NLRP12 suppresses colon inflammation and tumorigenesis through the negative regulation of noncanonical NF-κB signaling

Insufficient CXCL13 secretion in leprosy foamy macrophages attenuates lymphocyte recruitment and antimicrobial protein production

Background

Pathogens trigger metabolic reprogramming, leading to the formation of foamy macrophages (FMs). This process provides a favorable environment for bacterial proliferation and enables bacteria to evade immune killing.

Objective

To elucidate the mechanisms by which pathogens escape immune surveillance and elimination via the formation of FMs.

Methods

We constructed a FM model using monocyte-derived macrophages (MDMs) that were incubated with oxidized low-density lipoprotein (oxLDL). Subsequently, we employed bulk RNA-sequencing (bulk RNA-seq) to comprehensively analyze the immune responses in MDMs and FMs against Mycobacterium leprae (M. leprae) infection in samples from 10 healthy individuals.

Results

We found that CXCL13, a component of the cytokine-cytokine receptor interaction pathway, was specifically upregulated in M. leprae infected MDMs, when compared with M. leprae infected FMs. Significantly, further functional analyses revealed that in vitro treatment with CXCL13 could enhance the expression of CXCR5, thereby promoting lymphocyte migration and secretion of antimicrobial proteins. Additionally, NLRP12 was found to be specifically and highly expressed in the NOD-like receptor signaling pathway, which was enriched in infected FMs. In macrophages, M. leprae infection increased CXCL13 expression via NF-κB signal pathway. Conversely, in FMs, mycobacteria induced upregulation of CXCL13 was suppressed by NLRP12 through the inhibition of p52 factor expression.

Conclusion

In conclusion, the NLRP12/NF-κB/CXCL13 axis is crucial for the immune response of FMs after mycobacterial infection. These findings contribute to a deeper understanding of the pathological mechanisms of mycobacterial infection.

Innate Immunity Never "NODs" Off: NLRs Regulate the Host Anti-Viral Immune Response

A robust innate immune response is essential in combating viral pathogens. However, it is equally critical to quell overzealous immune signaling to limit collateral damage and enable inflammation resolution. Pattern recognition receptors are critical regulators of these processes. The cytosolic nucleotide-binding domain leucine-rich repeat (NLR; NOD-like receptor) family of pattern recognition receptors plays essential roles in the sensing of viral pathogen-associated molecular patterns and is best characterized for itsr pro-inflammatory biological functions. Specifically, these include the formation of multi-protein complexes, defined as inflammasomes or NODosomes that regulate the production of IL-1beta, IL-18, and pyroptosis, or the induction of NF-ΚB signaling. While these biological effects are inherently pro-inflammatory, it is also important to recognize that other NLR family members conversely function to negatively regulate inflammation through modulating signaling initiated by other families of pattern recognition receptors. Mechanistically, these unique NLRs also form multiprotein complexes that act to attenuate a variety of biological signaling pathways, such as the inhibition of NF-ΚB. This inhibition facilitates inflammation resolution and functions to restore cellular homeostasis. Despite extensive characterization of individual NLR family members, the mechanisms of immune system regulation are highly nuanced and remain enigmatic. This is especially true for non-inflammasome-forming, regulatory NLRs. Here, we discuss recent findings associated with NLR family members that play essential roles in the host immune response to viruses and mechanisms by which these pattern recognition receptors may function to regulate antiviral immunity.

Integrative Bioinformatics Analysis and Experimental Study of NLRP12 Reveal Its Prognostic Value and Potential Functions in Ovarian Cancer

NLRP12 plays a significant role in cellular functional behavior and immune homeostasis, influencing inflammation, tumorigenesis, and prognosis. This study aimed to explore its specific effects on the tumor microenvironment (TME) and its contribution to heterogeneity in ovarian cancer (OV) through bioinformatics analysis and experimental verification. Utilizing various bioinformatics databases and clinical specimens, we investigated NLRP12 expression and its relationship with OV prognosis and immune infiltration. In vitro assays were conducted to assess the impact of NLRP12 on the proliferation and invasion of OV cells. Our findings indicate that NLRP12 is upregulated in OV, with high expression correlating with a negative prognosis. Furthermore, NLRP12 expression demonstrated a positive correlation with the infiltration of various immune cells and the expression of immune checkpoint molecules in OV. Analysis of The Cancer Immunome Atlas (TCIA) database revealed that OV patients with lower NLRP12 expression may exhibit an enhanced response to immunotherapy, particularly CTLA4 blockers, a finding validated in animal experiments. Additionally, the study emphasized the role of NLRP12 in influencing the prognosis of OV patients by promoting epithelial-mesenchymal transition (EMT) in ovarian cancer cells. Finally, we identified a potential therapeutic compound, Schisandrin B (Schi B), which decreases NLRP12 expression in ovarian cancer cells by binding to the transcription factor SPI1 associated with NLRP12. Our findings suggest that NLRP12 serves as a crucial immune-related biomarker predicting poor outcomes in OV, and targeting NLRP12 may represent a promising therapeutic approach for OV patients in the future.

The underlying mechanism and therapeutic potential of IFNs in viral-associated cancers

Interferons (IFNs) are a diverse family of cytokines secreted by various cells, including immune cells, fibroblasts, and certain viral-parasitic cells. They are classified into three types and encompass 21 subtypes based on their sources and properties. The regulatory functions of IFNs closely involve cell surface receptors and several signal transduction pathways. Initially investigated for their antiviral properties, IFNs have shown promise in combating cancer-associated viruses, making them a potent therapeutic approach. Most IFNs have been identified for their role in inhibiting cancer; however, they have also demonstrated cancer-promoting effects under specific conditions. These mechanisms primarily rely on immune regulation and cytotoxic effects, significantly impacting cancer progression. Despite widespread use of IFN-based therapies in viral-related cancers, ongoing research aims to develop more effective treatments. This review synthesizes the signal transduction pathways and regulatory capabilities of IFNs, highlighting their connections with viruses, cancers, and emerging clinical treatments.

Alternative Splicing at the Crossroad of Inflammatory Bowel Diseases and Colitis-Associated Colon Cancer

The risk of developing colorectal cancer (CRC) is increased in ulcerative colitis patients compared to the general population. This increased risk results from the state of chronic inflammation, a well-known tumour-promoting condition. This review explores the pathologic and molecular characteristics of colitis-associated colon cancer (CAC), emphasizing the distinct features from sporadic CRC. We focus on the key signalling pathways involved in the transition to CAC, highlighting the emerging role of alternative splicing in these processes, namely on how inflammation-induced alternative splicing can significantly contribute to the increased CRC risk observed among UC patients. This review calls for more transcriptomic studies to elucidate the molecular mechanisms through which inflammation-induced alternative splicing drives CAC pathogenesis. A better understanding of these splicing events is crucial as they may reveal novel biomarkers for disease progression and have the potential to target changes in alternative splicing as a therapeutic strategy.

Molecular mechanisms of emerging inflammasome complexes and their activation and signaling in inflammation and pyroptosis

Inflammasomes are multi-protein complexes that assemble within the cytoplasm of mammalian cells in response to pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs), driving the secretion of the pro-inflammatory cytokines IL-1β and IL-18, and pyroptosis. The best-characterized inflammasome complexes are the NLRP3, NAIP-NLRC4, NLRP1, AIM2, and Pyrin canonical caspase-1-containing inflammasomes, and the caspase-11 non-canonical inflammasome. Newer inflammasome sensor proteins have been identified, including NLRP6, NLRP7, NLRP9, NLRP10, NLRP11, NLRP12, CARD8, and MxA. These inflammasome sensors can sense PAMPs from bacteria, viruses and protozoa, or DAMPs in the form of mitochondrial damage, ROS, stress and heme. The mechanisms of action, physiological relevance, consequences in human diseases, and avenues for therapeutic intervention for these novel inflammasomes are beginning to be realized. Here, we discuss these emerging inflammasome complexes and their putative activation mechanisms, molecular and signaling pathways, and physiological roles in health and disease.

Disturbed shear stress promotes atherosclerosis through TRIM21-regulated MAPK6 degradation and consequent endothelial inflammation

RATIONALE

Coronary artery plaques often develop in regions subjected to disturbed shear stress (DSS), yet the mechanisms underlying this phenomenon remain poorly understood. Our study aimed to elucidate the unknown role of MAPK6 in shear stress and plaque formation.

METHODS

In vitro and in vivo experiments, RNA-seq, CO-IP and proteomic analysis, combined with single-cell RNA-seq datasets were used to reveal the upstream and downstream mechanisms involved. AAV-MAPK6, ApoE-/-MAPK6flox/floxTEKCre mice and the CXCL12 neutraligand were used to confirm the beneficial effects of MAPK6 against atherosclerosis.

