Related Experiment Video
Updated: Apr 16, 2026
Visualizing Lung Cellular Adaptations during Combined Ozone and LPS Induced Murine Acute Lung Injury
Published on: March 21, 2021
Intratracheal administration of mitochondrial DNA directly provokes lung inflammation through the TLR9-p38 MAPK
Xiaoling Gu1, Guannan Wu1, Yanwen Yao1
1Department of Respiratory Medicine, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu Province 210002, People's Republic of China.
Abstract:
An increasing number of studies have focused on the phenomenon that mitochondrial DNA (mtDNA) activates innate immunity responses. However, the specific role of mtDNA in inflammatory lung disease remains elusive. This study was designed to examine the proinflammatory effects of mtDNA in lungs and to investigate the putative mechanisms. C57BL/6 mice were challenged intratracheally with mtDNA with or without pretreatment with chloroquine. Changes in pulmonary histopathology, cytokine concentrations, and phosphorylation levels of p38 MAPK were assayed at four time points. In in vitro experiments, THP-1 macrophages were pretreated or not pretreated with chloroquine, TLR9 siRNA, p38 MAPK siRNA, or SB203580 and then incubated with mtDNA. The levels of cytokines and p-p38 MAPK were detected by ELISA and Western blot, respectively. The intratracheal administration of mtDNA induced infiltration of inflammatory cells, production of proinflammatory cytokines (including IL-1β, IL-6, and TNF-α), and activation of p38 MAPK. The chloroquine pretreatment resulted in an abatement of mtDNA-induced local lung inflammation. In vitro experiments showed that the exposure of THP-1 macrophages to mtDNA also led to a significant upregulation of IL-1β, IL-6, and TNF-α and the activation of p38 MAPK. And these responses were inhibited either by chloroquine and TLR9 siRNA or by SB203580 and p38 MAPK siRNA pretreatment. The intratracheal administration of mtDNA induced a local inflammatory response in the mouse lung that depended on the interactions of mtDNA with TLR9 and may be correlated with infiltrating macrophages that could be activated by mtDNA exposure via the TLR9-p38 MAPK signal transduction pathway.
Insights
Mitochondrial DNA (mtDNA) triggers lung inflammation by activating Toll-like receptor 9 (TLR9) and p38 MAPK signaling. Inhibiting this pathway reduces inflammatory responses in lung tissues.
Area of Science:
- Immunology
- Cell Biology
- Pulmonary Medicine
Background:
- Mitochondrial DNA (mtDNA) is increasingly recognized for its role in activating innate immunity.
- The specific involvement of mtDNA in inflammatory lung diseases requires further elucidation.
Purpose of the Study:
- To investigate the proinflammatory effects of mtDNA in the lungs.
- To explore the underlying mechanisms of mtDNA-induced lung inflammation.
Main Methods:
- Mice were intratracheally administered mtDNA with or without chloroquine pretreatment.
- In vitro studies utilized THP-1 macrophages pretreated with chloroquine, TLR9 siRNA, p38 MAPK siRNA, or SB203580.
- Assays included pulmonary histopathology, cytokine concentration measurement, and Western blotting for p38 MAPK phosphorylation.
Main Results:
- Intratracheal mtDNA induced lung inflammation, characterized by inflammatory cell infiltration, elevated IL-1β, IL-6, TNF-α, and p38 MAPK activation.
- Chloroquine pretreatment attenuated mtDNA-induced lung inflammation.
- In vitro, mtDNA exposure upregulated cytokines and activated p38 MAPK in macrophages, which was inhibited by chloroquine, TLR9 siRNA, or p38 MAPK inhibitors.
Conclusions:
- Mitochondrial DNA induces local lung inflammation via TLR9-dependent activation of the p38 MAPK pathway.
- This pathway involves macrophages activated by mtDNA, highlighting a potential therapeutic target for inflammatory lung diseases.
