RESUMO
A diet rich in n-3/n-6 polyunsaturated fatty acids (PUFAs) is cardioprotective. Dietary PUFAs affect the cellular phospholipids composition, which may influence the function of membrane proteins. We investigated the impact of the membrane incorporation of several PUFAs on ABCA1-mediated cholesterol efflux, a key antiatherogenic pathway. Arachidonic acid (AA) (C20:4 n-6) and docosahexaenoic acid (DHA) (C22:6 n-3) decreased or increased cholesterol efflux from J774 mouse macrophages, respectively, whereas they had no effect on efflux from human monocyte-derived macrophages (HMDM). Importantly, eicosapentaenoic acid (EPA) (C20:5 n-3) induced a dose-dependent reduction of ABCA1 functionality in both cellular models (-28% for 70µM of EPA in HMDM), without any alterations in ABCA1 expression. These results show that PUFA membrane incorporation does not have the same consequences on cholesterol efflux from mouse and human macrophages. The EPA-treated HMDM exhibited strong phospholipid composition changes, with high levels of both EPA and its elongation product docosapentaenoic acid (DPA) (C22:5 n-3), which is associated with a decreased level of AA. In HMDM, EPA reduced the ATPase activity of the membrane transporter. Moreover, the activation of adenylate cyclase by forskolin and the inhibition of cAMP phosphodiesterase by isobutylmethylxanthine restored ABCA1 cholesterol efflux in EPA-treated human macrophages. In conclusion, EPA membrane incorporation reduces ABCA1 functionality in mouse macrophages as well as in primary human macrophages and this effect seems to be PKA-dependent in human macrophages.
Assuntos
Transportador 1 de Cassete de Ligação de ATP/metabolismo , Membrana Celular/efeitos dos fármacos , Colesterol/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Ácido Eicosapentaenoico/farmacologia , Macrófagos/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , 3',5'-AMP Cíclico Fosfodiesterases/metabolismo , Transportador 1 de Cassete de Ligação de ATP/genética , Adenilil Ciclases/metabolismo , Animais , Ácido Araquidônico/farmacologia , Transporte Biológico , Membrana Celular/metabolismo , Células Cultivadas , Ácidos Docosa-Hexaenoicos/farmacologia , Relação Dose-Resposta a Droga , Regulação para Baixo , Ácido Eicosapentaenoico/metabolismo , Ácidos Graxos Insaturados/metabolismo , Humanos , Macrófagos/enzimologia , Camundongos , Cultura Primária de Células , Células RAW 264.7 , Especificidade da EspécieRESUMO
Transplant vasculopathy may be considered as an accelerated form of atherosclerosis resulting in chronic rejection of vascularized allografts. After organ transplantation, a diffuse intimal thickening is observed, leading to the development of an atherosclerosis plaque due to a significant monocyte infiltration. This results from a chronic inflammatory process induced by the immune response. In this study, we investigated the impact of two immunosuppressive drugs used in therapy initiated after organ transplantation, mycophenolate mofetil, and rapamycin, on the apoptotic response of monocytes induced or not by oxidized LDL. Here we show the pro-apoptotic effect of these two drugs through two distinct signaling pathways and we highlight a synergistic effect of rapamycin on apoptosis induced by oxidized LDL. In conclusion, since immunosuppressive therapy using mycophenolate mofetil or rapamycin can increase the cell death in a monocyte cell line, this treatment could exert similar effects on human monocytes in transplant patients, and thus, prevent transplant vasculopathy, atherosclerosis development, and chronic allograft rejection. J. Cell. Biochem. 118: 3480-3487, 2017. © 2017 Wiley Periodicals, Inc.