RESULTS

Our study revealed a substantial decrease in MAPK6 protein levels in endothelial cells in response to DSS, both in vivo and in vitro, which was contingent on the binding of the ubiquitin ligase TRIM21 to MAPK6. Endothelium-specific MAPK6 overexpression exerts antiatherosclerotic effects in ApoE-/- mice, elucidating the unexplored role of MAPK6 in atherosclerosis. Comprehensive RNA-seq, integrated single-cell mapping and further experiments unveiled the involvement of MAPK6 in inflammation through the EGR1/CXCL12 axis. ApoE-/-MAPK6flox/floxTEKCre mice finally confirmed that conditional MAPK6 knockout resulted in endothelial inflammation and significant increases in plaque areas. Notably, these effects could be reversed through the neutralization of CXCL12.

CONCLUSIONS

Our study illuminates the advantages of MAPK6 in decelerating plaque progression, highlighting the potential of safeguarding MAPK6 as a novel therapeutic strategy against atherosclerosis.

KEY POINTS

Disturbed flow activates the ubiquitin‒proteasome degradation pathway of MAPK6 in endothelial cells, which is contingent on the binding of the ubiquitin ligase TRIM21 to MAPK6. Endothelial MAPK6 has an advantageous impact on decelerating plaque progression. MAPK6 regulates endothelial inflammation via the EGR1/CXCL12 axis.

NLRP12 c.1382dup promotes the development of Crohn's disease through the ERK/NLRP3/ IL-1β pathway

Whole-genome sequencing was used to identify a dominant inherited NLRP12 c.1382dup mutation in refractory familial Crohn's disease (CD) patients. Additionally, we observed a T insertion at position 1382 in the third exon of NLRP12, leading to a frameshift mutation. Isolation of peripheral blood from mutation carriers and subsequent experiments demonstrated increased interleukin (IL)-1β in CD patients with the NLRP12 c.1382dup mutation. However, the mechanisms by which the NLRP12 c.1382dup mutation mediates IL-1β remain unclear. Our research findings reveal a close correlation between elevated p-ERK levels and increased expression of NLRP3 and IL-1β in the presence of the NLRP12 c.1382dup mutation. Further experiments demonstrate that inhibiting p-ERK with PD98059 effectively reduces the production of NLRP3 and IL-1β. This discovery provides new insights into the pathogenesis of CD, highlighting the significant role of the ERK/NLRP3/IL-1β pathway in the progression of CD. Not only does this offer novel therapeutic targets for treating CD, but it also lays the groundwork for the development of treatment strategies targeting this pathway.

Inflammasomes and their role in PANoptosomes

Inflammasomes are multiprotein signaling structures in the innate immune system that drive cell death and inflammatory responses. These protein complexes generally comprise an innate immune sensor, the adaptor protein ASC, and the inflammatory protease caspase-1. Inflammasomes are formed when a cytosolic sensor, also known as a pattern recognition receptor, senses its cognate ligand, which can include microbial components, endogenous damage/danger signals, or environmental stimuli. Inflammasome assembly leads to autoproteolytic cleavage and activation of caspase-1. This activation, in turn, induces proteolytic maturation and release of the proinflammatory cytokines interleukin (IL)-1β and IL-18, and the activation of the pore-forming molecule gasdermin D to induce cell death, known as pyroptosis. Recent studies have identified inflammasomes as integral components of larger cell death complexes, known as PANoptosomes. These PANoptosomes regulate PANoptosis, an innate immune cell death pathway initiated by innate immune sensors and driven by caspases and receptor-interacting serine/threonine protein kinases. PANoptosome assembly and activation leads to cell lysis, inflammation, and the release of proinflammatory cytokines, damage-associated molecular patterns, and alarmins. In this review, we discuss the current understanding of different inflammasomes and their role in PANoptosomes.

Regulation of NLRPs by reactive oxygen species: A story of crosstalk

The nucleotide oligomerization domain (NOD)-like receptors containing pyrin (NLRP) family of cytosolic pattern-recognition receptors play an integral role in host defense following exposure to a diverse set of pathogenic and sterile threats. The canonical event following ligand recognition is the formation of a heterooligomeric signaling complex termed the inflammasome that produces pro-inflammatory cytokines. Dysregulation of this process is associated with many autoimmune, cardiovascular, metabolic, and neurodegenerative diseases. Despite the range of activating stimuli which affect varied cell types, recent literature makes evident that reactive oxygen species (ROS) are integral to the initiation and propagation of inflammasome signaling. Notably, ROS production and inflammasome activation act in a positive feedback loop to promote this potent immune response. While NLRP3 is by far the most extensively studied NLRP, there is also sufficient literature to make these conclusions for other NLRPs family members. In all cases, a knowledge gap exists regarding the molecular targets and effects of ROS. Future research to define these targets and to parse the order and timing of ROS-mediated NLRP activation will provide meaningful insights into inflammasome biology. This will create novel therapeutic opportunities for the numerous illnesses that are impacted by inflammasome activity.

Unraveling the NLRP family: Structure, function, activation, critical influence on tumor progression, and potential as targets for cancer therapy

The innate immune system serves as the body's initial defense, swiftly detecting danger via pattern recognition receptors (PRRs). Among these, nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing proteins (NLRPs) are pivotal in recognizing pathogen-associated and damage-associated molecular patterns, thereby triggering immune responses. NLRPs, the most extensively studied subset within the NLR family, form inflammasomes that regulate inflammation, essential for innate immunity activation. Recent research highlights NLRPs' significant impact on various human diseases, including cancer. With differential expression across organs, NLRPs influence cancer progression by modulating immune reactions, cell fate, and proliferation. Their clinical significance in cancer makes them promising therapeutic targets. This review provides a comprehensive overview of the structure, function, activation mechanism of the NLRPs family and its potential role in cancer progression. In addition, we particularly focused on the concept of NLRP as a therapeutic target and its potential value in combination with immune checkpoint inhibitors.

The role of pyroptosis in cancer: key components and therapeutic potential

Pyroptosis is a lytic and inflammatory form of gasdermin protein-mediated programmed cell death that is typically initiated by inflammasomes. The inflammasome response is an effective mechanism for eradicating germs and cancer cells in the event of cellular injury. The gasdermin family is responsible for initiating pyroptosis, a process in which holes are made in the cell membrane to allow inflammatory chemicals to escape. Mounting evidence indicates that pyroptosis is critical for controlling the development of cancer. In this review, we provide a general overview of pyroptosis, examine the relationship between the primary elements of pyroptosis and tumors, and stress the necessity of pyroptosis-targeted therapy in tumors. Furthermore, we explore its dual nature as a double-edged sword capable of both inhibiting and facilitating the growth of cancer, depending on the specific conditions. Ultimately, pyroptosis is a phenomenon that has both positive and negative effects on tumors. Using this dual impact in a reasonable manner may facilitate investigation into the initiation and progression of tumors and offer insights for the development of novel treatments centered on pyroptosis.

Identification of immune-associated genes for the diagnosis of ulcerative colitis-associated carcinogenesis via integrated bioinformatics analysis

Background

UC patients suffer more from colorectal cancer (CRC) than the general population, which increases with disease duration. Early colonoscopy is difficult because ulcerative colitis-associated colorectal cancer (UCAC) lesions are flat and multifocal. Our study aimed to identify promising UCAC biomarkers that are complementary endoscopy strategies in the early stages.

Methods

The datasets may be accessed from the Gene Expression Omnibus and The Cancer Genome Atlas databases. The co-expressed modules of UC and CRC were determined via weighted co-expression network analysis (WGCNA). The biological mechanisms of the shared genes were exported for analysis using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. To identify protein interactions and hub genes, a protein-protein interaction network and CytoHubba analysis were conducted. To evaluate gene expression, external datasets and experimental validation of human colon tissues were utilized. The diagnostic value of core genes was examined through receiver operating characteristic (ROC) curves. Immune infiltration analysis was employed to investigate the associations between immune cell populations and hub genes.

Results

Three crucial modules were identified from the WGCNA of UC and CRC tissues, and 33 coexpressed genes that were predominantly enriched in the NF-κB pathway were identified. Two biomarkers (CXCL1 and BCL6) were identified via Cytoscape and validated in external datasets and human colon tissues. CRC patients expressed CXCL1 at the highest level, whereas UC and CRC patients showed higher levels than the controls. The UC cohort expressed BCL6 at the highest level, whereas the UC and CRC cohorts expressed it more highly than the controls. The hub genes exhibited significant diagnostic potential (ROC curve > 0.7). The immune infiltration results revealed a correlation among the hub genes and macrophages, neutrophils and B cells.

Conclusions

The findings of our research suggest that BCL6 and CXCL1 could serve as effective biomarkers for UCAC surveillance. Additionally, they demonstrated a robust correlation with immune cell populations within the CRC tumour microenvironment (TME). Our findings provide a valuable insight about diagnosis and therapy of UCAC.

