Clinical significance of measuring plasminogen activator inhibitor-1 in sepsis

PAI-1 as a critical factor in the resolution of sepsis and acute kidney injury in old age

Elevated plasma levels of plasminogen activator inhibitor type 1 (PAI-1) are documented in patients with sepsis and levels positively correlate with disease severity and mortality. Our prior work demonstrated that PAI-1 in plasma is positively associated with acute kidney injury (AKI) in septic patients and mice. The objective of this study was to determine if PAI-1 is causally related to AKI and worse sepsis outcomes using a clinically-relevant and age-appropriate murine model of sepsis. Sepsis was induced by cecal slurry (CS)-injection to wild-type (WT, C57BL/6) and PAI-1 knockout (KO) mice at young (5-9 months) and old (18-22 months) age. Survival was monitored for at least 10 days or mice were euthanized for tissue collection at 24 or 48 h post-insult. Contrary to our expectation, PAI-1 KO mice at old age were significantly more sensitive to CS-induced sepsis compared to WT mice (24% vs. 65% survival, p = 0.0037). In comparison, loss of PAI-1 at young age had negligible effects on sepsis survival (86% vs. 88% survival, p = 0.8106) highlighting the importance of age as a biological variable. Injury to the kidney was the most apparent pathological consequence and occurred earlier in aged PAI-1 KO mice. Coagulation markers were unaffected by loss of PAI-1, suggesting thrombosis-independent mechanisms for PAI-1-mediated protection. In summary, although high PAI-1 levels are clinically associated with worse sepsis outcomes, loss of PAI-1 rendered mice more susceptible to kidney injury and death in a CS-induced model of sepsis using aged mice. These results implicate PAI-1 as a critical factor in the resolution of sepsis in old age.

Trimester-specific reference intervals of hemostasis biomarkers for healthy pregnancy

Physiological changes in hemostasis during pregnancy have been reported by several authors. This study aimed at establishing reference intervals for the hemostasis biomarkers thrombin-antithrombin complex (TAT), α2-plasmininhibitor-plasmin complex (PIC), thrombomodulin (TM) and tissue plasminogen activator-inhibitor complex (tPAI-C), in healthy pregnancies. After excluding outliers, a total of 496 healthy pregnant women (128 first-trimester, 142 second-trimester, 107 third-trimester and 119 pre-labor) and 103 healthy nonpregnant women were enrolled from Shenzhen Bao'an Women's and Children's Hospital. Hemostasis biomarkers, TAT, PIC, TM and tPAI-C, were measured by using a quantitative chemiluminescence enzyme immunoassay performed on HISCL automated analysers. The median and reference intervals (the 2.5th and 97.5th percentiles) were calculated to establish trimester-specific reference intervals for healthy pregnant women. The reference intervals for TAT, PIC, TM and tPAI-C in the first trimester were 0.7-7.6 1 µg/L, 0.2-0.9 mg/L, 2.8-11.0 TU/ml, and 1.2-6.5 1 µg/L, respectively. The reference intervals in the second trimester were 1.7-12.0 1 µg/L, 0.2-1.0 mg/L, 3.7-11.6 TU/ml, and 2.8-8.8 1 µg/L, respectively. The reference intervals in the third trimester were 2.7-16.1 1 µg/L, 0.1-1.4 mg/L, 2.9-12.9 TU/ml, and 1.9-8.0 1 µg/L, respectively. At pre-labor, the reference intervals were 4.8-32.9 1 µg/L, 0.2-1.9 mg/L, 4.2-12.6 TU/ml, and 2.8-15.4 1 µg/L, respectively. Gestational reference intervals for TAT, PIC, TM and tPAI-C in healthy pregnancies are provided, but only for TAT with increasing concentrations throughout pregnancy, the reference intervals for non-pregnant were not applicable.

