Inflammatory microcrystals stimulate interleukin-6 production and secretion by human monocytes and synoviocytes

Calcium Pyrophosphate Crystal Formation and Deposition: Where Do we Stand and What Does the Future hold?

PURPOSE OF THE REVIEW

Although calcium pyrophosphate deposition (CPPD) has been known since the 1960s, our understanding of its pathogenesis remains rudimentary. This review aims to illustrate the known mechanisms underlying calcium pyrophosphate (CPP) crystal formation and deposition and explore future directions in research. By examining various perspectives, from basic research to clinical and imaging assessments, as well as new emerging methodologies, we can establish a starting point for a deeper understanding of CPPD pathogenesis.

RECENT FINDINGS

Recent years have seen significant advances in CPPD research, particularly in the clinical field with the development of the 2023 ACR/EULAR classification criteria for CPPD disease, and in imaging with the introduction of the OMERACT ultrasonographic definitions and scoring system. However, progress in basic research has been slower. New laboratory approaches, such as Raman spectroscopy and omics sciences, offer promising insights that may help piece together the puzzle of CPPD. CPPD is a common yet understudied condition. As the population ages and CPPD becomes more prevalent, there is an urgent need to better understand the disease and the mechanisms involved in crystal formation and deposition, in order to improve diagnosis and therapeutic approaches.

Advancements in the study of IL-6 and its receptors in the pathogenesis of gout

Gout is an autoinflammatory disease characterized by the deposition of monosodium urate crystals in or around the joints, primarily manifesting as inflammatory arthritis that recurs and resolves spontaneously. Interleukin-6 (IL-6) is a versatile cytokine with both anti-inflammatory and pro-inflammatory capabilities, linked to a variety of inflammatory diseases such as gouty arthritis, rheumatoid arthritis, inflammatory bowel disease, vasculitis, and several types of cancer. The rapid production of IL-6 during infections and tissue damage aids in host defense. However, excessive synthesis of IL-6 and dysregulation of its receptor signaling (IL-6R) might contribute to the pathology of diseases. Recent advancements in clinical and basic research, along with developments in animal models, have established the significant role of IL-6 and its receptors in the pathogenesis of gout, although the precise mechanisms remain to be fully elucidated. This review discusses the role of IL-6 and its receptors in gout progression and examines contemporary research on modulating IL-6 and its signaling pathways for treatment. It aims to provide insights into the pathogenesis of gout and to advance the development of targeted therapies for gout-related inflammation.

Identification of potential biomarkers of gout through weighted gene correlation network analysis

Background

Although hyperuricemia is not always associated with acute gouty arthritis, uric acid is a significant risk factor for gout. Therefore, we investigated the specific mechanism of uric acid activity.

Methods

Using the gout-associated transcriptome dataset GSE160170, we conducted differential expression analysis to identify differentially expressed genes (DEGs). Moreover, we discovered highly linked gene modules using weighted gene coexpression network analysis (WGCNA) and evaluated their intersection. Subsequently, we screened for relevant biomarkers using the cytoHubba and Mcode algorithms in the STRING database, investigated their connection to immune cells and constructed a competitive endogenous RNA (ceRNA) network to identify upstream miRNAs and lncRNAs. We also collected PBMCs from acute gouty arthritis patients and healthy individuals and constructed a THP-1 cell gout inflammatory model, RT-qPCR and western blotting (WB) were used to detect the expression of C-X-C motif ligand 8 (CXCL8), C-X-C motif ligand 2 (CXCL2), and C-X-C motif ligand 1 (CXCL1). Finally, we predicted relevant drug targets through hub genes, hoping to find better treatments.

Results

According to differential expression analysis, there were 76 upregulated and 28 downregulated mRNAs in GSE160170. Additionally, WGCNA showed that the turquoise module was most strongly correlated with primary gout; 86 hub genes were eventually obtained upon intersection. IL1β, IL6, CXCL8, CXCL1, and CXCL2 are the principal hub genes of the protein-protein interaction (PPI) network. Using RT-qPCR and WB, we found that there were significant differences in the expression levels of CXCL8, CXCL1, and CXCL2 between the gouty group and the healthy group, and we also predicted 10 chemicals related to these proteins.

Conclusion

In this study, we screened and validated essential genes using a variety of bioinformatics tools to generate novel ideas for the diagnosis and treatment of gout.

Immune cell targeted fumaric esters support a role of GPR109A as a primary target of monomethyl fumarate in vivo

Dimethyl fumarate (DMF) is approved as a treatment for multiple sclerosis (MS), however, its mode of action remains unclear. One hypothesis proposes that Michael addition to thiols by DMF, notably glutathione is immunomodulatory. The alternative proposes that monomethyl fumarate (MMF), the hydrolysis product of DMF, is a ligand to the fatty acid receptor GPR109A found in the lysosomes of immune cells. We prepared esters of MMF and macrolides derived from azithromycin, which were tropic to immune cells by virtue of lysosomal trapping. We tested the effects of these substances in an assay of response to Lipopolysaccharide (LPS) in freshly isolated human peripheral blood mononuclear cells (PBMCs). In this system, we observed that the 4'' ester of MMF (compound 2 and 3) reduced levels of Interleukins (IL)-1β, IL-12 and tumor necrosis factor alpha (TNFα) significantly at a concentration of 1 µM, while DMF required about 25 µM for the same effect. The 2' esters of MMF (compound 1 and 2) were, like MMF itself, inactive in vitro. The 4'' ester formed glutathione conjugates rapidly while the 2' conjugates did not react with thiols but did hydrolyze slowly to release MMF in these cells. We then tested the substances in vivo using the imiquimod/isostearate model of psoriasis where the 2' ester was the most active at 0.06-0.12 mg/kg (approximately 0.1 µmol/kg), improving skin score, body weight and cytokine levels (TNFα, IL-17A, IL-17F, IL-6, IL-1β, NLRP3 and IL-23A). In contrast, the thiol reactive 4'' ester was less active than the 2' ester while DMF was ca. 300-fold less active. The thiol reactive 4'' ester was not easily recovered from either plasma or organs while the 2' ester exhibited conventional uptake and elimination. The 2' ester also reduced levels of IL-6 in acute monosodium urate (MSU) induced inflammation. These data suggest that mechanisms that are relevant in vivo center on the release of MMF. Given that GPR109A is localized to the lysosome, and that lysosomal trapping increases 2' ester activity by > 300 fold, these data suggest that GPR109A may be the main target in vivo. In contrast, the effects associated with glutathione (GSH) conjugation in vitro are unlikely to be as effective in vivo due to the much lower dose in use which cannot titrate the more concentrated thiols. These data support the case for GPR109A modulation in autoimmune diseases.

