GBP5 promotes NLRP3 inflammasome assembly and immunity in mammals

Trained immunity is regulated by T cell-induced CD40-TRAF6 signaling

Trained immunity is characterized by histone modifications and metabolic changes in innate immune cells following exposure to inflammatory signals, leading to heightened responsiveness to secondary stimuli. Although our understanding of the molecular regulation of trained immunity has increased, the role of adaptive immune cells herein remains largely unknown. Here, we show that T cells modulate trained immunity via cluster of differentiation 40-tissue necrosis factor receptor-associated factor 6 (CD40-TRAF6) signaling. CD40-TRAF6 inhibition modulates functional, transcriptomic, and metabolic reprogramming and modifies histone 3 lysine 4 trimethylation associated with trained immunity. Besides in vitro studies, we reveal that single-nucleotide polymorphisms in the proximity of CD40 are linked to trained immunity responses in vivo and that combining CD40-TRAF6 inhibition with cytotoxic T lymphocyte antigen 4-immunoglobulin (CTLA4-Ig)-mediated co-stimulatory blockade induces long-term graft acceptance in a murine heart transplantation model. Combined, our results reveal that trained immunity is modulated by CD40-TRAF6 signaling between myeloid and adaptive immune cells and that this can be leveraged for therapeutic purposes.

The role of galectins in the regulation of autophagy and inflammasome in host immunity

Galectins, a family of glycan-binding proteins have been shown to bind a wide range of glycans. In the cytoplasm, these glycans can be endogenous (or "self"), originating from damaged endocytic vesicles, or exogenous (or "non-self"), found on the surface of invading microbial pathogens. Galectins can detect these unusual cytosolic exposures to glycans and serve as critical regulators in orchestrating immune responses in innate and adaptive immunity. This review provides an overview of how galectins modulate host cellular responses, such as autophagy, xenophagy, and inflammasome-dependent cell death program, to infection.

Diminished Immune Response and Elevated Abundance in Gut Microbe Dubosiella in Mouse Models of Chronic Colitis with GBP5 Deficiency

Guanylate binding protein 5 (GBP5) is an emerging immune component that has been increasingly recognized for its involvement in autoimmune diseases, particularly inflammatory bowel disease (IBD). IBD is a complex disease involving inflammation of the gastrointestinal tract. Here, we explored the functional significance of GBP5 using Gbp5 knockout mice and wildtype mice exposed to dextran sulfate sodium (DSS) to generate chronic colitis model. We found that Gbp5 deficiency protected mice from DSS-induced chronic colitis. Transcriptome analysis of colon tissues showed reduced immune responses in Gbp5 knockout mice compared to those in corresponding wildtype mice. We further observed that after repeated DSS exposure, the gut microbiota was altered, both in wildtype mice and Gbp5 knockout mice; however, the gut microbiome health index was higher in the Gbp5 knockout mice. Notably, a probiotic murine commensal bacterium, Dubosiella, was predominantly enriched in these knockout mice. Our findings suggest that GBP5 plays an important role in promoting inflammation and dysbiosis in the intestine, the prevention of which might therefore be worth exploring in regards to IBD treatment.

Bacillus cereus CwpFM induces colonic tissue damage and inflammatory responses through oxidative stress and the NLRP3/NF-κB pathway

Bacillus cereus (B. cereus) from cow milk poses a threat to public health, causing food poisoning and gastrointestinal disorders in humans. We identified CwpFM, an enterotoxin from B. cereus, caused oxidative stress and inflammatory responses in mouse colon and colonic epithelial cells. Colon proteomics revealed that CwpFM elevated proteins associated with inflammation and oxidative stress. Notably, CwpFM induced activation of the NLRP3/NF-κB signaling, but suppressed antioxidant NFE2L2/HO-1 expression in the intestine and epithelial cells. Consistently, CwpFM exposure led to cytotoxicity and ROS accumulation in Caco-2 cells in a dose-dependent manner. Further, NAC (ROS inhibitor) treatment abolished NLRP3/NF-κB activation due to CwpFM. Moreover, overexpression of Nfe2l2 or activation of NFE2L2 by NK-252 reduced ROS production and inhibited activation of the NLRP3/NF-κB pathway. Inhibition of NF-κB by ADPC and/or suppression of NLRP3 by MCC950 attenuated CwpFM-induced inflammatory responses in Caco-2 cells. Collectively, CwpFM induced oxidative stress and NLRP3/NF-κB activation by inhibiting the NFE2L2/HO-1 signaling and ROS accumulation, leading to the development of intestinal inflammation. Our data elucidate the role of oxidative stress and innate immunity in CwpFM enterotoxicity and contribute to developing diagnostic and therapeutic products for B. cereus-related food safety issues.

A Synthetic Steroid 5α-Androst-3β, 5, 6β-triol Alleviates Radiation-Induced Brain Injury in Mice via Inhibiting GBP5/NF-κB/NLRP3 Signal Axis

Radiotherapy for head and neck tumors can lead to a severe complication known as radiation-induced brain injury (RIBI). However, the underlying mechanism of RIBI development remains unclear, and limited prevention and treatment options are available. Neuroactive steroids have shown potential in treating neurological disorders. 5α-Androst-3β, 5, 6β-triol (TRIOL), a synthetic neuroprotective steroid, holds promise as a treatment candidate for RIBI patients. However, the neuroprotective effects and underlying mechanism of TRIOL on RIBI treatment are yet to be elucidated. In the present study, our findings demonstrate TRIOL's potential as a neuroprotective agent against RIBI. In gamma knife irradiation mouse model, TRIOL treatment significantly reduced brain necrosis volume, microglial activation, and neuronal loss. RNA-sequencing, immunofluorescence, real-time quantitative polymerase chain reaction, siRNA transfection, and western blotting techniques revealed that TRIOL effectively decreased microglial activation, proinflammatory cytokine release, neuron loss, and guanylate-binding protein 5 (GBP5) expression, along with its downstream signaling pathways NF-κB and NLRP3 activation in vitro. In summary, TRIOL effectively alleviate RIBI by inhibiting the GBP5/NF-κB/NLRP3 signal axis, reducing microglia activation and pro-inflammation cytokines release, rescuing neuron loss. This study highlights the potential of TRIOL as a novel and promising therapy drug for RIBI treatment.

Guanylate binding protein 5 is an immune-related biomarker of oral squamous cell carcinoma: A retrospective prognostic study with bioinformatic analysis

BACKGROUND

Cancer utilizes immunosuppressive mechanisms to create a tumor microenvironment favorable for its progression. The purpose of this study is to histologically characterize the immunological properties of the tumor microenvironment of oral squamous cell carcinoma (OSCC) and identify key molecules involved in the immunological microenvironment and patient prognosis.

METHODS

First, overlapping differentially expressed genes (DEGs) were screened from OSCC transcriptome data in public databases. Correlation analysis of DEGs with known immune-related genes identified genes involved in the immune microenvironment of OSCC. Next, stromal patterns of tumor were classified and immunohistochemical staining was performed for immune cell markers (CD3, CD4, Foxp3, CD8, CD20, CD68, and CD163), programmed death-ligand 1 (PD-L1), and guanylate binding protein 5 (GBP5) in resected specimens obtained from 110 patients with OSCC who underwent resection. Correlations between each factor and their prognostic impact were analyzed.

RESULTS

Among the novel OSCC-specific immune-related genes screened (including ADAMDEC1, CXCL9, CXCL13, DPT, GBP5, IDO1, and PLA2G7), GBP5 was selected as the target gene. Histopathologic analysis showed that multiple T-cell subsets and CD20-positive cells were less common in the advanced stages, whereas CD163-positive cells were more common in advanced stages. The immature type in the stromal pattern category was associated with less immune cell infiltration, lower expression of PD-L1 in immune cells, lower expression of GBP5 in the stroma, and shorter overall survival and recurrence-free survival. Expression of GBP5 in the tumor and stroma correlated with immune cell infiltration of tumors and PD-L1 expression in tumor and immune cells. Patients with low tumor GBP5 expression and high stromal expression had significantly longer overall survival and recurrence-free survival.

CONCLUSIONS

The stromal pattern category may reflect both invasive and immunomodulatory potentials of cancer-associated fibroblasts in OSCC. GBP5 has been suggested as a potential biomarker to predict the prognosis and therapeutic efficacy of immune checkpoint inhibitors.

