The contribution of matrix metalloproteinases and their inhibitors to the development, progression, and rupture of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) account for up to 8% of deaths in men aged 65 years and over and 2.2% of women. Patients with AAAs often have atherosclerosis, and intimal atherosclerosis is generally present in AAAs. Accordingly, AAAs are considered a form of atherosclerosis and are frequently referred to as atherosclerotic aneurysms. Pathological observations advocate inflammatory cell infiltration alongside adverse extracellular matrix degradation as key contributing factors to the formation of human atherosclerotic AAAs. Therefore, macrophage production of proteolytic enzymes is deemed responsible for the damaging loss of ECM proteins, especially elastin and fibrillar collagens, which characterise AAA progression and rupture. Matrix metalloproteinases (MMPs) and their regulation by tissue inhibitors metalloproteinases (TIMPs) can orchestrate not only ECM remodelling, but also moderate the proliferation, migration, and apoptosis of resident aortic cells, alongside the recruitment and subsequent behaviour of inflammatory cells. Accordingly, MMPs are thought to play a central regulatory role in the development, progression, and eventual rupture of abdominal aortic aneurysms (AAAs). Together, clinical and animal studies have shed light on the complex and often diverse effects MMPs and TIMPs impart during the development of AAAs. This dichotomy is underlined from evidence utilising broad-spectrum MMP inhibition in animal models and clinical trials which have failed to provide consistent protection from AAA progression, although more encouraging results have been observed through deployment of selective inhibitors. This review provides a summary of the supporting evidence connecting the contribution of individual MMPs to AAA development, progression, and eventual rupture. Topics discussed include structural, functional, and cell-specific diversity of MMP members; evidence from animal models of AAA and comparisons with findings in humans; the dual role of MMPs and the requirement to selectively target individual MMPs; and the advances in identifying aberrant MMP activity. As evidenced, our developing understanding of the multifaceted roles individual MMPs perform during the progression and rupture of AAAs, should motivate clinical trials assessing the therapeutic potential of selective MMP inhibitors, which could restrict AAA-related morbidity and mortality worldwide.

A Nrf2-OSGIN1&2-HSP70 axis mediates cigarette smoke-induced endothelial detachment: implications for plaque erosion

AIMS

Endothelial erosion of plaques is responsible for ∼30% of acute coronary syndromes (ACS). Smoking is a risk factor for plaque erosion, which most frequently occurs on the upstream surface of plaques where the endothelium experiences elevated shear stress. We sought to recreate these conditions in vitro to identify potential pathological mechanisms that might be of relevance to plaque erosion.

METHODS AND RESULTS

Culturing human coronary artery endothelial cells (HCAECs) under elevated flow (shear stress of 7.5 Pa) and chronically exposing them to cigarette smoke extract (CSE) and tumour necrosis factor-alpha (TNFα) recapitulated a defect in HCAEC adhesion, which corresponded with augmented Nrf2-regulated gene expression. Pharmacological activation or adenoviral overexpression of Nrf2 triggered endothelial detachment, identifying Nrf2 as a mediator of endothelial detachment. Growth/Differentiation Factor-15 (GDF15) expression was elevated in this model, with protein expression elevated in the plasma of patients experiencing plaque erosion compared with plaque rupture. The expression of two Nrf2-regulated genes, OSGIN1 and OSGIN2, was increased by CSE and TNFα under elevated flow and was also elevated in the aortas of mice exposed to cigarette smoke in vivo. Knockdown of OSGIN1&2 inhibited Nrf2-induced cell detachment. Overexpression of OSGIN1&2 induced endothelial detachment and resulted in cell cycle arrest, induction of senescence, loss of focal adhesions and actin stress fibres, and disturbed proteostasis mediated in part by HSP70, restoration of which reduced HCAEC detachment. In ACS patients who smoked, blood concentrations of HSP70 were elevated in plaque erosion compared with plaque rupture.

CONCLUSION

We identified a novel Nrf2-OSGIN1&2-HSP70 axis that regulates endothelial adhesion, elevated GDF15 and HSP70 as biomarkers for plaque erosion in patients who smoke, and two therapeutic targets that offer the potential for reducing the risk of plaque erosion.

Inhibition of Intimal Thickening By PRH (Proline-Rich Homeodomain) in Mice

BACKGROUND

Late vein graft failure is caused by intimal thickening resulting from endothelial cell (EC) damage and inflammation which promotes vascular smooth muscle cell (VSMC) dedifferentiation, migration, and proliferation. Nonphosphorylatable PRH (proline-rich homeodomain) S163C:S177C offers enhanced stability and sustained antimitotic effect. Therefore, we investigated whether adenovirus-delivered PRH S163C:S177C protein attenuates intimal thickening via VSMC phenotype modification without detrimental effects on ECs.

METHODS

PRH S163C:S177C was expressed in vitro (human saphenous vein-VSMCs and human saphenous vein-ECs) and in vivo (ligated mouse carotid arteries) by adenoviruses. Proliferation, migration, and apoptosis were quantified and phenotype was assessed using Western blotting for contractile filament proteins and collagen gel contraction. EC inflammation was quantified using VCAM (vascular cell adhesion protein)-1, ICAM (intercellular adhesion molecule)-1, interleukin-6, and monocyte chemotactic factor-1 measurement and monocyte adhesion. Next Generation Sequencing was utilized to identify novel downstream mediators of PRH action and these and intimal thickening were investigated in vivo.

RESULTS

PRH S163C:S177C inhibited proliferation, migration, and apoptosis and promoted contractile phenotype (enhanced contractile filament proteins and collagen gel contraction) compared with virus control in human saphenous vein-VSMCs. PRH S163C:S177C expression in human saphenous vein-ECs significantly reduced apoptosis, without affecting cell proliferation and migration, while reducing TNF (tumor necrosis factor)-α-induced VCAM-1 and ICAM-1 and monocyte adhesion and suppressing interleukin-6 and monocyte chemotactic factor-1 protein levels. PRH S163C:S177C expression in ligated murine carotid arteries significantly impaired carotid artery ligation-induced neointimal proliferation and thickening without reducing endothelial coverage. Next Generation Sequencing revealed STAT-1 (signal transducer and activator of transcription 1) and HDAC-9 (histone deacetylase 9) as mediators of PRH action and was supported by in vitro and in vivo analyses.

CONCLUSIONS

We observed PRH S163C:S177C attenuated VSMC proliferation, and migration and enhanced VSMC differentiation at least in part via STAT-1 and HDAC-9 signaling while promoting endothelial repair and anti-inflammatory properties. These findings highlight the potential for PRH S163C:S177C to preserve endothelial function whilst suppressing intimal thickening, and reducing late vein graft failure.

Pro-inflammatory role of Wnt/β-catenin signaling in endothelial dysfunction

Background

Endothelial dysfunction is a critical component of both atherosclerotic plaque formation and saphenous vein graft failure. Crosstalk between the pro-inflammatory TNF-α-NFκB signaling axis and the canonical Wnt/β-catenin signaling pathway potentially plays an important role in regulating endothelial dysfunction, though the exact nature of this is not defined.

Results

In this study, cultured endothelial cells were challenged with TNF-α and the potential of a Wnt/β-catenin signaling inhibitor, iCRT-14, in reversing the adverse effects of TNF-α on endothelial physiology was evaluated. Treatment with iCRT-14 lowered nuclear and total NFκB protein levels, as well as expression of NFκB target genes, IL-8 and MCP-1. Inhibition of β-catenin activity with iCRT-14 suppressed TNF-α-induced monocyte adhesion and decreased VCAM-1 protein levels. Treatment with iCRT-14 also restored endothelial barrier function and increased levels of ZO-1 and focal adhesion-associated phospho-paxillin (Tyr118). Interestingly, inhibition of β-catenin with iCRT-14 enhanced platelet adhesion in cultured TNF-α-stimulated endothelial cells and in an ex vivo human saphenous vein model, most likely via elevating levels of membrane-tethered vWF. Wound healing was moderately retarded by iCRT-14; hence, inhibition of Wnt/β-catenin signaling may interfere with re-endothelialisation in grafted saphenous vein conduits.

