Neutrophil-derived circulating free DNA (cf-DNA/NETs), a potential prognostic marker for mortality in patients with severe burn injury

Association of inflammatory biomarkers with overall survival in burn patients: a systematic review and meta-analysis

INTRODUCTION

The inflammatory response to burn injuries can lead to organ dysfunction that ultimately results in increased mortality and morbidity. This meta-analysis was conducted to determine the efficacy of inflammatory biomarkers, including the neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), procalcitonin (PCT), and C-reactive protein (CRP) as predictive tools of mortality among burn patients.

MATERIAL AND METHODS

The biomarker levels of survivors and non-survivors were consolidated according to guidelines for Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Three main databases were searched electronically: PubMed, Web of Science, and Scopus, on December 8, 2022. The Newcastle-Ottawa Quality Assessment Scale (NOS) was used to evaluate and score the methodological quality of the included studies. The standard mean difference (SMD) with a 95% confidence interval (CI) was utilized.

RESULTS

Twenty-four studies were included in our systematic review and meta-analysis, (3636 total burn patients), of whom 2878 survived. We found that deceased burn patients had elevated levels of NLR (SMD = 0.60, 95% CI; 0.19-1.00, P < 0.001), CRP (SMD = 0.80, 95% CI; 0.02-1.58, P = 0.04), and PCT (SMD = 0.85, 95% CI; 0.45-1.24, P < 0.001), compared to survivors. However, we found no association between PLR and mortality among burn patients (SMD = 0.00, 95% CI; -0.14-0.15, P < 0.001). In addition, CRP was significantly higher in non-survivors (SMD = 0.80, 95% CI; 0.02-1.58, P =0.04). Similar results were also found about PCT (SMD = 0.85, 95% CI; 0.45-1.24, P < 0.001). When we analyzed the PCT data, collected in the first 24-48 hours, we found similar results; the PCT level was significantly higher in non-survivors in the immediate postinjury-period (SMD = 0.67, 95% CI; 0.31-1.02, P < 0.001). There was no publication bias among studies on the role of NLR in burn (Egger's test P = 0.91). The based cut-off values for NLR (13), CRP (71), and PCT (1.77) yielded sensitivities of 69.2%, 100%, and 93.33%, and specificities of 76%, 72.22%, and 72.22% respectively.

DISCUSSION/CONCLUSIONS

PCT is a marker of sepsis, therefore its elevated level is presumably associated with a higher incidence and severity of sepsis among non-survivors. In addition, NLR and CRP are promising biomarkers for predicting and guiding prevention against burn deaths in clinical settings.

Real-Time Micromotor Probe for Immune Neutrophil Activation State

Neutrophil activation is a hallmark of the immune response. Approaches to identify neutrophil activation in real time are necessary but are still lacking. In this study, magnetic Spirulina micromotors are used as label-free probes that exhibit differences in motility under different neutrophil activation states. This is correlated with different secretions into the extracellular environment by activated/non-activated cells and local environmental viscoelasticity. The micromotor platform can bypass non-activated immune cells while being stopped by activated cells. Thus, the micromotors can serve as label-free biomechanical probes of the immune cell state. They can detect the activation state of target immune cells in real time and with single-cell precision, which provides new ideas for the diagnosis and treatment of diseases while deepening understanding of the biomechanics of activated immune cells.

Murine scald models characterize the role of neutrophils and neutrophil extracellular traps in severe burns

Introduction

Severe burns cause unique pathophysiological alterations especially on the immune system. A murine scald model was optimized as a basis for the understanding of immunological reactions in response to heat induced injury. The understanding of the roles of neutrophil extracellular traps (NETs) and DNases will support the development of new surgical or pharmacological strategies for the therapy of severe burns.

Methods

We studied C57BL/6 mice (n=30) and employed four scalding protocols with varying exposure times to hot water. An additional scald group with a shorter observational time was generated to reduce mortality and study the very early phase of pathophysiology. At 24h or 72h, blood was drawn and tissue (wound, liver, lung, spleen) was analyzed for the presence of NETs, oxidative stress, apoptosis, bacterial translocation, and extracellular matrix re-organization. In addition, we analyzed the transcriptome from lung and liver tissues.

Results

Exposure to hot water for 7s led to significant systemic and local effects and caused considerable late mortality. Therefore, we used an observation time of 24h in this groups. To study later phases of burns (72h) an exposure time of 6s is optimal. Both conditions led to significant disorganization of collagen, increased oxidative stress, NET formation (by immunodetection of H3cit, NE, MPO), apoptosis (cC3) and alterations of the levels of DNase1 and DNase1L3. Transcriptome analysis revealed remarkable alterations in genes involved in acute phase signaling, cell cohesion, extracellular matrix organization, and immune response.

Conclusion

We identified two scald models that allow the analysis of early (24h) or late (72h) severe burn effects, thereby generating reproducible and standardized scald injuries. The study elucidated the important involvement of neutrophil activity and the role of NETs in burns. Extensive transcriptome analysis characterized the acute phase and tissue remodeling pathways involved in the process of healing and may serve as crucial basis for future in-depth studies.

