Acute DNase1 treatment improves left ventricular remodeling after myocardial infarction by disruption of free chromatin

Systemic mechanisms of necrotic cell debris clearance

Necrosis is an overarching term that describes cell death modalities caused by (extreme) adverse conditions in which cells lose structural integrity. A guaranteed consequence of necrosis is the production of necrotic cell remnants, or debris. Necrotic cell debris is a strong trigger of inflammation, and although inflammatory responses are required for tissue healing, necrotic debris may lead to uncontrolled immune responses and collateral damage. Besides local phagocytosis by recruited leukocytes, there is accumulating evidence that extracellular mechanisms are also involved in necrotic debris clearance. In this review, we focused on systemic clearance mechanisms present in the bloodstream and vasculature that often cooperate to drive the clearance of cell debris. We reviewed the contribution and cooperation of extracellular DNases, the actin-scavenger system, the fibrinolytic system and reticuloendothelial cells in performing clearance of necrotic debris. Moreover, associations of the (mis)functioning of these clearance systems with a variety of diseases were provided, illustrating the importance of the mechanisms of clearance of dead cells in the organism.

Neutrophil extracellular traps contributing to atherosclerosis: From pathophysiology to clinical implications

Neutrophil extracellular traps (NETs) are network-like structures of chromatin filaments decorated by histones, granules, and cytoplasmic-derived proteins expelled by activated neutrophils under multiple pathogenic conditions. NETs not only capture pathogens in innate immunity but also respond to sterile inflammatory stimuli in atherosclerosis, such as lipoproteins and inflammatory cytokines. Atherosclerosis is a lipid-driven chronic inflammatory disease characterized by the accumulation and transformation of inflammatory cells, and smooth muscle cells in the intimal space. NETs-derived extracellular components possess toxic and proinflammatory properties leading to cellular dysfunction and tissue damage, which may establish a link among lipid metabolism, inflammatory immunity, and atherosclerosis. In this review, we discuss recent advances regarding the role of NETs engaged in the pathogenesis of atherosclerosis, particularly focusing on the interaction with lipids and inflammasomes, crosstalk with smooth muscle cells and inflammatory cells, and the association with aging. We also evaluate the current knowledge on the potential of NETs as biomarkers and therapeutic targets for atherosclerosis and its related diseases in clinical practice.

Extracellular histones as damage-associated molecular patterns in neuroinflammatory responses

The four core histones H2A, H2B, H3, H4, and the linker histone H1 primarily bind DNA and regulate gene expression within the nucleus. Evidence collected mainly from the peripheral tissues illustrates that histones can be released into the extracellular space by activated or damaged cells. In this article, we first summarize the innate immune-modulatory properties of extracellular histones and histone-containing complexes, such as nucleosomes, and neutrophil extracellular traps (NETs), described in peripheral tissues. There, histones act as damage-associated molecular patterns (DAMPs), which are a class of endogenous molecules that trigger immune responses by interacting directly with the cellular membranes and activating pattern recognition receptors (PRRs), such as toll-like receptors (TLR) 2, 4, 9 and the receptor for advanced glycation end-products (RAGE). We then focus on the available evidence implicating extracellular histones as DAMPs of the central nervous system (CNS). It is becoming evident that histones are present in the brain parenchyma after crossing the blood-brain barrier (BBB) or being released by several types of brain cells, including neurons, microglia, and astrocytes. However, studies on the DAMP-like effects of histones on CNS cells are limited. For example, TLR4 is the only known molecular target of CNS extracellular histones and their interactions with other PRRs expressed by brain cells have not been observed. Nevertheless, extracellular histones are implicated in the pathogenesis of a variety of neurological disorders characterized by sterile neuroinflammation; therefore, detailed studies on the role these proteins and their complexes play in these pathologies could identify novel therapeutic targets.

Inhibitors of Polyphosphate and Neutrophil Extracellular Traps

The contact pathway of blood clotting has received intense interest in recent years as studies have linked it to thrombosis, inflammation, and innate immunity. Because the contact pathway plays little to no role in normal hemostasis, it has emerged as a potential target for safer thromboprotection, relative to currently approved antithrombotic drugs which all target the final common pathway of blood clotting. Research since the mid-2000s has identified polyphosphate, DNA, and RNA as important triggers of the contact pathway with roles in thrombosis, although these molecules also modulate blood clotting and inflammation via mechanisms other than the contact pathway of the clotting cascade. The most significant source of extracellular DNA in many disease settings is in the form of neutrophil extracellular traps (NETs), which have been shown to contribute to incidence and severity of thrombosis. This review summarizes known roles of extracellular polyphosphate and nucleic acids in thrombosis, with an emphasis on novel agents under current development that target the prothrombotic activities of polyphosphate and NETs.

Neutrophil extracellular traps as a unique target in the treatment of chemotherapy-induced peripheral neuropathy

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a severe dose-limiting side effect of chemotherapy and remains a huge clinical challenge. Here, we explore the role of microcirculation hypoxia induced by neutrophil extracellular traps (NETs) in the development of CIPN and look for potential treatment.