Circulating cell-free RNA in blood as a host response biomarker for detection of tuberculosis

Tuberculosis (TB) remains a leading cause of death from an infectious disease worldwide, partly due to a lack of effective strategies to screen and triage individuals with potential TB. Whole blood RNA signatures have been tested as biomarkers for TB, but have failed to meet the World Health Organization's (WHO) optimal target product profiles (TPP). Here, we use RNA sequencing and machine-learning to investigate the utility of plasma cell-free RNA (cfRNA) as a host-response biomarker for TB in cohorts from Uganda, Vietnam and Philippines. We report a 6-gene cfRNA signature, which differentiates TB-positive and TB-negative individuals with AUC = 0.95, 0.92, and 0.95 in test, training and validation, respectively. This signature meets WHO TPPs (sensitivity: 97.1% [95% CI: 80.9-100%], specificity: 85.2% [95% CI: 72.4-100%]) regardless of geographic location, sample collection method and HIV status. Overall, our results identify plasma cfRNA as a promising host response biomarker to diagnose TB.

Influences of bacterial extracellular vesicles on macrophage immune functions

Bacterial extracellular vesicles (EVs) are crucial mediators of information transfer between bacteria and host cells. Macrophages, as key effector cells in the innate immune system, have garnered widespread attention for their interactions with bacterial EVs. Increasing evidence indicates that bacterial EVs can be internalized by macrophages through multiple pathways, thereby influencing their immune functions. These functions include inflammatory responses, antimicrobial activity, antigen presentation, and programmed cell death. Therefore, this review summarizes current research on the interactions between bacterial EVs and macrophages. This will aid in the deeper understanding of immune modulation mediated by pathogenic microorganisms and provide a basis for developing novel antibacterial therapeutic strategies.

A microglia-containing cerebral organoid model to study early life immune challenges

Prenatal infections and activation of the maternal immune system have been proposed to contribute to causing neurodevelopmental disorders (NDDs), chronic conditions often linked to brain abnormalities. Microglia are the resident immune cells of the brain and play a key role in neurodevelopment. Disruption of microglial functions can lead to brain abnormalities and increase the risk of developing NDDs. How the maternal as well as the fetal immune system affect human neurodevelopment and contribute to NDDs remains unclear. An important reason for this knowledge gap is the fact that the impact of exposure to prenatal risk factors has been challenging to study in the human context. Here, we characterized a model of cerebral organoids (CO) with integrated microglia (COiMg). These organoids express typical microglial markers and respond to inflammatory stimuli. The presence of microglia influences cerebral organoid development, including cell density and neural differentiation, and regulates the expression of several ciliated mesenchymal cell markers. Moreover, COiMg and organoids without microglia show similar but also distinct responses to inflammatory stimuli. Additionally, IFN-γ induced significant transcriptional and structural changes in the cerebral organoids, that appear to be regulated by the presence of microglia. Specifically, interferon-gamma (IFN-γ) was found to alter the expression of genes linked to autism. This model provides a valuable tool to study how inflammatory perturbations and microglial presence affect neurodevelopmental processes.

Caspase-11 drives macrophage hyperinflammation in models of Polg-related mitochondrial disease

Mitochondrial diseases (MtD) represent a significant public health challenge due to their heterogenous clinical presentation, often severe and progressive symptoms, and the lack of effective therapies. Environmental exposures, such bacterial and viral infection, can further compromise mitochondrial function and exacerbate the progression of MtD. Infections in MtD patients more frequently progress to sepsis, pneumonia, and other detrimental inflammatory endpoints. However, the underlying immune alterations that enhance immunopathology in MtD remain unclear, constituting a key gap in knowledge that complicates treatment and increases mortality in this population. Here we employ in vitro and in vivo approaches to clarify the molecular and cellular basis for innate immune hyperactivity in models of polymerase gamma (Polg)-related MtD. We reveal that type I interferon (IFN-I)-mediated upregulation of caspase-11 and guanylate-binding proteins (GBPs) increase macrophage sensing of the opportunistic microbe Pseudomonas aeruginosa (PA) in Polg mutant mice. Furthermore, we show that excessive macrophage cytokine secretion and pyroptotic cell death contribute to lung inflammation and morbidity after infection with PA. Our work sheds new light on innate immune dysregulation in MtD and reveals potential targets for limiting infection- and inflammation-related complications in Polg-related MtD.

NLRP inflammasomes in health and disease

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

Inhibition of GBP5 activates autophagy to alleviate inflammatory response in LPS-induced lung injury in mice

BACKGROUND

Pulmonary emphysema is a condition that causes damage to the lung tissue over time. GBP5, as part of the guanylate-binding protein family, is dysregulated in mouse pulmonary emphysema. However, the role of GBP5 in lung inflammation in ARDS remains unveiled.

METHODS

To investigate whether GBP5 regulates lung inflammation and autophagy regulation, the study employed a mouse ARDS model and MLE-12 cell culture. Vector transfection was performed for the genetic manipulation of GBP5. Then, RT-qPCR, WB and IHC staining were conducted to assess its transcriptional and expression levels. Histological features of the lung tissue were observed through HE staining. Moreover, ELISA was conducted to evaluate the secretion of inflammatory cytokines, autophagy was assessed by immunofluorescent staining, and MPO activity was determined using a commercial kit.

RESULTS

Our study revealed that GBP5 expression was altered in mouse ARDS and LPS-induced MLE-12 cell models. Moreover, the suppression of GBP5 reduced lung inflammation induced by LPS in mice. Conversely, overexpression of GBP5 diminished the inhibitory impact of LPS on ARDS during autophagy, leading to increased inflammation. In the cell line of MLE-12, GBP5 exacerbates LPS-induced inflammation by blocking autophagy.

CONCLUSION

The study suggests that GBP5 facilitates lung inflammation and autophagy regulation. Thus, GBP5 could be a potential therapeutic approach for improving ARDS treatment outcomes, but further research is required to validate these findings.

The XPO1 inhibitor selinexor ameliorates bleomycin-induced pulmonary fibrosis in mice via GBP5/NLRP3 inflammasome signaling

Pulmonary fibrosis is an irreversible and progressive lung disease with limited treatments available. Selinexor (Sel), an orally available, small-molecule, selective inhibitor of XPO1, exhibits notable antitumor, anti-inflammatory and antiviral activities. However, its potential role in treating pulmonary fibrosis is unknown. C57BL/6J mice were used to establish a pulmonary fibrosis model by intratracheal administration of bleomycin (BLM). Subsequently, Sel was administered intraperitoneally. Our data demonstrated that Sel administration ameliorated BLM-induced pulmonary fibrosis by increasing mouse body weights; reducing H&E staining, Masson staining scores, and shadows in mouse lung computed tomography (CT) images, decreasing the total cell and neutrophil counts in the lung and bronchoalveolar lavage fluid (BALF); and decreasing the levels of TGF-β1. We next confirmed that Sel reduced the deposition of extracellular matrix (ECM) components in the lungs of BLM-induced pulmonary fibrosis mice. We showed that collagen I, alpha-smooth muscle actin (α-SMA), and hydroxyproline levels and the mRNA levels of Col1a1, Eln, Fn1, Ctgf, and Fgf2 were reduced. Mechanistically, tandem mass tags (TMT)- based quantitative proteomics analysis revealed a significant increase in GBP5 in the lungs of BLM mice but a decrease in that of BLM + Sel mice; this phenomenon was confirmed by western blotting and RT-qPCR. NLRP3 inflammasome signaling was significantly enriched in both the BLM group and BLM + Sel group based on GO and KEGG analyses of differentially expressed proteins between the groups. Furthermore, Sel reduced the expression of NLRP3, cleaved caspase 1, and ASC in vivo and in vitro, and decreased the levels of IL-1β, IL-18, and IFN-r in lung tissue and BALF. SiRNA-GBP5 inhibited NLRP3 signaling in vitro, and overexpression of GBP5 inhibited the protective effect of Sel against BLM-induced cellular injury. Taken together, our findings indicate that Sel ameliorates BLM-induced pulmonary fibrosis by targeting GBP5 via NLRP3 inflammasome signaling. Thus, the XPO1 inhibitor - Sel might be a potential therapeutic agent for pulmonary fibrosis.

Transcriptomic analysis delineates preterm prelabor rupture of membranes from preterm labor in preterm fetal membranes

BACKGROUND

Globally, preterm birth remains the leading cause of death in children younger than 5 years old. Spontaneous preterm birth is comprised of two events that may or may not occur simultaneously: preterm labor and preterm prelabor rupture of membranes (PPROM). To further explore the concept that spontaneous preterm birth can result from the initializing of two separate but overlapping pathological events, we compared fetal membrane tissue from preterm labor deliveries to fetal tissue from preterm labor with PPROM deliveries. We hypothesized that the fetal membrane tissue from preterm labor with PPROM cases will have an RNA-seq profile divergent from the fetal membrane tissue from preterm labor controls.

