In advanced atherosclerosis, macrophage apoptosis coupled with defective phagocytic clearance of the apoptotic cells (efferocytosis) promotes plaque necrosis, which precipitates acute ...atherothrombotic cardiovascular events. Oxidative and endoplasmic reticulum (ER) stress in macrophages are important causes of advanced lesional macrophage apoptosis. We now show that proapoptotic oxidative/ER stress inducers trigger another stress reaction in macrophages, autophagy. Inhibition of autophagy by silencing ATG5 or other autophagy mediators enhances apoptosis and NADPH oxidase-mediated oxidative stress while at the same time rendering the apoptotic cells less well recognized by efferocytes. Most importantly, macrophage ATG5 deficiency in fat-fed Ldlr−/− mice increases apoptosis and oxidative stress in advanced lesional macrophages, promotes plaque necrosis, and worsens lesional efferocytosis. These findings reveal a protective process in oxidatively stressed macrophages relevant to plaque necrosis, suggesting a mechanism-based strategy to therapeutically suppress atherosclerosis progression and its clinical sequelae.
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► Proapoptotic oxidative stress induces autophagy in macrophages (Mϕs) ► Inhibition of autophagy enhances oxidative stress and apoptosis in Mϕs ► Atheromata of Mϕ-Atg5−/−Ldlr−/− mice have increased apoptosis and plaque necrosis ► Apoptotic Atg5−/− Mϕs are poorly recognized by phagocytes in vitro and in atheromata
Plaque microvascularization and increased endothelial permeability are key players in the development of atherosclerosis, from the initial stages of plaque formation to the occurrence of acute ...cardiovascular events. First, endothelial dysfunction and increased permeability facilitate the entry of diverse inflammation-triggering molecules and particles such as low-density lipoproteins into the artery wall from the arterial lumen and vasa vasorum (VV). Recognition of entering particles by resident phagocytes in the vessel wall triggers a maladaptive inflammatory response that initiates the process of local plaque formation. The recruitment and accumulation of inflammatory cells and the subsequent release of several cytokines, especially from resident macrophages, stimulate the expansion of existing VV and the formation of new highly permeable microvessels. This, in turn, exacerbates the deposition of pro-inflammatory particles and results in the recruitment of even more inflammatory cells. The progressive accumulation of leukocytes in the intima, which trigger proliferation of smooth muscle cells in the media, results in vessel wall thickening and hypoxia, which further stimulates neoangiogenesis of VV. Ultimately, this highly inflammatory environment damages the fragile plaque microvasculature leading to intraplaque hemorrhage, plaque instability, and eventually, acute cardiovascular events. This review will focus on the pivotal roles of endothelial permeability, neoangiogenesis, and plaque microvascularization by VV during plaque initiation, progression, and rupture. Special emphasis will be given to the underlying molecular mechanisms and potential therapeutic strategies to selectively target these processes.
Noncoding RNAs (long noncoding RNAs and small RNAs) are emerging as critical modulators of phenotypic changes associated with physiological and pathological contexts in a variety of cardiovascular ...diseases (CVDs). Although it has been well established that hereditable genetic alterations and exposure to risk factors are crucial in the development of CVDs, other critical regulators of cell function impact on disease processes. Here we discuss noncoding RNAs have only recently been identified as key players involved in the progression of disease. In particular, we discuss micro RNA (miR)-143/145 since they represent one of the most characterised microRNA clusters regulating smooth muscle cell (SMC) differentiation and phenotypic switch in response to vascular injury and remodelling. MiR143HG is a well conserved long noncoding RNA (lncRNA), which is the host gene for miR-143/145 and recently implicated in cardiac specification during heart development. Although the lncRNA-miRNA interactions have not been completely characterised, their crosstalk is now beginning to emerge and likely requires further research focus. In this review we give an overview of the biology of the genomic axis that is miR-143/145 and MiR143HG, focusing on their important functional role(s) in the cardiovascular system.
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Atherosclerosis, the leading cause of cardiovascular death, is driven by hyperlipidemia, inflammation and aggravated by aging. As chaperone-mediated autophagy (CMA), a selective type of lysosomal ...degradation for intracellular proteins, diminishes with age and is inhibited by lipid excess, we studied if the decline in CMA could contribute to atherosclerosis pathogenesis. We found that CMA declines in human and murine vasculature with disease progression. Inhibition and reactivation of CMA using transgenic mouse models establishes a protective effect of CMA against atherogenesis. CMA upregulation ameliorates both systemic metabolic parameters, and vascular cell function. Our work suggests CMA reactivation could be a viable therapeutic strategy to prevent and reduce cardiovascular disease.
