Macrophage death in atherosclerosis: potential role in calcification.

Cell death is an important aspect of atherosclerotic plaque development. Insufficient efferocytosis of death cells by phagocytic macrophages leads to the buildup of a necrotic core that impacts stability of the plaque. Furthermore, in the presence of calcium and phosphate, apoptotic bodies resulting from death cells can act as nucleation sites for the formation of calcium phosphate crystals, mostly in the form of hydroxyapatite, which leads to calcification of the atherosclerotic plaque, further impacting plaque stability. Excessive uptake of cholesterol-loaded oxidized LDL particles by macrophages present in atherosclerotic plaques leads to foam cell formation, which not only reduces their efferocytosis capacity, but also can induce apoptosis in these cells. The resulting apoptotic bodies can contribute to calcification of the atherosclerotic plaque. Moreover, other forms of macrophage cell death, such as pyroptosis, necroptosis, parthanatos, and ferroptosis can also contribute by similar mechanisms to plaque calcification. This review focuses on macrophage death in atherosclerosis, and its potential role in calcification. Reducing macrophage cell death and/or increasing their efferocytosis capacity could be a novel therapeutic strategy to reduce the formation of a necrotic core and calcification and thereby improving atherosclerotic plaque stability.

Roles of Nuclear Receptors in Vascular Calcification.

Vascular calcification is defined as an inappropriate accumulation of calcium depots occurring in soft tissues, including the vascular wall. Growing evidence suggests that vascular calcification is an actively regulated process, sharing similar mechanisms with bone formation, implicating both inhibitory and inducible factors, mediated by osteoclast-like and osteoblast-like cells, respectively. This process, which occurs in nearly all the arterial beds and in both the medial and intimal layers, mainly involves vascular smooth muscle cells. In the vascular wall, calcification can have different clinical consequences, depending on the pattern, localization and nature of calcium deposition. Nuclear receptors are transcription factors widely expressed, activated by specific ligands that control the expression of target genes involved in a multitude of pathophysiological processes, including metabolism, cancer, inflammation and cell differentiation. Some of them act as drug targets. In this review we describe and discuss the role of different nuclear receptors in the control of vascular calcification.

Regulation of Monocytes/Macrophages by the Renin-Angiotensin System in Diabetic Nephropathy: State of the Art and Results of a Pilot Study.

Diabetic nephropathy (DN) is characterized by albuminuria, loss of renal function, renal fibrosis and infiltration of macrophages originating from peripheral monocytes inside kidneys. DN is also associated with intrarenal overactivation of the renin-angiotensin system (RAS), an enzymatic cascade which is expressed and controlled at the cell and/or tissue levels. All members of the RAS are present in the kidneys and most of them are also expressed in monocytes/macrophages. This review focuses on the control of monocyte recruitment and the modulation of macrophage polarization by the RAS in the context of DN. The local RAS favors the adhesion of monocytes on renal endothelial cells and increases the production of monocyte chemotactic protein-1 and of osteopontin in tubular cells, driving monocytes into the kidneys. There, proinflammatory cytokines and the RAS promote the differentiation of macrophages into the M1 proinflammatory phenotype, largely contributing to renal lesions of DN. Finally, resolution of the inflammatory process is associated with a phenotype switch of macrophages into the M2 anti-inflammatory subset, which protects against DN. The pharmacologic interruption of the RAS reduces albuminuria, improves the trajectory of the renal function, decreases macrophage infiltration in the kidneys and promotes the switch of the macrophage phenotype from M1 to M2.

TREM-1 orchestrates angiotensin II-induced monocyte trafficking and promotes experimental abdominal aortic aneurysm.

The triggering receptor expressed on myeloid cells 1 (TREM-1) drives inflammatory responses in several cardiovascular diseases but its role in abdominal aortic aneurysm (AAA) remains unknown. Our objective was to explore the role of TREM-1 in a mouse model of angiotensin II-induced (AngII-induced) AAA. TREM-1 expression was detected in mouse aortic aneurysm and colocalized with macrophages. Trem1 gene deletion (Apoe-/-Trem1-/-), as well as TREM-1 pharmacological blockade with LR-12 peptide, limited both AAA development and severity. Trem1 gene deletion attenuated the inflammatory response in the aorta, with a reduction of Il1b, Tnfa, Mmp2, and Mmp9 mRNA expression, and led to a decreased macrophage content due to a reduction of Ly6Chi classical monocyte trafficking. Conversely, antibody-mediated TREM-1 stimulation exacerbated Ly6Chi monocyte aorta infiltration after AngII infusion through CD62L upregulation and promoted proinflammatory signature in the aorta, resulting in worsening AAA severity. AngII infusion stimulated TREM-1 expression and activation on Ly6Chi monocytes through AngII receptor type I (AT1R). In human AAA, TREM-1 was detected and TREM1 mRNA expression correlated with SELL mRNA expression. Finally, circulating levels of sTREM-1 were increased in patients with AAA when compared with patients without AAA. In conclusion, TREM-1 is involved in AAA pathophysiology and may represent a promising therapeutic target in humans.

