The role of extracellular histone in organ injury

Quercetin inhibits platelet activation and ER-stress mediated autophagy in response to extracellular histone

BACKGROUND

Cellular histones are DNA-binding nuclear proteins involved in chromatin remodelling and regulation of gene expression. However, extracellular histones act as damage-associated molecular patterns (DAMPs) and contribute to multiorgan damage in conditions with sepsis and diseases with acute critical illnesses. Alongside, histones are associated with thrombocytopenia due to dysfunctional platelets that regulate hemostasis and thrombosis. There is no drug available to prevent histone-induced platelet toxicity. Therefore, we for the first time examined quercetin (QUE) as a novel therapeutic to protect histone-induced platelet toxicity.

PURPOSE

To delineate how histones induce platelet toxicity and investigate the protective efficacy of quercetin (QUE), a natural dietary phytochemical.

STUDY DESIGN/METHOD

Histone-treated platelets were evaluated for platelet aggregation/activation markers, various autophagy-related signaling proteins, and cytotoxicity in vitro. For the inhibition study, QUE and other standard inhibitors were pre-treated before stimulation with histones. Further, we injected histones into mice in the presence or absence of QUE and evaluated the tail bleeding, lung toxicity, and circulatory platelet stress markers. Additionally, QUE-treated mice were challenged for histone-primed Collagen-epinephrine-induced pulmonary thromboembolism.

RESULT

Extracellular histones induce platelet activation and aggregation by interacting with sialic acid in TLR1/2 or TLR4. Also, we have demonstrated for the first time that histones induce ER stress-mediated autophagy in platelets. QUE inhibited histone-induced platelet activation, aggregation, and ER-stress-mediated autophagy in response to histone treatment. Ex vivo experiments indicate that oral administration of QUE can safeguard platelets while concurrently mitigating their response to histone stimulation. In addition, quercetin increased the survival rates of histone-primed, collagen-epinephrine-induced acute pulmonary thromboembolism in mice.

CONCLUSION

In summary, this study demonstrated the beneficial effect of QUE in protecting platelets with possible implications for addressing histone-accelerated pathologies.

Calycosin extracted from Astragali Radix reduces NETs formation to improve renal fibrosis via TLR4/NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Astragali Radix (A. Radix) is the dry root of the leguminous plants Astragalus membranaceus (Fisch) Beg. var. mongholicus (Beg) Hsiao, and Astragalus membranaceus (Fisch) Bge., being used as a medicinal and edible resource. AR is used in traditional Chinese medicine prescriptions to treat chronic nephritis. Calycosin (CA), the primary active compound derived from Astragali Radix, shows significant antifibrotic effects in multiple organs, but the anti-renal fibrosis effect of CA is rarely reported, and the associated mechanism of action is still need to be elucidated.

AIM OF THE STUDY

The objective of this study was to investigate the protective effects of CA on the kidney against renal fibrosis and the underlying molecular mechanisms. Evaluation of the effects of CA on renal fibrosis using unilateral ureteral obstruction (UUO) mice and transforming growth factor β1 (TGF β1)-induced cell fibrosis. The mechanism of action supporting the investigated anti-renal fibrosis effects were studied by a series of biochemical experiments.

RESULTS

Our research demonstrated that CA reduced kidney cell fibrosis in mice with UUO and in TGF-β1-stimulated NRK-52E cells. Additionally, CA mitigated renal fibrosis via toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) and had a synergistic effect with resatorvid (TAK-242). Our findings revealed an unobserved impact of CA in inhibiting neutrophil extracellular traps (NETs) formation in UUO mice and neutrophils activated by phorbol 12-myristate 13-acetate.

CONCLUSIONS

Our findings revealed that calycosin reduces NETs production to alleviate renal fibrosis via TLR4 and NF-κB, supporting its potential as a strategy for treating renal fibrosis.

RNA aptamer-mediated RNA nanotechnology for potential treatment of cardiopulmonary diseases

Ribonucleic acid (RNA) aptamers are single-stranded RNAs that bind to target proteins or other molecules with high specificity and affinity, modulating biological functions through distinct mechanisms. These aptamers can act n as antagonists to block pathological interactions, agonists to activate signaling pathways, or delivery vehicles for therapeutic cargos such as siRNAs and miRNAs. The advances in RNA nanotechnology further enhances the versatility of RNA aptamers, offering scalable platforms for engineering. In this review, we have summarized recent developments in RNA aptamer-mediated RNA nanotechnology and provide an overview of its potential in treating cardiovascular and respiratory disorders, including atherosclerosis, acute coronary syndromes, heart failure, lung cancer, pulmonary hypertension, asthma, chronic obstructive pulmonary disease (COPD), acute lung injury, viral respiratory infections, and pulmonary fibrosis. By integrating aptamer technologies with innovative delivery systems, RNA aptamers hold the potential to revolutionize the treatment landscape for cardiopulmonary diseases.

Oxidative modification of extracellular histones by hypochlorous acid modulates their ability to induce β-cell dysfunction

Histones are nuclear proteins that play a key role in chromatin assembly and regulation of gene expression by their ability to bind to DNA. Histones can also be released from cells owing to necrosis or extracellular trap release from neutrophils (NETs) and other immune cells. The presence of histones in the extracellular environment has implications for many pathologies, including diabetes mellitus, owing to the cytotoxic nature of these proteins, and their ability to promote inflammation. NETs also contain myeloperoxidase, a defensive enzyme that produces hypochlorous acid (HOCl), to kill pathogens, but also readily damages host proteins. In this study, we examined the reactivity of histones with and without HOCl modification, with a pancreatic β-cell model. Exposure of β-cells to histones resulted in a loss of metabolic activity and cell death by a combination of apoptosis and necrosis. This toxicity was increased on pretreatment of the β-cells with tumour necrosis factor α and interleukin 1β. Histones upregulated endoplasmic reticulum (ER) stress genes, including the pro-apoptotic transcription factor CHOP. There was also evidence for alterations to the cellular redox environment and upregulation of antioxidant gene expression. However, downregulation of insulin-associated genes and insulin was observed. Interestingly, modification of the histones with HOCl reduced their toxicity and altered the patterns of gene expression observed, and a further decrease in the expression of insulin-associated genes was observed. These findings could be relevant to the development of Type 2 diabetes, where low-grade inflammation favours NET release, resulting in elevated histones in the circulation.

In Silico Discovery of Antigenic-Secreted Proteins to Diagnostic Human Toxocariasis

BACKGROUND

Human toxocariasis is a helminthic zoonosis caused by infection of Toxocara canis or T. cati. Humans can be infected by through ingestion of embryonated eggs from contaminated water, food or soil. Diagnosis is challenging, immunodiagnosis tests are commonly implemented with major pitfalls in the cross-reactivity with other pathogens, particularly in endemic areas.

METHODS

With the aim of identify species-specific genes encoding for highly expressed antigenic proteins, a list of parasites that may infect humans and that might present similar clinical symptoms to T. canis infections was built. Only organisms whose genomes were completely sequenced and the proteome predicted were included. First, orthologous proteins were detected and the subcellular localization of T. canis proteins was predicted. In order to identify differentially expressed genes encoding proteins in larvae L3, pair-wise comparisons among transcriptomes from body parts and genders were performed. Finally, all secreted proteins classified as species-specific of T. canis, whose genes were upregulated in larvae L3 were included in an antigenic prediction.

RESULTS

Twenty-eight parasites were included in the analyses, proteins of T. canis were clustered in 11,399 groups, however, 279 were species-specific groups which represent 816 proteins. Three hundred and twenty-two proteins were predicted to be secreted and upregulated in larvae L3, however, after filtering these proteins by their orthology inference, only three proteins met all the features included in this study (species-specific, upregulated, secreted, and antigenic potential). To conclude, our strategy in the study is a rational approach for discovering antigenic proteins to be used in diagnosis.

"The NET effect": Neutrophil extracellular traps-a potential key component of the dysregulated host immune response in sepsis

Neutrophils release neutrophil extracellular traps (NETs) as part of a healthy host immune response. NETs physically trap and kill pathogens as well as activating and facilitating crosstalk between immune cells and complement. Excessive or inadequately resolved NETs are implicated in the underlying pathophysiology of sepsis and other inflammatory diseases, including amplification of the inflammatory response and inducing thrombotic complications. Here, we review the growing evidence implicating neutrophils and NETs as central players in the dysregulated host immune response. We discuss potential strategies for modifying NETs to improve patient outcomes and the need for careful patient selection.

Extracellular Histones as Exosome Membrane Proteins Regulated by Cell Stress

Histones are conserved nuclear proteins that function as part of the nucleosome in the regulation of chromatin structure and gene expression. Interestingly, extracellular histones populate biofluids from healthy individuals, and when elevated, may contribute to various acute and chronic diseases. It is generally assumed that most extracellular histones exist as nucleosomes, as components of extracellular chromatin. We analysed cell culture models under normal and stressed conditions to identify pathways of histone secretion. We report that core and linker histones localize to extracellular vesicles (EVs) and are secreted via the multivesicular body/exosome pathway. Upregulation of EV histone secretion occurs in response to cellular stress, with enhanced vesicle secretion and a shift towards a population of smaller EVs. Most histones were membrane associated with the outer surface of EVs. Degradation of EV-DNA did not impact significantly on EV-histone association. Individual histones  and histone octamers bound strongly to liposomes and EVs, but nucleosomes did not, showing histones do not require DNA for EV binding. Histones colocalized to tetraspanin positive EVs but using genetic or pharmacological intervention, we found that all known pathways of exosome biogenesis acted positively on histone secretion. Inhibition of autophagy and lysosomal degradation had a strong positive effect on EV histone release. Unexpectedly, EV-associated histones lacked the extensive post-translational modification of their nuclear counterparts, suggesting loss of PTMs may be involved in their trafficking or secretion. Our data does not support a significant role for EV-histones existing as nucleosomes. We show for the first time that histones are secreted from cells as membrane proteins via EVs/exosomes. This fundamental discovery provides support for further investigation of the biological activity of exosome associated histones and their role in disease.

