Pathogenesis of crystal-induced inflammation

The mechanism of NLRP3 inflammasome activation and its pharmacological inhibitors

NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3) is a cytosolic pattern recognition receptor (PRR) that recognizes multiple pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). Once activated, NLRP3 initiates the inflammasome assembly together with the adaptor ASC and the effector caspase-1, leading to caspase-1 activation and subsequent cleavage of IL-1β and IL-18. Aberrant NLRP3 inflammasome activation is linked with the pathogenesis of multiple inflammatory diseases, such as cryopyrin-associated periodic syndromes, type 2 diabetes, non-alcoholic steatohepatitis, gout, and neurodegenerative diseases. Thus, NLRP3 is an important therapeutic target, and researchers are putting a lot of effort into developing its inhibitors. The review summarizes the latest advances in the mechanism of NLRP3 inflammasome activation and its pharmacological inhibitors.

Natural Products as a Novel Therapeutic Strategy for NLRP3 Inflammasome-Mediated Gout

Gout is the most common form of inflammatory arthritis. It occurs when monosodium urate crystals (MSU) are deposited within joints due to hyperuricemia and persistent elevations of serum uric acid levels. Traditional gout treatment such as urate-lowering therapy is difficult to continue for a long period of time due to the risk of side effects. Recent studies have shown that the modulation of MSU-induced inflammatory responses is dependent on the inflammatory cytokine IL-1β, which has a central role in a chain of processes involving multiple cytokines and mediators. In this regard, the NLRP3 inflammasome is known to play a crucial part and thus has been proposed as a novel target in the treatment for gout. However, the biochemical mechanism for NLRP3 inflammasome activation has not yet been clearly elucidated. Therefore, this report can provide an overview of natural extractions targeted to prevent or treat NLRP3 inflammasome-mediated gout in the MSU-induced gout model. In addition, the research and development of such natural products are suggested as a potential strategy in the treatment of gout.

Associations between Sjögren Syndrome, Sociodemographic Factors, Comorbid Conditions, and Scleritis in a Taiwanese Population-Based Study

This nationwide, population-based, retrospective, matched case–control study included 111,960 newly diagnosed patients with scleritis who were identified by the International Classification of Diseases, Ninth Revision, Clinical Modification code 379.0, selected from the Taiwan National Health Insurance Research Database. Demographic characteristics, Sjögren syndrome, and comorbid conditions within 1 year before the scleritis diagnosis were examined using univariate logistic regression analyses, and a paired t-test was used for continuous variables. Adjusted logistic regression was used to compare the prognosis odds ratio (OR) of the patients with scleritis with the controls. After adjustment for confounders, patients with Sjögren syndrome were remarkably more likely to have scleritis than the controls (OR = 33.53, 95% confidence interval (CI) = 27.43–40.97, p < 0.001). Other conditions found to have increased odds of scleritis included post ocular pterygium, glaucoma, and scleral surgery (OR  =  4.01, 95% CI  =  3.64–4.43; OR  =  3.16, 95% CI  =  2.24–4.47; OR  =  6.83, 95% CI  =  5.34–8.74, respectively); systemic infections, such as syphilis, tuberculosis, and a human herpes viral infection (OR  =  4.01, 95% CI  =  2.93–5.50; OR  =  2.24, 95% CI  =  1.94–2.58; OR  =  8.54, 95% CI  =  8.07–9.03, respectively); and systemic diseases, such as rheumatoid arthritis, granulomatous vasculitis, systemic lupus erythematosus, ankylosing spondylitis, and gout (OR  =  2.93, 95% CI  =  2.66–3.23; OR  =  7.37, 95% CI  =  3.91–13.88; OR  =  3.18, 95% CI  =  2.63–3.85; OR  =  5.57, 95% CI  =  4.99–6.22; OR  =  2.84, 95% CI  =  2.72–2.96, respectively). The results strongly support an association between Sjögren syndrome, post ocular surgery, systemic infection disease, systemic autoimmune disease, and scleritis.

Ameliorative Effects of Cardamonin on Monosodium Urate-Induced Gouty Arthritis through Inhibiting NLRP3 Inflammasome Mediation

Background and Objectives: Gouty arthritis is an acute inflammatory response caused by the precipitation of monosodium urate (MSU) crystals in joints. The triggering of MSU leads to increased production of inflammatory cytokines, such as interleukin-1β, which in turn lead to the formation of macromolecular complexes, referred to as inflammasomes. Thorough characterization of the NLRP3 inflammasome can be used as an indicator of an immune response against harmful stimuli. Cardamonin is a chalcone, mainly found in the seeds of Alpinia katsumadai, and exhibits anti-inflammatory activity by inhibiting the release of pro-inflammatory cytokines in vitro. However, the mechanism by which cardamonin treatment alleviates gouty arthritis has yet to be fully elucidated. Materials and Methods: In vitro or in vivo models were used to study whether cardamonimn inhibited NLRP3 inflammasome activation or suppressed gouty inflammation. Results: In the current study, we determined that most NLRP3 was released passively after MSU stimulation, and this release of NLRP3 promoted caspase-1 activation and IL-1β secretion. Cardamonin was shown to decrease both the activity of caspase-1 and secretion of IL-1β in J774A.1 macrophage cells subjected to MSU stimulation. Cardamonin was also shown to attenuate the production of COX-2 in MSU-stimulated J774A.1 macrophage cells. Finally, cardamonin reduced the thickness of the synovial lining and the infiltration of gouty arthritis in a rat model. Conclusions: Overall, cardamonin significantly attenuated IL-1β secretion, caspase-1 activity, and COX-2 production stimulated by MSU. These findings provide new insights into the molecular mechanisms underlying the effects of cardamonin treatment for gouty arthritis.

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.

Therapeutic regulation of the NLRP3 inflammasome in chronic inflammatory diseases

Inflammasomes are cytosolic pattern recognition receptors that recognize pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) derived from invading pathogens and damaged tissues, respectively. Upon activation, the inflammasome forms a complex containing a receptor protein, an adaptor, and an effector to induce the autocleavage and activation of procaspase-1 ultimately culminating in the maturation and secretion of IL-1β and IL-18 and pyroptosis. Inflammasome activation plays an important role in host immune responses to pathogen infections and tissue repair in response to cellular damage. The NLRP3 inflammasome is a well-characterized pattern recognition receptor and is well known for its critical role in the regulation of immunity and the development and progression of various inflammatory diseases. In this review, we summarize recent efforts to develop therapeutic applications targeting the NLRP3 inflammasome to cure and prevent chronic inflammatory diseases. This review extensively discusses NLRP3 inflammasome-related diseases and current development of small molecule inhibitors providing beneficial information on the design of therapeutic strategies for NLRP3 inflammasome-related diseases. Additionally, small molecule inhibitors are classified depending on direct or indirect targeting mechanism to describe the current status of the development of pharmacological inhibitors.

