The strategies of targeting the NLRP3 inflammasome to treat inflammatory diseases

Identification and verification of inflammatory biomarkers for primary Sjögren's syndrome

INTRODUCTION

Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by inflammatory infiltration, and dysfunction of the salivary and lacrimal glands. This research aimed to explore the disease pathogenesis and improve the diagnosis and treatment of pSS by mining inflammation-associated biomarkers.

METHODS

Five pSS-related datasets were retrieved from the Gene Expression Omnibus (GEO) database. Inflammation-associated biomarkers were determined by the least absolute shrinkage and selection operator (LASSO) and support vector machines recursive feature elimination (SVM-RFE). Single sample gene set enrichment analysis (ssGSEA) was implemented to profile the infiltration levels of immune cells. Real-time quantitative PCR (RT-qPCR) verified the expression of biomarkers in clinical samples.

RESULTS

Four genes (LY6E, EIF2AK2, IL15, and CXCL10) were screened as inflammation-associated biomarkers in pSS, the predictive performance of which were determined among three pSS-related datasets (AUC > 0.7). Functional enrichment results suggested that the biomarkers were involved in immune and inflammation-related pathways. Immune infiltration analysis revealed that biomarkers were notably connected with type 2 T helper cells, regulatory T cells which were significantly expressed between pSS and control. TESTOSTERONE and CYCLOSPORINE were predicted to take effect by targeting CXCL10 and IL15 in pSS, respectively.

CONCLUSION

Four inflammation-associated biomarkers (LY6E, EIF2AK2, IL15, and CXCL10) were explored, and the underlying regulatory mechanisms and targeted drugs associated with these biomarkers were preliminarily investigated according to a series of bioinformatics methods based on the online datasets of pSS, which provided a reference for understanding the pathogenesis of pSS. Key Points • Inflammation-associated biomarkers (LY6E, EIF2AK2, IL15, and CXCL10) were firstly identified in Sjögren's syndrome based on LASSO and SVM-RFE analyses. • CXCL10, EIF2AK2 and LY6E were prominently positively correlated with immature B cells, while IL15 were significantly negatively correlated with memory B cells in Sjögren's syndrome. • LY6E, EIF2AK2, IL15, and CXCL10 were significantly more highly expressed in clinical Sjögren's syndrome samples compared to healthy control samples, which was consistent with the analysis results of the GEO database. •LY6E, EIF2AK2, IL15, and CXCL10 might be used as the biomarkers for the treatment and diagnosis of Sjögren's syndrome.

Terminalia chebula Retz. aqueous extract inhibits the Helicobacter pylori-induced inflammatory response by regulating the inflammasome signaling and ER-stress pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Terminalia chebula Retz., known as the King of Traditional Tibetan Medicine, is widely used for treating various ailments, particularly stomach disorders. It exhibited inhibitory activity against helicobacter pylori.

AIM OF THE STUDY

The exact mechanism by which T. chebula combats H. pylori infection remains unclear. Therefore, this study aimed to investigate its mechanism of action and the key pathways and targets involved.

MATERIAL AND METHODS

Minimum inhibitory concentration (MIC) assay, scanning electron microscope, and inhibiting kinetics curves were conducted. The mRNA expressions were measured by RNA-seq analysis and RT-QPCR. ELISA and Western blot were used to detect the changes in proteins. The main compounds were analyzed by High-performance Liquid Chromatography. The interaction between the compound and target was predicted by Molecular Docking.

RESULTS

The study revealed that T. chebula disrupted the structure of H. pylori bacteria and inhibited Cag A protein expression. Additionally, T. chebula can reduce the expression of flaA, flaB, babA, alpA, alpB, ureE, and ureF genes. Furthermore, T. chebula demonstrated its effectiveness in inhibiting the H. pylori-induced inflammatory response by regulating the inflammasome signaling and ER-stress pathway. Moreover, the study discovered that chebulagic acid has anti-HP activity and inhibits the expression of Cag A protein.

CONCLUSIONS

T. chebula acts as a natural remedy for combating H. pylori infection. Its ability to disrupt the bacterial structure, inhibit key proteins, regulate inflammatory pathways, and the presence of chebulagic acid contribute to its anti-H. pylori activity.

Discovery of Novel 2,3-Dihydro-1H-indene-5-sulfonamide NLRP3 Inflammasome Inhibitors Targeting Colon as a Potential Therapy for Colitis

The NLRP3 inflammasome is a multiprotein complex that plays a crucial role in the pathophysiology of multiple inflammation-related diseases. In this study, we designed and synthesized a series of novel 2,3-dihydro-1H-indene-5-sulfonamide analogues as NLRP3 inflammasome inhibitors, and then identified compound 15z as a potent and specific inhibitor (IC50: 0.13 μM) with low toxicity. Mechanistic studies indicate that 15z binds directly to NLRP3 protein (KD: 102.7 nM), blocking the assembly and activation of the NLRP3 inflammasome and effectively inhibiting cell pyroptosis. Given the notable distribution of 15z in the colon, the DSS-induced colitis model was employed to evaluate its in vivo effectiveness. 15z significantly impacted NLRP3 inflammasome activation and relieved inflammatory bowel disease symptoms in this model. Acute and subacute toxicity studies suggested that 15z has a favorable safety profile. Our results indicate that 15z has great potential to be further developed as a candidate for the treatment of inflammatory bowel disease.

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.

Tabersonine, a natural NLRP3 inhibitor, suppresses inflammasome activation in macrophages and attenuate NLRP3-driven diseases in mice

Aberrant activation of NLRP3 inflammasome causes the progression of various inflammation-related diseases, but the small-molecule inhibitors of NLRP3 are not currently available for clinical use. Tabersonine (Tab) is a natural product derived from a traditional Chinese herb Catharanthus roseus that is usually used as an anti-tumor agent. In this study we investigated the anti-inflammatory effects and molecular targets of Tab. We first screened 151 in-house natural compounds for their inhibitory activity against IL-1β production in BMDMs. We found that Tab potently inhibited NLRP3-mediated IL-1β production with an IC50 value of 0.71 μM. Furthermore, we demonstrated that Tab suppressed the assembly of NLRP3 inflammasome, especially the interaction between NLRP3 and ASC. Interestingly, we found that Tab directly bound to NLRP3 NACHT domain, thereby reducing the self-oligomerization of NLRP3. In addition, we showed that administration of Tab significantly ameliorated NLRP3-driven diseases, such as peritonitis, acute lung injury, and sepsis in mouse models. The preventive effects of Tab were not observed in the models of NLRP3 knockout mouse. In conclusion, we have identified Tab as a natural NLRP3 inhibitor and a lead compound for the design and discovery of novel NLRP3 inhibitors.

