Various genetic and environmental factors appear to be involved in systemic lupus erythematosus (SLE). Epstein–Barr virus (EBV) is among the environmental factors that are suspected of predisposing to SLE, based on the characteristics of EBV itself and on sequence homologies between autoantigens and EBV antigens. In addition, higher titers of anti-EBV antibodies and increased EBV seroconversion rates have been observed in SLE patients as compared with healthy control individuals. Serologic responses do not directly reflect EBV status within the body. Clarification of the precise status of EBV infection in SLE patients would help to improve our understanding of the role played by EBV in this disease. In the present study we determined EBV types in SLE patients (n = 66) and normal control individual (n = 63) by direct PCR analysis of mouthwash samples. We also compared EBV load in blood between SLE patients (n = 24) and healthy control individuals (n = 29) using semiquantitative PCR assay. The number of infections and EBV type distribution were similar between adult SLE patients and healthy control individuals (98.5% versus 94%). Interestingly, the EBV burden in peripheral blood mononuclear cells (PBMCs) was over 15-fold greater in SLE patients than in healthy control individuals (mean ± standard deviation: 463 ± 570 EBV genome copies/3 μg PBMC DNA versus 30 ± 29 EBV genome copies/3 μg PBMC DNA; P = 0.001), suggesting that EBV infection is abnormally regulated in SLE. The abnormally increased proportion of EBV-infected B cells in the SLE patients may contribute to enhanced autoantibody production in this disease.

Circulating autoantibodies and immune complex deposition are pathological hallmarks of systemic lupus erythematosus (SLE). B cell differentiation into plasma cells (PCs) and some T cell subsets that function as B cell helpers can be therapeutic targets of SLE. Mechanistic target of rapamycin (mTOR) signaling is implicated in the formation of B cells and germinal centers (GCs). We assessed the effect of metformin, which inhibits mTOR, on the development of autoimmunity using Roquin^san/san mice. Oral administration of metformin inhibited the formation of splenic follicles and inflammation in kidney and liver tissues. It also decreased serum levels of anti-dsDNA Abs without affecting serum glucose levels. Moreover, metformin inhibited CD21^highCD23^low marginal zone B cells, B220⁺GL7⁺ GC B cells, B220⁻CD138⁺ PCs, and GC formation. A significant reduction in ICOS⁺ follicular helper T cells was found in the spleens of the metformin-treated group compared with the vehicle-treated group. In addition, metformin inhibited Th17 cells and induced regulatory T cells. These alterations in B and T cell subsets by metformin were associated with enhanced AMPK expression and inhibition of mTOR–STAT3 signaling. Furthermore, metformin induced p53 and NF erythroid-2–related factor-2 activity in splenic CD4⁺ T cells. Taken together, metformin-induced alterations in AMPK–mTOR–STAT3 signaling may have therapeutic value in SLE by inhibiting B cell differentiation into PCs and GCs.

Objective: To evaluate associations of genetic polymorphisms in cytochrome P450 (CYP) isoforms 2D6, 3A5, and 3A4 with blood concentrations of hydroxychloroquine (HCQ) and its metabolite, N‐desethyl HCQ (DHCQ), in patients with systemic lupus erythematosus (SLE).Methods: SLE patients taking HCQ for >3 months were recruited and were genotyped for 4 single‐nucleotide polymorphisms in CYP2D6*10, CYP3A5*3, and CYP3A4*18B. Blood HCQ and DHCQ concentrations ([HCQ] and [DHCQ]) were measured and their association with corresponding genotypes was investigated.Results: A total of 194 patients were included in the analysis. CYP2D6*10 polymorphisms (rs1065852 and rs1135840) were significantly associated with the [DHCQ]:[HCQ] ratio after adjustment for age, sex, dose per weight per day, and SLE Disease Activity Index score (P = 0.03 and P < 0.01, respectively). In adjusted models, the [DHCQ]:[HCQ] ratio was highest in patients with the G/G genotype of the CYP2D6*10 (rs1065852) polymorphism and lowest in those with the A/A genotype (P = 0.03). Similarly, the [DHCQ]:[HCQ] ratio was highest in patients with the C/C genotype of the CYP2D6*10 (rs1135840) polymorphism and lowest in those with the G/G genotype (P < 0.01). The CYP2D6*10 (rs1065852) polymorphism was significantly related to the [DHCQ] (P = 0.01). However, the polymorphisms of CYP3A5*3 and CYP3A4*18B did not show any significant association with the [HCQ], [DHCQ], or [DHCQ]:[HCQ] ratio.Conclusion: Our study showed that the [DHCQ]:[HCQ] ratio was related to CYP2D6 polymorphisms in Korean lupus patients taking oral HCQ. CYP polymorphisms may explain why there is wide variation in blood HCQ concentrations. The role of an individual's CYP polymorphisms should be considered when prescribing oral HCQ.