Conclusion

Inhibition of the Wnt/β-catenin signaling pathway with iCRT-14 significantly recovered normal endothelial function by decreasing inflammatory cytokine production, monocyte adhesion and endothelial permeability. However, treatment of cultured endothelial cells with iCRT-14 also exerted a pro-coagulatory and moderate anti-wound healing effect: these factors may affect the suitability of Wnt/β-catenin inhibition as a therapy for atherosclerosis and vein graft failure.

Monoclonal Autoantibody Against a Cryptic Epitope on Tissue-Adherent Low-Density Lipoprotein for Molecular Imaging in Atherosclerosis

BACKGROUND

Antibody-based constructs for molecular imaging and therapeutic delivery provide promising opportunities for the diagnosis and treatment of atherosclerosis.

OBJECTIVES

The authors aimed to generate and characterize immunoglobulin (Ig)G monoclonal autoantibodies in atherosclerosis for targeting of novel molecular determinants.

METHODS

The authors created hybridomas from an unimmunized low-density lipoprotein (LDL) receptor-deficient (Ldlr-/-) mouse and selected an IgG2b isotype autoantibody, LO9, for further characterization.

RESULTS

LO9 reacted well with native LDL bound to immobilized matrix components and less well to oxidized LDL. LO9 binding to immobilized native LDL was not neutralized by fluid-phase native LDL, indicating an adhesion-dependent epitope. The authors localized the epitope to a 20 amino-acid peptide sequence (P5) in the globular amino-terminus of apolipoprotein B. LO9 reacted with antigen in mouse atherosclerosis and in both human stable and ruptured coronary atherosclerosis. Furthermore, in vivo near-infrared fluorescence molecular tomographic imaging, and ex vivo confocal microscopy showed that intravenously injected LO9 localized beneath endothelium of the aortic arch in Ldlr-/- mice, in the vicinity of macrophages.

CONCLUSIONS

The authors believe LO9 is the first example of an IgG autoantibody that reacts with a native LDL epitope revealed by adherence to tissue matrix. Antibodies against adherent native LDL have potential as molecular targeting agents for imaging of and therapeutic delivery to atherosclerosis.

Use of Mouse Carotid Artery Ligation Model of Intimal Thickening to Probe Vascular Smooth Muscle Cell Remodeling and Function in Atherosclerosis

The thickening of the intima is a critical underlying component of atherosclerosis. Consequently, robust and reproducible animal models of intimal thickening are essential for a greater understanding of the mechanisms underlying the process of intimal thickening and to evaluate new approaches for the reduction of intimal thickening and thereby atherosclerosis. The ligation of the carotid artery in the mouse causes the thickening of the intimal layer of the artery. This model is relatively simple and is reproducible and therefore is a preferred and well-established model of intimal thickening. Here, we detail a protocol for carotid artery ligation in the mouse and methods for histological examination and quantification of intimal thickening.

Monitoring Cellular Proliferation, Migration, and Apoptosis Associated with Atherosclerosis Plaques In Vitro

Bromodeoxyuridine/5-bromo-2'-deoxyuridine (BrdU) is a nucleoside analog of thymidine and its incorporation into DNA during replication within S-phase of the cell cycle is used to quantify cell proliferation. Quantification of incorporated BrdU is considered the most direct measure of cell proliferation, and here we describe BrdU incorporation into cultured vascular smooth muscle cells (VSMCs) and endothelial cells in vitro. Incorporation of fluorescent-labeled ethynyldeoxyuridine/5-ethynyl-2'-deoxyuridine (EdU) is a novel alternative to BrdU assays and presents significant advantages. This method of detection of EdU based on a simple "click" chemical reaction, which covalently bonds EdU to a fluorescent dye is also outlined in this chapter with a protocol for quantitative analysis of EdU incorporation using a Fiji-based macro. We also describe how proliferation can be assessed by quantification of classical proliferative markers such as phopsho-Ser807/811 retinoblastoma (Rb), proliferating cell nuclear antigen (PCNA) and cyclin D1 by Western blotting. As these markers are involved in different aspects of the cell cycle regulation, examining their expression levels can not only reveal the relative population of proliferating cells but can also improve our understanding of the mechanism of action of a given treatment or intervention. The scratch wound assay is a simple and cost-effective technique to quantify cell migration. A protocol which involves creating a wound in a cell cultured monolayer and measuring the distance migrated by the cells after a predefined time period is also described. Gap creation can also be achieved via physical cell exclusion where cells are seeded in distinct reservoirs of a cell culture insert which reveal a gap upon removal. Cell migration may then be quantified by monitoring the rate of gap closure. The presence of cleaved caspase-3 is a marker of programmed cell death (apoptosis). To detect cleaved caspase-3 in vitro, immunocytochemistry and fluorescence can be performed as outlined in this chapter.

Aneurysm severity is suppressed by deletion of CCN4

Patients with abdominal aortic aneurysms are frequently treated with high-risk surgery. A pharmaceutical treatment to reverse aneurysm progression could prevent the need for surgery and save both lives and healthcare resources. Since CCN4 regulates cell migration, proliferation and apoptosis, processes involved in aneurysm progression, it is a potential regulator of aneurysm progression. We investigated the role of CCN4 in a mouse aneurysm model, using apolipoprotein-E knockout (ApoE^-/-) mice fed high fat diet and infused with Angiotensin II (AngII). Blood pressure was similarly elevated in CCN4^-/-ApoE^-/- mice and CCN4^+/+ApoE^-/- mice (controls) in response to AngII infusion. Deletion of CCN4 significantly reduced the number of ruptured aortae, both thoracic and abdominal aortic area, and aneurysm grade score, compared to controls. Additionally, the frequency of vessel wall remodelling and the number of elastic lamina breaks was significantly suppressed in CCN4^-/-ApoE^-/- mice compared to controls. Immunohistochemistry revealed a significantly lower proportion of macrophages, while the proportion of smooth muscle cells was not affected by the deletion of CCN4. There was also a reduction in both proliferation and apoptosis in CCN4^-/-ApoE^-/- mice compared to controls. In vitro studies showed that CCN4 significantly increased monocyte adhesion beyond that seen with TNFα and stimulated macrophage migration by more than threefold. In summary, absence of CCN4 reduced aneurysm severity and improved aortic integrity, which may be the result of reduced macrophage infiltration and cell apoptosis. Inhibition of CCN4 could offer a potential therapeutic approach for the treatment of aneurysms.

Abstract P126: Pro-Inflammatory Macrophage Secretome Promotes Cardiac Fibroblast Activation

Introduction: Following myocardial infarction, an acute immune response occurs, and infiltrating monocytes and monocyte-derived macrophages migrate into the infarct. Under the influence of intricate pro- and anti-inflammatory stimuli, macrophages drive cardiac fibroblast (CF) activation. The interaction between macrophages and CFs regulates fibrosis-driven wound healing.

Hypothesis: We hypothesised that pro- and anti-inflammatory macrophages divergently effect CF activation. We aimed to identify macrophage proteins that regulate CFs as potential intervention targets.

Methods: Monocytes from healthy volunteers were differentiated towards pro- or anti-inflammatory macrophages using GM-CSF (20 ng/mL) and M-CSF (20 ng/mL) or M-CSF (40 ng/mL) alone, respectively. CF activation was characterised by α-SMA expression, contraction, and migration. Proteomics were performed on macrophage secretome and subjected to bioinformatics (IPA, Qiagen). CFs were cultured with macrophage-conditioned medium (CM) in the presence of recombinant proteins or neutralising antibodies, as indicated.