ROLE OF PEPTIDYLARGININE DEIMINASE AND NEUTROPHIL EXTRACELLULAR TRAPS IN INJURIES: FUTURE NOVEL DIAGNOSTICS AND THERAPEUTIC TARGETS

ABSTRACT

Injuries lead to an early systemic inflammatory state with innate immune system activation. Neutrophil extracellular traps (NETs) are a complex of chromatin and proteins released from the activated neutrophils. Although initially described as a response to bacterial infections, NETs have also been identified in the sterile postinjury inflammatory state. Peptidylarginine deiminases (PADs) are a group of isoenzymes that catalyze the conversion of arginine to citrulline, termed citrullination or deimination. PAD2 and PAD4 have been demonstrated to play a role in NET formation through citrullinated histone 3. PAD2 and PAD4 have a variety of substrates with variable organ distribution. Preclinical and clinical studies have evaluated the role of PADs and NETs in major trauma, hemorrhage, burns, and traumatic brain injury. Neutrophil extracellular trap formation and PAD activation have been shown to contribute to the postinjury inflammatory state leading to a detrimental effect on organ systems. This review describes our current understanding of the role of PAD and NET formation following injury and burn. This is a new field of study, and the emerging data appear promising for the future development of targeted biomarkers and therapies in trauma.

Severity of thermal burn injury is associated with systemic neutrophil activation

Burn injuries elicit a unique and dynamic stress response which can lead to burn injury progression. Though neutrophils represent crucial players in the burn-induced immunological events, the dynamic secretion pattern and systemic levels of neutrophil-derived factors have not been investigated in detail so far. Serum levels of neutrophil elastase (NE), myeloperoxidase (MPO), citrullinated histone H3 (CitH3), and complement factor C3a were quantified in burn victims over 4 weeks post injury. Furthermore, the potential association with mortality, degree of burn injury, and inhalation trauma was evaluated. In addition, leukocyte, platelet, neutrophil, and lymphocyte counts were assessed. Lastly, we analyzed the association of neutrophil-derived factors with clinical severity scoring systems. Serum levels of NE, MPO, CitH3, and C3a were remarkably elevated in burn victims compared to healthy controls. Leukocyte and neutrophil counts were significantly increased on admission day and day 1, while relative lymphocytes were decreased in the first 7 days post burn trauma. Though neutrophil-derived factors did not predict mortality, patients suffering from 3rd degree burn injuries displayed increased CitH3 and NE levels. Accordingly, CitH3 and NE were elevated in cases with higher abbreviated burn severity indices (ABSI). Taken together, our data suggest a role for neutrophil activation and NETosis in burn injuries and burn injury progression. Targeting exacerbated neutrophil activation might represent a new therapeutic option for severe cases of burn injury.

cfDNA and DNases: New Biomarkers of Sepsis in Preterm Neonates-A Pilot Study

INTRODUCTION

An early and accurate diagnosis of early onset neonatal sepsis (EONS) and late onset neonatal sepsis (LONS) is essential to improve the outcome of this devastating conditions. Especially, preterm infants are at risk. Reliable biomarkers are rare, clinical decision-making depends on clinical appearance and multiple laboratory findings. Markers of NET formation and NET turnover might improve diagnostic precision. Aim of this study was to evaluate the diagnostic value of NETs in sepsis diagnosis in neonatal preterm infants.

METHODS

Plasma samples of neonatal preterm infants with suspected sepsis were collected. Blood samples were assayed for markers of NET formation and NET turnover: cfDNA, DNase1, nucleosome, NE, and H3Cit. All clinical findings, values of laboratory markers, and epidemiological characteristics were collected retrospectively. Two subpopulations were created to divide EONS from LONS. EMA sepsis criteria for neonatal sepsis were used to generate a sepsis group (EMA positive) and a control group (EMA negative).

RESULTS

A total of 31 preterm neonates with suspected sepsis were included. Out of these, nine patients met the criteria for sepsis according to EMA. Regarding early onset neonatal sepsis (3 EONS vs. 10 controls), cfDNA, DNase I, nucleosome, and CRP were elevated significantly. H3Cit and NE did not show any significant elevations. In the late onset sepsis collective (6 LONS vs. 12 controls), cfDNA, DNase I, and CRP differed significantly compared to control group.

Methylprednisolone Induces Extracellular Trap Formation and Enhances Bactericidal Effect of Canine Neutrophils

Methylprednisolone is a glucocorticoid and can negatively influence immune defense mechanisms. During bacterial infections in the dog, neutrophils infiltrate infected tissue and mediate antimicrobial effects with different mechanisms such as phagocytosis and neutrophil extracellular trap (NET) formation. Here, we investigated the influence of methylprednisolone on canine NET formation and neutrophil killing efficiency of Gram positive and Gram negative bacteria. Therefore, canine blood derived neutrophils were treated with different concentrations of methylprednisolone over time. The survival factor of Staphylococcus pseudintermedius, Streptococcus canis or Escherichia coli was determined in presence of stimulated neutrophils. Additionally, free DNA and nucleosomes as NET marker were analyzed in supernatants and neutrophils were assessed for NET formation by immunofluorescence microscopy. Methylprednisolone concentrations of 62.5 and 625 µg/mL enhanced the neutrophil killing of Gram positive bacteria, whereas no significant influence was detected for the Gram negative Escherichia coli. Interestingly, higher amounts of free DNA were detected under methylprednisolone stimulation in a concentration dependency and in the presence of Streptococcus canis and Escherichia coli. The nucleosome release by neutrophils is induced by bacterial infection and differs depending on the concentration of methylprednisolone. Furthermore, immunofluorescence microscopy analysis identified methylprednisolone at a concentration of 62.5 µg/mL as a NET inducer. In summary, methylprednisolone enhances NET-formation and time-dependent and concentration-dependent the bactericidal effect of canine neutrophils on Gram positive bacteria.

