How location and cellular signaling combine to activate the NLRP3 inflammasome

Inhibition of the cGAS-STING pathway: contributing to the treatment of cerebral ischemia-reperfusion injury

The cGAS-STING pathway plays an important role in ischemia-reperfusion injury in the heart, liver, brain, and kidney, but its role and mechanisms in cerebral ischemia-reperfusion injury have not been systematically reviewed. Here, we outline the components of the cGAS-STING pathway and then analyze its role in autophagy, ferroptosis, cellular pyroptosis, disequilibrium of calcium homeostasis, inflammatory responses, disruption of the blood-brain barrier, microglia transformation, and complement system activation following cerebral ischemia-reperfusion injury. We further analyze the value of cGAS-STING pathway inhibitors in the treatment of cerebral ischemia-reperfusion injury and conclude that the pathway can regulate cerebral ischemia-reperfusion injury through multiple mechanisms. Inhibition of the cGAS-STING pathway may be helpful in the treatment of cerebral ischemia-reperfusion injury.

Immunomodulatory effect of lithium treatment on in vitro model of neuroinflammation

Bipolar disorder (BD) is psychiatric disorder of not fully acknowledged pathophysiology. Studies show the involvement of innate-immune system activation and inflammation in BD course and treatment efficiency. Microglia are crucial players in the inflammatory response possibly responsible for BD innate-immune activity. Lithium is a mood stabilizer used in treatment for 75 years. Immunomodulation was previously described as one of the potential modes of its action. We hypothesized that lithium might modulate the microglia response to innate-immune-associated cytokines (10 ng/mL TNF-α, 50 ng/mL IL-1β, 20 ng/mL IFN-γ). We aimed to investigate whether lithium treatment and pretreatment of microglia modify the expression of genes associated with NLRP3 inflammasome. We also aimed to verify lithium treatment effect on caspase activity and extracellular IL-1β concentration. For the first time, our study used human microglial cell line - HMC3, the cytokine stimuli and lithium in concentration corresponding to that in the brains of patients. To analyze lithium mode of action, we analyzed the short- and long-term treatment and pretreatment. To assess the influence on microglia responding to innate-immune cytokines, we analyzed the expression of genes involved in innate-immune and inflammasome (TSPO, TLR4, NFKB1, CASP1, CASP4, NLRP3, IL-1β, IL-6), caspase activity, extracellular IL-1β concentration, phospho-GSK-3β(Ser9) expression and lactate concentration. We found that lithium treatment significantly reduced NLRP3 inflammasome-related genes expression. We observed that lithium treatment reduces inflammasome activity, which may attenuate the inflammatory state. Interestingly, the lithium pretreatment resulted in significantly elevated inflammasome activity, suggesting that lithium does not impair the immune response to additional stimuli.

Cell inspired delivery system equipped with natural membrane structures in applications for rescuing ischemic stroke

Ischemic stroke (IS), accounting for 87 % of stroke incidences, constitutes a paramount health challenge owing to neurological impairments and irreversible tissue damage arising from cerebral ischemia. Chief among therapeutic obstacles are the restrictive penetration of the blood-brain barrier (BBB) and insufficient targeting precision, hindering the accumulation of drugs in ischemic brain areas. Motivated by the remarkable capabilities of natural membrane-based delivery vehicles in achieving targeted delivery and traversing the BBB, thanks to their biocompatible architecture and bioactive components, numerous membrane-engineered systems such as cells, cell membranes and extracellular vesicles have emerged as promising platforms to augment IS treatment efficacy with the help of nanotechnology. This review consolidates the primary pathological manifestations following IS, elucidates the unique functionalities of natural membrane drug delivery systems (DDSs) with nanotechnology, as well as delineates the structural characteristics of various natural membranes alongside rational design strategies employed. The review illuminates both the potential and challenges encountered when employing natural membrane DDSs in IS drug therapy, offering fresh perspectives and insights for devising efficacious and practical delivery systems tailored to IS intervention.

MAP Kinase Signaling at the Crossroads of Inflammasome Activation

Inflammasomes are crucial mediators of both antimicrobial host defense and inflammatory pathology, requiring stringent regulation at multiple levels. This review explores the pivotal role of mitogen-activated protein kinase (MAPK) signaling in modulating inflammasome activation through various regulatory mechanisms. We detail recent advances in understanding MAPK-mediated regulation of NLRP3 inflammasome priming, licensing and activation, with emphasis on MAPK-induced activator protein-1 (AP-1) signaling in NLRP3 priming, ERK1 and JNK in NLRP3 licensing, and TAK1 in connecting death receptor signaling to NLRP3 inflammasome activation. Furthermore, we discuss novel insights into MAPK signaling in human NLRP1 inflammasome activation, focusing on the MAP3K member ZAKα as a key kinase linking ribosomal stress to inflammasome activation. Lastly, we review recent work elucidating how Bacillus anthracis lethal toxin (LeTx) manipulates host MAPK signaling to induce macrophage apoptosis as an immune evasion strategy, and the counteraction of this effect through genotype-specific Nlrp1b inflammasome activation in certain rodent strains.

Inflammasomes: potential therapeutic targets in hematopoietic stem cell transplantation

The realm of hematopoietic stem cell transplantation (HSCT) has witnessed remarkable advancements in elevating the cure and survival rates for patients with both malignant and non-malignant hematologic diseases. Nevertheless, a considerable number of patients continue to face challenges, including transplant-related complications, infection, graft failure, and mortality. Inflammasomes, the multi-protein complexes of the innate immune system, respond to various danger signals by releasing inflammatory cytokines and even mediating cell death. While moderate activation of inflammasomes is essential for immune defense and homeostasis maintenance, excessive activation precipitates inflammatory damage. The intricate interplay between HSCT and inflammasomes arises from their pivotal roles in immune responses and inflammation. This review examines the molecular architecture and composition of various types of inflammasomes, highlighting their activation and effector mechanisms within the context of the HSCT process and its associated complications. Additionally, we summarize the therapeutic implications of targeting inflammasomes and related factors in HSCT.

Gelsevirine ameliorates sepsis-associated encephalopathy by inhibiting the STING signalling-mediated pyroptosis pathway in microglia

BACKGROUND

Sepsis-associated encephalopathy (SAE) is among the most prevalent and deadly complications associated with sepsis, but satisfactory treatments and therapeutic agents are lacking. Gelsevirine, an active ingredient derived from Gelsemium elegans Benth., has shown promising effects in animal models of anxiety, ischaemic stroke and osteoarthritis. However, its protective effect against SAE and its mechanism of action are still unknown.

PURPOSE

To elucidate the efficacy of gelsevirine against SAE and the mechanism of its protective effect through the STING signalling-mediated pyroptosis pathway.

METHODS

We constructed a mouse model of caecum ligation and puncture (CLP)-induced sepsis and explored the protective effects of gelsevirine in mice with SAE by assessing survival rates and behavioural alterations. To further explore its mechanism of action, we investigated the modulatory effects of gelsevirine on the levels of inflammatory factors, microglial activation and pyroptosis by Western blotting, immunohistochemistry staining and PCR. STING knockout mice were used to verify the protective effect of gelsevirine against SAE through the STING pathway.

RESULTS

Gelsevirine increased the survival rate of mice with SAE. The Morris water maze and open field tests revealed that gelsevirine significantly alleviated cognitive dysfunction and increased exploratory behaviour in mice with SAE. Gelsevirine inhibited the activation of microglia and decreased inflammatory factor levels in the hippocampus of mice with SAE. In mice with SAE and in vitro BV2 microglia, gelsevirine reduced levels of inflammatory factors and inhibited STING protein phosphorylation and microglial pyroptosis. However, after STING knockout, the inhibitory effect of gelsevirine on microglial pyroptosis was significantly weakened, and gelsevirine-mediated protective effects were abolished.

CONCLUSIONS

Gelsevirine increased the survival rate, ameliorated cognitive impairment, inhibited glial cell activation and reduced inflammation in the hippocampi of mice with SAE; the mechanism may be related to the inhibition of STING signalling pathway-mediated pyroptosis in microglia.

The role of NLRP3 inflammasome in type 2 inflammation related diseases

Type 2 inflammation related diseases, such as atopic dermatitis, asthma, and allergic rhinitis, are diverse and affect multiple systems in the human body. It is common for individuals to have multiple co-existing type 2 inflammation related diseases, which can impose a significant financial and living burden on patients. However, the exact pathogenesis of these diseases is still unclear. The NLRP3 inflammasome is a protein complex composed of the NLRP3 protein, ASC, and Caspase-1, and is activated through various mechanisms, including the NF-κB pathway, ion channels, and lysosomal damage. The NLRP3 inflammasome plays a role in the immune response to pathogens and cellular damage. Recent studies have indicated a strong correlation between the abnormal activation of NLRP3 inflammasome and the onset of type 2 inflammation. Additionally, it has been demonstrated that suppressing NLRP3 expression effectively diminishes the inflammatory response, highlighting its promising therapeutic applications. Therefore, this article reviews the role of NLRP3 inflammasome in the development and therapy of multiple type 2 inflammation related diseases.

