Intracellular communication and immunothrombosis in sepsis

Deranged Balance of Hemostasis and Fibrinolysis in Disseminated Intravascular Coagulation: Assessment and Relevance in Different Clinical Settings

The disruption of hemostasis/fibrinolysis balance leads to disseminated intravascular coagulation, manifested clinically by bleeding or thrombosis, and multiorgan failure. This study reviews hemostatic assessment and therapeutic strategies that restore this balance in critically ill patients.

Immunological alterations in the endothelial barrier: a new predictive and therapeutic paradigm for sepsis

INTRODUCTION

Despite the fact incidence and mortality vary widely among regions, sepsis remains a major cause of morbidity and cost worldwide. The importance of the endothelial barrier in sepsis and infectious diseases is increasingly recognized; however, the underlying pathophysiology of the endothelial barrier in sepsis remains poorly understood.

AREAS COVERED

Here we review the advances in basic and clinical research for relevant papers in PubMed database. We attempt to provide an updated overview of immunological alterations in endothelial dysfunction, discussing the central role of endothelial barrier involved in sepsis to provide new predictive and therapeutic paradigm for sepsis.

EXPERT OPINION

Given its physiological and immunological functions in infectious diseases, the endothelial barrier has been dramatically altered in sepsis, suggesting that endothelial dysfunction may play a critical role in the pathogenesis of sepsis. Although many reliable biomarkers have been investigated to monitor endothelial activation and injury in an attempt to find diagnostic and therapeutic tools, there are no specific therapies to treat sepsis due to its complex pathophysiology. Since sepsis is initiated by both hyperinflammation and immunoparalysis occurring simultaneously, a 'one-treatment-fits-all' strategy for sepsis-induced immune injury and immunoparalysis is bound to fail, and an individualized 'precision medicine' approach is required.

The role of thromboinflammation in acute kidney injury among patients with septic coagulopathy

Inflammation and coagulation are critical self-defense mechanisms for mitigating infection that can nonetheless induce tissue injury and organ dysfunction. In severe cases, like sepsis, a dysregulated thromboinflammatory response may result in multiorgan dysfunction. Sepsis-associated acute kidney injury (AKI) is a significant contributor to patient morbidity and mortality. The connection between AKI and thromboinflammation is largely due to unique aspects of the renal vasculature. Specifically, the interaction between blood cells with the endothelial, glomerular, and peritubular capillary systems during thromboinflammation reduces oxygen supply to tubular epithelial cells. Previous studies have focused on tubular epithelial cell damage due to hypoxia, oxidative stress, and nephrotoxins. Although these factors are pivotal in acute tubular injury or necrosis, recent studies have demonstrated that AKI in sepsis encompasses a mixture of tubular and glomerular damage subtypes. In cases of sepsis-induced coagulopathy, thromboinflammation within the glomerulus and peritubular capillaries is an important pathogenic mechanism for AKI. Unfortunately, and despite the use of renal replacement therapy, the development of AKI in sepsis continues to be associated with high morbidity, mortality, and clinical challenges requiring alternative approaches. This review introduces the important role of thromboinflammation in AKI pathogenesis and details innovative vascular-targeting therapeutic strategies.

Prognostic gene landscapes and therapeutic insights in sepsis-induced coagulopathy

BACKGROUND

Sepsis is a common and critical condition encountered in clinical practice that can lead to multi-organ dysfunction. Sepsis-induced coagulopathy (SIC) significantly affects patient outcomes. However, the precise mechanisms remain unclear, making the identification of effective prognostic and therapeutic targets imperative.

METHODS

The analysis of transcriptome data from the whole blood of sepsis patients, facilitated the identification of key genes implicated in coagulation. Then we developed a prognostic model and a nomogram to predict patient survival. Consensus clustering classified sepsis patients into three subgroups for comparative analysis of immune function and immune cell infiltration. Single-cell sequencing elucidated alterations in intercellular communication between platelets and immune cells in sepsis, as well as the role of the coagulation-related gene FYN. Real-time quantitative PCR determined the mRNA levels of critical coagulation genes in septic rats' blood. Finally, administration of a FYN agonist to septic rats was observed for its effects on coagulation functions and survival.

