Wenfeng Tan

Association of PPP2CA polymorphisms with systemic lupus erythematosus susceptibility in multiple ethnic groups

OBJECTIVE T cells from patients with systemic lupus erythematosus (SLE) express increased amounts of PP2Ac, which contributes to decreased production of interleukin-2 (IL-2). Because IL-2 is important in the regulation of several aspects of the immune response, it has been proposed that PP2Ac contributes to the expression of SLE. This study was designed to determine whether genetic variants of PPP2AC are linked to the expression of SLE and specific clinical manifestations and account for the increased expression of PP2Ac. METHODS We conducted a trans-ethnic study of 8,695 SLE cases and 7,308 controls of 4 different ancestries. Eighteen single-nucleotide polymorphisms (SNPs) across PPP2CA were genotyped using an Illumina custom array. PPP2CA expression in SLE and control T cells was analyzed by real-time polymerase chain reaction. RESULTS A 32-kb haplotype comprising multiple SNPs of PPP2CA showed significant association with SLE in Hispanic Americans, European Americans, and Asians, but not in African Americans. Conditional analyses revealed that SNP rs7704116 in intron 1 showed consistently strong association with SLE across Asian, European American, and Hispanic American populations (odds ratio 1.3 [95% confidence interval 1.14-1.31], meta-analysis P=3.8×10(-7)). In European Americans, the largest ethnic data set studied, the risk A allele of rs7704116 was associated with the presence of renal disease, anti-double-stranded DNA, and anti-RNP antibodies. PPP2CA expression was ∼2-fold higher in SLE patients carrying the rs7704116 AG genotype than those carrying the GG genotype (P=0.007). CONCLUSION Our data provide the first evidence of an association between PPP2CA polymorphisms and elevated PP2Ac transcript levels in T cells, which implicates a new molecular pathway for SLE susceptibility in European Americans, Hispanic Americans, and Asians.

A functional RANKL polymorphism associated with younger age at onset of rheumatoid arthritis.

OBJECTIVE We previously observed the association of the co-occurrence of the HLA-DRB1 shared epitope (SE) and RANKL single-nucleotide polymorphisms (SNPs) with younger age at the onset of rheumatoid arthritis (RA) in 182 rheumatoid factor (RF)-positive European American patients with early-onset RA. The aim of this study was to fine-map the 48-kb RANKL region in the extended cohort of 210 European American RF-positive patients with early RA, to seek replication of RA-associated SNPs in additional RA cohorts of 501 European Americans and 298 African Americans, and to explore the functional consequences of RA-associated SNPs. METHODS SNP genotyping was conducted using pyrosequencing or TaqMan polymerase chain reaction (PCR) assays. Associations of rs7984870 with RANKL expression in plasma, peripheral blood mononuclear cells, and isolated T cells were quantified using enzyme-linked immunosorbent assay and reverse transcription-PCR. Site-directed mutagenesis of rs7984870 within the 2-kb RANKL promoter was performed to drive the luciferase reporter gene in osteoblast and stromal cell lines. Interaction of DNA and protein was determined by electrophoretic mobility shift assay. RESULTS A single promoter SNP, rs7984870, was consistently significantly associated with earlier age at the onset of RA in 3 independent seropositive (RF or anti-cyclic citrullinated peptide antibody) RA cohorts but not in seronegative RA patients. The C risk allele of rs7984870 conferred 2-fold higher plasma RANKL levels in RF-positive patients with RA, significantly elevated RANKL messenger RNA expression in activated normal T cells, and increased promoter activity after stimulation in vitro via differential binding to the transcription factor SOX5. CONCLUSION The RANKL promoter allele that increased transcription levels upon stimulation might promote interaction between activated T cells and dendritic cells, predisposing to a younger age at the onset of RA in seropositive European American and African American patients.

A missense variant in NCF1 is associated with susceptibility to multiple autoimmune diseases

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease with a strong genetic component characterized by autoantibody production and a type I interferon signature. Here we report a missense variant (g.74779296G>A; p.Arg90His) in NCF1, encoding the p47phox subunit of the phagocyte NADPH oxidase (NOX2), as the putative underlying causal variant that drives a strong SLE-associated signal detected by the Immunochip in the GTF2IRD1–GTF2I region at 7q11.23 with a complex genomic structure. We show that the p.Arg90His substitution, which is reported to cause reduced reactive oxygen species (ROS) production, predisposes to SLE (odds ratio (OR) = 3.47 in Asians (Pmeta = 3.1 × 10−104), OR = 2.61 in European Americans, OR = 2.02 in African Americans) and other autoimmune diseases, including primary Sjögrens syndrome (OR = 2.45 in Chinese, OR = 2.35 in European Americans) and rheumatoid arthritis (OR = 1.65 in Koreans). Additionally, decreased and increased copy numbers of NCF1 predispose to and protect against SLE, respectively. Our data highlight the pathogenic role of reduced NOX2-derived ROS levels in autoimmune diseases.