A Multilayered Imaging and Microfluidics Approach for Evaluating the Effect of Fibrinolysis in Staphylococcus aureus Biofilm Formation

The recognition of microbe and extracellular matrix (ECM) is a recurring theme in the humoral innate immune system. Fluid-phase molecules of innate immunity share regulatory roles in ECM. On the other hand, ECM elements have immunological functions. Innate immunity is evolutionary and functionally connected to hemostasis. Staphylococcus aureus (S. aureus) is a major cause of hospital-associated bloodstream infections and the most common cause of several life-threatening conditions such as endocarditis and sepsis through its ability to manipulate hemostasis. Biofilm-related infection and sepsis represent a medical need due to the lack of treatments and the high resistance to antibiotics. We designed a method combining imaging and microfluidics to dissect the role of elements of the ECM and hemostasis in triggering S. aureus biofilm by highlighting an essential role of fibrinogen (FG) in adhesion and formation. Furthermore, we ascertained an important role of the fluid-phase activation of fibrinolysis in inhibiting biofilm of S. aureus and facilitating an antibody-mediated response aimed at pathogen killing. The results define FG as an essential element of hemostasis in the S. aureus biofilm formation and a role of fibrinolysis in its inhibition, while promoting an antibody-mediated response. Understanding host molecular mechanisms influencing biofilm formation and degradation is instrumental for the development of new combined therapeutic approaches to prevent the risk of S. aureus biofilm-associated diseases.

Disseminated intravascular coagulation and its immune mechanisms

Disseminated intravascular coagulation (DIC) is a syndrome triggered by infectious and noninfectious pathologies characterized by excessive generation of thrombin within the vasculature and widespread proteolytic conversion of fibrinogen. Despite diverse clinical manifestations ranging from thrombo-occlusive damage to bleeding diathesis, DIC etiology commonly involves excessive activation of blood coagulation and overlapping dysregulation of anticoagulants and fibrinolysis. Initiation of blood coagulation follows intravascular expression of tissue factor or activation of the contact pathway in response to pathogen-associated or host-derived, damage-associated molecular patterns. The process is further amplified through inflammatory and immunothrombotic mechanisms. Consumption of anticoagulants and disruption of endothelial homeostasis lower the regulatory control and disseminate microvascular thrombosis. Clinical DIC development in patients is associated with worsening morbidities and increased mortality, regardless of the underlying pathology; therefore, timely recognition of DIC is critical for reducing the pathologic burden. Due to the diversity of triggers and pathogenic mechanisms leading to DIC, diagnosis is based on algorithms that quantify hemostatic imbalance, thrombocytopenia, and fibrinogen conversion. Because current diagnosis primarily assesses overt consumptive coagulopathies, there is a critical need for better recognition of nonovert DIC and/or pre-DIC states. Therapeutic strategies for patients with DIC involve resolution of the eliciting triggers and supportive care for the hemostatic imbalance. Despite medical care, mortality in patients with DIC remains high, and new strategies, tailored to the underlying pathologic mechanisms, are needed.

Circulating LIGHT (TNFSF14) and Interleukin-18 Levels in Sepsis-Induced Multi-Organ Injuries

The novel therapeutic target cytokine LIGHT (TNFSF14) was recently shown to play a major role in COVID-19-induced acute respiratory distress syndrome (ARDS). This study aims to investigate the associations of plasma LIGHT and another potentially targetable cytokine, interleukin-18 (IL-18), with ARDS, acute hypoxic respiratory failure (AHRF), or acute kidney injury (AKI), caused by non-COVID-19 viral or bacterial sepsis. A total of 280 subjects diagnosed with sepsis, including 91 cases with sepsis triggered by viral infections, were investigated in this cohort study. Day 0 plasma LIGHT and IL-18, as well as 59 other biomarkers (cytokines, chemokines, and acute-phase reactants) were measured by sensitive bead immunoassay and associated with symptom severity. We observed significantly increased LIGHT level in both bacterial sepsis patients (p = 1.80 × 10⁻⁵) and patients with sepsis from viral infections (p = 1.78 × 10⁻³). In bacterial sepsis, increased LIGHT level was associated with ARDS, AKI, and higher Apache III scores, findings also supported by correlations of LIGHT with other biomarkers of organ failure. IL-18 levels were highly variable across individuals and consistently correlated with Apache III scores, mortality, and AKI in both bacterial and viral sepsis. There was no correlation between LIGHT and IL-18. For the first time, we demonstrate independent effects of LIGHT and IL-18 in septic organ failure. The association of plasma LIGHT with AHRF suggests that targeting the pathway warrants exploration, and ongoing trials may soon elucidate whether this is beneficial. Given the large variance of plasma IL-18 among septic subjects, targeting this pathway requires precise application.

