Unified polymerization mechanism for the assembly of ASC-dependent inflammasomes

FUBP3 mediates the amyloid-β-induced neuronal NLRP3 expression

JOURNAL/nrgr/04.03/01300535-202507000-00028/figure1/v/2024-09-09T124005Z/r/image-tiff Alzheimer's disease is characterized by deposition of amyloid-β, which forms extracellular neuritic plaques, and accumulation of hyperphosphorylated tau, which aggregates to form intraneuronal neurofibrillary tangles, in the brain. The NLRP3 inflammasome may play a role in the transition from amyloid-β deposition to tau phosphorylation and aggregation. Because NLRP3 is primarily found in brain microglia, and tau is predominantly located in neurons, it has been suggested that NLRP3 expressed by microglia indirectly triggers tau phosphorylation by upregulating the expression of pro-inflammatory cytokines. Here, we found that neurons also express NLRP3 in vitro and in vivo, and that neuronal NLRP3 regulates tau phosphorylation. Using biochemical methods, we mapped the minimal NLRP3 promoter and identified FUBP3 as a transcription factor regulating NLRP3 expression in neurons. In primary neurons and the neuroblastoma cell line Neuro2A, FUBP3 is required for endogenous NLRP3 expression and tau phosphorylation only when amyloid-β is present. In the brains of aged wild-type mice and a mouse model of Alzheimer's disease, FUBP3 expression was markedly increased in cortical neurons. Transcriptome analysis suggested that FUBP3 plays a role in neuron-mediated immune responses. We also found that FUBP3 trimmed the 5' end of DNA fragments that it bound, implying that FUBP3 functions in stress-induced responses. These findings suggest that neuronal NLRP3 may be more directly involved in the amyloid-β-to-phospho-tau transition than microglial NLRP3, and that amyloid-β fundamentally alters the regulatory mechanism of NLRP3 expression in neurons. Given that FUBP3 was only expressed at low levels in young wild-type mice and was strongly upregulated in the brains of aged mice and Alzheimer's disease mice, FUBP3 could be a safe therapeutic target for preventing Alzheimer's disease progression.

Viral myocarditis: From molecular mechanisms to therapeutic prospects

Myocarditis is characterized as local or diffuse inflammatory lesions in the myocardium, primarily caused by viruses and other infections. It is a common cause of sudden cardiac death and dilated cardiomyopathy. In recent years, the global prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the widespread vaccination have coincided with a notable increase in the number of reported cases of myocarditis. In light of the potential threat that myocarditis poses to global public health, numerous studies have sought to elucidate the pathogenesis of this condition. However, despite these efforts, effective treatment strategies remain elusive. To collate the current research advances in myocarditis, and thereby provide possible directions for further research, this review summarizes the mechanisms involved in viral invasion of the organism and primarily focuses on how viruses trigger excessive inflammatory responses and in result in different types of cell death. Furthermore, this article outlines existing therapeutic approaches and potential therapeutic targets for the acute phase of myocarditis. In particular, immunomodulatory treatments are emphasized and suggested as the most extensively studied and clinically promising therapeutic options.

Igniting hope: Harnessing NLRP3 inflammasome-GSDMD-mediated pyroptosis for cancer immunotherapy

In the contemporary landscape of oncology, immunotherapy, represented by immune checkpoint blockade (ICB) therapy, stands out as a beacon of innovation in cancer treatment. Despite its promise, the therapy's progression is hindered by suboptimal clinical response rates. Addressing this challenge, the modulation of the NLRP3 inflammasome-GSDMD-mediated pyroptosis pathway holds promise as a means to augment the efficacy of immunotherapy. In the pathway, the NLRP3 inflammasome serves as a pivotal molecular sensor that responds to inflammatory stimuli within the organism. Its activation leads to the release of cytokines interleukin 1β and interleukin 18 through the cleavage of GSDMD, thereby forming membrane pores and potentially resulting in pyroptosis. This cascade of processes exerts a profound impact on tumor development and progression, with its function and expression exhibiting variability across different tumor types and developmental stages. Consequently, understanding the specific roles of the NLRP3 inflammasome and GSDMD-mediated pyroptosis in diverse tumors is imperative for comprehending tumorigenesis and crafting precise therapeutic strategies. This review aims to elucidate the structure and activation mechanisms of the NLRP3 inflammasome, as well as the induction mechanisms of GSDMD-mediated pyroptosis. Additionally, we provide a comprehensive overview of the involvement of this pathway in various cancer types and its applications in tumor immunotherapy, nanotherapy, and other fields. Emphasis is placed on the feasibility of leveraging this approach to enhance ICB therapy within the field of immunotherapy. Furthermore, we discuss the potential applications of this pathway in other immunotherapy methods, such as chimeric antigen receptor T-cell (CAR-T) therapy and tumor vaccines.

Applications of pyroptosis activators in tumor immunotherapy

Contemporary progress in tumor immunotherapy has solidified its role as an effective approach in combating cancer. Nonetheless, the prevalent "immune cold" state within the tumor microenvironment poses a substantial barrier to its efficacy. Addressing this, pyroptosis-a gasdermin-mediated programmed cell death characterized by its inflammatory profile-emerges as a crucial mechanism. It catalyzes the release of vast quantities of pro-inflammatory cytokines and immunogens, potentially transforming immunosuppressive "cold" tumors into reactive "hot" ones. Herein, we will initially present an overview of pyroptosis as a distinct form of cell death, along with its molecular mechanisms. Subsequently, we will focus on introducing how pyroptosis activators are utilized in the field of tumor immunotherapy. Insights gained from applications of pyroptosis activators in tumor immunotherapy could lead to the development of safe and efficient pyroptosis activators, significantly enriching the arsenal for tumor immunotherapy.

Design, Synthesis, and Bioevaluation of Novel NLRP3 Inhibitor with IBD Immunotherapy from the Virtual Screen

NLRP3, a crucial member of the NLRP family, plays a pivotal role in immune regulation and inflammatory modulation. Here, we report a potent and specific NLRP3 inhibitor Z48 obtained though docking-based virtual screening and structure-activity relationship studies with an IC50 of 0.26 μM in THP-1 cells and 0.21 μM in mouse bone marrow-derived macrophages. Mechanistic studies indicated that Z48 could bind directly to the NLRP3 protein (KD = 1.05 μM), effectively blocking the assembly and activation of the NLRP3 inflammasome, consequently manifesting anti-inflammatory properties. Crucially, with acceptable mouse pharmacokinetic profiles, Z48 demonstrated notable therapeutic efficacy in a mouse model of DSS-induced ulcerative colitis, while displaying no significant therapeutic impact on NLRP3KO mice. In conclusion, this study provided a promising NLRP3 inflammasome inhibitor with novel molecular scaffold, poised for further development as a therapeutic candidate in the treatment of inflammatory bowel disease.

Characterization of NLRP3 inflammasome components in the endangered Chinese giant salamander (Andrias davidianus)

Chinese giant salamander (Andrias davidianus) is the largest extant urodela species and has unique evolutionary position. Studying the immune system of Chinese giant salamander contributes to understanding the evolution of immune systems of vertebrates. The NLR-related protein 3 (NLRP3) inflammasome comprised of NLRP3, ASC and caspase-1 play important roles in the host innate immunity. However, little is know about the NLRP3 inflammasome components in Chinese giant salamander. In this study, the NLRP3, apoptosis-associated speck-like protein (ASC) and caspase-1 (adaNLRP3, adaASC and adaCaspase-1) were characterized from Chinese giant salamander. The proteins of these three genes shared similar motifs and structures with their mammalian counterparts, with a PYD motif, a nucleotide-binding domain (NACHT) motif, and four leucine-rich repeat domain (LRR) motifs identified in adaNLRP3, a pyrin domain (PYD) motif and a caspase recruitment domain (CARD) motif in adaASC, and a CARD motif and a CASc motif in adaCaspase-1. These three genes were constitutively expressed in the skin, heart, lung, kidney, muscle, brain, spleen, and liver of Chinese giant salamander. Following Aeromonas hydrophia infection, all the three genes were up-regulated in various tissues. Molecular docking analysis revealed that the key residues involved in forming the adaNLRP3/adaASC complex were located in the PYD motifs, and that involved in forming the adaASC/adaCaspase-1 complex were located in the CARD motifs. Further analysis revealed that the hydrogen bonds and salt bridges had crucial roles in the formation of adaNLRP3/acaASC and adaASC/adaCaspase-1 complexes. To the best of our knowledge, this is the first report on the NLRP3 inflammasome components in Chinese giant salamander which will be helpful in further understanding the function of the NLRP3 inflammasome and in elucidating its role in the immune response to microbes.