Comparative Study of Anti-Gouty Arthritis Effects of Sam-Myo-Whan according to Extraction Solvents

Sam-Myo-Whan (SMW) has been used in Korean and Chinese traditional medicine to help treat gout, by reducing swelling and inflammation and relieving pain. This study compared the effects of SMW extracted by using different solvents, water (SMWW) and 30% EtOH (SMWE), in the treatment of gouty arthritis. To this end, we analyzed the main components of SMWW and SMWE, using high-performance liquid chromatography (HPLC). Anti-hyperuricemic activity was evaluated by measuring serum uric acid levels in hyperuricemic rats. The effects of SMWW and SMWE on swelling, pain, and inflammation in gouty arthritis were investigated by measuring affected limb swelling and weight-bearing, as well as by enzyme-linked immunosorbent assays, to assess the levels of proinflammatory cytokines and myeloperoxidase (MPO). In potassium oxonate (PO)-induced hyperuricemic rats, SMWW and SMWE both significantly decreased serum uric acid to similar levels. In monosodium urate (MSU)-induced gouty arthritis mice, SMWE more efficiently decreased paw swelling and attenuated joint pain compare to SMWW. Moreover, SMWE and SMWW suppressed the level of inflammation by downregulating proinflammatory cytokines (interleukin-1β, tumor necrosis factor-α, and interleukin-6) and MPO activity. HPLC analysis further revealed that berberine represented one of the major active ingredients demonstrating the greatest change in concentration between SMWW and SMWE. Our data demonstrate that SMWE retains a more effective therapeutic concentration compared to SMWW, in a mouse model of gouty arthritis.

Identification of Active Compounds From Yi Nationality Herbal Formula Wosi Influencing COX-2 and VCAM-1 Signaling

The Yi nationality herbal formula Wosi is used in China as a folk medicine to treat arthritis and related diseases. Despite its widespread use, the active ingredients, and pharmacological mechanisms are not performed. This is the first time to identify the active compounds from Wosi with the aim at providing the potential effect of Wosi and exploring its underlying anti-inflammatory mechanism in monosodium urate crystals (MSU)-induced arthritis rats. In this study, anti-hyperuricemia effect was assessed by reducing the serum uric acid levels and increasing uric acid excretion in the urine for the hyperuricemia rat model. Wosi significantly suppressed the degree of joint swelling and improved the symptoms of inflammation induced by MSU crystals. The inhibition of IL-2, IL-1β, IFN-γ, and IL-6 secretion and IL-10 increase in the serum were also observed. This study also focuses on the screening of the main compounds from Wosi against cyclooxygenase for anti-inflammatory properties using molecular docking. The result showed 3-O-[α-L-pyran rhamnose(1-3)-β-D-pyran glucuronic acid]- oleanolic acid, 3-O-(β-D-pyran glucuronic acid)-oleanolic acid-28-O-β-D-pyran glucoside, and 3-O-[α-L-pyran rhamnose(1-3)-β-D-pyran glucuronic acid]-oleanolic acid-28-O-β-D-pyran glucoside with a higher binding affinity for COX-2 than COX-1 which indicated relatively higher interaction than COX-1. The preferential selectivity toward inhibiting COX-2 enzyme over COX-1 of three compounds from Wosi were evaluated using in-vitro cyclooxygenases 1 and 2 (COX-1/2) inhibition assays. Meanwhile, the down-regulated protein expression of COX-2 and VCAM-1 in synovial tissue sections from ankle joints of experiments rats were confirmed by immunohistochemistry analysis after the Wosi treatment. In conclusion, three oleanolic acid glycosides were implied as mainly efficient compounds in Yi nationality herbal formula Wosi for arthritis therapy via selectively influencing COX-2 and VCAM-1 signaling.

The Extraction Solvent Influences the Anti-Inflammatory Effects of Jakyakgamcho-Tang in Lipopolysaccharide-Stimulated Macrophages and Mice with Gouty Arthritis

Jakyakgamcho-Tang (JGT) is a traditional medicine used to treat muscular tension, spasm, and pain. Several studies have reported its clinical use as an anti-inflammatory and in gynaecological treatment. This study aimed to compare the anti-inflammatory effects of JGT according to extraction solvent, water (JGTW) and 30% EtOH (JGTE) on lipopolysaccharide (LPS)—stimulated macrophages and in mice with monosodium urate (MSU)—induced gouty arthritis. We evaluated the production of inflammatory mediators and cytokines and the expression of inducible nitric oxide (iNOS) and cyclooxygenase-2 (COX-2) in RAW 264.7 cells. We also examined oedema, pain, and inflammation in MSU-induced mice by measuring affected hind paw swelling, weight-bearing, pro-inflammatory cytokines levels, and myeloperoxidase (MPO) activity. In LPS-stimulated RAW264.7 cells, JGTW and JGTE significantly decreased prostaglandin (PG) E2(PGE2) production via suppressing COX-2 expression and cytokines interleukin-1β and interleukin-6. Only JGTE reduced the production of NO and cytokines and the mRNA levels of iNOS and cytokines. In MSU-induced mice, JGTE and JGTW efficiently decreased paw swelling and attenuated joint pain. JGTE (200 and 300 mg/kg) effectively suppressed inflammation by downregulating pro-inflammatory cytokines (tumour necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6) and MPO activity, which were only slightly reduced by JGTW. Our data demonstrate the anti-inflammatory activity of JGT in macrophage and gouty arthritis animal models and show that JGTE is more effective than JGTW at lower concentrations.

Advances in our understanding of gout as an auto-inflammatory disease

Gout, the most common inflammatory arthritis, is the result of hyperuricemia and inflammation induced by monosodium urate (MSU) crystal deposition. However, most people with hyperuricemia will never develop gout, implying a molecular-genetic contribution to the development of gout. Recent genomic studies reveal links between certain genetic variations and gout. We highlight recent advances in our understanding of gout as an auto-inflammatory disease. We review the auto-inflammatory aspects of gout, including the inflammasome and thirteen gout-associated inflammatory-pathway genes and associated comorbidities. This information provides important insights into emerging immune-modulating targets in the management of gout, and future novel therapeutic targets in gout treatment. Cumulatively, this has important implications for treating gout as an auto-inflammatory disease, as opposed to a purely metabolic disease.

The clinical efficacy of urate-lowering therapy in acute gout: a meta-analysis of randomized controlled trials

BACKGROUND

Gout is a common chronic disease with a high recurrence rate. To date, the debate continues about the best time for using urate lowering therapy (ULT) during an acute gout attack.

OBJECTIVE

This updated meta-analysis is designed to assess the clinical efficacy of ULT in the management of acute exacerbations of gout. Through the results, we hope to determine whether uric acid lowering agents should be used to manage acute exacerbations of gout.

METHODS

A comprehensive search of six databases without language restrictions includes PubMed, Cochrane Library, Web of Science, EMBASE, CNKI, and WanFang data. The literature used was published before October 2019. Six randomized controlled trials (RCTs) with 557 patients met the inclusion criteria. Standardized mean difference (SMD), weighted mean difference (WMD), risk ratio (RR), and 95% confidence interval (CI) were used for estimating the clinical efficacy of ULT in acute gout.

RESULTS

Data results showed no statistical difference in the pain visual analogue score (VAS) by day 3 (weighted mean difference (WMD), 0.06; 95% CI, - 0.13 to 0.25; I² 0%; P = 0.55), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) between the group using uric acid lowering agents and the group that was not using such agents. Moreover, the patients using ULT agents had lower serum uric acid level (standardized mean difference (SMD), - 0.73; 95% CI, -0.92 to -0.54; I² 23%; P < 0.00001) and showed better adherence to medication (risk ratio (RR), 1.40; 95% CI, 1.18 to 1.65; I² 0%; P < 0.0001) as compared with the patients not that were not using such agents. However, there was no substantial difference in the recurrence rate of acute gout attacks (RR, 0.84; 95% CI, 0.59 to 1.19; I² 0%; P = 0.33).The evidence for this is, however, very moderate.

