IFN-γ-dependent nitric oxide suppresses Brucella-induced arthritis by inhibition of inflammasome activation

Differentiating early and advanced Brucella spondylitis using an MRI-based radiomics nomogram model

BackgroundAccurate differentiation between early and advanced Brucella spondylitis is crucial for effective treatment.PurposeTo develop a magnetic resonance imaging (MRI)-based radiomics nomogram model for distinguishing between early and advanced stages of Brucella spondylitis.Material and MethodsWe conducted a retrospective analysis of clinical and imaging data from 100 patients with early Brucella spondylitis and 100 patients with advanced Brucella spondylitis. Regions of interest were marked on sagittal T2-weighted fat-suppressed lumbar MRI scans. Radiomic features were extracted and used to build a radiomics model. The significance of these features was evaluated using the Shapley Additive Explanations (SHAP) method. Intravoxel incoherent motion (IVIM) quantitative parameters were also included as clinical features, with key parameters selected to create a clinical model. A nomogram model was developed by combining clinical and radiomic features. The performance of the three models was compared and validated using receiver operating characteristic curves, calibration curves, and decision curves.ResultsEight radiomic features were selected. The clinical feature's D-value showed significant differences between the training and test sets. The nomogram model integrating both clinical and radiomic features achieved an AUC of 0.998 in the training set and 0.992 in the test set, surpassing the performance of both the clinical and radiomic models alone. Calibration and decision curves confirmed the model's strong predictive performance.ConclusionThis study shows that the MRI-based radiomics nomogram model effectively differentiates between early and advanced Brucella spondylitis, offering clinicians a valuable tool for personalized treatment across different disease stages.

Brucella osteoarthritis: recent progress and future directions

Brucellosis is a common zoonosis, and Brucella osteoarthritis is the most common chronic complication of brucellosis. Development of brucellosis osteoarthritis involves multiple organs, tissues, and cells. Brucella grows and multiplies in intrinsic cells of the skeleton, including osteoblasts, osteocyte and osteoclasts, which results in sustained release of bacteria that leads to exacerbation of the immune response. Concurrently, activation of the immune system caused by invasion with Brucella may affect the dynamic balance of the skeleton. A variety of in vitro and in vivo models have been employed to study Brucella osteoarthritis, such as using bone marrow-derived macrophages to establish cell models and mice to develop animal models of Brucella osteoarthritis. However, limited studies on the molecular pathological mechanisms of Brucella osteoarthritis have been performed and inadequate animal models have been developed due to the challenging parameters of Brucella research. This paper reviews recent advances in the clinical features, molecular pathological mechanisms, and animal models of Brucella osteoarticular infections. This review underscores the complexity of the pathogenesis of Brucella osteoarticular infections and highlights inflammation as a contributing factor to bone loss caused by Brucella. Additionally, the significant proliferation of Brucella in skeletal resident cells also is an important factor leading to bone loss. A deeper understanding of the molecular pathological mechanism of Brucella osteoarthrosis and their animal models could provide robust support for the prevention and treatment of Brucella osteoarticular disease.

Intraperitoneal Treatment of Cambinol, a Synthetic SIRT1 and SIRT2 Inhibitory Compound, Exacerbates Brucella abortus 544 Burden in the Spleens of Institute of Cancer Research Mice

Our preliminary data using bone marrow-derived macrophages (BMDMs) collected from ICR mice treated with anti-sirtuin (anti-SIRT) 1 antibody showed that Brucella uptake was significantly attenuated. We then further investigated the effect of an inhibitor of SIRT1/2, cambinol, in the progression of Brucella. The in vitro results using RAW264.7 cells revealed that cambinol treatment had no effect on adhesion, uptake, intracellular survival and nitric oxide (NO) production during B. abortus infection, nor did it directly affect bacterial growth for up to 72 h. Finally, intraperitoneal treatment of 8-week-old female ICR mice infected with Brucella showed no differences in the total average weights of spleens and livers; however, the treated mice displayed higher Brucella colony-forming units (CFUs) from the spleens. Furthermore, the interleukin (IL)-10 serum level was observed to be lower in treated mice at 7 d post-infection, and none of the cytokines tested showed a change at 14 d post-infection. The overall findings showed that cambinol treatment had no effect on the proliferation of Brucella in RAW264.7 macrophages but exacerbated the splenic proliferation of the bacteria in mice and displayed reduced anti-inflammatory cytokine IL-10 at the first week of infection, suggesting that cambinol as an inhibitory of SIRT1/2 could be beneficial in the context of Brucella dissemination in animal hosts and that exploration of activating SIRTs could be an alternative treatment against Brucella infection.

