Reversible Nuclear-Lipid-Droplet Morphology Induced by Oleic Acid: A Link to Cellular-Lipid Metabolism.

Neutral lipids-involved in many cellular processes-are stored as lipid droplets (LD), those mainly cytosolic (cLD) along with a small nuclear population (nLD). nLD could be involved in nuclear-lipid homeostasis serving as an endonuclear buffering system that would provide or incorporate lipids and proteins involved in signalling pathways as transcription factors and as enzymes of lipid metabolism and nuclear processes. Our aim was to determine if nLD constituted a dynamic domain. Oleic-acid (OA) added to rat hepatocytes or HepG2 cells in culture produced cellular-phenotypic LD modifications: increases in TAG, CE, C, and PL content and in cLD and nLD numbers and sizes. LD increments were reversed on exclusion of OA and were prevented by inhibition of acyl-CoA synthetase (with Triacsin C) and thus lipid biosynthesis. Under all conditions, nLD corresponded to a small population (2-10%) of total cellular LD. The anabolism triggered by OA, involving morphologic and size changes within the cLD and nLD populations, was reversed by a net balance of catabolism, upon eliminating OA. These catabolic processes included lipolysis and the mobilization of hydrolyzed FA from the LD to cytosolic-oxidation sites. These results would imply that nLD are actively involved in nuclear processes that include lipids. In conclusion, nLD are a dynamic nuclear domain since they are modified by OA through a reversible mechanism in combination with cLD; this process involves acyl-CoA-synthetase activity; ongoing TAG, CE, and PL biosynthesis. Thus, liver nLD and cLD are both dynamic cellular organelles.

Inhibition of Mevalonate Pathway and Synthesis of the Storage Lipids in Human Liver-Derived and Non-liver Cell Lines by Lippia alba Essential Oils.

The essential oils (EOs) of Lippia alba, an herb extensively used as a folk medicine in Latin America, are today promoted as an effective means of eliminating problems caused by hyperlipemia. We hypothesized that L.alba EOs inhibited cholesterol and triacylglycerols synthesis and decreased the intracellular depots of those lipids (lipid droplets), mechanisms involving the induction of a hypolipidemic response. Our aim was, therefore, to evaluate the hypolipogenic capability of the EOs of four L. alba chemotypes on liver-derived (HepG2) and non-liver (A549) human cell lines and to identify the potential biochemical targets of those chemotypes, particularly within the mevalonate pathway (MP). [14C]Acetate was used as radioactive precursor for assays. Lipid analyses were performed by thin-layer and capillary gas chromatography, lipid droplets analyzed by fluorescence microscopy, and HMGCR levels determined by Western blot. In both cell lines, all four chemotypes exerted hypocholesterogenic effects within a concentration range of 3.2-32 µg/mL. Nonsaponifiable lipids manifested a decrease in incorporation of [14C]acetate into squalene, lanosterol, lathosterol, and cholesterol, but not into ubiquinone, thus suggesting an inhibition of enzymes in the MP downstream from farnesyl pyrophosphate. The tagetenone chemotype, the most efficacious hypocholesterogenic L. alba EO, lowered HMGCR protein levels; inhibited triacylglycerols, cholesteryl esters, and phospholipids synthesis; and diminished lipid droplets in size and volume. These results revealed that L. alba EOs inhibited different lipogenic pathways and such lipid-lowering effects could prove essential to prevent cardiovascular diseases.

Synergistic antiproliferative and anticholesterogenic effects of linalool, 1,8-cineole, and simvastatin on human cell lines.

Monoterpenes are naturally occurring plant hydrocarbons with multiple effects on the mevalonate pathway (MP), while statins competitively inhibit hydroxymethylglutarylcoenzyme-A reductase (HMGCR), the rate-limiting enzyme in the MP. Monoterpenes and statins proved capable of inhibiting both proliferation and cholesterogenesis. In the present study we assess the in vitro antiproliferative and anticholesterogenic effects of two monoterpenes: linalool and 1,8-cineole-either alone, in combination with each other, or combined individually with simvastatin-on liver-derived (HepG2) and extrahepatic (A549) cell lines. The three compounds alone inhibited cell proliferation in a dose-dependent fashion, while their pairwise combination produced synergistic antiproliferative effects in both cell lines. Incorporation experiments with [(14)C]acetate revealed that linalool and 1,8-cineole inhibited the MP, probably at different points, resulting in a reduction in cholesterogenesis and an accumulation of other MP intermediates and products. Linalool or 1,8-cineole, either together or individually with simvastatin, synergistically inhibited cholesterol synthesis. At low concentrations both monoterpenes inhibited steps specifically involved in cholesterol synthesis, whereas at higher concentrations HMGCR levels became down-regulated. Added exogenous mevalonate failed to reverse the inhibition of proliferation exerted by linalool and 1,8-cineole, suggesting that HMGCR inhibition alone is not responsible for the antiproliferative activity of those agents. This work demonstrates that monoterpenes in combination with each other, or individually in combination with simvastatin synergistically inhibits proliferation and cholesterogenesis in the human cell lines investigated, thus contributing to a clearer understanding of the action of essential-oil components, and their combination with the statins, in the targeting of specific points within a complex metabolic pathway.