Cartilage calcification in osteoarthritis: mechanisms and clinical relevance

Pathological calcification of cartilage is a hallmark of osteoarthritis (OA). Calcification can be observed both at the cartilage surface and in its deeper layers. The formation of calcium-containing crystals, typically basic calcium phosphate (BCP) and calcium pyrophosphate dihydrate (CPP) crystals, is an active, highly regulated and complex biological process that is initiated by chondrocytes and modified by genetic factors, dysregulated mitophagy or apoptosis, inflammation and the activation of specific cellular-signalling pathways. The links between OA and BCP deposition are stronger than those observed between OA and CPP deposition. Here, we review the molecular processes involved in cartilage calcification in OA and summarize the effects of calcium crystals on chondrocytes, synovial fibroblasts, macrophages and bone cells. Finally, we highlight therapeutic pathways leading to decreased joint calcification and potential new drugs that could treat not only OA but also other diseases associated with pathological calcification.

Joint Application of Multiple Inflammatory Cytokines in Diagnosis of Gout Flare

Purpose

This study aimed to explore the accuracy for joint application of inflammatory cytokines in diagnosis of gout flare by comparison with peripheral blood cells.

Methods

We collected the clinical data of 96 acute gout patients and 144 remission gout patients, and compared the levels of peripheral blood cells, inflammatory cytokines and blood biochemistry indexes between acute and remission gout. We respectively assessed the area under curves (AUCs) for single and multiple inflammatory cytokines including C-reactive protein (CRP), interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), and single and multiple peripheral blood cells including platelet (PLT), white blood cell (WBC), percentages of neutrophils (N%), lymphocytes (L%), eosinophils (E%), basophils (B%) in diagnosis of acute gout by receiver operating characteristic (ROC) curve analysis.

Results

By contrast with remission gout, the levels of PLT, WBC, N%, CRP, IL-1β, IL-6 and TNF-α increased, and the levels of L%, E% and B% decreased in acute gout. The AUCs of PLT, WBC, N%, L%, E% and B% in diagnosis of acute gout were respectively 0.591, 0.601, 0.581, 0.567, 0.608 and 0.635, while the AUC for joint application of these peripheral blood cells was 0.674. Moreover, the AUCs of CRP, IL-1β, IL-6 and TNF-α in diagnosis of acute gout were respectively 0.814, 0.683, 0.622 and 0.746, while the AUC for joint application of these inflammatory cytokines was 0.883, reflecting significantly higher levels than peripheral blood cells.

Conclusion

The joint application of multiple inflammatory cytokines can better distinguish acute gout from remission gout compared with peripheral blood cells.

Clinical and immunologic differences in cellulitis vs. pseudocellulitis

Introduction: The immunologic mechanisms between cellulitis and pseudocellulitis differ greatly, even though their clinical presentations may overlap.Areas covered: This article discusses cellulitis and common entities within the pseudocellulitis spectrum including acute lymphedema, superficial venous thrombosis, allergic contact dermatitis, lipodermatosclerosis, stasis dermatitis, erythema nodosum, cutaneous gout, and bursitis. The literature search was conducted from PubMed search engine between March and May 2021.Expert commentary: While immunologic differences in cellulitis and the various entities of pseudocellulitis are clear, there is a practice gap in applying these differences to the clinic and hospital setting. Further, existing studies are weakened by the lack of a gold-standard diagnosis in this disease category. Additional work is necessary in developing a gold-standard for the diagnosis and secondly, to project these immunologic differences as biomarkers to differentiate sterile inflammation from a potential life threatening bacterial or fungal infection.

Modified Simiaowan prevents articular cartilage injury in experimental gouty arthritis by negative regulation of STAT3 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Modified Simiaowan (MSW) is a traditional Chinese medicine formula that is composed of six herbs. It has been widely used in the treatment of gouty arthritis.

AIM OF THE STUDY

This study was designed to investigate the effect of MSW on gouty arthritis and explore the possible mechanisms.

MATERIAL AND METHODS

The rat gouty arthritis model was established by intra-articular injection of Monosodium Urate (MSU) crystal, and then treated with MSW for 5 days. The perimeter of the knee joints was measured in a time-dependent manner and serum samples were collected for the detection of TNF-α, IL-1β, and IL-6 protein levels by ELISA. The protein expressions of MMP-3, TIMP-3, STAT3, and p-STAT3 in cartilage tissues and C28/I2 cells were detected by Western blot, and the levels of proteoglycan in primary chondrocytes and cartilage tissues were determined by toluidine blue staining. In addition, AG490 and IL-6 were used in vitro to explore the function of IL-6/STAT3 pathway in the protective effect of MSU.

RESULTS

MSW reduced the joint swelling rate in gouty arthritis model and inhibited MSU induced up-regulation of IL-1β, TNF-α, and IL-6 protein levels in serum and synovial fluid. IL-1β induced an increase in p-STAT3 and MMP-3 protein expression in C28/I2 cells, as well as a decrease in TIMP-3. MSW serum inhibited the protein expression changes induced by IL-1β in vitro. Furthermore, inhibition of STAT3 signaling negated the effect of MSW serum on p-STAT3, MMP-3, and TIMP-3 protein levels in C28/I2 cells. MSW also increased the content of proteoglycan significantly both in vivo and in vitro.

CONCLUSION

Our data indicated that MSW protected rats from MSU-induced experimental gouty arthritis and IL-1β/IL-6/STAT3 pathway played an essential role in the protective effect of MSU against GA.

Soluble Uric Acid Is an Intrinsic Negative Regulator of Monocyte Activation in Monosodium Urate Crystal-Induced Tissue Inflammation

Although monosodium urate (MSU) crystals are known to trigger inflammation, published data on soluble uric acid (sUA) in this context are discrepant. We hypothesized that diverse sUA preparation methods account for this discrepancy and that an animal model with clinically relevant levels of asymptomatic hyperuricemia and gouty arthritis can ultimately clarify this issue. To test this, we cultured human monocytes with different sUA preparation solutions and found that solubilizing uric acid (UA) by prewarming created erroneous results because of UA microcrystal contaminants triggering IL-1β release. Solubilizing UA with NaOH avoided this artifact, and this microcrystal-free preparation suppressed LPS- or MSU crystal-induced monocyte activation, a process depending on the intracellular uptake of sUA via the urate transporter SLC2A9/GLUT9. CD14⁺ monocytes isolated from hyperuricemic patients were less responsive to inflammatory stimuli compared with monocytes from healthy individuals. Treatment with plasma from hyperuricemic patients impaired the inflammatory function of CD14⁺ monocytes, an effect fully reversible by removing sUA from hyperuricemic plasma. Moreover, Alb-creERT2;Glut9 ^lox/lox mice with hyperuricemia (serum UA of 9-11 mg/dl) showed a suppressed inflammatory response to MSU crystals compared with Glut9 ^lox/lox controls without hyperuricemia. Taken together, we unravel a technical explanation for discrepancies in the published literature on immune effects of sUA and identify hyperuricemia as an intrinsic suppressor of innate immunity, in which sUA modulates the capacity of monocytes to respond to danger signals. Thus, sUA is not only a substrate for the formation of MSU crystals but also an intrinsic inhibitor of MSU crystal-induced tissue inflammation.

