scholarly journals Genetic functions of the NAIP family of inflammasome receptors for bacterial ligands in mice

2016 ◽  
Vol 213 (5) ◽  
pp. 647-656 ◽  
Author(s):  
Yue Zhao ◽  
Jianjin Shi ◽  
Xuyan Shi ◽  
Yupeng Wang ◽  
Fengchao Wang ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Type Iii Secretion ◽  
Physiological Function ◽  
Shigella Flexneri ◽  
Critical Role ◽  
Bacterial Virulence ◽  
Infection Model ◽  
Inflammasome Activation ◽  
Inflammatory Damage

Biochemical studies suggest that the NAIP family of NLR proteins are cytosolic innate receptors that directly recognize bacterial ligands and trigger NLRC4 inflammasome activation. In this study, we generated Naip5−/−, Naip1−/−, and Naip2−/− mice and showed that bone marrow macrophages derived from these knockout mice are specifically deficient in detecting bacterial flagellin, the type III secretion system needle, and the rod protein, respectively. Naip1−/−, Naip2−/−, and Naip5−/− mice also resist lethal inflammasome activation by the corresponding ligand. Furthermore, infections performed in the Naip-deficient macrophages have helped to define the major signal in Legionella pneumophila, Salmonella Typhimurium and Shigella flexneri that is detected by the NAIP/NLRC4 inflammasome. Using an engineered S. Typhimurium infection model, we demonstrate the critical role of NAIPs in clearing bacterial infection and protecting mice from bacterial virulence–induced lethality. These results provide definitive genetic evidence for the important physiological function of NAIPs in antibacterial defense and inflammatory damage–induced lethality in mice.

scholarly journals Stress Response Protein BolA Influences Fitness and PromotesSalmonella entericaSerovar Typhimurium Virulence

2018 ◽  
Vol 84 (8) ◽  
pp. e02850-17 ◽  
Author(s):  
Dalila Mil-Homens ◽  
Susana Barahona ◽  
Ricardo N. Moreira ◽  
Inês J. Silva ◽  
Sandra N. Pinto ◽  
...  
Keyword(s):  
Host Defense ◽  
Defense Mechanisms ◽  
Cellular Response ◽  
Critical Role ◽  
Bacterial Virulence ◽  
Public Health Care ◽  
Infection Model ◽  
Content Type ◽  
Determining Factor

ABSTRACTThe intracellular pathogenSalmonella entericaserovar Typhimurium has emerged as a major cause of foodborne illness, representing a severe clinical and economic concern worldwide. The capacity of this pathogen to efficiently infect and survive inside the host depends on its ability to synchronize a complex network of virulence mechanisms. Therefore, the identification of new virulence determinants has become of paramount importance in the search of new targets for drug development. BolA-like proteins are widely conserved in all kingdoms of life. InEscherichia coli, this transcription factor has a critical regulatory role in several mechanisms that are tightly related to bacterial virulence. Therefore, in the present work we used the well-established infection modelGalleria mellonellato evaluate the role of BolA protein inS. Typhimurium virulence. We have shown that BolA is an important player inS. Typhimurium pathogenesis. Specifically, the absence of BolA leads to a defective virulence capacity that is most likely related to the remarkable effect of this protein onS. Typhimurium evasion of the cellular response. Furthermore, it was demonstrated that BolA has a critical role in bacterial survival under harsh conditions since BolA conferred protection against acidic and oxidative stress. Hence, we provide evidence that BolA is a determining factor in the ability ofSalmonellato survive and overcome host defense mechanisms, and this is an important step in progress to an understanding of the pathways underlying bacterial virulence.IMPORTANCEBolA has been described as an important protein for survival in the late stages of bacterial growth and under harsh environmental conditions. High levels of BolA in stationary phase and under stresses have been connected with a plethora of phenotypes, strongly suggesting its important role as a master regulator. Here, we show that BolA is a determining factor in the ability ofSalmonellato survive and overcome host defense mechanisms, and this is an important step in progress to an understanding of the pathways underlying bacterial virulence. This work constitutes a relevant step toward an understanding of the role of BolA protein and may have an important impact on future studies in other organisms. Therefore, this study is of utmost importance for understanding the genetic and molecular bases involved in the regulation ofSalmonellavirulence and may contribute to future industrial and public health care applications.

