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Intra-Peritoneal Administration of Mitochondrial DNA Provokes Acute Lung Injury and Systemic Inflammation via Toll-Like Receptor 9

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus

Intra-peritoneal administration of mtDNA leads to systemic inflammation. WT mice were treated with PBS, nuclear DNA (nDNA), or mtDNA via intra-peritoneal injection for 2, 8, and 24 h. Systemic inflammation and circulating levels of IL-1β (A); IL-6 (B); and HMGB1 (C) were measured by ELISA. * p < 0.05 versus mtDNA group; # p < 0.05 versus mtDNA group. Eight mice were used in each set and data are mean ± SEM of three separate experiments.
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ijms-17-01425-f003: Intra-peritoneal administration of mtDNA leads to systemic inflammation. WT mice were treated with PBS, nuclear DNA (nDNA), or mtDNA via intra-peritoneal injection for 2, 8, and 24 h. Systemic inflammation and circulating levels of IL-1β (A); IL-6 (B); and HMGB1 (C) were measured by ELISA. * p < 0.05 versus mtDNA group; # p < 0.05 versus mtDNA group. Eight mice were used in each set and data are mean ± SEM of three separate experiments.

Mentions: To provide further evidence of mtDNA-induced systemic inflammation, WT mice were treated with NS, nDNA, or mtDNA via intra-peritoneal injection 2, 8, and 16 h. Circulating levels of IL-1β, IL-6, and high-mobility group protein B1 (HMGB1) were then measured by ELISA. Proinflammatory cytokines (IL-1β, IL-6, and HMGB1) were significantly higher in the mtDNA administration group compared with the levels in the nDNA and control groups (p < 0.05). The concentrations of IL-1β and HMGB1 peaked 8 h, and the concentration of IL-6 peaked 2 h, after mtDNA administration and then gradually decreased, however the levels were still significantly higher compared to the nDNA and control groups (Figure 3A–C). Administration of nDNA did not cause systemic inflammation (Figure 3A–C). These data indicated that mtDNA triggers a significant increase in IL-1β, IL-6, and HMGB1 production.


Intra-Peritoneal Administration of Mitochondrial DNA Provokes Acute Lung Injury and Systemic Inflammation via Toll-Like Receptor 9
Intra-peritoneal administration of mtDNA leads to systemic inflammation. WT mice were treated with PBS, nuclear DNA (nDNA), or mtDNA via intra-peritoneal injection for 2, 8, and 24 h. Systemic inflammation and circulating levels of IL-1β (A); IL-6 (B); and HMGB1 (C) were measured by ELISA. * p < 0.05 versus mtDNA group; # p < 0.05 versus mtDNA group. Eight mice were used in each set and data are mean ± SEM of three separate experiments.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037704&req=5

ijms-17-01425-f003: Intra-peritoneal administration of mtDNA leads to systemic inflammation. WT mice were treated with PBS, nuclear DNA (nDNA), or mtDNA via intra-peritoneal injection for 2, 8, and 24 h. Systemic inflammation and circulating levels of IL-1β (A); IL-6 (B); and HMGB1 (C) were measured by ELISA. * p < 0.05 versus mtDNA group; # p < 0.05 versus mtDNA group. Eight mice were used in each set and data are mean ± SEM of three separate experiments.
Mentions: To provide further evidence of mtDNA-induced systemic inflammation, WT mice were treated with NS, nDNA, or mtDNA via intra-peritoneal injection 2, 8, and 16 h. Circulating levels of IL-1β, IL-6, and high-mobility group protein B1 (HMGB1) were then measured by ELISA. Proinflammatory cytokines (IL-1β, IL-6, and HMGB1) were significantly higher in the mtDNA administration group compared with the levels in the nDNA and control groups (p < 0.05). The concentrations of IL-1β and HMGB1 peaked 8 h, and the concentration of IL-6 peaked 2 h, after mtDNA administration and then gradually decreased, however the levels were still significantly higher compared to the nDNA and control groups (Figure 3A–C). Administration of nDNA did not cause systemic inflammation (Figure 3A–C). These data indicated that mtDNA triggers a significant increase in IL-1β, IL-6, and HMGB1 production.

View Article: PubMed Central - PubMed

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-1&beta;, 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-1&beta;, 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.

No MeSH data available.


Related in: MedlinePlus