Plasminogen activator inhibitor-1 augments damage by impairing fibrinolysis after traumatic brain injury

Association of fibrinolysis phenotype with patient outcomes following traumatic brain injury

BACKGROUND

Impaired coagulation is associated with elevated risk of mortality in trauma patients. Prior studies have demonstrated increased mortality in patients with hyperfibrinolysis (HF) and fibrinolysis shutdown (SD). In addition, prior studies have demonstrated no effect of tranexamic acid (TXA) on fibrinolysis phenotypes. We examined the association of admission fibrinolysis phenotype with traumatic brain injury (TBI) patient outcomes.

METHODS

Data were extracted from a placebo-controlled multicenter clinical trial. Patients ≥15 years with TBI (Glasgow Coma Scale score, 3-12) and systolic blood pressure ≥90 mm Hg were randomized in the out-of-hospital setting to receive placebo bolus/placebo infusion (Placebo), 1 gram (g) TXA bolus/1 g TXA infusion (bolus maintenance [BM]); or 2 g TXA bolus/placebo infusion (bolus only [BO]). Fibrinolysis phenotypes on admission were determined by clot lysis at 30 minutes (LY30): SD, ≤0.8%; physiologic, 0.9% to 2.9%; HF, ≥3%. Logistic regression was used to control for age, sex, penetrating injury, Injury Severity Score, maximum head AIS, and TXA treatment group.

RESULTS

Seven hundred forty-seven patients met inclusion criteria. Fibrinolysis shutdown was the most common phenotype in all treatment groups and was associated with increased age, Injury Severity Score, and presence of intracranial hemorrhage (ICH). Inpatient mortality was 15.2% for SD and HF, and 10.6% for physiologic ( p = 0.49). No differences in mortality, disability rating scale at 6 months, acute kidney injury, acute respiratory distress syndrome, or multi-organ failure were noted between fibrinolysis phenotypes.

CONCLUSION

SD is the most common phenotype expressed in moderate to severe TBI. In TBI, there is no association between fibrinolysis phenotype and mortality or other major complications.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level IV.

Combination of aspirin and rosuvastatin for reduction of venous thromboembolism in severely injured patients: a double-blind, placebo-controlled, pragmatic randomized phase II clinical trial (The STAT Trial)

INTRODUCTION

Venous thromboembolism (VTE) remains a significant source of postinjury morbidity and mortality. Beta-hydroxy beta-methylglutaryl-CoA (HMG-CoA) reductase inhibitors (rosuvastatin) significantly reduced pathologic clotting events in healthy populations in a prior trial. Furthermore, acetylsalicylic acid (ASA) has been shown to be noninferior to prophylactic heparinoids for VTE prevention following orthopedic surgery. We hypothesized that a combination of rosuvastatin/ASA, in addition to standard VTE chemoprophylaxis, would reduce VTE in critically ill trauma patients.

METHODS

This was a double-blind, placebo-controlled, randomized trial, evaluating VTE rates in two groups: ASA + statin (Experimental) and identical placebos (Control). Injured adults, 18-65 years old, admitted to the surgical intensive care unit without contraindications for VTE prophylaxis were eligible. Upon initiation of routine VTE chemoprophylaxis (i.e. heparin/heparin-derivatives), they were randomized to the Experimental or Control group. VTE was the primary outcome.

RESULTS

Of 112 potentially eligible patients, 33% (n = 37, median new injury severity scale = 27) were successfully randomized, of whom 11% had VTEs. The Experimental group had no VTEs, while the Control group had 6 VTEs (4 PEs and 2 DVTs) in 4 (22%) patients (P = 0.046). The Experimental treatment was not associated with any serious adverse events. Due to the COVID-19 pandemic, the study was interrupted at the second interim analysis at <10% of the planned enrollment, with significance declared at P < 0.012 at that stage.

DISCUSSION

The combination of ASA and rosuvastatin with standard VTE prophylaxis showed a favorable trend toward reducing VTEs with no serious adverse events. An appropriately powered phase III multicenter trial is needed to further investigate this therapeutic approach.

LEVEL OF EVIDENCE

Level II, Therapeutic.

Effects of Hypobaric Hypoxia on Coagulation in Healthy Subjects Exposed to 3,500 m Altitude

Kammerer, Tobias, Anna Walzl, Thomas Müller, Philipp Groene, Giulia Roveri, Rachel Turner, Johanna Roche, Hannes Gatterer, Christoph Siebenmann, and Simon T. Schäfer. Effects of hypobaric hypoxia on coagulation in healthy subjects exposed to 3,500 m altitude. High Alt Med Biol. 24:94-103, 2023. Background: Hypoxia is discussed as a trigger for prothrombotic changes both in intensive care and high altitude medicine. This research study aimed to evaluate the effect of isolated hypobaric hypoxia (HH) on coagulation in females in a highly standardized setting. Methods: Twelve healthy female subjects were studied under HH (equivalent to 3,500 m) and normoxia (NX) during two 4-day sojourns, in a strictly controlled crossover design. Nutrition, fluid intake, hormonal status (i.e., menstrual cycle variation), and physical stress were standardized. Functional coagulation and blood lysis were measured by viscoelastometry and compared between HH and NX. In addition, plasma-based coagulation tests (PBCTs), namely prothrombin time, activated partial thromboplastin time, fibrinogen, factor VIII coagulation activity (FVIII:C), von Willebrand factor antigen (vWF:Ag), and von Willebrand factor ristocetin cofactor activity (vWF:RCo) were measured. Results: Neither for Viscoelastic Haemostatic Assays nor for PBCTs significant changes were found for HH compared with NX (all p > 0.05). Specifically, the lysis ability, as well as clotting time, clot formation, clot amplitude, and maximum clot firmness unchanged were similar between HH and NX. This also applied to all other variables. Conclusion: We demonstrate that moderate HH per se has no influence on blood coagulation in healthy females.

