Intratracheal administration of mitochondrial DNA directly provokes lung inflammation through the TLR9-p38 MAPK pathway.

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.

• Authors: Xiaoling Gu, Guannan Wu, Yanwen Yao, Junli Zeng, Donghong Shi, Tangfeng Lv, Liang Luo, Yong Song
• Journal: Free radical biology & medicine (Free Radic Biol Med) Vol. 83 Pg. 149-58 (Jun 2015) ISSN: 1873-4596 [Electronic] United States
• PMID: 25772007 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 Elsevier Inc. All rights reserved.

Chemical References

• Cytokines
• DNA, Mitochondrial
• Tlr9 protein, mouse
• Toll-Like Receptor 9
• p38 Mitogen-Activated Protein Kinases

Topics

• Animals
• Blotting, Western
• Cytokines
• DNA, Mitochondrial (administration & dosage, metabolism)
• Drug Administration Routes
• Enzyme-Linked Immunosorbent Assay
• Fluorescent Antibody Technique
• Macrophages (metabolism, pathology)
• Male
• Mice
• Mice, Inbred C57BL
• Phosphorylation
• Pneumonia (genetics, metabolism, pathology)
• Signal Transduction
• Toll-Like Receptor 9 (metabolism)
• Trachea
• p38 Mitogen-Activated Protein Kinases (metabolism)