RESULTS

This study identified four pivotal genes-CFD, FYN, ITGAM, and VSIG4-as significant predictors of survival in patients with sepsis. Among them, CFD, FYN, and ITGAM were underexpressed, while VSIG4 was upregulated in patients with sepsis. Moreover, a nomogram that incorporates the coagulation-related genes (CoRGs) risk score with clinical features of patients accurately predicted survival probabilities. Subgroup analysis of CoRGs expression delineated three molecular sepsis subtypes, each with distinct prognoses and immune profiles. Single-cell sequencing shed light on heightened communication between platelets and monocytes, T cells, and plasmacytoid dendritic cells, alongside reduced interactions with neutrophils in sepsis. The collagen signaling pathway was found to be essential in this dynamic. FYN may affect platelet function by modulating factors such as ELF1, PTCRA, and RASGRP2. The administration of the FYN agonist can effectively improve coagulation dysfunction and survival in septic rats.

CONCLUSIONS

The research identifies CoRGs as crucial prognostic markers for sepsis, highlighting the FYN gene's central role in coagulation disorders associated with the condition and suggesting novel therapeutic intervention strategies.

Tea polyphenol-derived nanomedicine for targeted photothermal thrombolysis and inflammation suppression

Thrombotic diseases impose a significant global health burden, and conventional drug-based thrombolytic therapies are encumbered by the risk of bleeding complications. In this study, we introduce a novel drug-free nanomedicine founded on tea polyphenols nanoparticles (TPNs), which exhibits multifaceted capabilities for localized photothermal thrombolysis. TPNs were synthesized through a one-pot process under mild conditions, deriving from the monomeric epigallocatechin-3-gallate (EGCG). Within this process, indocyanine green (ICG) was effectively encapsulated, exploiting multiple intermolecular interactions between EGCG and ICG. While both TPNs and ICG inherently possessed photothermal potential, their synergy significantly enhanced photothermal conversion and stability. Furthermore, the nanomedicine was functionalized with cRGD for targeted delivery to activated platelets within thrombus sites, eliciting robust thrombolysis upon laser irradiation across diverse thrombus types. Importantly, the nanomedicine's potent free radical scavenging abilities concurrently mitigated vascular inflammation, thus diminishing the risk of disease recurrence. In summary, this highly biocompatible multifunctional nanomaterial holds promise as a comprehensive approach that combines thrombolysis with anti-inflammatory actions, offering precision in thrombosis treatment.

Thromboinflammation and microcirculation damage in heatstroke

Rising temperatures associated with climate change have significantly increased the risk of heatstroke. Unfortunately, the trend is anticipated to persist and increasingly threaten vulnerable populations, particularly older adults. According to Japan's environment ministry, over 1000 people died from heatstroke in 2021, and 86% of deaths occurred in those above 65. Since the precise mechanism of heatstroke is not fully understood, we examined the pathophysiology by focusing on the microcirculatory derangement. Online search of published medical literature through MEDLINE and Web of Science using the term "heatstroke," "heat-related illness," "inflammation," "thrombosis," "coagulation," "fibrinolysis," "endothelial cell," and "circulation." Articles were chosen for inclusion based on their relevance to heatstroke, inflammation, and thrombosis. Reference lists were reviewed to identify additional relevant articles. Other than preexisting conditions (genetic background, age, etc.), factors such as hydration status, acclimatization, dysregulated coagulation, and inflammation are the additional major factors that promote tissue malcirculation in heatstroke. The fundamental pathophysiologic mechanisms significantly overlap with those seen in the systemic inflammatory response to sepsis, and as a result, coagulation-predominant coagulopathy develops during heat stress. Although a bleeding tendency is not common, bleeding frequently occurs in the microcirculation, causing additional injury. Sterile inflammation is mediated by proinflammatory cytokines, chemokines, and other humoral mediators in concert with cellular factors, including monocytes, neutrophils, platelets, and endothelial cells. Excess inflammation results in inflammatory cell death, including pyroptosis and necroptosis, and the release of danger signals that further propagate systemic inflammation and coagulopathy. Consequently, thromboinflammation is the critical factor that induces microcirculatory disturbance in heatstroke.

