Histamine and Histamine H4 Receptor Promotes Osteoclastogenesis in Rheumatoid Arthritis

Effects of the DL76 Antagonist/Inverse Agonist of Histamine H3 Receptors on Experimental Periodontitis in Rats: Morphological Studies

BACKGROUND

Periodontitis preceded by gingivitis is the most common form of periodontal disease and occurs due to the interaction of microorganisms present in the complex bacterial aggregates of dental plaque biofilm and their metabolism products with periodontal tissues. Histamine is a heterocyclic biogenic amine acting via four types of receptors. Histamine H3 receptors act as presynaptic auto/heteroreceptors to regulate the release of histamine and other neurotransmitters.

AIM

Since the nervous system is able to regulate the progression of the inflammatory process and bone metabolism, the aim of this study was to investigate the effects of DL76, which acts as an antagonist/inverse agonist of H3 receptors, on the course of experimental periodontitis.

MATERIALS AND METHODS

This study was conducted in 24 mature male Wistar rats weighing 245-360 g, aged 6-8 weeks. A silk ligature was placed on the second maxillary molar of the right maxilla under general anesthesia. From the day of ligating, DL76 and 0.9% NaCl solutions were administered subcutaneously for 28 days in the experimental and control groups, respectively. After the experiment, histopathological, immunohistochemical and radiological examinations were performed.

RESULTS

Ligation led to the development of the inflammatory process with lymphocytic infiltration, increased epithelial RANKL and OPG expression as well as bone resorption. DL76 evoked a reduction in (1) lymphocytic infiltration, (2) RANKL and OPG expression as well as (3) bone resorption since the medians of the mesial and distal interdental spaces in the molars with induced periodontitis were 3.56-fold and 10-fold lower compared to the corresponding values in saline-treated animals with periodontitis.

CONCLUSION

DL76 is able to inhibit the progression of experimental periodontitis in rats, as demonstrated by a reduction in the inflammatory cell infiltration, a decrease in the RANKL/RANK OPG pathway expression and a reduction in the alveolar bone resorption.

Exploring the significance of microbiota metabolites in rheumatoid arthritis: uncovering their contribution from disease development to biomarker potential

Rheumatoid arthritis (RA) is a multifaceted autoimmune disorder characterized by chronic inflammation and joint destruction. Recent research has elucidated the intricate interplay between gut microbiota and RA pathogenesis, underscoring the role of microbiota-derived metabolites as pivotal contributors to disease development and progression. The human gut microbiota, comprising a vast array of microorganisms and their metabolic byproducts, plays a crucial role in maintaining immune homeostasis. Dysbiosis of this microbial community has been linked to numerous autoimmune disorders, including RA. Microbiota-derived metabolites, such as short-chain fatty acids (SCFAs), tryptophan derivatives, Trimethylamine-N-oxide (TMAO), bile acids, peptidoglycan, and lipopolysaccharide (LPS), exhibit immunomodulatory properties that can either exacerbate or ameliorate inflammation in RA. Mechanistically, these metabolites influence immune cell differentiation, cytokine production, and gut barrier integrity, collectively shaping the autoimmune milieu. This review highlights recent advances in understanding the intricate crosstalk between microbiota metabolites and RA pathogenesis and also discusses the potential of specific metabolites to trigger or suppress autoimmunity, shedding light on their molecular interactions with immune cells and signaling pathways. Additionally, this review explores the translational aspects of microbiota metabolites as diagnostic and prognostic tools in RA. Furthermore, the challenges and prospects of translating these findings into clinical practice are critically examined.

Comprehensive analysis revealed the immunoinflammatory targets of rheumatoid arthritis based on intestinal flora, miRNA, transcription factors, and RNA-binding proteins databases, GSEA and GSVA pathway observations, and immunoinfiltration typing

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic inflammatory arthritis. This study aimed to identify potential biomarkers and possible pathogenesis of RA using various bioinformatics analysis tools.

METHODS

The GMrepo database provided a visual representation of the analysis of intestinal flora. We selected the GSE55235 and GSE55457 datasets from the Gene Expression Omnibus database to identify differentially expressed genes (DEGs) separately. With the intersection of these DEGs with the target genes associated with RA found in the GeneCards database, we obtained the DEGs targeted by RA (DERATGs). Subsequently, Disease Ontology, Gene Ontology, and the Kyoto Encyclopedia of Genes and Genomes were used to analyze DERATGs functionally. Gene Set Enrichment Analysis (GSEA) and Gene Set Variation Analysis (GSVA) were performed on the data from the gene expression matrix. Additionally, the protein-protein interaction network, transcription factor (TF)-targets, target-drug, microRNA (miRNA)-mRNA networks, and RNA-binding proteins (RBPs)-DERATGs correlation analyses were built. The CIBERSORT was used to evaluate the inflammatory immune state. The single-sample GSEA (ssGSEA) algorithm and differential analysis of DERATGs were used among the infiltration degree subtypes.

