DTX3L/ARTD9 contributes to inflammation of fibroblast-like synoviocytes by increasing STAT1 translocation.

Deltex-3-like (DTX3L), an E3 ligase, which is also known as B-lymphoma and BAL-associated protein (BBAP), is a member of the Deltex (DTX) family and was originally identified as a binding partner of diphtheria-toxin-like ADP-ribosyltransferase-9 (ARTD9). The present study found that DTX3L and ARTD9 were upregulated in synovial tissues obtained from rheumatoid arthritis (RA) patients compared with those from the controls. Healthy synovial tissues were obtained by arthroscopic biopsy from patients with meniscus injury (n = 10 samples) without a history of RA in the Orthopedic Department of the Affiliated Hospital of Nantong University. FLSs were isolated from RA patients who underwent total knee arthroplasty. We performed dual immunofluorescence staining on DTX3L and ARTD9, and these data strongly demonstrated that DTX3L and ARTD9 were colocalized with fibroblast-like synoviocytes (FLSs) in patients with RA. Furthermore, Western blot assays were performed to confirm that the expression levels of DTX3L and ARTD9 in the FLSs increased in a time-dependent manner and peaked at 24 h after TNF-α stimulation. Further, the inhibition of endogenous DTX3L and ARTD9 expression by RNA interference significantly suppressed the TNF-α-induced MMP-9 and IL-6 expression, as shown by Western blots. In contrast, overexpressing DTX3L and ARTD9 increased the MMP-9 and IL-6 mRNA levels in the TNF-α-stimulated FLSs. Moreover, DTX3L and ARTD9 associated with STAT1 under TNF-α-stimulated conditions to modulate STAT1 nuclear localization and transcriptional activity in an immunofluorescence staining assay. Collectively, our findings provide evidence that DTX3L and ARTD9 contribute to the production of inflammatory cytokines in FLSs from RA patients and may play a key role in the inflammatory process of RA via the STAT1 signal transduction pathway.

Correction to: Sam68 Promotes Invasion, Migration, and Proliferation of Fibroblast-like Synoviocytes by Enhancing the NF-κB/P65 Pathway in Rheumatoid Arthritis.

Unfortunately the author name, Rongqing Qin, was wrongly spelt as Rongqin Qin in the original version. It has been updated and the complete corrected author group is given below.

Sam68 Promotes Invasion, Migration, and Proliferation of Fibroblast-like Synoviocytes by Enhancing the NF-κB/P65 Pathway in Rheumatoid Arthritis.

Src-associated substrate during mitosis of 68 KDa (Sam68), also known as KH domain containing, RNA binding, signal transduction associated 1 (KHDRBS1), is the prototypic member of the signal transduction activator of RNA (STAR) family of RNA-binding proteins. Previous studies have indicated that Sam68 regulates nuclear transcription factor kappa B (NF-κB) to mediate inflammation. In this study, we analyzed the effect and possible mechanisms of Sam68 in rheumatoid arthritis (RA). By western blot analysis and immunohistochemistry, we found that the expression of Sam68 in synovial tissue of RA patients was increased compared with the control group. Immunoflourescent staining demonstrated that Sam68 co-localized with fibroblast-like synoviocytes (FLS) of RA patients. Additionally, the expression of Sam68 in FLS was increased by tumor necrosis factor (TNF)-α stimulation, in a time-dependent manner. Upon TNF-α treatment, Sam68 translocated from the cytoplasm to the nucleus where it interacted with the p65 subunit of NF-κB, as examined by immunoprecipitation and immunofluorescent staining assay. Furthermore, inhibiting the expression of Sam68 by siRNA significantly suppressed the TNF-α-induced expression of interleukin (IL)-6, and matrix metalloproteinase (MMP)-1, reduced the proliferation, migration, and invasion, and markedly decreased the phosphorylation of P65 and IκBα in FLS. Collectively, our findings suggested that Sam68 contributed to the production of inflammatory cytokines, proliferation, migration, and invasion of RA FLS through the NF-κB P65 signal transduction pathway and underscored the importance of Sam68 in the inflammation process of RA.

Astrocyte elevated gene-1 promotes inflammation and invasion of fibroblast-like synoviocytes in rheumatoid arthritis.

Astrocyte elevated gene-1 (AEG-1) was initially induced by HIV-1 infection and involved in tumor progression, migration and invasion as a nuclear factor-κB (NF-κB)-dependent gene. The present study we intended to investigate the protein expression of AEG-1 significantly associated with rheumatoid arthritis. Western blot analysis and immunohistochemistry demonstrated that AEG-1 was upregulated in synovial tissue of RA patients compared with the controls. Double immunofluorescent staining suggested that AEG-1 was expressed in fibroblast-like synoviocytes (FLS) of RA patients. Furthermore, the expression of AEG-1 in FLS was increased in time-dependent manner by TNF-α stimulation. Upon TNF-α-treated FLS, AEG-1 transferred from the cytoplasm to nucleus where it interacted with the p65 subunit of NF-κB, as examined by immunoprecipitation and immunofluorescent staining assay. Moreover, the inhibition of AEG-1 by RNA interference significantly suppressed TNF-α-induced IL-6 and MMP-3 expression, leading to attenuation of FLS migration and invasion and markedly decreased the phosphorylation of P65 and IκBα, as well as AKT in FLS. Collectively, Our findings provided evidence that AEG-1 contributed to the production of inflammatory cytokines, migration and invasion of RA FLS, and underscored the importance of AEG-1 in the inflammation process of RA.