Investigation of von Willebrand factor multimer abnormalities before and after aortic valve replacement using the Hydragel-5 assay.

BACKGROUND: Severe aortic stenosis (sAS) is associated with acquired von Willebrand syndrome (AVWS) by loss of high-molecular-weight multimers (HMWM) of von Willebrand factor (VWF), potentially resulting in perioperative bleeding. Analysis of VWF multimers remains challenging. Recently, the new, rapid Hydragel 5 assay has been developed, using electrophoretic protein separation for dividing VWF-multimers into low (LMWM), intermediate (IMWM), and HMWM, the hemostatically active part of VWF. Here, we evaluated its impact on predicting blood loss in presence of AVWS after surgical aortic valve replacement (SAVR). METHODS: We prospectively examined 52 patients (age: 68 ± 7 years; 54 % male) admitted to SAVR. They were divided in two groups (A: normal VWF, n = 28; B: abnormal VWF, n = 24, defined as VWF-activity/antigen (VWF:Ac/Ag)-ratio < 0.7 and/or HMWM loss). Blood samples and echocardiographic data were collected before, seven days and three months after SAVR. Blood loss and transfusions were recorded. RESULTS: Baseline characteristics and clinical data were similar in both groups. HMWM loss was present in 38.5 % of all patients. HMWM, the VWF:Ac/Ag- and HMWM/(IMWM+LMWM)-ratios were significantly decreased preoperatively in group B but normalized after SAVR. Bleeding, re-thoracotomy and transfusion rates were comparable. HMWM loss was inversely correlated with the peak aortic gradient (Pmax) and positively with the aortic valve area (AVA), while HMWM/(IMWM+LMWM)-ratio negatively correlated with the mean aortic gradient (Pmean). CONCLUSION: HMWM and HMWM/(IMWM+LMWM)-ratio inversely correlate with severity of AS and normalize after SAVR. The Hydragel-5 assay's might be valuable for routine diagnostics to assess bleeding risk and postoperative normalization of AS and VWF abnormalities in SAVR patients.

Establishing Expectancy Values for Fibrin Monomer in Uncomplicated Pregnancy.

Background During pregnancy, a physiological increase of molecular activation markers (MAM) of hemostasis such as prothrombin fragments 1 + 2, thrombin-antithrombin complex, and D-dimers (DD) occurs. Therefore, monitoring MAM levels during pregnancy to evaluate the risk of venous thromboembolism (VTE) may be unreliable; nevertheless, DD analysis in pregnancy is widely performed. In contrast to DD, fibrin monomer (FM) levels have been reported to remain stable during pregnancy. Objectives The main aim of this study was to define the expected range for FM levels in pregnant outpatients. In addition, we examined the impact of the individual VTE risk, as calculated by the pregnancy risk score of the Royal College of Obstetricians and Gynaecologists (RCOG), as well as that of antithrombotic treatment on FM levels. Methods A total of 342 pregnant women seen at our hemostasis unit were included throughout 350 pregnancies in 899 samples. Results Low-risk thrombophilia, but not the RCOG score itself, was found to influence all MAM levels, whereas antithrombotic treatment had only an impact on DD. For FM, a reference range could be calculated irrespective of the pregnancy term, in contrast to other MAMs, which fluctuated throughout pregnancy. Conclusions Our findings suggest a stronger impact of inherited thrombophilia on hemostasis activity during pregnancy as compared with acquired or other predisposing thrombophilic risk factors. FM levels showed a marginal increase during pregnancy in contrast to other MAM and remain a potential candidate to improve the laboratory assessment of VTE risk during pregnancy. Further prospective studies in pregnant patients with suspicion of VTE are needed.

Laboratory Limitations of Excluding Hereditary Protein C Deficiency by Chromogenic Assay: Discrepancies of Phenotype and Genotype.

