The NLRP3 Inflammasome as a Pharmacological Target

Marine natural products and human immunity: novel biomedical resources for anti-infection of SARS-CoV-2 and related cardiovascular disease

Marine natural products (MNPs) and marine organisms include sea urchin, sea squirts or ascidians, sea cucumbers, sea snake, sponge, soft coral, marine algae, and microalgae. As vital biomedical resources for the discovery of marine drugs, bioactive molecules, and agents, these MNPs have bioactive potentials of antioxidant, anti-infection, anti-inflammatory, anticoagulant, anti-diabetic effects, cancer treatment, and improvement of human immunity. This article reviews the role of MNPs on anti-infection of coronavirus, SARS-CoV-2 and its major variants (such as Delta and Omicron) as well as tuberculosis, H. Pylori, and HIV infection, and as promising biomedical resources for infection related cardiovascular disease (irCVD), diabetes, and cancer. The anti-inflammatory mechanisms of current MNPs against SARS-CoV-2 infection are also discussed. Since the use of other chemical agents for COVID-19 treatment are associated with some adverse effects in cardiovascular system, MNPs have more therapeutic advantages. Herein, it's time to protect this ecosystem for better sustainable development in the new era of ocean economy. As huge, novel and promising biomedical resources for anti-infection of SARS-CoV-2 and irCVD, the novel potential mechanisms of MNPs may be through multiple targets and pathways regulating human immunity and inhibiting inflammation. In conclusion, MNPs are worthy of translational research for further clinical application.

NLRP3 and cancer: Pathogenesis and therapeutic opportunities

More than a decade ago IL-1 blockade was suggested as an add-on therapy for the treatment of cancer. This proposal was based on the overall safety record of anti-IL-1 biologics and the anti-tumor properties of IL-1 blockade in animal models of cancer. Today, a new frontier in IL-1 activity regulation has developed with several orally active NLRP3 inhibitors currently in clinical trials, including cancer. Despite an increasing body of evidence suggesting a role of NLRP3 and IL-1-mediated inflammation driving cancer initiation, immunosuppression, growth, and metastasis, NLRP3 activation in cancer remains controversial. In this review, we discuss the recent advances in the understanding of NLRP3 activation in cancer. Further, we discuss the current opportunities for NLRP3 inhibition in cancer intervention with novel small molecules.

Salvianolic acid B inhibits atherosclerosis and TNF-α-induced inflammation by regulating NF-κB/NLRP3 signaling pathway

BACKGROUND

Inflammation is critical in the pathophysiology of atherosclerosis (AS). The aim of this study was to investigate the protective effect of salvianolic acid B (Sal B) on AS and to explore the molecular mechanism of tumor necrosis factor-α (TNF-α)-induced damage in human umbilical vein endothelial cells (HUVECs).

METHODS

In vivo studies, LDLR-/- mice were fed a high-fat diet (HFD) for 14 weeks to establish an AS model to evaluate the protective effect of Sal B on the development of AS. Total cholesterol (TC), triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) levels were determined in the blood serum. En face and cross section lipid deposits were measured and quantified with Oil Red O staining. Hematoxylin and eosin (H&E) and Masson's trichrome staining were used to quantify atherosclerotic plaque size and collagen fiber content in aortic root sections. Reactive oxygen species (ROS) were detected in aortic root using dihydroethylenediamine (DHE) staining. Apoptosis rate was determined by TdT-mediated dUTP nick end labeling (TUNEL) staining. Immunofluorescence (IF) staining was used to detect the expression of the nuclear factor kappa-B (NF-κB) p65 and NOD-like receptor family pyrin domain containing 3 (NLRP3). To further investigate the protective effect of Sal B, we used TNF-α induced HUVECs inflammation model. We examined cell viability, lactate dehydrogenase (LDH) content, and ROS production. The transcription of NF-κB was evaluated by immunofluorescence. The mRNA levels of NLRP3, caspase-1, and IL-1β were detected by RT-PCR. Pyroptosis related proteins were detected by Western blot.

RESULTS

The change in the weight of the mice over time was an indication that Sal B had an effect on weight gain.

