The role of platelets in sepsis

Comparative assessment of hemostasis in septic patients and healthy controls using standard coagulation tests and whole-blood thromboelastometry

BACKGROUND

Sepsis is associated with dysregulation of procoagulant, anticoagulant, and fibrinolytic pathways.

AIMS

To compare the measurements of coagulation activation, clot formation, stabilization, and lysis between rotational thromboelastometry (ROTEM) and standard coagulation tests (SCTs) on patients with early sepsis (SP) and healthy controls (HC).

METHODS

This observational study included 30 SP and 30 HC. At study inclusion, SCTs and ROTEM analyses were conducted. A modified ROTEM with exogenous tPA was used to investigate fibrinolysis resistance.

RESULTS

SP had longer prothrombin time, higher fibrinogen levels and lower platelet count compared to HC. On ROTEM, clotting initiation was longer in SP than in HC but median clotting time maintained within reference ranges. SP had higher maximum velocity of clot formation, clot firmness, elasticity, and platelet component than HC. Clot lysis indices (CLI) were higher in EXTEM and APTEM (without and with added tPA) in SP compared to HC. The difference in CLI between APTEM and EXTEM was lower for both native and tPA-spiked samples in SP compared with HC.

CONCLUSIONS

While SCTs suggest SP are hypocoagulable, VET revealed normal coagulation initiation in more than 80 % of SP. Compared to HC, SP had increased clot propagation, firmness and elasticity, and decreased platelet-mediated clot retraction and lysis. In sepsis, VET provide more comprehensive information about hemostatic changes than SCTs.

Roles and Therapeutic Targeting of Exosomes in Sepsis-Induced Cardiomyopathy

Sepsis-induced cardiomyopathy (SICM) is a complex and fatal manifestation of sepsis, characterised by myocardial dysfunction that exacerbates the clinical prognosis in septic patients. While the pathophysiology of SICM remains incompletely understood, emerging evidence highlights the multifaceted functions of exosomes, small membrane-bound extracellular vesicles, in mediating the inflammatory responses and cardiac dysfunction involved in this condition. During sepsis, exosomes are secreted by various cells, such as cardiomyocytes, endothelial cells and macrophages, which serve as critical messengers, transferring proteins, lipids and RNA molecules that influence recipient cells, thus affecting cellular functions and disease progression. This review summarises the pathophysiology of SICM and the basics of exosomes and focuses on exosome-mediated mechanisms in SICM, including their role in inflammation, oxidative stress, mitochondrial dysfunction and myocardial injury, offering novel insights into the exosome-based therapeutic strategies in SICM.

C-reactive protein to platelet ratio as an early biomarker in differentiating neonatal late-onset sepsis in neonates with pneumonia

Neonates with pneumonia (NWP) may experience unidentified life-threatening sepsis, yet distinguishing NWP from neonates with sepsis (NWS) based solely on clinical presentation remains challenging. This study aimed to evaluate the diagnostic utility of the C-reactive protein to platelet ratio (CPR) in distinguishing neonatal late-onset sepsis (LOS) among NWPs. From February 2016 to March 2022, a total of 1385 NWPs aged over 3 days were included. Of these, 174 neonates with confirmed positive blood cultures were categorized into the sepsis cohort, while the remainder formed the pneumonia cohort. All clinical data were retrospectively extracted from electronic medical records. CPR was calculated as the ratio of C-reactive protein levels to platelet count. Independent risk factors (IRFs) for neonatal LOS were identified through multivariate logistic regression. The diagnostic performance of CPR in identifying LOS among NWPs was analyzed using receiver operating characteristic (ROC) curve metrics. Statistical analyses were conducted using SPSS version 24.0 and MedCalc version 15.2.2. Neonates with NWS demonstrated significantly higher CPR compared to those with NWP alone. Further analysis revealed a notably increased incidence of sepsis among neonates exhibiting elevated CPR levels relative to those with lower values. Correlation analysis identified a direct association between CPR and elevated procalcitonin, creatinine, and urea nitrogen levels, as well as prolonged hospitalization. Multiple logistic regression analysis identified CPR as an IRF for late-onset NWS. ROC curve analysis demonstrated that CPR outperformed CRP and platelet count individually in diagnosing NWS, with a diagnostic sensitivity of 54% and specificity of 85%. CPR serves as an effective initial diagnostic marker with superior accuracy in distinguishing delayed NWS from NWP compared to CRP and platelet count alone.

Disrupting the dangerous alliance: Dual anti-inflammatory and anticoagulant strategy targets platelet-neutrophil crosstalk in sepsis

Sepsis is a life-threatening disease characterized by excessive systemic inflammation and coagulopathy. Platelets and neutrophils form a "dangerous alliance" through crosstalk, promoting the inflammatory cytokine storm and coagulation disorders during sepsis. Platelet-neutrophil crosstalk leads to the formation of platelet-neutrophil complexes (PNCs), which are the central "protagonists" of this "dangerous alliance." These PNCs further enhance the crosstalk between platelets and neutrophils, amplifying immune and coagulation responses through positive feedback loops. Although some targeted therapies have been reported recently, they primarily focus on inducing neutrophil apoptosis or degrading existing neutrophil extracellular traps (NETs). Limited strategies are available for targeting platelets and suppressing sepsis-associated PNCs. Herein, we propose a two-pronged approach to intercept platelet-neutrophil crosstalk by simultaneously targeting drugs to both platelets and neutrophils of the "dangerous alliance." This strategy not only effectively alleviates inflammation induced by platelet-neutrophil crosstalk but also reduces PNC formation, thereby dismantling the structural scaffold of microthrombi. In a sepsis mouse model, this approach significantly decreased markers of platelet-neutrophil crosstalk, reduced the cytokine storm, and lowered the risk of thrombosis. Moreover, it alleviated organ damage caused by PNC infiltration and prolonged the survival of septic mice. Overall, this work combines anti-inflammatory and anticoagulant therapies to effectively disrupt the "dangerous alliance" between platelets and neutrophils, offering a promising strategy for treating sepsis.

Streptococcus pyogenes Activates Human Platelets via Streptolysin S-Mediated Calcium Ion Influx

INTRODUCTION

Streptococcus pyogenes (group A streptococcus, GAS) is an exclusively human pathogen. It causes a wide spectrum of diseases, ranging from mild infections such as pharyngitis to severe life-threatening conditions such as streptococcal toxic shock syndrome (STSS). Thrombocytopenia is a common feature of STSS and is associated with severe outcome. GAS produce a plethora of virulence factors, including streptolysin S (SLS), which has lytic as well as immunomodulatory properties. However, its role in platelet activation remains unclear.

METHODS

Washed human platelets were infected with GAS wild-type and SLS-deficient mutant (ΔsagA) strains. Platelet activation was assessed by measuring degranulation (CD62P expression). The role of calcium influx and the involvement of purinergic type 2 receptors (P2R) in platelet activation by GAS were assessed using chemical antagonists and calcium chelators.

RESULTS

GAS activate human platelets via SLS-mediated calcium influx, marked by increased surface expression of CD62P. IVIG treatment improved platelet viability in wild-type infections but failed to prevent SLS-mediated activation. Blocking of P2 receptors via suramin or NF449 as well as the use of calcium chelators reduced SLS-mediated platelet activation.

CONCLUSION

This study identified SLS as an M-protein and consequently a serotype-independent activator of human platelets. While IVIG partially improved platelet viability in GAS infections, its inability to prevent excessive platelet activation underscores the need for additional treatment options in severe GAS infections.

INTRODUCTION

Streptococcus pyogenes (group A streptococcus, GAS) is an exclusively human pathogen. It causes a wide spectrum of diseases, ranging from mild infections such as pharyngitis to severe life-threatening conditions such as streptococcal toxic shock syndrome (STSS). Thrombocytopenia is a common feature of STSS and is associated with severe outcome. GAS produce a plethora of virulence factors, including streptolysin S (SLS), which has lytic as well as immunomodulatory properties. However, its role in platelet activation remains unclear.

