NOD1 and NOD2 in inflammation, immunity and disease

Identification of Mycoplasma pneumoniae proteins interacting with NOD2 and their role in macrophage inflammatory response

Mycoplasma pneumoniae (M. pneumoniae, Mp) is a cell wall-deficient microorganism known to cause chronic respiratory infections in both children and adults. Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) is an intracellular pattern recognition receptor primarily responsible for identifying muramyl dipeptide (MDP) found in bacterial cell walls. Previous experiments have demonstrated that Mycoplasma ovipneumoniae induces macrophage autophagy through NOD2. In this study, we conducted RNA-seq analysis on macrophages infected with M. pneumoniae and observed an up-regulation in the expression of genes associated with the NOD2 signaling pathway. Mechanistic investigations further revealed the involvement of the NOD2 signaling pathway in the inflammatory response of macrophages activated by M. pneumoniae. We utilized GST pull-down technology in conjunction with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to pinpoint the M. pneumoniae proteins that interact with NOD2. Additionally, co-immunoprecipitation (Co-IP) and immunofluorescence co-localization techniques were used to confirm the interaction between DUF16 protein and NOD2. We found that DUF16 protein can enter macrophages and induce macrophage inflammatory response through the NOD2/RIP2/NF-κB pathway. Notably, the region spanning amino acids 13-90 was identified as a critical region necessary for DUF16-induced inflammation. This research not only broadens our comprehension of the recognition process of the intracellular receptor NOD2, but also deepens our understanding of the development of M. pneumoniae infection.

Characterization of PANoptosis-related genes in Crohn's disease by integrated bioinformatics, machine learning and experiments

Currently, the biological understanding of Crohn's disease (CD) remains limited. PANoptosis is a revolutionary form of cell death reported to participate in numerous diseases, including CD. In our study, we aimed to uncover the roles of PANoptosis in CD. Differentially expressed PANoptosis-related genes (DE-PRGs) were identified by overlapping PANoptosis-related genes and differentially expressed genes between CD and normal samples in a combined microarray dataset. Three machine learning algorithms were adopted to detect hub DE-PRGs. To stratify the heterogeneity within CD patients, nonnegative matrix factorization clustering was conducted. In terms of immune landscape analysis, the "ssGSEA" method was applied. qRT-PCR was performed to examine the expression levels of the hub DE-PRGs in CD patients and colitis model mice. Ten hub DE-PRGs with satisfactory diagnostic performance were identified and validated: CD44, CIDEC, NDRG1, NUMA1, PEA15, RAG1, S100A8, S100A9, TIMP1 and XBP1. These genes displayed significant associations with certain immune cell types and CD-related genes. We also constructed gene‒microRNA, gene‒transcription factor and drug‒gene interaction networks. CD samples were classified into two PANoptosis patterns according to the expression levels of the hub DE-PRGs. Our results suggest that PANoptosis plays a nonnegligible role in CD by modulating the immune system and interacting with CD-related genes.

Germline polymorphisms of the NOD2 pathway may predict the effectiveness of radioiodine in differentiated thyroid cancer treatment

PURPOSE

Differentiated thyroid cancer (DTC) presents a complex clinical challenge, especially in patients with distant metastases and resistance to standard treatments. This study aimed to investigate the influence of specific genes and their germline single nucleotide polymorphisms (SNPs) linked to both inflammatory processes and other neoplasms on the clinical and pathological characteristics of DTC, particularly their potential impact on radioiodine (RAI) treatment efficacy.

METHODS

This retrospective analysis involved a cohort of 646 patients diagnosed with DTC after thyroidectomy. Study covering 1998-2014, updated in 2023, included 567 women and 79 men (median age: 49; range: 7-83). SNP selection targeted functional significance, while mutational status was assessed by pyrosequencing for comprehensive characterization. Patient genetic profiles were assessed for associations with disease characteristics, RAI response, and cancer pathology.

RESULTS

Significant correlations emerged between certain SNPs and DTC features. Notably, the NOD2 c.802 T > C variant (rs2066842) was identified as a marker distinguishing between papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC). Moreover, the c.802 T allele was associated with an enhanced response to RAI treatment, indicating a more substantial decrease in posttreatment stimulated thyroglobulin (sTg) concentrations. The NFKB1A allele c.126A (rs696) exhibited connections with lower FTC stages and a reduced probability of multifocality.

CONCLUSION

This study explored the molecular mechanisms of particular SNPs, highlighting the role of NOD2 in innate immunity and the stress response, and its potential impact on RAI efficacy. This research underscores the clinical promise of SNP analysis and contributes to personalized treatment strategies for DTC, emphasizing the relevance of genetic factors in cancer progression and treatment outcomes.

Transcription of NOD1 and NOD2 and their interaction with CARD9 and RIPK2 in IFN signaling in a perciform fish, the Chinese perch, Siniperca chuatsi

NOD1 and NOD2 as two representative members of nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family play important roles in antimicrobial immunity. However, transcription mechanism of nod1 and nod2 and their signal circle are less understood in teleost fish. In this study, with the cloning of card9 and ripk2 in Chinese perch, the interaction between NOD1, NOD2, and CARD9 and RIPK2 were revealed through coimmunoprecipitation and immunofluorescence assays. The overexpression of NOD1, NOD2, RIPK2 and CARD9 induced significantly the promoter activity of NF-κB, IFNh and IFNc. Furthermore, it was found that nod1 and nod2 were induced by poly(I:C), type I IFNs, RLR and even NOD1/NOD2 themselves through the ISRE site of their proximal promoters. It is thus indicated that nod1 and nod2 can be classified also as ISGs due to the presence of ISRE in their proximal promoter, and their expression can be mechanistically controlled through PRR pathway as well as through IFN signaling in antiviral immune response.

A Systemic Review and Meta-analysis on Natural Resistance-associated Macrophage Protein 1 (3'-Untranslated Region) and Nucleotide-binding Oligomerization Domain-2 (rs8057341) Polymorphisms and Leprosy Susceptibility in Asian and Caucasian Populations

The current meta-analysis aims to explore the potential correlation between natural resistance-associated macrophage protein 1 (NRAMP1) (3'-Untranslated region [3'-UTR]) and nucleotide-binding oligomerization domain-2 (NOD2 [rs8057341]) gene polymorphisms and their association with leprosy susceptibility in both Asian and Caucasian populations. Datas were retrieved from case control studies with NOD 2 and NRAMP 1 gene polymorphism associated with leprosy disease. Leprosy emerges as a particularly distinctive ailment among women on a global scale. The NRAMP1 (3'-UTR) and NOD2 (rs8057341) genetic variations play a crucial role in the progression of leprosy. A systematic review of relevant case-control studies was conducted across several databases, including ScienceDirect, PubMed, Google Scholar, and Embase. Utilizing MetaGenyo and Review Manager 5.4 Version, statistical analyses were carried out. Nine case-control studies totaling 3281 controls and 3062 leprosy patients are included in the research, with the objective of examining the potential association between NRAMP1 (3'-UTR) and NOD2 (rs8057341) gene polymorphisms and leprosy risk. The review methodology was registered in PROSPERO (ID520883). The findings reveal a robust association between NRAMP1 (3'-UTR) and NOD2 (rs8057341) gene polymorphisms and leprosy risk across various genetic models. Although the funnel plot analysis did not identify publication bias, bolstering these findings and elucidating potential gene-gene and gene-environment interactions require further comprehensive epidemiological research. This study identified a strong correlation between polymorphisms in the NOD2 (rs8057341) genes and susceptibility to leprosy across two genetic models. Further comprehensive epidemiological investigations are warranted to validate these findings and explore potential interactions between these genes and environmental factors.