Vitamin D can mitigate sepsis-associated neurodegeneration by inhibiting exogenous histone-induced pyroptosis and ferroptosis: Implications for brain protection and cognitive preservation

BACKGROUND

Sepsis-induced neurodegeneration and cognitive dysfunction remain critical challenges worldwide. Vitamin D was reported to reduce neuronal injury and neurotoxicity and its deficiency was associated with neurocognitive disorders. This study investigates the mechanisms by which vitamin D exerts neuroprotective potential against damage-associated molecular patterns (DAMPs), specifically extracellular histones, in sepsis-related brain dysfunction.

METHODS

The cultured mouse hippocampal neuronal HT22 cells were exposed to 20 µg/ml exogenous histone for 24 h to induce pyroptosis and ferroptosis in the presence or absence of the active form of vitamin D, calcitriol (1 nM). A cecal ligation and puncture mouse sepsis model was used to evaluate histone release and pyroptosis/ferroptosis biomarkers in the brain together with neurobehavioral performance with or without calcitriol treatment (1 µg/kg, i.p. injection) at 24 h or 1 week after sepsis onset.

RESULTS

In vitro, histone exposure triggered both pyroptosis and ferroptosis in neuronal cells, which was significantly suppressed by calcitriol treatment with the reduced expression of caspase-1 by 38 %, GSDMD by 30 %, ACSL4 by 33 %, and the increased expression of GPX4 by 35 % (n = 6, P < 0.05). Similarly, in vivo, calcitriol treatment inhibited both neuronal pyroptosis and ferroptosis by reducing expression of pyroptosis marker, GSDMD/NeuN (11.6 ± 1.2 % vs. 19.4 ± 1.1 %) and increasing expression of ferroptosis marker, GPX4/NeuN (21.4 ± 1.7 % vs. 13.5 ± 1.1 %), in the brain of septic mice (n = 6, P < 0.01). In addition, calcitriol increased survival rate (72 % vs. 41 %) and ameliorated cognitive dysfunction of septic mice (n = 8-13, P < 0.05).

CONCLUSIONS

This study demonstrates that vitamin D exerts a neuroprotective effect against sepsis by attenuating histone-induced pyroptosis and ferroptosis. These findings highlight the potential therapeutic role of vitamin D supplementation in mitigating brain dysfunction associated with sepsis which needs for further investigation.

Fantastic proteins and where to find them - histones, in the nucleus and beyond

Animal genomes are packaged into chromatin, a highly dynamic macromolecular structure of DNA and histone proteins organised into nucleosomes. This accommodates packaging of lengthy genomic sequences within the physical confines of the nucleus while also enabling precise regulation of access to genetic information. However, histones existed before chromatin and have lesser-known functions beyond genome regulation. Most notably, histones are potent antimicrobial agents, and the release of chromatin to the extracellular space is a defence mechanism nearly as ancient and widespread as chromatin itself. Histone sequences have changed very little throughout evolution, suggesting the possibility that some of their 'non-canonical' functions are at play in parallel or in concert with their genome regulatory functions. In this Review, we take an evolutionary perspective of histone, nuclear chromatin and extracellular chromatin biology and describe the known extranuclear and extracellular functions of histones. We detail molecular mechanisms of chromatin release and extracellular chromatin sensing, and we discuss their roles in physiology and disease. Finally, we present evidence and give a perspective on the potential of extracellular histones to act as bioactive, cell modulatory factors.

Therapeutic potential of DNases in immunothrombosis: promising succor or uncertain future?

Sepsis, a life-threatening condition characterized by systemic inflammation and multiorgan dysfunction, is closely associated with the excessive formation of neutrophil extracellular traps (NETs) and the release of cell-free DNA. Both play a central role in sepsis progression, acting as major contributors to immunothrombosis and associated complications. Endogenous DNases play a pivotal role in degrading NETs and cell-free DNA, yet their activity is often dysregulated during thrombotic disease. Although exogenous DNase1 administration has shown potential in reducing NET burden and mitigating the detrimental effects of immunothrombosis, its therapeutic efficacy upon intravenous administration remains uncertain. The development of engineered DNase formulations and combination therapies may further enhance its therapeutic effectiveness by modifying its pharmacodynamic properties and avoiding the adverse effects associated with NET degradation, respectively. Although NETs are well-established targets of DNase1, it remains uncertain whether the positive effects of DNase1 on immunothrombosis are exclusively related to it's targeting of NETs or if other components contributing to immunothrombosis are also affected. This review examines the endogenous regulation of NETs in circulation and the therapeutic potential of DNases in immunothrombosis, underscoring the necessity for further investigation to optimize their clinical application.

Entamoeba histolytica-induced NETs are highly cytotoxic on hepatic and colonic cells due to serine proteases and myeloperoxidase activities

During intestinal and liver invasion by the protozoan parasite Entamoeba histolytica, extensive tissue destruction linked to large neutrophil infiltrates is observed. It has been proposed that microbicidal components of neutrophils are responsible for the damage, however, the mechanism by which they are released and act in the extracellular space remains unknown. In previous studies, we have shown that E. histolytica trophozoites induce NET formation, leading to the release of neutrophil granule content into extruded DNA. In this work, we evaluate the possible participation of NETs in the development of amoeba-associated pathology and analyze the contribution of anti-microbial components of the associated granules. E. histolytica-induced NETs were isolated and their effect on the viability and integrity of HCT 116 colonic and Hep G2 liver cultures were evaluated. The results showed that simple incubation of cell monolayers with purified NETs for 24 h resulted in cell detachment and death in a dose-dependent manner. The effect was thermolabile and correlated with the amount of DNA and protein present in NETs. Pretreatment of NETs with specific inhibitors of some microbicidal components suggested that serine proteases, are mostly responsible for the damage caused by NETs on HCT 116 cells, while the MPO activity was the most related to Hep G2 cells damage. Our study also points to a very important role of DNA as a scaffold for the activity of these proteins. We show evidence of the development of NETs in amoebic liver abscesses in hamsters as a preamble to evaluate their participation in tissue damage. In conclusion, these studies demonstrate that amoebic-induced NETs have potent cytotoxic effects on target cells and, therefore, may be responsible for the intense damage associated with tissue invasion by this parasite.

Ionotropic purinergic receptor 7 (P2X7) channel structure and pharmacology provides insight regarding non-nucleotide agonism

P2X7 is a member of the Ionotropic Purinergic Receptor (P2X) family. The P2X family of receptors is composed of seven (P2X1-7), ligand-gated, nonselective cation channels. Changes in P2X expression have been reported in multiple disease models. P2Xs have large complex extracellular domains that function as receptors for a variety of ligands, including endogenous and synthetic agonists and antagonists. ATP is the canonical agonist. ATP affinity ranges from nanomolar to micromolar for most P2XRs, but P2X7 has uniquely poor ATP affinity. In many physiological settings, it may be difficult to achieve the millimolar extracellular ATP concentrations needed for P2X7 channel activation; however, channel function is implicated in pain sensation, immune cell function, cardiovascular disease, cancer, and osteoporosis. Multiple high-resolution P2X7 structures have been solved in apo-, ATP-, and antagonist-bound states. P2X7 structural data reveal distinct allosteric and orthosteric antagonist-binding sites. Both allosteric and orthosteric P2X7 antagonists are well documented to inhibit ATP-evoked channel current. However, a growing body of evidence supports P2X7 activation by non-nucleotide agonists, including extracellular histone proteins and human cathelicidin-derived peptides (LL-37). Interestingly, P2X7 non-nucleotide agonism is not inhibited by allosteric antagonists, but is inhibited by orthosteric antagonists. Herein, we review P2X7 function with a focus on the efficacy of available pharmacology on P2X7 channel current activation by non-nucleotide agonists in effort to understand agonist/antagonist efficacy, and consider the impact of these data on the current understanding of P2X7 in physiology and disease given these limitations of P2X7-selective antagonists and incomplete knockout mouse models.

The impact of circulating nucleosomes on inflammation in acute lung injury

Extracellular histones are released in two major forms: free histones and nucleosomes (DNA-bound histones). However, little distinction has been made between these two forms of circulating extracellular histones. Our study detected increased circulating nucleosomes in acute lung injury patients. Further, our group identified nucleosomes as the leading form of extracellular histones compared to free histones in the plasma of COVID-19 patients, underscoring the necessity to reassess the forms of circulating histones and nucleosome contributions to immunopathology. Functionally, nucleosomes activated macrophages and induced inflammation in different organs. Mechanistically, we observed nucleosomes activating the NF-κB signaling, while inhibition of NF-κB by sulfasalazine attenuated nucleosome-induced macrophage activation. Taken together, our study indicates that extracellular histones are predominantly released as nucleosomes, playing a critical role in the inflammation of the lungs and other organs.

