Abstract
Erythropoietin (EPO) has been shown to protect neurons from ischemic stroke, but can also increase thrombotic events and mortality rates in patients with ischemic heart disease. We reasoned that benefits of EPO might be offset by increases in hematocrit and evaluated the direct effects of EPO in the ischemic heart. We show that preconditioning with EPO protects H9c2 myoblasts in vitro and cardiomyocytes in vivo against ischemic injury. EPO treatment leads to significantly improved cardiac function following myocardial infarction. This protection is associated with mitigation of myocyte apoptosis, translating into more viable myocardium and less ventricular dysfunction. EPO-mediated myocyte survival appears to involve Akt activation. Importantly, cardioprotective effects of EPO were seen without an increase in hematocrit (eliminating oxygen delivery as an etiologic factor in myocyte survival and function), demonstrating that EPO can directly protect the ischemic and infarcted heart.
Authors
Cyrus J. Parsa, Akio Matsumoto, Jihee Kim, Ryan U. Riel, Laura S. Pascal, G. Brant Walton, Richard B. Thompson, Jason A. Petrofski, Brian H. Annex, Jonathan S. Stamler, Walter J. Koch
Abstract
Activation of multiple pathways is associated with cardiac hypertrophy and heart failure. Repression of antihypertrophic pathways has rarely been demonstrated to cause cardiac hypertrophy in vivo. Hop is an unusual homeodomain protein that is expressed by embryonic and postnatal cardiac myocytes. Unlike other homeodomain proteins, Hop does not bind DNA. Rather, it modulates cardiac growth and proliferation by inhibiting the transcriptional activity of serum response factor (SRF) in cardiomyocytes. Here we show that Hop can inhibit SRF-dependent transcriptional activation by recruiting histone deacetylase (HDAC) activity and can form a complex that includes HDAC2. Transgenic mice that overexpress Hop develop severe cardiac hypertrophy, cardiac fibrosis, and premature death. A mutant form of Hop, which does not recruit HDAC activity, does not induce hypertrophy. Treatment of Hop transgenic mice with trichostatin A, an HDAC inhibitor, prevents hypertrophy. In addition, trichostatin A also attenuates hypertrophy induced by infusion of isoproterenol. Thus, chromatin remodeling and repression of otherwise active transcriptional processes can result in hypertrophy and heart failure, and this process can be blocked with chemical HDAC inhibitors.
Authors
Hyun Kook, John J. Lepore, Aaron D. Gitler, Min Min Lu, Wendy Wing-Man Yung, Joel Mackay, Rong Zhou, Victor Ferrari, Peter Gruber, Jonathan A. Epstein
Abstract
Hypertension is a clinical syndrome characterized by increased vascular tone. However, the molecular mechanisms underlying vascular dysfunction during acquired hypertension remain unresolved. Localized intracellular Ca2+ release events through ryanodine receptors (Ca2+ sparks) in the sarcoplasmic reticulum are tightly coupled to the activation of large-conductance, Ca2+-activated K+ (BK) channels to provide a hyperpolarizing influence that opposes vasoconstriction. In this study we tested the hypothesis that a reduction in Ca2+ spark–BK channel coupling underlies vascular smooth muscle dysfunction during acquired hypertension. We found that in hypertension, expression of the β1 subunit was decreased relative to the pore-forming α subunit of the BK channel. Consequently, the BK channels were functionally uncoupled from Ca2+ sparks. Consistent with this, the contribution of BK channels to vascular tone was reduced during hypertension. We conclude that downregulation of the β1 subunit of the BK channel contributes to vascular dysfunction in hypertension. These results support the novel concept that changes in BK channel subunit composition regulate arterial smooth muscle function.
Authors
Gregory C. Amberg, Adrian D. Bonev, Charles F. Rossow, Mark T. Nelson, Luis F. Santana
Abstract
Increased production of reactive oxygen species and loss of endothelial NO bioactivity are key features of vascular disease states such as diabetes mellitus. Tetrahydrobiopterin (BH4) is a required cofactor for eNOS activity; pharmacologic studies suggest that BH4 may mediate some of the adverse effects of diabetes on eNOS function. We have now investigated the importance and mechanisms of BH4 availability in vivo using a novel transgenic mouse model with endothelial-targeted overexpression of the rate-limiting enzyme in BH4 synthesis, guanosine triphosphate–cyclohydrolase I (GTPCH). Transgenic (GCH-Tg) mice demonstrated selective augmentation of endothelial BH4 levels. In WT mice, induction of diabetes with streptozotocin (STZ) increased vascular oxidative stress, resulting in oxidative loss of BH4, forming BH2 and biopterin. Endothelial cell superoxide production in diabetes was increased, and NO-mediated endothelium-dependent vasodilatation was impaired. In diabetic GCH-Tg mice, superoxide production from the endothelium was markedly reduced compared with that of WT mice, endothelial BH4 levels were maintained despite some oxidative loss of BH4, and NO-mediated vasodilatation was preserved. These findings indicate that BH4 is an important mediator of eNOS regulation in diabetes and is a rational therapeutic target to restore NO-mediated endothelial function in diabetes and other vascular disease states.