Cell-Free Nonequilibrium Assembly for Hierarchical Protein/Peptide Nanopillars

Cells contain intricate protein nanostructures, but replicating them outside of cells presents challenges. One such example is the vertical fibronectin pillars observed in embryos. Here, we demonstrate the creation of cell-free vertical fibronectin pillar mimics using nonequilibrium self-assembly. Our approach utilizes enzyme-responsive phosphopeptides that assemble into nanotubes. Enzyme action triggers shape changes in peptide assemblies, driving the vertical growth of protein nanopillars into bundles. These bundles, with peptide nanotubes serving as a template to remodel fibronectin, can then recruit collagen, which forms aggregates or bundles depending on their types. Nanopillar formation relies on enzyme-catalyzed nonequilibrium self-assembly and is governed by the concentrations of enzyme, protein, peptide, the structure of the peptide, and peptide assembly morphologies. Cryo-EM reveals unexpected nanotube thinning and packing after dephosphorylation, indicating a complex sculpting process during assembly. Our study demonstrates a cell-free method for constructing intricate, multiprotein nanostructures with directionality and composition.

Comparative Analysis of Canonical Inflammasome Activation by Flow Cytometry, Imaging Flow Cytometry and High-Content Imaging

Inflammasome activation occurs in various diseases, including rare diseases that require multicenter studies for investigation. Flow cytometric analysis of ASC speck+ cells in patient samples can be used to detect cell type-specific inflammasome activation. However, this requires standardized sample processing and the ability to compare data from different flow cytometers. To address this issue, we analyzed stimulated and unstimulated PBMCs from healthy donors using seven different flow cytometers. Additionally, human PBMCs were analyzed by fluorescence microscopy, imaging flow cytometry and high-content imaging (HCI). Flow cytometers differed significantly in their ability to detect ASC speck+ cells. Aria III, Astrios EQ, and Canto II performed best in separating ASC speck+ from diffuse ASC cells. Imaging flow cytometry and HCI provided additional insight into ASC speck formation based on image-based parameters. For optimal results, the ability to separate cells with diffuse ASC from ASC speck+ cells is decisive. Image-based parameters can also differentiate cells with diffuse ASC from ASC speck+ cells. For the first time, we analyzed ASC speck detection by HCI in PBMCs and demonstrated advantages of this technique, such as high-throughput, algorithm-driven image quantification and 3D-rendering. Thus, inflammasome activation by ASC speck formation can be detected by various technical methods. However, the results may vary depending on the device used.

Inflammasome components as new therapeutic targets in inflammatory disease

Inflammation drives pathology in many human diseases for which there are no disease-modifying drugs. Inflammasomes are signalling platforms that can induce pathological inflammation and tissue damage, having potential as an exciting new class of drug targets. Small-molecule inhibitors of the NLRP3 inflammasome that are now in clinical trials have demonstrated proof of concept that inflammasomes are druggable, and so drug development programmes are now focusing on other key inflammasome molecules. In this Review, we describe the potential of inflammasome components as candidate drug targets and the novel inflammasome inhibitors that are being developed. We discuss how the signalling biology of inflammasomes offers mechanistic insights for therapeutic targeting. We also discuss the major scientific and technical challenges associated with drugging these molecules during preclinical development and clinical trials.

Genetic and epigenetic regulation of inflammasomes: Role in atherosclerosis

The cardiovascular complications of atherosclerosis are thought to arise from an inflammatory response to the accumulation of cholesterol-rich lipoproteins in the arterial wall. The positive outcome of CANTOS (Canakinumab Anti-inflammatory Thrombosis Outcome Study) provided key evidence to support this concept and suggested that inflammasomes and IL-1β are important inflammatory mediators in human atherosclerotic cardiovascular diseases (ACVD). In specific settings NLRP3 or AIM2 inflammasomes can induce inflammatory responses in the arterial wall and promote the formation of unstable atherosclerotic plaques. Clonal hematopoiesis (CH) has recently emerged as a major independent risk factor for ACVD. CH mutations arise during ageing and commonly involves variants in genes mediating epigenetic modifications (TET2, DNMT3A, ASXL1) or cytokine signaling (JAK2). Accumulating evidence points to the role of inflammasomes in the progression of CH-induced ACVD events and has shed light on the regulatory pathways and possible therapeutic approaches that specifically target inflammasomes in atherosclerosis. Epigenetic dynamics play a vital role in regulating the generation and activation of inflammasome components by causing changes in DNA methylation patterns and chromatin assembly. This review examines the genetic and epigenetic regulation of inflammasomes, the intersection of macrophage cholesterol accumulation with inflammasome activation and their roles in atherosclerosis. Understanding the involvement of inflammasomes in atherosclerosis pathogenesis may lead to customized treatments that reduce the burden of ACVD.

Mesenchymal stem cells and their extracellular vesicles in bone and joint diseases: targeting the NLRP3 inflammasome

The nucleotide-binding oligomerization domain-like-receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a cytosolic multi-subunit protein complex, and recent studies have demonstrated the vital role of the NLRP3 inflammasome in the pathological and physiological conditions, which cleaves gasdermin D to induce inflammatory cell death called pyroptosis and mediates the release of interleukin-1 beta and interleukin-18 in response to microbial infection or cellular injury. Over-activation of the NLRP3 inflammasome is associated with the pathogenesis of many disorders affecting bone and joints, including gouty arthritis, osteoarthritis, rheumatoid arthritis, osteoporosis, and periodontitis. Moreover, mesenchymal stem cells (MSCs) have been discovered to facilitate the inhibition of NLRP3 and maybe ideal for treating bone and joint diseases. In this review, we implicate the structure and activation of the NLRP3 inflammasome along with the detail on the involvement of NLRP3 inflammasome in bone and joint diseases pathology. In addition, we focused on MSCs and MSC-extracellular vesicles targeting NLRP3 inflammasomes in bone and joint diseases. Finally, the existing problems and future direction are also discussed.

Innate immune sensing of cell death in disease and therapeutics

Innate immunity, cell death and inflammation underpin many aspects of health and disease. Upon sensing pathogens, pathogen-associated molecular patterns or damage-associated molecular patterns, the innate immune system activates lytic, inflammatory cell death, such as pyroptosis and PANoptosis. These genetically defined, regulated cell death pathways not only contribute to the host defence against infectious disease, but also promote pathological manifestations leading to cancer and inflammatory diseases. Our understanding of the underlying mechanisms has grown rapidly in recent years. However, how dying cells, cell corpses and their liberated cytokines, chemokines and inflammatory signalling molecules are further sensed by innate immune cells, and their contribution to further amplify inflammation, trigger antigen presentation and activate adaptive immunity, is less clear. Here, we discuss how pattern-recognition and PANoptosome sensors in innate immune cells recognize and respond to cell-death signatures. We also highlight molecular targets of the innate immune response for potential therapeutic development.

Britannilactone 1-O-acetate induced ubiquitination of NLRP3 inflammasome through TRIM31 as a protective mechanism against reflux esophagitis-induced esophageal injury

BACKGROUND

Reflux esophagitis (RE) is a disease in which inflammation of the esophageal mucosa owing to the reflux of gastric contents into the esophagus results in cytokine damage. Britannilactone 1-O-acetate (Brt) has anti-inflammatory effects, significantly inhibiting the activation of the NLRP3 inflammasome, leading to a decrease in inflammatory factors including IL-1 β, IL-6, and TNF-α. However, the mechanism underlying its protective effect against RE-induced esophageal injury remains unclear. In the present study, we investigated the protective mechanism of TRIM31 against NLRP3 ubiquitination-induced RE both in vivo and in vitro.