The role of quercetin in NLRP3-associated inflammation

Quercetin is a natural flavonoid that is widely found in fruits and vegetables. As an important flavonoid, it exhibits a wide range of biological activities, including antioxidant, anti-inflammatory, antiviral, immunomodulatory, and analgesic activities. Quercetin exerts powerful antioxidant activity by regulating glutathione, enzyme activity, and the production of reactive oxygen species (ROS). Quercetin exerts powerful anti-inflammatory effects by acting on the Nod-like receptor protein 3 (NLRP3) inflammasome. In diabetes, quercetin has been shown to improve insulin sensitivity and reduce high blood sugar level, while, in neurological diseases, it potentially prevents neuronal degeneration and cognitive decline by regulating neuroinflammation. In addition, in liver diseases, quercetin may improve liver inflammation and fibrosis by regulating the NLRP3 activity. In addition, quercetin may improve inflammation in other diseases based on the NLRP3 inflammasome. With this background, in this review, we have discussed the progress in the study on the mechanism of quercetin toward improving inflammation via NLRP3 inflammasome in the past decade. In addition, from the perspective of quercetin glycoside derivatives, the anti-inflammatory mechanism of hyperoside, rutin, and isoquercetin based on NLRP3 inflammasome has been discussed. Moreover, we have discussed the pharmacokinetics of quercetin and its nanoformulation application, with the aim to provide new ideas for further research on the anti-inflammatory effect of quercetin and its glycoside derivatives based on NLRP3 inflammasome, as well as in drug development and application.

Potential role of the antimicrobial peptide Tachyplesin III in regulating nontypeable Haemophilus influenzae-induced inflammation in airway epithelial cells

The respiratory bacterium nontypeable (non-encapsulated) Haemophilus influenzae (NTHi) is a key pathogen driving exacerbations in chronic obstructive pulmonary disease (COPD), and is associated with an excessive airway inflammation. Increasing issues with tolerance and unwanted side effects of existing pharmaceuticals present an urgent need for new, effective and minimally toxic therapeutic options. This study aimed to investigate the potential role of Tachyplesin III, an antimicrobial peptide derived from the hemolysates of Southeast Asian horseshoe crabs, in regulating NTHi-induced airway inflammation. The results revealed that Tachyplesin III effectively inhibited the production of IL-1β in NTHi-stimulated human lung epithelial cells (A549), without causing cytotoxic effects. Additionally, Tachyplesin III significantly reduced TNF-α, PGE2 and NO production in NTHi-stimulated A549 cells. Moreover, this peptide inhibited the nuclear translocation of the NF-κB p65 subunit in NTHi-stimulated lung epithelial cells. It also reduced transcriptional activation of NF-κB target genes, as shown by lower mRNA levels of IL-1β, TNF-α, COX-2 and iNOS, which correlated with corresponding decreases in their protein expression. Tachyplesin III peptide also inhibited pro-IL-1β and NLRP3 protein expression and prevented NTHi-induced caspase-1 cleavage and IL-1β maturation. Together, our findings demonstrate that Tachyplesin III effectively reduced NTHi-mediated inflammation via the NF-κB/NLRP3 inflammasome signaling pathway, highlighting its important anti-inflammatory activity. Complementing these findings, in silico analysis revealed key pharmacokinetic and toxicological attributes, establishing a foundational understanding of Tachyplesin III as a promising therapeutic agent for managing NTHi-associated inflammation.

Balanced regulation of ROS production and inflammasome activation in preventing early development of colorectal cancer

Reactive oxygen species (ROS) production and inflammasome activation are the key components of the innate immune response to microbial infection and sterile insults. ROS are at the intersection of inflammation and immunity during cancer development. Balanced regulation of ROS production and inflammasome activation serves as the central hub of innate immunity, determining whether a cell will survive or undergo cell death. However, the mechanisms underlying this balanced regulation remain unclear. Mitochondria and NADPH oxidases are the two major sources of ROS production. Recently, NCF4, a component of the NADPH oxidase complex that primarily contributes to ROS generation in phagocytes, was reported to balance ROS production and inflammasome activation in macrophages. The phosphorylation and puncta distribution of NCF4 shifts from the membrane-bound NADPH complex to the perinuclear region, promoting ASC speck formation and inflammasome activation, which triggers downstream IL-18-IFN-γ signaling to prevent the progression of colorectal cancer (CRC). Here, we review ROS signaling and inflammasome activation studies in colitis-associated CRC and propose that NCF4 acts as a ROS sensor that balances ROS production and inflammasome activation. In addition, NCF4 is a susceptibility gene for Crohn's disease (CD) and CRC. We discuss the evidence demonstrating NCF4's crucial role in facilitating cell-cell contact between immune cells and intestinal cells, and mediating the paracrine effects of inflammatory cytokines and ROS. This coordination of the signaling network helps create a robust immune microenvironment that effectively prevents epithelial cell mutagenesis and tumorigenesis during the early stage of colitis-associated CRC.

Streptococcus mutans outer membrane vesicles affect inflammasome activation and the glycolysis of macrophages

Recent studies indicate that bacterial outer membrane vesicles (OMVs) play a significant role in bacterial virulence and pathogenicity. Streptococcus mutans (S. mutans), a principal pathogen in dental caries, secretes a substantial number of OMVs. However, the impact of S. mutans OMVs on oral health and their underlying pathogenic mechanisms remain poorly understood. Macrophages were the initial innate immune cells to respond to bacterial invaders and their products. Therefore, we purified S. mutans OMVs, which stimulated macrophages. Compared to controls, RT-PCR and ELISA analyses revealed that S. mutans OMVs significantly increased the production of IL-1β, IL-6, TNF-α and IL-8, with IL-1β being notably elevated. IL-1β production and secretion are tightly regulated by the inflammasome. Western blot analyses demonstrated that S. mutans OMVs upregulated the expression of inflammasome components, including NLRP3, NLRC4, ASC and AIM2, with a marked increase in NLRP3 expression. Silencing different inflammasome components with siRNA revealed a reduction in IL-1β secretion induced by S. mutans OMVs, particularly through NLRP3. Additionally, ATP production and K+ efflux were found to be crucial for NLRP3 activation. Prolonged stimulation with S. mutans OMVs resulted in increased lactate production and elevated expression of glycolysis-related genes Glut-1, PFKFB3, and HK I, indicating that S. mutans OMVs significantly induce macrophage glycolysis. Furthermore, S. mutans OMVs were shown to enhance biofilm formation, increase S. mutans colonisation on epithelial cells, and inhibit macrophage phagocytosis, thereby improving the survival of S. mutans in the oral cavity. In summary, S. mutans OMVs promote the survival of S. mutans in the mouth through multiple mechanisms, potentially influencing the development of dental caries.

Discovery of novel NLRP3 inhibitors based on machine learning and physical methods

The NLRP3 inflammasome plays a crucial role in inflammatory responses, particularly in alcohol-related liver disease (ALD). Given that NLRP3 has emerged as a potential therapeutic target for ALD, the development of effective inhibitors is of great importance. In this study, we trained 11 regression models, and the results showed that LightGBM, Random Forest, and XGBoost performed the best, achieving R² values of 0.774, 0.755, and 0.719, respectively. Using machine learning models and physical methods, we screened more than 11.5 million compounds from Asinex, Princeton, UkrOrgSynthesis, Chemdiv, Chembridge, Alinda, Enamine, and Lifechemicals, which led to the identification of 26 potential NLRP3 inhibitors. Furthermore, molecular dynamics simulations and MMGBSA binding energy calculations confirmed the stability of the interactions between NLRP3 and three key molecules: 19,655,631 (source Chembridge), 38,214,692 (source Chembridge), and Z1180203703 (source Enamine). Additionally, ADMET analysis revealed their favorable pharmacokinetic properties. This study provides insights and candidate molecules for discovering NLRP3 inhibitors, potentially applicable in treating related diseases.

