IL-1β Production In Mice Research Articles

Barrier-protective properties of pterostilbene against LPS-induced sepsis

Background: Sepsis is a major clinical problem and the leading cause of death in patients in intensive care units worldwide. Objective: The present study aimed to explore whether pterostilbene (PTS) could protect mice against experimental endotoxemia. Methodology: Forty-eight mice were randomly divided into 4 groups and challenged with LPS. Mouse mortality was observed twice daily for 7 days and survival rates were reported. Mice were randomly treated with pterostilbene or vehicle intraperitoneally (i.p.). One hour later, the animals were exposed to LPS (20 mg/kg). Cytokine responses were then assessed in serum isolated from blood collected after LPS administration to the mice. Results: The results showed that pterostilbene significantly reduced mouse body weight loss and attenuated inflammatory responses by inhibiting TNF-α, IL-6 and IL-1β production in mice exposed to LPS. Conclusion: This study highlights the role of pterostilbene in the pathogenesis of LPS-induced sepsis and its potential in the treatment of patients with sepsis.

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 IL1β production in mice, and gouty patients demonstrate a robust positive correlation between TLR4 mRNA level and serum IL1β. 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.

The Specific NLRP3 Antagonist IFM-514 Decreases Fibrosis and Inflammation in Experimental Murine Non-Alcoholic Steatohepatitis.

Background and Aims: Activation of the inflammasome NLRP3 (NOD-, LRR- and pyrin domain containing 3) contributes to the development of non-alcoholic fatty liver disease (NAFLD) and progression to non-alcoholic steatohepatitis (NASH). Therefore, this study explored the therapeutic effects of a novel and selective NLRP3 antagonist in a murine dietary model of NASH.Methods: Groups of 12-week-old ApoE -/- mice were fed ad lib for 7 weeks with a methionine/choline deficient (MCD) and western diet (WD). After 3 weeks of diet-induced injury, mice were injected i. p. with the NLRP3 antagonist IFM-514 (100 mg/kg body weight) or vehicle (0.5% carmellose) every day, 5 days/week for a further 4 weeks. Several markers of inflammation, fibrosis and steatosis were evaluated. Whole transcriptome sequencing and panel RNA expression analysis (NanoString) were performed.Results: IFM-514 inhibited IL-1β production in mice challenged with 20 mg/kg lipopolysaccharide, and in mouse and human inflammatory cells in vitro. IFM-514 inhibited hepatic inflammation in the in vivo non-alcoholic steatohepatitis model assessed by H&E staining and in the hepatic gene expression of inflammasome-related proinflammatory cytokines. This effect was associated with significant reduction in caspase-1 activation. Similarly, IFM-514 was efficacious in vivo in MDC-fed ApoE -/- mice, markedly reducing portal pressure, Sirius red staining and 4-hydroxyproline content compared to vehicle-treated mice. Moreover, IFM-514 significantly reduced hepatic steatosis in MCD-fed ApoE -/- mice, as evidenced by NAFLD scores, oil red O staining, hepatic triglycerides and gene expression. In WD treated animals, similar trends in inflammation and fibrosis were observed, although not sufficient IFM-514 levels were reached.Conclusion: Overall, IFM-514 reduced liver inflammation and fibrosis, with mild effects on liver steatosis in experimental murine NASH. Blocking of NLRP3 may be an attractive therapeutic approach for NASH patients.

Koumine Suppresses IL-1β Secretion and Attenuates Inflammation Associated With Blocking ROS/NF-κB/NLRP3 Axis in Macrophages

Koumine (KM), one of the primary constituents of Gelsemium elegans, has been used for the treatment of inflammatory diseases such as rheumatoid arthritis, but whether KM impacts the activation of the NOD-like receptor protein 3 (NLRP3) inflammasome remains unknown. This study aimed to explore the inhibitory effect of KM on NLRP3 inflammasome activation and the underlying mechanisms both in vitro using macrophages stimulated with LPS plus ATP, nigericin or monosodium urate (MSU) crystals and in vivo using an MSU-induced peritonitis model. We found that KM dose-dependently inhibited IL-1β secretion in macrophages after NLRP3 inflammasome activators stimulation. Furthermore, KM treatment efficiently attenuated the infiltration of neutrophils and suppressed IL-1β production in mice with MSU-induced peritonitis. These results indicated that KM inhibited NLRP3 inflammasome activation, and consistent with this finding, KM effectively inhibited caspase-1 activation, mature IL-1β secretion, NLRP3 formation and pro-IL-1β expression in LPS-primed macrophages treated with ATP, nigericin or MSU. The mechanistic study showed that, KM exerted a potent inhibitory effect on the NLRP3 priming step, which decreased the phosphorylation of IκBα and p65, the nuclear localization of p65, and the secretion of TNF-α and IL-6. Moreover, the assembly of NLRP3 was also interrupted by KM. KM blocked apoptosis-associated speck-like protein containing a CARD (ASC) speck formation and its oligomerization and hampered the NLRP3-ASC interaction. This suppression was attributed to the ability of KM to inhibit the production of reactive oxygen species (ROS). In support of this finding, the inhibitory effect of KM on ROS production was completely counteracted by H2O2, an ROS promoter. Our results provide the first indication that KM exerts an inhibitory effect on NLRP3 inflammasome activation associated with blocking the ROS/NF-κB/NLRP3 signal axis. KM might have potential clinical application in the treatment of NLRP3 inflammasome-related diseases.

