Red cell DAMPs and inflammation

Establishment and Verification of a Risk Prediction Model for Chronic Rhinosinusitis

Objective: Factors influencing chronic rhinosinusitis (CRS) are usually studied in terms of genetics and environment; however, clinical indicators have not been reported. This case-control study was conducted in Ningbo, China, to explore new independent risk factors for CRS. Methods: A total of 695 participants, including 440 healthy controls and 255 patients with CRS, were included in this study. Clinical data were retrieved from questionnaires and electronic medical record systems of hospitals. Independent risk factors were screened using logistic regression and 10-fold cross-validation combined with the least absolute shrinkage and selection operator. A CRS risk prediction model was established using logistic regression, and nomograms were visualized. The model was validated and evaluated using receiver operating characteristic (ROC) curves, calibration curves, and decision curve analysis (DCA). Results: Ten independent risk factors, including alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, creatinine, triglyceride, total cholesterol, red blood cell count, hemoglobin, lymphocyte percentage, and monocyte percentage were screened. ROC analysis showed that the area under the curve of the training set was 0.890, indicating that the predictive model had excellent discriminant ability. The calibration curves showed that the fitting curves of the training set were close to the reference curves, indicating that the model had a good fit. The DCA showed that the threshold probability range of the training set was 1% to 89%. Conclusions: Independent risk factors for CRS were screened, and a prediction model was constructed, which is of significance for the prevention, control, and treatment of the disease.

Exploring the destructive synergy between IL-33 and Suilysin hemolysis on blood-brain barrier stability

Streptococcus suis type 2 (SS2) is a zoonotic pathogen capable of eliciting meningitis, presenting significant challenges to both the swine industry and public health. Suilysin (Sly), one of SS2 most potent virulence determinants, releases a surfeit of inflammatory agents following red blood cell lysis. Notably, while current research on Sly role in SS2-induced meningitis predominantly centers on its interaction with the blood-brain barrier (BBB), the repercussions of Sly hemolytic products on BBB function have largely been sidestepped. In this vein, our study delves into the ramifications of Sly-induced hemolysis on BBB integrity. We discern that Sly hemolytic derivatives exacerbate the permeability of Sly-induced in vitro BBB models. Within these Sly hemolytic products, Interleukin-33 (IL-33) disrupts the expression and distribution of Claudin-5 in brain microvascular endothelial cells, facilitating the release of Interleukin-6 (IL-6) and Interleukin-8 (IL-8), thereby amplifying BBB permeability. Preliminary mechanistic insights suggest that IL-33-driven expression of IL-6 and IL-8 is orchestrated by the p38-mitogen-activated protein kinase signaling, whereas matrix metalloproteinase 9 mediates IL-33-induced suppression of Claudin-5. To validate these in vitro findings, an SS2-infected mouse model was established, and upon intravenous administration of growth stimulation expressed gene 2 (ST2) antibodies, in vivo results further underscored the pivotal role of the IL-33/ST2 axis during SS2 cerebral invasion. In summation, this study pioneerly illuminates the involvement of Sly hemolytic products in SS2-mediated BBB compromise and spotlights the instrumental role and primary mechanism of IL-33 therein. These insights enrich our comprehension of SS2 meningitis pathogenesis, laying pivotal groundwork for therapeutic advancements against SS2-induced meningitis.IMPORTANCEThe treatment of meningitis caused by Streptococcus suis type 2 (SS2) has always been a clinical challenge. Elucidating the molecular mechanisms by which SS2 breaches the blood-brain barrier (BBB) is crucial for the development of meningitis therapeutics. Suilysin (Sly) is one of the most important virulence factors of SS2, which can quickly lyse red blood cells and release large amounts of damage-associated molecular patterns, such as hemoglobin, IL-33, cyclophilin A, and so on. However, the impact of these hemolytic products on the function of BBB is unknown and ignored. This study is the first to investigate the effect of Sly hemolytic products on BBB function. The data are crucial for the study of the pathogenesis of SS2 meningitis and can provide an important reference for the development of meningitis therapeutics.

Impacts of oxidative stress and anti-oxidants on the development, pathogenesis, and therapy of sickle cell disease: A comprehensive review

Sickle cell disease (SCD) is the most severe monogenic hemoglobinopathy caused by a single genetic mutation that leads to repeated polymerization and depolymerization of hemoglobin resulting in intravascular hemolysis, cell adhesion, vascular occlusion, and ischemia-reperfusion injury. Hemolysis causes oxidative damage indirectly by generating reactive oxygen species through various pathophysiological mechanisms, which include hemoglobin autoxidation, endothelial nitric oxide synthase uncoupling, reduced nitric oxide bioavailability, and elevated levels of asymmetric dimethylarginine. Red blood cells have a built-in anti-oxidant system that includes enzymes like sodium dismutase, catalase, and glutathione peroxidase, along with free radical scavenging molecules, such as vitamin C, vitamin E, and glutathione, which help them to fight oxidative damage. However, these anti-oxidants may not be sufficient to prevent the effects of oxidative stress in SCD patients. Therefore, in line with a recent FDA request that the focus to be placed on the development of innovative therapies for SCD that address the root cause of the disease, there is a need for therapies that target oxidative stress and restore redox balance in SCD patients. This review summarizes the current state of knowledge regarding the role of oxidative stress in SCD and the potential benefits of anti-oxidant therapies. It also discusses the challenges and limitations of these therapies and suggests future directions for research and development.

Hemocompatibility studies in nanotoxicology: Hemolysis or eryptosis? (A review)

Hemocompatibility evaluation is an important step in nanotoxicological studies. It is generally accepted that nanomaterials promote lysis of erythrocytes, blood clotting, alter phagocytosis, and upregulate pro-inflammatory cytokines. However, there are no standardized guidelines for testing nanomaterials hemocompatibility despite the fact that nanomaterials enter the bloodstream and interact with blood cells. In this review, the current knowledge on the ability of nanomaterials to induce distinct cell death modalities of erythrocytes is highlighted primarily focusing on hemolysis and eryptosis. This review aims to summarize the molecular mechanisms underlying erythrotoxicity of nanomaterials and critically compare the sensitivity and efficiency of hemolysis or eryptosis assays for nanomaterials blood compatibility testing. The list of eryptosis-inducing nanomaterials is growing, but it is still difficult to generalize how physico-chemical properties of nanoparticles affect eryptosis degree and molecular mechanisms involved. Thus, another aim of this review is to raise the awareness of eryptosis as a nanotoxicological tool to encourage the corresponding studies. It is worthwhile to consider adding eryptosis to in vitro nanomaterials hemocompatibility testing protocols and guidelines.

Phenotype and function of IL-10 producing NK cells in individuals with malaria experience

Plasmodium falciparum infection can trigger high levels of inflammation that lead to fever and sometimes severe disease. People living in malaria-endemic areas gradually develop resistance to symptomatic malaria and control both parasite numbers and the inflammatory response. We previously found that adaptive natural killer (NK) cells correlate with reduced parasite load and protection from symptoms. We also previously found that murine NK cell production of IL-10 can protect mice from experimental cerebral malaria. Human NK cells can also secrete IL-10, but it was unknown what NK cell subsets produce IL-10 and if this is affected by malaria experience. We hypothesize that NK cell immunoregulation may lower inflammation and reduce fever induction. Here, we show that NK cells from subjects with malaria experience make significantly more IL-10 than subjects with no malaria experience. We then determined the proportions of NK cells that are cytotoxic and produce interferon gamma and/or IL-10 and identified a signature of adaptive and checkpoint molecules on IL-10-producing NK cells. Lastly, we find that co-culture with primary monocytes, Plasmodium -infected RBCs, and antibody induces IL-10 production by NK cells. These data suggest that NK cells may contribute to protection from malaria symptoms via IL-10 production.

DAMPs and DAMP-sensing receptors in inflammation and diseases

Damage-associated molecular patterns (DAMPs) are endogenous danger molecules produced in cellular damage or stress, and they can activate the innate immune system. DAMPs contain multiple types of molecules, including nucleic acids, proteins, ions, glycans, and metabolites. Although these endogenous molecules do not trigger immune response under steady-state condition, they may undergo changes in distribution, physical or chemical property, or concentration upon cellular damage or stress, and then they become DAMPs that can be sensed by innate immune receptors to induce inflammatory response. Thus, DAMPs play an important role in inflammation and inflammatory diseases. In this review, we summarize the conversion of homeostatic molecules into DAMPs; the diverse nature and classification, cellular origin, and sensing of DAMPs; and their role in inflammation and related diseases. Furthermore, we discuss the clinical strategies to treat DAMP-associated diseases via targeting DAMP-sensing receptors.

