Human RA Research Articles

Association Between Plasma Aldosterone Concentration and Intraglomerular Hemodynamics in Primary Aldosteronism.

In primary aldosteronism (PA), aldosterone could affect glomerular hemodynamics by elevating renal vascular resistance and glomerular capillary pressure. However, the relationship between plasma aldosterone concentrations (PAC) and glomerular hemodynamics including efferent arteriolar resistance (Re), and afferent arteriolar resistance (Ra) in humans is still unclear. The aim of this study was to investigate the relationships of PAC with intraglomerular hemodynamic parameters in patients with PA. An observational study of glomerular hemodynamics was performed using simultaneous measurements of plasma clearance of para-aminohippurate and inulin (Cin; glomerular filtration rate (GFR)) in 17 patients with PA. Kidney function was evaluated by Cin, estimated GFR based on serum creatine (eGFRcre) and serum cystatin C (eGFRcys) and creatine clearance (Ccr). Intraglomerular hemodynamic parameters, including Re, Ra, and intraglomerular hydrostatic pressure (Pglo) were calculated using Gomez's formulae. In the 17 PA cases, PAC was significantly correlated with Cin (rho = 0.752, P = 0.001) and eGFRcys (rho = 0.567, P = 0.018), but was not correlated with eGFRcre and Ccr. PAC was also significantly correlated with Pglo, Re, and urinary protein/day (rho = 0.775, P = 0.0004, rho = 0.625, P = 0.009, and rho = 0.625, P = 0.007, respectively). Multivariable regression analysis showed that PAC was significantly associated with Cin and Re. In comparing aldosterone-producing adenoma (APA) and non-APA cases, Cin was significantly elevated in APA (P = 0.037), whereas eGFRcre, eGFRcys, and Ccr were not. Re tended to be higher in APA (P = 0.064). These results suggest high aldosterone causes glomerular hyperfiltration by constricting Re. Cin, but not eGFRcre and Ccr, may be useful for evaluating kidney function in PA.

Mid1 promotes synovitis in rheumatoid arthritis via ubiquitin-dependent post-translational modification

IntroductionCurrent anti-rheumatic drugs are primarily modulating immune cell activation, yet their effectiveness remained suboptimal. Therefore, novel therapeutics targeting alternative mechanisms, such as synovial activation, is urgently needed. ObjectivesTo explore the role of Midline-1 (Mid1) in synovial activation. MethodsNOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice were used to establish a subcutaneous xenograft model. Wild-type C57BL/6, Mid1-/-, Dpp4-/-, and Mid1-/-Dpp4-/- mice were used to establish a collagen-induced arthritis model. Cell viability, cell cycle, qPCR and western blotting analysis were used to detect MH7A proliferation, dipeptidyl peptidase-4 (DPP4) and Mid1 levels. Co-immunoprecipitation and proteomic analysis identified the candidate protein of Mid1 substrates. Ubiquitination assays were used to determine DPP4 ubiquitination status. ResultsAn increase in Mid1, an E3 ubiquitin ligase, was observed in human RA synovial tissue by GEO dataset analysis, and this elevation was confirmed in a collagen-induced mouse arthritis model. Notably, deletion of Mid1 in a collagen-induced arthritis model completely protected mice from developing arthritis. Subsequent overexpression and knockdown experiments on MH7A, a human synoviocyte cell line, unveiled a previously unrecognized role of Mid1 in synoviocyte proliferation and migration, the key aspects of synovial activation. Co-immunoprecipitation and proteomic analysis identified DPP4 as the most significant candidate of Mid1 substrates. Mechanistically, Mid1 promoted synoviocyte proliferation and migration by inducing ubiquitin-mediated proteasomal degradation of DPP4. DPP4 deficiency led to increased proliferation, migration, and inflammatory cytokine production in MH7A, while reconstitution of DPP4 significantly abolished Mid1-induced augmentation of cell proliferation and activation. Additionally, double knockout model showed that DPP4 deficiency abolished the protective effect of Mid1 defect on arthritis. ConclusionOverall, our findings suggest that the ubiquitination of DPP4 by Mid1 promotes synovial cell proliferation and invasion, exacerbating synovitis in RA. These results reveal a novel mechanism that controls synovial activation, positioning Mid1 as a promising target for therapeutic intervention in RA.

