DUSP1 Mitigates MSU-Induced Immune Response in Gouty Arthritis Reinforcing Autophagy.

BACKGROUND: Persistent hyperuricemia can lead to the generation and deposition of monosodium urate (MSU) crystals. This can trigger gouty arthritis (GA), which in turn induces inflammation. Activation of the Nod-like receptor pyrin domain containing 3 (NLRP3) inflammasome plays a critical role in the onset and progression of GA. Autophagy may have a dual effect on GA with regard to the NLRP3 inflammasome. Therefore, the present study aimed to gain a deeper comprehension of the interaction between autophagy and NLRP3 inflammasome activation is imperative for developing more efficacious treatments for GA. METHODS: Peripheral blood monocytes (PBMCs) were first isolated from GA patients and healthy controls and underwent bulk RNA sequencing analysis. Overexpression and knockdown of dual specificity phosphatase 1 (DUSP1) was performed in THP-1 monocytes to investigate its role in the immune response and mitochondrial damage. The luciferase assay and Western blot analysis were used to study the interaction between autophagy and NLRP3 inflammasome activation. RESULTS: Bulk RNA sequencing analysis showed significant upregulation of DUSP1 expression in PBMCs from GA patients compared to healthy controls. This result was subsequently verified by reverse transcription quantitative polymerase chain reaction (RT-qPCR). DUSP1 expression in human THP-1 monocytes was also shown to increase after MSU treatment. Downregulation of DUSP1 expression increased the secretion of inflammatory cytokines after MSU treatment, whereas the overexpression of DUSP1 decreased the secretion levels. Lipopolysaccharides (LPS) combined with adenosine-triphosphate (ATP) led to mitochondrial damage, which was rescued by overexpressing DUSP1. DUSP1 overexpression further increased the level of autophagy following MSU treatment, whereas downregulation of DUSP1 decreased autophagy. Treatment with the autophagy inhibitor 3-Methyladenine (3-MA) restored inflammatory cytokine secretion levels in the DUSP1 overexpression group. MSU caused pronounced pathological ankle swelling in vivo. However, DUSP1 overexpression significantly mitigated this phenotype, accompanied by significant downregulation of inflammatory cytokine secretion levels in the joint tissues. CONCLUSIONS: This study revealed a novel function and mechanism for DUSP1 in promoting autophagy to mitigate the MSU-induced immune response in GA. This finding suggests potential diagnostic biomarkers and anti-inflammatory targets for more effective GA therapy.

BRD4 promotes gouty arthritis through MDM2-mediated PPARγ degradation and pyroptosis.

BACKGROUND: Gouty arthritis (GA) is characterized by monosodium urate (MSU) crystal accumulation that instigates NLRP3-mediated pyroptosis; however, the underlying regulatory mechanisms have yet to be fully elucidated. The present research endeavors to elucidate the regulatory mechanisms underpinning this MSU-induced pyroptotic cascade in GA. METHODS: J774 cells were exposed to lipopolysaccharide and MSU crystals to establish in vitro GA models, whereas C57BL/6 J male mice received MSU crystal injections to mimic in vivo GA conditions. Gene and protein expression levels were evaluated using real-time quantitative PCR, Western blotting, and immunohistochemical assays. Inflammatory markers were quantified via enzyme-linked immunosorbent assays. Pyroptosis was evaluated using immunofluorescence staining for caspase-1 and flow cytometry with caspase-1/propidium iodide staining. The interaction between MDM2 and PPARγ was analyzed through co-immunoprecipitation assays, whereas the interaction between BRD4 and the MDM2 promoter was examined using chromatin immunoprecipitation and dual-luciferase reporter assays. Mouse joint tissues were histopathologically evaluated using hematoxylin and eosin staining. RESULTS: In GA, PPARγ was downregulated, whereas its overexpression mitigated NLRP3 inflammasome activation and pyroptosis. MDM2, which was upregulated in GA, destabilized PPARγ through the ubiquitin-proteasome degradation pathway, whereas its silencing attenuated NLRP3 activation by elevating PPARγ levels. Concurrently, BRD4 was elevated in GA and exacerbated NLRP3 activation and pyroptosis by transcriptionally upregulating MDM2, thereby promoting PPARγ degradation. In vivo experiments showed that BRD4 silencing ameliorated GA through this MDM2-PPARγ-pyroptosis axis. CONCLUSION: BRD4 promotes inflammation and pyroptosis in GA through MDM2-mediated PPARγ degradation, underscoring the therapeutic potential of targeting this pathway in GA management.