Population-enriched innate immune variants may identify candidate gene targets at the intersection of cancer and cardio-metabolic disease

Both cancer and cardio-metabolic disease disparities exist among specific populations in the US. For example, African Americans experience the highest rates of breast and prostate cancer mortality and the highest incidence of obesity. Native and Hispanic Americans experience the highest rates of liver cancer mortality. At the same time, Pacific Islanders have the highest death rate attributed to type 2 diabetes (T2D), and Asian Americans experience the highest incidence of non-alcoholic fatty liver disease (NAFLD) and cancers induced by infectious agents. Notably, the pathologic progression of both cancer and cardio-metabolic diseases involves innate immunity and mechanisms of inflammation. Innate immunity in individuals is established through genetic inheritance and external stimuli to respond to environmental threats and stresses such as pathogen exposure. Further, individual genomes contain characteristic genetic markers associated with one or more geographic ancestries (ethnic groups), including protective innate immune genetic programming optimized for survival in their corresponding ancestral environment(s). This perspective explores evidence related to our working hypothesis that genetic variations in innate immune genes, particularly those that are commonly found but unevenly distributed between populations, are associated with disparities between populations in both cancer and cardio-metabolic diseases. Identifying conventional and unconventional innate immune genes that fit this profile may provide critical insights into the underlying mechanisms that connect these two families of complex diseases and offer novel targets for precision-based treatment of cancer and/or cardio-metabolic disease.

Transcriptome analysis identifies genetic risk markers and explores the pathogenesis for inflammatory bowel disease

Inflammatory bowel disease (IBD) is an incurable and disabling bowel disease driven by multiple risk factors that severely limit patients' quality of life. We integrated the RNA-sequencing data of 1238 IBD patients, and investigated the pathogenesis of IBD by combining transcriptional element prediction analysis and immune-related analysis. Here, we first determined that KIAA1109 is inhibited in IBD patients. The expression of KIAA1109 and NOD2, the key receptor of NOD-like receptors, showed a negative correlation. The NOD-like receptor signaling pathway is activated and exerts transcriptional regulation on the chemokines CXCL1 and CXCL2 through the activation of the transcription factors NFκB and AP1. Analysis of immune infiltration revealed that the expression of chemokines CXCL1 and CXCL2 may regulate the inflammatory response induced by immune cells. These findings suggest that the KIAA1109-NOD2-NFκB/AP1-CXCL1/CXCL2 regulatory axis is the molecular mechanism of IBD pathogenesis, which will provide a new perspective for the diagnosis, treatment and management of IBD patients.

Role of the nucleotide-binding oligomerization domain-containing protein 1 pathway in the development of periodontitis

OBJECTIVES

During innate immune defense, host pattern recognition receptors, including toll-like receptors and nucleotide-binding oligomerization domain-like receptors (NLRs), can activate downstream pathways by recognizing pathogen-associated molecular patterns produced by microorganisms, triggering immune responses. NOD1, an important cell membrane protein in the NLR-like receptor protein family, exerts anti-infective effects through γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP) recognition. Oral epithelial cells resist bacterial invasion through iE-DAP-induced interleukin (IL)-8 production, recruiting neutrophils to sites of inflammation in response to bacterial threats to periodontal tissues. To date, the regulatory mechanisms of iE-DAP in gingival epithelial cells (GECs) are poorly understood. This study was conducted to investigate the role of the NOD1 pathway in the development of periodontitis by examining the effect of iE-DAP on IL-8 production in Ca9-22 cells.

METHODS

IL-8 production by iE-DAP-stimulated-Ca9-22 cells was assessed using an enzyme-linked immunosorbent assay. Phosphorylation levels of intracellular signaling molecules were evaluated using western blot analyses.

RESULTS

iE-DAP induced NOD1 receptor expression in Ca9-22 cells. Additionally, iE-DAP induced expression of pro-IL-1β protein without extracellular secretion. Our results suggest that iE-DAP regulates IL-8 production by activating p38 mitogen-activated protein kinase (MAPK) and ERK1/2 signaling pathways. iE-DAP also promoted nuclear factor kappa-B p65 phosphorylation, facilitating its nuclear translocation. Notably, p38 MAPK and ERK1/2 inhibitors suppressed iE-DAP-stimulated IL-8 production, suggesting that JNK is not involved in this mechanism.

CONCLUSIONS

Our results indicate that p38 MAPK and ERK1/2, but not JNK, are involved in innate immune responses in GECs.

Discovery of 2,3-Diaminoindole Derivatives as a Novel Class of NOD Antagonists

NOD1 and NOD2 are members of the pattern recognition receptors involved in the innate immune response. Overactivation of NOD1 is implicated in inflammatory disorders, multiple sclerosis, and cancer cell metastases. NOD1 antagonists would represent valuable pharmacological tools to gain further insight into protein roles, potentially leading to new therapeutic strategies. We herein report the expansion of the chemical space of NOD1 antagonists via a multicomponent synthetic approach affording a novel chemotype, namely, 2,3-diaminoindoles. These efforts resulted in compound 37, endowed with low micromolar affinity toward NOD1. Importantly, a proof-of-evidence of direct binding to NOD1 of Noditinib-1 and derivative 37 is provided here for the first time. Additionally, the combination of computational studies and NMR-based displacement assays enabled the characterization of the binding modality of 37 to NOD1, thus providing key unprecedented knowledge for the design of potent and selective NOD1 antagonists.

Novel role of peptidoglycan recognition protein 2 in activating NOD2-NFκB inflammatory axis in coronary artery disease

BACKGROUNDS AND AIMS

The role of inflammation in driving atherosclerosis is well-established. It exerts systemic effects beyond the local site of plaque formation. In the context of coronary artery disease (CAD), the proteins that show altered levels in the plasma, are potentially important for understanding the key regulatory mechanism in the pathogenesis of atherosclerosis. A case-control study revealed that plasma soluble Peptidoglycan Recognition Protein 2 (PGLYRP2) primarily produced by the liver, is increased in subjects with CAD. Furthermore, the concentration of PGLYRP2 in the blood correlates with the severity of coronary artery disease. Thus, it raises interest in understanding the exact role of the protein in aortic inflammation and plaque progression.

METHODS

We evaluated the plasma concentration of PGLYRP2 in three distinct groups: patients with CAD (N = 68), asymptomatic individuals (N = 34), and healthy volunteers (N = 20). Furthermore, we investigated the correlation between disease severity and PGLYRP2 levels in CAD patients. To identify potential binding partners of PGLYRP2, we employed computational analysis. We verified the PGLYRP2-NOD2 interaction in macrophage cells and elucidated the inflammatory pathways activated by PGLYRP2 within these cells. To assess the impact of PGLYRP2, we examined its effects in the atherosclerotic mice model (ApoE-/-).

RESULTS

In this study, we report for the first time that Nucleotide-binding Oligomerization domain 2 (NOD2) which is expressed on the surface of macrophages, is a receptor of PGLYRP2. The N-terminal domain of PGLYRP2 directly binds to NOD2 and activates the NOD2-RIP2-NFκB cascade that promotes the secretion of proinflammatory cytokines like TNFα, IL1β, and IL-8. In the atherosclerotic mice model (ApoE-/-) we demonstrate that elevated PGLYRP2 level is parallel with increased proinflammatory cytokines in the plasma when fed a High Cholesterol Diet (HCD). Immunohistochemical analysis reveals that PGLYRP2 is co-localized with NOD2 on the macrophages at the site of the lesion.

CONCLUSIONS

Taken together, our data demonstrate that NOD2 acts as a receptor of PGLYRP2 on macrophages, which mediates the activation of the NOD2-RIP2-NFκB pathway and promotes inflammation, thus significantly contributing to the development and progression of atherosclerosis.

Manganese@Albumin Nanocomplex and Its Assembled Nanowire Activate TLR4-Dependent Signaling Cascades of Macrophages

The immunomodulatory effect of divalent manganese cations (Mn2+ ), such as activation of the cGAS-STING pathway or NLRP3 inflammasomes, positions them as adjuvants for cancer immunotherapy. In this study, it is found that trace Mn2+ ions, bound to bovine serum albumin (BSA) to form Mn@BSA nanocomplexes, stimulate pro-inflammatory responses in human- or murine-derived macrophages through TLR4-mediated signaling cascades. Building on this, the assembly of Mn@BSA nanocomplexes to obtain nanowire structures enables stronger and longer-lasting immunostimulation of macrophages by regulating phagocytosis. Furthermore, Mn@BSA nanocomplexes and their nanowires efficiently activate peritoneal macrophages, reprogramme tumor-associated macrophages, and inhibit the growth of melanoma tumors in vivo. They also show better biosafety for potential clinical applications compared to typical TLR4 agonists such as lipopolysaccharides. Accordingly, the findings provide insights into the mechanism of metalloalbumin complexes as potential TLR agonists that activate macrophage polarization and highlight the importance of their nanostructures in regulating macrophage-mediated innate immunity.