Visceral fat-specific regulation of plasminogen activator inhibitor-1 in aged septic mice

Elevated plasma levels of plasminogen activator inhibitor-1 (PAI-1) are documented in patients with sepsis and levels positively correlate with disease severity and mortality. Our previous work demonstrated that visceral adipose tissues (VAT) are a major source of PAI-1, especially in the aged (murine endotoxemia), that circulating PAI-1 protein levels match the trajectory of PAI-1 transcript levels in VAT (clinical sepsis), and that PAI-1 in both VAT and plasma are positively associated with acute kidney injury (AKI) in septic patients. In the current study utilizing preclinical sepsis models, PAI-1 tissue distribution was examined and cellular sources, as well as mechanisms mediating PAI-1 induction in VAT, were identified. In aged mice with sepsis, PAI-1 gene expression was significantly higher in VAT than in other major organs. VAT PAI-1 gene expression correlated with PAI-1 protein levels in both VAT and plasma. Moreover, VAT and plasma levels of PAI-1 were positively associated with AKI markers, modeling our previous clinical data. Using explant cultures of VAT, we determined that PAI-1 is secreted robustly in response to recombinant transforming growth factor β (TGFβ) and tumor necrosis factor α (TNFα) treatment; however, neutralization was effective only for TNFα indicating that TGFβ is not an endogenous modulator of PAI-1. Within VAT, TNFα was localized to neutrophils and macrophages. PAI-1 protein levels were fourfold higher in stromal vascular fraction (SVF) cells compared with mature adipocytes, and among SVF cells, both immune and nonimmune compartments expressed PAI-1 in a similar fashion. PAI-1 was localized predominantly to macrophages within the immune compartment and preadipocytes and endothelial cells within the nonimmune compartment. Collectively, these results indicate that induction and secretion of PAI-1 from VAT is facilitated by a complex interaction among immune and nonimmune cells. As circulating PAI-1 contributes to AKI in sepsis, understanding PAI-1 regulation in VAT could yield novel strategies for reducing systemic consequences of PAI-1 overproduction.

Endothelial METTL3 (Methyltransferase-Like 3) Inhibits Fibrinolysis by Promoting PAI-1 (Plasminogen Activator Inhibitor-1) Expression Through Enhancing Jun Proto-Oncogene N6-Methyladenosine Modification

OBJECTIVE

METTL3 (methyltransferase-like protein 3)-mediated N6-methyladenosine modification is the most abundant RNA modification on eukaryote mRNAs and plays a crucial role in diverse physiological and pathological processes. However, whether N6-methyladenosine modification has function in thrombosis is unknown. This study aims to determine the role of METTL3 in the endothelial cells-mediated thrombosis. Approach and Results: RNA-sequencing and real-time quantitative PCR revealed that the expression of PAI-1 (plasminogen activator inhibitor-1) was downregulated in METTL3 knockdown human umbilical vein endothelial cells. In vitro experiments showed that METTL3 suppressed fibrinolysis. Mechanically, RNA methylation sequencing and meRIP-quantitative real-time PCR showed that METTL3 catalyzed N6-methyladenosine modification on 3' UTR of JUN mRNA. Western blotting analysis showed that METTL3 promoted JUN protein expression. Chromatin immunoprecipitation analysis demonstrated that JUN bound to the PAI-1 promoter in human umbilical vein endothelial cells. Furthermore, mice challenged with lipopolysaccharide resulted in higher METTL3 expression in vessels. Endothelial-specific knockdown of Mettl3 decreased expression of active PAI-1 in plasma and attenuated fibrin deposition in livers and lungs during endotoxemia.

CONCLUSIONS

Our study reveals that METTL3-mediated N6-methyladenosine modification plays a crucial role in fibrinolysis and is an underlying target for the therapy of thrombotic disorders.

Elevation of Circulating LIGHT (TNFSF14) and Interleukin-18 Levels in Sepsis-Induced Multi-Organ Injuries

Objective

The cytokines, LIGHT (TNFSF14) and Interleukin-18 (IL-18), are two important therapeutic targets due to their central roles in the function of activated T cells and inflammatory injury. LIGHT was recently shown to play a major role in COVID19 induced acute respiratory distress syndrome (ARDS), reducing mortality and hospital stay. This study aims to investigate the associations of LIGHT and IL-18 with non-COVID19 related ARDS, acute hypoxic respiratory failure (AHRF) or acute kidney injury (AKI), secondary to viral or bacterial sepsis.

