Chunming Dong

Microtubule Binding to Smads May Regulate TGFβ Activity

Abstract Smad proteins are intracellular signaling effectors of the TGFβ superfamily. We show that endogenous Smad2, 3, and 4 bind microtubules (MTs) in several cell lines. Binding of Smads to MTs does not require TGFβ stimulation. TGFβ triggers dissociation from MTs, phosphorylation, and nuclear translocation of Smad2 and 3, with consequent activation of transcription in CCL64 cells. Destabilization of the MT network by nocodazole, colchicine, or a tubulin mutant disrupts the complex between Smads and MTs and increases TGFβ-induced Smad2 phosphorylation and transcriptional response in CCL64 cells. These data demonstrate that MTs may serve as a cytoplasmic sequestering network for Smads, controlling Smad2 association with and phosphorylation by activated TGFβ receptor I, and suggest a novel mechanism for the MT network to negatively regulate TGFβ function.

Antitumorigenesis of antioxidants in a transgenic Rac1 model of Kaposi's sarcoma

Kaposis sarcoma (KS) is the major AIDS-associated malignancy. It is characterized by the proliferation of spindle cells, inflammatory infiltrate, and aberrant angiogenesis caused by Kaposis sarcoma herpesvirus (KSHV) infection. Small GTPase Rac1, an inflammatory signaling mediator triggering reactive oxygen species (ROS) production by NADPH-oxidases, is implicated in carcinogenesis and tumor angiogenesis. Here, we show that expression of a constitutively active Rac1 (RacCA) driven by the α-smooth muscle actin promoter in transgenic mice is sufficient to cause KS-like tumors through mechanisms involving ROS-driven proliferation, up-regulation of AKT signaling, and hypoxia-inducible factor 1-α–related angiogenesis. RacCA-induced tumors expressed KS phenotypic markers; displayed remarkable transcriptome overlap with KS lesions; and were, like KS, associated with male gender. The ROS scavenging agent N-acetyl-cysteine inhibited angiogenesis and completely abrogated transgenic RacCA tumor formation, indicating a causal role of ROS in tumorigenesis. Consistent with a pathogenic role in KS, immunohistochemical analysis revealed that Rac1 is overexpressed in KSHV+ spindle cells of AIDS-KS biopsies. Our results demonstrate the direct oncogenicity of Rac1 and ROS and their contribution to a KS-like malignant phenotype, further underscoring the carcinogenic potential of oxidative stress in the context of chronic infection and inflammation. They define the RacCA transgenic mouse as a model suitable for studying the role of oxidative stress in the pathogenesis and therapy of KS, with relevance to other inflammation-related malignancies. Our findings suggest host and viral genes triggering Rac1 or ROS production as key determinants of KS onset and potential KS chemopreventive or therapeutic targets.

Fas-mediated apoptosis in accelerated graft arteriosclerosis

Pathological conditions have been recognized where vessel destruction is a prominent feature of the pathogenic process. One such condition consists of the chronic rejection of blood vessels in transplanted solid organs. Accelerated graft arteriosclerosis (AGA) is a multifactorial process characterized by the concentric proliferation of smooth muscle cells (SMCs) within the intima of the vessel wall of transplanted organs. Proliferation of SMCs within the intima corresponds to a response of these cells to injury. In situations like restenosis post-angioplasty, the mechanism of injury: the mechanical disruption of the tunica media, is evident. However, in the case of AGA, the mechanism of injury has remained elusive. In this report, we provide evidence that injury to SMCs in AGA vessels requires an intact Fas pathway. The resulting damage to the tunica media and internal elastic lamina, in turn, might trigger the proliferation of intimal smooth muscle cells that appear to be less sensitive to Fas mediated killing, particularly when supported by a favorable context of inflammatory cytokines and growth factors, as it is the case in AGA. This pathogenic process results in a absolute loss of functional blood vessels that is not being compensated by an efficient angiogenic response.

