Extracellular histones disarrange vasoactive mediators release through a COX-NOS interaction in human endothelial cells

Validation of circulating histone detection by mass spectrometry for early diagnosis, prognosis, and management of critically ill septic patients

BACKGROUND

As leading contributors to worldwide morbidity and mortality, sepsis and septic shock are considered a major global health concern. Proactive biomarker identification in patients with sepsis suspicion at any time remains a daunting challenge for hospitals. Despite great progress in the understanding of clinical and molecular aspects of sepsis, its definition, diagnosis, and treatment remain challenging, highlighting a need for new biomarkers with potential to improve critically ill patient management. In this study we validate a quantitative mass spectrometry method to measure circulating histone levels in plasma samples for the diagnosis and prognosis of sepsis and septic shock patients.

METHODS

We used the mass spectrometry technique of multiple reaction monitoring to quantify circulating histones H2B and H3 in plasma from a monocenter cohort of critically ill patients admitted to an Intensive Care Unit (ICU) and evaluated its performance for the diagnosis and prognosis of sepsis and septic shock (SS).

RESULTS

Our results highlight the potential of our test for early diagnosis of sepsis and SS. H2B levels above 121.40 ng/mL (IQR 446.70) were indicative of SS. The value of blood circulating histones to identify a subset of SS patients in a more severe stage with associated organ failure was also tested, revealing circulating levels of histones H2B above 435.61 ng/ml (IQR 2407.10) and H3 above 300.61 ng/ml (IQR 912.77) in septic shock patients with organ failure requiring invasive organ support therapies. Importantly, we found levels of H2B and H3 above 400.44 ng/mL (IQR 1335.54) and 258.25 (IQR 470.44), respectively in those patients who debut with disseminated intravascular coagulation (DIC). Finally, a receiver operating characteristic curve (ROC curve) demonstrated the prognostic value of circulating histone H3 to predict fatal outcomes and found for histone H3 an area under the curve (AUC) of 0.720 (CI 0.546-0.895) p < 0.016 on a positive test cut-off point at 486.84 ng/mL, showing a sensitivity of 66.7% and specificity of 73.9%.

CONCLUSIONS

Circulating histones analyzed by MS can be used to diagnose SS and identify patients at high risk of suffering DIC and fatal outcome.

Plasma Cyclooxygenase-2 as a Potential Biomarker for Early Diagnosis of Kawasaki Disease

Background: Previous research demonstrated the association between cyclooxygenase-2 (COX-2) gene polymorphisms and susceptibility to Kawasaki disease (KD). This study aims to detect the plasma concentration of COX-2 in different phases of KD patients and evaluate the relationship between COX-2 level and coronary artery lesion formation, therapeutic response to intravenous immunoglobulin. Methods: Plasma COX-2 levels were measured by enzyme-linked immunosorbent assay in KD patients during the acute (a-KD, n = 52), subacute (s-KD, n = 46), and convalescent (c-KD, n = 43) phase. Results: The concentration of COX-2 in the a-KD group was significantly higher than that in the s-KD, c-KD, healthy control or febrile control group, respectively. There was no difference in the levels of COX-2 between the KD with or without coronary artery lesion subgroups, intravenous immunoglobulin resistant, and sensitive subgroups in the a-KD group, respectively. Conclusions: The plasma concentration of COX-2 might be a novel potential biomarker of acute KD.

Histone Citrullination Mediates a Protective Role in Endothelium and Modulates Inflammation

NETosis is a key host immune process against a pathogenic infection during innate immune activation, consisting of a neutrophil "explosion" and, consequently, NET formation, containing mainly DNA, histones, and other nuclear proteins. During sepsis, an exacerbated immune host response to an infection occurs, activating the innate immunity and NETosis events, which requires histone H3 citrullination. Our group compared the circulating histone levels with those citrullinated H3 levels in plasma samples of septic patients. In addition, we demonstrated that citrullinated histones were less cytotoxic for endothelial cells than histones without this post-translational modification. Citrullinated histones did not affect cell viability and did not activate oxidative stress. Nevertheless, citrullinated histones induced an inflammatory response, as well as regulatory endothelial mechanisms. Furthermore, septic patients showed elevated levels of circulating citrullinated histone H3, indicating that the histone citrullination is produced during the first stages of sepsis, probably due to the NETosis process.

Extracellular histones trigger oxidative stress-dependent induction of the NF-kB/CAM pathway via TLR4 in endothelial cells

Extracellular histones have been reported to aggravate different pathophysiological processes by increasing vascular permeability, coagulopathy, and inflammation. In the present study, we elucidate how extracellular histones (10–100 µg/mL) concentration dependently increase cytosolic reactive oxygen species (ROS) production using human umbilical vein endothelial cells (HUVECs). Furthermore, we identify cyclooxygenase (COX) and NADPH oxidase (NOX) activity as sources of ROS production in extracellular histone-treated HUVEC. This COX/NOX-mediated ROS production is also involved in enhanced NF-kB activity and cell adhesion molecules (VCAM1 and ICAM1) expression in histone-treated HUVEC. Finally, by using different toll-like receptor (TLR) antagonists, we demonstrate the role of TLR4 in CAMs overexpression triggered by extracellular histones in endothelial cells. In conclusion, our data suggest that through TLR4 signaling, extracellular histones increase endothelial cell activation, a mechanism involving increased COX- and NOX-mediated ROS. These findings increase our understanding on how extracellular histones enhance systemic inflammatory responses in diseases in which histone release occurs as part of the pathological processes.