Chinese medicine Di-long (Pheretima vulgaris) and its active fraction exhibit anti-rheumatoid arthritis effects by inhibiting CXCL10/CXCR3 chemotaxis in synovium

Ethnopharmacological relevanceDi-Long (Pheretima vulgaris) is a classic animal sourced traditional Chinese medicine. It has been used for the treatment of joint inflammation and arthralgia for over two thousand years due to its effects of Tong-Luo-Zhi-Tong (dredging collaterals and alleviating pain). Our previous study showed that Chinese medicine Di-Long has significant anti-rheumatoid arthritis (RA) effects. Aim of the studyConsidering Di-Long as a potential source of active compounds with specific anti-RA therapeutic effects, this research was to obtain the anti-RA target-specific active fraction from Di-Long extracts (DL), and to further explore the chemical basis and verify the anti-RA mechanism of this active fraction. Materials and methodsTranscriptomic was applied to obtain the main anti-RA targets of DL on human RA fibroblast-like synoviocytes (FLS) and validated by qPCR. The target-corresponding active fraction was isolated from DL by ethanol precipitation and gel chromatography, and analyzed by nanoliter chromatography-mass spectrometry. Anti-RA effects of this active fraction was investigated by collagen-induced arthritis (CIA) in mice, and anti-RA mechanisms were verified in cocultured model of rat FLS and peripheral blood lymphocytes. ResultsWe confirmed that CXCL10/CXCR3 was the main anti-RA target of DL. The active fraction - A (2182 - 890 Da) was isolated from DL based on its CXCL10 inhibiting effects in RA-FLS. Fraction A contains 195 peptides (192 were newly discovered), 26 of which might be bioactive and were considered to be the chemical basis of its anti-RA effects. Fraction A significantly ameliorated the joint destruction and overall inflammation in CIA mice, and downregulated CXCR3 expression in mice joint. Fraction A inhibited the chemotaxis of Th-cells in rat peripheral blood lymphocytes towards the TNF-α-induced rat FLS through CXCL10/CXCR3 pathway. ConclusionsOur work indicated that active fraction from DL containing small peptides exhibits promising therapeutic effects for RA through inhibiting CXCL10/CXCR3 chemotaxis.

Targeting TNF-α-induced expression of TTR and RAGE in rheumatoid arthritis: Apigenin's mediated therapeutic approach

BackgroundRheumatoid arthritis (RA) is a chronic inflammatory disease induced by TNF-α, which increases fibroblast-like synoviocytes inflammation, resulting in cartilage destruction. The current work sought to comprehend the pathophysiological importance of TNF-α stimulation on differential protein expression and their regulation by apigenin using in-vitro and in-vivo models of RA. MethodsThe human RA synovial fibroblast cells were stimulated with or without TNF-α (10 ng/ml) and treated with 40 μM apigenin. In-silico, in-vitro and in-vivo studies were performed to confirm the pathophysiological significance of apigenin on pro-inflammatory cytokines and on differential expression of TTR and RAGE proteins. ResultsTNF-α induced inflammatory response in synoviocytes revealed higher levels of IL-6, IL-1β, and TNF-α cytokines and upregulated differential expression of TTR and RAGE. In-silico results demonstrated that apigenin has a binding affinity towards TNF-α, indicating its potential effect in the inflammatory process. Both in-vitro and in-vivo results obtained by Western Blot analysis suggested that apigenin reduced the level of p65 (p = 0.005), TTR (p = 0.002), and RAGE (p = 0.020). ConclusionThe findings of this study suggested that TNF-α promotes the differential expression of pro-inflammatory cytokines, TTR, and RAGE via NF-kB pathways activation. Anti-inflammatory effect of apigenin impedes TNF-α mediated dysregulation or expression associated with RA pathogenesis.

Exosome-mediated delivery of super-repressor IκBα alleviates inflammation and joint damages in rheumatoid arthritis.

This study aims to investigate the potential anti-inflammatory effects of exosomes engineered to carry super-repressor IκB (Exo-srIκB), an exosome-based NF-κB inhibitor, in the context of RA. Peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) were collected from patients diagnosed with RA and treated with Exo-srIκB to test the therapeutic potential. Flow cytometry analysis was performed to assess the production of inflammatory cytokines (IL-17A and GM-CSF) by the cells. ELISA was utilized to measure the levels of TNF-α, IL-17A, IL-6, and GM-CSF. Arthritis was induced in SKG mice by intraperitoneal injection of curdlan. DBA/1J mice were used in collagen-induced arthritis (CIA) experiments. After the development of arthritis, mice were injected with either Exo-Naïve (control exosome) or Exo-srIκB. Arthritis scores were recorded biweekly, and histological observations of the ankle joint were conducted using H&E and safranin-O staining. Additionally, bone erosion was evaluated using micro-CT imaging. In the ex vivo study involving human PBMCs and SFMCs, treatment with Exo-srIκB demonstrated a notable reduction in inflammatory cytokines. Furthermore, in both the SKG and CIA models, Exo-srIκB treatment exhibited significant reductions in inflammation, cartilage destruction, and bone erosion within the joint tissues when compared to the Exo-Naive control group. Additionally, the radiographic score assessed through microCT showed a significant decrease compared to the Exo-Naive control group. Overall, these findings suggest that Exo-srIκB possesses anti-inflammatory properties in human RA cells and animal models, making it a promising therapeutic candidate for the treatment of RA.

