The antirheumatic drug leflunomide inhibits osteoclastogenesis by interfering with receptor activator of NF-κB ligand-stimulated induction of nuclear factor of activated T cells c1

Analgesic and Anti-Arthritic Activities of Polysaccharides in Chaenomeles speciosa

Chaenomeles speciosa (Sweet) Nakai has been long used as a folk medicine for rheumatic diseases treatment. This study aimed to investigate the effects and underlying mechanism of polysaccharides in Chaenomeles speciosa (CSP) on the pro-inflammatory cytokines and MAPK pathway in complete Freund’s adjuvant (CFA)-induced arthritis and LPS-induced NR8383 cells. We used acetic acid (HAc)-induced writhing and CFA induced paw edema to determine the analgesic activity and anti-inflammatory activity, respectively. CFA rats were administered CSP (12.5, 25.0, and 50.0 mg/kg) daily for 3 weeks via oral gavage. The analgesic test was done using three different doses of the extract (50, 100, and 200 mg/kg). The anti-arthritic evaluation involved testing for paw swelling, swelling inhibition, and histological analysis in CFA rats. Finally, ELISA, western blot, qRT-PCR were done to determine the effect of CSP on the activation of MAPK pathway, production of pro-inflammatory cytokines in lipopolysaccharide (LPS)-stimulated NR838 macrophage cells. In pain models, oral uptake of CSP greatly reduced pain perception. Furthermore, in CFA rats, CSP substantially decreased paw swelling as well as synovial tissue proliferation and inflammatory cell infiltration. In addition, CSP was shown to inhibit pro-inflammatory cytokines (TNF-α, IL-1β, and COX-2) as well as JNK and ERK1/2 phosphorylation in LPS-stimulated NR8383 cells. Thus, pro-inflammatory cytokine secretion and MAPK signaling downregulation promoted the analgesic and anti-arthritic effects of CSP.

Cell-Based Double-Screening Method to Identify a Reliable Candidate for Osteogenesis-Targeting Compounds

Small-molecule compounds strongly affecting osteogenesis can form the basis of effective therapeutic strategies in bone regenerative medicine. A cell-based high-throughput screening system might be a powerful tool for identifying osteoblast-targeting candidates; however, this approach is generally limited with using only one molecule as a cell-based sensor that does not always reflect the activation of the osteogenic phenotype. In the present study, we used the MC3T3-E1 cell line stably transfected with the green fluorescent protein (GFP) reporter gene driven by a fragment of type I collagen promoter (Col-1a1GFP-MC3T3-E1) to evaluate a double-screening system to identify osteogenic inducible compounds using a combination of a cell-based reporter assay and detection of alkaline phosphatase (ALP) activity. Col-1a1GFP-MC3T3-E1 cells were cultured in an osteogenic induction medium after library screening of 1280 pharmacologically active compounds (Lopack¹²⁸⁰). After 7 days, GFP fluorescence was measured using a microplate reader. After 14 days of osteogenic induction, the cells were stained with ALP. Library screening using the Col-1a1/GFP reporter and ALP staining assay detected three candidates with significant osteogenic induction ability. Furthermore, leflunomide, one of the three detected candidates, significantly promoted new bone formation in vivo. Therefore, this double-screening method could identify candidates for osteogenesis-targeting compounds more reliably than conventional methods.

[Drug-induced osteopathy in rheumatology]

Osteopathy in rheumatology can either be primary a condition as a consequence of inflammatory rheumatic diseases but can also be drug induced. The most severe clinical manifestations are insufficiency fractures and osteonecrosis. The risk of fractures is highest for patients treated with glucocorticoids depending on the daily intake, the cumulative glucocorticoid dosage and the duration of administration. An incidence rate of nearly 13% was reported after administration of glucocorticoids lasting > 1 year. Cases of osteonecrosis under glucocorticoids are, in contrast, less frequent and not associated with glucocorticoid-induced osteoporosis. The antiresorptive substances bisphosphonates and denosumab, as well as romosumab are effective and important in treating osteoporosis; however, they can also cause atypical fractures, particularly of the femur as well as osteonecrosis of the jawbone. According to the most recent guidelines the benefits of bisphosphonate treatment have only been verified for 3-5 years and for denosumab for 3 years. There are clear preventive recommendations to avoid osteonecrosis of the jaw. Ultimately, the disease-modifying antirheumatic drugs (DMARD) methotrexate and leflunomide also affect the metabolism of bones. There is a rare but very characteristic form of osteopathy associated with methotrexate, mainly occurring in cases of long-term treatment. The typical manifestations are insufficiency fractures, particularly of the distal tibia, which persist for many years under continuous methotrexate administration. The treatment is the discontinuation of methotrexate and in most cases the fractures will heal within 3-4 months. Leflunomide has been associated with cases of persisting pseudarthrosis that only disappeared after a wash-out of the active metabolite.

Associations between osteoporosis and drug exposure: A post-marketing study of the World Health Organization pharmacovigilance database (VigiBase®)

BACKGROUND

Bone remodeling is a complex process, and many conditions (including drug exposure) lead to osteoporosis. Here, we sought to detect new disproportionality signals for drugs associated with osteoporosis.

METHODS

We performed a disproportionality analysis of the World Health Organization's VigiBase® pharmacovigilance database through April 12, 2020. The frequency of reports on osteoporosis for all identified drug classes was compared with that for all other drugs and quoted as the reporting odds ratio (ROR) [95% confidence interval (CI)].

RESULTS

Of the 7,594,968 cases spontaneously recorded to VigiBase®, 4758 concerned osteoporosis. New disproportionality signals with a pharmacologically plausible mechanism were found for drugs used in neurology (levodopa (ROR [95%CI]: 10.18 [4.33-25.10]), selective serotonin agonists (4.22 [2.34-7.00]) and memantine (4.10 [1.56-8.93])), hematology (romiplostim (4.93 [1.15-21.10])), pulmonology (macitentan (3.02 [1.84-4.90])), ophthalmology (ranibizumab (3.31 [1.00-10.51])) and rheumatology (tofacitinib (3.65 [3.00-4.40])). The robustness of these new results is supported by the significant RORs for the vast majority of drugs already known to induce osteoporosis and/or increase the fracture risk, namely glucocorticoids, gonadotropin-releasing hormone analogs, anti-aromatases, androgen receptor blockers, thyroid hormones, proton pump inhibitors, thiazolidinediones, vitamin K antagonists, loop diuretics, protease inhibitors, nucleoside and nucleotide reverse transcriptase inhibitors, and enzyme-inducing antiepileptics including barbiturates and derivatives, hydantoin derivatives, carboxamide derivatives and fatty acid derivatives.