METHODS

The expression of NETs in plasma and dorsal root ganglion (DRG) are examined by ELISA, IHC, IF and Western blotting. IVIS Spectrum imaging and Laser Doppler Flow Metry are applied to explore the microcirculation hypoxia induced by NETs in the development of CIPN. Stroke Homing peptide (SHp)-guided deoxyribonuclease 1 (DNase1) is used to degrade NETs.

FINDINGS

The level of NETs in patients received chemotherapy increases significantly. And NETs accumulate in the DRG and limbs in CIPN mice. It leads to disturbed microcirculation and ischemic status in limbs and sciatic nerves treated with oxaliplatin (L-OHP). Furthermore, targeting NETs with DNase1 significantly reduces the chemotherapy-induced mechanical hyperalgesia. The pharmacological or genetic inhibition on myeloperoxidase (MPO) or peptidyl arginine deiminase-4 (PAD4) dramatically improves microcirculation disturbance caused by L-OHP and prevents the development of CIPN in mice.

INTERPRETATION

In addition to uncovering the role of NETs as a key element in the development of CIPN, our finding provides a potential therapeutic strategy that targeted degradation of NETs by SHp-guided DNase1 could be an effective treatment for CIPN.

FUNDING

This study was funded by the National Natural Science Foundation of China81870870, 81971047, 81773798, 82271252; Natural Science Foundation of Jiangsu ProvinceBK20191253; Major Project of "Science and Technology Innovation Fund" of Nanjing Medical University2017NJMUCX004; Key R&D Program (Social Development) Project of Jiangsu ProvinceBE2019732; Nanjing Special Fund for Health Science and Technology DevelopmentYKK19170.

Extracellular traps and the role in thrombosis

Thrombotic complications pose serious health risks worldwide. A significant change in our understanding of the pathophysiology of thrombosis has occurred since the discovery of extracellular traps (ETs) and their prothrombotic properties. As a result of immune cells decondensing chromatin into extracellular fibers, ETs promote thrombus formation by acting as a scaffold that activates platelets and coagulates them. The involvement of ETs in thrombosis has been reported in various thrombotic conditions including deep vein thrombosis (DVT), pulmonary emboli, acute myocardial infarction, aucte ischemic stroke, and abdominal aortic aneurysms. This review summarizes the existing evidence of ETs in human and animal model thrombi. The authors described studies showing the existence of ETs in venous or arterial thrombi. In addition, we studied potential novel therapeutic opportunities related to the resolution or prevention of thrombosis by targeting ETs.

Neutrophil Extracellular Traps in Atherosclerosis and Thrombosis

Despite effective therapeutic and preventive strategies, atherosclerosis and its complications still represent a substantial health burden. Leukocytes and inflammatory mechanisms are increasingly recognized as drivers of atherosclerosis. Neutrophil granulocytes within the circulation were recently shown to undergo neutrophil extracellular trap (NET) formation, linking innate immunity with acute complications of atherosclerosis. In this chapter, we summarize mechanisms of NET formation, evidence for their involvement in atherosclerosis and thrombosis, and potential therapeutic regimens specifically targeting NET components.

Culprit site extracellular DNA and microvascular obstruction in ST-elevation myocardial infarction

AIMS

Extracellular chromatin and deoxyribonuclease (DNase) have been identified as important players of thrombosis, inflammation and homeostasis in a murine model. We previously demonstrated that activated neutrophils release neutrophil extracellular traps (NETs) at the culprit site in ST elevation myocardial infarction (STEMI), which significantly contribute to extracellular chromatin burden, and are associated with larger infarcts. To understand the correlation between neutrophil activation, extracellular chromatin and infarct size (IS), we investigated these parameters in a porcine myocardial infarction model, and at different time points and sites in a prospective STEMI trial with cardiac magnetic resonance (CMR) endpoints.

METHODS AND RESULTS

In a prospective STEMI trial (NCT01777750), 101 STEMI patients were included and blood samples were obtained from first medical contact until 6 months after primary percutaneous coronary intervention (pPCI) including direct sampling from the culprit site. CMR was performed 4 ± 2 days and 6 months after pPCI. Neutrophil counts, markers of extracellular chromatin and inflammation were measured. Double-stranded DNA (dsDNA), citrullinated histone 3, nucleosomes, myeloperoxidase, neutrophil elastase and interleukin (IL)-6 were significantly increased, while DNase activity was significantly decreased at the culprit site in STEMI patients. High neutrophil counts and dsDNA levels at the culprit site correlated with high microvascular obstruction (MVO) and low ejection fraction (EF). High DNase activity at the culprit site correlated with low MVO and high EF.In correspondence, dsDNA correlated with IS in the porcine myocardial infarction model. In porcine infarcts, neutrophils and extracellular chromatin were detected in congested small arteries corresponding with MVO. Markers of neutrophil activation, extracellular chromatin, DNase activity and CMR measurements correlated with markers of systemic inflammation C-reactive protein and IL-6 in patients.

