Role of C-reactive protein in osteoclastogenesis in rheumatoid arthritis

Association of advanced lung cancer inflammation index with all-cause and cardiovascular mortality in US patients with rheumatoid arthritis

Introduction

As a systemic autoimmune disorder, the prognosis of rheumatoid arthritis (RA) is intricately linked to inflammation. This study aimed to investigate the association between the advanced lung cancer inflammation index (ALI), a comprehensive indicator of inflammation combined with nutritional status, and all-cause and cardiovascular mortality among patients diagnosed with RA.

Methods

The 2,305 RA patients from NHANES (2001-2018) included in the analysis were categorized into three groups according to ALI tertiles. Weighted Kaplan-Meier and multivariate COX regression analyses evaluated the relationship between ALI and mortality. The time-dependent characteristic curve (ROC) was used to assess the prediction accuracy of ALI.

Results

During a median follow-up of 7.92 years, 591 participants died from all causes, including 197 from cardiovascular diseases. Increased ALI was associated with a decreased probability of death. The full COX model revealed lower all-cause mortality hazard risks in the T2 (HR: 0.67, 95%CI: 0.54-0.83) and T3 (HR: 0.47 95%CI: 0.33-0.67, p for tend <0.001) groups compared to T1, and the risk of cardiovascular mortality was also lower in the groups of T2 (HR: 0.47, 95%CI: 0.31-0.70) and T3 (HR: 0.34, 95%CI: 0.19-0.62, p for trend <0.001). Furthermore, the ROC analysis underscored the strong predictive capability of ALI (AUC for 1-year all-cause and cardiovascular mortality were 0.73 and 0.79, respectively).

Conclusion

This cohort study demonstrated the higher accuracy of ALI in predicting mortality in RA patients, highlighting the important clinical value of ALI in risk assessment and prognosis evaluation.

Metabolic Syndrome Is Associated With an Increased Risk of Rheumatoid Arthritis: A Prospective Cohort Study Including 369,065 Participants

OBJECTIVE

To explore the associations between metabolic syndrome (MetS) and its individual components and the risk of rheumatoid arthritis (RA).

METHODS

A total of 369,065 individuals were included in the present study based on the UK Biobank. Multivariable Cox proportional hazards regression models were applied to estimate the associations between MetS and its individual components and the risk of RA. Mediation analysis was performed to further assess the potential mediating role of C-reactive protein (CRP) in the relationship between MetS and RA.

RESULTS

During a median follow-up period of 12.04 years, a total of 4901 incident RA cases were documented. MetS (hazard ratio [HR] 1.22, 95% CI 1.14-1.30) and 4 of its 5 components (elevated waist circumference [WC; HR 1.21, 95% CI 1.12-1.32], elevated triglyceride [TG] level [HR 1.12, 95% CI 1.05-1.19], reduced high-density lipoprotein cholesterol [HDL-C] level [HR 1.31, 95% CI 1.23-1.39], and hyperglycemia [HR 1.15, 95% CI 1.05-1.25]) were associated with an increased risk of RA. In addition, the risk of RA increased as the number of diagnosed MetS components increased, with the highest risk in participants with all 5 components. Mediation analysis showed that CRP might mediate the association between MetS and RA, accounting for 9.27% of the total effect.

CONCLUSION

These findings indicated positive associations between MetS and 4 of its components (WC, TG, HDL-C, and hyperglycemia) and the risk of RA, highlighting the importance of MetS management in the prevention of RA.

Phytochemical and antimicrobial properties of different plants and in silico investigation of their bioactive compounds in wound healing and rheumatism

In the current study the assessment of the antimicrobial and phytochemical properties of Cassia fistula, Musa paradisiaca, Ficus religiosa and Murraya koenigii plants extracts was carried out. The antibacterial potential of these plants extracts was tested against S. aureus and E. coli. The Cassia fistula and Ficus religiosa leaves showed the larger zone of inhibition in aqueous and butanolic extract respectively against Escherichia coli. Musa paradisiaca and Murraya koenigii leaves showed larger zone of inhibition in ethanolic extract against S. aureus. Qualitative phytochemical analysis showed the presence of alkaloids, flavonoids, phenols, terpenoids, steroids, glycosides, saponins, carbohydrates, proteins and tannins in all extracts while phylobatannins, emodins, anthocyanins and leucoanthocyanins were not present in these extracts. Quantitative phytochemical analysis showed the highest alkaloid content in the Murraya koenigii leaves. Highest tannin content and flavonoid content was found in Ficus religiosa leaves, while highest phenolic content was found in case of Cassia fistula. In addition to this antioxidant potential of all the extracts was determined. Musa paradisiaca leaves showed highest antioxidant potential as compared to other plant extracts. In silico analysis of bioactive components present in plant extracts was performed by molecular docking. The rutin and Glu from Musa paradisiaca and Murraya koenigii respectively, were docked with Glycogen Synthase Kinase 3 beta (1GSK-3beta) protein. Quercetin and rutin from Cassia fistula and Ficus religiosa respectively, were docked with C- reactive protein (CRP). The tested bioactive compounds showed good binding affinity with significant number of hydrogen bonds and can be used as a good alternative of synthetic drugs to treat rheumatism and wounds.

The pentraxin family in autoimmune disease

The pentraxins represent a family of multifunctional proteins composed of long and short pentamers. The latter includes serum amyloid P component (SAP) and C-reactive protein (CRP) whereas the former includes neuronal PTX1 and PTX2 (NPTX1 and NPTX2, respectively), PTX3 and PTX4. These serve as a bridge between adaptive immunity and innate immunity and a link between inflammation and immunity. Similarities and differences between long and short pentamers are examined and their roles in autoimmune disease are discussed. Increased CRP and PTX3 could indicate the activity of rheumatoid arthritis, systemic lupus erythematosus or other autoimmune diseases. Mechanistically, CRP and PTX3 may predict target organ injury, regulate bone metabolic immunity and maintain homeostasis as well as participate in vascular endothelial remodeling. Interestingly, PTX3 is pleiotropic, being involved in inflammation and tissue repair. Given the therapeutic potential of PTX3 and CRP, targeting these factors to exert a beneficial effect is the focus of research efforts. Unfortunately, studies on NPTX1, NPTX2, PTX4 and SAP are scarce and more research is clearly needed to elaborate their potential roles in autoimmune disease.

Investigation of Peptides for Molecular Recognition of C-Reactive Protein-Theoretical and Experimental Studies

We investigate the interactions between C-reactive protein (CRP) and new CRP-binding peptide materials using experimental (biological and physicochemical) methods with the support of theoretical simulations (computational modeling analysis). Three specific CRP-binding peptides (P2, P3, and P9) derived from an M13 bacteriophage have been identified using phage-display technology. The binding efficiency of the peptides exposed on phages toward the CRP protein was demonstrated via biological methods. Fibers of the selected phages/peptides interact differently due to different compositions of amino acid sequences on the exposed peptides, which was confirmed by transmission electron microscopy. Numerical and experimental studies consistently showed that the P3 peptide is the best CRP binder. A combination of theoretical and experimental methods demonstrates that identifying the best binder can be performed simply, cheaply, and fast. Such an approach has not been reported previously for peptide screening and demonstrates a new trend in science where calculations can replace or support laborious experimental techniques. Finally, the best CRP binder─the P3 peptide─was used for CRP recognition on silicate-modified indium tin oxide-coated glass electrodes. The obtained electrodes exhibit a wide range of operation (1.0-100 μg mL-1) with a detection limit (LOD = 3σ/S) of 0.34 μg mL-1. Moreover, the dissociation constant Kd of 4.2 ± 0.144 μg mL-1 (35 ± 1.2 nM) was evaluated from the change in the current. The selectivity of the obtained electrode was demonstrated in the presence of three interfering proteins. These results prove that the presented P3 peptide is a potential candidate as a receptor for CRP, which can replace specific antibodies.

Bioactive fraction of Tragia involucrata Linn leaves attenuates inflammation in Freund's complete adjuvant-induced arthritis in Wistar albino rats via inhibiting NF-κB

Tragia involucrata Linn. (T. involucrata) belongs to the family of Euphorbiaceae found in the subtropical regions. Traditionally, the plant parts are used to treat inflammation, wounds and skin infection by people of the Western Ghats, India. Few studies on the acute anti-inflammatory activity of T. involucrata extracts were reported earlier. The present study aims to identify the bioactive fraction of T. involucrata and to evaluate its mechanism in Complete Freund's Adjuvant-induced arthritic rat model. The leaf extract was highly effective among the methanolic leaf and root extracts. The hexane (HF) and a methanolic fraction (MF) of the leaf extract of T involucrata were further identified as a bioactive fraction evaluated through protein denaturation assay. The HF and MF were further studied for their anti-inflammatory potential in a chronic inflammatory model, and their mechanism of action was explored further. Arthritis was induced by administering 0.1 ml of CFA intradermally. The treatment was started the next day with HF (100 and 250 mg/kg/day) and MF (100 and 250 mg/kg/day), while the HF and MF alone group served as the drug control, Indomethacin-treated group served as the positive control. On the 25th day, the animals were euthanized, and their body weight, paw thickness, arthritic score, spleen and thymus weight, haematological parameters, biochemical parameters, radiographs and histopathology were analyzed. Results showed that the MF-treated animals maintained dry weight, reduced paw thickness, arthritic scores, and haematological and biological parameters compared to the HF-treated and CFA-induced arthritic rats. Both radiological and histopathological analyses of the joints revealed that the MF-treated groups restored bone architecture without any erosion and normal tissue architecture with nil signs of active inflammation. Western blot analysis revealed that MF has effectively inhibited the protein expression levels of MMP-3, MMP-9, and NF-κB in the synovial tissues compared to that of CFA-induced arthritic rats. Besides, HPLC analysis revealed the presence of flavonoids, including gallic acid, rutin and Quercetin, in the MF of T. involucrata, which had shown to have potent anti-inflammatory potential. Thus, it can be emphasized that T. involucrata could be a potential therapeutic candidate for treating inflammatory diseases, which needs further experimental studies to confirm its safety and efficacy.