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

Background: Although hyperuricemia is not always associated with acute gouty arthritis, uric acid is a significant risk factor for gout. Therefore, we investigated the specific mechanism of uric acid activity. Methods: Using the gout-associated transcriptome dataset GSE160170, we conducted differential expression analysis to identify differentially expressed genes (DEGs). Moreover, we discovered highly linked gene modules using weighted gene coexpression network analysis (WGCNA) and evaluated their intersection. Subsequently, we screened for relevant biomarkers using the cytoHubba and Mcode algorithms in the STRING database, investigated their connection to immune cells and constructed a competitive endogenous RNA (ceRNA) network to identify upstream miRNAs and lncRNAs. We also collected PBMCs from acute gouty arthritis patients and healthy individuals and constructed a THP-1 cell gout inflammatory model, RT-qPCR and western blotting (WB) were used to detect the expression of C-X-C motif ligand 8 (CXCL8), C-X-C motif ligand 2 (CXCL2), and C-X-C motif ligand 1 (CXCL1). Finally, we predicted relevant drug targets through hub genes, hoping to find better treatments. Results: According to differential expression analysis, there were 76 upregulated and 28 downregulated mRNAs in GSE160170. Additionally, WGCNA showed that the turquoise module was most strongly correlated with primary gout; 86 hub genes were eventually obtained upon intersection. IL1ß, IL6, CXCL8, CXCL1, and CXCL2 are the principal hub genes of the protein-protein interaction (PPI) network. Using RT-qPCR and WB, we found that there were significant differences in the expression levels of CXCL8, CXCL1, and CXCL2 between the gouty group and the healthy group, and we also predicted 10 chemicals related to these proteins. Conclusion: In this study, we screened and validated essential genes using a variety of bioinformatics tools to generate novel ideas for the diagnosis and treatment of gout.

Correlation analysis of serum TLR4 protein levels and TLR4 gene polymorphisms in gouty arthritis patients.

OBJECTIVE: The Toll-like receptor (TLR) 4-mediated nuclear factor kappa B (NF-κB) signaling pathway regulates the production of inflammatory factors and plays a key role in the pathogenesis of gouty arthritis. The aim of the present study was to investigate the link among TLR4 gene polymorphisms at various loci, protein expression, and gouty arthritis susceptibility. METHODS: Between 2016 and 2021, a case-control study was used to collect a total of 1207 study subjects, including 317 male patients with gouty arthritis (gout group) and 890 healthy males (control group). The association between gout susceptibility and different genetic models was analyzed by typing three loci of the TLR4 gene (rs2149356, rs2737191, and rs10759932) using a multiplex point mutation rapid assay, and the association between protein expression and gout was confirmed by measuring TLR4 protein concentrations using enzyme-linked immunosorbent assays (ELISAs). RESULTS: In a codominant models AA and AG, the rs2737191 polymorphism in the gout group increased the risk of gout compared to the AA genotype (OR = 2.249, 95%CI 1.010~5.008), and the risk of gout was higher for those carrying the G allele compared to the A allele (OR = 2.227, 95%CI 1.006~4.932). TLR4 protein expression was different between the two groups with different locus genotypes. The differences in TLR4 protein expression between the gout group and control group were statistically significant between the following genotypes: the GG and GT genotypes of the rs2149356 polymorphism; the AA and AG genotypes of the rs2737191 polymorphism; and the TT and TC genotypes of the rs10759932 polymorphism(P<0.05). The TLR4 protein level in the gout group (19.19±3.09 ng/ml) was significantly higher than that in the control group (15.85±4.75 ng/ml). CONCLUSION: The AG genotype of the TLR4 gene rs2737191 polymorphism may be correlated with the development of gouty arthritis. The level of TLR4 protein expression is significantly higher in patients with gouty arthritis than in controls, and there is a correlation between high TLR4 protein expression and the development of gouty arthritis.

The NADase CD38 is a central regulator in gouty inflammation and a novel druggable therapeutic target.