CONCLUSIONS

NETs and extracellular chromatin are important determinants of MVO in STEMI. Rapid degradation of extracellular chromatin by DNases appears to be crucial for microvascular patency and outcome.

TRANSLATIONAL PERSPECTIVE

We show that NETs and extracellular DNA obstruct microvessels in the porcine myocardial infarction model and is connected to increased infarct size. We are able to prove this observation in human STEMI patients. DNase is capable to counteract these effects. Extracellular DNA could be a new treatment target in STEMI.

Deoxyribonuclease 1 Q222R single nucleotide polymorphism and long-term mortality after acute myocardial infarction

Upon activation, neutrophils release neutrophil extracellular traps (NETs), which contribute to circulating DNA burden and thrombosis, including ST-segment elevation myocardial infarction (STEMI). Deoxyribonuclease (DNase) 1 degrades circulating DNA and NETs. Lower DNase activity correlates with NET burden and infarct size. The DNase 1 Q222R single nucleotide polymorphism (SNP), impairing DNase 1 function, is linked with myocardial infarction. We assessed whether the Q222R SNP is connected to increased NET burden in STEMI and influences long-term outcomes. We enrolled 711 STEMI patients undergoing primary percutaneous coronary intervention (pPCI), and 1422 controls. Genotyping was performed for DNase 1 Q222R SNP. DNase activity, double-stranded (ds)DNA and citrullinated histone H3 were determined in culprit site and peripheral plasma during pPCI. The association of the Q222R variant on cardiovascular and all-cause mortality was assessed by multivariable Cox regression adjusted for cardiovascular risk factors. Homozygous Q222R DNase 1 variant was present in 64 (9.0%) STEMI patients, at the same frequency as in controls. Patients homozygous for Q222R displayed less DNase activity and increased circulating DNA burden. In overall patients, median survival was 60 months. Homozygous Q222R variant was independently associated with cardiovascular and all-cause mortality after STEMI. dsDNA/DNase ratio independently predicted cardiovascular and all-cause mortality. These findings highlight that the Q222R DNase 1 SNP is associated with increased NET burden and decreased compensatory DNase activity, and may serve as an independent risk factor for poor outcome after STEMI.

Genetic ablation of fibroblast activation protein alpha attenuates left ventricular dilation after myocardial infarction

Introduction

Regulating excessive activation of fibroblasts may be a promising target to optimize extracellular matrix deposition and myocardial stiffness. Fibroblast activation protein alpha (FAP) is upregulated in activated fibroblasts after myocardial infarction (MI), and alters fibroblast migration in vitro. We hypothesized that FAP depletion may have a protective effect on left ventricular (LV) remodeling after MI.

Materials and methods

We used the model of chronic MI in homozygous FAP deficient mice (FAP-KO, n = 51) and wild type mice (WT, n = 55) to analyze wound healing by monocyte and myofibroblast infiltration. Heart function and remodeling was studied by echocardiography, morphometric analyses including capillary density and myocyte size, collagen content and in vivo cell-proliferation. In non-operated healthy mice up to 6 months of age, morphometric analyses and collagen content was assessed (WT n = 10, FAP-KO n = 19).

Results

Healthy FAP-deficient mice did not show changes in LV structure or differences in collagen content or cardiac morphology. Infarct size, survival and cardiac function were not different between FAP-KO and wildtype mice. FAP-KO animals showed less LV-dilation and a thicker scar, accompanied by a trend towards lower collagen content. Wound healing, assessed by infiltration with inflammatory cells and myofibroblasts were not different between groups.

Conclusion

We show that genetic ablation of FAP does not impair cardiac wound healing, and attenuates LV dilation after MI in mice. FAP seems dispensable for normal cardiac function and homeostasis.

The Role of Histones and Heparin in Sepsis: A Review

Septic shock with multiple organ failure is a devastating situation in clinical settings. Through the past decades, much progress has been made in the management of sepsis and its underlying pathogenesis, but a highly effective therapeutic has not been developed. Recently, macromolecules such as histones have been targeted in the treatment of sepsis. Histones primarily function as chromosomal organizers to pack DNA and regulate its transcription through epigenetic mechanisms. However, a growing body of research has shown that histone family members can also exert cellular toxicity once they relocate from the nucleus into the extracellular space. Heparin, a commonly used anti-coagulant, has been shown to possess life-saving capabilities for septic patients, but the potential interplay between heparin and extracellular histones has not been investigated. In this review, we summarize the pathogenic roles of extracellular histones and the therapeutic roles of heparin in the development and management of sepsis and septic shock.

Targeting inflammation in atherosclerosis - from experimental insights to the clinic

Atherosclerosis, a dominant and growing cause of death and disability worldwide, involves inflammation from its inception to the emergence of complications. Targeting inflammatory pathways could therefore provide a promising new avenue to prevent and treat atherosclerosis. Indeed, clinical studies have now demonstrated unequivocally that modulation of inflammation can forestall the clinical complications of atherosclerosis. This progress pinpoints the need for preclinical investigations to refine strategies for combatting inflammation in the human disease. In this Review, we consider a gamut of attractive possibilities for modifying inflammation in atherosclerosis, including targeting pivotal inflammatory pathways such as the inflammasomes, inhibiting cytokines, manipulating adaptive immunity and promoting pro-resolution mechanisms. Along with lifestyle measures, pharmacological interventions to mute inflammation could complement traditional targets, such as lipids and hypertension, to make new inroads into the management of atherosclerotic risk.