Transforming growth factor ß neutralization finely tunes macrophage phenotype in elastase-induced abdominal aortic aneurysm and is associated with an increase of arginase 1 expression in the aorta.

OBJECTIVE: Macrophages play a critical role in the initiation and progression of abdominal aortic aneurysm (AAA) and are classically distinguished into M1 "proinflammatory" and M2 "anti-inflammatory" macrophages. Topical application of elastase associated with transforming growth factor ß (TGF-ß) systemic neutralization reproduces the main pathologic features of human AAA, offering a new model to investigate their role. The aim of this study was to investigate whether macrophages contribute to the expression of canonical M1/M2 markers in the aorta in the AAA model induced by elastase and systemic blockade of TGF-ß and whether blocking of TGF-ß activity affects macrophage phenotype and the expression of the M2 marker arginase 1 (ARG1). METHODS: C57Bl/6J male mice (6-8 weeks old) were randomly assigned to three experimental groups: mice that had local application of heat-inactivated elastase or elastase and mice that had elastase application and received injection of anti-TGF-ß (elastase + anti-TGF-ß group). Monocyte-macrophage depletion was achieved in the elastase + anti-TGF-ß group using liposome clodronate. Macrophage phenotype was characterized by quantitative polymerase chain reaction, flow cytometry, and immunohistochemistry. Human infrarenal AAA tissues (n = 10) were obtained to analyze ARG1 expression. RESULTS: Analysis of gene expression in the infrarenal aortic wall revealed that after 14 days, no significant difference for the expression of CCL2, NOS2, and Ym1/2 was observed in the elastase group compared with the elastase + anti-TGF-ß group, whereas the expression of ARG1, interleukin (IL) 1ß, and IL-6 was significantly increased. Macrophage depletion in the elastase + anti-TGF-ß group led to a significant decrease of IL-1ß, IL-6, ARG1, and Ym1/2 gene expression. Immunofluorescent staining confirmed that TGF-ß neutralization significantly enhanced ARG1 protein expression in the aneurysmal tissue. Flow cytometry analysis revealed an increase of macrophages expressing ARG1 in the aorta of mice treated with elastase + anti-TGF-ß compared with the elastase group, and their proportion increased with aneurysmal dilation. In humans, ARG1 protein expression was increased in aneurysmal tissues compared with controls, and positive cells were mainly found in the adventitia. CONCLUSIONS: TGF-ß neutralization finely tunes macrophage phenotype in elastase-induced AAA and leads to an increase in ARG1 gene and protein expression in the aortic wall. Even if further studies are required to elucidate its role in AAA development, ARG1 could represent a new prognostic or therapeutic target in aneurysmal disease.

Diabetes and aortic aneurysm: current state of the art.

Aortic aneurysm is a life-threatening disease due to the risk of aortic rupture. The only curative treatment available relies on surgical approaches; drug-based therapies are lacking, highlighting an unmet need for clinical practice. Abdominal aortic aneurysm (AAA) is frequently associated with atherosclerosis and cardiovascular risk factors including male sex, age, smoking, hypertension, and dyslipidaemia. Thoracic aortic aneurysm (TAA) is more often linked to genetic disorders of the extracellular matrix and the contractile apparatus but also share similar cardiovascular risk factors. Intriguingly, a large body of evidence points to an inverse association between diabetes and both AAA and TAA. A better understanding of the mechanisms underlying the negative association between diabetes and aortic aneurysm could help the development of innovative diagnostic and therapeutic approaches to tackle the disease. Here, we summarize current knowledge on the relationship between glycaemic parameters, diabetes, and the development of aortic aneurysm. Cellular and molecular pathways that underlie the protective effect of diabetes itself and its treatment are reviewed and discussed, along with their potential implications for clinical translation.

Investigation of Plasma Inflammatory Profile in Diabetic Patients With Abdominal Aortic Aneurysm: A Pilot Study.

