RANKL inhibition by osteoprotegerin prevents bone loss without affecting local or systemic inflammation parameters in two rat arthritis models: comparison with anti-TNFalpha or anti-IL-1 therapies

Formulation of a dual drug-loaded nanoparticulate co-delivery hydrogel system and its validation in rheumatoid arthritis animal model

Rheumatoid arthritis (RA), a systemic autoimmune disease that dramatically affects patients' quality of life. Given the intricacy of RA's pathophysiology, no single treatment can completely halt the disease progression. Here, we attempted to treat RA holistically and synergistically by co-delivering methotrexate (MTX), a standard slow-acting anti-rheumatic drug, and phenethyl isothiocyanate (PEITC), a bioactive phytochemical, using a sodium alginate (SA)-pluronic F127 (PF-127) in situ hydrogel formulation. Therefore, in the current study, the co-delivery of MTX and PEITC in the nanoparticulate form could help enhance stability and solubility and facilitate greater penetration in the target arthritic tissues. The fabricated MTX NP and PEITC NE were found to have a minimum particle size, PDI, and good zeta potential. Results from in vitro release studies showed that MTX and PEITC were simultaneously released from the DD NP HG matrix over 6-7 days through diffusion and erosion mechanisms. An intra-articular (IA) injection of DD NP HG dramatically reduced chronic inflammation in adjuvant-induced arthritis (AIA) rats, delayed the onset of bone erosion, significantly reduced synovitis, and down-regulated the inflammatory cytokine expression. Most notably, the co-delivery strategy almost entirely restored the morphological features of the ankle joints of RA rats. The hepatic and renal function tests indicated good biological safety for DD NP HG in RA conditions. Taken together, these findings indicated that DD NP HG could achieve good anti-inflammatory activity and reverse cartilage disruption through a synergistic effect between two nanoparticulate forms of MTX and PEITC, which can effectively improve the drawbacks of their free forms.

Mechanisms of Systemic Osteoporosis in Rheumatoid Arthritis

Rheumatoid arthritis (RA), an autoimmune disease, is characterized by the presence of symmetric polyarthritis predominantly of the small joints that leads to severe cartilage and bone destruction. Based on animal and human data, the pathophysiology of osteoporosis, a frequent comorbidity in conjunction with RA, was delineated. Autoimmune inflammatory processes, which lead to a systemic upregulation of inflammatory and osteoclastogenic cytokines, the production of autoantibodies, and Th cell senescence with a presumed disability to control the systemic immune system's and osteoclastogenic status, may play important roles in the pathophysiology of osteoporosis in RA. Consequently, osteoclast activity increases, osteoblast function decreases and bone metabolic and mechanical properties deteriorate. Although a number of disease-modifying drugs to treat joint inflammation are available, data on the ability of these drugs to prevent fragility fractures are limited. Thus, specific treatment of osteoporosis should be considered in patients with RA and an associated increased risk of fragility fractures.

'SMASH' recommendations for standardised microscopic arthritis scoring of histological sections from inflammatory arthritis animal models

Animal models for inflammatory arthritides such as rheumatoid arthritis (RA) and psoriatic arthritis are widely accepted and frequently used to identify pathological mechanisms and validate novel therapeutic strategies. Unfortunately, many publications reporting on these animal studies lack detailed description and appropriate assessment of the distinct histopathological features of arthritis: joint inflammation, cartilage damage and bone erosion. Therefore, the European consortium BeTheCure, consisting of 38 academic and industrial partners from 15 countries, set as goal to standardise the histological evaluation of joint sections from animal models of inflammatory arthritis. The consensual approach of a task force including 16 academic and industrial scientists as well as laboratory technicians has resulted in the development of the Standardised Microscopic Arthritis Scoring of Histological sections (‘SMASH’) recommendations for a standardised processing and microscopic scoring of the characteristic histopathological features of arthritis, exemplified by four different rodent models for arthritis: murine collagen-induced arthritis, collagen–antibody-induced arthritis, human tumour necrosis factor transgenic Tg197 mice and rat pristane-induced arthritis, applicable to any other inflammatory arthritis model. Through standardisation, the SMASH recommendations are designed to improve and maximise the information derived from in vivo arthritis experiments and to promote reproducibility and transparent reporting on such studies. In this manuscript, we will discuss and provide recommendations for analysis of histological joint sections: identification of the regions of interest, sample preparation, staining procedures and quantitative scoring methods. In conclusion, awareness of the different features of the arthritis pathology in animal models of inflammatory arthritis is of utmost importance for reliable research outcome, and the standardised histological processing and scoring methods in these SMASH recommendations will help increase uniformity and reproducibility in preclinical research on inflammatory arthritis.

The safety profile of denosumab in oncology beyond the safety of denosumab as an anti-osteoporotic agent: still more to learn

INTRODUCTION

Initially endorsed as an antiosteoporotic agent, denosumab ‒ human monoclonal antibody inhibiting the receptor activator of nuclear factor kappa-B ligand (RANKL)‒ has currently shown an anticancer potential, rationalizing its exploitation in oncology. A prerequisite for leveraging denosumab in oncology is a favorable safety profile.

AREAS COVERED

The present review provides an overview of the adverse events of denosumab in oncology, with a focus on hypocalcemia, medication-related osteonecrosis of the jaw, atypical femoral fracture(s), post-denosumab vertebral fractures, increased risk of infections, and excess of second primary cancer. Representative studies addressing the safety and efficacy of denosumab compared to bisphosphonates in oncology are summarized. Critical gaps in the literature concerning the safety of denosumab in oncology are highlighted as opposed to plenty of available safety data on denosumab as an antiosteoporotic agent.

EXPERT OPINION

Despite the generally acceptable safety profile of denosumab in oncology, many issues remain unresolved. Further research is mandatory to counteract current challenges, namely: (i) validation of risk factors for adverse events; (ii) elucidation of the pathophysiology of the adverse events in search of actionable molecular pathways; (iii) illumination of the association of denosumab with increased risk of infections and/or second primary cancer; (iv) establishment of optimal diagnostic, and therapeutic protocols.

Celastrol Efficacy by Oral Administration in the Adjuvant-Induced Arthritis Model

Background: We previously demonstrated that celastrol has significant anti-inflammatory and bone protective effects when administered via the intraperitoneal route. For further preclinical evaluation, an effective oral administration of celastrol is crucial. Here we aimed to study the therapeutic dose range for its oral administration.

Methods: Celastrol (1–25 μg/g/day, N = 5/group) was administrated orally to female adjuvant-induced arthritis (AIA) rats after 8 days of disease induction for a period of 14 days. A group of healthy (N = 8) and arthritic (N = 15) gender- and age-matched Wistar rats was used as controls. During the treatment period, the inflammatory score, ankle perimeter, and body weight were measured. At the end of the treatment, the animals were sacrificed, blood was collected for clinical pathology, necropsy was performed with collection of internal organs for histopathological analysis, and paw samples were used for disease scoring.

Results: Doses higher than 2.5 μg/g/day of celastrol reduced the inflammatory score and ankle swelling, preserved joint structure, halted bone destruction, and diminished the number of synovial CD68+ macrophages. Bone resorption and turnover were also reduced at 5 and 7.5 μg/g/day doses. However, the dose of 7.5 μg/g/day was associated with thymic and liver lesions, and higher doses showed severe toxicity.

Conclusion: Oral administration of celastrol above 2.5 μg/g/day ameliorates arthritis. This data supports and gives relevant information for the development of a preclinical test of celastrol in the setting of a chronic model of arthritis since rheumatoid arthritis is a long-term disease.

