Abstract
The role of the renin angiotensin system (RAS) in atherosclerosis is complex because of the involvement of multiple peptides and receptors. Renin is the rate-limiting enzyme in the production of all angiotensin peptides. To determine the effects of renin inhibition on atherosclerosis, we administered the novel renin inhibitor aliskiren over a broad dose range to fat-fed LDL receptor–deficient (Ldlr–/–) mice. Renin inhibition resulted in striking reductions of atherosclerotic lesion size in both the aortic arch and the root. Subsequent studies demonstrated that cultured macrophages expressed all components of the RAS. To determine the role of macrophage-derived angiotensin in the development of atherosclerosis, we transplanted renin-deficient bone marrow to irradiated Ldlr–/– mice and observed a profound decrease in the size of atherosclerotic lesions. In similar experiments, transplantation of bone marrow deficient for angiotensin II type 1a receptors failed to influence lesion development. We conclude that renin-dependent angiotensin production in macrophages does not act in an autocrine/paracrine manner. Furthermore, in vitro studies demonstrated that coculture with renin-expressing macrophages augmented monocyte adhesion to endothelial cells. Therefore, although previous work suggests that angiotensin peptides have conflicting effects on atherogenesis, we found that renin inhibition profoundly decreased lesion development in mice.
Authors
Hong Lu, Debra L. Rateri, David L. Feldman, Richard J. Charnigo Jr., Akiyoshi Fukamizu, Junji Ishida, Elizabeth G. Oesterling, Lisa A. Cassis, Alan Daugherty
Abstract
Although the differentiation of ES cells to cardiomyocytes has been firmly established, the extent to which corresponding cardiac precursor cells can contribute to other cardiac populations remains unclear. To determine the molecular and cellular characteristics of cardiac-fated populations derived from mouse ES (mES) cells, we isolated cardiac progenitor cells (CPCs) from differentiating mES cell cultures by using a reporter cell line that expresses GFP under the control of a cardiac-specific enhancer element of Nkx2-5, a transcription factor expressed early in cardiac development. This ES cell–derived CPC population initially expressed genetic markers of both stem cells and mesoderm, while differentiated CPCs displayed markers of 3 distinct cell lineages (cardiomyocytes, vascular smooth muscle cells, and endothelial cells) — Flk1 (also known as Kdr), c-Kit, and Nkx2-5, but not Brachyury — and subsequently expressed Isl1. Clonally derived CPCs also demonstrated this multipotent phenotype. By transcription profiling of CPCs, we found that mES cell–derived CPCs displayed a transcriptional signature that paralleled in vivo cardiac development. Additionally, these studies suggested the involvement of genes that we believe were previously unknown to play a role in cardiac development. Taken together, our data demonstrate that ES cell–derived CPCs comprise a multipotent precursor population capable of populating multiple cardiac lineages and suggest that ES cell differentiation is a valid model for studying development of multiple cardiac-fated tissues.
Authors
Nicolas Christoforou, Ronald A. Miller, Christine M. Hill, Chunfa C. Jie, Andrew S. McCallion, John D. Gearhart
Abstract
Atherosclerosis is an inflammatory disease that is associated with monocyte recruitment and subsequent differentiation into lipid-laden macrophages at sites of arterial lesions, leading to the development of atherosclerotic plaques. PLC is a key member of signaling pathways initiated by G protein–coupled ligands in macrophages. However, the role of this enzyme in the regulation of macrophage function is not known. Here, we studied macrophages from mice lacking PLC β2, PLC β3, or both PLC isoforms and found that PLC β3 is the major functional PLC β isoform in murine macrophages. Although PLC β3 deficiency did not affect macrophage migration, adhesion, or phagocytosis, it resulted in macrophage hypersensitivity to multiple inducers of apoptosis. PLC β3 appeared to regulate this sensitivity via PKC-dependent upregulation of Bcl-XL. The significance of PLC β signaling in vivo was examined using the apoE-deficient mouse model of atherosclerosis. Mice lacking both PLC β3 and apoE exhibited fewer total macrophages and increased macrophage apoptosis in atherosclerotic lesions, as well as reduced atherosclerotic lesion size when compared with mice lacking only apoE. These results demonstrate what we believe to be a novel role for PLC activity in promoting macrophage survival in atherosclerotic plaques and identify PLC β3 as a potential target for treatment of atherosclerosis.
