Coagulation and fibrinolysis after injury

Nrf2 alleviates spaceflight-induced immunosuppression and thrombotic microangiopathy in mice

Spaceflight-related stresses impact health via various body systems, including the haematopoietic and immune systems, with effects ranging from moderate alterations of homoeostasis to serious illness. Oxidative stress appears to be involved in these changes, and the transcription factor Nrf2, which regulates expression of a set of cytoprotective and antioxidative stress response genes, has been implicated in the response to spaceflight-induced stresses. Here, we show through analyses of mice from the MHU-3 project, in which Nrf2-knockout mice travelled in space for 31 days, that mice lacking Nrf2 suffer more seriously from spaceflight-induced immunosuppression than wild-type mice. We discovered that a one-month spaceflight-triggered the expression of tissue inflammatory marker genes in wild-type mice, an effect that was even more pronounced in the absence of Nrf2. Concomitant with induction of inflammatory conditions, the consumption of coagulation-fibrinolytic factors and platelets was elevated by spaceflight and further accelerated by Nrf2 deficiency. These results highlight that Nrf2 mitigates spaceflight-induced inflammation, subsequent immunosuppression, and thrombotic microangiopathy. These observations reveal a new strategy to relieve health problems encountered during spaceflight.

Plasmin and plasminogen prevent sepsis severity by reducing neutrophil extracellular traps and systemic inflammation

Sepsis is a lethal syndrome characterized by systemic inflammation and abnormal coagulation. Despite therapeutic advances, sepsis mortality remains substantially high. Herein, we investigated the role of the plasminogen/plasmin (Plg/Pla) system during sepsis. Plasma levels of Plg were significantly lower in mice subjected to severe compared with nonsevere sepsis, whereas systemic levels of IL-6, a marker of sepsis severity, were higher in severe sepsis. Plg levels correlated negatively with IL-6 in both septic mice and patients, whereas plasminogen activator inhibitor-1 levels correlated positively with IL-6. Plg deficiency render mice susceptible to nonsevere sepsis induced by cecal ligation and puncture (CLP), resulting in greater numbers of neutrophils and M1 macrophages, liver fibrin(ogen) deposition, lower efferocytosis, and increased IL-6 and neutrophil extracellular trap (NET) release associated with organ damage. Conversely, inflammatory features, fibrin(ogen), and organ damage were substantially reduced, and efferocytosis was increased by exogenous Pla given during CLP- and LPS-induced endotoxemia. Plg or Pla protected mice from sepsis-induced lethality and enhanced the protective effect of antibiotics. Mechanistically, Plg/Pla-afforded protection was associated with regulation of NET release, requiring Pla-protease activity and lysine binding sites. Plg/Pla are important host-protective players during sepsis, controlling local and systemic inflammation and collateral organ damage.

Arsenite Inhibits Tissue-Type Plasminogen Activator Synthesis through NRF2 Activation in Cultured Human Vascular Endothelial EA.hy926 Cells

Chronic arsenic exposure is known to be related to the progression of atherosclerosis. However, the pathogenic mechanisms of arsenic-induced atherosclerosis have not been fully elucidated. Because disruption of the blood coagulation/fibrinolytic system is involved in the development of arteriosclerosis, we investigated the effect of arsenite on fibrinolytic activity in human vascular endothelial EA.hy926 cells in the present study. Fibrinolysis depends on the balance between tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1) secreted from vascular endothelial cells. We found that arsenite reduced fibrinolytic t-PA activity by inhibiting its synthesis without affecting PAI-1 production. The inhibitory effect of arsenite on t-PA expression was partially recovered by the reactive oxygen species (ROS) scavenger Trolox. The nuclear factor erythroid 2 related factor 2 (NRF2) pathway is known to be activated by arsenite via ROS production. We confirmed that arsenite activated the NRF2 pathway, and arsenite-induced inhibition of fibrinolytic t-PA activity was abrogated in NRF2-knockdown EA.hy926 cells. These results suggest that arsenite inhibits the fibrinolytic activity of t-PA by selectively suppressing its synthesis via activation of the NRF2 pathway in vascular endothelial cells.

