title: Acid Sphingomyelinase Promotes Endothelial Stress Response in Systemic Inflammation and Sepsis.
abstract: The pathophysiology of sepsis involves activation of acid sphingomyelinase (SMPD1) with subsequent generation of the bioactive mediator ceramide. We herein evaluated the hypothesis that the enzyme exerts biological effects in endothelial stress response. Plasma-secreted sphingomyelinase activity, ceramide generation and lipid raft formation were measured in human microcirculatory endothelial cells (HMEC-1) stimulated with serum obtained from sepsis patients. Clustering of receptors relevant for signal transduction was studied by immuno staining. The role of SMPD1 for macrodomain formation was tested by pharmacological inhibition. To confirm the involvement of the stress enzyme, direct inhibitors (amino bisphosphonates) and specific downregulation of the gene was tested with respect to ADAMTS13 expression and cytotoxicity. Plasma activity and amount of SMPD1 were increased in septic patients dependent on clinical severity. Increased breakdown of sphingomyelin to ceramide in HMECs was observed following stimulation with serum from sepsis patientsin vitro. Hydrolysis of sphingomyelin, clustering of receptor complexes, such as the CD95L/Fas-receptor, as well as formation of ceramide enriched macrodomains was abrogated using functional inhibitors (desipramine and NB6). Strikingly, the stimulation of HMECs with serum obtained from sepsis patients or mixture of proinflammatory cytokines resulted in cytotoxicity and ADAMTS13 downregulation which was abrogated using desipramine, amino bisphosphonates and genetic inhibitors. SMPD1 is involved in the dysregulation of ceramide metabolism in endothelial cells leading to macrodomain formation, cytotoxicity and downregulation of ADAMTS13 expression. Functional inhibitors, such as desipramine, are capable to improve endothelial stress response during sepsis and might be considered as a pharmacological treatment strategy to favor the outcome.
authors.affiliation: Center for Sepsis Control & Care (CSCC), Jena University Hospital, Germany.|Department for Anesthesiology & Intensive Care Medicine, Jena University Hospital, Germany.
authors.forename: Ha-Yeun
authors.initials: HY
authors.lastname: Chung
authors.affiliation: Department for Anesthesiology & Intensive Care Medicine, Jena University Hospital, Germany.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Hupe
authors.affiliation: Center for Sepsis Control & Care (CSCC), Jena University Hospital, Germany.|Department for Anesthesiology & Intensive Care Medicine, Jena University Hospital, Germany.
authors.forename: Gordon P
authors.initials: GP
authors.lastname: Otto
authors.affiliation: Department for Anesthesiology & Intensive Care Medicine, Jena University Hospital, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Sprenger
authors.affiliation: Department of Radiology, University Hospital Cologne, Cologne, Germany.
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Bunck
authors.affiliation: Department for Anesthesiology & Intensive Care Medicine, Jena University Hospital, Germany.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dorer
authors.affiliation: Department of Nephropathology, University Hospital Erlangen, Erlangen, Germany.
authors.forename: Clemens L
authors.initials: CL
authors.lastname: Bockmeyer
authors.affiliation: Hochschule Furtwangen University, Faculty Medical and Life Sciences, Villingen-Schwenningen, Germany.|Fraunhofer Institute for Cell Therapy and Immunology IZI, Leipzig, Germany.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Deigner
authors.affiliation: Center for Sepsis Control & Care (CSCC), Jena University Hospital, Germany.|Department for Anesthesiology & Intensive Care Medicine, Jena University Hospital, Germany.
authors.forename: Markus H
authors.initials: MH
authors.lastname: Gräler
authors.affiliation: Center for Sepsis Control & Care (CSCC), Jena University Hospital, Germany.|Department for Anesthesiology & Intensive Care Medicine, Jena University Hospital, Germany.
authors.forename: Ralf A
authors.initials: RA
authors.lastname: Claus
keywords: Infectious Diseases; acid sphingomyelinase; ceramide; endothelial dysfunction; lipid rafts; multiple organ failure