Early DNase-I therapy delays secondary brain damage after traumatic brain injury in adult mice

Traumatic brain injury (TBI) causes the release of danger-associated molecular patterns (DAMP) from damaged or dead cells, which contribute to secondary brain damage after TBI. Cell-free DNA (cfDNA) is a DAMP known to cause disruption of the blood-brain barrier (BBB), promote procoagulant processes, brain edema, and neuroinflammation. This study tested the hypothesis that administration of deoxyribonuclease-I (DNase-I) has a beneficial effect after TBI. Mice (n = 84) were subjected to controlled cortical impact (CCI) and posttraumatic intraperitoneal injections of low dose (LD) or high dose (HD) of DNase-I or vehicle solution at 30 min and 12 h after CCI. LD was most effective to reduce lesion volume (p = 0.003), brain water content (p < 0.0001) and to stabilize BBB integrity (p = 0.019) 1 day post-injury (dpi). At 6 h post injury LD-treated animals showed less cleavage of fibrin (p = 0.0014), and enhanced perfusion as assessed by micro-computer-tomography (p = 0.027). At 5 dpi the number of Iba1-positive cells (p = 0.037) were reduced, but the number of CD45-positive cells, motoric function and brain lesion volume was not different. Posttraumatic-treatment with DNase-I therefore stabilizes the BBB, reduces the formation of brain edema, immune response, and delays secondary brain damage. DNase-I might be a new approach to extend the treatment window after TBI.

"Super" SERPINs-A stabilizing force against fibrinolysis in thromboinflammatory conditions

The superfamily of serine protease inhibitors (SERPINs) are a class of inhibitors that utilise a dynamic conformational change to trap and inhibit their target enzymes. Their powerful nature lends itself well to regulation of complex physiological enzymatic cascades, such as the haemostatic, inflammatory and complement pathways. The SERPINs α2-antiplasmin, plasminogen-activator inhibitor-1, plasminogen-activator inhibitor-2, protease nexin-1, and C1-inhibitor play crucial inhibitory roles in regulation of the fibrinolytic system and inflammation. Elevated levels of these SERPINs are associated with increased risk of thrombotic complications, obesity, type 2 diabetes, and hypertension. Conversely, deficiencies of these SERPINs have been linked to hyperfibrinolysis with bleeding and angioedema. In recent years SERPINs have been implicated in the modulation of the immune response and various thromboinflammatory conditions, such as sepsis and COVID-19. Here, we highlight the current understanding of the physiological role of SERPINs in haemostasis and inflammatory disease progression, with emphasis on the fibrinolytic pathway, and how this becomes dysregulated during disease. Finally, we consider the role of these SERPINs as potential biomarkers of disease progression and therapeutic targets for thromboinflammatory diseases.

Hyperfibrinolysis and fibrinolysis shutdown in patients with traumatic brain injury

Traumatic brain injury (TBI) is associated with coagulation/fibrinolysis disorders. We retrospectively evaluated 61 TBI cases transported to hospital within 1 h post-injury. Levels of thrombin-antithrombin III complex (TAT), D-dimer, and plasminogen activator inhibitor-1 (PAI-1) were measured on arrival and 3 h, 6 h, 12 h, 1 day, 3 days and 7 days after injury. Multivariate logistic regression analysis was performed to identify prognostic factors for coagulation and fibrinolysis. Plasma TAT levels peaked at admission and decreased until 1 day after injury. Plasma D-dimer levels increased, peaking up to 3 h after injury, and decreasing up to 3 days after injury. Plasma PAI-1 levels increased up to 3 h after injury, the upward trend continuing until 6 h after injury, followed by a decrease until 3 days after injury. TAT, D-dimer, and PAI-1 were elevated in the acute phase of TBI in cases with poor outcome. Multivariate logistic regression analysis showed that D-dimer elevation from admission to 3 h after injury and PAI-1 elevation from 6 h to 1 day after injury were significant negative prognostic indicators. Post-TBI hypercoagulation, fibrinolysis, and fibrinolysis shutdown were activated consecutively. Hyperfibrinolysis immediately after injury and subsequent fibrinolysis shutdown were associated with poor outcome.

AT2 activation does not influence brain damage in the early phase after experimental traumatic brain injury in male mice

Antagonism of the angiotensin II type 1 receptor (AT1) improves neurological function and reduces brain damage after experimental traumatic brain injury (TBI), which may be partly a result of enhanced indirect angiotensin II type 2 receptor (AT2) stimulation. AT2 stimulation was demonstrated to be neuroprotective via anti-inflammatory, vasodilatory, and neuroregenerative mechanisms in experimental cerebral pathology models. We recently demonstrated an upregulation of AT2 after TBI suggesting a protective mechanism. The present study investigated the effect of post-traumatic (5 days after TBI) AT2 activation via high and low doses of a selective AT2 agonist, compound 21 (C21), compared to vehicle-treated controls. No differences in the extent of the TBI-induced lesions were found between both doses of C21 and the controls. We then tested AT2-knockdown animals for secondary brain damage after experimental TBI. Lesion volume and neurological outcomes in AT2-deficient mice were similar to those in wild-type control mice at both 24 h and 5 days post-trauma. Thus, in contrast to AT1 antagonism, AT2 modulation does not influence the initial pathophysiological mechanisms of TBI in the first 5 days after the insult, indicating that AT2 plays only a minor role in the early phase following trauma-induced brain damage.

Cold-stored platelets are effective in an in vitro model of massive transfusion protocol assessed by rotational thromboelastometry

BACKGROUND

Platelets are a key component of massive transfusion in treating actively bleeding patients. While optimized for prophylactic transfusions, the effectiveness of the current standard room temperature stored platelets (RPs) in treating actively bleeding patients is not clear. Cold-stored platelets (CPs) have been shown to have superior hemostatic functions and the potential to extend shelf life. In this study, we explored the effect of using CPs versus RPs in an in vitro transfusion model based on the massive transfusion protocol.

STUDY DESIGN AND METHODS

RPs or CPs were combined with RBCs and plasma in a 1:1:1 volume ratio to make transfusion packages. Whole blood was collected and then either diluted to 20% hematocrit or mixed with tPA (8.8 μg/ml). By volume, 70% of transfusion package was mixed with 30% whole blood to simulate massive transfusions and analyzed by rotational thromboelastometry. Transfusion package supernatant was analyzed for PAI-1 activity as well.

