Efficacy and safety of tranexamic acid in elderly patients with femoral neck fracture treated with hip arthroplasty: A systematic review and meta-analysis.

BACKGROUND: Elderly patients with femoral neck fracture have high perioperative blood loss according to the trauma and hip arthroplasty surgery. Tranexamic acid is a fibrinolytic inhibitor and has been widely used in hip fracture patients to against perioperative anemia. The aim of the present meta-analysis was to evaluate the efficacy and safety of Tranexamic acid (TXA) in elderly patients with femoral neck fracture undergoing hip arthroplasty. METHODS: We performed search using Pubmed, EMBASE, Cochrane Reviews, and Web of Science databases to identify all relevant research studies published from inception to June 2022. Randomized controlled studies and high-quality cohort studies that reported the perioperative use of TXA in patients with femoral neck fractures treated with arthroplasty, and made a comparison with the control group were included. Meta-analysis was performed using Review Manager 5.3 to assess the efficacy and safety of TXA. Subgroup analysis was conducted to further investigate the impact caused by surgery types and administration routes on the efficacy and safety outcomes. RESULTS: Five randomized controlled trials (RCTs) and eight cohort studies published from January 2015 to June 2022 were included in this meta-analysis. The results showed significant reductions in the rate of allogeneic blood transfusion, total blood loss (TBL) and postoperative hemoglobin (Hb) drop in the TXA group compared with the control group, while no significant difference was found in the intraoperative blood loss, postoperative drainage, hospital length of stay (LOS), re-admission rate, and wound complications between the two groups. The incidence of thromboembolic events and mortality showed no significant difference. Subgroup analysis indicated that surgery types and administration routes did not change the overall tendency. CONCLUSION: The current evidence shows that both intravascular administration (IV) and topical administration of TXA can significantly decrease the perioperative transfusion rate and TBL without increasing the risk of thromboembolic complications in elderly patients with femoral neck fracture.

Cytotoxicity and Effect of Topical Application of Tranexamic Acid on Human Fibroblast in Spine Surgery.

OBJECTIVE: In spinal surgery, considerable blood loss is increasingly treated with the local application of tranexamic acid (TXA). However, little is known about its cytotoxicity and effect on human fibroblasts. This study was to identify the effect of TXA solution on human fibroblast at different concentrations and exposure times in vitro. METHODS: To mimic the actual clinical situation, human fibroblasts were subjected to both limited and chronic exposure to various clinically relevant concentrations of TXA to mimic different ways of topical administration. At time points after treatment, the viability, proliferation, apoptosis, collagen synthesis, adhesion, and migration of fibroblasts were analyzed in vitro. RESULTS: Limited exposure (10 minutes) to a high concentration of TXA (100 mg/mL) did not affect the viability, proliferation, and apoptosis of fibroblasts, and chronic exposure to low concentration of TXA (≤12.5 mg/mL) exerted little effect on viability, proliferation, apoptosis, collagen synthesis, adhesion, and migration of human fibroblasts (P > 0.05). However, the chronic exposure to a high concentration of TXA (≥25 mg/mL) can inhibit the viability, proliferation, collagen synthesis, adhesion and migration, and induce apoptosis of fibroblasts. CONCLUSIONS: Although limited exposure to high concentration of TXA and chronic exposure to low concentration of TXA exerted little effect on fibroblasts, chronic exposure to high concentration of TXA can lead to fibroblast injury.

Cytotoxicity and effect on wound re-epithelialization after topical administration of tranexamic acid.

Background: Topical administration of tranexamic acid (TXA) reduces bleeding from surgical wounds similarly to intravenous use, but with negligible risk of adverse systemic events. Topical use is expanding, but is off-label. Surgeons lack guidelines regarding safe topical dosages and modes of administration. The effects of topical TXA on skin cells and wound healing are unknown. This study investigated whether topical TXA might be cytotoxic or affect wound re-epithelialization. Methods: Human keratinocytes and fibroblast cell cultures and an ex vivo human skin wound model were subjected to both short (limited) and long (chronic) exposure to various clinically relevant concentrations of TXA to mimic different modalities of topical administration. Cytotoxicity and effects on wound re-epithelialization were evaluated. Results: In cell culture, toxicity from chronic exposure was associated with increasing concentration and exposure time. Limited exposure to TXA did not cause significant cytotoxicity even at high concentrations. Re-epithelialization was completely absent in wounds chronically exposed to TXA concentrations of 25 mg/ml or above, and 50-100 mg/ml induced epidermolysis of normal epithelium, possibly by a non-toxic mechanism. Wound re-epithelialization was slightly delayed, but not impaired, by limited exposure to 100 mg/ml or chronic exposure to 6·25 mg/ml. Conclusion: Although short exposure to even high concentrations of topical TXA seems well tolerated in vitro, prolonged exposure can be cytotoxic and may affect wound re-epithelialization. Surgeons should adjust the TXA concentration to the planned mode of topical administration in clinical practice.