The Use of Collagen-Induced Arthritis Animal Model on Studying Bone Metabolism

CIA is a well-studied animal model of autoimmune arthritis. It resembles rheumatoid arthritis as far as histopathological changes and molecular pathogenesis are concerned. CIA is induced by immunization with collagen type II in susceptible strains. The purpose of this review is to assess the use of CIA animal model on bone metabolism and the potential therapeutic agents that could reverse this effect. A database search from their inception to 2019 was conducted to identify experimental animal studies pertinent to CIA model and bone examination. Studies including ovariectomy or without a direct comparison between control and CIA groups were excluded. Forty-eight articles were considered suitable for inclusion. Imaging techniques, biomechanical analysis, histopathological studies, and molecular biology techniques were employed. A decrease in bone mineral density in CII arthritic animals was established. Bone loss was either periarticular, generalized or both. Although trabecular bone loss was clear, the effect on cortical bone is yet to be determined. The proposed mechanism is an imbalance between bone formation and resorption as a result of osteoclast activation. The signal pathways implicated appear to be the RANKL/RANK/OPG and the Wnt pathway. Many therapeutic targets were investigated with promising results.

Osteoprotegerin promotes islet β cell proliferation in intrauterine growth retardation rats through the PI3K/AKT/FoxO1 pathway

Osteoprotegerin (OPG) is a critical factor involved in bone metabolism. The level of OPG is increased in the serum of diabetic patients; however, there is no consensus in prior studies on the role of OPG in regulating the function of islet β cells. A rat model of intrauterine growth retardation (IUGR) was established in the present study to investigate whether OPG could enhance the proliferation of β cells; and an in vitro culture model of rat islet β cell line INS-1 was used, to confirm the effect of OPG supplementation and reveal the possible mechanism. The results showed that endogenous OPG expression was reduced and normal proliferation of β cells was impaired in the IUGR islets. Exogenous supplement of OPG restored β cell proliferation to an extent in the IUGR rats, possibly associated with regulation of the PI3K/AKT/FoxO1 signalling, as evidenced by the changes of protein expression in the pathway. Furthermore, treating rat islet INS-1 cells with a PI3K inhibitor, LY294002, blunted the effects of OPG supplement in promoting cell cycle and suppressing cell apoptosis. Taken together, the present work demonstrated that OPG supplementation could improve the proliferation of islet β cells in IUGR, and the PI3K/AKT/FoxO1 pathway is involved in the underlying mechanism.

Terpenes as possible drugs for the mitigation of arthritic symptoms - A systematic review

BACKGROUND

Arthritis is a syndrome associated with exacerbated inflammation, joint destruction and chronic pain and disability. Chronic treatment of arthritis is associated with several side effects and high abandonment. Therefore, there has been an ongoing search for alternative treatments to overcome these problems.

PURPOSE

Natural products, which are already widely used for their biological, cosmetic and pharmacotechnic properties, are a possible source for new drugs. Terpenes, a large class of organic compounds produced mainly by plants and trees, are a promising natural product and have already been shown to be effective in treating chronic pain, particularly of an inflammatory origin.

STUDY DESIGN AND METHODS

This review identifies the main terpenes with anti-arthritic activity reported in the last 10 years. A survey was conducted between December 2017 and June 2018 in the PUBMED, SCOPUS and Science Direct databases using combinations of the descriptors terpenes, arthritis and inflammation.

RESULTS

The results showed that terpenes have promising biological effects in relation to the treatment of arthritis, with the 24 terpenes identified in our survey being effective in the modulation of inflammatory mediators important to the physiopathology of arthritis, such as IL-6, IL-17, TNF-α, NFκB, and COX-2, among others. It is important to note that most of the studies used animal models, which limits, at least in part, the direct translation to humans of the experimental evidence produced by the studies.

CONCLUSION

Together, our finds suggest that terpenes can modulate the immuno-regulatory and destructive tissue events that underlie the clinical presentation and the progression of arthritis and are worthy of further clinical investigation.

Pharmacokinetic and Pharmacodynamic Considerations for Drugs Binding to Alpha-1-Acid Glycoprotein

According to the free drug hypothesis only the unbound drug is available to act at physiological sites of action, and as such the importance of plasma protein binding primarily resides in its impact on pharmacokinetics and pharmacodynamics. Of the major plasma proteins, alpha-1-acid glycoprotein (AAG) represents an intriguing one primarily due to the high affinity, low capacity properties of this protein. In addition, there are marked species and age differences in protein expression, homology and drug binding affinity. As such, a thorough understanding of drug binding to AAG can help aid and improve the translation of pharmacokinetic/pharmacodynamic (PK/PD) relationships from preclinical species to human as well as adults to neonates. This review provides a comprehensive overview of our current understanding of the biochemistry of AAG; endogenous function, impact of disease, utility as a biomarker, and impact on PK/PD. Experimental considerations are discussed as well as recommendations for understanding the potential impact of AAG on PK through drug discovery and early development.

Trichinella spiralis Infection Mitigates Collagen-Induced Arthritis via Programmed Death 1-Mediated Immunomodulation

Helminth infection induces Th2-biased immune responses and inhibitory/regulatory pathways that minimize excessive inflammation to facilitate the chronic infection of helminth in the host and in the meantime, prevent host hypersensitivity from autoimmune or atopic diseases. However, the detailed molecular mechanisms behind modulation on inflammatory diseases are yet to be clarified. Programmed death 1 (PD-1) is one of the important inhibitory receptors involved in the balance of host immune responses during chronic infection. Here, we used the murine model to examine the role of PD-1 in CD4+ T cells in the effects of Trichinella spiralis infection on collagen-induced arthritis (CIA). Mice infected with T. spiralis demonstrated higher expression of PD-1 in the spleen CD4+ T cells than those without infection. Mice infected with T. spiralis 2 weeks prior to being immunized with type II collagen displayed lower arthritis incidence and significantly attenuated pathology of CIA compared with those of uninfected mice. The therapeutic effect of T. spiralis infection on CIA was reversed by blocking PD-1 with anti-PD-1 antibody, associated with enhanced Th1/Th17 pro-inflammatory responses and reduced Th2 responses. The role of PD-1 in regulating CD4+ T cell differentiation and proliferation during T. spiralis infection was further examined in PD-1 knockout (PD-1-/-) C57BL/6 J mice. Interestingly, T. spiralis-induced alteration of attenuated Th1 and enhanced Th2/regulatory T cell differentiation in wild-type (WT) mice was effectively diminished in PD-1-/- mice characterized by recovered Th1 cytokine levels, reduced levels of Th2 and regulatory cytokines and CD4+CD25+Foxp3+ cells. Moreover, T. spiralis-induced CD4+ T cell proliferation suppression in WT mice was partially restored in PD-1-/- mice. This study introduces the first evidence that PD-1 plays a critical role in helminth infection-attenuated CIA in a mouse model by regulating the CD4+ T cell function, which may provide the new insights into the mechanisms of helminth-induced immunomodulation of host autoimmunity.

RANKL Triggers Treg-Mediated Immunoregulation in Inflammatory Osteolysis

The chronic inflammatory immune response triggered by the infection of the tooth root canal system results in the local upregulation of RANKL, resulting in periapical bone loss. While RANKL has a well-characterized role in the control of bone homeostasis/pathology, it can play important roles in the regulation of the immune system, although its possible immunoregulatory role in infectious inflammatory osteolytic conditions remains largely unknown. Here, we used a mouse model of infectious inflammatory periapical lesions subjected to continuous or transitory anti-RANKL inhibition, followed by the analysis of lesion outcome and multiple host response parameters. Anti-RANKL administration resulted in arrest of bone loss but interfered in the natural immunoregulation of the lesions observed in the untreated group. RANKL inhibition resulted in an unremitting proinflammatory response, persistent high proinflammatory and effector CD4 response, decreased regulatory T-cell (Treg) migration, and lower levels of Treg-related cytokines IL-10 and TGFb. Anti-RANKL blockade impaired the immunoregulatory process only in early disease stages, while the late administration of anti-RANKL did not interfere with the stablished immunoregulation. The impaired immunoregulation due to RANKL inhibition is characterized by increased delayed-type hypersensitivity in vivo and T-cell proliferation in vitro to the infecting bacteria, which mimic the effects of Treg inhibition, reinforcing a possible influence of RANKL on Treg-mediated suppressive response. The adoptive transfer of CD4+FOXp3+ Tregs to mice receiving anti-RANKL therapy restored the immunoregulatory capacity, attenuating the inflammatory response in the lesions, reestablishing normal T-cell response in vivo and in vitro, and preventing lesion relapse upon anti-RANKL therapy cessation. Therefore, while RANKL inhibition efficiently limited the periapical bone loss, it promoted an unremitting host inflammatory response by interfering with Treg activity, suggesting that this classic osteoclastogenic mediator plays a role in immunoregulation.