METHODS

Washed human platelets were infected with GAS wild-type and SLS-deficient mutant (ΔsagA) strains. Platelet activation was assessed by measuring degranulation (CD62P expression). The role of calcium influx and the involvement of purinergic type 2 receptors (P2R) in platelet activation by GAS were assessed using chemical antagonists and calcium chelators.

RESULTS

GAS activate human platelets via SLS-mediated calcium influx, marked by increased surface expression of CD62P. IVIG treatment improved platelet viability in wild-type infections but failed to prevent SLS-mediated activation. Blocking of P2 receptors via suramin or NF449 as well as the use of calcium chelators reduced SLS-mediated platelet activation.

CONCLUSION

This study identified SLS as an M-protein and consequently a serotype-independent activator of human platelets. While IVIG partially improved platelet viability in GAS infections, its inability to prevent excessive platelet activation underscores the need for additional treatment options in severe GAS infections.

ABO Blood Group and Risk Associated With Sepsis-Associated Thrombocytopenia: A Single-Center Retrospective Study

OBJECTIVES

This study aimed to investigate the relationship between ABO blood group and sepsis-associated thrombocytopenia (SAT).

DESIGN AND SETTING

The primary outcome was SAT within the first 72 hours of ICU admission.

PATIENTS

The retrospective study included 9113 patients diagnosed with sepsis from January 2014 to December 2022. A total of 6296 patients eventually were included into the study, who were divided into four groups based on ABO blood group.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 2494 patients (39.6%) were diagnosed with SAT, and 712 (11.3%) of them experiencing severe SAT. The occurrence of SAT among the ABO blood groups was significantly lower in AB blood group compared with the other groups ( p = 0.032). Individuals in AB blood group were less likely to experience severe SAT ( p = 0.028). In multivariate analysis, B blood group (odds ratio [OR], 1.32; 95% CI, 1.05-1.67) and O (OR, 1.37; 95% CI, 1.09-1.72) were significantly associated with a higher occurrence of SAT compared with AB blood group. In multivariate analyses, A blood group (OR, 1.68; 95% CI, 1.16-2.42), B blood group (OR, 1.74; 95% CI, 1.74-2.50), and O blood group (OR, 1.72; 95% CI, 1.20-2.48) remained significantly risk factors associated with a higher occurrence of severe SAT compared with AB blood group.

CONCLUSIONS

B blood group and O were associated with an increased risk of SAT and severe SAT.

Relationship between thrombocytopenia and prognosis in children with septic shock: a retrospective cohort study

Septic shock is a life-threatening disease worldwide often associated with thrombocytopenia. Platelets play a crucial role in bridging the gap between immunity, coagulation, and endothelial cell activation, potentially influencing the course of the disease. However, there are few studies specifically evaluating the impact of thrombocytopenia on the prognosis of pediatric patients. Therefore, the study investigates effects of early thrombocytopenia in the prognosis of children with septic shock. Pediatric patients with septic shock from 2015 to 2022 were included monocentrically. Thrombocytopenia was defined as a platelet count of <100 × 109/L during the first 24 hours of septic shock onset. The primary outcome was the 28-day mortality. Propensity score matching was used to pair patients with different platelet counts on admission but comparable disease severity. A total of 419 pediatric patients were included in the analysis. Patients with thrombocytopenia had higher 28-day mortality (55.5% vs. 38.7%, p = .005) compared to patients with no thrombocytopenia. Thrombocytopenia was associated with reduced 28-PICU free days (median value, 0 vs. 13 days, p = .003) and 28-ventilator-free (median value, 0 vs. 19 days, p = .001) days. Among thrombocytopenia patients, those with platelet count ≤50 × 109/L had a higher 28-day mortality rate (63.6% vs. 45%, p = .02). Multiple logistic regression showed that elevated lactate (adjusted odds ratio (OR) = 1.11; 95% confidence interval (CI): 1.04-1.17; P <0.001) and white blood cell (WBC) count (OR = 0.97; 95% CI: 0.95-0.99; p = .003) were independent risk factors for the development of thrombocytopenia. Thrombocytopenia group had increased bleeding events, blood product transfusions, and development of organ failure. In Kaplan-Meier survival estimates, survival probabilities at 28 days were greater in patients without thrombocytopenia (p value from the log-rank test, p = .004). There were no significant differences in the type of pathogenic microorganisms and the site of infection between patients with and without thrombocytopenia. In conclusion, thrombocytopenia within 24 hours of shock onset is associated with an increased risk of 28-day mortality in pediatric patients with septic shock.

The role of platelets and megakaryocytes in sepsis and ARDS

Since the global COVID-19 pandemic, there has been a renewed focus on lung injury during infection. Systemic inflammatory responses such as acute respiratory distress syndrome (ARDS) and sepsis are a leading cause of morbidity and mortality for both adults and children. Improvements in clinical care have improved outcomes but mortality remains ∼40% and significant morbidity persists for those patients with severe disease. Mechanistic studies of the underlying biological processes remain essential to identifying therapeutic targets. Furthermore, methods for identifying the underlying drivers of organ failure are key to treating and preventing tissue injury. In this review, we discuss the contribution of megakaryocytes (MKs) and platelets to the pathogenesis of systemic inflammatory syndromes. We explore the role of MKs and the new identification of extramedullary MKs during sepsis. We describe the alterations in the platelet transcriptome during sepsis. Lastly, we explore platelet function as defined by aggregation, activation and the formation of heterotypic aggregates. Much more work is necessary to explore the contribution of platelets to these heterogenous syndromes, but the foundation of platelets as key contributors to inflammation has been laid.

The Correlation of Hemostatic Parameters with the Development of Early Sepsis-Associated Encephalopathy. A Retrospective Observational Study

Introduction

Sepsis-associated encephalopathy (SAE) is one of the most common complications seen both in early and late stages of sepsis, with a wide spectrum of clinical manifestations ranging from mild neurological dysfunction to delirium and coma. The pathophysiology of SAE is still not completely understood, and the diagnosis can be challenging especially in early stages of sepsis and in patients with subtle symptoms.

Aim of the study

The objective of this study was to assess the coagulation profile in patients with early SAE and to compare the hemostatic parameters between septic patients with and without SAE in the first 24 hours from sepsis diagnosis.

Material and methods

This retrospective observational study included 280 patients with sepsis in the first 24 hours after sepsis diagnosis. A complete blood count was available in all patients; a complex hemostatic assessment including standard coagulation tests, plasmatic levels of coagulation factors, inhibitors, D-dimers, and Rotation thromboelastometry (ROTEM, Instrumentation Laboratory) was performed in a subgroup of patients.

Results

Early SAE was diagnosed in 184 patients (65.7%) and was correlated with a higher platelet count, after adjusting for age and leucocyte count. Compared to patients without neurological dysfunction, patients with early SAE presented a more active coagulation system revealed by faster propagation phase, increased clot firmness and elasticity with a higher platelet contribution to clot strength. The initiation of coagulation and clot lysis were not different between the groups.

Conclusion

In the early stages of sepsis, the development of SAE is correlated with increased systemic clotting activity where platelets seem to have an important role. More research is needed to investigate the role of platelets and the coagulation system in relation to the development of early SAE.

Immune cell composition and its impact on prognosis in children with sepsis

BACKGROUND

Given the critical role of immune cells and their responses in sepsis pathogenesis, this study aimed to evaluate the prognostic significance of various immune cell ratios in septic children through the collection and analysis of clinical data.