scholarly journals Bacterial T6SS Effector EvpP Inhibits Neutrophil Recruitment via Jnk-Caspy Inflammasome Signaling In vivo

2018 ◽  
Author(s):  
Jinchao Tan ◽  
Dahai Yang ◽  
Zhuang Wang ◽  
Xin Zheng ◽  
Yuanxing Zhang ◽  
...  
Keyword(s):  
Bacterial Colonization ◽  
Critical Role ◽  
Neutrophil Recruitment ◽  
Host Cells ◽  
Infection Model ◽  
Inflammasome Activation ◽  
Type Vi Secretion System ◽  
Zebrafish Larvae

ABSTRACTThe type VI secretion system (T6SS) comprises dynamic complex bacterial contractile nanomachines and is used by many bacteria to inhibit or kill other prokaryotic or eukaryotic cells. Previous studies have revealed that T6SS is constitutively active in response to various stimuli, or fires effectors into host cells during infection. It has been proposed that the T6SS effector EvpP in Edwardsiella piscicida can inhibit NLRP3 inflammasome activation via the Ca2+-dependent JNK pathways. Here, we developed an in vivo infection model by microinjecting bacteria into the tail vein muscle of 3-day-post-fertilized zebrafish larvae, and found that both macrophages and neutrophils are essential for bacterial clearance. Further study revealed that EvpP plays a critical role in promoting the pathogenesis of E. piscicida via inhibiting the phosphorylation of Jnk signaling to reduce the expression of cxcl8a, mmp13 and IL-1β in vivo. Subsequently, by utilizing Tg (mpo:eGFP+/+) zebrafish larvae for E. piscicida infection, we found that the EvpP-inhibited Jnk-caspy inflammasome signaling axis significantly suppressed the recruitment of neutrophils to infection sites, and the caspy‐ or IL-1β-MO knockdown larvae were more susceptible to infection and failed to restrict bacterial colonization in vivo.IMPORTANCEInnate immunity is regulated by phagocytic cells and is critical for host control of bacterial infection. In many bacteria, T6SSs can affect bacterial virulence in certain environments, but little is known about the mechanisms underlying T6SS regulation of innate immune responses during infection in vivo. Here, we investigated the role of an E. piscicida T6SS effector EvpP in manipulating the reaction of neutrophils in vivo. We show that EvpP inhibits the activation of Jnk-caspy inflammasome pathway in zebrafish larvae, and reveal that macrophages are essential for neutrophil recruitment in vivo. This interaction improves our understanding about the complex and contextual role of a bacterial T6SS effector in modulating the action of myeloid cells during infection, and offers new insights into the warfare between bacterial weapons and host immunological surveillance.

scholarly journals SlyA Is a Transcriptional Regulator Involved in the Virulence of Enterococcus faecalis

2011 ◽  
Vol 79 (7) ◽  
pp. 2638-2645 ◽  
Author(s):  
Charlotte Michaux ◽  
Maurizio Sanguinetti ◽  
Fany Reffuveille ◽  
Yanick Auffray ◽  
Brunella Posteraro ◽  
...  
Keyword(s):  
Enterococcus Faecalis ◽  
Galleria Mellonella ◽  
Peritoneal Macrophages ◽  
Bacterial Virulence ◽  
Transcriptional Analysis ◽  
Infection Model ◽  
Wild Type ◽  
Content Type ◽  
Wild Type Parent

ABSTRACTPhylogenetic analysis of the crystal structure of theEnterococcus faecalisSlyA (EF_3002) transcriptional factor places it between the SlyA and MarR regulator subfamilies. Proteins of these families are often involved in the regulation of genes important for bacterial virulence and stress response. To gather evidence for the role of this putative regulator inE. faecalisbiology, we dissected the genetic organization of theslyA-EF_3001 locus and constructed aslyAdeletion mutant as well as complemented strains. Interestingly, compared to the wild-type parent, the ΔslyAmutant is more virulent in an insect infection model (Galleria mellonella), exhibits increased persistence in mouse kidneys and liver, and survives better inside peritoneal macrophages. In order to identify a possible SlyA regulon, global microarray transcriptional analysis was performed. This study revealed that theslyA-EF_3001 locus appears to be autoregulated and that 117 genes were differentially regulated in the ΔslyAmutant. In the mutant strain, 111 were underexpressed and 6 overexpressed, indicating that SlyA functions mainly as an activator of transcription.