Assuntos
Apoptose/efeitos dos fármacos , Monócitos/metabolismo , Ácido Micofenólico/farmacologia , Transdução de Sinais/efeitos dos fármacos , Sirolimo/farmacologia , Humanos , Lipoproteínas LDL/farmacologia , Células U937RESUMO
A diet containing a high n-3/n-6 polyunsaturated fatty acids (PUFA) ratio has cardioprotective properties. PUFAs incorporation into membranes influences the function of membrane proteins. We investigated the impact of the membrane incorporation of PUFAs, especially eicosapentaenoic acid (EPA) (C20:5 n-3), on the anti-atherogenic cholesterol efflux pathways. We used cholesteryl esters (CE)-loaded human monocyte-derived macrophages (HMDM) to mimic foam cells exposed to the FAs for a long period of time to ensure their incorporation into cellular membranes. Phospholipid fraction of EPA cells exhibited high levels of EPA and its elongation product docosapentaenoic acid (DPA) (C22:5 n-3), which was associated with a decreased level of arachidonic acid (AA) (C20:4 n-6). EPA 70µM reduced ABCA1-mediated cholesterol efflux to apolipoprotein (apo) AI by 30% without any alteration in ABCA1 expression. The other tested PUFAs, DPA, docosahexaenoic acid (DHA) (C22:6 n-3), and AA, were also able to reduce ABCA1 functionality while the monounsaturated oleic FA slightly decreased efflux and the saturated palmitic FA had no impact. Moreover, EPA also reduced cholesterol efflux to HDL mediated by the Cla-1 and ABCG1 pathways. EPA incorporation did not hinder efflux in free cholesterol-loaded HMDM and did not promote esterification of cholesterol. Conversely, EPA reduced the neutral hydrolysis of cytoplasmic CE by 24%. The reduced CE hydrolysis was likely attributed to the increase in cellular TG contents and/or the decrease in apo E secretion after EPA treatment. In conclusion, EPA membrane incorporation reduces cholesterol efflux in human foam cells by reducing the cholesteryl ester mobilization from lipid droplets.
Assuntos
Membrana Celular/metabolismo , Ésteres do Colesterol/metabolismo , Ácido Eicosapentaenoico , Gotículas Lipídicas/metabolismo , Macrófagos/metabolismo , Transportador 1 de Cassete de Ligação de ATP/biossíntese , Membro 1 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/biossíntese , Ácido Eicosapentaenoico/farmacocinética , Ácido Eicosapentaenoico/farmacologia , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Lipoproteínas HDL/metabolismo , Masculino , Receptores Depuradores Classe B/biossínteseRESUMO
A high intake in polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) (C20:5 n-3), is cardioprotective. Dietary PUFAs incorporate into membrane phospholipids, which may modify the function of membrane proteins. We investigated the consequences of the membrane incorporation of several PUFAs on the key antiatherogenic ABCA1-mediated cholesterol efflux pathway. Human THP-1 macrophages were incubated with EPA, arachidonic acid (AA) (C20:4 n-6) or docosahexaenoic acid (DHA) (C22:6 n-3) for a long time to mimic a chronic exposure. EPA 70 µM, but not AA 50 µM or DHA 15 µM, increased ABCA1-mediated cholesterol efflux to apolipoprotein (apo) AI by 28% without altering aqueous diffusion. No variation in ABCA1 expression or localization was observed after EPA treatment. EPA incorporation did not affect the phenotype of THP-1 macrophages. The membrane phospholipids composition of EPA cells displayed higher levels of both EPA and its elongation product docosapentaenoic acid, which was associated with drastic lower levels of AA. Treatment by EPA increased the ATPase activity of the transporter, likely through a PKA-dependent mechanism. Eicosanoids were not involved in the stimulated ABCA1-mediated cholesterol efflux from EPA-enriched macrophages. In addition, EPA supplementation increased the apo AI binding capacity from macrophages by 38%. Moreover, the increased apo AI binding in EPA-enriched macrophages can be competed. In conclusion, EPA membrane incorporation increased ABCA1 functionality in cholesterol-normal human THP-1 macrophages, likely through a combination of different mechanisms. This beneficial in vitro effect may partly contribute to the cardioprotective effect of a diet enriched with EPA highlighted by several recent clinical trials.