The anti-tumor effect of RANKL inhibition in malignant solid tumors - A systematic review

At present, accumulating evidence suggests that inhibition of receptor activator of nuclear factor kappa-B ligand (RANKL) does not only induce an increase in bone mass and strength, but also has anti-tumor effects. Denosumab, an antibody targeting RANKL, is used to treat osteoporosis and to prevent skeletal related events (SREs) in patients with bone metastases originating from solid tumors. However, expression of RANKL and its receptor activator of nuclear factor kappa-B (RANK) is not solely restricted to cells involved in homeostasis of the bone and RANKL-RANK signalling appears to play a substantial role in many other processes in the body like mammary physiology, mammary tumorigenesis and the immune system. In pre-clinical models, RANKL inhibition has been shown to reduce skeletal tumor burden and distant metastases as well as to decrease mammary carcinogenesis. Clinically, RANKL inhibition improves bone-metastasis free survival in patients with prostate cancer and disease-free survival in patients with breast cancer. In addition, RANKL treatment may form a preventative strategy in patients at high risk for malignancies of the breast. Current clinical studies are evaluating the effect of denosumab on survival, the immune system and other biomarkers into a greater extent. To that purpose, a systematic review of the literature was performed and a narrative review synthesized, describing the present pre-clinical and clinical evidence of an anti-tumor effect of RANKL inhibition and the potential role of the immune system as one of the underlying mechanisms.

Postmenopausal osteoporosis in rheumatoid arthritis: The estrogen deficiency-immune mechanisms link

Rheumatoid arthritis (RA) is characterized, among other factors, by systemic bone loss, reaching ~50% prevalence of osteoporosis in postmenopausal women. This is roughly a doubled prevalence in comparison with age-matched non-RA women. Postmenopausal RA women are more likely to be sero-positive for the anti-citrullinated peptide antibody (ACPA). Our extensive review of recent scientific literature enabled us to propose several mechanisms as responsible for the accelerated bone loss in ACPA(+) RA postmenopausal women. Menopause-associated estrogen deficiency plays a major role in these pathological mechanisms, as follows.

Effect of celastrol on bone structure and mechanics in arthritic rats

OBJECTIVE

Rheumatoid arthritis (RA) is characterised by chronic inflammation leading to articular bone and cartilage damage. Despite recent progress in RA management, adverse effects, lack of efficacy and economic barriers to treatment access still limit therapeutic success. Therefore, safer and less expensive treatments that control inflammation and bone resorption are needed. We have previously shown that celastrol is a candidate for RA treatment. We have observed that it inhibits both interleukin (IL)-1β and tumor necrosis factor (TNF) in vitro, and that it has anti-inflammatory properties and ability to decrease synovial CD68+ macrophages in vivo. Herein our goal was to evaluate the effect of celastrol in local and systemic bone loss.

METHODS

Celastrol was administrated intraperitoneally at a dose of 1 µg/g/day to female Wistar adjuvant-induced arthritic rats. Rats were sacrificed after 22 days of disease progression, and blood, femurs, tibiae and paw samples were collected for bone remodelling markers quantification, 3-point bending test, micro-CT analysis, nanoindentation and Fourier transform infrared spectroscopy measurements, and immunohistochemical evaluation.

RESULTS

We have observed that celastrol preserved articular structures and decreased the number of osteoclasts and osteoblasts present in arthritic joints. Moreover, celastrol reduced tartrate-resistant acid phosphatase 5b, procollagen type 1 amino-terminal propeptide and C terminal crosslinked telopeptide of type II collagen serum levels. Importantly, celastrol prevented bone loss and bone microarchitecture degradation. Celastrol also preserved bone nanoproperties and mineral content. Additionally, animals treated with celastrol had less fragile bones, as depicted by an increase in maximum load and yield displacement.

CONCLUSIONS

These results suggest that celastrol reduces both bone resorption and cartilage degradation, and preserves bone structural properties.

Osteoprotegerin Is the Strongest Predictor for Progression of Arterial Calcification in Peritoneal Dialysis Patients

BACKGROUND

Arterial calcification (AC) is frequent in patients with end stage renal disease and is also considered a risk factor for later morbidity and mortality. However, long-term factors associated with the process are not well known. We analyzed the trends over time of biomarkers related with development and progression of AC in incident patients on peritoneal dialysis (PD).

METHODS

We performed a prospective study with 186 patients on PD followed up for 1 year. We analyzed the progression of AC in the abdominal aorta and pelvic vessels by calcification score (CaSc), using16-cut computerized multidetector tomography at baseline and 1 year. Variables related with PD treatment, inflammation, and mineral metabolism were measured at baseline, 6, and 12 months of follow-up. Changes in biochemical variables were analyzed for their relationship with changes in AC.

RESULTS

Over 1 year, the number of patients with AC increased from 47 to 56%, and CaSc from 355 (interquartile range [IQR] 75-792) to 529 (IQR 185-1632). A total of 43.5% of patients remained free of calcification, 11.7% had new calcifications, and 44.8% had progression of calcification. Older age, diabetes, high systolic blood pressure, body mass index, cholesterol, and osteoprotegerin (OPG), as well as lower levels of albumin, serum creatinine, and osteocalcin, were associated with development of new, and rapid progression of, calcification. In multivariate logistic analysis, OPG remained the most significant (OR 1.27, 95% CI 1.11-1.47, p < 0.001).

CONCLUSION

OPG was the strongest risk factor associated with new development and rapid progression of AC in incident PD patients.

Rheumatoid arthritis onset in postmenopausal women: Does the ACPA seropositive subset result from genetic effects, estrogen deficiency, skewed profile of CD4(+) T-cells, and their interactions?

Rheumatoid arthritis (RA) incidence displays a differentiated age-dependent female-to-male ratio in which women outnumber men. Evidence that the peak incidence of RA in women coincides with menopause age, suggests a potential estrogenic role to disease etiology. Estrogens exert physiologically both stimulatory and inhibitory effects on the immune system. Epidemiologic and animal model studies with estrogen deprivation or supplementation suggested estrogens as to play, mainly, a protective role in RA immunopathology. In this review, we propose that some yet unidentified disturbances associated with estrogen circulating levels, differentiated by the menopausal status, play a major role in women's RA susceptibility. We focus on the interaction between estrogen deprivation and genetic risk alleles for anti-citrullinated protein antibodies (ACPA) seropositive RA, as a major driving force for increased immune reactivity and RA susceptibility, in postmenopausal women. This opens up new fields for research concerning the association among different irregular estrogenic conditions, the cytokine milieu, and age/menopausal status bias in RA.

Possibilities for preventive treatment in rheumatoid arthritis? Lessons from experimental animal models of arthritis: a systematic literature review and meta-analysis

OBJECTIVE

Current research in rheumatoid arthritis focuses on preclinical disease phases as it is hypothesised that early preclinical treatment might prevent progression to full-blown disease. Since performance of studies in prearthritis phases in humans is challenging, animal models offer an opportunity to evaluate preventive treatments. We performed a systematic literature review and summarised treatment effects during different stages of arthritis development in animal models.

