Orthopedic surgery increases atherosclerotic lesions and necrotic core area in ApoE-/- mice

Background and aims Observational studies show a peak incidence of cardiovascular events after major surgery. For example, the risk of myocardial infarction increases 25-fold early after hip replacement. The acuteness of this increased risk suggests abrupt enhancement in plaque vulnerability, which may be related to intra-plaque inflammation, thinner fibrous cap and/or necrotic core expansion. We hypothesized that acute systemic inflammation following major orthopedic surgery induces such changes. Methods ApoE−/− mice were fed a western diet for 10 weeks. Thereafter, half the mice underwent mid-shaft femur osteotomy followed by realignment with an intramedullary K-wire, to mimic major orthopedic surgery. Mice were sacrificed 5 or 15 days post-surgery (n = 22) or post-saline injection (n = 13). Serum amyloid A (SAA) was measured as a marker of systemic inflammation. Paraffin embedded slides of the aortic root were stained to measure total plaque area and to quantify fibrosis, calcification, necrotic core, and inflammatory cells. Results Surgery mice showed a pronounced elevation of serum amyloid A (SAA) and developed increased plaque and necrotic core area already at 5 days, which reached significance at 15 days (p = 0.019; p = 0.004 for plaque and necrotic core, respectively). Macrophage and lymphocyte density significantly decreased in the surgery group compared to the control group at 15 days (p = 0.037; p = 0.024, respectively). The density of neutrophils and mast cells remained unchanged. Conclusions Major orthopedic surgery in ApoE−/− mice triggers a systemic inflammatory response. Atherosclerotic plaque area is enlarged after surgery mainly due to an increase of the necrotic core. The role of intra-plaque inflammation in this response to surgical injury remains to be fully elucidated. © 2016 Elsevier Ireland Lt

Evaluation of pliable bioresorbable, elastomeric aortic valve prostheses in sheep during 12 months post implantation

Pliable microfibrous, bioresorbable elastomeric heart valve prostheses are investigated in search of sustainable heart valve replacement. These cell-free implants recruit cells and trigger tissue formation on the valves in situ. Our aim is to investigate the behaviour of these heart valve prostheses when exposed to the high-pressure circulation. We conducted a 12-month follow-up study in sheep to evaluate the in vivo functionality and neo-tissue formation of these valves in the aortic position. All valves remained free from endocarditis, thrombotic complications and macroscopic calcifications. Cell colonisation in the leaflets was mainly restricted to the hinge area, while resorption of synthetic fibers was limited. Most valves were pliable and structurally intact (10/15), however, other valves (5/15) showed cusp thickening, retraction or holes in the leaflets. Further research is needed to assess whether in-situ heart valve tissue engineering in the aortic position is possible or whether non-resorbable synthetic pliable prostheses are preferred.</p

Myocardial Infarction Accelerates Atherosclerosis

During progression of atherosclerosis, myeloid cells destabilize lipid-rich plaque in the arterial wall and cause its rupture, thus triggering myocardial infarction and stroke. Survivors of acute coronary syndromes have a high risk of recurrent events for unknown reasons. Here we show that the systemic response to ischemic injury aggravates chronic atherosclerosis. After myocardial infarction or stroke, apoE$^{−/−}$ mice developed larger atherosclerotic lesions with a more advanced morphology. This disease acceleration persisted over many weeks and was associated with markedly increased monocyte recruitment. When seeking the source of surplus monocytes in plaque, we found that myocardial infarction liberated hematopoietic stem and progenitor cells from bone marrow niches via sympathetic nervous system signaling. The progenitors then seeded the spleen yielding a sustained boost in monocyte production. These observations provide new mechanistic insight into atherogenesis and provide a novel therapeutic opportunity to mitigate disease progression

NOX2, p22phox and p47phox are targeted to the nuclear pore complex in ischemic cardiomyocytes colocalizing with local reactive oxygen species.

BACKGROUND: NADPH oxidases play an essential role in reactive oxygen species (ROS)-based signaling in the heart. Previously, we have demonstrated that (peri)nuclear expression of the catalytic NADPH oxidase subunit NOX2 in stressed cardiomyocytes, e.g. under ischemia or high concentrations of homocysteine, is an important step in the induction of apoptosis in these cells. Here this ischemia-induced nuclear targeting and activation of NOX2 was specified in cardiomyocytes. METHODS: The effect of ischemia, mimicked by metabolic inhibition, on nuclear localization of NOX2 and the NADPH oxidase subunits p22(phox) and p47(phox), was analyzed in rat neonatal cardiomyoblasts (H9c2 cells) using Western blot, immuno-electron microscopy and digital-imaging microscopy. RESULTS: NOX2 expression significantly increased in nuclear fractions of ischemic H9c2 cells. In addition, in these cells NOX2 was found to colocalize in the nuclear envelope with nuclear pore complexes, p22(phox), p47(phox) and nitrotyrosine residues, a marker for the generation of ROS. Inhibition of NADPH oxidase activity, with apocynin and DPI, significantly reduced (peri)nuclear expression of nitrotyrosine. CONCLUSION: We for the first time show that NOX2, p22(phox) and p47(phox) are targeted to and produce ROS at the nuclear pore complex in ischemic cardiomyocytes

Homocysteine Induces Phosphatidylserine Exposure in Cardiomyocytes through Inhibition of Rho Kinase and Flippase Activity.