CONCLUSION

Our finding shows that it is beneficial in many aspects to use uric-acid-lowering drugs at the initial stage of an acute gout attack. However, larger sample size studies are still needed to prove our results.

TRIAL REGISTRATION

Registration number: PROSPERO (CRD42020153924). Key Points • This is a first meta-analysis about the clinical efficacy of urate-lowering therapy (ULT) in acute gout without language restrictions. • ULT in acute gout may not aggravate the pain (WMD, 0.06; 95% CI, - 0.13 to 0.25). • ULT at the initial stage of an acute gout attack can reduce serum uric acid level (SMD, -0.73; 95% CI, - 0.92 to - 0.54) and improve medication compliance in patients (RR, 1.40; 95% CI, 1.18 to 1.65). • ULT in acute gout is not associated with the risk of gout flares (RR, 0.84; 95% CI, 0.59 to 1.19).

Genetic association of polymorphism rs2230054 in CXCR2 gene with gout in Chinese Han male population

Neutrophils are crucial in the process of gout flare and remission. The signal transduction pathway of chemokine plays a vital role in the chemotaxis and activation of neutrophils. CXCR2 gene knocked out can avoid the acute neutrophilic inflammation stimulated by monosodium urate (MSU) crystals in mice. To investigate the relationship among CXCR1 rs2234671, CXCR2 rs1126579, and rs2230054 polymorphisms with gout arthritis flare in the Chinese Han male population, a case-control study was carried out in 412 gout patients and 508 gout-free individuals. TaqMan probes fluorescence real-time polymerase chain reaction (PCR) was used to genotype CXCR1 rs2234671, CXCR2 rs1126579, and rs2230054 SNPs. There was a clear link between CXCR2 rs2230054 T included genotypic and T allelic frequencies and gout cases (c² = 9.286, p = 0.002 by genotype, c² = 8.639, p = 0.003 by allele), while no significant differences were observed between the gouty arthritis group and the control group in CXCR1 rs2234671 and CXCR2 rs1126579 genotypic and allelic frequencies. Multivariate logistic regression analysis showed that the T genotype included in rs2230054 can decrease the risk of gouty arthritis (adjusted OR = 0.47; 95% CI: 0.31-0.74) compared with the CC genotype. Our study might suggest that rs2230054 in CXCR2 is associated with susceptibility to gout in Chinese males.

Total saponin of Dioscorea collettii attenuates MSU crystal‑induced inflammation via inhibiting the activation of the NALP3 inflammasome and caspase‑1 in THP‑1 macrophages

Total saponins extracted from Dioscorea collettii (TSD), extracts of the Chinese herb Dioscorea, are thought to exhibit therapeutic benefit in gouty arthritis. However, its exact mechanism remains unclear. The current study aimed to elucidate the underlying mechanisms by investigating the effects of TSD on the inflammation induced by monosodium urate (MSU) crystals in THP-1 macrophages. The viability of THP-1 macrophages was examined using the MTT assay and the levels of inflammatory cytokines, including interleukin (IL)-1β, IL-18 and tumor necrosis factor (TNF)-α, released by the cells were quantitatively measured using ELISA kits. The results revealed that the protein level of cluster of differentiation 11b increased in THP-1 cells treated with 100 ng/ml phorbol ester, suggesting that monocytic THP-1 cells were successfully differentiated into macrophages. TSD decreased the levels of inflammatory cytokines, including TNF-α, IL-18 and IL-1β, secreted by THP-1 macrophages. As the release of IL-1β and IL-18 is dependent on the NLR family pyrin domain containing 3 (NALP3) inflammasome and caspase-1, the current study investigated the effect of TSD on the aforementioned proteins. The results revealed that TSD decreased the protein levels of NALP3 and apoptosis-associated speck-like, which serve important roles in the assembly of the NALP3 inflammasome. Furthermore, NALP3 inflammasome-related proteins were also decreased by TSD in rotenone induced THP-1 macrophages, TSD inhibited the activation of caspase-1 and rotenone-induced NALP3 inflammasome activation in THP-1 macrophages. The results obtained in the current study revealed that TSD attenuated MSU crystal-induced inflammation by inhibiting rotenone-induced activation of the NALP3 inflammasome and caspase-1, suggesting that these two proteins may be novel targets for the treatment of gouty arthritis.

Chondrocalcinosis is associated with increased knee joint degeneration over 4 years: data from the Osteoarthritis Initiative

OBJECTIVE

To determine if presence of calcium-containing crystals (CaC) is associated with increased knee joint degeneration over 4 years and assess if total number of CaCs deposited is a useful measure of disease burden.

DESIGN

Seventy subjects with CaCs in right knees at baseline were selected from the Osteoarthritis Initiative and matched to 70 subjects without evidence of CaCs. T1-weighted gradient-echo sequences were used to confirm presence of CaCs and count the numbers of distinct circumscribed CaCs. Morphological abnormalities were assessed at baseline and 4-year follow-up using the modified semi-quantitative Whole-Organ Magnetic Resonance Imaging Score (WORMS). Linear regression models were used to analyze the associations between presence of CaCs at baseline and changes in WORMS and to analyze the associations between numbers of circumscribed CaCs at baseline and changes in WORMS.

RESULTS

Presence of CaCs was associated with increased cartilage degeneration in the patella (coefficient: 0.33; 95% confidence interval (CI): 0.04-0.63), the medial femur (coefficient: 0.51; 95% CI: 0.18-0.83), the lateral tibia (coefficient: 0.36; 95% CI: 0.01-0.71) as well as the medial and lateral meniscus (coefficient: 0.38; 95% CI: 0.00-0.75 and coefficient: 0.72; 95% CI: 0.12-1.32). Knees with higher numbers of CaCs had increased cartilage degeneration in the patella and medial femur (coefficient: 0.09; 95% CI: 0.05-0.14; P < 0.001 and coefficient: 0.08; 95% CI: 0.02-0.14; P = 0.005).

CONCLUSIONS

CaCs were associated with increased cartilage and meniscus degeneration over a period of 4 years. Assessing the number of CaC depositions may be useful to evaluate risk of onset and worsening of degenerative disease.

Omega-3-carboxylic acids provide efficacious anti-inflammatory activity in models of crystal-mediated inflammation

This study assesses the efficacy and exposure–response relationship of omega-3-carboxylic acids (OM-3 CA) in models of crystal-based inflammation. Human THP-1 macrophages and primary peripheral blood mononuclear cells exposed to multiple inflammatory crystal types were used to determine the anti-inflammatory potential of omega-3 (OM-3) fatty acids in vitro. Anti-inflammatory effects of OM-3 CA in vivo were tested in rat monosodium urate (MSU) crystal air pouch and rat knee intra-articular MSU injection models. Acute treatment with the OM-3 fatty acid docosahexaenoic acid suppressed MSU-, cholesterol crystal-, and calcium pyrophosphate crystal-mediated interleukin-1β (IL-1β) production in vitro. In vivo, OM-3 CA dose-dependently reduced crystal-mediated cell migration, exudate volume, and levels of IL-1β and prostaglandin E₂. Following intra-articular injection of MSU, treatment with OM-3-CA (1 mL/kg) and indomethacin (1 mg/kg) resulted in similar mean reductions in pain (23% and 41%, respectively) and swelling (58% and 50%, respectively), compared with controls. Additionally, in complex formulations of OM-3 fatty acids, high levels of palmitic acid could reduce the in vivo effect on crystal-mediated IL-1β elevation. OM-3 CA has a broadly efficacious anti-inflammatory effect with a strong exposure–response relationship that could be beneficial in prevention and treatment of crystal arthritis, with potential applications in other IL-1β-mediated diseases.

