Antifibrinolytic drugs have become almost ubiquitous in their use during major surgery when bleeding is expected or commonplace. Inhibition of the fibrinolytic pathway after tissue injury has been consistently shown to reduce postoperative or traumatic bleeding. There is also some evidence for a reduction of perioperative blood transfusion. However, evidence of complications associated with exaggerated thrombosis also exists, although this appears to be influenced by the choice of the individual agent and the dose administered. There is controversy over the use of the serine protease inhibitor aprotinin, whose license was recently withdrawn but may shortly become available on the market again. In the UK, tranexamic acid, a tissue plasminogen and plasmin inhibitor, is most commonly used, with evidence for benefit in cardiac, orthopaedic, urological, gynaecological, and obstetric surgery. In the USA, ε-aminocaproic acid, which also inhibits plasmin, is commonly used. We have reviewed the current literature for this increasingly popular class of drugs to support clinical judgement in daily anaesthetic practice.

Group B Streptococcus (GBS) is the leading cause of meningitis in neonates. We have previously shown that plasminogen, once recruited to the GBS cell surface and converted into plasmin by host-derived activators, leads to an enhancement of bacterial virulence. Here, we investigated whether plasmin(ogen) bound at the GBS surface contributes to blood-brain barrier penetration and invasion of the central nervous system. For that purpose, GBS strain NEM316 preincubated with or without plasminogen plus tissue type plasminogen activator was analyzed for the capacity to adhere to, invade and transmigrate the human brain microvascular endothelial cell (hBMEC) monolayer, and to penetrate the central nervous system using a neonatal mouse model. At earlier times of infection, plasmin(ogen)-treated GBS exhibited a significant increase in adherence to and invasion of hBMECs. Later, injury of hBMECs were observed with plasmin(ogen)-treated GBS that displayed a plasmin-like activity. The same results were obtained when hBMECs were incubated with whole human plasma and infected with untreated GBS. To confirm that the observed effects were due to the recruitment and activation of plasminogen on GBS surface, the bacteria were first incubated with epsilon-aminocaproic acid (εACA), an inhibitor of plasminogen binding, and thereafter with plasmin(ogen). A significant decrease in the hBMECs injury that was correlated with a decrease of the GBS surface proteolytic activity was observed. Furthermore, plasmin(ogen)-treated GBS infected more efficiently the brain of neonatal mice than the untreated bacteria, indicating that plasmin(ogen) bound to GBS surface may facilitate the traversal of the blood-brain barrier. A higher survival rate was observed in offspring born from εACA-treated mothers, compared to untreated mice, and no brain infection was detected in these neonates. Our findings suggest that capture of the host plasmin(ogen) by the GBS surface promotes the crossing of the blood-brain barrier and contributes to the establishment of meningitis.

Trauma-induced coagulopathy (TIC) has been recognized as a potential preventable cause of mortality in 40% [1] of civilian deaths and 80% of military casualties [2]. Recent studies indicate that fibrinolysis may be a significant component of TIC in the most severely injured patients [3] and the CRASH2 study [4] has stimulated worldwide interest in this arena. Although treatment is available to prevent plasmin induced hyperfibrinolysis in the forms of aminocaproic acid and tranexamic acid, it is important to confirm the diagnosis of systematic hyperfibrinolysis before subjecting a patient to a potentially thrombogenic agent. Raza et al. [5] have questioned the validity of thrombelastometry (ROTEM) to identify pathologic fibrinolysis in injured patients, but we respectfully caution that their conclusions may be misleading due to a number of reasons. This article is protected by copyright. All rights reserved.

Angiotensin II receptor type I (AT1R) is a G-protein coupled receptor involved in regulation of body water-electrolyte balance and blood pressure. Oxidative stress promotes AT1R oligomerization and hyper-responsiveness to its cognate ligand Ang II. In this study, bivalent Ang II, synthesized by linking with aminocaproic acid (Acp) at the N-terminus, was used to induce AT1R dimerization and hyper-responsiveness in AT1R-expressed human embryonic kidney (AT1R-HEK) cells, determined using image correlation spectroscopy (ICS) and by measuring AT1R-mediated change in intracellular Ca(2+) concentration, respectively. In addition, ICS was employed to determine distribution pattern of cell-surface AT1R and its degree of aggregation when stimulated by monomeric (monovalent) and bivalent Ang II under oxidative stress (100 μM H2O2) condition in comparison with normal (unoxidized) AT1R-HEK cells. Bivalent Ang II induced cell-surface AT1R aggregation/clustering but maintained AT1R normal signaling response under oxidative stress condition, whereas stimulation by monomeric Ang II or a mixture of monomeric and Acp-modified Ang II (used in the synthesis of bivalent form) resulted in AT1R hyper-responsiveness. These results suggest that bivalent ligand (viz. Ang II) provides another strategy in the development of novel drugs specifically designed for attenuating aberrant responsiveness of cognate receptor (AT1R) under pathological (oxidative stress) conditions.

