Proefferocytic Therapy Promotes Transforming Growth Factor-β Signaling and Prevents Aneurysm Formation

Intracellular and extracellular synergistic therapy for restoring macrophage functions via anti-CD47 antibody-conjugated bifunctional nanoparticles in atherosclerosis

Atherosclerosis is a significant contributor to global cardiovascular disease. Reducing the formation of atherosclerotic plaque effectively can lead to a decrease in cardiovascular diseases. Therefore, controlling macrophage function is crucial. This study presents the creation of a bifunctional nanoparticle that is specific to macrophages to achieve intracellular and extracellular synergistic therapy for restoring macrophage functions. The nanoparticle is conjugated with anti-CD47 antibody to modulate extracellular CD47-SIRPα phagocytic signaling axis on the outer surface of macrophages and encapsulates the NLRP3 inhibitor (CY-09) to regulate intracellular inflammation response of macrophages. The results showed that the nanoparticles accumulate in the atherosclerotic plaque, alter macrophage phagocytosis, inhibit NLRP3 inflammasome activation, and decrease the plaque burden in Apoe-/- mice whilst ensuring safety. Examination of single-cell RNA sequencing indicates that this multifunctional nanoparticle decreases the expression of genes linked to inflammation and manages inflammatory pathways in the plaque lesion. This study proposes a synergistic therapeutic approach that utilizes a bifunctional nanoparticle, conjugated with anti-CD47, to regulate the microenvironment of plaques.

SIRPα controls CD47-dependent platelet clearance in mice and humans

Over the last decade, more data has revealed that increased surface expression of the "don't eat me" CD47 protein on cancer cells plays a role in immune evasion and tumor progression, with CD47 blockade emerging as a new therapy in immuno-oncology. CD47 is critical in regulating cell homeostasis and clearance, as binding of CD47 to the inhibitory receptor SIRPα can prevent phagocytosis and macrophage-mediated cell clearance. The purpose of this study was to examine the role of the CD47-SIRPα signal in platelet homeostasis and clearance. Therapeutic reagents targeting the CD47-SIRPα axis are very promising for treatment of hematologic malignancies and solid tumors, but lead to transient anemia or thrombocytopenia in a subset of patients. We found that platelet homeostatic clearance is regulated through the CD47-SIRPα axis and that therapeutic blockade to disrupt this interaction in mice and in humans has a significant impact on platelet levels. Furthermore, we identified genetic variations at the SIRPA locus that impact platelet levels in humans such that higher SIRPA gene expression is associated with higher platelet levels. SIRPA expression at either end of the normal range may affect clinical outcomes of treatment with anti-CD47 therapy.

Smooth Muscle Heterogeneity and Plasticity in Health and Aortic Aneurysmal Disease

Vascular smooth muscle cells (VSMCs) are the predominant cell type in the medial layer of the aorta, which plays a critical role in the maintenance of aortic wall integrity. VSMCs have been suggested to have contractile and synthetic phenotypes and undergo phenotypic switching to contribute to the deteriorating aortic wall structure. Recently, the unprecedented heterogeneity and diversity of VSMCs and their complex relationship to aortic aneurysms (AAs) have been revealed by high-resolution research methods, such as lineage tracing and single-cell RNA sequencing. The aortic wall consists of VSMCs from different embryonic origins that respond unevenly to genetic defects that directly or indirectly regulate VSMC contractile phenotype. This difference predisposes to hereditary AAs in the aortic root and ascending aorta. Several VSMC phenotypes with different functions, for example, secreting VSMCs, proliferative VSMCs, mesenchymal stem cell-like VSMCs, immune-related VSMCs, proinflammatory VSMCs, senescent VSMCs, and stressed VSMCs are identified in non-hereditary AAs. The transformation of VSMCs into different phenotypes is an adaptive response to deleterious stimuli but can also trigger pathological remodeling that exacerbates the pathogenesis and development of AAs. This review is intended to contribute to the understanding of VSMC diversity in health and aneurysmal diseases. Papers that give an update on VSMC phenotype diversity in health and aneurysmal disease are summarized and recent insights on the role of VSMCs in AAs are discussed.