Relationship between plasma fibrinogen degradation products(FDP) and D-dimer levels and disease activity in rheumatoid arthritis: A STROBE compliant article

In this study, we aimed to investigate whether fibrinogen degradation products(FDP)and D-dimer could be used as serological indicators of rheumatoid arthritis(RA) activity, such as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and platelets (PLT). A total of 112 consecutive patients with RA between July 2018 and July 2020 were divided into moderate and high disease activity groups (disease activity score 28(DAS28) > 3.2, n = 60) and low disease activity and remission groups (DAS28≤3.2, n = 52). A total of 50 healthy volunteers were included in the control group, and FDP and D-dimer levels were compared across the three groups. The correlations of FDP and D-dimer levels with ESR, CRP, PLT, and DAS28 were analyzed. Analyses of the receiver operating characteristic(ROC) curves and area under the ROC curve (AUC) of FDP, D-dimer, ESR, CRP, and PLT levels were performed. FDP and D-dimer levels were significantly higher in the high-activity compared to the low-activity and remission (P < .001), and the control (P < .001). No significant differences in FDP and D-dimer were observed between the low-activity and remission and the control (P > .05). FDP and D-dimer levels were positively correlated with ESR, CRP, PLT, and DAS28 (all P < .001). The ROC curves showed that the FDP and D-dimer levels could be used to evaluate the RA activity (all P < .001). The AUC of FDP was significantly larger than that of PLT (P = .047). FDP and D-dimer can be used as supplementary serological indicators to assess RA activity, in addition to ESR, CRP, and PLT.

Similarities Between Disuse and Age-Induced Bone Loss

Disuse and aging are known risk factors associated with low bone mass and quality deterioration, resulting in increased fracture risk. Indeed, current and emerging evidence implicate a large number of shared skeletal manifestations between disuse and aging scenarios. This review provides a detailed overview of current preclinical models of musculoskeletal disuse and the clinical scenarios they seek to recapitulate. We also explore and summarize the major similarities between bone loss after extreme disuse and advanced aging at multiple length scales, including at the organ/tissue, cellular, and molecular level. Specifically, shared structural and material alterations of bone loss are presented between disuse and aging, including preferential loss of bone at cancellous sites, cortical thinning, and loss of bone strength due to enhanced fragility. At the cellular level bone loss is accompanied, during disuse and aging, by increased bone resorption, decreased formation, and enhanced adipogenesis due to altered gap junction intercellular communication, WNT/β-catenin and RANKL/OPG signaling. Major differences between extreme short-term disuse and aging are discussed, including anatomical specificity, differences in bone turnover rates, periosteal modeling, and the influence of subject sex and genetic variability. The examination also identifies potential shared mechanisms underlying bone loss in aging and disuse that warrant further study such as collagen cross-linking, advanced glycation end products/receptor for advanced glycation end products (AGE-RAGE) signaling, reactive oxygen species (ROS) and nuclear factor κB (NF-κB) signaling, cellular senescence, and altered lacunar-canalicular connectivity (mechanosensation). Understanding the shared structural alterations, changes in bone cell function, and molecular mechanisms common to both extreme disuse and aging are paramount to discovering therapies to combat both age-related and disuse-induced osteoporosis. © 2022 American Society for Bone and Mineral Research (ASBMR).

Preliminary Report: Osteoarthritis and Rheumatoid Arthritis Synovial Fluid Increased Osteoclastogenesis In Vitro by Monocyte Differentiation Pathway Regulating Cytokines

Background. Rheumatoid arthritis (RA) and osteoarthritis (OA) are common joint diseases associated with changes in local, as well as systemic bone structure and osteoclast function. We investigated how the different soluble inflammatory stimuli in these diseases can affect osteoclastogenesis and bone resorption in vitro. Methods. Human peripheral blood mononuclear cell-derived osteoclasts were cultured on bone slices with serum from treatment-naïve RA patients and healthy controls and with synovial fluid samples acquired from RA and OA patients. The concentrations of 29 different cytokines and related proteins, including RANKL and OPG, were analyzed in the fluids tested. Results. RA serum and synovial fluid increased both osteoclastogenesis and bone resorption. Osteoclastogenesis and activity increased more in the cultures containing OA than RA synovial fluid. The osteoclasts cultured in different culture media exhibited different phenotypes, especially the cells cultured with OA synovial fluid were generally larger and had more nuclei. A general increase in proinflammatory cytokines in RA synovial fluid and serum was found. Surprisingly, OA synovial fluid showed lower levels of osteoclastogenesis inhibiting cytokines, such as IL-4 and IL-10, than RA synovial fluid, which at least partly explains more pronounced osteoclastogenesis. No significant difference was found in RANKL or OPG levels. Conclusion. The proinflammatory stimulus in OA and RA drives the monocyte differentiation towards inflammatory osteoclastogenesis and altered osteoclast phenotype.

Analysis of rheumatoid factor and acute phase proteins using microarrays in patients with rheumatoid arthritis

One of the biomarkers of biggest clinical importance in rheumatoid arthritis (RA) is rheumatoid factor (IgM RF). The rheumatoid factor has insufficient sensitivity and specificity, therefore, to increase the diagnostic information of the test, acute phase proteins were used as concomitant biomarkers. Using biological microchips, we measured IgM RF, C-reactive protein (CRP) and Serum amyloid protein A (SAA) in patients with RA (n = 60), ankylosing spondylitis (AS) (n=55), systemic lupus erythematosus (SLE) (n=20) and healthy donors (HD) (n=9). It was shown that the medians of IgM RF concentrations are significantly higher (p<0.01) in patients with RA compared to patients suffering from other diseases and healthy donors. CRP and SAA were also significantly increased (p<0.05) in patients with RA and AS compared with SLE and HD. It has been shown that the complex determination of three biomarkers in differentiating RA patients with the comparison group had a higher diagnostic sensitivity than the isolated determination of IgM RF, while the addition of SAA makes the greatest contribution to improving the diagnostic characteristics of the biomarker panel: the use of a logistic regression model based on IgM RF and SAA allowed to increase the diagnostic sensitivity of the analysis from 58.3% to 65%. Thus, the developed microarray-based method can be used to detect and elucidate the diagnostic characteristics of RA biomarkers; however, further use requires validation of the obtained results on an expanded sampling.

C-Reactive Protein Knockout Attenuates Temporomandibular Joint Inflammation in Rats

BACKGROUND

C-reactive protein (CRP), a biomarker of inflammation, is highly expressed in osteoarthritis- (OA-) related diseases, but its exact role remains unknown. In this study, we evaluated the biological effect of CRP on temporomandibular joint (TMJ) inflammation.

METHODS

Freund's complete adjuvant (CFA) was used to induce TMJ inflammation in CRP-knockout (CRP-/-) and control rats. Degenerative changes in the TMJ were compared to elucidate the role of CRP in TMJ inflammation. In addition, inflammatory cytokines, macrophage activation, and osteoclast differentiation were evaluated by real-time quantitative polymerase chain reaction, immunohistochemistry, and tartrate-resistant phosphatase staining to explore the potential regulatory mechanism.

RESULTS

Compared to the control, CFA induced TMJ inflammation, which increased systemic and local CRP expression. Furthermore, CRP-/- rats exhibited less severe inflammatory symptoms. The downregulation of proinflammatory cytokines (interleukin- (IL-) 1β and IL-6) and upregulation of the anti-inflammatory cytokine IL-10 were detected in CRP-/- rats, which also exhibited reduced macrophage activation and osteoclast differentiation.

CONCLUSION

These results indicated that controlling the highly elevated levels of CRP during inflammation could modify the cytokine profile, macrophage activation, and osteoclast differentiation, thus, providing beneficial effects for TMJ-OA prevention and treatment.

OUP accepted manuscript

Rheumatoid arthritis (RA) and osteoporosis (OP) are two comorbid complex inflammatory conditions with evidence of shared genetic background and causal relationships. We aimed to clarify the genetic architecture underlying RA and various OP phenotypes while additionally considering an inflammatory component, C-reactive protein (CRP). Genome-wide association study summary statistics were acquired from the GEnetic Factors for OSteoporosis Consortium, Cohorts for Heart and Aging Research Consortium and UK Biobank. Mendelian randomization (MR) was used to detect the presence of causal relationships. Colocalization analysis was performed to determine shared genetic variants between CRP and OP phenotypes. Analysis of pleiotropy between traits owing to shared causal single nucleotide polymorphisms (SNPs) was performed using PL eiotropic A nalysis under CO mposite null hypothesis (PLACO). MR analysis was suggestive of horizontal pleiotropy between RA and OP traits. RA was a significant causal risk factor for CRP (β = 0.027, 95% confidence interval = 0.016–0.038). There was no evidence of CRP→OP causal relationship, but horizontal pleiotropy was apparent. Colocalization established shared genomic regions between CRP and OP, including GCKR and SERPINA1 genes. Pleiotropy arising from shared causal SNPs revealed through the colocalization analysis was all confirmed by PLACO. These genes were found to be involved in the same molecular function ‘protein binding’ (GO:0005515) associated with RA, OP and CRP. We identified three major components explaining the epidemiological relationship among RA, OP and inflammation: (1) Pleiotropy explains a portion of the shared genetic relationship between RA and OP, albeit polygenically; (2) RA contributes to CRP elevation and (3) CRP, which is influenced by RA, demonstrated pleiotropy with OP.

