CD1d1 intrinsic signaling in macrophages controls NLRP3 inflammasome expression during inflammation.
ABSTRACT: Dysregulation of immune responses in the gut often associates with inflammatory bowel diseases (IBD). Mouse CD1d1, an ortholog of human CD1d mainly participating in lipid-antigen presentation to NKT cells, is able to generate intrinsic signals upon stimulation. Mice with macrophage-specific CD1d1 deficiency (LymCD1d1-/- ) acquire resistance to dextran sodium sulfate (DSS)-induced colitis, attributing to the transcriptional inhibition of NLRP3 inflammasome components. The hyperactivation of NLRP3 inflammasome accounts for gut epithelial proliferation and intestine-blood barrier integrity. Mechanistically, occupancy by the natural ligand glycosphingolipid iGb3, CD1d1 responds with intracellular Ser330 dephosphorylation thus to reduce the Peroxiredoxin 1 (PRDX1)-associated AKT-STAT1 phosphorylation and subsequent NF-?B activation, eventually causing transcriptional down-regulation of Nlrp3 and its immediate substrates Il1b and Il18 in macrophages. Therefore, the counterbalancing role of CD1d1 in macrophages appears to determine severity of DSS-mediated colitis in mice. These findings propose new intervention strategies for treating IBD and other inflammatory disorders.
Project description:<h4>Background</h4>Neuroinflammation is a major driver of age-related brain degeneration and concomitant functional impairment. In patients with Alzheimer's disease, the most common form of age-related dementia, factors that enhance neuroinflammation may exacerbate disease progression, in part by impairing the glymphatic system responsible for clearance of pathogenic beta-amyloid. Inflammatory bowel diseases (IBDs) induce neuroinflammation and exacerbate cognitive impairment in the elderly. The NACHT-LRR and pyrin (PYD) domain-containing protein 3 (NLRP3) inflammasome has been implicated in neuroinflammation. Therefore, we examined if the NLRP3 inflammasome contributes to glymphatic dysfunction and cognitive impairment in an aging mouse model of IBD.<h4>Methods</h4>Sixteen-month-old C57BL/6J and NLRP3 knockout (KO) mice received 1% wt/vol dextran sodium sulfate (DSS) in drinking water to model IBD. Colitis induction was confirmed by histopathology. Exploratory behavior was examined in the open field, associative memory by the novel-object recognition and Morris water maze tests, glymphatic clearance by in vivo two-photon imaging, and neuroinflammation by immunofluorescence and western blotting detection of inflammatory markers.<h4>Results</h4>Administration of DSS induced colitis, impaired spatial and recognition memory, activated microglia, and increased A1-like astrocyte numbers. In addition, DSS treatment impaired glymphatic clearance, aggravated amyloid plaque accumulation, and induced neuronal loss in the cortex and hippocampus. These neurodegenerative responses were associated with increased NLRP3 inflammasome expression and accumulation of gut-derived T lymphocytes along meningeal lymphatic vessels. Conversely, NLRP3 depletion protected against cognitive dysfunction, neuroinflammation, and neurological damage induced by DSS.<h4>Conclusions</h4>Colitis can exacerbate age-related neuropathology, while suppression of NLRP3 inflammasome activity may protect against these deleterious effects of colitis.
Project description:Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD), which is a chronic, relapsing condition associated with the disorder of gut microbial communities. A previous study reported that levels of Roseburia intestinalis (R.I), a butyrate?producing bacterium, are significantly decreased in patients with IBD and exert an anti?inflammatory function in dextran sulfate sodium (DSS)?induced colitis. However, the role of R.I flagellin in UC and its underlying molecular mechanism are not yet fully understood. Therefore, a DSS?induced colitis model in C57Bl/6 mice and the LPS/ATP?induced THP?1 macrophages were treated with R.I flagellin, which were used to investigate the anti?inflammatory effects of R.I flagellin. The results demonstrated that R.I flagellin decreased colitis?associated disease activity index, colonic shortening and the pathological damage of the colon tissues in murine colitis models. Furthermore, R.I flagellin decreased the serum levels of proinflammatory cytokines and inhibited activation of the nucleotide?binding oligomerization segment?like receptor family 3 (NLRP3) inflammasome in murine colitis. R.I flagellin was also demonstrated to decrease the Gasdermin D to yield the N?terminal fragment membrane pore and inhibit inflammasome?triggered pyroptosis. In vitro analysis indicated that microRNA (miR)?223?3p was involved in the regulation of R.I flagellin on NLRP3 inflammasome activation. Taken together, the results of the present study demonstrated that R.I flagellin inhibited activation of the NLRP3 inflammasome and pyroptosis via miR?223?3p/NLRP3 signaling in macrophages, suggesting that R.I flagellin may be used as a novel probiotic product for the treatment of UC.