Actividad antiproliferativa y anticolesterogénica de estatinas y monoterpenos / Antiproliferative and anticholesterogenic activityof statins and monoterpenes / Atividade antiproliferativa e anticolesterogÛnicade estatinas e monoterpenos

Las estatinas son inhibidores competitivos de la 3-hidroxi-3-metilglutaril-coenzima A (HMG-CoA) reductasa ampliamente usados en los tratamientos contra las hipercolesterolemias. Los monoterpenos son componentes no nutritivos de la dieta presentes en aceites esenciales de varias plantas que han demostrado tener múltiples efectos en la vía del mevalonato. Se estudia el efecto y mecanismo de acción de monoterpenos presentes en aceites esenciales, así como la combinación de éstos entre sí y con simvastatina sobre la síntesis de colesterol, el metabolismo lipídico y la proliferación celular in vitro en células hepáticas Hep G2 y no hepáticas A549, e in vivo en ratones atímicos huéspedes y no huéspedes de tumores derivado de células A549 implantados en ellos. Se abre así una gran expectativa sobre la potencialidad de la administración conjunta de distintos monoterpenos y de extractos naturales de aceites esenciales en el mejoramiento de las terapias antihipercolesterolemiantes y/o el tratamiento del cáncer, como así también en el potencial sinergismo con estatinas como una alternativa para disminuir las dosis efectivas y los efectos indeseados y/o tóxicos.(AU)

Statins are competitive inhibitors of HMG-CoA reductase used in hypercholesterolemic patients. Monoterpenes are non-nutritive dietary components found in the essential oils of many plants with pharmacologic effects on mevalonate metabolism. The study is centered on the effects and action mechanisms of the monoterpene components of essential oils and the combination of monoterpenes between them and combined with simvastatin on cholesterogenesis, lipid metabolism and cellular proliferation in vitro using two established cell lines, Hep G2 (derived from a human hepatoblastoma), A549 (derived from a human lung adenocarcinoma) and in vivo in no host and host nude mice carrying implanted tumors derived from A549. This opens up great expectations about the potential of co-administration of different natural isoprenoids and essential oils in improving anti-cholesterolemic therapies and/or cancer treatment as well as in the potential synergism with statins as an alternative to lower effective doses, decreasing the likelihood of undesired and/or toxic effects.(AU)

As estatinas sÒo inibidores competitivos da 3-hidroxi-3-metilglutaril - coenzima A (HMG-CoA) reductase amplamente utilizados nos tratamentos contra as hipercolesterolemias. Os monoterpenos sÒo componentes nÒo nutritivos da dieta encontrados em óleos essenciais de várias plantas que demonstraram ter múltiplos efeitos na via do mevalonato. Estudamos o efeito e o mecanismo de aþÒo de monoterpenos encontrados em óleos essenciais, bem como a combinaþÒo deles entre si e com sinvastatina sobre a síntese de colesterol, o metabolismo lipídico e a proliferaþÒo celular in vitro em células hepáticas Hep G2 e nÒo hepáticas A549 e in vivo em camundongos atímicos hospedeiros ou nÒo hospedeiros de tumores derivados de células A549 implantadas neles. Isto abre grandes expectativas sobre o potencial da co-administraþÒo de diferentes monoterpenos e de extratos naturais de óleos essenciais na melhoria das terapias anti-hipercolesterolemiantes e/ou tratamento do cÔncer, assim como no potencial sinergismo com estatinas como uma alternativa para reduzir as doses efetivas e os efeitos indesejáveis e/ou tóxicos.(AU)

Actividad antiproliferativa y anticolesterogénica de estatinas y monoterpenos / Antiproliferative and anticholesterogenic activityof statins and monoterpenes / Atividade antiproliferativa e anticolesterogênicade estatinas e monoterpenos

