Intracellular innate immunity in gouty arthritis: role of NALP3 inflammasome

Ginsenoside Rd protects against acute liver injury by regulating the autophagy NLRP3 inflammasome pathway

Ginsenoside Rd (Rd) is a bioactive compound predominantly found in Panax ginseng C.A. Meyer and Panax notoginseng (Burkill) F.H. Chen ex C.H. Chow, both species belonging to genus Panax in the Araliaceae family. However, its hepatic protective effect against acute liver injury and related mechanistic action remain unexplored. To investigate the protective effect of Rd against thioacetamide (TAA)-induced acute liver injury and assess its underlying regulatory mechanisms related to autophagy and inflammation. Forty-eight 8 weeks old C57BL/6 mice were treated with saline (control or model group), Rd (12.5 mg/kg, 25 mg/kg or 50 mg/kg), and diammonium glycyrrhizinate (DG, 30 mg/kg) for three days. Then the mice were stimulated with TAA to establish acute liver injury model, excluding the control group. HSC-T6 cells were treated with Rd at concentrations of 2.5, 5, or 10 µM, for 12 h with or without Lipopolysaccharide (LPS) stimulation at 100 ng/mL. Immunofluorescence staining, qPCR and Western blot were employed to analyze the expressions of genes and proteins associated with inflammation and autophagy. To validate the role of Rd in regulating autophagy and inflammation, the autophagy inducers, rapamycin and GSK621, were utilised in reverse validation experiments in cells. Rd exhibited significant hepatic protective effects in mice by reducing the serum levels of Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Glutathione S-transferase (GST) and Lactate dehydrogenase (LDH) with acute liver injury. It exhibited strong anti-inflammatory effect by reducing inflammation associated protein, such as cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), nod-like receptor protein 3 (NLRP3), associated speck-like protein containing a CARD (ASC), interleukin-18 (IL-18) and interleukin-1β(IL-1β) proteins and the mRNA expression levels of COX-2, Tumor Necrosis Factor α (TNF α), interleukin-6 (IL-6) and iNOS were decreased in liver tissue. And Rd inhibited LPS-induced inflammation by reducing the expression of COX-2 and NLRP3 in HSC-T6 cells. Moreover, not only in vivo but also in vitro, Rd downregulated the expression of LC3II, Beclin1, phosphorylation-AMP-activated protein kinase (p-AMPK), phosphorylation-ULK1 (p-ULK1) and upregulated the expression of p62 and phosphorylation-mechanistic target of rapamycin (p-mTOR) to suppress autophagy via the AMPK/mTOR/ULK1 pathway. Finally, the inhibitory effects of Rd on autophagy and inflammation in HSC-T6 cells were partially blocked by rapamycin and GSK621. Rd is a promising therapeutic agent to protect liver against TAA-induced acute liver injury by regulating the autophagy-NLRP3 inflammasome pathway.

A Novel Subset of Regulatory T Cells Induced by B Cells Alleviate the Severity of Immunological Diseases

Regulatory T (Treg) cells are crucial for maintaining immune tolerance by suppressing response to self-antigens and harmless antigens to prevent autoimmune diseases and uncontrolled immune responses. Therefore, using Treg cells is considered a therapeutic strategy treating inflammatory diseases. Based on their origin, Treg cells are classified into thymus-derived, peripherally induced, and in vitro induced Treg cells. Our group discovered a novel Treg cell subset, namely, Treg-of-B (Treg/B) cells, generated by culturing CD4+CD25- T cells with B cells, including Peyer's patch B cells, splenic B cells and peritoneal B1a cells, for 3 days. Treg/B cells express CD44, OX40 (CD134), cytotoxic T-lymphocyte-associated antigen-4 (CD152), glucocorticoid-induced tumor necrosis factor receptor family-related protein (CD357), interleukin-10 receptor, lymphocyte activation gene-3 (CD223), inducible co-stimulator (CD278), programmed-death 1 (CD279), tumor necrosis factor receptor II, and high levels of IL-10, but not forkhead box protein P3, similar to type 1 Treg (Tr1) cells. However, unlike Tr1 cells, Treg/B cells do not express CD103, CD226, and latency-associated peptide. Treg/B cells have been applied for the treatment of some murine models of inflammatory diseases, including allergic asthma, inflammatory bowel disease, collagen-induced arthritis, gout, psoriasis and primary biliary cholangitis. This review summarizes the current knowledge of Treg/B cells.

Traditional herbal medicine: Therapeutic potential in acute gouty arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Acute gouty arthritis (AGA) is characterized by a rapid inflammatory reaction caused by the build-up of monosodium urate (MSU) crystals in the tissues surrounding the joints. This condition often associated with hyperuricemia (HUA), is distinguished by its symptoms of intense pain, active inflammation, and swelling of the joints. Traditional approaches in AGA management often fall short of desired outcomes in clinical settings. However, recent ethnopharmacological investigations have been focusing on the potential of Traditional Herbal Medicine (THM) in various forms, exploring their therapeutic impact and targets in AGA treatment.

AIM OF THE REVIEW

This review briefly summarizes the current potential pharmacological mechanisms of THMs - including active ingredients, extracts, and prescriptions -in the treatment of AGA, and discusses the relevant potential mechanisms and molecular targets in depth. The objective of this study is to offer extensive information and a reference point for the exploration of targeted AGA treatment using THMs.

MATERIALS AND METHODS

This review obtained scientific publications focused on in vitro and in vivo studies of anti-AGA THMs conducted between 2013 and 2023. The literature was collected from various journals and electronic databases, including PubMed, Elsevier, ScienceDirect, Web of Science, and Google Scholar. The retrieval and analysis of relevant articles were guided by keywords such as "acute gouty arthritis and Chinese herbal medicine," "acute gouty arthritis herbal prescription," "acute gouty arthritis and immune cells," "acute gouty arthritis and inflammation," "acute gouty arthritis and NOD-like receptor thermoprotein domain associated protein 3 (NLRP3)," "acute gouty arthritis and miRNA," and "acute gouty arthritis and oxidative stress."

RESULTS

We found that AGA has a large number of therapeutic targets, highlighting the effectiveness the potential of THMs in AGA treatment through in vitro and in vivo studies. THMs and their active ingredients can mitigate AGA symptoms through a variety of therapeutic targets, such as influencing macrophage polarization, neutrophils, T cells, natural killer (NK) cells, and addressing factors like inflammation, NLRP3 inflammasome, signaling pathways, oxidative stress, and miRNA multi-target interactions. The anti-AGA properties of THMs, including their active components and prescriptions, were systematically summarized and categorized based on their respective therapeutic targets.

CONCLUSION

phenolic, flavonoid, terpenoid and alkaloid compounds in THMs are considered the key ingredients to improve AGA. THMs and their active ingredients achieve enhanced efficacy through interactions with multiple targets, of which NLRP3 is a main therapeutic target. Nonetheless, given the intricate composition of traditional Chinese medicine (TCM), additional research is required to unravel the underlying mechanisms and molecular targets through which THMs alleviate AGA.