METHODS

Clinical data were collected from septic children admitted to the pediatric intensive care unit (PICU) of Shenzhen Children's Hospital between January 2019 and September 2021. The peripheral blood immune cell ratios included the neutrophil to lymphocyte ratio (NLR), the derived neutrophil to lymphocyte ratio (dNLR), the neutrophil to lymphocyte and platelet ratio (NLPR), the monocyte to lymphocyte ratio (MLR), and the platelet to lymphocyte ratio (PLR). To investigate the associations between these immune cell ratios and mortality, we utilized the locally weighted scatterplot smoothing (LOWESS) method, receiver operating characteristic (ROC) analysis, and Kaplan‒Meier (K‒M) analysis.

RESULTS

A total of 230 septic children were enrolled in the study. When comparing the immune cell ratios between the deceased and surviving groups, all ratios except for the PLR were elevated in the deceased group. Using the LOWESS method, we observed that the MLR, NLR, dNLR, and NLPR exhibited an approximately linear association with in-hospital mortality. Among the various immune cell ratios, the NLPR exhibited the highest AUC of 0.748, which was statistically comparable to that of the Pediatric Critical Illness Score (PCIS) (0.748 vs. 0.738, P = 0.852). The NLR (0.652), MLR (0.638), and dNLR (0.615) followed in terms of AUC values. K‒M analysis revealed that children with elevated MLR, NLR, dNLR, and NLPR exhibited increased 30-day mortality.

CONCLUSION

The predictive capacity of the NLPR is comparable to that of the PCIS, suggesting that the NLPR has potential as a robust prognostic indicator for septic children.

Red ginseng extract inhibits lipopolysaccharide-induced platelet-leukocyte aggregates in mice

Background

Platelet-leukocyte aggregates (PLAs) play important roles in cardiovascular disease and sepsis. Red ginseng extract (RGE) has been well-studied for its antiplatelet and anti-inflammatory activities. However, the potential inhibitory effects of RGE on PLA have not been investigated.

Methods

Six-week-old ICR mice were given oral gavage of RGE for 7 days, followed by an intraperitoneal injection of 15 mg/kg of lipopolysaccharide. Mice were euthanized 24 h later, and blood samples were collected for further analysis. Flow cytometry was utilized to sort populations of PLAs and platelet-neutrophil aggregates (PNAs). By using confocal microscopy, PNAs were validated. Morphological changes in platelets and leukocytes were visualized with scanning electron microscopy. Expressions of tissue factor (TF) and platelet factor 4 (PF4) were investigated using enzyme-linked immunosorbent assay.

Results

Populations of activated platelets, PLAs and PNAs, were significantly increased with LPS-induction. Treatment with 200 and 400 mg/kg of RGE decreased platelet activation. Moreover, the populations of PLAs and PNAs were reduced. PNAs were visible in the blood of septic mice, and this was attenuated by treatment with 400 mg/kg of RGE. Morphologically, sepsisinduced platelet activation and fibrin formation in the blood. This was reduced with RGE treatment. Sepsis-induced increase in the plasma levels of TF and PF4 was also reduced with RGE treatment.

Conclusion

This study shows that RGE is a potential therapeutic that reduces the activation of platelets and targets PLA and PNA formation. Detailed inhibitory mechanisms of RGE should be studied.

Neutrophil NLRP3 promotes cardiac injury following acute myocardial infarction through IL-1β production, VWF release and NET deposition in the myocardium

NLRP3 inflammasome has been implicated in neutrophil polarization and extrusion of neutrophil extracellular traps (NETs) in vitro and facilitates secretion of Il1-beta (IL-1β). Permanent ligation of the left anterior descending artery was used to induce MI in WT and NLRP3-/- mice as well as in NLRP3-/- recipient mice transfused with either WT or NLRP3-/- neutrophils. NLRP3 deficiency reduced infarct size to roughly a third of WT heart injury and preserved left ventricular (LV) function at 12 h after MI as assessed by echocardiography and triphenyltetrazolium chloride staining of live tissue. Transfusion of WT but not NLRP3-/- neutrophils after MI increased infarct size in NLRP3-/- mice and significantly reduced LV function. The key features of myocardial tissue in WT neutrophil transfused recipients were increased H3Cit-positive deposits with NET-like morphology and increased tissue levels of IL-1β and plasma levels of von Willebrand Factor (VWF). Flow cytometry analysis also revealed that neutrophil NLRP3 increased the number of labeled and transfused neutrophils in the bone marrow of recipient mice following MI. Our data suggest a key role for neutrophil NLRP3 in the production of IL-1β and deposition of NETs in cardiac tissue exacerbating injury following MI. We provide evidence for a link between neutrophil NLRP3 and VWF release likely enhancing thromboinflammation in the heart. Neutrophil NLRP3 deficiency conferred similar cardioprotective effects to general NLRP3 deletion in MI rendering anti-neutrophil NLRP3 therapy a promising target for early cardioprotective treatment.

Characteristics and Risk Factors for Pediatric Sepsis

OBJECTIVE

Sepsis is considered a major cause of health loss in children and had high mortality and morbidity. Currently, there is no reliable model for predicting the prognosis of pediatric patients with sepsis. This study aimed to analyze the clinical characteristics of sepsis in children and assess the risk factors associated with poor prognosis in pediatric sepsis patients to identify timely interventions and improve their outcomes.

METHODS

This study analyzed the clinical indicators and laboratory results of septic patients hospitalized in the Pediatric Intensive Care Unit of Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, China, from January 1, 2019, to December 31, 2021. Risk factors for sepsis were identified by logistic regression analyses.

RESULTS

A total of 355 children with sepsis were enrolled, with 333 children (93.8%) in the good prognosis group, and 22 children (6.2%) in the poor prognosis group. Among them, there were 255 patients (71.8%) in the sepsis group, and 100 patients (28.2%) in the severe sepsis group. The length of hospital stay in the poor prognosis group was longer than that in the good prognosis group (P<0.01). The levels of interleukin 1β (IL-1β) in the poor prognosis group were higher than those in the good prognosis group (P>0.05), and the platelet (PLT), albumin (ALB), and hemoglobin (Hb) levels were lower in the poor prognosis group (P<0.01). The IL-8 levels in the severe sepsis group were higher than those in the sepsis group (P<0.05). Multiple logistic regression analysis suggested that lower Hb levels, ALB levels, peak PLT counts, and higher IL-1β levels were independent risk factors for poor prognosis in children with sepsis.

CONCLUSION

Lower Hb, ALB, and PLT counts and elevated IL-1β are independent risk factors for poor prognosis in children with sepsis.

Unraveling the Intricate Web: Complement Activation Shapes the Pathogenesis of Sepsis-Induced Coagulopathy

BACKGROUND

Sepsis-associated coagulopathy specifically refers to widespread systemic coagulation activation accompanied by a high risk of hemorrhage and organ damage, which in severe cases manifests as disseminated intravascular coagulation (DIC), or even develops into multiple organ dysfunction syndrome (MODS). The complement system and the coagulation system as the main columns of innate immunity and hemostasis, respectively, undergo substantial activation after sepsis.

SUMMARY

Dysfunction of the complement, coagulation/fibrinolytic cascades caused by sepsis leads to "thromboinflammation," which ultimately amplifies the systemic inflammatory response and accelerates the development of MODS. Recent studies have revealed that massive activation of the complement system exacerbates sepsis-induced coagulation and even results in DIC, which suggests that inhibition of complement activation may have therapeutic potential in the treatment of septic coagulopathy.

KEY MESSAGES

Sepsis-associated thrombosis involves the upregulation or activation of procoagulant factors, down-regulation or inactivation of anticoagulant factors, and impairment of the fibrinolytic mechanism. This review aims to summarize the latest literature and analyze the underlying molecular mechanisms of the activation of the complement system on the abnormal coagulation cascades in sepsis.