CONCLUSION

We established up a comprehensive list of drugs potentially associated with osteoporosis and highlighted those with pharmacologically plausible mechanisms leading to bone fragility. Our results might pave the way for additional exploration of these mechanisms.

Disease-Modifying Anti-rheumatic Drug Prescription Baihu-Guizhi Decoction Attenuates Rheumatoid Arthritis via Suppressing Toll-Like Receptor 4-mediated NLRP3 Inflammasome Activation

As a traditional Chinese medicine-originated disease-modifying anti-rheumatic drug prescription, Baihu-Guizhi decoction (BHGZD) is extensively used for the treatment of rheumatoid arthritis (RA) with a satisfying therapeutic efficacy. Mechanically, our previous data indicated that BHGZD may ameliorate RA partially by restoring the balance of the “inflammation-immune” system through regulating the TLR4-c-Fos-IL2-TNF-alpha axis. Toll-like receptor 4 (TLR4) has been revealed to be involved in the activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome complex. Thus, the aim of the current study was to determine the regulatory effects of BHGZD on the TLR4–mediated inflammasome activation during RA progression based on the modified adjuvant-induced arthritis model (AIA-M) and the lipopolysaccharide/adenosine triphosphate (LPS/ATP)–induced pyroptosis cellular models. As a result, oral administration of BHGZD exhibited prominent improvement in the disease severity of AIA-M rats, such as reducing the redness and swelling of joints, arthritis incidence, arthritic scores, and diameter of the limb and increasing pain thresholds. In line with the in vivo findings, BHGZD treatment effectively inhibited the LPS/ATP–induced pyroptosis of both Raw264.7 macrophage and MH7A cells in vitro by reducing pyroptotic cell death morphology (swollen cells) and decreasing propidium iodide–positive and terminal deoxynucleotidyl transferase–mediated dUTP-fluorescein nick end labeling (TUNEL)–positive cells. Notably, the increased expression levels of TLR4, NLRP3, interleukin 1β, and interleukin 18 proteins and the elevated activities of caspase-1 and lactic dehydrogenase in in vivo and in vitro disease models were markedly reversed by the treatment with BHGZD. In conclusion, the above findings proved the immunomodulatory and anti-inflammatory activities of BHGZD, especially in pyroptosis, which may be attributed to the activation of TLR4–mediated NLRP3 inflammasome signaling.

Radiographic changes in the temporomandibular joint related to medication in rheumatic diseases

OBJECTIVES

The purpose of this study was to assess radiographical changes on temporomandibular joint (TMJ) in relation the autoimmune rheumatic diseases and the medicines that treat this diseases with cone beam computed tomography(CBCT).

METHODS

65 people with rheumatoid diseases were included in the study and divided into five subgroups according to drugs they used. Condyle height (CH), anteroposterior dimension (APD), mesiolateral dimension (MLD) and superior joint space (SJS) were measured in order to evaluate mandibular condyle dimensions. Further, were evaluated in terms of osteoarthritic changes such as erosion, flattening, osteophyte and subchondral cyst in the mandibular condyle. TMJ measurements were compared between study-control groups and subgroups by using Student's t-test, Mann-Whitney-U test, one-way analysis of variance (ANOVA) and Kruskal-Wallis test. The association between osteoarthritic features, rheumatoid status was tested by using χ2 test. Observers were blinded to all groups. Cohen κ values (0853-0945) and Spearman's correlation coefficient (0.959-0.997) indicated high interexaminer reliability.

RESULTS

Condylar dimentions were significantly lower in CH and SJS in rheumatic diseases group (p < 0.001), however APD (p = 0,681) and MLD (p = 0,757) was not different significantly. Osteoarthritic changes such as erosion (p < 0.001), flattening (p = 0.005), osteophyte (p = 0.001) and subchondral cyst (p = 0.001) were significantly higher in the patient group. None of the parameters were different significantly according to subgroups determined according to drugs used(p > 0.05).

CONCLUSIONS

Degenerative changes may cause decrease in condyle size and changes in condyle position. It is a process that can continue despite the use of antirheumatic or immunosuppressive drugs. All of these can become the source of possible TMJ problems.

The pathway to pyrimidines: The essential focus on dihydroorotate dehydrogenase, the mitochondrial enzyme coupled to the respiratory chain

This paper is based on the Anne Simmonds Memorial Lecture, given by Monika Löffler at the International Symposium on Purine and Pyrimidine Metabolism in Man, Lyon 2019. It is dedicated to H. Anne Simmonds (died 2010) - a founding member of the ESSPPMM, since 2003 Purine and Pyrimidine Society - and her outstanding contributions to the identification and study of inborn errors of purine and pyrimidine metabolism. The distinctive intracellular arrangement of pyrimidine de novo synthesis in higher eukaryotes is important to cells with a high demand for nucleic acid synthesis. The proximity of the enzyme active sites and the resulting channeling in CAD and UMP synthase is of kinetic benefit. The intervening enzyme dihydroorotate dehydrogenase (DHODH) is located in the mitochondrion with access to the ubiquinone pool, thus ensuring efficient removal of redox equivalents through the constitutive activity of the respiratory chain, also a mechanism through which the input of 2 ATP for carbamylphosphate synthesis is balanced by Oxphos. The obligatory contribution of O₂ to de novo UMP synthesis means that DHODH has a pivotal role in adapting the proliferative capacity of cells to different conditions of oxygenation, such as hypoxia in growing tumors. DHODH also is a validated drug target in inflammatory diseases. This survey of selected topics of personal interest and reflection spans some 40 years of our studies from tumor cell cultures under hypoxia to in vitro assays including purification from mitochondria, localization, cloning, expression, biochemical characterization, crystallisation, kinetics and inhibition patterns of eukaryotic DHODH enzymes.