Titanium Dioxide Promotes the Growth and Aggregation of Calcium Phosphate and Monosodium Urate Mixed Crystals

The increased utilization of titanium dioxide (TiO2) nanoparticles (TNPs) in various industrial and consumer products has raised concerns regarding its harmful effect due to its accumulation within the different systems of the human body. Here, we focused on the influence of TNPs on the growth and aggregation of two crucial crystalline substances, calcium phosphate (CaP) and monosodium urate (MSU), particularly its implications in gout disease. In this study, we adopted microscopic techniques and generated kinetic models to examine the interactions between TNPs, CaP and MSU, and crystallization, under controlled laboratory conditions. Our findings reveal that TNPs not only facilitate the growth of these crystals but also promote their co-aggregations. Crystal dissolution kinetics also exhibit that an increase in TNPs concentration corresponds to a reduction in the dissolution rate of CaP and MSU crystals in presence of the dissoluting agent hydroxycitrate (Hcit). These observations suggest that TNPs can stabilize CaP+MSU mixed crystals, which underscores the significance of TNPs' exposure in the pathogenesis of gout disease.

Anethole ameliorates inflammation induced by monosodium urate in an acute gouty arthritis model via inhibiting TLRs/MyD88 pathway

OBJECTIVE

To assess the effects of anethole on monosodium urate (MSU)-induced inflammatory response, investigate its role in acute gouty arthritis (AGA), and verify its molecular mechanism.

METHODS

Hematoxylin and eosin staining assay and time-dependent detection of degree of ankle swelling were performed to assess the effects of anethole on joint injury in MSU-induced AGA mice. Enzyme-linked-immunosorbent serologic assay was performed to demonstrate the production levels of inflammatory factors (interleukin 1β [IL-1β], interleukin 6 [IL-6], interleukin 8 [IL-8], tumor necrosis factor α [TNF-α], and monocyte chemo-attractant protein-1 [MCP-1]) in MSU-induced AGA mice. Western blot assays were used to confirm the effects of anethole on oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activity and the activation of toll-like receptors (TLRs)-myeloid differentiation factor 88 (MyD88) pathway in MSU-induced AGA mice.

RESULTS

We observed that a significant joint injury occurred in MSU-induced AGA mice. Anethole could alleviate the pathological injury of the synovium in MSU-induced AGA mice and suppressed ankle swelling. In addition, we observed that anethole could inhibit MSU-induced inflammatory response and inflammasome activation in MSU-induced AGA mice. Moreover, we discovered that anethole enabled to inhibit the activation of TLRs/MyD88 pathway in MSU-induced AGA mice. Our findings further confirmed that anethole contributed to the inhibitory effects on progression in MSU-induced AGA mice.

CONCLUSION

It confirmed that anethole ameliorated the MSU-induced inflammatory response in AGA mice in vivo via inhibiting TLRs-MyD88 pathway.

Targeting of Nrf2/PPARγ/NLRP3 Signaling Pathway by Stevia rebudiana Bertoni Extract Provides a Novel Insight into Its Protective Effect against Acute Gouty Arthritis-Induced Synovial Inflammation, Oxidative Stress and Apoptosis in a Rat Model

Our research work examined the potential protection of Stevia rebaudiana extract against monosodium urate crystals (MSU)-induced acute gouty arthritis in a rat model and its possible underlying mechanism. Forty rats were allocated into four groups (n = 10); a control group; an MSU group, whose rats received 0.1 of MSU single intra-articular injection in the ankle joint on the fifth day of the experiment; an MSU + Stevia group, which received 250 mg/kg/day of Stevia extract orally for seven days and MSU crystals on the fifth day; and an MSU + colchicine group, which was administered colchicine at 0.28 mg/kg daily for seven days and MSU crystals on the fifth day. Pretreatment with Stevia extract mitigated MSU-induced inflammation as evidenced by a decrease of the ankle edema and inflammatory cell infiltration and a significant downregulation of the protein level of NFκB, TNFα, IL-1β, IL6, and IL18 as well as NLRP3 gene expression. Additionally, there was a markedly increased PPARγ gene expression (p < 0.001) compared with the MSU group (p < 0.001) and alleviated oxidative stress via significant upregulating of Nrf2/HO-1. Moreover, the pretreatment attenuated apoptosis by significantly decreasing cytochrome c, Bax, Caspase-3, and by increasing Bcl-2 protein. In conclusion, Stevia extract exhibited strong anti-inflammatory, antioxidant, and antiapoptotic effects against MSU-induced gouty arthritis similar to the standard anti-inflammatory colchicine drugs.

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.

MicroRNAs Involved in the Therapeutic Functions of Noni (Morinda citrifolia L.) Fruit Juice in the Treatment of Acute Gouty Arthritis in Mice Induced with Monosodium Urate

We investigated the functions of microRNAs in the therapeutic effects of noni (Morinda citrifolia L.) fruit juice on mouse models of acute gouty arthritis induced with monosodium urate (MSU). Compared with the model group (treated with MSU), mice in both the positive control group (treated with both MSU and colchicine) and noni fruit juice group (treated with MSU and noni fruit juice) showed a significantly decreased degree of paw swelling in 5 days, as well as the contents of two types of proinflammatory cytokines (i.e., NALP3 and TNF-α). Based on the next-generation sequencing technology, a total of 3896 microRNAs (234 known and 3662 novel) were identified in mice treated with noni fruit juice. A large amount of differentially expressed miRNAs were identified in the noni fruit juice group, suggesting the significant effects of noni fruit juice on the mice with acute gouty arthritis, while the different patterns of change in the numbers of both upregulated and downregulated miRNAs in both noni fruit juice and positive control groups indicated that the mice of acute gouty arthritis may be regulated by differential mechanisms between the treatments of noni fruit juice and colchicine. The target genes of microRNAs involved in the pathogenesis and pathology of acute gouty arthritis in mice were identified and further annotated by both Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. Our results revealed the therapeutic effects of noni fruit juice on acute gouty arthritis in mice with a group of microRNAs involved in the pharmacological mechanisms of noni fruit juice, providing scientific evidence to support both the agricultural cultivation and pharmacological significance of noni plants.

Regulatory T cells induced by B cells suppress NLRP3 inflammasome activation and alleviate monosodium urate-induced gouty inflammation

Regulatory T cells induced by B cells (Treg-of-B cells), a distinct Foxp3^- Treg cell subset, have established the roles in the suppression of inflammatory conditions, including asthma and intestinal inflammation. However, little is known about the regulatory effects of Treg-of-B cells on innate immunity. Herein, we examined whether Treg-of-B cells could regulate macrophage function and prevent NLRP3-associated diseases, particularly inflammatory gouty arthritis. Treg-of-B cells, but not thymus-derived Treg or effector T cells, inhibited inflammasome-mediated IL-1β secretion, caspase-1 activation, and NLRP3 production by LPS/ATP stimulation in a cell contact-dependent manner. In addition, Treg-of-B cells inhibited monosodium urate-induced NLRP3 inflammasome activation in vitro via NF-κB signaling. Treg-of-B cells ameliorated gouty inflammation in a mouse air pouch model by reducing neutrophil and leukocyte influx and cytokine and chemokine production. Our results demonstrated that Treg-of-B cells exerted regulatory effects on innate immunity by suppressing NLRP3 inflammasome activation and feasible for future therapeutic applications.