The effects of NOD-like receptors on adaptive immune responses

It has long been appreciated that cues from the innate immune system orchestrate downstream adaptive immune responses. Although previous work has focused on the roles of Toll-like receptors in this regard, relatively little is known about how Nod-like receptors instruct adaptive immunity. Here we review the functions of different members of the Nod-like receptor family in orchestrating effector and anamnestic adaptive immune responses. In particular, we address the ways in which inflammasome and non-inflammasome members of this family affect adaptive immunity under various infectious and environmental contexts. Furthermore, we identify several key mechanistic questions that studies in this field have left unaddressed. Our aim is to provide a framework through which immunologists in the adaptive immune field may view their questions through an innate-immune lens and vice-versa.

Orange-spotted grouper nervous necrosis virus-encoded protein A induces interferon expression via RIG-I/MDA5-MAVS-TBK1-IRF3 signaling in fish cells

IMPORTANCE

As a major pathogen, nervous necrosis virus (NNV) infects more than 120 fish species worldwide and is virulent to larvae and juvenile fish, hampering the development of the fish fry industry. Understanding virus-host interaction and underlying mechanisms is an important but largely unknown issue in fish virus studies. Here, using channel catfish ovary and fathead minnow cells as models for the study of innate immunity signaling, we found that NNV-encoded ProA activated interferon signaling via the retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) pathway which was still suppressed by the infection of wild-type NNV. This finding has important implications for the comprehension of NNV protein function and the immune response from different cells. First, RIG-I is the key node for anti-NNV innate immunity. Second, the response intensity of RLR signaling determines the degree of NNV proliferation. This study expands our knowledge regarding the overview of signal pathways affected by NNV-encoded protein and also highlights potential directions for the control of aquatic viruses.

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.

Effect of aqueous extract of Millettia speciosa Champ on intestinal health maintenance and immune enhancement of Cyprinus carpio

Millettia speciosa Champ (MSP) is a natural Chinese herb that improves gastrointestinal health and enhances animal immunity. An 8-week feeding trial with different MSP levels (0, 150, 300, and 600 mg/kg) was conducted to evaluate the promotive effects of MSP in Cyprinus carpio. Results indicate that MSP improved intestinal immunity to some extent evidenced by the immuno-antioxidant parameters and the 16S rRNA in the Illumina MiSeq platform. With the analysis of transcriptome sequencing, 4685 differentially expressed genes (DEGs) were identified, including 2149 up-regulated and 2536 down-regulated. According to the GO and KEGG enrichments, DEGs were mainly involved in the immune system. Transcriptional expression of the NOD-like signaling pathway and key genes retrieved from the transcriptome database confirmed that innate immunity was improved in response to dietary MSP administration. Therefore, MSP could be used as a feed supplement that enhances immunity. This may provide insight into Chinese herb additive application in aquaculture production.

Identification of a muropeptide precursor transporter from gut microbiota and its role in preventing intestinal inflammation

The gut microbiota is a considerable source of biologically active compounds that can promote intestinal homeostasis and improve immune responses. Here, we used large expression libraries of cloned metagenomic DNA to identify compounds able to sustain an anti-inflammatory reaction on host cells. Starting with a screen for NF-κB activation, we have identified overlapping clones harbouring a heterodimeric ATP-binding cassette (ABC)-transporter from a Firmicutes. Extensive purification of the clone's supernatant demonstrates that the ABC-transporter allows for the efficient extracellular accumulation of three muropeptide precursor, with anti-inflammatory properties. They induce IL-10 secretion from human monocyte-derived dendritic cells and proved effective in reducing AIEC LF82 epithelial damage and IL-8 secretion in human intestinal resections. In addition, treatment with supernatants containing the muropeptide precursor reduces body weight loss and improves histological parameters in Dextran Sulfate Sodium (DSS)-treated mice. Until now, the source of peptidoglycan fragments was shown to come from the natural turnover of the peptidoglycan layer by endogenous peptidoglycan hydrolases. This is a report showing an ABC-transporter as a natural source of secreted muropeptide precursor and as an indirect player in epithelial barrier strengthening. The mechanism described here might represent an important component of the host immune homeostasis.

Characterization of genomic regions escaping epigenetic reprogramming in sheep

The mammalian genome undergoes two global epigenetic reprogramming events during the establishment of primordial germ cells and in the pre-implantation embryo after fertilization. These events involve the erasure and re-establishment of DNA methylation marks. However, imprinted genes and transposable elements (TEs) maintain their DNA methylation signatures to ensure normal embryonic development and genome stability. Despite extensive research in mice and humans, there is limited knowledge regarding environmentally induced epigenetic marks that escape epigenetic reprogramming in other species. Therefore, the objective of this study was to examine the characteristics and locations of genomic regions that evade epigenetic reprogramming in sheep, as well as to explore the biological functions of the genes within these regions. In a previous study, we identified 107 transgenerationally inherited differentially methylated cytosines (DMCs) in the F1 and F2 generations in response to a paternal methionine-supplemented diet. These DMCs were found in TEs, non-repetitive regions, and imprinted and non-imprinted genes. Our findings suggest that genomic regions, rather than TEs and imprinted genes, have the propensity to escape reprogramming and serve as potential candidates for transgenerational epigenetic inheritance. Notably, 34 transgenerational methylated genes influenced by paternal nutrition escaped reprogramming, impacting growth, development, male fertility, cardiac disorders, and neurodevelopment. Intriguingly, among these genes, 21 have been associated with neural development and brain disorders, such as autism, schizophrenia, bipolar disease, and intellectual disability. This suggests a potential genetic overlap between brain and infertility disorders. Overall, our study supports the concept of transgenerational epigenetic inheritance of environmentally induced marks in mammals.

NOD2 attenuates osteoarthritis via reprogramming the activation of synovial macrophages

OBJECTIVE

Synovial inflammation, which precedes other pathological changes in osteoarthritis (OA), is primarily initiated by activation and M1 polarization of macrophages. While macrophages play a pivotal role in the inflammatory process of OA, the mechanisms underlying their activation and polarization remain incompletely elucidated. This study aims to investigate the role of NOD2 as a reciprocal modulator of HMGB1/TLR4 signaling in macrophage activation and polarization during OA pathogenesis.

DESIGN

We examined NOD2 expression in the synovium and determined the impact of NOD2 on macrophage activation and polarization by knockdown and overexpression models in vitro. Paracrine effect of macrophages on fibroblast-like synoviocytes (FLS) and chondrocytes was evaluated under conditions of NOD2 overexpression. Additionally, the in vivo effect of NOD2 was assessed using collagenase VII induced OA model in mice.

RESULTS

Expression of NOD2 was elevated in osteoarthritic synovium. In vitro experiments demonstrated that NOD2 serves as a negative regulator of HMGB1/TLR4 signaling pathway. Furthermore, NOD2 overexpression hampered the inflammatory paracrine effect of macrophages on FLS and chondrocytes. In vivo experiments revealed that NOD2 overexpression mitigated OA in mice.

CONCLUSIONS

Supported by convincing evidence on the inhibitory role of NOD2 in modulating the activation and M1 polarization of synovial macrophages, this study provided novel insights into the involvement of innate immunity in OA pathogenesis and highlighted NOD2 as a potential target for the prevention and treatment of OA.

