L-4F对oxLDL刺激下脂肪细胞表达单核细胞趋化蛋白-1的影响

Effect of L-4F on monocyte chemoattractant protein-1 expression in 3T3-L1 adipocytes induced by oxidized low-density lipoprotein

目的观察载脂蛋白A-I模拟肽L-4F对氧化型低密度脂蛋白(oxLDL)刺激下3T3-L1脂肪细胞分泌表达单核细胞趋化蛋白-1(MCP-1)的影响,并探讨其可能的作用机制。方法 3T3-L1脂肪细胞促分化成熟后,oxLDL(50μg/ml)刺激脂肪细胞,给予L-4F(1-50μg/ml),H-89(10μmol/L)及H-89+L-4F(50μg/ml)干预,收集细胞,测定脂肪细胞MCP-1上清液中的浓度和mRNA表达水平,以及脂肪细胞核因子C/EBPα、β的蛋白质水平;改良Boyden小室法检测不同干预组上清液对人外周血单核细胞趋化活性的影响。结果 OxLDL(50μg/ml)刺激使分化成熟的3T3-L1脂肪细胞表达及分泌MCP-1明显增加,并使得诱导的单核细胞移动距离明显增加。L-4F以浓度依赖的方式减少脂肪细胞MCP-1的表达和分泌,降低单核细胞趋化活性;50μg/ml L-4F使MCP-1 mRNA的表达降低(91±6)%(P<0.01)。PKA抑制剂H-89(10μmol/L)干预oxLDL刺激的脂肪细胞后MCP-1 m RNA的表达也显著减少(P<0.01),但是,在50μg/ml L-4F作用的基础上,H-89(10μmol/L)的孵育并未使得MCP-1 mRNA的表达进一步降低(P>0.05)。50μg/ml oxLDL刺激对脂肪细胞C/EBPα的含量无明显影响,但增加C/EBPβ蛋白量,且该作用呈时间依赖性;L-4F和H-89干预均降低C/EBPβ的蛋白质含量。结论 OxLDL时间依赖性地诱导脂肪细胞C/EBPβ的蛋白合成,并增强脂肪细胞MCP-1的表达分泌,L-4F以浓度依赖的方式对抗oxLDL的致炎作用,cAMP/PKA-C/EBPβ信号通道可能是L-4F的作用途径之一。

Objective To evaluate the effect of apolipoprotein A-I mimetic peptide L-4F on the secretion and expression of monocyte chemoattractant protein-1（MCP-1） in 3T3-L1 adipocytes induced by oxidized low-density lipoprotein（oxLDL）.Methods Fully differentiated 3T3-L1 adipocytes were preincubated in the medium containing different concentrations of L-4F（0,1,10,and 50 μg/ml）,H-89（10 μmol/L） and H-89（10 μmol/L） combined with L-4F（50 μg/ml）,respectively.Then the adipocytes were treated by oxLDL（50 μg/ml）.The concentration of MCP-1,the mRNA expression of MCP-1,and the protein levels of CCAAT/enhancer binding protein（C/EBP）α and C/EBPβ in cell supernatant were evaluated.The effect of the supernatant on the chemotactic activity of human peripheral blood monocytes was detected by micropore filter method using a modified Boyden chamber.Results OxLDL（50 μg/ml） treatment induced a significant increase of MCP-1 expression and secretion in 3T3-L1 adipocytes,and the mean of migration distance of human peripheral blood monocytes induced by the cell supernatant was significantly longer than that of the random migration group.MCP-1 secretion and expression as well as the chemotactic activity of human peripheral blood monocyte were decreased by the L-4F pre-incubation in a dose-dependent manner.MCP-1 expression in the adipocytes pretreated with L-4F（50 μg/ml） decreased by（91±6）%（P0.01）.PKA inhibitor H-89（10 μmol/L） significantly reduced the oxLDL-induced MCP-1 expression（P0.01）,but no further decrease was observed when H-89（10 μmol/L） was used in combination with L-4F（50 μg/ml）（P0.05）.OxLDL（50 μg/ml） treatment showed no significant effect on C/EBPα content,but increased C/EBPβ content in a time-dependent manner.H-89 and L-4F both attenuated C/EBPβ protein content in oxLDL-treated 3T3-L1 adipocytes.Conclusion OxLDL induces C/EBPβ protein synthesis and enhances MCP-1 secretion and expression in 3T3-L1 adipocytes in a time-dependent manner.L-4F dose-dependently counterbalances the proinflammatory effect of oxLDL,which may involve cAMP/PKA-C/EBPβ signaling pathway.