Las estatinas son inhibidores competitivos de la 3-hidroxi-3-metilglutaril-coenzima A (HMG-CoA) reductasa ampliamente usados en los tratamientos contra las hipercolesterolemias. Los monoterpenos son componentes no nutritivos de la dieta presentes en aceites esenciales de varias plantas que han demostrado tener múltiples efectos en la vía del mevalonato. Se estudia el efecto y mecanismo de acción de monoterpenos presentes en aceites esenciales, así como la combinación de éstos entre sí y con simvastatina sobre la síntesis de colesterol, el metabolismo lipídico y la proliferación celular in vitro en células hepáticas Hep G2 y no hepáticas A549, e in vivo en ratones atímicos huéspedes y no huéspedes de tumores derivado de células A549 implantados en ellos. Se abre así una gran expectativa sobre la potencialidad de la administración conjunta de distintos monoterpenos y de extractos naturales de aceites esenciales en el mejoramiento de las terapias antihipercolesterolemiantes y/o el tratamiento del cáncer, como así también en el potencial sinergismo con estatinas como una alternativa para disminuir las dosis efectivas y los efectos indeseados y/o tóxicos.

Statins are competitive inhibitors of HMG-CoA reductase used in hypercholesterolemic patients. Monoterpenes are non-nutritive dietary components found in the essential oils of many plants with pharmacologic effects on mevalonate metabolism. The study is centered on the effects and action mechanisms of the monoterpene components of essential oils and the combination of monoterpenes between them and combined with simvastatin on cholesterogenesis, lipid metabolism and cellular proliferation in vitro using two established cell lines, Hep G2 (derived from a human hepatoblastoma), A549 (derived from a human lung adenocarcinoma) and in vivo in no host and host nude mice carrying implanted tumors derived from A549. This opens up great expectations about the potential of co-administration of different natural isoprenoids and essential oils in improving anti-cholesterolemic therapies and/or cancer treatment as well as in the potential synergism with statins as an alternative to lower effective doses, decreasing the likelihood of undesired and/or toxic effects.

As estatinas são inibidores competitivos da 3-hidroxi-3-metilglutaril - coenzima A (HMG-CoA) reductase amplamente utilizados nos tratamentos contra as hipercolesterolemias. Os monoterpenos são componentes não nutritivos da dieta encontrados em óleos essenciais de várias plantas que demonstraram ter múltiplos efeitos na via do mevalonato. Estudamos o efeito e o mecanismo de ação de monoterpenos encontrados em óleos essenciais, bem como a combinação deles entre si e com sinvastatina sobre a síntese de colesterol, o metabolismo lipídico e a proliferação celular in vitro em células hepáticas Hep G2 e não hepáticas A549 e in vivo em camundongos atímicos hospedeiros ou não hospedeiros de tumores derivados de células A549 implantadas neles. Isto abre grandes expectativas sobre o potencial da co-administração de diferentes monoterpenos e de extratos naturais de óleos essenciais na melhoria das terapias anti-hipercolesterolemiantes e/ou tratamento do câncer, assim como no potencial sinergismo com estatinas como uma alternativa para reduzir as doses efetivas e os efeitos indesejáveis e/ou tóxicos.

Transcriptional and posttranscriptional inhibition of HMGCR and PC biosynthesis by geraniol in 2 Hep-G2 cell proliferation linked pathways.

Geraniol, present in the essential oils of many aromatic plants, has in vitro and in vivo antitumor activity against several cell lines. We investigated the effects of geraniol on lipid metabolic pathways involved in Hep-G2 cell proliferation and found that geraniol inhibits the mevalonate pathway, phosphatidylcholine biosynthesis, cell growth, and cell cycle progression (with an arrest occurring at the G0/G1 interphase) and increases apoptosis. The expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), the rate-limiting step in cholesterol synthesis, was inhibited at the transcriptional and posttranscriptional levels, as assessed by real-time RT-PCR, Western blots, and [(14)C]HMG-CoA-conversion radioactivity assays. That geraniol decreased cholesterogenesis but increased the incorporation of [(14)C]acetate into other nonsaponifiable metabolites indicated the existence of a second control point between squalene and cholesterol involved in redirecting the flow of cholesterol-derived carbon toward other metabolites of the mevalonate pathway. That exogenous mevalonate failed to restore growth in geraniol-inhibited cells suggests that, in addition to the inhibition of HMGCR, other dose-dependent actions exist through which geraniol can impact the mevalonate pathway and consequently inhibit cell proliferation. These results suggest that geraniol, a nontoxic compound found in many fruits and herbs, exhibits notable potential as a natural agent for combatting cancer and (or) cardiovascular diseases.