NLRP3 Regulation Research Articles

Abstract B050: Convergent signaling via C/EBPβ regulates MDSC-intrinsic NLRP3 inflammasomes to drive inflammatory CAF polarization

Abstract OBJECTIVE: Pivotal contributors to therapeutic resistance in pancreatic ductal adenocarcinoma (PDAC) are myeloid cell infiltration and signaling, and interleukin-1 (IL1)-mediated inflammatory polarization of cancer-associated fibroblasts (iCAF). We have shown that granulocytic myeloid- derived suppressor cell (gMDSC) promote iCAF polarization via NLRP3 inflammasome-derived IL-1β. Here, we sought to dissect the mechanisms regulating NLRP3 inflammasome induction in gMDSCs that drive iCAF polarization in PDAC. METHODS: Single-cell RNA sequencing (scRNA-seq) was performed in PKT mice treated with NLRP3i SB-NL02 vs vehicle. Single-Cell rEgulatory Network Inference and Clustering (SCENIC) analysis identified putative regulons binding upstream to Nlrp3 Transcription Start Site (TSS) in gMDSC subclusters in scRNA-seq data. CRISPR/cas9 silencing of Nlrp3 and Cebpb was performed in gMDSC-like J774M cells in vitro. These edited gMDSCs and J774M cells treated with/without SB-NL02 were co-cultured with Il6/Acta2 dual-reporter CAFs to examine iCAF polarization. RESULTS: PKT mice treated with NLRP3i SB-NL02 showed reduced tumor burden, gMDSC-intrinsic ASC oligomerization, and iCAF polarization in vivo. In silico analysis of intercellular single-cell communication showed striking attenuation in gMDSC-Nlrp3/Il1b:CAF-Il1r1 ligand-receptor crosstalk following NLRP3i treatment. To dissect mechanisms underlying NLRP3 regulation in gMDSCs that drive iCAF skewness, lineage trajectory inference revealed strong co-expression of Tlr4, Cxcr2, Nlrp3 and Il1b genes. Mechanistic studies in J774M gMDSCs showed activation of NLRP3 inflammasomes and IL-1βsecretion not only via canonical TLR4-MyD88 signaling, but also via CXCR2-mediated p38 MAPK induction. This was corroborated in vivo where ASC speck formation in intratumoral Ly6G+ gMDSCs was diminished in mice treated with CXCR2i AZD5069 and p38i peximetinib. To dissect how TLR4 and CXCR2-p38 signaling converge to regulate NLRP3, SCENIC analysis in single-cell gMDSCs transcriptomes revealed Cebpb as the top predicted regulon at the Nlrp3 TSS. In vitro studies using peximetinib and TLR4i (and combinations) revealed that p38 MAPK and TLR4-Myd88 signaling cooperatively regulate C/EBPβ, which in turn dictates Nlrp3 transcription. Cebpb silencing in J774M gMDSCs abolished Nlrp3 transcription, ASC assembly, and IL-1β secretion. ChIP-seq analysis showed strong occupancy of Cebpb on promoter regions of Nlrp3 upon inflammasome induction in gMDSCs. Finally, gMDSC-mediated CAF-Il6 induction in dual-reporter CAFs was significantly disrupted by co-culture with J774M-Cebpb KO cells, recapitulating the effect on iCAF mitigation demonstrated by co-cultures with J774M-Nlrp3 KO or gMDSCs pre-treated with SB-NL02. CONCLUSIONS: CXCR2-p38 and TLR4 signaling converge on C/EBPβ to regulate gMDSC-intrinsic NLRP3 inflammasomes, which drives iCAF polarization in PDAC. The role of C/EBPβ activation as a central node in imparting myeloid checkpoint function in gMDSCs warrants further exploration. Citation Format: Karthik Rajkumar, Andrew Adams, Haleh Amirian, Manan Patel, Erin Dickey, Harper Margaret Marsh, Siddharth Mehra, Nagaraj Nagathihalli, Nipun Merchant, Anna Bianchi, Jashodeep Datta. Convergent signaling via C/EBPβ regulates MDSC-intrinsic NLRP3 inflammasomes to drive inflammatory CAF polarization [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B050.

Role of HIF1A gene polymorphisms with serum uric acid and HIF-1α levels in monosodium urate crystal-induced arthritis.