The gut ecosystem and immune tolerance

The gastrointestinal tract is home to the largest microbial population in the human body. The gut microbiota plays significant roles in the development of the gut immune system and has a substantial impact on the maintenance of immune tolerance beginning in early life. These microbes interact with the immune system in a dynamic and interdependent manner. They generate immune signals by presenting a vast repertoire of antigenic determinants and microbial metabolites that influence the development, maturation and maintenance of immunological function and homeostasis. At the same time, both the innate and adaptive immune systems are involved in modulating a stable microbial ecosystem between the commensal and pathogenic microorganisms. Hence, the gut microbial population and the host immune system work together to maintain immune homeostasis synergistically. In susceptible hosts, disruption of such a harmonious state can greatly affect human health and lead to various auto-inflammatory and autoimmune disorders. In this review, we discuss our current understanding of the interactions between the gut microbiota and immunity with an emphasis on: a) important players of gut innate and adaptive immunity; b) the contribution of gut microbial metabolites; and c) the effect of disruption of innate and adaptive immunity as well as alteration of gut microbiome on the molecular mechanisms driving autoimmunity in various autoimmune diseases.

The crosstalk between microbial sensors ELMO1 and NOD2 shape intestinal immune responses

Microbial sensors play an essential role in maintaining cellular homoeostasis. Our knowledge is limited on how microbial sensing helps in differential immune response and its link to inflammatory diseases. Recently we have confirmed that ELMO1 (Engulfment and Cell Motility Protein-1) present in cytosol is involved in pathogen sensing, engulfment, and intestinal inflammation. Here, we show that ELMO1 interacts with another sensor, NOD2 (Nucleotide-binding oligomerization domain-containing protein 2), that recognizes bacterial cell wall component muramyl dipeptide (MDP). The polymorphism of NOD2 is linked to Crohn's disease (CD) pathogenesis. Interestingly, we found that overexpression of ELMO1 and mutant NOD2 (L1007fs) were not able to clear the CD-associated adherent invasive E. coli (AIEC-LF82). The functional implications of ELMO1-NOD2 interaction in epithelial cells were evaluated by using enteroid-derived monolayers (EDMs) from ELMO1 and NOD2 KO mice. Subsequently we also assessed the immune response in J774 macrophages depleted of either ELMO1 or NOD2 or both. The infection of murine EDMs with AIEC-LF82 showed higher bacterial load in ELMO1-KO, NOD2 KO EDMs, and ELMO1 KO EDMs treated with NOD2 inhibitors. The murine macrophage cells showed that the downregulation of ELMO1 and NOD2 is associated with impaired bacterial clearance that is linked to reduce pro-inflammatory cytokines and reactive oxygen species. Our results indicated that the crosstalk between microbial sensors in enteric infection and inflammatory diseases impacts the fate of the bacterial load and disease pathogenesis.

Host Transcriptional Regulatory Genes and Microbiome Networks Crosstalk through Immune Receptors Establishing Normal and Tumor Multiomics Metafirm of the Oral-Gut-Lung Axis

The microbiome has shown a correlation with the diet and lifestyle of each population in health and disease, the ability to communicate at the cellular level with the host through innate and adaptative immune receptors, and therefore an important role in modulating inflammatory process related to the establishment and progression of cancer. The oral cavity is one of the most important interaction windows between the human body and the environment, allowing the entry of an important number of microorganisms and their passage across the gastrointestinal tract and lungs. In this review, the contribution of the microbiome network to the establishment of systemic diseases like cancer is analyzed through their synergistic interactions and bidirectional crosstalk in the oral-gut-lung axis as well as its communication with the host cells. Moreover, the impact of the characteristic microbiota of each population in the formation of the multiomics molecular metafirm of the oral-gut-lung axis is also analyzed through state-of-the-art sequencing techniques, which allow a global study of the molecular processes involved of the flow of the microbiota environmental signals through cancer-related cells and its relationship with the establishment of the transcription factor network responsible for the control of regulatory processes involved with tumorigenesis.

Synthesis and validation of click-modified NOD1/2 agonists

NOD1 and NOD2 sense small bacterial peptidoglycan fragments, often called muropeptides, that access the cytosol. These muropeptides include iE-DAP and MDP, the minimal agonists for NOD1 and NOD2, respectively. Here, we synthesized and validated alkyne-modified muropeptides, iE-DAP-Alk and MDP-Alk, for use in click-chemistry reactions. While it has long been known that many cell types respond to extracellular exposure to muropeptides, it is unclear how these innate immune activators access their cytosolic innate immune receptors, NOD1 and NOD2. The subcellular trafficking and transport mechanisms by which muropeptides access these cytosolic innate immune receptors are a major gap in our understanding of these critical host responses. The click-chemistry-enabled agonists developed here will be particularly powerful to decipher the underlying cell biology and biochemistry of NOD1 and NOD2 innate immune sensing.

Discovery and Anti-Inflammatory Activity of a Cyanobacterial Fatty Acid Targeting the Keap1/Nrf2 Pathway

The monounsaturated fatty acid 7(E)-9-keto-hexadec-7-enoic acid (1) and three structurally related analogues with different oxidation states and degrees of unsaturation (2-4) were discovered from a marine benthic cyanobacterial mat collected from Delta Shoal, Florida Keys. Their structures were elucidated using NMR spectroscopy and mass spectrometry. The structure of 1 contained an α,β-unsaturated carbonyl system, a key motif required for the activation of the Keap1/Nrf2-ARE pathway that is involved in the activation of antioxidant and phase II detoxification enzymes. Compounds 1-4 were screened in ARE-luciferase reporter gene assay using stably transfected HEK293 cells, and only 1 significantly induced Nrf2 activity at 32 and 10 µM, whereas 2-4 were inactive. As there is crosstalk between inflammation and oxidative stress, subsequent biological studies were focused on 1 to investigate its anti-inflammatory potential. Compound 1 induced Nqo1, a well-known target gene of Nrf2, and suppressed iNos transcript levels, which translated into reduced levels of nitric oxide in LPS-activated mouse macrophage RAW264.7 cells, a more relevant model for inflammation. RNA sequencing was performed to capture the effects of 1 on a global level and identified additional canonical pathways and upstream regulators involved in inflammation and immune response, particularly those related to multiple sclerosis. A targeted survey of marine cyanobacterial samples from other geographic locations, including Guam, suggested the widespread occurrence of 1. Furthermore, the previous isolation of 1 from marine diatoms and green algae implied a potentially important ecological role across marine algal eukaryotes and prokaryotes. The previous isolation from sea lettuce raises the possibility of dietary intervention to attenuate inflammation and related disease progression.

Case Report: Methotrexate and hydroxychloroquine in combination for the treatment of NOD2-mutation-associated Blau syndrome

Mutations in nucleotide binding oligomerization domain containing 2 receptor (NOD2) are associated with Blau syndrome (also known as early-onset sarcoidosis)-a rare autosomal dominant, chronic granulomatous disease that typically presents before 5 years of age. Blau syndrome is characterized by the clinical triad of arthritis, granulomatous dermatitis, and recurrent uveitis. Here, we report a case of NOD2-mutation-associated early-onset sarcoidosis in which a combination of methotrexate and hydroxychloroquine was used to achieve improvement in arthritis, granulomatous dermatitis, and uveitis. A 13-month-old boy presented with a sudden-onset cutaneous eruption affecting the face, trunk, and extremities that initially mimicked papular atopic dermatitis but progressively worsened despite topical steroid therapy. The patient had no other known medical comorbidities or abnormalities except for heterochromia of the right eye. However, prior to presentation to dermatology, the patient began experiencing frequent falls, conjunctival injection, and apparent eye and joint pain. Skin biopsy from the right shoulder demonstrated rounded aggregates of epithelioid histiocytes and multinucleated giant cells without a significant lymphocytic component ("naked granulomas"), consistent with sarcoidal granulomatous dermatitis. Given the concern for Blau syndrome, the patient was sent for evaluation by ophthalmology and was found to have bilateral subconjunctival nodules. Our patient underwent genetic testing and was found to have a mutation in codon 1000 C > T (protein R334W) in the NOD2 gene. The patient responded to oral prednisolone 2 mg/kg/day for 8 weeks, but quickly relapsed, requiring a second 8-week course with taper upon starting methotrexate 7.5 mg subcutaneously weekly with 1 mg folic acid orally daily. After 8 weeks on methotrexate, due to persistent arthritis, conjunctival injection, and pruritus, and in consultation with rheumatology, the patient was started on hydroxychloroquine 75 mg orally daily along with continuation of 7.5 mg methotrexate subcutaneously weekly for 8 weeks, achieving significant reduction in arthritis, pruritus, and uveitis. After 8 weeks of this combination therapy, due to concerns of long-term macular toxicity, hydroxychloroquine was discontinued in favor of continuing methotrexate alone. The patient has remained free of significant side effects and stable with good disease control on 7.5 mg methotrexate weekly injected subcutaneously.

