Signaling Events Involved in Macrophage Chemokine Expression in Response to Monosodium Urate Crystals

GOLM1 Promotes Atherogenesis by Activating Macrophage EGFR-ERK Signaling Cascade

BACKGROUND

Atherosclerosis is a chronic inflammatory disease. GOLM1 (Golgi membrane protein 1) is an inflammation-responsive protein and a mediator in some inflammation-associated pathological processes. Because we found a positive correlation between GOLM1 expression and atherosclerosis progression by checking the gene expression data set of human atherosclerotic lesions, we explored the potential significance of GOLM1 in atherosclerosis in this study.

METHODS

GOLM1 levels in serums and lesions of patients with atherosclerosis and mice with atherosclerosis were examined by immunostaining and ELISA. Gain-of-function and loss-of-function approaches were used to study the impacts of GOLM1 in inflammation and atherogenesis of Apoe-/- mice on a Western diet. The effects of GOLM1 on macrophage behaviors were determined by OxLDL (oxidized low-density lipoprotein) uptake assay, single-cell sequencing analysis, global phosphoproteomics analysis, and molecular biological techniques. The therapeutic potential of GOLM1 neutralization for atherosclerosis was evaluated in Apoe-/- mice.

RESULTS

GOLM1 was elevated in serums and lesions of patients with atherosclerosis and mice with atherosclerosis. Global deletion of GOLM1 ameliorated mouse inflammation and atherosclerosis, while knock-in of GOLM1 exacerbated these pathological manifestations. Furthermore, hepatic GOLM1 deletion reduced circulating GOLM1 and attenuated atherogenesis. Mechanistically, the expression and secretion of GOLM1 were induced in multiple mouse tissues by atherogenic stimulus, leading to the elevation of extracellular GOLM1. Extracellular GOLM1 then stimulated ERK (extracellular signal-regulated kinase) signaling cascade by binding to its putative receptor EGFR (epidermal growth factor receptor) to promote macrophage uptake of LDL (low-density lipoprotein) and enhance the corresponding macrophage immune response. Moreover, neutralizing GOLM1 by an antibody suppressed mouse inflammation and atherogenesis.

CONCLUSIONS

GOLM1 is an atherogenic mediator and a promising therapeutic target for the intervention of atherosclerotic diseases.

Mechanism of ShuiJingDan in Treating Acute Gouty Arthritis Flares Based on Network Pharmacology and Molecular Docking

Purpose

This study examined the underlying mechanisms of SJD's anti-inflammatory and analgesic effects on acute GA flares.

Methods

This study used pharmacology network and molecular docking methods. The active ingredients of ShuiJingDan (SJD) were obtained from the Traditional Chinese Medicine Systems Pharmacology Analysis Platform (TCMSP), and the relevant targets of GA were obtained from the Online Mendelian Inheritance in Man (OMIM) database and Therapeutic Target Database (TTD). The core drug group-target-disease Venn diagram was formed by crossing the active ingredients of SJD and the relevant targets. Gene Ontology (GO) analysis was conducted for functional annotation, DAVID was used for Kyoto Encyclopedia of Genes, and Genomes pathway enrichment analysis, and R was used to find the core targets. The accuracy of SJD network pharmacology analysis in GA treatment was verified by molecular docking simulations. Finally, a rat GA model was used to further verify the anti-inflammatory mechanism of SJD in the treatment of GA.

Results

SJD mainly acted on target genes including IL1B, PTGS2, CXCL8, EGF, and JUN, as well as signal pathways including NF-κB, Toll-like receptor (TLR), IL-17, and MAPK. The rat experiments showed that SJD could significantly relieve ankle swelling, reduce the local skin temperature, and increased the paw withdrawal threshold. SJD could also reduce synovial inflammation, reduced the concentrations of interleukin-1β (IL-1β), IL-8, and COX-2 in the synovial fluid, and suppressed the expression of IL1B, CXCL8, and PTGS2 mRNA in the synovial tissue.

Conclusion

SJD has a good anti-inflammatory effect to treat GA attacks, by acting on target genes such as IL-1β, PTGS2, and CXCL8.

IL-6/ERK signaling pathway participates in type I IFN-programmed, unconventional M2-like macrophage polarization

Type I interferons (IFN-Is) have been harnessed for cancer therapies due to their immunostimulatory functions. However, certain tumor-tolerating activities by IFN-Is also exist, and may potentially thwart their therapeutic effects. In this respect, our previous studies have demonstrated a monocyte-orchestrated, IFN-I-to-IL-4 cytokine axis, which can subsequently drive M2-skewed pro-tumoral polarization of macrophages. Whether other IFN-dependent signals may also contribute to such an unconventional circumstance of M2-like macrophage skewing remain unexplored. Herein, we first unveil IL-6 as another ligand that participates in IFN-dependent induction of a typical M2 marker (ARG1) in transitional monocytes. Indeed, IL-6 significantly promotes IL-4-dependent induction of a major group of prominent M2 markers in mouse bone marrow-derived macrophages (BMDMs) and human peripheral blood-derived macrophages, while it alone does not engage marked increases of these markers. Such a pattern of regulation is confirmed globally by RNAseq analyses in BMDMs, which in turn suggests an association of IL-6-amplified subset of M2 genes with the ERK1/2 signaling pathway. Interestingly, pharmacological experiments establish the role of SHP2-ERK cascade in mediating IL-6's enhancement effect on these M2 targets. Similar approaches also validate the involvement of IL-6/ERK signaling in promoting the IFN-dependent, unconventional M2-skewing phenotype in transitional monocytes. Furthermore, an inhibitor of ERK signaling cooperates with an IFN-I inducer to enable a greater antitumor effect, which correlates with suppression of treatment-elicited ARG1. The present work establishes a role of IL-6/ERK signaling in promoting M2-like macrophage polarization, and suggests this axis as a potential therapeutic target for combination with IFN-I-based cancer treatments.

Mechanism Investigation of Wuwei Shexiang Pills on Gouty Arthritis via Network Pharmacology, Molecule Docking, and Pharmacological Verification

Background

Gout is a common crystal-related arthritis caused by the deposition of monosodium urates (MSU). Tibetan medicine Wuwei Shexiang Pills (WSP) has been demonstrated to exhibit anti-inflammatory, antihyperuricemia, and antigout activities. However, the underlying mechanism is unknown.

Objectives

To explore the mechanisms of Wuwei Shexiang Pills on gouty arthritis via network pharmacology, molecule docking, and pharmacological verification.

Methods

The ingredients and targets of WSP were obtained by searching and screening in BATMAN-TCM and SwissADME. The targets involving the gout were acquired from public databases. The shared targets were put onto STRING to construct a PPI network. Furthermore, Metascape was applied for the GO and KEGG enrichment analysis to predict the biological processes and signaling pathways. And molecular docking was performed to validate the binding association between the key ingredients and the relative proteins of TNF signaling. Based on the serum pharmacology, the predicted antigout mechanism of WSP was validated in MSU-induced THP-1 macrophages. The levels of inflammatory cytokines and mRNA were measured by ELISA and qRT-PCR, respectively, and MAPK, NF-κB, and NLRP3 signaling-associated proteins were determined by western blot and immunofluorescence staining.