Genetically predicted C-reactive protein mediates the association between rheumatoid arthritis and atlantoaxial subluxation

OBJECTIVE

Investigating the causal relationship between rheumatoid arthritis (RA) and atlantoaxial subluxation (AAS) and identifying and quantifying the role of C-reactive protein (CRP) as a potential mediator.

METHODS

Using summary-level data from a genome-wide association study (GWAS), a two-sample Mendelian randomization (MR) analysis of genetically predicted rheumatoid arthritis (14,361 cases, and 43,923 controls) and AAS (141 cases, 227,388 controls) was performed. Furthermore, we used two-step MR to quantitate the proportion of the effect of c-reactive protein-mediated RA on AAS.

RESULTS

MR analysis identified higher genetically predicted rheumatoid arthritis (primary MR analysis odds ratio (OR) 0.61/SD increase, 95% confidence interval (CI) 1.36-1.90) increased risk of AAS. There was no strong evidence that genetically predicted AAS had an effect on rheumatoid arthritis risk (OR 1.001, 95% CI 0.97-1.03). The proportion of genetically predicted rheumatoid arthritis mediated by C-reactive protein was 3.7% (95%CI 0.1%-7.3%).

CONCLUSION

In conclusion, our study identified a causal relationship between RA and AAS, with a small proportion of the effect mediated by CRP, but a majority of the effect of RA on AAS remains unclear. Further research is needed on additional risk factors as potential mediators. In clinical practice, lesions of the upper cervical spine in RA patients need to be given more attention.

Augmenting MNK1/2 activation by c-FMS proteolysis promotes osteoclastogenesis and arthritic bone erosion

Osteoclasts are bone-resorbing cells that play an essential role in homeostatic bone remodeling and pathological bone erosion. Macrophage colony stimulating factor (M-CSF) is abundant in rheumatoid arthritis (RA). However, the role of M-CSF in arthritic bone erosion is not completely understood. Here, we show that M-CSF can promote osteoclastogenesis by triggering the proteolysis of c-FMS, a receptor for M-CSF, leading to the generation of FMS intracellular domain (FICD) fragments. Increased levels of FICD fragments positively regulated osteoclastogenesis but had no effect on inflammatory responses. Moreover, myeloid cell-specific FICD expression in mice resulted in significantly increased osteoclast-mediated bone resorption in an inflammatory arthritis model. The FICD formed a complex with DAP5, and the FICD/DAP5 axis promoted osteoclast differentiation by activating the MNK1/2/EIF4E pathway and enhancing NFATc1 protein expression. Moreover, targeting the MNK1/2 pathway diminished arthritic bone erosion. These results identified a novel role of c-FMS proteolysis in osteoclastogenesis and the pathogenesis of arthritic bone erosion.

Comparison of individual and combination treatments with naproxen, prednisolone and hydroxychloroquine to treat Complete Freund's Adjuvant induced arthritis

Aim of this study was to evaluate and compare the efficacy of anti-arthritic drugs (naproxen, prednisolone, and hydroxychloroquine) alone and in combination. The in vitro anti-arthritic activity was evaluated by stabilization of human erythrocytes (HRBCs) membrane assays. In vivo activity was carried out using Complete Freund's Adjuvant (CFA) induced arthritic model in Wistar rat. Individual and combination drugs were administered for 21 days in rats 8 days post inoculation with CFA (0.15 ml injected in right hind paw). Body weight and paw edema were measured at different intervals. Combination treatments exhibited more HRBC stabilization than individual treatments. All individual and combination treatments reduced the level of C-reactive protein (CRP), liver function enzymes, malondialdehyde, white blood cells and platelets, with the most pronounced activity exhibited by the combination of three drugs. The level of oxidative stress biomarkers (reduced glutathione, catalase, and superoxide dismutase), red blood cells, and hemoglobin were notably increased in all treatment groups in contrasts to diseased control rats. Histopathological evaluation of the paw showed that all the treatments had reduced (p < 0.05-0.001) the arthritic indices in contrasts to diseased control rats. The serum concentrations of TNF-α and PGE2 were provoked in diseased control rats but had been notably (p < 0.0001) restored by treatments with individual and combination drugs. It was also found that combination treatments, more precisely triple drug was remarkably effective in treating arthritis. It can be concluded that naproxen, prednisolone, and hydroxychloroquine effectively ameliorated the CFA-induced arthritis and were more effective in combination as compared to individual drug therapy probably due to reduction in oxidative stress and inflammatory markers. Moreover, two lower doses (half NPH/2 and one-third NPH/3) of triple combination therapy naproxen, prednisolone, and hydroxychloroquine (NPH) showed no significant difference in anti-arthritic effect as compared to the highest dose level of NPH.

Comparative study evaluating antihistamine versus leukotriene receptor antagonist as adjuvant therapy for rheumatoid arthritis

PURPOSE

Investigating the efficacy and safety of rupatadine (RUP) versus montelukast (MON) as adjuvant therapy for patients with rheumatoid arthritis (RA).

METHODS

From December 2018 to December 2019, 75 patients with active RA were enrolled in this randomized double-blind placebo-controlled study. The patients were randomized into three groups (n = 25 in each group); methotrexate (MTX) group which received MTX 15-25 mg/week plus placebo tablet once daily; MTX/RUP group which received MTX plus RUP 10 mg once daily; and MTX/MON group which received MTX plus MON 10 mg once daily. The treatment duration was 3 months. At baseline and 3 months after treatment, blood samples were collected for the biochemical analysis of high-sensitivity C-reactive protein (hs-CRP), interleukins 8 and 17 (IL-8, IL-17), E-selectin, and clusterin (CLU) levels. Clinical and functional assessments using Disease Activity Score-CRP (DAS28-CRP) and Multidimensional Health Assessment Questionnaire (MDHAQ) were performed.

RESULTS

Both RUP and MON produced clinical and functional improvements which were translated by significant improvements in DAS28-CRP score and MDHAQ. Rupatadine significantly reduced all measured parameters (P < 0.05) except for IL-17 and CLU. Montelukast significantly decreased all measured variables (P < 0.05) except for E-selectin. Interleukin-8 was positively correlated with IL-17 and CLU, while hs-CRP was positively correlated with E-selectin and body mass index (BMI). Both drugs were well tolerated; somnolence was the common side effect for RUP. No neuropsychiatric events were reported with MON.

CONCLUSION

Rupatadine or montelukast may serve as a potential adjuvant therapy for patients with rheumatoid arthritis secondary to the preliminary evidence of efficacy and safety. ClinicalTrials.gov identifier NCT03770923, December 10, 2018.

Activation of the Nrf2/HO-1 signaling pathway by dimethyl fumarate ameliorates complete Freund's adjuvant-induced arthritis in rats

The nuclear factor erythroid 2-related factor (Nrf2) signaling pathway has recently emerged as a novel therapeutic target in treating various diseases. Therefore, the present study aimed to assess the protective role of the Nrf2 activator, dimethyl fumarate (DMF) in the complete Freund's adjuvant (CFA)- induced arthritis model. DMF (25, 50, and 100 mg/kg) and dexamethasone (2 mg/kg) were orally administered for 14 days. Pain-related tests, paw volume, and arthritic scores were measured weekly. Serum TNF-α, IL-1β, cyclic citrullinated peptide (CCP), C-reactive protein (CRP), and rheumatoid factor (RF) levels were estimated. Nitrite, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (GSH), catalase (CAT), and myeloperoxidase (MPO) levels were also evaluated. NF-κB, Nrf2, HO-1, and COX-2 levels were estimated in the joint tissue. DMF treatment exerted anti-arthritic activity by enhancing the nociceptive threshold, improving arthritis scores, and reducing paw edema. Also, DMF suppressed changes in oxidative stress markers and inflammatory mediators and enhanced Nrf2 and HO-1 levels in CFA-injected rats. These findings indicate that the anti-arthritic activity of DMF may be mediated by the activation of the Nrf2/HO-1 pathway, which reduced oxidative damage and inflammation.

Chromatin accessibility landscapes of immune cells in rheumatoid arthritis nominate monocytes in disease pathogenesis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease that involves a variety of cell types. However, how the epigenetic dysregulations of peripheral immune cells contribute to the pathogenesis of RA still remains largely unclear.

RESULTS

Here, we analysed the genome-wide active DNA regulatory elements of four major immune cells, namely monocytes, B cells, CD4⁺ T cells and CD8⁺ T cells, in peripheral blood of RA patients, osteoarthritis (OA) patients and healthy donors using Assay of Transposase Accessible Chromatin with sequencing (ATAC-seq). We found a strong RA-associated chromatin dysregulation signature in monocytes, but no other examined cell types. Moreover, we found that serum C-reactive protein (CRP) can induce the RA-associated chromatin dysregulation in monocytes via in vitro experiments. And the extent of this dysregulation was regulated through the transcription factor FRA2.

CONCLUSIONS

Together, our study revealed a CRP-induced pathogenic chromatin dysregulation signature in monocytes from RA patients and predicted the responsible signalling pathway as potential therapeutic targets for the disease.

