Enhanced Anti-Tumor Effect of Folate-Targeted FA-AMA-hyd-DOX Conjugate in a Xenograft Model of Human Breast Cancer

Folate-aminocaproic acid-doxorubicin (FA-AMA-hyd-DOX) was firstly synthesized by our group. It was indicated that FA-AMA-hyd-DOX was pH-responsive, and had strong cytotoxicity on a folate receptor overexpressing cell line (KB cells) in vitro. The aim of our study was to further explore the potential use of FA-AMA-hyd-DOX as a new therapeutic drug for breast cancer. The cellular uptake and the antiproliferative activity of the FA-AMA-hyd-DOX in MDA-MB-231 cells were measured. Compared with DOX, FA-AMA-hyd-DOX exhibited higher targeting ability and cytotoxicity to FR-positive tumor cells. Subsequently, the tissue distribution of FA-AMA-hyd-DOX was studied, and the result confirmed that DOX modified by FA can effectively increase the selectivity of drugs in vivo. After determining the maximum tolerated dose (MTD) of FA-AMA-hyd-DOX in MDA-MB-231 tumor-bearing nude mice, the antitumor effects and the in vivo safety of FA-AMA-hyd-DOX were systematically evaluated. The data showed that FA-AMA-hyd-DOX could effectively increase the dose of DOX tolerated by tumor-bearing nude mice and significantly inhibit MDA-MB-231 tumor growth in vivo. Furthermore, FA-AMA-hyd-DOX treatment resulted in almost no obvious damage to the mice. All the positive data suggest that FA-targeted FA-AMA-hyd-DOX is a promising tumor-targeted compound for breast cancer therapy.

Termination of bleeding by a specific, anticatalytic antibody against plasmin

BACKGROUND

Excessive, plasmin-mediated fibrinolysis augments bleeding and contributes to death in some patients. Current therapies for fibrinolytic bleeding are limited by modest efficacy, low potency, and off-target effects.

OBJECTIVES

To determine whether an antibody directed against unique loop structures of the plasmin protease domain may have enhanced specificity and potency for blocking plasmin activity, fibrinolysis, and experimental hemorrhage.

METHODS

The binding specificity, affinity, protease cross-reactivity and antifibrinolytic properties of a monoclonal plasmin inhibitor antibody (Pi) were examined and compared with those of epsilon aminocaproic acid (EACA), which is a clinically used fibrinolysis inhibitor.

RESULTS

Pi specifically recognized loop 5 of the protease domain, and did not bind to other serine proteases or nine other non-primate plasminogens. Pi was ~7 logs more potent in neutralizing plasmin cleavage of small-molecule substrates and >3 logs more potent in quenching fibrinolysis than EACA. Pi was similarly effective in blocking catalysis of a small-molecule substrate as α2 -antiplasmin, which is the most potent covalent inhibitor of plasmin, and was a more potent fibrinolysis inhibitor. Fab or chimerized Fab fragments of Pi were equivalently effective. In vivo, in a humanized model of fibrinolytic surgical bleeding, Pi significantly reduced bleeding to a greater extent than a clinical dose of EACA.

CONCLUSIONS

A mAb directed against unique loop sequences in the protease domain is a highly specific, potent, competitive plasmin inhibitor that significantly reduces experimental surgical bleeding in vivo.

Temporary inhibition of the plasminogen activator inhibits periosteal chondrogenesis and promotes periosteal osteogenesis during appendicular bone fracture healing

INTRODUCTION

Aminocaproic acid is approved as an anti-fibrinolytic for use in joint replacement and spinal fusion surgeries to limit perioperative blood loss. Previous animal studies have demonstrated a pro-osteogenic effect of aminocaproic acid in spine fusion models. Here, we tested if aminocaproic acid enhances appendicular bone healing and we sought to uncover the effect of aminocaproic acid on osteoprogenitor cells (OPCs) during bone regeneration.

METHODS

We employed a well-established murine femur fracture model in adult C57BL/6J mice after receiving two peri-operative injections of aminocaproic acid. Routine histological assays, biomechanical testing and micro-CT analyses were utilized to assess callus volume, and strength, progenitor cell proliferation, differentiation, and remodeling in vivo. Two disparate ectopic transplantation models were used to study the effect of the growth factor milieu within the early fracture hematoma on osteoprogenitor cell fate decisions.

RESULTS

Aminocaproic acid treated femur fractures healed with a significantly smaller cartilaginous callus, and this effect was also observed in the ectopic transplantation assays. We hypothesized that aminocaproic acid treatment resulted in a stabilization of the early fracture hematoma, leading to a change in the growth factor milieu created by the early hematoma. Gene and protein expression analysis confirmed that aminocaproic acid treatment resulted in an increase in Wnt and BMP signaling and a decrease in TGF-β-signaling, resulting in a shift from chondrogenic to osteogenic differentiation in this model of endochondral bone formation.

CONCLUSION

These experiments demonstrate for the first time that inhibition of the plasminogen activator during fracture healing using aminocaproic acid leads to a change in cell fate decision of periosteal osteoprogenitor cells, with a predominance of osteogenic differentiation, resulting in a larger and stronger bony callus. These findings may offer a promising new use of aminocaproic acid, which is already FDA-approved and offers a very safe risk profile.

Using antifibrinolytics in the peripartum period - concern for a hypercoagulable effect?

INTRODUCTION

Although antifibrinolytic agents are used to prevent and treat hemorrhage, there are concerns about a potential increased risk for peripartum venous thromboembolism. We sought to determine the impact of tranexamic acid and ɛ-aminocaproic acid on in vitro clotting properties in pregnancy.

METHODS

Blood samples were obtained from healthy pregnant, obese, and preeclamptic pregnant women (n = 10 in each group) prior to delivery as well as from healthy non-pregnant controls (n = 10). Maximum clot firmness (MCF) and clotting time (CT) were measured using rotation thromboelastometry in the presence of tranexamic acid (3, 30, or 300 μg/mL) or ɛ-aminocaproic acid (30, 300, or 3000 μg/mL). ANOVA and regression analyses were performed.

RESULTS

Mean whole blood MCF was significantly higher in healthy pregnant vs. non-pregnant women (66.5 vs. 57.5 mm, p < 0.001). Among healthy pregnant women, there was no significant difference between mean MCF (whole blood alone, and with increasing tranexamic acid doses = 66.5, 66.1, 66.4, 66.3 mm, respectively; p = 0.25) or mean CT (409, 412, 420, 424 sec; p = 0.30) after addition of tranexamic acid. Similar results were found using ɛ-aminocaproic acid. Preeclamptic women had a higher mean MCF after the addition of ɛ-aminocaproic acid and tranexamic acid (p = 0.05 and p = 0.04, respectively) compared to whole blood alone.

CONCLUSIONS

Pregnancy is a hypercoagulable state, as reflected by an increased MCF compared to non-pregnant women. Addition of antifibrinolytic therapy in vitro does not appear to increase MCF or CT for non-pregnant, pregnant, and obese women. Whether antifibrinolytics are safe in preeclampsia may require further study.

Collagen Degradation by Host-derived Enzymes during Aging

Incompletely infiltrated collagen fibrils in acid-etched dentin are susceptible to degradation. We hypothesize that degradation can occur in the absence of bacteria. Partially demineralized collagen matrices (DCMs) prepared from human dentin were stored in artificial saliva. Control specimens were stored in artificial saliva containing proteolytic enzyme inhibitors, or pure mineral oil. We retrieved them at 24 hrs, 90 and 250 days to examine the extent of degradation of DCM. In the 24-hour experimental and 90- and 250-day control specimens, we observed 5- to 6-μm-thick layers of DCM containing banded collagen fibrils. DCMs were almost completely destroyed in the 250-day experimental specimens, but not when incubated with enzyme inhibitors or mineral oil. Functional enzyme analysis of dentin powder revealed low levels of collagenolytic activity that was inhibited by protease inhibitors or 0.2% chlorhexidine. We hypothesize that collagen degradation occurred over time, via host-derived matrix metalloproteinases that are released slowly over time.