Abietane diterpenoids from Orthosiphon wulfenioides with NLRP3 inflammasome inhibitory activity

Wulfenioidones A - K (1-11) were abietane diterpenoids with highly oxidized 6/6/6 aromatic tricyclic skeleton isolated from the whole plant of Orthosiphon wulfenioides, and their planar structures and absolute configurations were elucidated by spectroscopic data interpretation, electronic circular dichroism calculation as well as X-ray crystallography analysis. Bioactivity screening indicated that compounds 1-4, 6 and 8 exhibited lactate dehydrogenase (LDH) inhibition effect with IC₅₀ values ranging from 0.23 to 3.43 μM by preventing the mononuclear macrophage cell pyroptosis induced by double signal stimulation of LPS and nigericin. Western Blot analyses of Caspase-1 and IL-1β down-regulation exhibited that compound 1 could selectively inhibit NLRP3 inflammasome, and the cell morphological observation further supported that compound 1 prevented macrophage cell pyroptosis.

Effectiveness of targeting the NLRP3 inflammasome by using natural polyphenols: A systematic review of implications on health effects

Globally, inflammation and metabolic disorders pose serious public health problems and are major health concerns. It has been shown that natural polyphenols are effective in the treatment of metabolic diseases, including anti-inflammation, anti-diabetes, anti-obesity, neuron-protection, and cardio-protection. NLRP3 inflammasome, which are multiprotein complexes located within the cytosol, play an important role in the innate immune system. However, aberrant activation of the NLRP3 inflammasome were discovered as essential molecular mechanisms in triggering inflammatory processes as well as implicating it in several major metabolic diseases, such as type 2 diabetes mellitus, obesity, atherosclerosis or cardiovascular disease. Recent studies indicate that natural polyphenols can inhibit NLRP3 inflammasome activation. In this review, the progress of natural polyphenols preventing inflammation and metabolic disorders via targeting NLRP3 inflammasome is systemically summarized. From the viewpoint of interfering NLRP3 inflammasome activation, the health effects of natural polyphenols are explained. Recent advances in other beneficial effects, clinical trials, and nano-delivery systems for targeting NLRP3 inflammasome are also reviewed. NLRP3 inflammasome is targeted by natural polyphenols to exert multiple health effects, which broadens the understanding of polyphenol mechanisms and provides valuable guidance to new researchers in this field.

Carnosic acid inhibits NLRP3 inflammasome activation by targeting both priming and assembly steps

Carnosic acid (CA) is a polyphenolic diterpene from rosemary extract with anti-tumor and anti-inflammatory activities. Numerous reports have focused on its anti-tumor ability, while the exact mechanisms underlying its anti-inflammation remains unclear. Here, we have identified that CA is a potent inhibitor of NLRP3 inflammasome in vitro and in vivo. CA not only reduces NLRP3 expression by blocking NF-κB activation, but also inhibits NLRP3 inflammasome assembly and activation by suppressing mitochondrial ROS production and interrupting NLRP3-NEK7 interaction. Furthermore, in mouse models, CA alleviates lipopolysaccharide-induced acute systemic inflammation and MSU-induced peritonitis via NLRP3. Taken together, our data demonstrated the inhibitory effect of CA on NLRP3 inflammasome and pointed out the potential application of CA in the treatment of NLRP3-driven diseases.

Costunolide covalently targets NACHT domain of NLRP3 to inhibit inflammasome activation and alleviate NLRP3-driven inflammatory diseases

The NLRP3 inflammasome's core and most specific protein, NLRP3, has a variety of functions in inflammation-driven diseases. Costunolide (COS) is the major active ingredient of the traditional Chinese medicinal herb Saussurea lappa and has anti-inflammatory activity, but the principal mechanism and molecular target of COS remain unclear. Here, we show that COS covalently binds to cysteine 598 in NACHT domain of NLRP3, altering the ATPase activity and assembly of NLRP3 inflammasome. We declare COS's great anti-inflammasome efficacy in macrophages and disease models of gouty arthritis and ulcerative colitis via inhibiting NLRP3 inflammasome activation. We also reveal that the α-methylene-γ-butyrolactone motif in sesquiterpene lactone is the certain active group in inhibiting NLRP3 activation. Taken together, NLRP3 is identified as a direct target of COS for its anti-inflammasome activity. COS, especially the α-methylene-γ-butyrolactone motif in COS structure, might be used to design and produce novel NLRP3 inhibitors as a lead compound.

Discovery of alantolactone as a naturally occurring NLRP3 inhibitor to alleviate NLRP3-driven inflammatory diseases in mice

BACKGROUND AND PURPOSE

The NLR family pyrin domain-containing 3 (NLRP3) inflammasome is activated in many inflammatory conditions. So far, no low MW compounds inhibiting NLRP3 have entered clinical use. Identification of naturally occurring NLRP3 inhibitors may be beneficial to the design and development of compounds targeting NLRP3. Alantolactone is a phytochemical from a traditional Chinese medicinal plant with anti-inflammatory activity, but its precise target remains unclear.

EXPERIMENTAL APPROACH

A bank of phytochemicals was screened for inhibitors of NLRP3-driven production of IL-1β in cultures of bone-marrow-derived macrophages from female C57BL/6 mice. Models of gouty arthritis and acute lung injury in male C57BL/6J mice were used to determine the in vivo effects of the most potent compound.

KEY RESULTS

Among the 150 compounds screened in vitro, alantolactone exhibited the highest inhibitory activity against LPS + ATP-induced production of IL-1β in macrophages, suppressing IL-1β secretion, caspase-1 activation and pyroptosis. Alantolactone directly bound to the NACHT domain of NLRP3 to inhibit activation and assembly of NLRP3 inflammasomes. Molecular simulation analysis suggested that Arg335 in NLRP3 was a critical residue for alantolactone binding, leading to suppression of NLRP3-NEK7 interaction. In vivo studies confirmed significant alleviation by alantolactone of two NLRP3-driven inflammatory conditions, acute lung injury and gouty arthritis.

CONCLUSION AND IMPLICATIONS

The phytochemical alantolactone inhibited activity of NLRP3 inflammasomes by directly targeting the NACHT domain of NLRP3. Alantolactone shows great potential in the treatment of NLRP3-driven diseases and could lead to the development of novel NLRP3 inhibitors.

Mitochondrial protective effects caused by the administration of mefenamic acid in sepsis

The pathophysiology of sepsis may involve the activation of the NOD-type receptor containing the pyrin-3 domain (NLPR-3), mitochondrial and oxidative damages. One of the primary essential oxidation products is 8-oxoguanine (8-oxoG), and its accumulation in mitochondrial DNA (mtDNA) induces cell dysfunction and death, leading to the hypothesis that mtDNA integrity is crucial for maintaining neuronal function during sepsis. In sepsis, the modulation of NLRP-3 activation is critical, and mefenamic acid (MFA) is a potent drug that can reduce inflammasome activity, attenuating the acute cerebral inflammatory process. Thus, this study aimed to evaluate the administration of MFA and its implications for the reduction of inflammatory parameters and mitochondrial damage in animals submitted to polymicrobial sepsis. To test our hypothesis, adult male Wistar rats were submitted to the cecal ligation and perforation (CLP) model for sepsis induction and after receiving an injection of MFA (doses of 10, 30, and 50 mg/kg) or sterile saline (1 mL/kg). At 24 h after sepsis induction, the frontal cortex and hippocampus were dissected to analyze the levels of TNF-α, IL-1β, and IL-18; oxidative damage (thiobarbituric acid reactive substances (TBARS), carbonyl, and DCF-DA (oxidative parameters); protein expression (mitochondrial transcription factor A (TFAM), NLRP-3, 8-oxoG; Bax, Bcl-2 and (ionized calcium-binding adaptor molecule 1 (IBA-1)); and the activity of mitochondrial respiratory chain complexes. It was observed that the septic group in both structures studied showed an increase in proinflammatory cytokines mediated by increased activity in NLRP-3, with more significant oxidative damage and higher production of reactive oxygen species (ROS) by mitochondria. Damage to mtDNA it was also observed with an increase in 8-oxoG levels and lower levels of TFAM and NGF-1. In addition, this group had an increase in pro-apoptotic proteins and IBA-1 positive cells. However, MFA at doses of 30 and 50 mg/kg decreased inflammasome activity, reduced levels of cytokines and oxidative damage, increased bioenergetic efficacy and reduced production of ROS and 8-oxoG, and increased levels of TFAM, NGF-1, Bcl-2, reducing microglial activation. As a result, it is suggested that MFA induces protection in the central nervous system early after the onset of sepsis.