Regulation of the NLRP3 inflammasome by autophagy and mitophagy

The NLRP3 inflammasome is a multiprotein complex that upon activation by the innate immune system drives a broad inflammatory response. The primary initial mediators of this response are pro-IL-1β and pro-IL-18, both of which are in an inactive form. Formation and activation of the NLRP3 inflammasome activates caspase-1, which cleaves pro-IL-1β and pro-IL-18 and triggers the formation of gasdermin D pores. Gasdermin D pores allow for the secretion of active IL-1β and IL-18 initiating the organism-wide inflammatory response. The NLRP3 inflammasome response can be beneficial to the host; however, if the NLRP3 inflammasome is inappropriately activated it can lead to significant pathology. While the primary components of the NLRP3 inflammasome are known, the precise details of assembly and activation are less well defined and conflicting. Here, we discuss several of the proposed pathways of activation of the NLRP3 inflammasome. We examine the role of subcellular localization and the reciprocal regulation of the NLRP3 inflammasome by autophagy. We focus on the roles of mitochondria and mitophagy in activating and regulating the NLRP3 inflammasome. Finally, we detail the impact of pathologic NLRP3 responses in the development and manifestations of pulmonary disease.

The molecular mechanism of berberine affecting psoriasis skin inflammation by regulating keratinocyte pyroptosis via the p38 MAPK/NF-κB pathway

Berberine (BBR), a Rhizoma Coptis-sourced isoquinoline alkaloid, is an effective drug for psoriasis treatment with its therapeutic mechanism remaining unclear. We delved into the mechanism of BBR affecting psoriatic skin inflammation by regulating keratinocyte pyroptosis. A psoriasis-like skin inflammation mouse model was induced by imiquimod (IMQ) and treated with BBR and a p38 activator anisomycin. Human epidermal keratinocytes (HEKs) were stimulated with five chemokines (M5) [interleukin (IL)-17A, IL-22A, oncostatin M, tumor necrosis factor-α, IL-1α] to simulate psoriasis immune microenvironment, then treated with BBR and anisomycin. Psoriasis skin lesions, skin tissue damage, cell viability and death, and gasdermin D-N (GSDMD-N) and NOD-like receptor protein 3 (NLRP3) positive cell numbers were assessed. The p38 mitogen-activated protein kinase (MAPK)/nuclear factor-kappa B (NF-κB) pathway and levels of the NLRP3/GSDMD pathway-related proteins and inflammatory factors were determined. BBR alleviated M5-induced HEK pyroptosis by inactivating NLRP3 inflammasomes. BBR inhibited the p38 MAPK/NF-κB pathway, and its effects on HEKs were partly averted by activating the p38 MAPK/NF-κB pathway. BBR repressed NLRP3 inflammasome activation and pyroptosis by inhibiting the p38 MAPK/NF-κB pathway. Collectively, BBR suppressed keratinocyte NLRP3/GSDMD pathway pyroptosis by suppressing the p38 MAPK/NF-κB pathway, thereby affecting psoriasis skin inflammation.

TXNIP Regulates NLRP3 Inflammasome-Induced Pyroptosis Related to Aging via cAMP/PKA and PI3K/Akt Signaling Pathways

Aging is an inevitable natural process with time-dependent dysfunction and the occurrence of various diseases, which impose heavy burdens on individuals, families, and society. It has been reported that NLRP3 inflammasome-induced pyroptosis contributes significantly to age-related diseases and aging, while TXNIP is suggested to be involved in regulating pyroptosis mediated by NLRP3. However, the mechanism between TXNIP and NLRP3 inflammasome is still unclear. In this study, we used HT-22 cells to explore the effect of TXNIP on pyroptosis and its potential association with the aging. Also, we delved into the underlying mechanisms. Our findings revealed that TXNIP significantly augmented pyroptosis in HT-22 cells, primarily by enhancing the activation of the NLRP3 inflammasome and promoting the release of proinflammatory cytokines. Remarkably, as TXNIP levels increased, we observed a corresponding rise in the number of p16-positive cells, which is indicative of aging. Furthermore, we conducted experiments to modulate the improvement of TXNIP on NLRP3 inflammasome-induced pyroptosis, that is, the PI3K activator 740 Y-P and the PKA activator DC2797 inhibited the effect, while the PI3K inhibitor LY294002 and the PKA inhibitor H89 enhanced the effect. In conclusion, our study demonstrated that TXNIP regulates NLRP3 inflammasome-induced pyroptosis in HT-22 cells related to aging via the PI3K/Akt and cAMP/PKA pathways.

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.

Innate Immune Response and Epigenetic Regulation: A Closely Intertwined Tale in Inflammation

Maintenance of delicate homeostasis is very important in various diseases because it ensures appropriate immune surveillance against pathogens and prevents excessive inflammation. In a disturbed homeostatic condition, hyperactivation of immune cells takes place and interplay between these cells triggers a plethora of signaling pathways, releasing various pro-inflammatory cytokines such as Tumor necrosis factor alpha (TNFα), Interferon-gamma (IFNƴ), Interleukin-6 (IL-6), and Interleukin-1 beta (IL-1β), which marks cytokine storm formation. To be precise, dysregulated balance can impede or increase susceptibility to various pathogens. Pathogens have the ability to hijack the host immune system by interfering with the host's chromatin architecture for their survival and replication in the host cell. Cytokines, particularly IL-6, Interleukin-17 (IL-17), and Interleukin-23 (IL-23), play a key role in orchestrating innate immune responses and shaping adaptive immunity. Understanding the interplay between immune response and the role of epigenetic modification to maintain immune homeostasis and the structural aspects of IL-6, IL-17, and IL-23 can be illuminating for a novel therapeutic regimen to treat various infectious diseases. In this review, the light is shed on how the orchestration of epigenetic regulation facilitates immune homeostasis.

S-acylation of NLRP3 provides a nigericin sensitive gating mechanism that controls access to the Golgi

NLRP3 is an inflammasome seeding pattern recognition receptor activated in response to multiple danger signals which perturb intracellular homeostasis. Electrostatic interactions between the NLRP3 polybasic (PB) region and negatively charged lipids on the trans-Golgi network (TGN) have been proposed to recruit NLRP3 to the TGN. In this study, we demonstrate that membrane association of NLRP3 is critically dependant on S-acylation of a highly conserved cysteine residue (Cys-130), which traps NLRP3 in a dynamic S-acylation cycle at the Golgi, and a series of hydrophobic residues preceding Cys-130 which act in conjunction with the PB region to facilitate Cys-130 dependent Golgi enrichment. Due to segregation from Golgi localised thioesterase enzymes caused by a nigericin induced breakdown in Golgi organisation and function, NLRP3 becomes immobilised on the Golgi through reduced de-acylation of its Cys-130 lipid anchor, suggesting that disruptions in Golgi homeostasis are conveyed to NLRP3 through its acylation state. Thus, our work defines a nigericin sensitive S-acylation cycle that gates access of NLRP3 to the Golgi.

Varying the hydrophobic core composition of polymeric nanoparticles affects NLRP3 inflammasome activation

Understanding the interactions of nanoparticle carriers with innate immune cells is crucial for informing the design and efficacy of future nano-immunotherapies. An intriguing aspect of their interaction with the immune system has recently emerged, i.e., their ability to activate the NLRP3 inflammasome, a key component of the innate immune response. While the effect of the surface properties of nanoparticles has been extensively investigated in the context of nanoparticle-immune cell interactions, the influence of core composition remains largely unexplored, particularly regarding its impact on inflammasome activation. To shed light on these interactions, we developed a library of supramolecular polymer nanoparticles (SNPs) with different core compositions, varying their hydrophobic quotient by virtue of the side chain length and the repeating units in the polymer construct. The impact of modulating SNP core hydrophobic properties was investigated in macrophages by evaluating their cellular internalization, cytokine release, lysosomal rupture-calcium signaling, calcium flux-mitochondrial ROS production and their ability to activate the NLRP3 inflammasome, providing mechanistic insights into inflammasome activation. We established a direct correlation between increasing the side chain length of the polymer construct, thereby increasing the core hydrophobicity of SNPs and enhanced NLRP3 complex formation, as indicated by ASC speck imaging analysis and the elevated 1L-1β expression. Furthermore, the results demonstrated that the inflammasome signaling cascades and kinetics varied based on the SNP's hydrophobic side chain length and repeating units. Specifically, the nanoparticle with the longest alkyl side chain effectuated NLRP3 activation preferentially through the mitochondrial damage pathway. In vivo evaluation of SNPs in C57BL/6 mice confirmed elevated proinflammatory cytokines, notably with the SNP having the longest C12-alkyl side chain. This confirms that the higher core hydrophobicity composition of the SNP results in inflammasome activation in vivo. In summary, this study established SNP core composition as a novel nanoparticle-associated molecular pattern (NAMP) responsible for NLRP3 inflammasome activation, shedding light on intricate cellular pathways for informed nanoparticle design in immunotherapy and vaccine applications.