IN VIVO STUDIES

we were able to show that the serum lipids TC, TG and LDL-C were increased in the model group and that the treatment with Sal B reduced the levels of serum lipids. Histological staining showed that the LDLR-/- mice had a large amount of foam cell deposition accompanied by inflammatory cell infiltration and the formation of atherosclerotic plaques in theMOD group. The pathological abnormalities were significantly improved by Sal B treatment. ROS release and apoptosis were significantly increased after HFD in aortic root, which was attenuated by Sal B. IF results showed that the expression of NF-κB p65 and NLRP3 was significantly increased in the MOD group and significantly decreased in the Sal B group, suggesting that Sal B may act through the NF-κB/NLRP3 pathway. And in vitro studies: inflammatory damage of HUEVCs was induced by TNF-α, and Sal B treatmented significantly increased cell viability and reduced LDH release. It was also found that Sal B inhibited ROS level increase after TNF-α-induced HUEVCs. Activation of NF-κB p65 by TNF-α stimulation, NF-κB p65 is transferred to the nucleus. Sal B treatment could reverse this effect. RT-PCR and Western blot showed that Sal B affected NF-κB transcription and NLRP3 inflammasome activation and could significantly inhibit TNF-α-induced NLRP3 inflammasome activation. These results suggest that Sal B may participate in antiatherosclerotic and inflammatory responses through the NF-κB/NLRP3 pathway.

CONCLUSIONS

This study shows that Sal B ameliorates the development of AS lesions in HFD-induced LDLR-/- mice. Furthermore, under TNF-α conditions, Sal B reduced ROS release and reversed nuclear translocation of NF-κB, and inhibited atherosclerosis and inflammation by modulating the NF-κB/NLRP3 pathway.

Pancreatic Ductal Adenocarcinoma Cells Regulate NLRP3 Activation to Generate a Tolerogenic Microenvironment

Defining feature of pancreatic ductal adenocarcinoma (PDAC) that participates in the high mortality rate and drug resistance is the immune-tolerant microenvironment which enables tumors to progress unabated by adaptive immunity. In this study, we report that PDAC cells release CSF-1 to induce nucleotide-binding domain, leucine-rich containing family, pyrin domain-containing-3 (NLRP3) activation in myeloid cells. Increased NLRP3 expression was found in the pancreas of patients with PDAC when compared with normal pancreas which correlated with the formation of the NLRP3 inflammasome. Using human primary cells and an orthotopic PDAC mouse model, we show that NLRP3 activation is responsible for the maturation and release of the inflammatory cytokine IL1β which selectively drives Th2-type inflammation via COX2/PGE2 induction. As a result of this inflammation, primary tumors were characterized by reduced cytotoxic CD8+ T-cell activation and increased tumor expansion. Genetic deletion and pharmacologic inhibition of NLRP3 enabled the development of Th1 immunity, increased intratumoral levels of IL2, CD8+ T cell–mediated tumor suppression, and ultimately limited tumor growth. In addition, we observed that NLRP3 inhibition in combination with gemcitabine significantly increased the efficacy of the chemotherapy. In conclusion, this study provides a mechanism by which tumor-mediated NLRP3 activation exploits a distinct adaptive immunity response that facilitates tumor escape and progression. Considering the ability to block NLRP3 activity with safe and small orally active molecules, this protein represents a new promising target to improve the limited therapeutic options in PDAC.

SIGNIFICANT

This study provides novel molecular insights on how PDAC cells exploit NLRP3 activation to suppress CD8 T-cell activation. From a translational perspective, we demonstrate that the combination of gemcitabine with the orally active NLRP3 inhibitor OLT1177 increases the efficacy of monotherapy.

Pharmacologic inhibition of NLRP3 reduces the levels of α-synuclein and protects dopaminergic neurons in a model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is characterized by a progressive degeneration of dopaminergic neurons, which leads to irreversible loss of peripheral motor functions. Death of dopaminergic neurons induces an inflammatory response in microglial cells, which further exacerbates neuronal loss. Reducing inflammation is expected to ameliorate neuronal loss and arrest motor dysfunctions. Because of the contribution of the NLRP3 inflammasome to the inflammatory response in PD, we targeted NLRP3 using the specific inhibitor OLT1177®.

METHODS

We evaluated the effectiveness of OLT1177® in reducing the inflammatory response in an MPTP neurotoxic model of PD. Using a combination of in vitro and in vivo studies, we analyzed the effects of NLRP3 inhibition on pro-inflammatory markers in the brain, α-synuclein aggregation, and dopaminergic neuron survival. We also determined the effects of OLT1177® on locomotor deficits associated with MPTP and brain penetrance.