Deciphering the chemical profile and pharmacological mechanisms of Baihu-Guizhi decoction using ultra-fast liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry coupled with network pharmacology-based investigation

BACKGROUND

Baihu-Guizhi decoction (BHGZD) has been extensively used for the treatment of rheumatoid arthritis (RA) with a satisfying therapeutic effect. However, the material basis and the underlying mechanisms of BHGZD against RA have not been fully elucidated.

PURPOSE

To investigate the chemical profile and the pharmacological mechanisms of BHGZD against RA.

METHODS

The chemical constituents containing in BHGZD were identified using UFLC-Q-TOF-MS/MS system, and the corresponding putative targets were predicted. Then, the differentially expressed genes (DEGs) between adjuvant-induced arthritis (AIA) and normal control groups were identified using microarray analysis. After constructing the interaction network of "RA-related gene-BHGZD putative target", BHGZD candidate targets against RA were screened by topological analysis and further experimentally validated based on AIA rat model.

RESULTS

A total of 41 chemical constituents were identified in the water extract of BHGZD, which were predicted to hit 1312 putative targets. Additionally, 26 DEGs between the AIA and normal control groups were defined as "RA-related genes", which were functionally involved into the imbalance of "inflammation-immune" system during RA progression. On the basis of the topological importance in the network of "RA-related gene-BHGZD putative target", 177 BHGZD candidate targets against RA were identified. Among them, TLR4, c-Fos/AP-1, IL2 and TNF had direct interactions with each other and also function as crucial components of toll-like receptor and T cell receptor signaling pathways, which may play important roles in maintaining the balance of "inflammation-immune" system. Experimentally, we verified that BHGZD dose-dependently attenuated the severity, pathological changes, as well as mechanical, cold, and heat hypersensitivities during RA progression based on the AIA rat model. Further western blot analysis demonstrated that BHGZD significantly reduced the protein levels of TLR4, c-Fos/AP-1, IL2 and TNF, which were induced by RA modeling, in the inflamed joints of AIA rats (all p<0.05).

CONCLUSION

This study combining the chemical and transcriptomic profilings, target prediction, network calculation and experimental validations identifies the chemical constituents containing in BHGZD and offers the convincing evidence that BHGZD may ameliorate RA partially by restoring the balance of "inflammation-immune" system and subsequently reversing the pathological events during RA progression through regulating the TLR4-c-Fos-IL2-TNF axis.

Apoptosis Induction of Fibroblast-Like Synoviocytes Is an Important Molecular-Mechanism for Herbal Medicine along with its Active Components in Treating Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a known chronic autoimmune disease can cause joint deformity and even loss of joint function. Fibroblast-like synoviocytes (FLS), one of the main cell types in synovial tissues of RA patients, are key effector cells in the development of RA and are considered as promising therapeutic targets for treating RA. Herbal medicines are precious resources for finding novel agents for treating various diseases including RA. It is reported that induction of apoptosis in FLS is an important mechanism for the herbal medicines to treat RA. Consequently, this paper reviewed the current available references on pro-apoptotic effects of herbal medicines on FLS and summarized the related possible signal pathways. Taken together, the main related signal pathways are concluded as death receptors mediated apoptotic pathway, mitochondrial dependent apoptotic pathway, NF-κB mediated apoptotic pathways, mitogen-activated protein kinase (MAPK) mediated apoptotic pathway, endoplasmic reticulum stress (ERS) mediated apoptotic pathway, PI3K-Akt mediated apoptotic pathway, and other reported pathways such as janus kinase/signal transducers and activators of transcription (JAK-STAT) signal pathway. Understanding the apoptosis induction pathways in FLS of these herbal medicines will not only help clear molecular mechanisms of herbal medicines for treating RA but also be beneficial for finding novel candidate therapeutic drugs from natural herbal medicines. Thus, we expect the present review will highlight the importance of herbal medicines and its components for treating RA via induction of apoptosis in FLS, and provide some directions for the future development of these mentioned herbal medicines as anti-RA drugs in clinical.

Caffeic acid phenethyl ester (CAPE): pharmacodynamics and potential for therapeutic application

Caffeic acid phenethyl ester (CAPE) is the major pharmacologically-active component of some propolis types, rich in polyphenols, such as poplar propolis types. CAPE has the potential to be applied as a pharmaceutical as it possesses most of the pharmacological activities of propolis, such as anti-proliferative, antioxidant, immunomodulatory, antidiabetic, anti-inflammatory and antimicrobial. Its advantage is that it lacks some of the downsides of total propolis extracts, such as inability for unified standardization, which is cornerstone for implementing its therapeutic potential as a drug. The current paper provides an overview on the pharmacodynamic principles of CAPE. We present literature search outcomes form ClinicalTrials.gov database and from scientific publications, available on Scopus and Crossref databases. We take a round view of CAPE’s potential therapeutic implications in light of approved drugs with related modes of action.

Yi Shen Juan Bi Pill Ameliorates Bone Loss and Destruction Induced by Arthritis Through Modulating the Balance of Cytokines Released by Different Subpopulations of T Cells

The Yi Shen Juan Bi Pill (YSJB), a traditional Chinese compound herbal drug, has been used as an anti-rheumatic drug in clinical practice. Cartilage and bone destruction of inflamed joints is the hallmark of rheumatoid arthritis (RA). Our previous study suggested that YSJB had a protective effect on joint damage in collagen-induced (CIA) rats. However, the role and the mechanism of YSJB in inflammation-induced bone loss are unavailable. The current study aimed to further evaluate the effect of YSJB on the joint destruction and the systemic bone loss, and to clarify the potential mechanism. CIA model was generated by using collagen II and incomplete Freund's adjuvant in Sprague-Dawley rats. After 4 weeks treatment, arthritic index, tissue pathology, micro-computed tomography scanning (μ-CT), and bone mineral density (BMD) analysis were performed. YSJB decreased arthritic scores and bone destruction; improved the BMD of lumbar vertebrae and bone volume fraction of inflamed joints. Moreover, YSJB significantly decreased the production of serum bone resorption markers, including Tartrate-Resistant Acid Phosphatase (TRACP), N-terminal telopeptide of type I collagen and C-terminal telopeptide of type I collagen. Meanwhile, it increased the level of serum bone formation marker type I collagen N-terminal propeptide. These results revealed that YSJB ameliorated bone destruction and reduced bone loss induced by arthritis. We have previously showed that Tregs inhibited osteoclast differentiation and bone resorption in vitro. Furthermore, others suggested that abnormality of Th1, Th17 may contribute to bone destruction. Here, we showed YSJB significantly up-regulated the percentage of Tregs, while also down-regulated the percentage of Th1 and Th17 cells. Our findings provide the evidence that YSJB ameliorates the severity of disease and joint degradation, and reduces systemic bone loss induced by arthritis. We propose YSJB modulates the balance of T cell phenotype, which affects the activation and differentiation of osteoclasts.