Non-canonical IKB kinases regulate YAP/TAZ and pathological vascular remodeling behaviors in pulmonary artery smooth muscle cells

Pulmonary arterial hypertension (PAH) causes pulmonary vascular remodeling, increasing pulmonary vascular resistance (PVR) and leading to right heart failure and death. Matrix stiffening early in the disease promotes remodeling in pulmonary artery smooth muscle cells (PASMCs), contributing to PAH pathogenesis. Our research identified YAP and TAZ as key drivers of the mechanobiological feedback loop in PASMCs, suggesting targeting them could mitigate remodeling. However, YAP/TAZ are ubiquitously expressed and carry out diverse functions, necessitating a cell-specific approach. Our previous work demonstrated that targeting non-canonical IKB kinase TBK1 reduced YAP/TAZ activation in human lung fibroblasts. Here, we investigate non-canonical IKB kinases TBK1 and IKKε in pulmonary hypertension (PH) and their potential to modulate PASMC pathogenic remodeling by regulating YAP/TAZ. We show that TBK1 and IKKε are activated in PASMCs in a rat PH model. Inflammatory cytokines, elevated in PAH, activate these kinases in human PASMCs. Inhibiting TBK1/IKKε expression/activity significantly reduces PAH-associated PASMC remodeling, with longer-lasting effects on YAP/TAZ than treprostinil, an approved PAH therapy. These results show that non-canonical IKB kinases regulate YAP/TAZ in PASMCs and may offer a novel approach for reducing vascular remodeling in PAH.

NFκB and NLRP3/NLRC4 inflammasomes regulate differentiation, activation and functional properties of monocytes in response to distinct SARS-CoV-2 proteins

Increased recruitment of transitional and non-classical monocytes in the lung during SARS-CoV-2 infection is associated with COVID-19 severity. However, whether specific innate sensors mediate the activation or differentiation of monocytes in response to different SARS-CoV-2 proteins remain poorly characterized. Here, we show that SARS-CoV-2 Spike 1 but not nucleoprotein induce differentiation of monocytes into transitional or non-classical subsets from both peripheral blood and COVID-19 bronchoalveolar lavage samples in a NFκB-dependent manner, but this process does not require inflammasome activation. However, NLRP3 and NLRC4 differentially regulated CD86 expression in monocytes in response to Spike 1 and Nucleoprotein, respectively. Moreover, monocytes exposed to Spike 1 induce significantly higher proportions of Th1 and Th17 CD4 + T cells. In contrast, monocytes exposed to Nucleoprotein reduce the degranulation of CD8 + T cells from severe COVID-19 patients. Our study provides insights in the differential impact of innate sensors in regulating monocytes in response to different SARS-CoV-2 proteins, which might be useful to better understand COVID-19 immunopathology and identify therapeutic targets.

MicroRNA-223-3p downregulates the inflammatory response in preeclampsia placenta via targeting NLRP3

OBJECTIVE

To investigate the regulatory role of miR-223-3p in the inflammatory response of PE placenta.

METHODS

PE and normal placental tissues were collected to measure the expression of NLRP3 and miR-223-3p. The targeting relationship between NLRP3 and miR-223-3P was verified by bioinformatics analysis and classical double-luciferase reporter gene assay. Lipopolysaccharide (LPS) was used to induce HTR8/SVneo cells as PE placental cell inflammation model. Then we transfected miR-223-3p overexpression/miR-223-3p negative control plasmid into the LPS-induced HTR8/SVneo cells. Next, the expressions of NLRP3, Caspase-1, GSDMD, IL-1β and IL-18 were evaluated to elucidate the regulatory effect of miR-223-3p on the inflammatory response mediated by NLRP3 in PE placenta.

RESULTS

Compared with normal controls, NLRP3 was significantly up-regulated in PE placenta, while miR-223-3p was down-regulated. In addition, NLRP3 was a direct target of miR-223-3p. Further research revealed that the expression of NLRP3, Caspase-1, GSDMD, IL-1β and IL-18 could be obviously promoted in HTR8/SVneo cells treated with LPS (500 ng/ml) for 24 h, nevertheless it could be significantly suppressesed under the overexpression of miR-223-3p.

CONCLUSION

MiR-223-3p suppressed NLRP3 inflamariomes activation, downstream inflammatory factors secretion and pyroptosis in LPS-induced HTR8/SVneo cells indicating that miR-223-3p could serve as an anti-inflammatory factor in preeclampsia.

Erythronecroptosis: an overview of necroptosis or programmed necrosis in red blood cells

Necroptosis is considered a programmed necrosis that requires receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3), and pore-forming mixed lineage kinase domain-like protein (MLKL) to trigger a regulated cell membrane lysis. Membrane rupture in necroptosis has been shown to fuel innate immune response due to release of damage-associated molecular patterns (DAMPs). Recently published studies indicate that mature erythrocytes can undergo necroptosis as well. In this review, we provide an outline of multiple cell death modes occurring in erythrocytes, discuss possible immunological aspects of diverse erythrocyte cell deaths, summarize available evidence related to the ability of erythrocytes to undergo necroptosis, outline key involved molecular mechanisms, and discuss the potential implication of erythrocyte necroptosis in the physiology and pathophysiology. Furthermore, we aim to highlight the interplay between necroptosis and eryptosis signaling in erythrocytes, emphasizing specific characteristics of these pathways distinct from their counterparts in nucleated cells. Thus, our review provides a comprehensive summary of the current knowledge of necroptosis in erythrocytes. To reflect critical differences between necroptosis of nucleated cells and necroptosis of erythrocytes, we suggest a term erythronecroptosis for necroptosis of enucleated cells.

A Versatile Nanovaccine Enhancement Strategy Based on Suction-Inspired Physical Therapy

Vaccine technology is effective in preventing and treating diseases, including cancers and viruses. The efficiency of vaccines can be improved by increasing the dosage and frequency of injections, but it would bring an extra burden to people. Therefore, it is necessary to develop vaccine-boosting techniques with negligible side effects. Herein, we reported a cupping-inspired noninvasive suction therapy that could enhance the efficacy of cancer/SARS-CoV-2 nanovaccines. Negative pressure caused mechanical immunogenic cell death and released endogenous adjuvants. This created a subcutaneous niche that would recruit and activate antigen-presenting cells. Based on this universal central mechanism, suction therapy was successfully applied in a variety of nanovaccine models, which include prophylactic/therapeutic tumor nanovaccine, photothermal therapy induced in situ tumor nanovaccine, and SARS-CoV-2 nanovaccine. As a well-established physical therapy method, suction therapy may usher in an era of noninvasive and high-safety auxiliary strategies when combined with vaccines.

NLRP3 Contributes to Sarcopenia Associated to Dependency Recapitulating Inflammatory-Associated Muscle Degeneration

Sarcopenia, a complex and debilitating condition characterized by progressive deterioration of skeletal muscle, is the primary cause of age-associated disability and significantly impacts healthspan in elderly patients. Despite its prevalence among the aging population, the underlying molecular mechanisms are still under investigation. The NLRP3 inflammasome is crucial in the innate immune response and has a significant impact on diseases related to inflammation and aging. Here, we investigated the expression of the NLRP3 inflammasome pathway and pro-inflammatory cytokines in skeletal muscle and peripheral blood of dependent and independent patients who underwent hip surgery. Patients were categorized into independent and dependent individuals based on their Barthel Index. The expression of NLRP3 inflammasome components was significantly upregulated in sarcopenic muscle from dependent patients, accompanied by higher levels of Caspase-1, IL-1β and IL-6. Among older dependent individuals with sarcopenia, there was a significant increase in the MYH3/MYH2 ratio, indicating a transcriptional shift in expression from mature to developmental myosin isoforms. Creatine kinase levels and senescence markers were also higher in dependent patients, altogether resembling dystrophic diseases and indicating muscle degeneration. In summary, we present evidence for the involvement of the NLRP3/ASC/NEK7/Caspase-1 inflammasome pathway with activation of pro-inflammatory SASP in the outcome of sarcopenia in the elderly.