The resolution of phagosomes

Phagocytosis is a fundamental immunobiological process responsible for the removal of harmful particulates. While the number of phagocytic events achieved by a single phagocyte can be remarkable, exceeding hundreds per day, the same phagocytic cells are relatively long-lived. It should therefore be obvious that phagocytic meals must be resolved in order to maintain the responsiveness of the phagocyte and to avoid storage defects. In this article, we discuss the mechanisms involved in the resolution process, including solute transport pathways and membrane traffic. We describe how products liberated in phagolysosomes support phagocyte metabolism and the immune response. We also speculate on mechanisms involved in the redistribution of phagosomal metabolites back to circulation. Finally, we highlight the pathologies owed to impaired phagosome resolution, which range from storage disorders to neurodegenerative diseases.

Unveiling the role of gut-brain axis in regulating neurodegenerative diseases: A comprehensive review

Emerging evidence have shown the importance of gut microbiota in regulating brain functions. The diverse molecular mechanisms involved in cross-talk between gut and brain provide insight into importance of this communication in maintenance of brain homeostasis. It has also been observed that disturbed gut microbiota contributes to neurological diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis and aging. Recently, gut microbiome-derived exosomes have also been reported to play an essential role in the development and progression of neurodegenerative diseases and could thereby act as a therapeutic target. Further, pharmacological interventions including antibiotics, prebiotics and probiotics can influence gut microbiome-mediated management of neurological diseases. However, extensive research is warranted to better comprehend this interconnection in maintenance of brain homeostasis and its implication in neurological diseases. Thus, the present review is aimed to provide a detailed understanding of gut-brain axis followed by possibilities to target the gut microbiome for improving neurological health.

Metabolic control from the endolysosome: lysosome-resident amino acid transporters open novel therapeutic possibilities

Amino acid transporters are generally recognized as machinery that transport amino acids from the extracellular environment into the cytoplasm. Although their primary function is the uptake of amino acids to supply the cell with nutrients and energy, endolysosome-resident amino acid (EL-aa) transporters possess several unique functions in accordance with their localization in intracellular vesicular membranes. They play pivotal roles in the maintenance of metabolic homeostasis via direct involvement in the amino acid sensing pathway, which regulates the activity of mechanistic target of rapamycin complex 1 (mTORC1), a master regulator of cellular metabolism. Additionally, some EL-aa transporters contribute to the maintenance of dynamic homeostasis of endolysosomes, including the regulation of endolysosomal acidity, by carrying amino acids out of endolysosomes. In addition, EL-aa transporters act as a scaffold to gather signaling molecules and multiple enzymes to control cellular metabolism on the endolysosomal membrane. Among EL-aa transporters, solute carrier family 15 member 4 (SLC15A4) is preferentially expressed in immune cells, including macrophages, dendritic cells, and B cells, and plays a key role in the integration of metabolic and inflammatory signals. In this review, we summarize our recent findings on EL-aa transporter contributions to inflammatory and metabolic signaling in the endolysosomes of immune cells by focusing on the SLC15 family, including SLC15A4 and SLC15A3, and discuss their uniqueness and universality. We also discuss the potential of targeting these EL-aa transporters in immune cells for the development of novel therapeutic strategies for inflammatory diseases. Because these transporters are highly expressed in immune cells and significantly alter the functions of immune cells, targeting them would provide a great advantage in ensuring a wide safety margin.

Antimicrobial overproduction sustains intestinal inflammation by inhibiting Enterococcus colonization

Loss of antimicrobial proteins such as REG3 family members compromises the integrity of the intestinal barrier. Here, we demonstrate that overproduction of REG3 proteins can also be detrimental by reducing a protective species in the microbiota. Patients with inflammatory bowel disease (IBD) experiencing flares displayed heightened levels of secreted REG3 proteins that mediated depletion of Enterococcus faecium (Efm) from the gut microbiota. Efm inoculation of mice ameliorated intestinal inflammation through activation of the innate immune receptor NOD2, which was associated with the bacterial DL-endopeptidase SagA that generates NOD2-stimulating muropeptides. NOD2 activation in myeloid cells induced interleukin-1β (IL-1β) secretion to increase the proportion of IL-22-producing CD4+ T helper cells and innate lymphoid cells that promote tissue repair. Finally, Efm was unable to protect mice carrying a NOD2 gene variant commonly found in IBD patients. Our findings demonstrate that inflammation self-perpetuates by causing aberrant antimicrobial activity that disrupts symbiotic relationships with gut microbes.

The role and mechanisms of gram-negative bacterial outer membrane vesicles in inflammatory diseases

Outer membrane vesicles (OMVs) are spherical, bilayered, and nanosized membrane vesicles that are secreted from gram-negative bacteria. OMVs play a pivotal role in delivering lipopolysaccharide, proteins and other virulence factors to target cells. Multiple studies have found that OMVs participate in various inflammatory diseases, including periodontal disease, gastrointestinal inflammation, pulmonary inflammation and sepsis, by triggering pattern recognition receptors, activating inflammasomes and inducing mitochondrial dysfunction. OMVs also affect inflammation in distant organs or tissues via long-distance cargo transport in various diseases, including atherosclerosis and Alzheimer's disease. In this review, we primarily summarize the role of OMVs in inflammatory diseases, describe the mechanism through which OMVs participate in inflammatory signal cascades, and discuss the effects of OMVs on pathogenic processes in distant organs or tissues with the aim of providing novel insights into the role and mechanism of OMVs in inflammatory diseases and the prevention and treatment of OMV-mediated inflammatory diseases.

Discovery of a novel RIPK2 inhibitor for the treatment of inflammatory bowel disease

Nucleotide-binding oligomerization domain-containing protein 1 and 2 (NOD 1/2) are important cytosolic pattern recognition receptors that initiate host immune response. The dysregulation of NOD signaling is highly associated with inflammatory bowel disease (IBD) that needs novel treatment options. Receptor-interacting protein kinase 2 (RIPK2) is a critical mediator of NOD signaling and considered a promising therapeutic target for IBD treatment. However, there are currently no RIPK2 inhibitors available for clinical use. Here, we report the discovery and characterization of Zharp2-1 as a novel and potent RIPK2 inhibitor that effectively blocks RIPK2 kinase function and NOD-mediated NF-κB/MAPK activation in both human and mouse cell lines. Zharp2-1 exhibits significantly superior solubility compared to the non-prodrug form of the advanced RIPK2 inhibitor prodrug GSK2983559. The improved solubility combined with favorable in vitro metabolic stability translated to excellent in vivo pharmacokinetic profiles for Zharp2-1. In addition, Zharp2-1 demonstrates better effects than GSK2983559 in inhibiting the muramyl dipeptide (MDP)-induced production of pro-inflammatory cytokines in human peripheral blood mononuclear cells (PBMCs) and MDP-induced peritonitis in mice. Furthermore, Zharp2-1 markedly reduces Listeria monocytogenes infection-induced cytokines release in both human and mouse cells. Importantly, Zharp2-1 significantly ameliorates DNBS-induced colitis in rats and suppressed pro-inflammatory cytokine release in intestinal specimens from IBD patients. Collectively, our findings indicate that Zharp2-1 is a promising RIPK2 inhibitor with the potential to be further developed for IBD therapy.

