Enhanced formation and impaired degradation of neutrophil extracellular traps in dermatomyositis and polymyositis: a potential contributor to interstitial lung disease complications

Abstract

SummaryDermatomyositis (DM) and polymyosits (PM) are systemic autoimmune diseases whose pathogeneses remain unclear. Neutrophil extracellular traps (NETs) are reputed to play an important role in the pathogenesis of autoimmune diseases. This study tests the hypothesis that NETs may be pathogenic in DM/PM. Plasma samples from 97 DM/PM patients (72 DM, 25 PM) and 54 healthy controls were tested for the capacities to induce and degrade NETs. Plasma DNase I activity was tested to further explore possible reasons for the incomplete degradation of NETs. Results from 35 DM patients and seven PM patients with interstitial lung disease (ILD) were compared with results from DM/PM patients without ILD. Compared with control subjects, DM/PM patients exhibited a significantly enhanced capacity for inducing NETs, which was supported by elevated levels of plasma LL-37 and circulating cell-free DNA (cfDNA) in DM/PM. NETs degradation and DNase I activity were also decreased significantly in DM/PM patients and were correlated positively. Moreover, DM/PM patients with ILD exhibited the lowest NETs degradation in vitro due to the decrease in DNase I activity. DNase I activity in patients with anti-Jo-1 antibodies was significantly lower than in patients without. Glucocorticoid therapy seems to improve DNase I activity. Our findings demonstrate that excessively formed NETs cannot be degraded completely because of decreased DNase I activity in DM/PM patients, especially in patients with ILD, suggesting that abnormal regulation of NETs may be involved in the pathogenesis of DM/PM and could be one of the factors that initiate and aggravate ILD.

Abnormally increased low-density granulocytes in peripheral blood mononuclear cells are associated with interstitial lung disease in dermatomyositis

“…Plasma cfDNA and LL-37 could be used as biomarkers for NET formation in vivo [4]. We compared plasma cfDNA and LL-37 in the different study groups and found that both were significantly increased in DM patients, especially in DM patients with ILD ( Figure 3A, B, D, and E), which indirectly indicates that NET formation is enhanced in DM patients with ILD.…”

“…In our previous study, we established that the formation of neutrophil extracellular traps (NETs) was enhanced and these increased NETs could not be completely degraded in vitro, which was associated with ILD in DM patients [4]. Activated by microbes, neutrophils can trap and kill invading microbes by releasing DNA, histones, and antimicrobial peptides to form NETs [5].…”

Role of Jo-1 in the Immunopathogenesis of the Anti-synthetase Syndrome

“…In a recent study, Zhang et al demonstrated that serum from patients with Jo-1 antibodies and/or subacute ILD promoted the in vitro development of NETs through enhanced formation as well as impaired DNAse I-mediated degradation [25]. Correlating with these in vitro studies, serum derived from patients with Jo-1 antibodies demonstrated higher levels of LL-37 and cell-free DNA [25]-both of which are markers of in vivo NET formation.…”

“…In a recent study, Zhang et al demonstrated that serum from patients with Jo-1 antibodies and/or subacute ILD promoted the in vitro development of NETs through enhanced formation as well as impaired DNAse I-mediated degradation [25]. Correlating with these in vitro studies, serum derived from patients with Jo-1 antibodies demonstrated higher levels of LL-37 and cell-free DNA [25]-both of which are markers of in vivo NET formation. Because NETs are comprised of proteases and other proteins capable of damaging endothelial/ epithelial components of various tissues, this mechanism provides a link between pro-inflammatory cytokine cascades, dysregulated formation/clearance of NETs, aberrant antigen exposure (e.g., HRS), autoreactivity, and specific organ manifestations such as ILD.…”

Neutrophil Extracellular Traps - The Invisible Inflammatory Mediator in Fibrosis

“…Similarly, a very recent study indicated the key role of neutrophil elastase in the promotion of myofibroblast differentiation in experimental lung fibrosis, confirming indirectly but clearly the significance of NETs and their decorative components in fibrotic process [16]. Furthermore, at the same time when the critical role of NETs in inflammation-driven fibrosis was revealed [9], an independent clinical study demonstrated that decreased DNase I activity in dermatomyositis/polymyositis patients is significantly associated with interstitial lung disease, linking the abnormal clearance of NETs with a well-defined, severe fibrotic complication [17]. Considering that the lifespan of neutrophils is very short, and in many fibrotic cases the biopsies are performed when the fibrosis is established, it is rational to explain why neutrophils cannot be visualized in fibrotic tissues by conventional methods used in everyday pathology practice (e.g.…”