AIMS: Increased levels of homocysteine (Hcy) form an independent risk factor for cardiovascular disease. In a previous study we have shown that Hcy induced phosphatidylserine (PS) exposure to the outer leaflet of the plasma membrane in cardiomyocytes, inducing a pro-inflammatory phenotype. In the present study the mechanism(s) involved in Hcy-induced PS exposure were analyzed. METHODS: H9c2 rat cardiomyoblasts were subjected to 2.5 mM D,L-Hcy and analyzed for RhoA translocation and activity, Rho Kinase (ROCK) activity and expression and flippase activity. In addition, the effect of ROCK inhibition with Y27632 on Hcy-induced PS exposure and flippase activity was analyzed. Furthermore, GTP and ATP levels were determined. RESULTS: Incubation of H9c2 cells with 2.5 mM D,L-Hcy did not inhibit RhoA translocation to the plasma membrane. Neither did it inhibit activation of RhoA, even though GTP levels were significantly decreased. Hcy did significantly inhibit ROCK activation, but not its expression, and did inhibit flippase activity, in advance of a significant decrease in ATP levels. ROCK inhibition via Y27632 did not have significant added effects on this. CONCLUSION: Hcy induced PS exposure in the outer leaflet of the plasma membrane in cardiomyocytes via inhibition of ROCK and flippase activity. As such Hcy may induce cardiomyocytes vulnerable to inflammation in vivo in hyperhomocysteinaemia patients

Group II secretory PLA2: A new cardiovascular risk factor

Inflammatory mediators contribute significantly to the induction and progression of cardiovascular diseases such as atherosclerosis and acute myocardial infarction (AMI). A mediator that has been shown to play a crucial role in both cardiovascular events is group-II secretory phospholipase A2 (sPLA2-II), as this mediator has been suggested to modulate atherosclerotic plaque formation, for example by increasing the accumulation of intracellular lipids in macrophages and stimulating the formation of foam cells. Furthermore, increased levels of sPLA2-II in the blood form a risk marker for the development of complications of coronary artery disease. In line with this, we recently found that extracellular sPLA2-II is more abundantly present in the extracellular matrix of atherosclerotic culprit lesions of coronary arteries in patients who developed AMI than in those of patients with stable or unstable angina pectoris. Another important feature of sPLA2-II is its ability to bind to and hydrolyze membrane phospholipids. Notably, sPLA2-II cannot bind to the tightly packed hydrophobic phospholipids in the outer leaflet of a normal membrane, but only to the disarranged or flip-flopped membranes of damaged cells, as is the case in ischemic jeopardized cardiomyocytes. Interestingly, we recently have observed that sPLA2-II cannot only bind to reversible damaged cardiomyocytes but also induces these cells to die, partly by potentiating binding of C-reactive protein and thus inducing an inflammatory response in the ischemically challenged heart. This review will discuss the pros and co ns of therapy with inhibitors of sPLA2-II to prevent complications of the process of atherosclerosis, and/or to limit the amount of cell death of cardiomyocytes subsequent to AMI

The role of complement in the acute phase response after burns

Severe burns induce a complex systemic inflammatory response characterized by a typical prolonged acute phase response (APR) that starts approximately 4–8 h after-burn and persists for months up to a year after the initial burn trauma. During this APR, acute phase proteins (APPs), including C-reactive protein (CRP) and complement (e.g. C3, C4 and C5) are released in the blood, resulting amongst others, in the recruitment and migration of inflammatory cells. Although the APR is necessary for proper wound healing, a prolonged APR can induce local tissue damage, hamper the healing process and cause negative systemic effects in several organs, including the heart, lungs, kidney and the central nervous system. In this review, we will discuss the role of the APR in burns with a specific focus on complement

Transient atrial inflammation in a murine model of Coxsackievirus B3-induced myocarditis

Atrial dysfunction is a relatively common complication of acute myocarditis, although its pathophysiology is unclear. There is limited information on myocarditis-associated histological changes in the atria and how they develop in time. The aim of this study therefore was to investigate inflammation, fibrosis and viral genome in the atria in time after mild CVB3-induced viral myocarditis (VM) in mice. C3H mice (n = 68) were infected with 105 PFU of Coxsackievirus B3 (CVB3) and were compared with uninfected mice (n = 10). Atrial tissue was obtained at days 4, 7, 10, 21, 35 or 49 post-infection. Cellular infiltration of CD45+ lymphocytes, MAC3+ macrophages, Ly6G+ neutrophils and mast cells was quantified by (immuno)histochemical staining. The CVB3 RNA was determined by in situ hybridization, and fibrosis was evaluated by elastic van Gieson (EvG) staining. In the atria of VM mice, the numbers of lymphocytes on days 4 and 7 (p <.05) and days 10 (p <.01); macrophages on days 7 (p <.01) and 10 (p <.05); neutrophils on days 4 (p <.05); and mast cells on days 4 and 7 (p <.05) increased significantly compared with control mice and decreased thereafter to basal levels. No cardiomyocyte death was observed, and the CVB3 genome was detected in only one infected mouse on Day 4 post-infection. No significant changes in the amount of atrial fibrosis were found between VM and control mice. A temporary increase in inflammation is induced in the atria in the acute phase of CVB3-induced mild VM, which may facilitate the development of atrial arrhythmia and contractile dysfunction