OBJECTIVES: Cellular NAD+ declines in inflammatory states associated with increased activity of the leukocyte-expressed NADase CD38. In this study, we tested the potential role of therapeutically targeting CD38 and NAD+ in gout. METHODS: We studied cultured mouse wild type and CD38 knockout (KO) murine bone marrow derived macrophages (BMDMs) stimulated by monosodium urate (MSU) crystals and used the air pouch gouty inflammation model. RESULTS: MSU crystals induced CD38 in BMDMs in vitro, associated with NAD+ depletion, and IL-1ß and CXCL1 release, effects reversed by pharmacologic CD38 inhibitors (apigenin, 78c). Mouse air pouch inflammatory responses to MSU crystals were blunted by CD38 KO and apigenin. Pharmacologic CD38 inhibition suppressed MSU crystal-induced NLRP3 inflammasome activation and increased anti-inflammatory SIRT3-SOD2 activity in macrophages. BMDM RNA-seq analysis of differentially expressed genes (DEGs) revealed CD38 to control multiple MSU crystal-modulated inflammation pathways. Top DEGs included the circadian rhythm modulator GRP176, and the metalloreductase STEAP4 that mediates iron homeostasis, and promotes oxidative stress and NF-κB activation when it is overexpressed. CONCLUSIONS: CD38 and NAD+ depletion are druggable targets controlling the MSU crystal- induced inflammation program. Targeting CD38 and NAD+ are potentially novel selective molecular approaches to limit gouty arthritis.

[miR-185-5p alleviates the inflammatory response of acute gouty arthritis by inhibiting of IL-1ß].

Objective To investigate the relationship between interleukin-1ß (IL-1ß) and miR-185-5p in the process of joint injury in acute gouty arthritis (AGA). Methods The serum miR-185-5p levels of 89 AGA patients and 91 healthy volunteers were detected by real-time quantitative PCR. The correlation between miR-185-5p expression level and VAS score or IL-1ß expression level was evaluated by Pearson correlation coefficient method. Receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of miR-185-5p in AGA. THP-1 cells were induced by sodium urate (MSU) to construct an in vitro acute gouty inflammatory cell model. After the expression level of miR-185-5p in THP-1 cells was upregulated or downregulated by transfection of miR-185-5p mimics or inhibitors in vitro, inflammatory cytokines of THP-1 cells, such as IL-1ß, IL-8 and tumor necrosis factor α (TNF-α), were detected by ELISA. The luciferase reporter gene assay was used to determine the interaction between miR-185-5p and the 3'-UTR of IL-1ß. Results Compared with the healthy control group, the expression level of serum miR-185-5p in AGA patients was significantly reduced. The level of serum miR-185-5p was negatively correlated with VAS score and IL-1ß expression level. The area under the curve (AUC) was 0.905, the sensitivity was 80.17% and the specificity was 83.52%. Down-regulation of miR-185-5p significantly promoted the expression of IL-1ß, IL-8 and tumor necrosis factor (TNF-α), while overexpression of miR-185-5p showed the opposite results. Luciferase reporter gene assay showed that IL-1ß was the target gene of miR-185-5p, and miR-185-5p negatively regulated the expression of IL-1ß. Conclusion miR-185-5p alleviates the inflammatory response in AGA by inhibiting IL-1ß.

Highly expressed long non-coding RNA SNHG14 activated MSU-induced inflammatory response in acute gout arthritis through targeting miR-223-3p.

AIM: According to reports, long non-coding RNAs (lncRNAs) are involved in the regulation of many inflammatory diseases. Here, our main purpose was to ascertain the expression data of lncRNA SNHG14 in acute gouty arthritis (AGA) and to explore its possible mechanism in the regulation of AGA. METHOD: Reverse transcription quantitative polymerase chain reaction technology was supplied to detect the lncRNA SNHG14 expression. A receiver operating characteristics curve was drawn to estimate the accuracy of lncRNA SNHG14 in AGA diagnosis. An in vitro AGA cell model was constructed by inducing THP-1 cells with monosodium urate (MSU). The concentrations of inflammatory factors such as interleukin-1ß, interleukin-6, and tumor necrosis factor-α were measured by enzyme-linked immunosorbent assay. The luciferase reporter gene was used to verify the relationship between lncRNA SNHG14 and miR-223-3p. RESULTS: In clinical analysis, the levels of serum lncRNA SNHG14 in AGA patients were significantly higher than those in the control group. Abnormally elevated lncRNA SNHG14 has high sensitivity and specificity for AGA diagnosis. In in vitro cell experiments, silencing lncRNA SNHG14 inhibited the inflammatory response of THP-1 cells stimulated by MSU, and the luciferase reporter gene proved that lncRNA SNHG14 could bind to miR-223-3p. In addition, the level of miR-223-3p declined in AGA patients and the AGA cell model. Overexpression of miR-223-3p is helpful to alleviate an MSU-induced inflammatory response. CONCLUSION: In the AGA cell model, lncRNA SNHG14, as an miR-223-3p sponge, induces a cellular inflammatory response by controlling the level of miR-223-3p, so aggravating the disease progress of AGA.

