• Ilona E Kammerl, Angela Dann, Alessandra Mossina, Dorothee Brech, Christina Lukas, Oliver Vosyka, Petra Nathan, Thomas M Conlon, Darcy E Wagner, Hermen S Overkleeft, Antje Prasse, Ivan O Rosas, Tobias Straub, Susanne Krauss-Etschmann, Melanie Königshoff, Gerhard Preissler, Hauke Winter, Michael Lindner, Rudolf Hatz, Jürgen Behr, Katharina Heinzelmann, Ali Ö Yildirim, Elfriede Noessner, Oliver Eickelberg, and Silke Meiners.
• 1 Comprehensive Pneumology Center, University Hospital, Ludwig-Maximilians University, Helmholtz Zentrum München, Member of the German Center for Lung Research (DZL), Munich, Germany.
• Am. J. Respir. Crit. Care Med. 2016 Jun 1; 193 (11): 123012411230-41.

RationalePatients with chronic obstructive pulmonary disease (COPD) and in particular smokers are more susceptible to respiratory infections contributing to acute exacerbations of disease. The immunoproteasome is a specialized type of proteasome destined to improve major histocompatibility complex (MHC) class I-mediated antigen presentation for the resolution of intracellular infections.ObjectivesTo characterize immunoproteasome function in COPD and its regulation by cigarette smoke.MethodsImmunoproteasome expression and activity were determined in bronchoalveolar lavage (BAL) and lungs of human donors and patients with COPD or idiopathic pulmonary fibrosis (IPF), as well as in cigarette smoke-exposed mice. Smoke-mediated alterations of immunoproteasome activity and MHC I surface expression were analyzed in human blood-derived macrophages. Immunoproteasome-specific MHC I antigen presentation was evaluated in spleen and lung immune cells that had been smoke-exposed in vitro or in vivo.Measurements And Main ResultsImmunoproteasome and MHC I mRNA expression was reduced in BAL cells of patients with COPD and in isolated alveolar macrophages of patients with COPD or IPF. Exposure of immune cells to cigarette smoke extract in vitro reduced immunoproteasome activity and impaired immunoproteasome-specific MHC I antigen presentation. In vivo, acute cigarette smoke exposure dynamically regulated immunoproteasome function and MHC I antigen presentation in mouse BAL cells. End-stage COPD lungs showed markedly impaired immunoproteasome activities.ConclusionsWe here show that the activity of the immunoproteasome is impaired by cigarette smoke resulting in reduced MHC I antigen presentation. Regulation of immunoproteasome function by cigarette smoke may thus alter adaptive immune responses and add to prolonged infections and exacerbations in COPD and IPF.

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