Ex Vivo Characterization of Peritoneal Macrophages from Novel ABCA1-LSL and ABCG1-LSL Mice for Macrophage-Specific ABC-Transporter Overexpression

We aimed to characterize peritoneal macrophages from two novel mouse models that enable macrophage-specific overexpression of ABCA1 and ABCG1 via Cre recombinase. Since ABCA1/ABCG1 expression in macrophages is acknowledged to be anti-atherogenic, overexpression of these two transporters may result in a potent atheroprotective effect. However, there are no current animal models that permit overexpression of ABCA1/ABCG1 to precisely occur in macrophages. The purpose of this work was to use ex vivo strategies to characterize the peritoneal macrophages from two novel mouse models: ABCA1-LSL mice and ABCG1-LSL mice. Overexpression of ABCA1/ABCG1 in peritoneal macrophages is controlled by Cre recombinase, due to the LoxP-Stop-LoxP (LSL) system regulating ABC-transporter overexpression. In this study, we first characterized cells isolated from the peritoneal cavities of mice via immunofluorescent staining with macrophage markers CD11b and F4/80 to confirm that we were successful with peritoneal macrophage isolation. We next isolated peritoneal macrophages from ABCA1-LSL mice and ABCG1-LSL mice, and then we incubated these cells with gesicle particles containing Cre recombinase to measure ABC-transporter expression via immunoblotting and measure apoAI/HDL-mediated efflux using cholesterol efflux assays. In our experiments, we observed increases in ABCA1 protein expression and apoAI-mediated cholesterol efflux within ABCA1-LSL peritoneal macrophages, and increased ABCG1 protein expression and HDL-mediated cholesterol efflux in ABCG1-LSL peritoneal macrophages, when compared to corresponding control peritoneal macrophage groups. In conclusion, this report shows that ABCA1-LSL mice and ABCG1-LSL mice may possibly be utilized to cross with macrophage-specific Cre mice to study ABC-transporter overexpression precisely in macrophages, thereby providing valuable tools to dissect the impact of macrophage-specific ABC-transporter overexpression on atherogenesis.