METHODS

A model of RE was established in vivo in rats by the method of "4.2 mm pyloric clamp + 2/3 fundoplication". In vitro, the mod was constructed by using HET-1A (esophageal epithelial cells) and exposing the cells to acid, bile salts, and acidic bile salts. The 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay was used to screen the concentration of administered drugs, and the viability of HET-1A cells in each group. HE staining was used to assess the degree of pathological damage in esophageal tissues. Toluidine blue staining was used to detect whether the protective function of the esophageal epithelial barrier was damaged and restored. The enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of IL-1 β, IL-6, and TNF-α factors in serum. Immunohistochemistry (IHC) was used to detect the expression level of NLRP3 in esophageal tissues. The molecular docking and Co-immunoprecipitation assay (Co-IP assay) were used to detect the TRIM31 interacts with NLRP3. Western blotting detected the Claudin-4, Claudin-5, The G-protein-coupled receptor calcium-sensitive receptor (CaSR), NLRP3, TRIM31, ASC, C-Caspase1, and Caspase1 protein expression levels.

RESULTS

Brt could alleviate RE inflammatory responses by modulating serum levels of IL-1 β, IL-6, and TNF-α. It also activated the expression of NLRP3, ASC, Caspase 1, and C-Caspase-1 in HET-1A cells. Brt also attenuated TRIM31/NLRP3-induced pathological injury in rats with RE through a molecular mechanism consistent with the in vitro results.

CONCLUSIONS

Brt promotes the ubiquitination of NLRP3 through TRIM31 and attenuates esophageal epithelial damage induced by RE caused by acidic bile salt exposure. This study provides valuable insights into the mechanism of action of Brt in the treatment of RE and highlights its promising application in the prevention of NLRP3 inflammatory vesicle-associated inflammatory pathological injury.

Inflammatory aspects of Alzheimer's disease

Alzheimer´s disease (AD) stands out as the most common chronic neurodegenerative disorder. AD is characterized by progressive cognitive decline and memory loss, with neurodegeneration as its primary pathological feature. The role of neuroinflammation in the disease course has become a focus of intense research. While microglia, the brain's resident macrophages, have been pivotal to study central immune inflammation, recent evidence underscores the contributions of other cellular entities to the neuroinflammatory process. In this article, we review the inflammatory role of microglia and astrocytes, focusing on their interactions with AD's core pathologies, amyloid beta deposition, and tau tangle formation. Additionally, we also discuss how different modes of regulated cell death in AD may impact the chronic neuroinflammatory environment. This review aims to highlight the evolving landscape of neuroinflammatory research in AD and underscores the importance of considering multiple cellular contributors when developing new therapeutic strategies.

Hua-Shi-Bai-Du decoction inactivates NLRP3 inflammasome through inhibiting PDE4B in macrophages and ameliorates mouse acute lung injury

BACKGROUND

Hua-Shi-Bai-Du decoction (HSBD) exerts significant effects on the prevention and treatment of COVID-19 in China. The activation of the NLRP3 inflammasome of macrophages plays a vital role in COVID-19 pathology. However, no previous studies have focused on this pathological process to explore the effect of HSBD.

PURPOSE

Our aim is to uncover the effect of HSBD on NLRP3 inflammasome activation and the underlying mechanisms.

METHODS

The NLRP3-activated J774A.1 cells primed by LPS and activated by nigericin/ATP/MSU were used to evaluate NLRP3 activation in vitro. ASC oligomerization and speck formation were assessed by western blot and immunofluorescence imaging. Intracellular K+ levels were determined by the colorimetric assay. Mitochondrial ROS (mtROS) level was detected by the flow cytometry and the fluorescence spectrophotometry. The intracellular cAMP level was determined by chemiluminescence method and ELISA, while phosphodiesterase (PDE) activity was measured using the fluorescent substrate MANT-cAMP. siRNA was applied to knockdown PDE4B. Two in vivo mouse models, MSU-induced peritonitis and LPS-induced acute lung injury (ALI), were used to evaluate the effects of HSBD on IL-1β and other inflammatory cytokines. Pathological changes in lung tissue were observed by histopathological examination.

RESULTS

HSBD not only decreased supernatant IL-1β, caspase-1 p20, and cleaved gasdermin D (GSDMD) in NLRP3-activated J774A.1 cells, but also reduced IL-1β in the peritoneal lavage fluid of mice with MSU-induced peritonitis, demonstrating the suppressive effect on NLRP3 inflammasome activation. The mechanism study showed that HSBD blocked ASC oligomerization and speck formation without affecting K+ efflux or mtROS production. Furthermore, it prevented the decrease of intracellular cAMP by inhibiting PDE4B activity. And in the PDE4B-deficient cells, its suppressive effect on IL-1β release was abolished. In LPS-induced ALI mice, oral administration of HSBD decreased several proinflammatory cytokines (IL-1β, IL-6, TNF-α, and CXCL-1) and attenuated the pathological damage to the lung.

CONCLUSION

HSBD suppresses the activation of NLRP3 inflammasome by inhibiting PDE4B activity to counteract the decrease of intracellular cAMP, thereby blocking ASC oligomerization in macrophages. Our findings may provide new insight into the clinical effets of HSBD for the treatment of COVID-19.

NLRP3 Inflammasomes: Dual Function in Infectious Diseases

The Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome has been the most distinctive polymer protein complex. After recognizing the endogenous and exogenous danger signals, NLRP3 can cause inflammation by pyroptosis and secretion of mature, bioactive forms of IL-1β and IL-18. The NLRP3 inflammasome is essential in the genesis and progression of infectious illnesses. Herein, we provide a comprehensive review of the NLRP3 inflammasome in infectious diseases, focusing on its two-sided effects. As an essential part of host defense with a protective impact, abnormal NLRP3 inflammasome activation, however, result in a systemic high inflammatory response, leading to subsequent damage. In addition, scientific evidence of small molecules, biologics, and phytochemicals acting on the NLRP3 inflammasome has been reviewed. We believe that the NLRP3 inflammasome helps us understand the pathological mechanism of different stages of infectious diseases and that inhibitors targeting the NLRP3 inflammasome will become a new and valuable research direction for the treatment of infectious diseases.

No Time to Die: How Cytomegaloviruses Suppress Apoptosis, Necroptosis, and Pyroptosis

Viruses are obligate intracellular pathogens as their replication depends on the metabolism of the host cell. The induction of cellular suicide, known as programmed cell death (PCD), has the potential to hinder viral replication and act as a first line of defense against viral pathogens. Apoptosis, necroptosis, and pyroptosis are three important PCD modalities. Different signaling pathways are involved in their execution, and they also differ in their ability to cause inflammation. Cytomegaloviruses (CMV), beta-herpesviruses with large double-stranded DNA genomes, encode a great variety of immune evasion genes, including several cell death suppressors. While CMV inhibitors of apoptosis and necroptosis have been known and studied for years, the first pyroptosis inhibitor has been identified and characterized only recently. Here, we describe how human and murine CMV interfere with apoptosis, necroptosis, and pyroptosis signaling pathways. We also discuss the importance of the different PCD forms and their viral inhibitors for the containment of viral replication and spread in vivo.

Angiogenin-mediated tsRNAs control inflammation and metabolic disorder by regulating NLRP3 inflammasome

The cellular stress response system in immune cells plays a crucial role in regulating the development of inflammatory diseases. In response to cellular damage or microbial infection, the assembly of the NLRP3 inflammasome induces pyroptosis and the release of inflammatory cytokines. Meanwhile, Angiogenin (Ang)-mediated transfer RNA-derived small RNAs (tsRNAs) promote cell survival under stressful conditions. While both tsRNAs and inflammasomes are induced under stress conditions, the interplay between these two systems and their implications in regulating inflammatory diseases remains poorly understood. In this study, it was demonstrated that Ang deficiency exacerbated sodium arsenite-induced activation of NLRP3 inflammasome and pyroptosis. Moreover, Ang-induced 5'-tsRNAs inhibited NLRP3 inflammasome activation and pyroptosis. Mechanistically, 5'-tsRNAs recruit DDX3X protein into stress granules (SGs), consequently inhibiting the interaction between DDX3X and NLRP3, thus leading to the suppression of NLRP3 inflammasome activation. Furthermore, in vivo results showed that Ang deficiency led to the downregulation of tsRNAs, ultimately leading to an exacerbation of NLRP3 inflammasome-dependent inflammation, including lipopolysaccharide-induced systemic inflammation and type-2 diabetes-related inflammation. Altogether, our study sheds a new light on the role of Ang-induced 5'-tsRNAs in regulating NLRP3 inflammasome activation via SGs, and highlights tsRNAs as a promising target for the treatment of NLRP3 inflammasome-related diseases.