Results: Pro-inflammatory macrophage CM enhanced CF activation, as evidenced by elevated α-SMA expression (1.6-fold change, p<0.05, n=7), contraction (1.3-fold change, p<0.05, n=4), and migration (1.2-fold change, p<0.05, n=4) in comparison to anti-inflammatory macrophage CM. Bioinformatics and validative Western blotting revealed that CTSZ and CXCL10 were significantly differentially expressed, and they were upregulated in the pro- and anti-inflammatory macrophage secretome, respectively. Neutralisation of CTSZ or addition of recombinant CXCL10 to pro-inflammatory macrophage CM reduced CF α-SMA expression, supporting a causal role for CTSZ and CXCL10 in CF activation. Finally, CTSZ cleaved CXCL10 in vitro (33% reduction in 2 hours, 37 o C), which, subsequently, abrogated the suppression of α-SMA expression by CXCL10 in CFs.

Conclusions: Our findings indicate that macrophage phenotype exerts divergent effects on CF behaviour, with pro-inflammatory macrophages promoting CF activation, through enhanced CTSZ secretion and associated CXCL10 cleavage, revealing both proteins as potential targets for modulating fibrosis-driven wound healing.

Aneurysm severity is suppressed by deletion of CCN4

Patients with abdominal aortic aneurysms are frequently treated with high-risk surgery. A pharmaceutical treatment to reverse aneurysm progression could prevent the need for surgery and save both lives and healthcare resources. Since CCN4 regulates cell migration, proliferation and apoptosis, processes involved in aneurysm progression, it is a potential regulator of aneurysm progression. We investigated the role of CCN4 in a mouse aneurysm model, using apolipoprotein-E knockout (ApoE^-/-) mice fed high fat diet and infused with Angiotensin II (AngII). Blood pressure was similarly elevated in CCN4^-/-ApoE^-/- mice and CCN4^+/+ApoE^-/- mice (controls) in response to AngII infusion. Deletion of CCN4 significantly reduced the number of ruptured aortae, both thoracic and abdominal aortic area, and aneurysm grade score, compared to controls. Additionally, the frequency of vessel wall remodelling and the number of elastic lamina breaks was significantly suppressed in CCN4^-/-ApoE^-/- mice compared to controls. Immunohistochemistry revealed a significantly lower proportion of macrophages, while the proportion of smooth muscle cells was not affected by the deletion of CCN4. There was also a reduction in both proliferation and apoptosis in CCN4^-/-ApoE^-/- mice compared to controls. In vitro studies showed that CCN4 significantly increased monocyte adhesion beyond that seen with TNFα and stimulated macrophage migration by more than threefold. In summary, absence of CCN4 reduced aneurysm severity and improved aortic integrity, which may be the result of reduced macrophage infiltration and cell apoptosis. Inhibition of CCN4 could offer a potential therapeutic approach for the treatment of aneurysms.

Effective decellularisation of human saphenous veins for biocompatible arterial tissue engineering applications: Bench optimisation and feasibility in vivo testing

Human saphenous vein (hSV) and synthetic grafts are commonly used conduits in vascular grafting, despite high failure rates. Decellularising hSVs (D-hSVs) to produce vascular scaffolds might be an effective alternative. We assessed the effectiveness of a detergent-based method using 0% to 1% sodium dodecyl sulphate (SDS) to decellularise hSV. Decellularisation effectiveness was measured in vitro by nuclear counting, DNA content, residual cell viability, extracellular matrix integrity and mechanical strength. Cytotoxicity was assessed on human and porcine cells. The most effective SDS concentration was used to prepare D-hSV grafts that underwent preliminary in vivo testing using a porcine carotid artery replacement model. Effective decellularisation was achieved with 0.01% SDS, and D-hSVs were biocompatible after seeding. In vivo xeno-transplantation confirmed excellent mechanical strength and biocompatibility with recruitment of host cells without mechanical failure, and a 50% patency rate at 4-weeks. We have developed a simple biocompatible methodology to effectively decellularise hSVs. This could enhance vascular tissue engineering toward future clinical applications.

NF-κB inhibition prevents acute shear stress-induced inflammation in the saphenous vein graft endothelium

The long saphenous vein (LSV) is commonly used as a conduit in coronary artery bypass grafting. However, long term patency remains limited by the development of vascular inflammation, intimal hyperplasia and accelerated atherosclerosis. The impact of acute exposure of venous endothelial cells (ECs) to acute arterial wall shear stress (WSS) in the arterial circulation, and the subsequent activation of inflammatory pathways, remain poorly defined. Here, we tested the hypothesis that acute exposure of venous ECs to high shear stress is associated with inflammatory responses that are regulated by NF-κB both in-vitro and ex-vivo. Analysis of the LSV endothelium revealed that activation of NF-κB occurred within 30 min after exposure to arterial rates of shear stress. Activation of NF-κB was associated with increased levels of CCL2 production and enhanced binding of monocytes in LSVECs exposed to 6 h acute arterial WSS. Consistent with this, ex vivo exposure of LSVs to acute arterial WSS promoted monocyte interactions with the vessel lumen. Inhibition of the NF-κB pathway prevented acute arterial WSS-induced CCL2 production and reduced monocyte adhesion, both in vitro and in human LSV ex vivo, demonstrating that this pathway is necessary for the induction of the acute arterial WSS-induced pro-inflammatory response. We have identified NF-κB as a critical regulator of acute endothelial inflammation in saphenous vein in response to acute arterial WSS. Localised endothelial-specific inhibition of the NF-κB pathway may be beneficial to prevent vein graft inflammation and consequent failure.

A Protocol for a Novel Human Ex Vivo Model of Aneurysm

Aortic aneurysm rupture is a significant cause of premature mortality worldwide. Although animal models exist, some frequently experience aortic rupture and sudden death. An alternative approach is therefore required that would use human material to aid translation. Accordingly, we present an optimized and validated protocol to isolate human umbilical cord arteries and their subsequent deployment within a bioreactor. Consequently, this reproducible ex vivo human model of aneurysm can be used for pathogenesis studies and accompanying assessment of potential novel therapeutics.

Non-coding RNAs in cardiovascular cell biology and atherosclerosis

Atherosclerosis underlies the predominant number of cardiovascular diseases and remains a leading cause of morbidity and mortality worldwide. The development, progression and formation of clinically relevant atherosclerotic plaques involves the interaction of distinct and over-lapping mechanisms which dictate the roles and actions of multiple resident and recruited cell types including endothelial cells, vascular smooth muscle cells, and monocyte/macrophages. The discovery of non-coding RNAs (ncRNAs) including microRNAs, long non-coding RNAs, and circular RNAs, and their identification as key mechanistic regulators of mRNA and protein expression has piqued interest in their potential contribution to atherosclerosis. Accruing evidence has revealed ncRNAs regulate pivotal cellular and molecular processes during all stages of atherosclerosis including cell invasion, growth, and survival; cellular uptake and efflux of lipids, expression and release of pro- and anti-inflammatory intermediaries, and proteolytic balance. The expression profile of ncRNAs within atherosclerotic lesions and the circulation have been determined with the aim of identifying individual or clusters of ncRNAs which may be viable therapeutic targets alongside deployment as biomarkers of atherosclerotic plaque progression. Consequently, numerous in vivo studies have been convened to determine the effects of moderating the function or expression of select ncRNAs in well-characterized animal models of atherosclerosis. Together, clinicopathological findings and studies in animal models have elucidated the multifaceted and frequently divergent effects ncRNAs impose both directly and indirectly on the formation and progression of atherosclerosis. From these findings' potential novel therapeutic targets and strategies have been discovered which may pave the way for further translational studies and possibly taken forward for clinical application.