A nod to the bond between NOD2 and mycobacteria

Mycobacteria are responsible for several human and animal diseases. NOD2 is a pattern recognition receptor that has an important role in mycobacterial recognition. However, the mechanisms by which mutations in NOD2 alter the course of mycobacterial infection remain unclear. Herein, we aimed to review the totality of studies directly addressing the relationship between NOD2 and mycobacteria as a foundation for moving the field forward. NOD2 was linked to mycobacterial infection at 3 levels: (1) genetic, through association with mycobacterial diseases of humans; (2) chemical, through the distinct NOD2 ligand in the mycobacterial cell wall; and (3) immunologic, through heightened NOD2 signaling caused by the unique modification of the NOD2 ligand. The immune response to mycobacteria is shaped by NOD2 signaling, responsible for NF-κB and MAPK activation, and the production of various immune effectors like cytokines and nitric oxide, with some evidence linking this to bacteriologic control. Absence of NOD2 during mycobacterial infection of mice can be detrimental, but the mechanism remains unknown. Conversely, the success of immunization with mycobacteria has been linked to NOD2 signaling and NOD2 has been targeted as an avenue of immunotherapy for diseases even beyond mycobacteria. The mycobacteria-NOD2 interaction remains an important area of study, which may shed light on immune mechanisms in disease.

Peptidoglycan NlpC/P60 peptidases in bacterial physiology and host interactions

The bacterial cell wall is composed of a highly crosslinked matrix of glycopeptide polymers known as peptidoglycan that dictates bacterial cell morphology and protects against environmental stresses. Regulation of peptidoglycan turnover is therefore crucial for bacterial survival and growth and is mediated by key protein complexes and enzyme families. Here, we review the prevalence, structure, and activity of NlpC/P60 peptidases, a family of peptidoglycan hydrolases that are crucial for cell wall turnover and division as well as interactions with antibiotics and different hosts. Understanding the molecular functions of NlpC/P60 peptidases should provide important insight into bacterial physiology, their interactions with different kingdoms of life, and the development of new therapeutic approaches.

Methotrexate suppresses psoriatic skin inflammation by inhibiting muropeptide transporter SLC46A2 activity

Cytosolic innate immune sensing is critical for protecting barrier tissues. NOD1 and NOD2 are cytosolic sensors of small peptidoglycan fragments (muropeptides) derived from the bacterial cell wall. These muropeptides enter cells, especially epithelial cells, through unclear mechanisms. We previously implicated SLC46 transporters in muropeptide transport in Drosophila immunity. Here, we focused on Slc46a2, which was highly expressed in mammalian epidermal keratinocytes, and showed that it was critical for the delivery of diaminopimelic acid (DAP)-muropeptides and activation of NOD1 in keratinocytes, whereas the related transporter Slc46a3 was critical for delivering the NOD2 ligand MDP to keratinocytes. In a mouse model, Slc46a2 and Nod1 deficiency strongly suppressed psoriatic inflammation, whereas methotrexate, a commonly used psoriasis therapeutic, inhibited Slc46a2-dependent transport of DAP-muropeptides. Collectively, these studies define SLC46A2 as a transporter of NOD1-activating muropeptides, with critical roles in the skin barrier, and identify this transporter as an important target for anti-inflammatory intervention.

RIPK2 as a promising druggable target for autoimmune diseases

Receptor Interacting Serine/Threonine Kinase 2 (RIPK2) is an essential regulator of the inflammatory process and immune response. In innate immunity, the NOD-RIPK2 signaling axis is an important pathway that directly mediates inflammation and immune response. In adaptive immunity, RIPK2 may affect T cell proliferation, differentiation and cellular homeostasis thereby involving T cell-driven autoimmunity, but the exact mechanism remains unclear. Recent advances suggest a key role of RIPK2 in diverse autoimmune diseases (ADs) such as inflammatory bowel diseases, rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, and Behcet's disease. This review aims to provide valuable therapeutic direction for ADs by focusing on the function and modulation of RIPK2 in innate and adaptive immunity, its involvement with various ADs and the application of RIPK2-related drugs in ADs. We raise the notion that drug targeting RIPK2 could be a promising therapeutic strategy for the treatment of ADs, though much work remains to be done for clinical application.

Peptidoglycan-induced modulation of metabolic and inflammatory responses

Bacterial cell wall peptidoglycan is composed of innate immune ligands and, due to its important structural role, also regulates access to many other innate immune ligands contained within the bacteria. There is a growing body of literature demonstrating how innate immune recognition impacts the metabolic functions of immune cells and how metabolic changes are not only important to inflammatory responses but are often essential. Peptidoglycan is primarily sensed in the context of the whole bacteria during lysosomal degradation; consequently, the innate immune receptors for peptidoglycan are primarily intracellular cytosolic innate immune sensors. However, during bacterial growth, peptidoglycan fragments are shed and can be found in the bloodstream of humans and mice, not only during infection but also derived from the abundant bacterial component of the gut microbiota. These peptidoglycan fragments influence cells throughout the body and are important for regulating inflammation and whole-body metabolic function. Therefore, it is important to understand how peptidoglycan-induced signals in innate immune cells and cells throughout the body interact to regulate how the body responds to both pathogenic and nonpathogenic bacteria. This mini-review will highlight key research regarding how cellular metabolism shifts in response to peptidoglycan and how systemic peptidoglycan sensing impacts whole-body metabolic function.

Modulation of long noncoding RNA (lncRNA) and messenger RNA (mRNA) expression in the liver of Beagle dogs by Toxocara canis infection

BACKGROUND

Long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) play crucial roles in regulating various physiological and pathological processes. However, the role of lncRNAs and mRNAs in mediating the liver response during Toxocara canis infection remains incompletely understood.

METHODS

In the present study, the expression profile of lncRNAs and mRNAs was investigated in the liver of Beagle dogs infected by T. canis using high-throughput RNA sequencing.

RESULTS

Compared with the control groups, 876 differentially expressed (DE) lncRNAs and 288 DEmRNAs were identified at 12 h post-infection (hpi), 906 DElncRNAs and 261 DEmRNAs were identified at 24 hpi, and 876 DElncRNAs and 302 DEmRNAs were identified at 36 days post-infection (dpi). A total of 16 DEmRNAs (e.g. dpp4, crp and gnas) were commonly identified at the three infection stages. Enrichment and co-localization analyses identified several pathways involved in immune and inflammatory responses during T. canis infection. Some novel DElncRNAs, such as LNC_015756, LNC_011050 and LNC_011052, were also associated with immune and inflammatory responses. Also, LNC_005105 and LNC_005401 were associated with the secretion of anti-inflammatory cytokines, which may play a role in the healing of liver pathology at the late stage of infection.

CONCLUSIONS

Our data provided new insight into the regulatory roles of lncRNAs and mRNAs in the pathogenesis of T. canis and improved our understanding of the contribution of lncRNAs and mRNAs to the immune and inflammatory response of the liver during T. canis infection.

The role of NOD-like receptors in innate immunity

The innate immune system in vertebrates and invertebrates relies on conserved receptors and ligands, and pathways that can rapidly initiate the host response against microbial infection and other sources of stress and danger. Research into the family of NOD-like receptors (NLRs) has blossomed over the past two decades, with much being learned about the ligands and conditions that stimulate the NLRs and the outcomes of NLR activation in cells and animals. The NLRs play key roles in diverse functions, ranging from transcription of MHC molecules to initiation of inflammation. Some NLRs are activated directly by their ligands, while other ligands may have indirect effects on the NLRs. New findings in coming years will undoubtedly shed more light on molecular details involved in NLR activation, as well as the physiological and immunological outcomes of NLR ligation.

