title: Intra-Peritoneal Administration of Mitochondrial DNA Provokes Acute Lung Injury and Systemic Inflammation via Toll-Like Receptor 9.
abstract: The pathogenesis of sepsis is complex. Mitochondrial dysfunction, which is responsible for energy metabolism, intrinsic apoptotic pathway, oxidative stress, and systemic inflammatory responses, is closely related with severe sepsis induced death. Mitochondria DNA (mtDNA) contain un-methylated cytosine phosphate guanine (CpG) motifs, which exhibit immune stimulatory capacities. The aim of this study was to investigate the role and mechanism of mtDNA release on lipopolysaccharide (LPS) induced acute lung injury (ALI) and systemic inflammation. Following LPS injection, plasma mtDNA copies peak at 8 h. Compared with wild-type (WT) mice, mtDNA in toll like receptor 4 knockout (TLR4 KO) mice were significantly decreased. MtDNA intra-peritoneal administration causes apparent ALI as demonstrated by increased lung injury score, bronchoalveolar lavage fluid (BALF) total protein and wet/dry (W/D) ratio; mtDNA injection also directly provokes systemic inflammation, as demonstrated by increased IL-1β, IL-6, high-mobility group protein B1 (HMGB1) level; while nuclear DNA (nDNA) could not induce apparent ALI and systemic inflammation. However, compared with WT mice, TLR4 KO could not protect from mtDNA induced ALI and systemic inflammation. Specific TLR9 inhibitor, ODN 2088 pretreatment can significantly attenuate mtDNA induced ALI and systemic inflammation, as demonstrated by improved lung injury score, decreased lung wet/dry ratio, BALF total protein concentration, and decreased systemic level of IL-1β, IL-6 and HMGB1. MtDNA administration activates the expression of p-P38 mitogen-activated protein kinases (MAPK) in lung tissue and specific TLR9 inhibitor pretreatment can attenuate this activation. Thus, LPS-induced mtDNA release occurs in a TLR4-dependent manner, and mtDNA causes acute lung injury and systemic inflammation in a TLR9-dependent and TLR4-independent manner.
authors: Department of Intensive Care Unit, Xiangya Hospital, Central South University, Changsha 410008, China. zlmddzyx@gmail.com.
authors: Lemeng
authors: L
authors: Zhang
authors: Department of Intensive Care Unit, Xiangya Hospital, Central South University, Changsha 410008, China. dengsy2014@foxmail.com.
authors: Songyun
authors: S
authors: Deng
authors: Department of Intensive Care Unit, Xiangya Hospital, Central South University, Changsha 410008, China. zsping8888@sina.cn.
authors: Shuangping
authors: S
authors: Zhao
authors: Department of Intensive Care Unit, Xiangya Hospital, Central South University, Changsha 410008, China. ayhicu1978@126.com.
authors: Yuhang
authors: Y
authors: Ai
authors: Department of Intensive Care Unit, Xiangya Hospital, Central South University, Changsha 410008, China. zln7095@163.com.
authors: Lina
authors: L
authors: Zhang
authors: Department of Respiratory Medicines, Xiangya Hospital, Central South University, Changsha 410008, China. pinhuapan668@126.com.
authors: Pinhua
authors: P
authors: Pan
authors: Department of Respiratory Medicines, Xiangya Hospital, Central South University, Changsha 410008, China. Suli8779@163.com.
authors: Xiaoli
authors: X
authors: Su
authors: Department of Respiratory Medicines, Xiangya Hospital, Central South University, Changsha 410008, China. leopard2a1980@hotmail.com.
authors: Hongyi
authors: H
authors: Tan
authors: Department of Respiratory Medicines, Xiangya Hospital, Central South University, Changsha 410008, China. wdd6688@126.com.
authors: Dongdong
authors: D
authors: Wu
mesh_terms: D055371:Acute Lung Injury / Q000209:etiology / Q000378:metabolism*; D000818:Animals; D004272:DNA, Mitochondrial / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D024243:HMGB1 Protein / Q000235:genetics / Q000378:metabolism; D007274:Injections, Intraperitoneal; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018805:Sepsis / Q000209:etiology / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D024243:HMGB1 Protein; C582808:HMGB1 protein, mouse; D053583:Interleukin-1beta; D015850:Interleukin-6; D008070:Lipopolysaccharides; C493487:Tlr4 protein, mouse; C495370:Tlr9 protein, mouse; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; D048051:p38 Mitogen-Activated Protein Kinases
keywords: acute lung injury; lipopolysaccharide; mitochondrial DNA; systemic inflammation