Alan R Tall

Clonal hematopoiesis (CH) is an independent risk factor for atherosclerotic cardiovascular disease. Murine models of CH suggest a central role of inflammasomes and IL-1β in accelerated atherosclerosis and plaque destabilization. Here we show using single-cell RNA sequencing in human carotid plaques that inflammasome components are enriched in macrophages, while the receptor for IL-1β is enriched in fibroblasts and smooth muscle cells (SMCs). To address the role of inflammatory crosstalk in features of plaque destabilization, we conducted SMC fate mapping in Ldlr−/− mice modeling Jak2VF or Tet2 CH treated with IL-1β antibodies. Unexpectedly, this treatment minimally affected SMC differentiation, leading instead to a prominent expansion of fibroblast-like cells. Depletion of fibroblasts from mice treated with IL-1β antibody resulted in thinner fibrous caps. Conversely, genetic inactivation of Jak2VF …

Abstract JAK2 V617F (JAK2VF) clonal hematopoiesis (CH) has been associated with atherothrombotic cardiovascular disease (CVD). We assessed the impact of Jak2VF CH on arterial thrombosis and explored the underlying mechanisms. A meta-analysis of 3 large cohort studies confirmed the association of JAK2VF with CVD and with platelet counts and adjusted mean platelet volume (MPV). In mice, 20% or 1.5% Jak2VF CH accelerated arterial thrombosis and increased platelet activation. Megakaryocytes in Jak2VF CH showed elevated proplatelet formation and release, increasing prothrombogenic reticulated platelet counts. Gp1ba-Cre–mediated expression of Jak2VF in platelets (VFGp1ba) increased platelet counts to a similar level as in 20% Jak2VF CH mice while having no effect on leukocyte counts. Like Jak2VF CH mice, VFGp1ba mice showed enhanced platelet …

The deposition of cholesterol-rich lipoproteins in the arterial wall triggers macrophage inflammatory responses, which promote atherosclerosis. The NLRP3 inflammasome aggravates atherosclerosis; however, cellular mechanisms connecting macrophage cholesterol accumulation to inflammasome activation are poorly understood. We investigated the mechanisms of NLRP3 inflammasome activation in cholesterol-loaded macrophages and in atherosclerosis-prone Ldlr−/− mice with defects in macrophage cholesterol efflux. We found that accumulation of cholesterol in macrophages treated with modified LDL or cholesterol crystals, or in macrophages defective in the cholesterol efflux promoting transporters ABCA1 and ABCG1, leads to activation of NLRP3 inflammasomes as a result of increased cholesterol trafficking from the plasma membrane to the ER, via Aster-B. In turn, the accumulation of cholesterol in the …

Older men with loss of the Y chromosome are more susceptible to heart failure but the responsible genes have not been identified. A study now shows that loss of a single Y chromosome gene in bone marrow cells induces heart failure by switching cardiac macrophages from an inflammatory to a fibrogenic pattern of gene activity.

In this issue of Blood, Arends et al find an association between mutations causing clonal hematopoiesis (CH) and large artery atherosclerosis and white matter lesions in patients with ischemic stroke. 1 In a prospective study, patients with CH showed an increase in recurrent vascular events, stroke, and death compared with those without CH. The event rate is related to clone size, specific CH mutations, and the presence of multiple mutations. The study supports a causal role of CH in large artery atherosclerotic cardiovascular disease (CVD).CH has recently emerged as a major genetic risk factor for CVD. 2 CH arises when somatic mutations in leukemogenic genes endow a fitness advantage to hematopoietic stem and progenitor cells, leading to the clonal expansion of blood cells. CH is common among older people, occurring in> 10% of people aged> 70 years old. 2, 3 CH commonly involves mutations in genes …

Clonal hematopoiesis (CH) increases the risk of atherosclerotic cardiovascular disease possibly due to increased plaque inflammation. Human studies suggest that limitation of interleukin-6 (IL-6) signaling could be beneficial in people with large CH clones, particularly in TET2 CH. Here we show that IL-6 receptor antibody treatment reverses the atherosclerosis promoted by Tet2 CH, with reduction of monocytosis, lesional macrophage burden and macrophage colony-stimulating factor 1 receptor (CSF1R) expression. IL-6 induces expression of Csf1r in Tet2-deficient macrophages through enhanced STAT3 binding to its promoter. In mouse and human Tet2-deficient macrophages, IL-6 increases CSF1R expression and enhances macrophage survival. Treatment with the CSF1R inhibitor PLX3397 reversed accelerated atherosclerosis in Tet2 CH mice. Our study demonstrates the causality of IL-6 signaling in Tet2 CH …

