NLRP12 negatively regulates proinflammatory cytokine production and host defense against Brucella abortus

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 intricate interactions between inflammasomes and bacterial pathogens: Roles, mechanisms, and therapeutic potentials

Inflammasomes are intracellular multiprotein complexes that consist of a sensor, an adaptor, and a caspase enzyme to cleave interleukin (IL)-1β and IL-18 into their mature forms. In addition, caspase-1 and -11 activation results in the cleavage of gasdermin D to form pores, thereby inducing pyroptosis. Activation of the inflammasome and pyroptosis promotes host defense against pathogens, whereas dysregulation of the inflammasome can result in various pathologies. Inflammasomes exhibit versatile microbial signal detection, directly or indirectly, through cellular processes, such as ion fluctuations, reactive oxygen species generation, and the disruption of intracellular organelle function; however, bacteria have adaptive strategies to manipulate the inflammasome by altering microbe-associated molecular patterns, intercepting innate pathways with secreted effectors, and attenuating inflammatory and cell death responses. In this review, we summarize recent advances in the diverse roles of the inflammasome during bacterial infections and discuss how bacteria exploit inflammasome pathways to establish infections or persistence. In addition, we highlight the therapeutic potential of harnessing bacterial immune subversion strategies against acute and chronic bacterial infections. A more comprehensive understanding of the significance of inflammasomes in immunity and their intricate roles in the battle between bacterial pathogens and hosts will lead to the development of innovative strategies to address emerging threats posed by the expansion of drug-resistant bacterial infections.

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.

NLRP12 inhibits PRRSV-2 replication by promoting GP2a degradation via MARCH8

NLRP12, a member of the NLR family, has been shown to exert a vital function in orchestrating immune responses. Here, using the immunosuppressive porcine reproductive and respiratory syndrome virus (PRRSV) as a model, the role of NLRP12 in virus infection was deciphered. We demonstrated that overexpression of NLRP12 significantly restrained PRRSV replication, while NLRP12 silencing resulted in increased viral titer. Mechanistically, NLRP12 interacts with glycoprotein 2a (GP2a) through its LRR domain and recruits the membrane-associated RING-CH E3 ubiquitin ligase 8 (MARCH8) via the PYD domain. NLRP12 facilitates the lysine-48 (K48)-linked polyubiquitination of GP2a at K128 and induces its lysosome degradation via the MARCH8-NDP52 (nuclear dot protein 52 kDa) pathway. To counteract this, PRRSV Nsp2 effectively prevented the polyubiquitination of GP2a induced by NLRP12 by its deubiquitinating activity. Meanwhile, the overexpression of Nsp4 decreased the mRNA of endogenous NLRP12 and cleaved NLRP12 in a 3C-like protease activity-dependent manner, which collaboratively counteracts the antiviral function of NLRP12. Collectively, this study revealed the mechanisms of the NLRP12-MARCH8-NDP52 axis in the host defense against PRRSV, which might be harnessed for the development of anti-PRRSV therapies.

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.

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.

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.

Genetic variations in NLRP3 and NLRP12 genes in adult-onset patients with autoinflammatory diseases: a comparative study

Objectives

Cryopyrin-associated periodic syndrome or NLRP3-associated autoinflammatory disease (NLRP3-AID) and NLRP12-AID are both Mendelian disorders with autosomal dominant inheritance. Both diseases are rare, primarily reported in the pediatric population, and are thought to be phenotypically indistinguishable. We provide the largest cohort of adult-onset patients and compared these diseases and the gene variant frequency to population controls.

Methods

A cohort of adult patients with AIDs were retrospectively studied. All underwent molecular testing for periodic fever syndrome gene panels after extensive and negative workups for systemic autoimmune and other related diseases. Patients were divided into Group 1- NLRP3-AID patients with NLRP3 variants (N=15), Group 2- NLRP12-AID with NLRP12 variants (N=14) and Group 3- both NLRP3 and NLRP12 (N=9) variants. Exome sequence data of two large control populations including the ARIC study were used to compare gene variant distribution and frequency.

Results

All 38 patients were Caucasian with women accounting for 82%. Median age at diagnosis was 41 ± 23 years and the disease duration at diagnosis was 14 ± 13 years. We identified statistically significant differences between the groups, notably that gastrointestinal symptoms as well as evaluations for same were significantly more frequent in patients with NLRP12 variants, and headaches/dizziness were less common among the NLRP12 patients. Livedo reticularis was noted in four patients, exclusively among NLRP12 carriers. Over 50% of patients in Groups 1 and 2 carry low-frequency disease-associated variants, while the remaining carry rare variants. We unprecedently identified digenic variants, i.e., the coexistence of NLRP3 and NLRP12, which were either both low frequency or low frequency/rare. Allele frequencies of all variants identified in our cohort were either absent or significantly lower in the control populations, further strengthening the evidence of susceptibility of these variants to SAID phenotypes.

Conclusion

Our comparative study shows that both NLRP3-AID and NLRP12-AID share similar clinical phenotypes, yet there are significant differences between them with regard to gastrointestinal and neurological symptoms. A spectrum of high to low genetic variations in both genes can contribute to SAID individually or in combination.

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.

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).

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.