RESULTS

Treatment with OLT1177® prevented the loss of motor function, reduced the levels of α-synuclein, modulated pro-inflammatory markers in the nigrostriatal areas of the brain, and protected dopaminergic neurons from degeneration in the MPTP model of PD. We also demonstrated that OLT1177® crosses the blood-brain barrier and reaches therapeutic concentrations in the brain.

CONCLUSIONS

These data suggest that targeting the NLRP3 inflammasome by OLT1177® may be a safe and novel therapeutic approach to arrest neuroinflammation and protect against neurological deficits of Parkinson's disease in humans.

Discovery of a novel 1,3,4-oxadiazol-2-one-based NLRP3 inhibitor as a pharmacological agent to mitigate cardiac and metabolic complications in an experimental model of diet-induced metaflammation

Inspired by the recent advancements in understanding the binding mode of sulfonylurea-based NLRP3 inhibitors to the NLRP3 sensor protein, we developed new NLRP3 inhibitors by replacing the central sulfonylurea moiety with different heterocycles. Computational studies evidenced that some of the designed compounds were able to maintain important interaction within the NACHT domain of the target protein similarly to the most active sulfonylurea-based NLRP3 inhibitors. Among the studied compounds, the 1,3,4-oxadiazol-2-one derivative 5 (INF200) showed the most promising results being able to prevent NLRP3-dependent pyroptosis triggered by LPS/ATP and LPS/MSU by 66.3 ± 6.6% and 61.6 ± 11.5% and to reduce IL-1β release (35.5 ± 8.8% μM) at 10 μM in human macrophages. The selected compound INF200 (20 mg/kg/day) was then tested in an in vivo rat model of high-fat diet (HFD)-induced metaflammation to evaluate its beneficial cardiometabolic effects. INF200 significantly counteracted HFD-dependent "anthropometric" changes, improved glucose and lipid profiles, and attenuated systemic inflammation and biomarkers of cardiac dysfunction (particularly BNP). Hemodynamic evaluation on Langendorff model indicate that INF200 limited myocardial damage-dependent ischemia/reperfusion injury (IRI) by improving post-ischemic systolic recovery and attenuating cardiac contracture, infarct size, and LDH release, thus reversing the exacerbation of obesity-associated damage. Mechanistically, in post-ischemic hearts, IFN200 reduced IRI-dependent NLRP3 activation, inflammation, and oxidative stress. These results highlight the potential of the novel NLRP3 inhibitor, INF200, and its ability to reverse the unfavorable cardio-metabolic dysfunction associated with obesity.

Protective effecs of baicalin magnesium on non-alcoholic steatohepatitis rats are based on inhibiting NLRP3/Caspase-1/IL-1β signaling pathway

Baicalin magnesium is a water-soluble compound isolated from the aqueous solution by Scutellaria baicalensis Georgi. Preliminary experiments have demonstrated that baicalin magnesium can exert protective effects against acute liver injury in rats induced by carbon tetrachloride or lipopolysaccharide combined with d-galactose by regulating lipid peroxidation and oxidative stress. The aim of this study was to investigate the protective effect of baicalin magnesium on non-alcoholic steatohepatitis (NASH) in rats and to elucidate the underlying mechanisms. NASH was induced through a high-fat diet (HFD) for 8 weeks, and Sprague-Dawley rats were intravenously injected with baicalin magnesium, baicalin, and magnesium sulfate for 2 weeks, respectively. Serum was obtained for biochemical analyses and the determination of oxidative stress indicators. Liver tissues were collected for use in liver index assessment, histopathological examination, inflammatory factor analysis, and protein and gene expression analysis. The results revealed that baicalin magnesium markedly improved HFD-induced lipid deposition, inflammatory response, oxidative stress, and histopathological impairments. And baicalin magnesium may exert a protective effect on NASH rats by inhibiting the NLR family pyrin domain involving the 3 (NLRP3)/caspase-1/interleukin (IL)-1β inflammatory pathway. Additionally, the effect of baicalin magnesium was remarkably superior to that of equimolar baicalin and magnesium sulfate in regard to ameliorating NASH symptoms. In conclusion, the findings suggested that baicalin magnesium may represent a potential drug for the treatment of NASH.

