scholarly journals TOR functions as a molecular switch connecting an iron cue with host innate defense against bacterial infection

PLoS Genetics ◽  
2021 ◽  
Vol 17 (3) ◽  
pp. e1009383
Author(s):  
Yi-Cheng Ma ◽  
Li-Li Dai ◽  
Bei-Bei Qiu ◽  
Ying Zhou ◽  
Yu-Qiang Zhao ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Bacterial Infection ◽  
Host Defense ◽  
Bacterial Infections ◽  
Iron Availability ◽  
Innate Defense ◽  
Iron Sequestration ◽  
Serovar Typhimurium ◽  
Important Regulator ◽  
Host Innate Immunity

As both host and pathogen require iron for survival, iron is an important regulator of host-pathogen interactions. However, the molecular mechanism by which how the availability of iron modulates host innate immunity against bacterial infections remains largely unknown. Using the metazoan Caenorhabditis elegans as a model, we demonstrate that infection with a pathogenic bacterium Salmonella enterica serovar Typhimurium induces autophagy by inactivating the target of rapamycin (TOR). Although the transcripts of ftn-1 and ftn-2 encoding two H-ferritin subunits are upregulated upon S. Typhimurium infection, the ferritin protein is kept at a low level due to its degradation mediated by autophagy. Autophagy, but not ferritin, is required for defense against S. Typhimurium infection under normal circumstances. Increased abundance of iron suppresses autophagy by activating TOR, leading to an increase in the ferritin protein level. Iron sequestration, but not autophagy, becomes pivotal to protect the host from S. Typhimurium infection in the presence of exogenous iron. Our results show that TOR acts as a regulator linking iron availability with host defense against bacterial infection.

scholarly journals Pregnane X Receptor Regulates Pathogen-Induced Inflammation and Host Defense against an Intracellular Bacterial Infection through Toll-like Receptor 4

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Zhijuan Qiu ◽  
Jorge L. Cervantes ◽  
Basak B. Cicek ◽  
Subhajit Mukherjee ◽  
Madhukumar Venkatesh ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Bacterial Infection ◽  
Host Defense ◽  
Negative Impact ◽  
Pregnane X Receptor ◽  
Negative Regulator ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Chemokine Production ◽  
Inflammatory Monocytes

Abstract The nuclear pregnane X receptor (PXR) plays a central role in regulating xenobiotic metabolism. We now report a novel role for PXR as a critical negative regulator of innate immunity after infection. Pxr −/− mice exhibited remarkably elevated pro-inflammatory cytokine and chemokine production following infection with Listeria monocytogenes (Lm). Despite the more robust innate immune response, Pxr −/− mice were highly susceptible to Lm infection. Surprisingly, disruption of the Toll-like receptor 4 (TLR4) but not TLR2 signaling restored the inflammation to normal levels and the ability to clear Lm in Pxr −/− mice. Mechanistically, the heightened inflammation in Pxr −/− mice resulted in the death of inflammatory monocytes that led to the enhanced susceptibility to Lm infection. These data demonstrated that PXR regulated pathogen-induced inflammation and host defense against Lm infection through modulating the TLR4 pathway. In summary, we discovered an apical role for PXR in regulating innate immunity. In addition, we uncovered a remarkable negative impact of the TLR4 pathway in controlling the quality of the inflammatory response and host defense against a gram-positive bacterial infection.

scholarly journals Roles of a Mast Cell–Specific Receptor MRGPRX2 in Host Defense and Inflammation

2020 ◽  
Vol 99 (8) ◽  
pp. 882-890 ◽  
Author(s):  
C. Chompunud Na Ayudhya ◽  
S. Roy ◽  
M. Thapaliya ◽  
H. Ali
Keyword(s):  
Mast Cells ◽  
Bacterial Infection ◽  
Host Defense ◽  
Immune Cells ◽  
Inflammatory Pain ◽  
Bacterial Infections ◽  
Neurogenic Inflammation ◽  
Inflammatory Diseases ◽  
Adaptive Immune Cells ◽  
Novel Approaches