MicroRNA-146a Induces Lineage-Negative Bone Marrow Cell Apoptosis and Senescence by Targeting Polo-Like Kinase 2 Expression.

Objective— Lineage-negative bone marrow cells (lin− BMCs) are enriched in endothelial progenitor cells and mediate vascular repair. Aging-associated senescence and apoptosis result in reduced number and functionality of lin− BMCs, impairing their prorepair capacity. The molecular mechanisms underlying lin− BMC senescence and apoptosis are poorly understood. MicroRNAs (miRNAs) regulate many important biological processes. The identification of miRNA-mRNA networks that modulate the health and functionality of lin− BMCs is a critical step in understanding the process of vascular repair. The aim of this study was to characterize the role of the miR-146a–Polo-like kinase 2 (Plk2) network in regulating lin− BMC senescence, apoptosis, and their angiogenic capability. Approach and Results— Transcriptome analysis in lin− BMCs isolated from young and aged wild-type and ApoE−/− (apolipoprotein E) mice showed a significant age-associated increase in miR-146a expression. In silico analysis, expression study and Luciferase reporter assay established Plk2 as a direct target of miR-146a. miR-146a overexpression in young lin− BMCs inhibited Plk2 expression, resulting in increased senescence and apoptosis, via p16Ink4a/p19Arf and p53, respectively, as well as impaired angiogenic capacity in vitro and in vivo. Conversely, suppression of miR-146a in aged lin− BMCs increased Plk2 expression and rejuvenated lin− BMCs, resulting in decreased senescence and apoptosis, leading to improved angiogenesis. Conclusions— (1) miR-146a regulates lin− BMC senescence and apoptosis by suppressing Plk2 expression that, in turn, activates p16Ink4a/p19Arf and p53 and (2) modulation of miR-146a or its target Plk2 may represent a potential therapeutic intervention to improve lin− BMC–mediated angiogenesis and vascular repair.

Bone Sialoprotein and the Paradox of Angiogenesis Versus Atherosclerosis

Bone sialoprotein (BSP) is a protein thought to be highly specific for bone. BSP contains an arginine-glycine-aspartic acid (RGD) cell attachment sequence involved in osteoclast adhesion to bone matrix via the vitronectin receptor and plays an important role in the early process of bone mineralization and resorption. The study by Bellahcene et al1 in this issue of Circulation Research indicates that BSP mediates adhesion and chemotactic migration of endothelial cells and promotes angiogenesis, suggesting that BSP may be an important factor in angiogenesis and the initiation of atherosclerosis, two processes that are probably related. In earlier studies, Folkman2 hypothesized that tumor growth beyond a few millimeters requires recruitment and growth of a new microcirculation, or angiogenesis, which is induced by tumors as lifelines for oxygen and nutrients. New blood vessels also provide exits for cancer cells to spread to other parts of the body. Angiogenesis is also involved in physiological conditions, such as embryogenesis, and other pathological conditions, such as wound healing. The process of angiogenesis requires a highly coordinated series of events, including endothelial cell proliferation, migration, tube and lumen formation, and, in some cases, recruitment of smooth muscle cells (SMCs) and other adventitial cells. Adhesive interaction of cells with components of the extracellular matrix is a recognized requirement for cell proliferation and migration. Evidence indicates that many of the adhesive interactions are mediated by members of the integrin family of heterodimeric adhesion receptors. Among these integrins, αvβ3, which is expressed by a variety of cell types, has been shown to play a key role in the cell migration involved in metastasis and angiogenesis.3 The work presented by Bellahcene et …

Contrast-Enhanced Magnetic Resonance Imaging as the Newest Tool to Detect Transplant Coronary Artery Disease⁎

The development of obstructive transplant coronary artery disease (TCAD) is the major factor limiting long-term survival after cardiac transplantation ([1][1]). TCAD is characterized as accelerated arteriosclerosis affecting the entire coronary tree with distal obliteration ([2][2]). A major problem

Perspective: Autonomic care systems for hospitalized patients.