Results

48 bioactive ingredients and 165 common targets were found in WSP. The data showed that 5-Cis-Cyclopentadecen-1-One, 5-Cis-Cyclotetradecen-1-One, (-)-isoshyobunone, etc. were potential active ingredients. TNF signaling, HIF-1 signaling, and Jak-STAT signaling were predicted to be the potential pathways against gout. The molecule docking analysis found that most ingredients had a high affinity for p65, NLRP3, IL-1β, TNF-α, and p38. The data from in vitro experiment showed that WSP suppressed the production and gene expression of inflammatory cytokines. Furthermore, WSP could inhibit the activation of MAPK, NF-κB, and NLRP3 signaling pathways.

Conclusion

Our finding suggested that the antigout effect of WSP could be achieved by inhibiting MAPK, NF-κB, and NLRP3 signaling pathways. WSP might be a candidate drug for gouty treatment.

The Essential Oil of Artemisia argyi H.Lév. and Vaniot Attenuates NLRP3 Inflammasome Activation in THP-1 Cells

Artemisia argyi H. Lév. and Vaniot is a traditional medical herb that has been used for a long time in China and other Asian counties. Essential oil is the main active fraction of Artemisia argyi H. Lév. and Vaniot, and its anti-inflammatory potential has been observed in vitro and in vivo. Here, we found that the essential oil of Artemisia argyi H. Lév. and Vaniot (EOAA) inhibited monosodium urate (MSU)- and nigericin-induced NLRP3 inflammasome activation. EOAA suppressed caspase-1 and IL-1β processing and pyroptosis. NF-κB p65 phosphorylation and translocation were also inhibited. In addition, EOAA suppressed nigericin-induced NLRP3 inflammasome activation without blocking ASC oligomerization, suggesting that it may inhibit NLRP3 inflammasome activation by preventing caspase-1 processing. Our study thus indicates that EOAA inhibits NLRP3 inflammasome activation and has therapeutic potential against NLRP3-driven diseases.

Cichorium intybus L. Extract Suppresses Experimental Gout by Inhibiting the NF-κB and NLRP3 Signaling Pathways

BACKGROUND

The production and maturation of interleukin (IL)-1β, regulated by the NF-κB and NLRP3 signaling pathways, lie at the core of gout. This study aimed to evaluate the antigout effect of Cichorium intybus L. (also known as chicory) in vivo and in vitro.

METHODS

A gout animal model was established with monosodium urate (MSU) crystal injections. Rats were orally administered with chicory extract or colchicine. Levels of ankle edema, inflammatory activity, and IL-1β release were observed. Several essential targets of the NF-κB and NLRP3 signaling pathways were detected. Primary macrophages were isolated to verify the antigout mechanism of chicory extract as well as chicoric acid in vitro.

RESULTS

Improvements of swelling degree, inflammatory activity, and histopathological lesion in MSU-injected ankles were observed in the treatment with chicory extract. Further, the chicory extract significantly decreased IL-1β release by suppressing the NF-κB and NLRP3 signaling pathways in gout rats. Similar to the in vivo results, IL-1β release was also inhibited by chicory extract and chicoric acid, a specific effective compound in chicory, through the NF-κB and NLRP3 signaling pathways.

CONCLUSION

This study suggests that chicory extract and chicoric acid may be used as promising therapeutic agents against gout by inhibiting the NF-κB and NLRP3 signaling pathways.

The Ins and Outs of Chemokine-Mediated Immune Cell Trafficking in Skin Cancer

Recent studies of the patterns of chemokine-mediated immune cell recruitment into solid tumors have enhanced our understanding of the role played by various immune cell subsets both in amplifying and inhibiting tumor cell growth and spread. Here we discuss how the chemokine/chemokine receptor networks bring together immune cells within the microenvironment of skin tumors, particularly melanomas, including their effect on disease progression, prognosis and therapeutic options.

Inflammatory Potential of Four Different Phases of Calcium Pyrophosphate Relies on NF-κB Activation and MAPK Pathways

Background: Calcium pyrophosphate (CPP) microcrystal deposition is associated with wide clinical phenotypes, including acute and chronic arthritis, that are interleukin 1β (IL-1β)-driven. Two CPP microcrystals, namely monoclinic and triclinic CPP dihydrates (m- and t-CPPD), have been identified in human tissues in different proportions according to clinical features. m-CPP tetrahydrate beta (m-CPPTβ) and amorphous CPP (a-CPP) phases are considered as m- and t-CPPD crystal precursors in vitro.

Objectives: We aimed to decipher the inflammatory properties of the three crystalline phases and one amorphous CPP phase and the intracellular pathways involved.

Methods: The four synthesized CPP phases and monosodium urate crystals (MSU, as a control) were used in vitro to stimulate the human monocytic leukemia THP-1 cell line or bone marrow-derived macrophages (BMDM) isolated from WT or NLRP3 KO mice. The gene expression of pro- and anti-inflammatory cytokines was evaluated by quantitative PCR; IL-1β, IL-6 and IL-8 production by ELISA; and mitogen-activated protein kinase (MAPK) activation by immunoblot analysis. NF-κB activation was determined in THP-1 cells containing a reporter plasmid. In vivo, the inflammatory potential of CPP phases was assessed with the murine air pouch model via cell analysis and production of IL-1β and CXCL1 in the exudate. The role of NF-κB was determined by a pharmacological approach, both in vivo and in vitro.

Results:In vitro, IL-1β production induced by m- and t-CPPD and m-CPPTβ crystals was NLRP3 inflammasome dependent. m-CPPD crystals were the most inflammatory by inducing a faster and higher production and gene expression of IL-1β, IL-6, and IL-8 than t-CPPD, m-CPPTβ and MSU crystals. The a-CPP phase did not show an inflammatory property. Accordingly, m-CPPD crystals led to stronger activation of NF-κB, p38, extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) MAPKs. Inhibition of NF-κB completely abrogated IL-1β and IL-8 synthesis and secretion induced by all CPP crystals. Also, inhibition of JNK and ERK1/2 MAPKs decreased both IL-1β secretion and NF-κB activation induced by CPP crystals. In vivo, IL-1β and CXCL1 production and neutrophil infiltration induced by m-CPPD crystals were greatly decreased by NF-κB inhibitor treatment.

Conclusion: Our results suggest that the inflammatory potential of different CPP crystals relies on their ability to activate the MAPK-dependent NF-κB pathway. Studies are ongoing to investigate the underlying mechanisms.

