Role Of Extracellular Histones Research Articles

The role of extracellular histones in COVID-19.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had spread from China and, within 2 months, became a global pandemic. The infection from this disease can cause a diversity of symptoms ranging from asymptomatic to severe acute respiratory distress syndrome with an increased risk of vascular hyperpermeability, pulmonary inflammation, extensive lung damage, and thrombosis. One of the host defense systems against coronavirus disease 2019 (COVID-19) is the formation of neutrophil extracellular traps (NETs). Numerous studies on this disease have revealed the presence of elevated levels of NET components, such as cell-free DNA, extracellular histones, neutrophil elastase, and myeloperoxidase, in plasma, serum, and tracheal aspirates of severe COVID-19 patients. Extracellular histones, a major component of NETs, are clinically very relevant as they represent promising biomarkers and drug targets, given that several studies have identified histones as key mediators in the onset and progression of various diseases, including COVID-19. However, the role of extracellular histones in COVID-19 per se remains relatively underexplored. Histones are nuclear proteins that can be released into the extracellular space via apoptosis, necrosis, or NET formation and are then regarded as cytotoxic damage-associated molecular patterns that have the potential to damage tissues and impair organ function. This review will highlight the mechanisms of extracellular histone-mediated cytotoxicity and focus on the role that histones play in COVID-19. Thereby, this paper facilitates a bench-to-bedside view of extracellular histone-mediated cytotoxicity, its role in COVID-19, and histones as potential drug targets and biomarkers for future theranostics in the clinical treatment of COVID-19 patients.

Prognostic role of levels of extracellular histones H3 for diagnosis of early dysfunction of transplant after hepatic transplantation

Objective. The aim of this study was to determine the prognostic role of extracellular histones in the diagnosis of early graft dysfunction after liver transplantation..
 Materials and methods. The 93 recipients undergoing LDLT were enrolled in this prospective study. Blood samples of patients were collected on postoperative day 1 and histone levels in the plasma samples were measured with Total Histone H3 sandwich ELISA kits. 19 (20.4%) subjects had early graft dysfunction (EAD) which was diagnosed on postoperative day 7 according to Ol-thoff’s criteria, based on liver function tests and coagulation profiles. Other 74 (79.6%) recipients did not have EGD.
 Results. Levels of circulating histones were depressed in patients with EGD (0,808±0.026, 95% (CI) 0.752-0.864) than in patients without EGD (0.820±0.017, 95% (CI) 0.786-0.854) (P=0.727). These differences were not significant. The sources of histones in the circulation are not etiologies specific and levels of total histone H 3 after 24 h of operation had not stronger predictive value with AUC 0.477 (95 % CI 0.329 to 0.625) for liver dysfunction. The AUC value of the total bilirubin (AUC 0.685, 95 % CI 0.546 to 0.825) in predicting early graft dysfunction outperformed other LFTs and was less than CRP (AUC 0.705, CI 0.573 to 0.838).
 The optimal cutoff value of total bilirubin obtained from the analysis of ROC curves was 4,5 and surpassed all other parameters with a sensitivity of 94.4% and a specificity of 40.7% respectively for prognoses of EGD (P=0.012). The univariate analysis determined that postoperative neutrophils level and CRP were identified as independent risk factors for early graft dysfunction. Neutrophils had a higher predictive value for liver dysfunction than any other parameter within 24 h (Odds ratio (OR) 16.3; 95% CI: 1.7-156.3, P = 0.016). 
 Conclusion. Collectively, extracellular histone H3 levels were depressed, total bilirubin and CRP levels were elevated in patients with EGD, which can be used as early predictors for liver tissue damage and early allograft dysfunction in patients after liver transplantation.

Kidney injury induced by elevated histones in community-acquired pneumonia.