Neutrophil extracellular trap components and myocardial recovery in post-ischemic acute heart failure

Objective

The role of neutrophil extracellular traps (NETs) in acute heart failure is unknown. We recently showed that interleukin 8, a putative NETs stimulator, was associated with myocardial recovery in acute heart failure complicating ST-elevation myocardial infarction (STEMI). In this exploratory post-hoc study, we aimed to investigate the role of NETs components in relation to myocardial function and interleukin 8 in STEMI patients with symptomatic acute heart failure.

Methods

In 61 STEMI patients developing acute heart failure within 48 hours of successful revascularization, wall motion score index (WMSI), global longitudinal strain (GLS) and left ventricular ejection fraction (LVEF) were assessed by echocardiography at baseline and on day 5. Blood drawn at baseline and days 1, 2 and 5 was used to quantify double-stranded DNA (dsDNA), myeloperoxidase-DNA complexes (MPO-DNA) and citrullinated histone 3 (CitH3). The area under the curve (AUC) of each NETs marker and interleukin 8 was approximated for the first 5 days.

Results

dsDNA_AUC and MPO-DNA_AUC correlated significantly with change in WMSI from baseline to day 5 (r_s = 0.28 for both, p≤0.05), whereas NETs AUCs did not correlate with changes in GLS and LVEF. dsDNA_AUC was significantly correlated with interleukin 8_AUC (r = 0.40, p = 0.003). However, mixed model regression could not identify a significant effect of the NETs components on myocardial function parameters.

Conclusions

In this cohort with acute heart failure complicating STEMI, NETs components were partly correlated with myocardial function and interleukin 8 levels, yet no causal relationship between NETs components and myocardial recovery could be established.

Clinical trial registration

ClinicalTrials.gov, identifier: NCT00324766.

Imbalance between plasma double-stranded DNA and deoxyribonuclease activity predicts mortality after out-of-hospital cardiac arrest

AIM

Despite an increased rate of return of spontaneous circulation (ROSC) in out-of-hospital cardiac arrest (OHCA) patients, almost half of patients do not survive up to hospital discharge. Understanding pathophysiological mechanisms of post-cardiac arrest syndrome is essential for developing novel therapeutic strategies. During systemic inflammatory responses and concomitant cell death, double-stranded (ds) DNA is released into circulation, exerting pro-inflammatory effects. Deoxyribonuclease (DNase) degrades dsDNA. The role of DNase activity in OHCA survivors and impact on clinical outcome has not been analyzed yet.

METHODS

In a prospective, single-center study, dsDNA and DNase activity were determined at hospital admission (acute phase) and 24 h (subacute phase) after ROSC. The ratio between dsDNA levels and DNase activity was calculated to determine the extent of dsDNA release in relation to the patients' capacity of degradation. Thirty-day mortality was defined as study end point.

RESULTS

We enrolled 64 OHCA survivors, of whom 26.6% (n = 17) died within 30 days. A peak of circulating dsDNA was observed at admission which decreased within 24 h. DNase activity did not differ between acute and subacute phase, while dsDNA load per DNase activity significantly decreased. The ratio between dsDNA levels and DNase activity in the subacute phase was the strongest predictor of 30-day mortality with an adjusted HR per 1 SD of 3.59 (95% CI, 1.80-7.18, p < 0.001).

CONCLUSION

Disproportionally increased dsDNA levels uncompensated by DNase activity are a strong predictor of mortality in OHCA survivors. This pilot study points to a potentially protective effect of DNase activity in patients undergoing cardiac arrest.

Double-Stranded DNA and NETs Components in Relation to Clinical Outcome After ST-Elevation Myocardial Infarction

Neutrophil extracellular traps (NETs) have been implicated in atherothrombosis; however, their potential role as markers of risk is unclear. We investigated whether circulating NETs-related components associated with clinical outcome and hypercoagulability in ST-elevation myocardial infarction (STEMI). In this observational cohort study, STEMI patients admitted for PCI (n = 956) were followed for median 4.6 years, recording 190 events (reinfarction, unscheduled revascularization, stroke, heart failure hospitalization, or death). Serum drawn median 18 hours post-PCI was used to quantify double-stranded DNA (dsDNA) and the more specific NETs markers myeloperoxidase-DNA and citrullinated histone 3. Levels of the NETs markers did not differ significantly between groups with/without a primary composite endpoint. However, patients who died (n = 76) had higher dsDNA compared to survivors (p < 0.001). Above-median dsDNA was associated with an increased number of deaths (54 vs. 22, p < 0.001). dsDNA in the upper quartiles (Q) was associated with increased mortality (Q3 vs. Q1 + 2 adjusted HR: 1.89 [95% CI 1.03 to 3.49], p = 0.041 and Q4 vs. Q1 + 2 adjusted HR: 2.28 [95% CI 1.19 to 4.36], p = 0.013). dsDNA was weakly correlated with D-dimer (r_s = 0.17, p < 0.001). dsDNA levels associated with increased all-cause mortality, yet weakly with hypercoagulability in STEMI patients. The prognostic significance of potentially NETs-related markers requires further exploration.