Gouty arthritis is a metabolic disease characterized by the deposition of monosodium urate crystals in the joints, which triggers the release of interleukin-1β (IL-β) by activating the NLRP3 inflammasome. Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor involved in IL-β production and as a regulator of NLRP3. The aims were to analyze the association of HIF1A rs11549465, rs11549467, and rs2057482 variants in patients with gouty arthritis, and to evaluate the correlation between urate and HIF-1α levels according to the associated genotypes. Cases and controls were genotyped using TaqMan probes, and urate and HIF-1α levels were quantified. Data were analyzed using SPSS v21 software and P-values < 0.05 were considered statistically significant. Urate and HIF-1α levels were higher in patients than in controls (P < 0.05). Under the three inheritance models (codominant, dominant, and recessive), the AA genotype of the rs11549467 variant was associated with gout risk (OR = 5.74, P = 0.009, OR = 3.33, P = 0.024, and OR = 9.09, P = 0.003, respectively). There were significant differences in the distribution of serum levels of both HIF-1α (P < 0.0001) and urate (P = 0.016) according to the genotypes of the rs11549467 variant. These results suggest that the HIF1A rs11549467 variant may play a key role in the pathogenesis of gouty arthritis. Key Points • The pathogenesis of gouty arthritis involves the HIF1A gene. • In patients with gout, the AA genotype of the rs11549467 (HIF1A) variant is associated with increased serum levels of urate and HIF-1α. • HIF-1α is involved in the regulation of IL-1β and NLRP3.

STAT3 promotes NLRP3 inflammasome activation by mediating NLRP3 mitochondrial translocation

Recognition of the translocation of NLRP3 to various organelles has provided new insights for understanding how the NLRP3 inflammasome is activated by different stimuli. Mitochondria have already been demonstrated to be the site of NLRP3 inflammasome activation, and the latest research suggests that NLRP3 is first recruited to mitochondria, then disassociated, and subsequently recruited to the Golgi network. Although some mitochondrial factors have been found to contribute to the recruitment of NLRP3 to mitochondria, the detailed process of NLRP3 mitochondrial translocation remains unclear. Here, we identify a previously unknown role for Signal transducer and activator of transcription-3 (STAT3) in facilitating the translocation of NLRP3 to mitochondria. STAT3 interacts with NLRP3 and undergoes phosphorylation at Ser727 in response to several NLRP3 agonists, enabling the translocation of STAT3 and thus the bound NLRP3 to mitochondria. Disruption of the interaction between STAT3 and NLRP3 impairs the mitochondrial localization of NLRP3, specifically suppressing NLRP3 inflammasome activation both in vitro and in vivo. In summary, we demonstrate that STAT3 acts as a transporter for mitochondrial translocation of NLRP3 and provide new insight into the spatial regulation of NLRP3.

Glycolytic enzyme PGK1 promotes M1 macrophage polarization and induces pyroptosis of acute lung injury via regulation of NLRP3

Acute lung injury (ALI) is characterized by an unregulated inflammatory reaction, often leading to severe morbidity and ultimately death. Excessive inflammation caused by M1 macrophage polarization and pyroptosis has been revealed to have a critical role in ALI. Recent study suggests that glycolytic reprogramming is important in the regulation of macrophage polarization and pyroptosis. However, the particular processes underlying ALI have yet to be identified. In this study, we established a Lipopolysaccharide(LPS)-induced ALI model and demonstrated that blocking glycolysis by using 2-Deoxy-D-glucose(2-DG) significantly downregulated the expression of M1 macrophage markers and pyroptosis-related genes, which was consistent with the in vitro results. Furthermore, our research has revealed that Phosphoglycerate Kinase 1(PGK1), an essential enzyme in the glycolysis pathway, interacts with NOD-, LRR- and pyrin domain-containing protein 3(NLRP3). We discovered that LPS stimulation improves the combination of PGK1 and NLRP3 both in vivo and in vitro. Interestingly, the absence of PGK1 reduces the phosphorylation level of NLRP3. Based on in vitro studies with mice bone marrow-derived macrophages (BMDMs), we further confirmed that siPGK1 plays a protective role by inhibiting macrophage pyroptosis and M1 macrophage polarization. The PGK1 inhibitor NG52 suppresses the occurrence of excessive inflammation in ALI. In general, it is plausible to consider a therapeutic strategy that focuses on modulating the relationship between PGK1 and NLRP3 as a means to mitigate the activation of inflammatory macrophages in ALI.

MLKL deficiency alleviates acute alcoholic liver injury via inhibition of NLRP3 inflammasome

Mixed lineage kinase domain-like protein (MLKL) is identified as the terminal executor of necroptosis. However, its role in acute alcoholic liver injury remains unclear. This study elucidates that MLKL can contribute to acute alcoholic liver injury independently of necroptosis. Although the expression of MLKL was upregulated, no significant increase in its phosphorylation or membrane translocation was observed in the liver tissues of mice treated with ethanol. This finding confirms that alcohol intake does not induce necroptosis in mouse liver tissue. Additionally, the deletion of Mlkl resulted in the downregulation of NLRP3 expression, which subsequently inhibited the activation of the NLRP3 inflammasome and the ensuing inflammatory response, thereby effectively mitigating liver injury induced by acute alcohol consumption. The knockout of Nlrp3 did not affect the expression of MLKL, further confirming that MLKL acts upstream of NLRP3. Mechanistically, inhibiting the nuclear translocation of MLKL reduced the nuclear entry of p65, the principal transcriptional regulator of NLRP3, thereby limiting the transcription of Nlrp3 mRNA and subsequent NLRP3 expression. Overall, this study unveils a novel mechanism of MLKL regulates the activation of NLRP3 inflammasomes in a necroptosis independent way in acute alcoholic liver injury