Modulation of IL-6 induced RANKL expression in arthritic synovium by a transcription factor SOX5

Receptor activator of nuclear factor κB ligand (RANKL) is critically involved in bone erosion of rheumatoid arthritis (RA). We previously reported association between younger age at onset of RA and a RANKL promoter SNP that conferred an elevated promoter activity via binding to a transcription factor SOX5. Here we study the regulation of SOX5 levels in relation to RANKL expression in RA synovial fibroblasts (SF) and the development of bone erosion in the collagen-induced arthritis (CIA) mouse. Our data indicated SOX5 levels were higher in synovium and synovial fluid from RA compared to osteoarthritis patients. Pro-inflammatory cytokines upregulated SOX5 and RANKL expression in both primary RA SF and the rheumatoid synovial fibroblast cell line, MH7A. Overexpression of SOX5 resulted in significantly increased RANKL levels, while knockdown of SOX5 resulted in diminished IL-6 mediated RANKL upregulation in MH7A cells. Chromatin immunoprecipitation (ChIP) showed approximately 3-fold enrichment of RANKL-specific DNA in anti-SOX5 immunoprecipitate in IL-6 treated MH7A cells as compared to untreated cells. Locally silencing SOX5 gene significantly diminished RANKL positive cells and bone erosion in CIA mice. These findings suggest SOX5 is an important regulator of IL-6-induced RANKL expression in RA SF.

Interleukin-29 Enhances Synovial Inflammation and Cartilage Degradation in Osteoarthritis

We have recently shown that IL-29 was an important proinflammatory cytokine in pathogenesis of rheumatoid arthritis (RA). Inflammation also contributes to the pathogenesis of osteoarthritis (OA). The aim of this study was to investigate the effect and mechanism of IL-29 on cytokine production and cartilage degradation in OA. The mRNA levels of IL-29 and its specific receptor IL-28Ra in peripheral blood mononuclear cells (PBMCs) were significantly increased in OA patients when compared to healthy controls (HC). In the serum, IL-29 protein levels were higher in OA patients than those in HC. Immunohistochemistry revealed that both IL-29 and IL-28Ra were dramatically elevated in OA synovium compared to HC; synovial fibroblasts (FLS) and macrophages were the main IL-29-producing cells in OA synovium. Furthermore, recombinant IL-29 augmented the mRNA expression of IL-1β, IL-6, IL-8, and matrix-metalloproteinase-3 (MMP-3) in OA FLS and increased cartilage degradation when ex vivo OA cartilage explant was coincubated with OA FLS. Finally, in OA FLS, IL-29 dominantly activated MAPK and nuclear factor-κB (NF-κB), but not Jak-STAT and AKT signaling pathway as examined by western blot. In conclusion, IL-29 stimulates inflammation and cartilage degradation by OA FLS, indicating that this cytokine is likely involved in the pathogenesis of OA.

Adiponectin aggravates bone erosion by promoting osteopontin production in synovial tissue of rheumatoid arthritis