IRF-7 Mediates Type I IFN Responses in Endotoxin-Challenged Mice.

IRF-7 mediates robust production of type I IFN via MyD88 of the TLR9 pathway in plasmacytoid dendritic cells (pDCs). Previous in vitro studies using bone marrow-derived dendritic cells lacking either Irf7 or Irf3 have demonstrated that only IRF-3 is required for IFN-β production in the TLR4 pathway. Here, we show that IRF-7 is essential for both type I IFN induction and IL-1β responses via TLR4 in mice. Mice lacking Irf7 were defective in production of both IFN-β and IL-1β, an IFN-β-induced pro-inflammatory cytokine, after LPS challenge. IFN-β production in response to LPS was impaired in IRF-7-deficient macrophages, but not dendritic cells. Unlike pDCs, IRF-7 is activated by the TRIF-, but not MyD88-, dependent pathway via TBK-1 in macrophages after LPS stimulation. Like pDCs, resting macrophages constitutively expressed IRF-7 protein. This basal IRF-7 protein was completely abolished in either Ifnar1−/− or Stat1−/− macrophages, which corresponded with the loss of LPS-stimulated IFN-β induction in these macrophages. These findings demonstrate that macrophage IRF-7 is critical for LPS-induced type I IFN responses, which in turn facilitate IL-1β production in mice.

Novel Pycard gene polymorphism impairs Nlpr3 inflammasome-induced IL-1β production in mice selected for low inflammatory response.

Abstract A SNP based linkage study in mouse lines phenotypically selected for maximal (AIRmax) or minimal (AIRmin) acute inflammatory response (AIR), mapped a major locus, Inflammatory response modulator 1 (Irm1) at 128Mb (3.5Mb interval) in chr 7 controlling AIR, measured by leukocyte and IL-6 levels in exudates and IL-1β production by circulating leukocytes after Nlpr3 inflammasome activation. Sequencing of this region in mice with extreme high or low IL-1β levels revealed 14 SNPs between the two groups, narrowing the locus interval to 420Kb. Candidate genes at Irm1 include Pycard with an undescribed exon 3 (C/T) mutation leading to E19K substitution at the pyrin domain, and Itgam, Rgs10 and BC017158 with intronic SNPs. In Pycard, the C allele was fixed in high responder AIRmax mice whereas the C and T alleles frequencies were 39% and 61%, respectively in AIRmin. We then investigated the effect of this novel Pycard SNP in inflammation phenotypes. Methods AIRmin mice bearing the 3 genotypes at Pycard: CC, CT, TT were produced by genotype-assisted mating. Inflammatory response was measured in AIRmax and in the 3 AIRmin sublines by the number of infiltrating cells and IL-6 concentration in the 24h exudate induced by sc Biogel P-100 bead injection and ex vivo IL-1β production by circulating leukocytes after E coli LPS (1 ug) and ATP (5mM) activation. Results IL-1β levels were similar in AIRmaxCC (4.5-±0.4 ng/ml) and AIRminCC (3.4±2.4 ng/ml) whereas AIRminCT produced 0.3±0.5 and AIRminTT <0.05 ng/ml IL-1β. Leukocyte influx and IL-6 levels in inflammatory exudates were not affected. Conclusion The E19K substitution in Pycard causes a negative effect in inflammasome activation for IL-1β production, without interfering in other inflammation phenotypes.

Roflupram, a Phosphodiesterase 4 Inhibitior, Suppresses Inflammasome Activation through Autophagy in Microglial Cells.

Inhibition of phosphodiesterase 4 (PDE4) suppressed the inflammatory responses in the brain. However, the underlying mechanisms are poorly understood. Roflupram (ROF) is a novel PDE4 inhibitor. In the present study, we found that ROF enhanced the level of microtubule-associated protein 1 light chain 3 II (LC3-II) and decreased p62 in microglial BV-2 cells. Enhanced fluorescent signals were observed in BV-2 cells treated with ROF by Lysotracker red and acridine orange staining. In addition, immunofluorescence indicated a significant increase in punctate LC3. Moreover, β amyloid 25-35 (Aβ25-35) or lipopolysaccharide (LPS) with ATP was used to activate inflammasome. We found that both LPS plus ATP and Aβ25-35 enhanced the conversion of pro-caspase-1 to cleaved-caspase-1 and increased the production of mature IL-1β in BV-2 cells. Interestingly, these effects were blocked by the treatment of ROF. Consistently, knocking down the expression of PDE4B in primary microglial cells led to enhanced level of LC-3 II and decreased activation of inflammasome. What's more, Hoechst staining showed that ROF decreased the apoptosis of neuronal N2a cells in conditioned media from microglia. Our data also showed that ROF dose-dependently enhanced autophagy, reduced the activation of inflammasome and suppressed the production of IL-1β in mice injected with LPS. These effects were reversed by inhibition of microglial autophagy. These results put together demonstrate that ROF inhibits inflammasome activities and reduces the release of IL-1β by inducing autophagy. Therefore, ROF could be used as a potential therapeutic compound for the intervention of inflammation-associated diseases in the brain.

