title: Mitochondrial DNA induces inflammation and increases TLR9/NF-κB expression in lung tissue.
abstract: Mitochondrial DNA (mtDNA) contains unmethylated CpG motifs that exhibit immune stimulatory capacities. The aim of this study was to investigate whether mtDNA activates the Toll-like receptor 9 (TLR9)/nuclear factor-κB (NF-κB) pathway, thereby contributing to post-traumatic systemic inflammatory response syndrome (SIRS) and lung injury in rats. The effects of mtDNA on macrophage culture were examined in order to elucidate the putative cellular mechanisms. Rats and macrophage cultures were treated with phosphate-buffered saline, nuclear DNA, or mtDNA for 2, 4, 8 and 24 h. Histological analysis of lung tissue was undertaken following hematoxylin and eosin staining, and cytokine levels were assessed by ELISA. NF-κB and IκB-α phosphorylation levels, as well as TLR9 protein expression were determined by western blot analysis; NF-κB, IκB-α and TLR9 mRNA levels were analyzed by RT-PCR. A greater degree of inflammation and lung injury was observed in response to mtDNA. In addition, mtDNA increased serum tumor necrosis factor-α, interleukin (IL)-6 and IL-10 levels in vivo and increased their secretion by cultured macrophages (p<0.05). In lung tissue, mtDNA increased NF-κB, IκB-α and TLR9 mRNA levels (p<0.05); it also increased phosphorylated NF-κB p65 and TLR9 protein levels in the macrophage cultures. Thus, mtDNA may be part of the danger-associated molecular patterns, contributing to the initiation of sterile SIRS through the activation of the TLR9/NF-κB pathway and the induction of pro-inflammatory cytokine production.
authors.affiliation: Department of Orthopedics, Beijing Army General Hospital, Dongcheng, Beijing 100700, P.R. China.
authors.forename: Jian-Zheng
authors.initials: JZ
authors.lastname: Zhang
authors.affiliation: Department of Orthopedics, Beijing Army General Hospital, Dongcheng, Beijing 100700, P.R. China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Orthopedics, Beijing Army General Hospital, Dongcheng, Beijing 100700, P.R. China.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Orthopedics, Beijing Army General Hospital, Dongcheng, Beijing 100700, P.R. China.
authors.forename: Ji-Xin
authors.initials: JX
authors.lastname: Ren
authors.affiliation: Department of Orthopedics, Beijing Army General Hospital, Dongcheng, Beijing 100700, P.R. China.
authors.forename: Tian-Sheng
authors.initials: TS
authors.lastname: Sun
mesh_terms: D055371:Acute Lung Injury / Q000097:blood / Q000235:genetics / Q000473:pathology; D000818:Animals; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis / Q000097:blood; D004272:DNA, Mitochondrial / Q000378:metabolism*; D005786:Gene Expression Regulation; D020672:I-kappa B Proteins / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism* / Q000473:pathology*; D008168:Lung / Q000378:metabolism* / Q000473:pathology*; D008264:Macrophages / Q000378:metabolism / Q000473:pathology; D008297:Male; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism*
chemical_list: D016207:Cytokines; D004272:DNA, Mitochondrial; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606206:Nfkbia protein, rat; D012333:RNA, Messenger; C489640:Tlr9 protein, rat; D051217:Toll-Like Receptor 9; D000072000:NF-KappaB Inhibitor alpha