scholarly journals A Duplicated ESAT-6 Region of ESX-5 Is Involved in Protein Export and Virulence of Mycobacteria

2015 ◽  
Vol 83 (11) ◽  
pp. 4349-4361 ◽  
Author(s):  
Swati Shah ◽  
Joe R. Cannon ◽  
Catherine Fenselau ◽  
Volker Briken
Keyword(s):  
Secretion System ◽  
Bacterial Virulence ◽  
Inflammasome Activation ◽  
Zebrafish Model ◽  
Content Type ◽  
Type Vii Secretion ◽  
Specific Subset ◽  
Host Cell Death ◽  
Type Vii Secretion System

ABSTRACTThe ESX-5 secretion system ofMycobacterium tuberculosisis important for bacterial virulence and for the secretion of the large PE/PPE protein family, whose genes constitute 10% of theM. tuberculosisgenome. A four-gene region of the ESX-5 system is duplicated three times in theM. tuberculosisgenome, but the functions of these duplicates are unknown. Here we investigated one of these duplicates: the region carrying theesxI,esxJ,ppe15, andpe8genes (ESX-5a). An ESX-5a deletion mutant in the model systemM. marinumbackground was deficient in the secretion of some members of the PE/PPE family of proteins. Surprisingly, we also identified other proteins that are not members of this family, thus expanding the range of ESX-5 secretion substrates. In addition, we demonstrated that ESX-5a is important for the virulence ofM. marinumin the zebrafish model. Furthermore, we showed the role of theM. tuberculosisESX-5a region in inflammasome activation but not host cell death induction, which is different from the case for theM. tuberculosisESX-5 system. In conclusion, the ESX-5a region is nonredundant with its ESX-5 paralog and is necessary for secretion of a specific subset of proteins inM. tuberculosisandM. marinumthat are important for bacterial virulence ofM. marinum. Our findings point to a role for the three ESX-5 duplicate regions in the selection of substrates for secretion via ESX-5, and hence, they provide the basis for a refined model of the molecular mechanism of this type VII secretion system.

scholarly journals Cellular Accumulation and Pharmacodynamic Evaluation of the Intracellular Activity of CEM-101, a Novel Fluoroketolide, against Staphylococcus aureus, Listeria monocytogenes, and Legionella pneumophila in Human THP-1 Macrophages

2009 ◽  
Vol 53 (9) ◽  
pp. 3734-3743 ◽  
Author(s):  
Sandrine Lemaire ◽  
Françoise Van Bambeke ◽  
Paul M. Tulkens
Keyword(s):  
Staphylococcus Aureus ◽  
Listeria Monocytogenes ◽  
Legionella Pneumophila ◽  
Critical Role ◽  
Intracellular Accumulation ◽  
Cellular Accumulation ◽  
Intracellular Activity ◽  
P Glycoprotein

ABSTRACT CEM-101 is a novel fluoroketolide with lower MICs than those of telithromycin and macrolides. Our aim was to assess the cellular accumulation and intracellular activity of CEM-101 using models developed for analyzing the pharmacokinetics and pharmacological properties of antibiotics against phagocytized bacteria. We used THP-1 macrophages and Staphylococcus aureus (ATCC 25923 [methicillin (meticillin) sensitive]), Listeria monocytogenes (strain EGD), and Legionella pneumophila (ATCC 33153). CEM-101 reached cellular-to-extracellular-concentration ratios of about 350 within 24 h (versus approximately 20, 30, and 160 for telithromycin, clarithromycin, and azithromycin, respectively). This intracellular accumulation was suppressed by incubation at a pH of ≤6 and by monensin (proton ionophore) and was unaffected by verapamil (P-glycoprotein inhibitor; twofold accumulation increase for azithromycin) or gemfibrozil. While keeping with the general properties of the macrolide antibiotics in terms of maximal efficacy (E max; approximately 1-log10-CFU decrease compared to the postphagocytosis inoculum after a 24-h incubation), CEM-101 showed significantly greater potency against phagocytized S. aureus than telithromycin, clarithromycin, and azithromycin (for which the 50% effective concentration [EC50] and static concentrations were about 3-, 6-, and 15-fold lower, respectively). CEM-101 was also about 50-fold and 100-fold more potent than azithromycin against phagocytized L. monocytogenes and L. pneumophila, respectively. These differences in EC50s and static concentrations between drugs were minimized when data were expressed as multiples of the MIC, demonstrating the critical role of intrinsic drug activity (MIC) in eliciting the antibacterial intracellular effects, whereas accumulation per se was unimportant. CEM-101 should show enhanced in vivo potency if used at doses similar to those of the comparators tested here.