Myeloid malignancies are characterized by the stepwise acquisition of somatic mutations in hematopoietic stem and progenitor cells (HSPCs) that promote subsequent leukemic transformation. This condition, termed clonal hematopoiesis (CH), has been recognized as a risk factor for the development of secondary heme malignancies and cardiovascular disease. Accumulating evidence indicates that inflammatory stressors can enhance myeloproliferation of mutant HSPCs. However, whether hijacking this inflammatory signaling will prevent clonal expansion and leukemogenesis is currently unknown. Our central hypothesis is that TET2-mutant CH progression to acute myeloid leukemia (AML) occurs in the setting of inflammatory stress mediated by JAK1, which acts as a signaling-hub for inflammation.To assess whether Tet2-mediated clonal expansion requires Jak1 signaling, we established a conditional Scl …

The CANTOS (Canakinumab Anti-inflammatory Thrombosis Outcome Study) and colchicine trials suggest an important role of inflammasomes and their major product IL-1β (interleukin 1β) in human atherosclerotic cardiovascular disease. Moreover, studies in mouse models indicate a causal role of inflammasomes and IL-1β in atherosclerosis. However, recent studies have led to a more granular view of the role of inflammasomes in atherosclerosis. Studies in hyperlipidemic mouse models suggest that prominent activation of the NLRP3 inflammasome requires a second hit such as defective cholesterol efflux, defective DNA repair, clonal hematopoiesis or diabetes. Similarly in humans some mutations promoting clonal hematopoiesis increase coronary artery disease risk in part by promoting inflammasome activation. Recent studies in mice and humans point to a wider role of the AIM2 (absent in melanoma 2 …

Increased eosinophil counts are associated with cardiovascular disease and may be an independent predictor of major cardiovascular events. However, the causality and underlying mechanisms are poorly understood. GWAS have shown an association of a common LNK variant (R262W, T allele) with eosinophilia and atherothrombotic disorders. LNK(TT) reduces LNK function and Lnk-deficient mice display accelerated atherosclerosis and thrombosis. This study was undertaken to assess the role of eosinophils in arterial thrombosis in mice with hematopoietic Lnk deficiency. Hematopoietic Lnk deficiency increased circulating and activated eosinophils, JAK/STAT signaling in eosinophils and carotid arterial thrombosis with increased eosinophil abundance and extracellular trap formation (EETosis) in thrombi. Depletion of eosinophils by anti-Siglec-F antibody or by the ∆dbIGata1 mutation eliminated eosinophils in …

Clonal hematopoiesis (CH), a highly prevalent condition in the elderly, arises from somatic mutations that endow a survival advantage to hematopoietic stem cells. In CANTOS IL-1β inhibition was particularly beneficial in subjects with TET2 CH. Amongst the common genetic variants giving rise to CH, JAK2V617F (JAK2VF) gain of function and TET2 loss of function mutations have been shown to increase macrophage inflammasome activation and atherosclerosis in mice. We have shown that macrophages harboring Jak2 mutations have increased AIM2 inflammasome activation and pyroptosis which promoted features of unstable atherosclerotic lesions marked by prominent necrotic cores and an accumulation of inflammatory macrophages. Inflammasome inhibition led to a thickening of fibrous caps, indicating plaque stabilization. scRNA-Seq analysis of human carotid plaques indicates that myeloid cells were …

BACKGROUND Clonal hematopoiesis (CH) has emerged as an independent risk factor for atherosclerotic cardiovascular disease, with activation of macrophage inflammasomes as a potential underlying mechanism. The NLRP3 (NLR family pyrin domain containing 3) inflammasome has a key role in promoting atherosclerosis in mouse models of Tet2 CH, whereas inhibition of the inflammasome product interleukin-1β appeared to particularly benefit patients with TET2 CH in CANTOS (Cardiovascular Risk Reduction Study [Reduction in Recurrent Major CV Disease Events]). TET2 is an epigenetic modifier that decreases promoter methylation. However, the mechanisms underlying macrophage NLRP3 inflammasome activation in TET2 (Tet methylcytosine dioxygenase 2) deficiency and potential links with epigenetic modifications are poorly understood. METHODS We used cholesterol-loaded TET2-deficient …