METHODS

Chorioamnion, separated into amnion and chorion, was collected from eight gestationally age-matched cases and controls within 15 min of birth, and analyzed using RNA sequencing. Pathway enrichment analyses and functional annotations of differentially expressed genes were performed using KEGG and Gene Ontogeny Pathway enrichment analyses.

RESULTS

A total of 1466 genes were differentially expressed in the amnion, and 484 genes were differentially expressed in the chorion (log2 fold change > 1, FDR < 0.05) in cases (preterm labor with PPROM), versus controls (preterm labor only). In the amnion, the most significantly enriched (FDR < 0.01) KEGG pathway among down-regulated genes was the extracellular matrix receptor interaction pathway. Seven of the most significantly enriched pathways were comprised of multiple genes from the COL family, including COL1A, COL3A1, COL4A4, and COL4A6. In the chorion, the most significantly enriched KEGG pathways in up-regulated genes were chemokine, NOD receptor, Toll-like receptor, and cytokine-cytokine receptor signaling pathways. Similarly, KEGG pathway enrichment analysis for up-regulated genes in the amnion included three inflammatory pathways: cytokine-cytokine interaction, TNF signaling and the CXCL family. Six genes were significantly up regulated in chorionic tissue discriminated between cases (preterm labor with PPROM) and controls (preterm labor only) including GBP5, CXCL9, ALPL, S100A8, CASP5 and MMP25.

CONCLUSIONS

In our study, transcriptome analysis of preterm fetal membranes revealed distinct differentially expressed genes for PPROM, separate from preterm labor. This study is the first to report transcriptome data that reflects the individual pathophysiology of amnion and chorion tissue from PPROM deliveries.

Fantastic voyage: The journey of NLRP3 inflammasome activation

NLRP3 inflammasome, an intracellular multiprotein complex, can be activated by a range of pathogenic microbes or endogenous hazardous chemicals. Its activation results in the release of cytokines such as IL-1β and IL-18, as well as Gasdermin D which eventually causes pyroptosis. The activation of NLRP3 inflammasome is under strict control and regulation by numerous pathways and mechanisms. Its excessive activation can lead to a persistent inflammatory response, which is linked to the onset and progression of severe illnesses. Recent studies have revealed that the subcellular localization of NLRP3 changes significantly during the activation process. In this review, we review the current understanding of the molecular mechanism of NLRP3 inflammasome activation, focusing on the subcellular localization of NLRP3 and the associated regulatory mechanisms. We aim to provide a comprehensive understanding of the dynamic transportation, activation, and degradation processes of NLRP3.

Native architecture of a human GBP1 defense complex for cell-autonomous immunity to infection

All living organisms deploy cell-autonomous defenses to combat infection. In plants and animals, large supramolecular complexes often activate immune proteins for protection. In this work, we resolved the native structure of a massive host-defense complex that polymerizes 30,000 guanylate-binding proteins (GBPs) over the surface of gram-negative bacteria inside human cells. Construction of this giant nanomachine took several minutes and remained stable for hours, required guanosine triphosphate hydrolysis, and recruited four GBPs plus caspase-4 and Gasdermin D as a cytokine and cell death immune signaling platform. Cryo-electron tomography suggests that GBP1 can adopt an extended conformation for bacterial membrane insertion to establish this platform, triggering lipopolysaccharide release that activated coassembled caspase-4. Our "open conformer" model provides a dynamic view into how the human GBP1 defense complex mobilizes innate immunity to infection.

Identification of diagnostic biomarkers correlate with immune infiltration in extra-pulmonary tuberculosis by integrating bioinformatics and machine learning

The diagnosis of tuberculosis depends on detecting Mycobacterium tuberculosis (Mtb). Unfortunately, recognizing patients with extrapulmonary tuberculosis (EPTB) remains challenging due to the insidious clinical presentation and poor performance of diagnostic tests. To identify biomarkers for EPTB, the GSE83456 dataset was screened for differentially expressed genes (DEGs), followed by a gene enrichment analysis. One hundred and ten DEGs were obtained, mainly enriched in inflammation and immune -related pathways. Weighted gene co-expression network analysis (WGCNA) was used to identify 10 co-expression modules. The turquoise module, correlating the most highly with EPTB, contained 96 DEGs. Further screening with the least absolute shrinkage and selection operator (LASSO) and support vector machine recursive feature elimination (SVM-RFE) narrowed down the 96 DEGs to five central genes. All five key genes were validated in the GSE144127 dataset. CARD17 and GBP5 had high diagnostic capacity, with AUC values were 0.763 (95% CI: 0.717-0.805) and 0.833 (95% CI: 0.793-0.869) respectively. Using single sample gene enrichment analysis (ssGSEA), we evaluated the infiltration of 28 immune cells in EPTB and explored their relationships with key genes. The results showed 17 immune cell subtypes with significant infiltrations in EPTB. CARD17, GBP5, HOOK1, LOC730167, and HIST1H4C were significantly associated with 16, 14, 12, 6, and 4 immune cell subtypes, respectively. The RT-qPCR results confirmed that the expression levels of GBP5 and CARD17 were higher in EPTB compared to control. In conclusion, CARD17 and GBP5 have high diagnostic efficiency for EPTB and are closely related to immune cell infiltration.

Guanylate binding protein 5 triggers NF-κB activation to foster radioresistance, metastatic progression and PD-L1 expression in oral squamous cell carcinoma

Radioresistance and metastasis are critical issues in managing oral squamous cell carcinoma (OSCC). Although immune checkpoint inhibitors (ICIs) has been recommended to treat OSCC, lacking useful biomarkers limited their anti-cancer effectiveness. We found that guanylate binding protein 5 (GBP5) is upregulated in primary tumors and associates with radioresistance in OSCC. GBP5 expression causally associated with cellular radioresistance and migration ability in the OSCC cell variants. GBP5 upregulation was examined to be correlated with NF-κB activation and programmed cell death-ligand 1 (PD-L1) elevation in OSCC samples. GBP5 knockdown was mitigated, but overexpression enhanced, NF-κB activity and PD-L1 expression in the OSCC cells. NF-κB inhibition by SN50 dramatically suppressed the GBP5-forested irradiation resistance, cellular migration ability and PD-L1 expression in OSCC cells. Importantly, GBP5 upregulation predicted a favorable outcome in cancer patients received ICI treatment. Our findings provide GBP5 as a useful biomarker to predict the anti-OSCC effectiveness of irradiation and ICIs.

Evolution of guanylate binding protein genes shows a remarkable variability within bats (Chiroptera)

Background

GBPs (guanylate binding proteins), an evolutionary ancient protein family, play a key role in the host's innate immune response against bacterial, parasitic and viral infections. In Humans, seven GBP genes have been described (GBP1-7). Despite the interest these proteins have received over the last years, evolutionary studies have only been performed in primates, Tupaia and rodents. These have shown a pattern of gene gain and loss in each family, indicative of the birth-and-death evolution process.

Results

In this study, we analysed the evolution of this gene cluster in several bat species, belonging to the Yangochiroptera and Yinpterochiroptera sub-orders. Detailed analysis shows a conserved synteny and a gene expansion and loss history. Phylogenetic analysis showed that bats have GBPs 1,2 and 4-6. GBP2 has been lost in several bat families, being present only in Hipposideidae and Pteropodidae. GBPs1, 4 and 5 are present mostly as single-copy genes in all families but have suffered duplication events, particularly in Myotis myotis and Eptesicus fuscus. Most interestingly, we demonstrate that GBP6 duplicated in a Chiroptera ancestor species originating two genes, which we named GBP6a and GBP6b, with different subsequent evolutionary histories. GBP6a underwent several duplication events in all families while GBP6b is present as a single copy gene and has been lost in Pteropodidae, Miniopteridae and Desmodus rotundus, a Phyllostomidae. With 14 and 15 GBP genes, Myotis myotis and Eptesicus fuscus stand out as having far more copies than all other studied bat species. Antagonistically, Pteropodidae have the lowest number of GBP genes in bats.

Conclusion

Bats are important reservoirs of viruses, many of which have become zoonotic diseases in the last decades. Further functional studies on bats GBPs will help elucidate their function, evolutionary history, and the role of bats as virus reservoirs.

