Human Atherosclerotic Lesions Research Articles

Abstract 4137895: Serum High-density Lipoprotein-Associated Paraoxonase-1 Levels Predict Recurrent Cardiovascular Events after Stent Implantation in Patients with Stable Angina Pectoris

Background: Poor clinical outcomes for patients undergoing hemodialysis (HD) after drug-eluting stent (DES) implantation have been reported. High-density lipoprotein (HDL) cholesterol is well-established as a negative risk factor for coronary artery disease, and its anti-oxidant property has been attributed mainly to the HDL-bound enzyme paraoxonase-1 (PON-1). Myeloperoxidase (MPO), a pro-oxidant enzyme released from activated neutrophils, has been shown to alter the atheroprotective function of HDL to a dysfunctional form. The aim of this study was to investigate the relationship between plasma MPO and serum PON-1 levels after implantation of DES in patients with stable angina pectoris (SAP) with and without HD. Methods: Serum PON-1 concentrations and PON-arylesterase activity were measured in 183 patients with SAP after DES implantation (HD group, n=37; non-HD group, n=146) with a sandwich ELISA method. Cardiovascular events were defined as sudden cardiac death, fatal or non-fatal myocardial infarction, cerebral infarction and other non-fatal events including unstable angina pectoris or coronary revascularization. Results: Serum PON-1 concentrations and PON-arylesterase activity were significantly lower in the HD group than in the non-HD group (PON-1 concentrations, P<0.0001; PON-arylesterase activity, P<0.0001). In addition, plasma MPO in patients undergoing HD were significantly higher than in patients not undergoing HD (P<0.0001). Moreover, plasma MPO showed a significant inverse correlation with serum PON-1 concentrations and PON-arylesterase activity (concentration: R= -0.24, P=0.0013; arylesterase-activity: R=-0.24, P=0.0014). Cardiovascular event rates were significantly higher in the HD group than in the non-HD group (67.6% vs. 43.8%, P<0.01). Kaplan-Meier survival analysis showed that the low-PON-1 group (<58.0 mg/mL, median) had a significantly worse outcome than the high-PON-1 group ( P =0.013). Multivariate analysis showed that a low serum PON-1 concentration was the only independent predictor of cardiovascular events (odds ratio, 1.93; 95% confidence interval, 1.10 to 3.40, P =0.024). Conclusions: These findings demonstrate that plasma MPO have a significant inverse correlation with PON-1 in patients undergoing HD and suggest that an imbalance between pro-oxidants and anti-oxidants may contribute to the progression and destabilization of human coronary atherosclerotic lesions in patients with SAP who undergo HD following DES implantation.

SPA Promotes Atherosclerosis Through Mediating Macrophage Foam Cell Formation-Brief Report.

Atherosclerosis is a progressive inflammatory disease in which macrophage foam cells play a central role in disease pathogenesis. SPA (surfactant protein A) is a lipid-associating protein involved with regulating macrophage function in various inflammatory diseases. However, the role of SPA in atherosclerosis and macrophage foam cell formation has not been investigated. SPA expression was assessed in healthy and atherosclerotic human coronary arteries and the brachiocephalic arteries of wild-type or ApoE-deficient mice fed high-fat diets for 4 weeks. Hypercholesteremic wild-type and SPA-deficient mice fed a high-fat diet for 6 weeks were investigated for atherosclerotic lesions in vivo. In vitro experiments using RAW264.7 macrophages, primary resident peritoneal macrophages extracted from wild-type or SPA-deficient mice, and human monocyte-derived macrophages from the peripheral blood of healthy donors determined the functional effects of SPA in macrophage foam cell formation. SPA expression was increased in atherosclerotic lesions in humans and ApoE-deficient mice and in response to a proatherosclerotic stimulus in vitro. SPA deficiency reduced the lipid profiles induced by hypercholesterolemia, attenuated atherosclerosis, and reduced the number of lesion-associated macrophage foam cells. In vitro studies revealed that SPA deficiency reduced intracellular cholesterol accumulation and macrophage foam cell formation. Mechanistically, SPA deficiency dramatically downregulated the expression of scavenger receptor CD36 (cluster of differentiation antigen 36) cellular and lesional expression. Importantly, SPA also increased CD36 expression in human monocyte-derived macrophages. Our results elucidate that SPA is a novel factor promoting atherosclerosis development. SPA enhances macrophage foam cell formation and atherosclerosis by increasing scavenger receptor CD36 expression, leading to increasing cellular OxLDL influx.