Assuntos
Transportador 1 de Cassete de Ligação de ATP/metabolismo , Colesterol/metabolismo , Ácido Eicosapentaenoico/farmacologia , Macrófagos/efeitos dos fármacos , Fosfolipídeos/metabolismo , Células Cultivadas , Relação Dose-Resposta a Droga , Ácido Eicosapentaenoico/metabolismo , Humanos , Macrófagos/metabolismoRESUMO
A high consumption of polyunsaturated fatty acids (PUFAs), particularly n-3 PUFAs, is atheroprotective. PUFAs incorporation into membrane phospholipids alters the functionality of membrane proteins. We studied the consequences of the in vitro supplementation of several PUFAs on the FA profiles and on ABCA1-dependent cholesterol efflux capacities from cholesterol-loaded macrophages. Arachidonic acid (AA, C20:4 n-6) and, to a lesser extent, eicosapentaenoic acid (EPA, C20:5 n-3), dose-dependently impaired cholesterol efflux from cholesterol-loaded J774 mouse macrophages without alterations in ABCA1 expression, whereas docosahexaenoic acid (DHA, C22:6 n-3) had no impact. AA cells exhibited higher proportions of arachidonic acid and adrenic acid (C22:4 n-6), its elongation product. EPA cells exhibited slightly higher proportions of EPA associated with much higher proportions of docosapentaenoic acid (C22:5 n-3), its elongation product and with lower proportions of AA. Conversely, both EPA and DHA and, to a lesser extent, AA decreased cholesterol efflux from cholesterol-loaded primary human macrophages (HMDM). The differences observed in FA profiles after PUFA supplementations were different from those observed for the J774 cells. In conclusion, we are the first to report that AA and EPA, but not DHA, have deleterious effects on the cardioprotective ABCA1 cholesterol efflux pathway from J774 foam cells. Moreover, the membrane incorporation of PUFAs does not have the same impact on cholesterol efflux from murine (J774) or human (HMDM) cholesterol-loaded macrophages. This finding emphasizes the key role of the cellular model in cholesterol efflux studies and may partly explain the heterogeneous literature data on the impact of PUFAs on cholesterol efflux.
Assuntos
Ácido Araquidônico/administração & dosagem , Membrana Celular/efeitos dos fármacos , Colesterol/metabolismo , Ácidos Docosa-Hexaenoicos/administração & dosagem , Ácido Eicosapentaenoico/administração & dosagem , Células Espumosas/efeitos dos fármacos , Transportador 1 de Cassete de Ligação de ATP/metabolismo , Animais , Aterosclerose/etiologia , Aterosclerose/prevenção & controle , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Colesterol/administração & dosagem , Colesterol/efeitos adversos , Suplementos Nutricionais , Células Espumosas/citologia , Células Espumosas/metabolismo , Voluntários Saudáveis , Humanos , Camundongos , Fosfolipídeos/metabolismo , Cultura Primária de CélulasRESUMO
Apolipoprotein A-V is an important determinant of plasma triglyceride level in both humans and mice. This study showed the physiological impact of apoA-V on insulin secretion in rat pancreatic beta-cells (INS-1 cells). In order to precise the mechanism of action, binding experiments coupled to mass spectrometry were performed to identify a potential membrane receptor. Results showed an interaction between apoA-V and midkine protein. Confocal microscopy confirmed the plasma membrane co-localisation of this two-proteins after the treatment of INS-1 cells with the apo-AV recombinant protein and indicated that the cell surface midkine could be involved in apoA-V endocytosis, since these two proteins were co-translocated at the plasma membrane or in the cytosol compartment. This co-localisation is correlated with an increase in insulin secretion in a dose dependant manner during short incubation period. Reduction of midkine expression by small interfering RNA duplexes revealed a decrease in the ability of these transfected cells to secrete insulin in presence of apoA-V. Competition experiments for the apoA-V-midkine binding at the cell surface using antibody directed against midkine is able to influence INS-1 cell function as insulin secretion. Our results showed apoA-V ability to enhance insulin secretion in beta-cells and provide evidence of an internalization pathway involving the midkine as partner.