Does systemic inflammation and immune activation contribute to fracture risk in HIV?

PURPOSE OF REVIEW

There is increasing evidence pointing toward an important role of heightened immune activation and inflammation in people living with HIV contributing to the development of non-AIDS comorbidities. This review aims to explore low bone mineral density (BMD) in HIV with a focus on the underlying mechanisms and relationships between the immune and skeletal systems.

RECENT FINDINGS

Baseline immune activation and inflammation negatively impact BMD at antiretroviral therapy (ART) initiation. B- and T-cell alterations in HIV lead to an imbalance in the osteoblastic osteoprotegerin (OPG) and osteoclastic receptor activator of NF-κB ligand (RANKL) cytokines which favours osteoclastogenesis and bone resorption. These findings suggest an important role for immune-mediated mechanisms in the pathogenesis of low BMD in HIV.

SUMMARY

Bone homeostasis is in part regulated by cells of the immune system through complex interactions with the RANK/RANKL/OPG axis. Disturbances in the normal functioning of T, B cells, and monocytes in HIV and the resulting proinflammatory state may contribute to dysregulation of this finely controlled balance leading to increased bone loss. Pre-ART levels of immune activation and inflammation have a consistently negative effect on BMD and further suggest the immunocentric basis of bone loss in HIV alongside supporting the benefits of earlier ART initiation. Further longitudinal studies will help determine the effect this will have on fracture risk in people living with HIV.

Guizhi-Shaoyao-Zhimu decoction attenuates rheumatoid arthritis partially by reversing inflammation-immune system imbalance

BACKGROUND

Guizhi-Shaoyao-Zhimu decoction (GSZD) has been extensively used for rheumatoid arthritis (RA) therapy. Marked therapeutic efficacy of GSZD acting on RA has been demonstrated in several long-term clinical trials without any significant side effects. However, its pharmacological mechanisms remain unclear due to a lack of appropriate scientific methodology.

METHODS

GSZD's mechanisms of action were investigated using an integrative approach that combined drug target prediction, network analysis, and experimental validation.

RESULTS

A total of 77 putative targets were identified for 165 assessed chemical components of GSZD. After calculating the topological features of the nodes and edges in the created drug-target network, we identified a candidate GSZD-targeted signal axis that contained interactions between two putative GSZD targets [histone deacetylase 1 (HDAC1) and heat shock protein 90 kDa alpha, class A member 1 (HSP90AA1)] and three known RA-related targets [NFKB2; inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase beta (IKBKB); and tumor necrosis factor-alpha (TNF-α)]. This signal axis could connect different functional modules that are significantly associated with various RA-related signaling pathways, including T/B cell receptor, Toll-like receptor, NF-kappa B and TNF pathways, as well as osteoclast differentiation. Furthermore, the therapeutic effects and putative molecular mechanisms of GSZD's actions on RA were experimentally validated in vitro and in vivo.

CONCLUSIONS

GSZD may partially attenuate RA by reversing inflammation-immune system imbalance and regulating the HDAC1-HSP90AA1-NFKB2-IKBKB-TNF-α signaling axis.

Individualization of leflunomide dosing in rheumatoid arthritis patients

Leflunomide is largely considered to be a second-line treatment option for rheumatoid arthritis (RA). Those who fail to respond, tend to progress to treatment with expensive biological agents, which can also be associated with serious toxicities. Optimizing leflunomide treatment to meet the needs of individuals would hence be beneficial in terms of patient outcomes and health care expenditure. In this respect, therapeutic drug monitoring (TDM) may be useful, as plasma concentrations of leflunomide's active metabolite, teriflunomide, correlate with response to treatment, but are highly variable between patients. A number of pharmacogenetic markers have also been identified that influence response and toxicity. Incorporation of these findings into clinical practice could facilitate more efficient use of leflunomide.

Relationships between inflammation, immune activation, and bone health among HIV-infected adults on stable antiretroviral therapy

BACKGROUND

The aim was to determine the association between bone health and inflammation, T-cell activation, and monocyte activation among HIV-infected persons on stable antiretroviral therapy.

METHODS

We performed a cross-sectional analysis of all the subjects enrolling in the Stopping Atherosclerosis and Treating Unhealthy bone with RosuvastatiN in HIV trial with available skeletal assessments by dual-energy x-ray absorptiometry, inflammation, and immune activation markers. Analyses used were Wilcoxon rank-sum tests, Spearman correlation coefficients, and linear regression.

RESULTS

One hundred forty-two subjects were included: 78% men, 69% African American, median age 46.3 years, CD4 count 604 cells per microliter, and 77% with undetectable HIV-1 RNA. Twenty-three percent had osteopenia/osteoporosis at the hip, and 21% had this at the lumbar spine. Soluble vascular cell adhesion molecule-1 was correlated with hip (r = -0.22) and spine (r = -0.23) bone mineral density (BMD), and bone turnover markers (r = 0.20-0.33; all P < 0.05). No significant correlations were observed between the BMD and T-cell activation (%CD38HLA-DR on CD4 or CD8 T cells), monocyte activation (CD14CD16, sCD14, and sCD163), or inflammatory markers [interleukin (IL)-6, tumor necrosis factor-α, highly sensitive C-reactive protein, D-dimer, receptor activator of NF-kB ligand, osteoprotegerin, soluble tumor necrosis factor-RI and II]. In regression models including traditional bone risk factors, hip BMD was associated with age, race, and body mass index; spine BMD was associated with race, family history of hip fracture, trunk fat, tenofovir, and HIV RNA; bone resorption (c-terminal collagen crosslinks) was associated with intracellular adhesion molecule-1 and trunk fat; bone formation (P1NP) was associated with soluble vascular cell adhesion molecule-1, trunk and limb fat (P ≤ 0.05).

CONCLUSIONS

Future studies should evaluate the longitudinal association of the adhesion molecules to further elucidate potential contributory mechanisms of bone loss among HIV-infected persons on stable antiretroviral therapy.