Targeting Nuclear Receptors for Chronic Inflammatory Pain: A Potential Alternative

Pain is the unpleasant consequence of detrimental neuronal activity that can be triggered by chronic inflammation, noxious stimuli, and nerve damage. In the case of chronic inflammatory pain, the establishment and maintenance of pain states often depend on the chronic activation and immune response occurring at the site of the peripheral nerve injury. Many current analgesic drugs lack efficacy in long-term pain management. Targeting the nuclear receptor family of transcription factors may provide a novel avenue for the treatment of chronic inflammatory pain. Peroxisome proliferator-activated receptor (PPAR) ligands have demonstrated efficacy in several diabetic-related neuropathic pain models, while the REV-ERB receptors play a key role in the regulation of both P2X7 receptor expression and NLRP3 inflammasome expression and activation. As such, activating the REV-ERB receptor may provide an anti-inflammatory and analgesic option for chronic inflammatory pain sufferers.

Effect of NLRP3 repression on NLRP3 inflammasome activation in human corneal epithelial cells with black carbon exposure

PURPOSE

To investigate the inhibitory effects of NLRP3 siRNA on NLRP3 inflammasome activation in human corneal epithelial cells (HCECs) with fresh black carbon (FBC) particles and ozone-oxidized BC (OBC) particles treatment.

METHODS

HCECs were transfected with NLRP3 siRNA or control siRNA for 48 h, followed by 200 μg/ml FBC or OBC suspension for an additional 72 h. Untreated controls were cells with no siRNA transfection or BC treatment. RT-qPCR and Western blot were used to measure mRNA and protein levels of components of the NLRP3 inflammasome (NLRP3, ASC, and Caspase-1) and downstream cytokine (IL-1β), respectively.

RESULTS

Compared with untreated control cells, mRNA levels of NLRP3, ASC, Caspase-1, and IL-1β were significantly higher (p < 0.05) in control siRNA transfected cells with BC treatments. Compared with the control siRNA transfected cells, NLRP3 siRNA transfection reduced the expression of NLRP3 and ASC, whereas it had a limited effect on the expression of Caspase-1 and IL-1β with FBC or OBC exposures. Under FBC treatment, the reductions of NLRP3 and Caspase-1 mRNA levels were 53.5% (p < 0.001) and 34.2% (p < 0. 01), respectively, and NLRP3 and ASC protein levels were lowered by 58.2% (p < 0.001) and 45.4% (p < 0.001), respectively. Under OBC treatment, the reductions of NLRP3 and Caspase-1 mRNA levels were 39.8% (p < 0.001) and 25.6% (p < 0.05), respectively, and NLRP3 and ASC protein levels were lowered by 44.8% (p < 0.001) and 41.7% (p < 0.001), respectively. Moreover, mRNA levels of ASC and IL-1β, the protein levels of Caspase-1 and IL-1β showed a tendency to decrease in NLRP3 siRNA transfected cells, it was statistically insignificant (p > 0.05).

CONCLUSIONS

NLRP3 siRNA transfection could partially reverse the increased mRNA levels of NLRP3 and Caspase-1, the protein levels of NLRP3 and ASC in HCECs with BC treatment, whereas the reductions of protein levels of Caspase-1 and IL-1β were not significant, indicating that NLRP3 siRNA has a limited inhibitory effect on the activation of NLRP3 inflammasome triggered by BC.

Differential involvement of the canonical and noncanonical inflammasomes in the immune response against infection by the periodontal bacteria Porphyromonas gingivalis and Fusobacterium nucleatum

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The canonical P2 × 7-Caspase-1 pathway is necessary for secretion of IL-1β in oral tissues and macrophages infected with P. gingivalis.

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P2 × 7 receptor controls bacterial load of F. nucleatum and P. gingivalis in macrophages and in mice.

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Caspase-11 is essential for F. nucleatum-induced secretion of IL-1β in macrophages, limits F. nucleatum infection in macrophages and in mice, and is required for cell death induced by F. nucleatum infection.

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The canonical inflammasome is activated preferentially in response to P. gingivalis infection, while the noncanonical inflammasome plays a predominant role during F. nucleatum infection.