Deciphering Abnormal Platelet Subpopulations in COVID-19, Sepsis and Systemic Lupus Erythematosus through Machine Learning and Single-Cell Transcriptomics

This study focuses on understanding the transcriptional heterogeneity of activated platelets and its impact on diseases such as sepsis, COVID-19, and systemic lupus erythematosus (SLE). Recognizing the limited knowledge in this area, our research aims to dissect the complex transcriptional profiles of activated platelets to aid in developing targeted therapies for abnormal and pathogenic platelet subtypes. We analyzed single-cell transcriptional profiles from 47,977 platelets derived from 413 samples of patients with these diseases, utilizing Deep Neural Network (DNN) and eXtreme Gradient Boosting (XGB) to distinguish transcriptomic signatures predictive of fatal or survival outcomes. Our approach included source data annotations and platelet markers, along with SingleR and Seurat for comprehensive profiling. Additionally, we employed Uniform Manifold Approximation and Projection (UMAP) for effective dimensionality reduction and visualization, aiding in the identification of various platelet subtypes and their relation to disease severity and patient outcomes. Our results highlighted distinct platelet subpopulations that correlate with disease severity, revealing that changes in platelet transcription patterns can intensify endotheliopathy, increasing the risk of coagulation in fatal cases. Moreover, these changes may impact lymphocyte function, indicating a more extensive role for platelets in inflammatory and immune responses. This study identifies crucial biomarkers of platelet heterogeneity in serious health conditions, paving the way for innovative therapeutic approaches targeting platelet activation, which could improve patient outcomes in diseases characterized by altered platelet function.

Macrophage-1 antigen exacerbates histone-induced acute lung injury and promotes neutrophil extracellular trap formation

Acute lung injury (ALI), which occurs in association with sepsis, trauma, and coronavirus disease 2019 (COVID-19), is a serious clinical condition with high mortality. Excessive platelet-leukocyte aggregate (PLA) formation promotes neutrophil extracellular trap (NET) release and thrombosis, which are involved in various diseases, including ALI. Macrophage-1 antigen (Mac-1, CD11b/CD18), which is expressed on the surface of leukocytes, is known to promote NET formation. This study aimed to elucidate the role of Mac-1 in extracellular histone-induced ALI. Exogenous histones were administered to Mac-1-deficient mice and wild-type (WT) mice with or without neutrophil or platelet depletion, and several parameters were investigated 1 h after histone injection. Depletion of neutrophils or platelets improved survival time and macroscopic and microscopic properties of lung tissues, and decreased platelet-leukocyte formation and plasma myeloperoxidase levels. These improvements were also observed in Mac-1-/- mice. NET formation in Mac-1-/- bone marrow neutrophils (BMNs) was significantly lower than that in WT BMNs. In conclusion, our findings suggest that Mac-1 is associated with exacerbation of histone-induced ALI and the promotion of NET formation in the presence of activated platelets.

Thrombocytopenia in Klebsiella pneumoniae liver abscess: a retrospective study on its correlation with disease severity and potential causes

Objective

Thrombocytopenia is commonly associated with infectious diseases and serves as an indicator of disease severity. However, reports on its manifestation in conjunction with Klebsiella pneumoniae liver abscess (KPLA) are scarce. The present study sought to elucidate the correlation between thrombocytopenia and KPLA severity and delve into the etiological factors contributing to the incidence of thrombocytopenia.

Materials and methods

A retrospective analysis of the clinical data from patients with KPLA admitted between June 2012 and June 2023 was performed. Baseline characteristics, biochemical assessments, therapeutic interventions, complications, and clinical outcomes were compared between patients with and without thrombocytopenia. To investigate the potential etiologies underlying thrombocytopenia, the association between platelet count reduction and thrombophlebitis was examined, with a particular focus on platelet consumption. Furthermore, bone marrow aspiration results were evaluated to assess platelet production anomalies.

Results

A total of 361 KPLA patients were included in the study, among whom 60 (17%) had concurrent thrombocytopenia. Those in the thrombocytopenia group exhibited significantly higher rates of thrombophlebitis (p = 0.042), extrahepatic metastatic infection (p = 0.01), septic shock (p = 0.024), admissions to the intensive care unit (p = 0.002), and in-hospital mortality (p = 0.045). Multivariate analysis revealed that thrombocytopenia (odds ratio, 2.125; 95% confidence interval, 1.114-4.056; p = 0.022) was independently associated with thrombophlebitis. Among the thrombocytopenic patients, eight underwent bone marrow aspiration, and six (75%) had impaired medullar platelet production. After treatment, 88.6% of thrombocytopenic patients (n = 47) demonstrated recovery in their platelet counts with a median recovery time of five days (interquartile range, 3-6 days).

Conclusions

Thrombocytopenia in patients with KPLA is indicative of increased disease severity. The underlying etiologies for thrombocytopenia may include impaired platelet production within the bone marrow and augmented peripheral platelet consumption as evidenced by the presence of thrombophlebitis.

Predictive value of thrombocytopenia for bloodstream infection in patients with sepsis and septic shock

BACKGROUND

Thrombocytopenia is common in patients with sepsis and septic shock.

AIM

To analyse the decrease in the number of platelets for predicting bloodstream infection in patients with sepsis and septic shock in the intensive care unit.

METHODS

A retrospective analysis of patients admitted with sepsis and septic shock in Xingtai People Hospital was revisited. Patient population characteristics and laboratory data were collected for analysis.

RESULTS

The study group consisted of 85 (39%) inpatients with bloodstream infection, and the control group consisted of 133 (61%) with negative results or contamination. The percentage decline in platelet counts (PPCs) in patients positive for pathogens [57.1 (41.3-74.6)] was distinctly higher than that in the control group [18.2 (5.1-43.1)] (P < 0.001), whereas the PPCs were not significantly different among those with gram-positive bacteraemia, gram-negative bacteraemia, and fungal infection. Using receiver operating characteristic curves, the area under the curve of the platelet drop rate was 0.839 (95%CI: 0.783-0.895).

CONCLUSION

The percentage decline in platelet counts is sensitive in predicting bloodstream infection in patients with sepsis and septic shock. However, it cannot identify gram-positive bacteraemia, gram-negative bacteraemia, and fungal infection.

Platelet P2Y12 signalling pathway in the dysregulated immune response during sepsis

Sepsis is a complicated pathological condition in response to severe infection. It is characterized by a strong systemic inflammatory response, where multiple components of the immune system are involved. Currently, there is no treatment for sepsis. Blood platelets are known for their role in haemostasis, but they also participate in inflammation through cell-cell interaction and the secretion of inflammatory mediators. Interestingly, an increase in platelet activation, secretion, and aggregation with other immune cells (such as monocytes, T-lymphocytes and neutrophils) has been detected in septic patients. Therefore, antiplatelet therapy in terms of P2Y12 antagonists has been evaluated as a possible treatment for sepis. It was found that blocking P2Y12 receptors decreased platelet marker expression and limited attachment to immune cells in some studies, but not in others. This review addresses the role of platelets in sepsis and discusses whether antagonizing P2Y12 signalling pathways can alter the disease outcome. Challenges in studying P2Y12 antagonists in sepsis also are discussed. LINKED ARTICLES: This article is part of a themed issue on Platelet purinergic receptor and non-thrombotic disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.4/issuetoc.

Genetic associations between autoimmune diseases and the risks of severe sepsis and 28-day mortality: a two-sample Mendelian randomization study

BACKGROUND

Autoimmune diseases exhibit heterogenous dysregulation of pro-inflammatory or anti-inflammatory cytokine expression, akin to the pathophysiology of sepsis. It is speculated that individuals with autoimmune diseases may have an increased likelihood of developing sepsis and face elevated mortality risks following septic events. However, current observational studies have not yielded consistent conclusions. This study aims to explore the causal relationship between autoimmune diseases and the risks of sepsis and mortality using Mendelian randomization (MR) analysis.

METHODS

We conducted a two-sample MR study involving a European population, with 30 autoimmune diseases as the exposure factors. To assess causal relationships, we employed the inverse variance-weighted (IVW) method and used Cochran's Q test for heterogeneity, as well as the MR pleiotropy residual sum and outlier (MR-PRESSO) global test for potential horizontal pleiotropy.