Cell-free hemoglobin triggers macrophage cytokine production via TLR4 and MyD88

Cell-free hemoglobin (CFH) is elevated in the airspace of patients with acute respiratory distress syndrome (ARDS) and is sufficient to cause acute lung injury in a murine model. However, the pathways through which CFH causes lung injury are not well understood. Toll-like receptor 4 (TLR4) is a mediator of inflammation after detection of damage- and pathogen-associated molecular patterns. We hypothesized that TLR4 signaling mediates the proinflammatory effects of CFH in the airspace. After intratracheal CFH, BALBc mice deficient in TLR4 had reduced inflammatory cell influx into the airspace [bronchoalveolar lavage (BAL) cell counts, median TLR4 knockout (KO): 0.8 × 104/mL [IQR 0.4-1.2 × 104/mL], wild-type (WT): 3.0 × 104/mL [2.2-4.0 × 104/mL], P < 0.001] and attenuated lung permeability (BAL protein, TLR4KO: 289 µg/mL [236-320], WT: 488 µg/mL [422-536], P < 0.001). These mice also had attenuated production of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in the airspace. C57Bl/6 mice lacking TLR4 on myeloid cells only (LysM.Cre+/-TLR4fl/fl) had reduced cytokine production in the airspace after CFH, without attenuation of lung permeability. In vitro studies confirm that WT primary murine alveolar macrophages exposed to CFH (0.01-1 mg/mL) had dose-dependent increases in IL-6, IL-1 β, CXC motif chemokine ligand 1 (CXCL-1), TNF-α, and IL-10 (P < 0.001). Murine MH-S alveolar-like macrophages show TLR4-dependent expression of IL-1β, IL-6, and CXCL-1 in response to CFH. Primary alveolar macrophages from mice lacking TLR4 adaptor proteins myeloid differentiation primary response 88 (MyD88) or TIR-domain-containing adapter-inducing interferon-β (TRIF) revealed that MyD88KO macrophages had 71-96% reduction in CFH-dependent proinflammatory cytokine production (P < 0.001), whereas macrophages from TRIFKO mice had variable changes in cytokine responses. These data demonstrate that myeloid TLR4 signaling through MyD88 is a key regulator of airspace inflammation in response to CFH.NEW & NOTEWORTHY Cell-free hemoglobin (CFH) is elevated in the airspace of most patients with acute respiratory distress syndrome and causes severe inflammation. Here, we identify that CFH contributes to macrophage-induced cytokine production via Toll-like receptor 4 (TLR4) and myeloid differentiation primary response 88 (MyD88) signaling. These data increase our knowledge of the mechanisms through which CFH contributes to lung injury and may inform development of targeted therapeutics to attenuate inflammation.

Isolation methods determine human neutrophil responses after stimulation

Studying neutrophils is challenging due to their limited lifespan, inability to proliferate, and resistance to genetic manipulation. Neutrophils can sense various cues, making them susceptible to activation by blood collection techniques, storage conditions, RBC lysis, and the isolation procedure itself. Here we assessed the impact of the five most used methods for neutrophil isolation on neutrophil yield, purity, activation status and responsiveness. We monitored surface markers, reactive oxygen species production, and DNA release as a surrogate for neutrophil extracellular trap (NET) formation. Our results show that neutrophils isolated by negative immunomagnetic selection and density gradient methods, without RBC lysis, resembled untouched neutrophils in whole blood. They were also less activated and more responsive to milder stimuli in functional assays compared to neutrophils obtained using density gradients requiring RBC lysis. Our study highlights the importance of selecting the appropriate method for studying neutrophils, and underscores the need for standardizing isolation protocols to facilitate neutrophil subset characterization and inter-study comparisons.

Hemocompatibility of dextran-graft-polyacrylamide/zinc oxide nanosystems: hemolysis or eryptosis?

Aim. In this study, blood compatibility of ZnO nanoparticles-polymer nanocomplex (D-PAA/ZnONPs(SO42-)) synthesizedin situinto dextran-graft-polyacrylamide (D-PAA) using zinc sulphate as a precursor was tested using hemolysis, osmotic fragility and eryptosis assays.Materials and methods. Dose-dependent ability to induce eryptosis was assessed following 24 h incubation at concentrations of 0-800 mg l-1analyzing hallmarks of eryptosis (cell shrinkage and phosphatidylserine externalization), as well as reactive oxygen species generation. Hemolysis was detected spectrophotometrically based on hemoglobin release following exposure to the D-PAA/ZnONPs(SO42-) nanocomplex. Osmotic fragility test (OFT) involved detection of hemolysis of red blood cells exposed to 0.2% saline solution following incubation with the D-PAA/ZnONPs(SO42-) nanocomplex. Additional incubation of the nanocomplex in the presence or absence of either ascorbic acid or EGTA was used to reveal the implication of oxidative stress- or Ca2+-mediated mechanisms in D-PAA/ZnONPs(SO42-) nanocomplex-induced erythrotoxicity.Results. Hemocompatibility assessment of the D-PAA/ZnONPs(SO42-) nanocomplex revealed that it induced hemolysis and reduced resistance of erythrocytes to osmotic stress at concentrations of above 400 and 200 mg l-1, respectively. Oxidative stress- or Ca2+-mediated mechanisms were not involved in D-PAA/ZnONPs(SO42-) nanocomplex-induced hemolysis. Strikingly, the D-PAA/ZnONPs(SO42-) nanocomplex did not promote cell membrane scrambling, cell shrinkage and oxidative stress in red blood cells following the direct exposure for 24 h. Thus, the D-PAA/ZnONPs(SO42-) nanocomplex did not induce eryptosisin vitro. Eryptosis is generally considered to occur earlier than hemolysis in response to stress in order to prevent hemolytic cell death. Counterintuitively, our data suggest that hemolysis can be triggered by nanomaterials prior to eryptosis indicating that eryptosis and hemolysis assays should be used in combination for testing blood compatibility of nanomaterials.Conclusions. The D-PAA/ZnONPs(SO42-) nanocomplex has a good hemocompatibility profile at low concentrations. Hemocompatibility testing in nanotoxicology should include both eryptosis and hemolysis assays.

Hemolysis dictates monocyte differentiation via two distinct pathways in sickle cell disease vaso-occlusion

Sickle cell disease (SCD) is a hereditary hemoglobinopathy characterized by painful vaso-occlusive crises (VOC) and chronic hemolysis. The mononuclear phagocyte system is pivotal to SCD pathophysiology, but the mechanisms governing monocyte/macrophage differentiation remain unknown. This study examined the influence of hemolysis on circulating monocyte trajectories in SCD. We discovered that hemolysis stimulated CSF-1 production, partly by endothelial cells via Nrf2, promoting classical monocyte (CMo) differentiation into blood patrolling monocytes (PMo) in SCD mice. However, hemolysis also upregulated CCL-2 through IFN-I, inducing CMo transmigration and differentiation into tissue monocyte-derived macrophages. Blocking CMo transmigration by anti-P selectin antibody in SCD mice increased circulating PMo, corroborating that CMo-to-tissue macrophage differentiation occurs at the expense of CMo-to-blood PMo differentiation. We observed a positive correlation between plasma CSF-1/CCL-2 ratios and blood PMo levels in patients with SCD, underscoring the clinical significance of these two opposing factors in monocyte differentiation. Combined treatment with CSF-1 and anti-P selectin antibody more effectively increased PMo numbers and reduced stasis compared with single-agent therapies in SCD mice. Altogether, these data indicate that monocyte fates are regulated by the balance between two heme pathways, Nrf2/CSF-1 and IFN-I/CCL-2, and suggest that the CSF-1/CCL-2 ratio may present a diagnostic and therapeutic target in SCD.

Activation of the Acute-Phase Response in Hemophilia

To identify recurrent inflammation in hemophilia, we assessed the acute-phase response in the blood of patients with hemophilia A and B. Compared to age- and weight-matched controls, blood levels of interleukin-6 (IL-6), C-reactive protein (CRP), and LPS-binding protein (LBP) were significantly elevated in the entire cohort of hemophilia patients but exhibited a particularly pronounced increase in obese hemophilia patients with a body mass index (BMI) ≥30. Subgroup analysis of the remaining nonobese hemophilia patients (BMI: 18-29.9) revealed a significant spike of IL-6, CRP, and LBP in connection with a de-novo increase of soluble IL-6 receptor α (sIL-6Rα) in patients with bleeding events within the last month. Hemophilia patients who did not experience recent bleeding had IL-6, CRP, and sIL-6Rα blood levels similar to healthy controls. We did not find increased IL-6 or acute-phase reactants in hemophilia patients with arthropathy or infectious disease. The role of IL-6 as a marker of bleeding in hemophilia was confirmed in hemophilia patients with acute bleeding events as well as in transgenic hemophilia mice after needle puncture of the knee, which exhibited an extensive hematoma and a 150-fold increase of IL-6 blood levels within 7 days of the injury compared to needle-punctured control mice. Notably, IL-6 blood levels shrunk to a fourfold elevation in hemophilia mice over controls after 28 days, when the hematoma was replaced by arthrofibrosis. These findings indicate that acute-phase reactants in combination with sIL-6Rα could be sensitive biomarkers for the detection of acute and recent bleeding events in hemophilia.