Genome-wide analysis of Brucella melitensis growth in spleen of infected mice allows rational selection of new vaccine candidates

Live attenuated vaccines (LAVs) whose virulence would be controlled at the tissue level could be a crucial tool to effectively fight intracellular bacterial pathogens, because they would optimize the induction of protective immune memory while avoiding the long-term persistence of vaccine strains in the host. Rational development of these new LAVs implies developing an exhaustive map of the bacterial virulence genes according to the host organs implicated. We report here the use of transposon sequencing to compare the bacterial genes involved in the multiplication of Brucella melitensis, a major causative agent of brucellosis, in the lungs and spleens of C57BL/6 infected mice. We found 257 and 135 genes predicted to be essential for B. melitensis multiplication in the spleen and lung, respectively, with 87 genes common to both organs. We selected genes whose deletion is predicted to produce moderate or severe attenuation in the spleen, the main known reservoir of Brucella, and compared deletion mutants for these genes for their ability to protect mice against challenge with a virulent strain of B. melitensis. The protective efficacy of a deletion mutant for the plsC gene, implicated in phospholipid biosynthesis, is similar to that of the reference Rev.1 vaccine but with a shorter persistence in the spleen. Our results demonstrate that B. melitensis faces different selective pressures depending on the organ and underscore the effectiveness of functional genome mapping for the design of new safer LAV candidates.

Th1 cells reduce the osteoblast-like phenotype in valvular interstitial cells by inhibiting NLRP3 inflammasome activation in macrophages

BACKGROUND AND AIMS

Inflammation is initiates the propagation phase of aortic valve calcification. The activation of NLRP3 signaling in macrophages plays a crucial role in the progression of calcific aortic valve stenosis (CAVS). IFN-γ regulates NLRP3 activity in macrophages. This study aimed to explore the mechanism of IFN-γ regulation and its impact on CAVS progression and valve interstitial cell transdifferentiation.

METHODS AND RESULTS

The number of Th1 cells and the expression of IFN-γ and STAT1 in the aortic valve, spleen and peripheral blood increased significantly as CAVS progressed. To explore the mechanisms underlying the roles of Th1 cells and IFN-γ, we treated CAVS mice with IFN-γ-AAV9 or an anti-IFN-γ neutralizing antibody. While IFN-γ promoted aortic valve calcification and dysfunction, it significantly decreased NLRP3 signaling in splenic macrophages and Ly6C+ monocytes. In vitro coculture showed that Th1 cells inhibited NLPR3 activation in ox-LDL-treated macrophages through the IFN-γR1/IFN-γR2-STAT1 pathway. Compared with untreated medium, conditioned medium from Th1-treated bone marrow-derived macrophages reduced the osteogenic calcification of valvular interstitial cells.

CONCLUSION

Inhibition of the NLRP3 inflammasome by Th1 cells protects against valvular interstitial cell calcification as a negative feedback mechanism of adaptive immunity toward innate immunity. This study provides a precision medicine strategy for CAVS based on the targeting of anti-inflammatory mechanisms.

Innate Lymphoid Cells and Interferons Limit Neurologic and Articular Complications of Brucellosis

Brucellosis is a globally significant zoonotic disease. Human patients with brucellosis develop recurrent fever and focal complications, including arthritis and neurobrucellosis. The current study investigated the role of innate lymphoid cells (ILCs) in the pathogenesis of focal brucellosis caused by Brucella melitensis. After footpad infection, natural killer cells and ILC1 cells both limited joint colonization by Brucella. Mice lacking natural killer cells, and in particular mice lacking all ILCs, also developed marked arthritis after footpad infection. Following pulmonary infection, mice lacking adaptive immune cells and ILCs developed arthritis, neurologic complications, and meningitis. Adaptive immune cells and ILCs both limited colonization of the brain by Brucella following pulmonary infection. Transcriptional analysis of Brucella-infected brains revealed marked up-regulation of genes associated with inflammation and interferon responses, as well as down-regulation of genes associated with neurologic function. Type II interferon deficiency resulted in colonization of the brain by Brucella, but mice lacking both type I and type II interferon signaling more rapidly developed clinical signs of neurobrucellosis, exhibited hippocampal neuronal loss, and had higher levels of Brucella in their brains than mice lacking type II interferon signaling alone. Collectively, these findings indicate ILCs and interferons play an important role in prevention of focal complications during Brucella infection, and that mice with deficiencies in ILCs or interferons can be used to study pathogenesis of neurobrucellosis.

