Peptidylarginine deiminases 2 and 4 modulate innate and adaptive immune responses in TLR-7–dependent lupus
Yudong Liu, … , Scott A. Coonrod, Mariana J. Kaplan
Yudong Liu, … , Scott A. Coonrod, Mariana J. Kaplan
Published December 6, 2018
Citation Information: JCI Insight. 2018;3(23):e124729. https://doi.org/10.1172/jci.insight.124729.
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Research Article Inflammation

Peptidylarginine deiminases 2 and 4 modulate innate and adaptive immune responses in TLR-7–dependent lupus

Abstract

The peptidylarginine deiminases PAD2 and PAD4 are implicated in the pathogenesis of several autoimmune diseases. PAD4 may be pathogenic in systemic lupus erythematosus (SLE) through its role in neutrophil extracellular trap (NET) formation that promotes autoantigen externalization, immune dysregulation, and organ damage. The role of this enzyme in mouse models of autoimmunity remains unclear, as pan-PAD chemical inhibitors improve clinical phenotype, whereas PAD4-KO models have given conflicting results. The role of PAD2 in SLE has not been investigated. The differential roles of PAD2 and PAD4 in TLR-7–dependent lupus autoimmunity were examined. Padi4–/– displayed decreased autoantibodies, type I IFN responses, immune cell activation, vascular dysfunction, and NET immunogenicity. Padi2–/– mice showed abrogation of Th subset polarization, with some disease manifestations reduced compared with WT but to a lesser extent than Padi4–/– mice. RNA sequencing analysis revealed distinct modulation of immune-related pathways in PAD-KO lymphoid organs. Human T cells express both PADs and, when exposed to either PAD2 or PAD4 inhibitors, displayed abrogation of Th1 polarization. These results suggest that targeting PAD2 and/or PAD4 activity modulates dysregulated TLR-7–dependent immune responses in lupus through differential effects of innate and adaptive immunity. Compounds that target PADs may have potential therapeutic roles in T cell–mediated diseases.

Authors

Yudong Liu, Yaíma L. Lightfoot, Nickie Seto, Carmelo Carmona-Rivera, Erica Moore, Rishi Goel, Liam O’Neil, Pragnesh Mistry, Victoria Hoffmann, Santanu Mondal, Padmavathy Nandha Premnath, Katherine Gribbons, Stefania Dell’Orso, Kan Jiang, Paul R. Thompson, Hong-Wei Sun, Scott A. Coonrod, Mariana J. Kaplan

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Figure 8

PAD2 and PAD4 are expressed on human T cells and modulate Th1 responses.

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PAD2 and PAD4 are expressed on human T cells and modulate Th1 responses....
(A) PAD2 protein expression levels (by geometric mean fluorescent intensity, MFI, relative to isotype control) in healthy control human neutrophils (CD15+), monocytes (CD14+), and T cells (CD3+CD4+). Box-and-whisker plots show median, lower and upper quartiles, and minimum and maximum MFI values of 5 independent experiments. (B and C) PAD2 protein expression quantified in SLE CD4+ T cells by Western blot (B) and immunofluorescence (C). In B, each lane represents an individual SLE subject (n = 4). C is a representative microphotograph of lupus CD4+ T cells (n = 2); magnification is 40×. (D) PAD4 protein expression levels assessed by geometric MFI relative to isotype control in healthy control human neutrophils (CD15+), monocytes (CD14+), and T cells (CD3+CD4+). Box-and-whisker plots show median, lower and upper quartiles, and minimum and maximum MFI values of 5 independent experiments. (E) Sorted healthy donor naive CD4+ T cells were activated with α-CD3 and soluble α-CD28 and polarized for 5 days in the presence or absence of the PAD2 inhibitor AFM30a or the PAD4 inhibitor GSK199. Left graph shows box-and-whisker plots displaying median, lower and upper quartiles, and minimum and maximum MFI values of IFN-γ in Th1 conditions, and right graph displays box-and-whisker plots with median, lower and upper quartiles, and minimum and maximum mRNA fold induction of IFNG in Th1 conditions relative to untreated control; n = 5 healthy controls. Statistical analysis was performed by 2-way ANOVA with Dunnett’s multiple comparisons test.