Antecedentes: La administración tópica de ácido tranexámico (tranexamic acid, TXA) reduce la hemorragia de las heridas quirúrgicas de forma equivalente a su uso endovenoso, pero con un riesgo insignificante de eventos adversos sistémicos. El uso tópico se está expandiendo, pero se realiza fuera de indicación. Los cirujanos no disponen de directrices sobre las dosis para uso tópico seguras y las formas de administración. Se desconocen los efectos del TXA tópico sobre las células de la piel y sobre la curación de las heridas. Nos propusimos investigar si el TXA tópico puede ser citotóxico o afectar la reepitelización de la herida. Métodos: Los cultivos de queratinocitos humanos y fibroblastos y un modelo ex vivo humano de herida en la piel se sometieron a una exposición corta (limitada) y larga (crónica) de varias concentraciones clínicamente relevantes de TXA para simular diferentes modalidades de administración tópica. Se evaluaron la citotoxicidad y los efectos sobre la reepitelización de la herida. Resultados: En los cultivos celulares, la toxicidad de la exposición crónica se correlacionó con el incremento de la concentración y el tiempo de exposición. La exposición limitada al TXA no causó toxicidad significativa incluso a elevadas concentraciones. No se observó reepitelización en heridas expuestas de forma crónica a concentraciones de TXA de 25 mg/ml o superiores, y 50­100 mg/ml provocó epidermólisis del epitelio normal, posiblemente por un mecanismo no tóxico. La reepitelización de la herida se retrasó ligeramente, pero no se deterioró por una exposición limitada de 100 mg/ml o exposición crónica de 6,25 mg/ml. Conclusión: Mientras que la exposición corta, incluso hasta concentraciones elevadas, de TXA tópico parecen ser bien toleradas in vitro, la exposición prolongada al TXA tópico puede ser citotóxica y afectar la reepitelización de la herida. Los cirujanos deben ajustar la concentración de TXA al modo previsto de administración tópica en la práctica clínica.

Urinary proteome analysis of acute hypercoagulable state in rat model induced by ε-aminocaproic acid.

The hypercoagulable state occurs in a group of prothrombotic disorders associated with an increased risk for thromboembolic events, but it is difficult to diagnose due to the lack of available biomarkers. This study aimed to investigate systematic changes of urinary proteome in acute hypercoagulable state induced by certain antifibrinolytics. To reduce the effects of both genetic and environmental factors on the urinary proteome, we used a rat model of acute hypercoagulable state induced by an antifibrinolytic agent ε-aminocaproic acid, resembling human hypercoagulable state. Urine samples were collected during acute hypercoagulable state for analysis by liquid chromatography-tandem mass spectrometry (LCMS/MS). Of 65 significantly changed proteins in acute hypercoagulable state, 38 proteins had human orthologs, and 18 proteins were identified as stable in normal human urine. None of the identified proteins have been found to be clotting factors, but 4 proteins are known to be involved in the regulation of blood coagulation factors. Two proteins were verified as the markers associated with acute hypercoagulable state by Western blot analysis. In addition, four common differential urinary proteins have been found in acute hypercoagulable state induced by another antifibrinolytics tranexamic acid. These four proteins are potential biomarkers for early diagnosis of hypercoagulable state to prevent the development of thrombotic diseases.

Is tranexamic acid toxic to articular cartilage when administered topically? What is the safe dose?