METHODS

Eight medical literature databases were systematically searched. Studies were selected if they reported effects of synthetic or biological disease-modifying antirheumatic drugs in animal models of arthritis (collagen-induced arthritis and adjuvant-induced arthritis) on arthritis severity, as measured with arthritis severity scores, paw swelling or paw volume. Quality was assessed using an 11-item checklist. Study characteristics were extracted and effect sizes obtained in high-quality studies were summarised in meta-analyses. Studies were categorised into three groups: prophylactic (prior to generation of autoantibody response), prearthritis (after induction of autoantibody response) and therapeutic intervention (after arthritis development).

RESULTS

Out of 1415 screened articles, 22 studies (including n=712 animals) were eligible of good quality and included in meta-analyses. Prophylactic (16 experiments, n=312 animals) and prearthritis treatment (9 experiments, n=156 animals) both were associated with a reduction of arthritis severity (p<0.001 and p=0.005, respectively). Stratified analyses for different antirheumatic drugs initiated in the prearthritis phase suggested higher efficacy of methotrexate than of anti-tumour necrosis factor.

CONCLUSIONS

Data of experimental studies in animal models of arthritis suggest that prophylactic and prearthritis treatment strategies are effective and hint at differences in efficacy between antirheumatic drugs.

OPG rs2073617 polymorphism is associated with upregulated OPG protein expression and an increased risk of intervertebral disc degeneration

The present study aimed to investigate the associations between three distinct osteoprotegerin (OPG) gene polymorphisms and the risk of intervertebral disc degeneration (IDD). A total of 200 IDD patients and 200 healthy controls were recruited from the Department of Spine Surgery at the First Affiliated Hospital of the University of South China (Hengyang, China) between January 2013 and May 2014. The allele, genotype and haplotype frequency distributions of three OPG polymorphisms in the study and control populations were analyzed by polymerase chain reaction prior to restriction fragment length polymorphism or high resolution melting assays. In addition, serum OPG levels were measured via an ELISA. The genotype and allele frequencies of the OPG rs2073617 polymorphisms were significantly higher in the IDD patients, as compared with the control group (P<0.05). Furthermore, carriers of the C allele exhibited a higher risk of IDD, as compared with carriers of the T allele (P<0.001). Conversely, the genotype and allele frequencies of the two other gene polymorphisms, rs2073618 and rs3102735, showed no significant differences between the patients and controls (P>0.05). The serum OPG levels were significantly higher in IDD patients with TT, TC and CC genotypes at the OPG rs2073617 polymorphism, as compared with the control group (P<0.05). Logistic-regression analysis suggested that high serum levels of OPG were positively correlated with IDD risk, whereas the T-C-A, T-G-A and T-G-G haplotypes were negatively correlated with IDD risk (P<0.05). Furthermore, the G-T-G haplotype was associated with protection against IDD (P=0.008), whereas the G-C-G haplotype was associated with an elevated susceptibility to IDD (P=0.007). The results of the present study suggested that OPG rs2073617 polymorphisms and upregulated serum levels of OPG were associated with an increased risk of IDD, whereas the T-C-A, T-G-A and T-G-G haplotypes were protective factors for IDD. The results of the present study suggested that the OPG gene polymorphism may have an important role in the progression of IDD, and its serum level may function as a valuable predictive indicator of the severity of degenerative disc diseases.

Mechanistic investigations into the species differences in pinometostat clearance: impact of binding to alpha-1-acid glycoprotein and permeability-limited hepatic uptake

1. The plasma clearance of the first-in-class DOT1L inhibitor, EPZ-5676 (pinometostat), was shown to be markedly lower in human compared to the preclinical species, mouse, rat and dog. 2. This led to vertical allometry where various interspecies scaling methods were applied to the data, with fold-errors between 4 and 13. We had previously reported the elimination and metabolic pathways of EPZ-5676 were similar across species. Therefore, the aim of this work was to explore the mechanistic basis for the species difference in clearance for EPZ-5676, focusing on other aspects of disposition. 3. The protein binding of EPZ-5676 in human plasma demonstrated a non-linear relationship suggesting saturable binding at physiologically relevant concentrations. Saturation of protein binding was not observed in plasma from preclinical species. Kinetic determinations using purified serum albumin and alpha-1-acid glycoprotein (AAG) confirmed that EPZ-5676 is a high affinity ligand for AAG with a dissociation constant (K_d) of 0.24 μM. 4. Permeability limited uptake was also considered since hepatocyte CL_int was much lower in human relative to preclinical species. Passive unbound CL_int for EPZ-5676 was estimated using a correlation analysis of logD and data previously reported on seven drugs in sandwich cultured human hepatocytes. 5. Incorporation of AAG binding and permeability limited hepatic uptake into the well-stirred liver model gave rise to a predicted clearance for EPZ-5676 within 2-fold of the observed value of 1.4 mL min^-1kg^-1. This analysis suggests that the marked species difference in EPZ-5676 clearance is driven by high affinity binding to human AAG as well as species-specific hepatic uptake invoking the role of transporters.

Dendritic-cell-derived osteoclasts: a new game changer in bone-resorption-associated diseases

Bone-resorbing cells, osteoclasts (OCs), and antigen-presenting cells, dendritic cells (DCs), share several features. They are derived from a common hematopoietic precursor, exhibit phagocytic activities and their functions are dependent upon receptor activator of nuclear factor κB ligand (RANKL). Upon inflammatory conditions, DCs can transdifferentiate toward functional OCs in the presence of RANKL. It has then been assumed that the increase in proinflammatory cytokines could provide a supportive environment for this transdifferentiation. In this review, we emphasize the molecular mechanisms underlying the potential for DCs to give rise to resorbing OCs in the context of bone-destruction-associated diseases upon inflammatory conditions. Whether these mechanisms reveal new strategies for the discovery of therapeutic targets and drugs is discussed extensively.

Improvement of spontaneous locomotor activity with JAK inhibition by JTE-052 in rat adjuvant-induced arthritis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic inflammatory disease that leads to joint destruction, disability, and decreased quality of life (QOL). Inhibition of Janus kinase (JAK) signaling ameliorates articular inflammation and joint destruction in animal models of RA, but its effects on behaviors indicating well-being are poorly understood. In this study, we evaluated the effect of JAK inhibition on spontaneous locomotor activity in rats with adjuvant-induced arthritis, a rodent model of RA.

METHODS

Arthritis was induced in male Lewis rats by a single subcutaneous injection of Freund's complete adjuvant. The novel JAK inhibitor JTE-052 was orally administered for 7 days after the onset of arthritis.

RESULTS

Induction of arthritis suppressed the spontaneous locomotor activity of the rats. Administration of JTE-052 completely improved the spontaneous locomotor activity, with partial reductions in articular inflammation and joint destruction. Hyperalgesia and motor functions were also improved, but the efficacy was not complete. However, serum interleukin (IL)-6 levels were completely decreased at 4 h after administration of the first dose of JTE-052.

CONCLUSIONS

This study demonstrated that JAK inhibition improved the spontaneous locomotor activity of rats with adjuvant-induced arthritis, in association with amelioration of pain and physical dysfunction as a consequence of suppression of joint inflammation. Moreover, although further studies are needed, there was possible participation of IL-6 downregulation in the improvement of locomotor activity by JAK inhibition.