Tryptanthrin suppresses multiple inflammasome activation to regulate NASH progression by targeting ASC protein

BACKGROUND

The adaptor protein apoptosis-associated speck-like protein (ASC) containing a caspase recruitment domain (CARD) can be activated through pyrin domain (PYD) interactions between sensors and ASC, and through CARD interactions between caspase-1 and ASC. Although the majority of ternary inflammasome complexes depend on ASC, drugs targeting ASC protein remain scarce. After screening natural compounds from Isatidis Radixin, we found that tryptanthrin (TPR) could inhibit NLRP3-induced IL-1β and caspase-1 production, but the underlying anti-inflammatory mechanisms remain to be elucidated.

PURPOSE

The purpose of this study was to determine the impact of TPR on the NLRP3, NLRC4, and AIM2 inflammasomes and the underlying mechanisms. Additionally, the efficacy of TPR was analysed in the further course of methionine- and choline-deficient (MCD)-induced NASH and lipopolysaccharide (LPS)-induced sepsis models of mice.

METHODS

In vitro studies used bone marrow-derived macrophages to assess the anti-inflammatory activity of TPR, and the techniques included western blot, testing of intracellular K+ and Ca2+, immunofluorescence, enzyme-linked immunosorbent assay (ELISA), co-immunoprecipitation, ASC oligomerization assay, surface plasmon resonance (SPR), and molecular docking. We used LPS-induced sepsis models and MCD-induced NASH models in vivo to evaluate the effectiveness of TPR in inhibiting inflammatory diseases.

RESULTS

Our observations suggested that TPR could inhibit NLRP3, NLRC4, and AIM2 inflammasome activation. As shown in a mouse model of inflammatory diseases caused by MCD-induced NASH and LPS-induced sepsis, TPR significantly alleviated the progression of diseases. TPR interrupted the interactions between ASC and NLRP3/NLRC4/AIM2 in the co-immunoprecipitation experiment, and stable binding of TPR to ASC was also evident in SPR experiments. The underlying mechanisms of anti-inflammatory activities of TPR might be associated with targeting ASC, in particular, PYD domain of ASC.

CONCLUSION

In general, the requirement for ASC in multiple inflammasome complexes makes TPR, as a novel broad-spectrum inflammasome inhibitor, potentially useful for treating a wide range of multifactorial inflammasome-related diseases.

NLRP3 inflammasome in atherosclerosis: Mechanisms and targeted therapies

Atherosclerosis (AS) is the primary pathology behind various cardiovascular diseases and the leading cause of death and disability globally. Recent evidence suggests that AS is a chronic vascular inflammatory disease caused by multiple factors. In this context, the NLRP3 inflammasome, acting as a signal transducer of the immune system, plays a critical role in the onset and progression of AS. The NLRP3 inflammasome is involved in endothelial injury, foam cell formation, and pyroptosis in AS. Therefore, targeting the NLRP3 inflammasome offers a new treatment strategy for AS. This review highlights the latest insights into AS pathogenesis and the pharmacological therapies targeting the NLRP3 inflammasome, focusing on optimal targets for small molecule inhibitors. These insights are valuable for rational drug design and the pharmacological assessment of new targeted NLRP3 inflammasome inhibitors in treating AS.

Emerging insights into the role of NLRP3 inflammasome and endoplasmic reticulum stress in renal diseases

NLRP3 inflammasome is a key component of the innate immune system, mediating the activation of caspase-1, and the maturity and secretion of the pro-inflammatory cytokine interleukin (IL)-1beta (IL-1β) and IL-18 to cope with microbial infections and cell injury. The NLRP3 inflammasome is activated by various endogenous danger signals, microorganisms and environmental stimuli, including urate, extracellular adenosine triphosphate (ATP) and cholesterol crystals. Increasing evidence indicates that the abnormal activation of NLRP3 is involved in multiple diseases including renal diseases. Hence, clarifying the mechanism of action of NLRP3 inflammasome in different diseases can help prevent and treat various diseases. Endoplasmic reticulum (ER) is an important organelle which participates in cell homeostasis maintenance and protein quality control. The unfolded protein response (UPR) and ER stress are caused by the excessive accumulation of unfolded or misfolded proteins in ER to recover ER homeostasis. Many factors can cause ER stress, including inflammation, hypoxia, environmental toxins, viral infections, glucose deficiency, changes in Ca2+ level and oxidative stress. The dysfunction of ER stress participates in multiple diseases, such as renal diseases. Many previous studies have shown that NLRP3 inflammasome and ER stress play an important role in renal diseases. However, the relevant mechanisms are not yet fully clear. Herein, we focus on the current understanding of the role and mechanism of ER stress and NLRP3 inflammasome in renal diseases, hoping to provide theoretical references for future related researches.

Screening NLRP3 drug candidates in clinical development: lessons from existing and emerging technologies

Decades of evidence positioned IL-1β as a master regulatory cytokine in acute and chronic inflammatory diseases. Approved biologics aimed at inhibiting IL-1 signaling have shown efficacy but variable safety. More recently, targeting NLRP3 activation, an upstream mediator of IL-1β, has garnered the most attention. Aberrant NLRP3 activation has been demonstrated to participate in the progression of several pathological conditions from neurogenerative diseases to cardio-metabolic syndromes and cancer. Pharmacological and genetic strategies aimed to limit NLRP3 function have proven effective in many preclinical models of diseases. These evidences have lead to a significant effort in the generation and clinical testing of small orally active molecules that can target NLRP3. In this report, we discuss different properties of these molecules with translational potential and describe the technologies currently available to screen NLRP3 targeting molecules highlighting advantages and limitations of each method.

Unraveling the role of NLRP3 inflammasome in allergic inflammation: implications for novel therapies

Allergic diseases like asthma, allergic rhinitis and dermatitis pose a significant global health burden, driving the search for novel therapies. The NLRP3 inflammasome, a key component of the innate immune system, is implicated in various inflammatory diseases. Upon exposure to allergens, NLRP3 undergoes a two-step activation process (priming and assembly) to form active inflammasomes. These inflammasomes trigger caspase-1 activation, leading to the cleavage of pro-inflammatory cytokines (IL-1β and IL-18) and GSDMD. This process induces pyroptosis and amplifies inflammation. Recent studies in humans and mice strongly suggest a link between the NLRP3 inflammasome, IL-1β, and IL-18, and the development of allergic diseases. However, further research is needed to fully understand NLRP3's specific mechanisms in allergies. This review aims to summarize the latest advances in NLRP3 activation and regulation. We will discuss small molecule drugs and natural products targeting NLRP3 as potential therapeutic strategies for allergic diseases.

The impact of AIM2 inflammasome-induced pyroptosis on acute gouty arthritis and asymptomatic hyperuricemia patients

Objective

This study aimed to evaluate the role of absent in melanoma 2 (AIM2) inflammasome-mediated pyroptosis in the pathogenesis of acute gouty arthritis (AGA) and asymptomatic hyperuricemia(AHU).

Methods

A cohort of 30 AGA patients, 30 AHU individuals, and 30 healthy controls (HC) was assembled. Demographic and biochemical data, along with blood samples, were collected. Serum double-stranded DNA (dsDNA) levels were quantified using a fluorescent assay. Transcriptomic and proteomic analysis of AIM2, Caspase-1, GSDMD, IL-1β, and IL-18 in peripheral blood mononuclear cells was performed using qRT-PCR and Western blot. Enzyme-linked immunosorbent assay (ELISA) was employed to measure serum IL-1β and IL-18. Spearman correlation analysis was utilized to assess relationships between variables.