Engineering Therapeutics to Detoxify Hemoglobin, Heme, and Iron

Hemolysis (i.e., red blood cell lysis) can increase circulatory levels of cell-free hemoglobin (Hb) and its degradation by-products, namely heme (h) and iron (Fe). Under homeostasis, minor increases in these three hemolytic by-products (Hb/h/Fe) are rapidly scavenged and cleared by natural plasma proteins. Under certain pathophysiological conditions, scavenging systems become overwhelmed, leading to the accumulation of Hb/h/Fe in the circulation. Unfortunately, these species cause various side effects such as vasoconstriction, hypertension, and oxidative organ damage. Therefore, various therapeutics strategies are in development, ranging from supplementation with depleted plasma scavenger proteins to engineered biomimetic protein constructs capable of scavenging multiple hemolytic species. In this review, we briefly describe hemolysis and the characteristics of the major plasma-derived protein scavengers of Hb/h/Fe. Finally, we present novel engineering approaches designed to address the toxicity of these hemolytic by-products.

Myoglobin-derived iron causes wound enlargement and impaired regeneration in pressure injuries of muscle

The reasons for poor healing of pressure injuries are poorly understood. Vascular ulcers are worsened by extracellular release of hemoglobin, so we examined the impact of myoglobin (Mb) iron in murine muscle pressure injuries (mPI). Tests used Mb-knockout or treatment with deferoxamine iron chelator (DFO). Unlike acute injuries from cardiotoxin, mPI regenerated poorly with a lack of viable immune cells, persistence of dead tissue (necro-slough), and abnormal deposition of iron. However, Mb-knockout or DFO-treated mPI displayed a reversal of the pathology: decreased tissue death, decreased iron deposition, decrease in markers of oxidative damage, and higher numbers of intact immune cells. Subsequently, DFO treatment improved myofiber regeneration and morphology. We conclude that myoglobin iron contributes to tissue death in mPI. Remarkably, a large fraction of muscle death in untreated mPI occurred later than, and was preventable by, DFO treatment, even though treatment started 12 hr after pressure was removed. This demonstrates an opportunity for post-pressure prevention to salvage tissue viability.

Molecular and cellular effects of in vivo chronic intravascular hemolysis and anti-inflammatory therapeutic approaches

Intravascular hemolysis (IVH) occurs in numerous inherited and acquired disorders, including sickle cell disease (SCD), malaria and sepsis. These diseases display unique symptoms, but often share complications, such as vasomotor dysfunction and pulmonary hypertension. Consequently, in vivo models are needed to study the effects of continuous intravascular hemolytic processes, independently of the molecular or extrinsic alteration that leads to erythrocyte destruction. We gave twice-weekly low-dose phenylhydrazine (LDPHZ) to C57BL/6 J mice for 4 weeks, and measured parameters indicative of anemia, hemoglobin-clearance pathways, inflammation and iron turnover, comparing these to those of a murine model of SCD, which displays associated IVH. LDPHZ administration provoked discreet anemia in mice and significant reticulocytosis, in association with hemoglobin/heme-clearance pathway protein depletion. Mice subjected to chronic hemolysis displayed elevated leukocyte counts and plasma levels of interleukin (IL)-1β, TNF-α, IL-6, soluble ICAM-1, endothelin-1 and anti-inflammatory IL-10, closely emulating alterations indicative of systemic inflammatory and endothelial activation in SCD, and confirming chronic IVH in itself as a serious complication. Discreet accelerations in hepatic and splenic iron turnover also occurred in LDPHZ mice, without alterations in liver damage markers. Examining the effects of two therapies on hemolysis-induced inflammation, the administration of hydroxyurea (and to a lesser extent, l-glutamine) significantly abrogated hemolytic inflammation in mice, without apparent inhibition of hemolysis. In conclusion, the isolation of chronic IVH, a common disease mechanism, using this model, may allow the study of hemolysis-specific sequelae at the cellular and systemic level, and the investigation of candidate agents that could potentially counter hemolytic inflammation.

Role of Macrophages in Sickle Cell Disease Erythrophagocytosis and Erythropoiesis

Sickle cell disease (SCD) is an inherited blood disorder caused by a β-globin gene point mutation that results in the production of sickle hemoglobin that polymerizes upon deoxygenation, causing the sickling of red blood cells (RBCs). RBC deformation initiates a sequence of events leading to multiple complications, such as hemolytic anemia, vaso-occlusion, chronic inflammation, and tissue damage. Macrophages participate in extravascular hemolysis by removing damaged RBCs, hence preventing the release of free hemoglobin and heme, and triggering inflammation. Upon erythrophagocytosis, macrophages metabolize RBC-derived hemoglobin, activating mechanisms responsible for recycling iron, which is then used for the generation of new RBCs to try to compensate for anemia. In the bone marrow, macrophages can create specialized niches, known as erythroblastic islands (EBIs), which regulate erythropoiesis. Anemia and inflammation present in SCD may trigger mechanisms of stress erythropoiesis, intensifying RBC generation by expanding the number of EBIs in the bone marrow and creating new ones in extramedullary sites. In the current review, we discuss the distinct mechanisms that could induce stress erythropoiesis in SCD, potentially shifting the macrophage phenotype to an inflammatory profile, and changing their supporting role necessary for the proliferation and differentiation of erythroid cells in the disease. The knowledge of the soluble factors, cell surface and intracellular molecules expressed by EBI macrophages that contribute to begin and end the RBC’s lifespan, as well as the understanding of their signaling pathways in SCD, may reveal potential targets to control the pathophysiology of the disease.

Neutrophils as drivers of vascular injury in sickle cell disease

While neutrophils are the main effectors of protective innate immune responses, they are also key players in inflammatory pathologies. Sickle cell disease (SCD) is a genetic blood disorder in which red blood cells (RBCs) are constantly destroyed in the circulation which generates a highly inflammatory environment that culminates in vascular occlusions. Vaso-occlusion is the hallmark of SCD and a predictor of disease severity. Neutrophils initiate and propagate SCD-related vaso-occlusion through adhesive interactions with the activated and dysfunctional endothelium, sickle RBCs, and platelets, leading to acute and chronic complications that progress to irreversible organ damage and ultimately death. The use of SCD humanized mouse models, in combination with in vivo imaging techniques, has emerged as a fundamental tool to understand the dynamics of neutrophils under complex inflammatory contexts and their contribution to vascular injury in SCD. In this review, we discuss the various mechanisms by which circulating neutrophils sense and respond to the wide range of stimuli present in the blood of SCD patients and mice. We argue that the central role of neutrophils in SCD can be rationalized to develop targets for the management of clinical complications in SCD patients.

The Role of Inflammation in The Cellular and Molecular Mechanisms of Cardiopulmonary Complications of Sickle Cell Disease

Cardiopulmonary complications remain the major cause of mortality despite newer therapies and improvements in the lifespan of patients with sickle cell disease (SCD). Inflammation has been identified as a major risk modifier in the pathogenesis of SCD-associated cardiopulmonary complications in recent mechanistic and observational studies. In this review, we discuss recent cellular and molecular mechanisms of cardiopulmonary complications in SCD and summarize the most recent evidence from clinical and laboratory studies. We emphasize the role of inflammation in the onset and progression of these complications to better understand the underlying pathobiological processes. We also discuss future basic and translational research in addressing questions about the complex role of inflammation in the development of SCD cardiopulmonary complications, which may lead to promising therapies and reduce morbidity and mortality in this vulnerable population.

A time-series analysis of blood-based biomarkers within a 25-year longitudinal dolphin cohort

Causal interactions and correlations between clinically-relevant biomarkers are important to understand, both for informing potential medical interventions as well as predicting the likely health trajectory of any individual as they age. These interactions and correlations can be hard to establish in humans, due to the difficulties of routine sampling and controlling for individual differences (e.g., diet, socio-economic status, medication). Because bottlenose dolphins are long-lived mammals that exhibit several age-related phenomena similar to humans, we analyzed data from a well controlled 25-year longitudinal cohort of 144 dolphins. The data from this study has been reported on earlier, and consists of 44 clinically relevant biomarkers. This time-series data exhibits three starkly different influences: (A) directed interactions between biomarkers, (B) sources of biological variation that can either correlate or decorrelate different biomarkers, and (C) random observation-noise which combines measurement error and very rapid fluctuations in the dolphin's biomarkers. Importantly, the sources of biological variation (type-B) are large in magnitude, often comparable to the observation errors (type-C) and larger than the effect of the directed interactions (type-A). Attempting to recover the type-A interactions without accounting for the type-B and type-C variation can result in an abundance of false-positives and false-negatives. Using a generalized regression which fits the longitudinal data with a linear model accounting for all three influences, we demonstrate that the dolphins exhibit many significant directed interactions (type-A), as well as strong correlated variation (type-B), between several pairs of biomarkers. Moreover, many of these interactions are associated with advanced age, suggesting that these interactions can be monitored and/or targeted to predict and potentially affect aging.