Epsilon Aminocaproic Acid Pretreatment Provides Neuroprotection Following Surgically Induced Brain Injury in a Rat Model

Neurosurgical procedures can damage viable brain tissue unintentionally by a wide range of mechanisms. This surgically induced brain injury (SBI) can be a result of direct incision, electrocauterization, or tissue retraction. Plasmin, a serine protease that dissolves fibrin blood clots, has been shown to enhance cerebral edema and hemorrhage accumulation in the brain through disruption of the blood brain barrier. Epsilon aminocaproic acid (EAA), a recognized antifibrinolytic lysine analogue, can reduce the levels of active plasmin and, in doing so, potentially can preserve the neurovascular unit of the brain. We investigated the role of EAA as a pretreatment neuroprotective modality in a SBI rat model, hypothesizing that EAA therapy would protect brain tissue integrity, translating into preserved neurobehavioral function. Male Sprague-Dawley rats were randomly assigned to one of four groups: sham (n = 7), SBI (n = 7), SBI with low-dose EAA, 150 mg/kg (n = 7), and SBI with high-dose EAA, 450 mg/kg (n = 7). SBI was induced by partial right frontal lobe resection through a frontal craniotomy. Postoperative assessment at 24 h included neurobehavioral testing and measurement of brain water content. Results at 24 h showed both low- and high-dose EAA reduced brain water content and improved neurobehavioral function compared with the SBI groups. This suggests that EAA may be a useful pretherapeutic modality for SBI. Further studies are needed to clarify optimal therapeutic dosing and to identify mechanisms of neuroprotection in rat SBI models.

Epsilon-aminocaproic acid improves postrecirculation hemodynamics by reducing intraliver activated protein C consumption in orthotopic liver transplantation

BACKGROUND

Activated protein C (APC) is related to regulating the inflammatory response and hemodynamic stability upon reperfusion in cardiac operations and orthotopic liver transplantation (OLT). Epsilon-aminocaproic acid (EACA) is frequently used to treat fibrinolysis during OLT. It also has inhibitory effects related to the inflammatory response. However, it remains to be determined whether EACA can attenuate intraliver APC consumption and improve hemodynamic stability after reperfusion during OLT.

METHODS

Fifty-nine recipients were randomized to receive either EACA (150 mg kg(-1) given intravenously prior to incision, followed by 15 mg kg(-1) h(-1) infusion until 2 h after the graft reperfusion) or the same volume of saline. Blood samples to assess plasma APC and protein C were obtained immediately before and after reperfusion from the inferior caval effluent or the portal veins for calculation of transliver differences (Δ). Hemodynamics and vasoactive medication use during the reperfusion period were observed in both groups.

RESULTS

No transhepatic changes in protein C were found in either group. Immediately after reperfusion, a marked intraliver consumption of APC was noted in all recipients (P < 0.001), and intraliver consumption of APC in the control group was greater than that in the EACA-treated group (P < 0.05). Fewer requirements for vasoactive medication use after reperfusion and better initial graft function were noted in the EACA-treated group (P < 0.05).

CONCLUSIONS

EACA can attenuate intraliver APC consumption and improve hemodynamic stability after reperfusion and initial graft function during OLT.

[A case of allergic contact dermatitis due to unit dose type purified sodium hyaluronate ophthalmic solution]

BACKGROUND

We report a patient who developed allergic contact dermatitis after using a purified sodium hyaluronate ophthalmic solution (Hyalein Mini) recognized as being extremely safe.

CASE REPORT

A 67-year-old woman presented to our hospital with a chief complaint of poor visual acuity. She had dry eye, cataract and ptosis in both eyes, and underwent crystalline lens reconstruction and ptosis surgery in both eyes. Postoperatively, her dry eye showed exacerbation and she developed Sjögren's syndrome. Keratoconjunctival epithelial disorders were controllable with lacrimal punctum plugs, Hyalein Mini and 0.1% fluorometholone ophthalmic suspension. The patient, however, repeatedly developed blepharitis, and allergic contact dermatitis was diagnosed with a positive patch test to epsilon-aminocaproic acid, an excipient in Hyalein Mini. Since switching to an ophthalmic solution without epsilon-aminocaproic acid, the allergic contact dermatitis has not recurred.

CONCLUSION

When the same ophthalmic solution is used for chronic disease for a long time, it should be noted that allergic contact dermatitis may develop.

[Effect of epsilon-aminocaproic acid, cyclophosphamide and their combination on the growth of autochthonous sarcomas of mice induced by benzo(a)pyrene]

Antifibrinolytic drug epsilon-aminocaproic acid as a therapeutic form (5% solution in saline) was tested for antitumor activity in the autochthonous subcutaneous tumors of mice, induced by benzo (a) pyrene, in monotherapy mode (instead animals received drinking water) and in combination with cyclophosphamide, which was administered once intraperitoneally in the dose of 200 mg/kg. In the control groups, treated with drinking water and saline solution instead of water, there was no stabilization and reduction in tumor volume, while in the groups receiving epsilon-aminocaproic acid, cyclophosphamide and their combination statistically significantly in comparison with the control groups there was increased the proportion of tumors with not changed or reduced volume; epsilon-aminocaproic acid enhanced the antitumor effect of cyclophosphamide. The data obtained are for further study of the antitumor effect of epsilon-aminocaproic acid.

Aprotinin, but not ε-aminocaproic acid and tranexamic acid, exerts neuroprotection against excitotoxic injury in an in vitro neuronal cell culture model

OBJECTIVE

Lack of availability of aprotinin has resulted in increased clinical use of the alternative antifibrinolytic agents, ε-aminocaproic acid (EACA) and tranexamic acid (TXA), which are known to be associated with an increased risk of seizures. In contrast, aprotinin has previously been demonstrated to be neuroprotective through suppression of excitotoxicity-mediated neuronal degeneration via the extracellular plasminogen/plasmin system. This study compares the effect of antifibrinolytic agents on neuronal and mixed glial/neuronal cell cultures.

METHODS

Mixed cortical cultures containing neuronal and glial cells were prepared from fetal mice and plated on a layer of confluent astrocytes from postnatal pups. A primary neuronal culture was obtained from the same gestational stage and plated in multiwall vessels. Slowly triggered excitotoxicity was induced by 24-hour exposure to 12.5 mM N-methyl-D-aspartate (NMDA). Apoptotic neuronal cell death was induced by exposure of primary neural cultures to 24 hours of serum deprivation.

RESULTS

Compared with NMDA alone, no significant changes in cell death were observed for any dose of TXA or EACA in mixed cultures. Conversely, a clinical dose of aprotinin significantly reduced cell death by -31% on average. Aprotinin reduced apoptotic neuronal cell death from 75% to 37.3%, and to 34.1% at concentrations of 100 and 200 kIU/mL, respectively, and significantly decreased neuronal nuclear damage. These concentrations of aprotinin significantly inhibited caspase 9 and 3/7 activations; 250 kIU/mL aprotinin exerted maximal protection on primary cortical neurons.

CONCLUSIONS

In contrast to aprotinin, EACA and TXA exert no protective effect against excitotoxic neuronal injury that can occur during cardiac surgery.

Effect of short peptides containing lysine and epsilon-aminocaproic acid on fibrinolytic activity of plasmin and topoisomerase II action on supercoiled DNA

Effects of eight short peptides containing lysine and epsilon-aminocaproic acid (EACA) on prolongation of the clot lysis time, as well as hemolytic and antibacterial activities were investigated. Interaction with plasmids pBR322 and pUC19 with the use of ethidium bromide assay and determination of influence on the activity of topoisomerase I and II were also tested. Examined compounds inhibited fibrinolytic activity of plasmin and five of them were more active than EACA. Amides of dipeptides were most active antifibrinolytics (IC50 < 0.2 mM). According to the obtained data, the significant inhibition of fibrinolytic activity of plasmin was not associated with hemolytic effects. Examined compounds did not show antibacterial activity (MIC > 512 mg/L). DNA binding effects determined with the use of ethidium bromide were weak for all peptides and similar to those observed with EACA. Six compounds inhibited topoisomerase II action on supercoiled DNA.

Cellular response to substrate rigidity is governed by either stress or strain

Cells sense the rigidity of their substrate; however, little is known about the physical variables that determine their response to this rigidity. Here, we report traction stress measurements carried out using fibroblasts on polyacrylamide gels with Young's moduli ranging from 6 to 110 kPa. We prepared the substrates by employing a modified method that involves N-acryloyl-6-aminocaproic acid (ACA). ACA allows for covalent binding between proteins and elastomers and thus introduces a more stable immobilization of collagen onto the substrate when compared to the conventional method of using sulfo-succinimidyl-6-(4-azido-2-nitrophenyl-amino) hexanoate (sulfo-SANPAH). Cells remove extracellular matrix proteins off the surface of gels coated using sulfo-SANPAH, which corresponds to lower values of traction stress and substrate deformation compared to gels coated using ACA. On soft ACA gels (Young's modulus <20 kPa), cell-exerted substrate deformation remains constant, independent of the substrate Young's modulus. In contrast, on stiff substrates (Young's modulus >20 kPa), traction stress plateaus at a limiting value and the substrate deformation decreases with increasing substrate rigidity. Sustained substrate strain on soft substrates and sustained traction stress on stiff substrates suggest these may be factors governing cellular responses to substrate rigidity.

