DX9065a, an Xa inhibitor, inhibits prothrombin-induced A549 lung adenocarcinoma cell proliferation

Self-immolative bioluminogenic quinone luciferins for NAD(P)H assays and reducing capacity-based cell viability assays

Highly sensitive self-cleavable trimethyl lock quinone-luciferin substrates for diaphorase were designed and synthesized to measure NAD(P)H in biological samples and monitor viable cells via NAD(P)H-dependent cellular oxidoreductase enzymes and their NAD(P)H cofactors.

Tissue factor, blood coagulation, and beyond: an overview

Emerging evidence shows a broad spectrum of biological functions of tissue factor (TF). TF classical role in initiating the extrinsic blood coagulation and its direct thrombotic action in close relation to cardiovascular risks have long been established. TF overexpression/hypercoagulability often observed in many clinical conditions certainly expands its role in proinflammation, diabetes, obesity, cardiovascular diseases, angiogenesis, tumor metastasis, wound repairs, embryonic development, cell adhesion/migration, innate immunity, infection, pregnancy loss, and many others. This paper broadly covers seminal observations to discuss TF pathogenic roles in relation to diverse disease development or manifestation. Biochemically, extracellular TF signaling interfaced through protease-activated receptors (PARs) elicits cellular activation and inflammatory responses. TF diverse biological roles are associated with either coagulation-dependent or noncoagulation-mediated actions. Apparently, TF hypercoagulability refuels a coagulation-inflammation-thrombosis circuit in “autocrine” or “paracrine” fashions, which triggers a wide spectrum of pathophysiology. Accordingly, TF suppression, anticoagulation, PAR blockade, or general anti-inflammation offers an array of therapeutical benefits for easing diverse pathological conditions.

Fibrin formation by wounded bronchial epithelial cell layers in vitro is essential for normal epithelial repair and independent of plasma proteins

BACKGROUND

The bronchial epithelium is in contact with, and continually damaged by, the environment. Animal models have indicated that normal epithelial repair is rapid and supported by the formation of a provisional fibrin matrix that is exclusively plasma-derived.

OBJECTIVES

Our objectives were to demonstrate the ability of normal human bronchial epithelial (NHBE) cells to produce coagulation cascade proteins and form fibrin in response to damage, independently of plasma proteins, and to show that formation of a cross-linked fibrin matrix is essential for normal epithelial repair in vitro.

METHODS

Primary NHBE cells and cells of the 16HBE 14o- bronchial epithelial cell line were grown and maintained in vitro prior to mechanical wounding of confluent monolayers in serum-free media. Tissue factor (TF) and factor XIII (FXIII) were visualized on 16HBE 14o- monolayers using immunohistochemistry. The time-dependent expression of TF, factor VII (FVII), factor X (FX), fibrinogen, soluble fibrin, FXIII subunit A (FXIIIA) and D-dimers following wounding of confluent 16HBE 14o- monolayers was investigated using immunoassays. TF and FVII expression at the mRNA level was investigated by RT-PCR. The role of coagulation cascade proteins in the repair response of NHBE and 16HBE 14o- monolayers was investigated using neutralizing antibodies.

RESULTS

Active TF was constitutively expressed in 16HBE 14o- cells. Levels of FVII, FX, fibrinogen, soluble fibrin, FXIIIA and D-dimers in culture supernatants increased rapidly and were maximal 20 min after wounding the monolayers. Expression of TF and FVII mRNA was significantly increased 10 and 4 h, respectively, after wounding. Neutralizing antibodies to TF, fibrinogen and FXIIIA significantly inhibited repair of NHBE and 16HBE 14o- cell layers.

CONCLUSIONS

The bronchial epithelium has the potential to respond rapidly to mechanical damage by forming a cross-linked fibrin matrix that is essential for normal epithelial repair, independently of plasma proteins.

