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

Padi4–/– neutrophils generate NETs lacking citrullinated Histone 3 (Cit-H3) and do not promote vascular damage.

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Padi4–/– neutrophils generate NETs lacking citrullinated Histone 3 (Cit...
(A and B) BM neutrophils of naive FVB, Padi2–/–, and Padi4–/– mice were stimulated with the calcium ionophore A23817 for 2 hours to induce NET formation and stained for Cit-H3 (A) and MPO (B). Total magnification is 40×. (C) Lack of Cit-H3 in Padi4–/– NETs was confirmed by Western blot of imiquimod-induced NETs. Results are representative of 3 experiments (D). Aorta rings were cultured in the presence of imiquimod-induced NETs prior to assessment of vasorelaxation capacity. Results represent % mean ± SEM vasorelaxation, n = 3 mice/group. (E) Splenocytes from naive FVB, Padi2–/–, and Padi4–/– mice (n = 3/group) were cultured for 24 hours in the presence of imiquimod-induced NETs, and the expression of type 1 IFN–inducible genes was analyzed by RT-PCR. *P < 0.05, **P < 0.005. Statistical analysis was performed with 2-tailed unpaired t test. For D, analysis was by 2-way ANOVA with post-hoc Tukey’s test to compare differences between the groups; *P < 0.05 for PAD4 KO vs. FVB; #P < 0.05 for PAD4 KO vs. PAD2 KO.