Results

Both AGA and AHU groups demonstrated elevated metabolic indicators and serum levels of dsDNA, IL-1β, and IL-18 compared to the HC group. AGA patients exhibited higher inflammatory markers than the AHU group. In the AGA group, there was a significant increase in the mRNA and protein levels of AIM2, Caspase-1, GSDMD, IL-1β, and IL-18 (P<0.05 to P<0.001). The AHU group showed higher AIM2, Caspase-1, GSDMD, and IL-18 mRNA levels than the HC group (P<0.001 to P<0.01), with a non-significant increase in AIM2, GSDMD, and IL-1β proteins (P>0.05). In contrast, Caspase-1 and IL-18 proteins were significantly higher in the AHU group (P<0.05). Notable correlations were observed between AIM2 protein expression and levels of Caspase-1 and GSDMD in both AGA and AHU groups. In the AGA group, AIM2 protein correlated with IL-1β, but not in the AHU group. The AIM2 protein in the AHU group was positively associated with IL-18, with no such correlation in the AGA group.

Conclusion

AIM2 inflammasome may play a role in the inflammatory processes of AGA and AHU and that its activation may be related to the pyroptosis pathway.

Ketone body metabolism and the NLRP3 inflammasome in Alzheimer's disease

Alzheimer's disease (AD) is a degenerative brain disorder and the most common form of dementia. AD pathology is characterized by senile plaques and neurofibrillary tangles (NFTs) composed of amyloid-β (Aβ) and hyperphosphorylated tau, respectively. Neuroinflammation has been shown to drive Aβ and tau pathology, with evidence suggesting the nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome as a key pathway in AD pathogenesis. NLRP3 inflammasome activation in microglia, the primary immune effector cells of the brain, results in caspase-1 activation and secretion of IL-1β and IL-18. Recent studies have demonstrated a dramatic interplay between the metabolic state and effector functions of immune cells. Microglial metabolism in AD is of particular interest, as ketone bodies (acetone, acetoacetate (AcAc), and β-hydroxybutyrate (BHB)) serve as an alternative energy source when glucose utilization is compromised in the brain of patients with AD. Furthermore, reduced cerebral glucose metabolism concomitant with increased BHB levels has been demonstrated to inhibit NLRP3 inflammasome activation. Here, we review the role of the NLRP3 inflammasome and microglial ketone body metabolism in AD pathogenesis. We also highlight NLRP3 inflammasome inhibition by several ketone body therapies as a promising new treatment strategy for AD.

Structural transitions enable interleukin-18 maturation and signaling

Several interleukin-1 (IL-1) family members, including IL-1β and IL-18, require processing by inflammasome-associated caspases to unleash their activities. Here, we unveil, by cryoelectron microscopy (cryo-EM), two major conformations of the complex between caspase-1 and pro-IL-18. One conformation is similar to the complex of caspase-4 and pro-IL-18, with interactions at both the active site and an exosite (closed conformation), and the other only contains interactions at the active site (open conformation). Thus, pro-IL-18 recruitment and processing by caspase-1 is less dependent on the exosite than the active site, unlike caspase-4. Structure determination by nuclear magnetic resonance uncovers a compact fold of apo pro-IL-18, which is similar to caspase-1-bound pro-IL-18 but distinct from cleaved IL-18. Binding sites for IL-18 receptor and IL-18 binding protein are only formed upon conformational changes after pro-IL-18 cleavage. These studies show how pro-IL-18 is selected as a caspase-1 substrate, and why cleavage is necessary for its inflammatory activity.

Mechanistic insights from inflammasome structures

Inflammasomes are supramolecular complexes that form in the cytosol in response to pathogen-associated and damage-associated stimuli, as well as other danger signals that perturb cellular homoeostasis, resulting in host defence responses in the form of cytokine release and programmed cell death (pyroptosis). Inflammasome activity is closely associated with numerous human disorders, including rare genetic syndromes of autoinflammation, cardiovascular diseases, neurodegeneration and cancer. In recent years, a range of inflammasome components and their functions have been discovered, contributing to our knowledge of the overall machinery. Here, we review the latest advances in inflammasome biology from the perspective of structural and mechanistic studies. We focus on the most well-studied components of the canonical inflammasome - NAIP-NLRC4, NLRP3, NLRP1, CARD8 and caspase-1 - as well as caspase-4, caspase-5 and caspase-11 of the noncanonical inflammasome, and the inflammasome effectors GSDMD and NINJ1. These structural studies reveal important insights into how inflammasomes are assembled and regulated, and how they elicit the release of IL-1 family cytokines and induce membrane rupture in pyroptosis.

GLUT1 Promotes NLRP3 Inflammasome Activation of Airway Epithelium in Lipopolysaccharide-Induced Acute Lung Injury

Acute lung injury (ALI) is a devastating clinical syndrome caused by different factors, with high morbidity and mortality. Lung injury and inflammation caused by lipopolysaccharide (LPS) can be modulated by NLRP3 inflammasome activation, yet its exact function within the airway epithelium is still unknown. Meanwhile, glucose transporter protein 1 (GLUT1) contributes to a number of inflammatory illnesses, including ALI. The present study aimed to assess GLUT1's function in NLRP3 inflammasome activation of airway epithelium in LPS-induced acute lung injury. BALB/c mice and BEAS-2B cells were exposed to LPS (5 mg/kg and 200 μg/mL, respectively), with or without GLUT1 antagonists (WZB117 or BAY876). LPS up-regulated pulmonary expression of NLRP3 and GLUT1 in mice, which could be blocked by WZB117 or BAY876. Pharmacological inhibition of GLUT1 in vivo significantly attenuated lung tissue damage, neutrophil accumulation, and proinflammatory factors release (TNF-α, IL-6, and IL-1β) in LPS-exposed mice. Meanwhile, the activation markers of NLRP3 inflammasome (ASC, caspase-1, IL-1β, and IL-18) induced by LPS were also suppressed. In cultured BEAS-2B cells, LPS induced an increase in GLUT1 expression and triggered activation of the NLRP3 inflammasome, both of which were inhibited by GLUT1 antagonists. These results illustrate that GLUT1 participates in LPS-induced ALI and promotes the activation of the NLRP3 inflammasome in airway epithelial cells.

Enzymatic control of intermolecular interactions for generating synthetic nanoarchitectures in cellular environment

Nanoarchitectonics, as a technology to arrange nano-sized structural units such as molecules in a desired configuration, requires nano-organization, which usually relies on intermolecular interactions. This review briefly introduces the development of using enzymatic reactions to control intermolecular interactions for generating artificial nanoarchitectures in a cellular environment. We begin the discussion with the early examples and uniqueness of enzymatically controlled self-assembly. Then, we describe examples of generating intracellular nanostructures and their relevant applications. Subsequently, we discuss cases of forming nanostructures on the cell surface via enzymatic reactions. Following that, we highlight the use of enzymatic reactions for creating intercellular nanostructures. Finally, we provide a summary and outlook on the promises and future direction of this strategy. Our aim is to give an updated introduction to the use of enzymatic reaction in regulating intermolecular interactions, a phenomenon ubiquitous in biology but relatively less explored by chemists and materials scientists. Our goal is to stimulate new developments in this simple and versatile approach for addressing societal needs.

Discovery and Development of NLRP3 Inhibitors Targeting the LRR Domain to Disrupt NLRP3-NEK7 Interaction for the Treatment of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease. Targeting NLRP3 inflammasome, specifically its interaction with NEK7 via the LRR domain of NLRP3, is a promising therapeutic strategy. Our research aimed to disrupt this interaction by focusing on the LRR domain. Through virtual screening, we identified five compounds with potent anti-inflammatory effects and ideal LRR binding affinity. Lead compound C878-1943 underwent structural optimization, yielding pyridoimidazole derivatives with different anti-inflammatory activities. Compound I-19 from the initial series effectively inhibited caspase-1 and IL-1β release in an adjuvant-induced arthritis (AIA) rat model, significantly reducing joint swelling and spleen/thymus indices. To further enhance potency and extend in vivo half-life, a second series including II-8 was developed, demonstrating superior efficacy and longer half-life. Both I-19 and II-8 bind to the LRR domain, inhibiting NLRP3 inflammasome activation. These findings introduce novel small molecule inhibitors targeting the LRR domain of NLRP3 protein and disrupt NLRP3-NEK7 interaction, offering a novel approach for RA treatment.