Aims: The intra-articular administration of tranexamic acid (TXA) has been shown to be effective in reducing blood loss in unicompartmental knee arthroplasty and anterior cruciate reconstruction. The effects on human articular cartilage, however, remains unknown. Our aim, in this study, was to investigate any detrimental effect of TXA on chondrocytes, and to establish if there was a safe dose for its use in clinical practice. The hypothesis was that TXA would cause a dose-dependent damage to human articular cartilage. Materials and Methods: The cellular morphology, adhesion, metabolic activity, and viability of human chondrocytes when increasing the concentration (0 mg/ml to 40 mg/ml) and length of exposure to TXA (0 to 12 hours) were analyzed in a 2D model. This was then repeated, excluding cellular adhesion, in a 3D model and confirmed in viable samples of articular cartilage. Results: Increasing concentrations above 20 mg/ml resulted in atypical morphology, reduced cellular adhesion and metabolic activity associated with increased chondrocyte death. However, the cell matrix was not affected by the concentration of TXA or the length of exposure, and offered cellular protection for concentrations below 20 mg/ml. Conclusion: These results show that when in vitro chondrocytes are exposed to higher concentrations of TXA, such as that expected following recommended intra-articular administration, cytotoxicity is observed. This effect is dose-dependent, such that a tissue concentration of 10 mg/ml to 20 mg/ml could be expected to be safe. Cite this article: Bone Joint J 2018;100-B:404-12.

Assessment of the anti-snakebite properties of extracts of Aniba fragrans Ducke (Lauraceae) used in folk medicine as complementary treatment in cases of envenomation by Bothrops atrox.

ETHNOPHARMACOLOGICAL RELEVANCE: Extracts of leaves and bark of Aniba fragrans are used as tea (decoction) to treat snakebites in communities in the Brazilian Amazon. The aqueous extract of the leaves of A. fragrans has been proven to be effective against Bothrops venom, but only when pre-incubated with the venom. This study sought to assess the potential of different types of extract of this species to inhibit the biological activities of Bothrops atrox venom (BaV) when used the same way as in folk medicine. The main classes of secondary metabolites and the concentrations of phenolics in the extracts were also determined. MATERIALS AND METHODS: Four types of extract of A. fragrans were prepared: aqueous extract of the leaf (AEL), aqueous extract of the bark (AEB), hydroalcoholic leaf extract (HLE) and extract of the residue from hydrodistillation of the leaf (ERHL). The phytochemical profiles of the aqueous extracts were determined using thin layer chromatography (TLC), and the concentrations of phenolics were measured by colorimetric assays. To investigate the potential of the extracts to inhibit the biological activities of BaV, in vitro tests for antiphospholipase and antifibrinolytic activities were performed. In vivo tests for antihemorrhagic and antidefibrinating activities were also carried out, as well as antimicrobial tests for activity against the main bacteria found in the oral cavity of snakes. Interaction between the extracts and the proteins in BaV was assessed by electrophoresis (SDS-PAGE) and Western blot (WB). The cytotoxicity of the extracts was assessed in a strain of MRC-5 human fibroblasts. RESULTS: Terpenoids, flavonoids and condensed and hydrolysable tannins were detected in all the extracts. Metabolites such as coumarins, fatty acids and alkaloids were present in some extracts but not in others, indicating different phytochemical profiles. Phenolics content varied between extracts, and there were more tannins in AEB and HLE. In the in vitro tests, the extracts inhibited the phospholipase and fibrinolytic activities of BaV in the two ratios of venom to extract used. HLE exhibited effective antimicrobial action as it inhibited growth of 11 of the 15 bacteria investigated, including Morganella morganii, the main bacteria described in the oral cavity of snakes. The extracts failed to inhibit the defibrinating activity of BaV, and only the Bothrops antivenom had a significant effect (96.1%) on this activity. BaV-induced hemorrhage was completely inhibited by AEL and AEB when the pre-incubation (venom:extract) protocol was used. When administered orally, as in folk medicine, both AEB and AEL produced significant inhibition of hemorrhagic activity (maximum inhibition 46.5% and 39.2%, respectively). SDS-PAGE and WB of the extracts pre-incubated with BaV showed that the main proteins in the venom had been precipitated by the extracts. None of the four extracts showed cytotoxic effects in the tests carried out with a human fibroblast cell line. CONCLUSION: In addition to being effective in reducing hemorrhage when administered orally, the extracts displayed a high antimicrobial potential against microorganisms involved in secondary infections at the site of the snakebite. Once the extracts have been tested in accordance with the appropriate regulations, this species could potentially be used to produce a phytomedicine for complementary treatment of the secondary infections due to bacteria that aggravate the local signs and symptoms after snakebite envenomation.