Protein biomarkers in assessing kidney quality before transplantation‑current status and future perspectives (Review)

To meet the demand for kidney transplants (KTx), organs are frequently retrieved not only from standard criteria donors (SCD; a donor who is aged <50 years and suffered brain death from any number of causes, such as traumatic injuries or a stroke) but also from expanded criteria donors (any donor aged >60 years or donors aged >50 years with two of the following: A history of high blood pressure, a creatinine serum level ≥1.5 mg/dl or death resulting from a stroke). This comes at the cost of a higher risk of primary non‑function (the permanent hyperkalemia, hyperuremia and fluid overload that result in the need for continuous dialysis after KTx), delayed graft function (the need for dialysis session at least once during the first week after KTx), earlier graft loss and urinary complications (vesico‑ureteral reflux, obstruction of the vesico‑ureteral anastomosis, urine leakage). At present, there are no commercially available diagnostic tools for assessing kidney quality prior to KTx. Currently available predictive models based on clinical data, such as the Kidney Donor Profile Index, are insufficient. One promising option is the application of perfusion solutions for protein biomarkers of kidney quality and predictors of short‑ and long‑term outcomes. However, to date, protein markers that can be detected with ELISA, western blotting and cytotoxic assays have not been identified to be a beneficial predictors of kidney quality. These include lactate dehydrogenases, glutathione S‑transferases, fatty acid binding proteins, extracellular histones, IL‑18, neutrophil gelatinase‑associated lipocalin, MMPs and kidney injury molecule‑1. However, novel methods, including liquid chromatography‑mass spectrometry (LC‑MS) and microarrays, allow the analysis of all renal proteins suspended/dissolved in the acellular preservation solution used for kidney storage before KTx (including hypothermic machine perfusion as one of kidney storage methods) e.g. Belzer University of Wisconsin. Recent proteomic studies utilizing LC‑MS have identified complement pathway elements (C3, C1QB, C4BPA, C1S, C1R and C1RL), desmoplakin, blood coagulation pathway elements and immunoglobulin heavy variable 2‑26 to be novel predictors of kidney quality before transplantation. This was because they were found to correlate with estimated glomerular filtration rate at 3 and 12 months after kidney transplantation. However, further proteomic studies focusing on distinct markers obtained from hypothermic and normothermic machine perfusion are needed to confirm their predictive value and to improve kidney storage methods. Therefore, the present literature review from PubMed, Scopus, Embase and Web of Science was performed with the aims of summarizing the current knowledge on the most frequently studied single protein biomarkers. In addition, novel analytical methods and insights into organ injury during preservation were documented, where future directions in assessing organ quality before kidney transplantation were also discussed.

Unraveling the intricacies of neutrophil extracellular traps in inflammatory bowel disease: Pathways, biomarkers, and promising therapies

The development of inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, involves various factors and is characterized by persistent inflammation of the mucosal lining. However, the role of neutrophils in this process remains controversial. Neutrophil extracellular traps (NETs), which consist of chromatin, antimicrobial proteins, and oxidative enzymes, are released by neutrophils to trap pathogens. They are also involved in various immune-mediated and vascular diseases. NETs act as a vital defense mechanisms at the gut-mucosal interface and are frequently exposed to bacterial, viral, and fungal threats. However, they can also contribute to inflammation and worsen imbalances in the gut bacteria. Recent studies have suggested that NETs have a significant impact on IBD development. Previous studies have shown increased levels of NETs in tissue and blood samples from patients with IBD, as well as in experimental colitis mouse models. Therefore, this review discusses how NETs are formed and their role in the pathophysiology of IBD. It discusses how NETs may lead to tissue damage and contribute to IBD-associated complications. Moreover, non-invasive biomarkers are needed to replace invasive procedures such as endoscopy to better evaluate the disease status. Given the crucial role of NETs in IBD progression, this review focuses on potential NET biomarkers that can help predict the evolution of IBD. Furthermore, this review identifies potential therapeutic targets for regulating NET production, which could expand the range of available treatment options for IBD.

Tracing troubles: Unveiling the hidden impact of inorganic contamination on juvenile green sea turtle

Human activities and climate change have negatively affected the world's oceans, leading to a decline of 30 to 60 % in coastal ecosystems' biodiversity and habitats. The projected increase in the human population to 9.7 billion by 2050 raises concerns about the sustainability of marine ecosystem conservation and exploitation. Marine turtles, as sentinel species, accumulate contaminants, including trace elements, due to their extensive migration and long-life span. However, there is a lack of data on the degree of contamination and their effects on marine turtles' health. This study focuses on assessing in-situ inorganic contamination in juvenile green sea turtles from La Réunion Island and its short-term impact on individual health, using conventional biomarkers and proteomics. The goals include examining contamination patterns in different tissues and identifying potential new biomarkers for long-term monitoring and conservation efforts. The study identified differential metal contamination between blood and scute samples, which could help illuminate temporal exposure to trace elements in turtle individuals. We also found that some conventional biomarkers were related to trace element exposure, while the proteome responded differently to various contaminant mixtures. Immune processes, cellular organization, and metabolism were impacted, indicating that contaminant mixtures in the wild would have an effect on turtle's health. Fifteen biomarker candidates associated with strong molecular responses of sea turtle to trace element contamination are proposed for future long-term monitoring. The findings emphasize the importance of using proteomic approaches to detect subtle physiological responses to contaminants in the wild and support the need for non-targeted analysis of trace elements in the biomonitoring of sea turtle health.

Identification and Analysis of Potential Biomarkers Associated with Neutrophil Extracellular Traps in Cervicitis

Early diagnosis of cervicitis is important. Previous studies have found that neutrophil extracellular traps (NETs) play pro-inflammatory and anti-inflammatory roles in many diseases, suggesting that they may be involved in the inflammation of the uterine cervix and NETs-related genes may serve as biomarkers of cervicitis. However, what NETs-related genes are associated with cervicitis remains to be determined. Transcriptome analysis was performed using samples of exfoliated cervical cells from 15 patients with cervicitis and 15 patients without cervicitis as the control group. First, the intersection of differentially expressed genes (DEGs) and neutrophil extracellular trap-related genes (NETRGs) were taken to obtain genes, followed by functional enrichment analysis. We obtained hub genes through two machine learning algorithms. We then performed Artificial Neural Network (ANN) and nomogram construction, confusion matrix, receiver operating characteristic (ROC), gene set enrichment analysis (GSEA), and immune cell infiltration analysis. Moreover, we constructed ceRNA network, mRNA-transcription factor (TF) network, and hub genes-drug network. We obtained 19 intersecting genes by intersecting 1398 DEGs and 136 NETRGs. 5 hub genes were obtained through 2 machine learning algorithms, namely PKM, ATG7, CTSG, RIPK3, and ENO1. Confusion matrix and ROC curve evaluation ANN model showed high accuracy and stability. A nomogram containing the 5 hub genes was established to assess the disease rate in patients. The correlation analysis revealed that the expression of ATG7 was synergistic with RIPK3. The GSEA showed that most of the hub genes were related to ECM receptor interactions. It was predicted that the ceRNA network contained 2 hub genes, 3 targeted miRNAs, and 27 targeted lnRNAs, and that 5 mRNAs were regulated by 28 TFs. In addition, 36 small molecule drugs that target hub genes may improve the treatment of cervicitis. In this study, five hub genes (PKM, ATG7, CTSG, RIPK3, ENO1) provided new directions for the diagnosis and treatment of patients with cervicitis.

Association of corticosteroid therapy with reduced acute kidney injury and lower NET markers in severe COVID-19: an observational study

BACKGROUND

Acute kidney injury (AKI) is common in critical cases of coronavirus disease 2019 (COVID-19) and associated with worse outcome. Dysregulated neutrophil extracellular trap (NET) formation is one of several suggested pathophysiological mechanisms involved in the development of COVID-19 associated AKI. The corticosteroid dexamethasone was implemented as a standard treatment for severe COVID-19 as of June 2020. A sub-analysis of a prospective observational single center study was performed to evaluate the effect of corticosteroid treatment on AKI development and NET markers in critical cases of COVID-19.

RESULTS

Two hundred and ten adult patients admitted to intensive care at a tertiary level hospital due to respiratory failure or shock secondary to SARS-CoV-2-infection between March 13th 2020 and January 14th 2021 were included in the study. Ninety-seven of those did not receive corticosteroids. One hundred and thirteen patients were treated with corticosteroids [dexamethasone (n = 98) or equivalent treatment (n = 15)], but the incidence of AKI was assessed only in patients that received corticosteroids before any registered renal dysfunction (n = 63). Corticosteroids were associated with a lower incidence of AKI (19% vs 55.8%, p < 0.001). Fewer patients demonstrated detectable concentrations of extracellular histones in plasma when treated with corticosteroids (8.7% vs 43.1%; p < 0.001). Extracellular histones and in particular non-proteolyzed histones were observed more frequently with increasing AKI severity (p < 0.001). MPO-DNA was found in lower concentrations in patients that received corticosteroids before established renal dysfunction (p = 0.03) and was found in higher concentrations in patients with AKI stage 3 (p = 0.03). Corticosteroids did not ameliorate established AKI during the first week of treatment.

CONCLUSION

Corticosteroid treatment in severe COVID-19 is associated with a lower incidence of AKI and reduced concentrations of NET markers in plasma.

Radix Sophorae Flavescentis of Sophora flavescens Aiton inhibits LPS-induced macrophage pro-inflammatory response via regulating CFHR2 expression

ETHNOPHARMACOLOGICAL RELEVANCE

Long-term chronic inflammation often leads to chronic diseases. Although Sophora flavescens has been shown to have anti-inflammatory properties, its detailed molecular mechanism is still unknown.