Previous studies showed that extracellular histones could damage organs, but the role of extracellular histones in pneumonia patients with acute kidney injury (AKI) is unknown. This study aims to investigate the impact of extracellular histones on patients with community-acquired pneumonia (CAP) developed AKI. Blood samples were obtained within 24h after admission to hospital from patients who were diagnosed with CAP. According to the discharge diagnosis, the patients were divided into 2 groups (Non-AKI and AKI). In vitro, A549 cells were treated with lipopolysaccharides (LPS) and conditioned media were collected. HK2 cells were exposed to the conditioned media or not. Cells proliferation and apoptosis of HK2 were determined. Clinically, Log2 Histones (OR 3.068; 95% CI 1.544-6.097, P = 0.001) and estimated glomerular filtration rate (eGFR) (OR 0.945; 95% CI 0.914-0.978, P = 0.001) were predictors of AKI in CAP patients. Compared to the lower histones group, patients in the higher histones group were more likely to be admitted to ICU, receive mechanical ventilation, and have a longer length of in-hospital stay. In vitro, A549 cells injured by LPS released extracellular histones, in conditioned media which significantly promoted HK2 cells apoptosis. Extracellular histones was a high risk factor for developing AKI in CAP patients and a predictor of worse short-term outcomes. We also showed that extracellular histones in conditioned media damaged HK2 cells.Trial registration number: KY20181102-03; Date of registration: 20181102.

The role of extracellular histones in the pathogenesis of acute respiratory distress syndrome

When tissue damage and cell necrosis happen, histones are released into the extracellular environment, and become extracellular histones. Recent studies indicate that, extracellular histones are as dangerous signal molecules or inflammatory mediators, which play important roles in the development of acute respiratory distress syndrome (ARDS). In this review, we summarized recent researches on extracellular histones and ARDS, and elaborated the structures and functions of histones and the sources of extracellular histones, and investigated the possible mechanisms of the extracellular histones in ARDS and some potential measures for ARDS treatment targeting extracellular histones. Further studies on the relationship between extracellular histones and ARDS may provide theoretical basis and new therapeutic targets for ARDS treatment. Key words: Extracellular histones; Acute respiratory distress syndrome

The role of extracellular histones in systemic-onset juvenile idiopathic arthritis

BackgroundTo explore the effects of extracellular histones released by activated neutrophils on systemic-onset juvenile idiopathic arthritis (SoJIA), and to study the change of serum histone level between the active and remissive stage of SoJIA, then to clarify the role of serum histone in the pathogenesis of SoJIA.MethodsTwenty-six patients with SoJIA were recruited, and clinical informations were collected, and the serum histone was detected by ELISA. While neutrophils from normal children were incubated with the serum from the patients with SoJIA, also including incubated with FeCL3 and histone, the extracellular histone was detected, respectively; heparin was added to the above-mentioned groups to observe the changes of extracellular histone levels. The proportions of neutrophils, which released NETs, were calculated by confocal microscope.ResultsThe levels of serum histones in active SoJIA group (0.90 ± 0.90) were significantly higher than in remissive SoJIA group (0.17 ± 0.10) (P = 0.0009), and also higher than in control group (0.14 ± 0.09) (P = 0.246). Histone affects on clinical manifestations (including fever, rash, joint pain, liver and spleen enlargement, and serositis), except for joint pain. The proportions of neutrophils releasing NETs, that neutrophils were incubated with the serum from active SoJIA group, were 31.93% significantly higher than 12.32% from remissive SoJIA group (P < 0.0001). The proportions of neutrophils releasing NETs, that neutrophils were incubated with different concentration FeCl3 or with different concentration histones respectively, were positively correlated with the concentration of incubation; while heparins were added, NETs from neutrophils could be reduced effectively.ConclusionsThe level of serum histone is positively correlated with the activity of SoJIA. Serum histone may be from NETs, which were released by activated neutrophils. Free iron can activate neutrophils to produce NETs, which may release histones, and histones can further promote NETs to be released, that results in a positive feedback loop of histones, and that may be one of the pathogenesis of acute SoJIA or MAS secondary to SoJIA. Histones maybe play one of important roles in the pathogenesis of SoJIA. Heparin can act on histones to prevent histone-induced inflammation.Trial registrationChiCTR-OOC-15006228. Registered 9 April 2015, http://www.chictr.org.cn/showproj.aspx?proj=10752

Increased Concentrations of Extracellular Histones in Patients with Tuberculous Pleural Effusion.

