Heiko Rühl

Thrombin inhibition profiles in healthy individuals and thrombophilic patients

Inhibition of thrombin by endogenous inhibitors plays a central role in the spatiotemporal control of clot formation. A failure to adequately inactivate thrombin such as in antithrombin deficiency generates a strong prothrombotic phenotype. To study if and to what extent delayed thrombin inactivation rates beyond antithrombin deficiency contribute to the prothrombotic phenotype we measured thrombin inhibition profiles in plasma samples obtained from 16 healthy individuals and 39 thrombophilic patients, including 17 patients diagnosed positive for anti-prothrombin/phospholipid antibodies. To test thrombin inhibition, thrombin was added to plasma, and endogenous thrombin inhibition stopped by addition of the reversible thrombin inhibitor argatroban. Subsequently, the amount of argatroban-complexed thrombin was measured using an oligonucleotide-based enzyme capture assay. In normal human plasma thrombin at concentrations up to 4 ng/ml (109 pM) became inactivated with an average half-life time of 56.4 ± 4.7 seconds (s). In antithrombin-deficient plasma the thrombin half-life was prolonged to 168.2 ± 14.9 s. Among the thrombophilic patients, only one with mild antithrombin deficiency showed impaired thrombin inactivation rates, whereas all other patients including the antiphospholipid positive patients showed thrombin inhibiting capacities within the normal range. We conclude that thrombin added to normal human plasma at subthreshold levels of ~100 pM or below becomes inactivated with a half-life time below 1 minute. Antiphospholipid antibodies do not prolong thrombin half-life times, making it unlikely that delayed thrombin inactivation contributes to the thrombotic phenotype of the antiphospholipid syndrome. In contrast, plasma levels of antithrombin falling below 80% of normal markedly prolong the thrombin half-life.

Tamoxifen induces resistance to activated protein C

INTRODUCTION The estrogen antagonist tamoxifen (TAM) increases the thrombotic risk similar to estrogen containing oral contraceptives (OC). In OC users this risk is attributed to alterations of hemostasis resulting in acquired resistance to activated protein C (APC). TAM-induced APC resistance has not been reported yet. MATERIALS AND METHODS Blood samples were collected prospectively from women with breast cancer before (n=25) and monthly after start of adjuvant TAM treatment (n=75). APC resistance was evaluated on basis of the effect of APC on the endogenous thrombin generation potential. To detect increased in vivo APC generation APC plasma levels were measured using a highly sensitive oligonucleotide-based enzyme capture assay. Routine hemostasis parameters were measured additionally. RESULTS APC sensitivity decreased by 41% (p=0.001) compared to baseline after one month of TAM application and remained significantly decreased during the study period. Free protein S increased (p=0.008) while other analyzed procoagulant factors, inhibitors, and activation markers of coagulation decreased or did not change significantly. In five patients the APC concentration increased to non-physiological levels but an overall significant increase of APC was not observed. CONCLUSIONS This is the first study showing acquired APC resistance under TAM therapy. Acquired APC resistance might explain the increased thrombotic risk during TAM treatment. Observed changes of hemostasis parameters suggest different determinants of TAM-induced APC resistance than in OC-induced APC resistance. The presence of acquired APC resistance in TAM patients warrants further evaluation if these patients may benefit from antithrombotic prophylaxis in the presence of additional thrombotic risk factors.