RESULTS

There were some correlations between the abundance of gut flora and the prevalence of RA. A total of 54 DERATGs were identified, mainly related to immune and inflammatory responses and immunodeficiency diseases. Through GSEA and GSVA analysis, we found pathway alterations related to metabolic regulations, autoimmune diseases, and immunodeficiency-related disorders. We obtained 20 hub genes and 2 subnetworks. Additionally, we found that 39 TFs, 174 drugs, 2310 miRNAs, and several RBPs were related to DERATGs. Mast, plasma, and naive B cells differed during immune infiltration. We discovered DERATGs' differences among subtypes using the ssGSEA algorithm and subtype grouping.

CONCLUSIONS

The findings of this study could help with RA diagnosis, prognosis, and targeted molecular treatment.

Lipoxygenase inhibitory synthetic derivatives of methyl gallate regulate gene expressions of COX-2 and cytokines to reduce animal model arthritis

Mammalian lipoxygenases (LOXs) are involved in the biosynthesis of mediators of anaphylactic reactions and have been implicated in cell maturation, the pathogenesis of bronchial asthma, atherosclerosis, rheumatoid arthritis, cardiovascular diseases, Alzheimer's disease and osteoporosis. Hence LOX inhibition in chronic conditions can lead to reducing the disease progression, which can be a good target for treating these diseases. The present study deals with designing methyl gallate derivatives and their anti-inflammatory effect by in silico, in vitro and in vivo methods. Designed derivatives were docked against LOX enzyme, and molecular dynamic simulations were carried out. Following the synthesis of derivatives, in vitro LOX inhibition assay, enzyme kinetics and fluorescence quenching studies were performed. One of the derivatives of methyl gallate (MGSD 1) was demonstrated as an anti-inflammatory agent for the treatment of rheumatoid arthritis in the animal model. Amelioration of Freund's complete adjuvant (FCA)-induced arthritis by methyl gallate and its derivative with a concentration of 10-40 mg.kg-1 has been assessed in vivo in a 28-day-long study. TNF-α and COX-2 gene expression were also studied. Methyl gallate synthetic derivatives (MGSDs) inhibited LOX with an IC50 of 100 nM, 304 nM, and 226 nM for MGSD 1, MGSD 2, and MGSD 3, respectively. Fluorescence quenching methods also prove their binding characteristics, and 200 ns simulations studies showed that the RMSDs for the entire complex were less than 2.8 Å. The in vivo results showed that methyl gallate was required approximately five times diclofenac for the same level of effect, and the synthesised (MGSD 1) compound required only approximately 1/12 of diclofenac for the same level of effect in in-vivo studies. The preeminent expression of COX-2 and TNF-α genes was significantly decreased after the treatment of the methyl gallate derivative. Hence, the in vivo results showed that the referenced synthetic derivative might have more arthritis-reducing properties than the parent compound methyl gallate and is more potent than the standard drug diclofenac, with no apparent induced toxicity.

Bone and Cytokine Markers Associated With Bone Disease in Systemic Mastocytosis

BACKGROUND

Mastocytosis encompasses a heterogeneous group of diseases characterized by tissue accumulation of clonal mast cells, which frequently includes bone involvement. Several cytokines have been shown to play a role in the pathogenesis of bone mass loss in systemic mastocytosis (SM), but their role in SM-associated osteosclerosis remains unknown.

OBJECTIVE

To investigate the potential association between cytokine and bone remodeling markers with bone disease in SM, aiming at identifying biomarker profiles associated with bone loss and/or osteosclerosis.

METHODS

A total of 120 adult patients with SM, divided into 3 age and sex-matched groups according to their bone status were studied: (1) healthy bone (n = 46), (2) significant bone loss (n = 47), and (3) diffuse bone sclerosis (n = 27). Plasma levels of cytokines and serum baseline tryptase and bone turnover marker levels were measured at diagnosis.

