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Ann Rheum Dis. 2019 Feb;78(2):238-248. doi: 10.1136/annrheumdis-2018-213181. Epub 2018 Dec 18.

REDD1/autophagy pathway promotes thromboinflammation and fibrosis in human systemic lupus erythematosus (SLE) through NETs decorated with tissue factor (TF) and interleukin-17A (IL-17A).

Author information

1
Laboratory of Immune Regulation and Tolerance, Autoimmunity and Inflammation, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.
2
Department of Internal Medicine, Medical School, University of Cyprus, Nicosia, Cyprus.
3
Department of Nephrology and Transplantation, Nicosia General Hospital, Nicosia, Cyprus.
4
Department of Internal Medicine, Laboratory of Molecular Hematology, Democritus University of Thrace, Alexandroupolis, Greece.
5
Department of Pathology, University Hospital of Alexandroupolis, Democritus University of Thrace, Alexandroupolis, Greece.
6
1st Department of Pathology, National and Kapodistrian University of Athens Medical School, Athens, Greece.
7
Rheumatology, Clinical Immunology and Allergy, University of Crete School of Medicine, Heraklion, Greece.
8
First Department of Internal Medicine, University Hospital of Alexandroupolis, Democritus University of Thrace, Alexandroupolis, Greece.
9
Laboratory of Immune Regulation and Tolerance, Autoimmunity and Inflammation, Biomedical Research Foundation of the Academy of Athens, Athens, Greece boumpasd@uoc.gr.
10
4th Department of Medicine, Attikon University Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece.
11
Joint Rheumatology Program, National and Kapodistrian University of Athens Medical School, Athens, Greece.
#
Contributed equally

Abstract

OBJECTIVES:

The release of neutrophil extracellular traps (NETs) represents a novel neutrophil effector function in systemic lupus erythematosus (SLE) pathogenesis. However, the molecular mechanism underlying NET release and how NETs mediate end-organ injury in SLE remain elusive.

METHODS:

NET formation and NET-related proteins were assessed in the peripheral blood and biopsies from discoid lupus and proliferative nephritis, using immunofluorescence, immunoblotting, quantitative PCR and ELISA. Autophagy was assessed by immunofluorescence and immunoblotting. The functional effects of NETs in vitro were assessed in a primary fibroblast culture.

RESULTS:

Neutrophils from patients with active SLE exhibited increased basal autophagy levels leading to enhanced NET release, which was inhibited in vitro by hydroxychloroquine. NETosis in SLE neutrophils correlated with increased expression of the stress-response protein REDD1. Endothelin-1 (ET-1) and hypoxia-inducible factor-1α (HIF-1α) were key mediators of REDD1-driven NETs as demonstrated by their inhibition with bosentan and L-ascorbic acid, respectively. SLE NETs were decorated with tissue factor (TF) and interleukin-17A (IL-17A), which promoted thrombin generation and the fibrotic potential of cultured skin fibroblasts. Notably, TF-bearing and IL-17A-bearing NETs were abundant in discoid skin lesions and in the glomerular and tubulointerstitial compartment of proliferative nephritis biopsy specimens.

CONCLUSIONS:

Our data suggest the involvement of REDD1/autophagy/NET axis in end-organ injury and fibrosis in SLE, a likely candidate for repositioning of existing drugs for SLE therapy. Autophagy-mediated release of TF-bearing and IL-17A-bearing NETs provides a link between thromboinflammation and fibrosis in SLE and may account for the salutary effects of hydroxychloroquine.

KEYWORDS:

autophagy; fibrosis; lupus; neutrophils; thromboinflammation

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