The maintenance of blood uidity within the vascular system is ensured by the balance between procoagulant and anticoagulant components. Hemostasis and blood coagulation are processes regulated by a complex network of interactions, involving plasma/tissue proteins and cells. Numerous epidemiologic studies indicate that deciencies in blood coagulation proteins cause serious bleeding problems, whereas the deciencies in coagulation inhibitors and certain mutations in coagulation factors may lead to thrombotic disorders. The coagulation process has been conceptualized as being dependent primarily on adequate levels of the coagulation proteins. From clinical studies it is assumed that the normal concentration range of proteins involved in blood coagulation and regulation of this process may vary in the average blood sample from 50% to 150% of their mean plasma values. This suggests that a wide range of factor levels is compatible with normal hemostatic function; however, even within the normal range, variations can aect the rate and extent of thrombin generation. As a consequence, the stimulus/response which follows tissue factor presentation to blood and the subsequent expression of thrombin activity is highly variable even in the normal population. In addition, the qualitative performance of these proteins is governed by many molecular events which are in uenced both by genetic background, and by environmental processes that alter coagulation proteins during circulation and may produce very dierent phenotypic responses. All these considerations emphasize the importance in measuring and monitoring variations of coagulation factor levels, providing potential correlations with non physiologic conditions. Also, the evidence of how the coagulation proteins are involved in the acute phase of in ammation and several other human diseases, confirm that analysis of their level changes and modulation, represent the way required for appropriate diagnosis and therapeutic intervention. Aims A number of molecular mechanisms intragenic, extragenic and environmental, acting at different levels of the gene information ow, could produce variations in the expression of coagulation protein or activity levels. To get inside this complex regulative network we report four different studies aimed at elucidate aspects of clotting factor modulation. Study of oscillations in coagulation factor levels, due to inherited or environmental factor, could establish novel relationships between coagulation and in ammatory components, or with determinant of other human pathologies. Methods Methods are included in articles published in 2007/2008; they are focused on thrombin generation assay, an overall assay measuring the amount of thrombin produced in plasma samples in standard condition. This method evidences subjects coagulation-phenotype, allowing the correlation with other clotting factors levels. Main Results The combined effect of ten common prothrombotic polymorphisms as a determinant of MI was tested in a population of 804 subject, half of whom affected by severe Coronary Artery Disease (CAD). The number of procoagulant alleles was signicantly associated with the Endogenous Thrombin Potential (ETP), similarly, subjects with a high number of procoagulant alleles had significantly higher ETP values as compared to subjects with fewer alleles. Similar approach was used to investigate a rare bleeding disorder, vitamin K-dependent clotting factor deficiency type 2 (VKCFD2), which offered several quantitative parameters providing us information on vitamin K-dependent regulation of plasma factor levels; a markedly variation in Thrombin Generation parameters and others clotting factors measurements improved the identification of a clear coagulation phenotype. We also probed the effects of an integrated healthy diet on a wide panel of hemostatic and in ammatory variables. The changes observed in coagulation initiation and amplification phases, body composition and lipid profile could translate into a remarkable decrease in the risk for cardiovascular disease, suggesting novel relationship between coagulation and in ammation components. Finally we investigate how Tissue Factor-bearing Microparticles was generated by monocyte-derived Dendritic Cells stimulated with the P2X7R ag- onist benzoyl ATP (BzATP); our observations identify a novel pathway for tissue factor release, providing new insights into the mechanisms underlying the generation and spreading of procoagulant activity. The activity of this potential circulating trigger of coagulation and in ammation stimuli could be involved in progression of several pathology and in ammation process. Conclusions Our studies provide quantitative evidence for genetic and environmental determinants of coagulation factor levels in plasma, and for their integrated eects on generation of thrombin. The consequent variation of coagulation phenotype produces ample temporal and individual variations in coagulation function. These ndings have implications on the diagnosis, prevention/prophylaxis and therapy of coagulation diseases, and encourage further investigations to better understand the clinical signicance of the molecular heterogeneity of the human hemostatic proteome.
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|Titolo:||Molecular bases of the modulation of coagulation factor levels|
|Supervisori e coordinatori:||BERNARDI, Francesco|
|Appare nelle tipologie:||10.2 Tesi di dottorato (EPrints)|