Role of NLRP3 in the pathogenesis and treatment of gout arthritis.

Gout arthritis (GA) is a common and curable type of inflammatory arthritis that has been attributed to a combination of genetic, environmental and metabolic factors. Chronic deposition of monosodium urate (MSU) crystals in articular and periarticular spaces as well as subsequent activation of innate immune system in the condition of persistent hyperuricemia are the core mechanisms of GA. As is well known, drugs for GA therapy primarily consists of rapidly acting anti-inflammatory agents and life-long uric acid lowering agents, and their therapeutic outcomes are far from satisfactory. Although MSU crystals in articular cartilage detected by arthrosonography or in synovial fluid found by polarization microscopy are conclusive proofs for GA, the exact molecular mechanism of NLRP3 inflammasome activation in the course of GA still remains mysterious, severely restricting the early diagnosis and therapy of GA. On the one hand, the activation of Nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome requires nuclear factor kappa B (NF-κB)-dependent transcriptional enhancement of NLRP3, precursor (pro)-caspase-1 and pro-IL-1ß, as well as the assembly of NLRP3 inflammasome complex and sustained release of inflammatory mediators and cytokines such as IL-1ß, IL-18 and caspase-1. On the other hand, NLRP3 inflammasome activated by MSU crystals is particularly relevant to the initiation and progression of GA, and thus may represent a prospective diagnostic biomarker and therapeutic target. As a result, pharmacological inhibition of the assembly and activation of NLRP3 inflammasome may also be a promising avenue for GA therapy. Herein, we first introduced the functional role of NLRP3 inflammasome activation and relevant biological mechanisms in GA based on currently available evidence. Then, we systematically reviewed therapeutic strategies for targeting NLRP3 by potentially effective agents such as natural products, novel compounds and noncoding RNAs (ncRNAs) in the treatment of MSU-induced GA mouse models. In conclusion, our present review may have significant implications for the pathogenesis, diagnosis and therapy of GA.

What do we know about Toll-Like Receptors Involvement in Gout Arthritis?

Toll-like receptors (TLRs) are a well-characterized family of cell-bound pattern recognition receptors able to identify and respond to conserved structures of external microorganisms or Pathogen Molecular-Associated Pattern (PAMPs). They can also interact with Damage-Associated Molecular Patterns (DAMPs) involved with any infectious and sterile cell stress of tissue injury. Accumulated knowledge about TLRs has revealed that these receptors and intracellular signaling pathways triggered through TLR activation contribute to the physiopathology of different inflammatory diseases, including arthritic conditions. Mostly, the literature focuses on exploring TLRs in rheumatoid and osteoarthritis. However, TLRs also seem to be an essential mediator for monosodium urate (MSU) crystals-induced gouty arthritis, both in animal models and humans. Accordingly, naked MSU crystals have a highly negatively charged surface recognized by TLRs; intracellular adapter protein MyD88 are significant mediators of MSU crystals-induced IL1ß production in mice, and gouty patients demonstrate a robust positive correlation between TLR4 mRNA level and serum IL1ß. Here, we revised the literature evidence regarding the involvement of TLRs in gout arthritis pathogenesis, with particular reference to TLR2 and TLR4, by analyzing the actual literature data.

LncRNA HOTTIP promotes inflammatory response in acute gouty arthritis via miR-101-3p/BRD4 axis.