RESULTS

Both transfusion packages restored the clot characteristics of hemodiluted or hyperfibrinolytic whole blood. Specifically, only transfusion packages made with CPs significantly reduced the maximum clot lysis of hyperfibrinolytic whole blood. PAI-1 activity in CPs transfusion packages were also significantly higher.

DISCUSSION

Transfusion packages containing cold-stored platelets may be able to restore the blood hemostatic profile of bleeding patients. In addition, transfusion packages made from CPs may provide additional benefit of resisting hyperfibrinolysis in bleeding patients. In trauma where post-transfusion platelet recovery is less of a concern, CPs are a viable option to restore hemostasis.

Neuroprotective Effect of Plasminogen Activator Inhibitor-1 Antagonist in the Rat Model of Mild Traumatic Brain Injury

Plasminogen activator inhibitor-1 (PAI-1) antagonists are known for their neuroprotective effects. In this study, it was aimed to investigate the possible protective effects of PAI-1 antagonists in a rat mild traumatic brain injury (TBI) model. Sprague-Dawley male rats were grouped as sham (n = 7), TBI (n = 9), and TBI + PAI-1 antagonist (5 and 10 mg/kg TM5441 and TM5484; n = 6-7). Under anesthesia, TBI was induced by dropping a metal 300-g weight from a height of 1 m on the skull. Before and 24-h after trauma neurological examination, tail suspension, Y-maze, and novel object recognition tests were performed. Twenty-four hours after TBI, the rats were decapitated and activities of myeloperoxidase, nitric oxide release, luminol-, and lucigenin-enhanced chemiluminescence were measured. Also, interleukin-1β, interleukin-6, tumor necrosis factor, interleukin-10, tumor growth factor-β, caspase-3, cleaved caspase-3, and PAI levels were measured with the ELISA method in the brain tissue. Brain injury was graded histopathologically following hematoxylin-eosin staining. Western blot and immunohistochemical investigation for low-density lipoprotein receptor, matrix metalloproteinase-3, and nuclear factor-κB were also performed. Data were analyzed using GraphPad Prism 8.0 (GraphPad Software, San Diego, CA, USA) and expressed as means ± SEM. Values of p < 0.05 were considered to be statistically significant. Higher levels of myeloperoxidase activity in the TBI group (p < 0.05) were found to be suppressed in 5 and 10 mg/kg TM5441 treatment groups (p < 0.05-p < 0.01). The tail suspension test score was increased in the TBI group (p < 0.001) and decreased in all treatment groups (p < 0.05-0.001). The histologic damage score was increased statistically significantly in the cortex, dentate gyrus, and CA3 regions in the TBI group (p < 0.01-0.001), decreased in the treatment groups in the cortex and dentate gyrus (p < 0.05-0.001). PAI antagonists, especially TM5441, have antioxidant and anti-inflammatory properties against mild TBI in the acute period. Behavioral test results were also improved after PAI antagonist treatment after mild TBI.

Fibrinolytic system activation immediately following trauma was quickly and intensely suppressed in a rat model of severe blunt trauma

In severe trauma, excessive fibrinolytic activation is associated with an increase in the transfusion volume and mortality rate. However, in the first several hours after a blunt trauma, changes in fibrinolytic activation, suppression, and activation–suppression balance have not yet been elucidated, which the present study aimed to clarify. Anesthetized 9-week-old male Wistar S/T rats experienced severe blunt trauma while being placed inside the Noble–Collip drum. Rats were randomly divided into four groups of seven. The no-trauma group was not exposed to any trauma; the remaining groups were analysed 0, 60, and 180 min after trauma. Immediately following trauma, total tissue-plasminogen activator (tPA) levels significantly increased in the plasma, and the balance of active tPA and active plasminogen activator inhibitor-1 (PAI-1) significantly tipped toward fibrinolytic activation. After trauma, both tPA and PAI-1 levels increased gradually in various organs and active and total PAI-1 levels increased exponentially in the plasma. Total plasma tPA levels 60 min after trauma returned quickly to levels comparable to those in the no-trauma group. In conclusion, fibrinolytic activation was observed only immediately following trauma. Therefore, immediately after trauma, the fibrinolytic system was activated; however, its activation was quickly and intensely suppressed.

Neutrophil extracellular traps contribute to tissue plasminogen activator resistance in acute ischemic stroke

Circulating neutrophil extracellular traps (NETs) resistant to t-PA have not been studied completely although NETs in thrombi may contribute to tissue plasminogen activator (t-PA) resistance. This research intended to elucidate whether circulating NETs are associated with t-PA resistance and the underlying mechanism. The levels of NETs were detected in the circulating neutrophils, ischemic brain tissue of acute ischemic stroke (AIS) patients, and transient middle cerebral artery occlusion (tMCAO) models. NET formation in blood, thrombi, and ischemic brain tissue of mice were analyzed by immunofluorescence. Exposed phosphatidylserine (PS) was assessed using flow cytometry and confocal microscopy. Procoagulant activity (PCA) was evaluated using fibrin formation assays, thrombin, and purified coagulation complex. The plasma levels of NETs in AIS patients were significantly higher than those in healthy individuals. After thrombolysis, a significant increase was noted in NET markers in no-improvement patients, while the changes in improvement patients were not significant. Importantly, NETs were decorated with von Willebrand factor (vWF) and plasminogen activator inhibitor-1 (PAI-1) in the blood and thrombi, which could reverse the fibrinolytic effects. In addition, NETs activated platelets (PLTs) and endothelial cells (ECs), stimulating a procoagulant phenotype and facilitating vWF and PAI-1 release. DNase I, activated protein C (APC), and sivelestat markedly inhibited these effects. Furthermore, targeting NETs protected mice from tMCAO-induced cerebral ischemia, possibly by regulating vWF and PAI-1. In summary, NETs may contribute to t-PA resistance in AIS through activation of PLTs and ECs. Strategies against NETs may present a promising therapeutic approach to improve the thrombolysis efficiency of t-PA in AIS patients.