Anti-Gouty Arthritis and Antihyperuricemia Effects of Sunflower (Helianthus annuus) Head Extract in Gouty and Hyperuricemia Animal Models

This study was performed to investigate the therapeutic effects and possible mechanisms of sunflower (Helianthus annuus) head extract (SHE) on gout. First, the components of sunflower head powder and SHE were analyzed systematically. SHE, especially SHEB (extracted with 20% ethanol and 80% double-distilled water), strongly suppressed the swelling of the ankles in rats with acute gout induced by monosodium urate (MSU) crystals and reduced the levels of uric acid and xanthine oxidase (XO) in mice with hyperuricemia induced by oteracil potassium and yeast extract powder. Hematoxylin and eosin staining indicated that SHEB reduced inflammation cells and increased the joint space in the ankle compared with the control rats with MSU-induced gout. In the rats with acute gout, among 13 detected inflammatory cytokines, SHEB significantly enhanced the serum levels of interleukin-10 and the monocyte chemoattractant protein 1α. In the mice with hyperuricemia, SHEB reduced the levels of glutathione peroxidase, superoxide dismutase, malondialdehyde, and nitrogen monoxide in liver tissues. The potential therapeutic effects of SHE on gout are probably due to the production of anti-inflammatory cytokines and the suppression of XO activity via the modulation of oxidative stress status.

Gout: an Asia-Pacific update

Even though, Hippocrates recognized gout as an affection of older men and a product of high living long back in 5th century BC, this painful condition promises to accompany humanity to the 21st century. The incidence is progressively rising and females are also affected in the modern era. There are also regional and ethnic variations in the incidence, the genetics of which is being studied. The recommended best therapy for the acute attacks and long term prophylaxis has improved remarkably in the recent years. However, patients are often treated inadequately and risk factors for their disease are not well explored in daily practice. Although well designed long term studies of current and newer treatment are welcomed, educating doctors especially the primary care physicians who manage majority of gout cases, in optimizing the currently available management options would improve the present care.

Effects of Berberine on NLRP3 and IL-1β Expressions in Monocytic THP-1 Cells with Monosodium Urate Crystals-Induced Inflammation

Background. Urate crystals-induced inflammation is a critical factor during the initiation of gouty arthritis. Berberine is well known for its anti-inflammatory activity. However, the underlying effects of berberine on monosodium urate crystals-induced inflammation remain obscure. Objectives. This study is set to explore the protective effect and mechanism of berberine on monosodium urate crystals-induced inflammation in human monocytic THP-1 cells. Methods. The mRNA levels of NLRP3 and IL-1β were measured by Real-Time PCR, and the protein levels of NLRP3 and IL-1β were determined by ELISA, Western blot, and immunofluorescence. Results. The NLRP3 and IL-1β expressions were significantly increased in model group compared to that in normal group (P < 0.05). Meanwhile, there was significant reduction in the expressions of NLRP3 and IL-1β mRNA in groups 6.25 μM berberine and 25 μM berberine when compared with model group (P < 0.05). Conclusions. Therefore, berberine alleviates monosodium urate crystals-induced inflammation by downregulating NLRP3 and IL-1β expressions. The regulatory effects of berberine may be related to the inactivation of NLRP3 inflammasome.

Comparison of Prednisolone, Etoricoxib, and Indomethacin in Treatment of Acute Gouty Arthritis: An Open-Label, Randomized, Controlled Trial

Background

At present there are several kinds of medicine for treating acute gout arthritis (AGA). This study compared the efficacy and safety of prednisolone, etoricoxib, and indomethacin in the treatment of AGA.

Material/Methods

This was an open-label, randomized, active-comparator study in patients with AGA. Patients were randomized to 4 days of prednisolone 35 mg qd, etoricoxib 120 mg qd, or indomethacin 50 mg tid. The primary efficacy endpoint was the reduction of self-assessed pain in the index joint from baseline. Secondary endpoints included changes in physician’s assessment of tenderness, erythema, swelling, and joint activity; patient assessment of response to therapy; and safety.

Results

We analyzed 113 patients. Baseline demographics were comparable among treatment groups. Oral prednisolone, etoricoxib, and indomethacin were similarly effective in improving pain, tenderness, and joint activity over 4 days. For inflammation, oral prednisolone, etoricoxib, and indomethacin were similarly effective in reducing erythema, but prednisolone might be more effective in reducing swelling than indomethacin. The patient response to therapy was similar in the 3 groups. There were more total adverse events with indomethacin compared with the other 2 drugs.

Conclusions

Efficacy was comparable among prednisolone, etoricoxib, and indomethacin for the treatment of AGA. Prednisolone might be more effective in reducing inflammation and it had a better safety profile.

Genetic Analysis of IL-17 Gene Polymorphisms in Gout in a Male Chinese Han Population

Interleukin (IL)-17 is a proinflammatory cytokine mainly secreted by activated T helper 17 cells and involved in inflammatory immune responses. This study aimed to investigate the association between IL-17 variants as well as serum IL-17 levels with gout in male Chinese Han individuals. A total of 1,101 male gout patients and 1,239 ethic-matched controls were enrolled. Genetic distributions of three variants (rs2275913 in IL-17A, rs763780 in IL-17F, and rs4819554 in IL-17RA) were detected by real-time polymerase chain reaction using the Taqman probe method. The plasma concentrations of IL-17A and IL-17F were measured in 228 gout patients and 198 controls that came from above samples by an enzyme-linked immunosorbent assay. No significant differences were observed in the genetic distribution of these polymorphisms between cases and controls (rs2275913: χ² = 0.15, p = 0.928 by genotype, χ² = 0.14, p = 0.711 by allele; rs763780: χ² = 2.24, p = 0.326 by genotype, χ² = 0.26, p = 0.609 by allele; rs4819554: χ² = 1.79, p = 0.409 by genotype, χ² = 1.46, p = 0.227 by allele). Levels of serum IL-17A and IL-17F were significantly decreased in gout patients (both p<0.001). However, no difference was observed in acute gout patients between different genotypic carriers of rs2275913 and rs763780 regarding serum IL-17A and IL-17F levels (p>0.05). Although the genetic variants in IL-17 we studied in this research do not appear to be involved in the development of gout in male Chinese Han individuals, the IL-17 cytokine family may participate in gouty inflammation in an undefined way, which requires further validation.

Effects of RuPeng15 Powder (RPP15) on Monosodium Urate Crystal-Induced Gouty Arthritis in Rats

RuPeng15 Powder (RPP15) is a herbal multicompound remedy that originates from traditional Tibetan medicine and possesses antigout, anti-inflammatory, and antihyperuricemic properties based on the traditional conceptions. The present study was undertaken to evaluate the therapeutic effect of PRP15 in rat gouty arthritis induced by monosodium urate (MSU) crystals. In the present study, we found that treatment with RPP15 (0.4, 0.8, and 1.2 g/kg) in rats with gouty arthritis induced by MSU crystals significantly attenuated the knee swelling. Histomorphometric and immunohistochemistry analyses revealed that MSU-induced inflammatory cell infiltration and the elevated expressions of nuclear transcription factor-κB p65 (NF-κB p65) in synovial tissues were significantly inhibited, and enzyme-linked immunosorbent assay (ELISA) result showed that MSU-induced high levels of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-8 (IL-8) in synovial fluid were reduced by treatment with RPP15 (0.4, 0.8, and 1.2 g/kg). We conclude that RPP15 may be a promising candidate for the development of a new treatment for gout and its activity of antigout may be partially related to inhibiting TNF-α, IL-1β, IL-8, and NF-κB p65 expression in the synovial tissues.