The effects of Amicar and TXA on lumbar spine fusion in an animal model.

STUDY DESIGN: Animal model. OBJECTIVE: To determine whether aminocaproic acid (Amicar) and tranexamic acid (TXA) inhibit spine fusion volume. SUMMARY OF BACKGROUND DATA: Amicar and TXA are antifibrinolytics used to reduce perioperative bleeding. Prior in vitro data showed that antifibrinolytics reduce osteoblast bone mineralization. This study tested whether antifibrinolytics Amicar and TXA inhibit spine fusion. METHODS: Posterolateral L4-L6 fusion was performed in 50 mice, randomized into groups of 10, which received the following treatment before and after surgery: (1) saline; (2) TXA 100 mg/kg; (3) TXA 1000 mg/kg; (4) Amicar 100 mg/kg; and (5) Amicar 1000 mg/kg. High-resolution plane radiography was performed after 5 weeks and micro-CT (computed tomography) was performed at the end of the 12-week study. Radiographs were graded using the Lenke scale. Micro-CT was used to quantify fusion mass bone volume. One-way analysis of variance by ranks with Kruskal-Wallis testing was used to compare the radiographical scores. One-way analysis of variance with least significant difference post hoc testing was used to compare the micro-CT bone volume. RESULTS: The average±standard deviation bone volume/total volume (%) measured in the saline, TXA 100 mg/kg, TXA 1000 mg/kg, Amicar 100 mg/kg, and Amicar 1000 mg/kg groups were 10.8±2.3%, 9.7±2.2%, 13.4±3.2%, 15.5±5.2%, and 17.9±3.5%, respectively. There was a significant difference in the Amicar 100 mg/kg (P<0.05) and Amicar 1000 mg/kg (P<0.001) groups compared with the saline group. There was greater bone volume in the Amicar groups compared with the TXA group (P<0.001). There was more bone volume in the TXA 1000 mg/kg group compared with TXA 100 mg/kg (P<0.05) but the bone volume in neither of the TXA groups was different to saline (P=0.49). There were no between-group differences observed using plane radiographical scoring. CONCLUSION: Amicar significantly "enhanced" the fusion bone mass in a dose-dependent manner, whereas TXA did not have a significant effect on fusion compared with saline control.These data are in contrast to prior in vitro data that antifibrinolytics inhibit osteoblast bone mineralization. LEVEL OF EVIDENCE: N/A.

Antifibrinolytic mechanisms in acute airway injury after sulfur mustard analog inhalation.

Acute lung injury in response to mustard gas (sulfur mustard [SM]) inhalation results in formation of fibrin casts, which obstruct the airway. The objective of this study was to identify fibrinolytic pathways that could be contributing to the persistence of airway casts after SM exposure. Rats were exposed to the SM analog, 2-chloroethyl ethyl sulfide, via nose-only aerosol inhalation. At 4 and 18 hours after exposure, animals were killed and airway-capillary leak estimated by measuring bronchoalveolar lavage fluid (BALF) protein and IgM content. The fibrin clot-degrading and plasminogen-activating capabilities of BALF were also assessed by activity assays, whereas Western blotting was used to determine the presence and activities of plasminogen activator inhibitor-1, thrombin activatable fibrinolytic inhibitor and α2-antiplasmin. Measurement of tissue-specific steady-state mRNA levels was also conducted for each fibrinolytic inhibitor to assess whether its synthesis occurs in lung or at extrapulmonary sites. The results of this study demonstrate that fibrin-degrading and plasminogen-activating capabilities of the airways become impaired during the onset of 2-chloroethyl ethyl sulfide-induced vascular leak. Findings of functionally active reservoirs of plasminogen activator inhibitor-1, thrombin activatable fibrinolysis inhibitor, and α2-antiplasmin in BALF indicate that airway fibrinolysis is inhibited at multiple levels in response to SM.

Discovery of N-((4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)-5-(6-methylpyridin-2-yl)-1H-imidazol-2-yl)methyl)-2-fluoroaniline (EW-7197): a highly potent, selective, and orally bioavailable inhibitor of TGF-ß type I receptor kinase as cancer immunotherapeutic/antifibrotic agent.