Bogomoletz National Medical University, Kyiv, Ukraine, Natrus L, Maltsev D, Bogomoletz National Medical University, Kyiv, Ukraine, Klys Y, Bogomoletz National Medical University, Kyiv, Ukraine, Panova T, Bogomoletz National Medical University, Kyiv, Ukraine, Kondratiuk V, Bogomoletz National Medical University, Kyiv, Ukraine, Konovalov S, Bogomoletz National Medical University, Kyiv, Ukraine. THE CORRELATIONS BETWEEN CYTOKINE PARAMETERS OF IMMUNE INFLAMMATION, ENDOTHELIAL GROWTH FACTOR AND BIOCHEMICAL PARAMETERS IN PATIENTS WITH GOUT

The correlations between cytokine status, vascular endothelial growth factor (VEGF) content, clinical and biochemical parameters in patients with various forms of gout were studied to improve the algorithm for monitoring of clinical condition and effectiveness of treatment. For patients with gout and volunteers clinical and biochemical studies were performed. The content of interleukins (IL-1β, IL-17, IL-22, IL-10), tumor necrosis factor alpha (TNF-α) and VEGF were investigated. Concentrations of TNF-α, IL-1β and IL-17 characterized of inflammation intensity at all stages of gout and increased linearly as the disease progressed. At the stage of asymptomatic hyperuricemia, there were an increased (75% of the control group) concentration of IL-22 on the background of lymphopenia, low concentrations of IL-10 and VEGF. This indicates that the content of IL-22 is a potentially informative biomarker of inflammation intensity as well as a possible predictor of the development of immune-dependent complications and vascular catastrophes in the early stages of gout without signs of joint damage. The concentration of TNF-α positively correlates with the content of IL-10 (r = 0.534); whereas the concentration of IL-1β is independent of the content of IL-10. The relationship between IL-1β and VEGF concentrations (r = 0.40) suggests that IL-1β is more closely associated with endothelial dysfunction and the risk of vascular complications. IL-22 levels do not correlate with other cytokine status, but are associated with lymphocyte counts, so signs of Th22-dependent immune inflammation may be a potential biomarker of lymphocytic depression status in gout. Cytokine status changes in different phases and stages of hyperuricemia. Comparing these changes with the clinical and laboratory picture improves monitoring of the disease development and effectiveness of treatment.

The Inflammasome in Times of COVID-19

Coronaviruses (CoVs) are members of the genus Betacoronavirus and the Coronaviridiae family responsible for infections such as severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and more recently, coronavirus disease-2019 (COVID-19). CoV infections present mainly as respiratory infections that lead to acute respiratory distress syndrome (ARDS). However, CoVs, such as COVID-19, also present as a hyperactivation of the inflammatory response that results in increased production of inflammatory cytokines such as interleukin (IL)-1β and its downstream molecule IL-6. The inflammasome is a multiprotein complex involved in the activation of caspase-1 that leads to the activation of IL-1β in a variety of diseases and infections such as CoV infection and in different tissues such as lungs, brain, intestines and kidneys, all of which have been shown to be affected in COVID-19 patients. Here we review the literature regarding the mechanism of inflammasome activation by CoV infection, the role of the inflammasome in ARDS, ventilator-induced lung injury (VILI), and Disseminated Intravascular Coagulation (DIC) as well as the potential mechanism by which the inflammasome may contribute to the damaging effects of inflammation in the cardiac, renal, digestive, and nervous systems in COVID-19 patients.

Immunomodulatory Effects of Diterpenes and Their Derivatives Through NLRP3 Inflammasome Pathway: A Review

Nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing protein (NLRP) inflammasomes are involved in the molecular pathogenesis of many diseases and disorders. Among NLRPs, the NLRP3 (in humans encoded by the NLRP3 gene) is expressed predominantly in macrophages as a component of the inflammasome and is associated with many diseases, including gout, type 2 diabetes, multiple sclerosis, atherosclerosis, and neurological diseases and disorders. Diterpenes containing repeated isoprenoid units in their structure are a member of some essential oils that possess diverse biological activities and are becoming a landmark in the field of drug discovery and development. This review sketches a current scenario of diterpenes or their derivatives acting through NLRPs, especially NLRP3-associated pathways with anti-inflammatory effects. For this, a literature survey on the subject has been undertaken using a number of known databases with specific keywords. Findings from the aforementioned databases suggest that diterpenes and their derivatives can exert anti-inflammatory effects via NLRPs-related pathways. Andrographolide, triptolide, kaurenoic acid, carnosic acid, oridonin, teuvincenone F, and some derivatives of tanshinone IIA and phorbol have been found to act through NLRP3 inflammasome pathways. In conclusion, diterpenes and their derivatives could be one of the promising compounds for the treatment of NLRP3-mediated inflammatory diseases and disorders.

Tu-Teng-Cao Extract Alleviates Monosodium Urate-Induced Acute Gouty Arthritis in Rats by Inhibiting Uric Acid and Inflammation

Gouty arthritis is an inflammatory joint disease closely related to hyperuricemia. It is characterized by deposition of monosodium urate crystals in the joints, resulting in an intense inflammatory process and pain. Control of hyperuricemia and anti-inflammation treatments are the main therapeutic approaches. However, the commonly used drugs for inhibiting uric acid and acute gouty arthritis have obvious gastrointestinal and renal toxicity; thus, there is an urgency to develop new alternative therapeutic drugs. An extract of Tu-Teng-Cao (TTC), a compound drug used in traditional Chinese medicine, has been widely applied to the clinical treatment of arthritis. In this study, we investigated the therapeutic effects of TTC on gouty arthritis. In this study, an animal model of acute gouty arthritis with hyperuricemia was established using potassium oxonate and monosodium urate crystals. After treatment with TTC, the results showed obvious therapeutic effects on the rat model of acute gouty arthritis. The treatment significantly attenuated the degree of ankle swelling, inflammation, and dysfunction index, and the levels of proinflammatory cytokines. In addition, TTC has significant antihyperuricemia activity in rats with hyperuricemia induced by potassium oxonate. Histological evaluation showed that TTC relieved pathological damage in rats with acute gouty arthritis induced by monosodium urate crystals. All the groups treated with TTC showed improvement in cartilage degeneration, cell degeneration, synovial hyperplasia, and inflammatory cell invasion in the ankle joint of rats. TTC significantly alleviated swelling, inflammation, and bleeding of the renal corpuscle and convoluted tubules of rats. The results of this study suggest that TTC is capable of treating gouty arthritis and decreasing ankle injury through the control of uric acid and inflammation.