Total Saponin from Anemone flaccida Fr. Schmidt Prevents Bone Destruction in Experimental Rheumatoid Arthritis via Inhibiting Osteoclastogenesis

Anemone flaccida Fr. Schmidt is used in the clinical compound prescription for the treatment of rheumatoid arthritis (RA) in China and has the traditional use of draining dampness, diminishing swelling, and relieving pain. Total saponins (TS) are the characteristic components and also the main active ingredients of A. flaccida. Previous reports indicated that TS possess anti-inflammatory and immunoregulatory properties; however, the effects of TS on bone destruction of RA have not been evaluated. In this study, our data first showed the therapeutic effects of TS on severity of arthritis and arthritis progression in collagen-induced arthritis (CIA) rats. Then, by microfocal computed tomography (CT) quantification, TS significantly increased bone mineral density, bone volume fraction, and trabecular thickness and decreased trabecular separation of inflamed joints both at peri-articular and extra-articular locations. TS also diminished the level of the bone resorption marker CTX-I and simultaneously increased the bone formation marker osteocalcin in sera of CIA rats. Interestingly, TS prevented bone destruction by reducing the number of osteoclasts in inflamed joints, reducing the expression of receptor activator of nuclear factor-κF (RANK) ligand (RANKL) and RANK, increasing the expression of osteoprotegerin (OPG), at both mRNA and protein levels, and decreasing the ratio of RANKL to OPG in inflamed joints and sera of CIA rats. This was further confirmed in the co-culture system of human fibroblast-like synovial and peripheral blood mononuclear cells. In addition, TS inhibited the levels of pro-inflammatory cytokines implicated in bone resorption, such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNFα), IL-6, IL-17, and IL-23 in sera and joints. These findings offer convincing evidence that TS attenuate RA partially by preventing both focal bone destruction and systemic bone loss. This anti-erosive effect results in part from inhibiting osteoclastogenesis by regulating the RANKL/RANK/OPG signaling pathway. The suppression of systemic and local pro-osteoclastogenic cytokines by TS was also highly effective.

RANKL pretreatment plays an important role in the differentiation of pit-forming osteoclasts induced by TNF-α on murine bone marrow macrophages

BACKGROUND

Osteoclasts differentiated from bone marrow macrophages (BMMs) induced by TNF-α alone do not have resorbing activity. When BMMs are stimulated with receptor activator of NF-κB ligand (RANKL) before TNF-α stimulation, pit-forming osteoclasts are differentiated. However, the details of the effect of RANKL pretreatment on the pit-forming osteoclast differentiation by TNF-α have not been established. The aim of this study is to examine the condition of RANKL pretreatment for differentiation of pit-forming osteoclasts induced by TNF-α. Murine BMMs were stimulated with various concentrations of RANKL for 24h in the presence of M-CSF, then the medium was changed and TNF-α was added. Osteoclasts and pits formation were examined. Osteoprotegerin (OPG), decoy receptor of RANKL, was added to the culture to examine the necessity of co-existing RANKL with TNF-α on the formation of pit-forming osteoclasts. To investigate the influence of RANKL of sufficient concentration as pretreatment for pit-forming osteoclast formation by TNF-α, dose- and time-dependent changes of osteoclast formation were checked.

RESULTS

The pit formation by osteoclasts in response to TNF-α required 10ng/mL RANKL pretreatment. Stimulation with this concentration of RANKL led to the differentiation of mature osteoclasts in the 72h culture. The pit formation was not inhibited by the OPG.

CONCLUSION

These results suggested that the concentration of RANKL pretreatment, which also alone can differentiate BMMs into osteoclasts, may be important in the differentiation of pit-forming osteoclasts by TNF-α. In addition, the effects of TNF-α after RANKL treatment might be independent of RANKL.

RANKL expressed on synovial fibroblasts is primarily responsible for bone erosions during joint inflammation

OBJECTIVE

RANKL is mainly expressed by synovial fibroblasts and T cells within the joints of rheumatoid arthritis patients. The relative importance of RANKL expression by these cell types for the formation of bone erosions is unclear. We therefore aimed to quantify the contribution of RANKL by each cell type to osteoclast differentiation and bone destruction during inflammatory arthritis.

METHODS

RANKL was specifically deleted in T cells (Tnfsf11(flox/Δ) Lck-Cre), in collagen VI expressing cells including synovial fibroblasts (Tnfsf11(flox/Δ) Col6a1-Cre) and in collagen II expressing cells including articular chondrocytes (Tnfsf11(flox/Δ) Col2a1-Cre). Erosive disease was induced using the collagen antibody-induced arthritis (CAIA) and collagen-induced arthritis (CIA) models. Osteoclasts and cartilage degradation were assessed by histology and bone erosions were assessed by micro-CT.

RESULTS

The inflammatory joint score during CAIA was equivalent in all mice regardless of cell-targeted deletion of RANKL. Significant increases in osteoclast numbers and bone erosions were observed in both the Tnfsf11(flox/Δ) and the Tnfsf11(flox/Δ) Lck-Cre groups during CAIA; however, the Tnfsf11(flox/Δ) Col6a1-Cre mice showed significant protection against osteoclast formation and bone erosions. Similar results on osteoclast formation and bone erosions were obtained in CIA mice. The deletion of RANKL on any cell type did not prevent articular cartilage loss in either model of arthritis used.

CONCLUSIONS

The expression of RANKL on synovial fibroblasts rather than T cells is predominantly responsible for the formation of osteoclasts and erosions during inflammatory arthritis. Synovial fibroblasts would be the best direct target in RANKL inhibition therapies.

Anti-RANKL treatment improves screw fixation in cancellous bone in rats

Bisphosphonates improve implant fixation in randomised clinical trials of knee prostheses, hip prostheses and dental implants. However, a limited amount of bone resorption is required for bisphosphonates to exert an effect. Anti-RANKL treatment does not have this limitation, and we therefore tested whether if they might be more effective for improvement of implant fixation. This is of interest, as anti-RANKL treatment with denosumab is now in common clinical use. Male SD rats received a stain-less steel screw in the right proximal tibia and a drill hole in the left (n = 42). They were randomised to subcutaneous injections of either alendronate (20 μg/kg/day), alendronate (200 μg/kg/day), osteoprotegerin with an Fc tag (OPG-Fc; 8 mg/kg, twice weekly), or saline control. After 4 weeks, the fixation of the steel screw was measured by pull-out test. The tibia with the drill hole was evaluated with μCT. OPG-Fc increased the pull-out force compared to saline controls by 153% (p < 0.001). There was no significant difference between OPG-Fc and the alendronate groups. OPG-Fc increased the bone density (BV/TV) in the previous drill hole compared to controls 7-fold (p < 0.001). This increase was higher than with any alendronate dose (p < 0.001). OPG-Fc increased the bone density of the L5 vertebral body, but there was no significant difference between OPG-Fc and alendronate. Our results suggest that screw fixation in cancellous bone can be dramatically improved by an anti-RANKL agent. The effect was comparable to very high bisphosphonate doses. Screw insertion in cancellous bone elicits a metaphyseal fracture healing response, and our findings might be relevant not only for implant fixation, but also for fracture healing in cancellous bone.

Effects of antibody to receptor activator of nuclear factor κ-B ligand on inflammation and cartilage degradation in collagen antibody-induced arthritis in mice

Background

Rheumatoid arthritis (RA) is an inflammatory disease that leads to destruction of both articular cartilage and bone tissues. In rheumatic joints, synoviocytes and T-lymphocytes as well as bone cells produce the receptor activator of nuclear factor κ-B (RANK) ligand (RANKL), which binds to RANK on the surface of osteoclasts and their precursor cells to induce differentiation and activation of osteoclasts. Hence, inhibition of RANKL may be a promising approach to suppress osteolysis in RA. On the other hand, RANKL production by lymphocytes indicates the possibility that its inhibition would be effective to suppress inflammation in RA. In addition, it has been reported that cathepsin K, a predominant cysteine protease in osteoclasts, is involved in cartilage destruction in RA model mice. Here, we evaluated the effects of an anti-RANKL antibody on inflammation in footpads and degradation of articular cartilage in RA model mice.

