The potential roles of type I interferon activated neutrophils and neutrophil extracellular traps (NETs) in the pathogenesis of primary Sjögren's syndrome.

Objective: Neutrophils and aberrant NETosis have been implicated in the pathogenesis of diverse autoimmune diseases; however, their roles in primary Sjögren's syndrome (pSS) remain unclear. We aimed to reveal the potential roles of neutrophils and neutrophil extracellular traps (NETs) in pSS.

Methods: pSS patients were enrolled and NETosis markers were measured in plasma and labial glands using ELISA and immunofluorescence. The gene signatures of neutrophils were assessed by RNA-Seq and RT-PCR. Reactive oxygen species (ROS), mitochondrial ROS (MitoSOX) production, and JC-1 were measured by flow cytometry.

Results: NETosis markers including cell-free DNA (cf-DNA) and myeloperoxidase (MPO) in plasma and labial glands from pSS patients were significantly higher than healthy controls (HCs) and were associated with disease activity. RNA sequencing and RT-qPCR revealed activated type I IFN signaling pathway and higher expression of genes related to type I interferon in pSS neutrophils. Further stimulating with IFN-α 2a in vitro significantly induced ROS production and JC-1 monomer percentage in pSS neutrophils.

Conclusions: Our data suggest the involvement of neutrophils and enhanced NETosis in pSS patients. Further mechanism study in vitro revealed that type I IFN activation in pSS neutrophils led to mitochondrial damage and related ROS production which finally result in the generation of NETs.