TRPV4 modulation participates in paraoxon-induced brain injury via NMDA and NLRP3 regulation

ABSTRACT Background Organophosphorus pesticide poisoning can lead to severe brain damage, but the specific mechanisms involved are not fully understood. Our research aims to elucidate the function of the TRPV4 ion channel in the development of brain injury induced by paraoxon (POX). Methods In vivo, we examined the survival rate, behavioral seizures, histopathological alterations, NMDA receptor phosphorylation, as well as the expression of the NLRP3-ASC-caspase-1 complex and downstream inflammatory factors in the POX poisoning model following intervention with the TRPV4 antagonist GSK2193874. In vitro, we investigated the effects of GSK2193874 on NMDA-induced inward current, cell viability, cell death rate, and Ca2+ accumulation in primary hippocampal neurons. Results The treatment with the TRPV4 antagonist increased the survival rate, suppressed the status epilepticus, improved pathological damage, and reduced the phosphorylation level of NMDA receptors after POX exposure. Additionally, it inhibited the upregulation of NLRP3 inflammasome and inflammatory cytokines expression after POX exposure. Moreover, the TRPV4 antagonist corrected the NMDA-induced increase in inward current and cell death rate, decrease in cell viability, and Ca2+ accumulation. Conclusion TRPV4 participates in the mechanisms of brain injury induced by POX exposure through NMDA-mediated excitotoxicity and NLRP3-mediated inflammatory response.

GITR exacerbates lysophosphatidylcholine-induced macrophage pyroptosis in sepsis via posttranslational regulation of NLRP3.

The NLRP3 inflammasome functions as an inflammatory driver, but its relationship with lipid metabolic changes in early sepsis remains unclear. Here, we found that GITR expression in monocytes/macrophages was induced by lysophosphatidylcholine (LPC) and was positively correlated with the severity of sepsis. GITR is a costimulatory molecule that is mainly expressed on T cells, but its function in macrophages is largely unknown. Our in vitro data showed that GITR enhanced LPC uptake by macrophages and specifically enhanced NLRP3 inflammasome-mediated macrophage pyroptosis. Furthermore, in vivo studies using either cecal ligation and puncture (CLP) or LPS-induced sepsis models demonstrated that LPC exacerbated sepsis severity/lethality, while conditional knockout of GITR in myeloid cells or NLRP3/caspase-1/IL-1β deficiency attenuated sepsis severity/lethality. Mechanistically, GITR specifically enhanced inflammasome activation by regulating the posttranslational modification (PTM) of NLRP3. GITR competes with NLRP3 for binding to the E3 ligase MARCH7 and recruits MARCH7 to induce deacetylase SIRT2 degradation, leading to decreasing ubiquitination but increasing acetylation of NLRP3. Overall, these findings revealed a novel role of macrophage-derived GITR in regulating the PTM of NLRP3 and systemic inflammatory injury, suggesting that GITR may be a potential therapeutic target for sepsis and other inflammatory diseases. GITR exacerbates LPC-induced macrophage pyroptosis in sepsis via posttranslational regulation of NLRP3. According to the model, LPC levels increase during the early stage of sepsis, inducing GITR expression on macrophages. GITR not only competes with NLRP3 for binding to the E3 ligase MARCH7 but also recruits MARCH7 to induce the degradation of the deacetylase SIRT2, leading to decreasing ubiquitination but increasing acetylation of NLRP3 and therefore exacerbating LPC-induced NLRP3 inflammasome activation, macrophage pyroptosis and systemic inflammatory injury.

Loss of myeloid-KLF2 mediates LPS-induced mortality in neonatal pups by NLRP3 inflammasome signaling and altered neutrophil aging