Variants of NOD2 in Leishmania guyanensis-infected patients with cutaneous leishmaniasis and correlations with plasma circulating pro-inflammatory cytokines

Leishmaniases, a group of vector-borne diseases, are caused by the protozoan intracellular parasite Leishmania (L.) and are transmitted by the phlebotomine sandflies. A wide range of clinical manifestations in L- infection is observed. The clinical outcome ranges from asymptomatic, cutaneous leishmaniasis (CL) to severe mucosal leishmaniasis (ML) or visceral leishmaniasis (VL), depending on the L. species. Interestingly, only a fraction of L.-infected individuals progress to disease development, suggesting a key role of host genetics in the clinical outcome. NOD2 plays a critical role in the control of host defense and inflammation. The NOD2-RIK2 pathway is involved in developing a Th1- type response in patients with VL and C57BL/6 mice infected with L. infantum. We investigated whether variants in the NOD2 gene (R702W rs2066844, G908R rs2066845, and L1007fsinsC rs2066847) are associated with susceptibility to CL caused by L. guyanensis (Lg) in 837 patients with Lg-Cl and 797 healthy controls (HC) with no history of leishmaniasis. Both patients and HC are from the same endemic area of the Amazonas state of Brazil. The variants R702W and G908R were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and L1007fsinsC was by direct nucleotide sequencing. The minor allele frequency (MAF) of L1007fsinsC was 0.5% among the patients with Lg-CL and 0.6% in the healthy controls group. R702W genotypes frequencies were similar in both groups. Only 1% and 1.6% were heterozygous for G908R among the patients with Lg-CL and HC, respectively. None of the variants revealed any association with susceptibility to the development of Lg-CL. Correlations of genotypes with the level of plasma cytokines revealed that individuals with the mutant alleles of R702W tend to have low levels of IFN-γ. G908R heterozygotes also tend to have low IFN-γ, TNF-α, IL-17, and IL-8. Variants of NOD2 are not involved in the pathogenesis of Lg-CL.

Antimicrobial overproduction sustains intestinal inflammation by inhibiting Enterococcus colonization

Loss of antimicrobial proteins such as REG3 family members compromises the integrity of the intestinal barrier. Here, we demonstrate that overproduction of REG3 proteins can also be detrimental by reducing a protective species in the microbiota. Patients with inflammatory bowel disease (IBD) experiencing flares displayed heightened levels of secreted REG3 proteins that mediated depletion of Enterococcus faecium ( Efm ) from the gut microbiota. Efm inoculation of mice ameliorated intestinal inflammation through activation of the innate immune receptor NOD2, which was associated with the bacterial DL-endopeptidase SagA. Microbiota sensing by NOD2 in myeloid cells mediated IL-1β secretion and increased the proportion of IL-22-producing CD4 + T helper cells and innate lymphoid cells. Finally, Efm was unable to protect mice carrying a NOD2 gene variant commonly found in IBD patients. Our findings demonstrate that inflammation self-perpetuates by causing aberrant antimicrobial activity that disrupts symbiotic relationships with gut microbes.

Transcriptome analysis of largemouth bass (Micropterus salmoides) challenged with LPS and polyI:C

Largemouth bass (Micropterus salmoides) is a worldwide commercially important aquatic species. In recent years, pathogenic diseases cause great economic losses and hinder the industry of largemouth bass. To further understand the immune response against pathogens in largemouth bass, splenic transcriptome libraries of largemouth bass were respectively constructed at 12 h post-challenged with phosphate-buffered saline (PBS), lipopolysaccharide (LPS) and polyinosinic-polycytidylic acid (polyI:C) by using RNA sequencing technology (RNA-seq). RNA libraries were constructed using 9 RNA splenic samples isolated from three biological replicates of the three groups and sequenced on the DNBSEQ platform. A total number of 86,306 unigenes were obtained. Through pairwise comparisons among the three groups, we identified 11,295 different expression genes (DEGs) exhibiting significant differences at the transcript level. There were 7, 7, and 13 signal pathways were significantly enriched in LPS-PBS comparison, polyI:C-PBS comparison, and LPS-polyI:C comparison, respectively, indicating that the immune response to different pathogens was distinct in largemouth bass. To the best of our knowledge, this is the first report on the immune response of largemouth bass against different pathogen-associated molecular patterns (PAMPs) stimuli using transcriptomic analysis. Our results provide a valuable resource and new insights to understanding the immune characteristics of largemouth bass against different pathogens.

Hypoxia and Intestinal Inflammation: Common Molecular Mechanisms and Signaling Pathways

The gastrointestinal tract (GI) has a unique oxygenation profile. It should be noted that the state of hypoxia can be characteristic of both normal and pathological conditions. Hypoxia-inducible factors (HIF) play a key role in mediating the response to hypoxia, and they are tightly regulated by a group of enzymes called HIF prolyl hydroxylases (PHD). In this review, we discuss the involvement of inflammation hypoxia and signaling pathways in the pathogenesis of inflammatory bowel disease (IBD) and elaborate in detail on the role of HIF in multiple immune reactions during intestinal inflammation. We emphasize the critical influence of tissue microenvironment and highlight the existence of overlapping functions and immune responses mediated by the same molecular mechanisms. Finally, we also provide an update on the development of corresponding therapeutic approaches that would be useful for treatment or prophylaxis of inflammatory bowel disease.

NOD2 inhibits the proliferation of esophageal adenocarcinoma cells through autophagy

AIM

To study the regulatory mechanism of NOD2 in the inhibition of esophageal adenocarcinoma cell proliferation.

METHODS

Cell experiments: after confirming the decrease in NOD2 expression in esophageal adenocarcinoma, we overexpressed NOD2 in esophageal adenocarcinoma cells via lentivirus, compared and verified the changes in esophageal adenocarcinoma cell proliferation before and after NOD2 overexpression, and compared the overexpression group with the control group by mRNA sequencing to identify pathways that may affect cell proliferation. Then, the autophagy level of multiple groups were assessed, and the results were verified by rescue experiments. In vivo experiments: we administered esophageal adenocarcinoma cells to nude mice to form tumors under their skin and then injected the tumors with NOD2 overexpression lentivirus and negative control lentivirus. After a period of time, the growth curve of the tumor was generated, and the tumor was removed to generate sections. Ki67 was labeled with immunohistochemistry to verify cell proliferation, and the protein was extracted from the tissue to detect the molecular indices of the corresponding pathway.

RESULTS

Upregulation of NOD2 expression inhibited the proliferation of esophageal adenocarcinoma cells. Upregulation of NOD2 expression increased the autophagy level of esophageal adenocarcinoma cells via ATG16L1. After ATG16L1 was inhibited, NOD2 had no significant effect on autophagy and proliferation of esophageal adenocarcinoma cells. Enhanced autophagy in esophageal adenocarcinoma cell lines inhibited cell proliferation. In vivo, the upregulation of NOD2 expression improved the autophagy level of tumor tissue and inhibited cells proliferation.

CONCLUSION

NOD2 can activate autophagy in esophageal adenocarcinoma cells through the ATG16L1 pathway and inhibit cell proliferation.

Deletion of Insulin-like growth factor II mRNA-binding protein 3 participates in the pathogenesis of recurrent spontaneous abortion by inhibiting IL-10 secretion and inducing M1 polarization

Insulin-like growth factor II mRNA-binding protein 3 (IGF2BP3) has been proved to affect trophoblast function and embryonic development, but its role and potential mechanism in recurrent spontaneous abortion (RSA) are not clear. RSA is a complex reproductive disease, causing physical and mental damage to patients. In recent years, many studies have found that immune microenvironment is vital to maintain successful pregnancy in the maternal fetal interface. Therefore, this study aims to explore the role of IGF2BP3 in affecting macrophage polarization and its possible mechanism. In this article, we found that IGF2BP3 expression was decreased in placental villous samples of human and RSA mouse model, and knockdown of IGF2BP3 in HTR8/SVneo cells promotes M1 Mφ polarization. Combining with RNA sequencing analysis, we found that IGF2BP3 may regulate the Mφ polarization by affecting the expression of trophoblast cytokines, especially IL-10 secretion. Further mechanistic studies showed that knockdown of IGF2BP3 decreased expression of IL-10 by activating NF-κB pathway. Moreover, we found that M2 Mφ promote trophoblast invasion not IGF2BP3 dependent. Our study reveals the interaction between trophoblast cells and macrophages at the maternal-fetal interface of RSA patients, and will provide theoretical guidance for its diagnosis and treatment of RSA patients.

Association of the rs2111234, rs3135499, rs8057341 polymorphisms in the NOD2 gene with leprosy: A case-control study in the Norte de Santander, Colombia population

BACKGROUND

Leprosy is a chronic infectious disease caused by Mycobacterium leprae. The development of leprosy involves several factors, including the causative agent, the individual host's immune response, environmental factors, and the genetic background of the host. Specifically, the host's innate immune response, encoded by genes, determines their susceptibility to developing leprosy post-infection. Polymorphic variants in the nucleotide-binding oligomerization domain 2 (NOD2) gene are associated with leprosy among populations in a variety of endemic areas around the world. Colombia, a country located in the tropical zone, has several leprosy-endemic regions, including Norte de Santander. The aim of this study was to analyze the rs7194886, rs2111234, rs3135499, and rs8057341 single nucleotide polymorphisms (SNPs) in the NOD2 gene using a case-control study to determine whether they confer greater or lesser susceptibility to the development of leprosy.