NLRP6 Induces Lung Injury and Inflammation Early in Brucella and Influenza Coinfection

(1) Background: With the resurgence of brucellosis epidemics in China in recent years, the chances of a brucella coinfection with other common respiratory pathogens, such as the influenza virus, have increased dramatically. However, little is known about the pathogenicity or the mechanisms of brucella and influenza coinfections. (2) Methods: To clarify the interventions in the early stages of lung damage due to brucella and influenza coinfections, we evaluated the effect of the coinfection on disease progression and mortality using a coinfection model in WT mice and NLRP6^-/- mice, and we verified the function of NLRP6 in infection and proinflammation. (3) Results: The coinfection induced significant respiratory symptoms, weight loss, and a high mortality rate in WT mice. Influenza in the coinfection group significantly increased brucella proliferation in a synergistic manner. Meanwhile, a histological examination showed severe lung tissue destruction and excessive inflammatory responses in coinfected WT animals, and the expression of NLRP6 and IL-18 was dramatically increased in the lung tissues. Furthermore, NLRP6 deletion attenuated lung injuries and inflammation, a reduced bacterial load, and decreased IL-18 protein expression. (4) Conclusions: Our findings indicated that NLRP6 plays a critical role and might be a promising potential therapeutic target for brucella-influenza coinfections.

The Multiple Faces of Nitric Oxide in Chronic Granulomatous Disease: A Comprehensive Update

Nitric oxide (NO), a signaling molecule, regulates multiple biological functions, including a variety of physiological and pathological processes. In this regard, NO participates in cutaneous inflammations, modulation of mitochondrial functions, vascular diseases, COVID-19, neurologic diseases, and obesity. It also mediates changes in the skeletal muscle function. Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder characterized by the malfunction of phagocytes caused by mutations in some of the genes encoding subunits of the superoxide-generating phagocyte NADPH (NOX). The literature consulted shows that there is a relationship between the production of NO and the NADPH oxidase system, which regulates the persistence of NO in the medium. Nevertheless, the underlying mechanisms of the effects of NO on CGD remain unknown. In this paper, we briefly review the regulatory role of NO in CGD and its potential underlying mechanisms.

Immunosuppressive Mechanisms in Brucellosis in Light of Chronic Bacterial Diseases

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

Nucleotide receptors mediate protection against neonatal sepsis and meningitis caused by alpha-hemolysin expressing Escherichia coli K1

Neonatal meningitis-associated Escherichia coli (NMEC) is among the leading causes of bacterial meningitis and sepsis in newborn infants. Several virulence factors have been identified as common among NMEC, and have been shown to play an important role in the development of bacteremia and/or meningitis. However, there is significant variability in virulence factor expression between NMEC isolates, and relatively little research has been done to assess the impact of variable virulence factor expression on immune cell activation and the outcome of infection. Here, we investigated the role of NMEC strain-dependent P2X receptor (P2XR) signaling on the outcome of infection in neonatal mice. We found that alpha-hemolysin (HlyA)-expressing NMEC (HlyA⁺ ) induced robust P2XR-dependent macrophage cell death in vitro, while HlyA^- NMEC did not. P2XR-dependent cell death was inflammasome independent, suggesting an uncoupling of P2XR and inflammasome activation in the context of NMEC infection. In vivo inhibition of P2XRs was associated with increased mortality in neonatal mice infected with HlyA⁺ NMEC, but had no effect on the survival of neonatal mice infected with HlyA^- NMEC. Furthermore, we found that P2XR-dependent protection against HlyA⁺ NMEC in vivo required macrophages, but not neutrophils or NLRP3. Taken together, these data suggest that HlyA⁺ NMEC activates P2XRs which in turn confers macrophage-dependent protection against infection in neonates. In addition, our findings indicate that strain-dependent virulence factor expression should be taken into account when studying the immune response to NMEC.