Results

We induced arthritis in mice by injection of anti-type II collagen antibodies and lipopolysaccharide (LPS). Inhibition of RANKL by an anti-RANKL antibody (OYC1, Oriental Yeast, Tokyo, Japan) was confirmed by increased bone volume in the metaphysis of tibias. Swelling in either limb until day 14 was seen in 5 of 6 mice injected with anti-collagen antibodies and LPS without treatment with OYC1, while that was seen in 4 of 5 mice treated with OYC1. The average arthritis scores on day 14 in those groups were 2.17 and 3.00, respectively, indicating that OYC1 did not ameliorate inflammation in the limbs. Histological analyses indicated that OYC1 does not protect articular cartilage from destruction in mice with arthritis.

Conclusions

Our present study failed to show the effectiveness of an anti-RANKL antibody to ameliorate inflammation in the limbs or protect articular cartilage from degradation in a collagen antibody-induced arthritis mouse model.

Electronic supplementary material

The online version of this article (doi:10.1186/s12952-014-0018-0) contains supplementary material, which is available to authorized users.

Transglutaminase factor XIII promotes arthritis through mechanisms linked to inflammation and bone erosion

Rheumatoid arthritis is a chronic inflammatory disease characterized by synovial hyperplasia, inflammatory cell infiltration, irreversible cartilage and bone destruction, and exuberant coagulation system activity within joint tissue. Here, we demonstrate that the coagulation transglutaminase, factor XIII (fXIII), drives arthritis pathogenesis by promoting local inflammatory and tissue degradative and remodeling events. All pathological features of collagen-induced arthritis (CIA) were significantly reduced in fXIII-deficient mice. However, the most striking difference in outcome was the preservation of cartilage and bone in fXIIIA(-/-) mice concurrent with reduced osteoclast numbers and activity. The local expression of osteoclast effectors receptor activator of nuclear factor-κB ligand (RANKL) and tartrate resistant acid phosphatase were significantly diminished in CIA-challenged and even unchallenged fXIIIA(-/-) mice relative to wild-type animals, but were similar in wild-type and fibrinogen-deficient mice. Impaired osteoclast formation in fXIIIA(-/-) mice was not due to an inherent deficiency of monocyte precursors, but it was linked to reduced RANKL-driven osteoclast formation. Furthermore, treatment of mice with the pan-transglutaminase inhibitor cystamine resulted in significantly diminished CIA pathology and local markers of osteoclastogenesis. Thus, eliminating fXIIIA limits inflammatory arthritis and protects from cartilage and bone destruction in part through mechanisms linked to reduced RANKL-mediated osteoclastogenesis. In summary, therapeutic strategies targeting fXIII activity may prove beneficial in limiting arthropathies and other degenerative bone diseases.

Neurostimulation of the cholinergic anti-inflammatory pathway ameliorates disease in rat collagen-induced arthritis

INTRODUCTION

The inflammatory reflex is a physiological mechanism through which the nervous system maintains immunologic homeostasis by modulating innate and adaptive immunity. We postulated that the reflex might be harnessed therapeutically to reduce pathological levels of inflammation in rheumatoid arthritis by activating its prototypical efferent arm, termed the cholinergic anti-inflammatory pathway. To explore this, we determined whether electrical neurostimulation of the cholinergic anti-inflammatory pathway reduced disease severity in the collagen-induced arthritis model.

METHODS

Rats implanted with vagus nerve cuff electrodes had collagen-induced arthritis induced and were followed for 15 days. Animals underwent active or sham electrical stimulation once daily from day 9 through the conclusion of the study. Joint swelling, histology, and levels of cytokines and bone metabolism mediators were assessed.

RESULTS

Compared with sham treatment, active neurostimulation of the cholinergic anti-inflammatory pathway resulted in a 52% reduction in ankle diameter (p = 0.02), a 57% reduction in ankle diameter (area under curve; p = 0.02) and 46% reduction overall histological arthritis score (p = 0.01) with significant improvements in inflammation, pannus formation, cartilage destruction, and bone erosion (p = 0.02), accompanied by numerical reductions in systemic cytokine levels, not reaching statistical significance. Bone erosion improvement was associated with a decrease in serum levels of receptor activator of NF-κB ligand (RANKL) from 132±13 to 6±2 pg/mL (mean±SEM, p = 0.01).

CONCLUSIONS

The severity of collagen-induced arthritis is reduced by neurostimulation of the cholinergic anti-inflammatory pathway delivered using an implanted electrical vagus nerve stimulation cuff electrode, and supports the rationale for testing this approach in human inflammatory disorders.

Effect of sclerostin-neutralising antibody on periarticular and systemic bone in a murine model of rheumatoid arthritis: a microCT study

Introduction

Patients with chronic inflammatory diseases have increased bone loss and bone fragility and are at increased risk of fracture. Although anti-resorptive drugs are effective in blocking inflammation-induced bone loss, they are less effective at rebuilding bone. We have previously shown that treatment with sclerostin antibody (Scl-AbI) builds bone and can prevent or restore bone loss in a murine model of inflammatory bowel disease. In this study, we tested the effect of Scl-AbI in a murine model of rheumatoid arthritis (the collagen-induced arthritis model, CIA). We hypothesised that sclerostin blockade can protect and restore bone both locally and systemically without affecting progression of inflammation.

Methods

CIA was induced in male DBA/1 mice, which were treated with either PBS or Scl-AbI (10 mg/kg, weekly) prophylactically for 55 days or therapeutically for 21 days (starting 14 days post onset of arthritis). Systemic inflammation was assessed by measuring the serum concentration of anti-CII IgG1, IgG2a and IgG2b by ELISA. Changes in bone mass and structure, either at sites remote from the joints or at periarticular sites, were measured using DEXA and microCT. Bone focal erosion was assessed in microCT scans of ankle and knee joints.

Results

Circulating anti-CII immunoglobulins were significantly elevated in mice with CIA and there were no significant differences in the levels of anti-CII immunoglobulins in mice treated with PBS or Scl-ABI. Prophylactic Scl-AbI treatment prevented the decrease in whole body bone mineral density (BMD) and in the bone volume fraction at axial (vertebral body) and appendicular (tibial proximal metaphysis trabecular and mid-diaphysis cortical bone) sites seen in PBS-treated CIA mice, but did not prevent the formation of focal bone erosions on the periarticular bone in the knee and ankle joints. In the therapeutic study, Scl-AbI restored BMD and bone volume fraction at all assessed sites but was unable to repair focal erosions.

Conclusions

Sclerostin blockade prevented or reversed the decrease in axial and appendicular bone mass in the murine model of rheumatoid arthritis, but did not affect systemic inflammation and was unable to prevent or repair local focal erosion.

The Role of Oral Pathobionts in Dysbiosis during Periodontitis Development

An emerging concept is the tight relationship between dysbiosis (microbiota imbalance) and disease. The increase in knowledge about alterations in microbial communities that reside within the host has made a strong impact not only on dental science, but also on immunology and microbiology as well as on our understanding of several diseases. Periodontitis is a well-characterized human disease associated with dysbiosis, characterized by the accumulation of multiple bacteria that play individual and critical roles in bone loss around the teeth. Dysbiosis is largely dependent on cooperative and competitive interactions among oral microbes during the formation of the pathogenic biofilm community at gingival sites. Oral pathobionts play different and synergistic roles in periodontitis development, depending on their host-damaging and immunostimulatory activities. Host immune responses to oral pathobionts act as a double-edged sword not only by protecting the host against pathobionts, but also by promoting alveolar bone loss. Recent studies have begun to elucidate the roles of individual oral bacteria, including a new type of pathobionts that possess strong immunostimulatory activity, which is critical for alveolar bone loss. Better understanding of the roles of oral pathobionts is expected to lead to a better understanding of periodontitis disease and to the development of novel preventive and therapeutic approaches for the disease.