We examined the involvement of the P2 × 7 receptor and the canonical and noncanonical inflammasomes in the control of single-species or dual-species infection by the periodontal bacteria Porphyromonas gingivalis and Fusobacterium nucleatum in cells and mice. Stimulation of the P2 × 7 receptor leads to activation of the canonical NLRP3 inflammasome and activation of caspase-1, which leads to cleavage of pro-IL-1β to IL-1β, a key cytokine in the host inflammatory response in periodontal disease. The non-canonical inflammasome pathway involves caspase-11. Thus, wildtype (WT), P2 × 7^−/−, caspase-11^−/− and caspase-1/11^−/− mice were co-infected with both bacterial species. In parallel, bone marrow-derived macrophages (BMDMs) from WT mice and the different knockout mice were infected with P. gingivalis and/or F. nucleatum, and treated or not with extracellular ATP, which is recognized by P2 × 7. F. nucleatum infection alone promoted secretion of IL-1β in BMDMs. Conversely, the canonical pathway involving P2 × 7 and caspase-1 was necessary for secretion of IL-1β in BMDMs infected with P. gingivalis and in the mandible of mice coinfected with P. gingivalis and F. nucleatum. The P2 × 7 pathway can limit bacterial load in single-species and dual-species infection with P. gingivalis and F. nucleatum in BMDMs and in mice. The non-canonical pathway involving caspase-11 was required for secretion of IL-1β induced by F. nucleatum infection in BMDMs, without treatment with ATP. Caspase-11 was also required for induction of cell death during infection with F. nucleatum and contributed to limiting bacterial load during F. nucleatum infection in BMDMs and in the gingival tissue of mice coinfected with P. gingivalis and F. nucleatum. Together, these data suggest that the P2 × 7-caspase-1 and caspase-11 pathways are involved in the immune response against infection by P. gingivalis and F. nucleatum, respectively.

Ginger: A complementary approach for management of cardiovascular diseases

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality worldwide. Inflammation and oxidative stress play critical roles in progression of various types of CVD. Broad pharmacological properties of ginger (the rhizome of Zingiber officinale) and its bioactive components have been reported, suggesting that they can be a therapeutic choice for clinical use. Consistent with its rich phenolic content, the anti-inflammatory and antioxidant properties of ginger have been confirmed in many studies. Ginger modifies many cellular processes and in particular was shown to have potent inhibitory effects against nuclear factor kappa B (NF-κB); signal transducer and activator of transcription; NOD-, LRR-, and pyrin domain-containing proteins; toll-like receptors; mitogen-activated protein kinase; and mammalian target of rapamycin signaling pathways. Ginger also blocks pro-inflammatory cytokines and the activation of the immune system. Ginger suppresses the activity of oxidative molecules such as reactive oxygen species, inducible nitric oxide synthase, superoxide dismutase, glutathione, heme oxygenase, and GSH-Px. In this report, we summarize the biochemical pathologies underpinning a variety of CVDs and the effects of ginger and its bioactive components, including 6-shogaol, 6-gingerol, and 10-dehydrogingerdione. The properties of ginger and its phenolic components, mechanism of action, biological functions, side effects, and methods for enhanced cell delivery are also discussed. Together with preclinical and clinical studies, the positive biological effects of ginger and its bioactive components in CVD support the undertaking of further in vivo and especially clinical studies.

Promise of the NLRP3 Inflammasome Inhibitors in In Vivo Disease Models

Nucleotide-binding oligomerization domain NOD-like receptors (NLRs) are conserved cytosolic pattern recognition receptors (PRRs) that track the intracellular milieu for the existence of infection, disease-causing microbes, as well as metabolic distresses. The NLRP3 inflammasome agglomerates are consequent to sensing a wide spectrum of pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs). Certain members of the NLR family have been documented to lump into multimolecular conglomerates called inflammasomes, which are inherently linked to stimulation of the cysteine protease caspase-1. Following activation, caspase-1 severs the proinflammatory cytokines interleukin (IL)-1β and IL-18 to their biologically active forms, with consequent commencement of caspase-1-associated pyroptosis. This type of cell death by pyroptosis epitomizes a leading pathway of inflammation. Accumulating scientific documentation has recorded overstimulation of NLRP3 (NOD-like receptor protein 3) inflammasome involvement in a wide array of inflammatory conditions. IL-1β is an archetypic inflammatory cytokine implicated in multiple types of inflammatory maladies. Approaches to impede IL-1β's actions are possible, and their therapeutic effects have been clinically demonstrated; nevertheless, such strategies are associated with certain constraints. For instance, treatments that focus on systemically negating IL-1β (i.e., anakinra, rilonacept, and canakinumab) have been reported to result in an escalated peril of infections. Therefore, given the therapeutic promise of an NLRP3 inhibitor, the concerted escalated venture of the scientific sorority in the advancement of small molecules focusing on direct NLRP3 inflammasome inhibition is quite predictable.