Role of the NLRP3 inflammasome in the transient release of IL-1β induced by monosodium urate crystals in human fibroblast-like synoviocytes

BACKGROUND

To investigate whether monosodium urate (MSU) crystals induce interleukin (IL)-1β in human fibroblast-like synoviocytes (FLS), and whether the NLRP3 inflammasome is involved in the inflammatory mechanism.

METHODS

Human FLS isolated from explants of synovial tissue were stimulated with MSU crystals (0.001 to 0.5 mg/ml) for different time course (6 hours to 48 hours). The expressions of IL-1β, IL-6, TNF-α and NLRP3 were evaluated with ELISA, Western blot and quantitative real-time PCR.

RESULTS

Exposure of FLS to MSU crystals transiently induced a significant increase in IL-1β expression in culture medium with a peak at 6 h. The mRNA level of IL-1β in the FLS cells had a similar pattern at this time point. Changes in IL-6 and TNF-α expression were not observed. Simultaneously, intercellular pro-IL-1β was detected at 6 h. Furthermore, MSU crystals also induced NLRP3 mRNA and protein expression at 6 h to 48 h after MSU treatment.

CONCLUSIONS

MSU crystals directly increased IL-1β and intercellular NLRP3 expression in FLS cells. It is suggested that the NLRP3 inflammasome may be associated with IL-1β in FLS treated with MSU. Altogether, MSU could induce production and release of IL-1β through the NLRP3 inflammasome in human synoviocytes.

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.

Effects of Modified Simiao Decoction on IL-1 β and TNF α Secretion in Monocytic THP-1 Cells with Monosodium Urate Crystals-Induced Inflammation

Simiao pill, a Chinese herbal formula containing four herbs, has been used in the treatment of gouty arthritis for many years. The aim of this study was to explore the effects of modified Simiao decoction (MSD) on IL-1β and TNFα secretion in monocytic THP-1 cells with monosodium urate (MSU) crystals-induced inflammation. The MSU crystals-induced inflammation model in THP-1 cells was successfully established by the stimulation of phorbol 12-myristate 13-acetate (PMA) and MSU crystals. Then, the MSD-derived serum or control serum extracted from rat was administered to different treatment groups. The morphology of MSU crystals and THP-1 cells was observed. IL-1β and TNFα protein expression in supernatant of THP-1 cells were determined by ELISA. Our data demonstrated that MSU crystals induced time-dependent increase of IL-1β and TNFα. Moreover, MSD significantly decreased IL-1β release in THP-1 cells with MSU crystals-induced inflammation. These results suggest that MSD is promising in the treatment of MSU crystals-induced inflammation in THP-1 cells. MSD may act as an anti-IL-1 agent in treating gout. The underlying mechanism may be related to NALP3 inflammasome which needs to be validated in future studies.

Phytochemical Compositions and Antioxidant and Anti-Inflammatory Activities of Crude Extracts from Ficus pandurata H. (Moraceae)

Background. Ficus pandurata H. (Moraceae) is widely used in traditional Chinese medicine as a healthy food condiment or a medicine for treatment of various diseases including inflammation. Objective. The purpose of the present study is to investigate the phytochemical compositions and antioxidant and anti-inflammatory activities of crude water (FPW) and ethanolic extracts (FPE) from Ficus pandurata H. Methods. Phytochemical compositions were identified by a high-performance liquid chromatography-electrospray ionization-mass spectrometry method (HPLC-ESI-MS). The antioxidant activities were evaluated by diphenylpicrylhydrazyl (DPPH) and hydroxyl radical assays, and the anti-inflammatory activities were evaluated by paw edema and levels of inflammatory mediator TNF-α and PGE2 in monosodium urate (MSU) crystal-induced rats. Results. Six compounds were identified by HPLC-MS method, and abundance of phenolics was found in FPE. The FPE showed concentration-dependent-significant scavenging of DPPH and hydroxyl radicals with IC50 values 118.4 and 192.9 μg/mL, respectively. The FPE treatment significantly inhibited the paw edema and the production of TNF-α and PGE2 in MSU crystal-induced rats. Conclusion. The FPE exerted stronger antioxidant and anti-inflammatory activities which may be attributed to its high phenolic content.

NLRP3 and IL-1β in macrophages as critical regulators of metabolic diseases

The activation of the NLRP3 inflammasome leads to the autocleavage and activation of caspase-1. Caspase-1 cleaves several substrates, including the pro-inflammatory cytokine IL-1β. Inflammation, in particular IL-1β, has long been associated with the progression of metabolic disorders, and recent evidence suggests that the NLRP3 inflammasome plays a critical role in this inflammation. This review concentrates on the activation of NLRP3 during the development of metabolic disorders and the effect this activation has on the inflammatory state as well as the metabolic state of the cell.

IL-8 -251T/A and IL-12B 1188A/C polymorphisms are associated with gout in a Chinese male population

OBJECTIVES

Gout is caused by monosodium urate (MSU) crystal-induced inflammation of the joints and periarticular tissues. MSU crystals activate NALP3 and mediate interleukin (IL)-1β generation from its inactive pro-form, resulting in cellular activation and an IL-8-mediated neutrophil influx into the joint. IL-8 and IL-12 are important chemokines related to the initiation and amplification of acute and chronic inflammatory processes. In this study, we investigated whether the IL-8 -251T/A and IL-12 1188A/C polymorphisms are associated with susceptibility to gout in a Chinese Han male population.

METHODS

Overall, 387 patients with gout and 576 controls were included in this study. Genotyping was performed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). An association analysis was carried out using the χ2 test. A genotype-phenotype analysis was also conducted.

RESULTS

The T allele of IL-8 -251 was associated with risk of gout [p = 0.031 (odds ratio (OR) 1.229, 95% confidence interval (CI) 1.019-1.483]. There was a clear link between the IL-12 1188 AA and AC genotypic and A allelic frequencies between gout cases and controls (p < 0.001, df = 2 by genotype; p < 0.001, OR 1.404, 95% CI 1.165-1.691 by allele).

CONCLUSIONS

Our results suggest that the IL-8 -251T/A and IL-12B 1188A/C polymorphisms may be relevant host susceptibility factors for the development of gout.

The antinociceptive and anti-inflammatory effects of the crude extract of Jatropha isabellei in a rat gout model

ETHNOPHARMACOLOGICAL RELEVANCE

Jatropha isabellei Müll Arg. (Euphorbiaceae) is a medicinal plant that has been used in South American folk medicine for the treatment of arthritic diseases, particularly gout.

AIM OF THE STUDY

This study was designed to verify the antinociceptive, anti-inflammatory and hypouricemic potential of Jatropha isabellei.

