Detlef Kozian

Association between the Thr325Ile polymorphism of the thrombin-activatable fibrinolysis inhibitor and stroke in the Ludwigshafen Risk and Cardiovascular Health Study

The thrombin-activatable fibrinolysis inhibitor (TAFI) is a key mediator in the regulation of endogenous fibrinolysis, down-regulating clot lysis by degrading the C-terminal lysine residues from fibrin, which are important for binding and activating plasminogen. Elevated TAFI antigen levels have been suggested to be associated with promoter variants and the Ala147Thr polymorphism; increased TAFI stability and antifibrinolytic potential instead have been associated with the Thr325Ile polymorphism. We investigated the influence of these two polymorphisms on cardiovascular and thrombotic events in patients of the Ludwigshafen Risk and Cardiovascular Health (LURIC) study. The LURIC study is a prospective cohort study comprising more than 3,300 patients aimed at identifying biochemical and genetic markers for metabolic and cardiovascular diseases. We demonstrate that the Ile/Ile genotype at position 325 of TAFI associates with the incidence of stroke and the age at onset of first stroke in patients of the LURIC cohort. Both the incidence of stroke and the risk of a premature event are higher in TAFI Ile325Ile patients with predisposing risk factors for thrombotic events such as diabetes mellitus, myocardial infarction or hypertension, alone or in combination. In contrast, no significant association was identified for the TAFI Ala147Thr polymorphism. The robust association of the TAFI Thr325Ile polymorphism with the incidence and the age at onset of first stroke strongly suggests a key role for TAFI in the pathogenetic mechanism of stroke.

Selective non-lipid modulator of LPA5 activity in human platelets.

Lysophosphatidic acid (LPA) is a potent activator of human platelets in vitro. Recently, the G protein-coupled receptor LPA5/GPR92 has been identified to be the relevant LPA receptor responsible for the activation of human platelets by LPA. In a high-throughput screening campaign we identified a diphenyl pyrazole carboxylic acid as a small-molecule inhibitor for LPA5. Confirmation for the specificity of this small molecule was achieved in human platelets as the relevant cellular in vitro model. We could confirm using antagonists for alternative LPA receptors that we identified in our work the first non-lipid, small-molecule inhibitor for LPA5/GPR92 specifically inhibiting LPA-mediated platelet activation in vitro.

Modulation of Hexadecyl-LPA-Mediated Activation of Mast Cells and Microglia by a Chemical Probe for LPA5.

Mast cells and microglia play a critical role in innate immunity and inflammation and can be activated by a wide range of endogenous and exogenous stimuli. Lysophosphatidic acid (LPA) has recently been reported to activate mast cells and microglia. Using the human mast cell line HMC‐1 and the mouse microglia cell line BV‐2, we show that LPA‐mediated activation can be prevented by blockade of the LPA receptor 5 (LPA5) in both cell lines. The identification of new LPA5‐specific antagonists as tool compounds to probe and modulate the LPA5/LPA axis in relevant in vitro and in vivo assays should contribute to better understanding of the underlying role of LPAs in the development and progression of (neuro‐) inflammatory diseases.

A Novel Val286Ala Polymorphism in the NPXXY Motif of the Sphingosine-1-Phosphate Receptor S1PR2 Associates with the Incidence and Age of Onset of Diabetes

Aim: S1PR2 is one of five known sphingosine-1-phosphate receptors and has recently been discussed to be implicated in the development or progression of diabetes. Our aim was to identify S1PR2 polymorphisms in the coding region of the human S1PR2 gene and perform association analyses between S1PR2 polymorphisms leading to amino acid exchanges and phenotypic parameters in a clinical study cohort. Method: We screened the coding region of the S1PR2 gene for polymorphisms resulting in amino acid exchanges in the S1PR2 protein in 40 Caucasian DNA samples from a CEPH control panel. The resulting polymorphisms were then analyzed in more than 3400 patients of the Ludwigshafen Risk and Cardiovascular Health (LURIC) study cohort. Results: In addition to the known Asn→Lys S1PR2 polymorphism at position 10 of the S1PR2 protein, we identified a novel polymorphism in the NPXXY motif of S1PR2, resulting in the amino acid exchange Val→Ala at position 286. The S1PR2 genotype Val286Ala showed strong association with the incidence and age at onset of diabetes in the studied patient cohort. Conclusion: With our analysis we substantiate previous reports on the possible implication of S1PR2 in the development of diabetes and identified the S1PR2 Val286Ala genotype to be significantly associated with incidence and age at onset of diabetes likely due to an altered function of S1PR2.