Serum-derived extracellular vesicles inhibit osteoclastogenesis in active-phase patients with SAPHO syndrome

Objective:

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome is a rare chronic inflammatory disorder and the underlying pathogenesis is unclear. In this study, 88 SAPHO patients and 118 healthy controls were recruited to investigate the role of serum-derived extracellular vesicles (SEVs) in SAPHO syndrome.

Methods:

Quantitative proteomics was applied for SEVs proteome identification, and ELISA and Western blotting was performed to verify the results of mass spectrum data. In vitro osteoclastogenesis and osteogenesis assay was used to confirm the effects of SEVs on bone metabolism.

Results:

Tandem mass tagging-based quantitative proteomic analysis of SAPHO SEVs revealed differential expressed proteins involved in bone metabolism. Of these, serum amyloid A-1 (SAA1) and C-reactive protein (CRP) were upregulated. Higher SAA1 levels in SAPHO patients were confirmed by ELISA. In addition, SAA1 levels were positively correlated with CRP, an inflammatory marker related to the condition of patients. In vitro celluler studies confirmed that SAPHO SEVs inhibited osteoclastogenesis in patients mainly in the active phase of the disease. Further analysis demonstrated that Nucleolin was upregulated in osteoclasts of active-phase patients under SAPHO SEVs stimulation.

Conclusion:

In this study, we identified SAA1 as an additional inflammation marker that can potentially assist the diagnosis of SAPHO syndrome, and speculated that Nucleolin is a key regulator of osteoclastogenesis in active-phase patients.

C-reactive protein and implications in rheumatoid arthritis and associated comorbidities

C-reactive protein (CRP) is routinely assessed as a marker of systemic inflammation in rheumatoid arthritis (RA). However, it is also an immune regulator that plays an important role in inflammatory pathways associated with RA and promotes atherogenic effects. Comorbidities linked to systemic inflammation are common in RA, and CRP has been associated with the risk for cardiovascular disease, diabetes, metabolic syndrome, pulmonary diseases, and depression. The relationship between systemic inflammation, CRP, and comorbidities in RA is complex, and it is challenging to determine how changing CRP levels may affect the risk or progression of these comorbidities. We review the biological role of CRP in RA and its implications for disease activity and treatment response. We also discuss the impact of treatment on CRP levels and whether reducing systemic inflammation and inhibiting CRP-mediated inflammatory pathways may have an impact on conditions commonly comorbid with RA.

Evaluation of anti rheumatic activity of Piper betle L. (Betelvine) extract using in silico, in vitro and in vivo approaches

Rheumatoid Arthritis is a chronic, inflammatory, and systemic autoimmune disease, it affects elders worldwide. Herbal medicines have been used for the treatment of various ailments from ancient times. Betelvine (Piper betle L.) leaves have long been used in Asian countries as a medicine to relieve pain and some metabolic diseases. The present study of methanolic extract of phytochemical analysis confirms the presence of alkaloids, tannins, terpenoids, saponins, steroids, total flavonoids and total phenols. GC-MS analysis of MeOH extract of Piper betle (PBME) revealed the presence of 40 bioactive compounds. In vitro antioxidant and anti-inflammatory assays showed greater inhibitory effect. The anti-arthritic effects of PBME at 250 and 500 mg/kg concentration showed recovery from joint damage in in vivo rat model. Among the 40 GC-MS derived bioactives, 4-Allyl-1,2-Diacetoxybenzene exhibited the higher interactions with minimized binding energy to the RA targets of MMP 1 (-6.4 kcal/mol), TGF-β (-6.9 kcal/mol), IL-1β (-5.9 kcal/mol). Further, the effect of PBME extract against RA molecular disease targets (IL-1β, MMP1 and TGF- β) were studied using Real-time PCR. These results substantiate that P. betle leaves could be a source of therapeutics for the treatment of rheumatoid arthritis.

CRP-binding bacteriophage as a new element of layer-by-layer assembly carbon nanofiber modified electrodes

Recently, bacteriophage particles have started to be applied as a new biomaterial for developing sensing platforms. They can be used as both a recognition element or/and as building blocks, template/scaffold. In this paper, we studied a bacteriophage selected through phage-display technology. The chosen bacteriophage acted as a building block for creating a carbon nanofiber-based electrode and as a new receptor/binding element that recognizes C-reactive protein (CRP) - one of the markers of inflammatory processes in the human body. The binding efficiency of the selected phage towards CRP is two orders of magnitude higher than in the wild type. We demonstrate that the phage-based sensor is selective against other proteins. Finally, we show that layer-by-layer methods are suitable for deposition of negatively charged phages (wild or CRP-binding) with positively charged carbon nanofibers for electrode surface modification. A three-layered electrode was successfully used for molecular recognition of CRP, and the molecular interactions were studied using electrochemical, biological, and optical methods, including microscopic and spectroscopic analyses.

Update on the Pathomechanism, Diagnosis, and Treatment Options for Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that involves multiple joints bilaterally. It is characterized by an inflammation of the tendon (tenosynovitis) resulting in both cartilage destruction and bone erosion. While until the 1990s RA frequently resulted in disability, inability to work, and increased mortality, newer treatment options have made RA a manageable disease. Here, great progress has been made in the development of disease-modifying anti-rheumatic drugs (DMARDs) which target inflammation and thereby prevent further joint damage. The available DMARDs are subdivided into (1) conventional synthetic DMARDs (methotrexate, hydrochloroquine, and sulfadiazine), (2) targeted synthetic DMARDs (pan-JAK- and JAK1/2-inhibitors), and (3) biologic DMARDs (tumor necrosis factor (TNF)-α inhibitors, TNF-receptor (R) inhibitors, IL-6 inhibitors, IL-6R inhibitors, B cell depleting antibodies, and inhibitors of co-stimulatory molecules). While DMARDs have repeatedly demonstrated the potential to greatly improve disease symptoms and prevent disease progression in RA patients, they are associated with considerable side-effects and high financial costs. This review summarizes our current understanding of the underlying pathomechanism, diagnosis of RA, as well as the mode of action, clinical benefits, and side-effects of the currently available DMARDs.

Zishen Tongluo formula ameliorates collagen-induced arthritis in mice by modulation of Th17/Treg balance

ETHNOPHARMACOLOGICAL RELEVANCE

Zishen Tongluo formula (ZTF) is simplified from the Qingluo Tongbi formula, which has been applied to treat rheumatoid arthritis (RA) in clinical practices for several decades. Our previous studies have verified the effects of ZTF on arthritis animal models. However, its mechanism of treating RA is not clear.

AIM OF THE STUDY

The present study was designed to investigate the effects of ZTF on the Th17/Treg balance in RA mice and the role of the different herb groups with the effect of Zishen yangyin (YY), Huatan quyu (HT), or Qufeng chushi (QF) in ZTF.

MATERIALS AND METHODS

A mouse model of collagen-induced arthritis (CIA) was established. The animals were randomly divided into the normal, model, positive drug, YY, QF, HT, and the whole compound (ZTF) groups. After oral administration for one-month, cytokine levels in the plasma and histopathological changes of the joint were measured by ELISA and hematoxylin-eosin staining, respectively. Meanwhile, the balance of Th17/Treg cells in blood, spleen or lymph nodes was detected using flow cytometry and qPCR.

RESULTS

ZTF or the different functional groups could improve the joint inflammation, decrease the levels of proinflammatory cytokines, restore the balance of Th17 and Treg cells in CIA mice. However, there were some differences in each functional group: YY mainly promoted the responses of Treg cells while QF inhibited the functions of Th17 cells. Besides, HT regulated both Th17 and Treg cells to keep the immune balance.

CONCLUSIONS

ZTF could notably ameliorate CIA mice by restoring the balance of Th17/Treg cells. Each functional group could target Th17 and/or Treg cells to produce synergistic/enhancement effects, and ZTF had a better holistic effect in RA treatment.

Venous thromboembolism events among RA patients

Background:

Rheumatoid arthritis (RA) is associated with an increased risk for venous thromboembolism. However, so far, relatively few and small size-based studies have been conducted. We aimed to investigate the link between RA and venous thromboembolism utilizing a large sample of subjects originating from a large data base.

Materials and methods:

The study was performed utilizing the medical database of Clalit Health Services, the largest healthcare provider in Israel. We enrolled all patients with RA and age- and gender-matched controls. Chi-square and t-tests were used for univariate analysis and a logistic regression model was used for a multivariate analysis. RA patients were compared to controls regarding the proportion of venous thromboembolic events (defined as deep vein thrombosis, pulmonary embolism or both). Multivariate logistic regression was employed to assess factors associated with thromboembolic events.

Results:

The study included 11,782 patients with RA and 57,973 age- and gender-matched controls. RA patients had a higher rate of venous thromboembolism events compared with controls (6.92% vs. 3.18%, respectively, p<0.001). RA and mean C-reactive protein levels were found to be independently associated with the proportion of thromboembolic events (OR 2.27 for RA and 1.07 for each 1 mg/dL increment of mean C-reactive protein, respectively).

Conclusion:

RA and C-reactive protein levels are independently associated with venous thromboembolic events. Physicians should be aware of such findings and have a lower threshold for suspecting detecting such events in patients with RA, mainly those with mean high levels of C-reactive protein.