An NLR family member X1 mutation (p.Arg707Cys) suppresses hepatitis B virus infection in hepatocytes and favors the interaction of retinoic acid-inducible gene 1 with mitochondrial antiviral signaling protein

NLR family member X1 (NLRX1) is an important member of the NOD-like receptor (NLR) family and plays unique roles in immune system regulation. Patients with hepatitis B virus (HBV) infection are more likely to have the NLRX1 mutation p.Arg707Cys than healthy individuals. It has been reported that NLRX1 increases the infection rate of HBV in HepG2 cells expressing sodium taurocholate cotransporting polypeptide (NTCP). However, the role of NLRX1 mutation (p.Arg707Cys) in hepatitis remains unclear. We constructed Huh7 cells that stably overexpressed NTCP, using LV003 lentivirus. First, wild-type (WT) and mutant (MT) NLRX1 overexpression plasmids were constructed. The MT plasmid contained a point mutation at position 707 of the WT overexpression plasmid. Then, Huh7-NTCP cells were transfected with the WT or MT NLRX1 overexpression plasmid, and subsequent NLRX1 expression was analyzed using real-time quantitative polymerase chain reaction (RT-qPCR) and western blot. HBV RNA levels were determined using RT-qPCR. HBsAg and HBcAg levels were confirmed immunohistochemically. Interferon alpha (IFN-α), interleukin 6 (IL-6), and type I interferon beta (IFN-β) levels were determined using enzyme-linked immunosorbent assay kits. p-p65, p-interferon regulatory factor (IRF) 3, and p-IRF7 expression levels were examined using western blot. The interaction of NLRX1 and retinoic acid-inducible gene (RIG)-1/mitochondrial antiviral signaling (MAVS) protein was confirmed by coimmunoprecipitation. The interaction of NLRX1 with IFN-α, IL-6, or IFN-β was analyzed by dual luciferase reporter gene assay. The levels of HBV RNA, HBsAg, and HBcAg in infected cells transfected with the WT NLRX1 or MT NLRX1 expression plasmid were higher than those in the untransfected control group; and these levels were lower in the cells transfected with MT NLRX1 than in those transfected with WT NLRX1. The levels of IFN-α, IFN-β, IL-6, p-p65, p-IRF3, and p-IRF7 were lower in cells transfected with WT NLRX1 or MT NLRX1 than in control cells. The levels of IFN-β, p-p65, p-IRF3, and p-IRF7 were higher in cells transfected with MT NLRX1 than in those transfected with WT NLRX1. Moreover, NLRX1 competitively inhibited RIG1 binding to MAVS, but the mutation in MT NLRX1 reduced this inhibitory effect. In addition, NLRX1 decreased the promoter activity of IFN-α, IFN-β, and IL-6. Our findings revealed that NLRX1 is a regulatory factor that inhibits the anti-HBV ability of hepatocytes and that the mutation p.Arg707Cys in NLRX1 suppresses HBV infection and activates the IFN/nuclear factor κB pathway.

A novel ferroptosis inhibitor, Thonningianin A, improves Alzheimer's disease by activating GPX4

Background: Ferroptosis, a recently unveiled iron-dependent form of cellular demise, has emerged as a pivotal process contributing to the pathology of Alzheimer's Disease (AD). Glutathione Peroxidase 4 (GPX4), a vital defense mechanism countering ferroptosis by nullifying lipid peroxides and maintaining cellular redox equilibrium, has garnered significant attention in AD. Thus, identifying ferroptosis inhibitors to target GPX4 activation may help mitigate neuronal damage and impede AD progression. Objectives: We aimed to screen potent ferroptosis inhibitors and investigate their mechanism of action and therapeutic potential in AD, as well as lay the groundwork for future research in this promising area of study. Methods: This study employed a natural compound library to screen potential ferroptosis inhibitors in RAS-selective lethal compounds 3 (RSL-3)-induced PC-12 cells. Ferroptosis was evaluated by examining the mitochondrial morphology and function, reactive oxygen species (ROS) production, and lipid peroxide levels. The ability to chelate iron and intracellular iron levels was determined by UHPLC-Q/TOF-MS/MS and PGSK staining, respectively. APP Swe/ind- or Tau P301L-overexpressing PC-12 cells, and Amyloid-β transgenic CL4176 and Tau transgenic BR5270 Caenorhabditis elegans were employed as cellular and animal models of AD. Results: Thonningianin A (ThA) was identified as a novel ferroptosis inhibitor, as demonstrated by augmented cellular viability, mitigated mitochondrial impairment, diminished lipid peroxides, iron levels, and ROS generation. Mechanistically, ThA binds with GPX4 and enhances the AMPK/Nrf2 signaling pathway to stimulate GPX4 activation, effectively inhibiting ferroptosis. Moreover, in cellular and Caenorhabditis elegans AD models, ThA substantially inhibits ferroptosis by reducing ROS, lipid peroxide generation, and iron accumulation. Furthermore, ThA significantly delays paralysis, ameliorates food-sensing deficits and increases worms' antioxidative capacity. Conclusion: ThA ameliorates AD by inhibiting neuronal ferroptosis mediated by GPX4 activation through its binding with GPX4 and the upregulation of the AMPK/Nrf2/GPX4 pathway.

Cyclophilin J limits linear ubiquitin signaling and controls colorectal cancer progression

Exorbitant sustained inflammation is closely linked to inflammation-associated disorders, including cancer. The initiation of gastrointestinal cancers such as colorectal cancer is frequently accelerated by uncontrollable chronic inflammation which is triggered by excessive activation of nuclear factor kappa-B (NF-κB) signaling. Linear ubiquitin chains play an important role in activating canonical NF-κB pathway. The only known E3 complex, linear ubiquitin chain assembly complex is responsible for the synthesis of linear ubiquitin chains, thus leading to the activation of NF-κB axis and promoting the development of inflammation and inflammation-associated cancers. We report here cyclophilin J (CYPJ) which is a negative regulator of the linear ubiquitin chain assembly complex. The N terminus of CYPJ binds to the second Npl4 zinc finger (NZF) domain of HOIL-1-interacting protein and the ubiquitin-like domain of Shank-associated RH domain-interacting protein to disrupt the interaction between HOIL-1-interacting protein and Shank-associated RH domain-interacting protein and thus restrains linear ubiquitin chain synthesis and NF-κB activation. Cypj-deficient mice are highly susceptible to dextran sulfate sodium-induced colitis and dextran sulfate sodium plus azoxymethane-induced colon cancer. Moreover, CYPJ expression is induced by hypoxia. Patients with high expression of both CYPJ and hypoxia-inducible factor-1α have longer overall survival and progression-free survival. These results implicate CYPJ as an unexpected robust attenuator of inflammation-driven tumorigenesis that exerts its effects by controlling linear ubiquitin chain synthesis in NF-κB signal pathway.

Focus on negatively regulated NLRs in inflammation and cancer

Nucleotide-binding and oligomerization structural domain (NOD)-like receptors (NLRs) play an important role in innate immunity as cytoplasmic pattern recognition receptors (PRRs). Over the past decade, considerable progress has been made in understanding the mechanisms by which NLR family members regulate immune system function, particularly the formation of inflammasome and downstream inflammatory signals. However, recent studies have shown that some members of the NLRs, including Nlrp12, NLRX1, and NLRC3, are important in the negative regulation of inflammatory signaling and are involved in the development of various diseases, including inflammatory diseases and cancer. Based on this, in this review, we first summarize the interactions between canonical and non-canonical nuclear factor-κB (NF-κB) signaling pathways that are mainly involved in NLRs, then highlight the mechanisms by which the above NLRs negatively regulate inflammatory signaling responses as well as their roles in tumor progression, and finally summarize the synthetic and natural derivatives with therapeutic effects on these NLRs, which are considered as potential therapeutic agents for overcoming inflammatory diseases.

NLRC5 senses NAD+ depletion, forming a PANoptosome and driving PANoptosis and inflammation

NLRs constitute a large, highly conserved family of cytosolic pattern recognition receptors that are central to health and disease, making them key therapeutic targets. NLRC5 is an enigmatic NLR with mutations associated with inflammatory and infectious diseases, but little is known about its function as an innate immune sensor and cell death regulator. Therefore, we screened for NLRC5's role in response to infections, PAMPs, DAMPs, and cytokines. We identified that NLRC5 acts as an innate immune sensor to drive inflammatory cell death, PANoptosis, in response to specific ligands, including PAMP/heme and heme/cytokine combinations. NLRC5 interacted with NLRP12 and PANoptosome components to form a cell death complex, suggesting an NLR network forms similar to those in plants. Mechanistically, TLR signaling and NAD+ levels regulated NLRC5 expression and ROS production to control cell death. Furthermore, NLRC5-deficient mice were protected in hemolytic and inflammatory models, suggesting that NLRC5 could be a potential therapeutic target.

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.