AIM OF STUDY

This study investigated the effect of Radix Sophorae Flavescentis on the LPS-induced inflammatory response in macrophages.

MATERIALS AND METHODS

LPS was used to induce the peritoneal macrophages to simulate the inflammatory environment in vitro. Different concentrations of Radix Sophorae Flavescentis-containing (medicated) serum were used for intervention. The peritoneal macrophages were identified by using hematoxylin-eosin and immunofluorescence staining. ELISA was used to measure the TNF-α and IL-6 expression to determine the concentration of LPS. ELISA and Western blot (WB) were used to detect the PGE2 and CFHR2 expression in each group, respectively. The lentiviral vector for interference and overexpression of the CFHR2 gene was constructed, packaged, and transfected into LPS-induced macrophages. The transfection efficiency was verified by WB. Then, ELISA was used to detect the TNF-α, PGE2, and IL-6 expression. WB was used to detect the CFHR2, iNOS, COX-2, TLR2, TLR4, IFN-γ, STAT1, and p-STAT1 expression.

RESULTS

The primary isolated cells were identified as macrophages. The LPS-treated macrophages exhibited significantly higher expression of PGE2 and CFHR2, and the inflammatory factors TNF-α and IL-6, as well as iNOS, COX-2, TLR2, TLR4, IFN-γ, STAT1, and p-STAT1 expression compared with the control group (P < 0.05). The TNF-α, PGE2, and IL-6 levels, as well as CFHR2, iNOS, COX-2, TLR2, TLR4, IFN-γ, STAT1, and p-STAT1 expression were considerably lower in the LPS-induced+10% medicated-serum group, LPS-induced+20% medicated-serum group, and shCFHR interference group compared with the LPS group (P < 0.05).

CONCLUSION

Radix Sophorae Flavescentis might mediate CFHR2 expression and play an important role in inhibiting the LPS-induced pro-inflammatory response of macrophages. Radix Sophorae Flavescentis could be a potential treatment for LPS-induced related inflammatory diseases.

CXCR1 and CXCR2 are potential neutrophil extracellular trap-related treatment targets in ulcerative colitis: insights from Mendelian randomization, colocalization and transcriptomic analysis

Objectives

There is already substantial evidence indicating that neutrophil extracellular trap (NET) formation contributes to the inflammatory cascade in ulcerative colitis (UC). However, the precise regulatory mechanisms governing this process remain elusive. This study aimed to determine the role of NET-related genes in UC and reveal possible mechanisms.

Methods

Employing a two-sample MR methodology, we investigated the correlations between NET-associated genes (NRGs) and UC with summary data derived from a genome-wide association study (12,366 cases vs. 33,609 controls) and FinnGen (8,279 cases vs. 261,098 controls). The main analysis employed the inverse variance weighted method, supplemented by the MR-Egger method and weighted median method. Sensitivity analysis was conducted to rule out the interference of heterogeneity and pleiotropy among utilized instrument variables. The colocalization analysis was used to determine whether the identified NRGs and UC shared casual variants. Cross-tissue expression analysis was performed to characterize the expression patterns of target NRGs, while multi-gene correlation analysis and GSEA analysis were conducted to explore the mechanisms by which target NRGs promote UC and NET formation. Immunohistochemistry was used to validate the protein expression of target NRGs in the colon tissue of UC patients.

Results

After the validation of two datasets, seven NRGs were associated with the risk of UC. The higher expression of ITGB2 was associated with increased UC risk, while the expression of CXCR1, CXCR2, IRAK4, MAPK3, SIGLEC14, and SLC22A4 were inversely associated with UC risk. Colocalization analysis supported the correlation between CXCR1/2 and UC risk. Expression analysis indicated that CXCR1/2 were down-regulated in peripheral blood, but up-regulated in colon tissue. GSEA analysis and correlation analysis indicated that CXCR1/2 promoted UC and NET formation through neutrophil chemotaxis and PAD4-mediated pathways, separately. Immunohistochemical results confirmed the high expression of CXCR1/2 in colon tissues of UC patients.

Conclusions

Our study identified CXCR1/2 as candidate targets in UC among all NRGs through multi-method argumentation, providing new insights of the regulation mechanisms of NET formation in the pathogenesis of UC.

Selective Clearance of Circulating Histones Based on Dodecapeptide-Grafted Copolymer Material for Sepsis Blood Purification

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. Research indicates that circulating histones, as pathogenic factors, may represent a therapeutic target for sepsis. However, effectively clearing circulating histones poses a challenge due to their structural similarity to normal blood proteins, their low abundance in the bloodstream, and serious interference from other blood biomacromolecules. Here we design a dodecapeptide-based functional polymer that can selectively adsorb circulating histones from the blood. The peptide, named P1 (HNHHQLALVESY), was discovered through phage display screening and demonstrated a strong affinity for circulating histones while exhibiting negligible affinities for common proteins in the blood, such as human serum albumin (HSA), immunoglobulin G (IgG), and transferrin (TRF). Furthermore, the P1 peptide was incorporated into a functional polymer design, poly(PEGMA-co-P1), which was immobilized onto a silica gel surface through reversible addition-fragmentation chain transfer polymerization. The resulting material was characterized using solid nuclear magnetic resonance, thermogravimetric analysis, and X-ray photoelectron spectroscopy. This material demonstrated the ability to selectively and efficiently capture circulating histones from both model solutions and whole blood samples while also exhibiting satisfactory blood compatibility, good antifouling properties, and resistance to interference. Satisfactory binding affinity and efficient capture capacity toward histone were also observed for the other screened peptide P2 (QMSMDLFGSNFV)-grafted polymer, validating phage display as a reliable ligand screening strategy. These findings present an approach for the specific clearance of circulating histones and hold promise for future clinical applications in blood purification toward sepsis.

Histon activities in the extracellular environment: regulation and prothrombotic implications

PURPOSE OF REVIEW

Thromboembolic complications are a major contributor to global mortality. The relationship between inflammation and coagulation pathways has become an emerging research topic where the role of the innate immune response, and specifically neutrophils in "immunothrombosis" are receiving much attention. This review aims to dissect the intricate interplay between histones (from neutrophils or cellular damage) and the haemostatic pathway, and to explore mechanisms that may counteract the potentially procoagulant effects of those histones that have escaped their nuclear localization.

RECENT FINDINGS

Extracellular histones exert procoagulant effects via endothelial damage, platelet activation, and direct interaction with coagulation proteins. Neutralization of histone activities can be achieved by complexation with physiological molecules, through pharmacological compounds, or via proteolytic degradation. Details of neutralization of extracellular histones are still being studied.

SUMMARY

Leveraging the understanding of extracellular histone neutralization will pave the way for development of novel pharmacological interventions to treat and prevent complications, including thromboembolism, in patients in whom extracellular histones contribute to their overall clinical status.

Emerging therapeutic strategies targeting extracellular histones for critical and inflammatory diseases: an updated narrative review

Extracellular histones are crucial damage-associated molecular patterns involved in the development and progression of multiple critical and inflammatory diseases, such as sepsis, pancreatitis, trauma, acute liver failure, acute respiratory distress syndrome, vasculitis and arthritis. During the past decade, the physiopathologic mechanisms of histone-mediated hyperinflammation, endothelial dysfunction, coagulation activation, neuroimmune injury and organ dysfunction in diseases have been systematically elucidated. Emerging preclinical evidence further shows that anti-histone strategies with either their neutralizers (heparin, heparinoids, nature plasma proteins, small anion molecules and nanomedicines, etc.) or extracorporeal blood purification techniques can significantly alleviate histone-induced deleterious effects, and thus improve the outcomes of histone-related critical and inflammatory animal models. However, a systemic evaluation of the efficacy and safety of these histone-targeting therapeutic strategies is currently lacking. In this review, we first update our latest understanding of the underlying molecular mechanisms of histone-induced hyperinflammation, endothelial dysfunction, coagulopathy, and organ dysfunction. Then, we summarize the latest advances in histone-targeting therapy strategies with heparin, anti-histone antibodies, histone-binding proteins or molecules, and histone-affinity hemoadsorption in pre-clinical studies. Finally, challenges and future perspectives for improving the clinical translation of histone-targeting therapeutic strategies are also discussed to promote better management of patients with histone-related diseases.

Bacillus cereus CwpFM induces colonic tissue damage and inflammatory responses through oxidative stress and the NLRP3/NF-κB pathway

Bacillus cereus (B. cereus) from cow milk poses a threat to public health, causing food poisoning and gastrointestinal disorders in humans. We identified CwpFM, an enterotoxin from B. cereus, caused oxidative stress and inflammatory responses in mouse colon and colonic epithelial cells. Colon proteomics revealed that CwpFM elevated proteins associated with inflammation and oxidative stress. Notably, CwpFM induced activation of the NLRP3/NF-κB signaling, but suppressed antioxidant NFE2L2/HO-1 expression in the intestine and epithelial cells. Consistently, CwpFM exposure led to cytotoxicity and ROS accumulation in Caco-2 cells in a dose-dependent manner. Further, NAC (ROS inhibitor) treatment abolished NLRP3/NF-κB activation due to CwpFM. Moreover, overexpression of Nfe2l2 or activation of NFE2L2 by NK-252 reduced ROS production and inhibited activation of the NLRP3/NF-κB pathway. Inhibition of NF-κB by ADPC and/or suppression of NLRP3 by MCC950 attenuated CwpFM-induced inflammatory responses in Caco-2 cells. Collectively, CwpFM induced oxidative stress and NLRP3/NF-κB activation by inhibiting the NFE2L2/HO-1 signaling and ROS accumulation, leading to the development of intestinal inflammation. Our data elucidate the role of oxidative stress and innate immunity in CwpFM enterotoxicity and contribute to developing diagnostic and therapeutic products for B. cereus-related food safety issues.