Experimental evidence on colchicine's mode of action in human carotid artery plaques

Abstract Background and aims Atherosclerosis driven by inflammation is a major cause of cardiovascular events. Recent clinical trials have demonstrated the therapeutic potential of anti-inflammatory treatments. Consequently, colchicine is recommended in current guidelines as a second-line therapy for secondary prevention, although the drug's mechanism of action is not fully understood. Methods To this end, we performed a multiomic study of the effect of colchicine on human carotid plaques. Sections from endarterectomy specimens were exposed ex vivo to colchicine at concentrations of 2 ng/ml and 10 ng/ml for 24 hours and compared with untreated segments of the same plaque. Changes in gene expression were analyzed by RNA sequencing, and plaque secretomes were subjected to proteomic analysis by mass spectrometry. In situ cell proliferation was examined histologically. Results Our data suggest that colchicine primarily suppresses neutrophil and platelet degranulation, collagen degradation, and macrophage proliferation in atheromatous plaques in a dose-dependent manner, while stimulating myofibroblast activation. Conclusion Our study demonstrates multifactorial pathways by which colchicine, the first anti-inflammatory drug recommended by cardiovascular guidelines, acts on human atherosclerotic lesions. Targeting neutrophil and platelet degranulation, collagen degradation and macrophage proliferation could provide significant therapeutic benefit in atherosclerotic cardiovascular disease without the adverse side effects of colchicine.

MIR181A1HG is a novel long noncoding RNA regulating vascular inflammation and atherosclerosis

Abstract Background Endothelial cell (EC) dysfunction and vascular inflammation are critical in the initiation and progression of atherosclerosis. Long noncoding RNAs (lncRNAs) plays a critical role in vascular pathology, but relatively little is known about their involvement in controlling vascular inflammation. MIR181A1HG is a lncRNA locating juxta-position with miR-181a1 and miR-181b1, both involved in vascular inflammation. However, the role of MIR181A1HG in vascular inflammation is still unknow. Purpose The study aims to investigate the role of MIR181A1HG in regulating vascular inflammation and atherosclerosis. Methods We examined expression of MIR181A1HG in both human and mouse atherosclerotic lesions. Loss-of-function and gain-of-function studies, multiple RNA–protein interaction assays luciferase reporter and chromatin immunoprecipitation assays were used to investigate the role and molecular mechanisms of MIR181A1HG in the vascular inflammation and atherosclerosis. The single-cell RNA-sequencing were used to analyze atherosclerotic phenotypes of MIR181A1HG-/-ApoE-/- mice. Results MIR181A1HG was abundant in ECs and significantly increased in both humans and mouse atherosclerotic lesions. Deficiency of MIR181A1HG effectively suppressed NLRP3 inflammasome, ECs activation, and atherosclerotic lesion formation. In contrast, EC-specific MIR181A1HG overexpression promoted NLRP3 inflammasome, ECs activation, and atherosclerotic lesion formation, which were reversed by pharmacological inhibition of NLRP3 (MCC950). MIR181A1HG functioned by regulating NLRP3 inflammation, ECs activation though decoying Foxp1 away from the promoters of targets genes, which is independently of miR181a1/b1 cluster. EC-specific Foxp1 silencing reversed in vivo anti-atherosclerotic effect mediated by MIR181A1HG-deletion.

Immunohistochemical Localization of Fibroblast Activation Protein in Coronary Arteries with Different Forms of Atherosclerosis

Background: Fibroblast activation protein (FAP) is a cell surface glycoprotein expressed by myofibroblasts in areas of active tissue remodeling. It plays a potentially important role in cardiac remodeling, atherosclerotic plaque formation, and plaque rupture. Given the distinct pathophysiology and morphology of different forms of atherosclerosis, we analyzed FAP expression in human coronary vessels with no coronary artery disease, atherosclerotic plaques at different levels of progression, and other distinct forms of coronary disease in post bypass vein grafting and cardiac allograft vasculopathy after a heart transplant. Methods: Immunohistochemical staining with monoclonal F19 mouse anti-human FAP antibody was performed to identify FAP in human atherosclerotic plaques, coronary bypass atherosclerosis, and post-transplant arteriosclerosis. The presence and distribution of FAP in different types and stages of human atherosclerosis were compared. Results: There was no FAP staining in patients with no significant coronary disease. All different types of human atherosclerotic lesioning lesions showed the presence of FAP expression, with different staining patterns in advanced atherosclerotic plaque, vein graft atherosclerosis lesions, and arteriosclerosis after a heart transplant. Conclusions: These data suggest that FAP may be a potential diagnostic marker and target for interventions, not only in coronary atherosclerotic plaque, but also in other forms of coronary disease, which have distinct pathophysiologies and currently limited treatment options.