Thrombomodulin Switches Signaling and Protease-Activated Receptor 1 Cleavage Specificity of Thrombin

BACKGROUND

Cleavage of the extracellular domain of PAR1 (protease-activated receptor 1) by thrombin at Arg41 and by APC (activated protein C) at Arg46 initiates paradoxical cytopathic and cytoprotective signaling in endothelial cells. In the latter case, the ligand-dependent coreceptor signaling by EPCR (endothelial protein C receptor) is required for the protective PAR1 signaling by APC. Here, we investigated the role of thrombomodulin in determining the specificity of PAR1 signaling by thrombin.

METHODS

We prepared a PAR1 knockout (PAR1-/-) EA.hy926 endothelial cell line by CRISPR/Cas9 and transduced PAR1-/- cells with lentivirus vectors expressing PAR1 mutants in which either Arg41 or Arg46 was replaced with an Ala. Furthermore, human embryonic kidney 293 cells were transfected with wild-type or mutant PAR1 cleavage reporter constructs carrying N-terminal Nluc (NanoLuc luciferase) and C-terminal enhanced yellow fluorescent protein tags.

RESULTS

Characterization of transfected cells in signaling and receptor cleavage assays revealed that, upon interaction with thrombomodulin, thrombin cleaves Arg46 to elicit cytoprotective effects by a β-arrestin-2 biased signaling mechanism. Analysis of functional data and cleavage rates indicated that thrombin-thrombomodulin cleaves Arg46>10-fold faster than APC. Upon interaction with thrombin, the cytoplasmic domain of thrombomodulin recruited both β-arrestin-1 and -2 to the plasma membrane. Thus, the thrombin cleavage of Arg41 was also cytoprotective in thrombomodulin-expressing cells by β-arrestin-1-biased signaling. APC in the absence of EPCR cleaved Arg41 to initiate disruptive signaling responses like thrombin.

CONCLUSIONS

These results suggest that coreceptor signaling by thrombomodulin and EPCR determines the PAR1 cleavage and signaling specificity of thrombin and APC, respectively.

Mechanism and role of mitophagy in the development of severe infection

Mitochondria produce adenosine triphosphate and potentially contribute to proinflammatory responses and cell death. Mitophagy, as a conservative phenomenon, scavenges waste mitochondria and their components in the cell. Recent studies suggest that severe infections develop alongside mitochondrial dysfunction and mitophagy abnormalities. Restoring mitophagy protects against excessive inflammation and multiple organ failure in sepsis. Here, we review the normal mitophagy process, its interaction with invading microorganisms and the immune system, and summarize the mechanism of mitophagy dysfunction during severe infection. We highlight critical role of normal mitophagy in preventing severe infection.

Organ Dysfunction in Sepsis-associated Intravascular Coagulation

Sepsis is frequently associated with disseminated intravascular coagulation (DIC) and multiple organ damage. It is widely accepted that DIC is not merely a complication but also plays a role in the development of organ dysfunction. Thrombus formation in the microvasculature leads to impaired tissue perfusion and organ damage. Activated neutrophils interacting with platelets, endothelial injury, and an imbalance of coagulation and fibrinolysis are the essence of thromboinflammation induced in sepsis-associated DIC. The above mechanisms are typically seen in sepsis-associated acute kidney injury (AKI), and the development of AKI is known to be strongly associated with the severity of sepsis. It is important to recognize the pathway of this mechanism in the context of sepsis management.

