Host DNases prevent vascular occlusion by neutrophil extracellular traps.

Platelet and fibrin clots occlude blood vessels in hemostasis and thrombosis. Here we report a noncanonical mechanism for vascular occlusion based on neutrophil extracellular traps (NETs), DNA fibers released by neutrophils during inflammation. We investigated which host factors control NETs in vivo and found that two deoxyribonucleases (DNases), DNase1 and DNase1-like 3, degraded NETs in circulation during sterile neutrophilia and septicemia. In the absence of both DNases, intravascular NETs formed clots that obstructed blood vessels and caused organ damage. Vascular occlusions in patients with severe bacterial infections were associated with a defect to degrade NETs ex vivo and the formation of intravascular NET clots. DNase1 and DNase1-like 3 are independently expressed and thus provide dual host protection against deleterious effects of intravascular NETs.

Prostate-specific antigen, prostate cancer, and disorders of hemostasis.

Prostate cancer is the most prevalent malignancy in men and the third leading cause of cancer deaths worldwide. Disorders of hemostasis are commonplace in patients with prostate cancer and include disseminated intravascular coagulation, venous thromboembolism, acute coronary syndrome, and postsurgical bleeding. These hemostatic disorders contribute to the mortality and morbidity of prostate cancer. The leading mechanisms proposed to underlie prostate cancer-related coagulopathies are thought to be a hyperexpression of tissue factor, cancer procoagulant, and platelet-activating factor, which is then accompanied by release of large amounts of both prothrombotic and profibrinolytic substances into the bloodstream. Given the generally accepted notion that prostate-specific antigen (PSA) represents an important biomarker in prostate cancer diagnostics, large population screenings were initiated for early detection of cancer. However, recent clinical and economic drawbacks have been recently raised, including evidence that screening exposes patients to a significant risk of both overdiagnosis and overtreatment. Nevertheless, several lines of evidence suggest that PSA may have tumor-suppressing activities. Despite being a member of the vast kallikrein family, which actively interplays with the coagulation cascade, the role of PSA in the pathogenesis of hemostatic disorders observed in prostate cancer patients remains circumstantial and speculative. However, observations that the levels of this cancer marker tend to correlate positively with those of several markers of thrombin generation, and with postsurgical bleeding as well as with coronary atherosclerosis and negative outcomes of myocardial infarction, raise a new and intriguing scenario regarding the pathophysiological role of this serine protease.

Clinical and laboratory phenotypes associated with the aspirin-like defect: a study in 17 unrelated families.

Aspirin-like defect (ALD) is a rare, mostly autosomal dominant inherited dysfunction of the intraplatelet arachidonic acid (AA) pathway leading to impaired thromboxane A2 signalling. We aimed to establish diagnostic criteria for ALD diagnosis and present clinical and laboratory phenotypes of 52 individuals from 17 unrelated families. Platelet in vitro function was determined on the basis of platelet aggregation response (PAR) to AA, adenosine diphosphate, collagen and ristocetin as well as PFA-100 closure times (CT). Using impaired PAR to AA (< or =10%) as the mandatory diagnostic criterion, ALD could be confirmed in 17 patients. Subsequently, family members were investigated and among 35 individuals an additional 13 ALD patients as well as 4 individuals with mild ALD (PAR to AA: 19-32%) were identified. At least one bleeding symptom was reported by 25 (74%) ALD patients and prolonged CT was detected in 24 (71%) of the cases, both significantly correlated with impaired PAR to AA (P = 0.001 and P = 0.002, respectively). An estimated 0.6% prevalence was determined for ALD in our paediatric patients with suspected coagulation disorders. Due to the mild bleeding symptoms, ALD is probably underdiagnosed. If ALD is suspected, PAR to AA is suitable for the identification of individuals at risk of increased haemorrhage.