The NLRP3 inflammasome fires up heme-induced inflammation in hemolytic conditions

Overactive inflammatory responses are central to the pathophysiology of many hemolytic conditions including sickle cell disease. Excessive hemolysis leads to elevated serum levels of heme due to saturation of heme scavenging mechanisms. Extracellular heme has been shown to activate the NLRP3 inflammasome, leading to activation of caspase-1 and release of pro-inflammatory cytokines IL-1β and IL-18. Heme also activates the non-canonical inflammasome pathway, which may contribute to NLRP3 inflammasome formation and leads to pyroptosis, a type of inflammatory cell death. Some clinical studies indicate there is a benefit to blocking the NLRP3 inflammasome pathway in patients with sickle cell disease and other hemolytic conditions. However, a thorough understanding of the mechanisms of heme-induced inflammasome activation is needed to fully leverage this pathway for clinical benefit. This review will explore the mechanisms of heme-induced NLRP3 inflammasome activation and the role of this pathway in hemolytic conditions including sickle cell disease.

Thrombo-Inflammation in COVID-19 and Sickle Cell Disease: Two Faces of the Same Coin

People with sickle cell disease (SCD) are at greater risk of severe illness and death from respiratory infections, including COVID-19, than people without SCD (Centers for Disease Control and Prevention, USA). Vaso-occlusive crises (VOC) in SCD and severe SARS-CoV-2 infection are both characterized by thrombo-inflammation mediated by endothelial injury, complement activation, inflammatory lipid storm, platelet activation, platelet-leukocyte adhesion, and activation of the coagulation cascade. Notably, lipid mediators, including thromboxane A2, significantly increase in severe COVID-19 and SCD. In addition, the release of thromboxane A2 from endothelial cells and macrophages stimulates platelets to release microvesicles, which are harbingers of multicellular adhesion and thrombo-inflammation. Currently, there are limited therapeutic strategies targeting platelet-neutrophil activation and thrombo-inflammation in either SCD or COVID-19 during acute crisis. However, due to many similarities between the pathobiology of thrombo-inflammation in SCD and COVID-19, therapies targeting one disease may likely be effective in the other. Therefore, the preclinical and clinical research spurred by the COVID-19 pandemic, including clinical trials of anti-thrombotic agents, are potentially applicable to VOC. Here, we first outline the parallels between SCD and COVID-19; second, review the role of lipid mediators in the pathogenesis of these diseases; and lastly, examine the therapeutic targets and potential treatments for the two diseases.

Changes in Heme Levels During Acute Vaso-occlusive Crisis in Sickle Cell Anemia

OBJECTIVE/BACKGROUND

Sickle cell anemia (SCA) is associated with increased levels of extracellular heme, which is a key mediator of inflammation in this condition. Despite abundant evidence supporting this concept in cell and animal models, few studies addressed the association between heme levels and the development and severity of acute vasoocclusive crises (VOC) in humans.

METHODS

A cross-sectional study was conducted in patients with acute VOC. Total extracellular heme levels were measured in both plasma and serum at admission and after convalescence, and correlated with other clinical and laboratory markers of SCA severity.

RESULTS

A total of 28 episodes of VOC in 25 patients were included. Heme levels were similar between admission and convalescence, and correlated with the difference between pre and post hemoglobin, and SCA severity estimated by a composite score of clinical and laboratory markers. Heme levels were neither associated with VOC severity nor with markers of hemostasis activation, and were similar to those reported in an independent population of SCA patients at steady state.

DISCUSSION

Acute VOC are not characterized by significant increases in total extracellular heme levels. Studies measuring the fraction of free extracellular heme unbound to proteins are warranted to further refine our understanding of the role of heme in acute VOC.

Redox Status of Erythrocytes as an Important Factor in Eryptosis and Erythronecroptosis

Overall, reactive oxygen species (ROS) signalling significantly contributes to initiation and mo-dulation of multiple regulated cell death (RCD) pathways. Lately, more information has become available about RCD modalities of erythrocytes, including the role of ROS. ROS accumulation has therefore been increasingly recognized as a critical factor involved in eryptosis (apoptosis of erythrocytes) and erythro-necroptosis (necroptosis of erythrocytes). Eryptosis is a Ca2+-dependent apoptosis-like RCD of erythrocytes that occurs in response to oxidative stress, hyperosmolarity, ATP depletion, and a wide range of xenobiotics. Moreover, eryptosis seems to be involved in the pathogenesis of multiple human diseases and pathological processes. Several studies have reported that erythrocytes can also undergo necroptosis, a lytic RIPK1/RIPK3/MLKL-mediated RCD. As an example, erythronecroptosis can occur in response to CD59-specific pore-forming toxins. We have systematically summarized available studies regarding the involvement of ROS and oxidative stress in these two distinct RCDs of erythrocytes. We have focused specifically on cellular signalling pathways involved in ROS-mediated cell death decisions in erythrocytes. Furthermore, we have summarized dysregulation of related erythrocytic antioxidant defence systems. The general concept of the ROS role in eryptotic and necroptotic cell death pathways in erythrocytes seems to be established. However, further studies are required to uncover the complex role of ROS in the crosstalk and interplay between the survival and RCDs of erythrocytes.

The inflammasomes: crosstalk between innate immunity and hematology

BACKGROUND

The inflammasome is a cytosolic multi-protein complex responsible for the proteolytic maturation of pro-inflammatory cytokines IL-1ß and IL-18 and of gasdermin-D, which mediates membrane pore formation and the cytokines release, or eventually a lytic cell death known as pyroptosis. Inflammation has long been accepted as a key component of hematologic conditions, either oncological or benign diseases.

OBJECTIVES

This study aims to review the current knowledge about the contribution of inflammasome in hematologic diseases. We attempted to depict the participation of specific inflammasome receptors, and the possible cell-specific consequence of complex activation, as well as the use of anti-inflammasome therapies.

METHODS

We performed a keyword-based search in public databases (Pubmed.gov, ClinicalTrials.gov.).

CONCLUSION

Different blood cells variably express inflammasome components. Considering the immunosuppression associated with both the disease and the treatment of some hematologic diseases, and a microenvironment that allows neoplastic cell proliferation, inflammasomes could be a link between innate immunity and disease progression, as well as an interesting therapeutic target.

Recent advances in "sickle and niche" research - Tribute to Dr. Paul S Frenette

In this retrospective, we review the two research topics that formed the basis of the outstanding career of Dr. Paul S. Frenette. In the first part, we focus on sickle cell disease (SCD). The defining feature of SCD is polymerization of the deoxygenated mutant hemoglobin, which leads to a vicious cycle of hemolysis and vaso-occlusion. We survey important discoveries in SCD pathophysiology that have led to recent advances in treatment of SCD. The second part focuses on the hematopoietic stem cell (HSC) niche, the complex microenvironment within the bone marrow that controls HSC function and homeostasis. We detail the cells that constitute this niche, and the factors that these cells use to exert control over hematopoiesis. Here, we trace the scientific paths of Dr. Frenette, highlight key aspects of his research, and identify his most important scientific contributions in both fields.

Pain in Hemophilia: Unexplored Role of Oxidative Stress

Hemophilia is the most common X-linked bleeding diathesis caused by the genetic deficiency of coagulation factors VIII or IX. Despite treatment advances and improvements in clinical management to prevent bleeding, management of acute and chronic pain remains to be established. Repeated bleeding of the joints leads to arthropathy, causing pain in hemophilia. However, mechanisms underlying the pathogenesis of pain in hemophilia remain underexamined. Herein, we describe the novel perspectives on the role for oxidative stress in the periphery and the central nervous system that may contribute to pain in hemophilia. Specifically, we cross examine preclinical and clinical studies that address the contribution of oxidative stress in hemophilia and related diseases that affect synovial tissue to induce acute and potentially chronic pain. This understanding would help provide potential treatable targets using antioxidants to ameliorate pain in hemophilia.