NLRP1 and NLRP3 inflammasomes as a new approach to skin carcinogenesis

Inflammasomes are key innate immune system receptors that detect pathogenic endo- and exogenous stressors like microorganisms or ultraviolet radiation (UVR) which activate the highly proinflammatory cytokines interleukin-1β and interleukin-18. Inflammasomes are not only involved in inflammation, but also in carcinogenesis and tumor progression. Due to the dynamic increase in non-melanoma skin cancers (NMSC), it has become necessary to determine how UVR, which plays a key role in NMSC development, can regulate the structure and function of inflammasomes. In the present study, the regulatory mechanisms of NOD-Like Receptor Family Pyrin Domain Containing 1 and 3 inflammasome activation as well as an effective inflammasome-mediated immune response after UVR exposition are discussed. The differences and similarities between these molecular complexes that monitor cellular health, inflammation, and skin carcinogenesis are also highlighted. Despite numerous scientific data, more studies are still required to better understand the biology of inflammasomes in skin cancer development and to explore their therapeutic potential.

Antioxidant and anti-gout effects of orally administered zinc oxide nanoparticles in gouty mice

BACKGROUND

Zinc is an essential trace element which is involved in controlling oxidative stress, growth and immune system by regulating inflammatory cytokines. Gouty arthritis is the inflammation of joints and tissues caused by the accumulation of monosodium urate crystals.

METHOD AND OBJECTIVE

This study involved the oral administration of zinc oxide nanoparticles at a various concentration (5 ppm, 10 ppm, and 20 ppm) and study their antioxidant and anti-gout effects on Balb/C mice. Various parameters such as ROS, superoxide, peroxide, catalase, TBARS, RFTs, LFTs, lipid profile and blood count were studied.

RESULTS

ZnO nanoparticles at the concentrations of 10 and 20 ppm were significant (P < 0.001) in reducing serum uric acid concentration thus treating gouty arthritis. Reactive oxygen species and thiobarbituric acid reactive substances were significantly increased in comparison to zinc oxide nanoparticles treated groups. Furthermore, blood count and LFTs also showed the effectiveness of zinc oxide in the reduction of hyperuricemia. Histopathological analysis showed no apparent changes in liver, kidney and muscles tissues.

CONCLUSION

Zinc oxide nanoparticles can be effective in reducing oxidative stress and the treatment of 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.

Rhein, An Anthraquinone Drug, Suppresses the NLRP3 Inflammasome and Macrophage Activation in Urate Crystal-Induced Gouty Inflammation

Rhein, an anthraquinone drug, is a widely used traditional Chinese medicine. Rhein is a major bioactive metabolite of diacerein which has been approved for treating osteoarthritis with a good safety profile in humans. Gouty arthritis is an inflammatory disease characterized by urate crystal-induced NLRP3 inflammasome activation with up-regulated caspase-1 protease and IL-1 β in macrophages. Inhibition of the NLRP3 inflammasome formation has been considered as a potential therapeutic avenue for treating or preventing many inflammatory diseases. This study aimed to evaluate the anti-inflammatory effects of rhein on gouty arthritis. Rhein within the physiological levels of humans showed no toxicity on the cell viability and differentiation, but significantly decreased the production of IL-1 β , TNF- α and caspase-1 protease in urate crystal-activated macrophages. Compared to medium controls, rhein at the therapeutic concentration (2.5 μ g/mL) effectively inhibited IL-1 β production by 47% ( P=0.002 ). Rhein did not affect the mRNA levels of CASP1, NLRP3 and ASC, but suppressed the protein expression and enzyme activity of caspase-1. Immunofluorescence confocal microscopy further revealed that rhein suppressed the aggregation of ASC speck and inhibited the formation of NLRP3 inflammasome. Rhein of 5 μ g/mL significantly decreased the ASC speck to 36% ( P=0.0011 ), and reduced the NLRP3 aggregates to 37.5% ( P=0.014 ). Our data demonstrate that rhein possesses pharmacological activity to suppress caspase-1 protease activity and IL-1 β production by interfering with the formation of NLRP3 multiprotein complex. These results suggest that rhein has therapeutic potential for treating NLRP3 inflammasome-mediated diseases such as gouty arthritis.

Association between post-transplant uric acid level and renal allograft fibrosis: Analysis using Banff pathologic scores from renal biopsies

Several experimental studies implicate uric acid in renal injury and fibrosis. The objective of this study was to examine the association between uric acid level and allograft fibrosis after kidney transplantation. 241 adult patients who underwent kidney transplantation between 2003 and 2014 were divided into three groups according to the sex specific tertiles of mean uric acid level within the first post-transplant year. The renal biopsies performed during 1 to 5 post-transplant year were analyzed to compare the degree of interstitial fibrosis and tubular atrophy (IF/TA). Mean interval between kidney transplantation and biopsy was similar between groups (23.7 ± 15.3 vs. 30.0 ± 18.6 vs. 27.5 ± 18.5 months, P = 0.072). The higher tertile uric acid level was, the more advanced grade of IF/TA was shown (P = 0.001). Multivariate analysis identified uric acid tertile was independent risk factor for severe IF/TA (odds ratio [95% confidence interval] was 3.16 [1.13-8.82] for tertile 2 and 3.70 [1.25-10.93] for tertile 3, versus tertile 1, respectively). Other independent factors were estimated glomerular filtration rate at 1year post-transplant (0.80 [CI 0.65-0.98]) and biopsy-proven rejection (2.34 [1.05-5.21]). Graft survival over 10 years was significantly lower in tertile 3 (P = 0.041). The results showed that higher uric acid level after kidney transplantation was associated with more severe IF/TA.

OLT1177, a β-sulfonyl nitrile compound, safe in humans, inhibits the NLRP3 inflammasome and reverses the metabolic cost of inflammation

The NLRP3 inflammasome is an intracellular oligomer regulating the activation of caspase-1 for the processing and secretion of IL-1β and IL-18. Although there is growing evidence to substantiate inflammasome inhibition as a therapeutic option for the treatment of inflammatory diseases, to date, there are no approved humans agents. OLT1177, a β-sulfonyl nitrile molecule, shown to be safe in humans, is a selective inhibitor of the NLRP3 inflammasome, with unique properties to reverse the metabolic costs of inflammation and to treat IL-1β– and IL-18–mediated diseases.