Combined Effect of MTHFR C677T and PAI-1 4G/5G Polymorphisms on the Risk of Venous Thromboembolism in Chinese Lung Cancer Patients

Venous thromboembolism (VTE) is a common and potentially fatal complication in cancer patients. Although several genetic risk factors related to thrombophilia have been identified, their contributions for the occurrence of VTE in cancer patients have conflicting results. The aim of this study was to evaluated the gene polymorphisms of methylenetetrahydrofolate reductase (MTHFR) C677T and plasminogen activator inhibitor-1 (PAI-1) 4G/5G in lung cancer patients, with and without VTE, and the combined effect on the risk of VTE. 92 lung cancer patients diagnosed with VTE (VTE group) and 122 lung cancer patients without VTE (non-VTE group) were enrolled in the study. The gene polymorphisms were analyzed by the method of polymerase chain reaction-restriction fragment length polymorphism. Gene mutation of factor V Leiden was not detected both in non-VTE group and VTE group. The frequency of MTHFR C677T homozygous mutation in VTE group was 25.00%, higher than that in the non-VTE group without statistical difference. It was found that the PAI-1 4G4G genotype is associated with a higher risk of VTE (OR: 2.62, 95%CI: 1.19-5.75). Interestingly, the interaction between MTHFR C677T and PAI-1 4G/5G polymorphisms showed that the coexistence of the 2 homozygous mutation could further increase the risk of VTE. In conclusion, PAI-1 4G/5G polymorphism may be an increased risk factor for VTE among lung cancer patients in Chinese population. The homozygous MTHFR C677T mutation may be not a risk factor for VTE but increases the risk, accompanied with PAI-1 4G5G genotype.

[Spontaneous fibrinolysis and possibilities of its acceleration in pulmonary embolism]

This review contains the data concerning the mechanisms of spontaneous fibrinolysis in pulmonary vessels and possibilities of its acceleration in pulmonary embolism. The spontaneous fibrinolysis system is known to be sequential and multifactorial, with the interaction of accelerators (t-PA and u-PA) and inhibitors (alpha-2-antiplasmin, PAI-1, TAFI). The fibrinolytic processes take place in case of prevailing reactions of accelerating factors over inhibiting ones. The endothelium of pulmonary vessels possesses pronounced antithrombogenic and profibrinolytic properties, therefore, the processes of fibrinolysis in the pulmonary vascular bed normally occur more intensively than in the vessels of the systemic circulation. The membrane proteins of the endothelium annexins A2 activate plasminogen, whereas thrombomodulin inhibits the activity of PAI-1. The main approaches to increase the fibrinolysis intensity in conditions of pulmonary embolism may be aimed at elevating the activity of fibrinolytic enzymes (enhancing the synthesis of annexins A2, the use of NMDA-receptor antagonists) and suppressing its inhibitors (the use of monoclonal antibodies to alpha-2-antiplasmin, as well as plasminogen activator inhibitor-1 (PAI-1) and thrombin-activatable fibrinolysis inhibitor (TAFI). Promising directions for future research can be the synthesis of a new generation of tissue-type plasminogen activators, and investigations of the possibility of clinical application of antithrombin and thrombomodulin, angiotensin converting enzyme inhibitors and cortisol antagonists. To meet these challenges, it is necessary to develop new models of venous thrombosis and acute pulmonary embolism in different animal species, with the assessment of the changes in the venous haemodynamics and pulmonary microcirculation on the background of administration of a new class of fibrinolytic agents.

Pulmonary coagulation and fibrinolysis abnormalities that favor fibrin deposition in the lungs of mouse antibody-mediated transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a life-threatening disease caused by blood transfusion. However, its pathogenesis is poorly understood and specific therapies are not available. Experimental and clinical studies have indicated that alveolar fibrin deposition serves a pathological role in acute lung injuries. The present study investigated whether pulmonary fibrin deposition occurs in a TRALI mouse model and the possible mechanisms underlying this deposition. The TRALI model was established by priming male Balb/c mice with lipopolysaccharide (LPS) 18 h prior to injection of an anti-major histocompatibility complex class I (MHC-I) antibody. Untreated mice and mice administered LPS plus isotype antibody served as controls. At 2 h after TRALI induction, blood and lung tissue were collected. Disease characteristics were assessed based on lung tissue histology, inflammatory responses and alterations in the alveolar-capillary barrier. Immunofluorescence staining was used to detect pulmonary fibrin deposition, platelets and fibrin-platelet interactions. Levels of plasminogen activator inhibitor-1 (PAI-1), thrombin-antithrombin complex (TATc), tissue factor pathway inhibitor (TFPI), coagulation factor activity and fibrin degradation product (FDP) in lung tissue homogenates were measured. Severe lung injury, increased inflammatory responses and a damaged alveolar-capillary barrier in the LPS-primed, anti-MHC-I antibody-administered mice indicated that the TRALI model was successfully established. Fibrin deposition, fibrin-platelet interactions and platelets accumulation in the lungs of mouse models were clearly promoted. Additionally, levels of TATc, coagulation factor V (FV), TFPI and PAI-1 were elevated, whereas FDP level was decreased in TRALI mice. In conclusion, both impaired fibrinolysis and enhanced coagulation, which might be induced by boosted FV activity, increased pulmonary platelets accumulation and enhanced fibrin-platelet interactions and contributed to pulmonary fibrin deposition in TRALI mice. The results provided a therapeutic rationale to target abnormalities in either coagulation or fibrinolysis pathways for antibody-mediated TRALI.

