Effects of IL-34 on the secretion of RANKL/OPG by fibroblast-like synoviocytes and peripheral blood mononuclear cells in rheumatoid arthritis.

OBJECTIVE: To detect the effect of interleukin (IL)-34 on the secretion of Receptor activator of nuclear factor kappa-B ligand (RANKL)/Osteoprotegerin (OPG) and Matrix metalloproteinase (MMP)-3 by fibroblast-like synoviocytes (FLS) and peripheral blood mononuclear cells (PBMCs) of rheumatoid arthritis (RA) patients and to investigate whether the effect is mediated by IL-17. METHOD: RA-FLS and RA-PBMCs were stimulated with recombinant human (rh) IL-34, with or without the IL-17 inhibitor Plumbagin. The supernatant of the culture medium was collected and the levels of RANKL, OPG, and MMP-3 were detected by enzyme-linked immunosorbent assay (ELISA). RESULTS: RhIL-34 promoted RANKL secretion and inhibited OPG secretion in RA-FLS. The effect was weakened by the addition of the IL-17 inhibitor. In contrast, rhIL-34 had no significant effect on MMP-3 secretion by FLS. RhIL-34 elevated the secretion of RANKL by RA-PBMCs but not by healthy-PBMCs. Furthermore, the secretion of RANKL by RA-PBMCs reduced after the addition of the IL-17 inhibitor. OPG secretion by both RA-FLS and FLS from healthy controls was inhibited by rhIL-34, but were elevated after the addition of the IL-17 inhibitor. RhIL-34 had no significant effect on MMP-3 secretion by both RA-PBMCs and healthy-PBMCs. CONCLUSION: IL-34 enhances RANKL/OPG expression by RA-FLS and RA-PBMCs, and this effect is, indirectly, mediated by IL-17. This cytokine is therefore likely to to play an important role in local joint destruction and systemic osteoporosis in RA, and is therefore a potential therapeutic target for the treatment of this disease.

Elevated Serum Interleukin-34 Level in Patients with Systemic Lupus Erythematosus Is Associated with Disease Activity.

We measured the interleukin-34 (IL-34) level in sera from patients with systemic lupus erythematosus (SLE) and discoid lupus erythematosus (DLE) using an enzyme-linked immunosorbent assay (ELISA). Blood tests, including assays to determine C-reactive protein (CRP), complement (C) 3, C4, immunoglobulin (Ig) A, IgG, IgM, anti-double-stranded DNA antibody (Anti-dsDNA Ab) and hemoglobin (Hb) levels and white blood cell (WBC) and platelet (PLT) counts, were performed using standard methods. Lupus nephritis (LN) was diagnosed according to the American College of Rheumatology (ACR) renal criteria. The SLE disease activity was scored using the SLE Disease Activity Index (SLEDAI). Among the 110 SLE cases, IL-34 could be detected in 79 cases (71.8%). IL-34 was barely detected in the control group. The serum level of IL-34 was significantly higher in the SLE group. No change was observed in the serum IL-34 concentration in the SLE patients regardless of LN status. Correlations were observed between the serum IL-34 level and the disease activity parameters. The SLE patients with detectable IL-34 levels had higher SLEDAI and IgG concentrations and lower C3 and Hb levels than patients with undetectable IL-34 levels. Therefore, IL-34 could be a potential disease activity marker for SLE.

Inhibitor of DNA binding 4 functions as a tumor suppressor and is targetable by 5-aza-2'-deoxycytosine with potential therapeutic significance in Burkitt's lymphoma.

Epigenetic gene silencing due to promoter methylation is observed in human neoplasia, including lymphoma and certain cancer types. One important target for gene methylation analysis in non-Hodgkin lymphoma (NHL) is inhibitor of DNA binding 4 (ID4). The present study aimed to investigate the gene methylation status of ID4, the expression of ID4 protein and the effect of demethylating agent 5-aza-2'-deoxycytosine (CdR) in the Raji human Burkitt's lymphoma cell line in vitro. Following assessment of the inhibition of Raji cell growth by various concentrations of CdR, the effects of CdR on the expression of ID4 protein were assessed using the immunocytochemical streptavidin-peroxidase method and semi-quantitative analysis, while apoptosis and cell cycle were determined by flow cytometry. The ID4 gene methylation status of Raji cells was tested using methylation-specific polymerase chain reaction analysis. ID4 was methylated and its protein expression was low in the control group, while ID4 was partly or completely demethylated and its protein expression was upregulated in Raji cells treated with CdR. In addition, CdR induced apoptosis and cell cycle arrest in Raji cells in a dose- and time-dependent manner. These results demonstrated that ID4 is hypermethylated and its protein expression is low in Burkitt's lymphoma cells, while CdR reversed the abnormal DNA methylation and induced re-expression of ID4 protein. Hypermethylation of ID4 promotes the proliferation of Burkitt's lymphoma cells; ID4 may function as a tumor suppressor and can be targeted with demethylating compounds such as CdR for the treatment of Burkitt's lymphoma.