A comparative study on anti-inflammatory drug combinations in domestic pigeons with experimentally induced acute arthritis

The study compares the effect of one-time administration of nonsteroidal and/or steroidal anti-inflammatory combinations by topical or intramuscular (IM) routes to pigeons with monosodium urate (MSU)-induced arthritis. Forty-five adult domestic pigeons were assigned into nine equal groups: NC, negative control; PC, positive control with arthritis; sham, sham control; T1, meloxicam + hydrocortisone; T2, dexamethasone + piroxicam; T3, meloxicam + dexamethasone; T4, hydrocortisone + piroxicam; T5, dexamethasone + hydrocortisone; T6, meloxicam + piroxicam. Arthritis was also induced in T1 to T6 birds. Meloxicam and dexamethasone were administered by IM injection and the other drugs topically right after the induction of arthritis. Different drug combinations significantly decreased one-leg standing time. Induction of arthritis significantly increased TNF-α and IL-6 levels in synovial fluid and serum corticosterone and epinephrine in the PC group. Administration of drugs to birds of Groups T1 and T5 did not significantly change corticosterone concentration, while all different drug combinations decreased epinephrine level. Drug combinations that demonstrated better analgesic effect more strongly reduced serum epinephrine concentration. Meloxicam + hydrocortisone was the most effective combination in reducing inflammatory cytokines. In conclusion, one-time combination therapy with anti-inflammatory agents was effective in the acute management of inflammatory pain due to MSU-induced arthritis in pigeons, even by the topical route.

Is there a role for cherries in the management of gout?

Despite the availability of effective urate-lowering therapy (ULT) and anti-inflammatory drugs for the treatment of gout, there is considerable interest in novel treatment approaches. Patients with gout often have a multitude of comorbidities, leading to concern over drug-drug interactions and medication adverse events. The cherry is a small nutrient-rich fruit that has garnered a great deal of attention in recent years as a nonpharmacologic option for the treatment of a multitude of disease manifestations. Perhaps a quarter of patients with gout try cherries or cherry products to treat their gout, which have antioxidant and anti-inflammatory (IL-6, TNF-α, IL-1β, IL-8, COX-I and -II) properties, hypouricemic effects, and the ability to downregulate NFkB-mediated osteoclastogenesis. Based on these properties, cherries may reduce both the acute and chronic inflammation associated with recurrent gout flares and its chronic destructive arthropathy. In this review, we explore the potential benefits of cherries and cherry products as a nonpharmacologic option for the treatment of gout.

Prominent Inflammatory Features of Monocytes/Macrophages in Acute Calcium Pyrophosphate Crystal Arthritis: a Comparison with Acute Gouty Arthritis

Calcium pyrophosphate (CPP) crystals can present as acute inflammatory arthritis which is known as an acute CPP crystal arthritis. Although monocytes/macrophages have been shown to play a role in the initiation of crystal-mediated inflammatory responses, differences in their phenotypes between acute CPP crystal arthritis and acute gouty arthritis have not yet been investigated. We examined the immunological characteristics of synovial monocytes/macrophages in patients with acute CPP crystal and acute gouty arthritis. CD14⁺CD3⁻CD19⁻CD56⁻ cell frequencies in synovial fluid mononuclear cells (SFMCs) were measured. Expression of pro- and anti-inflammatory cytokines and markers was determined. The SFMCs were dominated by a population of monocytes/macrophages in acute CPP crystal arthritis similar to that in acute gout. Synovial monocytes/macrophages showed the phenotypes of infiltrated monocytes as shown by expression of CD88, C-C chemokine receptor type 2, myeloid-related protein (MRP)8 and MRP14 but not proto-oncogene tyrosine-protein kinase MER. Comparatively, the CD14⁺ cells from patients with acute CPP crystal arthritis had similar high levels of IL-1β and TNF-α production but significantly lower expression of IL-10 and M2 marker (CD163). The monocytes/macrophages had the capacity to produce IL-8 in response to CPP crystals. Proinflammatory features were more dominant in monocytes/macrophages during acute CPP crystal arthritis than those during acute gouty arthritis.

[Ru(bpy)2(NO)SO3](PF6), a Nitric Oxide Donating Ruthenium Complex, Reduces Gout Arthritis in Mice

Monosodium urate crystals (MSU) deposition induces articular inflammation known as gout. This disease is characterized by intense articular inflammation and pain by mechanisms involving the activation of the transcription factor NFκB and inflammasome resulting in the production of cytokines and oxidative stress. Despite evidence that MSU induces iNOS expression, there is no evidence on the effect of nitric oxide (NO) donors in gout. Thus, the present study evaluated the effect of the ruthenium complex donor of NO {[Ru(bpy)₂(NO)SO₃](PF₆)} (complex I) in gout arthritis. Complex I inhibited in a dose-dependent manner MSU-induced hypersensitivity to mechanical stimulation, edema and leukocyte recruitment. These effects were corroborated by a decrease of histological inflammation score and recruitment of Lysm-eGFP⁺ cells. Mechanistically, complex I inhibited MSU-induced mechanical hypersensitivity and joint edema by triggering the cGMP/PKG/ATP-sensitive K (+) channels signaling pathway. Complex I inhibited MSU-induced oxidative stress and pro-inflammatory cytokine production in the knee joint. These data were supported by the observation that complex I inhibited MSU-induced NFκB activation, and IL-1β expression and production. Complex I also inhibited MSU-induced activation of pro-IL-1β processing. Concluding, the present data, to our knowledge, is the first evidence that a NO donating ruthenium complex inhibits MSU-induced articular inflammation and pain. Further, complex I targets the main physiopathological mechanisms of gout arthritis. Therefore, it is envisaged that complex I and other NO donors have therapeutic potential that deserves further investigation.

Phagocytosis of monosodium urate crystals by human synoviocytes induces inflammation

IMPACT STATEMENT

Gout is distinguished by an inflammatory process that is mediated by phagocytosis of monosodium urate (MSU) crystals in synoviocytes by regulation of unknown mechanisms. Here we suggest that the synovial cells play a crucial role in gouty arthritis by activating inflammation by MSU uptake and increasing the secretion of pro-inflammatory cytokines IL-1β, IL-6, IL-8, TNF-α, MCP-1, and the growth factors NGF and HGF. We discuss some co-existing features in synoviocytes, including anomalous morphologies of the cells, and microvesicle formation, dysregulation in VEGF gene expression. We provide evidence that phagocytosis of MSU crystals triggers an inflammatory cellular state in synoviocytes in the pathogenesis of crystal-induced arthritis.

Current strategy in the treatment of calcium pyrophosphate crystal deposition disease

The paper considers currently available drugs used to treat calcium pyrophosphate crystal deposition disease. It discusses the advantages and disadvantages of the most widely used drugs, such as  nonsteroidal anti-inflammatory drugs, colchicine, glucocorticoids, traditional immunosuppressants, as well as prospects for the use of biologic agents.

