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Peptidylarginine deiminase 4 (PAD4), encoded by PADI4, 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 Padi4-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 Padi4 KO neutrophils. Padi4 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. Padi4 KO mice showed decreased neutrophil infiltration in the kidneys. Adoptively transferred Padi4 KO neutrophils showed decreased migration to the kidneys of IMQ-treated WT mice, and adhesion to ICAM-1 was impaired in Padi4 KO neutrophils. Padi4 KO neutrophils exhibited reduced upregulation of p38 mitogen-activated protein kinase (MAPK) pathways. Toll-like receptor 7 (TLR7)-primed Padi4 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 Jlp 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.

Gefitinib and erlotinib are epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs). Although EGFR-TKIs are effective as anti-cancer drugs, cancer cells sometimes gain tolerance to the drugs. Previous studies suggested that the fibroblast growth factor receptor (FGFR)-signaling pathway could serve as compensation for the EGFR-signaling pathway inhibited by EGFR-TKIs. Our study further suggested that FGF2, a FGFR ligand, leaked out from naïve cells killed by gefitinib could initiate the FGFR-signaling pathway in surviving cells; i.e., altruistic survival may occur in naïve cells immediately after EGFR-TKI treatment. Altruistic survival may be temporal, and cells need to change their gene regulation toward gaining resistance to EGFR-TKIs. Changes in such gene regulation after EGFR-TKI treatment are poorly understood. In this study, we examined early events of such gene regulation changes in human adenocarcinoma PC-9 cells that are capable of changing their nature from susceptibility to resistance to EFGR-TKIs. Our study indicated that activation of nuclear factor-kappa B (NF-κB) occurred in the cells immediately after EGFR-TKI treatment and also by gene silencing against oncogenic EGFR; and, MG132 treatment for inhibiting NF-κB activation affected cell viability. Taken together, our findings (including the previous study) suggest that altruistic survival and NF-κB activation might be vital for initiating the acquisition of EGFR-TKI resistance.

Background NKG2D is an activating receptor expressed by natural killer and T cells, which have crucial functions in tumor and microbial immunosurveillance. Several cytokines have been identified as modulators of NKG2D receptor expression. However, little is known about NKG2D gene regulation. In this study, we found that microRNA 1245 attenuated the expression of NKG2D in natural killer cells.Design and Methods We investigated the potential interactions between the 3′-untranslated region of the NKG2D gene and microRNA as well as their functional roles in the regulation of NKG2D expression and cytotoxicity in natural killer cells.Results Transforming growth factor-β1, a major negative regulator of NKG2D expression, post-transcriptionally up-regulated mature microRNA-1245 expression, thus down-regulating NKG2D expression and impairing NKG2D-mediated immune responses in natural killer cells. Conversely, microRNA-1245 down-regulation significantly increased the expression of NKG2D expression in natural killer cells, resulting in more efficient NKG2D-mediated cytotoxicity.Conclusions These results reveal a novel NKG2D regulatory pathway mediated by microRNA-1245, which may represent one of the mechanisms used by transforming growth factor-β1 to attenuate NKG2D expression in natural killer cells.