Activation of the NLRP3 inflammasome induces maturation of IL-1β and IL-18, both validated targets for treating acute and chronic inflammatory diseases. Here, we demonstrate that OLT1177, an orally active β-sulfonyl nitrile molecule, inhibits activation of the NLRP3 inflammasome. In vitro, nanomolar concentrations of OLT1177 reduced IL-1β and IL-18 release following canonical and noncanonical NLRP3 inflammasome activation. The molecule showed no effect on the NLRC4 and AIM2 inflammasomes, suggesting specificity for NLRP3. In LPS-stimulated human blood-derived macrophages, OLT1177 decreased IL-1β levels by 60% and IL-18 by 70% at concentrations 100-fold lower in vitro than plasma concentrations safely reached in humans. OLT1177 also reduced IL-1β release and caspase-1 activity in freshly obtained human blood neutrophils. In monocytes isolated from patients with cryopyrin-associated periodic syndrome (CAPS), OLT1177 inhibited LPS-induced IL-1β release by 84% and 36%. Immunoprecipitation and FRET analysis demonstrated that OLT1177 prevented NLRP3-ASC, as well as NLRP3-caspase-1 interaction, thus inhibiting NLRP3 inflammasome oligomerization. In a cell-free assay, OLT1177 reduced ATPase activity of recombinant NLRP3, suggesting direct targeting of NLRP3. Mechanistically, OLT1177 did not affect potassium efflux, gene expression, or synthesis of the IL-1β precursor. Steady-state levels of phosphorylated NF-κB and IkB kinase were significantly lowered in spleen cells from OLT1177-treated mice. We observed reduced IL-1β content in tissue homogenates, limited oxidative stress, and increased muscle oxidative metabolism in OLT1177-treated mice challenged with LPS. Healthy humans receiving 1,000 mg of OLT1177 daily for 8 d exhibited neither adverse effects nor biochemical or hematological changes.

Genetic variants of PPAR-gamma coactivator 1B augment NLRP3-mediated inflammation in gouty arthritis

Objective

Gout is characterized by recurrent attacks of arthritis with hyperuricaemia and urate crystal-induced inflammation. Although urate transporters are known as risk factors, the immunogenetics of gouty inflammation remains unclear. This study aimed to investigate the genetic association between immune/metabolism regulators and gout.

Methods

We enrolled 448 gout patients and 943 population controls from Taiwan; all were Han Chinese. We screened association between gout and 22 variants of candidate genes, including NLRP3 , caspase 1, peroxisome proliferator-activated receptor-γ, proliferator-activated receptor-γ coactivator 1α ( PPARGC1A ) and 1β ( PPARGC1B ). The association was validated by replication and combined-sample analyses. Functional assays were performed by quantitative PCR, ELISA, siRNA knockdown and transfection using THP-1 cells, peripheral blood mononuclear cells and synovial cells from patients.

Results

Gouty arthritis exhibited significant association with variants of peroxisome PPARGC1B , which included a missense single nucleotide polymorphism, rs45520937 [P = 6.66 × 10 -9 ; odds ratio (95% CI): 1.85 (1.51, 2.28)]. Expression of PPARGC1B and NLRP3 was induced in urate crystal-activated THP-1, peripheral blood mononuclear cells and synovial cells from gout patients in acute stage. siRNA knockdown of PPARGC1B upregulated NLRP3 in urate crystal-activated macrophages. Compared with the wild-type carriers, patients with the risk A allele of rs45520937 showed statistically increased NLRP3 (P = 0.044) and plasma IL-1β (P = 0.006). Transfection of PPARGC1B cDNA with rs45520937 A allele to macrophages significantly augmented the expression of NLRP3 and IL-1β.

Conclusion

Genetic variants of PPARGC1B are significantly associated with gout, and a missense single nucleotide polymorphism, rs45520937, augments NLRP3 and IL-1β expression. These data suggest that variants of PPARGC1B , a regulator of metabolism and inflammation, contribute to the pathogenesis of gouty arthritis.

Risk of infections in patients with gout: a population-based cohort study

To investigate the risk of various types of infections (pneumonia and urinary tract infection (UTI)), and infection-related mortality in patients with gout compared with population-based controls. A retrospective cohort study was conducted using data from the UK Clinical Practice Research Datalink (CPRD). All patients with a first diagnosis of gout and aged >40 years between January 1987-July 2014, were included and matched with up to two controls. Time-varying Cox proportional hazards models were used to estimate the risk of infections and mortality. 131,565 patients and 252,763 controls (mean age: 64 years, 74% males, mean follow-up of 6.7 years) were included in the full cohort. After full statistical adjustment, the risk of pneumonia was increased (adj. HR 1.27, 95% CI 1.18 to 1.36), while the risk of UTI (adj. HR 0.99, 95% CI 0.97 to 1.01) was similar in patients compared to controls. No differences between patients and controls were observed for infection-related mortality due to pneumonia (adj. HR 1.03, 95% CI 0.93 to 1.14) or UTI (adj. HR 1.16, 95% CI 0.98 to 1.37). In conclusion, patients with gout did not have decreased risks of pneumonia, UTI or infection-related mortality compared to population-based controls.

Increased expression of NLRP3 inflammasome components and interleukin-18 in patients with bullous pemphigoid

BACKGROUND

Bullous pemphigoid (BP) is the most common blistering autoimmune disease severely affecting older people. The complex interplay between innate and adaptive immunity is critical in the development of BP. Inflammasomes, which lead to cleavage-induced maturation of pro-inflammatory cytokines, have been shown to participate in a variety of autoimmune diseases. However, the role of inflammasomes in BP has not been delineated.

OBJECTIVE

The present work aimed to investigate whether inflammasomes are involved in the pathogenesis and progression of BP.

METHODS

Expressions of inflammasome components at the messenger RNA (mRNA) and protein levels in peripheral blood mononuclear cells (PBMCs) from patients with BP and from healthy controls were investigated by quantitative real-time PCR (qRT-PCR) and western blot, respectively. ELISA was employed to evaluate interleukin (IL)-1β, IL-18, lactate dehydrogenase (LDH), and high-mobility group-1 (HMGB1) levels in the serum and blister fluid of patients with BP. Immunohistochemical staining was used to detect IL-18 expression in the skin lesion of patients with BP.

RESULTS

The mRNA levels of NLRP3 inflammasome components (NLRP3, pro-caspase-1, and pro-IL-18) in PBMCs were significantly up-regulated in BP patients compared with those in healthy controls, and were positively correlated with the autoantibody titers for BP180-NC16A. Western Blot analysis showed that the baseline expressions of NLRP3 inflammasome components were increased in PBMCs of BP patients compared with healthy controls, and we failed to observe the mature IL-1β and IL-18. Further analysis showed that IL-18 was elevated in serum, blister fluid and lesional skin from patients with BP, and the serum IL-18 level was positively correlated with the titers of anti-BP180-NC16A autoantibody in BP patient. Most importantly, we found that mRNA expressions of the NLRP3-caspase-1-IL-18 axis components and the serum IL-18 level in BP patients decreased dramatically after effective treatment, which indicated that the up-regulation of NLRP3 inflammasome was responsible, at least to a great degree, for the enhanced IL-18 level in BP patients.

CONCLUSIONS

This study demonstrates that the expression of the NLRP3-caspase-1-IL-18 axis is highly expressed in the PBMCs of patients with BP, and correlated with disease activity, suggesting its involvement in the pathogenesis and progression of BP.

Soluble uric acid primes TLR-induced proinflammatory cytokine production by human primary cells via inhibition of IL-1Ra

OBJECTIVES

The study of the proinflammatory role of uric acid has focused on the effects of its crystals of monosodium urate (MSU). However, little is known whether uric acid itself can directly have proinflammatory effects. In this study, we investigate the priming effects of uric acid exposure on the cytokine production of primary human cells upon stimulation with gout-related stimuli.

