Accumulation of lipid-laden macrophages within the arterial neointima is a critical step in atherosclerotic plaque formation. Here, we show that reduced levels of the cellular plasticity factor ZEB1 ...in macrophages increase atherosclerotic plaque formation and the chance of cardiovascular events. Compared to control counterparts (Zeb1
/Apoe
), male mice with Zeb1 ablation in their myeloid cells (Zeb1
/Apoe
) have larger atherosclerotic plaques and higher lipid accumulation in their macrophages due to delayed lipid traffic and deficient cholesterol efflux. Zeb1
/Apoe
mice display more pronounced systemic metabolic alterations than Zeb1
/Apoe
mice, with higher serum levels of low-density lipoproteins and inflammatory cytokines and larger ectopic fat deposits. Higher lipid accumulation in Zeb1
macrophages is reverted by the exogenous expression of Zeb1 through macrophage-targeted nanoparticles. In vivo administration of these nanoparticles reduces atherosclerotic plaque formation in Zeb1
/Apoe
mice. Finally, low ZEB1 expression in human endarterectomies is associated with plaque rupture and cardiovascular events. These results set ZEB1 in macrophages as a potential target in the treatment of atherosclerosis.
Selective estrogen receptor modulators (SERMs) are nonsteroidal drugs that display an estrogen‐agonist or estrogen‐antagonist effect depending on the tissue targeted. SERMs have attracted great ...clinical interest for the treatment of several pathologies, most notably breast cancer and osteoporosis. There is strong evidence that SERMs secondarily affect cholesterol metabolism, although the mechanism has not been fully elucidated. In this study, we analysed the effect of the SERMs tamoxifen, raloxifene, and toremifene on the expression of lipid metabolism genes by microarrays and quantitative PCR in different cell types, and ascertained the main mechanisms involved. The three SERMs increased the expression of sterol regulatory element‐binding protein (SREBP) target genes, especially those targeted by SREBP-2. In consonance, SERMs increased SREBP‐2 processing. These effects were associated to the interference with intracellular LDL-derived cholesterol trafficking. When the cells were exposed to LDL, but not to cholesterol/methyl-cyclodextrin complexes, the SERM-induced increases in gene expression were synergistic with those induced by lovastatin. Furthermore, the SERMs reduced the stimulation of the transcriptional activity of the liver X receptor (LXR) by exogenous cholesterol. However, their impact on the expression of the LXR canonical target ABCA1 in the presence of LDL was cell-type dependent. These actions of SERMs were independent of estrogen receptors. We conclude that, by inhibiting the intracellular trafficking of LDL-derived cholesterol, SERMs promote the activation of SREBP-2 and prevent the activation of LXR, two master regulators of cellular cholesterol metabolism. This study highlights the impact of SERMs on lipid homeostasis regulation beyond their actions as estrogen receptor modulators.
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•SERMs disrupt intracellular trafficking of LDL-derived colesterol.•SERMs stimulate SREBP processing and the expression of SREBP target genes.•SERMs have a synergistic effect with that of lovastatin in an LDL-dependent manner.•SERMs impair the transcriptional response of LXR to exogenous colesterol.•The actions of SERMs on SREBP and LXR pathways are independent of estrogen receptors.
Atherosclerosis is a chronic inflammatory disease of the arteries that can lead to thrombosis, infarction, and stroke and is the leading cause of mortality worldwide. Immunization of pro-atherogenic ...mice with malondialdehyde-modified low-density lipoprotein (MDA-LDL) neo-antigen is athero-protective. However, the immune response to MDA-LDL and the mechanisms responsible for this athero-protection are not completely understood. Here, we find that immunization of mice with MDA-LDL elicits memory B cells, plasma cells, and switched anti-MDA-LDL antibodies as well as clonal expansion and affinity maturation, indicating that MDA-LDL triggers a bona fide germinal center antibody response. Further, Prdm1fl/flAicda-Cre+/kiLdlr−/− pro-atherogenic chimeras, which lack germinal center-derived plasma cells, show accelerated atherosclerosis. Finally, we show that MDA-LDL immunization is not athero-protective in mice lacking germinal-center-derived plasma cells. Our findings give further support to the development of MDA-LDL-based vaccines for the prevention or treatment of atherosclerosis.
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•MDA-LDL immunization triggers a GC response•Pro-atherogenic mice deficient for GC-derived PCs show accelerated atherosclerosis•MDA-LDL-driven athero-protection is impaired in mice lacking GC-derived PCs
Martos-Folgado et al. show that immunization with MDA-LDL elicits a GC-derived antibody immune response. Furthermore, the authors demonstrate that GC-derived antibodies drive MDA-LDL-induced athero-protection. These results uncover the mechanism underlying MDA-LDL-driven athero-protection and support the development of MDA-LDL-based vaccines for the prevention or treatment of atherosclerosis.