NETosis in the pathogenesis of acute lung injury following cutaneous chemical burns

Despite the high morbidity and mortality among patients with extensive cutaneous burns in the intensive care unit due to the development of acute respiratory distress syndrome, effective therapeutics remain to be determined. This is primarily because the mechanisms leading to acute lung injury (ALI) in these patients remain unknown. We test the hypothesis that cutaneous chemical burns promote lung injury due to systemic activation of neutrophils, in particular, toxicity mediated by the deployment of neutrophil extracellular traps (NETs). We also demonstrate the potential benefit of a peptidyl arginine deiminase 4 (PAD4) inhibitor to prevent NETosis and to preserve microvascular endothelial barrier function, thus reducing the severity of ALI in mice. Our data demonstrated that phenylarsine oxide (PAO) treatment of neutrophils caused increased intracellular Ca²⁺-associated PAD4 activity. A dermal chemical burn by lewisite or PAO resulted in PAD4 activation, NETosis, and ALI. NETs disrupted the barrier function of endothelial cells in human lung microvascular endothelial cell spheroids. Citrullinated histone 3 alone caused ALI in mice. Pharmacologic or genetic abrogation of PAD4 inhibited lung injury following cutaneous chemical burns. Cutaneous burns by lewisite and PAO caused ALI by PAD4-mediated NETosis. PAD4 inhibitors may have potential as countermeasures to suppress detrimental lung injury after chemical burns.

SARS-CoV-2-triggered neutrophil extracellular traps mediate COVID-19 pathology

Severe COVID-19 patients develop acute respiratory distress syndrome that may progress to cytokine storm syndrome, organ dysfunction, and death. Considering that neutrophil extracellular traps (NETs) have been described as important mediators of tissue damage in inflammatory diseases, we investigated whether NETs would be involved in COVID-19 pathophysiology. A cohort of 32 hospitalized patients with a confirmed diagnosis of COVID-19 and healthy controls were enrolled. The concentration of NETs was augmented in plasma, tracheal aspirate, and lung autopsies tissues from COVID-19 patients, and their neutrophils released higher levels of NETs. Notably, we found that viable SARS-CoV-2 can directly induce the release of NETs by healthy neutrophils. Mechanistically, NETs triggered by SARS-CoV-2 depend on angiotensin-converting enzyme 2, serine protease, virus replication, and PAD-4. Finally, NETs released by SARS-CoV-2-activated neutrophils promote lung epithelial cell death in vitro. These results unravel a possible detrimental role of NETs in the pathophysiology of COVID-19. Therefore, the inhibition of NETs represents a potential therapeutic target for COVID-19.

SARS-CoV-2-triggered neutrophil extracellular traps mediate COVID-19 pathology

Severe COVID-19 patients develop acute respiratory distress syndrome that may progress to cytokine storm syndrome, organ dysfunction, and death. Considering that neutrophil extracellular traps (NETs) have been described as important mediators of tissue damage in inflammatory diseases, we investigated whether NETs would be involved in COVID-19 pathophysiology. A cohort of 32 hospitalized patients with a confirmed diagnosis of COVID-19 and healthy controls were enrolled. The concentration of NETs was augmented in plasma, tracheal aspirate, and lung autopsies tissues from COVID-19 patients, and their neutrophils released higher levels of NETs. Notably, we found that viable SARS-CoV-2 can directly induce the release of NETs by healthy neutrophils. Mechanistically, NETs triggered by SARS-CoV-2 depend on angiotensin-converting enzyme 2, serine protease, virus replication, and PAD-4. Finally, NETs released by SARS-CoV-2–activated neutrophils promote lung epithelial cell death in vitro. These results unravel a possible detrimental role of NETs in the pathophysiology of COVID-19. Therefore, the inhibition of NETs represents a potential therapeutic target for COVID-19.

Enhanced formation of neutrophil extracellular traps in Kawasaki disease

BACKGROUND

Neutrophils contribute to the clearance of pathogens through the formation of neutrophil extracellular traps (NETs) in a process known as NETosis, but the excessive release of NETs has been reported to be involved in the pathogenesis of various diseases, including vasculitis, by inducing tissue injury. The aim of the present study was to investigate whether or not NETosis is enhanced in the acute phase of Kawasaki disease (KD).

METHODS

After neutrophils isolated from the peripheral blood of patients with KD and healthy control (HC) were cultured in vitro, the degree of spontaneous NETosis was evaluated by measuring the number of NETs formed and the titers of cell-free DNA (cfDNA) and neutrophil elastase (NE)-DNA complex.

RESULTS

Spontaneous NET formation in vitro was observed in neutrophils isolated from KD patients, and the number of NET formations was significantly higher in acute KD than in convalescent KD and HC. The increased levels of cfDNA and NE-DNA complexes in the acute phase of KD tended to decrease in the convalescent phase.

CONCLUSIONS

Spontaneous NET formation was enhanced in neutrophils from patients with acute KD, suggesting that circulating neutrophils may be primed to undergo NETosis in KD vasculitis.

Rapid diagnosis and comprehensive bacteria profiling of sepsis based on cell-free DNA

Background

Sepsis remains a major challenge in intensive care units, causing unacceptably high mortality rates due to the lack of rapid diagnostic tools with sufficient sensitivity. Therefore, there is an urgent need to replace time-consuming blood cultures with a new method. Ideally, such a method also provides comprehensive profiling of pathogenic bacteria to facilitate the treatment decision.

Methods

We developed a Random Forest with balanced subsampling to screen for pathogenic bacteria and diagnose sepsis based on cell-free DNA (cfDNA) sequencing data in a small blood sample. In addition, we constructed a bacterial co-occurrence network, based on a set of normal and sepsis samples, to infer unobserved bacteria.

Results

Based solely on cfDNA sequencing information from three independent datasets of sepsis, we distinguish sepsis from healthy samples with a satisfactory performance. This strategy also provides comprehensive bacteria profiling, permitting doctors to choose the best treatment strategy for a sepsis case.