scholarly journals Microglial ApoD Induced NLRC4 Inflammasome Activation Promotes Alzheimer’s Disease Progression

2021 ◽  
Author(s):  
Yaliang Yu ◽  
Jianzhou Lv ◽  
Dan Ma ◽  
Ya Han ◽  
Yaheng Zhang ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Critical Role ◽  
Microglia Activation ◽  
Inflammatory Factors ◽  
Inflammasome Activation ◽  
Cellular Interactions ◽  
Brain Functions ◽  
Chronic Neuroinflammation

Abstract Alzheimer’s disease (AD) is a progressive neurodegenerative disease with no effective therapies. It’s well-known that chronic neuroinflammation plays a critical role in the onset and progression of AD. Proper neuronal-microglial interactions are essential for brain functions. However, as the main existence of immune cells, determining the role of microglia in Alzheimer’s neuroinflammation and the associated molecular basis has been challenging. Herein, the inflammatory factors in the sera of AD patients were detected and the association with microglia activation was analyzed. The mechanism regarding the microglial inflammation was investigated. The IL6 and TNF-α were found to be significantly increased in the AD stage. Further analysis revealed microglia were extensively activated in AD cerebra releasing mounts of cytokines to impair the neural stem cells (NSCs) function. Moreover, ApoD induced NLRC4 inflammasome was activated in microglia, which gave rise to the proinflammatory phenotype. Targeting the microglial ApoD promoted NSCs self-renewal and inhibited neuron apoptosis. These findings demonstrate the critical role of ApoD in microglial inflammasome activation, and for the first time reveal that microglia-induced inflammation suppresses neuronal proliferation. Our studies establish the cellular basis for microglia activation in AD progression, and shed lights on cellular interactions important for AD treatment.

NLRP3 inflammasome is involved in uterine activation for labor at term and preterm

Reproduction ◽  
2021 ◽  
Vol 162 (6) ◽  
pp. 449-460
Author(s):  
Zixi Chen ◽  
Yali Shan ◽  
Xingji You ◽  
Hang Gu ◽  
Chen Xu ◽  
...  
Keyword(s):  
Mouse Model ◽  
Nlrp3 Inflammasome ◽  
Inflammatory Diseases ◽  
Critical Role ◽  
Inflammasome Activation ◽  
Pyrin Domain ◽  
Nlrp3 Inflammasome Activation ◽  
Pregnant Mice ◽  
Labor Onset

The nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome plays a critical role in various inflammatory diseases. We sought to investigate the role of NLRP3 inflammasome in uterine activation for labor at term and preterm. We found that NLRP3 inflammasome was activated in the myometrium tissues obtained from the pregnant women undergoing labor at term (TL) compared with those not undergoing labor (TNL) at term. NLRP3 inflammasome was also activated in amnion and chorion-deciduas in TL and preterm labor (PTL) groups. In the mouse model, uterine NLRP3 inflammasome and nuclear factor kappaB (NF-κB) were activated toward term and during labor. Treatment of pregnant mice with lipopolysaccharide (LPS) and RU38486 induced preterm birth (PTB) and also promoted uterine NLRP3 inflammasome and NF-κB activation. Treatment of pregnant mice with NLRP3 inflammasome inhibitor BAY11-7082 and MCC950 delayed the onset of labor and suppressed NLRP3 inflammasome and NF-κB activation in uterus. MCC950 postponed labor onset of the mice with LPS and RU38486 treatment and inhibited NLRP3 inflammasome activation in uterus. Our data provide the evidence that NLRP3 inflammasome is involved in uterine activation for labor onset in term and PTB in humans and mouse model.

scholarly journals Monoclonal immunoglobulin A antibody directed against serotype-specific epitope of Shigella flexneri lipopolysaccharide protects against murine experimental shigellosis.