The critical role of neutrophil-endothelial cell interactions in sepsis: new synergistic approaches employing organ-on-chip, omics, immune cell phenotyping and in silico modeling to identify new therapeutics

Sepsis is a global health concern accounting for more than 1 in 5 deaths worldwide. Sepsis is now defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Sepsis can develop from bacterial (gram negative or gram positive), fungal or viral (such as COVID) infections. However, therapeutics developed in animal models and traditional in vitro sepsis models have had little success in clinical trials, as these models have failed to fully replicate the underlying pathophysiology and heterogeneity of the disease. The current understanding is that the host response to sepsis is highly diverse among patients, and this heterogeneity impacts immune function and response to infection. Phenotyping immune function and classifying sepsis patients into specific endotypes is needed to develop a personalized treatment approach. Neutrophil-endothelium interactions play a critical role in sepsis progression, and increased neutrophil influx and endothelial barrier disruption have important roles in the early course of organ damage. Understanding the mechanism of neutrophil-endothelium interactions and how immune function impacts this interaction can help us better manage the disease and lead to the discovery of new diagnostic and prognosis tools for effective treatments. In this review, we will discuss the latest research exploring how in silico modeling of a synergistic combination of new organ-on-chip models incorporating human cells/tissue, omics analysis and clinical data from sepsis patients will allow us to identify relevant signaling pathways and characterize specific immune phenotypes in patients. Emerging technologies such as machine learning can then be leveraged to identify druggable therapeutic targets and relate them to immune phenotypes and underlying infectious agents. This synergistic approach can lead to the development of new therapeutics and the identification of FDA approved drugs that can be repurposed for the treatment of sepsis.

Thromboinflammation in acute injury: infections, heatstroke, and trauma

Tissue microcirculation is essential for the maintenance of organ homeostasis. Following acute infections, activation of coagulation and inflammation, which are critical interconnected responses, lead to thromboinflammation and microthrombosis, thereby contributing to multiorgan dysfunction. Sepsis is the most common underlying disease and has been extensively studied. However, the COVID-19 pandemic further illustrated the pathomechanisms of diseases in which thromboinflammation plays a critical role. During thromboinflammation, injury to monocytes, neutrophils, platelets, and endothelial cells, along with coagulation and complement activation, was further characterized. Thrombin is pivotal in orchestrating thrombosis and inflammation and has long been considered a potential therapeutic target in sepsis. Although thromboprophylaxis for venous thromboembolism with heparins is part of standard management for COVID-19, it also potentially attenuates organ dysfunction due to thrombotic sequela. In contrast, the effectiveness of anticoagulation with heparin, antithrombin, or thrombomodulin to reduce mortality has not conclusively been proven in sepsis. Nonetheless, thromboinflammation has also been reported as an important pathophysiologic mechanism in other critical illnesses, including heatstroke, trauma, and ischemia/reperfusion injury, and may provide a potential therapeutic target for future clinical studies.

Lacticaseibacillus rhamnosus CRL1505 Peptidoglycan Modulates the Inflammation-Coagulation Response Triggered by Poly(I:C) in the Respiratory Tract