Interleukin-1β Signaling Contributes to Cell Cycle Arrest and Apoptotic Cell Death by Leptin via Modulation of AKT and p38MAPK in Hepatocytes

Leptin, an adipose tissue-derived hormone, has exhibited the potent hepatotoxic effects. However, the underlying molecular mechanisms are not fully understood. In this study, we have elucidated the mechanisms by which leptin exerts cytotoxic effects in hepatocytes, particularly focusing on the role of interleukin-1β (IL-1β) signaling. Leptin significantly induced maturation and secretion of IL-1β in cultured rat hepatocytes. Interestingly, inhibition of IL-1β signaling by pretreatment with an IL-1 receptor antagonist (IL-1Ra) or gene silencing of type I IL-1 receptor (IL-1R1) markedly abrogated leptin-induced cell cycle arrest. The critical role of IL-1β signaling in leptin-induced cell cycle arrest is mediated via upregulation of p16, which acts as an inhibitor of cyclin-dependent kinase. In addition, leptin-induced apoptotic cell death was relieved by inhibition of IL-1β signaling, as determined by annexin V/7-AAD binding assay. Mechanistically, IL-1β signaling contributes to apoptotic cell death and cell cycle arrest by suppressing AKT and activation of p38 mitogen-activated protein kinase (p38MAPK) signaling pathways. Involvement of IL-1β signaling in cytotoxic effect of leptin was further confirmed in vivo using hepatocyte specific IL-1R1 knock out (IL-1R1 KO) mice. Essentially similar results were obtained in vivo, where leptin administration caused the upregulation of apoptotic markers, dephosphorylation of AKT, and p38MAPK activation were observed in wild type mice liver without significant effects in the livers of IL-1R1 KO mice. Taken together, these results demonstrate that IL-1β signaling critically contributes to leptin-induced cell cycle arrest and apoptosis, at least in part, by modulating p38MAPK and AKT signaling pathways.

STAT3 promotes NLRP3 inflammasome activation by mediating NLRP3 mitochondrial translocation

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

Increased expression of ER stress, inflammasome activation, and mitochondrial biogenesis-related genes in peripheral blood mononuclear cells in major depressive disorder

A subset of major depressive disorder (MDD) is characterized by immune system dysfunction, but the intracellular origin of these immune changes remains unclear. Here we tested the hypothesis that abnormalities in endoplasmic reticulum (ER) stress, inflammasome activity and mitochondrial biogenesis contribute to the development of systemic inflammation in MDD. RT-qPCR was used to measure mRNA expression of key organellar genes from peripheral blood mononuclear cells (PBMCs) isolated from 186 MDD and 67 healthy control (HC) subjects. The comparative CT (2-ΔΔCT) method was applied to quantify mRNA expression using GAPDH as the reference gene. After controlling for age, sex, BMI, and medication status using linear regression models, expression of the inflammasome (NLRC4 and NLRP3) and the ER stress (XBP1u, XBP1s, and ATF4) genes was found to be significantly increased in the MDD versus the HC group. Sensitivity analyses excluding covariates yielded similar results. After excluding outliers, expression of the inflammasome genes was no longer statistically significant but expression of the ER stress genes (XBP1u, XBP1s, and ATF4) remained significant and the mitochondrial biogenesis gene, MFN2, was significantly increased in the MDD group. NLRC4 and MFN2 were positively correlated with serum C-reactive protein concentrations, while ASC trended significant. The altered expression of inflammasome activation, ER stress, and mitochondrial biogenesis pathway components suggest that dysfunction of these organelles may play a role in the pathogenesis of MDD.

Mechanism of Reactive Oxygen Species-Guided Immune Responses in Gouty Arthritis and Potential Therapeutic Targets

Gouty arthritis (GA) is an inflammatory disease caused by monosodium urate (MSU) crystals deposited in the joint tissues causing severe pain. The disease can recur frequently and tends to form tophus in the joints. Current therapeutic drugs for the acute phase of GA have many side effects and limitations, are unable to prevent recurrent GA attacks and tophus formation, and overall efficacy is unsatisfactory. Therefore, we need to advance research on the microscopic mechanism of GA and seek safer and more effective drugs through relevant targets to block the GA disease process. Current research shows that the pathogenesis of GA is closely related to NLRP3 inflammation, oxidative stress, MAPK, NET, autophagy, and Ferroptosis. However, after synthesizing and sorting out the above mechanisms, it is found that the presence of ROS is throughout almost the entire spectrum of micro-mechanisms of the gout disease process, which combines multiple immune responses to form a large network diagram of complex and tight connections involved in the GA disease process. Current studies have shown that inflammation, oxidative stress, cell necrosis, and pathological signs of GA in GA joint tissues can be effectively suppressed by modulating ROS network-related targets. In this article, on the one hand, we investigated the generative mechanism of ROS network generation and its association with GA. On the other hand, we explored the potential of related targets for the treatment of gout and the prevention of tophus formation, which can provide effective reference ideas for the development of highly effective drugs for the treatment of GA.

Chaperone- and PTM-mediated activation of IRF1 tames radiation-induced cell death and the inflammatory response

The key role of structural cells in immune modulation has been revealed with the advent of single-cell multiomics, but the underlying mechanism remains poorly understood. Here, we revealed that the transcriptional activation of interferon regulatory factor 1 (IRF1) in response to ionizing radiation, cytotoxic chemicals and SARS-CoV-2 viral infection determines the fate of structural cells and regulates communication between structural and immune cells. Radiation-induced leakage of mtDNA initiates the nuclear translocation of IRF1, enabling it to regulate the transcription of inflammation- and cell death-related genes. Novel posttranslational modification (PTM) sites in the nuclear localization sequence (NLS) of IRF1 were identified. Functional analysis revealed that mutation of the acetylation site and the phosphorylation sites in the NLS blocked the transcriptional activation of IRF1 and reduced cell death in response to ionizing radiation. Mechanistically, reciprocal regulation between the single-stranded DNA sensors SSBP1 and IRF1, which restrains radiation-induced and STING/p300-mediated PTMs of IRF1, was revealed. In addition, genetic deletion or pharmacological inhibition of IRF1 tempered radiation-induced inflammatory cell death, and radiation mitigators also suppressed SARS-CoV-2 NSP-10-mediated activation of IRF1. Thus, we revealed a novel cytoplasm-oriented mechanism of IRF1 activation in structural cells that promotes inflammation and highlighted the potential effectiveness of IRF1 inhibitors against immune disorders.

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.

High-Throughput Molecular Modeling and Evaluation of the Anti-Inflammatory Potential of Açaí Constituents against NLRP3 Inflammasome

The search for bioactive compounds in natural products holds promise for discovering new pharmacologically active molecules. This study explores the anti-inflammatory potential of açaí (Euterpe oleracea Mart.) constituents against the NLRP3 inflammasome using high-throughput molecular modeling techniques. Utilizing methods such as molecular docking, molecular dynamics simulation, binding free energy calculations (MM/GBSA), and in silico toxicology, we compared açaí compounds with known NLRP3 inhibitors, MCC950 and NP3-146 (RM5). The docking studies revealed significant interactions between açaí constituents and the NLRP3 protein, while molecular dynamics simulations indicated structural stabilization. MM/GBSA calculations demonstrated favorable binding energies for catechin, apigenin, and epicatechin, although slightly lower than those of MCC950 and RM5. Importantly, in silico toxicology predicted lower toxicity for açaí compounds compared to synthetic inhibitors. These findings suggest that açaí-derived compounds are promising candidates for developing new anti-inflammatory therapies targeting the NLRP3 inflammasome, combining efficacy with a superior safety profile. Future research should include in vitro and in vivo validation to confirm the therapeutic potential and safety of these natural products. This study underscores the value of computational approaches in accelerating natural product-based drug discovery and highlights the pharmacological promise of Amazonian biodiversity.

Exploring the common mechanisms and biomarker ST8SIA4 of atherosclerosis and ankylosing spondylitis through bioinformatics analysis and machine learning

Background

Atherosclerosis (AS) is a major contributor to cerebrovascular and cardiovascular events. There is growing evidence that ankylosing spondylitis is closely linked to AS, often co-occurring with it; however, the shared pathogenic mechanisms between the two conditions are not well understood. This study employs bioinformatics approaches to identify common biomarkers and pathways between AS and ankylosing spondylitis.