Background and objective: Human GWAS have shown association of a common single nucleotide polymorphism in LNK (R262W, T allele) with neutrophilia, eosinophilia, and atherothrombotic cardiovascular disease (ACD). We have shown that LNK(TT) reduces LNK function and LNK-deficiency promotes neutrophil extracellular traps (NETosis) and arterial thrombosis. However, the potential role of eosinophils in the LNK(R262W) associated risk of ACD has not been evaluated. Recent evidence suggests that eosinophils act to stabilize arterial thrombi by forming eosinophil extracellular traps (EETs). The primary goal of this study is to investigate the role of eosinophils and EETs in arterial thrombosis in hematopoietic LNK deficiency. Methods: We used pharmacological and genetic approaches that specifically inhibits eosinophils and EET formation. Chow-fed and WTD-fed WT and Lnk-/- BMT recipient mice received …

Clonal hematopoiesis of indeterminate potential (CHIP) is associated with an increased risk of cardiovascular diseases (CVDs), putatively via inflammasome activation. We pursued an inflammatory gene modifier scan for CHIP-associated CVD risk among 424,651 UK Biobank participants. We identified CHIP using whole-exome sequencing data of blood DNA and modeled as a composite, considering all driver genes together, as well as separately for common drivers (DNMT3A, TET2, ASXL1, and JAK2). We developed predicted gene expression scores for 26 inflammasome-related genes and assessed how they modify CHIP-associated CVD risk. We identified IL1RAP as a potential key molecule for CHIP-associated CVD risk across genes and increased AIM2 gene expression leading to heightened JAK2- and ASXL1-associated CVD risk. We show that CRISPR-induced Asxl1-mutated murine macrophages had a …

Aims Neutrophil extracellular trap formation (NETosis) increases atherosclerotic plaque vulnerability and athero-thrombosis. However, mechanisms promoting NETosis during atherogenesis are poorly understood. We have shown that cholesterol accumulation due to myeloid cell deficiency of the cholesterol transporters ATP Binding Cassette A1 and G1 (ABCA1/G1) promotes NLRP3 inflammasome activation in macrophages and neutrophils and induces prominent NETosis in atherosclerotic plaques. We investigated whether NETosis is a cell-intrinsic effect in neutrophils or is mediated indirectly by cellular crosstalk from macrophages to neutrophils involving IL-1β. Methods and results We generated mice with neutrophil or macrophage-specific Abca1/g1 deficiency (S100A8CreAbca1fl/flAbcg1fl/fl or CX3CR1CreAbca1fl/flAbcg1fl/fl mice, respectively), and transplanted their bone …

Serum apolipoprotein C3 (APOC3) predicts incident cardiovascular events in people with type 1 diabetes, and silencing of APOC3 prevents both lesion initiation and advanced lesion necrotic core expansion in a mouse model of type 1 diabetes. APOC3 acts by slowing the clearance of triglyceride-rich lipoproteins, but lipid-free APOC3 has recently been reported to activate an inflammasome pathway in monocytes. We therefore investigated the contribution of hematopoietic inflammasome pathways to atherosclerosis in mouse models of type 1 diabetes. LDL receptor–deficient diabetes mouse models were transplanted with bone marrow from donors deficient in NOD, LRR and pyrin domain–containing protein 3 (NLRP3), absent in melanoma 2 (AIM2) or gasdermin D (GSDMD), an inflammasome-induced executor of pyroptotic cell death. Mice with diabetes exhibited inflammasome activation and …

ABCA1 promotes the efflux of cholesterol from cells to HDL and has anti-atherogenic activities. Sun and Li present cryo-EM structures of ABCA1 in the ATP-free and ATP-bound states, which reveal bound cholesterol molecules and suggest a transmembrane cholesterol-transport mechanism.