Single intracerebroventricular progranulin injection adversely affects the blood-brain barrier in experimental traumatic brain injury

Progranulin (PGRN) is a neurotrophic and anti-inflammatory factor with protective effects in animal models of ischemic stroke, subarachnoid hemorrhage, and traumatic brain injury (TBI). Administration of recombinant (r) PGRN prevents exaggerated brain pathology after TBI in Grn-deficient mice, suggesting that local injection of recombinant progranulin (rPGRN) provides therapeutic benefit in the acute phase of TBI. To test this hypothesis, we subjected adult male C57Bl/6N mice to the controlled cortical impact model of TBI, administered a single dose of rPGRN intracerebroventricularly (ICV) shortly before the injury, and examined behavioral and biological effects up to 5 days post injury (dpi). The anti-inflammatory bioactivity of rPGRN was confirmed by its capability to inhibit the inflammation-induced hypertrophy of murine primary microglia and astrocytes in vitro. In C57Bl/6N mice, however, ICV administration of rPGRN failed to attenuate behavioral deficits over the 5-day observation period. (Immuno)histological gene and protein expression analyses at 5 dpi did not reveal a therapeutic benefit in terms of brain injury size, brain inflammation, glia activation, cell numbers in neurogenic niches, and neuronal damage. Instead, we observed a failure of TBI-induced mRNA upregulation of the tight junction protein occludin and increased extravasation of serum immunoglobulin G into the brain parenchyma at 5 dpi. In conclusion, single ICV administration of rPGRN had not the expected protective effects in the acute phase of murine TBI, but appeared to cause an aggravation of blood-brain barrier disruption. The data raise questions about putative PGRN-boosting approaches in other types of brain injuries and disease.

Potential differences in cleavage of the S protein and type-1 interferon together control human coronavirus infection, propagation, and neuropathology within the central nervous system

Human coronaviruses (HCoV) are respiratory pathogens which have been known since the 1960's. In December 2019, a new betacoronavirus, SARS-CoV-2, was reported and is responsible for one of the biggest pandemics of the last two centuries. Similar to the HCoV-OC43 strain, available evidence suggests SARS-CoV-2 neuroinvasion associated with potential neurological disorders. Coronavirus infection of the central nervous system (CNS) is largely controlled by a viral factor, the spike glycoprotein (S) and a host factor, innate immunity. However, the interaction between these two factors remains elusive. Proteolytic cleavage of the S protein can occur at the interface between receptor binding (S1) and fusion (S2) domains (S1/S2), as well as in a position adjacent to a fusion peptide within S2 (S2'). Herein, using HCoV-OC43 as a surrogate for SARS-CoV-2, we report that both S protein sites are involved in neurovirulence and are required for optimal CNS infection. Whereas efficient cleavage at S1/S2 is associated with decreased virulence, the potentially cleavable putative S2' site is essential for efficient viral infection. Furthermore, type 1 interferon (IFN 1)-related innate immunity also plays an important role in the control of viral spread towards the spinal cord, by preventing infection of ependymal cells. Our results underline the link between the differential S cleavage and IFN 1 in the prevention of viral spread, to control the severity of infection and pathology in both immunocompetent and immunodeficient mice. Taken together, these results point towards two potential therapeutic anti-viral targets: cleavage of the S protein in conjunction with efficient IFN 1-related innate immunity to prevent or at least reduce neuroinvasion, neural spread, and potential associated neurovirulence of human coronaviruses.ImportanceHuman coronaviruses (HCoV) are recognized respiratory pathogens. The emergence of the novel pathogenic member of this family in December 2019 (SARS-CoV-2, which causes COVID-19) poses a global health emergency. As with other coronaviruses reported previously, invasion of the human central nervous system (CNS), associated with diverse neurological disorders, was suggested for SARS-CoV-2. Herein, using the related HCoV-OC43 strain, we show that the viral spike protein constitutes a major neurovirulence factor and that type 1 interferon (IFN 1), in conjunction with cleavage of S protein by host proteases, represent important host factors that participate in the control of CNS infection.To our knowledge, this is the first demonstration of a direct link between cleavage of the S protein, innate immunity and neurovirulence. Understanding mechanisms of viral infection and spread in neuronal cells is essential to better design therapeutic strategies, and to prevent infection by human coronaviruses such as SARS-CoV-2 in human CNS especially in the vulnerable populations such as the elderly and immune-compromised individuals.

Fibrinolysis in Traumatic Brain Injury: Diagnosis, Management, and Clinical Considerations

Posttraumatic coagulopathy involves disruption of both the coagulation and fibrinolytic pathways secondary to tissue damage, hypotension, and inflammatory upregulation. This phenomenon contributes to delayed complications after traumatic brain injury (TBI), including intracranial hemorrhage progression and systemic disseminated intravascular coagulopathy. Development of an early hyperfibrinolytic state may result in uncontrolled bleeding and is associated with increased mortality in patients with TBI. Although fibrinolytic assays are not routinely performed in the assessment of posttraumatic coagulopathy, circulating biomarkers such as D-dimer and fibrin degradation products have demonstrated potential utility in outcome prediction. Unfortunately, the relatively delayed nature of these tests limits their clinical utility. In contrast, viscoelastic tests are able to provide a rapid global assessment of coagulopathy, although their ability to reliably identify disruptions in the fibrinolytic cascade remains unclear. Limited evidence supports the use of hypertonic saline, cryoprecipitate, and plasma to correct fibrinolytic disruption; however, some studies suggest more harm than benefit. Recently, early use of tranexamic acid in patients with TBI and confirmed hyperfibrinolysis has been proposed as a strategy to further improve clinical outcomes. Moving forward, further delineation of TBI phenotypes and the clinical implications of fibrinolysis based on phenotypic variation is needed. In this review, we summarize the clinical aspects of fibrinolysis in TBI, including diagnosis, treatment, and clinical correlates, with identification of targeted areas for future research efforts.

TGF-β1-Mediated Activation of SERPINE1 is Involved in Hemin-Induced Apoptotic and Inflammatory Injury in HT22 Cells

BACKGROUND

Intracerebral hemorrhage (ICH) is a severe subtype of stroke with high mortality and morbidity. Serpin Family E Member 1 (SERPINE1) has been documented to be upregulated following ICH, however, the participation of SERPINE1 in the development of ICH has never been studied.

METHODS

Hemin was utilized to develop an in vitro model of ICH. Gene levels were evaluated by the use of quantitative reverse transcription polymerase chain reaction, Western blot, as well as enzyme-linked immunoassay assay. The activity of caspase-3 was determined using a commercial kit. Cell viability and apoptosis were assessed using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and Terminal deoxynucleotidyl transferase (TdT) d UTP Nick-End Labeling assay.