Methods

Gene expression datasets for AS (GSE100927, GSE28829, GSE155512) and ankylosing spondylitis (GSE73754, GSE25101) were obtained from the Gene Expression Omnibus (GEO). Differential expression genes (DEGs) and module genes for AS and ankylosing spondylitis were identified using the Limma R package and weighted gene co-expression network analysis (WGCNA) techniques, respectively. The machine learning algorithm SVM-RFE was applied to pinpoint promising biomarkers, which were then validated in terms of their expression levels and diagnostic efficacy in AS and ankylosing spondylitis, using two separate GEO datasets. Furthermore, the interaction of the key biomarker with the immune microenvironment was investigated via the CIBERSORT algorithm, single-cell analysis was used to identify the locations of common diagnostic markers.

Results

The dataset GSE100927 contains 524 DEGs associated with AS, whereas dataset GSE73754 includes 1,384 genes categorized into modules specific to ankylosing spondylitis. Analysis of these datasets revealed an overlap of 71 genes between the DEGs of AS and the modular genes of ankylosing spondylitis. Utilizing the SVM-RFE algorithm, 15 and 24 central diagnostic genes were identified in datasets GSE100927 and GSE73754, respectively. Further validation of six key genes using external datasets confirmed ST8SIA4 as a common diagnostic marker for both conditions. Notably, ST8SIA4 is upregulated in samples from both diseases. Additionally, ROC analysis confirmed the robust diagnostic utility of ST8SIA4. Moreover, analysis through CIBERSORT suggested an association of the ST8SIA4 gene with the immune microenvironment in both disease contexts. Single-cell analysis revealed that ST8SIA4 is primarily expressed in Macrophages, Monocytes, T cells, and CMPs.

Conclusion

This study investigates the role of ST8SIA4 as a common diagnostic gene and the involvement of the lysosomal pathway in both AS and ankylosing spondylitis. The findings may yield potential diagnostic biomarkers and offer new insights into the shared pathogenic mechanisms underlying these conditions.

NLRP3, NLRP6, and NLRP12 are inflammasomes with distinct expression patterns

Inflammasomes are sensors that detect cytosolic microbial molecules or cellular damage, and in response they initiate a form of lytic regulated cell death called pyroptosis. Inflammasomes signal via homotypic protein-protein interactions where CARD or PYD domains are crucial for recruiting downstream partners. Here, we screened these domains from NLR family proteins, and found that the PYD domain of NLRP6 and NLRP12 could activate caspase-1 to induce cleavage of IL-1β and GSDMD. Inflammasome reconstitution verified that full length NLRP6 and NLRP12 formed inflammasomes in vitro, and NLRP6 was more prone to auto-activation. NLRP6 was highly expressed in intestinal epithelial cells (IEC), but not in immune cells. Molecular phylogeny analysis found that NLRP12 was closely related to NLRP3, but the activation mechanisms are different. NLRP3 was highly expressed in monocytes and macrophages, and was modestly but appreciably expressed in neutrophils. In contrast, NLRP12 was specifically expressed in neutrophils and eosinophils, but was not detectable in macrophages. NLRP12 mutations cause a periodic fever syndrome called NLRP12 autoinflammatory disease. We found that several of these patient mutations caused spontaneous activation of caspase-1 in vitro, which likely causes their autoinflammatory disease. Different cell types have unique cellular physiology and structures which could be perturbed by a pathogen, necessitating expression of distinct inflammasome sensors to monitor for signs of infection.

Macrophage α7nAChR alleviates the inflammation of neonatal necrotizing enterocolitis through mTOR/NLRP3/IL-1β pathway

BACKGROUND

Neonatal necrotizing enterocolitis (NEC) is one of the most prevalent and severe intestinal emergencies in newborns. The inflammatory activation of macrophages is associated with the intestinal injury of NEC. The neuroimmune regulation mediated by α7 nicotinic acetylcholine receptor (α7nAChR) plays an important role in regulating macrophage activation and inflammation progression, but in NEC remains unclear. This study aims to explore the effect of macrophage α7nAChR on NEC.

METHODS

Mice NEC model were conducted with high-osmolarity formula feeding, hypoxia, and cold stimulation. The α7nAChR agonist PNU-282987 and mTOR inhibitor rapamycin were treated by intraperitoneal injections in mice. The expression and distribution of macrophages, α7nAChR, and phospho-mammalian target of rapamycin (p-mTOR) in the intestines of NEC patients and mice was assessed using immunohistochemistry, immunofluorescence, and flow cytometry. The expression of NLRP3, activated caspase-1 and IL-1β in mice intestines was detected by flow cytometry, western blot or ELISA. In vitro, the mouse RAW264.7 macrophage cell line was also cultured followed by various treatments. Expression of p-mTOR, NLRP3, activated caspase-1, and IL-1β in macrophages was determined.

RESULTS

Macrophages accumulated in the intestines and the expression of α7nAChR in the mucosal and submucosal layers of the intestines was increased in both the NEC patients and mice. The p-mTOR and CD68 were increased and co-localized in intestines of NEC patients. In vitro, α7nAChR agonist PNU-282987 significantly reduced the increase of NLRP3, activated caspase-1, and IL-1β in macrophages. PNU-282987 also significantly reduced the increase of p-mTOR. The effect was blocked by AMPK inhibitor compound C. The expression of NLRP3, activated caspase-1, and IL-1β was inhibited after mTOR inhibitor rapamycin treatment. In NEC model mice, PNU-282987 reduced the expression of p-mTOR, NLRP3, activated caspase-1, and IL-1β in the intestine. Meanwhile, rapamycin significantly attenuated NLRP3 activation and the release of IL-1β. Moreover, the proportion of intestinal macrophages and intestinal injury decreased after PNU-282987 treatment.

CONCLUSION

Macrophage α7nAChR activation mitigates NLRP3 inflammasome activation by modulating mTOR phosphorylation, and subsequently alleviates intestinal inflammation and injury in NEC.

Anti-Inflammatory Effect of Atorvastatin and Rosuvastatin on Monosodium Urate-Induced Inflammation through IL-37/Smad3-Complex Activation in an In Vitro Study Using THP-1 Macrophages

Objective: The pleiotropic effect of hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) is responsible for potent defense against inflammatory response. This study evaluated the inhibitory effects of HMG-CoA reductase inhibitors on the monosodium urate (MSU)-induced inflammatory response through the regulation of interleukin-37 (IL-37) expression. Methods: Serum was collected from patients with gout (n = 40) and from healthy controls (n = 30). The mRNA and protein expression of the target molecules IL-1β, IL-37, caspase-1, and Smad3 were measured in THP-1 macrophages stimulated with MSU, atorvastatin, or rosuvastatin using a real-time quantitative polymerase chain reaction and Western blot assay. Transfection with IL-1β or Smad3 siRNA in THP-1 macrophages was used to verify the pharmaceutical effect of statins in uric-acid-induced inflammation. Results: Serum IL-37 levels in gout patients were significantly higher than in controls (p < 0.001) and was associated with the serum uric acid level (r = 0.382, p = 0.008). THP-1 cells stimulated with MSU markedly induced IL-37 mRNA expression and the transition of IL-37 from the cytoplasm to the nucleus. Recombinant IL-37 treatment dose-dependently inhibited activation of caspase-1 and IL-1β in MSU-induced inflammation. Atorvastatin and rosuvastatin attenuated caspase-1 activation and mature IL-1β expression but augmented translocation of IL-37 from the cytoplasm to the nucleus. Atorvastatin and rosuvastatin induced phosphorylation of Smad3 in THP-1 cells treated with MSU crystals. Statins potently attenuated translocation of IL-37 from the cytoplasm to the nucleus in THP-1 macrophages transfected with Smad3 siRNA compared to cells with negative control siRNA. Conclusions: This study revealed that statins inhibit the MSU-induced inflammatory response through phosphorylated Smad3-mediated IL-37 expression in THP-1 macrophages.

NLRP3 inflammasome signalling in Alzheimer's disease

Every year, 10 million people develop dementia, the most common of which is Alzheimer's disease (AD). To date, there is no way to prevent cognitive decline and therapies are limited. This review provides a neuroimmunological perspective on the progression of AD, and discusses the immune-targeted therapies that are in preclinical and clinical trials that may impact the development of this disease. Specifically, we look to the role of the NLRP3 inflammasome, its triggers in the brain and how its activation can contribute to the progression of dementia. We summarise the range of inhibitors targeting the NLRP3 inflammasome and its downstream pathways that are under investigation, and discuss future therapeutic perspectives for this devastating condition.