INTRODUCTION: Acute gouty arthritis (AGA) is characterized by the accumulation of pro-inflammatory factors. This research aimed to examine the regulation of long non-coding RNA HOXA distal transcript antisense RNA (HOTTIP) in AGA on inflammation and its potential mechanisms. METHODS: Serum levels of HOTTIP in AGA patients were examined by reverse-transcription quantitative polymerase chain reaction. The receiver operating characteristic curve was performed in the diagnosis of AGA patients. Monosodium urate (MSU) stimulation of THP-1-derived macrophages was used to establish an in vitro AGA model. Enzyme-linked immunosorbent assay was carried out to assess the levels of pro-inflammatory cytokines. Pearson correlation was applied to examine the correlation. RNA immunoprecipitation assay and dual-luciferase reporter assay were employed to identify the targeting relationship between miR-101-3p and HOTTIP or bromodomain-containing 4 (BRD4). RESULTS: HOTTIP and BRD4 were statistically overexpressed in AGA patients compared with controls, while miR-101-3p was reduced (P < 0.05). Serum HOTTIP can significantly distinguish AGA patients from healthy controls. HOTTIP bound with miR-101-3p then augmented BRD4 via a competing endogenous RNA mechanism. Additionally, HOTTIP levels were elevated in a dose-dependent manner by MSU (P < 0.05). Weakened HOTTIP significantly inhibited MSU-induced release of pro-inflammatory factors interleukin (IL)-1ß, IL-8, and transforming growth factor-α in macrophages (P < 0.05), but this inhibition was reversed by silencing miR-101-3p (P < 0.05). CONCLUSION: In short, HOTTIP contributes to inflammation via miR-101-3p/BRD4 axis, and serves as a new diagnostic biomarker. This study offers a renewed perspective on the diagnosis and treatment of AGA.

MicroRNA-486-5p suppresses inflammatory response by targeting FOXO1 in MSU-treated macrophages.

Gouty arthritis (GA) is mainly caused by the precipitation of monosodium urate (MSU) crystals in the joint. Recently, different regulatory roles of microRNAs (miRNAs) in arthritis have been widely verified. Nevertheless, the specific function of microRNA-486-5p (miR-486-5p) in GA is still unclear. GA cell models in vitro were established by the treatment of 250 µg/mL MSU crystals into THP-1 cells or J774A.1 cells. Then, the accumulation of tumor necrosis factor (TNF)-α, interleukin (IL)-8, and IL-ß was estimated by ELISA. The mRNA levels of TNF-α, IL-8, and IL-ß were measured through RT-qPCR. The protein level of forkhead box protein O1 (FOXO1) was tested via western blot. Furthermore, the interplay of miR-486-5p and FOXO1 was evaluated via the luciferase reporter assay. In this study, MSU treatment successfully stimulated the inflammatory response in macrophage cells. MiR-486-5p downregulation was observed in THP-1 and J774A.1 cells treated with MSU, and its upregulation markedly decreased the concentration and mRNA levels of TNF-α, IL-8, and IL-ß. Furthermore, FOXO1 was demonstrated to be negatively modulated by miR-486-5p. The rescue assay indicated that overexpressing FOXO1 reversed the effects of overexpressing miR-486-5p on inflammatory cytokines. Overall, this study proves that miR-486-5p inhibits GA inflammatory response via modulating FOXO1.

NLRP3 Susceptible Gene Polymorphisms in Patients with Primary Gouty Arthritis and Hyperuricemia.

Polymorphisms have been identified to predispose to primary gouty arthritis (GA) and hyperuricemia (HUA). Here, we accessed the five polymorphisms of rs10754558, rs35829419, rs3738448, rs3806268, and rs7525979 in NLRP3 on GA and HUA susceptibility. We collected 1198 samples (314 GA, 377 HUA, and 507 controls) for this case-control study. Our data detected that the rs3806268 (GA vs. AA: OR = 0.65, p = 0.012) was significantly associated with the susceptibility to GA. The rs3738448 (TT vs. GG: OR = 2.05, p = 0.024) and rs7525979 (TT vs. CC: OR = 1.96, p = 0.037) were significantly associated with the susceptibility to HUA. The rs3806268 AG genotype presented decreased risk of GA among the hypertension (OR = 0.54, p = 0.0093), smoking (OR = 0.59, p = 0.018), and no obesity (OR = 0.60, p = 0.0097) subjects compared to the GG genotype group. The rs3738448 TT genotype demonstrated increased risk of HUA among the hypertension (OR = 4.10, p = 0.0056) and no drinking population (OR = 3.56, p = 0.016) compared to the GG genotype group. The rs7525979 TT genotype demonstrated increased risk of HUA among the hypertension (OR = 4.01, p = 0.0064) and no drinking population (OR = 3.24, p = 0.034) compared to the CC genotype group. Furthermore, a significant haplotype effect of rs10754558/C-rs35829419/C-rs3738448/G-rs3806268/A-rs7525979/C was found (OR = 1.60, p = 0.0046) compared with GCGAC haplotype. Bioinformatics analyses indicated that rs3738448, rs3806268, and rs7525979 might influence the gene regulation, while the T-allele of rs3738448 increased the stability of NLRP3-mRNA. Collectively, our case-control study confirms NLRP3 polymorphisms might participate in regulating immune and inflammation responses in GA and HUA.