Galectin-3 Identifies a Subset of Macrophages With a Potential Beneficial Role in Atherosclerosis

OBJECTIVE

Galectin-3 (formerly known as Mac-2), encoded by the LGALS3 gene, is proposed to regulate macrophage adhesion, chemotaxis, and apoptosis. We investigated the role of galectin-3 in determining the inflammatory profile of macrophages and composition of atherosclerotic plaques. Approach and Results: We observed increased accumulation of galectin-3-negative macrophages within advanced human, rabbit, and mouse plaques compared with early lesions. Interestingly, statin treatment reduced galectin-3-negative macrophage accrual in advanced plaques within hypercholesterolemic (apolipoprotein E deficient) Apoe-/- mice. Accordingly, compared with Lgals3+/+:Apoe-/- mice, Lgals3-/-:Apoe-/- mice displayed altered plaque composition through increased macrophage:smooth muscle cell ratio, reduced collagen content, and increased necrotic core area, characteristics of advanced plaques in humans. Additionally, macrophages from Lgals3-/- mice exhibited increased invasive capacity in vitro and in vivo. Furthermore, loss of galectin-3 in vitro and in vivo was associated with increased expression of proinflammatory genes including MMP (matrix metalloproteinase)-12, CCL2 (chemokine [C-C motif] ligand 2), PTGS2 (prostaglandin-endoperoxide synthase 2), and IL (interleukin)-6, alongside reduced TGF (transforming growth factor)-β1 expression and consequent SMAD signaling. Moreover, we found that MMP12 cleaves macrophage cell-surface galectin-3 resulting in the appearance of a 22-kDa fragment, whereas plasma levels of galectin-3 were reduced in Mmp12-/-:Apoe-/- mice, highlighting a novel mechanism where MMP12-dependent cleavage of galectin-3 promotes proinflammatory macrophage polarization. Moreover, galectin-3-positive macrophages were more abundant within plaques of Mmp12-/-:Apoe-/- mice compared with Mmp12+/+:Apoe-/- animals.

CONCLUSIONS

This study reveals a prominent protective role for galectin-3 in regulating macrophage polarization and invasive capacity and, therefore, delaying plaque progression.

P5000Wnt/b-catenin signalling drives angiotensin II induced cardiac fibrosis via WISP-1

Background

Myocardial infarction (MI) and hypertension lead to myocardial injury, which induces negative remodelling and cardiac fibrosis. Cardiac fibrosis, which involves inflammatory cell infiltration and myofibroblast activation, causes worldwide mortality and morbidity. In response to MI or hypertension induced by prolonged angiotensin II (AngII) exposure, activated myofibroblasts produce extracellular matrix proteins. However, if unchecked, excessive collagen deposition occurs leading to myocardial stiffening, heart failure and arrhythmias.

Purpose

The underlying mechanisms leading to pathological collagen deposition are not fully elucidated. There is debate regarding the involvement of the Wnt signalling pathway and its product Wnt Inducible Signalling pathway protein-1 (WISP-1) in cardiac fibrosis. Therefore, this project aimed to investigate the interaction of AngII and the Wnt/β-catenin signalling pathway in cardiac fibrosis.

Methods

The effect of AngII (100nM) on collagen levels in human cardiac fibroblasts was investigated in vitro (data expressed as fold change from control ± SEM). In vivo experiments (n=6–8) determined the involvement of the Wnt/b-catenin pathway, specifically WISP-1, in response to AngII infusion (500ng/kg/min) for 4 weeks (Apolipoprotein E−/−/WISP-1+/+ vs. ApolipoproteinE−/−/WISP-1−/− mice on a high-fat diet, data expressed as mean positive pixel % ± SEM).

Results

AngII significantly increased collagen type 1 protein levels produced by human cardiac fibroblasts (2.94±0.75 vs 1±0, p<0.05). Inhibition of Wnt/b-catenin signalling with 25nM iCRT14 significantly suppressed AngII-induced collagen levels (0.46±0.07 vs. 1±0, p<0.05). As expected, AngII infusion significantly induced hypertension in all mice. Immunohistochemistry demonstrated type 1 collagen was markedly higher in AngII mice than control mice (1.07±0.27 vs. 0.29±0.06, p<0.05). However, in the absence of WISP-1, AngII did not enhance collagen type 1 levels. Further immunohistochemical analysis of murine hearts demonstrated that AngII infusion caused significant alterations in the Wnt/β-catenin signalling markers AXIN-2 (35±3.9 vs. 10.7±2.6 p<0.05) and PPAR-d (92±1.4 vs. 17.3±4.3 p<0.05). This effect was reduced by WISP-1 deletion. Furthermore, AngII-infusion disrupted N-cadherin junctions (0.55±0.08 vs. 0.29±0.02 p<0.05) suggesting modulation of cell-to-cell contacts and enhanced β-catenin signalling.

Conclusion

This study indicates that AngII enhances cardiac fibrosis via modulation of the Wnt signalling pathway, in part via WISP-1. Further delineation of this interaction may lead to the use of Wnt/β-catenin or WISP-1 inhibitors to suppress myocardial injury induced cardiac fibrosis in post-MI or hypertensive patients.

Acknowledgement/Funding

Elizabeth Blackwell Institute, British Heart Foundation

Sputum smear-positive, culture-negative state during anti-tuberculosis treatment in the MGIT liquid culture era

The sputum smear-positive, culture-negative state poses a challenge for clinicians. Previous studies have shown that most samples with positive smears during the later stages of treatment are culture-negative. Earlier studies generally used solid culture media, which tend to be less sensitive than current liquid culture systems. We examined the smear-positive, culture-negative state in the era of MGIT™ 960™ liquid cultures. We found that the smear-positive, culture-negative state occurred less frequently with MGIT culture, and that the majority of the samples with late positive smears were culture-negative, regardless of media type.

Simulating Transplant Small-for-size Grafts Using Human Liver Monosegments: The Impact of Portal Perfusion Pressure

Small-for-size-liver grafts (SFSG) in adult transplant recipients have elevated risk of graft failure, limiting its application in clinical liver transplantation. Relevant preclinical model of SFSG is lacking. Relevant to deceased-donor split liver transplant and living-donor liver transplant in adult recipients, in this study, we present our initial characterization of SFSG model using monosegments of a discarded human donor liver.

Aging differentially modulates the Wnt pro-survival signalling pathways in vascular smooth muscle cells

We previously reported pro-survival effects of Wnt3a and Wnt5a proteins in vascular smooth muscle cells (VSMCs). Wnt5a achieved this through induction of Wnt1-inducible signalling pathway protein-1 (WISP-1) consequent to β-catenin/CREB-dependent, TCF-independent, signalling. However, we found that as atherosclerosis advances, although Wnt5a protein was increased, WISP-1 was reduced. We hypothesized this disconnect could be due to aging. In this study, we elucidate the mechanism underlying Wnt3a pro-survival signalling and demonstrate the differential effect of age on Wnt3a- and Wnt5a-mediated survival. We show Wnt3a protein was expressed in human atherosclerotic coronary arteries and co-located with macrophages and VSMCs. Meanwhile, Wnt3a stimulation of primary mouse VSMCs increased β-catenin nuclear translocation and TCF, but not CREB, activation. Wnt3a increased mRNA expression of the pro-survival factor WISP-2 in a TCF-dependent manner. Functionally, β-catenin/TCF inhibition or WISP-2 neutralization significantly impaired Wnt3a-mediated VSMC survival. WISP-2 was upregulated in human atherosclerosis and partly co-localized with Wnt3a. The pro-survival action of Wnt3a was effective in VSMCs from young (2 month) and old (18-20 month) mice, whereas Wnt5a-mediated rescue was impaired with age. Further investigation revealed that although Wnt5a induced β-catenin nuclear translocation in VSMCs from both ages, CREB phosphorylation and WISP-1 upregulation did not occur in old VSMCs. Unlike Wnt5a, pro-survival Wnt3a signalling involves β-catenin/TCF and WISP-2. While Wnt3a-mediated survival was unchanged with age, Wnt5a-mediated survival was lost due to impaired CREB activation and WISP-1 regulation. Greater understanding of the effect of age on Wnt signalling may identify targets to promote VSMC survival in elderly patients with atherosclerosis.