P2X7 receptor as the regulator of T-cell function in intestinal barrier disruption

The intestinal mucosa is a highly compartmentalized structure that forms a direct barrier between the host intestine and the environment, and its dysfunction could result in a serious disease. As T cells, which are important components of the mucosal immune system, interact with gut microbiota and maintain intestinal homeostasis, they may be involved in the process of intestinal barrier dysfunction. P2X7 receptor (P2X7R), a member of the P2X receptors family, mediates the effects of extracellular adenosine triphosphate and is expressed by most innate or adaptive immune cells, including T cells. Current evidence has demonstrated that P2X7R is involved in inflammation and mediates the survival and differentiation of T lymphocytes, indicating its potential role in the regulation of T cell function. In this review, we summarize the available research about the regulatory role and mechanism of P2X7R on the intestinal mucosa-derived T cells in the setting of intestinal barrier dysfunction.

Challenges in the Detection of Clinically Useful Biomarkers for the Diagnosis of Delirium in Older People in the Emergency Department-A Case-Control Study

Background: The identification of biomarkers associated with delirium in the emergency department could contribute to the understanding, prediction and diagnosis of this disorder. The present study was carried out to identify biomarkers included in easily and quickly obtained standard blood examinations in older patients with delirium in the emergency department. Methods: A case–control study was carried out in the emergency department of Francesc de Borja Hospital (Gandía, Valencia, Spain). Older adults (≥65 years of age) diagnosed with delirium (n = 128) were included. Cases due to alcohol or substance abuse were excluded. Controls were selected on a randomized basis from the remaining patients (n = 128). All laboratory test parameters included in the routine blood and urine tests of the emergency department were collected. Results: The mean age of the patients was 81.24 ± 7.51 years, and 56.2% were males, while the mean age of the controls was 78.97 ± 7.99 years, and 45.3% were males. Significant differences were found between the cases and controls in relation to the following parameters: urea 43 (32–58) mg/dL versus 50 (37–66) mg/dL, respectively; neutrophils 69.6 (62.05–78.75)% versus 75.5 (65.1–83.2)%; monocytes 8.7 (7–10.4)% versus 7.6 (5.5–9.2)%; platelets 213 (159–266) × 10⁹/L versus 224 (182–289) × 10⁹/L; neutrophil–lymphocyte ratio 3.88 (2.45–7.07) versus 5 (2.75–8.83); platelet–lymphocyte ratio 281.4 (210–360) versus 357.1 (257.8–457.1); and mean platelet volume 10.6 (10–11.5) fl versus 10.4 (9.67–10.9) fl. Although the mean values were above desirable levels in both groups, they were higher for most parameters in the control group. No significant differences were observed in C-reactive protein concentration (9.99 (1.69–51) mg/L versus 12.3 (3.09–65.97) mg/L). Conclusions: The identification of delirium biomarkers poses difficulties due to the urgent nature of the disorders found in older people admitted to the emergency department. Research in this field is needed, since it would allow early identification and treatment of delirium.

STING mediates neuroinflammatory response by activating NLRP3-related pyroptosis in severe traumatic brain injury

Long-term neurological deficits after severe traumatic brain injury (TBI), including cognitive dysfunction and emotional impairments, can significantly impair rehabilitation. Glial activation induced by inflammatory response is involved in the neurological deficits post-TBI. This study aimed to investigate the role of the stimulator of interferon genes (STING)-nucleotide-binding oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3) signaling in a rodent model of severe TBI. Severe TBI models were established using weight-drop plus blood loss-reinfusion. Selective STING agonist ADU-S100 or antagonist C-176 was given as a single dose after modeling. Further, NLRP3 inhibitor MCC950 or activator nigericin, or caspase-1 inhibitor VX765, was given as an intracerebroventricular injection 30 min before modeling. After that, a novel object recognition test, open field test, force swimming test, western blot, and immunofluorescence assays were used to assess behavioral and pathological changes in severe TBI. Administration of C-176 alleviated TBI-induced cognitive dysfunction and emotional impairments, neuronal loss, and inflammatory activation of glia cells. However, the administration of STING agonist ADU-S100 exacerbated TBI-induced behavioral and pathological changes. In addition, STING activation exacerbated pyroptosis-associated neuroinflammation via promoting glial activation, as evidenced by increased cleaved caspase-1 and GSDMD N-terminal expression. In contrast, the administration of C-176 showed anti-pyroptotic effects. The neuroprotective effects of C-176 were partially reversed by the NLRP3 activator, nigericin. Collectively, glial STING is responsible for neuroinflammation post-TBI. However, pharmacologic inhibition of STING led to a remarkable improvement of neuroinflammation partly through suppressing NLRP3 signaling. The STING-NLRP3 signaling is a potential therapeutic target in TBI-induced neurological dysfunction.

Astragaloside IV alleviates PM2.5-caused lung toxicity by inhibiting inflammasome-mediated pyroptosis via NLRP3/caspase-1 axis inhibition in mice

Exposure to particulate matter (PM)2.5 in air pollution is a serious health issue worldwide. At present, effective prevention measures and modalities of treatment for PM2.5-caused lung toxicity are lacking. This study elucidated the protective effect of astragaloside IV (Ast), a natural product from Astragalus membranaceous Bunge, against PM2.5-caused lung toxicity and its possible molecular mechanisms. The mice model of lung toxicity was performed by intratracheal instillation of PM2.5 dust suspension. The investigation was performed with Ast or in combination with nigericin, which is a NOD-like receptor protein 3 (NLRP3) activator. The results revealed that PM2.5 lead significant lung inflammation and promoted the pyroptosis pattern of cell death by upregulating pro-inflammatory cytokines and causing oxidative stress related to the NLRP3 inflammasome-mediated pyroptosis pathway. Ast protected against PM2.5 resulted lung toxicity via suppressing NLRP3 inflammasome-mediated pyroptosis via NLRP3/caspase-1 axis inhibition, thereby protecting the lung against PM2.5-induced lung inflammation and oxidative damage, eventually resulting in prolonged survival in mice. Nigericin partially reversed the protective effects of Ast. The present research provides new insights into the therapeutic potential of Ast, demonstrating that it might be a possible candidate for the prevention of PM2.5-caused respiratory diseases. Targeting the NLRP3 inflammasome might be a novel therapeutic tactic for PM2.5-caused respiratory diseases.