Current Approaches Targeting the Wound Healing Phases to Attenuate Fibrosis and Scarring

Cutaneous fibrosis results from suboptimal wound healing following significant tissue injury such as severe burns, trauma, and major surgeries. Pathologic skin fibrosis results in scars that are disfiguring, limit normal movement, and prevent patient recovery and reintegration into society. While various therapeutic strategies have been used to accelerate wound healing and decrease the incidence of scarring, recent studies have targeted the molecular regulators of each phase of wound healing, including the inflammatory, proliferative, and remodeling phases. Here, we reviewed the most recent literature elucidating molecular pathways that can be targeted to reduce fibrosis with a particular focus on post-burn scarring. Current research targeting inflammatory mediators, the epithelial to mesenchymal transition, and regulators of myofibroblast differentiation shows promising results. However, a multimodal approach addressing all three phases of wound healing may provide the best therapeutic outcome.

The Role of Extracellular DNA and Histones in Ischaemia-Reperfusion Injury of the Myocardium

Despite an increase in the rates of survival in patients suffering myocardial infarction, as yet there is no therapy specifically targeting ischaemia and reperfusion injury of the myocardium. With a greater understanding of immune activation during infarction, more potential treatment targets are now being identified. The innate immune system is believed to play an important role in the myocardium after ischaemia-driven cardiomyocyte death. The release of intracellular contents including DNA into the extracellular space during necrosis and cell rupture is now believed to create a pro-inflammatory milieu which propagates the inflammatory process. DNA and DNA fragments have been shown to activate the innate immune system by acting as Danger-Associated Molecular Patterns (DAMPs), which act as ligands on toll-like receptors (TLRs). Stimulation of TLRs, in turn, can activate intracellular cell death pathways such as pyroptosis. Here, we review the role of DNA fragments during ischaemia and reperfusion, and assess their potential as a target in the quest to preserve cardiomyocyte viability following myocardial infarction.

Targeting of cell-free DNA by DNase I diminishes endothelial dysfunction and inflammation in a rat model of cardiopulmonary bypass

The use of cardiopulmonary bypass (CPB) results in the activation of leukocytes, release of neutrophil extracellular traps (NETs) and severe inflammation. We hypothesize that targeting of circulating cell-free DNA (cfDNA) by DNases might represent a feasible therapeutic strategy to limit CPB-associated side effects. Male Wistar rats (n = 24) underwent CPB with deep hypothermic circulatory arrest (DHCA) and were divided into 3 groups: control (group 1), one i.v. bolus DNase I before CPB start (group 2) and a second DNase I dose before reperfusion (group 3). We found a positive correlation between plasma cfDNA/NETs levels and compromised endothelial vasorelaxation after CPB. DNase I administration significantly diminished plasma cfDNA/NETs levels. Further, a dose-dependent improvement in endothelial function accompanied by significant reduction of circulating intercellular adhesion molecule (ICAM)-1 was observed. Rats of group 3 had significantly reduced plasma IL-6 levels and downregulated expression of adhesion molecules resulting in impaired leukocyte extravasation and reduced MPO activity in lungs. Mechanistically, digestion of NETs by DNase I significantly diminished NETs-dependent upregulation of adhesion molecules in human endothelial cells. Altogether, systemic DNase I administration during CPB efficiently reduced cfDNA/NETs-mediated endothelial dysfunction and inflammation and might represents a promising therapeutic strategy for clinical practice.

Mining Clinical Case Reports to Identify New Lines of Investigation in Alzheimer's Disease: The Curious Case of DNase I

Mining the case report literature identified an intriguing, yet neglected finding: Deoxyribonuclease I (DNase I) as a possible treatment for Alzheimer’s disease. This finding is speculative, both because it is based on one patient, and because the underlying mechanism(s) of action remain obscure. However, further literature review revealed that there are several plausible mechanisms by which DNase I might affect the course of Alzheimer’s disease. Given that DNase I is an FDA-approved drug, with extensive studies in both animals and man in the context of other diseases, I suggest that investigation of DNAse I in Alzheimer’s disease is worthwhile.

Degradation of Extracellular DNA Significantly Ameliorates Necrotizing Enterocolitis Severity in Mice

BACKGROUND

Necrotizing enterocolitis (NEC) is one of the most devastating diseases in neonates and is characterized by high morbidity and mortality. It has been suggested that neutrophils play a crucial role in NEC pathogenesis and contribute to the hyperinflammatory reaction after bacterial colonization, which ultimately induces NEC. The aim of this study was to investigate whether dissolution of neutrophil extracellular traps (NETs) by systemic DNase1 therapy reduces NEC manifestation and morbidity.

