Circulation research [journal]
- Proliferation and Recruitment Contribute to Myocardial Macrophage Expansion in Chronic Heart Failure. [JOURNAL ARTICLE]
- Circ Res 2016 Jul 21.
Macrophages reside in the healthy myocardium, participate in ischemic heart disease and modulate myocardial infarction (MI) healing. Their origin and roles in post-MI remodeling of non-ischemic remote myocardium, however, remain unclear.This study investigated the number, origin, phenotype and function of remote cardiac macrophages residing in the non-ischemic myocardium in mice with chronic heart failure after coronary ligation.Eight weeks post-MI, fate mapping and flow cytometry revealed that a 2.9-fold increase in remote macrophages results from both increased local macrophage proliferation and monocyte recruitment. Heart failure produced by extensive MI, through activation of the sympathetic nervous system, expanded medullary and extramedullary hematopoiesis. Circulating Ly6C(high) monocytes rose from 64±5 to 108±9 /µl blood (p<0.05). Cardiac monocyte recruitment declined in Ccr2(-/-) mice, reducing macrophage numbers in the failing myocardium. Mechanical strain of primary murine and human macrophage cultures promoted cell cycle entry, suggesting that the increased wall tension in post-MI heart failure stimulates local macrophage proliferation. Strained cells activated the MAPK pathway, while specific inhibitors of this pathway reduced macrophage proliferation in strained cell cultures and in the failing myocardium (p<0.05). Steady-state cardiac macrophages, monocyte-derived and locally sourced macrophages isolated from failing myocardium expressed different genes in a pattern distinct from the M1/M2 macrophage polarization paradigm. In vivo silencing of endothelial cell adhesion molecules curbed post-MI monocyte recruitment to the remote myocardium and preserved ejection fraction (27.4±2.4 vs.19.1±2%, p<0.05).Myocardial failure is influenced by an altered myeloid cell repertoire.
- AMP-Activated Protein Kinase Alpha 2 Deletion Induces VSMC Phenotypic Switching and Reduces Features of Atherosclerotic Plaque Stability. [JOURNAL ARTICLE]
- Circ Res 2016 Jul 20.
AMP-activated protein kinase (AMPK) has been reported to play a protective role in atherosclerosis. However, whether or not AMPKα2 controls atherosclerotic plaque stability remains unknown.The aim of this study was to evaluate the impact of AMPKα2 deletion on atherosclerotic plaque stability in advanced atherosclerosis at the brachiocephalic arteries (BA) and to elucidate the underlying mechanisms.Features of atherosclerotic plaque stability and the markers for contractile or synthetic vascular smooth muscle cell (VSMC) phenotypes were monitored in the BA from Apoe(-/-)AMPKα2(-/-) mice or VSMC-specific AMPKα2(-/-) mice in an Apoe(-/-) background (Apoe(-/-)AMPKα2sm(-/-)) fed western diet for 10 weeks. We identified that Apoe(-/-)AMPKα2(-/-) mice and Apoe(-/-)AMPKα2sm(-/-) mice exhibited similar unstable plaque features, aggravated VSMC phenotypic switching and significant upregulation of Kruppel-like factor 4 (KLF4) in the plaques located in the BA compared to those found in Apoe(-/-) and Apoe(-/-)AMPKα2sm(+/+) control mice. Pravastatin, an AMPK activator, suppressed VSMC phenotypic switching and alleviated features of atherosclerotic plaque instability in Apoe(-/-)AMPKα2sm(+/+) mice, but not in Apoe(-/-)AMPKα2sm(-/-) mice. VSMC isolated from AMPKα2(-/-) mice displayed a significant reduction of contractile proteins(SM α-actin, calponin and SM-MHC) in parallel with increased detection of synthetic proteins (vimentin and osteopontin) and KLF4, as observed in vivo. KLF4-specific siRNA abolished AMPKα2 deletion-induced VSMC phenotypic switching. Further, pharmacological or genetic inhibition of NF-κB significantly decreased KLF4 upregulation in VSMC from AMPKα2(-/-) Finally, we found AMPKα2 deletion markedly promoted the binding of NF-κBp65 to KLF4 promoter.This study demonstrated that AMPKα2 deletion induces VSMC phenotypic switching and promotes features of atherosclerotic plaque instability in NF-κB-KLF4 dependent manner.
- Enhanced HDL Functionality in Small HDL Species Produced Upon Remodeling of HDL by Reconstituted HDL, CSL112: Effects on Cholesterol Efflux, Anti-Inflammatory and Antioxidative Activity. [JOURNAL ARTICLE]
- Circ Res 2016 Jul 19.