CCDC50 suppresses NLRP3 inflammasome activity by mediating autophagic degradation of NLRP3

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 diseases. 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.

Piperlongumine Is an NLRP3 Inhibitor With Anti-inflammatory Activity

Piperlongumine (PL) is an alkaloid from Piper longum L. with anti-inflammatory and antitumor properties. Numerous studies have focused on its antitumor effect. However, the underlying mechanisms of its anti-inflammation remain elusive. In this study, we have found that PL is a natural inhibitor of Nod-like receptor family pyrin domain-containing protein-3 (NLRP3) inflammasome, an intracellular multi-protein complex that orchestrates host immune responses to infections or sterile inflammations. PL blocks NLRP3 activity by disrupting the assembly of NLRP3 inflammasome including the association between NLRP3 and NEK7 and subsequent NLRP3 oligomerization. Furthermore, PL suppressed lipopolysaccharide-induced endotoxemia and MSU-induced peritonitis in vivo, which are NLRP3-dependent inflammation. Thus, our study identified PL as an inhibitor of NLRP3 inflammasome and indicated the potential application of PL in NLRP3-relevant diseases.

Autophagy Induced by Micheliolide Alleviates Acute Irradiation-Induced Intestinal Injury via Inhibition of the NLRP3 Inflammasome

Radiation-induced enteropathy (RIE) is one of the most common and fatal complications of abdominal radiotherapy, with no effective interventions available. Pyroptosis, a form of proinflammatory regulated cell death, was recently found to play a vital role in radiation-induced inflammation and may represent a novel therapeutic target for RIE. To investigate this, we found that micheliolide (MCL) exerted anti-radiation effects in vitro. Therefore, we investigated both the therapeutic effects of MCL in RIE and the possible mechanisms by which it may be therapeutic. We developed a mouse model of RIE by exposing C57BL/6J mice to abdominal irradiation. MCL treatment significantly ameliorated radiation-induced intestinal tissue damage, inflammatory cell infiltration, and proinflammatory cytokine release. In agreement with these observations, the beneficial effects of MCL treatment in RIE were abolished in Becn1^+/− mice. Furthermore, super-resolution microscopy revealed a close association between NLR pyrin domain three and lysosome-associated membrane protein/light chain 3-positive vesicles following MCL treatment, suggesting that MCL facilitates phagocytosis of the NLR pyrin domain three inflammasome. In summary, MCL-mediated induction of autophagy can ameliorate RIE by NLR pyrin domain three inflammasome degradation and identify MCL as a novel therapy for RIE.

Geranylgeranyl diphosphate synthase 1 knockdown suppresses NLRP3 inflammasome activity via promoting autophagy in sepsis-induced acute lung injury

BACKGROUND

NOD-like receptor protein 3 (NLRP3) inflammasome activation has emerged as a crucial contributor to sepsis-induced lung injury. Geranylgeranyl diphosphate synthase 1 (GGPPS1) reportedly exerts the pro-inflammatory capability via activation of NLRP3 inflammasome. However, little is known about the role and mechanism of GGPPS1 in sepsis-induced lung injury.

METHODS

Mice underwent cecal ligation and puncture (CLP) surgery to establish the in vivo model of sepsis. The lung injury of mice was assessed by analyzing the histological changes, the lung wet/dry ratio, PaO2/FiO2 ratio, myeloperoxidase (MPO) activity, total protein content, total cell, and polymorphonuclear leukocyte counts. Mouse alveolar macrophages MH-S were exposed to LPS for developing in vitro model of sepsis. The mRNA and protein expression levels of GGPPS1, beclin-1, and autophagy and inflammasome-related genes were detected using quantitative reverse transcription-polymerase chain reaction and western blot assays. Enzyme-linked immunosorbent assay was conducted to determine the levels of interleukin (IL)-1β and IL-18.

RESULTS

We successfully established sepsis-induced acute lung injury in vivo by CLP surgery. GGPPS1 was upregulated in the lung tissues of CLP-induced septic mice. The activation of autophagy and NLRP3 inflammasome were found in the lung tissues of CLP-induced septic mice. The addition of exogenous GGPP (synthesis products catalyzed by GGPPS1) and autophagic inhibitor 3-MA aggravated sepsis-induced hypoxemia, alveolar inflammatory response, intrapulmonary hemorrhage, and pulmonary edema, as evidenced by increased lung injury score, lung wet/dry weight ratio, MPO activity, total protein content, total cell, and PMNs counts, and decreased PaO2/FiO2 ratio. While NLRP3 inhibitor MCC950 exerted the opposite effects. Additionally, administration of exogenous GGPP could inhibit the activation of autophagy, enhance the activity of NLRP3 inflammasome, and the production of IL-1β and IL-18. Inhibition of autophagy by 3-MA treatment also promoted the activity of NLRP3 inflammasome and the production of IL-1β and IL-18. While MCC950 restrained the activity of NLRP3 inflammasome, but did not affect the activation of autophagy. Notably, the expression of GGPPS1 was unaltered in CLP-induced mice following GGPP, 3-MA, or MCC950 treatment. Moreover, GGPPS1 was upregulated in MH-S cells stimulated with LPS, and GGPPS1 knockdown enhanced the activation of autophagy and inhibited the activity of NLRP3 inflammasome in vitro. Importantly, depletion of GGPPS1 could alleviate LPS-induced inflammatory response by inducing autophagy-dependent NLRP3 inflammasome inhibition.

CONCLUSION

GGPPS1 knockdown suppressed NLRP3 inflammasome activity via promoting autophagy and then attenuated sepsis-induced acute lung injury, revealing a novel target for treating sepsis-induced lung injury.

NLRP3 Inflammasome Mediates Neurodegeneration in Rats with Chronic Neuropathic Pain

ABSTRACT

Patients with chronic neuropathic pain (NP) have a significantly increased risk of central nervous degeneration. Trigeminal neuralgia (TN) is a typical NP, and this manifestation is more obvious. In addition to severe pain, patients with TN are often accompanied by cognitive dysfunction and have a higher risk of central nervous system degeneration, but the mechanism is not clear. The NOD-like receptor 3 (NLRP3) inflammasome assembles inside of microglia on activation, which plays an important role in neurodegeneration such as Alzheimer disease. MCC950 is a specific blocker of NLRP3 inflammasome, which can improve the performance of degenerative diseases. Although NLRP3 inflammasome assembles inside of microglia on activation has been shown to be essential for the development and progression of amyloid pathology, its whether it mediates the neurodegeneration caused by NP is currently unclear. By constructing a rat model of chronic TN, we found that as the course of the disease progresses, TN rats have obvious cognitive and memory deficit. In addition, Tau hyperphosphorylation and Aβ expression increase in the cortex and hippocampus of the brain. At the same time, we found that NLRP3 expression increased significantly in model rats. Interestingly, NLRP3 specific blocker MCC950 can alleviate the neurodegeneration of trigeminal neuralgia rats to a certain extent. It is suggested that our NLRP3 inflammasome plays an important role in the neurodegeneration of trigeminal neuralgia rats. And it is related to the activation of central nervous system inflammation.