Elucidating the contributory role of microRNA to cardiovascular diseases (a review)

Cardiovascular diseases encompassing atherosclerosis, aortic aneurysms, restenosis, and pulmonary arterial hypertension, remain the leading cause of morbidity and mortality worldwide. In response to a range of stimuli, the dynamic interplay between biochemical and biomechanical mechanisms affect the behaviour and function of multiple cell types, driving the development and progression of cardiovascular diseases. Accumulating evidence has highlighted microRNAs (miRs) as significant regulators and micro-managers of key cellular and molecular pathophysiological processes involved in predominant cardiovascular diseases, including cell mitosis, motility and viability, lipid metabolism, generation of inflammatory mediators, and dysregulated proteolysis. Human pathological and clinical studies have aimed to identify select microRNA which may serve as biomarkers of disease and their progression, which are discussed within this review. In addition, I provide comprehensive coverage of in vivo investigations elucidating the modulation of distinct microRNA on the pathophysiology of atherosclerosis, abdominal aortic aneurysms, restenosis, and pulmonary arterial hypertension. Collectively, clinical and animal studies have begun to unravel the complex and often diverse effects microRNAs and their targets impart during the development of cardiovascular diseases and revealed promising therapeutic strategies through which modulation of microRNA function may be applied clinically.

Carotid artery ligation induced intimal thickening and proliferation is unaffected by ageing

Following interventions to treat atherosclerosis, such as coronary artery bypass graft surgery, restenosis occurs in approximately 40% of patients. Identification of proteins regulating intimal thickening could represent targets to prevent restenosis. Our group previously demonstrated that in a murine model of vascular occlusion, Wnt4 protein expression and β-catenin signalling was upregulated which promoted vascular smooth muscle cell (VSMC) proliferation and intimal thickening. In this study, the effect of age on VSMC proliferation, intimal hyperplasia and Wnt4 expression was investigated. In vitro proliferation of VSMCs isolated from young (2 month) or old (18-20 month) C57BL6/J mice was assessed by immunocytochemistry for EdU incorporation. As previously reported, 400 ng/mL recombinant Wnt4 protein increased proliferation of VSMCs from young mice. However, this response was absent in VSMCs from old mice. As our group previously reported reduced intimal hyperplasia in Wnt4+/- mice compared to wildtype controls, we hypothesised that impaired Wnt4 signalling with age may result in reduced neointimal formation. To investigate this, carotid artery ligation was performed in young and old mice and neointimal area was assessed 21 days later. Surprisingly, neointimal area and percentage lumen occlusion were not significantly affected by age. Furthermore, neointimal cell density and proliferation were also unchanged. These data suggest that although Wnt4-mediated proliferation was impaired with age in primary VSMCs, carotid artery ligation induced neointimal formation and proliferation were unchanged in old mice. These results imply that Wnt4-mediated proliferation is unaffected by age in vivo, suggesting that therapeutic Wnt4 inhibition could inhibit restenosis in patients of all ages.

Reader variability and validation of the Timika X-ray score during treatment of pulmonary tuberculosis

SETTING

Chest radiographs (CXRs) are widely used for diagnosing pulmonary TB and assessing response to therapy. The Timika X-ray score has been proposed as a tool for measuring disease severity and predicting treatment outcome.

OBJECTIVE

To evaluate inter- and intra-reader agreement of Timika scores and assess the ability of the score to predict microbiologic outcome at 2 months.

DESIGN

Analytical validation study. Disease severity was measured by two readers using pretreatment radiographs and follow-up films taken at 2, 6 and 12 months after the start of treatment among 110 human immunodeficiency virus negative adults with pulmonary TB. One fourth of the films were reread to assess intra-reader agreement.

RESULTS

The two-component Timika score had high inter- and intra-reader agreement (intraclass correlation (ICC)_inter = 75%, ICC_intra > 0.81). Baseline Timika score was associated with positive month 2 smear (P = 0.0004) and culture status (P = 0.03). The average Timika score declined significantly over the course of successful treatment.

CONCLUSION

The Timika score showed good inter- and intra-reader agreement and a significant association with microbiological outcomes after 2 months of treatment. The results of this study strengthen the evidence supporting the use of the Timika score for measuring disease severity on CXR.

Defining the optimal dose of rifapentine for pulmonary tuberculosis: Exposure-response relations from two phase II clinical trials

Rifapentine is a highly active antituberculosis antibiotic with treatment-shortening potential; however, exposure-response relations and the dose needed for maximal bactericidal activity have not been established. We used pharmacokinetic/pharmacodynamic data from 657 adults with pulmonary tuberculosis participating in treatment trials to compare rifapentine (n = 405) with rifampin (n = 252) as part of intensive-phase therapy. Population pharmacokinetic/pharmacodynamic analyses were performed with nonlinear mixed-effects modeling. Time to stable culture conversion of sputum to negative was determined in cultures obtained over 4 months of therapy. Rifapentine exposures were lower in participants who were coinfected with human immunodeficiency virus, black, male, or fasting when taking drug. Rifapentine exposure, large lung cavity size, and geographic region were independently associated with time to culture conversion in liquid media. Maximal treatment efficacy is likely achieved with rifapentine at 1,200 mg daily. Patients with large lung cavities appear less responsive to treatment, even at high rifapentine doses.

Functional and cardioprotective effects of simultaneous and individual activation of protein kinase A and Epac

Background and Purpose

Myocardial cAMP elevation confers cardioprotection against ischaemia/reperfusion (I/R) injury. cAMP activates two independent signalling pathways, PKA and Epac. This study investigated the cardiac effects of activating PKA and/or Epac and their involvement in cardioprotection against I/R.

Experimental Approach

Hearts from male rats were used either for determination of PKA and PKC activation or perfused in the Langendorff mode for either cardiomyocyte isolation or used to monitor functional activity at basal levels and after 30 min global ischaemia and 2 h reperfusion. Functional recovery and myocardial injury during reperfusion (LDH release and infarct size) were evaluated. Activation of PKA and/or Epac in perfused hearts was induced using cell permeable cAMP analogues in the presence or absence of inhibitors of PKA, Epac and PKC. H9C2 cells and cardiomyocytes were used to assess activation of Epac and effect on Ca²⁺ transients.

Key Results

Selective activation of either PKA or Epac was found to trigger a positive inotropic effect, which was considerably enhanced when both pathways were simultaneously activated. Only combined activation of PKA and Epac induced marked cardioprotection against I/R injury. This was accompanied by PKCε activation and repressed by inhibitors of PKA, Epac or PKC.

Conclusion and Implications

Simultaneous activation of both PKA and Epac induces an additive inotropic effect and confers optimal and marked cardioprotection against I/R injury. The latter effect is mediated by PKCε activation. This work has introduced a new therapeutic approach and targets to protect the heart against cardiac insults.

MicroRNA-181b Controls Atherosclerosis and Aneurysms Through Regulation of TIMP-3 and Elastin

Supplemental Digital Content is available in the text.

Rationale:

Atherosclerosis and aneurysms are leading causes of mortality worldwide. MicroRNAs (miRs) are key determinants of gene and protein expression, and atypical miR expression has been associated with many cardiovascular diseases; although their contributory role to atherosclerotic plaque and abdominal aortic aneurysm stability are poorly understood.

Objective:

To investigate whether miR-181b regulates tissue inhibitor of metalloproteinase-3 expression and affects atherosclerosis and aneurysms.