Abstract Preterm neonates have disrupted myeloid cell activation and aging. KLF2 inhibits myeloid cell activation by repressing NF-kB, which controls NLRP3 transcription. In our myeloid-KLF2 deleted (MKO) murine model, postnatal day (P) 4 pups have higher LPS-induced mortality than controls but 100% survival in both groups after LPS at P12. P4 and P12 reflect preterm and term physiology, respectively. We aimed to to determine the role of neutrophil-NLRP3 and neutrophil aging in LPS-induced mortality in P4 MKO pups. Serum IL-1β was measured 4h post-LPS injection. BM neutrophils were treated with LPS and nigericin for NLRP3 protein expression in lysate and IL-1b levels in the supernatant. Daily MCC950 injections (P1-P4) were used to inhibit NLRP3 before LPS injection on P4. BM neutrophils were treated with LPS ex vivo and flow-sorted to examine CXCR4/CD62L expression. MKO pups have increased serum IL-1β, neutrophil-NLRP3 expression, and IL-1b release, P4&amp;gt;P12. In vivo NLRP3 inhibition rescued survival in P4 MKO and controls. P4 MKO have reduced BM and higher circulating neutrophils. MKO BM neutrophils are more aged (CD62Llo), but CXCR4lo, affecting aged neutrophil homing to the BM. Myeloid-KLF2 loss increases LPS mortality via NLRP3 activation in P4 pups. It accelerates neutrophil aging, but leads to persistence of aged neutrophils in the circulation by reducing CXCR4 expression. Future mechanistic studies will focus on KLF2's regulation of NLRP3 and CXCR4 expression at P4 and P12.

NLRP3 Cys126 palmitoylation by ZDHHC7 Promotes Inflammasome Activation

Abstract Macrophages could response to pathogen and damage-associated molecular patterns through NLRP3-mediated inflammasome. Hyperactivation of NLRP3 is associated with human chronic inflammatory diseases. Therefore, accurate regulation of NLRP3 activation is important. Recent works show that NLRP3 is localized on trans-Golgi network (TGN), which is crucial for NLRP3 activation and consequently ASC recruitment. However, what regulates NLRP3 TGN localization is unknown. Here, we demonstrated that NLRP3 is palmitoylated on Cys126 by palmitoyl-acyltransferase ZDHHC7 in macrophages, which promotes resting NLRP3 localization to TGN and activated NLRP3 localization on dispersed TGN. As a result, ZDHHC7-mediated NLRP3 Cys126 palmitoylation is critical for recruitment and oligomerization of ASC after NLRP3 activation. Perturbating NLRP3 palmitoylation by ZDHHC7 knockout, pharmaceutically inhibition, or modification site mutation, will diminish NLRP3 activation and consequential Caspase-1/GSDMD cleavage, and cytokines secretion in macrophages. Furthermore, NLRP3 palmitoylation on Cys126 is vital for inflammasome activation in vivo, including endotoxic shock and peritonitis mouse models. Notably, this palmitoylation-regulated NLRP3 activation also contributes to multiple sclerosis development in mice. Therefore, our study provides new insight into NLRP3 regulation and suggests targeting ZDHHC7 or NLRP3 Cys126 could be a potential therapeutic strategy to treat human NLRP3-related disorders.

Mangiferin, A Naturally Occurring Glucosylxanthone, Induces Apoptosis in Caco-2 Cells In Vitro and Exerts Protective Effects on Acetic Acid-Induced Ulcerative Colitis in Mice through the Regulation of NLRP3.

Inflammatory bowel diseases (IBD), an inflammatory disease, include Crohn's disease and ulcerative colitis. Dysregulated autoimmune response to gut dysbiosis is mainly involved in the pathogenesis of IBD and is triggered by various inciting environmental factors. With its rising prevalence in every continent, IBD has evolved into a global disease, which is on the rise, affecting people of all ages. There is a growing incidence of IBD in the elderly population, as evidenced by epidemiological data. IBD is characterized by an inflammatory process that requires a lifelong treatment. The main challenge in IBD management is the adverse side effects associated with almost all of the currently available drugs. Hence, there is a search for drugs with more efficacy and fewer side effects. Natural products with great structural diversity and ease of modification chemically are being explored, as they were shown to control IBD by safely suppressing pro-inflammatory pathways. The present study aims at understanding the role of mangiferin, a COX-2 inhibitor isolated from tubers of Pueraria tuberosa in the treatment of IBD and colon cancer, in vitro on the Caco-2 human colon cancer cell line and in vivo in the acetic acid-induced IBD mouse model. In the acetic acid-induced colitis model, it prevented the decrease in length of the colon, mucosal erosion, and cellular infiltration in a dose-dependent manner. The expression levels of various pro-inflammatory markers like COX-2, IL1β, TNF-α, INF-γ, IL-6, NLRP3, and caspase-1 were downregulated in an acetic acid-induced mouse model on treatment with mangiferin in a dose dependent manner. Mangiferin also showed anticancer effects on Caco-2 cells by increasing the expression of Fas ligand, Fas receptor, FADD, caspase-8, and caspase-3 proteins, whereas Bid and Bcl-2 proteins showed decreased expression. These data suggest that mangiferin, an inhibitor of COX, induces apoptosis in colon cancer cells in vitro and protects mice from acetic acid-induced colitis in vivo.

GSNOR negatively regulates the NLRP3 inflammasome via S-nitrosation of MAPK14.