Schistosome secretomes

Schistosomes are intravascular parasitic platyhelminths (blood flukes) that infect over 200 million people globally. Biomolecules secreted by the worms likely contribute to their ability to survive in the bloodstreams of immunocompetent hosts for many years. Here we review what is known about the protein composition of material released by the worms. Prominent among cercarial excretions/secretions (ES) is a ∼ 30 kDa serine protease called cercarial elastase (SmCE in Schistosoma mansoni), likely important in host invasion. Also prominent is a 117 amino acid non-glycosylated polypeptide (Sm16) that can impact several host cell-types to impinge on immunological outcomes. Similarly, components of the egg secretome (notably the 134 amino acid homodimeric glycoprotein "IL-4 inducing principle of schistosome eggs", IPSE, and the 225-amino acid monomeric T2 ribonuclease - omega-1) are capable of driving Th2-biased immune responses. A ∼36kDa chemokine binding glycoprotein SmCKBP, secreted by eggs, can negate the impact of several cytokines and can impede neutrophil migration. Of special interest is a disparate collection of classically cytosolic proteins that are surprisingly often identified in schistosome ES across life stages. These proteins, perhaps released as components of extracellular vesicles (EVs), include glycolytic enzymes, redox proteins, proteases and protease inhibitors, heat shock proteins, proteins involved in translation/turnover, histones, and others. Some such proteins may display "moonlighting" functions and, for example, impede blood clot formation around the worms. More prosaically, since several are particularly abundant soluble proteins, their appearance in the ES fraction may be indicative of worm damage ex vivo leading to protein leakage. Some bioactive schistosome ES proteins are in development as novel therapeutics against autoimmune, inflammatory, and other, non-parasitic, diseases.

Endothelial Cells Activated by Extracellular Histones Promote Foxp3+ Suppressive Treg Cells In Vitro

Histones are widely recognized as pro-inflammatory mediators upon their release from the nucleus into the extracellular space. However, their impact on endothelial cell immunogenicity is unknown. Endothelial cells, Human Microvascular Endothelial cells 1 (HMEC1), have been exposed to recombinant histones in order to study their effect on the endothelial phenotype. We then studied the differentiation of CD4⁺-T lymphocytes subpopulations after three days of interaction with endothelial cells in vitro and observed that histone-treated endothelial cells differentiate a suppressive FoxP3⁺ T regulator subpopulation that expressed Human Leucocyte Antigen DR (HLA-DR) and Cytotoxic T-Lymphocyte-Associated protein 4 (CTLA4). Toll-Like Receptor 4 (TLR4) inhibition significantly decreased the expansion of these Treg cells. Moreover, blockade of Interleukin (IL)-6 and Intercellular Adhesion Molecule (ICAM)-1 in cocultures significantly decreased the expansion of Tregs, suggesting an IL-6 and ICAM-1 dependent pathway. Thus, beyond their inflammatory effects, extracellular histones may induce an increase of immunosuppressive Treg population via their action on endothelial cells. Further studies are needed to evaluate the impact on immunosuppression of an increase of peripheral suppressive Treg via endothelial cell activation by histones in vivo.

Autophagy-driven neutrophil extracellular traps: The dawn of sepsis

Sepsis is a systemic inflammatory syndrome caused by infection disorders. The core mechanism of sepsis is immune dysfunction. Neutrophils are the most abundant circulating white blood cells, which play a crucial role in mediating the innate immune response. Previous studies have shown that an effective way to treat sepsis is through the regulation of neutrophil functions. Autophagy, a highly conserved degradation process, is responsible for removing denatured proteins or damaged organelles within cells and protecting cells from external stimuli. It is a key homeostasis process that promotes neutrophil function and differentiation. Autophagy has been shown to be closely associated with inflammation and immunity. Neutrophils, the first line of innate immunity, migrate to inflammatory sites upon their activation. Neutrophil-mediated autophagy may participate in the clinical course of sepsis. In this review, we summarized and analyzed the latest research findings on the changes in neutrophil external traps during sepsis, the regulatory role of autophagy in neutrophil, and the potential application of autophagy-driven NETs in sepsis, so as to guide clinical treatment of sepsis.