Schistosoma mansoni SmKI-1 serine protease inhibitor binds to elastase and impairs neutrophil function and inflammation

Protease inhibitors have important function during homeostasis, inflammation and tissue injury. In this study, we described the role of Schistosoma mansoni SmKI-1 serine protease inhibitor in parasite development and as a molecule capable of regulating different models of inflammatory diseases. First, we determine that recombinant (r) SmKI-1 and its Kunitz domain but not the C-terminal region possess inhibitory activity against trypsin and neutrophil elastase (NE). To better understand the molecular basis of NE inhibition by SmKI-1, molecular docking studies were also conducted. Docking results suggest a complete blockage of NE active site by SmKI-1 Kunitz domain. Additionally, rSmKI-1 markedly inhibited the capacity of NE to kill schistosomes. In order to further investigate the role of SmKI-1 in the parasite, we designed specific siRNA to knockdown SmKI-1 in S. mansoni. SmKI-1 gene suppression in larval stage of S. mansoni robustly impact in parasite development in vitro and in vivo. To determine the ability of SmKI-1 to interfere with neutrophil migration and function, we tested SmKI-1 anti-inflammatory potential in different murine models of inflammatory diseases. Treatment with SmKI-1 rescued acetaminophen (APAP)-mediated liver damage, with a significant reduction in both neutrophil recruitment and elastase activity. In the model of gout arthritis, this protein reduced neutrophil accumulation, IL-1β secretion, hypernociception, and overall pathological score. Finally, we demonstrated the ability of SmKI-1 to inhibit early events that trigger neutrophil recruitment in pleural cavities of mice in response to carrageenan. In conclusion, SmKI-1 is a key protein in S. mansoni survival and it has the ability to inhibit neutrophil function as a promising therapeutic molecule against inflammatory diseases.

Schistosoma mansoni is one of the main agents of schistosomiasis, which is the most important human helminthic infection in terms of global morbidity and mortality. Although schistosomiasis represents a major public health problem in endemic countries, evidences show that S. mansoni downregulates inflammatory responses in many diseases. Fortunately, the control of inflammatory responses is extended to pathogen-derived antigens, leading us to study one S. mansoni Kunitz type protease inhibitor (SmKI-1), found in larval and adult phases of the parasite. We demonstrate that SmKI-1 inhibits trypsin and neutrophil elastase (NE). Additionally, live parasites that SmKI-1 gene has been suppressed using siRNA displayed an impaired schistosome development both in vitro and in vivo. Further, we demonstrate that SmKI-1 possesses an anti-inflammatory potential in three different murine models of inflammatory diseases: acetaminophen (APAP)-mediated liver damage, gout arthritis, and pleural inflammation in response to carrageenan. In these inflammatory disease models, we evaluated SmKI-1 effect on neutrophil and our results demonstrate this molecule is able to inhibit neutrophil migration and function, regulating inflammation. Thus, our data suggest that SmKI-1 is a promising therapeutic molecule against inflammatory diseases.

Effects of Mollugo pentaphylla extract on monosodium urate crystal-induced gouty arthritis in mice

Background

Gout is an inflammatory condition induced by the deposition of monosodium urate (MSU) crystals in joints and soft tissues, and it can lead to acute or chronic arthritis. MSU are pro-inflammatory stimuli that can initiate, amplify and sustain an intense inflammatory response. In this study, we evaluated the anti-inflammatory effect of an extract of Mollugo pentaphylla (MPE) on MSU-induced gouty arthritis in a mouse model.

Method

An MSU crystal suspension (4 mg/50 μL) was injected intradermally into the right paw. The mice were orally administered MPE (150 mg/kg or 300 mg/kg) or the positive control drug colchicine (1 mg/kg) 1 h before the MSU crystals were injected and then once daily for 3 days. The effects of MPE included inflammatory paw edema and pain upon weight-bearing activity, and we evaluated the inflammatory cytokine expression and paw tissue inflammation-related gene expression.

Results

MPE suppressed inflammatory paw edema and pain in the MSU-induced mice. MPE showed anti-inflammatory activity by inhibiting the production of TNF-α, interleukin (IL)-1β, NLRP3 inflammasome and NF-κB.

Conclusion

These results suggest that MPE has potent anti-inflammatory activities and may be useful as a therapeutic agent against gouty arthritis.

Berberine, an isoquinoline alkaloid suppresses TXNIP mediated NLRP3 inflammasome activation in MSU crystal stimulated RAW 264.7 macrophages through the upregulation of Nrf2 transcription factor and alleviates MSU crystal induced inflammation in rats

The current study was designed to investigate the therapeutic potential of berberine on monosodium urate (MSU) crystal stimulated RAW 264.7 macrophages and in MSU crystal induced rats. Our results indicate that berberine (25, 50 and 75μM) suppressed the levels of pro-inflammatory cytokines (interleukin-1beta (IL-1β) and tumor necrosis factor alpha (TNFα)) and intracellular reactive oxygen species in MSU crystal stimulated RAW 264.7 macrophages. The mRNA expression levels of IL-1β, caspase 1, nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3 (NLRP3), thioredoxin interacting protein (TXNIP) and kelch-like ECH-associated protein 1 (Keap1) were found downregulated with the upregulation of nuclear factor erythroid-2-related factor 2 (Nrf2) transcription factor and its associated anti-oxidant enzymes: Heme oxygenase I (HO-1), superoxide dismutase (SOD1), glutathione peroxidase (GPx), NADPH quinone oxidoreductase-1 (NQO1) and catalase (CAT) in MSU crystal stimulated RAW 264.7 macrophages upon berberine treatment. Subsequently, western blot analysis revealed that berberine decreased the protein expression of IL-1β and caspase 1 and increased Nrf2 expression in RAW 264.7 macrophages. Immunofluorescence analysis also explored increased expression of Nrf2 in MSU crystal stimulated RAW 264.7 macrophages by berberine treatment. In addition, the paw edema, pain score, pro-inflammatory cytokines (IL-1β and TNFα) and articular elastase activity were found significantly reduced in berberine (50mg/kgb·wt) administered MSU crystal-induced rats. Conclusively, our current findings suggest that berberine may represent as a potential candidate for the treatment of gouty arthritis by suppressing inflammatory mediators and activating Nrf2 anti-oxidant pathway.

