A subset of patients with systemic lupus erythematosus fails to degrade DNA from multiple clinically relevant sources

Abstract

IntroductionPatients with systemic lupus erythematosus (SLE) have a decreased ability to clear cell remnants and multiple deficiencies in the ability to degrade cellular chromatin have been linked to the disease. Since the discovery of neutrophil extracellular traps (NETs), a renewed interest has been sparked in this field of research with multiple studies reporting a decreased ability of patients with SLE to degrade NETs. In this study we extend these findings by investigating the ability of patients with SLE to degrade chromatin from multiple clinically relevant sources.MethodsWe use flow cytometry in combination with NET degradation and DNA zymogram assays to investigate the ability of sera from SLE patients to degrade chromatin from three different sources of DNA such as NETs, apoptotic and necrotic cells. This ability was further associated with clinical manifestations.ResultsWe found that 61 % of the patients had an affected degradation of at least one chromatin source. Further, degradation of NETs correlated with degradation of chromatin from secondary necrotic cells but not with degradation of chromatin from primary necrotic cells. Patients who fail to degrade several forms of DNA more often display anti-nuclear and nephritic involvement whereas this is not observed in patients with decreased ability to degrade chromatin from primary necrotic cells.ConclusionsThe majority of patients with SLE has a decreased ability to degrade chromatin from clinically relevant sources. This decreased ability is further reflected in their clinical presentation.

Active NET formation in Libman–Sacks endocarditis without antiphospholipid antibodies: A dramatic onset of systemic lupus erythematosus

“…The finding of high levels of anti-dsDNA antibodies at disease-onset may also have important implications for active NET formation and reduced clearance since these autoantibodies reportedly interfere with the degradation process of NET-borne chromatin [8,43]. Thus, it is plausible that the anti-dsDNA antibodies detected in the patient may have enhanced NET formation and/or hindered NET dismantling in the mitral valve.…”

“…The latter consist of decondensed chromatin decorated with neutrophilderived proteases and antimicrobial peptides that may trap and kill pathogens [7]. Furthermore, "classical" lupus autoantigens, such as histones and double-stranded (ds) DNA have been identified as constituents of NETs and their corresponding autoantibodies may potentially protect the NETs from degradation [8]. In MRL/lpr mice, inhibition of NET release containing mitochondrial DNA ameliorates lupuslike autoimmune disease by down-regulating the type I IFN response [9].…”

NETopathies? Unraveling the Dark Side of Old Diseases through Neutrophils

“…Interestingly, there is a disease-associated defect in the clearance of NETs, due to the reduced activity of DNase I and the increased amounts of DNase I inhibitors (17, 20, 94, 103–106), supporting the hypothesis that dysregulation of NET clearance may be one of the initial steps that lead to lupus-specific autoantibody production.…”

Decreased Neutrophil Extracellular Trap Degradation in Shiga Toxin-Associated Haemolytic Uraemic Syndrome

“…Freshly isolated neutrophils (50,000 cells/sample) were seeded onto a 96-well flat-bottom plate (Nunc) and incubated with 20 n M PMA (Sigma-Aldrich) for 4 h at 37 ° C and 5% CO 2 to generate NETs according to a previously published method [15,16,19] . NET formation was confirmed visually by staining NETs with propidium iodide (Molecular Probes) and analysed using a Zeiss LSM 510 Meta confocal microscope (Zeiss).…”

“…NETs consist of decondensed chromatin covered with antimicrobial proteins/peptides and are released from mainly activated neutrophils in a ROS/NADPH-dependent manner [12,13] . NETs, while beneficial in antimicrobial responses, are also involved in a number of pathologies and in particular in autoimmune disorders such as systemic lupus erythematosus [14] , where a decreased ability to degrade NETs [15] , and other types of chromatin [16] , is associated with kidney disease [15,17] . Given the kidney damage observed in TMA, we aimed to investigate whether this was associated with a decreased ability to degrade NETs, as has recently been suggested [10] .…”