Research

Translational Research

Robert Arch, Ph.D.

The main interest of our lab focuses on signal transduction pathways that regulate the balance between cell survival and apoptosis/programmed cell death (PCD). Members of the tumor necrosis factor receptor (TNFR) superfamily play an essential role in these processes. The TNFR family of surface proteins can be divided into two subfamilies: I) Members of the TNFR family that contain a death domain (DD) have been shown to trigger cascades that culminate in PCD. II) TNFR-related molecules that lack a DD are thought to function as costimulatory receptors that promote cell survival.

We and others have shown that many TNFR-related molecules use cytoplasmic adapter proteins known as TNFR-associated factors (TRAFs) as signaling intermediates. Accumulating evidence suggests that recruitment of TRAFs to receptors at the cell surface plays an important role in processes that lead to either PCD or survival of cells. Little is known about the molecular mechanisms by which TRAF proteins mediate these decisions. TRAF molecules function most likely as adapter proteins that mediate the formation of larger signaling complexes. These complexes can contain a variety of recently described kinases (e.g. NIK, JNK) and proteases of the caspase family involved in TRAF-mediated signaling.

Our recent findings suggest a novel mechanism of regulation of TRAF-mediated signaling pathways. Receptor-induced relocalization of TRAFs results in increased sensitivity to TNF-a-induced apoptosis. Interestingly, the TNFR-related molecules CD30 that is expressed on Reed-Sternberg cells of Hodgkin's Disease, on lymphoma cells, and on chronically activated lymphocytes not only leads to the most efficient depletion of TRAF molecules, but also to a dramatically increased sensitivity of cells to PCD. Current studies in our lab aim to address molecular mechanisms of this phenomenon and focus on the development of therapeutical approaches that utilize the effects of CD30 to eradicate malignant cell types. See the Arch Lab website.

Steven L. Brody, M.D.

Abnormalities of the airway epithelium characterize many lung diseases including bronchitis, cystic fibrosis, and bronchogenic carcinoma. To understand the molecular mechanisms which regulate pulmonary epithelial cell growth and differentiation in disease, we are investigating the normal mechanisms for airway epithelial cell growth and differentiation in the developing lung. We have cloned and characterized a transcription factor expressed early in the developing proximal airway epithelium. This factor is a member of the forkhead family of transcription factors, proteins with important roles in development and the determination of tissue-specific patterns of gene expression. We have found that this protein is expressed only in ciliated cells and that its expression is temporally related to ciliogenesis. We have generated a mouse that is deficient ("Knock out mouse") in this gene and found that the mouse has situs inversus and absent ciliogenesis. This mimics the human Kartegener's syndrome. Current studies are directed toward understanding the regulation of ciliogenesis in the airway. These studies are also linked to disorders of epithelial cell differentiation such as cystic fibrosis, chronic bronchitis, and lung cancer.

Mario Castro, M.D.

My clinical research interests focus on the pathogenesis of asthma. In particular we are evaluating the genetic, biologic, and immunologic determinants of asthma in a large cohort of infants with respiratory syncytial virus bronchiolitis (RBEL study). Furthermore we have utilized the fiberoptic bronchoscope to investigate what happens to the lower airways in mild to severe asthma and following segmental allergen challenge or glucocorticoid withdrawal. In addition, methods to improve outcomes in asthma health care delivery are currently being investigated in both outpatient and inpatient settings.

Translational Research Unit in Asthma

Link to Translational Research Unit in Asthma

Jonathan M. Green, M.D.

The focus of my laboratory is to understand the role of accessory molecules on the surface of T lymphocytes in modulating the T cells response to antigen. In particular, we are investigating the cell surface proteins CD28 and CD43. T cell recognition of antigen occurs through the interaction of the T cell receptor with an antigen-MHC complex on the surface of an antigen presenting cell. In addition to this, many other cell surface proteins play critical roles in modulating both the initial response to antigen as well as regulating the differentiation of the activated cells into phenotypically distinct effector cells. CD28 has been shown to be critical in the initial activation of T cells. However, its role in the subsequent development of an inflammatory response is only now being explored. Similarly, we have recently identified CD43 as a potential critical mediator of T cell activation. Using both knockout and transgenic mice, as well as a variety of specific reagents, we are investigating the roles of these 2 critical proteins in the regulation of the immune response, as well as the role they may play specifically in models of inflammatory lung disease.