Mechanisms of efferocytosis in determining inflammation resolution: Therapeutic potential and the association with cardiovascular disease

Efferocytosis is defined as the clearance of apoptotic cells (ACs) in physiological and pathological states and is performed by efferocytes, such as macrophages. Efferocytosis can lead to the resolution of inflammation and restore tissue homoeostasis; however, the mechanisms of efferocytosis in determining inflammation resolution are still not completely understood, and the effects of efferocytosis on other proresolving properties need to be explored and explained. In this review, the process of efferocytosis will be summarized briefly, and then these mechanisms and effects will be thoroughly discussed. In addition, the association between the mechanisms of efferocytosis in determining inflammation resolution and cardiovascular diseases will also be reviewed, as an understanding of this association may provide information on novel treatment targets.

2021 Jeffrey M. Hoeg Award Lecture: Defining the Role of Efferocytosis in Cardiovascular Disease: A Focus on the CD47 (Cluster of Differentiation 47) Axis

A key feature of atherogenesis is the accumulation of diseased and dying cells within the lesional necrotic core. While the burden of intraplaque apoptotic cells may be driven in part by an increase in programmed cell death, mounting evidence suggests that their presence may primarily be dictated by a defect in programmed cell removal, or efferocytosis. In this brief review, we will summarize the evidence suggesting that inflammation-dependent changes within the plaque render target cells inedible and reduce the appetite of lesional phagocytes. We will present the genetic causation studies, which indicate these phenomena promote lesion expansion and plaque vulnerability, and the interventional data which suggest that these processes can be reversed. Particular emphasis is provided related to the antiphagocytic CD47 (cluster of differentiation 47) do not eat me axis, which has emerged as a novel antiatherosclerotic translational target that is predicted to provide benefit independent of traditional cardiovascular risk factors.

Maresin 1 activates LGR6 signaling to inhibit smooth muscle cell activation and attenuate murine abdominal aortic aneurysm formation

The specialized pro-resolving lipid mediator maresin 1 (MaR1) is involved in the resolution phase of tissue inflammation. It was hypothesized that exogenous administration of MaR1 would attenuate abdominal aortic aneurysm (AAA) growth in a cytokine-dependent manner via LGR6 receptor signaling and macrophage-dependent efferocytosis of smooth muscle cells (SMCs). AAAs were induced in C57BL/6 wild-type (WT) mice and smooth muscle cell specific TGF-β2 receptor knockout (SMC-TGFβr2^-/- ) mice using a topical elastase AAA model. MaR1 treatment significantly attenuated AAA growth as well as increased aortic SMC α-actin and TGF-β2 expressions in WT mice, but not SMC-TGFβr2^-/- mice, compared to vehicle-treated mice. In vivo inhibition of LGR6 receptors obliterated MaR1-dependent protection in AAA formation and SMC α-actin expression. Furthermore, MaR1 upregulated macrophage-dependent efferocytosis of apoptotic SMCs in murine aortic tissue during AAA formation. In vitro studies demonstrate that MaR1-LGR6 interaction upregulates TGF-β2 expression and decreases MMP2 activity during crosstalk of macrophage-apoptotic SMCs. In summary, these results demonstrate that MaR1 activates LGR6 receptors to upregulate macrophage-dependent efferocytosis, increases TGF-β expression, preserves aortic wall remodeling and attenuate AAA formation. Therefore, this study demonstrates the potential of MaR1-LGR6-mediated mitigation of vascular remodeling through increased efferocytosis of apoptotic SMCs via TGF-β2 to attenuate AAA formation.

TGF-β signaling and microRNA cross-talk regulates abdominal aortic aneurysm progression

Abdominal aortic aneurysms (AAA) are permanent and irreversible local dilatations of the abdominal aortic wall. Recent data indicate that the transforming growth factor-beta (TGF-β) signaling pathway exerts a protective effect on the development of AAA. Some dysregulated microRNAs (miRNA) also appear involved in the expansion of AAA and miRNA-based therapeutics have been shown to effectively inhibit this process. New evidence has revealed that TGF-β signaling and miRNA interaction may of physiologic and pathophysiologic significance including the progression of AAA. As such, miRNA that regulate TGF-β signaling may hold promise as potential therapeutic targets. This review explores potential crosstalk between TGF-β signaling and miRNA in AAA in order improve our understanding of this pathology and explore development of potential therapeutic targets.