Methods and Results:

Here, we demonstrate that miR-181b was overexpressed in symptomatic human atherosclerotic plaques and abdominal aortic aneurysms and correlated with decreased expression of predicted miR-181b targets, tissue inhibitor of metalloproteinase-3, and elastin. Using the well-characterized mouse atherosclerosis models of Apoe^−/− and Ldlr^−/−, we observed that in vivo administration of locked nucleic acid anti-miR-181b retarded both the development and the progression of atherosclerotic plaques. Systemic delivery of anti-miR-181b in angiotensin II–infused Apoe^−/− and Ldlr^−/− mice attenuated aneurysm formation and progression within the ascending, thoracic, and abdominal aorta. Moreover, miR-181b inhibition greatly increased elastin and collagen expression, promoting a fibrotic response and subsequent stabilization of existing plaques and aneurysms. We determined that miR-181b negatively regulates macrophage tissue inhibitor of metalloproteinase-3 expression and vascular smooth muscle cell elastin production, both important factors in maintaining atherosclerotic plaque and aneurysm stability. Validation studies in Timp3^−/− mice confirmed that the beneficial effects afforded by miR-181b inhibition are largely tissue inhibitor of metalloproteinase-3 dependent, while also revealing an additional protective effect through elevating elastin synthesis.

Conclusions:

Our findings suggest that the management of miR-181b and its target genes provides therapeutic potential for limiting the progression of atherosclerosis and aneurysms and protecting them from rupture.

Wnt2 and WISP-1/CCN4 Induce Intimal Thickening via Promotion of Smooth Muscle Cell Migration

OBJECTIVE

Increased vascular smooth muscle cell (VSMC) migration leads to intimal thickening which acts as a soil for atherosclersosis, as well as causing coronary artery restenosis after stenting and vein graft failure. Investigating factors involved in VSMC migration may enable us to reduce intimal thickening and improve patient outcomes. In this study, we determined whether Wnt proteins regulate VSMC migration and thereby intimal thickening.

APPROACH AND RESULTS

Wnt2 mRNA and protein expression were specifically increased in migrating mouse aortic VSMCs. Moreover, VSMC migration was induced by recombinant Wnt2 in vitro. Addition of recombinant Wnt2 protein increased Wnt1-inducible signaling pathway protein-1 (WISP-1) mRNA by ≈1.7-fold, via β-catenin/T-cell factor signaling, whereas silencing RNA knockdown of Wnt-2 reduced WISP-1 mRNA by ≈65%. Treatment with rWISP-1 significantly increased VSMC migration by ≈1.5-fold, whereas WISP-1 silencing RNA knockdown reduced migration by ≈40%. Wnt2 and WISP-1 effects were integrin-dependent and not additive, indicating that Wnt2 promoted VSMC migration via WISP-1. Additionally, Wnt2 and WISP-1 were significantly increased and colocated in human coronary arteries with intimal thickening. Reduced Wnt2 and WISP-1 levels in mouse carotid arteries from Wnt2(+/-) and WISP-1(-/-) mice, respectively, significantly suppressed intimal thickening in response to carotid artery ligation. In contrast, elevation of plasma WISP-1 via an adenovirus encoding WISP-1 significantly increased intimal thickening by ≈1.5-fold compared with mice receiving control virus.

CONCLUSIONS

Upregulation of Wnt2 expression enhanced WISP-1 and promoted VSMC migration and thereby intimal thickening. As novel regulators of VSMC migration and intimal thickening, Wnt2 or WISP-1 may provide a potential therapy for restenosis and vein graft failure.

Differential effects of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 on atherosclerosis and monocyte/macrophage invasion

AIMS

MMPs contribute to atherosclerotic plaque progression and instability, but the relative potency of their endogenous tissue inhibitors of metalloproteinases (TIMPs) as protective factors has not been defined. We therefore investigated the impact of TIMP-1 and TIMP-2 knockout on atherosclerotic plaque burden and composition in apolipoprotein E-knockout (Apoe(-/-)) mice and studied the underlying effects on monocyte/macrophage behaviour.

METHODS AND RESULTS

Analysis of brachiocephalic artery plaques revealed comparable atherosclerotic lesion areas between TIMP-1(-/-) Apoe(-/-) or TIMP-2(-/-) Apoe(-/-) double deficient mice and relevant age-matched, strain-matched Apoe(-/-) controls after 8 weeks of high-fat feeding. However, lesions from TIMP-2(-/-) Apoe(-/-) mice had higher levels of markers associated with plaque vulnerability, including increased macrophage: vascular smooth muscle cell ratios, larger necrotic core areas, reduced collagen contents, increased macrophage proliferation, and apoptosis frequencies, compared with TIMP-1(-/-)Apoe(-/-) and controls. In contrast, TIMP-1(-/-) Apoe(-/-) animals only had a significant reduction in vascular smooth muscle cell content compared with Apoe(-/-) controls. In vitro and in vivo findings implicated heightened monocyte/macrophage invasion in the detrimental effects observed on atherosclerotic plaque composition in TIMP-2(-/-) Apoe(-/-) mice. Moreover, TIMP-2 specifically decreased MMP-14-dependent monocyte/macrophage infiltration into sites of experimentally induced inflammation and established atherosclerotic lesions.

CONCLUSION

Our data demonstrate that TIMP-2 plays a greater protective role than TIMP-1 during the pathogenesis of atherosclerosis, in part by suppressing MMP-14-dependent monocyte/macrophage accumulation into plaques.

Platelet-Associated Matrix Metalloproteinases Regulate Thrombus Formation and Exert Local Collagenolytic Activity

Objective—

Platelets are increasingly implicated in processes beyond hemostasis and thrombosis, such as vascular remodeling. Members of the matrix metalloproteinase (MMP) family not only remodel the extracellular matrix but also modulate platelet function. Here, we made a systematic comparison of the roles of MMP family members in acute thrombus formation under flow conditions and assessed platelet-dependent collagenolytic activity over time.

Approach and Results—

Pharmacological inhibition of MMP-1 or MMP-2 (human) or deficiency in MMP-2 (mouse) suppressed collagen-dependent platelet activation and thrombus formation under flow, whereas MMP-9 inhibition/deficiency stimulated these processes. The absence of MMP-3 was without effect. Interestingly, MMP-14 inhibition led to the formation of larger thrombi, which occurred independently of its capacity to activate MMP-2. Platelet thrombi exerted local collagenolytic activity capable of cleaving immobilized dye-quenched collagen and fibrillar collagen fibers within hours, with loss of the majority of the platelet adhesive properties of collagen as a consequence. This collagenolytic activity was redundantly mediated by platelet-associated MMP-1, MMP-2, MMP-9, and MMP-14 but occurred independently of platelet α-granule release ( Nbeal2 −/− mice). The latter was in line with subcellular localization experiments, which indicated a granular distribution of MMP-1 and MMP-2 in platelets, distinct from α-granules. Whereas MMP-9 protein could not be detected inside platelets, activated platelets did bind plasma-derived MMP-9 to their plasma membrane. Overall, platelet MMP activity was predominantly membrane-associated and influenced by platelet activation status.

Conclusions—

Platelet-associated MMP-1, MMP-2, MMP-9, and MMP-14 differentially modulate acute thrombus formation and at later time points limit thrombus formation by exerting collagenolytic activity.

Magnetic resonance imaging visualization of vulnerable atherosclerotic plaques at the brachiocephalic artery of apolipoprotein E knockout mice by the blood-pool contrast agent B22956/1

The aim of this study was to identify, by magnetic resonance imaging (MRI), the ability of the blood-pool contrast agent B22956/1 to detect atherosclerotic plaques developing at the brachiocephalic artery of apolipoprotein E knockout (apoE-KO) mice and to possibly identify vulnerable atherosclerotic lesions. After high-fat feeding for 8 or 12 weeks, MRIs of brachiocephalic arteries were acquired before and after B22956/1 administration; then vessels were removed and analyzed by histology. B22956/1 injection caused a rapid increase in plaque signal enhancement and plaque to muscle contrast values, which remained stable up to 70 minutes. A linear correlation between signal enhancement and macrophage content was found 10 minutes after B22956/1 injection (p < .01). Signal enhancement and plaque to muscle contrast values correlated with macrophage content 40 minutes after contrast agent administration (p < .01). Finally, 70 minutes after B22956/1 infusion, plaque to muscle contrast significantly correlated with the percentage of stenosis (p < .005). B22956/1 administration to high fat-fed apoE-KO mice resulted in a rapid enhancement of atherosclerotic plaques and in a great ability to rapidly visualize vulnerable plaques, characterized by a high macrophage content. These results suggest that B22956/1 could represent an interesting tool for the identification of atherosclerotic plaques potentially leading to acute cardiovascular events.