Plasmin inhibitors prevent leukocyte accumulation and remodeling events in the postischemic microvasculature

Clinical trials revealed beneficial effects of the broad-spectrum serine protease inhibitor aprotinin on the prevention of ischemia-reperfusion (I/R) injury. The underlying mechanisms remained largely unclear. Using in vivo microscopy on the cremaster muscle of male C57BL/6 mice, aprotinin as well as inhibitors of the serine protease plasmin including tranexamic acid and ε-aminocaproic acid were found to significantly diminish I/R-elicited intravascular firm adherence and (subsequent) transmigration of neutrophils. Remodeling of collagen IV within the postischemic perivenular basement membrane was almost completely abrogated in animals treated with plasmin inhibitors or aprotinin. In separate experiments, incubation with plasmin did not directly activate neutrophils. Extravascular, but not intravascular administration of plasmin caused a dose-dependent increase in numbers of firmly adherent and transmigrated neutrophils. Blockade of mast cell activation as well as inhibition of leukotriene synthesis or antagonism of the platelet-activating-factor receptor significantly reduced plasmin-dependent neutrophil responses. In conclusion, our data suggest that extravasated plasmin(ogen) mediates neutrophil recruitment in vivo via activation of perivascular mast cells and secondary generation of lipid mediators. Aprotinin as well as the plasmin inhibitors tranexamic acid and ε-aminocaproic acid interfere with this inflammatory cascade and effectively prevent postischemic neutrophil responses as well as remodeling events within the vessel wall.

Cytotoxic activity of epsilon-aminocaproylamino acids in breast cancer MCF-7 and fibroblast cell lines

The effect of H-EACA-L-Cys(S-Bzl)-OH, H-EACA-L-Leu-OH, H-EACA-L-Nle-OH and EACA on the viability of MCF-7 and fibroblast cells was examined. The antibacterial activity of these compounds was also tested. H-EACA-L-Leu-OH and H-EACA-L-Nle-OH showed cytotoxic activity against MCF-7 and fibroblast cell lines, particularly in the highest studied 20 mM concentration. None of the examined dipeptides showed antibacterial activity.

Short peptides containing L-lysine and epsilon-aminocaproic acid as potential plasmin inhibitors

Eight short peptides containing L-lysine and epsilon-aminocaproic acid were obtained and their effect on the amidolytic activities of plasmin, thrombin and trypsin was examined. Tripeptide amide Boc-EACA-L-Lys-EACA-NH2 was the most effective and specific plasmin inhibitor.

Effect of epsilon-aminocaproyl-S-benzyl-L-cysteine on the activity of plasminogen activators

The effect of epsilon-aminocaproyl-S-benzyl-L-cysteine on the activation of plasminogen by t-PA. streptokinase and urokinase has been examined using fibrinolytic method. The obtained results have been compared with the obtained results for epsilon-aminocaproic acid and trans-4-(aminomethyl)cyclohexanecarboxylic acid. The inhibition of the plasminogen activation determined with the use of epsilon-aminocaproyl-S-benzyl-L-cysteine was weaker than the inhibition determined by using antifibrinolytic aminoacids.

Epsilon-aminocaproic acid (EACA)

Epsilon-aminocaproic acid (EACA) is a synthetic inhibitor of the plasmin-plasminogen system. It is the only potent antifibrinolytic agent which is commercially available in the United States. Effective blood levels of the drug are readily obtainable with either oral or intravenous administration, with very high levels of the drug being found in the urine since the drug is greatly concentrated during excretion. EACA has been used in numerous clinical situations to control bleeding and has been claimed to be an effective agent in subarachnoid hemorrhage, genitourinary bleeding from many causes, and in dental surgery in hemophiliacs. It may also be effective in several less well studied situations such as prophylaxis of bleeding episodes in hemophiliacs, control of menorrhagia, gastrointestinal bleeding, obstetrical bleeding and in bleeding following cardiac and thoracic surgery. Major side effects from EACA include hypotension, cardiac arrhythmias, rhabdomyolysis, and generation of thrombi. The incidence of thrombotic events secondary to the inhibition of the fibrinolytic system by EACA is unknown, but may be particularly increased in those patients who have some underlying predisposition to develop thrombosis. The potential benefit from the use of EACA must be weighed against the possible serious complications, particularly the development of widespread thrombi.

Increased incidence of acute kidney injury with aprotinin use during cardiac surgery detected with urinary NGAL

BACKGROUND

Use of aprotinin has been associated with acute kidney injury after cardiac surgery. Neutrophil gelatinase-associated lipocalin (NGAL) is a novel, very sensitive marker for renal injury. Urinary NGAL may be able to detect renal injury caused by aprotinin. This study determined if the use of aprotinin is associated with an increased incidence of acute kidney injury and increased levels of urinary NGAL.

METHODS

In this prospective, observational study 369 patients undergoing cardiac surgery were enrolled. 205 patients received aprotinin and 164 received epsilon amino-caproic acid intraoperatively. Urinary NGAL was measured before and immediately after cardiac surgery and 3, 18 and 24 h later. The association of aprotinin use with the incidence of acute kidney injury (increase of serum creatinine >0.5 mg/dl) and NGAL levels was determined using logistic and linear regression models.

RESULTS

51 of 205 patients (25%) who received aprotinin developed acute kidney injury compared to 19 of 164 patients (12%) who received epsilon amino-caproic acid (p = 0.0013). Aprotinin use was associated with a two-fold higher risk of acute kidney injury when adjusted for potential confounders (age, Parsonnet score, preoperative serum creatinine, cardiopulmonary bypass and cross-clamp times; multiple logistic regression: OR = 2.164; CI (95%) = 1.102 to 4.249; p = 0.0249. Urinary NGAL was 19 times higher immediately after cardiopulmonary bypass and 18 times higher 3 h later in patients who had received aprotinin (postoperative: 19.23; CI (95%) = 12.60 to 29.33; p < 0.0001; 3 h post-cardiopulmonary bypass 18.67; CI (95%) = 11.45 to 30.43; p < 0.0001).

CONCLUSIONS

Postoperative urinary NGAL - a novel marker for renal injury - is increased in cardiac surgical patients receiving aprotinin compared to patients receiving epsilon amino-caproic acid. These results further support the hypothesis that aprotinin may cause renal injury. The substantial rise of urinary NGAL associated with aprotinin use may in part be due to aprotinin blocking the uptake of NGAL by megalin/gp330 receptors in the proximal tubules.

Pharmacokinetics and pharmacodynamics of ε-aminocaproic acid in horses

OBJECTIVE

To determine the pharmacokinetics and pharmacodynamics of epsilon-aminocaproic acid (EACA), including the effects of EACA on coagulation and fibrinolysis in healthy horses.

ANIMALS

6 adult horses.

PROCEDURES

Each horse received 3.5 mg of EACA/kg/min for 20 minutes, i.v. Plasma EACA concentration was measured before (time 0), during, and after infusion. Coagulation variables and plasma alpha(2)-antiplasmin activity were evaluated at time 0 and 4 hours after infusion; viscoelastic properties of clot formation were assessed at time 0 and 0.5, 1, and 4 hours after infusion. Plasma concentration versus time data were evaluated by use of a pharmacokinetic analysis computer program.

RESULTS

Drug disposition was best described by a 2-compartment model with a rapid distribution phase, an elimination half-life of 2.3 hours, and mean residence time of 2.5 +/- 0.5 hours. Peak plasma EACA concentration was 462.9 +/- 70.1 microg/mL; after the end of the infusion, EACA concentration remained greater than the proposed therapeutic concentration (130 microg/mL) for 1 hour. Compared with findings at 0 minutes, EACA administration resulted in no significant change in plasma alpha(2)-antiplasmin activity at 1 or 4 hours after infusion. Thirty minutes after infusion, platelet function was significantly different from that at time 0 and 1 and 4 hours after infusion. The continuous rate infusion that would maintain proposed therapeutic plasma concentrations of EACA was predicted (ie, 3.5 mg/kg/min for 15 minutes, then 0.25 mg/kg/min).

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that EACA has potential clinical use in horses for which improved clot maintenance is desired.