[2, 6-dimethoxy-1, 4-benzoquinone alleviates septic shock in mice by inhibiting NLRP3 inflammasome activation]

OBJECTIVE

To investigate the mechanism of 2, 6-dimethoxy-1, 4-benzoquinone (DMQ), an active ingredients in fermented wheat germ extract, for inhibiting NLRP3 inflammasome activation and alleviating septic shock in mice.

METHODS

Cultured murine bone marrow-derived macrophages (BMDM) stimulated with lipopolysaccharide (LPS) were treated with DMQ, followed by treatment with Nigericin, ATP, and MSU for activating the canonical NLRP3 inflammasome; the noncanonical NLRP3 inflammasome was activated by intracellular transfection of LPS, and AIM2 inflammasome was activated using Poly A: T.In human monocytic THP-1 cells, the effect of Nigericin on inflammasome activation products was examined using Western blotting and ELISA.Co-immunoprecipitation was performed to explore the mechanism of DMQ-induced blocking of NLRP3 inflammasome activation.In a male C57BL/6J mouse model of LPS-induced septic shock treated with 20 and 40 mg/kg DMQ, the levels of IL-1β and TNF-α in the serum and peritoneal lavage fluid were determined using ELISA, and the survival time of the mice within 36 h was observed.

RESULTS

Treatment with DMQ effectively inhibited LPS-induced activation of canonical NLRP3 inflammasome in mouse BMDM and human THP-1 cells and also inhibited non-canonical NLRP3 inflammasome activation in mouse BMDM, but produced no significant effect on AIM2 inflammasome activation.DMQ significantly blocked the binding between ASC and NLRP3.In the mouse models of septic shock, DMQ treatment significantly reduced the levels of IL-1β in the serum and peritoneal fluid and obviously prolonged survival time of the mice.

CONCLUSION

DMQ can effectively block ASC-NLRP3 interaction to inhibit NLRP3 inflammasome activation and alleviate LPSinduced septic shock in mice.

Role of NLRP3 inflammasome in nanoparticle adjuvant-mediated immune response

The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome is pivotal in orchestrating the immune response induced by nanoparticle adjuvants. Understanding the intricate mechanisms underlying the activation of NLRP3 inflammasome by these adjuvants is crucial for deciphering their immunomodulatory properties. This review explores the involvement of the NLRP3 inflammasome in mediating immune responses triggered by nanoparticle adjuvants. It delves into the signaling pathways and cellular mechanisms involved in NLRP3 activation, highlighting its significance in modulating the efficacy and safety of nanoparticle-based adjuvants. A comprehensive grasp of the interplay between NLRP3 inflammasome and nanoparticle adjuvants holds promise for optimizing vaccine design and advancing immunotherapeutic strategies.

ER-mitochondria association negatively affects wound healing by regulating NLRP3 activation

Methicillin-resistant Staphylococcus aureus (MRSA) is the most common causative agent of acute bacterial skin and skin-structure infections (ABSSSI), one of the major challenges to the health system worldwide. Although the use of antibiotics as the first line of intervention for MRSA-infected wounds is recommended, important side effects could occur, including cytotoxicity or immune dysregulation, thus affecting the repair process. Here, we show that the oxazolidinone antibiotic linezolid (LZD) impairs wound healing by aberrantly increasing interleukin 1 β (IL-1β) production in keratinocytes. Mechanistically, LZD triggers a reactive oxygen species (ROS)-independent mitochondrial damage that culminates in increased tethering between the endoplasmic reticulum (ER) and mitochondria, which in turn activates the NLR family pyrin domain-containing 3 (NLRP3) inflammasome complex by promoting its assembly to the mitochondrial surface. Downregulation of ER-mitochondria contact formation is sufficient to inhibit the LZD-driven NLRP3 inflammasome activation and IL-1β production, restoring wound closure. These results identify the ER-mitochondria association as a key factor for NLRP3 activation and reveal a new mechanism in the regulation of the wound healing process that might be clinically relevant.

Reactive oxygen species in endothelial signaling in COVID-19: Protective role of the novel peptide PIP-2

INTRODUCTION

Recent research suggests that endothelial activation plays a role in coronavirus disease 2019 (COVID-19) pathogenesis by promoting a pro-inflammatory state. However, the mechanism by which the endothelium is activated in COVID-19 remains unclear.

OBJECTIVE

To investigate the mechanism by which COVID-19 activates the pulmonary endothelium and drives pro-inflammatory phenotypes.

HYPOTHESIS

The "inflammatory load or burden" (cytokine storm) of the systemic circulation activates endothelial NADPH oxidase 2 (NOX2) which leads to the production of reactive oxygen species (ROS) by the pulmonary endothelium. Endothelial ROS subsequently activates pro-inflammatory pathways.

METHODS

The inflammatory burden of COVID-19 on the endothelial network, was recreated in vitro, by exposing human pulmonary microvascular endothelial cells (HPMVEC) to media supplemented with serum from COVID-19 affected individuals (sera were acquired from patients with COVID-19 infection that eventually died. Sera was isolated from blood collected at admission to the Intensive Care Unit of the Hospital of the University of Pennsylvania). Endothelial activation, inflammation and cell death were assessed in HPMVEC treated with serum either from patients with COVID-19 or from healthy individuals. Activation was monitored by measuring NOX2 activation (Rac1 translocation) and ROS production; inflammation (or appearance of a pro-inflammatory phenotype) was monitored by measuring the induction of moieties such as intercellular adhesion molecule (ICAM-1), P-selectin and the NLRP3 inflammasome; cell death was measured via SYTOX™ Green assays.

RESULTS

Endothelial activation (i.e., NOX2 activation and subsequent ROS production) and cell death were significantly higher in the COVID-19 model than in healthy samples. When HPMVEC were pre-treated with the novel peptide PIP-2, which blocks NOX2 activation (via inhibition of Ca2+-independent phospholipase A2, aiPLA2), significant abrogation of ROS was observed. Endothelial inflammation and cell death were also significantly blunted.

CONCLUSIONS

The endothelium is activated during COVID-19 via cytokine storm-driven NOX2-ROS activation, which causes a pro-inflammatory phenotype. The concept of endothelial NOX2-ROS production as a unifying pathophysiological axis in COVID-19 raises the possibility of using PIP-2 to maintain vascular health.

Mechanism of NLRP3 Inflammasome in Epilepsy and Related Therapeutic Agents

Epilepsy is one of the most widespread and complex diseases in the central nervous system (CNS), affecting approximately 65 million people globally, an important factor resulting in neurological disability-adjusted life year (DALY) and progressive cognitive dysfunction. Medication is the most essential treatment. The currently used drugs have shown drug resistance in some patients and only control symptoms; the development of novel and more efficacious pharmacotherapy is imminent. Increasing evidence suggests neuroinflammation is involved in the occurrence and development of epilepsy, and high expression of NLRP3 inflammasome has been observed in the temporal lobe epilepsy (TLE) brain tissue of patients and animal models. The inflammasome is a crucial cause of neuroinflammation by activating IL-1β and IL-18. Many preclinical studies have confirmed that regulating NLRP3 inflammasome pathway can prevent the development of epilepsy, reduce the severity of epilepsy, and play a neuroprotective role. Therefore, regulating NLRP3 inflammasome could be a potential target for epilepsy treatment. In summary, this review describes the priming and activation of inflammasome and its biological function in the progression of epilepsy. In addition, we reviewes the current pharmacological researches for epilepsy based on the regulation of NLRP3 inflammasome, aiming to provide a basis and reference for developing novel antiepileptic drugs.

Endotoxin tolerance ameliorates lipopolysaccharide/D-galactosamine-induced acute liver failure by negative regulation of the NF-κB/NLRP3 and activation of Nrf2/HO-1 via Sitr1

Acute liver failure (ALF) is a potentially fatal disorder characterized by extensive hepatocyte necrosis and rapid decline in liver function. Numerous factors, including oxidative stress, cell death, and inflammatory responses, are associated with its pathogenesis. Endotoxin tolerance (ET) refers to the phenomenon in which the body or cells exhibit low or no response to high-dose lipopolysaccharide (LPS) stimulation after pre-stimulation with low-dose LPS. However, the specific mechanism through which ET regulates LPS/D-galactosamine (D-GalN)-induced ALF remains unclear. An ALF mouse model was established by intraperitoneal injection of D-GalN (400 mg/kg) and LPS (10 mg/kg). A low dose of LPS (0.1 mg/kg/d) was continuously administered to mice for 5 d before modeling to assess the protective effect of ET. The data from this study showed that ET alleviated the inflammatory response in mice with LPS/D-GalN-induced ALF. ET inhibited LPS-induced oxidative damage and pyroptosis in macrophages in vitro. RNA sequencing analysis showed that the NF-κB/NLRP3 pathway was linked to the anti-inflammatory and antioxidative effects of ET. Furthermore, using western blot, RT-qPCR, and immunofluorescence, we verified that ET inhibited the NF-κB/NLRP3 pathway and triggered the Nrf2/HO-1 signaling pathway to attenuate oxidative stress and cell pyroptosis. Sirt1 knockdown reversed this protective effect. In summary, our research elucidates that ET prevents ALF advancement by upregulating Sirt1 levels, triggering the Nrf2/HO-1 signaling axis, and suppressing the NF-κB/NLRP3 signaling cascade to inhibit oxidative stress and cell pyroptosis. Our results provide a mechanistic explanation for the protective effect of ET against ALF.

