title: Extrusion of mitochondrial contents from lipopolysaccharide-stimulated cells: Involvement of autophagy.
abstract: Sepsis/endotoxemia is elicited by the circulatory distribution of pathogens/endotoxins into whole bodies, and causes profound effects on human health by causing inflammation in multiple organs. Mitochondrial damage is one of the characteristics of the cellular degeneration observed during sepsis/endotoxemia. Elimination of damaged mitochondria through the autophagy-lysosome system has been reported in the liver, indicating that autophagy should play an important role in liver homeostasis during sepsis/endotoxemia. An increased appearance of mitochondrial DNA and proteins in the plasma is another feature of sepsis/endotoxemia, suggesting that damaged mitochondria are not only eliminated within the cells, but also extruded through currently unknown mechanisms. Here we provide evidence for the secretion of mitochondrial proteins and DNA from lipopolysaccharide (LPS)-stimulated rat hepatocytes as well as mouse embryonic fibroblasts (MEFs). The secretion of mitochondrial contents is accompanied by the secretion of proteins that reside in the lumenal space of autolysosomes (LC3-II and CTSD/cathepsin D), but not by a lysosomal membrane protein (LAMP1). The pharmacological inhibition of autophagy by 3MA blocks the secretion of mitochondrial constituents from LPS-stimulated hepatocytes. LPS also stimulates the secretion of mitochondrial as well as autolysosomal lumenal proteins from wild-type (Atg5(+/+)) MEFs, but not from atg5(-/-) MEFs. Furthermore, we show that direct exposure of purified mitochondria activates polymorphonuclear leukocytes (PMNs), as evident by the induction of IL1B/interlekin-1β, a pro-inflammatory cytokine. Taken together, the data suggest the active extrusion of mitochondrial contents, which provoke an inflammatory response of immune cells, through the exocytosis of autolysosomes by cells stimulated with LPS.
authors.affiliation: a Department of Forensic Medicine ; Graduate School of Medical and Dental Sciences; Tokyo Medical and Dental University ; Tokyo , Japan.
authors.forename: Kana
authors.initials: K
authors.lastname: Unuma
authors.affiliation: a Department of Forensic Medicine ; Graduate School of Medical and Dental Sciences; Tokyo Medical and Dental University ; Tokyo , Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Aki
authors.affiliation: a Department of Forensic Medicine ; Graduate School of Medical and Dental Sciences; Tokyo Medical and Dental University ; Tokyo , Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Funakoshi
authors.affiliation: a Department of Forensic Medicine ; Graduate School of Medical and Dental Sciences; Tokyo Medical and Dental University ; Tokyo , Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Hashimoto
authors.affiliation: a Department of Forensic Medicine ; Graduate School of Medical and Dental Sciences; Tokyo Medical and Dental University ; Tokyo , Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Uemura
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001343:Autophagy / Q000187:drug effects* / Q000235:genetics; D000071187:Autophagy-Related Protein 5; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008247:Lysosomes / Q000187:drug effects / Q000235:genetics; D008297:Male; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D008954:Models, Biological; D018375:Neutrophil Activation / Q000187:drug effects; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000378:metabolism; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism
chemical_list: C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004272:DNA, Mitochondrial; D008070:Lipopolysaccharides; D008869:Microtubule-Associated Proteins; D024101:Mitochondrial Proteins; C574124:TFEB protein, rat; C025946:3-methyladenine; D000225:Adenine
keywords: LPS; autophagy; hepatocyte; lysosomal exocytosis; mitochondria