Conclusions

The combination of sepsis identification and bacteria-inferring strategies is a success for noninvasive cfDNA-based diagnosis, which has the potential to greatly enhance efficiency in disease detection and provide a comprehensive understanding of pathogens. For comparison, where a culture-based analysis of pathogens takes up to 5 days and is effective for only a third to a half of patients, cfDNA sequencing can be completed in just 1 day and our method can identify the majority of pathogens in all patients.

Detection, Visualization, and Quantification of Neutrophil Extracellular Traps (NETs) and NET Markers

Neutrophil extracellular traps (NETs) have been identified as a key player in the pathogenesis of infection and inflammation in human and animals. On the one hand, NETs have been characterized as fundamental to the innate immune defense against different pathogens since they are able to entrap and immobilize invading pathogens. On the other hand, NETs have been shown to contribute to several diseases, based on their detrimental consequences. This chapter describes methods to detect NETs and NET markers in blood-derived isolated neutrophils of human, pigs, and horses in vitro, as well as NETs and NET marker detection in body fluids from in vivo studies. To avoid nonspecific background in NET-formation, a well-established isolation method for the neutrophils from fresh blood is needed. After stimulation of neutrophils to release NETs, NETs are stained with different antibodies to confirm the presence of extracellular DNA extrusion consisting of histone-DNA complexes, as well as granule components (e.g., myeloperoxidase or elastase). Furthermore, specific methods to quantify NETs and NET markers in the cerebrospinal fluid (CSF) and bronchoalveolar lavage fluid (BALF) are described in detail. In addition to immunofluorescence microscopy, quantification of NET markers from in vivo experiments in various body fluids is described (e.g., nuclease activity, free extracellular DNA, or cationic host defense peptides, such as the porcine PR-39 in BALF and CSF).

Neutrophil Extracellular Traps Are Markers of Wound Healing Impairment in Patients with Diabetic Foot Ulcers Treated in a Multidisciplinary Setting

Objective: Neutrophil extracellular traps (NETs) are associated with impaired wound healing in diabetes. This study evaluates the association between NET-specific markers and wound healing among diabetic foot ulcer (DFU) patients treated in a multidisciplinary setting. Approach: Clinical data of diabetic patients with active foot ulcers who presented to our team between January 1, 2016 and June 30, 2017 were recorded. The diabetic ulcer severity score (DUSS) and wound, ischemia, and foot infection (WIfI) score were calculated. NET-specific markers in plasma and wound tissues were tested. The capacity for plasma and platelets to prime neutrophils to release NETs was assessed. The prognostic value of NET-specific markers for wound healing was evaluated. Results: NET-specific markers were significantly higher in DFU patients than in diabetic patients without DFU or healthy controls and were found to correlate positively with DUSS or WIfI score. Elastase levels in ulcer tissue significantly increased in wounds with infections and delayed healing. Higher levels of NET release were observed after the stimulation of plasma or platelets from ulcer-related vessels than from nonulcer-related vessels of the DFU patients. Citrullinated histone 3 (citH3) was identified as a risk factor for wound healing impairment and amputation. The patients with the highest quartile of citH3 levels presented significantly lower healing rates and higher amputation rates than those with the lower three quartiles. Innovation: This study extended current knowledge of NETs on wound healing in DFU patients. Conclusion: NET-specific markers negatively correlated with wound healing in DFU patients, and citH3 is a potential marker.

Resolvin D2 Limits Secondary Tissue Necrosis After Burn Wounds in Rats

Secondary burn necrosis is the expansion and deepening of the original burn injury several days after injury. Limiting the extent of secondary burn necrosis may improve outcomes. In this study, we examined the ability of the lipid mediator of inflammation-resolution resolvin D2 (RvD2) and chromatin-lysing enzyme (DNase) to reduce secondary burn necrosis. Male Wistar rats were injured using a brass comb with 4 prongs heated in boiling water. This method created 2 parallel rows of 4 rectangular burned areas separated by 3 unburned interspaces. Starting at 2 hours after the burn injury, rats received either 25 ng/kg RvD2 intravenously daily for 7 days or 200 U/kg DNase every 12 hours for 3 days. We documented the necrosis around the initial wounds by digital photography. We used laser Doppler to assess the total blood flux in the burn area. We evaluated the functionality of the capillary network in the interspaces by optical coherence tomography angiography. We performed histological examination of wound skin tissue samples collected at 14 days postburn. We found that the interspace areas were preserved and had higher blood flow in the RvD2-treated group, while the burn areas expanded into the interspace areas, which were confluent by 7 days postburn, in the control-untreated group. We found a larger monocyte-to-neutrophil ratio in the RvD2-treated group compared with the DNase-treated and control groups (P < .05). Overall, RvD2 suppresses secondary necrosis and starts regeneration, highlighting the role of inflammation resolution as a potential therapeutic target in burn care.

Does Neutrophil Phenotype Predict the Survival of Trauma Patients?

According to the World Health Organization (WHO), trauma is responsible for 10% of deaths and 16% of disabilities worldwide. This is considerably higher than those for malaria, tuberculosis, and HIV/AIDS combined. While the human suffering and death caused by injury is well-recognized, injury has a significant medical care cost. Better prediction of the state of trauma patients in the days immediately after trauma may reduce costs. Traumatic injuries to multiple organs can cause dysfunction in all systems of the body especially the immune system placing patients at high risk of infections and inflammatory complications which are often fatal. Neutrophils are the most abundant leukocyte in the human circulation and are crucial for the prevention of microbial disease. Significant changes in neutrophil functions such as enhanced chemotaxis, Neutrophil extracellular trap (NET)-induced cell death (NETosis), and phagocytosis occur early after injury followed by prolonged functional defects such as phagocytosis, killing mechanisms, and receptor expression. Analysis of these changes may improve the prediction of the patient's condition over time. We provide a comprehensive and up-to-date review of the literature investigating the effect of trauma on neutrophil phenotype with an underlying goal of using this knowledge to examine the predictive potential of neutrophil alterations on secondary complications in patients with traumatic injuries. We conclude that alterations in neutrophil surface markers and functions may be potential biomarkers that predict the outcome of trauma patients.