Project description:The NLRP3-directed inflammasome complex is crucial for the host to resist microbial infection and monitor cellular damage. However, the hyperactivation of NLRP3 inflammasome is implicated in pathogenesis of inflammatory diseases, including inflammatory bowel disease (IBD). Autophagy and autophagy-related genes are closely linked to NLRP3-mediated inflammation in these inflammatory disorders. Here, we report that CCDC50, a novel autophagy cargo receptor, negatively regulates NLRP3 inflammasome assembly and suppresses the cleavage of pro-caspase-1 and interleukin 1β (IL-1β) release by delivering NLRP3 for autophagic degradation. Transcriptome analysis showed that knockdown of CCDC50 results in upregulation of signaling pathways associated with autoinflammatory disease. CCDC50 deficiency leads to enhanced proinflammatory cytokine response triggered by a wide range of endogenous and exogenous NLRP3 stimuli. Ccdc50-deficient mice are more susceptible to dextran-sulfate (DSS)-induced colitis and exhibit more severe gut inflammation with elevated NLRP3 inflammasome activity. These results illustrate the physiological significance of CCDC50 in the pathogenicity of inflammatory diseases, suggesting protective roles of CCDC50 in keeping gut inflammation under control.
Project description:Inflammatory bowel disease (IBD) has been reported to be associated with NLRP3 inflammasome activation. Therefore inhibiting inflammasome activation could be a new approach to treat IBD. Inflammasome inhibitors NLRP3-IN-2, JC124, and 3,4-methylenedioxy-β-nitrostyrene (MNS) were previously reported to exert anti-inflammatory effects in various disease models but not in the dextran sulfate sodium (DSS)-induced colitis model. Here, we showed that MNS was more efficient in inhibiting the secretion of interleukin-1β (IL-1β) by blocking oligomerization of apoptosis-associated speck-like protein (ASC) than NLRP3-IN-2 and JC124. To investigate the protective effects of MNS on enteritis, we administered intragastric MNS to DSS-induced colitis mice. The results demonstrated that MNS attenuated DSS-induced body weight loss, colon length shortening, and pathological damage. In addition, MNS inhibited the infiltration of macrophages and inflammatory cells and reduced IL-1β and IL-12p40 pro-inflammatory cytokines but had no significant effect on tumor necrosis factor α (TNF-α) and IL-6. Furthermore, we also found that the differentiation of IL-17A<sup>+</sup>interferon-γ (IFN-γ)<sup>+</sup>CD4<sup>+</sup> T cell was decreased in the colon after MNS treatment, which might be mediated by IL-1β, etc. cytokine release. Taken together, MNS alleviated DSS-induced intestinal inflammation by inhibiting NLRP3 inflammasome activation, which may function as an effective therapeutic for IBD.