BackgroundExtracellular histones have recently been suggested as critical mediators in many inflammatory diseases. However, the role of extracellular histones in tuberculous pleural effusion (TPE) is unclear. The goal of this study was to explore the potential involvement of extracellular histones in patients with TPE.Material/MethodsSamples of pleural effusion and peripheral blood were obtained from 58 patients with tuberculosis. Extracellular histones were determined in both TPE and serum samples. Moreover, the biomarkers for cellular damage, inflammatory cell activation, and systemic inflammation including lactate dehydrogenase (LDH), myeloperoxidase (MPO), S100A8/A9, as well as multiple inflammatory cytokines were measured.ResultsExtracellular histone levels were significantly elevated in TPE (4.762 mg/mL [3.336, 7.307]) and serum samples (1.502 mg/mL [1.084, 2.478]) from tuberculosis patients as compared with the serum (0.585 mg/mL [0.285, 0.949]) from healthy controls. Notably, extracellular histones in TPE were also much higher than in serum of patients (P=0.002). LDH, MPO, and S100A8/A9 levels were all increased in TPE, along with a remarkable elevation of various cytokines. A correlation analysis showed that extracellular histones were positively associated with LDH, MPO, and S100A8/A9, and a panel of inflammatory cytokines in TPE.ConclusionsThese results suggest that high concentrations of extracellular histones are markedly present in TPE, which may play an inflammatory role towards the progression of tuberculosis.

Effect of extracellular histones on intestinal mucosa barrier function in mice and role of extracellular histones in development of sepsis

Objective To investigate the effect of extracellular histones (EH) on intestinal mucosal barrier function in mice and the correlation of EH with the pathogenesis of sepsis. Methods Twenty male C57BL/6 mice were assigned into experiment group (n=10) and control group (n=10) according to the random number table. Same dose (50 mg/kg) of EH and saline were administered through the caudal vein of mice in experiment and control groups respectively. Blood and intestinal samples in each group were collected 3 h after the administration. Morphology of intestinal mucosal tissue was detected by light scope and transmission electron microscope. Expressions of tight junction related proteins (ZO-1, Occludin and Claudin-1) were detected by western blot. Plasma levels of diamine oxidase (DAO) and intestinal fatty acid binding protein (I-FABP) were determined by ELISA method. Plasma level of endotoxin (ET) was determined by limulus test. Results Under transmission electron microscope, experiment group showed disorganized microvilli of intestinal epithelial cells with partially twisted, broken and lost, unclear tight junctions, and widened cellular space. Under light scope, experiment group showed substantial inflammatory cell infiltration in the intestinal wall, disorganized intestinal villi, edema and hemorrhage of mucosa and submucosa, and edematous goblet cells. Experimental versus control group showed significant reduction in levels of Claudin-1 (0.587 7±0.060 6 vs. 0.677 2±0.038 3), Occludin (0.127 7±0.085 7 vs. 0.430 6±0.086 9) and ZO-1 (0.393 3±0.080 8 vs. 0.812 8±0.096 3) (P<0.05). Experimental versus control group showed significantly up-regulated plasma levels of DAO [(1.61±0.20)U/ml vs. (0.69±0.15)U/ml], I-FABP [(548.5±36.8)EU/ml vs. (178.8±26.9) EU/ml] and ET [(0.182±0.076) EU/ml vs. (0.091±0.029) EU/ml](P<0.05). Conclusion EH can obviously impair the integrity of intestinal mucosal barrier in mice and hence induce endotoxin translocation. Key words: Histones; Intestines; Sepsis

The role of extracellular histones in haematological disorders.

Over the past decades, chromosomal alterations have been extensively investigated for their pathophysiological relevance in haematological malignancies. In particular, epigenetic modifications of intra-nuclear histones are now known as key regulators of healthy cell cycles that have also evolved into novel therapeutic targets for certain blood cancers. Thus, for most haematologists, histones are DNA-chained proteins that are buried deep within chromatin. However, the plot has deepened with recent revelations on the function of histones when unchained and released extracellularly upon cell death or from activated neutrophils as part of neutrophil extracellular traps (NETs). Extracellular histones and NETs are increasingly recognized for profound cytotoxicity and pro-coagulant effects. This article highlights the importance of recognizing this new paradigm of extracellular histones as a key player in host defence through its damage-associated molecular patterns, which could translate into novel diagnostic and therapeutic biomarkers in various haematological and critical disorders.

