Gene expression profile reveals that APOA-I levels modulate inflammation and lysosomal activity in murine advances atherosclerosis

Background and Aims: With the aim of identifying new genes/pathways involved in dyslipidemia-driven atherosclerosis, modulated by different apoA-I/HDL levels, a transcriptome analysis by high-throughput RNA-seq was conducted on the aorta of three mouse models. Methods: Eight-week-old wild-type mice (expressing physiological levels of apoA-I), EKO mice (with halved apoA-I levels), and EKO mice over- expressing human apoA-I (with apoA-I levels comparable to those of wild- type), were fed either chow or Western diet for 6 or 22 weeks. Atherosclerosis was quantified in the whole aorta. High-throughput sequencing technologies were used to analyse the aorta transcriptome. Results: The reduced atherosclerotic burden in the aorta of EKO mice expressing high levels of apoA-I was accompanied by a reduced activation of immune system markers. The most enriched KEGG pathways in EKO mice, lysosome and phagosome, were indicative of an increased heterophagy-mediated lipid uptake in aortas with advanced plaques. The activation of lysosomal pathways restricted to EKO mice was backed by the finding that binding sites for transcription factors involved in lysosome function and biogenesis were over-represented in EKO mice fed Western diet for 22 weeks with respect to EKO/hA-I. A possible direct effect of HDL on lysosomal activity was assessed on peritoneal macrophages from EKO mice: acetylated LDL treatment boosted lysosomal activation in EKO-derived peritoneal macrophages, but HDL administration, mimicking the HDL makeup of EKO/hA-I, reduced it in a dose-dependent manner. Conclusions: Our results indicate that apoA-I modulates atherosclerosis development in the aorta of EKO mice by reducing immune system activation as well as the involvement of the phagosome-lysosome system.