Exploring Scopoletin's Therapeutic Efficacy in DSS-Induced Ulcerative Colitis: Insights into Inflammatory Pathways, Immune Modulation, and Microbial Dynamics

This study aimed to investigate the therapeutic potential of scopoletin in ulcerative colitis, with a primary focus on its impact on crucial inflammatory pathways and immune responses. A male mouse model of DSS-induced colitis was employed with six distinct groups: a control group, a group subjected to DSS only, three groups treated with varying scopoletin doses, and the final group treated with dexamethasone. The investigation included an assessment of the effects of scopoletin on colitis symptoms, including alterations in body weight, Disease Activity Index (DAI), and histopathological changes in colonic tissue. Furthermore, this study scrutinized the influence of scopoletin on cytokine production, PPARγ and NF-κB expression, NLRP3 inflammasome, and the composition of intestinal bacteria. Scopoletin treatment yielded noteworthy improvements in DSS-induced colitis in mice, as evidenced by reduced weight loss and colonic shortening (p < 0.05, < 0.01, respectively). It effectively diminished TNF-α, IL-1β, and IL-12 cytokine levels (p < 0.01, p < 0.05), attenuated NLRP3 inflammasome activation and the associated cytokine release (p < 0.05, p < 0.01), and modulated the immune response by elevating PPARγ expression while suppressing NF-κB pathway activation (p < 0.05, p < 0.01). Additionally, scopoletin induced alterations in the gut microbiota composition, augmenting beneficial Lactobacillus and Bifidobacteria while reducing E. coli (p < 0.05). It also enhanced tight junction proteins, signifying an improvement in the intestinal barrier integrity (p < 0.05, < 0.01). Scopoletin is a promising therapeutic agent for managing ulcerative colitis, showing benefits that extend beyond mere anti-inflammatory actions to encompass regulatory effects on gut microbiota and restoration of intestinal integrity.

Acute Lung Injury and the NLRP3 Inflammasome

Acute lung injury (ALI) manifests through harm to the capillary endothelium and alveolar epithelial cells, arising from a multitude of factors, leading to scattered interstitial alterations, pulmonary edema, and subsequent acute hypoxic respiratory insufficiency. Acute lung injury (ALI), along with its more serious counterpart, acute respiratory distress syndrome (ARDS), carry a fatality rate that hovers around 30-40%. Its principal pathological characteristic lies in the unchecked inflammatory reaction. Currently, the main strategies for treating ALI are alleviation of inflammation and prevention of respiratory failure. Concerning the etiology of ALI, NLRP3 Inflammasome is essential to the body's innate immune response. The composition of this inflammasome complex includes NLRP3, the pyroptosis mediator ASC, and pro-caspase-1. Recent research has reported that the inflammatory response centered on NLRP3 inflammasomes plays a key part in inflammation in ALI, and may hence be a prospective candidate for therapeutic intervention. In the review, we present an overview of the ailment characteristics of acute lung injury along with the constitution and operation of the NLRP3 inflammasome within this framework. We also explore therapeutic strategies targeting the NLRP3 inflammasome to combat acute lung injury.

Pyroptosis: A spoiler of peaceful coexistence between cells in degenerative bone and joint diseases

BACKGROUND

As people age, degenerative bone and joint diseases (DBJDs) become more prevalent. When middle-aged and elderly people are diagnosed with one or more disorders such as osteoporosis (OP), osteoarthritis (OA), and intervertebral disc degeneration (IVDD), it often signals the onset of prolonged pain and reduced functionality. Chronic inflammation has been identified as the underlying cause of various degenerative diseases, including DBJDs. Recently, excessive activation of pyroptosis, a form of programed cell death (PCD) mediated by inflammasomes, has emerged as a primary driver of harmful chronic inflammation. Consequently, pyroptosis has become a potential target for preventing and treating DBJDs.

AIM OF REVIEW

This review explored the physiological and pathological roles of the pyroptosis pathway in bone and joint development and its relation to DBJDs. Meanwhile, it elaborated the molecular mechanisms of pyroptosis within individual cell types in the bone marrow and joints, as well as the interplay among different cell types in the context of DBJDs. Furthermore, this review presented the latest compelling evidence supporting the idea of regulating the pyroptosis pathway for DBJDs treatment, and discussed the potential, limitations, and challenges of various therapeutic strategies involving pyroptosis regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In summary, an interesting identity for the unregulated pyroptosis pathway in the context of DBJDs was proposed in this review, which was undertaken as a spoiler of peaceful coexistence between cells in a degenerative environment. Over the extended course of DBJDs, pyroptosis pathway perpetuated its activity through crosstalk among pyroptosis cascades in different cell types, thus exacerbating the inflammatory environment throughout the entire bone marrow and joint degeneration environment. Correspondingly, pyroptosis regulation therapy emerged as a promising option for clinical treatment of DBJDs.

Hit-to-Lead Optimization of the Natural Product Oridonin as Novel NLRP3 Inflammasome Inhibitors with Potent Anti-Inflammation Activity

Targeting NLRP3 inflammasome with inhibitors is a novel strategy for NLRP3-driven diseases. Herein, hit compound 5 possessing an attractive skeleton was identified from our in-house database of oridonin, and then a potential lead compound 32 was obtained by optimization of 5, displaying two-digit nanomolar inhibition on NLRP3. Moreover, compound 32 showed enhanced safety index (SI) relative to oridonin (IC50 = 77.2 vs 780.4 nM, SI = 40.5 vs 8.5) and functioned through blocking ASC oligomerization and interaction of NLRP3-ASC/NEK7, thereby suppressing NLRP3 inflammasome assembly and activation. Furthermore, diverse agonists-induced activations of NLRP3 could be impeded by compound 32 without altering NLRC4 or AIM2 inflammasome. Crucially, compound 32 possessed tolerable pharmaceutical properties and significant anti-inflammatory activity in MSU-induced gouty arthritis model. Therefore, this work enriched the SAR of NLRP3 inflammasome inhibitors and provided a potential candidate for the treatment of NLRP3-associated diseases.

Dicoumarol attenuates NLRP3 inflammasome activation to inhibit inflammation and fibrosis in knee osteoarthritis

Knee osteoarthritis (KOA) is a major cause of disability in elderly individuals. Dicoumarol is a coumarin‑like compound derived from sweet clover [Melilotus officinalis (L.) Pall]. It has been suggested that dicoumarol exhibits various types of pharmacological activities, including anticoagulant, antitumor and antibacterial effects. Due to its various biological activities, dicoumarol has a potential protective effect against OA. Therefore, the present study aimed to assess the effects of dicoumarol on knee osteoarthritis. In the present study, dicoumarol was found to protect rat synoviocytes from lipopolysaccharide (LPS)‑induced cell apoptosis. Western blot analysis showed that dicoumarol significantly reduced the protein expression levels of fibrosis‑related markers and inflammatory cytokines (Tgfb, Timp, Col1a, Il1b and Il18). The inhibitory rates of these proteins were all >50% (P<0.01) compared with those in the LPS and ATP‑induced group. Consistently, the mRNA expression levels of these markers and cytokines were decreased to normal levels by dicoumarol after the treatment of rat synovial fibroblasts with LPS and ATP. Mechanistic studies demonstrated that dicoumarol did not affect NF‑κB signaling, but it did directly interact with NOD‑like receptor protein 3 (NLRP3) to promote its protein degradation, which could be reversed by MG132, but not NH4Cl. The protein half‑life of NLRP3 was accelerated from 26.1 to 4.3 h by dicoumarol. Subsequently, dicoumarol could alleviate KOA in vivo; knee joint diameter was decreased from 11.03 to 9.93 mm. Furthermore, the inflammation and fibrosis of the knee joints were inhibited in rats. In conclusion, the present findings demonstrated that dicoumarol could impede the progression of KOA by inhibiting NLRP3 activation, providing a potential treatment strategy for KOA.

Early signaling pathways in virus-infected cells

Virus infection activates specific pattern recognition receptors and immune signal transduction, resulting in pro-inflammatory cytokine production and activation of innate immunity. We describe here the molecular organization of early signaling pathways downstream of viral recognition, including conformational changes, post-translational modifications, formation of oligomers, and generation of small-molecule second messengers. Such molecular organization allows tight regulation of immune signal transduction, characterized by swift but transient responses, nonlinearity, and signal amplification. Pathologies of early immune signaling caused by genomic mutations illustrate the fine regulation of the immune transduction cascade.