RESULTS

Genetically predicted Crohn's disease (β = 0.067, se = 0.034, p = 0.046, OR = 1.069, 95% CI = 1.001-1.141) and idiopathic thrombocytopenic (β = 0.069, se = 0.031, p = 0.023, OR = 1.071, 95% CI = 1.009-1.136) were positively associated with an increased risk of sepsis in critical care. Conversely, rheumatoid arthritis (β = -0.104, se = 0.047, p = 0.025, OR = 0.901, 95% CI = 0.823-0.987), ulcerative colitis (β = -0.208, se = 0.084, p = 0.013, OR = 0.812, 95% CI = 0.690-0.957), and narcolepsy (β = -0.202, se = 0.092, p = 0.028, OR = 0.818, 95% CI = 0.684-0.978) were associated with a reduced risk of sepsis in critical care. Moreover, Crohn's disease (β = 0.234, se = 0.067, p = 0.001, OR = 1.263, 95% CI = 1.108-1.440) and idiopathic thrombocytopenic (β = 0.158, se = 0.061, p = 0.009, OR = 1.171, 95% CI = 1.041-1.317) were also linked to an increased risk of 28-day mortality of sepsis in critical care. In contrast, multiple sclerosis (β = -0.261, se = 0.112, p = 0.020, OR = 0.771, 95% CI = 0.619-0.960) and narcolepsy (β = -0.536, se = 0.184, p = 0.003, OR = 0.585, 95% CI = 0.408-0.838) were linked to a decreased risk of 28-day mortality of sepsis in critical care.

CONCLUSION

This MR study identified causal associations between certain autoimmune diseases and risks of sepsis in critical care, and 28-day mortality in the European population. These findings suggest that exploring the mechanisms underlying autoimmune diseases may offer new diagnostic and therapeutic strategies for sepsis prevention and treatment.

Platelets promote human macrophages-mediated macropinocytosis of Clostridioides difficile

Clostridioides difficile is the main causative agent of hospital-acquired diarrhea and the potentially lethal disease, C. difficile infection. The cornerstone of the current therapy is the use of antibiotics, which is not fully effective. The molecular mechanisms, inflammatory conditions and host-immune responses that could benefit the persistence or elimination of C. difficile remain unclear. Macrophages perform different ways of endocytosis as part of their immune surveillance functions and platelets, classically known for their coagulatory role, are also important modulators of the immune system. The aim of this study was to evaluate the endocytosis of vegetative C. difficile by human macrophages and the involvement of platelets in this process. Our results showed that both macrophages and platelets interact with live and heat-killed C. difficile. Furthermore, platelets form complexes with human monocytes in healthy donor's fresh blood and the presence of C. difficile increased these cell-cell interactions. Using flow cytometry and confocal microscopy, we show that macrophages can internalize C. difficile and that platelets improve this uptake. By using inhibitors of different endocytic pathways, we demonstrate that macropinocytosis is the route of entry of C. difficile into the cell. Taken together, our findings are the first evidence for the internalization of vegetative non-toxigenic and hypervirulent C. difficile by human macrophages and highlight the role of platelets in innate immunity during C. difficile infection. Deciphering the crosstalk of C. difficile with immune cells could provide new tools for understanding the pathogenesis of C. difficile infection and for the development of host-directed therapies.

Serotonin Signaling and the Hyperpermeable Endothelial Barrier in Sepsis: Clues to a Molecular Mechanism

Sepsis is characterized by a severe systemic inflammatory response caused by hyperpermeability of the endothelial barrier resulting microvascular leakage, which is a leading factor to multiorgan failure. In sepsis, the hyperpermeable endothelial cells contribute to the activation of platelets, which release numerous mediators that affect coagulation, inflammatory response and are believed to directly or indirectly affect the integrity of the endothelial barrier. One such mediator is serotonin (5-hydroxytryptamine, 5-HT), a signaling molecule which mediates a number of cellular functions including regulation of cytoskeletal dynamics associated with barrier function of endothelial cells. The actions of 5-HT are mediated by different types of receptors and terminated via an uptake mechanism of a 5-HT transporter (SERT) on the platelet and endothelial cell. Earlier studies revealed unexpected discoveries concerning the impact of 5-HT signaling on the permeability of the endothelial barrier. These findings have been supported by the clinical reports on the anti-inflammatory property of 5-HT reuptake inhibitor, SSRIs in treating sepsis-related morbidity and mortality. This review focuses on a wide-range of literature to pinpoint cellular and molecular mechanisms that mediate 5-HT-induced microvascular injury in sepsis pathogenesis.

Alterations in the megakaryocyte transcriptome impacts platelet function in sepsis and COVID-19 infection

Platelets and their parent cell, the megakaryocyte (MK), are increasingly recognized for their roles during infection and inflammation. The MK residing in the bone marrow or arising from precursors trafficked to other organs for development go on to form platelets through thrombopoiesis. Infection, by direct and indirect mechanisms, can alter the transcriptional profile of MKs. The altered environment, whether mediated by inflammatory cytokines or other signaling mechanisms results in an altered platelet transcriptome. Platelets released into the circulation, in turn, interact with each other, circulating leukocytes and endothelial cells and contribute to the clearance of pathogens or the potentiation of pathophysiology through such mechanisms as immunothrombosis. In this article we hope to identify key contributions that explore the impact of an altered transcriptomic landscape during severe, systemic response to infection broadly defined as sepsis, and viral infections, including SARS-CoV2. We include current publications that outline the role of MKs from bone-marrow and extra-medullary sites as well as the circulating platelet. The underlying diseases result in thrombotic complications that exacerbate organ dysfunction and mortality. Understanding the impact of platelets on the pathophysiology of disease may drive therapeutic advances to improve the morbidity and mortality of these deadly afflictions.

Common laboratory tests and their correlation with the clinical presentation and prognosis of Lemierre syndrome

INTRODUCTION

Lemierre syndrome is a thromboembolic complication following an acute bacterial infection of the head/neck area, often due to anaerobes. Data on the prognostic role of laboratory parameters is lacking.

METHODS

We analyzed individual-patient level data from a multinational cohort of patients with Lemierre-syndrome. Patients had an infection in the head/neck area, and contiguous vein thrombosis or septic embolism, irrespective of the causal pathogen. We studied the patterns of white blood cell count, platelet count, and C-reactive protein concentration investigating their association with baseline characteristics and in-hospital clinical outcomes (septic embolism, major bleeding, all-cause death).

RESULTS

A total of 447 (63%) patients had complete data for analysis. White blood cells were elevated across all subgroups (median 17 × 103/μL; Q1-Q3:12-21). Median platelet count was 61 × 103/μL (Q1-Q3:30-108) with decreasing levels with increasing age. Males, patients with renal failure or cardiopulmonary impairment, and those with typical Lemierre syndrome (tonsillitis, septic thromboembolism, positivity for Fusobacterium spp.) had the lowest platelet count. Median C-reactive protein was 122 (Q1-Q3:27-248) mg/L with higher values in patients who also had more severe thrombocytopenia. The overall risk of complications was similar across subgroups of patients stratified according to white blood cell and C-reactive protein levels. Patients in the lowest third of platelet count (<42 × 103/μL) had the highest rate of complications (26%), as opposed to those in the highest third (11%), notably septic embolic events.

CONCLUSIONS

Common laboratory tests correlate with the clinical presentation of Lemierre syndrome. However, extreme values did not appear to be prognostically relevant for in-hospital complications and potentially able to improve clinical management.

Prognostic value of APTT combined with fibrinogen and creatinine in predicting 28-Day mortality in patients with septic shock caused by acute enteric perforation

BACKGROUND

Septic shock is one of the leading causes of mortality in intensive care units. This retrospective study was carried out to evaluate the association of clinical available factors with 28-day mortality.