Platelets: emerging facilitators of cellular crosstalk in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease in which a variety of circulating pro-inflammatory cells and dysregulated molecules are involved in disease aetiology and progression. Platelets are an important cellular element in the circulation that can bind several dysregulated molecules (such as collagen, thrombin and fibrinogen) that are present both in the synovium and the circulation of patients with RA. Platelets not only respond to dysregulated molecules in their environment but also transport and express their own inflammatory mediators, and serve as regulators at the boundary between haemostasis and immunity. Activated platelets also produce microparticles, which further convey signalling molecules and receptors to the synovium and circulation, thereby positioning these platelet-derived particles as strategic regulators of inflammation. These diverse functions come together to make platelets facilitators of cellular crosstalk in RA. Thus, the receptor functions, ligand binding potential and dysregulated signalling pathways in platelets are becoming increasingly important for treatment in RA. This Review aims to highlight the role of platelets in RA and the need to closely examine platelets as health indicators when designing effective pharmaceutical targets in this disease.

Effects of Hyperbaric Oxygen on T helper 17/regulatory T Polarization in Antigen and Collagen-induced Arthritis: Hypoxia-inducible Factor-1α as a Target

Objectives

We sought to investigate and prove the effect of hyperbaric oxygen therapy (HBOT) on T helper 17 (Th17)/regulatory T (Treg) cell polarization through changes in the expression of hypoxia-inducible factor-1 alpha (HIF-1α) in rheumatoid arthritis (RA) animal model.

Methods

We used antigen and collagen-induced arthritis (ACIA) as a RA animal model. Sixteen male BALB/c models of ACIA mice were divided into two groups, the non-HBOT group as the control group and the HBOT group as the treatment group. Expression of HIF-1α, Th17 anti-cluster differentiation 196 (CD196), and Treg anti-interleukine 2 receptor β-chain cells (IL-2Rβ) in tissue from the left knee joint tissue were determined histologically. Oxidative stress and systemic inflammation were assessed by levels of superoxide dismutase (SOD), interleukin 17a (IL-17a), C-reactive protein (CRP), and rheumatoid factor (RF) using the enzyme-linked immune-sorbent assay. The degree of arthritis was assessed by clinical scoring of paw swelling and the diameter of paw swelling.

Results

We found a significant decrease (p < 0.050) in the expression of HIF-1α, Th17 (CD196), IL-17a, RF levels, and the clinical scores and the diameter of paw swelling when comparing both groups. There was no significant decrease in the level of CRP in the treatment group compared to the control group. The expression of Treg (IL-2Rβ) increased significantly (p < 0.050) and the level of SOD increased but not significantly (p > 0.050) in the treatment group compared to the control group.

Conclusions

HBOT has effects on the polarization of Th17 to Treg through a decrease in expression of HIF-1α in mice with ACIA. HBOT is recommended for use as a support therapy for RA in combination with drug therapy.

Decreased H19, GAS5, and linc0597 Expression and Association Analysis of Related Gene Polymorphisms in Rheumatoid Arthritis

Long noncoding RNAs (lncRNAs) widely participate in human diseases by regulating gene transcription, modulating protein function, or acting as ceRNAs. Yet, their roles in rheumatoid arthritis (RA) remain obscure. In this study, the expression of three lncRNAs (H19, GAS5, and linc0597) in peripheral blood mononuclear cells (PBMCs) were detected in 77 RA patients and 78 controls using quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The association of lncRNAs related gene polymorphisms with RA were evaluated in 828 RA patients and 780 controls using TaqMan single nucleotide polymorphism (SNP) genotyping assays. We observed that the expression levels of H19, GAS5 and linc0597 were down-regulated in PBMCs of RA patients, of which GAS5 level decreased in patients with hypocomplementemia, and negatively correlated with C-reactive protein (CRP) level in RA patients. Moreover, we highlighted two related potential functional SNPs, GAS5 rs6790 and linc0597 rs2680700 for associations with RA susceptibility. The precise roles of these lncRNAs in mechanism of RA remain to be further explored.

Astaxanthin attenuates oxidative stress and inflammatory responses in complete Freund-adjuvant-induced arthritis in rats

BACKGROUND

Astaxanthin (ATX), a natural xanthophyll carotenoid, has shown to exert significant protective effects against various diseases via its antioxidant and anti-inflammatory properties. However, its potential role in arthritis is still not reported. Therefore, the aim of the present study was to investigate the potential anti-arthritic properties of ATX against complete Freund's adjuvant (CFA)-induced arthritis rats.

METHODS

Adjuvant arthritis was induced by single intraplantar injection of complete Freund's adjuvant (CFA) in the left hind paw of adult female Wistar rats. ATX (25, 50 and 100 mg/kg) and indomethacin (5 mg/kg) were given orally from days 14 to 28. The anti-arthritic activity was evaluated through various nociceptive behavioral tests (mechanical allodynia, mechanical hyperalgesia, cold allodynia, and thermal hyperalgesia), paw edema assessment, and arthritis scores. Serum tumor necrosis factor-α (TNF-α), C-reactive protein (CRP) and cyclic citrullinated peptide (CCP) antibody levels were assessed. Moreover, malondialdehyde (MDA), nitrite, glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) levels were also evaluated.

RESULTS

Oral administration of ATX (50 and 100 mg/kg) exhibited significant anti-arthritic activity via enhancing the nociceptive threshold, reducing paw edema and improving arthritis scores. Moreover, ATX treatment also markedly suppressed inflammatory and oxidative mediators in adjuvant-administered rats.

CONCLUSIONS

Our findings suggest that ATX possesses potential anti-arthritic activity, which could be attributed to its anti-inflammatory and antioxidant properties.

Electrochemical Detection of C-Reactive Protein in Human Serum Based on Self-Assembled Monolayer-Modified Interdigitated Wave-Shaped Electrode

An electrochemical capacitance immunosensor based on an interdigitated wave-shaped micro electrode array (IDWµE) for direct and label-free detection of C-reactive protein (CRP) was reported. A self-assembled monolayer (SAM) of dithiobis (succinimidyl propionate) (DTSP) was used to modify the electrode array for antibody immobilization. The SAM functionalized electrode array was characterized morphologically by atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX). The nature of gold-sulfur interactions on SAM-treated electrode array was probed by X-ray photoelectron spectroscopy (XPS). The covalent linking of anti-CRP-antibodies onto the SAM modified electrode array was characterized morphologically through AFM, and electrochemically through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The application of phosphate-buffered saline (PBS) and human serum (HS) samples containing different concentrations of CRP in the electrode array caused changes in the electrode interfacial capacitance upon CRP binding. CRP concentrations in PBS and HS were determined quantitatively by measuring the change in capacitance (ΔC) through EIS. The electrode immobilized with anti-CRP-antibodies showed an increase in ΔC with the addition of CRP concentrations over a range of 0.01-10,000 ng mL-1. The electrode showed detection limits of 0.025 ng mL-1 and 0.23 ng mL-1 (S/N = 3) in PBS and HS, respectively. The biosensor showed a good reproducibility (relative standard deviation (RSD), 1.70%), repeatability (RSD, 1.95%), and adequate selectivity in presence of interferents towards CRP detection. The sensor also exhibited a significant storage stability of 2 weeks at 4 °C in 1× PBS.

Inhibitory effect of serotype a of Aggregatibacter actinomycetemcomitans on the increased destructive potential of serotype b

OBJECTIVE

The serotype b of Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) induces higher cytokine production in dendritic cells (DCs) compared with the other serotypes. However, this increased immunostimulatory potential was modified when DCs were co-infected with the other A. actinomycetemcomitans serotypes. This study aimed to analyze whether the production of interferon gamma (IFN-γ), C-reactive protein (CRP), matrix metalloproteinase (MMP)-2, and MMP-9, as well as the activity of osteoclasts, also varies when DCs are co-infected with the A. actinomycetemcomitans serotypes.

MATERIALS AND METHODS

Human DCs were stimulated with the A. actinomycetemcomitans serotypes using the following stimulatory conditions: serotype a/b/c/a+b/a+c/b+c/a+b+c. The IFN-γ, CRP, and MMP-2 levels were quantified by ELISA. The active form of MMP-9 was quantified using fluorescent functional assays. The MMP-2 gelatinolytic activity was identified by zymogram. The osteoclast activity was determined by quantifying the TRAP expression and resorption-pit formation using cytochemistry and osteoassays.

RESULTS

Higher levels of IFN-γ, CRP, MMP-2, MMP-9, and osteoclast activity were detected when DCs were stimulated with the serotype b of A. actinomycetemcomitans compared with the others. This increased immunostimulatory potential attributed to serotype b diminished when DCs were co-infected with the serotype a.

CONCLUSIONS

This study provides new insights into the virulence of A. actinomycetemcomitans and reveals important differences in the immunostimulatory and pro-destructive potential among its serotypes.

Investigation of the curative effects of palm vitamin E tocotrienols on autoimmune arthritis disease in vivo

The tocotrienol-rich fraction (TRF) from palm oil contains vitamin E, which possesses potent antioxidant and anti-inflammatory activities. Rheumatoid arthritis (RA) is a chronic joint inflammatory disease characterised by severe joint pain, cartilage destruction, and bone erosion owing to the effects of various pro-inflammatory mediators and cytokines. Here, we investigated the therapeutic effects of TRF in a rat model of collagen-induced arthritis (CIA). Arthritis was induced by a single intradermal injection of collagen type II in Dark Agouti (DA) rats. Rats were then treated with or without TRF by oral gavage from day 28 after the first collagen injection. Arthritic rats supplemented with TRF showed decreased articular index scores, ankle circumferences, paw volumes, and radiographic scores when compared with untreated rats. The untreated arthritic rats showed higher plasma C-reactive protein levels (p < 0.05) and production of pro-inflammatory cytokines than arthritic rats fed TRF. Moreover, there was a marked reduction in the severity of histopathological changes observed in arthritic rats treated with TRF compared with that in untreated arthritic rats. Overall, the results show that TRF had beneficial effects in this rat model of RA.