CD64 as novel molecular imaging marker for the characterization of synovitis in rheumatoid arthritis

BackgroundRheumatoid arthritis (RA) is one of the most prevalent and debilitating joint diseases worldwide. RA is characterized by synovial inflammation (synovitis), which is linked to the development of joint destruction. Magnetic resonance imaging and ultrasonography are widely being used to detect the presence and extent of synovitis. However, these techniques do not reveal the activation status of inflammatory cells such as macrophages that play a crucial role in synovitis and express CD64 (Fc gamma receptor (FcγR)I) which is considered as macrophage activation marker.ObjectivesWe aimed to investigate CD64 expression and its correlation with pro-inflammatory cytokines and pro-damaging factors in human-derived RA synovium. Furthermore, we aimed to set up a molecular imaging modality using a radiolabeled CD64-specific antibody as a novel imaging tracer that could be used to determine the extent and phenotype of synovitis using optical and nuclear imaging.MethodsFirst, we investigated CD64 expression in synovium of early- and late-stage RA patients and studied its correlation with the expression of pro-inflammatory and tissue-damaging factors. Next, we conjugated an anti-CD64 antibody with IRDye 800CW and diethylenetriamine penta-acetic acid (DTPA; used for 111In labeling) and tested its binding on cultured THP1 cells, ex vivo RA synovium explants and its imaging potential in SCID mice implanted with human RA synovium explants obtained from RA patients who underwent total joint replacement.ResultsWe showed that CD64 is expressed in synovium of early and late-stage RA patients and that FCGR1A/CD64 expression is strongly correlated with factors known to be involved in RA progression. Combined, this makes CD64 a useful marker for imaging the extent and phenotype of synovitis. We reported higher binding of the [111In]In-DTPA-IRDye 800CW anti-CD64 antibody to in vitro cultured THP1 monocytes and ex vivo RA synovium compared to isotype control. In human RA synovial explants implanted in SCID mice, the ratio of uptake of the antibody in synovium over blood was significantly higher when injected with anti-CD64 compared to isotype and injecting an excess of unlabeled antibody significantly reduced the antibody-binding associated signal, both indicating specific receptor binding.ConclusionTaken together, we successfully developed an optical and nuclear imaging modality to detect CD64 in human RA synovium in vivo.

Nanotechnology-based drug delivery for targeted therapy of autoimmune arthritis improves the therapeutic profile of anti-arthritis drugs

Abstract Rheumatoid arthritis (RA) is among the major human autoimmune diseases, and it affects over 1 percent of the population. Although many anti-arthritis drugs are available for RA therapy, their long-term use may lead to severe adverse effects. This, combined with high cost of many newer drugs, poses a hurdle for the effective control of RA as well as patient compliance with therapeutic regimens. Therefore, novel treatment modalities are required to overcome these limitations. In this context, we have developed a nanotechnology-based drug delivery system for targeted therapy of arthritic inflammation. Liposomal entrapment of drugs increases their shelf-life in vivo, whereas the display of a joint-homing peptide ligand on liposomal surface aids in guiding them to the site of inflammation. One such peptide (denoted as ART-1) was previously identified by us by phage peptide-display library screening of arthritic Lewis rats. When administered subcutaneously or intravenously, fluorescence-labeled ART-1 shows preferential homing to arthritic joints compared to normal (control) joints. We exploited this drug delivery system for the treatment of experimental arthritis with dexamethasone (Dex) using the rat adjuvant arthritis (AA) model. At the time of onset of AA, rats were treated with liposomal Dex, unpackaged (free) Dex, or the vehicle on alternate days. All rats were observed and graded regularly for arthritis severity. Sera obtained at the terminal step were tested for a panel of enzymes indicating tissue/organ toxicity. Liposomal Dex showed improved therapeutic profile (efficacy/toxicity ratio) over that of free Dex. We propose that this peptide ligand-targeted drug delivery approach can be adapted for effective control of human RA. "Supported by grants from NIH (R01 AT004321), Veterans Affairs (5 I01 BX002424) and Silo Pharma"