1995 ◽  
Vol 182 (3) ◽  
pp. 769-778 ◽  
Author(s):  
A Phalipon ◽  
M Kaufmann ◽  
P Michetti ◽  
J M Cavaillon ◽  
M Huerre ◽  
...  
Keyword(s):  
Interleukin 6 ◽  
Shigella Flexneri ◽  
Bacterial Load ◽  
Immunoglobulin A ◽  
Mucosal Immune Response ◽  
Hybridoma Cells ◽  
Infection Model ◽  
Local Concentration ◽  
Iga Antibody

To determine the role of humoral mucosal immune response in protection against shigellosis, we have obtained a monoclonal dimeric immunoglobulin A (IgA) antibody specific for Shigella flexneri serotype 5a lipopolysaccharide (mIgA) and used a murine pulmonary infection model that mimics the lesions occurring in natural intestinal infection. Adult BALB/c mice challenged with 10(7) S. flexneri organisms developed a rapid inflammatory response characterized by polymorphonuclear cell infiltration around and within the bronchi and strong systemic interleukin 6 response. Implantation of hybridoma cells in the back of mice, resulting in the development of a myeloma tumor producing mIgA in the serum and subsequently secretory mIgA in local secretions, or direct intranasal administration of these antibodies, protected the animals against subsequent intranasal challenge with S. flexneri serotype 5a. Absence of histopathological lesion and significant decrease in bacterial load of the lungs and of systemic interleukin 6 response were the three major criteria of protection. This protection was shown to be serotype-specific and dependent on local concentration of mIgA. These data demonstrate that mucosal antibodies directed against a single polysaccharidic surface epitope of Shigella can protect against the disease.

scholarly journals Regulation of the Ysa Type III Secretion System of Yersinia enterocolitica by YsaE/SycB and YsrS/YsrR

2004 ◽  
Vol 186 (13) ◽  
pp. 4056-4066 ◽  
Author(s):  
Kimberly A. Walker ◽  
Virginia L. Miller
Keyword(s):  
Yersinia Enterocolitica ◽  
Type Iii Secretion ◽  
Shigella Flexneri ◽  
Wild Type ◽  
Secretion Systems ◽  
Type Iii ◽  
Regulatory Cascade ◽  
Two Component

ABSTRACT Yersinia enterocolitica biovar 1B contains two type III secretion systems (TTSSs), the plasmid-encoded Ysc-Yop system and the chromosomally encoded Ysa-Ysp system. Proteins secreted from the Ysa TTSS (Ysps) have only been detected in vitro when cells are cultured at 26°C in a high-NaCl medium. However, the exact role of the Ysa TTSS is unclear. Thus, investigations into the regulation of this system may help elucidate the role of the Ysps during the life cycle of Y. enterocolitica. Here we present evidence that the AraC-like regulator YsaE acts together with the chaperone SycB to regulate transcription of the sycByspBCDA operon, a phenomenon similar to that seen in the closely related Salmonella SPI-1 and Shigella flexneri Mxi-Spa-Ipa TTSSs. Deletion of either sycB or ysaE results in a twofold reduction in the activity of a sycB-lacZ fusion compared to the wild type. In a reconstituted Escherichia coli system, transcription of sycB was activated sixfold only when both YsaE and SycB were present, demonstrating that they are necessary for activation. ysrR and ysrS are located near the ysa genes and encode a putative two-component regulatory system. Mutations in either gene indicated that both YsrR and YsrS were required for secretion of Ysps. In addition, transcription from sycB-lacZ and ysaE-lacZ fusions was decreased 6.5- and 25-fold, respectively, in the ysrS mutant compared to the wild type. Furthermore, in the absence of NaCl, the activity of ysaE-lacZ was reduced 25-fold in the wild-type and ΔysrS strains, indicating that YsrS is probably required for the salt-dependent expression of the ysa locus. These results suggest that the putative two-component system YsrRS may be a key element in the regulatory cascade for the Ysa TTSS.

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