Inflammasomes in human reproductive diseases

Inflammasomes are multi-protein complexes localized within immune and non-immune cells that induce caspase activation, proinflammatory cytokine secretion, and ultimately pyroptosis-a type of cell death. Inflammasomes are involved in a variety of human diseases, especially acute or chronic inflammatory diseases. In this review, we focused on the strong correlation between the NLRP3 inflammasome and various reproductive diseases, including ovarian aging or premature ovarian insufficiency, PCOS, endometriosis, recurrent spontaneous abortion, preterm labor, pre-eclampsia, and male subfertility, as well as the multifaceted role of NLRP3 in the pathogenesis and treatment of these diseases. In addition, we provide an overview of the structure and amplification of inflammasomes. This comprehensive review demonstrates the vital role of NLRP3 inflammasome activation in human reproductive diseases together with the underlying mechanisms, offers new insights for mechanistic studies of reproduction, and provides promising possibilities for the development of drugs targeting the NLRP3 inflammasome for the treatment of reproductive disorders in the future.

NOD-like Receptor Signaling Pathway in Gastrointestinal Inflammatory Diseases and Cancers

Nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) are intracellular proteins with a central role in innate and adaptive immunity. As a member of pattern recognition receptors (PRRs), NLRs sense specific pathogen-associated molecular patterns, trigger numerous signaling pathways and lead to the secretion of various cytokines. In recent years, cumulative studies have revealed the significant impacts of NLRs in gastrointestinal (GI) inflammatory diseases and cancers. Deciphering the role and molecular mechanism of the NLR signaling pathways may provide new opportunities for the development of therapeutic strategies related to GI inflammatory diseases and GI cancers. This review presents the structures and signaling pathways of NLRs, summarizes the recent advances regarding NLR signaling in GI inflammatory diseases and GI cancers and describes comprehensive therapeutic strategies based on this signaling pathway.

Bacillus Calmette-Guérin-Trained Macrophages Elicit a Protective Inflammatory Response against the Pathogenic Bacteria Brucella abortus

The bacillus Calmette-Guérin (BCG) can elicit enhanced innate immune responses against a wide range of infections, known as trained immunity. Brucella abortus is the causative agent of brucellosis, a debilitating disease that affects humans and animals. In this study, we demonstrate that C57BL/6 mouse bone marrow-derived macrophages under BCG training enhance inflammatory responses against B. abortus. BCG-trained macrophages showed increased MHC class II and CD40 expression on the cell surface and higher IL-6, IL-12, and IL-1β production. The increase in IL-1β secretion was accompanied by enhanced activation of canonical and noncanonical inflammasome platforms. We observed elevated caspase-11 expression and caspase-1 processing in BCG-trained macrophages in response to B. abortus compared with untrained cells. In addition, these BCG-trained cells showed higher NLRP3 expression after B. abortus infection. From a metabolic point of view, signaling through the Akt/mammalian target of rapamycin/S6 kinase pathway was also enhanced. In addition, BCG training resulted in higher inducible NO synthase expression and nitrite production, culminating in an improved macrophage-killing capacity against intracellular B. abortus. In vivo, we monitored a significant reduction in the bacterial burden in organs from BCG-trained C57BL/6 mice when compared with the untrained group. In addition, previous BCG immunization of RAG-1-deficient mice partially protects against Brucella infection, suggesting the important role of the innate immune compartment in this scenario. Furthermore, naive recipient mice that received BM transfer from BCG-trained donors showed greater resistance to B. abortus when compared with their untrained counterparts. These results demonstrate that BCG-induced trained immunity in mice results in better control of intracellular B. abortus in vivo and in vitro.

Inflammasome-Independent Roles of NLR and ALR Family Members

Pattern recognition receptors, including members of the NLR and ALR families, are essential for recognition of both pathogen- and host-derived danger signals. Several members of these families, including NLRP1, NLRP3, NLRC4, and AIM2, are capable of forming multiprotein complexes, called inflammasomes, that result in the activation of pro-inflammatory caspase-1. However, in addition to the formation of inflammasomes, a number of these family members exert inflammasome-independent functions. Here, we will discuss inflammasome-independent functions of NLRC4, NLRP12, and AIM2 and examine their roles in regulating innate and adaptive immune processes.

Expression of NLRP3 and AIM2 inflammasome in Peripheral blood in Chinese patients with acute and chronic brucellosis

Brucellosis is a zoonotic disease caused by Brucella abortus. An efficient immune response is crucial for curing brucellosis. The inflammasome plays a significant role in the immune response. It is unclear which inflammasome is active in acute and chronic brucellosis and how its levels relate to inflammatory cytokines. A total of 40 patients with acute or chronic brucellosis and 20 healthy volunteers had peripheral blood samples collected. The expression levels of AIM2, NLRP3, ASC, and Caspase-1 were determined by a real-time polymerase chain reaction from RNA and serum samples, and IL-1β, IL-18, and IFN-γ were measured by enzyme-linked immunosorbent assay. In the acute brucellosis group, AIM2 expression was significantly higher, while ACS expression was significantly lower than that of healthy volunteers. In patients with chronic brucellosis, AIM2 expression was significantly lower, while Caspase-1 expression was significantly higher than that of healthy volunteers. Serum IL-18 and IFN-γ levels were significantly higher in patients with acute brucellosis than in healthy controls. The IFN-γ level was also significantly higher in patients with chronic brucellosis than in healthy controls. The inflammasome responds differently in different stages of brucellosis. The inflammasome may be the site of action of immune escape in brucellosis.