Unlocking the potential of flavonoids: Natural solutions in the fight against colon cancer

Colorectal cancer (CRC) is a major cause of cancer-related deaths worldwide, underscoring the importance of understanding the diverse molecular and genetic underpinnings of CRC to improve its diagnosis, prognosis, and treatment. This review delves into the adenoma-carcinoma-metastasis model, emphasizing the "APC-KRAS-TP53" signature events in CRC development. CRC is categorized into four consensus molecular subtypes, each characterized by unique genetic alterations and responses to therapy, illustrating its complexity and heterogeneity. Furthermore, we explore the role of chronic inflammation and the gut microbiome in CRC progression, emphasizing the potential of targeting these factors for prevention and treatment. This review discusses the impact of dietary carcinogens and lifestyle factors and the critical role of early detection in improving outcomes, and also examines conventional chemotherapy options for CRC and associated challenges. There is significant focus on the therapeutic potential of flavonoids for CRC management, discussing various types of flavonoids, their sources, and mechanisms of action, including their antioxidant properties, modulation of cell signaling pathways, and effects on cell cycle and apoptosis. This article presents evidence of the synergistic effects of flavonoids with conventional cancer therapies and their role in modulating the gut microbiome and immune response, thereby offering new avenues for CRC treatment. We conclude by emphasizing the importance of a multidisciplinary approach to CRC research and treatment, incorporating insights from genetic, molecular, and lifestyle factors. Further research is needed on the preventive and therapeutic potential of natural compounds, such as flavonoids, in CRC, underscoring the need for personalized and targeted treatment strategies.

Unmasking the NLRP3 inflammasome in dendritic cells as a potential therapeutic target for autoimmunity, cancer, and infectious conditions

Proper and functional immune response requires a complex interaction between innate and adaptive immune cells, which dendritic cells (DCs) are the primary actors in this coordination as professional antigen-presenting cells. DCs are armed with numerous pattern recognition receptors (PRRs) such as nucleotide-binding and oligomerization domain-like receptors (NLRs) like NLRP3, which influence the development of their activation state upon sensation of ligands. NLRP3 is a crucial component of the immune system for protection against tumors and infectious agents, because its activation leads to the assembly of inflammasomes that cause the formation of active caspase-1 and stimulate the maturation and release of proinflammatory cytokines. But, when NLRP3 becomes overactivated, it plays a pathogenic role in the progression of several autoimmune disorders. So, NLRP3 activation is strictly regulated by diverse signaling pathways that are mentioned in detail in this review. Furthermore, the role of NLRP3 in all of the diverse immune cells' subsets is briefly mentioned in this study because NLRP3 plays a pivotal role in modulating other immune cells which are accompanied by DCs' responses and subsequently influence differentiation of T cells to diverse T helper subsets and even impact on cytotoxic CD8+ T cells' responses. This review sheds light on the functional and therapeutic role of NLRP3 in DCs and its contribution to the occurrence and progression of autoimmune disorders, prevention of diverse tumors' development, and recognition and annihilation of various infectious agents. Furthermore, we highlight NLRP3 targeting potential for improving DC-based immunotherapeutic approaches, to be used for the benefit of patients suffering from these disorders.

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

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

NF-κB Inducing Kinase Attenuates Colorectal Cancer by Regulating Noncanonical NF-κB Mediated Colonic Epithelial Cell Regeneration

BACKGROUND & AIMS

Dysregulated colonic epithelial cell (CEC) proliferation is a critical feature in the development of colorectal cancer. We show that NF-κB-inducing kinase (NIK) attenuates colorectal cancer through coordinating CEC regeneration/differentiation via noncanonical NF-κB signaling that is unique from canonical NF-kB signaling.

METHODS

Initial studies evaluated crypt morphology/functionality, organoid generation, transcriptome profiles, and the microbiome. Inflammation and inflammation-induced tumorigenesis were initiated in whole-body NIK knockout mice (Nik-/-) and conditional-knockout mice following administration of azoxymethane and dextran sulfate sodium.

RESULTS

Human transcriptomic data revealed dysregulated noncanonical NF-kB signaling. In vitro studies evaluating Nik-/- crypts and organoids derived from mature, nondividing CECs, and colonic stem cells exhibited increased accumulation and stunted growth, respectively. Transcriptomic analysis of Nik-/- cells revealed gene expression signatures associated with altered differentiation-regeneration. When assessed in vivo, Nik-/- mice exhibited more severe colitis with dextran sulfate sodium administration and an altered microbiome characterized by increased colitogenic microbiota. In the inflammation-induced tumorigenesis model, we observed both increased tumor burdens and inflammation in mice where NIK is knocked out in CECs (NikΔCEC). Interestingly, this was not recapitulated when NIK was conditionally knocked out in myeloid cells (NikΔMYE). Surprisingly, conditional knockout of the canonical pathway in myeloid cells (RelAΔMYE) revealed decreased tumor burden and inflammation and no significant changes when conditionally knocked out in CECs (RelAΔCEC).

CONCLUSIONS

Dysregulated noncanonical NF-κB signaling is associated with the development of colorectal cancer in a tissue-dependent manner and defines a critical role for NIK in regulating gastrointestinal inflammation and regeneration associated with colorectal cancer.

Critical role of the gut microbiota in immune responses and cancer immunotherapy

The gut microbiota plays a critical role in the progression of human diseases, especially cancer. In recent decades, there has been accumulating evidence of the connections between the gut microbiota and cancer immunotherapy. Therefore, understanding the functional role of the gut microbiota in regulating immune responses to cancer immunotherapy is crucial for developing precision medicine. In this review, we extract insights from state-of-the-art research to decipher the complicated crosstalk among the gut microbiota, the systemic immune system, and immunotherapy in the context of cancer. Additionally, as the gut microbiota can account for immune-related adverse events, we discuss potential interventions to minimize these adverse effects and discuss the clinical application of five microbiota-targeted strategies that precisely increase the efficacy of cancer immunotherapy. Finally, as the gut microbiota holds promising potential as a target for precision cancer immunotherapeutics, we summarize current challenges and provide a general outlook on future directions in this field.

Blockade of PI3K/AKT signaling pathway by Astragaloside IV attenuates ulcerative colitis via improving the intestinal epithelial barrier

BACKGROUND

The specific pathogenesis of UC is still unclear, but it has been clear that defects in intestinal barrier function play an important role in it. There is a temporary lack of specific drugs for clinical treatment. Astragaloside IV (AS-IV) is one of the main active ingredients extracted from Astragalus root and is a common Chinese herbal medicine for the treatment of gastrointestinal diseases. This study aimed to determine whether AS-IV has therapeutic value for DSS or LPS-induced intestinal epithelial barrier dysfunction in vivo and in vitro and its potential molecular mechanisms.

METHODS

The intestinal tissues from UC patients and colitis mice were collected, intestinal inflammation was observed by colonoscopy, and mucosal barrier function was measured by immunofluorescence staining. PI3K/AKT signaling pathway activator YS-49 and inhibitor LY-29 were administered to colitic mice to uncover the effect of this pathway on gut mucosal barrier modulation. Then, network pharmacology was used to screen Astragaloside IV (AS-IV), a core active component of the traditional Chinese medicine Astragalus membranaceus. The potential of AS-IV for intestinal barrier function repairment and UC treatment through blockade of the PI3K/AKT pathway was further confirmed by histopathological staining, FITC-dextran, transmission electron microscopy, ELISA, immunofluorescence, qRT-PCR, and western blotting. Finally, 16 S rRNA sequencing was performed to uncover whether AS-IV can ameliorate UC by regulating gut microbiota homeostasis.

RESULTS

Mucosal barrier function was significantly damaged in UC patients and murine colitis, and the activated PI3K/AKT signaling pathway was extensively involved. Both in vivo and vitro showed that the AS-IV-treated group significantly relieved inflammation and improved intestinal epithelial permeability by inhibiting the activation of the PI3K/AKT signaling pathway. In addition, microbiome data found that gut microbiota participates in AS-IV-mediated intestinal barrier recovery as well.

CONCLUSIONS

Our study highlights that AS-IV exerts a protective effect on the integrality of the mucosal barrier in UC based on the PI3K/AKT pathway, and AS-IV may serve as a novel AKT inhibitor to provide a potential therapy for UC.

NLRP inflammasomes in health and disease

NLRP inflammasomes are a group of cytosolic multiprotein oligomer pattern recognition receptors (PRRs) involved in the recognition of pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) produced by infected cells. They regulate innate immunity by triggering a protective inflammatory response. However, despite their protective role, aberrant NLPR inflammasome activation and gain-of-function mutations in NLRP sensor proteins are involved in occurrence and enhancement of non-communicating autoimmune, auto-inflammatory, and neurodegenerative diseases. In the last few years, significant advances have been achieved in the understanding of the NLRP inflammasome physiological functions and their molecular mechanisms of activation, as well as therapeutics that target NLRP inflammasome activity in inflammatory diseases. Here, we provide the latest research progress on NLRP inflammasomes, including NLRP1, CARD8, NLRP3, NLRP6, NLRP7, NLRP2, NLRP9, NLRP10, and NLRP12 regarding their structural and assembling features, signaling transduction and molecular activation mechanisms. Importantly, we highlight the mechanisms associated with NLRP inflammasome dysregulation involved in numerous human auto-inflammatory, autoimmune, and neurodegenerative diseases. Overall, we summarize the latest discoveries in NLRP biology, their forming inflammasomes, and their role in health and diseases, and provide therapeutic strategies and perspectives for future studies about NLRP inflammasomes.

