Background： Adipocytes behave like a rich source of pro-inflammatory cytokines including monocyte chemoattractant protein- 1 （MCP- 1）. Oxidized low-density lipoprotein （oxLDL） participates in the local chronic in...Background： Adipocytes behave like a rich source of pro-inflammatory cytokines including monocyte chemoattractant protein- 1 （MCP- 1）. Oxidized low-density lipoprotein （oxLDL） participates in the local chronic inflammatory response, and high-density lipoprotein could counterbalance the proinftammatory function of αLDL, but the underlying mechanism is not completely understood. This study aimed to evaluate the effect of apolipoprotein A-I mimetic peptide L-4F on the secretion and expression of MCP-1 in fully differentiated 3T3-L 1 adipocytes induced by oxLDL and to elucidate the possible mechanisms. Methods： Fully differentiated 3T3-L 1 adipocytes were incubated in the medium containing various concentration of L-4F （0-50 gg/ml） with oxLDL （50 Lag/ml） stimulated, with/without protein kinase A （PKA） inhibitor H-89 （10 gmol/L） preincubated. The concentrations of MCP- 1 in the supematant, the mRNA expression of MCP- 1, the levels of CCAAT/enhancer binding protein α （C/EBPα）, and CCAAT/ enhancer binding protein 13 （C/EBPβ） were evaluated. The monocyte chemotaxis assay was performed by micropore filter method using a modified Boyden chamber. Results： OxLDL stimulation induced a significant increase ofMCP-1 expression and secretion in 3T3-L 1 adipocytes, which were inhibited by L-4F preincubation in a dose-dependent manner. PKA inhibitor H-89 markedly reduced the oxLDL-induced MCP-1 expression, but no further decrease was observed when H-89 was used in combination with L-4F （50 μg/ml） （P 〉 0.05）. OxLDL stimulation showed no significant effect on C/EBPa protein level but increased C/EBPβ protein level in a time-dependent manner. H-89 and L-4F both attenuated C/EBPI3 protein level in oxLDL-induced 3T3-L1 adipocytes. Conclusions： OxLDL induces C/EBPI3 protein synthesis in a time-dependent manner and enhances MCP-1 secretion and expression in 3T3-L 1 adipocytes. L-4F dose-dependently counterbalances the pro-inflammatory effect of oxLDL, and cyclic AMP/PKA-C/EBP-β sign展开更多
基金This work was supported by grants from the National Natural Science Foundation of China （No. 30470705 and No. 81270154）.
文摘Background： Adipocytes behave like a rich source of pro-inflammatory cytokines including monocyte chemoattractant protein- 1 （MCP- 1）. Oxidized low-density lipoprotein （oxLDL） participates in the local chronic inflammatory response, and high-density lipoprotein could counterbalance the proinftammatory function of αLDL, but the underlying mechanism is not completely understood. This study aimed to evaluate the effect of apolipoprotein A-I mimetic peptide L-4F on the secretion and expression of MCP-1 in fully differentiated 3T3-L 1 adipocytes induced by oxLDL and to elucidate the possible mechanisms. Methods： Fully differentiated 3T3-L 1 adipocytes were incubated in the medium containing various concentration of L-4F （0-50 gg/ml） with oxLDL （50 Lag/ml） stimulated, with/without protein kinase A （PKA） inhibitor H-89 （10 gmol/L） preincubated. The concentrations of MCP- 1 in the supematant, the mRNA expression of MCP- 1, the levels of CCAAT/enhancer binding protein α （C/EBPα）, and CCAAT/ enhancer binding protein 13 （C/EBPβ） were evaluated. The monocyte chemotaxis assay was performed by micropore filter method using a modified Boyden chamber. Results： OxLDL stimulation induced a significant increase ofMCP-1 expression and secretion in 3T3-L 1 adipocytes, which were inhibited by L-4F preincubation in a dose-dependent manner. PKA inhibitor H-89 markedly reduced the oxLDL-induced MCP-1 expression, but no further decrease was observed when H-89 was used in combination with L-4F （50 μg/ml） （P 〉 0.05）. OxLDL stimulation showed no significant effect on C/EBPa protein level but increased C/EBPβ protein level in a time-dependent manner. H-89 and L-4F both attenuated C/EBPI3 protein level in oxLDL-induced 3T3-L1 adipocytes. Conclusions： OxLDL induces C/EBPI3 protein synthesis in a time-dependent manner and enhances MCP-1 secretion and expression in 3T3-L 1 adipocytes. L-4F dose-dependently counterbalances the pro-inflammatory effect of oxLDL, and cyclic AMP/PKA-C/EBP-β sign