RESULTS

Bone loss was associated with significantly higher levels of serum baseline tryptase (P = .01), IFN-γ (P = .05), IL-1β (P = .05), and IL-6 (P = .05) versus those found in patients with healthy bone. In contrast, patients with diffuse bone sclerosis showed significantly higher levels of serum baseline tryptase (P < .001), C-terminal telopeptide (P < .001), amino-terminal propeptide of type I procollagen (P < .001), osteocalcin (P < .001), bone alkaline phosphatase (P < .001), osteopontin (P < .01), and the C-C Motif Chemokine Ligand 5/RANTES chemokine (P = .01), together with lower IFN-γ (P = .03) and RANK-ligand (P = .04) plasma levels versus healthy bone cases.

CONCLUSIONS

SM with bone mass loss is associated with a proinflammatory cytokine profile in plasma, whereas diffuse bone sclerosis shows increased serum/plasma levels of biomarkers related to bone formation and turnover, in association with an immunosuppressive cytokine secretion profile.

Untargeted metabolomics reveals the effect of rearing systems on bone quality parameters in chickens

The objective of this study was to investigate the effects of rearing systems on the bone quality parameters in chickens using a metabolomics strategy. A total of 419 male one-day-old chicks were randomly allocated to two groups, a floor rearing group (FRG, n = 173) and a cage rearing group (CRG, n = 246). At 6, 8, 10, and 12 weeks of age, all chickens were radiographed by a digital X-ray machine, and body weight was recorded. At 12 weeks of age, 12 birds were selected from each group to obtain tibia and femur, and bone quality parameters of bone mineral density (BMD), mineral content (BMC), breaking strength (BBS), stiffness, Young's modulus (YM), ash content, calcium content, and phosphorus content were determined. An untargeted metabolomics assay was performed to identify changes in the serum metabolic profile (n = 8 birds/group). The results showed that cage-reared chickens had wider tibiae and greater body weight compared with floor-reared chickens. There were no significant differences in BMC or BBS between the two groups (p > 0.05), but BMD, ash content, calcium content, and phosphorus content of the tibia and femur of FRG were significantly higher than those of CRG (p < 0.05). Greater stiffness and YM of the femur were also observed in birds raised in the FRG compared with those raised in the CRG (p < 0.05). Taken together, the results suggest that rearing systems affected bone quality parameters. Furthermore, 148 and 149 differential metabolites were identified in positive and negative ion modes by LC-MS/MS analysis, among which 257 metabolites were significantly correlated with 16 bone quality parameters, including leucine, myristoleic acid, glycocholic acid, and N-phenylacetamide. KEGG analysis indicated that 15 metabolic pathways, including six pathways of amino acid metabolism, two pathways of lipid metabolism, and two pathways of carbohydrate metabolism, were responsible for bone quality. Overall, the present study demonstrated the effect of rearing systems on bone quality parameters, and identified several metabolites and metabolic pathways associated with bone quality parameters.

Unraveling the venom chemistry with evidence for histamine as key regulator in the envenomation by caterpillar Automeris zaruma

Over the past decades, envenomation by caterpillars of Automeris spp. became an increasing health problem in Latin America. Accidental contact with the stinging spines of these caterpillars cause acute local pain, itching, inflammation and skin rashes that persists for days. Even when the cause is obvious, the exact molecular mechanisms responsible for the observed symptoms are yet to be elucidated. Here, we describe for the first time, an active compound in the venom and the study of the bioactivity of the venom extracted from the spines of the caterpillar Automeris zaruma. Electrophysiological screening of a library of membrane proteins important for pain and itch enabled us to investigate and reveal the mode of action of the venom of A. zaruma. Further mass spectrometric analysis (Q-TOF-MS) made it possible to establish a link between the bioactivity and the components found in the venom. We show that the spine extract of A. zaruma contains histamine that potently activates the four types of the human histamine receptors (H1R, H2R, H3R and H4R) with a selectivity preference towards H3R and H4R. Furthermore, a modulation of the target MRGPRX2 was found. Together, these findings are the first to explain the symptomology of A. zaruma envenomation, enabling us a better understanding of caterpillar envenomation and predict that the hurdle of the scarce efficacy of the currently used antihistaminic drugs can be overcome by including H3R and H4R blockers in the clinical used medication. Such an approach might be used for other caterpillar envenomation in the world and represent a significant improvement for the well-being of the patient.

Metabolic discrimination of synovial fluid between rheumatoid arthritis and osteoarthritis using gas chromatography/time-of-flight mass spectrometry

INTRODUCTION

Rheumatoid arthritis (RA) and osteoarthritis (OA) are clinicopathologically different.

OBJECTIVES

We aimed to assess the feasibility of metabolomics in differentiating the metabolite profiles of synovial fluid between RA and OA using gas chromatography/time-of-flight mass spectrometry.