Hesperidin Methylchalcone Suppresses Experimental Gout Arthritis in Mice by Inhibiting NF-κB Activation

Gout arthritis is a painful inflammatory disease induced by monosodium urate (MSU) crystals. We evaluate the therapeutic potential of the flavonoid hesperidin methylchalcone (HMC) in a mouse model of gout arthritis induced by intra-articular injection of MSU (100 μg/10 μL). Orally given HMC (3-30 mg/kg, 100 μL) reduced in a dose-dependent manner the MSU-induced hyperalgesia (44%, p < 0.05), edema (54%, p < 0.05), and leukocyte infiltration (70%, p < 0.05). HMC (30 mg/kg) inhibited MSU-induced infiltration of LysM-eGFP⁺ cells (81%, p < 0.05), synovitis (76%, p < 0.05), and oxidative stress (increased GSH, FRAP, and ABTS by 62, 78, and 73%, respectively; reduced O₂^- and NO by 89 and 48%, p < 0.05) and modulated cytokine production (reduced IL-1β, TNF-α, IL-6, and IL-10 by 35, 72, 37, and 46%, respectively, and increased TGF-β by 90%, p < 0.05). HMC also inhibited MSU-induced NF-κB activation (41%, p < 0.05), gp91^phox (66%, p < 0.05) and NLRP3 inflammasome components mRNA expression in vivo (72, 77, 71, and 73% for NLRP3, ASC, pro-caspase-1, and pro-IL-1 β, respectively, p < 0.05), and induced Nrf2/HO-1 mRNA expression (3.9- and 5.1-fold increase, respectively, p < 0.05). HMC (30, 100, and 300 μM) did not inhibit IL-1β secretion by macrophages primed by LPS and challenged with MSU (450 μg/mL), demonstrating that the anti-inflammatory effect of HMC in gout arthritis depends on inhibiting NF-κB but not on direct inhibition of inflammasome. The pharmacological effects of HMC indicate its therapeutic potential for the treatment of gout.

Therapy for CPPD: Options and Evidence

PURPOSE OF REVIEW

Current evidence and accumulated experience for the management of calcium pyrophosphate deposition disease (CPPD) are presented.

RECENT FINDINGS

Contrary to other rheumatic inflammatory conditions that account for high interest and growing research, advances in treating CPPD are still very limited and mostly derive from those achieved in gout. Once formed, calcium pyrophosphate crystals cannot be dissolved; therefore, management relies on the control of crystal-derived inflammation. Besides classical agents-such as colchicine, glucocorticoids, or NSAIDs-the use of targeted therapies, mostly against interleukin-1, has provided a relevant relief for refractory CPPD patients in recent years. Meanwhile, former enthusiasm about conventional disease-modifying agents such as methotrexate is currently controversial.

Elderly Patients Exhibit Stronger Inflammatory Responses during Gout Attacks

Gout attacks are often accompanied by systemic inflammatory response. The aim of the retrospective study was to compare gout patients in different age groups in terms of their clinical features at gout attacks. Patients, who were treated for gout attack in two tertiary medical centers between January 2000 and April 2014, were divided into young (≤ 50 years), middle-aged, and elderly (> 65 years) groups. Patients in three age groups were compared in terms of presence of fever (> 37.8°C), C-reactive protein (CRP) levels, and erythrocyte sedimentation ratio (ESR) at the gout attacks. Monocytes, which were isolated from 10 consecutive patients who previously experienced gout attacks, were stimulated with monosodium urate (MSU) crystals and cytokine production was measured by flow cytometry. Among 254 patients analyzed in this study, 48 were young, 65 were middle-aged, and 141 were elderly. The elderly patients were more likely to have fever (51.1%) during the attack than the young (20.8%) and middle-aged (30.8%) patients (P < 0.001 by χ² test). They were also more likely to have higher ESR and CRP levels than the young patients (P = 0.002 for ESR, P < 0.001 for CRP). Patients' age correlated significantly with CRP and ESR levels (both P < 0.001). After stimulation with MSU, the production of interleukin-1β by monocytes increased with patients' age (r = 0.670, P = 0.03). In conclusion, gout attacks in elderly patients are associated with fever and higher ESR and CRP levels, often resembling a septic arthritis.

Calcific tendonitis of the rotator cuff: From formation to resorption

Calcific tendonitis of the rotator cuff is due to apatite deposits in the shoulder tendons. Patients affected by calcific tendonitis have chronic shoulder pain and disability. Although the disease is frequent, about 10 to 42% of painful shoulders, mechanisms leading to this pathological mineralization are still largely unknown. Research reported in the 1990s suggested that the formation of calcific deposits is linked to cells looking like chondrocytes identified around calcium deposits within a fibrocartilage area. They were considered to be derived from tenocytes but more recently, tendon stem cells, able to differentiate into chondrocytes, were isolated. The pro-mineralizing properties of these chondrocytes-like cells, especially the role of alkaline phosphatase, are not currently clarified. The calcium deposits contain poorly crystalline carbonated apatite associated with protein. Among these proteins, only osteopontin has been consistently identified as a potential regulating factor. During the disease, spontaneous resorption can occur with migration of apatite crystals into the subacromial bursa causing severe pain and restriction of movement. In in vivo and in vitro experiments, apatite crystals were able to induce an influx of leucocytes and a release of IL-1β and IL-18 through the activation of the NLRP3 inflammasome. However, mechanisms leading to spontaneous resolution of this inflammation and disappearance of the calcification still need to be elucidated.

Platelet-Released Growth Factors Modulate the Secretion of Cytokines in Synoviocytes under Inflammatory Joint Disease

The etiology and pathogenesis of rheumatoid arthritis (RA) are marked by a complex interplay of various cell populations and is mediated by different signaling pathways. Traditionally, therapies have primarily focused on pain relief, reducing inflammation and the recovery of joint function. More recently, however, researchers have discussed the therapeutic efficacy of autologous platelet-rich plasma (PRP). The main objective of this work is to examine the influences of platelet-released growth factor (PRGF) on human synoviocytes under inflammatory conditions. Additionally, it is checked to which extend treatment with platelet concentrate influences the release of cytokines form synoviocytes. For this purpose, an in vitro RA model was created by stimulating the cells with the TNF-α. The release of cytokines was measured by ELISA. The cytokine gene expression was analyzed by real-time PCR. It has been observed that the stimulation concentration of 10 ng/ml TNF-α resulted in a significantly increased endogenous secretion and gene expression of IL-6 and TNF-α. The anti-inflammatory effect of PRGF could be confirmed through significant reduction of TNF-α and IL-1β. An induced inflammatory condition seems to cause PRGF to inhibit the release of proinflammatory cytokines. Further study is required to understand the exact effect mechanism of PRGF on synoviocytes.