Perioperative Immunosuppressive Factors during Cancer Surgery: An Updated Review

Surgical excision of the primary tumor represents the most frequent and curative procedure for solid malignancies. Compelling evidence suggests that, despite its beneficial effects, surgery may impair immunosurveillance by triggering an immunosuppressive inflammatory stress response and favor recurrence by stimulating minimal residual disease. In addition, many factors interfere with the immune effectors before and after cancer procedures, such as malnutrition, anemia, or subsequent transfusion. Thus, the perioperative period plays a key role in determining oncological outcomes and represents a short phase to circumvent anesthetic and surgical deleterious factors by supporting the immune system through the use of synergistic pharmacological and non-pharmacological approaches. In line with this, accumulating studies indicate that anesthetic agents could drive both protumor or antitumor signaling pathways during or after cancer surgery. While preclinical investigations focusing on anesthetics' impact on the behavior of cancer cells are quite convincing, limited clinical trials studying the consequences on survival and recurrences remain inconclusive. Herein, we highlight the main factors occurring during the perioperative period of cancer surgery and their potential impact on immunomodulation and cancer progression. We also discuss patient management prior to and during surgery, taking into consideration the latest advances in the literature.

Circulating Nucleosomes as a Novel Biomarker for Sepsis: A Scoping Review

Circulating nucleosome levels are commonly elevated in physiological and pathological conditions. Their potential as biomarkers for diagnosing and prognosticating sepsis remains uncertain due, in part, to technical limitations in existing detection methods. This scoping review explores the possible role of nucleosome concentrations in the diagnosis, prognosis, and therapeutic management of sepsis. A comprehensive literature search of the Cochrane and Medline libraries from 1996 to 1 February 2024 identified 110 potentially eligible studies, of which 19 met the inclusion criteria, encompassing a total of 39 SIRS patients, 893 sepsis patients, 280 septic shock patients, 117 other ICU control patients, and 345 healthy volunteers. The enzyme-linked immunosorbent assay [ELISA] was the primary method of nucleosome measurement. Studies consistently reported significant correlations between nucleosome levels and other NET biomarkers. Nucleosome levels were higher in patients with sepsis than in healthy volunteers and associated with disease severity, as indicated by SOFA and APACHE II scores. Non-survivors had higher nucleosome levels than survivors. Circulating nucleosome levels, therefore, show promise as early markers of NETosis in sepsis, with moderate diagnostic accuracy and strong correlations with disease severity and prognosis. However, the available evidence is drawn mainly from single-center, observational studies with small sample sizes and varied detection methods, warranting further investigation.

Cytotoxic Oxidative Stress Effects of Neutrophil Extracellular Traps' Components on Cattle Spermatozoa

Bovine spermatozoa are highly susceptible to oxidative stress (OS), and it is known to affect their cellular functions. The main leukocyte producers of reactive oxygen species (ROS) in mammalian semen are polymorphonuclear neutrophils (PMN). PMN activation can result in the formation of neutrophil extracellular traps (NETs), which have been shown to affect the motility and function of spermatozoa. However, OS effects on bull spermatozoa derived from individual NETs components have not been investigated. The hypothesis of this study was that specific NETs components might generate OS on bull spermatozoa. Bovine sperm cells were incubated with five NETs-associated molecules, including 30 μg/mL histone 2A (H2A), neutrophil elastase (NE), 1 μg/mL myeloperoxidase (MPO), cathepsin G (Cat-G), and cathelicidin LL37 (LL-37), for a time course ranging from 15 to 240 min. Fluorescence microscopy was used to evaluate the coincubation of bovine PMN and sperm cells. Within 15 min, H2A, NE, and LL-37 caused membrane disruption, while MPO and Cat-G caused OS on bull spermatozoa after 1 h of coincubation. NET formation was observed within 15 min of coincubation in co-cultures of bovine PMN/sperm cells. This study is the first to report on the role of cytotoxic OS effects caused by NETs-derived components in bovine sperm in vitro.

Inflammatory and hypoxic stress-induced islet exosomes released during isolation are associated with poor transplant outcomes in islet autotransplantation

Islets experience enormous stress during the isolation process, leading to suboptimal endocrine function after total pancreatectomy with islet autotransplantation (TPIAT). Our investigation focused on inducing isolation stress in islets ex vivo, where proinflammatory cytokines and hypoxia prompted the release of stress exosomes (exoS) sized between 50 and 200 nm. Mass spectrometry analysis revealed 3 distinct subgroups of immunogenic proteins within these exoS: damage-associated molecular patterns (DAMPs), chaperones, and autoantigens. The involvement of endosomal-sorting complex required for transport proteins including ras-associated binding proteins7A, ras-associated binding protein GGTA, vacuolar protein sorting associated protein 45, vacuolar protein sorting associated protein 26B, and the tetraspanins CD9 and CD63, in exoS biogenesis was confirmed through immunoblotting. Next, we isolated similar exoS from the islet infusion bags of TPIAT recipients (N = 20). The exosomes from infusion bags exhibited higher DAMP (heat shock protein family A [Hsp70] member 1B and histone H2B) levels, particularly in the insulin-dependent TPIAT group. Additionally, elevated DAMP protein levels in islet infusion bag exosomes correlated with increased insulin requirements (P = .010) and higher hemoglobin A1c levels 1-year posttransplant. A deeper exploration into exoS functionality revealed their potential to activate monocytes via the toll-like receptor 3/7: DAMP axis. This stimulation resulted in the induction of inflammatory phenotypes marked by increased levels of CD68, CD80, inducible nitric oxide synthase, and cyclooxygenase-2. This activation mechanism may impact the successful engraftment of transplanted islets.

The role of neutrophils and neutrophil extracellular traps (NETs) in stages, outcomes and pregnancy complications

Neutrophils are the main components of innate immunity to eliminate infectious pathogens. Neutrophils play a role in several stages of the reproductive cycle, and their presence in the female reproductive system is highly regulated, so their function may change during pregnancy. Emerging evidence suggests that neutrophils are important at all stages of pregnancy, from implantation, placentation, and connective tissue regeneration to birth, as well as birth itself. Neutrophil extracellular traps (NETs) are defined as extracellular strands of unfolded DNA together with histone complexes and neutrophil granule proteins. NET formation is a new mechanism of these cells for their defense function. These strands containing DNA and antimicrobial peptides were initially recognized as one of the defense mechanisms of neutrophils, but later it was explained that they are involved in a variety of non-infectious diseases. Since the source of inflammation and tissue damage is the irregular activity of neutrophils, it is not surprising that NETosis are associated with a number of inflammatory conditions and diseases. The overexpression of NET components or non-principled NET clearance is associated with the risk of production and activation of autoantibodies, which results in participation in autoinflammatory and autoimmune disorders (SLE, RA), fibrosis, sepsis and other disorders such as vascular diseases, for example, thrombosis and atherosclerosis. Recent published articles have shown the role of neutrophils and extracellular traps (NETs) in pregnancy, childbirth and pregnancy-related diseases. The aim of this study was to identify and investigate the role of neutrophils and neutrophil extracellular traps (NETs) in the stages of pregnancy, as well as the complications caused by these cells.

Magnesium alleviates extracellular histone-induced apoptosis and defective bacterial phagocytosis in macrophages by regulating intracellular calcium signal

Extracellular histones have been determined as important mediators of sepsis, which induce excessive inflammatory responses in macrophages and impair innate immunity. Magnesium (Mg2+), one of the essential nutrients of the human body, contributes to the proper regulation of immune function. However, no reports indicate whether extracellular histones affect survival and bacterial phagocytosis in macrophages and whether Mg2+ is protective against histone-induced macrophage damage. Our clinical data revealed a negative correlation between circulating histone and monocyte levels in septic patients, and in vitro experiments confirmed that histones induced mitochondria-associated apoptosis and defective bacterial phagocytosis in macrophages. Interestingly, our clinical data also indicated an association between lower serum Mg2+ levels and reduced monocyte levels in septic patients. Moreover, in vitro experiments demonstrated that Mg2+ attenuated histone-induced apoptosis and defective bacterial phagocytosis in macrophages through the PLC/IP3R/STIM-mediated calcium signaling pathway. Importantly, further animal experiments proved that Mg2+ significantly improved survival and attenuated histone-mediated lung injury and macrophage damage in histone-stimulated mice. Additionally, in a cecal ligation and puncture (CLP) + histone-induced injury mouse model, Mg2+ inhibited histone-mediated apoptosis and defective phagocytosis in macrophages and further reduced bacterial load. Overall, these results suggest that Mg2+ supplementation may be a promising treatment for extracellular histone-mediated macrophage damage in sepsis.