Targeting tumor-derived NLRP3 reduces melanoma progression by limiting MDSCs expansion

The nucleotide-binding domain, leucine-rich containing family, pyrin domain-containing-3 (NLRP3) inflammasome, an intracellular complex that regulates maturation and release of interleukin (IL)-1β, is active in biopsies of metastatic melanoma. Here, we demonstrate that NLRP3 activation in melanoma cells drives tumor progression in mice. Subsequent to NLRP3 activation in melanoma cells, IL-1β induces melanoma-associated inflammation, resulting in immunosuppression. Oral administration of a single NLRP3 inhibitor (OLT1177) reduces melanoma growth and melanoma-associated myeloid-derived suppressor cell expansion. Inhibition of the NLRP3 signaling in combination with anti–PD-1 revealed augmented efficacy compared to monotherapy. These data propose that NLRP3 is a therapeutic target for human melanoma.

Interleukin-1β (IL-1β)–mediated inflammation suppresses antitumor immunity, leading to the generation of a tumor-permissive environment, tumor growth, and progression. Here, we demonstrate that nucleotide-binding domain, leucine-rich containing family, pyrin domain-containing-3 (NLRP3) inflammasome activation in melanoma is linked to IL-1β production, inflammation, and immunosuppression. Analysis of cancer genome datasets (TCGA and GTEx) revealed greater NLRP3 and IL-1β expression in cutaneous melanoma samples (n = 469) compared to normal skin (n = 324), with a highly significant correlation between NLRP3 and IL-1β (P < 0.0001). We show the formation of the NLRP3 inflammasome in biopsies of metastatic melanoma using fluorescent resonance energy transfer analysis for NLRP3 and apoptosis-associated speck-like protein containing a CARD. In vivo, tumor-associated NLRP3/IL-1 signaling induced expansion of myeloid-derived suppressor cells (MDSCs), leading to reduced natural killer and CD8⁺ T cell activity concomitant with an increased presence of regulatory T (Treg) cells in the primary tumors. Either genetic or pharmacological inhibition of tumor-derived NLRP3 by dapansutrile (OLT1177) was sufficient to reduce MDSCs expansion and to enhance antitumor immunity, resulting in reduced tumor growth. Additionally, we observed that the combination of NLRP3 inhibition and anti–PD-1 treatment significantly increased the antitumor efficacy of the monotherapy by limiting MDSC-mediated T cell suppression and tumor progression. These data show that NLRP3 activation in melanoma cells is a protumor mechanism, which induces MDSCs expansion and immune evasion. We conclude that inhibition of NLRP3 can augment the efficacy of anti–PD-1 therapy.

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.

Electroacupuncture Relieves Pain and Attenuates Inflammation Progression Through Inducing IL-10 Production in CFA-Induced Mice

The therapeutic effect of electroacupuncture (EA) on inflammatory pain has been well recognized clinically, but the mechanism is unclear. Interleukin-10 (IL-10), which is produced by regulatory T (Treg) cell, is a key anti-inflammatory cytokine for relieving inflammatory pain. Therefore, the aim of this study is to investigate whether EA could inhibit CFA-induced pain and attenuate inflammation progression by regulating the activation of immunocyte and inducing the expression of IL-10. In this study, mice were treated with EA (2/100 Hz, 2 mA) for five consecutive days after 1 day of CFA injection. The behavioral tests were measured and analyzed after the daily EA treatment; then, hind paw, spinal cord, and spleen tissues were prepared for assessment. The results showed that EA treatment significantly increased the mechanical threshold and thermal latency after CFA injection and boosted the expression of IL-10 in paw and spinal cord tissues. EA treatment promoted Treg cells; suppressed macrophage and neutrophils cells; reduced the expression of IL-1β, NLRP3, and TNF-α; and ultimately relieved inflammatory pain. The findings suggested that the analgesic and anti-inflammatory effect of EA treatment could be partially associated with suppression of pro-inflammatory cytokines mediated by induction of IL-10.