METHODS

We first compared the global metabolomic changes in the synovial fluid of 19 patients with RA and OA. Partial least squares-discriminant, hierarchical clustering, and univariate analyses were performed to distinguish metabolites of RA and OA. These findings were then validated using synovial fluid samples from another set of 15 patients with RA and OA.

RESULTS

We identified 121 metabolites in the synovial fluid of the first 19 samples. The score plot of PLS-DA showed a clear separation between RA and OA. Twenty-eight crucial metabolites, including hypoxanthine, xanthine, adenosine, citrulline, histidine, and tryptophan, were identified to be capable of distinguishing RA metabolism from that of OA; these were found to be associated with purine and amino acid metabolism.

CONCLUSION

Our results demonstrated that metabolite profiling of synovial fluid could clearly discriminate between RA and OA, suggesting that metabolomics may be a feasible tool to assist in the diagnosis and advance the comprehension of pathological processes for diseases.

Molecular and Cellular Heterogeneity in Rheumatoid Arthritis: Mechanisms and Clinical Implications

Rheumatoid arthritis is an autoimmune disease that exhibits significant clinical heterogeneity. There are various treatments for rheumatoid arthritis, including disease-modifying anti-rheumatic drugs (DMARDs), glucocorticoids, non-steroidal anti-inflammatory drugs (NSAIDs), and inflammatory cytokine inhibitors (ICI), typically associated with differentiated clinical effects and characteristics. Personalized responsiveness is observed to the standard treatment due to the pathophysiological heterogeneity in rheumatoid arthritis, resulting in an overall poor prognosis. Understanding the role of individual variation in cellular and molecular mechanisms related to rheumatoid arthritis will considerably improve clinical care and patient outcomes. In this review, we discuss the source of pathophysiological heterogeneity derived from genetic, molecular, and cellular heterogeneity and their possible impact on precision medicine and personalized treatment of rheumatoid arthritis. We provide emphasized description of the heterogeneity derived from mast cells, monocyte cell, macrophage fibroblast-like synoviocytes and, interactions within immune cells and with inflammatory cytokines, as well as the potential as a new therapeutic target to develop a novel treatment approach. Finally, we summarize the latest clinical trials of treatment options for rheumatoid arthritis and provide a suggestive framework for implementing preclinical and clinical experimental results into clinical practice.

Regulation of osteoclastogenesis by mast cell in rheumatoid arthritis

Background

In the pathogenesis of rheumatoid arthritis (RA), the role of mast cells has not been revealed clearly. We aimed to define the inflammatory and tissue-destructive roles of mast cells in rheumatoid arthritis (RA).

Methods

Serum and synovial fluid (SF) concentration levels of tryptase, chymase, and histamine were quantified using ELISA. After activating mast cells using IL-33, the production of TNF-α, IL-1β, IL-6, IL-17, RANKL, and MMPs was determined using real-time PCR and ELISA. Osteoclastogenesis was assessed in CD14+ monocytes from peripheral blood and SF, which were cultured with IL-33-activated mast cells, by counting TRAP-positive multinucleated cells.

Results

The concentration levels of serum tryptase, chymase, and histamine and SF histamine were higher in patients with RA than in controls. FcεR1 and c-kit-positive mast cells were higher in RA synovium than in osteoarthritic (OA) synovium. Stimulation of mast cells by IL-33 increased the number of trypatse+chymase− and tryptase+chymase+ mast cells. IL-33 stimulation also increased the gene expression levels of TNF-α, IL-1β, IL-6, IL-17, RANKL, and MMP-9 in mast cells. Furthermore, IL-33 stimulated human CD14+ monocytes to differentiate into TRAP+ multinucleated osteoclasts. When CD14+ monocytes were co-cultured with mast cells, osteoclast differentiation was increased. Additionally, IL-33-activated mast cells stimulated osteoclast differentiation. The inhibition of intercellular contact between mast cells and monocytes using inserts reduced osteoclast differentiation.

Conclusions

IL-33 increased inflammatory and tissue-destructive cytokines by activation of mast cells. Mast cells stimulated osteoclast differentiation in monocytes. Mast cells could stimulate osteoclastogenesis indirectly through production of tissue-destructive cytokines and directly through stimulation of osteoclast precursors.