Lacticaseibacillus rhamnosus CRL1505 beneficially modulates the inflammation-coagulation response during respiratory viral infections. This study evaluated the capacity of the peptidoglycan obtained from the CRL1505 strain (PG-Lr1505) to modulate the immuno-coagulative response triggered by the viral pathogen-associated molecular pattern poly(I:C) in the respiratory tract. Adult BALB/c mice were nasally treated with PG-Lr1505 for two days. Treated and untreated control mice were then nasally challenged with poly(I:C). Mice received three doses of poly(I:C) with a 24 h rest period between each administration. The immuno-coagulative response was studied after the last administration of poly(I:C). The challenge with poly(I:C) significantly increased blood and respiratory pro-inflammatory mediators, decreased prothrombin activity (PT), and increased von Willebrand factor (vWF) levels in plasma. Furthermore, tissue factor (TF), tissue factor pathway inhibitor (TFPI), and thrombomodulin (TM) expressions were increased in the lungs. PG-Lr1505-treated mice showed significant modulation of hemostatic parameters in plasma (PT in %, Control = 71.3 ± 3.8, PG-Lr1505 = 94.0 ± 4.0, p < 0.01) and lungs. Moreover, PG-Lr1505-treated mice demonstrated reduced TF in F4/80 cells from lungs, higher pro-inflammatory mediators, and increased IL-10 compared to poly(I:C) control mice (IL-10 in pg/mL, Control = 379.1 ± 12.1, PG-Lr1505 = 483.9 ± 11.3, p < 0.0001). These changes induced by PG-Lr1505 correlated with a significant reduction in lung tissue damage. Complementary in vitro studies using Raw 264.7 cells confirmed the beneficial effect of PG-Lr1505 on poly(I:C)-induced inflammation, since increased IL-10 expression, as well as reduced damage, production of inflammatory mediators, and hemostatic parameter expressions were observed. In addition, protease-activated receptor-1 (PAR1) activation in lungs and Raw 264.7 cells was observed after TLR3 stimulation, which was differentially modulated by PG-Lr1505. The peptidoglycan from L. rhamnosus CRL1505 is able to regulate inflammation, the procoagulant state, and PAR1 activation in mice and macrophages in the context of the activation of TLR3 signaling pathways, contributing to a beneficial modulation of inflammation-hemostasis crosstalk.

Role of Neutrophil Extracellular Traps in Health and Disease Pathophysiology: Recent Insights and Advances

Neutrophils are the principal trouper of the innate immune system. Activated neutrophils undergo a noble cell death termed NETosis and release a mesh-like structure called neutrophil extracellular traps (NETs) as a part of their defensive strategy against microbial pathogen attack. This web-like architecture includes a DNA backbone embedded with antimicrobial proteins like myeloperoxidase (MPO), neutrophil elastase (NE), histones and deploys in the entrapment and clearance of encountered pathogens. Thus NETs play an inevitable beneficial role in the host's protection. However, recent accumulated evidence shows that dysregulated and enhanced NET formation has various pathological aspects including the promotion of sepsis, pulmonary, cardiovascular, hepatic, nephrological, thrombotic, autoimmune, pregnancy, and cancer diseases, and the list is increasing gradually. In this review, we summarize the NET-mediated pathophysiology of different diseases and focus on some updated potential therapeutic approaches against NETs.

A Global Assessment of Coagulation Profile and a Novel Insight into Adamts-13 Implication in Neonatal Sepsis

Neonatal sepsis is a life-threatening condition associated with significant morbidity and mortality. Sepsis-induced coagulopathy is a well-recognized entity, signifying the strong cross-talk between inflammation and coagulation. The aim of the present study was to compare the coagulation profile between the acute phase of sepsis and recovery in term and preterm neonates. Additional comparisons to healthy neonates were undertaken. Levels of clotting, anti-clotting factors and ADAMTS-13 (A disintegrin and metalloprotease with thrombospondin type-1 motives), the cleaving protein of von Willebrand factor (VWF), were measured in 16 term and preterm neonates in the acute phase of infection and following recovery, as well as in 18 healthy neonates. Clotting times were prolonged, while levels of particular clotting factors were lower in the acute phase of infection compared to controls and recovery. On the other hand, levels of fibrinogen, factor VIII (FVIII) and VWF were significantly higher in the acute phase in comparison to controls and recovery, while they remained persistently higher in the infection group compared to controls. In regard to the anticlotting mechanism, a clear suppression was observed in septic neonates. ADAMTS-13 levels were significantly lower in the acute phase of infection in comparison to controls and recovery (p = 0.015 and 0.004, respectively), while a trend toward superimposed normalization was demonstrated post infection, as higher ADAMTS-13 levels were measured in recovered neonates compared to controls (p = 0.002). The coagulation profile is considerably deranged in neonatal sepsis. ADAMTS-13 deficiency in septic neonates is a novel finding with promising future implications, as ADAMTS-13 substitution may serve as a useful therapeutic option in neonatal sepsis, prompting further investigation in future studies.