Latexin deficiency limits foam cell formation and ameliorates atherosclerosis by promoting macrophage phenotype differentiation

Latexin (LXN) is abundant in macrophages and plays critical roles in inflammation. Much is known about macrophages in atherosclerosis, the role of macrophage LXN in atherosclerosis has remained elusive. Here, the expression of LXN in human and mouse atherosclerotic lesions was examined by immunofluorescence and immunohistochemistry. LXN knockout and LXN/ApoE double-knockout mice were generated to evaluate the functions of LXN in atherosclerosis. Bone marrow transplantation (BMT) experimentation was carried out to determine whether macrophage LXN regulates atherosclerosis. We found that LXN is enriched in human and murine atherosclerotic lesions, mainly localized to macrophages. LXN deletion ameliorated atherosclerosis in ApoE-/- mice. BMT demonstrate that deletion of LXN in bone marrow protects ApoE-/- mice against atherosclerosis. Mechanistically, we found that LXN targets and inhibits JAK1 in macrophages. LXN deficiency stimulates the JAK1/STAT3/ABC transporter pathway, thereby enhancing the anti-inflammatory and anti-oxidant phenotype, cholesterol efflux, subsequently minimizing foam cell formation and atherosclerosis. Gene therapy by treatment of atherosclerotic mice with adeno-associated virus harbouring LXN-depleting shRNA attenuated the disease phenotype. In summary, our study provides new clues for the role of LXN in the pathological regulation of atherosclerosis, and determines that LXN is a target for preventing atherosclerosis, which may be a potential new anti-atherosclerosis therapeutic target.

Lysyl oxidase expression in smooth muscle cells determines the level of intima calcification in hypercholesterolemia-induced atherosclerosis

IntroductionCardiovascular calcification is an important public health issue with an unmeet therapeutic need. We had previously shown that lysyl oxidase (LOX) activity critically influences vascular wall smooth muscle cells (VSMCs) and valvular interstitial cells (VICs) calcification by affecting extracellular matrix remodeling. We have delved into the participation of LOX in atherosclerosis and vascular calcification, as well as in the mineralization of the aortic valve. MethodsImmunohistochemical and expression studies were carried out in human atherosclerotic lesions and experimental models, valves from patients with aortic stenosis, VICs, and in a genetically modified mouse model that overexpresses LOX in CMLV (TgLOXCMLV). Hyperlipemia and atherosclerosis was induced in mice through the administration of adeno-associated viruses encoding a PCSK9 mutated form (AAV-PCSK9D374Y) combined with an atherogenic diet. ResultsLOX expression is increased in the neointimal layer of atherosclerotic lesions from human coronary arteries and in VSMC-rich regions of atheromas developed both in the brachiocephalic artery of control (C57BL/6 J) animals transduced with PCSK9D374Y and in the aortic root of ApoE−/− mice. In TgLOXCMLV mice, PCSK9D374Y transduction did not significantly alter the enhanced aortic expression of genes involved in matrix remodeling, inflammation, oxidative stress and osteoblastic differentiation. Likewise, LOX transgenesis did not alter the size or lipid content of atherosclerotic lesions in the aortic arch, brachiocephalic artery and aortic root, but exacerbated calcification. Among lysyl oxidase isoenzymes, LOX is the most expressed member of this family in highly calcified human valves, colocalizing with RUNX2 in VICs. The lower calcium deposition and decreased RUNX2 levels triggered by the overexpression of the nuclear receptor NOR-1 in VICs was associated with a reduction in LOX. ConclusionsOur results show that LOX expression is increased in atherosclerotic lesions, and that overexpression of this enzyme in VSMC does not affect the size of the atheroma or its lipid content, but it does affect its degree of calcification. Further, these data suggest that the decrease in calcification driven by NOR-1 in VICs would involve a reduction in LOX. These evidences support the interest of LOX as a therapeutic target in cardiovascular calcification.

Multiplex Imaging for Cell Phenotyping of Early Human Atherosclerosis.

Previous studies using animal models and cultured cells suggest that vascular smooth muscle cells (SMCs) and inflammatory cytokines are important players in atherogenesis. Validating these findings in human disease is critical to designing therapeutics that target these components. Multiplex imaging is a powerful tool for characterizing cell phenotypes and microenvironments using biobanked human tissue sections. However, this technology has not been applied to human atherosclerotic lesions and needs to first be customized and validated. For validation, we created an 8-plex imaging panel to distinguish foam cells from SMC and leukocyte origins on tissue sections of early human atherosclerotic lesions (n=9). The spatial distribution and characteristics of these foam cells were further analyzed to test the association between SMC phenotypes and inflammation. Consistent with previous reports using human lesions, multiplex imaging showed that foam cells of SMC origin outnumbered those of leukocyte origin and were enriched in the deep intima, where the lipids accumulate in early atherogenesis. This new technology also found that apoptosis or the expression of pro-inflammatory cytokines were not more associated with foam cells than with nonfoam cells in early human lesions. More CD68+ SMCs were present among SMCs that highly expressed interleukin-1β. Highly inflamed SMCs showed a trend of increased apoptosis, whereas leukocytes expressing similar levels of cytokines were enriched in regions of extracellular matrix remodeling. The multiplex imaging method can be applied to biobanked human tissue sections to enable proof-of-concept studies and validate theories based on animal models and cultured cells.

Novel Mouse Model of Myocardial Infarction, Plaque Rupture, and Stroke Shows Improved Survival With Myeloperoxidase Inhibition.