A series of 2-substituted-4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)-5-(6-methylpyridin-2-yl)imidazoles was synthesized and evaluated to optimize a prototype inhibitor of TGF-ß type I receptor kinase (ALK5), 6. Combination of replacement of a quinoxalin-6-yl moiety of 6 with a [1,2,4]triazolo[1,5-a]pyridin-6-yl moiety, insertion of a methyleneamino linker, and a o-F substituent in the phenyl ring markedly increased ALK5 inhibitory activity, kinase selectivity, and oral bioavailability. The 12b (EW-7197) inhibited ALK5 with IC50 value of 0.013 µM in a kinase assay and with IC50 values of 0.0165 and 0.0121 µM in HaCaT (3TP-luc) stable cells and 4T1 (3TP-luc) stable cells, respectively, in a luciferase assay. Selectivity profiling of 12b using a panel of 320 protein kinases revealed that it is a highly selective ALK5/ALK4 inhibitor. Pharmacokinetic study with 12b·HCl in rats showed an oral bioavailability of 51% with high systemic exposure (AUC) of 1426 ng × h/mL and maximum plasma concentration (Cmax) of 1620 ng/mL. Rational optimization of 6 has led to the identification of a highly potent, selective, and orally bioavailable ALK5 inhibitor 12b.

Towards a three-dimensional microfluidic liver platform for predicting drug efficacy and toxicity in humans.

Although the process of drug development requires efficacy and toxicity testing in animals prior to human testing, animal models have limited ability to accurately predict human responses to xenobiotics and other insults. Societal pressures are also focusing on reduction of and, ultimately, replacement of animal testing. However, a variety of in vitro models, explored over the last decade, have not been powerful enough to replace animal models. New initiatives sponsored by several US federal agencies seek to address this problem by funding the development of physiologically relevant human organ models on microscopic chips. The eventual goal is to simulate a human-on-a-chip, by interconnecting the organ models, thereby replacing animal testing in drug discovery and development. As part of this initiative, we aim to build a three-dimensional human liver chip that mimics the acinus, the smallest functional unit of the liver, including its oxygen gradient. Our liver-on-a-chip platform will deliver a microfluidic three-dimensional co-culture environment with stable synthetic and enzymatic function for at least 4 weeks. Sentinel cells that contain fluorescent biosensors will be integrated into the chip to provide multiplexed, real-time readouts of key liver functions and pathology. We are also developing a database to manage experimental data and harness external information to interpret the multimodal data and create a predictive platform.

Safety and toxicological evaluation of a synthetic vitamin K2, menaquinone-7.

Menaquinone-7 (MK-7) is part of a family of vitamin K that are essential co-factors for the enzyme γ-glutamyl carboxylase, which is involved in the activation of γ-carboxy glutamate (Gla) proteins in the body. Gla proteins are important for normal blood coagulation and normality of bones and arteries. The objective of this study was to examine the potential toxicity of synthetic MK-7 in BomTac:NMRI mice and in Sprague-Dawley rats. In an acute oral toxicity test, mice were administered a single oral dose of 2000 mg/kg body weight (limit dose) and no toxicity was observed during the 14-day observation period. In the subchronic oral toxicity test in rats, animals were administered MK-7 for 90 days by gavage at the following doses: 0 (vehicle control, corn oil), 2.5, 5, and 10 mg/kg body weight/day. All generated data, including clinical observations, ophthalmology, clinical pathology, gross necropsy, and histopathology, revealed no compound-related toxicity in rats. Any statistically significant findings in clinical pathology parameters and/or organ weights noted were considered to be within normal biological variability. Therefore, under the conditions of this experiment, the median lethal dose (LD(50)) of MK-7 after a single oral administration in mice was determined to be greater than the limit dose level of 2000 mg/kg body weight. The no observed adverse effect level (NOAEL) of MK-7, when administered orally to rats for 90 days, was considered to be equal to 10 mg/kg body weight/day, the highest dose tested, based on lack of toxicity during the 90-day study period.

Vitamin K in parenteral nutrition.