Study on enhancement of fibronectin-mediated bacillus Calmette-Guérin attachment to urinary bladder wall in rabbits

To clarify whether intravesical usage of fibrin clot stabilizer epsilon-aminocaproic acid (EACA) or p-aminomethyl benzoic acid (PAMBA) and different injuries enhance fibronectin (FN)-mediated bacillus Calmette-Guérin (BCG) attachment to bladder wall. Thirty New Zealand male white rabbits were randomly divided into five groups and the bladder wall of each rabbit was injured by electrocautery, cryocautery or knife cutting on left lateral wall, right lateral wall and posterior wall in different groups, respectively. Different drug was instilled into the bladder: Group A: pure PBS; B: PBS and radiolabeled BCG ((3)H-BCG); C: EACA and (3)H-BCG; D: PAMBA and (3)H-BCG; E: heparin and (3)H-BCG. After instillation, each injured and non-injured bladder wall were surgically harvested and digested. The quantity of BCG attachment was detected by liquid scintillation counter (scintillation times per min, STPM). Quantity of BCG attachment to injured bladder wall was significantly (P < 0.01) greater than that of non-injured one, no matter which injury was performed. The BCG attachment to bladder wall in Group C or Group D was significantly (P < 0.05) greater than that of Group B. The quantity of BCG attachment to bladder of Group E was significantly (P < 0.05) less than that of Group B, C and D, respectively. Intravesical instillation of fibrin clot stabilizer (PAMBA, EACA) enhances FN-mediated BCG attachment to bladder wall while heparin inhibits this process. Injuries; e.g., cutting, cryocautery or electrocautery of bladder wall can significantly increase BCG attachment to the bladder wall.

Plasmin decreases the BH3-only protein BimEL via the ERK1/2 signaling pathway in hepatocytes

Since the signal transduction mechanisms responsible for liver regeneration mediated by the plasminogen/plasmin system remain largely undetermined, we have investigated whether plasmin regulates the pro-apoptotic protein Bim(EL) in primary hepatocytes. Plasmin bound to hepatocytes in part via its lysine binding sites (LBS). Plasmin also triggered phosphorylation of ERK1/2 without cell detachment. The plasmin-induced phosphorylation of ERK1/2 was inhibited by the LBS inhibitor epsilon-aminocaproic acid (EACA), the serine protease inhibitor aprotinin, and the MEK inhibitor PD98059. DFP-inactivated plasmin failed to phosphorylate ERK1/2. Plasmin temporally decreased the starvation-induced expression of Bim(EL) and activation of caspase-3 via the ERK1/2 signaling pathway, resulting in an enhancement of cell survival. The amount of mRNA for Bim increased 1 day after the injection of CCl(4) in livers of plasminogen knockout (Plg-KO) and the wild-type (WT) mice. The increase in Bim(EL) protein persisted for at least 7 days post-injection in livers of Plg-KO mice, whereas WT mice showed an increase in Bim(EL) protein 1 day after the injection. Plg-KO and WT mice showed notable phosphorylation of ERK1/2 7 and 3 days after the injection of CCl(4), respectively. Our data suggest that the plasminogen/plasmin system could decrease Bim(EL) expression via the ERK1/2 signaling pathway during liver regeneration.

Proteolysis on maturing enamel surface, as shown by gel-coating methods

Degradation of enamel matrix proteins, and their removal during early maturation, is critical for the growth of large enamel crystals in the subsequent processes of enamel maturation. In this study, we sought to demonstrate, using in vivo zymography, the exact sites of proteolysis in maturing enamel and its relationship to the overlying ameloblasts. The maturing enamel surfaces of rat and bovine incisors were exposed and painted either with pre-exposed autoradiographic emulsion or with densely fluorescein-conjugated (DQ) gelatin. After a few hours, photographic development of the emulsion revealed alternate black and white banding patterns over the maturing enamel surface. DQ gelatin also revealed similar banding patterns of fluorescent and non-fluorescent regions. White, powdery areas of emulsion and fluorescent bands of DQ gelatin both corresponded to the areas of ruffle-ended ameloblasts, at least up to the mid stages of enamel maturation, implicating a predominant contribution of ruffle-ended ameloblasts in the degradation of enamel matrix proteins. Powdery white bands in autoradiographic emulsion shifted from the areas of ruffle-ended to smooth-ended ameloblasts in late maturation in both bovine and rat incisors and were not influenced by proteinase inhibitors or heat inactivation, implicating non-enzymatic interactions. DQ gelatin, in fact, did not generate any fluorescence in such smooth-ended ameloblast regions.

Effects of Tissucol and epsilon aminocaproic acid in the healing process following dental extraction in dehydrated rats

A histological study was conducted of the alveolar bone healing process following tooth extraction of dehydrated rats after the implantation of fibrin adhesive (TISSUCOL) associated to previous irrigation of the wound with a 5% epsilon aminocaproic acid solution (EACA). Seventy two rats were used, divided into three groups receiving different treatments after the surgical procedure. In group I, the gingival mucosa was sutured after extraction of the right upper incisor. In groups II and III, chronic dehydration was produced by water deprivation for 9 days (3 days in the preoperative period and 6 days in the postoperative period). In the animals of Group II, after tooth extraction, the gingival mucosa was sutured in the same way as performed in group I. In group III, after extraction, the dental socket was irrigated with 5% EACA, followed by implantation of the fibrin adhesive (TISSUCOL). The mucosa was sutured in the same way as performed in the other groups. At 3, 7, 15 and 21 postoperative days, the animals were sacrificed in number of 6 for each group. Specimens containing the dental socket were removed and fixed in 10% formalin and decalcified in an equal part formic acid and sodium citrate solution. After routine processing, the specimens were embedded in paraffin for microtomy. We obtained 6 microm semi-serial slices that were stained with hematoxylin and eosin for histological evaluation. The results showed that the water deprivation in the pre- and postoperative periods caused a delay in the alveolar bone healing process. The use of the fibrin adhesive (TISSUCOL) produced an improvement in the fibrinolytic picture caused by dehydration.

Synthesis and Enhancing Effect of Transkarbam 12 on the Transdermal Delivery of Theophylline, Clotrimazole, Flobufen, and Griseofulvin

PURPOSE

Dodecyl-6-aminohexanoate (DDEAC) is a transdermal permeation enhancer with excellent activity, low toxicity, and no dermal irritation. We hypothesized that DDEAC reacts with air CO2 to form a two-chain ammonium carbamate--Transkarbam 12 (T12)--which is responsible for the enhancing effect.

METHODS

DDEAC and T12 were synthesized, their structures were confirmed by spectral methods, and their enhancing activity was studied using the Franz diffusion cell and human skin. A high-performance liquid chromatography method was developed for determination of T12, and its biodegradability was evaluated using porcine esterase.

RESULTS

Only the carbamate salt T12 was responsible for the high enhancing activity; DDEAC tested under argon to avoid reaction with CO2 was inactive. T12 enhanced transdermal permeation of drugs covering a wide range of physicochemical properties, including theophylline (enhancement ratio up to 55.6), clotrimazole (7.7), flobufen (5.0), and griseofulvin (24). The activity was pH-dependent, further confirming the importance of the carbamate structure. The metabolization of T12 followed a second-order kinetics with t(1/2) = 31 min.

CONCLUSION

Our results indicate that T12 is a promising biodegradable permeation enhancer for a wide range of drugs, and the structurally novel group of carbamate enhancers warrants further investigation.

Requirement of the enzymatic and signaling activities of plasmin for phorbol-ester-induced scattering of colon cancer cells

Colon cancer progression is associated with the activation of protein kinase C (PKC), the downregulation of functional E-cadherin and an increased expression of the serine protease urokinase (u-PA) and its receptor (u-PAR). HT29-M6 intestinal epithelial cells represent an in vitro model to study colon cancer progression. These cells are induced to scatter and to invade by phorbol esters. Using proteolytic and cell signaling inhibitors, we show that HT29-M6 cells require plasminogen for the acquisition of the scattering response to PMA. Our results indicate that, prior to inducing a state of competency for plasminogen-dependent scattering, PMA triggers an ordered succession of events where upregulation of the activity of u-PA precedes proteolysis of u-PAR and active degradation of the extracellular matrix (ECM). These events poise HT29-M6 cells to a scatter-competent state that allows the subsequent localized proteolytic activation of plasminogen to plasmin, required for the execution of scattering. Finally, we show that, in addition to its enzymatic activity directed at the degradation of ECM, plasmin generates an intracellular signal resulting in the phosphorylation of ERK 1/2. For a full motogenic activity, plasmin requires this signal since the use of a MEK inhibitor (PD98059) specifically blocks the plasmin-dependent phase of cell scattering. Our observations suggest that plasmin exerts a dual role in PMA-induced scattering of HT29-M6 cells, one directed extracellularly to promote proteolysis of the ECM and one directed to generate intracellular signaling.

