paper is to present new developments that indicate PGE2 functions by promoting antibody driven responses at the expense of inflammatory responses.

Functional Characterization and Purification of an Intracellular Vitamin D-binding Protein in Vitamin D-resistant New World Primate Cells: AMINO ACID SEQUENCE HOMOLOGY WITH PROTEINS IN THE HSP-70 FAMILY

Most genera of New World primates exhibit resistance to vitamin D. These monkeys harbor high circulating concentrations of the prohormone 25-hydroxyvitamin D and the active vitamin D hormone 1, 25-dihydroxyvitamin D. Previous work from this laboratory indicated that resistance is associated with the overexpression of a 60-65-kDa intracellular protein that binds vitamin D metabolites competitively. In the current studies 25-[3H]hydroxyvitamin D3 (25-OHD3) was used as a competitive ligand to investigate the ability of a number of small lipid molecules to interact with this intracellular vitamin D-binding protein (IDBP) in post-nuclear extracts of a prototypical lymphoblast cell line from the common marmoset, a vitamin D-resistant New World primate. Only those vitamin D metabolites with a hydroxyl moiety in the C-25 position were bound by IDBP. Disruption of the C-25 hydroxyl obviated binding, whereas more proximal alterations in the vitamin D side chain did not. Modifications in the A-ring of 25-hydroxylated vitamin D metabolites, most specifically hydroxylation of C-1, diminished but did not abolish ligand binding. Of more than two dozen other small lipid molecules examined, only the C-19 17-hydroxysteroids, 17beta-estradiol and testosterone, and the C-21 steroid progesterone were found to be capable of binding specifically to IDBP. Using a combination of physical and serial chromatographic techniques, we enriched IDBP 25-OHD3 binding activity 17,588-fold in extracts of B95-8 cells. Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of this purified fraction demonstrated a predominant 65-kDa molecular species with a pI approximately 4.5. Seven different peptide fragments were isolated from the 65-kDa protein, each possessing sequence similarity to the hsp-70 family of proteins. Ligand binding analyses confirmed that human inducibly expressed hsp-70-bound 25-OHD3 with approximately similar affinity ( approximately 10(-7) M) as did purified IDBP. In summary, these results suggest a novel action for the hsp-70 family of proteins as intracellular vitamin D- and gonadal steroid hormone-binding molecules.

Relationship of total lipids, proteins, and albumin in human cerebrospinal fluid with age

A study of the changes with age in the concentrations of macro- and micromolecular components in human cerebrospinal fluid (CSF) was conducted to assess indirectly the alterations in blood-brain-CSF barriers during the aging process. Human CSF was obtained from adult patients ranging in age from 27 to 71 years during routine clinical myelographic examinations. Total lipids in the CSF were assayed spectrophotometrically using the sulfo-phospho-vanillin reaction. Albumin contents were assayed by immuno-nephelometry and the total protein levels were assayed by the Lowry method. The 42 subjects were divided into the normal CSF protein group (protein concentration ≤50 mg/dl) and the elevated CSF protein group (protein concentration >50 mg/dl). The average CSF total lipid level on these subjects was very low: 0.78 mg/dl for the group with normal CSF protein levels, and 1.4 mg/dl for the elevated-CSF protein group. The CSF total lipid levels had a significantly positive correlation with total protein in both groups, suggesting that the entry of the small endogenous lipid molecules into the CSF is governed by their affinity of binding to the macromolecular proteins. There were no significant correlations between CSF total lipids, total proteins, or albumins with age in either the low or high CSF protein groups. It is suggested by the data that in man the blood-brain-CSF barriers are not altered with age.