INTRODUCTION:: Clinical studies have unraveled a negative association between diabetes and abdominal aortic aneurysm (AAA), but the mechanisms involved are still poorly understood. The aim of this study was to determine whether diabetic patients with AAA had a distinct plasma inflammatory profile compared to nondiabetic patients. METHODS:: Plasma samples were obtained from 10 diabetic patients with AAA and 10 nondiabetic patients with AAA. The relative protein expression of 92 inflammatory-related human protein biomarkers was assessed by proximity extension assay technology using Proseek Multiplex Inflammation I kit (Olink). RESULTS:: Clinical characteristics were similar in diabetic patients with AAA compared to nondiabetic patients with AAA, the median ages being 67 and 73 years, respectively ( P = .61). The AAA diameters were, respectively, 50 and 49 mm ( P = .72). Among the 92 markers screened, 67 (72.8%) were detected in all samples. Diabetic patients had significantly lower protein expression of C-C motif chemokine 19 (CCL19) and C-C motif chemokine 23 (CCL23; 542.3 vs 980.3, P = .01 and 1236 vs 1406, P = .04, respectively). They tended to have higher expression of tumor necrosis factor ligand superfamily member 14 (TNFSF14) compared to controls (14.6 vs 10.8, P = .05). CONCLUSION:: Diabetic patients with AAA differentially expressed CCL19, CCL23 and TNFSF14 in plasma compared to nondiabetic patients with AAA. Further studies are required to determine whether the markers identified could play a role in the negative association between diabetes and AAA pathogenesis.

Monocytes and macrophages in abdominal aortic aneurysm.

Abdominal aortic aneurysm (AAA) is a life-threatening disease associated with high morbidity, and high mortality in the event of aortic rupture. Major advances in open surgical and endovascular repair of AAA have been achieved during the past 2 decades. However, drug-based therapies are still lacking, highlighting a real need for better understanding of the molecular and cellular mechanisms involved in AAA formation and progression. The main pathological features of AAA include extracellular matrix remodelling associated with degeneration and loss of vascular smooth muscle cells and accumulation and activation of inflammatory cells. The inflammatory process has a crucial role in AAA and substantially influences many determinants of aortic wall remodelling. In this Review, we focus specifically on the involvement of monocytes and macrophages, summarizing current knowledge on the roles, origin, and functions of these cells in AAA development and its complications. Furthermore, we show and propose that distinct monocyte and macrophage subsets have critical and differential roles in initiation, progression, and healing of the aneurysmal process. On the basis of experimental and clinical studies, we review potential translational applications to detect, assess, and image macrophage subsets in AAA, and discuss the relevance of these applications for clinical practice.

Fasting Circulating Glicentin Increases After Bariatric Surgery.

INTRODUCTION: Bariatric surgery including the Roux-en-Y gastric bypass (RYGB) and the laparoscopic sleeve gastrectomy (LSG) is a well-established therapeutic option for patients with morbid or severe obesity. Metabolic modifications observed after bariatric surgery are thought to be, at least partly, linked to hormonal changes. While variation of several proglucagon-derived peptides during bariatric surgery is well documented, little is known about glicentin. The aim of this study was to investigate circulating glicentin variations after bariatric surgery. MATERIAL AND METHODS: Thirty patients eligible for bariatric surgery (18 RYGB and 12 LSG procedures) were prospectively included in the University Hospital of Nice. Clinical data and fasting biological parameters were recorded preoperatively, at 3, 6, and 12 months after bariatric surgery. RESULTS: The median age of patients was 51 years (35-56) with 33.3% men. Fasting glicentin concentration increased progressively after bariatric surgery from 6 months and was more marked at 12 months (14 ± 3.6 pmol/L at baseline vs 19.7 ± 2.7 pmol/L at 12 months for RYGB and 12.5 ± 1.4 vs 16.4 ± 1.8 pmol/L for LSG, respectively). Compared to preoperative values, the fold increase of glicentin at 12 months was 2 ± 0.2 in the RYGB group and 1.6 ± 0.3 in the LSG group. Glicentin variation after surgery did not correlate with anthropometric, glycemic, or lipid parameter modifications. CONCLUSION: Fasting glicentin level increases after bariatric surgery suggesting the potential interest of this peptide as a player and/or a marker of physiological changes after bariatric surgery.

Association between a thyroid hormone receptor-α gene polymorphism and blood pressure but not with coronary heart disease risk.