Specific conformational changes of plasminogen induced by chloride ions, 6-aminohexanoic acid and benzamidine, but not the overall openness of plasminogen regulate, production of biologically active angiostatins

The overall conformation of plasminogen depends upon the presence of anions and molecules such as AHA (6-aminohexanoic acid) and BZ (benzamidine). The purpose of the present study was to determine the effect of conformation on the initial and secondary cleavages of plasminogen to generate active angiostatins. Plasminogen was digested with the physiologically relevant neutrophil elastase in one of the four Tris/acetate buffers: buffer alone or buffer plus NaCl, AHA or BZ. The initial cleavage of Glu1-plasminogen was much slower in the tight NaCl-induced alpha-conformation, fastest in the intermediate BZ-induced beta-conformation and intermediate both in the control and in the AHA-induced open gamma-conformation. Although the buffer system determined the relative amounts of the initial cleavage products, the same four cleavage sites were utilized under all conditions. A fifth major initial cleavage within the protease domain was observed in the presence of BZ. N-terminal peptide cleavage required for angiostatin formation occurred as either the initial or the secondary cleavage. Angiostatins were generated fastest in the presence of BZ and slowest in the presence of NaCl. Both the initial and secondary cleavages were affected by the modifying agents, indicating that they influence the conformation of both Glu-plasminogen and the initial cleavage products. The angiostatins produced under the different conditions inhibited proliferation of human umbilical-vein endothelial cells. These results suggest that plasminogen conversion into active angiostatins is dependent more on the specific conformation changes induced by the various modifying reagents rather than on the overall openness of the molecule.

The fibrinolytic system facilitates tumor cell migration across the blood-brain barrier in experimental melanoma brain metastasis

BACKGROUND

Patients with metastatic tumors to the brain have a very poor prognosis. Increased metastatic potential has been associated with the fibrinolytic system. We investigated the role of the fibrinolytic enzyme plasmin in tumor cell migration across brain endothelial cells and growth of brain metastases in an experimental metastatic melanoma model.

METHODS

Metastatic tumors to the brain were established by direct injection into the striatum or by intracarotid injection of B16F10 mouse melanoma cells in C57Bl mice. The role of plasminogen in the ability of human melanoma cells to cross a human blood-brain barrier model was studied on a transwell system.

RESULTS

Wild type mice treated with the plasmin inhibitor epsilon-aminocaproic acid (EACA) and plg-/- mice developed smaller tumors and survived longer than untreated wild type mice. Tumors metastasized to the brain of wild type mice treated with EACA and plg-/- less efficiently than in untreated wild type mice. No difference was observed in the tumor growth in any of the three groups of mice. Human melanoma cells were able to cross the human blood-brain barrier model in a plasmin dependent manner.

CONCLUSION

Plasmin facilitates the development of tumor metastasis to the brain. Inhibition of the fibrinolytic system could be considered as means to prevent tumor metastasis to the brain.

Effect of epsilon-aminocaproylamino acids on fibrin formation

Effect of three epsilon-aminocaproylamino acids with significant antifibrinolytic activity on polymerization of fibrin monomer, clot retraction, fibrin structure, prothrombin consumption and thrombin activity was examined. epsilon-Aminocaproyl-L-norleucine and epsilon-aminocaproyl-L-leucine were weak inhibitors of thrombin activity and epsilon-aminocaproyl-L-norleucine slightly inhibited polymerization of fibrin monomers.

Lipoprotein(a) in atherosclerotic plaques recruits inflammatory cells through interaction with Mac‐1 integrin

Lipoprotein(a) [Lp(a)], consisting of LDL and the unique constituent apolipoprotein(a) [apo(a)], which contains multiple repeats resembling plasminogen kringle 4, is considered a risk factor for the development of atherosclerotic disorders. However, the underlying mechanisms for the atherogenicity of Lp(a) are not completely understood. Here, we define a novel function of Lp(a) in promoting inflammatory cell recruitment that may contribute to its atherogenicity. Through its apo(a) moiety Lp(a) specifically interacts with the beta2-integrin Mac-1, thereby promoting the adhesion of monocytes and their transendothelial migration in a Mac-1-dependent manner. Interestingly, the interaction between Mac-1 and Lp(a) was strengthened in the presence of proatherogenic homocysteine and was blocked by plasminogen/angiostatin kringle 4. Through its interaction with Mac-1, Lp(a) induced activation of the proinflammatory transcription factor NFkappaB, as well as the NFkappaB-related expression of prothrombotic tissue factor. In atherosclerotic coronary arteries Lp(a) was found to be localized in close proximity to Mac-1 on infiltrating mononuclear cells. Taken together, our data demonstrate that Lp(a), via its apo(a) moiety, is a ligand for the beta2-integrin Mac-1, thereby facilitating inflammatory cell recruitment to atherosclerotic plaques. These observations suggest a novel mechanism for the atherogenic properties of Lp(a).

Trehalose and 6-aminohexanoic acid stabilize and renature glucose-6-phosphate dehydrogenase inactivated by glycation and by guanidinium hydrochloride

A number of naturally occurring small organic molecules, primarily involved in maintaining osmotic pressure in the cell, display chaperone-like activity, stabilizing the native conformation of proteins and protecting them from various kinds of stress. Most of them are sugars, polyols, amino acids or methylamines. In addition to their intrinsic protein-stabilizing activity, these small organic stress molecules regulate the activity of some molecular chaperones, and may stabilize the folded state of proteins involved in unfolding or in misfolding diseases, such as Alzheimer's and Parkinson's diseases, or alpha1-antitrypsin deficiency and cystic fibrosis, respectively. Similar to molecular chaperones, most of these compounds have no substrate specificity, but some specifically stabilize certain proteins, e.g., 6-aminohexanoic acid (AHA) stabilizes apolipoprotein A. In the present work, the capacity of 6-aminohexanoic acid to stabilize non-specifically other proteins is demonstrated. Both trehalose and AHA significantly protect glucose-6-phosphate dehydrogenase (G6PD) against glycation-induced inactivation, and renatured enzyme already inactivated by glycation and by guanidinium hydrochloride (GuHCl). To the best of our knowledge, there are no data on the effect of these compounds on protein glycation. The correlation between the recovery of enzyme activity and structural changes indicated by fluorescence spectroscopy and Western blotting contribute to better understanding of the protein stabilization mechanism.

Esters of 6-aminohexanoic acid as skin permeation enhancers: The effect of branching in the alkanol moiety

In order to investigate the effect of branching and cyclization in the hydrophobic part of skin permeation enhancers, 17 novel branched-chain and cyclic 6-aminohexanoic acid esters were prepared. Their permeation enhancing activity was evaluated in vitro using human skin and theophylline as a model drug, and compared to that of the corresponding linear-chain analogues. The results showed that chain branching and cyclization has a negative influence on the enhancing activity of 6-aminohexanoates. For example, the enhancement ratios (ERs) of dodecan-1-yl, dodecan-2-yl, dodecan-4-yl, and cyclododecyl ester were 39.7, 29.3, 3.1, and 2.2, respectively. No significant change in the optimum length of the chain was observed. Dodecan-2-yl 6-aminohexanoate, the most active branched derivative, still maintains a remarkable enhancing activity (ER 29.3). Presumably, the relatively small degree of branching of these molecules does not prevent them from interacting with the lipid components of the stratum corneum. However, a higher degree of branching, cyclization of the chain, and presence of an aromatic ring resulted in a loss of activity.

Aprotinin and epsilon aminocaproic acid are effective in reducing blood loss after primary total hip arthroplasty--a prospective randomized double-blind placebo-controlled study

A prospective randomized double-blind placebo-controlled study was undertaken to determine the efficacy and mechanism of action of two antifibrinolytic drugs aprotinin and epsilon aminocaproic acid (EACA) in reducing blood loss in primary unilateral total hip arthroplasty (THA). Aprotinin was administered as a bolus of 2 x 10(6) kallikrein inhibitor units (KIU) followed by 0.5 x 10(6) KIU h(-1) for 3 h, EACA was given as 10 g over 30 min followed by 5 g over 3 h. The median postoperative blood loss 24 h postoperatively was reduced from 450 mL in the placebo group to 180 mL for aprotinin (60% reduction, P < 0.001) and to 210 mL for EACA (53% reduction, P < 0.01). In this population, there was no reduction in the perioperative transfusion requirements. The mechanism of both drugs was independent of platelets as indicated by flow cytometric measurement of change of their expression of P-selectin, platelet-monocyte aggregates, V/Va and CD40 ligand. There were no thrombotic or infective complications and no adverse events were attributable to use of either drug. Infusion of either aprotinin or EACA at the doses described is a safe and effective means of reducing blood loss after THA. These therapies provide a means of reducing blood loss in THA patients.