Role of extracellular histones in liver failure

Role of extracellular histones in liver failure

Role of extracellular histones in sepsis

Sepsis is a common desease with a high mortality in pediatric intensive care unit.The pathogenesis of sepsis remains unclear.Recent studies have found that extracellular histones play an important role in the incidence of sepsis.This review provides new ideas for the diagnosis and treatment of sepsis. Key words: Extracellular histones; Sepsis; Inflammation; Coagulation

Study in the role of extracellular histones in the pathogenesis of acute lung injury caused by acid aspiration

Objective To investigate the effects of extracellular histones as a major mediator and the target for intervention in the pathogenesis of ALI in the wake of acid aspiration. Methods The correlation of circulating histones and aspiratory acid was determined with normal saline and 4 different concentrations of acid (0.01 mol/L, 0.1 mol/L, 0.3 mol/L and 0.5 mol/L) . The dynamic change of circulating histones was observed at 6 intervals of 1, 3, 6, 12, 24 and 72 h after injury. The protection of anti-histone-4 antibody was assessed by survival rates, blood gas, lung edema, MPO activity and lung pathological change. Results After acid aspiration, extracellular histone H4 increased significantly. The circulating histone levels were closely correlative with the concentrations of aspiratory acid (r =0.874 6, P =0.031 7) . The anti-histone-4 antibody could decrease mortality (P =0.034 5) and improve blood gas, lung edema, MPO activity and lung pathological change. Conclusions The results showed that extracellular histones were not only the key mediators in the pathogenesis of ALI but also the target for intervention. Key words: Extracellular histones; Acute lung injury; Acid aspiration; Inflammation; Neutralizing antibody

Role of extracellular histones in the cardiomyopathy of sepsis.

The purpose of this study was to define the relationship in polymicrobial sepsis (in adult male C57BL/6 mice) between heart dysfunction and the appearance in plasma of extracellular histones. Procedures included induction of sepsis by cecal ligation and puncture and measurement of heart function using echocardiogram/Doppler parameters. We assessed the ability of histones to cause disequilibrium in the redox status and intracellular [Ca(2+)]i levels in cardiomyocytes (CMs) (from mice and rats). We also studied the ability of histones to disturb both functional and electrical responses of hearts perfused with histones. Main findings revealed that extracellular histones appearing in septic plasma required C5a receptors, polymorphonuclear leukocytes (PMNs), and the Nacht-, LRR-, and PYD-domains-containing protein 3 (NLRP3) inflammasome. In vitro exposure of CMs to histones caused loss of homeostasis of the redox system and in [Ca(2+)]i, as well as defects in mitochondrial function. Perfusion of hearts with histones caused electrical and functional dysfunction. Finally, in vivo neutralization of histones in septic mice markedly reduced the parameters of heart dysfunction. Histones caused dysfunction in hearts during polymicrobial sepsis. These events could be attenuated by histone neutralization, suggesting that histones may be targets in the setting of sepsis to reduce cardiac dysfunction.

N-acetyl-heparin attenuates acute lung injury caused by acid aspiration mainly by antagonizing histones in mice.

Acute lung injury (ALI) is the leading cause of death in intensive care units. Extracellular histones have recently been recognized to be pivotal inflammatory mediators. Heparin and its derivatives can bind histones through electrostatic interaction. The purpose of this study was to investigate 1) the role of extracellular histones in the pathogenesis of ALI caused by acid aspiration and 2) whether N-acetyl-heparin (NAH) provides more protection than heparin against histones at the high dose. ALI was induced in mice via intratracheal instillation of hydrochloric acid (HCl). Lethality rate, blood gas, myeloperoxidase (MPO) activity, lung edema and pathological changes were used to evaluate the degree of ALI. Heparin/NAH was administered intraperitoneally, twice a day, for 3 days or until death. Acid aspiration caused an obvious increase in extracellular histones. A significant correlation existed between the concentration of HCl aspirated and the circulating histones. Heparin/NAH (10 mg/kg) improved the lethality rate, blood gas, MPO activity, lung edema and pathological score. At a dose of 20 mg/kg, NAH still provided protection, however heparin tended to aggravate the injury due to hemorrhagic complications. The specific interaction between heparin and histones was verified by the binding assay. In summary, high levels of extracellular histones can be pathogenic in ALI caused by acid aspiration. By neutralizing extracellular histones, heparin/NAH can offer similar protection at the moderate doses. At the high dose, NAH provides better protection than heparin.