The NLR family of innate immune and cell death sensors

Nucleotide-binding oligomerization domain (NOD)-like receptors, also known as nucleotide-binding leucine-rich repeat receptors (NLRs), are a family of cytosolic pattern recognition receptors that detect a wide variety of pathogenic and sterile triggers. Activation of specific NLRs initiates pro- or anti-inflammatory signaling cascades and the formation of inflammasomes-multi-protein complexes that induce caspase-1 activation to drive inflammatory cytokine maturation and lytic cell death, pyroptosis. Certain NLRs and inflammasomes act as integral components of larger cell death complexes-PANoptosomes-driving another form of lytic cell death, PANoptosis. Here, we review the current understanding of the evolution, structure, and function of NLRs in health and disease. We discuss the concept of NLR networks and their roles in driving cell death and immunity. An improved mechanistic understanding of NLRs may provide therapeutic strategies applicable across infectious and inflammatory diseases and in cancer.

The interaction of inflammasomes and gut microbiota: novel therapeutic insights

Inflammasomes are complex platforms for the cleavage and release of inactivated IL-1β and IL-18 cytokines that trigger inflammatory responses against damage-associated molecular patterns (DAMPs) or pathogen-associated molecular patterns (PAMPs). Gut microbiota plays a pivotal role in maintaining gut homeostasis. Inflammasome activation needs to be tightly regulated to limit aberrant activation and bystander damage to the host cells. Several types of inflammasomes, including Node-like receptor protein family (e.g., NLRP1, NLRP3, NLRP6, NLRP12, NLRC4), PYHIN family, and pyrin inflammasomes, interact with gut microbiota to maintain gut homeostasis. This review discusses the current understanding of how inflammasomes and microbiota interact, and how this interaction impacts human health. Additionally, we introduce novel biologics and antagonists, such as inhibitors of IL-1β and inflammasomes, as therapeutic strategies for treating gastrointestinal disorders when inflammasomes are dysregulated or the composition of gut microbiota changes.

Inhibition of HMGB1 improves experimental mice colitis by mediating NETs and macrophage polarization

OBJECTIVE

Inflammatory bowel disease (IBD) is listed by the World Health Organization as one of the modern intractable diseases. High mobility histone box 1 (HMGB1), originally described as a non-histone nucleoprotein involved in transcriptional regulation, was later identified as a pro-inflammatory cytokine that may contribute to the pathogenesis of inflammatory diseases such as IBD. Neutrophil extracellular traps (NETs) play an important role in the pathophysiology of IBD The aim of this study was to investigate the role of HMGB1 in experimental colitis mice and its potential mechanisms of action.

METHODS

We first constructed the experimental colitis mouse model. Intervention of mice by rhHMGB1 supplementation or HMGB1 inhibition. The pathological morphology of the colon was observed using HE staining. Apoptosis of colonic tissue intestinal epithelial cells was evaluated using Tunel assay. The expression of HMGB1, ZO-1 and occludin in colon tissue was detected by immunohistochemistry, ELISA and western-blot. We also assessed the effects of HMGB1 on colonic injury, NETs content, macrophage polarization and inflammatory cells in mice. The regulatory effect of HMGB1 inhibition on NETs was assessed by combining DNase I.

RESULTS

Inhibition of HMGB1 significantly reduced the inflammatory model in experimental colitis mice, as evidenced by reduced body weight, increased colonic length, reduced DAI scores and apoptosis, reduced inflammatory response, and improved colonic histopathological morphology and intestinal mucosal barrier function. Meanwhile, inhibition of HMGB1 was able to reduce the expression of CD86, citH3 and MPO and increase the expression of CD206 in the colonic tissue of mice. In addition, DNase I intervention was also able to improve colonic inflammation in mice. And the best effect was observed when DNase I and inhibition of HMGB1 were intervened together.

CONCLUSION

Inhibition of HMGB1 ameliorates IBD by mediating NETs and macrophage polarization.

Sulforaphane inhibits the migration and invasion of BPDE-induced lung adenocarcinoma cells by regulating NLRP12

This study aims to explore the impact and underlying mechanism of sulforaphane (SFN) intervention on the migration and invasion of lung adenocarcinoma induced by 7, 8-dihydroxy-9, 10-epoxy-benzo (a) pyrene (BPDE). Human lung adenocarcinoma A549 cells were exposed to varying concentrations of BPDE (0.25, 0.50, and 1.00 μM) and subsequently treated with 5 μM SFN. Cell viability was determined using CCK8 assay, while migration and invasion were assessed using Transwell assays. Lentivirus transfection was employed to establish NLRP12 overexpressing A549 cells. ELISA was utilized to quantify IL-33, CXCL12, and CXCL13 levels in the supernatant, while quantitative real-time PCR (qRT-PCR) and Western Blot were used to analyze the expression of NLRP12 and key factors associated with canonical and non-canonical NF-κB pathways. Results indicated an increase in migratory and invasive capabilities, concurrent with heightened expression of IL-33, CXCL12, CXCL13, and factors associated with both canonical and non-canonical NF-κB pathways. Moreover, mRNA and protein levels of NLRP12 were decreased in BPDE-stimulated A549 cells. Subsequent SFN intervention attenuated BPDE-induced migration and invasion of A549 cells. Lentivirus-mediated NLRP12 overexpression not only reversed the observed phenotype in BPDE-induced cells but also led to a reduction in the expression of critical factors associated with both canonical and non-canonical NF-κB pathways. Collectively, we found that SFN could inhibit BPDE-induced migration and invasion of A549 cells by upregulating NLRP12, thereby influencing both canonical and non-canonical NF-κB pathways.

Harnessing innate immune pathways for therapeutic advancement in cancer

The innate immune pathway is receiving increasing attention in cancer therapy. This pathway is ubiquitous across various cell types, not only in innate immune cells but also in adaptive immune cells, tumor cells, and stromal cells. Agonists targeting the innate immune pathway have shown profound changes in the tumor microenvironment (TME) and improved tumor prognosis in preclinical studies. However, to date, the clinical success of drugs targeting the innate immune pathway remains limited. Interestingly, recent studies have shown that activation of the innate immune pathway can paradoxically promote tumor progression. The uncertainty surrounding the therapeutic effectiveness of targeted drugs for the innate immune pathway is a critical issue that needs immediate investigation. In this review, we observe that the role of the innate immune pathway demonstrates heterogeneity, linked to the tumor development stage, pathway status, and specific cell types. We propose that within the TME, the innate immune pathway exhibits multidimensional diversity. This diversity is fundamentally rooted in cellular heterogeneity and is manifested as a variety of signaling networks. The pro-tumor effect of innate immune pathway activation essentially reflects the suppression of classical pathways and the activation of potential pro-tumor alternative pathways. Refining our understanding of the tumor's innate immune pathway network and employing appropriate targeting strategies can enhance our ability to harness the anti-tumor potential of the innate immune pathway and ultimately bridge the gap from preclinical to clinical application.

Lycopene Ameliorated DSS-Induced Colitis by Improving Epithelial Barrier Functions and Inhibiting the Escherichia coli Adhesion in Mice

Adherent-invasive Escherichia coli plays an important role in the pathogenesis of inflammatory bowel disease. Blocking the adhesion of E. coli to intestinal epithelial cells appears to be useful for attenuating inflammatory bowel disease. Lycopene has been reported to have anti-inflammatory and antimicrobial activities. The aim of this study was to test the intervention effect of lycopene on colitis in mice and to investigate the possible mechanism through which lycopene affects the adhesion of E. coli to intestinal epithelial cells. Lycopene (12 mg/kg BW) attenuated dextran sulfate sodium (DSS)-induced colitis, decreased the proportion of E. coli, and activated the NLR family pyrin domain containing 12 and inactivated nuclear factor kappa B pathways. Furthermore, lycopene inhibited the adhesion of E. coli O157:H7 to Caco-2 cells by blocking the interaction between E. coli O157:H7 and integrin β1. Lycopene ameliorated DSS-induced colitis by improving epithelial barrier functions and inhibiting E. coli adhesion. Overall, these results show that lycopene may be a promising component for the prevention and treatment of colitis.