Platinum coat color in red fox (Vulpes vulpes) is caused by a mutation in an autosomal copy of KIT

The red fox (Vulpes vulpes) demonstrates a variety of coat colors including platinum, a common phenotype maintained in farm-bred fox populations. Foxes heterozygous for the platinum allele have a light silver coat and extensive white spotting, whereas homozygosity is embryonic lethal. Two KIT transcripts were identified in skin cDNA from platinum foxes. The long transcript was identical to the KIT transcript of silver foxes, whereas the short transcript, which lacks exon 17, was specific to platinum. The KIT gene has several copies in the fox genome: an autosomal copy on chromosome 2 and additional copies on the B chromosomes. To identify the platinum-specific KIT sequence, the genomes of one platinum and one silver fox were sequenced. A single nucleotide polymorphism (SNP) was identified at the first nucleotide of KIT intron 17 in the platinum fox. In platinum foxes, the A allele of the SNP disrupts the donor splice site and causes exon 17, which is part of a segment that encodes a conserved tyrosine kinase domain, to be skipped. Complete cosegregation of the A allele with the platinum phenotype was confirmed by linkage mapping (LOD 25.59). All genotyped farm-bred platinum foxes from Russia and the US were heterozygous for the SNP (A/G), whereas foxes with different coat colors were homozygous for the G allele. Identification of the platinum mutation suggests that other fox white-spotting phenotypes, which are allelic to platinum, would also be caused by mutations in the KIT gene.

cAMP-induced actin cytoskeleton remodelling inhibits MKL1-dependent expression of the chemotactic and pro-proliferative factor, CCN1

Elevation of intracellular cAMP concentration has numerous vascular protective effects that are in part mediated via actin cytoskeleton-remodelling and subsequent regulation of gene expression. However, the mechanisms are incompletely understood. Here we investigated whether cAMP-induced actin-cytoskeleton remodelling modulates VSMC behaviour by inhibiting expression of CCN1. In cultured rat VSMC, CCN1-silencing significantly inhibited BrdU incorporation and migration in a wound healing assay. Recombinant CCN1 enhanced chemotaxis in a Boyden chamber. Adding db-cAMP, or elevating cAMP using forskolin, significantly inhibited CCN1 mRNA and protein expression in vitro; transcriptional regulation was demonstrated by measuring pre-spliced CCN1 mRNA and CCN1-promoter activity. Forskolin also inhibited CCN1 expression in balloon injured rat carotid arteries in vivo. Inhibiting RhoA activity, which regulates actin-polymerisation, by cAMP-elevation or pharmacologically with C3-transferase, or inhibiting its downstream kinase, ROCK, with Y27632, significantly inhibited CCN1 expression. Conversely, expression of constitutively active RhoA reversed the inhibitory effects of forskolin on CCN1 mRNA. Furthermore, CCN1 mRNA levels were significantly decreased by inhibiting actin-polymerisation with latrunculin B or increased by stimulating actin-polymerisation with Jasplakinolide. We next tested the role of the actin-dependent SRF co-factor, MKL1, in CCN1 expression. Forskolin inhibited nuclear translocation of MKL1 and binding of MKL1 to the CCN1 promoter. Constitutively-active MKL1 enhanced basal promoter activity of wild-type but not SRE-mutated CCN1; and prevented forskolin inhibition. Furthermore, pharmacological MKL-inhibition with CCG-1423 significantly inhibited CCN1 promoter activity as well as mRNA and protein expression. Our data demonstrates that cAMP-induced actin-cytoskeleton remodelling regulates expression of CCN1 through MKL1: it highlights a novel cAMP-dependent mechanism controlling VSMC behaviour.

Classical and Alternative Activation and Metalloproteinase Expression Occurs in Foam Cell Macrophages in Male and Female ApoE Null Mice in the Absence of T and B Lymphocytes

BACKGROUND

Rupture of advanced atherosclerotic plaques accounts for most life-threatening myocardial infarctions. Classical (M1) and alternative (M2) macrophage activation could promote atherosclerotic plaque progression and rupture by increasing production of proteases, including matrix metalloproteinases (MMPs). Lymphocyte-derived cytokines may be essential for generating M1 and M2 phenotypes in plaques, although this has not been rigorously tested until now.

METHODS AND RESULTS

We validated the expression of M1 markers (iNOS and COX-2) and M2 markers (arginase-1, Ym-1, and CD206) and then measured MMP mRNA levels in mouse macrophages during classical and alternative activation in vitro. We then compared mRNA expression of these genes ex vivo in foam cells from subcutaneous granulomas in fat-fed immune-competent ApoE knockout (KO) and immune-compromised ApoE/Rag-1 double-KO mice, which lack all T and B cells. Furthermore, we performed immunohistochemistry in subcutaneous granulomas and in aortic root and brachiocephalic artery atherosclerotic plaques to measure the extent of M1/M2 marker and MMP protein expression in vivo. Classical activation of mouse macrophages with bacterial lipopolysaccharide in vitro increased MMPs-13, -14, and -25 but decreased MMP-19 and TIMP-2 mRNA expressions. Alternative activation with IL-4 increased MMP-19 expression. Foam cells in subcutaneous granulomas expressed all M1/M2 markers and MMPs at ex vivo mRNA and in vivo protein levels, irrespective of Rag-1 genotype. There were also similar percentages of foam cell macrophages (FCMs) carrying M1/M2 markers and MMPs in atherosclerotic plaques from ApoE KO and ApoE/Rag-1 double-KO mice.

CONCLUSION

Classical and alternative activation leads to distinct MMP expression patterns in mouse macrophages in vitro. M1 and M2 polarization in vivo occurs in the absence of T and B lymphocytes in either granuloma or plaque FCMs.

MicroRNA-24 regulates macrophage behavior and retards atherosclerosis

OBJECTIVE

Our recent studies have highlighted membrane type-1 matrix metalloproteinase (MMP)-14 as a selective marker for an invasive subset of macrophages potentially related to atherosclerotic plaque progression. Moreover, colony stimulating factors (CSF) may exert divergent effects on macrophage MMP expression, possibly through microRNAs. We, therefore, aim to identify and test the pathophysiological role of microRNAs, which modulate macrophage MMP-14 expression in atherosclerotic plaque progression.

APPROACH AND RESULTS

Compared with macrophage CSF-differentiated macrophages, granulocyte/macrophage CSF-matured macrophages exhibited reduced MMP-14 mRNA levels but increased protein expression and activity, which resulted in heightened macrophage invasion. MicroRNA-24, identified to target MMP-14, was accordingly increased in macrophage CSF compared with granulocyte/macrophage CSF macrophages. Silencing microRNA-24 in macrophage CSF macrophages significantly increased MMP-14 expression and enhanced their invasive capacity, mimicking granulocyte/macrophage CSF macrophages, and suggesting that granulocyte/macrophage CSF modulates MMP-14 protein expression and subsequent macrophage invasion in a microRNA-24-dependent manner. In human coronary atherosclerotic plaques, increased MMP-14 protein expression in foam cell macrophages was associated with lesions exhibiting histological characteristics associated with an unstable phenotype. Furthermore, microRNA-24 expression in these atherosclerotic plaques was inversely related to MMP-14 protein expression. Moreover, stable plaques contained higher microRNA-24 levels than unstable plaques, and microRNA-24 colocalized with foam cell macrophages that exhibited low MMP-14 protein expression. Finally, in atherosclerotic mice (apolipoprotein E-deficient), microRNA-24 inhibition increased plaque size and macrophage MMP-14 expression.

CONCLUSIONS

Taken together, our data demonstrates that downregulation of microRNA-24 promotes an invasive macrophage subset and plays a novel regulatory role in MMP-14 proteolytic activity and, therefore, plaque stability, highlighting its therapeutic potential.