The murine neutrophil NLRP3 inflammasome is activated by soluble but not particulate or crystalline agonists.

Neutrophils express pattern recognition receptors (PRRs) and regulate immune responses via PRR-dependent cytokine production. An emerging theme is that neutrophil PRRs often exhibit cell type-specific adaptations in their signalling pathways. This prompted us to examine inflammasome signalling by the PRR NLRP3 in murine neutrophils, in comparison to well-established NLRP3 signalling pathways in macrophages. Here, we demonstrate that while murine neutrophils can indeed signal via the NLRP3 inflammasome, neutrophil NLRP3 selectively responds to soluble agonists but not to the particulate/crystalline agonists that trigger NLRP3 activation in macrophages via phagolysosomal rupture. In keeping with this, alum did not trigger IL-1βproduction from human PMN, and the lysosomotropicpeptide Leu-Leu-OMe stimulated only weak NLRP3-dependent IL-1βproduction from murine neutrophils, suggesting that lysosomal rupture is not a strong stimulus for NLRP3 activation in neutrophils. We validated our in vitro findings for poor neutrophil NLRP3 responses to particles in vivo, where we demonstrated that neutrophils do not significantly contribute to alum-induced IL-1β production in mice. In all, our studies highlight that myeloid cell identity and the nature of the danger signal can strongly influence signalling by a single PRR, thus shaping the nature of the resultant immune response.

<i>Sphaeranthus indicus</i>: Traditional Wisdom to Modern Medicine—An Orally Active, Potent Cytokine Inhibitor for the Management of Inflammatory Disorders

Tumor necrosis factor (TNF-α) is a key regulator of the inflammatory and tissue destruc-tive pathways in rheumatoid arthritis (RA). The clinical success of anti-TNF-α and an-ti-IL-17 biologics has validated the concept that cytokine blockade is beneficial in RA. However, as these drugs are parenterally administered, our efforts are directed at identifying a novel orally active TNF-α inhibitor with a therapeutic profile similar to that of biologics. Since plants are natural immunomodulators, we explored the immunomodulatory potential of Sphaeranthus indicus extract. In our studies, the extract dose-dependently inhibited the release of cytokines in stimulated human peripheral blood mononuclear cells (hPBMCs), and their spontaneous release in synovial cells derived from patients suffering from RA. TNF-α and IFN-γ induced release of p40 subunit of IL-12/ IL-23, and p19 subunit of IL-23 in differentiated THP-1 cells is potently blocked. The expression of endothelial cell adhesion molecules in TNF-α-stimulated HUVECs was also potently inhibited. The oral treatment significantly and dose-dependently reduced LPS-induced TNF-α and IL-1β production in mice. Disease regression was seen in collagen-induced arthritis in DBA/1J mice, which was validated along with radiological and histopathological evaluation. Therefore, the extract of Sphaeranthus indicus could be used in the management of inflammatory conditions.

Biotin Status Affects Nickel Allergy via Regulation of Interleukin-1β Production in Mice

Biotin, a water-soluble B complex vitamin, is possibly involved in chronic inflammatory diseases, although the detailed mechanisms are unclear. In this study, we investigated the effects of biotin status on nickel (Ni) allergy in mice. Mice were fed a basal or biotin-deficient (BD) diet for 8 wk and sensitized with an intraperitoneal injection of NiCl2 and lipopolysaccharide. Ten days after sensitization, NiCl2 was intradermally injected into pinnas and ear swelling was measured. For in vitro analysis, we cultured a murine macrophage cell line, J774.1, under a biotin-sufficient (C, meaning control) or BD condition for 4 wk and analyzed interleukin (IL)-1 production. Significantly higher ear swelling was induced in BD mice than C mice. Adaptive transfer of splenocytes from both C and BD mice induced Ni allergy in unsensitized mice. Regardless of donor mice, ear swelling was significantly higher in BD recipient mice than C recipient mice. Ni allergy was not induced in either C or BD IL-1−/− mice. Splenocytes from BD mice produced a significantly higher amount of IL-1β than those from C mice. Production and mRNA expression of IL-1β were significantly higher in BD J774.1 cells than in C cells. Biotin supplementation inhibited the augmentation of IL-1β production in vitro. In vivo supplementation of biotin in drinking water dose-dependently decreased ear swelling in C and BD mice. These results indicate that biotin status affects Ni allergy in the elicitation phase via the upregulation of IL-1β production in mice, suggesting that biotin supplementation may have therapeutic effects on human metal allergy.