Impact of cholesterol on proinflammatory monocyte production by the bone marrow.

AIM: Preclinical work indicates that low-density lipoprotein cholesterol (LDL-C) not only drives atherosclerosis by directing the innate immune response at plaque level but also augments proinflammatory monocyte production in the bone marrow (BM) compartment. In this study, we aim to unravel the impact of LDL-C on monocyte production in the BM compartment in human subjects. METHODS AND RESULTS: A multivariable linear regression analysis in 12 304 individuals of the EPIC-Norfolk prospective population study showed that LDL-C is associated with monocyte percentage (β = 0.131 [95% CI: 0.036-0.225]; P = 0.007), at the expense of granulocytes (β = -0.876 [95% CI: -1.046 to -0.705]; P < 0.001). Next, we investigated whether altered haematopoiesis could explain this monocytic skewing by characterizing CD34+ BM haematopoietic stem and progenitor cells (HSPCs) of patients with familial hypercholesterolaemia (FH) and healthy normocholesterolaemic controls. The HSPC transcriptomic profile of untreated FH patients showed increased gene expression in pathways involved in HSPC migration and, in agreement with our epidemiological findings, myelomonocytic skewing. Twelve weeks of cholesterol-lowering treatment reverted the myelomonocytic skewing, but transcriptomic enrichment of monocyte-associated inflammatory and migratory pathways persisted in HSPCs post-treatment. Lastly, we link hypercholesterolaemia to perturbed lipid homeostasis in HSPCs, characterized by lipid droplet formation and transcriptomic changes compatible with increased intracellular cholesterol availability. CONCLUSIONS: Collectively, these data highlight that LDL-C impacts haematopoiesis, promoting both the number and the proinflammatory activation of circulating monocytes. Furthermore, this study reveals a potential contributory role of HSPC transcriptomic reprogramming to residual inflammatory risk in FH patients despite cholesterol-lowering therapy

Targeting macrophage Histone deacetylase 3 stabilizes atherosclerotic lesions

Macrophages are key immune cells found in atherosclerotic plaques and critically shape atherosclerotic disease development. Targeting the functional repertoire of macrophages may hold novel approaches for future atherosclerosis management. Here, we describe a previously unrecognized role of the epigenomic enzyme Histone deacetylase 3 (Hdac3) in regulating the atherosclerotic phenotype of macrophages. Using conditional knockout mice, we found that myeloid Hdac3 deficiency promotes collagen deposition in atherosclerotic lesions and thus induces a stable plaque phenotype. Also, macrophages presented a switch to anti-inflammatory wound healing characteristics and showed improved lipid handling. The pro-fibrotic phenotype was directly linked to epigenetic regulation of the Tgfb1 locus upon Hdac3 deletion, driving smooth muscle cells to increased collagen production. Moreover, in humans, HDAC3 was the sole Hdac upregulated in ruptured atherosclerotic lesions, Hdac3 associated with inflammatory macrophages, and HDAC3 expression inversely correlated with pro-fibrotic TGFB1 expression. Collectively, we show that targeting the macrophage epigenome can improve atherosclerosis outcome and we identify Hdac3 as a potential novel therapeutic target in cardiovascular disease

Myeloid IκBα Deficiency Promotes Atherogenesis by Enhancing Leukocyte Recruitment to the Plaques

Activation of the transcription factor NF-κB appears to be involved in different stages of atherogenesis. In this paper we investigate the role of NF-κB inhibitor IκBα in atherosclerosis. Myeloid-specific deletion of IκBα results in larger and more advanced lesions in LDL-R-deficient mice without affecting the compositional phenotype of the plaques or systemic inflammatory markers in the plasma. We show that IκBα-deleted macrophages display enhanced adhesion to an in vitro endothelial cell layer, coinciding with an increased expression of the chemokine CCL5. Also, in vivo we found that IκBαdel mice had more leukocytes adhering to the luminal side of the endothelial cell layers that cover the atherosclerotic plaques. Moreover, we introduce ER-MP58 in this paper as a new immunohistochemical tool for quantifying newly recruited myeloid cells in the atherosclerotic lesion. This staining confirms that in IκBαdel mice more leukocytes are attracted to the plaques. In conclusion, we show that IκBα deletion in myeloid cells promotes atherogenesis, probably through an induced leukocyte recruitment to plaques

Transcriptomic-based clustering of human atherosclerotic plaques identifies subgroups with different underlying biology and clinical presentation