MATERIALS AND METHODS

Rats were orally administered with the crude extract (100-300 mg/kg) or a fraction that is rich in alkaloids (0.15 mg/kg) of Jatropha isabellei. An intra-articular (i.a.) injection of 50 μl of monosodium urate (MSU) crystals (1.25mg/site) was used to generate the gout model to assess the effect of the treatment on nociception (thermal and mechanical hyperalgesia) and inflammation (oedema and neutrophil infiltration). The effect of Jatropha isabellei on the serum levels of uric acid was evaluated in a model of hyperuricaemia induced by the intraperitoneal injection of potassium oxonate (250 mg/kg). The side effects were analysed using an open-field test, gastric lesion assessment and by measuring the levels of the ALT and AST enzymes.

RESULTS

Our study demonstrated that the crude extract of Jatropha isabellei and a fraction rich in alkaloids were able to prevent the thermal hyperalgesia, mechanical allodynia, oedema and neutrophil infiltration induced by intra-articular MSU injection in rats. On the other hand, treatment with Jatropha isabellei did not alter the uric acid levels increased by potassium oxonate in the hyperuricaemia model. In addition, Jatropha isabellei did not induce gastric lesions or liver damage and did not alter spontaneous locomotor activity.

CONCLUSION

The crude extract of Jatropha isabellei and its fraction rich in alkaloid presents antinociceptive and anti-inflammatory effects in a rat gout model, similar to that observed after treatment with colchicine, supporting the traditional use of this plant in gouty patients.

Gouty tophi in the penis: a case report and review of the literature

Gout is a metabolic disease characterized by hyperuricemia and the deposition of monosodium urate crystals in different anatomical locations. We report the case of a 61-year-old man who received consultation for gouty tophi in the penis, which is an unusual location for this type of pathology, that was resolved with the surgical removal of the tophi. We provide a review on gout and its treatment as well as other locations where atypical gouty tophi have been described.

Polymorphisms -1082 G/A and -819 C/T in the interleukin-10 gene are not associated with gout susceptibility in the Chinese Han male population

BACKGROUND

Gout is caused by monosodium urate crystal-induced inflammation of the joints and periarticular tissues. Interleukin 10 (IL-10) is an important immunoregulatory cytokine, levels of which can be influenced by functional single-nucleotide polymorphisms in the promoter.

OBJECTIVE

To investigate the association of -1082 G/A and -819 C/T polymorphisms in the IL-10 promoter with gout susceptibility in the Chinese Han male population.

METHODS

A case-control study was performed in 302 patients and 284 controls. Genotyping of IL-10 -1082 G/A and -819 C/T polymorphisms was performed by DNA sequencing techniques. An association analysis was analyzed by the χ(2) test.

RESULTS

No significant differences were found in -819T/C and -1082 A/G genotypic and allelic frequencies between gout cases and controls (for -819T/C, χ(2)=0.212, df=1, p=0.645 by genotype; χ(2)=0.079, df=1, p=0.779 by allele; for -1082 A/G, χ(2)=2.116, df=1, p=0.146 by genotype; χ(2)=1.854, df=1, p=0.173 by allele).

CONCLUSIONS

IL-10 -1082 G/A and -819 C/T polymorphisms may not be associated with susceptibility to gout and thus do not play a major role in the development of gout in the Chinese Han male population.

Enhanced interleukin-1β production of PBMCs from patients with gout after stimulation with Toll-like receptor-2 ligands and urate crystals

Introduction

Monosodium urate monohydrate (MSU) crystals synergize with various toll-like receptor (TLR) ligands to induce cytokine production via activation of the NOD-like receptor (NLR) family, pyrin domain-containing 3 (NLPR3) inflammasome. This has been demonstrated in vitro using human cell lines or monocytes of healthy volunteers. In the present study, we have investigated the effect of MSU crystals and of their combination with TLR ligands in peripheral blood mononuclear cells (PBMC) of patients with gout.

Methods

PBMCs from 18 patients with primary gout and 12 healthy donors were exposed to MSU crystals in the presence or absence of saturated fatty acid C18:0 (free fatty acid, TLR2 ligand), palmitoyl-3-cystein (Pam₃Cys, TLR1/2 ligand) and fibroblast stimulating factor-1 (FSL-1, TLR 2/6 ligand). Production of IL-1β, IL-6, IL-8, IL-17 and tumor necrosis factor alpha (TNFα) was determined by ELISA. mRNA transcripts of IL-1β were measured by real-time PCR.

Results

MSU crystals alone failed to induce IL-1β, IL-6 or TNFα in both patients and control groups, but a stronger synergy between MSU/Pam₃Cys and MSU/C18:0 for the induction of IL-1β was found in patients with gout compared to healthy controls. IL-6, but not IL-8, followed the kinetics of IL-1β. No production of the neutrophil-recruiting IL-17 was detectable after stimulation of the patients' PBMCs with MSU in both the presence or absence of TLR ligands. No change of gene transcripts of IL-1β after stimulation with MSU and Pam₃Cys or with MSU and C18:0 was found. A positive correlation was found between synergy in IL-1β production from PBMCs of patients between C18:0 and MSU crystals, as well as the annual number of attacks of acute gouty arthritis (r_s: +0.649, P: 0.022).

Conclusions

The synergy between MSU crystals and TLR-2 ligands is more prominent in patients with gout than in controls. This is likely mediated by the enhanced maturation of pro-IL-1β into IL-1β.

A randomized trial of a single-dose rasburicase versus five-daily doses in patients at risk for tumor lysis syndrome

BACKGROUND

Tumor lysis syndrome (TLS) is a life-threatening disorder characterized by hyperuricemia and metabolic derangements. The efficacy of rasburicase, administered daily for 5 days, has been well established. However, the optimal duration of therapy is unknown in adults.

PATIENTS AND METHODS

We evaluated the efficacy of rasburicase (0.15 mg/kg) administered as single dose followed by as needed dosing (maximum five doses) versus daily dosing for 5 days in adult patients at risk for TLS.

RESULTS

Eighty of the 82 patients enrolled received rasburicase; 40 high risk [median uric acid (UA) 8.5 mg/dl; range, 1.5-19.7] and 40 potential risk (UA = 5.6 mg/dl; range, 2.4-7.4). Seventy-nine patients (99%) experienced normalization in their UA within 4 h after the first dose; 84% to an undetectable level (<0.7 mg/dl). Thirty-nine of 40 (98%) patients in the daily-dose arm and 34 of 40 (85%) patients in single-dose arm showed sustained UA response. Six high-risk patients within the single-dose arm required second dose for UA >7.5 mg/dl. Rasburicase was well tolerated; one patient with glucose-6-phosphate dehydrogenase deficiency developed methemoglobinemia and hemolysis.

CONCLUSIONS

Rasburicase is highly effective for prevention and management of hyperuricemia in adults at risk for TLS. Single-dose rasburicase was effective in most patients; only a subset of high-risk patients required a second dose.

The role of uric acid as an endogenous danger signal in immunity and inflammation

Gout is an ancient disease that still plagues us. Its pathogenic culprit, uric acid crystal deposition in tissues, is a strong inflammatory stimulant. In recent years, the mechanisms through which uric acid crystals promote inflammation have been a subject of increasing interest among rheumatologists and immunologists. Uric acid has been identified as an endogenous adjuvant that drives immune responses in the absence of microbial stimulation. Because uric acid is a ubiquitous metabolite that is produced in high quantities upon cellular injury, the ramifications of its effects may be considerable in health and in disease. Uric acid crystals also have been shown to trigger interleukin-1β-mediated inflammation via activation of the NOD-like receptor protein (NLRP)3 inflammasome, a multimolecular complex whose activation appears to be central to many pathological inflammatory conditions. In this article, we review the possible mechanisms of uric acid-mediated inflammation and offer some historical perspectives on what has been learned about the complex effects of a relatively simple substance.