Immunosuppressive Mechanisms in Brucellosis in Light of Chronic Bacterial Diseases

Brucellosis is considered one of the major zoonoses worldwide, constituting a critical livestock and human health concern with a huge socio-economic burden. Brucella genus, its etiologic agent, is composed of intracellular bacteria that have evolved a prodigious ability to elude and shape host immunity to establish chronic infection. Brucella's intracellular lifestyle and pathogen-associated molecular patterns, such as its specific lipopolysaccharide (LPS), are key factors for hiding and hampering recognition by the immune system. Here, we will review the current knowledge of evading and immunosuppressive mechanisms elicited by Brucella species to persist stealthily in their hosts, such as those triggered by their LPS and cyclic β-1,2-d-glucan or involved in neutrophil and monocyte avoidance, antigen presentation impairment, the modulation of T cell responses and immunometabolism. Attractive strategies exploited by other successful chronic pathogenic bacteria, including Mycobacteria, Salmonella, and Chlamydia, will be also discussed, with a special emphasis on the mechanisms operating in brucellosis, such as granuloma formation, pyroptosis, and manipulation of type I and III IFNs, B cells, innate lymphoid cells, and host lipids. A better understanding of these stratagems is essential to fighting bacterial chronic infections and designing innovative treatments and vaccines.

Inflammasomes and Pyroptosis of Liver Cells in Liver Fibrosis

Inflammasomes are multiprotein complexes that can sense danger signals and activate caspase-1 to mediate pro-inflammatory cytokines release and pyroptotic cell death. There are two main canonical and non-canonical signaling pathways that trigger inflammasome activation. Inflammasomes are expressed and assembled in parenchymal and nonparenchymal cells in response to liver injury in the liver. Additionally, the hepatocytes, biliary epithelial cells (cholangiocytes), hepatic stellate cells (HSCs), hepatic macrophages, and liver sinusoidal endothelial cells (LSECs) contribute to liver fibrosis via different mechanisms. However, the underlying mechanism of the inflammasome and pyroptosis in these liver cells in liver fibrosis remains elusive. This review summarizes the activation and function of inflammasome complexes and then discusses the association between inflammasomes, pyroptosis, and liver fibrosis. Unlike other similar reviewers, we will focus on the effect of inflammasome activation and pyroptosis in the various liver cells during the development of liver fibrosis. We will also highlight the latest progress of pharmacological intervention in inflammasome-mediated liver fibrosis.

The innate immune receptor Nlrp12 suppresses autoimmunity to the retina

Background

Nod-like receptors (NLRs) are critical to innate immune activation and induction of adaptive T cell responses. Yet, their role in autoinflammatory diseases of the central nervous system (CNS) remains incompletely defined. The NLR, Nlrp12, has been reported to both inhibit and promote neuroinflammation in an animal model of multiple sclerosis (experimental autoimmune encephalomyelitis, EAE), where its T cell-specific role has been investigated. Uveitis resulting from autoimmunity of the neuroretina, an extension of the CNS, involves a breach in immune privilege and entry of T cells into the eye. Here, we examined the contribution of Nlrp12 in a T cell-mediated model of uveitis, experimental autoimmune uveitis (EAU).

Methods

Mice were immunized with interphotoreceptor retinoid-binding protein peptide 1–20 (IRBP_1–20) emulsified in Complete Freund’s adjuvant, CFA. Uveitis was evaluated by clinical and histopathological scoring, and comparisons were made in WT vs. Nlrp12^−/− mice, lymphopenic Rag1^−/− mice reconstituted with WT vs. Nlrp12^−/− CD4⁺ T cells, or among bone marrow (BM) chimeric mice. Antigen-specific Th-effector responses were evaluated by ELISA and intracellular cytokine staining. Cellular composition of uveitic eyes from WT or Nlrp12^−/− mice was compared using flow cytometry. Expression of Nlrp12 and of cytokines/chemokines within the neuroretina was evaluated by immunoblotting and quantitative PCR.

Results

Nlrp12^−/− mice developed exacerbated uveitis characterized by extensive vasculitis, chorioretinal infiltrates and photoreceptor damage. Nlrp12 was dispensable for T cell priming and differentiation of peripheral Th1 or Th17 cells, and uveitis in immunodeficient mice reconstituted with either Nlrp12^−/− or WT T cells was similar. Collectively, this ruled out T cells as the source of Nlrp12-mediated protection to EAU. Uveitic Nlrp12^−/− eyes had more pronounced myeloid cell accumulation than uveitic WT eyes. Transplantation of Nlrp12^−/− BM resulted in increased susceptibility to EAU regardless of host genotype, but interestingly, a non-hematopoietic origin for Nlrp12 function was also observed. Indeed, Nlrp12 was found to be constitutively expressed in the neuroretina, where it suppressed chemokine/cytokine induction.

Conclusions

Our data identify a combinatorial role for Nlrp12 in dampening autoimmunity of the neuroretina. These findings could provide a pathway for development of therapies for uveitis and potentially other autoinflammatory/autoimmune diseases of the CNS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02425-x.

Advances in the Relationship Between Pyroptosis and Diabetic Neuropathy

Pyroptosis is a novel programmed cell death process that promotes the release of interleukin-1β (IL-1β) and interleukin-18 (IL-18) by activating inflammasomes and gasdermin D (GSDMD), leading to cell swelling and rupture. Pyroptosis is involved in the regulation of the occurrence and development of cardiovascular and cerebrovascular diseases, tumors, and nerve injury. Diabetes is a metabolic disorder characterized by long-term hyperglycemia, insulin resistance, and chronic inflammation. The people have paid more and more attention to the relationship between pyroptosis, diabetes, and its complications, especially its important regulatory significance in diabetic neurological diseases, such as diabetic encephalopathy (DE) and diabetic peripheral neuropathy (DPN). This article will give an in-depth overview of the relationship between pyroptosis, diabetes, and its related neuropathy, and discuss the regulatory pathway and significance of pyroptosis in diabetes-associated neuropathy.

