title: Mitochondrial DNA released by trauma induces neutrophil extracellular traps.
abstract: Neutrophil extracellular traps (NETs) are critical for anti-bacterial activity of the innate immune system. We have previously shown that mitochondrial damage-associated molecular patterns (mtDAMPs), including mitochondrial DNA (mtDNA), are released into the circulation after injury. We therefore questioned whether mtDNA is involved in trauma-induced NET formation. Treatment of human polymorphoneutrophils (PMN) with mtDNA induced robust NET formation, though in contrast to phorbol myristate acetate (PMA) stimulation, no NADPH-oxidase involvement was required. Moreover, formation of mtDNA-induced NETs was completely blocked by TLR9 antagonist, ODN-TTAGGG. Knowing that infective outcomes of trauma in elderly people are more severe than in young people, we measured plasma mtDNA and NET formation in elderly and young trauma patients and control subjects. MtDNA levels were significantly higher in the plasma of elderly trauma patients than young patients, despite lower injury severity scores in the elderly group. NETs were not visible in circulating PMN isolated from either young or old control subjects. NETs were however, detected in PMN isolated from young trauma patients and to a lesser extent from elderly patients. Stimulation by PMA induced widespread NET formation in PMN from both young volunteers and young trauma patients. NET response to PMA was much less pronounced in both elderly volunteers' PMN and in trauma patients' PMN. We conclude that mtDNA is a potent inducer of NETs that activates PMN via TLR9 without NADPH-oxidase involvement. We suggest that decreased NET formation in the elderly regardless of higher mtDNA levels in their plasma may result from decreased levels of TLR9 and/or other molecules, such as neutrophil elastase and myeloperoxidase that are involved in NET generation. Further study of the links between circulating mtDNA and NET formation may elucidate the mechanisms of trauma-related organ failure as well as the greater susceptibility to secondary infection in elderly trauma patients.
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, United States of America.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Itagaki
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, United States of America; Center for Vascular Biology Research, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, United States of America.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Kaczmarek
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, United States of America.
authors.forename: Yen Ting
authors.initials: YT
authors.lastname: Lee
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, United States of America.
authors.forename: I Tien
authors.initials: IT
authors.lastname: Tang
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, United States of America.
authors.forename: Burak
authors.initials: B
authors.lastname: Isal
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, United States of America.
authors.forename: Yashar
authors.initials: Y
authors.lastname: Adibnia
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, United States of America.
authors.forename: Nicola
authors.initials: N
authors.lastname: Sandler
authors.affiliation: Departments of Medicine and Immunology, Roswell Park Cancer Institute, Buffalo, NY, United States of America.
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Grimm
authors.affiliation: Departments of Medicine and Immunology, Roswell Park Cancer Institute, Buffalo, NY, United States of America; Department of Medicine, University at Buffalo School of Medicine, Buffalo, NY, United States of America.
authors.forename: Brahm H
authors.initials: BH
authors.lastname: Segal
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, United States of America.
authors.forename: Leo E
authors.initials: LE
authors.lastname: Otterbein
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, United States of America.
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Hauser
mesh_terms: D000367:Age Factors; D000368:Aged; D016022:Case-Control Studies; D002478:Cells, Cultured; D004272:DNA, Mitochondrial / Q000378:metabolism* / Q000494:pharmacology; D065206:Extracellular Traps / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism; D014947:Wounds and Injuries / Q000378:metabolism*
chemical_list: D004272:DNA, Mitochondrial; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9