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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.


Intra-peritoneal administration of mtDNA leads to p38 MAPK activation via TLR9. WT mice were randomly assigned a group pretreated with TLR9 specific inhibitor ODN2088 or a control group. Mice in the ODN2088 group were pretreated 1h before mtDNA administration (n = 8/group). Total and phosphorylation levels of ERK1/2, JNK, and p38 expression in lung tissue were measured by Western blot. Three separate independent experiments got the similar results.
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ijms-17-01425-f006: Intra-peritoneal administration of mtDNA leads to p38 MAPK activation via TLR9. WT mice were randomly assigned a group pretreated with TLR9 specific inhibitor ODN2088 or a control group. Mice in the ODN2088 group were pretreated 1h before mtDNA administration (n = 8/group). Total and phosphorylation levels of ERK1/2, JNK, and p38 expression in lung tissue were measured by Western blot. Three separate independent experiments got the similar results.

Mentions: Considering that p38 MAPK is known as an early downstream molecule of TLR9 [9,29], Western blot was used to explore the expression of total and phosphorylated p38, JNK and Erk1/2 MAPK in lung tissues following mtDNA administration. Intra-peritoneal injection of mtDNA leads to a significant up-regulation of phosphorylated p38 MAPK at 2 h; the level returned to baseline 16 h after mtDNA administration (Figure 6). Specific TLR9 inhibitor ODN2088 pretreatment significantly suppressed mtDNA-induced p38 MAPK phosphorylation in the lung tissues compared with the control group. However, the expression of total p38 MAPK, as well as phosphorylated and total Erk1/2 MAPK and JNK, was not significantly changed following mtDNA exposure and TLR9 inhibitor pretreatment (Figure 6). These results indicate that mtDNA may induce p38 MAPK phosphorylation through TLR9 in vivo, which may be involved in mtDNA induced lung inflammatory responses.


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 p38 MAPK activation via TLR9. WT mice were randomly assigned a group pretreated with TLR9 specific inhibitor ODN2088 or a control group. Mice in the ODN2088 group were pretreated 1h before mtDNA administration (n = 8/group). Total and phosphorylation levels of ERK1/2, JNK, and p38 expression in lung tissue were measured by Western blot. Three separate independent experiments got the similar results.
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Related In: Results  -  Collection

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

ijms-17-01425-f006: Intra-peritoneal administration of mtDNA leads to p38 MAPK activation via TLR9. WT mice were randomly assigned a group pretreated with TLR9 specific inhibitor ODN2088 or a control group. Mice in the ODN2088 group were pretreated 1h before mtDNA administration (n = 8/group). Total and phosphorylation levels of ERK1/2, JNK, and p38 expression in lung tissue were measured by Western blot. Three separate independent experiments got the similar results.
Mentions: Considering that p38 MAPK is known as an early downstream molecule of TLR9 [9,29], Western blot was used to explore the expression of total and phosphorylated p38, JNK and Erk1/2 MAPK in lung tissues following mtDNA administration. Intra-peritoneal injection of mtDNA leads to a significant up-regulation of phosphorylated p38 MAPK at 2 h; the level returned to baseline 16 h after mtDNA administration (Figure 6). Specific TLR9 inhibitor ODN2088 pretreatment significantly suppressed mtDNA-induced p38 MAPK phosphorylation in the lung tissues compared with the control group. However, the expression of total p38 MAPK, as well as phosphorylated and total Erk1/2 MAPK and JNK, was not significantly changed following mtDNA exposure and TLR9 inhibitor pretreatment (Figure 6). These results indicate that mtDNA may induce p38 MAPK phosphorylation through TLR9 in vivo, which may be involved in mtDNA induced lung inflammatory responses.

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.