Nitric oxide production and inducible nitric oxide synthase expression in inflammatory arthritides

Mitochondrial DNA variants and microbiota: An experimental strategy to identify novel therapeutic potential in chronic inflammatory diseases

We previously demonstrated that mice carrying natural mtDNA variants of the FVB/NJ strain (m.7778 G>T in the mt-Atp8 gene in mitochondrial complex V), namely C57BL/6 J-mtFVB/NJ (B6-mtFVB), exhibited (i) partial protection from experimental skin inflammatory diseases in an anti-murine type VII collagen antibody-induced skin inflammation model and psoriasiform dermatitis model; (ii) significantly altered metabolites, including short-chain fatty acids, according to targeted metabolomics of liver, skin and lymph node samples; and (iii) a differential composition of the gut microbiota according to bacterial 16 S rRNA gene sequencing of stool samples compared to wild-type C57BL/6 J (B6) mice. To further dissect these disease-contributing factors, we induced an experimental antibody-induced skin inflammatory disease in gnotobiotic mice. We performed shotgun metagenomic sequencing of caecum contents and untargeted metabolomics of liver, CD4+ T cell, and caecum content samples from conventional B6-mtFVB and B6 mice. We identified D-glucosamine as a candidate mediator that ameliorated disease severity in experimental antibody-induced skin inflammation by modulating immune cell function in T cells, neutrophils and macrophages. Because mice carrying mtDNA variants of the FVB/NJ strain show differential disease susceptibility to a wide range of experimental diseases, including diet-induced atherosclerosis in low-density lipoprotein receptor knockout mice and collagen antibody-induced arthritis in DBA/1 J mice, this experimental approach is valuable for identifying novel therapeutic options for skin inflammatory conditions and other chronic inflammatory diseases to which mice carrying specific mtDNA variants show differential susceptibility.

Mitochondrial-Targeted Ratiometric Near-Infrared Fluorescence Probe for Monitoring Nitric Oxide in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a destructive autoimmune disease, where nitric oxide (NO) is closely implicated in the inflammatory processes of RA. Therefore, direct visualization of NO is essential to assess the pathological changes in RA. Herein, a mitochondrial-targeted near-infrared ratiometric fluorescent probe (NFL-NH2), based on the intramolecular charge transfer effect, was synthesized and applied to monitor the changes of NO content in early RA. Specially, probe NFL-NH2 showed a 44-fold fluorescent intensity ratio (I705/I780) response toward NO with a detection limit of 0.536 nM, enabling qualitative and quantitative analysis of NO. Additionally, NFL-NH2 can accurately target mitochondria and sensitively detect exogenous and endogenous NO in RAW 264.7 cells. Notably, in vivo RA monitoring assays demonstrated that NFL-NH2 can rapidly detect NO levels associated with the inflammatory damage degree in RA mice models by ratiometric fluorescence imaging. These results validate that NFL-NH2 holds significant potential for diagnosing NO-mediated RA diseases.

Rheumatoid Arthritis and Reactive Oxygen Species: A Review

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disease that causes progressive joint damage and can lead to lifelong disability. Numerous studies support the hypothesis that reactive oxygen species (ROS) are associated with RA pathogenesis. Recent advances have clarified the anti-inflammatory effect of antioxidants and their roles in RA alleviation. In addition, several important signaling pathway components, such as nuclear factor kappa B, activator-protein-1, nuclear factor (erythroid-derived 2)-like 2/kelch-like associated protein, signal transducer and activator of transcription 3, and mitogen-activated protein kinases, including c-Jun N-terminal kinase, have been identified to be associated with RA. In this paper, we outline the ROS generation process and relevant oxidative markers, thereby providing evidence of the association between oxidative stress and RA pathogenesis. Furthermore, we describe various therapeutic targets in several prominent signaling pathways for improving RA disease activity and its hyper oxidative state. Finally, we reviewed natural foods, phytochemicals, chemical compounds with antioxidant properties and the association of microbiota with RA pathogenesis.

Serum nitric oxide concentration in generalized chronic and aggressive periodontitis in the Mexican population is not related to the severity of the disease

Introduction: Periodontitis is an inflammatory disease that affects the supporting tissues of teeth, the effects of excess of nitric oxide, may contribute to the symptoms of periodontitis. Objective: To determine the serum nitric oxide concentration in generalized chronic and aggressive periodontitis patients and to compare it with a healthy subject group from the Mexican population. Materials and methods: A case and control study was performed. Sixty-nine individuals were recruited from the Clínica de Posgrado de Periodoncia of the Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, México. Patients with clinical features of generalized chronic periodontitis (GCP group, n=19), generalized aggressive periodontitis (GAP group, n=11), and a group of healthy subjects (HS group, n=39) were included in the study. Informed consent was obtained from each subject, and serum nitric oxide concentration was measured by an enzyme-linked immunosorbent assay. Results: Nitric oxide concentration in the study groups was greater in the GCP group (462.57 ± 16.57 μmol/L) than in the GAP group (433.84 ± 18.61 μmol/L) and the HS group (422.46 ± 12.07 μmol/L). A comparison using Student’s t-test (one-tailed) between healthy subjects and generalized chronic periodontitis showed borderline significance (p<0.04), whereas no significant differences were observed in HS and GAP groups, with a p-value of 0.64, and the GAP vs. GCP p-value was 0.33. Conclusion: The serum nitric oxide concentration observed in the present study suggests that nitric oxide plays a major role in the inflammatory process, which cannot necessarily be linked to the severity of the disease and periodontal tissue destruction.

2-Styrylchromones Prevent IL-1β-Induced Pro-Inflammatory Activation of Fibroblast-like Synoviocytes while Increasing COX-2 Expression

Rheumatoid arthritis (RA) is characterized by systemic immune and chronic inflammatory features, leading to the destruction of the joints. Presently, there are no effective drugs able to control synovitis and catabolism in the process of RA. 2-Styrylchromones (2-SC) are a small group of compounds characterized by the attachment of a styryl group to the chromone core that have already been associated to a wide range of biological activities, including antioxidant and anti-inflammatory activities. The present study investigated the effect of a set of six 2-SC on the interleukin-1β (IL-1β)-induced increase of nitric oxide (•NO), inducible form of nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and matrix metalloproteinase-3 (MMP-3) expression levels in human fibroblast-like synoviocytes (HFLS), pointing to the role of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation in the process. From a set of six 2-SC, presenting hydroxy and methoxy substituents, the one presenting two methoxy substituents at C-5 and C-7 of A ring and a catechol group on B ring, significantly reduced •NO production and the expression of its inducible synthase (iNOS). It also significantly reduced the catabolic MMP-3 protein expression. This 2-SC inhibited the NF-κB pathway by reversing the IL-1β - induced levels of cytoplasmatic NF-kB inhibitor alpha (IκBα), and decreasing the p65 nuclear levels, suggesting the involvement of these pathways in the observed effects. The same 2-SC significantly increased the COX-2 expression, which may indicate a negative feedback loop mechanism of action. The properties of 2-SC may be of great value in the development of new therapies with improved efficacy and selectivity towards RA, and thus deserve further exploitation and evaluation to disclose the full potential of 2-SC.

