BACKGROUND: Uridine diphosphate (UDP) is an extracellular nucleotide signaling molecule implicated in diverse biological processes via specific activation of pyrimidinergic receptor P2Y, G Protein-Coupled, 6 (P2Y6). There is very little knowledge about the function and mechanism of UDP in rheumatoid arthritis (RA).METHODS: This study used a quasi-targeted liquid chromatography-mass spectrometry (LC-MS) approach to investigate the unique expression of metabolites in RA synovial fluids (SF) (n = 10) with samples from osteoarthritis (OA) as controls (n = 10). RA fibroblast-like synoviocytes (FLSs) were collected from synovial tissues (n = 5) and cultured with UDP or MRS2578, a P2Y6 antagonist, and FLSs from OA were used as controls (n = 5). Rats with collagen-induced arthritis (CIA) were injected with UDP, MRS2578 or both (n = 9 for each group). P2Y6 expression was examined using real-time PCR, Western blotting and immunohistochemistry. Cell proliferation, apoptosis and migration of RA FLSs were measured using CCK-8 assay, real-time cell analysis, flow cytometry, wound healing assay and Transwell assay, respectively. The UDP levels in the culture medium, synovial fluid (n = 36) and peripheral blood (n = 36) of RA and CIA rats were measured using a Transcreener UDP Assay. Levels of proinflammatory cytokines were measured using a flow assay. Interleukin-6 (IL-6) levels were measured using ELISA and flow.RESULTS: LC-MS analysis detected significantly increased UDP levels in RA SF compared with OA SF, and the level was positively correlated with anticyclic citrullinated peptide (anti-CCP) and rheumatoid factor (RF)levels in RA. The increased UDP concentration was verified in the blood and synovial fluids of RA patients compared with samples from OA patients and healthy volunteers, respectively. UDP stimulated cell proliferation, migration and IL-6 secretion in RA FLSs and inhibited their apoptosis in culture, and MRS2578 inhibited these effects of UDP. UDP injection accelerated CIA and stimulated IL-6 production rather than other proinflammatory cytokines in the rat model, but simultaneous injection of MRS2578 suppressed these effects and alleviated CIA. P2Y6 expression was increased in RA and CIA synovial tissues.CONCLUSION: These results suggest that UDP is highly expressed in RA and stimulates RA pathogenesis by promoting P2Y6 activities to increase IL-6 production.

Tregs and M2-type macrophages are essential for immune surveillance. CD38 + NK cells are involved in immunoregulation by modulating cytokine secretion. This study investigated how CD38 + NKs affect Tregs and macrophages in colorectal cancer (CRC). Higher proportions of CD38 + NKs and Tregs were detected in bloods and tumor tissues of CRC patients than that in the samples from healthy controls (HCs). Compared with CD38 + NKs from HCs, the NK cells from CRC promoted the differentiation of Tregs from CD4 + T cells, and secreted increased levels of IL-10, TGF-β and TNF-α and decreased levels of IFN-γ. CD38 + NKs from CRC expressed higher levels of CD38, NF-κB and acetyl-NF-κB and lower levels of Sirt1. When CRC CD38 + NK cells were treated with anti-CD38 monoclonal antibody, the above trends were reversed. CRC CD38 + NKs with treatment of NF-κB inhibitor also showed opposite effects on cytokine secretion and CD4 + T-cell differentiation. After treatment with a Sirt1 activator, NF-κB signaling was inhibited in these CD38 + NKs, whereas treatment with a Sirt1 inhibitor activated NF-κB signaling. The supernatants of CRC CD38 + NK culture promoted M0 macrophage polarization to M2-type. We suggest that CD38 modulates cytokine secretion by NK cells through Sirt1/NF-κB signaling pathway, thereby suppressing immune surveillance in tumorigenesis.

It has been reported that carbonic anhydrase I (CA1) is a target for the diagnosis and therapy of atherosclerosis (AS) since CA1 can promote AS aortic calcification. We also found that methazolamide (MTZ), a drug for glaucoma treatment and an inhibitor of carbonic anhydrases, can treat AS by inhibiting calcification in aortic tissues. This study focused on the therapeutic mechanism of MTZ and the pathogenic mechanism of AS. In this study, a routine AS animal model was established in ApoE−/− mice, which were treated with MTZ. The aortic tissues were analyzed using single‐cell sequencing. MTZ significantly increased the proportions of B‐1/MZB B cells with high expressions of Nr4A1 and Ccr7, CD8+CD122+ Treg‐like cells with high Nr4A1 expression, and smooth muscle cells with high Tpm2 expression. These cells or their marker genes were reported to exert immunosuppressive, anti‐proinflammatory, and atheroprotective effects. MTZ also decreased the proportions of endothelial cells with high expressions of Retn, Apoc1, Lcn2, Mt1, Serpina3, Lpl, and Lgals3; nonclassical CD14+CD16++ monocytes with high expressions of Mt1, Tyrobp, Lgals3, and Cxcl2; and Spp1+ macrophages with high expressions of Mmp‐12, Trem2, Mt1, Lgals3, Cxcl2, and Lpl. These cells or their marker genes have been reported to promote inflammation, calcification, tissue remodeling, and atherogenesis. A significant decrease in the proportion of CD8+CD183 (CXCR3)+ T cells, the counterpart of murine CD8+CD122+ T cells, was detected in the peripheral blood of newly diagnosed AS patients rather than in that of patients receiving anti‐AS treatments. These results suggest that MTZ can treat AS by increasing immunosuppressive cells and decreasing expressions of genes related to inflammation, calcification, and tissue remodeling.