H2O2-responsive VEGF/NGF gene co-delivery nano-system achieves stable vascularization in ischemic hindlimbs

Peripheral vascular disease (PVD) is a common clinical manifestation of atherosclerosis. Vascular endothelial growth factor (VEGF) gene therapy is a promising approach for PVD treatment. However, due to single-gene therapy limitations and high H₂O₂ pathological microenvironment, VEGF gene therapy are not as expectations and its clinical application are limited. Synergistic effects of Nerve factors and vascular factors in angiogenesis have attracted attention in recent years. In this study, VEGF and nerve growth factor (NGF) genes co-delivery nanoparticles (VEGF/NGF-NPs) were prepared by using H₂O₂ responsive 6s-PLGA-Po-PEG as a carrier. 6s-PLGA-Po-PEG could react with H₂O₂ specifically due to the internal peroxalate bond. Angiogenic effects of VEGF/NGF-NPs has been evaluated in cells and hindlimb ischemia mice model. Results showed that VEGF/NGF-NPs promoted VEGF and NGF co-expression simultaneously, eliminated excessive H₂O₂, strengthened reactions between SH-SY5Ys and HUVECs, and finally enhanced migration, tube formation, proliferation and H₂O₂ damage resistance of HUVECs. VEGF/NGF-NPs also recovered blood perfusion, promoted the expression of VEGF, NGF, eNOS and NO, and enhanced vascular coverage of pericytes. Treatment effects of VEGF/NGF-NPs may related to VEGF/eNOS/NO pathway. Altogether, VEGF/NGF-NPs eliminated excessive H₂O₂ while achieving gene co-delivery, and promoted stable angiogenesis. It’s a promising way for PVD treatment by using VEGF/NGF-NPs.

Arterial thromboxane A2-induced transient contraction after IL-1β exposure

The involvement of thromboxane A2 (TXA2) in systemic inflammation and infection is well recognized. However, there are few reports on the involvement of prostanoids in warm shock (the initial pathology of sepsis). Previous studies showed that interleukin (IL)-1β causes a rapid inducible nitric oxide synthase/nitric oxide (iNOS/NO)-mediated relaxation in peripheral blood vessels during warm shock. Furthermore, a transient contraction was seen before this relaxation occurred. The present study aimed to elucidate the mechanism of this transient contraction. We measured isometric tension changes in the superior mesenteric arteries from normal male Wistar rats by adding IL-1β at the point of maximum contraction by phenylephrine (Ph). The same study was performed for each vessel pretreated with various inhibitors, including SQ29548, a TXA2 receptor antagonist, 30 min before Ph contraction. In addition, the concentration of thromboxane B2 (TXB2) in SMA was measured by probe electrospray ionization. Treatment of endothelial vessels with cyclooxygenase 1 (COX1)/2 inhibitors SC560/NS398 and TXA2 receptor antagonist SQ29548 suppressed IL-1β–induced transient contractions. This transient contraction reaction was derived from TXA2. Additionally, gene expression of COX2/TXA2 synthetase and the concentration of TXB2 were significantly increased in IL-1β-exposed vessels. It was demonstrated for the first time in inflamed blood vessels that endothelial cell-derived COX2/TXA2 is induced before iNOS and causes transient contractions. TXA2 may be considered an early sign of warm shock or as a biological defense mechanism in the early stages of septic shock.

Comparative Analysis of Chromatin-Delivered Biomarkers in the Monitoring of Sepsis and Septic Shock: A Pilot Study

Sepsis management remains one of the most important challenges in modern clinical practice. Rapid progression from sepsis to septic shock is practically unpredictable, hence the critical need for sepsis biomarkers that can help clinicians in the management of patients to reduce the probability of a fatal outcome. Circulating nucleoproteins released during the inflammatory response to infection, including neutrophil extracellular traps, nucleosomes, and histones, and nuclear proteins like HMGB1, have been proposed as markers of disease progression since they are related to inflammation, oxidative stress, endothelial damage, and impairment of the coagulation response, among other pathological features. The aim of this work was to evaluate the actual potential for decision making/outcome prediction of the most commonly proposed chromatin-related biomarkers (i.e., nucleosomes, citrullinated H3, and HMGB1). To do this, we compared different ELISA measuring methods for quantifying plasma nucleoproteins in a cohort of critically ill patients diagnosed with sepsis or septic shock compared to nonseptic patients admitted to the intensive care unit (ICU), as well as to healthy subjects. Our results show that all studied biomarkers can be used to monitor sepsis progression, although they vary in their effectiveness to separate sepsis and septic shock patients. Our data suggest that HMGB1/citrullinated H3 determination in plasma is potentially the most promising clinical tool for the monitoring and stratification of septic patients.

Recent advances in Extracellular Vesicles and their involvements in vasculitis

Systemic vasculitis is a heterogeneous group of multisystem autoimmune disorders characterized by inflammation of blood vessels. Although many progresses in diagnosis and immunotherapies have been achieved over the past decades, there are still many unanswered questions about vasculitis from pathological understanding to more advanced therapies. Extracellular vesicles (EVs) are double-layer phospholipid membrane vesicles harboring various cargoes. EVs can be classified into exosomes, microvesicles (MVs), and apoptotic bodies depending on their size and origin of cellular compartment. EVs can be released by almost all cell types and may be involved in physical and pathological processes including inflammation and autoimmune responses. In systemic vasculitis, EVs may have pathogenic involvement in inflammation, autoimmune responses, thrombosis, endothelium injury, angiogenesis and intimal hyperplasia. EV-associated redox reaction may also be involved in vasculitis pathogenesis by inducing inflammation, endothelial injury and thrombosis. Additionally, EVs may serve as specific biomarkers for diagnosis or monitoring of disease activity and therapeutic efficacy, i.e. AAV-associated renal involvement. In this review, we have discussed the recent advances of EVs, especially their roles in pathogenesis and clinical involvements in vasculitis.