METHODS

Peripheral blood mononuclear cells (PBMCs) were harvested from patients with gout and healthy volunteers. Cells were pretreated with or without uric acid in soluble form for 24 h and then stimulated for 24 h with toll-like receptor (TLR)2 or TLR4 ligands in the presence or absence of MSU crystals. Cytokine production was measured by ELISA; mRNA levels were assessed using qPCR.

RESULTS

The production of interleukin (IL)-1β and IL-6 was higher in patients compared with controls and this correlated with serum urate levels. Proinflammatory cytokine production was significantly potentiated when cells from healthy subjects were pretreated with uric acid. Surprisingly, this was associated with a significant downregulation of the anti-inflammatory cytokine IL-1 receptor antagonist (IL-1Ra). This effect was specific to stimulation by uric acid and was exerted at the level of gene transcription. Epigenetic reprogramming at the level of histone methylation by uric acid was involved in this effect.

CONCLUSIONS

In this study we demonstrate a mechanism through which high concentrations of uric acid (up to 50 mg/dL) influence inflammatory responses by facilitating IL-1β production in PBMCs. We show that a mechanism for the amplification of IL-1β consists in the downregulation of IL-1Ra and that this effect could be exerted via epigenetic mechanisms such as histone methylation. Hyperuricaemia causes a shift in the IL-1β/IL-1Ra balance produced by PBMCs after exposure to MSU crystals and TLR-mediated stimuli, and this phenomenon is likely to reinforce the enhanced state of chronic inflammation.

NLRP3 Inflammasome Plays an Important Role in the Pathogenesis of Collagen-Induced Arthritis

Objective. To investigate the relationship between NLRP3 and the pathogenesis of collagen-induced arthritis. Methods. We used the collagen-induced arthritis (CIA) mouse model. The mice were divided into two groups: the model group (CIA, n = 16) and the control group (Normal, n = 8). The mice were sacrificed seven weeks after immunization. The arthritis score and imaging evaluation (X-rays, Micro-CT, and MRI) were performed. Synovial tissue NLRP3 expression and peripheral blood cytokine levels were analyzed. Results. The arthritis score (6.00 ± 2.52), imaging score (4.63 ± 0.92), and synovial tissue NLRP3 expression (4.00 ± 2.03) significantly increased in the CIA mice. The expression of synovial NLRP3 was positively correlated with arthritis clinical and radiographic scores (r = 0.792 and r = 0.669, resp.). Conclusions. The synovial NLRP3 expression increased at the early onset of RA. Synovial NLRP3 expression level was correlated with the clinical arthritis severity and extent of radiological destruction, suggesting that NLRP3 is involved in the pathogenesis of RA.

C-type lectin domain family 12, member A: A common denominator in Behçet's syndrome and acute gouty arthritis

C-type lectin domain family 12, member A (CLEC12A) is a C-type lectin-like pattern recognition receptor capable of recognizing monosodium urate crystals. Monosodium urate crystals, the causative agents of gout are also among the danger-associated molecular patterns reflecting cellular injury/cell death. In response to monosodium urate crystals, CLEC12A effectively inhibits granulocyte and monocyte/macrophage functions and hence acts as a negative regulator of inflammation. Behçet's syndrome and gout are autoinflammatory disorders sharing certain pathological (neutrophilic inflammation), clinical (exaggerated response to monosodium urate crystals) and therapeutic (colchicine) features. We propose the hypothesis that decreased expression of CLEC12A is a common denominator in the hyperinflammatory responses observed in Behçet's syndrome and gout. Major lines of evidence supporting this hypothesis are: (1) Downregulation/deficiency of CLEC12A is associated with hyperinflammatory responses. (2) CLEC12A polymorphisms with functional and clinical implications have been documented in other inflammatory diseases. (3) Colchicine, a fundamental therapeutic agent used both in Behçet's syndrome and gout is shown to oppose the downregulation of CLEC12A. (4) Behçet's syndrome and gout are characterized by a hyperinflammatory response to monosodium urate crystals and other than gout, Behçet's syndrome is the only inflammatory condition exhibiting this exaggerated response. (5) Genomewide linkage and association studies of Behçet's syndrome collectively point to 12p12-13, the chromosomal region harboring CLEC12A. (6) Patients with severe forms of Behçet's syndrome underexpress CLEC12A with respect to patients with mild forms of the disease. If supported by well-designed, rigorous experiments, the forementioned hypothesis pertinent to CLEC12A will carry important implications for therapy, designing experimental models, and uncovering immunopathogenic mechanisms in Behçet's syndrome and gout.

Purification and analysis of the interactions of caspase-1 and ASC for assembly of the inflammasome

Inflammasomes are intracellular macromolecular complexes assembled to activate inflammatory caspases such as caspase-1 and caspase-5, which perform critical roles during innate immune response. The NALP3 inflammasome comprises three protein components, NALP3, ASC, and caspase-1. ASC, which contains both a pyrin domain (PYD) and a caspase recruitment domain (CARD), acts as a bridge to recruit NALP3 using the PYD/PYD interaction and to recruit caspase-1 via the CARD/CARD interaction. In this study, we successfully purified and characterized ASC CARD and caspase-1 CARD. The results showed that ASC CARD was unable to interact with caspase-1 CARD in vitro; therefore, we proposed an interaction mode between ASC CARD and caspase-1 CARD from a structural based modeling study.

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.

PYRIN domains and their interactions in the apoptosis and inflammation signaling pathway

The PYRIN domain (PYD) is a well known protein interaction module and a prime mediator of the protein interactions necessary for apoptosis, inflammation and innate immune signaling pathway. Because PYD-mediated apoptosis, inflammation and innate immune processes are associated with many human diseases, studies in these areas are of great biological importance. Intensive biochemical and structural studies of PYD have been conducted in the past decade to elucidate PYD-mediated signaling events, and evaluations of the molecular structure of PYDs have shown the underlying molecular basis for the assembly of PYD-mediated complexes and for the regulation of inflammation and innate immunity. This review summarizes the structure and function of various PYDs and proposes a PYD:PYD interaction for assembly of the complexes involved in those signaling pathways.

Research progress on the NLRP3 inflammasome and its role in the central nervous system

The NLRP3 inflammasome, which consists of the NLRP3 (nucleotide-binding oligomerization domain (Nod)-like receptor 3) scaffold, the ASC (apoptosis-associated speck-like protein containing a CARD) adaptor and procaspase- 1, is assembled after the cytoplasmic LRRs (leucine-rich repeats) of NLRP3 sense pathogens or danger signals. The NLRP3 inflammasome controls the activation of the proteolytic enzyme caspase-1. Caspase-1 in turn regulates the maturation of the proinflammasome cytokines IL-1β and IL-18, which leads to an inflammatory response. The inflammasome plays an important role in the development of Alzheimer's disease and bacterial meningitis, and the NLRP3 inflammasome may become a new target for the prevention and treatment of central nervous system diseases.

