RNA Externalized by Neutrophil Extracellular Traps Promotes Inflammatory Pathways in Endothelial Cells

Abstract

Objective. Neutrophil extracellular traps (NETs) are extracellular lattices composed of nucleic material bound to neutrophil granule proteins. NETs may play pathogenic roles in the development and severity of autoimmune diseases such as systemic lupus erythematosus (SLE), at least in part, through induction of type I interferon (IFN) responses via externalization of oxidized immunostimulatory DNA. A distinct subset of SLE proinflammatory neutrophils (lowdensity granulocytes [LDGs]) displays enhanced ability to form proinflammatory NETs that damage the vasculature. We undertook this study to assess whether NET-bound RNA can contribute to inflammatory responses in endothelial cells (ECs) and the pathways that mediate this effect.Methods. Expression of newly synthesized and total RNA was quantified in NETs from healthy controls and lupus patients. The ability of ECs to take up NET-bound RNA and downstream induction of type I IFN responses were quantified. RNAs present in NETs were sequenced and specific small RNAs were tested for induction of endothelial type I IFN pathways.Results. NETs extruded RNA that was internalized by ECs, and this was enhanced when NET-bound nucleic acids were oxidized, particularly in lupus LDG-derived NETs. Internalization of NET-bound RNA by ECs was dependent on endosomal Toll-like receptors (TLRs) and the actin cytoskeleton and induced type I IFN-stimulated genes (ISGs). This ISG induction was dependent on NET-associated microRNA let-7b, a small RNA expressed at higher levels in LDGderived NETs, which acted as a TLR-7 agonist.Conclusion. These findings highlight underappreciated roles for small RNAs externalized in NETs in the induction of proinflammatory responses in vascular cells, with implications for lupus vasculopathy.

Endothelial Dysfunction Induced by Extracellular Neutrophil Traps Plays Important Role in the Occurrence and Treatment of Extracellular Neutrophil Traps-Related Disease

“…More experiments are needed to prove the specific role of HMGB1 in NETs-induced ED. Moreover, the internalization of NET-bound RNA by ECs is induced type I IFN-stimulated genes and leads to ED, which depends on the endosomal TLR7 and the actin cytoskeleton [ 55 ]. From the previous discussion, it can be summarized that many molecules in NETs participate in ED as DAMPs, including histone, eCIRP and so on.…”

Thrombosis and Anticoagulation Therapy in Systemic Lupus Erythematosus

“…NETs include histones, antimicrobial peptides, and oxidizing enzymes such as neutrophil elastase and myeloperoxidase [ 42 ]. Neutrophils have been shown to have an enhanced ability to produce NETs in patients with SLE [ 43 ]. Moreover, most patients with SLE have an impaired ability to degrade NETs [ 44 ].…”

Neutrophil phenotypes and functions in cancer: A consensus statement

“…In addition, emerging studies indicate that some neutrophils can present antigens, co-regulate T cell responses, and kill in an antibody-dependent manner ( Mantovani et al, 2011 ; Matlung et al, 2018 ). Usually, neutrophil cytotoxicity is beneficial and necessary to fight off infection; however, under chronic conditions, it can cause collateral tissue damage, particularly within highly vascularized tissues ( Adrover et al, 2020 ; Adrover et al, 2019 ; Blanco et al, 2021 ; Clark et al, 2007 ).…”