Nod-like Receptors: Critical Intracellular Sensors for Host Protection and Cell Death in Microbial and Parasitic Infections

Cell death is an essential immunological apparatus of host defense, but dysregulation of mutually inclusive cell deaths poses severe threats during microbial and parasitic infections leading to deleterious consequences in the pathological progression of infectious diseases. Nucleotide-binding oligomerization domain (NOD)-Leucine-rich repeats (LRR)-containing receptors (NLRs), also called nucleotide-binding oligomerization (NOD)-like receptors (NLRs), are major cytosolic pattern recognition receptors (PRRs), their involvement in the orchestration of innate immunity and host defense against bacteria, viruses, fungi and parasites, often results in the cleavage of gasdermin and the release of IL-1β and IL-18, should be tightly regulated. NLRs are functionally diverse and tissue-specific PRRs expressed by both immune and non-immune cells. Beyond the inflammasome activation, NLRs are also involved in NF-κB and MAPK activation signaling, the regulation of type I IFN (IFN-I) production and the inflammatory cell death during microbial infections. Recent advancements of NLRs biology revealed its possible interplay with pyroptotic cell death and inflammatory mediators, such as caspase 1, caspase 11, IFN-I and GSDMD. This review provides the most updated information that caspase 8 skews the NLRP3 inflammasome activation in PANoptosis during pathogen infection. We also update multidimensional roles of NLRP12 in regulating innate immunity in a content-dependent manner: novel interference of NLRP12 on TLRs and NOD derived-signaling cascade, and the recently unveiled regulatory property of NLRP12 in production of type I IFN. Future prospects of exploring NLRs in controlling cell death during parasitic and microbial infection were highlighted.

Molecular biology of autoinflammatory diseases

The long battle between humans and various physical, chemical, and biological insults that cause cell injury (e.g., products of tissue damage, metabolites, and/or infections) have led to the evolution of various adaptive responses. These responses are triggered by recognition of damage-associated molecular patterns (DAMPs) and/or pathogen-associated molecular patterns (PAMPs), usually by cells of the innate immune system. DAMPs and PAMPs are recognized by pattern recognition receptors (PRRs) expressed by innate immune cells; this recognition triggers inflammation. Autoinflammatory diseases are strongly associated with dysregulation of PRR interactomes, which include inflammasomes, NF-κB-activating signalosomes, type I interferon-inducing signalosomes, and immuno-proteasome; disruptions of regulation of these interactomes leads to inflammasomopathies, relopathies, interferonopathies, and proteasome-associated autoinflammatory syndromes, respectively. In this review, we discuss the currently accepted molecular mechanisms underlying several autoinflammatory diseases.

Pyroptosis in diabetic nephropathy

Diabetic nephropathy (DN), a sterile inflammatory disease, is a serious complication of diabetes mellitus. However, recent evidence indicates that pyroptosis, a new term for pro-inflammatory cell death featured by gasdermin D (GSDMD)-stimulated plasma membrane pore generation, cell expansion and rapid lysis with the extensive secretion of pro-inflammatory factors, including interleukin-1β (IL-1β) and -18 (IL-18) may be involved in DN. Caspase-1-induced canonical and caspase-4/5/11-induced non-canonical inflammasome-signaling pathways are mainly believed to participate in pyroptosis-mediated cell death. Further research has uncovered that activation of the caspase-3/8 signaling pathway may also activate pyroptosis. Accumulating evidence has shown that NLRP3 inflammasome activation plays a critical role in promoting the pathogenesis of DN. In addition, current studies have suggested that pyroptosis-induced cell death promotes several diabetic complications that include DN. Our present study briefs the cellular mechanisms of pyroptosis-related signaling pathways and their impact on the promotion of DN. In this review, several investigational compounds suppressing pyroptosis-mediated cell death are explored as promising therapeutics in DN.

Overexpression of ASMT likely enhances the resistance of transgenic sheep to brucellosis by influencing immune-related signaling pathways and gut microbiota

Melatonin is a pleiotropic molecule with a variety of biological functions, which include its immunoregulatory action in mammals. Brucellosis is a worldwide endemic zoonotic disease caused by the Brucella, which not only causes huge economic losses for the livestock industry but also impacts human health. To target this problem, in current study, two marker-free transgenic sheep overexpressing melatonin synthetic enzyme ASMT (acetylserotonin O-methyltransferase) gene were generated and these melatonin enrich transgenic sheep were challenged by Brucella infection. The results showed that the serum melatonin concentration was significantly higher in transgenic sheep than that of wild type (726.92 ± 70.6074 vs 263.10 ± 34.60 pg/mL, P < .05). Brucella challenge test showed that two thirds (4/6) of the wild-type sheep had brucellosis, while none of the transgenic sheep were infected. Whole-blood RNA-seq results showed that differential expression genes (DEGs) were significantly enriched in natural killer cell-mediated cytotoxicity, phagosome, antigen processing, and presentation signaling pathways in overexpression sheep. The DEGs of toll-like receptors (TLRs) and NOD-like receptors (NLRs) families were verified by qPCR and it showed that TLR1, TLR2, TLR7, CD14, NAIP, and CXCL8 expression levels in overexpression sheep were significantly higher and NLRP1, NLRP3, and TNF expression levels were significantly lower than those of wild type. The rectal feces were subjected to 16S rDNA amplicon sequencing, and the microbial functional analysis showed that the transgenic sheep had significantly lower abundance of microbial genes related to infectious diseases compared to the wild type, indicating overexpression animals are likely more resistant to infectious diseases than wild type. Furthermore, exogenous melatonin treatment relieved brucellosis inflammation by upregulating anti-inflammatory cytokines IL-4 and downregulating pro-inflammatory IL-2, IL-6, and IFN-γ. Our preliminary results provide an informative reference for the study of the relationship between melatonin and brucellosis.