Elevated hematocrit is associated with cardiovascular risk; however, the causality and mechanisms are unclear. The JAK2V617F (Jak2VF) mutation increases cardiovascular risk in myeloproliferative disorders and in clonal hematopoiesis. Jak2VF mice with elevated WBCs, platelets, and RBCs display accelerated atherosclerosis and macrophage erythrophagocytosis. To investigate whether selective erythroid Jak2VF expression promotes atherosclerosis, we developed hyperlipidemic erythropoietin receptor Cre mice that express Jak2VF in the erythroid lineage (VFEpoR mice). VFEpoR mice without elevated blood cell counts showed increased atherosclerotic plaque necrosis, erythrophagocytosis, and ferroptosis. Selective induction of erythrocytosis with low-dose erythropoietin further exacerbated atherosclerosis with prominent ferroptosis, lipid peroxidation, and endothelial damage. VFEpoR RBCs had reduced …

Clonal hematopoiesis arises from somatic mutations that provide a fitness advantage to hematopoietic stem cells and the outgrowth of clones of blood cells. Clonal hematopoiesis commonly involves mutations in genes that are involved in epigenetic modifications, signaling and DNA damage repair. Clonal hematopoiesis has emerged as a major independent risk factor in atherosclerotic cardiovascular disease, thrombosis and heart failure. Studies in mouse models of clonal hematopoiesis have shown an increase in atherosclerosis, thrombosis and heart failure, involving increased myeloid cell inflammatory responses and inflammasome activation. Although increased inflammatory responses have emerged as a common underlying principle, some recent studies indicate mutation-specific effects. The discovery of the association of clonal hematopoiesis with cardiovascular disease and the recent demonstration of …

Background Cholesterol loaded macrophage foam cells are a prominent feature of atherosclerotic plaques. Single-cell RNA sequencing has identified foam cells as TREM2 (triggering receptor expressed on myeloid cells 2) positive populations with low expression of inflammatory genes, resembling the TREM2 positive microglia of neurodegenerative diseases. Cholesterol loading of macrophages in vitro results in activation of LXR (liver X receptor) transcription factors and suppression of inflammatory genes. Methods To test the hypothesis that LXRs mediate anti-inflammatory effects in Trem2 expressing atherosclerotic plaque foam cells, we performed RNA profiling on plaque cells from hypercholesterolemic mice with myeloid LXR deficiency. Results Myeloid LXR deficiency led to a dramatic increase in atherosclerosis with increased monocyte entry, foam cell formation, and plaque inflammation. Bulk cell-RNA …

In the present invention, inventors have used high through put sequencing to identify novel mutations in ABCA1 in CM ML patient samples. Further studies in a mouse model of myelomonocytic leukemia driven by hematopoietic Tet2 deficiency have shown that these somatic mutations abro gate the tumor suppressor function of WT ABCA1, resulting in the failure to suppress canonical IL3-receptor beta sig naling-driven myelopoiesis. The loss of the myelo-suppres sive function of ABCA1 mutants can be overcome by raising HDL levels through overexpression of the human apolipo protein A-1 (apoA-1) transgene. Inventors have also shown that both IL-3Rbeta blocking antibody and cyclodextrin prevented the proliferation of ABCA1 mutant-transducedTet2 deficient BM cells similar to the effect of ABCA1-WT overexpression. Accordingly, the invention relates to a method for predicting the survival time of a subject NI …

Background & AimsMolecular mechanisms underlying the different susceptibility of men and women to non-alcoholic fatty liver disease (NAFLD) are poorly understood. The TTC39B locus encodes a scaffolding protein, associates with gynecological disorders and its deletion protects mice from diet-induced steatohepatitis. This study aimed to elucidate the molecular mechanisms linking TTC39B (T39) to the expression of lipogenic genes and to explore sex-specific effects.MethodsCo-expression in HEK293A cells validated the novel T39/pRb interaction predicted by a protein-protein interaction algorithm. T39 was knocked down using an antisense oligonucleotide (ASO) in mice with dietary NAFLD and a genetic deficiency of pRb or its downstream effector E2F1, as well as in primary human hepatocytes.ResultsT39 interacts with pRb via its C-terminal TPR domain and promotes its proteasomal degradation. In female …

Patients with JAK2V617F (JAK2VF) clonal hematopoiesis (CH) have increased JAK/STATsignaling that imparts an increased risk of premature coronary heart disease. We have shown that mice with Jak2VF mutations modeling CH have increased AIM2 inflammasome activation that promotes atherosclerosis. Genetic inhibition of the inflammasome through deletion of Caspase1/11 or Gasdermin D in hematopoietic stem and progenitor cells (HSPC) harboring Jak2VFmutations increased fibrous caps thickness. Therefore, we hypothesized that inhibition of IL-1β derived from Jak2VF macrophages promotes smooth muscle cell (SMC) reprograming and accumulation in fibrous caps. To test this hypothesis, we transplanted bone marrow (BM) with Jak2VF expression in all HSPCs into Ldlr-/- mice and then administered the IL-1 receptor antagonist Anakinra. After 12 weeks of Western type diet (WTD) feeding, mice treated …