Thromboembolic events, including myocardial infarction (MI) or stroke, caused by the rupture or erosion of unstable atherosclerotic plaques are the leading cause of death worldwide. Although most mouse models of atherosclerosis develop lesions in the aorta and carotid arteries, they do not develop advanced coronary artery lesions. Moreover, they do not undergo spontaneous plaque rupture with MI and stroke or do so at such a low frequency that they are not viable experimental models to study late-stage thrombotic events or to identify novel therapeutic approaches for treating atherosclerotic disease. This has stymied the development of more effective therapeutic approaches for reducing these events beyond what has been achieved with aggressive lipid lowering. Here, we describe a diet-inducible mouse model that develops widespread advanced atherosclerosis in coronary, brachiocephalic, and carotid arteries with plaque rupture, MI, and stroke. We characterized a novel mouse model with a C-terminal mutation in the scavenger receptor class B, type 1 (SR-BI), combined with Ldlr knockout (designated SR-BI∆CT/∆CT/Ldlr-/-). Mice were fed Western diet (WD) for 26 weeks and analyzed for MI and stroke. Coronary, brachiocephalic, and carotid arteries were analyzed for atherosclerotic lesions and indices of plaque stability. To validate the utility of this model, SR-BI∆CT/∆CT/Ldlr-/- mice were treated with the drug candidate AZM198, which inhibits myeloperoxidase, an enzyme produced by activated neutrophils that predicts rupture of human atherosclerotic lesions. SR-BI∆CT/∆CT/Ldlr-/- mice show high (>80%) mortality rates after 26 weeks of WD feeding because of major adverse cardiovascular events, including spontaneous plaque rupture with MI and stroke. Moreover, WD-fed SR-BI∆CT/∆CT/Ldlr-/- mice displayed elevated circulating high-sensitivity cardiac troponin I and increased neutrophil extracellular trap formation within lesions compared with control mice. Treatment of WD-fed SR-BI∆CT/∆CT/Ldlr-/- mice with AZM198 showed remarkable benefits, including >90% improvement in survival and >60% decrease in the incidence of plaque rupture, MI, and stroke, in conjunction with decreased circulating high-sensitivity cardiac troponin I and reduced neutrophil extracellular trap formation within lesions. WD-fed SR-BI∆CT/∆CT/Ldlr-/- mice more closely replicate late-stage clinical events of advanced human atherosclerotic disease than previous models and can be used to identify and test potential new therapeutic agents to prevent major adverse cardiac events.

Macrophage-derived FGFR1 drives atherosclerosis through PLCγ-mediated activation of NF-κB inflammatory signalling pathway.

Atherosclerosis (AS) is a leading cause of cardiovascular morbidity and mortality. Atherosclerotic lesions show increased levels of proteins associated with the fibroblast growth factor receptor (FGFR) pathway. However, the functional significance and mechanisms governed by FGFR signalling in AS are not known. In the present study, we investigated fibroblast growth factor receptor 1 (FGFR1) signalling in AS development and progression. Examination of human atherosclerotic lesions and aortas of Apoe-/- mice fed a high-fat diet (HFD) showed increased levels of FGFR1 in macrophages. We deleted myeloid-expressed Fgfr1 in Apoe-/- mice and showed that Fgfr1 deficiency reduces atherosclerotic lesions and lipid accumulations in both male and female mice upon HFD feeding. These protective effects of myeloid Fgfr1 deficiency were also observed when mice with intact FGFR1 were treated with FGFR inhibitor AZD4547. To understand the mechanistic basis of this protection, we harvested macrophages from mice and show that FGFR1 is required for macrophage inflammatory responses and uptake of oxidized LDL. RNA sequencing showed that FGFR1 activity is mediated through phospholipase-C-gamma (PLCγ) and the activation of nuclear factor-κB (NF-κB) but is independent of FGFR substrate 2. Our study provides evidence of a new FGFR1-PLCγ-NF-κB axis in macrophages in inflammatory AS, supporting FGFR1 as a potentially therapeutic target for AS-related diseases.

Decreased atherosclerosis and abdominal aortic aneurysm in mice deficient in polymeric immunoglobulin receptor