NLRP12 Senses the SARS-CoV-2 Membrane Protein and Promotes an Inflammatory Response

COVID-19 is an acute respiratory disorder that is caused by SARS-CoV-2, in which excessive systemic inflammation is associated with adverse patient clinical outcomes. Here, we observed elevated expression levels of NLRP12 (nucleotide-binding leucine-rich repeat-containing receptor 12) in human peripheral monocytes and lung tissue during infection with SARS-CoV-2. Co-immunoprecipitation analysis revealed that NLRP12 directly interacted with the M protein through its leucine-rich repeat domain. Moreover, in vitro studies demonstrated that NLRP12 interacted with TRAF3 and promoted its ubiquitination and degradation, which counteracted the inhibitory effect of TRAF3 on the NF-κB/MAPK signaling pathway and promoted the production of inflammatory cytokines. Furthermore, an in vivo study revealed that NLRP12 knockout mice displayed attenuated tissue injury and ameliorated inflammatory responses in the lungs when infected with a SARS-CoV-2 M protein-reconstituted pseudovirus and mouse coronavirus. Taken together, these findings suggest that NLRP12 mediates the inflammatory responses during coronavirus infection.

Dynamic modulation of the non-canonical NF-κB signaling pathway for HIV shock and kill

HIV cure still remains an elusive target. The "Shock and Kill" strategy which aims to reactivate HIV from latently infected cells and subsequently kill them through virally induced apoptosis or immune mediated clearance, is the subject of widespread investigation. NF-κB is a ubiquitous transcription factor which serves as a point of confluence for a number of intracellular signaling pathways and is also a crucial regulator of HIV transcription. Due to its relatively lower side effect profile and proven role in HIV transcription, the non-canonical NF-κB pathway has emerged as an attractive target for HIV reactivation, as a first step towards eradication. A comprehensive review examining this pathway in the setting of HIV and its potential utility to cure efforts is currently lacking. This review aims to summarize non-canonical NF-κB signaling and the importance of this pathway in HIV shock-and-kill efforts.

Identification of a Novel NLRP12 Frameshift Mutation (Val730Glyfs∗41) by Whole-Exome Sequencing in Patients with Crohn's Disease

NLRP12 encodes the nucleotide-binding leucine-rich repeat-containing receptor 12 protein and has been linked to familial cold autoinflammatory syndrome 2 (FCAS2). Previous studies have reported that NLRP12 protein can dampen inflammatory responses in DSS-induced mice colitis. To date, only four alterations in the NLRP12 gene have been associated with Crohn's disease (CD). Here, we reported a novel heterozygous NLRP12 frameshift mutation (c.2188dupG, p.Val730Glyfs∗41) identified by whole-exome sequencing in the proband with CD. The Sanger sequencing confirmed that his sister and father also carried this NLRP12 mutation, which cosegregated well with the CD phenotype. In silico analysis predicted this mutation to be disease-causing. Patients heterozygous for this mutation exhibited decreased NLRP12 protein levels in the peripheral blood and colon. Functional assays showed that mutant NLRP12 plasmid-transfected HEK293T cells exhibited significantly lower NLRP12 mRNA and protein levels than wild-type plasmid-transfected cells. The nonsense-mediated decay inhibitor NMDI14 significantly increased NLRP12 mRNA and protein levels in mutant plasmid-transfected cells. Overall, our results demonstrated that this heterozygous NLRP12 mutation (c.2188dupG) resulted in decreased NLRP12 expression, which might contribute to the mechanism underlying CD.

Dubosiella newyorkensis modulates immune tolerance in colitis via the L-lysine-activated AhR-IDO1-Kyn pathway

Commensal bacteria generate immensely diverse active metabolites to maintain gut homeostasis, however their fundamental role in establishing an immunotolerogenic microenvironment in the intestinal tract remains obscure. Here, we demonstrate that an understudied murine commensal bacterium, Dubosiella newyorkensis, and its human homologue Clostridium innocuum, have a probiotic immunomodulatory effect on dextran sulfate sodium-induced colitis using conventional, antibiotic-treated and germ-free mouse models. We identify an important role for the D. newyorkensis in rebalancing Treg/Th17 responses and ameliorating mucosal barrier injury by producing short-chain fatty acids, especially propionate and L-Lysine (Lys). We further show that Lys induces the immune tolerance ability of dendritic cells (DCs) by enhancing Trp catabolism towards the kynurenine (Kyn) pathway through activation of the metabolic enzyme indoleamine-2,3-dioxygenase 1 (IDO1) in an aryl hydrocarbon receptor (AhR)-dependent manner. This study identifies a previously unrecognized metabolic communication by which Lys-producing commensal bacteria exert their immunoregulatory capacity to establish a Treg-mediated immunosuppressive microenvironment by activating AhR-IDO1-Kyn metabolic circuitry in DCs. This metabolic circuit represents a potential therapeutic target for the treatment of inflammatory bowel diseases.

NLRP12 interacts with NLRP3 to block the activation of the human NLRP3 inflammasome

Inflammasomes are multiprotein complexes that drive inflammation and contribute to protective immunity against pathogens and immune pathology in autoinflammatory diseases. Inflammasomes assemble when an inflammasome scaffold protein senses an activating signal and forms a signaling platform with the inflammasome adaptor protein ASC. The NLRP subfamily of NOD-like receptors (NLRs) includes inflammasome nucleators (such as NLRP3) and also NLRP12, which is genetically linked to familial autoinflammatory disorders that resemble diseases caused by gain-of-function NLRP3 mutants that generate a hyperactive NLRP3 inflammasome. We performed a screen to identify ASC inflammasome-nucleating proteins among NLRs that have the canonical pyrin-NACHT-LRR domain structure. Only NLRP3 and NLRP6 could initiate ASC polymerization to form "specks," and NLRP12 failed to nucleate ASC polymerization. However, wild-type NLRP12 inhibited ASC inflammasome assembly induced by wild-type and gain-of-function mutant NLRP3, an effect not seen with disease-associated NLRP12 mutants. The capacity of NLRP12 to suppress NLRP3 inflammasome assembly was limited to human NLRP3 and was not observed for wild-type murine NLRP3. Furthermore, peripheral blood mononuclear cells from patients with an NLRP12 mutant-associated inflammatory disorder produced increased amounts of the inflammatory cytokine IL-1β in response to NLRP3 stimulation. Thus, our findings provide insights into NLRP12 biology and suggest that NLRP3 inhibitors in clinical trials for NLRP3-driven diseases may also be effective in treating NLRP12-associated autoinflammatory diseases.

The NF-κB signaling system in the immunopathogenesis of inflammatory bowel disease

Inflammatory bowel disease (IBD) is an idiopathic, chronic condition characterized by episodes of inflammation in the gastrointestinal tract. The nuclear factor κB (NF-κB) system describes a family of dimeric transcription factors. Canonical NF-κB signaling is stimulated by and enhances inflammation, whereas noncanonical NF-κB signaling contributes to immune organogenesis. Dysregulation of NF-κB factors drives various inflammatory pathologies, including IBD. Signals from many immune sensors activate NF-κB subunits in the intestine, which maintain an equilibrium between local microbiota and host responses. Genetic association studies of patients with IBD and preclinical mouse models confirm the importance of the NF-κB system in host defense in the gut. Other studies have investigated the roles of these factors in intestinal barrier function and in inflammatory gut pathologies associated with IBD. NF-κB signaling modulates innate and adaptive immune responses and the production of immunoregulatory proteins, anti-inflammatory cytokines, antimicrobial peptides, and other tolerogenic factors in the intestine. Furthermore, genetic studies have revealed critical cell type-specific roles for NF-κB proteins in intestinal immune homeostasis, inflammation, and restitution that contribute to the etiopathology of IBD-associated manifestations. Here, we summarize our knowledge of the roles of these NF-κB pathways, which are activated in different intestinal cell types by specific ligands, and their cross-talk, in fueling aberrant intestinal inflammation. We argue that an in-depth understanding of aberrant immune signaling mechanisms may hold the key to identifying predictive or prognostic biomarkers and developing better therapeutics against inflammatory gut pathologies.

NLRP12 is a prognostic biomarker and correlated with immune infiltrates in epithelial ovarian cancer

BACKGROUND

NLRP12 is a member of the intracellular Nod-like receptor (NLR) family, suggesting it is an innate immune receptor for the initiation and progression of several cancers. However, its role on prognosis and immune infiltrates in epithelial ovarian cancer (EOC) is still unknown. The present study aimed to evaluate its prognostic value and its association with immune infiltrates in EOC.

METHODS

The mRNA expression of NLRP12 of EOC from The Cancer Genome Atlas (TCGA) was analyzed. The association between NLRP12 and clinicopathological characters was evaluated with logistic regression. The association between NLRP12 expression and survival was analyzed by Cox regression and Kaplan-Meier analyses. A nomogram was used to predict the impact of NLRP12 on prognosis. Gene Ontology term analysis and gene set enrichment analysis (GSEA) were performed to identify the signaling pathways related to NLRP12 expression. Immune cells infiltration for NLRP12 was analyzed using single-sample GSEA. The relationship between NLRP12 and tumor-infiltrating immune cells (TICs) was investigated by a Wilcoxon rank sum test. The expression of NLRP12 were also further verified in EOC tissues and cell lines. Additionally, we confirmed the biological function of NLRP12 in vitro.

