Neutrophil defensin 8

Aims: Neutrophils/platelet interactions are involved in abdominal aortic aneurysm (AAA). The intraluminal thrombus (ILT) is a human model of platelet/neutrophil interactions. The present study focused on mediators involved in neutrophil recruitment in AAA. Methods and results: Conditioned media from luminal, intermediate, and abluminal layers of 29 human ILTs were analysed for neutrophil markers [elastase/alpha1-antitrypsin and MMP9/NGAL complexes, myeloperoxidase (MPO), and alpha-defensin peptides], RANTES, platelet factor 4 (PF4), and interleukin-8 (IL-8). Their time-dependent release into serum from clots generated in vitro and their plasma concentrations in AAA patients and controls were determined. Immunohistochemistry for neutrophils, platelets, IL-8, PF4, and RANTES on AAA sections was performed; and molecules involved in ILT neutrophil chemotactic function were analysed in vitro. Neutrophils and platelets colocalized in the luminal layer of the thrombus. Consistently, neutrophil markers and platelet-derived RANTES and PF4 were released predominantly by the luminal thrombus pole, where their concentrations were significantly correlated. The luminal ILT layer was also the main source of IL-8, whose immunostaining colocalized with neutrophils. All were also released time dependently from clots and were increased in plasma of AAA patients. Luminal ILT layers displayed potent neutrophil chemotactic activity in vitro, which was inhibited by RANTES- and IL-8-blocking antibodies as well as by reparixin, an antagonist of the IL-8 receptors CXCR1 and CXCR2. Conclusion: Taken together, these results suggest that platelet-derived RANTES and neutrophil-derived IL-8 are involved in attracting neutrophils to the luminal layer of AAA ILT.

Background: IL-17A is a key driver of human autoimmune diseases, particularly psoriasis. Objective: We sought to determine the role of IL-17A in psoriasis pathogenesis and to identify a robust and measurable biomarker of IL-17A-driven pathology. Methods: We studied 8 healthy subjects and 8 patients with psoriasis before and after administration of secukinumab, a fully human anti-IL-17A mAb, and used a combination of classical techniques and a novel skin microperfusion assay to evaluate the expression of 170 proteins in blood, nonlesional skin, and lesional skin. For validation, we also tested stored sera from 601 patients with a variety of autoimmune diseases. Results: IL-17A was specifically expressed in lesional compared with nonlesional psoriatic skin (9.8 vs 0.8 pg/mL, P < .001). Proteomic and gene transcription analyses revealed dysregulated antimicrobial peptides, proinflammatory cytokines, and neutrophil chemoattractants, levels of which returned to normal after treatment with secukinumab. β-Defensin 2 (BD-2) was identified as a biomarker of IL-17A-driven pathology by comparing protein expression in patients with psoriasis versus that in healthy subjects (5746 vs 82 pg/mL in serum, P < .0001; 2747 vs <218 pg/mL in dermis, P < .001), responsiveness to secukinumab therapy, and synergistic induction by IL-17A and TNF-α in epidermal keratinocytes. In a validation set of sera from 601 patients with autoimmune diseases thought to be IL-17A driven, we found that BD-2 levels are most highly increased in patients with psoriatic skin lesions, and in patients with psoriasis, BD-2 levels correlated well with IL-17A levels (r = 0.70, n = 199, P < .001) and Psoriasis Area and Severity Index scores (r = 0.53, n = 281, P < .001). Conclusion: IL-17A is a primary driver of skin pathology in patients with psoriasis, and serum BD-2 is an easily measurable biomarker of IL-17A-driven skin pathology.

Sepsis claims an estimated 30 million episodes and 6 million deaths per year, and treatment options are rather limited. Human neutrophil peptides 1-3 (HNP1-3) are the most abundant neutrophil granule proteins but their neutrophil content varies because of unusually extensive gene copy number polymorphism. A genetic association study found that increased copy number of the HNP-encoding gene DEFA1/DEFA3 is a risk factor for organ dysfunction during sepsis development. However, direct experimental evidence demonstrating that these risk alleles are pathogenic for sepsis is lacking because the genes are present only in some primates and humans. Here, we generate DEFA1/DEFA3 transgenic mice with neutrophil-specific expression of the peptides. We show that mice with high copy number of DEFA1/DEFA3 genes have more severe sepsis-related vital organ damage and mortality than mice with low copy number of DEFA1/DEFA3 or wild-type mice, resulting from more severe endothelial barrier dysfunction and endothelial cell pyroptosis after sepsis challenge. Mechanistically, HNP-1 induces endothelial cell pyroptosis via P2X7 receptor-mediating canonical caspase-1 activation in a NLRP3 inflammasome-dependent manner. Based on these findings, we engineered a monoclonal antibody against HNP-1 to block the interaction with P2X7 and found that the blocking antibody protected mice carrying high copy number of DEFA1/DEFA3 from lethal sepsis. We thus demonstrate that DEFA1/DEFA3 copy number variation strongly modulates sepsis development in vivo and explore a paradigm for the precision treatment of sepsis tailored by individual genetic information.