title: IL-36γ is secreted in microparticles and exosomes by lung macrophages in response to bacteria and bacterial components.
abstract: Interleukin-36 is a family of novel interleukin-1-like proinflammatory cytokines that are highly expressed in epithelial tissues and several myeloid-derived cell types. Like those of classic interleukin-1 cytokines, the secretion mechanisms of interleukin-36 are not well understood. Interleukin-36γ secretion in dermal epithelial cells requires adenosine 5'-triphosphate, which suggests a nonclassical mechanism of secretion. In this study, murine pulmonary macrophages and human alveolar macrophages were treated with recombinant pathogen-associated molecular patterns (intact bacteria: Klebsiella pneumoniae or Streptococcus pneumoniae). Cell lysates were analyzed for messenger ribonucleic acid by quantitative real-time polymerase chain reaction, and conditioned medium was analyzed for interleukin-36γ by enzyme-linked immunosorbent assay, with or without sonication. In addition, conditioned medium was ultracentrifuged at 25,000 g and 100,000 g, to isolate microparticles and exosomes, respectively, and interleukin-36γ protein was assessed in each fraction by Western blot analysis. Interleukin-36γ mRNA was induced in both murine and human lung macrophages by a variety of pathogen-associated molecular patterns, as well as heat-killed and live Klebsiella pneumoniae and Streptococcus pneumoniae, and induction occurred in a myeloid differentiation response gene 88-dependent manner. Secretion of interleukin-36γ protein was enhanced by adenosine 5'-triphosphate. Furthermore, extracellular interleukin-36γ protein detection was markedly enhanced by sonication to disrupt membrane-bound structures. Interleukin-36γ protein was detected by Western blot in microparticles and exosome fractions isolated by ultracentrifugation. Interleukin-36γ was induced and secreted from lung macrophages in response to Gram-negative and -positive bacterial stimulation. The results suggest that interleukin-36γ is secreted in a non-Golgi-dependent manner by lung macrophages in response to Gram-positive and -negative bacterial challenge.
authors: Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine makovach@umich.edu.
authors: Melissa A
authors: MA
authors: Kovach
authors: Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine.
authors: Benjamin H
authors: BH
authors: Singer
authors: Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine.
authors: Michael W
authors: MW
authors: Newstead
authors: Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine.
authors: Xianying
authors: X
authors: Zeng
authors: Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine.
authors: Thomas A
authors: TA
authors: Moore
authors: Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine.
authors: Eric S
authors: ES
authors: White
authors: Department of Pathology, University of Michigan Medical Center, Ann Arbor, Michigan.
authors: Steven L
authors: SL
authors: Kunkel
authors: Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine.
authors: Marc
authors: M
authors: Peters-Golden
authors: Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine.
authors: Theodore J
authors: TJ
authors: Standiford
mesh_terms: D000818:Animals; D055252:Cell-Derived Microparticles / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D002478:Cells, Cultured; D055354:Exosomes / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D005260:Female; D007375:Interleukin-1 / Q000378:metabolism*; D007711:Klebsiella pneumoniae / Q000502:physiology*; D016676:Macrophages, Alveolar / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000502:physiology; D013296:Streptococcus pneumoniae / Q000502:physiology*
chemical_list: C569167:IL1F9 protein, mouse; D007375:Interleukin-1; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88
keywords: cytokines; innate immune response; nonclassic secretion; pneumonia