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): La Caixa Banking Foundation and Comunidad de Madrid Background Polymeric immunoglobulin receptor (PIGR) is a transmembrane protein involved in the transcytosis of polymeric immunoglobulins that is widely expressed in mucosal epithelial cells. Recent data from our group described increased PIGR levels in plasma and tissue of atherosclerotic subjects. However, the role for PIGR in the mechanisms involved in vascular remodeling has not been addressed. Purpose To analyse the role for PIGR in experimental mouse models of atherosclerosis and abdominal aortic aneurysm (AAA). Methods We analyzed PIGR expression, secretion and distribution in early atherosclerotic plaques and AAA tissues compared to healthy aortic samples, as well as in macrophages derived from the human monocytic THP-1 cell line. Next, we studied the effect of global PIGR deficiency in experimental atherosclerosis (Ldlr-/- Pigr-/- mice fed with atherogenic diet for 10 weeks). In addition, the contribution of hematopoietic PIGR was assessed in both experimental atherosclerosis and AAA (Ldlr-/- mice fed with atherogenic diet and 1 µg/Kg/min angiotensin II infusion for 28 days) by bone marrow transplantation experiments. Finally, bone marrow-derived macrophages (BMDMs) from Pigr-/- and control mice were isolated to assess their inflammatory expression profile and modulation of polarization in response to oxidized LDL (ox-LDL), as well as their ability to promote foam cell formation. Results PIGR expression was increased in the intima of early human atherosclerotic lesions and showed colocalization with CD68+ expression. PIGR expression was also increased during the in vitro differentiation of THP-1 monocytes to macrophages with phorbol myristate acetate. Both global and hematopoietic-specific PIGR deficient mice displayed reduced plaque size in the aortic sinuses as well as a strong decrease in macrophage infiltration (CD68+ cells), while no changes in smooth muscle cells (α-SMA+ cells) and collagen content were observed. Regarding AAA, increased PIGR levels were found in human AAA tissues, associated with infiltrating CD68+ cells. PIGR deficiency in hematopoietic cells also showed significantly reduced AAA dilatation and reduced macrophage infiltration. In vitro experiments with BMDMs obtained from Pigr-/- mice and stimulated with ox-LDL showed reduced proinflammatory gene expression (TNF-a and IL-6) and M1 markers (iNOS and CD11c) as well as diminished foam cell formation. Conclusions PIGR deficiency in hematopoietic cells decreases atherosclerosis and AAA progression by modulating macrophage inflammatory responses, suggesting a novel proinflammatory role for PIGR in vascular pathologies. Future experiments will test the potential therapeutic effect of modulating PIGR to dampen the inflammatory profile in vascular diseases.Results in human and mouse studies

Human atherosclerotic plaque transcriptomics reveals endothelial beta-2 spectrin as a potential regulator a leaky plaque microvasculature phenotype

The presence of atherosclerotic plaque vessels is a critical factor in plaque destabilization. This may be attributable to the leaky phenotype of these microvessels, although direct proof for this notion is lacking. In this study, we investigated molecular and cellular patterns of stable and hemorrhaged human plaque to identify novel drivers of intraplaque vessel dysfunction. From transcriptome data of a human atherosclerotic lesion cohort, we reconstructed a co-expression network, identifying a gene module strongly and selectively correlated with both plaque microvascular density and inflammation. Spectrin Beta Non-Erythrocytic 1 (sptbn1) was identified as one of the central hubs of this module (along with zeb1 and dock1) and was selected for further study based on its predominant endothelial expression. Silencing of sptbn1 enhanced leukocyte transmigration and vascular permeability in vitro, characterized by an increased number of focal adhesions and reduced junctional VE-cadherin. In vivo, sptbn1 knockdown in zebrafish impaired the development of the caudal vein plexus. Mechanistically, increased substrate stiffness was associated with sptbn1 downregulation in endothelial cells in vitro and in human vessels. Plaque SPTBN1 mRNA and protein expression were found to correlate with an enhanced presence of intraplaque hemorrhage and future cardiovascular disease (CVD) events during follow-up. In conclusion, we identify SPTBN1 as a central hub gene in a gene program correlating with plaque vascularisation. SPTBN1 was regulated by substrate stiffness in vitro while silencing blocked vascular development in vivo, and compromised barrier function in vitro. Together, SPTBN1 is identified as a new potential regulator of the leaky phenotype of atherosclerotic plaque microvessels.

Abstract 124: IRG1-Itaconate Axis Protects From Cholesterol-Induced Inflammation And Atherosclerosis

Atherosclerosis, the major underlying cause of cardiovascular disease (CVD) mortality, is fueled by a failure to resolve lipid-driven inflammation within the vessel wall. Understanding the immunometabolic mechanisms underpinning sustained inflammation within this microenvironment is needed for the development of novel targeted therapies. Immune responsive gene 1 (IRG) is an enzyme that diverts the TCA cycle intermediate, cis-aconitate, to produce itaconate, a metabolite with anti-microbial and anti-inflammatory functions. We used a translational approach to investigate the therapeutic potential of the Irg1-itaconate axis for human atherosclerosis. Using single cell RNA-sequencing, we found that IRG1 is upregulated in human coronary atherosclerotic lesions compared to patient-matched healthy vasculature, and is primarily expressed by plaque monocytes and macrophages. In mouse models of atherosclerosis, Irg1 was expressed by plaque monocytes, macrophage and neutrophils, but declined with disease progression. Global or hematopoietic Irg1 -deficiency increased atherosclerosis burden, plaque lipid content, and expression of interleukin (IL)-1b. Mechanistically, absence of Irg1 potentiates lipid accumulation and lipid-mediated inflammation via a feed-forward cycle involving increased neutrophil extracellular trap (NET) formation, NET-induced NLRP3 inflammasome priming in macrophages, and subsequent IL-1b release. Conversely, supplementation of the Irg1 pathway using the derivative 4-octyl itaconate (4-OI) reduced atherosclerotic inflammation and promoted beneficial plaque remodeling in mice. To assess the therapeutic potential of 4-OI in humans, we leveraged a validated systems-immunology approach to investigate CVD-related inflammation ex vivo . Using high dimensional single cell analyses, we showed that 4-OI supplementation attenuated pro-inflammatory phospho-signaling in human peripheral blood mononuclear cells treated with plasma from CVD patients, and caused an anti-inflammatory rewiring of macrophage populations. Our data highlight the relevance of pursuing Irg1 -itaconate axis supplementation as a therapeutic approach to treat atherosclerosis in humans.