Assuntos
Apolipoproteínas/metabolismo , Citocinas/metabolismo , Células Secretoras de Insulina/metabolismo , Insulina/metabolismo , Sequência de Aminoácidos , Animais , Apolipoproteína A-V , Apolipoproteínas/análise , Linhagem Celular Tumoral , Citocinas/análise , Citocinas/genética , Endocitose , Imunoprecipitação , Secreção de Insulina , Midkina , Dados de Sequência Molecular , Ligação Proteica , RNA Interferente Pequeno/metabolismo , Ratos , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/farmacologia , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
The apolipoprotein A5 gene (APOA5) has been repeatedly implicated in lowering plasma triglyceride levels. Since several studies have demonstrated that hyperinsulinemia is associated with hypertriglyceridemia, we sought to determine whether APOA5 is regulated by insulin. Here, we show that cell lines and mice treated with insulin down-regulate APOA5 expression in a dose-dependent manner. Furthermore, we found that insulin decreases human APOA5 promoter activity, and subsequent deletion and mutation analyses uncovered a functional E box in the promoter. Electrophoretic mobility shift and chromatin immunoprecipitation assays demonstrated that this APOA5 E box binds upstream stimulatory factors (USFs). Moreover, in transfection studies, USF1 stimulates APOA5 promoter activity, and the treatment with insulin reduced the binding of USF1/USF2 to the APOA5 promoter. The inhibition of the phosphatidylinositol 3-kinase (PI3K) pathway abolished insulin's effect on APOA5 gene expression, while the inhibition of the P70 S6 kinase pathway with rapamycin reversed its effect and increased APOA5 gene expression. Using an oligonucleotide precipitation assay for USF from nuclear extracts, we demonstrate that phosphorylated USF1 fails to bind to the APOA5 promoter. Taken together, these data indicate that insulin-mediated APOA5 gene transrepression could involve a phosphorylation of USFs through the PI3K and P70 S6 kinase pathways that modulate their binding to the APOA5 E box and results in APOA5 down-regulation. The effect of exogenous hyperinsulinemia in men showed a decrease in the plasma ApoAV level. These results suggest a potential contribution of the APOA5 gene in hypertriglyceridemia associated with hyperinsulinemia.
Assuntos
Apolipoproteínas/metabolismo , Regulação para Baixo/efeitos dos fármacos , Insulina/farmacologia , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Quinases S6 Ribossômicas 70-kDa/metabolismo , Adulto , Animais , Apolipoproteína A-V , Apolipoproteínas A , Células Cultivadas , Primers do DNA/genética , Proteínas de Ligação a DNA/metabolismo , Ensaio de Desvio de Mobilidade Eletroforética , Feminino , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Humanos , Camundongos , Inibidores de Fosfoinositídeo-3 Quinase , Fosforilação/efeitos dos fármacos , Regiões Promotoras Genéticas/genética , Ligação Proteica/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia , Ratos , Proteínas Quinases S6 Ribossômicas 70-kDa/antagonistas & inibidores , Sirolimo/farmacologia , Fatores de Transcrição/metabolismo , Fatores Estimuladores UpstreamRESUMO
AIM: Dietary supplements in polyunsaturated fatty acids (PUFA), particularly omega-3, are well known for their beneficial effects in preventing cardiovascular diseases (CVD). The aim of this study was to determine the role of PUFA on the modulation of apoptosis induced by hypochlorous acidoxidized LDL (HOCl-oxLDL) in U937 cells. METHODS: We tested the effect of monocyte cell line U937 supplementation with eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), arachidonic acid (ARA) or oleic acid (OA) on the modulation of HOCl-oxLDL-induced apoptosis. RESULTS: First, we showed the incorporation of fatty acids in the cellular membrane in U937 cells. Then, we showed that both EPA and ARA exerted a pro-apoptotic effect through the intrinsic mitochondrial apoptotic pathway including the dissipation of mitochondrial membrane potential followed by cardiolipin depletion, the downstream activation of caspase-3 and the increase in DNA fragmentation. The pro-apoptotic effect of EPA or ARA was completely blocked in U937/Bcl-2 cells. CONCLUSIONS: A new mechanism of dietary supplements in PUFA with likely consequences in apoptosis could be suggested through the mitochondrial pathway in monocytes.
Assuntos
Apoptose , Ácido Araquidônico/farmacologia , Ácidos Docosa-Hexaenoicos/farmacologia , Ácido Eicosapentaenoico/farmacologia , Lipoproteínas LDL/metabolismo , Mitocôndrias/efeitos dos fármacos , Monócitos/efeitos dos fármacos , Cardiolipinas/metabolismo , Caspase 3/metabolismo , Suplementos Nutricionais , Ativação Enzimática/efeitos dos fármacos , Ácidos Graxos/metabolismo , Humanos , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Mitocôndrias/metabolismo , Monócitos/citologia , Monócitos/metabolismo , Células U937RESUMO
The apolipoprotein A5 gene (APOA5) is a key player in determining triglyceride concentrations in humans and mice. Since diabetes is often associated with hypertriglyceridemia, this study explores whether APOA5 gene expression is regulated by alteration in glucose homeostasis and the related pathways. d-Glucose activates APOA5 gene expression in a time- and dose-dependent manner in hepatocytes, and the glycolytic pathway involved was determined using d-glucose analogues and metabolites. Together, transient transfections, electrophoretic mobility shift assays and chromatin immunoprecipitation assays show that this regulation occurs at the transcriptional level through an increase of USF1/2 binding to an E-box in the APOA5 promoter. We show that this phenomenon is not due to an increase of mRNA or protein expression levels of USF. Using protein phosphatases 1 and 2A inhibitor, we demonstrate that d-glucose regulates the APOA5 gene via a dephosphorylation mechanism, resulting in an enhanced USF1/2-promoter binding. Last, subsequent suppressions of USF1/2 and phosphatases mRNA through siRNA gene silencing abolished the regulation. We demonstrate that the APOA5 gene is up regulated by d-glucose and USF through phosphatase activation. These findings may provide a new cross-talk between glucose and lipid metabolism.