Polymeric micelles are promising carriers for anti-cancer agents due to their small size, ease of assembly, and versatility for functionalization. A current challenge in the use of polymeric micelles is the sensitive balance that must be achieved between stability during prolonged blood circulation and release of active drug at the tumor site. Stimuli-responsive materials provide a mechanism for triggered drug release in the acidic tumor and intracellular microenvironments. In this work, we synthesized a series of dual pH- and temperature-responsive block copolymers containing a poly(ε-caprolactone) (PCL) hydrophobic block with a poly(triethylene glycol) block that were copolymerized with an amino acid-functionalized monomer. The block copolymers formed micellar structures in aqueous solutions. An optimized polymer that was functionalized with 6-aminocaproic acid (ACA) possessed pH-sensitive phase transitions at mildly acidic pH and body temperature. Doxorubicin-loaded micelles formed from these polymers were stable at blood pH (~7.4) and showed increased drug release at acidic pH. In addition, these micelles displayed more potent anti-cancer activity than free doxorubicin when tested in a tumor xenograft model in mice.

To compare the effect of aprotinin with the effect of lysine analogues (tranexamic acid and ε-aminocaproic acid) on early mortality in three subgroups of patients: low, intermediate and high risk of cardiac surgery.We performed a meta-analysis of randomised controlled trials and observational with the following data sources: Medline, Cochrane Library, and reference lists of identified articles. The primary outcome measure was early (in-hospital/30-day) mortality. The secondary outcome measures were any transfusion of packed red blood cells within 24 hours after surgery, any re-operation for bleeding or massive bleeding, and acute renal dysfunction or failure within the selected cited publications, respectively. Out of 328 search results, 31 studies (15 trials and 16 observational studies) included 33,501 patients. Early mortality was significantly increased after aprotinin vs. lysine analogues with a pooled risk ratio (95% CI) of 1.58 (1.13-2.21), p<0.001 in the low (n = 14,297) and in the intermediate risk subgroup (1.42 (1.09-1.84), p<0.001; n = 14,427), respectively. Contrarily, in the subgroup of high risk patients (n = 4,777), the risk for mortality did not differ significantly between aprotinin and lysine analogues (1.03 (0.67-1.58), p = 0.90).Aprotinin may be associated with an increased risk of mortality in low and intermediate risk cardiac surgery, but presumably may has no effect on early mortality in a subgroup of high risk cardiac surgery compared to lysine analogues. Thus, decisions to re-license aprotinin in lower risk patients should critically be debated. In contrast, aprotinin might probably be beneficial in high risk cardiac surgery as it reduces risk of transfusion and bleeding complications.

Multifunctional KGdF4:18%Yb(3+),2%Er(3+) nanoparticles with upconversion fluorescence and paramagnetism are synthesized. The average sizes of the nanoparticles capped with branched polyethyleneimine (PEI) and 6-aminocaproic acid (6AA) are ~14 and ~13 nm, respectively. Our KGdF4 host does not exhibit any phase change with the decrease of particle size, which can prevent the detrimental significant decrease in upconversion luminescence caused by this effect observed in the well-known NaYF4 host. The branched PEI and 6AA capping ligands endow our nanoparticles with water-dispersibility and biocompatibility, which can favor internalization of our nanoparticles into the cytoplasm of HeLa cells and relatively high cell viability. The strong upconversion luminescence detected at the cytoplasm of HeLa cells incubated with the branched PEI-capped nanoparticles is probably attributed to the reported high efficiency of cellular uptake. The magnetic mass susceptibility of our nanoparticle is 8.62 × 10(-5) emu g(-1) Oe(-1). This is the highest value ever reported in trivalent rare-earth ion-doped KGdF4 nanoparticles of small size (≤14 nm), and is very close to that of nanoparticles used as T1 contrast agents in magnetic resonance imaging. These suggest the potential of our KGdF4:Yb(3+),Er(3+) nanoparticles as small-sized multifunctional bioprobes.