Vitamin K (as phylloquinone and menaquinones) is an essential cofactor for the conversion of peptide-bound glutamate to gamma-carboxy glutamic acid (Gla) residues in a number of specialized Gla-containing proteins. The only unequivocal deficiency outcome is a bleeding syndrome caused by an inability to synthesize active coagulation factors II, VII, IX, and X, although there is growing evidence for roles for vitamin K in bone and vascular health. An adult daily intake of about 100 microg of phylloquinone is recommended for the maintenance of hemostasis. Traditional coagulation tests for assessing vitamin K status are nonspecific and insensitive. Better tests include measurements of circulating vitamin K and inactive proteins such as undercarboxylated forms of factor II and osteocalcin to assess tissue and functional status, respectively. Common risk factors for vitamin K deficiency in the hospitalized patient include inadequate dietary intakes, malabsorption syndromes (especially owing to cholestatic liver disease), antibiotic therapy, and renal insufficiency. Pregnant women and their newborns present a special risk category because of poor placental transport and low concentrations of vitamin K in breast milk. Since 2000, the Food and Drug Administration has mandated that adult parenteral preparations should provide a supplemental amount of 150 microg phylloquinone per day in addition to that present naturally, in variable amounts, in the lipid emulsion. Although this supplemental daily amount is probably beneficial in preventing vitamin K deficiency, it may be excessive for patients taking vitamin K antagonists, such as warfarin, and jeopardize their anticoagulant control. Natural forms of vitamin K have no proven toxicity.

Oxidant stress-induced liver injury in vivo: role of apoptosis, oncotic necrosis, and c-Jun NH2-terminal kinase activation.

Oxidant stress is critically involved in various liver diseases. Superoxide formation causes c-Jun NH2-terminal kinase (JNK)- and caspase-dependent apoptosis in cultured hepatocytes. To verify these findings in vivo, male Fisher rats were treated with diquat and menadione. The oxidant stress induced by both compounds was confirmed by increased formation of glutathione disulfide and 4-hydroxynonenal protein adducts. Plasma alanine aminotransferase activities increased from 46+/-4 U/l in controls to 955+/-90 U/l at 6 h after diquat treatment. Hematoxylin and eosin staining of liver sections revealed large areas of necrotic cells at 3 and 6 h. DNA strandbreaks, evaluated with the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, showed clusters of TUNEL-positive cells, where the staining was predominantly cytosolic and the cells were swollen, indicating oncotic necrosis. There was no significant increase in caspase-3 activities or relevant release of DNA fragments into the cytosol at any time between 0 and 6 h after diquat treatment. Despite the activation of JNK after high doses of diquat, the JNK inhibitor SP-600125 did not protect against diquat-induced necrosis. Menadione alone did not cause liver injury, but, in combination with phorone and FeSO4, induced moderate oncotic necrosis. On the other hand, if animals were treated with galactosamine/endotoxin as positive control for apoptosis, caspase-3 activities were increased by 259%, the number of TUNEL-positive cells with apoptotic morphology was increased 103-fold, and DNA fragmentation was enhanced 6-fold. The data indicate that liver cell death initiated by diquat-induced superoxide formation in vivo is mediated predominantly by oncotic necrosis and is independent of JNK activation.

Comparison of structure, strength and cytocompatibility of a fibrin matrix supplemented either with tranexamic acid or aprotinin.

Fibrin sealants are used as hemostats, sealants, tissue adhesives, and as matrix for substances/cells in a number of surgical and tissue engineering procedures. Main characteristics of fibrin are high tensile strength, adhesive strength, biocompatibility, and resorption. A major adverse event would be premature fibrin lysis and recurrent bleeding. This must be prevented by fibrinolysis inhibitors. The most common fibrinolysis inhibitors used are aprotinin and tranexamic acid (t-AMCA). Comparison of commercially available fibrin sealants utilizing aprotinin or t-AMCA revealed a lower sealing efficacy in an in vivo lung resection model for a t-AMCA containing product. Therefore, we compared the influence of t-AMCA and aprotinin on structure, mechanical properties, and cytocompatibility of a fibrin matrix. In our experiments, we found that substitution of aprotinin with t-AMCA reduced the tensile strength and formation of fibrin fibers and affected viability of a fibroblast cell-line. In conclusion, t-AMCA negatively affects physical and biological properties of fibrin relevant for clinical application as well as tissue regeneration.

Mitochondrial catalase overexpression protects insulin-producing cells against toxicity of reactive oxygen species and proinflammatory cytokines.