Hyperactivation of the NLRP3 inflammasome has been implicated in the pathogenesis of numerous diseases. However, the precise molecular mechanisms that modulate the transcriptional regulation of NLRP3 remain largely unknown. In this study, we demonstrated that S-nitrosoglutathione reductase (GSNOR) deficiency in macrophages leads to significant increases in the Nlrp3 and Il-1β expression levels and interleukin-1β (IL-1β) secretion in response to NLRP3 inflammasome stimulation. Furthermore, in vivo experiments utilizing Gsnor-/- mice revealed increased disease severity in both lipopolysaccharide (LPS)-induced septic shock and dextran sodium sulfate (DSS)-induced colitis models. Additionally, we showed that both LPS-induced septic shock and DSS-induced colitis were ameliorated in Gsnor-/- Nlrp3-/- double-knockout (DKO) mice. Mechanistically, GSNOR deficiency increases the S-nitrosation of mitogen-activated protein kinase 14 (MAPK14) at the Cys211 residue and augments MAPK14 kinase activity, thereby promoting Nlrp3 and Il-1β transcription and stimulating NLRP3 inflammasome activity. Our findings suggested that GSNOR is a regulator of the NLRP3 inflammasome and that reducing the level of S-nitrosylated MAPK14 may constitute an effective strategy for alleviating diseases associated with NLRP3-mediated inflammation.

Suppression of inflammation-induced lung cancer cells proliferation and metastasis by exiguaflavanone A and exiguaflavanone B from Sophora exigua root extract through NLRP3 inflammasome pathway inhibition.

Objective: Non-small cell lung cancer (NSCLC) is recognized for its aggressive nature and propensity for high rates of metastasis. The NLRP3 inflammasome pathway plays a vital role in the progression of NSCLC. This study aimed to investigate the effects of S. exigua extract and its active compounds on NLRP3 regulation in NSCLC using an in vitro model. Methods: S. exigua was extracted using hexane, ethyl acetate and ethanol to obtain S. exigua hexane fraction (SE-Hex), S. exigua ethyl acetate fraction (SE-EA), and S. exigua ethanol fraction (SE-EtOH) respectively. The active compounds were identified using column chromatography and NMR analysis. A549 cells were primed with lipopolysaccharide (LPS) and adenosine triphosphate (ATP) for activated NLRP3 inflammasome. The anti-inflammatory properties were determined using ELISA assay. The anti-proliferation and anti-metastasis properties against LPS-ATP-induced A549 cells were determined by colony formation, cell cycle, wound healing, and trans-well migration and invasion assays. The inflammatory gene expressions and molecular mechanism were determined using RT-qPCR and Western blot analysis, respectively. Results: SE-EA exhibited the greatest anti-inflammation properties compared with other two fractions as evidenced by the significant inhibition of IL-1β, IL-18, and IL-6, cytokine productions from LPS-ATP-induced A549 cells in a dose-dependent manner (p < 0.05). The analysis of active compounds revealed exiguaflavanone A (EGF-A) and exiguaflavanone B (EGF-B) as the major compounds present in SE-EA. Then, SE-EA and its major compound were investigated for the anti-proliferation and anti-metastasis properties. It was found that SE-EA, EGF-A, and EGF-B could inhibit the proliferation of LPS-ATP-induced A549 cells through cell cycle arrest induction at the G0/G1 phase and reducing the expression of cell cycle regulator proteins. Furthermore, SE-EA and its major compounds dose-dependently suppressed migration and invasion of LPS-ATP-induced A549 cells. At the molecular level, SE-EA, EGF-A, and EGF-B significantly downregulated the mRNA expression of IL-1β, IL-18, IL-6, and NLRP3 in LPS-ATP-induced A549 cells. Regarding the mechanistic study, SE-EA, EGF-A, and EGF-B inhibited NLRP3 inflammasome activation through suppressing NLRP3, ASC, pro-caspase-1(p50 form), and cleaved-caspase-1(p20 form) expressions. Conclusion: Targeting NLRP3 inflammasome pathway holds promise as a therapeutic approach to counteract pro-tumorigenic inflammation and develop novel treatments for NSCLC.

The E3 ubiquitin ligase RNF31 mediates the development of ulcerative colitis by regulating NLRP3 inflammasome activation