Enigmatic Histamine Receptor H4 for Potential Treatment of Multiple Inflammatory, Autoimmune, and Related Diseases

The histamine H4 receptor, belonging to the family of G-protein coupled receptors, is an increasingly attractive drug target. It plays an indispensable role in many cellular pathways, and numerous H4R ligands are being studied for the treatment of several inflammatory, allergic, and autoimmune disorders, including pulmonary fibrosis. Activation of H4R is involved in cytokine production and mediates mast cell activation and eosinophil chemotaxis. The importance of this receptor has also been shown in inflammatory models: peritonitis, respiratory tract inflammation, colitis, osteoarthritis, and rheumatoid arthritis. Recent studies suggest that H4R acts as a modulator in cancer, neuropathic pain, vestibular disorders, and type-2 diabetes, however, its role is still not fully understood.

The Role of Mast Cells in Bone Metabolism and Bone Disorders

Mast cells (MCs) are important sensor and effector cells of the immune system that are involved in many physiological and pathological conditions. Increasing evidence suggests that they also play an important role in bone metabolism and bone disorders. MCs are located in the bone marrow and secrete a wide spectrum of mediators, which can be rapidly released upon activation of mature MCs following their differentiation in mucosal or connective tissues. Many of these mediators can exert osteocatabolic effects by promoting osteoclast formation [e.g., histamine, tumor necrosis factor (TNF), interleukin-6 (IL-6)] and/or by inhibiting osteoblast activity (e.g., IL-1, TNF). By contrast, MCs could potentially act in an osteoprotective manner by stimulating osteoblasts (e.g., transforming growth factor-β) or reducing osteoclastogenesis (e.g., IL-12, interferon-γ). Experimental studies investigating MC functions in physiological bone turnover using MC-deficient mouse lines give contradictory results, reporting delayed or increased bone turnover or no influence depending on the mouse model used. By contrast, the involvement of MCs in various pathological conditions affecting bone is evident. MCs may contribute to the pathogenesis of primary and secondary osteoporosis as well as inflammatory disorders, including rheumatoid arthritis and osteoarthritis, because increased numbers of MCs were found in patients suffering from these diseases. The clinical observations could be largely confirmed in experimental studies using MC-deficient mouse models, which also provide mechanistic insights. MCs also regulate bone healing after fracture by influencing the inflammatory response toward the fracture, vascularization, bone formation, and callus remodeling by osteoclasts. This review summarizes the current view and understanding of the role of MCs on bone in both physiological and pathological conditions.

Does Allergy Break Bones? Osteoporosis and Its Connection to Allergy

: Osteoporosis and allergic diseases are important causes of morbidity, and traditionally their coexistence has been attributed to causality, to independent processes, and they were considered unrelated. However, the increasing knowledge in the field of osteoimmunology and an increasing number of epidemiological and biological studies have provided support to a correlation between bone and allergy that share pathways, cells, cytokines and mediators. If the link between allergic pathology and bone alterations appears more subtle, there are conditions such as mastocytosis and hypereosinophilic or hyper-IgE syndromes characterized by the proliferation of cells or hyper-production of molecules that play a key role in allergies, in which this link is at least clinically more evident, and the diseases are accompanied by frank skeletal involvement, offering multiple speculation cues. The pathophysiological connection of allergy and osteoporosis is currently an intriguing area of research. The aim of this review is to summarize and bring together the current knowledge and pursue an opportunity to stimulate further investigation.

Roles of mast cells in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory arthritis, and the complex interaction and activation of innate and adaptive immune cells are involved in RA pathogenesis. Mast cells (MCs) are one of the tissue-resident innate immune cells, and they contribute to RA pathogenesis. In the present review, the evidence of the pathologic role of MC in RA is discussed based on human and animal data. In addition, the potential role of MC in RA pathogenesis and the research area that should be focused on in the future are suggested.

Molecular characterisation of the synovial fluid microbiome in rheumatoid arthritis patients and healthy control subjects

METHODS

The presence and identity of bacterial and fungal DNA in the synovial fluid of rheumatoid arthritis (RA) patients and healthy control subjects was investigated through amplification and sequencing of the bacterial 16S rRNA gene and fungal internal transcribed spacer region 2 respectively. Synovial fluid concentrations of the cytokines IL-6, IL-17A, IL22 and IL-23 were determined by ELISA.