Lipid oxidation dysregulation: an emerging player in the pathophysiology of sepsis

Sepsis is a life-threatening organ dysfunction caused by abnormal host response to infection. Millions of people are affected annually worldwide. Derangement of the inflammatory response is crucial in sepsis pathogenesis. However, metabolic, coagulation, and thermoregulatory alterations also occur in patients with sepsis. Fatty acid mobilization and oxidation changes may assume the role of a protagonist in sepsis pathogenesis. Lipid oxidation and free fatty acids (FFAs) are potentially valuable markers for sepsis diagnosis and prognosis. Herein, we discuss inflammatory and metabolic dysfunction during sepsis, focusing on fatty acid oxidation (FAO) alterations in the liver and muscle (skeletal and cardiac) and their implications in sepsis development.

Low-molecular-weight heparin therapy reduces 28-day mortality in patients with sepsis-3 by improving inflammation and coagulopathy

Background and aim

Sepsis is a syndromic response to infection and is associated with high mortality, thus imposing a significant global burden of disease. Although low-molecular-weight heparin (LMWH) has been recommended to prevent venous thromboembolism, its anticoagulant and anti-inflammatory effects in sepsis remain controversial. Owing to the modification of the Sepsis-3 definition and diagnostic criteria, further evaluation of the efficacy and benefit population of LMWH is required.

Methods

We performed a retrospective cohort study to assess whether LMWH improved the inflammation, coagulopathy, and clinical outcomes against Sepsis-3 and to identify the target patients. All patients diagnosed with sepsis at the First Affiliated Hospital of Xi'an Jiaotong University (the largest general hospital in northwest China) from January 2016 to December 2020 were recruited and re-evaluated using Sepsis-3 criteria.

Results

After 1:1 propensity score matching, 88 pairs of patients were categorized into the treatment and control groups based on subcutaneous LMWH administration. Compared with the control group, a significantly lower 28-day mortality was observed in the LMWH group (26.1 vs. 42.0%, p = 0.026) with a comparable incidence of major bleeding events (6.8 vs. 8.0%, p = 0.773). Cox regression analysis showed that LMWH administration was the independent protective factor for septic patients (aHR, 0.48; 95% CI, 0.29-0.81; p = 0.006). Correspondingly, the LMWH treatment group showed a significant improvement in inflammation and coagulopathy. Further subgroup analysis showed that LMWH therapy was associated with favorable outcomes in patients younger than 60 years and diagnosed with sepsis-induced coagulopathy (SIC), ISTH overt DIC, non-septic shock, or non-diabetics and in patients included in the moderate-risk group (APACHE II score 20-35 or SOFA score 8-12).

Conclusion

Our study results showed that LMWH improves 28-day mortality by improving inflammatory response and coagulopathy in patients meeting Sepsis-3 criteria. The SIC and ISTH overt DIC scoring systems can better identify septic patients who are likely to benefit more from LMWH administration.

The pathophysiology, diagnosis, and management of sepsis-associated disseminated intravascular coagulation

BACKGROUND

The International Society on Thrombosis and Haemostasis (ISTH) released overt disseminated intravascular coagulation (DIC) diagnostic criteria in 2001. Since then, DIC has been understood as the end-stage consumptive coagulopathy and not the therapeutic target. However, DIC is not merely a decompensated coagulation disorder, but also includes early stages with systemic activation in coagulation. Thus, the ISTH has recently released sepsis-induced coagulopathy (SIC) criteria that can diagnose compensated-phase of coagulopathy with readily available biomarkers.