Ulcerative colitis (UC) is characterized by dysregulated inflammation and disruption of the intestinal barrier. The NLRP3 inflammasome, which is composed of NLRP3, ASC, and caspase-1, plays a crucial role in UC pathogenesis by triggering the production of proinflammatory cytokines. In this study, we investigated the regulatory role of RNF31 in NLRP3 inflammasome activation during UC development. Through comprehensive analysis of ulcerative colitis tissues using the GEO database and immunohistochemistry, we found that RNF31 expression was elevated in UC tissues, which prompted further investigation into its function. We constructed an RNF31 knockdown cell model and observed a significant reduction in NLRP3 inflammasome activation, indicating the involvement of RNF31 in regulating NLRP3. Mechanistically, RNF31 could interact with NLRP3 through the RBR structural domain, leading to increased K63-linked ubiquitination of NLRP3 and consequent stabilization. Coimmunoprecipitation experiments revealed a mutual interaction between RNF31 and NLRP3, substantiating their functional association. Finally, an in vivo mouse model with RNF31 knockdown showed a notable reduction in NLRP3 expression, which was accompanied by a decrease in the proinflammatory cytokines IL-18 and IL-1β. The successful attenuation of DSS-induced tissue inflammation by this treatment confirmed the physiological relevance of RNF31-mediated regulation of NLRP3. This study unveils a novel regulatory pathway by which RNF31 affects NLRP3 inflammasome activation, providing new insights into UC pathogenesis and potential therapeutic targets for UC treatment.

Dapagliflozin decreases atherosclerotic plaque instability via regulating macrophage pyroptosis

Abstract Background Vulnerable plaques are characterized by infiltration of inflammatory cells, playing a key role in the progression of acute coronary events. It’s important to clarify the inflammatory mechanism of unstable plaque formation. Several clinical trials have demonstrated that dapagliflozin could reduce major adverse cardiac events in whether diabetic or non-diabetic patients. However, the underlying cardioprotective mechanism of dapagliflozin remains unclear. This study was aimed to investigate the role of dapagliflozin in regulating macrophage pyroptosis and vulnerable plaque formation. Methods 20 ApoE-/- mice (control) were fed with high fat diet while another 20 ApoE-/- mice were challenged with high fat diet plus dapagliflozin for 12 weeks. The extent and instability of atherosclerotic plaque was determined by oil-red staining, HE staining, immunofluorescence staining and electron microscopy. Changes in subsets of immune cells were evaluated by flow cytometry. Plasma cytokines were assessed by ELISA. Microarray analysis was applied to detect gene expressions while Western blot and real-time PCR was used to assess gene expression levels. Results Morphology studies revealed that dapagliflozin could inhibit plaque formation and reduce instability in ApoE-/- mice. FACS data showed that dapagliflozin could decrease CD11b+Ly6Chigh M1 macrophages differentiation and inhibit foam cells formation in ApoE-/- mice. Microarray analysis and in vitro studies exhibited that dapagliflozin could induce the down regulation of NLRP3, caspase-1, IL-1β, IL-18 and MMP-7/10/12/14 to retard macrophage pyroptosis and foam cell formation. Conclusions We have characterized a novel role for dapagliflozin in modulating atherosclerotic lesion development and progression. We envision that this study may provide several potential therapeutic targets for treatment of acute coronary syndromes.

Betanin combined with virgin coconut oil inhibits neuroinflammation in aluminum chloride-induced toxicity in rats by regulating NLRP3 inflammasome

Background and aimActivating NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3) is crucial in the pathogenesis of Alzheimer's disease (AD). A multimodal treatment intervention is the most feasible way to alter the course of AD progression. Hence, the current study was conducted to study the combination of betanin (BET) and virgin coconut oil (VCO) on NLRP3 regulation in aluminum chloride-induced AD in Wistar rats. Experimental procedureBET (100,200 mg/kg) and VCO (1, 5 g/kg) alone and in combination (BET 100 mg/kg + VCO 1 g/kg and BET 200 mg/kg + VCO 5 g/kg) were given orally for 42 days. On day 21 and 42nd, the behavioral test was performed to check the animal's cognition. Acetylcholinesterase (AChE) activity, oxidative stress markers, estimation of NLRP3 and IL-1β, and histological examinations were conducted in the hippocampus (H) and cortex (C). Results and conclusionTreatment with BET and VCO alone or combined improved behavioral characteristics (MWM and PA p < 0.0001; EPM p = 0.5184), inhibited AChE activity (C, p = 0.0101; H, p < 0.0001), and lowered oxidative stress in the brain. Also, combination treatment restored the levels of NLRP3 (C, p = 0.0062; H, p < 0.0001) and IL1β (C, p = 0.0005; H, p = 0.0098). The combination treatment significantly reduced the degree of neuronal degeneration, amyloid deposition, and necrosis in the brain tissue. The current study revealed that the combination strategy effectively controlled neuroinflammation via modulation of the NLRP3 inflammasome pathway, paving the way for the new treatment.