Liquid biopsies to guide therapeutic decisions in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic, immune-mediated inflammatory disease that has transitioned from a debilitating disease to a chronic, controllable disease. This has been possible due to the introduction of new treatment strategies like "treat-to-target," in which the clinician treats the patient aggressively enough to reach low disease activity or remission, and the introduction of new therapeutic agents, such as biological therapies, which can lead to the prevention of damage by early diagnosis and initiation of treatment. Attention is now being directed toward identifying the optimal treatment for each patient, one that will be the most efficient and have the least number of side effects. Much work has been done to find serologic and synovial biomarkers of response to various RA treatments. Proteomics, genomics and, in the past few years, metabolomics, have all been used in the quest of identifying these biomarkers. Blood-based liquid biopsies provide a minimally invasive alternative to synovial biopsies to identify cellular and molecular signatures that can be used to longitudinally monitor response and allow for personalized medicine approach. Liquid biopsies are comprised of cell-free DNA, immune circulating cells, and extracellular vesicles, and are being increasingly and successfully used in the field of oncology for diagnosis, progression, prognosis, and prediction of response to treatment. Recently, researchers have also begun investigating the usefulness of liquid biopsies in the field of rheumatology; in this review, we will focus on the potential of liquid biopsy blood samples as biomarkers of response to treatment in patients with RA.

Paving the way for precision medicine v2.0 in intensive care by profiling necroinflammation in biofluids

Current clinical diagnosis is typically based on a combination of approaches including clinical examination of the patient, clinical experience, physiologic and/or genetic parameters, high-tech diagnostic medical imaging, and an extended list of laboratory values mostly determined in biofluids such as blood and urine. One could consider this as precision medicine v1.0. However, recent advances in technology and better understanding of molecular mechanisms underlying disease will allow us to better characterize patients in the future. These improvements will enable us to distinguish patients who have similar clinical presentations but different cellular and molecular responses. Treatments will be able to be chosen more “precisely”, resulting in more appropriate therapy, precision medicine v2.0. In this review, we will reflect on the potential added value of recent advances in technology and a better molecular understanding of necrosis and inflammation for improving diagnosis and treatment of critically ill patients. We give a brief overview on the mutual interplay between necrosis and inflammation, which are two crucial detrimental factors in organ and/or systemic dysfunction. One of the challenges for the future will thus be the cellular and molecular profiling of necroinflammation in biofluids. The huge amount of data generated by profiling biomolecules and single cells through, for example, different omic-approaches is needed for data mining methods to allow patient-clustering and identify novel biomarkers. The real-time monitoring of biomarkers will allow continuous (re)evaluation of treatment strategies using machine learning models. Ultimately, we may be able to offer precision therapies specifically designed to target the molecular set-up of an individual patient, as has begun to be done in cancer therapeutics.

Critical care mostly implies life-threatening situations involving systemic infection, inflammation and necrosis. Biofluids are an easily accessible source of liquid biopsies that can be used to monitor the evolution of the patient’s critical illness. The cellular and molecular profiling of necrosis and inflammation in biofluids using cutting-edge technologies such as realtime immunodiagnostics, next-generation sequencing and mass spectrometry will pave the way for precision medicine v2.0 in critical care. This is needed for data mining approaches to allow patientclustering, identify novel biomarkers and develop novel intervention strategies controlling necrosis and inflammation. The real-time monitoring of biomarkers will allow continued (re)evaluation of treatment strategies using machine learning models.

Circulating cell-free DNA: A potential biomarker to differentiate inflammation and infection during radiochemotherapy

BACKGROUND AND PURPOSE

Radiochemotherapy is a standard treatment option for patients with head and neck cancer (HNSCC). During radiation, local toxicities are common and need to be differentiated from infections. As levels of circulating cell-free DNA (cfDNA) are known to be elevated during infections, cfDNA might complement clinical parameters. The aim of the study was to investigate the dynamics of cfDNA during radiochemotherapy.

MATERIAL AND METHODS

In total, 78 blood samples of 20 patients with HNSCC were analysed in this prospective biomarker study. Blood samples were taken before and during treatment. CfDNA levels were quantified fluorometrically and results were compared to laboratory and clinical parameters.

RESULTS

Elevated cfDNA levels were associated with the pre-treatment volumes of lymph node metastases (p = 0.0002), gastrostomy tube placement (20.23 ng/ml vs. 9.04 ng/ml (median), p = 0.025), the application of antibiotics (16.47 ng/ml vs. 9.04 ng/ml, p = 0.006) and manifest infections (16.81 ng/ml vs. 9.04 ng/ml, p = 0.010). Furthermore, a significant difference between moderate inflammation (radiation-induced toxicity RTOG grade 2-3) and manifest infections could be observed (8.97 ng/ml vs. 16.81 ng/ml, p = 0.014), allowing for a more pronounced differentiation than by CRP levels (p = 0.119). There might be an association between the application of G-CSF and elevated cfDNA levels.

CONCLUSION

CfDNA levels are correlated with infections during radiochemotherapy and could represent an informative complemental biomarker to drive therapeutic decision-making. Estimated levels of circulating cell-free tumour DNA (ctDNA) in plasma should be interpreted cautiously when monitoring tumour outcome by next-generation-sequencing, as confounders like infections or drug application might influence the fraction of ctDNA in total cfDNA.