Remodeling Osteoarthritic Articular Cartilage under Hypoxic Conditions

Osteoarthritis (OA) is one of the leading joint diseases induced by abnormalities or inflammation in the synovial membrane and articular cartilage, causing severe pain and disability. Along with the cartilage malfunction, imbalanced oxygen uptake occurs, changing chondrocytes into type I collagen- and type X collagen-producing dedifferentiated cells, contributing to OA progression. However, mounting evidence suggests treating OA by inducing a hypoxic environment in the articular cartilage, targeting the inhibition of several OA-related pathways to bring chondrocytes into a normal state. This review discusses the implications of OA-diseased articular cartilage on chondrocyte phenotypes and turnover and debates the hypoxic mechanism of action. Furthermore, this review highlights the new understanding of OA, provided by tissue engineering and a regenerative medicine experimental design, modeling the disease into diverse 2D and 3D structures and investigating hypoxia and hypoxia-inducing biomolecules and potential cell therapies. This review also reports the mechanism of hypoxic regulation and highlights the importance of activating and stabilizing the hypoxia-inducible factor and related molecules to protect chondrocytes from mitochondrial dysfunction and apoptosis occurring under the influence of OA.

Cardiovascular Responses During Sepsis

Sepsis is the life-threatening organ dysfunction arising from a dysregulated host response to infection. Although the specific mechanisms leading to organ dysfunction are still debated, impaired tissue oxygenation appears to play a major role, and concomitant hemodynamic alterations are invariably present. The hemodynamic phenotype of affected individuals is highly variable for reasons that have been partially elucidated. Indeed, each patient's circulatory condition is shaped by the complex interplay between the medical history, the volemic status, the interval from disease onset, the pathogen, the site of infection, and the attempted resuscitation. Moreover, the same hemodynamic pattern can be generated by different combinations of various pathophysiological processes, so the presence of a given hemodynamic pattern cannot be directly related to a unique cluster of alterations. Research based on endotoxin administration to healthy volunteers and animal models compensate, to an extent, for the scarcity of clinical studies on the evolution of sepsis hemodynamics. Their results, however, cannot be directly extrapolated to the clinical setting, due to fundamental differences between the septic patient, the healthy volunteer, and the experimental model. Numerous microcirculatory derangements might exist in the septic host, even in the presence of a preserved macrocirculation. This dissociation between the macro- and the microcirculation might account for the limited success of therapeutic interventions targeting typical hemodynamic parameters, such as arterial and cardiac filling pressures, and cardiac output. Finally, physiological studies point to an early contribution of cardiac dysfunction to the septic phenotype, however, our defective diagnostic tools preclude its clinical recognition. © 2021 American Physiological Society. Compr Physiol 11:1605-1652, 2021.

Skeletal muscle redox signaling in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by synovitis and the presence of serum autoantibodies. In addition, skeletal muscle weakness is a common comorbidity that contributes to inability to work and reduced quality of life. Loss in muscle mass cannot alone account for the muscle weakness induced by RA, but instead intramuscular dysfunction appears as a critical factor underlying the decreased force generating capacity for patients afflicted by arthritis. Oxidative stress and associated oxidative post-translational modifications have been shown to contribute to RA-induced muscle weakness in animal models of arthritis and patients with RA. However, it is still unclear how and which sources of reactive oxygen and nitrogen species (ROS/RNS) that are involved in the oxidative stress that drives the progression toward decreased muscle function in RA. Nevertheless, mitochondria, NADPH oxidases (NOX), nitric oxide synthases (NOS) and phospholipases (PLA) have all been associated with increased ROS/RNS production in RA-induced muscle weakness. In this review, we aim to cover potential ROS sources and underlying mechanisms of oxidative stress and loss of force production in RA. We also addressed the use of antioxidants and exercise as potential tools to counteract oxidative stress and skeletal muscle weakness.

Lymphatic muscle cells contribute to dysfunction of the synovial lymphatic system in inflammatory arthritis in mice

BACKGROUND

Our previous studies reveal that impaired draining function of the synovial lymphatic vessel (LV) contributes to the pathogenesis of inflammatory arthritis, but the cellular and molecular mechanisms involved are not fully understood.

OBJECTIVE

To investigate the involvement of lymphatic muscle cells (LMCs) in mediating impaired LV function in inflammatory arthritis.

METHODS

TNF transgenic (TNF-Tg) arthritic mice were used. The structure and function of the LVs that drained the hind limbs were examined by whole-mount immunofluorescence staining, electron microscopy, and near-infrared lymphatic imaging. Primary LMCs were treated with TNF, and the changes in proliferation, apoptosis, and functional gene expression were assessed. The roles of the herbal drug, Panax notoginseng saponins (PNS), in arthritis and LVs were studied.

RESULTS

TNF-Tg mice developed ankle arthritis with age, which was associated with abnormalities of LVs: (1) dilated capillary LVs with few branch points, (2) mature LVs with reduced LMC coverage and draining function, and (3) degenerative and apoptotic appearance of LMCs. TNF caused LMC apoptosis, reduced expression of muscle functional genes, and promoted the production of nitric oxide (NO) by lymphatic endothelial cells (LECs). PNS attenuated arthritis, restored LMC coverage and draining function of mature LVs, inhibited TNF-mediated NO expression, and reduced LMC apoptosis.

CONCLUSION

The impaired draining function of LVs in TNF-Tg mice involves LMC apoptosis. TNF promotes LMC death directly and indirectly via NO production by LECs. PNS attenuates arthritis, improves LVs, and prevents TNF-induced LMC apoptosis by inhibiting NO production of LECs. LMCs contribute to the dysfunction of synovial LVs in inflammatory arthritis.

Immunotherapy of Autoimmune Diseases with Nonantibiotic Properties of Tetracyclines

Tetracyclines, which have long been used as broad-spectrum antibiotics, also exhibit a variety of nonantibiotic activities including anti-inflammatory and immunomodulatory properties. Tetracyclines bind to the 30S ribosome of the bacteria and inhibit protein synthesis. Unlike antimicrobial activity, the primary molecular target for the nonantibiotic activity of tetracycline remains to be clarified. Nonetheless, the therapeutic efficacies of tetracyclines, particularly minocycline and doxycycline, have been demonstrated in various animal models of autoimmune disorders, such as multiple sclerosis, rheumatoid arthritis, and asthma. In this study, we summarized the anti-inflammatory and immunomodulatory activities of tetracyclines, focusing on the mechanisms underlying these activities. In addition, we highlighted the on-going or completed clinical trials with reported outcomes.

Nitric Oxide in Macrophage Immunometabolism: Hiding in Plain Sight

Nitric Oxide (NO) is a soluble endogenous gas with various biological functions like signaling, and working as an effector molecule or metabolic regulator. In response to inflammatory signals, immune myeloid cells, like macrophages, increase production of cytokines and NO, which is important for pathogen killing. Under these proinflammatory circumstances, called “M1”, macrophages undergo a series of metabolic changes including rewiring of their tricarboxylic acid (TCA) cycle. Here, we review findings indicating that NO, through its interaction with heme and non-heme metal containing proteins, together with components of the electron transport chain, functions not only as a regulator of cell respiration, but also a modulator of intracellular cell metabolism. Moreover, diverse effects of NO and NO-derived reactive nitrogen species (RNS) involve precise interactions with different targets depending on concentration, temporal, and spatial restrictions. Although the role of NO in macrophage reprogramming has been in evidence for some time, current models have largely minimized its importance. It has, therefore, been hiding in plain sight. A review of the chemical properties of NO, past biochemical studies, and recent publications, necessitates that mechanisms of macrophage TCA reprogramming during stimulation must be re-imagined and re-interpreted as mechanistic results of NO exposure. The revised model of metabolic rewiring we describe here incorporates many early findings regarding NO biochemistry and brings NO out of hiding and to the forefront of macrophages immunometabolism.