A clinical therapeutic protein drug-drug interaction study: coadministration of denosumab and midazolam in postmenopausal women with osteoporosis

Drug–disease interactions involving therapeutic proteins that target cytokines and potentially impact cytochrome P450 (CYP) enzymes have been of increased interest to drug regulatory agencies and industry sponsors in recent years. This parallel-group open-label study evaluated the effects of the monoclonal antibody denosumab, an inhibitor of the cytokine RANKL, on the pharmacokinetics of the probe CYP3A4 substrate midazolam in postmenopausal women with osteoporosis. The pharmacokinetics of a 2 mg oral dose of midazolam was evaluated on days 1 and 16. Subjects in Group A received a 60 mg subcutaneous dose of denosumab on day 2, 2 weeks before the second midazolam dose, while subjects in Group B did not. For Group A (n = 17), point estimates for the ratio of least square means for midazolam exposures based on maximum observed plasma concentration (C_max) and areas under the plasma concentration–time curve (AUCs) on day 16 versus day 1 ranged from 1.02 to 1.04 and 90% confidence intervals were within 0.80–1.25. No period effect was observed for Group B (n = 8). Midazolam and denosumab coadministration was safe and well tolerated. Inhibition of the cytokine RANKL by denosumab does not affect CYP3A4 in postmenopausal women with osteoporosis and will not alter the pharmacokinetics of drugs metabolized by this enzyme. These results are consistent with data suggesting that RANKL does not impact markers of inflammation and represent the first clinical data demonstrating a lack of effect on CYP3A4 of a therapeutic protein that is a cytokine modulator.

IL-17A-mediated sRANK ligand elevation involved in postmenopausal osteoporosis

The role of proinflammatory IL-17 cytokine was studied in postmenopausal bone loss between 31 osteopenic and 41 osteoporotic women. The effect of serum IL-17A, soluble receptor activator of NF-κB (sRANK) ligand, and osteoprotegerin (OPG) levels on lumbar bone mineral densities was measured. The results demonstrated an increased IL-17A-mediated sRANK ligand elevation in postmenopausal osteoporotic bone loss.

INTRODUCTION

IL-17 proinflammatory cytokine is a new inducer of bone loss. Postmenopausal osteoporosis represents a cross talk between estrogen deprivation and increased immune reactivity. The role of IL-17 was studied in the bone loss of postmenopausal osteoporosis.

METHODS

Serum IL-17A, sRANK ligand, and OPG levels were investigated on bone mineral densities (BMDs) in the total lumbar (L1-L4) region in 18 pre- and 72 postmenopausal women. IL-17A, sRANK ligand, OPG levels, and BMDs were measured with enzyme-linked immunosorbent assay (ELISA) and dual-energy X-ray absorptiometry (DXA).

RESULTS

Increased serum IL-17A, sRANK ligand, and OPG levels were demonstrated in postmenopausal osteoporotic women compared to osteopenic women (3.65 ± 0.61 vs 3.31 ± 0.43 ng/ml for IL-17A, P < 0.007; 2.88 ± 0.84 vs 2.49 ± 0.61 ng/ml for sRANK ligand, P < 0.027; and 1.43 ± 0.07 vs 1.39 ± 0.07 ng/ml for OPG, P < 0.038). In postmenopausal women, IL-17A levels correlated inversely with total lumbar BMDs (P < 0.008, r = -0.279) and positively with sRANK ligand levels (P < 0.0001, r = 0.387) or the ratio of sRANK ligand and OPG (P < 0.013, r = 0.261), but did not with OPG levels alone.

CONCLUSION

Increased IL-17A levels are involved in postmenopausal osteoporosis, playing a role in the bone-resorpting processes.

Bone effects of biologic drugs in rheumatoid arthritis

Biologic agents used in the treatment of rheumatoid arthritis (RA) are able to reduce both disease activity and radiographic progression of joint disease. These drugs are directed against several proinflammatory cytokines (TNF α , IL-6, and IL-1) which are involved both in the pathogenesis of chronic inflammation and progression of joint structural damage and in systemic and local bone loss typically observed in RA. However, the role of biologic drugs in preventing bone loss in clinical practice has not yet clearly assessed. Many clinical studies showed a trend to a positive effect of biologic agents in preventing systemic bone loss observed in RA. Although the suppression of inflammation is the main goal in the treatment of RA and the anti-inflammatory effects of biologic drugs exert a positive effect on bone metabolism, the exact relationship between the prevention of bone loss and control of inflammation has not been clearly established, and if the available biologic drugs against TNF α , IL-1, and IL-6 can exert their effect on systemic and local bone loss also through a direct mechanism on bone cell metabolism is still to be clearly defined.

Osteoprotegerin reduces the development of pain behaviour and joint pathology in a model of osteoarthritis

BACKGROUND

Increased subchondral bone turnover may contribute to pain in osteoarthritis (OA).

OBJECTIVES

To investigate the analgesic potential of a modified version of osteoprotegerin (osteoprotegerin-Fc (OPG-Fc)) in the monosodium iodoacetate (MIA) model of OA pain.

METHODS

Male Sprague Dawley rats (140-260 g) were treated with either OPG-Fc (3 mg/kg, subcutaneously) or vehicle (phosphate-buffered saline) between days 1 and 27 (pre-emptive treatment) or days 21 and 27 (therapeutic treatment) after an intra-articular injection of MIA (1 mg/50 µl) or saline. A separate cohort of rats received the bisphosphonate zoledronate (100 µg/kg, subcutaneously) between days 1 and 25 post-MIA injection. Incapacitance testing and von Frey (1-15 g) hind paw withdrawal thresholds were used to assess pain behaviour. At the end of the study, rats were killed and the knee joints and spinal cord removed for analysis. Immunohistochemical studies using Iba-1 and GFAP quantified levels of activation of spinal microglia and astrocytes, respectively. Joint sections were stained with haematoxylin and eosin or Safranin-O fast green and scored for matrix proteoglycan and overall joint morphology. The numbers of tartrate-resistant acid phosphatase-positive osteoclasts were quantified. N=10 rats/group.

RESULTS

Pre-emptive treatment with OPG-Fc significantly attenuated the development of MIA-induced changes in weightbearing, but not allodynia. OPG-Fc decreased osteoclast number, inhibited the formation of osteophytes and improved structural pathology within the joint similarly to the decrease seen after pretreatment with the bisphosphonate, zoledronate. Therapeutic treatment with OPG-Fc decreased pain behaviour, but did not improve pathology in rats with established joint damage.

CONCLUSIONS

Our data suggest that early targeting of osteoclasts may reduce pain associated with OA.

NSAIDs can have adverse effects on bone healing

The science of osteoimmunology, a relatively new field of research, reveals the important interactions between the immune system and skeletal system. Interactions occur between prostaglandin metabolism, inflammatory proteins and bone metabolism. Systemic as well as local sources of inflammation appear to be actively involved in both bone formation and resorption. Non Steroidal Anti-Inflammatory Drugs (NSAIDs) can play a detrimental role in bone fractures, opposing the aim of the intervention, and can have such a negative impact on the synthesis of prostaglandins that they could even promote bone resorption. When used for a prolonged time, NSAIDs can also cause the development of an inflammatory cascade starting from the gastro-intestinal system, possibly resulting in bone resorption. Several studies show that the use of either selective or non-selective NSAIDs are intimately related to disturbances in immunological allostasis, bone metabolism and the inhibition or impediment of bone healing.

The role of interleukin-1β in arthritic pain: main involvement in thermal, but not mechanical, hyperalgesia in rat antigen-induced arthritis

OBJECTIVE

Interleukin-1β (IL-1β) is considered a pronociceptive cytokine, but its role in the generation of arthritic pain is unknown. The aim of this study was to investigate the role of IL-1β in arthritic pain and to explore the antinociceptive potential of the IL-1 receptor type I (IL-1RI) antagonist anakinra.