The role of small molecules in bone regeneration

Although several methods have been used in bone regeneration medicine, current methods still have many limitations. The tissue used for autogenous bone graft is limited and allograft has weak osteoinductive activity. Tissue engineering provides a good choice for bone regeneration. However, the growth factors needed have a high price and short half-life. Recently, a number of small molecules have been confirmed to have osteoinductive activity and some have been clinically used. Natural small molecules including decalpenic acid, flavonoids, quinones can be extracted from plants and others can be synthesized according to the structure designed or mimicking the structure of natural small molecules. Small molecules can act as co-activator of BMP2 pathway or activate Wnt pathway; others can be the inhibitors of NF-κB signaling pathway. This review gives an overview on the small molecules with osteoinductive activity and discusses the mechanism of the small molecules.

The effects of disease modifying anti-rheumatic drugs on osteoclastogenesis and bone destruction in rheumatoid arthritis

Finding the means to ameliorate and prevent bone destruction as well as control inflammation is an urgent issue in the treatment of rheumatoid arthritis (RA). Recently, it has been demonstrated that osteoclastogenesis plays an important role in the bone destruction and pathogenesis of RA. Here, we review the effects of disease modifying anti-rheumatic drugs (DMRAD) on the amelioration of bone destruction and osteoclastogenesis.

The transcription factor FBI-1/OCZF/LRF is expressed in osteoclasts and regulates RANKL-induced osteoclast formation in vitro and in vivo

OBJECTIVE

Since transcription factors expressed in osteoclasts are possible targets for regulation of bone destruction in bone disorders, we investigated the expression of the transcription factor FBI-1/OCZF/LRF (in humans, factor that binds to inducer of short transcripts of human immunodeficiency virus type 1; in rats, osteoclast-derived zinc finger; in mice, leukemia/lymphoma-related factor) in patients with rheumatoid arthritis (RA), and assessed its role in osteoclastogenesis in vivo.

METHODS

Expression of FBI-1/OCZF was investigated in subchondral osteoclasts in human RA and in rat adjuvant-induced arthritis (AIA) using immunostaining and in situ hybridization, respectively. Transgenic mice overexpressing OCZF (OCZF-Tg) under the control of the cathepsin K promoter were generated, and bone mineral density and bone histomorphometric features were determined by peripheral quantitative computed tomography, calcein double-labeling, and specific staining for osteoclasts and osteoblasts. LRF/OCZF expression and the consequence of LRF inhibition were assessed in vitro with RANKL-induced osteoclast differentiation.

RESULTS

FBI-1/OCZF was detected in the nuclei of osteoclasts in rat AIA and human RA. RANKL increased the levels of LRF messenger RNA and nuclear-localized LRF protein in primary macrophages. In OCZF-Tg mice, bone volume was significantly decreased, the number of osteoclasts, but not osteoblasts, was increased in long bones, and osteoclast survival was promoted. Conversely, inhibition of LRF expression suppressed the formation of osteoclasts from macrophages in vitro.

CONCLUSION

FBI-1/OCZF/LRF regulates osteoclast formation and apoptosis in vivo, and may become a useful marker and target in treating disorders leading to reduced bone density, including chronic arthritis.

Inhibiting effects of Leflunomide metabolite on overexpression of CD147, MMP-2 and MMP-9 in PMA differentiated THP-1 cells

Recent studies have reported elevated expression of cluster of differentiation (CD) 147 on CD14(+) monocytes of the peripheral blood of patients with active rheumatoid arthritis and a correlation of CD147 expression with Disease Activity Score. Thus, CD147 may be a new target for treatment of rheumatoid arthritis. Leflunomide is a disease-modifying antirheumatic drug that is commonly used to treat rheumatoid arthritis. The effect of leflunomide in blocking the up-regulation of CD147 and in blocking the down-regulation of metalloproteinases (MMP)-2 and MMP-9 in active macrophages has not yet been established. In this study we investigated the effect of A771726, the active metabolite of leflunomide, on expression of CD147 and on the gelatinolytic activity of MMP-2 and MMP-9 in phorbol myristate acetate (PMA) differentiated THP-1 cells. The expression of CD147, MMP-2, and MMP-9 mRNAs were determined by real-time quantitative reverse transcription PCR, the levels of cellular surface expression of CD147 were determined by flow cytometry, and the gelatinolytic activity of MMP-2 and MMP-9 were determined by zymography. Our results showed that A771726 significantly inhibited the expression of CD147 on the cell surface of activated THP-1 cells in a dose-dependent manner (P<0.01), inhibited the expression of MMP-2 and MMP-9 mRNAs in a dose-dependent manner (P<0.01), and inhibited the gelatinolytic activity of MMP-2 and MMP-9 at concentration of 15 μg/ml and 45 μg/ml (P<0.01). Our results indicate that A771726, the active metabolite of leflunomide, inhibited CD147 expression at the protein level and inhibited gelatinolytic activity of MMP-2 and MMP-9 in PMA-differentiated THP-1 cells.

Control of RANKL gene expression

Osteoclasts are highly specialized cells capable of degrading mineralized tissue and form at different regions of bone to meet different physiological needs, such as mobilization of calcium, modeling of bone structure, and remodeling of bone matrix. Osteoclast production is elevated in a number of pathological conditions, many of which lead to loss of bone mass. Whether normal or pathological, osteoclastogenesis strictly depends upon support from accessory cells which supply cytokines required for osteoclast differentiation. Only one of these cytokines, receptor activator of NFkappaB ligand (RANKL), is absolutely essential for osteoclast formation throughout life and is thus expressed by all cell types that support osteoclast differentiation. The central role of RANKL in bone resorption is highlighted by the fact that it is the basis for a new therapy to inhibit bone loss. This review will discuss mechanisms that control RANKL gene expression in different osteoclast-support cells and how the study of such mechanisms may lead to a better understanding of the cellular interactions that drive normal and pathological bone resorption.

Multiparameter phospho-flow analysis of lymphocytes in early rheumatoid arthritis: implications for diagnosis and monitoring drug therapy

Background

The precise mechanisms involved in the initiation and progression of rheumatoid arthritis (RA) are not known. Early stages of RA often have non-specific symptoms, delaying diagnosis and therapy. Additionally, there are currently no established means to predict clinical responsiveness to therapy. Immune cell activation is a critical component therefore we examined the cellular activation of peripheral blood mononuclear cells (PBMCs) in the early stages of RA, in order to develop a novel diagnostic modality.