Alteration of PBMC transcriptome profile after interaction with multipotent mesenchymal stromal cells under "physiological" hypoxia

Multipotent mesenchymal stromal cells (MSCs) have demonstrated a pronounced immunosuppressive activity, the manifestation of which depends on the microenvironmental factors, including O2 level. Here we examined the effects of MSCs on transcriptomic profile of allogeneic phytohemagglutinin-stimulated peripheral blood mononuclear cells (PBMCs) after interaction at ambient (20%) or "physiological" hypoxia (5%) O2. As revealed with microarray analysis, PBMC transcriptome at 20% O2 was more affected, which was manifested as differential expression of more than 300 genes, whereas under 5% O2 220 genes were changed. Most of genes at 20% O2 were downregulated, while at hypoxia most of genes were upregulated. Altered gene patterns were only partly overlapped at different O2 levels. A set of altered genes at hypoxia only was of particular interest. According to Gene Ontology a part of above genes was responsible for adhesion, cell communication, and immune response. At both oxygen concentrations, MSCs demonstrated effective immunosuppression manifested as attenuation of T cell activation and proliferation as well as anti-inflammatory shift of cytokine profile. Thus, MSC-mediated immunosuppression is executed with greater efficacy at a "physiological" hypoxia, since the same result has been achieved through a change in the expression of a fewer genes in target PBMCs.

The IRF1/GBP5 axis promotes osteoarthritis progression by activating chondrocyte pyroptosis

Background

Osteoarthritis (OA) is a chronic degenerative joint disease that primarily affects middle-aged and elderly individuals. The decline in chondrocyte function plays a crucial role in the development of OA. Inflammasome-mediated chondrocyte pyroptosis is implicated in matrix degradation and cartilage degeneration in OA patients. Guanylate binding protein 5 (GBP5), a member of the GTPase family induced by Interferon-γ (IFN-γ), significantly influences cellular inflammatory responses, including intracellular inflammasome activation and cytokine release. However, the role of GBP5 in chondrocyte pyroptosis and OA progression remains unclear.

Methods

In this study, we used tumor necrosis factor-α (TNF-α) to induce inflammation and created an OA mouse model with surgically-induced destabilization of the medial meniscus (DMM). We isolated and cultured primary chondrocytes from the knee joints of suckling C57 mice. TNF-α-stimulated primary chondrocytes served as an in vitro model for OA and underwent RNA sequencing. Chondrocytes were transfected with GBP5-overexpression plasmids and small interfering RNA and were subsequently treated with TNF-α. We assessed the expression of cartilage matrix components (COL2A1 and aggrecan), catabolic factors (MMP9 and MMP13), and NLRP3 inflammasome pathway genes (NLRP3, Caspase1, GSDMD, Pro-IL-1β, and Pro-Caspase1) using RT-qPCR and Western blotting. We analyzed the expression of GBP5, NLRP3, and Caspase1 in the cartilage of DMM-induced post-traumatic OA mice and human OA patients. Immunohistochemistry (IHC) was used to detect the expression of GBP5, NLRP3 and GSDMD in cartilage specimens from OA patients and mouse DMM models. Chondrocyte pyroptosis was assessed using flow cytometry, and the levels of interleukin-1β (IL-1β) and interleukin-18 (IL-18) were measured with ELISA. We conducted double luciferase reporter gene and chromatin immunoprecipitation (ChIP) assays to confirm the relationship between IRF1 and GBP5.

Results

GBP5 expression increased in TNF-α-induced chondrocytes, as revealed by RNA sequencing. GBP5 inhibited COL2A1 and aggrecan expression while promoting the expression of MMP9, MMP13, NLRP3, Caspase1, GSDMD, Pro-IL-1β, and Pro-Caspase1. GBP5 expression also increased in the cartilage of DMM-induced post-traumatic OA mice and human OA patients. Knockout of GBP5 reduced chondrocyte injury in OA mice. GBP5 promoted chondrocyte pyroptosis and the production of IL-1β and IL-18. Additionally, we found that IRF1 bound to the promoter region of GBP5, enhancing its expression. After co-transfected with ad-IRF1 and siGBP5, the expression of pyroptosis-related genes was significantly decreased compared with ad-IRF1 group.

Conclusions

The IRF1/GBP5 axis enhances extracellular matrix (ECM) degradation and promotes pyroptosis during OA development, through the NLRP3 inflammasome signaling pathway.

The translational potential of this article

This study underscores the significance of the IRF1/GBP5 axis in NLRP3 inflammasome-mediated chondrocyte pyroptosis and osteoarthritic chondrocyte injury. Modulating IRF1 and GBP5 expression could serve as a novel therapeutic target for OA.

Redox regulation of the NLRP3-mediated inflammation and pyroptosis

The review considers modern data on the mechanisms of activation and redox regulation of the NLRP3 inflammasome and gasdermins, as well as the role of selenium in these processes. Activation of the inflammasome and pyroptosis represent an evolutionarily conserved mechanism of the defense against pathogens, described for various types of cells and tissues (macrophages and monocytes, microglial cells and astrocytes, podocytes and parenchymal cells of the kidneys, periodontal tissues, osteoclasts and osteoblasts, as well as cells of the digestive and urogenital systems, etc.). Depending on the characteristics of redox regulation, the participants of NLRP3 inflammation and pyroptosis can be subdivided into 2 groups. Members of the first group block the mitochondrial electron transport chain, promote the formation of reactive oxygen species and the development of oxidative stress. This group includes granzymes, the mitochondrial antiviral signaling protein MAVS, and others. The second group includes thioredoxin interacting protein (TXNIP), erythroid-derived nuclear factor-2 (NRF2), Kelch-like ECH-associated protein 1 (Keap1), ninjurin (Ninj1), scramblase (TMEM16), inflammasome regulatory protein kinase NLRP3 (NEK7), caspase-1, gasdermins GSDM B, D and others. They have redox-sensitive domains and/or cysteine residues subjected to redox regulation, glutathionylation/deglutathionylation or other types of regulation. Suppression of oxidative stress and redox regulation of participants in NLRP3 inflammation and pyroptosis depends on the activity of the antioxidant enzymes glutathione peroxidase (GPX) and thioredoxin reductase (TRXR), containing a selenocysteine residue Sec in the active site. The expression of GPX and TRXR is regulated by NRF2 and depends on the concentration of selenium in the blood. Selenium deficiency causes ineffective translation of the Sec UGA codon, translation termination, and, consequently, synthesis of inactive selenoproteins, which can cause various types of programmed cell death: apoptosis of nerve cells and sperm, necroptosis of erythrocyte precursors, pyroptosis of infected myeloid cells, ferroptosis of T- and B-lymphocytes, kidney and pancreatic cells. In addition, suboptimal selenium concentrations in the blood (0.86 μM or 68 μg/l or less) have a significant impact on expression of more than two hundred and fifty genes as compared to the optimal selenium concentration (1.43 μM or 113 μg/l). Based on the above, we propose to consider blood selenium concentrations as an important parameter of redox homeostasis in the cell. Suboptimal blood selenium concentrations (or selenium deficiency states) should be used for assessment of the risk of developing inflammatory processes.

Sinomenine ameliorates collagen-induced arthritis in mice by targeting GBP5 and regulating the P2X7 receptor to suppress NLRP3-related signaling pathways

Sinomenine (SIN) is an isoquinoline alkaloid isolated from Sinomenii Caulis, a traditional Chinese medicine used to treat rheumatoid arthritis (RA). Clinical trials have shown that SIN has comparable efficacy to methotrexate in treating patients with RA but with fewer adverse effects. In this study, we explored the anti-inflammatory effects and therapeutic targets of SIN in LPS-induced RAW264.7 cells and in collagen-induced arthritis (CIA) mice. LPS-induced RAW264.7 cells were pretreated with SIN (160, 320, 640 µM); and CIA mice were administered SIN (25, 50 and 100 mg·kg-1·d-1, i.p.) for 30 days. We first conducted a solvent-induced protein precipitation (SIP) assay in LPS-stimulated RAW264.7 cells and found positive evidence for the direct binding of SIN to guanylate-binding protein 5 (GBP5), which was supported by molecular simulation docking, proteomics, and binding affinity assays (KD = 3.486 µM). More importantly, SIN treatment markedly decreased the expression levels of proteins involved in the GBP5/P2X7R-NLRP3 pathways in both LPS-induced RAW264.7 cells and the paw tissue of CIA mice. Moreover, the levels of IL-1β, IL-18, IL-6, and TNF-α in both the supernatant of inflammatory cells and the serum of CIA mice were significantly reduced. This study illustrates a novel anti-inflammatory mechanism of SIN; SIN suppresses the activity of NLRP3-related pathways by competitively binding GBP5 and downregulating P2X7R protein expression, which ultimately contributes to the reduction of IL-1β and IL-18 production. The binding specificity of SIN to GBP5 and its inhibitory effect on GBP5 activity suggest that SIN has great potential as a specific GBP5 antagonist.