Objective: Bone destruction is a critical pathology involved in the functional disability caused by rheumatoid arthritis (RA). Osteoclasts, which are specialized bone‐resorbing cells regulated by cytokines such as RANKL, are implicated in bone destruction in RA. The aim of this study was to determine whether interleukin‐21 (IL‐21), a potent immunomodulatory 4–α‐helical bundle type 1 cytokine, has osteoclastogenic activity in patients with RA and in mice with collagen‐induced arthritis (CIA).Methods: The expression of IL‐21 in synovial tissue was examined using immunohistochemistry. The concentrations of IL‐21 in serum and synovial fluid were determined by enzyme‐linked immunosorbent assay. The levels of RANKL and osteoclastogenic markers were measured using real‐time polymerase chain reaction. CD14+ monocytes from patients with RA or mouse bone marrow cells were cocultured with fibroblast‐like synoviocytes (FLS) from patients with RA or CD4+ T cells from mice with CIA in the presence of IL‐21 and subsequently stained for tartrate‐resistant acid phosphatase activity to determine osteoclast formation.Results: IL‐21 was up‐regulated in the synovium, synovial fluid, and serum of patients with RA and in the synovium and serum of mice with CIA. IL‐21 induced RANKL expression in mixed joint cells and CD4+ T cells from mice with CIA and in CD4+ T cells and FLS from patients with RA. Moreover, IL‐21 enhanced in vitro osteoclastogenesis without the presence of RANKL‐providing cells and by inducing RANKL expression in CD4+ T cells and FLS.Conclusion: Our data suggest that IL‐21 promotes osteoclastogenesis in RA. We believe that therapeutic strategies targeting IL‐21 might be effective for the treatment of patients with RA, especially in preventing bone destruction.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial inflammation of the joints and extra-articular manifestations. Recent studies have shown that microorganisms affect RA pathogenesis. However, few studies have examined the microbial distribution of early RA patients, particularly female patients. In the present study, we investigated the gut microbiome profile and microbial functions in early RA female patients, including preclinical and clinically apparent RA cases. Changes in microbiological diversity, composition, and function in each group were analyzed using quantitative insights into microbial ecology (QIIME) and phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt). The results revealed the dysbiosis due to decreased diversity in the early RA patients compared with healthy subjects. There were significant differences in the microbial distribution of various taxa from phylum to genus levels between healthy subjects and early RA patients. Phylum Bacteroidetes was enriched in early RA patients, while Actinobacteria, including the genus Collinsella, was enriched in healthy subjects. Functional analysis based on clusters of orthologous groups revealed that the genes related to the biosynthesis of menaquinone, known to be derived from gram-positive bacteria, were enriched in healthy subjects, while iron transport-related genes were enriched in early RA patients. Genes related to the biosynthesis of lipopolysaccharide, the gram-negative bacterial endotoxin, were enriched in clinically apparent RA patients. The obvious differences in microbial diversity, taxa, and associated functions of the gut microbiota between healthy subjects and early RA patients highlight the involvement of the gut microbiome in the early stages of RA.

Introduction: Fibroblast-like synoviocytes (FLSs) are a major cell population of the pannus that invades adjacent cartilage and bone in rheumatoid arthritis (RA). The study was undertaken to determine the effect of interleukin-17 (IL-17) on the survival and/or proliferation of FLSs from RA patients and to investigate whether signal tranducer and activator of transcription 3 (STAT3) is implicated in this process. Methods: Bcl-2 and Bax expression in FLSs was determined using the real-time PCR and western blot analysis. The expression of Bcl-2 and phosphoSTAT3 in synovial tissues was investigated by confocal microscope. Apoptosis of FLSs was detected by Annexin V/propidium iodide staining and/or phase contrast microscopy. The proliferation of FLSs was determined by CCK-8 ELISA assay. Results: The pro-apoptotic Bax is decreased and anti-apoptotic Bcl-2 is increased in FLSs from RA patients compared with those from patients with osteoarthritis (OA). IL-17 upregulated the expression of Bcl-2 in FLSs from RA patients, but not in FLSs from OA patients. STAT3 was found to mediate IL-17-induced Bcl-2 upregulation in FLSs from RA patients. Additionally, IL-17 promoted the survival and proliferation of FLSs from RA patients. Most importantly, treatment with STAT3 inhibitor reversed the protective effect of IL-17 on FLSs apoptosis induced by sodium nitroprusside (SNP). Conclusions: Our data demonstrate that STAT3 is critical in IL-17-induced survival of FLS from RA patients. Therefore, therapeutic strategies that target the IL-17/STAT3 pathway might be strong candidates for RA treatment modalities.