Circulating Histones in Sepsis: Potential Outcome Predictors and Therapeutic Targets

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection and is associated with high morbidity and mortality. Circulating histones (CHs), a group of damage-associated molecular pattern molecules mainly derived from neutrophil extracellular traps, play a crucial role in sepsis by mediating inflammation response, organ injury and death through Toll-like receptors or inflammasome pathways. Herein, we first elucidate the molecular mechanisms of histone-induced inflammation amplification, endothelium injury and cascade coagulation activation, and discuss the close correlation between elevated level of CHs and disease severity as well as mortality in patients with sepsis. Furthermore, current state-of-the-art on anti-histone therapy with antibodies, histone-binding proteins (namely recombinant thrombomodulin and activated protein C), and heparin is summarized to propose promising approaches for sepsis treatment.

Extract from Rostellularia procumbens (L.) Nees Inhibits Thrombosis and Platelet Aggregation by Regulating Integrin β3 and MAPK Pathways

AIM OF STUDY

The main objective of this study was to investigate the antithrombotic and antiplatelet effect of the extract from Rostellularia procumbenss (L.) Nees and understand the mechanisms by which it exerts its antithrombotic and antiplatelet mechanisms.

MATERIALS AND METHODS

The antithrombotic effective parts (RPE) were isolated using D101 macroporous adsorption resin and potential active ingredients (JAC) were isolated using the preparative liquid-phase method. The lactate dehydrogenase kit was used to determine the toxicity of RPE and JAC to platelets. The antiadhesion effect of RPE and JAC on platelets was observed by fluorescence microscopy with rhodamine phalloidin. Antithrombotic efficacy of RPE and JAC in vivo was evaluated by establishing a rat tail thrombosis model. Contents of p-selectin, TXB₂, and 6-keto-PGF_1α in rat serum were measured using an enzyme-linked immunosorbent (ELISA) assay, and the rat black tail rate was measured to prove the protective effect of RPE and JAC on the tail thrombus rat model. Western blot was used for detection of serum-related proteins in the tail thrombus rat model.

RESULTS

The results showed that RPE had antithrombotic and antiplatelet effects. RPE and JAC have no toxicity to platelets. In vitro experiments showed that RPE and JAC had antiadhesion effects on platelets. In vivo experiments showed that RPE significantly inhibited the increase of p-selectin and TXB₂ and significantly increased the content of 6-keto-PGF_1α in the serum of rats. Western blot results demonstrated that RPE and JDB significantly inhibited the phosphorylation of the MAPK protein family in the platelets of rats, and RPE also significantly inhibited the phosphorylation of β₃ protein.

CONCLUSIONS

RPE has antithrombotic and antiplatelet activity in vivo and vitro. Its mechanism may be via preventing integrin α_IIbβ₃ activation, which in turn leads to the inhibition of the phosphorylation of the MAPK family and further suppresses TXA₂, which leads to the antithrombotic and antiplatelet effects.

Cystathionine β-synthase and methylenetetrahydrofolate reductase mutations in Mexican individuals with hyperhomocysteinemia

Background:

Hyperhomocysteinemia, a thrombotic risk factor, may have several causes. Among the genetic causes of hyperhomocysteinemia, there are polymorphisms in the enzymes methylenetetrahydrofolate reductase (C677T) and cystathionine β-synthase (C699T, C1080T, and 844ins68). Although the frequency of hyperhomocysteinemia in our country is high, there is no evidence about the frequencies of these polymorphisms.

Methods:

We analyzed 80 healthy individuals from several regions in our country. We evaluated the fasting and post-oral methionine load plasma Hcy and the genotypes in order to obtain the allele frequencies of the polymorphisms C677T of methylenetetrahydrofolate reductase and C699T, C1080T, and 844ins68 of the cystathionine β-synthase.

Results:

No individual had deficiency of folic acid, vitamins B12, or B6, but 80% had post-oral methionine load hyperhomocysteinemia. We found a significant increase in the Hcy plasma concentration associated with age and gender. Only the polymorphism C1080T was significantly associated with hyperhomocysteinemia.

Conclusion:

There is an association between fasting and post-oral methionine load plasma Hcy concentrations with the allelic frequencies of the polymorphisms C669T, 844ins68, and C1080T of the cystathionine β-synthase and C667T of the methylenetetrahydrofolate reductase in healthy Mexican individuals. As compared with individuals with normal fasting or post-oral methionine load Hcy plasma levels, only C1080T was significantly associated with hyperhomocysteinemia.