Histopathological studies have revealed key processes of atherosclerotic plaque thrombosis. However, the diversity and complexity of lesion types highlight the need for improved sub-phenotyping. Here we analyze the gene expression profiles of 654 advanced human carotid plaques. The unsupervised, transcriptome-driven clustering revealed five dominant plaque types. These plaque phenotypes were associated with clinical presentation and showed differences in cellular compositions. Validation in coronary segments showed that the molecular signature of these plaques was linked to coronary ischemia. One of the plaque types with the most severe clinical symptoms pointed to both inflammatory and fibrotic cell lineages. Further, we did a preliminary analysis of potential circulating biomarkers that mark the different plaques phenotypes. In conclusion, the definition of the plaque at risk for a thrombotic event can be fine-tuned by in-depth transcriptomic-based phenotyping. These differential plaque phenotypes prove clinically relevant for both carotid and coronary artery plaques and point to distinct underlying biology of symptomatic lesions

A Pro-Inflammatory Gut Microbiota Increases Systemic Inflammation and Accelerates Atherosclerosis

RATIONALE: Several studies have suggested a role for the gut microbiota in inflammation and atherogenesis. A causal relation relationship between gut microbiota, inflammation and atherosclerosis has not been explored previously. OBJECTIVE: Here, we investigated whether a pro-inflammatory microbiota from Caspase1-/- ( Casp1-/-) mice accelerates atherogenesis in Ldlr-/- mice. METHODS AND RESULTS: We treated female Ldlr-/- mice with antibiotics and subsequently transplanted them with fecal microbiota from Casp1-/- mice based on a co-housing approach. Autologous transplantation of fecal microbiota of Ldlr-/- mice served as control. Mice were co-housed for 8 or 13 weeks and fed chow or a high-fat cholesterol-rich (HFC) diet. Fecal samples were collected, and factors related to inflammation, metabolism, intestinal health and atherosclerotic phenotypes were measured. Unweighted Unifrac distances of 16S rDNA sequences confirmed the introduction of the Casp1-/- and Ldlr-/- microbiota into Ldlr-/- mice (referred to as Ldlr-/-( Casp1-/-) or Ldlr-/-( Ldlr-/-) mice). Analysis of atherosclerotic lesion size in the aortic root demonstrated a significant 29% increase in plaque size in 13-week HFC-fed Ldlr-/-( Casp1-/-) mice compared to Ldlr-/-( Ldlr-/-) mice. We found increased numbers of circulating monocytes and neutrophils and elevated pro-inflammatory cytokine levels in plasma in HFC-fed Ldlr-/-( Casp1-/-) compared to Ldlr-/-( Ldlr-/-) mice. Neutrophil accumulation in the aortic root of Ldlr-/-( Casp1-/-) mice was enhanced compared to Ldlr-/-( Ldlr-/-) mice. 16S-rDNA-encoding sequence analysis in feces identified a significant reduction in the short-chain fatty acid (SCFA)-producing taxonomies Akkermansia, Christensenellaceae, Clostridium and Odoribacter in Ldlr-/-( Casp1-/-) mice. Consistent with these findings, cumulative concentrations of the anti-inflammatory SCFAs proprionate, acetate and butyrate in the cecum were significantly reduced in 13-week HFC-fed Ldlr-/-( Casp1-/-) compared to Ldlr-/-( Ldlr-/-) mice. CONCLUSIONS: Introduction of the pro-inflammatory Casp1-/- microbiota into Ldlr-/- mice enhances systemic inflammation and accelerates atherogenesis

A Pro-Inflammatory Gut Microbiota Increases Systemic Inflammation and Accelerates Atherosclerosis