Borrelia burgdorferi initiates early transcriptional re-programming in macrophages that supports long-term suppression of inflammation

Borrelia burgdorferi (Bb), the causative agent of Lyme disease, establishes a long-term infection and leads to disease manifestations that are the result of host immune responses to the pathogen. Inflammatory manifestations resolve spontaneously despite continued bacterial presence, suggesting inflammatory cells become less responsive over time. This is mimicked by in vitro repeated stimulations, resulting in tolerance, a phenotypic subset of innate immune memory. We performed comparative transcriptional analysis of macrophages in acute and memory states and identified sets of Tolerized, Hyper-Induced, Secondary-Induced and Hyper-Suppressed genes resulting from memory induction, revealing previously unexplored networks of genes affected by cellular re-programming. Tolerized gene families included inflammatory mediators and interferon related genes as would be predicted by the attenuation of inflammation over time. To better understand how cells mediate inflammatory hypo-responsiveness, we focused on genes that could mediate maintenance of suppression, such as Hyper-Induced genes which are up-regulated in memory states. These genes were notably enriched in stress pathways regulated by anti-inflammatory modulators. We examined one of the most highly expressed negative regulators of immune pathways during primary stimulation, Aconitate decarboxylase 1 (Acod1), and tested its effects during in vivo infection with Bb. As predicted by our in vitro model, we show its inflammation-suppressive downstream effects are sustained during in vivo long-term infection with Bb, with a specific role in Lyme carditis.

Evaluation of the Cepheid 3-gene host response blood test for tuberculosis diagnosis and treatment response monitoring in a primary-level clinic in rural China

A rapid, accurate, non-sputum-based triage test for diagnosing tuberculosis (TB) is a high-priority need. Cepheid developed a novel prototype blood test, Xpert Mycobacterium tuberculosis Host Response (Xpert-MTB-HR), which generates a TB score based on the mRNA expression of three genes. We conducted a case-control study with prospective recruitment to evaluate its accuracy in the clinic of the Wusheng County Centers for Disease Prevention and Control in China. We enrolled 149 TB patients, 248 other respiratory diseases (ORD) patients, and 193 healthy controls. In addition, whole-blood samples taken from TB patients after 2, 5, and 6 months of treatment were tested with Xpert-MTB-HR to evaluate its ability to monitor treatment response. Xpert-MTB-HR discriminated between TB and healthy controls with an area under the curve (AUC) of 0.912 (95% CI, 0.878-0.945). With the specificity of 70% envisioned for a triage test, its sensitivity was 90.1% (84.9%-94.6%). Xpert-MTB-HR discriminated between TB and ORD with an AUC of 0.798 (0.750-0.847), and at specificity of 70%, the sensitivity was only 75.8% (68.5%-82.8%). In patients determined by Ultra to have medium or high sputum bacillary loads, with specificity of 70%, the sensitivity for discriminating patients with TB from healthy controls was 100.0% (100.0-100.0) and from patients with ORD, 95.1% (89.8-100.0). The TB scores generally increased by 2 months of treatment and then remained stable. Xpert-MTB-HR met the criteria for a triage test to discriminate between TB and healthy controls, but not between TB and ORD, except when limited to patients with high sputum bacillary loads. Xpert-MTB-HR showed promise for monitoring response to treatment but needs to be further evaluated in larger prospective studies.

PLK1 inhibition dampens NLRP3 inflammasome-elicited response in inflammatory disease models

Unabated activation of the NLR family pyrin domain-containing 3 (NLRP3) inflammasome is linked with the pathogenesis of various inflammatory disorders. Polo-like kinase 1 (PLK1) has been widely studied for its role in mitosis. Here, using both pharmacological and genetic approaches, we demonstrate that PLK1 promoted NLRP3 inflammasome activation at cell interphase. Using an unbiased proximity-dependent biotin identification (Bio-ID) screen for the PLK1 interactome in macrophages, we show an enhanced proximal association of NLRP3 with PLK1 upon NLRP3 inflammasome activation. We further confirmed the interaction between PLK1 and NLRP3 and identified the interacting domains. Mechanistically, we show that PLK1 orchestrated the microtubule-organizing center (MTOC) structure and NLRP3 subcellular positioning upon inflammasome activation. Treatment with a selective PLK1 kinase inhibitor suppressed IL-1β production in in vivo inflammatory models, including LPS-induced endotoxemia and monosodium urate-induced peritonitis in mice. Our results uncover a role of PLK1 in regulating NLRP3 inflammasome activation during interphase and identify pharmacological inhibition of PLK1 as a potential therapeutic strategy for inflammatory diseases with excessive NLRP3 inflammasome activation.

Human GBP1 facilitates the rupture of the Legionella-containing vacuole and inflammasome activation

IMPORTANCE

Inflammasomes are essential for host defense against intracellular bacterial pathogens like Legionella, as they activate caspases, which promote cytokine release and cell death to control infection. In mice, interferon (IFN) signaling promotes inflammasome responses against bacteria by inducing a family of IFN-inducible GTPases known as guanylate-binding proteins (GBPs). Within murine macrophages, IFN promotes the rupture of the Legionella-containing vacuole (LCV), while GBPs are dispensable for this process. Instead, GBPs facilitate the lysis of cytosol-exposed Legionella. In contrast, the functions of IFN and GBPs in human inflammasome responses to Legionella are poorly understood. We show that IFN-γ enhances inflammasome responses to Legionella in human macrophages. Human GBP1 is required for these IFN-γ-driven inflammasome responses. Furthermore, GBP1 co-localizes with Legionella and/or LCVs in a type IV secretion system (T4SS)-dependent manner and promotes damage to the LCV, which leads to increased exposure of the bacteria to the host cell cytosol. Thus, our findings reveal species- and pathogen-specific differences in how GBPs function to promote inflammasome responses.

Whole exome sequencing of patients with varicella-zoster virus and herpes simplex virus induced acute retinal necrosis reveals rare disease-associated genetic variants

Purpose

Herpes simplex virus (HSV) and varicella-zoster virus (VZV) are neurotropic human alphaherpesviruses endemic worldwide. Upon primary infection, both viruses establish lifelong latency in neurons and reactivate intermittently to cause a variety of mild to severe diseases. Acute retinal necrosis (ARN) is a rare, sight-threatening eye disease induced by ocular VZV or HSV infection. The virus and host factors involved in ARN pathogenesis remain incompletely described. We hypothesize an underlying genetic defect in at least part of ARN cases.

Methods

We collected blood from 17 patients with HSV-or VZV-induced ARN, isolated DNA and performed Whole Exome Sequencing by Illumina followed by analysis in Varseq with criteria of CADD score > 15 and frequency in GnomAD < 0.1% combined with biological filters. Gene modifications relative to healthy control genomes were filtered according to high quality and read-depth, low frequency, high deleteriousness predictions and biological relevance.

Results

We identified a total of 50 potentially disease-causing genetic variants, including missense, frameshift and splice site variants and on in-frame deletion in 16 of the 17 patients. The vast majority of these genes are involved in innate immunity, followed by adaptive immunity, autophagy, and apoptosis; in several instances variants within a given gene or pathway was identified in several patients.

Discussion

We propose that the identified variants may contribute to insufficient viral control and increased necrosis ocular disease presentation in the patients and serve as a knowledge base and starting point for the development of improved diagnostic, prophylactic, and therapeutic applications.

Posttranslational ISGylation of NLRP3 by HERC enzymes facilitates inflammasome activation in models of inflammation

The NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome is a crucial component of the innate immune system that initiates inflammatory responses. Posttranslational modifications (PTMs) of NLRP3, including ubiquitination and phosphorylation, control inflammasome activation and determine the intensity of inflammation. However, the role of other PTMs in controlling NLRP3 inflammasome activation remains unclear. This study found that TLR priming induced NLRP3 ISGylation (a type of PTM in which ISG15 covalently binds to the target protein) to stabilize the NLRP3 protein. Viral infection, represented by SARS-COV-2 infection, and type I IFNs induced expression of ISG15 and the predominant E3 ISGylation ligases HECT domain- and RCC1-like domain-containing proteins (HERCs; HERC5 in humans and HERC6 in mice). HERCs promoted NLRP3 ISGylation and inhibited K48-linked ubiquitination and proteasomal degradation, resulting in the enhancement of NLRP3 inflammasome activation. Concordantly, Herc6 deficiency ameliorated NLRP3-dependent inflammation as well as hyperinflammation caused by viral infection. The results illustrate the mechanism by which type I IFNs responses control inflammasome activation and viral infection-induced aberrant NLRP3 activation. This work identifies ISGylation as a PTM of NLRP3, revealing a priming target that modulates NLRP3-dependent immunopathology.