Methods and Findings

PBMCs were isolated from individuals diagnosed with early RA (ERA) (n = 38), longstanding RA (n = 10), osteoarthritis (OA) (n = 19) and from healthy individuals (n = 10). PBMCs were examined for activation of 15 signaling effectors, using phosphorylation status as a measure of activation in immunophenotyped cells, by flow cytometry (phospho-flow). CD3+CD4+, CD3+CD8+ and CD20+ cells isolated from patients with ERA, RA and OA exhibited activation of multiple phospho-epitopes. ERA patient PBMCs showed a bias towards phosphorylation-activation in the CD4+ and CD20+ compartments compared to OA PBMCs, where phospho-activation was primarily observed in CD8+ cells. The ratio of phospho (p)-AKT/p-p38 was significantly elevated in patients with ERA and may have diagnostic potential. The mean fluorescent intensity (MFI) levels for p-AKT and p-H3 in CD4+, CD8+ and CD20+ T cells correlated directly with physician global assessment scores (MDGA) and DAS (disease activity score). Stratification by medications revealed that patients receiving leflunomide, systemic steroids or anti-TNF therapy had significant reductions in phospho-specific activation compared with patients not receiving these therapies. Correlative trends between medication-associated reductions in the levels of phosphorylation of specific signaling effectors and lower disease activity were observed.

Conclusions

Phospho-flow analysis identified phosphorylation-activation of specific signaling effectors in the PB from patients with ERA. Notably, phosphorylation of these signaling effectors did not distinguish ERA from late RA, suggesting that the activation status of discrete cell populations is already established early in disease. However, when the ratio of MFI values for p-AKT and p-p38 is >1.5, there is a high likelihood of having a diagnosis of RA. Our results suggest that longitudinal sampling of patients undergoing therapy may result in phospho-signatures that are predictive of drug responsiveness.

Long-term efficacy of leflunomide on disease activity and inhibition of joint damage: retrospective comparison with methotrexate for Japanese rheumatoid arthritis patients

We retrospectively compared treatment impact with leflunomide (LEF) or methotrexate (MTX) on retarding joint damage and clinical symptom including a 28-joint-count Disease Activity Score/erythrocyte sedimentation rate (DAS28-ESR) between two similar groups in patients with rheumatoid arthritis (RA) over an approximately 3-year treatment. One group included 29 patients treated with LEF alone (average dose 16.1 mg/day); the other group included 26 patients treated with MTX (average dose 7.4 mg/week) alone or combined with other disease-modifying antirheumatic drugs. At baseline, mean disease duration was 7.1 and 6.9 years, and mean DAS28-ESR was 5.79 and 5.69, respectively. The average DAS28-ESR improvement of 1.750 (from 5.79 to 4.04) in the LEF-treated group was significantly greater than the effect of 1.007 (from 5.69 to 4.68) seen in the MTX group (P = 0.0455), with the same results being observed on European League Against Rheumatism (EULAR) response criteria. Annual changes observed in Larsen score in total joints were 0.030 in the LEF group and 0.085 in the MTX group: LEF retards joint damage significantly better than MTX (P = 0.003). This inhibitory effect was better in small joints (P = 0.004) than in middle and large joints (P = 0.075). A negative correlation was noticed between improved DAS28-ESR and the progression of joint damage in the LEF group (r = -0.7068, P < 0.0001), whereas there was no correlation in the MTX group (r = -0.0311, P = 0.882). In daily clinical practice, LEF showed significant clinical and radiological improvement compared with the standard MTX regimen in Japan.

Osteoimmunology: crosstalk between the immune and bone systems

INTRODUCTION

The interaction between the immune and skeletal systems has long been acknowledged, but investigation into rheumatoid arthritis (RA) as well as the various bone phenotypes found in immunocompromised gene-deficient mice has highlighted the importance of the dynamic interplay between the two systems. This has led to the recent emergence and subsequent rapid evolution of the field of osteoimmunology. BONE DESTRUCTION WITH ARTHRITIS AS A RANKL DISEASE: In the bone destruction associated with RA, IL-17-producing helper T cells (T(H)17) play a major role by inducing receptor activator of nuclear factor-kappaB ligand (RANKL). RANKL stimulates osteoclastogenesis through nuclear factor of activated T cells cytoplasmic 1 (NFATc1), which is well known as a crucial regulator of immunity.

NEW PLAYERS IN OSTEOIMMUNOLOGY

In addition to cellular interactions via cytokines, the immune and skeletal systems share various molecules, including transcription factors, signaling molecules, and membrane receptors.

CONCLUSION

The scope of osteoimmunology has grown to encompass a wide range of molecular and cellular interactions, the elucidation of which will provide a scientific basis for future therapeutic approaches to diseases of both the immune and skeletal systems.

Osteoclasts and the immune system

Investigation into arthritis as well as the numerous bone phenotypes found in mice lacking immune-related genes has highlighted the importance of the dynamic interplay between the bone and immune systems. It has recently led to both the emergence and subsequent rapid evolution of the field of osteoimmunology. Receptor activator of nuclear factor-kappaB ligand (RANKL) stimulates osteoclastogenesis through the nuclear factor of activated T cells, cytoplasmic 1 (NFATc1), which is well known as a crucial regulator of immunity. Studies on RANKL signaling revealed various immune-related genes which are involved in the regulation of osteoclastogenesis. Bone destruction in rheumatoid arthritis is caused by the enhanced activity of osteoclasts resulting from the activation of T cells. Here we describe our efforts to address the challenging question as to how abnormal T-cell activation mechanistically induces bone destruction. The scope of osteoimmunology has been extended to encompass a wide range of molecular and cellular interactions, the elucidation of which will provide a scientific basis for future therapeutic approaches to diseases related to both the bone and immune systems.