Assuntos
Apolipoproteínas A/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Glucose/farmacologia , Animais , Apolipoproteína A-V , Apolipoproteínas A/genética , Linhagem Celular , Linhagem Celular Tumoral , Relação Dose-Resposta a Droga , Ativação Enzimática/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Glicólise , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Humanos , Regiões Promotoras Genéticas , Ligação Proteica , Proteína Fosfatase 1/farmacologia , Proteína Fosfatase 2/farmacologia , RNA Mensageiro/metabolismo , Ratos , Fatores de Tempo , Transcrição Gênica , Fatores Estimuladores Upstream/metabolismoRESUMO
Hypertriglyceridemia is an independent risk factor for the development of cardiovascular disease and is often associated with diabetes, inflammation and the metabolic syndrome. Recently, apolipoprotein A5 (APOA5) was identified as a novel member of the APOA1/C3/A4 gene cluster. Data from mice over-expressing or lacking APOA5 provide direct evidence that this apolipoprotein plays a role in triglyceride metabolism. Moreover, plasma triglyceride levels were found to be strongly associated with APOA5 polymorphisms. The human APOA5 gene is regulated by transcription factors known to affect triglyceride metabolism such as PPARa, RORa, LXR and SREBP-1c and this supports its function. Insulin and interleukins regulate APOA5 gene expression and provide novel clues for the role of this apolipoprotein. To date, the triglyceride lowering action of apoA-V is attributed to the activation of lipoprotein lipase and an acceleration of very low density lipoprotein catabolism. Recent findings indicate that APOA5 could also influence cholesterol homeostasis and probably play a role in hypertriglyceridemia associated with diabetes and inflammation. This review aims to give a comprehensive summary of the current literature and supports the view that APOA5 plays a relevant role in lipid metabolism.
Assuntos
Apolipoproteínas/genética , Regulação da Expressão Gênica , Hipertrigliceridemia/genética , Lipoproteínas VLDL/sangue , Triglicerídeos/sangue , Animais , Apolipoproteína A-V , Apolipoproteínas A , Humanos , Hipertrigliceridemia/sangue , Polimorfismo GenéticoRESUMO
Human data raised the possibility that coronary heart disease is associated with mutations in the apolipoprotein gene cluster APOA1/C3/A4 that result in multideficiency of cluster-encoded apolipoproteins and hypoalphalipoproteinemia. To test this hypothesis, we generated a mouse model for human apolipoprotein A-I (apoA-I)/C-III/A-IV deficiency. Homozygous mutants (Apoa1/c3/a4(-/-)) lacking the three cluster-encoded apolipoproteins were viable and fertile. In addition, feeding behavior and growth were apparently normal. Total cholesterol (TC), high density lipoprotein cholesterol (HDLc), and triglyceride levels in the plasma of fasted mutants fed a regular chow were 32% (P < 0.001), 17% (P < 0.001), and 70% (P < 0.01), respectively, those of wild-type mice. When fed a high-fat Western-type (HFW) diet, Apoa1/c3/a4(-/-) mice showed a further decrease in HDLc concentration and a moderate increase in TC, essentially in non-HDL fraction. The capacity of Apoa1/c3/a4(-/-) plasma to promote cholesterol efflux in vitro was decreased to 75% (P < 0.001), and LCAT activity was decreased by 38% (P < 0.01). Despite the very low total plasma cholesterol, the imbalance in lipoprotein distribution caused small but detectable aortic lesions in one-third of Apoa1/c3/a4(-/-) mice fed a HFW diet. In contrast, none of the wild-type mice had lesions. These results demonstrate that Apoa1/c3/a4(-/-) mice display clinical features similar to human apoA-I/C-III/A-IV deficiency (i.e., marked hypoalphalipoproteinemia) and provide further support for the apoa1/c3/a4 gene cluster as a minor susceptibility locus for atherosclerosis in mice.