TNFAIP3-upregulated RIP3 exacerbates acute pancreatitis via activating NLRP3 inflammasome

Acute pancreatitis (AP) is an inflammatory disease of the pancreas. Accumulating studies have revealed the involvement of tumor necrosis factor alpha-induced protein 3 (TNFAIP3) in the progression of AP. Here, the current study was conducted to elucidate the role of TNFAIP3 and the underlying molecular mechanisms on the progression of AP. The in vivo animal model and in vitro cell model of AP were generated by retrograde injection of sodium taurocholate and stimulation of cerulein into AR42J cells, respectively. Relationships among TNFAIP3, receptor interacting protein 3 (RIP3) and nod-like receptor protein 3 (NLRP3) were predicted on bioinformatics websites and verified by co-immunoprecipitation. AR42J cells were transfected with overexpressing plasmid or shRNA to study the effects of TNFAIP3/RIP3/NLRP3 axis on cell proliferation and apoptosis, secretion of inflammatory cytokines and production of ROS. The effect of TNFAIP3/RIP3/NLRP3 axis in AP was further confirmed in vivo. High expression of TNFAIP3 was observed in AP pancreatic tissues and AP cell model. TNFAIP3 increased RIP phosphorylation through deubiquitination. RIP activated the NLRP3 inflammasome. Silencing of TNFAIP3 or RIP3T led to elevated proliferation and inhibited apoptosis in AR42J cells, accompanied by decreased inflammatory cytokine levels and ROS production. The protective role of inhibited TNFAIP3 in AP was confirmed evidenced by reduced levels of AMY, LIPA, and ROS in vivo. Collectively, overexpressed TNFAIP3 could contribute to the progression of AP by activating RIP3/NLRP3 axis, providing a potential therapeutic target for AP treatment.

The role of NLRP3 inflammasome in the pathogenesis of rheumatic disease

Inflammasome is a molecular platform that is formed in the cytosolic compartment to mediate host immune responses to infection and cellular damage. Inflammasome can activate caspase-1, leading to the maturation of two inflammatory cytokines interleukin 1β (IL-1β) and IL-18 and initiation of a proinflammatory form of cell death called pyroptosis. Among various inflammasome complexes, the NLRP3 inflammasome is by far the most studied inflammasome. NLRP3 inflammasome is a key factor in regulating host immune defense against infectious microbes and cellular damage. However, the dysregulated NLRP3 inflammasome activation also participates in the pathogenesis of many human disorders. NLRP3 inflammasome plays an important role in the pathogenesis of rheumatic disease such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), ankylosing spondylitis (AS), Sjögren's syndrome (SS), dermatomyositis/polymyositis (DM/PM), gout, and systemic sclerosis (SSc). For example, NLRP3 inflammasome has been found highly activated in synovial tissues and peripheral blood mononuclear cells from RA patients. In this paper, we will discuss the role of NLRP3 inflammasome in the pathogenesis of rheumatic disease.

Mitochondria as a Cellular Hub in Infection and Inflammation

Mitochondria are the energy center of the cell. They are found in the cell cytoplasm as dynamic networks where they adapt energy production based on the cell’s needs. They are also at the center of the proinflammatory response and have essential roles in the response against pathogenic infections. Mitochondria are a major site for production of Reactive Oxygen Species (ROS; or free radicals), which are essential to fight infection. However, excessive and uncontrolled production can become deleterious to the cell, leading to mitochondrial and tissue damage. Pathogens exploit the role of mitochondria during infection by affecting the oxidative phosphorylation mechanism (OXPHOS), mitochondrial network and disrupting the communication between the nucleus and the mitochondria. The role of mitochondria in these biological processes makes these organelle good targets for the development of therapeutic strategies. In this review, we presented a summary of the endosymbiotic origin of mitochondria and their involvement in the pathogen response, as well as the potential promising mitochondrial targets for the fight against infectious diseases and chronic inflammatory diseases.

Treponema pallidum (syphilis) antigen TpF1 induces activation of macrophages and accelerates P2X7R-induced NLRP3-dependent release of IL-1β

BACKGROUND

Syphilis is a chronic infectious disease caused by Treponema pallidum (Tp) infection, which causes local inflammation in the host. TpF1 is an oligomeric protein expressed by the Tp-infected host that can induce the host immune response. There are few studies regarding the role of TpF1 in macrophage activation and the subsequent release of cytokines.

OBJECTIVE

To elucidate the effects of TpF1 on the pathological process of Syphilis. In addition, we explored how purinergic 2X7 (P2X7R) induced NOD-like receptor family protein 3 (NLRP3) -dependent release of interleukin-1β (IL-1β) and the underlying mechanisms.

METHODS

We explored the influence of TpF1 on cytokine release by macrophages using qRT-PCR and ELISA. The specific phenotype of activated macrophages was determined by flow cytometry.

RESULTS

TpF1 was able to activate macrophages and induce the M1 macrophage phenotype. Moreover, TpF1 activated the NLRP3 inflammasome in macrophages, which was mediated by P2X7R.

CONCLUSIONS

The Tp-induced protein TpF1 is able to induce macrophage activation and P2X7R-induced NLRP3-dependent release of IL-1β. Our findings provide a theoretical basis for clarifying the clinical symptoms and pathogenesis of syphilis.

The E3 Ubiquitin Ligase TRIM65 Negatively Regulates Inflammasome Activation Through Promoting Ubiquitination of NLRP3

The dysregulation of NLRP3 inflammasome plays a critical role in pathogenesis of various human inflammatory diseases, thus NLRP3 inflammasome activation must be tightly controlled at multiple levels. However, the underlying mechanism regulating NLRP3 inflammasome activation remains unclear. Herein, the effects of Tripartite motif-containing protein 65 (TRIM65) on NLRP3 inflammasome activation and the underlying molecular mechanism were investigated in vitro and in vivo. Inhibition or deletion of Trim65 could significantly strengthen agonist induced NLRP3 inflammasome activation in THP-1 cells and BMDMs, indicated by increased caspase-1 activation and interleukin-1β secretion. However, TRIM65 had no effect on poly (dA: dT)-induced AIM2 inflammasome activation or flagellin-induced IPAF inflammasome activation. Mechanistically, immunoprecipitation assays demonstrated that TRIM65 binds to NACHT domain of NLRP3, promotes lys48- and lys63- linked ubiquitination of NLRP3 and restrains the NEK7-NLRP3 interaction, thereby inhibiting NLRP3 inflammasome assembly, caspase-1 activation, and IL-1β secretion. In vivo, three models of inflammatory diseases were used to confirm the suppression role of TRIM65 in NLRP3 inflammasome activation. TRIM65-deficient mice had a higher production of IL-1β induced by lipopolysaccharide in sera, and more IL-1β secretion and neutrophil migration in the ascites, and more severity of joint swelling and associated IL-1β production induced by monosodium urate, suggesting that TRIM65 deficiency was susceptible to inflammation. Therefore, the data elucidate a TRIM65-dependent negative regulation mechanism of NLRP3 inflammasome activation and provide potential therapeutic strategies for the treatment of NLRP3 inflammasome-related diseases.