Genome-wide transcriptome induced by Porphyromonas gingivalis LPS supports the notion of host-derived periodontal destruction and its association with systemic diseases

Chronic periodontitis (CP) is a prevalent pathogen-associated inflammatory disorder characterized by the destruction of tooth-supporting tissues, and linked to several systemic diseases. Both the periodontopathogen Porphyromonas gingivalis (Pg), and the genetically determined host immune response, are hypothesized to play a crucial role in this association. To identify new target genes for CP and its associated systemic diseases, we investigated the transcriptome induced by Pg in human monocytes using a genome-wide approach. Monocytes were isolated from healthy male volunteers of European origin and challenged with the Pg virulence factor LPS. Array-based gene expression analysis comprising >47,000 transcripts was performed followed by pathway analyses. Transcriptional data were validated by protein and cell surface markers. LPS Pg challenge led to the significant induction of 902 transcripts. Besides known periodontitis-associated targets, several new candidates were identified (CCL23↑, INDO↑, GBP 1/4↑, CFB↑, ISG20↑, MIR155HG↑, DHRS9↓). Moreover, various transcripts correspond to the host immune response, and have been linked to cancer, atherosclerosis and arthritis, thus highlighting the systemic impact of CP. Protein data of immunological markers validated our results. The present findings expand understanding of Pg elicited immune responses, and indicate new target genes and pathways of relevance to diagnostic and therapeutic strategies.

Variable resistance to freezing and thawing of CD34-positive stem cells and lymphocyte subpopulations in leukapheresis products

BACKGROUND AIMS Leukapheresis products for hematopoietic stem cell transplantation can be cryopreserved for various indications. Although it is known that CD34(+) cells tolerate cryopreservation well, a significant loss of CD3(+) cells has been observed, which has been ascribed to several factors, including transport, storage conditions and granulocyte-colony stimulating factor (G-CSF) administration. METHODS To assess the tolerance of CD34(+) cells and lymphocyte subpopulations for cryopreservation and thawing, the post-thaw recoveries of CD34(+) cells, CD3(+)CD4(+) cells, CD3(+)CD8(+) cells, CD19(+) cells and CD16(+)CD56(+) cells were determined in 90 cryopreserved apheresis products, among which 65 were from G-CSF-mobilized donors, and 34 from unrelated donors that underwent transport before cryopreservation at our center. A controlled rate freezer and 5% dimethyl sulfoxide were used for cryopreservation. RESULTS We could detect statistically significant differences for CD34(+) cell recovery (93.0 ± 20.7%) when compared to CD3(+)CD4(+) cell (83.1 ± 15.4%, P = 0.014), and CD3(+)CD8(+) cell recovery (83.3 ± 13.9%, P = 0.001). Similarly, CD19(+) cell recovery (98.6 ± 15.1%) was higher than CD3(+)CD4(+) cell (P = 2.5 × 10(-7)) and CD3(+)CD8(+) cell recovery (P = 1.2 × 10(-8)). Post-thaw recovery rates of all cell populations were not impaired in G-CSF-mobilized products compared with non-mobilized products nor in unrelated compared with related donor products. DISCUSSION Our data suggest a lower tolerance of CD3(+) cells for cryopreservation and demonstrate that freezing-thawing resistance thawing is cell-specific and independent from other factors that affect post-thaw recovery of cryopreserved cells. Thus, a clinical consequence may be the monitoring of post-thaw CD3(+) cell doses of cryopreserved products, such as donor lymphocyte infusions.

Label-Free Kinetic Studies of Hemostasis-Related Biomarkers Including D-Dimer Using Autologous Serum Transfusion

The objective of this study was to evaluate the elimination kinetics of hemostasis-related biomarkers including the prothrombin activation fragment F1+2, thrombin-antithrombin complex (TAT), plasmin-α2-antiplasmin complex (PAP), and D-dimer in humans. Autologous serum was used as a biomarker source and infused into 15 healthy volunteers. Serum was prepared from whole blood in the presence of recombinant tissue-type plasminogen activator (final concentration 20 μg/mL) to induce plasmin generation required for PAP and D-dimer formation. Serum transfusions (50 mL/30 min) were well tolerated by all subjects. Endogenous thrombin formation was not induced by serum infusions as measured using a highly sensitive oligonucleotide-based enzyme capture assay. Median peak levels (x-fold increase over baseline) of F1+2, TAT, PAP, and D-dimer of 3.7 nmol/L (28.9), 393 ng/mL (189.6), 3,829 ng/mL (7.0), and 13.4 mg/L (34.2) were achieved at the end of serum infusions. During a 48 h lasting follow-up period all biomarkers showed elimination kinetics of a two-compartment model. Median (interquartile range) terminal half-lives were 1.9 (1.3–3.6) h for F1+2, 0.7 (0.7–2.6) h for TAT, and 10.8 (8.8–11.4) h for PAP. With 15.8 (13.1–23.1) h the D-dimer half-life was about twice as long as previously estimated from radiolabeling studies in animals and small numbers of human subjects. The serum approach presented here allows label-free and simultaneous analysis of the elimination kinetics of various hemostasis-related biomarkers. Based on these data changes in biomarker levels could more precisely used to estimate the activity level of the hemostatic system.