CD14+ Cells with the Phenotype of Infiltrated Monocytes Consist of Distinct Populations Characterized by Anti-inflammatory as well as Pro-inflammatory Activity in Gouty Arthritis

It has been suggested that inflammasome-mediated IL-1β production in monocytic cells is responsible for the acute inflammatory response in gouty arthritis. However, phenotypical and functional analyses of monocytes during gouty arthritis have yet to be conducted. Therefore, we investigated the characteristics of monocytes/macrophages in the synovial fluid cells of patients with acute gout. The number and frequency of monocytes/macrophages in the synovial fluid mononuclear cells (SFMCs) of patients was examined. The expression of markers for monocyte recruitment and tissue-resident macrophages, the production of pro-inflammatory and anti-inflammatory cytokines, and phagocytosis were analyzed in the monocytes/macrophages of patients with acute gout attacks. The number and frequency of CD14⁺CD3⁻CD19⁻CD56⁻ monocytes/macrophages was markedly increased in the SFMCs of patients with gout compared to those of patients with rheumatoid arthritis (RA). CD14⁺ cells showed the phenotypes of infiltrated monocytes rather than tissue-resident macrophages, characterized by a high expression of CCR2, MRP8, and MRP14, but a low expression of MERTK and 25F9. These cells had the capacity to produce pro-inflammatory cytokines such as TNF-α and IL-1β after stimulation with lipopolysaccharides. In addition, anti-inflammatory features, including CD163 expression and IL-10 production from CD14⁺ cells, were significantly higher in patients with gout than in those with RA. CD14⁺ cells with phenotype of M2 macrophages had high phagocytic activity for monosodium urate crystals. Thus, our results indicate that monocytes/macrophages from patients with gout have the phenotype of infiltrated monocytes, and these cells consist of different populations characterized by anti-inflammatory activities as well as pro-inflammatory functions.

Mast Cell Stabilizer Ketotifen Inhibits Gouty Inflammation in Rats

Gout, an extremely painful arthritis with relapsing inflammatory attacks, is a common inflammatory joint disease in adults. We examined the therapeutic effect of ketotifen, a mast cell stabilizer, on monosodium urate (MSU) crystal-induced acute inflammation. Eight-week-old male Wistar rats were injected with MSU crystals (5 mg per rat) into air pouch. Ketotifen (0, 0.1, 03, and 1 mg/kg) was given 1 hour before MSU crystal injection. Lavage histamine, leukocyte counts, mast cell counts, nitric oxide, and proinflammatory mediator levels were assessed 12 hours after MSU injection. Ketotifen significantly inhibited MSU-induced mast cell activation and histamine concentration in air pouch lavage. Ketotifen dose-dependently inhibited MSU-initiated leukocyte infiltration into the air pouch. Furthermore, ketotifen significantly decreased proinflammatory mediators, including nitric oxide, interleukin-1β, and interleukin-6, production in MSU-treated rats. Ketotifen may attenuate MSU-induced acute inflammation by inhibiting mast cell activation and leukocyte infiltration in rats. Furthermore, ketotifen has the potential to be a new approach in managing patients with gouty inflammation in the future.

Cytokine Profile in Gout: Inflammation Driven by IL-6 and IL-18?

INTRODUCTION

Gout is considered to be an autoinflammatory disease and the presence of monosodium urate (MSU) crystals stimulates activation of NPRL3 inflammasome and subsequently caspase-1, generating production of active IL-1β and IL-18. However, the association between serum cytokines levels and clinical manifestations of the disease is not yet well understood. We evaluated the serum profile of proinflammatory cytokines (IL-1β, IL-6, IL-8, IL-17A, IL-18, IL-22, and IL-23) and described their relationship with clinical and laboratory data.

METHODOLOGY

Thirty-nine male patients with gout (GG) were assessed for clinical and laboratory variables and cytokine levels were measured by ELISA. For the purposes of comparison, 34 males with no previous history of arthritis were also included in the study (CG).

RESULTS

Seventeen participants (43%) exhibited active arthritis on evaluation. Levels of IL-18 were significantly higher in patients in relation to the CG (p = 0.0013). No statistically significant differences were found between the GG and CG for the other measured cytokines. There was a moderate correlation between IL-18 and ESR (R = 0.43, p = 0.0073), CRP (R = 0.47, p = 0.0025), and serum levels of IL-6 (R = 0.36, p = 0.023). An association was observed between serum levels of IL-6 and the presence of tophi (p = 0.005) and deformities (p = 0.0008), as well as a correlation between this cytokine and ESR (R = 0.41, p = 0.011) and CRP (R = 0.48, p = 0.02).

CONCLUSIONS

IL-18 is associated with inflammatory activity in gout, as well as with IL-6 levels, while IL-6 is associated with clinical and laboratory activity, the presence of tophi and articular deformities, and may be a prognostic marker of this pathology.

Toll-like receptors and chronic inflammation in rheumatic diseases: new developments

In the past few years, new developments have been reported on the role of Toll-like receptors (TLRs) in chronic inflammation in rheumatic diseases. The inhibitory function of TLR10 has been demonstrated. Receptors that enhance the function of TLRs, and several TLR inhibitors, have been identified. In addition, the role of the microbiome and TLRs in the onset of rheumatic diseases has been reported. We review novel insights on the role of TLRs in several inflammatory joint diseases, including rheumatoid arthritis, systemic lupus erythematosus, gout and Lyme arthritis, with a focus on the signalling mechanisms mediated by the Toll-IL-1 receptor (TIR) domain, the exogenous and endogenous ligands of TLRs, and the current and future therapeutic strategies to target TLR signalling in rheumatic diseases.

Gout Is a Chronic Inflammatory Disease in Which High Levels of Interleukin-8 (CXCL8), Myeloid-Related Protein 8/Myeloid-Related Protein 14 Complex, and an Altered Proteome Are Associated With Diabetes Mellitus and Cardiovascular Disease

OBJECTIVE

The frequent association of gout with metabolic syndrome and cardiovascular disease (CVD) suggests that it has a systemic component. Our objective was to study whether circulating proinflammatory cytokines are associated with comorbidities in gout patients.

METHODS

We studied 330 gout patients from 3 independent cohorts and compared them with 144 healthy individuals and 276 disease controls. We measured circulating levels of interleukin-8 (IL-8)/CXCL8, IL-1β, IL-6, IL-10, IL-12, and tumor necrosis factor, after which we performed proteome-wide analysis in a selection of samples to identify proteins that were possibly prognostic for the development of comorbidities. Replication analysis was performed specifically for myeloid-related protein 8 (MRP-8)/MRP-14 complex.