Mast cells are multifunctional immune cells that are found most abundantly at host-environment interfaces, such as the skin, respiratory tract, and oral/gastrointestinal mucosa. Not surprisingly, mast cells act as sentinel cells that sense microbial attacks and initiate a protective immune response and promote healing. Although mast cells share many features with other innate immune effector cells, such as neutrophils and macrophages, they uniquely interact closely with blood vessels and release an extensive set of mediators for the recruitment of innate and adaptive immune cells. A novel human G protein-coupled receptor (GPCR), known as Mas-related GPCR-X2 (MRGPRX2, mouse ortholog, MrgprB2), has recently been identified, which is expressed on mast cells but not neutrophils and macrophages. Interestingly, activation of MrgprB2 by bacteria-derived quorum-sensing peptides inhibits bacterial growth, prevents biofilm formation, and leads to the recruitment of neutrophils to effectively clear bacteria. Furthermore, host defense antimicrobial peptides and small-molecule peptide mimetics also activate mast cells via MRGPRX2/B2. MrgprB2-mediated activation of local mast cells also clears cutaneous bacterial infection, promotes healing, and protects against reinfection. In addition to their role in host defense, mast cells contribute to a number of chronic inflammatory diseases such as periodontitis, neurogenic inflammation, and inflammatory pain likely via the activation of MRGPRX2. In this review, we discuss the roles of MRGPRX2/B2 in the clearance of bacterial infection, wound healing, periodontal disease, neurogenic inflammation, and inflammatory pain. We propose that harnessing mast cells’ host defense and immunomodulatory properties via the activation of MRGPRX2 may lead to novel approaches for the treatment of drug-resistant bacterial infections. On the other hand, increased MRGPRX2 expression on mast cells and their inappropriate activation may contribute to periodontitis, neurogenic inflammation, and inflammatory pain. Thus, targeting MRGPRX2 could provide novel approaches to modulate these conditions.

scholarly journals Interferon-induced guanylate-binding proteins: Guardians of host defense in health and disease

2019 ◽  
Vol 216 (3) ◽  
pp. 482-500 ◽  
Author(s):  
Kyle Tretina ◽  
Eui-Soon Park ◽  
Agnieszka Maminska ◽  
John D. MacMicking
Keyword(s):  
Innate Immunity ◽  
Bacterial Infection ◽  
Host Defense ◽  
Tissue Damage ◽  
Binding Proteins ◽  
Wide Spectrum ◽  
Cell Types ◽  
Microbial Pathogens ◽  
Health And Disease ◽  
Basic Biology

Guanylate-binding proteins (GBPs) have recently emerged as central orchestrators of immunity to infection, inflammation, and neoplastic diseases. Within numerous host cell types, these IFN-induced GTPases assemble into large nanomachines that execute distinct host defense activities against a wide variety of microbial pathogens. In addition, GBPs customize inflammasome responses to bacterial infection and sepsis, where they act as critical rheostats to amplify innate immunity and regulate tissue damage. Similar functions are becoming evident for metabolic inflammatory syndromes and cancer, further underscoring the importance of GBPs within infectious as well as altered homeostatic settings. A better understanding of the basic biology of these IFN-induced GTPases could thus benefit clinical approaches to a wide spectrum of important human diseases.

Deletion of OLFM4 Rescues Defective Host Defense Against Staphylococcus Aureus, but Not Aspergillus Fumigatus in Murine X-Linked Chronic Granulomatous Disease

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3276-3276
Author(s):  
Wenli Liu ◽  
Janyce A Sugui ◽  
Hongzhen Li ◽  
Kyung J Kwon-Chung ◽  
Griffin P. Rodgers
Keyword(s):  
Staphylococcus Aureus ◽  
Innate Immunity ◽  
Chronic Granulomatous Disease ◽  
Host Defense ◽  
Cathepsin G ◽  
Granulomatous Disease ◽  
Wild Type ◽  
Cathepsin C ◽  
Host Innate Immunity ◽  
Deficient Mice