Galectin-3 regulates proinflammatory cytokine function and favours Brucella abortus chronic replication in macrophages and mice

In this study, we provide evidence that galectin-3 (Gal-3) plays an important role in Brucella abortus infection. Our results showed increased Gal-3 expression and secretion in B. abortus infected macrophages and mice. Additionally, our findings indicate that Gal-3 is dispensable for Brucella-containing vacuoles disruption, inflammasome activation and pyroptosis. On the other hand, we observed that Brucella-induced Gal-3 expression is crucial for induction of molecules associated to type I IFN signalling pathway, such as IFN-β: Interferon beta (IFN-β), C-X-C motif chemokine ligand 10 (CXCL10) and guanylate-binding proteins. Gal-3 KO macrophages showed reduced bacterial numbers compared to wild-type cells, suggesting that Gal-3 facilitates bacterial replication in vitro. Moreover, priming Gal-3 KO cells with IFN-β favoured B. abortus survival in macrophages. Additionally, we also observed that Gal-3 KO mice are more resistant to B. abortus infection and these animals showed elevated production of proinflammatory cytokines when compared to control mice. Finally, we observed an increased recruitment of macrophages, dendritic cells and neutrophils in spleens of Gal-3 KO mice compared to wild-type animals. In conclusion, this study demonstrated that Brucella-induced Gal-3 is detrimental to host and this molecule is implicated in inhibition of recruitment and activation of immune cells, which promotes B. abortus spread and aggravates the infection. TAKE AWAYS: Brucella abortus infection upregulates galectin-3 expression Galectin-3 regulates guanylate-binding proteins expression but is not required for Brucella-containing vacuole disruption Galectin-3 modulates proinflammatory cytokine production during bacterial infection Galectin-3 favours Brucella replication.

NLRP6-associated host microbiota composition impacts in the intestinal barrier to systemic dissemination of Brucella abortus

Brucella abortus is a Gram-negative bacterium responsible for a worldwide zoonotic infection—Brucellosis, which has been associated with high morbidity rate in humans and severe economic losses in infected livestock. The natural route of infection is through oral and nasal mucosa but the invasion process through host gut mucosa is yet to be understood. Studies have examined the role of NLRP6 (NOD-like receptor family pyrin domain-containing-6 protein) in gut homeostasis and defense against pathogens. Here, we investigated the impact of gut microbiota and NLRP6 in a murine model of Ba oral infection. Nlrp6^-/- and wild-type (WT) mice were infected by oral gavage with Ba and tissues samples were collected at different time points. Our results suggest that Ba oral infection leads to significant alterations in gut microbiota. Moreover, Nlrp6^-/- mice were more resistant to infection, with decreased CFU in the liver and reduction in gut permeability when compared to the control group. Fecal microbiota transplantation from WT and Nlrp6^-/- into germ-free mice reflected the gut permeability phenotype from the donors. Additionally, depletion of gut microbiota by broad-spectrum-antibiotic treatment prevented Ba replication in WT while favoring bacterial growth in Nlrp6^-/-. Finally, we observed higher eosinophils in the gut and leukocytes in the blood of infected Nlrp6^-/- compared to WT-infected mice, which might be associated to the Nlrp6^-/- resistance phenotype. Altogether, these results indicated that gut microbiota composition is the major factor involved in the initial stages of pathogen host replication and partially also by the resistance phenotype observed in Nlrp6 -/- mice regulating host inflammation against Ba infection.

Brucella abortus (Ba) is an intracellular bacterium that causes zoonotic and clinical problems worldwide. Although the common route of infection is through oral and nasal, the mechanisms toward the gastrointestinal mucosa response is still unexplored. It is well known that microbiota promotes and maintains host intestinal homeostasis during bacterial infections. However, mechanisms by which the gut microbiota affects the Ba infection have not yet been demonstrated. Here, we provide significant insights into the relationship between gut microbiota and B. abortus oral infection and demonstrate the gut microbiota contribution to the gut permeability and dissemination of Ba. Furthermore, we investigated the participation of the gut microbiota from Nlrp6 deficient mice, on the gut permeability and Ba infection. Substantial experiments performed, mostly in vivo, showed that gut microbiota alterations promote gut barrier disruption, as indicated by increased gut permeability after Ba oral infection. Thus, our work highlights the role of gut mucosal environment through gut microbiota and Nlrp6 molecule involved in host innate immune responses to Ba infection.