NLRP3 Inflammasome Inhibitors in Cardiovascular Diseases

Virtually all types of cardiovascular diseases are associated with pathological activation of the innate immune system. The NACHT, leucine-rich repeat (LRR), and pyrin domain (PYD)-containing protein 3 (NLRP3) inflammasome is a protein complex that functions as a platform for rapid induction of the inflammatory response to infection or sterile injury. NLRP3 is an intracellular sensor that is sensitive to danger signals, such as ischemia and extracellular or intracellular alarmins during tissue injury. The NLRP3 inflammasome is regulated by the presence of damage-associated molecular patterns and initiates or amplifies inflammatory response through the production of interleukin-1β (IL-1β) and/or IL-18. NLRP3 activation regulates cell survival through the activity of caspase-1 and gasdermin-D. The development of NLRP3 inflammasome inhibitors has opened the possibility to targeting the deleterious effects of NLRP3. Here, we examine the scientific evidence supporting a role for NLRP3 and the effects of inhibitors in cardiovascular diseases.

NLRP1 Functions Downstream of the MAPK/ERK Signaling via ATF4 and Contributes to Acquired Targeted Therapy Resistance in Human Metastatic Melanoma

The BRAF V600E mutation leads to constitutive activation of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway and its downstream effector responses. Uncovering the hidden downstream effectors can aid in understanding melanoma biology and improve targeted therapy efficacy. The inflammasome sensor, NACHT, LRR, and PYD domains-containing protein 1 (NLRP1), is responsible for IL-1β maturation and itself is a melanoma tumor promoter. Here, we report that NLRP1 is a downstream effector of MAPK/ERK signaling through the activating transcription factor 4 (ATF4), creating regulation in metastatic melanoma cells. We confirmed that the NLRP1 gene is a target of ATF4. Interestingly, ATF4/NLRP1 regulation by the MAPK/ERK pathway uses distinct mechanisms in melanoma cells before and after the acquired resistance to targeted therapy. In parental cells, ATF4/NLRP1 is regulated by the MAPK/ERK pathway through the ribosomal S6 kinase 2 (RSK2). However, vemurafenib (VEM) and trametinib (TRA)-resistant cells lose the signaling via RSK2 and activate the cAMP/protein kinase A (PKA) pathway to redirect ATF4/NLRP1. Therefore, NLRP1 expression and IL-1β secretion were downregulated in response to VEM and TRA in parental cells but enhanced in drug-resistant cells. Lastly, silencing NLRP1 in drug-resistant cells reduced their cell growth and inhibited colony formation. In summary, we demonstrated that NLRP1 functions downstream of the MAPK/ERK signaling via ATF4 and is a player of targeted therapy resistance in melanoma. Targeting NLRP1 may improve the therapeutic efficacy of targeted therapy in melanoma.

The NLRP3 inflammasome inhibitor OLT1177 rescues cognitive impairment in a mouse model of Alzheimer's disease

Numerous studies demonstrate that neuroinflammation is a key player in the progression of Alzheimer's disease (AD). Interleukin (IL)-1β is a main inducer of inflammation and therefore a prime target for therapeutic options. The inactive IL-1β precursor requires processing by the the nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome into a mature and active form. Studies have shown that IL-1β is up-regulated in brains of patients with AD, and that genetic inactivation of the NLRP3 inflammasome improves behavioral tests and synaptic plasticity phenotypes in a murine model of the disease. In the present study, we analyzed the effect of pharmacological inhibition of the NLRP3 inflammasome using dapansutrile (OLT1177), an oral NLRP3-specific inhibitor that is safe in humans. Six-month-old WT and APP/PS1 mice were fed with standard mouse chow or OLT1177-enriched chow for 3 mo. The Morris water maze test revealed an impaired learning and memory ability of 9-mo-old APP/PS1 mice (P = 0.001), which was completely rescued by OLT1177 fed to mice (P = 0.008 to untreated APP/PS1). Furthermore, our findings revealed that 3 mo of OLT1177 diet can rescue synaptic plasticity in this mouse model of AD (P = 0.007 to untreated APP/PS1). In addition, microglia were less activated (P = 0.07) and the number of plaques was reduced in the cortex (P = 0.03) following NLRP3 inhibition with OLT1177 administration. We also observed an OLT1177 dose-dependent normalization of plasma metabolic markers of AD to those of WT mice. This study suggests the therapeutic potential of treating neuroinflammation with an oral inhibitor of the NLRP3 inflammasome.