Steatotic Donor Transplant Livers: Preservation Strategies to Mitigate against Ischaemia-Reperfusion Injury

Liver transplantation (LT) is the only definitive treatment for end-stage liver disease, yet the UK has seen a 400% increase in liver disease-related deaths since 1970, constrained further by a critical shortage of donor organs. This shortfall has necessitated the use of extended criteria donor organs, including those with evidence of steatosis. The impact of hepatic steatosis (HS) on graft viability remains a concern, particularly for donor livers with moderate to severe steatosis which are highly sensitive to the process of ischaemia-reperfusion injury (IRI) and static cold storage (SCS) leading to poor post-transplantation outcomes. This review explores the pathophysiological predisposition of steatotic livers to IRI, the limitations of SCS, and alternative preservation strategies, including novel organ preservation solutions (OPS) and normothermic machine perfusion (NMP), to mitigate IRI and improve outcomes for steatotic donor livers. By addressing these challenges, the liver transplant community can enhance the utilisation of steatotic donor livers which is crucial in the context of the global obesity crisis and the growing need to expand the donor pool.

Trauma-associated extracellular histones mediate inflammation via a MYD88-IRAK1-ERK signaling axis and induce lytic cell death in human adipocytes

Despite advances in the treatment and care of severe physical injuries, trauma remains one of the main reasons for disability-adjusted life years worldwide. Trauma patients often suffer from disturbances in energy utilization and metabolic dysfunction, including hyperglycemia and increased insulin resistance. White adipose tissue plays an essential role in the regulation of energy homeostasis and is frequently implicated in traumatic injury due to its ubiquitous body distribution but remains poorly studied. Initial triggers of the trauma response are mainly damage-associated molecular patterns (DAMPs) such as histones. We hypothesized that DAMP-induced adipose tissue inflammation contributes to metabolic dysfunction in trauma patients. Therefore, we investigated whether histone release during traumatic injury affects adipose tissue. Making use of a murine polytrauma model with hemorrhagic shock, we found increased serum levels of histones accompanied by an inflammatory response in white adipose tissue. In vitro, extracellular histones induced an inflammatory response in human adipocytes. On the molecular level, this inflammatory response was mediated via a MYD88-IRAK1-ERK signaling axis as demonstrated by pharmacological and genetic inhibition. Histones also induced lytic cell death executed independently of caspases and RIPK1 activity. Importantly, we detected increased histone levels in the bloodstream of patients after polytrauma. Such patients might benefit from a therapy consisting of activated protein C and the FDA-approved ERK inhibitor trametinib, as this combination effectively prevented histone-mediated effects on both, inflammatory gene activation and cell death in adipocytes. Preventing adipose tissue inflammation and adipocyte death in patients with polytrauma could help minimize posttraumatic metabolic dysfunction.

C-TYPE LECTIN-2D RECEPTOR CONTRIBUTES TO HISTONE-INDUCED VASCULAR BARRIER DYSFUNCTION DURING BURN INJURY

ABSTRACT

Severe burns are associated with massive tissue destruction and cell death where nucleus histones and other damage-associated molecular patterns are released into the circulation and contribute to the pathogenesis of multiple-organ dysfunction. Currently, there is limited information regarding the pathophysiology of extracellular histones after burns, and the mechanisms underlying histone-induced vascular injury are not fully understood. In this study, by comparing the blood samples from healthy donors and burn patients, we confirmed that burn injury promoted the release of extracellular histones into the circulation, evidenced by increased plasma levels of histones correlating with injury severity. The direct effects of extracellular histones on human endothelial monolayers were examined, and the results showed that histones caused cell-cell adherens junction discontinuity and barrier dysfunction in a dose-related manner. Like burn patients, mice subjected to a scald burn covering 25% total body surface area also displayed significantly increased plasma histones. Intravital microscopic analysis of mouse mesenteric microcirculation indicated that treatment with a histone antibody greatly attenuated burn-induced plasma leakage in postcapillary venules, supporting the pathogenic role of extracellular histones in the development of microvascular barrier dysfunction during burns. At the molecular level, intrigued by the recent discovery of C-type lectin domain family 2 member D (Clec2d) as a novel receptor of histones, we tested its potential involvement in the histone interaction with endothelial cells. Indeed, we identified abundant expression of Clec2d in vascular endothelial cells. Further proximity ligation assay demonstrated a close association between extracellular histones and endothelial expressing Clec2d. Functionally, in vivo administration of an anti-Clec2d antibody attenuated burn-induced plasma leakage across mesenteric microvessels. Consistently, Clec2d knockdown in endothelial cells partially inhibited histone-induced endothelial barrier dysfunction. Together, our data suggest that burn injury-induced increases in circulating histones contribute to microvascular leakage and endothelial barrier dysfunction via a mechanism involving the endothelial Clec2d receptor.

Circulating nucleosomes as potential biomarkers for cancer diagnosis and treatment monitoring

Nucleosomes play a crucial role in regulating gene expression through their composition and post-translational modifications. When cells die, intracellular endonucleases are activated and cleave chromatin into oligo- and mono-nucleosomes, which are then released into the body fluids. Studies have shown that the levels of nucleosomes are increased in serum and plasma in various cancer types, suggesting that analysis of circulating nucleosomes can provide an initial assessment of carcinogenesis. However, it should be noted that elevated serum nucleosome levels may not accurately diagnose certain tumor types, as increased cell death may occur in different pathological conditions. Nevertheless, detection of circulating nucleosomes and their histone modifications, along with specific tumor markers, can help diagnose certain types of cancer. Furthermore, monitoring changes in circulating nucleosome levels during chemotherapy or radiotherapy in patients with malignancies can provide valuable insights into clinical outcomes and therapeutic efficacy. The utilization of circulating nucleosomes as biomarkers is an exciting and emerging area of research, with the potential for early detection of various diseases and monitoring of treatment response. Integrating nucleosome-based biomarkers with existing ones may improve the specificity and sensitivity of current assays, offering the possibility of personalized precision medical treatment for patients.

Trauma-induced innate immune activation and disseminated intravascular coagulation

Dysregulated innate immunity participates in the pathomechanisms of disseminated intravascular coagulation (DIC) in trauma-induced coagulopathy. Accidental and regulated cell deaths and neutrophil extracellular traps release damage-associated molecular patterns (DAMPs), such as histones, nuclear and mitochondrial DNA, and high-mobility group box 1, into circulation immediately after trauma. DAMP-induced inflammation activation releases tissue factor-bearing procoagulant extracellular vesicles through gasdermin D-mediated pore formation and plasma membrane rupture by regulated cell death. DAMPs also evoke systemic inflammation, platelet, coagulation activation, and impaired fibrinolysis associated with endothelial injury, leading to the dysfunction of anticoagulation systems, which are the main pathophysiological mechanisms of DIC. All these processes induce systemic thrombin generation in vivo, not restricted to the injury sites immediately after trauma. Thrombin generation at the site of injury stops bleeding and maintains homeostasis. However, DIC associated with endothelial injury generates massive thrombin, enhancing protease-activated, receptor-mediated bidirectional interplays between inflammation and coagulation, aggravating the diverse actions of thrombin and disturbing homeostasis. Insufficiently regulated thrombin causes disseminated microvascular thrombosis, resulting in tissue hypoxia due to reduced oxygen delivery, and mitochondrial dysfunction due to DAMPs causes tissue dysoxia. In addition, DAMP-induced calcium influx and overload, as well as neutrophil activation, play a role in endothelial cell injury. Tissue hypoxia and cytotoxicity result in multiple organ dysfunction in DIC after trauma. Controls against dysregulated innate immunity evoking systemic inflammation, thrombin generation, and cytotoxicity are key issues in improving the prognosis of DIC in trauma-induced coagulopathy.

Extracellular histones exacerbate heat stroke-induced liver injury by triggering hepatocyte pyroptosis and liver injury via the TLR9-NLRP3 pathway

BACKGROUND

Severe heat stroke is often complicated by multiple organ failure, including liver injury. Recent evidence indicates that the underlying mechanism constitutes sterile inflammation triggered by cell damage, in which hepatocyte NOD-like receptor family pyrin domain-containing 3 inflammasome activation and pyroptosis play key roles. As extracellular histones act as damage-associated molecular patterns and mediate tissue toxicity and inflammation, we aimed to investigate whether extracellular histones contribute to inducing hepatocyte pyroptosis following heat stroke, promoting the development of liver inflammation and injury, and elucidate the potential underlying mechanisms.

METHODS

Exogenous histones were administered to AML-12 murine hepatocytes or male aged 8-12 week mice following hyperthermic treatment (at 39 °C in a chamber with 60 % relative humidity). Prior to heat exposure, endogenous histones were neutralized using neutralizing antibodies, inflammasomes were inhibited by RNA silencing, and Toll-like receptor 9 was modulated using a pharmacological agonist or antagonist. Inflammasome assembly, caspase-1 activation, histological changes, and liver enzyme levels were measured. Statistical comparison of more than two groups was performed using one-way ANOVA with Tukey's post-hoc testing. The correlations were analyzed using Pearson's correlation test. All experiments were repeated thrice. A p-value < 0.05 was considered significant.

RESULTS

Heat stroke induced histone release into the extracellular space at levels correlating with liver injury. Moreover, extracellular histones augmented heat stroke-induced liver injury both in vitro and in vivo in a dose- and time-dependent manner, whereas neutralizing histones conferred protection following heat stroke. Histones mediated NOD-like receptor family pyrin domain-containing 3 inflammasome activation through the Toll-like receptor 9 signaling pathway, which resulted in hepatocyte pyroptosis and liver inflammation.

CONCLUSIONS

Our findings show that histones are critical mediators of hepatocyte pyroptosis that aggravate liver injury in a heat stroke setting. Therefore, we suggest extracellular histones as potential therapeutic targets to limit heat stroke-induced cell death and liver injury.