E076 To investigate the mechanisms of action of novel compounds ex vivo in cells obtained from the inflammatory synovium of patients with rheumatoid arthritis

Abstract Background/Aims To investigate the ex vivo effect of JAK1/2 inhibitor baricitinib on the expression of pro-inflammatory mediators in normal and RA diseased fibroblasts stimulated with oncostatin M (OSM) as well as in cells derived from RA inflamed synovial membrane cells (RA SMC). Methods RA SMC and fibroblast like synoviocytes (RA FLS) were isolated from synovial membranes of patients undergoing surgery using enzymatic digestion and cell propagation. Normal fibroblast-like synoviocytes (FLS) and normal human skin fibroblasts (HSF) were purchased from commercial sources. All fibroblasts were cultured in media supplemented foetal bovine serum and antibiotics in incubators using established laboratory procedures, and serum-starved prior to stimulation with OSM with or without baricitinib. RA SMC were cultured in the presence of baricitinib without OSM as they spontaneously release pro-inflammatory cytokines. Levels of mRNA and proteins of the various inflammatory cytokines (IL-6, IL-8, MCP-1, CCL5 and IP-10) were determined by qPCR, ELISA and MSD. Western blot was used to measure levels of phospho-JAK specific components. Results qPCR analysis found that baricitinib inhibited OSM induced IP-10 and MCP-1 mRNA expression but not RANTES mRNA expression in normal human skin fibroblasts and RA FLS. In normal FLS however, baricitinib was found to inhibit RANTES and MCP-1 mRNA expression, but not IP-10 mRNA expression. Expression levels of IL-8 were too low for accurate conclusions to be drawn in all cell types apart from the RA SMCs, and in this case baricitinib did not inhibit IL-8 expression. ELISA results showed that baricitinib inhibited OSM induced MCP-1 expression in all cell types investigated. OSM induced IL-6 expression was inhibited in RA FLS but no other cell type. Conclusion Baricitinib inhibits OSM stimulated pro-inflammatory cytokine production through JAK1, 2. It has a varying inhibitory effect on the production of different cytokines: it is shown to particularly inhibit MCP-1. Baricitinib was found to have no effect on the production of spontaneously released pro-inflammatory cytokines in RA mixed cell populations. Disclosure M. Turner: None.

HOXA5 is a key regulator of class 3 semaphorins expression in the synovium of rheumatoid arthritis patients.

Class 3 semaphorins are reduced in the synovial tissue of RA patients and these proteins are involved in the pathogenesis of the disease. The aim of this study was to identify the transcription factors involved in the expression of class 3 semaphorins in the synovium of RA patients. Protein and mRNA expression in synovial tissue from RA and individuals at risk (IAR) patients, human umbilical vein endothelial cells (HUVEC) and RA fibroblast-like synoviocytes (FLS) was determined by ELISA, immunoblotting and quantitative PCR. TCF-3, EBF-1 and HOXA5 expression was knocked down using siRNA. Cell viability, migration and invasion were determined using MTT, calcein, wound closure and invasion assays, respectively. mRNA expression of all class 3 semaphorins was significantly lower in the synovium of RA compared with IAR patients. In silico analysis suggested TCF-3, EBF-1 and HOXA5 as transcription factors involved in the expression of these semaphorins. TCF-3, EBF-1 and HOXA5 silencing significantly reduced the expression of several class 3 semaphorin members in FLS and HUVEC. Importantly, HOXA5 expression was significantly reduced in the synovium of RA compared with IAR patients and was negatively correlated with clinical disease parameters. Additionally, TNF-α down-regulated the HOXA5 expression in FLS and HUVEC. Finally, HOXA5 silencing enhanced the migratory and invasive capacities of FLS and the viability of HUVEC. HOXA5 expression is reduced during the progression of RA and could be a novel therapeutic strategy for modulating the hyperplasia of the synovium, through the regulation of class 3 semaphorins expression.