MicroRNA-142-3p facilitates inflammatory response by targeting ZEB2 and activating NF-κB signaling in gouty arthritis.

Gouty arthritis (GA) is caused by monosodium urate (MSU) crystal accumulation in the joints. MSU-mediated inflammation is an important inducing factor in gouty arthritis (GA). Recent studies have demonstrated that microRNAs can influence GA progression. Herein, the role and mechanism of miRNA-142-3p in GA were explored. To establish the in vitro and in vivo GA models, MSU was used to induce inflammatory response in human monocyte cell line THP-1 and male C57BL/6 mice. Protein levels, gene expression and proinflammatory cytokine secretion were respectively tested by Western blotting, RT-qPCR, and enzyme-linked immunosorbent assay (ELISA). Pathological changes in sagittal sections of ankle tissues were exhibited by hematoxylin-eosin (HE) staining. Binding relationship between miRNA-142-3p and zinc finger E-box binding homeobox 2 (ZEB2) was predicted and confirmed by bioinformatics analysis and luciferase reporter assay. In this study, MSU induced inflammatory response and upregulated miRNA-142-3p in THP-1 cells. Functionally, miRNA-142-3p knockdown inhibited inflammatory response in MSU-stimulated THP-1 cells and alleviated pathological symptoms of GA mice. Mechanically, miRNA-142-3p targeted ZEB2 in THP-1 cells. ZEB2 expression was elevated in MSU-administrated THP-1 cells and GA mice. ZEB2 downregulation reserved the inhibitory effect of miRNA-142-3p deficiency on inflammatory response in MSU-treated THP-1 cells. In addition, miRNA-142-3p activated NF-κB signaling by binding with ZEB2 in THP-1 cells upon MSU stimulation. Overall, miRNA-142-3p facilitates inflammatory response by targeting ZEB2 and activating NF-κB signaling in GA.

H19 is involved in the regulation of inflammatory responses in acute gouty arthritis by targeting miR-2-3p.

A great number of studies have confirmed that long noncoding RNA (lncRNA) are involved in the regulation of inflammatory response in acute gouty arthritis (AGA). This paper aimed to survey the regulatory mechanism of H19 on AGA. The expression of serum H19 in all subjects was examined by qRT-PCR. The ROC curve was used to estimate the diagnostic value of H19 for AGA. THP-1 cells were induced by MSU to establish in vitro AGA cell model. The concentrations of cytokines such as IL-1ß, IL-8, and TNF-α were tested by ELISA. Luciferase reporter gene analysis was used to verify the interaction between H19 and the 3'-UTR of miR-22-3p. Expressions of serum H19 in AGA patients were significantly higher than that in controls. The ROC curve indicated the potential of H19 as a diagnostic marker for AGA. Cell experiments revealed that the downregulation of H19 significantly inhibited the expressions of IL-1ß, IL-8, and TNF-α. The luciferase reporter gene assay manifested that miR-22-3p is the target gene of H19. And knockdown of miR-22-3p overturned the downregulation of inflammatory factors caused by H19 inhibition. H19 aggravated MSU-induced THP-1 inflammation by negatively targeting miR-22-3p, suggesting a new regulatory mechanism and potential therapeutic target for AGA.

Long noncoding RNA SNHG8 accelerates acute gouty arthritis development by upregulating AP3D1 in mice.

