Reducing Abdominal Aortic Aneurysm Progression by Blocking Neutrophil Extracellular Traps Depends on Thrombus Formation.

Neutrophil extracellular traps (NETs) are implicated in the pathogenesis of abdominal aortic aneurysm (AAA), located in adventitia and intraluminal thrombus. We compared the therapeutic potential of targeting upstream or downstream effector molecules of NET formation in 2 murine AAA models based on angiotensin II or peri-adventitial elastase application. In both models, NETs were detected in formed aneurysms at treatment start. Although NET inhibitors failed in the elastase model, they prevented progression of angiotensin II-induced aneurysms with thrombus, which resembles established human disease (including thrombus development). Blockade of upstream NET mediators was more effective than interference with downstream NET molecules.

Neutrophils in lung cancer patients: Activation potential and neutrophil extracellular trap formation.

Background: Patients with cancer have an increased risk of developing venous thromboembolism. Neutrophils and neutrophil extracellular traps (NETs) reportedly influence the risk of cancer-associated thrombosis. Subpopulations of high and low-density neutrophils (HDN/LDN) are of specific interest, as they might have different functions in cancer patients. Objectives: We aimed to investigate differences between HDNs and LDNs of patients with lung cancer and healthy controls, and their ability of activation and NET formation. Methods: Within the framework of the Vienna Cancer and Thrombosis Study, a prospective observational cohort study, HDNs and LDNs from 20 patients with lung cancer and 20 controls were isolated by density gradient centrifugation. The ability of neutrophil subpopulations for activation and NET formation was investigated by flow cytometry. Results: Compared to controls, patients with cancer had higher numbers of total leukocytes, HDNs, and LDNs. LDNs of patients were more frequently in an activated state (CD62L↓/CD16↑) at baseline (median [IQR] 5.9% [3.4-8.8] vs 2.5% [1.6-6.7]). HDNs and LDNs from patients showed a significantly increased response to stimulation with ionomycin (CD11b HDN: 98.5 [95.4-99.4] vs 41.7 [13.4-91.6]; LDN: 82.9 [63-94] vs 39.6 [17.3-72.1]). In addition, HDNs from patients showed a higher capability of NET formation after ionomycin stimulation compared to HDNs from healthy controls (18509.5 [12242.5-29470.3] vs 10001 [6618.8-18384.3]). Conclusion: Protumorigenic LDNs were elevated, and neutrophil subpopulations showed an increased activation profile and ability for NET formation in patients with cancer. These mechanisms might be involved in tumor promotion and contribute to the prothrombotic phenotype of neutrophils in cancer.

Neutrophil subpopulations and their activation potential in patients with antiphospholipid syndrome and healthy individuals.

OBJECTIVES: Patients with APS are at increased risk of thromboembolism. Neutrophils have been shown to play a role in inducing thrombosis. We aimed to investigate differences in neutrophil subpopulations, their potential of activation and neutrophil extracellular trap (NET) formation comparing high and low-density neutrophils (HDNs/LDNs) as well as subpopulations in patients with APS and controls to gain deeper insight into their potential role in thrombotic manifestations in patients with APS. METHODS: HDNs and LDNs of 20 patients with APS and 20 healthy donors were isolated by density gradient centrifugation and stimulated. Neutrophil subpopulations, their activation and NET release were assessed by flow cytometry. RESULTS: LDNs of both groups showed higher baseline activation, lower response to stimulation (regulation of activation markers CD11b/CD66b), but higher NET formation compared with HDNs. In patients with APS, the absolute number of LDNs was higher compared with controls. HDNs of APS patients showed higher spontaneous activation [%CD11b high: median (interquartile range): 2.78% (0.58-10.24) vs 0.56% (0.19-1.37)] and response to stimulation with ionomycin compared with HDNs of healthy donors [%CD11b high: 98.20 (61.08-99.13) vs 35.50% (13.50-93.85)], whereas no difference was found in LDNs. NET formation was increased in patients' HDNs upon stimulation. CONCLUSION: HDNs and LDNs act differently, unstimulated and upon various stimulations in both healthy controls and APS patients. Differences in HDNs and LDNs between patients with APS and healthy controls indicate that neutrophils may enhance the risk of thrombosis in these patients and could thus be a target for prevention of thrombosis in APS.

Functional characterization of novel germline TP53 variants in Swedish families.

Pathogenic germline TP53 variants predispose to a wide range of early onset cancers, often recognized as the Li-Fraumeni syndrome (LFS). They are also identified in 1% of families with hereditary breast cancer (HrBC) that do not fulfill the criteria for LFS. In this study, we present a total of 24 different TP53 variants identified in 31 Swedish families with LFS or HrBC. Ten of these variants, nine exonic and one splice, have previously not been described as germline pathogenic variants. The nine exonic variants were functionally characterized and demonstrated partial transactivation activity compared to wild-type p53. Some show nuclear localization similar to wild-type p53 while others possess cytoplasmic or perinuclear localization. The four frameshift variants (W91Gfs*32, L111 Wfs*12, S227 Lfs*20 and S240Kfs*25) had negligible, while F134 L and T231del had low level of p53 activity. The L111 Wfs*12 and T231del variants are also deficient for induction of apoptosis. The missense variant R110C retain p53 effects and the nonsense E349* shows at least partial transcription factor activity but has reduced ability to trigger apoptosis. This is the first functional characterization of novel germline TP53 pathogenic or likely pathogenic variants in the Swedish cohort as an attempt to understand its association with LFS and HrBC, respectively.