Intra-Articular Route for the System of Molecules 14G1862 from Centella Asiatica: Pain Relieving and Protective Effects in a Rat Model of Osteoarthritis

Current pharmacological therapies for the management of chronic articular diseases are far from being satisfactory, so new strategies need to be investigated. We tested the intra-articular pain relieving properties of a system of molecules from a characterized Centella asiatica extract (14G1862) in a rat model of osteoarthritis induced by monoiodoacetate (MIA). 14G1862 (0.2–2 mg mL⁻¹) was intra-articularly (i.a.) injected 7 days after MIA, behavioural and histological evaluations were performed 14, 30 and 60 days after treatments. Moreover, the effect of 14G1862 on nitrate production and iNOS expression in RAW 264.7 macrophages stimulated with LPS was assessed. In vitro, 14G1862 treatment attenuated LPS-induced NO production and iNOS expression in a comparable manner to celecoxib. In vivo, 14G1862 significantly reduced mechanical allodynia and hyperalgesia, spontaneous pain and motor alterations starting on day 14 up to day 60. The efficacy was higher or comparable to that evoked by triamcinolone acetonide (100 μg i.a.) used as reference drug. Histological evaluation highlighted the improvement of several morphological parameters in MIA + 14G1862-treated animals with particularly benefic effects on joint space and fibrin deposition. In conclusion, i.a. treatment with Centella asiatica is a candidate to be a novel effective approach for osteoarthritis therapy.

Modulating inflammatory macrophages with an apoptotic body-inspired nanoparticle

Macrophages play a critical role in the initiation, maintenance, and resolution of inflammation because of their diverse and plastic phenotypic responses to extracellular stimuli. Inflammatory stimuli drive the recruitment and activation of inflammatory (M1) macrophages, capable of significant cytokine production that potentiates inflammation. Local environmental signals including apoptotic cell efferocytosis drive a phenotypic transition toward pro-reparative (M2) macrophages to facilitate the resolution of inflammation. However, prolonged or dysregulated inflammatory macrophage response contributes to many disease states and tissue damage. We have developed a nanoparticle to help resolve macrophage-mediated inflammation by mimicking the anti-inflammatory effect of apoptotic cell engulfment. The nanoparticle, comprised of a poly(lactide-co-glycolide) core, is coated in phosphatidylserine (PS)-supplemented cell plasma membrane to emulate key characteristics of the apoptotic cell surface. These apoptotic body-inspired PS/membrane-coated nanoparticles (PS-MNPs) reduce inflammatory cytokine expression to promote an anti-inflammatory, phenotypic shift in macrophages in vitro, without the use of small molecule inhibitors or other drugs. Specifically, PS-MNP treatment before lipopolysaccharide (LPS)-induced inflammatory challenge resulted in a 2.5-fold reduction in secreted tumor necrosis factor α (TNFα) at 24 h, with co-treatment of PS-MNPs and LPS demonstrating a 5-fold TNFα reduction compared to LPS alone. Reduced TNFα production, as well as gene expression of several pro-inflammatory cytokines, correlated with a reduction in NFκB activation from PS-MNP treatment. The development of a nanoparticle to reduce the production of multiple inflammatory cytokines and transition away from an inflammatory macrophage phenotype, through the use of a physiologic anti-inflammatory pathway, illustrates a new potential strategy in creating anti-inflammatory therapeutics. STATEMENT OF SIGNIFICANCE: Macrophages propagate inflammation as the major source of cytokine production in the body. In inflammatory diseases, pro-inflammatory macrophages persist in the site of inflammation and exacerbate tissue destruction. Current anti-inflammatory drugs have significant drawbacks, including variable response rates and off-target effects. Here, we have developed an apoptotic-body inspired nanoparticle to modulate inflammatory macrophage phenotype. This polymeric nanoparticle is coated with phosphatidylserine-supplemented cell plasma membrane to mimic the anti-inflammatory effect of apoptotic cell engulfment. Nanoparticle delivery reduces inflammatory cytokine production and promotes an anti-inflammatory phenotypic macrophage shift. The capacity of these nanoparticles to help resolve macrophage-mediated inflammation may be a useful tool to study macrophage-apoptotic cell interactions, the role of macrophages in inflammatory diseases, and in the design of anti-inflammatory therapeutics.

The Effect of Aqueous Extract of Trachyspermum ammi Seeds and Ibuprofen on Inflammatory Gene Expression in the Cartilage Tissue of Rats with Collagen-Induced Arthritis

Background and Objectives

Rheumatoid arthritis (RA) is an inflammatory disease treated with nonsteroidal anti–inflammatory drugs that have different side effects. One of the plants used for this purpose in the traditional medicine is Trachyspermum ammi. The present study aimed at investigating the anti–inflammatory effect of this plant on type II collagen-induced arthritis (CIA) in Wistar rats.

Materials and Methods

The study was performed on 35 male Wistar rats. Seven rats were considered as the healthy control group (normal group), and CIA was stablished in the rest. The rats with a model of inflammatory arthritis were divided into four groups. One group did not receive any treatment and three groups were treated orally with ibuprofen (15 mg/kg), aqueous extract of the T. ammi seeds (100 mg/kg), or their combination for 30 days. The effect of different treatments was investigated on the paw thickness, arthritis score, and mRNA level of COX2 and iNOS genes.

Results

CIA increased paw thickness, arthritis score, and COX2 and iNOS mRNA levels compared to those of the normal group. Treatment with ibuprofen and aqueous extract alone or in combination reduced the studied variables. Reduction in the paw thickness, arthritis score, and iNOS mRNA level was more in the ibuprofen-treated group than the T. ammi extract-treated group, but treatment with T. ammi extract reduced COX2 mRNA level more than ibuprofen.

Conclusion

It seems that the aqueous extract of T. ammi can be used alone or in combination with ibuprofen to treat RA.

Circulating Insulin-like Growth Factor-1 Levels in Patients with Rheumatoid Arthritis: A Meta-analysis

BACKGROUND AND OBJECTIVES

Insulin-like growth factor-1 (IGF-1) levels have been investigated in rheumatoid arthritis (RA), however, produced inconsistent results. The purpose of this meta-analysis was to derive a more precise conclusion about serum/plasma IGF-1 levels in RA patients.

METHODS

PubMed, Embase and the Cochrane Library databases were searched up to December 2018 in English, and the studies comparing serum/plasma IGF-1 levels between RA group and healthy control group were what we are interested in. The Newcastle-Ottawa Scale (NOS) was used to assess the methodological quality of the included studies. The heterogeneity test was performed by the Cochrane Q statistic and I2 -statistic. The publication bias was evaluated by the funnel plot and Egger's test. The standard mean difference (SMD) with 95% confidence interval (CI) was calculated by the fixed-effects or random-effects model.

RESULTS

A total of eleven articles with 334 cases and 261 controls were finally included. Compared with the healthy group, the RA group had lower circulating IGF-1 levels (pooled SMD= -0.936, 95% CI= -1.382 to -0.489, p<0.001). The subgroup analysis showed that RA patients from Asia (SMD= -0.645, 95% CI= -1.063 to -0.228, p= 0.002) and Europe (SMD= -1.131, 95% CI= -1.767 to -0.495, p<0.001) had lower circulating IGF-1 levels, no significant difference in plasma/serum IGF-1 levels was observed in RA patients from America. Sensitivity analysis indicated the stability and credibility of the overall effect sizes.

CONCLUSION

Patients with RA have lower circulating IGF-1 level than healthy controls, particularly for patients from Asia and Europe. Further studies are necessary to elucidate the role of IGF-1 in the pathological process of RA.