Abstract 2060: Hv1 Contributes To Atherosclerosis

Atherosclerosis is a complex process that involves the interaction between oxidized low-density lipoprotein (oxLDL) and macrophage. It is an inflammatory disease of the large artery driven by macrophage activation and infiltration. Through scavenger receptors, macrophages can uptake oxLDL and other lipids, leading to foam cell formation and the progression of atherosclerosis. Hv1 proton channel is highly expressed in phagocytes and promotes NADPH oxidase-derived ROS (reactive oxygen species) production. So far, most of the research on Hv1 has been focused on immune, reproductive, and neurological diseases. However, the role of Hv1 in cardiovascular diseases, such as arteriosclerosis, remains unclear. To explore the potential roles of Hv1 in atherosclerosis, we detected the expression of Hv1 in atherosclerotic lesions. It was shown that Hv1 is abundantly expressed in human and murine atherosclerotic lesions and highly expressed in macrophages in the aortic root lesions. In addition, Hv1 knockout mice fed with a high-fat western diet exhibit remarkably decreased atherosclerotic plaques compared with control mice. Moreover, deficiency of Hv1 in macrophages impedes macrophage phagocytosis and foam cell formation essential for atherosclerosis development, and Hv1 enhances macrophage ROS production associated with the progression of atherosclerosis. Our results suggested that Hv1 is a pro-atherosclerotic factor and contributes to the pathogenesis of atherosclerosis. The research identified a new function of the Hv1 channel in human diseases and may present a novel target against atherosclerosis and atherosclerosis-related diseases.

Abstract 2079: Single-cell And Spatially Resolved Transcriptome Analysis Reveals A Novel Lncrna Regulator Of Human Atherosclerosis

Cardiovascular diseases, such as atherosclerosis, are the major cause of death in Western societies. Still, molecular mechanisms of plaque destabilization remain unclear. Vascular Smooth Muscle Cells (VSMCs) are the most abundant cell type in atherosclerotic lesions. These cells keep their plasticity also with disease progression and are, therefore, an ideal target cell type for potential therapies. Long non-coding RNAs (lncRNAs) are one example of highly cell type- and disease-state-specific novel molecular modulators. We utilized combined total (bulk) RNA and single cell (sc) RNA sequencing of advanced human carotid artery lesions (patients who underwent carotid endarterectomy in our vascular surgery clinic) to discover novel regulators. Additionally, we performed hybridization-based RNA in situ sequencing (HybRISS, Xenium) to indicate where these genes are located within the plaques. We also performed scSeq in our inducible carotid artery plaque rupture mice ( ApoE-/- ). In vivo and in vitro modulation (KD; knock-down) of the newly identified lncRNA DLX6-AS1 ( D istal- L ess Homeobo x 6 A nti s ense 1 ) using Antisense LNA (Locked nucleic acid) GapmeRs is performed in this mouse model as well as in primary human VSMC culture. DLX6-AS1 shows a highly specific expression pattern in a distinct sub-cluster of VSMCs, as well as a striking location within human atherosclerotic lesions shown by spatial transcriptomics in advanced plaques. DLX6-AS1 is mainly expressed in the nucleus of cells, and KD of this lncRNA leads to changes in VSMC behavior in vitro and in vivo . The KD also has only little effect on the other genes of this locus, DLX6 and DLX5 ( D istal- L ess Homeobo x 6 and 5 ) We found Dlx6os1 ( D istal- l ess homeobo x 6, o pposite s trand 1 ) in our scRNA-seq dataset of the inducible carotid artery plaque rupture mice ( ApoE-/- ) where the KD leads to an increased plaque rupture rate. Taken together, our datasets, methods, and animal models demonstrate that utilizing bulk- and scRNA-seq data, together with spatially resolved sequencing methods, are powerful tools to identify and characterize novel lncRNA regulators that can facilitate fate decisions in VSMCs in atherosclerosis. DLX6-AS1 is one of these novel regulators and will be further analyzed in vivo and in vitro .