Project description:NLRP3 inflammasome is a novel therapeutic target for inflammatory bowel disease (IBD). The aim of this study was to investigate the anti-inflammatory effect of a bioactive flavonoid-oroxylin A on the treatment of dextran sulfate sodium (DSS)-induced murine colitis via targeting NLRP3 inflammasome. In this study, we found that oroxylin A attenuated experimental colitis in mice, including loss of body weights, shortening of the colon lengths and infiltration of inflammatory cells. The production of IL-1?, IL-6 and TNF-? in colon was also markedly reduced by oroxylin A. Moreover, oroxylin A significantly decreased the expression of NLRP3 in intestinal mucosal tissue. In addition, NLRP3-/- mice were observably protected from DSS-induced acute colitis, and oroxylin A treatment had no effects on attenuating inflammation in NLRP3-/- mice. Further study found that the activation of NLRP3 inflammasome was dose-dependently inhibited by oroxylin A in both THP-Ms and BMDMs, followed by decrease in the cleavage of caspase-1 and secretion of IL-1?. This inhibitory effect of oroxylin A was due to restraint of the NLRP3 protein expression and the inflammasome formation in macrophages. Furthermore, the reduction of NLRP3 protein expression by oroxylin A was dependent on the inhibition of NF-?B p65 expression and nuclear translocation. Besides, oroxylin A directly suppressed the ASC speck formation and the inflammasome assembly which in turn restrained the activation of NLRP3 inflammasome. Our findings demonstrated that oroxylin A inhibited NLRP3 inflammasome activation and could potentially be used for the treatment of IBD.
Project description:Inflammatory bowel disease (IBD) is one of the most common diseases in the gastrointestinal tract related to aberrant inflammation. Pyroptosis, which is characterized by inflammasome formation, the activation of caspase-1, and the separation of the N- and C-terminals of GSDMD, might be related to IBD pathogenesis. NEK7 is an important component of the NLRP3 inflammasome in macrophages. We attempted to investigate the mechanism of NEK7 interacting with NLRP3 to modulate the pyroptosis in IBD. NEK7 mRNA and protein expression and pyroptosis-associated factors, including Caspase-1 (p45, p20), NLRP3, and GSDMD, were upregulated in IBD tissues. NEK7 knockdown abolish ATP?+?LPS-induced pyroptosis in vitro and improved DSS-induced chronic colitis in vivo. NEK7 interacted with NLRP3, as revealed by Co-IP and GST pull-down assays, to exert its effects. Moreover, short-term LPS treatment alone induced no significant changes in NEK7 protein level. TLR4/NF-?B signaling in MODE-K cells could be activated by LPS treatment. LPS-induced NEK7 upregulation could be significantly reversed by JSH-23, an inhibitor of p65. Furthermore, LUC and ChIP assays revealed that RELA might activate the transcription of NEK7 via targeting its promoter region. LPS-induced TLR4/NF-?B activation causes an increase in NEK7 expression by RELA binding NEK7 promoter region. In conclusion, NEK7 interacts with NLRP3 to modulate NLRP3 inflammasome activation, therefore modulating the pyroptosis in MODE-K cells and DSS-induced chronic colitis in mice. We provide a novel mechanism of NEK7-NLRP3 interaction affecting IBD via pyroptosis.
Project description:Fungi represent a significant proportion of the gut microbiota. Aberrant immune responses to fungi are frequently observed in inflammatory bowel diseases (IBD) and colorectal cancer (CRC), and mutations in the fungal-sensing pathways are associated with the pathogenesis of IBD. Fungal recognition receptors trigger downstream signaling via the common adaptor protein CARD9 and the kinase SYK. Here we found that commensal gut fungi promoted inflammasome activation during AOM-DSS-induced colitis. Myeloid cell-specific deletion of Card9 or Syk reduced inflammasome activation and interleukin (IL)-18 maturation and increased susceptibility to colitis and CRC. IL-18 promoted epithelial barrier restitution and interferon-? production by intestinal CD8+ T cells. Supplementation of IL-18 or transfer of wild-type myeloid cells reduced tumor burden in AOM-DSS-treated Card9-/- and Sykfl/flLysMCre/+ mice, whereas treatment with anti-fungal agents exacerbated colitis and CRC. CARD9 deletion changes the gut microbial landscape, suggesting that SYK-CARD9 signaling maintains a microbial ecology that promotes inflammasome activation and thereby restrains colitis and colon tumorigenesis.