Impaired Cell Viability and Functionality of Hepatocytes After Incubation With Septic Plasma-Results of a Second Prospective Biosensor Study

Liver dysfunction (LD) and liver failure are associated with poor outcome in critically ill patients. In patients with severe sepsis or septic shock, LD occurred in nearly 19% of patients. An early diagnosis of LD at time of initial damage of the liver can lead to a better prognosis of these patients because an early start of therapy is possible. We performed a second prospective study with septic patients to test a new cell-based cytotoxicity device (biosensor) to evaluate clinical relevance for early diagnosis of LD and prognostic capacity. In the clinical study, 99 intensive care unit patients were included in two groups. From the patients of the septic group (n = 51, SG), and the control (non-septic) group [n = 49, control group (CG)] were drawn 20 ml blood at inclusion, after 3, and 7 days for testing with the biosensor. Patients’ data were recorded for hospital survival, organ function, and demographic data, illness severity [acute physiology and chronic health evaluation (APACHE) II-, sepsis-related organ failure assessment (SOFA) scores], cytokines, circulating-free deoxyribonucleic acid/neutrophil-derived extracellular traps (cf-DNA/NETs), microbiological results, and pre-morbidity. For the developed cytotoxicity test, the human liver cell line HepG2/C3A was used. Patients’ plasma was incubated in a microtiter plate assay with the test cells and after 6 days incubation the viability (trypan blue staining, XTT-test) and functionality (synthesis of albumin, cytochrome 1A2 activity) was analyzed. An impairment of viability and functionality of test cells was only seen in the SG compared with the CG. The plasma of non-survivors in the SG led to a more pronounced impairment of test cells than the plasma of survivors at inclusion. In addition, the levels of cf-DNA/NETs were significantly higher in the SG at inclusion, after 3, and after 7 days compared with the CG. The SG showed an in-hospital mortality of 24% and the values of bilirubin, APACHE II-, and SOFA scores were markedly higher at inclusion than in the CG. Hepatotoxicity of septic plasma was already detected with the liver cell-based biosensor at inclusion and also in the course of disease. The biosensor may be a tool for early diagnosis of LD in septic patients and may have prognostic relevance.

Extracellular Trap Formation in Response to Trypanosoma cruzi Infection in Granulocytes Isolated From Dogs and Common Opossums, Natural Reservoir Hosts

Granulocytes mediate the first line of defense against infectious diseases in humans as well as animals and they are well known as multitasking cells. They can mediate antimicrobial activity by different strategies depending on the pathogen they encounter. Besides phagocytosis, a key strategy against extracellular pathogens is the formation of extracellular traps (ETs). Those ETs mainly consist of DNA decorated with antimicrobial components and mediate entrapment of various pathogens. In the last years, various studies described ET formation as response to bacteria, viruses and parasites e.g., Trypanosma (T.) cruzi. Nevertheless, it is not fully understood, if ET formation helps the immune system to eliminate intracellular parasites. The goal of this study was to analyze ET formation in response to the intracellular parasite Trypanosma (T.) cruzi by granulocytes derived from animals that serve as natural reservoir. Thus, we investigated the ET formation in two T. cruzi reservoirs, namely dogs as domestic animal and common opossums (Didelphis marsupialis) as wild animal. Granulocytes were harvested from fresh blood by density gradient centrifugation and afterwards incubated with T. cruzi. We conducted the analysis by determination of free DNA and immunofluorescence microscopy. Using both methods, we show that T. cruzi efficiently induces ET formation in granulocytes derived from common opossum as well as dog blood. Most ETs from both animal species as response to T. cruzi are decorated with the protease neutrophil elastase. Since T. cruzi is well known to circulate over years in both analyzed animals as reservoirs, it may be assumed that T. cruzi efficiently evades ET-mediated killing in those animals. Therefore, ETs may not play a major role in efficient elimination of the pathogen from the blood of dogs or common opossums as T. cruzi survives in niches of their body. The characterization of granulocytes in various animals and humans may be helpful to understand the anti-pathogenic capacity and overall role of ETs against zoonotic pathogens like T. cruzi.

The value of cell-free DNA for molecular pathology

Over the past decade, advances in molecular biology and genomics techniques have revolutionized the diagnosis and treatment of cancer. The technological advances in tissue profiling have also been applied to the study of cell-free nucleic acids, an area of increasing interest for molecular pathology. Cell-free nucleic acids are released from tumour cells into the surrounding body fluids and can be assayed non-invasively. The repertoire of genomic alterations in circulating tumour DNA (ctDNA) is reflective of both primary tumours and distant metastatic sites, and ctDNA can be sampled multiple times, thereby overcoming the limitations of the analysis of single biopsies. Furthermore, ctDNA can be sampled regularly to monitor response to treatment, to define the evolution of the tumour genome, and to assess the acquisition of resistance and minimal residual disease. Recently, clinical ctDNA assays have been approved for guidance of therapy, which is an exciting first step in translating cell-free nucleic acid research tests into clinical use for oncology. In this review, we discuss the advantages of cell-free nucleic acids as analytes in different body fluids, including blood plasma, urine, and cerebrospinal fluid, and their clinical applications in solid tumours and haematological malignancies. We will also discuss practical considerations for clinical deployment, such as preanalytical factors and regulatory requirements. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Nucleosomes and neutrophil extracellular traps in septic and burn patients

NETosis is a host defense mechanism associated with inflammation and tissue damage. Experimental models show that platelets and von Willebrand factor (VWF) are key elements for intravascular NETosis. We determined NETosis in septic and burn patients at 1 and 4days post-admission (dpa). Nucleosomes were elevated in patients. In septics, they correlated with Human Neutrophil Elastase (HNE)-DNA complexes and SOFA score at 1dpa, and were associated with mortality. Patient's neutrophils had spontaneous NETosis and were unresponsive to stimulation. Although platelet P-selectin and TNF-α were increased in both groups, higher platelet TLR-4 expression, VWF levels and IL-6 were found in septics at 1dpa. Neither platelet activation markers nor cytokines correlated with nucleosomes or HNE-DNA. Nucleosomes could be indicators of organ damage and predictors of mortality in septic but not in burn patients. Platelet activation, VWF and cytokines do not appear to be key mediators of NETosis in these patient groups.