Atherosclerosis is an inflammatory disease characterized by the accumulation of macrophages in the vessel wall. Macrophages depend on their polarization to exert either pro‐inflammatory or ...anti‐inflammatory effects. Macrophages of the anti‐inflammatory phenotype express high levels of CD163, a scavenger receptor for the hemoglobin‐haptoglobin complex. CD163 can also bind to the pro‐inflammatory cytokine TWEAK. Using ApoE‐deficient or ApoE/CD163 double‐deficient mice we aim to investigate the involvement of CD163 in atherosclerosis development and its capacity to neutralize the TWEAK actions. ApoE/CD163 double‐deficient mice displayed a more unstable plaque phenotype characterized by an increased lipid and macrophage content, plaque size, and pro‐inflammatory cytokine expression. In vitro experiments demonstrated that the absence of CD163 in M2‐type macrophages‐induced foam cell formation through upregulation of CD36 expression. Moreover, exogenous TWEAK administration increased atherosclerotic lesion size, lipids, and macrophages content in ApoE−/−/CD163−/− compared with ApoE−/−/CD163+/+ mice. Treatment with recombinant CD163 was able to neutralize the proatherogenic effects of TWEAK in ApoE/CD163 double‐deficient mice. Recombinant CD163 abolished the pro‐inflammatory actions of TWEAK on vascular smooth muscle cells, decreasing NF‐kB activation, cytokines and metalloproteinases expression, and macrophages migration. In conclusion, CD163‐expressing macrophages serve as a protective mechanism to prevent the deleterious effects of TWEAK on atherosclerotic plaque development and progression.
Scope
Extra virgin olive oil has numerous cardiopreventive effects, largely due to its high content of (poly)phenols such as hydroxytyrosol (HT). However, some animal studies suggest that its ...excessive consumption may alter systemic lipoprotein metabolism. Because human lipoprotein metabolism differs from that of rodents, this study examines the effects of HT in a humanized mouse model that approximates human lipoprotein metabolism.
Methods and results
Mice are treated as follows: control diet or diet enriched with HT. Serum lipids and lipoproteins are determined after 4 and 8 weeks. We also analyzed the regulation of various genes and miRNA by HT, using microarrays and bioinformatic analysis.
An increase in body weight is found after supplementation with HT, although food intake was similar in both groups. In addition, HT induced the accumulation of triacylglycerols but not cholesterol in different tissues. Systemic dyslipidemia after HT supplementation and impaired glucose metabolism are observed. Finally, HT modulates the expression of genes related to lipid metabolism, such as Pltp or Lpl.
Conclusion
HT supplementation induces systemic dyslipidemia and impaired glucose metabolism in humanized mice. Although the numerous health‐promoting effects of HT far outweigh these potential adverse effects, further carefully conducted studies are needed.
In animal models, hydroxytyrosol (HT) consumption may alter systemic lipoprotein metabolism. ApoB100 humanized mouse model better reflects the human lipoprotein metabolism. HT supplementation increases body weight, induces systemic dyslipidemia, causes impaired glucose metabolism, and induces the accumulation of TG in different tissues. HT modulates the expression of genes related to lipid metabolism and several miRNAs, including miR‐21.
Scope
High plasma homocysteine concentrations have been associated with increased risk of cardiovascular disease both in humans and experimental animal models, whereas plasma HDL‐cholesterol ...concentration is inversely correlated with such disorders. This work aimed to study the impact of methionine‐induced hyperhomocysteinemia (HHcy) on two major antiatherogenic functions of HDL, namely their capacity to prevent LDL oxidation and induce in vivo macrophage‐specific reverse cholesterol transport.
Methods and results
Methionine‐induced HHcy in mice resulted in an approximately 20% decreased concentration of HDL‐cholesterol and HDL main protein component, apolipoprotein A‐I. The HDL potential to resist oxidation as well as to prevent LDL oxidative modification was impaired in hyperhomocysteinemic mice. Activities of paraoxonase‐1 and platelet activation factor acetylhydrolase, two of the main HDL‐associated enzymes with antioxidant activity, were reduced. The ability of HDL to efflux cholesterol from macrophages was decreased in hyperhomocysteinemic mice; however, the in vivo macrophage‐specific reverse cholesterol transport measured as the output of labeled cholesterol into feces did not significantly differ between groups.
Conclusion
Our data indicate that the HDL from methionine‐induced hyperhomocysteinemic mice was more prone to oxidation and displayed lower capacity to protect LDL against oxidative modification than that of control mice, highlighting a mechanism by which a diet‐induced HHcy may facilitate progression of atherosclerosis.