RESULTS

SERPINE1 was upregulated in hemin-treated HT22 cells. Silencing of SERPINE1 attenuated hemin-induced inhibition of cell viability. Moreover, knockdown of SERPINE1 repressed hemin-induced apoptosis in HT22 cells, as evidenced by the decrease in the number of TUNEL positive cells, caspase-3 activity, and Bax expression, and the increase in Bcl-2 expression. Meanwhile, knockdown of SERPINE1 repressed hemin-induced inflammation in HT22 cells, as indicated by reduced levels of tumor necrosis factor-α, interleukin-6 (IL-6), IL-1β, and inducible nitric oxide synthase. We also found that transforming growth factor-beta 1 (TGF-β1) induced SERPINE1 expression in a dose-dependent manner. Besides, SERPINE1 knockdown attenuated the effects of TGF-β1 on hemin-induced neuronal damage.

CONCLUSION

TGF-β1-induced SERPINE1 activation exacerbated hemin-induced apoptosis and inflammation in HT22 cells, manifesting a novel mechanism for ICH progression.

Deletion of Protocadherin Gamma C3 Induces Phenotypic and Functional Changes in Brain Microvascular Endothelial Cells In Vitro

Inflammation of the central nervous system (CNS) is associated with diseases such as multiple sclerosis, stroke and neurodegenerative diseases. Compromised integrity of the blood-brain barrier (BBB) and increased migration of immune cells into the CNS are the main characteristics of brain inflammation. Clustered protocadherins (Pcdhs) belong to a large family of cadherin-related molecules. Pcdhs are highly expressed in the CNS in neurons, astrocytes, pericytes and epithelial cells of the choroid plexus and, as we have recently demonstrated, in brain microvascular endothelial cells (BMECs). Knockout of a member of the Pcdh subfamily, PcdhgC3, resulted in significant changes in the barrier integrity of BMECs. Here we characterized the endothelial PcdhgC3 knockout (KO) cells using paracellular permeability measurements, proliferation assay, wound healing assay, inhibition of signaling pathways, oxygen/glucose deprivation (OGD) and a pro-inflammatory cytokine tumor necrosis factor alpha (TNFα) treatment. PcdhgC3 KO showed an increased paracellular permeability, a faster proliferation rate, an altered expression of efflux pumps, transporters, cellular receptors, signaling and inflammatory molecules. Serum starvation led to significantly higher phosphorylation of extracellular signal-regulated kinases (Erk) in KO cells, while no changes in phosphorylated Akt kinase levels were found. PcdhgC3 KO cells migrated faster in the wound healing assay and this migration was significantly inhibited by respective inhibitors of the MAPK-, β-catenin/Wnt-, mTOR- signaling pathways (SL327, XAV939, or Torin 2). PcdhgC3 KO cells responded stronger to OGD and TNFα by significantly higher induction of interleukin 6 mRNA than wild type cells. These results suggest that PcdhgC3 is involved in the regulation of major signaling pathways and the inflammatory response of BMECs.

Functional Testing for Tranexamic Acid Duration of Action Using Modified Viscoelastometry

Introduction

Tranexamic acid (TXA) is the standard medication to prevent or treat hyperfibrinolysis. However, prolonged inhibition of lysis (so-called "fibrinolytic shutdown") correlates with increased mortality. A new viscoelastometric test enables bedside quantification of the antifibrinolytic activity of TXA using tissue plasminogen activator (TPA).

Materials and Methods

Twenty-five cardiac surgery patients were included in this prospective observational study. In vivo, the viscoelastometric TPA test was used to determine lysis time (LT) and maximum lysis (ML) over 96 h after TXA bolus. Additionally, plasma concentrations of TXA and plasminogen activator inhibitor 1 (PAI-1) were measured. Moreover, dose effect curves from the blood of healthy volunteers were performed in vitro. Data are presented as median (25-75th percentile).

Results

In vivo TXA plasma concentration correlated with LT (r = 0.55; p < 0.0001) and ML (r = 0.62; p < 0.0001) at all time points. Lysis was inhibited up to 96 h (LT_TPA-test: baseline: 398 s [229-421 s] vs. at 96 h: 886 s [626-2,175 s]; p = 0.0013). After 24 h, some patients (n = 8) had normalized lysis, but others (n = 17) had strong lysis inhibition (ML <30%; p < 0.001). The high- and low-lysis groups differed regarding kidney function (cystatin C: 1.64 [1.42-2.02] vs. 1.28 [1.01-1.52] mg/L; p = 0.002) in a post hoc analysis. Of note, TXA plasma concentration after 24 h was significantly higher in patients with impaired renal function (9.70 [2.89-13.45] vs.1.41 [1.30-2.34] µg/mL; p < 0.0001). In vitro, TXA concentrations of 10 µg/mL effectively inhibited fibrinolysis in all blood samples.

Conclusions

Determination of antifibrinolytic activity using the TPA test is feasible, and individual fibrinolytic capacity, e.g., in critically ill patients, can potentially be measured. This is of interest since TXA-induced lysis inhibition varies depending on kidney function.

Sex-dependent effects of tranexamic acid on blood-brain barrier permeability and the immune response following traumatic brain injury in mice

BACKGROUND

Tranexamic acid (TXA) is an anti-fibrinolytic agent used to reduce bleeding in various conditions including traumatic brain injury (TBI). As the fibrinolytic system also influences the central nervous system and the immune response, TXA may also modulate these parameters following TBI.

OBJECTIVES

To determine the effect of TXA on blood-brain barrier (BBB) integrity and changes in immune and motor function in male and female mice subjected to TBI.

METHODS

Wild-type and plasminogen deficient (plg-/-) mice were subjected to TBI then administered either TXA/vehicle. The degree of BBB breakdown, intracerebral hemorrhage (ICH), motor dysfunction, and changes in inflammatory subsets in blood and brain were determined.