RESULTS

NLRP12 was highly expressed in patients with EOC from TCGA. High NLRP12 expression correlated with poor disease-specific survival (p < 0.001) and overall survival (p < 0.001). Multivariate analysis revealed that NLRP12 expression was an independent prognostic marker for overall survival (p = 0.042). The C-indexes and calibration plots of the nomogram based on multivariate analysis indicated an effective predictive performance for EOC patients. GSEA showed enrichment of cell adhesion, tumorigenesis and immune response in the NLRP12 high expression group. Increased NLRP12 expression correlated positively with several TICs, including macrophages, neutrophils, T effector memory cells and immature dendritic cells (p < 0.001). In addition, NLRP12 silencing inhibited cell proliferation and migration in EOC cells.

CONCLUSIONS

In conclusion, increased NLRP12 expression correlated significantly with poor survival and immune infiltration in EOC.

Harnessing the innate immune system by revolutionizing macrophage-mediated cancer immunotherapy

Immunotherapy is a promising and safer alternative to conventional cancer therapies. It involves adaptive T-cell therapy, cancer vaccines, monoclonal antibodies, immune checkpoint blockade (ICB), and chimeric antigen receptor (CAR) based therapies. However, most of these modalities encounter restrictions in solid tumours owing to a dense, highly hypoxic and immune-suppressive microenvironment as well as the heterogeneity of tumour antigens. The elevated intra-tumoural pressure and mutational rates within fastgrowing solid tumours present challenges in efficient drug targeting and delivery. The tumour microenvironment is a dynamic niche infiltrated by a variety of immune cells, most of which are macrophages. Since they form a part of the innate immune system, targeting macrophages has become a plausible immunotherapeutic approach. In this review, we discuss several versatile approaches (both at pre-clinical and clinical stages) such as the direct killing of tumour-associated macrophages, reprogramming pro-tumour macrophages to anti-tumour phenotypes, inhibition of macrophage recruitment into the tumour microenvironment, novel CAR macrophages, and genetically engineered macrophages that have been devised thus far. These strategies comprise a strong and adaptable macrophage-toolkit in the ongoing fight against cancer and by understanding their significance, we may unlock the full potential of these immune cells in cancer therapy.

Mechanisms of PANoptosis and relevant small-molecule compounds for fighting diseases

Pyroptosis, apoptosis, and necroptosis are mainly programmed cell death (PCD) pathways for host defense and homeostasis. PANoptosis is a newly distinct inflammatory PCD pathway that is uniquely regulated by multifaceted PANoptosome complexes and highlights significant crosstalk and coordination among pyroptosis (P), apoptosis (A), and/or necroptosis(N). Although some studies have focused on the possible role of PANpoptosis in diseases, the pathogenesis of PANoptosis is complex and underestimated. Furthermore, the progress of PANoptosis and related agonists or inhibitors in disorders has not yet been thoroughly discussed. In this perspective, we provide perspectives on PANoptosome and PANoptosis in the context of diverse pathological conditions and human diseases. The treatment targeting on PANoptosis is also summarized. In conclusion, PANoptosis is involved in plenty of disorders including but not limited to microbial infections, cancers, acute lung injury/acute respiratory distress syndrome (ALI/ARDS), ischemia-reperfusion, and organic failure. PANoptosis seems to be a double-edged sword in diverse conditions, as PANoptosis induces a negative impact on treatment and prognosis in disorders like COVID-19 and ALI/ARDS, while PANoptosis provides host protection from HSV1 or Francisella novicida infection, and kills cancer cells and suppresses tumor growth in colorectal cancer, adrenocortical carcinoma, and other cancers. Compounds and endogenous molecules focused on PANoptosis are promising therapeutic strategies, which can act on PANoptosomes-associated members to regulate PANoptosis. More researches on PANoptosis are needed to better understand the pathology of human conditions and develop better treatment.

NLRP12-associated autoinflammatory disease in Chinese adult patients: a single-centre study

BACKGROUND

NLRP12-associated autoinflammatory disease (NLRP12-AID) is an autosomal dominant autoinflammatory disorder caused by variants of NLRP12 gene. We aimed to report a cohort of Chinese adult patients with NLRP12-AID and summarised phenotypes and genotypes.

METHODS

Twenty patients were diagnosed with NLRP12-AID after performing whole-exome sequencing and were included in our cohort. Demographic information, clinical data and treatment response were collected and evaluated. A literature review of NLRP12-AID was performed, and the clinical features and mutated sites were summarised and compared with our cohort.

RESULTS

Among the 20 NLRP12-AID patients, the main clinical features of NLRP12-AID included fever, cutaneous rash, arthralgia/arthritis, pharyngitis/tonsillitis, lymphadenopathy, myalgia and abdominal pain/diarrhoea. Thirteen NLRP12 variants were detected as F402L, G39V, R1030X, R7G, E24A, Q90X, A218V, A259V, W581X, G729R, R859W, c.-150T>C and c.*126G>C. Glucocorticoids were used in 14 patients, immunosuppressive agents in 13, and tocilizumab in 2. Seventeen patients had good responses to therapy. When compared with 50 NLRP12-AID patients from other countries, Chinese patients had fewer variants in exon 3, higher incidences of cutaneous rash, pharyngitis/tonsillitis and lymphadenopathy. Among all these 70 NLRP12-AID patients, patients carrying non-exon-3 variants had higher frequencies of ocular involvement, pharyngitis/tonsillitis, headache and lymphadenopathy than those with exon-3 variants.

CONCLUSION

This is the largest cohort of NLRP12-AID in the world and seven novel variants of NLRP12 were identified. Chinese adult patients of NLRP12-AID had more non-specific symptoms such as pharyngitis/tonsillitis and lymphadenopathy when compared with patients from other countries, for which the less occurrence of exon-3 variants might be one possible reason.

QingXiaoWuWei decoction alleviates methicillin-resistant Staphylococcus aureus-induced pneumonia in mice by regulating metabolic remodeling and macrophage gene expression network via the microbiota-short-chain fatty acids axis

IMPORTANCE

Methicillin-resistant Staphylococcus aureus (MRSA) colonizes the upper respiratory airways and is resistant to antibiotics. MRSA is a frequently acquired infection in hospital and community settings, including cases of MRSA-induced pneumonia. Multidrug-resistant Staphylococcus aureus and the limited efficacy of antibiotics necessitate alternative strategies for preventing or treating the infection. QingXiaoWuWei decoction (QXWWD) protects against both gut microbiota dysbiosis and MRSA-induced pneumonia. Furthermore, the QXWWD-regulated metabolic remodeling and macrophage gene expression network contribute to its protective effects through the microbiota-short-chain fatty acid axis. The results of this study suggest that QXWWD and its pharmacodynamic compounds might have the potential to prevent and treat pulmonary infections, especially those caused by multidrug-resistant organisms. Our study provides a theoretical basis for the future treatment of pulmonary infectious diseases by manipulating gut microbiota and their metabolites via traditional Chinese medicine.

Inhibited Expression of NLRP12 Promotes the Development of Triple-Negative Breast Cancer by Activating the NF-κB Pathway

NLRP12 can affect the progression of different diseases, including hepatocellular carcinoma. However, no report on triple-negative breast cancer (TNBC) has been found. Thus, this study aimed to explore the role of NLRP12 in TNBC. In our study, immunohistochemistry, real-time quantitative PCR (qPCR), and Western blot assays were used to evaluate NLRP12 expression in TNBC tissues and cells. Then, NLRP12 lentivirus was constructed and infected into MDA-MB-231 and MDA-MB-157 cells with or without PTD-p65-P1 treatment. Next, cells were collected for cell function detection using the following procedures: colony formation assay for proliferation, Transwell for migration and invasion, and Western blot for NF-κB and MAPK pathway-associated proteins. Finally, a xenograft mouse model was applied; the tumor volume and weight were determined, and NLRP12, p-IκBb-α, and p-IκBb-α expressions were evaluated using qPCR and Western blot. Results indicated that NLRP12 was lowly expressed in TNBC tissues and cells. The inhibition of NLRP12 could induce the proliferation, migration, and invasion of TNBC cells, which also could be reversed by inhibiting the NF-κB pathway (PTD-p65-P1). Moreover, silencing of NLRP12 could upregulate p-IκBb-α, while IκBb-α, p-ERK, ERK, p-p38, p38, p-JNK, and JNK expressions remained unchanged, thereby indicating that only the NF-κB pathway could be activated by NLRP12 silencing. Furthermore, the xenograft mouse model confirmed the abovementioned findings. Therefore, the low expression of NLRP12 promoted the proliferation, migration, and invasion in TNBC cells by activating the NF-κB pathway. This study might provide insights into TNBC therapy.