CSL112, human apolipoprotein A-I (apoA-I) reconstituted with phosphatidylcholine, is known to cause a dramatic rise in small high-density lipoprotein (HDL).To explore the mechanisms by which the formation of small HDL particles is induced by CSL112.Infusion of CSL112 into humans caused elevation of two small diameter HDL fractions and one large diameter fraction. Ex vivo studies showed that this remodeling does not depend on lipid transfer proteins or lipases. Rather, interaction of CSL112 with purified HDL spontaneously gave rise to three HDL species: a large, spherical species composed of apoA-I from native HDL and CSL112; a small, disc-shaped species composed of apoA-I from CSL112, but smaller due to the loss of phospholipids; and the smallest species, lipid-poor apoA-I composed of apoA-I from HDL and CSL112. Time-course studies suggest remodeling occurs by an initial fusion of CSL112 with HDL and subsequent fission leading to the smaller forms. Functional studies showed that ATP-binding cassette transporter 1-dependent cholesterol efflux and anti-inflammatory effects in whole blood were carried by the two small species with little activity in the large species. In contrast, the ability to inactivate lipid hydroperoxides in oxidized low-density lipoprotein was carried predominantly by the two largest species and was very low in lipid-poor apoA-I.We have described a mechanism for the formation of small, highly functional HDL species involving spontaneous fusion of discoidal HDL with spherical HDL and subsequent fission. Similar remodeling is likely to occur during the life cycle of apoA-I in vivo.
- Age and Human Regenerative Capacity: Impact of Cardiovascular Risk Factors. [JOURNAL ARTICLE]
- Circ Res 2016 Jul 19.
We investigated aging of human endogenous reparative capacity and aimed to clarify whether it is affected by presence of cardiovascular disease or its risk factors.Circulating progenitor cell (PC) levels reflect endogenous regenerative potential. The effect on PC of healthy aging compared to aging with risk factors (RF) or cardiovascular disease (CVD) is unknown. We examined whether exposure to RF and CVD leads to an accelerated decline in circulating PC with increasing age.In 2,792 adult subjects, 498 were free of RFs (smoking, diabetes, hypertension or hyperlipidemia); 1036 subjects had 1-2 RF, and 1253 had ≥3 RFs and/or CVD. PC were enumerated by flow cytometry as CD45(med+) mononuclear cells expressing CD34 and subsets co-expressing CD133, CXCR4, and vascular endothelial growth factor receptor-2 (VEGF2R) epitopes. Younger age, male gender and larger body size correlated with higher PC counts (p<0.01). After multivariable adjustment, both age and RF categories were independently associated with PC counts (p<0.05), with lower PC counts in older subjects and those with higher RF burden or CVD. PC counts remained unchanged with increasing age in healthy individuals. There were significant interactions between age and RF categories (p≤0.005), such that for younger subjects (60 years), RFs and CVD were associated with lower PC counts.Circulating PC levels do not decline with healthy aging; RF exposure at a younger age stimulates PC mobilization whereas continued exposure is associated with lower PC levels in later life. Over the lifespan, exposure to RFs and CVD is associated with an initial stimulation and subsequent decline in circulating PC levels, which reflect endogenous regenerative capacity.
- LNK/SH2B3 Loss of Function Promotes Atherosclerosis and Thrombosis. [JOURNAL ARTICLE]
- Circ Res 2016 Jul 18.
Human genome wide association studies (GWAS) have revealed novel genetic loci that are associated with coronary heart disease (CHD). One such locus resides in LNK/SH2B3 which in mice is expressed in hematopoietic cells and suppresses thrombopoietin (TPO) signaling via its receptor MPL. However, the mechanisms underlying the association of LNK snps with CHD are poorly understood.To understand the functional effects of LNK snps and explore the mechanisms whereby LNK loss of function impacts atherosclerosis and thrombosis.Using human cord blood, we show that the common TT risk genotype (R262W) of LNK is associated with expansion of hematopoietic stem cells and enhanced megakaryopoiesis, demonstrating reduced LNK function and increased MPL signaling. In mice hematopoietic LNK deficiency leads to accelerated arterial thrombosis and atherosclerosis, but only in the setting of hypercholesterolemia. Hypercholesterolemia acts synergistically with LNK deficiency to increase IL-3/GM-CSF receptor signaling in bone marrow myeloid progenitors, while in platelets cholesterol loading combines with Lnk deficiency to increase activation. Platelet LNK deficiency increases MPL signaling and AKT activation, while cholesterol loading decreases SHIP-1 phosphorylation, acting convergently to increase AKT and platelet activation. Together with increased myelopoiesis, platelet activation promotes pro-thrombotic and pro-atherogenic platelet/leukocyte aggregate formation.LNK (R262W) is a loss of function variant that promotes TPO/MPL signaling, platelet and leukocyte production. In mice, LNK deficiency is associated with both increased platelet production and activation. Hypercholesterolemia acts in platelets and hematopoietic progenitors to exacerbate thrombosis and atherosclerosis associated with LNK deficiency.