PIM1 controls GBP1 activity to limit self-damage and to guard against pathogen infection

Disruption of cellular activities by pathogen virulence factors can trigger innate immune responses. Interferon-γ (IFN-γ)-inducible antimicrobial factors, such as the guanylate binding proteins (GBPs), promote cell-intrinsic defense by attacking intracellular pathogens and by inducing programmed cell death. Working in human macrophages, we discovered that GBP1 expression in the absence of IFN-γ killed the cells and induced Golgi fragmentation. IFN-γ exposure improved macrophage survival through the activity of the kinase PIM1. PIM1 phosphorylated GBP1, leading to its sequestration by 14-3-3σ, which thereby prevented GBP1 membrane association. During Toxoplasma gondii infection, the virulence protein TgIST interfered with IFN-γ signaling and depleted PIM1, thereby increasing GBP1 activity. Although infected cells can restrain pathogens in a GBP1-dependent manner, this mechanism can protect uninfected bystander cells. Thus, PIM1 can provide a bait for pathogen virulence factors, guarding the integrity of IFN-γ signaling.

Activation of inflammasomes and mechanisms for intracellular recognition of Listeria monocytogenes

The high mortality rate associated with Listeria monocytogenes can be attributed to its ability to invade the body systemically and to activate inflammasomes. Both of these processes are facilitated by expressing a major virulence factor known as listeriolysin O, a 56 kDa pore-forming protein encoded by the hly gene. Listeriolysin O plays a crucial role in the pathogenesis of the bacterium by facilitating the escape of the pathogen from the phagosome into the cytosol. This process is essential for the successful establishment of infection. In addition, listeriolysin O is known as an immunomodulator that activates host signal transduction. In addition to listeriolysin O, Listeria expresses a variety of bacterial ligands, such as lipoteichoic acid, nucleotide, and flagellin, that are recognized by host intracellular pattern-recognition receptors including Nod-like receptors, AIM2-like receptors, and RIG-I-like receptors. This review introduces intracellular recognition of Listeria monocytogenes since recent studies have revealed that the activation of inflammasome exacerbates Gram-positive bacteria infection.

Human guanylate-binding proteins in intracellular pathogen detection, destruction, and host cell death induction

Cell-intrinsic defense is an essential part of the immune response against intracellular pathogens regulated by cytokine-induced proteins and pathways. One of the most upregulated families of proteins in this defense system are the guanylate-binding proteins (GBPs), large GTPases of the dynamin family, induced in response to interferon gamma. Human GBPs (hGBPs) exert their antimicrobial activity through detection of pathogen-associated molecular patterns and/or damage-associated molecular patterns to execute control mechanisms directed at the pathogen itself as well as the vacuolar compartments in which it resides. Consequently, hGBPs are also inducers of canonical and noncanonical inflammasome responses leading to host cell death. The mechanisms are both cell-type and pathogen-dependent with hGBP1 acting as a pioneer sensor for intracellular invaders. This review focuses on the most recent functional roles of hGBPs in pathways of pathogen detection, destruction, and host cell death induction.

Single-cell transcriptomics delineates the immune cell landscape in equine lower airways and reveals upregulation of FKBP5 in horses with asthma

Equine asthma (EA) is a heterogenous, complex disease, with a significant negative impact on horse welfare and performance. EA and human asthma share fundamental similarities, making EA a useful model for studying the disease. One relevant sample type for investigating chronic lung inflammation is bronchoalveolar lavage fluid (BALF), which provides a snapshot of the immune cells present in the alveolar space. To investigate the immune cell landscape of the respiratory tract in horses with mild-to-moderate equine asthma (mEA) and healthy controls, single-cell RNA sequencing was conducted on equine BALF cells. We characterized the major immune cell populations present in equine BALF, as well as subtypes thereof. Interestingly, the most significantly upregulated gene discovered in cases of mEA was FKBP5, a chaperone protein involved in regulating the activity of the glucocorticoid receptor.

Defensive-lipid droplets: Cellular organelles designed for antimicrobial immunity

Microbes have developed many strategies to subvert host organisms, which, in turn, evolved several innate immune responses. As major lipid storage organelles of eukaryotes, lipid droplets (LDs) are an attractive source of nutrients for invaders. Intracellular viruses, bacteria, and protozoan parasites induce and physically interact with LDs, and the current view is that they "hijack" LDs to draw on substrates for host colonization. This dogma has been challenged by the recent demonstration that LDs are endowed with a protein-mediated antibiotic activity, which is upregulated in response to danger signals and sepsis. Dependence on host nutrients could be a generic "Achilles' heel" of intracellular pathogens and LDs a suitable chokepoint harnessed by innate immunity to organize a front-line defense. Here, we will provide a brief overview of the state of the conflict and discuss potential mechanisms driving the formation of the 'defensive-LDs' functioning as hubs of innate immunity.

IL-1β turnover by the UBE2L3 ubiquitin conjugating enzyme and HECT E3 ligases limits inflammation

The cytokine interleukin-1β (IL-1β) has pivotal roles in antimicrobial immunity, but also incites inflammatory disease. Bioactive IL-1β is released following proteolytic maturation of the pro-IL-1β precursor by caspase-1. UBE2L3, a ubiquitin conjugating enzyme, promotes pro-IL-1β ubiquitylation and proteasomal disposal. However, actions of UBE2L3 in vivo and its ubiquitin ligase partners in this process are unknown. Here we report that deletion of Ube2l3 in mice reduces pro-IL-1β turnover in macrophages, leading to excessive mature IL-1β production, neutrophilic inflammation and disease following inflammasome activation. An unbiased RNAi screen identified TRIP12 and AREL1 E3 ligases of the Homologous to E6 C-terminus (HECT) family in adding destabilising K27-, K29- and K33- poly-ubiquitin chains on pro-IL-1β. We show that precursor abundance determines mature IL-1β production, and UBE2L3, TRIP12 and AREL1 limit inflammation by shrinking the cellular pool of pro-IL-1β. Our study uncovers fundamental processes governing IL-1β homeostasis and provides molecular insights that could be exploited to mitigate its adverse actions in disease.

Race between virus and inflammasomes: inhibition or escape, intervention and therapy

The inflammasome is a multiprotein complex that further regulates cell pyroptosis and inflammation by activating caspase-1. The assembly and activation of inflammasome are associated with a variety of diseases. Accumulative studies have shown that inflammasome is a key modulator of the host's defense response to viral infection. Indeed, it has been established that activation of inflammasome occurs during viral infection. At the same time, the host has evolved a variety of corresponding mechanisms to inhibit unnecessary inflammasome activation. Therefore, here, we review and summarize the latest research progress on the interaction between inflammosomes and viruses, highlight the assembly and activation of inflammosome in related cells after viral infection, as well as the corresponding molecular regulatory mechanisms, and elucidate the effects of this activation on virus immune escape and host innate and adaptive immune defenses. Finally, we also discuss the potential therapeutic strategies to prevent and/or ameliorate viral infection-related diseases via targeting inflammasomes and its products.

Human GBP1 Is Involved in the Repair of Damaged Phagosomes/Endolysosomes

Mouse guanylate-binding proteins (mGBPs) are recruited to various invasive pathogens, thereby conferring cell-autonomous immunity against these pathogens. However, whether and how human GBPs (hGBPs) target M. tuberculosis (Mtb) and L. monocytogenes (Lm) remains unclear. Here, we describe hGBPs association with intracellular Mtb and Lm, which was dependent on the ability of bacteria to induce disruption of phagosomal membranes. hGBP1 formed puncta structures which were recruited to ruptured endolysosomes. Furthermore, both GTP-binding and isoprenylation of hGBP1 were required for its puncta formation. hGBP1 was required for the recovery of endolysosomal integrity. In vitro lipid-binding assays demonstrated direct binding of hGBP1 to PI4P. Upon endolysosomal damage, hGBP1 was targeted to PI4P and PI(3,4)P2-positive endolysosomes in cells. Finally, live-cell imaging demonstrated that hGBP1 was recruited to damaged endolysosomes, and consequently mediated endolysosomal repair. In summary, we uncover a novel interferon-inducible mechanism in which hGBP1 contributes to the repair of damaged phagosomes/endolysosomes.