Inhibition of the Inflammasome Activity of NLRP3 Attenuates HDM-Induced Allergic Asthma

Inhaled allergens promote inflammatory response, tissue damage, and airway hyperresponsiveness in the lungs, leading to allergic asthma. NLRP3, as an immune sensor of infections and cellular stress, is associated with the development and exacerbation of asthma. However, the mechanism by which NLRP3 affects asthma requires further investigation. Here, we showed that inhaled house dust mite (HDM) promotes NLRP3 inflammasome activation in the lungs and specifically induces the maturation of caspase-1 and IL-1β in alveolar macrophages (AMs). Using Nlrp3-mutant mice, we found that NLRP3 promotes the inflammatory response and pathogenesis in HDM-induced allergic asthma in an inflammasome-dependent manner. Treatment with RRx-001, an NLRP3 inhibitor, significantly reduced inflammatory cell infiltration and mucus secretion in the airway. Our results showed that NLRP3 in myeloid cells promoted the development and progression of allergic asthma in an inflammasome-dependent manner. Small molecules targeting the NLRP3 inflammasome may provide new treatment options for this disease.

Salmonella spvC Gene Inhibits Autophagy of Host Cells and Suppresses NLRP3 as Well as NLRC4

Salmonella spvC gene, encoding a phosphothreonine lyase on host mitogen-activated protein kinases, facilitates systemic infection of Salmonella while the precise mechanisms remain elusive. Autophagy and pyroptosis dependent on the activation of inflammasomes, as parts of innate immune response, contribute to host defense against Salmonella infection. Recently, we reported that spvC could inhibit pyroptosis. To explore the effect of spvC on autophagy and the relationship between its function in pyroptosis and autophagy, infection models of macrophages J774A.1 and epithelial HeLa cells co-cultured with Salmonella Typhimurium wild type, spvC deletion, site-directed mutant which lacks phosphothreonine lyase activity, or complemented strain were established. The levels of LC3 turnover and Beclin 1 of J774A.1 cells were determined by western blot. Confocal laser scanning microscopy was used to visualize the autophagic flux after being transfected with mRFP-GFP-LC3 plasmid in HeLa cells. Results showed that SpvC inhibited autophagosome formation through its phosphothreonine lyase activity. Additionally, analysis of nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 (NLRP3) and NLR with CARD domain-containing 4 (NLRC4) in J774A.1 cells indicated that spvC decreased the protein levels of NLRP3 and NLRC4, which were significantly changed by autophagy inhibitor Bafilomycin A1. Together, our observations reveal a novel mechanism of spvC in Salmonella pathogenesis and host inflammatory response via inhibiting autophagy and NLRP3 as well as NLRC4. These pathways and their subversion by diverse pathogen virulence determinants are expected to throw light on the design of anti-infective agents.

Chemical Modulation of the 1-(Piperidin-4-yl)-1,3-dihydro-2H-benzo[d]imidazole-2-one Scaffold as a Novel NLRP3 Inhibitor

In the search for new chemical scaffolds able to afford NLRP3 inflammasome inhibitors, we used a pharmacophore-hybridization strategy by combining the structure of the acrylic acid derivative INF39 with the 1-(piperidin-4-yl)1,3-dihydro-2H-benzo[d]imidazole-2-one substructure present in HS203873, a recently identified NLRP3 binder. A series of differently modulated benzo[d]imidazole-2-one derivatives were designed and synthesised. The obtained compounds were screened in vitro to test their ability to inhibit NLRP3-dependent pyroptosis and IL-1β release in PMA-differentiated THP-1 cells stimulated with LPS/ATP. The selected compounds were evaluated for their ability to reduce the ATPase activity of human recombinant NLRP3 using a newly developed assay. From this screening, compounds 9, 13 and 18, able to concentration-dependently inhibit IL-1β release in LPS/ATP-stimulated human macrophages, emerged as the most promising NLRP3 inhibitors of the series. Computational simulations were applied for building the first complete model of the NLRP3 inactive state and for identifying possible binding sites available to the tested compounds. The analyses led us to suggest a mechanism of protein–ligand binding that might explain the activity of the compounds.

Moxibustion Ameliorates Ovarian Reserve in Rats by Mediating Nrf2/HO-1/NLRP3 Anti-Inflammatory Pathway

Diminished ovarian reserve (DOR) is an increasingly emerging reproductive disorder that disturbs reproductive-aged women, which is closely linked with inflammation. In clinic, moxibustion has already been applied for reproductive problems. In the present study, we examined the involvement of inflammation in DOR and investigated the effect of moxibustion for its anti-inflammatory activities. Methods. DOR rat model was established using tripterygium glycosides A tablets (TGs) suspension by intragastric administration and was then treated with either moxibustion or hormone replacement therapy (HRT), respectively. Estrus cycles were observed through vaginal cytology. Ovarian morphological alterations were observed by HE staining. The serum levels of follicle-stimulating hormone (FSH), estradiol (E₂), anti-Müllerian hormone (AMH), tumor necrosis factor alpha (TNF-α), and interleukin-10 (IL-10) were measured through ELISA. The expression levels of Nrf2, HO-1, and NLRP3 were detected using immunohistochemistry. Nrf2, HO-1, and NLRP3 mRNA were examined by RT-PCR. Results. Moxibustion improved estrus cycles, FSH, E₂, and AMH levels relative to DOR rats as well as HRT, while also inhibiting ovarian tissue injury. Anti-inflammatory cytokine IL-10 in peripheral blood was upregulated, and proinflammatory factor TNF-α was decreased after treatment with moxibustion. Moxibustion enhanced the expression of mRNA and protein of nuclear factor erythroid 2-related factor (Nrf2) and heme oxygenase-1 (HO-1); in the mean time, nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) was suppressed. Conclusions. We demonstrated that moxibustion could ameliorate the ovarian reserve in rats induced by TGs. Overall, the effect of moxibustion was comparable to that of HRT. The underlying mechanism could be attributed to the anti-inflammatory effects of moxibustion, which suppressed NLRP3 activation by upregulating Nrf2/HO-1 signaling pathway.

Identification of Tubocapsanolide A as a novel NLRP3 inhibitor for potential treatment of colitis

Increasing evidence have reported that NLRP3 inflammasome has a crucial role in various kinds of immunological diseases including colitis. However, there have only a few drug candidates directly targeting inflammasomes for the therapy of colitis. Here, we first reported that Tubocapsanolide A (TA), a natural small molecule, as a novel inhibitor of NLRP3 inflammasome for the treatment of colitis. TA inhibited the activation of NLRP3 inflammasome and suppressed the secretion of IL-1β and IL-18 in macrophages. Moreover, the ASC oligomerization was inhibited by TA. The assembly of the NLRP3 inflammasome was also restrained by TA, while had little effects on potassium and chloride efflux. Biolayer interferometry analysis showed that TA could directly bind to NLRP3. Importantly, LC-MS/MS analysis further demonstrated that TA covalently bound to the cysteine 514 residue (Cys514) of NLRP3. In vivo experiments showed that TA remarkably ameliorated DSS-induced experimental colitis in mice. However, the protection of TA against DSS-induced experimental colitis was abrogated in NLRP3-deficient (Nlrp3^-/-) mice. Taken together, this study indicates TA as a novel inhibitor of NLRP3, which identifies Cys514 as a novel regulatory site of NLRP3 and suggests TA as a promising candidate compound for the treatment of colitis.