Clot penetration and fibrin binding of amediplase,a chimeric plasminogen activator (K2 tu-PA)

Amediplase (K(2) tu-PA) is a hybrid plasminogen activator, consisting of the kringle 2 domain of alteplase and the protease domain of urokinase. The objective of this study was to determine the in vitro clot penetration of amediplase in relation to its fibrin binding and to compare the properties with those of alteplase. The clot lysis activity of amediplase in internal clot lysis models (both purified system and plasma system) was about 10 times less than that of alteplase. The clot lysis activity of amediplase in an external clot lysis model (plasma system) was similar to that of alteplase at therapeutic concentrations around 1 micro g/ml. The fibrin-clot binding properties of amediplase and alteplase were studied in a purified system as well as in a plasma system. In both systems amediplase bound to fibrin although to a significantly lower extent than alteplase. The binding of amediplase or alteplase did not increase during plasmin-mediated degradation of fibrin. The binding of amediplase was fully inhibited by epsilon-aminocaproic acid, indicating that the observed binding was specific and occurred via the lysine binding site in the kringle of amediplase. Clot penetration was studied during pressure-driven fluid permeation using syringes containing plasma clots. Amediplase was able to enter the clot without significant hindrance, while alteplase was concentrated on the top of the plasma clot and hardly entered into the inner parts of the clot. Diffusion-driven clot penetration was studied during clot lysis using confocal microscopy. Alteplase was detected on or close to the clot surface, while two-chain urokinase, which has no affinity to fibrin, was also detected deep inside the clot. Amediplase showed a penetration behaviour, which was distinct from that of alteplase and similar to that of two-chain urokinase. We concluded that the fibrin binding of amediplase is moderate and does not hinder clot penetration under permeation-driven or diffusion-driven transport conditions. Enhanced clot penetration, especially in large clots, could allow a more efficient lysis during thrombolytic therapy.

Cultured muscle cells from insulin-resistant type 2 diabetes patients have impaired insulin, but normal 5-amino-4-imidazolecarboxamide riboside-stimulated, glucose uptake

Impaired insulin action is a characteristic feature of type 2 diabetes. The study aims were to investigate whether after prolonged culture skeletal muscle cultures from insulin-resistant, type 2 diabetic patients (taking >100 U insulin/d) displayed impaired insulin signaling effects compared with cultures from nondiabetic controls and to determine whether retained abnormalities were limited to insulin action by studying an alternative pathway of stimulated glucose uptake. Studies were performed on myotubes differentiated for 7 d between passages 4 and 6. Insulin-stimulated glucose uptake (100 nm; P < 0.05) and insulin-stimulated glycogen synthesis (1 nm; P < 0.01) were significantly impaired in the diabetic vs. control cultures. Protein kinase B (PKB) expression and phosphorylated PKB levels in response to insulin stimulation (20 nm) were comparable in the diabetic and control cultures. 5-Amino-4-imidazolecarboxamide riboside (AICAR) mimics the effect of exercise on glucose uptake by activating AMP-activated protein kinase. There was no difference in AICAR (2 mm)-stimulated glucose uptake between diabetic vs. control myotube cultures (P = not significant). In conclusion, diabetic muscle cultures retain signaling defects after prolonged culture that appear specific to the insulin signaling pathway, but not involving PKB. This supports an intrinsic abnormality of the diabetic muscle cells that is most likely to have a genetic basis.

Nonlysine-analog plasminogen modulators promote autoproteolytic generation of plasmin(ogen) fragments with angiostatin-like activity

We recently discovered several nonlysine-analog conformational modulators for plasminogen. These include SMTP-6, thioplabin B and complestatin that are low molecular mass compounds of microbial origin. Unlike lysine-analog modulators, which increase plasminogen activation but inhibit its binding to fibrin, the nonlysine-analog modulators enhance both activation and fibrin binding of plasminogen. Here we show that some nonlysine-analog modulators promote autoproteolytic generation of plasmin(ogen) derivatives with its catalytic domain undergoing extensive fragmentation (PMDs), which have angiostatin-like anti-endothelial activity. The enhancement of urokinase-catalyzed plasminogen activation by SMTP-6 was followed by rapid inactivation of plasmin due to its degradation mainly in the catalytic domain, yielding PMD with a molecular mass ranging from 68 to 77 kDa. PMD generation was observed when plasmin alone was treated with SMTP-6 and was inhibited by the plasmin inhibitor aprotinin, indicating an autoproteolytic mechanism in PMD generation. Thioplabin B and complestatin, two other nonlysine-analog modulators, were also active in producing similar PMDs, whereas the lysine analog 6-aminohexanoic acid was inactive while it enhanced plasminogen activation. Peptide sequencing and mass spectrometric analyses suggested that plasmin fragmentation was due to cleavage at Lys615-Val616, Lys651-Leu652, Lys661-Val662, Lys698-Glu699, Lys708-Val709 and several other sites mostly in the catalytic domain. PMD was inhibitory to proliferation, migration and tube formation of endothelial cells at concentrations of 0.3-10 microg.mL(-1). These results suggest a possible application of nonlysine-analog modulators in the treatment of cancer through the enhancement of endogenous plasmin(ogen) fragment formation.

The fibrinolytic system attenuates vascular tone: effects of tissue plasminogen activator (tPA) and aminocaproic acid on renal microcirculation

1. The renal medulla is a major source of plasminogen activators (PA), recently shown to induce vasodilation in vitro. Treatment with PA inhibitors has been associated with renal dysfunction, suggesting compromised renal microvasculature. We investigated the impact of the PA inhibitor epsilon amino-caproic acid (EACA) upon vascular tone in vitro, and studied the effect of both tPA and EACA upon intrarenal hemodynamics in vivo. 2. In vitro experiments were carried out in isolated aortic rings and with cultured vascular smooth muscle cells. Studies of renal microcirculation and morphology were conducted in anesthetized Sprague-Dawley rats. 3. In isolated aortic rings, EACA (but not the other inhibitors of the fibrinolytic system PAI-1 or alpha-2 antiplasmin) reduced the half-maximal effective concentration of phenylephrine (PE) required to induce contraction (from 32 nm in control solution to 2 and 0.1 nm at EACA concentrations of 1 and 10 microm, respectively). Using reteplase (retavase) in the same model, we also provide evidence that the vasoactivity of tPA is in part kringle-dependent. In cultured vascular smooth muscle cells, Ca(2+) internalization following PE was enhanced by EACA, and retarded by tPA. 4. In anesthetized rats, EACA (150 mg x kg(-1)) did not affect systemic blood pressure, total renal or cortical blood flow. However, the outer medullary blood flow declined 12+/-2% below the baseline (P<0.03). By contrast, tPA (2 mg x kg(-1)), transiently increased outer medullary blood flow by 8+/-5% (P<0.02). Fibrin microthrombi were not found within the renal microvasculature in EACA-treated animals. 5. In conclusion, both fibrinolytic and antifibrinolytic agents modulate medullary renal blood flow with reciprocal effects of vasodilation (PA) and vasoconstriction (EACA). In vitro studies suggest that these hemodynamic responses are related to direct modulation of the vascular tone.

Effects of epsilon-aminocaproic acid and aprotinin on leukocyte-platelet adhesion in patients undergoing cardiac surgery

BACKGROUND

The administration of aprotinin during cardiopulmonary bypass (CPB) is hypothesized to decrease activation of leukocytes and platelets and possibly reduce their adhesion. Although epsilon-aminocaproic acid (EACA) shares the ability of aprotinin to inhibit excessive plasmin activity after CPB, its effect on leukocyte and platelet activation and leukocyte-platelet (heterotypic) adhesion is largely unknown. This study was performed to determine the relative effectiveness of the antifibrinolytics, aprotinin and EACA, at reducing leukocyte and platelet activation and leukocyte-platelet conjugate formation in patients undergoing CPB.

METHODS

Thirty-six patients scheduled to undergo cardiac surgery with CPB were randomized in a double-blind fashion to receive EACA, aprotinin, or saline (placebo). Markers of plasmin activity (D-dimer concentrations), platelet activation (CD62P), leukocyte activation (CD11b), and leukocyte-platelet adhesion (monocyte- and neutrophil-platelet conjugates) were measured before, during, and after CPB.

RESULTS

Platelet CD62P (P-selectin), monocyte CD11b, and monocyte-platelet conjugates were all significantly increased (compared with baseline) in the saline group during and after CPB. Despite equivalent reductions in D-dimer formation in patients receiving EACA (P < 0.0001) and aprotinin (P < 0.0001), decreases in platelet CD62P and monocyte CD11b expression were incomplete (not significantly different from saline control). In contrast, peak monocyte-platelet conjugate formation was significantly reduced by both EACA (P = 0.026) and aprotinin (P = 0.039) immediately after CPB.