Project description:A westernized high-fat diet (HFD) is associated with the development of inflammatory bowel disease (IBD). High-level fecal deoxycholic acid (DCA) caused by HFD contributes to the colonic inflammatory injury of IBD; however, the mechanism concerning the initiation of inflammatory response by DCA remains unclear. In this study, we sought to investigate the role and mechanism of DCA in the induction of inflammation <i>via</i> promoting NLRP3 inflammasome activation. Here, we, for the first time, showed that DCA dose-dependently induced NLRP3 inflammasome activation and highly pro-inflammatory cytokine-IL-1? production in macrophages. Mechanistically, DCA-triggered NLRP3 inflammasome activation by promoting cathepsin B release at least partially through sphingosine-1-phosphate receptor 2. Colorectal instillation of DCA significantly increased mature IL-1? level in colonic tissue and exacerbated DSS-induced colitis, while <i>in vivo</i> blockage of NLRP3 inflammasome or macrophage depletion dramatically reduced the mature IL-1? production and ameliorated the aggravated inflammatory injury imposed by DCA. Thus, our findings show that high-level fecal DCA may serve as an endogenous danger signal to activate NLRP3 inflammasome and contribute to HFD-related colonic inflammation. NLRP3 inflammasome may represent a new potential therapeutical target for treatment of IBD.
Project description:Inflammatory bowel disease (IBD) is an important high-risk factor that promotes the occurrence and development of colon cancer. Research on the mechanism of regulating NLRP3 can provide potential targets for treating NLRP3 inflammasome-related diseases and changing the inflammatory potential of immune cells. In this study, the effects of atractylenolide I on colitis-associated CRC (caCRC) and inflammasome activation were investigated both <i>in vivo</i> and <i>in vitro</i>. Furthermore, the role of atractylenolide I on Drp1-mediated mitochondrial fission was analyzed <i>via</i> Western blotting and transmission electron microscopy (TEM). Moreover, the Drp1 overexpression lentiviral vector was used to study the role of Drp1 on the signaling mechanisms of atractylenolide I. Atractylenolide I treatment significantly reduced the cell viability of human HCT116 and SW480 cells and induced apoptosis, and effectively inhibited colon tumors in the AOM/DSS mouse model. The reduction of NLRP3 inflammasome activation and excessive fission of mitochondria mediated by Drp1 were associated with the administration of atractylenolide I. Upregulation of Drp1 reversed the inhibitory effect of atractylenolide I on the activation of NLRP3 inflammasomes. Overexpressing the Drp1 expression counteracted the restraint of atractylenolide I on the release of IL-1β of LPS/DSS-stimulated BMDMs. Atractylenolide I inhibited NLRP3 and caspase-1 expression in mice BMDMs, with no influence in the Drp1-overexpressed BMDMs. These results demonstrated that atractylenolide I inhibits NLRP3 inflammasome activation in colitis-associated colorectal cancer <i>via</i> suppressing Drp1-mediated mitochondrial fission.
Project description:Activation of cannabinoid receptor 2 (CB2R) ameliorates inflammation, but the underlying mechanism remains unclear. In the present study, we examined whether activation of CB2R could suppress the nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome. In peritoneal macrophages isolated from C57BL/6 mice, LPS/DSS challenge for 24 h increased the expression of the components of NLRP3 inflammasome NLRP3, Casp-1 p20/Casp-1 p45 ratio, proIL-1? and IL-1? and also enhanced autophagy (LC3-II/LC3-I ratio, Beclin-1 and SQSTM1). Pretreatment of peritoneal macrophages with HU 308, a selective CB2R agonist, attenuated LPS/DSS-induced NLRP3 inflammasome activation, but further enhanced autophagy. In comparison with wild-type (WT) control, peritoneal macrophages from CB2R knockout (KO) mice had more robust NLRP3 inflammasome activation and attenuated autophagy upon LPS/DSS challenge. Knockdown autophagy-related gene 5 (Atg5) with a siRNA in peritoneal macrophages attenuated the inhibitory effects of HU 308 on LPS/DSS-induced NLRP3 inflammasome activation in vitro. In vivo, HU308 treatment attenuated DSS-induced colitis mice associated with reduced colon inflammation and inhibited NLRP3 inflammasome activation in wild-type mice. In CB2R KO mice, DSS-induced inflammation and NLRP3 inflammasome activation were more pronounced than those in WT control. Finally, we demonstrated that AMPK-mTOR-P70S6K signaling pathway was involved in this CB2R-mediated process. We conclude that activation of CB2R ameliorates DSS-induced colitis through enhancing autophagy that may inhibit NLRP3 inflammasome activation in macrophages.