HIF1α inhibition facilitates Leflunomide-AHR-CRP signaling to attenuate bone erosion in CRP-aberrant rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disorder characterized by progressive bone erosion. Leflunomide is originally developed to suppress inflammation via its metabolite A77 1726 to attenuate bone erosion. However, distinctive responsiveness to Leflunomide is observed among RA individuals. Here we show that Leflunomide exerts immunosuppression but limited efficacy in RA individuals distinguished by higher serum C-reactive protein (CRP^Higher, CRP^H), whereas the others with satisfactory responsiveness to Leflunomide show lower CRP (CRP^Lower, CRP^L). CRP inhibition decreases bone erosion in arthritic rats. Besides the immunomodulation via A77 1726, Leflunomide itself induces AHR-ARNT interaction to inhibit hepatic CRP production and attenuate bone erosion in CRP^L arthritic rats. Nevertheless, high CRP in CRP^H rats upregulates HIF1α, which competes with AHR for ARNT association and interferes Leflunomide-AHR-CRP signaling. Hepatocyte-specific HIF1α deletion or a HIF1α inhibitor Acriflavine re-activates Leflunomide-AHR-CRP signaling to inhibit bone erosion. This study presents a precision medicine-based therapeutic strategy for RA.

Leflunomide is used for the treatment of rheumatoid arthritis. Here, the authors show that effectiveness is limited in patients with higher levels of serum c-reactive protein (CRP). Using animal models, they show that higher CRP induces HIF1a expression, which in turn interferes with Leflunomide signalling, and that effectiveness of the drug is restored when HIF1a is pharmacologically inhibited.

Association of biomarkers of inflammation and HLA-DRB1 gene locus with risk of developing rheumatoid arthritis in females

Rheumatoid arthritis (RA) is an autoimmune disease causing chronic inflammation of the joints. Multiple factors, including HLA-DRB1 gene variants, influence the susceptibility to RA. The HLA-DRB1 gene is part of a family of genes called the human leukocyte antigen (HLA) complex. In this study, we compared the inflammatory biomarkers values, including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), between patients with RA and healthy control group of females of the Public Institution Health Centre of Sarajevo Canton. In addition, we estimated the frequencies of the HLA-DRB1 gene variants and their association with the risk for RA development in females. The haematological and biochemical tests were completed on automated analyzers. To assess the association between the HLA-DRB genes and the risk of RA in females, low-resolution genotyping of the HLA-DRB1, DRB3, DRB4, and DRB5 gene loci was performed by the sequence-specific polymerase chain reaction method (PCR-SSP). ESR and CRP were the most sensitive acute-phase reactants in females with RA and there was a correlation between ESR and CRP values in RA patients. There was significantly positive association between of the HLA-DRB1*03, *04, *08, *10, *11, and *14 variants and elevated values of ESR in RA patients, but negative between HLA-DRB1*03, *13 and *15 alleles and elevated CRP values. Furthermore, our results confirm genetic susceptibility to RA in a female population to the members of the HLA-DRB1*04 and *03 allelic groups, the DRB1*04/DRB1*04 and DRB1*03/DRB1*04 genotypes, and the DRB1*04-DRB4* or DRB1*03-DRB3* haplotypes, which, therefore, represent risk factors for the development of this disease. According to our results, the DRB1*01/DRB1*15 and DRB1*07/DRB1*16 genotypes and the HLA-DRB5 gene locus represent a protective factor for RA. The presence of specific HLA-DRB1 gene variants increases the risk of developing RA, while other variants provide protection against disease. Therefore, HLA typing could be helpful in the prediction of RA development and establishing and confirming a definitive diagnosis of autoimmune diseases in some subjects. A strong association with the higher levels of ESR and CRP could be used to establish definitive diagnosis and introduce of early treatment of RA to prevent the occurrence of RA symptoms.

Up-regulation of syndecan-2 in proximal colon correlates with acute inflammation

We previously reported that syndecan-2 expression is increased on the colonic epithelium during chronic inflammation. Here, we report that syndecan-2 exhibits a different pattern of site-specific colonic expression during acute inflammation. Syndecan-2 expression was up-regulated predominantly in the proximal colon of dextran sulfate sodium-induced colitis mice. The colitis-associated up-regulation of syndecan-2 was barely detected in Rag-1^-/- (recombination activating gene 1 knockout) mice under colitis-inducing conditions. Increased syndecan-2 expression correlated with increased levels of infiltrated CD4⁺ IL-17A⁺ T cells in the proximal colon. Serum levels of IL-17A were increased during the acute inflammatory response in normal mice but not Rag-1^-/- mice. IL-17A directly induced IL-17 receptor (IL-17RA) and syndecan-2 expression in ex vivo-cultured proximal colon tissues and adenoma cell lines from proximal colon. IL-17RA knockdown reduced the IL-17A-mediated syndecan-2 expression in SNU1235 cells. No elevation of syndecan-2 or IL-17RA was observed in colonic tissues from IL-17A^-/- mice during colitis induction. Finally, increased expression of syndecan-2 and IL-17RA was observed in the proximal colons of cecal ligation and puncture-induced sepsis mice and infectious pan colitis patients. Together, these data suggest that acute inflammation induces syndecan-2 expression predominantly in the proximal colon via IL-17A-IL-17RA signaling during the early stage of the inflammatory response and that proximal colonic syndecan-2 might be a biomarker for acute inflammation.-Hong, H., Song, H.-K., Hwang, E. S., Lee, A. R., Han, D. S., Kim, S.-E., Oh, E.-S. Up-regulation of syndecan-2 in proximal colon correlates with acute inflammation.

Circulating microRNA-23b as a new biomarker for rheumatoid arthritis

MicroRNA-23b (miR-23b) is associated with inflammation and autoimmune diseases. This study evaluated miR-23b expression and assessed its potential as a biomarker of disease activity for rheumatoid arthritis (RA). Differential expression of microRNAs was determined by miRNA microarray analysis in fibroblast-like synoviocytes (FLSs) from four trauma patients as healthy controls (HCs) and eight RA patients. The microarray results showed elevated expression of miR-23b in FLSs from RA patients and this finding was corroborated by real-time quantitative polymerase chain reaction (RT-qPCR) and in situ hybridization using synovial tissues (STs). Furthermore, we found miR-23b levels in plasma of RA patients were significantly higher than in HCs, and plasma miR-23b levels positively correlated with the erythrocyte sedimentation rate (ESR), hypersensitive C-reactive protein (hs-CRP), C-reactive protein (CRP), DAS28, and platelet (PLT) count (P < 0.05). MiR-23b levels in plasma inversely correlated with the levels of hemoglobin (Hb), total bilirubin (TBIL), direct bilirubin (DBIL), indirect bilirubin (IBIL), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) (P < 0.05), but not with rheumatoid factor (RF) or anti-cyclic citrullinated peptide antibodies (ACPA) (P > 0.05). Moreover, patients with anorexia showed higher levels of miR-23b in plasma than those without anorexia. Similar results were observed with fatigue. Appropriate treatment for RA not only ameliorated the disease condition but also reversed the elevated plasma miR-23b level remarkably. These results suggest that circulating miR-23b may be a promising biomarker for RA disease activity.

The possible role of heat shock protein-70 induction in collagen-induced arthritis in rats

AIM

This study aimed to evaluate the possible role of heat shock protein-70 (HSP70) induction by 17-allylaminodemethoxygeldanamycin (17-AAG) in collagen-induced arthritis in rats.

MATERIAL AND METHODS

Male Wistar rats were divided into five groups (n = 10/group) and were treated intraperitoneally twice a week for 4 weeks, namely normal control (saline), arthritis control (AR; saline), AR + 17-AAG, AR + methotrexate (MTX), and AR + 17-AAG + MTX. At the end of the treatments, arthritic score was determined and then the animals were sacrificed. Erythrocyte sedimentation rate (ESR), serum levels of HSP70, interleukin-17 (IL-17), tumor necrosis factor-alpha (TNF-α), rheumatic factor (RF), C-reactive protein (CRP), malondialdehyde (MDA), glutathione peroxidase (GPx), and matrix metalloproteinase-9 (MMP-9) were determined.

RESULTS

In the AR group, all parameters increased significantly, except for GPx, which showed a pronounced decrease. The 17-AAG and/or MTX treatments significantly reduced arthritic score, ESR, IL-17, TNF-α, RF, CRP, MDA, and MMP-9 with significant increase in GPx compared to the AR group. The HSP70 level was significantly higher in the AR + 17-AAG and the AR + 17-AAG + MTX groups but significantly lower in the AR + MTX group as compared to the AR group. Also, it was significantly lower in the AR + MTX group as compared to the AR + 17-AAG group.

CONCLUSION

We concluded that HSP70 induction by 17-AAG attenuated the inflammatory process in a rheumatoid arthritis (RA) model induced by collagen, which suggested that HSP70 inducers can be promising agents in the treatment of RA.

Rheumatology practice in Japan: challenges and opportunities

This article aims to and describes the characteristics of rheumatology practice in Japan, focusing on the medical environment for the treatment of rheumatoid arthritis (RA). In Japan, the introduction of biological disease-modifying anti-rheumatic drugs (bDMARDs) has led to a significant paradigm shift in medical care; satisfactory safety outcomes have been demonstrated by periodic analysis, post-market surveillance and the development of guidelines via an industry-academia-government collaboration. Drug discontinuation is also considered an option, as well as medical economic analysis of any increase in the financial burden engendered by use of bDMARDs. Tocilizumab, a bDMARD established in Japan, was developed in an environment that facilitates translational research. The rheumatology community in Japan is expected to continue to develop novel therapies, while ensuring consistent quality of medical care despite limited healthcare resources.