Rebamipide Suppresses Monosodium Urate Crystal-Induced Interleukin-1β Production Through Regulation of Oxidative Stress and Caspase-1 in THP-1 Cells

This study investigated the effect of rebamipide on activation of the NLRP3 inflammasome and generation of reactive oxygen species (ROS) in monosodium urate (MSU) crystal-induced interleukin-1β (IL-1β) production. Human monocyte cell line THP-1 and human umbilical venous endothelial cells (HUVECs) were used to assess the inflammatory response to MSU crystals. NADP/NADPH activity assays were used as a marker of ROS generation. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were performed to evaluate levels of IL-1β, caspase-1, NLRP3, associated speck-like protein (ASC), nuclear factor-κB (NF-κB), p65, IκBα, intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1). Experimental pharmaceuticals included rebamipide, colchicine, dexamethasone, and ascorbic acid. In THP-1 cells, treatment with MSU crystals increased NADP/NADPH ratios and IL-1β expression, and both of these responses were potently inhibited by addition of rebamipide. Rebamipide also attenuated enhanced expression of caspase-1 gene by MSU crystals (p < 0.05). Western blotting demonstrated that MSU crystals stimulated caspase-1 but not NLRP3 and ASC activation. Similarly, MSU crystals activated the NF-κB pathway, which in turn was blocked by rebamipide. Stimulation of HUVECs with MSU crystals increased expression of VCAM-1 and ICAM-1, which were markedly inhibited by both rebamipide and dexamethasone. This study demonstrated that rebamipide inhibits IL-1β activation through suppression of ROS-mediated NF-κB signaling pathways and caspase-1 activation in MSU crystal-induced inflammation.

Zisheng Shenqi decoction ameliorates monosodium urate crystal-induced gouty arthritis in rats through anti-inflammatory and anti-oxidative effects

Based on traditional Chinese medicinal theories on gouty arthritis, Zisheng Shenqi decoction (ZSD), a novel Chinese medicinal formula, was developed due to its multiple functions, including reinforcing renal function, promoting blood circulation and relieving pain. In the present study, the effect of ZSD on monosodium urate (MSU) crystal-induced gouty arthritis in rats was investigated and the underlying mechanisms were examined. The data from these investigations showed that the injection of MSU crystals into the ankle joint cavity caused significant elevations in ankle swelling and inflammatory cell infiltration into the synovium, whereas these abnormal changes were markedly suppressed by oral administration of ZSD (40 mg/kg) for 7 days. Mechanically, ZSD treatment prevented MSU crystal-induced inflammatory responses, as evidenced by downregulation in the expression levels of NACHT domain, leucine-rich repeat and pyrin domain containing protein (NALP) 1 and NALP6 inflammasomes, decreased serum levels of tumor necrosis factor-α and interleukin-1β, and inhibited activation of nuclear factor-κB. In addition, ZSD administration markedly enhanced the anti-oxidant status in MSU crystal-induced rats by the increase in the activities of superoxide dismutase and glutathione peroxidase, and the levels of reduced glutathione. These results indicated that ZSD effectively prevented MSU crystal-induced gouty arthritis via modulating multiple anti-oxidative and anti-inflammatory pathways, suggesting a promising herbal formula for the prevention and treatment of gouty arthritis.

ALPK1 affects testosterone mediated regulation of proinflammatory cytokines production

Alpha-protein kinase 1, also known as alpha-kinase 1 (ALPK1), is associated with chronic kidney disease (CKD), myocardial infarction, gout and type 2 diabetes mellitus (DM). In addition to having an inductive effect on the proinflammatory cytokines in monocytic THP1 cells, ALPK1 is expressed abundantly in the mouse testes. Low testosterone levels are commonly associated with arthritis, CKD, type 2 DM, cardiovascular disease and inflammation. The testosterone's anti-inflammatory effect has been demonstrated to reduce proinflammatory cytokines and adhesion molecules. In this study, we found that ALPK1 transgenic mice showed lower levels of testosterone in both the testes and the serum. Decreasing endogenous ALPK1 enhanced testosterone levels and transcripts of testosterone-regulated genes (P450scc, 3beta-HSD, P450C17, 17beta-HSD, StAR, and INSL3) in TM3 Leydig cells. In contrast, increasing testosterone decreased ALPK1 in both TM3 and monocytic THP1 cells. This decrease was accompanied by a reduction of the proinflammatory cytokines. Increased ALPK1 levels attenuated the testosterone effects in THP1 cells. Finally, we also found that ALPK1 increased the release of TNF-alpha and TGF-beta1 in the human embryonic kidney 293 cells, while testosterone inhibited ALPK1 in the primary kidney cells. Taken together, this data suggests that the balance between ALPK1 and testosterone plays a critical role in the testosterone-mediated inhibition of proinflammatory cytokines.

Effect of uric-acid-lowering therapy on progression of chronic kidney disease: a meta-analysis

The efficacy and safety of uric-acid-lowering therapy (UALT) on slowing the progression of chronic kidney disease (CKD) accompanied by hyperuricemia were assessed. We searched Cochrane Library, PubMed, EMbase, CNKI, Wanfang and Vip databases up to November 15, 2012 for randomized controlled trials (RCTs) which compared the effect of UALT to control therapy in hyperuricemic patients secondary to CKD, and then performed quality evaluation and meta-analysis on the included studies. Seven RCTs involving 451 cases were included. UALT delayed the increase of serum creatinine (MD=-62.55 μmol/L, 95% CI: -98.10 to -26.99) and blood urea nitrogen (MD= -6.15 mmol/L, 95% CI: -8.17 to -4.13) as well as the decrease of glomerular filtration rate [MD=5.65 mL/(min·1.73 m2), 95% CI: 1.88 to 9.41], decreased systolic blood pressure (SBP) (MD= -6.08 mmHg, 95% CI: -11.67 to -0.49), and reduced the risk of the renal disease progression (RR=0.30, 95% CI: 0.19 to 0.46). However, there was no statistically significant difference in 24-h urinary protein quantity and diastolic blood pressure (P>0.05). We identified that UALT could delay the progression of CKD with secondary hyperuricemia. And this also indirectly proved that hyperuricemia was a risk factor for the CKD progression.

Immunopathological effects of malaria pigment or hemozoin and other crystals

Blood-stage malaria parasites produce insoluble hemozoin (Hz) crystals that are released in the blood circulation upon schizont rupture. In general, endogenous crystal formation or inhalation of crystalline materials is often associated with pathology. As the immune system responds differently to crystalline particles than to soluble molecules, in this review, the properties, immunological recognition, and pathogenic responses of Hz are discussed, and compared with two other major pathogenic crystals, monosodium urate (MSU) and asbestos. Because of the size and shape of MSU crystals and asbestos fibers, phagolysosomal formation is inefficient and often results in leakage of lysosomal content in the cell cytoplasm and/or in the extracellular environment with subsequent cell damage and cell death. Phagolysosomal formation after Hz ingestion is normal, but Hz remains stored inside these cells for months or even longer without any detectable degradation. Nonetheless, the different types of crystals are recognized by similar immune receptors, involving Toll-like receptors, the inflammasome, antibodies, and/or complement factors, and through similar signaling cascades, they activate both proinflammatory and anti-inflammatory immune responses that contribute to inflammation-associated pathology.