G Protein-Coupled Receptor 120 Mediates Host Defense against Clostridium perfringens Infection through Regulating NOD-like Receptor Family Pyrin Domain-Containing 3 Inflammasome Activation

Clostridium perfringens is a major cause of infectious foodborne disease, frequently associated with the consumption of raw and undercooked food. Despite intensive studies on clarifying C. perfringens pathogenesis, the molecular mechanisms of host-pathogen interactions remain poorly understood. In soft tissue and mucosal infection models, Gpr120^-/- mice, G protein-coupled receptor 120 (GPR120), are more susceptible to C. perfringens infection. Gpr120 deficiency leads to a low survival rate (30 and 10%, p < 0.01), more bacterial loads in the muscle (2.26 × 10⁸ ± 2.08 × 10⁸ CFUs/g, p < 0.01), duodenum (2.80 × 10⁷ ± 1.61 × 10⁷ CFUs/g, p < 0.01), cecum (2.50 × 10⁸ ± 2.05 × 10⁸ CFUs/g, p < 0.01), and MLN (1.23 × 10⁶ ± 8.06 × 10⁵ CFUs/g, p < 0.01), less IL-18 production in the muscle (8.54 × 10³ ± 1.20 × 10³ pg/g, p < 0.01), duodenum (3.34 × 10³ ± 2.46 × 10² pg/g, p < 0.01), and cecum (3.81 × 10³ ± 5.29 × 10² pg/g, p < 0.01), and severe organ injury. Obviously, GPR120 facilitates IL-18 production and pathogen control via potassium efflux-dependent NOD-like receptor family pyrin domain-containing 3 (NLRP3) signaling. Mechanistically, GPR120 interaction with NLRP3 potentiates the NLRP3 inflammasome assembly. Thus, this study uncovers a novel role of GPR120 in host protection and reveals that GPR120 may be a potential therapeutic target for limiting pathogen infection.

Restricting genomic actions of innate immune mediators on fetal hematopoietic progenitor cells

Innate immune signaling protects against pathogens, controls hematopoietic development, and functions in oncogenesis, yet the relationship between these mechanisms is undefined. Downregulating the GATA2 transcription factor in fetal hematopoietic progenitor cells upregulates genes encoding innate immune regulators, increases Interferon-γ (IFNγ) signaling, and disrupts differentiation. We demonstrate that deletion of an enhancer that confers GATA2 expression in fetal progenitors elevated Toll-like receptor (TLR) TLR1/2 and TLR2/6 expression and signaling. Rescue by expressing GATA2 downregulated elevated TLR signaling. IFNγ amplified TLR1/2 and TLR2/6 signaling in GATA2-deficient progenitors, synergistically activating cytokine/chemokine genes and elevating cytokine/chemokine production in myeloid cell progeny. Genomic analysis of how innate immune signaling remodels the GATA2-deficient progenitor transcriptome revealed hypersensitive responses at innate immune genes harboring motifs for signal-dependent transcription factors and factors not linked to these mechanisms. As GATA2 establishes a transcriptome that constrains innate immune signaling, insufficient GATA2 renders fetal progenitor cells hypersensitive to innate immune signaling.

Chemotherapy-induced phlebitis via the GBP5/NLRP3 inflammasome axis and the therapeutic effect of aescin

BACKGROUND AND PURPOSE

Intravenous infusion of chemotherapy drugs can cause severe chemotherapy-induced phlebitis (CIP) in patients. However, the underlying mechanism of CIP development remains unclear.

EXPERIMENTAL APPROACH

RNA-sequencing analysis was used to identify potential disease targets in CIP. Guanylate binding protein-5 (GBP5) genetic deletion approaches also were used to investigate the role of GBP5 in NLR family pyrin domain containing 3 (NLRP3) inflammasome activation in lipopolysaccharide (LPS) primed murine bone-marrow-derived macrophages (BMDMs) induced by vinorelbine (VIN) in vitro and in mouse models of VIN-induced CIP in vivo. The anti-CIP effect of aescin was evaluated, both in vivo and in vivo.

KEY RESULTS

Here, we show that the expression of GBP5 was upregulated in human peripheral blood mononuclear cells from CIP patients. Genetic ablation of GBP5 in murine macrophages significantly alleviated VIN-induced CIP in the experimental mouse model. Mechanistically, GBP5 contributed to the inflammatory responses through activating NLRP3 inflammasome and driving the production of the inflammatory cytokine IL-1β. Moreover, aescin, a mixture of triterpene saponins extracted from horse chestnut seed, can alleviate CIP by inhibiting the GBP5/NLRP3 axis.

CONCLUSION AND IMPLICATIONS

These findings suggest that GBP5 is an important regulator of NLRP3 inflammasome in CIP mouse model. Our work further reveals that aescin may serve as a promising candidate in the clinical treatment of CIP.

Functional cross-species conservation of guanylate-binding proteins in innate immunity

Guanylate binding proteins (GBPs) represent an evolutionary ancient protein family widely distributed among eukaryotes. They are interferon (IFN)-inducible guanosine triphosphatases that belong to the dynamin superfamily. GBPs are known to have a major role in the cell-autonomous innate immune response against bacterial, parasitic and viral infections and are also involved in inflammasome activation. Evolutionary studies depicted that GBPs present a pattern of gain and loss of genes in each family with several genes pseudogenized and some genes more divergent, indicative for the birth-and-death evolution process. Most species harbor large GBP gene clusters encoding multiple paralogs. Previous functional studies mainly focused on mouse and human GBPs, but more data are becoming available, broadening the understanding of this multifunctional protein family. In this review, we will provide new insights and give a broad overview about GBP evolution, conservation and their roles in all studied species, including plants, invertebrates and vertebrates, revealing how far the described features of GBPs can be transferred to other species.

GBP5 exacerbates rosacea-like skin inflammation by skewing macrophage polarization towards M1 phenotype through the NF-κB signalling pathway

BACKGROUND

Rosacea is a chronic inflammatory skin disease with increased macrophage infiltration. However, the molecular mechanism remains unclear.

OBJECTIVES

To determine the significance of macrophage infiltration, and the correlation between Guanylate-binding protein 5 (GBP5) and polarization of macrophages in rosacea-like inflammation.

METHODS

Here we tested the hypothesis that Guanylate-binding protein 5 (GBP5) aggravates rosacea-like skin inflammation by promoting the polarization of the M1 macrophages through the NF-κB signalling pathway. We depleted macrophage by injecting clodronate-containing liposomes. We next explored the association between GBP5 and macrophage in rosacea tissue through transcriptome analysis and immunofluorescence analysis. We evaluated the severity of rosacea-like skin inflammation when BALB/c mice were injected with GBP5 siRNA intradermally daily for three consecutive days. At last, to study the causality of knocking down GBP5-blunted M1 macrophage polarization, THP-1 cell was treated with GBP5 siRNA.

RESULTS

Macrophage depletion ameliorated rosacea-like skin inflammation in mice, implying the important role of macrophages in rosacea. Based on the transcriptome analysis, Guanylate-binding protein 5 (GBP5) was identified as hub gene that was associated with macrophage infiltration in rosacea. Next, we found that GBP5 expression was significantly upregulated in rosacea tissues and positively correlated with macrophage infiltration, the immunofluorescence analysis revealed the co-localization between GBP5 and macrophages. In vivo, silencing of GBP5 attenuated rosacea-like skin inflammation in the LL-37-induced mouse model and suppressed the expression of M1 signature genes such as IL-6, iNOS and TNF-a. In vitro, knocking down GBP5 significantly blunted the polarization of the M1 macrophages partly by repressing the activation of the NF-κB signalling pathways.

CONCLUSIONS

Together, our study revealed the important role of macrophages in rosacea and identified GBP5 as a key regulator of rosacea by inducing M1 macrophage polarization via NF-κB signalling pathways.

Hedgehog-induced ZFYVE21 promotes chronic vascular inflammation by activating NLRP3 inflammasomes in T cells

The zinc finger protein ZFYVE21 is involved in immune signaling. Using humanized mouse models, primary human cells, and patient samples, we identified a T cell-autonomous role for ZFYVE21 in promoting chronic vascular inflammation associated with allograft vasculopathy. Ischemia-reperfusion injury (IRI) stimulated endothelial cells to produce Hedgehog (Hh) ligands, which in turn induced the production of ZFYVE21 in a population of T memory cells with high amounts of the Hh receptor PTCH1 (PTCHhi cells, CD3+CD4+CD45RO+PTCH1hiPD-1hi), vigorous recruitment to injured endothelia, and increased effector responses in vivo. After priming by interferon-γ (IFN-γ), Hh-induced ZFYVE21 activated NLRP3 inflammasome activity in T cells, which potentiated IFN-γ responses. Hh-induced NLRP3 inflammasomes and T cell-specific ZFYVE21 augmented the vascular sequelae of chronic inflammation in mice engrafted with human endothelial cells or coronary arteries that had been subjected to IRI before engraftment. Moreover, the population of PTCHhi T cells producing high amounts of ZFYVE21 was expanded in patients with renal transplant-associated IRI, and sera from these patients expanded this population in control T cells in a manner that depended on Hh signaling. We conclude that Hh-induced ZFYVE21 activates NLRP3 inflammasomes in T cells, thereby promoting chronic inflammation.