PATIENTS AND METHOD

In this observational study, patients with perioperative septic shocks secondary to intra-abdominal infection caused by enteric perforation were included. A total of 328 sepsis patients were admitted to the surgical intensive care units from January 2012 to December 2016. A total of 138 patients met the enrolment criteria and were included in the study. The data of demographic, clinical and laboratory were all recorded.

RESULT

All these 138 patients received abdominal surgery prior to surgical intensive care units caused by acute enteric perforation. These patients were all met the diagnostic criteria of septic shock according to Sepsis-3. Statistical analysis showed that lactic acid, blood platelet, fibrinogen, creatinine and activated partial thromboplastin time were found to be associated with 28-day mortality. A combination of serum activated partial thromboplastin time combined with fibrinogen and creatinine could predict in-hospital 28-day mortality. The area under the curve of serum activated partial thromboplastin time combined with fibrinogen and creatinine is 0.875 (0.806-0.944).

CONCLUSION

In conclusion, this pilot study demonstrated that these factors can predict the prognosis of septic shock caused by enteric perforation. In order to reduce the mortality, surgeons and intensive care units physician may consider these data in perioperative period.

Effects of prior antiplatelet and/or nonsteroidal anti-inflammatory drug use on mortality in patients undergoing abdominal surgery for abdominal sepsis

BACKGROUND

The effects of prior antiplatelet and/or nonsteroidal anti-inflammatory drug (NSAID) use on mortality in critically ill patients remain unclear. We investigated the relationship between antiplatelet and/or NSAID use and mortality in patients who had undergone surgery for sepsis caused by intra-abdominal infection.

METHODS

We obtained data from adult patients (aged >18 years) admitted to the intensive care unit after abdominal surgery due to intra-abdominal infection. The patients were categorized into those with and without prior antiplatelet and/or NSAID use.

RESULTS

Overall, 241 patients were enrolled, with 76 in the antiplatelet and/or NSAID use group and 165 in the non-use group. The 60-day survival probabilities for the antiplatelet and/or NSAID use and non-use groups were 85.5% and 73.3%, respectively, and this difference was significant (P = .040). In the multivariate analysis of 28-day mortality, higher Acute Physiology and Chronic Health Evaluation II score (P < .001), Simplified Acute Physiology Score III (P < .001), and blood transfusion within 5 days postoperatively (P = .034) were significant mortality risk factors. In the multivariate analysis of 60-day mortality, higher Acute Physiology and Chronic Health Evaluation II score (P = .002), Simplified Acute Physiology Score III (P < .001), and blood transfusion within 5 days postoperatively (P = .006) were also significant mortality risk factors. However, prior drug use (P = .036) was a factor in reducing mortality.

CONCLUSION

Patients with a prior history of antiplatelet and/or NSAID use had a higher 60-day survival than those who did not use these drugs. Prior antiplatelet and/or NSAID use was significantly associated with a reduction in 60-day mortality.

Prognostic value of platelet combined with serum procalcitonin in patients with sepsis

Sepsis, a common and life-threatening condition in critically ill patients, is a leading cause of death in intensive care units. Over the past few decades, there has been significant improvement in the understanding and management of sepsis. However, the mortality rate remains unacceptably high, posing a prominent challenge in modern medicine and a significant global disease burden. A total of 295 patients with sepsis admitted to the hospital from January 2021 to December 2022 were collected and divided into survival group and death group according to their 28-day survival status. The differences in general clinical data and laboratory indicators between the 2 groups were compared. Receiver operating characteristic curve analysis was used to evaluate the predictive value of platelet (PLT) and procalcitonin (PCT) for the prognosis of sepsis patients within 28 days. A total of 295 patients were diagnosed with sepsis, and 79 died, with a mortality rate of 26.78%. The PLT level in the death group was lower than that in the survival group; the PCT level in the death group was higher than that in the survival group. The receiver operating characteristic curve showed that the area under the curve of PCT and PLT for evaluating the prognosis of sepsis patients were 0.808 and 0.804, respectively. Kaplan-Meier survival analysis showed that the 28-day survival rate of the low PLT level group was 19.0% and that of the high PLT level group was 93.1% at the node of 214.97 × 109/L, and the difference between the 2 groups was statistically significant (χ2 = 216.538, P < .001). The 28-day survival rate of the low PCT level group was 93.4% and that of the high PCT level group was 51.7% at the node of 2.85 ng/mL, and the difference between the 2 groups was statistically significant (χ2 = 63.437, P < .001). There was a negative correlation between PCT level and PLT level (r = -0.412, P < .001). Platelet combined with serum procalcitonin detection has high predictive value for judging the 28-day prognosis of sepsis, and it can be used as an index for evaluating the patient's condition and prognosis, and is worthy of clinical promotion and application.

The Crossroads of the Coagulation System and the Immune System: Interactions and Connections

The coagulation and immune systems, two vital systems in the human body, share intimate connections that fundamentally determine patient health. These systems work together through several common regulatory pathways, including the Tissue Factor (TF) Pathway. Immune cells expressing TF and producing pro-inflammatory cytokines can influence coagulation, while coagulation factors and processes reciprocally impact immune responses by activating immune cells and controlling their functions. These shared pathways contribute to maintaining health and are also involved in various pathological conditions. Dysregulated coagulation, triggered by infection, inflammation, or tissue damage, can result in conditions such as disseminated intravascular coagulation (DIC). Concurrently, immune dysregulation may lead to coagulation disorders and thrombotic complications. This review elucidates these intricate interactions, emphasizing their roles in the pathogenesis of autoimmune diseases and cancer. Understanding the complex interplay between these systems is critical for disease management and the development of effective treatments. By exploring these common regulatory mechanisms, we can uncover innovative therapeutic strategies targeting these intricate disorders. Thus, this paper presents a comprehensive overview of the mutual interaction between the coagulation and immune systems, highlighting its significance in health maintenance and disease pathology.

The severity and infection of acute pancreatitis may increase the risk of bleeding in patients undergoing EUS-guided drainage and endoscopic necrosectomy: a large retrospective cohort

BACKGROUND

There has been great progress in the use of endoscopic ultrasound (EUS)-guided drainage in acute pancreatitis patients using a novel lumen-apposing metal stent (LAMS) in the last decade, but some patients experience bleeding. Our research analyzed the preprocedural risk factors for bleeding.

METHODS

From July 13, 2016 to June 23, 2021, we retrospectively analyzed all patients who received endoscopic drainage by the LAMS in our hospital. Univariate and multivariate statistical analyses were used to identify the independent risk factors. We plotted ROC curves based on the independent risk factors.

RESULTS

A total of 205 patients were analyzed and 5 patients were excluded. A total of 200 patients were included in our research. Thirty (15%) patients presented with bleeding. In the multivariate analysis, computed tomography severity index score (CTSI) score [odds ratio (OR), 2.66; 95% CI: 1.31-5.38; P = 0.007], positive blood cultures [odds ratio (OR), 5.35; 95% CI: 1.31-21.9; P = 0.02], and Acute Physiology and Chronic Health Evaluation II (APACHE II) score [odds ratio (OR), 1.14; 95% CI: 1. 01-1.29; P = 0.045] were associated with bleeding. The area under the ROC curve of the combined predictive indicator was 0.79.

CONCLUSION

Bleeding in endoscopic drainage by the LAMS is significantly associated with the CTSI score, positive blood cultures, and APACHE II score. This result could help clinicians make more appropriate choices.