Impact of neutrophil-secreted myeloid related proteins 8 and 14 (MRP 8/14) on leishmaniasis progression

The myeloid-related proteins (MRPs) 8/14 are small proteins mainly produced by neutrophils, which have been reported to induce NO production in macrophages. On the other hand, Leishmania survives and multiplies within phagocytes by inactivating several of their microbicidal functions. Whereas MRPs are rapidly released during the innate immune response, their role in the regulation of Leishmaniasis is still unknown. In vitro experiments revealed that Leishmania infection alters MRP-induced signaling, leading to inhibition of macrophage functions (NO, TNF-α). In contrast, MRP-primed cells showed normal signaling activation and NO production in response to Leishmania infection. Using a murine air-pouch model, we observed that infection with L. major induced leukocyte recruitment and MRP secretion comparable to LPS-treated mice. Depletion of MRPs significantly reduced these inflammatory events and augmented both parasite load and footpad swelling during the first 8 weeks post-infection, as also observed in MRP KO mice. On the contrary, mouse treatment with recombinant MRPs (rMRPs) had the opposite effect. Collectively, our results suggest that rapid secretion of MRPs by neutrophils at the site of infection may protect uninfected macrophages and favor a more efficient innate inflammatory response against Leishmania infection. In summary, our study reveals the critical role played by MRPs in the regulation of Leishmania infection and how this pathogen can subvert its action.

Parasites of the Leishmania genus have developed multiple mechanisms to subvert the immune response. Among these mechanisms are the activation of host phosphatases and inactivation of cell signaling pathways, which in turn activate the immune response. On the other hand, it has been observed that the Myeloid Related Proteins (MRPs) 8 and 14 are potent activators of some components of the immune response. In this study, we evaluated the effect of MRPs 8 and 14 on the progression of cutaneous Leishmaniasis. To do so, we used immortalized macrophages and stimulated them with MRPs before or after infection with L. major. We observed that stimulating macrophages with MRPs prior to infection induced NO and TNF-α production, as well as phosphorylation of MAPKs and nuclear translocation of transcription factors NF-κB and AP-1. However, when MRP stimulation was performed after infection, these effects where subverted. Moreover, using a murine model of cutaneous infection, we observed that depletion of MRPs caused increased parasite burden and bigger lesions. On the contrary, injection of recombinant MRPs directly into the lesion, considerably reduced lesion size and parasite burden. Our study suggests that MRPs could have a potential therapeutic use in the control of Leishmania infection.

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.

Effects of Extracts from Paederia scandens (LOUR.) MERRILL (Rubiaceae) on MSU Crystal-Induced Rats Gouty Arthritis

The effects of extract of Paederia scandens (LOUR.) MERRILL (Rubiaceae) (EPS), a Chinese traditional herbal medicine, on inflammatory and immune responses and their mechanisms in MSU crystals-induced (GA) rats were studied. GA rats were established. Ankle joint volume of rats was measured by volume meter; the level of TNF-α and IL-1β was determined by radioimmunoassay. mRNA expressions of TNF-α and IL-1β in synovial tissue of GA rats were analyzed by RT-PCR, and the expression of NF-κB was detected by immunohistochemistry. The administration of EPS (2.25, 4.5 g/kg, ig 9 days) inhibited the inflammatory response in GA rats. The mRNA expressions of TNF-α and IL-1β were also significantly suppressed in synovial tissue. In addition, EPS (2.25, 4.5 g/kg, ig 9 days) inhibited the expression of TNF-α and IL-1β and the biological activity of NF-κB. These results suggested that EPS possesses antiinflammatory effects by modulating pro-inflammatory mediators' production in synovial tissue and inactivating NF-κB pathway transmembrane signal transduction which plays a crucial role in the pathogenesis of this disease.

Lymphocyte α-kinase is a gout-susceptible gene involved in monosodium urate monohydrate-induced inflammatory responses

The molecular functions and pathophysiologic role of the lymphocyte α-kinase gene (ALPK1) in gout are unknown. We aimed to examine ALPK1 expression in patients with gout and investigate its role in monosodium urate monohydrate (MSU)-induced inflammatory responses. Microarray data mining was performed with six datasets containing three clinical gout and three volunteer samples. Real-time quantitative polymerase chain reaction (qPCR) assay was used to profile ALPK1 mRNA expression in 62 independent samples. RNA interference for ALPK1 suppression in THP1 cells (human monocytic cell line) was used to scrutinize the functional role of ALPK1 in MSU-mediated inflammatory responses, and ALPK1 expression in MSU-treated THP1 cells was determined by qPCR and Western blot analysis. Cytokine mRNA expression in HEK293 cells after incubation with different concentrations of MSU crystals in the presence or absence of ALPK1 was also detected by qPCR, and ERK1/2, p38, and JNK expressions were investigated by Western blot analysis. ALPK1 mRNA was overexpressed in the clinical gout samples. MSU treatment promoted ALPK1 expression at the mRNA and protein levels. Furthermore, ALPK1 knockdown in THP1 cells resulted in a markedly decreased IL-1β, TNF-α, and IL-8 mRNA expression; plasmid ALPK1 transfection and MSU stimulation synergistically increased the mRNA expression of these cytokines in a concentration-dependent manner. The synergistic effect also led to ERK1/2 activation. ALPK1 is a gout-susceptible gene involved in MSU-induced inflammatory responses. It may contribute to the development of gout by enhancing the inflammatory responses via the mitogen-activated protein kinase pathway.

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.

Inhaled therapies for tuberculosis and the relevance of activation of lung macrophages by particulate drug-delivery systems

Pathogenic strains of Mycobacterium tuberculosis (Mtb) induce ‘alternative activation’ of lung macrophages that they colonize, in order to create conditions that promote the establishment and progression of infection. There is some evidence to indicate that such macrophages may be rescued from alternative activation by inhalable microparticles containing a variety of drugs. This review summarizes the experience of various groups of researchers, relating to observations of induction of a number of classical macrophage activation pathways. Restoration of a ‘respiratory burst’ and upregulation of reactive oxygen species and nitrogen intermediates through the phagocyte oxidase and nitric oxide synthetase enzyme systems; induction of proinflammatory macrophage cytokines; and finally induction of apoptosis rather than necrosis of the infected macrophage are discussed. It is suggested that there is scope to co-opt host responses in the management of tuberculosis, through the route of pulmonary drug delivery.

Octacalcium phosphate crystals induce inflammation in vivo through interleukin-1 but independent of the NLRP3 inflammasome in mice

OBJECTIVE

To determine the mechanisms involved in inflammatory responses to octacalcium phosphate (OCP) crystals in vivo.

METHODS

OCP crystal-induced inflammation was monitored using a peritoneal model of inflammation in mice with different deficiencies affecting interleukin-1 (IL-1) secretion (IL-1α(-/-) , IL-1β(-/-) , ASC(-/-) , and NLRP3(-/-) mice) or in mice pretreated with IL-1 inhibitors (anakinra [recombinant IL-1 receptor antagonist] and anti-IL-1β). The production of IL-1α, IL-1β, and myeloid-related protein 8 (MRP-8)-MRP-14 complex was determined by enzyme-linked immunosorbent assay. Peritoneal neutrophil recruitment and cell viability were determined by flow cytometry. Depletion of mast cells or resident macrophages was performed by pretreatment with compound 48/80 or clodronate liposomes, respectively.

