The ₉₅RGD₉₇ sequence on the A alpha chain of fibrinogen is essential for binding to its erythrocyte receptor

Background: Erythrocyte aggregation, a cardiovascular risk factor, is increased by high plasma fibrinogen levels. Here, the effect of different fibrinogen mutations on binding to its human erythrocyte receptor was assessed in order to identify the interaction sites. Methods: Three fibrinogen variants were tested, specifically mutated in their putative integrin recognition sites on the Aα chain (mutants D97E, D574E and D97E/D574E) and compared with wild-type fibrinogen. Results: Atomic force microscopy-based force spectroscopy measurements showed a significant decrease both on the fibrinogen–erythrocyte binding force and on its frequency for fibrinogen with the D97E mutation, indicating that the corresponding arginine–glycine–aspartate sequence (residues 95–97) is involved in this interaction, and supporting that the fibrinogen receptor on erythrocytes has a β3 subunit. Changes in the fibrin clot network structure obtained with the D97E mutant were observed by scanning electron microscopy. Conclusion: These findings may lead to innovative perspectives on the development of new therapeutic approaches to overcome the risks of fibrinogen-driven erythrocyte hyperaggregation

Mixtures of four organochlorines enhance human breast cancer cell proliferation.

In view of the large differences between the concentrations of estrogenic chemicals needed to elicit effects in in vitro assays and their levels in human tissues, it is hard to explain possible health risks in terms of exposure to individual compounds. Human populations, however, are exposed to mixtures of estrogenic and estrogen-like agents and it is necessary to consider the impact of combined effects. We assessed the combined effects of 1-(o-chlorophenyl)-1-(p-chlorophenyl)-2,2,2-trichloroethane (o,p'-DDT), 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), beta-hexachlorocyclohexane (beta-HCH), and 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (p,p'-DDT) on the induction of cell proliferation in MCF-7 cells. All four compounds are persistent organochlorines that can be found in human tissues. We performed extensive concentration-response analyses with the single agents to predict the effects of two mixtures of all four compounds with different mixture ratios. We calculated the predictions by using the pharmacologically well-founded models of concentration addition and independent action and then tested them experimentally. o,p'-DDT, p,p'-DDE, beta-HCH, and p,p'-DDT acted together to produce proliferative effects in MCF-7 cells. The combined effect of the four agents could be predicted on the basis of data about single agent concentration-response relationships. Regression analysis demonstrated that there were combination effects even when each mixture component was present at levels at or below its individual no-observed-effect-concentration. We assessed combination effects in two ways: First, evaluations in relation to the proliferative responses induced by single mixture components revealed that the combination effects were stronger than the effects of the most potent constituent. Thus, according to this method of evaluation, the combined effects may be termed synergistic. Second, comparisons with the expected effects, as predicted by concentration addition and independent action, showed excellent agreement between prediction and observation. With this approach, the combined effect of all four compounds can be termed additive

A COMPARISON OF CHOLINESTERASE DISTRIBUTION IN THE CEREBELLUM OF SEVERAL SPECIES *

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65142/1/j.1471-4159.1964.tb06717.x.pd

Escitalopram—translating molecular properties into clinical benefit: reviewing the evidence in major depression

The majority of currently marketed drugs contain a mixture of enantiomers; however, recent evidence suggests that individual enantiomers can have pharmacological properties that differ importantly from enantiomer mixtures. Escitalopram, the S-enantiomer of citalopram, displays markedly different pharmacological activity to the R-enantiomer. This review aims to evaluate whether these differences confer any significant clinical advantage for escitalopram over either citalopram or other frequently used antidepressants. Searches were conducted using PubMed and EMBASE (up to January 2009). Abstracts of the retrieved studies were reviewed independently by both authors for inclusion. Only those studies relating to depression or major depressive disorder were included. The search identified over 250 citations, of which 21 studies and 18 pooled or meta-analyses studies were deemed suitable for inclusion. These studies reveal that escitalopram has some efficacy advantage over citalopram and paroxetine, but no consistent advantage over other selective serotonin reuptake inhibitors. Escitalopram has at least comparable efficacy to available serotonin-norepinephrine reuptake inhibitors, venlafaxine XR and duloxetine, and may offer some tolerability advantages over these agents. This review suggests that the mechanistic advantages of escitalopram over citalopram translate into clinical efficacy advantages. Escitalopram may have a favourable benefit-risk ratio compared with citalopram and possibly with several other antidepressant agents