Abstract
Cellular characteristics and their adjustment to a state of disease have become more evident due to recent advances in imaging, fluorescent reporter mice, and whole genome RNA sequencing. ...The uncovered cellular heterogeneity and/or plasticity potentially complicates experimental studies and clinical applications, as markers derived from whole tissue ‘bulk’ sequencing is unable to yield a subtype transcriptome and specific markers. Here, we propose definitions on heterogeneity and plasticity, discuss current knowledge thereof in the vasculature and how this may be improved by single-cell sequencing (SCS). SCS is emerging as an emerging technique, enabling researchers to investigate different cell populations in more depth than ever before. Cell selection methods, e.g. flow assisted cell sorting, and the quantity of cells can influence the choice of SCS method. Smart-Seq2 offers sequencing of the complete mRNA molecule on a low quantity of cells, while Drop-seq is possible on large numbers of cells on a more superficial level. SCS has given more insight in heterogeneity in healthy vasculature, where it revealed that zonation is crucial in gene expression profiles among the anatomical axis. In diseased vasculature, this heterogeneity seems even more prominent with discovery of new immune subsets in atherosclerosis as proof. Vascular smooth muscle cells and mesenchymal cells also share these plastic characteristics with the ability to up-regulate markers linked to stem cells, such as Sca-1 or CD34. Current SCS studies show some limitations to the number of replicates, quantity of cells used, or the loss of spatial information. Bioinformatical tools could give some more insight in current datasets, making use of pseudo-time analysis or RNA velocity to investigate cell differentiation or polarization. In this review, we discuss the use of SCS in unravelling heterogeneity in the vasculature, its current limitations and promising future applications.
Only recently have we begun to appreciate the importance and complexity of the non-coding genome, owing in some part to truly significant advances in genomic technology such as RNA sequencing and ...genome-wide profiling studies. Previously thought to be non-functional transcriptional "noise," non-coding RNAs (ncRNAs) are now known to play important roles in many diverse biological pathways, not least in vascular disease. While microRNAs (miRNA) are known to regulate protein-coding gene expression principally through mRNA degradation, long non-coding RNAs (lncRNAs) can activate and repress genes by a variety of mechanisms at both transcriptional and translational levels. These versatile molecules, with complex secondary structures, may interact with chromatin, proteins, and other RNA to form complexes with an array of functional consequences. A body of emerging evidence indicates that both classes of ncRNAs regulate multiple physiological and pathological processes in vascular physiology and disease. While dozens of miRNAs are now implicated and described in relative mechanistic depth, relatively fewer lncRNAs are well described. However, notable examples include
,
, and
in vascular smooth muscle cells;
in endothelial cells; and mitochondrial lncRNA
as a powerful biomarker. Due to such ubiquitous involvement in pathology and well-known biogenesis and functional genetics, novel miRNA-based therapies and delivery methods are now in development, including some early stage clinical trials. Although lncRNAs may hold similar potential, much more needs to be understood about their relatively complex molecular behaviours before realistic translation into novel therapies. Here, we review the current understanding of the mechanism and function of ncRNA, focusing on miRNAs and lncRNAs in vascular disease and atherosclerosis. We discuss existing therapies and current delivery methods, emphasising the importance of miRNAs and lncRNAs as effectors and biomarkers in vascular pathology.
Atherosclerosis is the underlying etiology of cardiovascular disease, the leading cause of death worldwide. Atherosclerosis is a heterogeneous disease in which only a small fraction of lesions lead ...to heart attack, stroke, or sudden cardiac death. A distinct type of plaque containing large necrotic cores with thin fibrous caps often precipitates these acute events. Here, we show that Ca2+/calmodulin-dependent protein kinase γ (CaMKIIγ) in macrophages plays a major role in the development of necrotic, thin-capped plaques. Macrophages in necrotic and symptomatic atherosclerotic plaques in humans as well as advanced atherosclerotic lesions in mice demonstrated activation of CaMKII. Western diet-fed LDL receptor-deficient (Ldlr-/-) mice with myeloid-specific deletion of CaMKII had smaller necrotic cores with concomitantly thicker collagen caps. These lesions demonstrated evidence of enhanced efferocytosis, which was associated with increased expression of the macrophage efferocytosis receptor MerTK. Mechanistic studies revealed that CaMKIIγ-deficient macrophages and atherosclerotic lesions lacking myeloid CaMKIIγ had increased expression of the transcription factor ATF6. We determined that ATF6 induces liver X receptor-α (LXRα), an Mertk-inducing transcription factor, and that increased MerTK expression and efferocytosis in CaMKIIγ-deficient macrophages is dependent on LXRα. These findings identify a macrophage CaMKIIγ/ATF6/LXRα/MerTK pathway as a key factor in the development of necrotic atherosclerotic plaques.
Peroxisome proliferator-activated receptor δ (PPARδ) is a critical regulator of energy metabolism in the heart. Here, we propose a mechanism that integrates two deleterious characteristics of heart ...failure, hypoxia and a metabolic shift toward glycolysis, involving the microRNA cluster miR-199a∼214 and PPARδ. We demonstrate that under hemodynamic stress, cardiac hypoxia activates DNM3os, a noncoding transcript that harbors the microRNA cluster miR-199a∼214, which shares PPARδ as common target. To address the significance of miR-199a∼214 induction and concomitant PPARδ repression, we performed antagomir-based silencing of both microRNAs and subjected mice to biomechanical stress to induce heart failure. Remarkably, antagomir-treated animals displayed improved cardiac function and restored mitochondrial fatty acid oxidation. Taken together, our data suggest a mechanism whereby miR-199a∼214 actively represses cardiac PPARδ expression, facilitating a metabolic shift from predominant reliance on fatty acid utilization in the healthy myocardium toward increased reliance on glucose metabolism at the onset of heart failure.
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•Myocardial hypoxia induces expression of the miR-199a:214 cluster•miR-199a:214 downregulates several mitochondrial and cardiac targets, including PPARδ•Downregulation of PPARδ provokes glycolytic metabolism in heart failure•Antagomir-mediated therapeutic inhibition of miR-199a:214 ameliorates heart failure
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