Abstract LB524: Discovery of highly selective RON kinase inhibitors

Abstract RON is a receptor tyrosine kinase of the MET proto-oncogene family, known as macrophage stimulating 1 receptor (MST1R) that recognizes macrophage-stimulating protein (MSP). RON has been known to be highly expressed in several epithelial tumors, promoting tumor progression and metastasis, and on macrophages surface, facilitating M2-like phenotype polarization of tumor-associated macrophages (TAM) to impair anti-tumor functions of CD8+ T cells. Although pharmacological inhibition of RON kinase has received attention from many research groups, monoclonal antibody drug showed a limited clinical efficacy due to RON variant of receptor region. Because the structure homology of kinase domain between RON and MET is 80%, discovery of RON-specific small molecule inhibitor is considered to be highly challenging to achieve. At first, we discovered a lead compound with about 50-fold of RON selectivity against MET kinase. Our medicinal chemistry efforts elevated RON/MET selectivity up to 500~10,000-fold (IC50 = 1~50 nM in RON enzyme assay), and the target specificity was proved through a panel assay of 372 kinases (Reaction Biology Corp.). A series of compounds effectively modulated p-RON and downstream signals (e.g. p-ERK and p-AKT) in MDA-MB-453, and inhibited cell proliferation of Ba/F3 cell-line engineered with human RON kinase. Significant anti-tumor effects were shown in syngeneic mouse models compared to a control group after oral administration, and studies related to immuno-oncology are ongoing in in-vitro or ex-/in-vivo assay systems. In conclusion, we have identified RON selective small molecule inhibitors that will be useful to figure out the biology following RON selective inhibition against MET kinase, and to validate the translational potential of RON kinase as a therapeutic target for human diseases including cancer. Citation Format: Young Jin Ham, GyeongHwan Kim, Juhyun Lee, Jaeyoung Lee, Min Kyung Kim, Sunhong Kim, Woosook Kim, Han Byoul Kim, Sung Woong Jang, Hee Dong Park, Seonguk Jeon, Seok-Joo Kim, Joongheui Cho, Jungjoon Kim, Hong bin Yoon, Youngshin Kwak. Discovery of highly selective RON kinase inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB524.

Fibronectin extra domain A as a drug delivery targeting epitope for rheumatoid arthritis

ObjectivesTo assess the ability of monoclonal antibodies (mAbs) specific for fibronectin extra-domain A (FnEDA) to target diseased tissues of mouse collagen induced arthritis (mCIA) models. To explore the parameters of the targeting exhibited by anti-FnEDA mAbs including timing and location.MethodsTargeting capabilities of anti-FnEDA mAbs were demonstrated by biodistribution study where i.v. injected antibodies were detected by conjugated near-infrared (NIR) fluorophore, 125I label and immunohistochemistry (IHC) of the injected antibody. Location of FnEDA expression in both mCIA and human RA tissue were mapped by IHC. Quantification of anti-FnEDA mAbs targeted to disease tissue was measured by whole-body autoradiography (WBA). Timing of the targeting was interrogated with fluorescent and confocal microscopy using anti-FnEDA mAbs labeled with different fluorophores and injected at different times.ResultsAnti-FnEDA mAbs show specific targeting to diseased paws of mCIA animal. The targeting was focused on inflamed synovium which is consistent with FnEDA expression profile in both mCIA and human RA tissues. Anti-FnEDA mAbs accumulated in diseased tissue at pharmacologically relevant concentrations, the targeting was sustained for up to 14 days and FnEDA was able to support targeting of multiple doses of anti-FnEDA mAbs given 5 days apart.ConclusionFnEDA is specifically upregulated in the inflamed tissues of mCIA. Antibodies specific for FnEDA can be useful as molecular delivery vehicles for disease specific targeting of payloads to inflamed joint tissue.

Splenectomy modulates the immune response but does not prevent joint inflammation in a mouse model of RA.

The spleen is the largest secondary lymphoid organ which is involved in the development of B cells and also in systemic (auto)immune responses. Using the recombinant human G1 domain-induced arthritis (GIA) model in splenectomized and control BALB/c mice, we investigated the role of the spleen in the induction and pathogenesis of autoimmune arthritis. Splenectomized mice developed GIA with a similar clinical picture to the control group. However, we observed significant alterations in the humoral and cellular immune responses in splenectomized mice. In the sera of the splenectomized mice, we found lower pro-inflammatory cytokine and anti-rhG1 IgM levels, but higher IL-4, anti-rhG1 IgG1 and anti-CCP and RF antibodies. The arthritis induction in the splenectomized group was associated with a significant expansion of activated helper T cells and an increase in the proportion of the circulating B1 and marginal zone B cell subsets. Importantly, immunization of the splenectomized mice with rhG1 induced the formation of germinal centers in the inguinal- and mesenteric lymph nodes (i/mLNs) which showed an active immune response to rhG1. Finally, both B and T cells from the mLNs of the splenectomized mice showed decreased intracellular Ca2+ signaling than those of the control group. Collectively, these findings indicate that the presence of the spleen is not critical for the induction of GIA, and in its absence the autoimmune arthritis is most likely promoted through the compensatory activity of the i/mLNs. However, our data implies the immunological role of the spleen in arthritis which could be further assessed in human RA.