We assessed the effect of the topical application of epsilon-aminocaproic antifibrinolytic acid (EACA) on the pericardium of patients submitted to coronary artery bypass graft (CABG) without the use of cardiopulmonary bypass (CPB). This is a prospective, randomized, and double-blind study. We evaluated 26 patients with chronic coronary heart disease indicated for CABG without CPB (EACA and placebo groups). The analysis of the postoperative hematological results showed no difference between groups in hemoglobin and hematocrit. There was no difference between the groups regarding the postoperative bleeding through the drains in the first 24 hours, 48 hours, and accumulated loss until removal of drains. The use of EACA in patients undergoing CABG without CPB presented no difference in the reduction of the amount of bleeding and the need for blood transfusions.

The objective of this study was to determine whether plasmin could induce morphological changes in human glial cells via PAR1. Human glioblastoma A172 cells were cultured in the presence of plasmin or the PAR1 specific activating hexapeptide, SFLLRN. Cells were monitored by flow cytometry to detect proteolytic activation of PAR1 receptor. Morphological changes were recorded by photomicroscopy and apoptosis was measured by annexinV staining. Plasmin cleaved the PAR1 receptor on glial cells at 5 minutes (P = 0.02). After 30 minutes, cellular processes had begun to retract from the basal substratum and by 4 hours glial cells had become detached. Similar results were obtained by generating plasmin de novo from plasminogen. Morphological transformation was blocked by plasmin inhibitors aprotinin or epsilon-aminocaproic acid (P = 0.03). Cell viability was unimpaired during early morphological changes, but by 24 hours following plasmin treatment 22% of glial cells were apoptotic. PAR1 activating peptide SFLLRN (but not inactive isomer FSLLRN) promoted analogous glial cell detachment (P = 0.03), proving the role for PAR1 in this process. This study has identified a plasmin/PAR1 axis of glial cell activation, linked to changes in glial cell morophology. This adds to our understanding of pathophysiological disease mechanisms of plasmin and the plasminogen system in neuroinjury.

Uncontrolled bleeding is an important cause of death in trauma victims. Antifibrinolytic treatment has been shown to reduce blood loss following surgery and may also be effective in reducing blood loss following trauma.To quantify the effects of antifibrinolytic drugs on mortality, vascular occlusive events, surgical intervention and receipt of blood transfusion after acute traumatic injury.We searched the PubMed, Science Citation Index, National Research Register, Zetoc, SIGLE, Global Health, LILACS, and Current Controlled Trials to March 2004 and the Cochrane Injuries Group Specialised Register, CENTRAL, MEDLINE and EMBASE to July 2010.We included all randomised controlled trials of antifibrinolytic agents (aprotinin, tranexamic acid [TXA] and epsilon-aminocaproic acid) following acute traumatic injury.The titles and abstracts identified in the electronic searches were screened by two independent authors to identify studies that had the potential to meet the inclusion criteria. The full reports of all such studies were obtained. From the results of the screened electronic searches, bibliographic searches, and contacts with experts, two authors independently selected trials meeting the inclusion criteria.Four trials met the inclusion criteria, including 20,548 randomised patients. Two trials with a combined total of 20,451 patients assessed the effects of TXA on mortality; TXA reduced the risk of death by 10% (RR=0.90, 95% CI 0.85 to 0.97; P=0.0035). Data from one trial involving 20,211 patients found that TXA reduced the risk of death due to bleeding by 15% (RR=0.85, 95% CI 0.76 to 0.96; P=0.0077). There was evidence that early treatment (≤ 3 hours) was more effective than late treatment (>3 hours). There was no evidence that TXA increased the risk of vascular occlusive events or need for surgical intervention. There was no substantial difference in the receipt of blood transfusion between the TXA and placebo groups. The two trials of aprotinin provided no reliable data.Tranexamic acid safely reduces mortality in bleeding trauma patients without increasing the risk of adverse events. TXA should be given as early as possible and within three hours of injury, as treatment later than this is unlikely to be effective. Further trials are needed to determine the effects of TXA in patients with isolated traumatic brain injury.