CARD-only proteins regulate in vivo inflammasome responses and ameliorate gout

Inflammatory responses are crucial for controlling infections and initiating tissue repair. However, excessive and uncontrolled inflammation causes inflammatory disease. Processing and release of the pro-inflammatory cytokines interleukin-1β (IL-1β) and IL-18 depend on caspase-1 activation within inflammasomes. Assembly of inflammasomes is initiated upon activation of cytosolic pattern recognition receptors (PRRs), followed by sequential polymerization of pyrin domain (PYD)-containing and caspase recruitment domain (CARD)-containing proteins mediated by homotypic PYD and CARD interactions. Small PYD- or CARD-only proteins (POPs and COPs, respectively) evolved in higher primates to target these crucial interactions to limit inflammation. Here, we show the ability of COPs to regulate inflammasome activation by modulating homotypic CARD-CARD interactions in vitro and in vivo. CARD16, CARD17, and CARD18 displace crucial CARD interactions between caspase-1 proteins through competitive binding and ameliorate uric acid crystal-mediated NLRP3 inflammasome activation and inflammatory disease. COPs therefore represent an important family of inflammasome regulators and ameliorate inflammatory disease.

Intravesical BCG in patients with non-muscle invasive bladder cancer induces trained immunity and decreases respiratory infections

BACKGROUND

BCG is recommended as intravesical immunotherapy to reduce the risk of tumor recurrence in patients with non-muscle invasive bladder cancer (NMIBC). Currently, it is unknown whether intravesical BCG application induces trained immunity.

METHODS

The aim of this research was to determine whether BCG immunotherapy induces trained immunity in NMIBC patients. We conducted a prospective observational cohort study in 17 NMIBC patients scheduled for BCG therapy and measured trained immunity parameters at 9 time points before and during a 1-year BCG maintenance regimen. Ex vivo cytokine production by peripheral blood mononuclear cells, epigenetic modifications, and changes in the monocyte transcriptome were measured. The frequency of respiratory infections was investigated in two larger cohorts of BCG-treated and non-BCG treated NMIBC patients as a surrogate measurement of trained immunity. Gene-based association analysis of genetic variants in candidate trained immunity genes and their association with recurrence-free survival and progression-free survival after BCG therapy was performed to investigate the hypothesized link between trained immunity and clinical response.

RESULTS

We found that intravesical BCG does induce trained immunity based on an increased production of TNF and IL-1β after heterologous ex vivo stimulation of circulating monocytes 6-12 weeks after intravesical BCG treatment; and a 37% decreased risk (OR 0.63 (95% CI 0.40 to 1.01)) for respiratory infections in BCG-treated versus non-BCG-treated NMIBC patients. An epigenomics approach combining chromatin immuno precipitation-sequencing and RNA-sequencing with in vitro trained immunity experiments identified enhanced inflammasome activity in BCG-treated individuals. Finally, germline variation in genes that affect trained immunity was associated with recurrence and progression after BCG therapy in NMIBC.

CONCLUSION

We conclude that BCG immunotherapy induces trained immunity in NMIBC patients and this may account for the protective effects against respiratory infections. The data of our gene-based association analysis suggest that a link between trained immunity and oncological outcome may exist. Future studies should further investigate how trained immunity affects the antitumor immune responses in BCG-treated NMIBC patients.

Domain motions, dimerization, and membrane interactions of the murine guanylate binding protein 2

Guanylate-binding proteins (GBPs) are a group of GTPases that are induced by interferon-[Formula: see text] and are crucial components of cell-autonomous immunity against intracellular pathogens. Here, we examine murine GBP2 (mGBP2), which we have previously shown to be an essential effector protein for the control of Toxoplasma gondii replication, with its recruitment through the membrane of the parasitophorous vacuole and its involvement in the destruction of this membrane likely playing a role. The overall aim of our work is to provide a molecular-level understanding of the mutual influences of mGBP2 and the parasitophorous vacuole membrane. To this end, we performed lipid-binding assays which revealed that mGBP2 has a particular affinity for cardiolipin. This observation was confirmed by fluorescence microscopy using giant unilamellar vesicles of different lipid compositions. To obtain an understanding of the protein dynamics and how this is affected by GTP binding, mGBP2 dimerization, and membrane binding, assuming that each of these steps are relevant for the function of the protein, we carried out standard as well as replica exchange molecular dynamics simulations with an accumulated simulation time of more than 30 μs. The main findings from these simulations are that mGBP2 features a large-scale hinge motion in its M/E domain, which is present in each of the studied protein states. When bound to a cardiolipin-containing membrane, this hinge motion is particularly pronounced, leading to an up and down motion of the M/E domain on the membrane, which did not occur on a membrane without cardiolipin. Our prognosis is that this up and down motion has the potential to destroy the membrane following the formation of supramolecular mGBP2 complexes on the membrane surface.

Circulating Cell-Free RNA in Blood as a Host Response Biomarker for the Detection of Tuberculosis

Tuberculosis (TB) remains a leading cause of death from an infectious disease worldwide. This is partly due to a lack of tools to effectively screen and triage individuals with potential TB. Whole blood RNA signatures have been extensively studied as potential biomarkers for TB, but they have failed to meet the World Health Organization's (WHOs) target product profiles (TPPs) for a non-sputum triage or diagnostic test. In this study, we investigated the utility of plasma cell-free RNA (cfRNA) as a host response biomarker for TB. We used RNA profiling by sequencing to analyze plasma samples from 182 individuals with a cough lasting at least two weeks, who were seen at outpatient clinics in Uganda, Vietnam, and the Philippines. Of these individuals, 100 were diagnosed with microbiologically-confirmed TB. Our analysis of the plasma cfRNA transcriptome revealed 541 differentially abundant genes, the top 150 of which were used to train 15 machine learning models. The highest performing model led to a 9-gene signature that had a diagnostic accuracy of 89.1% (95% CI: 83.6-93.4%) and an area under the curve of 0.934 (95% CI: 0.8674-1) for microbiologically-confirmed TB. This 9-gene signature exceeds the optimal WHO TPPs for a TB triage test (sensitivity: 96.2% [95% CI: 80.9-100%], specificity: 89.7% [95% CI: 72.4-100%]) and was robust to differences in sample collection, geographic location, and HIV status. Overall, our results demonstrate the utility of plasma cfRNA for the detection of TB and suggest the potential for a point-of-care, gene expression-based assay to aid in early detection of TB.

GBP5 Inhibition Ameliorates the Progression of Lupus Nephritis by Suppressing NLRP3 Inflammasome Activation

BACKGROUND

The inflammatory response and NLRP3 inflammasome activation are typical characteristics of lupus nephritis (LN). Guanylate-binding protein 5 (GBP5) has effects on the release of proinflammatory cytokines and the activation of NLRP3 inflammasome. However, it is largely unknown whether and how GBP5 contributes to the progression of LN.

METHODS

To detect the role of GBP5 in LN, MRL/lpr mice were administrated with the lentiviral vectors that knockdown GBP5 via tail vein. Proximal tubular epithelial HK-2 cells were treated with LPS and ATP to mimic the inflammatory response of LN in vitro.

RESULTS

GBP5 expression was increased in the renal cortical tissues of LN mice. The in vivo results showed that GBP5 inhibition prevented the progression of LN, as evidenced by the decreased levels of 24-hour proteinuria, blood urea nitrogen and creatinine, accompanied by the ameliorated renal pathological damages. The increased mRNA and protein levels of proinflammatory factors (IL-6, TNF-α, iNOS and COX-2) in the renal cortex of LN mice were suppressed by GBP5 knockdown. In vitro, we demonstrated that the treatment of LPS combined with ATP induced an increase in GBP5 mRNA and protein expression in HK-2 cells. Mechanically, knockdown of GBP5 inhibited the activation of NLRP3 inflammasome and the secretion of IL-1β and IL-18 both in vivo and in vitro.

CONCLUSION

Our findings reveal that GBP5 inhibition prevents the progression of LN, most likely by suppressing NLRP3 inflammasome activation. It provides a novel insight into the therapeutic interventions for LN.

Malian children infected with Plasmodium ovale and Plasmodium falciparum display very similar gene expression profiles

Plasmodium parasites caused 241 million cases of malaria and over 600,000 deaths in 2020. Both P. falciparum and P. ovale are endemic to Mali and cause clinical malaria, with P. falciparum infections typically being more severe. Here, we sequenced RNA from nine pediatric blood samples collected during infections with either P. falciparum or P. ovale, and characterized the host and parasite gene expression profiles. We found that human gene expression varies more between individuals than according to the parasite species causing the infection, while parasite gene expression profiles cluster by species. Additionally, we characterized DNA polymorphisms of the parasites directly from the RNA-seq reads and found comparable levels of genetic diversity in both species, despite dramatic differences in prevalence. Our results provide unique insights into host-pathogen interactions during malaria infections and their variations according to the infecting Plasmodium species, which will be critical to develop better elimination strategies against all human Plasmodium parasites.