Background
Extracellular mitochondrial DNA (mtDNA) was demonstrated to be capable of inducing pulmonary inflammation through TLR9 while its role in NLRP3 inflammation activation remains unknown.
Conclusions
Extracellular mtDNA promote NLRP3 inflammasome activation, acute pulmonary inflammation and injury through TLR9, p38 MAPK and NF-κB pathways.
Methods
C57BL/6 mice were challenged intratracheally with mtDNA. Pulmonary pathology, the NLRP3 and caspase-1 p20 in lung tissues were assayed. PMA-primed THP-1 macrophages were incubated with mtDNA in vitro and cell-free medium were concentrated to detect caspase-1 p20 subunit and NLRP3 by Western blotting. Additionally, IL-1β, L-18, TNF-α and caspase-1 activity in culture were also analyzed by ELISA kits and activity assay kit.
Results
Intratracheal administration of mtDNA increased NLRP3 and caspase-1 p20 subunit in lung together with excessive inflammation and damage. Inhibition of caspase-1 substantially diminished mtDNA-induced lung injury and inflammation. Exposed to mtDNA in THP-1 macrophages resulted in significant up-regulation of NLRP3 and increased caspase-1 p20 subunit release in culture. It also led to significant increased transcripts of NLRP3, ASC, caspase-1 and release of IL-1β, IL-18 and TNF-α in culture media. Futhermore, mtDNA exposure resulted in significant up-regulation of phosho -p38 MAPK and nucleus translocation of NF-κB. mtDNA-induced Transcripts of NLRP3 and ASC were inhibited by p38 siRNA inhibitor or NF-κB inhibitor. Conclusions: Extracellular mtDNA promote NLRP3 inflammasome activation, acute pulmonary inflammation and injury through TLR9, p38 MAPK and NF-κB pathways.