METHODS

NEC was induced in neonatal mice by gavage feeding of lipopolysaccharide mixed in Neocate, followed by hypoxia q12 h for 5d. Inactivated DNase1 and DNase1 were administered intraperitoneally twice daily in the control and treatment groups, respectively, starting on day 5 for 72 h. Survival, NEC score, intestinal damage (Chiu score, malondialdehyde [MDA], glutathione peroxidase [GPx]), inflammation (neutrophil elastase [NE], myeloperoxidase [MPO], toll-like receptor 4 [TLR4]), and NETs markers (SYTOX orange, cell-free DNA [cfDNA], DNase, citrullinated Histone 3 [H3cit]) were then assessed.

RESULTS

In total, 44 neonatal mice were used in the experiment. Mice in the treatment group demonstrated significantly reduced NEC rates (44 versus 86%, P = 0.029) and improved survival in comparison to controls (65 versus 35%, P = 0.01). Furthermore, mice treated with DNase1 showed significantly less tissue damage (cfDNA, Chiu score), oxidative stress (MDA, GPx), and inflammation (NE, MPO, H3cit, TLR4), which ultimately lead to a significant reduction in mortality.

CONCLUSIONS

The results of the study indicate that systemic DNase1 treatment leads to a significant reduction in tissue damage, NEC severity, and mortality. Therefore, after validation of our findings in human subjects, DNase1 treatment should be considered as a therapeutic option in neonates diagnosed with NEC.

Elevated extracellular nucleosomes and their relevance to inflammation in stage 5 chronic kidney disease

BACKGROUND

Chronic kidney disease is a disorder characterized by a pro-inflammatory state that is associated with increased morbidity and mortality. Endogenous damage-associated molecular patterns, including nucleosomes, may contribute to this persistent inflammation. The aim of this study was to profile and evaluate the clinical significance of circulating nucleosomes in patients with Stage 5 chronic kidney disease (CKD5) on hemodialysis (HD).

METHODS

Under institutional review board approval, plasma samples were collected from 90 CKD5-HD patients (45 male and 45 female) prior to hemodialysis. Normal human plasma samples (25 male and 25 female) were used as a control group. Commercial enzyme-linked immunosorbent and colorimetric assays were used to profile nucleosome levels and biochemical markers of kidney injury, inflammation, thrombosis, and renal function in CKD5-HD and control groups. Clinical laboratory parameters were documented from the electronical medical record and correlated to nucleosome levels in the CKD5-HD cohort.

RESULTS

In comparison to healthy volunteers, the plasma from CKD5-HD patients exhibited markedly elevated nucleosomes (P<0.0001). Furthermore, nucleosome levels correlated with WBC count (P=0.025, R=0.243) and CRP (P=0.019, R=0.266) levels. No correlation was found between nucleosomes and the other parameters studied.

CONCLUSIONS

Our findings indicate extracellular nucleosomes are significantly elevated in CKD5-HD, suggesting increased cell death and/or inflammation. The observed correlations between nucleosomes and parameters of inflammation is suggestive of a complex, systemic inflammatory process underlying renal deterioration, consistent with the literature. Thus, nucleosomes may play a role in the pathogenesis and outcome of CKD5-HD.

Dunye Guanxinning Improves Acute Myocardial Ischemia-Reperfusion Injury by Inhibiting Neutrophil Infiltration and Caspase-1 Activity

Acute myocardial infarction is the most serious manifestation of cardiovascular disease, and it is a life-threatening condition. Dunye Guanxinning (DG) is a protective traditional Chinese patent herbal medicine with high clinical efficacy and suitable for the treatment of myocardial infarction. However, the mechanism through which it is beneficial is unclear. In this study, we hypothesized that DG improves acute myocardial ischemia-reperfusion injury by inhibiting neutrophil infiltration and caspase-1 activity. We found that DG administration decreased infarct size and cardiomyocyte apoptosis and improved left ventricular ejection fraction, fractional shortening, end-systolic volume index, end-systolic diameter, and carotid arterial blood flow output in rats. DG administration also improved hemorheological parameters, myocardial damage biomarkers, and oxidative stress indexes. The findings showed that DG administration inhibited neutrophil infiltration and reduced the serum interleukin-1 beta (IL-1β) level and myocardial IL-1β maturation. Moreover, DG administration inhibited caspase-1 activity and activated adenosine monophosphate-activated protein kinase (AMPK) phosphorylation in rat hearts. These results suggested that DG administration inhibits inflammasome activity and IL-1β release through the AMPK pathway. Our findings support the clinical efficacy of DG and partially reveal its mechanism, which is beneficial for understanding the therapeutic effects of this protective traditional Chinese patent drug.

Guidelines for experimental models of myocardial ischemia and infarction

Myocardial infarction is a prevalent major cardiovascular event that arises from myocardial ischemia with or without reperfusion, and basic and translational research is needed to better understand its underlying mechanisms and consequences for cardiac structure and function. Ischemia underlies a broad range of clinical scenarios ranging from angina to hibernation to permanent occlusion, and while reperfusion is mandatory for salvage from ischemic injury, reperfusion also inflicts injury on its own. In this consensus statement, we present recommendations for animal models of myocardial ischemia and infarction. With increasing awareness of the need for rigor and reproducibility in designing and performing scientific research to ensure validation of results, the goal of this review is to provide best practice information regarding myocardial ischemia-reperfusion and infarction models.