Authors
Nicholas J. Alp, Shafi Mussa, Jeffrey Khoo, Shijie Cai, Tomasz Guzik, Andrew Jefferson, Nicky Goh, Kirk A. Rockett, Keith M. Channon
Abstract
The thin filament protein cardiac troponin T (cTnT) is an important regulator of myofilament activation. Here we report a significant change in cardiac energetics in transgenic mice bearing the missense mutation R92Q within the tropomyosin-binding domain of cTnT, a mutation associated with a clinically severe form of familial hypertrophic cardiomyopathy. This functional domain of cTnT has recently been shown to be a crucial modulator of contractile function despite the fact that it does not directly interact with the ATP hydrolysis site in the myosin head. Simultaneous measurements of cardiac energetics using 31P NMR spectroscopy and contractile performance of the intact beating heart revealed both a decrease in the free energy of ATP hydrolysis available to support contractile work and a marked inability to increase contractile performance upon acute inotropic challenge in hearts from R92Q mice. These results show that alterations in thin filament protein structure and function can lead to significant defects in myocardial energetics and contractile reserve.
Authors
Maryam M. Javadpour, Jil C. Tardiff, Ilka Pinz, Joanne S. Ingwall
Abstract
Ectopic calcification is a frequent complication of many degenerative diseases. Here we identify the serum protein α2–Heremans-Schmid glycoprotein (Ahsg, also known as fetuin-A) as an important inhibitor of ectopic calcification acting on the systemic level. Ahsg-deficient mice are phenotypically normal, but develop severe calcification of various organs on a mineral and vitamin D–rich diet and on a normal diet when the deficiency is combined with a DBA/2 genetic background. This phenotype is not associated with apparent changes in calcium and phosphate homeostasis, but with a decreased inhibitory activity of the Ahsg-deficient extracellular fluid on mineral formation. The same underlying principle may contribute to many calcifying disorders including calciphylaxis, a syndrome of severe systemic calcification in patients with chronic renal failure. Taken together, our data demonstrate a critical role of Ahsg as an inhibitor of unwanted mineralization and provide a novel therapeutic concept to prevent ectopic calcification accompanying various diseases.
Authors
Cora Schäfer, Alexander Heiss, Anke Schwarz, Ralf Westenfeld, Markus Ketteler, Jürgen Floege, Werner Müller-Esterl, Thorsten Schinke, Willi Jahnen-Dechent
Abstract
Hepatic lipase (HL) has a well-established role in lipoprotein metabolism. However, its role in atherosclerosis is poorly understood. Here we demonstrate that HL deficiency raises the proatherogenic apoB-containing lipoprotein levels in plasma but reduces atherosclerosis in lecithin cholesterol acyltransferase (LCAT) transgenic (Tg) mice, similar to results previously observed with HL-deficient apoE-KO mice. These findings suggest that HL has functions that modify atherogenic risk that are separate from its role in lipoprotein metabolism. We used bone marrow transplantation (BMT) to generate apoE-KO and apoE-KO × HL-KO mice, as well as LCAT-Tg and LCAT-Tg × HL-KO mice, chimeric for macrophage HL gene expression. Using in situ RNA hybridization, we demonstrated localized production of HL by donor macrophages in the artery wall. We found that expression of HL by macrophages enhances early aortic lesion formation in both apoE-KO and LCAT-Tg mice, without changing the plasma lipid profile, lipoprotein lipid composition, or HL and lipoprotein lipase activities. HL does, however, enhance oxidized LDL uptake by peritoneal macrophages. These combined data demonstrate that macrophage-derived HL significantly contributes to early aortic lesion formation in two independent mouse models and identify a novel mechanism, separable from the role of HL in plasma lipoprotein metabolism, by which HL modulates atherogenic risk in vivo.