Heparin Attenuates Histone-Mediated Cytotoxicity in Septic Acute Kidney Injury

Histones are considered potential risk factors that contribute to the development of septic acute kidney injury (SAKI) by inducing apoptosis and inflammation. This study aimed to explore the protective effects of heparin on septic acute kidney injury through the neutralization of extracellular histones (EH) and to uncover the underlying mechanism. C57BL mice (16 each) were randomly divided into the sham group, the sepsis group (established by cecal ligation and puncture operation, CLP), and the heparin intervention group. Mice in the heparin intervention group received a subcutaneous injection of unfractionated heparin (0.03 IU/g) 4 h after CLP. At 6 h after the operation, nine mice from each group were sacrificed by the removal of the eyeballs to harvest blood samples; the upper half of the right kidney was used as the study sample. Mice renal tubular epithelial cells cultivated in six-well plates were equally divided into five groups. We cultured cells treated with either histone (40 U), histone (40 U) + heparin (25 IU/ml), histone(40U) + lipopolysaccharides (LPS; 10 μg/ml), or histone (40 U) + LPS (10 μg/ml) + heparin (25 IU/ml) for 6 h. For the histone + heparin group and the histone + LPS + heparin group, histone (and LPS) were treated with heparin simultaneously. Mice in the heparin intervention group showed decreased levels of EH4, neutrophil gelatinase-associated lipocalin (NAGL), kidney injury molecule-1 (KIM-1), tumor necrosis factor-α (TNF-α), and interleukin (IL)-6 in the blood serum, longer average 72-h survival rate, significantly decreased kidney tissue edema, and a clearer glomerular structure coupled with decreased protein and mRNA expression levels of kidney apoptosis-related proteins (cleaved Caspase-3/Caspase-3 and Bax/Bcl-2) compared with those in the sepsis group at 6 h after CLP (P < 0.05). Meanwhile, cells in the heparin intervention group exhibited lower expression levels of serum EH4 and inflammatory cytokines, a lower apoptosis rate, and decreased expression of apoptosis-related proteins, both at protein and mRNA levels, than those in the histone-stimulated group at 6 h after stimulation (P < 0.05). Heparin may alleviate apoptosis and inflammation through the neutralization of histones, thus playing a protective role against septic acute kidney injury.

Exosomes from adipose tissue-derived mesenchymal stem cells ameliorate histone-induced acute lung injury by activating the PI3K/Akt pathway in endothelial cells

BACKGROUND

Mesenchymal stem cells (MSCs), including adipose-derived mesenchymal stem cells (ADSCs), have been shown to attenuate organ damage in acute respiratory distress syndrome (ARDS) and sepsis; however, the underlying mechanisms are not fully understood. In this study, we aimed to explore the potential roles and molecular mechanisms of action of ADSCs in histone-induced endothelial damage.

METHODS

Male C57BL/6 N mice were intravenously injected with ADSCs, followed by histones or a vehicle. The mice in each group were assessed for survival, pulmonary vascular permeability, and histological changes. A co-culture model with primary human umbilical vein endothelial cells (HUVECs) exposed to histones was used to clarify the paracrine effect of ADSCs. Overexpression and inhibition of miR-126 ADSCs were also examined as causative factors for endothelial protection.

RESULTS

The administration of ADSCs markedly improved survival, inhibited histone-mediated lung hemorrhage and edema, and attenuated vascular hyper-permeability in mice. ADSCs were engrafted in the injured lung and attenuated histone-induced endothelial cell apoptosis. ADSCs showed endothelial protection (via a paracrine effect) and Akt phosphorylation in the histone-exposed HUVECs. Notably, increased Akt phosphorylation by ADSCs was mostly mediated by exosomes in histone-induced cytotoxicity and lung damage. Moreover, the expression of miR-126 was increased in exosomes from histone-exposed ADSCs. Remarkably, the inhibition of miR-126 in ADSCs failed to increase Akt phosphorylation in histone-exposed HUVECs.

CONCLUSION

ADSC-derived exosomes may exert protective effects on endothelial cells via activation of the PI3K/Akt pathway.

Epigenetic biomarkers for human sepsis and septic shock: insights from immunosuppression

Sepsis is a life-threatening condition that occurs when the body responds to an infection damaging its own tissues. Sepsis survivors sometimes suffer from immunosuppression increasing the risk of death. To our best knowledge, there is no 'gold standard' for defining immunosuppression except for a composite clinical end point. As the immune system is exposed to epigenetic changes during and after sepsis, research that focuses on identifying new biomarkers to detect septic patients with immunoparalysis could offer new epigenetic-based strategies to predict short- and long-term pathological events related to this life-threatening state. This review describes the most relevant epigenetic mechanisms underlying alterations in the innate and adaptive immune responses described in sepsis and septic shock, and their consequences for immunosuppression states, providing several candidates to become epigenetic biomarkers that could improve sepsis management and help predict immunosuppression in postseptic patients.

The Role of Neutrophils and Neutrophil Extracellular Traps in Vascular Damage in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune syndrome of unknown etiology, characterized by multi-organ inflammation and clinical heterogeneity. SLE affects mostly women and is associated with a high risk of cardiovascular disease. As the therapeutic management of SLE improved, a pattern of early atherosclerotic disease became one of the hallmarks of late disease morbidity and mortality. Neutrophils emerged as important players in SLE pathogenesis and they are associated with increased risk of developing atherosclerotic disease and vascular damage. Enhanced neutrophil extracellular trap (NET) formation was linked to vasculopathy in both SLE and non-SLE subjects and may promote enhanced coronary plaque formation and lipoprotein dysregulation. Foundational work provided insight into the complex relationship between NETs and immune and tissue resident cells within the diseased artery. In this review, we highlight the mechanistic link between neutrophils, NETs, and atherosclerosis within the context of both SLE and non-SLE subjects. We aim to identify actionable pathways that will drive future research toward translational therapeutics, with the ultimate goal of preventing early morbidity and mortality in SLE.