RESULTS

Bacterial 16S rRNA genes were detected in 87.5% RA patients, and all healthy control subjects. At the phylum level, the microbiome was predominated by Proteobacteria (Control = 83.5%, RA = 79.3%) and Firmicutes (Control = 16.1%, RA = 20.3%), and to a much lesser extent, Actinobacteria (Control = 0.2%, RA = 0.3%) and Bacteroidetes (Control = 0.1%, RA = 0.1%). Fungal DNA was identified in 75% RA samples, and 88.8% healthy controls. At the phylum level, synovial fluid was predominated by members of the Basidiomycota (Control = 53.9%, RA = 46.9%) and Ascomycota (Control = 35.1%, RA = 50.8%) phyla. Statistical analysis revealed key taxa that were differentially present or abundant dependent on disease status.

CONCLUSIONS

This study reports the presence of a synovial fluid microbiome, and determines that this is modulated by disease status (RA) as are other classical microbiome niches.

The histamine-4 receptor antagonist JNJ7777120 prevents immune abnormalities by inhibiting RORγt/T-bet transcription factor signaling pathways in BTBR T+ Itpr3tf/J mice exposed to gamma rays

Autism is a neurodevelopmental disorder characterized by deficits and qualitative impairments in communication and implicit skill learning. Its prevalence is higher than previous estimates, and treatments have limited efficacy and are costly. Here, we assessed the therapeutic potential of JNJ77777120 (JNJ), a histamine-4 receptor (H4R) antagonist, using BTBR T⁺ Itpr3^tf/J (BTBR) mice, a confirmed model of autism, and C57BL/6J (C57) mice, a commonly chosen reference strain. We first examined the effects of JNJ treatment on BTBR mice exposed to gamma-rays (irradiation-exposed) using a three-chambered apparatus. We further investigated the possible molecular mechanisms through which JNJ administration modulates IL-17A-, RORγT-, IL-22-, T-bet-, STAT3-, ICOS-, and Foxp3-producing CD8⁺ T cells in the spleens of irradiation-exposed BTBR mice. The effects of JNJ administration on the mRNA and protein expression of IL-17A, RORγT, IL-22, T-bet, STAT-3, pSTAT3, IL-10, and Foxp3 in brain tissue were also explored. Results showed that JNJ treatment with irradiation exposure increased social interactions in BTBR mice compared to that in irradiation-exposed BTBR mice. Additionally, JNJ-treated and irradiation-exposed BTBR mice exhibited decreases in IL-17A-, RORγT-, IL-22-, T-bet-, and STAT3-producing CD8⁺ T cells and increases in ICOS- and Foxp3-producing CD8⁺ T cells. Moreover, JNJ treatment and irradiation exposure in BTBR mice regulated the mRNA and protein expression levels of IL-17A, RORγT, IL-22, T-bet, STAT3, pSTAT-3, IL-10, and Foxp3 in the brain tissue. These results suggest that JNJ is useful for the treatment of autism, as this H4R antagonist could block inflammatory cytokine production and transcription factor signaling.

Regulation of Th17 Cytokine-Induced Osteoclastogenesis via SKI306X in Rheumatoid Arthritis

This study aimed to investigate the regulatory effect of SKI306X, a mixed extract of three herbs, in T helper (Th)17 cytokine-induced inflammation and joint destruction in rheumatoid arthritis (RA). Synovial fibroblasts were isolated from RA patients and cultured with Th17 cytokines including interleukin (IL)-17, IL-21, and IL-22 and SKI306X, and tumor necrosis factor (TNF)-α, IL-1β, and receptor activator of nuclear factor kappa-Β ligand (RANKL) expression and production were investigated using real-time PCR and ELISA of culture media. After peripheral blood (PB) cluster of differentiation (CD)14⁺ monocytes were cultured in media supplemented with Th17 cytokines and SKI306X, tartrate-resistant acid phosphatase positive (TRAP⁺) multinucleated giant cells (mature osteoclasts) were enumerated and gene expression associated with osteoclast maturation was assessed via real-time PCR analysis. After PB monocytes were co-cultured with IL-17-stimulated RA synovial fibroblasts in the presence of SKI306X, osteoclast differentiation was assessed. When RA synovial fibroblasts were cultured with IL-17, IL-21, and IL-22, TNF-α, IL-1β, and RANKL expression and production were increased; however, SKI306X reduced cytokine expression and production. When PB monocytes were cultured in media supplemented with Th17 cytokines, osteoclast differentiation was stimulated; however, SKI306X decreased osteoclast differentiation and osteoclast maker expression. When PB monocytes were co-cultured with IL-17-stimulated RA synovial fibroblasts, osteoclast differentiation was increased; however, SKI306X decreased osteoclast differentiation and osteoclast maker expression. SKI306X reduced Th17 cytokine-induced TNF-α, IL-1β, and RANKL expression and osteoclast differentiation, providing novel insights into adjuvant therapy for regulating inflammation and joint destruction in RA.