Authors
Zhenglong Wang, Bei Liu, Ping Wang, Xuemei Dong, Carlos Fernandez-Hernando, Zhong Li, Timothy Hla, Zihai Li, Kevin Claffey, Jonathan D. Smith, Dianqing Wu
Abstract
Endothelial dysfunction is a key triggering event in atherosclerosis. Following the entry of lipoproteins into the vessel wall, their rapid modification results in the generation of advanced glycation endproduct epitopes and subsequent infiltration of inflammatory cells. These inflammatory cells release receptor for advanced glycation endproduct (RAGE) ligands, specifically S100/calgranulins and high-mobility group box 1, which sustain vascular injury. Here, we demonstrate critical roles for RAGE and its ligands in vascular inflammation, endothelial dysfunction, and atherosclerotic plaque development in a mouse model of atherosclerosis, apoE–/– mice. Experiments in primary aortic endothelial cells isolated from mice and in cultured human aortic endothelial cells revealed the central role of JNK signaling in transducing the impact of RAGE ligands on inflammation. These data highlight unifying mechanisms whereby endothelial RAGE and its ligands mediate vascular and inflammatory stresses that culminate in atherosclerosis in the vulnerable vessel wall.
Authors
Evis Harja, De-xiu Bu, Barry I. Hudson, Jong Sun Chang, Xiaoping Shen, Kellie Hallam, Anastasia Z. Kalea, Yan Lu, Rosa H. Rosario, Sai Oruganti, Zana Nikolla, Dmitri Belov, Evanthia Lalla, Ravichandran Ramasamy, Shi Fang Yan, Ann Marie Schmidt
Abstract
Secretoneurin (SN), a neuropeptide derived from secretogranin II, promotes neurite outgrowth of immature cerebellar granule cells. SN also aids in the growth and repair of neuronal tissue, although the precise mechanisms underlying the promotion of brain tissue neuroprotection and plasticity by SN are not understood. Here, in a rat model of stroke and in ischemic human brain tissue, SN was markedly upregulated in both neurons and endothelial cells. SN-mediated neuroprotection rescued primary cortical cell cultures from oxygen/glucose deprivation. SN also induced expression of the antiapoptotic proteins Bcl-2 and Bcl-xL through the Jak2/Stat3 pathway and inhibited apoptosis by blocking caspase-3 activation. In addition, rats with occluded right middle cerebral arteries showed less cerebral infarction, improved motor performance, and increased brain metabolic activity following i.v. administration of SN. Furthermore, SN injection enhanced stem cell targeting to the injured brain in mice and promoted the formation of new blood vessels to increase local cortical blood flow in the ischemic hemisphere. Both in vitro and in vivo, SN not only promoted neuroprotection, but also enhanced neurogenesis and angiogenesis. Our results demonstrate that SN acts directly on neurons after hypoxia and ischemic insult to further their survival by activating the Jak2/Stat3 pathway.
Authors
Woei-Cherng Shyu, Shinn-Zong Lin, Ming-Fu Chiang, Der-Cherng Chen, Ching-Yuan Su, Hsiao-Jung Wang, Ren-Shyan Liu, Chang-Hai Tsai, Hung Li
Abstract
The adult heart responds to excessive neurohumoral signaling and workload by a pathological growth response characterized by hypertrophy of cardiomyocytes and activation of a fetal program of cardiac gene expression. These responses culminate in diminished pump function, ventricular dilatation, wall thinning, and fibrosis, and can result in sudden death. Myocyte enhancer factor–2 (MEF2) transcription factors serve as targets of the signaling pathways that drive pathological cardiac remodeling, but the requirement for MEF2 factors in the progression of heart disease in vivo has not been determined. MEF2A and MEF2D are the primary MEF2 factors expressed in the adult heart. To specifically determine the role of MEF2D in pathological cardiac remodeling, we generated mice with a conditional MEF2D allele. MEF2D-null mice were viable, but were resistant to cardiac hypertrophy, fetal gene activation, and fibrosis in response to pressure overload and β-chronic adrenergic stimulation. Furthermore, we show in a transgenic mouse model that forced overexpression of MEF2D was sufficient to drive the fetal gene program and pathological remodeling of the heart. These results reveal a unique and important function for MEF2D in stress-dependent cardiac growth and reprogramming of gene expression in the adult heart.