Research Design and Methods

A cohort of 280 subjects diagnosed with sepsis, including 91 cases with sepsis triggered by viral infections, were investigated in this study and compared to healthy controls. Serum LIGHT, IL-18, and 59 other biomarkers (cytokines, chemokines and acute-phase reactants) were measured and associated with symptom severity.

Results

ARDS was observed in 36% of the patients, with 29% of the total patient cohort developing multi-organ failure (failure of two or more organs). We observed significantly increased LIGHT level (>2SD above mean of healthy subjects) in both bacterial sepsis patients (P=1.80E-05) and patients with sepsis from viral infections (P=1.78E-03). In bacterial sepsis, increased LIGHT level associated with ARDS, AKI and higher Apache III scores, findings also supported by correlations of LIGHT with other biomarkers of organ failures, suggesting LIGHT may be an inflammatory driver. IL-18 levels were highly variable across individuals, and consistently correlated with Apache III scores, mortality, and AKI, in both bacterial and viral sepsis.

Conclusions

For the first time, we demonstrate independent effects of LIGHT and IL-18 in septic organ failures. LIGHT levels are significantly elevated in non-COVID19 sepsis patients with ARDS and/or multi-organ failures suggesting that anti-LIGHT therapy may be effective therapy in a subset of patients with sepsis. Given the large variance of plasma IL-18 among septic subjects, targeting this pathway raises opportunities that require a precision application.

A Translational Investigation of IFN-α and STAT1 Signaling in Endothelial Cells during Septic Shock Provides Therapeutic Perspectives

Septic shock and disseminated intravascular coagulation (DIC) are known to be characterized by an endothelial cell dysfunction. The molecular mechanisms underlying this relationship are, however, poorly understood. In this work, we aimed to investigate human circulating IFN-α in patients with septic shock-induced DIC and tested the potential role of endothelial Stat1 (signal transducer and activator of transcription 1) as a therapeutic target in a mouse model of sepsis. For this, circulating type I, type II, and type III IFNs and procoagulant microvesicles were quantified in a prospective cohort of patients with septic shock. Next, we used a septic shock model induced by cecal ligation and puncture in wild-type mice, in Ifnar1 (type I IFN receptor subunit 1)-knockout mice, and in Stat1 conditional knockout mice. In human samples, we observed higher concentrations of circulating IFN-α and IFN-α1 in patients with DIC compared with patients without DIC, whereas concentrations of IFN-β, IFN-γ, IFN-λ1, IFN-λ2, and IFN-λ3 were not different. IFN-α concentration was positively correlated with CD105 microvesicle concentrations, reflecting endothelial injury. In Ifnar1^-/- mice, cecal ligation and puncture did not induce septic shock and was characterized by lesser endothelial cell injury, with lower aortic inflammatory cytokine expression, endothelial inflammatory-related gene expression, and fibrinolysis. In mice in which Stat1 was specifically ablated in endothelial cells, a marked protection against sepsis was also observed, suggesting the relevance of an endothelium-targeted strategy. Our work highlights the key roles of type I IFNs as pathogenic players in septic shock-induced DIC and the potential pertinence of endothelial STAT1 as a therapeutic target.

Effect of a Recombinant Human Soluble Thrombomodulin on Baseline Coagulation Biomarker Levels and Mortality Outcome in Patients With Sepsis-Associated Coagulopathy

OBJECTIVES

To assess the effects of recombinant human soluble thrombomodulin treatment on 28-day all-cause mortality in subgroups categorized by baseline coagulation biomarker levels (prothrombin fragment 1.2, thrombin-antithrombin complex, D-dimer) in patients with sepsis-associated coagulopathy in the Sepsis Coagulopathy Asahi Recombinant LE Thrombomodulin trial (SCARLET) (NCT01598831).

DESIGN

Post hoc, subgroup analysis of a randomized, double-blind, placebo-controlled, multinational, multicenter phase 3 study.

SETTING

ICUs at 159 sites in 26 countries.

PATIENTS

Eight-hundred adults with sepsis-associated coagulopathy defined as international normalized ratio greater than 1.40 and platelet count between 30 × 10/L and 150 × 10/L or greater than 30% decrease within 24 hours with concomitant cardiovascular and/or respiratory failure.

INTERVENTIONS

Patients randomized and treated with recombinant human soluble thrombomodulin (0.06 mg/kg/d; n = 395) or equivalent placebo (n = 405) for 6 days.