The role of GPCRs in bone diseases and dysfunctions

The superfamily of G protein-coupled receptors (GPCRs) contains immense structural and functional diversity and mediates a myriad of biological processes upon activation by various extracellular signals. Critical roles of GPCRs have been established in bone development, remodeling, and disease. Multiple human GPCR mutations impair bone development or metabolism, resulting in osteopathologies. Here we summarize the disease phenotypes and dysfunctions caused by GPCR gene mutations in humans as well as by deletion in animals. To date, 92 receptors (5 glutamate family, 67 rhodopsin family, 5 adhesion, 4 frizzled/taste2 family, 5 secretin family, and 6 other 7TM receptors) have been associated with bone diseases and dysfunctions (36 in humans and 72 in animals). By analyzing data from these 92 GPCRs, we found that mutation or deletion of different individual GPCRs could induce similar bone diseases or dysfunctions, and the same individual GPCR mutation or deletion could induce different bone diseases or dysfunctions in different populations or animal models. Data from human diseases or dysfunctions identified 19 genes whose mutation was associated with human BMD: 9 genes each for human height and osteoporosis; 4 genes each for human osteoarthritis (OA) and fracture risk; and 2 genes each for adolescent idiopathic scoliosis (AIS), periodontitis, osteosarcoma growth, and tooth development. Reports from gene knockout animals found 40 GPCRs whose deficiency reduced bone mass, while deficiency of 22 GPCRs increased bone mass and BMD; deficiency of 8 GPCRs reduced body length, while 5 mice had reduced femur size upon GPCR deletion. Furthermore, deficiency in 6 GPCRs induced osteoporosis; 4 induced osteoarthritis; 3 delayed fracture healing; 3 reduced arthritis severity; and reduced bone strength, increased bone strength, and increased cortical thickness were each observed in 2 GPCR-deficiency models. The ever-expanding number of GPCR mutation-associated diseases warrants accelerated molecular analysis, population studies, and investigation of phenotype correlation with SNPs to elucidate GPCR function in human diseases.

Quercetin, a Plant Polyphenol, Has Potential for the Prevention of Bone Destruction in Rheumatoid Arthritis

We investigated the immune-regulatory function of quercetin, in interleukin (IL)-17-produced osteoclastogenesis in rheumatoid arthritis (RA). RA fibroblasts-like synoviocytes (RA-FLS) were stimulated with IL-17, and the mRNA expression and secretion of receptor activator of nuclear factor kappa-B ligand (RANKL) were detected by real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. CD14⁺ monocytes (osteoclast precursors) were stimulated with IL-17, RANKL, with/without quercetin, and tartrate-resistant acid phosphatase activity was evaluated to assess osteoclast differentiation. Osteoclast differentiation was investigated after coculturing IL-17-stimulated RA-FLS and Th17 cells with monocytes. CD4⁺ T cells were cocultured with quercetin under Th17-inducing conditions, and their differentiation to Th17 cells and Treg cells was determined by flow cytometry analysis. We found that IL-17 stimulated RA-FLS to produce RANKL and quercetin decreased the IL-17-induced RANKL protein levels. Quercetin decreased the IL-17-produced activation of mammalian target of rapamycin, extracellular signal-regulated kinase and inhibitor of kappa B-alpha. When monocytes were stimulated with IL-17, macrophage colony-stimulating factor or RANKL, mature osteoclasts were formed, and quercetin decreased this osteoclastogenesis. When monocytes were cultured with IL-17-prestimulated RA-FLS or Th17 cells, osteoclasts were produced, and quercetin decreased this osteoclast differentiation. In Th17-differentiation conditions, quercetin suppressed Th17 cell and the production of IL-17, but quercetin did not affect Treg cells. Quercetin inhibits IL-17-stimulated RANKL production in RA-FLS and IL-17-stimulated osteoclast formation. Quercetin reduces Th17 differentiation. Quercetin could be an additional therapeutic option for bone destructive processes in RA.