Method Matters: Effect of Purification Technology on Neutrophil Phenotype and Function

Neutrophils are the most abundant leukocytes in human blood and the first cells responding to infection and injury. Due to their limited ex vivo lifespan and the impossibility to cryopreserve or expand them in vitro, neutrophils need to be purified from fresh blood for immediate use in experiments. Importantly, neutrophil purification methods may artificially modify the phenotype and functional characteristics of the isolated cells. The aim of this study was to expose the effects of ‘classical’ density-gradient purification versus the more expensive but faster immunomagnetic isolation on neutrophil phenotype and functionality. We found that in the absence of inflammatory stimuli, density-gradient-derived neutrophils showed increased polarization responses as well as enhanced release of reactive oxygen species (ROS), neutrophil extracellular traps (NETs) and granular proteins compared to cells derived from immunomagnetic isolation, which yields mostly quiescent neutrophils. Upon exposure to pro-inflammatory mediators, immunomagnetic isolation-derived neutrophils were significantly more responsive in polarization, ROS production, phagocytosis, NETosis and degranulation assays, in comparison to density-gradient-derived cells. We found no difference in chemotactic response in Multiscreen and under-agarose migration assays, but Boyden assays showed reduced chemotaxis of immunomagnetic isolation-derived neutrophils. Finally, we confirmed that density-gradient purification induces artificial activation of neutrophils, evidenced by e.g. higher expression of CD66b, formyl peptide receptor 1 (FPR1) and CD35, and the appearance of a separate neutrophil population expressing surface molecules atypical for neutrophils (e.g. CXCR3, MHC-II and CD14). Based on these results, we recommend using immunomagnetic separation of neutrophils for studying neutrophil polarization, phagocytosis, ROS production, degranulation and NETosis, whereas for Boyden chemotaxis assays, the density-gradient purification is more suitable.

Medical Gas Plasma—A Potent ROS-Generating Technology for Managing Intraoperative Bleeding Complications

Cold medical gas plasmas are under pre-clinical investigation concerning their hemostatic activity and could be applied for intra-operative bleeding control in the future. The technological leap innovation was their generation at body temperature, thereby causing no thermal harm to the tissue and ensuring tissue integrity. This directly contrasts with current techniques such as electrocautery, which induces hemostasis by carbonizing the tissue using a heated electrode. However, the necrotized tissue is prone to fall, raising the risk of post-operative complications such as secondary bleedings or infection. In recent years, various studies have reported on the ability of medical gas plasmas to induce blood coagulation, including several suggestions concerning their mode of action. As non-invasive and gentle hemostatic agents, medical gas plasmas could be particularly eligible for vulnerable tissues, e.g., colorectal surgery and neurosurgery. Further, their usage could be beneficial regarding the prevention of post-operative bleedings due to the absence or sloughing of eschar. However, no clinical trials or individual healing attempts for medical gas plasmas have been reported to pave the way for clinical approvement until now, despite promising results in experimental animal models. In this light, the present mini-review aims to emphasize the potential of medical gas plasmas to serve as a hemostatic agent in clinical procedures. Providing a detailed overview of the current state of knowledge, feasible application fields are discussed, and possible obstacles are addressed.

A targetable ‘rogue’ neutrophil-subset, [CD11b+DEspR+] immunotype, is associated with severity and mortality in acute respiratory distress syndrome (ARDS) and COVID-19-ARDS

Neutrophil-mediated secondary tissue injury underlies acute respiratory distress syndrome (ARDS) and progression to multi-organ-failure (MOF) and death, processes linked to COVID-19-ARDS. This secondary tissue injury arises from dysregulated neutrophils and neutrophil extracellular traps (NETs) intended to kill pathogens, but instead cause cell-injury. Insufficiency of pleiotropic therapeutic approaches delineate the need for inhibitors of dysregulated neutrophil-subset(s) that induce subset-specific apoptosis critical for neutrophil function-shutdown. We hypothesized that neutrophils expressing the pro-survival dual endothelin-1/VEGF-signal peptide receptor, DEspR, are apoptosis-resistant like DEspR+ cancer-cells, hence comprise a consequential pathogenic neutrophil-subset in ARDS and COVID-19-ARDS. Here, we report the significant association of increased peripheral DEspR+CD11b+ neutrophil-counts with severity and mortality in ARDS and COVID-19-ARDS, and intravascular NET-formation, in contrast to DEspR[-] neutrophils. We detect DEspR+ neutrophils and monocytes in lung tissue patients in ARDS and COVID-19-ARDS, and increased neutrophil RNA-levels of DEspR ligands and modulators in COVID-19-ARDS scRNA-seq data-files. Unlike DEspR[-] neutrophils, DEspR+CD11b+ neutrophils exhibit delayed apoptosis, which is blocked by humanized anti-DEspR-IgG4^S228P antibody, hu6g8, in ex vivo assays. Ex vivo live-cell imaging of Rhesus-derived DEspR+CD11b+ neutrophils showed hu6g8 target-engagement, internalization, and induction of apoptosis. Altogether, data identify DEspR+CD11b+ neutrophils as a targetable ‘rogue’ neutrophil-subset associated with severity and mortality in ARDS and COVID-19-ARDS.

Interplay Between Iron Overload and Osteoarthritis: Clinical Significance and Cellular Mechanisms

There are multiple diseases or conditions such as hereditary hemochromatosis, hemophilia, thalassemia, sickle cell disease, aging, and estrogen deficiency that can cause iron overload in the human body. These diseases or conditions are frequently associated with osteoarthritic phenotypes, such as progressive cartilage degradation, alterations in the microarchitecture and biomechanics of the subchondral bone, persistent joint inflammation, proliferative synovitis, and synovial pannus. Growing evidences suggest that the conditions of pathological iron overload are associated with these osteoarthritic phenotypes. Osteoarthritis (OA) is an important complication in patients suffering from iron overload-related diseases and conditions. This review aims to summarize the findings and observations made in the field of iron overload-related OA while conducting clinical and basic research works. OA is a whole-joint disease that affects the articular cartilage lining surfaces of bones, subchondral bones, and synovial tissues in the joint cavity. Chondrocytes, osteoclasts, osteoblasts, and synovial-derived cells are involved in the disease. In this review, we will elucidate the cellular and molecular mechanisms associated with iron overload and the negative influence that iron overload has on joint homeostasis. The promising value of interrupting the pathologic effects of iron overload is also well discussed for the development of improved therapeutics that can be used in the field of OA.

Plasma-Derived Hemopexin as a Candidate Therapeutic Agent for Acute Vaso-Occlusion in Sickle Cell Disease: Preclinical Evidence

People living with sickle cell disease (SCD) face intermittent acute pain episodes due to vaso-occlusion primarily treated palliatively with opioids. Hemolysis of sickle erythrocytes promotes release of heme, which activates inflammatory cell adhesion proteins on endothelial cells and circulating cells, promoting vaso-occlusion. In this study, plasma-derived hemopexin inhibited heme-mediated cellular externalization of P-selectin and von Willebrand factor, and expression of IL-8, VCAM-1, and heme oxygenase-1 in cultured endothelial cells in a dose-responsive manner. In the Townes SCD mouse model, intravenous injection of free hemoglobin induced vascular stasis (vaso-occlusion) in nearly 40% of subcutaneous blood vessels visualized in a dorsal skin-fold chamber. Hemopexin administered intravenously prevented or relieved stasis in a dose-dependent manner. Hemopexin showed parallel activity in relieving vascular stasis induced by hypoxia-reoxygenation. Repeated IV administration of hemopexin was well tolerated in rats and non-human primates with no adverse findings that could be attributed to human hemopexin. Hemopexin had a half-life in wild-type mice, rats, and non-human primates of 80–102 h, whereas a reduced half-life of hemopexin in Townes SCD mice was observed due to ongoing hemolysis. These data have led to a Phase 1 clinical trial of hemopexin in adults with SCD, which is currently ongoing.

Immunomonitoring of Monocyte and Neutrophil Function in Critically Ill Patients: From Sepsis and/or Trauma to COVID-19

Immune cells and mediators play a crucial role in the critical care setting but are understudied. This review explores the concept of sepsis and/or injury-induced immunosuppression and immuno-inflammatory response in COVID-19 and reiterates the need for more accurate functional immunomonitoring of monocyte and neutrophil function in these critically ill patients. in addition, the feasibility of circulating and cell-surface immune biomarkers as predictors of infection and/or outcome in critically ill patients is explored. It is clear that, for critically ill, one size does not fit all and that immune phenotyping of critically ill patients may allow the development of a more personalized approach with tailored immunotherapy for the specific patient. In addition, at this point in time, caution is advised regarding the quality of evidence of some COVID-19 studies in the literature.