EC4, a truncation of soluble N-cadherin, reduces vascular smooth muscle cell apoptosis and markers of atherosclerotic plaque instability

Atherosclerotic plaque instability is precipitated by vascular smooth muscle cell apoptosis in the fibrous cap, weakening it and leading to plaque rupture. We previously showed that reducing smooth muscle cell apoptosis with soluble N-cadherin (SNC) increased features of plaque stability. We have now identified the active site of SNC and examined whether a truncated form containing this site retains the antiapoptotic effect. SNC was mutated to prevent interaction with N-cadherin or fibroblast growth factor receptor (FGFR). Interaction with FGFR in the extracellular (EC) 4 domain of SNC was essential for the antiapoptotic effect. Therefore, we made a truncated form consisting of the EC4 domain. EC4 significantly reduced smooth muscle cell, macrophage, and endothelial cell apoptosis in vitro by ~70%, similar to SNC. Elevation of plasma levels of EC4 in male apolipoprotein E-deficient mice with existing atherosclerosis significantly reduced apoptosis in brachiocephalic artery plaques by ~50%. EC4 reduced plaque size and the incidence of buried fibrous layers and the macrophage:smooth muscle cell ratio (surrogate markers of plaque instability). Interaction of EC4 with FGFR induced potent antiapoptotic signaling in vitro and in vivo. EC4 modulates atherosclerosis in mice demonstrating its therapeutic potential for retarding plaque size and instability.

The anti-atherogenic cytokine interleukin-33 inhibits the expression of a disintegrin and metalloproteinase with thrombospondin motifs-1, -4 and -5 in human macrophages: Requirement of extracellular signal-regulated kinase, c-Jun N-terminal kinase and phosphoinositide 3-kinase signaling pathways

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Cytokines, and proteases expressed by macrophages play key roles in atherosclerosis.

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The proteases ADAMTS-1, -4 and -5 were expressed in human atherosclerotic lesions.

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The anti-atherogenic cytokine interleukin-33 (IL-33) inhibited the expression of these ADAMTS proteases in human macrophages.

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This action of IL-33 required extracellular signal-regulated kinase, c-Jun N-terminal kinase and phosphoinositide 3-kinase signaling pathways.

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These studies reveal novel anti-atherogenic action of IL-33 along with the underlying molecular mechanisms involved.

Atherosclerosis is an inflammatory disorder of the vasculature regulated by cytokines. Amongst the cytokines, IL-33 attenuates the development of atherosclerosis in mouse model systems via several mechanisms, including inhibition of macrophage foam cell formation and promotion of a Th1 to Th2 shift. Proteases produced by macrophages, such as matrix metalloproteinases and members of ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) family, play potential roles in regulating atherosclerotic plaque stability. Despite such importance, the action of IL-33 on the expression of such proteases has not been analyzed. We have therefore investigated the effect of IL-33 on the expression of ADAMTS-1, -4 and -5 in human macrophages. Immunohistochemical analysis showed that these three proteases were expressed in human atherosclerotic lesions, particularly by macrophages and, to a lesser extent, by smooth muscle cells and endothelial cells. The expression of ADAMTS-1, -4 and -5 in human macrophages was specifically inhibited by IL-33. The action of IL-33 on the expression of these ADAMTS members was mediated through its receptor ST2. IL-33 activated ERK1/2, JNK1/2 and c-Jun, but not p38 MAPK or Akt, in human macrophages. RNA interference assays using a combination of adenoviral encoding small hairpin RNA and small interfering RNA showed a requirement of ERK1/2, JNK1/2, c-Jun, PI3Kγ and PI3Kδ, but not p38α, in the IL-33-inhibited expression of these ADAMTS isoforms. These studies provide novel insights into the expression of ADAMTS-1, -4 and -5 in human atherosclerotic lesions and the regulation of their expression in human macrophages by the key anti-atherogenic cytokine IL-33.

Relapse more common than reinfection in recurrent tuberculosis 1-2 years post treatment in urban Uganda

OBJECTIVE

To determine the proportion of recurrent tuberculosis (TB) due to relapse with the patient's initial strain or reinfection with a new strain of Mycobacterium tuberculosis 1-2 years after anti-tuberculosis treatment in Uganda, a sub-Saharan TB-endemic country.

DESIGN

Records of patients with culture-confirmed TB who completed treatment at an urban Ugandan clinic were reviewed. Restriction fragment length polymorphism (RFLP) patterns were used to determine relapse or reinfection. Associations between human immunodeficiency virus (HIV) positivity and type of TB recurrence were determined.

RESULTS

Of 1701 patients cured of their initial TB episode with a median follow-up of 1.24 years, 171 (10%) had TB recurrence (8.4 per 100 person-years). Rate and risk factors for recurrence were similar to other studies from sub-Saharan Africa. Insertion sequence (IS) 6110-based RFLP of paired isolates from 98 recurrences identified 80 relapses and 18 reinfections. Relapses among HIV-positive and -negative patients were respectively 79% and 85% of recurrences.

CONCLUSIONS

Relapse was more common and presented earlier than reinfection in both HIV-positive and -negative TB patients 1-2 years after completing treatment. These findings impact both the choice of retreatment drug regimen, as relapsing patients are at higher risk for acquired drug resistance, and clinical trials of new TB regimens with relapse as clinical endpoint.

Smoking and 2-month culture conversion during anti-tuberculosis treatment

OBJECTIVE

To investigate risk factors for delayed sputum culture conversion to negative during anti-tuberculosis treatment, with an emphasis on smoking.

DESIGN

Nested case-control study of adults with non-cavitary, culture-confirmed pulmonary tuberculosis (TB) participating in an anti-tuberculosis treatment trial in Brazil. A case of delayed culture conversion was a patient who remained culture-positive after 2 months of treatment. Odds ratios with 95% confidence intervals were calculated.

RESULTS

Fifty-three cases and 240 control patients were analyzed. Smokers had three-fold greater odds of remaining culture-positive after 2 months of treatment (P = 0.007) than non-smokers, while smokers and ex-smokers who smoked >20 cigarettes a day had two-fold greater odds of remaining culture-positive after 2 months of treatment (P = 0.045).

CONCLUSION

Cigarette smoking adversely affects culture conversion during anti-tuberculosis treatment. Support for smoking cessation should be considered to improve outcomes in TB control programs.

Anti-tuberculosis treatment outcomes in HIV-infected adults exposed to isoniazid preventive therapy in Botswana

SETTING

Eight public health clinics in Gaborone and Francistown, Botswana.

OBJECTIVES

To describe the characteristics and outcomes of incident tuberculosis (TB) cases in human immunodeficiency virus (HIV) infected adults exposed to isoniazid preventive therapy (IPT) with access to antiretroviral and anti-tuberculosis treatment.

DESIGN

In 1995 HIV-infected adults, TB disease was excluded before commencing IPT. During and after receipt of 6 or 36 months of IPT, symptomatic participants were evaluated using chest radiographs, sputum microscopy, cultures and drug susceptibility testing (DST). Incident TB cases received ≥6 months of anti-tuberculosis treatment.

RESULTS

Seventy-five incident TB cases were identified among 619 symptomatic participants. The median duration of IPT in these cases was 6 months (range 1-35), and the median time to initiation of anti-tuberculosis treatment was 12 months after IPT cessation. Antiretroviral therapy (ART) was initiated before anti-tuberculosis treatment in 37 cases. Culture was positive in 43/58 (74%) TB cultures. DST was available for 38 cases, of which six (16%) were resistant to isoniazid (INH); 67/75 (89%) cases, including four with INH-monoresistant TB, completed anti-tuberculosis treatment or were cured.

CONCLUSIONS

With prompt initiation of anti-tuberculosis treatment and access to ART, excellent outcomes were achieved in a public health setting in HIV-infected adults who developed TB disease.