Histamine H4 receptor mediates chemotaxis of human lung mast cells

The diverse effects of histamine are mediated by discrete histamine receptors. The principal repository of histamine in the body is the mast cell. However, the effects of histamine on mast cells, especially those of human origin, have not been fully elucidated. In this study, the expression of histamine receptors in human lung mast cells was evaluated. Moreover, the effects of histamine receptor engagement on both mediator release and chemotaxis were investigated. Mast cells were isolated and purified from human lung tissue. Histamine receptor expression was determined by RT-PCR and q-PCR. Both methods for the detection of histamine receptors were in accordance and human lung mast cells expressed mRNA for histamine H₄ and histamine H₁ receptors, variably expressed histamine H₂ receptor but did not express histamine H₃ receptor. The effects of selective histamine receptor agonists on the release of both pre-formed (histamine) and newly-synthesised (cysteinyl-leukotriene, prostaglandin D₂) mediators were investigated. None of the agonists tested had any direct effects on mediator release. None of the agonists modulated release stimulated by anti-IgE. Further studies showed that histamine induced migration of mast cells. Chemotaxis appeared to be mediated by the histamine H₄ receptor since JNJ28610244 (H₄ agonist) was chemotactic for mast cells whereas 2-(2-pyridyl) ethylamine (H₁ agonist) was not. Furthermore, the selective histamine H₄ receptor antagonist, JNJ7777120, effectively reversed the chemotaxis of mast cells induced by JNJ28610244. Overall, these experiments identify the histamine H₄ receptor as chemotactic for human lung mast cells. This mechanism might influence mast cell accumulation in the lung.

A Microdialysis in Adjuvant Arthritic Rats for Pharmacokinetics⁻Pharmacodynamics Modeling Study of Geniposide with Determination of Drug Concentration and Efficacy Levels in Dialysate

Microdialysis, a sampling method for pharmacokinetics–pharmacodynamics (PK–PD) modeling in preclinical and clinical studies, is a convenient in vivo sampling technique. Geniposide (GE), an iridoid glycoside compound, is the major active ingredient of Gardenia jasminoides Ellis fruit which has an anti-inflammatory effect. In this study, an articular cavity microdialysis sampling system for adjuvant arthritic (AA) rats was established to study the effect of GE on the release of prostaglandin E₂ (PGE₂) in AA rats induced by Freund’s complete adjuvant (FCA). An UHPLC-MS/MS method was developed to determine the concentrations of GE and PGE₂ in the dialysate. Through the determination of drug concentrations and PGE₂ efficacy levels in the dialysate, the developed methods were successfully applied to set up concentration–time and effect–time profiles followed by PK–PD modeling of GE’s effect on decreasing PGE₂ release after oral administration of GE. The effect was well described by the developed PK–PD modeling, indicating that GE may play an anti-inflammatory role via decreasing AA-induced elevated PGE₂ levels. In the selection of suitable endogenous small molecules as effect markers, the establishment of AA rat joint-cavity microdialysis is an attractive technique for rational PK–PD studies.

Nicorandil and theophylline can protect experimental rats against complete Freund's adjuvant-induced rheumatoid arthritis through modulation of JAK/STAT/RANKL signaling pathway

Signaling pathways are interesting fields of study of pathogenesis and treatment trials. We elucidated the possible protective effects of nicorandil (15mg/kg/day) and theophylline (20mg/kg/day) on experimentally-induced RA, focusing on the role of JAK (Janus Kinase) / STAT (Signal Transducer and Activator of Transcription) / RANKL (Receptor Activator of Nuclear factor-Kappa B Ligand) / cytokine signaling pathway. Four sets of experiments were performed. First, effect of test agents on normal animals was evaluated. Second, effect of test agents was evaluated on Complete Freund's Adjuvant (CFA; 0.3ml, s.c.)-induced RA to investigate anti-arthritic effect. Third, effect of test agents was evaluated on growth hormone (GH; 2mg/kg/day, s.c.)-induced stimulation of JAK/STAT/RANKL/cytokine signaling pathway to investigate the role of this signaling pathway in their anti-arthritic effect. Fourth, the effect of test agents was performed on CFA/GH-induced RA. To fulfill this purpose, serum anti-citrullinated peptide antibody (ACPA), interleukin-6 (IL-6), and cartilage oligomeric matrix protein (COMP), together with tissue JAK2, STAT3, RANKL, inducible and endothelial nitric oxide synthases (iNOS and eNOS) as well as macrophage inflammatory protein (MIP_1α) were estimated using ELISA, Western blotting and PCR techniques, confirmed by a histopathological study. Test agents significantly corrected JAK2, STAT3, RANKL and IL-6 values in animals receiving GH. Additionally, test agents could correct ACPA, IL-6, COMP, JAK2, STAT3, RANKL, iNOS, eNOS and MIP_1α levels compared with the respective CFA or CFA/GH controls. These results conclude that nicorandil and theophylline have good anti-arthritic effects related to modulation of JAK/STAT/RANKL signaling pathway. Further clinical trials are claimed.