The evaluation of oxidative stress in osteoarthritis

Osteoarthritis (OA) is a whole joint disease driven by abnormal biomechanics and attendant cell-derived and tissue-derived factors. The disease is multifactorial and polygenic, and its progression is significantly related to oxidative stress and reactive oxygen species (ROS). Augmented ROS generation can cause the damage of structural biomolecules of the joint and, by acting as intracellular signaling component, ROS are associated with various inflammatory responses. By activating several signaling pathways, ROS have a vital importance in the patho-physiology of OA. This review is focused on the mechanism of ROS which regulate intracellular signaling processes, chondrocyte senescence and apoptosis, extracellular matrix synthesis and degradation, along with synovial inflammation and dysfunction of the subcondral bone, targeting the complex oxidative stress signaling pathways.

The expression of Kruppel-like factor 2 in mice with collagen-induced arthritis and its role in the induction of nitric oxide synthase production

Kruppel-like factor 2 (KLF2) is associated with acute and chronic inflammation. However, the role of KLF2 in rheumatoid arthritis (RA) remains unknown. Here, we investigated the expression of KLF2 in mice with collagen-induced arthritis (CIA) to determine whether KLF2 levels correlate with inducible nitric oxide synthase (iNOS) production in vitro. Hematoxylin and eosin staining was used to assess the synovitis and bone destruction in mice. The concentration of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and nitric oxide (NO) in synovial fluid was determined by enzyme-linked immunosorbent assay, while western blot (WB) analysis was employed to detect the expression of KLF2 and iNOS in the synovium, heart, and kidneys. The expression of iNOS in MH7A cells was analyzed by quantitative polymerase chain reaction (PCR) and WB. The expression of KLF2 and iNOS was significantly elevated in the synovium, heart, and kidneys of CIA mice. This was correlated to an increase in the severity of arthritis and the concentration of inflammatory mediators including TNF-α, IL-6, and NO in joint fluid. KLF2 and iNOS expression in vitro was induced by TNF-α and KLF2 knockdown significantly reduced the TNF-α-induced iNOS expression. These findings indicate that KLF2 influences synovial inflammation in CIA mice by regulating iNOS production in synoviocytes.

Mitochondrial dysfunction in rheumatoid arthritis: A comprehensive analysis by integrating gene expression, protein-protein interactions and gene ontology data

Several studies have reported mitochondrial dysfunction in rheumatoid arthritis (RA). Many nuclear DNA (nDNA) encoded proteins translocate to mitochondria, but their participation in the dysfunction of this cell organelle during RA is quite unclear. In this study, we have carried out an integrative analysis of gene expression, protein-protein interactions (PPI) and gene ontology data. The analysis has identified potential implications of the nDNA encoded proteins in RA mitochondrial dysfunction. Firstly, by analysing six synovial microarray datasets of RA patients and healthy controls obtained from the gene expression omnibus (GEO) database, we found differentially expressed nDNA genes that encode mitochondrial proteins. We uncovered some of the roles of these genes in RA mitochondrial dysfunction using literature search and gene ontology analysis. Secondly, by employing gene co-expression from microarrays and collating reliable PPI from seven databases, we created the first mitochondrial PPI network that is specific to the RA synovial joint tissue. Further, we identified hubs of this network, and moreover, by integrating gene expression and network analysis, we found differentially expressed neighbours of the hub proteins. The results demonstrate that nDNA encoded proteins are (i) crucial for the elevation of mitochondrial reactive oxygen species (ROS) and (ii) involved in membrane potential, transport processes, metabolism and intrinsic apoptosis during RA. Additionally, we proposed a model relating to mitochondrial dysfunction and inflammation in the disease. Our analysis presents a novel perspective on the roles of nDNA encoded proteins in mitochondrial dysfunction, especially in apoptosis, oxidative stress-related processes and their relation to inflammation in RA. These findings provide a plethora of information for further research.

Cysteinyl leukotriene receptor antagonism: a promising pharmacological strategy for lowering the severity of arthritis

BACKGROUND AND AIMS

Though cyclooxygenase inhibitors are employed in rheumatoid arthritis treatment, modulators of leukotrienes are underexplored. We investigated the therapeutic potential of montelukast, a known cysteinyl leukotriene receptor-1 (CysLT1) inhibitor in an experimental rat model of arthritis.

METHODS

Arthritis was induced in rats, and montelukast (5 mg/kg body wt.) was administered prophylactically (PAM) and therapeutically (TAM) through oral route.

RESULTS AND DISCUSSION

Blood and joint tissue markers of oxidative stress (lipid peroxidation, protein carbonyls, and nitric oxides) were significantly (p < 0.05) reduced in montelukast administered rats. Paw inflammation, RA markers (RF and CRP), eicosanoids (PGE₂, LTB₄, and LTC₄), cytokines (IL-1β and MCP-1), activity of hydrolytic enzymes (collagenase, elastase, and hyaluronidase), expression of matrix metalloproteinases (MMP), and EP-4 receptor were significantly (p < 0.05) reduced in montelukast administered rats. This study established that leukotriene inhibition through montelukast lowered the severity of arthritis and thus a potential strategy for reducing the severity of arthritis.

Dopamine-melanin nanoparticles scavenge reactive oxygen and nitrogen species and activate autophagy for osteoarthritis therapy

Anti-oxidative agents hold great potential in osteoarthritis (OA) therapy. However, most radical scavengers have poor biocompatibility and potential cytotoxicity, which limit their applications. Herein we explore dopamine melanin (DM) nanoparticles as a novel scavenger of reactive oxygen species (ROS) and reactive nitrogen species (RNS). DM nanoparticles show low cytotoxicity and a strong ability to sequester a broad range of ROS and RNS, including superoxides, hydroxyl radicals, and peroxynitrite. This translates to excellent anti-inflammatory and chondro-protective effects by inhibiting intracellular ROS and RNS and promoting antioxidant enzyme activities. With an average diameter of 112.5 nm, DM nanoparticles can be intra-articularly (i.a.) injected into an affected joint and retained at the injection site. When tested in vivo in rodent OA models, DM nanoparticles showed diminished inflammatory cytokine release and reduced proteoglycan loss, which in turn slowed down cartilage degradation. Mechanistic studies suggest that DM nanoparticles also enhance autophagy that benefits OA control. In summary, our study suggests DM nanoparticles as a safe and promising therapeutic for OA.

Effect of ethanol and aqueous extracts of seed pod of Copaifera salikounda (Heckel) on complete Freund's adjuvant-induced rheumatoid arthritis in rats

The antirheumatoid arthritis potential of ethanol and aqueous extracts of seed pod of Copaifera salikounda (SPCS) was evaluated using the chicken collagen/complete Freund's adjuvant-induced arthritic rats model. Adjuvat-induced rats were treated with varied doses of the extracts (400, 600, and 800 mg/kg body weight) and with reference drug, indomethacin for 21 days. Antiarthritic evaluation was done through measurement of body weight, paw size, inflammatory makers, hematological parameters, cytokines, antioxidant enzymes, reduced glutathione, lipid peroxidation as well as histopathological examinations. Treatment with the ethanol and aqueous extracts of SPCS markedly inhibited the paw size and caused weight gain. The extracts considerably modulated the hematological as well as the antioxidant parameters. Likewise, the extract restored the altered lipid peroxidation, pro-inflammatory mediators, and inflammatory factors which further accentuate the implication in adjuvant-induced arthritis. Thus, the ethanol and aqueous extracts of SPCS showed a significant antiarthritic activity that was statistically analogous to that of indomethacin. Practical applications Copaifera salikounda (Heckel) has been used in treatment of different ailments including rheumatoid arthritis in folklore medicine. This is the first reported proof of the antiarthritic potential of the seed pod. Oxidative stress has been implicated in rheumatoid arthritis. Ethanol extract of SPCS has been shown to be predominantly rich in phenols, terpenoids, alkaloids, and flavonoids which are natural antioxidant. The present study has demonstrated that ethanol and aqueous extracts of SPCS can exert antioxidative and antiinflammatory effects, thus strengthening its antiarthritic potentials.