Immobilized fibrinogen activates human platelets through GPVI

GPVI, a major platelet activation receptor for collagen and fibrin, is considered as a particularly promising safe antithrombotic target. In this study, we show that human GPVI signals upon platelet adhesion to fibrinogen. Full spreading of human platelets on fibrinogen is abolished in platelets from GPVI-deficient patients suggesting that fibrinogen activates platelets through GPVI. While mouse platelets fail to spread on fibrinogen, human-GPVI-transgenic mouse platelets show full spreading and increased Ca2+ signalling through the tyrosine kinase Syk. Direct binding of fibrinogen to human GPVI was shown by surface plasmon resonance and by increased adhesion of human GPVI-transfected Rbl-2H3 cells to fibrinogen relative to mock-transfected cells. Blockade of human GPVI with the Fab of the monoclonal antibody 9O12 impairs platelet aggregation on preformed platelet aggregates in flowing blood independent of collagen and fibrin exposure. These results demonstrate that human GPVI binds to immobilized fibrinogen and show that this contributes to platelet spreading and platelet aggregation under flow

Hemostasis and ageing

On March 19, 2008 a Symposium on Pathophysiology of Ageing and Age-Related Diseases was held in Palermo, Italy. The lecture of D. Mari on Hemostasis and ageing is summarized herein. Physiological ageing is associated with increased plasma levels of many proteins of blood coagulation together with fibrinolysis impairment. This may be of great concern in view of the known association between vascular and thromboembolic diseases and ageing. On the other hand, centenarians are characterized by a state of hypercoagulability and possession of several high-risk alleles and well-known atherothrombotic risk markers but this appears to be compatible with longevity and/or health. Parameters considered risk factors for atherosclerotic vascular diseases in young people may lose their biological significance in advanced age and assume a different role

Pharmacogenomic and structural analysis of constitutive G-protein coupled receptor activity

Premi a l'excel·lència investigadora. Àmbit de les Ciències de la Salut. 2008G-protein coupled receptors (GPCRs) respond to a chemically diverse plethora of signal transduction molecules. The notion that GPCRs also signal without an external chemical trigger, i.e. in a constitutive or spontaneous manner, resulted in a paradigm shift in the field of GPCR pharmacology. With the recognition of constitutive GPCR activity and the fact that GPCR binding and signaling can be strongly affected by a single point mutation, GPCR pharmacogenomics obtained a lot of attention. For a variety of GPCRs, point mutations have been convincingly linked to human disease. Mutations within conserved motifs, known to be involved in GPCR activation, might explain the properties of some naturally occurring constitutively active GPCR variants linked to disease. A brief history historical introduction to the present concept of constitutive receptor activity is given and the pharmacogenomic and the structural aspects of constitutive receptor activity are described

In Vivo Near-Infrared Imaging of Fibrin Deposition in Thromboembolic Stroke in Mice

imaging of activated factor XIII (FXIIIa), an important mediator of thrombosis or fibrinolytic resistance. The present study was to investigate the fibrin deposition in a thromboembolic stroke mice model by FXIIIa–targeted near-infrared fluorescence (NIRF) imaging., which were correlated with histology after animal euthanasia. NIRF images and lesion volume.Non-invasive detection of fibrin deposition in ischemic mouse brain using NIRF imaging is feasible and this technique may provide an in vivo experimental tool in studying the role of fibrin in stroke