Endoplasmic reticulum stress sensor IRE1α propels neutrophil hyperactivity in lupus
Gautam Sule, … , Mary X. O’Riordan, Jason S. Knight
Gautam Sule, … , Mary X. O’Riordan, Jason S. Knight
Published February 9, 2021
Citation Information: J Clin Invest. 2021;131(7):e137866. https://doi.org/10.1172/JCI137866.
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Research Article Autoimmunity Immunology

Endoplasmic reticulum stress sensor IRE1α propels neutrophil hyperactivity in lupus

Abstract

Neutrophils amplify inflammation in lupus through the release of neutrophil extracellular traps (NETs). The endoplasmic reticulum stress sensor inositol-requiring enzyme 1 α (IRE1α) has been implicated as a perpetuator of inflammation in various chronic diseases; however, IRE1α has been little studied in relation to neutrophil function or lupus pathogenesis. Here, we found that neutrophils activated by lupus-derived immune complexes demonstrated markedly increased IRE1α ribonuclease activity. Importantly, in neutrophils isolated from patients with lupus, we also detected heightened IRE1α activity that was correlated with global disease activity. Immune complex–stimulated neutrophils produced both mitochondrial ROS (mitoROS) and the activated form of caspase-2 in an IRE1α-dependent fashion, whereas inhibition of IRE1α mitigated immune complex–mediated NETosis (in both human neutrophils and a mouse model of lupus). Administration of an IRE1α inhibitor to lupus-prone MRL/lpr mice over 8 weeks reduced mitoROS levels in peripheral blood neutrophils, while also restraining plasma cell expansion and autoantibody formation. In summary, these data identify a role for IRE1α in the hyperactivity of lupus neutrophils and show that this pathway is upstream of mitochondrial dysfunction, mitoROS formation, and NETosis. We believe that inhibition of the IRE1α pathway is a novel strategy for neutralizing NETosis in lupus, and potentially other inflammatory conditions.

Authors

Gautam Sule, Basel H. Abuaita, Paul A. Steffes, Andrew T. Fernandes, Shanea K. Estes, Craig Dobry, Deepika Pandian, Johann E. Gudjonsson, J. Michelle Kahlenberg, Mary X. O’Riordan, Jason S. Knight

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Figure 2

mitoROS generation is potentiated by IRE1α.

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mitoROS generation is potentiated by IRE1α. Neutrophils from healthy vol...
Neutrophils from healthy volunteers were stimulated as indicated in the presence of IRE1α inhibitors (4μ8C, KIRA6) or the mitoROS scavenger NecroX-5. (A) MitoPY1 and (B) mitoROS (MitoSOX) were quantified by flow cytometry. Representative histograms and quantifications are shown. n = 3 independent biological replicates for MitoPY1; n = 4 independent biological replicates for MitoSOX. ***P < 0.001 and ##P < 0.01, compared with the RNP–anti-RNP (DMSO) group, by 1-way ANOVA followed by Holm-Sidak’s multiple-comparison test. (C) Total cellular ROS production was assessed by flow cytometry using CM-H2DCFDA dye. n = 4 independent biological replicates. ****P < 0.0001 and ###P < 0.001, compared with the RNP–anti-RNP (DMSO) group, by 1-way ANOVA followed by Holm-Sidak’s multiple-comparison test. (D) BALB/c mice were treated with R848 and the IRE1α inhibitor 4μ8C as described in Methods. mitoROS (MitoSOX) and total cellular ROS (CM-H2DCFDA) were measured in peripheral blood neutrophils by flow cytometry. n = 10 mice per group. *P < 0.05, #P < 0.05, and ##P < 0.01, by 1-way ANOVA followed by Holm-Sidak’s multiple-comparison test, compared with the DMSO control in R848 mice.