AUTHOR=Hanata Norio , Shoda Hirofumi , Hatano Hiroaki , Nagafuchi Yasuo , Komai Toshihiko , Okamura Tomohisa , Suzuki Akari , Gunarta I Ketut , Yoshioka Katsuji , Yamamoto Kazuhiko , Fujio Keishi 

TITLE=Peptidylarginine Deiminase 4 Promotes the Renal Infiltration of Neutrophils and Exacerbates the TLR7 Agonist-Induced Lupus Mice

JOURNAL=Frontiers in Immunology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2020.01095

DOI=10.3389/fimmu.2020.01095

ISSN=1664-3224

ABSTRACT=<p>Peptidylarginine deiminase 4 (PAD4), encoded by <italic>PADI4</italic>, plays critical roles in the immune system; however, its contribution to the pathogenesis of lupus nephritis remains controversial. The pathological roles of PAD4 were investigated in lupus model mice. An imiquimod (IMQ)-induced lupus model was analyzed in wild-type (WT) and <italic>Padi4</italic>-knockout (KO) mice. Proteinuria, serum anti-double stranded DNA (anti-dsDNA) antibody, and renal infiltrated cells were evaluated. Neutrophil migration and adhesion were assessed using adoptive transfer and adhesion assay. PAD4-regulated pathways were identified by RNA-sequencing of <italic>Padi4</italic> KO neutrophils. <italic>Padi4</italic> KO mice exhibited significant improvements in proteinuria progression compared with WT mice, whereas, serum anti-dsDNA antibody and immune complex deposition in the glomeruli showed no difference between both mice strains. <italic>Padi4</italic> KO mice showed decreased neutrophil infiltration in the kidneys. Adoptively transferred <italic>Padi4</italic> KO neutrophils showed decreased migration to the kidneys of IMQ-treated WT mice, and adhesion to ICAM-1 was impaired in <italic>Padi</italic>4 KO neutrophils. <italic>Padi4</italic> KO neutrophils exhibited reduced upregulation of p38 mitogen-activated protein kinase (MAPK) pathways. Toll-like receptor 7 (TLR7)-primed <italic>Padi4</italic> KO neutrophils demonstrated reduced phosphorylation of p38 MAPK and lower expression of JNK-associated leucine zipper protein (JLP), a p38 MAPK scaffold protein. Neutrophils from heterozygous <italic>Jlp</italic> KO mice showed impaired adhesion to ICAM-1 and decreased migration to the kidneys of IMQ-treated WT mice. These results indicated a pivotal role of PAD4-p38 MAPK pathway in renal neutrophil infiltration in TLR7 agonist-induced lupus nephritis, and the importance of neutrophil-mediated kidney inflammation. Inhibition of the PAD4-p38 MAPK pathway may help in formulating a novel therapeutic strategy against lupus nephritis.</p>