Abstract 1045: Using Multiplex Imaging For Cell Phenotyping Of Early Human Atherosclerosis

Background: In the past few years, animal models and cultured cells have shown that smooth muscle cells (SMCs) and inflammatory cytokines are important new players in atherosclerotic disease. Validating the roles of these new players in human atherogenesis is crucial for the development of therapeutics targeting them. Multiplex imaging is a powerful tool for mapping cell phenotypes and microenvironment in tissue sections, enabling proof-of-concept studies using biobanked human specimens. However, this technology has seldom been applied to human atherosclerotic lesions. This study is a trial to benchmark the application of the multiplex imaging platform PhenoCycler to biobanked human coronary lesions. We hypothesize that this technology is a powerful tool to prove theories raised by previous studies: SMCs initiate foam cell formation and inflammation is associated with phenotypic switching in SMCs. Methods: We created an 8-plex imaging panel to map lesion cells previously identified as key players in atherogenesis, including foam cells from SMC and macrophage origins, CD68 + SMCs, apoptotic cells, and cells expressing inflammatory cytokines interleukin-1β and tumor necrosis factor α. They were imaged simultaneously on each section of early human lesions (n=9) to test theories related to foam cell formation, phenotypic transition, and inflammatory cytokines. Results: Foam cells of SMC origin greatly outnumbered those of macrophage origin and were enriched in the deep intima, where lipids accumulate in early atherogenesis, distinct from macrophage foam cells in the superficial intima. A higher presence of CD68 + SMCs was observed among lesion SMCs highly expressing interleukin-1β, but not TNF-α. Highly inflamed SMCs exhibited a trend of increased apoptosis compared to macrophages with similar cytokine levels. Conclusions: Our multiplex imaging results confirmed that SMCs form the majority of foam cells in early atherogenesis, and their phenotypic transition to macrophage-like is related to inflammation. Applying multiplex imaging to biobanked human lesions unlocks opportunities to prove that theories based on animal models and cultured cells apply to human atherogenesis.

Resident Memory T Cells in the Atherosclerotic Lesion Associate With Reduced Macrophage Content and Increased Lesion Stability.

Tissue resident memory T (TRM) cells are a T-cell subset that resides at the site of prior antigen recognition to protect the body against reoccurring encounters. Besides their protective function, TRM cells have also been implicated in inflammatory disorders. TRM cells are characterized by the expression of CD69 and transcription factors Hobit (homolog of Blimp-1 [B lymphocyte-induced maturation protein 1] in T cells) and Blimp-1. As the majority of T cells in the arterial intima expresses CD69, TRM cells may contribute to the pathogenesis of atherosclerosis as well. Here, we aimed to assess the presence and potential role of TRM cells in atherosclerosis. To identify TRM cells in human atherosclerotic lesions, a single-cell RNA-sequencing data set was interrogated, and T-cell phenotypes were compared with that of integrated predefined TRM cells. The presence and phenotype of TRM in atherosclerotic lesions was corroborated using a mouse model that enabled tracking of Hobit-expressing TRM cells. To explore the function of TRM cells during atherogenesis, RAG1-/- (recombination activating gene 1 deficient) LDLr-/- (low-density lipoprotein receptor knockout) mice received a bone marrow transplant from HobitKO/CREBlimp-1flox/flox mice, which exhibit abrogated TRM cell formation, whereafter the mice were fed a Western-type diet for 10 weeks. Human atherosclerotic lesions contained T cells that exhibited a TRM cell-associated gene signature. Moreover, a fraction of these T cells clustered together with predefined TRM cells upon integration. The presence of Hobit-expressing TRM cells in the atherosclerotic lesion was confirmed in mice. These lesion-derived TRM cells were characterized by the expression of CD69 and CD49α. Moreover, we demonstrated that this small T-cell subset significantly affects lesion composition, by reducing the amount of intralesional macrophages and increasing collagen content. TRM cells, characterized by the expression of CD69 and CD49α, constitute a minor population in atherosclerotic lesions and are associated with increased lesion stability in a Hobit and Blimp-1 knockout mouse model.

Single-cell ‘omic profiles of human aortic endothelial cells in vitro and human atherosclerotic lesions ex vivo reveal heterogeneity of endothelial subtype and response to activating perturbations