BackgroundWe have previously reported that adiponectin (AD), an adipokine that is secreted by adipocytes, correlates well with progressive bone erosion in rheumatoid arthritis (RA). The exact mechanism of AD in promoting joint destruction remains unclear. Osteopontin (OPN) is required for osteoclast recruitment. We hypothesized that AD exacerbates bone erosion by inducing OPN expression in synovial tissue. This study aimed to evaluate a novel role for AD in RA.MethodsThe serum levels of AD and OPN were determined in 38 patients with RA, 40 patients with osteoarthritis (OA), and 20 healthy controls using enzyme-linked immunosorbent assay (ELISA). AD and OPN production were measured by double immunofluorescence in RA and OA synovial tissue. Quantitative real-time PCR and immunofluorescence were used to evaluate the mRNA and protein expression levels of OPN in RA synovial fibroblasts (RASFs) and OA synovial fibroblasts after pre-incubation with AD, respectively. Migration of the RAW264.7 osteoclast precursor cell line was assessed using the Transwell migration assay and co-culture system. Bone destruction and osteoclastogenesis were assessed by immunohistochemical staining, microcomputed tomography and tartrate-resistant acid phosphatase (TRAP) staining in AD-treated collagen-induced arthritis (CIA) mice with or without OPN silencing. The expression levels of OPN and integrin αvβ3 in the ankle joint tissues of the mice were examined by double immunofluorescence.ResultsOur results indicated that the AD and OPN expression levels increased noticeably and were associated with each other in the RA serum. The AD distribution was coincident with that of OPN in the RA synovial tissue. AD stimulation of RASFs increased OPN production in a dose-dependent manner. AD-treated RASFs promoted RAW264.7 cell migration, and the effect was blocked with a specific antibody against OPN. Silencing of OPN using lentiviral-OPN short hairpin RNA reduced the number of TRAP-positive osteoclasts and the extent of bone erosion in the AD-treated CIA mice. When bound to integrin αvβ3, OPN functions as a mediator of AD and osteoclasts.ConclusionsOur study provides new evidence of AD involvement in bone erosion. AD induces the expression of OPN, which recruits osteoclasts and initiates bone erosion. These data highlight AD as a novel target for RA treatment.

LC-MS-based serum metabolomics reveals a distinctive signature in patients with rheumatoid arthritis

Metabolomics has been applied to explore altered metabolite profiles in disease and identify unique metabolic signatures in recent years. We aim to characterize the metabolic profile of rheumatoid arthritis patients and explore its underlying pathological processes using metabolomics approach. Serum samples from 30 rheumatoid arthritis (RA) patients, 30 primary Sjogren’s syndrome (pSS) patients, and 32 healthy controls (HC) were collected. The sample was analyzed by ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UPLC-HRMS). Potential biomarkers were screened from orthogonal projection to latent structure discriminate analysis (OPLS-DA) and further evaluated by receiver operating characteristic analysis (ROC). Compared with HC and pSS patients, the RA patients had increased serum levels of 4-methoxyphenylacetic acid, glutamic acid, L-leucine, L-phenylalanine, L-tryptophan, L-proline, glyceraldehyde, fumaric acid, and cholesterol as well as decreased capric acid, argininosuccinic acid, and billirubin. A total of eight potential biomarkers were screened and tentatively identified for RA. A panel of three metabolites (4-methoxyphenylacetic acid, L-phenylalanine, and L-leucine) was identified as specific biomarkers of RA. ROC analysis showed that the panel had a sensitivity of 93.30% with a specificity of 95.20% in discrimination RA from other groups. UPLC-HRMS-based quantification of circulating metabolites was a useful tool for identifying RA patients from pSS patients and healthy controls. The potential biomarkers indicated that the RA metabolic disturbance might be associated with inflammation injury, amino acid metabolism, oxidative stress, and phospholipid metabolism.

Interleukin 29 inhibits RANKL-induced osteoclastogenesis via activation of JNK and STAT, and inhibition of NF-κB and NFATc1

&NA; Interleukin (IL)‐29 is known to modulate immune functions of monocytes or macrophages. In this study, we investigated the effect and its underlying mechanism of IL‐29 on receptor activator of nuclear factor &kgr;B ligand (RANKL)‐induced osteoclastogenesis using murine macrophage cell line RAW264.7 cells and bone‐marrow‐derived monocyte/macrophage precursor cells (BMMs), and human peripheral blood mononuclear cells (PBMCs). In response to human recombinant IL‐29, cell viability and apoptosis were assessed by Cell Counting Kit‐8 and flow cytometry; the osteoclast formation and activity by tartrate‐resistant acid phosphatase (TRAP) staining and pit formation assay, respectively; the expression and activation of molecules that associated with osteoclastogenesis by real time‐PCR, immunoblotting or immunofluorescent analysis. IL‐28 receptor &agr; (IL‐28R&agr;), a specific receptor of IL‐29 was expressed on RAW264.7 cells. Although IL‐29 did not affect the viability and apoptosis of RAW264.7 cells, it inhibited multinucleated cells in the differentiation of osteoclastogenesis, the bone‐resorbing activity of mature osteoclasts and osteoclastic specific genes expression including TRAP, cathepsin K (CTSK), nuclear factor of activated T‐cells, cytoplasmic 1 (NFATc1), C‐Fos and matrix metallopeptidase 9 (MMP‐9). This inhibitory effect of IL‐29 was confirmed on BMMs and PBMCs and mediated via IL‐28R&agr; through the activation of Stat1 and 3 and the suppression of nuclear factor kappa B (NF‐&kgr;B) and NFATc1 nuclear translocation in RAW264.7 cells. In conclusion, IL‐29 inhibited osteoclastogenesis via activation of STAT signaling pathway, prevention of NF‐&kgr;B activation and NFATc1 translocation, and suppression of downstream osteoclastogenic genes expression.