Tranexamic Acid for Hyperfibrinolytic Hemorrhage During Conservative Management of Placenta Percreta.

BACKGROUND: Complications of conservative management of abnormal placentation in which the placenta is left in situ for resorption include secondary hemorrhage, infection, and disseminated intravascular coagulation. CASE: A 41-year old woman received conservative treatment for placenta percreta. Nine weeks after delivery, she developed gingival bleeding, easy bruising, and moderate-to-severe vaginal bleeding. Hemostasis testing established the diagnosis of isolated hyperfibrinolysis; acute disseminated intravascular coagulation was excluded. Bleeding was successfully treated using the antifibrinolytic agent tranexamic acid. Eight weeks later uncomplicated curettage was performed. CONCLUSION: Isolated hyperfibrinolysis is a potential cause of bleeding during conservative management of placenta increta and percreta. Management of this treatment approach should include hemostasis monitoring, because hyperfibrinolysis can be successfully controlled using fibrinolysis inhibitors.

Genome-wide transcriptome induced by nickel in human monocytes.

UNLABELLED Nickel-containing alloys are frequently used in the biomedical field, although, owing to corrosive processes metal ion leaching is inevitable. Due to nickel ion (Ni(2+)) leaching several adverse effects are described in the literature. However, only a few studies evaluated the genetic profile of Ni(2+) in human cells which is of great importance since nickel-induced effects differ between humans and mice as a result of species-specific receptor variability. Thus, we investigated gene expression induced by Ni(2+)in human monocytes using a transcriptome-wide approach determining new target genes implicated in nickel-induced pathologies. Monocytes were isolated from healthy volunteers of Central European origin using stringent inclusion criteria. Cells were challenged with different Ni(2+) concentrations. Array-based gene expression analysis was performed comprising more than 47,000 transcripts followed by pathway analyses. Transcriptional data were validated by protein and cell surface markers. Ni(2+) significantly influenced the expression of 1385 transcripts in a dose-dependent manner. Apart from known targets (CCL20↑, PTGS2↑, MTs↑, SLCs↑), we identified new candidates implicated in Ni(2+)-elicited processes (various microRNAs↑, INSIG1↑, NAMPT↑, MS4A6A↓, DHRS9↓). Several of these transcripts correspond to immunity, inflammation and were shown to be involved in cellular reactions related to hypersensitivity, cancer, colitis, and encephalitis. Moreover, 459 canonical pathways/signaling, 500 pathologies and 2687 upstream regulators were detected. Protein results validated our findings. To our knowledge, the present systematic transcriptome-wide expression study is the first which explored Ni(2+)-elicited cell responses in human primary monocytes identifying new target genes, pathways and upstream regulators of relevance to diagnostic and therapeutic strategies. STATEMENT OF SIGNIFICANCE Nickel is widely applied in the biomedical field, although several adverse effects are documented in the literature due to nickel ion (Ni(2+)) leaching. In humans, allergic reactions like contact dermatitis are the most common adverse effect to Ni(2+), whereas serious concerns relate to possible systemic and carcinogenic activities. Using a systematic genome-wide transcriptional approach in human primary monocytes unveil new target genes, pathways and upstream regulators implicated in nickel-elicited immune response which are of significance to diagnostic and therapeutic strategies. This approach provides new information of how host-derived immune response contributes to the interaction with antigens and supports the interplay between metal ions and systemic diseases.

