Mitochondrial DNA Stimulates TLR9-Dependent Neutrophil Extracellular Trap Formation in Primary Graft Dysfunction.

Abstract

The immune system is designed to robustly respond to pathogenic stimuli but to be tolerant to endogenous ligands to not trigger autoimmunity. Here, we studied an endogenous damage-associated molecular pattern, mitochondrial DNA (mtDNA), during primary graft dysfunction (PGD) after lung transplantation. We hypothesized that cell-free mtDNA released during lung ischemia-reperfusion triggers neutrophil extracellular trap (NET) formation via TLR9 signaling. We found that mtDNA increases in the BAL fluid of experimental PGD (prolonged cold ischemia followed by orthotopic lung transplantation) and not in control transplants with minimal warm ischemia. The adoptive transfer of mtDNA into the minimal warm ischemia graft immediately before lung anastomosis induces NET formation and lung injury. TLR9 deficiency in neutrophils prevents mtDNA-induced NETs, and TLR9 deficiency in either the lung donor or recipient decreases NET formation and lung injury in the PGD model. Compared with human lung transplant recipients without PGD, severe PGD was associated with high levels of BAL mtDNA and NETs, with evidence of relative deficiency in DNaseI. We conclude that mtDNA released during lung ischemia-reperfusion triggers TLR9-dependent NET formation and drives lung injury. In PGD, DNaseI therapy has a potential dual benefit of neutralizing a major NET trigger (mtDNA) in addition to dismantling pathogenic NETs.

• Authors: Beñat Mallavia, Fengchun Liu, Emma Lefrançais, Simon J Cleary, Nicholas Kwaan, Jennifer J Tian, Mélia Magnen, David M Sayah, Allison Soong, Joy Chen, Rajan Saggar, Michael Y Shino, David J Ross, Ariss Derhovanessian, Joseph P Lynch 3rd, Abbas Ardehali, S Sam Weigt, John A Belperio, Steven R Hays, Jeffrey A Golden, Lorriana E Leard, Rupal J Shah, Mary Ellen Kleinhenz, Aida Venado, Jasleen Kukreja, Jonathan P Singer, Mark R Looney
• Journal: American journal of respiratory cell and molecular biology (Am J Respir Cell Mol Biol) Vol. 62 Issue 3 Pg. 364-372 (03 2020) ISSN: 1535-4989 [Electronic] United States
• PMID: 31647878 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• DNA, Mitochondrial
• Tlr9 protein, mouse
• Toll-Like Receptor 9
• Deoxyribonuclease I
• Protein-Arginine Deiminase Type 4
• peptidylarginine deiminase 4, mouse

Topics

• Acute Lung Injury (etiology)
• Animals
• Bronchoalveolar Lavage Fluid (cytology)
• Citrullination
• Cold Ischemia (adverse effects)
• DNA, Mitochondrial (administration & dosage, pharmacology)
• Deoxyribonuclease I (metabolism)
• Extracellular Traps (metabolism)
• Humans
• Lung Transplantation
• Male
• Mice
• Mice, Inbred C57BL
• Neutrophils (drug effects, immunology)
• Primary Graft Dysfunction (immunology, metabolism)
• Protein-Arginine Deiminase Type 4 (deficiency, physiology)
• Reperfusion Injury (etiology, metabolism)
• Specific Pathogen-Free Organisms
• Toll-Like Receptor 9 (deficiency, physiology)
• Warm Ischemia (adverse effects)