P191 To investigate the mechanisms of action of novel compounds ex vivo in cells obtained from the inflammatory synovium of patients with rheumatoid arthritis

Abstract Background/Aims To investigate the ex vivo effect of JAK1/2 inhibitor baricitinib on the expression of pro-inflammatory mediators in normal and RA diseased fibroblasts stimulated with oncostatin M (OSM) as well as in cells derived from RA inflamed synovial membrane cells (RA SMC). Methods RA SMC and fibroblast like synoviocytes (RA FLS) were isolated from synovial membranes of patients undergoing surgery using enzymatic digestion and cell propagation. Normal fibroblast-like synoviocytes (FLS) and normal human skin fibroblasts (HSF) were purchased from commercial sources. All fibroblasts were cultured in media supplemented foetal bovine serum and antibiotics in incubators using established laboratory procedures, and serum-starved prior to stimulation with OSM with or without baricitinib. RA SMC were cultured in the presence of baricitinib without OSM as they spontaneously release pro-inflammatory cytokines. Levels of mRNA and proteins of the various inflammatory cytokines (IL-6, IL-8, MCP-1, CCL5 and IP-10) were determined by qPCR, ELISA and MSD. Western blot was used to measure levels of phospho-JAK specific components. Results qPCR analysis found that baricitinib inhibited OSM induced IP-10 and MCP-1 mRNA expression but not RANTES mRNA expression in normal human skin fibroblasts and RA FLS. In normal FLS however, baricitinib was found to inhibit RANTES and MCP-1 mRNA expression, but not IP-10 mRNA expression. Expression levels of IL-8 were too low for accurate conclusions to be drawn in all cell types apart from the RA SMCs, and in this case baricitinib did not inhibit IL-8 expression. ELISA results showed that baricitinib inhibited OSM induced MCP-1 expression in all cell types investigated. OSM induced IL-6 expression was inhibited in RA FLS but no other cell type. Conclusion Baricitinib inhibits OSM stimulated pro-inflammatory cytokine production through JAK1, 2. It has a varying inhibitory effect on the production of different cytokines: it is shown to particularly inhibit MCP-1. Baricitinib was found to have no effect on the production of spontaneously released pro-inflammatory cytokines in RA mixed cell populations. Disclosure M.P. Turner: None.

Derivation of a Ni bioaccessibility value for screening-level risk assessment of Ni substances in ingested materials including soils.

The objective of the present study was to derive a Ni bioaccessibility value for screening-level risk assessment of Ni substances in ingested materials including soils where multiple Ni substances are expected but not definitively identified. Broad ranges of Ni mass loading and dissolution time of a simple gastric assay were applied to pure Ni substances (removing the confounding factors of soil constituents on dissolution), thus broadening the applicability of the conclusions. The data were also used to support current knowledge of 'read across' for Ni substances. Release of Ni from pure manufactured Ni substances (Ni metal, NiO, NiSO4, Ni3S2, and NiS) was determined relative to Ni mass and substance surface area loading. Mass loadings ranged from 0.33 to 20.0g Ni per L of 0.15M HCl, and dissolution time ranged from 1 to 168h. Proton exhaustion was indicated only at the highest loading (20g/L) of NiO and Ni-M. Dissolution of substances other than NiSO4 was most likely limited by formation of intermediate products at the particle surface or particle agglomeration, impeding access to the principal Ni substance. The bioaccessibility of Ni for these substances was consistent with previously published data: substances other than NiSO4 were < 48% bioaccessible for a variety of gastric assays, which is much lower than all data for NiSO4, the usual reference substance. Thus, we suggest that Ni bioaccessibility data from gastric assays that are most relevant to human exposure can be relied upon to develop scientifically sound screening-level human health RA decisions for Ni contamination in soils and sediments in the absence of detailed Ni speciation.