RESULTS

OCP crystals induced peritoneal inflammation, as demonstrated by neutrophil recruitment and up-modulation of IL-1α, IL-1β, and MRP-8-MRP-14 complex, to levels comparable with those induced by monosodium urate monohydrate crystals. This OCP crystal-induced inflammation was both IL-1α- and IL-1β-dependent, as shown by the inhibitory effects of anakinra and anti-IL-1β antibody treatment. Accordingly, OCP crystal stimulation resulted in milder inflammation in IL-1α(-/-) and IL-1β(-/-) mice. Interestingly, ASC(-/-) and NLRP3(-/-) mice did not show any alteration in their inflammation status in response to OCP crystals. Depletion of the resident macrophage population resulted in a significant decrease in crystal-induced neutrophil infiltration and proinflammatory cytokine production in vivo, whereas mast cell depletion had no effect. Finally, OCP crystals induced apoptosis/necrosis of peritoneal cells in vivo.

CONCLUSION

These data indicate that macrophages, rather than mast cells, are important for initiating and driving OCP crystal-induced inflammation. Additionally, OCP crystals induce IL-1-dependent peritoneal inflammation without requiring the NLRP3 inflammasome.

Xanthine oxidoreductase promotes the inflammatory state of mononuclear phagocytes through effects on chemokine expression, peroxisome proliferator-activated receptor-{gamma} sumoylation, and HIF-1{alpha}

The protective effects of pharmacological inhibitors of xanthine oxidoreductase (XOR) have implicated XOR in many inflammatory diseases. Nonetheless, the role played by XOR during inflammation is poorly understood. We previously observed that inhibition of XOR within the inflammatory mononuclear phagocytes (MNP) prevented neutrophil recruitment during adoptive transfer demonstrating the role of XOR in MNP-mediated neutrophil recruitment. To further explore the role of XOR in the inflammatory state of MNP, we studied MNP isolated from inflammatory lungs combined with analyses of MNP cell lines. We demonstrated that XOR activity was increased in inflammatory MNP following insufflation of Th-1 cytokines in vivo and that activity was specifically increased by MNP differentiation. Inhibition of XOR reduced levels of CINC-1 secreted by MNP. Expression of peroxisome proliferator-activated receptor γ (PPARγ) in purified rat lung MNP and MNP cell lines reflected both the presence of PPARγ isoforms and PPARγ SUMOylation, and XOR inhibitors increased levels of SUMO-PPARγ in MNP cell lines. Both ectopic overexpression of XOR cDNA and uric acid supplementation reduced SUMO-PPARγ in MNP cells. Levels of the M2 markers CD36, CD206, and arginase-1 were modulated by uric acid and oxonic acid, whereas siRNA to SUMO-1 or PIAS-1 also reduced arginase-1 in RAW264.7 cells. We also observed that HIF-1α was increased by XOR inhibitors in inflammatory MNP and in MNP cell lines. These data demonstrate that XOR promotes the inflammatory state of MNP through effects on chemokine expression, PPARγ SUMOylation, and HIF-1α and suggest that strategies for inhibiting XOR may be valuable in modulating lung inflammatory disorders.

Monosodium urate crystals in inflammation and immunity

Uric acid crystals [monosodium urate (MSU)] have emerged as an important factor for both gouty arthritis and immune regulation. This simple crystalline structure appears to activate innate host defense mechanisms in multiple ways and triggers robust inflammation and immune activation. The recognition mechanisms of MSU following its phase change from soluble uric acid are diverse, involving both protein receptors and non-specific plasma membrane attachment. Upon contact with host cells, MSU induces a set of membrane events that trigger Syk and PI3K activation, phagocytosis, and cytokine production. Having entered the cell, MSU further triggers NALP3 inflammasome activation and induces the production of IL-1 beta, likely inducing a full spectrum of inflammation. This review describes the recognition mechanisms and activation pathways involved in MSU-mediated inflammation and adjuvanticity and hypothesizes that direct membrane binding by solid surfaces, such as MSU, may function as a generic mechanism in tissue responses to particulate and crystalline structures.

The sterile inflammatory response

The acute inflammatory response is a double-edged sword. On the one hand, it plays a key role in initial host defense, particularly against many infections. On the other hand, its aim is imprecise, and as a consequence, when it is drawn into battle, it can cause collateral damage in tissues. In situations where the inciting stimulus is sterile, the cost-benefit ratio may be high; because of this, sterile inflammation underlies the pathogenesis of a number of diseases. Although there have been major advances in our understanding of how microbes trigger inflammation, much less has been learned about this process in sterile situations. This review focuses on a subset of the many sterile stimuli that can induce inflammation-specifically dead cells and a variety of irritant particles, including crystals, minerals, and protein aggregates. Although this subset of stimuli is structurally very diverse and might appear to be unrelated, there is accumulating evidence that the innate immune system may recognize them in similar ways and stimulate the sterile inflammatory response via common pathways. Here we review established and emerging data about these responses.

The role of protein tyrosine phosphatases in the regulation of allergic asthma: implication of TC-PTP and PTP-1B in the modulation of disease development

Protein tyrosine phosphorylation is an important early event in the signal transduction of numerous cell receptors involved in the immune response. The implication of protein tyrosine kinases in allergic asthma is well recognized, but the role of protein tyrosine phosphatases (PTPs) remains poorly understood. However, we recently reported that global inhibition of PTPs during either the allergen-sensitization phase or the allergen-challenge phase reduced the development of asthma and that this correlated with an increased T helper 1 (Th1) response in both lung and spleen tissues. Therefore, in this study we investigated individual roles of PTPs involved in regulating the immune response. We observed that genetic deficiency for PTP-1B resulted in increased recruitment of lung inflammatory cells, while protein tyrosine phosphatase-phosphatase and tensin homologue deleted (PTP-PEST)-deficient mice exhibited a phenotype similar to that of wild-type mice. Importantly, we found that a heterozygous mutation of T cell PTP (TC-PTP) dramatically abrogates immunoglobulin E production and reduces the recruitment of inflammatory cells to the lung, conferring an important role for TC-PTP in the development of allergic asthma. As opposed to other studies on Src homology phosphatase-1 (SHP-1) deficiency, specific acute SHP-1 inhibition during allergen challenge did not affect disease outcome. Collectively, our results underscore the importance of PTPs in the development of allergic asthma.

Innate inflammation and resolution in acute gout

Acute gout is an inflammatory arthritis that is controlled by the innate arm of the immune response. Although the causative feature of gout has long been recognized, it is surprising that the cellular activities that underpin the initiation and resolution of acute gout remain poorly described. This review article summarizes what are currently thought to be the key cellular mechanisms at play during an inflammatory episode of acute gout. The emerging role of mononuclear phagocytes is highlighted as having a central role in both the initiation and resolution of acute gout, and the interplay between monocytes and other elements of the innate immune response, including neutrophils, and complement protein activation are discussed.