We assessed the cross-sectional and longitudinal relationships of high-density lipoprotein (HDL)-mediated cholesterol mass efflux capacity (CMEC) with coronary artery calcium (CAC) score and CAC density. CMEC was measured in 1626 Multi-Ethnic Study of Atherosclerosis (MESA) participants in samples obtained between 2000 and 2002 as part of two nested case-control studies, one with cases of incident cardiovascular disease and the other with cases of carotid plaque progression by ultrasound. Cardiac CT examinations for the presence of CAC were performed at baseline and at two additional examinations. CAC scores (Agatston and volume) and density scores (for those with positive CAC) were calculated. Multivariable linear regression modeling per SD increment of CMEC was used to estimate the associations of CMEC with each of these CAC measures. We found no association between higher CMEC …

Despite the success of LDL-lowering drugs in reducing cardiovascular disease (CVD), there remains a large burden of residual disease due in part to persistent dyslipidemia characterized by elevated levels of triglyceride-rich lipoproteins (TRLs) and reduced levels of HDL. This form of dyslipidemia is increasing globally as a result of the rising prevalence of obesity and metabolic syndrome. Accumulating evidence suggests that impaired hepatic clearance of cholesterol-rich TRL remnants leads to their accumulation in arteries, promoting foam cell formation and inflammation. Low levels of HDL may associate with reduced cholesterol efflux from foam cells, aggravating atherosclerosis. While fibrates and fish oils reduce TRL, they have not been uniformly successful in reducing CVD, and there is a large unmet need for new approaches to reduce remnants and CVD. Rare genetic variants that lower triglyceride levels …

Diabetes accelerates atherosclerosis progression in part by increasing lesional necrotic core expansion, but the underlying mechanisms remain elusive. Previous studies have shown that systemic inhibition of the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome prevents atherosclerosis progression in a mouse model of diabetes. Gasdermin D (GSDMD), which acts downstream of inflammasome activation, contributes to pyroptosis and IL-1β and IL-18 release. To explore if hematopoietic inflammasome activation mediates diabetes-related necrotic core expansion, we first generated hematopoietic GSDMD-deficient chimeras in an LDL receptor-deficient (Ldlr-/-) virally-induced mouse model of type 1 diabetes (T1D)-accelerated atherosclerosis. Mice with T1D demonstrated elevated plasma glucose, triglycerides, cholesterol, and plasma IL-18 (non-diabetes [ND]=180.4 pg/ml, diabetes [D …

The AIM2 inflammasome is activated by host and pathogen DNA. Work from the past 5 years indicates that the AIM2 inflammasome has an important role in advanced atherosclerosis driven by clonal haematopoiesis and possibly in atherosclerosis accelerated by acute infection. Therefore, the AIM2 inflammasome might be an important target for precision medicine.

Efferocytosis, the clearance of apoptotic cells (ACs) by macrophages, is critical for tissue resolution, with defects driving many diseases. Mechanisms of efferocytosis-mediated resolution are incompletely understood. Here, we show that AC-derived methionine regulates resolution through epigenetic repression of the extracellular signal-regulated kinase 1/2 (ERK1/2) phosphatase Dusp4. We focus on two key efferocytosis-induced pro-resolving mediators, prostaglandin E2 (PGE2) and transforming growth factor beta 1 (TGF-β1), and show that efferocytosis induces prostaglandin-endoperoxide synthase 2/cyclooxygenase 2 (Ptgs2/COX2), leading to PGE2 synthesis and PGE2-mediated induction of TGF-β1. ERK1/2 phosphorylation/activation by AC-activated CD36 is necessary for Ptgs2 induction, but this is insufficient owing to an ERK−DUSP4 negative feedback pathway that lowers phospho-ERK. However …

2. Fritsche LG, Igl W, Bailey JN, et al. A large genome-wide association study of age-related macular degeneration highlights contributions of rare and common variants. Nat Genet. 2016; 48 (2): 134-143. doi: 10.1038/ng. 3448 3. Schmidt AF, Hunt NB, Gordillo-Marañón M, et al. Cholesteryl ester transfer protein (CETP) as a drug target for cardiovascular disease. Nat Commun. 2021; 12 (1): 5640. doi: 10.1038/s41467-021-25703-3 4. Bowman L, Hopewell JC, Chen F, et al; HPS3/TIMI55–REVEAL Collaborative Group. Effects of anacetrapib in patients with atherosclerotic vascular disease. N Engl J Med. 2017; 377 (13): 1217-1227. doi: 10.1056/NEJMoa1706444 5. Zhang M, Charles R, Tong H, et al. HDL surface lipids mediate CETP binding as revealed by electron microscopy and molecular dynamics simulation. Sci Rep. 2015; 5: 8741. doi: 10.1038/srep08741In Reply We appreciate the thoughtful comments from …