Listen to this article’s corresponding podcast at ajpheart.podbean.com/e/guidelines-for-experimental-models-of-myocardial-ischemia-and-infarction/.

Neutrophil extracellular traps are increased in patients with acute ischemic stroke: prognostic significance

Neutrophil extracellular traps (NETs) are networks of DNA, histones, and proteolytic enzymes produced by activated neutrophils through different mechanisms. NET formation is promoted by activated platelets and can in turn activate platelets, thus favoring thrombotic processes. NETs have been detected in venous and arterial thrombosis, but data in stroke are scarce. The aim of this study was to evaluate NETs in the plasma of patients with acute ischemic stroke and their potential association with baseline clinical characteristics, stroke severity, and one-year clinical outcomes. The study included 243 patients with acute ischemic stroke. Clinical and demographic data and scores of stroke severity (NIHSS and mRs) at onset and discharge were recorded. Markers of NETs (cell-free DNA, nucleosomes, and citrullinated histone 3 (citH3)), were determined in plasma. Patients were followed-up for 12 months after the ischemic event. NETs were significantly elevated in the plasma of patients with acute ischemic stroke when compared to healthy subjects. NETs were increased in patients who were over 65 years of age and in those with a history of atrial fibrillation (AF), cardioembolic stroke, high glucose levels, and severe stroke scores at admission and discharge. In multivariate analysis, elevated levels of citH3, the most specific marker of NETs, at onset were independently associated with AF and all-cause mortality at oneyear follow-up. NETs play a role in the pathophysiology of stroke and are associated with severity and mortality. In conclusion, citH3 may constitute a useful prognostic marker and therapeutic target in patients with acute stroke.

Proteomic footprint of myocardial ischemia/reperfusion injury: Longitudinal study of the at-risk and remote regions in the pig model

Reperfusion alters post-myocardial infarction (MI) healing; however, very few systematic studies report the early molecular changes following ischemia/reperfusion (I/R). Alterations in the remote myocardium have also been neglected, disregarding its contribution to post-MI heart failure (HF) development. This study characterizes protein dynamics and contractile abnormalities in the ischemic and remote myocardium during one week after MI. Closed-chest 40 min I/R was performed in 20 pigs sacrificed at 120 min, 24 hours, 4days, and 7days after reperfusion (n = 5 per group). Myocardial contractility was followed up by cardiac magnetic resonance (CMR) and tissue samples were analyzed by multiplexed quantitative proteomics. At early reperfusion (120 min), the ischemic area showed a coordinated upregulation of inflammatory processes, whereas interstitial proteins, angiogenesis and cardio-renal signaling processes increased at later reperfusion (day 4 and 7). Remote myocardium showed decreased contractility at 120 min- and 24 h-CMR accompanied by transient alterations in contractile and mitochondrial proteins. Subsequent recovery of regional contractility was associated with edema formation on CMR and increases in inflammation and wound healing proteins on post-MI day 7. Our results establish for the first time the altered protein signatures in the ischemic and remote myocardium early after I/R and might have implications for new therapeutic targets to improve early post-MI remodeling.

Neutrophil Extracellular Traps and Endothelial Dysfunction in Atherosclerosis and Thrombosis

Cardiovascular diseases are a leading cause of mortality and morbidity worldwide. Neutrophils are a component of the innate immune system which protect against pathogen invasion; however, the contribution of neutrophils to cardiovascular disease has been underestimated, despite infiltration of leukocyte subsets being a known driving force of atherosclerosis and thrombosis. In addition to their function as phagocytes, neutrophils can release their extracellular chromatin, nuclear protein, and serine proteases to form net-like fiber structures, termed neutrophil extracellular traps (NETs). NETs can entrap pathogens, induce endothelial activation, and trigger coagulation, and have been detected in atherosclerotic and thrombotic lesions in both humans and mice. Moreover, NETs can induce endothelial dysfunction and trigger proinflammatory immune responses. Overall, current data indicate that NETs are not only present in plaques and thrombi but also have causative roles in triggering formation of atherosclerotic plaques and venous thrombi. This review is focused on published findings regarding NET-associated endothelial dysfunction during atherosclerosis, atherothrombosis, and venous thrombosis pathogenesis. The NET structure is a novel discovery that will find its appropriate place in our new understanding of cardiovascular disease. In addition, NETs have high potential to be further explored toward much better treatment of atherosclerosis and venous thromboembolism in clinic.