Nitric oxide controls proliferation of Leishmania major by inhibiting the recruitment of permissive host cells

Nitric oxide (NO) is an important antimicrobial effector but also prevents unnecessary tissue damage by shutting down the recruitment of monocyte-derived phagocytes. Intracellular pathogens such as Leishmania major can hijack these cells as a niche for replication. Thus, NO might exert containment by restricting the availability of the cellular niche required for efficient pathogen proliferation. However, such indirect modes of action remain to be established. By combining mathematical modeling with intravital 2-photon biosensors of pathogen viability and proliferation, we show that low L. major proliferation results not from direct NO impact on the pathogen but from reduced availability of proliferation-permissive host cells. Although inhibiting NO production increases recruitment of these cells, and thus pathogen proliferation, blocking cell recruitment uncouples the NO effect from pathogen proliferation. Therefore, NO fulfills two distinct functions for L. major containment: permitting direct killing and restricting the supply of proliferation-permissive host cells.

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Direct killing of L. major by NO occurs only during the peak of the immune response

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Efficient L. major proliferation requires newly recruited monocyte-derived cells

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Loss of NO production increases both pathogen proliferation and monocyte recruitment

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NO dampens L. major proliferation indirectly, limiting the pathogen’s cellular niche

MyD88-Dependent Glucose Restriction and Itaconate Production Control Brucella Infection

Brucellosis is one of the most common global zoonoses and is caused by facultative intracellular bacteria of the genus Brucella. Numerous studies have found that MyD88 signaling contributes to protection against Brucella, however the underlying mechanism has not been entirely defined. Here we show that MyD88 signaling in hematopoietic cells contributes both to inflammation and to control of Brucella melitensis infection in vivo. While the protective role of MyD88 in Brucella infection has often been attributed to promotion of IFN-γ production, we found that MyD88 signaling restricts host colonization by B. melitensis even in the absence of IFN-γ. In vitro, we show that MyD88 promotes macrophage glycolysis in response to B. melitensis. Interestingly, a B. melitensis mutant lacking the glucose transporter, GluP, was more highly attenuated in MyD88^-/- than in WT mice, suggesting MyD88 deficiency results in an increased availability of glucose in vivo which Brucella can exploit via GluP. Metabolite profiling of macrophages identified several metabolites regulated by MyD88 in response to B. melitensis, including itaconate. Subsequently, we found that itaconate has antibacterial effects against Brucella and also regulates the production of pro-inflammatory cytokines in B. melitensis-infected macrophages. Mice lacking the ability to produce itaconate were also more susceptible to B. melitensis in vivo. Collectively, our findings indicate that MyD88-dependent changes in host metabolism contribute to control of Brucella infection.

Nitric oxide inhibits interleukin-1-mediated protection against Escherichia coli K1-induced sepsis and meningitis in a neonatal murine model

Neonatal meningitis-associated Escherichia coli (NMEC) is a leading cause of sepsis and meningitis in newborn infants. Neonates are known to have impaired inflammasome activation and interleukin (IL)-1 production. However, it is unknown what role this plays in the context of NMEC infection. Here we investigated the role of IL-1 signaling in the pathogenesis of NMEC infection. We found both IL-1β and IL-1α were secreted from macrophages and microglial cells in response to NMEC in a Toll-like receptor 4- and NLR family pyrin domain containing 3 (NPLR3)-dependent manner. Intracerebral infection of adult mice indicated a protective role of IL-1 signaling during NMEC infection. However, IL-1 receptor blockade in wild-type neonatal mice did not significantly alter bacterial loads in the blood or brain, and we, therefore, investigated whether protection conferred by IL-1 was age dependent. Neonates are known to have increased nitric oxide (NO) levels compared with adults, and we found NO inhibited the secretion of IL-1 by macrophages in response to NMEC. In contrast to our results in wild-type neonates, blockade of IL-1 receptor in neonates lacking inducible nitric oxide synthase (iNOS) led to significantly increased bacterial loads in the blood and brain. These data indicate IL-1 signaling is protective during NMEC infection in neonates only when iNOS is absent. Collectively, our findings suggest that increased NO production by neonates inhibits IL-1 production, and that this suppresses the protective role of IL-1 signaling in response to NMEC infection. This may indicate a general mechanism for increased susceptibility of neonates to infection and could lead to new therapeutic strategies in the future.