Myristica fragrans Extract Inhibits Platelet Desialylation and Activation to Ameliorate Sepsis-Associated Thrombocytopenia in a Murine CLP-Induced Sepsis Model

Sepsis, characterized by an uncontrolled host inflammatory response to infections, remains a leading cause of death in critically ill patients worldwide. Sepsis-associated thrombocytopenia (SAT), a common disease in patients with sepsis, is an indicator of disease severity. Therefore, alleviating SAT is an important aspect of sepsis treatment; however, platelet transfusion is the only available treatment strategy for SAT. The pathogenesis of SAT involves increased platelet desialylation and activation. In this study, we investigated the effects of Myristica fragrans ethanol extract (MF) on sepsis and SAT. Desialylation and activation of platelets treated with sialidase and adenosine diphosphate (platelet agonist) were assessed using flow cytometry. The extract inhibited platelet desialylation and activation via inhibiting bacterial sialidase activity in washed platelets. Moreover, MF improved survival and reduced organ damage and inflammation in a mouse model of cecal ligation and puncture (CLP)-induced sepsis. It also prevented platelet desialylation and activation via inhibiting circulating sialidase activity, while maintaining platelet count. Inhibition of platelet desialylation reduces hepatic Ashwell-Morell receptor-mediated platelet clearance, thereby reducing hepatic JAK2/STAT3 phosphorylation and thrombopoietin mRNA expression. This study lays a foundation for the development of plant-derived therapeutics for sepsis and SAT and provides insights into sialidase-inhibition-based sepsis treatment strategies.

Sepsis-Induced Coagulopathy: An Update on Pathophysiology, Biomarkers, and Current Guidelines

Significant cross talk occurs between inflammation and coagulation. Thus, coagulopathy is common in sepsis, potentially aggravating the prognosis. Initially, septic patients tend to exhibit a prothrombotic state through extrinsic pathway activation, cytokine-induced coagulation amplification, anticoagulant pathways suppression, and fibrinolysis impairment. In late sepsis stages, with the establishment of disseminated intravascular coagulation (DIC), hypocoagulability ensues. Traditional laboratory findings of sepsis, including thrombocytopenia, increased prothrombin time (PT) and fibrin degradation products (FDPs), and decreased fibrinogen, only present late in the course of sepsis. A recently introduced definition of sepsis-induced coagulopathy (SIC) aims to identify patients at an earlier stage when changes to coagulation status are still reversible. Nonconventional assays, such as the measurement of anticoagulant proteins and nuclear material levels, and viscoelastic studies, have shown promising sensitivity and specificity in detecting patients at risk for DIC, allowing for timely therapeutic interventions. This review outlines current insights into the pathophysiological mechanisms and diagnostic options of SIC.

Predictive role of selected biomarkers in differentiating gram-positive from gram-negative sepsis in surgical patients: a retrospective study

INTRODUCTION

Patients after major surgery are at high risk of developing sepsis, which is accompanied by elevated serum levels of C-reactive protein (CRP) and procalcitonin (PCT). This study aimed to examine the differences in serum biomarker levels concerning the causative agent of sepsis in surgical patients.

MATERIAL AND METHODS

A retrospective study was carried out in the surgical intensive care unit (ICU) and included 81 septic patients admitted from January 2019 to May 2022, who had positive blood cultures (BC). Serum levels of PCT, CRP, white blood cells (WBC) and platelet counts were recorded on the day of the positive BC and over the following 3 days.

RESULTS

Patients with gram(-) sepsis had significantly higher PCT levels, and lower platelet count compared to patients with gram(+) sepsis. High PCT and low platelets levels in all measurements were a significant predictor of gram(-) isolate with the highest predictive value on the third day after BC sampling, with AUROC 0.821 (95% CI: 0.692-0.950), P = 0.001, and AUROC 0.676 (95% CI: 0.541-0.811), P = 0.02, respectively. In multivariate logistic regression, platelets the day after BC sampling and PCT on the third day made a significant contribution in distinguishing gam(+) from gram(-) BC. Age and high serum CRP levels were significant predictors of poor outcomes.

CONCLUSIONS

PCT and platelets may be useful biomarkers for predicting the causative agent of sepsis in surgical patients.

S100A8/A9 drives the formation of procoagulant platelets through GPIbα

S100A8/A9, also known as "calprotectin" or "MRP8/14," is an alarmin primarily secreted by activated myeloid cells with antimicrobial, proinflammatory, and prothrombotic properties. Increased plasma levels of S100A8/A9 in thrombo-inflammatory diseases are associated with thrombotic complications. We assessed the presence of S100A8/A9 in the plasma and lung autopsies from patients with COVID-19 and investigated the molecular mechanism by which S100A8/A9 affects platelet function and thrombosis. S100A8/A9 plasma levels were increased in patients with COVID-19 and sustained high levels during hospitalization correlated with poor outcomes. Heterodimeric S100A8/A9 was mainly detected in neutrophils and deposited on the vessel wall in COVID-19 lung autopsies. Immobilization of S100A8/A9 with collagen accelerated the formation of a fibrin-rich network after perfusion of recalcified blood at venous shear. In vitro, platelets adhered and partially spread on S100A8/A9, leading to the formation of distinct populations of either P-selectin or phosphatidylserine (PS)-positive platelets. By using washed platelets, soluble S100A8/A9 induced PS exposure but failed to induce platelet aggregation, despite GPIIb/IIIa activation and alpha-granule secretion. We identified GPIbα as the receptor for S100A8/A9 on platelets inducing the formation of procoagulant platelets with a supporting role for CD36. The effect of S100A8/A9 on platelets was abolished by recombinant GPIbα ectodomain, platelets from a patient with Bernard-Soulier syndrome with GPIb-IX-V deficiency, and platelets from mice deficient in the extracellular domain of GPIbα. We identified the S100A8/A9-GPIbα axis as a novel targetable prothrombotic pathway inducing procoagulant platelets and fibrin formation, in particular in diseases associated with high levels of S100A8/A9, such as COVID-19.

Nanomaterials targeting macrophages in sepsis: A promising approach for sepsis management

Sepsis is a life-threatening organ dysfunction resulting from dysregulated host responses to infection. Macrophages play significant roles in host against pathogens and the immunopathogenesis of sepsis, such as phagocytosis of pathogens, secretion of cytokines, and phenotype reprogramming. However, the rapid progression of sepsis impairs macrophage function, and conventional antimicrobial and supportive treatment are not sufficient to restore dysregulated macrophages roles. Nanoparticles own unique physicochemical properties, surface functions, localized surface plasmon resonance phenomenon, passive targeting in vivo, good biocompatibility and biodegradability, are accessible for biomedical applications. Once into the body, NPs are recognized by host immune system. Macrophages are phagocytes in innate immunity dedicated to the recognition of foreign substances, including nanoparticles, with which an immune response subsequently occurs. Various design strategies, such as surface functionalization, have been implemented to manipulate the recognition of nanoparticles by monocytes/macrophages, and engulfed by them to regulate their function in sepsis, compensating for the shortcomings of sepsis traditional methods. The review summarizes the mechanism of nanomaterials targeting macrophages and recent advances in nanomedicine targeting macrophages in sepsis, which provides good insight for exploring macrophage-based nano-management in sepsis.

Risk factors for the prognosis of patients with sepsis in intensive care units

Background and purpose

To date, sepsis remains the main cause of mortality in intensive care units (ICU). This study aimed analyze the risk factors of the prognosis in sepsis patients.

Methods

In this case-control study, patients with sepsis admitted to the intensive care unit of a Chinese hospital between January and November 2020 were analyzed. Ultrasound and clinical data were analyzed and compared between non-survivors and survivors. The ROC curve analysis was also performed to determine the best indicator for predicting mortality.

Results

A total of 72 patients with sepsis in ICU were included for analysis. The basic characteristics between the survivals and non-survivals were similar, except for acute physiology and chronic health evaluation (APACHE) Ⅱ score, sepsis-related organ failure assessment (SOFA) score, lactate level, ultrasound parameters from superior mesenteric artery (SMA) such as peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistive index (RI). Univariate analysis revealed that the APACHE Ⅱ score, SOFA score, lactate, low PSV, EDV, and RI were potential risk factors for mortality in sepsis, while multivariate analysis suggested that low PSV was an independent risk factor for mortality, and the adjusted odds ratio was 0.295 (95% CI: 0.094–0.925). The ROC analysis showed that the PSV (AUC = 0.99; sensitivity and specificity were 0.99 and 0.96, respectively) had good predictive value for mortality in sepsis.