Role of NLRs in the Regulation of Type I Interferon Signaling, Host Defense and Tolerance to Inflammation

Type I interferon signaling contributes to the development of innate and adaptive immune responses to either viruses, fungi, or bacteria. However, amplitude and timing of the interferon response is of utmost importance for preventing an underwhelming outcome, or tissue damage. While several pathogens evolved strategies for disturbing the quality of interferon signaling, there is growing evidence that this pathway can be regulated by several members of the Nod-like receptor (NLR) family, although the precise mechanism for most of these remains elusive. NLRs consist of a family of about 20 proteins in mammals, which are capable of sensing microbial products as well as endogenous signals related to tissue injury. Here we provide an overview of our current understanding of the function of those NLRs in type I interferon responses with a focus on viral infections. We discuss how NLR-mediated type I interferon regulation can influence the development of auto-immunity and the immune response to infection.

NLRP12 in innate immunity and inflammation

Nucleotide-binding leucine-rich repeat-containing proteins, or NOD-like receptors (NLRs), are intracellular innate immune sensors that can regulate several signaling pathways, including MyD88- and TRIF-dependent pathways. In addition to these regulatory roles, some NLRs can assemble into multimeric protein complexes known as inflammasomes. NLRP12 is a member of the NLR family that contains an N-terminal pyrin domain, a central nucleotide-binding domain, and a C-terminal leucine-rich repeat. It has been shown to play a role in forming an inflammasome in response to specific infections, and it can also function as a regulator of inflammatory signaling. During Yersinia pestis or Plasmodium chabaudi infection, NLRP12 induces the release of the inflammasome-dependent cytokines IL-1β and IL-18. These NLRP12-dependent cytokines confer protection against severe infections caused by these pathogens. Conversely, during infection with Salmonella enterica serovar Typhimurium, vesicular stomatitis virus, Klebsiella pneumoniae, or Mycobacterium tuberculosis, and in colonic tumorigenesis, NLRP12 acts as a negative regulator of the NFκB and MAPK signaling pathways. NLRP12 also negatively regulates canonical and non-canonical signaling in T cells and causes exacerbated autoimmune diseases. Furthermore, NLRP12 acts as a central component in maintaining intestinal inflammation and gut homeostasis. Therefore, the ability of NLRP12 to function as an inflammasome or as a negative regulator is context-dependent. In this review, we provide an overview of the NLR family members and summarize recent insights into the roles of NLRP12 as an inflammasome and as a negative regulator.

The microbiome and cytosolic innate immune receptors

The discovery of innate immune sensors (pattern recognition receptors, PRRs) has profoundly transformed the notion of innate immunity, in providing a mechanistic basis for host immune interactions with a wealth of environmental signals, leading to a variety of immune-mediated outcomes including instruction and activation of the adaptive immune arm. As part of this growing understanding of host-environmental cross talk, an intimate connection has been unveiled between innate immune sensors and signals perceived from the commensal microbiota, which may be regarded as a hub integrating a variety of environmental cues. Among cytosolic PRRs impacting on host homeostasis by interacting with the commensal microbiota are nucleotide-binding domain, leucine-rich repeat-containing protein receptors (NLRs), together with a number of cytosolic DNA sensors and the family of absent in melanoma (AIM)-like receptors (ALRs). NLR sensors have been a particular focus of research, and some NLRs have emerged as key orchestrators of inflammatory responses and host homeostasis. Some NLRs achieve this through the formation of cytoplasmic multiprotein complexes termed inflammasomes. More recently discovered PRRs include retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), cyclic GMP-AMP synthase (cGAS), and STING. In the present review, they summarize recent advancements in knowledge on structure and function of cytosolic PRRs and their roles in host-microbiota cross talk and immune surveillance. In addition, we discuss their relevance for human health and disease and future therapeutic applications involving modulation of their activation and signaling.

A new research hot spot: The role of NLRP3 inflammasome activation, a key step in pyroptosis, in diabetes and diabetic complications

Pyroptosis is a form of cell death mediated by gasdermin D (GSDMD); it is characterised by NLRP3 inflammasome activation, caspase activation, cell membrane pore formation, and the release of interleukin-1β and interleukin-18. NLRP3 inflammasome activation plays a central role in pyroptosis. Recent research has suggested that NLRP3 inflammasome activation may be involved in the occurrence and development of diabetes mellitus and its associated complications. This finding provided the impetus for us to clarify the significance of pyroptosis in diabetes. In this review, we summarise the current understanding of the molecular mechanisms involved in pyroptosis, as well as recent advances in the role of NLRP3 inflammasome activation and pyroptosis in the development of diabetes and diabetic complications.

Canonical and noncanonical inflammasomes in intestinal epithelial cells

Inflammasomes are cytosolic, multimeric protein complexes capable of activating pro-inflammatory cytokines such as IL-1β and IL-18, which play a key role in host defence. Inflammasome components are highly expressed in the intestinal epithelium. In recent years, studies have begun to demonstrate that epithelial-intrinsic inflammasomes play a critical role in regulating epithelial homeostasis, both by defending the epithelium from pathogenic insult and through the regulation of the mucosal environment. However, the majority of research regarding inflammasome activation has focused on professional immune cells, such as macrophages. Here, we present an overview of the current understanding of inflammasome function in epithelial cells and at mucosal surfaces and, in particular, in the intestine.

Adaptive innate immunity or innate adaptive immunity?

The innate immunity is frequently accepted as a first line of relatively primitive defense interfering with the pathogen invasion until the mechanisms of ‘privileged’ adaptive immunity with the production of antibodies and activation of cytotoxic lymphocytes ‘steal the show’. Recent advancements on the molecular and cellular levels have shaken the traditional view of adaptive and innate immunity. The innate immune memory or ‘trained immunity’ based on metabolic changes and epigenetic reprogramming is a complementary process insuring adaptation of host defense to previous infections.