METHODS

Antigen-induced arthritis (AIA) was induced in rats. Expression of IL-1RI in the dorsal root ganglia (DRGs) was determined, and the effects of anakinra on inflammation, pain-related behavior, and receptor expression were assessed. In cultured DRG neurons, the effect of IL-1β on the expression of the transient receptor potential vanilloid 1 (TRPV-1) ion channel was examined. Recordings of action potentials from joint nociceptors were made after intraarticular injection of IL-1β into the rat knee joints.

RESULTS

AIA generated pronounced and persistent mechanical and thermal hyperalgesia, and IL-1RI expression in the lumbar DRGs was significantly up-regulated. Treatment with anakinra did not significantly reduce the severity of arthritis or mechanical hyperalgesia, but did result in a pronounced reduction in thermal hyperalgesia. In cultured DRG neurons, IL-1β up-regulated the expression of TRPV-1, a major transduction molecule involved in thermal hyperalgesia. During AIA, anakinra treatment down-regulated the expression of TRPV-1, consistent with the pronounced reduction in thermal hyperalgesia. IL-1β increased the mechanosensitivity of C-fibers of the joint, but reduced the mechanosensitivity of Aδ-fibers, thus having opposite effects on these mechanonociceptive nerve fibers.

CONCLUSION

In the context of arthritic knee pain, IL-1β and IL-1 receptors appear to be involved in thermal, rather than mechanical, hyperalgesia. Therefore, neutralization of IL-1β may be mainly antinociceptive in disease states characterized by thermal hyperalgesia, but not in disease states mainly characterized by mechanical hyperalgesia.

Triptolide Prevents Bone Destruction in the Collagen-Induced Arthritis Model of Rheumatoid Arthritis by Targeting RANKL/RANK/OPG Signal Pathway

Focal bone destruction within inflamed joints is the most specific hallmark of rheumatoid arthritis (RA). Our previous study indicated that the therapeutic efficiency of triptolide in RA may be due partially to its chondroprotective and anti-inflammatory effects. However, its roles in bone destruction are still unclear. In this study, our data firstly showed the therapeutic effects of triptolide on severity of arthritis and arthritis progression in collagen-induced arthritis (CIA) mice. Then, by micro-CT quantification, triptolide treatment significantly increased bone mineral density, bone volume fraction, and trabecular thickness and decreased trabecular separation of inflamed joints. Interestingly, triptolide treatment could prevent the bone destruction by reducing the number of osteoclasts in inflamed joints, reducing the expression of receptor activator of NF-κB (RANK) ligand (RANKL) and RANK, increasing the expression of osteoprotegerin (OPG), at both mRNA and protein levels, and decreasing the ratio of RANKL to OPG in sera and inflamed joints of CIA mice, which were further confirmed in the coculture system of human fibroblast-like synovial and peripheral blood mononuclear cells. These findings offer the convincing evidence for the first time that triptolide may attenuate RA partially by preventing the bone destruction and inhibit osteoclast formation by regulating RANKL/RANK/OPG signal pathway.

Advances in osteoimmunology: pathophysiologic concepts and treatment opportunities

Osteoimmunology is an emerging research area that deals with the mutual interactions between bone and the immune system. Osteoclasts have long been the center of attention in osteoimmunological research due to their hematopoietic origin and strong activation through cytokines. However, also the osteoclast's opponent - the osteoblast - has recently sought the spotlight, and novel functions of its descendant - the osteocyte - have been unraveled. A considerable number of investigations carried out over the past decade have identified critical proteins with osteoimmune functions including the pro-osteoclastic cytokine receptor activator of NF-ĸB ligand and inhibitors of the pro-osteoblastic Wnt signaling pathway. These discoveries have also led to the development of targeted therapies to counteract not only inflammation-induced bone loss but also postmenopausal osteoporosis and osteoporosis associated with aging.

The natural flavonoid galangin inhibits osteoclastic bone destruction and osteoclastogenesis by suppressing NF-κB in collagen-induced arthritis and bone marrow-derived macrophages

We investigated the effect of galangin, a natural flavonoid, on osteoclastic bone destruction in collagen-induced arthritis and examined the molecular mechanisms by which galangin affects osteoclastogenesis in bone marrow derived macrophages. In mice with collagen-induced arthritis, administration of galangin significantly reduced the arthritis clinical score, edema and severity of disease without toxicity. Interestingly, galangin treatment during a later stage of collagen-induced arthritis, using mice with a higher clinical arthritis score, still significantly slowed the progression of the disease. Extensive cartilage and bone erosive changes as well as synovial inflammation, synovial hyperplasia and pannus formation were dramatically inhibited in arthritic mice treated with galangin. Furthermore, galangin-treated arthritic mice showed a significant reduction in the concentrations of IL-1β, TNF-α and IL-17. We found that galangin inhibited osteoclastogenic factors and osteoclast formation in bone marrow-derived macrophages and osteoblast co-cultured cells, and increased osteoprotegerin (OPG) levels in osteoblasts. Galangin and NF-κB siRNA suppressed RANKL-induced phosphorylation of the c-jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), but not AKT and extracellular signal-regulated kinase 1/2 (ERK1/2). Also, the JNK inhibitor SP600125 and p38 inhibitor SB203580 reduced RANKL-induced expressions of phospho-c-Jun, c-fos and NFATc1 genes during osteoclast development. In addition, galangin suppressed RANKL-induced phosphorylation of NF-κB, phospho-IκBα, inflammatory cytokines and osteoclast formation in bone marrow-derived macrophages. Our data suggest that galangin prevented osteoclastic bone destruction and osteoclastogenesis in osteoclast precursors as well as in collagen-induced arthritis mice without toxicity via attenuation of RANKL-induced activation of JNK, p38 and NF-κB pathways.

Inhibition of osteoclastogenesis by RNA interference targeting RANK

Background

Osteoclasts and osteoblasts regulate bone resorption and formation to allow bone remodeling and homeostasis. The balance between bone resorption and formation is disturbed by abnormal recruitment of osteoclasts. Osteoclast differentiation is dependent on the receptor activator of nuclear factor NF-kappa B (RANK) ligand (RANKL) as well as the macrophage colony-stimulating factor (M-CSF). The RANKL/RANK system and RANK signaling induce osteoclast formation mediated by various cytokines. The RANK/RANKL pathway has been primarily implicated in metabolic, degenerative and neoplastic bone disorders or osteolysis. The central role of RANK/RANKL interaction in osteoclastogenesis makes RANK an attractive target for potential therapies in treatment of osteolysis. The purpose of this study was to assess the effect of inhibition of RANK expression in mouse bone marrow macrophages on osteoclast differentiation and bone resorption.

Methods

Three pairs of short hairpin RNAs (shRNA) targeting RANK were designed and synthesized. The optimal shRNA was selected among three pairs of shRNAs by RANK expression analyzed by Western blot and Real-time PCR. We investigated suppression of osteoclastogenesis of mouse bone marrow macrophages (BMMs) using the optimal shRNA by targeting RANK.

Results

Among the three shRANKs examined, shRANK-3 significantly suppressed [88.3%] the RANK expression (p < 0.01). shRANK-3 also brought about a marked inhibition of osteoclast formation and bone resorption as demonstrated by tartrate–resistant acid phosphatase (TRAP) staining and osteoclast resorption assay. The results of our study show that retrovirus-mediated shRANK-3 suppresses osteoclast differentiation and osteolysis of BMMs.

Conclusions

These findings suggest that retrovirus-mediated shRNA targeting RANK inhibits osteoclast differentiation and osteolysis. It may appear an attractive target for preventing osteolysis in humans with a potential clinical application.