Redox and NF-κB signaling in osteoarthritis

Human cells have to deal with the constant production of reactive oxygen species (ROS). Although ROS overproduction might be harmful to cell biology, there are plenty of data showing that moderate levels of ROS control gene expression by maintaining redox signaling. Osteoarthritis (OA) is the most common joint disorder with a multi-factorial etiology including overproduction of ROS. ROS overproduction in OA modifies intracellular signaling, chondrocyte life cycle, metabolism of cartilage matrix and contributes to synovial inflammation and dysfunction of the subchondral bone. In arthritic tissues, the NF-κB signaling pathway can be activated by pro-inflammatory cytokines, mechanical stress, and extracellular matrix degradation products. This activation results in regulation of expression of many cytokines, inflammatory mediators, transcription factors, and several matrix-degrading enzymes. Overall, NF-κB signaling affects cartilage matrix remodeling, chondrocyte apoptosis, synovial inflammation, and has indirect stimulatory effects on downstream regulators of terminal chondrocyte differentiation. Interaction between redox signaling and NF-κB transcription factors seems to play a distinctive role in OA pathogenesis.

Malnutrition and Fracture Healing: Are Specific Deficiencies in Amino Acids Important in Nonunion Development?

With the increasing incidence of fractures now, and in the future, the absolute number of bone-healing complications such as nonunion development will also increase. Next to fracture-dependent factors such as large bone loss volumes and inadequate stabilization, the nutritional state of these patients is a major influential factor for the fracture repair process. In this review, we will focus on the influence of protein/amino acid malnutrition and its influence on fracture healing. Mainly, the arginine-citrulline-nitric oxide metabolism is of importance since it can affect fracture healing via several precursors of collagen formation, and through nitric oxide synthases it has influences on the bio-molecular inflammatory responses and the local capillary growth and circulation.

Novel iron oxide-cerium oxide core-shell nanoparticles as a potential theranostic material for ROS related inflammatory diseases

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are key signaling molecules that play an important role in the inflammation and progression of many diseases such as cardiovascular disease, especially atherosclerosis. ROS are in particular a significant factor in the development of rheumatoid arthritis and other autoimmune diseases such as allergies. In this study, novel Fe₃O₄/CeO₂ core-shell theranostic nanoparticles capable of reacting with ROS and of being detected by MRI were synthesized and thoroughly characterized. In vitro studies, such as measurement of cell uptake, magnetic resonance imaging, toxicity and ROS scavenging, were conducted. The results indicate that the novel Fe₃O₄/CeO₂ theranostic nanoparticles are effective for scavenging ROS and show excellent magnetic resonance (MR) imaging performance. These theranostic nanomaterials, therefore, show great potential for the treatment and diagnosis of ROS-related inflammatory diseases.

Metabolic syndrome and the decreased levels of uric acid by leflunomide favor redox imbalance in patients with rheumatoid arthritis

Oxidative stress plays a role in the pathophysiology of rheumatoid arthritis (RA). The aim of the present study was to verify the influence of metabolic syndrome (MetS) and disease-modifying antirheumatic drugs on nitrosative and oxidative biomarkers in patients with RA. A total of 177 patients with RA and 150 healthy volunteers participated in this study, which measured lipid hydroperoxides, advanced oxidation protein products (AOPP), nitric oxide metabolites (NOx), carbonyl protein, total radical-trapping antioxidant parameter (TRAP), uric acid (UA), and C-reactive protein (CRP). NOx and the NOx/TRAP ratio were significantly increased in RA, while no significant differences in lipid hydroperoxides, AOPP, UA, and TRAP levels were found between both groups. Treatment with leflunomide was associated with increased levels of carbonyl protein, and lowered levels in TRAP and UA, while the NOx/TRAP ratio further increased. NOx and the NOx/TRAP ratio were significantly higher in women than in men, while TRAP and UA were significantly lower in women. MetS was accompanied by increased AOPP and UA levels. RA was best predicted by increased NOx/TRAP ratio, CRP, and BMI. In conclusion, our data demonstrated that NOx and NOx/TRAP are strongly associated with RA physiopathology. Our findings suggest that inhibition of iNOS may become an interesting therapeutic approach for the treatment of RA. In addition, the presence of MetS and a decrease in levels of UA by leflunomide favor redox imbalance in RA patients. More studies are needed to evaluate the impact of antioxidant capacity reduction on RA progression.

Inducible nitric oxide synthase as a target for osteoarthritis treatment

INTRODUCTION

Inducible nitric oxide synthase (iNOS) is the enzyme responsible for the production of nitric oxide (NO), a major proinflammatory and destructive mediator in osteoarthritis (OA). Areas covered: This is a comprehensive review of the recent literature on the involvement of iNOS in osteoarthritis and its potential to be used as a target for OA treatment. Evidence from in vitro, in vivo and human studies was systematically collected using medical search engines. Preclinical studies have focused on the effect of direct and indirect iNOS inhibitors in both animal and human tissues. Apart from direct inhibitors, common pharmacological agents, herbal and dietary medicines as well as hyperbaric oxygen, low level laser and low intensity pulsed ultrasound have been shown to exhibit a chondroprotective effect by inhibiting the expression of iNOS. Expert opinion: Data support the further investigation of iNOS inhibitors for the treatment of OA in human studies and clinical trials. Indirect iNOS inhibitors such as interleukin 1 inhibitors also need to be studied in greater detail. Finally, human studies need to be conducted on the herbal and dietary medicines and on the non-invasive, non-pharmacological treatments.

Therapeutic Effects of Olive and Its Derivatives on Osteoarthritis: From Bench to Bedside

Osteoarthritis is a major cause of morbidity among the elderly worldwide. It is a disease characterized by localized inflammation of the joint and destruction of cartilage, leading to loss of function. Impaired chondrocyte repair mechanisms, due to inflammation, oxidative stress and autophagy, play important roles in the pathogenesis of osteoarthritis. Olive and its derivatives, which possess anti-inflammatory, antioxidant and autophagy-enhancing activities, are suitable candidates for therapeutic interventions for osteoarthritis. This review aimed to summarize the current evidence on the effects of olive and its derivatives, on osteoarthritis and chondrocytes. The literature on animal and human studies has demonstrated a beneficial effect of olive and its derivatives on the progression of osteoarthritis. In vitro studies have suggested that the augmentation of autophagy (though sirtuin-1) and suppression of inflammation by olive polyphenols could contribute to the chondroprotective effects of olive polyphenols. More research and well-planned clinical trials are required to justify the use of olive-based treatment in osteoarthritis.

Krüppel-like factor 4 regulates the expression of inducible nitric oxide synthase induced by TNF-α in human fibroblast-like synoviocyte MH7A cells

Krüppel-like factor 4 (KLF4), a zinc finger transcription factor, has been implicated in the inflammation mediated by macrophages and endothelial cells by regulating the expression of inflammatory mediators. Here, we investigated whether KLF4 affects the expression of inducible nitric oxide synthase (iNOS), an important inflammatory mediator, in the human RA fibroblast-like synovial cell line MH7A. A pcDNA3.1-KLF4 plasmid or short interfering RNA KLF4 was transfected into MH7A cells, and the iNOS expression and nitric oxide (NO) production were analyzed by quantitative PCR, immunoblotting, and nitrite measurement. The iNOS promoter activity was determined by luciferase assay. The results showed overexpression of KLF4 increased iNOS expression and NO production in the presence or absence of TNF-α. Conversely, KLF4 knockdown markedly reduced iNOS expression and NO production induced by TNF-α. KLF4 activated the transcription activity of iNOS promoter in MH7A cells stimulated by TNF-α. This study indicates that KLF4 is important for regulating the expression of iNOS by TNF-α in human synoviocytes.