Neutrophil extracellular traps coincide with a pro-coagulant status of microcirculatory endothelium in burn wounds

Burn-induced tissue loss is partly related to secondary expansion of necrosis into vital dermis neighboring the initial burn injury. An important factor herein is the severe loss of perfusion of the burn wound, probably caused by microvascular damage induced by the intense local inflammatory responses as well as burn-induced hypercoagulation. We hypothesize that the formation of neutrophilic extracellular traps (NETs) play an important role in this. The purpose of this study was to investigate postburn intravascular thrombosis, NETs formation and the coagulant state in the microvasculature of burns in both animal models and patients. We used two in vivo burn wound models: rats and pigs. In rats, the entire wound was excised at day 14 postburn and in pigs burn wound biopsies were collected at different time points up to 60 days postburn. To confirm the data in patients, eschar from the burn wound was obtained from burn wound patients at different time points after wounding. The number of intravascular thrombi, the presence of intravascular NETs and the number of tissue factor (TF) positive blood vessels in the burn wound was determined. In rats, a significant increase in intravascular thrombi and TF expression was observed 14 days postburn, that in majority coincided with NETs. In pigs, a significant increase in intravascular thrombi and TF expression was found over time up to 60 days postburn, that in majority coincided with NETs too. Also in eschar of burn wound patients, a significant increase in intravascular thrombi was noted, that in majority coincided with NETs, already 0.5 days postburn and remained elevated up to 46 days postburn. This study shows the presence of NETosis in microcirculatory thrombosis of burn wounds and a switch in the microcirculatory endothelium toward a procoagulant phenotype.

Sera from severe trauma patients with pneumonia and without infectious complications have differential effects on neutrophil biology

BACKGROUND

Major trauma patients (TP) developing imbalanced immune response are at high risk for infectious post-injury complications including pneumonia. Neutrophils play a central role in the host defense against bacteria and thereby pathogenesis of infections. While there are numerous studies about neutrophil function after trauma, data about their biology in patients who suffer from pneumonia following trauma are sparse. Here, we studied the effect of serum isolated from patients who do and do not develop infection (inf.) on the biology of neutrophils from healthy volunteers.

METHODS

Sera samples from eighteen TP with an injury severity score above 16 were obtained. Nine patients were grouped to no inf. group (TP without pneumonia), and nine to inf. group (TP with pneumonia). Samples were obtained at admission to emergency department (ED), a day prior pneumonia diagnosis (1 d prior inf) or at the day of diagnosis (1 d prior inf). Samples from the equal post-injury days in the corresponding no inf. group were used. Neutrophils from nine healthy volunteers were isolated. Effects for sera isolated from infected and non-infected patients on neutrophil biology were analyzed. Migratory capacity of neutrophils towards TP's serum, their CD11b and CD62L membrane receptor expression and oxidative burst activity after stimulation with TP's serum were determined and compared between groups.

RESULTS

Migratory capacity of neutrophils was significantly increased after trauma and persisted during the study period. CD11b expression in all groups was significantly increased. CD62L expression decreased generally in samples from ED and recovered later to baseline. Stratifying no inf. and inf. groups showed significantly decreased migratory capacity, increased CD11b and significantly decreased CD62L expression in the no inf. group. These differences persisted during the complete observational period. ROS production was strongly reduced in the no inf. group compared to the inf. group at later experimental time points.

CONCLUSIONS

This data indicate that patients at risk for pneumonia development have differentially and early activated neutrophils following trauma compared to patients who are not at risk for post-injury complication. Studies about the differential biology of neutrophils and their immediately after trauma modified activity depending on the post-injury clinical course are warranted, and may deliver predictive or even therapeutic strategies to control inflammation.

Kidney and Liver Injuries After Major Burns in Rats Are Prevented by Resolvin D2

OBJECTIVES

Innate immune dysfunction after major burn injuries increases the susceptibility to organ failure. Lipid mediators of inflammation resolution, e.g., resolvin D2, have been shown recently to restore neutrophil functionality and reduce mortality rate in a rat model of major burn injury. However, the physiological mechanisms responsible for the benefic activity of resolvin D2 are not well understood.

DESIGN

Prospective randomized animal investigation.

SETTING

Academic research setting.

SUBJECTS

Wistar male rats.

INTERVENTIONS

Animals were subjected to a full-thickness burn of 30% total body surface area. Two hours after burn, 25 ng/kg resolvin D2 was administered IV and repeated every day, for 8 days. At day 10 post burn, 2 mg/kg of lipopolysaccharide was administered IV, and the presence of renal and hepatic injuries was evaluated at day 11 post burn by histology, immunohistochemistry, and relevant blood chemistry.