Liquid-liquid phase separation in innate immunity

Intrinsic and innate immune responses are essential lines of defense in the body's constant surveillance of pathogens. The discovery of liquid-liquid phase separation (LLPS) as a key regulator of this primal response to infection brings an updated perspective to our understanding of cellular defense mechanisms. Here, we review the emerging multifaceted role of LLPS in diverse aspects of mammalian innate immunity, including DNA and RNA sensing and inflammasome activity. We discuss the intricate regulation of LLPS by post-translational modifications (PTMs), and the subversive tactics used by viruses to antagonize LLPS. This Review, therefore, underscores the significance of LLPS as a regulatory node that offers rapid and plastic control over host immune signaling, representing a promising target for future therapeutic strategies.

Reynosin protects neuronal cells from microglial neuroinflammation by suppressing NLRP3 inflammasome activation mediated by NADPH oxidase

Neuroinflammation, mediated by the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing-3 (NLRP3) inflammasome, is a significant contributor to the pathogenesis of neurodegenerative diseases (NDDs). Reynosin, a natural sesquiterpene lactone (SL), exhibits a broad spectrum of pharmacological effects, suggesting its potential therapeutic value. However, the effects and mechanism of reynosin on neuroinflammation remain elusive. The current study explores the effects and mechanisms of reynosin on neuroinflammation using mice and BV-2 microglial cells treated with lipopolysaccharide (LPS). Our findings reveal that reynosin effectively reduces microglial inflammation in vitro, as demonstrated by decreased CD11b expression and lowered interleukin-1 beta (IL-1β) and interleukin-18 (IL-18) mRNA and protein levels. Correspondingly, in vivo, results showed a reduction in the number of Iba-1 positive cells and alleviation of morphological alterations, alongside decreased expressions of IL-1β and IL-18. Further analysis indicates that reynosin inhibits NLRP3 inflammasome activation, evidenced by reduced transcription of NLRP3 and caspase-1, diminished NLRP3 protein expression, inhibited apoptosis-associated speck-like protein containing a CARD (ASC) oligomerization, and decreased caspase-1 self-cleavage. Additionally, reynosin curtailed the activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, demonstrated by reduced NADP+ and NADPH levels, downregulation of gp91phox mRNA, protein expression, suppression of p47phox expression and translocation to the membrane. Moreover, reynosin exhibited a neuroprotective effect against microglial inflammation in vivo and in vitro. These collective findings underscore reynosin's capacity to mitigate microglial inflammation by inhibiting the NLRP3 inflammasome, thus highlighting its potential as a therapeutic agent for managing neuroinflammation.

Exploring the therapeutic potential of Anastatica hierochuntica essential oil in DSS-induced colitis

The aim of this investigation was to explore the protective impacts and mechanisms of Anastatica hierochuntica essential oil (EOAH) against dextran sulfate sodium (DSS)-induced experimental colitis in mice. EOAH demonstrated a reduction in DSS-induced body weight decline, disease activity index (DAI), colon length reduction, colonic tissue damage, and myeloperoxidase (MPO) activity. The essential oil significantly mitigated the production of pro-inflammatory agents including TNF-α, IL-1β, and IL-12. Further analysis revealed that EOAH's anti-inflammatory effects involved the regulation of NF-κB and PPARγ pathways, as well as the inhibition of NLRP3 activation in colitis mice. Notably, EOAH treatment elevated the levels of beneficial commensal bacteria such as Lactobacillus and Bifidobacteria, while reducing Escherichia coli levels in the mice's feces. In addition, EOAH restored the expression of occludin and ZO-1 proteins in colonic tissues affected by ulcerative colitis (UC). These findings indicate that supplementing with EOAH might offer a novel therapeutic approach for UC prevention.

Role of pattern recognition receptors in the development of MASLD and potential therapeutic applications

Metabolic dysfunction-associated steatotic liver disease (MASLD) has become one of the most prevalent liver diseases worldwide, and its occurrence is strongly associated with obesity, insulin resistance (IR), genetics, and metabolic stress. Ranging from simple fatty liver to metabolic dysfunction-associated steatohepatitis (MASH), even to severe complications such as liver fibrosis and advanced cirrhosis or hepatocellular carcinoma, the underlying mechanisms of MASLD progression are complex and involve multiple cellular mediators and related signaling pathways. Pattern recognition receptors (PRRs) from the innate immune system, including Toll-like receptors (TLRs), C-type lectin receptors (CLRs), NOD-like receptors (NLRs), RIG-like receptors (RLRs), and DNA receptors, have been demonstrated to potentially contribute to the pathogenesis for MASLD. Their signaling pathways can induce inflammation, mediate oxidative stress, and affect the gut microbiota balance, ultimately resulting in hepatic steatosis, inflammatory injury and fibrosis. Here we review the available literature regarding the involvement of PRR-associated signals in the pathogenic and clinical features of MASLD, in vitro and in animal models of MASLD. We also discuss the emerging targets from PRRs for drug developments that involved agent therapies intended to arrest or reverse disease progression, thus enabling the refinement of therapeutic targets that can accelerate drug development.

NLRP3 inflammasome and its role in autoimmune diseases: A promising therapeutic target

The NOD-like receptor protein 3 (NLRP3) inflammasome is a protein complex that regulates innate immune responses by activating caspase-1 and the inflammatory cytokines IL-1β and IL-18. Numerous studies have highlighted its crucial role in the pathogenesis and development of inflammatory bowel disease, rheumatoid arthritis, systemic lupus erythematosus, autoimmune thyroid diseases, and other autoimmune diseases. Therefore, investigating the underlying mechanisms of NLRP3 in disease and targeted drug therapies holds clinical significance. This review summarizes the structure, assembly, and activation mechanisms of the NLRP3 inflammasome, focusing on its role and involvement in various autoimmune diseases. This review also identifies studies where the involvement of the NLRP3 inflammasome in the disease mechanism within the same disease appears contradictory, as well as differences in NLRP3-related gene polymorphisms among different ethnic groups. Additionally, the latest therapeutic advances in targeting the NLRP3 inflammasome for autoimmune diseases are outlined, and novel clinical perspectives are discussed. Conclusively, this review provides a consolidated source of information on the NLRP3 inflammasome and may guide future research efforts that have the potential to positively impact patient outcomes.

Release of damaged mitochondrial DNA: A novel factor in stimulating inflammatory response

Mitochondrial DNA (mtDNA) is a circular double-stranded genome that exists independently of the nucleus. In recent years, research on mtDNA has significantly increased, leading to a gradual increase in understanding of its physiological and pathological characteristics. Reactive oxygen species (ROS) and other factors can damage mtDNA. This damaged mtDNA can escape from the mitochondria to the cytoplasm or extracellular space, subsequently activating immune signaling pathways, such as NLR family pyrin domain protein 3 (NLRP3), and triggering inflammatory responses. Numerous studies have demonstrated the involvement of mtDNA damage and leakage in the pathological mechanisms underlying various diseases including infectious diseases, metabolic inflammation, and immune disorders. Consequently, comprehensive investigation of mtDNA can elucidate the pathological mechanisms underlying numerous diseases. The prevention of mtDNA damage and leakage has emerged as a novel approach to disease treatment, and mtDNA has emerged as a promising target for drug development. This article provides a comprehensive review of the mechanisms underlying mtDNA-induced inflammation, its association with various diseases, and the methods used for its detection.

HAX-1 interferes in assembly of NLRP3-ASC to block microglial pyroptosis in cerebral I/R injury

Acute cerebral ischemia has a high rate of disability and death. Although timely recanalization therapy may rescue the ischemic brain tissue, cerebral ischemia-reperfusion injury has been shown to limit the therapeutic effects of vascular recanalization. Protein HAX-1 has been reported as a pro-survival protein that plays an important role in various disorders, particularly in association with the nervous system. However, the effects and mechanisms of HAX-1 in cerebral IR injury have yet to be elucidated. So, we aimed to investigate the effect of HAX-1 on microglial pyroptosis and explore its potential neuroprotective effects in ischemia-reperfusion injury. Our results show that the expression of HAX-1 decreased after cerebral IR injury, accompanied by an increase in pyroptosis pathway activation. In addition, HAX-1 could inhibit microglial pyroptosis both in vivo and in vitro and reduce the release of inflammatory mediators. The above neuroprotective effects might be partially mediated by inhibiting of interaction of NLRP3 and ASC through competitive binding, followed by the attenuation of NLRP3 inflammasome formation. In conclusion, Our findings support that HAX-1 exhibits a protective role in cerebral I/R injury, and further study on HAX-1 expression regulation will contribute to cerebral infarction therapy.