Abstract Abstract 3276 Introduction: Chronic granulomatous disease (CGD) patients have recurrent life-threating bacterial and fungal infections due to the mutation of one of four subunits of the respiratory burst oxidase (NADPH-oxidase). Currently, the overall fatality rate in CGD patients remains high, making it necessary to better understand the basic biological processes governing host defense against bacteria and fungi in CGD. Olfactomedin 4 (OLFM4) is a neutrophil granule protein, which has been recently identified as a negative regulator of host innate immunity against bacteria infection in mice through modulation of neutrophil protease activity. The goal of this study was to evaluate the impact of OLFM4 deletion on host innate immunity against Staphylococcus aureus and Aspergillus fumigatus, two major pathogens encountered in CGD patients, in a murine X-linked CGD model. Results: We created gp91phox-and OLFM4-double deficient mice and investigated the mice defense against S. aureus and A. fumigatus infection. We found that neutrophil intracellular killing and in vivo clearance of S. aureus have been significantly increased in gp91phox- and OLFM4-double deficiency mice compared with CGD mice. The mice survival to S. aureus sepsis in gp91phox- and OLFM4-double deficiency mice has also been significantly prolonged compared with CGD mice. Our study has shown that the CGD mice immune deficiency against S. aureus has been totally corrected by additional loss of OLFM4 gene. To explore the mechanism that OLFM4 deletion rescued the bactericidal activities of CGD neutrophils, we analyzed cathepsin C and its downstream protease (neutrophil elastase and cathepsin G) activities in the mice neutrophils. Cathepsin C activities in OLFM4 deficient as well as double deficient mice neutrophils were significantly higher than those in WT mouse neutrophils. Cathepsin C activities in the neutrophils of CGD were similar to those in WT mice. Accordingly, the elastase and cathepsin G activities in the neutrophils of OLFM4 deficient and double deficient mice were also substantially higher than those in WT mice as well as CGD mice. However, we have not observed enhanced innate immunity against A. fumigatus in OLFM4 deficiency mice compared with wild-type mice using a lung infection model. The lung histopathology showed similar inflammation and fungal burden in the OLFM4 deficiency mice compared with wild-type mice. Correspondingly, mice survival to severe A. fumigatus infection did not show significant difference in gp91phox- and OLFM4-double deficiency mice compared with CGD mice, suggesting that OLFM4 may not play a role in mice host defense against A. fumigatus. Conclusion: 1. The damaged neutrophil bacterial killing and host innate immunity against S. aureus in CGD mice due to oxidative mechanism deficiency could be successfully rescued by deletion of OLFM4. 2. These results showed that the granule protease activities in CGD neutrophils could be substantially enhanced above the level in normal neutrophils by deletion of OLFM4, suggesting that the increased of serine proteinase activities due to OLFM4 deletion is NADPH-independent. 3. OLFM4 may not play a role in mice host defense against pulmonary A. fumigatus infection. 4. OLFM4 might prove to be an important target in CGD patients to augment host defense against bacterial infection. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Severe Altered Immune Status After Burn Injury Is Associated With Bacterial Infection and Septic Shock

2021 ◽  
Vol 12 ◽  
Author(s):  
Hélène Moins-Teisserenc ◽  
Debora Jorge Cordeiro ◽  
Vincent Audigier ◽  
Quentin Ressaire ◽  
Mourad Benyamina ◽  
...  
Keyword(s):  
Septic Shock ◽  
Innate Immunity ◽  
Bacterial Infection ◽  
Adaptive Immunity ◽  
Bacterial Infections ◽  
Burn Injury ◽  
Inflammatory Responses ◽  
Burn Patients ◽  
Down Regulation ◽  
Risk Of Death

Introduction: Burn injury is associated with a high risk of death. Whether a pattern of immune and inflammatory responses after burn is associated with outcome is unknown. The aim of this study was to explore the association between systemic immune and inflammatory responses and outcome in severely-ill burn patients.Materials and Methods: Innate immunity, adaptive immunity, activation and stress and inflammation biomarkers were collected at admission and days 2, 7, 14, and 28 in severely-ill adult burn patients. Primary endpoint was mortality at day 90, secondary endpoint was secondary infections. Healthy donors (HD) served as controls. Multiple Factorial Analysis (MFA) was used to identify patterns of immune response.Results: 50 patients were included. Age was 49.2 (44.2–54.2) years, total burn body surface area was 38.0% (32.7–43.3). Burn injury showed an upregulation of adaptive immunity and activation biomarkers and a down regulation of innate immunity and stress/inflammation biomarkers. High interleukin-10 (IL-10) at admission was associated with risk of death. However, no cluster of immune/inflammatory biomarkers at early timepoints was associated with mortality. HLA-DR molecules on monocytes at admission were associated with bacterial infections and septic shock. Later altered immune/inflammatory responses in patients who died may had been driven by the development of septic shock.Conclusion: Burn injury induced an early and profound upregulation of adaptive immunity and activation biomarkers and a down regulation of innate immunity and stress/inflammation biomarkers. Immune and inflammatory responses were associated with bacterial infection and septic shock. Absence of immune recovery patterns was associated with poor prognosis.