Background LNK/SH2B3 inhibits Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling by hematopoietic cytokine receptors. Genome-wide association studies have shown association of a common single nucleotide polymorphism in LNK (R262W, T allele) with neutrophilia, thrombocytosis, and coronary artery disease. We have shown that LNK(TT) reduces LNK function and that LNK-deficient mice display prominent platelet–neutrophil aggregates, accelerated atherosclerosis, and thrombosis. Platelet–neutrophil interactions can promote neutrophil extracellular trap (NET) formation. The goals of this study were to assess the role of NETs in atherosclerosis and thrombosis in mice with hematopoietic Lnk deficiency. Methods We bred mice with combined deficiency of Lnk and the NETosis-essential enzyme PAD4 (peptidyl arginine deiminase 4) and transplanted their bone marrow into …

Plasma levels of high-density lipoprotein (HDL) inversely correlate with the incidence of cardiovascular diseases (CVD). The causal relationship between plasma HDL-cholesterol levels and CVD has been called into question by Mendelian randomization studies and the majority of clinical trials not showing any benefit of plasma HDL-cholesterol raising drugs on CVD. Nonetheless, recent Mendelian randomization studies including an increased number of CVD cases compared to earlier studies have confirmed that HDL-cholesterol levels and CVD are causally linked. Moreover, several studies in large population cohorts have shown that the cholesterol efflux capacity of HDL inversely correlates with CVD. Cholesterol efflux pathways exert anti-inflammatory and anti-atherogenic effects by suppressing proliferation of hematopoietic stem and progenitor cells, and inflammation and inflammasome activation in …

Clonal haematopoiesis, which is highly prevalent in older individuals, arises from somatic mutations that endow a proliferative advantage to haematopoietic cells. Clonal haematopoiesis increases the risk of myocardial infarction and stroke independently of traditional risk factors. Among the common genetic variants that give rise to clonal haematopoiesis, the JAK2V617F (JAK2VF) mutation, which increases JAK–STAT signalling, occurs at a younger age and imparts the strongest risk of premature coronary heart disease,. Here we show increased proliferation of macrophages and prominent formation of necrotic cores in atherosclerotic lesions in mice that express Jak2VF selectively in macrophages, and in chimeric mice that model clonal haematopoiesis. Deletion of the essential inflammasome components caspase 1 and 11, or of the pyroptosis executioner gasdermin D, reversed these adverse changes. Jak2VF …

The first large population-based study to show an inverse relationship between circulating HDL-cholesterol (HDL-C) concentrations and coronary heart disease (CHD) was a cross-sectional analysis of men of Japanese ancestry living in Hawaii (1). Four prospective epidemiological studies extended these finding showing that a 1mg/dL increase in HDL-C was associated with a 2% decrease in CHD in men and a 3% decrease in CHD in women (2). The inverse relationship was independent of age, smoking, low density lipoprotein cholesterol (LDL-C), blood pressure, and body mass index (BMI), but was attenuated by adjustment for non-HDL-C (ie, VLDL+ LDL-C) concentrations. These findings suggested that raising HDL-C could be therapeutically beneficial but were insufficient to completely disentangle the close relationship between HDL and triglyceriderich lipoproteins. The subsequent failure of most clinical …

Mendelian randomization (MR) of lipid traits in CAD has provided evidence for causal associations of LDL-C and TGs in CAD, but many lipid trait genetic variants have pleiotropic effects on other cardiovascular risk factors that may bias MR associations. The goal of this study was to evaluate pleiotropic effects of lipid trait genetic variants and to account for these effects in MR of lipid traits in CAD. We performed multivariable MR using inverse variance-weighted and MR-Egger methods in large (n ≥ 300,000) GWAS datasets. We found that 30% of lipid trait genetic variants have effects on metabolic syndrome traits, including BMI, T2D, and systolic blood pressure (SBP). Nonetheless, in multivariable MR analysis, LDL-C, HDL-C, TGs, BMI, T2D, and SBP are independently associated with CAD, and each of these associations is robust to adjustment for directional pleiotropy. MR at loci linked to direct effects on HDL-C …