Authors
Zengxuan Nong, Herminia González-Navarro, Marcelo Amar, Lita Freeman, Catherine Knapper, Edward B. Neufeld, Beverly J. Paigen, Robert F. Hoyt, Jamila Fruchart-Najib, Silvia Santamarina-Fojo
Abstract
The ECM protein Del-1 is one of several novel ECM proteins that accumulate around angiogenic blood vessels in embryonic and tumor tissue and promote angiogenesis in the absence of exogenous growth factors. Del-1 expressed in mouse or rabbit ischemic hind-limb muscle by gene transfer rapidly promotes new blood vessel formation and restores muscle function. This angiogenic ECM protein initiates angiogenesis by binding to integrin αvβ5 on resting endothelium, thereby resulting in expression of the transcription factor Hox D3 and integrin αvβ3. Hox D3 converts resting endothelium to angiogenic endothelium by inducing expression of proangiogenic molecules such as integrin αvβ3. These findings provide evidence for an angiogenic switch that can be initiated in the absence of exogenous growth factors and indicate that the angiogenic matrix protein Del-1 may be a useful tool for the therapy of ischemic disease.
Authors
Jingping Zhong, Brian Eliceiri, Dwayne Stupack, Kalyani Penta, Gordon Sakamoto, Thomas Quertermous, Mike Coleman, Nancy Boudreau, Judith A. Varner
Abstract
Previously we showed that neuropeptide Y (NPY), a sympathetic vasoconstrictor neurotransmitter, stimulates endothelial cell migration, proliferation, and differentiation in vitro. Here, we report on NPY’s actions, receptors, and mediators in ischemic angiogenesis. In rats, hindlimb ischemia stimulates sympathetic NPY release (attenuated by lumbar sympathectomy) and upregulates NPY-Y2 (Y2) receptor and a peptidase forming Y2/Y5-selective agonist. Exogenous NPY at physiological concentrations also induces Y5 receptor, stimulates neovascularization, and restores ischemic muscle blood flow and performance. NPY-mediated ischemic angiogenesis is not prevented by a selective Y1 receptor antagonist but is reduced in Y2–/– mice. Nonischemic muscle vascularity is also lower in Y2–/– mice, whereas it is increased in NPY-overexpressing rats compared with their WT controls. Ex vivo, NPY-induced aortic sprouting is markedly reduced in Y2–/– aortas and spontaneous sprouting is severely impaired in NPY–/– mice. NPY-mediated aortic sprouting, but not cell migration/proliferation, is blocked by an antifetal liver kinase 1 antibody and abolished in mice null for eNOS. Thus, NPY mediates neurogenic ischemic angiogenesis at physiological concentrations by activating Y2/Y5 receptors and eNOS, in part due to release of VEGF. NPY’s effectiveness in revascularization and restoring function of ischemic tissue suggests its therapeutic potential in ischemic conditions.
Authors
Edward W. Lee, Mieczyslaw Michalkiewicz, Joanna Kitlinska, Ivana Kalezic, Hanna Switalska, Peter Yoo, Amarin Sangkharat, Hong Ji, Lijun Li, Teresa Michalkiewicz, Milos Ljubisavljevic, Hakan Johansson, Derrick S. Grant, Zofia Zukowska
Abstract
TNF-α activates ASK1 in part by dissociating 14-3-3 from apoptosis signal–regulating kinase 1 (ASK1). In the present study, we identified a novel Ras GTPase-activating protein (Ras-GAP) as an ASK1-interacting protein (AIP1). AIP1 binds to the C-terminal domain of ASK1 via a lysine-rich cluster within the N-terminal C2 domain. AIP1 exists in a closed form through an intramolecular interaction between the N-terminus and the C-terminus, and TNF-α induces unfolding of AIP1 leading to association of AIP1 with ASK1. Thus, the N-terminus of AIP1 containing the C2 and GAP domains constitutively binds to ASK1 and facilitates the release of 14-3-3 from ASK1. In contrast to 14-3-3, AIP1 binds preferentially to dephosphorylated ASK1. Recruited AIP1 enhances ASK1-induced JNK activation, and the ASK1 binding and the GAP activity of AIP1 are critical for AIP1-enhanced ASK1 activation. Furthermore, TNF-induced ASK1/JNK activation is significantly blunted in cells where AIP1 is knocked down by RNA interference. These data suggest that AIP1 mediates TNF-α–induced ASK1 activation by facilitating dissociation of inhibitor 14-3-3 from ASK1, a novel mechanism by which TNF-α activates ASK1.
Authors
Rong Zhang, Xiangrong He, Weimin Liu, Meng Lu, Jer-Tsong Hsieh, Wang Min
Copyright © 2026 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)