Vascular Protection of TPE-CA on Hyperhomocysteinemia-induced Vascular Endothelial Dysfunction through AA Metabolism Modulated CYPs Pathway

A high concentration of homocysteine (Hcy) in plasma induces vascular endothelial dysfunction, and it may ultimately accelerate the development of cardiovascular diseases (CVDs). Although several B vitamins have been clinically applied for hyperhomocysteinemia (HHcy) treatment, the outcomes are not satisfied due to their limited therapeutic mechanism. Hence, in order to improve the curative effect, development of new effective therapeutic strategies should be put on the agenda. Total phenolic extracts of Citrus aurantium L. (TPE-CA) is a naturally obtained phenolic mixture, mainly containing flavones, flavanones and their glycosyl derivatives, flavonols, polymethoxyflavones and coumarins. Previous reports indicated that bioactive phenolic compounds possessed potent vascular protective effects and regarded as a protective agent against CVDs. Intriguingly, the exact mechanism underlying the suppressed effects of TPE-CA on HHcy could assist in revealing their therapy on CVDs. Here, the multi-targeted synergistic mechanism of TPE-CA on HHcy-induced vascular endothelial dysfunction was uncovered in a deduced manner. TPE-CA treatment exhibited an obvious superiority than that of B vitamins treatment. Network pharmacology was employed to identify the interrelationships among compounds, potential targets and putative pathways. Further experimental validation suggested that the treatment of TPE-CA for HHcy could not only effectively reduce the Hcy level in plasma through up-regulating transsulfuration pathway in Hcy metabolism, but also restore the HHcy-induced vascular endothelial dysfunction by activating cytochrome P450 enzymes (CYPs) epoxygenase signal cascades and inhibiting CYPs hydroxylase signal cascades in arachidonic acid (AA) metabolism.

Flavin Oxidase-Induced ROS Generation Modulates PKC Biphasic Effect of Resveratrol on Endothelial Cell Survival

Background: Dietary intake of natural antioxidants is thought to impart protection against oxidative-associated cardiovascular diseases. Despite many in vivo studies and clinical trials, this issue has not been conclusively resolved. Resveratrol (RES) is one of the most extensively studied dietary polyphenolic antioxidants. Paradoxically, we have previously demonstrated that high RES concentrations exert a pro-oxidant effect eventually elevating ROS levels leading to cell death. Here, we further elucidate the molecular determinants underpinning RES-induced oxidative cell death. Methods: Using human umbilical vein endothelial cells (HUVECs), the effect of increasing concentrations of RES on DNA synthesis and apoptosis was studied. In addition, mRNA and protein levels of cell survival or apoptosis genes, as well as protein kinase C (PKC) activity were determined. Results: While high concentrations of RES reduce PKC activity, inhibit DNA synthesis and induce apoptosis, low RES concentrations elicit an opposite effect. This biphasic concentration-dependent effect (BCDE) of RES on PKC activity is mirrored at the molecular level. Indeed, high RES concentrations upregulate the proapoptotic Bax, while downregulating the antiapoptotic Bcl-2, at both mRNA and protein levels. Similarly, high RES concentrations downregulate the cell cycle progression genes, c-myc, ornithine decarboxylase (ODC) and cyclin D1 protein levels, while low RES concentrations display an increasing trend. The BCDE of RES on PKC activity is abrogated by the ROS scavenger Tempol, indicating that this enzyme acts downstream of the RES-elicited ROS signaling. The RES-induced BCDE on HUVEC cell cycle machinery was also blunted by the flavin inhibitor diphenyleneiodonium (DPI), implicating flavin oxidase-generated ROS as the mechanistic link in the cellular response to different RES concentrations. Finally, PKC inhibition abrogates the BCDE elicited by RES on both cell cycle progression and pro-apoptotic gene expression in HUVECs, mechanistically implicating PKC in the cellular response to different RES concentrations. Conclusions: Our results provide new molecular insight into the impact of RES on endothelial function/dysfunction, further confirming that obtaining an optimal benefit of RES is concentration-dependent. Importantly, the BCDE of RES could explain why other studies failed to establish the cardio-protective effects mediated by natural antioxidants, thus providing a guide for future investigation looking at cardio-protection by natural antioxidants.

Extracellular vesicles in autoimmune vasculitis - Little dirts light the fire in blood vessels

Systemic vasculitis is diverse group of autoimmune disorders which are characterized by inflammation of blood vessel walls with deep aching and burning pain. Their underlying etiology and pathophysiology still remain poorly understood. Extracellular vesicles (EVs), including exosomes, microvesicles (MVs), and apoptotic bodies, are membrane vesicular structures that are released either during cell activation, or when cells undergo programmed cell death, including apoptosis, necroptosis, and pyroptosis. Although EVs were thought as cell dusts, but now they have been found to be potently active since they harbor bioactive molecules, such as proteins, lipids, nucleic acids, or multi-molecular complexes. EVs can serve as novel mediators for cell-to-cell communications by delivery bioactive molecules from their parental cells to the recipient cells. Earlier studies mainly focused on MVs budding from membrane surface. Recent studies demonstrated that EVs may also carry molecules from cytoplasm or even from nucleus of their parental cells, and these EVs may carry autoantigens and are important in vasculitis. EVs may play important roles in vasculitis through their potential pathogenic involvements in inflammation, autoimmune responses, procoagulation, endothelial dysfunction/damage, angiogenesis, and intimal hyperplasia. EVs have also been used as specific biomarkers for diagnostic use or disease severity monitoring. In this review, we have focused on the aspects of EV biology most relevant to the pathogenesis of vasculitis, discussed their perspective insights, and summarized the exist literature on EV relevant studies in vasculitis, therefore provides an integration of current knowledge regarding the novel role of EVs in systemic vasculitis.