Assuntos
Apolipoproteína A-I/deficiência , Apolipoproteínas A/deficiência , Apolipoproteínas C/deficiência , Gorduras na Dieta/efeitos adversos , Modelos Animais de Doenças , Dislipidemias/genética , Animais , Apolipoproteína C-III , Colesterol/metabolismo , Doença da Artéria Coronariana/patologia , Dislipidemias/patologia , Feminino , Humanos , Lipídeos/sangue , Lipoproteínas/sangue , Masculino , Camundongos , RatosRESUMO
Alterations in the expression of the recently discovered apolipoprotein A5 gene strongly affect plasma triglyceride levels. In this study, we investigated the contribution of APOA5 to the liver X receptor (LXR) ligand-mediated effect on plasma triglyceride levels. Following treatment with the LXR ligand T0901317, we found that APOA5 mRNA levels were decreased in hepatoma cell lines. The observation that no down-regulation of APOA5 promoter activity was obtained by LXR-retinoid X receptor (RXR) co-transfection prompted us to explore the possible involvement of the known LXR target gene SREBP-1c (sterol regulatory element-binding protein 1c). In fact, we found that co-transfection with the active form of SREBP-1c down-regulated APOA5 promoter activity in a dose-dependent manner. We then scanned the human APOA5 promoter sequence and identified two putative E-box elements that were able to bind specifically SREBP-1c in gel-shift assays and were shown to be functional by mutation analysis. Subsequent suppression of SREBP-1 mRNA through small interfering RNA interference abolished the decrease of APOA5 mRNA in response to T0901317. Finally, administration of T0901317 to hAPOA5 transgenic mice revealed a significant decrease of APOA5 mRNA in liver tissue and circulating apolipoprotein AV protein in plasma, confirming that the described down-regulation also occurs in vivo. Taken together, our results demonstrate that APOA5 gene expression is regulated by the LXR ligand T0901317 in a negative manner through SREBP-1c. These findings may provide a new mechanism responsible for the elevation of plasma triglyceride levels by LXR ligands and support the development of selective LXR agonists, not affecting SREBP-1c, as beneficial modulators of lipid metabolism.
Assuntos
Anticolesterolemiantes/farmacologia , Apolipoproteínas/genética , Proteínas Estimuladoras de Ligação a CCAAT/fisiologia , Proteínas de Ligação a DNA/fisiologia , Regulação da Expressão Gênica , Fatores de Transcrição/fisiologia , Animais , Apolipoproteína A-V , Apolipoproteínas/análise , Apolipoproteínas A , Sequência de Bases , Linhagem Celular Tumoral , Regulação para Baixo , Feminino , Humanos , Hidrocarbonetos Fluorados , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Dados de Sequência Molecular , Regiões Promotoras Genéticas , RNA Mensageiro/análise , Elementos de Resposta/fisiologia , Proteína de Ligação a Elemento Regulador de Esterol 1 , Sulfonamidas , Transfecção , Triglicerídeos/sangueRESUMO
The recently discovered APOA5 gene has been shown in humans and mice to be important in determining plasma triglyceride levels, a major cardiovascular disease risk factor. apoAV represents the first described apolipoprotein where overexpression lowers triglyceride levels. Since fibrates represent a commonly used therapy for lowering plasma triglycerides in humans, we investigated their ability to modulate APOA5 gene expression and consequently influence plasma triglyceride levels. Human primary hepatocytes treated with Wy 14,643 or fenofibrate displayed a strong induction of APOA5 mRNA. Deletion and mutagenesis analyses of the proximal APOA5 promoter firmly demonstrate the presence of a functional peroxisome proliferator-activated receptor response element. These findings demonstrate that APOA5 is a highly responsive peroxisome proliferator-activated receptor alpha target gene and support its role as a major mediator for how fibrates reduce plasma triglycerides in humans.