The Neglected Sibling: NLRP2 Inflammasome in the Nervous System

While classical NOD-like receptor pyrin domain containing protein 1 (NLRP1) and NLRP3 inflammasomal proteins have been extensively investigated, the contribution of NLRP2 is still ill-defined in the nervous system. Given the putative significance of NLRP2 in orchestrating neuroinflammation, further inquiry is needed to gain a better understanding of its connectome, hence its specific targeting may hold a promising therapeutic implication. Therefore, bioinformatical approach for extracting information, specifically in the context of neuropathologies, is also undoubtedly preferred. To the best of our knowledge, there is no review study selectively targeting only NLRP2. Increasing, but still fragmentary evidence should encourage researchers to thoroughly investigate this inflammasome in various animal- and human models. Taken together, herein we aimed to review the current literature focusing on the role of NLRP2 inflammasome in the nervous system and more importantly, we provide an algorithm-based protein network of human NLRP2 for elucidating potentially valuable molecular partnerships that can be the beginning of a new discourse and future therapeutic considerations.

Spatiotemporal proteomic profiling of cellular responses to NLRP3 agonists

Nucleotide-binding domain and leucine-rich repeat pyrin-domain containing protein 3 (NLRP3) is an innate immune sensor that forms an inflammasome in response to various cellular stressors. Gain-of-function mutations in NLRP3 cause autoinflammatory diseases and NLRP3 signalling itself exacerbates the pathogenesis of many other human diseases. Despite considerable therapeutic interest, the primary drivers of NLRP3 activation remain controversial due to the diverse array of signals that are integrated through NLRP3. Here, we mapped subcellular proteome changes to lysosomes, mitochondrion, EEA1-positive endosomes, and Golgi caused by the NLRP3 inflammasome agonists nigericin and CL097. We identified several common disruptions to retrograde trafficking pathways, including COPI and Shiga toxin-related transport, in line with recent studies. We further characterized mouse NLRP3 trafficking throughout its activation using temporal proximity proteomics, which supports a recent model of NLRP3 recruitment to endosomes during inflammasome activation. Collectively, these findings provide additional granularity to our understanding of the molecular events driving NLRP3 activation and serve as a valuable resource for cell biological research. We have made our proteomics data accessible through an open-access Shiny browser to facilitate future research within the community, available at: https://harperlab.connect.hms.harvard.edu/inflame/. We will display anonymous peer review for this manuscript on pubpub.org (https://harperlab.pubpub.org/pub/nlrp3/) rather than a traditional journal. Moreover, we invite community feedback on the pubpub version of this manuscript, and we will address criticisms accordingly.

Kaempferol-induced mitochondrial damage promotes NF-κB-NLRP3-caspase-1 signaling axis-mediated pyroptosis in gastric cancer cells

GC is a gastrointestinal tumor with high morbidity and mortality. Owing to the high rate of postoperative recurrence associated with GC, the effectiveness of radiotherapy and chemotherapy may be compromised by the occurrence of severe undesirable side effects. In light of these circumstances, KP, a flavonoid abundantly present in diverse herbal and fruit sources, emerges as a promising therapeutic agent with inherent anti-tumor properties. This study endeavors to demonstrate the therapeutic potential of KP in the context of GC while unraveling the intricate underlying mechanisms. Notably, our investigations unveil that KP stimulation effectively promotes the activation of NLRP3 inflammatory vesicles within AGS cells by engaging the NF-κB signaling pathway. Consequently, the signal cascade triggers the cleavage of Caspase-1, culminating in the liberation of IL-18. Furthermore, we ascertain that KP facilitate AGS cell pyroptosis by inducing mitochondrial damage. Collectively, our findings showcase KP as a compelling candidate for the treatment of GC-related diseases, heralding new possibilities for future therapeutic interventions.

Increased miR-3074-5p expression promotes M1 polarization and pyroptosis of macrophages via ERα/NLRP3 pathway and induces adverse pregnancy outcomes in mice

Decidual macrophages (dMϕs) play critical roles in regulation of immune-microhomeostasis at maternal-fetal interface during pregnancy, but the underlying molecular mechanisms are still unclear. In this study, it was found that litter size and fetal weight were significantly reduced, whereas the rate of embryo resorption was increased in miR-3074-5p knock-in (3074-KI) pregnant mice, compared to that of wild-type (WT) pregnant mice. Plasma levels of pro-inflammatory cytokines in 3074-KI pregnant mice were also significantly elevated compared to WT pregnant mice at GD7.5. The quantity of M1-Mϕs in uterine tissues of 3074-KI pregnant mice was significantly increased compared to WT pregnant mice at GD13.5. Estrogen receptor-α (ERα) was validated to be a target of miR-3074-5p. Either miR-3074-5p overexpression or ERα knockdown promoted transcriptional activity of NF-κB/p65, induced M1-polarization and pyroptosis of THP1-derived Mϕs, accompanied with increased intracellular levels of cleaved Caspase-1, cleaved IL-1β, NLRP3, cleaved GSDMD and ASC aggregation. Furthermore, ERα could not only bind to NLRP3 or ASC directly, but also inhibit the interaction between NLRP3 and ASC. The endometrial miR-3074-5p expression level at the middle secretory stage of repeated implantation failure (RIF) patients was significantly decreased compared to that of control fertile women. These data indicated that miR-3074-5p could promote M1 polarization and pyroptosis of Mϕs via activation of NLRP3 inflammasome by targeting ERα, and the dysregulation of miR-3074-5p expression in dMϕs might damage the embryo implantation and placentation by interfering with inflammatory microenvironment at the maternal-fetal interface during early pregnancy.

Oleic acid induces lipogenesis and NLRP3 inflammasome activation in organotypic mouse meibomian gland and human meibomian gland epithelial cells

The accumulation of oleic acid (OA) in the meibum from patients with meibomian gland dysfunction (MGD) suggests that it may contribute to meibomian gland (MG) functional disorder, as it is a potent stimulator of acne-related lipogenesis and inflammation in sebaceous gland. Therefore, we investigate whether OA induces lipogenesis and inflammasome activation in organotypic cultured mouse MG and human meibomian gland epithelial cells (HMGECs). Organotypic cultured mouse MG and HMGECs were exposed to OA or combinations with specific AMPK agonists 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR). Lipogenic status, ductal keratinization, squamous metaplasia, NLRP3/ASC/Caspase-1 inflammasome activation, proinflammatory cytokine IL-1β production, and AMPK pathway phosphorylation in MG were subsequently examined by lipid staining, immunofluorescence staining, immunohistochemical staining, ELISA assay, and Western blot analyses. We found that OA significantly induced lipid accumulation, ductal keratinization, and squamous metaplasia in organotypic cultured MG, as evidenced by increased lipids deposition within acini and duct, upregulated expression of lipogenic proteins (SREBP-1 and HMGCR), and elevation of K10/Sprr1b. Additionally, OA induced NLRP3/ASC/Caspase-1 inflammasome activation, cleavage of Caspase-1, and production of downstream proinflammatory cytokine IL-1β. The findings of lipogenesis and NLRP3-related proinflammatory response in OA-stimulated HMGECs were consistent with those in organotypic cultured MG. OA exposure downregulated phospho-AMPK in two models, while AICAR treatment alleviated lipogenesis by improving AMPK/ACC phosphorylation and SREBP-1/HMGCR expression. Furthermore, AMPK amelioration inhibited activation of the NLRP3/ASC/Caspase-1 axis and secretion of IL-1β, thereby relieving the OA-induced proinflammatory response. These results demonstrated that OA induced lipogenic disorder and NLRP3 inflammasome activation in organotypic cultured mouse MG and HMGECs by suppressing the AMPK signaling pathway, indicating OA may play an etiological role in MGD.

