Traumatic Injury and Exposure to Mitochondrial-Derived Damage Associated Molecular Patterns Suppresses Neutrophil Extracellular Trap Formation

Abstract

Major traumatic injury induces significant remodeling of the circulating neutrophil pool and loss of bactericidal function. Although a well-described phenomenon, research to date has only analyzed blood samples acquired post-hospital admission, and the mechanisms that initiate compromised neutrophil function post-injury are therefore poorly understood. Here, we analyzed pre-hospital blood samples acquired from 62 adult trauma patients (mean age 44 years, range 19–95 years) within 1 h of injury (mean time to sample 39 min, range 13–59 min). We found an immediate impairment in neutrophil extracellular trap (NET) generation in response to phorbol 12-myristate 13-acetate (PMA) stimulation, which persisted into the acute post-injury phase (4–72 h). Reduced NET generation was accompanied by reduced reactive oxygen species production, impaired activation of mitogen-activated protein kinases, and a reduction in neutrophil glucose uptake and metabolism to lactate. Pre-treating neutrophils from healthy subjects with mitochondrial-derived damage-associated molecular patterns (mtDAMPs), whose circulating levels were significantly increased in our trauma patients, reduced NET generation. This mtDAMP-induced impairment in NET formation was associated with an N-formyl peptide mediated activation of AMP-activated protein kinase (AMPK), a negative regulator of aerobic glycolysis and NET formation. Indeed, activation of AMPK via treatment with the AMP-mimetic AICAR significantly reduced neutrophil lactate production in response to PMA stimulation, a phenomenon that we also observed for neutrophils pre-treated with mtDAMPs. Furthermore, the impairment in NET generation induced by mtDAMPs was partially ameliorated by pre-treating neutrophils with the AMPK inhibitor compound C. Taken together, our data demonstrate an immediate trauma-induced impairment in neutrophil anti-microbial function and identify mtDAMP release as a potential initiator of acute post-injury neutrophil dysfunction.

Early increase in anti-inflammatory biomarkers is associated with the development of multiple organ dysfunction syndrome in severely injured trauma patients

“…Furthermore, underlining these results, a study performed in 166 polytrauma patients revealed a similar pattern of early IL-10 release and a decrease in human leukocyte antigen—DR isotype expression, potentially reducing macrophage functions 36. Additionally, although based on a small number of patients (n=44), major trauma was associated with an impairment of neutrophil function 37. Interestingly, in mice with TBI and tibia fracture receiving IL-1RA treatment, a decrease in neutrophil activation markers and cerebral edema was seen 38.…”

Preclinical models for studying immune responses to traumatic injury

“…As a result, the number of circulating mature neutrophils is rapidly increased (<1 h), and they remain elevated for ~72 h 12,35 . Interestingly, the number of circulating immature granulocytes also increased in trauma patients within the same time frames, 12,36 which is likely to impact on their ability to have antimicrobial actions. Traumatic injury also initiates significant changes in neutrophil function and phenotype (Figure 2), which has been reviewed extensively elsewhere 37 .…”

“…Furthermore, neutrophils isolated from trauma patients have an increased oxidative burst capacity, 38 increased neutrophil extracellular trap (NET) production 36 and a prolonged life span due to impaired apoptosis 39 . However, they have a reduced phagocytic capacity 38 and, when stimulated ex vivo , demonstrate a reduced capacity for integrin up‐regulation, ROS generation and NET release 12,36 . Furthermore, a neutrophil subset that suppresses T‐cell activation and proliferation 40 is elevated in the circulation within an hour of injury, which persists for up to 72 h 12 …”

“Empowering” Cardiac Cells via Stem Cell Derived Mitochondrial Transplantation- Does Age Matter?

“…These molecules, also called mitochondrial Damage-Associated Molecular Patterns (DAMPs), which are typically released during the course of cell death, mediate inflammatory immune responses and are associated with pathogenicity and severity of various diseases. Mitochondrial DNA/DAMPs have been found in brain death, trauma patients, sepsis, neurologic (ischemic stroke and bacterial meningitis) and myocardial injury and were associated with early allograft dysfunction and acute respiratory distress syndrome (ARDS) [ 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 ]. McCully et al compared the transplantation of whole mitochondria, mitochondrial components and frozen-thawed mitochondria [ 4 ].…”