In Vitro Macrophage Phagocytosis Assay

The key roles of macrophages in atherosclerosis include the phagocytosis of apoptotic and necrotic cells and cell debris, whose accumulation in atherosclerotic lesions exacerbates inflammation and promotes plaque vulnerability. Evidence is accumulating that macrophage phagocytic functions peak at the early stages of atherosclerosis and that the reduced phagocytosis at the late stages of disease leads to the generation of necrotic cores and a defective resolution of inflammation, which in turn promotes plaque rupture, thrombus formation, and life-threatening acute ischemic events (myocardial infarction and stroke). The impaired resolution of inflammation in advanced lesions featuring loss of macrophage phagocytic activity may be in part due to an imbalance between M1 and M2 subsets of polarized macrophages. A better understanding of the mechanisms that regulate macrophage phagocytic activity in the context of atherosclerosis may therefore help identify novel therapeutic targets. This chapter presents a protocol for establishing primary mouse macrophage cultures, a method for polarizing macrophages to the M1 and M2 states, and a method for the in vitro study of macrophage phagocytosis of IgG-opsonized or IgM/complement component 3-opsonized erythrocytes.M.R.H. is supported by an FPI predoctoral fellowship from the Spanish Government (BES-2011-043938) and R.V-B. by a Juan de la Cierva postdoctoral contract from the Spanish Government (JCI-2011- 09663). Work in V.A.’s laboratory is supported by grants from the Spanish Ministry of Economy and Competitivity (MINECO) (SAF201346663-R), Fondo Europeo de Desarrollo Regional (FEDER), Instituto de Salud Carlos III (RD12/0042/0028), the Progeria Research Foundation (Innovator Award 2012, Established Investigator Award 2014), and the European Union (Liphos, Grant Agreement 317916). The Centro Nacional de Investigaciones Cardiovasculares (CNIC) is supported by the MINECO and the Pro-CNIC Foundation.S

Mineralisation of collagen rich soft tissues and osteocyte lacunae in Enpp1(-/-) mice

Ecto-nucleotide pyrophosphatase/phosphodiesterases (NPPs) hydrolyse nucleotide triphosphates to the corresponding nucleotide monophosphates and the mineralisation inhibitor, pyrophosphate (PPi). This study examined the role of NPP1 in osteocytes, osteoclasts and cortical bone, using a mouse model lacking NPP1 (Enpp1−/−). We used microcomputed tomography (μCT) to investigate how NPP1 deletion affects cortical bone structure; excised humerus bones from 8, 15 and 22-week old mice were scanned at 0.9 μm. Although no changes were evident in the cortical bone of 8-week old Enpp1−/− mice, significant differences were observed in older animals. Cortical bone volume was decreased 28% in 22-week Enpp1−/− mice, whilst cortical porosity was reduced 30% and 60% at 15 and 22-weeks, respectively. This was accompanied by up to a 15% decrease in closed pore diameter and a 55% reduction in the number of pores. Cortical thickness was reduced up to 35% in 15 and 22-week Enpp1−/− animals and the endosteal diameter was increased up to 23%. Thus, the cortical bone from Enpp1−/− mice was thinner and less porous, with a larger marrow space. Scanning electron microscopy (SEM) revealed a decrease in the size and number of blood vessel channels in the cortical bone as well as a 40% reduction in the mean plan area of osteocyte lacunae. We noted that the number of viable osteocytes isolated from the long bones of Enpp1−/− mice was decreased ≤ 50%. In contrast, osteoclast formation and resorptive activity were unaffected by NPP1 deletion. μCT and histological analysis of Enpp1−/− mice also revealed calcification of the joints and vertebrae as well as soft tissues including the whisker follicles, ear pinna and trachea. This calcification worsened as the animals aged. Together, these data highlight the key role of NPP1 in regulating calcification of both soft and skeletal tissues

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

Novel phosphate-activated macrophages prevent ectopic calcification by increasing extracellular ATP and pyrophosphate.

PURPOSE:Phosphorus is an essential nutrient involved in many pathobiological processes. Less than 1% of phosphorus is found in extracellular fluids as inorganic phosphate ion (Pi) in solution. High serum Pi level promotes ectopic calcification in many tissues, including blood vessels. Here, we studied the effect of elevated Pi concentration on macrophage polarization and calcification. Macrophages, present in virtually all tissues, play key roles in health and disease and display remarkable plasticity, being able to change their physiology in response to environmental cues. METHODS AND RESULTS:High-throughput transcriptomic analysis and functional studies demonstrated that Pi induces unpolarized macrophages to adopt a phenotype closely resembling that of alternatively-activated M2 macrophages, as revealed by arginine hydrolysis and energetic and antioxidant profiles. Pi-induced macrophages showed an anti-calcifying action mediated by increased availability of extracellular ATP and pyrophosphate. CONCLUSION:We conclude that the ability of Pi-activated macrophages to prevent calcium-phosphate deposition is a compensatory mechanism protecting tissues from hyperphosphatemia-induced pathologic calcification