The Function and Mechanism of Anti-Inflammatory Factor Metrnl Prevents the Progression of Inflammatory-Mediated Pathological Bone Osteolytic Diseases

Metrnl, recently identified as an adipokine, is a secreted protein notably expressed in white adipose tissue, barrier tissues, and activated macrophages. This adipokine plays a pivotal role in counteracting obesity-induced insulin resistance. It enhances adipose tissue functionality by promoting adipocyte differentiation, activating metabolic pathways, and exerting anti-inflammatory effects. Extensive research has identified Metrnl as a key player in modulating inflammatory responses and as an integral regulator of muscle regeneration. These findings position Metrnl as a promising biomarker and potential therapeutic target in treating inflammation-associated pathologies. Despite this, the specific anti-inflammatory mechanisms of Metrnl in immune-mediated osteolysis and arthritis remain elusive, warranting further investigation. In this review, we will briefly elaborate on the role of Metrnl in anti-inflammation function in inflammation-related osteolysis, arthritis, and pathological bone resorption, which could facilitate Metrnl's clinical application as a novel therapeutic strategy to prevent bone loss. While the pathogenesis of elbow stiffness remains elusive, current literature suggests that Metrnl likely exerts a pivotal role in its development.

The Role of Oxidative Stress in Tumorigenesis and Progression

Oxidative stress refers to the imbalance between the production of reactive oxygen species (ROS) and the endogenous antioxidant defense system. Its involvement in cell senescence, apoptosis, and series diseases has been demonstrated. Advances in carcinogenic research have revealed oxidative stress as a pivotal pathophysiological pathway in tumorigenesis and to be involved in lung cancer, glioma, hepatocellular carcinoma, leukemia, and so on. This review combs the effects of oxidative stress on tumorigenesis on each phase and cell fate determination, and three features are discussed. Oxidative stress takes part in the processes ranging from tumorigenesis to tumor death via series pathways and processes like mitochondrial stress, endoplasmic reticulum stress, and ferroptosis. It can affect cell fate by engaging in the complex relationships between senescence, death, and cancer. The influence of oxidative stress on tumorigenesis and progression is a multi-stage interlaced process that includes two aspects of promotion and inhibition, with mitochondria as the core of regulation. A deeper and more comprehensive understanding of the effects of oxidative stress on tumorigenesis is conducive to exploring more tumor therapies.

Emerging Roles of Macrophage Polarization in Osteoarthritis: Mechanisms and Therapeutic Strategies

Osteoarthritis (OA) is the most common chronic degenerative joint disease in middle-aged and elderly people, characterized by joint pain and dysfunction. Macrophages are key players in OA pathology, and their activation state has been studied extensively. Various studies have suggested that macrophages might respond to stimuli in their microenvironment by changing their phenotypes to pro-inflammatory or anti-inflammatory phenotypes, which is called macrophage polarization. Macrophages accumulate and become polarized (M1 or M2) in many tissues, such as synovium, adipose tissue, bone marrow, and bone mesenchymal tissues in joints, while resident macrophages as well as other stromal cells, including fibroblasts, chondrocytes, and osteoblasts, form the joint and function as an integrated unit. In this study, we focus exclusively on synovial macrophages, adipose tissue macrophages, and osteoclasts, to investigate their roles in the development of OA. We review recent key findings related to macrophage polarization and OA, including pathogenesis, molecular pathways, and therapeutics. We summarize several signaling pathways in macrophage reprogramming related to OA, including NF-κB, MAPK, TGF-β, JAK/STAT, PI3K/Akt/mTOR, and NLRP3. Of note, despite the increasing availability of treatments for osteoarthritis, like intra-articular injections, surgery, and cellular therapy, the demand for more effective clinical therapies has remained steady. Therefore, we also describe the current prospective therapeutic methods that deem macrophage polarization to be a therapeutic target, including physical stimulus, chemical compounds, and biological molecules, to enhance cartilage repair and alleviate the progression of OA.

Progress in the Correlation Between Inflammasome NLRP3 and Liver Fibrosis

Liver fibrosis is a reversible condition that occurs in the early stages of chronic liver disease. To develop effective treatments for liver fibrosis, understanding the underlying mechanism is crucial. The NOD-like receptor protein 3 (NLRP3) inflammasome, which is a part of the innate immune system, plays a crucial role in the progression of various inflammatory diseases. NLRP3 activation is also important in the development of various liver diseases, including viral hepatitis, alcoholic or nonalcoholic liver disease, and autoimmune liver disease. This review discusses the role of NLRP3 and its associated molecules in the development of liver fibrosis. It also highlights the signal pathways involved in NLRP3 activation, their downstream effects on liver disease progression, and potential therapeutic targets in liver fibrosis. Further research is encouraged to develop effective treatments for liver fibrosis.

SERTAD1 initiates NLRP3-mediated inflammasome activation through restricting NLRP3 polyubiquitination

We here demonstrate that SERTAD1 is an adaptor protein responsible for the regulation of lysine 63 (K63)-linked NLRP3 polyubiquitination by the Cullin1 E3 ubiquitin ligase upon inflammasome activation. SERTAD1 specifically binds to NLRP3 but not to other inflammasome sensors. This endogenous interaction increases after inflammasome activation, interfering with the interaction between NLRP3 and Cullin1. Interleukin (IL)-1β and IL-18 secretion, as well as the cleavage of gasdermin D, are decreased in SERTAD1 knockout bone-marrow-derived macrophages, together with reduced formation of the NLRP3 inflammasome complex. Additionally, SERTAD1-deficient mice show attenuated severity of monosodium-uric-acid-induced peritonitis and experimental autoimmune encephalomyelitis. Analysis of public datasets indicates that expression of SERTAD1 mRNA is significantly increased in the patients of autoimmune diseases. Thus, our findings uncover a function of SERTAD1 that specifically reduces Cullin1-mediated NLRP3 polyubiquitination via direct binding to NLRP3, eventually acting as a crucial factor to regulate the initiation of NLRP3-mediated inflammasome activation.

The pomegranate-derived peptide Pug-4 alleviates nontypeable Haemophilus influenzae-induced inflammation by suppressing NF-kB signaling and NLRP3 inflammasome activation

The respiratory pathogen nontypeable Haemophilus influenzae (NTHi) is the most common cause of exacerbation of chronic obstructive pulmonary disease (COPD), of which an excessive inflammatory response is a hallmark. With the limited success of current medicines there is an urgent need for the development of novel therapeutics that are both safe and effective. In this study, we explored the regulatory potential of pomegranate-derived peptides Pug-1, Pug-2, Pug-3, and Pug-4 on NTHi-induced inflammation. Our results clearly showed that to varying degrees the Pug peptides inhibited NTHi-induced production of IL-1β, a pivotal cytokine in COPD, and showed that these effects were not related to cytotoxicity. Pug-4 peptide exhibited the most potent inhibitory activity. This was demonstrated in all studied cell types including murine (RAW264.7) and human (differentiated THP-1) macrophages as well as human lung epithelial cells (A549). Substantial reduction by Pug-4 of TNF-α, NO and PGE2 in NTHi-infected A549 cells was also observed. In addition, Pug-4 strongly inhibited the expression of nuclear-NF-κB p65 protein and the NF-κB target genes (determined by IL-1β, TNF-α, iNOS and COX-2 mRNA expression) in NTHi-infected A549 cells. Pug-4 suppressed the expression of NLRP3 and pro-IL-1β proteins and inhibited NTHi-mediated cleavage of caspase-1 and mature IL-1β. These results demonstrated that Pug-4 inhibited NTHi-induced inflammation through the NF-κB signaling and NLRP3 inflammasome activation. Our findings herein highlight the significant anti-inflammatory activity of Pug-4, a newly identified peptide from pomegranate, against NTHi-induced inflammation. We therefore strongly suggest the potential of the Pug-4 peptide as an anti-inflammatory medicine candidate for treatment of NTHi-mediated inflammation.

Application of calcium overload-based ion interference therapy in tumor treatment: strategies, outcomes, and prospects

Low selectivity and tumor drug resistance are the main hinderances to conventional radiotherapy and chemotherapy against tumor. Ion interference therapy is an innovative anti-tumor strategy that has been recently reported to induce metabolic disorders and inhibit proliferation of tumor cells by reordering bioactive ions within the tumor cells. Calcium cation (Ca2+) are indispensable for all physiological activities of cells. In particular, calcium overload, characterized by the abnormal intracellular Ca2+ accumulation, causes irreversible cell death. Consequently, calcium overload-based ion interference therapy has the potential to overcome resistance to traditional tumor treatment strategies and holds promise for clinical application. In this review, we 1) Summed up the current strategies employed in this therapy; 2) Described the outcome of tumor cell death resulting from this therapy; 3) Discussed its potential application in synergistic therapy with immunotherapy.