Neuroinflammation in Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disease associated with human aging. Ten percent of individuals over 65 years have AD and its prevalence continues to rise with increasing age. There are currently no effective disease modifying treatments for AD, resulting in increasingly large socioeconomic and personal costs. Increasing age is associated with an increase in low-grade chronic inflammation (inflammaging) that may contribute to the neurodegenerative process in AD. Although the exact mechanisms remain unclear, aberrant elevation of reactive oxygen and nitrogen species (RONS) levels from several endogenous and exogenous processes in the brain may not only affect cell signaling, but also trigger cellular senescence, inflammation, and pyroptosis. Moreover, a compromised immune privilege of the brain that allows the infiltration of peripheral immune cells and infectious agents may play a role. Additionally, meta-inflammation as well as gut microbiota dysbiosis may drive the neuroinflammatory process. Considering that inflammatory/immune pathways are dysregulated in parallel with cognitive dysfunction in AD, elucidating the relationship between the central nervous system and the immune system may facilitate the development of a safe and effective therapy for AD. We discuss some current ideas on processes in inflammaging that appear to drive the neurodegenerative process in AD and summarize details on a few immunomodulatory strategies being developed to selectively target the detrimental aspects of neuroinflammation without affecting defense mechanisms against pathogens and tissue damage.

Importance of NLRP3 Inflammasome in Abdominal Aortic Aneurysms

Abdominal aortic aneurysm (AAA) is a chronic inflammatory degenerative aortic disease, which particularly affects older people. Nucleotide-binding oligomerization domain-like receptor family protein 3 (NLRP3) inflammasome is a multi-protein complex and mediates inflammatory responses by activating caspase 1 for processing premature interleukin (IL)-1β and IL-18. In this review, we first summarize the principle of NLRP3 inflammasome activation and the functionally distinct classes of small molecule NLRP3 inflammasome inhibitors. Next, we provide a comprehensive literature review on the expression of NLRP3 inflammasome effector mediators (IL-1β and IL-18) and components (caspase 1, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and NLRP3) in clinical and experimental AAAs. Finally, we discuss the influence of genetic deficiency or pharmacological inhibition of individual effector mediators and components of NLRP3 inflammasome on experimental AAAs. Accumulating clinical and experimental evidence suggests that NLRP3 inflammasome may be a promise therapeutic target for developing pharmacological strategies for clinical AAA management.

Pharmacological targeting of NLRP3 deubiquitination for treatment of NLRP3-associated inflammatory diseases

Pharmacologically inhibiting nucleotide-binding domain and leucine-rich repeat-containing (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome activation results in potent therapeutic effects in a wide variety of preclinical inflammatory disease models. NLRP3 deubiquitination is essential for efficient NLRP3 inflammasome activity, but it remains unclear whether this process can be harnessed for therapeutic benefit. Here, we show that thiolutin (THL), an inhibitor of the JAB1/MPN/Mov34 (JAMM) domain-containing metalloprotease, blocks NLRP3 inflammasome activation by canonical, noncanonical, alternative, and transcription-independent pathways at nanomolar concentrations. In addition, THL potently inhibited the activation of multiple NLRP3 mutants linked with cryopyrin-associated periodic syndromes (CAPS). Treatment with THL alleviated NLRP3-related diseases in mouse models of lipopolysaccharide-induced sepsis, monosodium urate-induced peritonitis, experimental autoimmune encephalomyelitis, CAPS, and methionine-choline-deficient diet-induced nonalcoholic fatty liver disease. Mechanistic studies revealed that THL inhibits the BRCC3-containing isopeptidase complex (BRISC)-mediated NLRP3 deubiquitination and activation. In addition, we show that holomycin, a natural methyl derivative of THL, displays an even higher inhibitory activity against NLRP3 inflammasome than THL. Our study validates that posttranslational modification of NLRP3 can be pharmacologically targeted to prevent or treat NLRP3-associated inflammatory diseases. Future clinical development of derivatives of THL may provide new therapies for NLRP3-related diseases.

Brevilin A inhibits NLRP3 inflammasome activation in vivo and in vitro by acting on the upstream of NLRP3-induced ASC oligomerization

Brevilin A (BA), is a natural biologically active ingredient derived from Centipeda minima with several reports of anti-cancer, while its anti-inflammatory activity is rarely reported. Current studies have found the dysregulated activation of NLRP3 inflammasome cause a variety of inflammatory diseases. Targeting the NLRP3 inflammasome contributes to the treatment of NLRP3-induced diseases. Here, we found that BA significantly attenuates the activation of caspase-1 and the subsequent secretion of the interleukin-1β (IL-1β) in mouse macrophages and human THP-1 cells, showing the inhibitory effect of BA on the NLRP3 inflammasome activation. Moreover, BA specifically inhibits NLRs inflammasomes activation triggered by multi-stimuli, but it has no effect on the AIM2 inflammasome activation, indicating that BA is a specific inhibitor of the NLRs inflammasomes. Research on the mechanism found BA inhibits NLRP3 inflammasome activation by blocking the upstream of ASC oligomerization. Importantly, in vivo experiments showed that BA markedly reduces the secretion of IL-1β to suppress NLRP3 inflammasome in the LPS-induced inflammation and MSU-challenged peritonitis model. In conclusion, our experiments show that BA is an effective NLRP3 inflammasome inhibitor and can be regarded as a drug candidate for NLRP3 inflammasome-driven diseases.

The anti-inflammatory and analgesic effects of intraperitoneal melatonin after spinal nerve ligation are mediated by inhibition of the NF-κB/NLRP3 inflammasome signaling pathway

OBJECTIVE

To explore the potential analgesic effect of melatonin and its underlying molecular mechanisms in a neuropathic pain model induced by spinal nerve ligation (SNL).

METHODS

The experimental animals were divided into different groups including sham, vehicle, melatonin (MT) treatment, caspase-1 inhibitor (VX-765) treatment and MT2 antagonist (4P-PDOT) treatment. On the first three successive postoperative days, rats were intraperitoneally administered with MT, VX-765 or combination of MT and 4P-PDOT. Hyperalgesic behavior after SNL was evaluated using the paw withdrawal threshold (PWT). We then assessed expression of tumor necrosis factor-α (TNF-α), IL-18, interleukin-1β (IL-1β), NLRP3 inflammasome components, and nuclear factor-κB (NF-κB) activation using enzyme-linked immunosorbent assay kits (ELISA), real-time PCR, immunohistochemistry, and western blot, respectively, in spinal cord horn tissues extracted on postoperative day 7.