ATP-P2X4 signaling mediates NLRP3 inflammasome activation: a novel pathway of diabetic nephropathy

Tubulointerstitial inflammation plays a key role in the development of diabetic nephropathy (DN). Cytokines in the IL-1 family are the key pro-inflammatory cytokines of tubulointerstitial inflammation. Extracellular ATP can cause P2X receptors to activate the NOD-like receptor 3 (NLRP3) inflammasome and cause IL-1β and IL-18 maturation and release. We investigated the role of ATP-P2X4 signaling in NLRP3 inflammasome activation and renal interstitial inflammation characteristic of DN. Ex vivo studies, P2X4 showed increased expression in renal tubule epithelial cells in patients with nephropathy due to type 2 diabetes compared to those in the control group. Linear correlation analysis shows that P2X4 expression was positively related with urine IL-1β and IL-18 levels. Moreover, P2X4 expression was co-localized with NLRP3, IL-1β, and IL-18 expression. In vitro culture experiments showed NLRP3 protein expression, cleavage of caspase-1 and IL-1β, and release of IL-1β, IL-18 and ATP in HK-2 cells significantly increased after high glucose stimulation. However, apyrase, which consumes extracellular ATP, completely blocked the changes caused by high glucose. The P2 receptor antagonist suramin, P2X receptor antagonist TNP-ATP, P2X4 selective antagonist 5-BDBD, and P2X4 gene silencing attenuated NLRP3 expression, cleavage of caspase-1 and IL-1β, and release of IL-1β and IL-18 induced by high glucose. Taken together, these results suggest that ATP-P2X4 signaling mediates high glucose-induced activation of the NLRP3 inflammasome, regulates IL-1 family cytokine secretion, and causes the development of tubulointerstitial inflammation in DN.

Comparison of non-crystalline silica nanoparticles in IL-1β release from macrophages

BACKGROUND

Respirable crystalline silica (silicon dioxide; SiO₂, quartz) particles are known to induce chronic inflammation and lung disease upon long-term inhalation, whereas non-crystalline (amorphous) SiO₂ particles in the submicrometre range are regarded as less harmful. Several reports have demonstrated that crystalline, but also non-crystalline silica particles induce IL-1β release from macrophages via the NALP3-inflammasome complex (caspase-1, ASC and NALP3) in the presence of lipopolysaccharide (LPS) from bacteria. Our aim was to study the potential of different non-crystalline SiO₂ particles from the nano- to submicro-sized range to activate IL-1β responses in LPS-primed RAW264.7 macrophages and primary rat lung macrophages. The role of the NALP3-inflammasome and up-stream mechanisms was further explored in RAW264.7 cells.

RESULTS

In the present study, we have shown that 6 h exposure to non-crystalline SiO₂ particles in nano- (SiNPs, 5-20 nm, 50 nm) and submicro-sizes induced strong IL-1β responses in LPS-primed mouse macrophages (RAW264.7) and primary rat lung macrophages. The primary lung macrophages were more sensitive to Si-exposure than the RAW-macrophages, and responded more strongly. In the lung macrophages, crystalline silica (MinUsil 5) induced IL-1β release more potently than the non-crystalline Si50 and Si500, when adjusted to surface area. This difference was much less pronounced versus fumed SiNPs. The caspase-1 inhibitor zYVAD and RNA silencing of the NALP3 receptor reduced the particle-induced IL-1β release in the RAW264.7 macrophages. Furthermore, inhibitors of phagocytosis, endosomal acidification, and cathepsin B activity reduced the IL-1β responses to the different particles to a similar extent.

CONCLUSIONS

In conclusion, non-crystalline silica particles in the nano- and submicro-size ranges seemed to induce IL-1β release from LPS-primed RAW264.7 macrophages via similar mechanisms as crystalline silica, involving particle uptake, phagosomal leakage and activation of the NALP3 inflammasome. Notably, rat primary lung macrophages were more sensitive with respect to silica-induced IL-1β release. The differential response patterns obtained suggest that silica-induced IL-1β responses not only depend on the particle surface area, but on factors and/or mechanisms such as particle reactivity or particle uptake. These findings may suggest that bacterial infection via LPS may augment acute inflammatory effects of non-crystalline as well as crystalline silica particles.

Safety of intradermal injection of monosodium urate crystals as a vaccine carrier in volunteers

Monosodium urate (MSU) crystals are known to induce gouty arthritis, but also evoke specific cell immunity and work as an adjuvant by delivering several kinds of binding proteins, including idiotypic cancer vaccine peptides into dendritic cells. To investigate the potency of MSU crystals as a cancer vaccine carrier in vivo, this preclinical study examined whether intradermal injection of MSU crystals was safe for healthy adults. Subjects comprised 12 volunteers. Four different dose levels of MSU crystals were injected as follows: 2 μg (n = 3), 20 μg (n = 3), 200 μg (n = 3), or 2000 μg (n = 3). At 24 hours after administration, documented erythema was seen around the injection site in a dose-dependent manner, particularly in all adults with MSU dose ≥200 μg. However, redness was limited to the grade I level of the National Cancer Institute toxicity criteria. Serum uric acid levels did not show any change before and after injection. Moreover, neither gouty arthritis nor tophi developed in any volunteers, indicating that intradermal injection of MSU crystals did not induce systemic inflammation at the doses that evoked significant local inflammation. These findings suggest that intradermal injection of MSU crystals is fundamentally safe and should be made available for clinical trials using MSU-crystal-conjugated cancer vaccines.

Crystal structure of NALP3 protein pyrin domain (PYD) and its implications in inflammasome assembly

NALP3 inflammasome, composed of the three proteins NALP3, ASC, and Caspase-1, is a macromolecular complex responsible for the innate immune response against infection with bacterial and viral pathogens. Formation of the inflammasome can lead to the activation of inflammatory caspases, such as Caspase-1, which then activate pro-inflammatory cytokines by proteolytic cleavage. The assembly of the NALP3 inflammasome depends on the protein-interacting domain known as the death domain superfamily. NALP3 inflammasome is assembled via a pyrin domain (PYD)/PYD interaction between ASC and NALP3 and a caspase recruitment domain/caspase recruitment domain interaction between ASC and Caspase-1. As a first step toward elucidating the molecular mechanisms of inflammatory caspase activation by formation of inflammasome, we report the crystal structure of the PYD from NALP3 at 1.7-Å resolution. Although NALP3 PYD has the canonical six-helical bundle structural fold similar to other PYDs, the high resolution structure reveals the possible biologically important homodimeric interface and the dynamic properties of the fold. Comparison with other PYD structures shows both similarities and differences that may be functionally relevant. Structural and sequence analyses further implicate conserved surface residues in NALP3 PYD for ASC interaction and inflammasome assembly. The most interesting aspect of the structure was the unexpected disulfide bond between Cys-8 and Cys-108, which might be important for regulation of the activity of NALP3 by redox potential.