MEASUREMENTS AND MAIN RESULTS

In untreated animals, we found significant tissue damage in the kidneys and liver, consistent with acute tubular necrosis and multifocal necrosis, and changes in blood chemistry, reflecting the deterioration of renal and hepatic functions. We detected less tissue damage and significantly lower values of blood urea nitrogen (26.4 ± 2.1 vs 36.0 ± 9.3 mg/dL; p ≤ 0.001), alanine aminotransferase (266.5 ± 295.2 vs 861.8 ± 813.7 U/L; p ≤ 0.01), and total bilirubin (0.13 ± 0.05 vs 0.30 ± 0.14 mg/dL; p ≤ 0.01) in resolvin D2-treated rats than in untreated animals. The mean blood pressure of all animals was above 65 mm Hg, indicating adequate tissue perfusion throughout the experiments. We measured significantly larger amounts of chromatin in the circulation of untreated than of resolvin D2-treated rats (575.1 ± 331.0 vs 264.1 ± 122.4 ng/mL; p ≤ 0.05) and identified neutrophil extracellular traps in kidney and liver tissues from untreated rats, consistent with the tissue damage.

CONCLUSIONS

Pathologic changes in kidney and liver tissues in a rat model of major burn and endotoxin insults are ameliorated by resolvin D2.

Circulating Cell-Free DNA Differentiates Severity of Inflammation

INTRODUCTION

As the U.S. population ages, the incidence of chronic disease will rise. Chronic diseases have been linked to chronic inflammation. The purpose of this review is to summarize the literature on cell-free DNA (cfDNA) in relation to inflammation.

METHODS

PubMed, EMBASE, and Web of Science were searched. Inclusion criteria were noninterventional studies on acute and chronic inflammation, autoimmunity, and infection published in English after 2000, conducted in humans using the fluorescence method of quantifying DNA. Of the 442 articles retrieved, 83 were identified for full-text review and 13 remained after application of inclusion criteria.

RESULTS

Of the reviewed studies, three involved acute inflammation, six involved chronic inflammation, and four involved infection. Healthy controls with interpretable results were included in six studies, three of which used the Quant-iT high-sensitivity DNA kit and found cfDNA quantities near 800 ng/ml, while the other three used other fluorescence methods and found quantities below 100 ng/ml. All 13 studies compared groups, and all but 1 found statistically significant differences between them. Among studies using the Quant-iT reagent, levels were higher in infection than in chronic inflammation. Among studies that used other reagents, levels increased from chronic to acute inflammation to severe infection. CfDNA levels were associated with mortality and with clinical outcomes in acute inflammation and infection. Most studies assessed cfDNA's correlation with other inflammation biomarkers and found inconclusive results.

CONCLUSION

There appears to be an association between inflammation and cfDNA. Further research is necessary before cfDNA can be used clinically as a measure of inflammation.

Origin of Circulating Free DNA in Sepsis: Analysis of the CLP Mouse Model

Recently, it has been reported that circulating free DNA (cf-DNA) in the blood is increased in various infectious diseases, including sepsis. Moreover, a relationship between cf-DNA and neutrophil extracellular traps (NETs) has been suggested. However, it is still unclear what the source and physiological role of cf-DNA in sepsis are. In this study, we examined the source of cf-DNA by detecting citrullinated histone H3, a characteristic feature of NET formation, in cecal ligation and puncture- (CLP-)operated mice. In addition, neutrophil depletion using anti-Ly6G antibodies was performed to assess the association between neutrophils and cf-DNA. Increased cf-DNA levels were observed only in CLP mice and not in the control groups; the qPCR findings revealed that the cf-DNA was mainly host-derived, even in bacteremic conditions. Citrullinated histone H3 was not increased in the neutrophils upon CLP, and the depletion of neutrophils showed limited effects on decreasing the amount of cf-DNA. Taken together, these results suggested that elevated cf-DNA levels during early-phase sepsis may represent a candidate biomarker for the severity of sepsis and that, contrary to previous findings, cf-DNA is not derived from neutrophils or NETs.

The impact of trauma on neutrophil function

A well described consequence of traumatic injury is immune dysregulation, where an initial increase in immune activity is followed by a period of immune depression, the latter leaving hospitalised trauma patients at an increased risk of nosocomial infections. Here, we discuss the emerging role of the neutrophil, the most abundant leucocyte in human circulation and the first line of defence against microbial challenge, in the initiation and propagation of the inflammatory response to trauma. We review the findings of the most recent studies to have investigated the impact of trauma on neutrophil function and discuss how alterations in neutrophil biology are being investigated as potential biomarkers by which to predict the outcome of hospitalised trauma patients. Furthermore, with trauma-induced changes in neutrophil biology linked to the development of such post-traumatic complications as multiple organ failure and acute respiratory distress syndrome, we highlight an area of research within the field of trauma immunology that is gaining considerable interest: the manipulation of neutrophil function as a means by which to potentially improve patient outcome.

Deoxyribonuclease is a potential counter regulator of aberrant neutrophil extracellular traps formation after major trauma

Introduction. Neutrophil extracellular traps (NET) consist of a DNA scaffold that can be destroyed by Deoxyribonuclease (DNase). Thus DNases are potential prerequisites for natural counter regulation of NETs formation. In the present study, we determined the relationship of NETs and DNase after major trauma. Methods. Thirty-nine major trauma patients, 14 with and 25 without sepsis development were enrolled in this prospective study. Levels of cell-free (cf)-DNA/NETs and DNase were quantified daily from admission until day 9 after admission. Results. Levels of cf-DNA/NETs in patients who developed sepsis were significantly increased after trauma. In the early septic phase, DNase values in septic patients were significantly increased compared to patients without sepsis (P < 0.05). cf-DNA/NETs values correlated to values of DNase in all trauma patients and patients with uneventful recovery (P < 0.01) but not in septic patients. Recombinant DNase efficiently degraded NETs released by stimulated neutrophils in a concentration-dependent manner in vitro. Conclusions. DNase degrades NETs in a concentration-dependent manner and therefore could have a potential regulatory effect on NET formation in neutrophils. This may inhibit the antibacterial effects of NETs or protect the tissue from autodestruction in inadequate NETs release in septic patients.