Insulin-producing cells are known for their extremely low antioxidant equipment with hydrogen peroxide (H(2)O(2))-inactivating enzymes. Therefore, catalase was stably overexpressed in mitochondria and for comparison in the cytoplasmic compartment of insulin-producing RINm5F cells and analyzed for its protective effect against toxicity of reactive oxygen species (ROS) and proinflammatory cytokines. Only mitochondrial overexpression of catalase provided protection against menadione toxicity, a chemical agent that preferentially generates superoxide radicals intramitochondrially. On the other hand, the cytoplasmic catalase overexpression provided better protection against H(2)O(2) toxicity. Mitochondrial catalase overexpression also preferentially protected against the toxicity of interleukin-1beta (IL-1beta) and a proinflammatory cytokine mixture (IL-1beta, tumor necrosis factor-alpha [TNF-alpha], and gamma-interferon [IFN-gamma]) that is more toxic than IL-1beta alone. Thus, it can be concluded that targeted overexpression of catalase in the mitochondria provides particularly effective protection against cell death in all situations in which ROS are generated intramitochondrially. The observed higher rate of cell death after exposure to a cytokine mixture in comparison with the weaker effect of IL-1beta alone may be due to an additive toxicity of TNF-alpha through ROS formation in mitochondria. The results emphasize the central role of mitochondrially generated ROS in the cytokine-mediated cell destruction of insulin-producing cells.

Development of an in vitro model for vascular injury with human endothelial cells.

The aim of the present work was to establish an in vitro screening assay for drug candidates using human endothelial cells as a model for vascular injury after intravenous application. Different endpoints for viability and functionality of endothelial cells were investigated in human umbilical vein endothelial cells (HUVEC) and in immortalised human endothelial cells (IVEC). Cellular viability was determined by measuring ATP content and by the AlamarBlue assay. For comparison, the toxicity of the selected compounds was also tested in a murine fibroblast cell line (3T3 cells). Selected endpoints for endothelial cell-specific function were vascular permeability, determined by measurement of the transendothelial resistance and the diffusion of tracer molecules (FITC-dextran), and the release of prostaglandin and thromboxane as indicators for prothrombotic or vasoconstrictory action. Five compounds (cyclosporin A, mitomycin C, menadione, amrinone and rolipram) were selected due to their known effects on the vasculature. The cytotoxicity of all compounds was similar in endothelial and 3T3 cells. ATP content and AlamarBlue metabolism did not differ significantly except for amrinone. A dose-dependent decrease of transendothelial resistance and an increase in FITC-dextran permeability could be measured in HUVEC cells for the tested compounds, but the sensitivity was not higher than that of the cytotoxicity assays. Increased prostaglandin or thromboxane release was detected for all compounds at cytotoxic concentrations and for rolipram also at non-toxic concentrations. In conclusion, for a first ranking of drug candidates, cytotoxicity assays on any of the three cell types used are appropriate. For a more detailed characterisation of individual compounds, functional assays on HUVEC cells are proposed.

In vivo exposure of Dreissena polymorpha mussels to the quinones menadione and lawsone: menadione is more toxic to mussels than lawsone.

The principal aim of this study was to assess whether the two quinones, menadione (2-methyl-1,4-naphthoquinone) and lawsone (2-hydroxy-1,4-naphthoquinone), elicit differential toxicity in mussels as has been reported for higher organisms. Therefore, the effects of short-term (48 h) and long-term (20 days) exposure of the two quinones at concentrations of 0.56 and 1 mg l(-1) to zebra mussels, Dreissena polymorpha, under laboratory conditions were studied. After the short-term exposure, the specific activities of the two-electron quinone oxidoreductase (DT-diaphorase) and the one-electron catalysing quinone reductases NADPH-cytochrome c reductase and NADH-cytochrome c reductase were determined in the gills and the rest of the soft tissues (soft mussel tissues minus the gills) of both treated and control mussels. At the higher concentrations of menadione and lawsone used, a significant reduction of the activity of NADPH-cytochrome c reductase in the gills and in the rest of the soft mussel tissues (by 33-34% and 31-43%, respectively) was observed. The activities of DT-diaphorase and NADH-cytochrome c reductase were not significantly affected. Interestingly, DT-diaphorase was observed in the gills, an organ requiring protection against antioxidants. Furthermore, a single-cell electrophoretic assay (comet assay) performed with gill cells to assess DNA damage by the quinones did not show any significant difference between the treated and the control organisms. This indicates that the formation of reactive species by the quinone metabolism in vivo in the mussels was possibly suppressed through the concerted action of DT-diaphorase and antioxidant enzymes. The results of in vitro experiments with gill extracts confirmed the protective role of DT-diaphorase. The rate of the two-electron quinone reduction was found to be five times that of the one-electron quinone reduction. The results of the long-term exposure unambiguously demonstrated that in mussels menadione, unlike in higher organisms, is more toxic than lawsone. The lack of detectability of xanthine oxidase in the mussel tissues could explain the comparatively lower toxicity of lawsone in the invertebtrate, lending support to a previous suggestion that xanthine oxidase might be responsible for the mechanism of toxicity of lawsone in higher organisms in vivo.

