TXNDC5 synergizes with HSC70 to exacerbate the inflammatory phenotype of synovial fibroblasts in rheumatoid arthritis through NF-κB signaling

The upregulated expression of thioredoxin domain-containing protein 5(TXNDC5)is associated with rheumatoid arthritis in patients and model mice.However,the underlying mechanism by which TXNDC5 influences the pathological activation of rheumatoid arthritis synovial fibroblasts(RASFs)remains unknown.In this study,we show that TXNDC5 expression in RASFs and their cytokine production are significantly upregulated in response to LPS,TNF-αand IL-6,but suppressed by transfection with TXNDC5-siRNA.TXNDC5 is further validated as the direct target of NF-κB signaling.Mechanistically,TXNDC5 directly interacts with heat shock cognate 70 protein(HSC70)to sequester it in the cytoplasm,and HSC70 silencing exerts the same effects as TXNDC5 on the biological activity of RASFs(for example,decreased cell viability,invasion and cytokine production).Furthermore,HSC70 activates NF-κB signaling by destabilizing IκBβprotein in the absence of LPS or facilitating its nuclear translocation in the presence of LPS.Importantly,TXNDC5 can also regulate the activity of NF-κB signaling in a HSC70-IκBβ-dependent manner.Taken together,by linking HSC70 and NF-κB signaling,TXNDC5 plays a pro-inflammatory role in RASFs,highlighting a potential approach to treat RA by blocking the TXNDC5/HSC70 interaction.

miR-573 is a negative regulator in the pathogenesis of rheumatoid arthritis

Rheumatoid arthritis （RA） is a chronic autoimmune disease characterized by abnormal inflammation, angiogenesis, and cartilage destruction. Our previous study demonstrated an increased expression of thioredoxin domain containing 5 （TXNDC5） in the synovial tissues of RA, and its overexpression was implicated in RA pathology. Although TXNDC5 variation is linked to genetic susceptibility to RA, the regulation of its abnormal expression has not been well defined. Here, we show that TXNDC5 is directly targeted by microRNA （miR）-573, and TXNDC5, in turn, mediates the suppressive effect of miR-573 on the invasion of synovial fibroblasts of RA （RASFs）. miR-573 overexpression suppressed the expression of interleukin 6 （I L-6） and cyclooxygenase 2 in RASFs, as well as the production of tumor necrosis factor-alpha and interleukin- 1 beta by activated THP-1 cells in response to lipopolysaccharide （LPS） stimulation. Moreover, treatment with conditioned medium of RASFs transfected with miR-573 mimic inhibited the angiogenic ability of human umbilical vein endothelial cells （HUVECs）. Of note, epidermal growth factor receptor and Toll-like receptor 2 were validated as new direct targets of miR-573, and mediate the regulation of miR-573 on IL-6 production as well as the angiogenesis of HUVECs. In addition, exogenous miR-573 expression suppressed the activation of mitogen-activated protein kinase （MAPK）, signal transducer and activator of transcription 3, and phosphatidylinositol-3 kinase/activate protein kinase B in RASFs in response to LPS. Indeed, MAPK signaling was essential to ensure the function of miR-573. Taken together, our study points toward the protective roles of miR-573 in the pathological process of RA and suggests a potential target in the treatment of RA.

Association Between Dentin Matrix Protein 1 （rs10019009） Polymorphism and Ankylosing Spondylitis in a Chinese Han Population from Shandong Province

Background： Ankylosing spondylitis （AS） is the most common rheumatic condition that is slowly progressive and predominantly affects adolescents. Pathological bone formation associated with AS is an important cause of disability. The aim of the study was to investigate the possible involvement of the genes related to endochondral ossification and ectopia ossification in genetic susceptibility to AS in a Chinese Han population. Methods： Sixty-eight single nucleotide polymorphisms （SNPs） from 13 genes were genotyped in discovery cohorts including 300 AS patients and 180 healthy controls. The rs10019009 in dentin matrix protein 1 （DMP1） gene shown as association with AS after multiple testing corrections in discovery cohorts was replicated in a validation independent cohort of 620 AS patients and 683 healthy controls. The rs 10019009 was assessed with bioin fomlatics including phylogenetic context, F-SNP and FastSNP functional predictions, secondary structure prediction, and molecular modeling. We performed a functional analysis of rs10019009 via reverse transcription-polymerase chain reaction, alkaline phosphatase （ALP） activity in human osteosarcoma U2OS cells. Results： Interestingly, the SNP rs10019009 was associated with AS in both the discovery cohort （P = 0.0012） and validation cohort （P - 0.0349）, as well as overall （P = 0.0004） in genetic case-control association analysis. After a multivariate logistic regression analysis, the effect of this genetic variant was observed to be independent of linkage disequilibrium. Via bioinformatics analysis, it was found that the amino acid change of the rs 10019009 led to changes of SNP function, secondary structure, tertiary confomlation, and splice mode. Finally, functional analysis ofrsl0019009 in U2OS cells demonstrated that the risk T allele of the rsl0019009 increased enzymatic activity of ALP, compared to that of the nonrisk allele （P = 0.0080）. Conclusions： These results suggested that the DMP1 gene seems to be involved in genetic predisposition to AS, which may contribute to the ectopic mineralization or ossification in AS. In addition, DMP1 gene may be a promising intervention target for AS in the future.