METHODOLOGY

The TaqMan qPCR amplification system was used for SNPs detection.

FINDINGS

An association between the A-rs8057341 SNP (p = 0,006286) and resistance to leprosy was found. However, the rs3135499 (p = 0,9063) and rs2111234 (p = 0.1492) were not found to be associated with leprosy susceptibility. In addition, the rs7194886 SNP was not found to be in Hardy-Weinberg equilibrium (HWE) in the study population. The GAG haplotype, consisting of SNPs rs2111234-G, rs3135499-A, and rs8057341G, acts as a susceptibility factor for the development of leprosy in women. SNPs rs3135499 and rs8057341 are functionally related to decreased NOD2 expression according to an in-silico analysis.

CONCLUSIONS

The SNPs rs8057341-A was related with resistance to leprosy and the haplotype rs2111234-G, rs3135499-A and rs8057341-G SNPs was related with susceptibility in the Norte de Santander Colombia, studied population.

The mechanisms and cross-protection of trained innate immunity

In recent years, the traditional cognition of immunological memory being specific to adaptive immunity has been challenged. Innate immunity can mount enhanced responsiveness upon secondary stimulation, and a phenomenon is termed trained innate immunity. Trained innate immunity is orchestrated by distinct metabolic and epigenetic reprogramming in both circulating myeloid cells and myeloid progenitor cells in bone marrow, leading to long-term resistance to related and non-related pathogens infections. The induction of trained innate immunity can also polarize innate immune cells towards a hyperresponsive phenotype in the tumor microenvironment to exert antitumor effects. This review will discuss the current understanding of innate immune memory and the mechanisms during the induction of innate immunity, including signaling pathways, metabolic changes, and epigenetic rewriting. We also provide an overview of cross-protection against infectious diseases and cancers based on trained innate immunity.

Induction of protective interferon-β responses in murine osteoblasts following Staphylococcus aureus infection

Introduction

The refractory and recurrent nature of chronic staphylococcal osteomyelitis may be due, at least in part, to the ability of Staphylococcus aureus to invade and persist within bone-forming osteoblasts. However, osteoblasts are now recognized to respond to S. aureus infection and produce numerous immune mediators and bone regulatory factors that can shape the host response. Type I interferons (IFNs) are best known for their antiviral effects, but it is becoming apparent that they impact host susceptibility to a wide range of pathogens including S. aureus.

Methods

Here, we have assessed the local expression of IFN-β by specific capture ELISA in an established in vivo mouse model of staphylococcal osteomyelitis. RNA Tag-Seq analysis, specific capture ELISAs, and/or immunoblot analyses, were then used to assess the expression of type I IFNs and select IFN stimulated genes (ISGs) in S. aureus infected primary murine osteoblasts. The effect of IFN-β on intracellular S. aureus burden was assessed in vitro following recombinant cytokine treatment by serial colony counts of liberated bacteria.

Results

We report the presence of markedly elevated IFN-β levels in infected bone tissue in a mouse model of staphylococcal osteomyelitis. RNA Tag-Seq analysis of S. aureus infected osteoblasts showed enrichment of genes associated with type I IFN signaling and ISGs, and elevated expression of mRNA encoding IFN-β and ISG products. IFN-β production was confirmed with the demonstration that S. aureus induces its rapid and robust release by osteoblasts in a dose-dependent manner. Furthermore, we showed increased protein expression of the ISG products IFIT1 and IFIT3 by infected osteoblasts and demonstrate that this occurs secondary to the release of IFN-β by these cells. Finally, we have determined that exposure of S. aureus-infected osteoblasts to IFN-β markedly reduces the number of viable bacteria harbored by these cells.

Discussion

Together, these findings indicate an ability of osteoblasts to respond to bacteria by producing IFN-β that can act in an autocrine and/or paracrine manner to elicit ISG expression and mitigate S. aureus infection.

Vasoactive Intestinal Peptide (VIP) Protects Nile Tilapia (Oreochromis niloticus) against Streptococcus agalatiae Infection

Vasoactive intestinal peptide (VIP), a member of secretin/glucagon family, is involved in a variety of biological activities such as gut motility, immune responses, and carcinogenesis. In this study, the VIP precursor gene (On-VIP) and its receptor gene VIPR1 (On-VIPR1) were identified from Nile tilapia (Oreochromis niloticus), and the functions of On-VIP in the immunomodulation of Nile tilapia against bacterial infection were investigated and characterized. On-VIP and On-VIPR1 contain a 450 bp and a 1326 bp open reading frame encoding deduced protein of 149 and 441 amino acids, respectively. Simultaneously, the transcript of both On-VIP and On-VIPR1 were highly expressed in the intestine and sharply induced by Streptococcus agalatiae. Moreover, the positive signals of On-VIP and On-VIPR1 were detected in the longitudinal muscle layer and mucosal epithelium of intestine, respectively. Furthermore, both in vitro and in vivo experiments indicated several immune functions of On-VIP, including reduction of P65, P38, MyD88, STAT3, and AP1, upregulation of CREB and CBP, and suppression of inflammation. Additionally, in vivo experiments proved that On-VIP could protect Nile tilapia from bacterial infection and promote apoptosis and pyroptosis. These data lay a theoretical basis for further understanding of the mechanism of VIP guarding bony fish against bacterial infection.

Early Pregnancy Modulates Expression of the Nod-like Receptor Family in Lymph Nodes of Ewes

NOD receptors (NLRs) mediate adaptive immune responses and immune tolerance. Nevertheless, it is not clear if gestation modulates the NLR signaling pathway in lymph nodes of ewes. In this study, lymph nodes of ewes were collected at day 16 of the estrous cycle, and at days 13, 16 and 25 of gestation (n = 6 for each group). RT-qPCR, Western blot and immunohistochemistry analysis were used to analyze the expression of the NLR family, including NOD1, NOD2, CIITA, NAIP, NLRP1, NLRP3 and NLRP7. The data showed that early gestation enhanced expression of NOD1, CIITA, NLRP1, NLRP3 and NLRP7 mRNA, as well as proteins at day 16 of gestation, and the expression levels of NOD2, CIITA, NLRP1 and NLRP7 were higher at days 13 and 25 of gestation than day 16 of the estrous cycle. However, NOD1 expression was lower on days 13 and 25 of gestation compared to day 16 of the estrous cycle, and early gestation suppressed NAIP expression. In summary, early pregnancy modulated expression of the NLR family in ovine lymph nodes, which participates in immune regulation, and this modulation may be necessary for pregnancy establishment in ewes.

Role of Receptor Interacting Protein (RIP) kinases in cancer

The Receptor Interacting Protein (RIP) kinase family consists of seven Serine/Threonine kinases, which plays a key signaling role in cell survival and cell death. Each RIP family member contains a conserved kinase domain and other domains that determine the specific kinase function through protein-protein interactions. RIP1 and RIP3 are best known for their critical roles in necroptosis, programmed necrosis and a non-apoptotic inflammatory cell death process. Dysregulation of RIP kinases contributes to a variety of pathogenic conditions such as inflammatory diseases, neurological diseases, and cancer. In cancer cells, alterations of RIP kinases at genetic, epigenetic and expression levels are frequently found, and suggested to promote tumor progression and metastasis, escape of antitumor immune response, and therapeutic resistance. However, RIP kinases can be either pro-tumor or anti-tumor depending on specific tumor types and cellular contexts. Therapeutic agents for targeting RIP kinases have been tested in clinical trials mainly for inflammatory diseases. Deregulated expression of these kinases in different types of cancer suggests that they represent attractive therapeutic targets. The focus of this review is to outline the role of RIP kinases in cancer, highlighting potential opportunities to manipulate these proteins in cancer treatment.