Design and characterization of novel activated protein C variants for the proteolysis of cytotoxic extracellular histone H3

BACKGROUND

Extracellular histone H3 is implicated in several pathologies including inflammation, cell death, and organ failure. Neutralization of histone H3 is a strategy that was shown beneficial in various diseases, such as rheumatoid arthritis, myocardial infarction, and sepsis. It was shown that activated protein C (APC) can cleave histone H3, which reduces histone cytotoxicity. However, due to the anticoagulant properties of APC, the use of APC is not optimal for the treatment of histone-mediated cytotoxicity, in view of its associated bleeding side effects.

OBJECTIVES

This study aimed to investigate the detailed molecular interactions between human APC and human histone H3, and subsequently use molecular docking and molecular dynamics simulation methods to identify key interacting residues that mediate the interaction between APC and histone H3 and to generate novel optimized APC variants.

METHODS

After molecular simulations, the designed APC variants 3D2D-APC (Lys37-39Asp and Lys62-63Asp) and 3D2D2A-APC (Lys37-39Asp, Lys62-63Asp, and Arg74-75Ala) were recombinantly expressed and their abilities to function as anticoagulant, to bind histones, and to cleave histones were tested and correlated with their cytoprotective properties.

RESULTS

Compared with wild type-APC, both the 3D2D-APC and 3D2D2A-APC variants showed a significantly decreased anticoagulant activity, increased binding to histone H3, and similar ability to proteolyze histone H3.

CONCLUSIONS

Our data show that it is possible to rationally design APC variants that may be further developed into therapeutic biologicals to treat histone-mediated disease, by proteolytic reduction of histone-associated cytotoxic properties that do not induce an increased bleeding risk.

Neutralization of extracellular histones by sodium-Β-O-methyl cellobioside sulfate in septic shock

BACKGROUND

Extracellular histones have been associated with severity and outcome in sepsis. The aim of the present study was to assess the effects of sodium-β-O-Methyl cellobioside sulfate (mCBS), a histone-neutralizing polyanion, on the severity and outcome of sepsis in an experimental model.

METHODS

This randomized placebo-controlled experimental study was performed in 24 mechanically ventilated female sheep. Sepsis was induced by fecal peritonitis. Animals were randomized to three groups: control, early treatment, and late treatment (n = 8 each). mCBS was given as a bolus (1 mg/kg) followed by a continuous infusion (1 mg/kg/h) just after sepsis induction in the early treatment group, and 4 h later in the late treatment group. Fluid administration and antimicrobial therapy were initiated 4 h T4 after feces injection, peritoneal lavage performed, and a norepinephrine infusion titrated to maintain mean arterial pressure (MAP) between 65-75 mmHg. The experiment was blinded and lasted maximum 24 h.

RESULTS

During the first 4 h, MAP remained > 65 mmHg in the early treatment group but decreased significantly in the others (p < 0.01 for interaction, median value at T4: (79 [70-90] mmHg for early treatment, 57 [70-90] mmHg for late treatment, and 55 [49-60] mmHg for the control group). mCBS-treated animals required significantly less norepinephrine to maintain MAP than controls (p < 0.01 for interaction) and had lower creatinine (p < 0.01), lactate (p < 0.01), and interleukin-6 (p < 0.01) levels, associated with reduced changes in H3.1 nucleosome levels (p = 0.02). Early treatment was associated with lower norepinephrine requirements than later treatment. Two control animals died; all the mCBS-treated animals survived.

CONCLUSIONS

Neutralization of extracellular histones with mCBS was associated with reduced norepinephrine requirements, improved tissue perfusion, less renal dysfunction, and lower circulating IL-6 in experimental septic shock and may represent a new therapeutic approach to be tested in clinical trials.

Neutrophils extracellular traps and ferroptosis in diabetic wounds

Wound healing is an extremely complex process involving multiple levels of cells and tissues. It is mainly completed through four stages: haemostasis, inflammation, proliferation, and remodelling. When any one of these stages is impaired, it may lead to delayed healing or even transformation into chronic refractory wounds. Diabetes is a kind of common metabolic disease that affects approximately 500 million people worldwide, 25% of whom develop skin ulcers that break down repeatedly and are difficult to heal, making it a growing public health problem. Neutrophils extracellular traps and ferroptosis are new types of programmed cell death identified in recent years and have been found to interact with diabetic wounds. In this paper, the normal wound healing and interfering factors of the diabetic refractory wound were outlined. The mechanism of two kinds of programmed cell death was also described, and the interaction mechanism between different types of programmed cell death and diabetic refractory wounds was discussed.

Effect of different sperm populations on neutrophils extracellular traps (NETs) formation in cattle

In cattle, clinical and subclinical inflammation in the bovine female reproductive tract (FRT) significantly reduces fertility. PMN participate in this FRT-associated inflammation by eliminating pathogens by eliciting various defense mechanisms, with the release of neutrophil extracellular traps NETs) being the latest process discovered. Consistently, human-, bovine- and porcine-derived spermatozoa induce release of NETs in exposed PMN of the same species origin, and thereby decreasing sperm motility through NETs-mediated entrapment. The release of NETs in the presence of different sperm sub-populations is evaluated in this work. Cryopreserved bovine sperm were selected and different sperm populations were used: viable sperm, sperm with oxidative stress, capacitated sperm, and sperm with loss of viability. Isolated PMN of dairy cows were co-incubated with these sperm populations for 4 h. Neutrophil elastase (NE) and DNA were detected by fluorescence microscopy analysis. It was noted that exposed bovine PMN released NETs in the presence of sperm. Moreover, sperm-triggered NETosis resulted different phenotypes of NETs, i. e. spread NETs (sprNETs), diffused NETs (diffNETs) and aggregated NETs (aggNETs). Viable/motile spermatozoa induced a higher proportion of NETotic cells at 15, 60 and 120 min in comparison to controls. In conclusion, all bovine sperm populations in co-culture with PMN generated NETs extrusion while viable sperm activated NETotic cells to a greater extent. With this being an early event in the activation of bovine PMN.

PREDICTIVE VALUE OF NEUTROPHIL EXTRACELLULAR TRAP COMPONENTS FOR 28-DAY ALL-CAUSE MORTALITY IN PATIENTS WITH CARDIAC ARREST: A PILOT OBSERVATIONAL STUDY

ABSTRACT

Background: Ischemia-reperfusion after cardiac arrest (CA) activates peptidyl arginine deiminase and citrullinated histone H3 (CitH3), which leads to the formation of neutrophil extracellular traps (NETs). This study attempted to determine the alterations in NET components in post-CA patients as well as analyze the association of NETs with 28-day all-cause mortality. Methods : In this study, 95 patients with restoration of spontaneous circulation (ROSC) after CA were included. They were categorized into the survivor group (n = 32) and the nonsurvivor group (n = 63) according to their 28-day survival statuses. The control group comprised 20 healthy individuals. The blood samples were collected from the patients on days 1, 3, and 7 after ROSC and from the control subjects at the time of enrollment. The serum cell-free DNA (cfDNA) level was determined using the fluorescent labeling method, and the serum concentrations of NET components, including CitH3, myeloperoxidase, neutrophil elastase, and nucleosomes, were estimated using the enzyme-linked immunosorbent assay. Results : Compared with the control group, the serum NET components were significantly increased in the patients 1 week after ROSC (all P < 0.05). These components were significantly higher in the nonsurvivor group than in the survivor group (all P < 0.05). Spearman correlational analysis revealed that the components were positively correlated with Acute Physiology and Chronic Health Evaluation II scores (both P < 0.05). Binary logistic regression analysis indicated that serum cfDNA, CitH3, and nucleosomes on days 1 and 3 after ROSC were independent predictors of 28-day all-cause mortality. Furthermore, these parameters on day 1 after ROSC had the biggest areas under the receiver operating characteristic curves (0.876, 0.862, and 0.861, respectively). Conclusions: Elevated serum levels of cfDNA, CitH3, myeloperoxidase, neutrophil elastase, and nucleosomes were positively correlated with disease severity after ROSC. However, only serum CitH3, cfDNA, and nucleosomes on day 1 after ROSC showed a good predictive value for 28-day all-cause mortality.

Novel function of transglutaminase 2 in extracellular histone-induced acute lung injury

Extracellular histones induce endothelial damage, resulting in lung haemorrhage; however, the underlying mechanism remains unclear. Factor XIII, as a Ca2+-dependent cross-linking enzyme in blood, mediates fibrin deposition. As another isozyme, transglutaminase 2 (TG2) has a catalytic activity distributing in most tissues. Herein, we investigated whether TG2 promotes fibrin deposition and mediates the adhesion of platelets to ECs in histone-induced acute lung injury (ALI). We evaluated the lung histology and the adhesion of platelets to endothelial cells (ECs) after injecting histones to wild-type (WT) C57BL/6J and TG2 knockout (TG2-/-) mice, and administered a TG2 inhibitor (NC9) to WT mice. Pulmonary haemorrhage was more severe in TG2-/- mice than that in WT mice. The area of fibrin deposition and the proportion of CD41+CD31+ cells were lower in TG2-/- mice than in WT mice. Pre-treatment of NC9 decreased the area of fibrin deposition and the proportion of CD41+CD31+ cells in WT mice. These results suggest that TG2 prevents from pulmonary haemorrhage in ALI by promoting the adhesion of platelets to ECs and the fibrin deposition.