Dangers within: DAMP responses to damage and cell death in kidney disease

The response to exogenous pathogens leads to activation of innate immunity through the release of pathogen-associated molecular patterns (PAMPs) and their binding to pattern recognition receptors. A classic example is septic shock where Toll receptor 4 recognizes PAMPs. Although well accepted, this concept does not explain the activation of innate immunity and inflammation occurs with transplantation, autoimmunity, or trauma. Increasingly recognized is that endogenous molecules released by dying cells (damage-associated molecular patterns; DAMPs) activate cellular receptors leading to downstream inflammation. Thus endogenous danger signals and exogenous PAMPs elicit similar responses through seemingly similar mechanisms. Also emerging is our understanding that normal repair processes benefit from dampening the immune response to these endogenous danger molecules. Here we focus on the role of DAMPs and their putative receptors in the pathogenesis of acute and chronic kidney diseases.

Inflammasomes and autoimmunity

The NOD-like receptor (NLR) family members are cytosolic sensors of microbial components and danger signals. A subset of NLRs control inflammasome assembly that results in caspase-1 activation and, in turn, IL-1β and IL-18 production. Excessive inflammasome activation can cause autoinflammatory disorders, including the hereditary periodic fevers. Autoinflammatory and autoimmune diseases form a disease spectrum of aberrant, immune-mediated inflammation against self, through innate and adaptive immunity. However, the role of inflammasomes in autoimmune disease is less clear than in autoinflammation, despite the numerous effects IL-1β and IL-18 can have on shaping adaptive immunity. We summarize the role of inflammasomes in autoimmune disorders, highlight the need for a better understanding of inflammasomes in these conditions and offer suggestions for future research directions.

New and improved strategies for the treatment of gout

The Western world appears to be in the midst of the third great gout epidemic of all time. In this century, gout is increasing in prevalence despite an increased understanding of its risk factors and pathophysiology, and the availability of reasonably effective treatment. The main cultural factors responsible for this appear to be diet, obesity, ethanol use and medications. Excess fructose consumption is a newly recognized modifiable risk factor. The debate has been renewed concerning hyperuricemia as an independent risk factor for renal insufficiency and cardiovascular disease. Prevention is still rooted in lifestyle choices. Existing treatments have proven to be unsatisfactory in many patients with comorbidities. New treatments are available today and on the horizon for tomorrow, which offer a better quality of life for gout sufferers. These include febuxostat, a nonpurine inhibitor of xanthine oxidase with a potentially better combination of efficacy and safety than allopurinol, and investigational inhibitors of URAT-1, an anion exchanger in the proximal tubule that is critical for uric acid homeostasis. New abortive treatments include interleukin-1 antagonists that can cut short the acute attack in 1 to 2 days in persons who cannot take nonsteroidal anti-inflammatory drugs, colchicine or corticosteroids. Lastly, newer formulations of uricase have the ability to dissolve destructive tophi over weeks or months in patients who cannot use currently available hypouricemic agents. Diagnostically, ultrasound and magnetic resonance imaging offer advanced ways to diagnose gout noninvasively, and just as importantly, a way to follow the progress of tophus dissolution. The close association of hyperuricemia with metabolic syndrome, hypertension and renal insufficiency ensures that nephrologists will see increasing numbers of gout-afflicted patients.

Gout: epitome of painful arthritis

Arthritic pain and disability are at or near the top of the list of reasons adult patients seek medical attention. At least 47.8 million US residents have arthritis. In Europe, the magnitude of the problem is similar, affecting 8 million in the United Kingdom and 108 million across the continent. Osteoarthritis is by far the most common form of arthritis. In a regional UK study, nearly half of adults 50 years or older reported some form of osteoarthritic knee pain over a 1-year period. Among the arthritides, gout is notable for the agonizing nature and unique pathogenesis of the pain it generates. Gout is the most common cause of inflammatory arthritis among men and postmenopausal women. Because of the atypical nature of some of its clinical manifestations, gout can present serious diagnostic challenges for practicing physicians. In recent years, knowledge about gout's pathogenesis, pathophysiology, and differential diagnosis has advanced on a broad front. Genetic variants within a newly identified transport gene, SLC2A9, have been associated with a low fractional excretion of uric acid and the presence of gout in several population samples. The SLC2A9 gene encodes glucose transporter 9-a unique hexose and high-capacity urate transporter. In addition, human ATP-binding cassette, subfamily G2 (ABCG2), encoded by the ABCG2 gene, has been found to mediate renal urate secretion. Introduction of a mutation encoded in a model system by a common single nucleotide polymorphism, rs2231142, resulted in a 53% reduction in urate transport rates compared with wild-type ABCG2. Based on a large population study, it has been estimated that at least 10% of all gout cases in white persons may be attributable to this single nucleotide polymorphism causal genetic variant. Of the various categories of arthritis, the crystal-induced arthropathies, gout and pseudogout, are manifested by acute inflammation and tissue damage arising from deposition in joints and periarticular tissues of monosodium urate (MSU), calcium pyrophosphate dehydrate, or basic calcium phosphate crystals. The innate immune system rapidly detects invading pathogenic microbes and nonmicrobial "danger signals" such as MSU crystals. When these crystals are deposited in synovial tissues, NLR proteins (NOD-like receptors) form multiprotein complexes known as inflammasomes that trigger secretion of inflammation-producing cytokines like interleukin-1β and interleukin-18. Usually, gout can be diagnosed by medical history, physical examination, and presence of hyperuricemia (urate >416 μmol/L). However, a urate concentration less than 416 does not by itself rule out gout. Confirmation of the diagnosis by identification of typical MSU crystals in aspirated synovial fluid is definitive. Analysis of joint fluid is mandatory to rule out septic arthritis, which can rapidly become lethal. Because of its special ability to identify and quantitate urate deposits in peripheral tissues, dual-energy computed tomography should prove valuable in the differential diagnosis of gout. Gout mimics a variety of illnesses; for example, spinal gout may masquerade as metastatic cancer, epidural abscess, and nerve compression syndrome.

Expression of NALP3 in the spleen of mice with portal hypertension

This study examined the mRNA expression of NALP3 in the spleen of the mice with hypersplenism due to portal hypertension (PH). The mouse hypersplenism models were established by oral administration of tetrachloromethane (2 mL/kg/week for 12 weeks by oral gavage). All the mice were randomly divided into a control group and an experimental group. The blood routine test was conducted, spleen index was calculated and spleen was histologically examined. Portal vein sera were taken for detection of the level of uric acid. The mRNA expressions of NALP3 and IL-1beta in the spleen were detected by reverse transcriptase-polymerase chain reaction (RT-PCR). The results showed that the platelet count was significantly lower in the experimental group [(674 + or - 102) x 10(9)/L] than in the control group [(1307 + or - 181) x 10(9)/L] (P<0.05), while the spleen index was significantly higher [(9.83 + or - 1.36) microg/g] in the experimental group than in the control group [(4.11 + or - 0.47) microg/g] (P<0.05). The histopathological changes of spleen followed the pattern of congestive splenomegaly. No significant difference was found in the uric acid level in the portal vein between the control group and the experiment group. The mRNA expressions of NALP3 and IL-1beta were up-regulated significantly in the spleen in the experimental group as compared with those in the control group (P<0.05). It was concluded that NALP3 and IL-1beta may play important roles in the pathogenesis of hypersplenism.