Monomeric C-Reactive Protein Binds and Neutralizes Receptor Activator of NF-κB Ligand-Induced Osteoclast Differentiation

C-reactive protein (CRP) is an established marker of rheumatoid arthritis (RA) but with ill-defined actions in the pathogenesis. Here, we show that CRP regulates the differentiation of osteoclasts, a central mediator of joint inflammation and bone erosion in RA, in a conformation- and receptor activator of NF-κB ligand (RANKL)-dependent manner. CRP in the native conformation is ineffective, whereas the monomeric conformation (mCRP) actively modulates osteoclast differentiation through NF-κB and phospholipase C signaling. Moreover, mCRP can bind RANKL, the major driver of osteoclast differentiation, and abrogate its activities. The binding and inhibition of RANKL are mediated by the cholesterol binding sequence (CBS) of mCRP. Corroborating the in vitro results, CRP knockout exacerbates LPS-induced bone resorption in mice. These results suggest that mCRP may be protective in joint inflammation by inhibiting pathological osteoclast differentiation and that the CBS peptide could be exploited as a potential RANKL inhibitor.

Human periodontal ligament fibroblasts synthesize C-reactive protein and Th-related cytokines in response to interleukin (IL)-6 trans-signalling

AIM

To characterize the potential of human periodontal ligament fibroblasts (HPLF) to synthesize CRP and Th-related cytokines in response to IL-6 in periodontal health and apical inflammation.

METHODOLOGY

Primary HPLF stimulated with IL-6, soluble(s) IL-6 receptor (R) and controls were assayed for CRP, Th1, Th2, Th17 and Treg-related cytokines by quantitative real-time PCR and ELISA, respectively. IL-6R mRNA expression and its soluble protein levels were screened in HPLF cultures, and ex vivo samples of healthy periodontal ligaments (n = 5) and apical lesions (n = 13). Data were analysed with ANOVA or unpaired t-test.

RESULTS

0.5 ng mL^-1 IL-6 plus 1 ng mL^-1 of its soluble receptor (sIL-6R) for 24 h was effective in inducing CRP production. IL-6 alone had a mild dose-dependent effect; co-stimulation with sIL-6R significantly enhanced this effect, whereas it was completely abolished by the addition of IL-6R blocking antibody (P < 0.05). Similarly, higher mRNA expression and protein levels of Th1, Th17 and partially Treg-related cytokines were found for IL-6 combined with its soluble receptor versus the nonstimulated group and IL-6R antibody (P < 0.05). IL-6R mRNA expression was slightly induced by IL-6 compared to THP-1 cells, but sILR-6 protein could not be detected in HPLF. High sIL-6R levels were detected in apical lesions and were immunolocalized to mononuclear inflammatory cells and proliferating epithelium.

CONCLUSION

IL-6 trans-signalling induced Th1 and Th17-related cytokines and represents an extra-hepatic mechanism for PCR synthesis in human periodontal ligament fibroblasts, contributing to explain the bone-destructive phenotype of apical lesions and eventually its systemic complications.

Sliding-strip microfluidic device enables ELISA on paper

This article describes a 3D microfluidic paper-based analytical device that can be used to conduct an enzyme-linked immunosorbent assay (ELISA). The device comprises two parts: a sliding strip (which contains the active sensing area) and a structure surrounding the sliding strip (which holds stored reagents—buffers, antibodies, and enzymatic substrate—and distributes fluid). Running an ELISA involves adding sample (e.g. blood) and water, moving the sliding strip at scheduled times, and analyzing the resulting color in the sensing area visually or using a flatbed scanner. We demonstrate that this device can be used to detect C-reactive protein (CRP)—a biomarker for neonatal sepsis, pelvic inflammatory disease, and inflammatory bowel diseases—at a concentration range of 1–100 ng/mL in 1000-fold diluted blood (1–100 µg/mL in undiluted blood). The accuracy of the device (as characterized by the area under the receiver operator characteristics curve) is 89% and 83% for cut-offs of 10 ng/mL (for neonatal sepsis and pelvic inflammatory disease) and 30 ng/mL (for inflammatory bowel diseases) CRP in 1000-fold diluted blood respectively. In resource-limited settings, the device can be used as a part of a kit (containing the device, a fixed-volume capillary, a pre-filled tube, a syringe, and a dropper); this kit would cost ~ $0.50 when produced in large scale (>100,000 devices/week). This kit has the technical characteristics to be employed as a pre-screening tool, when combined with other data such as patient history and clinical signs.

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3D microfluidic paper-based analytical device performs ELISA with colorimetric results.

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Two components enable separation of reagents in the device: a sliding-strip and a functional dock.

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All required reagents (antibodies, enzyme, substrate, buffers) are stored in the device.

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User only needs to add sample and water using the provided kit.

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Device can detect C-reactive protein for possible pre-screening of neonatal sepsis, pelvic inflammatory disease, or inflammatory bowel diseases.

Altered glycan accessibility on native immunoglobulin G complexes in early rheumatoid arthritis and its changes during therapy

The goal of this study was to investigate the glycosylation profile of native immunoglobulin (Ig)G present in serum immune complexes in patients with rheumatoid arthritis (RA). To accomplish this, lectin binding assays, detecting the accessibility of glycans present on IgG-containing immune complexes by biotinylated lectins, were employed. Lectins capturing fucosyl residues (AAL), fucosylated tri-mannose N-glycan core sites (LCA), terminal sialic acid residues (SNA) and O-glycosidically linked galactose/N-acetylgalactosamine (GalNac-L) were used. Patients with recent-onset RA at baseline and after 3-year follow-up were investigated. We found that native IgG was complexed significantly more often with IgM, C1q, C3c and C-reactive protein (CRP) in RA patients, suggesting alterations of the native structure of IgG. The total accessibility of fucose residues on captured immune complexes to the respective lectin was significantly higher in patients with RA. Moreover, fucose accessibility on IgG-containing immune complexes correlated positively with the levels of antibodies to cyclic citrullinated peptides (anti-CCP). We also observed a significantly higher accessibility to sialic acid residues and galactose/GalNAc glyco-epitopes in native complexed IgG of patients with RA at baseline. While sialic acid accessibility increased during treatment, the accessibility of galactose/GalNAc decreased. Hence, successful treatment of RA was associated with an increase in the SNA/GalNAc-L ratio. Interestingly, the SNA/GalNAc-L ratio in particular rises after glucocorticoid treatment. In summary, this study shows the exposure of glycans in native complexed IgG of patients with early RA, revealing particular glycosylation patterns and its changes following pharmaceutical treatment.

Prolactin blocks the expression of receptor activator of nuclear factor κB ligand and reduces osteoclastogenesis and bone loss in murine inflammatory arthritis

Background

Prolactin (PRL) reduces joint inflammation, pannus formation, and bone destruction in rats with polyarticular adjuvant-induced arthritis (AIA). Here, we investigate the mechanism of PRL protection against bone loss in AIA and in monoarticular AIA (MAIA).

Methods

Joint inflammation, trabecular bone loss, and osteoclastogenesis were evaluated in rats with AIA treated with PRL (via osmotic minipumps) and in mice with MAIA that were null (Prlr-/-) or not (Prlr+/+) for the PRL receptor. To help define target cells, synovial fibroblasts from Prlr+/+ mice were treated or not with proinflammatory cytokines ((Cyt), including TNFα, IL-1β, and interferon (IFN)γ) with or without PRL, and these synovial cells were co-cultured or not with bone marrow osteoclast progenitors from Prlr+/+ or Prlr-/- mice.

Results

In AIA, PRL treatment reduced joint swelling, increased trabecular bone area, lowered osteoclast density, and reduced mRNA levels of osteoclast-associated genes (tartrate-resistant acid phosphatase (Trap)), cathepsin K (Ctsk), matrix metalloproteinase 9 (Mmp9), and receptor activator of nuclear factor κB or RANK (Tnfrsf11a)), of genes encoding cytokines with osteoclastogenic activity (Tnfa, Il1b, Il6, and receptor activator of nuclear factor κB ligand or RANKL (Tnfrsf11)), and of genes encoding for transcription factors and cytokines related to T helper (Th)17 cells (Rora, Rorc, Il17a, Il21, Il22) and to regulatory T cells (Foxp3, Ebi3, Il12a, Tgfb1, Il10). Prlr-/- mice with MAIA showed enhanced joint swelling, reduced trabecular bone area, increased osteoclast density, and elevated expression of Tnfa, Il1b, Il6, Trap, Tnfrsf11a, Tnfrsf11, Il17a, Il21, Il22, 1 l23, Foxp3, and Il10. The expression of the long PRL receptor form increased in arthritic joints, and in synovial membranes and cultured synovial fibroblasts treated with Cyt. PRL induced the phosphorylation/activation of signal transducer and activator of transcription-3 (STAT3) and inhibited the Cyt-induced expression of Il1b, Il6, and Tnfrsf11 in synovial fibroblast cultures. The STAT3 inhibitor S31-201 blocked inhibition of Tnfrsf11 by PRL. Finally, PRL acted on both synovial fibroblasts and osteoclast precursor cells to downregulate Cyt-induced osteoclast differentiation.