RESULTS

Compared to healthy controls and disease control patients, patients with gouty arthritis (n = 48) had significantly higher mean levels of CXCL8 (P < 0.001), while other cytokines were almost undetectable. Similarly, patients with intercritical gout showed high levels of CXCL8. CXCL8 was independently associated with diabetes mellitus in patients with intercritical gout (P < 0.0001). Proteome-wide analysis in gouty arthritis (n = 18) and intercritical gout (n = 39) revealed MRP-8 and MRP-14 as the proteins with the greatest differential expression between low and high levels of CXCL8 and also showed a positive correlation of MRP8/MRP14 complex with CXCL8 levels (R(2)  = 0.49, P < 0.001). These findings were replicated in an independent cohort. The proteome of gout patients with high levels of CXCL8 was associated with diabetes mellitus (odds ratio 16.5 [95% confidence interval 2.8-96.6]) and CVD (odds ratio 3.9 [95% confidence interval 1.0-15.3]).

CONCLUSION

Circulating levels of CXCL8 are increased during both the acute and intercritical phases of gout, and they coincide with a specific circulating proteome that is associated with risk of diabetes mellitus and CVD. Further research focused on the roles of CXCL8 and MRP8/MRP14 complex in patients with gout is warranted.

Therapeutic Effects of Chinese Medicine Herb Pair, Huzhang and Guizhi, on Monosodium Urate Crystal-Induced Gouty Arthritis in Rats Revealed by Anti-Inflammatory Assessments and NMR-Based Metabonomics

The present study was undertaken to evaluate the therapeutic effects of Huzhang-Guizhi herb pair (HG), firstly included in Hu-Zhang Power documented in Taiping Shenghui Fang, on monosodium urate (MSU) crystals-induced gouty arthritis in rats. We found that pretreatment with HG in rats with gouty arthritis could significantly attenuate the ankle joint swelling, and this beneficial antigout effect might be mediated, at least in part, by inhibiting tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) production in synovial fluid as well as nuclear transcription factor-κB p65 (NF-κB p65) protein expression in synovial tissue. Moreover, metabonomic analysis demonstrated that 5 and 6 potential biomarkers associated with gouty arthritis in plasma and urine, respectively, which were mainly involved in energy metabolism, amino acid metabolism, and gut microbe metabolism, were identified. HG could reverse the pathological process of MSU-induced gouty arthritis through regulating the disturbed metabolic pathways. These results provided important mechanistic insights into the protective effects of HG against MSU-induced gouty arthritis in rats.

Monosodium Urate Crystal-Induced Chondrocyte Death via Autophagic Process

Monosodium urate (MSU) crystals, which are highly precipitated in the joint cartilage, increase the production of cartilage-degrading enzymes and pro-inflammatory mediators in cartilage, thereby leading to gouty inflammation and joint damage. In this study, we investigated the effect of MSU crystals on the viability of human articular chondrocytes and the mechanism of MSU crystal-induced chondrocyte death. MSU crystals significantly decreased the viability of primary chondrocytes in a time- and dose-dependent manner. DNA fragmentation was observed in a culture medium of MSU crystal-treated chondrocytes, but not in cell lysates. MSU crystals did not activate caspase-3, a marker of apoptosis, compared with actinomycin D and TNF-α-treated cells. MSU crystals did not directly affect the expression of endoplasmic reticulum (ER) stress markers at the mRNA and protein levels. However, MSU crystals significantly increased the LC3-II level in a time-dependent manner, indicating autophagy activation. Moreover, MSU crystal-induced autophagy and subsequent chondrocyte death were significantly inhibited by 3-methyladenine, a blocker of autophagosomes formation. MSU crystals activated autophagy via inhibition of phosporylation of the Akt/mTOR signaling pathway. These results demonstrate that MSU crystals may cause the death of chondrocytes through the activation of the autophagic process rather than apoptosis or ER stress.

Transdermal cannabidiol reduces inflammation and pain-related behaviours in a rat model of arthritis

BACKGROUND

Current arthritis treatments often have side-effects attributable to active compounds as well as route of administration. Cannabidiol (CBD) attenuates inflammation and pain without side-effects, but CBD is hydrophobic and has poor oral bioavailability. Topical drug application avoids gastrointestinal administration, first pass metabolism, providing more constant plasma levels.

METHODS

This study examined efficacy of transdermal CBD for reduction in inflammation and pain, assessing any adverse effects in a rat complete Freund's adjuvant-induced monoarthritic knee joint model. CBD gels (0.6, 3.1, 6.2 or 62.3 mg/day) were applied for 4 consecutive days after arthritis induction. Joint circumference and immune cell invasion in histological sections were measured to indicate level of inflammation. Paw withdrawal latency (PWL) in response to noxious heat stimulation determined nociceptive sensitization, and exploratory behaviour ascertained animal's activity level.

RESULTS

Measurement of plasma CBD concentration provided by transdermal absorption revealed linearity with 0.6-6.2 mg/day doses. Transdermal CBD gel significantly reduced joint swelling, limb posture scores as a rating of spontaneous pain, immune cell infiltration and thickening of the synovial membrane in a dose-dependent manner. PWL recovered to near baseline level. Immunohistochemical analysis of spinal cord (CGRP, OX42) and dorsal root ganglia (TNFα) revealed dose-dependent reductions of pro-inflammatory biomarkers. Results showed 6.2 and 62 mg/day were effective doses. Exploratory behaviour was not altered by CBD indicating limited effect on higher brain function.

CONCLUSIONS

These data indicate that topical CBD application has therapeutic potential for relief of arthritis pain-related behaviours and inflammation without evident side-effects.

The metastatic tumor antigen 1-transglutaminase-2 pathway is involved in self-limitation of monosodium urate crystal-induced inflammation by upregulating TGF-β1

INTRODUCTION

Transglutaminase 2 (TG2), a protein crosslinking enzyme with multiple biochemical functions, has been connected to various inflammatory processes. In this study, the involvement of TG2 in monosodium urate (MSU) crystal-induced inflammation was studied.

METHODS

Immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR) were performed to detect TG2 expression in synovial fluid mononuclear cells (SFMCs) and synovial tissue from patients with gouty arthritis. MSU crystal-exposed RAW264.7 mouse macrophages were analyzed for interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), transforming growth factor β1 (TGF-β1) and TG2 expression by RT-PCR and enzyme-linked immunosorbent assay (ELISA). TG2 small interfering (si)-RNA-mediated silencing and overexpression in RAW264.7 cells were used to evaluate the involvement of TG2 in resolving MSU crystal-induced inflammation. The role of metastatic tumor antigen 1 (MTA1), a master chromatin modifier, was investigated by MTA1 si-RNA-mediated knockdown. In addition, the inflammatory responses were followed in wild type and TG2 null mice after being challenged with MSU crystals in an in vivo peritonitis model.