Innate immune cells are able to recognize large number of pathogen- or danger- associated molecular patterns (PAMPs and DAMPs) to behave in a highly specific manner and regulate adaptive immune responses. Innate lymphoid cells (ILC1, ILC2, ILC3) and NK cells express transcription factors and cytokines related to subsets of T helper cells (Th1, Th2, Th17). On the other hand, T and B lymphocytes exhibit functional properties traditionally attributed to innate immunity such as phagocytosis or production of tissue remodeling growth factors. They are also able to benefit from the information provided by pattern recognition receptors (PRRs), e.g. γδT lymphocytes use T-cell receptor (TCR) in a manner close to PRR recognition. Innate B cells represent another example of limited combinational diversity usage participating in various innate responses. In the view of current knowledge, the traditional black and white classification of immune mechanisms as either innate or an adaptive needs to be adjusted and many shades of gray need to be included.

NLRP12 Regulates Anti-viral RIG-I Activation via Interaction with TRIM25

Establishing the balance between positive and negative innate immune mechanisms is crucial for maintaining homeostasis. Here we uncover the regulatory crosstalk between two previously unlinked innate immune receptor families: RIG-I, an anti-viral cytosolic receptor activated type I interferon production, and NLR (nucleotide-binding domain, leucine repeat domain-containing protein). We show that NLRP12 dampens RIG-I-mediated immune signaling against RNA viruses by controlling RIG-I's association with its adaptor MAVS. The nucleotide-binding domain of NLRP12 interacts with the ubiquitin ligase TRIM25 to prevent TRIM25-mediated, Lys63-linked ubiquitination and activation of RIG-I. NLRP12 also enhances RNF125-mediated, Lys48-linked degradative ubiquitination of RIG-I. Vesicular stomatitis virus (VSV) infection downregulates NLRP12 expression to allow RIG-I activation. Myeloid-cell-specific Nlrp12-deficient mice display a heightened interferon and TNF response and are more resistant to VSV infection. These results indicate that NLRP12 functions as a checkpoint for anti-viral RIG-I activation.

Assessment of Survival and Replication of Brucella spp. in Murine Peritoneal Macrophages

Brucella spp. are bacteria that naturally infect a variety of domesticated and wild animals leading to abortions and infertility, and these bacteria are also capable of causing debilitating human infections, which often result from human exposure to infected animals and animal products. The brucellae are intracellular pathogens that reside in host cells, including macrophages and dendritic cells, and it is paramount for the pathogenesis of Brucella that the bacteria are able to survive and replicate in these host cells. The methods outlined in this chapter can be employed to study the interactions between Brucella strains and primary murine peritoneal macrophages.

C57BL/6J and C57BL/6NJ Mice Are Differentially Susceptible to Inflammation-Associated Disease Caused by Influenza A Virus

Influenza viruses cause seasonal epidemics and sporadic pandemics, and are a major burden on human health. To develop better countermeasures and improve influenza disease outcomes, a clearer understanding of influenza pathogenesis is necessary. Host genetic factors have emerged as potential regulators of human influenza disease susceptibility, and in the mouse model, genetic background has been clearly linked to influenza pathogenicity. Here, we show that C57BL/6J mice are significantly more susceptible to disease caused by a 2009 pandemic H1N1 virus, an H7N9 virus, and a highly pathogenic H5N1 influenza virus compared to the closely related substrain, C57BL/6NJ. Mechanistically, influenza virus infection in C57BL/6J mice results in earlier presentation of edema, increased immune cell infiltration, higher levels of inflammatory cytokines, greater tissue damage, and delayed activation of regenerative processes in infected lung tissues compared to C57BL/6NJ mice. These differences are not dependent on virus replication levels. Six genes with known coding region differences between C57BL/6J and C57BL/6NJ strains exhibit increased transcript levels in influenza virus-infected mouse lungs, suggesting potential contributions to regulation of disease susceptibility. This work uncovers a previously unappreciated difference in disease susceptibility between the closely related C57BL/6J and C57BL/6NJ mice, which may be exploited in future studies to identify host factors and/or specific genetic elements that regulate host-dependent inflammatory mechanisms involved in influenza virus pathogenicity.

The Dual Immunoregulatory function of Nlrp12 in T Cell-Mediated Immune Response: Lessons from Experimental Autoimmune Encephalomyelitis

Although the etiology of multiple sclerosis (MS) remains enigmatic, the role of T cells is unquestionably central in this pathology. Immune cells respond to pathogens and danger signals via pattern-recognition receptors (PRR). Several reports implicate Nlrp12, an intracellular PRR, in the development of a mouse MS-like disease, called Experimental Autoimmune Encephalomyelitis (EAE). In this study, we used induced and spontaneous models of EAE, as well as in vitro T cell assays, to test the hypothesis that Nlrp12 inhibits Th1 response and prevents T-cell mediated autoimmunity. We found that Nlrp12 plays a protective role in induced EAE by reducing IFNγ/IL-4 ratio in lymph nodes, whereas it potentiates the development of spontaneous EAE (spEAE) in 2D2 T cell receptor (TCR) transgenic mice. Looking into the mechanism of Nlrp12 activity in T cell response, we found that it inhibits T cell proliferation and suppresses Th1 response by reducing IFNγ and IL-2 production. Following TCR activation, Nlrp12 inhibits Akt and NF-κB phosphorylation, while it has no effect on S6 phosphorylation in the mTOR pathway. In conclusion, we propose a model that can explain the dual immunoregulatory function of Nlrp12 in EAE. We also propose a model explaining the molecular mechanism of Nlrp12-dependent regulation of T cell response.