Propofol suppresses tumor necrosis factor-alpha biosynthesis in lipopolysaccharide-stimulated macrophages possibly through downregulation of nuclear factor-kappa B-mediated toll-like receptor 4 gene expression

Lipopolysaccharide (LPS), a gram-negative bacterial outer membrane component, can activate macrophages via a toll-like receptor 4-dependent pathway. Our previous study has shown that propofol, an intravenous anesthetic reagent, has anti-inflammatory effects. This study was further aimed to evaluate the roles of toll-like receptor 4 in propofol-caused suppression of tumor necrosis factor-alpha (TNF-alpha) biosynthesis in LPS-stimulated macrophages and its possible molecular mechanisms. Exposure of macrophages to propofol and LPS did not affect cell viability. Meanwhile, the LPS-caused augmentations in the productions of TNF-alpha protein and mRNA were significantly decreased following incubation with a therapeutic concentration of propofol (50 microM). Analysis of toll-like receptor 4 small interference (si)RNA revealed that this membrane receptor might participate in the propofol-caused suppression of TNF-alpha biosynthesis. Treatment of macrophages with LPS-induced toll-like receptor 4 protein and mRNA productions. Propofol at a clinically relevant concentration could inhibit such induction. In parallel, the LPS-induced translocation and transactivation of transcription factor nuclear factor-kappa B (NFkappaB) were significantly alleviated following propofol incubation. There are several NFkappaB DNA-binding motifs found in the promoter region of toll-like receptor 4. Therefore, this study shows that propofol at a therapeutic concentration can downregulate TNF-alpha biosynthesis possibly via inhibition of NFkappaB-mediated toll-like receptor 4 gene expression.

Transcriptional regulation of monocyte chemotactic protein-1 release by endothelin-1 in human airway smooth muscle cells involves NF-kappaB and AP-1

BACKGROUND AND PURPOSE

Endothelin-1 (ET-1) is implicated in airway inflammation in asthma, but the mechanisms of its effects are poorly understood. We studied the effect of ET-1 on expression of the chemokine, monocyte chemotactic protein-1 (MCP-1), in primary cultures of human airway smooth muscle cells.

EXPERIMENTAL APPROACH

MCP-1 release was measured by elisa. Pharmacological antagonists/inhibitors, reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting were used to study ET receptors and kinase cascades. Transcriptional regulation was studied by real-time RT-PCR, transient transfection studies and chromatin immunoprecipitation assay. Major findings were confirmed in cells from three donors and mechanistic studies in cells from one donor.

KEY RESULTS

ET-1 increased MCP-1 release through an ET(A) and ET(B) receptor-dependent mechanism. ET-1 increased MCP-1 mRNA levels but not mRNA stability suggesting it was acting transcriptionally. ET-1 increased the activity of an MCP-1 promoter-reporter construct. Serial deletions of the MCP-1 promoter mapped ET-1 effects to a region between -213 and -128 base pairs upstream of the translation start codon, containing consensus sequences for activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB). ET-1 promoted binding of AP-1 c-Jun subunit and NF-kappaB p65 subunit to the MCP-1 promoter. Blocking the inhibitor of kappaB kinase-2 with 2-[(aminocarbonyl)amino]-5-[4-fluorophenyl]-3-thiophenecarboxamide (TPCA-1) decreased ET-1-stimulated MCP-1 production. p38 and p44/p42 mitogen-activated protein kinases were involved in upstream signalling.

CONCLUSIONS AND IMPLICATIONS

ET-1 regulated MCP-1 transcriptionally, via NF-kappaB and AP-1. The upstream signalling involved ET(A), ET(B) receptors, p38 and p44/p42 mitogen-activated protein kinases. These may be targets for novel asthma therapies.

Resident macrophages initiating and driving inflammation in a monosodium urate monohydrate crystal-induced murine peritoneal model of acute gout

OBJECTIVE

To determine whether infiltrating monocytes, neutrophils, or resident macrophages contribute to the early inflammatory response to monosodium urate monohydrate (MSU) crystals in vivo.

METHODS

MSU crystal-induced inflammation was monitored using a peritoneal model of acute gout. The production of proinflammatory cytokines (interleukin-1beta [IL-1beta], tumor necrosis factor alpha [TNFalpha], IL-6) by resident macrophages, infiltrating monocytes, and neutrophils during the onset of gout was determined by flow cytometry. Infiltrating and resident peritoneal cells were cultured with MSU crystals ex vivo, and proinflammatory cytokine production was determined by multiplex cytokine array. Activated macrophages on the visceral epithelial lining of the peritoneum were identified by immunofluorescence histochemistry. The inflammatory immune response to MSU crystals was then compared with the inflammatory response in mice depleted of resident macrophages by pretreatment with clodronate liposomes.

RESULTS

The production of cytokines in vivo preceded the influx of Gr-1(intermediate)7/4+ monocytes. Monocytes and neutrophils recruited during the inflammatory phase of the response to MSU crystals failed to produce proinflammatory cytokines either in vivo, or ex vivo following restimulation with MSU crystals. Stimulation of the naive peritoneal resident cell population with MSU crystals ex vivo resulted in positive staining of resident macrophages for the proinflammatory cytokines IL-1beta, TNFalpha, and IL-6. Depletion of the resident macrophage population resulted in a significant decrease in both MSU crystal-induced neutrophil infiltration and proinflammatory cytokine production in vivo despite the presence of infiltrating monocytes.

CONCLUSION

These data indicate that resident macrophages, rather than infiltrating monocytes or neutrophils, are important for initiating and driving the early proinflammatory phase of acute gout.

Crystals of monosodium urate monohydrate enhance lipopolysaccharide-induced release of interleukin 1 beta by mononuclear cells through a caspase 1-mediated process

OBJECTIVE

Recent studies suggest that crystals of monosodium urate (MSU), deposited in joints of patients with acute gouty arthritis, activate the NACHT domain, leucine-rich repeat and pyrin domain-containing protein (NALP)3 inflammasome. In the present study we have investigated whether production of proinflammatory cytokines by crystals was exacerbated during costimulation with Toll-like receptor (TLR) ligands.

METHODS

Mononuclear cells of 22 healthy donors were stimulated by various concentrations of MSU crystals in the absence or presence of lipopolysaccharide (LPS), Pam3Cys and flagellin. Production of tumour necrosis factor alpha (TNFalpha), interleukin (IL)1 beta and IL6, as well as the intracellular concentrations of proIL1 beta were measured by ELISA. mRNA transcripts of TNFalpha and IL1 beta were assessed by real-time PCR. Stimulation experiments were also performed with peripheral blood mononuclear cells (PBMCs) of one patient carrying a NALP3 mutation.