Slc11a1 (Nramp-1) gene modulates immune-inflammation genes in macrophages during pristane-induced arthritis in mice

OBJECTIVE AND DESIGN

Pristane-induced arthritis (PIA) in AIRmax mice homozygous for Slc11a1 R and S alleles was used to characterize the influence of Slc11a1 gene polymorphism on immune responses during disease manifestation. Previous reports demonstrated that the presence of the Slc11a1 S allele increased the incidence and severity of PIA in AIRmax ^SS , suggesting that this gene could interact with inflammatory loci to modulate PIA. We investigated the effects of Slc11a1 alleles on the activation of phagocytes during PIA.

TREATMENT

Mice were injected intraperitoneally with two doses of 0.5 mL of mineral oil pristane at 60-day intervals. Arthritis development was accompanied for 180 days.

RESULTS

AIRmax ^SS mice showed differential peritoneal macrophage gene expression profiles during PIA, with higher expression and production of H₂O₂, NO, IL-1β, IL-6, TNF-α, and several chemokines. The presence of the Slc11a1 R allele, on the other hand, diminished the intensity of macrophage activation, restricting arthritis development.

CONCLUSION

Our data demonstrated the fine-tuning roles of Slc11a1 alleles modulating macrophage activation, and consequent PIA susceptibility, in those mouse lines.

Pentosan polysulfate inhibits IL-1β-induced iNOS, c-Jun and HIF-1α upregulation in canine articular chondrocytes

Osteoarthritic (OA) chondrocytes are shown to express inducible nitric oxide synthase (iNOS) which produces high concentrations of nitric oxide (NO), particularly when stimulated with proinflammatory cytokines. NO is involved in OA cartilage degradation. On the other hand, c-Jun N-terminal Kinase (JNK) pathway mediates the activation and transcription of c-Jun, which is required for interleukin-1 (IL-1)-induction of matrix metalloproteinases-13 (MMP-13) in OA pathogenesis. Therefore, the selective inhibition of iNOS and c-Jun is a promising target for treatment and prevention of OA. The purpose of the study was to investigate the inhibitory effects of pentosan polysulfate (PPS) on IL-1β-induced iNOS, c-Jun and HIF-α isoforms upregulation in canine articular chondrocytes (CACs). Primary (P0) chondrocytes were isolated and cultured from femoral head cartilages of three (3) dogs. First passage (P1) chondrocytes were preincubated with 0, 1, 5, 15 and 40 μg/mL of PPS for 4 hr before treatment with 10 ng/mL rhIL-1β for a further 8 hr. In addition, we evaluated the effects of single and multiple cytokine with or without LPS on iNOS protein induction. PPS significantly inhibited (P < 0.05) IL-1β-induced iNOS, c-Jun and HIF-1α mRNA upregulation in a dose-dependent pattern. iNOS mRNA was significantly inhibited at 15 and 40 μg/mL whereas c-Jun and HIF-1α were significantly downregulated at 5, 15 and 40 μg/mL of PPS compared to chondrocytes treated with only rhIL-1β. Intriguingly, CACs were recalcitrant to single IL-1β, TNF-α or LPS-induction of iNOS protein including to a combination of IL-1β+TNF-α, IL-1β+LPS except to TNF-α+LPS and IL-1β+TNF-α+LPS suggestive of a protective mechanism from iNOS detrimental effects on perpetuating OA. IL-1β+TNF-α+LPS-induced iNOS protein expression was significantly abrogated by PPS. We demonstrate for the first time that PPS is a novel inhibitor of IL-1β-induced iNOS, c-Jun, and HIF-1α mRNA upregulation and iNOS protein induction which may be beneficial for prevention and treatment OA.

Celastrol reduces IL-1β induced matrix catabolism, oxidative stress and inflammation in human nucleus pulposus cells and attenuates rat intervertebral disc degeneration in vivo

Celastrol has been reported to exert therapeutic potential on pro-inflammatory diseases including asthma, Crohn's disease, arthritis and neurodegenerative disorders via inhibiting NF-κB pathway. While the effect of celastrol on intervertebral disc degeneration (IDD), which is also a pro-inflammatory disease, remains unknown. In this study, we evaluated the effect of celastrol on IDD in IL-1β treated human nucleus pulposus cells in vitro as well as in puncture induced rat IDD model in vivo. Our results showed that celastrol reduced the expression of catabolic genes (MMP-3, 9, 13, ADAMTS-4, 5), oxidative stress factors (COX-2, iNOS) and pro-inflammatory factors (IL-6, TNF-a) induced by IL-1β in nucleus pulposus cells, also phosphorylation of IκBα and p65 were attenuated by celastrol, indicating NF-κB pathway was inhibited by celastrol in nucleus pulposus cells. In vivo study showed that celastrol treated rats had stronger T2-weighted signal than vehicle-treated rats at 2 weeks and 6 weeks' time point, suggesting celastrol could attenuate intervertebral disc degeneration in vivo. Together, our study demonstrates that celastrol could reduce IL-1β induced matrix catabolism, oxidative stress and inflammation in human nucleus pulposus cells and attenuates rat intervertebral disc degeneration in vivo, which shows its potential to be a therapeutic drug for IDD.

The protective role of nitric oxide-dependent innate immunosuppression in the early stage of cartilage damage in rats: Role of nitric oxide in cartilage damage

Objectives

Osteoarthritis (OA) is the most common form of arthritis, affecting approximately 15% of the human population. Recently, increased concentration of nitric oxide in serum and synovial fluid in patients with OA has been observed. However, the exact role of nitric oxide in the initiation of OA has not been elucidated. The aim of the present study was to investigate the role of nitric oxide in innate immune regulation during OA initiation in rats.

Methods

Rat OA was induced by performing meniscectomy surgery while cartilage samples were collected 0, 7, and 14 days after surgery. Cartilage cytokine levels were determined by using enzyme-linked immunosorbent assay, while other proteins were assessed by using Western blot

Results

In the time course of the study, nitric oxide was increased seven and 14 days after OA induction. Pro-inflammatory cytokines including tumour necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 were decreased. L-NG-Nitroarginine methyl ester (L-NAME, a non-specific nitric oxide synthase inhibitor) significantly decreased cartilage nitric oxide and blocked immune suppression. Further, L-NAME decreased Matrix metalloproteinase (MMPs) and increased tissue inhibitor of metalloproteinase (TIMP) expression in meniscectomised rats.

Conclusion

Nitric oxide-dependent innate immune suppression protects cartilage from damage in the early stages of OA initiation in rats.

Cite this article: C-C. Hsu, C-L. Lin, I-M. Jou, P-H. Wang, J-S. Lee. The protective role of nitric oxide-dependent innate immunosuppression in the early stage of cartilage damage in rats: Role of nitric oxide in ca rtilage da mage. Bone Joint Res 2017;6:253–258. DOI: 10.1302/2046-3758.64.BJJ-2016-0161.R1.

Vlasouliolides A-D, four rare C17/C15 sesquiterpene lactone dimers with potential anti-inflammatory activity from Vladimiria souliei

Vlasouliolides A-D (1–4), four rare sesquiterpene lactone dimers, were isolated from Vladimiria souliei. The common structural characteristic of 1–4 is the C₃₂ skeleton comprising two sesquiterpene lactone units linked by a C11-C13′ single bond with one acetyl connected to the C-13 position of one of the two sesquiterpene lactone units. The stereochemistries of 1–4 were assigned by a combination of NOESY correlations and Cu-Κα X-ray crystallographic analyses. Compounds 1–4 strongly inhibited the production of NO in LPS-stimulated RAW 264.7 cells. Furthermore, 1 and 2 inhibited the activation of NF-κB in LPS-induced 293T cells.