The Inflammasome: Regulation of Nitric Oxide and Antimicrobial Host Defence

Nitric oxide (NO) is a gaseous signalling molecule that plays diverse physiological functions including antimicrobial host defence. During microbial infection, NO is synthesized by inducible NO synthase (iNOS), which is expressed by host immune cells through the recognition of microbial pattern molecules. Therefore, sensing pathogens or their pattern molecules by pattern recognition receptors (PRRs), which are located at the cell surface, endosomal and phagosomal compartment, or in the cytosol, is key in inducing iNOS and eliciting antimicrobial host defence. A group of cytosolic PRRs is involved in inducing NO and other antimicrobial molecules by forming a molecular complex called the inflammasome. Assembled inflammasomes activate inflammatory caspases, such as caspase-1 and caspase-11, which in turn process proinflammatory cytokines IL-1β and IL-18 into their mature forms and induce pyroptotic cell death. IL-1β and IL-18 play a central role in immunity against microbial infection through activation and recruitment of immune cells, induction of inflammatory molecules, and regulation of antimicrobial mediators including NO. Interestingly, NO can also regulate inflammasome activity in an autocrine and paracrine manner. Here, we discuss molecular mechanisms of inflammasome formation and the inflammasome-mediated regulation of host defence responses during microbial infections.

NLR-Dependent Regulation of Inflammation in Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) associated with inappropriate activation of lymphocytes, hyperinflammatory responses, demyelination, and neuronal damage. In the past decade, a number of biological immunomodulators have been developed that suppress the peripheral immune responses and slow down the progression of the disease. However, once the inflammation of the CNS has commenced, it can cause serious permanent neuronal damage. Therefore, there is a need for developing novel therapeutic approaches that control and regulate inflammatory responses within the CNS. Nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are intracellular regulators of inflammation expressed by many cell types within the CNS. They redirect multiple signaling pathways initiated by pathogens and molecules released by injured tissues. NLR family members include positive regulators of inflammation, such as NLRP3 and NLRC4 and anti-inflammatory NLRs, such as NLRX1 and NLRP12. They exert immunomodulatory effect at the level of peripheral immune responses, including antigen recognition and lymphocyte activation and differentiation. Also, NLRs regulate tissue inflammatory responses. Understanding the molecular mechanisms that are placed at the crossroad of innate and adaptive immune responses, such as NLR-dependent pathways, could lead to the discovery of new therapeutic targets. In this review, we provide a summary of the role of NLRs in the pathogenesis of MS. We also summarize how anti-inflammatory NLRs regulate the immune response within the CNS. Finally, we speculate the therapeutic potential of targeting NLRs in MS.

Inflammasomes in the gastrointestinal tract: infection, cancer and gut microbiota homeostasis

Inflammasome signalling is an emerging pillar of innate immunity and has a central role in the regulation of gastrointestinal health and disease. Activation of the inflammasome complex mediates both the release of the pro-inflammatory cytokines IL-1β and IL-18 and the execution of a form of inflammatory cell death known as pyroptosis. In most cases, these mediators of inflammation provide protection against bacterial, viral and protozoal infections. However, unchecked inflammasome activities perpetuate chronic inflammation, which underpins the molecular and pathophysiological basis of gastritis, IBD, upper and lower gastrointestinal cancer, nonalcoholic fatty liver disease and obesity. Studies have also highlighted an inflammasome signature in the maintenance of gut microbiota and gut-brain homeostasis. Harnessing the immunomodulatory properties of the inflammasome could transform clinical practice in the treatment of acute and chronic gastrointestinal and extragastrointestinal diseases. This Review presents an overview of inflammasome biology in gastrointestinal health and disease and describes the value of experimental and pharmacological intervention in the treatment of inflammasome-associated clinical manifestations.

Modulation of Immune Signaling and Metabolism Highlights Host and Fungal Transcriptional Responses in Mouse Models of Invasive Pulmonary Aspergillosis

Incidences of invasive pulmonary aspergillosis, an infection caused predominantly by Aspergillus fumigatus, have increased due to the growing number of immunocompromised individuals. While A. fumigatus is reliant upon deficiencies in the host to facilitate invasive disease, the distinct mechanisms that govern the host-pathogen interaction remain enigmatic, particularly in the context of distinct immune modulating therapies. To gain insights into these mechanisms, RNA-Seq technology was utilized to sequence RNA derived from lungs of 2 clinically relevant, but immunologically distinct murine models of IPA on days 2 and 3 post inoculation when infection is established and active disease present. Our findings identify notable differences in host gene expression between the chemotherapeutic and steroid models at the interface of immunity and metabolism. RT-qPCR verified model specific and nonspecific expression of 23 immune-associated genes. Deep sequencing facilitated identification of highly expressed fungal genes. We utilized sequence similarity and gene expression to categorize the A. fumigatus putative in vivo secretome. RT-qPCR suggests model specific gene expression for nine putative fungal secreted proteins. Our analysis identifies contrasting responses by the host and fungus from day 2 to 3 between the two models. These differences may help tailor the identification, development, and deployment of host- and/or fungal-targeted therapeutics.