Protein C (PC) deficiency is associated with an increased risk for venous thromboembolism (VTE). In daily practice, exclusion of a hereditary PC deficiency is often based on a single determination of PC activity, by either clotting time-based or mostly chromogenic assay. However, diagnosis of hereditary PC deficiency is challenging due to several laboratory and clinical limitations. We compared the potential of PC activity values measured by either chromogenic or clotting time-based assay to predict a variation in the PROC gene. One hundred one (35%) of 287 patients carried variations within the PROC gene, including 2 previously not published variations. In 20 (20%) patients with identified variation, PC activity, determined by chromogenic assay, was within the reference range. For prediction of an underlying genetic defect determined by chromogenic and clotting time-based assay, sensitivity was 80% versus 99%, specificity 75% versus 18%, positive predictive value 64% versus 39%, and negative predictive value (NPV) 88% versus 97%. The lower NPV of chromogenic versus clotting time-based PC assay can be mainly explained by the presence of PC deficiency type IIb. Following our proposed diagnostic algorithm, additional measurement of PC activity by clotting time-based assay in case of a positive VTE history improves detection of this subtype of PC deficiency. Considering potential therapeutic consequences for primary and especially for secondary VTE prophylaxis, genetic analysis is required not only for confirmation but also for clarification of PC deficiency.

Inter-ictal assay of peripheral circulating inflammatory mediators in migraine patients under adjunctive cervical non-invasive vagus nerve stimulation (nVNS): A proof-of-concept study.

OBJECTIVE: To assay peripheral inter-ictal cytokine serum levels and possible relations with non-invasive vagus nerve stimulation (nVNS) responsiveness in migraineurs. METHODS: This double-blinded, sham-controlled study enrolled 48 subjects and measured headache severity, frequency [headache days/month, number of total and mild/moderate/severe classified attacks/month], functional state [sleep, mood, body weight, migraine-associated disability] and serum levels of inflammatory markers [inter-ictal] using enzyme-linked immunoassays at baseline and after 2 months of adjunctive nVNS compared to sham stimulation and suitably matched controls. RESULTS: No significant differences were observed at baseline and after 2 months for headache severity, total attacks/month, headache days/month and functional outcome [sleep, mood, disability] between verum and sham nVNS. However, the number of severe attacks/month significantly decreased in the verum nVNS group and circulating pro-inflammatory IL-1ß was elevated significantly in the sham group compared to nVNS. Levels of anti-inflammatory IL-10 were significantly higher at baseline in both groups compared to healthy controls, but not at 2 months follow-up [p < 0.05]. Concentrations of high-mobility group box-1 (HMGB-1), IL-6, tumor-necrosis factor-α (TNF-α), leptin, adiponectin, ghrelin remained unchanged [p > 0.05]. No severe device-/stimulation-related adverse events occurred. CONCLUSION: 2 months of adjunctive cervical nVNS significantly declined the number of severe attacks/month. Pro-inflammatory IL-1ß plasma levels [inter-ictal] were higher in sham-treated migraine patients compared to verum nVNS. However, pro- [IL-6, HMGB-1, TNF-α, leptin] and anti-inflammatory [IL-10, adiponectin, ghrelin] mediators did not differ statistically. Profiling of neuroinflammatory circuits in migraine to predict nVNS responsiveness remains an experimental approach, which may be biased by pre-analytic variables warranting large-scale biobank-based systematic investigations [omics].

Selective L4 Dorsal Root Ganglion Stimulation Evokes Pain Relief and Changes of Inflammatory Markers: Part I Profiling of Saliva and Serum Molecular Patterns.

OBJECTIVES: Complex regional pain syndrome (CRPS) and associated comorbidities have been linked to a pro-inflammatory state driven by different mediators. Targeted dorsal root ganglion stimulation (DRGSTIM ) suppressed pain levels and improved functional capacity in intractable CRPS. However, clinical trials assessing the impact of DRG stimulation on the neuroimmune axis are lacking. METHODS: This study enrolled 24 subjects (12 refractory CRPS patients plus suitably matched healthy controls) and performed immunoassays of inflammatory mediators in saliva and serum along with score-based assessments of pain, mood, and sleep quality at baseline and after three months of selective L4-DRGSTIM . RESULTS: After three-month L4-DRGSTIM CRPS associated pain significantly decreased. In addition, disturbed sleep and mood improved post-DRGSTIM , although statistically not significant. Significantly increased serum values of pro-inflammatory markers were detected pre- and post L4-DRGSTIM for high-mobility group box 1, tumor-necrosis factor α, interleukin (IL) 6, and leptin. IL-1ß was significantly elevated pre-L4 DRGSTIM , but not posttreatment. Elevated anti-inflammatory IL-10 significantly decreased after three months in serum, while saliva oxytocin concentrations increased in CRPS subjects after L4-DRGSTIM (p = 0.65). No severe implantation and stimulation associated adverse events were recorded. CONCLUSIONS: Selective L4-DRGSTIM improved neuropathic pain and functional impairment in CRPS as previously reported. CRPS patients displayed a pro-inflammatory molecular pattern in serum. Serum anti-inflammatory IL-10 significantly declined, while saliva oxytocin nonsignificantly increased after L4-DRGSTIM . An evidence-based relational interpretation of our study is limited due to the uncontrolled study design. However, molecular profiling of biofluids (saliva, serum) represents a novel and experimental field in applied neuromodulation, which warrant further investigations to unveil mechanisms of neuroimmune modulation.