Monosodium urate monohydrate crystal-recruited noninflammatory monocytes differentiate into M1-like proinflammatory macrophages in a peritoneal murine model of gout

OBJECTIVE

To profile monosodium urate monohydrate (MSU) crystal-recruited monocyte inflammatory function during the course of in vivo differentiation, in a murine model of peritoneal MSU crystal-induced inflammation.

METHODS

C57BL/6J mice were injected intraperitoneally with MSU crystals, and the peritoneal cells were harvested at different time points. The MSU crystal-recruited monocyte/macrophage population was analyzed for the expression of differentiation and activation markers, cytokine production following MSU crystal restimulation ex vivo and in vivo, expression of NLRP3-associated proteins (ASC, caspase 1) and pro-interleukin-1β (proIL-1β), and phagocytic capacity.

RESULTS

Monocytes recruited 8 hours after MSU crystal stimulation (F4/80(low) Gr-1(int) 7/4+) exhibited poor phagocytic capacity, expressed low levels of proIL-1β, and failed to produce proinflammatory cytokines in response to MSU crystal restimulation. In the absence of MSU crystal restimulation, differentiating monocytes produced low levels of transforming growth factor β1 ex vivo, and this was abrogated following MSU crystal restimulation. Over time these cells developed a proinflammatory phenotype in vivo, characterized by the production of IL-1β, tumor necrosis factor α, IL-6, CCL2 (monocyte chemotactic protein 1), and CXCL1 (cytokine-induced neutrophil chemoattractant) following ex vivo MSU crystal restimulation, and leading to IL-1β production and cell infiltration following MSU crystal rechallenge in vivo. Proinflammatory function was associated with differentiation toward a macrophage phenotype (F4/80(high) Gr-1-7/4-), an increase in phagocytic capacity, and an increase in the expression of proIL-1β.

CONCLUSION

MSU crystal-recruited monocytes differentiate into proinflammatory M1-like macrophages in vivo. This proinflammatory macrophage phenotype is likely to play a key role in perpetuating inflammation in gouty arthritis in the presence of ongoing deposition of fresh MSU crystals.

The role of the NLRP3 inflammasome in gout

Gout is an inflammatory arthritis characterized by abrupt self-limiting attacks of inflammation caused by precipitation of monosodium urate crystals (MSU) in the joint. Recent studies suggest that orchestration of the MSU-induced inflammatory response is dependent on the proinflammatory cytokine IL-1β, underlined by promising results in early IL-1 inhibitor trials in gout patients. This IL-1-dependent innate inflammatory phenotype, which is observed in a number of diseases in addition to gout, is now understood to rely on the formation of the macromolecular NLRP3 inflammasome complex in response to the MSU 'danger signal'. This review focuses on our current understanding of the NLRP3 inflammasome and its critical role in MSU-crystal induced inflammatory gout attacks. It also discusses the management of treatment-resistant acute and chronic tophaceous gout with IL-1 inhibitors; early clinical studies of rilonacept (IL-1 Trap), canakinumab (monoclonal anti-IL-1β antibody), and anakinra have all demonstrated treatment efficacy in such patients.

Role of the leucine-rich repeat domain of cryopyrin/NALP3 in monosodium urate crystal-induced inflammation in mice

OBJECTIVE

The mechanism by which monosodium urate monohydrate (MSU) crystals intracellularly activate the cryopyrin inflammasome is unknown. The aim of this study was to use a mouse molecular genetics-based approach to test whether the leucine-rich repeat (LRR) domain of cryopyrin is required for MSU crystal-induced inflammation.

METHODS

Cryopyrin-knockout lacZ (Cryo(-Z/-Z)) mice and mice with the cryopyrin LRR domain deleted and fused to the lacZ reporter (Cryo(DeltaLRR Z/DeltaLRR Z)) were generated using bacterial artificial chromosome-based targeting vectors, which allow for large genomic deletions. Bone marrow-derived macrophages from Cryo(DeltaLRR Z/DeltaLRR Z) mice, Cryo(-Z/-Z) mice, and congenic wild-type (WT) mice were challenged with endotoxin-free MSU crystals under serum-free conditions. Phagocytosis and cytokine expression were assessed by flow cytometry and enzyme-linked immunosorbent assay. MSU crystals also were injected into mouse synovial-like subcutaneous air pouches. The in vivo inflammatory responses were examined.

RESULTS

Release of interleukin-1beta (IL-1beta), but not CXCL1 and tumor necrosis factor alpha, was impaired in Cryo(DeltaLRR Z/DeltaLRR Z) and Cryo(-Z/-Z) mouse bone marrow-derived macrophages compared with WT mouse bone marrow-derived macrophages in response to not only MSU crystals but also other known stimuli that activate the cryopyrin inflammasome. In addition, a comparable percentage of MSU crystals taken up by each type of bone marrow-derived macrophage was observed. Moreover, total leukocyte infiltration in the air pouch and IL-1beta production were attenuated in Cryo(-Z/-Z) and Cryo(DeltaLRR Z/DeltaLRR Z) mice at 6 hours postinjection of MSU crystals compared with WT mice.

CONCLUSION

MSU crystal-induced inflammatory responses were comparably attenuated both in vitro and in vivo in Cryo(DeltaLRR Z/DeltaLRR Z) and Cryo(-Z/-Z) mice. Hence, the LRR domain of cryopyrin plays a role in mediating MSU crystal-induced inflammation in this model.

6-Shogaol inhibits monosodium urate crystal-induced inflammation--an in vivo and in vitro study

Gout is a rheumatic disease that is manifestated by an intense inflammation secondary to monosodium urate crystal deposition in joints. In the present study, we assessed the effect of 6-shogaol (isolated active principle from ginger) on monosodium urate crystal-induced inflammation in mice; an experimental model for gouty arthritis and compared it with that of the non-steroidal anti-inflammatory drug, indomethacin. Paw volume and levels/activities of lysosomal enzymes, lipid peroxidation, anti-oxidant status and inflammatory mediator TNF-alpha were determined in control and monosodium urate crystal-induced mice. The levels of beta-glucuronidase and lactate dehydrogenase were also measured in monosodium urate crystal-incubated polymorphonuclear leucocytes (PMNL) in vitro. The levels of lysosomal enzymes, lipid peroxidation, and inflammatory mediator tumour necrosis factor-alpha and paw volume were increased significantly and the activities of anti-oxidant status were in turn decreased in monosodium urate crystal-induced mice, whereas these changes were reverted to near normal levels upon 6-shogaol administration. In vitro, 6-shogaol reduced the level of beta-glucuronidase and lactate dehydrogenase in monosodium urate crystal-incubated polymorphonuclear leucocytes in concentration dependent manner when compared to control cells. The present results clearly indicated that 6-shogaol exerted a strong anti-inflammatory effect and can be regarded as useful tool for the treatment of acute gouty arthritis.

Intracellular innate immunity in gouty arthritis: role of NALP3 inflammasome

Gout is an inflammatory disease caused by the deposition of monosodium urate (MSU) crystals in the joint. Recent studies have significantly advanced our knowledge on the understanding of mechanisms underlying MSU crystal-induced inflammation. MSU crystals act as a 'danger signal' that can be recognized by pattern recognition receptors both at cell surface and cytoplasm, indicating the importance of innate immunity in gout. This review focuses on the critical role of intracellular NALP3 inflammasome in MSU crystal-induced inflammation.