Dietary phytosterols, which comprise plant sterols and stanols, reduce plasma Low-Density Lipoprotein-Cholesterol (LDL-C) levels when given 2 g/day. Since this dose has not been reported to cause ...health-related side effects in long-term human studies, food products containing these plant compounds are used as potential therapeutic dietary options to reduce LDL-C and cardiovascular disease risk. Several mechanisms have been proposed to explain the cholesterol-lowering action of phytosterols. They may compete with dietary and biliary cholesterol for micellar solubilization in the intestinal lumen, impairing intestinal cholesterol absorption. Recent evidence indicates that phytosterols may also regulate other pathways. Impaired intestinal cholesterol absorption is usually associated with reduced cholesterol transport to the liver, which may reduce the incorporation of cholesterol into Very-Low- Density Lipoprotein (VLDL) particles, thereby lowering the rate of VLDL assembly and secretion. Impaired liver VLDL production may reduce the rate of LDL production. On the other hand, significant evidence supports a role for plant sterols in the Transintestinal Cholesterol Excretion (TICE) pathway, although the exact mechanisms by which they promote the flow of cholesterol from the blood to enterocytes and the intestinal lumen remains unknown. Dietary phytosterols may also alter the conversion of bile acids into secondary bile acids, and may lower the bile acid hydrophobic/hydrophilic ratio, thereby reducing intestinal cholesterol absorption. This article reviews the progress to date in research on the molecular mechanisms underlying the cholesterol-lowering effects of phytosterols.
Selective estrogen receptor modulators (SERMs) are widely prescribed drugs that alter cellular and whole-body cholesterol homeostasis. Here we evaluate the effect of SERMs on the macrophage-specific ...reverse cholesterol transport (M-RCT) pathway, which is mediated by HDL. Treatment of human and mouse macrophages with tamoxifen, raloxifene or toremifene induced the accumulation of cytoplasmic vesicles of acetyl-LDL-derived free cholesterol. The SERMs impaired cholesterol efflux to apolipoprotein A-I and HDL, and lowered ABCA1 and ABCG1 expression. These effects were not altered by the antiestrogen ICI 182,780 nor were they reproduced by 17β-estradiol. The treatment of mice with tamoxifen or raloxifene accelerated HDL-cholesteryl ester catabolism, thereby reducing HDL-cholesterol concentrations in serum. When (3)Hcholesterol-loaded macrophages were injected into mice intraperitoneally, tamoxifen, but not raloxifene, decreased the (3)Hcholesterol levels in serum, liver and feces. Both SERMs downregulated liver ABCG5 and ABCG8 protein expression, but tamoxifen reduced the capacity of HDL and plasma to promote macrophage cholesterol efflux to a greater extent than raloxifene. We conclude that SERMs interfere with intracellular cholesterol trafficking and efflux from macrophages. Tamoxifen, but not raloxifene, impair M-RCT in vivo. This effect is primarily attributable to the tamoxifen-mediated reduction of the capacity of HDL to promote cholesterol mobilization from macrophages.
Epidemiologic studies have demonstrated that increased high-density lipoprotein cholesterol (HDL-C) is a protective factor against cardiovascular disease. However, the beneficial therapeutic effects ...of raising HDL-C are proving difficult to confirm in humans. Macrophage-specific reverse cholesterol transport (RCT) is thought to be one of the most important HDL-mediated cardioprotective mechanisms. A new approach was developed to measure in vivo RCT from labeled cholesterol macrophages to liver and feces in mice. Since its original publication, this method has been extensively used to assess the effects of genetic manipulation of pivotal genes involved in HDL metabolism on this major HDL antiatherogenic function in mice. These studies indicate that in vivo macrophage-specific RTC is a strong predictor of atherosclerosis susceptibility compared with steady-state plasma HDL-C levels or other global RCT measurements. This review aims to identify the best molecular targets for improving this HDL antiatherogenic function. Strong evidence supports a positive effect of interventions on macrophage adenosine triphosphate-binding cassette transporter (ABC) A1 and neutral cholesteryl ester hydrolase, apolipoprotein (apo) A-I, apoE, liver scavenger receptor class B type I and ABCG5/G8 on in vivo macrophage-specific RCT and atherosclerosis susceptibility. However, other genetic modifications have yielded conflicting results. Several preclinical studies tested the effects on macrophage-specific RCT in vivo of promising new HDL-based therapeutic agents, which include cholesteryl ester transfer protein inhibitors, apoA-I-directed therapies, liver X receptor and peroxisome proliferator-activated receptor agonists, intestinal cholesterol absorption inhibitors, fish oil and phenolic acid intake, inflammatory modulation and non-nucleoside reverse transcriptase inhibitors. This review also discusses recent findings on the potential effects of these therapeutic approaches on macrophage RCT in mice and cardiovascular risk in humans.
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