Mitochondrial DNA induces inflammation and increases TLR9/NF-κB expression in lung tissue

Area of Science:

• Immunology
• Cell Biology
• Pathology

Background:

• Mitochondrial DNA (mtDNA) possesses unmethylated CpG motifs with immune-stimulating properties.
• The role of mtDNA in initiating post-traumatic inflammatory responses requires further elucidation.

Purpose of the Study:

• To investigate if mtDNA activates the Toll-like receptor 9 (TLR9)/nuclear factor-κB (NF-κB) pathway.
• To determine mtDNA's contribution to post-traumatic systemic inflammatory response syndrome (SIRS) and lung injury.
• To explore the cellular mechanisms of mtDNA's effects on macrophages.

Main Methods:

• Rats and macrophage cultures were treated with phosphate-buffered saline, nuclear DNA, or mtDNA.
• Histological analysis, ELISA, western blot, and RT-PCR were employed to assess inflammation, cytokine levels, and pathway activation.
• Key markers analyzed included NF-κB, IκB-α, and TLR9 at both mRNA and protein levels.

Main Results:

• mtDNA administration led to increased inflammation and lung injury in rats.
• mtDNA significantly elevated serum levels of TNF-α, IL-6, and IL-10 in vivo and in cultured macrophages.
• In lung tissue and macrophages, mtDNA upregulated NF-κB, IκB-α, and TLR9 mRNA and protein expression, including phosphorylated NF-κB p65.

Conclusions:

• Mitochondrial DNA acts as a danger-associated molecular pattern (DAMP).
• mtDNA initiates sterile SIRS by activating the TLR9/NF-κB pathway.
• This activation leads to the production of pro-inflammatory cytokines, contributing to organ injury.