Extracellular Histones Activate Plasma Membrane Toll-Like Receptor 9 to Trigger Calcium Oscillations in Rat Pancreatic Acinar Tumor Cell AR4-2J

In acute pancreatitis, histones are released by infiltrating neutrophils, but how histones modulate pancreatic acinar cell function has not been investigated. We have examined histone modulation of rat pancreatic acini and pancreatic acinar tumor cell AR4-2J by calcium imaging. Histones were found to have no effect on calcium in pancreatic acini but blocked calcium oscillations induced by cholecystokinin or acetylcholine. Both mixed (Hx) and individual (H1, H2A, H2B, H3, H4) histones induced calcium oscillations in AR4-2J. RT-PCR and Western blot verified the expression of histone-targeted Toll-like receptor (TLR) 2, 4 and 9. Immunocytochemistry identified TLR2/TLR4 on apical plasma membrane and TLR9 in zymogen granule regions in pancreatic acini. TLR2 was found on neighboring and TLR9 on peripheral plasma membranes, but TLR4 was in the nucleus in AR4-2J clusters. Neither TLR2 agonist zymosan-A nor TLR4 agonist lipopolysaccharide had any effect on calcium, but TLR9 agonist ODN1826 induced calcium oscillations; TLR9 antagonist ODN2088 blocked H4-induced calcium oscillations in AR4-2J, which also disappeared after treatment of AR4-2J with glucocorticoid dexamethasone, with concurrent TLR9 migration from plasma membrane to cell interiors. TLR9 down regulation with siRNA suppressed H4-induced calcium oscillations. These data together suggest that extracellular histones activate plasma membrane TLR9 to trigger calcium oscillations in AR4-2J cells.

Influence of Active Exposure to Tobacco Smoke on Nitric Oxide Status of Pregnant Women

Smoking tobacco can impair proper vascular endothelial functioning. This is exhibited through reduced nitric oxide synthesis as well as activity due to accompanying oxidative stress. We examined the relationship between nitric oxide and markers of oxidative stress/antioxidant defense in serum of smoking and non-smoking pregnant women. Subjects included 99 healthy pregnant women, who were tested for nitric oxide (NO), endothelial (eNOS) and inducible (iNOS) nitric oxide synthase, total oxidant capacity (TOC), and total antioxidant capacity (TAC). NO, eNOS, and TAC serum concentrations were significantly lower (p < 0.005), but iNOS (p < 0.05) and TOC (p < 0.001) were higher in smokers than in non-smokers. Multivariate regression analysis showed associations between NO concentration and eNOS, TAC, and smoking status in the whole group of patients. In the model estimated separately for smokers, the highest impact of eNOS (β = 0.375; p = 0.021) and cotinine (β = −0.323; p = 0.037) was indicated for NO concentration. In the model of non-smokers, eNOS (β = 0.291, p = 0.030) and TAC (β = 0.350; p = 0.015) were important for NO level. Smoking during pregnancy could exacerbate oxidative stress, impair the action of nitric oxide synthases, and adversely affect the balance of oxygen and nitrogen metabolism. Relationships between NO concentrations and TAC in the studied women’s blood can confirm the antioxidant nature of nitric oxide.

A Comparative Review of Neutrophil Extracellular Traps in Sepsis

Sepsis is the leading cause of critical illness and mortality in human beings and animals. Neutrophils are the primary effector cells of innate immunity during sepsis. Besides degranulation and phagocytosis, neutrophils also release neutrophil extracellular traps (NETs), composed of cell-free DNA, histones, and antimicrobial proteins. Although NETs have protective roles in the initial stages of sepsis, excessive NET formation has been found to induce thrombosis and multiple organ failure in murine sepsis models. Since the discovery of NETs nearly a decade ago, many investigators have identified NETs in various species. However, many questions remain regarding the exact mechanisms and fate of neutrophils following NET formation. In humans and mice, platelet-neutrophil interactions via direct binding or soluble mediators seem to play an important role in mediating NET formation during sepsis. Preliminary data suggest that these interactions may be species dependent. Regardless of these differences, there is increasing evidence in human and veterinary medicine suggesting that NETs play a crucial role in the pathogenesis of intravascular thrombosis and multiple organ failure in sepsis. Because the outcome of sepsis is highly dependent on early recognition and intervention, detection of NETs or NET components can aid in the diagnosis of sepsis in humans and veterinary species. In addition, the use of novel therapies such as deoxyribonuclease and non-anticoagulant heparin to target NET components shows promising results in murine septic models. Much work is needed in translating these NET-targeting therapies to clinical practice.