CONCLUSIONS

EACA seems to be as effective as aprotinin at reducing peak monocyte-platelet adhesion after CPB. Furthermore, inhibition of excessive plasmin activity seems to influence monocyte-platelet adhesion. The findings suggest that monocyte-platelet conjugate formation may be a useful marker of monocyte and platelet activation in this clinical setting.

Effects of epsilon-aminocaproiloaminoacids on the amidolytic activity of tissue plasminogen activator, urokinase and kallikrein

Effect of three epsilon-aminocaproylaminoacids with a significant antifibrinolytic activity on amidolytic activity of tissue plasminogen activator (t-PA), urokinase and kallikrein was examined. epsilon-Aminocaproyl-S-benzyl)-L-cysteine and epsilon-aminocaproyl-L-norleucine were weak inhibitors of kallikrein. Weak activation of t-PA activity was observed at high concentration of the tested compounds. Only one of the examined dipeptides was a weak inhibitor of amidolytic activity of urokinase.

The effect of some epsilon-aminocaproic acid derivatives on platelet responses

epsilon-Aminocaproic acid (EACA) is a synthetic low molecular drug with antifibrinolytic activity. However, treatment with this drug can be incidentally associated with an increased thrombotic tendency. The aim of the present work was to test synthetic EACA derivatives for their antiplatelet activities. We investigated the effect of three EACA derivatives with antifibrinolytic activity: I. epsilon-aminocaproyl-L-leucine hydrochloride (HCl*H-EACA-L-Leu-OH), II. epsilon-aminocaproyl-L-(S-benzyl)-cysteine hydrochloride (HCl*H-EACA-L-Cys(S-Bzl)-OH) and III. epsilon-aminocaproyl-L-norleucine (H-EACA-L-Nle-OH) on platelet responses (aggregation and adhesion) and on their integrity. It was found that: 1. as judged by LDH release test, none of the tested compounds, up to 20 mM, was toxic to platelets, 2. in comparison with EACA, all the synthetic derivatives inhibited much stronger the ADP- and collagen-induced aggregation of platelets suspended in plasma (platelet rich plasma) and aggregation of these cells in whole blood, 3. EACA and its derivatives exerted a similar inhibitory effect on the thrombin-induced adhesion of platelets to fibrinogen-coated surfaces. Since platelet activation and blood coagulation are tightly associated processes, the antiplatelet properties of EACA derivatives are expected to indicate reduced thrombotic properties of these derivatives compared to EACA.

Mechanism of the stimulatory effect of 6-aminohexanoic acid on plasminogen activation by streptokinase or tissue plasminogen activator: The role of chloride

Studies were conducted on the mechanism of the stimulatory effect of 6-aminohexanoic acid (6-AH) during the in vitro activation of human glutamic plasminogen (Glu-Plg) by streptokinase or by tissue plasminogen activator (t-PA) and the possible role of the addition of physiological concentrations of NaCl to the buffer solution. Enhancement by 6-AH was investigated by measuring the rate of plasmin generation using chromogenic substrate H-D-glu-phe-lys-pNA (S-2403). Control studies using plasmin showed that the addition of 6-AH at concentrations below 20 mM did not significantly affect the initial rate of the amidolytic activity of plasmin with or without the addition of NaCl to 0.05 M Tris buffer (pH 7.4). On the other hand, addition of NaCl to the buffer slowed down the initial rate of activation of Glu-Plg by streptokinase or by t-PA while increasing the percent enhancement by 6-AH when compared with the controls. The ratios of the initial rates of plasmin generation in the presence or in the absence of 6-AH were plotted against the inverse of the volume fraction of Glu-Plg, streptokinase or t-PA after serial dilutions. The results showed that when the activation reactions were performed in 50 mM of Tris buffer (pH 7.4), the enhancements by 6-AH were related to its interaction with streptokinase or t-PA, while using the same Tris buffer containing 0.6 % NaCl, the enhancements by 6-AH were related to its interaction with both Glu-Plg and streptokinase or t-PA. However, upon increasing the NaCl to 0.9%, the results showed that the enhancements by 6-AH of the activation of Glu-Plg by streptokinase or t-PA were related to its interaction with Glu-Plg. The results suggested that changes in the concentrations of NaCl play a regulatory role during the activation process.

Alteration in serum and bone component findings induced in streptozotocin-diabetic rats is restored by zinc acexamate

The effect of zinc acexamate in streptozotocin (STZ)-induced diabetic rats was investigated. Rats received a single subcutaneous administration of STZ (6.0 mg/100 g body weight), and the animals were orally administered once daily for 14 days with zinc acexamate (2.5, 5 or 10 mg/100 g body weight). The administration of STZ caused a significant increase in serum glucose, triglyceride and calcium levels and a significant decrease in body weight, serum zinc and inorganic phosphorus levels, indicating diabetic condition. Moreover, calcium content, alkaline phosphatase activity and deoxyribonucleic acid (DNA) content in the femoral-diaphyseal and -metaphyseal tissues were significantly reduced in STZ-diabetic rats. The change in these serum and bone components of STZ-diabetic rats was significantly restored by the oral administration of zinc acexamate (2.5, 5 or 10 mg Zn/100 g body weight). The restoration of bone components was not seen by the oral administration of zinc sulfate (2.5 mg Zn/100 g) for 14 days. Moreover, when the femoral-diaphyseal and -metaphyseal tissues obtained at 14 days after STZ administration were cultured for 48 h in a medium containing either vehicle or zinc acexamate (10(-5) M), the femoral calcium content and alkaline phosphatase activity were significantly increased in vitro. The effect of zinc acexamate was completely abolished in the presence of cycloheximide (10(-6) M), an inhibitor of protein synthesis. The present study demonstrates that the oral administration of zinc acexamate has a preventive effect on STZ-induced diabetic condition in rats, and that it can restorate bone loss of STZ-induced diabetes in vivo.

Preventive effect of zinc acexamate administration in streptozotocin-diabetic rats: Restoration of bone loss

The preventive effect of zinc compounds on bone loss in streptozotocin (STZ)-diabetic rats was investigated. Rats received a single subcutaneous administration of STZ (6.0 mg/100 g body weight), and 7, 14 or 21 days later the animals were sacrificed by bleeding. STZ administration caused a significant decrease in body weight and a significant increase in serum glucose and triglyceride levels, indicating diabetic condition. Femoral-diaphyseal and -metaphyseal alkaline phosphatase activity, calcium and deoxyribonucleic acid (DNA) contents were significantly decreased by STZ administration, showing that diabetic condition causes bone loss. Zinc sulfate (2.5 mg Zn/100 g) or zinc acexamate (2.5 mg Zn/100 g) was orally administered once daily for 14 days to rats received a single subcutaneous administration of STZ (6.0 mg/100 g). STZ administration-induced increase in serum glucose and triglyceride levels and decrease in body weight, femoral-diaphyseal and -metaphyseal alkaline phosphatase activity, DNA and calcium contents were significantly prevented by the administration of zinc acexamate. The preventive effect of zinc sulfate on bone components was not seen. The present results demonstrate that the administration of zinc acexamate has a preventive effect on bone loss in STZ-diabetic rats in vivo.

FTIR determination of ligand-induced secondary and tertiary structural changes in bovine plasminogen

Human plasminogen undergoes a large tertiary structural change in the presence of lysine derivatives (e.g. ε-amino caproic acid, EACA). This change facilitates human plasminogen activation by human plasminogen activators, resulting in elevated blood plasmin levels. It is hypothesized that this structure-function relationship is similar for bovine plasminogen. The objectives of this study were to investigate the effect of the ligand EACA on the secondary structure of plasminogen (bovine, human, and rabbit) and the tertiary structure of bovine plasminogen using Fourier-transform infrared spectroscopy (FTIR). Spectra of plasminogen, EACA, and a mixture of plasminogen and EACA in water and deuterium were collected using FTIR. Fourier-self deconvoluted spectra in the amide I region (1700–1600 cm−1) were used to detect changes in secondary structure of plasminogen after EACA addition. Change in bovine plasminogen tertiary structure was determined by comparing ratios of amide II (1600–1500 cm−1) to amide I bond intensities over time for samples in deuterium. No differences in secondary structure were observed for any plasminogen in the presence of EACA; however, addition of EACA significantly changed tertiary structure of bovine plasminogen. This tertiary structural change indicates a transition from a folded to an unfolded state, which could be more easily converted to plasmin. These results are consistent with reported human plasminogen studies using neutron scattering (tertiary structure) and circular dichroism (secondary structure) methods.