Association of pronounced elevation of NET formation and nucleosome biomarkers with mortality in patients with septic shock

BACKGROUND

Understanding the mechanisms underlying immune dysregulation in sepsis is a major challenge in developing more individualized therapy, as early and persistent inflammation, as well as immunosuppression, play a significant role in pathophysiology. As part of the antimicrobial response, neutrophils can release extracellular traps (NETs) which neutralize and kill microorganisms. However, excessive NETs formation may also contribute to pathogenesis, tissue damage and organ dysfunction. Recently, a novel automated assay has been proposed for the routine measurement of nucleosomes H3.1 (fundamental units of chromatin) that are released during NETs formation. The aim of the present study was to measure nucleosome levels in 151 septic shock patients (according to sepsis-3 definition) and to determine association with mortality.

RESULTS

The nucleosome H3.1 levels (as determined by a chemiluminescence immunoassay performed on an automated immunoanalyzer system) were markedly and significantly elevated at all-time points in septic shock patients compared to the control group. Immunological parameters indicated tremendous early inflammation (IL-6 = 1335 pg/mL at day 1-2) along with marked immunosuppression (e.g., mHLA-DR = 3853 AB/C and CD4 = 338 cell /µL at day 3-4). We found significantly positive correlation between nucleosome levels and organ failure and severity scores, IL-6 concentrations and neutrophil count. Significantly higher values (day 1-2 and 3-4) were measured in non-survivor patients (28-day mortality). This association was still significant after multivariate analysis and was more pronounced with highest concentration. Early (day 1-2) increased nucleosome levels were also independently associated with 5-day mortality. At day 6-8, persistent elevated nucleosome levels were negatively correlated to mHLA-DR values.

CONCLUSIONS

This study reports a significant elevation of nucleosome in patients during a one-week follow-up. The nucleosome levels showed correlation with neutrophil count, IL-6 and were found to be independently associated with mortality assessed at day 5 or 28. Therefore, nucleosome concentration seems to be a promising biomarker for detecting hyper-inflammatory phenotype upon a patient's admission. Additional investigations are required to evaluate the potential association between sustained elevation of nucleosome and sepsis-induced immunosuppression.

Surface antibody changes protein corona both in human and mouse serum but not final opsonization and elimination of targeted polymeric nanoparticles

BACKGROUND

Nanoparticles represent one of the most important innovations in the medical field. Among nanocarriers, polymeric nanoparticles (PNPs) attracted much attention due to their biodegradability, biocompatibility, and capacity to increase efficacy and safety of encapsulated drugs. Another important improvement in the use of nanoparticles as delivery systems is the conjugation of a targeting agent that enables the nanoparticles to accumulate in a specific tissue. Despite these advantages, the clinical translation of therapeutic approaches based on nanoparticles is prevented by their interactions with blood proteins. In fact, the so-formed protein corona (PC) drastically alters the biological identity of the particles. Adsorbed activated proteins of the complement cascade play a pivotal role in the clearance of nanoparticles, making them more easily recognized by macrophages, leading to their rapid elimination from the bloodstream and limiting their efficacy. Since the mouse is the most used preclinical model for human disease, this work compared human and mouse PC formed on untargeted PNPs (uPNPs) and targeted PNPs (tPNPs), paying particular attention to complement activation.

RESULTS

Mouse and human serum proteins adsorbed differently to PNPs. The differences in the binding of mouse complement proteins are minimal, whereas human complement components strongly distinguish the two particles. This is probably due to the human origin of the Fc portion of the antibody used as targeting agent on tPNPs. tPNPs and uPNPs mainly activate complement via the classical and alternative pathways, respectively, but this pattern did not affect their binding and internalization in macrophages and only a limited consumption of the activity of the human complement system was documented.

CONCLUSIONS

The results clearly indicate the presence of complement proteins on PNPs surface but partially derived from an unspecific deposition rather than an effective complement activation. The presence of a targeting antibody favors the activation of the classical pathway, but its absence allows an increased activation of the alternative pathway. This results in similar opsonization of both PNPs and similar phagocytosis by macrophages, without an impairment of the activity of circulating complement system and, consequently, not enhancing the susceptibility to infection.

Application of microphysiologic system to assess neutrophil extracellular trap in xenotransplantation

Transplantation of organs, cells, or tissues from one species to another, known as xenotransplantation, has the potential to alleviate organ donor shortages and enhance the success of organ transplantation. However, the possibility of immunological rejection by the recipient is one of the biggest difficulties associated with xenotransplantation. The creation of neutrophil extracellular traps (NETs), also known as NETosis, is hypothesized as a mechanism of rejection. Innovations in microfluidics and co-culturing techniques have provided access to several classes of microengineered model systems in experimental models, connecting animal research and traditional in vitro methods such as organoids, microphysiological systems, and organs-on-chip. To achieve this goal, we established a perfusable 3D Xeno vessel chip using a porcine aortic endothelial cell line and examined how NETs grow when isolated human and primate neutrophils were used. Neutrophils from both humans and monkeys displayed the usual NETosis phases, including nuclear decondensation, enlargement, and rounding of DNA, occupying the entire cytoplasm, and discharge of fragmented DNA after cell membrane rupture. Using confocal fluorescence imaging of DNA and citrullinated histone colocalization and DNA histone complex formation in supernatants from xeno vessel chips, we confirmed NETs generation by human and monkey neutrophils when cocultured in a xeno-vessel chip.

The Polyanionic Drug Suramin Neutralizes Histones and Prevents Endotheliopathy

Drugs are needed to protect against the neutrophil-derived histones responsible for endothelial injury in acute inflammatory conditions such as trauma and sepsis. Heparin and other polyanions can neutralize histones but challenges with dosing or side effects such as bleeding limit clinical application. In this study, we demonstrate that suramin, a widely available polyanionic drug, completely neutralizes the toxic effects of individual histones, but not citrullinated histones from neutrophil extracellular traps. The sulfate groups on suramin form stable electrostatic interactions with hydrogen bonds in the histone octamer with a dissociation constant of 250 nM. In cultured endothelial cells (Ea.Hy926), histone-induced thrombin generation was significantly decreased by suramin. In isolated murine blood vessels, suramin abolished aberrant endothelial cell calcium signals and rescued impaired endothelial-dependent vasodilation caused by histones. Suramin significantly decreased pulmonary endothelial cell ICAM-1 expression and neutrophil recruitment caused by infusion of sublethal doses of histones in vivo. Suramin also prevented histone-induced lung endothelial cell cytotoxicity in vitro and lung edema, intra-alveolar hemorrhage, and mortality in mice receiving a lethal dose of histones. Protection of vascular endothelial function from histone-induced damage is a novel mechanism of action for suramin with therapeutic implications for conditions characterized by elevated histone levels.

Effects of recombinant human soluble thrombomodulin on neutrophil extracellular traps in the kidney of a mouse model of endotoxin shock

OBJECTIVES

Sepsis is a life-threatening condition characterized by multi-organ dysfunction due to host immune system dysregulation in response to an infection. During sepsis, neutrophils release neutrophil extracellular traps (NETs) as part of the innate immune response. However, excessive NETs play a critical role in the development of organ failure during sepsis. Although recombinant human soluble thrombomodulin (rTM) can inhibit NET formation in the lungs and liver of a mouse model of endotoxin shock, its effects on the kidneys are unclear.

METHODS

The specific effects of NETs and rTM on the renal cortex and renal medulla were examined in a mouse model of endotoxin shock generated by intraperitoneal (i.p.) injection of lipopolysaccharide (LPS), followed by i.p. injection of rTM or an identical volume of saline 1 h later.

RESULTS

LPS injection increased serum creatinine, blood urea nitrogen, and histone H3 levels. However, rTM administration significantly decreased histone H3 and citrullinated histone H3 (citH3) levels. Immunohistochemical analysis revealed no significant changes in citH3 quantity in the renal cortex of any group. However, in the renal medulla, the increase in citH3 induced by LPS was abolished in the LPS+rTM group.

CONCLUSIONS

Our findings demonstrate that rTM can suppress NETs in the renal medulla of mice with endotoxin-induced acute kidney injury.

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.

Monocyte distribution width alterations and cytokine storm are modulated by circulating histones

OBJECTIVES

Extracellular histone levels are associated with the severity of many human pathologies, including sepsis and COVID-19. This study aimed to investigate the role of extracellular histones on monocyte distribution width (MDW), and their effect on the release of cytokines by blood cells.

METHODS

Peripheral venous blood was collected from healthy subjects and treated with different doses of a histone mixture (range 0-200 μg/mL) to analyze MDW modifications up-to 3 h and digital microscopy of blood smears. Plasma obtained after 3 h of histone treatment were assayed to evaluate a panel of 24 inflammatory cytokines.

RESULTS

MDW values significantly increased in a time- and dose-dependent manner. These findings are associated with the histone-induced modifications of cell volume, cytoplasmic granularity, vacuolization, and nuclear structure of monocytes, promoting their heterogeneity without affecting their count. After 3 h of treatment almost all cytokines significantly increased in a dose-dependent manner. The most relevant response was shown by the significantly increased G-CSF levels, and by the increase of IL-1β, IL-6, MIP-1β, and IL-8 at the histone doses of 50, 100, and 200 µg/mL. VEGF, IP-10, GM-CSF, TNF-α, Eotaxin, and IL-2 were also up-regulated, and a lower but significant increase was observed for IL-15, IL-5, IL-17, bFGF, IL-10, IFN-γ, MCP-1, and IL-9.

CONCLUSIONS

Circulating histones critically induce functional alterations of monocytes mirrored by MDW, monocyte anisocytosis, and hyperinflammation/cytokine storm in sepsis and COVID-19. MDW and circulating histones may be useful tools to predict higher risks of worst outcomes.