A possible suppressive role of galectin-3 in upregulated osteoclastogenesis accompanying adjuvant-induced arthritis in rats

Galectin-3 is a beta-galactoside-binding animal lectin having pleiotropic effects on cell growth, differentiation, and apoptosis. This lectin has been shown to be involved in phagocytosis by macrophages and in inflammation. Here we investigated an involvement of galectin-3 in the regulatory process of inflammatory bone resorption in rats with adjuvant-induced arthritis (AA rats) accompanying severe bone destruction in the ankle joints. The protein level of galectin-3 in the ankle-joint extracts was markedly augmented at week 3 after adjuvant injection, at the time when severe bone destruction was observed. Immunohistochemical analysis revealed an extremely high expression of galectin-3 in macrophages and granulocytes infiltrated in the area of severe bone destruction. To estimate the role of galectin-3 in osteoclastogenesis and osteoclastic bone resorption, recombinant galectin-3 was added to in vitro culture systems. Galectin-3 markedly inhibited the formation of osteoclasts in cultures of murine osteoclast precursor cell line as well as in rat bone marrow culture systems. This inhibition was not observed by heat-inactivated galectin-3 or by galectin-7. Although recombinant galectin-3 did not affect signaling through mitogen-activated protein kinase (MAPK) or nuclear factor-kappaB (NF-kappaB), it specifically suppressed the induction of nuclear factor of activated T-cells c1 (NFATc1). Galectin-3 significantly inhibited dentine resorption by mature osteoclasts in vitro. Furthermore, in vivo studies clearly showed a significant suppression of bone destruction and osteoclast recruitment accompanying arthritis, when galectin-3 was injected into the cavity of ankle joint of AA rats. Thus, abundant galectin-3 observed in the area of severe bone destruction may act as a negative regulator for the upregulated osteoclastogenesis accompanying inflammation to prevent excess bone destruction.

The dynamic interplay between osteoclasts and the immune system

Investigation into arthritis, as well as numerous bone phenotypes found in mice lacking immune-related genes, has highlighted the importance of the interplay between the bone and immune systems, which has led to the emergence and evolution of the field of osteoimmunology. RANKL stimulates osteoclastogenesis through nuclear factor of activated T cells (NFAT) c1, which is also a crucial regulator of immunity. In rheumatoid arthritis, bone destruction is caused by the enhanced activity of osteoclasts, which is mainly dependent on interleukin-17-producing helper T cells (T(H)17). The scope of osteoimmunology has been extended to encompass a wide range of molecular and cellular interactions. The framework of osteoimmunology will provide a scientific basis for future therapeutic approaches to diseases related to both of these systems.

Selective cyclooxygenase-2 inhibitor prevents reduction of trabecular bone mass in collagen-induced arthritic mice in association with suppression of RANKL/OPG ratio and IL-6 mRNA expression in synovial tissues but not in bone marrow cells

We performed this study to clarify whether celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, prevents trabecular bone mass reduction by suppressing arthritis-related increase of bone resorption, and to discriminate differences in actions on bone among celecoxib, SC-58560 (a selective COX-1 inhibitor), and indomethacin. Eight-week-old DBA/1J male mice were divided into six groups as follows. Control untreated (Normal) and collagen-induced arthritic (CIA) mice were compared with four treatment groups: celecoxib was orally administered to CIA mice at doses of 0 (Vehicle), 16 (COX2L), and 75 (COX2H) mg/kg, in addition to two groups of mice treated with SC-58560 (COX1) or indomethacin (IND). Histomorphometry showed a significant decrease in tibial trabecular bone volume in arthritic mice, which was corrected by COX2H. The increased osteoclast surface and number in the Vehicle group were suppressed by COX2L, COX2H, and IND. The decreased bone formation rate in Vehicle was elevated by COX2H without statistical significance. A high ratio of mRNA expression of receptor activator of NF-kappaB ligand (RANKL)/osteoprotegerin (OPG) in Vehicle synovial tissue was suppressed by COX2L and COX2H. The increased expression of interleukin (IL)-6 mRNA in Vehicle was suppressed by COX2L, COX2H, and IND, although no difference in this expression was observed in bone marrow cells among all groups. In conclusion, in CIA mice, celecoxib suppresses arthritis-related increase in bone resorption at low and high doses and prevents trabecular bone mass reduction at high doses in association with suppression of osteoclast development in bone marrow through inhibition of RANKL/OPG ratio and IL-6 mRNA expression in inflammatory synovial tissue.

Osteoimmunological insight into bone damage in rheumatoid arthritis

Research into the bone destruction associated with rheumatoid arthritis has highlighted the importance of the interplay of the immune and skeletal systems. Arthritic bone destruction is attributable to the defective control of osteoclastogenesis by T cells. We revealed that excessive expression of receptor activator of NF-kappaB ligand (RANKL) and a paucity of interferon-gamma underlie the enhanced osteoclastogenesis in arthritis. The interdisciplinary research field called osteoimmunology has attracted further attention after identification of a number of unexpected bone phenotypes in mice lacking immunomodulatory molecules. Accumulating evidence suggests that the immune and skeletal systems share not only cytokines but also various signaling molecules, transcription factors, and membrane receptors. Thus, bone turns out to be a dynamic tissue that is constantly renewed, where the immune system participates to a hitherto unexpected extent. This emerging field will be of great importance for a better understanding and treatment of rheumatic diseases.

Interaction between the immune system and bone metabolism: an emerging field of osteoimmunology

The interaction between the immune and bone systems has long been appreciated, but recent research into arthritis as well as various bone phenotypes found in immune-related knockout mice has highlighted the importance of the interplay and the interdisciplinary field called osteoimmunology. In rheumatoid arthritis, IL-17-producing helper T cells (TH17) induces receptor activator of NF-κB ligand (RANKL), which stimulates osteoclast differentiation through nuclear factor of activated T cells (NFAT)c1. Accumulating evidence suggests that the immune and skeletal systems share cytokines, signaling molecules, transcription factors and membrane receptors. In addition, the immune cells are maintained in the bone marrow, which provides a space for mutual interaction. Thus, bone turns out to be a dynamic tissue that is constantly renewed, where the immune system participates to a hitherto unexpected extent. This emerging field of osteoimmunology will be of great importance not only to the better understanding of the two systems but also to the development of new treatment for rheumatic diseases.