Evaluation of a semi-automated von Willebrand factor multimer assay, the Hydragel 5 von Willebrand multimer, by two European Centers.

BACKGROUND: The phenotypic diagnosis of von Willebrand disease (VWD) is a multistep process with classification dependent on the quantification of von Willebrand factor (VWF) multimeric structure. VWF multimer analysis is a technically challenging, lengthy and non-standardised assay, usually performed in specialist laboratories. Recently, a new semi-automated multimer assay, the Hydragel 5 von Willebrand multimers (H5VWM) has become available. OBJECTIVES: This study, performed in two European centres, compared existing in-house multimer assays to the H5VWM in individuals with and without VWD. RESULTS: Overall agreement of 91.1% was observed in 74 individuals with normal VWF levels, 57 patients grouped as type 1 VWD, 33 type 2A, 16 type 2B, 28 type 2M, 11 type 2N. Patients tested following Desmopressin or VWF concentrate, with thrombotic thrombocytopenic purpura and acquired von Willebrand syndrome were also evaluated. Many of the discrepancies between methods were in patients with genetic mutations linked to more than one type of VWD including p.R1374C/H and p.R1315C. Quantifiable multimer results were available within one working day. Densitometry improved the interpretation of the multimers with slight structural variations that were not apparent by visual inspection of the in-house method. CONCLUSIONS: 5VWM was a rapid, sensitive, standardised assay which used existing technology and could be included as an initial screen of VWF multimers in a VWD diagnostic algorithm in conjunction with traditional multimer analysis.

Two enzymes catalyze vitamin K 2,3-epoxide reductase activity in mouse: VKORC1 is highly expressed in exocrine tissues while VKORC1L1 is highly expressed in brain.

VKORC1 and VKORC1L1 are enzymes that both catalyze the reduction of vitamin K2,3-epoxide via vitamin K quinone to vitamin K hydroquinone. VKORC1 is the key enzyme of the classical vitamin K cycle by which vitamin K-dependent (VKD) proteins are γ-carboxylated by the hepatic γ-glutamyl carboxylase (GGCX). In contrast, the VKORC1 paralog enzyme, VKORC1L1, is chiefly responsible for antioxidative function by reduction of vitamin K to prevent damage by intracellular reactive oxygen species. To investigate tissue-specific vitamin K 2,3-epoxide reductase (VKOR) function of both enzymes, we quantified mRNA levels for VKORC1, VKORC1L1, GGCX, and NQO1 and measured VKOR enzymatic activities in 29 different mouse tissues. VKORC1 and GGCX are highly expressed in liver, lung and exocrine tissues including mammary gland, salivary gland and prostate suggesting important extrahepatic roles for the vitamin K cycle. Interestingly, VKORC1L1 showed highest transcription levels in brain. Due to the absence of detectable NQO1 transcription in liver, we assume this enzyme has no bypass function with respect to activation of VKD coagulation proteins. Our data strongly suggest diverse functions for the vitamin K cycle in extrahepatic biological pathways.

Human VKORC1 mutations cause variable degrees of 4-hydroxycoumarin resistance and affect putative warfarin binding interfaces.