Susceptibility of cyclin-dependent kinase inhibitor 1-deficient mice to rheumatoid arthritis arising from interleukin-1\u03b2-induced inflammation

We recently reported that cyclin-dependent kinase inhibitor 1 (p21) deficiency induces osteoarthritis susceptibility. Here, we determined the mechanism underlying the effect of p21 in synovial and cartilage tissues in RA. The knee joints of p21-knockout (p21−/−) (n = 16) and wild type C57BL/6 (p21+/+) mice (n = 16) served as in vivo models of collagen antibody-induced arthritis (CAIA). Arthritis severity was evaluated by immunological and histological analyses. The response of p21 small-interfering RNA (siRNA)-treated human RA FLSs (n = 5 per group) to interleukin (IL)-1β stimulation was determined in vitro. Arthritis scores were higher in p21−/− mice than in p21+/+ mice. More severe synovitis, earlier loss of Safranin-O staining, and cartilage destruction were observed in p21−/− mice compared to p21+/+ mice. p21−/− mice expressed higher levels of IL-1β, TNF-α, F4/80, CD86, p-IKKα/β, and matrix metalloproteinases (MMPs) in cartilage and synovial tissues via IL-1β-induced NF-kB signaling. IL-1β stimulation significantly increased IL-6, IL-8, and MMP expression, and enhanced IKKα/β and IκBα phosphorylation in human FLSs. p21-deficient CAIA mice are susceptible to RA phenotype alterations, including joint cartilage destruction and severe synovitis. Therefore, p21 may have a regulatory role in inflammatory cytokine production including IL-1β, IL-6, and TNF-α.

Do human sinoatrial node cells have t-tubules?

Every heartbeat is generated by spontaneously depolarizing specialised nodal cells that make up the sinoatrial node (SN). The SN's unique properties depend on two complex mechanisms - the membrane-voltage and the Ca2+ clocks, regulated by strictly defined expression of ion channels, connexins and Ca2+-handling proteins. In the working myocardium these proteins are accumulated in specialised membrane structures– the transverse tubules (t-tubules). It is well known that small mammals do not exhibit t-tubules in their atrium, but such structures are observed in the atria of bigger mammals such as sheep. No information on t-tubules in the human SN is present yet. The aim of our study was to determine if t-tubules are present in the human SN, as well as surrounding atrial myocardium. Dystrophin (cytoplasmic protein connecting the muscle fibres to the surrounding extracellular membrane), Na+-Ca2+ exchanger (NCX1), sarcoplasmic-endoplasmic reticulum calcium adenosine triphosphatase (SERCA2a), α-actinin, and ryanodine receptor 2 (RyR2) were investigated. Staining with wheat germ agglutinin (WGA, specific marker of t-tubules) demonstrated that human RA cells contain t-tubules, but these structures are very sparse in the SN. Experiments in single nodal cells from rat and mouse showed no expression of t-tubular network, but striated pattern of expression of RyR2 was obtained similar to the human sections, suggesting its manner of organization is dependent on α-actinin colocalization.

Recombinant CD300c-Ig fusion protein attenuates collagen-induced arthritis in mice.

RA is a chronic autoimmune disease characterized by joint inflammation and tissue destruction. Immune responses mediated by T cells and autoantibodies are known to play critical roles in RA. Collagen type II (CII)-induced arthritis (CIA) is a commonly used animal model of human RA. We have previously reported the identification of a new T cell inhibitory molecule CD300c. Here we investigate the ability of recombinant CD300c-IgG2a Fc (CD300c-Ig) fusion protein to prevent and treat CIA. Mice were induced to develop CIA by CII and injected with CD300c-Ig or control Ig protein before or after CIA symptoms occur. The mice were examined for CIA clinical and pathological scores, and analysed for the expression of proinflammatory cytokines, the percentage and activation of CD4 T cells and regulatory T cells, CII-specific T cell proliferation and cytokine production, and CII-specific autoantibody production. In a prevention model, CD300c-Ig significantly decreases CIA incidence, and reduces clinical and pathological arthritis scores. In the treatment model, CD300c-Ig ameliorates established CIA. The beneficial effects of CD300c-Ig are related to decreased expansion and activation of T cells in the spleen and reduced expression of proinflammatory cytokines in the joints. CD300c-Ig also inhibits CII-specific T cell proliferation and Th1 and Th17 cytokine production. In addition, CD300c-Ig treatment reduced the production of CII autoantibodies in the serum. Furthermore, CD300c-Ig inhibits the proliferation and activation of T cells from RA patients in vitro. CD300c-Ig protein has the potential to be used in the treatment of patients with RA.