RESULTS AND CONCLUSIONS

Tranexamic acid significantly reduced BBB breakdown, and increased blood neutrophils in male mice 3 hours post-TBI. In contrast, TXA treatment of female mice increased BBB permeability and ICH but had no effect on blood neutrophils at the same time-point. TXA improved motor function in male mice but still increased BBB breakdown in female mice 24 hours post-TBI. Brain urokinase-type plasminogen activator (u-PA) antigen and activity levels were significantly higher in injured females compared to males. Because TXA can promote a pro-fibrinolytic effect via u-PA, these sex differences may be related to brain u-PA levels. TXA also increased monocyte subsets and dendritic cells in the injured brain of wild-type male mice 1 week post-TBI. Plg-/- mice of both sexes had reduced BBB damage and were protected from TBI irrespective of treatment indicating that TXA modulation of the BBB is plasmin-dependent. In conclusion, TXA is protective post-TBI but only in male mice.

tPA Deficiency Underlies Neurovascular Coupling Dysfunction by Amyloid-β

The amyloid-β (Aβ) peptide, a key pathogenic factor in Alzheimer's disease, attenuates the increase in cerebral blood flow (CBF) evoked by neural activity (functional hyperemia), a vital homeostatic response in which NMDA receptors (NMDARs) play a role through nitric oxide, and the CBF increase produced by endothelial factors. Tissue plasminogen activator (tPA), which is reduced in Alzheimer's disease and in mouse models of Aβ accumulation, is required for the full expression of the NMDAR-dependent component of functional hyperemia. Therefore, we investigated whether tPA is involved in the neurovascular dysfunction of Aβ. tPA activity was reduced, and the tPA inhibitor plasminogen inhibitor-1 (PAI-1) was increased in male mice expressing the Swedish mutation of the amyloid precursor protein (tg2576). Counteracting the tPA reduction with exogenous tPA or with pharmacological inhibition or genetic deletion of PAI-1 completely reversed the attenuation of the CBF increase evoked by whisker stimulation but did not ameliorate the response to the endothelium-dependent vasodilator acetylcholine. The tPA deficit attenuated functional hyperemia by suppressing NMDAR-dependent nitric oxide production during neural activity. Pharmacological inhibition of PAI-1 increased tPA activity, prevented neurovascular uncoupling, and ameliorated cognition in 11- to 12-month-old tg2576 mice, effects associated with a reduction of cerebral amyloid angiopathy but not amyloid plaques. The data unveil a selective role of the tPA in the suppression of functional hyperemia induced by Aβ and in the mechanisms of cerebral amyloid angiopathy, and support the possibility that modulation of the PAI-1-tPA pathway may be beneficial in diseases associated with amyloid accumulation.SIGNIFICANCE STATEMENT Amyloid-β (Aβ) peptides have profound neurovascular effects that may contribute to cognitive impairment in Alzheimer's disease. We found that Aβ attenuates the increases in blood flow evoked by neural activation through a reduction in tissue plasminogen activator (tPA) caused by upregulation of its endogenous inhibitor plasminogen inhibitor-1 (PAI-1). tPA deficiency prevents NMDA receptors from triggering nitric oxide production, thereby attenuating the flow increase evoked by neural activity. PAI-1 inhibition restores tPA activity, rescues neurovascular coupling, reduces amyloid deposition around blood vessels, and improves cognition in a mouse model of Aβ accumulation. The findings demonstrate a previously unappreciated role of tPA in Aβ-related neurovascular dysfunction and in vascular amyloid deposition. Restoration of tPA activity could be of therapeutic value in diseases associated with amyloid accumulation.

Functional testing of tranexamic acid effects in patients undergoing elective orthopaedic surgery

Tranexamic acid (TXA) can reduce blood loss and transfusion rates in orthopaedic surgery. In this regard, a new viscoelastometric test (TPA-test, ClotPro), enables the monitoring of TXA effects. This prospective observational study evaluated and correlated TXA plasma concentrations (cTXA) following intravenous and oral administration in patients undergoing elective orthopaedic surgery with lysis variables of TPA-test. Blood samples of 42 patients were evaluated before TXA application and 2, 6, 12, 24 and 48 h afterwards. TPA-test was used to determine lysis time (LT) as well as maximum lysis (ML) and cTXA was measured using Ultra-High-Performance-Liquid-Chromatography/Mass-Spectrometry. Data are presented as median (min-max). LT_TPA-test and ML_TPA-test correlated with cTXA (r = 0.9456/r = 0.5362; p < 0.0001). 2 h after intravenous TXA administration all samples showed complete lysis inhibition (LT_TPA-test prolongation: T1: 217 s (161-529) vs. T2: 4500 s (4500-4500);p < 0.0001), whereas after oral application high intraindividual variability was observed as some samples showed only moderate changes in LT_TPA-test (T1: 236 s (180-360) vs. T2: 4500 s (460-4500); p < 0.0001). Nevertheless, statistically LT_TPA-test did not differ between groups. ML_TPA-test differed 2 h after application (i.v.: 9.0% (5-14) vs. oral: 31% (8-97); p = 0.0081). In 17/21 samples after oral and 0/21 samples after intravenous administration cTXA was < 10 µg ml^-1 2 h after application. TPA-test correlated with cTXA. ML_TPA-test differed between intravenous and oral application 2 h after application. Most patients with oral application had TXA plasma concentration < 10 µg ml^-1. The duration of action did not differ between intravenous and oral application. Additional studies evaluating clinical outcomes and side-effects based on individualized TXA prophylaxis/therapy are required.