RESULTS

MSU induced a moderate release of IL1 beta and IL6, but not of TNFalpha. Urate crystals amplified IL1 beta production stimulated by the TLR4 ligand LPS, while no synergy was apparent for IL6 production. In addition, no synergy between urate crystals and Pam3Cys (TLR2 ligand) or flagellin (TLR5 ligand) was apparent. The synergy between urate crystals and LPS was directed at the level of the NALP3 inflammasome, as it was present only when active IL1 beta was measured, but not at the level of IL1 mRNA or proIL1 beta. The synergy between LPS and MSU crystals ceased to exist in the presence of a caspase 1 inhibitor.

CONCLUSIONS

MSU crystals act in synergy with LPS for the induction of enhanced release of IL1 beta. Increased cleavage of proIL1 beta by urate-activated caspase 1 is proposed as the underlying mechanism.

Targeting NF-kappaB: a promising molecular therapy in inflammatory arthritis

The nuclear factor-kappa B family of transcription factors is intimately involved in the regulation of the inflammatory responses that play a fundamental role in the damage of articular tissues. Thus, many studies have examined the important contributions of components of the NF-kappaB signaling pathways to the pathogenesis of various rheumatic diseases and their pharmacologic modulation. Currently available therapeutic agents including nonsteroidal anti-inflammatory drugs, corticosteroids, nutraceuticals, and disease-modifying antirheumatic drugs, as well as novel specific small-molecule inhibitors have been employed. In addition, promising nucleic acid-based strategies have shown encouraging results. However, further research will be needed before NF-kappaB-aimed strategies become an effective therapy for inflammatory arthritis.

RETRACTED: Effects of ethanol on monosodium urate crystal-induced inflammation

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief. Image duplication has been observed within Figure 3. The corresponding author has been asked to provide an acceptable explanation for this duplication but has not been able to do so, neither have the original source files been supplied.

Anti-tumor necrosis factor-alpha antibody treatment reduces serum CXCL16 levels in patients with rheumatoid arthritis

The aim of this study was to analyze the change of serum chemokins levels of CXCL16, CX3CL1/Fractalkine, and CXCL10/interferon-gamma inducible protein-10 (IP-10) with rheumatoid arthritis (RA), by infliximab treatment. The effects of infliximab treatment were studied in 23 patients with RA, over a period of 30 weeks. The serum levels of CXCL16, Fractalkine, and IP-10, were measured at the baseline, just before initial treatment, and at 14 and 30 weeks after the initial treatment, with infliximab by ELISA. The higher levels of serum CXCL16 in the RA patients before treatment with infliximab significantly decreased at 14 and 30 weeks after the initial treatment with infliximab, but the serum Fractalkine and IP-10 levels did not decrease significantly. Infliximab treatment significantly lowered the serum levels of CXCL16 in patients with RA. CXCL16 is one of the crucial chemokines regulated by infliximab treatment.

Induction of triggering receptor expressed on myeloid cells 1 in murine resident peritoneal macrophages by monosodium urate monohydrate crystals

OBJECTIVE

Triggering receptor expressed on myeloid cells 1 (TREM-1) is a cell surface molecule that was recently identified on monocytes and neutrophils. TREM-1 has been implicated in the early inflammatory responses induced by microbes, but its pathophysiologic role in nonmicrobial inflammation remains unknown. In the present study, we investigated the role of TREM-1 in acute inflammation induced by monosodium urate monohydrate (MSU) crystals. Induction of TREM-1 expression by MSU crystal-stimulated murine resident peritoneal macrophages and infiltrating leukocytes in a murine air-pouch model of crystal-induced acute inflammation was determined. The biologic role of TREM-1 in crystal-induced cytokine production by resident peritoneal macrophages was also investigated.

METHODS

TREM-1 expression by resident peritoneal macrophages and infiltrating leukocytes in a murine air-pouch model was determined by quantitative real-time polymerase chain reaction, Western blot analysis, and flow cytometry. Cytokine production by resident peritoneal macrophages after incubation with MSU crystals in the presence or absence of an anti-TREM-1 agonist antibody was determined by enzyme-linked immunosorbent assay.

RESULTS

TREM-1 expression by resident peritoneal macrophages was significantly induced after stimulation with the crystals. Maximum expression of TREM-1 transcripts and protein occurred at 1 and 4 hours after exposure to the crystals, respectively. Costimulation of resident peritoneal macrophages with MSU crystals and an anti-TREM-1 agonist antibody synergistically increased the production of both interleukin-1beta and monocyte chemotactic protein 1 compared with stimulation with the crystals alone. MSU crystals also induced TREM-1 expression in infiltrating leukocytes in a murine air-pouch model of crystal-induced acute inflammation.

CONCLUSION

These findings suggest that rapid induction of TREM-1 expression on resident peritoneal macrophages and neutrophils by MSU crystals may contribute to the development of acute gout through enhancement of inflammatory responses.

Innate immunity conferred by Toll-like receptors 2 and 4 and myeloid differentiation factor 88 expression is pivotal to monosodium urate monohydrate crystal-induced inflammation

OBJECTIVE

In gout, incompletely defined molecular factors alter recognition of dormant articular and bursal monosodium urate monohydrate (MSU) crystal deposits, thereby inducing self-limiting bouts of characteristically severe neutrophilic inflammation. To define primary determinants of cellular recognition, uptake, and inflammatory responses to MSU crystals, we conducted a study to test the role of Toll-like receptor 2 (TLR-2), TLR-4, and the cytosolic TLR adapter protein myeloid differentiation factor 88 (MyD88), which are centrally involved in innate immune recognition of microbial pathogens.

METHODS

We isolated bone marrow-derived macrophages (BMDMs) in TLR-2-/-, TLR-4-/-, MyD88-/-, and congenic wild-type mice, and assessed phagocytosis and cytokine expression in response to endotoxin-free MSU crystals under serum-free conditions. MSU crystals also were injected into mouse synovium-like subcutaneous air pouches.

RESULTS

TLR-2-/-, TLR-4-/-, and MyD88-/- BMDMs demonstrated impaired uptake of MSU crystals in vitro. MSU crystal-induced production of interleukin-1beta (IL-1beta), tumor necrosis factor alpha, keratinocyte-derived cytokine/growth-related oncogene alpha, and transforming growth factor beta1 also were significantly suppressed in TLR-2-/- and TLR-4-/- BMDMs and were blunted in MyD88-/- BMDMs in vitro. Neutrophil influx and local induction of IL-1beta in subcutaneous air pouches were suppressed 6 hours after injection of MSU crystals in TLR-2-/- and TLR-4-/- mice and were attenuated in MyD88-/- mice.

CONCLUSION

The murine host requires TLR-2, TLR-4, and MyD88 for macrophage activation and development of full-blown neutrophilic, air pouch inflammation in response to MSU crystals. Our findings implicate innate immune cellular recognition of naked MSU crystals by specific TLRs as a major factor in determining the inflammatory potential of MSU crystal deposits and the course of gouty arthritis.