RESULTS

TG2 expression was up-regulated in the synovium tissue and SFMCs from patients with gouty arthritis. The levels of MTA1, TG2, TGF-β1, IL-1β and TNF-α mRNAs were consistently increased in MSU crystal-stimulated RAW264.7 cells. si-MTA1 impaired the basal, as well as the MSU crystal-induced expression of TG2 and TGF-β1, but increased that of IL-1β and TNF-α. TG2 overexpression dramatically suppressed MSU crystal-induced IL-1β and TNF-α, but significantly enhanced the TGF-β1 production. Neutralizing TGF-β antibodies or inhibition of the crosslinking activity of TG2 attenuated these effects. On the contrary, loss of TG2 resulted in a reduced TGF-β, but in an increased IL-1β and TNF-α production in MSU crystal-stimulated RAW264.7 cells and mouse embryonic fibroblasts (MEFs). MSU crystal-stimulated IL-1β production was Janus kinase 2 (JAK2)-signaling dependent and TG2-induced TGF-β suppressed the activity of it. Finally, TG2-deficient mice exhibited hyper inflammatory responses after being challenged with MSU crystals in an in vivo peritonitis model.

CONCLUSIONS

These findings reveal an inherent regulatory role of the MTA1-TG2 pathway in the self-limitation of MSU crystal-induced inflammation via positively regulating the levels of active TGF-β1 in macrophages that opposes the MSU crystal-induced JAK2-dependent pro-inflammatory cytokine formation.

The rs7517847 polymorphism in the IL-23R gene is associated with gout in a Chinese Han male population

OBJECTIVES

Gout is a polygenic auto-inflammatory disease, in which inflammation plays an important role in disease pathogenesis. The cytokine interleukin (IL)-23 promotes inflammation and helps to guide inflammatory cells, while studies have shown that the IL-23R gene is associated with susceptibility to several immune-related diseases. This study aimed to determine whether the IL-23R rs7517847 (G/T) polymorphism is associated with gout in a Chinese Han male population.

METHODS

We recruited 400 patients with gout and 582 gout-free controls. After obtaining blood samples for DNA extraction, genotyping of the rs7517847 polymorphism was performed by fluorescence-based quantitative PCR using TaqMan probes. An association analysis was carried out using the χ(2) test. A genotype-phenotype analysis was also conducted.

RESULTS

Both genotypic and allelic frequencies of rs7517847 differed significantly between gout patients and controls (χ(2) = 6.792, df = 2, P = 0.034 by genotype; χ(2) = 4.202, df = 1, P = 0.04 by allele).

CONCLUSIONS

IL-23R may be associated with gout in a Chinese Han male population, although our findings should be confirmed using larger sample sizes and other independent populations.

Mechanism of action of colchicine in the treatment of gout

PURPOSE

The aims of this article were to systematically review the literature about the mechanism of action of colchicine in the multimodal pathology of acute inflammation associated with gout and to consider the clinical utility of colchicine in other chronic inflammatory diseases.

METHODS

The English-language literature on PubMed was searched for articles published between 1990 and October 2013, with a cross-reference to citations across all years. Relevant articles pertaining to the mechanism of action of colchicine and the clinical applications of colchicine in gout and other inflammatory conditions were identified and reviewed.

FINDINGS

The molecular pathology of acute inflammation associated with gouty arthritis involves several concurrent pathways triggered by a variety of interactions between monosodium urate crystals and the surface of cells. Colchicine modulates multiple pro- and antiinflammatory pathways associated with gouty arthritis. Colchicine prevents microtubule assembly and thereby disrupts inflammasome activation, microtubule-based inflammatory cell chemotaxis, generation of leukotrienes and cytokines, and phagocytosis. Many of these cellular processes can be found in other diseases involving chronic inflammation. The multimodal mechanism of action of colchicine suggests potential efficacy of colchicine in other comorbid conditions associated with gout, such as osteoarthritis and cardiovascular disease.

IMPLICATIONS

Colchicine has multiple mechanisms of action that affect inflammatory processes and result in its utility for treating and preventing acute gout flare. Other chronic inflammatory diseases that invoke these molecular pathways may represent new therapeutic applications for colchicine.

Mechanisms of spontaneous resolution of acute gouty inflammation

Acute gout is an auto-inflammatory disease characterized by self-limiting inflammation in response to the deposition of monosodium urate (MSU) crystals in the joints or tissues. Recognition of MSU triggers activation of the NLRP3 inflammasome, release of active interleukin (IL)-1β, and amplification of the inflammatory response by the surrounding tissue followed by recruitment and activation of inflammatory leukocytes. The shutdown of this inflammatory response is linked to a number of regulatory events ranging from crystal coating and apoptotic cell clearance through to pro-inflammatory cytokine regulation and transforming growth factor β1 (TGFβ1) production. This review will highlight mechanisms that limit acute inflammation triggered by MSU crystals and suggests areas for further research.

An old disease with new insights: Update on diagnosis and treatment of gout

Gout is an acute and chronic inflammatory disorder associated with high morbidity and impaired quality of life. There has been a substantial increase in the prevalence and incidence of gout in recent years. Novel diagnostic and therapeutic options have provided new insights into the pathogenesis and management of hyperuricemia and gout in the last decade. This clinical review aims to summarize the diagnostic process and management of acute and chronic gout.

The emerging role of biotechnological drugs in the treatment of gout

One of the most important therapeutic advances obtained in the field of rheumatology is the availability of the so-called bio(techno)logical drugs, which have deeply changed treatment perspectives in diseases such as rheumatoid arthritis and ankylosing spondylitis. According to the steadily increasing attention on gout, due to well-established prognostic and epidemiology implications, in the last 5 years, the same change of perspective has been observed also for this disease. In fact, several bio(techno)logical agents have been investigated both for the management of the articular gout symptoms, targeting mainly interleukin-1β, as well as urate-lowering therapies such as recombinant uricases. Among the IL-1β inhibitors, the majority of studies involve drugs such as anakinra, canakinumab, and rilonacept, but other compounds are under development. Moreover, other potential targets have been suggested, as, for example, the TNF alpha and IL-6, even if data obtained are less robust than those of IL-1β inhibitors. Regarding urate-lowering therapies, the recombinant uricases pegloticase and rasburicase clearly showed their effectiveness in gout patients. Also in this case, new compounds are under development. The aim of this review is to focus on the various aspects of different bio(techno)logical drugs in gouty patients.

Tocilizumab improved clinical symptoms of a patient with systemic tophaceous gout who had symmetric polyarthritis and fever: An alternative treatment by blockade of interleukin-6 signaling

Chronic tophaceous gout is the end stage of gout. We employed a blockade of interleukin-6 signaling therapy by tocilizumab instead of anakinra, an interleukin-1 receptor antagonist, for a 61-year-old Japanese woman diagnosed with tophaceous gout. Laboratory data showed that serum interleukin-6 concentration was elevated. Serum interleukin-1β concentration was under the detectable level, although serum uric acid was elevated due to renal dysfunction. The secretion patterns of interleukin-1β, tumor-necrosis factor-α, interleukin-6, and interleukin-8 from peripheral mononuclear cells isolated from the patient exhibited no remarkable differences compared with those of healthy volunteers. After treatment with the interleukin-6 receptor antagonist tocilizumab, serum interleukin-6 concentration decreased followed by improved clinical symptoms, such as reduced size of the subcutaneous nodules, no fever, and no acute gouty attacks during the treatment. Our case suggests that tocilizumab markedly improves clinical and laboratory manifestations in tophaceous gout with arthritis and fever as well as interleukin-1 blockade therapy.