Conclusion

PRL protects against osteoclastogenesis and bone loss in inflammatory arthritis by inhibiting cytokine-induced expression of RANKL in joints and synovial fibroblasts via its canonical STAT3 signaling pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1290-4) contains supplementary material, which is available to authorized users.

Long noncoding RNA expression profile in fibroblast-like synoviocytes from patients with rheumatoid arthritis

Background

Long noncoding RNAs (lncRNAs) have recently received wide attention as key molecules that mediate a variety of physiological and pathological processes by regulating gene expression; however, knowledge of lncRNAs in rheumatoid arthritis (RA) is limited. Thus, we investigated the lncRNA expression profile in fibroblast-like synoviocytes (FLSs) from patients with RA and explored the function of abundantly expressed lncRNAs.

Methods

LncRNA and mRNA microarrays were performed to identify differentially expressed lncRNAs in RA FLSs compared with normal FLSs. Quantitative polymerase chain reaction (qPCR) was used to validate the results, and correlation analysis was used to analyze the relationship between these aberrantly expressed lncRNAs and clinical characteristics. A receiver operating characteristic (ROC) curve was constructed to evaluate the diagnostic value of the lncRNAs identified.

Results

According to the gene expression profiles, 135 lncRNAs were differentially expressed between RA and normal FLSs. Furthermore, qPCR data showed that lncRNA ENST00000483588 was up-regulated and that three lncRNAs (ENST00000438399, uc004afb.1, and ENST00000452247) were down-regulated in RA FLSs. The expression level of ENST00000483588 was positively correlated with the level of C-reactive protein and the Simplified Disease Activity Index score. Moreover, the areas under the ROC curve were 0.85, 0.92, 0.97, and 0.92 for ENST00000483588, ENST00000438399, uc004afb.1, and ENST00000452247, respectively.

Conclusions

The results indicate that the dysregulation of ENST00000483588, ENST00000438399, uc004afb.1, and ENST00000452247 may be involved in the pathological processes of RA and that these lncRNAs may have potential value for the diagnosis and assessment of the disease activity of RA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1129-4) contains supplementary material, which is available to authorized users.

Salvia plebeia R.Br. inhibits signal transduction of IL-6 and prevents ovariectomy-induced bone loss by suppressing osteoclastogenesis

The interleukin-6 (IL-6) family of cytokines plays a key role in the pathogenesis of rheumatoid arthritis and osteoporosis through the regulation of bone formation and resorption. In this study, it was observed that ethanol extract of Salvia plebeia R.Br. (S.P-EE) inhibited IL-6-induced signaling cascade including phosphorylation of JAK2/STAT3 and ERK. Subsequently, it was examined whether S.P-EE treatment could recover bone loss in ovariectomized (OVX) mice. Indeed, S.P-EE exhibited both preventive and therapeutic effect on OVX-induced bone loss in trabecular microarchitecture along with significant increase in bone mineral density and content. To understand the mechanism of action of S.P-EE in bone metabolism, the effect of S.P-EE on osteoclast differentiation and activity was investigated. S.P-EE significantly inhibited RANKL-induced osteoclast differentiation by suppressing phosphorylation of MAPK and Akt, and expression of NFATc1 and osteoclast marker genes. S.P-EE also inhibited bone-resorbing activity of osteoclasts. Furthermore, isolation and identification of the active compounds which are responsible for the inhibitory effect of S.P-EE on osteoclast differentiation was carried out. Six major flavonoids and plebeiolide A-C were isolated and examined their effects on osteoclast differentiation. Luteolin and hispidulin, and plebeiolide A and C, not B exhibited potent inhibitory activity on RANKL-induced osteoclast formation.

Effect of N-Feruloylserotonin and Methotrexate on Severity of Experimental Arthritis and on Messenger RNA Expression of Key Proinflammatory Markers in Liver

Rheumatoid arthritis (RA) is a chronic inflammatory disease, leading to progressive destruction of joints and extra-articular tissues, including organs such as liver and spleen. The purpose of this study was to compare the effects of a potential immunomodulator, natural polyphenol N-feruloylserotonin (N-f-5HT), with methotrexate (MTX), the standard in RA therapy, in the chronic phase of adjuvant-induced arthritis (AA) in male Lewis rats. The experiment included healthy controls (CO), arthritic animals (AA), AA given N-f-5HT (AA-N-f-5HT), and AA given MTX (AA-MTX). N-f-5HT did not affect the body weight change and clinical parameters until the 14th experimental day. Its positive effect was rising during the 28-day experiment, indicating a delayed onset of N-f-5HT action. Administration of either N-f-5HT or MTX caused reduction of inflammation measured as the level of CRP in plasma and the activity of LOX in the liver. mRNA transcription of TNF-α and iNOS in the liver was significantly attenuated in both MTX and N-f-5HT treated groups of arthritic rats. Interestingly, in contrast to MTX, N-f-5HT significantly lowered the level of IL-1β in plasma and IL-1β mRNA expression in the liver and spleen of arthritic rats. This speaks for future investigations of N-f-5HT as an agent in the treatment of RA in combination therapy with MTX.

ICPMS analysis of proteins separated by Native-PAGE: Evaluation of metaloprotein profiles in human synovial fluid with acute and chronic arthritis

The role of trace elements bound to proteins in the etiology and pathogenesis of rheumatoid arthritis (RA) remains unclear. In this sense, the identification and detection of metalloproteins has a strong and growing interest. Metalloprotein studies are currently carried out by polyacrylamide gel electrophoresis (PAGE) associated to inductively coupled plasma mass spectrometry (ICPMS), and despite that complete information can be obtained for metals such as Fe, Cu and Zn, difficulties due to poor sensitivity for other trace elements such as Sn, As, etc, are currently faced. In the present work, a simple and fast method for the determination of trace metals bound to synovial fluid (SF) proteins was optimized. Proteins from SF (long and short-term RA) were separated in ten fractions by native PAGE, then dissolved in nitric acid and peroxide hydrogen, and analyzed by ICPMS. Fifteen metals were determined in each separated protein fraction (band). Adequate calibration of proteins molecular weight allowed stablishing which protein type were bound to different metals.

The Elevated Secreted Immunoglobulin D Enhanced the Activation of Peripheral Blood Mononuclear Cells in Rheumatoid Arthritis

Immunoglobulin D (IgD) is a surface immunoglobulin that is expressed as either membrane IgD (mIgD) or secreted IgD (sIgD). Researchers have shown that sIgD is often elevated in patients with autoimmune diseases. The possible roles of sIgD on the function of peripheral blood mononuclear cells (PBMCs) in rheumatoid arthritis (RA) are still unclear. In this study, we compared the expression of sIgD, mIgD and IgD receptor (IgDR) in RA patients and healthy controls, and investigated the effect of sIgD on the function of PBMCs. We found that the levels of sIgD, mIgD and IgDR were significantly higher in RA patients compared with healthy controls. The concentrations of sIgD were positively correlated with soluble receptor activator of nuclear factor-κB ligand (sRANKL), rheumatoid factor (RF) and C-reactive protein (CRP) in RA patients. Strikingly, IgD could enhance the proliferation of PBMCs and induce IL-1α, IL-1β, TNF-α, IL-6 and IL-10 production from PBMCs. Moreover, the percentage of activated T cell subsets (CD4⁺CD69⁺, CD4⁺CD154⁺) and activated B cell subsets (CD19⁺CD23⁺, CD19⁺CD21⁺, CD19⁺IgD⁺ and CD19^-CD138⁺) were increased by IgD. The percentage of unactivated T cell subset (CD4⁺CD62L⁺) and immature B cell subset (CD19⁺IgM⁺IgD^-) were decreased by IgD in PBMCs. Furthermore, the expressions of IgDR on T and B cells were significantly increased by treatment with IgD. Our results demonstrate that IgD enhanced the activation of PBMCs, which may contribute to RA pathogenesis. Therefore, IgD could be a potential novel immunotherapeutic target for the management of RA.

Effects of C-reactive protein on bone cells

AIMS

Inflammatory processes are involved in bone remodeling. C-reactive protein (CRP) is an acute phase reactant that reflects different degrees of inflammation. Accumulating evidence suggests that CRP is an inflammatory marker and a direct cause of disease. Therefore, we examined the direct effects of CRP on bone cells.

MAIN METHODS

We used RAW 264.7 cells to evaluate the direct effects of CRP on osteoclast differentiation. We carried out alkaline phosphatase (ALP) and bone nodule formation assays using MC3T3-E1 cells to evaluate osteoblast differentiation. Expression of osteoclast-specific and osteoblast-specific genes and effects on cell signaling pathways associated with cell differentiation were analyzed by reverse transcription polymerase chain reaction and Western blotting.

KEY FINDINGS

CRP significantly and dose-dependently inhibited TRAP-positive multinucleated cell formation in RANKL-induced RAW 264.7 cell cultures. We observed suppression of p38, ERK and AKT mitogen-activated protein kinases induced by RANKL in Western blots after CRP treatment of RAW 264.7 cells. CRP also suppressed ALP activity and mineralization by Alizarin red S staining of MC3T3-E1 cell cultures. CRP suppressed osteoclast-specific and osteoblast-specific genes. Furthermore, CRP increased interferon beta (IFN-β) mRNA expression and protein levels in RAW 264.7 and MC3T3-E1 cells, and these effects were suppressed by oxPAPC, an inhibitor of Toll-like receptor (TLR) signaling.

SIGNIFICANCE

These data indicated that CRP may have a direct role on osteoclast and osteoblast differentiation via TLR signaling pathways.