Plasminogen activation in the musculoskeletal acute phase response: Injury, repair, and disease

The musculoskeletal system is critical for movement and the protection of organs. In addition to abrupt injuries, daily physical demands inflict minor injuries, necessitating a coordinated process of repair referred to as the acute-phase response (APR). Dysfunctional APRs caused by severe injuries or underlying chronic diseases are implicated in pathologic musculoskeletal repair, resulting in decreased mobility and chronic pain. The molecular mechanisms behind these phenomena are not well understood, hindering the development of clinical solutions. Recent studies indicate that, in addition to regulating intravascular clotting, the coagulation and fibrinolytic systems are also entrenched in tissue repair. Although plasmin and fibrin are considered antithetical to one another in the context of hemostasis, in a proper APR, they complement one another within a coordinated spatiotemporal framework. Once a wound is contained by fibrin, activation of plasmin promotes the removal of fibrin and stimulates angiogenesis, tissue remodeling, and tissue regeneration. Insufficient fibrin deposition or excessive plasmin-mediated fibrinolysis in early convalescence prevents injury containment, causing bleeding. Alternatively, excess fibrin deposition and/or inefficient plasmin activity later in convalescence impairs musculoskeletal repair, resulting in tissue fibrosis and osteoporosis, while inappropriate fibrin or plasmin activity in a synovial joint can cause arthritis. Together, these pathologic conditions lead to chronic pain, poor mobility, and diminished quality of life. In this review, we discuss both fibrin-dependent and -independent roles of plasminogen activation in the musculoskeletal APR, how dysregulation of these mechanisms promote musculoskeletal degeneration, and the possibility of therapeutically manipulating plasmin or fibrin to treat musculoskeletal disease.

Local hemostasis, immunothrombosis, and systemic disseminated intravascular coagulation in trauma and traumatic shock

Knowing the pathophysiology of trauma-induced coagulopathy is important for the management of severely injured trauma patients. The aims of this review are to provide a summary of the recent advances in our understanding of thrombosis and hemostasis following trauma and to discuss the pathogenesis of disseminated intravascular coagulation (DIC) at an early stage of trauma. Local hemostasis and thrombosis respectively act to induce physiological wound healing of injuries and innate immune responses to damaged-self following trauma. However, if overwhelmed by systemic inflammation caused by extensive tissue damage and tissue hypoperfusion, both of these processes foster systemic DIC associated with pathological fibrin(ogen)olysis. This is called DIC with the fibrinolytic phenotype, which is characterized by the activation of coagulation, consumption coagulopathy, insufficient control of coagulation, and increased fibrin(ogen)olysis. Irrespective of microvascular thrombosis, the condition shows systemic thrombin generation as well as its activation in the circulation and extensive damage to the microvasculature endothelium. DIC with the fibrinolytic phenotype gives rise to oozing-type non-surgical bleeding and greatly affects the prognosis of trauma patients. The coexistences of hypothermia, acidosis, and dilution aggravate DIC and lead to so-called trauma-induced coagulopathy.

He that would know what shall be must consider what has been.

The Analects of Confucius.

Trauma, shock, and disseminated intravascular coagulation: lessons from the classical literature

A trauma patient's survival depends on the ability to control 2 opposing conditions, bleeding at the early phase and thrombosis at a late phase of trauma. The mixed existence of physiological responses for hemostasis and wound healing and pathological hemostatic responses makes it difficult to understand the mechanisms of the 2 stages of coagulopathy after trauma. Traumatic coagulopathy is multifactorial but disseminated intravascular coagulation (DIC) with the fibrinolytic phenotype is the predominant and initiative pathogenesis of coagulopathy at the early stage of trauma. High levels of inflammatory cytokines and severe tissue injuries activate the tissue-factor-dependent coagulation pathway followed by massive thrombin generation and its activation. Low levels of protein C and antithrombin induce insufficient coagulation control and the inhibition of the anticoagulation pathway. Primary and secondary fibrin(ogen)olysis is highly activated by the shock-induced tissue hypoxia and disseminated fibrin formation, respectively. Consumption coagulopathy and severe bleeding are subsequently observed in trauma patients. Persistently high levels of plasminogen activator inhibitor-1 expressed in the platelets and endothelium then change the DIC with the fibrinolytic phenotype into the thrombotic phenotype at approximately 24 to 48 hours after the onset of trauma. All of these changes coincide with the definition of DIC, which can be clearly distinguished from normal responses for hemostasis and wound healing by using sensitive molecular markers and DIC diagnostic criteria such as those outlined by the Japanese Association for Acute Medicine and the International Society on Thrombosis and Haemostasis. Treatments of DIC with the fibrinolytic phenotype involve the surgical repair of the trauma, improvement of shock, and the rapid and sufficient replacement of platelet concentrate, fresh frozen plasma, and depleted coagulation factors. The administration of an antifibrinolytic agent (tranexamic acid) may reduce the risk of death in bleeding trauma patients associated with this type of DIC.