Authors
Yuri Kim, Dillon Phan, Eva van Rooij, Da-Zhi Wang, John McAnally, Xiaoxia Qi, James A. Richardson, Joseph A. Hill, Rhonda Bassel-Duby, Eric N. Olson
Abstract
Parasympathetic stimulation of the heart, which provides protection from arrhythmias and sudden death, involves activation of the G protein–coupled inward rectifying K+ channel GIRK1/4 and results in an acetylcholine-sensitive K+ current, IKACh. We describe a unique relationship between lipid homeostasis, the lipid-sensitive transcription factor SREBP-1, regulation of the cardiac parasympathetic response, and the development of ventricular arrhythmia. In embryonic chick atrial myocytes, lipid lowering by culture in lipoprotein-depleted serum increased SREBP-1 levels, GIRK1 expression, and IKACh activation. Regulation of the GIRK1 promoter by SREBP-1 and lipid lowering was dependent on interaction with 2 tandem sterol response elements and an upstream E-box motif. Expression of dominant negative SREBP-1 (DN–SREBP-1) reversed the effect of lipid lowering on IKACh and GIRK1. In SREBP-1 knockout mice, both the response of the heart to parasympathetic stimulation and the expression of GIRK1 were reduced compared with WT. IKACh, attenuated in atrial myocytes from SREBP-1 knockout mice, was stimulated by SREBP-1 expression. Following myocardial infarction, SREBP-1 knockout mice were twice as likely as WT mice to develop ventricular tachycardia in response to programmed ventricular stimulation. These results demonstrate a relationship between lipid metabolism and parasympathetic response that may play a role in arrhythmogenesis.
Authors
Ho-Jin Park, Serban P. Georgescu, Chuang Du, Christopher Madias, Mark J. Aronovitz, C. Michael Welzig, Bo Wang, Ulrike Begley, Yali Zhang, Robert O. Blaustein, Richard D. Patten, Richard H. Karas, Herbert H. Van Tol, Timothy F. Osborne, Hitoshi Shimano, Ronglih Liao, Mark S. Link, Jonas B. Galper
Nuclear receptors PPARβ/δ and PPARα direct distinct metabolic regulatory programs in the mouse heart
Abstract
In the diabetic heart, chronic activation of the PPARα pathway drives excessive fatty acid (FA) oxidation, lipid accumulation, reduced glucose utilization, and cardiomyopathy. The related nuclear receptor, PPARβ/δ, is also highly expressed in the heart, yet its function has not been fully delineated. To address its role in myocardial metabolism, we generated transgenic mice with cardiac-specific expression of PPARβ/δ, driven by the myosin heavy chain (MHC-PPARβ/δ mice). In striking contrast to MHC-PPARα mice, MHC-PPARβ/δ mice had increased myocardial glucose utilization, did not accumulate myocardial lipid, and had normal cardiac function. Consistent with these observed metabolic phenotypes, we found that expression of genes involved in cellular FA transport were activated by PPARα but not by PPARβ/δ. Conversely, cardiac glucose transport and glycolytic genes were activated in MHC-PPARβ/δ mice, but repressed in MHC-PPARα mice. In reporter assays, we showed that PPARβ/δ and PPARα exerted differential transcriptional control of the GLUT4 promoter, which may explain the observed isotype-specific effects on glucose uptake. Furthermore, myocardial injury due to ischemia/reperfusion injury was significantly reduced in the MHC-PPARβ/δ mice compared with control or MHC-PPARα mice, consistent with an increased capacity for myocardial glucose utilization. These results demonstrate that PPARα and PPARβ/δ drive distinct cardiac metabolic regulatory programs and identify PPARβ/δ as a potential target for metabolic modulation therapy aimed at cardiac dysfunction caused by diabetes and ischemia.