The abnormalities of coagulation and fibrinolysis in acute lung injury caused by gas explosion

Acute lung injury (ALI) caused by gas explosion is common, and warrants research on the underlying mechanisms. Specifically, the role of abnormalities of coagulation and fibrinolysis in this process has not been defined. It was hypothesized that the abnormal coagulation and fibrinolysis promoted ALI caused by gas explosion. Based on the presence of ALI, 74 cases of gas explosion injury were divided into the ALI and non-ALI groups. The results of prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (FIB), and platelet count (PLT) were collected within 24 hours and compared between the groups. ALI models caused by gas explosion were established in Sprague Dawley rats, and injuries were evaluated using hematoxylin and eosin (HE) staining and histopathological scoring. Moreover, the bronchoalveolar lavage fluid (BALF) was collected to examine thrombin-antithrombin complex (TAT), tissue factor (TF), tissue factor pathway inhibitor (TFPI), and plasminogen activator inhibitor-1 (PAI-1) levels by enzyme-linked immunosorbent assay (ELISA). The patients in ALI group had shorter PT and longer APTT, raised concentration of FIB and decreased number of PLT, as compared to the non-ALI group. In ALI rats, the HE staining revealed red blood cells in alveoli and interstitial thickening within 2 hours which peaked at 72 hours. The levels of TAT/TF in the BALF increased continually until the seventh day, while the PAI-1 was raised after 24 hours and 7 days. The TFPI was elevated after 2 hours and 24 hours, and then decreased after 72 hours. Abnormalities in coagulation and fibrinolysis in lung tissues play a role in ALI caused by gas explosion.

Using antifibrinolytics to tackle neuroinflammation

Plasmin is generally known as a promotor of inflammation. Recent advancement suggests that it has a complex role as immunity modulator. Pharmacological inhibition of plasmin production and activity has been proven to improve neurological outcomes in traumatic brain injury and subarachnoid hemorrhage, most probably by preventing re-bleeding. The immune-modulatory properties of antifibrinolytics, however, suggest that they probably have effects unrelated to fibrinolysis inhibition, which are currently not adequately harnessed. The present work aims to give an account of the existing data regarding antifibrinolytics as agents influencing neuroinflammation. Preclinical and clinical studies on the possible influence of antifibrinolytics on neuroinflammation are scarce. However, the emerging evidence suggests that inhibition of plasmin(ogen) activity can ameliorate neuroinflammation to some extent. This data demonstrate that plasmin(ogen) is not exclusively involved in fibrinolysis, but also has other substrates and can precipitate in inflammatory processes. Investigation on the role of plasmin as the factor for the development of neuroinflammation shows the significant potential of antifibrinolytics as pharmacotherapy of neuroinflammationm, which is worthy of further exploration.

Sparganin A alleviates blood stasis syndrome and its key targets by molecular docking

Blood stasis syndrome is implicated in the development of chronic conditions, including cardio- and cerebrovascular diseases. Cyclo-(Tyr-Leu), named Sparganin A (SA), is a compound isolated from the ethanol extract of Rhizoma Sparganii. Here, the successful extraction of SA from Rhizoma Sparganii was verified by extensive spectral analysis using 1H NMR and 13C NMR. To determine the biological effects of SA, a mouse model of acute blood stasis was established by subcutaneous injection of adrenaline hydrochloride and placing the animals in an ice water bath. In this model, the concentration of TXB2, PAI-1, FIB, ET-1 was measured by ELISA, and thymus index (TI), hepatic index (HI), and spleen index (SI) were calculated. Molecular docking by SYBYL and functional analysis of the putative targets by STRING and Cytoscape were employed to identify the key targets of SA. The accumulated results documented that SA exhibits anticoagulative activity, and its key targets are VEGFA and SERPINE1. SA may be involved in the pathological process of complement and coagulation cascades. This study demonstrates that SA may be a promising drug to control coagulation in blood stasis syndrome.

Analgesic treatment limits surrogate parameters for early stress and pain response after experimental subarachnoid hemorrhage

Background

In animal research, authorities require a classification of anticipated pain levels and a perioperative analgesia protocol prior to approval of the experiments. However, data on this topic is rare and so is the reported use of analgesics. We determined surrogate parameters of pain and general well-being after subarachnoid hemorrhage (SAH), as well as the potential for improvement by different systemic analgesia paradigms. Brain injury was induced by filament perforation to mimic SAH. Sham-operated mice were included as surgical control groups with either neck or no-neck preparation. Mice with controlled cortical impact (CCI) injury were included as a control group with traumatic brain injury (TBI), but without neck preparation. Mice were randomized to buprenorphine, carprofen, meloxicam, or vehicle treatment. 24 h after SAH, CCI or sham surgery, pain and stress levels were assessed with a visual assessment score and the amount of food intake was recorded.

Results

Neck preparation, which is required to expose the surgical field for SAH induction, already increased pain/stress levels and sham surgeries for both CCI and SAH reduced food intake. Pain/stress levels were higher and food intake was lower after SAH compared with CCI. Pain/stress levels after CCI without analgesic treatment were similar to levels after SAH sham surgery. Pain treatment with buprenorphine was effective to reduce pain after SAH, whereas lower pain/stress intensity levels after CCI were not improved.

Conclusion

This study emphasizes the importance of pain and stress assessment after surgeries and the efficacy of buprenorphine to improve pain and comfort levels after experimental SAH.

Neutrophils mediate early cerebral cortical hypoperfusion in a murine model of subarachnoid haemorrhage

Cerebral hypoperfusion in the first hours after subarachnoid haemorrhage (SAH) is a major determinant of poor neurological outcome. However, the underlying pathophysiology is only partly understood. Here we induced neutropenia in C57BL/6N mice by anti-Ly6G antibody injection, induced SAH by endovascular filament perforation, and analysed cerebral cortical perfusion with laser SPECKLE contrast imaging to investigate the role of neutrophils in mediating cerebral hypoperfusion during the first 24 h post-SAH. SAH induction significantly increased the intracranial pressure (ICP), and significantly reduced the cerebral perfusion pressure (CPP). At 3 h after SAH, ICP had returned to baseline and CPP was similar between SAH and sham mice. However, in SAH mice with normal neutrophil counts cortical hypoperfusion persisted. Conversely, despite similar CPP, cortical perfusion was significantly higher at 3 h after SAH in mice with neutropenia. The levels of 8-iso-prostaglandin-F2α in the subarachnoid haematoma increased significantly at 3 h after SAH in animals with normal neutrophil counts indicating oxidative stress, which was not the case in neutropenic SAH animals. These results suggest that neutrophils are important mediators of cortical hypoperfusion and oxidative stress early after SAH. Targeting neutrophil function and neutrophil-induced oxidative stress could be a promising new approach to mitigate cerebral hypoperfusion early after SAH.