Biomedical subjects

Sophie Gandrille

Publications and source records attributed to Sophie Gandrille.

7 recordsLinked to original sources

PubMed2006

[Coagulation factor mutations and thrombosis].

The coagulation system is governed by a subtle balance between clotting activators and inhibitors. Many genes can contribute to the overall phenotype, and polymorphisms may act to up regulate or down regulate the generation of thrombin, the coagulation-key enzyme. An increase in coagulation factor (gain function) or/and a decrease in coagulation inhibitors (loss of function) may favor venous thromboembolism (VTE). It has been observed since a long time that VTE may be a familial disease, but it was only in 1965 that Egeberg published the first case of inherited antithrombin (AT) deficiency. This was followed by similar reports of protein C (PC) and protein S (PS) deficiencies. Hereditary thrombophilia was thus initially considered as a rare monogenic disorder with incomplete penetrance. AT, PC and PS deficiencies are due to multiple and mostly private mutations of the corresponding genes. Most patients are heterozygous and experience VTE at adult age. Homozygosity associated with severe thrombosis at birth has been observed in newborns with undetectable PC or PS concentrations. The discovery of factor (F) V Leiden and F2 g.20210 G>A, two gain of function mutations, challenged the view of thrombophilia as a rare monogenic disorder. FV Leiden and F2 g.20210 G>A are due to a founder effect and affect populations of European descent with frequencies at 5% and 3% respectively. These two mutations are moderate of risk factor for thrombosis and paved the way for gene-gene and gene-environment interactions. Patients carrying more than one genetic risk factor are at higher risk to develop VTE. The exposition to acquired risk factors such as estrogen based oral contraception may also have a synergistic effect favoring thrombosis in patients with FV Leiden or other genetic risk factors.

Blood Coagulation Disorders↗

PubMed2006

Identification of functional polymorphisms of the thromboxane A2 receptor gene in healthy volunteers.

Thromboxane A2 receptor (TP) is an important actor in vascular physiology and plays a crucial role in the platelet activation process. Genetic polymorphisms of the gene coding for the TP have been described, but their impacts on platelet function tests are unknown. The aim of this study was to investigate the relationship between genetic polymorphisms of the coding sequence of the TP gene and platelet function tests. We investigated 100 healthy volunteers twice, one week apart by performing platelet aggregation and secretion tests. We sequenced the coding region of the TP gene and confronted the genetic variants with the phenotypic results. We identified five single nucleotide polymorphisms (SNP); one of them, T1712C, replaces Leu by Pro at position 133 of the isoform beta of the TP. Homozygosity for the minor allele of the C795T, C924T or the G1686A SNP was associated with a decreased expression of CD62P when platelets were stimulated with the TP agonist U46619. As C795T and C924T have been linked to clinical disorders in which TxA2 plays a key role, the possible role of the G1686A and T1712C SNP should also be examined in selected diseases.

Adolescent↗

PubMed2004

The gamma-carboxyglutamic acid domain of anticoagulant protein S is involved in activated protein C cofactor activity, independently of phospholipid binding.

We expressed 2 chimeras between human protein S (PS) and human prothrombin (FII) in which the prothrombin gamma-carboxyglutamic acid (Gla) domain replaced the PS Gla domain in native PS (Gla(FII)-PS) or in PS deleted of the thrombin-sensitive region (TSR) (Gla(FII)-DeltaTSR-PS). Neither PS/FII chimera had activated protein C (APC) cofactor activity in plasma clotting assays or purified systems, but both bound efficiently to phospholipids. This pointed to a direct involvement of the PS Gla domain in APC cofactor activity through molecular interaction with APC. Using computational methods, we identified 2 opposite faces of solvent-exposed residues on the PS Gla domain (designated faces 1 and 2) as potentially involved in this interaction. Their importance was supported by functional characterization of a PS mutant in which the face 1 and face 2 PS residues were reintroduced into Gla(FII)-PS, leading to significant APC cofactor activity, likely through restored interaction with APC. Furthermore, by characterizing PS mutants in which PS face 1 and PS face 2 were individually replaced by the corresponding prothrombin faces, we found that face 1 was necessary for efficient phospholipid binding but that face 2 residues were not strictly required for phospholipid binding and were involved in the interaction with APC.

1-Carboxyglutamic Acid↗

PubMed2003

A haplotype of the EPCR gene is associated with increased plasma levels of sEPCR and is a candidate risk factor for thrombosis.

The endothelial cell protein C (PC) receptor (EPCR) facilitates PC activation by the thrombin-thrombomodulin complex. A soluble form of this receptor (sEPCR) found in plasma inhibits both activated PC (aPC) activity and PC activation by competing for PC with membrane-associated EPCR. Elevated sEPCR levels are found in approximately 20% of healthy subjects, but the mechanisms underlying this interindividual variability are unknown. We measured sEPCR levels in 100 healthy male volunteers, and observed 2 phenotypic groups of subjects. The temporal stability of sEPCR levels suggested genetic control. Extensive analysis of the EPCR gene in these subjects revealed 13 polymorphisms in complete linkage disequilibrium; these defined 3 haplotypes, 1 of which (A3) was strongly associated with high sEPCR levels. The high constitutive sEPCR levels observed in A3 haplotype carriers might reduce the efficiency of the PC system and predispose these subjects to venous thrombosis. By studying 338 patients with venous thrombosis and 338 age- and sex-matched healthy subjects, we found that the A3 haplotype was overrepresented in the patients. In multivariate analysis, subjects carrying the A3 haplotype had an increased risk of thrombosis (odds ratio [OR] = 1.8; P =.004). Thus, the A3 haplotype, which is associated with elevated plasma sEPCR levels, is a candidate risk factor for venous thrombosis.