scholarly journals MicroRNA-30e-5p Regulates SOCS1 and SOCS3 During Bacterial Infection

2021 ◽  
Vol 10 ◽  
Author(s):  
Richa Mishra ◽  
Pandikannan Krishnamoorthy ◽  
Himanshu Kumar
Keyword(s):  
Innate Immunity ◽  
Immune Responses ◽  
Bacterial Infection ◽  
Messenger Rna ◽  
Bacterial Infections ◽  
Pathogenic Bacteria ◽  
Innate Immune ◽  
Host Cells ◽  
Microbial Infection ◽  
Major Player

Host innate immunity is the major player against continuous microbial infection. Various pathogenic bacteria adopt the strategies to evade the immunity and show resistance toward the various established therapies. Despite the advent of many antibiotics for bacterial infections, there is a substantial need for the host-directed therapies (HDTs) to combat the infection. HDTs are recently being adopted to be useful in eradicating intracellular bacterial infection. Changing the innate immune responses of the host cells alters pathogen’s ability to reside inside the cell. MicroRNAs are the small non-coding endogenous molecules and post-transcriptional regulators to target the 3’UTR of the messenger RNA. They are reported to modulate the host’s immune responses during bacterial infections. Exploiting microRNAs as a therapeutic candidate in HDTs upon bacterial infection is still in its infancy. Here, initially, we re-analyzed the publicly available transcriptomic dataset of macrophages, infected with different pathogenic bacteria and identified significant genes and microRNAs common to the differential infections. We thus identified and miR-30e-5p, to be upregulated in different bacterial infections which enhances innate immunity to combat bacterial replication by targeting key negative regulators such as SOCS1 and SOCS3 of innate immune signaling pathways. Therefore, we propose miR-30e-5p as one of the potential candidates to be considered for additional clinical validation toward HDTs.

scholarly journals NHR-49/PPAR-α and HLH-30/TFEB promote C. elegans host defense via a flavin-containing monooxygenase

2020 ◽  
Author(s):  
Khursheed A. Wani ◽  
Debanjan Goswamy ◽  
Stefan Taubert ◽  
Ramesh Ratnappan ◽  
Arjumand Ghazi ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Host Defense ◽  
Bacterial Infections ◽  
Model Organism ◽  
Defense Responses ◽  
Cellular Level ◽  
Nuclear Hormone Receptor ◽  
Multiple Infection ◽  
C Elegans ◽  
Transcriptional Signature

SUMMARYDuring bacterial infection, the host is confronted with multiple overlapping signals that are integrated at the organismal level to produce defensive host responses. How multiple infection signals are sensed by the host and how they elicit the transcription of host defense genes is much less understood at the whole-animal level than at the cellular level. The model organism Caenorhabditis elegans is known to mount transcriptional defense responses against intestinal bacterial infections that elicit overlapping starvation and infection responses, but the regulation of such responses is not well understood. Direct comparison of C. elegans that were starved or infected with Staphylococcus aureus revealed a large infection-specific transcriptional signature. This signature was almost completely abrogated by deletion of transcription factor hlh-30/TFEB, except for six genes including a flavin-containing monooxygenase (FMO) gene, fmo-2/FMO5. Deletion of fmo-2/FMO5 severely compromised infection survival, thus identifying the first FMO with innate immunity functions in animals. Moreover, the mechanism of fmo-2/FMO5 induction required the nuclear hormone receptor, NHR-49/PPAR-α, which induced fmo-2/FMO5 and host defense cell non-autonomously. These findings for the first time reveal an infection-specific host response to S. aureus, identify HLH-30/TFEB as its main regulator, reveal that FMOs are important innate immunity effectors in animals, and identify the mechanism of FMO regulation through NHR-49/PPAR-α in C. elegans, with important implications for innate host defense in higher organisms.

scholarly journals The Innate Immune Response to Salmonella enterica Serovar Typhimurium by Macrophages Is Dependent on TREM2-DAP12