MiR-223-3p attenuates radiation-induced inflammatory response and inhibits the activation of NLRP3 inflammasome in macrophages

Macrophage pyroptosis plays an important role in the development of radiation-induced cell and tissue damage, leading to acute lung injury. However, the underlying mechanisms of NOD-like receptor thermal protein domain–associated protein 3 (NLRP3)-mediated macrophage pyroptosis and the regulatory factors involved in radiation-induced pyroptosis are unclear. In this study, the expression of the NLRP3 inflammasome and pyroptosis-associated factors in murine macrophage cell lines was investigated after ionizing radiation. High-throughput RNA sequencing was performed to identify and characterize miRNAs and mRNA transcripts associated with NLRP3-mediated cell death. Our results demonstrated that cleaved-caspase-1 (p10) and N-terminal domain of gasdermin-D (GSDMD-N) were upregulated, and the number of NLRP3 inflammasomes and pyroptotic cells increased in murine macrophage cell lines after irradiation (8 Gy). Comparativeprofiling of 300miRNAs revealed that 41 miRNAsexhibited significantly different expression after 8 Gy of irradiation. Granulocyte-specific microRNA-223-3p (miR-223-3p) is a negative regulator of NLRP3. In vitro experiments revealed that the expression of miR-223-3p was significantly altered by irradiation. Moreover, miR-223-3p decreased the expression of NLRP3 and proinflammatory factors, resulting in reduced pyroptosis in irradiated murine macrophages. Subsequently, in vivo experiments revealed the efficacy of miR-223-3p supplementation in ameliorating alveolar macrophage (AM) pyroptosis, attenuating the infiltration of inflammatory monocytes, and significantly alleviating the severity of acute radiation-induced lung injury (ARILI). Our findings suggest that the miR-223-3p/NLRP3/caspase-1 axis is involved in radiation-induced AM pyroptosis and ARILI.

Spatiotemporal On–Off Immunomodulatory Hydrogel Targeting NLRP3 Inflammasome for the Treatment of Biofilm‐Infected Diabetic Wounds

AbstractBiofilm‐infected diabetic wounds (BIDWs) with hyperglycemia and bacterial colonization are characterized by disordered inflammation and abnormal activation of NLRP3 inflammasome, leading to sustained macrophage M1 polarization and neutrophil extracellular traps (NETs) formation. An immoderate anti‐inflammatory treatment that downregulates NLRP3 in turn promotes the persistence of biofilm infections and impairs the healing of BIDWs. Therefore, reconciling biofilm elimination and immune regulation holds the promise of curing BIDWs. Herein, a novel spatiotemporal on–off immunomodulatory therapy (SOIT) is proposed for treating BIDWs through biphasic regulation of NLRP3. Methacrylate gelatin hydrogels (Gel‐MA) incorporated with graphene oxide (GO) and metformin‐loaded mesoporous silicone nanospheres are synthesized and photo cross‐linked to construct a nanocomposite hydrogel (MGO@GM). First, GO nanosheets released from MGO@GM inhibit bacterial biofilm formation and disrupt mature biofilms under near‐infrared irradiation. Meanwhile, GO activates the NLRP3 to induce a macrophage‐associated proinflammatory response against biofilms. Afterward, with the subsequent degradation of MGO@GM, released metformin reduces local hyperglycemia, downregulates NLRP3, and inhibits NETs formation. Furthermore, repolarized M2 macrophages alleviate the inflammatory microenvironment and promote tissue regeneration. Briefly, this SOIT strategy regulates the NLRP3 and rescues impaired innate immunity to facilitate anti‐infection and tissue repair, which provides a new perspective for the future clinical treatment of BIDWs.

A protective erythropoietin evolutionary landscape, NLRP3 inflammasome regulation, and multisystem inflammatory syndrome in children.

The low incidence of pediatric severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and the associated multisystem inflammatory syndrome (MIS-C) lack a unifying pathophysiological explanation, impeding effective prevention and therapy. Activation of the NACHT, LRR, and PYD domains-containing protein(NLRP) 3 inflammasome in SARS-CoV-2 with perturbed regulation in MIS-C, has been reported. We posit that, early age physiological states and genetic determinants, such as certain polymorphisms of renin-angiotensin aldosterone system (RAAS) molecules, promote a controlled RAAS hyperactive state, and form an evolutionary landscape involving an age-dependent erythropoietin (EPO) elevation, mediating ancestral innate immune defenses that, through appropriate NLRP3 regulation, mitigate tissue injury and pathogen invasion. SARS-CoV-2-induced downregulation of angiotensin-converting enzyme (ACE)2 expression in endothelial cells (EC), impairment of endothelial nitric oxide (NO) synthase (eNOS) activity and downstream NO bioavailability, may promote a hyperactive RAAS with elevated angiotensin II and aldosterone that, can trigger, and accelerate NLRP3 inflammasome activation, while EPO-eNOS/NO abrogate it. Young age and a protective EPO evolutionary landscape may successfully inhibit SARS-CoV-2 and contain NLRP3 inflammasome activation. By contrast, increasing age and falling EPO levels, in genetically susceptible children with adverse genetic variants and co-morbidities, may lead to unopposed RAAS hyperactivity, NLRP3 inflammasome dysregulation, severe endotheliitis with pyroptotic cytokine storm, and development of autoantibodies, as already described in MIS-C. Our haplotype estimates, predicted from allele frequencies inpopulation databases, are in concordance with MIS-C incidence reports in Europeans but indicate lower risks for Asians and African Americans. Targeted Mendelian approaches dissecting the influence of relevant genetic variants are needed.