Coagulopathy and the role of recombinant human activated protein C in sepsis and following polytrauma

Recombinant human activated protein C (rhAPC) also known as drotrecogin alfa (activated) has known antithrombotic, anti-inflammatory, and profibrinolytic properties in severe sepsis. Treatment with rhAPC (Xigris) has been shown to reduce mortality in patients with severe sepsis. The lack of any trials of rhAPC in trauma patients means that a definitive recommendation regarding its use in the polytraumatised patient, in whom severe head trauma or other contraindications for the use of rhAPC have been excluded remains controversial at present. This article describes the current evidence of its efficacy and safety in severe sepsis with relation to surgery and trauma.

Contrasting post-traumatic serial changes for D-dimer and PAI-1 in critically injured patients

We measured D-dimer and plasminogen activator inhibitor-1 (PAI-1) activity in 45 trauma patients to assess their efficacy in predicting the post-traumatic hemostatic perturbations. We found the correlation between D-dimer measured by Simpli Red test and ELISA to be highly significant (p=0.0001). The D-dimer ELISA indicated that the serial changes of D-dimer after trauma were variable. However, the increases of D-dimer were associated with clinical conditions of the patient, such as trauma surgery, infections, or thrombotic complications. A significant correlation was found for D-dimer levels measured by ELISA versus the injury severity score (ISS) in all the trauma patients on day 1 (p=0.0153) and on day 2 (p=0.0495). The PAI-1 activity was increased at admission and showed a progessive decline from day 2 onward, and the correlation for the daily decline of PAI-1 was highly significant (p=0.0001). The PAI-1 activity and plasminogen activator activity showed a significant negative correlation on days 1, 2, and 3. PAI-1 activity correlated moderately with D-dimer level only on day 1 (p=0.0569). Three out of forty-five patients developed thrombotic complications: one patient who died from pulmonary embolism and two patients who developed adult respiratory distress syndrome (ARDS). In summary: 1) PAI-1 activity and D-dimer exhibited contrasting serial changes after trauma. 2) There was also a negative correlation between PAI-1 activity and PA activity. 3) A significant correlation of D-dimer with ISS confirms, as might be anticipated, that there is increased activation of the coagulation mechanism in severe injury, and suggests that D-dimer levels may prove useful to screen for patients at strong risks of thrombotic complications.

Blood fibrinolytic activity before and after oral surgery

Blood smaples were collected in cold O.1 M sodium citrate from 30 healthy young persons whose mandibular impacted molars were to be removed. Blood sampling was repeated immediately after operation. Fibrinolytic activity of the euglobin fraction, precipitated at pH 5.9, was measured by the fibrin plate method. Three different fibrinogen solutions were used: 1) bovine fibrinogen, 2) bovine plasminogen-free fibrinogen, and 3) human fibrinogen. The differences between preoperative and postoperative fibrinolytic activity were evaluated. No increase of fibrinolytic activity was seen in general, indicating that oral surgery does not necessarily influence the fibrinolytic activity of the blood. Dividing the patients according to sex or to a long/short surgical procedure did not influence the activity either. However, in four patients who developed alveolitis sicca (dry socket), a significant rise of activity on all the fibrin plats was seen (P less than 0.01) when compared with the variations measured in patients with normal healing. The result suggests that a rise of blood fibrinolytic activity of a certain magnitude during oral surgery may predispose to the devlopement of alveolitis sicca. Four females who took oral contraceptives showed a higher postoperative fibrinolytic activity (P less than 0.05) than the other females. The importance of this observation is to be investigated in further studies.