RESUMEN
Objective To investigate the effects of apolipoproteinA1 (apoA1) on levels of cholesterol, cholesteryl ester (CE), and expression of ATP-bindiag cassette transporter A1 (ABCA1) in human acute monocytie leukemia cell line (THP-1) macrophage-derived foam cells.Methods The cultured THP-1 cells were induced into foam cells by exposing first to phorbol myristate acetate (PMA, 50 ng/ml) for 48 h, and then to oxidized-low density lipoprotein (ox-LDL, 50μg/ml) for 48 h.Under treatment of apoA1 in different doses (5, 10, 15 and 20 μg/ml) and one simple dose (10 μg/ml) for different time (6, 12 and 24 h), THP-1 macrophage-derived foam cells were incubated to observe the expression of cholesterol and ABCA1.The concentrations of cellular total cholesterol (TC), free cholesterol (FC) and CE were determined by oxidization enzymatic methods.Oil red O dyeing experiment was used to show the cellular lipid droplets in the cells.The expression of ABCA1 was tested by immunofluorescence method.Reverse transcription-polymerase chain reaction was applied to investigate mRNA expression of ABCA1.Results The THP-1 cells turned into typical foam cells after treated with PMA (50 ng/ml) for 48 h, and ox-LDL (50 μg/ml) for 48 h.apoA1 could lower the levels of TC, FC and CE in THP-1 macrophage-derived foam cells in a dose-dependent and a time-dependant manner, apoA1 could increase the expression of ABCA1 protein in THP-1maerophage-derived foam cells without up-regulation of mRNA.Antibody of ABCA1 could up- regulate the expression of ABCA1.Conclusions apoA1 may decrease the levels of cholesterols in THP-1 macrophage-derived foam cells, by promoting the expression of ABCA1 and the reverse cholesterol transport of high density lipoprotein.
RESUMEN
Introdução: A lipoproteína de baixa densidade (LDL) e suas formas oxidadas (LDLox) possuem múltiplas propriedades aterogênicas, atuando na deposição de colesterol, indução e manutenção da inflamação, disfunção endotelial, surgimento de células espumosas na parede arterial e conseqüente formação da placa de ateroma. Adicionalmente, LDLox induz apoptose de células endoteliais humanas (HMEC). A lipoproteína de alta densidade (HDL) possui inúmeras atividades antiaterogênicas, incluindo ações antioxidante, anti-inflamatória e anti-trombótica. A HDL é capaz de proteger as HMEC contra apoptose. As subfrações de HDL (sHDL) são heterogêneas em sua composição físico-química e atividades biológicas. A atividade antioxidante das sHDL aumenta com a densidade (HDL2b100% - anexina V) e 3b (43% e 67%, respectivamente) de indivíduos normolipidêmicos apresentaram atividade anti-apoptótica mais potente do que as subfrações HDL2a (29% e 28%; p<0,01 vs. HDL3c, respectivamente) e 2b (25% e 62%; p<0,001 vs. HDL3c, respectivamente). Todas sHDL reduziram geração de espécies reativas de oxigênio (ROS) induzida pela LDLox, sendo a HDL3c (54%) mais potente do que HDL2b (21%; p<0.05 vs. HDL3c). Houve correlação positiva entre as atividades anti-apoptótica e antioxidante intracelular com conteúdo de apoA-I e esfingosina 1-fosfato (E1F) das sHDL, senda HDL3b e 3c ricas em E1F. A atividade anti-apoptótica da E1F e das sHDL parece depender da interação com as células endoteliais via apoA-I e seu receptor SR-BI. Finalmente, as HDL3c (n=5) isoladas de pacientes com SMet possuem conteúdo significativamente menor de apoA-I e reduzida atividade anti-apoptótica (60%, p<0,01), quando comparada aos controles normolipidêmicos (n=5). Houve tendência à diminuição da proteção contra a geração de ROS (SMet, n=10). Conclusão: As subfrações HDL3c protegem de forma potente as células endoteliais humanas contra toxicidade e apoptose induzidas pela LDLox, assim como contra geração de ROS...
Background: Low density lipoprotein (LDL) and its oxidized forms (oxLDL) have several atherogenic properties, including cholesterol deposition, inflammation, endothelial dysfunction and foam cell formation on the arterial wall, leading to atherosclerotic plaque development. In addition, oxLDL induces human endothelial cell apoptosis (HMEC). High-density lipoprotein (HDL) has number of antiatherogenic activities, as antioxidative, anti-inflammatory and anti-thrombotic actions. HDL displays anti-apoptotic activity and is able to protect endothelial cells against oxLDL-induced apoptosis. HDL subfractions (sHDL) are highly heterogeneous in their physical and chemical composition and biological functions. Antioxidative activity of HDL subfractions increases with increment in density, HDL2b100% in annexin V biding) and 3b subfractions (43% and 67%, respectively) were more potent against oxLDL-induced toxicity and apoptosis as compared to HDL2a (29% and 28%; p<0.01 vs. HDL3c, respectively) and 2b subfractions (25% and 62%; p<0.001 vs. HDL3c, respectively). All HDL subfractions attenuated of reactive oxygen species (ROS) generation in HMEC induced by oxLDL. Again, HDL3c (54% inhibition) were more potent as compared to HDL2b (21%; p<0.05 vs. HDL3c). The anti-apoptotic and intracellular antioxidative activities of HDL3 were positively correlated with apoA-I and sphingosine 1-phosphate (S1P) content of sHDL and, possibly, depend on their cellular interaction through apoA-I and its SR-BI receptor. The sHDL3c isolated from MetS patients (n=5) possess reduced content of apoA-I and less potent anti-apoptotic activity (-60%, p<0.01) than controls (n=5). Conclusion: Normolipidemic small dense HDL3 provide potent protection of human endothelial cells from oxLDL-induced apoptosis; this anti-apoptotic activity is reduced in the MetS.