The role of extracellular histone in organ injury

Histones are intra-nuclear cationic proteins that are present in all eukaryotic cells and are highly conserved across species. Within the nucleus, they provide structural stability to chromatin and regulate gene expression. Histone may be released into the extracellular space in three forms: freely, as a DNA-bound nucleosome or as part of neutrophil extracellular traps, and all three can be detected in serum after significant cellular death such as sepsis, trauma, ischaemia/reperfusion injury and autoimmune disease. Once in the extracellular space, histones act as damage-associated molecular pattern proteins, activating the immune system and causing further cytotoxicity. They interact with Toll-like receptors (TLRs), complement and the phospholipids of cell membranes inducing endothelial and epithelial cytotoxicity, TLR2/TLR4/TLR9 activation and pro-inflammatory cytokine/chemokine release via MyD88, NFκB and NLRP3 inflammasome-dependent pathways. Drugs that block the release of histone, neutralise circulating histone or block histone signal transduction provide significant protection from mortality in animal models of acute organ injury but warrant further research to inform future clinical applications.

Neutrophil Extracellular Traps in Atherosclerosis and Atherothrombosis

Neutrophil extracellular traps expelled from suicidal neutrophils comprise a complex structure of nuclear chromatin and proteins of nuclear, granular, and cytosolic origin. These net-like structures have also been detected in atherosclerotic lesions and arterial thrombi in humans and mice. Functionally, neutrophil extracellular traps have been shown to induce activation of endothelial cells, antigen-presenting cells, and platelets, resulting in a proinflammatory immune response. Overall, this suggests that they are not only present in plaques and thrombi but also they may play a causative role in triggering atherosclerotic plaque formation and arterial thrombosis. This review will focus on current findings of the involvement of neutrophil extracellular traps in atherogenesis and atherothrombosis.

SUV39H1 mediated SIRT1 trans-repression contributes to cardiac ischemia-reperfusion injury

Ischemic reperfusion (I/R) contributes to deleterious cardiac remodeling and heart failure. The deacetylase SIRT1 has been shown to protect the heart from I/R injury. We examined the mechanism whereby I/R injury represses SIRT1 transcription in the myocardium. There was accumulation of trimethylated histone H3K9 on the proximal SIRT1 promoter in the myocardium in mice following I/R injury and in cultured cardiomyocytes exposed to hypoxia-reoxygenation (H/R). In accordance, the H3K9 trimethyltransferase SUV39H1 bound to the SIRT1 promoter and repressed SIRT1 transcription. SUV39H1 expression was up-regulated in the myocardium in mice following I/R insults and in H/R-treated cardiomyocytes paralleling SIRT1 down-regulation. Silencing SUV39H1 expression or suppression of SUV39H1 activity erased H3K9Me3 from the SIRT1 promoter and normalized SIRT1 levels in cardiomyocytes. Meanwhile, SUV39H1 deficiency or inhibition attenuated I/R-induced infarction and improved heart function in mice likely through influencing ROS levels in a SIRT1-dependent manner. Therefore, our data uncover a novel mechanism for SIRT1 trans-repression during cardiac I/R injury and present SUV39H1 as a druggable target for the development of therapeutic strategies against ischemic heart disease.

Theranostic Nucleic Acid Binding Nanoprobe Exerts Anti-inflammatory and Cytoprotective Effects in Ischemic Injury

Extracellular nucleic acids are proinflammatory molecules that have been implicated in a diverse range of diseases. We report here the development of a multivalent nucleic acid scavenging nanoprobe, where the fluorochrome thiazole orange (TO) is conjugated to a polymeric 40 kDa dextran carrier. Dextran-TO (Dex-TO) has nanomolar affinity for mammalian and bacterial nucleic acids and attenuates the production of inflammatory cytokines from activated macrophages exposed to DNA and RNA. Mice with myocardial ischemia reperfusion that were treated with Dex-TO showed a decrease in myocardial macrophage infiltration at 24 hours (p<0.05) and a decrease in infarct size (18% ± 9%, p<0.01) on day 7. Dex-TO allows sites of injury to be identified with fluorescence imaging, while simultaneously exerting an anti-inflammatory and cytoprotective effect. Dex-TO could be of significant diagnostic and therapeutic (theranostic) utility in a broad range of conditions including ischemia, trauma, burns, sepsis and autoimmune disease.

DNase-targeted natural product screening based on a sensitive and selective DNase I detecting system

As a widely used deoxyribonuclease, DNase I is involved in many physiological processes including tumor cell proliferation, metastasis and apoptosis.

From basic mechanisms to clinical applications in heart protection, new players in cardiovascular diseases and cardiac theranostics: meeting report from the third international symposium on "New frontiers in cardiovascular research"

In this meeting report, particularly addressing the topic of protection of the cardiovascular system from ischemia/reperfusion injury, highlights are presented that relate to conditioning strategies of the heart with respect to molecular mechanisms and outcome in patients' cohorts, the influence of co-morbidities and medications, as well as the contribution of innate immune reactions in cardioprotection. Moreover, developmental or systems biology approaches bear great potential in systematically uncovering unexpected components involved in ischemia-reperfusion injury or heart regeneration. Based on the characterization of particular platelet integrins, mitochondrial redox-linked proteins, or lipid-diol compounds in cardiovascular diseases, their targeting by newly developed theranostics and technologies opens new avenues for diagnosis and therapy of myocardial infarction to improve the patients' outcome.