PADI4, an enzyme catalyzing arginine residues to citrulline residues, is highly expressed in malignant tumors. This study prepared a monoclonal anti-human PADI4 antibody and investigated the therapeutic effect of the antibody on breast tumors and the functional mechanism. After treatment with PADI4 antibody, the changes in tumor-bearing mice were examined by PET-CT, pathological assays, biochemical tests, routine blood tests, cytokine assays and metabolic assays. We used PADI4 recombinant protein to catalyze fibronectin (Fn) and then used citrullinated fibronectin (Cit-Fn) to culture MDA-MB-231 cells. We also treated Cit-Fn cultured cells with PADI4 antibody. The cultured cells were examined using cell proliferation, apoptosis, colony formation, migration and glycolic ATP production. Citrullination in the tumor tissues and peripheral blood was measured using Western blotting and ELISA, respectively. Following PADI4 antibody treatment, tumor growth was significantly suppressed, and the number of apoptotic cells in tumor tissues was increased. The citrullination level in peripheral blood and tumor tissues was decreased, EMT-related gene expression in tumors was also decreased, and the spontaneous movement of tumor-bearing mice was increased following treatment. Following antibody treatment, the serum concentrations of IL-10, IL-12p70, IL-23, ALT and AST were significantly decreased. MDA-MB-231 cells treated with Cit-Fn showed increased cell proliferation, cell migration, colony formation and glycolytic ATP production and decreased apoptosis. The growth and migration of MDA-MB-231 cells were reduced following PADI4 antibody treatment, and PADI4 antibody inhibited the citrullination of fibronectin in vitro. The PADI4 antibody had a therapeutic effect on breast tumors by inhibiting the citrullination of fibronectin to change the tumor tissue microenvironment. PADI4 antibody is a potential means for tumor treatment.

Background: Peptidyl arginine deiminase 4 (PADI4) is a post-translational modification enzymecan that converts arginine in protein into citrulline in the presence of calcium ions, which is called citrullination. PADI4 has been reported to be expressed in the cytoplasm and nucleus in a variety of malignant tumors. Based on the GeneCards database and our previous research, it is speculated that PADI4 may also be expressed on the cell membrane. This study aimed to confirm the membrane expression of PADI4 and the effect of anti-PADI4 antibodies on cell membrane PADI4. This may be another mechanism of action of anti-PADI4 monoclonal antibodies in the treatment of breast cancer. Methods: The subcellular localizations of PADI4 in MDA-MB-231 and MCF-7 breast cancer cells were determined by immunofluorescence, immunoelectron microscopy, and Western blot analysis. The tumor cells were treated with PADI4 antibody, and cell proliferation, migration, colony formation, apoptosis, glycolysis, and epithelial-mesenchymal transition (EMT) were measured as well as the expression of some essential tumor genes. Results: PADI4 was not only localized in the nucleus and cytoplasm of breast cancer cells but was also detected on the cell membrane. Following PADI4 antibody treatment, cell proliferation, migration, colony formation, EMT, and ATP production through glycolysis were decreased, and the mRNA expression of MYC proto-oncogene (MYC), FAT atypical cadherin 1 (FAT1), nuclear factor kappa B subunit 1 (NFκB), and tumor necrosis factor (TNF-α) in breast cancer cells was downregulated, while the mRNA expression of tumor protein p63 (TP63) was upregulated. Conclusions: PADI4 is expressed on the cell membrane in breast cancer cells. Anti-PADI4 antibodies can affect the biological functions of cell membrane PADI4, including proliferation, migration, apoptosis, and glycolysis, thereby inhibiting tumor progression. Graphical

Carbonic anhydrase I (CA1) has been reported to be a diagnostic and therapeutic target for atherosclerosis (AS). This study aimed to verify the essential role of CA1 in AS progression in CA1-overexpressing mice. A ApoE [-/-] CA1-overexpressing knock-in mouse model was constructed via CRISPR/Cas9-mediated genome engineering. AS was then induced in these transgenic mice via the administration of a high-fat diet, and a second group simultaneously received treatment with methazolamide (MTZ), a carbonic anhydrase inhibitor. Compared with ApoE [-/-] mice without CA1 overexpression, CA1-overexpressing mice had a greater average body weight, regardless of whether their treatment with MTZ or their AS induction status. Sudan IV, hematoxylin and eosin and Oil Red O staining revealed more plaques and fat deposits in the cardiac aortas of CA1-overexpressing mice than in those of ordinary ApoE-/- mice when AS was induced. Moreover, the atherogenic index; low-density lipoprotein, total cholesterol and triglyceride levels were significantly elevated, and high-density lipoprotein levels were declined in the peripheral blood of CA1-overexpressing mice than in that of ordinary ApoE [-/-] mice, regardless of whether these animals were induced to AS. Immunohistochemistry, Von Kossa staining and fluorescence immunohistochemistry revealed increases in CA1 expression, calcium deposition and M1 macrophages in the aortic tissues of CA1-overexpressing mice with AS. MTZ treatment significantly suppressed AS pathologies in the above experiments. These findings revealed aggravated AS in ApoE [-/-] CA1-overexpressing mice and suggest that CA1 aggravates AS by increasing M1-type macrophages, a proinflammatory macrophage subtype.