MAIN BODY

DIC is a laboratory-based diagnosis due to various critical conditions, although sepsis is the most common underlying disease. The pathophysiology of sepsis-associated DIC is multifactorial, and in addition to coagulation activation with suppressed fibrinolysis, multiple inflammatory responses are initiated by activated leukocytes, platelets, and vascular endothelial cells as part of thromboinflammation. Although overt DIC diagnostic criteria were established by ISTH to diagnose the advanced stage of DIC, additional criteria that can detect an earlier stage of DIC were needed for potential therapeutic considerations. Accordingly, the ISTH introduced SIC criteria in 2019 that are easy to use and require only platelet count, prothrombin time-international normalized ratio, and Sequential Organ Failure Assessment Score. SIC score can be used to evaluate disease severity and determine the timing of potential therapeutic interventions. One of the major disadvantages in treating sepsis-associated DIC is the lack of availability of specific therapeutic approaches beyond treating the underlying infection. Clinical trials to date have failed because included patients who were not coagulopathic. Nevertheless, in addition to infection control, anticoagulant therapy will be the choice for sepsis-associated DIC. Therefore, the efficacy of heparin, antithrombin, and recombinant thrombomodulin has to be proven in future clinical studies.

CONCLUSION

It is necessary to develop a novel therapeutic strategy against sepsis-associated DIC and improve the outcomes. Consequently, we recommend screening and monitoring DIC using SIC scoring system.

Blood Platelets in Infection: The Multiple Roles of the Platelet Signalling Machinery

Platelets are classically recognized for their important role in hemostasis and thrombosis but they are also involved in many other physiological and pathophysiological processes, including infection. Platelets are among the first cells recruited to sites of inflammation and infection and they exert their antimicrobial response actively cooperating with the immune system. This review aims to summarize the current knowledge on platelet receptor interaction with different types of pathogens and the consequent modulations of innate and adaptive immune responses.

Endothelial dysfunction and immunothrombosis in sepsis

Sepsis is a life-threatening clinical syndrome characterized by multiorgan dysfunction caused by a dysregulated or over-reactive host response to infection. During sepsis, the coagulation cascade is triggered by activated cells of the innate immune system, such as neutrophils and monocytes, resulting in clot formation mainly in the microcirculation, a process known as immunothrombosis. Although this process aims to protect the host through inhibition of the pathogen’s dissemination and survival, endothelial dysfunction and microthrombotic complications can rapidly lead to multiple organ dysfunction. The development of treatments targeting endothelial innate immune responses and immunothrombosis could be of great significance for reducing morbidity and mortality in patients with sepsis. Medications modifying cell-specific immune responses or inhibiting platelet–endothelial interaction or platelet activation have been proposed. Herein, we discuss the underlying mechanisms of organ-specific endothelial dysfunction and immunothrombosis in sepsis and its complications, while highlighting the recent advances in the development of new therapeutic approaches aiming at improving the short- or long-term prognosis in sepsis.

Extracellular Vesicles: New Players in the Mechanisms of Sepsis- and COVID-19-Related Thromboinflammation

Sepsis and COVID-19 patients often manifest an imbalance in inflammation and coagulation, a complex pathological mechanism also named thromboinflammation, which strongly affects patient prognosis. Extracellular vesicles (EVs) are nanoparticles released by cells into extracellular space that have a relevant role in cell-to-cell communication. Recently, EVs have been shown to act as important players in a variety of pathologies, including cancer and cardiovascular disease. The biological properties of EVs in the mechanisms of thromboinflammation during sepsis and COVID-19 are still only partially known. Herein, we summarize the current experimental evidence on the role of EVs in thromboinflammation, both in bacterial sepsis and in COVID-19. A better understanding of EV involvement in these processes could be useful in describing novel diagnostic and therapeutic applications of EVs in these diseases.