Transcription Factor SOX5 Promotes the Migration and Invasion of Fibroblast-Like Synoviocytes in Part by Regulating MMP-9 Expression in Collagen-Induced Arthritis

Objectives Fibroblast-like synoviocytes (FLS) exhibit a unique aggressive phenotype in rheumatoid arthritis (RA). Increased FLS migration and subsequent invasion of the extracellular matrix are essential to joint destruction in RA. Our previous research reported that transcription factor SOX5 was highly expressed in RA-FLS. Here, the effects of SOX5 in RA-FLS migration and invasion will be investigated. Methods The migration and invasion of RA-FLS were evaluated using a transwell chamber assay. The expression of several potential SOX5-targeted genes, including matrix metalloproteinases (MMP-1, 2, 3 and 9), chemokines (CCL4, CCL2, CCR5 and CCR2), and pro-inflammatory cytokines (TNF-α and IL-6), were examined in RA-FLS using SOX5 gain- and loss-of-function study. The molecular mechanisms of SOX5-mediated MMP-9 expressions were assayed by luciferase reporter gene and chromatin immunoprecipitation (ChIP) studies. The in vivo effect of SOX5 on FLS migration and invasion was examined using collagen-induced arthritis (CIA) in DBA/1J mice. Results Knockdown SOX5 decreased lamellipodium formation, migration, and invasion of RA-FLS. The expression of MMP-9 was the only gene tested to be concomitantly affected by silencing or overexpressing SOX5. ChIP assay revealed that SOX5 was bound to the MMP-9 promoter in RA-FLS. The overexpression of SOX5 markedly enhanced the MMP-9 promoter activity, and specific deletion of a putative SOX5-binding site in MMP-9 promoter diminished this promoter-driven transcription in FLS. Locally knocked down SOX5 inhibited MMP-9 expression in the joint tissue and reduced pannus migration and invasion into the cartilage in CIA mice. Conclusion SOX5 plays a novel role in mediating migration and invasion of FLS in part by regulating MMP-9 expression in RA.

Rheumatoid Arthritis: An Orchestra of Genetic, Autoimmune and Environmental Factors

Clinical presentation of rheumatoid arthritis (RA) may be the results of a combination of genetic and environmental risk factors resulting in a prominent autoimmune component. Evidence from case-control studies, either using the candidate gene or genome-wide association approaches, have revealed more than 30 loci that are associated with RA susceptibility. Many RA-associated gene variants are involved in pathways of T-cell, B-cell and NF-κB signaling. HLA-DRB1 shared epitope is a major determinant of genetic predisposition to RA development in different ethnic groups, which is involved in T-cell antigen presentation and the production of anti-cyclic citrullinated peptides antibodies (ACPA). The presence or absence of ACPA appears to stratify RA patients into two distinct subsets with different genetic profiles, clinical courses and histological findings. In addition to the shared epitope, a growing number of gene variants is associated with RA in multiple ethnic groups, including STAT4, AFF3, CCR6, CCL21, and BLK. Some of the RA-associated gene variants may be particularly important in a specific ethnic group; for example, PTPN22 in populations of European ancestry and PADI4 in Asians. Emerging evidence has shown that many disease-associated loci are shared among multiple autoimmune diseases, including type 1 diabetes, systemic lupus erythematosus, inflammatory bowel disease and multiple sclerosis, suggesting the presence of common pathways in the pathophysiology of these diseases. In addition to genetic risk factors, recent data have implicated cigarette smoking and infection of P. ginivitis as environmental risk factors that may potentiate disease risk in genetically susceptible individuals. Frequent and long-term exposure to insecticides also may increase risks for RA development. Further studies to understand functional consequences of disease-associated gene variants and gene-environment interactions that impact on the immune system are likely to lead to the development of novel therapies and/or prevention strategies for RA.