BACKGROUND: Thyroid hormones (THs) exert multiple biological roles including effects on the cardiovascular system (lipid profile, blood pressure (BP) and cardiac output). The lipid-lowering actions of TH are mediated by the TH receptor-ß whereas the mechanisms explaining the BP variations concomitant with the thyroid disorders are less understood. As the TH receptor-α (TR-α) has been associated with many of TH actions on the cardiovascular system in mice models, we hypothesized that it could be involved in the latter. We thus tested whether polymorphisms in TR-α (THRA gene) could be associated with BP level variation. Secondarily, we tested for association with coronary heart disease (CHD) risk. METHODS: We analyzed the associations between five THRA polymorphisms and (i) BP level in two population-based studies (MONICA Lille n = 1,155; MONICA Toulouse n = 1,170) and (ii) the risk of CHD in two case-control studies (Lille CHD n = 558 cases/568 controls; PRIME n = 527 cases/584 controls). RESULTS: Individuals carrying the rs939348 T allele had higher systolic BP (~+1.3 mm Hg) than CC individuals in both the MONICA Lille (P = 0.02) and Toulouse (P = 0.03) studies. The odds ratio (OR) for hypertension was 1.25 (P = 0.02) in the combined sample. Concerning the CHD risk, no significant association could be detected. CONCLUSIONS: For the first time, our study showed associations between the THRA rs939348 polymorphism and systolic BP and the risk of hypertension but not with CHD, although we admit that the statistical power available to study any relationship with CHD was very limited. Further larger association studies are needed to confirm our findings.

Peroxisome proliferator-activated receptor alpha induces NADPH oxidase activity in macrophages, leading to the generation of LDL with PPAR-alpha activation properties.

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors controlling lipid and glucose metabolism as well as inflammation. PPARs are expressed in macrophages, cells that also generate reactive oxygen species (ROS). In this study, we investigated whether PPARs regulate ROS production in macrophages. Different PPAR-alpha, but not PPAR-gamma agonists, increased the production of ROS (H2O2 and ) in human and murine macrophages. PPAR-alpha activation did not induce cellular toxicity, but significantly decreased intracellular glutathione levels. The increase in ROS production was not attributable to inherent prooxidant effects of the PPAR-alpha agonists tested, but was mediated by PPAR-alpha, because the effects were lost in bone marrow-derived macrophages from PPAR-alpha-/- mice. The PPAR-alpha-induced increase in ROS was attributable to the induction of NADPH oxidase, because (1) preincubation with the NADPH oxidase inhibitor diphenyleneiodinium prevented the increase in ROS production; (2) PPAR-alpha agonists increased production measured by superoxide dismutase-inhibitable cytochrome c reduction; (3) PPAR-alpha agonists induced mRNA levels of the NADPH oxidase subunits p47(phox), p67phox, and gp91phox and membrane p47phox protein levels; and (4) induction of ROS production was abolished in p47phox-/- and gp91phox-/- macrophages. Finally, induction of NADPH oxidase by PPAR-alpha agonists resulted in the formation of oxidized LDL metabolites that exert PPAR-alpha-independent proinflammatory and PPAR-alpha-dependent decrease of lipopolysaccharide-induced inducible nitric oxide synthase expression in macrophages. These data identify a novel mechanism of autogeneration of endogenous PPAR-alpha ligands via stimulation of NADPH oxidase activity.

Peroxisome proliferator-activated receptors: new targets for the pharmacological modulation of macrophage gene expression and function.

PURPOSE OF REVIEW: This review focuses on recent advances on the roles of peroxisome proliferator-activated receptors in the control of lipid metabolism, and the inflammatory response of macrophages and the potential participation of these actions in the modulation of atherogenesis. RECENT FINDINGS: Altered macrophage functions contribute to the pathogenesis of many infectious, immunological and inflammatory disease processes. Pharmacological modulation of macrophage gene expression therefore represents an important strategy for the prevention and treatment of inflammation-related diseases, such as atherosclerosis. Peroxisome proliferator-activated receptors are lipid-activated transcription factors that control lipid and lipoprotein metabolism, glucose and energy homeostasis, as well as cellular differentiation and proliferation. Recent data suggest that peroxisome proliferator-activated receptor alpha and peroxisome proliferator-activated receptor gamma activators may decrease the incidence of cardiovascular disease, not only by correcting metabolic disorders, but also by directly acting at the level of the vascular wall. In this context, ligand-activated peroxisome proliferator-activated receptors control cellular functions by regulating gene expression in different cell types, including monocytes, macrophages and foam cells. SUMMARY: These findings identify the crucial roles of peroxisome proliferator-activated receptors in macrophages, improving the comprehension of the patho-physiological mechanisms of atherogenesis. Moreover, a scientific rationale for the evaluation of peroxisome proliferator-activated receptor activators in the treatment of inflammatory disorders such as atherosclerosis is thus provided.