Therapeutic potential of ginseng leaf extract in inhibiting mast cell-mediated allergic inflammation and atopic dermatitis-like skin inflammation in DNCB-treated mice

Ginseng leaves are known to contain high concentrations of bioactive compounds, such as ginsenosides, and have potential as a treatment for various conditions, including fungal infections, cancer, obesity, oxidative stress, and age-related diseases. This study assessed the impact of ginseng leaf extract (GLE) on mast cell-mediated allergic inflammation and atopic dermatitis (AD) in DNCB-treated mice. GLE reduced skin thickness and lymph node nodules and suppressed the expression and secretion of histamine and pro-inflammatory cytokines. It also significantly lowered the production of inflammatory response mediators including ROS, leukotriene C4 (LTC4), prostaglandin E2 (PGE2), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS). GLE inhibited the phosphorylation of MAPKs (ERK, P38, JNK) and the activation of NF-κB, which are both linked to inflammatory cytokine expression. We demonstrated that GLE's inhibitory effect on mast cell-mediated allergic inflammation is due to the blockade of the NF-κB and inflammasome pathways. Our findings suggest that GLE can be an effective therapeutic agent for mast-cell mediated and allergic inflammatory conditions.

SARS-CoV-2 ORF3a drives dynamic dense body formation for optimal viral infectivity

SARS-CoV-2 uses the double-membrane vesicles as replication organelles. However, how virion assembly occurs has not been fully understood. Here we identified a SARS-CoV-2-driven membrane structure named the 3a dense body (3DB). 3DBs have unusual electron-dense and dynamic inner structures, and their formation is driven by the accessory protein ORF3a via hijacking a specific subset of the trans-Golgi network (TGN) and early endosomal membranes. 3DB formation is conserved in related bat and pangolin coronaviruses yet lost during the evolution to SARS-CoV. 3DBs recruit the viral structural proteins spike (S) and membrane (M) and undergo dynamic fusion/fission to facilitate efficient virion assembly. A recombinant SARS-CoV-2 virus with an ORF3a mutant specifically defective in 3DB formation showed dramatically reduced infectivity for both extracellular and cell-associated virions. Our study uncovers the crucial role of 3DB in optimal SARS-CoV-2 infectivity and highlights its potential as a target for COVID-19 prophylactics and therapeutics.

Strategies of bacterial detection by inflammasomes

Mammalian innate immunity is regulated by pattern-recognition receptors (PRRs) and guard proteins, which use distinct strategies to detect infections. PRRs detect bacterial molecules directly, whereas guards detect host cell manipulations by microbial virulence factors. Despite sensing infection through different mechanisms, both classes of innate immune sensors can activate the inflammasome, an immune complex that can mediate cell death and inflammation. Inflammasome-mediated immune responses are crucial for host defense against many bacterial pathogens and prevent invasion by non-pathogenic organisms. In this review, we discuss the mechanisms by which inflammasomes are stimulated by PRRs and guards during bacterial infection, and the strategies used by virulent bacteria to evade inflammasome-mediated immunity.

A Perfect Storm: The Convergence of Aging, Human Immunodeficiency Virus Infection, and Inflammasome Dysregulation

The emergence of combination antiretroviral therapy (cART) has greatly transformed the life expectancy of people living with HIV (PWH). Today, over 76% of the individuals with HIV have access to this life-saving therapy. However, this progress has come with a new challenge: an increase in age-related non-AIDS conditions among patients with HIV. These conditions manifest earlier in PWH than in uninfected individuals, accelerating the aging process. Like PWH, the uninfected aging population experiences immunosenescence marked by an increased proinflammatory environment. This phenomenon is linked to chronic inflammation, driven in part by cellular structures called inflammasomes. Inflammatory signaling pathways activated by HIV-1 infection play a key role in inflammasome formation, suggesting a crucial link between HIV and a chronic inflammatory state. This review outlines the inflammatory processes triggered by HIV-1 infection and aging, with a focus on the inflammasomes. This review also explores current research regarding inflammasomes and potential strategies for targeting inflammasomes to mitigate inflammation. Further research on inflammasome signaling presents a unique opportunity to develop targeted interventions and innovative therapeutic modalities for combating HIV and aging-associated inflammatory processes.

Polysaccharides from an edible mushroom, Hericium erinaceus, alleviate ulcerative colitis in mice by inhibiting the NLRP3 inflammasomes and reestablish intestinal homeostasis

This study aimed to assess the effects of polysaccharides extracted from Hericium erinaceus fruiting bodies (HEFPs) on the inflammatory response to oxidative stress in a mouse model of ulcerative colitis (UC) induced by ingestion of dextran sodium sulfate. The results indicated reduced oxidative damage in the HEFPs groups, as evidenced by significantly decreased malondialdehyde levels and significantly increased levels of the antioxidant enzymes superoxide dismutase and catalase in colon homogenates, compared with those in the Model Control (MC) group. Additionally, compared with the levels in the MC group, the levels of the pro-inflammatory factors IL-6, IL-1β, and TNF-α in the positive-control (PC) and HEFPs groups were significantly lower, and that of the anti-inflammatory factor IL-10 was significantly higher. qRT-PCR analyses revealed that the colon expression patterns of IL-6, IL-1β, TNF-α, and IL-18 were consistent with the serum levels. Western-blotting results indicated significantly lower levels of NLRP3, ASC, and caspase 1 P20 in the HEFPs and PC groups than in the MC group. These findings suggest that HEFPs alleviate UC by suppressing the NLRP3 inflammasome/Caspase-1 pathway. Lachnospiraceae, Clostridiales, Parabacteroides, Oscillibacter, and Clostridium XlVa genera were more abundant in the gut microbiota of the HEFPs group than that of the MC group.

Fluorochrome-labeled inhibitors of caspase-1 require membrane permeabilization to efficiently access caspase-1 in macrophages

Caspase-1 location in cells has been studied with fluorochrome-labeled inhibitors of caspase-1 (FLICA reagents). We report that FLICA reagents have limited cell-membrane permeability. This impacts experimental design as cells with intact membranes, including caspase-1 knockout cells, are not appropriate controls for cells with inflammasome-induced gasdermin D membrane pores.

Transcutaneous vagus nerve stimulation modulates depression-like phenotype induced by high-fat diet via P2X7R/NLRP3/IL-1β in the prefrontal cortex

BACKGROUND

Depression is a common psychiatric disorder in diabetic patients. Depressive mood associated with obesity/metabolic disorders is related to the inflammatory response caused by long-term consumption of high-fat diets, but its molecular mechanism is unclear. In this study, we investigated whether the antidepressant effect of transcutaneous auricular vagus nerve stimulation (taVNS) in high-fat diet rats works through the P2X7R/NLRP3/IL-1β pathway.

METHODS

We first used 16S rRNA gene sequencing analysis and LC-MS metabolomics assays in Zucker diabetic fatty (ZDF) rats with long-term high-fat diet (Purina #5008) induced significant depression-like behaviors. Next, the forced swimming test (FST) and open field test (OFT) were measured to evaluate the antidepressive effect of taVNS. Immunofluorescence and western blotting (WB) were used to measure the microglia state and the expression of P2X7R, NLRP3, and IL-1β in PFC.

RESULTS

Purina#5008 diet induced significant depression-like behaviors in ZDF rats and was closely related to purine and inflammatory metabolites. Consecutive taVNS increased plasma insulin concentration, reduced glycated hemoglobin and glucagon content in ZDF rats, significantly improved the depressive-like phenotype in ZDF rats through reducing the microglia activity, and increased the expression of P2X7R, NLRP3, and IL-1β in the prefrontal cortex (PFC).

CONCLUSION

The P2X7R/NLRP3/IL-1β signaling pathway may play an important role in the antidepressant-like behavior of taVNS, which provides a promising mechanism for taVNS clinical treatment of diabetes combined with depression.