Gout can affect the quality of life of patients due to monosodium urate monohydrate (MSU) crystals. Numerous studies have proposed that long noncoding RNAs (lncRNAs) regulate gout. We aimed to reveal the function of lncRNA small nucleolar RNA host gene 8 (SNHG8) in acute gouty arthritis (GA). A GA mouse model was established by injection of MSU into footpads. The levels of SNHG8, miR-542-3p and adaptor-related protein complex 3 subunit delta 1 (AP3D1) in footpads were detected via polymerase chain reaction analysis. Hematoxylin-eosin staining revealed the paw swelling in mice. Enzyme-linked immunosorbent assay and western blot analysis were applied to determine the concentrations of proinflammatory cytokines. SNHG8 expression was identified to be upregulated after MSU treatment. Ablation of SNHG8 decreased the MSU-induced enhancement of paw swelling and foot thickness. In addition, SNHG8 depletion decreased the protein levels of proinflammatory factors in GA mice. Mechanically, SNHG8 was verified to be a sponge of miR-542-3p, and miR-542-3p targeted AP3D1 3' untranslated region. SNHG8 competitively bound with miR-542-3p to upregulate AP3D1 expression. Finally, results of rescue assays illustrated that AP3D1 upregulation offset the SNHG8-mediated inhibition on paw swelling and protein levels of proinflammatory factors in GA mice. In conclusion, SNHG8 accelerates acute GA development by upregulating AP3D1 in an miR-542-3p-dependent way in mice, providing an effective therapeutic approach to treat acute GA.

Erianin: A Direct NLRP3 Inhibitor With Remarkable Anti-Inflammatory Activity.

Erianin (Eri) is the extract of Dendrobium chrysotoxum Lindl. The NLRP3 inflammasome is a multiprotein complex that plays key roles in a wide variety of chronic inflammation-driven human diseases. Nevertheless, little is known about the protection of Eri against NLRP3 inflammasome-related diseases. In this study, we demonstrated that Eri inhibited NLRP3 inflammasome activation in vitro and in vivo. Mechanistically, Eri directly interacted with NLRP3, leading to inhibition of NLRP3 inflammasome assembly. Eri associated with the Walker A motif in the NACHT domain and suppressed NLRP3 ATPase activity. In mouse models, Eri had therapeutic effects on peritonitis, gouty arthritis and type 2 diabetes, via NLRP3. More importantly, Eri was active ex vivo for synovial fluid cells and monocytes from patients with IAV infection and gout. Eri may serve as a potential novel therapeutic compound against NLRP3-driven diseases.

MiR-192-5p suppresses M1 macrophage polarization via epiregulin (EREG) downregulation in gouty arthritis.

Gouty arthritis (GA) is a chronic inflammatory disease characterized by the deposition of monosodium urate (MSU) crystals within joints. MiR-192-5p is shown to be low-expressed in GA patients. However, the potential mechanism involving miR-192-5p in GA remains unclear. In the current study, a significant reduction in miR-192-5p and an increase in epiregulin (EREG) were observed in serum of GA patients, suggesting that miR-192-5p and EREG were involved in the pathogenic process of GA. A mouse GA model was established via 0.5 mg/20 µL MSU crystal administration. To investigate the effect of miR-192-5p on GA, mice were injected with miR-192-5p agomir or NC agomir before modeling. We found that miR-192-5p overexpression induced by miR-192-5p agomir reduced EREG expression, attenuated ankle joint swelling and synovial inflammatory cell infiltration and improved bone erosion in MSU-induced GA mice. MiR-192-5p decreased CD16/32+ (M1 marker) macrophages, but increased CD206 (M2 marker) expression in synovium of GA models. In vitro, RAW264.7 macrophages were stimulated with miR-192-5p mimic or NC mimic under IFNγ plus LPS-stimulated M1 polarization condition. MiR-192-5p reduced the release of inflammatory cytokines TNF-α and IL-1ß, decreased iNOS expression, and inhibited CD16/32 expression, indicating the blockade of M1 macrophage activation. Luciferase reporter system revealed the target interaction between miR-192-5p and EREG. Further rescue experiments demonstrated that EREG overexpression partly reversed the inhibitory role of miR-192-5p on M1 macrophage polarization manifested by elevated iNOS and CD16/32 levels. Collectively, miR-192-5p ameliorates inflammatory response in GA by inhibiting M1 macrophage activation via inhibiting EREG protein.

Efficacy of fire needle on acute gouty arthritis induced by monosodium urate in rat.