Despite the initial success of some drugs and vaccines targeting COVID-19, understanding the mechanism underlying SARS-CoV-2 disease pathogenesis remains crucial for the development of further approaches to treatment. Some patients with severe Covid-19 experience a cytokine storm and display evidence of inflammasome activation leading to increased levels of IL-1β and IL-18; however, other reports have suggested reduced inflammatory responses to Sars-Cov-2. In this study we have examined the effects of the Sars-Cov-2 envelope (E) protein, a virulence factor in coronaviruses, on inflammasome activation and pulmonary inflammation. In cultured macrophages the E protein suppressed inflammasome priming and NLRP3 inflammasome activation. Similarly, in mice transfected with E protein and treated with poly(I:C) to simulate the effects of viral RNA, the E protein, in an NLRP3-dependent fashion …

ObjectiveIn mouse models, deficiency of TTC39B (T39) decreases hepatic lipogenic gene expression and protects against diet-induced steatohepatitis. While assessing the therapeutic potential of antisense oligonucleotides (ASOs) targeting T39, we discovered an unexpected weight loss phenotype. The objective of this study was to determine the mechanism of the resistance to diet-induced obesity.MethodsTo assess therapeutic potential, we used antisense oligonucleotides (ASO) to knock down T39 expression in a Western or high-fat, high-cholesterol, high-sucrose-diet-fed Ldlr−/− or wild-type mice.ResultsT39 ASO treatment led to decreased hepatic lipogenic gene expression and decreased hepatic triglycerides. Unexpectedly, T39 ASO treatment protected against diet-induced obesity. The reduced weight gain was seen with two different ASOs that decreased T39 mRNA in adipose tissue macrophages (ATMs …

Cardiovascular disease (CVD) is the leading cause of death in patients with diabetes, and tight glycemic control fails to reduce the risk of developing CVD. Thiazolidinediones (TZDs), a class of peroxisome proliferator–activated receptor γ (PPARγ) agonists, are potent insulin sensitizers with antiatherogenic properties, but their clinical use is limited by side effects. PPARγ deacetylation on two lysine residues (K268 and K293) induces brown remodeling of white adipose tissue and uncouples the adverse effects of TZDs from insulin sensitization. Here we show that PPARγ deacetylation confers antiatherogenic properties and retains the insulin-sensitizing effects of TZD while circumventing its detriments. We generated mice homozygous with mice with deacetylation-mimetic PPARγ mutations K268R/K293R (2KR) on an LDL-receptor knockout (Ldlr−/−) background. 2KR:Ldlr−/− mice showed smaller atherosclerotic …

Defective cholesterol efflux pathways in mice promote the expansion of hematopoietic stem and progenitor cells and a bias toward the myeloid lineage, as observed in chronic myelomonocytic leukemia (CMML). Here, we identify 5 somatic missense mutations in ABCA1 in 26 patients with CMML. These mutations confer a proliferative advantage to monocytic leukemia cell lines in vitro. In vivo inactivation of ABCA1 or expression of ABCA1 mutants in hematopoietic cells in the setting of Tet2 loss demonstrates a myelosuppressive function of ABCA1. Mechanistically, ABCA1 mutations impair the tumor-suppressor functions of WT ABCA1 in myeloproliferative neoplasms by increasing the IL-3Rβ signaling via MAPK and JAK2 and subsequent metabolic reprogramming. Overexpression of a human apolipoprotein A-1 transgene dampens myeloproliferation. These findings identify somatic mutations in ABCA1 that subvert …

The thymus is a primary lymphoid organ necessary for optimal T cell development. Here, we show that liver X receptors (LXRs)—a class of nuclear receptors and transcription factors with diverse functions in metabolism and immunity—critically contribute to thymic integrity and function. LXRαβ-deficient mice develop a fatty, rapidly involuting thymus and acquire a shrunken and prematurely immunoinhibitory peripheral T cell repertoire. LXRαβ’s functions are cell specific, and the resulting phenotypes are mutually independent. Although thymic macrophages require LXRαβ for cholesterol efflux, thymic epithelial cells (TECs) use LXRαβ for self-renewal and thymocytes for negative selection. Consequently, TEC-derived LXRαβ protects against homeostatic premature involution and orchestrates thymic regeneration following stress, while thymocyte-derived LXRαβ limits cell disposal during negative selection and confers …