CYP2E1 overexpression alters hepatocyte death from menadione and fatty acids by activation of ERK1/2 signaling.

Chronic oxidative stress induced by overexpression of the cytochrome P450 isoform 2E1 (CYP2E1) has been implicated in hepatocyte injury and death. However, the mechanism by which CYP2E1 overexpression may promote cell death is unknown. Acute oxidative stress activates mitogen-activated protein kinases (MAPK), suggesting that chronic oxidant generation by CYP2E1 may regulate cellular responses through these signaling pathways. The effect of CYP2E1 overexpression on MAPK activation and their function in altering death responses of CYP2E1-overexpressing hepatocytes were investigated. Chronic CYP2E1 overexpression led to increased extracellular signal-regulated kinase 1/2 (ERK1/2) activation constitutively and in response to oxidant stress from the superoxide generator menadione. CYP2E1-overexpressing cells were resistant to menadione toxicity through an ERK1/2-dependent mechanism. Similar to menadione, the polyunsaturated fatty acid (PUFA) arachidonic acid (AA) induced an increased activation of ERK1/2 in hepatocytes that overexpressed CYP2E1. However, CYP2E1-overexpressing cells were sensitized to necrotic death from AA and the PUFA gamma-linolenic acid, but not from saturated or monounsaturated fatty acids. Death from PUFA resulted from oxidative stress and was blocked by inhibition of ERK1/2, but not p38 MAPK or activator protein-1 signaling. CYP2E1 expression induced ERK1/2 activation through increased epidermal growth factor receptor (EGFR)/c-Raf signaling. Inhibition of EGFR signaling reversed CYP2E1-induced resistance to menadione and sensitization to AA toxicity. In conclusion, chronic CYP2E1 overexpression leads to sustained ERK1/2 activation mediated by EGFR/c-Raf signaling. This adaptive response in hepatocytes exposed to chronic oxidative stress confers differential effects on cellular survival, protecting against menadione-induced apoptosis, but sensitizing to necrotic death from PUFA.

Effects of genotoxic compounds on DNA and development of early and late grass shrimp embryo stages.

Early and late developmental stages of grass shrimp embryos were exposed to different concentrations of two genotoxicants, 2-methyl-1,4-naphthoquinone (MNQ) and 4-nitroquinoline-N-oxide (NQO). DNA strand breaks were assessed by the comet assay while embryo development effects were determined by % of embryos hatching. Early embryo stage embryos were significantly more sensitive to genotoxicants than late stages. For example, all stage 4 embryos failed to hatch at 1 microM NQO while 95% of stage 8 hatched at this concentration. High DNA tail moments, which are a measure of the number of DNA strand breaks, were found in late stage embryos exposed to genotoxicants. Early stage embryo development was effected by low concentrations of genotoxicants but no changes were observed in DNA tail moments. We suggest that high DNA moments in late embryo stages reflect high DNA repair activity, while early stages may lack a fully developed DNA repair system.

Enhanced menadione cytotoxicity in platelets isolated from streptozotocin-induced diabetic rats.

To study whether chemically induced cytotoxicity occurs in diabetic platelets, platelets isolated from rats made hyperglycemic (diabetic) by a prior intravenous administration of streptozotocin were incubated with menadione and the cytotoxicity was assessed by the amount of lactate dehydrogenase (LDH) released from the menadione exposed platelets as a function of time. Platelets isolated from diabetic rats released greater amount of LDH in response to menadione than those from normal rats. Consistent with this finding, induction of menadione cytotoxicity was not dependent on glutathione depletion, but on greater generation of free radicals in diabetic platelets. Greater sensitivity of diabetic platelets to the menadione-induced cytotoxicity was accompanied by release of serotonin from dense granules, suggesting that this mechanism contributes to cardiovascular diseases in diabetic subjects.