Oxidative Stress-induced DNA Damage in the Synovial Cells of the Temporomandibular Joint in the Rat

Synovial hyperplasia is a feature of degenerative temporomandibular joint (TMJ) disease. However, the mechanism by which hyperplasia progresses in the TMJ is unknown. Based on the hypothesis that the oxidative stress generated by mechanical loading causes degenerative changes in the TMJ synovium, we investigated the generation of the highly reactive species, peroxynitrite, and the occurrence of DNA damage in the synovium. After condylar hypermobility of rat TMJs, a marker of peroxynitrite, nitrotyrosine, was localized to the nuclei and cytoplasm of the synovial lining cells and fibroblasts in synovitis-induced TMJ. DNA single-strand breaks were found in the nuclei of the synovial cells only after enzyme treatment, whereas DNA double-strand breaks were not detected. These findings indicate that condylar hypermovement induces the proliferation of synovial cells, and suggest that oxidative stress leads to the progression of synovial hyperplasia via DNA damage of the synovial cells in TMJs after mechanical loading.

The Presence of the Neuronal Nitric Oxide Synthase Isoform in the Intervertebral Disk

Intervertebral disk degeneration is a progressive and debilitating disease with multifactorial causes. Nitric oxide (NO) might contribute to the cell death pathway. We evaluated the presence of the constitutive form of the neuronal NOS (nNOS) in both health and degenerated intervertebral disk through qPCR and immunohistochemistry. We also analyzed the potential role of nNOS modulation in the tail needle puncture model of intervertebral disk degeneration. Male Wistar rats were submitted to percutaneous disk puncture with a 21-gauge needle of coccygeal vertebras. The selective nNOS pharmacological inhibitor N ^(ω)-propyl-L-arginine (NPLA) or a nNOS-target siRNA (siRNAnNOShum_4400) was injected immediately after the intervertebral disk puncture with a 30-gauge needle. Signs of disk degeneration were analyzed by in vivo magnetic resonance imaging and histological score. We found that intact intervertebral disks express low levels of nNOS mRNA. Disk injury caused a 4 fold increase in nNOS mRNA content at 5 h post disk lesion. However, NPLA or nNOS-target siRNA slight mitigate the intervertebral disk degenerative progress. Our data show evidence of the nNOS presence in the intervertebral disk and its upregulation during degeneration. Further studies would disclose the nNOS role and its potential therapeutical value in the intervertebral disk degeneration.

A Cytokine Signalling Network for the Regulation of Inducible Nitric Oxide Synthase Expression in Rheumatoid Arthritis

In rheumatoid arthritis (RA), nitric oxide (NO) is implicated in inflammation, angiogenesis and tissue destruction. The enzyme inducible nitric oxide synthase (iNOS) is responsible for the localised over-production of NO in the synovial joints affected by RA. The pro- and anti-inflammatory cytokines stimulate the synovial macrophages and the fibroblast-like synoviocytes to express iNOS. Therefore, the cytokine signalling network underlying the regulation of iNOS is essential to understand the pathophysiology of the disease. By using information from the literature, we have constructed, for the first time, the cytokine signalling network involved in the regulation of iNOS expression. Using the differential expression patterns obtained by re-analysing the microarray data on the RA synovium and the synovial macrophages available in the Gene Expression Omnibus (GEO) database, we aimed to establish the role played by the network genes towards iNOS regulation in the RA synovium. Our analysis reveals that the network genes belonging to interferon (IFN) and interleukin-10 (IL-10) pathways are always up-regulated in the RA synovium whereas the genes which are part of the anti-inflammatory transforming growth factor-beta (TGF-β) signalling pathway are mostly down-regulated. We observed a consistent up-regulation of the transcription factor signal transducers and activators of transcription 1 (STAT1) in the RA synovium and the macrophages. Interestingly, we found a consistent up-regulation of the iNOS interacting protein ras-related C3 botulinum toxin substrate 2 (RAC2) in the RA synovium as well as the macrophages. Importantly, we have constructed a model to explain the impact of IFN and IL-10 pathways on Rac2-iNOS interaction leading to over-production of NO and thereby causing chronic inflammation in the RA synovium. The interplay between STAT1 and RAC2 in the regulation of NO could have implications for the identification of therapeutic targets for RA.

Pruinosanones A-C, anti-inflammatory isoflavone derivatives from Caragana pruinosa

Pruinosanone A (1), a novel spirochromone, was isolated from the roots of Caragana pruinosa. Two biogenetically related isoflavone intermediates, pruinosanones B and C (2 and 3), were also isolated, together with five known analogs identified as 3-hydroxy-9-methoxypterocarpan (4), 7,2'-dihydroxy-4'-methoxyisoflavanol (5), retusin-8-methylether (6), 7,2'-dihydroxy-8,4'-dimethoxy isoflavone (7) and 7,3'-dihydroxy-8,4'-dimethoxy isoflavone (8). The structures of 1-3 were elucidated based on extensive spectroscopic methods. Notably, 1 is the first example of a spirochromone possessing an unprecedented pentacyclic skeleton containing a spiro[benzo[d][1,3]dioxole-2,3'-chroman]-4'-one motif, which was confirmed by X-ray diffraction analysis. A plausible biosynthetic pathway for 1 was also proposed. Compounds 1-8 were tested for their ability to inhibit nitric oxide (NO) production in LPS-induced RAW 264.7 macrophages, and compounds 1-3 were the most potent inhibitors of NO production, with IC50 values of 1.96, 1.93 and 1.58 μM, respectively. A structure-activity relationship analysis revealed that the fused 2-isopropenyl-2,3-dihydrofuran moiety plays a vital role in the potency of these compounds. Moreover, 1 was found to significantly inhibit inducible nitric oxide synthase (iNOS) protein expression, which accounts for the potent inhibition of NO production by this spirochromone.

A Comparison of the Effects of Neuronal Nitric Oxide Synthase and Inducible Nitric Oxide Synthase Inhibition on Cartilage Damage

The objective of this study was to investigate the effects of selective inducible nitric oxide synthase and neuronal nitric oxide synthase inhibitors on cartilage regeneration. The study involved 27 Wistar rats that were divided into five groups. On Day 1, both knees of 3 rats were resected and placed in a formalin solution as a control group. The remaining 24 rats were separated into 4 groups, and their right knees were surgically damaged. Depending on the groups, the rats were injected with intra-articular normal saline solution, neuronal nitric oxide synthase inhibitor 7-nitroindazole (50 mg/kg), inducible nitric oxide synthase inhibitor amino-guanidine (30 mg/kg), or nitric oxide precursor L-arginine (200 mg/kg). After 21 days, the right and left knees of the rats were resected and placed in formalin solution. The samples were histopathologically examined by a blinded evaluator and scored on 8 parameters. Although selective neuronal nitric oxide synthase inhibition exhibited significant (P = 0.044) positive effects on cartilage regeneration following cartilage damage, it was determined that inducible nitric oxide synthase inhibition had no statistically significant effect on cartilage regeneration. It was observed that the nitric oxide synthase activation triggered advanced arthrosis symptoms, such as osteophyte formation. The fact that selective neuronal nitric oxide synthase inhibitors were observed to have mitigating effects on the severity of the damage may, in the future, influence the development of new agents to be used in the treatment of cartilage disorders.