Macrophage Biology in Cardiovascular Diseases

Macrophages have a key functional role in the pathogenesis of various cardiovascular diseases, such as atherosclerosis and aortic aneurysms. Their accumulation within the vessel wall leads to sustained local inflammatory responses characterized by secretion of chemokines, cytokines, and matrix protein degrading enzymes. Here, we summarize some recent findings on macrophage contribution to cardiovascular disease. We focus on the origin, survival/death, and phenotypic switching of macrophages within vessel walls.

Targeting senescent cells to attenuate cardiovascular disease progression

Cardiovascular disease (CVD) is the most common disease to increase as life expectancy increases. Most high-profile pharmacological treatments for age-related CVD have led to inefficacious results, implying that novel approaches to treating these pathologies are needed. Emerging data have demonstrated that senescent cardiovascular cells, which are characterized by irreversible cell cycle arrest and a distinct senescence-associated secretory phenotype, accumulate in aged or diseased cardiovascular systems, suggesting that they may impair cardiovascular function. This review discusses the evidence implicating senescent cells in cardiovascular ageing, the onset and progression of CVD, and the molecular mechanisms underlying cardiovascular cell senescence. We also review eradication of senescent cardiovascular cells by small-molecule-drug-mediated apoptosis and immune cell-mediated efferocytosis and toxicity as promising and precisely targeted therapeutics for CVD prevention and treatment.

Pathogenic mechanisms and the potential of drug therapies for aortic aneurysm

Aortic aneurysm is a permanent focal dilation of the aorta. It is usually an asymptomatic disease but can lead to sudden death due to aortic rupture. Aortic aneurysm-related mortalities are estimated at ∼200,000 deaths per year worldwide. Because no pharmacological treatment has been found to be effective so far, surgical repair remains the only treatment for aortic aneurysm. Aortic aneurysm results from changes in the aortic wall structure due to loss of smooth muscle cells and degradation of the extracellular matrix and can form in different regions of the aorta. Research over the past decade has identified novel contributors to aneurysm formation and progression. The present review provides an overview of cellular and noncellular factors as well as enzymes that process extracellular matrix and regulate cellular functions (e.g., matrix metalloproteinases, granzymes, and cathepsins) in the context of aneurysm pathogenesis. An update of clinical trials focusing on therapeutic strategies to slow abdominal aortic aneurysm growth and efforts underway to develop effective pharmacological treatments is also provided.

Inflammation and TGF-β Signaling Differ between Abdominal Aneurysms and Occlusive Disease

Abdominal aortic aneurysms (AAA), are usually asymptomatic until rupture causes fatal bleeding, posing a major vascular health problem. AAAs are associated with advanced age, male gender, and cardiovascular risk factors (e.g. hypertension and smoking). Strikingly, AAA and AOD (arterial occlusive disease) patients have a similar atherosclerotic burden, yet develop either arterial dilatation or occlusion, respectively. The molecular mechanisms underlying this diversion are yet unknown. As this knowledge could improve AAA treatment strategies, we aimed to identify genes and signaling pathways involved. We compared RNA expression profiles of abdominal aortic AAA and AOD patient samples. Based on differential gene expression profiles, we selected a gene set that could serve as blood biomarker or as pharmacological intervention target for AAA. In this AAA gene list we identified previously AAA-associated genes COL11A1, ADIPOQ, and LPL, thus validating our approach as well as novel genes; CXCL13, SLC7A5, FDC-SP not previously linked to aneurysmal disease. Pathway analysis revealed overrepresentation of significantly altered immune-related pathways between AAA and AOD. Additionally, we found bone morphogenetic protein (BMP) signaling inhibition simultaneous with activation of transforming growth factor β (TGF-β) signaling associated with AAA. Concluding our gene expression profiling approach identifies novel genes and an interplay between BMP and TGF-β signaling regulation specifically for AAA.