Conclusion

Low PSV as found to be an independent risk factor and good predictor for mortality in patients with sepsis. This study shows the promise of ultrasound in predicting mortality in patients with sepsis; however, further studies are needed to validate these results.

Machine learning for the prediction of acute kidney injury in critical care patients with acute cerebrovascular disease

Purpose

Acute kidney injury (AKI) is a common complication and associated with a poor clinical outcome. In this study, we developed and validated a model for predicting the risk of AKI through machine learning methods in critical care patients with acute cerebrovascular disease.

Methods

This study was a retrospective study based on two different cohorts. Five machine learning methods were used to develop AKI risk prediction models. We used six popular metrics (AUROC, F2-Score, accuracy, sensitivity, specificity and precision) to evaluate the performance of these models.

Results

We identified 2935 patients in the MIMIC-III database and 499 patients in our local database to develop and validate the AKI risk prediction model. The incidence of AKI in these two different cohorts was 18.3% and 61.7%, respectively. Analysis showed that several laboratory parameters (serum creatinine, hemoglobin, white blood cell count, bicarbonate, blood urea nitrogen, sodium, albumin, and platelet count), age, and length of hospital stay, were the top ten important factors associated with AKI. The analysis demonstrated that the XGBoost had higher AUROC (0.880, 95%CI: 0.831–0.929), indicating that the XGBoost model was better at predicting AKI risk in patients with acute cerebrovascular disease than other models.

Conclusions

This study developed machine learning methods to identify critically ill patients with acute cerebrovascular disease who are at a high risk of developing AKI. This result suggested that machine learning techniques had the potential to improve the prediction of AKI risk models in critical care.

Administration of recombinant human thrombopoietin is associated with alleviated thrombocytopenia in adult intensive care unit patients with pneumonia: A single-center retrospective study

Background: Recombinant human thrombopoietin (rhTPO) is reported to stimulate platelet production and increase peripheral platelet counts; it is primarily used to manage chemotherapy-induced thrombocytopenia and idiopathic thrombocytopenic purpura. However, the effect of rhTPO in patients with pneumonia and thrombocytopenia remains uncertain. Objective: To assess the association of rhTPO and platelet counts in ICU patients with pneumonia and thrombocytopenia. Materials and Methods: A retrospective cohort study was performed in the ICU department, Nanfang Hospital, Southern Medical University, Guangzhou, China. From January 2016 to April 2021, patients with pneumonia and thrombocytopenia were allocated to two groups-the rhTPO and no-rhTPO groups-according to whether they received rhTPO treatment or not during their ICU stay. Demographical and clinical data were collected and analyzed using statistical software; p < 0.05 was considered statistically significant. Results: Out of 327 patients, 149 were in the rhTPO group and 178 were in the no-rhTPO group. Within the first 7 days, platelet counts increased more for patients in the rhTPO group compared with those in the no-rhTPO group (99.21 ± 102.613 vs. 2.08 ± 43.877, p = 0.000). The clinical recovery rate of platelets increased within 7 days (65.8 vs. 18.5%, p = 0.000) and, after 7 days of enrollment, hemorrhagic scores decreased more apparently in the rhTPO group (2.81 ± 2.856 vs. 1.16 ± 2.123, p = 0.000). Further, bleeding events ceased in 66.7% of the patients in the rhTPO group compared with 37.3% of the patients in the no-rhTPO group (p = 0.000). Less red-blood-cells transfusions were needed in the rhTPO group (3.639 ± 4.630 vs. 5.818 ± 6.858, p = 0.009). Furthermore, through logistic regression, rhTPO administration was found to be an independent indicator that affected the platelet recovery rate within 7 days. Conclusion: This study finds that rhTPO administration is associated with increased platelet counts, alleviated bleeding, and reduced blood transfusion. For patients with pneumonia and thrombocytopenia, rhTPO may be an effective therapeutic drug; however, more RCT trails are needed to confirm our observation.

Distinct serotypes of streptococcal M proteins mediate fibrinogen-dependent platelet activation and pro-inflammatory effects

Sepsis is a life-threatening complication of infection that is characterized by a dysregulated inflammatory state and disturbed hemostasis. Platelets are the main regulators of hemostasis, and they also respond to inflammation. The human pathogen Streptococcus pyogenes can cause local infection that may progress to sepsis. There are more than 200 serotypes of S. pyogenes defined according to sequence variations in the M protein. The M1 serotype is among 10 serotypes that are predominant in invasive infection. M1 protein can be released from the surface and has previously been shown to generate platelet, neutrophil, and monocyte activation. The platelet-dependent proinflammatory effects of other serotypes of M protein associated with invasive infection (M3, M5, M28, M49, and M89) are now investigated using a combination of multiparameter flow cytometry, enzyme-linked immunosorbent assay (ELISA), aggregometry, and quantitative mass spectrometry. We demonstrate that only M1, M3, and M5 protein serotypes can bind fibrinogen in plasma and mediate fibrinogen- and IgG-dependent platelet activation and aggregation, release of granule proteins, upregulation of CD62P to the platelet surface, and complex formation with neutrophils and monocytes. Neutrophil and monocyte activation, determined as upregulation of surface CD11b, is also mediated by M1, M3, and M5 protein serotypes, while M28, M49, and M89 proteins failed to mediate activation of platelets or leukocytes. Collectively, our findings reveal novel aspects of the immunomodulatory role of fibrinogen acquisition and platelet activation during streptococcal infections.

Physical Exercise as a Modulator of Vascular Pathology and Thrombin Generation to Improve Outcomes After Traumatic Brain Injury

Disruption of the blood-brain barrier and occurrence of coagulopathy after traumatic brain injury (TBI) have important implications for multiple secondary injury processes. Given the extent of post-traumatic changes in neuronal function, significant alterations in some targets, such thrombin (a protease that plays a physiological role in maintaining blood coagulation), play an important role in TBI-induced pathophysiology. Despite the magnitude of thrombin in synaptic plasticity being concentration-dependent, the mechanisms underlying TBI have not been fully elucidated. The understanding of this post-injury neurovascular dysregulation is essential to establish scientific-based rehabilitative strategies. One of these strategies may be supporting physical exercise, considering its relevance in reducing damage after a TBI. However, there are caveats to consider when interpreting the effect of physical exercise on neurovascular dysregulation after TBI. To complete this picture, this review will describe how the interactions established between blood-borne factors (such as thrombin) and physical exercise alter the TBI pathophysiology.

Distinct phenotypes of platelet, monocyte, and neutrophil activation occur during the acute and convalescent phase of COVID-19

SARS-CoV-2 has spread rapidly worldwide, causing the COVID-19 pandemic. Platelet activation and platelet-leukocyte complex formation are proposed to contribute to disease progression. Here, we report platelet and leukocyte activation during acute and convalescent COVID-19 in patients recruited between May-July 2020. Blood samples were analyzed by flow cytometry and ELISA using paired comparison between inclusion (day 0) and 28 days later. The majority of patients were mildly or moderately ill with significantly higher cytokine levels (IL-6 and IL-10) on day 0 as compared with day 28. Platelet activation and granule release were significantly higher on day 0 compared with day 28, as determined by ADP- or thrombin-induced surface CD62P expression, baseline released CD62P, and thrombin-induced platelet-monocyte complex formation. Monocyte activation and procoagulant status at baseline and post activation were heterogeneous but generally lower on day 0 compared with day 28. Baseline and thrombin- or fMLF-induced neutrophil activation and procoagulant status were significantly lower on day 0 compared with day 28. We demonstrate that during the acute phase of COVID-19 compared with the convalescent phase, platelets are more responsive while neutrophils are less responsive. COVID-19 is associated with thromboembolic events where platelet activation and interaction with leukocytes may play an important role.