Interleukin-1 and the Inflammasome as Therapeutic Targets in Cardiovascular Disease

The intracellular sensing protein termed NLRP3 (for NACHT, LRR, and PYD domains-containing protein 3) forms a macromolecular structure called the NLRP3 inflammasome. The NLRP3 inflammasome plays a major role in inflammation, particularly in the production of IL (interleukin)-1β. IL-1β is the most studied of the IL-1 family of cytokines, including 11 members, among which are IL-1α and IL-18. Here, we summarize preclinical and clinical findings supporting the key pathogenetic role of the NLRP3 inflammasome and IL-1 cytokines in the formation, progression, and complications of atherosclerosis, in ischemic (acute myocardial infarction), and nonischemic injury to the myocardium (myocarditis) and the progression to heart failure. We also review the clinically available IL-1 inhibitors, although not currently approved for cardiovascular indications, and discuss other IL-1 inhibitors, not currently approved, as well as oral NLRP3 inflammasome inhibitors currently in clinical development. Canakinumab, IL-1β antibody, prevented the recurrence of ischemic events in patients with prior acute myocardial infarction in a large phase III clinical trial, including 10 061 patients world-wide. Phase II clinical trials show promising data with anakinra, recombinant IL-1 receptor antagonist, in patients with ST-segment-elevation acute myocardial infarction or heart failure with reduced ejection fraction. Anakinra also improved outcomes in patients with pericarditis, and it is now considered standard of care as second-line treatment for patients with recurrent/refractory pericarditis. Rilonacept, a soluble IL-1 receptor chimeric fusion protein neutralizing IL-1α and IL-1β, has also shown promising results in a phase II study in recurrent/refractory pericarditis. In conclusion, there is overwhelming evidence linking the NLRP3 inflammasome and the IL-1 cytokines with the pathogenesis of cardiovascular diseases. The future will likely include targeted inhibitors to block the IL-1 isoforms, and possibly oral NLRP3 inflammasome inhibitors, across a wide spectrum of cardiovascular diseases.

Effect of dehydroepiandrosterone on the immune response and gut microbiota in dextran sulfate sodium-induced colitis mice

Dehydroepiandrosterone (DHEA) possess anti-inflammatory, anti-oxidant and immune-regulating function in animals and humans, but there is not enough information about the mechanisms underlying its beneficial effects. The present study investigated the effect and mechanism of DHEA in dextran sulfate sodium (DSS)-induced colitis mice. The findings showed that DHEA relieved the decreasing of body weight, the increasing of disease activity index, the enhancing of spleen weight, the shortening of colon length and the rising of myeloperoxidase activity; meanwhile, histopathological analysis showed that DHEA maintained a relatively intact structure of colon in DSS-induced colitis mice. DHEA decreased the malondialdehyde content, superoxide dismutase activity and inducible nitric oxide synthase protein level; meanwhile, DHEA also inhibited the secretion of tumor necrosis factor-α, interleukin-1β and interleukin-6 in DSS-induced colitis mice. Importantly, our results showed that DHEA blocked the activation of nuclear factor-kappa B (NF-κB) and p38 mitogen-activated protein kinase (MAPK) pathways; and it inhibited the Nod-like receptor protein 3 inflammasome activation in DSS-induced colitis mice. Furthermore, DHEA markedly promoted the intestinal barrier function by up-regulation zonula occludens-1 expression level. The 16S rDNA gene sequencing demonstrated that DHEA decreased the Pseudomonas abundance in DSS-induced colitis mice. In conclusion, our data demonstrated that DHEA reduces oxidative damage through regulating antioxidant enzyme activity; inhibits pro-inflammatory cytokines production by blocking the activation of p38 MAPK and NF-κB signal pathway; protects colon barrier integrity via increasing tight junction protein expression and modulating gut microbiota taxa; all that finally alleviates DSS-induced experimental colitis in mice.