Mitochondrial DNA-Mediated Immune Activation After Resuscitation from Cardiac Arrest

Area of Science:

• Immunology
• Cardiology
• Molecular Biology

Background:

• Post-cardiac arrest syndrome (PCAS) involves significant inflammation, contributing to poor outcomes after sudden cardiac arrest (SCA).
• The role of mitochondrial DNA (mtDNA) as a pro-inflammatory stimulus in PCAS was previously unstudied.

Purpose of the Study:

• To investigate the elevation and release of circulating mtDNA in PCAS.
• To determine how mtDNA activates immune cells and if targeting mtDNA sensing pathways can reduce this activation.

Main Methods:

• Plasma mtDNA and nuclear DNA (nucDNA) levels were measured in swine and human patients post-resuscitation.
• In vitro studies exposed peripheral blood mononuclear cells (PBMCs) to mtDNA or extracellular vesicles (EVs).
• Pharmacological inhibitors of TLR9 and cGAS pathways were used to assess mtDNA sensing inhibition.

Main Results:

• A significant elevation in circulating mtDNA, but not nucDNA, was observed post-resuscitation in both swine and humans, indicating selective mtDNA release.
• Circulating mtDNA was primarily encapsulated within EVs, suggesting a conserved release mechanism.
• EV-encapsulated mtDNA activated PBMCs, leading to a pro-inflammatory phenotype and increased cytokine release (TNFα, IL-1β, IL-6).
• Inhibition of TLR9 or cGAS pathways significantly reduced mtDNA-induced inflammation.

Conclusions:

• Resuscitation from SCA triggers selective release of EV-encapsulated mtDNA, which potently drives immune activation in PCAS.
• The findings link EV-mtDNA to TLR9 and cGAS activation, providing a basis for novel therapeutic interventions.
• Targeting mtDNA release or its downstream sensing pathways may improve outcomes after SCA.