Microbial sensing in the intestine

The gut microbiota plays a key role in host health and disease, particularly through their interactions with the immune system. Intestinal homeostasis is dependent on the symbiotic relationships between the host and the diverse gut microbiota, which is influenced by the highly co-evolved immune-microbiota interactions. The first step of the interaction between the host and the gut microbiota is the sensing of the gut microbes by the host immune system. In this review, we describe the cells of the host immune system and the proteins that sense the components and metabolites of the gut microbes. We further highlight the essential roles of pattern recognition receptors (PRRs), the G protein-coupled receptors (GPCRs), aryl hydrocarbon receptor (AHR) and the nuclear receptors expressed in the intestinal epithelial cells (IECs) and the intestine-resident immune cells. We also discuss the mechanisms by which the disruption of microbial sensing because of genetic or environmental factors causes human diseases such as the inflammatory bowel disease (IBD).

Unraveling the intricate relationship: Influence of microbiome on the host immune system in carcinogenesis

BACKGROUND

Cancer is an outcome of various disrupted or dysregulated metabolic processes like apoptosis, growth, and self-cell transformation. Human anatomy harbors trillions of microbes, and these microbes actively influence all kinds of human metabolic activities, including the human immune response. The immune system which inherently acts as a sentinel against microbes, curiously tolerates and even maintains a distinct normal microflora in our body. This emphasizes the evolutionarily significant role of microbiota in shaping our adaptive immune system and even potentiating its function in chronic ailments like cancers. Microbes interact with the host immune cells and play a part in cancer progression or regression by modulating immune cells, producing immunosuppressants, virulence factors, and genotoxins.

RECENT FINDINGS

An expanding plethora of studies suggest and support the evidence of microbiome impacting cancer etiology. Several studies also indicate that the microbiome can supplement various cancer therapies, increasing their efficacy. The present review discusses the relationship between bacterial and viral microbiota with cancer, discussing different carcinogenic mechanisms influenced by prokaryotes with special emphasis on their immunomodulatory axis. It also elucidates the potential of the microbiome in transforming the efficacy of immunotherapeutic treatments.

CONCLUSION

This review offers a thorough overview of the complex interaction between the human immune system and the microbiome and its impact on the development of cancer. The microbiome affects the immune responses as well as progression of tumor transformation, hence microbiome-based therapies can vastly improve the effectiveness of cancer immunotherapies. Individual variations of the microbiome and its dynamic variability in every individual impacts the immune modulation and cancer progression. Therefore, further research is required to understand these underlying processes in detail, so as to design better microbiome-immune system axis in the treatment of cancer.

A novel phenotype of B cells associated with enhanced phagocytic capability and chemotactic function after ischemic stroke

Accumulating evidence has demonstrated the involvement of B cells in neuroinflammation and neuroregeneration. However, the role of B cells in ischemic stroke remains unclear. In this study, we identified a novel phenotype of macrophage-like B cells in brain-infiltrating immune cells expressing a high level of CD45. Macrophage-like B cells characterized by co-expression of B-cell and macrophage markers, showed stronger phagocytic and chemotactic functions compared with other B cells and showed upregulated expression of phagocytosis-related genes. Gene Ontology analysis found that the expression of genes associated with phagocytosis, including phagosome- and lysosome-related genes, was upregulated in macrophage-like B cells. The phagocytic activity of macrophage-like B cells was verified by immunostaining and three-dimensional reconstruction, in which TREM2-labeled macrophage-like B cells enwrapped and internalized myelin debris after cerebral ischemia. Cell-cell interaction analysis revealed that macrophage-like B cells released multiple chemokines to recruit peripheral immune cells mainly via CCL pathways. Single-cell RNA sequencing showed that the transdifferentiation to macrophage-like B cells may be induced by specific upregulation of the transcription factor CEBP family to the myeloid lineage and/or by downregulation of the transcription factor Pax5 to the lymphoid lineage. Furthermore, this distinct B cell phenotype was detected in brain tissues from mice or patients with traumatic brain injury, Alzheimer's disease, and glioblastoma. Overall, these results provide a new perspective on the phagocytic capability and chemotactic function of B cells in the ischemic brain. These cells may serve as an immunotherapeutic target for regulating the immune response of ischemic stroke.

Pulsatillae radix extract alleviates DSS-induced colitis via modulating gut microbiota and inflammatory signaling pathway in mice

Ethnopharmacological relevance

Ulcerative colitis (UC) is a chronic relapsing intestinal disease with complex pathogenesis. The increasing morbidity and mortality of UC become a global public health threat. Baitouweng decoction (BD), a formulated prescription of Traditional Chinese Medicine, has been applied to cure UC for many centuries. However, the therapeutic efficacy and working mechanisms of this medicine are not well studied.

Aim of study

In this study we determined whether Pulsatillae radix, one of four ingredients in BD, had a therapeutic effect on colitis. And explore the underlying mechanism of Pulsatilla chinensis (Bunge) Regel radix in the improvement of DSS-induced colitis in mice model.

Methods

The active compounds of Pulsatilla chinensis was identified by UPLC. The composition of the mice's cecum microbiota was determined by 16S rRNA sequencing. And gene expression profile of colon was detected by transcriptome.

Results

The results showed that Pulsatillae radix significantly improved the clinical symptom, prevented the shorten of colon length, and decreased the diseased activity index (DAI) in an 3 % DSS-induced ulcerative colitis mouse model. We found that Pulsatillae radix reversed the dysbiosis of gut microbiota as evidenced by increase in the relative abundance of Bacteroidetes, Deferribacteres, and Proteobacteria phyla and decrease in Firmicutes, as well as by decrease in the genera levels of Bacteroides, Parabacteroides, Prevotella, Mucispirillum, Coprococcus, Oscillospira, and Escherichia. The results of transcriptome showed Pulsatillae radix administration led to 128 genes up-regulation, and 122 genes down-regulation, up-regulate NOD-like receptor signaling pathway, down-regulate Cytokine-cytokine receptor interaction, and TNF and IL-17 signaling pathways.

Conclusion

in this study, we demonstrate Pulsatillae radix alleviates DSS-induced colitis probably via modulating gut microbiota and inflammatory signaling pathway in DSS-induced colitis mouse model.

NLRC3 deficiency promotes hypoxia-induced pulmonary hypertension development via IKK/NF-κB p65/HIF-1α pathway

Hypoxia-induced pulmonary hypertension is a subgroup of type 3 pulmonary hypertension (PH) with the recommended treatment limited to oxygen therapy and lacks potential therapeutic targets. To investigate the role of NLRC3 in hypoxia-induced PH and its potential mechanism, we first collected lung tissues of high-altitude pulmonary hypertension (HAPH) patients. Immunohistochemistry and immunofluorescence showed that NLRC3 was downregulated and was mainly co-localized with the smooth muscle cells of the pulmonary vessels in HAPH patients. Besides, we found that NLRC3 was also expressed in endothelial cells in HAPH patients for the first time. Then, wild type (WT) and NLRC3 knockout (NLRC3-/-) mice were used to construct hypoxia models and primary pulmonary arterial smooth muscle cells (PASMCs) of rats and endothelial cells were cultured for verification. Right heart catheterization and echocardiography suggested that NLRC3 knockout promoted right ventricular systolic pressure (RVSP) up-regulation, right ventricular hypertrophy and fibrosis in hypoxia-induced mice. This study first demonstrated that NLRC3 deficiency promoted hypoxia-stimulated PASMCs proliferation, Human umbilical vein endothelial cells (HUVECs) apoptosis, migration and inflammation through IKK/NF-κB p65/HIF-1α pathway in vitro and in vivo, further promoted vascular remodeling and PH progression, which provided a new target for the treatment of hypoxia-induced PH.

The role of NLRP12 in inflammatory diseases

Nucleotide-binding leucine-rich repeat-containing receptor 12 (NLRP12), a highly conserved protein containing an N-terminal pyrin domain (PYD), a nucleotide-binding domain and a C-terminal leucine-rich repeat region, belongs to the nucleotide-binding oligomerization domain-like receptor-containing PYD (NLRP) family and is a cytoplasmic sensor that plays a negative role in inflammation. NLRP12 is involved in multiple disease processes, including formation of inflammasomes and regulation of both canonical and noncanonical inflammatory signaling pathways. NLRP12 and pathogenic infections are closely linked, and alterations in NLRP12 expression and activity are associated with inflammatory diseases. In this review, we begin with a summary of the mechanisms of negative regulation by NLRP12. We then underscore the important roles of NLRP12 in the onset and progression of inflammation, infectious disease, host defense, carcinogenesis and COVID-19. Finally, we highlight factors that influence NLRP12 activity, including synthetic and naturally derived agonists, and are regarded as potential therapeutic agents to overcome inflammatory diseases.