MEASUREMENTS AND MAIN RESULTS

Recombinant human soluble thrombomodulin did not significantly reduce 28-day all-cause mortality in the Sepsis Coagulopathy Asahi Recombinant LE Thrombomodulin trial: absolute risk reduction was 2.55% (p = 0.32) in patients with sepsis-associated coagulopathy. In this post hoc analysis, mortality steadily increased with increasing baseline prothrombin fragment 1.2 and thrombin-antithrombin complex levels in the placebo group; for those values exceeding the upper limit of normal, the mortality increases in the recombinant human soluble thrombomodulin group were lower or negligible with increasing baseline prothrombin fragment 1.2 and thrombin-antithrombin complex. Consequently, absolute risk reductions were greater in subgroups with higher baseline prothrombin fragment 1.2 or thrombin-antithrombin complex. Absolute risk reductions were also greater in subgroups with baseline coagulation biomarker levels at or above median of the entire study population, ranging from 4.2% (95% CI, -5.0% to 13.4%) to 5.5% (95% CI, -4.0% to 14.9%).

CONCLUSIONS

Compared with patients receiving placebo, patients treated with recombinant human soluble thrombomodulin having higher baseline thrombin generation biomarker levels had lower mortality. Further research regarding the predictive role of coagulation biomarkers for recombinant human soluble thrombomodulin treatment response in sepsis-associated coagulopathy is warranted to evaluate clinical relevance.

Advance in the Management of Sepsis-Induced Coagulopathy and Disseminated Intravascular Coagulation

Coagulopathy commonly occurs in sepsis as a critical host response to infection that can progress to disseminated intravascular coagulation (DIC) with an increased mortality. Recent studies have further defined factors responsible for the thromboinflammatory response and intravascular thrombosis, including neutrophil extracellular traps, extracellular vesicles, damage-associated molecular patterns, and endothelial glycocalyx shedding. Diagnosing DIC facilitates sepsis management, and is associated with improved outcomes. Although the International Society on Thrombosis and Haemostasis (ISTH) has proposed criteria for diagnosing overt DIC, these criteria are not suitable for early detection. Accordingly, the ISTH DIC Scientific Standardization Committee has proposed a new category termed "sepsis-induced coagulopathy (SIC)" to facilitate earlier diagnosis of DIC and potentially more rapid interventions in these critically ill patients. Therapy of SIC includes both treatment of the underlying infection and correcting the coagulopathy, with most therapeutic approaches focusing on anticoagulant therapy. Recently, a phase III trial of recombinant thrombomodulin was performed in coagulopathic patients. Although the 28-day mortality was improved by 2.6% (absolute difference), it did not reach statistical significance. However, in patients who met entry criteria for SIC at baseline, the mortality difference was approximately 5% without increased risk of bleeding. In this review, we discuss current advances in managing SIC and DIC.

Thromboelastometric prediction of mortality using the kinetics of clot growth in critically ill septic patients

: Sepsis induces alterations in blood coagulation which are associated with mortality. Using rotational thromboelastometry (ROTEM), these states are often characterized by changes in parameters representing terminal clot lysis. However, the ROTEM changes are often subtle, making them difficult to recognize and interpret. The objective of this study is to evaluate a new ROTEM clot velocity parameter representing clot formation kinetics in septic ICU patients. We hypothesized that this time-based parameter was significantly different in critically ill septic survivors vs. nonsurvivors. This retrospective observational study included severe sepsis and septic shock patients having a minimum of two organ dysfunctions by Sequential Organ Failure Assessment criteria (study group), and a control group of healthy adults without infection . ROTEM with EXTEM activation was performed in all groups. The time from maximal clot formation velocity to zero velocity, representing the latter portion of time during active clot formation prior to achieving maximal clot firmness (t-AUCi) was calculated along with other ROTEM parameters and compared between septic survivors, nonsurvivors and healthy controls. A total of 76 septic patients, of which 26.3%, survived, were included in the study group, and 26 healthy control individuals were included in the control group. t-AUCi correlated with terminal clot lysis (P < 0.001), and was significantly prolonged in septic nonsurvivors compared with survivors and healthy controls (P < 0.001). t-AUCi also differentiated nonsurvivors vs. survivors among those patients having similar ROTEM lysis indices. t-AUCi was useful to differentiate critically ill septic patients, and could be useful to identify septic patients with high-risk of ICU mortality.