Osteoimmunology: shared mechanisms and crosstalk between the immune and bone systems

Osteoimmunology is an interdisciplinary research field focused on the molecular understanding of the interplay between the immune and skeletal systems. Although osteoimmunology started with the study of the immune regulation of osteoclasts, its scope has been extended to encompass a wide range of molecular and cellular interactions, including those between osteoblasts and osteoclasts, lymphocytes and osteoclasts, and osteoblasts and haematopoietic cells. Therefore, the two systems should be understood to be integrated and operating in the context of the 'osteoimmune' system, a heuristic concept that provides not only a framework for obtaining new insights by basic research, but also a scientific basis for the discovery of novel treatments for diseases related to both systems.

NF-kappaB p50 and p52 regulate receptor activator of NF-kappaB ligand (RANKL) and tumor necrosis factor-induced osteoclast precursor differentiation by activating c-Fos and NFATc1

Postmenopausal osteoporosis and rheumatoid joint destruction result from increased osteoclast formation and bone resorption induced by receptor activator of NF-kappaB ligand (RANKL) and tumor necrosis factor (TNF). Osteoclast formation induced by these cytokines requires NF-kappaB p50 and p52, c-Fos, and NFATc1 expression in osteoclast precursors. c-Fos induces NFATc1, but the relationship between NF-kappaB and these other transcription factors in osteoclastogenesis remains poorly understood. We report that RANKL and TNF can induce osteoclast formation directly from NF-kappaB p50/p52 double knockout (dKO) osteoclast precursors when either c-Fos or NFATc1 is expressed. RANKL- or TNF-induced c-Fos up-regulation and activation are abolished in dKO cells and in wild-type cells treated with an NF-kappaB inhibitor. c-Fos expression requires concomitant RANKL or TNF treatment to induce NFATc1 activation in the dKO cells. Furthermore, c-Fos expression increases the number and resorptive capacity of wild-type osteoclasts induced by TNF in vitro. We conclude that NF-kappaB controls early osteoclast differentiation from precursors induced directly by RANKL and TNF, leading to activation of c-Fos followed by NFATc1. Inhibition of NF-kappaB should prevent RANKL- and TNF-induced bone resorption.

Scientific basis for the efficacy of combined use of antirheumatic drugs against bone destruction in rheumatoid arthritis

Finding a means to ameliorate and prevent bone destruction is one of the urgent issues in the treatment of rheumatoid arthritis. Recent studies revealed bone-resorbing osteoclasts to be essential for arthritic bone destruction, but to date there has been scarce experimental evidence for the underlying mechanism of the bone-protective effect of antirheumatic drugs. Here we examined the effects of one or a combination of disease-modifying antirheumatic drugs (DMARDs) on osteoclast differentiation to provide a cellular and molecular basis for their efficacy against bone destruction. The effects on osteoclast precursor cells and osteoclastogenesis-supporting cells were distinguished by two in vitro osteoclast culture systems. Methotrexate (MTX), bucillamine (Buc) and salazosulphapyridine (SASP) inhibited osteoclastogenesis by acting on osteoclast precursor cells and interfering with receptor activator of NF-kappaB ligand (RANKL)-mediated induction of the nuclear factor of activated T cells (NFAT) c1. MTX and SASP also suppressed RANKL expression on osteoclastogenesis-supporting mesenchymal cells. Interestingly, the combination of three antirheumatic drugs exerted a marked inhibitory effect on osteoclastogenesis even at a low dose at which there was much less of an effect when administered individually. These results are consistent with the reported efficacy of combined DMARDs therapy in humans and suggest that osteoclast culture systems are useful tools to provide an experimental basis for the bone-protective effects of antirheumatic drugs.

Interplay between the immune and skeletal cells in the regulation of inflammatory bone destruction

The immune and skeletal systems share a number of regulatory molecules including cytokines, signaling molecules, transcription factors and membrane receptors, in common. Consequently, the physiology and pathology of one system may very well affect the other. Research into the cartilage and bone destruction associated with rheumatoid arthritis (RA) has highlighted the importance of the interplay between the immune and skeletal systems. This interdisciplinary field called osteoimmunology has attracted much attention in recent years. Recently, animal models deficient in immunomodulatory molecules have been found frequently to develop an unexpected skeletal phenotype. Receptor activator of NF-kappaB ligand (RANKL) is an essential factor for the induction of osteoclastogenesis that links the immune and skeletal systems. Thus, osteoimmunology is becoming increasingly important for understanding the pathogenesis of bone destruction in RA and for developing new therapeutic strategies for diseases affecting both systems. Here we summarize recent advances on the study of the regulation of cartilage and bone destruction by the immune system.

Mechanisms of disease: Transcription factors in inflammatory arthritis

Studies on the pathogenesis of inflammatory arthritides have begun to delve into the molecular and cellular mechanisms behind the development of these diseases, and transcription factors, as key regulators of immune-effector-cell development and function, have received growing attention. Their involvement in immune cells, such as T and B lymphocytes, macrophages and neutrophils, and cells from diseased tissues, such as synoviocytes, has been investigated, revealing dominant roles for members of the nuclear factor kappaB family, signal-transducer and activator of transcription family, and activator protein 1 family. This review summarizes recent findings and current knowledge regarding the roles of transcription factors in inflammatory arthritis, as evidenced by both biological and genetic studies, and discusses the relevance of these findings for anti-inflammatory therapies.

Osteoclasts, rheumatoid arthritis, and osteoimmunology

PURPOSE OF REVIEW

Osteoclasts are terminally differentiated cells of the monocyte/macrophage lineage that resorb bone matrix. Bone destruction in rheumatoid arthritis is mainly attributable to the abnormal activation of osteoclasts, and studies on activation of osteoclasts by the immune system have led to the new research field called osteoimmunology. This interdisciplinary field is very important to biologic research and to the treatment of diseases associated with the bone and immune systems.

RECENT FINDINGS

The T-cell-mediated regulation of osteoclast differentiation is dependent on cytokines and membrane-bound factors expressed by T cells. The cross-talk between receptor activator of nuclear factor-kappaB ligand and interferon-gamma has been shown to be crucial for the regulation of osteoclast formation in arthritic joints. Recent studies indicate that an increasing number of immunomodulatory factors are associated with the regulation of bone metabolism: nuclear factor of activated T cells c1 has been shown to be the key transcription factor for osteoclastogenesis, the activation of which requires calcium signaling induced by the immunoglobulin-like receptors.

SUMMARY

New findings in osteoimmunology will be instrumental in the development of strategies for research into the treatment of various diseases afflicting the skeletal and immune systems.