Heterogeneity in endothelial cell (EC) sub-phenotypes is becoming increasingly appreciated in atherosclerosis progression. Still, studies quantifying EC heterogeneity across whole transcriptomes and epigenomes in both in vitro and in vivo models are lacking. Multiomic profiling concurrently measuring transcriptomes and accessible chromatin in the same single cells was performed on six distinct primary cultures of human aortic ECs (HAECs) exposed to activating environments characteristic of the atherosclerotic microenvironment in vitro. Meta-analysis of single-cell transcriptomes across 17 human ex vivo arterial specimens was performed and two computational approaches quantitatively evaluated the similarity in molecular profiles between heterogeneous in vitro and ex vivo cell profiles. HAEC cultures were reproducibly populated by four major clusters with distinct pathway enrichment profiles and modest heterogeneous responses: EC1-angiogenic, EC2-proliferative, EC3-activated/mesenchymal-like, and EC4-mesenchymal. Quantitative comparisons between in vitro and ex vivo transcriptomes confirmed EC1 and EC2 as most canonically EC-like, and EC4 as most mesenchymal with minimal effects elicited by siERG and IL1B. Lastly, accessible chromatin regions unique to EC2 and EC4 were most enriched for coronary artery disease (CAD)-associated single-nucleotide polymorphisms from Genome Wide Association Studies (GWAS), suggesting that these cell phenotypes harbor CAD-modulating mechanisms. Primary EC cultures contain markedly heterogeneous cell subtypes defined by their molecular profiles. Surprisingly, the perturbations used here only modestly shifted cells between subpopulations, suggesting relatively stable molecular phenotypes in culture. Identifying consistently heterogeneous EC subpopulations between in vitro and ex vivo models should pave the way for improving in vitro systems while enabling the mechanisms governing heterogeneous cell state decisions.

Single-cell 'omic profiles of human aortic endothelial cells in vitro and human atherosclerotic lesions ex vivo reveal heterogeneity of endothelial subtype and response to activating perturbations.

Heterogeneity in endothelial cell (EC) sub-phenotypes is becoming increasingly appreciated in atherosclerosis progression. Still, studies quantifying EC heterogeneity across whole transcriptomes and epigenomes in both in vitro and in vivo models are lacking. Multiomic profiling concurrently measuring transcriptomes and accessible chromatin in the same single cells was performed on six distinct primary cultures of human aortic ECs (HAECs) exposed to activating environments characteristic of the atherosclerotic microenvironment in vitro. Meta-analysis of single-cell transcriptomes across 17 human ex vivo arterial specimens was performed and two computational approaches quantitatively evaluated the similarity in molecular profiles between heterogeneous in vitro and ex vivo cell profiles. HAEC cultures were reproducibly populated by four major clusters with distinct pathway enrichment profiles and modest heterogeneous responses: EC1-angiogenic, EC2-proliferative, EC3-activated/mesenchymal-like, and EC4-mesenchymal. Quantitative comparisons between in vitro and ex vivo transcriptomes confirmed EC1 and EC2 as most canonically EC-like, and EC4 as most mesenchymal with minimal effects elicited by siERG and IL1B. Lastly, accessible chromatin regions unique to EC2 and EC4 were most enriched for coronary artery disease (CAD)-associated single-nucleotide polymorphisms from Genome Wide Association Studies (GWAS), suggesting that these cell phenotypes harbor CAD-modulating mechanisms. Primary EC cultures contain markedly heterogeneous cell subtypes defined by their molecular profiles. Surprisingly, the perturbations used here only modestly shifted cells between subpopulations, suggesting relatively stable molecular phenotypes in culture. Identifying consistently heterogeneous EC subpopulations between in vitro and ex vivo models should pave the way for improving in vitro systems while enabling the mechanisms governing heterogeneous cell state decisions.

The IRG1–itaconate axis protects from cholesterol-induced inflammation and atherosclerosis

Atherosclerosis is fueled by a failure to resolve lipid-driven inflammation within the vasculature that drives plaque formation. Therapeutic approaches to reverse atherosclerotic inflammation are needed to address the rising global burden of cardiovascular disease (CVD). Recently, metabolites have gained attention for their immunomodulatory properties, including itaconate, which is generated from the tricarboxylic acid-intermediate cis-aconitate by the enzyme Immune Responsive Gene 1 (IRG1/ACOD1). Here, we tested the therapeutic potential of the IRG1-itaconate axis for human atherosclerosis. Using single-cell RNA sequencing (scRNA-seq), we found that IRG1 is up-regulated in human coronary atherosclerotic lesions compared to patient-matched healthy vasculature, and in mouse models of atherosclerosis, where it is primarily expressed by plaque monocytes, macrophages, and neutrophils. Global or hematopoietic Irg1-deficiency in mice increases atherosclerosis burden, plaque macrophage and lipid content, and expression of the proatherosclerotic cytokine interleukin (IL)-1β. Mechanistically, absence of Irg1 increased macrophage lipid accumulation, and accelerated inflammation via increased neutrophil extracellular trap (NET) formation and NET-priming of the NLRP3-inflammasome in macrophages, resulting in increased IL-1β release. Conversely, supplementation of the Irg1-itaconate axis using 4-octyl itaconate (4-OI) beneficially remodeled advanced plaques and reduced lesional IL-1β levels in mice. To investigate the effects of 4-OI in humans, we leveraged an ex vivo systems-immunology approach for CVD drug discovery. Using CyTOF and scRNA-seq of peripheral blood mononuclear cells treated with plasma from CVD patients, we showed that 4-OI attenuates proinflammatory phospho-signaling and mediates anti-inflammatory rewiring of macrophage populations. Our data highlight the relevance of pursuing IRG1-itaconate axis supplementation as a therapeutic approach for atherosclerosis in humans.