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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

LPS-induced circulating Mitochondria DNA (mtDNA) release occurs in a TLR4 dependent manner. (A) Wild-type (WT) mice were given LPS (20 mg/kg) via intra-peritoneal injection. Plasma was collected 2, 8, and 16 h later for mtDNA copy quantification by Q-PCR. * p < 0.05 versus control group; (B) WT and matched TLR4 knockout (KO) mice were randomly assigned to groups and given either PBS or LPS via intra-peritoneal injection and plasma was collected for mtDNA quantification by Q-PCR. * p < 0.05 versus TLR4 KO/LPS group; + p > 0.05 versus TLR4 KO/LPS group. Eight mice were used in each set and data are mean ± standard error of mean (SEM) of three separate experiments.
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ijms-17-01425-f001: LPS-induced circulating Mitochondria DNA (mtDNA) release occurs in a TLR4 dependent manner. (A) Wild-type (WT) mice were given LPS (20 mg/kg) via intra-peritoneal injection. Plasma was collected 2, 8, and 16 h later for mtDNA copy quantification by Q-PCR. * p < 0.05 versus control group; (B) WT and matched TLR4 knockout (KO) mice were randomly assigned to groups and given either PBS or LPS via intra-peritoneal injection and plasma was collected for mtDNA quantification by Q-PCR. * p < 0.05 versus TLR4 KO/LPS group; + p > 0.05 versus TLR4 KO/LPS group. Eight mice were used in each set and data are mean ± standard error of mean (SEM) of three separate experiments.

Mentions: LPS has been shown to induce mtDNA release [31]. LPS was administered to C57BL/6 mice via intra-peritoneal injection and plasma was collected at indicated time points for mtDNA quantification by Q-PCR in order to further explore the time course and mechanism of LPS-induced mtDNA release. As shown, LPS led to systemic mtDNA release in a time-dependent manner. There was a marked elevation in circulatory mtDNA as early as 2 h post-LPS administration and mtDNA copies peaked 8 h following administration of LPS and then gradually decreased (Figure 1A). To clarify the mechanism(s) involved in LPS-induced mtDNA release, both wild-type (WT) mice and matched TLR4 knockout (KO) mice were used. As demonstrated previously, TLR4 activation in sepsis leads to mitochondrial structure damage [31]. Thus, the role of TLR4 in LPS-induced mtDNA release was explored. Following LPS treatment, plasma mtDNA copies in TLR4 KO mice were significantly lower than in WT mice (p < 0.05) (Figure 1B). There was no increase in circulating mtDNA release in the TLR4 KO group following LPS administration (p > 0.05) (Figure 1B). Thus, LPS-induced circulating mtDNA release occurred in both a time- and TLR4-dependent manner.


Intra-Peritoneal Administration of Mitochondrial DNA Provokes Acute Lung Injury and Systemic Inflammation via Toll-Like Receptor 9
LPS-induced circulating Mitochondria DNA (mtDNA) release occurs in a TLR4 dependent manner. (A) Wild-type (WT) mice were given LPS (20 mg/kg) via intra-peritoneal injection. Plasma was collected 2, 8, and 16 h later for mtDNA copy quantification by Q-PCR. * p < 0.05 versus control group; (B) WT and matched TLR4 knockout (KO) mice were randomly assigned to groups and given either PBS or LPS via intra-peritoneal injection and plasma was collected for mtDNA quantification by Q-PCR. * p < 0.05 versus TLR4 KO/LPS group; + p > 0.05 versus TLR4 KO/LPS group. Eight mice were used in each set and data are mean ± standard error of mean (SEM) of three separate experiments.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5037704&req=5

ijms-17-01425-f001: LPS-induced circulating Mitochondria DNA (mtDNA) release occurs in a TLR4 dependent manner. (A) Wild-type (WT) mice were given LPS (20 mg/kg) via intra-peritoneal injection. Plasma was collected 2, 8, and 16 h later for mtDNA copy quantification by Q-PCR. * p < 0.05 versus control group; (B) WT and matched TLR4 knockout (KO) mice were randomly assigned to groups and given either PBS or LPS via intra-peritoneal injection and plasma was collected for mtDNA quantification by Q-PCR. * p < 0.05 versus TLR4 KO/LPS group; + p > 0.05 versus TLR4 KO/LPS group. Eight mice were used in each set and data are mean ± standard error of mean (SEM) of three separate experiments.
Mentions: LPS has been shown to induce mtDNA release [31]. LPS was administered to C57BL/6 mice via intra-peritoneal injection and plasma was collected at indicated time points for mtDNA quantification by Q-PCR in order to further explore the time course and mechanism of LPS-induced mtDNA release. As shown, LPS led to systemic mtDNA release in a time-dependent manner. There was a marked elevation in circulatory mtDNA as early as 2 h post-LPS administration and mtDNA copies peaked 8 h following administration of LPS and then gradually decreased (Figure 1A). To clarify the mechanism(s) involved in LPS-induced mtDNA release, both wild-type (WT) mice and matched TLR4 knockout (KO) mice were used. As demonstrated previously, TLR4 activation in sepsis leads to mitochondrial structure damage [31]. Thus, the role of TLR4 in LPS-induced mtDNA release was explored. Following LPS treatment, plasma mtDNA copies in TLR4 KO mice were significantly lower than in WT mice (p < 0.05) (Figure 1B). There was no increase in circulating mtDNA release in the TLR4 KO group following LPS administration (p > 0.05) (Figure 1B). Thus, LPS-induced circulating mtDNA release occurred in both a time- and TLR4-dependent manner.

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