Authors
Eileen M. Burkart, Nandakumar Sambandam, Xianlin Han, Richard W. Gross, Michael Courtois, Carolyn M. Gierasch, Kooresh Shoghi, Michael J. Welch, Daniel P. Kelly
Abstract
The clinical utility of anthracycline anticancer agents, especially doxorubicin, is limited by a progressive toxic cardiomyopathy linked to mitochondrial damage and cardiomyocyte apoptosis. Here we demonstrate that the post-doxorubicin mouse heart fails to upregulate the nuclear program for mitochondrial biogenesis and its associated intrinsic antiapoptosis proteins, leading to severe mitochondrial DNA (mtDNA) depletion, sarcomere destruction, apoptosis, necrosis, and excessive wall stress and fibrosis. Furthermore, we exploited recent evidence that mitochondrial biogenesis is regulated by the CO/heme oxygenase (CO/HO) system to ameliorate doxorubicin cardiomyopathy in mice. We found that the myocardial pathology was averted by periodic CO inhalation, which restored mitochondrial biogenesis and circumvented intrinsic apoptosis through caspase-3 and apoptosis-inducing factor. Moreover, CO simultaneously reversed doxorubicin-induced loss of DNA binding by GATA-4 and restored critical sarcomeric proteins. In isolated rat cardiac cells, HO-1 enzyme overexpression prevented doxorubicin-induced mtDNA depletion and apoptosis via activation of Akt1/PKB and guanylate cyclase, while HO-1 gene silencing exacerbated doxorubicin-induced mtDNA depletion and apoptosis. Thus doxorubicin disrupts cardiac mitochondrial biogenesis, which promotes intrinsic apoptosis, while CO/HO promotes mitochondrial biogenesis and opposes apoptosis, forestalling fibrosis and cardiomyopathy. These findings imply that the therapeutic index of anthracycline cancer chemotherapeutics can be improved by the protection of cardiac mitochondrial biogenesis.
Authors
Hagir B. Suliman, Martha Sue Carraway, Abdelwahid S. Ali, Chrystal M. Reynolds, Karen E. Welty-Wolf, Claude A. Piantadosi
Abstract
Statins inhibit HMG-CoA reductase, a key enzyme in cholesterol synthesis, and are widely used to treat hypercholesterolemia. These drugs can lead to a number of side effects in muscle, including muscle fiber breakdown; however, the mechanisms of muscle injury by statins are poorly understood. We report that lovastatin induced the expression of atrogin-1, a key gene involved in skeletal muscle atrophy, in humans with statin myopathy, in zebrafish embryos, and in vitro in murine skeletal muscle cells. In cultured mouse myotubes, atrogin-1 induction following lovastatin treatment was accompanied by distinct morphological changes, largely absent in atrogin-1 null cells. In zebrafish embryos, lovastatin promoted muscle fiber damage, an effect that was closely mimicked by knockdown of zebrafish HMG-CoA reductase. Moreover, atrogin-1 knockdown in zebrafish embryos prevented lovastatin-induced muscle injury. Finally, overexpression of PGC-1α, a transcriptional coactivator that induces mitochondrial biogenesis and protects against the development of muscle atrophy, dramatically prevented lovastatin-induced muscle damage and abrogated atrogin-1 induction both in fish and in cultured mouse myotubes. Collectively, our human, animal, and in vitro findings shed light on the molecular mechanism of statin-induced myopathy and suggest that atrogin-1 may be a critical mediator of the muscle damage induced by statins.
Authors
Jun-ichi Hanai, Peirang Cao, Preeti Tanksale, Shintaro Imamura, Eriko Koshimizu, Jinghui Zhao, Shuji Kishi, Michiaki Yamashita, Paul S. Phillips, Vikas P. Sukhatme, Stewart H. Lecker
Copyright © 2026 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)