- Measurement of Reactive Oxygen Species, Reactive Nitrogen Species, and Redox-Dependent Signaling in the Cardiovascular System: A Scientific Statement From the American Heart Association. [JOURNAL ARTICLE]
- Circ Res 2016 Jul 14.
Reactive oxygen species and reactive nitrogen species are biological molecules that play important roles in cardiovascular physiology and contribute to disease initiation, progression, and severity. Because of their ephemeral nature and rapid reactivity, these species are difficult to measure directly with high accuracy and precision. In this statement, we review current methods for measuring these species and the secondary products they generate and suggest approaches for measuring redox status, oxidative stress, and the production of individual reactive oxygen and nitrogen species. We discuss the strengths and limitations of different methods and the relative specificity and suitability of these methods for measuring the concentrations of reactive oxygen and reactive nitrogen species in cells, tissues, and biological fluids. We provide specific guidelines, through expert opinion, for choosing reliable and reproducible assays for different experimental and clinical situations. These guidelines are intended to help investigators and clinical researchers avoid experimental error and ensure high-quality measurements of these important biological species.
- Anti-Inflammatory Effects of Metformin Irrespective of Diabetes Status. [JOURNAL ARTICLE]
- Circ Res 2016 Jul 14.
The diabetes drug metformin is under investigation in cardiovascular disease but the molecular mechanisms underlying possible benefits are poorly understood.Here we have studied anti-inflammatory effects of the drug and their relationship to anti-hyperglycaemic properties.In primary hepatocytes from healthy animals, metformin and the IKKβ inhibitor BI605906 both inhibited TNFα-dependent IκB degradation and expression of pro-inflammatory mediators IL-6, IL-1b, and CXCL1/2. Metformin suppressed IKKα/β activation, an effect which could be separated from some metabolic actions, in that BI605906 did not mimic effects of metformin on lipogenic gene expression, glucose production and AMPK activation. Equally AMPK was not required either for mitochondrial suppression of IκB degradation. Consistent with discrete anti-inflammatory actions, in macrophages metformin specifically blunted secretion of pro-inflammatory cytokines, without inhibiting M1/M2 differentiation or activation. In a large treatment naïve diabetes population cohort, we observed differences in the systemic inflammation marker, Neutrophil to Lymphocyte Ratio (NLR), following incident treatment with either metformin or sulfonylurea monotherapy. Compared to sulfonylurea exposure, metformin reduced the mean log-transformed NLR after 8-16 months by 0.09 units (95% CI=0.02-0.17, p=0.013), and increased the likelihood that NLR would be lower than baseline after 8-16 months (OR 1.83, 95% CI=1.22-2.75, p=0.00364). Following up these findings in a double blind placebo controlled trial in nondiabetic heart failure (trial registration: NCT00473876), metformin suppressed plasma cytokines including the ageing-associated cytokine CCL11.We conclude that anti-inflammatory properties of metformin are exerted irrespective of diabetes status. This may accelerate investigation of drug utility in non-diabetic cardiovascular disease groups.
- NF2 Activates Hippo Signaling and Promotes Ischemia/Reperfusion Injury in Heart. [JOURNAL ARTICLE]
- Circ Res 2016 Jul 11.
Neurofibromin 2 (NF2) is an established tumor suppressor that promotes apoptosis and inhibits growth in a variety of cell types, yet its function in cardiomyocytes remains largely unknown.We sought to determine the role of NF2 in cardiomyocyte apoptosis and ischemia/reperfusion (I/R) injury in the heart.We investigated the function of NF2 in isolated cardiomyocytes and mouse myocardium at baseline and in response to oxidative stress. NF2 was activated in cardiomyocytes subjected to H2O2 and in murine hearts subjected to I/R. Increased NF2 expression promoted the activation of Mst1 and the inhibition of Yap, whereas knockdown of NF2 attenuated these responses following oxidative stress. NF2 increased apoptosis of cardiomyocytes that appeared dependent on Mst1 activity. Mice deficient for NF2 in cardiomyocytes, NF2 CKO, were protected against global I/R ex vivo and showed improved cardiac functional recovery. Moreover, NF2 CKO mice were protected against I/R injury in vivo and showed upregulation of Yap target gene expression. Mechanistically, we observed nuclear association between NF2 and its activator MYPT-1 in cardiomyocytes, and a subpopulation of stress-induced nuclear Mst1 was diminished in NF2 CKO hearts. Finally, mice deficient for both NF2 and Yap failed to show protection against I/R indicating that Yap is an important target of NF2 in the adult heart.NF2 is activated by oxidative stress in cardiomyocytes and mouse myocardium and facilitates apoptosis. NF2 promotes I/R injury through activation of Mst1 and inhibition of Yap, thereby regulating Hippo signaling in the adult heart.
- Letter by Marlicz et al Regarding Article, "Proton Pump Inhibitors Accelerate Endothelial Senescence". [Letter]
- Circ Res 2016 Jul 8; 119(2):e31-2.