[Examination of cases of pseudogout in succession to inflammatory disease in the elderly]

AIM

Pseudogout is an important causative disease of febrile illness in elderly patients. We experienced cases of pseudogout during or after the progression of inflammatory disease.

METHODS

We investigated 14 patients with pseudogout admitted to the Department of Geriatric Medicine at Kyorin University Hospital. Seven patients who developed inflammatory disease prior to the onset of pseudogout are described in greater detail.

RESULTS

The affected joint was the knee joint in 12 of 14 cases. Other joints were affected in four cases, and four patients had more than two affected joints in this series. Clear joint cartilage calcification was noted on X-rays in nine of 14 cases, and CPPD crystals were detected in two patients treated with joint puncture. NSAIDs were administered in all cases for treatment. Seven patients had a preceding inflammatory disease, with infectious disease in all cases. Repeat elevation of temperature and inflammatory reactions were seen in seven cases, with progression to bimodal disease in two cases. The average duration of antimicrobial use was 11 days. In three cases, the average duration of antimicrobial use was 33 days, and two or more antimicrobials were used for long-term treatment.

CONCLUSIONS

Pseudogout appears as delayed infective disease and fever of unknown origin in the elderly. This condition may easily be overlooked until joint symptoms become apparent. It is extremely important to keep pseudogout in mind as a differential diagnosis of thermogenesis in elderly patients.

Therapeutic effects of sesame oil on monosodium urate crystal-induced acute inflammatory response in rats

Sesame oil has been used in traditional Taiwanese medicine to relieve the inflammatory pain in people with joint inflammation, toothache, scrapes, and cuts. However, scientific evidence related to the effectiveness or action mechanism of sesame oil on relief of pain and inflammation has not been examined experimentally. Here, we investigated the therapeutic effect of sesame oil on monosodium urate monohydrate (MSU) crystal-induced acute inflammatory response in rats. Air pouch, a pseudosynovial cavity, was established by injecting 24 mL of filtered sterile air subcutaneously in the backs of the rats. At day 0, inflammation in air pouch was induced by injecting MSU crystal (5 mg/rat, suspended in sterilized phosphate buffered saline, pH 7.4), while sesame oil (0, 1, 2, or 4 mL/kg, orally) was given 6 h after MSU crystal injection. Parameters in lavage and skin tissue from the air pouches were assessed 6 h after sesame oil was given. Sesame oil decreased MSU crystal-induced total cell counts, tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 levels in lavage and pouch tissue. Sesame oil significantly decreased leukocyte and neutrophil counts in lavage compared with MSU crystal alone group. Sesame oil decreased activated mast cell counts in skin tissue in MSU crystal-treated rats. Sesame oil significantly decreased nuclear factor (NF)-κB activity and IL-4 level in isolated mast cells from rats treated with MSU crystal. Furthermore, sesame oil decreased lavage complement proteins C3a and C5a levels in MSU crystal-treated rats. In conclusion, sesame oil shows a potent therapeutic effect against MSU crystal-induced acute inflammatory response in rats.

Dolichos falcata Klein attenuated the inflammation induced by monosodium urate crystals in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Dolichos falcata Klein (DF), a Chinese Dai ethnic medicine popularly known as "Tuoyeteng" in Yunnan province of China, has been widely used as a traditional herbal medicine for the treatment of fracture and beriberoid disease for a long time in China. The present study was carried out to investigate the anti-inflammatory activity and the bioactive chemical constituents of DF, and further to assess its possible mechanism on gouty arthritis in an animal model of the MSU crystals-induced gouty inflammation.

MATERIALS AND METHODS

The ethanol extract (EE) of DF at the doses of 10, 20 and 40 mg/kg was administered to the rats treated with MSU crystals to evaluate the anti-gouty arthritis effect. Subsequently, the components of EE were isolated and identified using classical methods. Phyto-chemical analysis of EE was further carried out by HPLC-DAD. Finally, the anti-inflammatory effect of EE and two isolated components were assessed using the MSU crystals-treated monocyte/macrophage cell line RAW 264.7 in vitro.

RESULTS

EE (10, 20 and 40 mg/kg) significantly attenuated the pain threshold value, the joint swelling degree, the inflammatory cell infiltration of articular tissue and the increased levels of pro-inflammatory cytokines in MSU crystals-treated rats. Moreover, doliroside A (DA) and medicagenic acid-3-O-β-D-glucopyranoside (MG) were isolated and identified from EE. The major components of EE, including DA, MG and other triterpenoids, were well confirmed by HPLC. A further study revealed that EE, DA and MG (10, 20, 40μg/mL) exhibited stronger inhibitory effects on the production of pro-inflammatory cytokines (including interleukin-1β, interleukin-6 and tumor necrosis factor-α) in MSU crystals-treated RAW 264.7 cells.

CONCLUSION

These findings indicate that the major triterpenoids present in DF have a remarkable effect on improving symptoms of acute gouty arthritis induced by MSU crystals through inhibiting the production of pro-inflammatory cytokines.

Acidosis drives damage-associated molecular pattern (DAMP)-induced interleukin-1 secretion via a caspase-1-independent pathway

The proinflammatory cytokine IL-1β is a key mediator of inflammatory responses that contribute to and exacerbate brain injury. IL-1β is synthesized by microglia in the brain as an inactive precursor (pro-IL-1β). Cleavage of pro-IL-1β to a mature form is stimulated by damage-associated molecular patterns (DAMPs). These DAMPs are sensed by a pattern recognition receptor called NLRP3, which forms an inflammasome, resulting in the activation of caspase-1 and cleavage of pro-IL-1β. To date, regulation of the inflammasome in culture has been studied under normal culture conditions, and it is not known how DAMPs signal under disease relevant conditions such as acidosis. Given the presence of acidosis in pathological states, our objective was to test the hypothesis that acidic conditions modify DAMP-induced IL-1β release from cultured primary mouse glial cells. When LPS-primed glial cells were stimulated with DAMPs under acidic conditions (pH 6.2), the predominant IL-1β form secreted was the 20-kDa rather than the 17-kDa caspase-1-dependent species. Lactic acidosis, induced by the addition of 25 mm lactic acid, also induced the release of 20-kDa IL-1β. This 20-kDa product was produced independently of NLRP3 and caspase-1 but was inhibited by the cathepsin D inhibitor pepstatin A. These data suggest that under disease relevant acidosis, DAMPs and lactic acid induce the secretion of IL-1β independently of the inflammasome. Therapeutic strategies directed to the inhibition of IL-1β processing should therefore consider alternative processing of IL-1β in addition to caspase-1-dependent processing.