RATIONALE: Several studies have suggested a role for the gut microbiota in inflammation and atherogenesis. A causal relation relationship between gut microbiota, inflammation and atherosclerosis has not been explored previously. OBJECTIVE: Here, we investigated whether a pro-inflammatory microbiota from Caspase1-/- ( Casp1-/-) mice accelerates atherogenesis in Ldlr-/- mice. METHODS AND RESULTS: We treated female Ldlr-/- mice with antibiotics and subsequently transplanted them with fecal microbiota from Casp1-/- mice based on a co-housing approach. Autologous transplantation of fecal microbiota of Ldlr-/- mice served as control. Mice were co-housed for 8 or 13 weeks and fed chow or a high-fat cholesterol-rich (HFC) diet. Fecal samples were collected, and factors related to inflammation, metabolism, intestinal health and atherosclerotic phenotypes were measured. Unweighted Unifrac distances of 16S rDNA sequences confirmed the introduction of the Casp1-/- and Ldlr-/- microbiota into Ldlr-/- mice (referred to as Ldlr-/-( Casp1-/-) or Ldlr-/-( Ldlr-/-) mice). Analysis of atherosclerotic lesion size in the aortic root demonstrated a significant 29% increase in plaque size in 13-week HFC-fed Ldlr-/-( Casp1-/-) mice compared to Ldlr-/-( Ldlr-/-) mice. We found increased numbers of circulating monocytes and neutrophils and elevated pro-inflammatory cytokine levels in plasma in HFC-fed Ldlr-/-( Casp1-/-) compared to Ldlr-/-( Ldlr-/-) mice. Neutrophil accumulation in the aortic root of Ldlr-/-( Casp1-/-) mice was enhanced compared to Ldlr-/-( Ldlr-/-) mice. 16S-rDNA-encoding sequence analysis in feces identified a significant reduction in the short-chain fatty acid (SCFA)-producing taxonomies Akkermansia, Christensenellaceae, Clostridium and Odoribacter in Ldlr-/-( Casp1-/-) mice. Consistent with these findings, cumulative concentrations of the anti-inflammatory SCFAs proprionate, acetate and butyrate in the cecum were significantly reduced in 13-week HFC-fed Ldlr-/-( Casp1-/-) compared to Ldlr-/-( Ldlr-/-) mice. CONCLUSIONS: Introduction of the pro-inflammatory Casp1-/- microbiota into Ldlr-/- mice enhances systemic inflammation and accelerates atherogenesis

Targeting the ACOD1-itaconate axis stabilizes atherosclerotic plaques

Inflammatory macrophages are key drivers of atherosclerosis that can induce rupture-prone vulnerable plaques. Skewing the plaque macrophage population towards a more protective phenotype and reducing the occurrence of clinical events is thought to be a promising method of treating atherosclerotic patients. In the current study, we investigate the immunomodulatory properties of itaconate, an immunometabolite derived from the TCA cycle intermediate cis-aconitate and synthesised by the enzyme Aconitate Decarboxylase 1 (ACOD1, also known as IRG1), in the context of atherosclerosis. Ldlr−/− atherogenic mice transplanted with Acod1−/− bone marrow displayed a more stable plaque phenotype with smaller necrotic cores and showed increased recruitment of monocytes to the vessel intima. Macrophages from Acod1−/− mice contained more lipids whilst also displaying reduced induction of apoptosis. Using multi-omics approaches, we identify a metabolic shift towards purine metabolism, in addition to an altered glycolytic flux towards production of glycerol for triglyceride synthesis. Overall, our data highlight the potential of therapeutically blocking ACOD1 with the aim of stabilizing atherosclerotic plaques

Macrophage MicroRNA-155 Promotes Cardiac Hypertrophy and Failure

BACKGROUND: Cardiac hypertrophy and subsequent heart failure triggered by chronic hypertension represent major challenges for cardiovascular research. Beyond neurohormonal and myocyte signaling pathways, growing evidence suggests inflammatory signaling pathways as therapeutically targetable contributors to this process. We recently reported that microRNA-155 is a key mediator of cardiac inflammation and injury in infectious myocarditis. Here, we investigated the impact of microRNA-155 manipulation in hypertensive heart disease. METHODS AND RESULTS: Genetic loss or pharmacological inhibition of the leukocyte-expressed microRNA-155 in mice markedly reduced cardiac inflammation, hypertrophy, and dysfunction on pressure overload. These alterations were macrophage dependent because in vivo cardiomyocyte-specific microRNA-155 manipulation did not affect cardiac hypertrophy or dysfunction, whereas bone marrow transplantation from wild-type mice into microRNA-155 knockout animals rescued the hypertrophic response of the cardiomyocytes and vice versa. In vitro, media from microRNA-155 knockout macrophages blocked the hypertrophic growth of stimulated cardiomyocytes, confirming that macrophages influence myocyte growth in a microRNA-155-dependent paracrine manner. These effects were at least partly mediated by the direct microRNA-155 target suppressor of cytokine signaling 1 (Socs1) because Socs1 knockdown in microRNA-155 knockout macrophages largely restored their hypertrophy-stimulating potency. CONCLUSIONS: Our findings reveal that microRNA-155 expression in macrophages promotes cardiac inflammation, hypertrophy, and failure in response to pressure overload. These data support the causative significance of inflammatory signaling in hypertrophic heart disease and demonstrate the feasibility of therapeutic microRNA targeting of inflammation in heart failure.status: publishe