BRD4 inhibition by JQ1 protects against LPS-induced cardiac dysfunction by inhibiting activation of NLRP3 inflammasomes

JQ1, a BRD4 inhibitor, first identified its therapeutic role in cancer, has gradually demonstrated a protective effect on the heart in recent years; however, it is unclear whether JQ1 also plays a role in LPS-induced cardiac dysfunction. A total of forty eight mice were randomly divided into control, LPS(7.5mg/kg), and LPS + JQ1 (50mg/kg). JQ1 was preprotected for 1h, and LPS was stimulated for 12h, mouse survival and cardiac function were observed, and histopathological, serum myocardial injury markers, and inflammatory indicators, and oxidative stress levels in heart tissue were examined. The experiment found that the cardiac BRD4 levels were upregulated and the heart severe damage in the LPS group compared with the control group. While compared with the LPS group, JQ1 preprotected increased survival rate and cardiac function, reducated cardiomypathological injury and CD45 infiltration, and reduced the release of LDH, CK-MB, IL-1, IL-18, reduced MDA generation, and increased SOD viability. In addition, JQ1 preprotected also upregulated SIRT1, and inhibited the expression of NLRP3, caspase-1p20, and GSDMD. Meanwhile, similar results were obtained in LPS-treated H9C2 cells, and further intervention with the SIRT1 inhibitor EX527 partially blocked the JQ1-mediated down regulation of NLRP3, caspase-1p20, and GSDMD. We propose that JQ1 may improve LPS-induced cardiac dysfunction by inhibiting SIRT1-dependent activation of NLRP3 inflammasomes, which may be a promising strategy for treating sepsis cardiomyopathy.

Study of the effect of liraglutide on the correlation between NLRP3 inflammasome and non-alcoholic fatty liver disease

Objective: To observe the effect of liraglutide on the correlation between nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing protein 3 (NLRP3) infl ammasome and nonalcoholic fatty liver disease (NAFLD). Methods: Thirty-nine NAFLD cases (group N) and thirty-nine healthy subjects (group C) were selected from the physical examination center, and their general data were collected to determine the serum levels of NLRP3, IL-1β, and IL-18. The differences and correlations were analyzed between the two sets of indicators. Thirty male SD rats were randomly divided into normal (NC, n=10) and high-fat diet group (HF, n=20). The normal group were fed with normal diet and high-fat diet group were fed with high-fat diet. After 12 weeks of feeding, HF group was randomly divided into HF group (n=10) and liraglutide group (100L, n=10), and were given 0.5 ml/kg sterile isotonic saline and 100 g/kg liraglutide subcutaneously twice a day, respectively. Four weeks later, serum biochemical indicators, liver NLRP3 infl ammasome protein expression, and infl ammatory cytokine conditions were detected in each group. Statistical analysis was performed using t test, oneway analysis of variance (ANOVA) or χ2 test. Results: There were no statistically signifi cant differences between N and C group in terms of age, gender, diastolic blood pressure, glycosylated hemoglobin, mean platelet volume, erythrocyte distribution width, serum low-density lipoprotein cholesterol (HDL-Ch), total cholesterol, and total bileacid. Compared with group C, group N had elevated systolic blood pressure, body mass index (BMI), fasting blood glucose, blood creatinine, alkaline phosphatase (ALP), NLRP3, interleukin (IL)-1β, IL-18, TG, blood uric acid, γ-glutamyltransferase (GGT), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and white blood cell counts, while HDL-Ch and total bilirubin were depleted than group C, and the difference was statistically significant (P< 0.05). NLRP3 was positively correlated with systolic blood pressure, BMI, fasting blood glucose, serum creatinine, IL-1β, IL-18, triglycerides, serum uric acid, GGT, ALT, AST, but negatively correlated with total bilirubin and HDL-Ch, and the difference was statistically signifi cant. Compared with NC group, HF group had significantly increased body mass, liver mass, serum biochemical indicators (triglycerides, AST, ALT), liver NLRP3 inflammasome protein expression, and inflammatory cytokines. After treatment with liraglutide, 100L group indicators were signifi cantly decreased when compared to HF group. Conclusion: Compared with healthy subjects, the infl ammation-related indicators, body mass, blood lipids and liver function-related indicators are signifi cantly changed in patients with NAFLD, which is also consistent with the results of rat model study. Liraglutide treatment had improved NAFLD to certain extent in NAFLD rats, so NLRP3 regulation may be one of the mechanisms to improve liver inflammation and steatosis.