Xuebijing inhibit inflammation, oxidative stress and promote apoptosis in human synovial cells via inhibition of MEK1/2 and NF-ĸB pathway

Abstract Rheumatoid arthritis (RA) is categorized as an autoimmune disease that leads to bone or joint deformity due to altered immune response. Studies have concluded the role of inflammation and oxidative stress in the progression of RA and agents inhibiting these processes showed benificial effect against the disease. Xuebijing (XBJ) injection is an intravenous patent preparation made from five-traditional Chinese medicines. Previous studies showed its excellent pharmacological activities, such as against sepsis, inflammation, and oxidative stress which has encouraged us to investigate the protective effect of XBJ against rheumatoid arthritis cell line (MH7A). For this purpose, the effect of XBJ was quantified on several parameters on the human synovial MH7A cell line activated with tumor necrosis factor-α (TNF-α). The results of the study showed that the level of tested interleukines (IL- 1β, IL- 6, IL- 8) and collagenases 1, and 13, and matrix metallo-proteinases 1, and 13 (MMP-1, and MMP-13) were found significantly reduced in XBJ treated group as compared to TNF-α treated MH7A cells. The XBJ treated group showed reduction in mRNA protein expression of COX-2 and iNOS in RT-qPCR assay. The rate of cellular apoptosis was found increased in XBJ treated group with reduction of cell viability of MH7A cells. The XBJ also showed attenuation of the expression of p-MEK/1/2 and p-p65 in MH7A cells in a western blot analysis. Our results demonstrated that XBJ significantly inhibits the inflammatory response, prevents cell viability, and induces apoptosis in human RA synovial cells by preventing the activation of the MEK/NF-κB pathway.

The immunomodulating enzyme indoleamine 2,3-dioxygenase 2 (IDO2) as a target for therapy in autoimmune disease

Abstract The enzyme indoleamine 2,3-dioxygenase 2 (IDO2) is an important mediator of inflammatory autoimmune responses. Unlike its better-known counterpart, IDO1, which is thought to act primarily in an immunosuppressive manner, IDO2 acts to promote inflammation via a B-cell intrinsic mechanism. Prior work has demonstrated that genetic knockout of IDO2 can inhibit both autoantibody production and joint inflammation in the KRN.g7 murine model of arthritis. IDO2 played a similar role in driving inflammation in collagen induced arthritis and contact hypersensitivity models. Given the clear role of IDO2 in mediating autoimmunity, we have worked to find novel ways to target IDO2 in vivo. In addition to previous research successfully targeting the intracellular IDO2 protein with a novel monoclonal antibody, we have recently described an innovative, targeted DNA nanostructure-based siRNA-delivery system to specifically inhibit IDO2 function in B cells. Treatment of KRN mice with this B cell-directed anti-IDO2 siRNA nanotherapy reduced autoantibodies and attenuated arthritis, mimicking the phenotype seen with genetic knockouts. These data provided preclinical proof-of-concept that IDO2 could be effectively targeted as a treatment strategy in murine arthritis and suggested a similar strategy could be used target IDO2 in human RA. Similar to our findings using murine B cells, we found that IDO2 expression was elevated in B cells isolated from RA patients and could be silenced using anti-IDO2 siRNA in vitro. These data provide the first indication for the relevance of IDO2 in human RA and suggest nanoparticle delivery systems are a potential therapeutic strategy to inhibit IDO2 in RA patient B cells.

'Methyl palmitate attenuates adjuvant induced arthritis in rats by decrease of CD68 synovial macrophages

The study was designed to investigate the potential anti-arthritic effects of methyl palmitate in an adjuvant arthritis model in rats that shares many histopathological similarities with human RA. The underlying mechanism and its effect on CD68 macrophages were investigated, as a further argument to its possible efficacy in RA treatment. A normal control group was injected only with saline, arthritic group, and three treatment groups with CFA induced arthritis received methyl palmitate (MP) at three different doses (75, 150, 300 mg/kg/week for 3 weeks, intraperitoneal). The degree of ipsilateral paw swelling, ankle diameter, spleen index, thymus index and the expression levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β were measured. In addition, the underlying molecular mechanism was investigated using CD68 expression. Methyl palpitate significantly and dose dependently decreased the arthritic symptoms as measured by ipsilateral paw volume and ankle diameter. It showed no effect on body weight but significantly decreased splenic, thymus index, serum TNF-α and IL-1β. CD68 macrophages expression and the overall synovial inflammatory cellularity were halted. Methyl palmitate exhibits significant anti-inflammatory and exerts a potential anti-arthritic effect in a rat model of adjuvant induced arthritis. Furthermore, it inhibits expression of synovial CD68 macrophage that validate its therapeutic potential adjuvant arthritis.