Since the discovery of warfarin-sensitive vitamin K 2,3-epoxide reductase complex subunit 1 (VKORC1), 26 human VKORC1 (hVKORC1) missense mutations have been associated with oral anticoagulant resistance (OACR). Assessment of warfarin resistance using the "classical" dithiothreitol-driven vitamin K 2,3-epoxide reductase (VKOR) assay has not reflected clinical resistance phenotypes for most mutations. Here, we present half maximal inhibitory concentrations (IC50) results for 21 further hVKORC1 mutations obtained using a recently validated cell-based assay (J Thromb Haemost 11(5):872). In contrast to results from the dithiothreitol-driven VKOR assay, all mutations exhibited basal VKOR activity and warfarin IC50 values that correspond well to patient OACR phenotypes. Thus, the present assay is useful for functional investigations of VKORC1 and oral anticoagulant inhibition of the vitamin K cycle. Additionally, we modeled hVKORC1 on the previously solved structure of a homologous bacterial enzyme and performed in silico docking of warfarin on this model. We identified one binding site delineated by 3 putative binding interfaces. These interfaces comprise linear sequences of the endoplasmic reticulum-lumenal loop (Ser52-Phe55) and the first (Leu22-Lys30) and fourth (Phe131-Thr137) transmembrane helices. All known OACR-associated hVKORC1 mutations are located in or around these putative interfaces, supporting our model.

VKORC1-dependent pharmacokinetics of intravenous and oral phylloquinone (vitamin K1) mixed micelles formulation.

OBJECTIVE: The pharmacokinetics of phylloquinone (vitamin K1) were evaluated in healthy human adult volunteers (15 male and 15 female) following oral and intravenous administration of a mixed micelles formulation (Konakion MM 2 mg) in an open label study design. The subjects were allocated to one of three genotype-specific groups (n = 10 in each group) in terms of VKORC1 promoter polymorphism c.-1639 G > A to explore the relationship between genotype and pharmacokinetic parameters. METHODS: Blood samples were collected for up to 24 h after administration. Phylloquinone serum levels were determined by reversed phase HPLC with fluorometric detection after post-column zinc reduction. Pharmacokinetic evaluation was performed using non-compartmental analysis. RESULTS: Pharmacokinetic analysis of serum phylloquinone concentration versus time profiles revealed significant differences in the main pharmacokinetic parameters between groups. Upon oral administration, VKORC1 AG carriers showed 41 % higher mean bioavailability (p = 0.01) compared with homozygous AA individuals. Furthermore, AG subjects exhibited 30 % (p = 0.042) and 36 % (p = 0.021) higher mean AUC compared with GG and AA respectively. Terminal half-life was 32 % and 27 % longer for AG carriers in comparison to GG (p = 0.004) and AA (p = 0.015) genotypes respectively. CONCLUSION: Pharmacokinetic differences indicated significant inter-individual variance of vitamin K fate in the human body. The influence of the VKORC1 promoter polymorphism c.-1639 G > A on the pharmacokinetic properties of phylloquinone could be demonstrated in humans. To gain deeper insight in other potential genetic determinants of systemic vitamin K exposure, further correlation of the phenotype-genotype relationship of different players in vitamin K turnover has to be gained.

Human vitamin K 2,3-epoxide reductase complex subunit 1-like 1 (VKORC1L1) mediates vitamin K-dependent intracellular antioxidant function.

Human vitamin K 2,3-epoxide reductase complex subunit 1-like 1 (VKORC1L1), expressed in HEK 293T cells and localized exclusively to membranes of the endoplasmic reticulum, was found to support both vitamin K 2,3-epoxide reductase (VKOR) and vitamin K reductase enzymatic activities. Michaelis-Menten kinetic parameters for dithiothreitol-driven VKOR activity were: K(m) (µM) = 4.15 (vitamin K(1) epoxide) and 11.24 (vitamin K(2) epoxide); V(max) (nmol·mg(-1)·hr(-1)) = 2.57 (vitamin K(1) epoxide) and 13.46 (vitamin K(2) epoxide). Oxidative stress induced by H(2)O(2) applied to cultured cells up-regulated VKORC1L1 expression and VKOR activity. Cell viability under conditions of no induced oxidative stress was increased by the presence of vitamins K(1) and K(2) but not ubinquinone-10 and was specifically dependent on VKORC1L1 expression. Intracellular reactive oxygen species levels in cells treated with 2,3-dimethoxy-1,4-naphthoquinone were mitigated in a VKORC1L1 expression-dependent manner. Intracellular oxidative damage to membrane intrinsic proteins was inversely dependent on VKORC1L1 expression and the presence of vitamin K(1). Taken together, our results suggest that VKORC1L1 is responsible for driving vitamin K-mediated intracellular antioxidation pathways critical to cell survival.