Background and aims We aimed to assess the relationship of HDL (high-density lipoprotein)-mediated cholesterol mass efflux capacity (CMEC) with risk of incident peripheral artery disease (PAD). Methods CMEC was measured in 1458 Multi-Ethnic Study of Atherosclerosis participants between 2000 and 2002 as part of a case-control study matched for incident cardiovascular disease and progression of carotid plaque by ultrasound. Incident clinical PAD, adjudicated on the basis of a positive history for the presence of disease-related symptoms or treatment, was ascertained through 2015 in 1419 individuals without clinical PAD at baseline. Subclinical PAD, defined as an ankle-brachial index (ABI)≤ 1.0, was assessed among 1255 individuals with a baseline ABI> 1.0 and at least one follow-up ABI measurement 3–10 years later. Cox proportional hazards and relative risk regression modeling per SD increment of …

Macrophage foam cells (ie, cholesteryl ester-laden macrophages) are abundant in atherosclerotic plaques, and increased macrophage foam cell content is associated with plaque instability (1, 2). Macrophages are generally thought to unload surplus cholesterol via efflux mediated by the ATP-binding cassette transporters A1 and G1 (ABCA1 and ABCG1) to apolipoprotein A1 [apoA1 (3, 4)] and high-density lipoproteins [HDLs (5, 6)], respectively. Several studies in large-population cohorts have shown that the cholesterol efflux capacity of HDL (ie, its potential to act as an acceptor for cholesterol efflux from macrophages) is an inverse predictor of cardiovascular disease (7–9), highlighting the importance of cholesterol efflux as an atheroprotective mechanism. In PNAS, He et al.(10) describe a mechanism for macrophage cholesterol efflux, which involves the transfer of surplus cholesterol from the macrophage plasma …

It is now clear that HDL (high-density lipoprotein) can induce both anti-inflammatory and proinflammatory effects in activated macrophages. The letter by Biessen et al addresses the important issue of whether HDL’s proinflammatory or anti-inflammatory effects predominate in macrophages in lesions of atherosclerosis. Our recent study confirmed that HDL can exert proinflammatory effects in lipopolysaccharide-stimulated macrophages, 1 consistent with a previous study by van der Vorst et al. 2 The proinflammatory effects of HDL in macrophages occur late (after 2 hours) and are dependent on the cellular cholesterol content and cholesterol efflux. 1 However, our studies clearly demonstrate that HDL also exerts anti-inflammatory effects in the same macrophages, responses that are likewise dependent on cholesterol efflux, and that the proinflammatory and antiinflammatory effects of HDL are mediated through distinct …

Introduction: Excessive macrophage proliferation and defective efferocytosis predominate in advanced atherosclerotic plaques. However, how cell cycle and its regulation may affect efferocytosis remains unclear. We hypothesize that cell cycle phase affects efferocytosis capacity and manipulating cell cycle status can alter macrophage efferocytic functions. Methods and Results: Efferocytosis assay was performed in murine bone marrow-derived macrophages (BMDM) using fluorescently labeled apoptotic Jurkat cells and quantified by flow cytometry and imaging-based analysis. Proliferating BMDM were marked by Ki67 staining and EdU incorporation. Ki67+ proliferating BMDM showed lower efferocytic capacity (A). Inhibiting cell proliferation using aphidicolin that inhibits DNA replication at early S phase enhanced macrophage efferocytosis (B). This association between cell cycle regulation and efferocytosis is …

Objective Increased myelopoiesis has been linked to risk of atherosclerotic cardiovascular disease (ACD). Excessive myelopoiesis can be driven by dyslipidemia and cholesterol accumulation in hematopoietic stem and progenitor cells (HSPC) and may involve increased signaling via Janus kinase 2 (JAK2). Constitutively activating JAK2 mutants drive biased myelopoiesis and promote development of myeloproliferative neoplasms (MPN) or clonal hematopoiesis, conditions associated with increased risk of ACD. JAK2 inhibitors have been developed as a therapy for MPNs. The potential for JAK2 inhibitors to protect against atherosclerosis has not been tested. We therefore assessed the impact of JAK2 inhibition on atherogenesis. Methods A selective JAK2 inhibitor TG101348 (fedratinib) or vehicle was given to high-fat high-cholesterol Western diet (WD)–fed wild-type (WT) or Apoe−/− mice. Hematopoietic cell …