Vitexin inhibits APEX1 to counteract the flow-induced endothelial inflammation.

Vascular endothelial cells are exposed to shear stresses with disturbed vs. laminar flow patterns, which lead to proinflammatory vs. antiinflammatory phenotypes, respectively. Effective treatment against endothelial inflammation and the consequent atherogenesis requires the identification of new therapeutic molecules and the development of drugs targeting these molecules. Using Connectivity Map, we have identified vitexin, a natural flavonoid, as a compound that evokes the gene-expression changes caused by pulsatile shear, which mimics laminar flow with a clear direction, vs. oscillatory shear (OS), which mimics disturbed flow without a clear direction. Treatment with vitexin suppressed the endothelial inflammation induced by OS or tumor necrosis factor-α. Administration of vitexin to mice subjected to carotid partial ligation blocked the disturbed flow-induced endothelial inflammation and neointimal formation. In hyperlipidemic mice, treatment with vitexin ameliorated atherosclerosis. Using SuperPred, we predicted that apurinic/apyrimidinic endonuclease1 (APEX1) may directly interact with vitexin, and we experimentally verified their physical interactions. OS induced APEX1 nuclear translocation, which was inhibited by vitexin. OS promoted the binding of acetyltransferase p300 to APEX1, leading to its acetylation and nuclear translocation. Functionally, knocking down APEX1 with siRNA reversed the OS-induced proinflammatory phenotype, suggesting that APEX1 promotes inflammation by orchestrating the NF-κB pathway. Animal experiments with the partial ligation model indicated that overexpression of APEX1 negated the action of vitexin against endothelial inflammation, and that endothelial-specific deletion of APEX1 ameliorated atherogenesis. We thus propose targeting APEX1 with vitexin as a potential therapeutic strategy to alleviate atherosclerosis.

DNA methyltransferase 1 and Krüppel-like factor 4 axis regulates macrophage inflammation and atherosclerosis.

Macrophage-mediated inflammatory responses occur throughout all stages of atherosclerosis. DNA methylation is one of the critical epigenetic mechanisms and is associated with the development of atherosclerosis. The underlying mechanism of epigenetic regulation of macrophage inflammation (M1 activation) remains unclear. Here we aim to study the role of DNA methyltransferase 1 (DNMT1) in modulating macrophage inflammation and atherosclerosis. DNMT1 expression is up-regulated in THP-1-derived macrophages upon treatment with lipopolysaccharide (LPS) and interferon-gamma (IFN-γ). Overexpression of DNMT1 promotes the LPS- and IFN-γ-induced M1 activation whereas inhibition of DNMT1 attenuates it. Consistently, DNMT1 expression is elevated in macrophages in atherosclerotic plaques from human and mouse specimens; compared with the Dnmt1wild-type, myeloid Dnmt1 deficiency in mice in an Apolipoprotein E (ApoE) knockout background or receiving AAV-PSCK9 injection and carotid partial ligation results in ameliorated atheroma formation and suppressed plaque inflammation. The promoter regions of atheroprotective Krüppel-like factor 4 (KLF4) are hypermethylated in M1- activated macrophages. DNMT1 down-regulates the expression of KLF4, probably through catalyzing DNA methylation of the promoter regions of KLF4. Gain- and loss-of function study of KLF4 indicates that the DNMT1-mediated macrophage M1 activation is dependent on KLF4. Our data demonstrate a proatherogenic role for DNMT1 as a defining factor in macrophage inflammation both in vitro and in vivo. DNMT1 promotes macrophage M1 activation by suppressing KLF4 expression. Thus macrophage-specific DNMT1 inhibition may provide an attractive therapeutic potential to prevent or reduce atherosclerosis.

An Innovative model of magnetically intercalated expanded graphite for calculating radar attenuation performance at 2-18 GHz.

With the emergence of various filtering technologies, the radar jamming efficiency of the technology based on radar cross section is ever lower, therefore cannot meet military requirements. In this context, the jamming technology based on attenuation mechanism has been developed and plays an increasingly important role in disturbing radar detecting. Magnetically expanded graphite (MEG) has excellent attenuation efficiency because it can cause dielectric loss as well as magnetic loss. Moreover, MEG features good impedance matching, which makes more incidence of electromagnetic waves into the material; and its multi-layer structure is conducive for electromagnetic wave reflection and absorption. In this work, the structure model of MEG was established by analyzing the layered structure of expanded graphite (EG) and the dispersion of intercalated magnetic particles. The electromagnetic parameters of thus-modeled MEG were calculated based on the equivalent medium theory; and effects of EG size, magnetic particle type and volume fraction on the attenuation performance were studied by the variational method. It is indicated that MEG with 500-µm diameter has the best attenuation effect and the highest increment of absorption cross section appears at 50% volume fraction of the magnetic particles at 2 GHz. The imaginary part of complex permeability of the magnetic material has the most significant influence on the attenuation effect of MEG. This study provides guidance for the design and application of MEG materials in disturbing radar detecting field.

The Mammalian Target of Rapamycin and DNA methyltransferase 1 axis mediates vascular endothelial dysfunction in response to disturbed flow.

The earliest atherosclerotic lesions preferentially develop in arterial regions experienced disturbed blood flow, which induces endothelial expression of pro-atherogenic genes and the subsequent endothelial dysfunction. Our previous study has demonstrated an up-regulation of DNA methyltransferase 1 (DNMT1) and a global hypermethylation in vascular endothelium subjected to disturbed flow. Here, we determined that DNMT1-specific inhibition in arterial wall ameliorates the disturbed flow-induced atherosclerosis through, at least in part, targeting cell cycle regulator cyclin A and connective tissue growth factor (CTGF). We identified the signaling pathways mediating the flow-induction of DNMT1. Inhibition of the mammalian target of rapamycin (mTOR) suppressed the DNMT1 up-regulation both in vitro and in vivo. Together, our results demonstrate that disturbed flow influences endothelial function and induces atherosclerosis in an mTOR/DNMT1-dependent manner. The conclusions obtained from this study might facilitate further evaluation of the epigenetic regulation of endothelial function during the pathological development of atherosclerosis and offer novel prevention and therapeutic targets of this disease.