A role of IgM antibodies in monosodium urate crystal formation and associated adjuvanticity

Uric acid is released from injured cells and can act as an adjuvant signal to the immune system. Uric acid crystals invoke strong inflammatory responses in tissues. Although their biological effects are evident and the associated signaling mechanisms are becoming clear, it remains unexplained as to why uric acid precipitates rapidly in vivo, in sharp contrast to the minimal crystallization in vitro. We report in this study that a group of IgM Abs is able to bind to these crystals, which is interesting in light that B cell-deficient mice do not sense the proinflammatory adjuvant effect of uric acid. The titers of these Abs increase upon immunization with uric acid crystals. We have produced large quantities of such mAbs. The purified IgM Abs can significantly facilitate uric acid precipitation to form the inflammatory crystals in vitro. Infusion of these Abs into B cell-deficient mice significantly increases the basal level of inflammation in these recipients and restores the host's ability to sense uric acid's adjuvanticity. Therefore, we have identified a factor in determining uric acid precipitation and possibly its ability to function as an endogenous adjuvant. This finding suggests a new mechanism of the pathogenesis of gouty arthritis and uric acid-induced immune activation.

Suppression of tumour necrosis factor production from mononuclear cells by a novel synthetic compound, CLX-090717

OBJECTIVES

To evaluate the clinical efficacy of a novel synthetic peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonist, CLX-090717, in several in vitro cell culture systems and murine CIA, an experimental model of RA.

METHODS

Peripheral blood monocytes purified by elutriation, and rheumatoid synovial cells isolated from clinical tissue were cultured with CLX-090717 and TNF-alpha release was measured. Molecular mechanism of action was analysed by western blotting and electrophoretic mobility shift assay. Thioglycollate-elicited murine peritoneal macrophages were cultured with CLX-090717 and lipopolysaccharide (LPS)-induced TNF-alpha release was assayed. Therapeutic studies were done in mice with established arthritis by evaluating clinical parameters and histology. In addition, type II collagen response of lymphocytes from mice with CIA was examined.

RESULTS

CLX-090717 significantly inhibited spontaneous TNF-alpha release by RA synovial membrane cells, as well as LPS-induced TNF-alpha release from human and murine monocytic cells. Inhibition of TNF-alpha in monocytes was mediated partially through a nuclear factor-kappaB (NF-kappaB)-dependent pathway, as judged by sustained levels of IkappaBalpha in cytosolic extracts and a reduced level of LPS-induced NF-kappaB activity in nuclear extracts. CLX-090717 reduced clinical signs of arthritis and damage to joint architecture when administered therapeutically to arthritic mice. Mechanisms of action in CIA involved the reduction in proliferation of arthritic lymphocytes to antigen in vitro as well as reduced TNF-alpha release.

CONCLUSIONS

Our data suggest that the synthetic compound CLX-090717 has potential as a small molecular weight anti-inflammatory therapeutic for chronic inflammatory conditions.

Characterization of articular calcium-containing crystals by synchrotron FTIR

OBJECTIVE

Sixty percent of synovial fluids from patients with severe osteoarthritis (OA) contain calcium pyrophosphate dihydrate (CPPD) or basic calcium phosphate (BCP) crystals. These bioactive crystals can be particularly difficult to accurately identify in complex biologic systems, such as in vitro models of crystal formation. We sought to determine if synchrotron Fourier Transform Infrared spectroscopy (sFTIR) could be used to identify and characterize calcium-containing crystals in mineralization models.

METHODS

CPPD and BCP crystals from porcine models of crystal formation were examined with an FTIR Microscope attached to a synchrotron light source. As a comparison, crystals from human synovial fluids were also examined. The sFTIR spectra generated were compared with known spectra of multiple forms of BCP and CPPD crystals, as well as spectra generated by synthetic CPPD and BCP crystals and cartilage proteoglycans, alone and in mixtures.

RESULTS

sFTIR readily identified CPPD and BCP crystals in porcine models as well as in fresh synovial fluids. Brushite was also present in human and porcine samples, and whitlockite was seen in some porcine samples. Mixtures of minerals were commonly found in a single crystal aggregate in both human and porcine samples. In spectra from many CPPD crystals, the peak at the 1134 cm(-1) found on the standard spectrum for CPPD was diminished. Addition of spectra from cartilage proteoglycans to those of synthetic CPPD crystals dampened the peak at this frequency region, much as this peak was diminished in biologically derived CPPD crystals.

CONCLUSION

sFTIR analysis allows for accurate identification of CPPD and BCP crystals generated in vitro and will be a useful research tool to study articular crystals.

Engagement of CD14 mediates the inflammatory potential of monosodium urate crystals

Phagocyte ingestion of monosodium urate (MSU) crystals can induce proinflammatory responses and trigger acute gouty inflammation. Alternatively, the uptake of MSU crystals by mature macrophages can be noninflammatory and promote resolution of gouty inflammation. Macrophage activation by extracellular MSU crystals involves apparent recognition and ingestion mediated by TLR2 and TLR4, with subsequent intracellular recognition linked to caspase-1 activation and IL-1beta processing driven by the NACHT-LRR-PYD-containing protein-3 inflammasome. In this study, we examined the potential role in gouty inflammation of CD14, a phagocyte-expressed pattern recognition receptor that functionally interacts with both TLR2 and TLR4. MSU crystals, but not latex beads, directly bound recombinant soluble (s) CD14 in vitro. CD14(-/-) bone marrow-derived macrophages (BMDMs) demonstrated unimpaired phagocytosis of MSU crystals but reduced p38 phosphorylation and approximately 90% less IL-1beta and CXCL1 release. Attenuated MSU crystal-induced IL-1beta release in CD14(-/-) BMDMs was mediated by decreased pro-IL-1beta protein expression and additionally by decreased caspase-1 activation and IL-1beta processing consistent with diminished NACHT-LRR-PYD-containing protein-3 inflammasome activation. Coating of MSU crystals with sCD14, but not sTLR2 or sTLR4, restored IL-1beta and CXCL1 production in CD14(-/-) BMDMs in vitro. Gain of function of CD14 directly enhanced TLR4-mediated signaling in response to MSU crystals in transfected Chinese hamster ovary cells in vitro. Last, MSU crystal-induced leukocyte influx at 6 h was reduced by approximately 75%, and local induction of IL-1beta decreased by >80% in CD14(-/-) mouse s.c. air pouches in vivo. We conclude that engagement of CD14 is a central determinant of the inflammatory potential of MSU crystals.

Innate immunity in triggering and resolution of acute gouty inflammation

Gout has long been recognized as a disease of recurrent bouts of acute inflammation that undergo self-resolution. This inflammation is triggered by the body's response to monosodium urate (MSU) crystals. In this paper, we focus on recent studies that describe how interactions of MSU crystals with the components of the innate immune system trigger acute gouty inflammation as well as mechanisms that are involved in the resolution of this inflammation. Specifically, we describe how toll-like receptors mediate the uptake of MSU crystals involved in the initiation and resolution of gouty inflammation. We also describe recent findings on the role of apoptotic clearance in the resolution of gouty inflammation. In addition, how therapies used to treat gout act on the innate immune system to inhibit MSU crystal-induced inflammation and promote the resolution of inflammation is discussed.