Lymphatic endothelial cells efferent to inflamed joints produce iNOS and inhibit lymphatic vessel contraction and drainage in TNF-induced arthritis in mice

Background

In this study, we sought to determine the cellular source of inducible nitric oxide synthase (iNOS) induced in lymphatic endothelial cells (LECs) in response to tumor necrosis factor (TNF), the effects of iNOS on lymphatic smooth muscle cell (LSMC) function and on the development of arthritis in TNF-transgenic (TNF-Tg) mice, and whether iNOS inhibitors improve lymphatic function and reduce joint destruction in inflammatory erosive arthritis.

Methods

We used quantitative polymerase chain reactions, immunohistochemistry, histology, and near-infrared imaging to examine (1) iNOS expression in podoplanin + LECs and lymphatic vessels from wild-type (WT) and TNF-Tg mice, (2) iNOS induction by TNF in WT LECs, (3) the effects of iNOS inhibitors on expression of functional muscle genes in LSMCs, and (4) the effects of iNOS inhibitors on lymphatic vessel contraction and drainage, as well as the severity of arthritis, in TNF-Tg mice.

Results

LECs from TNF-Tg mice had eight fold higher iNOS messenger RNA levels than WT cells, and iNOS expression was confirmed immunohistochemically in podoplanin + LECs in lymphatic vessels from inflamed joints. TNF (0.1 ng/ml) increased iNOS levels 40-fold in LECs. LSMCs cocultured with LECs pretreated with TNF had reduced expression of functional muscle genes. This reduction was prevented by ferulic acid, which blocked nitric oxide production. Local injection of L-N⁶-(1-iminoethyl)lysine 5-tetrazole-amide into inflamed paws of TNF-Tg mice resulted in recovery of lymphatic vessel contractions and drainage. Treatment of TNF-Tg mice with ferulic acid reduced synovial inflammation as well as cartilage and bone erosion, and it also restored lymphatic contraction and drainage.

Conclusions

iNOS is produced primarily by LECs in lymphatic vessel efferent from inflamed joints of TNF-Tg mice in response to TNF and inhibits LSMC contraction and lymph drainage. Ferulic acid represents a potential new therapy to restore lymphatic function and thus improve inflammatory arthritis by inhibiting local production of nitric oxide by LSMCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0963-8) contains supplementary material, which is available to authorized users.

Aortic VCAM-1: an early marker of vascular inflammation in collagen-induced arthritis

Cardiovascular disease (CVD) is a major cause of morbidity and mortality in rheumatoid arthritis (RA). There are limited experimental data on vascular involvement in arthritis models. To study the link between CVD and inflammation in RA, we developed a model of vascular dysfunction and articular inflammation by collagen‐induced arthritis (CIA) in C57Bl/6 (B6) mice. We studied the expression of vascular inflammatory markers in CIA with and without concomitant hyperlipidic diet (HD). Collagen‐induced arthritis was induced with intradermal injection of chicken type‐II collagen followed by a boost 21 days later. Mice with and without CIA were fed a standard diet or an HD for 12 weeks starting from the day of the boost. Arthritis severity was evaluated with a validated clinical score. Aortic mRNA levels of vascular cell adhesion molecule‐1 (VCAM‐1), inducible nitric oxide synthase (iNOS) and interleukin‐17 were analysed by quantitative RT‐PCR. Vascular cell adhesion molecule‐1 localization in the aortic sinus was determined by immunohistochemistry. Atherosclerotic plaque presence was assessed in aortas. Collagen‐induced arthritis was associated with increased expression of VCAM‐1, independent of diet. VCAM‐1 overexpression was detectable as early as 4 weeks after collagen immunization and persisted after 15 weeks. The HD induced atheroma plaque formation and aortic iNOS expression regardless of CIA. Concomitant CIA and HD had no additive effect on atheroma or VCAM‐1 or iNOS expression. CIA and an HD diet induced a distinct and independent expression of large‐vessel inflammation markers in B6 mice. This model may be relevant for the study of CVD in RA.

Is matching ruthenium with dithiocarbamato ligands a potent chemotherapeutic weapon in oncology?

In the last years, several metal-based compounds have been designed and biologically investigated worldwide in order to obtain chemotherapeutics with a better toxicological profile and comparable or higher antiblastic activity than the clinically-established platinum-based drugs. In this context, researchers have addressed their attention to alternative nonplatinum derivatives able to maximize the anticancer activity of the new drugs and to minimize the side effects. Among them, a number of ruthenium complexes have been developed, including the compounds NAMI-A and KP1019, now in clinical trials. Here, we report the results collected so far for a particular class of ruthenium complexes - the ruthenium(II/III)-dithiocarbamates - which proved more potent than cisplatin in vitro, even at nanomolar concentrations, against a wide panel of human tumor cell lines.

ROS/oxidative stress signaling in osteoarthritis

Osteoarthritis is the most common joint disorder with increasing prevalence due to aging of the population. Its multi-factorial etiology includes oxidative stress and the overproduction of reactive oxygen species, which regulate intracellular signaling processes, chondrocyte senescence and apoptosis, extracellular matrix synthesis and degradation along with synovial inflammation and dysfunction of the subchondral bone. As disease-modifying drugs for osteoarthritis are rare, targeting the complex oxidative stress signaling pathways would offer a valuable perspective for exploration of potential therapeutic strategies in the treatment of this devastating disease.

Chitosan enriched three-dimensional matrix reduces inflammatory and catabolic mediators production by human chondrocytes

This in vitro study investigated the metabolism of human osteoarthritic (OA) chondrocytes encapsulated in a spherical matrix enriched of chitosan. Human OA chondrocytes were encapsulated and cultured for 28 days either in chitosan-alginate beads or in alginate beads. The beads were formed by slowly passing dropwise either the chitosan 0.6%-alginate 1.2% or the alginate 1.2% solution through a syringe into a 102 mM CaCl2 solution. Beads were analyzed histologically after 28 days. Interleukin (IL)-6 and -8, prostaglandin (PG) E2, matrix metalloproteinases (MMPs), hyaluronan and aggrecan were quantified directly in the culture supernatant by specific ELISA and nitric oxide (NO) by using a colorimetric method based on the Griess reaction. Hematoxylin and eosin staining showed that chitosan was homogeneously distributed through the matrix and was in direct contact with chondrocytes. The production of IL-6, IL-8 and MMP-3 by chondrocytes significantly decreased in chitosan-alginate beads compared to alginate beads. PGE2 and NO decreased also significantly but only during the first three days of culture. Hyaluronan and aggrecan production tended to increase in chitosan-alginate beads after 28 days of culture. Chitosan-alginate beads reduced the production of inflammatory and catabolic mediators by OA chondrocytes and tended to stimulate the synthesis of cartilage matrix components. These particular effects indicate that chitosan-alginate beads are an interesting scaffold for chondrocytes encapsulation before transplantation to repair cartilage defects.

Inhibition of neuroinflammation by synthetic androstene derivatives incorporating amino acid methyl esters on activated BV-2 microglia

Androstene derivatives incorporating amino acid methyl esters were prepared, and their anti-inflammatory effects were evaluated in lipopolysaccharide (LPS)-activated BV-2 microglial cells. Several compounds exhibited dose-dependent inhibition. The most active compound, methyl ((3S,10R,13S)-3-hydroxy-10,13-dimethyl-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthrene-17-carbonyl)-L-phenylalaninate (10) significantly suppressed LPS-induced expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Mechanistic studies revealed that compound 10 markedly inhibits phosphorylation of p38 mitogen-activated protein kinases (MAPKs) and subsequent transcription factor (NF-κB) and activator protein-1 (AP-1) activation. Furthermore, compound 10 decreased LPS-activated microglial neurotoxicity in a condition medium/HT-22 neuroblastoma co-culture model. Taken together, these results suggest 10 is a potential lead compound for the development of a novel therapeutic agent for neurodegenerative diseases.