2008 ◽  
Vol 76 (6) ◽  
pp. 2439-2447 ◽  
Author(s):  
Julia F. Charles ◽  
Mary Beth Humphrey ◽  
Xiaodan Zhao ◽  
Ellen Quarles ◽  
Mary C. Nakamura ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Innate Immune ◽  
Ros Production ◽  
Innate Response ◽  
Innate Defense ◽  
Early Stages ◽  
Serovar Typhimurium ◽  
Important Regulator ◽  
Dependent Pathway

ABSTRACT Macrophage recognition of Salmonella enterica serovar Typhimurium leads to a cascade of signaling events, including the activation of Src family and Syk kinases and the production of reactive oxygen species (ROS), which are critical for host innate defense during early stages of bacterial infection. ROS production depends on the NADPH oxidase, but little is known about the innate immune receptors and proximal adapters that regulate Salmonella-induced ROS. Herein, we demonstrate that serovar Typhimurium induces ROS through a pathway that requires both triggering receptor expressed on myeloid cells 2 (TREM2) and DAP12. This pathway is highly analogous to the pathways utilized by Fc receptors and integrins to regulate ROS production. Oral infection of mice with serovar Typhimurium demonstrates that the DAP12-dependent pathway regulates cecal colonization during early stages of Salmonella infection. Thus, DAP12 is an important regulator of Salmonella-induced ROS production in macrophages, and TREM2 is essential for linking DAP12 to the innate response to serovar Typhimurium.

scholarly journals Neonatal Host Defense against Staphylococcal Infections

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Melanie R. Power Coombs ◽  
Kenny Kronforst ◽  
Ofer Levy
Keyword(s):  
Innate Immunity ◽  
Host Defense ◽  
Bacterial Infections ◽  
Late Onset ◽  
Staphylococcal Infection ◽  
Antimicrobial Proteins ◽  
Late Onset Sepsis ◽  
Skin Integrity ◽  
Term Newborns

Preterm infants are especially susceptible to late-onset sepsis that is often due to Gram-positive bacterial infections resulting in substantial morbidity and mortality. Herein, we will describe neonatal innate immunity toStaphylococcusspp. comparing differences between preterm and full-term newborns with adults. Newborn innate immunity is distinct demonstrating diminished skin integrity, impaired Th1-polarizing responses, low complement levels, and diminished expression of plasma antimicrobial proteins and peptides, especially in preterm newborns. Characterization of distinct aspects of the neonatal immune response is defining novel approaches to enhance host defense to prevent and/or treat staphylococcal infection in this vulnerable population.

scholarly journals Mitofusin-2 boosts innate immunity through the maintenance of aerobic glycolysis and activation of xenophagy in mice

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Prashanta Silwal ◽  
Jin Kyung Kim ◽  
Sang Min Jeon ◽  
June-Young Lee ◽  
Young Jae Kim ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Bacterial Infection ◽  
Host Defense ◽  
Inflammatory Responses ◽  
Aerobic Glycolysis ◽  
Hypoxia Inducible Factor ◽  
Chain Complex ◽  
Mitochondrial Respiratory Chain ◽  
Mitofusin 2 ◽  
Mitochondrial Respiratory Chain Complex

AbstractMitochondrial function and innate immunity are intimately linked; however, the mechanisms how mitochondrion-shaping proteins regulate innate host defense remains largely unknown. Herein we show that mitofusin-2 (MFN2), a mitochondrial fusion protein, promotes innate host defense through the maintenance of aerobic glycolysis and xenophagy via hypoxia-inducible factor (HIF)-1α during intracellular bacterial infection. Myeloid-specific MFN2 deficiency in mice impaired the antimicrobial and inflammatory responses against mycobacterial and listerial infection. Mechanistically, MFN2 was required for the enhancement of inflammatory signaling through optimal induction of aerobic glycolysis via HIF-1α, which is activated by mitochondrial respiratory chain complex I and reactive oxygen species, in macrophages. MFN2 did not impact mitophagy during infection; however, it promoted xenophagy activation through HIF-1α. In addition, MFN2 interacted with the late endosomal protein Rab7, to facilitate xenophagy during mycobacterial infection. Our findings reveal the mechanistic regulations by which MFN2 tailors the innate host defense through coordinated control of immunometabolism and xenophagy via HIF-1α during bacterial infection.

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