Journal Article

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

Singer, Jonathan P., Cleary, Simon J., Ross, David J., Looney, Mark R., Kukreja, Jasleen, Ardehali, Abbas, Lynch, Joseph P., Weigt, S. Sam, Hays, Steven R., Belperio, John A., Venado, Aida, Kleinhenz, Mary Ellen, Kwaan, Nicholas, Mallavia, Beñat, Sayah, David M., Shino, Michael Y., Liu, Fengchun, Tian, Jennifer J., Magnen, Mélia, Shah, Rupal J., Soong, Allison, Lefrançais, Emma, Saggar, Rajan, Derhovanessian, Ariss, Golden, Jeffrey A., Chen, Joy, Leard, Lorriana E.

2020

Overview

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.

• Publisher: American Thoracic Society
• Subject: Acute Lung Injury - etiology / Animals / Autoimmunity / Biochemistry, Molecular Biology / Bronchoalveolar Lavage Fluid - cytology / Cell Behavior / Cellular Biology / Citrullination / Cold Ischemia - adverse effects / Deoxyribonuclease / Deoxyribonuclease I - metabolism / Deoxyribonucleic acid / DNA / DNA, Mitochondrial - administration & dosage / DNA, Mitochondrial - pharmacology / Extracellular Traps - metabolism / Human health and pathology / Humans / Immune system / Immunology / Innate immunity / Ischemia / Life Sciences / Lung diseases / Lung Transplantation / Male / Mice / Mice, Inbred C57BL / Mitochondrial DNA / Neutrophils - drug effects / Neutrophils - immunology / Original Research / Primary Graft Dysfunction - immunology / Primary Graft Dysfunction - metabolism / Protein-Arginine Deiminase Type 4 - deficiency / Protein-Arginine Deiminase Type 4 - physiology / Pulmonology and respiratory tract / Reperfusion / Reperfusion Injury - etiology / Reperfusion Injury - metabolism / Specific Pathogen-Free Organisms / Surgical outcomes / Tissues and Organs / TLR9 protein / Toll-Like Receptor 9 - deficiency / Toll-Like Receptor 9 - physiology / Toll-like receptors / Transplants & implants / Warm Ischemia - adverse effects