With advancements of medical technology and improved diagnostic and treatment options, children with severe birth defects who would otherwise have no chance of surviving post birth survive to go home every day. The average lifespan in the United States has increased substantially over the last century. These successes and many other medical breakthroughs in managing complex illnesses, particularly in frail, elderly patients, have resulted in an increasing percentage of patients with comorbidities. This, coupled with a policy change by Medicare (i.e., Medicare will no longer reimburse hospitals for costs associated with treating preventable errors and injuries that a patient acquires while in the hospital), creates an enormous challenge to health care providers. To meet the challenge, the authors propose a new model of health care--the autonomic care system (ACS)--a concept derived from the intensive care unit and the autonomic computing initiative in the computer industry. Using wound care as an example, the authors examine the necessity, feasibility, design, and challenges related to ACS. Specifically, they discuss the role of the human operator, the potential combination of ACS and existing hospital information technology (e.g., electronic medical records and computerized provider order entry), and the costs associated with ACS. ACS may serve as a roadmap to revamp the health care system, bringing down the barriers among different specialties and improving the quality of care for each problem for all hospitalized patients.

Ras activation of NF-κB and superoxide

Publisher Summary This chapter describes the Ras activation of NF- K B and superoxide. p21 ras (c-Ras) participates in various cellular processes, including proliferation, differentiation, apoptosis, and cytoskeletal organization. Mutations in a ras allele that render it constitutively active have been described in approximately 30% of all human tumors, making it the most widely mutated human protooncogene. NF- K B is a transcription factor that regulates genes involved in immune and inflammatory responses, cell proliferation, differentiation, and apoptosis. There are five members in the NF- K B family: p50/ NF- K B 1, p52/ NF- K B 2, RelA/p65, RelB, and c-RelY. The Rel homology domain found in each of these proteins functions in DNA binding, dimerization among family members, and interaction with a family of inhibitory proteins known as I- K B, including 1- K B α and I- K Bβ, which bind to NF- K B and sequester it in the cytoplasm. Previously, Rac activation assay involved the use of the radioisotope 32 P. The chapter adopted a nonradioisotope protocol developed by Upstate Biotechnology, Inc. to detect Rac activation.

Journey in antithrombotic strategies for ST-elevation myocardial infarction.

Our understanding and treatment of the ST-elevation myocardial infarction (STEMI) has led to a tremendous improvement in the care and preservation of life affecting millions yearly. As the medical community continues to discover novel strategies in therapeutics and innovations in prevention, it is imperative to understand the scientific journey the treatment of STEMI has traveled. Furthermore, the research pillars that led to our understanding of the current paradigm of STEMI will be highlighted in an effort to illuminate the foundation on which we now stand.

Erratum: Deficient Smad7 expression: A putative molecular defect in scleroderma (PNAS (2016) 113:15 (E2208))

MEDICAL SCIENCES Retraction for “Deficient Smad7 expression: A putative molecular defect in scleroderma,” by Chunming Dong, Shoukang Zhu, Tao Wang, Woohyun Yoon, Zhiru Li, Rene J. Alvarez, Peter ten Dijke, Barbara White, Fredrick M. Wigley, and Pascal J. GoldschmidtClermont, which appeared in issue 6, March 19, 2002, of Proc Natl Acad Sci USA (99:3908–3913; 10.1073/pnas.062010399). The authors wish to note the following: “It has recently been brought to our attention that some of the elements in Fig. 3 of our paper may have been fabricated. Unfortunately, because of the time elapsed since publication, we no longer have in our possession the original gels and blots that were used to produce the figure. While we trust that the other data in the paper is genuine and the overall conclusions sound, we have no alternative but to request a retraction of our paper. We apologize for any inconvenience this may cause.”