Factor X inhibitors

Factor X plays a central role in coagulation, being the point of convergence of the extrinsic and intrinsic pathways of blood clotting. It may also act as one of the links between the coagulation and inflammatory pathways. These findings suggest that factor X may represent an attractive target for a new antithrombotic drug. Indeed, a factor X inhibitor, fondaparinux, has already been approved for clinical use to prevent post-operative deep vein thrombosis. Factor X inhibitors are also being evaluated for use in the treatment of the acute coronary syndromes, pulmonary embolism and deep vein thrombosis. Oral factor X inhibitors are also being developed, which may be of use in the outpatient prevention and/or treatment of stroke and thromboembolism.

A peptide derived from human prothrombin fragment 2 inhibits prothrombinase and angiogenesis

We constructed the synthetic peptide library representing human prothrombin fragment 2 (F2) sequence and explored the inhibitory sequence for prothrombinase, which was reconstituted in vitro by adding factor Xa, factor Va, and calcium into phospholipids. The nonapeptide NSAVLQVEN (NSA9) suppressed prothrombinase reconstituted not only on phospholipid vesicles but also on the bovine capillary endothelial (BCE) cell surface. Kinetic analyses demonstrated that NSA9 is a mixed-type inhibitor of Xa. Furthermore, the nonapeptide inhibited the proliferation of BCE cells and also suppressed angiogenesis in chicken embryos. The inhibitory activities of NSA9 were abrogated by pre-incubation with anti-F2 monoclonal antibody, 4E7. These data demonstrate that anti-angiogenic activity of F2 may be related to its ability to inhibit prothrombinase.

A synthetic inhibitor of factor Xa, DX-9065a, reduces proliferation of vascular smooth muscle cells in vivo in rats

The effect of factor Xa inactivation on the proliferation of vascular smooth muscle cells in vivo was investigated in an experimental restenosis model in rats by using the direct factor Xa inhibitor DX-9065a. In the left common carotid artery, an injury of the vascular endothelium was produced by four external vessel clamps for 60 minutes. After 14 days, 3H-labeled methyl thymidine and 5-bromo-2'-deoxyuridine, respectively, were injected intraperitoneally. After 24 hours, both the left (damaged) and right (nondamaged) carotid arteries were removed, and the incorporation of 3H-methyl thymidine/microg protein was determined. For morphological analysis, the cells were labeled with hematoxylin as well as 5-bromo-2'-deoxyuridine. Stained vascular smooth muscle cell nuclei were counted, and the proliferation index (percentage of 5-bromo-2'-deoxyuridine-positive nuclei to total nuclei stained with hematoxylin) was determined. An external damage of the carotid artery induced proliferation of vascular smooth muscle cells and formation of a neointima within 2 weeks after vessel injury. As compared with control animals, single subcutaneous injection of DX-9065a (2.5, 5, and 10 mg/kg) given 30 minutes before vessel injury significantly reduced the incorporation of 3H-methyl thymidine/microg protein and the total cell number, as well as the proliferation index. The antiproliferative action of DX-9065a was not dose dependent in the range from 2.5 to 10 mg/kg s.c. A combination of bolus injection (5 mg/kg s.c.) with continuous administration (5 mg/kg/d s.c. for 7 and 14 days, respectively) did not increase the antiproliferative effect of DX-9065a. The results indicate a role of factor Xa in the complex pathogenesis of restenosis and the usefulness of a highly effective and selective inhibitor of factor Xa to inhibit proliferative processes.

DX-9065a, a specific factor Xa inhibitor, as a universal anticoagulant for blood collection tubes

DX-9065a is a direct and selective factor Xa inhibitor. We evaluated the usefulness of DX-9065a in anticoagulating specimens for routine laboratory tests. Results using blood anticoagulated with DX9065a corresponded well with results with blood treated with ethylendiamine tetraacetic acid (EDTA) in the complete blood count (CBC), including white blood cell (WBC) differential count and morphology of blood cells. Clinical chemistry results from DX-9065a-treated samples were similar to results obtained with serum specimens except for leucine aminopeptidase (LAP) and cholinesterase (Ch-E). Thus, DX-9065a may be a useful universal anticoagulant for laboratory medicine.