Medical gas plasma promotes blood coagulation via platelet activation

Major blood loss still is a risk factor during surgery. Electrocauterization often is used for necrotizing the tissue and thereby halts bleeding (hemostasis). However, the carbonized tissue is prone to falling off, putting patients at risk of severe side effects, such as dangerous internal bleeding many hours after surgery. We have developed a medical gas plasma jet technology as an alternative to electrocauterization and investigated its hemostatic (blood clotting) effects and mechanisms of action using whole human blood. The gas plasma efficiently coagulated anticoagulated donor blood, which resulted from the local lysis of red blood cells (hemolysis). Image cytometry further showed enhanced platelet aggregation. Gas plasmas release reactive oxygen species (ROS), but neither scavenging of long-lived ROS nor addition of chemically-generated ROS were able to abrogate or recapitulate the gas plasma effect, respectively. However, platelet activation was markedly impaired in platelet-rich plasma when compared to gas plasma-treated whole blood that moreover contained significant amounts of hemoglobin indicative of red blood cell lysis (hemolysis). Finally, incubation of whole blood with concentration-matched hemolysates phenocopied the gas plasmas-mediated platelet activation. These results will spur the translation of plasma systems for hemolysis into clinical practice.

Increased Neutrophil-Subset Associated With Severity/Mortality In ARDS And COVID19-ARDS Expresses The Dual Endothelin-1/VEGFsignal-Peptide Receptor (DEspR): An Actionable Therapeutic Target

Neutrophil-mediated secondary tissue injury underlies acute respiratory distress syndrome (ARDS) and progression to multi-organ-failure (MOF) and death, processes linked to severe COVID19. This 'innocent bystander' tissue injury arises in dysregulated hyperinflammatory states from neutrophil functions and neutrophil extracellular traps (NETs) intended to kill pathogens, but injure cells instead, causing MOF. Insufficiency of prior therapeutic approaches suggest need to identify dysregulated neutrophil-subset(s) and induce subset-specific apoptosis critical for neutrophil function-shutdown and clearance. We hypothesized that neutrophils expressing the pro-survival dual endothelin-1/signal peptide receptor, DEspR, are apoptosis-resistant just like DEspR+ cancer cells, hence comprise a consequential pathogenic neutrophil-subset in ARDS and COVID19-ARDS. Here, we report correlation of circulating DEspR+CD11b+ activated neutrophils (DESpR+actNs) and NETosing-neutrophils with severity in ARDS and in COVID19-ARDS, increased DEspR+ neutrophils and monocytes in post-mortem ARDS-patient lung sections, and neutrophil DEspR/ET1 receptor/ligand autocrine loops in severe COVID19. Unlike DEspR[-] neutrophils, ARDS patient DEspR+actNs exhibit apoptosis-resistance, which decreased upon ex vivo treatment with humanized anti-DEspR-IgG4S228P antibody, hu6g8. Ex vivo live-cell imaging of non-human primate DEspR+actNs showed hu6g8 target-engagement, internalization, and induction of apoptosis. Altogether, data differentiate DEspR+actNs as a targetable neutrophil-subset associated with ARDS and COVID19-ARDS severity, and suggest DEspR-inhibition as a potential therapeutic paradigm.

Is haem the real target of COVID-19?

Although a vaccination campaign has been launched in many countries, the COVID-19 pandemic is not under control. The main concern is the emergence of new variants of SARS-CoV-2; therefore, it is important to find approaches to prevent or reduce the virulence and pathogenicity of the virus. Currently, the mechanism of action of SARS-CoV-2 is not fully understood. Considering the clinical effects that occur during the disease, attacking the human respiratory and hematopoietic systems, and the changes in biochemical parameters (including decreases in haemoglobin [Hb] levels and increases in serum ferritin), it is clear that iron metabolism is involved. SARS-CoV-2 induces haemolysis and interacts with Hb molecules via ACE2, CD147, CD26, and other receptors located on erythrocytes and/or blood cell precursors that produce dysfunctional Hb. A molecular docking study has reported a potential link between the virus and the beta chain of haemoglobin and attack on haem. Considering that haem is involved in miRNA processing by binding to the DGCR8-DROSHA complex, we hypothesised that the virus may check this mechanism and thwart the antiviral response.

Iron-Driven Alterations on Red Blood Cell-Derived Microvesicles Amplify Coagulation during Hemolysis via the Intrinsic Tenase Complex

Hemolytic disorders characterized by complement-mediated intravascular hemolysis, such as autoimmune hemolytic anemia and paroxysmal nocturnal hemoglobinuria, are often complicated by life-threatening thromboembolic complications. Severe hemolytic episodes result in the release of red blood cell (RBC)-derived proinflammatory and oxidatively reactive mediators (e.g., extracellular hemoglobin, heme, and iron) into plasma. Here, we studied the role of these hemolytic mediators in coagulation activation by measuring factor Xa (FXa) and thrombin generation in the presence of RBC lysates. Our results show that hemolytic microvesicles (HMVs) formed during hemolysis stimulate thrombin generation through a mechanism involving FVIII and FIX, the so-called intrinsic tenase complex. Iron scavenging during hemolysis using deferoxamine decreased the ability of the HMVs to enhance thrombin generation. Furthermore, the addition of ferric chloride (FeCl₃) to plasma propagated thrombin generation in a FVIII- and FIX-dependent manner suggesting that iron positively affects blood coagulation. Phosphatidylserine (PS) blockade using lactadherin and iron chelation using deferoxamine reduced intrinsic tenase activity in a purified system containing HMVs as source of phospholipids confirming that both PS and iron ions contribute to the procoagulant effect of the HMVs. Finally, the effects of FeCl₃ and HMVs decreased in the presence of ascorbate and glutathione indicating that oxidative stress plays a role in hypercoagulability. Overall, our results provide evidence for the contribution of iron ions derived from hemolytic RBCs to thrombin generation. These findings add to our understanding of the pathogenesis of thrombosis in hemolytic diseases.

Circulating mitochondrial DNA is a proinflammatory DAMP in sickle cell disease

The pathophysiology of sickle cell disease (SCD) is driven by chronic inflammation fueled by damage associated molecular patterns (DAMPs). We show that elevated cell-free DNA (cfDNA) in patients with SCD is not just a prognostic biomarker, it also contributes to the pathological inflammation. Within the elevated cfDNA, patients with SCD had a significantly higher ratio of cell-free mitochondrial DNA (cf-mtDNA)/cell-free nuclear DNA compared with healthy controls. Additionally, mitochondrial DNA in patient samples showed significantly disproportionately increased hypomethylation compared with healthy controls, and it was increased further in crises compared with steady-state. Using flow cytometry, structured illumination microscopy, and electron microscopy, we showed that circulating SCD red blood cells abnormally retained their mitochondria and, thus, are likely to be the source of the elevated cf-mtDNA in patients with SCD. Patient plasma containing high levels of cf-mtDNA triggered the formation of neutrophil extracellular traps (NETs) that was substantially reduced by inhibition of TANK-binding kinase 1, implicating activation of the cGAS-STING pathway. cf-mtDNA is an erythrocytic DAMP, highlighting an underappreciated role for mitochondria in sickle pathology. These trials were registered at www.clinicaltrials.gov as #NCT00081523, #NCT03049475, and #NCT00047996.

Erythrocytes: Central Actors in Multiple Scenes of Atherosclerosis

The development and progression of atherosclerosis (ATH) involves lipid accumulation, oxidative stress and both vascular and blood cell dysfunction. Erythrocytes, the main circulating cells in the body, exert determinant roles in the gas transport between tissues. Erythrocytes have long been considered as simple bystanders in cardiovascular diseases, including ATH. This review highlights recent knowledge concerning the role of erythrocytes being more than just passive gas carriers, as potent contributors to atherosclerotic plaque progression. Erythrocyte physiology and ATH pathology is first described. Then, a specific chapter delineates the numerous links between erythrocytes and atherogenesis. In particular, we discuss the impact of extravasated erythrocytes in plaque iron homeostasis with potential pathological consequences. Hyperglycaemia is recognised as a significant aggravating contributor to the development of ATH. Then, a special focus is made on glycoxidative modifications of erythrocytes and their role in ATH. This chapter includes recent data proposing glycoxidised erythrocytes as putative contributors to enhanced atherothrombosis in diabetic patients.

