Impaired DNase1-mediated degradation of neutrophil extracellular traps is associated with acute thrombotic microangiopathies.

BACKGROUND: Acute thrombotic microangiopathies (TMAs) are characterized by excessive microvascular thrombosis and are associated with markers of neutrophil extracellular traps (NETs) in plasma. NETs are composed of DNA fibers and promote thrombus formation through the activation of platelets and clotting factors. OBJECTIVE: The efficient removal of NETs may be required to prevent excessive thrombosis such as in TMAs. To test this hypothesis, we investigated whether TMAs are associated with a defect in the degradation of NETs. METHODS AND RESULTS: We show that NETs generated in vitro were efficiently degraded by plasma from healthy donors. However, NETs remained stable after exposure to plasma from TMA patients. The inability to degrade NETs was linked to a reduced DNase activity in TMA plasma. Plasma DNase1 was required for efficient NET degradation and TMA plasma showed decreased levels of this enzyme. Supplementation of TMA plasma with recombinant human DNase1 restored NET-degradation activity. CONCLUSIONS: Our data indicate that DNase1-mediated degradation of NETs is impaired in patients with TMAs. The role of plasma DNases in thrombosis is, as of yet, poorly understood. Reduced plasma DNase1 activity may cause the persistence of pro-thrombotic NETs and thus promote microvascular thrombosis in TMA patients.

Polymorphism in NFKBIA gene is associated with recurrent acute rejections in liver transplant recipients.

The nuclear factor of kappa light polypeptide gene enhancer B-cells inhibitor-alpha (NFKBIA) gene encodes a member of the nuclear factor-kappa-B inhibitor family. Polymorphisms in this gene might be associated with a susceptibility to acute rejection episodes following liver transplantation, as they may cause an increased activation level of the proinflammatory transcription factor nuclear factor of kappa light polypeptide gene enhancer in B-cells (NFκB). The aim of this study was to evaluate whether the NFKBIA polymorphisms -297 C/T (rs2233409), -826 C/T (rs2233406) and 126 G/A (rs696) affect the incidence of acute liver graft rejection. A total of 199 liver transplant recipients was analyzed, 100 without (NAR) and 99 with early acute rejection (AR). Thirty-two individuals with multiple acute rejections (MAR) were analyzed as a subgroup of AR. Polymerase chain reaction-allele specific restriction enzyme analysis (PCR-ASRA) and allele-specific hybridization with fluorescence resonance energy transfer (FRET) were used for genotyping. We identified the genotype NFKBIA 126 AA (P = 0.002) as well as the haplotype NFKBIA-126A-297T-826T (P = 0.002) as a potential risk factor for the occurrence of recurrent acute rejections. Furthermore, we assessed an association between the 126 A allele and susceptibility to recurrent acute rejections (P = 0.027). Our data suggest that the NFKBIA 126 G/A polymorphism might be potentially helpful to identify liver transplant recipients with an increased susceptibility to develop recurrent acute rejections.

[Platelet retention test Homburg (RTH) and drug monitoring of platelet adhesive properties of von Willebrand factor]. / Plättchen-Retentionstest Homburg: Drugmonitoring der Plättchenadhäsivität des von-Willebrand-Faktors.

Platelet plug formation is initiated by the process of platelet adhesion, mainly mediated by the von Wille-brand factor (VWF). Therefore, apart from established criteria the platelet adhesion property is a further criterion to determine VWF e. g. in diagnosis and treatment of von Willebrand disease (VWD). The new platelet retention test Homburg (RTH) is designed to close this gap. It is characterized by its non-thrombogenic filter with interconnecting pores, which retains platelets from blood when pressed through this filter due to the resulting shear stress. The RTH, in particular, proved to be highly sensitive in detecting the platelet adhesive property of VWF after its release from endogenous storage sites by desmopressin or infusion in VWD patients or its supplementation in vitro.