A ligand-induced conformational change in apolipoprotein(a) enhances covalent Lp(a) formation

Lipoprotein(a) (Lp(a)) assembly proceeds via a two-step mechanism in which initial non-covalent interactions between apolipoprotein(a) (apo(a)) and low density lipoprotein precede disulfide bond formation. In this study, we used analytical ultracentrifugation, differential scanning calorimetry, and intrinsic fluorescence to demonstrate that in the presence of the lysine analog epsilon-aminocaproic acid, apo(a) undergoes a substantial conformational change from a "closed" to an "open" structure that is characterized by an increase in the hydrodynamic radius (approximately 10%), an alteration in domain stability, as well as a decrease in tryptophan fluorescence. Although epsilon-aminocaproic acid is a well characterized inhibitor of the non-covalent interaction between apo(a) and low density lipoprotein, we report the novel observation that this ligand at low concentrations (100 microm-1 mm) significantly enhances covalent Lp(a) assembly by altering the conformation of apo(a). We developed a model for the kinetics of Lp(a) assembly that incorporates the conformational change as a determinant of the efficiency of the process; this model quantitatively explains our experimental observations. Interestingly, an analogous conformational change has been previously described for plasminogen resulting in an increase in the hydrodynamic radius, an increase in tryptophan fluorescence, and an acceleration of the rate of plasminogen activation. Although the functions of apo(a) and plasminogen have diverged considerably, elements of structural and conformational homology have been retained leading to similar regulation of two unrelated biological processes.

The effect of fucoidan, heparin and cyanogen bromide-fibrinogen on the activation of human glutamic-plasminogen by tissue plasminogen activator

Earlier studies on the stimulatory effect of fucoidan, heparin, and cyanogen bromide (CNBr)-fibrinogen digest on the in-vitro activation of glutamic type plasminogen by tissue plasminogen activator, which were performed using subphysiologic ionic strengths of buffers, gave inconsistent results because of the variation in the ionic strengths of the buffers used. Studies were therefore conducted on the effect of these cofactors using 0.05 mol/l Tris buffer containing a physiologic concentration of sodium chloride. The double reciprocal plots of the activation of glutamic type plasminogen by tissue plasminogen activator in the presence of fucoidan and 6-aminohexanoic acid (6-AH) or heparin and 6-AH showed a four- to six-fold increase in K(cat), while the K(m) remained unchanged. On the other hand, there was greater than six-fold lowering of K(m) from 0.213 to 0.035 micromol/l in the presence of CNBr-fibrinogen, while K(cat) was only slightly increased. The ratios of the initial rate of plasmin generation in the presence or absence of the cofactors were plotted against the inverse of the volume fraction of glutamic type plasminogen or of tissue plasminogen activator after serial dilution. The results suggested that the enhancements by fucoidan and 6-AH or CNBr-fibrinogen were due to their interactions directed towards glutamic type plasminogen, while for heparin and 6-AH, the interaction was directed towards tissue plasminogen activator. Circular dichroism studies in the near ultraviolet range (250-308 nm) showed that 6-AH enhanced the circular dichroism spectra of glutamic type plasminogen around certain chromophores, while fucoidan and heparin had no effect, suggesting that the enhancement by the cofactors may be related to the favorable conformational changes of glutamic type plasminogen by 6-AH.

Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation

Apolipoprotein[a] (apo[a]) is a large disulfide linked glycoprotein synthesized by hepatocytes. We have examined the role of disulfide bond formation in the processing of apo[a] using human and rat hepatoma cells expressing apo[a] isoforms containing varying numbers of kringle 4 (K4) domains, following treatment with DTT. Hepatoma cells expressing 6- or 9-K4 isoforms revealed approximately 90% inhibition of apo[a] secretion following DTT treatment, although larger isoforms containing 13- or 17-K4 domains demonstrated continued secretion (up to 30% of control values), suggesting that a fraction of the larger isoforms is at least partially DTT resistant. Wash-out experiments demonstrated that these effects were completely reversible for all isoforms studied, with no enhanced degradation associated with prolonged intracellular retention. DTT treatment was associated with enhanced binding of apo[a] with the endoplasmic reticulum-associated chaperone proteins calnexin, calreticulin, and BiP, which was reversible upon DTT removal. The chemical chaperone 6-aminohexanoic acid, previously demonstrated by others to rescue defective apo[a] secretion associated with alterations in glycosylation, failed to alter the secretion of apo[a] following DTT treatment. The demonstration that DTT modulates apo[a] secretion in a manner influenced by both the type and number of K4 repeats extends understanding of the mechanisms that regulate its exit from the endoplasmic reticulum.

Anti-plasminogen autoantibodies from plasma of patients with systemic lupus erythematosus having anti-phospholipid antibody syndrome: isolation and some immunochemical properties

Blood plasma samples from patients with systemic lupus erythematosus having the anti-phospholipid antibody syndrome were found to contain anti-plasminogen antibodies of the IgG class. The titers of anti-plasminogen autoantibodies of the IgG class were elevated in these patients compared with normal controls. Part of the pool of IgG anti-plasminogen antibodies reacts with an epitope in the lysine-binding sites of plasminogen. Anti-plasminogen IgG isolated from patients' blood plasma is specific only for a native epitope of human plasminogen passively adsorbed on immunosorbent micro-titration plate. As shown by enzyme immunoassay, autoantibodies to plasminogen of the IgG class cross-react with human fibrinogen.

Candida albicans binds human plasminogen: identification of eight plasminogen-binding proteins

Several microbial pathogens augment their invasive potential by binding and activating human plasminogen to generate the proteolytic enzyme plasmin. Yeast cells and cell wall proteins (CWP) of the human pathogenic fungus Candida albicans bound plasminogen with a K(d) of 70 +/- 11 nM and 112 +/- 20 nM respectively. Bound plasminogen could be activated to plasmin by mammalian plasminogen activators; no C. albicans plasminogen activator was detected. Binding of plasminogen to CWP and whole cells was inhibited by epsilon ACA, indicating that binding was predominantly to lysine residues. Candida albicans mutant strains defective in protein glycosylation did not show altered plasminogen binding, suggesting that binding was not mediated via a surface lectin. Binding was sensitive to digestion by basic carboxypeptidase, implicating C-terminal lysine residues in binding. Proteomic analysis identified eight major plasminogen-binding proteins in isolated CWP. Five of these (phosphoglycerate mutase, alcohol dehydrogenase, thioredoxin peroxidase, catalase, transcription elongation factor) had C-terminal lysine residues and three (glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase and fructose bisphosphate aldolase) did not. Activation of plasminogen could potentially increase the capacity of this pathogenic fungus for tissue invasion and necrosis. Although surface-bound plasmin(ogen) degraded fibrin, no direct evidence for a role in invasion of endothelial matrix or in penetration and damage of endothelial cells was found.

[Role of lysine binding sites in activation of plasminogen by streptokinase]

The function of lysine-binding sites in kringle domains K1-4 and K5 of plasminogen (Pg) during its activation by streptokinase (SK) was studied. Activation rates of Glu- and Lys-Pg exceed activation rate of mini- and micro-Pg 26 and 40 times, respectively. 6-Animohexanoic acid (6-AHA) in concentrations from 10(-5) to 10(-2) M inhibits activation of Glu-, Lys- and mini-Pg and does not impact the activation of micro-Pg. Complete inhibition of Lys-Pg activation occurs with presence of 10(-3) M 6-AHA while 90% inhibition of mini-Pg activation and 70% inhibition of Glu-Pg activation occur with 10(-2) M 6-AHA. Isolated kringles K1-3 and K4 of Pg inhibit activation of Glu-Pg by SK and concentrations [I]50 are 4.0 and 8.1 x 10(-6) M, respectively. Catalytic activity of Glu-Pg-SK, Lys-Pg-SK and Pm-SK complexes with respect to S 2251 is not inhibited by 6-AHA in concentrations from 10(-5) to 10(-2) M. Activation of substrate Pg by Pm-SK complex is also inhibited by 6-AHA in concentrations from 10(-5) to 10(-2) M; however, this effect of inhibition is significantly weaker than that with activation by SK. Cleavage of C-terminal Lys or chemical modification of NH2-groups of amino acid residues in SK molecule also results in the decrease of the Glu-Pg activation rate. Lysin-binding sites in K1-4 and K5 of Pg molecule are important at different steps of Pg activation process which includes formation of equimolar complex; structural reorganizations resulted in formation of active center in Pg; and binding of substrate Pg with Pg-SK complex. Lysin-binding sites in K1-4 of Pg are necessary for maintenance of high rate of Pg activation by SK.