Michael J. Holtzman, M.D.

My lab focuses on the signal-transduction and genetic basis for mucosal immunity, inflammation, and remodeling, especially in relation to airway disease. We concentrate on the response to respiratory paramyxoviruses, since these agents are closely associated with common acute and chronic airway diseases, i.e., bronchiolitis and asthma. We focus on innate immune components and their interaction with the adaptive immune system. We use viral, cellular, and mouse models as well as human subjects for study, and we take advantage of comparisons between theses systems. Our approach aims to answer two major questions: first, what are the factors that control acute paramyxoviral infection; and second, how can these transient infections cause long-term airway disease? We have shown that viral immunity depends on a special network of immune-response genes in host epithelial cells and macrophages that signal to the adaptive immune system. These signals are being refined as targets for anti-viral strategies. Viruses ordinarily trigger this network, but it is also permanently activated in asthma even in the absence of viral infection. In a model of this chronic process, we determined that paramyxoviruses first target airway epithelial cells for apoptosis and then re-program the system so there is abnormal cell survival in the pattern of an asthmatic phenotype. This alteration exhibits viral specificity, genetic susceptibility, and immune cell memory, so we are identifying the responsible viral genes using reverse genetics, host genes using molecular markers (SNPs) and oligonucleotide microarray, and immune cell components using in vitro and in vivo cell transfer systems.

• Keywords: apoptosis, immunology, functional genomics, microbial pathogenesis, signal transduction.

Daniel P. Schuster

The focus of my lab is on the use of imaging to translate new basic discoveries to human investigations concerning lung physiology and pathophysiology. Two current areas of focus are on inflammation imaging in acute lung injury, cystic fibrosis, and bronciolitis obliterans syndrome after lung transplantation, and on gene expression imaging. Imaging techniques are developed and validated in a variety of animal models and then implemented in studies in humans.

Robert M. Senior, M.D.

This laboratory is interested in lung injury and repair. Our focus is on lung basement membranes and matrix metalloproteinases (MMPs) that degrade lung basement membranes. We study production of basement membrane components by lung cells in models of lung injury, including interstitial fibrosis caused by bleomycin and alveolar air space enlargement (emphysema) induced by chronic inhalation of cigarette smoke. Alveolar basement membrane production during lung development is another area of our research. We use mice extensively for these studies and a substantial effort is to define the role of certain genes in lung injury and repair using mice with altered genetic profiles as a result of transgenes and targeted gene deletions (knockouts) .

Michael J. Walter, M.D.

The focus of the laboratory is understanding the role of airway epithelial cell derived proteins in mediating airway immunity and inflammation. Along these lines we have demonstrated interleukin-12 p80 (p80) is expressed by airway epithelial cells during a mouse viral bronchitis and in subjects with asthma but not in normal or chronic bronchitis subjects. Furthermore, we have determined p80 acts as a macrophage chemoattractant and this response is mediated through the cytoplasmic tail of IL-12 receptor b1 (IL-12Rb1). We are currently using site-directed mutagenesis to identify the intracellular domains of IL-12Rb1 that mediate macrophage chemotaxis. Additionally, this approach is being employed to examine the downstream intracellular signaling cascades that generate this chemotactic response. To further evaluate the role of p80-dependent chemotaxis in vivo we have begun to examine airway inflammatory patterns in IL-12Rb1 deficient mice and transgenic mice that selectively overexpress p80 in the airway. Understanding the molecular signals that culminate in p80-dependent macrophage chemotaxis will aid in developing strategies to modify airway diseases that are associated with enhanced p80 expression, such as asthma and respiratory viral infection.

Division of Pulmonary and Critical Care Medicine
Department of Medicine
Washington University School of Medicine