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New Findings What is the central question of this study?What is the mechanism of miR‐211 in an Alzheimer's disease cell model? What is the main finding and its importance?miR‐211 was upregulated in an Alzheimer's disease cell model. It targeted neurogenin 2, reduced the activation of the phosphoinositide 3‐kinase–Akt signalling pathway, inhibited the proliferation of the Alzheimer's disease cell model and promoted apoptosis. Abstract MicroRNAs (miRs) are aberrantly expressed in Alzheimer's disease (AD) patients. This study was intended to investigate the effect of miR‐211 on an AD cell model and the involvement of neurogenin 2 (Ngn2). The appropriate dose and time for the effect of Aβ1–42 on PC12 cells were determined to establish an AD cell model. An effect of miR‐211 expression on cell viability, proliferation and apoptosis was detected after cell transfection. Online prediction and a dual luciferase reporter gene assay were utilized to confirm the binding sequence of miR‐211 and Ngn2. qRT‐PCR and western blot analysis were applied to measure Ngn2 expression. A gain and loss of function assay of miR‐211 and Ngn2 was performed, and activation of the phosphoinositide 3‐kinase (PI3K)–Akt signaling pathway was detected. The AD cell model was induced by Aβ1–42 treatment. miR‐211 expression was significantly enhanced after miR‐211 transfection, leading to suppressed proliferation and promotion of apoptosis in Aβ1–42‐treated PC12 cells. In addition, miR‐211 could downregulate Ngn2 mRNA and protein expression, while overexpression of Ngn2 could reverse the effects of miR‐211 on Aβ1–42‐treated PC12 cells and significantly enhance the phosphorylated Akt and PI3K protein levels. miR‐211 could inhibit growth of PC12 cells by suppressing Ngn2 expression and inactivating the PI3K–Akt signalling pathway.

Phospholipid transfer protein is expressed in various cell types and secreted into plasma, where it transfers phospholipids between lipoproteins and modulates the composition of high-density lipoprotein particles. Phospholipid transfer protein deficiency in vivo can lower high-density lipoprotein cholesterol level significantly and impact the biological quality of high-density lipoprotein. Considering high-density lipoprotein was a critical determinant for reverse cholesterol transport, we investigated the role of systemic phospholipid transfer protein deficiency in macrophage reverse cholesterol transport in vivo After the littermate phospholipid transfer protein KO and WT mice were fed high-fat diet for one month, they were injected intraperitoneally with (3)H-cholesterol-labeled and acLDL-loaded macrophages. Then the appearance of (3)H-tracer in plasma, liver, bile, intestinal wall, and feces over 48 h was determined. Plasma lipid analysis indicated phospholipid transfer protein deficiency lowered total cholesterol, high-density lipoprotein-C and apolipoprotein A1 levels significantly but increased triglyceride level in mice. The isotope tracing experiment showed (3)H-cholesterol of plasma was decreased by 68% for male and 62% for female, and (3)H-tracer of bile was decreased by 37% for male and 21% for female in phospholipid transfer protein KO mice compared with WT mice. However, there was no difference in liver, and (3)H-tracer of intestinal wall was increased by 43% for male and 27% for female. Finally, (3)H-tracer of fecal excretion in phospholipid transfer protein KO mice was reduced significantly by 36% for male and 43% for female during 0-24 h period, but there was no significant difference during 24-48 h period. Meanwhile, Western Blot analysis showed the expressions of reverse cholesterol transport -related protein liver X receptor α (LXRα), ATP binding cassette transporter A1, and cholesterol 7α-hydroxylase A1 were upregulated in liver of phospholipid transfer protein KO mice compared with WT mice. These data reveal that systemic phospholipid transfer protein deficiency in mice impairs macrophage-specific reverse cholesterol transport in vivo.