The Relationship of COX-2 Gene Polymorphisms and Susceptibility to Kawasaki Disease in Chinese Population

BACKGROUND

Kawasaki disease (KD) is an acute systemic vasculitis that predominantly affects children, and it can result in coronary artery lesions. Cyclooxygenase-2 (COX-2) is involved in the conversion of arachidonic acid to prostaglandin H2, an important precursor of several prostaglandins. The aim of this study was to examine the association between COX-2 gene polymorphisms and susceptibility to KD.

METHODS

A total of 276 subjects (136 KD and 140 controls) were recruited. The analysis of two single nucleotide polymorphisms rs689466 (-1195G/A) and rs20417 (-765G/C) was respectively detected with polymerase chain reaction sequence-based typing methods.

RESULTS

Polymorphisms of rs689466 were significantly different between the normal controls and KD patients (χ² = 6.070 and 5.435, both p < 0.05). The frequencies of AA genotype and A allele of rs689466 in Kawasaki disease group were higher than that of control group (χ² = 4.832, p = 0.028, OR = 1.832, 95%CI = 1.064-3.124; χ² = 5.435, p = 0.028, OR = 1.491, 95%CI = 1.065-2.088).

CONCLUSION

This study provides the first evidence supporting an association between COX-2 gene polymorphisms and susceptibility of KD. The AA genotype and A allele of rs689466 confer predisposing factors to KD.

Increased Concentrations of Extracellular Histones in Patients with Tuberculous Pleural Effusion

Background

Extracellular histones have recently been suggested as critical mediators in many inflammatory diseases. However, the role of extracellular histones in tuberculous pleural effusion (TPE) is unclear. The goal of this study was to explore the potential involvement of extracellular histones in patients with TPE.

Material/Methods

Samples of pleural effusion and peripheral blood were obtained from 58 patients with tuberculosis. Extracellular histones were determined in both TPE and serum samples. Moreover, the biomarkers for cellular damage, inflammatory cell activation, and systemic inflammation including lactate dehydrogenase (LDH), myeloperoxidase (MPO), S100A8/A9, as well as multiple inflammatory cytokines were measured.

Results

Extracellular histone levels were significantly elevated in TPE (4.762 mg/mL [3.336, 7.307]) and serum samples (1.502 mg/mL [1.084, 2.478]) from tuberculosis patients as compared with the serum (0.585 mg/mL [0.285, 0.949]) from healthy controls. Notably, extracellular histones in TPE were also much higher than in serum of patients (P=0.002). LDH, MPO, and S100A8/A9 levels were all increased in TPE, along with a remarkable elevation of various cytokines. A correlation analysis showed that extracellular histones were positively associated with LDH, MPO, and S100A8/A9, and a panel of inflammatory cytokines in TPE.

Conclusions

These results suggest that high concentrations of extracellular histones are markedly present in TPE, which may play an inflammatory role towards the progression of tuberculosis.

Extracellular histones activate autophagy and apoptosis via mTOR signaling in human endothelial cells

Circulating histones have been proposed as targets for therapy in sepsis and hyperinflammatory symptoms. However, the proposed strategies have failed in clinical trials. Although different mechanisms for histone-related cytotoxicity are being explored, those mediated by circulating histones are not fully understood. Extracellular histones induce endothelial cell death, thereby contributing to the pathogenesis of complex diseases such as sepsis and septic shock. Therefore, the comprehension of cellular responses triggered by histones is capital to design effective therapeutic strategies. Here we report how extracellular histones induce autophagy and apoptosis in a dose-dependent manner in cultured human endothelial cells. In addition, we describe how histones regulate these pathways via Sestrin2/AMPK/ULK1-mTOR and AKT/mTOR. Furthermore, we evaluate the effect of Toll-like receptors in mediating autophagy and apoptosis demonstrating how TLR inhibitors do not prevent apoptosis and/or autophagy induced by histones. Our results confirm that histones and autophagic pathways can be considered as novel targets to design therapeutic strategies in endothelial damage.

A new mass spectrometry-based method for the quantification of histones in plasma from septic shock patients

The aim of this study was to develop a novel method to detect circulating histones H3 and H2B in plasma based on multiple reaction monitoring targeted mass spectrometry and a multiple reaction monitoring approach (MRM-MS) for its clinical application in critical bacteriaemic septic shock patients. Plasma samples from 17 septic shock patients with confirmed bacteraemia and 10 healthy controls were analysed by an MRM-MS method, which specifically detects presence of histones H3 and H2B. By an internal standard, it was possible to quantify the concentration of circulating histones in plasma, which were significantly higher in patients, and thus confirmed their potential as biomarkers for diagnosing septic shock. After comparing surviving patients and non-survivors, a correlation was found between higher levels of circulating histones and unfavourable outcome. Indeed, histone H3 proved a more efficient and sensitive biomarker for septic shock prognosis. In conclusion, these findings suggest the accuracy of the MRM-MS technique and stable isotope labelled peptides to detect and quantify circulating plasma histones H2B and H3. This method may be used for early septic shock diagnoses and for the prognosis of fatal outcomes.