Iron-driven alterations on red blood cell-derived microvesicles amplify coagulation during hemolysis via the intrinsic tenase complex

Hemolytic disorders characterized by complement-mediated intravascular hemolysis, such as autoimmune hemolytic anemia and paroxysmal nocturnal hemoglobinuria, are often complicated by life-threatening thromboembolic complications. Severe hemolytic episodes result in the release of red blood cell (RBC)-derived pro-inflammatory and oxidatively reactive mediators (e.g. extracellular hemoglobin, heme and iron) into plasma. Here, we studied the role of these hemolytic mediators in coagulation activation by measuring FXa and thrombin generation in the presence of RBC lysates. Our results show that hemolytic microvesicles (HMVs) formed during hemolysis stimulate thrombin generation through a mechanism involving FVIII and FIX, the so-called intrinsic tenase complex. Iron scavenging during hemolysis using deferoxamine decreased the ability of the HMVs to enhance thrombin generation. Furthermore, the addition of ferric chloride (FeCl3) to plasma propagated thrombin generation in a FVIII and FIX-dependent manner suggesting that iron positively affects blood coagulation. Phosphatidylserine (PS) blockade using lactadherin and iron chelation using deferoxamine reduced intrinsic tenase activity in a purified system containing HMVs as source of phospholipids confirming that both PS and iron ions contribute to the procoagulant effect of the HMVs. Finally, the effects of FeCl3 and HMVs decreased in the presence of ascorbate and glutathione indicating that oxidative stress plays a role in hypercoagulability. Overall, our results provide evidence for the contribution of iron ions derived from hemolytic RBCs to thrombin generation. These findings add to our understanding of the pathogenesis of thrombosis in hemolytic diseases.

Increased zinc and albumin but lowered copper in children with transfusion-dependent thalassemia

BACKGROUND

Measurements of copper and zinc in transfusion-dependent thalassemia (TDT) show contradictory results.

AIM OF THE STUDY

To examine serum levels of these minerals in TDT in relation to iron overload indices and erythron variables.

METHODS

This study recruited 60 children with TDT and 30 healthy controls aged 3-12 years old.

RESULTS

Zinc was significantly higher in TDT children than in controls, while copper and the copper to zinc ratio were significantly lowered in TDT. Serum zinc was significantly associated with the number of blood transfusions and iron overload variables (including serum iron and TS%) and negatively with erythron variables (including hemoglobin, mean corpuscular volume, mean corpuscular hemoglobin). Serum copper was significantly and negatively associated with the same iron overload and erythron variables. The copper to zinc ratio was significantly correlated with iron, TS%, ferritin, hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin. Albumin levels were significantly higher in TDT children than in control children.

CONCLUSION

Our results suggest that the increase in zinc in children with TDT may be explained by iron loading anemia and hemolysis and the consequent shedding of high amounts of intracellular zinc into the plasma. Increased albumin levels and treatment with Desferral may further contribute towards higher zinc levels in TDT. We suggest that the elevations in zinc in TDT are a compensatory mechanism protecting against infection, inflammation, and oxidative stress. Previous proposals for prophylactic use of zinc supplements in TDT may not be warranted.

Sickle cell vaso-occlusion: The dialectic between red cells and white cells

The pathophysiology of sickle cell anemia, a hereditary hemoglobinopathy, has fascinated clinicians and scientists alike since its description over 100 years ago. A single gene mutation in the HBB gene results in the production of abnormal hemoglobin (Hb) S, whose polymerization when deoxygenated alters the physiochemical properties of red blood cells, in turn triggering pan-cellular activation and pathological mechanisms that include hemolysis, vaso-occlusion, and ischemia-reperfusion to result in the varied and severe complications of the disease. Now widely regarded as an inflammatory disease, in recent years attention has included the role of leukocytes in vaso-occlusive processes in view of the part that these cells play in innate immune processes, their inherent ability to adhere to the endothelium when activated, and their sheer physical and potentially obstructive size. Here, we consider the role of sickle red blood cell populations in elucidating the importance of adhesion vis-a-vis polymerization in vaso-occlusion, review the direct adhesion of sickle red cells to the endothelium in vaso-occlusive processes, and discuss how red cell- and leukocyte-centered mechanisms are not mutually exclusive. Given the initial clinical success of crizanlizumab, a specific anti-P selectin therapy, we suggest that it is appropriate to take a holistic approach to understanding and exploring the complexity of vaso-occlusive mechanisms and the adhesive roles of the varied cell types, including endothelial cells, platelets, leukocytes, and red blood cells.

Vasculopathy in Sickle Cell Disease: From Red Blood Cell Sickling to Vascular Dysfunction

Sickle cell disease (SCD) is a hereditary disorder that leads to the production of an abnormal hemoglobin, hemoglobin S (HbS). HbS polymerizes in deoxygenated conditions, which can prompt red blood cell (RBC) sickling and leaves the RBCs more rigid, fragile, and prone to hemolysis. SCD patients suffer from a plethora of complications, ranging from acute complications, such as characteristic, frequent, and debilitating vaso-occlusive episodes to chronic organ damage. While RBC sickling is the primary event at the origin of vaso-occlusive processes, other factors that can further increase RBC transit times in the microcirculation may also be required to precipitate vaso-occlusive processes. The adhesion of RBC and leukocytes to activated endothelium and the formation of heterocellular aggregates, as well as increased blood viscosity, are among the mechanisms involved in slowing the progress of RBCs in deoxygenated vascular areas, favoring RBC sickling and promoting vascular occlusion. Chronic inflammatory processes and oxidative stress, which are perpetuated by hemolytic events and ischemia-reperfusion injury, result in this pan cellular activation and some acute events, such as stroke and acute chest syndrome, as well as chronic end-organ damage. Furthermore, impaired vasodilation and vasomotor hyperresponsiveness in SCD also contribute to vaso-occlusive processes. Treating SCD as a vascular disease in addition to its hematological perspective, the present article looks at the interplay between abnormal RBC physiology/integrity, vascular dysfunction and clinical severity in SCD, and discusses existing therapies and novel drugs in development that may ameliorate vascular complications in the disease. © 2021 American Physiological Society. Compr Physiol 11:1785-1803, 2021.

Packed red blood cells inhibit T-cell activation via ROS-dependent signaling pathways

Numerous observations indicate that red blood cells (RBCs) affect T-cell activation and proliferation. We have studied effects of packed RBCs (PRBCs) on T-cell receptor (TCR) signaling and the molecular mechanisms whereby (P)RBCs modulate T-cell activation. In line with previous reports, PRBCs attenuated the expression of T-cell activation markers CD25 and CD69 upon costimulation via CD3/CD28. In addition, T-cell proliferation and cytokine expression were markedly reduced when T-cells were stimulated in the presence of PRBCs. Inhibitory activity of PRBCs required direct cell–cell contact and intact PRBCs. The production of activation-induced cellular reactive oxygen species, which act as second messengers in T-cells, was completely abrogated to levels of unstimulated T-cells in the presence of PRBCs. Phosphorylation of the TCR-related zeta chain and thus proximal TCR signal transduction was unaffected by PRBCs, ruling out mechanisms based on secreted factors and steric interaction restrictions. In large part, downstream signaling events requiring reactive oxygen species for full functionality were affected, as confirmed by an untargeted MS-based phosphoproteomics approach. PRBCs inhibited T-cell activation more efficiently than treatment with 1 mM of the antioxidant N-acetyl cysteine. Taken together, our data imply that inflammation-related radical reactions are modulated by PRBCs. These immunomodulating effects may be responsible for clinical observations associated with transfusion of PRBCs.

Anti-bacterial and wound healing-promoting effects of zinc ferrite nanoparticles

BACKGROUND

Increasing antibiotic resistance continues to focus on research into the discovery of novel antimicrobial agents. Due to its antimicrobial and wound healing-promoting activity, metal nanoparticles have attracted attention for dermatological applications. This study is designed to investigate the scope and bactericidal potential of zinc ferrite nanoparticles (ZnFe₂O₄ NPs), and the mechanism of anti-bacterial action along with cytocompatibility, hemocompatibility, and wound healing properties.

RESULTS

ZnFe₂O₄ NPs were synthesized via a modified co-precipitation method. Structure, size, morphology, and elemental compositions of ZnFe₂O₄ NPs were analyzed using X-ray diffraction pattern, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. In PrestoBlue and live/dead assays, ZnFe₂O₄ NPs exhibited dose-dependent cytotoxic effects on human dermal fibroblasts. In addition, the hemocompatibility assay revealed that the NPs do not significantly rupture red blood cells up to a dose of 1000 µg/mL. Bacterial live/dead imaging and zone of inhibition analysis demonstrated that ZnFe₂O₄ NPs showed dose-dependent bactericidal activities in various strains of Gram-negative and Gram-positive bacteria. Interestingly, NPs showed antimicrobial activity through multiple mechanisms, such as cell membrane damage, protein leakage, and reactive oxygen species generation, and were more effective against gram-positive bacteria. Furthermore, in vitro scratch assay revealed that ZnFe₂O₄ NPs improved cell migration and proliferation of cells, with noticeable shrinkage of the artificial wound model.

CONCLUSIONS

This study indicated that ZnFe₂O₄ NPs have the potential to be used as a future antimicrobial and wound healing drug.