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Indianapolis, IN, United States

Devlin C.M.,Indiana University | Lahm T.,Indiana University | Lahm T.,udebush Veterans Affairs Medical Center | Hubbard W.C.,Johns Hopkins University | And 8 more authors.
Journal of Biological Chemistry

To understand the mechanisms of ceramide-based responses to hypoxia, we performed a mass spectrometry-based survey of ceramide species elicited by a wide range of hypoxic conditions (0.2-5% oxygen). We describe a rapid, time-dependent, marked up-regulation of dihydroceramides (DHCs) in mammalian cells and in the lungs of hypoxic rats. The increase affected all DHC species and was proportional with the depth and duration of hypoxia, ranging from 2- (1 h) to 10-fold (24 h), with complete return to normal after 1 h of reoxygenation at the expense of increased ceramides. We demonstrate that a DHC-based response to hypoxia occurs in a hypoxia-inducible factor-independent fashion and is catalyzed by the DHC desaturase (DEGS) in the de novo ceramide pathway. Both the impact of hypoxia on DHC molecular species and its inhibitory effect on cell proliferation were reproduced by knockdown of DEGS1 or DEGS2 by siRNA during normoxia. Conversely, overexpression of DEGS1 or DEGS2 attenuated the DHC accumulation and increased cell proliferation during hypoxia. Based on the amplitude and kinetics of DHC accumulation, the enzymatic desaturation of DHCs fulfills the criteria of an oxygen sensor across physiological hypoxic conditions, regulating the balance between biologically active components of ceramide metabolism. Source

Corridon P.R.,Indiana University | Rhodes G.J.,Indiana University | Leonard E.C.,Indiana University | Basile D.P.,Indiana University | And 5 more authors.
American Journal of Physiology - Renal Physiology

Gene therapy has been proposed as a novel alternative to treat kidney disease. This goal has been hindered by the inability to reliably deliver transgenes to target cells throughout the kidney, while minimizing injury. Since hydrodynamic forces have previously shown promising results, we optimized this approach and designed a method that utilizes retrograde renal vein injections to facilitate transgene expression in rat kidneys. We show, using intravital fluorescence two-photon microscopy, that fluorescent albumin and dextrans injected into the renal vein under defined conditions of hydrodynamic pressure distribute broadly throughout the kidney in live animals. We found injection parameters that result in no kidney injury as determined by intravital microscopy, histology, and serum creatinine measurements. Plasmids, baculovirus, and adenovirus vectors, designed to express EGFP, EGFP-actin, EGFP-occludin, EGFP-tubulin, tdTomato-H2B, or RFP-actin fusion proteins, were introduced into live kidneys in a similar fashion. Gene expression was then observed in live and ex vivo kidneys using two-photon imaging and confocal laser scanning microscopy. We recorded widespread fluorescent protein expression lasting more than 1 mo after introduction of transgenes. Plasmid and adenovirus vectors provided gene transfer efficiencies ranging from 50 to 90%, compared with 10-50% using baculovirus. Using plas-mids and adenovirus, fluorescent protein expression was observed 1) in proximal and distal tubule epithelial cells; 2) within glomeruli; and 3) within the peritubular interstitium. In isolated kidneys, fluorescent protein expression was observed from the cortex to the papilla. These results provide a robust approach for gene delivery and the study of protein function in live mammal kidneys. © 2013 the American Physiological Society. Source

Green L.A.,Indiana University | Green L.A.,udebush Veterans Affairs Medical Center | Yi R.,Indiana University | Yi R.,udebush Veterans Affairs Medical Center | And 10 more authors.
American Journal of Physiology - Lung Cellular and Molecular Physiology

Chronic lung diseases, such as pulmonary emphysema, are increasingly recognized complications of infection with the human immunodeficiency virus (HIV). Emphysema in HIV may occur independent of cigarette smoking, via mechanisms that are poorly understood but may involve lung endothelial cell apoptosis induced by the HIV envelope protein gp120. Recently, we have demonstrated that lung endothelial apoptosis is an important contributor to the development of experimental emphysema, via upregulation of the proinflammatory cytokine endothelial monocyte-activating polypeptide II (EMAP II) in the lung. Here we investigated the role of EMAP II and its receptor, CXCR3, in gp120-induced lung endothelial cell apoptosis. We could demonstrate that gp120 induces a rapid and robust increase in cell surface expression of EMAP II and its receptor CXCR3. This surface expression occurred via a mechanism involving gp120 signaling through its CXCR4 receptor and p38 MAPK activation. Both EMAP II and CXCR3 were essentially required for gp120-induced apoptosis and exposures to low gp120 concentrations enhanced the susceptibility of endothelial cells to undergo apoptosis when exposed to soluble cigarette smoke extract. These data indicate a novel mechanism by which HIV infection causes endothelial cell loss involved in lung emphysema formation, independent but potentially synergistic with smoking, and suggest therapeutic targets for emphysema prevention and/or treatment. Source

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