Recurrent VTE in a heterozygote of the fibrinogen Aα IVS4+1G>T and Aα p.Arg168Ter mutation

Recurrent VTE in a heterozygote of the fibrinogen Aα IVS4+1G>T and Aα p.Arg168Ter mutation -

Impact of hormone-associated resistance to activated protein C on the thrombotic potential of oral contraceptives: a prospective observational study.

Introduction The increased thrombotic risk of oral contraceptives (OC) has been attributed to various alterations of the hemostatic system, including acquired resistance to activated protein C (APC). To evaluate to what extent OC-associated APC resistance induces a prothrombotic state we monitored plasma levels of thrombin and molecular markers specific for thrombin formation in women starting OC use. Elevated plasma levels of thrombin have been reported to characterize situations of high thrombotic risk such as trauma-induced hypercoagulability, but have not yet been studied during OC use. Patients and Methods Blood samples were collected prospectively from healthy women (n = 21) before and during three menstruation cycles after start of OC. APC resistance was evaluated using a thrombin generation-based assay. Plasma levels of thrombin and APC were directly measured using highly sensitive oligonucleotide-based enzyme capture assay (OECA) technology. Thrombin generation markers and other hemostasis parameters were measured additionally. Results All women developed APC resistance as indicated by an increased APC sensitivity ratio compared with baseline after start of OC (p = 0.0003). Simultaneously, plasma levels of thrombin, prothrombin fragment 1+2, and of thrombin-antithrombin complexes did not change, ruling out increased thrombin formation. APC plasma levels were also not influenced by OC use, giving further evidence that increased thrombin formation did not occur. Conclusions In the majority of OC users no enhanced thrombin formation occurs despite the development of APC resistance. It cannot be ruled out, however, that thrombin formation might occur to a greater extent in the presence of additional risk factors. If this were the case, endogenous thrombin levels might be a potential biomarker candidate to identify women at high thrombotic risk during OC treatment. Large-scale studies are required to assess the value of plasma levels of thrombin as predictors of OC-associated thrombotic risk.

Activated Factor X-Based versus Thrombin-Based Antithrombin Testing in Thrombophilia Workup in the DOAC Era

Antithrombin (AT) activity tests are used for diagnosing hereditary AT deficiency, a main genetic determinant of thrombophilia. They are either based on inhibition of thrombin (FIIa) or activated factor X (FXa). FXa-based assays have been suggested to be preferable to FIIa-based assays due to their higher sensitivity for certain AT deficiency causing mutations. To assess the performance of these two methods in a real-world scenario, 745 consecutively collected samples from patients referred to our institute during a 3-month period for thrombophilia testing were analysed. In samples from patients not receiving direct-acting oral anticoagulants or heparins (n = 485), both methods showed good agreement (r = 0.874, Bland-Altman limits of agreement 6.57%, -15.76%). While similar results were obtained in patients receiving low-molecular-weight heparin (LMWH, n = 76, r = 0.891, 4.09%, -14.35%), the agreement was lower in patients receiving rivaroxaban (n = 86, r = 0.570, 5.97%, -49.43%) and apixaban (n = 72, r = 0.735, 3.77%, -42.45%). Direct FXa inhibitors but not LMWH increased FXa-based assay results in a dose-dependent manner, while the FIIa-based test was unaffected. Both assay types were equally successful in detecting hereditary AT deficiency in our study population, as samples from 9 out of 10 patients with AT deficiency causing mutations were detected by each method. These data suggest that FXa-based AT testing can be preferred over FIIa-based methods only in the absence of direct FXa inhibitors. In patients receiving direct FXa inhibitors, AT activity testing should be performed using FIIa-based assays.