Adolescent↗

PubMed2003

Adenosine diphosphate-induced platelet aggregation is associated with P2Y12 gene sequence variations in healthy subjects.

BACKGROUND: The adenosine diphosphate (ADP) receptor P2Y12 plays a pivotal role in platelet aggregation, as demonstrated by the benefit conferred by its blockade in patients with cardiovascular disease. Some studies have shown interindividual differences in ADP-induced platelet aggregation responses ex vivo, but the mechanisms underlying this variability are unknown. METHODS AND RESULTS: We examined ADP-induced platelet aggregation responses in 98 healthy volunteers, and we identified 2 phenotypic groups of subjects with high and low responsiveness to 2 micromol/L ADP. This prompted us to screen the recently identified Gi-coupled ADP receptor gene P2Y12 for sequence variations. Among the 5 frequent polymorphisms thus identified, 4 were in total linkage disequilibrium, determining haplotypes H1 and H2, with respective allelic frequencies of 0.86 and 0.14. The number of H2 alleles was associated with the maximal aggregation response to ADP in the overall study population (P=0.007). Downregulation of the platelet cAMP concentration by ADP was more marked in 10 selected H2 carriers than in 10 noncarriers. CONCLUSIONS: In healthy subjects, ADP-induced platelet aggregation is associated with a haplotype of the P2Y12 receptor gene. Given the crucial role of the P2Y12 receptor in platelet functions, carriers of the H2 haplotype may have an increased risk of atherothrombosis and/or a lesser clinical response to drugs inhibiting platelet function.

Adenosine Diphosphate↗

PubMed2003

Functional properties of the sex-hormone-binding globulin (SHBG)-like domain of the anticoagulant protein S.

Protein S (PS) possesses a sex-hormone-binding globulin (SHBG)-like domain in place of the serine-protease domain found in other vitamin K-dependent plasma proteins. This SHBG-like domain is able to bind a complement fraction, C4b-binding protein (C4b-BP). To establish whether the PS SHBG-like domain can fold normally in the absence of other domains, and to obtain information on the specific functions of this region, we expressed the PS SHBG-like domain alone or together with its adjacent domain EGF4. The folding of the two recombinant modules was studied by analyzing their binding to C4b-BP. The apparent dissociation constants of this interaction indicated that both recombinant modules adopted the conformation of native PS, indicating that the PS SHBG-like region is an independent folding unit. We also obtained the first direct evidence that the SHBG-like domain alone is sufficient to support the interaction with C4b-BP. In addition, both recombinant modules were able to bind Ca2+ directly, as shown by the migration shift in agarose gel electrophoresis in the presence of Ca2+, together with the results of equilibrium dialysis and the functional effect of Ca2+ on the C4b-BP/PS interaction, confirming the presence of one Ca2+ binding site within the SHBG-like domain. Neither recombinant module exhibited activated protein C (aPC) cofactor activity in a clotting assay, suggesting that the PS SHBG-like region must be part of the intact molecule for it to contribute to aPC cofactor activity, possibly by constraining the different domains in a conformation that permits optimal interaction with aPC.

Anticoagulants↗

PubMed2003

Cleaved protein S (PS), total PS, free PS, and activated protein C cofactor activity as risk factors for venous thromboembolism.

BACKGROUND: Although hereditary protein S (PS) deficiency is clearly associated with venous thromboembolism (VTE), the importance of low PS concentrations as a risk factor for VTE in other patients is still a matter of debate. To clarify this issue, we designed a case-control study to evaluate the role of different molecular forms of plasma PS. METHODS: We quantified plasma cleaved, total, and free PS and activated protein C (APC) cofactor activity in 87 VTE patients and 174 controls matched for age, sex, and hormonal treatment. Free PS was measured by ELISA or by enzyme-linked ligand sorbent assay (ELSA). Cleaved and total PS were measured by ELISA. RESULTS: In controls, the mean (SD) concentration of circulating cleaved PS was 39 (14) nmol/L, corresponding to 10% (3.5%) of total PS. Concentrations of cleaved PS and total PS were not significantly different in patients with VTE compared with controls. However, in our population, low free PS measured by ELISA or ELSA, as well as APC cofactor activity values were significantly associated with VTE with odds ratios (95% confidence intervals) of 2.9 (1.3-6.3), 2.5 (1.1-5.6), and 2.9 (1.3-6.4), respectively, in multivariate analyses. CONCLUSION: Phenotypic low PS detected by APC cofactor activity assay or by an assay specific for free PS should be considered a risk factor for VTE.

Adult↗