Dysregulation of the actin scavenging system and inhibition of DNase activity following severe thermal injury

Abstract

Background Circulating cell‐free DNA (cfDNA) is not found in healthy subjects, but is readily detected after thermal injury and may contribute to the risk of multiple organ failure. The hypothesis was that a postburn reduction in DNase protein/enzyme activity could contribute to the increase in cfDNA following thermal injury. Methods Patients with severe burns covering at least 15 per cent of total body surface area were recruited to a prospective cohort study within 24 h of injury. Blood samples were collected from the day of injury for 12 months. Results Analysis of blood samples from 64 patients revealed a significant reduction in DNase activity on days 1–28 after injury, compared with healthy controls. DNase protein levels were not affected, suggesting the presence of an enzyme inhibitor. Further analysis revealed that actin (an inhibitor of DNase) was present in serum samples from patients but not those from controls, and concentrations of the actin scavenging proteins gelsolin and vitamin D‐binding protein were significantly reduced after burn injury. In a pilot study of ten military patients with polytrauma, administration of blood products resulted in an increase in DNase activity and gelsolin levels. Conclusion The results of this study suggest a novel biological mechanism for the accumulation of cfDNA following thermal injury by which high levels of actin released by damaged tissue cause a reduction in DNase activity. Restoration of the actin scavenging system could therefore restore DNase activity, and reduce the risk of cfDNA‐induced host tissue damage and thrombosis.

Traumatic injury is associated with reduced deoxyribonuclease activity and dysregulation of the actin scavenging system

“…Combined with the post-trauma dysregulation in the EASS that persists in the days and weeks following injury [ 39–44 ], raised concentrations of G-actin would promote the formation of G-actin–DNase complexes, an association that negatively impacts upon the activity of DNase-1 [ 32–34 ]. Interestingly, in a small pilot study of polytrauma patients, we measured significantly increased GSN concentrations and DNase activity in blood samples acquired from individuals that had received fresh frozen plasma (FFP) prior to hospital admission [ 68 ]. Although the underlying mechanism was not directly demonstrated, we speculated that GSN-mediated scavenging of circulating actin was responsible for this FFP-induced enhancement in DNase activity [ 68 ].…”

“…Interestingly, in a small pilot study of polytrauma patients, we measured significantly increased GSN concentrations and DNase activity in blood samples acquired from individuals that had received fresh frozen plasma (FFP) prior to hospital admission [ 68 ]. Although the underlying mechanism was not directly demonstrated, we speculated that GSN-mediated scavenging of circulating actin was responsible for this FFP-induced enhancement in DNase activity [ 68 ]. Recently, a multicentre phase 3 clinical trial demonstrated that pre-hospital administration of thawed plasma to trauma patients at risk of haemorrhagic shock was safe and associated with a reduced risk of mortality when compared to standard care [ 69 ].…”

“…Recently, a multicentre phase 3 clinical trial demonstrated that pre-hospital administration of thawed plasma to trauma patients at risk of haemorrhagic shock was safe and associated with a reduced risk of mortality when compared to standard care [ 69 ]. As we have provided evidence of elevated cfDNA levels and reduced DNase activity within minutes of injury, a large-scale pre-hospital based trial of trauma patients that investigates whether administration of FFP or recombinant GSN enhances DNase-mediated clearance of cfDNA, via restoration of the EASS, would build upon our previous pilot study [ 68 ]. This would help determine whether increasing DNase activity is a potential therapeutic strategy by which to improve the clinical outcomes of severely injured patients.…”

Neutrophils and COVID-19: Active Participants and Rational Therapeutic Targets

“…Responsible for the clearance of circulating actin is the extracellular actin scavenger system (EASS), which comprises of two plasma proteins: vitamin D binding protein (VDBP) and gelsolin (GSN) ( 258 ). In the setting of thermal injury, we have recently demonstrated dysregulation of the EASS, where reduced circulating concentrations of GSN and VDBP were associated with impaired serum DNase activity and an accumulation of cfDNA ( 259 ). A similar scenario is emerging in COVID-19, where a significant reduction in total serum DNase activity ( 233 ) is accompanied by increased and decreased circulating concentrations of actin and GSN respectively ( 179 , 260 , 261 ), with GSN levels negatively associated with disease severity ( 260 ).…”

AAV‐mediated gene transfer of DNase I in the liver of mice with colorectal cancer reduces liver metastasis and restores local innate and adaptive immune response

“…For example, actin, a major constituent of the microfilament system of eukaryotic cells can bind DNase I with nanomolar affinity and inhibit DNase I enzymatic activity almost entirely. Upon apoptotic and necrotic cell death, a significant amount of monomeric actin is released into the circulation thereby inhibiting DNase I catalytic activity in blood [43]. Methods to address this limitation in clinical use include studies utilizing DNase I‐coated nanoparticles [36].…”