OBJECTIVE: To explore the therapeutic effect and inflammatory mechanism of fire needles on gouty arthritis. METHODS: Sixty male Sprague-Dawley rats were divided into four groups, that is, control group, the model group, the colchicine group, and the fire needle treatment group. Acute gouty arthritis was prepared by injection of monosodium urate in the ankle joint. The inflammation-related protein [toll-like receptor 4 (TLR4), pyrin domain-containing protein 3 (NLRP3), interleukin (IL)-1ß, myeloid differentiation factor 88 (MyD88), nuclear factorkappa B (NF-κB), phosphorylated NF-κB (p-NF-κB), caspase-1, and p-caspase-1] in swollen tissues, the inflammation-related mRNAs indicators (TLR4, NLRP3, NF-κB, and caspase-1) and the inflammatory factors [IL-1ß, IL-6, IL-8, tumor necrosis factor-α (TNF-α), and C-reactive protein (CRP)] in the serum were detected by Western blot, real-time quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay, respectively. RESULTS: The fire needle treatment could reduce joint swelling, increase mechanical pain threshold and decrease the inflammation index score in the fire needle treatment group. It could also significantly decreased the protein expression of IL-1ß, TLR4, MyD88, p-NF-κB and NLRP3 in joint tissue, markedly downregulated the mRNA levels of TLR4 and NLRP3 in joint tissue, and significantly reduce serum levels of IL-1ß, IL-6, IL-8, TNF-α, and CRP. CONCLUSION: The fire needle treatment had positive effect of treating gouty arthritis, and its under- lying mechanism might be associated with NF-κB activation and related inflammatory response.

No Association of MicroRNA-146a rs2910164 Polymorphism and Risk of Primary Gout Development in Chinese Han Populations: A Case-control Study.

BACKGROUND: Previous studies demonstrated that MicroRNA-146a (miR-146a) plays an important role in the regulation of autoinflammatory diseases including primary gout. The G/C polymorphism (rs2910164) in the precursor sequence of miR-146a caused its stem region to change from G: U to C: U,which can contribute to the susceptibility of human diseases. However, no genetic relevance studies of miR-146a gene polymorphisms to gout have been reported by now. OBJECTIVE: The purpose of this study was to analyze the association between the miR-146a rs2910164 genetic polymorphism and the susceptibility of the Chinese Han population to primary gout. METHODS: 1130 Chinese Han participants (including 606 primary gout patients and 524 gender and age-matched healthy control subjects) were recruited and the 5'exonuclease TaqMan® technology was used to perform miR-146a rs2910164 genotyping. RESULTS: After statistical analysis, no significant differences were observed between gout patients and healthy controls in genotype and allele frequency. CONCLUSION: Our results indicate that there is no evidence for the involvement of the miR-146a rs2910164 polymorphisms in susceptibility to primary gout in the Chinese Han population.

Melatonin Alleviates Acute Gouty Inflammation In Vivo and In Vitro.

The aim of this study was to identify the effects of melatonin on acute gouty inflammation and to investigate the underlying mechanisms. We found significantly lower serum melatonin levels in gout patients in the acute phase than in those in the remission phase or in normal individuals. The mRNA expression of melatonin receptor 2 (MT2) was also lower in gout patients than in normal individuals. To verify the in-vivo role of melatonin, a gouty arthritis model was established by intraarticular injection of monosodium urate (MSU, 1 mg) crystals into the paws of C57BL/6 mice. Joint inflammation in the mouse model was evaluated by measuring the thickness of the right paw/left paw, and the inflammation index was determined by examining infiltrating neutrophils with haematoxylin and eosin (H&E) staining. Melatonin was found to reduce both paw thickness and the inflammation index in the mouse model, and melatonin also reduced the mRNA levels of interleukin-1 beta (IL-1ß), IL-6 and NLR family pyrin domain containing 3 (NLRP3) inflammasome. To mimic gouty inflammation in vitro, mouse peritoneal macrophages were stimulated with lipopolysaccharides (LPS) plus MSU. Melatonin was revealed to reduce IL-1ß secretion by stimulated macrophages. The mRNA expression levels of IL-1ß and IL-6 were also inhibited by melatonin. Western blot analysis showed that the expression of NLRP3, caspase-1 and pro-IL-1ß was also inhibited by melatonin. In conclusion, our study demonstrated that melatonin alleviated gouty inflammation in vivo and in vitro, and the underlying mechanism may involve inhibiting the assembly of the NLRP3 inflammasome.