RESULTS

The results showed that melatonin treatment alleviated SNL-induced allodynia. We observed an SNL-induced upregulation of TNF-α, IL-18, IL-1β, NLRP3, ASC, cleaved caspase-1, and NF-κB in the lumbar spinal cord horn of rats, which was significantly attenuated by intraperitoneal injection of melatonin or VX-765. Additionally, co-treatment of melatonin and 4P-PDOT abrogated the analgesic and anti-inflammatory effect of melatonin.

CONCLUSION

Melatonin had potent analgesic and anti-inflammatory effects in SNL-induced neuropathic pain via NF-κB/NLRP3 inflammasome signaling pathway. Our results therefore suggested that this pathway could represent a novel therapeutic target for the management of neuropathic pain.

Psoralidin, a major component of Psoraleae Fructus, induces inflammasome activation and idiosyncratic liver injury

Idiosyncratic drug-induced liver injury (IDILI) is a rare but potentially fatal disease that is unpredictable and independent of the dose of the drug. Increasing evidence suggests that the majority of IDILI cases are immune-mediated, and the aberrant activation of inflammasome plays a vital role in progression. Psoraleae Fructus (PF), a tonic Chinese medicine, has been able to cause IDILI, but the precise mechanism of hepatotoxicity remains unclear. In this study, eight bioactive compounds involved in PF-induced inflammasome activation were investigated. The results demonstrated that psoralidin activated the inflammasomes followed by secreting caspase-1 and interleukin 1β (IL-1β) in a dose-dependent manner. Interestingly, MCC950, a potent inhibitor of the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, could not entirely suppress the psoralidin-induced inflammasome activation. Moreover, psoralidin significantly induced IL-1β maturation and caspase-1 activation in NLRP3-knockout bone marrow-derived macrophages (BMDMs), suggesting that psoralidin not only activates the NLRP3 inflammasome but also activates other types of inflammasomes. The results also demonstrated that psoralidin activated the inflammasomes by promoting the C-terminal caspase recruitment domain (ASC) oligomerization, and the production of mitochondrial reactive oxygen species (mtROS) is a decisive factor in psoralidin-induced inflammasome activation. Importantly, in vivo data revealed that psoralidin induced hepatic inflammation, increased aminotransferase activity and increased the production of IL-1β and tumor necrosis factor(TNF-α) in a susceptible mouse model of lipopolysaccharide (LPS)-mediated IDILI. In summary, these results confirmed that psoralidin causes IDILI by inducing inflammasome activation. The study suggests that psoralidin is a possible risk factor and is responsible for PF-induced IDILI.

Cashew (Anacardium occidentale L.) Nuts Modulate the Nrf2 and NLRP3 Pathways in Pancreas and Lung after Induction of Acute Pancreatitis by Cerulein

BACKGROUND

One of the most common co-morbidities, that often leads to death, associated with acute pancreatitis (AP) is represented by acute lung injury (ALI). While many aspects of AP-induced lung inflammation have been investigated, the involvement of specific pathways, such as those centered on nuclear factor E2-related factor 2 (Nrf2) and nucleotide-binding domain leucine-rich repeat (NLR) and pyrin domain containing receptor 3 (NLRP3), has not been fully elucidated.

METHODS

To investigate the effect of cashew (Anacardium occidentale L.) nuts on pancreatic and lung injury induced by cerulein injection, cerulein (50 μg/kg) was administered to CD1 mice for 10 h. Oral treatment with cashew nuts at a dose of 100 mg/kg was given 30 min and 2 h after the first cerulein injection. One hour after the final cerulein injection, mice were euthanized and blood, lung and pancreatic tissue samples were collected.

RESULTS

Cashew nuts were able to (1) reduce histological damage; (2) mitigate the induction of mast cell degranulation as well as the activity of myeloperoxidase and malondialdehyde; (3) decrease the activity levels of amylase and lipase as well as the levels of pro-inflammatory cytokines; and (4) enhance the activation of the Nrf2 pathway and suppress the activation of the NLRP3 pathway in response to cerulein in both pancreas and lung.

CONCLUSIONS

Cashew nuts could have a beneficial effect not only on pancreatitis but also on lung injury induced by cerulein.

The NLRP3 Inflammasome: Role and Therapeutic Potential in Pain Treatment

Pain is a fundamental feature of inflammation. The immune system plays a critical role in the activation of sensory neurons and there is increasing evidence of neuro-inflammatory mechanisms contributing to painful pathologies. The inflammasomes are signaling multiprotein complexes that are key components of the innate immune system. They are intimately involved in inflammatory responses and their activation leads to production of inflammatory cytokines that in turn can affect sensory neuron function. Accordingly, the contribution of inflammasome activation to pain signaling has attracted considerable attention in recent years. NLRP3 is the best characterized inflammasome and there is emerging evidence of its role in a variety of inflammatory pain conditions. In vitro and in vivo studies have reported the activation and upregulation of NLRP3 in painful conditions including gout and rheumatoid arthritis, while inhibition of NLRP3 function or expression can mediate analgesia. In this review, we discuss painful conditions in which NLRP3 inflammasome signaling has been pathophysiologically implicated, as well as NLRP3 inflammasome-mediated mechanisms and signaling pathways that may lead to the activation of sensory neurons.

NLRP3 inflammasome inhibitor MCC950 attenuates primary dysmenorrhea in mice via the NF-κB/COX-2/PG pathway

Background

Primary dysmenorrhea (PD) constitutes a common gynecological disease among young women. The NLRP3 inflammasome may be activated and expressed in PD, but the mechanistic link between NLRP3 inflammasome activation and PD is still unclear.

Methods

To investigate the potential role of NLRP3 inflammasome activation in the pathogenesis of PD, 30 female Kunming mice without pregnancy were used for experiments. The PD mouse model was constructed by 11 days of successive co-treatment with estradiol and oxytocin. MCC950, a potent and specific small-molecule inhibitor of the NLRP3 inflammasome, was used to treat PD mice. The disease level was assessed by the writhing response and hot water tail-flick test. The levels of prostaglandin E₂ (PGE₂) and prostaglandin F₂ alpha (PGF_2α) in the uterine tissues of mice were detected by ELISA. The expression levels of protein and cytokines, including NLRP3, cysteine aspartic acid-specific protease 1 (caspase-1), interleukin (IL)-1β, IL-18, nuclear factor kappa B (NF-κB) p65, phospho-NF-κB p65, and cyclooxygenase-2 (COX-2) were revealed by western blot analysis.

Results

MCC950 greatly ameliorated the writhing response induced by the combination of oxytocin and estradiol, with an increasing length of tail-flick latency. MCC950 also significantly decreased the levels of PGF_2α and PGE₂, and the expressions of NLRP3, caspase-1, IL-1β, IL-18, phospho-NF-κB p65, NF-κB p65, and COX-2 in the uterus.

Conclusions

MCC950 markedly alleviated the pain and pathological damage in PD mice by inhibiting NLRP3 activation. The underlying mechanism may be related to hypoactive uterine inflammation via suppression of NLRP3 activation and the NF-κB/COX-2/PG pathway in uteruses of PD mice.